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Simulations provide new evidence for powerful plasma jets

This visualization of a general relativistic collisionless plasma simulation shows the density of positrons near the event horizon of a rotating black hole. Plasma instabilities produce island-like structures in the area of ​​high electric current. Picture credits: Kyle Parfrey et al. / Berkeley Lab

Black holes are known for their voracious appetite, which acts so heavily on matter that not even light can escape after ingestion.

What is less understood, however, is how black holes consume energy encased in their rotation and fling plasmas into near-light-speed opposite sides into one of the universe's most powerful displays into space. These jets can span millions of light years.

New simulations, led by researchers from the US Department of Energy's (Berkeley Lab) Lawrence Berkeley National Laboratory (Berkeley Lab) and UC Berkeley, have combined decades of theories to provide new insights into the driving mechanisms in the plasma jets they steal the strong gravitational fields of black holes and drive them away from their gaping mouths.

The simulations could provide a useful comparison for high-resolution observations of the Event Horizon Telescope, an array that allows this The first direct images of the regions where the plasma jets are formed are designed that way.

The telescope provides new views of the black hole at the center of our own Milky Way, as well as detailed views of other supermassive black holes

"How can the energy be extracted in the rotation of a black hole to create rays?" said Kyle Parfrey, who led the work on the simulations when he was an Einstein Postdoctoral Fellow affiliated with the Berkeley Lab's Nuclear Science Division. "This has been a question for a long time."

Parfrey, a senior associate at NASA's Goddard Space Flight Center in Maryland, is the lead author of a study published in Physical Review Letters on January 23, which details simulation research.

The simulations unite for the first time a theory that explains how electric currents around a black hole form magnetic fields into jets, with a separate theory explaining how particles cross through a black hole. A point of no return ̵

1; the event horizon – can give you one remote observers appear to carry negative energy and reduce the rotational energy of the black hole.

It's like eating a snack that causes you to lose calories instead of gaining them. The black hole actually loses mass as a result of these "negative energy" particles.

This simulation shows a rotating black hole (bottom) and a collisionless plasma jet (top). The simulation shows the densities of electrons and positrons as well as magnetic field lines. The "ergosurface" of the black hole, in which all particles must rotate in the same direction as the hole, is shown in green. Credit: Kyle Parfrey et al. ./ Berkeley Lab

Computer simulations have difficulty in modeling the complex physics involved in plasma jet initiation, which must explain the generation of electron and positrons. the acceleration mechanism for particles and the emission of light in the nozzles.

The Berkeley Lab has contributed much to plasma simulations in its long history. Plasma is a gas-like mixture of charged particles, which is the most common state of the universe.

Parfrey said he realized that more complex simulations describing the jets require a combination of expertise in plasma physics and the general theory of relativity.

"I thought it would be a good time to bring these two things together," he said.

In a supercomputing center at the NASA's Ames Research Center in Mountain View, California, the simulations include new aspects of numerical techniques, which are the first model of a collisionless plasma in which collisions between charged particles do not play a major role in the present a strong gravitational field connected to a black hole.

The simulations typically produce the Blandford-Znajek mechanism, which describes the twisted magnetic fields that form jets, and a separate Penrose process that describes what happens when negative energy particles are swallowed by the black hole ,

The Penrose Process: "Although it does not necessarily do so much to extract the rotational energy of the black hole," Parfrey says, "this may be directly related to the electrical currents that the jets turn & # 39; Magnetic Fields. "

Although Parfrey was more detailed than some earlier models, he found that his team's simulations were still consistent with observations and, to some extent, idealized to simplify the calculations needed to perform the simulations.

The team intends to better model the process by which electron-positron pairs are generated in the jets to more realistically investigate the plasma distribution of the jets and their radiation emission for comparison with observations. They also plan to extend the scope of the simulations to the event horizon of the black hole, the so-called accretion flux.

"We hope to provide a more consistent picture of the entire problem," he said.

Explore Further:
Confused magnetic fields drive cosmic particle accelerators

Further information:
Kyle Parfrey et al., First Principal Plasma Simulations on Black Hole Launch, Physical Review Letters (2019). DOI: 10.1103 / PhysRevLett.122.035101

Magazine Reference:
Physical overview letters

Provided by:
Lawrence Berkeley National Laboratory

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