Polarization changes in solar radio emission caused by scattering from high-frequency plasma turbulence^*

¹ Institute of Solar-Terrestrial Physics, Irkutsk, 664033, PO Box 4026, Russia
² Institute of Laser Physics, Irkutsk Branch, Russia
³ Trieste Astronomical Observatory, via G. B. Tiepolo 11, 34131 Trieste, Italy

Corresponding author: V. G. Ledenev, leden@iszf.irk.ru

Received: 29 March 2002
Accepted: 13 May 2002

Abstract

This paper deals with the scattering of electromagnetic radiation during propagation through a plasma layer with developed Langmuir turbulence. The ordinary component is slightly lowered, while the extraordinary component undergoes the most effective scattering. This leads to a change in the polarization characteristics of the original radiation, namely: the extraordinarily polarized emission can undergo a substantial decrease and even the polarization sign can be changed. As a consequence the radiation increases its polarization degree in the ordinary mode.
We performed calculations of the polarization of the radio emission propagating through a layer of turbulent plasma and examined the complex event that occurred on July 14, 2000; specifically, this event showed long-lasting emissions and the polarization varied both in time and in frequency range. Assuming that the variation of the polarization degree during the lifetime of the phenomenon is determined by the scattering from Langmuir turbulence, we obtained an estimate of the level of turbulence and of the magnetic field intensity in the emission region.