A Global Look at the Plasmasphere/Ring Current Overlap as a Source of Heat Flux Into the Upper Ionosphere C. Gurgiolo (Bitterroot Basic Research, Hamilton, MT 59840), B. Larsen, D. Mitchell, J. Perez, C. Pollock, and B. Sandel Interactions occurring within the overlap of the ring-current and plasmasphere have long been considered to be the source of the mid-latitude SAR Arc. There is observational evidence to support a number of different mechanisms that might be active in providing the necessary heat flux. Using data from the IMAGE EUV, MENA and HENA instruments as well as data from the DMSP F12, F13 and F15 SSIES experiments we present a global view of the relationship between topside ambient electron heating events and the ring-current plasmasphere overlap as well as discuss which of the postulated heat transfer mechanisms might be active. Inversions of the EUV data provide a global geomagnetic equatorial mapping of the plasmaspheric He+ density, while inversions of the NAI MENA and HENA data provide global equatorial mappings of the energetic ion density from which the build-up and evolution of ring-current can be followed. The DMSP SSIES data provide in-situ measurements of top-side ionospheric ambient plasma including the electron temperature. Projection of the SSIES data back into the equatorial plane allows correlations to be made between the state of the topside ionosphere and the conjugate magnetospheric state. ________________ Presentation at the Yosemite Conference of Inner Magnetospheric Interactions, 3 - 6 February 2004, Yosemite, California, USA