Abstract
Information on the vertical angle of arrival (elevation) is crucial in determining propagation modes of high-frequency (HF, 3–30 MHz) radio waves travelling through the ionosphere. The most advanced network of ionospheric HF radars, SuperDARN (Super Dual Auroral Radar Network), relies on interferometry to measure elevation, but this information is rarely used due to intrinsic difficulties with phase calibration as well as with the physical interpretation of the measured elevation patterns. In this work, we propose an empirical method of calibration for SuperDARN interferometry. The method utilises a well-defined dependence of elevation on range of ground scatter returns. “Fine tuning” of the phase is achieved based on a detailed analysis of phase fluctuation effects at very low elevation angles. The proposed technique has been successfully applied to data from the mid-latitude Hokkaido East SuperDARN radar. It can also be used at any other installation that utilises HF interferometry.
Highlights
High-frequency (HF, 10–20 MHz) radars are actively used for monitoring ionospheric conditions at high and mid-latitudes and provide information on plasma dynamics at E- and F-region heights
SuperDARN typically consists of pairs of radars with overlapping fields of view which allows for the estimate of a horizontal vector of ionospheric plasma drift based on the Doppler frequency shift of the ionospheric backscatter returns
The method is based on analysing the progression of elevation angle with range for ground scatter echoes and uses a gradual adjustment of the phase shift until the observed dependence agrees with that expected from a reflecting ionospheric layer
Summary
High-frequency (HF, 10–20 MHz) radars are actively used for monitoring ionospheric conditions at high and mid-latitudes and provide information on plasma dynamics (drifts, diffusion etc.) at E- and F-region heights. SuperDARN typically consists of pairs of radars with overlapping fields of view which allows for the estimate of a horizontal vector of ionospheric plasma drift based on the Doppler frequency shift of the ionospheric backscatter returns. This information is used for the reconstruction of ionospheric electric potential at F-region heights (Ruohoniemi and Baker 1998). Among the multitude of the HF propagation modes existing in the ionosphere, the conventional software distinguishes only between the
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