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If substorm onset triggers tail reconnection, what triggers substorm onset?
Liu, W. W.; Liang, J.; Donovan, E. F.; Spanswick, E.; Liu, WW (reprint author), Chinese Acad Sci, Natl Space Sci Ctr, 52 Sanlihe Rd, Beijing 100864, Peoples R China.
Department空间科学部
Source PublicationJOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
2012
Volume117Pages:A11220
ISSN0148-0227
Language英语
AbstractDespite 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.; 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.
Indexed BySCI
Funding Project中国科学院空间科学与应用研究中心
Document Type期刊论文
Identifierhttp://ir.nssc.ac.cn/handle/122/3035
Collection空间科学部
Corresponding AuthorLiu, WW (reprint author), Chinese Acad Sci, Natl Space Sci Ctr, 52 Sanlihe Rd, Beijing 100864, Peoples R China.
Recommended Citation
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.,&Liu, WW .(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.
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