The luminosity and current characteristics of M-component from triggered-lightning in Shandong

Channel base current from a rocket-triggered lightning was measured by a 0.5mΩ coaxial current measuring resistor at Shandong Province, China, during summer 2009. Additionally, high-speed camera records with 167μs resolution were also obtained. The characteristics of M-components were deduced from the comparison between the relative brightening of high-speed images and channel base current. This flash contained a total of 26 M-components, all of which were superimposed on a slowly-varying current. These M-components had geometric mean (GM) duration of 2.3ms and peak of 1.47kA varied form 0.06kA to 6.99kA. Also the statistics were given for the following M-components parameters: half-peak width, rise time (10%~90%), M-component interval, preceding continuing current level, charge transferred and action integral. Our statistic results indicated that the peak, half-peak width and charge transferred had obviously different geometric mean values from other researchers' statistic results. The main reason was the lightning included six large magnitude, exceeding 3kA, M-components. Generally, the channel was non-luminous preceding the return-stroke that indicated the cut-off of current, but our optical observation results indicated that a weak detectable luminosity or low current existed in whole channel preceding return stroke (RS). Similar to M-components, RS could also superimpose on a slowly-varying current and the continuing current and luminosity level of preceding RS was lower than that of M-component. The result showed cut-off of channel current was probably not necessary for RS.