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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 28, issue 7 | Copyright
Ann. Geophys., 28, 1463-1466, 2010
https://doi.org/10.5194/angeo-28-1463-2010
© Author(s) 2010. This work is distributed under
the Creative Commons Attribution 3.0 License.

  16 Jul 2010

16 Jul 2010

Size of the coming solar cycle 24 based on Ohl's Precursor Method, final estimate

R. P. Kane R. P. Kane
  • Instituto Nacional de Pesquisas Espacias, INPE C.P. 515, 12201-970 São Jose dos Campos, SP, Brazil

Abstract. In Ohl's Precursor Method (Ohl, 1966, 1976), the geomagnetic activity during the declining phase of a sunspot cycle is shown to be well correlated with the size (maximum sunspot number Rz(max)) of the next cycle. For solar cycle 24, Kane (2007a) used aa(min)=15.5 (12-month running mean), which occurred during March–May of 2006 and made a preliminary estimate Rz(max)=124±26 (12-month running mean). However, in the next few months, the aa index first increased and then decreased to a new low value of 14.8 in July 2007. With this new low value, the prediction was Rz(max)=117±26 (12-month running mean). However, even this proved a false signal. Since then, the aa values have decreased considerably and the last 12-monthly value is 8.7, centered at May 2009. For solar cycle 24, using aa(min)=8.7, the latest prediction is, Rz(max)=58.0±25.0.

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