Self-similar Model of Type III Solar Radio Bursts

Type III solar radio bursts occur when suprathermal electrons, energized by solar flares, stream outward along open magnetic field lines, producing radio emission at the local plasma frequency and its harmonic. Typical frequency drift rates of type III bursts over a wide range of frequencies have a power law dependence with frequency (Alvarez and Haddock, 1973). Typical excitation times and decay times also show a power law dependence on frequency (Fainberg and Stone, 1974). We derive these fundamental characteristics of the satellite-observed type III bursts by assuming that time and frequency form a single self-similar parameter, which we use to express time variation of the radiation intensity from an individual source. The self-similar profiles are very useful for modeling type III bursts and for understanding the underlying physics. Comparisons of our theoretical profiles with observed intensity profiles will be presented. H. Alvarez and F. T. Haddock, Solar wind density model from km-wave type III bursts, Solar Physics, 29, 197- 209, 1973. J. Fainberg, R. G. Stone, Satellite observations of type III solar radio bursts at low frequencies, Space Science Rev., 16, 145-188, 1974.