Journal article
EMM EMUS Observations of FUV Aurora on Mars: Dependence on Magnetic Topology, Local Time, and Season
Journal of geophysical research. Planets, Vol.129(6), e2024JE008336
06/2024
DOI: 10.1029/2024JE008336
Abstract
We present a comprehensive study of the nightside aurora phenomenon on Mars, utilizing observations from EMUS onboard Emirates Mars Mission. The oxygen emission at 130.4 nm is by far the brightest FUV auroral emission line observed at Mars. Our statistical analysis reveals geographic, solar zenith angle, local time, and seasonal dependencies of auroral occurrence. Higher occurrence of aurora is observed in regions of open magnetic topology, where crustal magnetic fields are either very weak or both strong and vertical. Aurora occurs more frequently closer to the terminator and is more likely on the dusk side than on the dawn side of the night hemisphere. A pronounced auroral feature appears close to midnight local times in the southern hemisphere, consistent with the spot of energetic electron fluxes previously identified in the Mars Global Surveyor data. This auroral spot is more frequent after midnight than before. Additionally, some regions on Mars are “aurora voids” where essentially no aurora occurs. Aurora exhibits a seasonal dependence, with a major enhancement near perihelion. Non–crustal field aurora additionally shows a secondary enhancement near Ls 30°. This seasonal variability is a combination of the variability in ionospheric photoelectrons and thermospheric atomic oxygen abundance. Auroral occurrence also shows an increase with the rise of Solar Cycle 25. The brightest auroral pixels are observed during space weather events such as Coronal Mass Ejections and Stream Interaction Regions. These observations not only shed light on where and when Martian aurora occurs, but also add to our understanding of Mars' magnetic environment and its interaction with the heliosphere.
Plain Language Summary
In this study, we explore the phenomenon of aurora on the nightside of Mars, using observations from the highly sensitive Emirates Mars Ultraviolet Spectrometer (EMUS) on the Emirates Mars Mission. Our analysis reveals distinct patterns in auroral occurrence on the planet. For instance, there is a higher rate of auroral activity in regions where Mars' magnetic field lines are open (i.e., connected to the collisional atmosphere at one end). We also found that aurora is more common near the terminator (with the occurrence decreasing as the solar zenith angle increases), and particularly during the evening hours, as opposed to early morning. Interestingly, these auroral events also show a seasonal dependence, peaking around perihelion in a Martian year, when Mars is closest to the sun. This seasonal pattern corresponds with the variation of photoelectrons in Mars' dayside ionosphere and the atomic oxygen abundance in the thermosphere. Auroral occurrence increases with increasing solar activity. Also, the auroral brightness increases during space weather events. Our study not only gives us a clearer picture of where and when the aurora occurs on Mars but also hints at the underlying processes influencing them, offering insights into the planet's magnetic and charged particle environment.
Key Points
Higher auroral occurrence is observed in regions of open magnetic topology, where crustal fields are either very weak or primarily vertical
Aurora occurs more frequently near the terminator compared to deep night, with higher occurrence at dusk than at dawn
Aurora occurs more frequently near perihelion, with the brightest auroral pixels observed during space weather events
Details
- Title: Subtitle
- EMM EMUS Observations of FUV Aurora on Mars: Dependence on Magnetic Topology, Local Time, and Season
- Creators
- Krishnaprasad Chirakkil - University of Colorado BoulderRobert J. Lillis - University of California, BerkeleyJustin Deighan - Laboratory for Atmospheric and Space PhysicsMichael S. Chaffin - University of Colorado BoulderSonal K. Jain - University of Colorado BoulderDavid A. Brain - Laboratory for Atmospheric and Space PhysicsMatthew O. Fillingim - University of California, BerkeleyRaghuram Susarla - Khalifa University of Science and TechnologyGreg Holsclaw - Laboratory for Atmospheric and Space PhysicsXiaohua Fang - Laboratory for Atmospheric and Space PhysicsNick M. Schneider - University of Colorado BoulderHoor AlMazmi - Environment Agency Abu DhabiHessa AlMatroushi - Mohammed Bin Rashid School of GovernmentMarko Gacesa - Khalifa University of Science and TechnologyNayla El-Kork - Khalifa University of Science and TechnologyEd Thiemann - Laboratory for Atmospheric and Space PhysicsJasper S. Halekas - University of Iowa
- Resource Type
- Journal article
- Publication Details
- Journal of geophysical research. Planets, Vol.129(6), e2024JE008336
- DOI
- 10.1029/2024JE008336
- ISSN
- 2169-9097
- eISSN
- 2169-9100
- Number of pages
- 20
- Grant note
- National Aeronautics and Space Administration (80NSSC19K0562) Khalifa University ‐ University of Colorado Boulder ‐ Laboratory for Atmospheric and Space Physics (8474000332‐KU‐CU‐LASP) UAE Space Agency
- Language
- English
- Date published
- 06/2024
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984648568802771
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