Abstract
Previous observation of a single hot flow anomaly (HFA) at Earth by MMS
mission reported solar wind protons effective acceleration inside these
structures to nearly 1 MeV under certain conditions via first-order
Fermi acceleration process. Current study focuses on the analysis of a
single HFA registered at Mars by MAVEN spacecraft. The event is
characterized by the presence of accelerated O+ and O2+ ions of
planetary origin on both sides from the current sheet associated with
the event. Ions with energies up to ~10 keV are detected
before the current sheet crossing, and over 30 keV after the current
sheet crossing. We report that the relationship between the ion mass and
the maximum energy to which acceleration occurs is consistent with the
above-mentioned Fermi acceleration process. We hypothetize that
effective planetary ions acceleration in HFAs is possible only at
unmagnetized planets due to closer bow shock stand-off distance.