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   

An indirect mechanism for the production of O(¹S) in the aurora     

B.H. Solheim  E.J. Llewellyn 《Planetary and Space Science》1979,27(4):473-479

Recent laboratory measurements of the deactivation rate constants for O(¹S) have suggested that the dominant production mechanism for the green line in the nightglow is a two-step process. A similar mechanism involving energy transfer from an excited state of molecular oxygen is considered as a potential source of the OI (5577 Å) emission in the aurora. It is shown that the mechanism, $\text{O}{}_2\text{+ e → O}{}_2{}^1\text{+ e O}{}_2{}^1\text{+ O → O}{}_2\text{+ O(}{}^1\text{S}\text{)}$, is consistent with auroral observations; the intermediate excited state has been tentatively identified as the O₂(c¹∑^?_u) state. For the proposed energy transfer mechanism to be the primary source of the auroral green line, the peak electron impact cross-section for O₂¹ production must be approximately 2 × 10^?17 cm².  相似文献   

Emission line shapes produced by dissociative excitation of atmospheric gases     

E.C. Zipf  W.C. Wells 《Planetary and Space Science》1980,28(8):859-866

Special line shapes are derived fro the λ 1356 Å (${}^5\text{S}{}^0\text{-}{}^3\text{P}$) transition of atomic oxygen from metastable (${}^5\text{S}{}^0\text{-}{}^3\text{P}$) time-of-flight spectra produced by electron impact dissociative excitation of O₂, CO₂, CO, and NO, and they are compared with the broadened λ 1304 A resonance line shapes deduced by Poland and Lawrence (1973) from atomic oxygen absorption studies. The non-thermal line shapes for both airglow emission features are shown to have an effective width comparable to a 60,000 K thermal doppler line shape for an electron impact energy of 100eV. The variation of the effective line width with electron-impact energy from threshold to 300 eV is given. Since the effective line width of the resonance radiation produced by dissociative excitation is very large compared with the doppler absorption widths of the ambient O atoms at normal exospheric temperatures, the anomalously broadened resonance lines will propagate through a planetary atmosphere as though they were optically thin. Thus, electron-impact dissociation of CO and CO₂ will contribute to the observed optically thin component of the λ 1304 Å emission in the upper atmospheres of Venus and Mars. However, the process cannot account for more than 10% of the observed optically thin emission because of the small magnitude of the excitation cross-section and the comparatively high-energy threshold for the process. The possibility that the source of the kinetically energetic $\text{O}\text{(}{}^3\text{S}$) atoms is the dissociative recombination of vibrationally excited CO₂⁺ ions is discussed.  相似文献   

The excitation of the 557.7 nm line and Herzberg bands in the nightglow     

L. Thomas  R.G.H. Greer  P.H.G. Dickinson 《Planetary and Space Science》1979,27(7):925-931

Measurements of the emission intensities of the 557.7 nm line and Herzberg bands and of O(³P) concentrations carried out on two coordinated rocket flights at South Uist during the night of 8/9 September 1975 are presented. An examination of the 557.7 nm emission and $\text{O}\text{(}{}^3\text{P}\text{)}$ data on the basis of recent data on relevant rate coefficients has shown that the results can be interpreted on the basis of the Barth mechanism for the production of $\text{O}\text{(}{}^1\text{S}\text{)}$ atoms but not the Chapman mechanism. Evidence is provided that the A³Σ⁺_u state of O₂ could be responsible for the $\text{O}\text{(}{}^1\text{S}\text{)}$ production in the Barth mechanism. Values of the rate coefficients involved are deduced from a comparison of the 557.7 nm and Herzberg emission rates.  相似文献   

Direct measurement of conjugate photoelectrons and predawn 630 nm airglow     

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 $\text{F = (1.3 ± 0.4) × 10}{}^{11}\text{exp}\text{[?}\text{E(}\text{eV}\text{)}\text{12}\text{]}$ 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, $\text{O}{}_2{}^{\mathrm{+}}\text{+}\text{e}\text{→}\text{O}{}^1\text{+}\text{O}{}^7$. The direct collisional excitation by ambient electrons is estimated to be negligibly small at the level of observed electron temperature.  相似文献   

Auroral implications of recent measurements on O(1S) and O(1S) formation in the reaction of N+ with O2     

Andrew O. Langford  Veronica M. Bierbaum  Stephen R. Leone 《Planetary and Space Science》1985,33(10):1225-1228

