Mozer [1984> has published some ISEE-1 data on the electric field in the magnetospheric equatorial plane which show a polarization of the low latitude boundary layer, consistent with tailward plasma flow. A reinterpretation of these data suggests that the potential difference may be typically 30 kV for the combined dawn and dusk layers, out of a total of 50--60 kV across the polar cap. Therefore, the LLBL is at least as important as the competing process of magnetic reconnection.