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1.
Jupiter was observed in six continuum wavelength channels in the region 4100–8300 Å, using a silicon vidicon imaging photometer. Spectral reflectivities and high spatial resolution limb-darkening curves for several belts and zones have been extracted from the data. Simple model fits to the data yield information regarding spectral and spatial variations in single-scattering albedos and shape of particle single-scattering phase functions. Belts appear to be more backscattering than zones, particularly in the blue. The data are in moderate agreement with limb-darkening predicted by models derived from the center-to-limb variation in equivalent width of the H2 4-0 S(1) quadrupole line (Cochran, 1976) in the South Tropical Zone, but strongly disagree with the results of such models for the North Equatorial Belt. 相似文献
2.
Robert A. West 《Icarus》1983,53(2):301-309
Spatially resolved measurements of Saturn's reflectivity in the 6190-, 7250-, and 8996-Å methane bands are analyzed to determine cloud vertical structures in the Equatorial Zone, South Equatorial Belt, and North and South Temperate Regions near latitudes ±30°. Radiative transfer models are computed for a simple two-parameter structure. The parameters are A0, the methane column abundance in an aerosol-free layer at the top of the atmosphere, and A1, the specific abundance of methane in a semi-infinite homogeneous gas and cloud mixture deep in the atmosphere. For the Equatorial Zone, a model with A0 = 37 ± 3 m-am and A1 = 26 ± 2 m-am fits all three bands. For the North Temperate Region, a model with A0 = 39 m-am and A1 = 47 m-am comes close to fitting all three bands. For the South Equatorial Belt and South Temperate Region, a single A0 and A1 do not fit all three bands. The structure for the South Equatorial Belt resembles that for the North Temperate Region. The level where unit cloud optical depth occurs in the South Temperate Region is deeper than the corresponding level at other latitudes. Some suggestions are proposed to explain differences between model parameters derived using different absorption bands. 相似文献
3.
We present cloud structure models for Jupiter's Great Red Spot, Equatorial Zone, North Tropical Zone, North and South Temperate Zones, North and South Polar Regions, and North and South Polar Hoods. The models are based on images of Jupiter in three methane bands (between 6190 and 8900 Å) and nearby continuum. Radiative transfer calculations include multiple scattering and absorption from three aerosol layers, the topmost of which is a high thin haze and the lower two are called clouds. All models are computed relative to a similar model for the South Tropical Zone which fits methane absorption data and Pioneer photometry data well. Outstanding features suggested by the model results are the transition in the upper-cloud altitude to about 3 km lower altitude from the tropical zones to temperate zones and polar regions, a N/S asymmetry in cloud thickness in the tropical and temperate zones, the presence of aerosols up to about 0.3 bar in the Great Red Spot and Equatorial Zone, the need for a significant (τ ～ 0.75 to 1.0) aerosol content in this region in the Equatorial Zone, and perhaps an even higher and thicker cloud in the South Polar Hood. The haze layer above both polar hoods may exhibit different scattering properties than the haze which covers lower latitudes. In comparing the present results with models derived from polarization and infrared observations we conclude that polarization data are sensitive to aerosols in and above the upper cloud layer but insensitive to deeper cloud structure, and the converse is true for infrared data. 相似文献
4.
Spatially resolved reflectivities from 3000 to 6600 Å of three positions from the center to the limb of the Jovian Equator, North Equatorial Belt, and North Tropical Zone are analyzed to determine the vertical distribution and wavelength dependence of various sources of blue and uv absorption. Six different models of the distribution of absorbing dust particles are examined. In each model, the variation of dust optical depth and cloud single-scattering albedo are determined. Only those models having dust above the upper NH3 cloud layer will fit the data. The high altitude dust distribution is approximately uniform over the three regions examined. The contrast in reflectivity of the belts and zones may be modeled by a different cloud single-scattering albedo in the different regions. 相似文献
5.
