Average plasma sheet polytropic index as observed by THEMIS
| Autor: | Dennis Frühauff, Karl-Heinz Glassmeier, Johannes Z. D. Mieth |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: |
Atmospheric Science
Equation of state 010504 meteorology & atmospheric sciences 01 natural sciences Article 0103 physical sciences Earth and Planetary Sciences (miscellaneous) Veröffentlichung der TU Braunschweig Magnetohydrodynamic drive lcsh:Science 010303 astronomy & astrophysics 0105 earth and related environmental sciences Thermodynamic process ddc:5 Magnetospheric physics -- magnetotail -- plasma sheet Physics ddc:538 lcsh:QC801-809 Plasma sheet Geology Astronomy and Astrophysics Plasma Geophysics Polytropic process lcsh:QC1-999 Computational physics lcsh:Geophysics. Cosmic physics Heat flux Space and Planetary Science ddc:53 Physics::Space Physics ddc:520 lcsh:Q ddc:52 Astrophysics::Earth and Planetary Astrophysics Parametrization lcsh:Physics |
| Zdroj: | Annales Geophysicae 35 (2017), S. 253–262--http://www.bibliothek.uni-regensburg.de/ezeit/?1458425--https://www.ann-geophys.net/--https://www.ann-geophys.net/volumes.html--http://link.springer.com/journal/585--1432-0576 Annales Geophysicae, Vol 35, Pp 253-262 (2017) |
| ISSN: | 1432-0576 |
| Popis: | Multi-spacecraft data from the years 2008 to 2015 of the THEMIS mission particularly in the near-Earth plasma sheet are used in order to empirically determine the polytropic index in the quiet and active time magnetotail. The results of a number of previous studies in the 1990s can be confirmed. An analysis of the total database, although showing poor correlation, results in an average polytropic index of γ = 1. 72. The active time plasma sheet is well correlated with an average γ = 1. 49. However, the data scattering suggests that the analysis of the data in total is not adequate. In order to reduce the timescales, individual spacecraft orbits are analyzed, giving a broad distribution of polytropic indices throughout the plasma sheet. The major part of the distribution falls in a range between γ = 0. 67 and γ = 2. Our results indicate a variety of thermodynamic processes in the magnetotail and an all-time presence of heat exchange of the plasma. A description of the plasma sheet using an equation of state with a single γ is probably inadequate. This necessitates the application of more sophisticated approaches, such as a parametrization of the heat flux vector in magnetohydrodynamic equations or a superposition of polytropic indices. |
| Databáze: | OpenAIRE |
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