Stellar Magnetic Fields as a Heating Source for Extrasolar Giant Planets

TL;DR

This paper proposes a magnetic interaction-based heating mechanism for hot Jupiters, demonstrating its potential to explain observed radius inflation and correlating stellar activity with planetary size anomalies.

Contribution

It introduces a novel magnetic heating mechanism involving stellar magnetic fields and planetary magnetospheres, supported by observational data analysis.

Findings

Magnetic interaction can supply sufficient energy for radius inflation.

Stellar activity correlates with inflated planetary radii.

Joule heating via global electric circuits is a plausible energy transfer process.

Abstract

It has been observed that hot Jupiters located within 0.08 AU of their host stars commonly display radii in excess of those expected based on models. A number of theoretical explanations for this phenomenon have been suggested, but the ability of any one mechanism to account for the full range of observations remains to be rigorously proven. I identify an additional heating mechanism, arising from the interaction of the interplanetary magnetic field and the planetary magnetosphere, and show that this is capable of providing enough energy to explain the observed planetary radii. Such a model predicts that the degree of heating should be dependent on the stellar magnetic field, for which stellar activity serves as a proxy. Accordingly, I examine populations of hot Jupiters from the Kepler database and confirm that stellar activity (determined using Kepler CDPP levels) is correlated with the presence of planetary radii inflated beyond the basal level of R = 0.87 R_J identified by previous researchers. I propose that the primary mechanism for transferring energy from the magnetosphere to the planetary interior is Joule heating arising from global electric circuits analogous to those seen in solar system objects.