It is shown that, assuming conditions of approximate steady state and that the low to medium electrons forming the plasma sheet inner edge originate from a source in the magnetail the radail electric field in the dusk sector can be related to the radial energy dispersion of the plasma sheet inner boundary as Er=-[(W⊥)e/e>(d/dr)(ln B), where (W&ngr;)e represents the energy of the electron inner boundary. An increasing electric field component with radial distance is obtained from recent measurements of plasma sheet inner edge electron energy dispersion.