Journal
ADVANCES IN SPACE RESEARCH
Volume 55, Issue 3, Pages 835-842Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.asr.2014.05.033
Keywords
Solar cycle; Sunspot; Magnetic field
Categories
Funding
- Russian Foundation for Basic Research (RFBR)
- Russian Academy of Sciences
- Russian Federal Agency for Science and Innovations
- Academy of Finland to the ReSoLVE Center of Excellence [272157]
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Using the software developed by us, we produced a digitized (tabulated) database of sunspot umbrae and pores observed at Mount Wilson Observatory (MWO) in 1917-2013. The database includes the heliographic coordinates, areas and the polarity and strength of magnetic fields of umbrae and pores in the MWO sunspot drawings. Using this database we study here the properties and long-term variation of sunspot umbrae and pores, separately for leading and trailing polarity spots. We find that the leading sunspots have tendency for larger umbrae and stronger magnetic field strength than the trailing spots. The average field strength and area of sunspot umbrae vary with sunspot cycle. Furthermore, the mean magnetic field strength in sunspot umbrae exhibits a gradual increase from early 1960s to 1990s. The nature of this increase is discussed. (C) 2014 COSPAR. Published by Elsevier Ltd. All rights reserved.
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