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

Wu, Siyuan1,2; Ye, Shengyi1; Taubenschuss, Ulrich3; Fischer, Georg4; Jackman, Caitriona M.4; Zarka, Philippe2; Kurth, William S.5; Wang, Mengmeng1; Cecconi, Baptiste2; Ning, Hao6,7; Long, Minyi8; Baskevitch, Claire2

2024-08-16

10.1029/2023GL106652

GEOPHYSICAL RESEARCH LETTERS   影响因子和分区

0094-8276

1944-8007

["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 (less than or similar to $\\lesssim $100 kHz) SKR is unable to enter the shadow region and is instead reflected toward high latitudes. In contrast, high-frequency SKR (greater than or similar to $\\gtrsim $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.","Saturn Kilometric Radiation (SKR) is a natural electromagnetic wave generated in Saturn's high-latitude region along its magnetic field lines. Variations in SKR frequency could offer insights into Saturn's magnetic conditions, especially its interaction with the solar wind. However, the observed frequency characteristics of SKR depend on viewing geometry due to its directional nature. While past studies assumed SKR travels in straight lines, this may not hold true for low-frequency SKR. These emissions can change direction when they encounter dense plasma, similar to light reflecting off a mirror or bending when entering water. At Saturn's equatorial region, the plasma torus created by Enceladus, one of Saturn's moons, contains dense plasma and significantly affects radio wave propagation. Our study investigates the distribution of SKR at different frequencies and identifies a shadow region where low-frequency SKR emissions are rarely seen. Using numerical simulations of ray propagation paths, we discover that low-frequency SKR emissions cannot reach these shadow regions because they are reflected by the dense plasma torus. However, occasionally, we observe low-frequency SKR in the shadow region, suggesting the possibility of reflection by Saturn's magnetosheath or leakage through the plasma torus.","The propagation characteristics of Saturn Kilometric Radiation (SKR) are established statistically and by ray-tracing A shadow region of the low-frequency SKR near the equatorial region at large radial distances is discovered and discussed Low-frequency SKR may enter the shadow region due to torus leakage or reflection at the magnetosheath"]

Saturn ray-tracing radio emission plasma torus magnetosphere propagation

SCI ; EI

英语

第一 ; 通讯

Strategic Priority Research Program of the Chinese Academy of Sciences[XDB 41000000] ; NSFC["42274221","42074180"] ; Science, Technology and Innovation Commission of Shenzhen Municipality program[STIC20200925153725002] ; Guangdong province program[2021CX02Z468] ; FWF-GACR international project[I4559-N/20-06802L]

Geology

Geosciences, Multidisciplinary

WOS:001288236400001

AMER GEOPHYSICAL UNION

GEOSCIENCES

Web of Science

1.Southern Univ Sci & Technol, Dept Earth & Space Sci, Shenzhen, Peoples R China
2.Univ Paris Meudon, Univ PSL, Sorbonne Univ, LESIA,Observ Paris,CNRS, Meudon, France
3.Czech Acad Sci, Dept Space Phys, Inst Atmospher Phys, Prague, Czech Republic
4.Dublin Inst Adv Studies, Sch Cosm Phys, Dublin, Ireland
5.Univ Iowa, Dept Phys & Astron, Iowa City, IA USA
6.Shandong Univ, Inst Frontier & Interdisciplinary Sci, Qingdao, Peoples R China
7.Shandong Univ, Inst Space Sci, Jinan, Peoples R China
8.Wuhan Univ, Sch Elect Informat, Dept Space Phys, Wuhan, Peoples R China

Wu, Siyuan,Ye, Shengyi,Taubenschuss, Ulrich,et al. Formation of an Extended Equatorial Shadow Zone for Low-Frequency Saturn Kilometric Radiation[J]. GEOPHYSICAL RESEARCH LETTERS,2024,51(15).

Wu, Siyuan.,Ye, Shengyi.,Taubenschuss, Ulrich.,Fischer, Georg.,Jackman, Caitriona M..,...&Baskevitch, Claire.(2024).Formation of an Extended Equatorial Shadow Zone for Low-Frequency Saturn Kilometric Radiation.GEOPHYSICAL RESEARCH LETTERS,51(15).

Wu, Siyuan,et al."Formation of an Extended Equatorial Shadow Zone for Low-Frequency Saturn Kilometric Radiation".GEOPHYSICAL RESEARCH LETTERS 51.15(2024).