Originally posted by WPRESTO Plasma thrown out by flares associated with sunspots is drawn into the poles by the Earth's magnetic field. As it crashes into the atmosphere, the plasma causes the beautiful erie glow we call an aurora.
Just to put this slightly differently, the "plasma" consists of charged particles ejected by the sun. Because they have a charge, they are attracted to the lines of force in the Earth's magnetic field, and follow those lines toward the north and south poles. As the particles hit the gases in the atmosphere, light is released. The strange shapes in the aurora are the parts of the Earth's magnetic field made visible by the impact of the particles onto the atmosphere. The density of the incoming particles (the "Solar Wind") is also uneven, so they interact randomly to result in these beautiful lightshows.
Great photos! I hope to see the aurora myself one day - whether Aurora australis (southern lights) or Aurora borealis (northern lights).