Scientists have demonstrated for the very first time how a laser can be used to stimulate the formation of magnetic fields, similar to those thought to be involved in the formation of the very first galaxies. The findings published in Nature (26 January 2012) could help solve the riddle of how the Universe originally got its magnetism.
Magnetic fields exist throughout galactic and intergalactic space and in the stars and planets. The magnetic fields in our solar system are important, since they shield us from the harmful effects of cosmic rays allowing life to thrive. What is puzzling is how they were originally created. A way of creating magnetic fields without a magnet has long been theorised, but never before has the process been demonstrated.
A team, led by Oxford University physicists, have 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. It was designed to prove a theory, known as the ‘Biermann battery effect’ that demonstrated how magnetic fields could form where none had existed before.
The team found that within a microsecond of the explosion strong electron currents and magnetic fields formed around a shock wave. Scientists including Bob Bingham and Alex Robinson at the Central Laser Facility at STFC’s Rutherford Appleton laboratory took these results and compared them to existing planetary data. Using computational resources from STFC’s e-science department, they scaled them through 22 orders-of-magnitude. They found that their measurements closely matched 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.
Professor Bingham said: “The advantage of using lasers to simulate the early processes in the formation of magnetic fields is that you can create, with a burst of laser light just a billionth of a second long, an effect that in space would take years to develop on an incomprehensible scale”.
Dr Gianluca Gregori from Oxford University, who led the work said: “Our experiment recreates what was happening in the early Universe and shows how galactic magnetic fields might have first appeared. It opens up the exciting prospect that we will be able to explore the physics of the cosmos, stretching back billions of years, in a laser laboratory here on Earth”.
The experiments were conducted at the Laboratoire pour l’Utilisation de Lasers Intenses laser facility in France.
For further details see the Oxford University press release (link opens in a new window).