High-resolution vector velocity determinations from the dynasonde

Abstract

Line-of-sight Doppler velocity V∗ and three-dimensional apparent echolocation (XL, YL, ZL), are among the principal parameters available for each ionospheric echo from most observing modes of the dynasonde. An ensemble of three or more echoes containing diverse XL, YL, ZL is sufficient to determine the full vector velocity VX, VY, VZ common to the ensemble. We present a procedure based on weighted least-squares, which may be applied to an entire recording or to suitably selected parts of it, to yield ‘best’ estimates of VX, VY, VZ and their confidence limits. Each observation is weighted according to an r.m.s. phase error incurred in the estimation of XL, YL, ZL and V∗. A measure of the fraction of observed Doppler variance expressed by the analysis is useful to decide if spatial or temporal variabilities are significant within the ensemble. Often at Tromsø the results are directly applicable to the estimation of prevailing electric fields with high (⪢10 s) time resolution