Abstract
One of the most striking aspects of the 11-year sunspot cycle is that there have been times in the past when some cycles went missing, a most well-known example of this being the Maunder minimum during 1645–1715. Analyses of cosmogenic isotopes ( and ) indicated that there were about 27 grand minima in the last 11 000 yrs, implying that about of the solar cycles had conditions appropriate for forcing the Sun into grand minima. We address the question of how grand minima are produced and specifically calculate the frequency of occurrence of grand minima from a theoretical dynamo model. We assume that fluctuations in the poloidal field generation mechanism and in the meridional circulation produce irregularities of sunspot cycles. Taking these fluctuations to be Gaussian and estimating the values of important parameters from the data of the last 28 solar cycles, we show from our flux transport dynamo model that about of the sunspot cycles may have conditions suitable for inducing grand minima.
- Received 30 March 2012
DOI:https://doi.org/10.1103/PhysRevLett.109.171103
© 2012 American Physical Society
Synopsis
Solar Down Time
Published 25 October 2012
A theoretical model of sunspots shows that their occasional disappearance may be due to a combination of fluctuations in the Sun’s polar magnetic field and outer layer flows.
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