Characterization of Mesoscale Waves in the Jupiter NEB by Jupiter InfraRed Auroral Mapper on board Juno

A Adriani,D Grassi,R Noschese,C Plainaki,F Altieri,A Cicchetti,R Sordini,F Tosi,M L Moriconi,A Olivieri,S K Atreya,G Sindoni,A Mura,S M Levin ,Andrew P Ingersoll ,Leigh N Fletcher ,Henrik Melin ,Glenn S Orton ,A A Simon-Miller ,Jonathan I Lunine ,J G Bolton

doi:10.3847/1538-3881/aae525

Abstract

Abstract In 2017, the Jupiter InfraRed Auroral Mapper (JIRAM), on board the NASA-ASI Juno mission, observed a wide longitude region (50° W–80° E in System III) that was perturbed by a wave pattern centered at 15° N in the Jupiter’s North Equatorial Belt (NEB). We analyzed JIRAM data acquired on 2017 July 10 using the M-channel and on 2017 February 2 with the spectrometer. The two observations occurred at different times and at slightly different latitudes. The waves appear as clouds blocking the deeper thermal emission. The wave crests are oriented north–south, and the typical wave packet contains 10 crests and 10 troughs. We used Fourier analysis to rigorously determine the wavenumbers associated with the observed patterns at a confidence level of 90%. Wavelet analysis was also used to constrain the spatial localization of the largest energies involved in the process and determine the wavelengths carrying the major contribution. We found wavelengths ranging from 1400 to 1900 km, and generally decreasing toward the west. Where possible, we also computed a vertical location of the cloud pressure levels from the inversion of the spectral radiances measured by the JIRAM spectrometer. The waves were detected at pressure levels consistent with the NH3 as well as NH4SH clouds. Phase velocities could not be determined with sufficient confidence to discriminate whether the alternating crests and troughs are a propagating wave or a manifestation of a fluid dynamical instability.

Highlights

Mesoscale atmospheric phenomena refer to horizontal motion scales ranging from ∼10 up to 1000 km on the Earth (Lin 2007)
In 2017, the Jupiter InfraRed Auroral Mapper (JIRAM), on board the NASA-ASI Juno mission, observed a wide longitude region (50° W–80° E in System III) that was perturbed by a wave pattern centered at 15° N in the Jupiter’s North Equatorial Belt (NEB)
The spectroscopic analysis of the wave observed during the PJ4 suggests that, in this case, the wave phenomenon occurs at different atmospheric altitudes and so affects both the NH4SH and the NH3 clouds

Summary

Introduction

Mesoscale atmospheric phenomena refer to horizontal motion scales ranging from ∼10 up to 1000 km on the Earth (Lin 2007). Voyager-ISS (Hunt & Muller 1979; Flasar & Gierasch 1986), New Horizon with its Multispectral Visible Imaging Camera (MVIC) and its Long Range Reconnaissance Imager (LORRI; Simon et al 2015a), and Galileo-NIMS (Arregi et al 2009) all detected wavy features on the underlying clouds at wavelengths ranging from the violet (416 nm) to the NIR (975 nm) All these wavelengths found similar pressure levels no deeper than 0.8 bar, corresponding to the upper troposphere, and where the ammonia cloud deck is predicted to occur (West et al 2004; Atreya et al 2005). The longitude coverage in this case was not sufficient to identify any wave patterns

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