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Title: Isolating auroral FUV emission lines using compact, broadband instrumentation
Authors: Molyneux, Philippa Mary
Bannister, Nigel P.
Bunce, Emma J.
Grodent, D.
Clarke, J. T.
Fleury-Frenette, K.
Gerard, J-C.
Lapington, Jonathan
Nichols, Jonathan
Renotte, E.
Rossi, L.
First Published: 20-Aug-2014
Publisher: Elsevier
Citation: Planetary And Space Science, 2014, 103, pp. 291-298 (8)
Abstract: Images of auroral emissions at far ultraviolet (FUV, 122–200 nm) wavelengths are useful tools with which to study magnetospheric–ionospheric coupling, as the scattered sunlight background in this region is low, allowing both dayside and nightside auroras to be imaged simultaneously. The ratio of intensities between certain FUV emission lines or regions can be used to characterise the precipitating particles responsible for auroral emissions, and hence is a useful diagnostic of magnetospheric dynamics. Here, we describe how the addition of simple transmission filters to a compact broadband imager design allows far ultraviolet emission ratios to be deduced while also providing large-scale instantaneous images of the aurora. The low mass and volume of such an instrument would make it well-suited for both small satellite Earth-orbiting missions and larger outer planet missions from which it could be used to characterise the tenuous atmospheres observed at several moons, as well as studying the auroral emissions of the gas giants. We present a study to investigate the accuracy of a technique to allow emission line ratio retrieval, as applied to the OI 130.4 nm and 135.6 nm emissions at Ganymede. The ratio of these emissions provides information about the atmospheric composition, specifically the relative abundances of O and O2. Using modelled FUV spectra representative of Ganymede׳s atmosphere, based on observations by the Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS), we find that the accuracy of the retrieved ratios is a function of the magnitude of the ratio, with the best measurements corresponding to a ratio of ~1.3
DOI Link: 10.1016/j.pss.2014.08.007
ISSN: 0032-0633
Version: Post-print
Status: Peer-reviewed
Type: Journal Article
Rights: Copyright © 2014 Elsevier Ltd. All rights reserved. This manuscript version is made available after the end of the embargo period under the CC-BY-NC-ND 4.0 license 
Description: The file associated with this record is under a 24-month embargo from publication in accordance with the publisher's self-archiving policy. The full text may be available through the publisher links provided above.
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

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