Effects of Magnetic Turbulence on the Dynamics of Pickup Ions in the Ionosheath of Mars

H. Aceves, M. Reyes-Ruiz, C. E. Chavez


We study some of the effects that magnetic turbulent fluctuations have on the dynamics of pickup O+ ions in the magnetic polar regions of the Mars ionosheath. In particular we study their effect on the bulk velocity profiles of ions as a function of altitude over the magnetic poles, in order to compare them with recent Mars Express data; that indicate that their average velocity is very low and essentially in the anti-sunward direction. We find that, while magnetic field fluctuations do give rise to deviations from simple E × B-drift gyromotion, even fluctuation amplitudes much greater than those of in situ measurements are not able to reproduce the vertical velocity profile of O+ ions. We conclude that other physical mechanisms, different from a pure charged particle dynamics, are acting on pickup ions at the Martian terminator. A possibility is a viscous-like interaction between the Solar Wind and the Martian ionosphere at low altitudes.

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