Long-term variations of solar magnetic fields derived from geomagnetic data

TL;DR

This study combines sunspot and geomagnetic data to reconstruct long-term variations of solar magnetic fields, addressing limitations of sunspot proxies alone.

Contribution

It introduces a method to estimate solar magnetic field variations using combined sunspot and geomagnetic records, improving historical reconstructions.

Findings

Geomagnetic data can serve as proxies for solar magnetic activity.

Sunspot parameters alone are insufficient for long-term magnetic field estimates.

The combined approach enhances understanding of solar magnetic evolution.

Abstract

Sunspots are dark spots on the solar surface associated with strong magnetic fields. The number, area, and brightness of sunspots are supposed to reflect the intensity of the solar magnetic fields and are often used as proxies for their long-term variations. However, the correlations between the sunspot parameters and solar magnetic fields are not constant, and the causes and the time profiles of the variations in these correlations are not quite clear. Therefore, the sunspot data alone cannot be used as proxy for deriving the variations of the sunspot magnetic fields for periods when no instrumental measurements are available. But the Earth is a sort of a probe reacting to interplanetary disturbances which are manifestation of the solar magnetic fields, so records of the geomagnetic activity can be used as diagnostic tools for reconstructing past solar magnetic fields evolution. In the present study we combine sunspot and geomagnetic data to estimate the long-term variations of sunspot magnetic fields.