Abstract

Elevation angles of returned backscatter are calculated at Super Dual Auroral Radar Network radars using interferometric techniques. These elevation angles allow the altitude of the reflection point to be estimated, an essential piece of information for many ionospheric studies. The elevation angle calculation requires knowledge of the azimuthal return angle. This directional angle is usually assumed to lie along a narrow beam from the front of the radar, even though the signals are known to return from both in front of and behind the radar. If the wrong direction of return is assumed, large uncertainties will be introduced through the azimuthal return angle. This paper introduces a means of automatically determining the correct direction of arrival and the propagation mode of backscatter. The application of this method will improve the accuracy of backscatter elevation angle data and aid in the interpretation of both ionospheric and ground backscatter observations.

Highlights

  • Coherent scatter high-frequency (HF) radars, such as those that make up the Super Dual Auroral Radar Network (SuperDARN) [Greenwald et al, 1995; Chisham et al, 2007], are sensitive to E and F region ionospheric irregularities

  • Investigations of the ambient and disturbed ionosphere both require accurate knowledge of the radar backscatter locations, which can be obtained with accurate knowledge of the elevation angle of arrival, azimuthal angle off the radar boresite, and the time of flight

  • The origin field of view is determined by examining the consistency of the elevation angle across all beams at a given range gate and along a single beam, using elevation angles calculated for backscatter assumed to originate from both the front and rear fields of view

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Summary

Introduction

Coherent scatter high-frequency (HF) radars, such as those that make up the Super Dual Auroral Radar Network (SuperDARN) [Greenwald et al, 1995; Chisham et al, 2007], are sensitive to E and F region ionospheric irregularities. These radars detect a significant amount of ground backscatter (groundscatter) via diffuse reflection, which can be used to study the ionosphere below the plasma density peak. The returning signals are detected at a gate length of 300 μs, translating to distance bins (or range gates) of 45 km This gate length is a compromise, chosen to provide sufficient frequency and spatial resolution to accurately determine the line-of-sight Doppler velocities. Backscatter assumed to originate from the wrong field of view causes the part of the elevation angle calculation that corrects for the 2π ambiguity in phase to fail, causing errors of tens of degrees in the calculated elevation angle

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