Is the Hemispheric Asymmetry of Monthly Sunspot Area an Irregular Process with Long-Term Memory?

Abstract

The hemispheric asymmetry of the sunspot cycle is a real feature of the Sun. However, its origin is still not well understood. Here we perform nonlinear time series analysis of the sunspot area (and number) asymmetry to explore its dynamics. By measuring the correlation dimension of the sunspot area asymmetry, we conclude that there is no strange attractor in the data. Further computing Higuchi's dimension, we conclude that the hemispheric asymmetry is largely governed by stochastic noise. However, the behaviour of Hurst exponent reveals that the time series is not completely determined by a memory-less stochastic noise, rather there is a long-term persistence, which can go beyond two solar cycles. Therefore, our study suggests that the hemispheric asymmetry of the sunspot cycle is predominantly originated due to some irregular process in the solar dynamo. The long-term persistence in the solar cycle asymmetry suggests that the solar magnetic field has some memory in the convection zone.

Under review in MNRAS

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Cited by in corpus (7)

• Models for the long-term variations of solar activity
• Dynamo modelling for cycle variability and occurrence of grand minima in Sun-like stars: Rotation rate dependence
• Hemispheric analysis of the magnetic flux in regular and irregular solar active regions
• Inferring Quadrupolar Dynamo Mode from Sunspot Statistics
• Hemispheric Distribution of Solar Active Regions During Solar Cycles 23-25
• Hemispheric asymmetry in the sunspot cycle as a nonextensive phenomenon
• Random walk with multiple memory channels: a new paradigm