ABSTRACT
This chapter intends to be an up-to-date overview on ultra low-frequency (ULF) pulsations as well as a tutorial for a wider community. It summarizes important observational findings on ULF pulsations. Besides the spatial variation of ULF pulsation wavefields along the ambient magnetospheric magnetic field and in north-west and east-west direction, their variation with local time is a very important parameter which should be explainable by any theoretical model. Ground-based observations of ULF pulsations are severely influenced by the terrestrial ionosphere. Studies of solar wind properties reveal the existence of many different kinds of plasma waves, among them species within the ULF pulsation frequency range. The field-line resonance mechanism described has developed into the paradigm of ULF pulsation theory. The theory of field-line resonances and other works on the mode coupling demonstrate that magnetohydrodynamics wave propagation in a realistic magnetospheric environment is governed by a plethora of types of couplings between fast and transverse oscillations.
