Disk Of Jupiter Research Articles

Changes in the activity of Jupiter’s hemispheres

Solar-induced changes in the reflective properties of the visible disk of Jupiter mostly depend on variations in the Earth’s jovimagnetic latitude. Since the orbit of Jupiter is eccentric (the eccentricity is e = 0.04845) and the planet passes perihelion at the time close to the summer solstice, the atmosphere receives 21% more solar energy in the northern hemisphere than in the southern one. According to the results of our studies, the ratio of the brightness values for the northern and southern tropical and temperate zones is a clear indicator of photometric activity of the processes in the atmosphere of Jupiter. From the analysis of the observational data for the period from 1962 to 2017, the cyclicity in changes of the activity factor of the hemispheres of the planet with a period of 11.87 years was found. This suggests that the atmosphere of Jupiter experiences seasonal restructuring.

Upgraded technique to analyze the vertical structure of the aerosol component of the atmospheres of giant planets

To analyze the behavior of the optical thickness of aerosols or the ratio of the optical thicknesses of the aerosol and gas components in the spectral absorption bands of atmospheric gases with depth, we developed a software package. The package structure includes the units for the following operations: (1) to calculate the Legendre expansion coefficients x i of the phase function and the volume scattering coefficient σ0 of the polydisperse medium with the specified refractive index and the size distribution function N(r) with the use of the code developed by M.I. Mishchenko; (2) to generate the array containing the pairs of the single scattering albedo ω and the geometric albedo A g for the models of a semi-infinite homogeneous medium with the parameters determined in the previous step; (3) to determine the single scattering albedo values from the comparison of the calculated and measured values of the geometric albedo for each of the measured points in the examined absorption band of the atmospheric gas (accounting for the change of the phase function due to Rayleigh scattering); (4) to calculate the spectral values of the effective optical depths τeff of the levels, where the intensity field of light diffusely reflected by the investigated atmosphere is formed; (5) to derive the scattering and absorption components of the effective optical depth (τ eff and τ eff ) from the values of ω and τeff; (6) from the values of τ eff to determine the amount of the absorbing gas NL (in km-amg) along the line of sight and, from these values, the atmospheric pressure p(NL) and the gas component of the scattering portion of the optical depth τ g (λ0) at the wavelength λ0 = 887.2 nm; (7) from the values of τ eff (λ) and τ g (λ, NL), to find the aerosol component τ a (λ, NL); (8) to build the plots of τ a (λ) or the ratio τ a (λ)/τ g (λ) reduced to λ0 = 887.2 nm versus the pressure. The software package was validated in the analysis of the spectrophotometric data obtained in the measurements of the whole disk of Jupiter in the profiles of the strong absorption bands of methane centered at λλ 841.6, 864, and 887.2 nm under the assumption on two versions of the size distribution of particles (the modified gamma distribution and the log-normal one). It was found that the model with the gamma distribution is analyzed several times more quickly than the log-normal one that yields the close results in computations performed for the same medium.

Changes in the Cloud Belts of Jupiter, 1630–1664, as Reported in the 1665 Astronomia Reformata of Giovanni Battista Riccioli

Abstract A translation of a section from the 1665 Astronomia Reformata of G. B. Riccioli discussing the appearance of the disk of Jupiter during the years 1630-1664; changes in the Jovian cloud belts as recorded by a variety of observers are a major feature of Riccioli’s discussion.

New determination of monochromatic methane absorption coefficients with regard to the thermal conditions in the atmospheres of giant planets. IV. Jupiter and Saturn

Based on the data on the wavelength dependence of geometrical albedo for the disks of Jupiter and Saturn, we determined the trends in the height variation of the aerosol optical depth in the upper atmospheric layers of these planets, the fractional methane concentration in the Jovian atmosphere (0.00125), and the monochromatic methane absorption coefficients (or the superposition of these coefficients for methane and ammonia) typical of the thermal conditions in the atmospheres of Jupiter and Saturn in the wavelength range from 527 to 956 nm.

