Structuring of the transition region (plasma mantle) of the Martian magnetosphere

Measurements made by the ASPERA plasma instrument onboard the Phobos‐2 spacecraft have shown that the transition from the Martian magnetosheath occupied mainly by the shocked solar wind to the boundary layer dominated by planetary plasma occurs by a sequence of step‐like drops and jumps of the proton bulk velocity and the magnetic field value. The plasma is stratified on alternating layers occupied either by protons or by heavy ions. The resemblance with shock‐like structures is emphasized by the fact of proton temperature enhancements which replicate drops of the bulk velocity. The observed striations are considered as peculiar discontinuities typical for multi‐ion plasma, or flute‐like modes which may be excited at the boundary of the Martian magnetosphere.