MEANDERING SHALLOW ATMOSPHERIC JET AS A MODEL OF SATURNʼS NORTH-POLAR HEXAGON
Autor: | Raul Morales-Juberias, Amy Simon, R. Cosentino, Kunio M. Sayanagi, Leigh N. Fletcher |
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Rok vydání: | 2015 |
Předmět: |
Physics
Jet (fluid) 010504 meteorology & atmospheric sciences Astronomy Astronomy and Astrophysics Jet stream 01 natural sciences Latitude law.invention Orbiter 13. Climate action Space and Planetary Science law Saturn Magnetosphere of Saturn Physics::Space Physics 0103 physical sciences Astrophysics::Earth and Planetary Astrophysics Phase velocity 010303 astronomy & astrophysics Saturn's hexagon 0105 earth and related environmental sciences |
Zdroj: | The Astrophysical Journal. 806:L18 |
ISSN: | 2041-8213 |
Popis: | 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. |
Databáze: | OpenAIRE |
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