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Scientists operate artificial particle accelerators here on Earth, like the world's largest one on the border with Switzerland and France'”CERN's Large Hadron Collider.
But, naturally occurring particle accelerators are operating in Earth's upper atmosphere and they are said to have energy levels 'comparable to some of the most exotic environments in the universe.' [University of California'”Santa Cruz press release (2.17.2005): 'New satellite observations of terrestrial gamma-ray flashes reveal surprising features of mysterious blasts from Earth']
Surprisingly, scientists didn't even know they existed until 1994 when the Burst And Transient Source Experiment (BATSE) detected them in Earth's upper atmosphere.
The BATSE was a scientific instrument that was onboard the now-defunct NASA Compton Gamma-Ray Observatory (CGRO), which was de-orbited from space in June 2000.
The orbiting instrument was used to calculate the location for all Gamma-Ray Bursts (GRBs) that were detected in space.
GRBs are flashes of gamma rays that are associated with highly energetic electromagnetic explosions out in the Universe, such as those associated with supernova events that result in black holes.
Gamma rays are a type of electromagnetic radiation (light) that has a very high frequency and very short wavelength.
Other types of electromagnetic radiation are x-rays (like those used in medical facilities to see your bones), visible light (like from the Sun and the lamp overhead), ultraviolet (UV), infrared (heat), microwaves (like in microwave ovens), and radio waves (listen, you'll hear sounds coming in from them on your car radio).
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With the discovery of our own locally grown gamma ray outbursts, scientists now call these naturally occurring particle accelerators high in our atmosphere by the term terrestrial gamma-ray flashes, or TGFs.
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Specifically, TGFs are very short in duration but highly energetic blasts of gamma rays'”lasting anywhere from about 0.2 to 1.0 millisecond (ms, where a millisecond is one thousandth of one second) and having energies up to 20 megaelectron-volts (MeV or 20 million electron volts).
TGFs come about, scientists think, when electrons are traveling very close to the speed of light (a speed of about 186,000 miles per second) in the upper atmosphere of Earth and suddenly collide with nuclei of atoms in the upper atmosphere.
The collisions slow down the electrons, while they also release energy in the form of invisible gamma rays. The collisions also release electrons from the atoms.
So, scientists conjecture (they don't really know yet, but they want to find out) that TGFs are produced by the build up of electric charges near the physical upper limit of thunderstorms, possibly due to the discharge of lightning.
The build up of these powerful electric fields could be the conduit where TGFs are created.
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After the discovery of TGFs, analysis of them from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) satellite found that about fifty of these TGFs are created each day in Earth's upper atmosphere.
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Dr. David Smith, an assistant professor of physics at the University of California'”Santa Cruz, states, "The idea that the Earth, a fairly small and tame planet, can be an accelerator of particles to ultrarelativistic energies is fascinating to me. The energies we see are as high as those of gamma rays emitted from black holes and neutron stars.' [UC'”Santa Cruz press release]
Smith adds, "Regardless of the exact mechanism, there is some enormous particle accelerator in the upper atmosphere that is accelerating electrons to these very high energies, so they emit gamma rays when they hit the sparse atoms of the upper atmosphere. What's exciting is that we are now getting data good enough for the theorists to really test their models."
The UC-Santa Crew article states, 'The findings raise many interesting questions, including whether the electrons that emit TGFs ultimately contribute to the high-energy electrons in Earth's radiation belts, Smith said. "This is a very interesting process involving extreme physics right here on Earth, and if we can understand the process here it might give us insights into similar processes in less accessible parts of the universe."
Scientists just don't know very much about TGFs. Consequently, the NASA satellite Firefly comes into play.
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The 1.29.2010 NASA article 'Firefly Mission to Study Terrestrial Gamma-ray Flashes' asks the questions: 'What causes these high-energy flashes? Do they help trigger lightning--or does lightning trigger them? Could they be responsible for some of the high-energy particles in the Van Allen radiation belts, which can damage satellites?'
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Developed under the National Science Foundation's CubeSat program, the mission will only cost about one million U.S. dollars because it is a secondary payload within a more expensive primary payload launch'”that of the Poly-Picosatellite Orbital Deployer (P-POD).
NASA's article states, 'If successful, Firefly will return the first simultaneous measurements of TGFs and lightning. Most of what's known about TGFs to date has been learned from missions meant to observe gamma rays coming from deep space, such as NASA's Compton Gamma Ray Observatory, which discovered TGFs in 1994. As it stared out into space, Compton caught fleeting glimpses of gamma rays out of the corner of its eye, so to speak. The powerful flashes were coming--surprise!--from Earth's atmosphere.'
And, 'Then again, Compton and other space telescopes before Firefly weren't actually looking for TGFs. So perhaps it's not surprising that they didn't find many. Firefly will specifically look for gamma ray flashes coming from the atmosphere, not space, conducting the first focused survey of TGF activity. Firefly's sensors will even be able to detect flashes that are mostly obscured by the intervening air, which is a strong absorber of gamma rays (a fact that protects people on the ground from the energy in these flashes). Firefly's survey will give scientists much better estimates of the number of TGFs worldwide and help determine if the link to lightning is real.'
Scientists hope to study TGFs with the use of Firefly to learn more about the physical process of lightning here on Earth and to learn more about gamma ray flashes (GRFs) way out there in outer space and terrestrial gamma-ray flashes (TGFs)more locally position here on Earth
Hopefully, this little spacecraft will produce major discoveries in the area of cosmic and local gamma-ray research.
