Sunspots can create beautiful auroras

Sunspots are by far the most remarkable of all solar features.

Long before telescopes were invented, sightings of dark areas on the sun's surface were abundant in ancient Chinese books, which were easier to see when the sun's rays were dimmed by clouds or smog, especially at sunrise and sunset. Ancient Chinese often referred to these black areas as "flying birds".

When Galileo looked directly at the sun with his crude homemade telescope in 1610, he was blind for a week and his vision was permanently damaged. But he found a solution: he darkened the entire room, placed a telescope through an opening in the blinds, and projected an image of the sun onto a piece of paper. In this way he can safely take images of the sun and track sunspots. During consecutive days of observation, the sunspot crossed the sun's surface, disappearing on one side and reappearing on the other. Obviously the sun revolves on an axis just like the earth does.

From sunspot observations, scientists have deduced that the sun spins fastest at the equator, where it takes only 25 days to turn, compared to 29 days at the poles.

The difference

Sunspots first appear to be black holes carved into the surface of the sun. The surface of the sun (called the photosphere) is about 11, 000 degrees Fahrenheit (6, 100 degrees Celsius). But sunspots are relatively cool, averaging around 8,000 degrees Fahrenheit (4,400 degrees Celsius). Because of its lower temperature, its area will appear black compared to the surrounding area of the sunspot, so it will emit less light on the sun's surface.

There is no doubt that if you could somehow peel a sunspot off the sun's surface and place it independently in the sky, it would be as bright as the moon at full moon.

The irregular black center of a sunspot, or umbra, can range in diameter from about 900 miles (1,400 kilometers) to more than 50,000 miles (80,000 kilometers). It's surrounded by a relatively dark area called the penumbra. The penumbra is usually more than twice the size of a sunspot, which can easily cover up to 20 Earths. The dots frequently travel in pairs or clusters of incandescent gas. They grow quickly and then fade away.

Sunspots appear as dark spots on a chaotic surface.

Photo source: NASA

Magnetic storm

Although astronomers have been studying sunspots for hundreds of years, the exact cause of sunspots remains a mystery. They have very strong magnetic fields and can develop into solar storms, which may be caused by even stronger cyclical changes. On Sept. 1, 1859, the English astronomer Richard C. Carrington was routinely mapping sunspots. To reduce the blinding brightness of the sun, he filtered images of the sun from his telescope. Suddenly, two bright points of light appeared in the middle of a sunspot cluster.

At first Carrington thought there was a gap in his filter that allowed the sun's rays to pass through, but the spots of light grew brighter and brighter. This made him the first person to witness a solar flare. Solar flares are geysers of hot gas that occur on the sun's surface caused by a sudden release of energy. In a matter of minutes, the magnetic needles at every observation station around the world failed and began to dance wildly.

Newly captured solar flare image on May 10, 2022.

Photo source: NASA

The relationship between solar flares and sunspots has since been established. In most cases, solar flares are bigger where there are more spots. Usually shortly after a flare erupts, large streams of charged particles rocket through interstellar space at 2 million miles per hour (3.2 million kilometers per hour) or more, eventually colliding with thin gas in the upper atmosphere. This gas burns into a colorful "battlefield" of arcs of flowing light known as the northern lights.

Most auroras are seen near the magnetic poles of the Earth's North Pole, but in rare cases, thanks to a large sunspot or solar flare, they can be seen as far as Canada and the central United States or even as far south as the United States. (The Aurora borealis produced by Carrington's flare was also visible farther south in the Caribbean!) But with this spectacular display in the sky, this electromagnetic disturbance sends power surges into the Earth's atmosphere, which can not only block radio communication but also cause utility circuit breakers to trip and cut off power. In March 1989 Quebec, Canada, suffered such an emergency and lost power for nine hours.

The aurora.

