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Making waves: Mirror Mode structures around Mars observed by the MAVEN spacecraft
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  • Cyril L. Simon Wedlund,
  • Martin Volwerk,
  • Christian Xavier Mazelle,
  • Jasper S. Halekas,
  • Diana Rojas-Castillo,
  • Jared Espley,
  • Christian Moestl
Cyril L. Simon Wedlund
Space Research Institute, OEAW

Corresponding Author:[email protected]

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Martin Volwerk
Space Research Institute, OEAW
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Christian Xavier Mazelle
IRAP; Université de Toulouse; CNRS; CNES; UPS-OMP; Toulouse, France
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Jasper S. Halekas
University of Iowa
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Diana Rojas-Castillo
Instituto de Geofísica, UNAM
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Jared Espley
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Christian Moestl
Austrian Academy of Sciences
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We present here an in-depth analysis of one time interval when quasi-linear mirror mode structures were detected by magnetic field and plasma measurements as observed by the NASA/Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. We employ ion and electron spectrometers in tandem to support the magnetic field measurements and confirm that the signatures are indeed mirror modes. Wedged against the magnetic pile-up boundary, the low-frequency signatures lasted on average ~10 s with corresponding sizes of the order of 15-30 upstream solar wind proton thermal gyroradii, or 10-20 proton gyroradii in the immediate wake of the quasi-perpendicular bow shock. Their peak-to-peak amplitudes were of the order of 30-35 nT with respect to the background field, and appeared as a mixture of dips and peaks, suggesting that they may have been at different stages in their evolution. Situated in a marginally stable plasma with β|| ~ 1, we hypothesise that these so-called magnetic bottles, containing a relatively higher energy and denser ion population with respect to the background plasma, were formed upstream of the spacecraft behind the quasi-perpendicular shock. These signatures are very reminiscent of magnetic bottles found at other unmagnetised objects such as Venus and comets, also interpreted as mirror modes. Our case study constitutes the first unambiguous detection of mirror modes around Mars, which had up until now only been surmised because of the lack of high-temporal resolution plasma measurements.
Jan 2022Published in Journal of Geophysical Research: Space Physics volume 127 issue 1. 10.1029/2021JA029811