| Balasis G, Papadimitriou C, Boutsi AZ, Daglis IA, Giannakis O, Hulot G, Coïsson P, Mann IR and Pakhotin I (2019),
"New indices derived from Swarm observations to investigate space weather and geomagnetic activity hazards", In Geophysical Research Abstracts. Vienna, Austria, 7-12 April, 2019. Vol. 21(EGU2019-11193) EGU. |
| Abstract: The ongoing Swarm mission of the European Space Agency provides an opportunity for a better knowledge of the near-Earth electromagnetic environment, including investigations of ultra-low frequency (ULF) and extremely-low frequency (ELF) wave events. In a recent study, we derived a Swarm orbit-by-orbit Pc3 (20–100 mHz) wave index for the topside ionosphere based on two years of low-resolution (LR) 1 Hz vector field magnetometer (VFM) data and compared its values to the corresponding variations of solar wind variables and geomagnetic activity indices. This was the first attempt, to our knowledge, to derive a ULF wave index from low-Earth orbit (LEO) satellite data. The technique developed for that study could now be used to define a new Level 2 product from the Swarm mission, the Pc3 wave index, which is suitable for space weather applications. In the context of a new ESA Swarm DISC (Data, Innovation, and Science Cluster) pre-study, an open community effort has, thus, been initiated aiming at the recommendation of new Swarm data products, services or tools focusing on the Pc1 (0.2–5 Hz) and Pc3 wave indices using the high-resolution (HR) 50 Hz VFM data and absolute scalar magnetometer (ASM) 250 Hz Burst mode data. This presentation reports on progress achieved within the context of this initiative, also discussing the possibility of providing a new ELF whistler dispersion index that could be used to improve ionospheric models such as the International Reference Ionosphere (IRI) model. Moreover, we will present a recently introduced Dst-like Swarm- derived index. |
BibTeX:
@inproceedings{Balasis:2019-EGU,
author = {G. Balasis and C. Papadimitriou and A. Z. Boutsi and I. A. Daglis and O. Giannakis and G. Hulot and P. Coïsson and I. R. Mann and I. Pakhotin},
title = {New indices derived from Swarm observations to investigate space weather and geomagnetic activity hazards},
booktitle = {Geophysical Research Abstracts},
publisher = {EGU},
year = {2019},
volume = {21},
number = {EGU2019-11193},
note = {EGU General Assembly 2019}
}
|
| Coïsson P, Hulot G, Vigneron P, Deram P, Léger JM and Jager T (2019),
"0_+ whistlers in the ELF band recorded by Swarm satellites used to reconstruct the ionosphere below the satellite height", In Geophysical Research Abstracts. Vienna, Austria, 7-12 April, 2019. Vol. 21(EGU2019-15764-1) EGU. |
| Abstract: The Swarm satellites record the variations of the intensity of the Earth magnetic field using the Absolute Scalar Magnetometers. Beside their nominal operation sampling the magnetic field at 1 Hz, these instruments can be operated in burst-mode and produce data at 250 Hz, enabling the observation of whistlers signals in the frequency band between 20 and 120 Hz. Seven burst session were operated at the beginning of Swarm mission in 2014 and an additional one in July 2018, collecting a total of 500 hours of burst data, in which several thousands of whistlers were detected, particularly in low latitudes regions. These whistlers have been characterised in terms of dispersion and intensity of the recorded signal. To assess the capability of using these data for monitoring the ionosphere below Swarm satellites, forward modeling of the propagation of ELF signals between the lower boundary of the ionosphere up to Swarm satellite position have been developed using ray-tracing calculation of electromagnetic signals propagating through the ionospheric plasma provided by IRI 2016 model and the magnetic field by IGRF model. Additional in-situ electron density measurements of Swarm Electric Field Instrument (EFI) have been used to constrain the vertical profile of ionospheric electron density provided by the climatological model. The combined experimental information from in-situ measurements and whistler characteristics are investigated with the aim of provide new constrains for modelling the ionospheric plasma. |
BibTeX:
@inproceedings{Coisson:2019-EGU,
author = {P. Coïsson and G. Hulot and P. Vigneron and P. Deram and J. M. Léger and T. Jager},
title = {0_+ whistlers in the ELF band recorded by Swarm satellites used to reconstruct the ionosphere below the satellite height},
booktitle = {Geophysical Research Abstracts},
publisher = {EGU},
year = {2019},
volume = {21},
number = {EGU2019-15764-1},
note = {EGU General Assembly 2019}
}
|
| Hulot G, Léger JM, Vigneron P, Jager T, Bertrand F, Coïsson P, Laurens A and Faure B (2019),
"The NanoMagSat (Swarm Delta) nanosatellite high-precision magnetic project", In Geophysical Research Abstracts. Vienna, Austria, 7-12 April, 2019. Vol. 21(EGU2019-15806) EGU. |
| Abstract: NanoMagSat (Swarm Delta) is a 12 U nanosatellite project aiming at complementing the ESA Swarm constellation of satellites currently monitoring the Earth’s magnetic field and ionospheric environment on LEO polar orbits (since November 2013). The orbit aimed at is an (approximately) 60◦ inclination circular 500 km altitude LEO that would allow a quick local time coverage (within a little more than a month) to compensate for the slow local time coverage of the Alpha, Bravo and Charlie of the Swarm constellation, as well as orbit crossing to provide tie points. Such an orbit would prove extremely useful for enhancing the science return of the Swarm mission. The NanoMagSat main science payload would consist of an improved miniaturized version of the ASM magnetometers, which currently provide the 1 Hz absolute scalar reference on the Swarm satellites but also have the experimental ability to either simultaneously provide 1 Hz self-calibrated vector data (vector mode) or 250 Hz scalar data (Burst mode). We will report on the science that has been achieved so far thanks to both these experimental modes on the Swarm satellites, establishing the ability of such ASM instruments to fulfil many of the science goals of NanoMagSat as a stand-alone magnetometer. We will also report on the way the lessons learnt from these ASM have been taken advantage of to considerably improve the design of these instruments, a prototype miniaturized sensor of which is currently under construction. We also expect to be able to report on the latest test results from this first prototype sensor. NanoMagSat already went through a phase 0 study within CNES and is now ready for a Phase A study, aiming at a launch before the demise (not expected before at least 2023) of Swarm. Beyond this maiden mission, additional similar low-cost nanosatellites could form the basis of a future constellation of multiple high-precision nanosatellites for permanent monitoring of the Earth’s magnetic field and ionospheric environment. |
BibTeX:
@inproceedings{Hulot:2019-EGU,
author = {G. Hulot and J. M. Léger and P. Vigneron and T. Jager and F. Bertrand and P. Coïsson and A. Laurens and B. Faure},
title = {The NanoMagSat (Swarm Delta) nanosatellite high-precision magnetic project},
booktitle = {Geophysical Research Abstracts},
publisher = {EGU},
year = {2019},
volume = {21},
number = {EGU2019-15806},
note = {EGU General Assembly 2019}
}
|
| Oehler J-F, Boivin J-P, Lucas S, Rouxel D, Salaun C and Lesur V (2019),
"A new geomagnetic reference station in Brest (France) dedicated to marine applications", In Geophysical Research Abstracts. Vienna, Austria, 7-12 April, 2019. Vol. 21(EGU2019-2240) EGU. |
| Abstract: The future installation of a new geomagnetic reference station at the Shom’s site in Brest (France) is validated through comparisons with measurements collected during several months at the French national magnetic obser- vatory of Chambon-La-Forêt (CLF), located more than 500 km inland. The Shom’s station is mainly needed to more accurately reduce external diurnal and agitation variations of the external magnetic field in marine magnetic data acquired in the Iroise Sea, the British Channel, the Bay of Biscay and to the North-East Atlantic Ocean. Com- parative tests are performed to correct marine surveys using both Shom and CLF reference data provided through Intermagnet (Love and Chuillat, 2013). Results show that external low frequency diurnal disturbances are clearly better mitigated with the local station. Moreover, the intrinsic quality and precision of surveys can be improved by over 5 to 30% for shallow coastal surveys. |
BibTeX:
@inproceedings{Oehler:2019-EGU,
author = {Jean-Francois Oehler and Jean-Pierre Boivin and Sylvain Lucas and Didier Rouxel and Corinne Salaun and Vincent Lesur},
title = {A new geomagnetic reference station in Brest (France) dedicated to marine applications},
booktitle = {Geophysical Research Abstracts},
publisher = {EGU},
year = {2019},
volume = {21},
number = {EGU2019-2240},
note = {EGU General Assembly 2019}
}
|
| Coïsson P, Hulot G, Deram P, Vigneron P, Léger JM and Jager T (2018),
"Swarm ASM burst mode to sound the ionosphere below the satellites", In 8th Swarm Data Quality Workshop. ESRIN, Frascati, Italy, 8-12 October, 2018. [BibTeX] |
BibTeX:
@inproceedings{Coisson:2018-8SwarmDQ,
author = {P. Coïsson and G. Hulot and P. Deram and P. Vigneron and J. M. Léger and T. Jager},
title = {Swarm ASM burst mode to sound the ionosphere below the satellites},
booktitle = {8th Swarm Data Quality Workshop},
year = {2018}
}
|
| Coïsson P, Deram P, Hulot G, Vigneron P, Léger JM and Jager T (2018),
"Experimental burst mode (250 Hz) magnetic scalar data reveal the possibility of using ELF whistlers to systematically probe the ionosphere below the Swarm satellites", In AGU Fall meeting. Washington, DC, 10-14 December, 2018. (SA21A-3157) |
| Abstract: The Absolute Scalar Magnetometers (ASM) onboard the Swarm satellites measure the strength of the Earth magnetic field, nominally producing 1 Hz data. These instruments, however, can also produce burst-mode data, when the sampling frequency is raised to 250 Hz. Burst sessions operated during the commissioning phase of the mission in early 2014 revealed the capability of these instruments to detect multiple whistlers excited by the lightning activity in the troposphere. Most of these whistlers appear to propagate from the base of the ionosphere up to the Swarm satellites, thus passing through the E and F regions of the ionosphere. For each detected whistler, ray-tracing calculation of the whistler ray-paths through a modeled ionosphere could be used to compute a theoretical whistler dispersion, which could next be compared to the observed dispersion. Systematic investigations of these comparisons revealed an exciting possibility of using such data to validate and possibly improve ionospheric models such as the International Reference Ionosphere (IRI) model. New regular ASM burst sessions are now expected to start in the second half of 2018. These will provide simultaneous data from two satellites on orbital planes at two different local time, enabling new unique opportunities of measuring the ionosphere from space. |
BibTeX:
@inproceedings{Coisson:2018-AGU,
author = {P. Coïsson and P. Deram and G. Hulot and P. Vigneron and J. M. Léger and T. Jager},
title = {Experimental burst mode (250 Hz) magnetic scalar data reveal the possibility of using ELF whistlers to systematically probe the ionosphere below the Swarm satellites},
booktitle = {AGU Fall meeting},
year = {2018},
number = {SA21A-3157}
}
|
| Coïsson P, Hulot G, Deram P, Vigneron P, Léger JM, Jager T and Beggan C (2018),
"First multipoint ELF whistler detection by Swarm satellites", In Geophysical Research Abstracts. Vienna, Austria, 23-28 April, 2018. Vol. 20(EGU2018-13979) EGU. |
| Abstract: It is known that lightning strikes generate broadband electromagnetic signals that propagate into the atmosphere and can reach into the ionosphere. Dispersion of the waves within the ionosphere separates the frequency content, generating whistler signals. During the commissioning phase of the ESA Swarm mission, the three satellites provided unique observation conditions when they were initially following each other in orbit at a distance of few hundred kilometres. Several burst-mode sessions of the Absolute Scalar Magnetometers (ASM) were acquired between December 2013 and February 2014, when the sampling frequency was raised from the nominal 1 Hz to 250 Hz. Although this ELF frequency band is well below the ionosphere-atmosphere cutoff frequency, the ASM instruments were sensitive enough to clearly detect several hundred whistlers over a few dozen hours of operation, more than a hundred of which were detected simultaneously by at least two satellites. By correlating these simultaneously detected whistlers with ground-detected lightnings from the World Wide Lightning Location Network and EarthNetworks, we were able to observe for the first time the dependence with distance of the ELF whistler intensity at Swarm altitudes. |
BibTeX:
@inproceedings{Coisson:2018-EGU,
author = {Coïsson, P. and G. Hulot and P. Deram and P. Vigneron and J. M. Léger and T. Jager and Beggan, C.},
title = {First multipoint ELF whistler detection by Swarm satellites},
booktitle = {Geophysical Research Abstracts},
publisher = {EGU},
year = {2018},
volume = {20},
number = {EGU2018-13979},
note = {EGU General Assembly 2018}
}
|
| Coïsson P, Deram P, Hulot G, Vigneron P, Léger JM and Jager T (2018),
"Ionospheric information obtained from ELF whistlers detected by the ESA Swarm satellites", In 15th European Space Weather Week. Leuven, Belgium, November (5-9), 2018. |
| Abstract: Lightning strikes generate broadband electromagnetic signals that propagate into the atmosphere and can reach into the ionosphere. Dispersion of the waves within the ionosphere generates a frequency dependent propagation time, producing whistler signals. At ELF frequencies the signal dispersion and the cutoff frequency depend on ions composition and their gyrofrequencies. The frequencies below 125 Hz thus provide additional information on the ionospheric status not accessible from other frequency bands. During the commissioning phase of the Swarm mission several burst-mode sessions of the Absolute Scalar Magnetometers (ASM) were operated between December 2013 and February 2014, during which the sampling frequency was raised from the nominal 1 Hz to 250 Hz. A large number of whistlers in the ELF frequency band were obtained during these sessions, associated with the lightning activity in the troposphere. By correlating the whistlers with ground-detected lightnings from the World Wide Lightning Location Network, we were able to study the lightning detection efficiency at Swarm altitude. By taking advantage of the simultaneous electron density measurements made by Swarm, we were also able to study the dependence of the whistler dispersion with the ionospheric and geomagnetic conditions encountered by the satellites. This appears to provide new way to derive information on the electron and ion density profiles over areas where no other measurements are available. As we shall illustrate, this information could in turn be used to better constrain ionospheric models such as IRI and NeQuick. New regular ASM burst-mode sessions are now planned for the rest of the Swarm mission that will provide additional data valuable for the investigation of the ionosphere below the satellites. |
BibTeX:
@inproceedings{Coisson:2018-ESWW,
author = {P. Coïsson and P. Deram and G. Hulot and P. Vigneron and J. M. Léger and T. Jager},
title = {Ionospheric information obtained from ELF whistlers detected by the ESA Swarm satellites},
booktitle = {15th European Space Weather Week},
year = {2018}
}
|
| Heumez B, Lesur V, Luc T, Telali K and Lalanne X (2018),
"Edea, Cameroon: the opening of a new geomagnetic observatory", In COBS Journal, Special Issue: IAGA Workshop 2018. Conrad Observatory, Austria, June (24-29), 2018. |
| Abstract: A new geomagnetic observatory that produce vector data sampled every second has been implemented in Edea, in the southwest of Cameroon since April 2018. Is is situated at 2600 km of the nearest magnetic observatory, TSU, Namibia. Following the closure of Bangui observatory, Edea area is an important site for magnetic measurements. The observatory is roughly at a symmetric location to M’bour observatory relative to the magnetic equator. It is too far to the south for studying the equatorial electrojet but its data carry important information on the behavior of the core and external (ionospheric, magnetospheric) fields in this region. This presentation focused on how the observatory was planned, built and installed, how the local staff was trained and the equipment was set to deliver real-time data sampled every second. |
