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We report observations of slowly drifting pulsating structures (DPS) in the 0.8-4.5 GHz frequency range of the RT4 and RT5 radio spectrographs at Ondrejov observatory, between 2002 and 2012. We found 106 events of drifting pulsating structures, which we classified into 4 cases: (I) single events with a constant frequency drift [12 events], (II) multiple events occurring in the same flare with constant frequency drifts [11 events], (III) single or multiple events with increasing or decreasing frequency drift rates [52 events], and (IV) complex events containing multiple events occurring at the same time in the different frequency range [31 events]. Many DPSs are associated with hard X-ray bursts (15-25 keV) and soft X-ray gradient peaks, as they typically occurred at the beginning of the hard X-ray peaks. This indicates that DPS events are related to the processes of fast energy release and particle acceleration. Furthermore, interpreting DPSs as signatures of plasmoids, we measured their ejection velocity, their width and their height from the DPS spectra, from which we also estimated the reconnection rate and the plasma beta. In this interpretation, constant frequency drift indicates a constant velocity of a plasmoid, and an increasing/decreasing frequency drift indicates a deceleration/acceleration of a plasmoid ejection. The reconnection rate shows a good positive correlation with the plasmoid velocity. Finally we confirmed that some DPS events show plasmoid counterparts in AIA/SDO images.
We investigate the type III radio bursts and X-ray signatures of accelerated electrons in a well observed solar flare in order to find the spatial properties of the acceleration region. Combining simultaneous RHESSI hard X-ray flare data and radio da
We report a strong association between the particle acceleration and plasma motions found in the 2010 August 18 solar flare. The plasma motions are tracked in the extreme-ultraviolet (EUV) images taken by the Atmospheric Imaging Assembly (AIA) on boa
The Soft X-ray Telescope (SXT) on board Yohkoh revealed that the ejection of X-ray emitting plasmoid is sometimes observed in a solar flare. It was found that the ejected plasmoid is strongly accelerated during a peak in the hard X-ray emission of th
Solar flares - the most powerful explosions in the solar system - are also efficient particle accelerators, capable of energizing a large number of charged particles to relativistic speeds. A termination shock is often invoked in the standard model o
We study the release of energy during the gradual phase of a flare, characterized by faint bursts of non-thermal hard X-ray (HXR) emission associated with decimetric radio spikes and type III radio bursts starting at high frequencies and extending to