Global MHD eigenmodes of the outer magnetosphere

In this review we concentrate on the behavior of Ultra-Low Frequency (ULF) Pc5 waves in the terrestrial magnetosphere, including the dayside, flanks, and magnetotail. Theory allows us to predict how the waves are excited, couple from one mode to another, and are damped. The details depend upon the equilibrium in which the waves exist, and have led to the development of "magnetospheric seismology" which compares the predictions of theory with observations. Throughout this article we show how observations and theory can give a remarkably consistent picture of the ULF waves in the magnetosphere, and the underlying structure of the magnetosphere itself. It is also demonstrated how the global nature of magnetohydrodynamic (MHD) waves brings together traditionally diverse and separate areas of study such as magnetopause stability, magnetosphere-ionosphere coupling, substorms, current circuits, and auroral arc formation as different aspects of a unified view of the dynamic magnetosphere.