SEPARATION OF CURRENT AND SOUND SPEED IN THE EFFECTIVE REFRACTIVE-INDEX FOR A TURBULENT ENVIRONMENT USING RECIPROCAL ACOUSTIC TRANSMISSION

Here a high-frequency acoustic experiment through a turbulent flow in Cordova Channel is described which is specifically designed to measure the contribution of scalar and vector fluctuations to the total scatt ered signal over a 48-h period. The effective refractive index fluctua tions are determined by both the random changes in sound speed (scalar s) and the random motion of the medium (vectors), and so in this paper it is demonstrated that reciprocal acoustic transmission is a techniq ue which unambiguously separates their effects, The effective refracti ve index structure parameter, C-eta eff(2) is defined as the sum of sc alar C-eta s(2) and vector C-eta v(2) contributions through the equati on C-eta s(2) + 11/6C(eta v)(2). The effective refractive index struct ure parameter is also measured from the forward propagation acoustical scintillation variances, thus providing an independent check on the i nterpretation. (C) 1998 Acoustical Society of America.