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1.
Previous studies based on radio scintillation measurements of the atmosphere of Venus have identified two regions of small-scale temperature fluctuations located in the vicinity of 45 and 60 km. A global study of the fluctuations near 60 km, which are consistent with wind-shear-generated turbulence, was conducted using the Pioneer Venus measurements. The structure constants of refractive index fluctuations cn2 and temperature fluctuations cT2 increase poleward, peak near 70° latitude, and decrease over the pole; cn2 varies from 2 × 10?15 to 1.5 × 10?14m and cT2 from 4 × 10?3 to 7 × 10?2°K2m. These results indicate greater turbulent activity at the higher latitudes. In the region near 45 km the refractive index fluctuations and the corresponding temperature fluctuations are substantially lower. Based on the analysis of one representative occultation measurement, in the 45-km region. The fluctuations in this region also appear to be consistent with wind-shear-generated turbulence. The turbulence level is considerably weaker than that at 60 km; the energy dissipation rate ε is 4.9 × 10?5m2sec?3 and the small-scale eddy diffusion coefficient K is 2 × 103 cm2 sec?1. 相似文献
2.
《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
3.
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
4.
A mechanism has been proposed for uv-accelerated desorption from Fe2+ sites on mineral surfaces that satisfies kinetic constraints determined in the laboratory by Huguenin. The process is an integral step of the photochemical weathering mechanism for producing dust on Mars, and it now appears that it may play primary roles in stabilizing CO2 against dissociation by sunlight and in controlling the oxidation state of the atmosphere. We propose that adsorption occurs at octahedrally coordinated Fe2+ surface sites to form seven-coordinate transition-state complexes. These complexes acquire 16–18 kcal mole?1 of ligand field stabilization energy. During illumination (λ ≤ 0.35 μm), electrons are photoemitted from the surfaced Fe2+, temporarily oxidizing them to Fe3+. Fe3+ has no ligand field stabilization energy, and the complexes lose 16–18 kcal mole?1 of stabilization energy. This is a large fraction of the 19- to 28-kcal mole?1 activation energy for dissociating the complexes, and desorption should proceed spontaneously. The gases that were observed to undergo adsorption-photodesorption include O2, CO2, CO, H2O, N2, and Ar. Photodesorption can drive several catalytic reactions, one of which is the oxidation of CO to CO2. The rate of this reaction should be limited by the supply of CO and O2 to the surface to ～2 × 1012 cm?2 sec?1 (column photodissociation rate of CO2). By including this surface reaction in models of Martian atmospheric CO2 chemistry, CO2 can be stabilized against photodissociation with eddy diffusion coefficients of only 3 × 105?1 × 107 cm2 sec?1 below 40 km, raising to ～ 109 cm2 sec?1 at 140 km. Odd hydrogen is not needed to catalyze the oxidation of CO below 40 km, and odd hydrogen mixing ratios need only to be to depress ozone concentrations below the observed upper limit in equatorial regions. Another catalytic reaction that should be driven by photodesorption on Mars is . This is an important source of atmospheric O2, amounting to 7 × 1013?2 × 1017 O2 molecules cm?2 yr?1, and it could have a significant effect on atmospheric oxidation state. 相似文献
5.
6.
Y.I. Feldstein A.E. Levitin D.S. Faermark R.G. Afonina B.A. Belov V.Y. Gaidukov 《Planetary and Space Science》1984,32(7):907-923
The potential ? of the electric field at high latitudes has been obtained by solving numerically the second order differential equation in spherical coordinates: , where θ is colatitude, λ is longitude, σH and σP are the height-integrated Hall and Perdersen ionospheric conductivities, r = sinθ, and ψ is the current function. The boundary condition is ? = 0 on the geomagnetic parallel θ = 34°. Values of ψ are determined from geomagnetic field variations at the Earth's surface from geomagnetic field variations at the Earth's surface for various conditions in interplanetary space. σP and σH are taken to vary with season, local time, tilt of the geomagnetic dipole axis (UT), and intensity of corpuscular precipitation (the model proposed by Wallis and Budzinski, 1981). The model distributions of ?M and EM = -▽?m so obtained are compared with observational results. The feasibility has been demonstrated of interpreting the statistical results and individual measurement data in terms of a unified dynamic model of ionospheric electric fields. The model makes allowance for the changes of electromagnetic “weather” in interplanetary space. 相似文献
7.
