Wave observations at the foreshock boundary in the near-Mars space

Abstract

Wave and plasma measurements carried out by the Phobos-2 spacecraft in the Martian environment indicate that a part of solar wind electrons and ions are reflected and accelerated at the Martian bow shock. These particles streaming back into the solar wind lead to the formation of the foreshock region upstream the planetary bow shock. It is shown that the general structure of the foreshock at Mars is similar to that of the foreshock region upstream the Earth's bow shock. However, the electric emissions observed at frequencies around 100 Hz at the leading edge of electron foreshock at Mars have been never reported for observations in the similar region at Earth. The burst of these waves occurs before the spacecraft enters the electron foreshock identified with the onset of electron plasma waves and calculations of the magnetic connection to the planetary bow shock.

The IMF bending upstream of the Martian bow shock

“…The fifth panel presents wave emissions measured at frequency of 100 Hz. Skalsky et al (1998) indicated that these waves are observed "upstream" of electron plasma oscillations, which have onset near the tangent line, in 30-40% of all circular orbits. No obvious correlation between waves and the magnetic field bending is found.…”

“…Picked-up exospheric protons, reflected from the electrostatic barrier at the bow shock, may supply "overreflection" of protons and contribute significantly to the population of backstreaming ions (Dubinin et al, 1994(Dubinin et al, , 1995. Martian ions can generate the wave activity not only in the foreshock region, what is happening in the earth, but also upstream of the tangent line Skalsky et al, 1998). As a consequence, extension of the foreshock study to include the Martian case would be beneficial.…”