- Title
- On the association between northward turnings of the interplanetary magnetic field and substorm onsets
- Creator
- Morley, S. K.; Freeman, M. P.
- Relation
- Geophysical Research Letters Vol. 34, Issue 8
- Publisher Link
- http://dx.doi.org/10.1029/2006GL028891
- Publisher
- American Geophysical Union
- Resource Type
- journal article
- Date
- 2007
- Description
- We re-examine whether substorms are triggered by solar wind fluctuations or an internal magnetospheric instability by comparing the statistical associations between substorm onsets and (1) an external trigger definition, (2) a simple internal trigger definition of only prior loading of solar wind energy that is a subset of the external trigger definition. Statistical associations are calculated both for observed substorm onsets and onsets generated by a Minimal Substorm Model in which substorms are purely internally triggered. Thence we argue that a minimum interval of prior loading is a necessary condition for substorm onset, a subsequent northward IMF turning is not necessary, and consequently that an internal trigger from a magnetospheric instability is a necessary and sufficient condition for substorm onset. We discuss how this result may explain a report that externally triggered substorms are systematically larger than non-externally triggered substorms.
- Subject
- IMF; substorm; triggering
- Identifier
- http://hdl.handle.net/1959.13/33566
- Identifier
- uon:3245
- Identifier
- ISSN:0094-8276
- Language
- eng
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