The ground magnetic fields of transient ULF pulsations at the plasmapause

Abstract

Simple empirical models of the ionospheric currents associated with transient toroidal mode eigenoscillations are used to model the effects of the plasmapause density gradient on ground magnetic field oscillations. In the vicinity of the plasmapause, the ground magnetometer waveforms show strong damping of the local toroidal eigenoscillation, and the appearance of additional monochromatic oscillations. These additional oscillations have periods corresponding to the turning points in the latitudinal period variation, and suggest that transient pulsations near the plasmapause might be a useful diagnostic. The strongly damped oscillation at the plasmapause gives way to more regular oscillations at lower (and higher) latitudes. This behaviour is similar to that seen in magnetometer data and used in support of the theory of plasmapause surface waves.