Last week, certain parts of the world were fortunate to glimpse the aurora borealis. If you have missed the spectacular sight, don’t worry. There is a possibility of another appearance as early as next month.

The aurora borealis, also known as the Northern Lights, grace the sky when charged particles from the sun journey through space and collide with the Earth’s atmosphere, resulting in mesmerising light displays. 

The vast sunspot cluster, which released energy and gas towards Earth a few days back, is expected to rotate back towards us in approximately two weeks, scientists say, as per BBC. They think it will still be big and complex enough to cause more explosions that could create more Northern Lights.

Since this past Saturday, the Sun has continued to emit heightened radiation levels. A significant solar flare occurred on Tuesday, disrupting high-frequency radio communications on a global scale. This particularly active sunspot is not an isolated event. The Sun is nearing what is referred to as “solar maximum” – a phase in its 11-year cycle when its activity is strongest. 

Last weekend’s Northern Lights were the result of a big solar storm, as reported by the US National Oceanic and Atmospheric Administration (NOAA). The storm was caused by a bunch of solar flares combining into a huge burst of solar plasma.

According to Sean Elvidge, a professor of space environment at the University of Birmingham, the geomagnetic storm that occurred last weekend was a once-in-30-year event and the most significant since 2003, reported BBC. It was triggered by at least five coronal mass ejections (giant bursts of charged particles). These CMEs took roughly 18 hours to travel from the Sun to Earth, where they interacted with our magnetic field, known as the magnetosphere.

According to Krista Hammond from the Met Office, the massive sunspot was about 15 times the size of Earth “on the Earth-facing side of the sun”, sending out a lot of solar flares and  CMEs, reported News Sky.

Some of these bursts met up with each other, making the resulting geomagnetic storm much stronger by the time it reached Earth. The intensity of the storm was so remarkable that it received a G5 alert rating, which is the highest designation given by forecasters at both the Met Office and the NOAA, as per BBC.

Rare severe solar storm could produce northern lights in the U.S., disrupt power and communications this weekend

NOAA alerted operators of power plants and spacecraft in orbit to take precautions, as well as the Federal Emergency Management Agency.

“For most people here on planet Earth, they won’t have to do anything,” said Rob Steenburgh, a scientist with NOAA’s Space Weather Prediction Center.

The storm could produce northern lights as far south in the U.S. as Alabama and Northern California, according to NOAA. But it was hard to predict and experts stressed it would not be the dramatic curtains of color normally associated with the northern lights, but more like splashes of greenish hues.

“That’s really the gift from space weather — the aurora,” said Mr. Steenburgh. He and his colleagues said the best aurora views may come from phone cameras, which are better at capturing light than the naked eye.

Snap a picture of the sky and “there might be actually a nice little treat there for you,” said Mike Bettwy, operations chief for the prediction center.

Also Watch: What causes the northern lights?

The most intense solar storm in recorded history, in 1859, prompted auroras in central America and possibly even Hawaii. “We are not anticipating that” but it could come close, said NOAA space weather forecaster Shawn Dahl.

This storm poses a risk for high-voltage transmission lines for power grids, not the electrical lines ordinarily found in people’s homes, Mr. Dahl told reporters. Satellites also could be affected, which in turn could disrupt navigation and communication services here on Earth.

An extreme geomagnetic storm in 2003, for example, took out power in Sweden and damaged power transformers in South Africa.

Even when the storm is over, signals between GPS satellites and ground receivers could be scrambled or lost, according to NOAA. But there are so many navigation satellites that any outages should not last long, Mr. Steenburgh noted.

The sun has produced strong solar flares since May 8, resulting in at least seven outbursts of plasma. Each eruption — known as a coronal mass ejection — can contain billions of tons of plasma and magnetic field from the sun’s outer atmosphere, or corona.

The flares seem to be associated with a sunspot that’s 16 times the diameter of Earth, according to NOAA. It’s all part of the solar activity that’s ramping up as the sun approaches the peak of its 11-year cycle.

NASA said the storm posed no serious threat to the seven astronauts aboard the International Space Station. The biggest concern is the increased radiation levels, and the crew could move to a better shielded part of the station if necessary, according to Mr. Steenburgh.

Increased radiation also could threaten some of NASA’s science satellites. Extremely sensitive instruments will be turned off, if necessary, to avoid damage, said Antti Pulkkinen, director of the space agency’s heliophysics science division.

Several sun-focused spacecraft are monitoring all the action.

“This is exactly the kinds of things we want to observe,” Mr. Pulkkinen said.