Observational evidence for cylindrically oriented zonal flows on Jupiter

Abstract

The atmospheric dynamics of Jupiter are dominated by strong zonal winds engulfing the planet. Since the first gravity measurements taken by Juno at Jupiter, the low-degree gravity harmonics (J₃–J₁₀) have been used to determine the depth and structure of the zonal winds observed at the cloud level, limiting inferences on the deep flows to the wide latitudinal structure of these harmonics. Here, using constraints on the dynamical contribution to gravity at high latitude, we present the gravity harmonics up to J₄₀. We find an excellent correlation between these measurements and the gravity harmonics resulting from the observed cloud-level winds extending inwards cylindrically to depths of ~10⁵ bar (3,000 km). These measurements provide direct evidence that the flows penetrate inwards along the direction of the spin axis, confirming the cylindrical nature of the flow, which has been postulated theoretically since the 1970s. Furthermore, this detailed new gravity spectrum allows us to quantify the contribution of the various jets to the gravity signal, showing the dominance of the strong zonal flows around 20° latitude in both hemispheres.

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