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Temporal and Spatial Analyses of Spectral Indices of Nonthermal Emissions Derived from Hard X-Rays and Microwaves View all abstracts by submitter

Ayumi Asai   Submitted: 2012-12-10 18:28

We studied electron spectral indices of nonthermal emissions seen in hard X-rays (HXRs) and in microwaves. We analyzed 12 flares observed by the Hard X-ray Telescope aboard {it Yohkoh}, Nobeyama Radio Polarimeters (NoRP), and the Nobeyama Radioheliograph (NoRH), and compared the spectral indices derived from total fluxes of hard X-rays and microwaves. Except for four events, which have very soft HXR spectra suffering from the thermal component, these flares show a gap Deltadelta between the electron spectral indices derived from hard X-rays deltaX and those from microwaves deltamu (Deltadelta = deltaX - deltamu) of about 1.6. Furthermore, from the start to the peak times of the HXR bursts, the time profiles of the HXR spectral index deltaX evolve synchronously with those of the microwave spectral index deltamu, keeping the constant gap. We also examined the spatially resolved distribution of the microwave spectral index by using NoRH data. The microwave spectral index deltamu tends to be larger, which means a softer spectrum, at HXR footpoint sources with stronger magnetic field than that at the loop tops. These results suggest that the electron spectra are bent at around several hundreds of keV, and become harder at the higher energy range that contributes the microwave gyrosynchrotron emission.

Authors: Ayumi Asai, Junko Kiyohara, Hiroyuki Takasaki, Noriyuki Narukage, Takaaki Yokoyama, Satoshi Masuda, Masumi Shimojo, and Hiroshi Nakajima
Projects: Nobeyama Radioheliograph,Yohkoh-HXT,Yohkoh-WBS

Publication Status: ApJ (accepted)
Last Modified: 2012-12-10 18:39
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