High-Resolution Modelling of Coronae and Winds in Solar-type Stars with Varying Rotation Rates II. Stellar Winds

Abstract

Observations suggest a connection between steady-wind mass loss and coronal X-ray activity in low-mass main-sequence stars. Interpreting this connection is challenging because the wind is controlled mainly by the large-scale open field, whereas X-ray emission traces heating in small-scale closed fields often unresolved in global wind models. Here we use Space Weather Modelling Framework-Alfvén-Wave Solar Model with global convective dynamo-generated magnetic maps and solar magnetograms. We model Alfvén-wave-heated winds for four solar-type stars plus the Sun, spanning rotation rates of $1.0$--$23.3$ times the solar rate, and magnetic field strengths of $6.0$--$1200$ G. Our models show that faster rotation yields a more tightly wound spiral, a larger Alfvén surface, higher terminal wind speeds, and a harsher wind-pressure environment for orbiting exoplanets, different from that of the present-day Sun. We estimate the mass- and angular-momentum-loss rates and find systematic differences from Zeeman-Doppler Imaging-based predictions. Building on the successful reproduction of X-ray coronae in our Paper~I, we obtain the first self-consistent activity--wind relation in a unified modelling framework: the mass-loss rate scales with the surface X-ray flux following a power law with an index of ${\sim}0.67$. We also re-examine magnetic braking via open-flux magnetisation, finding that the effective Alfvénic lever arm depends on the magnetisation parameter with a power-law index of ${\sim}0.35$. Finally, we quantify the stellar wind pressure at the orbits of several super-Earths. Together with our Paper~I, the series of results shows the distinct roles of multi-scale magnetic fields and provides physically grounded inputs for assessing habitable-zone space weather.