Geometric Considerations in Hot Jupiter Magnetic Drag Models

TL;DR

This paper investigates how including vertical and meridional magnetic drag, beyond just zonal drag, affects atmospheric flow models of hot Jupiters, revealing that these additional forces can significantly alter flow patterns.

Contribution

It introduces a more comprehensive magnetic drag model for hot Jupiter atmospheres, accounting for vertical and meridional components, improving upon previous zonal-only models.

Findings

Meridional and vertical drag limit polar flows in hot atmospheres.

Ignoring meridional currents underestimates equatorial drag.

Including full drag components alters atmospheric flow predictions.

Abstract

Magnetic fields are expected to impact the atmospheric dynamics of hot and ultra-hot Jupiters due to their increased ionization fractions, compared to that of cooler exoplanets, but our ability to model these magnetic processes is limited by the different coupling regimes between the day and night sides of the planets. One common approach is to approximate the magnetic interactions as a drag acting on the atmosphere. In this work, we examine, within the context of this drag approximation, the impact of including vertical and meridional drag, in addition to zonal drag, from a background dipole magnetic field on the flows in hot Jupiter atmospheres as well as a relaxation of the assumption of solely meridional currents and demonstrate that the inclusion of meridional and vertical drag can limit flows over the poles in hotter atmospheres, something not seen in models that only consider zonal drag, and the assumption of only meridional currents results in an underestimation of the equatorial drag in all cases examined.