Rotation of the photospheric magnetic field through solar cycles 21, 22, 23

TL;DR

This study analyzes 30 years of solar magnetic field data to understand its rotation patterns, revealing differential rotation, torsional waves with an 11-year period, and latitude-dependent rotation rates linked to solar activity cycles.

Contribution

It provides new insights into the rotation behavior of the solar magnetic field, including the detection of torsional waves and their relation to solar cycle phases.

Findings

Magnetic field rotation is nearly rigid above 55° latitude.

Torsional waves of magnetic rotation propagate from poles to equator with an 11-year cycle.

Rotation rate varies with solar activity and magnetic field strength.

Abstract

Rotation of the large scale solar magnetic field has a great importance for the understanding of solar dynamic, for the search of longitidinal structure and for the study of solar-terrestrial relations. 30-year long observations taken at the Wilcox Solar Observatory (USA) in 21-23 cycles have been analysed carefully to deduce magnetic field rotation rate at different latitudes in both hemispheres and its variability in time. The WSO data appear to indicate that additionally to the differential rotation along the latitudes there are running waves of fast rotation of the magnetic field. These torsional waves are running from the poles to the equator with a period of 11 years. The rotation of the magnetic field (RMF) is almost rigid at latitudes above 55 degrees in both hemispheres. The rotation rate in the sub-polar regions is slower when the magnetic field is strong there (during minima of solar activity), and faster when the magnetic field changes polarity (during maxima of solar activity).