Drift & Anisotropy Parameters from First & Second Order Reflections Recorded at Spaced Aerials

Abstract

The apparent as well as the steady and random drift parameters as derived from the fadings of the first and second order echoes at the equatorial station Thumba (0.6°S dip) are compared. The apparent drift speed for the second multiple is found to be nearly two-thirds of that for the first multiple, whereas the apparent drift direction is same for the first and second multiples. The steady drift shows a slightly higher value for the second order echo whereas the random drift shows a slightly lower value. The anisotropy parameters of the characteristic ellipse fitted to the ground diffraction pattern are also compared for the first and second multiples. The axial ratio of the ellipse is found to be considerably lower for the second multiple than for the first, whereas the semi-minor axis and orientation do not show much difference. The auto-correlation functions for the first and the second multiple fadings are found to satisfy the theoretical relation ρ₂(<i>t</i>) =[ρ₂(<i>t</i>)]² for a rough diffracting screen [Booker, G. H., Ratcliffe, J. A. &amp; Shinn, D. H., <i>Proc. phys. Soc., </i> A242 (1950), 856].