A Comparison of Solar Cycle Variations in the Equatorial Rotation Rates of the Sun's Subsurface, Surface, Corona, and Sunspot Groups

摘要

Using the Solar Optical Observing Network (SOON) sunspot-group data for theperiod 1985-2010, the variations in the annual mean equatorial-rotation ratesof the sunspot groups are determined and compared with the known variations inthe solar equatorial-rotation rates determined from the following data: i) theplasma rotation rates at 0.94Rsun, 0.95Rsun,...,1.0Rsun measured by GlobalOscillation Network Group (GONG) during the period 1995-2010, ii) the data onthe soft X-ray corona determined from Yohkoh/SXT full disk images for the years1992-2001, iii) the data on small bright coronal structures (SBCS) which weretraced in Solar and Heliospheric Observatory (SOHO)/EIT images during theperiod 1998-2006, and iv) the Mount Wilson Doppler-velocity measurements duringthe period 1986-2007. A large portion (up to approximate 30 deg latitude) ofthe mean differential-rotation profile of the sunspot groups lies between thoseof the internal differential-rotation rates at 0.94Rsun and 0.98Rsun.Thevariation in the yearly mean equatorial-rotation rate of the sunspot groupsseems to be lagging that of the equatorial-rotation rate determined from theGONG measurements by one to two years.The amplitude of the latter is verysmall.The solar-cycle variation in the equatorial-rotation rate of the solarcorona closely matches that determined from the sunspot-group data.Thevariation in the equatorial-rotation rate determined from the Mount WilsonDoppler-velocity data closely resembles the corresponding variation in theequatorial-rotation rate determined from the sunspot-group data that includedthe values of the abnormal angular motions (> 3 deg per day) of the sunspotgroups. Implications of these results are pointed out.