The Revolution Revolution: magnetic morphology driven spin-down

TL;DR

This paper introduces a new stellar spin-down model that incorporates magnetic field morphology, explaining observed bimodal rotation distributions in young stars by linking magnetic complexity with stellar rotation evolution.

Contribution

It presents the first model to include stellar surface magnetic field configuration in spin-down calculations, connecting magnetic complexity evolution to rotation period bimodality.

Findings

Magnetic field morphology significantly influences stellar angular momentum loss.

Evolving magnetic complexity from complex to simple explains bimodal rotation distributions.

The model aligns with observed rotation period distributions in young open clusters.

Abstract

Observations of young open clusters show a bimodal distribution of rotation periods that has been difficult to explain with existing stellar spin-down models. Detailed MHD stellar wind simulations have demonstrated that surface magnetic field morphology has a strong influence on wind-driven angular momentum loss. Observations suggest that faster rotating stars store a larger fraction of their magnetic flux in higher-order multipolar components of the magnetic field. In this work, we present a new model for stellar spin-down that, for the first time, accounts for the stellar surface magnetic field configuration. We show how a magnetic complexity that evolves from complex toward simple configurations as a star spins down can explain the salient features of stellar rotation evolution, including the bimodal distribution of both slow and fast rotators seen in young open clusters.