Helicity, Vorticity Beltrami Flows and Magnetohydrodynamics

Substituting MHD analogs of Magnetic helicity and superhelicity with Beltrami flows for the hydrodynamic equivalents. Potential vorticity considerations based on Ertel's Theorem [with B = 0, see eq. (4) in document] play a central role in modern theoretical research in dynamical
meteorology and oceanography. Dynamical Potential Vorticity described by University of Michigan