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Astron. Astrophys. 351, 1165-1189 (1999)

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Radiowave propagation in a statistically inhomogeneous plasma

K. Arzner 1 and A. Magun 2

1 Institut für Extraterrestrische Physik, P.O. Box 1603, 85740 Garching, Germany (kja@mpe.mpg.de)
2 Institute of Applied Physics, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland (magun@mw.iap.unibe.ch)

Received 30 October 1997 / Accepted 1 October 1999

Abstract

The present work investigates the propagation of a radio pulse in an unmagnetized, statistically inhomogeneous plasma causing regular refraction and anisotropic scattering. Using the framework of geometrical optics, a Fokker-Planck equation is derived and integrated within a two-moment approximation. The method allows a continuous transition from weak to strong angular scattering and yields pulse shape, pulse delay and angular broadening detected by a distant observer. The results are compared to Monte Carlo simulations and the method is applied to coronal scattering of a burst emitted close to the local plasma frequency. It is shown that the two-moment approximation reproduces many of the features found in earlier simulations (Steinberg et al. 1971, Riddle 1972b) within a small fraction of needed computation time. Although the method was developed for solar radio bursts, it can be applied to general transport-diffusion problems due to the equivalence of geometrical optics and Hamiltonian mechanics.

Key words: Sun: radio radiation – scattering – radiative transfer

Send offprint requests to: K. Arzner

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© European Southern Observatory (ESO) 1999

Online publication: November 16, 1999
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