Coherence and phase structure of compressional ULF waves at low-Earth orbit observed by the Swarm satellites

Abstract

In this paper we present results of a study of Pc3 compressional waves observed at low-Earth orbit (LEO) by the Swarm satellites. The particular emphasis has been to investigate the distribution of wave coherence and phase difference as functions of magnetic latitude and local time. This is the first time that a study of this nature has been carried out using magnetic field data from multiple LEO satellites. We have also for the first time shown how our analysis technique can be used to discriminate between static spatial and simultaneous temporal wave structures observed in the ionosphere. We believe that our study provides the first observational evidence to support the prediction by the inductive thin ionosphere model that incident Alfvén mode waves are partially converted into compressional mode waves by the ionosphere.