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Cassini observations of ion and electron beams at Saturn and their relationship to infrared auroral arcs

Badman, S. V. and Achilleos, N. and Arridge, C. S. and Baines, K. H. and Brown, R. H. and Bunce, E. J. and Coates, A. J. and Cowley, S. W. H. and Dougherty, M. K. and Fujimoto, M. and Hospodarsky, G. and Kasahara, S. and Kimura, T. and Melin, H. and Mitchell, D. G. and Stallard, T. and Tao, C. (2012) Cassini observations of ion and electron beams at Saturn and their relationship to infrared auroral arcs. Journal of Geophysical Research, 117 (A1). ISSN 0148-0227

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    Abstract

    We present Cassini Visual and Infrared Mapping Spectrometer observations of infrared auroral emissions from the noon sector of Saturn's ionosphere revealing multiple intense auroral arcs separated by dark regions poleward of the main oval. The arcs are interpreted as the ionospheric signatures of bursts of reconnection occurring at the dayside magnetopause. The auroral arcs were associated with upward field-aligned currents, the magnetic signatures of which were detected by Cassini at high planetary latitudes. Magnetic field and particle observations in the adjacent downward current regions showed upward bursts of 100–360 keV light ions in addition to energetic (hundreds of keV) electrons, which may have been scattered from upward accelerated beams carrying the downward currents. Broadband, upward propagating whistler waves were detected simultaneously with the ion beams. The acceleration of the light ions from low altitudes is attributed to wave-particle interactions in the downward current regions. Energetic (600 keV) oxygen ions were also detected, suggesting the presence of ambient oxygen at altitudes within the acceleration region. These simultaneous in situ and remote observations reveal the highly energetic magnetospheric dynamics driving some of Saturn's unusual auroral features. This is the first in situ identification of transient reconnection events at regions magnetically conjugate to Saturn's magnetopause.

    Item Type: Article
    Journal or Publication Title: Journal of Geophysical Research
    Additional Information: Copyright 2012 by the American Geophysical Union
    Uncontrolled Keywords: Saturn ; aurora ; magnetosphere
    Subjects:
    Departments: Faculty of Science and Technology > Physics
    ID Code: 67080
    Deposited By: ep_importer_pure
    Deposited On: 10 Oct 2013 11:47
    Refereed?: Yes
    Published?: Published
    Last Modified: 24 Nov 2017 05:29
    Identification Number:
    URI: http://eprints.lancs.ac.uk/id/eprint/67080

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