Sunspots and Solar Flares: Understanding Solar Activity


By Emily LevesqueUniversity of Washington

Studying the Sun can tell us a great deal about stars as a whole, but it can also give us crucial information about the Sun itself, information that might prove particularly valuable to anyone. The magnetic field of the Sun holds crucial clues for understanding solar activity. If you’ve ever heard about sunspots, or a solar flare, then you have some familiarity with what solar activity means.

A massive sun eruption in March 2012
The Sun’s magnetic field gives multiple clues to understand solar activity. (Image: NASA/SDO/AIA/Goddard Space Flight Center/Public domain)

How Sunspots Form

Sunspots are cool patches that sometimes appear on the Sun’s surface, showing up as dark spots thanks to their lower temperatures. We think that sunspots form because of the Sun’s tangled magnetic field lines. To understand how these happen, take a look at the Sun with standard magnetic fields drawn, connecting its north and south magnetic poles. It’s a simple illustration, and the magnetic field lines look nice and neat, but we’ve forgotten something: the Sun spins. It also spins at different rates, with the equator moving faster than the poles. This varying rotation distorts and curves the Sun’s magnetic field lines.

The Sun’s magnetic field
It appears that sunspots occur due to the Sun’s tangled magnetic field. (Image: NASA Goddard Space Flight Center from Greenbelt/Public domain)

You can try something similar by picking up a piece of string and twisting it between your fingers in opposite directions. Eventually, you’ll see twisted loops pop out of the increasingly twisted string. Those loops that you’ve made are a pretty good representation of how the Sun’s magnetic field can cause sunspots. 

Sunspots Come in Pairs

Those magnetic field loops will sometimes protrude through the Sun’s surface, producing cool spots where they poke through, which we see as sunspots. This is why sunspots tend to come in pairs; you’ll see one spot associated with the end of the loop that’s closer to the northern magnetic pole, and another for the southern magnetic pole.

The number of sunspots on the Sun’s surface increases and decreases on an 11-year cycle. The sunspots themselves make very little difference to anyone on Earth—they have only an extremely tiny effect on the Sun’s brightness. 

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Understanding Solar Activity

Solar activity is worth understanding for another reason. The solar activity cycle also associates with the number of solar flares and coronal mass ejections that we see from the Sun.

Solar flares are eruptive phenomena that emit light and charged particles; spectacular events that, if they’re strong enough, can disrupt satellite communications. Coronal mass ejections have the potential to cause even more problems. These are explosions of material in the Sun’s atmosphere that can transport an immense burst of particles from the Sun’s corona hurtling toward Earth.

Understanding solar activity—the Sun’s physical properties, its magnetic field, its corona, and the workings of its interior and surface—is crucial both for our understanding of solar physics and for our potential to analyze and anticipate things like solar flares and coronal mass ejections.

Studying the Sun

Today, astronomers are studying the Sun in a myriad of different ways. We lead expeditions to observe solar eclipses, using neutrino detectors and specialized telescopes to keep an eye on the Sun inside and out, and we’re even sending space probes to get incredible new and close-up views of the Sun. We still have a lot of questions left to answer about the Sun, but it certainly offers us a wealth of data to work with.

The Sun is so important to us in part because it’s our Sun: our closest star, the object that gave rise to the entire solar system that we call home. But what about other planets, ones far beyond our own solar system that might see another star as a Sun?

The Carrington Event

Solar astronomer Richard Carrington recorded a massive blast of solar activity in 1859 that became known as the Carrington Event. He first noted a large number of sunspots on the Sun’s surface, followed by an enormous geomagnetic storm. At the time the telegraph was the most widely used form of long-distance communication, and the storm was powerful enough to wreak havoc with the system. 

A vintage drawing of sunspots by Richard Carrington from 1859
The Carrington Event was powerful enough to affect the telegraph system of that time. (Image: Richard Carrington/Public domain)

Some telegraph operators were shocked by their equipment and communication towers hurled sparks. In desperation some operators turned off their haywire equipment, only to realize that the telegraphs kept working even after being unplugged, suggesting that an eerie amount of charge was still present even in the ambient air.

Now imagine something on the scale of the Carrington Event happening today, in a world where we’re incredibly reliant on satellite communications and electronics! Even with solar astronomers closely watching the Sun, we wouldn’t have much warning and there’s not much we can do! 

Currently, emergency plans focus mostly on what to do in the aftermath, setting up emergency equipment to get our power grid back up and running. Until we can predict events like this well in advance and execute emergency shutdowns to keep our satellites and electronics safe, we’re stuck with watching and waiting.

Common Questions about Understanding Solar Activity

Q: What is the solar activity cycle associated with? 

Solar activity is associated with coronal mass ejections. These are eruptive explosions in the Sun’s atmosphere, sending massive blasts of charged particles toward the Earth. Solar activity is also related to solar flares, which are eruptive events capable of releasing charged particles and light.

Q: Why is it crucial to understand solar activity?

Solar activity is worth understanding as it helps us understand solar physics. It also gives us the ability to predict and explain eruptive events such as solar flares and coronal mass ejections because they can impact our lives on Earth.

Q: What was the Carrington Event?

In 1859, astronomer Richard Carrington recorded an immense burst of solar activity that later became known as the Carrington Event. During this event, which was very strong, telegraph communication was widely impacted because of a massive amount of charged particles were present in the ambient air.

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