Fluctuations in Babcock‐Leighton Dynamos. II. Revisiting the Gnevyshev‐Ohl Rule

Abstract

The Gnevyshev-Ohl rule refers to a pattern of alternating higher and lower than average solar cycle amplitudes observed in the sunspot number record. In this paper, we show that such a pattern arises naturally in Babcock-Leighton models of the solar cycle as a consequence of the long time delay built into the dynamo regenerative loop. This is investigated using a simple but well-validated iterative map formulation, as well as a seasoned two-dimensional axisymmetric kinematic dynamo model. The good agreement between the results obtained via these two very different modeling approaches offers confidence that Gnevyshev-Ohl-like patterns of cycle amplitude fluctuations are a robust feature of this class of solar cycle models.