Is the dynamic magnetosphere an avalanching system?

The analogy between the dynamic magnetosphere and an avalanche system is examined by using the global auroral energy deposition obtained by the Polar UVI as a measure of the energy output of the magnetosphere. The analysis reveals two types of energy dissipation: those internal to the magnetosphere occurring at all activity levels with no intrinsic scale, and those associated with active times corresponding to global energy dissipation with a characteristic scale. The internal events exhibit the same power law index in both active and quiet times. These features are consistent with a simple avalanche (‘sandpile’) numerical model.