Interference patterns in solar radio spectra: high-resolution structural analysis of the corona

Astronomical Institute of the Academy of Sciences of the Czech Republic, Fričova 298, 25165 Ondřejov, Czech Republic e-mail: [barta;karlicky]@asu.cas.cz

Received: 9 August 2005
Accepted: 29 November 2005

Abstract

Aims.We present a new method for high-resolution structural analysis of the solar corona.Methods.The relationship between the spectral features of various types of solar radio bursts and the physical properties of their sources have been extensively studied by many authors. On the other hand, it is plausible to accept that the spectral properties of the solar radio radiation received on the Earth are – besides the physics of the radio source – influenced by an inter-laying medium that radio waves propagate through. In particular, the regular structures in the solar corona – such as coronal waves, oscillations in shock fronts, the fine structures of coronal loops, streamer current sheets, etc. – might efficiently filter transferred radio radiation just as (broad-band) X-rays are filtered by a periodic atomic structure of crystals; the difference is only in the spatial scale. Using the wave optics methods, we investigate the prospective influence of considered coronal structures on the propagating radio waves originating in an external remote source.Results.Preliminary results have shown that the resulting modelled radio emission may recall the spectra of observed zebra patterns for the simple 1D density structure considered here and for a reasonable set of parameters. Conversely, it is suggested that the spectra of the zebra patterns might be used for an analysis of those coronal structures that made these traces on the radiation by methods similar to those used in crystallography. The possibility of the presence of such regular small scale structures in the solar corona is demonstrated. For completeness, a brief review of contemporary models of the zebra patterns is provided.