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The shape of the sunspot cycle described by sunspot areas
Received 21 October 1998 / Accepted 13 January 1999
The temporal behavior of the sunspot cycles 12-22, as described by quarterly mean values of sunspot areas, can be represented by a single function containing only two parameters: the starting time and the amplitude of a cycle. The parameters are determined for the more recent 11 sunspot cycles and examined for any predictable behavior. As a sunspot cycle progresses, the amplitude parameter can be better determined to within 10% at 4.3 years into its cycle, and the starting time can be well determined to within 0.3 year at 4.6 years into the cycle, thereby providing a good prediction both for the timing and size of sunspot maximum and for the behavior of the remaining 5-10 years of the cycle. Characteristics of the sunspot cycle shape are investigated in this paper. The shape of the sunspot area cycle is generally asymmetric, taking less time rising from minimum to maximum than reaching the next minimum from the maximum, and cycles with larger amplitude are more asymmetric and take less time to reach maximum, the same as the so-called Waldmeier effect of the cycles described by the sunspot relative numbers.
Key words: Sun: sunspots Sun: activity
© European Southern Observatory (ESO) 1999
Online publication: April 28, 1999