The Unique Seasonal Influence of the Interplanetary Magnetic Field on
Martian Proton Aurora
Abstract
We evaluate for the first time the large-scale influence of the upstream
interplanetary magnetic field (IMF) magnitude and orientation on Martian
proton aurora. We identify a correlation between proton aurora activity
and IMF magnitude that varies seasonally, with highest correlations
around Mars southern summer solstice when proton aurora activity reaches
an annual high. We identify preferentially increased proton aurora
emission enhancements at IMF cone and clock angles consistent with the
shape of the Parker spiral at Mars’s heliocentric distance. An increased
proton aurora occurrence rate is observed for near-radial IMF
orientations, particularly evident when the hydrogen corona and bow
shock are annually decreased. Lastly, our results suggest that dayside
magnetic reconnection may influence proton aurora, which are observed to
have preferentially higher occurrence under strong ±Bz orientations.
These findings enhance our understanding of the upstream IMF’s influence
on Martian proton aurora as an important driver for auroral brightness
and occurrence.