Flow angle effects in E region 398‐MHz auroral backscatter at small aspect angle

Abstract

A study of flow angle effects on small aspect angle backscatter from the auroral E region has been made using data obtained in the 1970s with the 398‐MHz radar at Homer, Alaska. Several findings differ from previous results obtained at 140 MHz with the Scandinavian Twin Auroral Radar Experiment and the Sweden and Britain Radar‐Auroral Experiment radars: (1) backscatter power is virtually independent of flow angle; (2) there is much less difference between type 1 and type 2 echoes; (3) as found in previous UHF studies, Doppler velocities of type 2 (low Doppler velocity) echoes vary with flow angle more rapidly than predicted by the “cosine law”. These differences are considered in the light of the recent strong turbulence theory developed by Hamza and St‐Maurice [1993a, b].