The effect of the equatorially symmetric zonal winds of Saturn on its gravitational field
Kong, Dali1,2; Zhang, Keke2,3; Schubert, Gerald4; Anderson, John D.5
Corresponding AuthorZhang, Keke(
AbstractThe penetration depth of Saturn's cloud-level winds into its interior is unknown. A possible way of estimating the depth is through measurement of the effect of the winds on the planet's gravitational field. We use a self-consistent perturbation approach to study how the equatorially symmetric zonal winds of Saturn contribute to its gravitational field. An important advantage of this approach is that the variation of its gravitational field solely caused by the winds can be isolated and identified because the leading-order problem accounts exactly for rotational distortion, thereby determining the irregular shape and internal structure of the hydrostatic Saturn. We assume that (i) the zonal winds are maintained by thermal convection in the form of non-axisymmetric columnar rolls and (ii) the internal structure of the winds, because of the Taylor-Proundman theorem, can be uniquely determined by the observed cloud-level winds. We calculate both the variation Delta J(n), n = 2, 4, 6 ... of the axisymmetric gravitational coefficients J(n) caused by the zonal winds and the non-axisymmetric gravitational coefficients Delta J(nm) produced by the columnar rolls, where m is the azimuthal wavenumber of the rolls. We consider three different cases characterized by the penetration depth 0.36 R-S, 0.2 R-S and 0.1 R-S, where R-S is the equatorial radius of Saturn at the 1-bar pressure level. We find that the high-degree gravitational coefficient (J(12) + Delta J(12)) is dominated, in all the three cases, by the effect of the zonal flow with vertical bar Delta J(12)/J(12)vertical bar > 100% and that the size of the non-axisymmetric coefficients Delta J(mn) directly reflects the depth and scale of the flow taking place in the Saturnian interior.
Keywordgravitation planets and satellites: individual (Saturn) planets and satellites: interiors
Indexed BySCI
WOS Research AreaAstronomy & Astrophysics
WOS SubjectAstronomy & Astrophysics
WOS IDWOS:000430282700003
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Document Type期刊论文
Corresponding AuthorZhang, Keke
Affiliation1.Chinese Acad Sci, Shanghai Astron Observ, Key Lab Planetary Sci, Shanghai 200030, Peoples R China
2.Univ Exeter, Coll Engn Math & Phys Sci, Exeter EX4 4QF, Devon, England
3.Macau Univ Sci & Technol, Lunar & Planetary Sci Lab, Macau, Peoples R China
4.Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA 90095 USA
5.Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA
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GB/T 7714
Kong, Dali,Zhang, Keke,Schubert, Gerald,et al. The effect of the equatorially symmetric zonal winds of Saturn on its gravitational field[J]. RESEARCH IN ASTRONOMY AND ASTROPHYSICS,2018,18(4):8.
APA Kong, Dali,Zhang, Keke,Schubert, Gerald,&Anderson, John D..(2018).The effect of the equatorially symmetric zonal winds of Saturn on its gravitational field.RESEARCH IN ASTRONOMY AND ASTROPHYSICS,18(4),8.
MLA Kong, Dali,et al."The effect of the equatorially symmetric zonal winds of Saturn on its gravitational field".RESEARCH IN ASTRONOMY AND ASTROPHYSICS 18.4(2018):8.
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