Large-Scale Properties of the Tilt of Sunspot Groups and Joy’s Law Near the Solar Equator

Abstract

A physical mechanism is proposed for the formation of the tilt angle of groups of sunspots during the formation of active regions under the sun’s photosphere. The phenomena associated with the influence of Coriolis forces on the large-scale flows in supergranular convection in turbulent media are studied in detail. Based on calculations of the magnetic field in a model of a solar nonlinear dynamo, the orders of magnitude of this effect are estimated and the tilt angle is estimated in the band of latitudes in the “royal zone” of sunspot activity. This dynamo model is based on the balance of small- and large-scale magnetic helicities, and describes the formation of sunspots over the last five activity cycles (since 1964) and has been adapted for a broader class of magnetic manifestations of solar activity. The variation in the average tilt over these five activity cycles has been plotted and latitude-time diagrams of the distribution of this value constructed which fully satisfy Joy’s law and also show the local deviations from it within a limited range of latitudes in isolated phases of the solar cycle. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.