Burst phenomena in solar flares

Solar flares are rapid dissipative processes in which the energy accumulated in the magnetic field is released in the forms of plasma heating, explosive plasma flows with flare shock generations, particle accelerations, and emissions in a very broad range of frequencies ranging from radio waves up to gamma rays. As solar flares and related phenomena influence not only the processes in the solar atmosphere, but also in the heliosphere, they belong to important components of space weather. While some of the flares pass quietly, other are very active. Courses of some flares are rather monotone while the others are accompanied by bursts during which sudden and usually short increase of the radiation outputs can be detected. Analyzing data from catalogues and various observations we studied rapid changes occurring in solar flare X-ray, radio and optical radiation, especially flare optical spectra including their possible polarization as well as other indirect evidence of accelerated particle beams occurrence.