Solar Physics Division Meeting 2000, June 19-22
Session 2. Corona, Solar Wind, Flares, CMEs, Solar-stellar, Instrumentation, Other
Display, Chair: J. Krall, Monday-Thursday, June 19, 2000, 8:00am-6:00pm, Forum Ballroom

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[2.116] The Violations of the Rule of Gnevyshev-Ohl in the Schove Series. Does the Current 11-year Cycle No. 23 Indicate a New Centurial Solar Minimum?\\

B. Komitov (Inst. of Astronomy - Bulgarian Academy of Sciences), B. Bonev (Ritter Astrophysical Research Center, Univ. of Toledo)

We examined the conditions for violations of the rule of Gnevyshev-Ohl which states that the even numbered 11-year solar cycles have been followed by higher odd numbered ones. We used the Schove series [1] which includes the main macro-characteristics of the 11-year cycles and is continuous since the end of the third century. A total of 154 cycles were investigated, the last one being No. 21 in the International sunspot number series. By discriminant analysis of the pairs of "even-odd" 11-year cycles in the Schove series, we showed that the main condition for violation of the rule of Gnevyshev-Ohl is a very high maximum of the even numbered cycle. In cases when this maximum corresponds to annual average Wolf number larger than 125, the probability for the following odd cycle to be lower in maximum is highly significant. The probability for violation of the rule of Gnevyshev-Ohl also increases with the decay time of the even cycle, which does not correlate well with the amplitude of the preceding maximum. These results allowed us as early as 1996 to predict a violation of Gnevyshev-Ohl's rule in the pair of cycles 22 and 23 [2]. This was based on the high maximum annual average Wolf number for cycle 22 (157.6). The consequent development of cycle 23 confirms our conclusion. The present cycle will probably be lower than the preceding cycle 22 as well as than the previous odd numbered cycles 19 and 21. We argue that this behavior of cycle 23 might be a signal for an upcoming centurial solar minimum [3].


[1] Schove, D.J. 1955, J. Geophys. Res, 60, 127 [2] Komitov, B. 1997, Bulg. Geophys. J., No. 1-2, 69 [3] Bonev, B., 1997, Bulg. Geophys. J., No. 3-4, 43

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