North Tropical Zone Research Articles

The aftermath of convective events near Jupiter’s fastest prograde jet: Implications for clouds, dynamics and vertical wind shear

The 24° N jet borders the North Tropical Belt and North Tropical Zone, and is the fastest prograde jet on Jupiter, reaching speeds above 170m∕s. In this region, observations have shown several periodic convective plumes, likely from latent heat release from water condensation, which affect the cloud and zonal wind structure of the jet. We model this region with the Explicit Planetary hybrid-Isentropic Coordinate model using its active microphysics scheme to study the phenomonology of water and ammonia clouds within the jet region. On perturbing the atmosphere, we find that an upper tropospheric wave develops that directly influences the cloud structure within the jet. This wave travels at a net (eastward) phase speed of ∼75m∕s in our model, and leads to periodic chevron-shaped features in the ammonia cloud deck. These features travel with the wave speed, and are subsequently much slower than the zonal wind at the cloud deck. This unique morphology of the ammonia cloud, and the slower drift rate, were both observed following the convective outbreak in this region in 2016 and 2020. We find that an upper level circulation is responsible for these cloud features in the aftermath of the convective outbursts. The comparatively slower observed drift rates of these features, relative to the wind speed of the jet, provides constraints on the vertical wind shear above the cloud tops, and we suggest that wind velocities determined from cloud tracking should correspond to a different altitude compared to the 680 hPa pressure level. We also diagnose the convective potential of the atmosphere due to water condensation, and find that it is strongly coupled to the wave.

Jupiter's third largest and longest-lived oval: Color changes and dynamics

The transition region between the North Equatorial Band (NEBn) and North Tropical Zone (NTrZ) in Jupiter is home to convective storms, systems of cyclones and anticyclones and atmospheric waves. Zonal winds are weak but have a strong latitudinal shear allowing the formation of cyclones (typically dark) and anticyclones (typically white) that remain close in latitude. A large anticyclone formed in the year 2006 at planetographic latitude 19°N and persists since then after a complex dynamic history, being possibly the third longest-lived oval in the planet after Jupiter's Great Red Spot and oval BA. This anticyclone has experienced close interactions with other ovals, merging with another oval in February 2013; it has also experienced color changes, from white to red (September 2013) and back to white with an external red ring (2015–2016). The oval survived the effects of the closely located North Temperate Belt Disturbance, which occurred in October 2016 and fully covered the oval, rendering it unobservable for a short time. When it became visible again at its expected longitude from its previous longitudinal track, it reappeared as a white large oval keeping this color and the same morphology since 2017 at least until the onset of the new convective disturbance in Jupiter's North Temperate Belt in August 2020. Here we describe the historic evolution of the properties of this oval. We use JunoCam and Hubble Space Telescope (HST) images to measure its size obtaining a mean value of (10,500 ± 1000) x (5,800 ± 600) km2 and its internal rotation finding a value of -(2 ± 1)·10−5 s−1 for its mean relative vorticity. We also used HST and PlanetCam-UPV/EHU multi-wavelength observations to characterize its color changes and Junocam images to unveil its detailed structure. The color and the altitude-opacity indices show that the oval is higher and has redder clouds than its environment but has lower cloud tops than other large ovals like the GRS, and it is less red than the GRS and oval BA. We show that in spite of the dramatic environmental changes suffered by the oval during all these years, its main characteristics are stable in time and therefore must be related with the atmospheric dynamics below the observable cloud decks.

A New, Long-Lived, Jupiter Mesoscale Wave Observed at Visible Wavelengths.

Small-scale waves were observed along the boundary between Jupiter's North Equatorial Belt and North Tropical Zone, ~16.5° N planetographic latitude in Hubble Space Telescope data in 2012 and throughout 2015 to 2018, observable at all wavelengths from the UV to the near IR. At peak visibility, the waves have sufficient contrast (~10%) to be observed from ground-based telescopes. They have a typical wavelength of about 1.2° (1400 km), variable-length wave trains, and westward phase speeds of a few m/s or less. New analysis of Voyager 2 data shows similar wave trains over at least 300 hours. Some waves appear curved when over cyclones and anticyclones, but most are straight, but tilted, shifting in latitude as they pass vortices. Based on their wavelengths, phase speeds, and faint appearance at high-altitude sensitive passbands, the observed NEB waves are consistent with inertia-gravity waves at the 500-mbar pressure level, though formation altitude is not well constrained. Preliminary General Circulation Model simulations generate inertia-gravity waves from vortices interacting with the environment and can reproduce the observed wavelengths and orientations. Several mechanisms can generate these waves, and all may contribute: geostrophic adjustment of cyclones; cyclone/anticyclone interactions; wind interactions with obstructions or heat pulses from convection; or changing vertical wind shear. However, observations also show that the presence of vortices and/or regions of convection are not sufficient by themselves for wave formation, implying that a change in vertical structure may affect their stability, or that changes in haze properties may affect their visibility.

