The sun begins to rise again.
An international panel of scientists announced on Tuesday that the sun had come out of the quiet part of its 11-year sunspot cycle and had now entered the 25th numbered cycle. (The numbering of sunspot cycles dates back to 1755.)
The researchers predicted that the coming cycle would be pretty quiet.
Solar scientists track the cycle through the ebb and flow in the number of sunspots, reflecting the level of hardness in the sun’s magnetic fields. Sunspots can shoot out of radiation called solar rays as well as giant eruptions of particles known as coronal mass emissions. If a giant coronal mass ejection hit Earth, it could elevate modern civilization, knock out satellites, and inflict continental power outages.
Just as economists wait months to declare the onset or end of a recession, researchers delay such statements for solar cycles because they average the sunspot over 13 months to avoid being fooled by short-term fluctuations in solar activity. Nine months ago, in December, the sunspot cycle reached its calmest state.
“Since then, it has been slowly but steadily increasing,” said Lisa Upton, a solar scientist at the Space Systems Research Corporation and co-chair of the Solar Cycle 25 Prediction Panel, which is sponsored by NASA and the National Oceanic and Atmospheric Administration.
Over the last half century, solar cycles have gradually weakened, leading some researchers to speculate that the sun may be heading for a longer quiet period. The last solar maximum with an average sunspot number of 114 was the weakest since 1928 and the fourth weakest ever.
The prediction panel expects that the activity during this solar cycle will be well below average with a peak of 115 in the sunspot number, give or take 10. It would be about the same as the last cycle. The maximum is expected to occur in July 2025.
“If this turned out to be true, this would make Cycle 25 almost identical to Solar Cycle 24,” said Douglas A. Biesecker of the Space Weather Prediction Center in Boulder, Colo., The other chairman of the panel. A very active cycle reaches a sunspot number greater than 200, he said.
Forecasts from individual researchers still vary widely, with some predicting an even quieter cycle and others predicting a rebound to higher levels. But Dr. Upton and Dr. Biesecker said the panel reached a consensus fairly easily and relied on models that use measurements of the magnetic fields in the sun’s polar regions to deduce what would happen in the coming years.
“We have become very good at modeling the evolution of the polar magnetic fields,” said Dr. Upton. “This is one of the best indicators of amplitude of the coming cycle and was one of the key features that the prediction panel looked at.”
She said there were other indicators that this cycle would remain quiet, including a large number of spotless days below the solar minimum. But if the sunspot cycle in the coming months ramps up faster than expected, it would be a sign that experts might be underestimating the intensity of the coming cycle, she said.
Even during weaker solar cycles, the sun can release giant explosions. In 2012, an eruption competing with the Carrington event broke out of the sun’s surface – but fortunately it was not aimed at Earth.
Still, a quieter chance increases that our planet will not be hit by a solar catastrophe for the next 11 years.