| Autor: |
Xu, Shaosui1 shaosui.xu@ssl.berkeley.edu, Mitchell, David L.1, Ma, Yingjuan2, Weber, Tristan3,4, Brain, David A.3, Halekas, Jasper5, Ruhunusiri, Suranga5, DiBraccio, Gina4, Mazelle, Christian6 |
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| Zdroj: |
Journal of Geophysical Research. Space Physics. Dec2021, Vol. 126 Issue 12, p1-11. 11p. |
| Abstrakt: |
The motion of charged particles is governed by electromagnetic forces at high altitudes at Mars and thus the characterization of electrostatic potential and electric fields is important for understanding ion escape at Mars. In this study, we utilize measurements from the Mars Atmosphere and Volatile EvolutioN mission to derive electrostatic potentials above the collisional atmosphere at Mars. We find averaged potentials to be up to ∼100 V in the magnetosheath and down to ∼−70 V in the tail, with respect to the upstream. We then derive electric fields based on averaged potential maps, ranging ∼0.01−0.1 $\sim 0.01-0.1$ V/km. These data‐derived electric fields are in good agreement with ambipolar electric fields from a multi‐fluid magnetohydrodynamic (MHD) model. MHD results also reveal that these large electric fields mainly originate from the electron pressure gradient in the magnetosheath and in the transition region from the hot solar wind flow to the cold ionospheric flow. This work provides the first data‐based characterization of global ambipolar electric fields at Mars (outside of the main ionosphere). Plain Language Summary: The motion of charged particles is governed by electric and magnetic force at high altitudes at Mars and thus the characterization of electric fields is important for understanding ion escape, a form of atmospheric escape, at Mars. In this study, we utilize measurements from the Mars Atmosphere and Volatile EvolutioN mission to derive electric fields at high altitudes, which occur at density and/or temperature gradients in a collisionless plasma to maintain charge neutrality with highly mobile electrons and much slower moving ions. These data‐derived electric fields are in good agreement with electric fields from a magnetohydrodynamic model. Model results also reveal the plasma source of these electric fields. Our characterization of these electric fields provides a better understanding of the interaction between Mars and the Sun and, to a large extent, Mars' atmospheric escape. Key Points: This work provides the first data‐based characterization of global ambipolar electric fields at Mars (outside of the main ionosphere)We find averaged ambipolar potentials ranging from ∼−70 to +100 V and ambipolar electric fields of ∼0.01−0.1 $\sim 0.01-0.1$ V/kmMHD results show a good agreement with data‐derived electric fields and also suggest the plasma source of these ambipolar electric fields [ABSTRACT FROM AUTHOR] |
| Databáze: |
GreenFILE |
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