A large active wave trapped in Jupiter's equator

Context. A peculiar atmospheric feature was observed in the equatorial zone (EZ) of Jupiter between September and December 2012 in ground-based and Hubble Space Telescope (HST) images. This feature consisted of two low albedo Y-shaped cloud structures (Y1 and Y2) oriented along the equator and centred on it (latitude 0.5°-1°N). Aims. We wanted to characterize these features, and also tried to find out their properties and understand their nature. Methods. We tracked these features to obtain their velocity and analyse their cloud morphology and the interaction with their surroundings. We present numerical simulations of the phenomenon based on one- and two-layer shallow water models under a Gaussian pulse excitation. Results. Each Y feature had a characteristic zonal length of ~15° (18¿000 km) and a meridional width (distance between the north-south extremes of the Y) of 5° (6000 km), and moved eastward with a speed of around 20-40 m¿s-1 relative to Jupiter’s mean flow. Their lifetime was 90 and 60 days for Y1 and Y2, respectively. In November, both Y1 and Y2 exhibited outbursts of rapidly evolving bright spots emerging from the Y vertex. The Y features were not visible at wavelengths of 255 or 890 nm, which suggests that they were vertically shallow and placed in altitude between the upper equatorial hazes and the main cloud deck. Numerical simulations of the dynamics of the Jovian equatorial region generate Kelvin and Rossby waves, which are similar to those in the Matsuno-Gill model for Earth’s equatorial dynamics, and reproduce the observed cloud morphology and the main properties the main properties of the Y features.Peer ReviewedPostprint (author's final draft

An enduring rapidly moving storm as a guide to Saturn's Equatorial jet's complex structure

This work is licensed under a Creative Commons Attribution 4.0Saturn has an intense and broad eastward equatorial jet with a complex three-dimensional structure mixed with time variability. The equatorial region experiences strong seasonal insolation variations enhanced by ring shadowing, and three of the six known giant planetary-scale storms have developed in it. These factors make Saturn’s equator a natural laboratory to test models of jets in giant planets. Here we report on a bright equatorial atmospheric feature imaged in 2015 that moved steadily at a high speed of 450 ms-1 not measured since 1980–1981 with other equatorial clouds moving within an ample range of velocities. Radiative transfer models show that these motions occur at three altitude levels within the upper haze and clouds. We find that the peak of the jet (latitudes 10ºN to 10º S) suffers intense vertical shears reaching þ2.5 ms-1 km-1, two orders of magnitude higher than meridional shears, and temporal variability above 1 bar altitude level.Peer ReviewedPostprint (published version

A large active wave trapped in Jupiter's equator

Context. A peculiar atmospheric feature was observed in the equatorial zone (EZ) of Jupiter between September and December 2012 in ground-based and Hubble Space Telescope (HST) images. This feature consisted of two low albedo Y-shaped cloud structures (Y1 and Y2) oriented along the equator and centred on it (latitude 0.5°-1°N). Aims. We wanted to characterize these features, and also tried to find out their properties and understand their nature. Methods. We tracked these features to obtain their velocity and analyse their cloud morphology and the interaction with their surroundings. We present numerical simulations of the phenomenon based on one- and two-layer shallow water models under a Gaussian pulse excitation. Results. Each Y feature had a characteristic zonal length of ~15° (18¿000 km) and a meridional width (distance between the north-south extremes of the Y) of 5° (6000 km), and moved eastward with a speed of around 20-40 m¿s-1 relative to Jupiter’s mean flow. Their lifetime was 90 and 60 days for Y1 and Y2, respectively. In November, both Y1 and Y2 exhibited outbursts of rapidly evolving bright spots emerging from the Y vertex. The Y features were not visible at wavelengths of 255 or 890 nm, which suggests that they were vertically shallow and placed in altitude between the upper equatorial hazes and the main cloud deck. Numerical simulations of the dynamics of the Jovian equatorial region generate Kelvin and Rossby waves, which are similar to those in the Matsuno-Gill model for Earth’s equatorial dynamics, and reproduce the observed cloud morphology and the main properties the main properties of the Y features.Peer Reviewe

