ANALYTIC APPROXIMATION TO RANDOMLY ORIENTED SPHEROID EXTINCTION

Authors
  1. Evans, B.T.N.
  2. Fournier, G.R.
Corporate Authors
Defence Research Establishment Valcartier, Valcartier QUE (CAN)
Abstract
An analytic semi-empirical approximation to the extinction efficiency, Qext, for randomly oriented spheroids, based on an extension of the anomalous diffraction formula, is given and compared with the extended boundary condition or T-matrix method. This will allow for the better and more general modelling of obscurants. Using this formula, Qext can be evaluated over E4 times faster than with previous methods. This approximation has been verified for complex refractive indices m = n - ik, where 1 less than or equal to n less than or equal to infinity and 0 less than or equal to k less than or equal to infinity and aspect ratios from 0.2 to 5. We beleive that the approximation is uniformly valid over all size parameters and aspect ratios. It has the correct Rayleigh, refractive index and large particle asymptotic behaviours. The accuracy and limitations of this formula are extensively discussed.
Report Number
DREV-4712/93 —
Date of publication
01 Dec 1993
Number of Pages
50
DSTKIM No
94-00102
CANDIS No
136163
Format(s):
Hardcopy;Originator's fiche received by DSIS

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