Models of the cometary coma in which abundances are calculated for various heliocentric distances     

Michael B. Swift  George F. Mitchell 《Icarus》1981,47(3):412-430

One-dimensional radial models of the chemistry in cometary comae have been constructed for heliocentric distances ranging from 2 to 0.125 AU. The coma's opacity to solar radiation is included and photolytic reaction rates are calculated. A parent volatile mixture similar to that found in interstellar molecular clouds is assumed. Profiles through the coma of number density and column density are presented for H₂O, OH, O, CN, C₂, C₃, CH, and NH₂. Whole-coma abundances are presented for NH₂, CH, C₂, C₃, CN, OH, CO⁺, H₂O⁺, CH⁺, N₂⁺, and CO₂⁺.  相似文献   

Mass spectrometric measurements of fractional ion abundances in the stratosphere—Positive ions     

F. Arnold  G. Henschen  E.E. Ferguson 《Planetary and Space Science》1981,29(2):185-193

Measured fractional abundances for stratospheric positive ions are reported for the first time. The measurements which were obtained from balloon-borne ion mass spectrometer experiments relied on recent simulation studies of electric field induced cluster ion dissociation conducted at our laboratory.The ion abundance data provide strong support for identifications of the observed ions as H⁺(H₂O)_n and Hx⁺x_L(H₂O)_m proposed previously. Moreover, it is found that x most likely cannot be identified as NaOH or MgOH which implies that gaseous metal compounds do not exist in the middle stratosphere in significant abundances.Implications of the present findings for the composition and chemistry of stratospheric ions as well as for stratospheric aerosols are discussed.  相似文献   

Radial distribution of production rates, loss rates and densities corresponding to ion masses ?40 amu in the inner coma of Comet Halley: Composition and chemistry     

S.A. Haider 《Icarus》2005,177(1):196-216

In this paper we have studied the chemistry of C, H, N, O, and S compounds corresponding to ions of masses ?40 amu in the inner coma of the Comet 1P/Halley. The production rates, loss rates, and ion mass densities are calculated using the Analytical Yield Spectrum approach and solving coupled continuity equation controlled by the steady state photochemical equilibrium condition. The primary ionization sources in the model are solar EUV photons, photoelectrons, and auroral electrons of the solar wind origin. The chemical model couples ion-neutral, electron-neutral, photon-neutral and electron-ion reactions among ions, neutrals, electrons, and photons through over 600 chemical reactions. Of the 46 ions considered in the model the chemistry of 24 important ions (viz., CH₃OH⁺₂, H₃CO⁺, NH⁺₄, H₃S⁺, H₂CN⁺, H₂O⁺, NH⁺₃, CO⁺, C₃H⁺₃, OH⁺, H₃O⁺, CH₃OH⁺, C₃H⁺₄, C₂H⁺₂, C₂H⁺, HCO⁺, S⁺, CH⁺₃, H₂S⁺, O⁺, C⁺, CH⁺₄, C⁺₂, and O⁺₂) are discussed in this paper. At radial distances <1000 km, the electron density is mainly controlled by 6 ions, viz., NH⁺₄, H₃O⁺, CH₃OH⁺₂, H₃S⁺, H₂CN⁺, and H₂O⁺, in the decreasing order of their relative contribution. However, at distances >1000 km, the 6 major ions are H₃O⁺, CH₃OH⁺₂, H₂O⁺, H₃CO⁺, C₂H⁺₂, and NH⁺₄; along with ions CO⁺, OH⁺, and HCO⁺, whose importance increases with further increase in the radial distance. It is found that at radial distances greater than ∼1000 km (±500 km) the major chemical processes that govern the production and loss of several of the important ions in the inner coma are different from those that dominate at distances below this value. The importance of photoelectron impact ionization, and the relative contributions of solar EUV, and auroral and photoelectron ionization sources in the inner coma are clearly revealed by the present study. The calculated ion mass densities are compared with the Giotto Ion Mass Spectrometer (IMS) and Neutral Mass Spectrometer (NMS) data at radial distances 1500, 3500, and 6000 km. There is a reasonable agreement between the model calculation and the Giotto measurements. The nine major peaks in the IMS spectra between masses 10 and 40 amu are reproduced fairly well by the model within a factor of two inside the ionopause. We have presented simple formulae for calculating densities of the nine major ions, which contribute to the nine major peaks in the IMS spectra, throughout the inner coma that will be useful in estimating their densities without running the complex chemical models.  相似文献   

