Modelling H-3(+) in planetary atmospheres: effects of vertical gradients on observed quantities

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Title: Modelling H-3(+) in planetary atmospheres: effects of vertical gradients on observed quantities
Authors: Moore, L
Melin, H
O'Donoghue, J
Stallard, TS
Moses, J
Galand, M
Miller, S
Schmidt, CA
Item Type: Journal Article
Abstract: Since its detection in the aurorae of Jupiter approximately 30 years ago, the H3+ ion has served as an invaluable probe of giant planet upper atmospheres. However, the vast majority of monitoring of planetary H3+ radiation has followed from observations that rely on deriving parameters from column-integrated paths through the emitting layer. Here, we investigate the effects of density and temperature gradients along such paths on the measured H3+ spectrum and its resulting interpretation. In a non-isothermal atmosphere, H3+ column densities retrieved from such observations are found to represent a lower limit, reduced by 20% or more from the true atmospheric value. Global simulations of Uranus' ionosphere reveal that measured H3+ temperature variations are often attributable to well-understood solar zenith angle effects rather than indications of real atmospheric variability. Finally, based on these insights, a preliminary method of deriving vertical temperature structure is demonstrated at Jupiter using model reproductions of electron density and H3+ measurements. The sheer diversity and uncertainty of conditions in planetary atmospheres prohibits this work from providing blanket quantitative correction factors; nonetheless, we illustrate a few simple ways in which the already formidable utility of H3+ observations in understanding planetary atmospheres can be enhanced. This article is part of a discussion meeting issue ‘Advances in hydrogen molecular ions: H3+, H5+ and beyond’.
Issue Date: 23-Sep-2019
Date of Acceptance: 7-Apr-2019
URI: http://hdl.handle.net/10044/1/72792
DOI: https://doi.org/10.1098/rsta.2019.0067
ISSN: 1364-503X
Publisher: Royal Society, The
Start Page: 1
End Page: 19
Journal / Book Title: Philosophical Transactions of the Royal Society A. Mathematical, Physical and Engineering Sciences
Volume: 377
Issue: 2154
Copyright Statement: © 2019 The Author(s).
Keywords: Science & Technology
Multidisciplinary Sciences
Science & Technology - Other Topics
aeronomy
ionosphere
H-3(+)
JUPITERS THERMOSPHERE
THERMAL STRUCTURE
GRAVITY-WAVES
IONOSPHERE
CHEMISTRY
SATURN
TEMPERATURE
NEPTUNE
DENSITY
ION
H3+
aeronomy
ionosphere
Science & Technology
Multidisciplinary Sciences
Science & Technology - Other Topics
aeronomy
ionosphere
H-3(+)
JUPITERS THERMOSPHERE
THERMAL STRUCTURE
GRAVITY-WAVES
IONOSPHERE
CHEMISTRY
SATURN
TEMPERATURE
NEPTUNE
DENSITY
ION
astro-ph.EP
astro-ph.EP
physics.space-ph
MD Multidisciplinary
General Science & Technology
Publication Status: Published
Article Number: ARTN 20190067
Online Publication Date: 2019-09
Appears in Collections:Space and Atmospheric Physics
Physics
Faculty of Natural Sciences



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