Inflated Hot Jupiters have Jovian-like magnetic fields: predictions from long-term evolutionary models with atmospherically-induced Ohmic dissipation

The inflated radii observed in hundreds of Hot Jupiters (HJs) represents a long-standing open issue, with Ohmic dissipation derived from atmospheric magnetic induction being one of the most promising mechanisms for a quantitative explanation. Using the evolutionary code MESA, we simulate the evolution of irradiated giant planets, spanning the observed range of masses and equilibrium temperatures. We incorporate Ohmic dissipation, accounting for atmospheric induction and realistic profiles of electrical conductivity, and, for the first time, we study how it couples with the dynamo-generated internal field, which is assumed to scale as the internal heat flux as in fully convective stars and Solar planets. We find that, contrarily to the widespread expectations of large magnetic fields in HJs, Ohmic dissipation can partially suppress convection and keep the dynamo-generated magnetic fields at Jovian-like values maximum (few gauss). This has consequence in terms of measurability of atmospheric wind velocities, which depend on the magnetic drag. This talk is based on Viganò et al. 2025, A&A.