Abstract
Theoretical studies concerning MHD source waves of long-period (T=10-600s) magnetic pulsations are reviewed. The source waves can be classified into two groups: One is external origins, that are upstream waves driven by the ion beam instabilities in the earth's foreshock, surface waves excited by the Kelvin-Helmholtz instabilities in the magnetospheric boundary, and sudden impulses caused by an interplanetary shock and dayside reconnection. The other is internal origins, e. g., drift mirror instabilities in ring current hot ions and sudden changes during substorm onset in the nightside magnetosphere. The upstream waves, the surface waves, and the drift waves associated with a finite energy distribution and a finite thickness of layered plasma show a narrow-band frequency, while the sudden impulses have a broad-band frequency. These source waves with a nearly monochromatic frequency and a broadband frequency can couple into standing field-line oscillations in the inner magnetosphere through the field-line resonance mechanism.
