Exploring key characteristics in Saturn’s infrared auroral emissions using VLT-CRIRES: H3+ intensities, ion line-of-sight velocities, and rotational temperatures
journal contributionposted on 2019-06-26, 09:21 authored by M. N. Chowdhury, T. S. Stallard, H. Melin, R. E. Johnson
We present a study of Saturn’s H+ 15 3 northern auroral emission using data from 19 May 2013 from the Very Large Telescope’s long-slit spectrometer Cryogenic Infrared Echelle Spectrograph (VLT-CRIRES). Adaptive optics, combined with the spectral resolution of VLT-CRIRES ( λ ∆λ ∼100,000), offers unprecedented spectrally resolved views of Saturn’s infrared aurora. Discrete H+3 emission lines – used to derive dawn-to-dusk profiles of auroral intensity, ion line-of-sight velocity, and thermospheric temperature – reveal a dawn-enhanced aurora with an average temperature of 361 (±48) K, and a localised dark region in the emission co-located with a noon-to-midnight (and vice versa) flow in the ion velocity on the scale of ∼1 km s−1 , resembling an ionospheric polar vortex. A temperature hotspot of 379 (±66) K may be driving an emission region, corresponding to a location where H+3 is failing to cool the thermosphere. Results presented here have implications for current understanding on the complex nature of Saturn’s thermosphere ionosphere-magnetosphere interaction.
This study is based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme 091.C-0257(A). M. N. C. and R. E. J were supported by UK Science and Technologies Facilities Council (STFC) studentships; studentship numbers ST/N504117/1 and ST/X423ST0/2, respectively. T. S. S. and H. M. were both supported by UK STFC Grant ST/N000749/1.
CitationGeophysical Research Letters, 2019
Author affiliation/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy
- AM (Accepted Manuscript)