44 results on '"Lars Tøffner-Clausen"'
Search Results
2. The CSES global geomagnetic field model (CGGM): an IGRF-type global geomagnetic field model based on data from the China Seismo-Electromagnetic Satellite
- Author
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Yanyan Yang, Gauthier Hulot, Pierre Vigneron, Xuhui Shen, Zeren Zhima, Bin Zhou, Werner Magnes, Nils Olsen, Lars Tøffner-Clausen, Jianpin Huang, Xuemin Zhang, Shigeng Yuan, Lanwei Wang, Bingjun Cheng, Andreas Pollinger, Roland Lammegger, Jianpin Dai, Jun Lin, Feng Guo, Jingbo Yu, Jie Wang, Yingyan Wu, Xudong Zhao, and Xinghong Zhu
- Subjects
CSES ,CGGM ,IGRF ,Geomagnetism ,Space magnetometry ,Geography. Anthropology. Recreation ,Geodesy ,QB275-343 ,Geology ,QE1-996.5 - Abstract
Abstract Using magnetic field data from the China Seismo-Electromagnetic Satellite (CSES) mission, we derive a global geomagnetic field model, which we call the CSES Global Geomagnetic Field Model (CGGM). This model describes the Earth’s magnetic main field and its linear temporal evolution over the time period between March 2018 and September 2019. As the CSES mission was not originally designed for main field modelling, we carefully assess the ability of the CSES orbits and data to provide relevant data for such a purpose. A number of issues are identified, and an appropriate modelling approach is found to mitigate these. The resulting CGGM model appears to be of high enough quality, and it is next used as a parent model to produce a main field model extrapolated to epoch 2020.0, which was eventually submitted on October 1, 2019 as one of the IGRF-13 2020 candidate models. This CGGM candidate model, the first ever produced by a Chinese-led team, is also the only one relying on a data set completely independent from that used by all other candidate models. A successful validation of this candidate model is performed by comparison with the final (now published) IGRF-13 2020 model and all other candidate models. Comparisons of the secular variation predicted by the CGGM parent model with the final IGRF-13 2020–2025 predictive secular variation also reveal a remarkable agreement. This shows that, despite their current limitations, CSES magnetic data can already be used to produce useful IGRF 2020 and 2020–2025 secular variation candidate models to contribute to the official IGRF-13 2020 and predictive secular variation models for the coming 2020–2025 time period. These very encouraging results show that additional efforts to improve the CSES magnetic data quality could make these data very useful for long-term monitoring of the main field and possibly other magnetic field sources, in complement to the data provided by missions such as the ESA Swarm mission.
- Published
- 2021
- Full Text
- View/download PDF
3. The CHAOS-7 geomagnetic field model and observed changes in the South Atlantic Anomaly
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Christopher C. Finlay, Clemens Kloss, Nils Olsen, Magnus D. Hammer, Lars Tøffner-Clausen, Alexander Grayver, and Alexey Kuvshinov
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Geomagnetism ,Secular variation ,Field modelling ,South Atlantic Anomaly ,Swarm ,Geography. Anthropology. Recreation ,Geodesy ,QB275-343 ,Geology ,QE1-996.5 - Abstract
Abstract We present the CHAOS-7 model of the time-dependent near-Earth geomagnetic field between 1999 and 2020 based on magnetic field observations collected by the low-Earth orbit satellites Swarm, CryoSat-2, CHAMP, SAC-C and Ørsted, and on annual differences of monthly means of ground observatory measurements. The CHAOS-7 model consists of a time-dependent internal field up to spherical harmonic degree 20, a static internal field which merges to the LCS-1 lithospheric field model above degree 25, a model of the magnetospheric field and its induced counterpart, estimates of Euler angles describing the alignment of satellite vector magnetometers, and magnetometer calibration parameters for CryoSat-2. Only data from dark regions satisfying strict geomagnetic quiet-time criteria (including conditions on IMF $$B_z$$ B z and $$B_y$$ B y at all latitudes) were used in the field estimation. Model parameters were estimated using an iteratively reweighted regularized least-squares procedure; regularization of the time-dependent internal field was relaxed at high spherical harmonic degree compared with previous versions of the CHAOS model. We use CHAOS-7 to investigate recent changes in the geomagnetic field, studying the evolution of the South Atlantic weak field anomaly and rapid field changes in the Pacific region since 2014. At Earth’s surface a secondary minimum of the South Atlantic Anomaly is now evident to the south west of Africa. Green’s functions relating the core–mantle boundary radial field to the surface intensity show this feature is connected with the movement and evolution of a reversed flux feature under South Africa. The continuing growth in size and weakening of the main anomaly is linked to the westward motion and gathering of reversed flux under South America. In the Pacific region at Earth’s surface between 2015 and 2018 a sign change has occurred in the second time derivative (acceleration) of the radial component of the field. This acceleration change took the form of a localized, east–west oriented, dipole. It was clearly recorded on ground, for example at the magnetic observatory at Honolulu, and was seen in Swarm observations over an extended region in the central and western Pacific. Downward continuing to the core–mantle boundary, we find this event originated in field acceleration changes at low latitudes beneath the central and western Pacific in 2017.
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- 2020
- Full Text
- View/download PDF
4. CM6: a comprehensive geomagnetic field model derived from both CHAMP and Swarm satellite observations
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Terence J. Sabaka, Lars Tøffner-Clausen, Nils Olsen, and Christopher C. Finlay
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Geomagnetism ,Field modeling ,CHAMP and Swarm satellites ,Tides ,Geography. Anthropology. Recreation ,Geodesy ,QB275-343 ,Geology ,QE1-996.5 - Abstract
Abstract From the launch of the Ørsted satellite in 1999, through the CHAMP mission from 2000 to 2010, and now with the Swarm constellation mission starting in 2013, satellite magnetometry has provided excellent monitoring of the near-Earth magnetic field regime. The advanced Comprehensive Inversion scheme has been applied to data before Swarm and to the Swarm data itself, but now for the first time to all the satellite data in this new era, culminating in the CM6 model. The highlights of this model include not only a continuous core magnetic field description over the entire time period 1999 to 2019.5 in good agreement with the CHAOS model series, but the addition of two new oceanic tidal magnetic sources: the larger lunar elliptic semi-diurnal constituent $$N_2$$ N 2 and the lunar diurnal constituent $$O_1$$ O 1 . CM6 is also the parent model of the NASA/GSFC candidates for the DGRF2015 and IGRF2020 in response to the IGRF-13 call. This paper provides a full report on the development of CM6.
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- 2020
- Full Text
- View/download PDF
5. Magnetic observations from CryoSat-2: calibration and processing of satellite platform magnetometer data
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Nils Olsen, Giuseppe Albini, Jerome Bouffard, Tommaso Parrinello, and Lars Tøffner-Clausen
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Geomagnetism ,Magnetic satellites ,Magnetometer calibration ,CryoSat-2 ,Geography. Anthropology. Recreation ,Geodesy ,QB275-343 ,Geology ,QE1-996.5 - Abstract
Abstract We describe and discuss the preprocessing and calibration steps applied to the magnetic data measured by the three “platform magnetometers” on-board the CryoSat-2 satellite. The calibration is performed by comparing the magnetometer sensor readings with magnetic field values for the time and position of the satellite as given by the CHAOS-6 geomagnetic field model. We allow for slow temporal variations of the calibration parameters by solving for scale values, offsets, and non-orthogonalities in monthly bins, and account for non-linearities as well as the magnetic disturbances caused by battery, solar panel and magnetorquer currents. Fully calibrated magnetic vector data, together with time and position, are provided as daily files in CDF data format at swarm-diss.eo.esa.int. The data show good agreement with Swarm satellite magnetic measurements during close encounters (rms difference between 1 and 5 nT for inter-satellite distances below 300 km).
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- 2020
- Full Text
- View/download PDF
6. A comprehensive model of Earth’s magnetic field determined from 4 years of Swarm satellite observations
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Terence J. Sabaka, Lars Tøffner-Clausen, Nils Olsen, and Christopher C. Finlay
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Geomagnetism ,Field modeling ,Swarm satellites ,Tides ,Geography. Anthropology. Recreation ,Geodesy ,QB275-343 ,Geology ,QE1-996.5 - Abstract
Abstract The European Space Agency’s three-satellite constellation Swarm, launched in November 2013, has provided unprecedented monitoring of Earth’s magnetic field via a unique set of gradiometric and multi-satellite measurements from low Earth orbit. In order to exploit these measurements, an advanced “comprehensive inversion” (CI) algorithm has been developed to optimally separate the various major magnetic field sources in the near-Earth regime. The CI algorithm is used to determine Swarm Level-2 (L2) magnetic field data products that include the core, lithospheric, ionospheric, magnetospheric, and associated induced sources. In addition, it has become apparent that the CI is capable of extracting the magnetic signal associated with the oceanic principal lunar semidiurnal tidal constituent $$M_2$$ M2 to such an extent that it has been added to the L2 data product line. This paper presents the parent model of the Swarm L2 CI products derived with measurements from the first 4 years of the Swarm mission and from ground observatories, denoted as “CIY4,” including the new product describing the magnetic signal of the $$M_2$$ M2 oceanic tide.
