Articles | Volume 15, issue 2
https://doi.org/10.5194/gi-15-273-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/gi-15-273-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
THEMIS: spin axis magnetic field reconstruction
Adrian Pöppelwerth
CORRESPONDING AUTHOR
Institute of Geophysics and Extraterrestrial Physics, TU Braunschweig, Braunschweig, Germany
Hans-Ulrich Auster
Institute of Geophysics and Extraterrestrial Physics, TU Braunschweig, Braunschweig, Germany
Vassilis Angelopoulos
Department of Earth, Planetary and Space Sciences, University of California Los Angeles, Los Angeles, CA, USA
James M. McTiernan
Space Sciences Laboratory, University of California Berkeley, Berkeley, CA, USA
James W. Lewis
Space Sciences Laboratory, University of California Berkeley, Berkeley, CA, USA
Ferdinand Plaschke
Institute of Geophysics and Extraterrestrial Physics, TU Braunschweig, Braunschweig, Germany
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Lars Klingenstein, Niklas Grimmich, Yuri Y. Shprits, Adrian Pöppelwerth, and Ferdinand Plaschke
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We applied machine learning to investigate how the solar wind and Earth's geomagnetic activity control the position of the magnetopause, the boundary layer of Earth's magnetic field. Our results demonstrate that geomagnetic activity strongly influences this boundary and should be incorporated in predictive models. Using data from multiple spacecraft, we developed a simple mathematical description of the magnetopause distance that improves understanding of solar wind–magnetosphere interactions.
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In the magnetosheath, a near-Earth region of space, we observe increases in plasma velocity and density, so-called jets. As they propagate towards Earth, jets interact with the ambient plasma. We study this interaction with three spacecraft simultaneously to infer their sizes. While previous studies have investigated their size almost exclusively statistically, we demonstrate a new method of determining the sizes of individual jets.
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Lars Klingenstein, Niklas Grimmich, Yuri Y. Shprits, Adrian Pöppelwerth, and Ferdinand Plaschke
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We've compared the amplitude spectral densities of a fluxgate magnetometer (FGM) and an anisotropic magnetoresistive (AMR) magnetometer during ground testing with the amplitude spectral densities obtained in different regions of near-Earth space. The FGM can measure the fields in the different space regions and their fluctuations within a frequency range of 1 mHz to 2.5 Hz. The AMR magnetometer is only suitable for more turbulent regions such as the magnetosheath due to its higher noise levels.
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The magnetic mirror force bends the orbits of electrons precipitating into the atmosphere. It has been suggested that relativistic electrons make much less ionization due to the force than if it did not exist, but the actual effectivity in the atmospheric electron density has not been revealed. We used conjugated observational data from the ELFIN (Electron Losses and Fields INvestigation) satellite and the EISCAT (European Incoherent SCATter scientific radar system) Tromsø radar to find that the electron density decreased by about 40 % at 80 km altitude because of the force.
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The boundary of Earth's magnetic field, the magnetopause, deflects and reacts to the solar wind, the energetic particles emanating from the Sun. We find that certain types of solar wind favour the occurrence of deviations between the magnetopause locations observed by spacecraft and those predicted by models. In addition, the turbulent region in front of the magnetopause, the foreshock, has a large influence on the location of the magnetopause and thus on the accuracy of the model predictions.
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In our study, we looked at the boundary between the Earth's magnetic field and the interplanetary magnetic field emitted by the Sun, called the magnetopause. While other studies focus on the magnetopause motion near Earth's Equator, we have studied it in polar regions. The motion of the magnetopause is faster towards the Earth than towards the Sun. We also found that the occurrence of unusual magnetopause locations is due to similar solar influences in the equatorial and polar regions.
Adrian Pöppelwerth, Georg Glebe, Johannes Z. D. Mieth, Florian Koller, Tomas Karlsson, Zoltán Vörös, and Ferdinand Plaschke
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The upper detection limit in reciprocal space, the spatial Nyquist limit, is derived for arbitrary spatial dimensions for the wave telescope analysis technique. This is important as future space plasma missions will incorporate larger numbers of spacecraft (>4). Our findings are a key element in planning the spatial distribution of future multi-point spacecraft missions. The wave telescope is a multi-dimensional power spectrum estimator; hence, this can be applied to other fields of research.
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In this study, we use a multipoint analysis of conjugate magnetospheric and ionospheric observations to investigate the magnetospheric and ionospheric responses to fast flow bursts that are associated with different space weather conditions. The results show that ionospheric currents are connected to the magnetospheric flows for different space weather conditions. The connection is more apparent and global for flows that are associated with a geomagnetically active condition.
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Short summary
The Time History of Events and Macroscale Interactions during Substorms mission studies how the solar wind interacts with Earth’s magnetic field using five rotating spacecraft. After one spacecraft lost its measurements along its rotation axis, we used the two remaining magnetometer components with the spacecraft's spin to reconstruct the missing component with lower time resolution. A comparison with earlier data, when all components were available, shows that reconstruction is possible.
The Time History of Events and Macroscale Interactions during Substorms mission studies how the...