Gnevyshev–Ohl Rule: Current Status

Abstract

A statistical study on the statements of the Gnevyshev–Ohl rule (GOR) and some of its interpretations has been carried out. The original formulation of the GOR states that for the summary index of solar activity over the 11-year cycle \(\Sigma W\), there is a close connection in pairs of even and subsequent odd cycles (EO), while opposite pairs (OE) exhibit no such connection. This statement strictly holds with the significance level \(\alpha = 0.01\) for the new version of the sunspot index SN 2.0 (Wolf numbers). In this case, an even cycle is followed by an odd cycle with a greater \(\Sigma W\). For amplitudes of cycles, the GOR is observed only as a trend, and the difference of connections in EO and OE pairs of cycles is statistically insignificant. The alternation of the cycle magnitude, both for the \(\Sigma W\) parameter and the amplitudes, is also not statistically confirmed. It has been found that various aspects of the GOR are statistically better fulfilled for the new version of the sunspot index SN 2.0, which speaks in favor of further use of this index in solar physics.