A mechanism of Pc 1 pearl formation based on the Alfven sweep maser

A self-consistent model for the generation of Pc 1 pearl emissions based on the nonlinear coupling between the magnetospheric and ionospheric resonato rs for Alfven waves is considered. Formation of pearls is attributed to the pulsating regime of the Alfven sweep maser with nonlinear selective mirror s. Such mirrors are formed by the conjugate ionospheres: their reflection c oefficient has an oscillatory frequency dependence due to eigenmodes of the ionospheric Alfven resonator. Nonlinear magnetosphere/ionosphere feedback is provided by the dependence of the value and frequency of the reflection maxima on the flux of energetic protons precipitated into the ionospheres i n the course of Alfven wave generation in the magnetosphere. A nonlinear so liton-like solution of this model is found which corresponds to a single wa ve packet having the positive frequency drift and oscillating between the c onjugate ionospheres, Properties of this solution are shown to explain many observational characteristics of Pc 1 pearls, such as their morningside pr edominance, correlation with low magnetic activity, spatio-temporal and spe ctral patterns. (C) 2000 Elsevier Science Ltd. All rights reserved.