Classification of magnetized star--planet interactions: bow shocks, tails, and inspiraling flows

TL;DR

This paper classifies the diverse magnetized star--planet interactions, such as bow shocks and tails, using 3D MHD simulations to understand their morphology based on system parameters.

Contribution

It introduces a new classification scheme for star--planet interactions based on physical parameters, supported by comprehensive 3D MHD simulations.

Findings

Four interaction types identified based on length scales

Flow structures include bow shocks, tails, and accretion streams

Morphologies can be predicted from system parameters

Abstract

Close-in exoplanets interact with their host stars gravitationally as well as via their magnetized plasma outflows. The rich dynamics that arises may result in distinct observable features. Our objective is to study and classify the morphology of the different types of interaction that can take place between a giant close-in planet (a Hot Jupiter) and its host star, based on the physical parameters that characterize the system. We perform 3D magnetohydrodynamic numerical simulations to model the star--planet interaction, incorporating a star, a Hot Jupiter, and realistic stellar and planetary outflows. We explore a wide range of parameters and analyze the flow structures and magnetic topologies that develop. Our study suggests the classification of star--planet interactions into four general types, based on the relative magnitudes of three characteristic length scales that quantify the effects of the planetary magnetic field, the planetary outflow, and the stellar gravitational field in the interaction region. We describe the dynamics of these interactions and the flow structures that they give rise to, which include bow shocks, cometary-type tails, and inspiraling accretion streams. We point out the distinguishing features of each of the classified cases and discuss some of their observationally relevant properties. The magnetized interactions of star--planet systems can be categorized, and their general morphologies predicted, based on a set of basic stellar, planetary, and orbital parameters.