The Effects of Solar Cycle Variability on D and H in the Upper
Atmosphere of Mars
Abstract
The upper atmosphere of Mars is directly affected by solar activity and
the resulting solar irradiance impinging upon it. Variations in solar
forcing can affect the rate at which atmospheric species escape from the
planetary system. Remotely sensed observations of the upper atmosphere
of Mars have been made during solar activity extrema of Solar Cycles 22
and 24. These observations were made of D and H Lyman-a emissions using
the Mars Atmosphere and Volatile Evolution (MAVEN) mission and the
Hubble Space Telescope (HST) high resolution spectrographs. Data
obtained from the two missions are analyzed and used to derive densities
and escape rates of D and H from the martian upper atmosphere. The
results show that the properties of these two water-spawned atoms vary
with solar cycle, and display significant inter-annual variability,
mainly due to variations in atmospheric temperature. The findings
suggest that cooler atmospheric temperatures due to reduced solar EUV
flux may enhance the abundance of H atoms in the upper atmosphere of
Mars, yet this does not increase their escape rates.