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Title: Control of the East‐West Component of the Interplanetary Magnetic Field on the Occurrence of Magnetic Substorms

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 SuperMAGSMLindex from 1995 to 2016. It is found, surprisingly, that substorm occurrence rates depend highly on the sign of IMFBy, with, on average, ~1/3 more substorms for IMFBy> 0 than for IMFBy< 0. We attribute this asymmetry to the enhanced convection (e.g., more energy in the tail) under IMFBy> 0 conditions. A superposed epoch analysis of the IMF indicates that the average IMFByprior 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.

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DOI PREFIX: 10.1029
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Journal Name:
Geophysical Research Letters
Medium: X
Sponsoring Org:
National Science Foundation
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