共查询到20条相似文献，搜索用时 109 毫秒
1.
We calculate the Love numbers kn for n = 2 to 10, and determine the “gravitational noise” from tides. The new values k2 for Jupiter, Saturn, and Uranus yield new estimates for the planetary dissipation functions: , . 相似文献
2.
3.
Ethane and acetylene, both of which possess more efficient emission bands than methane, have been incorporated into a thermal structure model for the atmosphere of Jupiter. Choosing for illustrative purposes the mixing ratios and , it is found that these hydrocarbon gases lower the atmospheric temperature within the thermal inversion region by as much as 20 K, subsequently reducing the emission intensity of the 7.7 μm CH4 band below the observed result. It is qualitatively shown, however, that this cooling by C2H6 and C2H2 could be compensated by aerosol heating resulting from a uniformily mixed aerosol which absorbs 15% of the incident solar radiation. Such aerosol heating has been suggested by uv albedo observations. 相似文献
4.
It is shown that Titan's surface and plausible atmospheric thermal opacity sources—gaseous N2, CH4, and H2, CH4 cloud, and organic haze—are sufficient to match available Earth-based and Voyager observations of Titan's thermal emission spectrum. Dominant sources of thermal emission are the surface for wavelenghts λ ? 1 cm, atmospheric N2 for 1 cm ? λ ? 200 μm,, condensed and gaseous CH4 for 200 μm ? λ ? 20 μm, and molecular bands and organic haze for λ ? 20 μm. Matching computed spectra to the observed Voyager IRIS spectra at 7.3 and 52.7° emission angles yields the following abundances and locations of opacity sources: CH4 clouds: 0.1 g cm? at a planetocentric radius of 2610–2625 km, 0.3 g cm?2 at 2590–2610 km, total 0.4 ± 0.1 g cm–2 above 2590 km; organic haze: above 2750 km; tropospheric H2: 0.3 ± 0.1 mol%. This is the first quantitative estimate of the column density of condensed methane (or CH4/C2H6) on Titan. Maximum transparency in the middle to far IR occurs at 19 μm where the atmospheric vertical absorption optical depth is A particle radius in the upper portion of the CH4 cloud is indicated by the apparent absence of scattering effects. 相似文献
5.
Graham Vixie Jason W. Barnes Jacob Bow Stéphane Le Mouélic Sébastien Rodriguez Robert H. Brown Priscilla Cerroni Federico Tosi Bonnie Buratti Christophe Sotin Gianrico Filacchione Fabrizio Capaccioni Angioletta Coradini 《Planetary and Space Science》2012,60(1):52-61
Titan shows its surface through many methane windows in the 1–5 region. Windows at shorter wavelengths also exist, polluted by scattering off of atmospheric haze that reduces the surface contrast. At visible wavelengths, the surface of Titan has been observed by Voyager I, the Hubble Space Telescope, and ground-based telescopes. We present here global surface mapping of Titan using the visible wavelength channels from Cassini's Visual and Infrared Mapping Spectrometer (VIMS). We show global maps in each of the VIMS-V channels extending from 0.35 to 1.05 . We find methane windows at 0.637, 0.681, 0.754, 0.827, 0.937, and and apply an RGB color scheme to the 0.754, 0.827 and windows to search for surface albedo variations. Our results show that Titan appears gray at visible wavelengths; hence scattering albedo is a good approximation of the Bond albedo. Maps of this genre have already been made and published using the infrared channels of VIMS. Ours are the first global maps of Titan shortward of . We compare the older IR maps to the new VIMS-V maps to constrain surface composition. For instance Tui Regio and Hotei Regio, referred to as bright spots in previous papers, do not distinguish themselves at all visible wavelengths. The distinction between the dune areas and the bright albedo spots, however, such as the difference between Xanadu and Senkyo, is easily discernible. We employ an empirically derived algorithm to remove haze layers from Titan, revealing a better look at the surface contrast. 相似文献
6.
W.T. Huntress 《Planetary and Space Science》1975,23(2):377-378
Laboratory data shows that the reaction of protons with methane proceeds at thermal ion energies to give both CH3+ and CH4+ ions in the ratio . The overall rate constant for the reaction is 3.8 ± 0.3 × 10?9 cm3/sec. This reaction may lead to the formation of hydrocarbon ions in the lower ionosphere of Jupiter, and the significance of this process for formation of hydrocarbons and HCN in the atmosphere of Jupiter is discussed. 相似文献
7.
The space erosion of stony meteorites has been determined to be 650μm 106y?1, while that of iron meteorites has been determined to be 22 μm 106y?1. The erosion rates are based on flux and size distributions of small particles in the solar system, meteoroid orbitals and the relation, determined by laboratory experiments, between excavated volume due to a collision and the size and velocity of the impacting small particle. Neither multiple collision or space erosion can explain the difference in cosmic ray exposure ages based on and those based on . It is concluded that there is a long term cosmic ray variation. 相似文献
8.
