Charge rearrangement by sprites over a north Texas mesoscale convective system

Abstract

Charge rearrangement by sprites is analyzed for a mesoscale convective system (MCS) situated in north Texas and east New Mexico on 15 July 2010. During the thunderstorm, electric field data were recorded by the Langmuir Electric Field Array (LEFA), while magnetic field data were recorded by the charge‐moment network near Duke University. A high speed (12500 fps) video system operated at Langmuir Laboratory recorded telescopic images of the sprites. Data from the National Lightning Detection Network (NLDN) show that each sprite was preceded by a series of cloud discharges and cloud‐to‐ground discharges. The triggering event preceding the sprite was typically a positive cloud‐to‐ground (+CG) stroke. For one out of the 10 sprites that were recorded, there was a positive hump in the electric field a few milliseconds after the +CG return stroke. The size and shape of the hump roughly matched the light intensity emitted from the sprite. The electric field hump is fit by a sprite current that originates in the ionosphere and propagates downward, producing the same effect as a downward moving positive current. The integral under the current hump was 23.9 C when the velocity of the current pulse was between 0.25 c and 0.55 c. The large sprite current was followed by impulsive electromagnetic radiation which has not been previously reported and could be a recoil effect similar to what is called a “K‐change” when it is observed in a lightning flash.