ИСТИНА

We analysed Hα spectra and filtergrams observed with the Ondrejov multichannel flare spectrograph (MFS) in flares located both on the solar disk and limb with a high temporal resolution. We measured values of FWHM (full width at the half-maximum) in the emission line profiles and compared them with the temporal evolution of soft X-ray (GOES 12, 1-8 Angstrems) and radio flux (Ondrejov RT3 radiotelescope on 3 GHz or RSTN at 2.7 GHz). All the flares were of observationally different types and of different importance. At the disk flares the rise of Hα FWHM is strongly correlated with the rise of X rays and microwave emission. The correlation is missing at the limb flares, where we found both positive and negative delay of beginning Hα FWHM rise. We found the behavior of FWHM of the Hα line profile as an auxiliary but still important parameter for a better understanding of energy release and transport processes in solar flares. The FWHM of the Hα emission line in flares depends on temperature, density and microturbulence. When we see a good correlation of the FWHM fast rise with microwaves, this could be explained by chromospheric response to the accelerated electron flux injection. This type of particles causes the microwave emission and they are also effective agents for immediate heating of the dense chromosphere. If we observe a delay more than several seconds between the FWHM and X-rays and microwave rise, we surely face the effect of gas-dynamic processes of chromospheric heating. These processes could be connected with increasing volume of heated plasma, evaporation or plasma movement. The effect of the very fast correlation of Hα FWHM and microwave with no doubts corresponds to a classical flare physics theory. But most interesting results were found for the limb flares where we really observed the flare loops but not the footpoints. In one flare we found the rise of FWHM before the flare beginning. It could be caused by the current sheet heatig before the flare onset. The same result, but for hard X-rays, was found by Battaglia et al. (2009). The observation of the 9 July 2002 flare when the FWHM rise was delayed to the X-ray and microwave, could be result of post-flare archade formation. This effect should be further investigated for a more statistically important amount of events.