Theoretical analysis uncovers new mechanisms in plasma turbulence

December 1, 2017 by David L. Chandler
Magnetic reconnection is a complicated phenomenon that Nuno Loureiro, an associate professor of nuclear science and engineering and of physics at MIT, has been studying in detail for more than a decade. To explain the process, he gives a well-studied example: “If you watch a video of a solar flare” as it arches outward and then collapses back onto the sun’s surface, “that’s magnetic reconnection in action. It’s something that happens on the surface of the sun that leads to explosive releases of energy.” Loureiro’s understanding of this process of magnetic reconnection has provided the basis for the new analysis that can now explain some aspects of turbulence in plasmas. Credit: NASA

Plasmas, gas-like collections of ions and electrons, make up an estimated 99 percent of the visible matter in the universe, including the sun, the stars, and the gaseous medium that permeates the space in between. Most of these plasmas, including the solar wind that constantly flows out from the sun and sweeps through the solar system, exist in a turbulent state. How this turbulence works remains a mystery; it's one of the most dynamic research areas in plasma physics.

Now, two researchers have proposed a new model to explain these dynamic turbulent processes.

The findings, by Nuno Loureiro, an associate professor of nuclear science and engineering and of physics at MIT, and Stanislav Boldyrev, a professor of physics at the University of Wisconsin at Madison, are reported today in the Astrophysical Journal. The paper is the third in a series this year explaining key aspects of how these turbulent collections of charged particles behave.

"Naturally occurring plasmas in space and astrophysical environments are threaded by magnetic fields and exist in a turbulent state," Loureiro says. "That is, their structure is highly disordered at all scales: If you zoom in to look more and more closely at the wisps and eddies that make up these materials, you'll see similar signs of disordered structure at every size level." And while is a common and widely studied phenomenon that occurs in all kinds of fluids, the turbulence that happens in plasmas is more difficult to predict because of the added factors of electrical currents and magnetic fields.

"Magnetized is fascinatingly complex and remarkably challenging," he says.

Theoretical analysis uncovers new mechanisms in plasma turbulence
Simulation conducted by MIT student Daniel Groselj. Credit: Massachusetts Institute of Technology

Magnetic reconnection is a complicated phenomenon that Loureiro has been studying in detail for more than a decade. To explain the process, he gives a well-studied example: "If you watch a video of a solar flare" as it arches outward and then collapses back onto the sun's surface, "that's in action. It's something that happens on the surface of the sun that leads to explosive releases of energy." Loureiro's understanding of this process of magnetic reconnection has provided the basis for the new analysis that can now explain some aspects of turbulence in plasmas.

Loureiro and Boldyrev found that magnetic reconnection must play a crucial role in the dynamics of turbulence, an insight that they say fundamentally changes the understanding of the dynamics and properties of space and astrophysical plasmas and "is indeed a conceptual shift in how one thinks about turbulence," Loureiro says.

Existing hypotheses about the dynamics of plasma turbulence "can correctly predict some aspects of what is observed," he says, but they "lead to inconsistencies."

Loureiro worked with Boldyrev, a leading theorist on plasma turbulence, and the two realized "we can fix this by essentially merging the existing theoretical descriptions of turbulence and magnetic reconnection," Loureiro explains. As a result, "the picture of turbulence gets conceptually modified and leads to results that more closely match what has been observed by satellites that monitor the , and many numerical simulations."

Loureiro hastens to add that these results do not prove that the model is correct, but show that it is consistent with existing data. "Further research is definitely needed," Loureiro says. "The theory makes specific, testable predictions, but these are difficult to check with current simulations and observations."

He adds, "The theory is quite universal, which increases the possibilities for direct tests." For example, there is some hope that a new NASA mission, the Parker Solar Probe, which is planned for launch next year and will be observing the sun's corona (the hot ring of plasma around the sun that is only visible from Earth during a total eclipse), could provide the needed evidence. That probe, Loureiro says, will be going closer to the sun than any previous spacecraft, and it should provide the most accurate data on turbulence in the corona so far.

Collecting this information is well worth the effort, Loureiro says: "Turbulence plays a critical role in a variety of astrophysical phenomena," including the flows of matter in the core of planets and stars that generate magnetic fields via a dynamo effect, the transport of material in accretion disks around massive central objects such as black holes, the heating of stellar coronae and winds (the gases constantly blown away from the surfaces of stars), and the generation of structures in the interstellar medium that fills the vast spaces between the stars. "A solid understanding of how turbulence works in a plasma is key to solving these longstanding problems," he says.