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- 2018
- Full Text
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7. Earth's Magnetic Field Models from Comprehensive Inversion of 9 Years of Swarm, CSES, and CryoSat Data
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Lars Tøffner-Clausen
- Abstract
The ESA Swarm DISC (Data, Innovation, and Science Cluster), a consortium of several research institutions, has been established with a goal of deriving science products by combination of data from the three ESA Swarm spacecraft as well as other spacecraft. Here we present the results of the Comprehensive Inversion (CI) magnetic field modelling by the Swarm DISC team at DTU Space and NASA Goddard. The CI chain takes full advantage of the Swarm constellation by doing a comprehensive co-estimation of the magnetic fields from Earth's core, lithosphere, ionosphere, and magnetosphere together with induced fields from Earth's mantle and oceans using single and dual satellite gradient information from Swarm supplemented by scalar data from the Chinese CSES (China Seismo-Electromagnetic Satellite), the platform magnetometers onboard CryoSat-2, as well as data from ground based magnetic observatories.
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- 2023
8. Swarm Langmuir probes' data quality validation and future improvements
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Filomena Catapano, Stephan Buchert, Enkelejda Qamili, Thomas Nilsson, Jerome Bouffard, Christian Siemes, Igino Coco, Raffaella D'Amicis, Lars Tøffner-Clausen, Lorenzo Trenchi, Poul Erik Holmdahl Olsen, and Anja Stromme
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Atmospheric Science ,Geology ,Oceanography - Abstract
Swarm is the European Space Agency (ESA)'s first Earth observation constellation mission, which was launched in 2013 to study the geomagnetic field and its temporal evolution. Two Langmuir probes aboard each of the three Swarm satellites provide in situ measurements of plasma parameters, which contribute to the study of the ionospheric plasma dynamics. To maintain a high data quality for scientific and technical applications, the Swarm products are continuously monitored and validated via science-oriented diagnostics. This paper presents an overview of the data quality of the Swarm Langmuir probes' measurements. The data quality is assessed by analysing short and long data segments, where the latter are selected to be sufficiently long enough to consider the impact of the solar activity. Langmuir probe data have been validated through comparison with numerical models, other satellite missions, and ground observations. Based on the outcomes from quality control and validation activities conducted by ESA, as well as scientific analysis and feedback provided by the user community, the Swarm products are regularly upgraded. In this paper, we discuss the data quality improvements introduced with the latest baseline, and how the data quality is influenced by the solar cycle. In particular, plasma measurements are more accurate in day-side regions during high solar activity, while electron temperature measurements are more reliable during night side at middle and low latitudes during low solar activity. The main anomalies affecting the Langmuir probe measurements are described, as well as possible improvements in the derived plasma parameters to be implemented in future baselines.
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- 2022
9. Magnetic observations from CryoSat-2: calibration and processing of satellite platform magnetometer data
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Tommaso Parrinello, Giuseppe Albini, Lars Tøffner-Clausen, Nils Olsen, and Jerome Bouffard
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CryoSat-2 ,lcsh:QB275-343 ,Scale (ratio) ,Magnetometer ,lcsh:Geodesy ,lcsh:QE1-996.5 ,lcsh:Geography. Anthropology. Recreation ,Geology ,Geomagnetism ,Magnetorquer ,law.invention ,Magnetic field ,Magnetic satellites ,lcsh:Geology ,Earth's magnetic field ,lcsh:G ,Space and Planetary Science ,law ,Position (vector) ,Physics::Space Physics ,Calibration ,Magnetometer calibration ,Satellite ,Remote sensing - Abstract
We describe and discuss the preprocessing and calibration steps applied to the magnetic data measured by the three “platform magnetometers” on-board the CryoSat-2 satellite. The calibration is performed by comparing the magnetometer sensor readings with magnetic field values for the time and position of the satellite as given by the CHAOS-6 geomagnetic field model. We allow for slow temporal variations of the calibration parameters by solving for scale values, offsets, and non-orthogonalities in monthly bins, and account for non-linearities as well as the magnetic disturbances caused by battery, solar panel and magnetorquer currents. Fully calibrated magnetic vector data, together with time and position, are provided as daily files in CDF data format at swarm-diss.eo.esa.int. The data show good agreement with Swarm satellite magnetic measurements during close encounters (rms difference between 1 and 5 nT for inter-satellite distances below 300 km).
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- 2020
10. Swarm Langmuir Probes' data quality and future improvements
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Filomena Catapano, Lorenzo Trenchi, Stephan Buchert, Thomas Nilsson, Poul Erik Holmdahl Olsen, Igino Coco, E. Qamili, Christian Siemes, Raffaella D'Amicis, Anja Stromme, Jerome Bouffard, and Lars Tøffner-Clausen
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Earth observation ,Earth's magnetic field ,Computer science ,Data quality ,media_common.quotation_subject ,Real-time computing ,Swarm behaviour ,Satellite ,Quality (business) ,Baseline (configuration management) ,Constellation ,media_common - Abstract
Swarm is ESA's (European Space Agency) first Earth observation constellation mission, which was launched in 2013 to study the geomagnetic field and its temporal evolution. Two Langmuir Probes (LPs) on board of each of the three Swarm satellites provide very accurate measurements of plasma parameters, which contribute to the the study of the ionospheric plasma dynamics. To maintain a high data quality for scientific and operational applications, the Swarm products are continuously monitored and validated via science-oriented diagnostics. This paper presents an overview of the data quality of the Swarm Langmuir Probes' measurements. The data quality is assessed by analysing short and long data segments, where the latter are selected sufficiently long to consider the impact of the solar activity. Langmuir Probes data have been validated through comparison with numerical models, other satellite missions, and ground observations. Based on the outcomes from quality control and validation activities conduced by ESA, as well as scientific analysis and feedback provided by the user community, the Swarm products are regularly upgraded. In this paper we discuss the data quality improvements introduced with the latest baseline, and how the data quality is influenced by the solar cycle. The main anomaly affecting the LP measurements is described, as well as possible improvements to be implemented in future baselines.
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- 2021
11. Correction to: Probing 3-D electrical conductivity of the mantle using 6 years of Swarm, CryoSat-2 and observatory magnetic data and exploiting matrix Q-responses approach
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Nils Olsen, Alexander Grayver, Lars Tøffner-Clausen, and Alexey Kuvshinov
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Physics ,QB275-343 ,QE1-996.5 ,Spherical harmonics ,Geology ,Ranging ,Geophysics ,Transfer function ,Electromagnetic induction ,Matrix (mathematics) ,Earth's magnetic field ,Space and Planetary Science ,Geography. Anthropology. Recreation ,Satellite ,Magnetic potential ,Geodesy - Abstract
This study presents results of mapping three-dimensional (3-D) variations of the electrical conductivity in depths ranging from 400 to 1200 km using 6 years of magnetic data from the Swarm and CryoSat-2 satellites as well as from ground observatories. The approach involves the 3-D inversion of matrix Q-responses (transfer functions) that relate spherical harmonic coefficients of external (inducing) and internal (induced) origin of the magnetic potential. Transfer functions were estimated from geomagnetic field variations at periods ranging from 2 to 40 days. We study the effect of different combinations of input data sets on the transfer functions. We also present a new global 1-D conductivity profile based on a joint analysis of satellite tidal signals and global magnetospheric Q-responses.
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- 2021
12. Swarm Mission: instruments performance, data availability, quality and future evolutions
- Author
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Enkelejda Qamili, Filomena Catapano, Lars Tøffner-Clausen, Stephan Buchert, Christian Siemes, Anna Mizerska, Jonas Bregnhøj Nielsen, Thomas Nilsson, Jan Miedzik, Maria Eugenia Mazzocato, Lorenzo Trenchi, Jerome Bouffard, Anja Stromme, Pierre Vogel, and Berta Hoyos ortega
- Abstract
The European Space Agency (ESA) Swarm mission, launched on November 2013, continue to provide very accurate measurements of the strength, direction and variation of the Earth’s magnetic field. These data together with precise navigation, accelerometer, electric field, plasma density and temperature measurements, are crucial for a better understanding of the Earth’s interior and its environment. This paper will provide a status update of the Swarm Instrument performance after seven years of operations. Moreover, we will provide full details on the new Swarm Level 1b product baseline of Magnet and Plasma data which will be generated and distributed soon to the whole Swarm Community. Please note that the main evolutions to be introduced in the Swarm L1B Algorithm are: i) computation of the Sun induced magnetic disturbance (dB_Sun) on the Absolute Scalar Magnetometer (ASM) and Vector Field Magnetometer (VFM) data; ii) computation of systematic offset between Langmuir Probes (LP) measurements ad ground observations derived from Incoherent Scatter Radars (IRS) located at middle, low, and equatorial latitudes. These and further improvements are planned to be included in the upcoming versions of the Swarm Level 1b products, aiming at achieving the best data quality for scientific applications.
