An Observing Plan of Wave Normal Direction of Auroral VLF Emissions on Board a Rocket at Syawa Station

摘要

Recent in situ observations of auroral VLF emissions have shown that there are two types of emissions; one is generated at high altitudes by incoherent Cerenkov radiation and the other is generated locally in the auroral ionosphere. Hence the determination of wave normal direction of auroral VLF emissions has been planned at Syowa Station, based on the measurement of the polarization ratio on a rocket. The measurement provides information on a u27cone angleu27 of the wave normal direction about the rocket spin axis. Since the rocket is planned to be launched along the geomagnetic field, such a cone angle is of sufficient use in the study of the generation and propagation mechanisms of auroral VLF emissions. The exact measurement of the electric field intensity is also proposed by adopting a positive feedback amplifier in an antenna-preamplifier network, which will enable us to know the ambient field intensity independently of the variation of plasma parameters.