Atmospheric Tides at Low Latitudes in the Martian Upper Atmosphere Observed by MAVEN IUVS

Abstract

The present work studies the variation of the wave 3 structure in the Martian upper atmosphere at low latitudes. CO2 densities produced by the Imaging Ultraviolet Spectrograph (IUVS) onboard the Mars Atmosphere and Volatile EvolutioN spacecraft from October 2014 to September 2021 are utilized to study the variation of the wave 3 structure under different seasons. By normalizing the densities to a fixed Extreme Ultraviolet level and applying harmonic fitting techniques, the wave 3 structures are derived from the IUVS observations. We find that the wave 3 structure tends to propagate eastward with increasing local time and altitude at low latitudes, which is consistent with the variability of the wave 3 structure at high latitudes. The altitudinal variation of the wave 3 structure also indicates that the dissipation effects become essential in the Martian upper atmosphere. By comparing the shifting speed of the wave structure with the phase speed of prominent tides in different seasons, we find that DE2 and SE1 jointly generate the wave 3 structure at low latitudes. This is confirmed by the seasonal variations of DE2 and SE1 proposed by Mars Climate Database (MCD) latitude‐Ls predictions. Comparisons of the MCD predictions with the height‐latitude amplitude distributions of the wave 3 structure reveal the existence of both DE2 and SE1 tides. By decomposing the wave 3 structure into latitudinal symmetric and antisymmetric components and comparing it with the first few Hough modes of DE2 and SE1, we confirm that DE2 and SE1 are the possible candidates that generate the wave 3 structure.

Martian atmospheric tides revealed from MAVEN and MCS Observations

“…The significant thermospheric DE2 tide is consistent with previous studies (e.g. Fu et al, 2023). The seasonal variations of DW1, SW2, and DE2 tides are significant in the Martian mesosphere and thermosphere.…”

“…The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, which is designed to study the structure and escape of the Martian atmosphere, provides observation of the upper atmosphere and magnetosphere of Mars (Jakosky et al, 2015). Based on the temperature and density observation from stellar occultation of the Imaging Ultraviolet Spectrograph (IUVS) aboard MAVEN, recent studies investigated diurnal thermal tide (Gupta et al, 2022) and the wave-3 structure in the upper atmosphere on Mars (Fu et al, 2023). As suggested by previous work, there is no signatures of vertical propagating diurnal thermal tide discovered in the upper mesosphere/lower thermosphere (∼80 to 160 km) of Mars, which are inconsistent with the MCD predictions (Gupta et al, 2022).…”

Martian Atmospheric Tides Revealed From MAVEN/IUVS and MRO/MCS Observations

“…The SW2 amplitude is largest (∼25 K) below 110 km and weaker above 120 km. Above 100 km, the tropical mean DE2 stands out as the third most pronounced mode besides DW1 and SW2, with the largest amplitude over 15 K at 120 km, consistent with previous studies (Fu et al, 2023). At 125-130 km, the peak amplitudes of DE3 and SS0 reach 10 K. Other tidal amplitudes are below 10 K at 100-130 km.…”

Martian atmospheric tides revealed from MAVEN/IUVS and MRO/MCS Observations

“…The SW2 amplitude is largest ( ~25 K) below 110 km and weaker above 120 km. Above 100 km, the tropical mean DE2 stands out as the third most pronounced mode besides DW1 and SW2, with the largest amplitude over 15 K at 120 km, consistent with previous studies (Fu et al, 2023). At Between 100 and 140 km, DW1 propagates downward during Ls=60° and Ls=120°, indicating a tidal source above 140 km, consistent with the dominant solar control over diurnal temperature variations (Gupta et al, 2022).…”

“…The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, designed to study the structure and escape of the Martian atmosphere, provides observation of Mars's upper atmosphere and magnetosphere (Jakosky et al, 2015). Based on the temperature and density observation from stellar occultation of the Imaging Ultraviolet Spectrograph (IUVS) aboard MAVEN, recent studies investigated the diurnal tide (Gupta et al, 2022) and the wave-3 structure in the upper atmosphere on Mars (England et al, 2016;Fu et al, 2023;Lo et al, 2015;Medvedev et al, 2016). As suggested by previous work, no signatures of vertical propagating diurnal tide were discovered in Mars's upper mesosphere and thermosphere (∼90 to 160 km), which are inconsistent with the MCD predictions (Gupta et al, 2022).…”