EGU2020-10596
https://doi.org/10.5194/egusphere-egu2020-10596
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Influence of foreshock electrons impact ionization on the amplitude of pickup protons generated waves at Mars

Christian Mazelle1, Karim Meziane2, Norberto Romanelli3, David L. Mitchell4, Suranga Ruhunisiri5, Hadi Madanian5, Ali Rahmati4, Steven J. Schwartz6, Jared R. Espley3, Jasper S. Halekas5, and Emmanuel Penou1
Christian Mazelle et al.
  • 1IRAP CNRS-University of Toulouse-UPS-CNES, PEPS, Toulouse, France (cmazelle@irap.omp.eu)
  • 2Physics Department, University of New Brunswick, Canada
  • 3NASA Goddard Space Flight Center, Greenbelt, USA
  • 4Space Sciences Laboratory, University of California, Berkeley, USA
  • 5Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa, USA
  • 6Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado, USA

Using MAVEN observations, we report variations of the amplitude of electromagnetic waves observed at the local proton cyclotron frequency upstream from the bow shock on short (plasma) time/length-scales: 1) a sharp sudden increase of the amplitude when crossing the electron foreshock boundary and 2) a decrease of this amplitude clearly correlated with the increasing distance from the shock along the magnetic field inside the foreshock without any simple relation to the planetary radial distance. These waves are excited by unstable ring-beam velocity distributions of newborn protons produced by ionization of exospheric hydrogen atoms. The amplitude of these waves is generally expected to depend only on different drivers including the observed large seasonality of the hydrogen exosphere, the EUV solar flux, the solar wind density and velocity or the IMF cone angle at different levels of importance. No noticeable wave amplitude change is expected when crossing the electron foreshock boundary and inside the pure electron foreshock. Surprisingly, we found that that these waves also display the two same aforementioned properties as the foreshock electrons fluxes at Mars though the wave origin is related to the ions only. We investigate the possibility that the extra free energy necessary to increase the wave amplitude could be due to supplementary ionization of hydrogen atoms by electron impact ionization inside the foreshock. Therefore, the electron foreshock also plays a role in the production of pickup protons which contribute to the planetary escape from high altitude.

How to cite: Mazelle, C., Meziane, K., Romanelli, N., Mitchell, D. L., Ruhunisiri, S., Madanian, H., Rahmati, A., Schwartz, S. J., Espley, J. R., Halekas, J. S., and Penou, E.: Influence of foreshock electrons impact ionization on the amplitude of pickup protons generated waves at Mars, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10596, https://doi.org/10.5194/egusphere-egu2020-10596, 2020