Global distribution and parameter dependences of gravity wave activity in the Martian upper thermosphere derived from MAVEN/NGIMS observations. Issue 2 (15th February 2017)

• Record Type: Journal Article
• Authors: Terada, Naoki; Leblanc, François; Nakagawa, Hiromu; Medvedev, Alexander S.; Yiğit, Erdal; Kuroda, Takeshi; Hara, Takuya; England, Scott L.; Fujiwara, Hitoshi; Terada, Kaori; Seki, Kanako; Mahaffy, Paul R.; Elrod, Meredith; Benna, Mehdi; Grebowsky, Joseph; Jakosky, Bruce M.
• Is Part Of: Journal of geophysical research. Volume 122:Issue 2(2017)
• Page Start: 2374
• Page End: 2397
• Publication Date: 2017-02-15
• Subjects: MAVEN -- gravity waves -- upper thermosphere -- Mars; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2016JA023476
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: Wavelike perturbations in the Martian upper thermosphere observed by the Neutral Gas Ion Mass Spectrometer (NGIMS) onboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft have been analyzed. The amplitudes of small‐scale perturbations with apparent wavelengths between ~100 and ~500 km in the Ar density around the exobase show a clear dependence on temperature ( T 0 ) of the upper thermosphere. The average amplitude of the perturbations is ~10% on the dayside and ~20% on the nightside, which is about 2 and 10 times larger than those observed in the Venusian upper thermosphere and in the low‐latitude region of Earth's upper thermosphere, respectively. The amplitudes are inversely proportional to T 0, suggesting saturation due to convective instability in the Martian upper thermosphere. After removing the dependence on T 0, dependences of the average amplitude on the geographic latitude and longitude and solar wind parameters are found to be not larger than a few percent. These results suggest that the amplitudes of small‐scale perturbations are mainly determined by convective breaking/saturation in the upper thermosphere on Mars, unlike those on Venus and Earth. Key Points: GW amplitudes in the upper thermosphere of Mars are about 2 and 10 times larger than on Venus and in low latitudes of Earth, respectively Amplitudes show a clear dependence on the background atmospheric temperature, suggesting saturation due to convective instability Dependences of the corrected amplitudes on the geographic latitude and longitude and solar wind parameters are less significant