X‐ray emission from the outer planets: Albedo for scattering and fluorescence of solar X rays

Soft X‐ray emission has been observed from the low‐latitude “disk” of both Jupiter and Saturn as well as from the auroral regions of these planets. The disk emission as observed by ROSAT, the Chandra X‐Ray Observatory, and XMM‐Newton appears to be uniformly distributed across the disk and to be correlated with solar activity. These characteristics suggest that the disk X rays are produced by (1) the elastic scattering of solar X rays by atmospheric neutrals and (2) the absorption of solar X rays in the carbon K‐shell followed by fluorescent emission. The carbon atoms are found in methane molecules located below the homopause. In this paper we present the results of calculations of the scattering albedo for soft X rays. We also show the calculated X‐ray intensity for a range of atmospheric abundances for Jupiter and Saturn and for a number of solar irradiance spectra. The model calculations are compared with recent X‐ray observations of Jupiter and Saturn. We conclude that the emission of soft X rays from the disks of Jupiter and Saturn can be largely explained by the scattering and fluorescence of solar soft X rays. We suggest that measured X‐ray intensities from the disk regions of Jupiter and Saturn can be used to constrain both the absolute intensity and the spectrum of solar X rays.

Constraints on Jupiter's hydrogen corona from Galileo UVS observations

During Galileo orbits C10 and E11, the Ultraviolet Spectrometer (UVS) obtained H Lyα scans at low latitudes across the disk of Jupiter from a phase angle of 90–109° and a distance of 18–21 jovian radii. Jupiter's nightside Lyα brightness was about 0.5kR, approximately half as bright as interplanetary space. From the nightside to the dayside, the Lyα brightness rose to a peak of ∼15kR near the sub-solar limb and then dropped sharply to interplanetary brightness levels. On orbit C10 three disk scans were obtained (near 30°N latitude, 20°S latitude, and along the equator), while a single equatorial scan was made on orbit E11. The steep falloff in Lyα brightness at the sub-solar point provides a strong constraint on the distribution of atomic hydrogen in the upper atmosphere. All disk scans are reasonably well fit by a resonance line radiative transfer model which assumes a total H column density of ∼1017cm−2 and a temperature profile consistent with the Galileo probe results with an exospheric temperature of 940K. However, we find that the inclusion of a small amount of “hot” hydrogen, with an abundance described by a Chapman profile, can substantially improve the fit to the UVS limb scan data. Exactly such a hot hydrogen component is expected in the upper atmosphere of Jupiter, and has been previously invoked to explain observations of the jovian Lyα line profile made from Earth orbit. The best fits to the UVS data occur with a hot H column density that is 0.1% of the ambient H column, with an effective temperature of 25,000K and a topside scale height of 1000km (in our empirical representation, the hot H scale height is unrelated to the hot H temperature). Other combinations of column abundance and the effective temperature can also provide good fits to the data. As long as the hot H is located above the homopause, there is no strong dependence on the height of the Chapman profile.

Gas Dissipation from the Protosatellite Disk of Jupiter

We consider the dissipation of the gaseous component from the gas–dust accretion disk of Jupiter in which the Galilean satellites were formed. The thermal dissipation of hydrogen and helium is shown to be ineffective. It could ensure the loss of gas only for a low-mass disk and only if the rarefied outer layers of the disk are heated to 104 K. Such a high disk temperature is not reached through Jupiter's radiation in existing models of its formation, but it could be provided by UV radiation of the early Sun after the dissipation of the protoplanetary disk. The viscous dissipation (with a viscosity parameter α ≥ 10–3 in the α-disk model) related to disk accretion onto Jupiter could disperse a low-mass disk in ≤107 years. A magnetocentrifugal mechanism, which produced a disk wind during accretion capable of carrying away ∼0.1 of the accreted gas mass, was probably also involved in the dispersal of the Jovian disk. Differential dispersion, with the loss of only hydrogen and helium and the retention of water vapor and heavier gases in the disk, is possible only in a low-mass disk model. We conclude that the water contained in the Galilean satellites was brought in mainly by solid planetesimals captured into the disk during mutual inelastic collisions in Jupiter's sphere of influence.

