Active region contributions to the solar wind over multiple solar cycles

TL;DR

This study quantifies active regions' variable contribution to the solar wind over four solar cycles, revealing a strong correlation with solar activity and potential influence of coronal mass ejections on magnetic field reconfigurations.

Contribution

It provides the first comprehensive estimate of active regions' contribution to the solar wind across multiple solar cycles using magnetic field data.

Findings

Active regions contribute 30% to 80% of the solar wind during solar maximum.

Contribution correlates strongly with sunspot number and CME rate.

Variations in contribution occur on monthly timescales, possibly due to CMEs.

Abstract

Both coronal holes and active regions are source regions of the solar wind. The distribution of these coronal structures across both space and time is well known, but it is unclear how much each source contributes to the solar wind. In this study we use photospheric magnetic field maps observed over the past four solar cycles to estimate what fraction of magnetic open solar flux is rooted in active regions, a proxy for the fraction of all solar wind originating in active regions. We find that the fractional contribution of active regions to the solar wind varies between 30% to 80% at any one time during solar maximum and is negligible at solar minimum, showing a strong correlation with sunspot number. While active regions are typically confined to latitudes $\pm$30$^{\circ}$ in the corona, the solar wind they produce can reach latitudes up to $\pm$60$^{\circ}$. Their fractional contribution to the solar wind also correlates with coronal mass ejection rate, and is highly variable, changing by $\pm$20% on monthly timescales within individual solar maxima. We speculate that these variations could be driven by coronal mass ejections causing reconfigurations of the coronal magnetic field on sub-monthly timescales.