ANALYSIS OF CHANNEL LUMINOSITY CHARACTERISTICS IN ROCKET TRIGGERED LIGHTNING

The comparison is made between the high-speed (2000 fps) photographic data in rocket-triggered negative lightning using two techniques. The analysis shows that: the initial speed of upward positive leader (UPL) in altitude-triggered negative lightning (ATNL) is about one order of magnitude lower than that inclassical triggered negative lightning (CTNL), while the triggering height of ATNL is higher than that of CTNL; the afterglow time of metal vaporized part of the lightning channel can endure for about 160-170 ms, so the luminosity of the air-ionized part can reflect the characteristics of the current in the lightning channel better than that of the metal vaporized part. According to the different characteristics of the luminosity change of the lightning channel, together with the observation of the electric field changes,three kinds of processes after return-stroke (RS) can be distinguished: the continuous decaying type without M component, the isolated type and continuing type with M component, corresponding to different wave shapes of the continuous current. The geometric mean of the interval of RS with M component is 77 ms, longer than that (37 ms) of RS without M component. And the initial continuous current (ICC) with M component also has a longer duration than does the ICC without M component. The distinction between the relative luminosity of the lightning channel before RS and that before M component is obvious: the former is very weak or even can't be observed, while the latter is still considerable luminous.