Partial polarization and propagation of Saturn kilometric radiation at low and very low frequencies

Saturn kilometric radiation (SKR) is known to be generated by the Cyclotron Maser Instability (CMI) mechanism by which it is largely generated in the right-hand extraordinary mode (R-X), but also left-hand ordinary mode (L-O) is possible. R-X mode SKR shows right-hand circular polarization when coming from the northern aurora and left-hand circular polarization from the southern aurora. Due to its short coherence length, SKR usually experiences incoherent superposition when it originates from various sources, and for this process the Stokes vectors need to be added. In case of two SKR sources with opposite circular polarization, the resultant superposed SKR gets depolarized leading to a partially polarized radio emission. In this paper we discuss the different ways how SKR can be depolarized and the influence of the Enceladus plasma torus on the polarization and propagation of SKR. We look at low and very low SKR frequencies below 100 kHz, and ray-tracing studies suggest that SKR is refracted in and around the meridian plane by the plasma torus. However, direction finding of SKR could not confirm this, since radio waves of low polarization degree show large errors for the incoming radio wave direction.