Detection and location of red sprites by VLF scattering of subionospheric transmissions

Scattering by the conductive columns of red sprites of VLF waves (“VLF sprites”) traveling in the Earth‐ionosphere waveguide is characterized by wide angle scattering (to 180°). This enabled the first VLF detection of sprite conductivity and is now used routinely for sprite detection and location by measurement of the phase and amplitude at both of the frequencies transmitted by NAA, NSS, NLK and NPM. In a blind test using only one VLF receiver and the first three of these transmitters, all of the VLF events fitting the criteria for VLF sprites were found to correspond to optical sprites and virtually all of the sprites observed optically corresponded to VLF events. Using only a single receiver in the high noise environment of local thunderstorms enabled the range to the sprite to be found to within 100 km and the direction to within 90°. Use of a large number (∼10) of suitably spaced antennas greatly increases the location accuracy and provides some information on the lateral structure of sprite conductivity.