THE biggest solar storm in two decades could wipe out GPS satellites and power grids today, space weather forecasters have warned.
A severe geomagnetic storm alert has been issued by the National Oceanic and Atmospheric Administration (NOAA) - the first since 2005.
The powerful solar storm is expected to reach Earth on Friday, the US agency said.
And it warned the "unusual event" could disrupt GPS satellites, power grids, electronic devices - including mobile phones - and the internet as early as 12pm ET (5pm UK time).
It could also cloak parts of the world in a "spectacular display" of light, known as an aurora or the Northern Lights.
Stormy gales wash walrus and seals ashore as urgent warnings for SNOW issued
The UK's Met Office said there is "a chance that aurora may become visible to all parts of the UK".
The rare storm alert comes after a series of "strong" solar flares - large explosions in the sun's atmosphere - that started on Wednesday.
Space weather watchers spotted five huge explosions of plasma from the sun - and it's these "mass ejections" that can cause geomagnetic storms when they reach Earth and disturb the magnetic field.
Scientists expect the eruptions to "merge and arrive at Earth" late on Friday or early Saturday.
Incredible photos showed sunspots "the size of 15 Earths" unleashing the solar flares that sparked the severe storm alert.
NOAA's Space Weather Prediction Center said it "is monitoring the sun following a series of solar flares and coronal mass ejections that began on May 8".
"Space weather forecasters have issued a Severe (G4) Geomagnetic Storm Watch for the evening of Friday," it said.
"Additional solar eruptions could cause geomagnetic storm conditions to persist through the weekend."
The agency warned that the geomagnetic storms "can impact infrastructure in near-Earth orbit and on Earth's surface" - and "potentially communications, the electric power grid, navigation, radio and satellite operations".
It also could "wipe out the internet" - meaning it may affect use of mobile phones, scientists warned.
Skiers in Austria make the most of the little snow left as slopes melt
The Space Weather Prediction Center "has notified the operators of these systems so they can take protective action".
Professor Peter Becker of George Mason University explained there is only a short amount of warning for when the solar storms will head to Earth after flares begin.
“We can tell when they're actually going to head towards Earth,” Becker said, Fox Weather reported.
“And that gives us about 18 hours of warning, maybe 24 hours of warning, before those particles actually get to Earth and start messing with Earth's magnetic field."
The last time the agency issued as severe geomagnetic storm watch alert was on January 20, 2005 when the world was hit with the highest levels of radiation in 50 years.
Solar eruptions could cause geomagnetic storm conditions to persist through the weekend
National Oceanic and Atmospheric Administration
The alert was issued at 2pm ET and a storm of energetic protons hit Earth just 15 minutes later - tripping radiation monitors all over world.
At the time, Richard Mewaldt of the California Institute of Technology, said: "This flare produced the largest solar radiation signal on the ground in nearly 50 years.
"But we were really surprised when we saw how fast the particles reached their peak intensity and arrived at Earth."
The alarming sunspot photographed earlier this week was reportedly compared in size to the Carrington sunspot from 1859.
The Carrington sunspot resulted in “geomagnetic storms set fire to telegraph offices and sparked auroras from Cuba to Hawaii,” Space Weather said.
There have been fears of an “internet apocalypse” if it repeats, the outlet added.
It's feared the sun could wipe out humanity within the next 100 years when it unleashes a huge "super flare".
The storm of deadly radiation threatens to take out all technology on Earth, potentially causing trillions in damage and sending the planet into chaos.
Scientists have repeatedly warned of the danger superflares pose to mankind - and a 2019 study predicted one will hit in the next century.
