September 15, 2006

Methods and Properties of Triggered Lightning

From the UF Lightning Research Facility, their list of publications.

Pay particular attention to:

The most effective technique for triggering lightning involves launching a small rocket trailing a thin grounded wire toward a charged cloud overhead. This triggering method is sometimes called "classical" triggering and is illustrated in Fig. 1. The cloud charge is indirectly sensed by measuring the electric field at ground, with values of 4 to 10 kV/m generally being good indicators of favorable conditions for lightning initiation. When the rocket, ascending at about 200 m/s, is about 200 to 300 m high, the field enhancement near the rocket tip launches a positively charged (for the common summer thunderstorm having predominantly negative charge at 5 to 7 km altitude) leader that propagates upward toward the cloud. This leader vaporizes the trailing wire and initiates a so-called "initial continuous current" of the order of several hundred amperes that effectively transports negative charge from the cloud charge source via the wire trace to the instrumented triggering facility. There often follows, after the cessation of the initial continuous current, several downward dart leader/upward return stroke sequences traversing the same path to the triggering facility.

V. A. Rakov, SIPDA V

Posted by mill1974 at September 15, 2006 8:39 AM