Journal article
THEMIS‐Based Model of the Ion‐to‐Electron Temperature Ratio in the Near‐Earth Magnetotail: Implications for Magnetosphere‐Ionosphere Coupling
Journal of geophysical research. Space physics, v 130(11), e2025JA034486
Nov 2025
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Abstract
Single‐fluid magnetohydrodynamic (MHD) simulations are one of the most advanced tools for investigating global magnetospheric dynamics. These simulations include magnetosphere–ionosphere (MI) coupling, which plays a key role in generating electric fields in the equatorial magnetosphere in response to energy input into the ionosphere. A critical component of this coupling is diffuse auroral precipitation from the magnetotail, typically modeled as a function of the thermal plasma pressure, , derived from the simulations. Since the energy flux of this precipitation is predominantly carried by electrons, the model must estimate the electron pressure contribution, . A common approach is to use the relation , where the ion‐to‐electron temperature ratio is prescribed based on magnetotail observations. In this technical report, we present a new model for that is parametrized by the equatorial magnetic field and the perpendicular plasma flow speed . This parametrization captures mesoscale variations of within fast plasma flows, thereby enabling incorporation of mesoscale physics of MI coupling into global MHD simulations.
We present a large statistics of the ion‐to‐electron temperature ratio in the near‐Earth's plasma sheet based on THEMIS for 2008–2024 We included the contribution of energetic ion population ( keV ions) in the ion temperature We constructed an empirical model of the ion‐to‐electron temperature ratio as a function of the plasma flow and the magnetic field
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Details
- Title
- THEMIS‐Based Model of the Ion‐to‐Electron Temperature Ratio in the Near‐Earth Magnetotail: Implications for Magnetosphere‐Ionosphere Coupling
- Creators
- Beckett Johnson-Walters - Coriell Institute For Medical ResearchDmitri L. Vainchtein (Corresponding Author) - Drexel UniversityAnton V. Artemyev - Planetary Science InstituteXiaojia Zhang - The University of Texas at Dallas
- Publication Details
- Journal of geophysical research. Space physics, v 130(11), e2025JA034486
- Publisher
- Wiley
- Number of pages
- 9
- Grant note
- NSF: 2400336 National Aeronautics and Space Administration: 80NSSC23K0658, 80NSSC22K0752
A.V.A. and X.J.Z. are grateful to Viacheslav Merkin, Kareem Sorathia, Anthony Sciola, and Michael Adam for very useful discussions of Ti/Te ${T}_{i}/{T}_{e}$ model implementation into global MHD simulations and to Vassilis Angelopoulos for helpful suggestions about THEMIS data analysis. Work of A.V.A. and X.J.Z. has been supported by NSF Grant 2400336 and NASA Grants 80NSSC23K0658, 80NSSC22K0752. We acknowledge support of NASA contract NAS5-02099 for the use of data from the THEMIS Mission, specifically K. H.Glassmeier, U. Auster and W. Baumjohann for the use of FGM data (provided under the lead of the Technical University of Braunschweig and with financial support through the German Ministry for Economy and Technology and the German Center for Aviation and Space (DLR) under contract 50 OC 0302).
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- C. and J. Nyheim Plasma Institute
- Web of Science ID
- WOS:001606991700001
- Scopus ID
- 2-s2.0-105020648125
- Other Identifier
- 991022130764104721