Left panels: evolution of the magnetic field strength and the magnetic diffusivity as a function of the WD radius for the 0.9 M _⊙ model. We numerically solved the induction equation for the radial component (Equation (19)) and assumed a dipole geometry to compute the strength of the field using Equation (20). Right panels: two-dimensional visualization of the evolution of the magnetic field lines with equal magnetic flux for the magnetic field obtained for the 0.9 M _⊙ model (as in the left panels) using Equation (20), the definition of the magnetic vector potential, and assuming an axisymmetric dipole field.