The Earth's plasmasphere
as viewed with the EUV instrument
on board the IMAGE spacecraft. The Earth is at the center of
the images. The Sun is to the upper left. The view is toward
Earth's north pole. The 30.4-nm emission from the
plasmaspheric helium ions appears in false color as a pale
blue cloud surrounding the Earth. The emission is brightest
near the Earth on the day side owing to the increase in
helium ion concentration with decreasing altitude and to the
contribution of other ionized species, primarily atomic
oxygen ions. The dark "bite out" seen in the lower right
portion of the emission is the Earth's shadow. A faint "tail" of
plasmaspheric material entrained in the sunward flow of
plasma from the magnetotail and being carried toward the
dayside magnetopause can be seen in the righthand image.
Also clearly visible is the Earth's northern aurora, with a
bright discrete arc near midnight evident in the lefthand
image. The auroral emissions are believed to be from atomic
oxygen ions at a wavelength of 53.9 nm, which the EUV
imager also detects, although it is not the target wavelength
for which the instrument was optimized.
The two images were acquired at different times during the same orbit on May 24, 2000. In the first image, the spacecraft is in the evening sector and has not yet passed over the north pole; in the second image, it has crossed the pole and is at or near apogee (7.2 Earth radii) on the morning side.
Click here for a selection of EUV plasmasphere movies. Also, visit the EUV web site at EUV web site at the University of Arizona for more movies and information about the EUV imager. (Information about the EUV instrument and investigation is also available on this web site as well.)
Photo and movie credit: B. Sandel and T. Forrester, Univ. of Arizona.