Stochastic Wave Growth in Diverse Space Plasmas: Theory, Simulation, Data

Burstiness of observed wave emissions in space plasmas has been addressed via stochastic theories of wave growth. These include elementary burst theories (EBT) of solar microwave spike burst, for example, and stochastic growth theory (SGT) of type II and III radio bursts and other planetary and heliospheric sources. These theories are unified here, the EBT and SGT regimes are elucidated, and a new SGT regime is uncovered. It is predicted that all the regimes have lognormal wave-intensity statistics, but that EBT regimes will have smaller numbers of random fluctuations than SGT. This is consistent with published data. Simplified equations for the dynamics of generalized SGT, covering both regimes, are proposed and their results are compared with quasilinear and PIC simulations, and with theory. This is the first direct evidence of SGT from simulations.