The sun has been known as the source of light and heat and the source of life since ancient times. Plants are recalled from the Earth by its rays, bringing spring and bountiful harvests thereafter. When information about the use of compass magnets to determine the direction of north became widespread in China, it became clear that the Earth itself had mystical properties. In 1600, after using the western compass for centuries, Queen Elizabeth I’s personal physician, William Gilbert, published a book on magnets that described the entire Earth as a single entity.

American astrophysicist George Ellery Hale rose to fame in the mid-20th century by building the world’s largest telescope. Gale began his career studying the Sun and, using polarized light, showed that certain regions of the Sun were highly magnetic, with fields thousands of times stronger than those of the Earth. This magnetism was strongest in dark regions called sunspots.

In the 17th century, Galileo, using a newly developed telescope, discovered that the Sun was covered in spots. He observed many of the features of the Sun, including showing that it rotates every month and its size changes over time. Although Galileo did some experiments with magnets in the form of electromagnets used as rough compasses, he could not establish a definitive connection with sunspots.

Observed changes

Sunspots attracted the attention of astronomers and were closely observed as far back as 1645, thanks to the increasing availability and quality of telescopes. Despite intense interest in them, astronomers have not found a single sunspot during the 70-year period known as the Maunder minimum.

Then, in 1715, they began to mysteriously reappear. Since then, sunspots appear and disappear in a cycle lasting about 11 years, called the solar cycle; The number of sunspots varies from zero to one hundred. Until 1859, attempts to explain solar cycles by relating them to other cyclical events were considered astrological and an unreal connection between heaven and earth was assumed.

In 1859, wealthy brewery owner and amateur astronomer Richard Carrington was making a drawing of sunspots when, to his surprise, one of them suddenly changed from dark to light.

This explosive “solar flare” lasted only a few minutes, but for two days it was accompanied by a massive aurora and magnetic storm called the Carrington event. Generally confined to subpolar latitudes, the aurora borealis has been observed worldwide. This influenced the technology of the time: telegraph systems that worked without batteries or flashes.

Since no event of this magnitude has occurred since then, it is debated what impact such an event would have on our modern technology. But in 1859 it was not immediately clear whether the Sun and Earth were actually connected, and many people believed that the solar flare and the ensuing storm were connected merely by coincidence.

Effect of solar magnetism

Hale’s discovery of solar magnetism some 50 years after the Carrington event, together with records showing that the aurora borealis had an 11-year cycle similar to that of the Sun, formed the basis of our modern understanding of “sun-earth relations.”

This connection is basically based on magnetism. Sunspots themselves accumulate magnetic energy; pressure allows sunspots to be cooler and therefore darker than adjacent regions of the Sun’s light-emitting surface, or photosphere.

Under the right conditions, magnetic energy can be released in a variety of ways. Flashes of white light, such as the Carrington saw, are very rare; mostly magnetic energy is converted into X-rays.

Gravity near the Sun’s surface is about 30 times stronger than on Earth, so any movement caused by explosions rarely escapes. Instead, regions above sunspots can successfully eject huge clouds of gas into space, called “coronal mass ejections.” If you accidentally crash into the edge of our planet, it could cause polar storms.

Energy could flow into the circumstellar region if the magnetism of the active region around the spot creates a cloud of gas that reaches Earth in the opposite magnetic direction as discovered by Gilbert in 1600. This energy is stored on the night side, rather than on the side facing the Sun from which it came, causing the aurora borealis.

If the magnetic direction is not aligned, there may be some compression due to the hot, fast gas cloud, but nothing else. We are currently at or near an unexpectedly high peak of sunspots and will likely continue to be subject to major magnetic storms like the one in May 2024 for several years.

Beauty and danger coexist in these events, but they are absolutely fascinating.

Martin Connors, Professor of Astronomy, Mathematics and Physics, Athabasca University

This article is republished from The Conversation under a Creative Commons license. Read the original article.