Deceleration of the solar wind upstream of the martian bow shock. Mass-loading or foreshock features?

Abstract

The role of different processes which could be responsible for deceleration of the solar wind upstream of the martian bow shock is discussed. It is shown that the geometry of the foreshock strongly controls variations of the solar wind velocity. Deceleration of the solar wind was observed on three elliptical orbits when the spacecraft approached the planet inside the foreshock. Variations of the solar wind speed are not consistent with the ones expected for ring-like distribution of pickup protons. Effects related with deceleration in the foreshock and transient phenomena (Alfven waves) dominate and mask mass-loading effects if they do exist.