Mutual Validation of Datasets for Analyzing Tilt Angles in Solar Active Regions

Abstract

The tilt angle of solar active regions (AR) is crucial for the Babcock-Leighton type dynamo models in the buildup of polar field. However, divergent results regarding properties of tilt angles were reported due to their wide scatter, caused by intrinsic solar mechanisms and measurement errors. Here, we mutually validate the magnetogram-based AR tilt angle dataset from Wang, Jiang, & Luo with the Debrecen Photoheliographic Data by identifying common data points where both datasets provide comparable tilt angles for the same AR/sunspot. The mutually validated datasets effectively reduce measurement errors, enabling a more accurate analysis of the intrinsic properties of tilt angles. Our mutually validated datasets reveal that the difference between white-light-based and magnetogram-based tilt angles has no significant difference. Also, the datasets show that an upward revision of average tilt angle ($\barα$) and a downward revision of the tilt scatter ($σ_α$) compared to previous results are necessary, with typical values of about 7$^\circ$ and 16$^\circ$, respectively. The $σ_α$ values demonstrate a strong correlation with AR flux and sunspot area, with the dependency functions re-evaluated using mutually validated datasets. Furthermore, both $\barα$ and the tilt coefficient for the weak cycle 24 are larger than those for cycle 23. This supports the tilt quenching mechanism, which posits an anti-correlation between the cycle-averaged tilt angle and cycle amplitude. Additionally, tilt angle from the mutually validated dataset has a weak non-monotonic relationship with magnetic flux and does not depend on the maximum magnetic field strength of ARs.