Precipitation signatures of ground‐based VLF transmitters

Numerical raytracing with Landau damping is used to calculate >100 keV electron precipitation signatures induced by hypothetical VLF transmitters distributed broadly in geomagnetic latitude and operating at a wide range of frequencies. A one‐half second pulse from each source is simulated and attenuation to the base of the magnetosphere for geomagnetic latitudes from 10° to 60° is calculated. Source location affects induced precipitation more strongly than operating frequency or radiated power. Sources located at 35° to 45° induce the most >100 keV precipitation for the 10 to 40 kHz waves typical of ground‐based VLF sources, while locations below λ ≃ 15° or above λ ≃ 55° are least effective at precipitating energetic electrons. In all cases, induced precipitation increases as the operating frequency decreases, with 10 kHz waves from a source at λ ≃ 35° the most effective at precipitating >100 keV electrons. Precipitation signatures produced by five existing ground‐based VLF transmitters are also simulated: the NAA, NLK, NAU, NPM, and NWC VLF transmitters. NWC induces the strongest >100 keV electron precipitation signature, followed by NPM, NAU, NAA, and NLK.