UCL Discovery
UCL home » Library Services » Electronic resources » UCL Discovery

Influence of local ionization on ionospheric densities in Titan's upper atmosphere

Sagnieres, LBM; Galand, M; Cui, J; Lavvas, PP; Vigren, E; Vuitton, V; Yelle, RV; ... Coates, AJ; + view all (2015) Influence of local ionization on ionospheric densities in Titan's upper atmosphere. Journal of Geophysical Research - Space Physics , 120 (7) pp. 5899-5921. 10.1002/2014JA020890. Green open access

[thumbnail of Coates_Research__Space_Physics.pdf]
Preview
Text
Coates_Research__Space_Physics.pdf - Published Version

Download (1MB) | Preview

Abstract

Titan has the most chemically complex ionosphere of the solar system. The main sources of ions on the dayside are ionization by EUV solar radiation and on the nightside include ionization by precipitated electrons from Saturn's magnetosphere and transport of ions from the dayside, but many questions remain open. How well do models predict local ionization rates? How strongly do the ionization processes drive the ionospheric densities locally? To address these questions, we have carried out an analysis of ion densities from the Ion and Neutral Mass Spectrometer (INMS) from 16 close flybys of Titan's upper atmosphere. Using a simple chemical model applied to the INMS data set, we have calculated the ion production rates and local ionization frequencies associated with primary ions urn:x-wiley:jgra:media:jgra51927:jgra51927-math-0001 and urn:x-wiley:jgra:media:jgra51927:jgra51927-math-0002. We find that on the dayside the solar energy deposition model overestimates the INMS‐derived urn:x-wiley:jgra:media:jgra51927:jgra51927-math-0003 production rates by a factor of 2. On the nightside, however, the model driven by suprathermal electron intensities from the Cassini Plasma Spectrometer Electron Spectrometer sometimes agrees and other times underestimates the INMS‐derived urn:x-wiley:jgra:media:jgra51927:jgra51927-math-0004 production rates by a factor of up to 2–3. We find that below 1200 km, all ion number densities correlate with the local ionization frequency, although the correlation is significantly stronger for short‐lived ions than long‐lived ions. Furthermore, we find that, for a given N2 local ionization frequency, urn:x-wiley:jgra:media:jgra51927:jgra51927-math-0005 has higher densities on the dayside than on the nightside. We explain that this is due to CH4 being more efficiently ionized by solar photons than by magnetospheric electrons for a given amount of N2 ionization.

Type: Article
Title: Influence of local ionization on ionospheric densities in Titan's upper atmosphere
Open access status: An open access version is available from UCL Discovery
DOI: 10.1002/2014JA020890
Publisher version: http://doi.org/10.1002/2014JA020890
Language: English
Additional information: Copyright © 2015. The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics
URI: https://discovery.ucl.ac.uk/id/eprint/1497224
Downloads since deposit
72Downloads
Download activity - last month
Download activity - last 12 months
Downloads by country - last 12 months

Archive Staff Only

View Item View Item