{"id":8489,"date":"2010-02-12T17:09:40","date_gmt":"2010-02-12T17:09:40","guid":{"rendered":"http:\/\/euvolution.com\/futurist-transhuman-news-blog\/are-tgfs-hazardous-to-air-travelers\/"},"modified":"2010-02-12T17:09:40","modified_gmt":"2010-02-12T17:09:40","slug":"are-tgfs-hazardous-to-air-travelers","status":"publish","type":"post","link":"https:\/\/www.euvolution.com\/futurist-transhuman-news-blog\/space-station\/are-tgfs-hazardous-to-air-travelers.php","title":{"rendered":"Are TGFs Hazardous to Air Travelers?"},"content":{"rendered":"
Instruments scanning outer space for cataclysmic explosions<\/span> called gamma-ray bursts<\/span> are detecting intense flashes of gamma-ray<\/span> energy right here in the friendly skies of Earth. These terrestrial gamma-ray flashes, or TGFs<\/span>, blast through thunderstorms close to the altitude where commercial airliners fly. <\/span> <\/div>

In fact, they could be too close for comfort.<\/span><\/p>

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In a recent study,* scientists estimated that airline passengers could be exposed to 400 chest X-rays<\/span> worth of radiation by being near the origin of a single millisecond blast. Joe Dwyer<\/span> of the Florida Institute of Technology took part in that research, which used observations from NASA's Reuven Ramaty High Energy Solar Spectroscopic Imager<\/span>, or RHESSI<\/span>, to estimate the danger TGFs pose.<\/span><\/p>

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\"see<\/a>\"We believe the risk of encountering a TGF <\/span>in an airplane is very small,\" says Dwyer<\/span>. \"I wouldn't hesitate to take a flight. Pilots already avoid thunderstorms because of turbulence, hail, and lightning, and we may just have to add TGFs <\/span>to the list of reasons to steer clear of those storms.\"<\/span><\/p>

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But, he stresses, \"it's worth looking into.\"<\/span><\/p>

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Right:<\/strong> Lightning might not be the only reason to avoid thunderstorms. TGFs <\/span>sometimes come blasting out of these clouds, too. Image credit: NOAA<\/span>. <\/span><\/p>

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NASA's Gamma-ray Burst Monitor <\/span>(GBM) on the Fermi Gamma-ray Telescope will help evaluate the hazards.<\/span><\/p>

\"GBM <\/span>provides the best TGF <\/span>data we have so far,\" says Dwyer<\/span>. \"It gets better measurements of their spectra than any previous instrument, giving us a more accurate idea of just how energetic they are.\"<\/span> <\/p>

Although TGFs are quite brief (1-2 milliseconds), they appear to be the most energetic events on Earth. They belch destructive gamma-rays packing over ten million times the energy of visible light photons – enough punch to penetrate several inches of lead. <\/span><\/p>

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\"It's amazing,\" says Jerry Fishman<\/span>, a co-investigator for the Gamma-ray Burst Monitor. \"They come blasting right through the whole Fermi spacecraft and light up all of our detectors. Very few cosmic gamma-ray bursts manage to do this!\" <\/span><\/p>

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The origin of TGFs <\/span>is still a mystery, but researchers know this much: TGFs <\/span>are associated with thunderstorms and lightning. \"We think the electric field in a thunderstorm may get so strong that the storm itself turns into a gamma-ray factory,\" says Dwyer<\/span>. \"But we don't know exactly how or why or where inside the storm this happens.\"<\/span><\/p>

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So no one yet knows how often, if ever, planes end up in the wrong place at the wrong time.<\/span><\/p>

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\"see<\/a><\/span><\/p>

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Above:<\/strong> A cartoon sketch of electric and magnetic fields in a thunderstorm and some of the phenomena they produce. TGFs may be just one aspect of thunderstorm activity in addition to elves, sprites, blue jets and ordinary lightning. Credit: Stanford University. [more<\/a>]<\/span><\/p>

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It's possible that lightning bolts trigger TGFs. Or maybe TGFs trigger lightning bolts. Researchers aren't sure which comes first. GBM's excellent timing accuracy<\/span> – to within 2 microseconds – will help solve this riddle. <\/span><\/p>

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\"For some of the TGFs, we've pinpointed the associated lightning,\" says Dwyer. \"This information along with the spectrum should help us figure out how deep in the atmosphere a TGF source is and how many gamma-rays it's emitting. Then we can determine the altitude and location they're coming from in the thunderstorm.\" <\/span><\/p>

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Fishman offers some good news: \"If TGFs originate near the tops of thunderstorms and propagate upward from there, airline passengers would be safe.\"<\/span><\/p>

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By looking closely at a TGF's life cycle, that is, how quickly it turns on and off, GBM may also help researchers calculate how large and concentrated the gamma-ray source is. If the gamma-rays are emitted over a large region, the radiation dose would be diluted and much less harmful.<\/span><\/p>

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\"see<\/a>\"But if the source is compact and the gamma-rays originate close to an aircraft, then that could be a problem,\" says Fishman<\/span>.<\/span><\/p>

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Right:<\/strong> The radiation dose from an ordinary lightning leader vs. the dose from a TGF. Both phenomena are associated with electron beams. Tighter, more compact beams deliver a greater effective dose. Details of this model may be found in an upcoming issue of the Journal of Geophysical Research (Atmospheres)<\/em>. Look for \"Estimation of the fluence of high-energy electron bursts produced by thunderclouds and the resulting radiation doses received in aircraft\" by J. Dwyer et al. (in press)<\/span>.<\/span><\/p>

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\"Of course the smaller the source the lower the odds of a plane ending up close to it,\" adds Dwyer. <\/span><\/p>

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GBM wasn't designed to look for TGFs, but GBM co-investigator Michael Briggs has greatly enhanced its sensitivity to them by writing new software.<\/span><\/p>

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\"TGFs have really been an afterthought for missions so far,\" says Dwyer<\/span>. RHESSI<\/span>, for example, points at the sun, but the RHESSI <\/span>team figured out a way to measure TGFs <\/span>by detecting gamma-rays coming in through the satellite's backside. \"All these instruments have been pointing across the universe, while right over our heads these monsters are going off!\" <\/span><\/p>

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\"Now the whole field of TGFs is on fire,\" says Fishman. \"People are jumping on the bandwagon to try to figure them out.\"<\/span><\/p>

View my blog's last three great articles....<\/span><\/div>