Long-term variation of statistical properties of sunspot field strengths and their relation to the characteristics of solar cycles in 1917-2013
Abstract
We use the digitized sunspot daily drawings from the Mount Wilson Observatory (MWO) from 1917—2013 to study the long-term variations in sunspot magnetic fields. Tabulated data include the heliographic coordinates, area and magnetic field strength of all sunspots on solar disk. Sunspot field strengths exhibit several trends, which can be of instrumental or truly solar in its nature. For example, in depth analysis of the sunspot field strength and the sunspot areas indicates long-term changes in the observing system at the MWO, when systematically larger number of measurements in sub-features (e.g., multiple umbrae) was made beginning mid-20th century. The final data set is used to study several properties of active regions including difference (in field strength and area) between leading and following sunspots, the orientation of magnetic field in sunspots and pores relative to vertical direction, and the Hale (polarity) and Joy (tilt) laws over the period of about ten solar cycles.
- Publication:
-
40th COSPAR Scientific Assembly
- Pub Date:
- 2014
- Bibcode:
- 2014cosp...40E3357T