High-frequency Wave Spectra in Magnetized Plasma of the Solar Corona

V.G. Ledenev$^1$, V.V. Tirsky$^2$, V.M. Tomozov$^1$

$^1$Institute of Solar-Terrestrial Physics Siberian Branch of the Russian Academy of Sciences, Lermontov St. 126, Irkutsk 664033, Russia
$^2$Institute of Laser Physics, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia

Based on numerical solving dispersion equation, we determined spectra of weakly damped high-frequency waves in the hot magnetized plasma for the weak (the electron cyclotron frequency $\omega_{He}$ is lower than the electron plasma frequency $\omega_{pe}$) and mildly strong ( $\omega_{He} \geq \omega_{pe}$) magnetic field. Eigen oscillation spectra of the hot magnetized plasma differ significantly from spectra of the cold one. At the fixed level of the solar corona longitudinal waves can be excited in wide frequency band (up to 40% of the plasma frequency) in the region of the refraction index n $>$ 10. There are waves with anomalous dispersion (i.e. waves whose frequency decreases when wave number increases) at the angles between the wave vector and the magnetic field close to $90{\hbox{$^\circ$}}$ and n $>$ 1. Under condition $\omega_{He} > \omega_{pe}$ dispersion curves corresponding to z-mode and ordinary waves approach and became practically indistinguishable under $\omega_{He}^2 \gg \omega_{pe}^2$. Obtained results allow us to explain more naturally the origin of such events in solar radio emission as type IV bursts, U-bursts and wideband pulsations.