RHESSI Investigation of X-Ray Coronal Sources During Decay Phase of Solar Flares: I. Observations

TL;DR

This study uses RHESSI's high-resolution imaging spectroscopy to analyze long-duration solar flare events, revealing large, evolving coronal sources with sustained high temperatures and periods of non-thermal emissions originating from loop top sources.

Contribution

It provides detailed observational data on coronal loop top sources during flare decay, highlighting their size, temperature, and emission characteristics over time.

Findings

LTS are large, evolving structures

High temperature components last for hours post-flare

Non-thermal emissions occur without footpoint signatures

Abstract

We analyse the observational characteristics for a set of Long Duration Events (LDE) using Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). Excellent energy resolution (1 keV) of HXR images reconstructed with RHESSI allowed us to perform imaging spectroscopy of coronal loop top sources (LTS) observed for hours after maximum of the flare. We found that the sources are large structures. The diameter of an LTS is changing with time and energy. High temperature component can be observed for few dozen hours after the maximum. For some time intervals clear non-thermal component was observed in spectra, but there was no significant footpoint emission at that time. All thermal and non-thermal emissions originate from the LTS. The obtained observational characteristics were used in calculating the energy balance within LTS, which are presented in Kolomanski, 2011 (this issue).