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

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.