Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Mysterious electron acceleration explained

29.02.2012
Computer simulation identifies source of aurora-causing high-speed electrons in space

A mysterious phenomenon detected by space probes has finally been explained, thanks to a massive computer simulation that was able to precisely align with details of spacecraft observations. The finding could not only solve an astrophysical puzzle, but might also lead to a better ability to predict high-energy electron streams in space that could damage satellites.


An artist's rendition of Earth's magnetosphere. A magnetic tail, or magnetotail, is formed by pressure from the solar wind on a planet's magnetosphere. Image: NASA

Jan Egedal, an associate professor of physics at MIT and a researcher at the Plasma Science and Fusion Center, working with MIT graduate student Ari Le and with William Daughton of the Los Alamos National Laboratory (LANL), report on this solution to the space conundrum in a paper published Feb. 26 in the journal Nature Physics.

Egedal had initially proposed a theory to explain this large-scale acceleration of electrons in Earth’s magnetotail — a vast and intense magnetic field swept outward from Earth by the solar wind — but until the new data was obtained from the computer simulation, “it used to be people said this was a crazy idea,” Egedal says. Thanks to the new data, “I don’t get that anymore,” he says.

The simulation shows that an active region in Earth’s magnetotail, where “reconnection” events take place in the magnetic field, is roughly 1,000 times larger than had been thought. This means a volume of space energized by these magnetic events is sufficient to explain the large numbers of high-speed electrons detected by a number of spacecraft missions, including the Cluster mission.

Solving the problem required a staggering amount of computer power from one of the world’s most advanced supercomputers, at the National Institute for Computational Science at Oak Ridge National Laboratory in Tennessee. The computer, called Kraken, has 112,000 processors working in parallel and consumes as much electricity as a small town. The study used 25,000 of these processors for 11 days to follow the motions of 180 billion simulated particles in space over the course of a magnetic reconnection event, Egedal says. The processing time accumulated gradually, squeezed in during idle time between other tasks. The simulation was performed using a plasma-physics code developed at LANL that rigorously analyzes the evolution of magnetic reconnection.

Egedal explains that as the solar wind stretches Earth’s magnetic-field lines, the field stores energy like a rubber band being stretched. When the parallel field lines suddenly reconnect, they release that energy all at once — like releasing the rubber band. That release of energy is what propels electrons with great energy (tens of thousands of volts) back toward Earth, where they impact the upper atmosphere. This impact is thought, directly or indirectly, to generate the glowing upper-atmosphere plasma called the aurora, producing spectacular displays in the night sky.

What had puzzled physicists is the number of energetic electrons generated in such events. According to theory, it should be impossible to sustain an electric field along the direction of the magnetic field lines, because the plasma (electrically charged gas) in the magnetotail should be a near-perfect conductor. But such a field is just what’s needed to accelerate the electrons. And, according to the new simulation, the volume of space where such fields can build up can, in fact, be at least 1,000 times larger than the theorists had thought possible — and thus large enough to explain the observed electrons.

“People have been thinking this region is tiny,” Egedal says. But now, “by analyzing the spacecraft data and doing the simulation, we’ve shown it can be very large, and can accelerate many electrons.” As a result, “for the first time, we can reproduce the features” observed by the Cluster spacecraft.

That could be important because, among other things, “these hot electrons can destroy spacecraft,” Egedal says, which is why both the military and NASA “would like to understand this better.”

Although this analysis was specific to the phenomena in Earth’s magnetotail, Egedal says similar phenomena may be taking place in much bigger regions of magnetized plasma in space — such as in mass ejections that erupt from the sun’s corona, which occupy regions 10,000 times larger, or even regions surrounding pulsars or other high-energy objects in deep space, which are much larger still. In the future, he hopes to carry out simulations that would apply to the sun’s coronal mass ejections. “We think we can scale up the simulation” by a hundredfold, he says.

Michael Brown, a professor of physics at Swarthmore College who was not involved in this research, says Egedal “is emerging as a real leader in experimental [and] observational aspects of magnetic reconnection,” and his co-author Daughton “is the recognized leader in state-of-the-art plasma simulations.” The new result “is very significant, and I think is surprising to the rest of the community. … I think this picture will gain more and more acceptance, and we have to go beyond” the presently accepted picture of plasmas, he says.

The work was supported by grants from NASA and the National Science Foundation.

Caroline McCall | EurekAlert!
Further information:
http://www.mit.edu

More articles from Physics and Astronomy:

nachricht Climate cycles may explain how running water carved Mars' surface features
02.12.2016 | Penn State

nachricht What do Netflix, Google and planetary systems have in common?
02.12.2016 | University of Toronto

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: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

Im Focus: Fraunhofer ISE Develops Highly Compact, High Frequency DC/DC Converter for Aviation

The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

UTSA study describes new minimally invasive device to treat cancer and other illnesses

02.12.2016 | Medical Engineering

Plasma-zapping process could yield trans fat-free soybean oil product

02.12.2016 | Agricultural and Forestry Science

What do Netflix, Google and planetary systems have in common?

02.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>