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- 2021
13. The CSES Global Geomagnetic Field Model (CGGM): An IGRF type global geomagnetic field model based on data from the China Seismo-Electromagnetic Satellite
- Author
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Xudong Zhao, Pierre Vigneron, Xuemin Zhang, Andreas Pollinger, Jingbo Yu, Feng Guo, Jie Wang, Werner Magnes, Xinghong Zhu, Shigeng Yuan, Bin Zhou, Roland Lammegger, Jianpin Huang, Lars Tøffner-Clausen, Nils Olsen, Yingyan Wu, Gauthier Hulot, Yanyan Yang, Jianpin Dai, Lanwei Wang, Xuhui Shen, Bingjun Cheng, Jun Lin, Zeren Zhima, National Institute of Natural Hazards, Ministry of Emergency Management of China, Beijing, 100085, China, Université de Paris, Institut de physique du globe de Paris, CNRS, F-75005 Paris, France, National Space Science Center, Chinese Academy of Sciences, Beijing, 100190, China, Space Research Institute, Austrian Academy of Sciences, Graz, 8042, Austria, DTU Space, National Space Institute, Technical University of Denmark, 2800 Kongens Lyngby, Denmark, Institute of Earthquake Forecasting, China Earthquake Administration, Beijing, 100036, China, DFH Satellite Co. Ltd., Beijing, 100081, China, Institute of Earthquake Forecasting, China Earthquake Administration, Beijing, 100036, Institute of Experimental Physics, Graz University of Technology, Graz, 8010, Austria, Beijing Special Engineering Design and research Institute, Beijing, 100028, China, China Centre for Resources Satellite Data and Application, Beijing, 100094, China, Hebei GEO University, Shijiazhuang 050031, China, Institute of Geophysics, China Earthquake Administration, Beijing, 100081, China, Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Space Research Institute of Austrian Academy of Sciences (IWF), Austrian Academy of Sciences (OeAW), and Graz University of Technology [Graz] (TU Graz)
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010504 meteorology & atmospheric sciences ,Computer science ,[SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph] ,lcsh:Geodesy ,010502 geochemistry & geophysics ,01 natural sciences ,CSES ,Space magnetometry ,0105 earth and related environmental sciences ,lcsh:QB275-343 ,CGGM ,Epoch (reference date) ,lcsh:QE1-996.5 ,lcsh:Geography. Anthropology. Recreation ,Swarm behaviour ,Geology ,Geomagnetism ,Geodesy ,Field (geography) ,Secular variation ,IGRF ,lcsh:Geology ,Data set ,Earth's magnetic field ,lcsh:G ,Space and Planetary Science ,Data quality ,Satellite - Abstract
Using magnetic field data from the China Seismo-Electromagnetic Satellite (CSES) mission, we derive a global geomagnetic field model, which we call the CSES Global Geomagnetic Field Model (CGGM). This model describes the Earth’s magnetic main field and its linear temporal evolution over the time period between March 2018 and September 2019. As the CSES mission was not originally designed for main field modelling, we carefully assess the ability of the CSES orbits and data to provide relevant data for such a purpose. A number of issues are identified, and an appropriate modelling approach is found to mitigate these. The resulting CGGM model appears to be of high enough quality, and it is next used as a parent model to produce a main field model extrapolated to epoch 2020.0, which was eventually submitted on October 1, 2019 as one of the IGRF-13 2020 candidate models. This CGGM candidate model, the first ever produced by a Chinese-led team, is also the only one relying on a data set completely independent from that used by all other candidate models. A successful validation of this candidate model is performed by comparison with the final (now published) IGRF-13 2020 model and all other candidate models. Comparisons of the secular variation predicted by the CGGM parent model with the final IGRF-13 2020–2025 predictive secular variation also reveal a remarkable agreement. This shows that, despite their current limitations, CSES magnetic data can already be used to produce useful IGRF 2020 and 2020–2025 secular variation candidate models to contribute to the official IGRF-13 2020 and predictive secular variation models for the coming 2020–2025 time period. These very encouraging results show that additional efforts to improve the CSES magnetic data quality could make these data very useful for long-term monitoring of the main field and possibly other magnetic field sources, in complement to the data provided by missions such as the ESA Swarm mission.
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- 2021
14. International Geomagnetic Reference Field: the thirteenth generation
- Author
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Ciaran Beggan, Santiago Marsal, Martin Rother, Johannes Wicht, Valeriy G. Petrov, Fco. Javier Pavón-Carrasco, Shin'ya Nakano, Nils Olsen, William R. Brown, Vincent Lesur, M. C. Nair, Xuhui Shen, Alexandre Fournier, N. R. Schnepf, Monika Korte, Terence J. Sabaka, Benoit Langlais, T. Bondar, Lars Tøffner-Clausen, Werner Magnes, Takuto Minami, Thomas Jager, Andrew Tangborn, Alexander Grayver, Gauthier Hulot, Guillaume Ropp, J. Matzka, Christopher C. Finlay, J. E. Mound, Joan Miquel Torta, Sabrina Sanchez, Grace Cox, Diana Saturnino, Foteini Vervelidou, Alexey Kuvshinov, A. Woods, Pierre Vigneron, M. C. Metman, Hagay Amit, Hiroaki Toh, Loïc Huder, Jean-Michel Leger, Matthias Holschneider, Nicolas Gillet, Erwan Thébault, Ingo Wardinski, Susan Macmillan, Weijia Kuang, Clemens Kloss, Achim Morschhauser, Yanyan Yang, Z. Zeren, Claudia Stolle, Julien Aubert, Philip W. Livermore, Patrick Alken, Aude Chambodut, S. Califf, Magnus Danel Hammer, Mioara Mandea, Bin Zhou, J. Varner, Julien Baerenzung, F. J. Lowes, Arnaud Chulliat, Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado [Boulder]-National Oceanic and Atmospheric Administration (NOAA), NOAA National Centers for Environmental Information (NCEI), National Oceanic and Atmospheric Administration (NOAA), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), British Geological Survey [Edinburgh], British Geological Survey (BGS), Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), University of Applied Sciences Potsdam (FHP), Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation (IZMIRAN), Russian Academy of Sciences [Moscow] (RAS), Institut de physique du globe de Strasbourg (IPGS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Louis Pasteur - Strasbourg I-Centre National de la Recherche Scientifique (CNRS), Division of Geomagnetism, DTU Space, Technical, Technical University of Denmark [Lyngby] (DTU), Université Grenoble Alpes (UGA), Institute of Geophysics [ETH Zürich], Department of Earth Sciences [Swiss Federal Institute of Technology - ETH Zürich] (D-ERDW), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich)- Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), Département Systèmes (DSYS), Commissariat à l'énergie atomique et aux énergies alternatives - Laboratoire d'Electronique et de Technologie de l'Information (CEA-LETI), Direction de Recherche Technologique (CEA) (DRT (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Technologique (CEA) (DRT (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), German Research Centre for Geosciences - Helmholtz-Centre Potsdam (GFZ), NASA Goddard Space Flight Center (GSFC), School of Earth and Environment [Leeds] (SEE), University of Leeds, University of Northumbria at Newcastle [United Kingdom], Austrian Academy of Sciences, Centre National d’Études Spatiales [Paris] (CNES), Observatori de l'Ebre (OE), Universitat Ramon Llull [Barcelona] (URL)-Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Graduate School of Environmental Studies [Nagoya], Nagoya University, The Institute of Statistical Mathematics (Tokyo ), Universidad Complutense de Madrid = Complutense University of Madrid [Madrid] (UCM), Instituto de Geociencias [Madrid] (IGEO), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC)-Universidad Complutense de Madrid = Complutense University of Madrid [Madrid] (UCM), Max Planck Institute for Solar System Research (MPS), Max-Planck-Gesellschaft, Institute of Crustal Dynamics [Beijing], China Earthquake Administration (CEA), Division of Earth and Planetary Sciences [Kyoto], Kyoto University [Kyoto], State Key Laboratory of Space Weather, National Space Science Center, Institut de Physique du Globe de Paris (IPGP (UMR_7154)), Institut national des sciences de l'Univers (INSU - CNRS)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Danmarks Tekniske Universitet = Technical University of Denmark (DTU), Universidad Complutense de Madrid = Complutense University of Madrid [Madrid] (UCM)-Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research (MPS), Kyoto University, and Consejo Superior de Investigaciones Científicas [Madrid] (CSIC)-Universitat Ramon Llull [Barcelona] (URL)
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Magnetic declination ,IGRF ,Magnetic feld modeling ,Geomagnetism ,010504 meteorology & atmospheric sciences ,Field (physics) ,[SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph] ,lcsh:Geodesy ,010502 geochemistry & geophysics ,01 natural sciences ,Physics::Geophysics ,0105 earth and related environmental sciences ,lcsh:QB275-343 ,Previous generation ,Epoch (reference date) ,Aeronomy ,lcsh:QE1-996.5 ,lcsh:Geography. Anthropology. Recreation ,Física atmosférica ,Spherical harmonics ,Geology ,Geodesy ,Secular variation ,lcsh:Geology ,lcsh:G ,Space and Planetary Science ,Physics::Space Physics ,International Geomagnetic Reference Field ,Astrophysics::Earth and Planetary Astrophysics ,Magnetic field modeling - Abstract
Earth, Planets and Space, 73 (1), ISSN:1343-8832, ISSN:1880-5981
- Published
- 2021
15. Mapping 3-D mantle electrical conductivity using Swarm, Cryosat-2 and ground observatory data
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Alexander Grayver, Alexey Kuvshinov, Nils Olsen, and Lars Tøffner-Clausen
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Electrical resistivity and conductivity ,Observatory ,Swarm behaviour ,Geophysics ,Geology ,Mantle (geology) - Abstract
In this contribution, we report on our recent attempts to detect lateral variations of the electrical conductivity at mid mantle depths (400 – 1600 km) using 6 years of Swarm, Cryosat-2 and observatory magnetic data. The approach involves a three-dimensional (3-D) inversion of matrix Q-responses. These responses relate spherical harmonic coefficients of external (inducing) and internal (induced) parts of the magnetic potential, derived for geomagnetic variations at periods longer than 1 day and hence mainly describing signals of magnetospheric origin (i.e. external also to satellites, as required). In addition to the inversion results, we discuss potential ways to improve the recovery of 3-D conductivity structures in the mantle.
