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1.
We have used the measurements of the solar flux obtained by the Venera 8 spacecraft inside the atmosphere of Venus and the values of the Venus spherical albedo to deduce the characteristics of the clouds and of the ground. The method used is the exponential kernel approximation and the results have been tested by exact computations with the spherical harmonics method.A cloud layer with an optical thickness , an albedo for single scattering in the rear infrared, above a Rayleigh layer between 0 and 32 km and a ground of reflectivity ? = 0.4, gives a good agreement with the experimental results. A model with two cloud layers is also discussed. 相似文献
2.
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
3.
The Stokes parameters of resonance radiation scattered by a Na atom with the angular momentum F aligned by directed unpolarized radiation in a magnetic field H ～ 10?5?10?1 Oe are presented. An influence of the orientation of the magnetic field on these parameters are studied; the intensity ratio changes within ±5%, and the polarization degree P(D2) within ±25%. Measurements of and P(D2), if the geometry of scattering is known, may give information on the direction of the magnetic field in the sodium atmospheres of comets, as well as Io's sodium cloud or man-made cosmic clouds. 相似文献
4.
Photolysis of NH3 in the presence of CH4 with a 185-nm light source results in the generation of hot hydrogen atoms that abstract hydrogen from the CH4 to produce CH3·. Subsequent reactions of CH3· and NH2· give hydrocarbons, CH3NH2, and HCN. The extent of reaction of CH4 was measured by the ratio of the moles of CH4 reacted per mole of NH3 decomposed (). This ratio increases with diminishing NH3 pressure at constant CH4 pressure but it remains constant if . The ratio is independent of temperature in the range 156–298° K, suggesting that hot hydrogen atoms were responsible for the reaction of CH4. This postulate was confirmed by the observation that this reaction was quenched when H2 or SF6 was added to the reaction mixture. 相似文献
5.
Kenneth Fox 《Icarus》1975,24(4):454-459
The basis for “quasipolar” absorption (QPA) by CH4 is the existence of a small electric dipole moment in its ground state. The integrated intensity αQPA at a temperature of 90K is calculated to be between 4.8 × 10?5 and 1.9 × 10?2 cm?2 atm?1. With an assumed mean pressure of 0.1 atm and a relative abundance of , it is estimated that the ratio of quasipolar to pressure-induced absorption (PIA) is 0.05 ? αQPA/αPIA ? 18 for the spectral range from 0 to 300 cm?1. This result suggests that quasipolar absorption may contribute to a weak, CH4-induced greenhouse in the atmosphere of Titan. 相似文献
6.
An analysis of Titan's solar phase variation as a function of wavelength together with the continuum geometric albedo makes it possible to set limits on the real part of the refractive index and on the average particle size of the aerosol component of Titan's atmosphere: . If nris known can be determined to within a few percent, and varies inversely with nr. Using this information in a two-layer model of a methane-aerosol atmosphere and comparing the result with Titan's visible and near-infrared methane spectrum leads to the conclusion that the top layer of Titan's atmosphere contains 0.01 km atm of methane and 2.5 extinction optical depths of aerosol, while the data are consistent with a bottom layer containing 2.2 km atm of methane and about 7.5 aerosol optical depths for . 相似文献
7.
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
8.
Absolute spectrophotometry of Neptune from 3390 to 7800 Å, with spectral resolution of 10 Å in the interval 3390–6055 and 20 Å in the interval 6055–7800 Å, is reported. The results are compared with filter photometry (Appleby, 1973; Wamsteker, 1973; Savage et al., 1980) and with synthetic spectra computed on the basis of a parameterization proposed by Podolak and Danielson (1977) for aerosol scattering and absorption. A CH4/H2 ratio of is derived for the convectively mixed part of Neptune's atmosphere, and constrains optical properties of hypothetical aerosol layers. 相似文献
9.
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
10.
Darrell F. Strobel 《Icarus》1974,21(4):466-470
Detailed photochemical models are constructed for two model atmospheres: (1) 100% CH4 and (2) 50% H2, 50% CH4. Both models predict large column densities of C2H2 and C2H6 (～1 cm atm) for eddy mixing rates ～105 cm2 sec?, which are comparable to rates appropriate for Jupiter. These column densities vary inversely with the eddy diffusion coefficient. The models confirm the interpretation by Danielson et al. (1973) of the 12μ feature in the spectra of Gillet et al. (1973) as emission by C2H6 in a thermal inversion region. The mixing ratio is sensitive to the net escape rate of H atoms from the exobase. 相似文献
11.
