High-frequency waves in the solar coronal plasma

We derived numerical solutions of a dispersion equation in order to analyze the effect of finite plasma temperature on the high-frequency wave dispersion characteristics in conditions of hot magnetized plasma in the solar corona. Spectra of the high-frequency eigen modes of these plasma were determined in conditions when the electron gyrofrequency is lower than the plasma one and when the eigen modes frequencies are higher than the electron gyrofrequency. The longitudinal wave mode is shown to turn to the Z-mode at refractive index $n < 1$. At refractive index $n \gg 1$, the longitudinal wave frequency increases when n grows, and these waves go to strongly damped ones with an anomalous dispersion. We interpret some spectral features of type II and IV radio bursts in the solar corona.

High-frequency waves in solar and stellar coronae

On the basis of a numerical solution of dispersion equation we analyze characteristics of low-damping high-frequency waves in hot magnetized solar and stellar coronal plasmas in conditions when the electron gyrofrequency is equal or higher than the electron plasma frequency. It is shown that branches that correspond to Z-mode and ordinary waves approach each other when the magnetic field increases and become practically indistinguishable in a broad region of frequencies at all angles between the wave vector and the magnetic field. At angles between the wave vector and the magnetic field close to 90\degr, a wave branch with an anomalous dispersion may occur. On the basis of the obtained results we suggest a new interpretation of such events in solar and stellar radio emission as broadband pulsations and spikes

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

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

Characteristics of plasma turbulence and radio emission from an interplanetary shock wave

Aims.We investigate the characteristics of energetic electron beams, plasma turbulence and radio emission from interplanetary shock waves. Methods.Numerical calculations of spectra and Landau damping of hot plasma eigen oscillations in the magnetic field are used. Results.It is shown that the longitudinal wave spectrum, excited in the solar wind plasma, extends with the increase of the refractive index n over range of values $n>$10. This result allows us to explain the broad band of emission, the constant value of the average ratio of frequency-band to radio emission frequency from interplanetary shock wave fronts, and to estimate the electron beam density and amplitude of Langmuir waves at the shock. It is shown that a spectrum of radio emission is determined by the spectrum of Langmuir waves excited upstream of the interplanetary shock wave by heated electrons escaping from the shock wave front