Two distinct electron populations in the 2001 April 25 event

Abstract:

We examine the release times of energetic electrons in the 2001 April 25 event. A M2.7 flare occurred in 2001 April 25, from AR09433, located at N18W09. The flare was observed in X-rays by GOES and the Yohkoh spacecraft. The Yohkoh observation also included hard X-ray images for all four energy channels: L, M1, M2, and H. We use Yohkoh observation times as a proxy for the release time of energetic electrons that propagated downward, which are responsible for the hard X-rays. In-situ $>\sim 25$ keV electrons were observed by the {\sl Wind} spacecraft. For these electrons, we obtain the release time at the Sun using the recently developed Fractional Velocity Dispersion Analysis (FVDA) method. We find that the release times of outward propagating energetic electrons are clearly delayed from those that propagated downward. Furthermore, these delayed releases are energy dependent. The implication of this delay on the underlying acceleration and trapping process of the $>\sim 25$ keV electrons at solar flares is discussed.