MAVEN NGIMS observations of atmospheric gravity waves in the Martian thermosphere

Abstract

Gravity waves have a significant impact on both the dynamics and energy budget of the Martian thermosphere. Strong density variations of spatial scales indicative of gravity waves have previously been identified in this region by using in situ observations. Here we use observations from the Neutral Gas and Ion Mass Spectrometer (NGIMS) mass spectrometer on Mars Atmosphere and Volatile EvolutioN Mission to identify such waves in the observations of different atmospheric species. The wave signatures seen in CO2 and Ar are almost identical, whereas the wave signature seen in N2, which is lighter and has a larger scale height, is generally smaller in amplitude and slightly out of phase with those seen in CO2 and Ar. Examination of the observed wave properties in these three species suggests that relatively long vertical wavelength atmospheric gravity waves are the likely source of the waves seen by NGIMS in the upper thermosphere. A two‐fluid linear model of the wave perturbations in CO2 and N2 has been used to find the best fit intrinsic wave parameters that match the observed features in these two species. We report the first observationally based estimate of the heating and cooling rates of the Martian thermosphere created by the waves observed in this region. The observed wave density amplitudes are anticorrelated with the background atmospheric temperature. The estimated heating rates show a weak positive correlation with the wave amplitude, whereas the cooling rates show a clearer negative correlation with the wave amplitude. Our estimates support previous model‐based findings that atmospheric gravity waves are a significant source of both heating and cooling.

Seasonal Variations and Global Wave Distributions in the Mars Thermosphere From MAVEN and Multisatellites Accelerometer‐Derived Mass Densities

“…Both observations and GCM simulations support that the dust storms have vital impacts on the Mars atmosphere up to the upper layers (e.g., England et al, ; Keating et al, ; Montabone et al, ; Rafkin et al, ), which means the dust terms in equation (6) are reasonable. The general impact of the dust storms on the Mars atmosphere is to expand and lift the atmospheric layers (Smith, ).…”

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