W.W. Mullins 《Icarus》1976,29(1):113-123
The stochastic model of lunar type impact-crater formation which assumes (a) random impacts, (b) circular craters, each obliterating any portions of earlier craters lying within, and (c) a probability Pi(t) that a newly formed crater (primary or secondary) has an area ai is analyzed to develop a method of estimating Pi from the final overlapping pattern. It is found that if each crater is weighted by the fraction of the rim which is visible and which lies in an observation area A, then the expected value of the weighted sum of craters of area ai is simply proportional to Pi for any degree of coverage under several conditions, including (a) constant Pi for all i, and (b) Pi stepping from a constant early value to zero (for some i's) with otherwise arbitrary bombardment. Furthermore, in the general case, the expected value of the contribution produced during t0 ± Δt/2 is found to be proportional to Pi(t0). Thus measurement of in the first two cases, or of if crater age data is available in the last case, provides an estimate of the desired Pi. Therefore the introduce the correct weighting factors that just compensate for the effect of overlap.Expressions for the variances of are derived from which it is shown that under the above conditions, are consistent estimators of Pi. Formal evaluation of the variances is carried out in the special case of constant Pi and no secondary cratering. A criterion for the degree of coverage is given; in particular it is shown that the expectation of at saturation is just A. 相似文献
12.
《Chinese Astronomy and Astrophysics》1982,6(1):20-23
Rosseland mean opacities [see Table 2] per unit hydrogen particle are calculated in this paper for the atmosphere of the solar type [see Table 1].The sources of the continuous opacities under consideration in this paper are as follows: (1) H?, HI, H?2, H+2 He?, HeI, HeII, CI, CII, CIII, NI, NII, NIII, OI, OII, NaI, MgI, MgII, AlI, AlII, SiI, SiII, CII, KI, CaII in the form of absorption. (2) HI, HeI, CI, NI, OI, H2 in the form of Rayleigh scattering. (3) Free electrons in the form of Thomson scattering. 相似文献
13.
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
14.
Observations of Uranus during the 1975, 1976, and 1978 apparitions reveal a weak absorption at the wavelength of the R5(1) line of HD with equivalent width . The ratio in Uranus' atmosphere implied by this line and other published spectra is (4.8 ± 1.5) × 10?5, and may not be significantly different from that in the atmospheres of Jupiter and Saturn. In addition, the spectra exhibit two weak absorption at which we were unable to identify. No trace of absorption is visible near these wavelengths or near the HD wavelength in a laboratory spectrum of 4.92 km-am CH4 which we obtained in an attempt to identify these absorption features and to verify that the HD feature does not arise from CH4. 相似文献
15.
The paper gives the results of detailed studies of the frequency spectra of the chain of the wave packets Fs(t) of geomagnetic pulsations PC-1 recorded at the Novolazarevskaya station. The bulk of the energy of Fs(t) is concentrated in the vicinity of the central frequencies of spectra—the carrier frequencies of the signals. The velocity of the flux of protons generating these signals correspond to them. The spectra of the signals have oscillations—“satellites” irregularly distributed in frequency. These satellites, as the authors believe, testify to the presence of the individual groups of protons of low concentration whose velocities vary within 103–104 km s?1.Their energy is only of the order of 10?2–10?3 of the energy of the main proton flux. Clearly pronounced maxima on double and triple frequencies are detected. They show that the generation of pulsations PC-1 is accompanied by the generation on the overtones of wave packets called in this paper “two-fold” and “three-fold” pulsations PC-1. Intensive symmetrical satellites of a modulation character have been discovered on frequencies . Frequency differences correspond to them. The authors believe that the values of Δ?±sK are resonance frequencies of the magnetospheric cavity in which geomagnetic pulsations PC-1 are generated. It is established that the values of Δ?±sK coincide closely with the carrier frequencies of geomagnetic pulsations PC-3 and PC-4 generated in the magnetosphere. This leads to the conclusion that the resonance oscillations of the magnetospheric cavity are their source. Thus, the generation of geomagnetic pulsations of different types and resonance oscillations in the magnetosphere are integrated into a unified process. The importance of the results obtained and the necessity to check further their trustworthiness and universality, using experimental data gathered in different conditions, is stressed. 相似文献
16.
