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Astro Bob: Solar Cycle 25 is on a hot streak

Flares and sunspots have been more frequent than predicted in the current solar cycle, offering an optimistic outlook for auroras in the next few years.

Ice Lake Superior 15 below Jan 10 2022 Stoney Point Sun in steam
The sun rises through wispy clouds formed by water vapor condensing in 15°-below-zero-air over Lake Superior on Monday, Jan. 10. Enhanced activity in the current solar cycle bodes well for aurora-watchers.
Contributed / Bob King
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It wasn't just my imagination. Sunspot and solar flare activity have ticked up more quickly than anticipated in the past year. We know our star has its ups and downs. About every 11 years, sunspot numbers and solar storms peak, then fade and disappear before cresting again. Each cycle is numbered; the first, called Solar Cycle 1 commenced in February 1755 and ended in June 1766. We're now into Solar Cycle 25, which began in December 2019 and is predicted to reach maximum in July 2025.

four sunspot groups
On Jan. 11, four sunspot groups freckled the solar disk. The largest one, active region 2924, clearly showed north and south "poles" or polarities, with the leading spot negative and the follower positive. During the previous solar cycle, the poles in a similar group in the sun's southern hemisphere would have been reversed.
Contributed / NASA, SDO

Sunspot groups are manifestations of powerful magnetic fields and have magnetic poles just like magnets — positive and negative. During one cycle, the leading spot will be the positive pole, and the following spot (or spots) the negative pole. When a new cycle begins, the poles switch, and the lead spot becomes negative and the follower positive. Astronomers can pinpoint the start of a new cycle by identifying the first spots that show this reversal .

Back in the fall of 2020, the Solar Cycle 25 Prediction Panel, an international group of experts co-sponsored by NASA and NOAA, announced their prediction for the current solar activity cycle. Based on observed trends they predicted a fairly weak cycle similar to the previous one. But the sun has so far defied those projections. Instead, sunspot numbers, according to the Spaceweather website, have "exceeded predictions for 15 straight months."

Graph showing predicted average monthly sunspot number for the current solar cycle
The red curve shows the predicted average monthly sunspot number for the current solar cycle, which is expected to peak in July 2025. Since the last solar minimum, the number of sunspots and solar flares has been rising more sharply than predicted (purple curve). For an interactive version of this graph, go to www.swpc.noaa.gov/products/solar-cycle-progression.
Contributed / NASA, NOAA

Take a look at the graph. It plots monthly sunspot numbers against time. The red curve is the prediction. You'll notice that soon after minimum, the monthly sunspot count (black dots) run higher than expected and then really take a leap in late 2021. In December, the predicted monthly sunspot number was 27, but the actual number was 68, more than twice the forecast. The last time the sun was this speckled was back in 2015.

Around solar minimum, the sun can be spotless for many weeks. But in a sign of good things to come, the year 2021 saw just 64 spotless days and nearly three times as many geomagnetic storms compared to 2020.


solar activity from 1610-2010
The cyclic nature of solar activity is clear in this timeline from 1610-2010. Early records of sunspots show that the sun went through a period of inactivity in the late 17th century called the Maunder Minimum. Very few sunspots were seen on the sun from about 1645 to 1715.
Contributed / NASA, MSFC

If the trend continues, Cycle 25 might be a barn burner or at least better than "weak." Powerful flares and coronal mass ejections have a good side and a bad side. Big storms can threaten poorly protected power grids and damage sensitive satellite electronics. On the flip side, they often lead to more frequent and intense northern and southern lights. Yeah, we'll take that.

Then there's the joy of observing sunspots.. No need to drive anywhere for dark skies. Just set up a telescope (covered with a safe solar filter, of course!) in the sunshine. At first glance, sunspots look like dark bugs on the sun's face, but a closer look reveals their two-part structure. Larger spots exhibit a dark core called an umbra encircled by pale, outer fringe with a cross-hatched texture called the penumbra.

Sunspots often display a dark core or umbra surrounded by a lighter penumbra. They appear dark because they're about 3,000° cooler than the sun's surface, called the photosphere. Spots can grow up to more than 30,000 miles (50,000 km) wide. Ones the size of the Earth are fairly common around solar peak.

As the sun rotates, the sunspots go along for the ride and take about four weeks to make a complete spin. Most groups are gone by the next rotation, but some can last up to about 100 days. Their appearance changes constantly as they grapple with the turbulent and super-hot solar surface which sizzles at around 10,000° F (5,500° C). Sunspots are several thousand degrees cooler than their surroundings, which makes them look dark in comparison. In truth, they would shine brilliantly if we could see them separate from the sun.

telescope and solar filter
Observing sunspots and other solar phenomena is fun, easy and safe to do. All you need is a telescope and an appropriate solar filter that fits over the front of your telescope.<br/>
Contributed / Bob King

Powerful magnetic fields within sunspot groups temporarily insulate them from the superheated plumes of incandescent hydrogen gas bubbling up from below. Oodles of energy stored in those fields are sometimes released in mind-boggling explosions called solar flares. This week (Jan. 10-16), at least four groups are visible in small telescopes fitted with a proper solar filter .

David Teske sunspot drawing
Former Duluthian David Teske made this sketch of the sun and sunspots with a 2.4-inch telescope and solar filter<br/>on Jan. 11, 2022.
Contributed / David Teske

My friend David has been sketching sunspots for decades. His careful work has sharpened his eye for detail as well as deeply informed him of the sun's volatility. Watching an astronomical object change is exciting and gratifying experience, whether it be cloud patterns on Jupiter, the light pulsations of a variable star or checking the sun's pulse through its spots.

"Astro" Bob King is a freelance writer for the Duluth News Tribune. Read more of his work at duluthnewstribune.com/astrobob .

"Astro" Bob King is a freelance writer and retired photographer for the Duluth News Tribune. You can reach him at nightsky55@gmail.com.
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