Well, we had a minor geomagnetic storm that day with Kp=5 [1].

Also, check out the HAARP Induction Magnetometer (an instrument that measures magnetic fields and has a web interface that plots the data it records) in [2].

All these could be factors, our could have no bearing at all. While I'm no expert in such phenomena, I think the CME may have impacted us at such an opportune time as to cause excessive heating over Greenland...

[1] [link to www.spaceweather.com]

[2] [link to cdn.imghack.se]