Average electric field behavior in the ionosphere above Arecibo

Plasma drift measurements taken at Arecibo during the solar minimum period of 1974-1977 are examined to determine their average behavior in the E, F2, and F regions. The drifts are generally diurnal in the E region and semidiurnal in the F1 region. These lower thermospheric drifts are set up by polarization fields generated by propagating and in situ atmospheric tides. In the F region the diurnal component is more pronounced, especially in the zonal direction. The magnitude of the drifts is of the order of 25-30 m/s (or 1 mV/m). Enhanced geomagnetic activity appears to increase the westward component of the drift in agreement with the theory of the ionospheric disturbance dynamo (Blanc and Richmond, 1980). Nighttime drifts appear to be at least partly explained in terms of polarization fields.