Multisatellite observations of geomagnetic pulsations

A review of results of using multiple satellite data taken simultaneously of ULF pulsations in the magnetosphere is presented. Attention is focused on Pc 3, 4, 5, and Pi 2 pulsations detected by OGO 5, ATS 1 and 6, SMS 1 and 2, and three ISEE spacecraft. At first only chance close encounters by spacecraft simultaneously entering the magnetosphere could be exploited to obtain some detail of the magnetospheric activity. The ISEE 1 and 2 spacecraft regularly enter the magnetosphere at distances less than 1/2 earth radius, and have revealed that a multiplicity of waveforms routinely occurs over short distances. The wave frequency increases closer to the earth surface, and the length scale of various resonances has been found to be less than one earth radius. A large difference has been noted between morning and afternoon signals in the Pc 4 period band. Pi 2s have been found to be localized in the GEO.