| Abstract : | It is known that the polar magnetic field determines the amplitude of the next solar cycle. Therefore, the variation in the polar field can cause variation in the solar cycle. The polar field is observed to be produced mainly through the decay and dispersal of tilted bipolar magnetic regions (BMRs). However, the rate of BMR eruptions as observed on the solar surface is not uniform and there is an irregularity in the emergence of its number with time in a cycle. Furthermore, there is a considerable scatter in the BMR tilt around Joy’s law. We explore the effect of this irregular BMR emergence rate and the tilt scatter on the variation of polar field and solar cycle using a 3D kinematic dynamo model by feeding synthetic BMR data in it. We find that the irregular BMR eruption produces a mixed polarity field on the solar surface and short-term variation in the polar magnetic field. This variation in the polar field produces variation in the next solar cycle. We find that the irregular emergence rate of the BMR gives a variation in polar field strength of about 11%, while the tilt scatter produces a variation of 18%. When we consider both effects, we find about 25% variation in the polar field. Our results indicate that tilt scatters produces more variation in the polar field than irregular BMRs emergence.
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