The Interconnected Relationship Between Hydrogen and Protons During Martian Proton Aurora Activity: A Combined MAVEN Remote Sensing and In Situ Analysis

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 also observe a notable spread in the trend between these two data sets. 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 the observed penetrating proton flux and a knowledge of local dust/solar activity at the time; this estimate provides a straightforward method for predicting auroral activity when direct observations are not possible or available. The results of this study advance our understanding of the interconnected relationship between H and protons during Martian proton aurora activity.