DOI: 10.1002/2017JA024792
Scopus记录号: 2-s2.0-85042292257
论文题名: Nightside Magnetosphere-Ionosphere Current Circuit: Implications for Auroral Streamers and Pi2 Pulsations
作者: Ohtani S. ; Uozumi T.
刊名: Journal of Geophysical Research: Space Physics
ISSN: 21699380
出版年: 2018
卷: 123, 期: 1 起始页码: 350
结束页码: 363
语种: 英语
英文关键词: auroral streamers
; fast plasma sheet flows
; field-aligned currents
; magnetosphere-ionosphere coupling
; Pi2 pulsations
; substorms
英文摘要: We investigate the electrodynamic coupling of the nightside magnetosphere-ionosphere system using the analogy of a current circuit. In our model circuit the generator drives a constant current, which flows through the magnetotail and ionosphere branches. The magnetotail branch has a capacitor C and resistor RT, whereas the ionospheric branch has an inductor L and resistor RI. Each element is physically described with local quantities and geometries. For RT ≪ RI the electric circuit is characterized by three time constants: τCR(=CRT), τLC(=√LC), and τL/R(=L/RI). It is found that τCR is of the order of the ion gyroperiod in the plasma sheet, and τLC and τL/R correspond to the eigenperiod and decay time of the field line oscillation, respectively. Therefore, despite the variability of each circuit element, τCR ≪ τLC ≪ τL/R holds generally. It is found that under this condition the current circuit is characterized as overdamped, and its decay time constant is given by τL/R. RI is smaller, and therefore, τL/R is longer as the structure is more elongated in the direction of convection. This may explain why the auroral streamers, which are considered to be the ionospheric manifestation of fast flows in the plasma sheet, last significantly longer than the flows themselves. Another application is the Pi2 pulsations at the substorm onsets. If RT increases by a factor of τLC/τCR, the system indeed becomes underdamped, and the oscillation period is given by 2πτLC. It is suggested that the substorm initiation is a distinct process with a significant enhancement of tail resistivity in a localized area. ©2017. American Geophysical Union. All Rights Reserved. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/114867
Appears in Collections: 气候减缓与适应
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作者单位: The Johns Hopkins University Applied Physics Laboratory, Laurel, MD, United States; International Center for Space Weather Science and Education, Kyushu University, Fukuoka, Japan
Recommended Citation:
Ohtani S.,Uozumi T.. Nightside Magnetosphere-Ionosphere Current Circuit: Implications for Auroral Streamers and Pi2 Pulsations[J]. Journal of Geophysical Research: Space Physics,2018-01-01,123(1)