The information comes from the National Institue of Information and Communications Technology (NICT), based out of Tokyo, Japan. The guy on youtube just takes these short clips and puts them together to create a video of the Earth's field each day. The last clip was posted the day after the quake, and no more have been posted since due to power outages
Heres another interesting clip on our magnetosphere. NASA has discovered that when the field of the Sun and Earth align, a phenomena known as 'magnetic reconnection" occurs. A hole in the magnetosphere FOUR TIMES THE SIZE OF EARTH can open, exposing the whole day side of Earth to the bombardment of high energy rays and particles.
So what does this mean for us?