The Magnetic Gauss’ Law node is used to impose the condition

on the magnetic flux density by introducing an auxiliary dependent variable ψ with the corresponding equation.

The variable ψ is used to impose a condition on the derivatives of the magnetic flux density, so its absolute value does not have particular significance; only its gradient enters the equations (the variable ψ acts more or less like a potential). The absolute value of the variable can be set by entering the Enter a value or expression for the Divergence condition variable scaling Ψ 0 (SI unit: A). The default is 1 A, which is appropriate in most cases.

To display this section, click the Show More Options button () and select Advanced Physics Options.

This section allows a more fine control on the boundary conditions for ψ applied by the Magnetic Gauss’ Law feature. The domain equation for ψ only imposes a condition on the gradient, so it is important to constrain the absolute value of ψ to ensure a nonsingular model. Select the Constrain variable in at least one point to ensure that there is always a constraint set on the value of the divergence condition variable ψ. The feature also sets up automatically the appropriate boundary conditions for ψ. Use the Method combo box to select the approach used to enforce the boundary condition: Constrain value (the default) or Constrain tangential gradient.