Photoionization of barium clouds via the 3D metastable levels

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.     

A global study of O2(1Δg) airglow: Day and twilight

Aircraft measurements of $\text{O}{}_2\text{(}{}^1\text{Δ}{}_{\mathrm{g}}\text{)}$ emission made over a 10-yr period provide information on the variation of ozone with latitude and season in the altitude region 50–90 km. Between 50 and 70 km there appears to be little variation (< ± 25%) whereas the abundance between 80 and 90 km exhibits a large seasonal change north of 30°N and much less at lower latitude. At mid and high latitude the column abundance above ～ 80 km changes from ? 1 × 10¹⁴ cm^?2 in summer to about 3 × 10¹⁴ cm^?2 in winter. There are occasional enhancements in both the day and twilight airglow which almost always occur in association with auroral activity or, at least, where such activity is statistically most likely. These enhancements appear to reflect a corresponding increase in the ozone mixing ratio in the upper stratosphere. While the gradient in ozone mixing ratio with latitude is generally small at altitudes between 50 and 90km there are occasions when a temporary latitude structure can be seen, particularly above 80 km.     

A discussion of the energy transfer from N2(A3Σu+) to O(1S) in pulsating aurora

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.     

A new interpretation of the 1304 Å triplet airglow intensity ratio with the fine structure levels O3Pj) in local thermodynamic equilibrium

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.     

The excitation of atomic oxygen to the O(1S) level by energy transfer from N2(A3∑u+) molecules in aurora

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.     

Chaotic behavior and the origin of the 31 Kirkwood gap

The sudden eccentricity increases discovered by J. Wisdom (Astron J.87, 577–593, 1982) are reproduced in numerical integrations of the planar-elliptic restricted three-body problem, verifying that this phenomenon is real. Maximum Lyapunov characteristic exponents for trajectories near the $\text{3}\text{1}$ commensurability are computed both with the mappings presented in Wisdom (1982) and by numerical integration of the planar-elliptic problem. In all cases the agreement is excellent, indicating that the mappings accurately reflect whether trajectories are chaotic or quasiperiodic. The mappings are used to trace out the chaotic zone near the $\text{3}\text{1}$ commensurability, both in the planar-elliptic problem and to a more limited extent in the three-dimensional elliptic problem. The outer boundary of the chaotic zone coincides with the boundary of the $\text{3}\text{1}$ Kirkwood gap in the actual distribution of asteroids within the errors of the asteroid orbital elements.     

Electron content power spectral estimates: Periods of 2 days to 12 year

The power spectra of the daily peak electron content measured at Hawaii are estimated via covariance estimations, bivariate autoregressive estimations and fast Fourier transforms for a year of data close to minimum solar activity (1965) and a year of data close to maximum solar activity (1969). The strong peaks about 6 days and 15 days in the 1965 and 1969 power spectra, respectively, suggest an influence of the interplanetary magnetic sector structure on the electron content at low latitude (21·3°N, geographic). The daily solar flux (Sa) at 2800 MHz of 1965 and 1969 are analysed similarly. The decrease in energy content with period range of 3–7 days in the 1969 Sa power spectrum supports the above point of view.     

The dissociative recombination of O2+ in the ionosphere

Aeronomical determinations of the dissociative recombination reaction rate coefficient for O₂⁺, α, depend directly on a knowledge of the rate coefficient for the charge exchange of O⁺ with O₂, k. A re-evaluation of the aeronomical determination of α using Atmosphere Explorer satellite data is necessary in the light of a subsequent laboratory measurement of k. The results reported here are in reasonable agreement with laboratory determinations to within the uncertainty of the analysis for night-time conditions. However, for data obtained under sunlit conditions the aeronomical determination differs significantly from the laboratory measurements. The results imply that the state of the O₂⁺ molecule resulting from the major thermospheric processes requires further examination.     

