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Study of flare energy release using events with numerous type III-like bursts in microwaves  

Natalia Meshalkina   Submitted: 2012-06-19 18:15

The analysis of narrowband drifting of type III-like structures in radio bursts dynamic spectra allows to obtain unique information about primary energy release mechanisms in solar flares. The SSRT spatially resolved images and a high spectral and temporal resolution allow direct determination not only the positions of its sources but also the exciter velocities along the flare loop. Practically, such measurements are possible during some special time intervals when the SSRT (about 5.7 GHz) is observing the flare region in two high-order fringes; thus, two 1D scans are recorded simultaneously at two frequency bands. The analysis of type III-like bursts recorded during the flare 14 Apr 2002 is presented. Using-muliwavelength radio observations recorded by SSRT, SBRS, NoRP, RSTN we study an event with series of several tens of drifting microwave pulses with drift rates in the range from -7 to 13 GHz/s. The sources of the fast-drifting bursts were located near the top of the flare loop in a volume of a few Mm in size. The slow drift of the exciters along the flare loop suggests a high pitch-anisotropy of the emitting electrons.

Authors: N. S. Meshalkina, A. T. Altyntsev, D. A. Zhdanov, S. V. Lesovoi, A. A. Kochanov, Yan Yihua, Tan Chengming
Projects: None

Publication Status: Solar Physics, in press
Last Modified: 2012-06-20 12:11
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High-Energy Emission from a Solar Flare in Hard X-rays and Microwaves  

Natalia Meshalkina   Submitted: 2009-08-16 18:24

We investigate accelerated electron energy spectra for different sources in a large flare using simultaneous observations obtained with two instruments, the Nobeyama Radio Heliograph (NoRH) at 17 and 34 GHz, and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) at hard X-rays. This flare is one of the few in which emission up to energies exceeding 200 keV can be imaged in hard X-rays. Furthermore, we can investigate the spectra of individual sources up to this energy. We discuss and compare the HXR and microwave spectra and morphology. Although the event overall appears to correspond to the standard scenario with magnetic reconnection under an eruptive filament, several of its features do not seem to be consistent with popular flare models. In particular we find that (1) microwave emissions might be optically thick at high frequencies despite a low peak frequency in the total flux radio spectrum, presumably due to the inhomogeneity of the emitting source; (2) magnetic fields in high-frequency radio sources might be stronger than sometimes assumed; (3) sources spread over a very large volume can show matching evolution in their hard X-ray spectra that may provide a challenge to acceleration models. Our results emphasize the importance of studies of sunspot-associated flares and total flux measurements of radio bursts in the millimeter range.

Authors: M.R. Kundu, V.V. Grechnev, S.M. White, E.J. Schmahl, N.S. Meshalkina, L.K. Kashapova
Projects: None

Publication Status: Solar Physics, in press
Last Modified: 2009-08-17 08:51
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Study of flare energy release using events with numerous type III-like bursts in microwaves
High-Energy Emission from a Solar Flare in Hard X-rays and Microwaves

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