"This important study represents a significant step forward toward a deeper physical understanding of magnetized plasma turbulence," says Dmitri Uzdensky, an associate professor of physics at the University of Colorado, who was not involved in this work. "By elucidating deep connections and interactions between two ubiquitous and fundamental plasma processes—magnetohydrodynamic turbulence and magnetic reconnection—this analysis changes our theoretical picture of how the energy of turbulent plasma motions cascades from large down to small scales."

He adds, "This work builds on a previous pioneering study published by these authors earlier this year and extends it into a broader realm of collisionless plasmas. This makes the resulting theory directly applicable to more realistic plasma environments found in nature. At the same time, this paper leads to new tantalizing questions about plasma turbulence and reconnection and thus opens new directions of research, hence stimulating future research efforts in space physics and plasma astrophysics."

Explore further: Table top plasma gets wind of solar turbulence

More information: Nuno F. Loureiro et al, Collisionless Reconnection in Magnetohydrodynamic and Kinetic Turbulence, The Astrophysical Journal (2017). DOI: 10.3847/1538-4357/aa9754 , dx.doi.org/10.3847/1538-4357/aa9754

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13 comments

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gculpex
5 / 5 (1) Dec 01, 2017
What are the scale limits to magnetic reconnection?
Chris_Reeve
1 / 5 (8) Dec 01, 2017
Re: "The theory makes specific, testable predictions"

But, notice that you've lowered the bar for proof by pretending there is no need to actually test it AGAINST any competing ideas.

"A widely-accepted foundation stone of scientific logic involves a process of elimination, requiring all available possibilities to be considered with incorrect ideas discarded when they fail to predict experimental results. Just as the police must consider all possible suspects during an investigation, so a scientist must, as a matter of professional responsibility and competence, consider all possible explanations when forming his conclusions. However, some scientists are able to ignore these duties, while the safeguards built into the scientific bureaucracy, supposedly to ensure quality, do not prevent such malpractice but rather enable it."

- John Hewitt, A Habit of Lies
Chris_Reeve
1 / 5 (8) Dec 01, 2017
"Alfvén's approach to science follows the prediction-testing method advocated by Popper and other philosophers of science, and is quite similar to the 'methodology of scientific research programmes' described by Imre Lakatos. By Popperian criteria his theories should have acquired credit by their successful predictions, and by Lakatosian standards his programme should be considered 'progressive.' Yet most of the scientific community refuses to follow it or to give Alfvén credit for his achievements although many of his basic concepts are now accepted."

- Stephen G. Brush
Chris_Reeve
1 / 5 (4) Dec 01, 2017
The observable distaste in the astrophysical and cosmological domains for creating cosmic plasma models which are fundamentally rooted in the existing set of laboratory plasma concepts would seem to simply be a manifestation of the momentum of prior belief:

We've got our former conception of the universe which completely predates any in situ measurements of space, and then there is the revised worldview which acknowledges that 99% of what we can see with our telescopes is matter in the plasma state.

It does not take a genius, a PhD or even a single mathematical calculation to understand that these two worldviews are going to clash over time. In the case of magnetic reconnection, each worldview leads to its own logical set of concepts and claims.

That academics have chosen to favor the older set of ideas conceived without any in situ measurements over the newer ones will eventually be recognized as a very risky and self-serving research strategy.
691Boat
4.4 / 5 (7) Dec 01, 2017
Re: "The theory makes specific, testable predictions"

But, notice that you've lowered the bar for proof by pretending there is no need to actually test it AGAINST any competing ideas.


So you would like every single press release, article or paper to explicitly describe every theory they compared against, could compare against or have thought about comparing against?

Give them a call and ask if this 14 paragraph article meticulously describes the entirety of their work and get back to us with the results, k? thanks!
Chris_Reeve
1.7 / 5 (6) Dec 01, 2017
Re: "So you would like every single press release, article or paper to explicitly describe every theory they compared against, could compare against or have thought about comparing against?"

I expect that when astrophysicists are interpreting the behaviors of cosmic plasmas that they take into consideration the observed behavior of laboratory plasmas and the full volume of laboratory research which has to date occurred in that domain.