- Published
- 2020
16. Six years of Swarm: instruments and data quality status
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Jerome Bouffard, Christian Siemes, Pierre Vogel, Stephan Buchert, Anja Stromme, Jan Miedzik, Lorenzo Trenchi, E. Qamili, Lars Tøffner-Clausen, and Filomena Catapano
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Computer science ,Data quality ,Swarm behaviour ,Data mining ,computer.software_genre ,computer - Abstract
The European Space Agency (ESA) Swarm mission, launched in November 2013, continue to provide the best ever survey of the geomagnetic field and its temporal evolution. These high quality measurements of the strength, direction and variation of the magnetic field, together with precise navigation, accelerometer, electric field, plasma density and temperature measurements, are crucial for a better understanding of the Earth’s interior and its environment. This paper will provide an overview of the Swarm Instruments and data quality status and product evolution after six years of operations, focusing on the most significant payload investigations to improve science quality, data validation activities and results along with future validation/calibration plans.
- Published
- 2020
17. CM6: a comprehensive geomagnetic field model derived from both CHAMP and Swarm satellite observations
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Nils Olsen, Christopher C. Finlay, Terence J. Sabaka, and Lars Tøffner-Clausen
- Subjects
lcsh:QB275-343 ,CHAMP and Swarm satellites ,Magnetometer ,lcsh:Geodesy ,lcsh:QE1-996.5 ,lcsh:Geography. Anthropology. Recreation ,Swarm behaviour ,Geology ,Inversion (meteorology) ,Chaos model ,Geomagnetism ,Tides ,Geodesy ,law.invention ,Magnetic field ,lcsh:Geology ,Earth's magnetic field ,lcsh:G ,Space and Planetary Science ,law ,Satellite data ,Field modeling ,Constellation - Abstract
From the launch of the Ørsted satellite in 1999, through the CHAMP mission from 2000 to 2010, and now with the Swarm constellation mission starting in 2013, satellite magnetometry has provided excellent monitoring of the near-Earth magnetic field regime. The advanced Comprehensive Inversion scheme has been applied to data before Swarm and to the Swarm data itself, but now for the first time to all the satellite data in this new era, culminating in the CM6 model. The highlights of this model include not only a continuous core magnetic field description over the entire time period 1999 to 2019.5 in good agreement with the CHAOS model series, but the addition of two new oceanic tidal magnetic sources: the larger lunar elliptic semi-diurnal constituent $$N_2$$N2 and the lunar diurnal constituent $$O_1$$O1. CM6 is also the parent model of the NASA/GSFC candidates for the DGRF2015 and IGRF2020 in response to the IGRF-13 call. This paper provides a full report on the development of CM6.
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- 2020
18. The CHAOS-7 geomagnetic field model and observed changes in the South Atlantic Anomaly
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Alexey Kuvshinov, Nils Olsen, Lars Tøffner-Clausen, Clemens Kloss, Magnus Danel Hammer, Alexander Grayver, and Christopher C. Finlay
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South Atlantic Anomaly ,010504 meteorology & atmospheric sciences ,Magnetometer ,lcsh:Geodesy ,FOS: Physical sciences ,010502 geochemistry & geophysics ,Computer Science::Digital Libraries ,01 natural sciences ,Latitude ,law.invention ,Physics::Geophysics ,Physics - Geophysics ,law ,Swarm ,14. Life underwater ,Physics::Atmospheric and Oceanic Physics ,0105 earth and related environmental sciences ,lcsh:QB275-343 ,Geomagnetism ,Secular variation ,Field modelling ,Full Paper ,lcsh:QE1-996.5 ,lcsh:Geography. Anthropology. Recreation ,Spherical harmonics ,Geology ,Geodesy ,Magnetic field ,Geophysics (physics.geo-ph) ,lcsh:Geology ,Dipole ,Earth's magnetic field ,lcsh:G ,13. Climate action ,Space and Planetary Science ,Physics::Space Physics - Abstract
We present the CHAOS-7 model of the time-dependent near-Earth geomagnetic field between 1999 and 2020 based on magnetic field observations collected by the low-Earth orbit satellites Swarm, CryoSat-2, CHAMP, SAC-C and Ørsted, and on annual differences of monthly means of ground observatory measurements. The CHAOS-7 model consists of a time-dependent internal field up to spherical harmonic degree 20, a static internal field which merges to the LCS-1 lithospheric field model above degree 25, a model of the magnetospheric field and its induced counterpart, estimates of Euler angles describing the alignment of satellite vector magnetometers, and magnetometer calibration parameters for CryoSat-2. Only data from dark regions satisfying strict geomagnetic quiet-time criteria (including conditions on IMF $$B_z$$ B z and $$B_y$$ B y at all latitudes) were used in the field estimation. Model parameters were estimated using an iteratively reweighted regularized least-squares procedure; regularization of the time-dependent internal field was relaxed at high spherical harmonic degree compared with previous versions of the CHAOS model. We use CHAOS-7 to investigate recent changes in the geomagnetic field, studying the evolution of the South Atlantic weak field anomaly and rapid field changes in the Pacific region since 2014. At Earth’s surface a secondary minimum of the South Atlantic Anomaly is now evident to the south west of Africa. Green’s functions relating the core–mantle boundary radial field to the surface intensity show this feature is connected with the movement and evolution of a reversed flux feature under South Africa. The continuing growth in size and weakening of the main anomaly is linked to the westward motion and gathering of reversed flux under South America. In the Pacific region at Earth’s surface between 2015 and 2018 a sign change has occurred in the second time derivative (acceleration) of the radial component of the field. This acceleration change took the form of a localized, east–west oriented, dipole. It was clearly recorded on ground, for example at the magnetic observatory at Honolulu, and was seen in Swarm observations over an extended region in the central and western Pacific. Downward continuing to the core–mantle boundary, we find this event originated in field acceleration changes at low latitudes beneath the central and western Pacific in 2017.
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- 2020
- Full Text
- View/download PDF
19. Joint inversion of satellite‐detected tidal and magnetospheric signals constrains electrical conductivity and water content of the upper mantle and transition zone
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Alexander Grayver, Lars Tøffner-Clausen, Federico D. Munch, Amir Khan, A. V. Kuvshinov, and Terence J. Sabaka
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010504 meteorology & atmospheric sciences ,Inversion (meteorology) ,Geophysics ,Conductivity ,010502 geochemistry & geophysics ,01 natural sciences ,Article ,Mantle (geology) ,Physics::Geophysics ,Magnetic field ,13. Climate action ,Electrical resistivity and conductivity ,Transition zone ,General Earth and Planetary Sciences ,Satellite ,Astrophysics::Earth and Planetary Astrophysics ,14. Life underwater ,Water content ,Geology ,0105 earth and related environmental sciences - Abstract
We present a new global electrical conductivity model of Earth's mantle. The model was derived by using a novel methodology, which is based on inverting satellite magnetic field measurements from different sources simultaneously. Specifically, we estimated responses of magnetospheric origin and ocean tidal magnetic signals from the most recent Swarm and CHAMP data. The challenging task of properly accounting for the ocean effect in the data was addressed through full three-dimensional solution of Maxwell's equations. We show that simultaneous inversion of magnetospheric and tidal magnetic signals results in a model with much improved resolution. Comparison with laboratory-based conductivity profiles shows that obtained models are compatible with a pyrolytic composition and a water content of 0.01 wt% and 0.1 wt% in the upper mantle and transition zone, respectively.
