The variations of the scaling parameters of the structure functions in solar active regions at the pre-flare stage

A series of subflares in active region NOAA 9077 (July 2000) and in the activity complex NOAA 0039 + NOAA 0050 were investigated. The structure functions and their characteristics for sets of images of active regions in the hydrogen-alpha line (H-line) were calculated. The ranges of the spatial scales of different scaling behavior of the structure functions were revealed. The existence of intermittent turbulence (multi-fractal structure) in active regions of the chromosphere is shown. Peculiarities of the scaling parameters variations of the structure functions at pre-flare stage are investigated. It was found that on average 20 min before a subflare onset considerable deviation of these variations from the mean occurs, which may be of importance for predictions. It was discovered that maximum variations of scaling parameters with an accuracy to 15 min (on average), in a number of cases coincide with variations of the elongated chromospheric structures in an active-region area. We used H_ filtergrams obtained with the chromospheric telescope of the Baikal observatory operated by ISTP SD RAS. The telescope is coupled with a Halle birefringent filter with a 0.05 nm bandpass, and a Princeton Instruments 2048 × 2048 pixel CCD camera with 16-bit amplitude resolution.