On the DC ratio in the atmosphere of Uranus

A method for deriving mixing ratios in the outer planets, mostly independent of scattering processes, is applied to Uranus. It is shown that scattering processes play a major role in the line formation in the atmospheres of Uranus and Neptune; consequently, abundance ratios derived from a reflecting-layer model can be questionable. Using our method, we derive for Uranus $\text{D}\text{C}\text{< 6 × 10}{}^{\mathrm{?3}}$, which is significantly smaller than our result on Jupiter. The simplest explanation implies a C/H enrichment by at least a factor of 6 relative to the solar value.     

Estimated conductivity ratio ∑H∑P in the auroral electrojets in connection with electrojet width and field-aligned currents

By using ground based magnetic observations and by assuming a three-dimensional current system model the conductivity ratio $\text{∑}{}_{\mathrm{<mtext>H</mtext>}}\text{∑}{}_{\mathrm{<mtext>P</mtext>}}$ is calculated for several substorms. It is shown that this ratio decreases when the field aligned current intensity is enhanced. The enhancement is connected with a broadening of the electrojet region.     

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

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.     

Diurnal variation of the (8−3)(5−0) intensity ratio of nightglow OH at Adi Ugri

Filter photometer data on OH intensities reveal a midnight maximum of the average ratio I(8?3)/I(5?0) in midwinter at Adi Ugri. This midnight maximum is a regular feature on those nights when the intensity also goes through a midnight maximum. An interpretation in terms of a dynamic model is presented. On nights of steadily decreasing OH intensity, the pre-midnight ratio variation is uncertain.     

An Einstein search for X-ray emission from comet Bradfield (1979l)

X-radiation may result from active plasma phenomena in the interactions of comets with the solar wind. We have carried out a limited but sensitive search for soft X-radiation from Comet Bradfield (1979$\text{l}$), on 1980 Feb. 5. No X-radiation was detected at a level (3σ) of 1.7 × 10^?13 erg(cm²sec keV)^?1 in the 0.2 – 4.0 kev range. This corresponds to a limit on the power dissipated in the comet by non-thermal electrons of approximately 10¹⁹ ergs sec^?1, averaged over the 2568-sec exposure to the comet. This energy deposition is near the magnitude suggested by simple theoretical ideas, and further searches of appropriate comets both in soft X-radiation and at radio wavelengths seem warranted.     

Changes in the ionospheric profile and the faraday factor M with Kp

Using incoherent scatter data from Millstone Hill, we investigated the variations in the shape of the daytime, mid-latitude ionospheric electron density profile associated with changes in geomagnetic activity. The analysis performed was to deduce the dependence upon the 3-hr geomagnetic index Kp of h(N_m), h(0·7 N_m) above and below N_m, the plasma scale height H_T in the range 500–1000 km, and the ratio $\text{N(1000)}\text{N(h}{}_{\mathrm{m}}\text{)}$. The electron density data used spanned the solar maximum years 1968–1971. Daytime data from the period 1000 to 1600 LT were averaged separately for summer, winter and spring-fall. It is shown that the mean value $\text{M}$ of the factor M = B cos θ sec χ used by Titheridge (1972) to relate the Faraday rotation $\text{Ω}$ from a geostationary satellite to the total electron content N_N up to 2000 km is practically the same (to within 1–2 per cent) as the $\text{M}$ value used to relate the N_T and $\text{Ω}$ values both computed up to 1000 km. Taking advantage of this identity, we have used the linear relationship obtained between the ionospheric parameters and Kp to deduce the height at which $\text{M}$ should be evaluated as a function of Kp.     

SAR arcs and 6300 Å emission by dissociative recombination of O2+ observed from Africa during severe magnetic storms

SAR arcs were observed from Southern Africa on 17/18 December 1971, 4/5 August 1972 and 1/2 April 1973 with the equatorwards edge at L = 1.8. Simultaneous with the latter event the intertropical arc was observed at an equatorial station. There was no apparent relationship. Calculations show that while the entire observed inter-tropical emission results from dissociative recombination of O₂⁺ this process may, in some cases, account for only a fraction of a percent of the observed SAR arc emission. More than five years of geomagnetic storm data shows that Southern African SAR arcs are unlikely unless disturbances exceed 150 γ. For very severe 300 γ disturbances main phase SAR arcs may be observed. Estimates of the fraction of storm energy used in production of the present arcs indicate they are inefficient sinks for magnetic storms.     

