Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New satellite observations reveal surprising features of mysterious gamma-ray blasts from Earth

18.02.2005


A particle accelerator operates in Earth’s upper atmosphere above major thunderstorms at energies comparable to some of the most exotic environments in the universe, according to new satellite observations of terrestrial gamma-ray flashes.



Terrestrial gamma-ray flashes (TGFs) are very short blasts of gamma rays, lasting about one millisecond, that are emitted into space from Earth’s upper atmosphere. The gamma rays are thought to be emitted by electrons traveling at near the speed of light when they scatter off of atoms and decelerate in the upper atmosphere. TGFs were first discovered in 1994 by the Burst and Transient Source Experiment (BATSE) on the Compton Gamma-Ray Observatory.

BATSE could only detect TGFs in a special observing mode and was limited in its ability to count them or measure their peak energies. New observations from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) satellite raise the maximum recorded energy of TGFs by a factor of ten and indicate that the Earth gives off about 50 TGFs every day, and possibly many more. The findings are reported in the February 18 issue of Science by a team of researchers from the University of California, Santa Cruz, UC Berkeley, and the University of British Columbia (UBC). "The idea that the Earth, a fairly small and tame planet, can be an accelerator of particles to ultrarelativistic energies is fascinating to me," said David Smith, an assistant professor of physics at UC Santa Cruz and first author of the paper. "The energies we see are as high as those of gamma rays emitted from black holes and neutron stars," Smith said.


The exact mechanism that accerates the electron beams to produce TGFs is still uncertain, he said, but it probably involves the build-up of electric charge at the tops of thunder clouds due to lightning discharges, resulting in a powerful electric field between the cloudtops and the ionosphere, the outer layer of Earth’s atmosphere. "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," Smith said. "What’s exciting is that we are now getting data good enough for the theorists to really test their models."

TGFs have been correlated with lightning strikes and may be related to visible phenomena that occur in the upper atmosphere over thunderstorms, such as red sprites and blue jets. Just how these various phenomena are related is a question the RHESSI investigators plan to pursue in collaboration with other researchers around the world, Smith said.

The Science paper presents the first analysis of RHESSI data for TGFs. RHESSI, a NASA Small Explorer spacecraft, was launched in 2002 to study x-rays and gamma-rays from solar flares. But RHESSI’s detectors pick up gamma rays from a variety of sources. Smith worked with RHESSI principal investigator Robert Lin at UC Berkeley and Christopher Barrington-Leigh, now at UBC, to plan ways they could use the satellite for a range of investigations in addition to studying solar flares.

Liliana Lopez, a UC Berkeley undergraduate, has been working with Smith to analyze the RHESSI data for TGFs. The Science paper presents the results from a search of three months of RHESSI data, and the analysis of additional data is ongoing.

The authors estimated a global average rate of about 50 TGFs a day, but the rate could be up to 100 times higher if, as some models indicate, TGFs are emitted as narrowly focused beams that would only be detected when the satellite is directly in their path.

The duration of TGFs recorded by RHESSI ranged from 0.2 to 3.5 milliseconds. The most energetic TGF photons detected by RHESSI were in the range of 10 to 20 million electron volts (10-20 MeV), or about 300 times as energetic as medical x-rays. The electrons that emitted these gamma rays would have been traveling at 99.99 percent of the speed of light, with energies on the order of 35 MeV.

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."

Tim Stephens | EurekAlert!
Further information:
http://www.ucsc.edu

More articles from Physics and Astronomy:

nachricht Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences

nachricht Nano-kirigami: 'Paper-cut' provides model for 3D intelligent nanofabrication
16.07.2018 | Chinese Academy of Sciences Headquarters

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Subaru Telescope helps pinpoint origin of ultra-high energy neutrino

16.07.2018 | Physics and Astronomy

Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides

16.07.2018 | Life Sciences

New research calculates capacity of North American forests to sequester carbon

16.07.2018 | Earth Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>