Laser hints at how Universe got its magnetism

26 January 2012

An international research team lead by Dr G Gregori with fellow Oxford physicists Prof A R Bell, Dr C Murphy and Dr B Reville (from Atomic and Laser Physics) have used a laser to create magnetic fields similar to those thought to be involved in the formation of the first galaxies; findings that could help to solve the riddle of how the Universe got its magnetism.

Magnetic fields exist throughout galactic and intergalactic space, what is puzzling is how they were originally created and how they became so strong. The experimental team used a high-power laser to explode a rod of carbon, similar to pencil lead, in helium gas. The explosion was designed to mimic the cauldron of plasma – an ionized gas containing free electrons and positive ions – out of which the first galaxies formed.

The team found that within a microsecond of the explosion strong electron currents and magnetic fields formed around a shock wave. Dr F Miniati (ETH-Zurich) then took these results and scaled them through 22 orders-of-magnitude to find that the measurements matched the ‘magnetic seeds’ predicted by theoretical studies of galaxy formation.

A report of the research is published in this week’s Nature (26 January 2012), and it has been featured on Discovery Channel and MSNBC.

The results closely match theories which predict that tiny magnetic fields – magnetic seeds – precede the formation of galaxies. These fields can be amplified by turbulent motions and can strongly affect the evolution of the galactic medium from its early stages.

Dr Gregori said:

In the future, we plan to use the largest lasers in the world, such as the National Ignition Facility at the Lawrence Livermore National Laboratory in California (USA), to study the evolution of cosmic plasma.

Image: The left side is a picture of a laser-produced shock wave. Brighter colors correspond to regions of higher density or temperature. The right side is a simulation of a collapsing shock wave arising during structure formation.
Credits: A Ravasio (LULI), A Pelka (LULI), J Meinecke (Oxford) and C Murphy (Oxford) for the shock measurements. The numerical simulation was performed by F Miniati (ETH).

The experiments were conducted at the Laboratoire pour l’Utilisation de Lasers Intenses laser facility in France. The team included scientists from; Oxford University, Rutherford Appleton Laboratory, Laboratoire pour l’Utilisation de Lasers Intenses, University of Strathclyde, University of California Los Angeles, University of Michigan, University of York, Osaka University, Lawrence Livermore National Laboratory, ETH-Zurich.