DIRENO is Lower Austria's scholarly repository for collecting and preserving digital assets, including current and historical regional literature.
WDC Sunspot Index and Long-term Solar Observations
SILSO preserves and distributes the international sunspot number, with current and historical solar observation data.
About WDC Sunspot Index and Long-term Solar Observations
WDC-SILSO at the Royal Observatory of Belgium produces, curates and preserves the International Sunspot Number, a long-running record of solar activity. It publishes sunspot data products and short-term forecasts for research, space-weather operations, climate-adjacent studies, education and outreach. The site also documents data versions and formats and maintains an observer network.
Pricing is not clearly stated.
Key features
- Preliminary EISN values are produced every five minutes from WOLF entries; provisional SN is monthly and final SN quarterly.
- Products include daily, monthly, monthly-smoothed and yearly SN, with hemispheric and total values.
- Base data are available as ASCII and CSV, with schema, units and error bars on download pages.
- Earlier versions remain available for reproducibility, and major releases carry DOIs.
- Outreach materials include PNG graphics and classroom-friendly CSV extracts.
- The observer network uses WOLF web entry with client-side checks, station codes, feedback and training resources.
- Data are licensed CC-BY-NC and should be cited by SN version and DOI.
Best for: Heliophysics researchers, space-weather operations staff, educators and sunspot observers.
WDC Sunspot Index and Long-term Solar Observations at a glance
- Website
- sidc.be/SILSO/home
- Category
- Research & Data › Open Data & Datasets
- Type
- Website
- Pricing
- Not confirmed. Check the site
- Platforms
- Web
- Details verified
- Oct 22, 2026 · Official source
- Open source
- Not stated
- Language
- English
- Last checked
- Oct 5, 2026 · Online when checked
- Listed
- Oct 5, 2026
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