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- 2017
20. In-flight scalar calibration and characterisation of the Swarm magnetometry package
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Niels Olsen Saraiva Camara, Vincent Lesur, Nils Olsen, Lars Tøffner-Clausen, and Christopher C. Finlay
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010504 meteorology & atmospheric sciences ,Field (physics) ,Magnetometer ,Scalar (mathematics) ,010502 geochemistry & geophysics ,01 natural sciences ,law.invention ,law ,Calibration ,Swarm ,Physics::Atomic Physics ,0105 earth and related environmental sciences ,Remote sensing ,Physics ,Spacecraft ,Basis (linear algebra) ,business.industry ,Swarm behaviour ,Geology ,Geomagnetism ,Instrument calibration ,Computational physics ,Satellite ,Space and Planetary Science ,Physics::Space Physics ,business - Abstract
We present the in-flight scalar calibration and characterisation of the Swarm magnetometry package consisting of the absolute scalar magnetometer, the vector magnetometer, and the spacecraft structure supporting the instruments. A significant improvement in the scalar residuals between the pairs of magnetometers is demonstrated, confirming the high performance of these instruments. The results presented here, including the characterisation of a Sun-driven disturbance field, form the basis of the correction of the magnetic vector measurements from Swarm which is applied to the Swarm Level 1b magnetic data.
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- 2016
21. International Geomagnetic Reference Field: the 12th generation
- Author
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Weijia Kuang, Valeriy G. Petrov, Aimin Du, Reyko Schachtschneider, Tatiana I. Zvereva, Ciaran Beggan, Stefan Maus, Vincent Lesur, Isabelle Fratter, Laura Brocco, Martin Rother, Olivier Sirol, Mohamed Hamoudi, Gauthier Hulot, Susan Macmillan, Arnaud Chulliat, Aude Chambodut, Terence J. Sabaka, Pierre Vigneron, F. J. Lowes, Benoit Langlais, Alan Thomson, T. Bondar, Andrew Tangborn, Alexandre Fournier, Ingo Wardinski, Xavier Lalanne, Julien Aubert, Elisabeth Canet, Diana Saturnino, Patrick Alken, François Civet, Brian Hamilton, Monika Korte, Jean-Michel Leger, François Bertrand, Nils Olsen, Lars Tøffner-Clausen, Erwan Thébault, Pierdavide Coïsson, Nicolas Gillet, Christopher C. Finlay, Olivier Barrois, Victoria Ridley, Mioara Mandea, Thomas Jager, A. Boness, Chandrasekharan Manoj, Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), National Space Institute [Lyngby] (DTU Space), Danmarks Tekniske Universitet = Technical University of Denmark (DTU), British Geological Survey [Edinburgh], British Geological Survey (BGS), Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado [Boulder]-National Oceanic and Atmospheric Administration (NOAA), NOAA Aeronomy Laboratory, National Oceanic and Atmospheric Administration (NOAA), Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS), Institut des Sciences de la Terre (ISTerre), Université Joseph Fourier - Grenoble 1 (UJF)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-PRES Université de Grenoble-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Commissariat à l'énergie atomique et aux énergies alternatives - Laboratoire d'Electronique et de Technologie de l'Information (CEA-LETI), Direction de Recherche Technologique (CEA) (DRT (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation (IZMIRAN), Russian Academy of Sciences [Moscow] (RAS), Earth and Planetary Magnetism Group [Zürich], Institut für Geophysik [Zürich], Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich)- Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), Institut de physique du globe de Strasbourg (IPGS), Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institute of Geology and Geophysics [Beijing] (IGG), Chinese Academy of Sciences [Beijing] (CAS), Centre National d'Études Spatiales [Toulouse] (CNES), German Research Centre for Geosciences - Helmholtz-Centre Potsdam (GFZ), Département de Géophysique, Université des Sciences et de la Technologie Houari Boumediene = University of Sciences and Technology Houari Boumediene [Alger] (USTHB), GeoForschungsZentrum - Helmholtz-Zentrum Potsdam (GFZ), Planetary Geodynamics Laboratory [Greenbelt], NASA Goddard Space Flight Center (GSFC), School of Chemistry [Newcastle], Newcastle University [Newcastle], Centre National d’Études Spatiales [Paris] (CNES), Joint Center for Earth Systems Technology [Baltimore] (JCET), NASA Goddard Space Flight Center (GSFC)-University of Maryland [Baltimore County] (UMBC), University of Maryland System-University of Maryland System, Laboratoire de Planétologie et Géodynamique UMR6112 (LPG), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Nantes - Faculté des Sciences et des Techniques, Université de Nantes (UN)-Université de Nantes (UN)-Université d'Angers (UA), Technical University of Denmark [Lyngby] (DTU), Centre National de la Recherche Scientifique (CNRS)-Université de La Réunion (UR)-Université Paris Diderot - Paris 7 (UPD7)-IPG PARIS-Institut national des sciences de l'Univers (INSU - CNRS), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut national des sciences de l'Univers (INSU - CNRS)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Université Joseph Fourier - Grenoble 1 (UJF), Laboratoire d'Electronique et des Technologies de l'Information (CEA-LETI), Université Grenoble Alpes (UGA)-Direction de Recherche Technologique (CEA) (DRT (CEA)), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology in Zürich [Zürich] (ETH Zürich)-Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology in Zürich [Zürich] (ETH Zürich), Université des Sciences et de la Technologie Houari Boumediene [Alger] (USTHB), University of Maryland [Baltimore County] (UMBC), University of Maryland System-University of Maryland System-NASA Goddard Space Flight Center (GSFC), Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), and Centre National de la Recherche Scientifique (CNRS)-PRES Université de Grenoble-Université Joseph Fourier - Grenoble 1 (UJF)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])
- Subjects
Magnetic declination ,010504 meteorology & atmospheric sciences ,Field (physics) ,Epoch (reference date) ,[SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph] ,Aeronomy ,Spherical harmonics ,Geology ,Geophysics ,Geomagnetism ,010502 geochemistry & geophysics ,Geodesy ,01 natural sciences ,7. Clean energy ,IGRF Correspondence/Findings ,Magnetic field ,Secular variation ,IGRF ,13. Climate action ,Space and Planetary Science ,Field modeling ,International Geomagnetic Reference Field ,0105 earth and related environmental sciences - Abstract
International audience; The 12th generation of the International Geomagnetic Reference Field (IGRF) was adopted in December 2014 by the Working Group V-MOD appointed by the International Association of Geomagnetism and Aeronomy (IAGA). It updates the previous IGRF generation with a definitive main field model for epoch 2010.0, a main field model for epoch 2015.0, and a linear annual predictive secular variation model for 2015.0-2020.0. Here, we present the equations defining the IGRF model, provide the spherical harmonic coefficients, and provide maps of the magnetic declination, inclination, and total intensity for epoch 2015.0 and their predicted rates of change for 2015.0-2020.0. We also update the magnetic pole positions and discuss briefly the latest changes and possible future trends of the Earth's magnetic field.
