A Universal Phase Function for Jovian Clouds from the Visible to Near-IR Wavelength Region. I. Zone Phase Function

Abstract

A set of wavelength-dependent scattering phase functions for Jupiter's clouds has been obtained; the Mie theory was employed to simulate well-defined scattering phase functions deduced from an analysis of the Pioneer 10 photometry data (Tomasko et al. 1978, AAA 021.099.011). A reasonable fit to the cloud-phase functions for the bright zone (STrZ) was obtained with a particle effective radius, reff, of 0.96 μ m and the real part of the refractive index, nr, being 1.591 for the blue and 1.535 for the red, slightly higher than the nominal values for ammonia ice. The derived Mie phase functions were tested against several STrZ data. The appropriateness of these phase functions has been demonstrated through the fact that they reproduce not only the observed limb-to-limb intensity profiles, but also the correct wavelength dependence of the haze optical thickness for a wide wavelength range from visible to near-infrared.

Directly imaged exoplanets in reflected starlight: the importance of knowing the planet radius

“…Our single-scattering albedo ω 0 = 0.90 is slightly low compared for example to Schmid et al (2011), but within the ranges usually considered in the literature (e.g. Satoh et al 2000;Pérez-Hoyos et al 2012). The methane abundance that we adopt ( f CH 4 = 5 × 10 −3 ) is comparable to that of Jupiter (2.1 × 10 −3 ) and Saturn (4.5 × 10 −3 ) but somewhat lower than for Uranus or Neptune (2.4 × 10 −2 and 3.5 × 10 −2 , respectively) (Sánchez-Lavega 2010).…”

The jovian anticyclone BAIII. Aerosol properties and color change

“…Although we cannot preclude this hypothesis, it must be noted that it would result in a particle phase function different from that determined from Pioneer observations (Satoh et al, 2000). Such a small particle population, although could be present in the upper levels of the tropospheric haze (West et al, 2004) is not expected to form the bulk of this haze.…”

“…We first need to know the corresponding imaginary refractive indices so we use a Mie phase function for spherical particles. The particle phase function used so far is similar to that of particles with mean particle radius of about 0.75 lm (Satoh et al, 2000). Assuming m r = 1.43, close to ammonia values, as the real refractive index (Martonchik et al, 1984), the imaginary refractive indices which produce modeled single scattering albedo values for the oval center are summarized in Table 4.…”

“…Such population of small particles may be present at the upper tropospheric or stratospheric levels, but it is not likely that we can find them closer to the ammonia level. It should be noted that the Pioneer phase function described by Tomasko et al (1978) is strongly forward scattering and it is probably not consistent with particles of such a small size (Satoh et al, 2000). Anyway, a small increase in the mean particle size could have produced a significant contribution to the reddening of the oval BA, but only if it is happening in a small-sized particle population.…”

“…The bottom cloud is located at a plausible ammonia condensation level but it could be also formed by ammonium hydrosulfide (Irwin et al, 2001). For the particle scattering properties, we assumed a Henyey-Greenstein (stratospheric particles) or double Henyey-Greenstein phase function (tropospheric particles) with the parameters already presented by Tomasko et al (1978) and Satoh et al (2000). The bottom cloud was represented using an isotropic phase function with a single scattering albedo…”