On January 23 around 0400 UTC a powerful M9 solar flare erupted, and this was right on the threshold of becoming an X-class flare. The CME hit Earth around 1500 UTC on January 24, causing bright aurora.
Watch a lovely video of the event:
Also check this British report: http://www.wired.co.uk/news/archive/2012-01/24/sunspot-explosion and this one from Montreal: http://montreal.ctv.ca/servlet/an/local/CTVNews/20120124/northern-lights-solar-storm-120124/20120124/?hub=MontrealHo