S ¼
I
IƤcos 2β A cos 2χ
IƤcos 2β A sin 2χ
IƤsin 2β A
0
B
B
B
@
1
C
C
C
A
ð4:11Þ
where Ƥ is the degree of polarization. The influence of linear and circular polarization on the Stokes vector is shown in Fig. 4.2 in which the Stokes parameters are
normalized by the intensity, I.
The degree of polarization can be expressed (Hovenier et al. 2004) as
Fig. 4.1 The vibration
(or polarization) ellipse for
an electric vector at a point
O of a polarized wave. The
direction of propagation is
into the paper. (Adapted by
permission from Springer
Nature from Hovenier et al.
2004)
Fig. 4.2 The pattern of Stokes parameters for various states of polarization. The upper four
diagrams indicate linear polarization with V ¼ 0. The bottom row indicates circular polarization
with Q ¼ U ¼ 0. The middle row indicates 45
polarization when Q ¼ 0
4.2 Scattering of Light by Dust
285