Photoionization of barium clouds via the ${}^3\text{D}$ metastable levels     

J.L. Carlsten 《Planetary and Space Science》1975,23(1):53-60

The photoionization of optically thin barium clouds is analyzed and shown to occur primarily by a two-step process involving the ${}^3\text{D}$ metastable term as the ntermediate state. The equilibrium populations of the ${}^1\text{D}$ and ${}^3\text{D}$ metastable levels are calculated and found to differ significantly from the values now in the literature. These populations are combined with our newly available photoionization data to calculate the resulting photoionization rate in the upper atmosphere.  相似文献   

Love numbers of the giant planets     

S.V. Gavrilov  V.N. Zharkov 《Icarus》1977,32(4):443-449

We calculate the Love numbers k_n 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: $\text{Q}{}_{\mathrm{<mtext>J</mtext>}}\text{? 2.5 × 10}{}^4$, $\text{Q}{}_{\mathrm{<mtext>S</mtext>}}\text{? 1.4 × 10}{}^4\text{, Q}{}_{\mathrm{<mtext>U</mtext>}}\text{? 5 × 10}{}^3$.  相似文献   

Linewidth studies on the NI(⁴S−⁴P) resonance multiplet     

P.W. Erdman  E.C. Zipf 《Planetary and Space Science》1983,31(11):1291-1298

We have measured the linewidths of the NI multiplets $\text{[2p}{}^2\text{3p}{}^4\text{D}{}^0\text{?2p}{}^2\text{3s}{}^4\text{P, λ8691}\text{A}\text{?}\text{; 2p}{}^2\text{3p}{}^4\text{P}{}^0\text{?2p}{}^2\text{3s}{}^4\text{P, λ8212}\text{A}\text{?}\text{; 2p}{}^2\text{3s}{}^4\text{P?2p}{}^3{}^4\text{S}{}^0\text{, λ1200}\text{A}\text{?}\text{]}$ produced in the dissociative excitation of N₂ by energy electrons. The infrared transitions excite the N(⁴P) resonance state by cascade and they account for > 50% of the total N(⁴P) cross section at 100 eV. Both the i.r. and v.u.v. lines are found to be highly Doppler broadened ( ～ 25 times the thermal Doppler line width). These results indicate that dissociative excitation of N₂ produces N (⁴P) atoms with sufficient kinetic energy so that the $\text{λ1200}\text{A}\text{?}$ resonance radiation $\text{[2p}{}^2\text{3s}{}^4\text{P ?2p}{}^3{}^4\text{S}{}^0\text{]}$ emitted by these excited atoms would be optically thin in the Earth's upper atmosphere. We also found that the line strength ratios for the resolved components of the $\text{λ1200}\text{A}\text{?}$ triplet excited by dissociative excitation differ from those predicted by the multiplicities of the states involved and used in current entrapment models; the intensity ratios also vary with the energy of the incident electron. These developments introduce new complications into the analysis of the terrestrial ultraviolet dayglow.  相似文献   

A discussion of the energy transfer from N₂(A³Σ_u⁺) to $\text{O}\text{(}{}^1\text{S}$) in pulsating aurora     

Asgeir Brekke 《Planetary and Space Science》1973,21(4):698-702

In a recent paper, Brekke and Pettersen (1972) have introduced a method for estimating any indirect process in the production of the $\text{O}\text{(}{}^1\text{S}$) atoms in pulsating aurora; for 38 per cent of their data they found that the decay time for the indirect mechanism was shorter than the effective lifetime of the ${}^1\text{S}$ state. These data are related to the energy transfer from the N₂(A³Σ) molecules to the $\text{O}\text{(}{}^1\text{S)}$ state, and evidence is found for this process to contribute in the altitude range below 125 km.  相似文献   

