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The last solar minimum was, by recent standards, unusually deep and long. Weare now close to the maximum of the subsequent solar cycle, which is relativelyweak. In this article we make comparisons between different global (unresolved)measures of the Sun's magnetic activity, to investigate how they are respondingto this weak-activity epoch. We focus on helioseismic data, which are sensitiveto conditions, including the characteristics of the magnetic field, in thesolar interior. Also considered are measures of the magnetic field in thephotosphere (sunspot number and sunspot area), the chromosphere and corona(10.7cm radio flux and 530.3nm green coronal index), and two measures of theSun's magnetic activity closer to Earth (the interplanetary magnetic field andthe galactic cosmic-ray intensity). Scaled versions of the activity proxiesdiverge from the helioseismic data around 2000, indicating a change inrelationship between the proxies. The degree of divergence varies from proxy toproxy with sunspot area and 10.7cm flux showing only small deviations, whilesunspot number, coronal index, and the two interplanetary proxies show muchlarger departures. In Cycle 24 the deviations in the solar proxies and thehelioseismic data decrease, raising the possibility that the deviationsobserved in Cycle 23 are just symptomatic of a 22-year Hale cycle. However, thedeviations in the helioseismic data and the interplanetary proxies increase inCycle 24. Interestingly the divergence in the solar proxies and thehelioseismic data are not reflected in the shorter-term variations (oftenreferred to as quasi-biennial oscillations) observed on top of the dominant11-year solar cycle. However, despite being highly correlated in Cycle 22, theshort-term variations in the interplanetary proxies show very littlecorrelation with the helioseismic data during Cycles 23 and 24.

A Comparison Between Global Proxies of the Sun's Magnetic Activity Cycle: Inferences from Helioseismology