Project porcupine : the MF mutual-impedance probe experiment. Part I : Flight F2 (March 1977)

Abstract

Results are presented from a medium-frequency (0.1 - 1.5 MHz) mutual-impedance probe flown on the three rockets in the auroral ionosphere. The main purpose of these experiments was to measure the field-aligned drift velocity of the thermal electrons, from the resulting non-reciprocal frequency- shift of the lower oblique resonance. In the first experiment (Porcupine F2), the data exhibited frequency-shifts much larger than expected, and which varied cyclically as the payload spun. These spurious shifts, which were partly of technological origin, masked any shifts due to field-aligned drift. They led to a redesign of the probe. In the second experiment (Porcupine F3), the data were consistent with downward electron drifts, but their apparent high velocity casts doubt on this interpretation. The data from the third experiment (Porcupine F4) exhibited frequency-shifts that clearly were related to the cross-field drift of the plasma under the influence of the perpendicular component of the auroral electric field, but again they were larger than the values expected theoretically. The conclusions are that this method for measu- ring field-aligned electron drift velocity is not yet ready for scientific use, but that it would become useful if its sensitivity could be improved by an order of magnitude. Suggestions are made as to how this improvement might be achieved