Astrophysics and Space Science

, Volume 225, Issue 2, pp 205–219 | Cite as

Average photon path-length in isotropically scattering finite atmospheres

  • Tõnu Viik


The determination of the average path-length of photons in a finite isotropically scattering plane-parallel homogeneous atmosphere is discussed. To solve this problem we have used the kernel approximation method which easily allows us to find the derivatives of the intensity with respect to optical depth, optical thickness and albedo of single scattering.

In order to check the results we have used another approach by exploiting the set of integrodifferential equations of Chandrasekhar for theX- andY-functions. This approach allows us to find the average path length only at the boundaries of the atmosphere but on the other hand it gives also the dispersion of the path-length distribution function, thus generating the input parameters for determining the approximate path-length distribution function. It occurred that the set so obtained is stable and the results are highly accurate.

As a by-product we obtain the first two derivatives of theX- andY-functions with respect to the albedo of single scattering and optical thickness, and the mixed derivative.


Atmosphere Distribution Function Input Parameter Path Length Approximation Method 
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Copyright information

© Kluwer Academic Publishers 1995

Authors and Affiliations

  • Tõnu Viik
    • 1
  1. 1.W. Struve Tartu Astrophysical ObservatoryTõravereEstonia

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