Paper#: 38
Poster #:
Session Name: Workshop 5C: Tail Processes
Room: West Ballroom
Day: Thursday
Time: 4:10-4:30 p.m.
Abstract Title: Magnetospheric Response to the Solar Wind Dynamic Pressure Inferred from Polar Cap Index
PresentSurname: Lukianova, R.Y.
All Authors: R.Y. Lukianova, O.A. Troshichev
Abstract : Polar cap index (PC) is derived from geomagnetic data from a single near-pole station. It is the measure of magnetic disturbances caused by transpolar portion of ionospheric current associated with global convection system. Comparison of interplanetary magnetic field and solar wind quantities with PC index shows an of polar cap magnetic activity in direct response to solar wind dynamic pressure enhancement during the period of stable IMF. Thirty strong magnetic storms occurred on 1998-2001 have been examined. We find that dynamic pressure has a major influence on polar cap currents throughout the period of interplanetary shock/magnetosphere interaction. It leads to a loss of linear dependence and a poor correlation of the PC index with the interplanetary electric field. The magnitude of PC index response to a southward IMF and to a dynamic pressure pulse can be of the same value. Another notable feature of the PC index is 1-3 min negative spikes that occur just before the sharp increase of polar cap magnetic activity. Negative spike coincides with a spike in the AE index and a sharp jump of H-SYM index that indicates intensification of auroral electrojets and sharp compression of the dayside magnetopause. Particle injections of the same duration as spikes are observed simultaneously at geosychronous orbit. Possible explanation of negative PC spike is suggested in framework of simplified nonlinear electric circuit.