What is faraday rotation in satellite Comm. ?

Faraday rotation

Faraday rotation is an effect that affects satellite propagation. Faraday rotation results from the fact that the ionosphere is a magneto-ionic region. The Faraday rotation of a signal causes different elements of a signal to travel in different ways, particularly rotating the plane of polarization. This can create some problems with reception. A linearly polarized signal can be considered as two contra-rotating circularly polarized signals. The phase velocities of these two signals vary in a magnetic medium such as the ionosphere and as a result the polarization of the signal changes. The degree of change is dependent upon the state of the ionosphere and it follows the same pattern as that experienced for HF ionospheric communications changing over the course of the day, with the seasons and over the sunspot cycle.