EGU23-8470
https://doi.org/10.5194/egusphere-egu23-8470
EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Sinuous Aurora at Mars: exploring a new phenomenon with data and models 

Robert Lillis1, Abigail Azari1, Yingjuan Ma2, Krishnaprasad Chirakkil3, Justin Deighan3, Michael Chaffin3, Sonal Jain3, Gregory Holsclaw3, David Brain3, Hessa Al Matroushi4, Scott England5, Nick Schneider3, Shaosui Xu1, Hoor Al Mazmi4, Jasper Halekas6, Robin Ramstad3, Jared Espley7, Jacob Gruesbeck7, and Shannon Curry1
Robert Lillis et al.
  • 1Space Sciences Laboratory, University of California, Berkeley, United States of America (rlillis@berkeley.edu)
  • 2Earth, Planetary, and Space Sciences, University of California, Los Angeles, United States of America
  • 3Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, USA
  • 4Mohammed Bin Rashid Space Center, Dubai, United Arab Emirates
  • 5Aerospace and Ocean Engineering, Virginia Institute of Technology, Blacksburg, Virginia, USA
  • 6Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa, USA
  • 7Goddard Space Flight Center, Greenbelt, Maryland, USA

Benefiting from a large orbit and high sensitivity, the Emirates Mars mission EMUS instrument has provided the first opportunity to regularly image Mars’ discrete FUV aurora synoptically.  EMUS has collected nearly 1000 synoptic observations of the Mars nightside have revealed at least three distinct types of discrete Aurora: 1) crustal field aurora, appearing in regions of mostly radial crustal magnetic fields, 2) patchy discrete aurora, observed away from strong crustal fields, and 3) sinuous discrete aurora, extending from the terminator typically thousands of kilometers onto the nightside, away from crustal fields.

Sinuous Discrete Aurora (SDA) is observed in approximately 5% of observations and is characterized by 2 primary attributes: morphology and the local time of its intersection with the terminator. Morphologies include serpentine, approximately linear, and short/lumpy. Dusk-side SDA does not occur preferentially for any particular interplanetary magnetic field (IMF) orientation, while Dawn and Midnight SDA appear to show a preference for northeastward IMF directions measured in situ by the MAVEN spacecraft. Dusk SDA observed about twice as often as Dawn or Midnight SDA. 

SDA reflect conditions whereby particular magnetic topologies connect the nightside atmosphere to a source of abundant electrons, whether dayside photoelectrons or sufficiently energetic magnetotail/sheath electrons.  In particular, midnight sinuous discrete aurora appear to be a projection of the tail current sheet, a persistent but highly variable feature of Mars’ double-lobed magnetotail resulting from the draping of the IMF around the conducting obstacle of Mars’ dayside ionosphere.  This interpretation is supported by magnetohydrodynamic (MHD) simulations, showing that the orientation of the tail current sheet approximately matches the orientation of midnight SDA.

EMM EMUS promises to be an invaluable tool in helping to understand the drivers of Martian Aurora.

How to cite: Lillis, R., Azari, A., Ma, Y., Chirakkil, K., Deighan, J., Chaffin, M., Jain, S., Holsclaw, G., Brain, D., Al Matroushi, H., England, S., Schneider, N., Xu, S., Al Mazmi, H., Halekas, J., Ramstad, R., Espley, J., Gruesbeck, J., and Curry, S.: Sinuous Aurora at Mars: exploring a new phenomenon with data and models , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-8470, https://doi.org/10.5194/egusphere-egu23-8470, 2023.