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

O'Donoghue, J. ORCID: https://orcid.org/0000-0002-4218-1191, Stallard, T. S., Melin, H., Cowley, S. W. H., Badman, S. V., Moore, L., Miller, S., Tao, C., Baines, K. H. and Blake, J. S. D. (2014) Conjugate observations of Saturn’s northern and southern H3+ aurorae. Icarus, 229. pp. 214-220. ISSN 0019-1035 doi: 10.1016/j.icarus.2013.11.009

Abstract/Summary

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.

Item Type	Article
URI	https://centaur.reading.ac.uk/id/eprint/120101
Identification Number/DOI	10.1016/j.icarus.2013.11.009
Refereed	Yes
Divisions	Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
Publisher	Elsevier
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