Internal energy, total viscous, and total ohmic heating as functions of viscosity ν at t = 12.5, before the onset of any null collapse, for all parameter choices. Isotropic (blue, solid) and switching viscosity (orange, dashed) are both shown. An upwards-facing triangle denotes the higher value of η = 10⁻³ and a downwards-facing triangle, η = 10⁻⁴. The anisotropic viscous heating can become significant for larger values of ν yet, when ν is smaller, the lack of viscous heating is compensated by enhanced ohmic heating.