Images from three filters of the Voyager 1 wide-angle camera were used to measure the continuum reflectivity and spectral gradient near 6000 Å and the 6190-Å band methane/continuum ratio for a variety of cloud features in Jupiter's atmosphere. The dark “barge” features in the North Equatorial Belt have anomalously strong positive continuum spectral gradients suggesting unique composition, probably not elemental sulfur. Methane absorption was shown at unprecedented spatial scales for the Great Red Spot and its immediate environment, for a dark barge feature in the North Equatorial Belt, and for two hot spot and plume regions in the North Equatorial Belt. Some small-scale features, unresolvable at ground-based resolution, show significant enhancement in methane absorption. Any enhancement in methane absorption is conspicuously absent in both hot spot regions with 5-μm brightness temperature 255°K. Methane absorption and 5-μm emission are correlated in the vicinity of the Great Red Spot but are anticorrelated in one of the plume hot spot regions. Methane absorption and simultaneously maps of 5-μm brightness temperature were quantitatively compared to realistic cloud structure models which include multiple scattering at 5 μm as well as in the visible. A curve in parameter space defines the solution to any observed quantity, ranging from a shallow atmosphere and thin NH3 cloud to a deep atmosphere with a thick ammonia cloud. Without additional constraints, such as center-to-limb information, it is impossible to specify the NH3 cloud optical depth and pressure of a deeper cloud top independently. Variability in H2 quadrupole lines was also investigated and it was found that the constancy of the 4-0 S(1)-line equivalent width is consistent with the constancy of the methane 6190-Å band equivalent width at ground-based resolution, but the much greater variability of the 3-0 S(1) line is inconsistent with either the methane band or 4-0 S(1) line. In hot spot regions the 255°K brightness temperature requires a cloud optical depth of about 2 or less at 5 μm in the NH3 cloud layer. To be consistent with the observed 6190-Å methane absorption in hot spot regions, the NH3 cloud optical depth in the visible is about 7.5, implying that aerosols in hot spot regions have effective radii near 1 μm or less. 相似文献
6.
Glenn S. Orton 《Icarus》1975,26(2):159-174
Observational determinations of the absolute spectral reflectivities of visually distinct regions of Jupiter are presented. The observations cover the 3390–8400 Å region at 10 Å resolution, and they are compared with observations using 150–200 Å filters in the 3400–6400 Å range. The effective reflectivities for several regions (on the meridian) in the 3400–8400 Å range are: South Tropical Zone, 0.76±0.05; North Tropical Zone, 0.68±0.08; South Equatorial Belt, 0.63±0.08; North Equatorial Belt, 0.62±0.04; and the Great Red Spot, 0.64±0.09. Reflectivities near the limb are also observed. The appropriate blue and red reflectivities are tabulated in support of the Pioneer 10 and 11 imaging photopolarimeter experiments. For the regions listed above, equivalent widths of molecular bands vary as: CH4 (6190 Å), 14–16 Å; CH4 (7250 Å), 77–86 Å; and NH3 (7900 Å), 87–95 Å. Significant differences from the results of C. B. Pilcher, R. G. Prinn, and T. B. McCord (“Spectroscopy of Jupiter: 3200 to 11200 Å,” J. Atmos. Sci.30, 302–307.) 相似文献
7.
P.G.J. IrwinU. Dyudina 《Icarus》2002,156(1):52-63
The cloud structure of the jovian atmosphere at pressures less than 2 bars has previously been estimated using near-infrared observations such as those by both the Solid State Imager (SSI) and Near-Infrared Mapping Spectrometer (NIMS) instruments on board the Galileo spacecraft. Unfortunately, complete near-infrared spectra, such as those measured by NIMS, take a long time to be analyzed with multiple-scattering radiative transfer models and thus it has until now been rather difficult to use these data to produce wide-area cloud maps.In this paper we show how principal component analysis may be employed to isolate a small number of empirical orthogonal functions (EOFs) from spectra of Jupiter made by Galileo/NIMS. These EOFs may be used to represent the variance of real NIMS spectra to a high degree of accuracy and with good noise and “drop-out” discrimination. Because of this, a small set of representative spectra may then be calculated using these EOFs and input into a retrieval model that generates a table of fitted cloud profiles for each case. This approach avoids the long times required for analyzing a large number of spectra with full multiple-scattering radiative transfer models and allows us to represent the variability of the 3000 spectra contained in the observations of the North Equatorial Belt (NEB) used in this study with only 75 representative spectra. The cloud structures fitted to these representative spectra were interpolated for the spectra found at individual locations in the measured NIMS data set to produce maps of cloud opacity and mean particle size. We find that the dominant opacity variation, anticorrelated with 5-μm brightness, exists in the 1-2 bar pressure range. The distribution of the cloud at 0.72 bars is mapped and found to be more zonally diffuse than the lower clouds. We find at least one 2000-km-sized deep convective cloud in the NEB vertically extending to all the pressure levels that can be sensed by NIMS. 相似文献
8.
