Multiple brightenings of transient dayside auroral forms during oval expansions

Abstract

Poleward moving transients have been proposed to be ionospheric signatures of plasma transfer events taking place at the dayside magnetopause. They are usually observed to brighten at the equatorward edge of the dayside auroral oval and fade as they move into the polar cap. This paper reports the observation of a new type of poleward moving dayside auroral transient which has several cycles of intensity variations. Observations of these transients show a series of intensifications in brightness along the arc or rayed band during poleward motion accompanied by a brightening in the auroral oval. As they reach their extreme poleward position they brighten and than fade from view. This brightening sequence may be explained by multiple reconnection of the magnetic flux tube associated with the transient.