A ground‐satellite study of wave‐particle correlations

This is the authors' abstract. We don't add key points for this paper.

Very low frequency lpar;VLF) waves recorded at Siple, Antarctica (L ∼4; 84°W, geographic), are compared with low‐energy (<50 keV) electron data from the geostationary satellite ATS 6. During the period of this study (August 10–21, 1974) the satellite was anchored at 6.6 R E and 106.5°W, near the outer edge of the nominal ‘viewing area’ of the Siple VLF receiver, which is estimated to be L ∼2–6 and ±20° longitude. The results reveal two distinct types of chorus observed at Siple. One type is closely correlated with enhanced fluxes of >5‐keV electrons detected at the synchronous altitude, and its generation region is inferred to be outside the plasmapause. The chorus upper cutoff frequency increases with time in a characteristic manner, consistent with the expected adiabatic motion of injected electrons in cyclotron resonance with the waves. The second type of chorus, which we refer to as ‘plasmaspheric chorus,’ occurs inside the plasmapause, has no apparent relationship to particle injection at the synchronous altitude and shows clear evidence of being triggered by whistlers, power line radiation, and other signals. The two different types of chorus are readily distinguishable in frequency‐time spectrograms.