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Asymmetric multiple auroral arcs and inertial Alfvén waves
Author(s) -
Trondsen T. S.,
Cogger L. L.,
Samson J. C.
Publication year - 1997
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/97gl52855
Subject(s) - arc (geometry) , physics , inertial frame of reference , geophysics , scale (ratio) , center (category theory) , intensity (physics) , alfvén wave , computational physics , geometry , geology , magnetohydrodynamics , optics , plasma , classical mechanics , mathematics , chemistry , quantum mechanics , crystallography
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.