The THEMIS probes were sent up to examine the magnetosphere, and were therefore surprised to fly through a huge bloody hole being ripped in the thing by the solar wind. Connections made between the solar and terran magnetic field lines allowed huge swathes of particles to plow through, breaching the magnetosphere, loading the field with plasma and a bunch of other things that sound more Star Trek than NASA.
So why aren’t we dead? Didn’t “The Core” teach us that without the field we’re all toast? Well, the first lesson is that “The Core” isn’t exactly a good source of science education. The other is the scale of the magnetosphere – the barrier created between Earth’s magnetic field and the solar wind is over sixty thousand kilometers away from the Earth. A hole “four times the size of Earth” is less than 4% of the whole thing, so it’s not exactly “hide in a cave and begin the breakdown of civilization” time just yet.
It is, however, “radically re-evaluate our understanding of a vital piece of the universe based on sweet, delicious new data” time. Which is a good scientist’s favorite time.
Posted by Luke McKinney.
Magnetosphere breach http://science.nasa.gov/headlines/y2008/16dec_giantbreach.htm?list58909