Marcel Nicolet 《Planetary and Space Science》1984,32(11):1467-1468
A recent determination by D. R. Bates of the Rayleigh scattering cross section (σRS) for air from 0.2 to 1 μm leads to a simple empirical formula (λ in μm) where for the spectral region 0.2 μm < λ < 0.55 μm ; the accuracy is within ±0.5%. From the visible at 0.55 μm to the infrared (i.r.) at 1 μm, the same accuracy can be obtained using a constant value, x = 0.04. The formula accounts for the degree of depolarization which varies with the wavelength according to the latest determination by Bates. 相似文献
9.
The photometric properties of local areas on Mars are studied using Minnaert's rule of surface scattering to analyze Mariner 6 and 7 Infrared Spectrometer data. Several bright deserts, Hellas, and the south polar cap are found to obey Minnaert's function well. The coefficients B0(α, λ) and k(α, λ) are obtained at α = 39, 48, 56, 84° and λ = 1.85, 2.23, 3.50 μm. Observed bright regions all have similar values of k, except for Hellas and the south polar cap. The lower k of Hellas is apparently caused by microscopic effects rather than by large-scale roughness due to cratering. The higher k of the cap is similar to terrestrial snows in the visual at the same phase angle. Using existing Earth-based observations, at smaller α and λ, a bolometric Bond albedo of is calculated. 相似文献
10.
Results are given of the calculations of the group delay time propagating τ(ω, φ0) of hydromagnetic whistlers, using outer ionospheric models closely resembling actual conditions. The τ(ω, φ0) dependencies were compared with the experimental data of τexp(ω, φ0) obtained from sonagrams. The sonagrams were recorded in the frequency range at observation points located at geomagnetic latitudes φ0 = (53?66)° and in the vicinity of the geomagnetic poles. This investigation has led us to new and important conclusions.The wave packets (W.P.) forming hydromagnetic whistlers (H.W.) are mainly generated in the plasma regions at L = 3.5?4.0. This is not consistent with ideas already expressed in the literature that their generation region is . The overwhelming majority of the τexp values differ considerably from the times at which wave packets would, in theory, propagate along the magnetic field lines corresponding to those of the geomagnetic latitudes φ0 of the observation points. The second important fact is that the W.P. frequency ω is less than everywhere along its propagation trajectory, including the apogee of the magnetic force line ( is the proton gyrofrequency). Proton flux spectra keV, responsible for H.W. generation, were determined. Comparison of the Explorer-45 and OGO-3 measurements published in the literature, with our data, showed that the proton flux density energy responsible for the H.W. excitation where Ha is the magnetic field force in the generation region of these W.P. The electron concentration is . The values given in the literature are . The e data considered also leads to the conclusion that the generating mechanism of the W.P. studied probably always co-exists with the mechanism of their amplification. 相似文献
11.
《Chinese Astronomy and Astrophysics》1982,6(1):24-27
Six times of maxima of the ultrashort-period cepheid variable EH Librae were measured in 1980 May to June and in 1981 January, with a three-channel photocounting high-speed photoelectric photometer. These, together with all the photoelectric times of maxima over the past 30 years, are used to re-examine the nature of the change of the period. We found that we can fix the times of maxima by the following formula where T0 = HJD 2433438.6088 and P0 = 0.0884132445 d represent the initial maximum epoch and the pulsation period, β = ?2.8 × 10?8/yr; A = 0.0015 d, P0 = 6251 d = 17.1 yr are the semi-amplitude and the period of the sine curve, and E is the number of periods elapsed since T0, and (E0 = 70700).If we interpret this 17.1 year periodicity as a modulation of the phase of maximum by binary motion, then the semi-amplitude of the orbital radial velocity variation is K = 2πasini/E0 = 0.45 km/s and the mass function is 相似文献
12.
Linear polarimetry of Ceres at 10 μm is presented. These data represent the first published polarization measurements of an asteroid in the thermal infrared. It is found that Ceres is polarized at the 0.2-0.6% level. This data set is compared with theoretical models of the linear polarization of emitted radiation from a spherical plane. These models are used to derive the pole position and thermal inertia of Ceres. Ceres is best fit with a thermal inertia of and a pole orientation of βp = 36° ± 5°, λp = 270° ± 3°. It is concluded that 10μm polarimetry is a potentially powerful technique for remotely sensing the pole orientation and thermal inertia of asteroids. 相似文献
13.
