Lightning's X-ray zap

     A team from the University of Florida's International Center for
     Lightning Research and Testing triggered strikes by firing rockets
     trailing grounded wires into storm clouds 

     The induced lightning hit a specially constructed tower, allowing
     the team to study the discharges in detail. 

     They measured intense bursts of X-rays, gamma rays and fast-moving
     electrons - just before each visible flash. 

     The bursts typically lasted less than 100 microseconds. 

    "I think it's really exciting," said co-researcher Martin Uman. "We
     didn't expect to see anything at all, and then, all of a sudden, 
     with almost every lightning stroke, we had X-rays." 

     High sprites 

     Uman, Joseph Dwyer and colleagues suggest that the breakdown of
     air - the process thought to generate the X-rays - is an important
     process for lightning and other atmospheric discharge phenomena. 

     The X-rays and other radiation may be generated when large 
     electric fields manipulate electrons during the "dart leader", 
     the phase that creates a path from clouds to ground for the 
     lightning to follow during a strike. 

    "These results provide strong evidence that the production of 
     runaway electrons is an important process during lightning," the
     researchers wrote in the journal Science.

     Friday, 31 January, 2003, 15:19 GMT 

     http://news.bbc.co.uk/1/hi/sci/tech/2713891.stm 

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     Evidence file for

     http://www.perceptions.couk.com/footnotes2.html#atmos

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