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Simultaneous multi-scale and multi-instrument observations of Saturn’s aurorae during the 2013 observing campaign

Melin, Henrik and Badman, S. V. and Stallard, T. S. and Cowley, S. W. H. and Dyudina, U. and Nichols, J. D. and Provan, G. and O’Donoghue, J. and Pryor, W. R. and Baines, K. H. and Miller, S. and Gustin, J. and Radioti, A. and Tao, C. and Meredith, C. J. and Blake, J. S. D. and Johnson, R. E. (2016) Simultaneous multi-scale and multi-instrument observations of Saturn’s aurorae during the 2013 observing campaign. Icarus, 263 (S1). pp. 56-74. ISSN 0019-1035. http://resolver.caltech.edu/CaltechAUTHORS:20151119-104900775

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Abstract

On 21 April 2013, during a co-ordinated Saturn auroral observing campaign, the northern and southern poles of the planet were observed from the Earth using the NASA Infrared Telescope Facility (IRTF), Keck, and Hubble Space Telescope (HST) simultaneously with the Cassini infrared, visible, and ultraviolet remote sensing instruments. We present simultaneous multi-scale and multi-wavelength analysis of the morphology of auroral emissions at Saturn. The visible main auroral emission vary between ∼2 and 10 kR on timescales of minutes and across spatial scales of down to ∼14 km on the planet. The H_2 Far Ultraviolet (FUV) brightness varies by a factor of ∼10, from ∼4–40 kR, over timescales of 1 min and spatial scales of 720 km. H^+_3 infrared emissions vary less than the H_2 emissions, from ∼5–10 μW m^(−2) sr^(−1), over similar spatial scales (∼300 km) and timescales of a few seconds to a few hours. The fine-scale temporal and spatial features seen in the main oval show that complex structures are present even during quiet solar wind conditions. Diffuse ultraviolet emissions southward of the southern midnight main oval that are not seen in the infrared, implying a steep temperature gradient of ∼50 K over 2–4° latitude equatorward of the main oval. Dynamics on scales of ∼100 km at the poles are revealed by lower spatial resolution observations, the morphologies of which are partly consistent with overlapping local-time fixed and co-rotating current systems. We also present the first direct comparison of simultaneous infrared, visible, and ultraviolet auroral emissions at Saturn. Finally, the main auroral emissions are found to be approximately co-located in the midnight sector, forming an arc with a width of ∼0.5–1°, at 72–74° southern latitude, moving slightly equatorward with increasing local-time.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/j.icarus.2015.08.021DOIArticle
http://www.sciencedirect.com/science/article/pii/S0019103515003656PublisherArticle
Additional Information:© 2015 Elsevier Inc. Received 2 April 2014, Revised 7 August 2015, Accepted 12 August 2015, Available online 20 August 2015. Part of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and NASA. This work includes observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc. for NASA. The observations were obtained during HST program GO 13051. HM, TSS, JO’D, JSDB, and REJ are visiting Astronomers at the Infrared Telescope Facility, which is operated by the University of Hawaii under Cooperative Agreement No. NNX-08AE38A with the NASA, Science Mission Directorate, Planetary Astronomy Program. This work was supported by the UK STFC Grant ST/K001000/1 for HM, TSS, SWHC, and GP, a Royal Astronomical Society Research Fellowship for SVB, and at SET by NASA CDAP grant NNX-13AG41G. JDN was supported by an STFC Advanced Fellowship. JO’D, JSDB, CJM, and REJ were supported by STFC studentships. JG is supported by the PRODEX program in collaboration with the Belgian Federal Science Policy Office (BELSPO). UD was supported by the NASA Cassini project. We thank G. M. Holsclaw for supplying the time-dependent UVIS calibration curves.
Funders:
Funding AgencyGrant Number
NASANNX-08AE38A
Science and Technology Facilities Council (STFC)ST/K001000/1
NASANNX-13AG41G
European Space Agency (ESA)PRODEX
Belgian Federal Science Policy Office (BELSPO)UNSPECIFIED
Subject Keywords:Saturn, atmosphere; Magnetosphere; Aeronomy
Record Number:CaltechAUTHORS:20151119-104900775
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20151119-104900775
Official Citation:Henrik Melin, S.V. Badman, T.S. Stallard, S.W.H. Cowley, U. Dyudina, J.D. Nichols, G. Provan, J. O’Donoghue, W.R. Pryor, K.H. Baines, S. Miller, J. Gustin, A. Radioti, C. Tao, C.J. Meredith, J.S.D. Blake, R.E. Johnson, Simultaneous multi-scale and multi-instrument observations of Saturn’s aurorae during the 2013 observing campaign, Icarus, Volume 263, 1 January 2016, Pages 56-74, ISSN 0019-1035, http://dx.doi.org/10.1016/j.icarus.2015.08.021. (http://www.sciencedirect.com/science/article/pii/S0019103515003656)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:62235
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:19 Nov 2015 19:45
Last Modified:19 Nov 2015 19:45

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