The ring current observed by IMAGE/HENA

P.C. Brandt, D. G. Mitchell, Y. Ebihara, E. C. Roelof 

This talk aims at discussing the contribution of global ENA imaging to our
understanding of the ring current. A brief review of our current knowledge
in ring-current dynamics and composition is given based on both recent
observations and recent modeling efforts. The Energetic Neutral Atom (ENA)
observations of the ring current from the High Energy Neutral Atom (HENA)
imager (10-60 keV) onboard IMAGE are discussed focussing on two events:
23-24 May, a -120 nT storm with rapid changes in the convective electric
field with equally rapid response of the ring-current configuration and
subsequent stabilization to stationary drift patterns and low-altitude
precipitation; 10 June, a period with both storm and sub-storm related
activity with clear signatures of energy-dependent drifts of newly
injected ions. We compare the first event with a time-dependent
ring-current model. Preliminary results of extracting the ion distribution
from the ENA images of the second event are presented.

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Presented at the Seventh Huntsville Workshop -
A New View of Geospace: Integration, Interpretation and Synthesis
October 30 - November 3, 2000, Callaway Gardens, Georgia