Lasers Provide Insights Into Formation of Galactic Magnetic Fields
The use of high-power lasers to study the mysterious origins of huge magnetic fields that span the galaxies was described by Gianluca Gregori of the University of Oxford at an Aug. 9 High Energy Density Science Seminar. Gregori said recent experiments at the Laboratory for the Use of Intense Lasers (LULI) near Paris have confirmed that the magnetic fields could have been “seeded” by misaligned temperature and pressure gradients during galaxy formation.
To test the theory, the researchers trained intense, short-duration laser pulses on a carbon rod held inside a helium-filled chamber to create shock waves. As the shock wave moved through the plasma in the chamber, a magnetic field was generated. The results are consistent with the simulations.
While the initial seed fields are miniscule, the simulations show that they could be amplified to galactic size over about 700 million years through a "dynamo" mechanism, in which the rotation and turbulence of the galaxy's interstellar medium – the gas and dust between stars – reinforces the original magnetic field.
"We need further studies to explain the large-scale magnetization of the universe," Gregori said. "Only at NIF can we achieve the (magnetic energy) regimes" required to test the theory, he said.
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