Rayleigh depolarization factor.  

rayleigh_depol value

 
The Rayleigh scattering phase function is p(\mu)=a+b\mu^{2} where a=1.5{(1+\texttt{depol})/(2+\texttt{depol})} and b=1.5{(1-\texttt{depol})/(2+\texttt{depol})}. By default the depolarization is calculated using the expressions from Bodhaine1999.