RHESSI Investigation of X-Ray Coronal Sources During Decay Phase of   Solar Flares: I. Observations
  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). 
Tomasz Mrozek, Zbigniew Koltun, Sylwester Kolomanski and Urszula   Bak-Steslicka
astro-ph.SR