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Conjugate observations of Saturn’s northern and southern H3+ aurorae

Research output: Contribution to journalJournal article

Published

  • James O'Donoghue
  • Tom S. Stallard
  • Henrik Melin
  • Stan W. H. Cowley
  • Sarah V. Badman
  • Luke Moore
  • Steve Miller
  • Chihiro Tao
  • Kevin H. Baines
  • James Blake
Journal publication date02/2014
JournalIcarus
Volume229
Number of pages7
Pages214-220
Original languageEnglish

Abstract

We present an analysis of recent high spatial and spectral resolution ground-based infrared observations of H3+ obtained with the 10-m Keck II telescope in April 2011. We observed H3+ emission from Saturn’s northern and southern auroral regions, simultaneously, over the course of more than 2 h, obtaining spectral images along the central meridian as Saturn rotated. Previous ground-based work has derived only an average temperature of an individual polar region, summing an entire night of observations. Here we analyse 20 H3+ spectra, 10 for each hemisphere, providing H3+ temperature, column density and total emission in both the northern and southern polar regions simultaneously, improving on past results in temporal cadence and simultaneity. We find that: (1) the average thermospheric temperatures are 527 ± 18 K in northern Spring and 583 ± 13 K in southern Autumn, respectively; (2) this asymmetry in temperature is likely to be the result of an inversely proportional relationship between the total thermospheric heating rate (Joule heating and ion drag) and magnetic field strength – i.e. the larger northern field strength leads to reduced total heating rate and a reduced temperature, irrespective of season, and (3) this implies that thermospheric heating and temperatures are relatively insensitive to seasonal effects.