Chromospheric turbulence as a regulator of stellar wind mass flux

TL;DR

This study demonstrates that chromospheric turbulence significantly influences stellar wind mass flux, with suppression leading to increased mass flux and better alignment with observed empirical scalings.

Contribution

It reveals the critical regulatory role of chromospheric turbulence in stellar wind models, improving understanding of mass flux scaling without extra energy mechanisms.

Findings

Suppressing chromospheric turbulence increases wind mass flux by up to ten times.

Model with turbulence suppression matches observed magnetic field and mass flux scaling.

Chromospheric turbulence acts as a key regulator in stellar wind mass flux.

Abstract

The mass flux of solar and stellar winds is a key quantity for stellar evolution and space weather, yet its physical regulation mechanism remains an unsolved problem. In particular, conventional Alfv\'en wave--driven models that self-consistently connect the stellar surface to the stellar wind fail to reproduce the observed scaling between stellar X-ray flux and mass-loss rate, a discrepancy that can be largely attributed to the dissipation of a substantial fraction of the wave energy by chromospheric turbulence. To address this issue, we aim to clarify the role of chromospheric turbulence in regulating the stellar wind mass flux. We perform one-dimensional wave-driven wind simulations, comparing cases with and without chromospheric turbulence suppression to assess its impact on coronal and wind properties. We find that suppressing chromospheric turbulence leads to a systematic increase in the coronal particle flux, and hence the wind mass flux, by up to an order of magnitude, particularly in regions of moderately strong magnetic field. This behavior arises from a combination of changes in the Poynting flux at the coronal base and in the asymptotic wind speed. Furthermore, the model with chromospheric turbulence suppression reproduces the observed empirical scaling between coronal magnetic field strength and mass flux without invoking additional energy input mechanisms such as interchange reconnection. These results identify the chromospheric turbulence as a key factor in regulating stellar wind mass flux and highlight the importance of incorporating its effects in models that connect the stellar surface and the stellar wind.