The spherical harmonics methods for polarized light computations. A note about the formation of the light scattered by optically thick planetary atmospheres

The polarized light scattered from a plane parallel atmosphere is considered. Computations are made, for a normal incident beam, using the Kuscer's generalised « Spherical Harmonics » method, in its exact form, and also using a successive approximations scheme. This last technique gives some insight about the formation of the scattered light. It is confirmed that the polarized part of the emergent radiation comes from a thin upper atmospheric layer, but this polarized light seems generated quite independently of the global radiation field.