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 in a terrestrial
gamma-ray flash (TGF), a brief burst produced inside thunderstorms and
shown to be associated with lightning. It is estimated that about 500
TGFs occur daily worldwide, but most go undetected.

http://www.nasa.gov/mission_pages/GL...derstorms.html