Astronomy and Astrophysics – Astronomy
Scientific paper
Jul 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004astl...30..480s&link_type=abstract
Astronomy Letters, vol. 30, p. 480-488 (2004)
Astronomy and Astrophysics
Astronomy
19
Scientific paper
We consider the modulation of nonthermal gyrosynchrotron emission from solar flares by the ballooning and radial oscillations of coronal loops. The damping mechanisms for fast magnetoacoustic modes are analyzed. We suggest a method for diagnosing the plasma of flare loops that allows their main parameters to be estimated from peculiarities of the microwave pulsations. Based on observational data obtained with the Nobeyama Radioheliograph (17 GHz) and using a technique developed for the event of May 8, 1998, we determined the particle density n ~ 3.7 x 1010 cm-3, the temperature T ~ 4 x 107 K, and the magnetic field strength B ~ 220 G in the region of flare energy release. A wavelet analysis for the solar flare of August 28, 1999, has revealed two main types of microwave oscillations with periods P1 = 7, 14 s and P2 = 2.4 s, which we attribute to the ballooning and radial oscillations of compact and extended flare loops, respectively. An analysis of the time profile for microwave emission shows evidence of coronal loop interaction. We determined flare plasma parameters for the compact (T ~ 5.3 x 107 K, n ~ 4.8 x 1010 cm-3, B ~ 280 G) and extended (T ~ 2.1 x 107 K, n ~ 1.2 x 1010 cm-3, B ~ 160 G) loops. The results of the soft X-ray observations are consistent with the adopted model.
Goldvarg T. B.
Kopylova Yu. G.
Melnikov Victor F.
Shibasaki Kazuo
Stepanov Alexander V.
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