Estimating the magnetic field strength in hot Jupiters

TL;DR

This paper estimates the magnetic field strength of hot Jupiters by considering energy injection from stellar irradiation, suggesting they may have magnetic fields over ten times stronger than Jupiter's.

Contribution

It introduces a scaling approach linking stellar energy input to planetary magnetic field strength, providing new estimates for hot Jupiter magnetic fields.

Findings

Hot Jupiters can have magnetic fields over ten times stronger than Jupiter's.

Energy injection from stellar irradiation significantly influences planetary dynamo activity.

Stellar light plays a fundamental role in determining magnetic field strength in hot Jupiters.

Abstract

A large fraction of known Jupiter like exoplanets are inflated as compared to Jupiter. These "hot" Jupiters orbit close to their parent star and are bombarded with intense starlight. Many theories have been proposed to explain their radius inflation and several suggest that a small fraction of the incident starlight is injected in to the planetary interior which helps to puff up the planet. How will such energy injection affect the planetary dynamo? In this Letter, we estimate the surface magnetic field strength of hot Jupiters using scaling arguments that relate energy available in planetary interiors to the dynamo generated magnetic fields. We find that if we take into account the energy injected in the planetary interior that is sufficient to inflate hot Jupiters to observed radii, then the resulting dynamo should be able generate magnetic fields that are more than an order of magnitude stronger than the Jovian values. Our analysis highlights the potential fundamental role of the stellar light in setting the field strength in hot Jupiters.