Plasma irregularities in the high-latitude ionospheric F-region and their diamagnetic signatures as observed by CHAMP

摘要

Diamagnetic effects of ionospheric irregularities have been investigated at low-latitudes before, but no corresponding effort has been made at high latitudes. In this study we demonstrate clear diamagnetic signatures of high-latitude ionospheric irregularities as observed by the CHAMP satellite. We also present the climatology of these diamagnetic signatures for the years 2001-2010 and compare it with a previous study based on Global Positioning System(GPS)scintillation measurements. The climatology of the diamagnetic signatures is in reasonable agreement with that of the scintillations. The occurrence rate of the ionospheric irregularities generally peaks along the auroral latitudes around the pole, but it is not uniform zonally. The occurrence rate exhibits a maximum at the dayside cusp and in the pre-midnight ionosphere. The occurrence rate increases with solar and/or auroral activity. The region of high occurrence rate expands equatorward with increasing auroral activity. Occurrence probabilities are higher in local winter than in local summer. The overall occurrence rate is smallest around June solstice and largest around December solstice. The ionospheric irregularities are generally accompanied by bursts of small-scale field-aligned currents(FACs), and they are related to Region 1 FACs.