MMS Observations of Electron Magnetic Reconnection without Ion Coupling in the Turbulent Magnetosheath*

In the standard model of magnetic reconnection, the process occurs in a minuscule electron-scale diffusion region. On larger scales, the ions couple to the newly-reconnected field lines and are ejected away from the diffusion region in the form of bi-directional ion jets at the ion Alfvén speed. Much of the magnetic energy is converted into ion jetting and heating in spatially extended ion exhausts.

In turbulent plasmas, which contain a large number of small-scale current sheets, reconnection has long been suggested to play a major role in the dissipation of turbulent energy at kinetic scales. In this talk, I will describe MMS observations of reconnection which involves only electrons in the turbulent magnetosheath region downstream of Earth’s quasi-parallel shocks. These observations reveal a form of reconnection that can drive turbulent energy transfer and dissipation in electron-scale current sheets without ion coupling.