Plasma sheet access to geosynchronous orbit

One year's worth of magnetospheric plasma analyzer data from three Los Alam os geosynchronous satellites are used for a statistical study of proton and electron fluxes at geosynchronous orbit and their dependence on local time (LT) and geomagnetic activity level as measured by Kp. When displayed as a function of LT and Kp, the fluxes exhibit distinct boundaries, which are s hown to be consistent with a combination of a global pattern of particle dr ift through the magnetosphere and loss processes mainly due to charge excha nge of the ions and auroral precipitation of the electrons. A Hamiltonian e nergy conservation approach combined with the (U, B, K) coordinate transfor mation introduced by Whipple [1978] is used to calculate the theoretical po sition of the separatrix between open and closed drift trajectories (Alfven layer) as a function of particle species, energy, local time, and geomagne tic activity level. The comparison of the theoretical boundaries with the o bservations confirms the predictions of plasma sheet access to the geosynch ronous region. The analysis also provides independent statistical support f or previously derived relationships between Kp and the strength of the glob al convection electric field.