Spatially resolved absolute spectral reflectivity of Jupiter : 3390-8400 angstroms. The Jovian thermal structure from Pioneer 10 infrared radiometer data. Observations and analysis of 8-14 micron thermal emission of Jupiter : a model of thermal structure and cloud properties
NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. Part 1 presents determinations of the absolute reflectivities of several visually distinct regions of Jupiter between 3390 and 8400Å, at 10Å resolution, from observations made on t...
| Summary: | NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.
Part 1 presents determinations of the absolute reflectivities of several visually distinct regions of Jupiter between 3390 and 8400Å, at 10Å resolution, from observations made on the 60-inch telescope at Mt.Wilson between June 1973 and June 1974. These have been checked independently by observations using 150-200Å wide filters from 3400 to 6400Å. The absolute scale of Oke and Schild (1970) is used, and solar irradiance values are taken from Arvesen et al.(1969).
The results are presented as a set of 9 figures showing the wavelength dependence of reflectivity. There is generally good internal consistency within the estimated errors. The effective reflectivities for several regions on the meridian in the 3390 to 8400Å range are: South Tropical Zone- 0.76±.05, North Tropical Zone- 0.68±.08, South Equatorial Belt- 0.63±.08, North Equatorial Belt- 0.62±.04, and Great Red Spot- 0.64±.09. Reflectivities nearer the limb are also observed. In support of the Pioneer imaging photopolarimeter experiment, the appropriate blue and red reflectivity values are also tabulated. For the regions on the meridian listed above, the equivalent widths of molecular bands vary as: CH[subscript 4] (6190Å): 14-16Å; CH[subscript 4](7250Å): 77-86Å; and NH[subscript 3](7900Å): 87-95Å. Significant differences from previous results of Pilcher et al. (1973) are noted.
Part 2 presents latitude sectors of the 20 and 40 micron maps of Jupiter obtained by the Pioneer 10 infrared radiometer. These data are used to derive simple models for the average vertical thermal structure over the South Equatorial Belt and the South Tropical Zone, with additional examples of models for the North Equatorial Belt and the Great Red Spot. The models assume gaseous absorption by H[subscript 2] and NH[subscript 3] alone. The models are predominantly composed of H[subscript 2] with He dilution constrained to 0-35% by volume.
For the South Equatorial Belt, the temperature is about 170°K at 1.0 atm pressure, assuming the deep atmosphere to be adiabatic. The temperature may be 113-121°K near 0.2 atm, depending on what is assumed for the overlying thermal structure. In a non-scattering model, as given above, the South Tropical Zone is some 8°K cooler than the SEB near 1.0 atm. However, the data may also be successfully modeled by a thermal structure at minimum variance from that of the SEB, but with an optically thick cloud close to the 150°K level. Such a model is consistent with the visible and 5 micron appearance of the planet, and the cloud is coincident with the location at which saturation of NH[subscript 3] is expected to begin. For this model, the STrZ temperature is 3°K cooler than the SEB near 0.2 atm. The Great Red Spot may be modeled by a thermal structure like the "cloudy" STrZ model, but 5°K cooler near 0.2 atm. The local effective temperatures for the SEB (129°K) and the STrZ (126°K) are both below the effective temperature of 134°K from earth-based measurements. The derived thermal structures are inconsistent with the neutral atmosphere inversion of the Pioneer 10 radio occultation (Kliore et al.,1974), but not with others in the literature, including the Gulkis et al. (1973) model for the microwave spectrum.
Part 3 reports: (1) observations of the limb structure near the equator of Jupiter at 8.15 and 8.44 microns using the Palomar 200-inch telescope at a resolution of about 3 arc seconds and a cooled filter-wheelspectrometer ([...]λ/λ[...]0.015), and (2) a model of the thermal structure and cloud properties of the atmosphere which is most consistent with spatially and spectrally resolved observations of the planet in the 8 - 14 micron range, including those reported in (1).
The thermal structure derived in Part 2 below the 0.2 atm level must be cooled by some 6°K in order to match the 12-14 micron spectrum, which is dominated by the opacity of H[subscript 2]. An NH[subscript 3] abundance defined by saturation equilibrium is consistent with the 9.5-12.0 micron spectrum, dominated by the opacity of that gas. The thermal structure above the 0.2 atm level is determined by fitting spectral and limb structure data in the 7.2-8.4 micron range, dominated by the opacity of CH[subscript 4]. The result is an inverted thermal structure with a base of about 110°K at 0.2 atm, rising through 150°K at about 0.03 atm. The mixing ratio of CH[subscript 4] most consistent with the spectral and limb structure data is 2.0 x 10[superscript -3] some three times that assumed in "solar abundance" models.
The 8.2-9.5 micron spectral region is not eerily matched by simple gaseous opacity sources. However, a haze of solid NH[subscript 3] particles above a thick cloud (which exists only in zones, as implied in Part 2) is consistent with the observed spectrum. Difficulty is encountered, however, with limb structure data at 8.44 microns and with some observations outside the 8-14 micron range.
Further observations of the separate spectral characteristics of belts and zones is recommended, as well as more accurate laboratory data for the opacity of atmospheric constituents in the relevant thermal regime and more sophisticated scattering approximations that used in this model.
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