What creates a magnetic storm?
Substorms have now been studied for many years, from space and from the ground. Their details vary from one event to the next, just as thunderstorms in the atmosphere never seem alike, but many scientists have nevertheless concluded that they are a fundamental mode of energy release and of particle acceleration. Magnetic storms usually have a well-defined trigger–often the arrival of an interplanetary shock. Their main effect on the magnetosphere is the injection of many energetic ions and electrons from the tail, causing the ring current to grow significantly. Yet substorms also inject such particles, as was shown in 1971 by the instruments aboard the synchronous ATS-1, an experimental communication satellite with a “piggyback” scientific payload. Many other satellites have studied substorm injections since then, confirming that substorms also injected ions and electrons into the ring current–only, not as many, penetrating less far and with lower average energy. Apart from its sudde
