Saturn's Ionosphere: Electron Density Altitude Profiles and D‐Ring Interaction From The Cassini Grand Finale. Issue 16 (22nd August 2019)

• Record Type: Journal Article
• Authors: Hadid, L. Z.; Morooka, M. W.; Wahlund, J.‐E.; Persoon, A. M.; Andrews, D. J.; Shebanits, O.; Kurth, W. S.; Vigren, E.; Edberg, N. J. T.; Nagy, A. F.; Eriksson, A. I.
• Is Part Of: Geophysical research letters. Volume 46:Issue 16(2019)
• Page Start: 9362
• Page End: 9369
• Publication Date: 2019-08-22
• Subjects: Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2018GL078004
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: We present the electron density ( n e ) altitude profiles of Saturn's ionosphere at near‐equatorial latitudes from all 23 orbits of Cassini's Grand Finale. The data are collected by the Langmuir probe part of the Radio and Plasma Wave Science investigation. A high degree of variability in the electron density profiles is observed. However, organizing them by consecutive altitude ranges revealed clear differences between the southern and northern hemispheres. The n e profiles are shown to be more variable and connected to the D‐ring below 5, 000 km in the southern hemisphere compared to the northern hemisphere. This observed variability is explained to be a consequence of an electrodynamic interaction with the D‐ring. Moreover, a density altitude profile is constructed for the northern hemisphere indicating the presence of three different ionospheric layers. Similar properties were observed during Cassini's final plunge, where the main ionospheric peak is crossed at ∼1, 550‐km altitude. Plain Language Summary: The Cassini Langmuir probe measured directly the uppermost layer of Saturn's atmosphere, the ionosphere, during its Grand Finale. The observations revealed a layered electron density altitude profile with evidence in the southern hemisphere of an electrodynamic type of interaction with the planet innermost D‐ring. Moreover, the main peak of the ionosphere is observed for the first time in the final plunge around 1, 550 km. Key Points: Cassini RPWS observations during the Grand Finale show an electrodynamic type of interaction between the topside ionosphere and the D‐ring in the southern hemisphere A layered electron density profile is observed, characterized by at least a diffusive and a chemical equilibrium region The main ionospheric peak is observed around 1, 550 km in the final plunge