Photo source: Wikipedia

Spot of periodicity

Heinrich Schwabe of Dessau, Germany, was the man who discovered the solar cycle. At first he wanted to complete his daily observations of the sun, which he had begun in 1825, in the hope of discovering a planet in Mercury's orbit that crossed the solar disk. Unfortunately, the planet didn't exist, but during his 17 years of observation, Schwabe wrote down the shape of every sunny solar disk, and recorded every dot and speck he could see, no matter how big or small. Gradually, Schwabe discovered a unique cycle -- an 11-year cycle of rising and falling sunspot activity. Since then, just about anything imaginable has been linked to the 11-year sunspot cycle: stock markets, wars, pandemics, whisky prices and even the fertility rates of Canadian fur-bearing animals.

Sunspot butterfly diagram.

Photo source: NASA

Do sunspots affect our climate?

Some scientists think that sunspots affect our climate. In the late 1800s, two astronomers, Edward Maunder and Gustav Sporer, published a paper suggesting that the period from 1645 to 1715 was extremely rare for sunspot activity. Interestingly, this 70-year interval coincided with the middle of the "Little Ice Age," a period when Europe and North America were experiencing cold temperatures well below average.

Over the past few decades, however, astronomers have noticed that the sun is experiencing an unusually long period of sunspot-free activity, with the number of sunspots falling 36 percent below normal even during the sun's peak year, 2014. Some think we're at the beginning of another period of sunspot inactivity similar to what happened 375 years ago, with the end result being another period of unusually cold weather known as global cooling.

But many environmentalists argue the exact opposite, pointing out that the Little Ice Age, which occurred in the late 17th and early 18th centuries, was more likely caused by unusually high levels of global volcanic activity. Volcanic activity sent huge clouds of ash floating in the atmosphere. According to NASA, these clouds act as a shield that shines through the atmosphere and reduces sunlight, which should be the most likely cause of the Little Ice Age.

At any rate, this is still a controversial issue.

A new tool for solar forecasting

The Space Environment Center changed its name to the Space Climate Prediction Center in 2007, and it recently added a new, first-of-its-kind space weather prediction model to its suite of work, which aims to improve forecasting capabilities and further protect the United States from hazardous weather from space.

The new tool, called the Whole Atmosphere Model-Ionospheric Plasma Spheroelectrodynamics (WAM-IPE) space-weather Prediction model, will predict how Earth's upper atmosphere will react to solar and geomagnetic storms. It will help predict the total electron content, which is important data for communication and navigation systems. This new central density field product will be useful for satellite operators and ground tracking systems for orbit prediction and space situation awareness.

The latest output of this model is available on the official website of the Space Climate Prediction Center (SWPC).

"Only inadequate preparation allows severe weather to wreak havoc." Said Jake Bleacher, chief scientist at NASA's Human Exploration and Mission Operations Agency. "Space weather is just that -- it's our job to be prepared."

Image of the interior office of the Space Climate Prediction Center

Photo source: NOAA

Conflicting predictions

Solar activity bottomed out in December 2019, marking the start of a new sunspot cycle -- Cycle 25. The latest forecast is that activity will peak around mid-2025. But even so, not all solar scientists can agree on how high its peak will eventually be. The current consensus is that Cycle 25 starts low, but it will eventually see a sunspot peak between 95 and 130. This figure is well below the average periodic sunspot number between 140 and 220.

However, a paper published in the journal Heliophysics in November 2020 predicts the exact opposite. Its predictions suggest that the intensity of cycle 25 is strong enough to compare with some of the highest on record.

So we'll just have to wait and see what happens in the next few months and years. But even if it really is a below-average solar cycle, that doesn't mean there's no risk of extreme weather in space. "The sun's impact on our daily lives is real and tangible. The Space Climate Prediction Center can be staffed 24 hours a day, seven days a week, 365 days a year, precisely because the sun always provides us with something predictable." Doug Biesecker, a solar physicist at the Space Climate Prediction Center.