Effects of auroral potential drops on plasma sheet dynamics. Issue 11 (26th November 2016)

• Record Type: Journal Article
• Authors: Xi, Sheng; Lotko, William; Zhang, Binzheng; Wiltberger, Michael; Lyon, John
• Is Part Of: Journal of geophysical research. Volume 121:Issue 11(2016:Nov.)
• Page Start: 11, 129
• Page End: 11, 144
• Publication Date: 2016-11-26
• Subjects: magnetosphere‐ionosphere coupling -- auroral potential drops -- plasma sheet structure -- field‐aligned currents -- magnetic reconnection; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2016JA022856
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: The reaction of the magnetosphere‐ionosphere system to dynamic auroral potential drops is investigated using the Lyon‐Fedder‐Mobarry global model including, for the first time in a global simulation, the dissipative load of field‐aligned potential drops in the low‐altitude boundary condition. This extra load reduces the field‐aligned current ( j || ) supplied by nightside reconnection dynamos. The system adapts by forcing the nightside X line closer to Earth, with a corresponding reduction in current lensing ( j || / B = constant) at the ionosphere and additional contraction of the plasma sheet during substorm recovery and steady magnetospheric convection. For steady and moderate solar wind driving and with constant ionospheric conductance, the cross polar cap potential and hemispheric field‐aligned current are lower by approximately the ratio of the peak field‐aligned potential drop to the cross polar cap potential (10–15%) when potential drops are included. Hemispheric ionospheric Joule dissipation is less by 8%, while the area‐integrated, average work done on the fluid by the reconnecting magnetotail field increases by 50% within | y | < 8 RE . Effects on the nightside plasma sheet include (1) an average X line 4 RE closer to Earth; (2) a 12% higher mean reconnection rate; and (3) dawn‐dusk asymmetry in reconnection with a 17% higher rate in the premidnight sector. Key Points: Auroral potential drops reduce hemispheric field‐aligned current and cross polar cap potential in global simulations Cause nightside reconnection to migrate earthward and reduce the area of the plasma sheet Increase the nightside reconnection rate, with a larger rate in the premidnight sector relative to the postmidnight