BibTeX:
@inproceedings{Heumez-2018-IAGAINTERMAGNET,
author = {Heumez, Benoit and Lesur, Vincent and Luc, Ted and Telali, Kader and Lalanne, Xavier},
title = {Edea, Cameroon: the opening of a new geomagnetic observatory},
booktitle = {COBS Journal, Special Issue: IAGA Workshop 2018},
year = {2018}
}
|
| Lesur V, Chambodut A and Maury V (2018),
"Digital Object Identifier (DOI) for the BCMT definitive data set", In IAGA Workshop 2018. Conrad Observatory, Austria, June (24-29), 2018. |
| Abstract: The French “Bureau Central de Magnetisme Terrestre” (BCMT) operates currently 16 magnetic observatories distributed all over the world and maintains a database of more than a hundred year of magnetic data, including additional former observatories in France (2) and in foreign countries (3). Most of them are or had been operated in collaboration with other institutions. With the aim of providing a simple, lasting and reliable way to refer to observatories definitive data, it has been proposed to the partner institutions to attribute a single Digital Object Identifier (DOI) for the complete dataset of BCMT definitive magnetic observatory data. The DOI has been available for nearly a year (since October 2017). The landing page for the BCMT dataset is hosted by the IPGP data centre and includes, through an XML file, a description of the dataset covered by this DOI, the list of partner institutions that agreed to be included in the DOI and other meta-data information. A licence has been set for the full data set. Direct links to the data for each observatory hosted on BCMT ftp server are also provided to facilitate data access. |
BibTeX:
@inproceedings{Lesur-2018-IAGAINTERMAGNET,
author = {Lesur, Vincent and Chambodut, Aude and Maury, Virginie},
title = {Digital Object Identifier (DOI) for the BCMT definitive data set},
booktitle = {IAGA Workshop 2018},
year = {2018},
note = {poster}
}
|
| Prokhorov BE, Foerster M, Lesur V, Namgaladze AA and Holschneider M (2018),
"Prediction of the magnetic field of ionospheric origin using the Potsdam version of the Upper Atmosphere Model", In Geophysical Research Abstracts. Vienna, Austria, 23-28 April, 2018. Vol. 20(EGU2018-5549-1) EGU. |
| Abstract: The ionospheric magnetic field is a highly variable part of the Earth's magnetic field. It is generated by the ionospheric currents. The ionospheric currents are a part of the global electrical chain of the Magnetosphere - Ionosphere - Thermosphere (MIT) system. This current system has external and internal drivers. The external drivers are the solar wind and Interplanetary Magnetic Field (IMF), which interact with the magnetosphere and transfer energy to the ionosphere via the Field Aligned Currents (FACs). The internal driver is the interaction between neutral and charged particles in the Earth's ionosphere, known as the thermospheric neutral wind dynamo. The aim of this investigation is the prediction of the magnetic field generated by the 3D ionospheric current system. For modeling of the ionospheric currents, we use the Potsdam version (UAM-P) of the global, first-principal, three-dimensional, time-dependent, numerical Upper Atmosphere Model (UAM). The magnetic field is calculated using the Biot-Savart law. The obtained prediction of the global ionospheric magnetic field and its temporal variations are validated by comparing them with ground-based measurements and satellite observations of the Earth's magnetic field. |
BibTeX:
@conference{Prokhorov-2018-EGU,
author = {Prokhorov, Boris E. and Foerster, Matthias and Lesur, Vincent and Namgaladze, Alexander A. and Holschneider, Matthias},
title = {Prediction of the magnetic field of ionospheric origin using the Potsdam version of the Upper Atmosphere Model},
booktitle = {Geophysical Research Abstracts},
publisher = {EGU},
year = {2018},
volume = {20},
number = {EGU2018-5549-1},
note = {EGU General Assembly 2018}
}
|
| Telali K, Heumez B, Lesur V and Coïsson P (2018),
"Results of the new French Magnetic Repeat Station Network, 2012-2017", In IAGA Workshop 2018. Conrad Observatory, Austria, June (24-29), 2018. |
| Abstract: The French Magnetic Repeat Stations have been recently redefined to improve the effectiveness of the network. For many decades it was composed of 32 stations that were reoccupied every five years. Such a large network presented increasing weaknesses related to the land-usage modification over time. These stations were realised on semi-burried monoliths in private or public areas, sometimes in the middle of agricultural fields. To avoid station deterioration or loss, the Repeat Station Network was transformed in 2012 to ensure a better durability. All stations are now located inside minor airports, where measurements can be done during the night. This new network consists of 11 stations reduced to CLF Observatory annual mean and it is reoccupied every 2 years. We present the results of the measurements obtained during the four campaigns from 2012 to 2017 and the more recent update of the declination map over France. |
BibTeX:
@inproceedings{Telali-2018-IAGAINTERMAGNET,
author = {Telali, Kader and Heumez, Benoit and Lesur, Vincent and Coïsson, Pierdavide},
title = {Results of the new French Magnetic Repeat Station Network, 2012-2017},
booktitle = {IAGA Workshop 2018},
year = {2018},
note = {poster}
}
|
| Ciaran B, Brown W, Hulot G, Deram P and Coïsson P (2017),
"Occurrence Of Schumann Resonances In Swarm ASM Burst Mode Data", In Fourth Swarm Science Meeting and Geodetic Missions Workshop. Banff, Canada, March (20-24), 2017. |
| Abstract: The Schumann Resonances (SR) consist of a series of peaks in spectral power in the magnetic and electric field at frequencies of around 8, 14, 22 and 27 Hz. They arise from the continuous occurrence of equatorial lightning strikes which are on average contained within a single source region at any one time during the day, following the sub-solar point. The broadband electromagnetic emission from each lightning strike is contained within a waveguide, bounded by the Earth’s surface and the ionosphere at around 110 km in altitude. Thus particular EM wavelengths can resonate effectively for a few cycles before dissipating. The strike rate is around 100/second which leads to the formation of a steady background signal. The SR are detectable on the ground using sensitive search-coil magnetometers and have peak power of around 5 pT/√(Hz) in the first resonance, diminishing with increased frequency in the magnetic components. They have a large Q-factor (i.e. broad peaks) and an obvious diurnal and seasonal variation due to the location of the continents.Although, the electric field from SR have been detected in space using the C/NOFS satellite in 2010/11 at altitudes of 600 km, there have been no confirmed measurements using magnetic field instruments. There are theoretical arguments that the ionosphere acts to fully shield the magnetic signal from penetrating out of the atmosphere to Swarm altitudes, though other models suggest some secondary signals may be excited by the SR. We examine the Swarm ASM Burst Mode data (250 Hz) collected on the 19-Jan-2014 during the commissioning phase of the mission to look for signals which could be attributable to the SR. |
BibTeX:
@inproceedings{Ciaran-2017-4SwarmSM,
author = {Ciaran, B. and Brown, W. and Hulot, G. and Deram, P. and Coïsson, P.},
title = {Occurrence Of Schumann Resonances In Swarm ASM Burst Mode Data},
booktitle = {Fourth Swarm Science Meeting and Geodetic Missions Workshop},
year = {2017}
}
|
| Coïsson P, Deram P, Hulot G, Beggan C, Léger JM and Jager T (2017),
"Lightning-Generated Whistlers Observed during ASM Burst Mode Sessions", In Fourth Swarm Science Meeting and Geodetic Missions Workshop. Banff, Canada, March (20-24), 2017. |
| Abstract: Lighting-released energy covers a wide band of the electromagnetic spectrum. The propagation of the corresponding electromagnetic signal is not limited to the neutral atmosphere, and specific whistler-modes of propagation can enter the ionosphere, thus allowing their detection by LEO satellites. Though most of the whistler energy is released between 1 and 10 kHz, part of it appears to be also released in the frequency band 10-125 Hz detectable by the Swarm Absolute Scalar Magnetometers (ASM) operated in burst mode (250 Hz). Several hundreds of whistler events were indeed recorded in this way when a few burst-mode sessions were operated during the commissioning phase of the Swarm mission, at the beginning of 2014. These events have been unambiguously correlated with strong lightning strikes detected and located on ground by the World Wide Lightning Location Network (WWLLN). We developed a simple ray-tracing software to understand the propagation properties of these low-frequency whistlers. It uses the Appleton refraction index through the ionosphere plasma in the Earth magnetic field and solves the Haselgrove equations of propagation. We have thus been able to recover satisfyingly the propagation time and dispersion relation observed in the Swarm data. |
BibTeX:
@inproceedings{Coisson-2017-4SwarmSM,
author = {Coïsson, P. and P. Deram and G. Hulot and Beggan, C. and J. M. Léger and T. Jager},
title = {Lightning-Generated Whistlers Observed during ASM Burst Mode Sessions},
booktitle = {Fourth Swarm Science Meeting and Geodetic Missions Workshop},
year = {2017}
}
|
| Coïsson P, Deram P, Hulot G, C. Beggan, Léger JM and Jager T (2017),
"A systematic investigation of lightning-generated ELF whistlers observed during Swarm ASM burst mode sessions", In Joint IAPSO-IAMAS-IAGA Assembly. Cape Town, South Africa, 27 August - 1 September, 2017. (913) |
| Abstract: Lightning-released energy covers a wide band of the electromagnetic spectrum. The propagation of the corresponding electromagnetic signal is not limited to the neutral atmosphere, and specific whistler-modes of propagation can enter the ionosphere, thus allowing their detection by LEO satellites. Though most of the whistler energy in the ionosphere propagates between 1 and 10 kHz, part of it also appears to propagate in the 10-125 Hz frequency band and is detectable by the Swarm Absolute Scalar Magnetometers (ASM) when operating in burst mode at 250 Hz. Many whistler events were indeed recorded in this way when a few burst-mode sessions were operated during the commissioning phase of the ESA Swarm mission, at the beginning of 2014. These events have been unambiguously correlated with the occurrence of lightning strikes detected and located on ground by the World Wide Lightning Location Network (WWLLN). A simple ray-tracing software (using the Appleton refraction index through the ionosphere plasma in the Earth magnetic field and solving the Haselgrove equations of propagation) could be used to recover satisfyingly the propagation time and dispersion relation observed in most of the events detected in the Swarm ASM burst mode data. However, not all lightning strikes lead to an observed whistler. In this presentation, we will report on our current efforts to identify exact conditions under which lightning strikes do lead to such whistlers, with the aim of providing some insight into both the physics of these phenomena and the ability of Swarm ASM burst mode data to provide valuable information about lightning and the way their extremely low frequency signals penetrate the ionosphere. |
BibTeX:
@inproceedings{Coisson-2017-IAGA,
author = {P. Coïsson and P. Deram and G. Hulot and C. Beggan, and J. M. Léger and T. Jager},
title = {A systematic investigation of lightning-generated ELF whistlers observed during Swarm ASM burst mode sessions},
booktitle = {Joint IAPSO-IAMAS-IAGA Assembly},
year = {2017},
number = {913}
}
|
| P. Coïsson, Deram P, Hulot G, Beggan C, Léger JM and Jager T (2017),
"Systematic study of lightningh-generated ELF whistlers detected during two days of ASM burst session", In 7th Swarm Data Quality Workshop. Delft University of Technology (TU Delft), Delft, the Netherlands, 24-27 October, 2017. [BibTeX] |
BibTeX:
@inproceedings{Coisson-2017-Swarm,
author = {P. Coïsson, and P. Deram and G. Hulot and C. Beggan and J. M. Léger and T. Jager},
title = {Systematic study of lightningh-generated ELF whistlers detected during two days of ASM burst session},
booktitle = {7th Swarm Data Quality Workshop},
year = {2017}
}
|
| Grott M, Vervelidou F, Lesur V, Lillis RJ and Morschhauser A (2017),
"Constraining the date of the martian dynamo shutdown by means of craters‘ magnetization signatures", In Joint IAPSO-IAMAS-IAGA Assembly. Cape Town, South Africa, 27 August - 1 September, 2017. (473) [BibTeX] |
BibTeX:
@conference{Grott-2017-IAGA,
author = {Grott, M. and Vervelidou, F. and Lesur, V. and Lillis, R. J. and Morschhauser, A.},
title = {Constraining the date of the martian dynamo shutdown by means of craters‘ magnetization signatures},
booktitle = {Joint IAPSO-IAMAS-IAGA Assembly},
year = {2017},
number = {473}
}
|
| Heumez B, Lesur V, Telali A, Lalanne X and Soloviev A (2017),
"Error statistics of Chambon la Forêt observatory definitive data ", In Joint IAPSO-IAMAS-IAGA Assembly. Cape Town, South Africa, 27 August - 1 September, 2017. (1286) [BibTeX] |
BibTeX:
@conference{Heumez-2017-IAGA,
author = {Heumez, B. and Lesur, V. and Telali, A. and Lalanne, X. and Soloviev, A.},
title = {Error statistics of Chambon la Forêt observatory definitive data },
booktitle = {Joint IAPSO-IAMAS-IAGA Assembly},
year = {2017},
number = {1286}
}
|
| Holschneider M, Ferrat K, Lesur V and Stolle C (2017),
"Spatial correlation structure of the ionosphere predicted by geomagnetic indices and application to global field modelling", In AGU Fall meeting. New Orleans, LA, 11-15 Dec. (GP43B-0990) AGU. |
| Abstract: Ionospheric fields are modelled in terms of random structures taking into account a mean behaviour as well as random fluctuations which are described through two point correlation kernels. These kernels are estimated from long time series of numerical simulations from various models. These correlations are best expressed in SM system of coordinates. For the moment we limit ourselves to spatial correlations only in this coordinate system. We study the influence of various indices as possible predictor parameters for these correlations as well as seasonal effects. The various time series of ionospheric fields are stored in a HDF5 database which is accessible via a web interface. The obtained correlation structures serve as prior information to separate external and internal field components from observatory based measurements. We present a model that predicts the correlations as a function of time and some geomagnetic indices. First results of the inversion from observatory data are presented. |
BibTeX:
@conference{Holschneider-2017-AGU,
author = {Holschneider, M. and Ferrat, K. and Lesur, V. and Stolle, C.},
title = {Spatial correlation structure of the ionosphere predicted by geomagnetic indices and application to global field modelling},
booktitle = {AGU Fall meeting},
publisher = {AGU},
year = {2017},
number = {GP43B-0990}
}
|
| Holschneider M, Ferrat K, Lesur V, Baerenzung J, Matuschek H, Mauerberger S and Stolle C (2017),
"Correlation based modelling of ionospheric magnetic fields", In Joint IAPSO-IAMAS-IAGA Assembly. Cape Town, South Africa, 27 August - 1 September, 2017. (1132) [BibTeX] |
BibTeX:
@conference{Holschneider-2017-IAGA,
author = {Holschneider, M. and Ferrat, K. and Lesur, V. and Baerenzung, J. and Matuschek, H. and Mauerberger, S. and Stolle, C.},
title = {Correlation based modelling of ionospheric magnetic fields},
booktitle = {Joint IAPSO-IAMAS-IAGA Assembly},
year = {2017},
number = {1132}
}
|
| Hulot G, Léger JM, Vigneron P, Jager T, Bertrand F, Coïsson P, Deram P, Boness A, L. Tomasini and Faure B (2017),
"Nanosatellite High-Precision Magnetic Missions Enabled by Advances in a Stand-Alone Scalar/Vector Absolute Magnetometer", In AGU Fall meeting. New Orleans, LA, 11-15 December, 2017. (A41I-2402) |
