Oblique extraordinary mode propagation in the magnetospheric plasma

Abstract

An approximate formula is obtained for the extraordinary mode refractive index for the case of almost perpendicular propagation in a hot anisotropic plasma with a loss cone. It is pointed out that the influence of finite electron temperature on perpendicular wave propagation is most significant when the wave frequency is close to the upper hybrid frequency and the second harmonic of the electron gyrofrequency. For oblique propagation this influence is significant when the wave frequency is close to the upper hybrid frequency and the first two harmonics of the electron gyrofrequency. Extraordinary mode energy focusing in the direction perpendicular to the magnetic field is considered for different plasma parameters. In particular, it is stressed that at frequencies close to the first harmonic of the electron gyrofrequency, this focusing occurs even for low temperature plasma, although this result does not originate from cold plasma theory. Extraordinary mode energy trapping in the vicinity of the equatorial plane of the magnetosphere is considered with a simple model plasma distribution function. It is emphasised that this kind of trapping provides a convincing explanation for Auroral Kilometric Radiation (AKR) observations at frequencies close to the second harmonic of the electron gyrofrequency.