Thermospheric neutral composition from auroral ion ratios     

W. Swider 《Planetary and Space Science》1983,31(1):49-52

For nighttime auroras, we find that positive ion ratios are only a function of the neutral atmospheric composition and of the pertinent ionic processes if the ions are depleted mainly by ion-molecule reactions. Ionic ratios calculated for $\text{[}\text{N}{}^{\mathrm{+}}\text{]}\text{[}\text{N}{}_2{}^{\mathrm{+}}\text{]}$ using the 1976 U.S. Standard Atmosphere and laboratory rate coefficients (with one exception) rise smoothly with altitude: 0.1 (120 km), 0.3 (140 km), 0.6 (160 km), 1.0 (180 km) and 1.5 (200 km). These values compare favorably with experimental ratios from three different auroral experiments. The exception refers to our use of a larger rate coefficient for N₂⁺ + O → NO⁺ + N than found in the laboratory. We also determine an $\text{[}\text{N}{}_2{}^{\mathrm{+}}\text{]}\text{[}\text{O}{}^{\mathrm{+}}\text{]}$ ratio with altitude: 0.36 (120 km), 0.078 (140 km), 0.030 (160 km), 0.014 (180 km) and 0.0075 (200 km). These values compare favorably with results from the same three auroral experiments. However, the match with a fourth auroral experiment is poor. Except for this last case, we conclude that the neutral composition at auroral latitudes in late winter is similar to the U.S. Standard for the altitudes examined.  相似文献   

Application of methane band-model parameters to the visible and near-infrared spectrum of Uranus     

D.Chris Benner  Uwe Fink 《Icarus》1980,42(3):343-353

Laboratory band-model absorption coefficients of CH₄ are used to calculate the Uranus spectrum from 5400 to 10,400 Å. A good fit of both strong and weak bands for the Uranus spectrum over the entire wavelength interval is achieved for the first time. Three different atmospheric models are employed: a reflecting layer model, a homogeneous scattering layer model, and a clear atmosphere sandwiched between two scattering layers. The spectrum for the reflecting layer model exhibits serious discrepancies but shows that large amounts of CH₄ (5–10 km-am) are necessary to reproduce the Uranus spectrum. Both scattering models give reasonably good fits. The homogeneous model requires a particle scattering albedo $\text{(}\text{g}\text{?}\text{w}{}_{\mathrm{<mtext>p</mtext>}}\text{) ? 0.998}$ and an abundance per scattering mean free path $\text{(}\text{a}\text{?}\text{)}\text{of}\text{a}\text{?}\text{1}\text{km-am}$. The parameters derived from the sandwich layer model are: forsb the upper scattering layer a continuum single scattering albedo ($\text{g}\text{?}\text{w}{}_0$) of 0.995 and a scattering optical depth variable with wavelength consistent with Rayleigh scattering; for the clear layer they are a CH₄ abundance (a) of 2.2 km-am and an effective pressure (p) ? 0.1 atm; for the lower cloud deck a Lambert reflectivity (L) of 0.9 resulted. A severe depletion of CH₄ in the upper scattering layer is required. An enrichment of CH₄/H₂ over the solar ratio by a factor of 4–14 in the lower atmosphere is, however, indicated.  相似文献   

An analysis of the OI 1304 a dayglow using a Monte Carlo resonant scattering model with partial frequency redistribution     

R.R. Meier 《Planetary and Space Science》1982,30(5):439-450

A Monte Carlo model of the atomic oxygen 1304 A airglow triplet has been developed which accurately describes the transport of resonance radiation under very optically thick conditions. Partial frequency redistribution, temperature gradients, pure absorption, and multilevel scattering are accounted for properly.Analysis of a recent rocket experiment which observed the 1304 A dayglow shows that all features of the data can be explained by photoelectron impact excitation and resonant scattering of sunlight. The latter source dominates below 100 and above 500 km, and is stronger at intermediate altitudes than previously thought. Recent observations of the photoelectron flux from AEE are consistent with both the 1304 and 1356 A dayglow, as are the laboratory cross-sections of Stone and Zipf (1974) for electron excitation of the $\text{OI}{}^3\text{S}$ and ${}^5\text{S}\text{levels}$. There is no need to lower the laboratory cross-sections by a factor of 2 as has been suggested by previous work.The OI 1304 A emission can now be used with confidence to study excitation processes and atomic oxygen densities in planetary atmospheres.  相似文献   

Space erosion of meteorites and the secular variation of cosmic rays (over 10⁹ years)     