Dale W. Smith 《Icarus》1980,44(1):116-133
The Galilean satellite eclipse technique for measuring the aerosol distribution in the Jovian lower stratosphere and upper troposphere is described and applied using 30 color observations of 12 natural satellite eclipses obtained with the 200-in Hale telescope. These events probe the North and South Polar Regions, the North Temperate Belt, the South Equatorial Belt, the South Tropical Zone, the South Temperate Zone, and the Great Red Spot. Aerosol is found above the visible cloud tops in all locations. It is very tenuous and varies with altitude, increasing rapidly with downward passage through the tropopause. The aerosol extinction coefficient at 1.05 μm is 1.0 ± 0.05 × 10?8 cm?1 at the tropopause and the mass density is a few times 10?13 g cm?3. The observations require some aerosol above the tropopause but do not clearly determine its structure. The present analysis emphasizes an extended haze distribution, but the alternate possibility that the stratospheric aerosol resides in a thin layer is not excluded. The vertical aerosol optical depth above the tropopause at 1.05 μm exceeds 0.04 in the NPR, SPR, NTB, SEB, and StrZ, is ～0.006 ± 0.003 in the STZ, and is ～ 0.003 ± 0.001 above the GRS. The aerosol extinction increases with decreasing wavelength in the STZ and NTB and indicates a particle radius of 0.2–0.5 μm; a radius of ～0.9 μm is indicated in the STrZ. 相似文献
9.
Spatially resolved absolute reflectivities of several regions of the Jovian disk in the wavelength region 3000 to 10760 Å are presented. Spectra were obtained of the central meridian and limbs of the Equatorial Region, North Equatorial Belt, and North Tropical Zone. Equivalent widths of several CH4 and NH3 bands are measured. The spatial variations of continuum reflectivity and absorption band profiles are shown in various ratio spectra. 相似文献
10.
We present spatial scans at eight wavelengths between 7.8 and 24 μm along Jupiter's meridian and along the Equatorial Zone, the North Equatorial Belt, and the South Tropical Zone. Some features of these scans are differences in brightness temperatures between the Great Red Spot and the surrounding South Tropical Zone, a higher temperature at high northern latitudes than high southern latitudes, equal or possibly higher temperatures of zones than belts at 7.8 μm in contrast to higher temperatures of belts at other observed wavelengths, very strong limb darkening at 8.9 μm possibly due to a large scale height or a nonuniform distribution of solid NH3 particles, and inhomogenities within belts and zones. 相似文献
11.
Ten-micrometer spectra of the North Tropical Zone, North Equatorial Belt, and Great Red Spot at a spectral resolution of 1.1 cm?1 are compared to synthetic spectra. These ground-based spectra were obtained simultaneously with the Voyager 1 encounter with Jupiter in March, 1979. The NH3 vertical distribution is found to decrease with altitude significantly faster than the saturated vapor pressure curve and is different for the three observed regions. Spatial variability in the NH3 mixing ratio could be caused by changes in the amount of NH3 condensation or in the degree of the NH3 photolysis. The C2H6 emission at 12 μm has approximately the same strength at the North Tropical Zone and North Equatorial Belt, but it is 30% weaker at the Great Red Spot. A cooler temperature inversion or a smaller abundance of C2H6 could explain the lower C2H6 emission over the Great Red Spot. 相似文献
12.
