A dispersion anomaly in whistlers received on Alouette 1

Abstract

Natural whistlers observed in the ionosphere, but not by nearby ground receivers, may exhibit a frequency versus time curve that differs appreciably from the typical curve of whistlers observed at ground level. For wave frequencies well below the minimum value of electron gyro‐frequency along the path, the frequency‐time curve of most ground‐observed whistlers can be approximated within a few per cent by the relation D=tƒ1/2=constant where t represents travel time at frequency ƒ. However, a number of recent Alouette whistler observations at 1000 km show relatively large departures from this relation. The purpose of this note is to describe a particular departure in which the quantity D(ƒ) = tƒ1/2 exhibits an anomalous increase with increasing frequency.

Effects of Ions on Whistler‐Mode Ray Tracing

“…Therefore whistler energy may reflect at a rather low altitude: say 1000 km, due to refraction through the region of transverse propagation. The initial purpose of the present work on ray tracing was to confirm the hypothesis of Smith for the SP y·histlers, and to investigate other phenomena such as the "transverse" whistler [Carpenter and Dunckel 1965;Kimura et al, 1965]. In the present work, w~ have adopted the ray-tracing technique of Haselgrove and Haselgrove [1960], and have used the magnetoionic theory with many ions as developed by Hines.…”

An interpretation of transverse whistlers

“…If the proposed model is correct, the highest frequency of the transverse whistler should always be below the lower hybrid resonance frequency. There is some suggestion in the data that this is, in fact, the case [Carpenter and Dunckel, 1965]. It remains to be shown that a propagation path such as that described above may exist.…”