Magnetic reconnection in the auroral acceleration region

• Published in: Geophysical research letters Vol. 42; no. 6; pp. 1646 - 1653
• Main Author: Chaston, C. C.
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 28-03-2015
• Subjects: Acceleration; aurora; Auroral arcs; Auroral zones; Auroras; Current sheets; Deposition; electric fields; Energy; Energy budgets; Geophysics; Identification; Imagery; Ionosphere; Magnetic fields; Magnetic reconnection; Magnetohydrodynamics; particle acceleration; Plasmas; Plasmas (physics); reconnection; Shear; Simulation; Tearing; tearing instability; Three dimensional; vorticity
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/2015GL063164

Evidence is presented for the operation of extreme guide field magnetic reconnection in the presence of sheared flows in a narrow current sheet through the auroral acceleration region. Using auroral imagery, magnetically conjugate particle measurements and a 3‐D reduced MHD simulation, vortical motions in a narrow, rapidly evolving auroral arc indicative of the operation of magnetic tearing are identified. An estimate of the contribution of this process to the observed rate of energy deposition at the ionosphere shows that while this contribution can be significant it remains a minor fraction of the total. These observations are placed in the context of low magnetic shear reconnection made possible in plasmas with low plasma beta.
Key Points
Magnetic reconnection occurs in narrow discrete auroral arcs
Magnetic reconnection can occur for extremely small magnetic shear
Magnetic reconnection contributes <20% to the auroral acceleration energy budget