The dynamo-wind feedback loop: Assessing their non-linear interplay

TL;DR

This study models the complex non-linear feedback loop between the solar dynamo and solar wind using 2.5D MHD simulations, revealing their mutual influence over activity cycles.

Contribution

It introduces a coupled dynamo-wind simulation framework that dynamically links the solar interior magnetic field with the outer wind, advancing understanding of their interplay.

Findings

The solar wind varies with the activity cycle phase.

Wind feedback influences the dynamo process.

The Alfvén radius evolves over the cycle.

Abstract

Though generated deep inside the convection zone, the solar magnetic field has a direct impact on the Earth space environment via the Parker spiral. It strongly modulates the solar wind in the whole heliosphere, especially its latitudinal and longitudinal speed distribution over the years. However the wind also influences the topology of the coronal magnetic field by opening the magnetic field lines in the coronal holes, which can affect the inner magnetic field of the star by altering the dynamo boundary conditions. This coupling is especially difficult to model because it covers a large variety of spatio-temporal scales. Quasi-static studies have begun to help us unveil how the dynamo-generated magnetic field shapes the wind, but the full interplay between the solar dynamo and the solar wind still eludes our understanding. We use the compressible magnetohydrodynamical (MHD) code PLUTO to compute simultaneously in 2.5D the generation and evolution of magnetic field inside the star via an alpha-Omega dynamo process and the corresponding evolution of a polytropic coronal wind over several activity cycles for a young Sun. A multi-layered boundary condition at the surface of the star connects the inner and outer stellar layers, allowing both to adapt dynamically. Our continuously coupled dynamo-wind model allows us to characterize how the solar wind conditions change as a function of the cycle phase, and also to quantify the evolution of integrated quantities such as the Alfv\'en radius. We further assess the impact of the solar wind on the dynamo itself by comparing our results with and without wind feedback.