Size and strength of self-excited dynamos in Jupiter-like extrasolar planets

TL;DR

This study models the magnetic field generation in Jupiter-like exoplanets using new conductivity data, revealing that most such planets likely have detectable magnetic fields and radio emissions, with implications for observational astronomy.

Contribution

It introduces a revised conductivity profile based on recent experiments and applies it to a broad range of exoplanets, providing new estimates of their magnetic field strengths and radio emission frequencies.

Findings

Most exoplanets have dipole magnetic fields of 0.1-10 Gauss.

Conducting cores are larger than previously thought, consistent with Juno data.

Radio emissions are predicted to peak below 30 MHz, lower than earlier estimates.

Abstract

The magnetization of solar and extrasolar gas giants is critically dependent on electronic and mass transport coefficients of their convective fluid interiors. We analyze recent laboratory experimental results on metallic hydrogen to derive a new conductivity profile for the Jovian-like planets. We combine this revised conductivity with a polytropic-based thermodynamic equation of state to study the dynamo action in 100 extrasolar giant planets varying from synchronous hot jupiters to fast rotators, with masses ranging from 0.3MJ to 15MJ. We find conducting cores larger than previous estimates, but consistent with the results from Juno, suggesting that the dynamos in the more massive planets might be shallow-seated. Our results reveal that most extrasolar giants are expected to possess dipole surface magnetic fields in the range of 0.1-10 Gauss. Assuming radio emission processes similar to our solar giants, most characterized planets should emit radiation with a maximum cyclotron frequency between few and 30 MHz, lower than previous estimates. Our work places new bounds on the observational detectability of extrasolar magnetic fields.