The 18 November 2015 Magnetopause Crossing: The GEM Dayside Kinetic Challenge Event Observed by MMS/HPCA

摘要

At Earth's dayside magnetopause, the fundamental process known as magnetic reconnection is responsible for connecting geomagnetic field lines to interplanetary magnetic field lines and converting magnetic energy into particle energy and heat. As part of a coordinated analysis effort by the Geospace Environment Modeling (GEM) community to determine the reconnection location and other aspects of reconnection, a magnetopause crossing by the Magnetospheric Multiscale (MMS) mission on 18 November 2015 was selected. The crossing occurred during stable solar wind and dominantly southward interplanetary magnetic field conditions. The MMS satellites were located close to the subsolar region and observed southward accelerated ion jets during encounters with the magnetopause boundary layers, indicating the presence of an active X-line north of the satellites. Using proton distributions from the Hot Plasma Composition Analyzer (HPCA) instruments, the distance from the spacecraft to the reconnection site was initially determined to be between 5 to 7 R_E. A slight rotation of the interplanetary magnetic field caused a change of the magnetic topology at the magnetopause. This topology change produced conditions which are known to change the location of the X-line. After the change, the location of the component reconnection line was estimated to be less than 4 R_E, but most likely was much closer to the observing satellites.