Equatorial electric field measurements by IMAGE EUV 

Jerry Goldstein 1 (jerru@hydra.ric.edu)
Richard A Wolf 1 (wolf@alfven.rice.edu)
Bill R Sandel 2 (sandel@arizona.edu)
Terry Forrester 2 (terryf@vega.lpl.arizona.edu)
Dennis L Gallagher 3 (dennis.gallagher@msfc.nasa.gov)
Patricia H. Reiff 1 (reiff@rice.edu)

1 Dept of Physics and Astronomy, Rice University, 6100 Main St., MS108,
  Houston, TX 77005, United States 
2 Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721,
  United States 
3 NASA Marshall Space Flight Center, MSFC Code SD50, Huntsville, AL 35812,
  United States 

Observations of the extreme ultraviolet imager (EUV) on the Imager for
Magnetopause-to-Aurora Global Exploration (IMAGE) satellite often show
distinctive features of the plasmasphere such as 'tails,' 'plasma
voids,' 'fingers,' 'biteouts,' and 'shoulders' that are identifiable
from one time snapshot to the next. These features can be mapped down to
the magnetic equatorial plane, and their time-dependent positions can be
analyzed to yield an equatorial (radial and/or azimuthal) velocity
measurement. Assuming that cold plasma motion is due to E-cross-B drift,
the equatorial electric field can then be extracted from the velocity.
We apply this technique to produce time-dependent electric field
measurements for some intervals of IMAGE EUV data which contain one or
more of the distinctive plasmaspheric features above.