O.A. Schaeffer  K. Nagel  H. Fechtig  G. Neukum 《Planetary and Space Science》1981,29(10):1109-1118

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 ${}^{40}\text{K}$ and those based on ${}^{36}\text{Cl}\text{,}{}^{39}\text{Ar and}{}^{10}\text{Be}$. It is concluded that there is a long term cosmic ray variation.  相似文献   

The excitation of atomic oxygen to the $\text{O(}{}^1\text{S)}$ level by energy transfer from N₂(A³∑_u⁺) molecules in aurora     

Kjell Henriksen 《Planetary and Space Science》1973,21(5):863-871

The part that the energy transfer reaction $\text{N}{}_2\text{(A}{}^3\text{∑}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{) + O(}{}^3\text{P) → N}{}_2\text{(X}{}^1\text{∑}{}_{\mathrm{g}}{}^{\mathrm{+}}\text{) + O(}{}^1\text{S)}$ plays in the excitation of the auroral green line has been investigated. The contribution is estimated to be 40 per cent in this case, containing pulsating aurora in class IBC 1. Due to greater quenching of the A³∑_u⁺ state, the centroid of the VK emission is displaced 10 km upwards of the green line height, which is centred at 110 km.  相似文献   

Thinning of the near-earth (10∼15 R_E) plasma sheet preceding the substorm expansion phase     

A. Nishida  K. Fujii 《Planetary and Space Science》1976,24(9):849-853

The timing of the plasma-sheet thinning relative to the onset of the expansion phase of substorms is examined by the analysis of the OGO 5 electron (79 ± 23 keV) and proton (100～150 keV) data with the aid of simultaneous magnetic field observations. It is found that the timing of the thinning is significantly dependent on the distance. At $\text{x}{}^2\text{+ y}{}^2\text{? 15 R}{}_{\mathrm{E}}$ the thinning often starts before the onset, while at $\text{x}{}^2\text{+ y}{}^2\text{? 15 R}{}_{\mathrm{E}}$ it tends to occur after the onset, where x and y refer to solar magnetospheric coordinates. The thinning that precedes the expansion-phase onset has been found to reduce the thickness to ～1 R_E, and further thinning may occur in a spatially limited region. Hence it is conceivable that the formation of the neutral line characterizing the substorm expansion phase is the consequence of the thinning of the plasma sheet in the near-Earth region.  相似文献   

Aeronomical determination of the efficiency of O¹D) production by dissociative recombination of O₂⁺     

L.L. Cogger  L.S. Smith  R.M. Harper 《Planetary and Space Science》1977,25(2):155-159

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 $\text{O}\text{(}{}^1\text{D}\text{)}$ and the electrons lost via NO⁺ recombination, the efficiency of $\text{O}\text{(}{}^1\text{D}\text{)}$ production by the dissociative recombination of O₂⁺ is determined to be 0.6 ± 0.2 including cascading from the $\text{O}\text{(}{}^1\text{S}\text{)}$ state. The uncertainty includes both random measurement errors and estimates of possible systematic errors.  相似文献   

Branching ratios for the photoionization cross section of atomic oxygen     

A.K. Pradhan 《Planetary and Space Science》1980,28(2):165-167

Branching ratios $\text{σ(}\text{O}{}^0{}^3\text{P}\text{→}\text{O}{}^{\mathrm{+}}{}^2\text{D}{}^0\text{)}\text{σ(}\text{O}{}^0{}^3\text{P}\text{→}\text{O}{}^{\mathrm{+}}{}^4\text{S}{}^0\text{)}$ and $\text{σ(}\text{O}{}^0{}^3\text{P}\text{→}\text{O}{}^{\mathrm{+}}{}^2\text{P}{}^0\text{)}\text{σ (}\text{O}{}^0{}^3\text{P}\text{→}{}^4\text{S}{}^0\text{)}$ 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 $\text{σ(}{}^2\text{D}{}^0\text{)}$ decreases more rapidly than $\text{σ(}{}^2\text{P}{}^0\text{)}$, and at the lower wavelength 304 Å, the ratio $\text{σ(}{}^2\text{D}{}^0\text{)}\text{σ(}{}^4\text{S}{}^0\text{)}\text{<}\text{σ(}{}^2\text{P}{}^0\text{)}\text{σ(}{}^4\text{S}{}^0\text{)}$. Present results at 304 Å differ considerably from previous work.  相似文献   