We have computed line profiles and curves of growth for both reflected and transmitted radiation for typical lines in CO2 bands (in the photographic infrared) which occur in the spectrum of Venus. In our model the pressure variation with altitude was considered and the base of the cloud deck was set at the 2 bar level. The temperature was held constant at 250K and a Voigt profile was used for the lineshape. We also assumed that the scale height of the cloud particles was equal to the scale height of the gas. The calculations were made for four values of the scattering optical thickness (τc = 0.1, 1.0, 10, and 100) using a continuum single scattering albedo (which gives a Bond albedo of 0.896 for τc = 100, the value observed for Venus at these wavelengths). Curves of growth are also presented for reflected radiation which has been averaged over the visible disk for three values of the Venus phase angle (0, 86, and 166°). 相似文献
17.
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
18.
Marcel Nicolet 《Planetary and Space Science》1984,32(7):871-880
The photodissociation of water vapour in the mesosphere depends on the absorption of solar radiation in the region (175–200 nm) of the O2 Schumann-Runge band system and also at H-Lyman alpha. The photodissociation products are OH + H, OH + H, O + 2H and H2 + O at Lyman alpha; the percentages for these four channels are 70, 8, 12 and 10%, respectively, but OH + H is the only channel between 175 and 200 nm. Such proportions lead to a production of H atoms corresponding to practically the total photodissociation of H2O, while the production of H2 molecules is only 10% of the H2O photodissociation by Lyman alpha.The photodissociation frequency (s?1) at Lyman alpha can be expressed by a simple formula where F10.7 cm is the solar radioflux at 10.7 cm and N the total number of O2 molecules (cm?2), and when the following conventional value is accepted for the Lyman alpha solar irradiance at the top of the Earth's atmosphere () qLyα,∞ = 3 × 1011 photons cm?2 s1?.The photodissociation frequency for the Schumann-Runge band region is also given for mesospheric conditions by a simple formula where JSRB,∞(H2O) = 1.2 × 10?6 and 1.4 × 10?6 s?1 for quiet and active sun conditions, respectively.The precision of both formulae is good, with an uncertainty less than 10%, but their accuracy depends on the accuracy of observational and experimental parameters such as the absolute solar irradiances, the variable transmittance of O2 and the H2O effective absorption cross sections. The various uncertainties are discussed. As an example, the absolute values deduced from the above formulae could be decreased by about 25-20% if the possible minimum values of the solar irradiances were used. 相似文献
19.
《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
20.
This paper presents the results of a laboratory study of the limb darkening, near opposition, of the carbonaceous chondrites Orgueil (C1), Murchison (C2), and Allende (C3), the ordinary chondrite Bruderheim (L6), and a stainless-steel powder. These materials represent possible analogs for the surface materials of C, S, and M asteroids respectively. At low phase angles, the limb-darkening behavior of all materials studied is well represented by Minnaert's law. For carbonaceous chondrites, the Minnaert limb-darkening parameter k is nearly independent of wavelength for wavelengths between 0.4 and 0.9 μm, with a typical value of k = 0.55. The reflectance parameter, B0, varies from 0.045 to 0.065 over the same range of wavelengths. Both k and B0 are larger for the stainless-steel powder and the ordinary chondrite, due to the increased importance of multiple scattering in the surface layer. If no limb darkening were present, k would equal and the geometric albedo (p) of an asteroid would equal the normal reflectance of its surface material. For bodies whose surface material is appreciably limb darkened, the geometric albedo measured at the telescope will be lower than the true normal reflectance of surface material; we estimate that for S and M objects rn ? 1.05 p. In the case of nonspherical asteroids, because the distribution of incidence and emission angles varies as the asteroid rotates, the geometric albedo must change with aspect. If limb darkening is not considered when interpreting asteroid light curves, the values of b/a derived will be too extreme. This effect is probably too small to be observed for C asteroids, because of their intrinsically low reflectances, but could be appreciable for S and M objects. 相似文献