The effect of Jupiter oscillations on Juno gravity measurements

TL;DR

This paper investigates how Jupiter's internal oscillations, especially f-modes, could influence gravity measurements taken by Juno, potentially affecting interpretations of the planet's internal structure and wind patterns.

Contribution

It models the gravitational perturbations caused by Jupiter's acoustic modes and assesses their impact on Juno's gravity data analysis, highlighting the importance of considering oscillations.

Findings

Juno is most sensitive to Jupiter's fundamental oscillation mode.

Oscillations could produce gravity signals comparable to shallow zonal winds.

Strong f-modes could significantly affect gravity measurements, complicating data interpretation.

Abstract

Seismology represents a unique method to probe the interiors of giant planets. Recently, Saturn's f-modes have been indirectly observed in its rings, and there is strong evidence for the detection of Jupiter global modes by means of ground-based, spatially-resolved, velocimetry measurements. We propose to exploit Juno's extremely accurate radio science data by looking at the gravity perturbations that Jupiter's acoustic modes would produce. We evaluate the perturbation to Jupiter's gravitational field using the oscillation spectrum of a polytrope with index 1 and the corresponding radial eigenfunctions. We show that Juno will be most sensitive to the fundamental mode ($n=0$), unless its amplitude is smaller than 0.5 cm/s, i.e. 100 times weaker than the $n \sim\ 4 - 11$ modes detected by spatially-resolved velocimetry. The oscillations yield contributions to Juno's measured gravitational coefficients similar to or larger than those expected from shallow zonal winds (extending to depths less than 300 km). In the case of a strong f-mode (radial velocity $\sim$ 30 cm/s), these contributions would become of the same order as those expected from deep zonal winds (extending to 3000 km), especially on the low degree zonal harmonics, therefore requiring a new approach to the analysis of Juno data.