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

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

Project porcupine : the MF mutual-impedance probe experiment. Part II : Flight F3 and F4 (March 1979)

This is the second part of a report on the results from the medium-frequency (MF) mutual-impedance probe experiment that was supplied by the Centre for Research in Environmental Physics (CRPE, Orléans, France) as a contribution to the West-German Porcupine program of research on auroral physics during the International Magnetospheric Study. The subject of Part 1 was the results from the first successful flight, named F2, which took place from ESRANGE (Kiruna, Sweden) on 20 March 1977. On that occasion, the MF probe experiment did not succeed in its objective of detecting field-aligned drift motion of the thermal electrons in the auroral ionosphere. The non-reciprocal shift of the lower oblique resonance (L.O.R.) frequency that this motion should have produced was masked by a similar but much larger shift that was obviously spurious, since it varied, more or less sinusoidally, as a function of the spin-phase angle. Various conceivable physical causes for this spurious shift were studied, but were rejected. The question of whether the true cause was some other physical phenomenon, as yet unidentified, or whether it was technological in nature, had to be left open. The results from the flight F2 nevertheless suggested a number of ways in which the experiment could be improved, and these were discussed in Section 5, which concluded Part 1 of the report. In Part 2, after the present preface, Section 7 describes how these and other modifications were made to the MF probe, in preparation for the flights F3 and F4. The changes that were made to some of the other instruments on board are mentioned also. The flight F3 took place on the evening of 19 March 1979, during a quiet interval within a period of repeated auroral activity. A weak negative magnetic bay of about 100 y (K = 2 ) was in progress at the time of launch : see § 7.2. of the report by Haüsler et al. [1982] . The aurora failed to evolve as anticipated, and the payload did not pass through any discrete arc. These relatively calm conditions, which disappointed the other experimenters, were ideal for determining whether the various modifications had improved the MF probe. In Section 8, where the results of the F3 experiment are presented, emphasis is therefore laid on analysis of the technical performance of the probe. The flight F4, on the evening of 31 March 1979, took place during a strong magnetic substorm ( p = 5+). At the time of launch, a discrete visual arc was present with a sharp northern edge, and the trajectory of the payload crossed this edge ; see § 7.3. of the report by Haüsler et al. [1982] . Stronger electric fields were encountered on this flight than on F3, and much of our study of the experimental results in Section 9 has been devoted to clarifying certain effects that appear to have been caused by these fields, and which resemble the spurious effects already observed on F2 inasmuch as they depended on spin phase and masked the interesting effects that we were looking for. The conclusions, presented in Section 10, are drawn from the results of all three successful flights. They substantiate the progress made in the development of the MF mutual-impedance probe as a means for measuring the field-aligned drift velocity of the thermal electrons, and indicate how, by further development, it might be made into a reliable instrument for this purpose

Project PROCUPINE: The MF mutual: impedance probe experiment. Part 1: Flight F2 (March 1977)

SIGLECNRS-CDST / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Projet PROCUPINE: the MF mutual-impedance probe experiment. Part 2: Flights F3 and F4 (March 1979)

SIGLECNRS-CDST / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc