Interesting post at http://phys.org/print361784158.html … Earth is like a big bar magnet – and its attract and repulse properties. A Swedish space balloon project is in progress. Space is big and the density of particles is small (electrons and protons) and they can move along field lines without bumping into each other. During geomagnetic storms the particles get pushed further down the field line, crowding each other and getting closer to the surface of the Earth. Then, they start to interact with the upper atmosphere and some of the particles disappear. The search is on.