Alternate Views: Get Data, FAQ, ISO Rubric, CSW, HTML, Components, XML Zurich Sunspot Numbers Slides SUNSPOTS In 1848 Rudolph Wolf devised a daily method of estimating solar activity by counting the number of individual spots and groups of spots on the face of the sun. Wolf chose to compute his sunspot number by adding 10 times the number of groups to the total count of individual spots, because neither quantity alone completely captured the level of activity. Each daily mean is computed as a weighted average of counts made by a network of cooperating observers in an effort to reduce the influence of personal judgment. Sunspots are optically dark regions in the solar atmosphere of relatively low temperature. They mark areas where the sun’s magnetic field has intensified by 1 or 2 powers of 10. The frequency of occurrence of sunspots rises and falls with an 11-year periodicity. Get the Data Access Format(s) Distributor(s) / Contact Info Instructions / Constraints http://www.ngdc.noaa.gov/stp/SOLAR/getdata.html http://www.ngdc.noaa.gov/stp ASCII Format version: (version is unknown) User Services DOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department of Commerce (303) 497-6826 7:30 - 5:00 Mountain Fees Depends on the Data Set Ordering Instructions Ordering Instructions: Price information is available upon request. Prepay by check, money order or bankcard There is a standard handling charge, with additional costs for special handling. Orders may be placed via fax, email, regular mail or telephone Custom Order Process: Contact data center for information Legal Constraints Access otherRestrictions Use Limitation otherRestrictions Other Access Constraints: No Constraints Use Constraints: None Distribution Liability: While every effort has been made to ensure that these data are accurate and reliable within the limits of the current state of the art, NOAA cannot assume liability for any damages caused by any errors or omissions in the data.