Recent flowing afterglow measurements have shown that the reaction of N⁺ with O₂ produces 70 ± 30% of the oxygen atom product as $\text{O}\text{(}{}^1\text{D}\text{)}$ and < 0.1% as $\text{O}\text{(}{}^1\text{S}\text{)}$. These results indicate that this reaction does not contribute to the auroral green line emission (5577 Å), but can account for ～10% of the observed red line (6300 Å) auroral emission.  相似文献   

Airglow from the inner comas of comets     

T.E. Cravens  A.E.S. Green 《Icarus》1978,33(3):612-623

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⁺ ($\text{A}\text{?}{}^2\text{A}{}_{\mathrm{1?}}\text{X}\text{?}{}^2\text{B}{}_1$), CO⁺ (first negative), CO (fourth positive), CO (Cameron), CO₂⁺ ($\text{B}\text{?}{}^2\text{?}{}_{\mathrm{u}}\text{?}\text{X}\text{?}{}^2\text{II}{}_{\mathrm{g}}$), 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   

A self-consistent evaluation of the rate constants for the production of the OI 6300 Å airglow     

R. Link  J.C. McConnell  G.G. Shepherd 《Planetary and Space Science》1981,29(6):589-594

The quenching rate k_N2 of $\text{O(}{}^1\text{D)}$ by N₂ and the specific recombination rate α_1D of O₂⁺ leading to $\text{O(}{}^1\text{D)}$ are re-examined in light of available laboratory and satellite data. Use of recent experimental values for the $\text{O(}{}^1\text{D)}$ transition probabilities in a re-analysis of AE-C satellite 6300 Å airglow data results in a value for k_N2 of 2.3 × 10^?11 cm³s^?1 at thermospheric temperatures, in excellent agreement with the laboratory measurements. This implies a value of J_O2 = 1.5 × 10^?6s^?1 for the O₂ photodissociation rate in the Schumann-Runge continuum. The specific recombination coefficient α_1D = 2.1 × 10^?7cm³s^?1 is also in agreement with the laboratory value. Implications for the suggested $\text{N}\text{(}{}^2\text{D) + O}{}_2\text{→ O(}{}^1\text{D) + NO}$ reaction are discussed.  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 photodissociation of water vapour in the mesosphere     

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 F_{10.7 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 ($\text{Δλ = 3.5}\text{A}\text{?}$) q_Lyα,∞ = 3 × 10¹¹ photons cm^?2 s^1?.The photodissociation frequency for the Schumann-Runge band region is also given for mesospheric conditions by a simple formula where J_SRB,∞(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   

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   

On fourier-analysis of geomagnetic pulsations pc-1, “two-fold” and “three-fold” pulsations pc-1 and fundamental frequencies of the magnetospheric cavity—I     

Ya.L. Alpert  D.S. Fligel 《Planetary and Space Science》1985,33(9):993-1012

The paper gives the results of detailed studies of the frequency spectra $\text{S}{}_{\mathrm{s}}\text{(?)}$ of the chain of the wave packets F_s(t) of geomagnetic pulsations PC-1 recorded at the Novolazarevskaya station. The bulk of the energy of F_s(t) is concentrated in the vicinity of the central frequencies $\text{?}{}_{\mathrm{s0}}$ of spectra—the carrier frequencies of the signals. The velocity $\text{V}{}_0\text{≌ 6.10}{}^3\text{km s}{}^{\mathrm{?1}}$ 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 $\text{? = 2?}{}_{\mathrm{s0}}\text{and}\text{3?}{}_{\mathrm{s0}}$ 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 $\text{?}{}^{\mathrm{\pm }}{}_{\mathrm{sK}}$. Frequency differences $\text{Δ?}{}_{\mathrm{sK}}{}^{\mathrm{\pm }}\text{=}\text{¦?}{}_{\mathrm{s0}}\text{? ?}{}_{\mathrm{sK}}{}^{\mathrm{\pm }}\text{¦}\text{= (0.011,0.022}\text{and}\text{0.035)}\text{Hz}$ 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   

