Ion bulk heating in magnetic reconnection exhausts at Earth's magnetopause: Dependence on the inflow Alfvén speed and magnetic shear angle. Issue 20 (24th October 2014)

• Record Type: Journal Article
• Authors: Phan, T. D.; Drake, J. F.; Shay, M. A.; Gosling, J. T.; Paschmann, G.; Eastwood, J. P.; Oieroset, M.; Fujimoto, M.; Angelopoulos, V.
• Is Part Of: Geophysical research letters. Volume 41:Issue 20(2014:Oct.)
• Page Start: 7002
• Page End: 7010
• Publication Date: 2014-10-24
• Subjects: Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2014GL061547
• Languages: English
• ISSNs: 0094-8276

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>We surveyed 87 magnetopause reconnection exhausts detected by the THEMIS spacecraft to investigate how the amount and anisotropy of ion bulk heating depend on the inflow boundary conditions. We find that the heating, Δ<italic>T_i</italic>, is correlated with the asymmetric Alfvén speed, <italic>V</italic>_{<italic>AL</italic>, asym}, based on the reconnecting magnetic field and the plasma number density measured in both inflow regions. Best fit to the data produces the empirical relation Δ<italic>T_i</italic> = 0.13 <italic>m_iV</italic>_{<italic>AL</italic>, asym}², where <italic>m_i</italic> is the proton mass, indicating that the increase in the ion internal (thermal) energy, 3Δ<italic>T_i</italic>/2, is 20% of the available magnetic energy per proton‐electron pair. The observed parallel heating generally exceeds perpendicular heating (by a factor of ~2), and there are some indications that the heating is reduced in the presence of a strong guide field. Finally, the ratio of ion to electron bulk heating is ~8 on average.</p> </abstract>