Two coherent bistatic radio systems were used to observe auroral radio reflections under geometrical conditions which would favor the detection of ion-acoustic waves in the auroral ionization. The displaced "line" spectrum, characteristic of scattering by ion-acoustic waves, was a prominent feature of some of the observations but the strength of the wave-scattered component varied widely relative to the non-wave-scattered components. It is concluded that ion-acoustic waves do indeed occur in the auroral plasma but that such waves cannot be the only source of radio-wave scattering in aurora.
An "Australian" type ionosonde with modifications to record virtual height versus time in addition to regular ionograms was used for 23 nights during the "pulsating aurora campaign". Height variations associated with pulsating auroras were noted on 14 nights. For the periods of two rocket firings during the campaign it was possible to reproduce the height variations using modeling techniques. From the ionosonde data, information about the auroral energies and fluxes, as well as total electron content and conductivity variation, was obtained.
The ionospheric electron content was measured at La Ronge, Sask. for a variety of auroral conditions during the Pulsating Aurora Campaign in February of 1980. The two-frequency differential phase technique was used with the NNSS satellite beacons. Comparisons of optical data and the radio results indicate that for quite strong pulsations the electron content is modulated by less than 2%. Even this small change is somewhat larger than the purely temporal variations to be expected on the basis of currently accepted relaxation times in the ionosphere. If the observed fluctuations are interpreted as representing both temporal and spatial variations, good agreement is obtained with model calculations. For irregularity sizes and strengths to which the experiment is sensitive, structure was present in diffuse or patchy aurora but absent from at least some well defined forms. This suggests that the technique can be used to explore the mechanism of formation of the irregularities.
The time-history of particle energies and fluxes associated with pulsating auroras in the morning sector is derived from ionosonde measurements. All the pulsating auroras studied showed a similar history with the pulsations occurring during a time interval of the order of an hour during which the average auroral Maxwellian characteristic energy stays relatively constant but the energy flux decreases progressively during the event. A possible explanation for this behaviour in terms of an injection of particles into a magnetospheric "bottle" near the midnight meridian and the progressive precipitation out of the bottle during the pulsating event is suggested.
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