Active current sheets at Mercury and across the solar system

Our recent analysis of MESSENGER observations has shown that Mercury's bow shock does not only mediate the interaction of the solar wind with the magnetosphere, but also provides conditions for local particle acceleration and heating, in some cases in the form of hot flow anomalies (HFAs) and other types of kinetically active current sheets. Together with earlier observations at Earth, Venus and Saturn, these results confirm that HFAs are a common property of planetary bow shocks. Here, we investigate characteristic parameters of HFA-like current sheets at Mercury and other planets searching for general tendencies describing the formation of these events across the solar system. This comparative study shows, for the first time, that the HFA size grows systematically with the heliocentric distance following the increase of characteristic ion scales in the expanding solar wind. The behavior of Hermean HFAs raises fundamental questions about the conditions of the solar wind - magnetosphere interaction at 0.3 AU which could be addressed by the upcoming BepiColombo mission.