Charge transfer and in‐cloud structure of large‐charge‐moment positive lightning strokes in a mesoscale convective system

Abstract

Lightning observations in the very high frequency band and measurements of ultra low frequency magnetic fields are analyzed to investigate the charge transfer and in‐cloud structure of eight positive cloud‐to‐ground (+CG) strokes in a mesoscale convective system. Although no high altitude images were recorded, these strokes contained large charge moment changes (1500–3200 C·km) capable of producing nighttime sprites. Even though the convective region of the storm was where the flashes originated and where the CG strokes could occur, the charge transferred to ground was mainly from the stratiform region. The post‐stroke long continuing currents were connected to highly branched negative leader extension into the stratiform region. While the storm dissipated, the altitude of negative leader propagation in the stratiform area dropped gradually from 8 to 5 km, indicating that in some and perhaps all of these strokes, it was the upper positive charge in the stratiform region that was transferred.