The effects of the strongest solar storm since 2005 will be felt on Earth today – but what exactly will it do?

What is a solar flare?

According to NASA, a solar flare is a sudden, powerful burst of magnetic energy that has built up in the Sun's atmosphere. They are associated with sunspots, which are areas of intense magnetic energy that move over the surface of the Sun at a different temperature to the surrounding region.

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The solar flare observed late Sunday came from sunspot 1402, an area which has become increasingly active lately, Space.com reported. NASA observed it as an extreme ultraviolet flash. It has been classed a long-duration M9 solar flare, which according to SpaceWeather.com makes it almost an X-flare, the most powerful kind. Sunspot 1402 is on the side of the Sun facing Earth, which is why we are being affected by its activity.

What does it do?

Solar flares are sometimes associated with events called coronal mass ejections (CMEs), explosions in which billions of charged particles are blasted into space at high speed. NASA has detected a CME in this case, which it says it is traveling toward Earth at almost 1,400 miles per second.

When will it hit Earth?

The CME was predicted to reach the Earth's magnetic field at 9 AM EST on Jan. 24. SpaceWeather reported that it hit at approximately 10 AM EST, showing up as a huge surge in ground currents.

What will happen when it does?

A CME can disturb the Earth's magnetosphere – the magnetic "envelope" that surrounds the planet and protects us from most of the Sun's radiation. Depending on the direction from which solar magnetic energy arrives, it can interact strongly with the oppositely oriented magnetic field of the Earth, NASA says, causing Earth's field to be "peeled open like an onion." That allows charged particles to stream into Earth's atmosphere and rain down along magnetic field lines, which is known as a geomagnetic storm.

Is it dangerous?

Geomagnetic storms can interfere with technology, including satellites, radio communications and electric power grids. Last year, researchers predicted that a major event of this type could cause a widespread power outage – which, if it lasts, could lead to "disruption of the transportation, communication, banking and finance system, and government services; the breakdown of the distribution potable water owing to pump failure; and the loss of perishable foods and medications because of lack of refrigeration," according to the National Academy of Sciences.

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However, a spokesman for the National Oceanic and Atmospheric Administration's Space Weather Prediction Center told the BBC that the effects of this solar eruption seem likely to be moderate.

NASA has modeled the likely impact and decided that astronauts aboard the International Space Station do not need to take any precautionary action. On Earth, some international airlines have rerouted planes from polar areas to routes where radio communication is less likely to be affected by the geomagnetic storm, while people in South Africa – near where the Earth's magnetic field is weakest – have been advised to stay out of the sun this afternoon.

Can I see it?

The changes in the Earth's magnetic field are not visible, but solar storms can cause unusually intense Northern Lights. The phenomenon may also be visible further south than usual. SpaceWeather.com has photos of recent displays so you know what to look out for.

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