Vol 15, No 1

Study of a solar flare on 2005 August 22 observed in hard X-rays and microwaves

Zhong-Yin Liu, You-Ping Li, Wei-Qun Gan, Kazi Firoz


Abstract We investigate the 2005 August 22 flare event (00:54 UT) exploiting hard X-ray (HXR) observations from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and microwave (MW) observations from the Nobeyama Solar Radio Observatory. The HXR time profile exposes well-damped quasi-periodic pulsations with four sequential peaks, and the MW time profile follows the corresponding peaks. Based on this feature, we derive the time relationship of HXRs and MWs with multifrequency data from the Nobeyama Radio Polarimeter, and the spatially resolvable data from RHESSI and the Nobeyama Radioheliograph. We find that both frequency dependent delays in MWs and energy dependent delays in HXRs are significant. Furthermore, MW emissions from the south source are delayed with respect to those from the north source at both 17 GHz and 34 GHz, but no significant delays are found in HXR emissions from the different sources at the same energies. To better understand all these long time delays, we derive the electron fluxes of different energies by fitting the observed HXR spectra with a single power-law thick-target model, and speculate that these delays might be related to an extended acceleration process. We further compare the time profile of a MW spectral index derived from 17 and 34 GHz fluxes with the flux densities, and find that the spectral index shows a strong anticorrelation with the HXR fluxes.


Keywords Sun: flares — Sun: radio radiation — Sun: X-rays, gamma rays

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