Relation of the auroral substorm to the substorm current wedge
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- 作者：Robert L. McPherron ; Xiangning Chu
- 关键词：Auroral substorm ; Magnetospheric substorm ; Auroral expansion ; Auroral bulge ; Polar magnetic substorm ; Westward electrojet ; Substorm current wedge ; Midlatitude positive bay index
- 刊名：Geoscience Letters
- 出版年：2016
- 出版时间：December 2016
- 年：2016
- 卷：3
- 期：1
- 全文大小：2,294 KB
- 刊物类别：Earth Sciences, general; Atmospheric Sciences; Geophysics/Geodesy; Oceanography; Planetology; Biogeo
- 刊物主题：Earth Sciences, general; Atmospheric Sciences; Geophysics/Geodesy; Oceanography; Planetology; Biogeosciences;
- 出版者：Springer International Publishing
- ISSN：2196-4092
文摘
The auroral substorm is an organized sequence of events seen in the aurora near midnight. It is a manifestation of the magnetospheric substorm which is a disturbance of the magnetosphere brought about by the solar wind transfer of magnetic flux from the dayside to the tail lobes and its return through the plasma sheet to the dayside. The most dramatic feature of the auroral substorm is the sudden brightening and poleward expansion of the aurora. Intimately associated with this expansion is a westward electrical current flowing across the bulge of expanding aurora. This current is fed by a downward field-aligned current (FAC) at its eastern edge and an upward current at its western edge. This current system is called the substorm current wedge (SCW). The SCW forms within a minute of auroral expansion. FAC are created by pressure gradients and field line bending from shears in plasma flow. Both of these are the result of pileup and diversion of plasma flows in the near-earth plasma sheet. The origins of these flows are reconnection sites further back in the tail. The auroral expansion can be explained by a combination of a change in field line mapping caused by the substorm current wedge and a tailward growth of the outer edge of the pileup region. We illustrate this scenario with a complex substorm and discuss some of the problems associated with this interpretation.