http://e-info.org.tw/node/63057 摘译自2011年1月18日美国，阿拉巴马州报导；张桂芳编译；蔡丽伶审校 科学家利用美国国家航空暨太空总署的费米伽玛射线太空望远镜（NASA's Fermi Gamma-ray Space Telescope）在雷电风暴上方发现反物质束，缔造首次地球上，反物质 在自然状态下出现的记录。 科学家认为反物质粒子是在雷暴圈内形成，闪电时地球高层大气中的伽玛射线闪光中。根 据他们的估计，全球各地每天约出现500次伽玛射线闪光，但大多数探测不到。 任职於亨茨维尔，阿拉巴马大学费米伽玛射线爆发监控小组成员迈克尔.布里格斯表示： 「这些信号是证明雷暴会产生反物质粒子束的第一个直接证据。」他上周在西雅图召开的 美国天文学会会议上公布了该小组的调查结果。 太阳耀斑在爆发过程中制造出反物质。在地球所在的银河系中曾观测到反物质云，但这种 现象从未出现在地球上。 如同巨大的粒子加速器，雷暴可以喷发地面伽玛射线闪光，称为 TGFs，以及高能量的电 子和正电子。正电子是电子的反粒子。 於2008年6月11日升空的美国国家航空暨太空总署的费米伽玛射线太空望远镜，其目的为 从距离地球上空350英里的轨道上，观测光的最高能量形式伽玛射线。 虽然费米伽玛射线爆发显示器设计用於观察宇宙中的高能事件，同时还让科学家对反物质 现象有更深的认识。 伽玛射线爆发监视器每90分钟环绕地球一圈，不断监测整个地球上空。自费米太空望远镜 发射至今，伽玛射线爆发监控小组已辨识出130个地面伽玛射线闪光。 科学家长期以来一直怀疑，地面伽玛射线闪光发生在雷暴顶部附近的强大电场。他们表示 ，在适当条件下，该电场强到足以将大量电子向上推升，释放出像雪崩般巨大的能量。 当前述高能量电子受到空气分子阻力偏折而释放出伽玛射线，其速度几乎可近光速。 通常这些被测到的伽玛射线为地面伽玛射线闪光。但如瀑布般喷泻而出的电子，释放出大 量的伽马射线，让电子和正电子远远爆喷出大气层。这种状况发生在当伽玛射线的能量转 换成一对粒子：一个电子和一个正电子的时候，而这些正是出现在地球上空350英里费米 轨道上的粒子。 观测到正电子意味着许多高能量粒子冲出大气层外。事实上科学家现在认为，所有TGFs皆 释放出电子 /正电子束。这些研究结果的论文已被接受并刊登在「地球物理研究通讯。」 Thunderstorms Emit Beams of Antimatter, NASA Discovers HUNTSVILLE, Alabama, January 18, 2011 (ENS) For the first time, antimatter has been observed occurring naturally on Earth, as scientists using NASA's Fermi Gamma-ray Space Telescope have documented beams of antimatter produced above thunderstorms. The scientists think the antimatter particles are formed inside thunderstorms in terrestrial gamma-ray flashes associated with lightning. They estimate that about 500 gamma-ray flashes 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 team at the University of Alabama in Huntsville. He presented the team's findings last week at the American Astronomical Society meeting in Seattle. Antimatter is created in solar flares on the Sun and clouds of antimatter have been observed in the Milky Way, our home galaxy, but the phenomenon has never before been seen on Earth. Acting like enormous particle accelerators, thunderstorms can emit terrestrial gamma-ray flashes, called TGFs, as well as high-energy electrons and positrons, which are the antiparticles of electrons. Launched June 11, 2008, NASA's Fermi Gamma-ray space telescope is designed to monitor gamma rays, the highest energy form of light, from its orbit 350 miles above the Earth. Although Fermi's Gamma-ray Burst Monitor is designed to observe high-energy events in the universe, it also provides insights into the antimatter phenomenon. The Gamma-ray Burst Monitor constantly monitors the entire sky, circling the Earth every 90 minutes. The Gamma-ray Burst Monitor team has identified 130 terrestrial gamma-ray flashes since the Fermi space telescope was launched. Scientists long have suspected terrestrial gamma-ray flashes 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 deflected by air molecules. Normally, these gamma rays are detected as a terrestrial gamma-ray flash. But the cascading electrons produce so many gamma rays that they blast electrons and positrons clear of the atmosphere. This happens when the gamma-ray energy transforms into a pair of particles: an electron and a positron. It is these particles that reach Fermi's orbit 350 miles above the Earth. 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 these findings has been accepted for publication in the journal "Geophysical Research Letters." --

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