Does the polar cap disappear under an extended strong northward IMF?

被引:16
作者
Zhang, Yongliang [1 ]
Paxton, Larry J. [1 ]
Newell, Patrick T. [1 ]
Meng, Ching-I [1 ]
机构
[1] Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA
关键词
Aurora; Double reconnection; Interplanetary magnetic field; Closed field fine; INTERPLANETARY MAGNETIC-FIELD; ULTRAVIOLET IMAGER GUVI; ELECTRON-PRECIPITATION; MAGNETOSPHERE; LONG; MAGNETOTAIL; SIMULATION; MISSION; MODEL; TAIL;
D O I
10.1016/j.jastp.2009.09.005
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
The suggestion that the polar cap can completely disappear under certain northward IMF conditions is still controversial. We know that the size of the polar cap is strongly controlled by the interplanetary magnetic field (IMF). Under a southward IMF, the polar cap is usually large and filled with weak diffuse polar rain electrons. The polar cap shrinks under a northward IMF. Here we use the global aurora[ images and coincident particle measurements on May 15, 2005 to show that the discrete arcs (due to precipitation of both electrons and ions) expanded from the dayside oval to the nightside oval and filled the whole polar ionosphere after a long (8 h) and strong (similar to 5-30 nT) northward IMF B,, The observations suggested that the polar cap disappeared under a closed magnetosphere. (C) 2009 Elsevier Ltd. All rights reserved.
引用
收藏
页码:2006 / 2012
页数:7
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