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Statistical azimuthal structuring of the substorm onset arc: implications for the onset mechanism

Kalmoni, N. M. E., Rae, I. J., Murphy, K. R., Forsyth, C., Watt, C. E. J. and Owen, C. J. (2017) Statistical azimuthal structuring of the substorm onset arc: implications for the onset mechanism. Geophysical Research Letters, 44 (5). pp. 2078-2087. ISSN 0094-8276

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To link to this item DOI: 10.1002/2016GL071826


The onset of an auroral substorm is generally thought to occur on a quiet, homogeneous auroral arc. We present a statistical study of independently-selected substorm onset arcs and find that over 90% of the arcs studied have resolvable characteristic spatial scales in the form of auroral beads. We find that the vast majority (~88%) of auroral beads have small amplitudes relative to the background, making them invisible without quantitative analysis. This confirms that auroral beads are highly likely to be ubiquitous to all onset arcs, rather than a special case phenomena as previously thought. Moreover, as these auroral beads grow exponentially through onset, we conclude that a magnetospheric plasma instability is fundamental to substorm onset itself.

Item Type:Article
Divisions:Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
ID Code:69202
Publisher:American Geophysical Union


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