Quiet time plasmaspheric electric fields and plasmasphere-ionosphere coupling fluxes at L = 2.5

Observations of whistler mode signals from the VLF transmitters NAA and NSS in the Northeast U.S.A., made at Faraday, Antarctica (65°S, 64°W), are used to deduce radial plasma drifts and plasmasphere- ionosphere coupling fluxes near L = 2.5. The fluxes measured represent the sum of the field-aligned plasma fluxes through 1000 km altitude in both hemispheres. The method used to obtain the cross-L drifts and fluxes is explained, and then the results from nine consecutive geomagnetically quiet days in July 1986 described. Data from the 9 days were averaged to find the mean diurnal variation in the East-West electric field (which causes the radial plasma drift) and the fluxes. The fluxes were of magnitude 1−3 × 1012 m−2 s−1 ; the plasmasphere started to fill at sunrise in the Northern (summer) Hemisphere, and to empty again at sunset in the Southern (winter) Hemisphere. The most noticeable features in the cross-L drift were an outward drift from 07:00–12:00 L.T. and an inward drift from 15:00–22:00 L.T. The electric fields in both cases are of magnitude ≈ 0.2 mV m−1 and are thought to be due to the ionospheric dynamo.