Earth Creates Powerful Gamma-Ray Flashes

[zavvy]

<b>Earth Creates Powerful Gamma-Ray Flashes</b><br /><br />LINK<br /><br />Gamma rays that flash briefly in Earth's atmosphere during lightning storms are much more frequent and powerful than previously thought, a new study reveals. The rays - high-energy photons - exceed the energies of those from cosmic sources such as the explosive births of black holes and the new observations support a phenomenon predicted in 1925.<br /><br />Brief bursts of gamma rays coming from space have been observed since the 1960s. But in 1994, astronomers using NASA's orbiting Compton Gamma-Ray Observatory discovered the energetic photons in Earth's upper atmosphere. These terrestrial gamma-ray flashes (TGFs) last about a millisecond - shorter than most space-based bursts.<br /><br />Compton observed about 70 TGFs during its nine years in orbit. But it was not designed to accurately measure high energies or respond quickly to such fleeting events. Now, astronomers have studied data from NASA's Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) satellite, launched in 2002. They found 86 TGFs over six months, extrapolating this data suggests that about 50 events occur around the world every day.<br /><br />And RHESSI's detectors showed the photons had about 100 times as much energy as those measured by Compton. "This is what interests me the most," says David Smith, a physicist at the University of California in Santa Cruz, US, who led the study. "The average energy per gamma ray is greater than the emission from all those cosmic sources."<br /><br />"Relativistic runaway breakdown"<br /><br />The events are the most energetic phenomena produced on Earth, agrees Umran Inan, a physicist at Stanford University in California, US. He says the photons appear to be produced in a "relativistic runaway breakdown" process, first suggested 80 years ago. <br /><br />In this process, a lightning strike leaves behind negative char

 

[tom_hobbes]

Fascinating Zav, thanks. <div class="Discussion_UserSignature"> <p><font size="2" color="#339966"> I wish I could remember<br /> But my selective memory<br /> Won't let me</font><font size="2" color="#99cc00"> </font><font size="3" color="#339966"><font size="2">- </font></font><font size="1" color="#339966">Mark Oliver Everett</font></p><p> </p> </div>