| Abstract: Satellites of the ESA Swarm mission currently in operation carry a new generation of Absolute Scalar Magnetometers (ASM), which nominally deliver 1 Hz scalar for calibrating the relative flux gate magnetometers that complete the magnetometry payload (together with star cameras, STR, for attitude restitution) and providing extremely accurate scalar measurements of the magnetic field for science investigations. These ASM instruments, however, can also operate in two additional modes, a high-frequency 250 Hz scalar mode and a 1 Hz absolute dual-purpose scalar/vector mode. The 250 Hz scalar mode already allowed the detection of until now very poorly documented extremely low frequency whistler signals produced by lightning in the atmosphere, while the 1 Hz scalar/vector mode has provided data that, combined with attitude restitution from the STR, could be used to produce scientifically relevant core field and lithospheric field models. Both ASM modes have thus now been fully validated for science applications. Efforts towards developing an improved and miniaturized version of this instrument is now well under way with CNES support in the context of the preparation of a 12U nanosatellite mission (NanoMagSat) proposed to be launched to complement the Swarm satellite constellation. This advanced miniaturized ASM could potentially operate in an even more useful mode, simultaneously providing high frequency (possibly beyond 500 Hz) absolute scalar data and self-calibrated 1 Hz vector data, thus providing scientifically valuable data for multiple science applications. In this presentation, we will illustrate the science such an instrument taken on board a nanosatellite could enable, and report on the current status of the NanoMagSat project that intends to take advantage of it. |
BibTeX:
@inproceedings{Hulot-2017-AGU,
author = {G. Hulot and J. M. Léger and P. Vigneron and T. Jager and F. Bertrand and P. Coïsson and P. Deram and A. Boness and L. Tomasini, and B. Faure},
title = {Nanosatellite High-Precision Magnetic Missions Enabled by Advances in a Stand-Alone Scalar/Vector Absolute Magnetometer},
booktitle = {AGU Fall meeting},
year = {2017},
number = {A41I-2402}
}
|
| Lesur V, Ferrat K and Holschneider M (2017),
"A core magnetic field model for 2000 – 2016 epochs", In Joint IAPSO-IAMAS-IAGA Assembly. Cape Town, South Africa, 27 August - 1 September, 2017. (1389) [BibTeX] |
BibTeX:
@conference{Lesur-2017-IAGA,
author = {Lesur, V. and Ferrat, K. and Holschneider, M.},
title = {A core magnetic field model for 2000 – 2016 epochs},
booktitle = {Joint IAPSO-IAMAS-IAGA Assembly},
year = {2017},
number = {1389}
}
|
| Lesur V, Wardinski I, Holschneider M and Baerenzung J (2017),
"On the frequency spectra of the magnetic field Gauss coefficients ", In Joint IAPSO-IAMAS-IAGA Assembly. Cape Town, South Africa, 27 August - 1 September, 2017. (1016) [BibTeX] |
BibTeX:
@conference{Lesur-2017-IAGAb,
author = {Lesur, V. and Wardinski, I. and Holschneider, M. and Baerenzung, J. },
title = {On the frequency spectra of the magnetic field Gauss coefficients },
booktitle = {Joint IAPSO-IAMAS-IAGA Assembly},
year = {2017},
number = {1016}
}
|
| Lesur V, Thébault E, Vigneron P, Hulot G, Matuschek H and Holschneider M (2017),
"Towards improved models of the core magnetic field over the satellite era", In 7th Swarm Data Quality Workshop. Delft University of Technology (TU Delft), Delft, the Netherlands, 24-27 October 2017, 2017. ESA. [BibTeX] |
BibTeX:
@conference{Lesur-2017-Swarm,
author = {Lesur, V. and Thébault, E. and Vigneron, P. and Hulot, G. and Matuschek, H. and Holschneider, M.},
title = {Towards improved models of the core magnetic field over the satellite era},
booktitle = {7th Swarm Data Quality Workshop},
publisher = {ESA},
year = {2017}
}
|
| Maury V, Coïsson P, Lesur V and Chambodut A (2017),
"Doi for BCMT magnetic observatories dataset", In Joint IAPSO-IAMAS-IAGA Assembly. Cape Town, South Africa, 27 August - 1 September, 2017. (1300) |
| Abstract: The French Bureau Central du Magnetisme Terrestre (BCMT) operates currently 16 magnetic observatories distributed all over the world and maintains a database of more than a hundred year of magnetic data, including additional former observatories in France (2) and in foreign countries (3). Most of them are or had been operated in collaboration with other institutions. With the aim of providing a simple, persistant and reliable way to refer to observatories definitive data, it has been proposed to the partner institutes to attribute a single doi for the complete dataset of BCMT definitive magnetic observatory data. The doi for this dataset is going to be available by July 2017. The landing page for the BCMT dataset is going to be hosted on the IPGP data center and includes a description of the dataset covered by this doi and all observatories which partner institutions agreed to this doi. Direct links to the data of each observatory hosted on BCMT ftp server are also provided to facilitate data access. |
BibTeX:
@inproceedings{Maury-2017-IAGA,
author = {Maury, V. and Coïsson, P. and Lesur, V. and Chambodut, A.},
title = {Doi for BCMT magnetic observatories dataset},
booktitle = {Joint IAPSO-IAMAS-IAGA Assembly},
year = {2017},
number = {1300}
}
|
| Morschhauser A, Mittelholz A, Thomas P, Vervelidou F, Grott M, Johnson C, Lesur V and Lillis RJ (2017),
"What can we learn about Mars from satellite magnetic field measurements?", In AGU Fall meeting. New Orleans, LA, 11-15 Dec. (GP34A-03) AGU. |
| Abstract: The Mars orbiters MGS and MAVEN provide vector magnetic field data for Mars at a variety of altitudes, locations, and local times. In spite of the abundance of data, there are many open questions concerning the crustal magnetic field of Mars. In this contribution, we present our efforts to estimate the shutdown time of the Martian core dynamo and to estimate Martian paleopole locations, using magnetic field satellite data and models derived from these data [1]. Models are primarily based on MGS data, and we shortly present our recent advances to include MAVEN data. There exists some controversy concerning the timing of the Martian core dynamo shutdown [e.g., 2-5]. We address this question by studying the so-called visible magnetization [6-7] of impact craters larger than 400 km in diameter, and conclude that the dynamo ceased to operate in the Noachian period [8]. Further, paleopole locations have been used to constrain the dynamics of the Martian core dynamo [e.g. 4-5, 9]. However, such estimates are limited by the inherent non-uniqueness of inferring magnetization from magnetic field measurements. Here, we discuss how estimated paleopoles are influenced by this non-uniqueness and the limited signal-to-noise ratio of satellite measurements [6]. Furthermore, we discuss how paleopole locations may still be obtained from satellite magnetic field measurements. In this context, we present some new paleopole estimates for Mars including estimates of uncertainties. References: [1] A. Morschhauser et al. (2014), JGR, doi: 10.1002/2013JE004555 [2] R.J. Lillis et al. (2015), JGR, doi: 10.1002/2014je004774 [3] L.L. Hood et al. (2010), Icarus, doi: 10.1016/j.icarus.2010.01.009 [4] C. Milbury et al. (2012), JGR, doi: 10.1029/2012JE004099 [5] B. Langlais and M. Purucker (2007), PSS, 10.1016/j.pss.2006.03.008 [6] F. Vervelidou et al., On the accuracy of paleopole estimations from magnetic field measurements, GJI, under revision 2017 [7] D. Gubbins et al. (2011), GJI, doi: 10.1111/j.1365-246X.2011.05153.x [8] B. Langlais and M. Purucker (2007), PSS, 10.1016/j.pss.2006.03.008 [8] F. Vervelidou et al., Constraining the date of the martian dynamo shutdown by means of craters' magnetization signatures, JGR, submitted 2017 [9] J. Arkani-Hamed and D. Boutin (2004), JGR, 10.1029/2003JE002229 |
BibTeX:
@conference{Morschhauser-2017-AGU,
author = {Achim Morschhauser and Anna Mittelholz and Paul Thomas and Foteini Vervelidou and Matthias Grott and Catherine Johnson and Vincent Lesur and Robert J Lillis},
title = {What can we learn about Mars from satellite magnetic field measurements?},
booktitle = {AGU Fall meeting},
publisher = {AGU},
year = {2017},
number = {GP34A-03},
note = {Invited}
}
|
| Prokhorov B, Foerster M, Lesur V, Namgaladze A, Holschneider M and Stolle C (2017),
"Using the UAM-P model to specify the additional magnetic field generated by the system of the ionospheric currents", In Geophysical Research Abstracts. Vienna, Austria, 23-28 April, 2017. Vol. 19(EGU2017-10822) EGU. |
| Abstract: The ionospheric currents are a part of the highly variable coupled Magnetosphere - Ionosphere - Thermosphere (MIT) system. These currents generate an additional portion to the main magnetic field. The ionospheric currents as well as its impact to the Earth's magnetic field depend on the solar wind, IMF, and geomagnetic conditions and have significant seasonal and UT variations. The first aim of this investigation is to obtain the global 3D system of the ionospheric currents. For this purposes, we use the Potsdam version of the Upper Atmosphere Model (UAM-P). This is a first-principle, time-dependent, and fully self-consistent numerical global model. It describes the thermosphere, ionosphere, plasmasphere and inner magnetosphere as well as the electrodynamics of the coupled MIT system for the altitudinal range from 80 (60) km up to the 15 Earth radii. The second aim is to calculate the contribution of the ionospheric current system calculated with the UAM-P model to the Earth's magnetic field. This contribution is calculated using the Biot-Savart law. The magnetic field generated by the system of the ionospheric currents is compared with measurements of the Earth's magnetic field variations. |
BibTeX:
@conference{Prokhorov-2017-EGU,
author = {Prokhorov, B. and Foerster, M. and Lesur, V. and Namgaladze, A. and Holschneider, M. and Stolle, C.},
title = {Using the UAM-P model to specify the additional magnetic field generated by the system of the ionospheric currents},
booktitle = {Geophysical Research Abstracts},
publisher = {EGU},
year = {2017},
volume = {19},
number = {EGU2017-10822},
note = {EGU General Assembly 2017}
}
|
| Valladares CE, Coïsson P, Buchert S, Huang C and Sheehan R (2017),
"C/NOFS, SWARM, and LISN Observations of Equatorial Plasma Bubbles", In AGU Fall meeting. New Orleans, LA, 11-15 December, 2017. (SA12A-08) [BibTeX] |
BibTeX:
@inproceedings{Valladares2017,
author = {Valladares, C. E. and Coïsson, P. and Buchert, S. and Huang, C. and Sheehan, R.},
title = {C/NOFS, SWARM, and LISN Observations of Equatorial Plasma Bubbles},
booktitle = {AGU Fall meeting},
year = {2017},
number = {SA12A-08}
}
|
| Valladares CE, Coïsson P, Khadka S and Buchert S (2017),
"Observations of the Drift of Plasma Depletions Using SWARM Constellation and LISN TEC Measurements", In Fourth Swarm Science Meeting and Geodetic Missions Workshop. Banff, Canada, March (20-24), 2017. |
| Abstract: During the early commissioning phase of the SWARM mission, the distance between the trajectories of all three satellites of the constellation was tens of km and the temporal separation was only a few minutes. This unique geometry allows us to conduct multiple and almost simultaneous in-situ measurements through the same low-latitude plasma depletion to investigate their spatial coherence and the motion of structures embedded within the equatorial plasma bubbles. We have used number density measured with the Langmuir Probe (LP) on board each of the three satellites of the SWARM constellation during December 2013 and concurrent TEC values obtained by ground-based GPS receivers to fully diagnose the bubble characteristics at multiple scale sizes. TEC values measured on the ground indicated that the plasma depletions moved with a velocity near 50 m/s and had a westward tilt of order 10°. Density depletions observed with SWARM indicated that the bubble velocities were also 50 m/s. We have also found the velocity of density structures within the bubbles with scale sizes less than 100 km. This presentation will show results for several specific days of SWARM observations during passes throughout the South American continent. |
BibTeX:
@inproceedings{Valladares-2017-4SwarmSM,
author = {Valladares, C. E. and Coïsson, P. and Khadka, S. and Buchert, S.},
title = {Observations of the Drift of Plasma Depletions Using SWARM Constellation and LISN TEC Measurements},
booktitle = {Fourth Swarm Science Meeting and Geodetic Missions Workshop},
year = {2017}
}
|
| Valladares CE, Coïsson P, Buchert S, Huang C and Sheehan R (2017),
"C/NOFS, SWARM, and LISN Observations of Equatorial Plasma Bubbles", In AGU Fall meeting. New Orleans, LA, 11-15 December, 2017. (SA12A-08) |
| Abstract: We have used Langmuir Probe densities measured during the early commissioning phase of the SWARM mission and simultaneous number densities recorded with the PLP instrument on board the C/NOFS satellite to investigate the geometric characteristics of equatorial plasma bubbles (EPB). The SWARM satellites orbit in a polar orbit and the C/NOFS satellite has a near equatorial trajectory making it possible to precisely measure the north-south and the east-west width of plasma depletions. This unique satellite database is complemented with TEC values collected with hundreds of GPS receivers that belong to LISN and other networks that operate in South and Central America. The GPS receivers provide multiple and almost concurrent observations of the TEC depletions that are required to calculate the velocity of plasma bubbles as a function of time, latitude, and longitude. The bubble velocity field commonly decreases through the night from 150 to 0 m/s and from low to higher latitudes at a rate equal to 5 m/s/degree. This bubble velocity field is used to trace backward and forward in time the satellite and GPS observations and reconstruct plasma depletions in 3 dimensions. The 3-D geometry indicates that in December 2013, the EPBs most of the time correspond to a series of embedded shells that drift eastward with velocities that vary between 125 and 20 m/s. The 3-D reconstructed EPBs can be used to perform close comparisons with results of numerical simulations and 2-D observations conducted with coherent radars or imagers. |
BibTeX:
@inproceedings{Valladares-2017-AGU,
author = {Valladares, C. E. and Coïsson, P. and Buchert, S. and Huang, C. and Sheehan, R.},
title = {C/NOFS, SWARM, and LISN Observations of Equatorial Plasma Bubbles},
booktitle = {AGU Fall meeting},
year = {2017},
number = {SA12A-08}
}
|
| Vervelidou F and Lesur V (2017),
"Inverting satellite magnetic field data for the Earth's magnetization", In Geophysical Research Abstracts. Vienna, Austria, 23-28 April, 2017. Vol. 19(EGU2017-8224) EGU. |
| Abstract: Satellite magnetic field data are traditionally used as input into various inversion schemes in order to obtain mod- els of the lithospheric magnetic field. The use of vector Spherical Harmonics allows us, however, to relate the Gauss coefficients of the lithospheric magnetic field to the Gauss coefficients of the part of the magnetization that contributes to this magnetic field. We make use of this formalism and invert magnetic field data directly for this visible part of the magnetization. Such an inversion offers the flexibility of applying appropriate constraints that depend on the characteristics of the magnetization distribution and not on the characteristics of the magnetic field. Here we present some preliminary results of the inversion of Swarm and CHAMP magnetic field data for a global magnetization model which accounts for the difference in thickness between the oceanic and the continental crust. |
BibTeX:
@conference{Vervelidou-2017-EGU,
author = {Vervelidou, F. and Lesur, V.},
title = {Inverting satellite magnetic field data for the Earth's magnetization},
booktitle = {Geophysical Research Abstracts},
publisher = {EGU},
year = {2017},
volume = {19},
number = {EGU2017-8224},
note = {EGU General Assembly 2017}
}
|
| Vervelidou F and Lesur V (2017),
"Inverting satellite magnetic field data for the Earth's magnetization ", In Joint IAPSO-IAMAS-IAGA Assembly. Cape Town, South Africa, August, 2017. (472) [BibTeX] |
BibTeX:
@conference{Vervelidou-2017-IAGA,
author = {Vervelidou, F. and Lesur, V.},
title = {Inverting satellite magnetic field data for the Earth's magnetization },
booktitle = {Joint IAPSO-IAMAS-IAGA Assembly},
year = {2017},
number = {472}
}
|
| Coïsson P, Deram P, Hulot G, Léger JM and Jager T (2016),
