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Interannual Variability of Atmospheric Gravity Waves in the Martian Thermosphere: Effects of the 2018 Planet‐Encircling Dust Event
Author(s) -
Leelavathi V.,
Venkateswara Rao N.,
Rao S. V. B.
Publication year - 2020
Publication title -
journal of geophysical research: planets
Language(s) - English
Resource type - Journals
eISSN - 2169-9100
pISSN - 2169-9097
DOI - 10.1029/2020je006649
Subject(s) - thermosphere , martian , atmosphere of mars , amplitude , atmospheric escape , mars exploration program , atmosphere (unit) , atmospheric sciences , gravity wave , wavelength , physics , daytime , atmospheric tide , geophysics , environmental science , astrophysics , gravitational wave , ionosphere , astronomy , meteorology , optoelectronics , quantum mechanics
We study the interannual variability of atmospheric gravity waves (GWs) in the Martian thermosphere and their relation to the background temperatures using Ar densities measured by Neutral Gas and Ion Mass Spectrometer/Mars Atmosphere and Volatile Evolution (MAVEN). The amplitudes and wavelengths of the GWs are extracted from the neutral density perturbations in the inbound segment of the MAVEN orbit. The GW amplitudes predominantly lie between 5% and 10% and are mostly less than 30% of the background densities. The horizontal wavelengths are between 50 km and 300 km with peak wavelengths of 100–130 km. GW amplitudes show a significant diurnal variation with larger amplitudes during nighttime and smaller amplitudes during daytime. In addition, the GW amplitudes negatively correlate with the background temperatures indicating the role of convective instability in the saturation of the GWs. Most importantly, the GW amplitudes are larger and the wavelengths are smaller when there was a planet‐encircling dust event in the Mars’ lower atmosphere during 2018. As a result, the typical diurnal variation of GW amplitudes is not apparent. During the lower atmospheric dust event, the GW amplitudes do not show any significant correlation with the background temperatures. It is proposed that the PEDE‐2018 led to changes in the circulation of the mesosphere and lower thermosphere, so that the modified circulation enhanced the upward propagation/reduced the filtering of GWs leading to their enhancement in the upper thermosphere.