P046-0014
Martian Discrete Aurorae Observed with MAVEN-IUVS: Spectral Composition and Altitude Modeling

Friday, 11 December 2020
Poster
Lauriane Soret, Université de Liège, STAR-LPAP, Liege, Belgium, Jean-Claude Gérard, Université de Liège, STAR-LPAP, Liège, Belgium, Birgit Ritter, Royal Observatory of Belgium, Brussels, Belgium, Nicholas McCord Schneider, Univ Colorado, Boulder, CO, United States, Sonal Jain, Laboratory for Atmospheric and Space Physics, Boulder, CO, United States and Zachariah Milby, University of Colorado, Boulder, CO, United States
Abstract:
Three types of aurorae have been observed in the Martian atmosphere: the discrete, the diffuse (Schneider, 2015) and the proton aurora (Deighan et al., 2018, Ritter et al., 2018). This work concentrates on discrete aurorae, which were first discovered with the ESA Mars Express SPICAM instrument (Bertaux et al., 2005).

Discrete aurorae are very localized in space, time and altitude (Leblanc et al., 2008, Gérard et al., 2015, Soret et al., 2016). They are generated by the precipitation of less energetic electrons than in diffuse aurorae (hundreds of eV compared to tens of keV). Bertaux et al. (2005) showed that discrete aurorae are characterized by the presence of the CO (a3Π–X1Σ) Cameron bands between 190 and 270 nm, the CO (A1Π–X1Σ+) Fourth Positive system (CO 4P) between 135 and 170 nm, the (B2Σu+–X2Πg) doublet at 289 nm, the OI at 297.2 nm and the 130.4 nm OI triplet emissions (see figure 1).

The discrete aurora can now be studied using limb observations from the MAVEN-IUVS ultraviolet spectrograph (Schneider et al., 2019). More than 10,000 orbits of the IUVS instrument acquired from 2014 to 2020 have been analyzed for this study. Auroral signatures were automatically selected in 69 different orbits. The spectral emissions intensities have been quantified and the auroral event altitudes of the tangent point have been estimated using limb profiles. We confirm that the CO Cameron bands emission layer is located between 105 and 165 km (Bertaux et al., 2005, Soret et al., 2016). We also analyze the ratio between the CO Cameron bands and the CO2+ UVD intensities.

Finally, we use the MAVEN Solar Wind Electron Analyzer (SWEA) measurements and a Monte-Carlo electron transport model to estimate the electron energy needed to produce these discrete auroral events.

See also the related abstract by Schneider et al., this conference, which looks in more detail at the occurrences and locations of the Martian discrete aurorae.

References:

Bertaux, 2005, Nature, 10.1038/nature03603

Deighan, 2018, Nature Astronomy, 10.1038/s41550-018-0538-5

Gérard, 2015, JGR Space Physics, 10.1002/2015JA021150

Leblanc, 2008, JGR, 10.1029/2008JA013033

Ritter, 2018, GRL, 10.1002/2017GL076235

Schneider, 2015, Science, 10.1126/science.aad0313

Schneider, 2019, AGU Fall meeting, SM42B-03

Soret, 2016, Icarus, 10.1016/j.icarus.2015.09.023

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