UPLIGHTS Lightning Spectra: Negative CG from Horizontally Extensive IC Flash

Abstract:

A horizontally extensive intracloud flash had positive leaders travel along cloud base while corresponding negative leaders traveled incloud. Branches of the visible positive leaders decayed and produced numerous recoil leaders. In one case, the negative end of the recoil leader transitioned to stepping in virgin air and traveled down to the ground initiating a negative cloud-to-ground return stroke. The return stroke traveled back up and out the path formed by the preceding recoil leader and to the tip of the decayed positive leader branch. Luminosity faded in the channel path formed by the recoil-to-stepped leader/ return stroke sequence and numerous other recoil leaders initiated along the same path and traveled to ground initiating subsequent negative return strokes. This flash was captured at 1,000 ips without spectra and at 11,001 ips with spectra. The spectra of the negative end of the recoil leader as it steps downward in virgin air is well resolved. Some of the subsequent dart leaders as well as resulting return strokes are also well resolved with spectra. The return strokes show typical channel cooling from the first frame of the return stroke sequence.