The problem of interaction between the interplanetary shock of 8 March, 1970 and the Earth's bow shock, magnetopause and plasmapause is considered. Estimates are made using existing models of the moments of initial impulsive interaction of interplanetary shocks with the bow shock and of the secondary interaction of the resulting split discontinuities with the magnetopause, plasmapause and a modified bow shock. Using computed data on the plasma's concentration jumps at discontinuities and on the latters' velocities, estimates have been carried out of remote sounding and the response signals' phase difference change rates Δf (which were found to be of the order of ～ 10?3?10?2Hz) appearing on the radio path with a non-coherent response near the subsolar region. It has been ascertained that the non-coherent response method permits, by using generators with a stability of , effective investigation (with a good time resolution) of the impulsive interaction of interplanetary shocks with the plasma discontinuities of the bow shockmagnetopause-plasmapause system. 相似文献
8.
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
9.
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
10.
Doreen M.C. Walker 《Planetary and Space Science》1984,32(6):717-725
The orbit of the satellite 1967-104B has been analysed as it passed through 29:2 resonance with the Earth's gravitational field between January 1977 and September 1978. From the changes in inclination and eccentricity the following lumped 29th-order geopotential harmonic coefficients were obtained: , , , , , . These values have been compared with existing comprehensive geopotential models: the best agreement is with the model of Rapp (1981). 相似文献
11.
Measurements of N2+ and supporting data made on the Atmosphere Explorer-C satellite in the ionosphere are used to study the charge exchange process The equality k = (5 ± 1.7) × 10?10cm3s?1. This value lies close to the lower limit of experimental uncertainty of the rate coefficient determined in the laboratory. We have also investigated atomic oxygen quenching of O+(2D) and find that the rate coefficient is 2 × 10?11 cm3s?1 to within approximately a factor of two. 相似文献
12.
The abundance of H2O is derived from the 1900- to 2100-cm?1 region of the Voyager 1 IRIS spectra. Scale variations of about a factor of 2 are seen in the water abundance between the North and South Equatorial Belts. Averaged over the full disk, the mixing ratio is , if H2O is uniformly mixed in the atmospheric region having temperatures of 230 to 270°K; this result implies a solar depletion by a factor of 100 in this region. In the belts, the best agreement is obtained for a H2O/H2 mixing ratio of 4.0 × 10?6 in the NEB and 7.2 × 10?6 in the SEB, assuming a constant mixing ratio. 相似文献
13.
K.M. Monahan W.T. Huntress A.L. Lane J.M. Ajello T.E. Burke P. Le Breton A. Williamson 《Planetary and Space Science》1974,22(1):143-149
The cross-section for dissociative photoionization of hydrogen by 584 Å radiation has been measured, yielding a value of 5 × 10?20 cm2. The process can be explained as a transition from the ground state to a continuum level of the ionized state of H2 The branching ratio for proton (H+) vs molecular ion (H2+) production at this energy is 8 × 10?3. This process is quite likely an important source of protons in the Jovian ionosphere near altitudes where peak ionization rates are found. 相似文献
14.
Ni Xiang-bin Jiang Yao-tiao Chen Zai-zhang Fang Cheng 《Chinese Astronomy and Astrophysics》1985,9(4):273-277
We propose a new heating mechanism of faculae. We think that the formation of faculae is a result of the Joule dissipation of the Hall current generated by the interaction of the convection field of granules in an active region and the inter-granular magnetic field. For a region to generate effectively Hall current, its characteristic length must be such that the magnetic Reynolds number is less than 1. The equation of energy balance in the facula region is .For five observational models of faculae, we calculated the corresponding velocity fields, and the results are in basic agreement with the observed fields. The present mechanism explains the dependence of the facula brightness on the magnetic and velocity fields, the apparent distribution of the faculae on the solar disk and suggest a possible interpretation of the five structures of faculae. 相似文献
15.
W.J. Boulton 《Planetary and Space Science》1985,33(8):965-982
The influence of aerodynamic drag and the geopotential on the motion of the satellite 1964-52B is considered. A model of the atmosphere is adopted that allows for oblateness, and in which the density behaviour approximates to the observed diurnal variation. A differential equation governing the variation of the orbital inclination combining the effects of air drag with those of the Earth's gravitational field is given.The 310 observed values of inclination are modified by the removal of perturbations due to luni-solar attraction, solid Earth and ocean tides, solar radiation pressure, low-order long-periodic tesseral harmonic perturbations and changes due to precession. The method of removal of these effects is given in some detail.The variations in inclination due to drag are analysed to give four values of the average atmospheric rotation rate at heights of 296–476 km at latitude 0–54°. These values are as expected from previous analyses.The analysis of the change in inclination due to solar radiation pressure shows that this rapidly tumbling cylindrical satellite may be considered as equivalent to a spherical satellite of a given area-to-mass ratio.Analysis of the inclination near 15:1 resonance with the geopotential yields values of lumped geopotential harmonics of order 15 and 30, namely, 相似文献
16.