Chemical effects of H2 formation excitation     

R.T. Garrod  J.M.C. Rawlings  D.A. Williams 《Astrophysics and Space Science》2003,286(3-4):487-499

The effects of the production on dust grain surfaces of molecular hydrogen in excited states have been investigated. On the assumption that all of the H₂ formed on the surface of grains has a sufficient level of excitation too vercome the energy barriers in the formation reactions for the important OH and CH⁺ radicals, we consider the likely abundances of excited H₂ (H₂ ^*), OH and CH⁺ in various situations. Two different models are employed; the first links the H₂ ^* abundance directly to that of H₂ using a steady-state approximation, whilst the second considers the time-dependence of H₂ ^*. The second model is applied to gas that has been subjected to a strong isothermal shock (specifically, the shock-induced collapse of a diffuse cloud), which results in an extreme (high density, high atomic hydrogen abundance) environment. In general, it is found that the presence of the excited H₂ has only marginal effects on the chemistry of interstellar clouds. However, in the isothermal shock model, the abundances of CH⁺ are significantly enhanced, but only on short timescales, whilst the effects on the OH abundances are smaller, but last longer. We conclude that other than in such exceptional environments there are no obvious chemical signatures of the formation of H₂ ^*. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The structure of cometary ionospheres: I. H2O dominated comets     

W-H. IP  D.A. Mendis 《Icarus》1976,28(3):389-400

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Chemical diagnostics of magnetized boundary layers     

L. A. M. Nejad  T. W. Hartquist 《Astrophysics and Space Science》1994,220(2):253-260

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Time dependent chemical study of contracting interstellar clouds. II. abundances of oxygen- and sulphur-bearing molecules     

M. Y. Amin  M. S. El Nawawy  B. G. Ateya  A. Aiad 《Earth, Moon, and Planets》1995,69(2):113-125

Abstract. We have constructed a chemical reaction system in a contracting interstellar cloud. In paper (I) we have presented the details of the physical and chemical scheme and the method of solution. The results of our chemical model produce fractional abundances of H₂CO, CO, OH, H₂O, SO and OCS which are in good agreement with the results of observations. On the other hand, the results of chlorine-bearing species are not in agreement with those of the observations. The calculated abundances of H₂CO, CO, OH, H₂O, SO, OCS and Cl⁺ are in agreement with the results of previous theoretical studies.  相似文献   

Electronic Sputtering Analysis of Astrophysical Ices     

L. S. Farenzena  P. Iza  R. Martinez  F. A. Fernandez-Lima  E. Seperuelo Duarte  G. S. Faraudo  C. R. Ponciano  M. G. P. Homem  A. Naves de Brito  K. Wien  E. F. da Silveira 《Earth, Moon, and Planets》2005,97(3-4):311-329

Experimental results on fast ion collision with icy surfaces having astrophysical interest are presented. ²⁵²Cf fission fragments projectiles were used to induce ejection of ionized material from H₂O, CO₂, CO, NH₃, N₂, O₂ and Ar ices; the secondary ions were identified by time-of-flight mass spectrometry. It is observed that all the bombarded frozen gas targets emit cluster ions which have the structure X_nR^±, where X is the neutral ice molecule and R^± is either an atomic or a molecular ion. The shape of the positive or negative ion mass spectra is characterized by a decreasing yield as the emitted ion mass increases and is generally described by the sum of two exponential functions. The positive ion water ice spectrum is dominated by the series (H₂O)_nH₃O⁺ and the negative ion spectrum by the series (H₂O)_nOH⁻ and (H₂O)_nO⁻. The positive ion CO₂ ice spectrum is characterized by R⁺ = C⁺, O⁺, CO⁺, O₂⁺ or CO₂⁺ and the negative one by R⁻ = CO₃⁻. The dominant series for ammonia ice correspond to R⁺ = NH₄⁺ and to R⁻ = NH₂⁻. The oxygen series are better described by (O₃)_nO_m⁺ secondary ions where m = 1, 2 or 3. Two positive ion series exist for N₂ ice: (N₂)_nN₂⁺ and (N₂)_nN⁺. For argon positive secondary ions, only the (Ar)_nAr⁺ series was observed. Most of the detected molecular ions were formed by one-step reactions. Ice temperature was varied from ∼20 K to complete sublimation.  相似文献   

