A multiwavelength study of three solar flares

In this paper we seek a self-consistent model for three strong limb flares observed at 17 and 34 GHz by the Nobeyama radioheliograph and also in soft X-rays and hard X-rays by the Yohkoh SXT (Soft X-Ray Telescope) and HXT (Ha rd X-Ray Telescope) instruments. Additional radio spectral data were provid ed by the Nobeyama polarimeter. The flare geometry is simple, with one well -defined flaring loop in each event. The 17 and 34 GHz emissions are optica lly thin gyrosynchrotron radiation from energetic electrons that outlines t he flaring loops and peaks close to the loop tops. We infer that the variat ion of magnetic field along the loops is vary small. We try to reproduce th e observed radio morphologies and fluxes using a model gyrosynchrotron loop . The results of our modeling rely on the model magnetic field geometry tha t we choose. Although the exact loop geometry cannot be constrained from a two-dimensional snapshot, we choose for simplicity a line-dipole magnetic f ield, and the model field lines are circular. The. SXT/HXT images are used to provide the physical parameters of the model loops. The high-frequency p olarimeter data give the energy spectral index of the radio-emitting electr ons. We could not reconcile the observed radio morphologies and fluxes usin g classic dipole magnetic field models. The best-fit model that uses the sa me input parameters for both frequencies and partly reconciles the observed 17 and 34 GHz morphologies and fluxes is produced when we invoke a magneti c field with constant strength along the model loop. These model loops have uniform thickness. The derived densities of the radio-emitting electrons a re (1-6) x 10(4) cm(-3) with energy limits between 60 and 5000 keV. These m odels are the best fits we can get under the best assumptions we can justif y, but they do not in fact match the radio morphologies very well; their pr oblems and limitations are discussed.