Takashi Abe 《Planetary and Space Science》1984,32(7):903-906
A theoretical consideration is given to the critical ionization velocity. A macroscopic theory is constructed, assuming that (1) the newly born ions have an unstable velocity distribution and (2) the resultant fluctuating electric field heats the electrons. For the critical ionization velocity to operate in the case of , the initial values of high speed ion (or newly ionized ion) density and suprathermal electron energy density should be above a certain threshold. This threshold depends upon the velocity diffusion co-efficient and the collisional loss rate of the newly ionized ion. 相似文献
17.
W.J. Boulton 《Planetary and Space Science》1985,33(6):735-756
The influence of aerodynamic drag and the geopotential on the motion of the satellite 1964-52B is considered. A model of the atmosphere is adopted that allows for oblateness, and in which the density behaviour approximates to the observed diurnal variation. A differential equation governing the variation of the eccentricity, e, combining the effects of air drag with those of the Earth's gravitational field is given. This is solved numerically using as initial conditions 310 computed orbits of 1964-52B.The observed values of eccentricity are modified by the removal of perturbations due to luni-solar attraction, solid Earth and ocean tides, solar radiation pressure and low-order long-periodic tesseral harmonic perturbations. The method of removal of these effects is given in some detail. The behaviour of the orbital eccentricity predicted by the numerical solution is compared with the modified observed eccentricity to obtain values of atmospheric parameters at heights between 310 and 430 km. The daytime maximum of air density is found to be at 14.5 hours local time. Analysis of the eccentricity near 15th order resonance with the geopotential yielded values of four lumped geopotential harmonics of order 15, namely: , , , at inclination 98.68°. 相似文献
18.
G.G. Shepherd J.F. Pieau T. Ogawa T. Tohmatsu K. Oyama Y. Watanabe 《Planetary and Space Science》1978,26(3):211-217
A sounding rocket was flown during the predawn on 17 January, 1976 from Uchinoura, Japan, to measure directly the behaviour of the conjugate photoelectrons at magnetically low latitudes. On board the rocket were an electron energy analyzer, 630 nm airglow photometer, and plasma probes to measure electron density and temperature. The incoming flux of the photoelectrons was measured in the altitude range between 210 and 340 km. The differential flux at the top of the atmosphere was determined to be electron · m?2 · sr?1 · s?1 in the energy range 10 ? E ? 50 eV. The emission rate of the 630 nm airglow was observed in the altitude range between 90 and 360 km. The apparent emission rate observed at 80 km was 32 ± 5 R. From a theoretical calculation of the optical excitation rate using the observed electron flux data along with a model distribution of atomic oxygen, it was estimated that more than 65% of the emission could be produced by direct impact of the photoelectrons with atomic oxygen in the thermosphere between 200 and 360 km. Using the observed electron density and the model distribution of oxygen molecules the residual of the emission was ascribed to the excitation of O(1D) through dissociative recombination, . The direct collisional excitation by ambient electrons is estimated to be negligibly small at the level of observed electron temperature. 相似文献
19.
The intensities of radiation from the inner comas of comets which are composed primarily of water and carbon monoxide have been calculated. Only “airglow” emissions initiated by the absorption of extreme ultraviolet radiation have been considered. The photoionizations of H2O, CO, CO2, and N2 are the most important emission sources, although photoelectron excitation is also considered. Among the emission features for which intensities were calculated are H2O+ (), CO+ (first negative), CO (fourth positive), CO (Cameron), CO2+ (), N2 (Vegard-Kaplan), N2+ (first negative), and OI (1304 Å). In the inner coma (collision region) these airglow mechanisms are shown to be possible competitors with the usually assumed resonance scattering and flourescence excitation mechanisms which are appropriate for the outer coma and tail. 相似文献
20.
P. Moore 《Planetary and Space Science》1984,32(9):1101-1109
The orbit of Tansei 3rocket(1977-12B) has been determined at 47 epochs between 1 October 1977 and 19 March 1979 using over 1700 observations and the RAE orbit refinement program PROP6. The rate of change of the inclination was examined to evaluate values of the atmospheric rotation rate, Λ rev day?1. Analysis yielded the value Λ = 1.1 ± 0.05 at height 315 ± 30 km, average conditions; or alternatively Λ = 1.1 ± 0.1 at height 347 ± 12 km, slight winter bias and Λ = 1.07 ± 0.1 at height 270 ± 18 km, average conditions, supplying further evidence of a decrease in rotation rates from the 1960s to the 1970s.Analysis of the inclination at 15th-order resonance yielded the lumped harmonic values for inclination 65.485°. 相似文献