MYSTERIOUS gamma ray bursts that occur in the first moments of a storm, as lightning jumps between clouds, hint at where lightning comes from.
It is even possible that passengers in planes flying above storms could be bathed in dangerous radiation.
Terrestrial gamma ray flashes (TGFs) were discovered in 1994 emanating from the tops of thunderclouds. To explore their origin, Xuan-Min Shao of Los Alamos National Laboratory, New Mexico, and of the University of California, Santa Cruz, compared TGFs detected by the with time lines of lightning. They confirmed the bursts were associated with intra-cloud lightning. Such lightning is more common than intense ground strikes, says Smith (Journal of Geophysical Research, ).
Advertisement
The pair also found that TGFs occur in the first few milliseconds of strikes. This is backed up by of Duke University in North Carolina and colleagues. They link TGFs to the initial 鈥渓eader鈥� of lightning flowing upwards between charged clouds (Geophysical Research Letters, ).
Morris Cohen of Stanford University, California, says that the studies give a clue to how lightning gets started. Electric fields in clouds often initiate a spark despite being apparently too weak to do so. 鈥淟ightning happens earlier than it should,鈥� says Cohen.
