SM23A-2535
Field-aligned Electric Field and Currents in the Polar cap
Tuesday, 15 December 2015
Poster Hall (Moscone South)
Simon Wing, Johns Hopkins University, Baltimore, MD, United States, Donald H Fairfield, NASA Goddard Space Flight Center, Greenbelt, MD, United States, Jay Johnson, Princeton University, Plasma Physics Laboratiry, Princeton, NJ, United States and Shinichi Ohtani, JHU/APL, Laurel, MD, United States
Abstract:
The Johns Hopkins University Applied Physics Laboratory open-field line particle precipitation model (APL-OPM) model predicts downward field-aligned electric field to maintain charge quasi-neutrality. Previous studies confirmed the existence of such electric fields. However, the present study shows that upward field-aligned electric field can be found within upward field-aligned current (FAC) region. In the upward FAC region, upward electric field that accelerates electron downward is seen with the occurrence rates of 82%–96%. In contrast, the occurrence rates in the downward FAC regions are 3%–11%. Polar rain electrons located in the upward FAC region adjacent to closed field lines often show a ramping up of energy with increasing latitude before reaching a plateau. This plateau may be attributed to the magnetosheath electrons that progressively have higher anti-sunward velocity and lower density with increasing distance from the subsolar point before they asymptotically reach the solar wind values.
