A&A 453, 729-736 (2006)
DOI: 10.1051/0004-6361:20054665

Solar bursts gyrosynchrotron emission from three-dimensional sources

P. J. A. Simões^{1, 2} and J. E. R. Costa<sup>1, 2

1</sup>  Instituto Nacional de Pesquisas Espaciais - INPE, Av. dos Astronautas, 1758 J. da Granja 515, 12227-010 São José dos Campos SP, Brazil
    e-mail: paulo@craam.mackenzie.br
²  Centro de Rádio Astronomia e Astrofísica Mackenzie - CRAAM, Rua da Consolação, 896, Ed. Amantino Vassão, 01302 São Paulo SP, Brazil

(Received 8 December 2005 / Accepted 23 February 2006 )

Abstract
Aims.In this study we have analyzed the spectral and spatial characteristics of gyrosynchrotron emission and the polarization of solar bursts in a highly inhomogeneous medium. Our main goal was to investigate the effects of the geometry of the source on the resulting spectrum.
Methods.The SOHO/EIT and TRACE high resolution images revealed structured magnetic configurations in detail over solar active regions. In our method, we represent the magnetic field geometry by three-dimensional structures obtained from magnetic field extrapolation, tomography, or any geometry that resembles the observed structures. The gyrosynchrotron radiation was numerically calculated through a modified version of Ramaty's code.
Results.We calculated the radiation produced by non-thermal electron distributions in this complex environment and solved the radiative transfer equation. The results, presented in brightness distribution maps, polarization maps, and spectra, are discussed. Our numerical results agree with statistical analyses of observed spectra present in the literature. We note a spectral broadening due to the spatial and intensity inhomogeneity of the magnetic field and no center-to-limb variations, which cannot be explained by homogeneous source models. The computed maps revealed a non uniform brightness distribution, with small-scale structures, and different spatial characteristics in each frequency. Also, we found different spectral characteristics at different regions of the emitting source. Polarization maps reveal its high dependence on geometry and on the position of the source on the solar disk.

Key words: Sun: flares -- Sun: radio radiation -- Sun: activity -- Sun: magnetic fields -- Sun: particle emission

© ESO 2006

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

• If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
• You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
• You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.