"Whistler-like Signals Detected Simultaneously by Swarm Satellites", In AGU Fall meeting. San Francisco, USA, December (12-16), 2016. (AE33B-0447) |
| Abstract: The three Swarm satellites embark an absolute scalar magnetometer (ASM) that generates nominally 1 Hz filtered data of the intensity of the magnetic field. Its internal frequency of operation however allows to record data at higher sampling rate, generating so-called “burst-mode” data at 250 Hz. During the commissioning phase of the Swarm mission, between December 2013 and February 2014 several burst-mode sessions have been recorded. At the beginning the satellites were still on a pearls-on-string orbital configuration and later each satellite was successively moved to its final orbit. During the last two burst sessions satellites B and C were still following each other, while satellite A was already orbiting at a lower altitude, on the opposite side of the Earth. We present an analysis of the burst data recorded on 22 and 23 February 2014, when several short signals were detected, usually lasting less than 1 second, presenting a descending tone in the frequency band accessible using burst data (1-125 Hz), similar to the whistlers signals in VLF band. These signals were detected nearly simultaneously by satellites B and C, at about 300 km distance, corresponding to a horizontal speed of about 1500 km/s. We present an analysis of these events and of their coincidence with lighting activity on the ground in the area of visibility of these satellites, as provided by the WWLN. |
BibTeX:
@inproceedings{Coisson-2016-AGU,
author = {Coïsson, P. and P. Deram and G. Hulot and J. M. Léger and T. Jager},
title = {Whistler-like Signals Detected Simultaneously by Swarm Satellites},
booktitle = {AGU Fall meeting},
year = {2016},
number = {AE33B-0447}
}
|
| Coïsson P, Heumez B, Telali K, Lesur V, Lalanne X and Xin C (2016),
"Time-stamp correction of observatory data acquired during unavailability of time-synchronization services", In Proceedings of the XVIIth IAGA Workshop on geomagnetic observatory instruments data acquisition and processing. Dourbes, Belgium, September (4-10), 2016. |
| Abstract: During magnetic observatory data acquisition, the time-stamp is kept synchronized with a precise source of time. This is usually done using a GPS controlled PPS signal. For some observatories located in remote areas or where internet restrictions are enforced, only magnetometer data are accessible, limiting the capabilities of monitoring the acquisition operations. The LZH observatory in Lanzhou, China, experienced an interruption of the PPS in 2013. The data-logger clock drifted slowly in time, in 6 months a delay of 28 s was accumulated. After a reboot in April 2014 the drift became faster, 2 s per day, before the PPS could be restored in July 2014. To estimate the time-delays, we compared LZH time-series with data from other observatories located in East Asia. A synchronization algorithm was developed. Natural sources providing synchronous events could be used as markers to obtain the time-lag. The analysis of slices of 30 minutes of 1-s data at an arbitrary UT allowed estimating lags with an uncertainty of 10 s, revealing the correct trends of drift. A precise estimation of the lag was obtained by comparing data of co-located instruments with independent PPS. In that case it was possible to take advantage of spikes and noise that constituted local time-markers events. It was therefore possible to obtain the lags of the time-stamps to produce corrected data files. |
BibTeX:
@inproceedings{Coisson-2016-IAGAINTERMAGNET,
author = {Coïsson, P. and B. Heumez and K. Telali and V. Lesur and X. Lalanne and C.J. Xin},
title = {Time-stamp correction of observatory data acquired during unavailability of time-synchronization services},
booktitle = {Proceedings of the XVIIth IAGA Workshop on geomagnetic observatory instruments data acquisition and processing},
year = {2016}
}
|
| Coïsson P, Hulot G, Deram P, Vigneron P, Léger J-M, Jager T and Brocco L (2016),
"Multi-points detection of ligthining-induced signals using Swarm ASM burst data", In 6th Swarm Data Quality Workshop. Edinburgh, United Kingdom, September (26-20), 2016. [BibTeX] |
BibTeX:
@inproceedings{Coisson-2016-Swarm,
author = {Coïsson, P. and G. Hulot and P. Deram and P. Vigneron and J.-M. Léger and T. Jager and L. Brocco},
title = {Multi-points detection of ligthining-induced signals using Swarm ASM burst data},
booktitle = {6th Swarm Data Quality Workshop},
year = {2016}
}
|
| Hejda P, Chambodut A, Curto J-J, Flower S, Kozlovskaya E, Kubasta P, Matzka J, Tanskanen E and Thomson A (2016),
"Incorporation of geomagnetic data and services into EPOS infrastructure", In Geophysical Research Abstracts. Vienna, Austria, April (17-22), 2016. Vol. 18(EGU2016-6933-1) |
| Abstract: Monitoring of the geomagnetic field has a long history across Europe that dates back to 1830’, and is currently experiencing an increased interest within Earth observation and space weather monitoring. Our goals within EPOS-IP are to consolidate the community, modernise data archival and distribution formats for existing services and create new services for magnetotelluric data and geomagnetic models. Specific objectives are: • Enhance existing services providing geomagnetic data (INTERMAGNET- INTErnational Real-time MAGnetic observatory NETwork; World Data Centre for Geomagnetism; IMAGE- International Monitor for Auroral Geomagnetic Effects) and existing services providing geomagnetic indices (ISGI - International Service of Geomagnetic Indices). • Develop and enhance the geomagnetic community’s metadata systems by creating a metadata database, filling it and putting in place processes to ensure that it is kept up to date in the future. • Develop and build access to magnetotelluric (MT) data including transfer functions and time series data from temporary, portable MT-arrays in Europe, as well as to lithospheric conductivity models derived from TM-data. • Develop common web and database access points to global and regional geomagnetic field and conductivity models. • Establish links from the geomagnetic data services, products and models to the Integrated Core Services. The immediate task in the current period is to identify data models of existing services, modify them and integrate into a common model of Geomagnetic Thematic Core Services. |
BibTeX:
@inproceedings{Hejda-2016-EGU,
author = {Hejda, P. and A. Chambodut and J.-J. Curto and S. Flower and E. Kozlovskaya and P. Kubasta and J. Matzka and E. Tanskanen and A. Thomson},
title = {Incorporation of geomagnetic data and services into EPOS infrastructure},
booktitle = {Geophysical Research Abstracts},
year = {2016},
volume = {18},
number = {EGU2016-6933-1},
note = {EGU General Assembly 2016}
}
|
| Hejda P, Chambodut A, Curto J-J, Flower S, Kozlovskaya E, Kubasta P, Matzka J, Tanskanen E and Thomson A (2016),
"The role of geomagnetic community in the development of EPOS Geomagnetism Thematic Core Services", In Proceedings of the XVIIth IAGA Workshop on geomagnetic observatory instruments data acquisition and processing. Dourbes, Belgium, September (4-10), 2016. |
| Abstract: European Plate Observing System (EPOS) is aimed at integrating geoscience data across scientific disciplines. EPOS Implementation Phase was supported by a four-year Horizon2020 grant that started on 1 October 2015. The goals of Geomagnetism Thematic Core Services are: • Enhance existing services providing geomagnetic data (INTERMAGNET, WDC for Geomagnetism, IMAGE) and existing services providing geomagnetic indices (ISGI). • Develop and enhance the geomagnetic community's metadata systems by creating a metadata database, filling it and putting in place processes to ensure that it is kept up to date in the future. • Develop and build access to magnetotelluric (MT) data including transfer functions and time series data from temporary, portable MT-arrays in Europe, as well as to lithospheric conductivity models derived from TM-data. • Develop common web and database access points to global and regional geomagnetic field and conductivity models. An important task of the project is to establish communication channels for the interaction with the geomagnetic community and use them for testing and validation of the services and for measuring their impact. |
BibTeX:
@inproceedings{Hejda-2016-IAGAINTERMAGNET,
author = {Hejda, P. and A. Chambodut and J.-J. Curto and S. Flower and E. Kozlovskaya and P. Kubasta and J. Matzka and E. Tanskanen and A. Thomson},
title = {The role of geomagnetic community in the development of EPOS Geomagnetism Thematic Core Services},
booktitle = {Proceedings of the XVIIth IAGA Workshop on geomagnetic observatory instruments data acquisition and processing},
year = {2016}
}
|
| Heumez B, Lesur V, Telali K, Sanchez A, Poncelet A, Gonsette A and Coïsson P (2016),
"Several months of robotized absolute measurements at Chambon-La-Forêt Observatory", In Proceedings of the XVIIth IAGA Workshop on geomagnetic observatory instruments data acquisition and processing. Dourbes, Belgium, September (4-10), 2016. |
| Abstract: A robotized instrument performing geomagnetic absolute measurements, named AUTODIF, was installed in Chambon-la-Forêt in July 2015 by the Geomagnetism Group of the Royal Meteorological Institute of Belgium. The instrument has been running continuously for several months in order to be tested in operational conditions in a regular magnetic observatory. We will present our feedback for this instrument; discuss the measurement uncertainties and comparison with our human-made calibration measurements. |
BibTeX:
@inproceedings{Heumez-2016-IAGAINTERMAGNET,
author = {B. Heumez and V. Lesur and K. Telali and A. Sanchez and A. Poncelet and A. Gonsette and P. Coïsson},
title = {Several months of robotized absolute measurements at Chambon-La-Forêt Observatory},
booktitle = {Proceedings of the XVIIth IAGA Workshop on geomagnetic observatory instruments data acquisition and processing},
year = {2016}
}
|
| X. Lalanne, Telali K, Heumez B and Lesur V (2016),
"New setting at Chambon-la-Forêt observatory", In Proceedings of the XVIIth IAGA Workshop on geomagnetic observatory instruments data acquisition and processing. Dourbes, Belgium, September (4-10), 2016. |
| Abstract: The continuous infiltration of water in the variometer vault of Chambon-la-Forêt observatory, built 80 years ago, leads to an early ageing of the electronic and instruments. We have therefore decided to change the observation setup and to build three new surface shelters to install three independent measurement chains leading to a concept of “virtual magnetometer”. We will present the new configuration of the observatory and some of the technical characteristics of the shelters. We will also describe the process of migration of the instruments, and differences between obtained data series. Environmental (humidity and temperature) and magnetic data collected over a year indicates that the provision of high data quality is sustainable for the coming years. |
BibTeX:
@inproceedings{Lalanne-2016-IAGAINTERMAGNET,
author = {X. Lalanne, and K. Telali and B. Heumez and V. Lesur},
title = {New setting at Chambon-la-Forêt observatory},
booktitle = {Proceedings of the XVIIth IAGA Workshop on geomagnetic observatory instruments data acquisition and processing},
year = {2016}
}
|
| H. Larnier, Chambodut A and Sailhac P (2016),
"Using magnetic observatories as reference stations in magnetotelluric data processing of geomagnetic pulsations", In Proceedings of the XVIIth IAGA Workshop on geomagnetic observatory instruments data acquisition and processing. Dourbes, Belgium, September (4-10), 2016. |
| Abstract: Magnetotellurics (MT) is a passive geophysical exploration technique which uses time series of natural magnetic and electric fields measured at the ground surface. It is based on the induction of electric currents in the ground by large scale geomagnetic waves. A wide collection of waves is used in MT, from lightning strikes emitted waves to magnetic pulsations induced by the interaction of the sun and the magnetosphere. In this work, we have developed a methodology based on the continuous wavelet transform to process MT data in the period range [1-500] seconds based on the time-frequency characteristics of geomagnetic pulsations. In this period range, geomagnetic pulsations are the preponderant signals. To properly detect geomagnetic pulsations in MT time series, we are generating Fourier surrogates of quiet magnetic time series. Then, by comparison between the distribution of wavelets coefficients of these surrogates and the original signal, we are recovering significant wavelet coefficients associated to geomagnetic pulsations. The magnetic observatories are of primary importance in this framework as their data are used as large-scale reference station for the occurrence of geomagnetic events. We are showing several datasets and their consecutive analysis with regards to improvement brought by magnetic observatories data onto the characterization of MT transfer functions. |
BibTeX:
@inproceedings{Larnier-2016-IAGAINTERMAGNET,
author = {H. Larnier, and A. Chambodut and P. Sailhac},
title = {Using magnetic observatories as reference stations in magnetotelluric data processing of geomagnetic pulsations},
booktitle = {Proceedings of the XVIIth IAGA Workshop on geomagnetic observatory instruments data acquisition and processing},
year = {2016}
}
|
| Lesur V, Heumez B, Telali K, Coïsson P and Lalanne X (2016),
"On the accuracy of CLF observatory data", In Proceedings of the XVIIth International Association of Geomagnetism and Aeronomy (IAGA) workshop. Dourbes, Belgium, September (4-10), 2016. |
| Abstract: Traditionally observatory data are provided without error estimates, although such information is a prerequisite for an optimum exploitation of these data. Estimating the errors in CLF requires first knowing the accuracy of the absolute measurements. In a second step, the propagation of these errors in the process leading to the estimation of the baseline has to be understood. We have investigated different sources of errors in absolute measurement for CLF settings. A new algorithm for the baseline estimation has been developed in order to account for error estimates. Preliminary estimates of CLF data accuracy will be presented. |
BibTeX:
@inproceedings{Lesur-2016-IAGAINTERMAGNET,
author = {V. Lesur and B. Heumez and K. Telali and P. Coïsson and X. Lalanne},
title = {On the accuracy of CLF observatory data},
booktitle = {Proceedings of the XVIIth International Association of Geomagnetism and Aeronomy (IAGA) workshop},
year = {2016}
}
|
| Lesur V, Wardinski I, Holschneider M and Baerenzung J (2016),
"Earth magnetic field temporal spectra from annual to decadal time scales", In Proceedings of the XVth Symposium of Study of the Earth's Deep Interior (SEDI). Nantes -- France, July (24-29), 2016. |
| Abstract: The spectrum of the observed geomagnetic field has been estimated – e.g. in Constable & Constable (2004), for frequencies ranging from thousands of Hertz to 10^-14 Hertz. At periods of decades the core field is dominating the spectrum. It decreases with frequencies like 1/k to the 4. For shorter periods, ranging from few months to few years, the spectrum of the core field is unknown, but it is often assumed that it has the same 1/k to the 4 decrease rate. It is an open question to know if that is verified at all spatial scales. In this work we investigate if such hypothesis is acceptable for the largest scales – i.e. for the Gauss coefficients of low spherical harmonic degrees. We used Secular Variation (SV) estimates between 1953 and 2014, derived from observatory data, and a magnetic field modelling technique based on correlations (Holschneider et al., 2016). We show that the spectra of the core field SV at observatory positions behave like 1/k to the power 2 down to periods as short as a year, and that the associated SV Gauss coefficients have generally the same behaviour, with possibly an exception for SH order 0 coefficients – i.e. zonal coefficients. We conclude that the 1/k to the 4 decrease rate hypothesis is generally valid for the core magnetic field at all spatial scales larger than five thousand kilometres (spherical harmonic degrees smaller than 6). |
BibTeX:
@inproceedings{Lesur-2016-SEDI,
