Black hole dynamo may be cosmos’ ultimate electricity generator

Researchers at the U.S. Department of Energy’s Los Alamos National Laboratory believe that magnetic field lines extending a few million light years from galaxies into space may be the result of incredibly efficient energy-producing dynamos within black holes that are somewhat analogous to an electric motor. Los Alamos researchers Philipp Kronberg, Quentin Dufton, Stirling Colgate and Hui Li today discussed this finding at the American Astronomical Society meeting in Albuquerque, N.M.

By interpreting radio waves emanating from the gigantic magnetic fields, the researchers were able to create pictures of the fields as they extended from an object believed to be a black hole at the center of a galaxy out into regions of intergalactic space. Because the class of galaxies they studied are isolated from other intergalactic objects and gas – which could warp, distort or compress the fields – the fields extend a distance of up to ten million light years, or about six times 1019 miles.

The energy in these huge magnetic fields is comparable to that released into space as light, X-rays and gamma rays. In other words, the black hole energy is being efficiently converted into magnetic fields. The mechanism is not yet fully understood, but Kronberg and his colleagues believe a black hole accretion disk could be acting similarly to an electric motor.

Colgate and Los Alamos colleagues Vladimir Pariev and John Finn have developed a model to perhaps explain what is happening. They believe that the naturally magnetized accretion disk rotating around a black hole is punctured by clouds of stars in the vicinity of the black hole, like bullet holes in a flywheel. This, in turn, leads nonlinearly to a system similar to an electric generator that gives rise to a rotating, but invisible magnetic helix.

In this way, huge amounts of energy are carried out and away from the center of a galaxy as a set of twisted magnetic field lines that eventually appear via radio waves from luminous cloud formations on opposite sides of the galaxy.

The Los Alamos researchers are calculating methods by which enormous amounts of expelled magnetic energy are converted into heat – manifested in the form of a relativistic gas of cosmic rays that create radio energy that can be detected by radio telescopes such as the Very Large Array. Although the exact mechanism is still a mystery, the Los Alamos researchers believe that a sudden reconnection or fusing of the magnetic field lines creates and accelerates the cosmic rays.

The researchers still don’t understand why this fast magnetic field reconnection occurs. But understanding the mechanism could have important applications here on Earth such as creating a system of magnetic confinement for a fusion energy reactor.

The Los Alamos research is supported by the Laboratory Directed Research and Development Program and the Institute of Geophysics and Planetary Physics. The Natural Sciences and Engineering Research Council of Canada also provided support.

Los Alamos recently joined Southwest Universities consortium, which is hoping to build a very low frequency radio telescope called “LOFAR” in New Mexico or West Texas. The new telescope will be an excellent instrument for detecting hidden magnetic energy of the type the Los Alamos research team is interested in studying.

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Los Alamos National Laboratory is operated by the University of California for the National Nuclear Security Administration (NNSA) of the U.S. Department of Energy and works in partnership with NNSA’s Sandia and Lawrence Livermore national laboratories to support NNSA in its mission.

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