1/1
2 files

Meandering Shallow Atmospheric Jet as a Model of Saturn's North-Polar Hexagon

journal contribution
posted on 15.03.2016, 14:02 by R. Morales-Juberias, K. M. Sayanagi, A. A. Simon, Leigh Nicholas Fletcher, R. G. Cosentino
The Voyager flybys of Saturn in 1980–1981 revealed a circumpolar Hexagon at ~78° north planetographic latitude that has persisted for over 30 Earth years, more than one Saturn year, and has been observed by ground-based telescopes, Hubble Space Telescope and multiple instruments on board the Cassini orbiter. Its average phase speed is very slow with respect to the System III rotation rate, defined by the primary periodicity in the Saturn Kilometric Radiation during the Voyager era. Cloud tracking wind measurements reveal the presence of a prograde jet-stream whose path traces the Hexagon's shape. Previous numerical models have produced large-amplitude, n = 6, wavy structures with westward intrinsic phase propagation (relative to the jet). However, the observed net phase speed has proven to be more difficult to achieve. Here we present numerical simulations showing that instabilities in shallow jets can equilibrate as meanders closely resembling the observed morphology and phase speed of Saturn's northern Hexagon. We also find that the winds at the bottom of the model are as important as the winds at the cloud level in matching the observed Hexagon's characteristics.

History

Citation

Astrophysical Journal Letters, 2015, 806, L18

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy

Version

VoR (Version of Record)

Published in

Astrophysical Journal Letters

Publisher

American Astronomical Society

issn

2041-8205

eissn

2041-8213

Acceptance date

18/05/2015

Copyright date

2015

Available date

15/03/2016

Publisher version

http://iopscience.iop.org/article/10.1088/2041-8205/806/1/L18/

Language

en