WAVE ACTIVITY IN THE NEIGHBORHOOD OF THE BOWSHOCK OF MARS

Plasma wave activity in the neighborhood of the Martian bow shock were measured for the first time by the Soviet spacecraft Phobos‐2 in a wide frequency range from dc to 150 kHz. The wave activity varied in character as the spacecraft moved across different plasma regions: in the neigborhood of the Martian bow shock, inside the magnetosheath and in the tail region. In this paper we provide suggestions for the processes responsible for these plasma waves. The most interesting peculiarities of the wave activity around Mars is the sharp increse of wave intensity in the magnetosheath region. This increase is attributed to two different physical mechanisms. High frequency waves are excited at the shock front due to currents flowing along the front; these ion acoustic waves are convected inside by the solar wind. The low frequency waves (∼100 Hz) close to the inside boundary were, we believe, generated by heavy Martian ions diffusing through the planetopause into the magnetosheath. Copyright 1990 by the American Geophysical Union.