Estimating the size and timing of maximum amplitude for cycle 23 from its early cycle behavior

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Abstract
On the basis of the lowest observed smoothed monthly mean sunspot number, cycle 23 appears to have conventionally begun in May 1996, in conjunction with the first appearance of a new cycle, high‐latitude spot group. Such behavior, however, is considered rather unusual, since, previously (based on the data‐available cycles 12–22), the first appearance of a new cycle, high‐latitude spot group has always preceded conventional onset by at least 3 months. Furthermore, accepting May 1996 as the official start for cycle 23 poses a dilemma regarding its projected size and timing of maximum amplitude. Specifically, from the maximum‐minimum and amplitude‐period relationships we infer that cycle 23 should be above average in size and a fast riser, with maximum amplitude occurring before May 2000 (being in agreement with projections for cycle 23 based on precursor information), yet from its initial languid rate of rise (during the first 6 months of the cycle) we infer that it should be below average in size and a slow riser, with maximum amplitude occurring after May 2000. The dilemma vanishes, however, when we use a slightly later‐occurring onset. For example, using August 1996, a date associated with a local secondary minimum prior to the rapid rise that began shortly thereafter (in early 1997), we infer that the cycle 23 rate of rise is above that for the mean of cycles 1–22, the mean of cycles 10–22 (the modern era cycles), the mean of the modern era “fast risers,” and the largest of the modern era “slow risers” (i.e., cycle 20), thereby suggesting that cycle 23 will be both fast rising and above average in size, peaking before August 2000. Additionally, presuming cycle 23 to be a well‐behaved fast‐rising cycle (regardless of whichever onset date is used), we also infer that its maximum amplitude likely will measure about 144.0 ± 28.8 (from the general behavior found for the bulk of modern era fast risers; i.e., 5 of 7 have had their maximum amplitude to lie within 20% of the mean curve for modern era fast risers). It is apparent, then, that sunspot number growth during 1998 will prove crucial for correctly establishing the size and shape of cycle 23.