Glenn S. Orton 《Icarus》1975,26(2):125-141
Temperature profiles for low latitude regions of Jupiter in the 1.0-0.1 bar pressure regime are recovered from Pioneer 10 infrared radiometer data. The temperature near 0.1 bar is 108–117K, depending on the overlying thermal structure assumed. For the South Equatorial Belt, the temperature at 1.0 bar is 170 K, assuming an adiabatic lapse rate in the deep atmosphere. The South Tropical Zone temperature at this level is 155K if pure gaseous absorption is assumed. Alternatively, the temperature is much closer to that in the SEB, assuming the presence of an optically opaque cloud near the 0.6atm (145K) level. Such a cloud presence in the STrZ may be correlated with the visible and 5 micron appearance of the planet and with NH3 saturation just below this position. The molar fraction of H2 most consistent with the data is 0.91 ± 0.08. conditional on the perfect validity of the model and the lack of systematic errors in the data. The effective temperatures of the SEB and STrZ are 127.6 and 124.2K, respectively. These temperature profiles are generally consistent with data at other wavelengths and radiative-equilibrium models, but a discrepancy with the preliminary neutral atmosphere inversion of Pioneer 10 radio occultation data remains unexplained. 相似文献
13.
Robert A. West 《Icarus》1979,38(1):34-53
This work presents results and analysis of center-to-limb variations and absolute reflectivity measurements of Jupiter's South Equatorial Belt (SEBs) and South Tropical Zone (STrZ) in three narrowband methane filters and three nearby continuum filters. The observations and data reduction are reported in Paper I. The data were analyzed in terms of plane-parallel but vertically inhomogeneous atmospheric models. Diffuse reflecting-scattering models (RSM) and two-cloud models (TCM) with and without an additional high, thin haze layer (required from Pioneer observations) were computed. Computations of multiple scattering were performed with a doubling technique. Anisotropic phase functions derived from Pioneer 10 photometry were used. Observations in the strong 8900-Å band severely constrain the position of the upper cloud top. To fit both the center-to-limb variations and absolute reflectivity, the STrZ cloud top must lie between 0.55 bar total pressure, if the aerosols are concentrated (small scattering mean free path), and 0.43 bar for the RSM model with 8 to 10 m-am CH4 per unit cloud optical depth. The 8900-Å data also constrain the cloud optical depth. If the cloud particles are concentrated, the top cloud must have optical depths between 1.5 and 2.5. The data at 7250 and 6190 Å are well suited to specify the level of the lower cloud. TCM models with concentrated aerosols have lower cloud-top pressure between 2.4 and 2.7 bars in the STrZ. To account for the small but significant differences between observations of the STrZ and SEBs, several configurations are allowed. An RSM model for the STrZ and a TCM model for the SEBs would constitute the greatest possible structural differences. RSM models were not satisfactory for the SEBs. If both the STrZ and SEBs are regions where the aerosols are concentrated, the upper cloud is slightly deeper (by 0.03 to 0.08 bar) in the SEBs; the cloud thickness is less (0 to 15%); and the lower cloud is deeper (by 0.4 to 0.8 bar). A forward scattering haze layer of the type derived from analysis of Pioneer 10 photometry is needed in the present STrZ and SEBs models at the 0.1-bar level to account for the limb darkening in the continuum. The haze could be concentrated in a thin layer or spread diffusely above the cloud top with little effect on the pressure level of the top cloud. A CH4/H2 mixing ratio of 1.2 to 1.5 × 10?3 is estimated from computations by W. D. Cochran of the hydrogen quadrupole absorption strength for present models. The smaller value was used to assign pressure levels stated above. 相似文献
14.
P. Chayer G. Fontaine M. Fontaine R. Lamontagne F. Wesemael J. Dupuis U. Heber R. Napiwotzki S. Moehler 《Astrophysics and Space Science》2004,291(3-4):359-366
We present a FUSE abundance analysis of EC14026 stars. We compare the abundances of heavy elements in the atmospheres of EC14026 stars to non-pulsating stars with similar atmospheric parameters, and investigate whether weak stellar winds could explain the coexistence of variable and non-variable sdB stars in the log g – Teff diagram. We also present preliminary results on time-dependent diffusion calculations of iron in presence of radiative levitation and mass loss, and show how weak stellar winds can affect the diffusive equilibrium between gravitational settling and radiative support. 相似文献
15.
