Long-Term Variations in the Growth and Decay Rates of Sunspot Groups

Abstract

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% per day and ~183% per day, respectively, whereas the corresponding values of the annually averaged daily mean decay rates are ~21% per day and ~44% per day, 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 Cycle 23 the growth rate is substantially decreased and near the end (2007-2008) the growth rate is lowest in the past about 100 years.

arXiv comment1 table, 13 figures, accepted by Solar Physics

References in corpus (5)

• Prime orbits for some smooth flows on ${\mathbb{T}}^2$
• Sun's retrograde motion and violation of even-odd cycle rule in sunspot activity
• Predicting the Amplitude of a Solar Cycle Using the North-South Asymmetry in the Previous Cycle: II. An Improved Prediction for Solar Cycle~24
• Long-term variations in the mean meridional motion of the sunspot groups
• Vainu Bappu Memorial Lecture: What is a sunspot?

Cited by in corpus (11)

• Revisiting the Sunspot Number
• A Comparison Between Global Proxies of the Sun's Magnetic Activity Cycle: Inferences from Helioseismology
• North-south asymmetry in small and large sunspot group activity and violation of even-odd solar cycle rule
• Time-dependent properties of sunspot groups -- I. Lifetime and asymmetric evolution
• Temporal Evolution of Sunspot Areas and Estimation of Related Plasma Flows
• Solar cycle variations in the growth and decay of sunspot groups
• On the Decay of Sunspot Groups and Their Internal Parts in Detail
• Long-term temporal variations in the areas of sunspot groups
• A statistical model of stellar variability. I. FENRIR: a physics-based model of stellar activity, and its fast Gaussian process approximation
• Variation of sunspot groups' polarity separation during their evolution
• The Decay Process of an α-configuration Sunspot