Evolution of the cloud field and wind structure of Jupiter's highest speed jet during a huge disturbance

Abstract

Aims. Despite the banded visual aspect of cloud patterns in Jupiter, high resolution images indicate that these regions are markedly turbulent. One region of particular interest is the north temperate belt (NTB) at 21 • N planetocentric latitude, where the most intense Jovian jet resides with eastward peak speeds of 160−180 m s −1 . Almost every 15 years, the NTB is known to experience an eruption or disturbance that dramatically changes its appearance, a phenomenon known as NTB disturbance (NTBD). In this work, we characterize the morphology of the disturbed cloud field in the wake of the plumes that caused the perturbation, and check for changes in the velocity or shape of the jet. Methods. The 2007 disturbance was witnessed with unprecedented resolution by the Hubble Space Telescope and by a long-term survey based on the "International Outer Planet Watch" (IOPW) network. Our analysis is based on the brightness spectral distribution to characterize both the typical spatial frequency of the perturbation and its turbulent and wavy nature. We also compare our characterization with non-linear dynamical simulations of the disturbance using the EPIC dynamical model. Finally, we obtain a renewed wind profile for the region of interest by cloud tracking. Results. We detect a change in the power spectral slope of the cloud brightness following the disturbance that is related to a change in the typical size of the observed structures. We model the initial disturbance as a Rossby wave. A comparison of the jet profile in the NTB just after the disturbance ended (June 2007) with one observed a year later (July 2008), illustrates a net change occurred in the westward jet at 16 • N with a speed change of 25 m s −1 . As implied by the power spectra analysis, the disturbance and its related Rossby wave dissipate. We propose that this dissipation produced a momentum transfer to the anticyclonic side of the NTB jet increasing the speed of the westward jet at 16 • N as also supported by numerical simulations.

A planetary‐scale disturbance in the most intense Jovian atmospheric jet from JunoCam and ground‐based observations

“…The SEBD and NTBD planetary‐scale disturbances represent one of the major challenges to understand Jupiter's atmospheric dynamics, but at the same time the underlying physics can give us important insights into the parameters that define the upper troposphere, beneath the upper clouds, such as the abundance of water needed to initiate moist convection and the vertical structure of winds and temperature. They are also important because they give us information about the nature of Jupiter's winds through the turbulence pattern the plumes generate in their wake (vortices, swirls, filaments, and waves) and on how they transfer or extract energy and momentum from or to the zonal flow, changing the wind profile as reported in this paper [ Sánchez‐Lavega et al ., ; Barrado‐Izagirre et al ., ].…”

Jupiter’s zonal winds and their variability studied with small-size telescopes

“…10 and 11). This is the latitude of the NTB, where the fastest jet stream lies and where planetaryscale convective disturbances (NTBD) developed with some recurrence (Sánchez-Lavega et al 1990;García-Melendo et al 2005), the last one having occurred in 2007 (Sánchez- Lavega et al 2008;Barrado-Izagirre et al 2009a). …”

“…Although some of the bands' morphology changes in periods of years (Peek 1958;Chapman & Reese 1968;Reese 1972;Minton 1972a,b;Smith & Hunt 1976;Sánchez-Lavega & Rodrigo 1985;Rogers 1995;Sánchez-Lavega & Gómez 1996;Sánchez-Lavega et al 1996;Fletcher et al 2011;Pérez-Hoyos et al 2012), the wind profile maintains a remarkable temporal stability. Furthermore, this zonal wind profile is not strongly affected by the dynamic perturbations at cloud level, such as those developed by convective storms like the South Equatorial Belt Disturbance (SEBD; Sánchez-Lavega et al 1996;Sánchez-Lavega & Gómez 1996) and the North Temperate Belt Disturbance (NTBD) (García-Melendo et al 2005Sánchez-Lavega et al 2008;Barrado-Izagirre et al 2009a). Even large impacts on the planet such as those of 1994 and 2009 (Hammel et al 1995(Hammel et al , 2010Sánchez-Lavega et al 1998, which released energies at the impact's locations of 10 22 and 10 20 joules, respectively, were not able to alter the winds at the latitudes of the impacts.…”

“…The changes in the NEB, for example, may be linked to the appearance of large-scale hot spots (García-Melendo et al 2011a) and those in the SEB to zonal distribution of chevrons and waves (Simon-Miller et al 2012). There are also some local changes in the NTB and in the westward 17 • N (planetocentric) jet (Barrado-Izagirre et al 2009a) that seem to be linked to planetary-size disturbances.…”

“…Previous studies using these kinds of images , 2011aBarrado-Izagirre et al 2009a;Sánchez-Lavega et al 2008, 2011Pérez-Hoyos et al 2012) inferred wind velocities by manual tracking of long-lived cloud details, which had been tracked over many different images or image pairs separated by several planetary rotations. We show that an automatic cloud correlation technique such as those used to analyze higher resolution HST or spacecraft data also works for ground-based observations with small telescopes obtained by keen amateur observers.…”