The vertical structure of Titan's upper atmosphere from Cassini Ion Neutral Mass Spectrometer measurements

Roger V. Yelle; N. Borggren; V. de la Haye; W. T. Kasprzak; H. B. Niemann; I. Müller-Wodarg; J. H. Waite

doi:10.1016/j.icarus.2005.10.029

The vertical structure of Titan's upper atmosphere from Cassini Ion Neutral Mass Spectrometer measurements

Roger V. Yelle, N. Borggren, V. de la Haye, W. T. Kasprzak, H. B. Niemann, I. Müller-Wodarg, J. H. Waite

Research output: Contribution to journal › Article › peer-review

90 Scopus citations

Abstract

Data acquired by the Ion Neutral Mass Spectrometer (INMS) on the Cassini spacecraft during its close encounter with Titan on 26 October 2004 reveal the structure of its upper atmosphere. Altitude profiles of N₂, CH₄, and H₂, inferred from INMS measurements, determine the temperature, vertical mixing rate, and escape flux from the upper atmosphere. The mean atmospheric temperature in the region sampled by the INMS is 149 ± 3 K, where the variance is a consequence of local time variations in temperature. The CH₄ mole fraction at 1174 km is 2.71 ± 0.1 %. The effects of diffusive separation are clearly seen in the data that we interpret as an eddy diffusion coefficient of 4_-3⁺⁴ × 10⁹ cm² s^-1, that, along with the measured CH₄ mole fraction, implies a mole fraction in the stratosphere of 2.2 ± 0.2 %. The H₂ distribution is affected primarily by upward flow and atmospheric escape. The H₂ mole fraction at 1200 km is 4 ± 1 × 10^-3 and analysis of the altitude profile indicates an upward flux of 1.2 ± 0.2 × 10¹⁰ cm^-2 s^-1, referred to the surface. If horizontal variations in temperature and H₂ density are small, this upward flux also represents the escape flux from the atmosphere. The CH₄ density exhibits significant horizontal variations that are likely an indication of dynamical processes in the upper atmosphere.

Original language	English (US)
Pages (from-to)	567-576
Number of pages	10
Journal	Icarus
Volume	182
Issue number	2
DOIs	https://doi.org/10.1016/j.icarus.2005.10.029
State	Published - Jun 2006

Keywords

Aeronomy
Planets

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

Access to Document

10.1016/j.icarus.2005.10.029

Cite this

@article{22c5a6e789fe4362947fe6454c97f934,

title = "The vertical structure of Titan's upper atmosphere from Cassini Ion Neutral Mass Spectrometer measurements",

abstract = "Data acquired by the Ion Neutral Mass Spectrometer (INMS) on the Cassini spacecraft during its close encounter with Titan on 26 October 2004 reveal the structure of its upper atmosphere. Altitude profiles of N2, CH4, and H2, inferred from INMS measurements, determine the temperature, vertical mixing rate, and escape flux from the upper atmosphere. The mean atmospheric temperature in the region sampled by the INMS is 149 ± 3 K, where the variance is a consequence of local time variations in temperature. The CH4 mole fraction at 1174 km is 2.71 ± 0.1 %. The effects of diffusive separation are clearly seen in the data that we interpret as an eddy diffusion coefficient of 4-3+4 × 109 cm2 s-1, that, along with the measured CH4 mole fraction, implies a mole fraction in the stratosphere of 2.2 ± 0.2 %. The H2 distribution is affected primarily by upward flow and atmospheric escape. The H2 mole fraction at 1200 km is 4 ± 1 × 10-3 and analysis of the altitude profile indicates an upward flux of 1.2 ± 0.2 × 1010 cm-2 s-1, referred to the surface. If horizontal variations in temperature and H2 density are small, this upward flux also represents the escape flux from the atmosphere. The CH4 density exhibits significant horizontal variations that are likely an indication of dynamical processes in the upper atmosphere.",

keywords = "Aeronomy, Planets",

author = "Yelle, {Roger V.} and N. Borggren and {de la Haye}, V. and Kasprzak, {W. T.} and Niemann, {H. B.} and I. M{\"u}ller-Wodarg and Waite, {J. H.}",

note = "Funding Information: This research has been supported by the NASA grant NAG5-12699 to the University of Arizona. We thank Allan Lee for supplying the data on Cassini thruster firing shown in Fig. 4 . ",

year = "2006",

month = jun,

doi = "10.1016/j.icarus.2005.10.029",

language = "English (US)",

volume = "182",

pages = "567--576",

journal = "Icarus",

issn = "0019-1035",

publisher = "Academic Press Inc.",

number = "2",

}

TY - JOUR

T1 - The vertical structure of Titan's upper atmosphere from Cassini Ion Neutral Mass Spectrometer measurements

AU - Yelle, Roger V.

