Open AccessRotational modulation and local time dependence of Saturn's infrared H 3 + auroral intensity
Author(s) -
Badman S. V.,
Andrews D. J.,
Cowley S. W. H.,
Lamy L.,
Provan G.,
Tao C.,
Kasahara S.,
Kimura T.,
Fujimoto M.,
Melin H.,
Stallard T.,
Brown R. H.,
Baines K. H.
Publication year - 2012
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2012ja017990
Subject(s) - noon , saturn , physics , equinox , northern hemisphere , magnetosphere of saturn , intensity (physics) , southern hemisphere , magnetosphere , local time , infrared , atmospheric sciences , magnetic field , astronomy , geophysics , ionosphere , planet , magnetopause , optics , statistics , mathematics , quantum mechanics
Planetary auroral emissions reveal the configuration of magnetospheric field‐aligned current systems. In this study, Cassini Visual and Infrared Mapping Spectrometer (VIMS) observations of Saturn's pre‐equinox infrared H 3 + aurorae were analysed to show (a) rotational modulation of the auroral intensity in both hemispheres and (b) a significant local time dependence of the emitted intensity. The emission intensity is modulated by the ‘planetary period’ rotation of auroral current systems in each hemisphere. The northern auroral intensity also displays a lesser anti‐phase dependence on the southern rotating current system, indicating that part of the southern current system closes in the northern hemisphere. The southern hemisphere aurorae were most intense in the post‐dawn sector, in agreement with some past measurements of auroral field‐aligned currents, UV aurora and SKR emitted power. A corresponding investigation of the northern hemisphere auroral intensity reveals a broader dawn‐noon enhancement, possibly due to the interaction of the southern rotating current system with that of the north. The auroral intensity was reduced around dusk and post‐midnight in both hemispheres. These observations can be explained by the interaction of a rotating field‐aligned current system in each hemisphere with one fixed in local time, which is related to the solar wind interaction with magnetospheric field lines.