- 1University of New Brunswick, Department, Physics, Fredericton, Canada (karim@unb.ca)
- 2IRAP, Universit ́e de Toulouse, CNRS, UPS, CNES, Toulouse, France
- 3Space Research Institute, Austrian Academy of Sciences, Graz, Austria
- 4Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa, USA
- 5IAFE, UBA CONICET, Buenos Aires, Argentina
- 6Space Sciences Laboratory, University of California, Berkeley, USA
- 7NASA Goddard Space Center, Greenbelt, Maryland, USA
The bow shock of Mars provides a compelling example of a mass-loaded, supercritical shock. A key challenge in space plasma physics is understanding the mechanisms of particle acceleration that occur at collisionless shocks. Due to extensive studies, the terrestrial foreshock is often considered a benchmark for interactions between planetary magnetospheres and the solar wind. The MAVEN mission at Mars is offering a wealth of data, simultaneously opening a window to study the Martian foreshock in detail.
In this context, we present new measurements of velocity distribution functions of suprathermal protons upstream of Mars' bow shock. We identify backstreaming beams aligned (FAB) and misaligned with the interplanetary magnetic field (IMF) direction for various shock geometries. FAB bulk velocities are found to be well-distributed in relation to the shock speed. Our analysis reveals that, compared to their terrestrial counterparts, Martian FABs exhibit slower sunward motion. Additionally, it appears that these FABs originate from a shock region where the IMF lines form an angle of 20-50 degrees with the shock normal— a smaller source region than that of Earth's bow shock.
These findings rule out specular reflection as the mechanism behind beam production. Typically, terrestrial FABs are produced through a quasi-adiabatic process that preserves the first invariant to some extent. In contrast, the new Martian observations provide a valuable comparison between the foreshocks of Earth and Mars, shedding light on key differences and enhancing our understanding of these planetary phenomena.
How to cite: Meziane, K., Mazelle, C., Simon-Wedlund, C., Halekas, J., Hamza, A., Bertucci, C., Mitchell, D., and Espley, J.: Ion acceleration at Mars Bow Shock - Results from MAVEN, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12526, https://doi.org/10.5194/egusphere-egu25-12526, 2025.
