Models of Saturn's Equatorial Ionosphere Based on In Situ Data From Cassini's Grand Finale

Moore, Luke; Cravens, T. E.; Müller‐Wodarg, I. C. F.; Perry, M. E.; Waite, J. H.; Perryman, R.; Nagy, Andrew F.; Mitchell, D. G.; Persoon, A. M.; Wahlund, Jan‐Erik

doi:10.1029/2018gl078162

Cited by 32 publications

(89 citation statements)

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“…They are consistent with previous ionospheric models where the main peak was observed around 1,900 km and a maximum electron densities around 10 4 cm −3 (Moore et al, ). This is further confirmed by ionospheric photochemical equilibrium models compared to data (Moore et al, ).…”

Section: Discussionmentioning

confidence: 99%

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

Hadid

Wahlund

Persoon

et al. 2019

Geophysical Research Letters

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We present the electron density (ne) 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 ne 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.

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Section: Discussionmentioning

confidence: 99%

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

Hadid

Wahlund

Persoon

et al. 2019

Geophysical Research Letters

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“…The He + density profile (m = 4) follows from the measured neutral He density and the expected ion chemistry for this species (see Moore et al, 2018). The measured H 2 density at CA for P288 was 7 × 10 9 cm À3 and at the equatorial plane (z = 0 or latitude λ = 0°) was 1.5 × 10 8 cm À3 .…”

Section: Overview Of Ionospheric Datamentioning

confidence: 92%

“…Schunk & Nagy, 2009) using a solar radiation spectrum and photoionization cross sections versus wavelength. Moore et al, 2018). The peak ion production rate takes place where the optical depth equals unity level for a typical extreme ultraviolet photon (e.g., ≈50 nm).…”

Section: Simple Ionospheric Chemistrymentioning

confidence: 99%

The Ion Composition of Saturn's Equatorial Ionosphere as Observed by Cassini

Cravens

Moore

Waite

et al. 2019

Geophysical Research Letters

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The Cassini Orbiter made the first in situ measurements of the upper atmosphere and ionosphere of Saturn in 2017. The Ion and Neutral Mass Spectrometer (INMS) found molecular hydrogen and helium as well as minor species including water, methane, ammonia, and organics. INMS ion mode measurements of light ion species (H+, H2+, H3+, and He+) and Radio and Plasma Wave Science instrument measurements of electron densities are presented. A photochemical analysis of the INMS and Radio and Plasma Wave Science data indicates that the major ion species near the ionospheric peak must be heavy and molecular with a short chemical lifetime. A quantitative explanation of measured H+ and H3+ densities requires that they chemically react with one or more heavy neutral molecular species that have mixing ratios of about 100 ppm.

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“…This simple ion analysis does not indicate the identity of the molecular volatile, which likely includes methane, ammonia, water, and carbon dioxide as measured by INMS. These compositional changes are discussed in (45).…”

Section: Ionospheric Structurementioning

confidence: 97%

Chemical interactions between Saturn’s atmosphere and its rings

Waite

Perryman

Perry

et al. 2018

Science

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The Pioneer and Voyager spacecraft made close-up measurements of Saturn’s ionosphere and upper atmosphere in the 1970s and 1980s that suggested a chemical interaction between the rings and atmosphere. Exploring this interaction provides information on ring composition and the influence on Saturn’s atmosphere from infalling material. The Cassini Ion Neutral Mass Spectrometer sampled in situ the region between the D ring and Saturn during the spacecraft’s Grand Finale phase. We used these measurements to characterize the atmospheric structure and material influx from the rings. The atmospheric He/H2 ratio is 10 to 16%. Volatile compounds from the rings (methane; carbon monoxide and/or molecular nitrogen), as well as larger organic-bearing grains, are flowing inward at a rate of 4800 to 45,000 kilograms per second.

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Models of Saturn's Equatorial Ionosphere Based on In Situ Data From Cassini's Grand Finale

Cited by 32 publications

References 50 publications

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

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

The Ion Composition of Saturn's Equatorial Ionosphere as Observed by Cassini

Chemical interactions between Saturn’s atmosphere and its rings

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