On an instrumented rocket payload flown through the polar ionospher.•, large-amplitude electrostatic ELF waves have been measured in the unstable E region. Using three-axis instantaneous measurements of the electric vector of the wave field, it was possible to confirm the electrostatic nature of the waves and to make a direct determination of the full k vector as a function of altitude during upleg and downleg passages through the E region. Simultaneous measurements were made of electron density and temperature, dc electric field, and ac and dc magnetic field. This allows comparisons to be made with theories of the crossed field two-stream instability, the conditions for which were well satisfied. The direction of propagation and the frequency range are in agreement with theory, but the phase velocity is lower than predicted, being only about one third of the electron drift velocity.
In a short communication [Olesen et al., 1976] we reported observations of an ionospheric plasma instability both from the ground and locally from a rocket launched from Sfindre Strfimfjord, Greenland (75.0 ø invariant latitude) on July 8, 1974, at 15.19 UT. In the present paper a thorough analysis is presented on the ELF waves in the E region, but first the ground-based ionospheric measurements are recapitulated. Then data from the rocket are presented for the upleg and downleg traversals of the E layer, followed by the analysis of the electrostatic waves. GEOPHYSICAL CONDITIONS DURING THE FLIGHT Figure 1 shows the general situation during the rocket flight. Ground-based ionosondes at Sfindre Strfimfjord and Godhavn and a 12.7-MHz backscatter radar at Sfindre Strfimfjord were used to detect the presence of a widespread ionosph•eric E region plasma instability [see Olesen et al., 1976]. As shown in that paper the Godhavn ionograms displayed a very intense slant E condition (SEC) with a strong slant Es trace, which is interpreted as backsatter signals from irregularities in the E region. The ionosonde measuring technique used selects the irregularity wavelength versus range in the way shown in Figure 1. This does not, however, exclude a wide irregularity spectrum at each range. The ionosonde cannot determine the azimuthal distribution, but the backscatter radar measures echoes at the positions shown in Figure 1, in good agreement with the Godhavn ionograms. The Kp index was greater than 5, corresponding to an average position of the equatorward boundary of the cleft lower than 72 ø invariant latitude [Pike, 1972]. This supports our assumption that the rocket ascended and descended in the polar cap ionosphere. The horizontal magnetic perturbations at Godhavn (77.5 ø invariant latitude) and Unmanak (78.5 ø invariant latitude) were fairly constant around 300 ? (nT) during the whole flight. At Sfindre Strfimfjord the magnetic perturbation decreased from around 200 ? at the time of the upleg passage of the E region to a very small value at the time of the downleg passage. The direction was at all locations very nearly geomagnetic south. Th...
The behavior of a rotating plasma machine has been investigated. It is found that when the gas pressure and the current are varied within very wide limits the burning voltage remains constant. The voltage is proportional to the magnetic field. The reason for this behavior seems to be the existence of a critical velocity, above which a strong interaction between a plasma and a neutral gas takes place.
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