Research

Speaker: Bibhuti Kumar Jha

The tilt of bipolar magnetic regions (BMRs) plays a pivotal role in the Babcock–Leighton mechanism responsible for generating the Sun's poloidal magnetic field. Building upon the prior work conducted by Jha et al. (2020), we have undertaken an extended analysis of BMR data tracked during the Michelson Doppler Imager mission (1996–2011) and the Helioseismic and Magnetic Imager mission (2010–2018). Our aim was to gain a robust insight into how the magnetic field characteristics influence BMR tilts. Our investigation reveals a notable relationship between the strength of the maximum magnetic field (Bmax) in BMRs and the slope of Joy's law (γ0) Initially, as Bmax rises, γ0 exhibits gradual growth. However, an intriguing trend emerges when Bmax surpasses 2 kG: γ0 starts to decrease. This decline in observed γ0 with increasing Bmax suggests the possibility of nonlinear tilt quenching within the Babcock–Leighton process. Additionally, our analysis uncovers a noteworthy correlation between the scatter of BMR tilts around Joy's law and the magnitude of Bmax. As BMRs grow, they appear to be less affected by convective forces, resulting in a systematic reduction in the scatter of their tilts. Recently we have further extended this work by tracking the BMRs using our newly developed algorithm AutoTAB, over their lifetime to get better insight into the BMRs evolution.