An unusually strong solar storm hitting Earth could cause northern lights in the United States (US) this weekend and potentially disrupt power and communications networks, the US National Oceanic and Atmospheric Administration (NOAA) said.
NOAA issued a geomagnetic storm warning when the effects of the solar explosion reached Earth on Friday afternoon, several hours earlier than expected.
The consequences will be felt on Earth over the weekend and possibly into next week. It is the first geomagnetic storm in almost 20 years.
NOAA warned operators of power plants and orbiting spacecraft to take precautions, as did the US Federal Emergency Management Agency (FEMA).
"Most people on Earth won't have to do anything," said Rob Stinberg, a scientist at the US NOAA.
The first effects of several coronal mass ejections (CMEs) -- ejecting plasma and magnetic fields from the Sun -- arrived early Friday afternoon ET, NOAA said.
Stronger geomagnetic storms are expected to persist through the weekend. They came as the Sun approaches the peak of an 11-year cycle that brings increased activity.
The storm could produce northern lights, also known as aurora borealis, that travel south to the US state of Alabama and northern California, NOAA said. But it is difficult to predict and experts have stressed that it will not be the dramatic curtains of color usually associated with the northern lights, but more like greenish flashes.
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"It's really a gift of space weather — the aurora," Stinberg said. He and his colleagues said the best views of the auroras can come from phone cameras, which capture the light better than the naked eye.
"Take a picture of the sky and you might get a gift for your eyes," said one expert.
The most intense solar storm on record, in 1859, caused auroras in Central America and possibly as far away as Hawaii, and NOAA expert Sean Dahl says that's not expected now but could be close.
The storm poses a risk to high-voltage transmission lines, not the power lines typically found in people's homes. Satellites can also be affected, which could then disrupt navigation and communication services on Earth.
An extreme geomagnetic storm in 2003, for example, caused power outages in Sweden and damaged electrical transformers in South Africa.
Even when the storm is over, signals between GPS satellites and receivers on the ground could be disrupted or lost, NOAA said, but experts say there are so many navigation satellites that any outages shouldn't last long.
The sun has been throwing off strong solar flares since Wednesday, causing coronal explosions.
It's all part of solar activity that intensifies as the Sun reaches the peak of its 11-year cycle.
The American space agency NASA announced that the storm does not pose a serious threat to the seven astronauts on the International Space Station. The biggest concern is increased radiation levels and the crew of the Station could be moved to a more shielded part of the station if necessary, experts said.
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