ion acceleration at the current sheet of the Martian magnetosphere

Plasma measurements of the Martian magnetosphere by the Phobos 2 spacecraft have revealed many interesting features connected with the mass and energy transport processes in the solar wind interaction. For example, the ASPERA instrument and the TAUS experiment showed that there is a very significant ionospheric outflow in the tail region which could lead to a depletion of the oxygen content of the present CO₂ ‐ atmosphere of Mars in just a few hundred million years. At the flank of the ionosphere where scavenging of the heavy exospheric ions is most effective, viscous effects and other mechanisms might play a role in accelerating the ionospheric plasma. However, a different process has to be invoked to explain the presence of field‐aligned ion (FAI) beams detected by the ASPERA experiment near the central tail. In the present work, we consider the acceleration effect of a thin current sheet. Furthermore, we wish to explore the possibility that the observed FAI outflow might be the signature of formation of neutral lines in the near‐tail region of Mars. Besides the tearing mode instability of the current sheet induced by the draping of the interplanetary magnetic field, magnetic neutral lines could also form as the result of a hybrid magnetosphere with a component of the intrinsic magnetic field interconnected with the interplanetary magnetic field.