Possible direct cloud-to-ionosphere current evidenced by sprite-initiated secondary TLEs

Abstract

Video-rate images of sprites observed from Langmuir Laboratory show slow, upward discharges from the cloud to the mesosphere following the sprite discharge. A single high-time-resolution (1000 fps) measurement of the tip of the upward discharge shows that it terminates at the base of the preceding sprite and persists for a total of ∼50 ms, compared to the sprite lifetime of ∼6 ms. Photometer data show that these events are likely to be predominantly blue. We propose a mechanism by which, in conjunction with intra-cloud activity following the causative CG discharge, charge is moved within the sprite body from the ionosphere to the lower altitude edge of the sprite at ∼50 km; this transfer of charge lowers the upper capacitive plate, whereupon a second breakdown is facilitated between the cloud-top and this charged plate, inducing electrical current between the cloud and the mesosphere and initiating the observed luminous discharges. Copyright 2007 by the American Geophysical Union.