Comparison of summer chlorophyll a concentration in the South China Sea and the Arabian Sea using remote sensing data

The South China Sea (SCS) and the Arabian Sea (AS) are both located roughly in the north tropical zone with a range of similar latitude (0°–24°N). Monsoon winds play similar roles in the upper oceanic circulations of the both seas. But the distinct patterns of chlorophyll a (Chl a) concentration are observed between the SCS and the AS. The Chl a concentration in the SCS is generally lower than that in the AS in summer (June–August); the summer Chl a concentration in the AS shows stronger interannual variation, compared with that in the SCS; Moderate resolution imaging spectroradiometer (MODIS)-derived data present higher atmospheric aerosol deposition and stronger wind speed in the AS. And it has also been found that good correlations exist between the index of the dust precipitation indicated by aerosol optical thickness (AOT) and the Chl a concentration, or between wind and Chl a concentration. These imply that the wind and the dust precipitation bring more nutrients into the AS from the sky, the sub-layer or coast regions, inducing higher Chl a concentration. The results indicate that the wind velocity and the dust precipitation can play important roles in the Chl a concentration for the AS and the SCS in summer. However aerosol impact is weak on the biological productivity in the west SCS and wind-induced upwelling is the main source.

Belt‐zone variations in the Jovian cloud structure

Voyager IRIS observations of Jupiter in the far infrared (180–1200 cm−1) are sensitive to emission originating from pressures less than 2 bars, while the 5‐μm (1800–2300 cm−1) observations are primarily sensitive to emission originating from pressures greater than 2 bars. We use these differences in the location of the peak emission level to constrain the properties of the upper tropospheric cloud structure from the far‐infrared observations and then use the 5‐μm observations, with the upper tropospheric cloud structure fixed, to constrain the deep cloud structure. The relationship between observed 45‐ and 5‐μm brightness temperatures reveals three distinct regions between ±25° latitude: North Equatorial Belt hot spots, which are “hot” at both 45 and 5 μm; Equatorial Zone spectra, which are “warm” at 45 μm and “cold” at 5 μm; and North Tropical Zone spectra, which are “cold” at both 45 and 5 μm. We find that the hot extreme spectral ensemble is unique to belts, and the cold extreme spectral ensembles are unique to zones, but that all other intermediate spectral ensembles are common to both regions. Analyses of these spectra using an anisotropic multiple scattering radiative transfer model reveal that the primary difference between belts and zones is the increased opacity and vertical extent of clouds in zones relative to their belt counterparts. In addition, we find a shift in the location of the para hydrogen gradient toward lower pressures in zones, with an increase in the “equilibrated” cloud‐top para fraction. We suggest that all of the variations in gas abundance profiles, temperature, and cloud structure are consistent with the effects of a simple mean circulation and large‐scale wave motions.

CARBON MONOXIDE AND DISEQUILIBRIUM DYNAMICS IN SATURN AND JUPITER

High-resolution (v/Av ~ 30,000) spectra of Jupiter and Saturn were obtained in order to study the composition and dynamics of Jupiter and Saturn. The shapes of CO absorption lines in Jupiter are broad, consistent with line formation at F ~ 2-9 bars. This is strong evidence in favor of internal mixing as the source of CO in Jupiter. Further, we find that the O abundance at 1100 K must be nearly solar. No variations in CO abundance were found between the North Equatorial Belt, the North Tropical Zone, and the Great Red Spot. Because CO is very sensitive to variations in the rate of mixing, we conclude that there are no gross variations in mixing with location on Jupiter. We observed CO in Saturn for the first time. The source of CO in Saturn is uncertain, although theoretical arguments favor an external source to an internal one. If the rings of Saturn are the source of the oxygen that eventually leads to CO in Saturn, the rate of influx required imposes an upper limit to the lifetime of the rings off < 100 million years. We have also found the first evidence for GeH4 in the atmosphere of Saturn. Absorption lines in the P and R branch of GeH4 are observed although no evidence of the stronger Q branch is found. We postulate that scattered solar radiation may be responsible for altering the thermal spectrum in regions of very low flux such as the Q -branch region. The abundance of GeH4 is consistent with the expected disequilibration from internal mixing in Saturn. Finally, we found more acetylene in the stratosphere of Saturn as compared to Jupiter, indicating possibly faster mixing in the upper atmosphere ofthat planet.