author = {Lesur, V. and Wardinski, I. and Holschneider, M. and Baerenzung, J.},
title = {Earth magnetic field temporal spectra from annual to decadal time scales},
booktitle = {Proceedings of the XVth Symposium of Study of the Earth's Deep Interior (SEDI)},
year = {2016}
}
|
| Morschhauser A, Vervelidou F, Lillis RJ, Dufek J, Grott M and Lesur V (2016),
"Constraints on the Martian Core Dynamo: The Magnetic Signature of Apollinaris Patera", In Proceeding of the AGU Fall meeting. San Francisco, USA, December (12-16), 2016. (GP23C-1347) |
| Abstract: It is widely accepted that the largest part of the observable magnetic field of Mars results from magnetic rocks which once obtained their magnetization in the presence of a core dynamo field . However, it is disputed how long this core dynamo was active. On one hand, the magnetic signatures of large (>300 km) impact craters and of some volcanoes are consistent with a shutdown in the Noachian period [1-3], whereas on the other hand, the study of paleopoles and the magnetic imprint of some other volcanoes suggest the possibility of dynamo activity in the Hesperian [4,5]. The strongest argument for the latter interpretation relies on the magnetic signature of the volcano Apollinaris Patera, whose flanks' most recent flows are Hesperian aged. Indeed, this volcano can directly be associated with an area of increased field intensity as seen in magnetic field data taken in orbit [4,6]. In this study, we reinvestigate the magnetic signature of Apollinaris Patera, and we show that it is compatible with a Noachian shutdown of the core dynamo. In particular, we present a map of the surface magnetic field along with the corresponding magnetization that is necessary to generate the observed field at Apollinaris Patera. This shows a very different pattern than at orbital altitude. Here, we use the magnetization map of F. Vervelidou et al. (see her poster of this meeting), which is based on a recent model of the Martian crustal magnetic field that has been optimized to reduce noise in the data and that allows to downward-continue the field to surface altitude [7]. Furthermore, we intend to use the thermal demagnetization code of [8] with the aim to investigate if the observed magnetic signature is better compatible with remanent magnetization or partial thermal demagnetization. For this exercise, we will also consider the covariance and resolution matrices of the magnetic field model in order to include its formal uncertainty and the effect of regularization, respectively. References:[1] Acuña et al. (1999), Science [2] R.J. Lillis et al. (2013), J. Geophys. Res. [3] R.J. Lillis et al. (2015), J. Geophys. Res. [4] L.L. Hoood et al. (2010), Icarus [5] C. Milbury et al. (2012), J. Geopys. Res. [6] B. Langlais and M. Purucker (2007), Planet. Space Sci. [7] A. Morschhauser et al. (2014), J. Geophys. Res. [8] J. Dufek and G.W. Bergantz (2005), J. Petrol |
BibTeX:
@inproceedings{Morschhauser-2016-AGU,
author = {Morschhauser, A. and Vervelidou, F. and Lillis, R. J. and Dufek, J. and Grott, M. and Lesur, V.},
title = {Constraints on the Martian Core Dynamo: The Magnetic Signature of Apollinaris Patera},
booktitle = {Proceeding of the AGU Fall meeting},
year = {2016},
number = {GP23C-1347}
}
|
| Prokhorov B, Förster M, Lesur V, Namgalagze A, Holschneider M and Stolle C (2016),
"The simulation of the ionospheric current system and its impact on the Earth's magnetic field", In AGU Chapman Conference. Dubrovnik, Croatia, May (22-27), 2016. |
| Abstract: The system of the ionospheric current is a part of the global magnetospheric electrical chain. In this electrical chain, the currents are generated by the solar wind and Interplanetary Magnetic Field (IMF) interaction with the Earth’s magnetosphere. Those currents are transferred to the ionosphere of the Earth via the Field Aligned Currents (FACs) and define the electrodynamics of the coupled Magnetosphere – Ionosphere – Thermosphere (MIT) system. For this study, we perform the modelling of the dynamic ionospheric current system. Those simulations are done with an improved version of the first-principle, time-dependent, and fully self-consistent numerical global Upper Atmosphere Model (UAM-P). This model describes the thermosphere, ionosphere, plasmasphere and inner magnetosphere as well as the electrodynamics of the coupled MIT system for the altitudinal range from 80 (60) km up to the 15 Earth radii. The equatorial and lower latitudinal ionosphere of this model was improved for the present investigation. Additionally, we calculate the contribution of the ionospheric currents to the Earth’s magnetic field. For this purpose, we obtain the additional magnetic field from the system of the ionospheric currents calculated with the UAM-P model. The magnetic field generated by the ionospheric currents is calculated using the Biot-Savart law. The ionospheric impact on the magnetic field is significant at dayside and high-latitudinal regions, where maximum values of these currents occur. The additional magnetic field of ionospheric origin depends on the geomagnetic conditions and has significant seasonal and UT variations. |
BibTeX:
@inproceedings{Prokhorov-2016-AGUChapman,
author = {B. Prokhorov and M. Förster and V. Lesur and A. Namgalagze and M. Holschneider and C. Stolle},
title = {The simulation of the ionospheric current system and its impact on the Earth's magnetic field},
booktitle = {AGU Chapman Conference},
year = {2016}
}
|
| Prokhorov BE, Förster M, Stolle C, Lesur V, Namgalagze A and Holschneider M (2016),
"The ionospheric current system and its contribution to the Earth's magnetic field", In Geophysical Research Abstracts. Vienna, Austria, April (17-22), 2016. Vol. 18(EGU2016-6902) |
| Abstract: The ionospheric currents are a highly variable part of the coupled Magnetosphere – Ionosphere – Thermosphere (MIT) system. This system is driven by the solar wind and Interplanetary Magnetic Field (IMF) interaction with the Earth’s magnetosphere. The solar wind and IMF interactions transfer energy to the MIT system via recon- nection processes at the magnetopause. The Field Aligned Currents (FACs) constitute the energetic link between the magnetosphere and the Earth’s ionosphere. The system of ionospheric currents depends on the geomagnetic conditions and has significant seasonal and UT variation. The first aim of the present investigation is to model the global dynamic ionospheric current system. For this pur- pose, we use an improved version of the first-principle, time-dependent, and fully self-consistent numerical global Upper Atmosphere Model (UAM-P). This model describes the thermosphere, ionosphere, plasmasphere and inner magnetosphere as well as the electrodynamics of the coupled MIT system for the altitudinal range from 80 (60) km up to the 15 Earth radii. For this study, the lower latitudinal and equatorial electrodynamics of the UAM-P model was improved. The second aim of this research is to calculate the ionospheric contribution to the Earth’s magnetic field. The ad- ditional magnetic field is obtained from the global ionospheric current system calculated with the UAM-P model. The ionospheric magnetic field is calculated using the Biot-Savart law. The maximum magnitudes of the iono- spheric magnetic field are located close to the areas of the auroral and equatorial electrojets. The contribution of the equatorial electrojet to the magnetic field is significant and comparable to the influence of the high latitude current system. |
BibTeX:
@inproceedings{Prokhorov-2016-EGU,
author = {B. E. Prokhorov and M. Förster and C. Stolle and V. Lesur and A. Namgalagze and M. Holschneider},
title = {The ionospheric current system and its contribution to the Earth's magnetic field},
booktitle = {Geophysical Research Abstracts},
year = {2016},
volume = {18},
number = {EGU2016-6902},
note = {EGU General Assembly 2016}
}
|
| Vervelidou F, Morschhauser A, Lesur V, Grott M and Lillis RJ (2016),
"Constraining the date of the martian dynamo shutdown by means of craters' magnetization signatures", In Proceeding of the AGU Fall meeting. San Francisco, USA, 12-16 December, 2016. (GP23C-1345) |
| Abstract: Mars is characterized by a strong crustal magnetic field, particularly over its southern hemisphere, which is the remnant of ancient core dynamo. The dynamo ceased operating approximately 4 Gyr ago, although the exact time is still under debate. The scope of this study is to introduce constraints on the possible timing of its cessation by studying the magnetization signatures over some craters which have reliable crater retention ages and are large enough for the impact to have reset the crustal magnetization within. It is well known that inverting magnetic field data for a magnetization distribution suffers from inherent non-uniqueness. However, the study of Gubbins et al. (2011) has shown that vector spherical harmonics allow the separation of a magnetization distribution into the part that generates the magnetic field observed in source-free regions, hereafter called the visible magnetization, and the null space, which does not contribute to the observed magnetic field. In the first step of our study, under the assumption of a 40 km thick magnetic layer and of a magnetization distribution that varies only laterally, we propose a model of the visible magnetization of Mars based on the lithospheric magnetic field model of Morschhauser et al. (2014). In the second step of our study, by means of a Monte Carlo approach, we generate various magnetization distributions that span its null space as this is described by the vector Spherical Harmonic bases. For this, we make the assumption that the visible part of the magnetization and its null-space are characterized by the same properties, e.g., concerning their intensity and their coherence wavelength. By adding the visible magnetization to these null space samples, we intend to infer the probability of a given crater to be magnetized, partially magnetized or demagnetized. Combining these probabilities with the date of each crater can lead to a probabilistic history for the martian dynamo. |
BibTeX:
@inproceedings{Vervelidou-2016-AGU,
author = {Vervelidou, F. and Morschhauser, A. and Lesur, V. and Grott, M. and Lillis, R. J.},
title = {Constraining the date of the martian dynamo shutdown by means of craters' magnetization signatures},
booktitle = {Proceeding of the AGU Fall meeting},
year = {2016},
number = {GP23C-1345}
}
|
| Vervelidou F, Lesur V, Thébault E, Dyment J and Holschneider M (2016),
"Remanent and induced contributions of the Earth's magnetization", In Geophysical Research Abstracts. Vienna, Austria, April (17-22), 2016. Vol. 18(EGU2016-17218) |
| Abstract: Inverting the magnetic field of crustal origin for the magnetization distribution that generates it suffers from non-uniqueness. The reason for this is the so-called annihilators, i.e. structures that produce no visible magnetic field outside the sources. Gubbins et al., 2011 uses the complex vector Spherical Harmonics notation in order to separate the Vertical Integrated Magnetization (VIM) distribution into the parts that do and do not contribute to the magnetic field measured in source free regions. We use their formalism and convert a crustal SH model based on the WDMAM into a model for the equivalent magnetization. However, we extend their formalism and assume that the magnetization is confined within a layer of finite thickness. A different thickness is considered for the oceanic crust than for the continental one. It is well known that the large scales of the crustal field are entirely masked by the Earth’s main field. Therefore, we complement the WDMAM based magnetization map (SH degrees 16 to 800) with the magnetization map for the large wavelengths (SH degrees 1-15) that was recently derived by Vervelidou and Thébault (2015) from a series of regional statistical analyses of the World Digital Magnetic Anomaly Map. Finally we propose a tentative separation of this magnetization map into induced and remanent contributions on a regional scale. We do so based on the direction of the core magnetic field. We discuss the implications of these results in terms of the tectonic history of the Earth. |
BibTeX:
@inproceedings{Vervelidou-2016-EGU,
author = {Foteini Vervelidou and Vincent Lesur and Erwan Thébault and Jérôme Dyment and Matthias Holschneider},
title = {Remanent and induced contributions of the Earth's magnetization},
booktitle = {Geophysical Research Abstracts},
year = {2016},
volume = {18},
number = {EGU2016-17218},
note = {EGU General Assembly 2016}
}
|
| Bocchialini K, Menvielle M, Chambodut A, Cornilleau-Wehrlin N, Fontaine D, Grison B, Lathuillère C, Marchaudon A, Pick M, Pitout F, Régnier S, Schmieder B, Vilmer N and Zouganelis Y (2015),
"Statistical analysis of CMEs' geoeffectiveness over one year of solar maximum during cycle 23", In 26th IUGG General Assembly, Prague, Czech Republic., 22 June - 2 July, 2015. |
| Abstract: Using different propagation models from the Sun to the Earth, we performed a statistical analysis over the year 2002 on CME's geoeffectiveness linked to sudden storm commencements (ssc). We also classified the perturbations of the interplanetary medium that trigger the sscs. For each CME, the sources on the Sun of the CME are identified as well as the properties of the parameters deduced from spacecraft measurements along the path of the CME related event, in the solar atmosphere, the interplanetary medium, and the Earth ionized (magnetosphere and ionosphere) and neutral (thermosphere) environments. The set of observations is statistically analysed so as to evaluate the geoeffectiveness of CMEs in terms of ionospheric and thermospheric signatures, with attention to possible differences related to different kinds of solar sources. The observed Sun-to-Earth travel times are compared to those estimated using the existing models of propagation in the interplanetary medium, and this comparison is used to statistically assess the performances of the various models. |
BibTeX:
@inproceedings{Bocchialini-2015-IUGG,
author = {Bocchialini, K. and M. Menvielle and A. Chambodut and N. Cornilleau-Wehrlin and D. Fontaine and B. Grison and C. Lathuillère and A. Marchaudon and M. Pick and F. Pitout and S. Régnier and B. Schmieder and N. Vilmer and Y. Zouganelis},
title = {Statistical analysis of CMEs' geoeffectiveness over one year of solar maximum during cycle 23},
booktitle = {26th IUGG General Assembly, Prague, Czech Republic},
year = {2015}
}
|
| Chambodut A, Marchaudon A, Lathuillère C and Menvielle M (2015),
"New geomagnetic indices alpha with 15 minutes time resolution", In 26th IUGG General Assembly, Prague, Czech Republic., 22 June - 2 July, 2015. |
| Abstract: New sub-auroral 15-minutes sector indices are proposed: alpha indices. They are based on an as dense as possible network of observatories in each hemisphere. The derivation scheme is at first presented. It is novel, and takes at the most advantage of the use of numerical minute values. At first, the variation with time over a solar cycle of local geomagnetic activity is determined at each magnetic station. Then, gathering all the stations, a normalisation with Corrected Geomagnetic Latitude is determined. For each 15-minutes interval magnetic activity on the horizontal component is averaged out and corrected using this normalization, before a spline modelling of the longitudinal variation in each hemisphere. Four Magnetic Local Time (MLT) sectors are considered, leading to four different MLT sector indices in each of the two hemispheres; hemispheric and planetary 15-minutes indices are also computed. Some examples of geomagnetic events and comparisons with other geomagnetic indices behaviours are presented. |
BibTeX:
@inproceedings{Chambodut-2015-IUGG,
author = {A. Chambodut and A. Marchaudon and C. Lathuillère and M. Menvielle},
title = {New geomagnetic indices alpha with 15 minutes time resolution},
booktitle = {26th IUGG General Assembly, Prague, Czech Republic},
year = {2015}
}
|
| Chambodut A, Menvielle M, Mendel V, Brendle JM, Bernard A, Marchaudon A and Lathullière C (2015),
"New international service of geomagnetic indices' web site", In 26th IUGG General Assembly, Prague, Czech Republic., 22 June - 2 July, 2015. |
