Solar-Cycle Variation of Newly Emerging Coronal Holes during Solar Cycle 24
Coronal holes (CHs) are regions of predominantly open magnetic field and important sources of high-speed solar wind streams. We present a manually compiled catalogue of newly emerging CHs during Solar Cycle 24 (2010-2019), identified from daily CHIMERA maps provided by SolarMonitor. Unlike existing area-based catalogues, our dataset tracks the daily emergence of new CHs in northern, southern, and equatorial latitude zones. The emergence rate of equatorial CHs is anti-correlated with the International Sunspot Number (Pearson r = -0.523, p = 6.2 x 10^-9), indicating reduced formation of low-latitude CHs near solar maximum. The hemispheric asymmetry of CH emergence is also anti-correlated with the hemispheric asymmetry of sunspot activity (r = -0.461, p = 5.2 x 10^-7), suggesting that new CHs preferentially emerge in the hemisphere with lower sunspot activity. The total CH emergence rate is lowest near solar maximum and highest during the declining phase. These results provide new observational constraints on the evolution of open magnetic flux over the solar cycle.