Methane, Ammonia, and Temperature Measurements of the Jovian Planets and Titan from CCD–Spectrophotometry

Full-disk albedo spectra of the jovian planets and Titan were derived from observations at the European Southern Observatory in July 1995. The spectra extend from 300 to 1050 nm wavelength. The spectral resolution is 0.4 nm between 520 and 995 nm, and 1 nm elsewhere. The accuracy of the albedo calibration is 4%. UBV magnitudes were also determined. Raman scattering was quantified for each planet. Methane and ammonia bands are shown at 0.4 nm spectral resolution, including a new band at 930 nm wavelength which is probably due to ammonia. Maps of the variation of these absorptions across the disks of Jupiter and Saturn are displayed. Saturn's spectrum is undisturbed by light from its rings due to the edge-on geometry during the observations. The albedo of Uranus near 1 μm wavelength has dropped almost 10% between 1993 and 1995, while there has been no change in the ultraviolet. The signature of light from Titan's surface yielded a path length of 4 km-am of methane in Titan's atmosphere. The temperature dependence of the width of the 890-nm methane band was used to measure temperature variations at three altitude levels, resulting in the first temperature maps of Jupiter and Saturn based on reflected sunlight. Jupiter displays a banded temperature structure with some discrete features of a few Kelvin amplitude. Saturn's north–south temperature asymmetry has reversed since the Voyager observations.

High-resolution ultraviolet spectrograph for sounding rocket measurements of planetary emission line profiles

We constructed a high-resolution imaging spectrograph for use as a payload in a sounding rocket experiment. The spectrograph employs a modified Ebert-Fastie design with a LiF objective prism and a replica of an El echelle grating developed for the Space Telescope Imaging Spectrograph. The instrument has a 5-arcmin-long adjustable width entrance aperture with two identical secondary apertures separated from the primary by ±2 arcmin. The secondary apertures are intended for simultaneous measurement of the sky background. The spectrograph has been optimized for measurement of the 221st order of Lyman-α at a resolution of 0.03 to 0.04 A. The detector system is a two-dimensional photon counting device that employs a microchannel plate intensifier and a wedge and strip anode readout. The spectrograph is used as a focal plane instrument of the Jupiter Telescope, a Cassegrain telescope constructed exclusively for use as a sounding rocket payload. The Jupiter Telescope is self-pointed, employing image motion compensation to achieve 2- to 3-arc sec image quality. The telescope/spectrograph payload was launched from the White Sands Missile Range on May 4, 1991, to observe the H Lyman-α line profile spatially resolved across the disk of Jupiter in the North-South (polar) and East-West (equatorial) directions, and to measure the H Lyman-α emission line profile from interplanetary hydrogen associated with the local insterstellar medium.

Observations of the limb darkening of jupiter at ultraviolet wavelengths and constraints on the properties and distribution of stratospheric aerosols

