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This study explains the observed colors of the annular rings around anticyclones of Jupiter.  Specifically, they try to determine the vertical structure of these jovian vortices (i.e. the GreatRed Spot (GRS), Red Oval BA, and the white ovals at 41S).  According to the authors, the structures are overall very similar. They said that the main distinction between the colors of the ovals is caused by varying particle densities in the tropospheric–stratospheric hazes.

I would have wanted to write more about this publication but I can’t squeeze some time. So I’ll just share the abstract below.  I may write another post about this paper in the future (cross fingers).

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Persistent rings in and around Jupiter’s anticyclones – Observations and theory Icarus, 210 (2), 742-762 DOI:10.1016/j.icarus.2010.07.027

Abstract

We present observations and theoretical calculations to derive the vertical structure of and secondary circulation in jovian vortices, a necessary piece of information to ultimately explain the red color in the annular ring inside Jupiter’s Oval BA. The observations were taken with the near-infrared detector NIRC2 coupled to the adaptive optics system on the 10-m W.M. Keck telescope (UT 21 July 2006; UT 11 May2008) and with the Hubble Space Telescope at visible wavelengths (UT 24 and 25 April 2006 usingACS; UT 9 and 10 May 2008 using WFPC2). The spatial resolution in the near-IR (0.1–0.1500 at 1–5μm) is comparable to that obtained at UV–visible wavelengths (0.05–0.100 at 250–890 nm). At 5 μm we are sensitive to Jupiter’s thermal emission, whereas at shorter wavelengths we view the planet inreflected sunlight. These data sets are complementary, as images at 0.25–1.8 μm provide information on the clouds/hazes in the troposphere–stratosphere, while the 5-μm emission maps yield information on deeper layers in the atmosphere, in regions without clouds. At the latter wavelength numerous tinyovals can be discerned at latitudes between 45S and 60S, which show up as rings with diameters less than or equal to 1000 km surrounding small ovals visible in HST data. Several white ovals at 41S, as well as a new red oval that was discovered to the west of the GRS, also reveal 5-μm bright rings around their peripheries,which coincide with dark/blue rings at visible wavelengths. Typical brightness temperatures inthese 5-μm bright rings are 225–250 K, indicative of regions that are cloud-free down to at least the ~4 bar level, and perhaps down to 5–7 bar, i.e., well within the water cloud.

I. de Pater, Icarus, 210 (2), 742-762

Radiative transfer modeling of the 1–2 μm observations indicates that all ovals, i.e., including the GreatRed Spot (GRS), Red Oval BA, and the white ovals at 41S, are overall very similar in vertical structure. The main distinction between the ovals is caused by variations in the particle densities in the tropospheric–stratospheric hazes (2–650 mbar). These are 5–8 times higher above the red ovals than above the whiteones at 41S. The combination of the 5-μm rings and the vertical structure derived from near-IR data suggests anticyclones to extend vertically from (at least) the water cloud (~5 bar) up to the tropopause(~100–200 mbar), and in some cases into the stratosphere.

I. de Pater, Icarus, 210 (2), 742-762

Based upon our observations, we propose that air is rising along the center of a vortex, and descending around the outer periphery, producing the 5-μm bright rings. Observationally, we constrain the maximum radius of these rings to be less than twice the local Rossby deformation radius, LR. If the radius of the visible oval (i.e., the clouds that make the oval visible) is >3000 km, our observations suggest that the descending part of the secondary circulation must be within these ovals. For the Red Oval BA, we postulate that the return flow is at the location of its red annulus, which has a radius of ~3000 km.

I. de Pater, Icarus, 210 (2), 742-762

We develop a theory for the secondary circulation, where air is (baroclinically) rising along the centerof a vortex in a subadiabatic atmosphere, and descending at a distance not exceeding ~2 the local Ross by deformation radius. Using this model, we find a time scale for mixing throughout the vortex of order several months, which suggests that the chromophores that are responsible for the red color of Oval BA’sred annulus must be produced locally, at the location of the annulus. This production most likely results from the adiabatic heating in the descending part of the secondary circulation. Such higher-than-ambient temperature causes NH3–ice to sublime, which will expose the condensation nuclei, such as the red chromophores.

Christopher Go is with the Physics Department of the University of San Carlos in Cebu.

de Pater, I., Wong, M., Marcus, P., Luszcz-Cook, S., Ádámkovics, M., Conrad, A., Asay-Davis, X., & Go, C. (2010). Persistent rings in and around Jupiter’s anticyclones – Observations and theory Icarus, 210 (2), 742-762 DOI: 10.1016/j.icarus.2010.07.027

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