The geoelectric field at Vostok, Antarctica: its relation to the interplanetary magnetic field and the cross polar cap potential difference

The vertical geoelectric field measured at Vostok, Antarctica (78.5 degrees S, 107 degrees E, L=75.0) over the 13 month interval May 1979-May 1980 is correlated with the interplanetary magnetic field (IMF) components B-y and B-z at times when Vostok is connected to the dayside magnetosphere. No sign ificant association with IMF B-x is found. The interaction of the solar win d and the Earth's magnetic held generally results in anti-sunward plasma fl ow in the high-latitude, polar ionosphere driven by a dawn-to-dusk, cross p olar cap potential difference pattern. Using the IZMEM model to infer the c ontribution of the cross polar cap potential difference to the potential di fference between the ionosphere and the ground at Vostok for the measured I MF conditions, we show that this provides a viable mechanism for the IMF as sociations found. We demonstrate that the direct association of the geoelec tric field with the cross polar cap potential difference is independent of a result (Park, 1976. Solar magnetic sector effects on the Vertical atmosph eric electric field at Vostok, Antartica. Geophysical Research Letters 3(8) , 475-478) showing an similar to 15% decrease in the vertical geoelectric f ield measured at Vostok, 1-3 days after the passage of IMF sector boundarie s. Evidence is also presented supporting the Park result, for which a mecha nism is yet to be confirmed. (C) 2000 Elsevier Science Ltd. All rights rese rved.