engleski

Solar differential rotation analysis from Kanzelhöhe sunspot drawings

Within the project intended to investigate the behavior of the solar differential rotation during several cycles we plan to process Kanzelhöhe sunspot drawings (Sonnenobservatorium Kanzelhöhe, University of Graz, Austria) for solar cycles nos. 20 - 24. As part of this analysis, we present here the results for the solar cycles no. 20 and no. 22. The positions of sunspot groups were determined using a special software Sungrabber. Sunspot groups were identified with the help of the Greenwich Photoheliographic Results (GPR) and Debrecen Photoheliographic Data (DPD) databases, covering solar cycles no. 20 and no. 22, respectively. In order to calculate the sidereal angular rotation rate ω and solar rotation parameters A, B and C we used two procedures: a) daily motion of sunspot groups and b) linear least-square fit from the function CMD(t) for each tracer. The sample was limited to ±58º in Central Meridian Distance (CMD) in order to avoid solar limb effects. We mainly investigated velocity patterns depending on the solar cycle phase and latitude.

solar differential rotation; solar cycle; sunspot groups

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