- Published
- 2015
22. The Swarm Initial Field Model for the 2014 geomagnetic field
- Author
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Rune Floberghagen, Pierre Vigneron, Nils Olsen, Lars Tøffner-Clausen, Terence J. Sabaka, Ciaran Beggan, Vincent Lesur, Gauthier Hulot, Christopher C. Finlay, Eigil Friis-Christensen, Roger Haagmans, Stavros Kotsiaros, Arnaud Chulliat, Hermann Lühr, National Space Institute [Lyngby] (DTU Space), Technical University of Denmark [Lyngby] (DTU), Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS), German Research Centre for Geosciences - Helmholtz-Centre Potsdam (GFZ), British Geological Survey [Edinburgh], British Geological Survey (BGS), NOAA National Geophysical Data Center (NGDC), National Oceanic and Atmospheric Administration (NOAA), Planetary Geodynamics Laboratory [Greenbelt], NASA Goddard Space Flight Center (GSFC), ESA Centre for Earth Observation (ESRIN), European Space Agency (ESA), European Space Research and Technology Centre (ESTEC), Centre National de la Recherche Scientifique (CNRS)-Université de La Réunion (UR)-Université Paris Diderot - Paris 7 (UPD7)-IPG PARIS-Institut national des sciences de l'Univers (INSU - CNRS), Directorate of Earth Observation Programmes, ESRIN, via Galileo Galilei, 2, 00044 Frascati, Italy, and Directorate of Earth Observation Programmes, ESRIN
- Subjects
Physics ,Field (physics) ,Magnetometer ,[SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph] ,Swarm behaviour ,Geodesy ,Secular variation ,Magnetic field ,law.invention ,Geophysics ,Earth's magnetic field ,law ,Physics::Space Physics ,General Earth and Planetary Sciences ,Satellite ,SWARM constellation mission ,Intensity (heat transfer) ,Geomagnetic field ,Physics::Atmospheric and Oceanic Physics - Abstract
International audience; Data from the first year of ESA's Swarm constellation mission are used to derive the Swarm Initial Field Model (SIFM), a new model of the Earth's magnetic field and its time variation. In addition to the conventional magnetic field observations provided by each of the three Swarm satellites, explicit advantage is taken of the constellation aspect by including east-west magnetic intensity gradient information from the lower satellite pair. Along-track differences in magnetic intensity provide further information concerning the north-south gradient. The SIFM static field shows excellent agreement (up to at least degree 60) with recent field models derived from CHAMP data, providing an initial validation of the quality of the Swarm magnetic measurements. Use of gradient data improves the determination of both the static field and its secular variation, with the mean misfit for east-west intensity differences between the lower satellite pair being only 0.12 nT.
- Published
- 2015
23. In-flight spacecraft magnetic field monitoring using scalar/vector gradiometry
- Author
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Peter Brauer, Lars Tøffner-Clausen, T. Risbo, José M.G. Merayo, and Fritz Primdahl
- Subjects
Physics ,Field (physics) ,Spacecraft ,business.industry ,Magnetometer ,Applied Mathematics ,Oersted ,Scalar (mathematics) ,Magnetic field ,law.invention ,Earth's magnetic field ,law ,Physics::Space Physics ,Satellite ,business ,Instrumentation ,Engineering (miscellaneous) ,Remote sensing - Abstract
Earth magnetic field mapping from planetary orbiting satellites requires a spacecraft magnetic field environment control program combined with the deployment of the magnetic sensors on a boom in order to reduce the measurement error caused by the local spacecraft field. Magnetic mapping missions (Magsat, Oersted, CHAMP, SAC-C MMP and the planned ESA Swarm project) carry a vector magnetometer and an absolute scalar magnetometer for in-flight calibration of the vector magnetometer scale values and for monitoring of the inter-axes angles and offsets over time intervals from months to years. This is done by comparing the two magnetometer outputs for several days and for as many different external field directions and amplitudes in the satellite frame as available. The vector and the scalar sensor may be placed of the order of 2 m apart and at the end of an about 10 m long boom counted from the spacecraft centre-of-gravity. In line with the classical dual vector sensors technique for monitoring the spacecraft magnetic field, this paper proposes and demonstrates that a similar combined scalar/vector gradiometry technique is feasible by using the measurements from the boom-mounted scalar and vector sensors onboard the Oersted satellite. For Oersted, a large difference between the pre-flight determined spacecraft magnetic field and the in-flight estimate exists causing some concern about the general applicability of the dual sensors technique.
- Published
- 2006
24. Calibration of the Ørsted vector magnetometer
- Author
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Lars Tøffner-Clausen, T. Risbo, O.V. Nielsen, Jean-Michel Leger, John Leif Jørgensen, José M.G. Merayo, Nils Olsen, Peter Brauer, Fritz Primdahl, and Terence J. Sabaka
- Subjects
Magnetometer ,Instrumentation ,Coordinate system ,Geology ,Geodesy ,Magnetic field ,law.invention ,Euler angles ,symbols.namesake ,Earth's magnetic field ,Space and Planetary Science ,law ,Calibration ,symbols ,Rotation (mathematics) - Abstract
The vector fluxgate magnetometer of the Orsted satellite is routinely calibrated by comparing its output with measurements of the absolute magnetic intensity from the Overhauser instrument, which is the second magnetometer of the satellite. We describe the method used for and the result obtained in that calibration. Using three years of data the agreement between the two magnetometers after calibration is 0.33 nT rms (corresponding to better than ± 1 nT for 98% of the data, and better than ± 2 nT for 99.94% of the data). We also report on the determination of the transformation between the magnetometer coordinate system and the reference system of the star imager. This is done by comparing the magnetic and attitude measurements with a model of Earth’s magnetic field. The Euler angles describing this rotation are determined in this way with an accuracy of better than 4 arcsec.
- Published
- 2003
25. Updating the CHAOS series of field models using Swarm data and resulting candidate models for IGRF-12
- Author
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Christopher C. Finlay, Nils Olsen, and Lars Tøffner-Clausen
- Subjects
Physics::Space Physics - Abstract
Ten months of data from ESA's Swarm mission, together with recent ground observatory monthly means, are used to update the CHAOS series of geomagnetic field models with a focus on time-changes of the core field. As for previous CHAOS field models quiet-time, night-side, data selection criteria are employed and the magnetic field data is used in the instrument frame with Euler angles for the rotation to the North-East-Center (NEC) frame co-estimated. The new model spans more than 15 years between 1999 and 2014, with the internal field being time-dependent up to spherical harmonic degree 20 using a 6th order spline representation with knot points spaced at 0.5 year intervals. The resulting field model is able to consistently fit data from six independent low Earth orbit satellites: Oersted, CHAMP, SAC-C and the three Swarm satellites. As an example, we present comparisons of the excellent model fit obtained to both the Swarm data and the CHAMP data. The new model also provides a good description of observatory secular variation, capturing rapid field evolution events during the past decade. Maps of the core surface field and its secular variation can already be extracted in the Swarm-era. We therefore conclude that Swarm data is suitable for building high-resolution models of the large-scale internal field, and proceed to extract IGRF-12 candidate models for the main field in epochs 2010 and 2015, as well as the predicted linear secular variarion for 2015-2020. The properties of these IGRF candidate models are briefly presented.
- Published
- 2014
26. Use of the Comprehensive Inversion method for Swarm satellite data analysis
- Author
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Terence J. Sabaka, Nils Olsen, and Lars Tøffner-Clausen
- Subjects
Space and Planetary Science ,Observatory ,Satellite constellation ,A priori and a posteriori ,Inverse transform sampling ,Swarm behaviour ,Geology ,Inversion (meteorology) ,Algorithm ,Synthetic data ,Remote sensing ,Weighting - Abstract
An advanced algorithm, known as the “Comprehensive Inversion” (CI), is presented for the analysis of Swarm measurements to generate a consistent set of Level-2 data products to be delivered by the Swarm “Satellite Constellation Application and Research Facility” (SCARF) to the European Space Agency (ESA). This new algorithm improves on a previously developed version in several ways, including the ability to process ground-based observatory data, estimation of rotations describing the alignment of vector magnetometer measurements with a known reference system, and the inclusion of ionospheric induction effects due to an a priori 3-dimensional conductivity model. However, the most substantial improvements entail the application of a mechanism termed “Selective Infinite Variance Weighting” (SIVW), which mitigates the effects of non-zero mean systematic noise and allows for the exploitation of gradient information from the low-altitude Swarm satellite pair to determine small-scale lithospheric fields, and an improvement in the treatment of attitude error due to noise in star-tracking systems over previously established methods. The advanced CI algorithm is validated by applying it to synthetic data from a full simulation of the Swarm mission, where it is found to significantly exceed all mandatory and most target accuracy requirements.
