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 Transportable laser
23.01.2018 | Physikalisch-Technische Bundesanstalt (PTB)

nachricht New for three types of extreme-energy space particles: Theory shows unified origin
23.01.2018 | Penn State

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: Optical Nanoscope Allows Imaging of Quantum Dots

Physicists have developed a technique based on optical microscopy that can be used to create images of atoms on the nanoscale. In particular, the new method allows the imaging of quantum dots in a semiconductor chip. Together with colleagues from the University of Bochum, scientists from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute reported the findings in the journal Nature Photonics.

Microscopes allow us to see structures that are otherwise invisible to the human eye. However, conventional optical microscopes cannot be used to image...

Im Focus: Artificial agent designs quantum experiments

On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.

We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Rutgers scientists discover 'Legos of life'

23.01.2018 | Life Sciences

Seabed mining could destroy ecosystems

23.01.2018 | Earth Sciences

Transportable laser

23.01.2018 | Physics and Astronomy

VideoLinks Science & Research
Overview of more VideoLinks >>>