Observations of dipolarization at geosynchronous orbits and its response in the polar cap convection during extreme southward interplanetary magnetic field conditions

摘要

Analysis of the polar cap convection and geosynchronous magnetic field measurements, in the context of dipolarization events, during extreme southward interplanetary magnetic field (IMF) conditions is presented in the paper. Clear dipolarization events at geosynchronous orbits are always followed by an increase in the polar cap convection with a time delay. The distribution of the time delay between the onset of dipolarization at geosynchronous orbit and polar cap convection response varied between 6 and 15 min with an average of 9 min. The polar cap convection response to the dipolarization events enabled the deduction of the dipolarization timescales at geosynchronous orbits and in the ionosphere. A comparison of these two timescales revealed that the timescales of dipolarization events deduced from geosynchronous magnetic field measurements were always shorter (average 11 min) than the timescales deduced from the polar cap convection measurements (average 33 min).