On Permanent and Sporadic Oscillations of the Magnetosphere

In this paper we investigate the impact of permanent oscillations Pc3 on the excitation of sporadic oscillations Pi2 ( their periods are 10-45 and 40-150 s, respectively ). The hypothesis is formulated that Pc3 oscillations originating in front of the magnetosphere penetrate into the geomagnetic tail, cause a local depression in the current in the neutral sheet, and under favorable conditions stimulate a tearing instability. This leads to reconnection of magnetic field lines and an explosive release of magnetic energy stored in the tail. As a result, a substorm breaks up, with sporadic pulsations Pi2 as an important element of this process. It is expected from theoretical estimates and kinematic considerations that the higher the Pc3 frequency, the earlier the Pi2 trains start. We test this prediction using observational data from satellite measurements of the interplanetary magnetic field and on-ground magnetic measurements. The results confirm the theoretical expectation. Additional routes are proposed to theoretically and experimentally test the hypothesis.