Saturn's Ionosphere: Electron Density Altitude Profiles and D‐Ring Interaction From The Cassini Grand Finale

Hadid, Lina; Wahlund, Jan‐Erik; Persoon, A. M.; Andrews, David; Shebanits, Oleg; Kurth, W. S.; Vigren, Erik; Edberg, Niklas J. T.; Nagy, Andrew F.; Eriksson, Anders

doi:10.1029/2018gl078004

Cited by 26 publications

(50 citation statements)

References 36 publications

(75 reference statements)

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“…The fit of the two‐part exponential scale height density model to the RPWS ionospheric electron densities shows a double‐layered Saturn ionosphere for both the northern and southern hemispheres. The low‐altitude layer below 4,500 km is similar in both the northern and southern hemispheres with derived scale heights of 545 and 575 km, respectively, in agreement with the scale height at similar altitudes for the Final Plunge (Hadid, Morooka, Wahlund, Persoon, et al, ). It is also similar to the value of 500 km from earlier dusk radio occultation observations (Nagy et al, ).…”

Section: Discussionsupporting

confidence: 80%

“…The orbit‐to‐orbit variability may be due to longitudinal differences in the orbits, especially at higher latitudes. But a strong contributing factor leading to temporal electron density variations is likely to be the dynamic nature of Saturn's ionosphere and the ring‐ionosphere interaction (Hadid, Morooka, Wahlund, Persoon, et al, ). Variability in the photolytic processes acting on the ring atmosphere and ionosphere and/or meteoroid impacts on the ring surface could cause temporal changes in the electron density through these interactions.…”

Section: Rpws Electron Density Distributions In Saturn's Ionospherementioning

confidence: 99%

“…The latitudinal electron density profiles also show a significant north‐south asymmetry in the latitude distribution due, in part, to the ring shadow effect in the southern hemisphere. The shadows of the opaque A and B rings result in reduced ionization in the upper atmosphere and associated electron density depletions (Hadid, Morooka, Wahlund, Persoon, et al, ; Wahlund et al, ). Hadid, Morooka, Wahlund, Persoon, et al () also notes a strong electrodynamic ring‐ionosphere interaction associated with the highly variable electron density profiles above 1.11 R S in the southern hemisphere.…”

Section: Rpws Electron Density Distributions In Saturn's Ionospherementioning

confidence: 99%

“…Cassini's 23 Grand Finale orbits in 2017 spanned 5 months and carried Cassini deep into Saturn's ionosphere, enabling the Cassini instruments to obtain the first in situ measurements of Saturn's ionospheric plasma. RPWS Langmuir Probe electron density measurements revealed a highly variable ionosphere with significant fine structure in the electron density profiles and a strong north/south asymmetry due to ring shadow effects (Hadid, Morooka, Wahlund, Persoon, et al, ; Wahlund et al, ). Using RPWS electron plasma frequency measurements derived from the upper frequency cutoff of the whistler mode emissions, Sulaiman et al () derived the lower hybrid frequency.…”

Section: Introductionmentioning

confidence: 99%

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Electron Density Distributions in Saturn's Ionosphere

Persoon

Kurth

Gurnett

et al. 2019

Geophysical Research Letters

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Between 26 April and 15 September 2017, Cassini executed 23 highly inclined Grand Finale orbits through a new frontier for space exploration, the narrow region between Saturn and the D Ring, providing the first opportunity for obtaining in situ ionospheric measurements. During the Grand Finale orbits, the Radio and Plasma Wave Science instrument observed broadband whistler mode emissions and narrowband upper hybrid frequency emissions. Using known wave propagation characteristics of these two plasma wave modes, the electron density is derived over a broad range of ionospheric latitudes and altitudes. A two‐part exponential scale height model is fitted to the electron density measurements. The model yields a double‐layered ionosphere with plasma scale heights of 545/575 km for the northern/southern hemispheres below 4,500 km and plasma scale heights of 4,780/2,360 km for the northern/southern hemispheres above 4,500 km. The interpretation of these layers involves the interaction between the rings and the ionosphere.

