Asymmetric multiple auroral arcs and inertial Alfvén waves

High‐resolution optical observations by the University of Calgary Portable Auroral Imager show a frequent occurrence of asymmetric multiple small‐scale auroral arc structures during auroral substorms. Whereas the classical multiple arc array tends to exhibit a fairly symmetrical configuration, with...

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Bibliographic Details
Published in:Geophysical research letters 1997-11, Vol.24 (22), p.2945-2948
Main Authors: Trondsen, T. S., Cogger, L. L., Samson, J. C.
Format: Article
Language:English
Subjects:
Airglow. Aurora
Earth, ocean, space
Exact sciences and technology
External geophysics
Physics of the high neutral atmosphere
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Summary:High‐resolution optical observations by the University of Calgary Portable Auroral Imager show a frequent occurrence of asymmetric multiple small‐scale auroral arc structures during auroral substorms. Whereas the classical multiple arc array tends to exhibit a fairly symmetrical configuration, with parallel motions within individual discrete arcs being opposite in direction across the center of the arc array, the multiple arcs to be discussed herein are distinguished by the presence of discrete arcs strictly equatorward of the two bright counter‐streaming arcs that would ordinarily define the center of the arc array. The intensity of these parallel equatorward‐lying arcs were in most cases found to decrease rapidly in the equatorward direction. By considering the topology of the structures and the spacing between arcs, observations are found to be consistent with recent theories suggesting inertial Alfvén waves as a possible cause of fine‐scale auroral arcs.
ISSN:0094-8276
1944-8007
DOI:10.1029/97GL52855