Radio spectral evolution of an X-ray-poor impulsive solar flare: Implications for plasma heating and electron acceleration

Document Type

Article

Publication Date

1-1-2007

Abstract

We present radio and X-ray observations of an impulsive solar flare that was moderately intense in microwaves, yet showed very meager EUVand X-ray emission. The flare occurred on 2001 October 24 and was well observed at radio wavelengths by the Nobeyama Radioheliograph (NoRH), the Nobeyama Radio Polarimeters (NoRP), and the Owens Valley Solar Array (OVSA). It was also observed in EUVand X-ray wavelength bands by the TRACE, GOES, and Yohkoh satellites. We find that the impulsive onset of the radio emission is progressively delayed with increasing frequency relative to the onset of hard X-ray emission. In contrast, the time of flux density maximum is progressively delayed with decreasing frequency. The decay phase is independent of radio frequency. The simple source morphology and the excellent spectral coverage at radio wavelengths allowed us to employ a nonlinear χ2- minimization scheme to fit the time series of radio spectra to a source model that accounts for the observed radio emission in terms of gyrosynchrotron radiation from MeV-energy electrons in a relatively dense thermal plasma. We discuss plasma heating and electron acceleration in view of the parametric trends implied by the model fitting. We suggest that stochastic acceleration likely plays a role in accelerating the radio-emitting electrons. © 2007. The American Astronomical Society. All rights reserved.

Identifier

35348830462 (Scopus)

Publication Title

Astrophysical Journal

External Full Text Location

https://doi.org/10.1086/520106

e-ISSN

15384357

ISSN

0004637X

First Page

1256

Last Page

1267

Issue

2 I

Volume

666

Grant

0607544

Fund Ref

National Science Foundation

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