Mesospheric sprite current triangulation

A network of three time‐synchronized high‐precision induction coil magnetometers is installed in North America to measure sprite‐associated lightning flash waveforms in the frequency range 0.1–1000 Hz during the Energetics of Upper Atmosphere Excitation by Lightning, 1998, sprite campaign in July 1998. Simultaneous intensified video observations on board an aircraft are used to investigate 16 sprites with long time delays >33.33 ms relative to the parent lightning discharge reported by the National Lightning Detection Network. Three different long‐delayed sprite‐associated waveforms can be distinguished: 38% do not exhibit any significant magnetic intensity variation, 25% exhibit slow variations ∼100 ms, and 25% exhibit short pulses ∼4 ms. The source locations of the sprite‐associated short pulses are triangulated by use of arrival time difference analysis. One source location exhibits a substantial spatial displacement ∼60 km relative to the parent lightning discharge, in agreement with the azimuths of sprite luminosity edges determined from the corresponding background star field of the video observations on board the aircraft. It is concluded from the temporal and spatial coincidence of the secondary short pulse and the sprite luminosity that this particular sprite is associated with current in the mesosphere.