The production of water-cluster positive ions in the quiet daytime D region     

George C. Reid 《Planetary and Space Science》1977,25(3):275-290

In the quiet daytime D region, the primary positive-ion species is thought to be NO⁺, produced by solar Lyman-alpha ionization of NO. Below the altitude of the mesopause, however, the dominant ambient species observed are water-cluster ions of the general type H⁺(H₂O)_n. No satisfactory reaction scheme for producing these cluster ions from NO⁺ has yet been proposed. Following earlier suggestions, a model calculation has been carried out in which successive hydrations of NO⁺ take place through clustering with N₂ and CO₂, followed by “switching” reactions with H₂O. The third hydrate of NO⁺ is then converted into the water-cluster species H⁺(H₂O)₃, and the other water-cluster species are produced by successive clustering and thermal breakup reactions. Many of the reactions involved have not been measured in the laboratory, but reasonable estimates of their rates can be made on the basis of existing measurements of other species. Since both temperature and water-vapor content are of major importance in the model, calculations were carried out for two temperature profiles and two water-vapor profiles. It is shown that the results are in reasonably good agreement with observations as far as the water-cluster species are concerned. Under low-temperature conditions, the model predicts relatively large concentrations of various clusters of NO⁺, in agreement with some observations but in disagreement with others. The importance of sampling breakup of these weakly bound clusters, and their relevance to the free electron concentrations are discussed.  相似文献   

Molecules in the early universe     

B. Novosyadlyj  O. Sergijenko  V. M. Shulga 《Kinematics and Physics of Celestial Bodies》2017,33(6):255-264

The formation of first molecules, negative Hydrogen ions, and molecular ions in a model of the Universe with cosmological constant and cold dark matter is studied. The cosmological recombination is described in the framework of modified model of the effective 3-level atom, while the kinetics of chemical reactions is described in the framework of the minimal model for Hydrogen, Deuterium, and Helium. It is found that the uncertainties of molecular abundances caused by the inaccuracies of computation of cosmological recombination are approximately 2–3%. The uncertainties of values of cosmological parameters affect the abundances of molecules, negative Hydrogen ions, and molecular ions at the level of up to 2%. In the absence of cosmological reionization at redshift z = 10, the ratios of abundances to the Hydrogen one are 3.08 × 10^–13 for H^–, 2.37 × 10^–6 for H₂, 1.26 × 10^–13 for H₂⁺, 1.12 × 10^–9 for HD, and 8.54 × 10^–14 for HeH⁺.  相似文献   

Ion composition and chemistry in the coma of Comet 1P/Halley—A comparison between Giotto's Ion Mass Spectrometer and our ion-chemical network     

Martin Rubin  Kenneth C. Hansen  Michael R. Combi  Hans Balsiger 《Icarus》2009,199(2):505-519

