On Thursday morning, the biggest solar flare of the year erupted from the sun. Shortly afterwards it was followed by a coronal mass ejection (CME) that sent tons of high energy particles hurtling towards Earth.

Solar flares can affect us almost instantly. This one was no exception, causing a radio blackout. But CMEs take longer to arrive.

Last night the CME that left the sun a few days ago hit Earth.

It was good news for all aurora watchers.

But as well as creating some beautiful displays of northern lights, it had an effect that was a bit more down to Earth. Literally.

According to my 3D Sun iPhone app, which alerted me to the geomagnetic activity the CME triggered this morning, the impact "rattled Earth's magnetic field and induced electrical currents in soil around the Arctic Circle."

Rob Stammes at the Polar Light Center in Lofoten, Norway, told spaceweather.com:

"On my instruments there was a clear signature of the incoming coronal mass ejection. The impact was not as strong as expected, but there were nice variations on my magnetometer and ground current instruments. There were also Northern Lights."

Geomagnetic activity is caused when a coronal mass ejection, a bunch of solar particles that erupt from the sun and travel away from it at speeds of hundreds of kilometres a second, reaches Earth and interacts with our planet's magnetic field.

This doesn't always induce currents in the ground. But when it does, sometimes there are disastrous effects. In March 1989, a geomagnetic storm caused the collapse of Hydro-Québec's electricity transmission system. Six million people were without power for nine hours.

The flare and CME that erupted from the sun on 11 April this year were nowhere near as powerful as the one that led to the Quebec blackout. And, since 1989, at least some power companies have developed mitigation strategies in case anything similar happens again.

But, nevertheless, this solar eruption is a little reminder that space weather can make for more than just pretty pictures.

(Although I'm a big fan of those too, as you can probably tell by this post.)