Theoretical simulation of micropulsations

The combined processes of cyclotron instability and quasilinear diffusion for low-energy protons are studied in some detail, and equations describing these processes are derived for a bounded plasma with reflecting walls. These equations are used by a computer to simulate micropulsation pulses (Pc 1). Average hydromagnetic wave amplitudes in the magnetosphere are calculated and are comparable to those observed on the ground in subauroral latitudes. Computed silhouette sonagrams bear a close resemblance to ground-based experimental data. Direct comparison of amplitudes can only be made with satellite data, which does not yet exist. When low-energy proton fluxes are near the saturation limit predicted by quasi-linear diffusion theory, the effective proton lifetime shows a highly nonlinear dependence on proton flux strength; the influence of this effect on radial diffusion processes is discussed qualitatively.