Fang Xiaohua, Forbes Jeffrey M, Gan Quan, Liu Guiping, Thaller Scott, Bougher Stephen, Andersson Laila, Benna Mehdi, Eparvier Francis, Ma Yingjuan, Pawlowski David, England Scott, Jakosky Bruce
Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO, USA.
Ann and H.J. Smead Department of Aerospace Engineering Sciences, University of Colorado, Boulder, CO, USA.
J Geophys Res Space Phys. 2020 Dec 31;126(2). doi: 10.1029/2020ja028562. Epub 2021 Feb 1.
Longitudinal structures in the Martian thermosphere and topside ionosphere between 150 and 200 km altitudes are studied using in situ electron and neutral measurements from the NASA Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. Four time intervals are selected for comparison, during which MAVEN sampled similar local time (9.3-10.3 h) and latitude (near 20°S) regions but at different solar longitude positions (two near northern summer solstice, one each at northern vernal and autumnal equinoxes). Persistent and pronounced tidal oscillations characterize the ionosphere and thermosphere, whose longitudinal variations in density are generally in-phase with each other. Our analysis of simultaneous and collocated neutral and electron data provides direct observational evidence for thermosphere-ionosphere coupling through atmospheric tides. We conclude that the ionosphere is subject to modulation by upward-propagating thermal tides, via both tide-induced vertical displacement and photochemical reactions. Atmospheric tides constitute a ubiquitous and significant perturbation source to the ionospheric electron density, up to ~15% near 200 km.
利用美国国家航空航天局（NASA）的火星大气与挥发演化（MAVEN）任务的原位电子和中性粒子测量数据，对火星热层和150至200千米高度的电离层顶中的纵向结构进行了研究。选择了四个时间间隔进行比较，在此期间，MAVEN对类似的地方时（9.3 - 10.3小时）和纬度（接近南纬20°）区域进行了采样，但处于不同的太阳经度位置（两个接近北半球夏至，一个分别位于北半球春分和秋分）。持续且明显的潮汐振荡是电离层和热层的特征，其密度的纵向变化通常彼此同相。我们对同步且共置的中性粒子和电子数据的分析为通过大气潮汐实现的热层 - 电离层耦合提供了直接的观测证据。我们得出结论，电离层受到向上传播的热潮汐的调制，这是通过潮汐引起的垂直位移和光化学反应实现的。大气潮汐是电离层电子密度普遍且重要的扰动源，在200千米附近可达约15%。
