Alfvén fluctuation and the earth's magnetospheric substorm.

In this paper, a mechanism of the earth's magnetospheric substorm is discussed. The magnetospheric configuration is converted from the nearly closed one into an open one, when the IMF has a large southward component. The Alfven waves with energy greater than 10 ergs/sec can pass through from the magnetosheath into the magne-totail, and the wave energy is dissipated in the plasma sheet. The particles are heated and accelerated in the plasma sheet, and then injected into the near earth space, and produce the ring current and auroral substorm. The propagation process of the Alfven wave in a shear velocity field is calculated, and the dissipation of Alfven waves in the magnetosphere is given.Using the results of this paper and the results of [4] we can explain the phenomena that the substorm is easy to appear when the IMF turn to south. But the sub-storm does not correspond to the IMF turning south uniquely; the substorm can be produced even if the IMF is directed to north.