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Section: Discussionsupporting

confidence: 80%

Section: Rpws Electron Density Distributions In Saturn's Ionospherementioning

confidence: 99%

Section: Rpws Electron Density Distributions In Saturn's Ionospherementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Electron Density Distributions in Saturn's Ionosphere

Persoon

Kurth

Gurnett

et al. 2019

Geophysical Research Letters

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“…This may be due to asymmetric current systems caused by seasonal effects. Indeed, Hadid, Morooka, Wahlund, Persoon, et al () found more pronounced ring‐planet electrodynamic interactions in the southern hemisphere during the Grand Finale orbits. Future results by the magnetometer instrument onboard Cassini will shed light on the large‐scale current system at Saturn, particularly during the Grand Finale orbits.…”

Section: Discussionmentioning

confidence: 99%

Auroral Hiss Emissions During Cassini's Grand Finale: Diverse Electrodynamic Interactions Between Saturn and Its Rings

Sulaiman

Kurth

Hospodarsky

et al. 2018

Geophysical Research Letters

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The Cassini Grand Finale orbits offered a new view of Saturn and its environment owing to multiple highly inclined orbits with unprecedented proximity to the planet during closest approach. The Radio and Plasma Wave Science instrument detected striking signatures of plasma waves in the southern hemisphere. These all propagate in the whistler mode and are classified as (1) a filled funnel‐shaped emission, commonly known as auroral hiss. Here however, our analysis indicates that they are likely associated with currents connected to the rings. (2) First observations of very low frequency saucers directly linked to the planet on field lines also connected to the rings. The latter observations are unique to low altitude orbits, and their presence at the Earth and Saturn alike shows that they are fundamental plasma waves in planetary ionospheres. Our results give an insight, from a unique perspective, into the dynamic and diverse nature of Saturn's environment.

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Conductivities of Titan's dusty ionosphere

Shebanits¹,

Wahlund²,

Waite³

et al. 2021

Preprint

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Titan is immersed in Saturn's magnetosphere (Bertucci et al., 2008;Garnier et al., 2010) and does not have its own magnetic field. Instead, an induced magnetic field is formed around Titan from the interactions with Saturn's magnetosphere (Wahlund et al., 2005), similarly to interactions of Venus and Mars with the solar wind and interplanetary magnetic field (e.g., Bertucci et al., 2011 and references therein). The interaction between Titan and the ambient magnetic field depends to a large degree on Titan's conductive ionosphere. Previously, the electrical properties of Titan's ionosphere were derived using only the ion and electron content (Rosenqvist et al., 2009). In the later years, the data sets have been significantly updated. Most notably, large amounts of charged dust were detected in Titan's ionosphere (Ågren et al., 2012;Coates et al., 2007;Shebanits et al., 2013) and a globally present dusty ion-ion plasma is expected (Shebanits et al., 2016). The charged dust grains in the ionosphere-like plasma of Enceladus plume (Morooka et al., 2011) and in the near-equatorial dusty ionosphere of Saturn (Morooka et al., 2019) were shown to have a profound effect on its electric conductivities by Simon et al. (2011) and Yaroshenko and Lühr (2016), and Shebanits et al. (2020, respectively. In this work we derive the electrical properties of Titan's ionosphere using the full plasma content: electrons, positive ions and negative ions/dust grains and investigate the impact of dusty plasma on an unmagnetized planetary body. The relevant in-situ measurements used here are from the Radio and Plasma Wave Science Langmuir Probe (RPWS/LP, Gurnett et al., 2004), the Ion and Neutral Mass Spectrometer (INMS, Teolis et al., 2015;Waite et al., 2004) and the Cassini Fluxgate Magnetometer (MAG, Dougherty et al., 2004). The data set spans the entire Cassini mission and is representative of a full solar cycle and nearly half Titan year.

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Saturn's Ionosphere: Electron Density Altitude Profiles and D‐Ring Interaction From The Cassini Grand Finale

Cited by 26 publications

References 36 publications

Electron Density Distributions in Saturn's Ionosphere

Electron Density Distributions in Saturn's Ionosphere

Auroral Hiss Emissions During Cassini's Grand Finale: Diverse Electrodynamic Interactions Between Saturn and Its Rings

Conductivities of Titan's dusty ionosphere

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