Low-Latitude Sunspot Group Tilt Angles in 15-24 Activity Cycles

An analysis of the tilt angles of the active regions in 15-24 activity cycles was performed. We used data from measurements of magnetic fields in the sunspot umbra in the period 1918 -2019 at the Mount Wilson Observatory, as well as the tilt angles of active regions in 'white' light at the Kodaikanal and Mount Wilson observatories in activity cycles 15-21. The mean tilt angles of active regions $\overline{\gamma}$ and the slope $\mu$ from latitude $\theta$ in the activity cycles are considered. Low-latitude bipoles are the most important in predicting the strength of solar cycles. In this work, we selected the cutoff latitude $\theta_{cut}$ at which the highest correlation is observed with the strength of the next activity cycle for active regions with latitude $\theta<\theta_{cut}$. It was found that for magnetic field measurement data, the highest correlation of the parameters $\overline{\gamma}$ and $\mu$ with the strength of the next solar activity cycle is characteristic of bipoles in the equatorial zone with $\theta<\theta_{cut}\approx 14.2^o$. For white light observation data, $\theta_{cut}\approx 8.5^o$ for Mount Wilson observatory and $\theta_{cut}\approx 9.4^o$ for Kodaikanal observatory.