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

We describe a huge planetary-scale disturbance in the highest-speed Jovian jet at latitude 23.5°N that was first observed in October 2016 during the Juno perijove-2 approach. An extraordinary outburst of four plumes was involved in the disturbance development. They were located in the range of planetographic latitudes from 22.2° to 23.0°N and moved faster than the jet peak with eastward velocities in the range 155 to 175 m s 1. In the wake of the plumes, a turbulent pattern of bright and dark spots (wave number 20–25) formed and progressed during October and November on both sides of the jet, moving with speeds in the range 100–125 m s 1 and leading to a new reddish and homogeneous belt when activity ceased in late November. Nonlinear numerical models reproduce the disturbance cloud patterns as a result of the interaction between local sources (the plumes) and the zonal eastward jet.Peer Reviewe

Bright features in Neptune on 2013-2015 from ground-based observations with small (40 cm) and large telescopes (10 m)

International audienceObservations of Neptune over the last few years obtained with small telescopes (30-50 cm) have resulted in several detections of bright features on the planet. In 2013, 2014 and 2015, different observers have repeatedly observed features of high contrast at Neptune's mid-latitudes using long-pass red filters. This success at observing Neptune clouds with such small telescopes is due to the presence of strong methane absorption bands in Neptune's spectra at red and near infrared wavelengths; these bands provide good contrast for elevated cloud structures. In each case, the atmospheric features identified in the images survived at least a few weeks, but were essentially much more variable and apparently shorter-lived, than the large convective system recently reported on Uranus [de Pater et al. 2015]. The latest and brightest spot on Neptune was first detected on July 13th 2015 with the 2.2m telescope at Calar Alto observatory with the PlanetCam UPV/EHU instrument. The range of wavelengths covered by PlanetCam (from 350 nm to the H band including narrow-band and wide-band filters in and out of methane bands) allows the study of the vertical cloud structure of this bright spot. In particular, the spot is particularly well contrasted at the H band where it accounted to a 40% of the total planet brightness. Observations obtained with small telescopes a few days later provide a good comparison that can be used to scale similar structures in 2013 and 2014 that were observed with 30-50 cm telescopes and the Robo-AO instrument at Palomar observatory. Further high-resolution observations of the 2015 event were obtained in July 25th with the NIRC2 camera in the Keck 2 10-m telescope. These images show the bright spot as a compact bright feature in H band with a longitudinal size of 8,300 km and a latitudinal extension of 5,300 km, well separated from a nearby bright band. The ensemble of observations locate the structure at -41º latitude drifting at about 24.27º/day or -92.3 m/s consistently with the zonal winds. This work demonstrates excellent opportunities for pro-am collaboration in the study of Neptune and the value of nearly continuous monitoring of the planet by a broad network of amateur collaborators

Bright features in Neptune on 2013-2015 from ground-based observations with small (40 cm) and large telescopes (10 m)

International audienceObservations of Neptune over the last few years obtained with small telescopes (30-50 cm) have resulted in several detections of bright features on the planet. In 2013, 2014 and 2015, different observers have repeatedly observed features of high contrast at Neptune's mid-latitudes using long-pass red filters. This success at observing Neptune clouds with such small telescopes is due to the presence of strong methane absorption bands in Neptune's spectra at red and near infrared wavelengths; these bands provide good contrast for elevated cloud structures. In each case, the atmospheric features identified in the images survived at least a few weeks, but were essentially much more variable and apparently shorter-lived, than the large convective system recently reported on Uranus [de Pater et al. 2015]. The latest and brightest spot on Neptune was first detected on July 13th 2015 with the 2.2m telescope at Calar Alto observatory with the PlanetCam UPV/EHU instrument. The range of wavelengths covered by PlanetCam (from 350 nm to the H band including narrow-band and wide-band filters in and out of methane bands) allows the study of the vertical cloud structure of this bright spot. In particular, the spot is particularly well contrasted at the H band where it accounted to a 40% of the total planet brightness. Observations obtained with small telescopes a few days later provide a good comparison that can be used to scale similar structures in 2013 and 2014 that were observed with 30-50 cm telescopes and the Robo-AO instrument at Palomar observatory. Further high-resolution observations of the 2015 event were obtained in July 25th with the NIRC2 camera in the Keck 2 10-m telescope. These images show the bright spot as a compact bright feature in H band with a longitudinal size of 8,300 km and a latitudinal extension of 5,300 km, well separated from a nearby bright band. The ensemble of observations locate the structure at -41º latitude drifting at about 24.27º/day or -92.3 m/s consistently with the zonal winds. This work demonstrates excellent opportunities for pro-am collaboration in the study of Neptune and the value of nearly continuous monitoring of the planet by a broad network of amateur collaborators

