First medium energy neutral atom (MENA) images of Earth's magnetosphere during 
substorm and storm-time

C.J. Pollock (1), K. Asamura (2), M.M. Balkey (3), J.L. Burch (1), H.O. Funsten (4), 
M. Grande (5), M. Gruntman (6), M. Henderson (4), J.-M. Jahn (1), M. Lampton (7), 
M.W. Liemohn (8), D.J. McComas (1), T. Mukai (2), S. Ritzau  (4), M.L. Schattenburg (9), 
E. Scime (3), R. Skoug (4), P. Valek (1,10), and M. Wuest (1)

1 Southwest Research Institute, San Antonio, TX
2 Institute of Space and Astronautical Sciences, Japan
3 West Virginia University, Morgantown, WV
4 Los Alamos National Laboratory, Los Alamos, NM
5 Rutherford Appleton Laboratory, Oxfordshire, England
6 University of Southern California, Los Angeles, CA
7 University of California at Berkeley, Berkeley, CA
8 University of Michigan, Ann Arbor, MI
9 MIT Center for Space Research, Cambridge, MA
10 Auburn University, Auburn, AL

Initial ENA images obtained with the MENA imager on the IMAGE observatory show
that ENAs emanating from Earth's magnetosphere at least crudely track both Dst and
Kp. Images obtained during the storm of August 12, 2000, clearly show strong ring
current asymmetry during storm main phase and early recovery phase, and a high
degree of symmetry during the late recovery phase. Thus, these images establish the
existence of both partial and complete ring currents during the same storm. Further,
they suggest that ring current loss through the day side magnetopause dominates 
other loss processes during storm main phase and early recovery phase. 

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Geophysical Research Letters, Vol. 28, No. 6, pp. 1147-1150, March 15, 2001