In order to understand the cometary plasma environment it is important to track the closely linked chemical reactions that dominate ion evolution. We used a coupled MHD ion-chemistry model to analyze previously unpublished Giotto High Intensity Ion Mass Spectrometer (HIS-IMS) data. In this way we study the major species, but we also try to match some minor species like the CH_x and the NH_x groups. Crucial for this match is the model used for the electrons since they are important for ion-electron recombination. To further improve our results we included an enhanced density of supersonic electrons in the ion pile-up region which increases the local electron impact ionization. In this paper we discuss the results for the following important ions: C⁺, CH⁺, CH⁺₂, CH⁺₃, N⁺, NH⁺, NH⁺₂, NH⁺₃, NH⁺₄, O⁺, OH⁺, H₂O⁺, H₃O⁺, CO⁺, HCO⁺, H₃CO⁺, and CH₃OH⁺₂. We also address the inner shock which is very distinctive in our MHD model as well as in the IMS data. It is located just inside the contact surface at approximately 4550 km. Comparisons of the ion bulk flow directions and velocities from our MHD model with the data measured by the HIS-IMS give indication for a solar wind magnetic field direction different from the standard Parker angle at Halley's position. Our ion-chemical network model results are in a good agreement with the experimental data. In order to achieve the presented results we included an additional short lived inner source for the C⁺, CH⁺, and CH⁺₂ ions. Furthermore we performed our simulations with two different production rates to better match the measurements which is an indication for a change and/or an asymmetric pattern (e.g. jets) in the production rate during Giotto's fly-by at Halley's comet.  相似文献   

Initial interpretation of Titan plasma interaction as observed by the Cassini plasma spectrometer: Comparisons with Voyager 1     

R.E. Hartle  E.C. Sittler  R.E. Johnson  F. Crary  D.T. Young  D. Simpson  D. Reisenfeld  J.J. Berthelier  J. Vilppola  N. Andre 《Planetary and Space Science》2006,54(12):1211-1224

The Cassini plasma spectrometer (CAPS) instrument made measurements of Titan's plasma environment when the Cassini Orbiter flew through the moon's plasma wake October 26, 2004 (flyby TA). Initial CAPS ion and electron measurements from this encounter will be compared with measurements made by the Voyager 1 plasma science instrument (PLS). The comparisons will be used to evaluate previous interpretations and predictions of the Titan plasma environment that have been made using PLS measurements. The plasma wake trajectories of flyby TA and Voyager 1 are similar because they occurred when Titan was near Saturn's local noon. These similarities make possible direct, meaningful comparisons between the various plasma wake measurements. They lead to the following: (A) The light and heavy ions, H⁺and N⁺/O⁺, were observed by PLS in Saturn's magnetosphere in the vicinity of Titan while the higher mass resolution of CAPS yielded H⁺ and H₂⁺as the light constituents and O⁺/CH₄⁺ as the heavy ions. (B) Finite gyroradius effects were apparent in PLS and CAPS measurements of ambient O⁺ ions as a result of their absorption by Titan's extended atmosphere. (C) The principal pickup ions inferred from both PLS and CAPS measurements are H⁺, H₂⁺, N⁺, CH₄⁺ and N₂⁺. (D) The inference that heavy pickup ions, observed by PLS, were in narrow beam distributions was empirically established by the CAPS measurements. (E) Slowing down of the ambient plasma due to pickup ion mass loading was observed by both instruments on the anti-Saturn side of Titan. (F) Strong mass loading just outside the ionotail by a heavy ion such as N₂⁺ is apparent in PLS and CAPS measurements. (G) Except for the expected differences due to the differing trajectories, the magnitudes and structures of the electron densities and temperatures observed by both instruments are similar. The high-energy electron bite-out observed by PLS in the magnetotail is consistent with that observed by CAPS.  相似文献   

H-implantation in SO₂ and CO₂ ices     

M. Garozzo  O. Gomis  G. Strazzulla 《Planetary and Space Science》2008,56(9):1300-1308

Ices in the solar system are observed on the surface of planets, satellites, comets and asteroids where they are continuously subordinate at particle fluxes (cosmic ions, solar wind and charged particles caught in the magnetosphere of the planets) that deeply modify their physical and structural properties. Each incoming ion destroys molecular bonds producing fragments that, by recombination, form new molecules also different from the original ones. Moreover, if the incoming ion is reactive (H⁺, Oⁿ⁺, Sⁿ⁺, etc.), it can concur to the formation of new molecules.Those effects can be studied by laboratory experiments where, with some limitation, it is possible to reproduce the astrophysical environments of planetary ices.In this work, we describe some experiments of 15-100 keV H⁺ and He⁺ implantation in pure sulfur dioxide (SO₂) at 16 and 80 K and carbon dioxide (CO₂) at 16 K ices aimed to search for the formation of new molecules. Among other results we confirm that carbonic acid (H₂CO₃) is formed after H-implantation in CO₂, vice versa H-implantation in SO₂ at both temperatures does not produce measurable quantity of sulfurous acid (H₂SO₃). The results are discussed in the light of their relevance to the chemistry of some solar system objects, particularly of Io, the innermost of Jupiter's Galilean satellites, that exhibits a surface very rich in frost SO₂ and it is continuously bombarded with H⁺ ions caught in Jupiter's magnetosphere.  相似文献   

