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Contributions to Jupiter's Gravity Field From Dynamics in the Dynamo Region
Author(s) -
Kulowski Laura,
Cao Hao,
Bloxham Jeremy
Publication year - 2020
Publication title -
journal of geophysical research: planets
Language(s) - English
Resource type - Journals
eISSN - 2169-9100
pISSN - 2169-9097
DOI - 10.1029/2019je006165
Subject(s) - dynamo , physics , jupiter (rocket family) , zonal flow (plasma) , dynamo theory , geophysics , harmonics , spherical harmonics , gravitational field , classical mechanics , magnetic field , astronomy , quantum mechanics , plasma , space shuttle , voltage , tokamak
The Juno gravity measurements indicate that zonal flows within Jupiter make an important contribution to the planet's gravity field. Atmospheric zonal flows extending ∼3,000 km deep can produce gravity harmonics that are consistent with the Juno inferred values. Deeper down, zonal flow in the dynamo region (i.e., below ∼0.90 R J , where R J is Jupiter's radius) may make a sizable contribution to the gravity harmonics. In this paper, we estimate the gravity harmonics ( J 2 – J 10 ) produced by zonal flows in Jupiter's dynamo region. Using Ferraro's law of isorotation, we construct physically motivated profiles for dynamo region zonal flow. We use the vorticity equation to determine the density perturbations associated with the flows and then calculate the gravity harmonics. We find that dynamo zonal flows with root mean square (RMS) velocities of 10 cm s −1 would produce J 3 values on the same order of magnitude as the Juno inferred value and J 2 and J 4 values on the same order as ∼3,000 km deep atmospheric zonal flow, but would not contribute much to higher‐order gravity harmonics. Zonal flows above Jupiter's dynamo region would be responsible for producing dynamical gravity harmonics above J 4 . Slower dynamo zonal flow with a RMS velocity of 1 cm s −1 would have a relatively small contribution to all of the gravity harmonics.