Solar-Synchronous Tides in Mars Thermosphere CO<SUB>2</SUB>, Ar, and N<SUB>2</SUB> Densities From MAVEN

Measurements of CO<SUB>2</SUB>, Ar and N<SUB>2</SUB> densities from the Neutral Gas and Ion Mass Spectrometer on the Mars Atmosphere and Volatile Evolution Mission (MAVEN) between 150 and 200 km altitude during 2015-2022 are analyzed to reveal diurnal (DW1), semidiurnal (SW2) and terdiurnal (TW3) solar-synchronous tides in Mars thermosphere. Multi-year-mean tidal perturbations on a diurnal- and zonal-mean background, corrected for solar flux variations, are reported as a function of latitude (48°S-48°N), altitude and solar longitude (Ls). The DW1, SW2 and TW3 amplitudes at for example, 180 km altitude are of order 90%-120%, 15%-20%, and ≲10% for CO<SUB>2</SUB> and Ar, and roughly 2/3 these values for N<SUB>2</SUB>, the latter presumably due to the difference in molecular weight from the other species. Through examination of vertical phase progressions, DW1 is concluded to be mainly excited in situ, but SW2 and TW3 contain significant contributions from tides propagating upward from lower altitudes. By analogy with studies for Earth's thermosphere, the DW1 amplitudes and phases are thought to reflect the combined influences of thermal expansion and vertical winds. Points of agreement and disagreement with DW1, SW2, and TW3 amplitudes and phases derived from the Mars Climate Database are noted and interpreted.