Mesospheric sprite current triangulation

A network of three time-synchronized high-precision induction coil magnetom eters 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 19 98. Simultaneous intensified video observations on board an aircraft are us ed to investigate 16 sprites with long time delays > 33.33 ms relative to t he parent lightning discharge reported by the National Lightning Detection Network. Three different long-delayed sprite-associated waveforms can be di stinguished: 38% do not exhibit any significant magnetic intensity variatio n, 25% exhibit slow variations similar to 100 ms, and 25% exhibit short pul ses similar to4 ms. The source locations of the sprite-associated short pul ses are triangulated by use of arrival time difference analysis. One source location exhibits a substantial spatial displacement similar to 60 km rela tive to the parent lightning discharge, in agreement with the azimuths of s prite luminosity edges determined from the corresponding background star fi eld of the video observations on board the aircraft. It is concluded from t he temporal and spatial coincidence of the secondary short pulse and the sp rite luminosity that this particular sprite is associated with current in t he mesosphere.