Spatial variations of low mass negative ions in Titan's upper atmosphere
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Published version
Author(s)
Mihailescu, Alexandra Teodora
Desai, Ravindra
Shebanits, Oleg
Haythornthwaite, Richard
Wellbrock, Anne
Type
Journal Article
Abstract
Observations with Cassini’s Electron Spectrometer discovered negative ions in Titan’s ionosphere,at altitudes between 1400 and 950 km. Within the broad mass distribution extending up to severalt housand amu, two distinct peaks were identified at 25.8-26.0 and 49.0-50.1 amu/q, corresponding to the carbon chain anions CN−and/orC2H−for the first peak and C3N−and/orC4H−for the second peak. In this study we present the spatial distribution of these low mass negative ions from 28 Titanflybys with favourable observations between 26 October 2004 and 22 May 2012. We report a trend of lower densities on the night side and increased densities up to twice as high on the day side at small solar zenith angles. To further understand this trend, we compare the negative ion densities to the total electron density measured by Cassini’s Langmuir Probe. We find the low mass negative ion density and the electron density to be proportional to each other on the dayside, but independent of each other on the night side. This indicates photochemical processes and is in agreement with the primary production route for the low mass negative ions being initiated by dissociative reactions with suprathermal electron populations produced by photoionisation. We also find the ratio ofCN−/C2H−toC3N−/C4H−highly constrained on the day-side, in agreement with this production channel, but notably displays large variations on the nightside.
Date Issued
2020-09-28
Date Acceptance
2020-08-14
Citation
The Planetary Science Journal, 2020, 1 (50), pp.1-8
ISSN
2632-3338
Publisher
American Astronomical Society
Start Page
1
End Page
8
Journal / Book Title
The Planetary Science Journal
Volume
1
Issue
50
Copyright Statement
© 2020. The Author(s). Published by the American Astronomical Society.
Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence http://creativecommons.org/licenses/by/4.0/. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence http://creativecommons.org/licenses/by/4.0/. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
License URL
Sponsor
Natural Environment Research Council (NERC)
Identifier
https://iopscience.iop.org/article/10.3847/PSJ/abb1ba
Grant Number
NE/P017347/1
Subjects
astro-ph.EP
astro-ph.EP
physics.space-ph
Publication Status
Published
Date Publish Online
2020-09-28