Observations of Double Layers in Earth’s Plasma Sheet

Abstract

We report the first direct observations of parallel electric fields ($E_{\parallel }$) carried by double layers (DLs) in the plasma sheet of Earth’s magnetosphere. The DL observations, made by the THEMIS spacecraft, have $E_{\parallel }$ signals that are analogous to those reported in the auroral region. DLs are observed during bursty bulk flow events, in the current sheet, and in plasma sheet boundary layer, all during periods of strong magnetic fluctuations. These observations imply that DLs are a universal process and that strongly nonlinear and kinetic behavior is intrinsic to Earth’s plasma sheet.