NONLINEAR PROBLEMS OF PHYSICS OF THE GEOMAGNETIC-PULSATIONS

The current state of research involving manifestations of nonlinearity in geomagnetic pulsations is reviewed. Traditionally, the attention of researchers was focused on the effects of resonant interaction of geomagnetic pulsations with small groups of energetic particles, which actually means the study of the quasi-linear relaxation of radiation belt ions, the modulation of auroral electron fluxes, etc. The present review concentrates on the problem of the nonlinear effect influence of pulsations on the background ('cold') plasma and on the geomagnetic field. This kind of interaction results in a significant modification of the plasma distribution in the magnetosphere. Self-consistent wave structures - solitons and vortices may occur as well. Such nonlinear effects contribute to physics of geomagnetic pulsations and are also of fundamental importance for general physics. Another set of more narrow problems considered in the review, is related to phenomenological modeling of fluctuational and critical phenomena in the magnetosphere. The essence of our approach is to present the magnetosphere as a black box, whose properties should be determined by the statistical characteristics of its output signals. This approach to phenomenology can be a useful supplement to the methods of microscopic modeling aimed at detecting nonlinear manifestations of geomagnetic pulsations.