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Martian Thermospheric Density Responses to the February and March 2017 C4.1~B3.3 Solar Flare-Induced EUV-Enhancement from MAVEN Observations
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  • Peng Han,
  • Jiandong Liu,
  • Yawen Li,
  • Haibing Ruan,
  • Wentao Duan
Peng Han
School of Remote Sensing and Geomatics Engineering,Nanjing University of Information Science and Technology
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Jiandong Liu
Nanjing University of Information Science and Technology

Corresponding Author:jd_liu@nuist.edu.cn

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Yawen Li
School of Remote Sensing and Geomatics Engineering, Nanjing University of Information Science and Technology
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Haibing Ruan
Nanjing University of Information Science & Technology
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Wentao Duan
Nanjing University of Information Science & Technology
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Abstract

Mars thermosphere is responsive to solar activities. Previous studies have not examined the neutral density responses to the solar flares thoroughly due to lack of observations. In this paper, Martian thermospheric mass density responses to the February and March 2017 C4.1 and B3.3 solar flare-induced Extreme Ultraviolet (EUV)-enhancement are studied using Mars Atmosphere and Volatile EvolutioN (MAVEN) accelerometer (ACC)-derived observations. We focus on analyzing the relationship between the reactions of density and the solar flare indexes. Firstly, the density experiences 2 to 5 times increases during the event, which is equivalent to a temperature increment of 150 to 250 K. Secondly, both nightside and dayside density rise with the EUV-enhancement, which is coupled with the solar flares at all the observed latitudes. Thirdly, the Martian Crustal Magnetic Field (CMF) could alter the thermospheric background thermal structure, which might also have influence on the heating-process caused by the EUV-enhancement. The nightside density inflation during the February event is due to day-night atmospheric transport, while the dayside density expansion is heated by EUV (17-22 nm)-enhancement during the March event directly. The region with an intensive CMF magnitude could restrain the precipitating ions,resulting in cooling of the atmosphere in that area. The thermal structure perturbations caused by these flares-induced EUV-enhancement might trigger considerable augmentation of the Jeans Escape rates of some light volatiles, such as atomic Hydrogen (H) or even short-term hydrodynamic escape in some extreme cases.