[ Video is no longer available. ]
The geomagnetic disturbance, expected to last throughout Thursday, could cause disruption to satellites, radio communications and power grids.
Two solar flares – sudden bursts of magnetic energy – occurred on March 6. According to NASA, they were both classed as X flares – the most powerful kind. There has been only one flare larger during this solar cycle, in August 2011.
As well as causing a temporary radio blackout on the side of the Earth facing the sun, the flares sent billions of charged particles into space at high speed, in an associated event known as a coronal mass ejection (CME).
The radiation and plasma released is now battering the Earth's magnetosphere – the magnetic "envelope" that surrounds the planet – and causing a geomagnetic storm.
"It's hitting us right in the nose," Joe Kunches, a scientist for the National Oceanic and Atmospheric Administration (NOAA), told the Associated Press.
According to Space.com, the storm is expected to prove the strongest overall solar storm since December 2006, even bigger than those triggered by larger flares, due to "an odd combination of intense magnetic, radio and radiation emissions."
The event will essentially "shake" the Earth's magnetic field, Doug Beisiecker of NOAA told the BBC. "And if you shake a magnetic field you generate things like electric currents in the atmosphere and, say, in the power grid that crisscrosses pretty much every country on the planet now."
The result could be disturbances for air traffic, satellites and any astronauts taking space walks, Reuters reported, as well as potential disruption of power grids, oil pipelines and certain industrial GPS systems.
It's also likely to cause intense displays of the Northern Lights, which may be visible further south than usual. Spaceweather.com advises sky watchers at all latitudes to look out for auroras.