Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

PPPL physicists find clue to formation of magnetic fields around stars and galaxies

10.11.2015

An enduring astronomical mystery is how stars and galaxies acquire their magnetic fields. Physicists Jonathan Squire and Amitava Bhattacharjee at the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL) have found a clue to the answer in the collective behavior of small magnetic disturbances. In a paper published in October in Physical Review Letters, the scientists report that small magnetic perturbations can combine to form large-scale magnetic fields just like those found throughout the universe. This research was funded by the DOE Office of Science.

Squire and Bhattacharjee analyzed the behavior of dynamos, which occur when an electrically charged fluid like plasma swirls in a way that creates and then amplifies a magnetic field. Scientists have known that plasma turbulence can create lots of small magnetic fields, but the mechanism by which those fields could produce a single large field is elusive. "We can observe magnetic fields all over the universe," said Squire. "But we currently lack a sound theoretical explanation for how they are generated."


This is an image of coronal loops on the sun that are linked to magnetic fields.

Credit: NASA/Solar Dynamics Observatory

The puzzle consists of the seeming unlikelihood of small disturbances coming together to form something large and organized. Throughout nature, order tends to dissolve into chaos, not the other way around. For instance, if you add a glob of milk to coffee, the glob will dissolve into a collection of tendrils and continue to dissipate until the milk has mixed with all of the coffee. Though not impossible, it's highly unlikely that the dissipated milk would spontaneously gather and reform the original glob.

This kind of natural organization occurs occasionally in the natural world, however. When a tornado forms, the myriad disturbances in the atmosphere during a severe storm coalesce into one giant vortex. But the tornado eventually collapses and the order disappears.

... more about:
»Galaxies »persist »phenomena »physics

Like tornados, the large-scale magnetic fields throughout the universe seem to be produced by lots of small disturbances. But unlike tornadoes, these magnetic fields persist. "Something is holding up the universe's magnetic fields for billions of years," said Amitava Bhattacharjee, head of PPPL's Theory Department and co-author of the paper. "But how exactly does the universe get these persistent magnetic properties?"

In the paper, Squire and Bhattacharjee show that under certain conditions small magnetic fields -- instead of small velocity fields, which have been studied more often -- can combine to form one large field. After running computer simulations on a PPPL computer named "Dawson," the scientists found that small disturbances can combine to form one large disturbance when there is a lot of velocity shear -- when two areas of a fluid are moving at different speeds. "We used a variety of computational and analytic methods to approach the problem from a few different angles," said Squire.

The team first used so-called statistical simulations, which create a kind of average of the behavior of the entire system. "Statistical simulations capture the properties of hundreds of simulations without actually running them all," said Bhattacharjee. The scientists also used numerical simulations that begin with initial conditions that are allowed to progress in lengthier runs.

"The results indicate that small-scale magnetic fluctuations can create large-scale magnetic fields that persist," Bhattacharjee said. "But in order to be conclusive about persistence for long times, we must run simulations for very low dissipation," a measure of energy loss. "It is impossible to run simulations for dissipation as low as those of real astrophysical plasmas, but our analytical and computational results, in the range in which they are done, strongly suggest that such dynamo action is possible."

These findings might lead to greater understanding of the behavior of many kinds of astronomical phenomena, including the disks of material that form around black holes and the 11-year solar cycle of our own sun. Computer programs cannot yet simulate these vast astronomical phenomena, so learning how to create simplified models that capture the workings of these large turbulent systems would be helpful.

###

PPPL, on Princeton University's Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas -- ultra-hot, charged gases -- and to developing practical solutions for the creation of fusion energy. Results of PPPL research have ranged from a portable nuclear materials detector for anti-terrorist use to universally employed computer codes for analyzing and predicting the outcome of fusion experiments. The Laboratory is managed by the University for the U.S. Department of Energy's Office of Science, which is the largest single supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

Media Contact

Raphael Rosen
rrosen@pppl.gov

 @PPPLab

http://www.pppl.gov 

Raphael Rosen | EurekAlert!

Further reports about: Galaxies persist phenomena physics

More articles from Physics and Astronomy:

nachricht A better way to weigh millions of solitary stars
15.12.2017 | Vanderbilt University

nachricht A chip for environmental and health monitoring
15.12.2017 | Friedrich-Alexander-Universität Erlangen-Nürnberg

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: First-of-its-kind chemical oscillator offers new level of molecular control

DNA molecules that follow specific instructions could offer more precise molecular control of synthetic chemical systems, a discovery that opens the door for engineers to create molecular machines with new and complex behaviors.

Researchers have created chemical amplifiers and a chemical oscillator using a systematic method that has the potential to embed sophisticated circuit...

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Engineers program tiny robots to move, think like insects

15.12.2017 | Power and Electrical Engineering

One in 5 materials chemistry papers may be wrong, study suggests

15.12.2017 | Materials Sciences

New antbird species discovered in Peru by LSU ornithologists

15.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>