Home South pole ice Astro Bob: Solar Cycle 25 is on a roll – Reuters

Astro Bob: Solar Cycle 25 is on a roll – Reuters

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It wasn’t just my imagination. Sunspot and solar flare activity has increased faster than expected over the past year. We know that our star has its ups and downs. Every 11 years or so, sunspot numbers and solar storms peak, then fade and disappear before peaking again. Each cycle is numbered; the first, called Solar Cycle 1, began in February 1755 and ended in June 1766. We are now in Solar Cycle 25, which began in December 2019 and is expected to peak in July 2025.

On January 11, four sunspot groups applied freckles to the sun’s disk. The largest, active region 2924, clearly showed the “poles” or north and south polarities, with the main spot negative and the next positive. During the previous solar cycle, the poles of a similar group in the southern hemisphere of the sun would have been reversed.

Contribution / NASA, SDO

Sunspot groups are manifestations of strong magnetic fields and have magnetic poles just like magnets – positive and negative. During a cycle, the spot before will be the positive pole, and the spot (or spots) following the negative pole. When a new cycle begins, the poles reverse, and the lead spot becomes negative and the follower positive. Astronomers can spot the start of a new cycle by spotting the first spots that show this reversal.

In fall 2020, the Solar Cycle 25 Prediction Panel, an international panel of experts co-sponsored by NASA and NOAA, announced its prediction for the current solar activity cycle. Based on the observed trends, they predicted a fairly weak cycle similar to the previous one. But the sun has so far defied those projections. Instead, the number of sunspots, according to the Spaceweather website, has “exceeded forecasts for 15 consecutive months.”

Graph showing the average monthly sunspot number predicted for the current solar cycle
The red curve shows the average monthly sunspot number forecast 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 increased more sharply than expected (purple curve ). For an interactive version of this graph, go to www.swpc.noaa.gov/products/solar-cycle-progress.

Contribution / NASA, NOAA

Take a look at the graph. It plots the monthly number of sunspots as a function of time. The red curve is the prediction. You will notice that shortly after the minimum, the monthly sunspot count (black dots) is higher than expected, then jumps forward in late 2021. In December, the monthly predicted sunspot count was 27, but the actual number was 68, more than twice The forecasts. The last time the sun was so dappled was in 2015.

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

solar activity from 1610 to 2010
The cyclical nature of solar activity is clear in this timeline from 1610-2010. Early sunspot records 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.

Contribution / NASA, MSFC

If the trend continues, Cycle 25 could be a barn burner or at least better than “weak”. Powerful flares and coronal mass ejections have a good side and a bad side. Large storms can threaten poorly protected power grids and damage sensitive satellite electronics. On the other hand, they often lead to more frequent and intense aurora borealis and southern lights. Yeah, we’ll take that.

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

Sunspots

Sunspots often display a dark core or an umbra surrounded by a lighter penumbra. They appear dark because they are about 3,000° cooler than the surface of the sun, called the photosphere. Spots can be over 30,000 miles (50,000 km) wide. Earth-sized ones are quite common around the solar peak.

As the sun turns, sunspots accompany the journey and take about four weeks to make a full turn. Most groups are gone on the next rotation, but some can last up to around 100 days. Their appearance constantly changes as they struggle with the turbulent, super-hot solar surface that sizzles at around 10,000°F (5,500°C). Sunspots are several thousand degrees cooler than their surroundings, making them dim in comparison. In truth, they would shine brightly if we could see them separated 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 a suitable solar filter that fits in the front of your telescope.

Contributed / Bob King

Strong magnetic fields within sunspot groups temporarily insulate them from superheated plumes of glowing hydrogen gas bubbling from below. Tons of energy stored in these fields are sometimes released in breathtaking explosions called solar flares. This week (January 10-16), at least four clusters are visible in small telescopes fitted with an appropriate solar filter.

Drawing of sunspots by David Teske
Former Duluthian David Teske made this sketch of the sun and sunspots with a 2.4-inch telescope and a solar filter
on January 11, 2022.

Contributed / David Teske

My friend David has been drawing sunspots for decades. His meticulous work sharpened his eye for detail and informed him deeply about the volatility of the sun. Watching an astronomical object change is an exciting and rewarding experience, whether it’s cloud patterns on Jupiter, the light pulsing from a variable star, or checking the pulse of the sun through its sunspots.

“Astro” Bob King is a freelance writer for the Duluth News Tribune. Learn more about his work at

duluthnewstribune.com/astrobob

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