Ground-based imaging of Jovian cloud morphologies and motions: II. The northern hemisphere from 1975 to 1985

Telescopic photographs of Jupiter obtained during one Jovian year (1975–1985) have been analyzed in order to study the morphology and motions of the great-scale cloud systems present in the northern hemisphere during the epoch pre- and post-Voyager flyby spacecraft mission (see Sanchez-Lavega and Rodrigo 1985, Astron. Astrophys. 148, 67–78, for a similar work in the southern hemisphere). The texture of the north equatorial belt (NEB) was characterized by a variable number of plumes, between 11 and 15 (a mean of 25% have high-albedo heads), rifts (tilted high-albedo clouds crossing the belt in the shear flow sense), and turbulent wavy patterns in the northern edge. We present interactions between these features as observed in 1985. Elongated dark “barges” and rows of small dark spots were observed near the northern edge of the NEB during specific epochs. The high-albedo north tropical zone (NTrZ) was generally homogeneous from 1977 to 1984, but in 1976 little red spots were observed in its interior, and a contrasting (visible and red wavelengths) narrow belt located in its center was present in 1985. However, the most interesting feature in this region was the development of a prominent double disturbance (NTrZD) during 1975 in the high-speed eastward jet at 24°N, of which we present a study of its morphology and kinematics. Pronounced albedo changes were observed in the NTB during the whole period analyzed. Color contrasts in the NTrZ-NTB-NTZ regions were measured in 1985 from broadband relative photometry. North of 34°N there were alternating albedo bands characterized by their longitudinal variability, by the presence of small light spots in the equatorial side of the eastward jets, and by elongated dark sections of the belts on the polar side. The zonal wind profile u( ϕ) measured during this Jovian year is in good agreement with that obtained from Voyager's images and from previous ground-based analysis.

Histoire de la végétation et du climat de l’Afrique nord-tropicale au Quaternaire recent*

LATE QUATERNARY HISTORY OF VEGETATION AND CLIMATE OF TROPICAL NORTH AFRICAThe critical examination o f available pollen data from the vegetation of the Sahara allows one to conclude that this vegetation has gone through but few qualitative changes during the last twenty thousand years. In particular, one notices an extension in the Sahara of tropical Sahel taxa about the middle of Holocene. Quantitatively, some pollen and geological data converge to Show that the Saharian plains were extremely arid between about 20 000 and 15 000 years BP and that on the mountains the vegetation became very sparse. A new colonization began on the mountains about 15 000 years ago.The pollen study of Holocene sediments from the central part o f the Chad basin was done in the Tjéri station. The results of this study exhibit a major change near 7 000 years BP, characterized in the Sahel zone by a dramatic extension o f arboreal taxa until about 5 000 years BP, probably corresponding to northward extension of the sahel savanna. One important change took place also at the same time in the wet north tropical zone where, between about 7 000 and 4 000 years BP, there occurred an extension of taxa growing presently on the well-leached soils of interfluves.Such a change near 7 000 years BP also appears in the available stratigraphical, sedimentological and pedological data from tropical north Africa. One observes particularly that, between 15 000 and 7 000 years BP, the

Near‐ultraviolet scattering properties of Jupiter

The Voyager 2 photopolarimeter experiment obtained photometric observations of Jupiter at four phase angles between 20° and 80° and at various illumination angles from limb to terminator. These data were analyzed to determine the altitude distribution and scattering properties of the material responsible for Jupiter's low geometric albedo at 2400 Å. In polar regions the absorber must be higher than 40 mbar. In mid‐latitudes, center‐to‐limb measurements indicate that most of the absorbing material lies deeper than 100 mbar. Absolute reflectivity requires a considerable amount above 400 mbar. The maximum amount of solar UV flux below 2550 Å available for heating the stratosphere at 20° latitude is only 10−4 of the solar constant at Jupiter. The latitudinal distribution of stratospheric absorbers suggests that energy deposition from the magnetosphere is important in their formation. We examine the scattering properties of model atmospheres containing three distinct aerosol size distributions. Rayleigh's phase function fits our data at several phase angles better than any particle phase function. We derive an upper limit to the column abundance of particles larger than 0.05‐µm radius in the north tropical zone and north equatorial belt. These regions contain less than one extinction optical depth at 2400 Å of such particles above the 100‐mbar altitude. Rayleigh scattering from the top 100 mbar obscures effects due to scattering from the deeper absorbing particles over our range of phase angles. We are unable to determine whether the absorbers are particulate or molecular.

