Magnetic fields emerging from below the surface of the sun influence the solar wind, a stream of particles that blows continuously from the sun’s atmosphere through the solar system. Researchers at NASA and its university partners are using high-fidelity computer simulations to learn how these magnetic fields emerge, heat the sun’s outer atmosphere and produce sunspots and flares. This visualization shows magnetic field loops in a portion of the sun, with colors representing magnetic field strength from weak (blue) to strong (red). The simulation was run on the Pleiades supercomputer at the NASA Advanced Supercomputing facility at NASA's Ames Research Center in Moffett Field, California. The knowledge gained through simulation results like this one help researchers better understand the sun, its variations, and its interactions with Earth and the solar system. Image Credit: Robert Stein, Michigan State University; Timothy Sandstrom, NASA/Ames
Many newly formed stars are surrounded by what are called protoplanetary disks, swirling masses of warm dust and gas that can constitute the core of a developing solar system.
Proof of the existence of such disks didn't come until 1994, when the Hubble telescope examined young stars in the Orion Nebula.
Protoplanetary disks may potentially become celestial bodies such as planets and asteroids but just how they make that transformation will remain a mystery to science until researchers can get a grasp on the disordered movement, or turbulence, that characterizes the constituent gases of the disks.
Turbulence is what some people regard as "the last great classical physics problem."
"By understanding the nature of the gases, we can learn something about how small particles interact with each other, coagulate to become larger particles and then ultimately form planets," says Jake Simon of the University of Colorado, principal investigator of a research project currently taking on two primary challenges in the quest to understand protoplanetary disk turbulence.
"In a particular region in these disks, the electrons are tied to magnetic fields, while the ions are not. This leads to something called the Hall effect and currently, our numerical algorithms cannot accurately capture the nature of this effect," he says.
Discovered by American physicist Edwin Hall in 1879, the Hall effect refers to a voltage-difference that occurs across an electrical conductor.
The voltage difference is crossways to an electrical current in the conductor and a magnetic field that is perpendicular to the current.
"If the ions and electrons don't collide with the neutrals frequently enough, ambipolar diffusion acts to damp out the turbulence," he says.
"The degree to which this happens has been explored with our high-resolution numerical simulations that we have run on the Kraken supercomputer. We believe we now have a much better understanding of how disks behave in their outer regions, far from the central star."
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