Numerical quantification of the wind properties of cool main sequence stars

Abstract

As a cool star evolves, it loses mass and angular momentum due to magnetized stellar winds which affect its rotational evolution. This change has consequences that range from the alteration of its activity to influences over the atmosphere of any orbiting planet. Despite their importance, observations constraining the properties of stellar winds in cool stars are extremely limited. Therefore, numerical simulations provide a valuable way to understand the structure and properties of these winds. In this work, we simulate the magnetized winds of 21 cool main-sequence stars (F-type to M-dwarfs), using a state-of-the-art 3D MHD code driven by observed large-scale magnetic field distributions. We perform a qualitative and quantitative characterization of our solutions, analyzing the dependencies between the driving conditions (e.g., spectral type, rotation, magnetic field strength) and the resulting stellar wind parameters (e.g., Alfvén surface size, mass loss rate, angular momentum loss rate, stellar wind speeds). We compare our models with the current observational knowledge on stellar winds in cool stars and explore the behaviour of the mass loss rate as a function of the Rossby number. Furthermore, our 3D models encompass the entire classical Habitable Zones (HZ) of all the stars in our sample. This allows us to provide the stellar wind dynamic pressure at both edges of the HZ and analyze the variations of this parameter across spectral type and orbital inclination. The results here presented could serve to inform future studies of stellar wind-magnetosphere interactions and stellar wind erosion of planetary atmospheres via ion escape processes.

Formulating Mass-loss Rates for Sun-like Stars: A Hybrid Model Approach

“…The purpose of this work is to establish a theoretical scaling law for  M w (Schröder & Cuntz 2005;Cranmer & Saar 2011;Suzuki et al 2013;Suzuki 2018;Chebly et al 2023) that aligns with both solar and stellar observations. Solar wind models generally rely on either Alfvén-wave acceleration (Ofman & Davila 1995, 1998Matthaeus et al 1999;Dmitruk et al 2002;Ofman 2004;Suzuki & Inutsuka 2005;Verdini & Velli 2007;Verdini et al 2010;Perez & Chandran 2013;van der Holst et al 2014;van Ballegooijen & Asgari-Targhi 2016;Usmanov et al 2018;Shoda et al 2019;Réville et al 2020;Matsumoto 2021;Schleich et al 2023) or loop-opening acceleration (Fisk et al 1999;Fisk 2003;Rappazzo et al 2012;Lionello et al 2016;Chitta et al 2023aChitta et al , 2023bBale et al 2023;Drake et al 2023;Kumar et al 2023;Raouafi et al 2023).…”