IMAGE/HENA: ENA Imaging of the Plasmasheet During Substorms

Pontus C:son Brandt 1 (240-228-3837; pontus.brandt@jhuapl.edu)
Edmond C Roelof 1 (edmond.roelof@jhuapl.edu)
Robert Demajistre 1 (robert.demajistre@jhuapl.edu)
Donald G Mitchell 1 (donald.mitchell@jhuapl.edu)
Stephen Mende 2 (mende@ssl.berkeley.edu)

1 The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd,
  Laurel, MD 20723-6099, United States 
2 Space Sciences Laboratory, University of California Centinnial Drive at
  Grizzly Peak Blvd, Berkeley, ca 94720-7450, United States 

The high energy neutral atom (HENA) imager onboard IMAGE obtained ENA
images of the plasmasheet ion distribution at distances out to 14 RE in
the nightside magnetosphere. The images were obtained during three
substorms with auroral onsets on the 4 october 2000 06:10, 09:22, and 19
September 2000 12:45 UT. We present equatorial ion distributions
inverted from the ENA images in the 27-39 keV energy range using a
linear inversion method presented by R. Demajistre et al. in this
conference. Just prior to dipolarization of the geomagnetic tail
observed at geosynchronous by the GOES satellite, the most intense ion
distributions start flowing Eartward. For one of the substorms there are
weak signatures of a tailward flow initiated at around 8 RE at onset. We
show the relation between geosynchronous measurements (LANL, GOES) and
global substorm sequences observed by IMAGE/HENA and auroral images
observed by IMAGE/FUV. We present estimations on the Earthward flow
velocities and discuss the significance and physical implications of the
observed tailward flow.