- Published
- 2013
27. The Swarm Satellite Constellation Application and Research Facility (SCARF) and Swarm data products
- Author
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Erwan Thébault, Jose van den IJssel, Vincent Lesur, Gauthier Hulot, Jan Rauberg, Christoph Püthe, Alan Thomson, Rune Floberghagen, Gernot Plank, Stefan Maus, Pieter Visser, Terence J. Sabaka, Martin Rother, Max Noja, Pierre Vigneron, Jaeheung Park, Ciaran Beggan, Lars Tøffner-Clausen, Alexey Kuvshinov, Arnaud Chulliat, Eelco Doornbos, Poul Erik Holmdahl Olsen, Nils Olsen, Claudia Stolle, J. Encarnacao, Reyko Schachtschneider, Brian Hamilton, Patricia Ritter, Patrick Alken, Hermann Lühr, Olivier Sirol, Eigil Friis-Christensen, Jakub Velímský, Susan Macmillan, National Space Institute [Lyngby] (DTU Space), Technical University of Denmark [Lyngby] (DTU), ESA Centre for Earth Observation (ESRIN), European Space Agency (ESA), NOAA National Geophysical Data Center (NGDC), National Oceanic and Atmospheric Administration (NOAA), Institut de Physique du Globe de Paris, British Geological Survey, Murchison House, British Geological Survey (BGS), Delft University of Technology (TU Delft), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), German Research Centre for Geosciences - Helmholtz-Centre Potsdam (GFZ), British Geological Survey [Edinburgh], Centre of Excellence for International Courts (iCourt), University of Copenhagenn, GeoForschungsZentrum - Helmholtz-Zentrum Potsdam (GFZ), European Space Research and Technology Centre (ESTEC), Planetary Geodynamics Laboratory [Greenbelt], NASA Goddard Space Flight Center (GSFC), Department of Geophysics, Faculty of Mathematics and Physics, Charles University in Prague, Faculty of Mathematics and Physics [Charles University of Praha], and Charles University [Prague] (CU)-Charles University [Prague] (CU)
- Subjects
010504 meteorology & atmospheric sciences ,Data products ,Meteorology ,Earth’s magnetic field ,[SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph] ,Real-time computing ,Satellite constellation ,Swarm behaviour ,Geology ,ionosphere ,electromagnetic induction ,010502 geochemistry & geophysics ,Swarm satellites ,01 natural sciences ,comprehensive inversion ,Earth system science ,core field ,Earth's magnetic field ,Space and Planetary Science ,Physics::Space Physics ,magnetosphere ,lithosphere ,0105 earth and related environmental sciences ,Constellation - Abstract
Swarm a three satellite constellation to study the dynamics of the Earth's magnetic field and its interactions with the Earth system is expected to be launched in late 2013. The objective of the Swarm mission is to provide the best ever survey of the geomagnetic field and its temporal evolution in order to gain new insights into the Earth system by improving our understanding of the Earth's interior and environment. In order to derive advanced models of the geomagnetic field (and other higher level data products) it is necessary to take explicit advantage of the constellation aspect of Swarm. The Swarm SCARF (Satellite Constellation Application and Research Facility) has been established with the goal of deriving Level 2 products by combination of data from the three satellites and of the various instruments. The present paper describes the Swarm input data products (Level lb and auxiliary data) used by SCARF the various processing chains of SCARF and the Level 2 output data products determined by SCARF. Copyright © The Society of Geomagnelism and Earth Planetary and Space Sciences (SGEPSS).
- Published
- 2013
28. CHAOS-2 - A geomagnetic field model derived from one decade of continuous satellite data
- Author
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Nils Olsen, Lars Tøffner-Clausen, Terence J. Sabaka, Mioara Mandea, and 2.3 Earth's Magnetic Field, 2.0 Physics of the Earth, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum
- Subjects
Physics ,Ionospheric dynamo region ,Mathematical analysis ,Spherical harmonics ,550 - Earth sciences ,Geodesy ,Magnetic field ,Time changes ,Geophysics ,Earth's magnetic field ,Geochemistry and Petrology ,Regularization (physics) ,Satellite data ,Time derivative - Abstract
SUMMARY We have derived a model of the near-Earth's magnetic field using more than 10 yr of high-precision geomagnetic measurements from the three satellites Orsted, CHAMP and SAC-C. This model is an update of the two previous models, CHAOS (Olsen et al. 2006) and xCHAOS (Olsen & Mandea 2008). Data selection and model parameterization follow closely those chosen for deriving these models. The main difference concerns the maximum spherical harmonic degree of the static field (n= 60 compared to n= 50 for CHAOS and xCHAOS), and of the core field time changes, for which spherical harmonic expansion coefficients up to n= 20 are described by order 5 splines (with 6-month knot spacing) spanning the years from 1997.0 to 2009.5. Compared to its predecessors, the temporal regularization of the CHAOS-2 model is also modified. Indeed, second and higher order time derivatives of the core field are damped by minimizing the second time derivative of the squared magnetic field intensity at the core–mantle boundary. The CHAOS-2 model describes rapid time changes, as monitored by the ground magnetic observatories, much better than its predecessors.
- Published
- 2009
29. Feasibility of a Constellation of Miniature Satellites for Perform ing Measurements of the Magnetic Field of the Earth
- Author
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Susanne Vennerstrøm, Michael Thomsen, José M.G. Merayo, Lars Tøffner-Clausen, Nils Olsen, and Peter Brauer
- Subjects
Solar minimum ,Solar wind ,Earth's magnetic field ,Geography ,Payload ,Drag ,Satellite ,Solar maximum ,Constellation ,Remote sensing - Abstract
This paper studies the requirements for a small constellation of satellites to perform measurements of the magnetic field of the Earth and a payload and boom design for such a mission is discussed. After studying communication, power and mass requirements it is found that it is feasible to develop a 10 x10 x 30 cm3 satellite with a mass of about 2.5,kg, which can fulfill such a mission. We also study the feasibility of controlling a constellation of such small satellites by means of air drag by extracting one or more flaps. It is found that it is indeed possible, but for best performance it is limited to altitudes around 450 to 550,km, depending on the time of launch with regard to the solar sunspot cycle.
- Published
- 2008
30. CHAOS - a model of the Earth’s magnetic field derived from CHAMP, Ørsted, and SAC-C magnetic satellite data
- Author
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Mioara Mandea, Nils Olsen, Terence J. Sabaka, Lars Tøffner-Clausen, Sungchan Choi, Martin Rother, and Hermann Lühr
- Subjects
Physics ,Field (physics) ,Geomagnetic secular variation ,Magnetometer ,Mathematical analysis ,Spherical harmonics ,550 - Earth sciences ,Geodesy ,law.invention ,Magnetic field ,Physics::Geophysics ,Euler angles ,symbols.namesake ,Geophysics ,Earth's magnetic field ,Geochemistry and Petrology ,law ,Time derivative ,symbols - Abstract
SUMMARY We have derived a model of the near-Earth magnetic field (up to spherical harmonic degree n = 50 for the static field, and up to n = 18 for the first time derivative) using more than 6.5 yr of high-precision geomagnetic measurements from the three satellites Orsted, CHAMP and SAC-C taken between 1999 March and 2005 December. Our modelling approach goes in several aspects beyond that used for recent models: (i) we use different data selection criteria and allow for higher geomagnetic activity (index Kp ≤ 2o), thus we include more data than previous models; (ii) we describe the temporal variation of the core field by splines (for n ≤ 14); (iii) we take magnetometer vector data in the instrument frame and co-estimate the Euler angles that describe the transformation from the magnetometer frame to the star imager frame, avoiding the inconsistency of using vector data that have been aligned using a different (pre-existing) field model; (iv) we account for the bending of the CHAMP optical bench connecting magnetometer and star imager by estimating Euler angles in 10 day segments and (v) we co-estimate degree-1 external fields separately for every 12 hr interval. The model provides a reliable representation of the static (core and crustal) field up to spherical harmonic degree n = 40, and of the first time derivative up to n = 15.
- Published
- 2006
31. The CHAOS-3 geomagnetic field model and candidates for the 11th generation IGRF
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Nils Olsen, Terence J. Sabaka, Mioara Mandea, and Lars Tøffner-Clausen
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010504 meteorology & atmospheric sciences ,Mathematical analysis ,Spherical harmonics ,Geology ,Chaos model ,010502 geochemistry & geophysics ,Geodesy ,01 natural sciences ,Secular variation ,Magnetic field ,Earth's magnetic field ,Observatory ,Space and Planetary Science ,Regularization (physics) ,Time derivative ,0105 earth and related environmental sciences - Abstract
As a part of the 11th generation IGRF defined by IAGA, we propose a candidate model for the DGRF 2005, a candidate model for IGRF 2010 and a candidate model for the mean secular variation between 2010 and 2015. These candidate models, the derivation of which is described in the following, are based on the latest model in the CHAOS model series, called “CHAOS-3”. This model is derived from more than 10 years of satellite and ground observatory data. Maximum spherical harmonic degree of the static field is n = 60. The core field time changes are expressed by spherical harmonic expansion coefficients up to n = 20, described by order 6 splines (with 6-month knot spacing) spanning the time interval 1997.0–2010.0. The third time derivative of the squared magnetic field intensity is regularized at the core-mantle boundary. No spatial regularization is applied.
