Flux Relations between Hard X-Rays and Microwaves for Both Impulsive and Extended Solar Flares

Abstract

Abstract The correlation of peak fluxes between hard X-rays and microwaves from solar flares was reexamined separately for impulsive and extended bursts using 61 events recorded with both the hard X-ray spectrometer aboard the Hinotori satellite and the 17-GHz polarimeter at Nobeyama. (1) For impulsive bursts FR = 37.2 Fx0.77 with a small scatter of 0.3 orders of magnitude (rms), where FR is the 17-GHz peak flux in sfu and Fx is the hard X-ray peak flux integrated over 67–152 keV in photons s–1 cm–2. (2) Extended bursts deviate systematically above the regression line derived for impulsive bursts by a factor of 2–10 (excess of radio emission). A strong constraint is derived on the magnetic field intensity in the radio emitting region of impulsive bursts: the magnetic field intensity must be constant from flare to flare (~ 1000 G with a scatter of less than a factor of 2). The radio excess of extended bursts can be explained by a relatively abundant population of relativistic electrons trapped in large magnetic loops.