Laser experiments verify ‘turbulent dynamo’ theory of how cosmic magnetic fields are created
February 9, 2018
A measurement technique developed at the Massachusetts Institute of Technology (MIT) has been instrumental in an international collaboration led by the University of Chicago and the University of Oxford to demonstrate for the first time in the laboratory the existence of turbulent dynamo, an astrophysical process that has long been theorized to explain the present-day magnetization of the Universe. They reported their findings in an article published this week in Nature Communications.
The paper describes laser-driven experiments at the Omega laser facility of the Laboratory for Laser Energetics (LLE) at the University of Rochester that achieve conditions in which the turbulent dynamo mechanism can operate, using laser beams whose power is equivalent to 100 trillion laser pointers. The scientists were able to unequivocally measure the magnetic field amplification caused by this mechanism, demonstrating its existence.
Essential to the experiments were measurements of the temperature and turbulent velocities of the hot plasma using a probe laser, and measurements of the magnetic fields using the probe laser and protons fired through the magnetized plasma, a technique developed by scientists at the MIT Plasma Science and Fusion Center
Advanced monoenergetic proton radiography, developed by MIT to probe the evolution and structure of fields and plasma flows in high-energy-density-plasma experiments, was used for measuring the spatial structure and temporal evolution of spontaneous magnetic fields which grew, due to plasma turbulence, from an initial value ~ 50 kG to ~ 500 kG. These field measurements, led by MIT senior research scientist Dr. Chikang Li, provided critical experimental evidence of the 10-fold turbulent amplification of the fields. Though the mechanism of field amplification is widely believed to be pervasive in generating strong cosmic magnetic fields, these experimental results are the first laboratory demonstration that many-fold field amplification can result from such plasma turbulence.
Topics: Chikang Li