@ProfRob's answer to Neutron star accurate visualization ends with:
...How their temperatures evolve after this is highly uncertain and none have been observed. The problem is that neutron stars have a very small heat capacity. They cool easily, but they can also be reheated easily by ohmic dissipation of their strong magnetic fields or accretion from the interstellar medium. This the surface temperature of most neutron stars is likely to be much lower than 106 K.
I think of neutron stars as fairly rigid objects with magnetic fields "frozen in" and co-rotating with the object.
Ohmic heating would happen if a current were induced due to a changing magnetic flux. One simple source for this would be a decaying field due to electromagnetic dipole radiation1, but I'm just grasping at straws here; there could be other more complicated mechanisms that are significant, see for example How do neutron stars maintain inhomogeneous surfaces and migrating "hot spots"? (e.g. SGR 1830-0645) So I'd like to ask:
Question: How does a neutron star "reheat" itself by ohmic dissipation of its magnetic field?