Thermal Structure and Composition of Saturn's Upper Atmosphere From Cassini/Ion Neutral Mass Spectrometer Measurements

Roger Yelle, J. Serigano, T. T. Koskinen, S. M. Hörst, M. E. Perry, R. S. Perryman, J. Hunter Waite

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Analysis of measurements of the H2 density in Saturn's equatorial thermosphere indicates temperatures from 340 to 370 K. The deepest measurements, obtained during Cassini's final plunge into the atmosphere, measure the thermospheric temperature profile. The measurements are well fit by a Bates profile with an exospheric temperature of 354 K and a temperature gradient at 1.2 × 10−4 Pa of 0.4 K/km, corresponding to a thermal conduction flux of 7.3 × 10−5 W/m2. The helium profiles are consistent with diffusive equilibrium. The CH4 profiles are not in diffusive equilibrium but instead have a roughly constant mixing ratio relative to H2. We interpret this as the signature of a downward external flux of ∼1013 m−2 s−1. Saturn's rings are the most likely source of this external material.

Original languageEnglish (US)
JournalGeophysical Research Letters
DOIs
StateAccepted/In press - Jan 1 2018

Fingerprint

upper atmosphere
Saturn
thermal structure
mass spectrometers
spectrometer
ion
thermosphere
profiles
temperature profile
mixing ratio
temperature gradient
helium
Saturn rings
ions
temperature
mixing ratios
temperature profiles
atmosphere
temperature gradients
signatures

Keywords

  • aeronomy
  • composition
  • rings
  • Saturn
  • thermosphere

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

Cite this

Thermal Structure and Composition of Saturn's Upper Atmosphere From Cassini/Ion Neutral Mass Spectrometer Measurements. / Yelle, Roger; Serigano, J.; Koskinen, T. T.; Hörst, S. M.; Perry, M. E.; Perryman, R. S.; Waite, J. Hunter.

In: Geophysical Research Letters, 01.01.2018.

Research output: Contribution to journalArticle

Yelle, Roger ; Serigano, J. ; Koskinen, T. T. ; Hörst, S. M. ; Perry, M. E. ; Perryman, R. S. ; Waite, J. Hunter. / Thermal Structure and Composition of Saturn's Upper Atmosphere From Cassini/Ion Neutral Mass Spectrometer Measurements. In: Geophysical Research Letters. 2018.
@article{6e66487048534509995b04876b61dd1c,
title = "Thermal Structure and Composition of Saturn's Upper Atmosphere From Cassini/Ion Neutral Mass Spectrometer Measurements",
abstract = "Analysis of measurements of the H2 density in Saturn's equatorial thermosphere indicates temperatures from 340 to 370 K. The deepest measurements, obtained during Cassini's final plunge into the atmosphere, measure the thermospheric temperature profile. The measurements are well fit by a Bates profile with an exospheric temperature of 354 K and a temperature gradient at 1.2 × 10−4 Pa of 0.4 K/km, corresponding to a thermal conduction flux of 7.3 × 10−5 W/m2. The helium profiles are consistent with diffusive equilibrium. The CH4 profiles are not in diffusive equilibrium but instead have a roughly constant mixing ratio relative to H2. We interpret this as the signature of a downward external flux of ∼1013 m−2 s−1. Saturn's rings are the most likely source of this external material.",
keywords = "aeronomy, composition, rings, Saturn, thermosphere",
author = "Roger Yelle and J. Serigano and Koskinen, {T. T.} and H{\"o}rst, {S. M.} and Perry, {M. E.} and Perryman, {R. S.} and Waite, {J. Hunter}",
year = "2018",
month = "1",
day = "1",
doi = "10.1029/2018GL078454",
language = "English (US)",
journal = "Geophysical Research Letters",
issn = "0094-8276",
publisher = "American Geophysical Union",

}

TY - JOUR

T1 - Thermal Structure and Composition of Saturn's Upper Atmosphere From Cassini/Ion Neutral Mass Spectrometer Measurements

AU - Yelle, Roger

AU - Serigano, J.

AU - Koskinen, T. T.

AU - Hörst, S. M.

AU - Perry, M. E.

AU - Perryman, R. S.

AU - Waite, J. Hunter

PY - 2018/1/1

Y1 - 2018/1/1

N2 - Analysis of measurements of the H2 density in Saturn's equatorial thermosphere indicates temperatures from 340 to 370 K. The deepest measurements, obtained during Cassini's final plunge into the atmosphere, measure the thermospheric temperature profile. The measurements are well fit by a Bates profile with an exospheric temperature of 354 K and a temperature gradient at 1.2 × 10−4 Pa of 0.4 K/km, corresponding to a thermal conduction flux of 7.3 × 10−5 W/m2. The helium profiles are consistent with diffusive equilibrium. The CH4 profiles are not in diffusive equilibrium but instead have a roughly constant mixing ratio relative to H2. We interpret this as the signature of a downward external flux of ∼1013 m−2 s−1. Saturn's rings are the most likely source of this external material.

AB - Analysis of measurements of the H2 density in Saturn's equatorial thermosphere indicates temperatures from 340 to 370 K. The deepest measurements, obtained during Cassini's final plunge into the atmosphere, measure the thermospheric temperature profile. The measurements are well fit by a Bates profile with an exospheric temperature of 354 K and a temperature gradient at 1.2 × 10−4 Pa of 0.4 K/km, corresponding to a thermal conduction flux of 7.3 × 10−5 W/m2. The helium profiles are consistent with diffusive equilibrium. The CH4 profiles are not in diffusive equilibrium but instead have a roughly constant mixing ratio relative to H2. We interpret this as the signature of a downward external flux of ∼1013 m−2 s−1. Saturn's rings are the most likely source of this external material.

KW - aeronomy

KW - composition

KW - rings

KW - Saturn

KW - thermosphere

UR - http://www.scopus.com/inward/record.url?scp=85054017952&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85054017952&partnerID=8YFLogxK

U2 - 10.1029/2018GL078454

DO - 10.1029/2018GL078454

M3 - Article

AN - SCOPUS:85054017952

JO - Geophysical Research Letters

JF - Geophysical Research Letters

SN - 0094-8276

ER -