The zonal mean ammonia abundance on Jupiter between the 400- and 500-mbar pressure levels is inferred as a function of latitude from Cassini Composite Infrared Spectrometer data. Near the Great Red Spot, the ammonia abundance is mapped as a function of latitude and longitude. The Equatorial Zone is rich in ammonia, with a relative humidity near unity. The North and South Equatorial Belts are depleted relative to the Equatorial Zone by an order of magnitude. The Great Red Spot shows a local maximum in the ammonia abundance. Ammonia abundance is highly correlated with temperature perturbations at the same altitude. Under the assumption that anomalies in ammonia and temperature are both perturbed from equilibrium by vertical motion, we find that the adjustment time constant for ammonia equilibration is about one third of the radiative time constant. 相似文献
16.
André Marten Daniel Rouan Jean Paul Baluteau Daniel Gautier Barney J. Conrath Rudolf A. Hanel Virgil Kunde Robert Samuelson Alain Chedin Noëlle Scott 《Icarus》1981,46(2):233-248
Spectra from the Voyager 1 infrared interferometer spectrometer (IRIS) obtained near the time of closest approach to Jupiter were analyzed for the purpose of inferring ammonia cloud properties associated with the Equatorial Region. Comparisons of observed spectra with synthetic spectra computed from a radiative transfer formulation, that includes multiple scattering, yielded the following conclusions: (1) very few NH3 ice particles with radii less than 3 μm contribute to the cloud opacity; (2) the major source of cloud opacity arises from particles with radii in excess of 30 μm; (3) column particle densities are between 1 and 2 orders of magnitude smaller than those derived from thermochemical considerations alone, implying the presence of important atmospheric motion; and (4) another cloud system is confirmed to exist deeper in the Jovian troposphere. 相似文献
17.
Linear polarization of radiation emitted by tidally distorted stars as a function of the binary system phase is computed, taking into account true absorption and the scattering of light on free and bound electrons within hot stellar atmospheres. Computations are made both for the linear distribution of true sources across the atmospheres and for radiative-stable model atmospheres presented by Kurcuzet al. (1974) and Kurucz (1979). Polarization variability was investigated as a function of wavelength . In a number of cases, polarization variability was found to be at an observable level. The most marked variability was expected in the ultraviolet range adjacent to the boundaries of the spectral series for H and He. Near the Lyman limit of approximately =912 Å for stars with an effective temperatureT
eff35 000 K and near the ionization boundary for HeII 226 Å for stars withT
eff>35 000 K, the amplitude of polarization variability is greater than in the case of pure electron atmospheres, sometimes reaching the level of 0.5–1%. For fairly long waves where the limb-darkening coefficient falls below a certain critical valueu
cr0.5, the plane of polarization is found to be turned by 90° as compared to the case of a pure electron atmosphere. For limb-darkening coefficients far from the value ofu
cr; the form of the polarization phase curves, as well as dependence on the parameters of a binary system, remain approximately the same as those in the case of pure electron scattering. 相似文献
18.