The evolution of charged particles in a model of contracting cloud     

M. S. El-Nawawy  M. Y. Amin 《Earth, Moon, and Planets》1996,75(1):41-51

The evolution of the charged particles are followed during contraction of a model of an interstellar cloud, with initial density number of n = 10 cm^–3. The contraction is followed up to density increase by five orders of magnitude. Special care is given to the details of the negative ions. In addition, we have tested the ambipolar diffusion according to the results of the ion density.The results predict the importance of atomic ions in the diffuse regions. H⁺ and C⁺ are distinctly enhanced in the beginning of contraction but decrease as contraction proceeds. Molecular ions enhance as contraction proceeds and becomes important in dense regions. The most enhanced molecular ions are HCO⁺, O₂ ⁺, C₂H₃ ⁺, H₃O⁺ and SO⁺, H₃ ⁺ is less abundant. The atomic ions (except metalic ions) decrease noticeably as density increases. In general the negative ions are of negligible fractional abundances. It has also been found that the time of ambipolar diffusion is shorter than the dynamical time, hence the magnetic field should be weakened in the central core as the central density increases to n = 10⁴ cm^–3.  相似文献   

Interstellar catalysis     

Ronald G. Tabak 《Astrophysics and Space Science》1978,54(1):211-232

Since gas-phase reactions alone cannot account for the observed abundances of H₂ in the typical interstellar cloud, one or more surface reactions are probably involved. Of the three possible candidates, only the catalytic production of H₂ on transition metal grains is supported by laboratory evidence. Using the rate equations developed in a previous paper for this process, the steady-state equilibrium abundances of H, H₂,e ^–, H⁺, H^–, H₂ ⁺, and H₃ ⁺ are calculated for large (r>10 pcs;M10² M ), tenuous (n=10²–10⁴ cm^–3) hydrogen dust clouds under a wide variety of conditions. In addition to the four rate equations involved in the catalytic reactions, 18 gas-phase and one additional surface reaction—the physical adsorption of H-atoms on cold, dielectric surfaces and their subsequent recombination and desorption as H₂ molecules—are included in the calculations. It is found that metal grains can produce as much interstellar H₂ as the best physical adsorption mechanism under optimum conditions if the extinction in the visible is less than 5^m.0. The three critical parameters for efficient catalysis (activation energy of desorption, grain temperature, and the number density of available sites) are examined, and it is shown that catalytic reactions are efficient producers of H₂ under all but the most unfavorable conditions.  相似文献   

Collisional vibrational quenching of O2+(v) and other molecular ions in planetary atmospheres     

H. Böhringer  M. Durup-Ferguson  E.E. Ferguson  D.W. Fahey 《Planetary and Space Science》1983,31(4):483-487

New experimental techniques have yielded several thermal energy vibrational quenching rate constants for O₂⁺(v). Rates for quenching of O₂⁺(v = 1) by O₂, N₂, Ar, CO₂, H₂, and CH₄ are 3(?10), 2(?12), 1(?12), 1(?10), 2.5(?12), and 6(?10) cm³s^?1 at 300 K. The quenching is somewhat faster for O₂⁺(v = 2). The triatomic ions CO₂⁺, NO₂⁺, N₂O⁺, SO₂⁺, and H₂O⁺ are all vibrationally deexcited with an efficiency greater than 10^?3 in Ar or Ne collisions. A theoretical rationalization of the experimental results leads to the prediction that vibrational quenching in planetary atmospheres will generally be efficient, k > 1(?12) cm³s^?1 for almost all ion and neutral gas pairs.  相似文献   

