Gnevyshev-Ohl rule

The Gnevyshev-Ohl rule (GO) is an empirical rule according to which the sum of Wolf’s sunspot numbers over an odd cycle exceeds that of the preceding even cycle[1][2]—see the Figure. The rule breaks down under certain conditions.[3] In particular, it invertes the sign across the Dalton minimum, but can be restored with the ``lost cycle´´ in the end of the 18th century.[4][5] The nature of the GO rule is still unclear.[2]

Illustration of the GO rule: Intensities of sunspot cycles in pairs of even (open circles) and odd (filled circles) numbered cycles.[4] The GO rule is expresses in the connecting lines pointing up. The break of the rule for cycles 2--3 and 4--5 is visible.

References
  1. Gnevishev, M. N.; Ohl, A. I. (1948). "On the 22-year cycle of solar activity". Astronomicheskii Zhurnal (in Russian). 25 (1): 18–20.
  2. Hathaway, D. (2015). "The solar cycle". Living Reviews in Solar Physics. 12 (1): 4. doi:10.1007/lrsp-2015-4.
  3. Komitov, Boris; Bonev, Boncho (2001). "Amplitude Variations of the 11 Year Cycle and the Current Solar Maximum 23". The Astrophysical Journal Letters. 554 (1): 119–122. doi:10.1086/320908.
  4. Usoskin, I.; Mursula, K.; Kovaltsov, G. (2001). "Was one sunspot cycle lost in late XVIII century?". Astronomy and Astrophysics. 370: L31. doi:10.1051/0004-6361:20010319.
  5. Usoskin, I.; Mursula, K.; Arlt, R.; Kovaltsov, G. (2009). "A Solar Cycle Lost in 1793-1800: Early Sunspot Observations Resolve the Old Mystery". Astrophysical Journal Letters. 700: L154. arXiv:0907.0063. doi:10.1088/0004-637X/700/2/L154.


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