Martian upper-atmosphere circulation and tides revealed through MAVEN/IUVS observations of nitric oxide nightglow

The nitric oxide δ and γ bands are ultraviolet emissions which reflect the production rate of nitric oxide (NO) from the recombination of excited nitrogen and oxygen atoms. We use it as a tracer of the dynamics between Mars’ upper- and middle-atmospheres, particularly of day-to-night and summer-to-winter pole circulation. We analyse this rate as it varies over Mars’ surface in mission-long aggregations and local-time divisions. Our data were gathered by the Mars Atmosphere and Volatile Evolution (MAVEN) mission’s Imaging UltraViolet Spectrograph (IUVS) and span different seasonal conditions and latitudes. The data span allows a limited comparison between two subsequent Mars years. In our previous study from a limited dataset of atmospheric limb scans (Stiepen 2017, doi:10.1002/2016JA023523), we discovered a wave-3 structure to the nightglow at equatorial latitudes. For this study, we use scans taken of the full disk of Mars as seen at apoapse over 1.25 Mars years. We observe the same wave-3 structure, and find strong seasonal and local-time dependencies on position and brightness. We also discovered a wave-2 structure in northern polar regions that persists through all observed local times and seasons. We compare our observations to model calculations from the LMD-MGCM. We find the model generally under-predicts the brightness of the nightglow at all sub-polar latitudes, suggesting it over-estimates the efficiency of atomic transport to the poles. However, we also find that the model reproduces the observed equatorial wave-3 and polar wave-2 structures. We identify the dominant atmospheric tide component of the equatorial wave-3 structure and analysis of the local-time dependencies of the wave structures and the brightness across all latitudes. We also compare the observed polar nightglow wave structure to contemporaneous dayside ozone distributions also measured by IUVS