Astro Lunch

The chiral magnetic effect in the early universe

The presence of asymmetry between left- and right-handed fermions in
plasmas of relativistic particles can lead to exponential growth of a
helical magnetic field via a small-scale chiral dynamo instability known
as the chiral magnetic effect. This produces chiral magnetically driven
turbulence with a k^{-2} magnetic energy spectrum and inverse transfer
over a certain range of wavenumbers. The total chirality (magnetic
helicity plus normalized chiral chemical potential) is conserved in
this system. Therefore, as the helical magnetic field grows, most of
the total chirality gets transferred into magnetic helicity until the
chiral magnetic effect terminates. Quantitative results for height,
slope, and extent of the spectrum are obtained. In the early universe,
a magnetic field can be produced whose strength today would be at most
10^{-18} Gauss on a scale of 1 Mpc.