DOI: 10.1002/2017JA025136
Scopus记录号: 2-s2.0-85045752236
论文题名: Seasonal and Temporal Variations of Field-Aligned Currents and Ground Magnetic Deflections During Substorms
作者: Forsyth C. ; Shortt M. ; Coxon J.C. ; Rae I.J. ; Freeman M.P. ; Kalmoni N.M.E. ; Jackman C.M. ; Anderson B.J. ; Milan S.E. ; Burrell A.G.
刊名: Journal of Geophysical Research: Space Physics
ISSN: 21699380
出版年: 2018
卷: 123, 期: 4 起始页码: 2696
结束页码: 2713
语种: 英语
英文关键词: AMPERE
; field-aligned currents
; seasonal variability
; SOPHIE
; space weather
; substorms
英文摘要: Field-aligned currents (FACs), also known as Birkeland currents, are the agents by which energy and momentum are transferred to the ionosphere from the magnetosphere and solar wind. This coupling is enhanced at substorm onset through the formation of the substorm current wedge. Using FAC data from the Active Magnetosphere and Planetary Electrodynamics Response Experiment and substorm expansion phase onsets identified using the Substorm Onsets and Phases from Indices of the Electrojet technique, we examine the Northern Hemisphere FACs in all local time sectors with respect to substorm onset and subdivided by season. Our results show that while there is a strong seasonal dependence on the underlying FACs, the increase in FACs following substorm onset only varies by 10% with season, with substorms increasing the hemispheric FACs by 420 kA on average. Over an hour prior to substorm onset, the dayside currents in the postnoon quadrant increase linearly, whereas the nightside currents show a linear increase starting 20–30 min before onset. After onset, the nightside Region 1, Region 2, and nonlocally closed currents and the SuperMAG AL (SML) index follow the Weimer (1994, https://doi.org/10.1029/93JA02721) model with the same time constants in each season. These results contrast earlier contradictory studies that indicate that substorms are either longer in the summer or decay faster in the summer. Our results imply that, on average, substorm FACs do not change with season but that their relative impact on the coupled magnetosphere-ionosphere system does due to the changes in the underlying currents. ©2018. The Authors. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/114214
Appears in Collections: 气候减缓与适应
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作者单位: Mullard Space Science Laboratory, UCL, Dorking, United Kingdom; Department of Physics and Astronomy, University of Southampton, Southampton, United Kingdom; British Antarctic Survey, Cambridge, United Kingdom; John Hopkins University Applied Physics Laboratory, Laurel, MD, United States; Department of Physics and Astronomy, University of Leicester, Leicester, United Kingdom; William B. Hanson Center for Space Sciences, University of Texas at Dallas, Dallas, TX, United States
Recommended Citation:
Forsyth C.,Shortt M.,Coxon J.C.,et al. Seasonal and Temporal Variations of Field-Aligned Currents and Ground Magnetic Deflections During Substorms[J]. Journal of Geophysical Research: Space Physics,2018-01-01,123(4)