Calibrating 100 Years of Polar Faculae Measurements: Implications for the Evolution of the Heliospheric Magnetic Field

Abstract

Although the Sun's polar magnetic fields are thought to provide important clues for understanding the 11-year sunspot cycle, including the observed variations of its amplitude and period, the current database of high-quality polar-field measurements spans relatively few sunspot cycles. In this paper we address this deficiency by consolidating Mount Wilson Observatory polar faculae data from four data reduction campaigns, validating it through a comparison with facular data counted automatically from MDI intensitygrams, and calibrating it against polar field measurements taken by the Wilcox Solar Observatory and average polar field and total polar flux calculated using MDI line-of-sight magnetograms. Our results show that the consolidated polar facular measurements are in excellent agreement with both polar field and polar flux estimates, making them an ideal proxy to study the evolution of the polar magnetic field. Additionally, we combine this database with sunspot area measurements to study the role of the polar magnetic flux in the evolution of the heliospheric magnetic field (HMF). We find that there is a strong correlation between HMF and polar flux at solar minimum and that, taken together, polar flux and sunspot area are better at explaining the evolution of the HMF during the last century than sunspot area alone.

14 pages, 17 figures

References in corpus (1)

• Predicting solar cycle 24 with a solar dynamo model

Cited by in corpus (26)

• Solar Cycle Propagation, Memory, and Prediction: Insights from a Century of Magnetic Proxies
• On Polar Magnetic Field Reversal and Surface Flux Transport During Solar Cycle 24
• Sympathetic Magnetic Breakout Coronal Mass Ejections from Pseudostreamers
• Hemispheric Coupling: Comparing Dynamo Simulations and Observations
• Forecasting Solar Cycle 25 using Deep Neural Networks
• Effects of Meridional Flow Variations on Solar Cycles 23 and 24
• Hemispheric sunspot numbers 1874--2020
• Improvement of solar cycle prediction: Plateau of solar axial dipole moment
• Solar cycle indices from the photosphere to the corona: measurements and underlying physics
• Nonlinear mechanisms that regulate the solar cycle amplitude
• Polar Network Index as a magnetic proxy for the solar cycle studies
• Physical Models for Solar Cycle Predictions
• A theoretical study of the build-up of the Sun's polar magnetic field by using a 3D kinematic dynamo model
• Torus-Stable Zone Above Starspots
• A 3D kinematic Babcock Leighton solar dynamo model sustained by dynamic magnetic buoyancy and flux transport processes
• Sunspot number second differences as a precursor of the following 11-year sunspot cycle
• Medium-term predictions of F10.7 and F30 cm solar radio flux with the adaptive Kalman filter
• Predicting the Timing of the the Solar Cycle 25 Polar Field Reversal
• Spatial-temporal forecasting the sunspot diagram
• Maximal growth rate of the ascending phase of a sunspot cycle for predicting its amplitude
• Algebraic Quantification of the Contribution of Active Regions to the Sun's Dipole Moment: Applications to Century-scale Polar Field Estimates and Solar Cycle Forecasting
• Minimal Roles of Solar Subsurface Meridional Flow in the distributed-shear Babcock-Leighton Dynamo
• Two New Methods for Counting and Tracking the Evolution of Polar Faculae
• Extreme Fluctuations in the Sun's Activity over the Modern Maximum: Understanding the Enigmatic Solar Cycles 19-20
• Using Polar Faculae to Determine the Sun's High-Latitude Rotation Rate. I. Techniques and Initial Measurements
• Solar Cycle Prediction: Challenges, Progress, and Future Perspectives