Correlations between Flare Parameters and Magnetic Parameters in Solar Flares

Abstract

Abstract We investigated correlations between flare parameters and magnetic parameters by picking up the largest and smaller flares in each sample region. The flare parameters that we used were the X-ray peak flux, characteristic duration time, and X-ray energy. These values were derived from Geostationary Operational Environmental Satellites (GOES) X-ray light curves (1–8Å). The magnetic parameters used were the averaged longitudinal field strength, averaged shear field strength, and characteristic length of flare ribbons. These magnetic parameters were derived from flaring areas. We used vector magnetograms obtained with the Solar Flare Telescope (National Astronomical Observatory of Japan) and SoHO/MDI (Michelson Doppler Imager) magnetograms. In this paper the regionally largest flare is defined as the flare whose X-ray peak flux exceeds one-fifth of the X-ray peak flux of the most intense flare in each region, and all the other flares are defined as smaller flares. From 1997 to 2003, we selected 20 flares as the regionally largest flares and 15 flares as smaller flares. We found that the X-ray peak flux of the regionally largest flares has definite correlations with the magnetic parameters, and the characteristic duration time has a definite correlation only with the characteristic length of flare ribbons. The regionally largest flares and smaller flares show different relations between the flare parameters and the magnetic parameters. They show, on the other hand, a single relation between the X-ray energy and the magnetic free energy index derived from the photospheric magnetic parameters.