Speaker
Description
Accurately measuring the Sun’s polar magnetic fields remains a challenge, whether using Earth-based telescopes or spacecraft operating near the ecliptic plane. Among various indicators, the strength of polar fields at the sunspot cycle minimum, representing the radial component of the poloidal magnetic field, has proven to be the most robust predictor of the toroidal component and thus the intensity of the following solar cycle. In this study, we focus on polar filaments as key tracers of polar field dynamics. Drawing on decades of archival measurements from the Meudon Observatory, combined with solar surface flux transport simulations, we reveal a shared physical basis linking the Babcock–Leighton dynamo mechanism for polar field reversal and build-up with the formation and evolution of these filaments. Our analysis further uncovers a novel relationship that the residual filament area remaining at the end of one solar cycle correlates strongly with the amplitude of the next cycle. This connection offers a new tool for forecasting solar activity. We conclude that polar filament properties encapsulate the physics of interaction of the poloidal magnetic field of the previous and current sunspot cycles, the resultant of which is the net poloidal magnetic field at the end of the current cycle -- which in turn determines the strength of the upcoming solar cycle.