Nav: Home

Table top plasma gets wind of solar turbulence

June 30, 2017

Turbulent magnetic field dynamics that explain astrophysical phenomena like the evolution of stars could thus far be obtained only through observations via telescopes and satellites. Now a team of scientists from India and Portugal have recreated such magnetic turbulence on a table top in the lab, using a high intensity ultrashort laser pulse to excite a hot, dense plasma on a solid surface and followed the extremely fast evolution of the giant magnetic field generated by the plasma dynamics. This ground-breaking study will be published in Nature Communications on 30 June.

Turbulence is everywhere- from tea cups to tokomaks and from water jets to weather systems, it is something we all see and experience. Yet, even after centuries of serious scientific study, fluid turbulence is still not properly understood and remains "Interesting. Vexing. Longstanding. Unsolved."[1]. While it is difficult to define turbulence simply, it has many recognizable features, the most common being the fluctuations in parameters like velocity and pressure, indicating randomization of the flow [2]. By the way, turbulence is not all bad and destructive as you might feel when tossed around on a flight during bad weather. One good feature is that it enables much faster mixing than possible only with normal, slow diffusion. For instance, the sugar you added in your cup of tea this morning would have taken hours and days to disperse but for your stirring which caused your tea to become turbulent. As you have surely noticed, you stirred the tea in a large circle, but the swirling spread to smaller and smaller lengths and eventually, the mixing occurred at the molecular level. The end result? Even the smallest drop of tea is as sweet as a large gulp! Turbulence also helps in mixing fuel and oxygen for efficient combustion in engines.

Much of our universe is of course not an ordinary fluid but consists of highly ionized gas known as plasma and this plasma can often be extremely hot and swirling at unimaginable speeds. Turbulence in a plasma is much more complex than that in neutral hydrodynamic fluids. In a charged plasma environment, the negatively charged, light electrons and positive heavy ions respond at vastly different length and time scales. The motion of these charged species is governed by electromagnetic forces and the current flow through the charge particle dynamics leads to magnetic field generation. Therefore the randomness of magnetic fields often mimics the fluid turbulence in plasmas.

The team of scientists leading this new study, at the Tata Institute of Fundamental Research, Mumbai, Institute of Plasma Research, Gandhinagar (both in India) and at the Instituto Superior Tecnico, Universidade de Lisboa, Portugal find that the turbulence in the magnetic field is initially driven by the electrons (at a trillionth of a second) and the ions step in and take over at longer times. This is the first time such a 'relay race' involving two different species has been glimpsed. Further, these lab observations have an uncanny resemblance to the satellite data on the magnetic field spectra measured for turbulent astrophysical plasmas in the solar wind, solar photosphere and earth's magnetosheath. Although in the laser experiment the electrons in the plasma get energised initially, the ion dominant response that kicks in at later times shows spectral features similar to those in the astro systems. These experiments thus establish clear connections between the two scenarios, even though the driver of turbulence in the lab plasma is very different from that in the astrophysical system.

Now that we have got wind of solar turbulence on a table top, can we use lab experiments to turn the tables on the intractable problem of turbulence? Well, that may still be a long way off but it is a tantalising prospect that reliable measurements in the lab might make us better and better at peeking into turbulent stellar scenarios.

And that should set off stars in our eyes!

[1] L.P. Kadanoff, Physics Today, Vol. 48, no.9, p11 (1995)
[2] K.R. Sreenivasan, McGraw-Hill Encyclopaedia of Science and Technology, 10th Edn., Vol. 18, p725.
[3] G. Chatterjee et al., Nature Communications, 10.1038/NCOMMS15970 (2017)

Tata Institute of Fundamental Research

Related Evolution Articles:

Genome evolution goes digital
Dr. Alan Herbert from InsideOutBio describes ground-breaking research in a paper published online by Royal Society Open Science.
Paleontology: Experiments in evolution
A new find from Patagonia sheds light on the evolution of large predatory dinosaurs.
A window into evolution
The C4 cycle supercharges photosynthesis and evolved independently more than 62 times.
Is evolution predictable?
An international team of scientists working with Heliconius butterflies at the Smithsonian Tropical Research Institute (STRI) in Panama was faced with a mystery: how do pairs of unrelated butterflies from Peru to Costa Rica evolve nearly the same wing-color patterns over and over again?
Predicting evolution
A new method of 're-barcoding' DNA allows scientists to track rapid evolution in yeast.
Insect evolution: Insect evolution
Scientists at Ludwig-Maximilians-Universitaet (LMU) in Munich have shown that the incidence of midge and fly larvae in amber is far higher than previously thought.
Evolution of aesthetic dentistry
One of the main goals of dental treatment is to mimic teeth and design smiles in the most natural and aesthetic manner, based on the individual and specific needs of the patient.
An evolution in the understanding of evolution
In an open-source research paper, a UVA Engineering professor and her former Ph.D. student share a new, more accurate method for modeling evolutionary change.
Chemical evolution -- One-pot wonder
Before life, there was RNA: Scientists at Ludwig-Maximilians-Universitaet (LMU) in Munich show how the four different letters of this genetic alphabet could be created from simple precursor molecules on early Earth -- under the same environmental conditions.
Catching evolution in the act
Researchers have produced some of the first evidence that shows that artificial selection and natural selection act on the same genes, a hypothesis predicted by Charles Darwin in 1859.
More Evolution News and Evolution Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Processing The Pandemic
Between the pandemic and America's reckoning with racism and police brutality, many of us are anxious, angry, and depressed. This hour, TED Fellow and writer Laurel Braitman helps us process it all.
Now Playing: Science for the People

#568 Poker Face Psychology
Anyone who's seen pop culture depictions of poker might think statistics and math is the only way to get ahead. But no, there's psychology too. Author Maria Konnikova took her Ph.D. in psychology to the poker table, and turned out to be good. So good, she went pro in poker, and learned all about her own biases on the way. We're talking about her new book "The Biggest Bluff: How I Learned to Pay Attention, Master Myself, and Win".
Now Playing: Radiolab

Invisible Allies
As scientists have been scrambling to find new and better ways to treat covid-19, they've come across some unexpected allies. Invisible and primordial, these protectors have been with us all along. And they just might help us to better weather this viral storm. To kick things off, we travel through time from a homeless shelter to a military hospital, pondering the pandemic-fighting power of the sun. And then, we dive deep into the periodic table to look at how a simple element might actually be a microbe's biggest foe. This episode was reported by Simon Adler and Molly Webster, and produced by Annie McEwen and Pat Walters. Support Radiolab today at