Phase lags of solar hemispheric cycles

TL;DR

This study investigates the long-term phase relationships between the northern and southern solar hemispheric cycles using sunspot data, revealing an alternating pattern and suggesting a connection to the Gleissberg cycle that impacts understanding of the solar dynamo.

Contribution

It introduces a new method analyzing entire hemispheric cycles to study phase relations and links these patterns to the Gleissberg cycle, offering insights into the solar dynamo mechanism.

Findings

Alternating phase lead and follow pattern in hemispheric cycles.

No significant correlation between phase and strength differences.

Possible connection of the 8-cycle pattern to the Gleissberg cycle.

Abstract

The North-South asymmetry of solar activity is variable in time and strength. We analyse the long-term variation of the phase lags of hemispheric cycles and check a conjectured relationship between these phase lags and the hemispheric cycle strengths. Sunspot data are used from cycles 12-23 in which the separation of northern and southern hemispheres is possible. The centers of mass of the hemispheric cycle profiles were used to study the phase relations and relative strengths of the hemispheric cycles. This approach considers a cycle as a whole and disregards the short-term fluctuations of the cycle time profile. The phase of the hemispheric cycles shows an alternating variation: the northern cycle leads in 4 cycles and follows in 4 cycles. No significant relationship is found between the phase and strength differences of the hemispheric cycles. The period of 4+4 cycles appears to be close to the Gleissberg cycle and may provide a key to its physical background. It may raise a new aspect in the solar dynamo mechanism because it needs a very long memory.