The auroral zone provides a natural laboratory for studies of plasma phenomena. In this laboratory, waves and nonlinear electrostatic and electromagnetic structures are produced and ions and electrons are accelerated and heated. The primary scientific objective of the Fast Auroral SnapshoT (FAST) Explorer is to study the microphysics of the low-altitude auroral acceleration region with extremely high time-resolution.
A wide variety of auroral plasma phenomena have been discovered by recent experiments, but are not yet understood in detail. These include electrostatic shocks, small-scale double layers, electrostatic and electromagnetic ion cyclotron waves, the fine structure of auroral kilometric radiation, counterstreaming field-aligned electron beams, and upward-flowing field-aligned ion beams. In most of these experiments, temporal resolution was limited to the spin period of the spacecraft and ultimately constrained by the capacity of the data systems. Recent sounding-rocket investigations have found that the plasma of the auroral zone possesses much finer temporal and spatial structures than have been resolved by satellites.