Bright features in Neptune on 2013-2015 from ground-based observations with small (40 cm) and large telescopes (10 m)

International audienceObservations of Neptune over the last few years obtained with small telescopes (30-50 cm) have resulted in several detections of bright features on the planet. In 2013, 2014 and 2015, different observers have repeatedly observed features of high contrast at Neptune's mid-latitudes using long-pass red filters. This success at observing Neptune clouds with such small telescopes is due to the presence of strong methane absorption bands in Neptune's spectra at red and near infrared wavelengths; these bands provide good contrast for elevated cloud structures. In each case, the atmospheric features identified in the images survived at least a few weeks, but were essentially much more variable and apparently shorter-lived, than the large convective system recently reported on Uranus [de Pater et al. 2015]. The latest and brightest spot on Neptune was first detected on July 13th 2015 with the 2.2m telescope at Calar Alto observatory with the PlanetCam UPV/EHU instrument. The range of wavelengths covered by PlanetCam (from 350 nm to the H band including narrow-band and wide-band filters in and out of methane bands) allows the study of the vertical cloud structure of this bright spot. In particular, the spot is particularly well contrasted at the H band where it accounted to a 40% of the total planet brightness. Observations obtained with small telescopes a few days later provide a good comparison that can be used to scale similar structures in 2013 and 2014 that were observed with 30-50 cm telescopes and the Robo-AO instrument at Palomar observatory. Further high-resolution observations of the 2015 event were obtained in July 25th with the NIRC2 camera in the Keck 2 10-m telescope. These images show the bright spot as a compact bright feature in H band with a longitudinal size of 8,300 km and a latitudinal extension of 5,300 km, well separated from a nearby bright band. The ensemble of observations locate the structure at -41º latitude drifting at about 24.27º/day or -92.3 m/s consistently with the zonal winds. This work demonstrates excellent opportunities for pro-am collaboration in the study of Neptune and the value of nearly continuous monitoring of the planet by a broad network of amateur collaborators

Long-Term Evolution of the Aerosol Debris Cloud Produced by the 2009 Impact on Jupiter

We present a study of the long-term evolution of the cloud of aerosols produced in the atmosphere of Jupiter by the impact of an object on 19 July 2009 (Sánchez-Lavega, A. et al. [2010]. Astrophys. J. 715, L155–L159). The work is based on images obtained during 5 months from the impact to 31 December 2009 taken in visible continuum wavelengths and from 20 July 2009 to 28 May 2010 taken in near-infrared deep hydrogen–methane absorption bands at 2.1–2.3 μm. The impact cloud expanded zonally from ∼5000 km (July 19) to 225,000 km (29 October, about 180° in longitude), remaining meridionally localized within a latitude band from 53.5°S to 61.5°S planetographic latitude. During the first two months after its formation the site showed heterogeneous structure with 500–1000 km sized embedded spots. Later the reflectivity of the debris field became more homogeneous due to clump mergers. The cloud was mainly dispersed in longitude by the dominant zonal winds and their meridional shear, during the initial stages, localized motions may have been induced by thermal perturbation caused by the impact’s energy deposition. The tracking of individual spots within the impact cloud shows that the westward jet at 56.5°S latitude increases its eastward velocity with altitude above the tropopause by 5–10 m s−1. The corresponding vertical wind shear is low, about 1 m s−1 per scale height in agreement with previous thermal wind estimations. We found evidence for discrete localized meridional motions with speeds of 1–2 m s−1. Two numerical models are used to simulate the observed cloud dispersion. One is a pure advection of the aerosols by the winds and their shears. The other uses the EPIC code, a nonlinear calculation of the evolution of the potential vorticity field generated by a heat pulse that simulates the impact. Both models reproduce the observed global structure of the cloud and the dominant zonal dispersion of the aerosols, but not the details of the cloud morphology. The reflectivity of the impact cloud decreased exponentially with a characteristic timescale of 15 days; we can explain this behavior with a radiative transfer model of the cloud optical depth coupled to an advection model of the cloud dispersion by the wind shears. The expected sedimentation time in the stratosphere (altitude levels 5–100 mbar) for the small aerosol particles forming the cloud is 45–200 days, thus aerosols were removed vertically over the long term following their zonal dispersion. No evidence of the cloud was detected 10 months after the impact