Electron-scale Magnetic Holes as a Possible Universal Signature of Energy Dissipation in Space Plasmas
Abstract
Electron-scale magnetic holes are observed depressions in total magnetic field strength |B| with spatial scales on the order of or less than the local proton gyroradius. These structures are indicative of electron vortices rotating perpendicular to the ambient magnetic field. How these vortices are generated and how they affect their environment are currently not well understood. They have been prevalently observed, however, in the terrestrial magnetosheath and plasmasheet and are commonly associated with electron trapping. In addition to the magnetosheath and plasmasheet, we present new observations that confirm the existence of electron-scale magnetic holes in the terrestrial bow shock, dayside magnetopause (taken by MMS), and even the Venusian magnetosphere (taken by Parker Solar Probe). The persistent observation of these structures in multiple varied regions in space indicate the presence of a universal process in space plasma. We also present observations of various wave activity, density enhancements and heating associated with electron-scale magnetic holes. These observations show varying degrees of electron heating in different plasma regions, ranging from a few to hundreds of eV.