A dynamical effect in the ionospheric f₁ layer     

C. Taieb  G. Scialom  G. Kockarts 《Planetary and Space Science》1978,26(11):1007-1016

Incoherent scatter observations of the ionospheric F₁ layer above Saint-Santin (44.6°N) are analyzed after correction of a systematic error at 165 and 180 km altitude. The daytime valley observed around 200 km during summer for low solar activity conditions is explained in terms of a downward ionization drift which reaches ?30 m s^?1 around 180 km. Experimental determinations of the ion drift confirm the theoretical characteristics required for the summer daytime valley as well as for the winter behaviour without a valley. The computations require an effective dissociative recombination rate of $\text{2.3 × 10}{}^{\mathrm{?7}}\text{(}\text{300/}\text{T}{}_{\mathrm{e}}\text{)}{}^{0.7}\text{(}\text{cm}{}^3\text{s}{}^{\mathrm{?1}}\text{)}$ and ionizing fluxes compatible with solar activity conditions at the time when the valley is observed.  相似文献   

On the molecular scattering in the terrestrial atmosphere : An empirical formula for its calculation in the homosphere     

Marcel Nicolet 《Planetary and Space Science》1984,32(11):1467-1468

A recent determination by D. R. Bates of the Rayleigh scattering cross section (σ_RS) for air from 0.2 to 1 μm leads to a simple empirical formula (λ in μm) $\text{σ}{}_{\mathrm{RS}}\text{=}\text{4.02 × 10}{}^{\mathrm{?28}}\text{λ}{}^{\mathrm{4+x}}\text{cm}{}^2$ where $\text{x =}\text{0.389λ + 0.09426}\text{λ ? 0.3228}$ 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   

The influence of ethane and acetylene upon the thermal structure of the Jovian atmosphere     

R.D. Cess  S.C. Chen 《Icarus》1975,26(4):444-450

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 $\text{[}\text{C}{}_2\text{H}{}_6\text{]}\text{[}\text{H}{}_2\text{]}\text{= 10}{}^{\mathrm{?5}}$ and $\text{[}\text{C}{}_2\text{H}{}_2\text{]}\text{[}\text{H}{}_2\text{]}\text{= 5 × 10}{}^{\mathrm{?7}}$, 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   

A new interpretation of the 1304 Å triplet airglow intensity ratio with the fine structure levels $\text{O}{}^3\text{P}{}_{\mathrm{j}}\text{)}$ in local thermodynamic equilibrium     

Toshihiro Ogawa 《Planetary and Space Science》1982,30(1):39-44

The intensity ratios of the 1304 Å triplet airglow of atomic oxygen observed by Fastie and Crosswhite (1964) are interpreted on the basis of the radiative transfer formulation for a model with complete frequency redistribution in a Voigt line profile. A model for the fine structure levels $\text{O(}{}^3\text{P}{}_{\mathrm{j}}\text{)}$ in local thermodynamic equilibrium is favorable to the observed intensity ratios, as far as a Voigt profile is applicable. In view of large cross sections as calculated theoretically by Allison and Burke (1969), the mutual relaxation among the ³P_j levels should occur rapidly enough to allow the population in the ³P_j levels to be in thermodynamic equilibrium with the ambient neutral gases.  相似文献   

