| Autor: |
Liou, Kan, Sotirelis, Thomas, Mitchell, Elizabeth |
| Předmět: |
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| Zdroj: |
Geophysical Research Letters; 3/16/2020, Vol. 47 Issue 5, p1-8, 8p |
| Abstrakt: |
We study the effects of the east‐west (y) component of the interplanetary magnetic field (IMF) on the occurrence of substorms by analyzing 16,743 magnetic substorm events identified with the SuperMAG SML index from 1995 to 2016. It is found, surprisingly, that substorm occurrence rates depend highly on the sign of IMF By, with, on average, ~1/3 more substorms for IMF By > 0 than for IMF By < 0. We attribute this asymmetry to the enhanced convection (e.g., more energy in the tail) under IMF By > 0 conditions. A superposed epoch analysis of the IMF indicates that the average IMF By prior to onset is positive but becomes less positive ~15 min prior to the onset, indicating that the release of the stress associated with a clockwise twisted magnetotail may be an important onset trigger. We conjecture that an asymmetry in the dayside merging efficiency may be the cause. Key Points: Substorms are more (less) frequent under positive (negative) IMF By conditionsThe majority of substorm events occur ~15 min after a reduction of the IMF By component [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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