The surface of the Sun is polarized by turbulent motions of gravity, plasma and magnetic fields, very similar to the weather on Earth and its behavior may appear unexpected with patterns that can be found upon closer inspection.
The first pattern observed on the surface of the Sun was the sunspot pattern. Sunspots were observed by some ancient astronomers, but they have been regularly studied since the 17th century.
And when astronomers counted the number of visible spots each year, they found that the sun goes through active years and quiet years. There is an 11-year cycle of rising and falling sunspots. And also other cycles, such as the Gleisberg Cycle, which lasts from 80 to 90 years.
These patterns resemble hurricane seasons in the American Midwest or the El Niño / La Niña cycles in the Pacific. These large patterns have a regularity that makes them easy to predict.
But while predicting sunspot cycles is relatively easy, predicting the appearance of a single sunspot is not.
One of the challenges with predicting sunspots is that we cannot place the sensors directly on the surface of the sun. It is difficult to measure the magnetic fields that create sunspots.
But astronomers learned that the sun can be studied using sound waves, and the technology began to allow them to predict individual sunspots. One project that studies the sun in this way is the Global Oscillation Network (GONG) group, made up of six solar telescopes that measure the movement of the sun’s surface around the clock, seven days a week.
The vibrations of the surface of the sun are caused by the movement of sound waves through the interior of the sun. Studying the sun in this way is known as “helioscience”.
While mainly used to study the interior of the sun, sound waves are also affected by surface features such as sunspots, and the GONG team recently used this feature to predict one of them.
About a week ago, the GONG team noticed that the solar acoustic vibrations appeared to be disrupted by a feature on the far side of the sun. They couldn’t see the feature, but it was compatible with that in sunspots.
So the team expected that the sunspot cluster could be seen from the ground on the famous Thanksgiving Day in the United States. And it turns out they were right.
This type of prediction is very useful, because large sunspots are often accompanied by other activities such as solar flares.
Extreme solar explosions can disrupt modern satellites like the Global Positioning System (GPS), and in extreme cases could threaten the collapse of our electrical grid. Anticipating these events several days in advance gives us time to mitigate their effects.
With more research, the GONG team and others may be able to predict the appearance of sunspots before they form. That should give us more than a week to prepare for any threat from solar flares.