The Sun Is Changing Because of a Solar Minimum, and Here's How It Works

The sun is changing.

These changes aren't visible to the naked eye, but after one good look under a properly filtered telescope, you'll see it: The mini-magnetic explosions that occur continually on the star's surface, known as sunspots, are diminishing. That's because the sun is on the brink of a period known as a solar minimum, according to NASA, something that occurs every 11 years.

Although a reduction of sunspots means fewer flashes of X-rays and extreme ultraviolet radiation to the Earth's atmosphere, the changes don't necessarily mean that the sun is less active. While the sunspots are diminishing, another type of solar activity is starting to take form.

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"During [a] solar minimum," Dean Pesnell of NASA's Goddard Space Flight Center explained to Phys.org on Wednesday, "we can see the development of long-lived coronal holes." These are the large areas across the sun's atmosphere that release solar particles from the star. During the total solar eclipse on August 21, viewers will have the rare chance of viewing the coronal holes in action, with the proper telescope, of course.

"We see these holes throughout the solar cycle, but during solar minimum, they can last for a long time—six months or more."

A solar minimum won't necessarily significantly affect the way people experience the sun here on Earth. But it does create changes in space weather that can result in disturbances to the Earth's magnetosphere, which in turn can lead to disruptions in communication and navigation systems like satellites and other devices floating around in space.

During a solar maximum, when sunspots are at their highest levels of activity, ultraviolet radiation from the star causes satellites traveling in low Earth orbit to experience friction. The friction creates a drag, which causes satellites to lose their speed over a period of time and fall back down to Earth. The drag also helps keep space junk including natural and man-made particles away from the Earth's atmosphere.

But when the sun is in solar minimum, space weather has the potential to limit the amount of drag, which leads to a higher chance of space junk remaining in the Earth's atmosphere. The cycle can create heightened and more dangerous circumstances for astronauts traveling in space during this time period, Pesnell said.

There are missions in the works—like NASA's plans to send astronauts to Mars post-2020—but by the time the next major space exploration occurs, the sun will be headed toward the start of a new solar maximum.