Survey and Merging of Sunspot Catalogs
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In view of the construction of new sunspot-based activity indices and proxies, we conducted a comprehensive survey of all existing catalogs providing detailed parameters of photospheric features over long time intervals. Although there are a fair number of such catalogs, a global evaluation showed that they suffer from multiple limitations: finite or fragmented time coverage, limited temporal overlap between catalogs, and, more importantly, a mismatch in contents and conventions. Starting from the existing material, we demonstrate how the information from parallel catalogs can be merged to form a much more comprehensive record of sunspots and sunspot groups. To do this, we use the uniquely detailed Debrecen Photoheliographic Data (DPD), which is already a composite of several ground-based observatories and of SOHO data, and the USAF/Mount Wilson catalog from the Solar Observing Optical Network (SOON). We also outline our cross-identification method, which was needed to match the non-overlapping solar active-region nomenclature. This proved to be the most critical and subtle step when working with multiple catalogs. This effort, focused here first on the last two solar cycles, should lead to a better central database that collects all available sunspot group parameters to address future solar-cycle studies beyond the traditional sunspot-index time series [R i].
KeywordsCatalogs Surveys Sun: photosphere Sunspots Methods: data analysis Statistical
This work was funded by the European Community’s Seventh Framework Program (FP7/2007-2013) under grant agreement No. 218816 ( www.soteria-space.eu ). We also wish to thank all the staff at the Konkoly Heliophysical Observatory for their invaluable help. We also acknowledge the support from the Belgian Solar-Terrestrial Center of Excellence (STCE) funded through the Belgian Science Policy Office (BELSPO).
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