First identification of mirror mode waves in Venus' magnetosheath?

Abstract

In this paper first time observations of mirror mode like structures in Venus' magnetosheath are presented. Using magnetometer data from the Venus Express spacecraft it is shown that in two regions in the Venusian magnetosheath strong compressional waves exist, which propagate nearly perpendicular to the ambient magnetic field. They are most likely mirror‐mode waves. The waves have periods between 5 and 15 sec, depending on the location in the magnetosheath. These waves show up just behind the quasi‐perpendicular bow shock, and near the magnetopause during compression of the magnetosheath due to increased solar wind pressure. The characteristics of the waves are similar to mirror mode waves found in the Earth's magnetosheath, however, they are down‐scaled in duration and frequency by a factor of 10, comparable with the difference in size of Venus' and Earth's magnetosheath.