The O(1S) quantum yield from O2+ dissociative recombination     

D.R. Bates  E.C. Zipf 《Planetary and Space Science》1980,28(11):1081-1086

Recent laboratory studies show that the $\text{O}\text{(}{}^1\text{S}\text{)}$ quantum yield, $\text{f}\text{(}{}^1\text{S}\text{)}$, from O₂⁺ dissociative recombination varies considerably with the degree r of vibrational excitation. However, the suggestion that the high values for $\text{f}\text{(}{}^1\text{S}\text{)}$ deduced from airglow and auroral observations can be explained by invoking vibrational excitation, creates a number of problems. Firstly, the rapid vibrational deactivation of O₂⁺ ions by collisions with O atoms will keep r too low to account for the magnitude of $\text{f}\text{(}{}^1\text{S}\text{)}$; secondly, r varies considerably from one atmospheric source to another but its relative values (which should be reliable) do not co-vary with those of $\text{f}\text{(}{}^1\text{S}\text{)}$; thirdly, because r increases markedly above the peak of the $\text{X5577}\text{A}\text{?}$ dissociative recombination layer, the fits which theorists have obtained to the observed volume emission rate profiles would have to be regarded as fortuitious. It is tentatively suggested that $\text{f}\text{(}{}^1\text{S}\text{)}$ is higher in the airglow and aurora than in the laboratory plasma studied by Zipf (1980) because of the electron temperature dependence of the $\text{O}\text{(}{}^1\text{S}\text{)}$ specific recombination coefficient for O₂⁺(v^' ? 3) ions.The repulsive ${}^1\text{Σ}{}_{\mathrm{<mtext>u</mtext>}}\text{[}{}^1\text{D}\text{+}{}^1\text{s}\text{]}$ state of O₂ does not provide a suitable channel for the dissociative recombination. A possible alternative is the bound ${}^3\text{Π}{}_{\mathrm{<mtext>u</mtext>}}\text{[}{}^5\text{S}\text{+}{}^3\text{s}\text{]}$ state with predissociation to the repulsive ${}^3\text{Π}{}_{\mathrm{<mtext>u</mtext>}}\text{[}{}^3\text{P}\text{+}{}^1\text{s}\text{]}$ state.  相似文献   

Resonant electron scattering by metastable nitrogen     

Iztok Čadež 《Planetary and Space Science》1983,31(8):843-848

The resonant electron impact quenching of metastable molecules might be important for understanding the phenomena in the upper atmosphere. In order to obtain information about the relative importance of this scattering event the resonant cross sections for electron scattering by metastable nitrogen in the $\text{A}{}^3\text{∑}\text{u}\text{+}$ state were calculated using the “boomerang” model and quenching rates for this state were evaluated for the altitudes of 130,170 and 210km. The obtained quenching rates are small (?5 × 10^?3 s^?1), even with respect to the radiative transition rate showing that under the considered conditions this process is unimportant for population of nitrogen $\text{A}{}^3\text{∑}\text{u}\text{+}$ state in the Earth's thermosphere.  相似文献   

Geopotential coefficients of order 29, from analysis of the orbit of satellite 1967-104B     

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: $\text{10}{}^9\text{C}\text{?}{}_{29}{}^{0.2}\text{= 4.1 ± 0.8}$, $\text{10}{}^9\text{S}\text{?}{}_{29}{}^{0.2}\text{= 10.3 ± 2.4}$, $\text{10}{}^9\text{C}\text{?}{}_{29}{}^{1.1}\text{= ? 160 ± 19}$, $\text{10}{}^9\text{S}\text{?}{}_{29}{}^{1.1}\text{= 79 ± 10}$, $\text{10}{}^9\text{C}\text{?}{}_{29}{}^{\mathrm{?1.3}}\text{= 38 ± 14}$, $\text{10}{}^9\text{S}\text{?}{}_{29}{}^{\mathrm{?1.3}}\text{= 19 ± 5}$. These values have been compared with existing comprehensive geopotential models: the best agreement is with the model of Rapp (1981).  相似文献   

The determination and analysis of the orbit of NIMBUS 1 ROCKET, 1964-52B: Part 2: Variations in orbital eccentricity     

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: $\text{10}{}^9\text{C}{}^{\mathrm{1,0}}{}_{15}\text{= ?78.8 ± 7.0}$, $\text{10}{}^9\text{S}{}^{\mathrm{1,0}}{}_{15}\text{= ?69.4 ± 5.3}$, $\text{10}{}^9\text{C}{}^{\mathrm{?1,2}}{}_{15}\text{= ?41.6 ± 3.5}$$\text{10}{}^9\text{S}{}^{\mathrm{?1,2}}{}_{15}\text{= ?26.1 ± 8.9}$, at inclination 98.68°.  相似文献