Interhemispheric contrasts in the ionospheric convection response to changes in the interplanetary magnetic field and substorm activity: a case-study

摘要

Interhemispheric contrasts in the ionosphericconvection response to variations of the interplanetary magnetic field (IMF) andsubstorm activity are examined, for an interval observed by the PolarAnglo-American Conjugate Experiment (PACE) radar system between ~1600 and ~2100MLT on 4 March 1992. Representations of the ionospheric convection patternassociated with different orientations and magnitudes of the IMF and nightsidedriven enhancements of the auroral electrojet are employed to illustrate apossible explanation for the contrast in convection flow response observed inradar data at nominally conjugate points. Ion drift measurements from theDefence Meteorological Satellite Program (DMSP) confirm these ionosphericconvection flows to be representative for the prevailing IMF orientation andmagnitude. The location of the fields of view of the PACE radars with respect tothese patterns suggest that the radar backscatter observed in each hemisphere iscritically influenced by the position of the ionospheric convection reversalboundary (CRB) within the radar field of view and the influence it has on thegeneration of the irregularities required as scattering targets byhigh-frequency coherent radar systems. The position of the CRB in eachhemisphere is strongly controlled by the relative magnitudes of the IMF B_zand B_y components, and hence so is the interhemisphericcontrast in the radar observations.Key words. Magnetospheric physics · Auroral phenomena· Magnetosphere-ionosphere interactions · Storms and substorms