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

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journal contribution
posted on 2020-03-30, 16:22 authored by L Moore, H Melin, J O'Donoghue, TS Stallard, J Moses, M Galand, S Miller, CA Schmidt
Since its detection in the aurorae of Jupiter approximately 30 years ago, the H+3 ion has served as an invaluable probe of giant planet upper atmospheres. However, the vast majority of monitoring of planetary H+3 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 H+3 spectrum and its resulting interpretation. In a non-isothermal atmosphere, H+3 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 H+3 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 usingmodel reproductions of electron density andH+3 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 H+3 observations in understanding planetary atmospheres can be enhanced. This article is part of a discussion meeting issue 'Advances in hydrogen molecular ions: H+3 , H+ 5 and beyond'.

Funding

L.M. was supported by the National Aeronautics and Space Administration (NASA) under Grant NNX17AF14G issued through the SSO Planetary Astronomy Program and grant no. 80NSSC19K0546 issued through the Solar System Workings Program. J.M. acknowledges support from NASA Solar System Workings grant no. NNX16AG10G and 80NSSC19K0546. M.G. acknowledges support from STFC of UK under grant ST/N000692/1.

History

Citation

PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES 377(2154) 23 Sep 2019

Version

  • AM (Accepted Manuscript)

Published in

PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES

Volume

377

Issue

2154

Pagination

(19)

Publisher

ROYAL SOC

issn

1364-503X

eissn

1471-2962

Acceptance date

2019-04-07

Copyright date

2019

Available date

2019-08-05

Publisher version

https://royalsocietypublishing.org/doi/10.1098/rsta.2019.0067

Spatial coverage

England

Language

English