Presentation Information
[PPS01-P12]Titan's Ionospheric Density Structure Derived by Polarized Saturnian Radio Occultations during Cassini's Titan 15 Flyby
Rikuto Yasuda1, *Hiroaki Misawa1, Baptiste Cecconi2, Corentin K. Louis2, Tomoki Kimura3, Takeru Kato1, Yasumasa Kasaba1, Thomas Gautier4,2, Lucas Grosset2, Shotaro Sakai5, Fuminori Tsuchiya1 (1.Planetary Plasma and Atmospheric Research Center, Graduate School of Science, Tohoku University, 2.LIRA, Observatoire de Paris, 3.Department of Physics, Faculty of Science, Tokyo University of Science, 4.LATMOS/IPSL, UVSQ Universite Paris-Saclay, Sorbonne Universite, CNRS, 5.Faculty of Environment and Information Studies, Keio University)
Keywords:
Saturn,Titan,radio occultation method,ionosphere,icy moon
Titan, Saturn's largest moon, possesses a dense nitrogen-rich atmosphere and a complex ionosphere shaped by photoionization and plasma precipitation. While Cassini's in situ measurements revealed key features such as solar zenith angle (SZA) dependence and variable electron densities, independent remote sensing techniques remain limited.
We present a new application of planetary radio occultation analysis using Saturn Kilometric Radiation (SKR) intensity and polarization data from Cassini's RPWS instrument. This study introduces a novel technique to independently estimate the radio source latitude by analyzing the cutoff frequency of each SKR polarization mode. By incorporating polarization analysis, we resolve the degeneracy between radio source location and ionospheric electron density structure, enabling accurate modeling of radio wave refraction during occultation.
Applied to the T15 flyby, the method yields peak electron densities of < 450 cm^-3 (altitudes < 1040 km) during ingress and >1200 cm^-3 (1290–1360 km) during egress. Comparison with 121 Langmuir Probe observations confirms a strong inverse correlation between electron density and SZA. We also identify a statistically significant negative correlation with solar EUV flux on the nightside (SZA > 100°), suggesting reduced ion precursor transport under high solar activity.
This technique offers a robust framework for remote sensing of dense ionospheres and is directly applicable to future JUICE/RPWI observations around icy moons.
We present a new application of planetary radio occultation analysis using Saturn Kilometric Radiation (SKR) intensity and polarization data from Cassini's RPWS instrument. This study introduces a novel technique to independently estimate the radio source latitude by analyzing the cutoff frequency of each SKR polarization mode. By incorporating polarization analysis, we resolve the degeneracy between radio source location and ionospheric electron density structure, enabling accurate modeling of radio wave refraction during occultation.
Applied to the T15 flyby, the method yields peak electron densities of < 450 cm^-3 (altitudes < 1040 km) during ingress and >1200 cm^-3 (1290–1360 km) during egress. Comparison with 121 Langmuir Probe observations confirms a strong inverse correlation between electron density and SZA. We also identify a statistically significant negative correlation with solar EUV flux on the nightside (SZA > 100°), suggesting reduced ion precursor transport under high solar activity.
This technique offers a robust framework for remote sensing of dense ionospheres and is directly applicable to future JUICE/RPWI observations around icy moons.