New findings indicate that the aurora and other near-Earth space weather are driven by the rate at which the Earth’s and sun’s magnetic fields connect, or merge, and not by the solar wind’s electric field as was previously assumed. The merging occurs at a spot between the Earth and sun, roughly 40.000 miles above the planet’s surface, and appears fundamental to the circulation of particles and magnetic fields throughout near-Earth space.
http://www.jhuapl.edu/newscenter/pressreleases/2006/061208b.asp