Empirical plasmapause models from magnetic indices

We use a database of CRRES in situ observations of plasmapause crossings to build empirical models of the plasmapause location as a function of geomagnetic indices. Previous models used the maximum value in Kp during the hours to days leading up to the plasmapause crossing. We find that a recent maximum in AE or minimum in Dst provides a better model of the plasmapause radius than does maximum Kp. AE and Dst measure specific current systems (the auroral electrojet and ring current, respectively). The AE model suggests that substorms may be involved in the erosion of the plasmapause. The Dst model suggests that ring current may be formed by the same electric field that erodes the plasmapause. In more complex models, Kp and AE can describe local time structure in the plasmapause, with the furthestplasmapausebeforedawnatquiettimes,premidnight at active times.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/165338/1/OBrienMoldwinLpp2003.pdfSEL

Large-scale fields and flows in the magnetosphere-ionosphere system

Advances in our understanding of the large-scale electric and magnetic fields in the coupled magnetosphere-ionosphere system 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 attention 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 these 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 electric 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 at the magnetopause. Several new techniques were introduced including ionospheric observations which yield reconnection rate as a function of time. The magnetospheric and ionospheric behaviour due to various quasi-steady interplanetary conditions was studied using magnetic cloud events. For northward IMF conditions, reverse convection in the polar cap was found to be predominantly a summer hemisphere phenomenon and 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