Three series of spectra of Jupiter covering the spectral range from 0.22 to 0.33 μm were obtained with the International Ultraviolet Explorer (IUE) satellite in November 1979. The absolute reflectivity of Jupiter was obtained in 50-Å-wide regions centered at 0.221, 0.233, 0.252, and 0.330 μm from these observations. One of the three spectral series includes 7 spectra at various latitudes along Jupiter's central meridian. These data show a strong decrease in reflectivity for latitudes greater than about 30°, in agreement with measurements made by Voyager ( C. W. Hord, R. A. West, K. E. Simmons, D. L. Coffeen, M. Sato, A. L. Lane, and J. T. Bergstrahl, 1979, Science ( Washington, D.C.) 206, 956–959). A total of 24 spectra were also obtained in a west-east series along the equator and another near 40°N latitude. Both west-east series of spectra were obtained by using the motion of a Galilean satellite to pull the 3-arcsec-diameter IUE aperture across the disk of Jupiter. Spectra which straddled the edge of the disk were used to determine the locations of all the spectra in both west-east series to high accuracy. The west-east series show limb darkening at high latitudes and brightening toward the illuminated limb at low latitudes. Comparisons of model calculations with the data obtained near 40°N indicate a significant absorption optical depth (increasing from ∼0.3 at 0.25 μm to nearly 0.6 at 0.22 μm) centered near pressure levels of 20 to 30 mbar. Models in which the haze particles have effective radii within a factor of about 2 of 0.2 μm are favored. Smaller particles have difficulty fitting the variation with wavelength in our data (even with rapidly varying amounts of absorption with wavelength) and larger particles rapidly fall out of the high atmospheric layers. The aerosol mass loading of the atmosphere at high latitudes is estimated at 20 μm/cm 2 above the 50-mbar level. The required variation of the imaginary index of refraction of the aerosol material with wavelength is derived for several possible aerosol distributions. The variation measured by M. Podolak, N. Noy, and A. Bar-Nun (1979, Icarus 40, 193–198) for polyacetylene photochemical products is in reasonable agreement with the IUE observations for one of the vertical haze distributions presented, although mixtures of materials produced by irradiating various combinations of methane, hydrogen, and some nitrogen-bearing compounds with energetic particles may also be able to reproduce the observations. Near the equator, the haze aerosols produce much less absorption than near 40°N, and the derived aerosol distributions and optical properties are more dependent on the assumed location and reflectivity of the top of the tropospheric cloud. The equatorial haze aerosols can be as optically thick as the high-latitude aerosols only if they are concentrated much deeper in the atmosphere (near 150 mbar). However, if the haze aerosols extend up to pressures as low as 50 mbar or less at low latitudes as suggested by the eclipse studies of D.W. Smith (1980, Icarus 44, 116–133), then they have 5 to 10 times less absorption optical depth near the equator than at 40°N. Comparisons with the satellite eclipse studies and analyses of polarimetry near the limb at large phase ( P.H. Smith and M.G. Tomasko, 1984, Icarus 58, 35–73) indicate that the haze aerosols at low latitudes can have sizes in the same range as found near 40°N. A radius estimate of 0.2 μm yields a mass loading of some 3 μm/cm 2 for the haze aerosols near the equator above the 150-mbar pressure level. Assuming that the haze aerosols have the same composition at high and low latitudes implies that the single-scattering albedo of the tropospheric cloud particles at low latitudes decreases strongly from 0.33 to 0.22 μm.

Phase effect for the brightness coefficient of the central disk of Saturn and features of Jupiter's disk

Spectral reflectivities ϱ(λ) of the features on the disk of Jupiter (NTrZ, NEB, EZ, SEB, STrZ) and the center of the disk of Saturn were measured for different phase angles. The phase dependence of ϱ(λ) is shown to correspond to the shape of the phase function.

The abundances of ammonia in the atmospheres of Jupiter, Saturn, and Titan

An investigation of low-resolution ratio spectra of Jupiter, Saturn, and Titan in the region 5400–6500 Å has permitted new evaluations of ammonia absorption bands. The distribution of ammonia over the disk of Jupiter is very inhomogeneous. The carbon-to-nitrogen ratio is distinctly different from the solar value, but this is probably a result of uneven mixing of methane and ammonia, as suggested previously by Kuiper, rather than a compositional anomaly. The abundance of ammonia on Saturn also shows spatial variations, but appears constant in time over a 3-yr period. Two weak, unidentified absorptions were discovered in the red region of Titan's spectrum, in the absence of any detectable ammonia. The new upper limit is ηN < 120 cm-am.

The effects of the atmospheric point-spread 'seeing' function on spatially resolved spectra of Jupiter

We present the results of an analysis of the effects of atmospheric seeing and of instrumental spectral and spatial resolution on the observed variation of absorption-line profiles across the disk of Jupiter. The technique described may be applied equally well to the analysis of observations of any extended astronomical source. These results show the necessity of obtaining accurate point-spread-function information during the course of observations of this nature. We also point out that in order to avoid the uncertainties and ambiguities inherent in attempts at deconvolution of observational data, one must properly convolve the appropriate spatial and spectral resolution functions with the models being tested and then compare the results with the observational data.