Mass composition of the escaping plasma at Mars     

E. Carlsson  A. Fedorov  E. Budnik  H. Gunell  J.-A. Sauvaud  Y. Futaana  H. Andersson  J.D. Winningham  J.R. Sharber  A.J. Coates  D.O. Kataria  H. Koskinen  P. Riihelä  J. Kozyra  E. Roelof  S. Livi  K.C. Hsieh  M. Grande  J.-J. Thocaven  S. Orsini  M. Maggi  P. Bochsler  J. Woch  K. Asamura 《Icarus》2006,182(2):320-328

Data from the Ion Mass Analyzer (IMA) sensor of the ASPERA-3 instrument suite on Mars Express have been analyzed to determine the mass composition of the escaping ion species at Mars. We have examined 77 different ion-beam events and we present the results in terms of flux ratios between the following ion species: CO⁺₂/O⁺ and O⁺₂/O⁺. The following ratios averaged over all events and energies were identified: CO⁺₂/O⁺ = 0.2 and O⁺₂/O⁺ = 0.9. The values measured are significantly higher, by a factor of 10 for O⁺₂/O⁺, than a contemporary modeled ratio for the maximum fluxes which the martian ionosphere can supply. The most abundant ion species was found to be O⁺, followed by O⁺₂ and CO⁺₂. We estimate the loss of CO⁺₂ to be by using the previous measurements of Phobos-2 in our calculations. The dependence of the ion ratios in relation to their energy ranges we studied, 0.3-3.0 keV, indicated that no clear correlation was found.  相似文献   

Mass spectrometer measurements of the positive ion composition in the D- and E-regions of the ionosphere     

P. A. Zbinden  M. A. Hidalgo  P. Eberhahdt  J. Geiss 《Planetary and Space Science》1975,23(12):1621-1642

On 14 December 1971, during the maximum of the Geminid Meteor Shower, the positive ion composition was measured in the D- and E-regions above Sardinia. The payload was launched at 12:11 UT, and measurements were made between 68.5 and 152 km altitude. A magnetic sector type mass spectrometer with dual collector and a liquid helium cryopump was used. The instrument covered the mass range from 11 to 73 AMU and had a resolution at the 1 % level of M/ΔM = 60.In the E-region two distinct metal ion layers were observed, centred at 95 and 119 km, respectively. In the lower layer Fe⁺ and Mg⁺ were the most abundant metal ions, and in the upper layer Si⁺ was dominant. Si⁺ ions were conspicuously absent in the lower layer (Si⁺/Mg⁺ < 2 × 10⁻³). This particular behaviour of Si could be due to the inability of atomic oxygen to reduce SiO, whereas in the upper layer Si⁺ions might be formed directly by the charge rearrangement reaction SiO + O⁺ → Si⁺+ O₂. In addition, Na⁺, Al⁺, K⁺, Ca⁺, Ti⁺, Cr⁺, Ni⁺ and Co⁺ were also identified. The metal oxide ions AlO⁺ and SiO⁺ were detected, and probably also MgO⁺ and SiOH⁺. The concentrations of NO⁺ and O₂⁺ show a deep minimum at the maximum of the lower metal ion layer. A very high neutral metal density of 6 × 10⁷ cm⁻³ would be required to explain this feature as resulting from charge transfer reactions between the molecular and metal ions Such a high metal density is in contradiction to direct measurements and to cosmic dust influx rates. The isotopic ratios of Mg⁺, Si⁺, and of the major isotopes of Fe⁺ and Ni⁺ were measured, some of them with an accuracy of a few per cent (²⁵Mg⁺/²⁴Mg⁺ = 0.124 ± 0.006; ²⁶Mg⁺/²⁴Mg⁺ = 0.139 ± 0.008; ²⁹Si⁺/²⁸Si⁺ = 0.050 ± 0.004; ⁵⁴Fe⁺/⁵⁶Fe⁺ = 0.069 ± 0.005; ⁵⁷Fe⁺/⁵⁶Fe⁺ = 0.029 ± 0.004; ⁶⁰Ni⁺/⁵⁸Ni⁺ = 0.31 ± 0.12). The isotopic ratios agree within the experimental errors with the corresponding terrestrial ratios, thus giving evidence that these elements have the same isotopic composition in the Geminid meteors as in the Earth's crust, in chrondrites, and in lunar material.In the D-region the ions Na⁺H₂O, Na⁺(H₂O)₂, NaO⁺ and NaOH⁺ were tentatively identified. Below 95 km altitude the relative abundances of the ions 32⁺, 33⁺ and 34⁺ deviate from the values expected for molecular oxygen isotopes. Their abundances can not be explained by the presence of S-ions only, and we conclude that HO₂⁺ and H₂O₂⁺ are present.The ion density profiles of the major D-region constituents show some remarkable deviations from typical D-region conditions. These deviations are related to the winter anomaly in ionospheric absorption observed over Spain during the launch day, and our data represent the first ion composition measurements during such conditions. In particular, H⁺(H₂O)₂ is the major ion only up to 77 km, and at 80 km altitude the NO⁺ concentration exceeds the total water cluster ion density by almost two orders of magnitude. An increase of the mesospheric NO, O₃ and O concentrations as well as of the O/H₂O ratio could explain the observed ion profiles. The low NO⁺/O₂⁺ ratios of approximately unity measured in the E-region are in agreement with a strong downward transport of NO and/or O into the mesosphere during the launch day. A simple four-ion model was used to interpret our D-region data. The calculated neutral NO concentration increases from about 2 × 10⁷ cm⁻³ at 85 km to 5 × 10⁷ cm⁻³ at 80 km. In addition, evidence for an increased O₂⁺ production rate above 83 km was found, probably due to an enhanced O₃ concentration. We conclude that our data strongly support vertical transport of minor neutral consituents as cause of the winter anomaly.  相似文献   