William D. Cochran 《Icarus》1977,31(3):325-347
An analysis of the structure of the Jovian atmosphere, primarily based on center-to-limb variations (CTLV) of the equivalent width of the hydrogen quadrupole 4-0 S(1) line, is presented. These data require that the atmosphere have regions of both long- and short- scattering mean free paths. Two alternative cloud structures which fit the data are developed. The first is a two-cloud model (TCM) consisting of a thin upper cloud and a lower semi-infinite cloud, with absorbing gas between the clouds and above the upper cloud. The second model is a reflecting-scattering model (RSM), in which a gas layer lies above a haze consisting of scattering particles and absorbing gas. The cloud-scattering phase function in both models must have a strong forward peak. The CTLV data require, however, the presence of a backscattering lobe on the phase function, with the backscattering intensity about 4% of the forward scattering. The decrease in reflectivity of all regions from the visible to the ultraviolet is explained by the presence of dust particles mixed with the gas. Most of the ultraviolet absorption in the atmosphere must occur above the upper cloud layer. Particles with a uniform distribution of radii from 0.0 to 0.1 μm with a complex index of refraction varying as λ?2.5 are used. The contrast in reflectivity between belts and zones may be explained by the larger concentration of dust in the belts than in the zones. Spatially resolved ultraviolet limb-darkening curves will help to determine the dust distribution of the Jovian atmosphere. The visible methane bands at λλ 6190, 5430, and 4860 Å are analyzed in terms of these models. We derive a methane-to-hydrogen mixing ratio of 2.8 × 10?3, which is about 4.5 times the value for solar composition. 相似文献
19.
Using slab model atmospheres that are irradiated from both sides by photospheric, chromospheric, and coronal radiation fields we have determined the ionization and excitation equilibrium for hydrogen.The model atom consists of two bound levels (n = 1 and n = 2) and a continuum. Ly- was assumed to be optically thick with the transition in detailed radiative balance. The Balmer continuum was assumed to be optically thin with the associated radiative ionization dominated by the photospheric radiation field (T
rad = 5940 K). The ionization equilibrium was determined from an exact treatment of the radiative transfer problem for the internally generated Ly-c field and the impressed chromospheric and coronal field (characterized by T
rad = 6500K).Our calculations corroborate the hypothesis that N2, the n = 2 population density, is uniquely determined by the electron density N
e. We also present ionization curves for 6000K, 7500K, and 10000K models ranging in total hydrogen density from 1 × 1010/cm3 to 3 × 1012/cm3. Using these curves it is possible to obtain the total hydrogen density from the n = 2 population density in prominences and spicules.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
20.
Earlier models of compressible, rotating, and homogeneous ellipsoids with gas pressure are generalized to include the presence of radiation pressure. Under the assumptions of a linear velocity field of the fluid and a bounded ellipsoidal surface, the dynamical behaviour of these models can be described by ordinary differential equations. These equations are used to study the finite oscillations of massive radiative models with masses 10M
and 30M
in which the effects of radiation pressure are expected to be important.Models with two different degrees of equilibrium are chosen: an equilibrium (i.e., dynamically stable) model with an initial asymmetric inward velocity, and a nonequilibrium model with a nonequilibrium central temperature and which falls inwards from rest. For each of these two degrees of equilibrium, two initial configurations are considered: rotating spheroidal and nonrotating spherical models.From the numerical integration of the differential equations for these models, we obtain the time evolution of their principal semi-diametersa
1 anda
3, and of their central temperatures, which are graphically displayed by making plots of the trajectories in the (a
1,a
3) phase space, and of botha
1 and the total central pressureP
c against time.It is found that in all the equilibrium radiative models (in which radiation pressure is taken into account), the periods of the oscillations of botha
1 andP
c are longer than those of the corresponding nonradiative models, while the reverse is true for the nonequilibrium radiative models. The envelopes of thea
1 oscillations of the equilibrium radiative models also have much longer periods; this result also holds for the nonequilibrium models whenever the envelope is well defined. Further, as compared to the nonradiative models, almost all the radiative models collapse to smaller volumes before rebouncing, with the more massive model undergoing a larger collapse and attaining a correspondingly larger peakP
c.When the mass is increased, the dynamical behavior of the radiative model generally becomes more nonperiodic. The ratio of the central radiation pressure to the central gas pressure, which is small for low mass models, increases with mass, and at the center of the more massive model, the radiation pressure can be comparable in magnitude to the gas pressure. In all the radiative models, the average periods as well as the average amplitudes of both thea
1 andP
c oscillations also increase with mass.When either rotation or radiation pressure effects or both are included in the equilibrium nonradiative model, the period of the envelope of thea
1 oscillations is increased. The presence of rotation in the equilibrium radiative model, however, decreases this period.Some astrophysical implications of this work are briefly discussed. 相似文献