The sun will be cooler and dimmer a few decades from now as researchers predicted that it might emit less radiation by the mid-century.
Grand Minimum
Scientists said that the cooldown would happen because of the "grand minimum," a period when sunspots form less frequently, the Sun's magnetism is reduced, and less ultraviolet radiation makes it to the surface of our planet. Scientists think this event is triggered at irregular intervals by random fluctuations linked to the magnetic field of the sun.
Dimming Of the Sun during the Next Grand Minimum
Physicist Dan Lubin, from Scripps Institution of Oceanography, and colleagues predicted a significant probability of a grand minimum occurring in the near future because of the downward sunspot pattern they observed in recent solar cycles that resembles those in the past grand minimum events. They were also able to estimate how much dimmer the sun would likely be during the next grand minimum.
In their study published in the Astrophysical Journal Letters, the researchers Lubin and colleagues studied almost 20 years of data collected by the International Ultraviolet Explorer satellite mission. They compared the radiation emitted by stars that are similar to the sun and identified which ones were experiencing grand minimum to get an idea of the extent the sun would dim in the next grand minimum.
Cycle of Peaks and Declines
The sun goes through an 11-year cycle in which its ultraviolet radiation peaks and declines because of sunspot activity. The researchers estimated that the UV radiation is reduced by 7 percent more than the lowest point of the cycle when a grand minimum takes place.
“From this linear regression we estimate a range in UV flux of 9.3 percent over solar cycle 22 and a reduction of 6.9 percent below solar cycle minimum under a grand minimum. The 95 percent confidence interval in this grand-minimum estimate is 5.5 percent to 8.4 percent,” the researchers wrote in their study.
What Happens During A Grand Minimum?
What happens during a grand minimum, when the sun is expected to be dimmer and cooler? The reduced energy produced by the sun will result in the thinning of the stratospheric ozone layer. The thinning will change the temperature structure of the stratosphere, which then affects the dynamics of the lower atmosphere, particularly the weather and wind patterns.
The cooling is not the same globally. During the Maunder Minimum, also called the “prolonged sunspot minimum” because sunspots became exceedingly rare when it occurred between 1645 and 1715, areas in Europe chilled, but southern Greenland and Alaska warmed.