High Spatial Resolution Observations of a Hot Region in a Solar Flare with the [ITAL]Transition Region and Coronal Explorer[/ITAL

Abstract

The Transition Region and Coronal Explorer (TRACE) provides some of the highest spatial resolution images ever taken of hot solar flare plasma. The TRACE 195 A channel is particularly sensitive to high-temperature flare plasma because of the presence of the Fe XXIV λ192 resonance line in this bandpass. The TRACE 171 A channel observes emission from thermal bremsstrahlung during a flare. Since this emission is generally weak, it is usually not possible to derive electron temperatures for flare plasma from TRACE observations. In this Letter, we present analysis of the 2000 March 24 X1.8 limb flare that produced high count rates in both the TRACE 195 and 171 A channels. We find evidence for a small, high-temperature region near the top of the flare arcade. This hot region appears to lie at the base of the cusp-shaped structure that extends above the arcade. The TRACE observations are consistent with a strong enrichment of Fe over its photospheric value in the hot region that suggests in situ heating of this plasma. We also find that multithermal simulations of flare evolution reproduce the observations much better than an isothermal model does.