Observational Consequences of Shallow-water Magnetohydrodynamics on Hot Jupiters

TL;DR

This study uses shallow-water magnetohydrodynamics to estimate the magnetic field strengths needed to produce observed atmospheric wind patterns, like westward hotspots, on hot Jupiters, guiding future observational efforts.

Contribution

It provides new estimates of magnetic field strengths influencing atmospheric dynamics on hot Jupiters, including predictions for additional planets likely to show magnetically-driven wind variations.

Findings

Magnetic field strengths between 4 G and 19 G can explain wind variations on certain hot Jupiters.

WASP-12b and WASP-33b's westward hotspots are explained by magnetic fields of 1 G and 2 G respectively.

Identified 61 hot Jupiters likely to exhibit magnetically-driven atmospheric wind variations.

Abstract

We use results of shallow-water magnetohydrodynamics (SWMHD) to place estimates on the minimum magnetic field strengths required to cause atmospheric wind variations (and therefore westward venturing hotspots) for a dataset of hot Jupiters (HJs), including HAT-P-7b, CoRoT-2b, Kepler-76, WASP-12b, and WASP-33b, on which westward hotspots have been observationally inferred. For HAT-P-7b and CoRoT-2b our estimates agree with past results; for Kepler-76b we find that the critical dipolar magnetic field strength, over which the observed wind variations can be explained by magnetism, lies between $4\mbox{ G}$ and $19\mbox{ G}$; for WASP-12b and WASP-33b westward hotspots can be explained by $1\mbox{ G}$ and $2\mbox{ G}$ dipolar fields respectively. Additionally, to guide future observational missions, we identify $61$ further HJs that are likely to exhibit magnetically-driven atmospheric wind variations and predict these variations are highly-likely in $\sim 40$ of the hottest HJs.