| Abstract: The International Service of Geomagnetic Indices (ISGI) is in charge of the elaboration and dissemination of IAGA endorsed geomagnetic indices and lists of remarkable magnetic events. This is possible thanks to reports of magnetic observatories distributed all over the planet and thanks to work done by the 6 ISGI-Collaborating-Institutes (Ebro Observatori, Spain; GFZ, Potsdam, Germany; WDC, Kyoto, Japan; AARI, St Petersburg, Russian Federation; DTU Space, Copenhagen, Denmark; EOST, Strasbourg, France). The official ISGI Web portal, which is hosted by ISGI headquarters at EOST, makes available online reference values of IAGA endorsed data. A new ISGI Web site has been designed in order to meet the actual requirements towards users. This Web site contains: - pages with synthetic information, and in particular main references and characteristics of IAGA endorsed geomagnetic indices and lists of events; - downloading and plotting tools; - a “playground area” that contains new sections dedicated to dissemination of indices that are not yet endorsed by IAGA but met expectations of the users (for testing purposes). |
BibTeX:
@inproceedings{Chambodut-2015-IUGGb,
author = {A. Chambodut and M. Menvielle and V. Mendel and J. M. Brendle and A. Bernard and A. Marchaudon and C. Lathullière},
title = {New international service of geomagnetic indices' web site},
booktitle = {26th IUGG General Assembly, Prague, Czech Republic},
year = {2015}
}
|
| Coïsson P, Brocco L, Hulot G, Léger JM, Jager T, Vigneron P, Bertrand F and Boness A (2015),
"Analysis of Plasma Irregularities and Electromagnetic Signals Based on Swarm Absolute Scalar Magnetometer Burst Mode Sessions", In AGU Fall meeting. San Francisco, USA, December (14-18), 2015. (GP43C-1262) |
| Abstract: The commissioning phase of Swarm satellites provided opportunities to acquire measurement during special acquisitions sessions. The Absolute Scalar Magnetometer (ASM) instrument of each satellite were operated in "burst mode": the recording frequency of the instruments were risen from the nominal 1 Hz to 250 Hz. A total of seven burst mode sessions, covering between 3 and 48 hours of continuous recording, were realized between December 2013 and February 2014. During that time, the local time of Swarm satellites orbits shifted from midnight-noon to post sunrise-post sunset. The last burst-mode session occurred during the recovery phase of a geomagnetic storm. Therefore ASM burst mode data allow to investigate both quiet and geomagnetic active periods. The analysis of burst mode data was focused on the phenomena that can be investigated only using this higher sampling rate, providing insight in the frequency band between few Hz to 125 Hz. From the analysis of the magnetic field data we could observe typical signals related to different geomagnetic phenomena, showing distinct features at low, mid and high latitude. We were able to detect fast magnetic field fluctuations with a typical pattern, associated with low-latitudes irregularities in the ionospheric plasma during the development of post-sunset plasma bubbles. We also present results of the analysis of short electromagnetic signals that were detected mostly in the mid-to-low latitudes evening sector, investigating their correlation with the occurrence of lightning on the ground. Over the high latitudes, we detected fast variations in the intensity of the magnetic field during the active periods and analyse their correlations with plasma irregularities. |
BibTeX:
@inproceedings{Coisson-2015-AGU,
author = {Coïsson, P. and L. Brocco and G. Hulot and J. M. Léger and T. Jager and P. Vigneron and F. Bertrand and A. Boness},
title = {Analysis of Plasma Irregularities and Electromagnetic Signals Based on Swarm Absolute Scalar Magnetometer Burst Mode Sessions},
booktitle = {AGU Fall meeting},
year = {2015},
number = {GP43C-1262}
}
|
| Coïsson P, Alken P, Chulliat A, Brocco L, Vigneron P, Lalanne X, Hulot G and Dembelé S (2015),
"Equatorial electrojet over West Africa from ground and Swarm satellites", In 14th International Symposium on Equatorial Aeronomy (ISEA), Bahir Dar, Ethiopia., October (19-23), 2015. |
| Abstract: We present a study of the variability of the equatorial electrojet in the West African sector using ground and space measurements. We analyze the ΔH values obtained between magnetometers installed below the equatorial electrojet (EEJ) and outside of it. Data below the EEJ are obtained from a chain of three magnetometers in Mali and Ivory Coast: the West African Magnetometer Network (WAMNET). Data outside the EEJ are obtained from the INTERMAGNET observatories of M’bour (Senegal) and Tamanrasset (Algeria). The database used for this study covers a period of 9 years. We compare the ground results with the observations obtained in this sector by the three Swarm satellites during 2014. Swarm satellites provide simultaneous multi-point observations of the magnetic field at 450 and 500 km of altitude. The increasing separation in longitude of the orbits of the lower and upper satellites allow measuring latitudinal cross-sections at four local times during one day. |
BibTeX:
@inproceedings{Coisson-2015-ISEA,
author = {Coïsson, P. and P. Alken and A. Chulliat and L. Brocco and P. Vigneron and X. Lalanne and G. Hulot and S. Dembelé},
title = {Equatorial electrojet over West Africa from ground and Swarm satellites},
booktitle = {14th International Symposium on Equatorial Aeronomy (ISEA), Bahir Dar, Ethiopia},
year = {2015}
}
|
| Coïsson P, Brocco L, Hulot G, Vigneron P, Lesur V, Grau RC, Lalanne X, Sirol O, Léger J-M, Jager T, Bertrand F, Boness A and Fratter I (2015),
"Geophysical signals detected during Swarm's Absolute Scalar Magnetometers burst mode sessions", In 26th IUGG General Assembly, Prague, Czech Republic., 22 June - 2 July, 2015. |
| Abstract: Swarm satellites carry an Absolute Scalar Magnetometer (ASM) to measure the magnetic field intensity with high accuracy and stability. Nominal ASM data acquisition is at 1 Hz, but there is the possibility to acquire data in a so-called 'burst mode' at 250 Hz. During the commissioning phase of the mission, seven burst mode acquisition campaigns have been run simultaneously for all satellites, obtaining a total of ten days of burst-mode data. We analyzed the burst mode data to identify high frequency geomagnetic signals, developing a detection algorithm to identify the occurrence of events and characterize them, discriminating between geophysical signals and possible instrumental perturbations. We found that during quiet time the detected events concentrate near the geomagnetic equator, showing a link with ionospheric irregularities and plasma bubbles. During geomagnetic active periods, these events are mostly observed in the auroral regions, related to polar region currents.Since these campaigns have been conducted during the initial months of the mission, the three satellites were still close to each other, allowing for an analysis of the spatial coherence of the observed signals. |
BibTeX:
@inproceedings{Coisson-2015-IUGG,
author = {Coïsson, P. and L. Brocco and G. Hulot and P. Vigneron and V. Lesur and R. Crespo Grau and X. Lalanne and O. Sirol and J.-M. Léger and T. Jager and F. Bertrand and A. Boness and I. Fratter},
title = {Geophysical signals detected during Swarm's Absolute Scalar Magnetometers burst mode sessions},
booktitle = {26th IUGG General Assembly, Prague, Czech Republic},
year = {2015}
}
|
| Larnier H, Sailhac P and Chambodut A (2015),
"Continuous Wavelet Transform and its applications to Magnetotelluric data processing", In 26th IUGG General Assembly, Prague, Czech Republic., 22 June - 2 July, 2015. |
| Abstract: The main issue in magnetotelluric data processing is the non-stationarity of electromagnetic signals. Most processing techniques are based on robust statistics to derive the frequency-dependant transfer function (MT tensor) linking the electric and magnetic fields. This transfer function is very sensitive to noise in EM time series and can be heavily biased. We propose here to use continuous wavelet transform to process MT data in the time-frequency domain. The methodology is to first seek these transitory signals (such as sferics, geomagnetic pulsations...) and then derive the impedance transfer function using their wavelet coefficients. To seek these locations, we use the theory of significance levels in the time-frequency domain to have access to high signal-to-noise ratio coefficients. By using this technique and wavelets adapted to the shape of geomagnetic events, processing is performed as a simple least squares inversion of selected wavelet coefficients; recovered impedance transfer function is comparable to the result of robust processing. Moreover, we are able to significantly reduce the noise bias in magnetotelluric data measurement for single station data processing. Finally, with this tool, we have access to the time locations of the transitory signals detected with the wavelet transform and can derive their properties which can be useful for geomagnetic studies. |
BibTeX:
@inproceedings{Larnier-2015-IUGG,
author = {Larnier, H. and P. Sailhac and A. Chambodut},
title = {Continuous Wavelet Transform and its applications to Magnetotelluric data processing},
booktitle = {26th IUGG General Assembly, Prague, Czech Republic},
year = {2015}
}
|
| Razafindranaivo LM, Chambodut A, Ranaivo-Nomenjanahary F and Menvielle M (2015),
"Review of magnetic field data and models over Madagascar Island", In 26th IUGG General Assembly, Prague, Czech Republic., 22 June - 2 July, 2015. |
| Abstract: The magnetic field over Madagascar Island is modelled through a large number of different magnetic models. All available magnetic data sets over the Madagascar Island - national magnetic observatory (TAN) observations and local magnetic surveys - have been compiled and organized in the MAGEDAB (MAdagascar GEomagnetic DAta Base) data base, which is presented. The main magnetic field and its secular variation, the crustal magnetic field and the external magnetic variations were modelled using different published tools. The obtained models are presented, and compared with observations. |
BibTeX:
@inproceedings{Razafindranaivo2015,
author = {Razafindranaivo, L. M. and A. Chambodut and F.N. Ranaivo-Nomenjanahary and M. Menvielle},
title = {Review of magnetic field data and models over Madagascar Island},
booktitle = {26th IUGG General Assembly, Prague, Czech Republic},
year = {2015}
}
|
| Razafindranaivo LM, Razafiarisera RT, Chambodut A, Ranaivo-Nomenjanahary F, Ralambomanana G, Harisoa CR, Fotze M, Blumetritt H, Bernard A and Menvielle M (2015),
"New Malagasy Magnetic Observatory", In 26th IUGG General Assembly, Prague, Czech Republic., 22 June - 2 July, 2015. |
| Abstract: Established in 1889, the magnetic observatory of Antananarivo (TAN) is the second oldest magnetic observatory in the Southern hemisphere (the oldest one being Melbourne, which moved to Toolangi then Canberra). The records, though discontinuous, offer a series of remarkable observations, more than one hundred and twenty five years long. Such series are rare (only about ten around the world) and are extremely valuable for studies on long term evolution of the magnetic field. In 2008, the total destruction of acquisition chain by lightning caused the stop of the magnetic observatory. The growing urbanization, around the historical site in Antananarivo, made it impossible to rapidly re-establish the magnetic observatory on the same location. A new site has been selected in 2011, during a first on-site mission. This site is located at approximately 60 km from the previous one. The new buildings of magnetic absolute measurements huts and variometers vaults were rapidly achieved on site, but unfortunately the new settlement was delayed. In May 2015, a new on-site mission has been conduced to install the new magnetic observatory structure: autonomous energy and data transmission elements, whole acquisition chain with variometers and scalar magnetometer. The new Malagasy Magnetic observatory is presented and the first raw data are displayed. |
BibTeX:
@inproceedings{Razafindranaivo-2015-IUGG,
author = {Razafindranaivo, L. M. and R. T. Razafiarisera and A. Chambodut and F.N. Ranaivo-Nomenjanahary and G. Ralambomanana and C. Rakotozafy Harisoa and M. Fotze and H. Blumetritt and A. Bernard and M. Menvielle},
title = {New Malagasy Magnetic Observatory},
booktitle = {26th IUGG General Assembly, Prague, Czech Republic},
year = {2015}
}
|
| Coïsson P, Vigneron P, Hulot G, Crespo-Grau R, Brocco L, Lalanne X and Sirol O (2014),
"Swarm's Absolute Scalar Magnetometers Burst Mode Results", In AGU Fall meeting. San Francisco, USA, December (15-19), 2014. (GP51A-3699) |
| Abstract: Each of the three Swarm satellites embarks an Absolute Scalar Magnetometer (ASM) to provide absolute scalar measurements of the magnetic field with high accuracy and stability. Nominal data acquisition of these ASMs is 1 Hz. But they can also run in a so-called "burst mode" and provide data at 250 Hz. During the commissioning phase of the mission, seven burst mode acquisition campaigns have been run simultaneously for all satellites, obtaining a total of ten days of burs-mode data. These campaigns allowed the identification of issues related to the operations of the piezo-electric motor and the heaters connected to the ASM, that do not impact the nominal 1 Hz scalar data. We analyze the burst mode data to identify high frequency geomagnetic signals, focusing the analysis in two regions: the low latitudes, where we seek signatures of ionospheric irregularities, and the high latitudes, to identify high frequency signals related to polar region currents. Since these campaigns have been conducted during the initial months of the mission, the three satellites where still close to each other, allowing to analyze the spatial coherency of the signals. Wavelet analysis have revealed 31 Hz signals appearing in the night-side in the equatorial region. |
BibTeX:
@inproceedings{Coisson-2014-AGU,
author = {Coïsson, P. and P. Vigneron and G. Hulot and R. Crespo-Grau and L. Brocco and X. Lalanne and O. Sirol},
title = {Swarm's Absolute Scalar Magnetometers Burst Mode Results},
booktitle = {AGU Fall meeting},
year = {2014},
number = {GP51A-3699}
}
|
| Coïsson P, Lalanne X, Telali K, Heumez B, Luc T, Chulliat A and Alken P (2014),
"Equatorial electrojet studies from the West African Magnetometer NETwork (WAMNET).", In XVI IAGA Workshop on Geomagnetic Observatory Instruments, Data Acquisition and Processing. NGRI, Hyderabad, India, October (7-16), 2014. |
| Abstract: The West African Magnetometer Network (WAMNET) had been established during the international electrojet year, and upgraded in 2006 with thermally isolated sensors and in 2009 to provide 1 second data. The chain consist of three stations in Mali and Ivory Coast, located near the magnetic equator, below the equatorial electrojet. Magnetometers data of WAMNET chains are available on BCMT website www.bcmt.fr/wamnet/DATABANK/WAMNET with a latency of few months in a modified IAGA format to include also temperature measurement. These data have been successfully used to obtain the day-time equatorial electric field (Alken et al. 2013) taking the difference between the horizontal magnetic field measured in these stations and at the observatories of Mbour and Tamanrasset, outside of the electrojet. A new station is ready to be installed in Djibouti. Together with the observatory of Addis Abeba it will provide data of the equatorial electrojet in the East African sector. This station will provide data in real time. |
BibTeX:
@inproceedings{Coisson-2014c-IAGAINTERMAGNET,
author = {Coïsson, P and X. Lalanne and K. Telali and B. Heumez and T. Luc and A. Chulliat and P. Alken},
title = {Equatorial electrojet studies from the West African Magnetometer NETwork (WAMNET).},
booktitle = {XVI IAGA Workshop on Geomagnetic Observatory Instruments, Data Acquisition and Processing},
year = {2014}
}
|
| Coïsson P, Heumez B, Telali K, Lalanne X, Luc T, Maury V and Chambodut A (2014),
"Detection of space weather events in magnetic data", In 11th European Space Weather Week. Liege, Belgium, November (17-21), 2014. |
