Analysing Magnetic Drag in the Atmosphere of WASP-18 b Using ExoRad

Ultra-hot Jupiters (UHJs) present unique laboratories for studying extreme atmospheric dynamics and their interactions with planetary magnetic fields with space missions like CHEOPS, JWST, and PLATO. WASP-18 b, a UHJ with an equilibrium temperature exceeding 2400 K, orbits an F6-type star at a close distance of 0.02 AU. Under these conditions, the atmosphere undergoes substantial thermal ionisation, resulting in partial ionisation that may interact with the planet’s internal magnetic field.

This study explores the influence of magnetic drag on the atmospheric dynamics of WASP-18 b. By incorporating an approximation of the Lorentz force into the General Circulation Model (GCM) ExoRad, we analyse how this mechanism impacts the planet’s atmospheric dynamics and compare our treatment to previous GCMs with active magnetic drag. Furthermore, the observational implications of JWST and CHEOPS data are discussed in the context of the magnetic field's influence on the atmosphere. This work is part of our science support efforts within the PLATO WPs 116700 and 116800.