Researchers simulate electrons in astrophysical plasma jets

November 19, 2013, Helmholtz-Zentrum Dresden-Rossendorf

Physicists of Helmholtz-Zentrum Dresden-Rossendorf have been able to simulate the motion of billions of electrons within astrophysical plasma jets and calculate the light they emit with the help of a high-performance computer. They have been nominated for the Gordon Bell Prize as a result of their work. On the 20th of Nov. they present their work at the Supercomputing Conference SC13 in Denver.

"When the wind blows over the ocean, waves form," Michael Bussmann, head of a HZDR junior research group, starts to explain. "At high wind speeds, water and wind swirl about one another, which is how spray and froth arise. Spray is thus a turbulent mixture of water and air. A similar thing occurs in space when a star ejects hot gas. The jet created by the hot plasma mixes with other gas that surrounds the star. Turbulent flows arise at the boundary region between the two gases." The staff members of the "Computational Radiation Physics" group recently studied the formation of these turbulent phenomena, known as Kelvin-Helmholtz instabilities, with the help of simulations.

"We hope to understand Kelvin-Helmholtz instabilities in detail. To do so, we have tried something that almost no one else has up to now," explains Bussmann. "We have simulated a plasma jet at such high resolution that we could follow the in the jet. That by itself requires enormous computing power, as we had to simulate almost a hundred billion particles." It is impossible even with the most modern telescopes to see individual particles in a stellar jet, however. Scientists were therefore faced with the problem of how to compare their theoretical results to observations. They solved it by making use of the fact that electrons emit light over a broad spectrum of wavelengths when they change their direction of motion or speed. They adapted their simulation program PIConGPU to allow light emitted in all directions to be calculated from the motion of the electrons.

"With luck, we are able to see the light emitted with telescopes from Earth," explains the physicist. "We can therefore simulate something that can be measured on earth. However, the computer power necessary for this is enormous." The light emitted had to be calculated individually for the billions of electrons in the simulation – and in hundreds of different directions. For this reason, the HZDR team used what was then the most powerful supercomputer in the world for their calculations in June of this year: TITAN at Oak Ridge National Laboratory. PIConGPU spent over 16 hours calculating the solution to this problem using 18,000 graphics cards. Few simulation programs can make use of such powerful compute capability. Simulations that operate the most efficiently are honored each year with the Gordon Bell Prize for outstanding achievement in the field of high-performance computing, for which the HZDR scientists have now been nominated.

"We will find out whether we have won at the Supercomputing Conference 2013 in Denver mid-November. It is already a real honor to be among the six finalists. I am very proud of what everyone has achieved. That was great teamwork!" emphasizes Bussmann. "We have obtained unique scientific data with the simulations run on TITAN. It is such a huge quantity that we are still busy evaluating it. Everyone on the team is very excited about what we will discover." Plasmas play a central role in research carried on by the Junior Research Group.

The HZDR researchers hope to understand the properties of laser-driven radiation sources more precisely with the help of analytical models and simulations. Compact accelerators for treating cancer with energetic particles could be developed with these radiation sources. The scientists want to use high-intensity to achieve this goal. They thus have to precisely understand the interaction of the laser light with matter in order to optimize these advanced radiation sources for applications. For this they simulate this interaction on the atomistic level, the level of individual electrons and atoms.

Explore further: Laser heating -- new light cast on electrons heated to several billion degrees

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not rated yet Nov 20, 2013
"Few simulation programs can make use of such powerful compute capability."

Nov 20, 2013
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1 / 5 (10) Nov 20, 2013
Once again, using gas laws to describe an electrified plasma. GIGO!
5 / 5 (6) Nov 20, 2013
Once again, using gas laws to describe an electrified plasma. GIGO!

I liked the part where you implied you know exactly what equations they use and mathematically proved why they were inadequate.
1 / 5 (11) Nov 20, 2013
Once again, using gas laws to describe an electrified plasma. GIGO!

I liked the part where you implied you know exactly what equations they use and mathematically proved why they were inadequate.

Silly goose, I didn't imply anything. I merely read the words, somewhere amongst all those words they mentioned "Kelvin-Helmholtz instabilities". Google it, it should make sense afterward then again the IQ of a rock is required to grasp the basics. Why do I have to "mathematically prove" them wrong again? It was done decades ago by those smarter than you or I, some just prefer their theoretical fantasyland to reality and ignore these facts.
5 / 5 (3) Nov 20, 2013
I see a lot of words and no mathematical refutation. In order to discredit an equation or system of equations, you have to show how those equations are incompatible with reality.
1 / 5 (9) Nov 21, 2013
As I said, the system of equations were proven wrong DECADES ago. Those same equations that suggested magnetically confined fusion should be possible, failed miserably. What you and most astrophysicists don't realize is that the equations that they currently use are the same failed equations used by nuclear physicists decades ago which did not work. As Hannes Alfven said in his Nobel speech;
"The cosmical plasma physics of today is far less advanced than the thermonuclear research physics. It is to some extent the playground of theoreticians who have never seen a plasma in a laboratory. Many of them still believe in formulae which we know from laboratory experiments to be wrong. The astrophysical correspondence to the thermonuclear crisis has not yet come."

Astrophysicists are still in the dark ages in regards to space plasmas.
5 / 5 (4) Nov 21, 2013
Your word and your Alfven quotes are not evidence.
1 / 5 (9) Nov 22, 2013
The evidence lies in the decades of fusion research and the complete failure to "magnetically confine" the fusion as is suggested possible by those theories. There is also much more evidence laid out by in situ research which has taken place since the start of the space age, a quick perusal of the history thereof will show the dramatic changes and profound surprises that took place in the explanation of near earth plasmas. Although I agree Alfven's quotes are not evidence, the years of laboratory research which took place that led him to such conclusions very definitely is evidence. Willful ignorance of salient facts is no excuse to remain in the dark ages.
5 / 5 (4) Nov 22, 2013
More words but no actual content. Big surprise.
1 / 5 (8) Nov 22, 2013
Look it up and stop being lazy, it's a forum where I've got a thousand characters or less.

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