Radiation from the most intense solar storm for 6 years hit the Earth on Tuesday 24th January 2012. The high-energy charged particles came from a powerful flare produced by a geomagnetic solar storm that erupted at 0400 UT on Monday. The bombardment is expected to last for at least a day or two.
There is no risk to people on Earth although as a rare precaution, some airlines re-routed polar flights to avoid communication lapses and exposing pilots and passengers to excessive radiation. NASA officials have modelled the flare's predicted impact and have decided that the six astronauts on the International Space Station are also safe and do not need to take any additional precautions to protect themselves from the incoming stream of particles.
For people on the ground the most obvious resulting impact is the chance to see the aurora or "northern and southern lights". Already there has been impressive displays witnessed over the UK, Canada and Norway. Normally the aurora are seen from the polar regions, but when an eruption such as this occurs they can be observed much further south of the north pole and likewise north of the south pole. For many people living in populated areas around the world, this is a good chance to see the spectacular lights over the next couple of days without having to travel to the far polar regions.
The Northern Lights are caused by particles from the Sun colliding with atoms in the outer reaches of Earth's atmosphere, 100 to 320 km (60 to 200 miles) high. These charged particles are attracted to the magnetic polar regions and when they hit the Earth atmosphere - at high speeds - they cause colourful usually green, red or blue light shows.
In northern latitudes, the effect is known as the aurora borealis or "northern lights". Its southern counterpart is the aurora australis or "southern lights".