Estimations for strong and weak hot Jupiter magnetism: A Python package with interpolators and scaling laws

Abstract

Hot Jupiters (HJs) are commonly thought to host the strongest dynamo-generated magnetic fields among exoplanets, exceeding Jupiter's by up to an order of magnitude, which can potentially induce observable star-planet interaction (SPI) and planetary radio emission. However, while several indirect, model-dependent estimates of HJ magnetic fields have been reported from SPIs and recent transmission spectroscopy diagnostics, no unambiguous direct (radio) detection has yet been achieved. We aim to provide a range of magnetic field estimates for HJs, considering the mechanisms responsible for inflation and the convective flux entering the magnetic field scaling law. Given that their dynamos operate in the fast-rotating regime (Rossby number <~ 0.1), we combine one-dimensional evolutionary interior models with magnetic field scaling laws under two limiting heating scenarios: deep and shallow energy depositions. The deep-heating scenario maximizes convective heat flux in the dynamo and predicts strong magnetic fields of up to ~100 G, whereas shallow heating, which is arguably more realistic for most proposed physical mechanisms, weakens convection and yields much weaker fields of O(1) G. The strong field scenario is compatible with SPI indirect detections, and the weak field scenario is in agreement with recent atmospheric constraints. We derive scaling law relations based on observables (planetary mass, radius, and/or incident stellar flux): Bstrong = 19 M_P^0.6 R_P^1.7 G; Bweak = 0.8 M_P^1.5 R_P^-1.2 G. These predictions provide a framework for interpreting future atmospheric wind measurements, SPI signatures, and radio observations, which may ultimately discriminate between competing interior-heating scenarios.