Twin 17-year solar cycles could be controlling the Sun’s activity
The 11-year solar cycle could soon be usurped, following a new study that has given strong evidence for a rival idea.
“We call it the Extended Solar Cycle (ESC),” says Scott McIntosh from the National Centre for Atmospheric Research, who led the study. “There are two overlapping patterns of activity on the Sun, each lasting about 17 years.”
McIntosh used data taken by the Wilcox Solar Observatory (WSO) since 1976 to measure the changing magnetic field of the Sun and compared that to sunspot numbers. This gave strong indications for two cycles, offset by five years from each other to create the illusion of an 11-year pattern.
“The Extended Solar Cycle may be telling us something crucial about what’s happening deep inside the Sun where sunspot magnetic fields are generated,” says McIntosh. “It poses significant challenges to prevalent dynamo theories of the solar cycle.” ncar.ucar.edu