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Field line resonances as a trigger and a tracer for substorm onset

Rae, I. J., Murphy, K.R., Watt, C.J., Rostoker, G., Rankin, R., Mann, I. R., Hodgson, C. R., Frey, H. U., Degeling, A. W. and Forsyth, C. (2014) Field line resonances as a trigger and a tracer for substorm onset. Journal of Geophysical Research: Space Physics, 119 (7). pp. 5343-5363. ISSN 2169-9402

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To link to this item DOI: 10.1002/2013JA018889


In this paper, we show that periodic auroral arc structures are seen at the location of one particular auroral substorm onset for the 15 min preceding onset, suggesting that field line resonances should be considered a strong candidate for triggering substorm onset. Irrespective of whether this field line resonance is coincidentally or causally linked to this substorm onset, the characteristics of the field line resonance can be used to remote sense the characteristics of the geomagnetic field line that supports substorm onset. In this instance, the eigenfrequency of this resonance is around 12 mHz. Interestingly, however, there is no evidence of this field line resonance in a seven satellite major Time History of Events and Macroscale Interactions during Substorms (THEMIS)-GOES conjunction, ranging from geosynchronous orbit to ~30 RE. However, using space-based cross-phase measurements of the local field line eigenfrequency at the inner THEMIS locations, we find that the local field line eigenfrequency is 6–10 mHz. Hence, we can reliably say that this 12 mHz Field Line Resonance (FLR) must lie inside of THEMIS locations. Our conclusion is that a high-m field line resonance can both represent a strong candidate for a trigger for substorm onset, as first proposed by Samson et al. (1992), and that its characteristics can provide invaluable information as to where substorm onset occurs in the magnetosphere.

Item Type:Article
Divisions:Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
ID Code:37837
Publisher:American Geophysical Union


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