Nature does not plan lightning storms around the location and time schedules of interested scientists, which made it difficult for early workers to study lightning-induced radiation. Joseph Dwyer of the Florida Institute of Technology and Martin Uman of the International Center for Lightning Research and Testing at the University of Florida circumvented this problem by triggering lightning during storms, a common practice among modern lightning researchers. To do this, the team launched a rocket tethered to the ground by a copper wire into a thunderhead, aiming to corral lightning bolts as they struck the rocket and followed the wire to the launch pad. They succeeded in harnessing 37 individual lightning strokes, and found intense bursts of x-ray radiation--each typically depositing tens of megaelectron volts into the detector--associated with 84 percent of them.
"How lightning works really needs to be revisited," Dwyer asserts. Several years ago, scientists working atop a mountain in New Mexico measured x-rays from naturally occurring lightning, but their experiment could not be replicated. The new work, detailed today in the journal Science, is the first controlled and repeatable experiment showing that lightning emits energetic radiation. Says Uman, "Our measurements with the controlled lightning will probably lead others to believe that the mountain top measurement was right."