Earth's magnetic shield is not all it's cracked up to be. Once thought of as continuous barrier, NASA have just announced that it has holes every now and then, holes that let in space weather like a draft underneath the back door...

"Immense cracks in our planet's magnetic field can remain open for hours, allowing the solar wind to gush through and power stormy space weather."

The cracks can remain open for as long as 9 hours, and can be as big as California.