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   

Charge exchange of metastable D oxygen ions with N₂ in the thermosphere     

D. G. Torr  N. Orsini 《Planetary and Space Science》1977,25(12):1171-1176

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   

The excitation of the infrared atmospheric oxygen bands in the nightglow     

E.J. Llewellyn  B.H. Solheim 《Planetary and Space Science》1978,26(6):533-538

Simultaneous observations of the nightgiow emission profiles of $\text{O}{}_2\text{(}{}^1\text{Δ)}$ and the OH Meinel bands have been used to show that the excitation mechanism for $\text{O}{}_2\text{(}{}^1\text{Δ)}$ in the night-time is through the reaction between OH¹ and atomic oxygen and the recombination of atomic oxygen. These reactions, and the proposed rate constants, have been used to derive the atomic oxygen profile appropriate to the observations. It is suggested that the atomic oxygen profile may exhibit significant structure near the mesopause at high latitude. It is also suggested that the extent of this structure may be influenced by transport effects related to stratospheric warming events.  相似文献   

The green light of the night sky     

D.R. Bates 《Planetary and Space Science》1981,29(10):1061-1067

The development of the theory of the 5577 Å emission from the upper atmosphere is reviewed. Evidence from both aeronomy and chemical kinetics shows that the Barth mechanism is a much more important source of $\text{O}\text{(}{}^1\text{S}\text{)}$ than in the Chapman process. The molecular oxygen state involved is probably c¹Σ^?_u (the upper state of the Herzberg II band system).  相似文献   

Cross-section for the dissociative photoionization of hydrogen by 584 Å radiation: The formation of protons in the Jovian ionosphere     

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 $\text{X}{}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}$ ground state to a continuum level of the $\text{X}{}^2\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}$ 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   

Changes in the concentration of mesospheric ozone during the total solar eclipse     

V.V. Agashe  S.M. Rathi 《Planetary and Space Science》1982,30(5):507-513

Measurements of dayglow radiance of $\text{O}{}_2\text{(}{}^1\text{Δ}{}_{\mathrm{g}}\text{)}$ and OH(7,2) bands are reported. Ground based photometers were used to monitor zenith radiance of 1270 and 694 nm emissions during the total solar eclipse of 16 February 1980. Altitude distribution of 1270 nm intensity was derived from ground based observations. A set of altitude distributions of $\text{O}{}_2\text{(}{}^1\text{Δ}{}_{\mathrm{g}}\text{)}$ were thus obtained throughout the eclipse. These altitude distributions were converted into ozone distributions using the rate equations for formation and loss of ozone and $\text{O}{}_2\text{(}{}^1\text{Δ}{}_{\mathrm{g}}\text{)}$ molecules. Results indicate an increase in the ozone concentration at mid-eclipse. OH(7,2) emission did not show enhancement during totality. This may mean that there was no increase in OH concentration during the eclipse.  相似文献   

The near infrared nightglow continuum     

P.C. Wraight 《Planetary and Space Science》1977,25(8):787-794

A review is given of observations of the nightglow continuum extending from about 7000 Å to longer wavelengths. It is suggested that the source of this emission is radiative association of atomic oxygen via the repulsive ${}^3\text{Π}{}_{\mathrm{u}}$ state to vibrationally excited O₂(³Σ_g^?). Predicted spectra are compared with nightglow and laboratory observations. Other implications for the physics of the thermosphere and upper mesosphere are discussed.  相似文献   

Electron runaway in turbulent astrophysical plasmas     

M.J. Houghton 《Planetary and Space Science》1975,23(3):409-418

An astrophysical electron acceleration process is described which involves turbulent plasma effects: the acceleration mechanism will operate in ‘collision free’ magnetoactive astrophysical plasmas when ion-acoustic turbulence is generated by an electric field which acts parallel to the ambient magnetic lines of force. The role of ‘anomalous’ (ion-sound) resistivity is crucial in maintaining the parallel electric field. It is shown that, in spite of the turbulence, a small fraction of the electron population can accelerate freely, i.e. runaway, in the high parallel electric potential. The number density n^(B) of the runaway electron component is of order $\text{n}{}^{\mathrm{(B)}}\text{?}\text{n}\text{2}\text{(}\text{c}{}_{\mathrm{s}}\text{U}{}_{\mathrm{\parallel }}{}^{\mathrm{?}}\text{)}{}^2$, where n = background electron number density, c_s = ion-sound speed and U_∥^? = relative drift velocity between the electron and ion populations. The runaway mechanism and the number density n^(B) do not depend critically on the details of the non-linear saturation of the ion-sound instability.  相似文献