The Range of Jupiter's Flow Structures That Fit the Juno Asymmetric Gravity Measurements

Abstract

The asymmetric gravity field measured by the Juno spacecraft has allowed the estimation of the depth of Jupiter's zonal jets, showing that the winds extend approximately 3,000 km beneath the cloud level. This estimate was based on an analysis using a combination of all measured odd gravity harmonics, J3, J5, J7, and J9, but the wind profile's dependence on each of them separately has yet to be investigated. Furthermore, these calculations assumed the meridional profile of the cloud‐level wind extends to depth. However, it is possible that the interior jet profile varies somewhat from that of the cloud level. Here we analyze in detail the possible meridional and vertical structure of Jupiter's deep jet streams that can match the gravity measurements. We find that each odd gravity harmonic constrains the flow at a different depth, with J3 the most dominant at depths below 3,000 km, J5 the most restrictive overall, whereas J9 does not add any constraint on the flow if the other odd harmonics are considered. Interior flow profiles constructed from perturbations to the cloud‐level winds allow a more extensive range of vertical wind profiles, yet when the meridional profiles differ substantially from the cloud level, the ability to match the gravity data significantly diminishes. Overall, we find that while interior wind profiles that do not resemble the cloud level are possible, they are statistically unlikely. Finally, inspired by the Juno microwave radiometer measurements, assuming the brightness temperature is dominated by the ammonia abundance, we find that depth‐dependent flow profiles are still compatible with the gravity measurements.

Constraints on the latitudinal profile of Jupiter's deep jets

“…S7), suggesting that if alternative jets exists in the mid-latitudes, their amplitude should be around ±40 m s −1 . These results are consistent with Duer et al (2020) replaced with random jets there (Fig. 1b).…”

Jupiter's Temperate Belt/Zone Contrasts Revealed at Depth by Juno Microwave Observations

“…This had been previously noted by Ingersoll et al (2017) based solely on the PJ1 (August 2016) observations, but they had suggested that the relationship between temperate brightness gradients and the zonal jets was rather poor. Using these same PJ1 data, Duer et al (2020) also showed the correlation between winds and MWR brightness observations. Using data from subsequent perijoves, filtering via the deconvolution process of Oyafuso et al (2020), and by taking the gradient ∆, we have shown that the correlation with the cloud-top winds is actually much better than originally thought.…”

“…It is natural to ask whether the inferred winds are consistent with the results of Juno's gravity measurements (Kaspi et al, 2018;Guillot et al, 2018), which suggest a variety of potential wind profiles decaying to the 3000-km level, depending on the sensitivity to the measured odd gravity harmonics J 3 , J 5 , J 7 and J 9 (Duer et al, 2020).…”

“…S3-S5. We also recomputed the correlation coefficients assuming winds that varied along cylinders parallel to the rotation axis (Duer et al, 2020), and found negligible changes to the strength of the correlations observed in Fig. 4.…”

“…The gravity measurements are not directly sensitive to the winds at the altitudes sensed by MWR, but the analysis must assume a vertical velocity profile, which happens to be well matched to the cloud-top winds (Kaspi et al, 2018). Indeed, Duer et al (2020) found that interior wind profiles that diverged from those measured at the cloud tops (i.e., depth-dependent flow profiles) could also be consistent with the gravity data, but concluded that they were statistically unlikely.…”