Formation of an Extended Equatorial Shadow Zone for Low-Frequency Saturn Kilometric Radiation

Abstract

Saturn Kilometric Radiation (SKR), being the dominant radio emission at Saturn, has been extensively investigated. The low-frequency extension of SKR is of particular interest due to its strong association with Saturn's magnetospheric dynamics. However, the highly anisotropic beaming of SKR poses challenges for observations. In most cases, the propagation of SKR is assumed to follow straight-line paths. We explore the propagation characteristics of SKR across different frequencies in this study. An extended equatorial shadow region for low-frequency SKR is identified, resulting from the merging of the Enceladus plasma torus and the previously known equatorial shadow zone. Ray-tracing simulations reveal that low-frequency ((Formula presented.) 100 kHz) SKR is unable to enter the shadow region and is instead reflected toward high latitudes. In contrast, high-frequency SKR ((Formula presented.) 100 kHz) generally propagates without hindrance. Observations suggest that some low-frequency SKR can enter the shadow region through reflection by the magnetosheath or leakage from the plasma torus.