A comparison between the Earth's and Mars' bow shocks detected by the Phobos Plasma-Wave System

Abstract

Among the scientific instruments on the Phobos spacecraft, one was expected to study the plasma and wave phenomena in the Martian environment: the Plasma-Wave System, PWS. Here we report on the PWS plasma and electric-field spectrum measurements during two Martian bow shock crossings by Phobos 2: one is located near the subsolar point and the other near the dusk terminator. A comparison is also made with the Earth's shock crossed by Phobos 1. As at Earth, three main regions were identified: the upstream region, the shock transition region and the downstream region. A shock foot boundary is often observed in front of the bow shock. This foot is known to be associated with gyrating ions reflected from the shock. Electric-field spectra are presented and tentatively interpreted. The dynamic spectrograms shown in this report differ from the ones published previously, for the fact that the filter channels are not sampled at the same time has been taken into account.