Ion and Electron Bulk Heating in Magnetic Reconnection: Dependence on the Inflow Alfvén Speed

Thursday, 18 December 2014: 2:00 PM
Tai-Duc Phan1, James Frederick Drake1,2, Michael A Shay3, John T Gosling4, Goetz Paschmann5, Marit Oieroset1, Masaki Fujimoto6, Jonathan P Eastwood7 and Vassilis Angelopoulos8, (1)University of California Berkeley, Berkeley, CA, United States, (2)University of Maryland, College Park, MD, United States, (3)University of Delaware, Newark, DE, United States, (4)Univ Colorado, Boulder, CO, United States, (5)The Max Planck Institute for Extraterrestrial Physics, Garching, Germany, (6)JAXA Japan Aerospace Exploration Agency, Sagamihara, Japan, (7)Imperial College London, London, United Kingdom, (8)University of California Los Angeles, Los Angeles, CA, United States
Based on observations of reconnection at Earth’s magnetopause we found that the amount of ion and electron heating, ΔTi and ΔTe, are both correlated with the Alfvén speed, VAL, based on the reconnecting magnetic field and the plasma number density measured in both inflow regions. Best fits to the data produce the empirical relations ΔTi = 0.13 miVAL2 and ΔTe = 0.017 miVAL2, where mi is the proton mass, indicating that the amount of ion (electron) heating is 13% (1.7%) of the inflowing magnetic energy per proton-electron pair. Our empirical relations may explain the relatively weak ion and electron heating in solar wind reconnection exhausts at 1 AU and strong heating to keV (~107-108 K) energies common in Earth’s magnetotail exhausts. The finding could potentially be used to evaluate the role of reconnection in plasma bulk heating in laboratory, solar and astrophysical contexts.