MEASUREMENT OF THE LARGE SPATIAL SCALE CONVECTION ELECTRIC FIELD IN THE EARTH'S MAGNETOSPHERE BY BALLOON AND SATELLITE BORNE DETECTORS

Measurements of the large spatial scale dc electric field in the earth's magnetosphere and ionosphere by both balloon and satellite borne electric field detectors have provided data on three general topics of interest in the study of magnetospheric physics.; (1) Comparison of the polar cap electric potential drop measured by the S3-3 satellite to the predictions of reconnection models calculated from measurements of solar wind parameters show: the decay constant of ionosphere convection in response to the turn-off of the solar wind-magnetosphere dynamo is about 1-3 hours; the extent to which processes other than magnetic field line reconnection (viscous coupling) contribute to the driving of ionospheric convection is less than 15 kilovolts (compared to 60 kilovolt average potential drops and (TURN)140 kilovolt maximum potential drops); and, the 'efficiency' of the reconnection process in driving ionospheric convection varies in a nonlinear maner with steady state solar wind conditions. The measured polar cap potential is consistent with reconnection of 100% of the magnetic flux (predicted from interplanetary data using reconnection electric field models) incident on the frontside magnetopause for dawn-dusk components of the solar wind electric field less than .6 mV/m and the polar cap potential is constant for larger values of the dawn-dusk component solar wind electric field.; (2) The second study compares the large scale electric field in the auroral ionosphere measured by radar and balloon borne detectors and the large scale electric field and field aligned currents measured by the S3-3 satellite to the tail lobe magnetic field measured by the ISEE-1 satellite. Two observations of this study are: (a) A strong correlation exists over time scales of about 20 minutes between 50 mV/m to 100 mV/m enhancements in the auroral ionospheric electric field and southward dipping and increases in the magnitude of the tail lobe magnetic field vector measured at distances of 14 R(,E) to 20 R(,E). (b) A constant proportion of the tail current system is diverted via the region 1 field-aligned current system through the high latitude ionosphere over a wide range of geomagnetic activity. This relation is evidence against a broad class of substorm models which postulate an abrupt increase in the proportion of current diverted from the near earth tail into the polar cap ionosphere during auroral substorm onset.; (3) Simultaneous measurements of the magnetospheric electric field at altitudes of 3,000 kilometers to 8,000 kilometers by the S3-3 satellite and electric fields at ionospheric altitudes by balloon-borne detectors and radar experiments demonstrate that the large scale convection electric field maps between these two plasma regimes in manner consistent with magnetic field-aligned potential drops of about 1 kilovolt compared to the perpendicular potential drops ranging between (+OR-) 7 kilovolts (the average magnitude was about 3 kilovolt) over the 100 kilometer radius of the horizontal averaging area of the low altitude experiments.