Electron Acceleration and Ion Outlflow in the Polar Cap Boundary Region During Magnetospheric Substorms Carlson, C W, McFadden, J P, Mende, S B Measurements from the FAST spacecraft find that the most intense precipitating electron energy fluxes and ion outflows are found in the polar cap boundary region during magnetospheric substorms. This boundary region begins at the open magnetic field boundary identified by polar rain electrons. Auroral images identify this region with the 'double oval' or substorm bulge. Here bursty, magnetic field-aligned electron fluxes are associated with intense Alfven waves rather than quasi-DC potential structures characteristic of typical auroral arcs, and the electrons have broad energy spectra, in contrast to the peaked spectra found in inverted-V arcs. Conjugate Auroral images observed by the WIC instrument on IMAGE spacecraft show corresponding turbulent spatial structure. We suggest that this region maps to merging regions and bursty flows in the magnetotail. Intense low frequency waves generated by the electron bursts produce intense ion heating. Ion conic outflows exceeding 10^{8}/cm^{2}-s are typical in the polar cap boundary region. Successive substorms associated with magnetic storms creat even larger ion outflows, exceeding 10^{9}/cm^{2}-s, with enhanced O+ composition. Since these ions are injected onto newly closed magnetic field lines, they can convect into the inner magnetopsphere where they are further heated and contribute to the ring current.