A hyperbolic system for obtaining VHF radio pictures of lightning

Abstract

A hyperbolic system with five VHF receivers is used to obtain three-dimensional fixes of sferics as a function of time. Data recorded during one complete flash and parts of several others have been reduced. The integrated picture of one lightning flash shows a ‘waist’ region of minimum cross section between 3.8 and 4.5 km high. Branching extends upward and downward from the waist. Downward branches do not always emerge from the cloud base. Lower regions of previously established channels tend not to radiate during high-order strokes. By far the greater part of the activity is confined to the cloud. The flash pervaded a volume 3×4×6 km. The instrument is particularly useful for tracking interstroke processes, higher regions of a flash to ground, and cloud flashes, but the accuracy of fixes obtained below the cloud is degraded by poor height resolution in this region. Noise is sometimes emitted by clouds that are not cumulonimbus. The method used to calculate the positions of the sferic sources is described, and the accuracy of the system is discussed.