A.K. Pradhan 《Planetary and Space Science》1980,28(2):165-167
Branching ratios and are calculated at 584 Å and 304 A employing the close-coupling approximation to compute the photoionization cross section values. The coupled channels include the states dominated by the ground configuration 1s22s2p3 of O+and the next excited configuration ls22s2p4. It is found that the partial c section decreases more rapidly than , and at the lower wavelength 304 Å, the ratio . Present results at 304 Å differ considerably from previous work. 相似文献
14.
《Chinese Astronomy and Astrophysics》1982,6(3):267-272
I consider the range of Hill stability in the restricted circular problem of three bodies when the larger one of the two principal bodies has a finite oblateness. I show that the range r satisfies the equation where μ is the mass parameter and v is an oblateness parameter. This result is applied to the solar system, the Earth-Moon system and binary star systems. It is then shown that, all the inner planets of the solar system, the great majority of asteroids and some short-period comets are Hill stable, that direct artificial satellites of the Earth are more stable than retrograde ones, and that contact binaries possess cores between which no mass exchange takes place. 相似文献
15.
From published ground-base, spacecraft, and rocket photometry and polarimetry of the zodiacal light, a number of optical and physical parameters have been derived. It was assumed that the number density, mean particle size, and albedo vary with heliocentric distance, and shown that average individual interplanetary particles have a small but definite opposition effect, a mean single-scattering albedo in the V band at 1-AU heliocentric distance of 0.09 ± 0.01, and a zero-phase geometric albedo of 0.04. Modeled by a power law, both albedos decrease with increasing heliocentric distance as r?0.54. The corresponding exponents for changes in mean particle size and number density are related in a simple way. The median orbital inclination of zodiacal light particles with respect to the ecliptic is 12°, close to the observed median value for faint asteroids and short-period comets. Furthermore, the color of dust particles and its variation with solar phase angle closely resemble those of C asteroids. These findings are, at least, consistent with the zodiacal cloud originating primarily from collisions among asteroids. Finally, a value of ?1018?ErmE g was derived for the mass of the zodiacal cloud, where ?E is the mean particle radius (in micrometers) at 1-AU-heliocentric distance. For extinction in the ecliptic, was obtained, where ? is the solar elongation in degrees. 相似文献
16.
17.
Photometric parameters of the asteroids 33 Polyhymnia and 386 Siegena were obtained during an international campaign performed at three observatoroes: Table Mountain Observatory (A. W. Harris), European Southern Observatory (ESO; C.-I. Lagerkvist), and Catania Astrophysical Observatory (V. Zappalá and F. Scaltriti). The photoelectric observations were carried out in the period August 15–September 14, 1980.The rotational periods and amplitudes observed are: for Siegena and (at ～10° phase angle) for 33 Polyhymnia.The multiple-scattering factor Q [as defined by K. Lumme and E. Bowell, Astron. J.86, 1694–1704, 1705–1721 (1981a,b)] is found to be 0.15 ± 0.06 for 386 and 0.26 ± 0.03 for 33, implying higher albedos in each case than expected according to their taxonomic classes, C and S, respectively [E. Bowell, T. Gehrels, and B. Zellner, in Asteroids, pp. 1108–1129, Univ. of Arizona Press, Tucson (1979)].The color indices B - V and U - B, were measured and found to differ significantly from those given by Bowell et al.. Our values are, for 386, B - V = 0.71 and U - B = 0.36; and for 33, B - V = 0.81 and U - B = 0.39. 相似文献
18.
Jupiter's innermost Galilean satellite Io is regarded as a fairly good conductor (). The trapping of magnetic field lines by Io and their deformation is described. A neutral point forms in the vicinity of the satellite. The magnetic field annihilation in the neutral point is enhanced by the emission of low frequency hmd waves. The power carried away by these waves may be as high 1015 W. The characteristic frequency of the wave and its variation while Io orbits around Jupiter is determined. 相似文献
19.
Simultaneous measurements of the 6300 Å airglow intensity, the electron density profile, and F-region ion temperatures and vertical ion velocities taken at the Arecibo Observatory in March 1971 are utilized in the height integrated continuity equation to extract the number of photons'of 6300 Å emitted per recombination. After accounting for quenching of and the electrons lost via NO+ recombination, the efficiency of production by the dissociative recombination of O2+ is determined to be 0.6 ± 0.2 including cascading from the state. The uncertainty includes both random measurement errors and estimates of possible systematic errors. 相似文献
20.
William D. Cochran 《Icarus》1984,58(3):440-445
Spectra of the “red” doublet and the 1S-1D “green” line in Comet IRAS-Araki-Alcock (1983d) were obtained during its close approach to the Earth. This is the first unequivocal photoelectric detection of the green line in a cometary spectrum. The population ratio of the O (1S) state to the O (1D) state in the inner coma is ≦0.03. This ratio eliminates CO or CO2 and points strongly to H2O as the primary parent for excited oxygen atoms. 相似文献