The DH ratio in the atmosphere of Uranus: Detection of the R5(1) line of HD

Observations of Uranus during the 1975, 1976, and 1978 apparitions reveal a weak absorption at the wavelength of the R₅(1) line of HD with equivalent width $\text{1.0 ± 0.4}\text{m}\text{A}\text{?}$. The $\text{D}\text{H}$ ratio in Uranus' atmosphere implied by this line and other published spectra is (4.8 ± 1.5) × 10^?5, and may not be significantly different from that in the atmospheres of Jupiter and Saturn. In addition, the spectra exhibit two weak absorption at $\text{6044.76 ± 0.02}\text{and}\text{6045.54 ± 0.02}\text{A}\text{?}$ which we were unable to identify. No trace of absorption is visible near these wavelengths or near the HD wavelength in a laboratory spectrum of 4.92 km-am CH₄ which we obtained in an attempt to identify these absorption features and to verify that the HD feature does not arise from CH₄.     

Characteristic frequencies of a non-maxwellian plasma: A method for localizing the exact frequencies of magnetospheric intense natural waves near ƒpe

Intense natural waves are commonly observed, onboard satellites, in the outer Earth's magnetosphere, inside a narrow frequency range, including the electron plasma and upper hybrid frequencies. In order to progress in the understanding of their emission processes, it is necessary to determine precisely the relationship which exists between their frequencies and the characteristic frequencies of the magnetospheric plasma. For this purpose, it is necessary to take into account the fact that some of these characteristic frequencies ($\text{?}{}_{\mathrm{qN}}$), which are provided by active sounding of the plasma, not only depend on the total density, but also on the shape of the distribution function (which has generally been assumed, in previous studies, to be maxwellian). A method providing a fine diagnosis of general non-maxwellian plasmas is developed. This method of analysis of the experimental data is based on a theoretical study, which points out the influence of the shape of the distribution function on the dispersion curves (for wave vectors perpendicular to the static magnetic field).     

The dissociative recombination of N2+ (v = 0, 1) as a source of metastable atoms in planetary atmospheres

The yield of metastable nitrogen atoms in dissociative recombination of N₂⁺ (v = 0, 1)ions has been tudied for different experimental conditions. In a first experiment, the branching ratio for N(²D) production was directly measured as being higher than 1.85; for N₂⁺ (v = 0) this implies that ²D + ²D is the main reaction channel; for N₂⁺ (v = 1) a minor channel could be ²P + ²D, ²P being then quenched toward ²D by electrons. In a second experiment, at higher electron densities, the influence of superelastic collisions was studied; a steady state analysis yields the quenching rate coefficient k₄, of ²D towards ⁴S equal to 2.4 × 10^?10 cm³ s^?1for T_e = 3900 K and shows that ²D + ²D is always the major channel of the reaction for N₂⁺ (v = 1), ²D + ²P being a minor channel. All these results are in good agreement with thermospheric models but imply that N₂⁺ dissociative recombination is a less important source for nitrogen escape of Mars.     

Agegraphic reconstruction of modified F(R) and F(G)F(\mathcal{G}) gravities

The cosmological reconstruction of modified F(R) and F(G)F(\mathcal{G}) gravities with agegraphic dark energy (ADE) model in a spatially flat universe without matter field is investigated by using e-folding “N” as a forward way. After calculating a consistent F(R) in ADE’s framework, we obtain conditions for effective equation of state parameter w _eff, and see that reconstruction is possible for both phantom and non-phantom era. These calculations also are done for F(G)F(\mathcal{G}) gravity and the condition for a consistent reconstruction is obtained.