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32. A Model of the Earth's Magnetic Field From Two Year of Swarm Satellite Constellation Data
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Nils Olsen, Finlay, Christopher C., Lars Tøffner-Clausen, and Stavros Kotsiaros
33. The CHAOS-4 Geomagnetic Field Model
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Christopher C. Finlay, Hermann Lühr, Ingo Michaelis, Lars Tøffner-Clausen, Terence J. Sabaka, Nils Olsen, and Jan Rauberg
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Chaos (genus) ,Ionospheric dynamo region ,Geophysics ,Earth's magnetic field ,biology ,Geomagnetic secular variation ,Geochemistry and Petrology ,Inverse theory ,biology.organism_classification ,Geology ,Physics::Geophysics - Abstract
We present CHAOS-4, a new version in the CHAOS model series, which aims to describe the Earth's magnetic field with high spatial and temporal resolution. Terms up to spherical degree of at least n = 85 for the lithospheric field, and up to n = 16 for the time-varying core field are robustly determined.More than 14 yr of data from the satellites Ørsted, CHAMP and SAC-C, augmented with magnetic observatory monthly mean values have been used for this model. Maximum spherical harmonic degree of the static (lithospheric) field is n = 100. The core field is expressed by spherical harmonic expansion coefficients up to n = 20; its time-evolution is described by order six splines, with 6-month knot spacing, spanning the time interval 1997.0-2013.5. The third time derivative of the squared radial magnetic field component is regularized at the core-mantle boundary. No spatial regularization is applied to the core field, but the high-degree lithospheric field is regularized for n > 85.CHAOS-4 model is derived by merging two submodels: its low-degree part has been derived using similar model parametrization and data sets as used for previous CHAOS models (but of course including more recent data), while its high-degree lithospheric field part is solely determined from low-altitude CHAMP satellite observations taken during the last 2 yr (2008 September-2010 September) of the mission. We obtain a good agreement with other recent lithospheric field models like MF7 for degrees up to n = 85, confirming that lithospheric field structures down to a horizontal wavelength of 500 km are currently robustly determined.
34. A model of Earth’s magnetic field derived from 2 years of Swarm satellite constellation data
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Niels Olsen Saraiva Camara, Nils Olsen, Lars Tøffner-Clausen, Christopher C. Finlay, and Stavros Kotsiaros
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Physics ,010504 meteorology & atmospheric sciences ,Field (physics) ,Satellite constellation ,Swarm behaviour ,Geology ,Dipole model of the Earth's magnetic field ,Geophysics ,Geomagnetism ,010502 geochemistry & geophysics ,01 natural sciences ,L-shell ,Magnetic field ,Earth's magnetic field ,Space and Planetary Science ,Field modeling ,Physics::Space Physics ,Magnetic potential ,Swarm satellites ,0105 earth and related environmental sciences - Abstract
More than 2 years of magnetic field data taken by the three-satellite constellation mission Swarm are used to derive a model of Earth’s magnetic field and its time variation. This model is called SIFMplus. In addition to the magnetic field observations provided by each of the three Swarm satellites, explicit advantage is taken of the constellation aspect of Swarm by including East–West magnetic intensity and vector field gradient information from the lower satellite pair. Along-track differences of the magnetic intensity as well as of the vector components provide further information concerning the North–South gradient. The SIFMplus model provides a description of the static lithospheric field that is very similar to models determined from CHAMP data, up to at least spherical harmonic degree $$n=75$$ . Also the core field part of SIFMplus, with a quadratic time dependence for $$n \le 6$$ and a linear time dependence for $$n=7$$ –15, demonstrates the possibility to determine high-quality field models from only 2 years of Swarm data, thanks to the unique constellation aspect of Swarm. To account for the magnetic signature caused by ionospheric electric currents at polar latitudes we co-estimate, together with the model of the core, lithospheric and large-scale magnetospheric fields, a magnetic potential that depends on quasi-dipole latitude and magnetic local time.
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35. Determination of the IGRF 2000 model
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Nils Olsen, Lars Tøffner-Clausen, and Terence J. Sabaka
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Magnetic measurements ,Earth's magnetic field ,Space and Planetary Science ,Epoch (astronomy) ,Estimation theory ,Oersted ,Scalar (mathematics) ,Geology ,Geophysics ,Geodesy ,Data selection ,Mathematics - Abstract
The IGRF 2000 has been estimated from magnetic measurements taken by the Orsted sattelite in summer 1999. For this purpose, three models have been derived: The first two models were estimated using a few geomagnetic quiet days in May and September 1999, respectively. The third model, called Oersted(10c/99), was derived from scalar data spanning six months and vector data spanning four months. In order to get a model for epoch 2000.0, the IGRF 95 secular variaion model has been applied to the data. The IGRF 2000 model was taken to be the internal degree/order 10 portion of Oersted(10c/99). We describe the data selection, model parameterization, parameter estimation and an evaluation of the three models.
36. Swarm: Recent Progress in Analysis of the Sun Induced Magnetic Disturbance
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Lars Tøffner-Clausen, Vincent Lesur, Peter Brauer, Nils Olsen, Christopher C. Finlay, and Enkelejda Qamili
37. Towards CHAOS-5 - How can Swarm contribute?
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Finlay, Christopher C., Nils Olsen, and Lars Tøffner-Clausen
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The launch of ESA's satellite trio Swarm in November 2013 opens an exciting new chapter in the observation and monitoring of Earth's magnetic field from space. We report preliminary results from an extension of the CHAOS series of geomagnetic field models to include both scalar and vector field observations from the three Swarm satellites, along with the most recent quasi-definitive ground observatory data. The fit of this new update CHAOS field model to the Swarm observations will be presented in detail providing useful insight the initial Swarm data. Enhancements of the CHAOS modelling scheme include a 1 minute time resolution for the RC index and anisotropic weighting of vector field data depending on quasi-dipole latitude. We shall also report on the perspective given by the initial Swarm data on rapid field changes currently taking place in the Atlantic sector.
38. DTU candidate field models for IGRF-12 and the CHAOS-5 geomagnetic field model
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Niels Olsen Saraiva Camara, Lars Tøffner-Clausen, Christopher C. Finlay, and Nils Olsen
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Physics ,Field (physics) ,Spherical harmonics ,Swarm behaviour ,Geology ,Geomagnetism ,Geodesy ,IGRF ,Secular variation ,Magnetic field ,Field modelling ,Acceleration ,Earth's magnetic field ,Space and Planetary Science ,Swarm ,Vector field - Abstract
We present DTU’s candidate field models for IGRF-12 and the parent field model from which they were derived,CHAOS-5. Ten months of magnetic field observations from ESA’s Swarm mission, together with up-to-date ground observatory monthly means, were used to supplement the data sources previously used to construct CHAOS-4. Theinternal field part of CHAOS-5, from which our IGRF-12 candidate models were extracted, is time-dependent up to spherical harmonic degree 20 and involves sixth-order splines with a 0.5 year knot spacing. In CHAOS-5, comparedwith CHAOS-4, we update only the low-degree internal field model (degrees 1 to 24) and the associated external field model. The high-degree internal field (degrees 25 to 90) is taken from the same model CHAOS-4h, based onlow-altitude CHAMP data, which was used in CHAOS-4.We find that CHAOS-5 is able to consistently fit magnetic field data from six independent low Earth orbit satellites:Ørsted, CHAMP, SAC-C and the three Swarm satellites (A, B and C). It also adequately describes the secular variationmeasured at ground observatories. CHAOS-5 thus contributes to an initial validation of the quality of the Swarmmagnetic data, in particular demonstrating that Huber weighted rms model residuals to Swarm vector field data arelower than those to Ørsted and CHAMP vector data (when either one or two star cameras were operating). CHAOS-5shows three pulses of secular acceleration at the core surface over the past decade; the 2006 and 2009 pulses have previously been documented, but the 2013 pulse has only recently been identified. The spatial signature of the 2013pulse at the core surface, under the Atlantic sector where it is strongest, is well correlated with the 2006 pulse, but anti-correlated with the 2009 pulse.
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39. Level-2 product generation for the Swarm satellite constellation mission
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Poul Erik Holmdahl Olsen, Lars Tøffner-Clausen, and Nils Olsen
40. Swarm Level 2 Comprehensive Inversion, 2016 Production
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Lars Tøffner-Clausen, Terence Sabaka, Nils Olsen, and Christopher C. Finlay
41. Use of Swarm data to study the core surface magnetic field
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Finlay, Christopher C., Nils Olsen, and Lars Tøffner-Clausen
42. Changes in Earth's core-generated magnetic field, as observed by Swarm
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Finlay, Christopher C., Nils Olsen, Nicolas Gillet, Stavros Kotsiaros, Lars Tøffner-Clausen, and Magnus Danel Hammer
43. Bridging the gap between champ and swarm using oersted and ground observatory data
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Finlay, Christopher C., Nils Olsen, Luehr Hermann, Sabaka, Terrence J., Lars Tøffner-Clausen, Corona, J. Jesus Silva, and Böhnel, Harald
44. Magnetic Package data quality overview
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Enkelejda Qamili, Giuseppe Ottavianelli, Nils Olsen, Lars Tøffner-Clausen, Riccardo Mecozzi, Igino Coco, Pierre Vogel, and Rune Floberghagen
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