Energy release rate inside the mantle of a planet orbiting a WD with a dipolar field of 13 MG. A magnetic field variation arises due to an inclination of the stellar magnetic dipole with respect to the stellar rotation axis. From left to right, the pictures illustrate the influence of the orbital distance (assuming a stellar inclination of 20° and a stellar rotation period of 2 h), stellar inclination (assuming an orbital distance of 0.01 au and a stellar rotation period of 2 h), and the stellar rotation periods (assuming a stellar inclination of 20° and an orbital distance of 0.01 au). The dashed horizontal line shows an average energy release inside Io of ~6.8 × 10⁻⁶ erg g⁻¹ s⁻¹ (Veeder et al. 2012), and the dash-dotted line shows the level of present-day Earth radiogenic heating of ~5 × 10⁻⁸ erg g⁻¹ s⁻¹ (Breuer 2009).