Spectrometry of Jupiter at selected locations on the disk during the 1979 apparition

view Abstract Citations (10) References (9) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Spectrometry of Jupiter at selected locations on the disk during the 1979 apparition Cochran, A. L. ; Trafton, L. ; Cochran, W. D. ; Barker, E. S. Abstract Jupiter's reflectivity was measured as a function of wavelength between 3000 and 10,500 Angstrom for two nights during the 1979 apparition. The spectra obtained were used to calibrate the wavelength response of Voyager images and to establish differences from previous apparitions. The observations were taken in the prominent belts and zones and both polar caps along the central meridian using a slit of dimensions 2.33 x 2.5 sq arcsec. The equivalent widths of the 6190 and 7270 Angstrom CH4 bands were measured; compared to the 1976 apparition, there was significantly less CH4 absorption in the north tropical zone. Such equivalent-width decreases are said to result from either a reduction in particle albedo or a decrease in the scattering mean free path owing to a greater concentration of aerosol particles in the NTrZ. Publication: The Astronomical Journal Pub Date: July 1981 DOI: 10.1086/112987 Bibcode: 1981AJ.....86.1101C Keywords: Astronomical Spectroscopy; Jupiter (Planet); Satellite-Borne Instruments; Emission Spectra; Methane; Planetary Rotation; Polar Caps; Tropical Regions; JUPITER; SPECTROMETRY; DISK; REFLECTIVITY; WAVELENGTHS; CALIBRATIONS; VOYAGER; OBSERVATIONS; ZONES; POLAR REGIONS; BANDS; BANDWIDTHS; DATA; METHANE; ABSORPTION; DATA REDUCTION; SPECTRUM; AMMONIA; SCATTERING; AEROSOLS; PARTICLES; ATMOSPHERE; ALBEDO; Lunar and Planetary Exploration; Jupiter full text sources ADS |

High spatial and spectral resolution 10-μm observations of jupiter

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 NH 3 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 NH 3 mixing ratio could be caused by changes in the amount of NH 3 condensation or in the degree of the NH 3 photolysis. The C 2H 6 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 C 2H 6 could explain the lower C 2H 6 emission over the Great Red Spot.

Spatially resolved methane band photometry of Jupiter: III. Cloud vertical structures for several axisymmetric bands and the Great Red Spot

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.

Spatially resolved reflectivities of Jupiter during the 1976 opposition

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 CH 4 and NH 3 bands are measured. The spatial variations of continuum reflectivity and absorption band profiles are shown in various ratio spectra.

On the nature of the blue and ultraviolet absorption in the Jovian atmosphere

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 NH 3 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.

Measures of Jupiter photographs—1974/1975 apparition

The 1974/1975 Jupiter apparition is described. Photographic images have been measured and zonal velocities are given for all spots observed on four or more dates. Global and localized zonal flow patterns are graphically presented. Methane absorption band imagery at 890 nm indicates that white ovals and red spots are high in altitude, and blue features are cloud-free areas. The motions of blue features are complex and unlike the motions of other features. Interactions or associations between spots at five adjacent atmospheric currents have been observed. Zonal motion within an equatorial plume has been observed. Evidence is presented for a probable source of red spots in the North Tropical Zone.

Spectrophotometry of Jupiter

Spectrophotometric maps of Jupiter were made between 24 and 27(UT) November 1974 on the McMath Solar Telescope at Kitt Peak National Observatory. We report a comparison between observed scaled reflectivities of the Jovian North Tropical Zone and the North Equatorial Belt at System II longitudes between 195 and 205 degrees. The belt/zone reflectivity ratios between 430 and 740nm are related to the optical transmission curves of the organic and/or sulfur polymers synthesized by Khare and Sagan in a simulated Jovian atmosphere.

Spatially resolved absolute spectral reflectivity of Jupiter: 3390–8400 Å

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: CH 4 (6190 Å), 14–16 Å; CH 4 (7250 Å), 77–86 Å; and NH 3 (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.)

