Bipolar lightning in winter at Maki, Japan

Abstract

The observation of winter lightning has been continued using magnetic links, digital recording systems for the current oscillograms, field mills, still cameras and video camera systems for the images of lightning channels on the west coast of Japan. Of the 59 magnetic link records, 59% were negative in polarity, 29% were positive, and the remaining 12% were unknown. The maximum peak current was over 270 kA in a positive flash, and the largest peak currents were found in positive flashes. The measured current oscillograms show that winter lightning stroke or ground flash often has a very long duration or continuing current. Moreover, two kinds of bipolar strokes were frequently recorded in the winter season. Nine of the 45 flashes showed bipolar strokes, 24 flashes were negative in polarity, seven were positive, and five were unknown.