Velocity of SuperDARN Echoes Received via 1&1/2-hop Propagation Path

SuperDARN HF radars often detect ionospheric echoes from over-the-horizon ranges. It has been suggested that some of these echoes are coming from the E region, after radio waves are reflected by the ground forward and then backscattered by electrojet irregularities. The hypothesis is based on the fact that Doppler velocity magnitudes are clustered around the nominal ion-acoustic speed of plasma Cs~300 m/s. This was one of the reasons for the removal of SuperDARN data at ranges above ~2000 km from convection mapping in the most advanced convection model Thomas and Shepherd - 2017. In this project, Doppler observations of the Rankin Inlet (and separately, Inuvik) SuperDARN radar are compared with measurements of the RISR-North incoherent scatter radar along about the same directions. Events with clear presence of ground scatter and ionospheric echoes at almost doubled distance in SuperDARN data were selected. The performed comparison shows no obvious support for the above scenario suggesting that the SuperDARN over-the-horizon echoes are likely to come from the F region and thus their Doppler velocity can be used for convection mapping.