The nature and origins of longitudinal density structures in Mars’ thermosphere between 100 and 120 km altitude, and −30° and −75° latitude around winter solstice (Ls = 70–122°), as measured by the accelerometer on the ExoMars Trace Gas Orbiter (TGO) Mission, are investigated. The methodology consists of deducing the responsible waves by comparing the observed longitude versus local time phase progressions of the structures with those of probable candidate waves in the Mars Climate Database (MCD) climatology. The observed wave‐1, wave‐2, and wave‐3 structures are interpreted as originating mainly from SPW1; (SPW2, S0, DE1); and (SPW3, DE2), respectively, where SPWm denotes a stationary planetary wave with zonal wavenumber s = m, S0 is the zonally symmetric semidiurnal tide, and DE1(DE2) are the eastward‐propagating diurnal tides with s = −1(−2). All of these waves exist in the MCD with amplitudes as large as those observed, although not wholly in the narrow height‐latitude regime accessed by TGO. This disparity between the MCD and TGO amplitude structures is hypothesized to result from the extreme intrusion of the polar‐region eastward winter jet into the thermosphere in the MCD. The winter polar jet blocks poleward expansion of DE1 and DE2 beyond −30° latitude, and also impacts the structures of SPW2, S0 and SPW3 that arise from in situ nonlinear interaction between DE1 and DE2, respectively, with the diurnal migrating tide (DW1).

中文翻译：

---

ExoMars微量气体轨道飞行器（TGO）气动制动密度中的纵向结构的波起源

由ExoMars示踪气体上的加速度计测得，火星热圈中100至120 km高度以及冬至周围30°至-75°纬度（Ls = 70–122°）之间的纵向密度结构的性质和起源对轨道飞行器（TGO）的任务进行了调查。该方法包括通过比较观测到的结构的经度和局部时相变化与火星气候数据库（MCD）气候学中可能的候选波的变化来推断出负责波。观察到的wave-1，wave-2和wave-3结构被解释为主要来自SPW1；（SPW2，S0，DE1）；和（SPW3，DE2），其中SPWm表示静止的行星波，其纬向波数s  =  m，S0是纬向对称的半日潮，DE1（DE2）是向东传播的日潮，s  = -1（-2）。所有这些波都存在于MCD中，其振幅与观察到的振幅相同，尽管并不完全存在于TGO进入的狭窄的高纬度区域。据推测，MCD和TGO振幅结构之间的这种差异是由于极地地区东侧冬季喷流极端侵入MCD的热圈而造成的。冬季极地急流阻碍了DE1和DE2的向极扩展，使其超出了纬度-30°，并且还影响了SPW2，S0和SPW3的结构，这些结构分别由DE1和DE2之间的原位非线性相互作用以及日间迁徙潮（DW1） 。