| Abstract: The magnetic signature of space weather events allows to follow the evolution of magnetic storms from their commencement to the end of the recovery phase. The French Bureau Central du Magnetisme Terrestre manages 16 magnetic observatories distributed all over the world and collects data from for most of them in real time. Detection of sudden storm commencement is operational and is disseminated to subscribers through e-mail. This service will be developed further to provide additional information about the main characteristics of the undergoing storm. Another focus of research is the equatorial region. IPGP maintains a chain of magnetometers in West Africa, WAMNET, and a second one will be available by the end of 2014 in East Africa, with a station in Djibouti, coupled with the Addis Ababa observatory. A couple of magnetometers, one located below and one outside the equatorial electrojet can infer the ionospheric ExB drift, responsible of the development of the equatorial anomaly. We present the result obtained from these chains of magnetometers and the related space weather products. |
BibTeX:
@inproceedings{Coisson-2014-ESWW,
author = {Coïsson, P. and B. Heumez and K. Telali and X. Lalanne and T. Luc and V. Maury and A. Chambodut},
title = {Detection of space weather events in magnetic data},
booktitle = {11th European Space Weather Week},
year = {2014}
}
|
| Crespo-Grau R, Vigneron P, Hulot G, Coïsson P, Brocco L, Lalanne X, Sirol O, Léger J-M, Jager T, Bertrand F, Boness A and Fratter I (2014),
"Early results from Swarm's Absolute Scalar Magnetometers burst mode", In 3rd Swarm Science Meeting. Copenhagen, Denmark, 19-20 June, 2014. |
| Abstract: Swarm’s Absolute Scalar Magnetometers (ASM) provides absolute scalar measurements of the magnetic field with high accuracy and stability on the three satellites of the mission. These ASMs nominally run at 1 Hz. But they can also run at 250 Hz frequency using a so-called “burst” mode. This possibility has been taken advantage of during commissioning, the burst mode having been run simultaneously on all three satellites over several days. These burst mode sessions were driven by the engineering need to explore the high frequency spectral content of the signal measured by the ASMs, to identify issues that could affect not only the nominal 1 Hz scalar data but also the 1 Hz vector data that the ASM simultaneously deliver on an experimental basis. Two unexpected issues have been identified, one related to the activation of a piezo-electric motor built in the instrument, the other related to the heaters used to keep the instruments within operating temperature range. Fortunately, these issues do not affect the nominal 1 Hz scalar data of the mission, and their impact on the 1 Hz experimental vector data can be handled. These burst mode data can now be used to look for meaningful high frequency geomagnetic signals. |
BibTeX:
@inproceedings{Crespo-2014-Swarm,
author = {Raül Crespo-Grau and Pierre Vigneron and Gauthier Hulot and Pierdavide Coïsson and Laura Brocco and Xavier Lalanne and Olivier Sirol and Jean-Michel Léger and Thomas Jager and François Bertrand and Axel Boness and Isabelle Fratter},
title = {Early results from Swarm's Absolute Scalar Magnetometers burst mode},
booktitle = {3rd Swarm Science Meeting},
year = {2014}
}
|
| Telali K, Lalanne X, Chulliat A, Luc T and Coïsson P (2014),
"Temperature calibration of vector magnetometer", In XVI IAGA Workshop on Geomagnetic Observatory Instruments, Data Acquisition and Processing. NGRI, Hyderabad, India, October (7-16), 2014. |
| Abstract: Alongside magnetic observatories, where magnetic field measurements are routinely made by human observer, magnetic stations can operate in areas where it is not possible to have measurements by trained observer. In both cases accurate preparation of the measuring site and system allows to obtain the most suitable conditions for continuous automatic records from magnetometers. It is necessary to perform proper calibration of the instruments before deployment, and usually it is aimed to obtain the transformation matrix from the instrument reference frame to the 3D magnetic components. External temperature variations could affect the instruments performances and therefore temperature is kept as constant as possible. However in the case of deployment of a station in an isolated area, where there might be strong diurnal variations of temperature, it is advisable to have also a temperature calibration of the magnetic sensor, to improve the accuracy of the measurements under any condition. We present here a temperature calibration technique that has been applied to the instruments that are going to be deployed at low latitudes, for the measurement of the equatorial electrojet. It is based on the Merayo et al. (2000) calibration technique: the sensor is mounted on a goniometer, in natural magnetic field conditions and it is rotated in all directions to obtain the transformation matrices. A simultaneous scalar measurement is done at the same time. In our case the calibration is performed in a thermally controlled chamber, and it is repeated for temperatures between 12° and 40°. A linear drift of calibration parameters has been found and it has been possible to reduce by an order of magnitude the effects on the measured data. This allows a reliable data acquisition even for installation of the station in harsh environment. |
BibTeX:
@inproceedings{Telali-2014-IAGAINTERMAGNET,
author = {Telali, K. and X. Lalanne and A. Chulliat and T. Luc and P. Coïsson},
title = {Temperature calibration of vector magnetometer},
booktitle = {XVI IAGA Workshop on Geomagnetic Observatory Instruments, Data Acquisition and Processing},
year = {2014}
}
|
| Chambodut A, Rambolamanana G, Rambolamanana M, IOGA Technical Team, Razafindranaivo L, Ranaivo-Nomenjanahary F and .Menvielle M (2013),
"Towards the reinstallation of Madagascar magnetic observatory", In Proceedings of the XVth IAGA Workshop on geomagnetic observatory instruments, Data acquisition and processing. Cadiz, Spain |
| Abstract: The magnetic observatory of Madagascar (IAGA code: TAN) opened in 1889. Operated by the geomagnetic department of the Institut et Observatoire Géophysique d'Antananarivo (I.O.G.A.), formerly Tananarive observatory, in close cooperation with Ecole et Observatoire des Sciences de la Terre (E.O.S.T.), it joined the INTERMAGNET Program in 1993. After several periods of major failures due to hard climatic conditions, an EOST-IOGA meeting was organised in order to fully assess the situation of the observatory embedded in the growing urbanization. A new site was thus defined and, thanks to IOGA team, construction work was undertaken. A gradual relocation of the observatory will be undertaken over the period 2012-2014. |
BibTeX:
@inproceedings{Chambodut-2013-IAGAINTERMAGNET,
author = {A. Chambodut and G. Rambolamanana and M. Rambolamanana and IOGA Technical Team and L.M. Razafindranaivo and F.N. Ranaivo-Nomenjanahary and M .Menvielle},
title = {Towards the reinstallation of Madagascar magnetic observatory},
booktitle = {Proceedings of the XVth IAGA Workshop on geomagnetic observatory instruments, Data acquisition and processing},
year = {2013}
}
|
| Heumez B, Lalanne X, Peltier A, Chulliat A and Chau HD (2013),
"Dalat, Vietnam: the reopening of a geomagnetic observatory", In Proceedings of the XVth IAGA Workshop on geomagnetic observatory instruments data acquisition and processing. Cadiz, Spain |
| Abstract: The Dalat geomagnetic observatory, Vietnam, was reinstalled in April 2011 and joined the INTERMAGNET global network in September 2012. It is run in collaboration between the Institute of Geophysics, Vietnam Academy of Science and Technology, and the Institut de Physique du Globe de Paris. The new observatory is located in the South East of Vietnam, at about 1000 km to the South of the Phu Thuy geomagnetic observatory, which was the first Vietnamese observatory to get the INTERMAGNET magnetic observatory (IMO) status in 1996. One-second and one-minute variation data have been provided on a continuous basis since April 2011. Absolute measurements began at the same time and have been used to calculate quasi-definitive data following the IPGP method. Due to its location, far away from the closest IMO and close to the geomagnetic dip-equator, the Dalat geomagnetic observatory will be particularly useful for global geomagnetic field modeling and the study of the equatorial electrojet. |
BibTeX:
@inproceedings{Heumez-2013-IAGAINTERMAGNET,
author = {Heumez, B. and X. Lalanne and A. Peltier and A. Chulliat and Ha Duyen Chau},
title = {Dalat, Vietnam: the reopening of a geomagnetic observatory},
booktitle = {Proceedings of the XVth IAGA Workshop on geomagnetic observatory instruments data acquisition and processing},
year = {2013}
}
|
| Lalanne X, Peltier A, Chulliat A, Telali A and Heumez B (2013),
"A new measurement method for magnetic repeat stations", In Proceedings of the XVth IAGA Workshop on geomagnetic observatory instruments, Data acquisition and processing. Cadiz, Spain |
| Abstract: The relevance of traditional magnetic repeat station networks to geomagnetic modeling has been increasingly challenged during the last decade, as the Ørsted and CHAMP satellites provided data of unprecedented precision and spatial resolution. Yet magnetic repeat networks organized on a national or regional basis can still be viewed as relatively inexpensive safety nets in case satellite data are not available. Here we present a new method for magnetic repeat measurements, where repeat stations are located on airports, azimuth sightings are determined using GNSS geodetic receivers and magnetic measurements are performed at night (around 0200 local time). This method aims at improving the measurement precision while keeping the cost low, by facilitating the measurement execution. It was first implemented in metropolitan France during the summer 2012. Its full evaluation will be made in 2013, after a first reoccupation of the new French repeat network. |
BibTeX:
@inproceedings{Lalanne-2013-IAGAINTERMAGNET,
author = {Lalanne, X. and A. Peltier and A. Chulliat and A. Telali and B. Heumez},
title = {A new measurement method for magnetic repeat stations},
booktitle = {Proceedings of the XVth IAGA Workshop on geomagnetic observatory instruments, Data acquisition and processing},
year = {2013}
}
|
| Menvielle M, Chambodut A, Marchaudon F, El-Lemdani M and Lathuillère C (2013),
"A statistical study of L.T. variations of K-derived sectorial geomagnetic indices", In Proceedings of the XVth IAGA Workshop on geomagnetic observatory instruments, Data acquisition and processing. Cadiz, Spain |
| Abstract: Solar-wind/magnetosphere interactions are not symmetrical and show a local time dependency. In order to better describe this effect, we use longitudinal and M.L.T. (Magnetic Local Time) K-derived sectorial geomagnetic activity indices. These indices are calculated on the basis of aλ regional sector geomagnetic activity indices (themselves derived from am network observatories) and thus reflect the geomagnetic activity at sub-auroral latitudes. In this study, we present a statistical study of the variations of the longitudinal and K-derived M.L.T. sectorial activity indices, as a function of local time and seasons. |
BibTeX:
@inproceedings{Menvielle-2013-IAGAINTERMAGNET,
author = {Menvielle, M. and Chambodut, A. and Marchaudon, F. and El-Lemdani, M. and Lathuillère, C.},
title = {A statistical study of L.T. variations of K-derived sectorial geomagnetic indices},
booktitle = {Proceedings of the XVth IAGA Workshop on geomagnetic observatory instruments, Data acquisition and processing},
year = {2013}
}
|
| Bernard A, Menvielle M and Chambodut A (2010),
"On the influence of data sampling interval on computer-derived K indices", In Proceedings of the XIVth IAGA Workshop on geomagnetic observatory instruments, Data acquisition and processing. Changchun, China, September (13-23), 2010. |
| Abstract: The K index was devised by Bartels et al. (1939) to provide an objective monitoring of the irregular geomagnetic activity, namely the magnetic signature of the solar wind and IMF effects on the Earth's magnetic field. It was then routinely used to monitor the magnetic activity at permanent magnetic observatories, as well as at temporary stations. The increasing number of digital and sometimes unmanned observatories and the creation of INTERMAGNET put the question of computer production of K at the centre of the debate. Four algorithms were selected during the Vienna meeting (1991), and endorsed by IAGA for computer production of K indices To start with, we recall how geomagnetic data sampling may impact on computer-derived values of K-indices, and lead to underestimated values resulting in a statistical bias. We use one of the algorithms endorsed by IAGA, the so-called FMI algorithm developed by the Finnish Meteorological Institute, to investigate the impact of the geomagnetic data sampling interval on computer produced K values. We use this algorithm since it gives results that are fairly comparable to those hand-scaled on analogue magnetograms by an experienced observer. The impact of the sampling interval on computer-produced K values is investigated through the comparison of the computer derived K values for the period 2009, January 1st to 2010, May 31 at the Port aux Français magnetic observatory using magnetic data series with different sampling rate (the smaller: 1 second; the larger 1 minute). The impact is investigated on both 3-hour range values and K indices data series, as a function of the activity level, for low and moderate geomagnetic activity (there was no intense magnetic storm during 2009, and very few during the first months of 2010). |
BibTeX:
@inproceedings{Bernard-2010-IAGAINTERMAGNET,
author = {A. Bernard and M. Menvielle and A. Chambodut},
title = {On the influence of data sampling interval on computer-derived K indices},
booktitle = {Proceedings of the XIVth IAGA Workshop on geomagnetic observatory instruments, Data acquisition and processing},
year = {2010}
}
|
| Schott J-J and Chambodut A (2010),
"A modelling example of anthropogenic magnetic disturbances: traffic on a road", In Proceedings of the XIVth IAGA Workshop on geomagnetic observatory instruments, Data acquisition and processing. Changchun, China, September (13-23), 2010. |
| Abstract: The magnetic measurements at the Welschbruch Geophysical Station in Vosges (France) are disturbed by the passes of vehicles on the nearby road. The signing of these disturbances is clearly identified and reproducible. The vehicles are assumed to produce a dipolar field. Tests have shown that the magnetic dipole is not simply due to induced magnetization and hence has an unknown orientation, not parallel to the ambient magnetic field. A first model, parameterized by the time of passage, speed and dipole components, provides already a fairly good prediction of the observed signal. This prediction may be improved if a small amount of induction field, produced by the time varying vehicle disturbance, is introduced in the model, by means of an empirical induction matrix. |
BibTeX:
@inproceedings{Chambodut-2010-IAGAINTERMAGNET,
author = {J.-J. Schott and A. Chambodut},
title = {A modelling example of anthropogenic magnetic disturbances: traffic on a road},
booktitle = {Proceedings of the XIVth IAGA Workshop on geomagnetic observatory instruments, Data acquisition and processing},
year = {2010}
}
|
| Chambodut A and Schott JJ (2010),
"Current status of permanent magnetic observatories in French Austral and Antarctic Territories", In Proceedings of i-DUST (Inter-Disciplinary Underground Science and Technology Conference), June. Apt, France, June (9-11), 2010. , pp. 9-11. [BibTeX] |
BibTeX:
@inproceedings{Chambodut-2010-iDUST,
author = {Chambodut, A. and J. J. Schott},
title = {Current status of permanent magnetic observatories in French Austral and Antarctic Territories},
booktitle = {Proceedings of i-DUST (Inter-Disciplinary Underground Science and Technology Conference), June},
year = {2010},
pages = {9-11}
}
|
| Chulliat A and Thebault E (2010),
"Application of quasi-definitive observatory data to the detection of geomagnetic jerks and the validation of igrf-11 candidate models", In Proceedings of the XIVth IAGA Workshop on geomagnetic observatory instruments, Data acquisition and processing. Changchun, China, September (13-23), 2010. |
