Ray tracing of Z‐mode emissions from source regions in the high‐altitude auroral zone

Abstract

Two‐dimensional ray tracing of Z‐mode radiation from sources in the auroral zone has been performed. The Z‐mode waves are assumed to be excited by the cyclotron maser mechanism at frequencies near the electron gyrofrequency and at wave normal angles near 90°. The emission is found to propagate primarily perpendicular to the magnetic field line (horizontal propagation) for all sources considered, and thus not to substantially lower altitudes. The frequency bandwidth estimated from the ray paths is much less than that observed by DE‐1. It is suggested that the wave source needs to be in the region of field‐aligned current in order for the cyclotron maser mechanism to explain the broad frequency bandwidth of Z‐mode emissions.