Group Travel Time of EM Waves with Frequencies near the Ion Cyclotron Frequency in the Two-ion Magnetosphere

Abstract

The oblique propagation of electromagnetic (EM) waves with frequencies below the equatorial proton cyclotron frequency is investigated for a two-ion magnetospheric plasma. Attention is focused on the wave group travel time along a geomagnetic field line rom the equatorial wave source region to the ionosphere or the location where the wave is reflected. It is found that the coupling between eft- and right-hand polarised waves occurring at a crossover frequency significantly modifies features of the frequency-time spectrum. ecause of this modification, the spectral tone change of Pc 1 waves observed on the ground (e.g. Dowden 1966; Gendrin and Laurent 1979) is not caused solely by dispersion effects in a multi-component plasma.