The Hall Electric Field in Earth's Magnetotail Thin Current Sheet

One of the most important properties of Earth's magnetotail thin current sheet (TCS) is that its current is predominantly contributed by magnetized electrons. The Hall electric field, normal to the TCS and generated by charge separation, is critical to the generation of this electron current as well as a dawn‐dusk asymmetry of the magnetotail, such as duskside preference of magnetic reconnection and related structures and phenomena. However, systematic investigation of the Hall electric field has so far been lacking. Utilizing observations of TCS by Magnetospheric Multiscale and Time History of Events and Macroscale Interactions during Substorm spacecraft, we study the properties of this field. Our results, from various, complementary methods, show that the Hall electric field Ez (in the geocentric solar magnetospheric, coordinate system) or En (normal to the TCS plane) can be clearly observed to point toward the center of the current sheet. The typical magnitude of this electric field is several tenths of 1 mV/m. Statistics of Magnetospheric Multiscale magnetotail TCS crossings show that the Hall electric field is stronger on the duskside, indicating a stronger Hall effect there, which confirms predictions from global‐scale hybrid and particle‐in‐cell simulations. Key Points We utilize MMS and THEMIS observations of the Hall electric field in Earth's magnetotail TCS The Hall electric field is directed toward the center of the TCS, with an average magnitude of several tenths of 1 mV/m Statistics show that the Hall electric field is stronger on the duskside, consistent with predictions from simulations