Is this a controversial idea?
Ojorf
4.1 / 5 (9) Dec 02, 2017
I expect that when astrophysicists are interpreting the behaviors of cosmic plasmas that they take into consideration the observed behavior of laboratory plasmas and the full volume of laboratory research which has to date occurred in that domain.


Well, they DID, you idiot

...the picture of turbulence gets conceptually modified and leads to results that more closely match what has been observed by satellites that monitor the solar wind, and many numerical simulations.


and furthermore

The theory makes specific, testable predictions, but these are difficult to check with current simulations and observations.


You literally cannot get any better than that, because those predictions mentioned can now be examined, now that they know what specifically to look for.
Why don't you read the article instead of convulsively regurgitating the same BS everywhere.
Maggnus
3.7 / 5 (9) Dec 02, 2017
The idiotic blather of an Acolyte of the Amassing Electric Dolt. Of course, the article mentions the All Holy word "plasma". I'm surprised the canthink hasn't chimed in with the usual misquote from Alfven.

This is amazing research on an incredibly difficult phenomena. Magnetic reconnection seems to be a major key to understanding the behavior of plasma. Truly, interesting stuff.
Chris_Reeve
1.8 / 5 (5) Dec 02, 2017
Maggnus, modern science's dysfunctions are much bigger than just plasmas. The numerous critiques exhibit common threads which run through multiple domains of inquiry.

Your refusal to take inventory of the critiques of modern science is what creates your confidence.

Once a person locks into the larger patterns, it becomes clear that alternative interpretations are always readily at hand for most astronomical observations today. Any approach which is rooted in an effort to dismiss or ignore competing explanations will not historically fare well.

Your mistake is in focusing upon the short-term conclusions you prefer while completely ignoring the out-in-the-open long-term biases which led us to this point. History of science is a LONG GAME -- which will eventually make it clear that the many emotional tirades here on physorg railing against electricity in space are completely inconsequential.
Captain Stumpy
4.2 / 5 (5) Dec 02, 2017
@idiot illiterate pseudoscience eu cult acolyte
I expect that when astrophysicists are interpreting lie lie blah bullsh*t blah lie
1- because you're an illiterate idiot, perhaps you should actually look up Nuno F. Loureiro - not an astrophysicists, but a plasma physicist. very specifically Nuclear Science and Engineering
https://scholar.g...hl=en-EN

2- you're making claims without being able to read the study, and that makes you not only a complete idiot, but also basing your comments on faith
IOW - religion

your entire argument is because you don't comprehend the science but you're willing to accept the dogma of your eu cult

how do you know your eu cult is making valid claims if you don't comprehend the basics of science?

especially considering that your eu cult has been/is still repeatedly debunked with facts and validated studies?
Caliban
4.2 / 5 (5) Dec 03, 2017
The idiotic blather of an Acolyte of the Amassing Electric Dolt. Of course, the article mentions the All Holy word "plasma". I'm surprised the canthink hasn't chimed in with the usual misquote from Alfven.

This is amazing research on an incredibly difficult phenomena. Magnetic reconnection seems to be a major key to understanding the behavior of plasma. Truly, interesting stuff.


Maggnus--

Please allow me to add one further qualification to the above:

These guys are speaking specifically and particularly about SOLAR phenomenon, as @gculpex alludes, and not to garden-variety, free-floating interstellar ionized gases, which are a different thing --the different thing that the EUpeople try to equate with these stellar-generated plasmas.

Therein lies the whole stupidity of the EUDelusion.
rrwillsj
3.7 / 5 (3) Dec 03, 2017
Since youse guys are arguing over "natural emissions"... I had a thought.

Muhahaha! Oops, how'd that get in there?

Anywho, as the gases of stars consist of the same gases as produced by biological functions. Thereinafore, the speciality of Proctology should be considered one of the Sciences for Cosmology.

As it is scientific to claim that "What goes up, must come down." Therealullaby "What goes in, must come out."

Science is fun!
Whydening Gyre
5 / 5 (1) Dec 03, 2017
Since youse guys are arguing over "natural emissions"... I had a thought.

Muhahaha! Oops, how'd that get in there?

Anywho, as the gases of stars consist of the same gases as produced by biological functions. Thereinafore, the speciality of Proctology should be considered one of the Sciences for Cosmology.

As it is scientific to claim that "What goes up, must come down." Therealullaby "What goes in, must come out."

Science is fun!

Isn't that a Dr. Evil quote from Austin Powers?

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