A case study of lightning, whistlers, and associated ionospheric effects during a substorm particle injection event

Simultaneous ground-based observations of narrowband and broadband VLF radio waves and of cloud-to-ground lightning were made at widely spaced locations during the 1987 Wave-Induced Particle Precipitation (WIPP) campaign, conducted from Wallops Island, Virginia. Based on these observations, the first case study has been made of the relationships among located cloud-to-ground (CG) lightning flashes, whistlers, and associated ionospheric effects during a substorm particle injection event. This event took place 2 days after the strongest geomagnetic storm of 1987, during a reintensification in geomagnetic activity (Kp = 5) that did not affect the high rate of whistlers observed at Faraday Station, Antarctica (L = 2.46). At the time of the injection event, several intense nighttime thunderstorms were located over Long Island and the coast of New England, between 400 km northwest and 600 km north of the region geomagnetically conjugate to Faraday. About two thirds of the CG flashes that were detected in these thunderstorms during the hour following the injection event onset were found to be causatively associated with whistlers received at Faraday. During the same period the amplitude of the 24.0-kHz signal from the NAA transmitter in Cutler, Maine, propagating over the thunderstorm centers toward Wallops Island was repeatedly perturbed in a manner characteristic of previously reported VLF signatures of transient and localized ionization enhancements at D region altitudes. Though such enhancements may have been caused by whistler-induced burst electron precipitation from the magnetosphere, the data in this case are insufficient to establish a clear connection between the NAA amplitude perturbations and the Faraday Station whistlers. In view of the proximity of the NAA great circle path to the storm center, heating of the lower ionosphere by intense radiation from lightning may also have played a role in the observed VLF perturbations. The onset of each of the NAA signal perturbation events coincided with an intense cluster of radio atmospherics. Detailed temporal variations in the ELF (0.3–3 kHz) and VLF (3–30 kHz) power of similar “sferic clusters” correlated well with variations in the power of simultaneous “anomalous” optical events (AOEs) observed by a down-looking photodiode detector on a rocket at altitudes between 150 and 412 km.


Publication status:
Authors: Rodriguez, J.V., Inan, U.S., Li, Y.Q., Holzworth, R.H., Smith, A.J., Orville, R.E., Rosenberg, T.J.

1 January, 1992
Journal of Geophysical Research / 97
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