New evidence of phase perturbations of subionospheric VLF/LF signals, produced by lightning-whistler-induced precipitation of bursts of radiation belt electrons, is reported. Phase changes of 0.1--1.0 &mgr;s on a 12.9-kHz signal arriving at Palmer, Antarctica (L~2.4), over a ~ 2400-km path are regularly observed with a characteristic signature of a rapid (≤1 s) onset followed by a relatively slow (10--30 s) recovery. Event occurrence peaks during equinoctial periods, with typical rates of 1--40 events per hour lasting for several hours per night. The observed phase perturbations can be interpreted to correspond to a rapid reduction of up to ~0.1--1.0 km in the effective nighttime ionospheric reflection height (~85 km) for the subionospheric VLF signals. The incident energetic particle fluxes that are required to produce the extra ionization are estimated to be ~10-3--10-2 ergs cm-2 s-1. Such flux levels are generally consistent with those estimated using theoretical models of whistler-particle resonant scattering as well as direct satellite-based observations of whistler-induced precipitation. This phenomenon provides a sensitive means for detecting wave-induced burst particle precipitation. The ionospheric perturbations resulting from such precipitation may cause significant error in certain global navigation aids, such as the Differential Omega and LORAN-C systems.