Distribution of Ammonia on Jupiter

Observations of the variation in intensity of an NH3: band at 1.53μ in different positions on the disk of Jupiter are presented with a simple physical interpretation model. It is shown that increased NH3 absorption at the polar regions of the planet can be understood if the cloud layer, or mean reflecting level, is lower than at the equator. Absorption along the equator was found to be variable with time, but absorption at the limbs was often less than at the center, indicating that band formation in the cloud layer involves scattering processes. The spectral data generally correlate with optical properties of the atmosphere deduced from polarization observations of Jupiter.

The motion of Jupiter's fifth satellite

A method is described for obtaining and reducing a series of photographic observations of the fifth satellite and the disk of Jupiter against a background of stars. A discussion of these and earlier observations leads to revised values for the mean motion and the regression of the nodes.

Hot Shadows on Jupiter

On the evenings of 26 October and 15 December 1962, while the disk of Jupiter was being scanned for thermal emission in the 8- to 14-micron wavelength region, a large enhancement was discovered in the emission from shadows cast on Jupiter by the Jovian satellites Ganymede and Europa. However, on the evening of 14 December 1964, the shadow of satellite Io was observed and no enhancement was detected. The effect is thus variable with time.

On the interpretation of thermal emission maps of Jupiter

In a paper in this issue of the Journal, Wildey et al. [1965] have presented the results of recent efforts to contour the isophotes over the disk of Jupiter for the thermal emission in the heterochromatic-magnitude band extending from 8 to 14 microns. Such brightness temperature maps represent an important constraint on Jovian model atmospheres in which over-all processes of energy transport and balance are considered. Because of the limitations on the accuracy of the present mapping procedures, important discrimination must be made between structural features of maps which are obviously noise and those which are good candidates for the extraction of theoretical implications. The peculiar nature of the noise warrants an elaboration of this discriminatory procedure.

Hot Shadows of Jupiter

On the evenings of 26 October and 15 December 1962, while the disk of Jupiter was being scanned for thermal emission in the 8- to 14-micron wavelength region, a large enhancement was discovered in the emission from shadows cast on Jupiter by the Jovian satellites Ganymede and Europa. However, on the evening of 14 December 1964, the shadow of satellite Io was observed and no enhancement was detected. The effect is thus variable with time.

Observations of Jupiter and the Galilean Satellites at 10 Microns.

The 200-inch Hale telescope has been used to map the 8-l4-it brightness-temperature distribut across the disk of Jupiter and to observe the integral brightness temperatures of the Galilean satelli Other than simple limb-darkening no latitudinal variation of brightness temperature greater than ab 1.00 K was observed, nor were there variations greater than about 0.50 K across the band structur the Great Red Spot. However, an enhancement of the 8-l4-it radiation of possibly as much as thirty tk was found to be associated with the position on the disk of a satellite shadow. The observed integral brightness temperatures of Ganymede, and especiaUy Callisto, exceed the li for an insulating gray body heated only by absorbed solar radiation. Thus either these satellites dep significantly from Planckian distribution of emitted radiation or there is a large systematic effect in' observations leading to overestimates of brightness temperature. If the latter were to be the case, should have to revise the 8-l4-it brightness temperature of Venus downward from the 2150 K va obtained concurrently with the observations of this paper, a correction which widens, rather than r rows, the disparity between our Venus temperature and other published values.

Variations in Atmospheric Absorption Over the Disks of Jupiter and Saturn.

view Abstract Citations (36) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Variations in Atmospheric Absorption Over the Disks of Jupiter and Saturn. Hess, Seymour L. Abstract Variations in the strength of absorption of methane at 6190 A on Jupiter and Saturn, and ammonia at 6441 A on Jupiter, were studied. The absorptions decrease slightly toward the edges of Jupiter, but increase somewhat toward the edges of Saturn. The conclusion is drawn that the cloud surface on Jupiter rises toward the limbs, but is more nearly level on Saturn. The ammonia results indicate a decrease in temperature from equator to poles on Jupiter. The morning limb is found to be cooler than the evening limb. Publication: The Astrophysical Journal Pub Date: July 1953 DOI: 10.1086/145735 Bibcode: 1953ApJ...118..151H full text sources ADS |