The current state of the theory of Pc1 range ULF pulsations in magnetospheric plasma with heavy ions: A review

The review considers the current state of the theory of short-period ULF waves in plasma with admixture of heavy ions (ions whose mass significantly exceeds the mass of protons). The presence of heavy ions influences the spectrum and propagation characteristics of waves in Pc1 range. We examine elements of the theory of quasi-parallel and quasi-perpendicular short-period ULF waves. It is usually suggested that quasi-parallel ion-cyclotron waves have a left circular polarization. Quasi-perpendicular ion-ion hybrid waves have linear polarization and can be poloidal and toroidal. We discuss the theory of an equatorial resonator for Pc1 waves and determine its size from the density of heavy ions. In the radial direction, the waves can be locked in the vicinity of the plasmapause or in the region of a local minimum in the density of heavy ions. The equatorial resonator for arbitrary values of the wave vector components is considered. We note that ion-ion hybrid waves, in contrast to Alfvén waves, have a large parallel component of the magnetic field.