AU - Borggren, N.

AU - de la Haye, V.

AU - Kasprzak, W. T.

AU - Niemann, H. B.

AU - Müller-Wodarg, I.

AU - Waite, J. H.

N1 - Funding Information: This research has been supported by the NASA grant NAG5-12699 to the University of Arizona. We thank Allan Lee for supplying the data on Cassini thruster firing shown in Fig. 4 .

PY - 2006/6

Y1 - 2006/6

N2 - Data acquired by the Ion Neutral Mass Spectrometer (INMS) on the Cassini spacecraft during its close encounter with Titan on 26 October 2004 reveal the structure of its upper atmosphere. Altitude profiles of N2, CH4, and H2, inferred from INMS measurements, determine the temperature, vertical mixing rate, and escape flux from the upper atmosphere. The mean atmospheric temperature in the region sampled by the INMS is 149 ± 3 K, where the variance is a consequence of local time variations in temperature. The CH4 mole fraction at 1174 km is 2.71 ± 0.1 %. The effects of diffusive separation are clearly seen in the data that we interpret as an eddy diffusion coefficient of 4-3+4 × 109 cm2 s-1, that, along with the measured CH4 mole fraction, implies a mole fraction in the stratosphere of 2.2 ± 0.2 %. The H2 distribution is affected primarily by upward flow and atmospheric escape. The H2 mole fraction at 1200 km is 4 ± 1 × 10-3 and analysis of the altitude profile indicates an upward flux of 1.2 ± 0.2 × 1010 cm-2 s-1, referred to the surface. If horizontal variations in temperature and H2 density are small, this upward flux also represents the escape flux from the atmosphere. The CH4 density exhibits significant horizontal variations that are likely an indication of dynamical processes in the upper atmosphere.

AB - Data acquired by the Ion Neutral Mass Spectrometer (INMS) on the Cassini spacecraft during its close encounter with Titan on 26 October 2004 reveal the structure of its upper atmosphere. Altitude profiles of N2, CH4, and H2, inferred from INMS measurements, determine the temperature, vertical mixing rate, and escape flux from the upper atmosphere. The mean atmospheric temperature in the region sampled by the INMS is 149 ± 3 K, where the variance is a consequence of local time variations in temperature. The CH4 mole fraction at 1174 km is 2.71 ± 0.1 %. The effects of diffusive separation are clearly seen in the data that we interpret as an eddy diffusion coefficient of 4-3+4 × 109 cm2 s-1, that, along with the measured CH4 mole fraction, implies a mole fraction in the stratosphere of 2.2 ± 0.2 %. The H2 distribution is affected primarily by upward flow and atmospheric escape. The H2 mole fraction at 1200 km is 4 ± 1 × 10-3 and analysis of the altitude profile indicates an upward flux of 1.2 ± 0.2 × 1010 cm-2 s-1, referred to the surface. If horizontal variations in temperature and H2 density are small, this upward flux also represents the escape flux from the atmosphere. The CH4 density exhibits significant horizontal variations that are likely an indication of dynamical processes in the upper atmosphere.

KW - Aeronomy

KW - Planets

UR - http://www.scopus.com/inward/record.url?scp=33646569973&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=33646569973&partnerID=8YFLogxK

U2 - 10.1016/j.icarus.2005.10.029

DO - 10.1016/j.icarus.2005.10.029

M3 - Article

AN - SCOPUS:33646569973

SN - 0019-1035

VL - 182

SP - 567

EP - 576

JO - Icarus

JF - Icarus

IS - 2

ER -

The vertical structure of Titan's upper atmosphere from Cassini Ion Neutral Mass Spectrometer measurements

Abstract

Keywords

ASJC Scopus subject areas

Access to Document

Other files and links

Fingerprint

Cite this