Discrete Aurora at Mars: Dependence on Upstream Solar Wind Conditions

Area of Science:

• Planetary Science
• Space Physics
• Atmospheric Science

Background:

• Discrete aurora on Mars are linked to particle precipitation in the upper atmosphere.
• Observations by the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft since 2014 have provided extensive data on these auroras.
• Previous studies indicated a sensitivity to the interplanetary magnetic field (IMF) clock angle near strong crustal magnetic fields.

Purpose of the Study:

• To investigate the influence of various solar wind properties on the detection frequency of discrete Martian aurora.
• To determine how solar wind dynamic pressure, IMF strength, and IMF cone angle affect aurora formation.
• To differentiate the controlling factors of aurora occurrence inside and outside the strong crustal field region (SCFR).

Main Methods:

• Utilizing ultraviolet discrete aurora observations from MAVEN's Imaging Ultraviolet Spectrograph (IUVS).
• Correlating aurora data with upstream solar wind measurements from MAVEN.
• Analyzing the relationship between aurora detection frequency and solar wind parameters (dynamic pressure, IMF strength, IMF clock and cone angles).

Main Results:

• Outside the SCFR, aurora detection frequency increases with solar wind dynamic pressure and IMF strength, but is less sensitive to IMF orientation.
• High dynamic pressure increases aurora occurrence but not brightness.
• Inside the SCFR, aurora detection is moderately dependent on dynamic pressure and highly sensitive to IMF clock and cone angles, with specific orientations inhibiting aurora.

Conclusions:

• Solar wind properties significantly influence discrete aurora formation at Mars.
• The strong crustal field region exhibits distinct sensitivities to solar wind conditions compared to other areas.
• This study provides the first comprehensive analysis of upstream solar wind impacts on Martian discrete aurora.