IMAGE in the Solar Wind During the October 31, 2003 Event

Michael R. Collier, Thomas E. Moore, Mei-Ching Fok, Benjamin Pilkerton,
Robert Benson, James Green, Scott Boardsen


During the large October 31, 2003 solar storm event, the Low Energy Neutral
Atom (LENA) Imager on the IMAGE spacecraft observed unusual behavior in the
neutral solar wind. For a nearly two-hour interval centered near 0630 UT,
the diffuse neutral solar wind signal which results from solar wind charge
exchange in the magnetosheath disappeared leaving only a weak signal from
the direction of the Earth and a stronger signal from the Sun direction. The
Radio Plasma Imager (RPI) data indicate that the IMAGE spacecraft was in
interplanetary space at the time of the unusual neutral solar wind
observations and based on an analysis of RPI-stimulated plasma resonance and
the cut-off frequency of a type III solar burst reveal a solar wind electron
number density of 20-40 cm-3. These densities are substantially larger than
the solar wind proton densities measured by ACE at this time, by a factor of
5-10. The LENA neutral solar wind observations can be qualitatively
reproduced by assuming the proton densities are comparable to the higher
RPI-derived electron densities, but not by using the observed ACE solar wind
proton densities. Furthermore, preliminary ring current simulations using
the observed ACE solar wind proton densities disagree with Dst* by about an
order of magnitude based on the simulated ring current energy.  We will also
discuss the effect of this density discrepancy on ring current simulations.

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Presentation, Fall A.G.U. Meeting, San Francisco, CA, 13-17 December 2004