If substorm onset triggers tail reconnection, what triggers substorm onset?

	If substorm onset triggers tail reconnection, what triggers substorm onset?
	Liu, W. W.; Liang, J.; Donovan, E. F.; Spanswick, E.
刊名	JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
	2012
卷号	117 页码:A11220
ISSN号	0148-0227
通讯作者	Liu, WW (reprint author), Chinese Acad Sci, Natl Space Sci Ctr, 52 Sanlihe Rd, Beijing 100864, Peoples R China.
中文摘要	Despite the claim that tail reconnection triggers substorm onset, there is an abundance of cases wherein substorm onset triggers tail reconnection. In such cases, the first observable precursor to onset is a periodic rippling (beads) along an equatorward auroral arc. In this study, through an example, we show that substorms arising out of arcs of this type have the classical "inside-out" evolution, including the triggering of tail reconnection as a possible result. We then investigate what the magnetospheric mode underlying the ripples along the arcs might be. The classical MHD ballooning invoked by some substorm theories is inconsistent with the observation, which exhibits a finite azimuthal wavelength comparable to the local ion gyroradius and the propensity of onset to occur under moderately high (1-10) rather than extremely high plasma beta. We show that the onset is due to a modified ballooning mode, subject to corrections by the General Ohm's Law and ion heat flux. The net result is that the necessary condition for the instability remains unchanged from the classical MHD, but the growth rate of the instability is heavily attenuated or quenched in the high beta and short azimuthal wavelength limits. In the actual magnetosphere, the mode has a wavelength similar to 1,500 km, growth timescale similar to 10 s, and critical plasma beta in the 3-13 range, all consistent with observations.
英文摘要	Despite the claim that tail reconnection triggers substorm onset, there is an abundance of cases wherein substorm onset triggers tail reconnection. In such cases, the first observable precursor to onset is a periodic rippling (beads) along an equatorward auroral arc. In this study, through an example, we show that substorms arising out of arcs of this type have the classical "inside-out" evolution, including the triggering of tail reconnection as a possible result. We then investigate what the magnetospheric mode underlying the ripples along the arcs might be. The classical MHD ballooning invoked by some substorm theories is inconsistent with the observation, which exhibits a finite azimuthal wavelength comparable to the local ion gyroradius and the propensity of onset to occur under moderately high (1-10) rather than extremely high plasma beta. We show that the onset is due to a modified ballooning mode, subject to corrections by the General Ohm's Law and ion heat flux. The net result is that the necessary condition for the instability remains unchanged from the classical MHD, but the growth rate of the instability is heavily attenuated or quenched in the high beta and short azimuthal wavelength limits. In the actual magnetosphere, the mode has a wavelength similar to 1,500 km, growth timescale similar to 10 s, and critical plasma beta in the 3-13 range, all consistent with observations.
学科主题	空间物理
收录类别	SCI
资助信息	Canadian Space Agency; NASA
语种	英语
公开日期	2014-12-15
内容类型	期刊论文
源URL	[http://ir.nssc.ac.cn/handle/122/3035]
专题	国家空间科学中心_空间科学部
推荐引用方式 GB/T 7714	Liu, W. W.,Liang, J.,Donovan, E. F.,et al. If substorm onset triggers tail reconnection, what triggers substorm onset?[J]. JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS,2012,117:A11220.
APA	Liu, W. W.,Liang, J.,Donovan, E. F.,&Spanswick, E..(2012).If substorm onset triggers tail reconnection, what triggers substorm onset?.JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS,117,A11220.
MLA	Liu, W. W.,et al."If substorm onset triggers tail reconnection, what triggers substorm onset?".JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS 117(2012):A11220.