The Chiral Anomaly, Dirac and Weyl Semimetals, and Force-Free Magnetic   Fields
  The chiral anomaly is a purely quantum mechanical phenomenon that has a long history dating back to the late 1960s. Surprisingly, it has recently made a macroscopic appearance in condensed matter physics. A brief introduction to the relevant features of this anomaly is given and it is shown that its appearance in condensed matter systems must involve force-free magnetic fields, which may help explain the long current relaxation times in Dirac and Weyl semimetals. 
Gerald E. Marsh
physics.gen-ph