Astrophysicists have, for the first time, proven one of the popular theories of the turbulent dynamo related to cosmic magnetic field generation through a lab based experiment thereby settling debate on magnetism of planets and stars.
Published in Nature Communications is a study by researchers wherein lab based experiment and its results show how turbulent motions can amplify a weak magnetic field to the strengths of those observed in our sun, distant stars, and galaxies. Researchers used the FLASH physics simulation code to design an experiment conducted at the OMEGA Laser Facility in Rochester, NY to recreate turbulent dynamo conditions.
A team of researchers led by University of Chicago scientists created a hot turbulent plasma the size of a penny that lasted for a few billionths of a second, but long enough to enable scientists to record data on turbulent motions and its amplifying effect on weak magnetic field to the strengths of those observed in our sun, distant stars, and galaxies.
The research confirms decades-old theory and numerical simulations about how turbulent plasma could dramatically boost a weak magnetic field up to the magnitude observed by astronomers in stars and galaxies.
A mechanical dynamo produces an electric current by rotating coils through a magnetic field. In astrophysics, dynamo theory proposes the reverse: the motion of electrically-conducting fluid creates and maintains a magnetic field. In the early 20th century, physicist Joseph Larmor proposed that such a mechanism could explain the magnetism of the Earth and Sun, inspiring decades of scientific debate and inquiry.
While numerical simulations demonstrated that turbulent plasma can generate magnetic fields at the scale of those observed in stars, planets, and galaxies, creating a turbulent dynamo in the laboratory was far more difficult. Confirming the theory requires producing plasma at extremely high temperature and volatility to produce the sufficient turbulence to fold, stretch and amplify the magnetic field.
Researchers created those conditions by running hundreds of two- and three-dimensional simulations with FLASH on the Mira supercomputer at Argonne National Laboratory. The final setup involved blasting two penny-sized pieces of foil with powerful lasers, propelling two jets of plasma through grids and into collision with each other, creating turbulent fluid motion.
The team also used FLASH simulations to develop two independent methods for measuring the magnetic field produced by the plasma: proton radiography, the subject of a recent paper from the FLASH group, and polarized light, based on how astronomers measure the magnetic fields of distant objects. Both measurements tracked the growth in mere nanoseconds of the magnetic field from its weak initial state to over 100 kiloGauss — stronger than a high-resolution MRI scanner and a million times stronger than the magnetic field of the Earth.