由MAVEN EUVM太阳掩星揭示的火星热层变率：在近日点和近日点的结构，以及对EUV强迫的响应
Mars Thermospheric Variability Revealed by MAVEN EUVM Solar Occultations: Structure at Aphelion and Perihelion, and Response to EUV Forcing
摘要：
火星热层保存着火星气候演变的线索，对访问火星的航天器具有实际意义，因为航天器通常在抵达火星时利用热层进行空气制动，或者对必须穿过热层的着陆器具有实际意义，然而，即使考虑到过去的加速计测量和远程观测，热层的特征也很少。火星大气层和挥发物演变轨道飞行器（MAVEN）包括一些用于确定热层特征的仪器，极大地扩展了现有的热层观测。本文介绍了使用MAVEN极紫外线（EUV）监测器对来自太阳掩星的密度和温度分布（120-200公里）进行的新的和未预料到的测量。这些新的测量补充和扩大了MAVEN计划的热层测量能力。特别是，由于当地时间固有地固定到终结者，太阳掩星非常适合表征长期和纬度变化。在大约一半的轨道上进行掩星测量，产生了数千个新的热层剖面。详细介绍了密度反演方法，包括不确定性分析。介绍了近日点和远日点的热层密度和温度的高度-纬度图，揭示了以前没有观测到的结构。还观察到了大气动力学的踪迹，包括中纬度的高海拔极地变暖特征，以及太阳自转期间对太阳极紫外线加热的明显的热响应，这表明高海拔的加热伴随着低海拔的冷却。
英文摘要：
The Mars thermosphere holds clues to the evolution of the Martian climate, and has practical implications for spacecraft visiting Mars, which often use it for aerobraking upon arrival, or for landers, which must pass through it. Nevertheless, it has been sparsely characterized, even when past accelerometer measurements and remote observations are taken into account. The Mars Atmosphere and Volatile EvolutioN (MAVEN) orbiter, which includes a number of instruments designed to characterize the thermosphere, has greatly expanded the available thermospheric observations. This paper presents new and unanticipated measurements of density and temperature profiles (120-200 km) derived from solar occultations using the MAVEN Extreme Ultraviolet (EUV) Monitor. These new measurements complement and expand MAVEN's intended thermospheric measurement capacity. In particular, because the local-time is inherently fixed to the terminator, solar occultations are ideally suited for characterizing long-term and latitudinal variability. Occultation measurements are made during approximately half of all orbits, resulting in thousands of new thermospheric profiles. The density retrieval method is presented in detail, including an uncertainty analysis. Altitude-latitude maps of thermospheric density and temperature at perihelion and aphelion are presented, revealing structures that have not been previously observed. Tracers of atmospheric dynamics are also observed, including a high altitude polar warming feature at intermediate latitudes, and an apparent thermostatic response to solar EUV heating during a solar rotation, which shows heating at high altitudes that is accompanied by cooling at lower altitudes.
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