IMAGE/HENA: Ring current - plasmasphere interaction 

P. C. Brandt, M. W. Liemohn, D. G. Mitchell, J. L. Burch, E. C. Roelof 
 
We present global energetic neutral atom (ENA) observations of the 
ring current during the geomagnetic storm on 24 May, 2000. The 
observations were carried out by the ENA imager HENA onboard the IMAGE 
spacecraft. Apart from the main phase of the storm, the convection 
through the magnetosphere was steady throughout the recovery phase, 
which lasted approximately three days. A comparison with images of the 
plasmasphere in extreme ultraviolet (EUV)reveal a spatial relation 
between the ENA emissions and the plasmasphere. There appears to be a 
lack of ENA emission coming from regions with enhanced plasmaspheric 
density (plasmaspheric tail and plasmapause). Data from the Polar 
satellite suggests that the ring current ion pitch angle distributions 
(PAD) from the region of enhanced plasmaspheric density are strongly 
peaked at 90 deg pitch angle in the magnetic equator. Just outside 
regions with enhanced plasmaspheric density the PADs are more 
isotropic. We present a scenario that involves adiabatic drifts and 
wave particle interactions. We use the University of Michigan version 
of the kinetic ring current originally developed by V. K. Jordanova to 
adddress the significance of each mechanism in forming the observed 
ring current. 

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Submitted to the Spring 2001 AGU Meeting, Boston, Massachusetts