| Abstract: Quasi-definitive data are a new observatory data product recommended by IAGA. They are defined as data corrected using temporary baselines shortly after their acquisition and very near to being the final data of the observatory. In July 2009, IPGP started to produce quasi-definitive data using an original method (Peltier and Chulliat, EPS, 2010) and with a latency of one month, at nine observatories: Addis Ababa (AAE), Borok (BOX), Chambon la Forêt (CLF), Kourou (KOU), Lanzhou (LZH), MBour (MBO), Phu Thuy (PHU), Pamataï (PPT) and Tamanrasset (TAM). Here we present two applications of these data. The first is the detection of a new geomagnetic jerk in 2007, localized in the Atlantic sector, using the data from KOU, MBO and TAM. Quasi-definitive data helped quantify the jerk amplitude as early as fall 2009, by providing almost one year of additional secular variation data with respect to definitive data (Chulliat et al., GRL, 2010). The second application is the validation of IGRF-11 candidate models, which occurred in November 2009. As part of the official validation process, quasi-definitive data from the nine selected observatories from January to October 2009 were used to assess the predictions of eight secular variation candidate models at epoch 2010.0. These two examples demonstrate the usefulness of quasi-definitive data for secular variation studies and geomagnetic modeling. It is hoped that more observatories will produce such data in the future, especially during the upcoming ESA Swarm mission (to be launched in 2012). |
BibTeX:
@inproceedings{Chulliat-2010-IAGAINTERMAGNET,
author = {A. Chulliat and E. Thebault},
title = {Application of quasi-definitive observatory data to the detection of geomagnetic jerks and the validation of igrf-11 candidate models},
booktitle = {Proceedings of the XIVth IAGA Workshop on geomagnetic observatory instruments, Data acquisition and processing},
year = {2010}
}
|
| Heumez B, Lalanne X, Peltier A and Chulliat A (2010),
"Easter Island: How to start a remote observatory from scratch", In Proceedings of the XIVth IAGA Workshop on geomagnetic observatory instruments, Data acquisition and processing. Changchun, China, September (13-23), 2010. |
| Abstract: Easter Island, for its geographic location, represents an important site for magnetic measurement. Situated at 3510Km from the coast of Chile, Easter Island is one of the world's most isolated inhabited islands. A geomagnetic observatory producing vector data sampled every second has been implemented in August 2008, absolute measurements started in spring 2009. The observatory is part of a collaboration project between the Institut de Physique du Globe de Paris (IPGP) and the Dirección Meteorológica de Chile (DMC). The observatory is designed to fulfill INTERMAGNET operational standards and data quality requirements. |
BibTeX:
@inproceedings{Heumez-2010-IAGAINTERMAGNET,
author = {Heumez, B. and X. Lalanne and A. Peltier and A. Chulliat},
title = {Easter Island: How to start a remote observatory from scratch},
booktitle = {Proceedings of the XIVth IAGA Workshop on geomagnetic observatory instruments, Data acquisition and processing},
year = {2010}
}
|
| Korepanov V, Marusenkov A, Chambodut A and Schott J-J (2010),
"Observatory magnetometer in-situ calibration", In Proceedings of the XIVth IAGA Workshop on geomagnetic observatory instruments, Data acquisition and processing. Changchun, China, September (13-23), 2010. |
| Abstract: The magnetic observatories are continuously striving to improve the accuracy of the field measurements. A renewed interest came up recently for instruments using a scalar sensor placed into the center of a coil system. They are able to reach very high accuracy , but at the expense of relatively high own noise background. So far, the majority of the observatories are still equipped by flux-gate or even photoelectric variometers. The baseline of these types of variometers are estimated using well-known absolute measurements, whereas the scale factors and orientation of the sensor reference frame, which are implicitly involved into the computation of the absolutes values of the field, usually are poorly known and almost everywhere not calibrated periodically, as should be required. The absence of the periodical calibration can be partly explained by fact that the metrological certification of the instruments should be provided in special laboratory by means of calibrations coils what requires to interrupt the measurements, transport the instrument to and from the calibration site and reinstall it again in the observatory. This way of doing is absolutely unacceptable, especially for remote observatories, because the time taken by the whole procedure can be very long, resulting in large gaps in the records. There is also a calibration method based upon magnetometer rotation in the approximately constant Earth’s magnetic field. However, whereas this method gives acceptable precision for, e.g., satellite magnetometers, it is not applicable to observatory magnetometers, due to the actual limited range of field variation, the large relative errors and the possibly unequal scale factors. In addition, the issue of the in-situ orientation of the triaxial magnetometer remains unsolved if we are seeking high accuracy. In this report we continue to discuss the possibility to calibrate in-situ the observatory instrument based upon the comparison of its records with the field recorded simultaneously by a reference magnetometer. The certified reference instrument has to be installed close to the tested one, its sensitivity axes properly oriented with respect to the geomagnetic frame and the records as synchronous as possible. The improved version of the observatory magnetometer LEMI-025 was specially designed as a reference instrument. In order to check practical aspects of the proposed in-situ calibration procedure two such magnetometers calibrated using a reference coil facility have been installed in the Strasbourg University geophysical station for intercalibration. The results obtained by processing synchronous records as well as the reliability of these results and estimations of the errors involved into the in-situ calibration procedure are discussed. This work is partly supported by STCU Project 4818. |
BibTeX:
@inproceedings{Korepanov-2010-IAGAINTERMAGNET,
author = {V. Korepanov and A. Marusenkov and A. Chambodut and J.-J. Schott},
title = {Observatory magnetometer in-situ calibration},
booktitle = {Proceedings of the XIVth IAGA Workshop on geomagnetic observatory instruments, Data acquisition and processing},
year = {2010}
}
|
| Peltier A, Chulliat A and Heumez B (2010),
"Toward a quality standard for quasi-definitive magnetic observatory data", In Proceedings of the XIVth IAGA Workshop on geomagnetic observatory instruments, Data acquisition and processing. Changchun, China, September (13-23), 2010. |
| Abstract: Since July 2009, quasi-definitive data are produced in routine operations at the end of each calendar month at nine INTERMAGNET observatories affiliated to the Bureau Central de Magnétisme Terrestre (BCMT) and are made available on the BCMT website (www.bcmt.fr). Quasi-definitive data are defined as data corrected using temporary baselines shortly after their acquisition and very near to being the final data of the observatory. This type of data addresses to the need of various users for baseline-corrected observatory data produced in a continuous manner. The main applications for such data include geomagnetic field modelling and the calculation of geomagnetic activity indices. We developed and implemented an original method for calculating quasi-definitive data every month. Shortly after the end of month M of year Y (noted M/Y hereafter), the following data processing steps are performed: (1) pre-processing of the one-minute variation data of M/Y; (2) calculation of a temporary baseline from 1st December of year Y-1 to the last day of M/Y; (3) calculation and validation of baseline-corrected data from 1st January of year Y to the last day of M/Y. Here we present an assessment of the method after one year of operations. The means and standard deviations of the differences between quasi-definitive data, produced in routine operations throughout 2009, and definitive data, produced after the end of the year, do not exceed 0.5 nT, well below the current INTERMAGNET standard of accuracy. This result shows that the production of high quality quasi-definitive data in INTERMAGNET observatories is feasible and even relatively easy. Based on our results, it seems realistic to extend to quasi-definitive data the 5 nT INTERMAGNET standard of accuracy used for definitive data. |
BibTeX:
@inproceedings{Peltier-2010-IAGAINTERMAGNET,
author = {A. Peltier and A. Chulliat and B. Heumez},
title = {Toward a quality standard for quasi-definitive magnetic observatory data},
booktitle = {Proceedings of the XIVth IAGA Workshop on geomagnetic observatory instruments, Data acquisition and processing},
year = {2010}
}
|
| Chulliat A, Lalanne X, Gaya-Piqué LR, Truong F and Savary J (2009),
"The new Easter Island magnetic observatory", In Proceedings of the XIIIth IAGA Workshop on geomagnetic observatory instruments, data acquisition and processing. Golden and Boulder, Colorado Vol. 271 p., pp. 2009-1226. |
| Abstract: A new magnetic observatory has been installed in 2008 in Easter Island, as part of a collaboration project between Direccion Meteorologica de Chile (DMC) and Institut de Physique du Globe de Paris (IPGP). The new observatory is located on the premises of Mataveri airport, at enough distance from the planes but still within the secured area. It is designed to meet INTERMAGNET’s operational standards and data quality requirements and to provide one-second data. Variation data are provided on a continuous basis since August 2008 and absolute measurements are expected to begin before the end of 2008. This new observatory is extremely isolated, at about 3900 km from the closest INTERMAGNET observatory in Huancayo, and will thus significantly improve the global distribution of magnetic observatories at the Earth’s surface. Data from the new Easter Island magnetic observatory will be particularly useful for main field and secular variation modeling, and for global studies of magnetic variations of external origin, such as geomagnetic pulsations and the Sq daily variation. |
BibTeX:
@inproceedings{Chulliat-2009a-IAGAINTERMAGNET,
author = {Chulliat, A. and X. Lalanne and Gaya-Piqué, L. R. and Truong, F. and J. Savary},
editor = {J. Love},
title = {The new Easter Island magnetic observatory},
booktitle = {Proceedings of the XIIIth IAGA Workshop on geomagnetic observatory instruments, data acquisition and processing},
year = {2009},
volume = {271 p.},
pages = {2009-1226}
}
|
| Chulliat A, Savary J, Telali K and Lalanne X (2009),
"Acquisition of 1-second data in IPGP magnetic observatories", In Proceedings of the XIIIth IAGA Workshop on geomagnetic observatory instruments, data acquisition and processing. Golden and Boulder, Colorado Vol. 271 p., pp. 2009-1226. |
| Abstract: Since 2003, INTERMAGNET has been recommending that magnetic observatories produce vector data sampled every second, instead of every minute. The scientific motivations for this upgrade are mainly that: (a) there is a growing demand from the space physics community of one-second magnetic data at the global scale for studying ULF waves in the ionosphere and the magnetosphere; (b) observatory data need to be synchronized with magnetic data produced by low-Earth orbiting satellites such as Oersted and CHAMP, which are sampled at 1 Hz. A user survey lead by Jeff Love (USGS) in 2005 helped define the scientific requirements for observatory one-second data, such as data resolution and accuracy, time-stamp accuracy and filtering specifications. Following this survey and the operational standards issued by INTERMAGNET, IPGP has been developing a new version of its VM391 3-axis, fluxgate magnetometer and a new acquisition system in order to meet these standards. These new instrument and system are now installed in Chambon la Forêt (CLF) magnetic observatory and will be installed in most IPGP magnetic observatories in the coming years, before the launch of the upcoming ESA Swarm mission. |
BibTeX:
@inproceedings{Chulliat-2009b-IAGAINTERMAGNET,
author = {Chulliat, A. and J. Savary and K. Telali and X. Lalanne},
editor = {J. Love},
title = {Acquisition of 1-second data in IPGP magnetic observatories},
booktitle = {Proceedings of the XIIIth IAGA Workshop on geomagnetic observatory instruments, data acquisition and processing},
year = {2009},
volume = {271 p.},
pages = {2009-1226}
}
|
| Fouassier D and Chulliat A (2009),
"Extending backwards to 1883 the French magnetic hourly data series", In Proceedings of the XIIIth IAGA Workshop on geomagnetic observatory instruments, data acquisition and processing. Golden and Boulder, Colorado Vol. 271, pp. 1226. |
| Abstract: Geomagnetic field variations have been continuously recorded near Paris since 1883: first in Parc St Maur (1883-1900), then in Val Joyeux (1901-1935) and eventually in Chambon la Forêt (since 1936). Until 1922, the field was recorded every hour, but only four instantaneous hourly values per day (every 6 hours) were published in yearbooks. Other hourly data, kept in hand-written notebooks, were never made available, even after the computer age. It was not until the end of 2006 that a systematic digitization began. Using a purposely designed software, 40 years of the 3 components H, D and Z (about 1,000,000 hourly values) were keyboarded, thoroughly checked and compared with the already digitized six-hour samples. These new data represent a significant improvement for external magnetic field studies, especially for rapid phenomena such as magnetic storms. To this date, the obtained series is the longest digitized, uninterrupted hourly data series to be made public. We hope this effort will trigger similar projects wherever old magnetic data are long forgotten in dusty observatory attics. |
BibTeX:
@inproceedings{Fouassier-2009-IAGAINTERMAGNET,
author = {Fouassier, D. and A. Chulliat},
editor = {J. Love},
title = {Extending backwards to 1883 the French magnetic hourly data series},
booktitle = {Proceedings of the XIIIth IAGA Workshop on geomagnetic observatory instruments, data acquisition and processing},
year = {2009},
volume = {271},
pages = {1226}
}
|
| Penquerc'h V and Chulliat A (2009),
"Variability of the Sq magnetic field with the solar radiation flux f10.7", In Proceedings of ESA's Second Swarm International Science Meeting. Potsdam, Germany [BibTeX] |
BibTeX:
@inproceedings{Penquerch-2009-Swarm,
author = {Penquerc'h, V. and A. Chulliat},
title = {Variability of the Sq magnetic field with the solar radiation flux f10.7},
booktitle = {Proceedings of ESA's Second Swarm International Science Meeting},
year = {2009}
}
|
| Truong F, Lalanne X and Chulliat A (2009),
"MAGIS: The information system of IPGP magnetic observatories", In Proceedings of the XIIIth IAGA Workshop on geomagnetic observatory instruments, data acquisition and processing. Golden and Boulder, Colorado Vol. 1226 |
| Abstract: The IPGP is in charge of twelve magnetic observatories, including 6 observatories run in cooperation with foreign institutions. These observatories are scattered all over the world. In order to improve collaboration between observers, daily maintenance and magnetic data processing, we created an information system where all technical information relevant to the network and all magnetic data in various stages of processing are archived. This system works like a community content sharing platform. It provides a simple way to access the technical information such as instrument characteristics, calibration data, observatory documentation, pictures, etc. The platform is now our only working tool for data loggers monitoring, routine scheduling, incidents logging, maintenance logging and absolute measurements collecting and pre-processing. The platform is based on web technology. This makes it independent from the local computer system of the user, simplifies software's updates and provides instant access to all technical information and magnetic data wherever the user is located. |
BibTeX:
@inproceedings{Truong-2009-IAGAINTERMAGNET,
author = {Truong, F. and X. Lalanne and A. Chulliat},
editor = {J. Love},
title = {MAGIS: The information system of IPGP magnetic observatories},
booktitle = {Proceedings of the XIIIth IAGA Workshop on geomagnetic observatory instruments, data acquisition and processing},
year = {2009},
volume = {1226}
}
|