Simulations of solar wind variations during an 11-year cycle and the influence of north-south asymmetry

TL;DR

This study models the 11-year solar cycle to understand how north-south magnetic asymmetry influences solar wind properties, reproducing observed solar wind features and revealing links between magnetic topology and wind variations.

Contribution

It introduces a coupled dynamo and solar wind simulation approach to analyze the impact of magnetic asymmetry on solar wind during an solar cycle, a novel integration of models.

Findings

Reproduces solar wind parameters such as mass loss rate and Alfvén radius.

Shows phase lag affects amplitude of magnetic and wind variations.

Links magnetic topology changes to magnetic torque variations.

Abstract

We want to study the connections between the magnetic field generated inside the Sun and the solar wind impacting Earth, especially the influence of north-south asymmetry on the magnetic and velocity fields. We study a solar-like 11-year cycle in a quasi-static way: an asymmetric dynamo field is generated through a 2.5-dimensional (2.5-D) flux-transport model with the Babcock-Leighton mechanism, and then is used as bottom boundary condition for compressible 2.5-D simulations of the solar wind. We recover solar values for the mass loss rate, the spin-down time scale and the Alfv\'en radius, and are able to reproduce the observed delay in latitudinal variations of the wind and the general wind structure observed for the Sun. We show that the phase lag between the energy of the dipole component and the total surface magnetic energy has a strong influence on the amplitude of the variations of global quantities. We show in particular that the magnetic torque variations can be linked to topological variations during a magnetic cycle, while variations in the mass loss rate appear to be driven by variations of the magnetic energy.