A Search for Spectral Variations in Auroral Emissions from Mars

The Imaging Ultraviolet Spectrograph (IUVS) instrument onboard the MAVEN mission has been used to study several forms of aurora in the atmosphere of Mars; discrete aurora, discovered by the SPICAM instrument on Mars Express, as well as two other forms discovered by MAVEN/IUVS referred to as diffuse aurora and proton aurora. Each type of aurora can be identified through unique spectral characteristics. In particular, discrete aurora events are ultraviolet emissions spread variably throughout Mars’ upper atmosphere, and are strongly correlated to Mars’ crustal magnetic field. Discrete aurora events can be identified by strong emissions of CO Cameron bands, and slightly weaker emissions of CO2+ Ultraviolet Doublet. Based on recent work from our group, we expect to see a ratio of approximately 7 between these two emissions. However, several exceptions display spectral features that do not agree with characteristics of any of the currently known aurora types. These observations show the same two emissions as discrete aurora events. However, the ratio between the CO Cameron bands and CO2+ Ultraviolet Doublet is much higher than expected, ranging from a ratio of 10 to over 500. We have collected the observations containing these variations and will search for patterns and trends among them, such as proximity to the terminator, locations relative to crustal fields, or timing relative to space weather events. Using these trends, we will discuss possible explanations for the differences between this data and common discrete aurora observations.