Thunderstorms Make Antimatter   
       
   Jan. 11, 2011:  Scientists using NASA's Fermi Gamma-ray Space Telescope have   
   detected beams of antimatter produced above thunderstorms on Earth, a   
   phenomenon never seen before.   
       
   Scientists think the antimatter particles were formed inside thunderstorms in   
   a terrestrial gamma-ray flash (TGF) associated with lightning. It is estimated   
   that about 500 TGFs occur daily worldwide, but most go undetected.   
       
   "These signals are the first direct evidence that thunderstorms make   
   antimatter particle beams," said Michael Briggs, a member of Fermi's Gamma-ray   
   Burst Monitor (GBM) team at the University of Alabama in Huntsville (UAH). He   
   presented the findings Monday, during a news briefing at the American   
   Astronomical Society meeting in Seattle.   
   [...]   
   An artist's concept of antimatter spraying above a thunderhead. [video]   
   Fermi is designed to monitor gamma rays, the highest energy form of light.     
   When antimatter striking Fermi collides with a particle of normal matter, both   
   particles immediately are annihilated and transformed into gamma rays. The GBM   
   has detected gamma rays with energies of 511,000 electron volts, a signal   
   indicating an electron has met its antimatter counterpart, a positron. [...]   
   Although Fermi's GBM is designed to observe high-energy events in the   
   universe, it's also providing valuable insights into this strange phenomenon.   
   The GBM constantly monitors the entire celestial sky above and the Earth   
   below. The GBM team has identified 130 TGFs since Fermi's launch in 2008.   
       
   "In orbit for less than three years, the Fermi mission has proven to be an   
   amazing tool to probe the universe. Now we learn that it can discover   
   mysteries much, much closer to home," said Ilana Harrus, Fermi program   
   scientist at NASA Headquarters in Washington.   
   [...]   
   Fermi was above Egypt on Dec. 14, 2009, when a burst of positrons emerged from   
   an African thunderstorm. [larger image]   
       
   The spacecraft was located immediately above a thunderstorm for most of the   
   observed TGFs, but in four cases, storms were far from Fermi. In addition,   
   lightning-generated radio signals detected by a global monitoring network   
   indicated the only lightning at the time was hundreds or more miles away.   
   During one TGF, which occurred on Dec. 14, 2009, Fermi was located over Egypt.   
   But the active storm was in Zambia, some 2,800 miles to the south. The distant   
   storm was below Fermi's horizon, so any gamma rays it produced could not have   
   been detected.   
       
   "Even though Fermi couldn't see the storm, the spacecraft nevertheless was   
   magnetically connected to it," said Joseph Dwyer at the Florida Institute of   
   Technology in Melbourne, Fla. "The TGF produced high-speed electrons and   
   positrons, which then rode up Earth's magnetic field to strike the spacecraft."   
       
   The beam continued past Fermi, reached a location, known as a mirror point,   
   where its motion was reversed, and then hit the spacecraft a second time just   
   23 milliseconds later. Each time, positrons in the beam collided with   
   electrons in the spacecraft. The particles annihilated each other, emitting   
   gamma rays detected by Fermi's GBM.   
       
   Scientists long have suspected TGFs arise from the strong electric fields near   
   the tops of thunderstorms. Under the right conditions, they say, the field   
   becomes strong enough that it drives an upward avalanche of electrons.   
   Reaching speeds nearly as fast as light, the high-energy electrons give off   
   gamma rays when they're deflected by air molecules. Normally, these gamma rays   
   are detected as a TGF.   
       
   [...]   
   Click to view the three steps thunderstorms must take to produce bursts of   
   anti-matter. [more]   
       
   But the cascading electrons produce so many gamma rays that they blast   
   electrons and positrons clear out of the atmosphere. This happens when the   
   gamma-ray energy transforms into a pair of particles: an electron and a   
   positron. It's these particles that reach Fermi's orbit.   
       
   The detection of positrons shows many high-energy particles are being ejected   
   from the atmosphere. In fact, scientists now think that all TGFs emit   
   electron/positron beams. A paper on the findings has been accepted for   
   publication in Geophysical Research Letters.   
       
   "The Fermi results put us a step closer to understanding how TGFs work," said   
   Steven Cummer at Duke University. "We still have to figure out what is special   
   about these storms and the precise role lightning plays in the process."   
       
       
    Editor: Dr. Tony Phillips | Credit: Science@NASA   
       
   More Information   
   Fermi Home Page -- from NASA   
       
   Are TGFs Hazardous to Air Travelers? --- Science@NASA   
       
   Firefly Mission to Study Terrestrial Gamma-ray Flashes -- (Science@NASA)   
       
   What Comes Out of the Top of a Thunderstorm? -- (Science@NASA)   
       
   NASA's Fermi Gamma-ray Space Telescope is an astrophysics and particle physics   
   partnership. It is managed by NASA's Goddard Space Flight Center in Greenbelt,   
   Md. It was developed in collaboration with the U.S. Department of Energy, with   
   important contributions from academic institutions and partners in France,   
   Germany, Italy, Japan, Sweden and the United States.   
       
   The GBM Instrument Operations Center is located at the National Space Science   
   Technology Center in Huntsville, Ala. The team includes a collaboration of   
   scientists from UAH, NASA's Marshall Space Flight Center in Huntsville, the   
   Max Planck Institute for Extraterrestrial Physics in Germany and other   
   institutions.   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.59   
    * Origin: NCS BBS (1:3828/7)