Stellar Wind Driven Alfv\'en Wing Dynamics in Planetary and Exoplanetary Magnetospheres

Abstract

Magnetized obstacles embedded within a plasma flow generate magnetohydrodynamic structures known as Alfv\'en wings, which act as primary conduits for the transfer of momentum and energy between the body and the surrounding medium. This study employs three-dimensional resistive magnetohydrodynamic simulations to explore how these wings and the magnetosphere respond to diverse stellar wind conditions. Our results, gleaned from a large number of systematic simulations spanning a wide range of stellar wind speed and magnetic field -- and planetary dipole field -- show that the global magnetospheric configuration is highly sensitive to the upstream Alfv\'en Mach number. We find that increasing stellar wind speed leads to a systematic closure and narrowing of Alfv\'en wing structures, while stronger stellar magnetic fields facilitate their opening. Analysis of the Alfv\'en wing morphology demonstrates a distinct dependence of wing opening angle on stellar wind speed, with internal wing analysis showing a reduction in plasma velocity and significant magnetic-flux accumulation. Our results exhibit a clear interdependence between the day-side magnetopause stand-off distance and the night-side magnetotail current sheet length. We find a linear scaling between the magnetotail dynamics and upstream forcing parameters. This study bridges the gap between solar system observations and (exo)planetary systems by demonstrating how Earth-like magnetospheres might transform into wing-dominated configurations during extreme stellar events or within the sub-Alfv\'enic regimes of close-in (exo)planets. Our findings can aid the interpretation of Alfv\'en wing signatures in observational data and enhance our understanding of how (exo)planetary magnetospheres respond to dynamic stellar wind forcing.