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Exploring Key Characteristics in Saturn's Infrared Auroral Emissions Using VLT‐CRIRES: H 3 + Intensities, Ion Line‐of‐Sight Velocities, and Rotational Temperatures
Author(s) -
Chowdhury M. N.,
Stallard T. S.,
Melin H.,
Johnson R. E.
Publication year - 2019
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2019gl083250
Subject(s) - thermosphere , physics , ionosphere , saturn , astronomy , emission spectrum , magnetosphere , noon , magnetosphere of saturn , spectral resolution , infrared , astrophysics , exosphere , spectrograph , airglow , ion , planet , spectral line , plasma , magnetopause , quantum mechanics
We present a study of Saturn'sH 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 Δ λ ∼ 100,000), offers unprecedented spectrally resolved views of Saturn's infrared aurora. DiscreteH 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 localized 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, resembling an ionospheric polar vortex. A temperature hotspot of 379 (±66) K may be driving an emission region, corresponding to a location where H3 +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.