A suppression of differential rotation in Jupiter’s deep interior

Abstract

Jupiter's atmosphere is rotating differentially, with zones and belts rotating at speeds that differ by up to 100 metres per second. Whether this is also true of the gas giant's interior has been unknown, limiting our ability to probe the structure and composition of the planet. The discovery by the Juno spacecraft that Jupiter's gravity field is north-south asymmetric and the determination of its non-zero odd gravitational harmonics J, J, J and J demonstrates that the observed zonal cloud flow must persist to a depth of about 3,000 kilometres from the cloud tops. Here we report an analysis of Jupiter's even gravitational harmonics J, J, J and J as observed by Juno and compared to the predictions of interior models. We find that the deep interior of the planet rotates nearly as a rigid body, with differential rotation decreasing by at least an order of magnitude compared to the atmosphere. Moreover, we find that the atmospheric zonal flow extends to more than 2,000 kilometres and to less than 3,500 kilometres, making it fully consistent with the constraints obtained independently from the odd gravitational harmonics. This depth corresponds to the point at which the electric conductivity becomes large and magnetic drag should suppress differential rotation. Given that electric conductivity is dependent on planetary mass, we expect the outer, differentially rotating region to be at least three times deeper in Saturn and to be shallower in massive giant planets and brown dwarfs.

A deeper look at Jupiter

“…Guillot et al 3 (page 227) confirmed the 3,000-kilometre depth reported by Kaspi and colleagues using the symmetrical component of Jupiter's gravitational field. They demonstrate that, below this depth, the planet's interior rotates as a solid body, despite its fluid nature.…”

“…If Angela knows Emmanuel is cooperative because she and Emmanuel have interacted before, her reciprocity is direct. If she has heard from others that Emmanuel is a cooperative person, her reciprocity is indirect -a mechanism of particular relevance to human societies 3 .…”

“…In particular, is the planet's interior as dynamic as its surface? In three papers [1][2][3] in this issue, scientists have used small signatures in the gravitational field of Jupiter to address these questions and to potentially revolutionize our understanding of the internal dynamics of such gas-giant planets.…”

Dynamo Action in the Steeply Decaying Conductivity Region of Jupiter‐Like Dynamo Models

“…A recent analysis by Kaspi et al (2018), based on the equatorially antisymmetric gravity moments J 3 to J 9 measured by the Juno mission , concludes that the wind speed must be significantly reduced at about 3,000 km depth, which corresponds to about 0.96 r J . This conclusion is supported by new interior models based on Juno data (Guillot et al, 2018). Kong et al (2018), however, point out that the problem is nonunique and that the gravity signal could also be explained by deeper reaching but weaker zonal flows that may not reflect zonal jets observed at cloud level.…”

Saturn's Deep Atmospheric Flows Revealed by the Cassini Grand Finale Gravity Measurements

“…In order to explore the range of gravity solutions consistent with the measurements we first construct interior models of Saturn that fit the observational constraints of Saturn's radius and gravity harmonic J 2 , under the assumption that the interior of the planet rotates as a RB following the methodology of Guillot et al (), which was effectively used for the analysis of Juno‐based Jupiter gravity field. Since J 2 is also affected by differential rotation (Galanti & Kaspi, ), we allow the RB solution to deviate from the measured value within the range , to cover a wide range of differential rotation scenarios corresponding to different rotation rates and depths of the zonal flows (Galanti & Kaspi, ).…”