抄録
A theory of one of several possible mechanisms responsible for micropulsations is presented. It is shown that hydromagnetic waves generated by an instability of the interface between solar wind and magnetosphere are transmitted through the magnetosphere and received on the surface of the earth as micropulsations. The bandwidth of the micropulsations essentially determined by the source mechanism is found to be a few tenths of a second to hundreds of seconds. The important role of the path in the magnetosphere, including that in the outer exosphere in determining the transmission characteristics of micropulsations is analyzed. The crucial role of the slightest variation of the path length in the outer magnetosphere (due to variations in the solar wind) in masking out the resonances of lower exosphere and upper ionosphere is discussed. The resonances in transmission due to the path in outer magnetosphere are seen to be more likely than those of the lower exosphere and upper ionosphere.
