Discrete aurora at Mars, characterized by their small spatial scale and; tendency to form near strong crustal magnetic fields, are emissions; produced by particle precipitation into the Martian upper atmosphere.; Since 2014, Mars Atmosphere and Volatile EvolutioN’s (MAVEN’s) Imaging; Ultraviolet Spectrograph (IUVS) has obtained a large collection of; nightside UV discrete aurora observations. Initial analysis of these; observations has shown that, near the strong crustal field region (SCFR); in the southern hemisphere, the aurora detection frequency is highly; sensitive to the interplanetary magnetic field (IMF) clock angle.; However, the role of other solar wind properties in controlling the; aurora detection frequency has not yet been determined. In this work, we; use IUVS discrete aurora observations, and MAVEN solar wind; observations, to determine how the discrete aurora detection frequency; varies with solar wind dynamic pressure, IMF strength, and IMF cone; angle. We find that, outside of the SCFR, the detection frequency is; relatively insensitive to the IMF orientation, but significantly; increases with solar wind dynamic pressure and moderately increases with; IMF strength. Interestingly, the auroral emission brightness outside the; SCFR is insensitive to the dynamic pressure. Inside the SCFR, the; detection frequency is moderately dependent on the dynamic pressure and; is much more sensitive to the IMF clock and cone angles. In the SCFR,; aurora are unlikely to occur when the IMF points near the radial or; anti-radial directions. Together, these results provide the first; comprehensive characterization of how upstream solar wind conditions; affect the formation of discrete aurora at Mars.
