, N.S. Meshalkina, Y. Yan
A.T. Altyntsev, N.S. Meshalkina, Y. Yan
Institute of Solar-Terrestrial Physics, Siberian Branch of the
Russian Academy of Sciences, Lermontov st. 126., Irkutsk 664033, Russia
National Astronomical Observatories, Chinese Academy of Sciences,
Datun Road A20, Chaoyang District, Beijing 100012, China
Observations of fine structures in radio bursts provide an opportunity to locate sites of the electron acceleration during the elementary acts of energy release, to determine parameters of plasma there and in loops where of tens-of-keV electron fluxes are propagating. The features of a fine structure in a centimeter range have allowed studying variations of plasma density along the flare loops, the effects caused by the evaporation waves. We describe various types of solar microwave bursts with subsecond pulses using data received with the Siberian Solar Radiotelescope (SSRT) and the Solar Radio Spectrometers (SRS) of National astronomical observatory of China. In some cases we analyze the SSRT observations with the sources localization at two neighboring frequencies simultaneously, and, as consequence, with separation out space and time variations of the drifting structures. The wave mode of emission was determined in a number of events, using the source localization in magnetograms. We have shown that the density variations due to a MHD processes can provide a main contribution to the frequency drift in the centimeter wavelengths. An intrinsic feature of energy release process - reconnection is plasma density enhancement in current sheets. A unique method to detect this effect is provided by the analysis of drifting bursts, whose emission frequency is close to the local Langmuir frequency or its harmonics. It is also argued that during the reconnection the electrons are accelerating predominantly across a magnetic field. This study was supported by Russian projects of RFBR No. 05-07-90147, 06-02-16295 and the Program of RAN No. 16.