SOUTH-POLE ELECTRIC-FIELD RESPONSES TO OVERHEAD IONOSPHERIC CONVECTION

Measurements of the vertical atmospheric electric field (E-z) at the S outh Pole between 1982 and 1986 have been analysed, and the results re veal an important component due to magnetospheric-ionospheric coupling processes. The results are consistent with the theoretical expectatio n that the ionospheric convection potential patterns in the polar caps , as measured by satellites, are superimposed on the otherwise nearly uniform (but varying in time) global ionospheric potential due to low- latitude thunderstorm sources. The analysis technique was to calculate the ionospheric convection potential from a satellite empirical model , using as input measured solar wind parameters, except that when sola r wind data were not available we used as inputs measured ground based magnetic disturbance parameters. We fitted the average low-latitude E -z variation (the Carnegie curve) to the individually measured South P ole E-z diurnal curves. We then subtracted the fitted Carnegie curves from the measured curves and performed a regression analysis of the re sidual on the calculated ionospheric convection potential values, aver aging the data in three hour intervals. Positive correlations with cor relation coefficients of about 0.5 were found. Most of the remaining v ariability in E-z can be attributed to local meteorologically induced noise (especially in winter) and the day-to-day variability of the low -latitude thunderstorm generators.