Intense auroral hiss was observed by a sounding rocket payload under circumstances that have allowed detailed comparison of the hiss spectrum with the predictions of a convective beam amplification hiss production model. The payload was launched from Poker Flat, Alaska at 0813 UT on March 9, 1978; it carried an electric field detector and electron detectors covering the energy range from 30 eV to 25 keV. A complete pitch angle scan was made every 0.2 s. The trajectory was close to the magnetic meridian and crossed the diffuse aurora, a dark region, and a quiet 40 kR auroral arc. Auroral hiss was first encountered at the poleward edge of the diffuse aurora, and was observed for the rest of the flight. A maximum intensity of 10-8(V/m)2/Hz at 30 kHz was seen in the dark region. Electron distribution functions were seen with Δf/Δv⊥∥⟩0 and a large enough slope to have produced appreciable VLF amplification. These distributions were found in a region of few kilometers wide on the equatorward boundary of the arc.

A model distribution function has been fitted to one of the observed distributions and used as input into an auroral beam noise generation model. Reasonable assumptions about the distribution of cold plasma and width of the unstable region yields a predicted VLF spectrum in good agreement with observation. Several secondary results were also obtained. The observed VLF hiss does not appear to have been produced by a payload-plasma interaction. The intensity of the hiss measured in situ, above the ionosphere, was greater equatorward of the arc than within the arc, thus ruling out the ionospheric transmission model as an explanation for this intensity pattern. Quasi-linear back reaction on the electron distribution was not found to be significant in this case. The correlation between 0.1-0.7 keV electron flux and hiss intensity was not better than the correlation with the flux of 5-keV electrons. The data did not suggest the occurrence of a 3 wave parametric decay. Finally, the possibility of a secondary source at ~100 km altitude is not ruled out by these data. ¿ American Geophysical Union