Sunspot

A sunspot is a region on the Sun's surface (photosphere) that is marked by a lower temperature than its surroundings, and intense magnetic activity. Although they are blindingly bright, at temperatures of roughly 5000 K, the contrast with the surrounding material at some 6000 K leaves them clearly visible as dark spots. If they were isolated from the surrounding photosphere they would be brighter than an electric arc.

External links

• Belgium World Data Center for the sunspot index
• http://www.tvweather.com/awpage/history_of_the_atmosphere.htm
• Current conditions: See Space weather
• NOAA Solar Cycle Progression: Current solar cycle.

Sunspot data

• {{Web reference | title=11,000 Year Sunspot Number Reconstruction | work=Global Change Master Directory | URL=http://gcmd.nasa.gov/KeywordSearch/Metadata.do?Portal=GCMD&KeywordPath=%5BParameters%3ACategory%3D%27EARTH+SCIENCE%27%2CTopic%3D%27SUN-EARTH+INTERACTIONS%27%2CTerm%3D%27SOLAR+ACTIVITY%27%2CVariable%3D%27SUNSPOTS%27%5D&OrigMetadataNode=GCMD&EntryId=NOAA_NCDC_PALEO_2005-015&MetadataView=Brief&MetadataType=0&lbnode=gcmd3b | date=11 March | year=2005}}
• {{Web reference | title= Unusual activity of the Sun during recent decades compared to the previous 11,000 years | work=WDC for Paleoclimatology | URL=http://www.ncdc.noaa.gov/paleo/pubs/solanki2004/ | date=11 March | year=2005}}
• {{Web reference | title=Sunspot Numbers from Ancient Times to Present from NOAA/NGDC | work=Global Change Master Directory | URL=http://gcmd.nasa.gov/KeywordSearch/Metadata.do?Portal=GCMD&KeywordPath=%5BParameters%3ACategory%3D%27EARTH+SCIENCE%27%2CTopic%3D%27SUN-EARTH+INTERACTIONS%27%2CTerm%3D%27SOLAR+ACTIVITY%27%2CVariable%3D%27SUNSPOTS%27%5D&OrigMetadataNode=GCMD&EntryId=FE00140&MetadataView=Brief&MetadataType=0&lbnode=gcmd3b | date=11 March | year=2005}}
• {{Web reference | title=SUNSPOT NUMBERS | work=NOAA NGDC Solar Data Services | URL=http://www.ngdc.noaa.gov/stp/SOLAR/ftpsunspotnumber.html | date=11 March | year=2005}}
• International Sunspot Number -- sunspot maximum and minimum 1610-present; annual numbers 1700-present; monthly numbers 1749-present; daily values 1818-present; and sunspot numbers by north and south hemisphere. The McNish-Lincoln sunspot prediction is also included.
• American sunspot numbers 1944-present
• Ancient sunspot data 165 BC to 1684 AD
• Group Sunspot Numbers (Doug Hoyt re-evaluation) 1610-1995