  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).
