SPORADIC AND PERMANENT OSCILLATIONS IN THE MAGNETOSPHERE: ARE THEY CONNECTED?

Abstract:

We study the impact of the Pc3 permanent oscillations on the excitation of Pi2 sporadic fluctuations (periods are 10-45 and 40-150 s respectively). The hypothesis is formulated that Pc3 oscillations which are originated in front of the magnetosphere penetrate into the geomagnetic tail, cause local depression of the current in the neutral sheet, and under favorable conditions stimulate the tearing instability. This leads to the reconnection of magnetic field lines and an explosive release of magnetic energy stored in the tail. As a result, the 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 Pc3 frequency, the faster Pi2 train starts. 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 ways for the theoretical and experimental testing of the hypothesis are proposed.