Click on the image for a 210KB animated gif . The magnetosphere, populated with ionized gases and electrons, is like an invisible shield around the Earth. The Earth's magnetic field forces the solar wind to part and slide around it. But at the same time, a gust in the solar wind can squeeze the magnetosphere, forcing some of the magnetosphere's particles earthward along the magnetic field lines. Particles energized enough to burrow as deep as the upper atmosphere produces the dazzling aurora borealis and magnetic storms.
Universal time is used, so local midnight is over western Canada, to the right of each frame.
Imagers aboard Polar, orbiting around the Earth's north and south poles, provide TV pictures of the aurora borealis. The STS-45 crew noted the interesting spiraling or corkscrew appearance of this particular sighting. In effect, the aurora acts as a mirror that reflects activities in the tail. His criterion for gusts is a sharp increase in pressure, ranging from 1 to 15 nanoPascals. That's 1 to 15 billionths of a Pascal - softer than a baby's breath.