Semenov, VS; Bogdanova, YV; Rijnbeek, RP; Buchan, MJ; (1999) A new mechanism for interpreting the motion of auroral arcs in the nightside ionosphere. Geophysical Research Letters , 26 (15) 2367 - 2370. 10.1029/1999GL900526.

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Abstract

A new mechanism is proposed for predicting and interpreting the motion of auroral arcs observed in the nightside ionosphere during the expansion phase of a substorm. This mechanism is centred on the idea that such arcs act as visible manifestations of the arrival of earthward-propagating shock waves in the near-Earth magnetosphere. These shock waves are generated at a near-Earth X-line, and propagate at the local Alfven speed. Because of the non-uniform nature of the magnetised plasma in the magnetotail, dispersion results in a change in the shape of the wave fronts as the shocks propagate towards the ionosphere. Theoretical analysis shows that a variety of are motions can occur as a result of this dispersion, depending on factors such as the reconnect ion rate, the location of the reconnection site, and gradients in the magnetic field strength and plasma density.

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