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Dingle & Carpenter 1981
Dingle, B. and Carpenter, D.L. (1981). Electron precipitation induced by VLF noise bursts at the plasmapause and detected at conjugate ground stations. Journal of Geophysical Research 86: doi: 10.1029/JA086iA06p04597. issn: 0148-0227.

A new type of wave-induced electron precipitation event has been identified. During observations at conjugate stations Siple, Antarctica, and Roberval, Canada (L-4.2), VLF noise bursts were found to be associated on a one-to-one basis with amplitude perturbations of subionispheric radio propagation. The amplitude perturbations are attributed to patches of enhanced ionization that extended below ~80 km in the nighttime ionosphere and that were produced by precipitating electron bursts. Similar amplitude perturbations seen previously were correlated with whistlers that propagated within the plasmasphere. For the new events the driving waves were structured collections of rising elements that propagated just beyond the plasmapause at roughly 5-min intervals over a several-hour period. These noise bursts were of relatively long duration (~10 s) and strong intensity (inferred to be >30 pT at the equator). Triggering of the noise bursts appears to have been mostly by whistlers but changed in character with time. Some later bursts had narrowband precursors at constant frequencies possibly locked to power line harmonic radiation. The burst initiation characteristics suggest the existence of a variable threshold for rapid temporal growth in the magnetosphere controlled by the trapped electron dynamics. The temporal signatures of the amplitude perturbations show that precipitation was maintained over multiple bounces of the trapped magnetospheric electrons. In some cases these signatures include a new undershoot effect during the recovery phase lasting 2--5 min. This effect may have been related to cutoff of background drizzle precipitation. Precipitation effects were observed on both long (~10 Mm) and short (~1/2 Mm) subionospheric paths and were monitored simultaneously at the conjugate stations. Similarities in the perturbation signatures on long and short paths suggest that the form of the signatures was governed by ionospheric changes and was not distorted by the subionospheric propagation mechanism. Some differences in the conjugate perturbation signatures are believed to be caused by the difference in loss cone widths for precipitation in the northern and southern hemispheres. Existence of this loss cone gap produced an estimated ~30-pT noise amplitude threshold for significant northern precipitation and possibly caused saturation of southern precipitation.

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Journal
Journal of Geophysical Research
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American Geophysical Union
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