48.5 kHz signals from a transmitter in Silver Creek, Nebraska, propagating to Huntsville (HU), Alabama over a ∼1200 km Great Circle Path (GCP) exhibit characteristic amplitude changes which appear within 20 ms of cloud‐to‐ground (CG) flashes located within 50 km of the path. Data are consistent with the heating of ionospheric electrons by the electromagnetic (EM) pulse from lightning producing ionization changes in the D‐region over the thund
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