Fundamental and harmonic plasma emission in different plasma environments

Aims. Emission of radio waves from plasmas through plasma emission with fundamental and harmonic frequencies is a familiar process known from solar type II radio bursts. Current models assume the existence of counterstreaming electron beam populations excited at shocks as sources for these emission features, which limits the plasma parameters to reasonable heliospheric shock conditions. However, situations in which counterstreaming electron beams are present can also occur with different plasma parameters, such as higher magnetisation, including but not limited to our Sun. Similar radio emissions might also occur from these situations. Methods. We used particle-in-cell simulations to compare plasma microphysics of radio emission processes from counterstreaming beams in different plasma environments that differed in density and magnetization. Results. Although large differences in wave populations are evident, the emission process of type II bursts appears to be qualitatively unaffected and shows the same behaviour in all environments.