The polarization state of transionospheric high frequency (HF) radio waves can be determined using the crossed-dipole antennas of the Radio Receiver Instrument (RRI) onboard Enhanced Polar Outflow Probe (e-POP) on the CAScade, Smallsat, and IOnospheric Polar Explorer/Swarm-E satellite. Coordinated experiments between ground radars and RRI showed that the radio waves have high ellipticity angles (elliptical or circular polarization) for propagation direction 6°–25° from the perpendicular direction to the local geomagnetic field. However, from magnetoionic theory and a typical assumption of roughly equal power in the O- and X-modes, radio waves can have high ellipticity angles only when the propagation direction is within 10° of perpendicularity. This investigation uses coordinated experiments between the Saskatoon SuperDARN radar and RRI. Magnetoionic modeling reveals that the relative strengths of the O- and X-modes for the HF radio waves transmitted from the Saskatoon SuperDARN change significantly poleward of the radar. Differences in the relative power between the two wave modes were found to significantly modify the polarization state of radio waves, and govern the sense of rotation of the wave. Even a relatively modest 2–5 dB power difference in the X-mode over the O-mode was found to result in unexpected observations of circularly polarized radio waves at aspect angles 6°–10° from perpendicular, and unexpected elliptically polarized waves observed at aspect angles more than 10° from perpendicular. Therefore, a combination of RRI observations and modeling, which accounts for relative differences in the O- and X-mode powers, was used here to better understand the unexpected observations of polarization states of transionospheric radio waves.

中文翻译：

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高频跨电离层无线电波的椭圆率

跨电离层高频 (HF) 无线电波的极化状态可以使用 CAScade、Smallsat 和 IOnopheric Polar Explorer/ 上的增强型极地流出探头 (e-POP) 上的无线电接收仪器 (RRI) 的交叉偶极天线来确定Swarm-E 卫星。地面雷达和RRI之间的协调实验表明，无线电波在与当地地磁场垂直方向6°–25°的传播方向上具有高椭圆角（椭圆或圆偏振）。然而，根据磁离子理论和 O 模式和 X 模式功率大致相等的典型假设，无线电波仅当传播方向与垂直度相差 10° 以内时才能具有高椭圆角。这项调查使用萨斯卡通 SuperDARN 雷达和 RRI 之间的协调实验。磁离子模型显示，从萨斯卡通 SuperDARN 发射的高频无线电波的 O 模式和 X 模式的相对强度在雷达的极地方向发生显着变化。人们发现两种波模式之间的相对功率差异会显着改变无线电波的偏振态，并控制波的旋转方向。即使 X 模式与 O 模式相对较小的 2–5 dB 功率差异也被发现会导致在与垂直方向成 6°–10° 方位角时观察到意外的圆偏振无线电波，以及在与垂线的方位角超过 10°。因此，这里使用 RRI 观测和建模相结合，解释了 O 模式和 X 模式功率的相对差异，以更好地理解跨电离层无线电波偏振态的意外观测。