Global ENA imaging of the plasma sheet: Implications for dipolarization region and 
plasma transport during substorms

P. C. Brandt, S. Ohtani, D. G. Mitchell, A. T. Y. Lui, E. C. Roelof, 
and R. Demajistre

The Johns Hopkins University Applied Physics Laboratory
(pontus.brandt@jhuapl.edu/fax: +1-240-228-0386)


The high energy neutral atom (HENA) imager onoard the IMAGE spacecraft has obtained 
energetic neutral atom (ENA) images of the plasma sheet on several occasions. In 
this presentation we present the ongoing analysis of the dynamics of the plasma
sheet out to at least 14 RE observed during substorms occuring during geomagnetic
storms. In general, the plasma sheet flux is enhanced before substorm onset and 
then rapidly decreases, first beyond 8RE at about substorm onset. A couple of 
minutes after the plasma sheet decrease, dipolarization at geosynchronous and 
proton injections are observed. There appears to be an Earthward motion related 
with the decrease of plasma sheet flux. An upper bound on this motion has been 
determined to ~70 km/s. There are indications also of tailward motion from about 
10RE . We will focus on giving better estimates of the motion and the spatial 
structure of the plasma sheet during substorms. The analysis aims at incorporating 
a stretched field configuration into the inversion technique used to retrieve the 
ion distributions from the ENA images.

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Presented at the 34th COSPAR Scientific Assembly, Houston, Texas, U.S.A.  
10-19 October 2002