The reaction of O+2 with atomic nitrogen and NO+· H2O and NO+2 with atomic oxygen     

F.C. Fehsenfeld 《Planetary and Space Science》1977,25(2):195-196

The reactions of atomic nitrogen with O⁺₂ and atomic oxygen and atomic nitrogen with NO⁺· H₂O and NO⁺₂ have been measured at 296 K. The rate constants are reported and the implication of the measurements to atmospheric ion chemistry is discussed.  相似文献   

On the structure of Mars' atmosphere at 120–220 km     

V.A. Krasnopolsky 《Icarus》1975,24(1):28-35

Altitude dependences of [CO₂] and [CO₂⁺] are deduced from Mariner 6 and 7 CO₂⁺ airglow measurements. CO₂ densities are also obtained from n_e radio occultation measurements. Both [CO₂] profiles are similar and correspond to the model atmosphere of Barth et al. (1972) at 120 km, but at higher altitudes they diverge and at 200–220 km the obtained [CO₂] values are three times less the model. Both the airglow and radio occultation observations show that a correction factor of 2.5 should be included into the values for solar ionization flux given by Hinteregger (1970). The ratio of [CO₂⁺]/n_e is 0.15–0.2 and, hence, [O]/[CO₂] is ～3% at 135 km. An atmospheric and ionospheric model is developed for 120–220 km. The calculated temperature profile is characterized by a value of T ≈ 370°K at h ? 220 km, a steep gradient (～2°/km) at 200-160 km, a bend in the profile at 160 km, a small gradient (～0.7°/km) below and a value of T ≈ 250°K at 120 km. The upper point agrees well with the results of the Lyman-α measurements; the steep gradient may be explained by molecular viscosity dissipation of gravity and acoustical waves (the corresponding energy flux is 4 × 10^?2 erg cm^?2sec^?1 at 180 km). The bend at 160 km may be caused by a sharp decrease of the eddy diffusion coefficient and defines K ≈ 2 × 10⁸cm²sec^?1; and the low gradient gives an estimate of the efficiency of the atmosphere heating by the solar radiation as ? ≈ 0.1.  相似文献