The Interconnected Relationship Between Hydrogen and Protons During
Martian Proton Aurora Activity: A Combined MAVEN Remote Sensing and In
Situ Analysis
Abstract
We compare observations of hydrogen (H) and protons associated with
Martian proton aurora activity, co-evaluating remote sensing and in situ
measurements during these events. Following the currently understood
relationship between penetrating protons and H energetic neutral atoms
(ENAs) in the formation of proton aurora, we observe an expected
correlation between the H Lyman-alpha (Ly-α) emission enhancement (used
herein as a proxy for H-ENAs) and penetrating proton flux. However, we
observe a notable spread in the trend between these two datasets. We
find that this spread is contemporaneous with one of two major impacting
events: high dust activity or extreme solar activity. Proton aurora
events exhibiting a relative excess in penetrating proton flux compared
to Ly-α enhancement tend to correspond with periods of high dust
activity. Conversely, proton aurora events exhibiting a relative deficit
of penetrating proton flux compared to Ly-α enhancement are
qualitatively associated with periods of extreme solar activity.
Moreover, we find that the largest proton aurora events occur during
concurrent dust storm and solar events, primarily due to the compounding
intensified increase in H column density above the bow shock. Finally,
we present a simplified empirical estimate for Ly-α emission enhancement
during proton aurora events based on observed penetrating proton flux
and a knowledge of local dust/solar activity at the time, providing a
straightforward method for predicting auroral activity when direct
observations are not available. The results of this study advance our
understanding of the interconnected relationship between H and protons
during Martian proton aurora activity.