A team including researchers at RIKEN’s Discovery Research Institute in Wako and the University of Tokyo has observed a burst of high-energy gamma radiation emerging from a thundercloud over the Sea of Japan (1). The discovery could help to reveal the complex electrical processes that cause lightning.
“Free electrons, originally produced by cosmic rays, can be accelerated by the strong electric fields in thunderclouds,” explains project scientist Harufumi Tsuchiya. “If they reach relativistic energies, they can knock other electrons out of their atoms, causing a ‘runaway electron avalanche’.”
When one of the high-energy electrons is deflected by the nucleus of an atom, it loses energy in the form of gamma rays called Bremsstrahlung—literally ‘braking radiation’. Bursts of these gamma rays have been detected by near-Earth satellites above thunderclouds, and very short bursts are often recorded near the ground. Longer bursts lasting up to a few minutes appear to be very rare events, and physicists are unsure where they come from or what they consist of.
To answer these questions, the researchers built new radiation detectors based on devices on board the Suzaku cosmic x-ray satellite. The detectors were installed on the roof of the Kashiwazaki–Kariwa nuclear power plant in Niigata. On 6 January 2007, during a violent winter thunderstorm, they recorded a large radiation spike lasting over a minute, which could not be attributed to background radiation or electrical noise.
The spectrum of radiation included high-energy gamma rays that could not have been produced by thermal processes—which would require temperatures of billions of degrees Celsius. Therefore the burst must have been caused by Bremsstrahlung processes.
The burst was recorded approximately 70 seconds before a large flash of lightning, leading the researchers to speculate on whether the two events are related. In theory the runaway electrons could produce a large number of slower electrons, leading to electrical imbalance and lightning. “If thunderclouds frequently generate gamma ray bursts prior to lightning discharges, detailed observations of such rays would allow us to predict when lightning will occur,” claims Tsuchiya.
However, more observations are needed to prove such a link. “We believe the burst behaves like a searchlight beam, illuminating only a limited area on the ground,” says Tsuchiya, “so we were probably fortunate that the beam happened to pass over our detector.” To test this hypothesis, the researchers plan to spread several detectors over a large area, so that they might trace the movement of a gamma ray burst.
1. Tsuchiya, H., Enoto, T., Yamada, T., Yuasa, T., Kawaharada, M., Kitaguchi, T., Kokubun, M., Kato, H., Okano, M., Nakamura, S. & Makishima, K. Detection of high-energy gamma rays from winter thunderclouds. Physical Review Letters 99, 165002 (2007).
Saeko Okada | ResearchSEA
Nanostructures taste the rainbow
29.06.2017 | California Institute of Technology
X-ray photoelectron spectroscopy under real ambient pressure conditions
28.06.2017 | National Institutes of Natural Sciences
Computer scientists use wave packet theory to develop realistic, detailed water wave simulations in real time. Their results will be presented at this year’s SIGGRAPH conference.
Think about the last time you were at a lake, river, or the ocean. Remember the ripples of the water, the waves crashing against the rocks, the wake following...
An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.
Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...
Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.
Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...
Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.
As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...
Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.
With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...
19.06.2017 | Event News
13.06.2017 | Event News
13.06.2017 | Event News
29.06.2017 | Physics and Astronomy
29.06.2017 | Life Sciences
29.06.2017 | Health and Medicine