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The Wolf number (also known as the relative sunspot number or Zürich number) is a quantity that measures the number of sunspots and groups of sunspots present on the surface of the Sun. Historically, it was only possible to detect sunspots on the far side of the Sun indirectly using helioseismology.
The Wolf number sunspot index counts the average number of sunspots and groups of sunspots during specific intervals. The 11-year solar cycles are numbered sequentially, starting with the observations made in the 1750s.
The smoothed sunspot number rose again towards this second peak over the last five months of 2016 and surpassed the level of the first peak (66.9 in February 2012). Many cycles are double peaked but this is the first in which the second peak in sunspot number was larger than the first. This was over five years into cycle 24.
At a solar-cycle minimum, the toroidal field is, correspondingly, at minimum strength, sunspots are few in number, and the poloidal field is at its maximum strength. With the rise of the next 11-year sunspot cycle, magnetic energy shifts back from the poloidal to the toroidal field, but with a polarity that is opposite to the previous cycle.
Solar cycles are nearly periodic 11-year changes in the Sun's activity that are based on the number of sunspots present on the Sun's surface. The first solar cycle conventionally is said to have started in 1755. The source data are the revised International Sunspot Numbers (ISN v2.0), as available at SILSO. [1]
The monthly mean sunspot number in the northern solar hemisphere peaked in November 2011, while the southern hemisphere appears to have peaked in February 2014, reaching a peak monthly mean of 102. Subsequent months declined to around 70 (June 2014). [54] In October 2014, sunspot AR 12192 became the largest observed since 1990. [55]
A sunspot this large is easy enough to see from Earth; all that is needed is a solar filter or pair of eclipse glasses to protect your eyes from the sun's dangerous rays. Sunspot AR3664 compared ...
A prediction for Sunspot Cycle 24 (2008-2020) gives a smoothed sunspot number maximum of about 66 in the Summer of 2013. Current observations make this the smallest sunspot cycle since records began in the 1750s. [1] Solar maximum is the regular period of greatest solar activity during the Sun's 11-year solar cycle.