caa a22 4500 445346167 CHVBK 20180317142829.0 cr unu---uuuuu 170323e20110601xx s 000 0 eng 10.1007/s11207-011-9768-8 doi (NATIONALLICENCE)springer-10.1007/s11207-011-9768-8 Javaraiah J. Indian Institute of Astrophysics, 560 034, Bangalore, India aut Long-Term Variations in the Growth and Decay Rates of Sunspot Groups [Elektronische Daten] [J. Javaraiah] Using the combined Greenwich (1874 - 1976) and Solar Optical Observatories Network (1977 - 2009) data on sunspot groups, we study the long-term variations in the mean daily rates of growth and decay of sunspot groups. We find that the minimum and the maximum values of the annually averaged daily mean growth rates are ≈ 52% day−1 and ≈ 183% day−1, respectively, whereas the corresponding values of the annually averaged daily mean decay rates are ≈ 21% day−1 and ≈ 44% day−1, respectively. The average value (over the period 1874 - 2009) of the growth rate is about 70% more than that of the decay rate. The growth and the decay rates vary by about 35% and 13%, respectively, on a 60-year time scale. From the beginning of Cycle23 the growth rate is substantially decreased and near the end (2007 - 2008) the growth rate is lowest in the past about 100 years. In the extended part of the declining phase of this cycle, the decay rate steeply increased and it is largest in the beginning of the current Cycle24. These unusual properties of the growth and the decay rates during Cycle23 may be related to cause of the very long declining phase of this cycle with the unusually deep and prolonged current minimum. A ≈ 11-year periodicity in the growth and the decay rates is found to be highly latitude and time dependent and seems to exist mainly in the 0° - 10° latitude interval of the southern hemisphere. The strength of the known approximate 33 - 44-year modulation in the solar activity seems to be related to the north-south asymmetry in the growth rate. Decreasing and increasing trends in the growth and the decay rates indicate that the next 2 - 3 solar cycles will be relatively weak. Springer Science+Business Media B.V., 2011 Solar Physics Springer Netherlands 270/2(2011-06-01), 463-483 0038-0938 270:2<463 2011 270 11207 https://doi.org/10.1007/s11207-011-9768-8 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s11207-011-9768-8 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Javaraiah J. Indian Institute of Astrophysics, 560 034, Bangalore, India aut NATIONALLICENCE 773 0- Solar Physics Springer Netherlands 270/2(2011-06-01), 463-483 0038-0938 270:2<463 2011 270 11207 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer