Large-scale fields and flows in the magnetosphere-ionosphere syst m

Abstract. Advances in our understanding of the large-scale electric and magnetic fields in the coupled magnetosphere-ionosphere syst m are reviewed. The literature appearing in the period January 1991-June 1993 is sorted into 8 general areas of study. The phenomenon of substorms receives the most aUention in this literature, with the location of onset being the single most discussed issue. However, if the magnetic topology in substorm phases was widely debated, less attention was paid to the relationship of convection to the substorm cycle. A significantly new consensus view of substorm expansion and recovery phases emerged, which was termed the 'Kiruna Conjecture ' after the conference at which it gained widespread acceptance. The second largest area of interest was dayside transient events, both near the magnetopause and the ionosphere. It became apparent that hese phenomena include at least two classes of events, probably due to transient reconnection bursts and sudden solar wind dynamic pressure changes. The contribution of both types of event to convection is controversial. The realisation that induction effects decouple lectric fields in the magnetosphere and ionosphere, on time scales shorter than several substorm cycles, calls for broadening of the range of measurement techniques in both the ionosphere and t the magnetopause. Several n w techniques were introduced including onospheric observations which yield reconnection rate as a function of time. The magnetospheric and io ospheric behaviour due to various quasi-steady interplanetary conditions was studied using magnetic loud events. For northward IMF conditions, reverse convection i the polar cap was found to be predominantly a summer hemisphere phenomenon a d even for extremely rare prolonged southward IMF conditions, the magnetosphere was observed to oscillate through various substorm cycles rather than forming a steady-state convection bay