Evolution of the Inner Magnetosphere from Quiet to Storm Times: MENA Observations

Scime, E.E., Zaniewski, A., Edlund, E., Pollock, C., Jahn, J. 


In this study, we will present energetic neutral atom (ENA) images from the Medium Energy
Neutral Atom (MENA) imager on the Imager for Magnetopause-to-Aurora Global Exploration
(IMAGE) observatory as a function of DST. The MENA instrument detects ENAs with 1-60 keV per
nucleon. To obtain sufficient counts during quiet times, i.e., small values of DST, we have
developed a code that combines into a single composite image, MENA images from different
times in a single IMAGE orbit and MENA images from different orientations of the IMAGE orbital
plane relative to the Earth-Sun direction. We find that with these techniques, composite images
of the quiet time magnetosphere can be constructed from approximately 1000 individual MENA
images. To improve MENA image sharpness, we have also developed an algorithm that removes
the effects of neutral scattering in the MENA instrument. Using these sharpened composite
images, the evolution of the inner ring current and plasmasheet structure as a function of DST
magnitude will be presented. As shown in previous work [Scime et al. GRL 2002], it is possible
to construct images of the plasma ion temperature from the images obtained at different ENA
energies. Therefore, the evolution of the ion temperature in the inner magnetosphere as a
function of DST will also be presented. 

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Fall 2002 Meeting of the American Geophysical Union
San Francisco, CA, USA, 6-10 December 2002