抄録
Observations of Pc waves in the magnetosphere are reviewed with emphasis on the discussion of satellite-ground correlations. Gross features of wave occurrence in the Pc 3-5 frequency range are shown to be well summarized by taking into account the polarization characteristics of the waves with respect to the ambient magnetic field. In the Pc 4-5 frequency range, azimuthally polarized-transverse waves, which occur predominantly on the morning side of the magnetosphere, show a good correlation with ground Pc events. Radially polarized waves dominate in the afternoon and dusk sectors and are less correlated with ground pulsations than azimuthal waves. Compressional waves, such as stormtime Pc 5 observed at synchronous altitude in the afternoon and compressional Pc 5 observed with HEOS 1 in the dusk, have not yet been identified on the ground. Only compressional waves in space, which belong to the radial class and show a strong ground correlation, are giant pulsations as observed in the morning sector on the ground. Although the problem remains to be studied further, the difference in degree of ground-satellite correlations of Pc waves seems to reflect the spatial extent of respective wave phenomena. As for most of ground-correlated Pc waves, observations appear to yield evidence that a rotation of the wave ellipse orientation occurs between the magnetosphere and the ground as predicted by theory.
