Active current sheets and candidate hot flow anomalies upstream of Mercury's bow shock

摘要: Hot flow anomalies (HFAs) represent a subset of solar wind discontinuities interacting with collisionless bow shocks. They are typically formed when the normal component motional (convective) electric field points toward embedded current sheet on at least one its sides. The core region an HFA contains hot and highly deflected ion flows rather low turbulent magnetic field. In this paper, we report observations possible HFA-like events Mercury identified over course two planetary years. Using data from orbital phase MESSENGER mission, identify representative ensemble active sheets magnetically connected to Mercury's shock. We show that some these exhibit particle signatures HFAs similar those observed other planets, present their key physical characteristics. Our analysis suggests shock does not only mediate supersonic plasma but also provides conditions for local acceleration heating as predicted by previous numerical simulations. Together earlier activity Earth, Venus, Mars, Saturn, our results confirm could be common property shocks characteristic size is controlled standoff distance and/or conditions.