BALLOON MEASUREMENTS ABOVE THE SOUTH-POLE - STUDY OF IONOSPHERIC TRANSMISSION OF ULF WAVES

We report here an experimental study of the Hughes and Southwood model of the transmission of electromagnetic signals from the ionosphere/ma gnetosphere to the lower atmosphere. The electric field data were obta ined from one of eight high-latitude balloon payloads launched above t he south geographic pole during the South Pole Balloon Campaign in the 1985-1986 austral summer. The magnetic held data are from the South P ole magnetometer. The balloon payloads were instrumented with double-p robe electric field detectors and bremsstrahlung X ray detectors. One of the events from flight 7 (January 8, 1986, at 1500-1800 UT (1130-14 30 MLT)) had an amplitude in the range of 10-20 mV/m and a period of s everal minutes. In the magnetosphere, the wave was probably an Alfven mode. The wave event was superimposed on background fluctuations that can be attributed to turbulence. The results agree with the prediction s of the model in that the best coherence is observed between parallel components of E versus B. The results disagree with the predictions o f the model in two respects. First, we find a frequency structure not predicted by the model, and second, we find intervals where the electr ic and magnetic field polarizations are of opposite handedness. The fi rst discrepancy was modeled by taking account of the measured electros tatic turbulence. The second problem remains a puzzle.