Magnetospheric disturbances excited by solar wind density enhancements on April 11, 1997

Abstract

Disturbances in the solar wind density, geomagnetic field, and magnetospheric plasma density and fluxes are analyzed. The disturbances have the same sign and are close to each other in time. They accompany the process of amplitude modulation of Pc 1 geomagnetic pulsations during the recovery phase of the moderate magnetic storm of April 10-11, 1997. The magnetospheric disturbances were recorded by ground-based obser- vatories and on spacecraft in all local time sectors with insignificant time delays. It is concluded that in this case variations in the geomagnetic field and magnetospheric plasma density are primary, whereas the amplitude modulation of Pc 1, 2 is a secondary manifestation of fast magnetosonic (FMS) waves that are generated during the interaction between the magnetosphere and solar wind density irregularities.