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    Cassini observations of ionospheric photoelectrons at large distances from Titan: implications for Titan's exospheric environment and magnetic tail

    Wellbrock, Anne and Coates, Andrew J. and Sillanpää, I. and Jones, Geraint H. and Arridge, Chris S. and Lewis, Gethyn R. and Young, D.T. and Crary, F.J. and Aylward, Alan D. (2012) Cassini observations of ionospheric photoelectrons at large distances from Titan: implications for Titan's exospheric environment and magnetic tail. Journal of Geophysical Research: Space Physics 117 (A3), ISSN 0148-0227.

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    Abstract

    Discrete peaks near 24.1 eV are seen in electron spectra measured in Titan's ionosphere by the ELS (Electron Spectrometer), part of the Cassini Plasma Spectrometer (CAPS), and are interpreted as photoelectrons. These photoelectrons are generated as a result of ionization of N2 by the strong solar He II (30.4 nm) line. They are generally observed in the dayside ionosphere, because this is where neutral N2 particles can be ionized by solar radiation. Coates et al. (2007) discussed initial observations of photoelectrons in Titan's distant tail during the T9 encounter. Here, we describe additional photoelectron peak observations at large distances from Titan, where they are unlikely to have originated because of low neutral N2 densities. We consider the tail structures during the encounters T15, T17, and T40. We infer that the distant photoelectrons may have traveled to the observation sites by means of a magnetic connection from lower altitudes in the dayside ionosphere, where they could have been produced. This idea is supported by results of hybrid modeling. Thus photoelectrons may be used as tracers of magnetic field lines and further improve our understanding of Titan's complex plasma environment.

    Metadata

    Item Type: Article
    Keyword(s) / Subject(s): Titan, atmospheric escape, interaction, ionosphere, moon, photoelectrons
    School: Birkbeck Schools and Departments > School of Science > Earth and Planetary Sciences > UCL/Birkbeck Centre for Planetary Sciences
    Depositing User: Administrator
    Date Deposited: 02 Dec 2014 13:05
    Last Modified: 02 Dec 2014 13:05
    URI: http://eprints.bbk.ac.uk/id/eprint/11155

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