Numerical Simulation of Nonlinear Beam-Plasma Interaction for the Application to Solar Radio Burst

Abstract

By the use of semi-analytical method (Takakura 1977, 1979a) the numerical simulations for the nonlinear scattering of axially symmetric plasma waves into plasma waves and radio waves have been made (Takakura 1979b, c). The initial electron beam has a finite length and one-dimensional velocity distribution of power law.

Induced back-scattering of plasma waves by thermal ions is strong even for a solar electron stream of rather low flux, say 2×10¹¹ cm^-2 above 5 keV at f_p of 40 MHz, which is enough to emit the observed type III bursts as the second harmonic.

The ratio between the energy densities of plasma waves and thermal electrons (nκT) is of the order of 10^-6, which may be a few orders lower than the threshold value for a caviton collapse of the plasma waves to occur.

The second harmonic radio emission as attributed to the coalescence of two plasma waves, i.e. one excited by electron beam and one back-scattered by ions, is several orders higher than the fundamental radio emission caused by the scattering of plasma waves by thermal ions.