Observation of electron diffusion region during magnetotail reconnection

Friday, 18 December 2015
Poster Hall (Moscone South)
Mitsuo Oka1, Tai Phan1, Marit Oieroset1 and Vassilis Angelopoulos2, (1)University of California Berkeley, Berkeley, CA, United States, (2)University of California Los Angeles, Earth, Planetary, and Space Sciences, Los Angeles, CA, United States
During magnetic reconnection, magnetic field lines reconfigure themselves within the diffusion region so that magnetic energies are converted to particle energies. However, it still remains unclear how electrons behave and gain energies within the diffusion region, particularly on electron-scale. Here we report a detection of the electron diffusion region (EDR) by the THEMIS P1 spacecraft during a magnetotail reconnection event of 2009 February 7 with no appreciable guide field. Heated electrons were found in association with correlated reversals of plasma flows and magnetic fields, and the heating were primarily in the direction perpendicular to the local magnetic field. Some of the distributions of the heated electrons were non-gyrotropic. We conclude that these features are evidences of EDR and that electron energization occurred in at least two steps because there was a pre-heating in the immediate upstream of the EDR. These established signatures of the EDR will help future analysis of data from MMS which, with its super high-time resolution, will be able to fully resolve the EDR.