Continuing currents in cloud-to-ground lightning discharges

Abstract

About 200 excellent photographs of cloud‐to‐ground discharges, taken with a newly designed rotating‐film camera, were obtained from very active thunderstorms in 1959 and 1960. The electric‐field changes and luminosity variations of the photographed discharges were recorded simultaneously on two oscilloscopes having different time resolution. Fifty per cent of the multiple‐stroke flashes, constituting about 90 per cent of cloud‐to‐ground flashes, are found to involve at least one stroke which is followed by very long continuing luminosity lasting for 40 to 500 msec. This continuing luminosity contains a number of relatively brighter components essentially the same as the M components which are known to follow some strokes having very short time intervals. The analysis of the electric field associated with the continuing luminosity reveals that, during the luminous period, negative charge from the cloud flows to ground continuously. The surges of current (M components) during the continuing luminosity are associated with the small rapid field changes (K changes), and the time interval between M components is statistically the same as that between the K changes generally observed during the interstroke and final period of cloud‐to‐ground flashes. During the period of continuing luminosity, the lightning channel maintains a level of conductivity which is high enough to support a momentary current increase without involving the leader process. After the channel loses its luminosity, it maintains a lower level of conductivity for 7 to 100 msec, and a subsequent stroke during this period can also follow the same channel. When a longer time elapses (>100 msec), a subsequent stroke, if any, takes a different channel with a new stepped leader.

Electric Field Signatures in Wideband, 3 MHz and 30 MHz of Negative Ground Flashes Pertinent to Swedish Thunderstorms

“…Out of 98 flashes (this study), about 87% were found to contain more than one stroke with the maximum multiplicity of 11 (shown Figure 7e). The observations of [34] in New Mexico found the maximum and the mean multiplicity were 26 and 6.4, respectively, which is the highest maximum multiplicity and mean multiplicity compared to other researchers and locations so far. The maximum multiplicity in Sri Lanka [1], Sweden [2], Malaysia [9], Brazil [25], China [26] and Florida [35] are 12, 10, 14, 16, 14 and 18, respectively.…”

“…For the comparative study, results from different geographical locations have also been incorporated in this study. The different locations include Sri Lanka [1], Sweden [2], Malaysia [9], Brazil [25], China [26], New Mexico [34] and Florida [35]. Table 9 shows the distribution of number of strokes per flash in Sweden (this study) together with other studies.…”

Peculiar transient events in the Schumann resonance band and their possible explanation

“…For example, they can be different strokes of the same lightning flash. Although the time difference between consecutive strokes usually varies between 10 and 100 ms (most frequently 40 ms; Schonland, 1956), inter-stroke intervals above 100 ms can occur when continuing current flows inside the discharge channel (Kitagawa et al, 1962). Relationship between spatially displaced discharges in possibly different cells of the same thunderstorm has been investigated by Mazur (1982), who observed ''associated discharges'' with a time difference of 100 ms and smaller.…”

Prevention of destructive tropical and extratropical storms, hurricanes, tornadoes, dangerous thunderstorms, and catastrophic floods

“…To ensure the development of the non-self-maintained discharge in powerful clouds, several important conditions must be fulfilled. It is obvious that recommendations with respect to these conditions can be derived from numerous studies of lightning discharges (Chalmers, 1967;Wormel, 1953;Shonland, 1964;Workman et al, 1960;Kitagawa et al, 1962). The lightning discharge is known to begin with the "stepped leader" near the caudal and upper borders of the negatively charged layer, since at these points, maximum values of an electric field potential gradient takes place, where a maximum volume electric charge density occurs.…”