Storms from the Sun: How they Form and What they Do

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A view of the Sun from the Solar Dynamics Observatory. The arching prominence at the top right is an outburst of solar plasma following along magnetic field lines. The bright areas are sunspots. NASA/SDO

Solar storms are the most fascinating and dangerous activities our star experiences. They lift off the Sun and send their fastest particles sleeting radiation across interplanetary space.  Very strong ones affect Earth and the other planets within a matter of minutes or hours. These days, with a flotilla of spacecraft studying the Sun, we get very quick warnings of upcoming storms. This gives satellite operators and others a chance to get ready for any "space weather" that may occur as a result.

The very strongest storms can do great damage to spacecraft and humans in space, and affect systems right here on the planet.

What Effects do Solar Storms Have?

When the Sun acts up, the result can be as benign as a great display of northern and southern lights, or it can be much worse. The charged particles released by the Sun have various effects on our atmosphere. At the height of a strong solar storm, these clouds of particles interact with our magnetic field, which causes strong electrical currents that can damage technology we depend on each day.

At the worst, solar storms have knocked out power grids and disrupted communications satellites. They can also bring communications and navigation systems to a halt. Some experts have testified before Congress that space weather affects people's ability to make phone calls, use the Internet, transfer (or withdraw) money, travel by plane, train, or ship, and even use GPS to navigate in cars.

So, when the Sun kicks up a little space weather due to a solar storm, it's something people want to know about. It can seriously affect our lives.

Why Does This Happen?

The Sun goes through regular cycles of high and low activity. The 11-year solar cycle is actually a complex beast, and it's not the only cycle the Sun experiences.

There are others that track other solar fluctuations over longer time periods, too. But, the 11-year cycle is the one that is most associated with the kinds of solar storms that affect the planet.

Why does this cycle occur? It's not completely understood, and solar physicists continue to debate the cause. the solar dynamo is involved, which is the interior process that creates the Sun's magnetic field. What drives that process is still under discussion. One way to think of it is is that the internal solar magnetic field gets twisted as the Sun rotates. As it becomes entangled, magnetic field lines will pierce the surface, prohibiting hot gas to rise to the surface. This creates points that are relatively cool compared to the rest of the surface (roughly 4500 Kelvin, compared to the Sun’s normal surface temperature of about 6000 Kelvin).

These cool points appear nearly black, surrounded by the yellow glow of the Sun. These are what we commonly call sunspots. As charged particles and heated gas stream from these sunspots, they create the brilliant arcs of light known as prominences. These are a normal part of the Sun's appearance.

The solar activities that have the most potential for destruction are solar flares and coronal mass ejection.

These incredibly powerful events result from these twisted magnetic field lines reconnect with other magnetic field lines in the atmosphere of the Sun.

During large flares, the reconnection can generate such energy that particles are accelerated to a high percentage of the speed of light. Causing an incredibly high flux of particles to stream toward the Earth from the Sun’s corona (upper atmosphere), where temperatures can reach into the millions of degrees. The resulting coronal mass ejection sends huge amounts of charged material out to space and is the type of event that currently worries scientists around the world.

Could the Sun Erupt in a Major Solar Storm in the Future?

The short answer to this question is "yes. The Sun goes through periods of solar minimum — a period of inactivity — and solar maximum, its time of highest activity.

During solar minimum, the Sun doesn't have as many sunspots, solar flares, and prominences.

During solar maximum, these sorts of events can occur frequently. It's not only the frequency of these events that we need to be worried about but also their intensity. The more intense the activity, the more potential for damage there is here on Earth. 

Scientists' ability to forecast solar storms is still in its infancy. Clearly, once something erupts from the Sun, scientists can issue a warning about increased solar activity. However, predicting exactly when an outburst will occur is still very difficult. Scientists track sunspots and give warnings if a particularly active one is aimed at Earth. Newer technology now allows them to track sunspots on the "back side" of the Sun, which helps with early warnings about the upcoming solar activity. 

 

Edited by Carolyn Collins Petersen