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Space and Physics

The Sun's Quietest Period Is Finally Upon Us

author

Dr. Alfredo Carpineti

Senior Staff Writer & Space Correspondent

clockDec 16 2019, 15:03 UTC

Ultraviolet image of the Sun from earlier today. SDO/NASA

In 2019, the Sun's surface was free of sunspots for 270 days, that’s about 77 percent of the year without any dark blotches. And that has an important implication – the solar minimum is about to happen.

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The Sun's activity is not constant but rather cycles through active and quiet periods about every 11 years. The minimum and maximum are defined statistically based on the average activity over the past 12 months, and solar scientists have recently updated the forecast regarding the current and upcoming solar cycle. The next solar minimum will happen in April 2020 plus or minus six months, so we are well within the range.

The solar minimum will mark the end of the 24th solar cycle on record, which has certainly been a curious one being among the weakest ones in the last 80 years, and if the forecast is correct cycle 25 will be equally weak peaking in July 2025 with an average of 115 sunspots over that period.

“It now looks like the latest cycle of activity on the Sun, cycle 24, is coming to a close after just over 11 years. That’s not so remarkable, but what has been remarkable is that the cycle had much less activity (many fewer sunspot regions) than the recent previous cycles did,” Dr David Williams, an instrument operations scientist for the ESA Solar Orbiter mission, told IFLScience. “All through the space age, the Sun had highly active cycles, so now we’re asking: was cycle 24 the exception in history, or the norm? Either way, it challenges our models of what we think is going on in the invisible interior of the Sun, where the magnetic field has to be generated.”

Solar Cycle 25 forecast. NOAA/NASA

Sunspots are regions on the Sun's surface that are colder than the surrounding areas, although still in the thousands of degrees. The formation of these spots is regulated by the intense magnetic field of our star. The field also shapes the solar corona (the outermost part of the Sun's atmosphere), and is responsible for flares and the interplanetary storm of particles that can damage technology and produce aurorae. Knowing what's going on is crucial to our civilization.  

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“If we don’t understand something, it means there’s information missing," Dr Williams continued. "In the case of the Sun, we have two important pieces of information missing: what happens in the deep interior where we think the magnetic field mostly comes from; and what happens to the magnetic field at the surface when it’s dragged by surface currents towards the poles of the Sun?” 

The European Space Agency’s Solar Orbiter, which will launch in February, and NASA’s Parker Solar Probe currently in orbit around the Sun, will work in tandem to provide answers to these mysteries. By the peak of the next cycle, we might finally know what’s going on.


Space and Physics