Indirect comparison of Debrecen and Greenwich daily sums of sunspot areas

TL;DR

This study compares long-term sunspot area datasets from Debrecen and Greenwich, estimating a correction factor to calibrate the data for consistent solar activity analysis.

Contribution

It introduces a method to determine time-dependent cross-calibration factors between sunspot datasets, improving data homogeneity.

Findings

Estimated correction factor: GPR=1.08(±0.11)*DPD

Identified systematic deviations in sunspot area data over time

Enhanced long-term solar activity analysis accuracy

Abstract

Sunspot area data play an important role in the studies of solar activity and its long-term variations. In order to reveal real long-term solar variations precise homogeneous sunspot area databases should be used. However, the measured areas may be burdened with systematic deviations, which may vary in time. Thus, there is a need to investigate the long-term variation of sunspot area datasets and to determine the time-dependent cross-calibration factors. In this study, we investigate the time-dependent differences between the available long-term sunspot databases. Using the results, we estimate the correction factor to calibrate the corrected daily sunspot areas of Debrecen Photoheliographic Data (DPD) to the same data of Greenwich Photoheliographic Results (GPR) by using the overlapping Kislovodsk and Pulkovo data. We give the correction factor as GPR=1.08(\pm 0.11)*DPD