Coincident ground-based and satellite observations are presented of a premidnight auroral surge over Amundsen-Scott South Pole station. The set of near-simultaneous measurements provides an excellent opportunity to gain a more quantitative understanding of the nature of premidnight substorm activity at high geomagnetic latitudes. The surge produced a rapid onset of cosmic radio noise absorption at the station. On the polar-orbiting DMSP F6 spacecraft, intense X ray emissions with E>2 keV energy were imaged 1¿ to 2¿ magnetically equatorward of South Pole approximately 1 min prior to the peak of the absorption event. The spectrum of precipitating electrons determined from the X ray measurements could be characterized by an e-folding energy of ~11 keV and is found to be adequate to account for the cosmic noise absorption and maximum auroral luminosity recorded at South Pole. Photometer, all-sky camera, riometer, and magnetometer data are used to estimate the velocity of motion and spatial extent of the auroral precipitation and the ionospheric currents associated with the surge. The electron precipitation region is deduced to have a latitudinal scale size of 2 keV) exceeded 200 ergs/cm2 s and contributed to a vertical current density of ~0.017 A/cm. This current density is comparable, to within a factor of ~2, with the horizontal ionospheric current density (~0.028 A/cm) inferred from the ground-based magnetometer measurements at South Pole station. A contribution of a large flux of electrons with E<2 keV to the vertical current density is discounted as an explanation for the difference on the basis that the expected 630-nm auroral luminosity would exceed by about an order of magnitude the less than 1 kR luminosity that was observed for this emission. ¿ American Geophysical Union 1987