Distortion of Trimpi shapes by high‐altitude winds

Phase and amplitude perturbations (Trimpis) on man‐made VLF signals propagating in the Earth‐ionosphere waveguide, due to lightning‐induced ionization occurring off the great circle path from VLF transmitter to receiver, are sensitive to the instantaneous lateral location of this ionization. High‐altitude winds of ∼100 m/s can move this ionization fast enough during its decay to change the rate, shape, and even sign of the phase and amplitude perturbation decays.