Size and Strength of Self-excited Dynamos in Jupiter-like Extrasolar Planets

Abstract

Abstract The magnetization of solar and extrasolar gas giants is critically dependent on the 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 0.3 M J to 15 M J. We find dynamo cores larger than previous estimates, but consistent with the results from Juno, suggesting that the field generation 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, the stronger emitters are expected to have maximal cyclotron frequencies between 20 and 40 MHz and for those within few 10 pc, few have flux densities greater than 1 mJy. Our work places new bounds on the observational detectability of extrasolar magnetic fields.