Abstract Details


Name: Bibhuti Kumar Jha
Affiliation: Southwest Research Institute (SwRI)
Conference ID: TVS202510142
Title: The Origin and Importance of Active Region Tilt in Solar Magnetism
Authors and Co-Authors: Anu Sreedevi, Bidya Binay Karak, Lisa Upton, Sudip Mandal, Dipanker Banerjee
Abstract Type: Invited by SOC
Abstract: The tilt of bipolar magnetic regions (BMRs) is a fundamental ingredient in the Babcock–Leighton process, the basis of many solar dynamo and surface flux transport (SFT) models. This process explains how tilted BMRs lead to the regeneration of the Sun’s poloidal magnetic field that drives the following solar cycle. In the thin flux tube model, tilts arise from the Coriolis force and are expected to vary with magnetic flux, though this dependence remains debated. Using magnetograms from the past two solar cycles, and to capture the full evolution of BMRs, we developed AutoTAB, an algorithm that detects and tracks individual BMRs throughout their lifetimes. Our analysis shows that the slope of Joy’s law increases with field strength but then start declines above ~2 kG, indicating nonlinear tilt quenching in the Babcock–Leighton process. The AutoTAB catalog further reveals systematic trends in polarity separation, tilt evolution, and butterfly patterns, while highlighting the distinct behavior of small BMRs and providing strong observational support for the thin flux tube paradigm. Convection introduces large scatter in tilt, while nonlinear feedback regulates BMR tilt, offering key constraints on solar dynamo and SFT models. Finally, we will briefly discuss the role of active-region tilt in modeling the solar cycle with SFT.