  In this study, we extracted the amplitudes of the gravity waves (GWs)from the
neutral densities measured in situ by the neutral gas and ion mass spectrometer
aboard the Mars atmosphere and volatile evolution mission. The spatial and
temporal variabilities of the GWs show that solar activity (the F10.7 cm solar
flux corrected for a heliocentric distance of 1.66 AU), solar insolation, and
the lower atmospheric dust are the dominant drivers of the GW variability in
the thermosphere. We developed a methodology in which a linear regression
analysis has been used to disentangle the complex variabilities of the GWs. The
three dominant drivers could account for most of the variability in the GW
amplitudes. Variability caused by the sources of GWs and the effects of winds
and the global circulation in the mesosphere and lower thermosphere are the
other factors that could not be addressed. The results of the present study
show that for every 100 sfu increase in the solar activity, the GW amplitudes
in the thermosphere decrease by ~9%. Solar insolation drives the diurnal,
seasonal and latitudinal variations of ~9%, ~4% and ~6%, respectively. Using
the historical data of the dust opacity and solar activity, we estimated the GW
amplitudes of the Martian thermosphere from MY 24 to MY 35. The GW amplitudes
were significantly reduced during the maximum of solar cycle 23 and were
highest in the solar minimum. The global dust storms of MY 25, 28, and 34 lead
to significant enhancements in the GW amplitudes.
