The American Astronomical Society, at it annual meeting, announced today:
A missing jet stream, fading spots, and slower activity near the poles say that our Sun is heading for a rest period even as it is acting up for the first time in years, according to scientists at the National Solar Observatory (NSO) and the Air Force Research Laboratory (AFRL).
As the current sunspot cycle, Cycle 24, begins to ramp up toward maximum, independent studies of the solar interior, visible surface, and the corona indicate that the next 11-year solar sunspot cycle, Cycle 25, will be greatly reduced or may not happen at all.
“This is highly unusual and unexpected,” Dr. Frank Hill, associate director of the NSO’s Solar Synoptic Network, said of the results. “But the fact that three completely different views of the Sun point in the same direction is a powerful indicator that the sunspot cycle may be going into hibernation.”
Spot numbers and other solar activity rise and fall about every 11 years, which is half of the Sun’s 22-year magnetic interval since the Sun’s magnetic poles reverse with each cycle. An immediate question is whether this slowdown presages a second Maunder Minimum, a 70-year period with virtually no sunspots during 1645-1715.
Full announcement here.
The sun’s magnetic field has a great influence on global temperature because it affects cloud cover. More on that later.
The graphics below show, first, reconstruction of solar maxima and minima. That is followed by several temperature reconstructions for approximately the same period.
You can see that the Maunder Minimum, part of the period called “the little ice age,” is a cold period in all the reconstructions. The Maunder Minimum, from 1645-1715 was a time of severe winters in Europe and North America, cold that caused many hardships. Rivers that were normally ice-free froze and snow fields remained at low altitudes.
The sun goes through cycles of solar intensity and magnetic flux. When the cycles are in a strong phase, the amount of cosmic rays entering the atmosphere is reduced, there are fewer clouds to block the sun, so it is warmer. When solar cycles wane, as is beginning to happen now, more cosmic rays enter the atmosphere and produce more clouds that block the sun, so it becomes cooler. The number of sunspots (hence magnetic flux) varies on an average cycle of 11 years. There are also 87-year (Gliessberg) and 210-year (DeVriess-Suess) cycles in the amplitude of the 11-year sunspot cycle which combine to form an approximately 1,500-year cycle of warming and cooling as seen on the graphic below.