Is Cycle 24 the Beginning of a Dalton-Like Minimum?
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The unexpected development of cycle 24 emphasizes the need for a better way to model future solar activity. In this article, we analyze the accumulation of spotless days during individual cycles from 1798 – 2010. The analysis shows that spotless days do not disappear abruptly in the transition toward an active Sun. A comparison with past cycles indicates that the ongoing accumulation of spotless days is comparable to that of cycle 5 near the Dalton minimum and to that of cycles 12, 14, and 15. It also suggests that the ongoing cycle has as much as 20±8 spotless days left, from July 2010, before it reaches the next solar maximum. The last spotless day is predicted to be in December 2012, with an uncertainty of 11 months. This trend may serve as input to the solar dynamo theories.
KeywordsCycle 24 Dalton minimum Prediction Spotless days
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