Simulations of Winds of Weak-Lined T Tauri Stars: The Magnetic Field Geometry and The Influence of the Wind on Giant Planet Migration

TL;DR

This study uses 3D MHD simulations to explore the magnetic configurations of weak-lined T Tauri stars' stellar winds and their impact on hot-Jupiter migration, highlighting the role of plasma-beta in magnetic structure formation.

Contribution

It introduces a self-consistent 3D MHD model to analyze stellar wind magnetic configurations and their influence on planetary migration, contrasting previous Weber & Davis model estimates.

Findings

Magnetic configuration varies with plasma-beta parameter.

Elongated magnetic features occur only when beta<<1.

Stellar winds likely have minimal impact on hot-Jupiter migration.

Abstract

By means of numerical simulations, we investigate magnetized stellar winds of pre-main-sequence stars. In particular we analyze under which circumstances these stars will present elongated magnetic features (e.g., helmet streamers, slingshot prominences, etc). We focus on weak-lined T Tauri stars, as the presence of the tenuous accretion disk is not expected to have strong influence on the structure of the stellar wind. We show that the plasma-beta parameter (the ratio of thermal to magnetic energy densities) is a decisive factor in defining the magnetic configuration of the stellar wind. Using initial parameters within the observed range for these stars, we show that the coronal magnetic field configuration can vary between a dipole-like configuration and a configuration with strong collimated polar lines and closed streamers at the equator (multi-component configuration for the magnetic field). We show that elongated magnetic features will only be present if the plasma-beta parameter at the coronal base is beta<<1. Using our self-consistent 3D MHD model, we estimate for these stellar winds the time-scale of planet migration due to drag forces exerted by the stellar wind on a hot-Jupiter. In contrast to the findings of Lovelace et al. (2008), who estimated such time-scales using the Weber & Davis model, our model suggests that the stellar wind of these multi-component coronae are not expected to have significant influence on hot-Jupiters migration. Further simulations are necessary to investigate this result under more intense surface magnetic field strengths (~2-3 kG) and higher coronal base densities, as well as in a tilted stellar magnetosphere.