Response of the Martian upper thermosphere to the lower atmospheric dust activity is studied using unique observations made together by the Mars Orbiter Mission (MOM) and the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft. The Mars Exospheric Neutral Composition Analyzer (MENCA)/MOM and the Neutral Gas and Ion Mass Spectrometer (NGIMS)/MAVEN have simultaneously (on the same day) measured the neutral densities in the Martian thermosphere on 5, 8, 10, 13, 16, and 29 June 2018. The measurement period falls in the onset and progression time of the planet‐encircling dust event (PEDE) in the Mars lower atmosphere. During this time, the inbound trajectories of MAVEN and MOM spacecraft occurred on the dawnside and duskside, respectively. Using these observations, we found that thermospheric densities both on the dawnside and duskside are enhanced associated with the onset and growth of PEDE‐2018. The enhancement, however, is more on the duskside than on the dawn, showing the dawn‐dusk asymmetry. The densities on the duskside reach their maximum on 29 June 2018, close to the time of peak dust activity. These results are explained by considering the local time asymmetries in radiative heating of the lower atmosphere and subsequent expansion of the thermosphere due to PEDE‐2018. Furthermore, O/CO₂ ratios below 220‐km altitude become one on the dawnside, whereas they are always <0.2 at the dusk. This indicates that radiative cooling is more effective on the dawnside than the duskside.

中文翻译：

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与2018年环绕地球的尘埃事件相关的火星热圈密度提高：MENCA / MOM和NGIMS / MAVEN的结果

利用火星轨道飞行器任务（MOM）和火星大气与挥发性演化（MAVEN）航天器共同进行的独特观测研究了火星高空热层对低层大气尘埃活动的响应。火星大气层中性成分分析仪（MENCA）/ MOM和中性气体和离子质谱仪（NGIMS）/ MAVEN同时（同一天）在5、8、10、13、16上测量了火星热层中的中性密度，以及2018年6月29日。测量期是在火星低层大气中的行星环绕尘埃事件（PEDE）的发生和进展时间。在此期间，MAVEN和MOM航天器的入轨分别发生在黎明和黄昏。利用这些观察，我们发现，黎明和黄昏时分的热层密度都随着PEDE-2018的发生和增长而增加。但是，增强效果更多地是在黄昏而不是黎明，这表明了黎明黄昏的不对称性。黄昏的密度在2018年6月29日达到最高值，接近粉尘活动高峰时。通过考虑低层大气的辐射加热的局部时间不对称性以及由于PEDE-2018而引起的热圈膨胀，可以解释这些结果。此外，O / CO 通过考虑低层大气的辐射加热的局部时间不对称性以及由于PEDE-2018而导致的热圈膨胀，可以解释这些结果。此外，O / CO 通过考虑低层大气的辐射加热的局部时间不对称性以及由于PEDE-2018而导致的热圈膨胀，可以解释这些结果。此外，O / CO海拔低于220 km的_2个比率在黎明时变为1，而在黄昏时总是<0.2。这表明辐射冷却在黎明时比黄昏时更有效。