Optical polarization measurements of the Jupiter atmosphere at 103° phase angle

The first measurements have been made of the linear polarization of sunlight scattered by the Jupiter atmosphere at phase angles greater than 12 deg, using the imaging photopolarimeter on Pioneer 10. The data are of high accuracy, in spite of several problems in the instrument. The polarization is positive at 440 nm. There is no direct evidence for spherical particles in the Jupiter clouds. Using a simple model of Rayleigh scattering above a Lambertian cloud layer, a unique fit is found to the observed intensity and polarization at each point on the planet. The resulting Rayleigh optical depths, if they are attributed to molecular scattering alone (i.e., no aerosols above the cloud tops), can be converted into physical altitudes of the cloud tops. The first results suggest that the north tropical zone, parts of the equatorial zone, and the red spot are all elevated regions.

Narrow-Band Photometry of the Bands of Jupiter

view Abstract Citations (18) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Narrow-Band Photometry of the Bands of Jupiter Pilcher, Carl B. ; McCord, Thomas B. Abstract Spectra of the North and South Tropical Zones and the combined North Equatorial Belt (NEB) and Equatorial Zone (EZ) were obtained from 0.30 to 1.60 with resolution between 0.02 and 0.05 . The NEB and the EZ are both regions that have been associated with marked coloration in recent years. When compared with spectra of the white North Tropical Zone, spectra of the combined NEB-EZ show a relative minimum centered at 0.38 p and slightly higher intensity beyond 0.54 . Less methane and ammonia absorption is observed over the NEB-EZ than over the North Tropical Zone. Spectral reflectivities of the combined NEB-EZ and the combined Tropical Zones are presented between 0.30 and 1.10 p. Spectral reflectivities of the NEB-EZ and the South Tropical Zoiie scaled relative to that of the North Tropical Zone are calculated on the assumption of Lambert-sphere limb darkening. Also presented are relative intensities in the visible and near-ultraviolet showing the spectral differences between the NEB and the EZ and between the two Tropical Zones. Publication: The Astrophysical Journal Pub Date: May 1971 DOI: 10.1086/150887 Bibcode: 1971ApJ...165..195P full text sources ADS |

Wavelength Dependence of the Band Structures of Jupiter and of Saturn.

view Abstract Citations (2) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Wavelength Dependence of the Band Structures of Jupiter and of Saturn. Younkin, Robert L. ; Münch, Guido Abstract Photoelectric measurements of the band structures of Jupiter and of Saturn were made during September 1963 by moving a small slot along the central meridian of the planetary image. The Mt. Wilson Ebert spectrometer was used on the 60-in. reflector as a monochromator to select wavelengths from X3200 A to 10400A. Curves obtained for Saturn show: (1) radiance of both equatorial zone and north tropical zone relative to B-ring exhibit broad maxima in X5800 - X7500 range, falling sharply to an ultraviolet minimum near X3800 A; (2) radiance of equatorial zone relative north tropical zone is slightly greater than unity beyond X6000 A, but falls to 0.58 in the ultraviolet. This ratio ~ecomes large in str9ng CH4 bands: 1.6 at X7270 A and 3.7 at X8912A with a fairly sharp discontinuity at the north equatorial belt. Consistent with these observations is an atmospheric model in which cloud particles over the entire planet possess similar selective absorption which increases with decreasing wavelength below X5200A, but a lower effective cloud level in the temperate and polar regions' than the equatorial zone. Thus at short wavelengths where Rayleigh scattering dominates particle scattering, the temperate and polar regions are brighter than the equatorial zone; and, conversely, at long wavelengths and particularly in the CH4 bands, where particle scattering dominates. For Jupiter, the north tropical zone was the brightest region of the planet throughout the range of wavelengths. Its radiance relative to the south tropical zone is anomalous in CH4 absorption, increasing in the X8900 A band, and decreasing in the X7270 A band. Contrast between tropical zones and adjacent equatorial belts increases with decreasing wavelength below X5500 A. In strong CH4 absorption bands the limb darkening with latitude greatly increases. The south equatorial belt becomes the brightest region of the' planet. In the X8900 A band both polar regions become bright at the limb. Publication: The Astronomical Journal Pub Date: October 1964 DOI: 10.1086/109334 Bibcode: 1964AJ.....69..565Y full text sources ADS |