Relative O- and X-mode transmitted power from SuperDARN as it relates to the RRI instrument on ePOP

Abstract. The Cascade Demonstrator Small-Sat and Ionospheric Polar Explorer (CASSIOPE) satellite is scheduled to be launched in 2010. On board this satellite will be a suite of eight scientific instruments comprising the enhanced Polar Outflow Probe (ePOP). One instrument is the Radio Receiver Instrument (RRI) which will be used to receive HF transmissions from various ground transmitters such as the Super Dual Auroral Radar Network (SuperDARN) array. Magnetoionic polarization and propagation theory have been used to model the relative power that SuperDARN delivers to the Ordinary (O) and Extraordinary (X) modes of propagation. These calculations have been performed for various frequencies in the SuperDARN transmitting band and for all five Canadian based SuperDARN radars. The geometry of the radars with respect to the background magnetic field results in the X-mode dominating the transmitted signal when the modelled wave propagates northward and is nearly perpendicular to the magnetic field lines. Other propagation directions (i.e., above or southwards of the radar) results in propagation which is anti-parallel to the magnetic field lines and an equal splitting of transmitted power between the O- and X-modes occurs. The modelling analysis shows that for either high transmitting frequencies or low ionospheric electron densities, the range of latitudes that signal will be received is quite large (up to ~90° of latitude). Also for these conditions, the range of elevations where the X-mode signal strongly dominates the O-mode signal will be apparent in the received signal. Conversely, for lower transmitting frequencies or higher ionospheric electron densities, the latitudinal range that signal will be received over is smaller. Here the X-mode-only band is not apparent in the received signal as both modes will be received with roughly equal power. These relative mode power calculations can be used to characterize the average electron density content in the ionosphere or provide a measure of relative absorption in the D- and E-regions when the satellite passes through the field-of-view of a SuperDARN radar.