Plasma temperatures from alouette 1 electron density profiles

Values of plasma temperature and vertical temperature gradient were obtained by fitting theoretical models to 60,000 observed electron density profiles, at heights of 400–1000 km. Results show the diurnal and seasonal changes in temperature from 75°S to 85°N near solar minimum. At night the temperature and temperature gradient are both low inside the plasmapause and high outside. Day-time temperatures increase almost linearly with latitude, from 1500 K at the magnetic equator to a maximum of 3500 K at the plasmapause. There is also a sharp peak at 77° latitude, beneath the magnetospheric cleft. Mean vertical temperature gradients are $\text{ca. 0.5}\text{K}\text{km}$ at night, and 1–4 K/km during the day. The downwards flow of heat, during the day, increases from about zero at 10° latitude to a maximum of $\text{4 × 10}{}^9\text{eV}\text{cm}{}^2\text{sec}$ at the plasmapause. Night-time flows are 5–20 times less, inside the plasmasphere. Increases in magnetic activity cause a temperature increase at 400 km, of about 70 K per unit increase in K_p at all latitudes greater than 65°. The temperature peaks at the plasmapause and the magnetospheric cleft show little increase with magnetic activity, but move equatorwards by ca. 2° in latitude per unit K_p.     

Small-scale turbulence in the atmosphere of Venus

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 c_n² and temperature fluctuations c_T² increase poleward, peak near 70° latitude, and decrease over the pole; c_n² varies from 2 × 10^?15 to 1.5 × 10^?14m^{$\text{2}\text{3}$} and c_T² from 4 × 10^?3 to 7 × 10^?2°K²m^{$\text{?2}\text{3}$}. 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, $\text{c}{}_{\mathrm{<mtext>n</mtext>}}{}^2\text{= 2 × 10}{}^{\mathrm{?16}}\text{m}{}^{\mathrm{<mtext>?2</mtext><mtext>3</mtext>}}\text{and}\text{c}{}_{\mathrm{<mtext>T</mtext>}}{}^2\text{= 7.3 × 10}{}^{\mathrm{?4}}\text{°}\text{K}{}^2\text{m}{}^{\mathrm{<mtext>?2</mtext><mtext>3</mtext>}}$ 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.     

Thermospheric neutral composition from auroral ion ratios

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.     

A dynamical effect in the ionospheric f1 layer

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.     

Quenching of O+(2D) by electrons in the thermosphere

A major loss process for the metastable species, O⁺(²D), in the thermosphere is quenching by electrons

$\text{O}{}^{\mathrm{+}}\text{(}{}^2\text{D) + e → O}{}^{\mathrm{+}}\text{(}{}^4\text{S) + e}$

.To date no laboratory measurement exists for the rate coefficient of this reaction. Thermospheric models involving this process have thus depended on a theoretically calculated value for the rate coefficient and its variation with electron temperature. Earlier studies of the O⁺(²D) ion based on the Atmosphere Explorer data gathered near solar minimum, could not quantify this process. However, Atmosphere Explorer measurements made during 1978 exhibit electron densities that are significantly enhanced over those occurring in 1974, due to the large increases that have occurred in the solar extreme ultraviolet flux. Under such conditions, for altitudes ? 280 km, the electron quenching process becomes the major loss mechanism for O⁺(²D), and the chemistry of the N⁺₂ ion, from which the O⁺(²D) density is deduced, simplifies to well determined processes. We are thus able to use the in situ satellite measurements made during 1978 to derive the electron quenching rate coefficient. The results confirm the absolute magnitude of the theoretical calculation of the rate coefficient, given by the analytical expression k(T_e) = 7.8 × 10^?8 (T_e/300)^?0.5cm³s^?1. There is an indication of a stronger temperature dependence, but the agreement is within the error of measurement.     

The chemistry of metastable species in the Venusian ionosphere

Reactions of metastable species are important in determining the densities of minor ions in the Venusian ionosphere. Calculations are carried out in which the coupled continuity and momentum equations are solved for twelve ions and four neutral species in the dayside ionosphere, including $\text{O}{}^{\mathrm{+}}\text{(}{}^2\text{D),}\text{O}{}^{\mathrm{+}}\text{(}{}^2\text{P),}\text{N}\text{(}{}^2\text{D),}\text{and N}\text{(}{}^2\text{P)}$. Altitude profiles of these metastable species are presented. Their reactions are shown to be a significant source of several minor ions, especially N₂⁺, CO⁺, and N⁺. The discrepancies which existed between model and measured densities of these ions are resolved.     

The 63 μm radiation field in the earth's thermosphere and its influence on the atomic hydrogen temperature

The thermal escape of hydrogen from the Earth's atmosphere is strongly affected by its temperature at the exobase. It has been suggested recently that the hydrogen temperature might be significantly lower than the thermospheric temperature as a result of a collisional exchange of energy with atomic oxygen. The tendency is to cool the hydrogen since the energy of the excited ${}^3\text{P}{}_1$ level of oxygen can be lost from the atmosphere via magnetic dipole emission of the 63 μm line (${}^3\text{P}{}_2\text{?}{}^3\text{P}{}_1$). We present here a detailed calculation of the net cooling effect as a function of altitude throughout the thermosphere. The calculations have been performed for both day and night conditions and for periods of maximum and minimum solar activity conditions. It is found that its effect on ΔT/T varies from a very small value to a maximum of ～3%. We also provide the theoretical framework for describing deviations of the 63 μm emission from local thermodynamic equilibrium and show that these effects can cause the emission to be reduced by as much as 40% near 500 km.     

Analysis of the orbital inclination of Tansei 3 rocket 1977-12B

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

$\text{10}{}^9\text{C}{}^{\mathrm{0,1}}{}_{15}\text{= 13.4 ± 6.2, 10}{}^9\text{S}{}^{\mathrm{0,1}}{}_{15}\text{= 0.7 ± 13.3}$

for inclination 65.485°.     

Reaction of protons with methane in the Jovian ionosphere

Laboratory data shows that the reaction of protons with methane proceeds at thermal ion energies to give both CH₃⁺ and CH₄⁺ ions in the ratio $\text{CH}{}_3{}^{\mathrm{+}}\text{CH}{}_4{}^{\mathrm{+}}\text{= 1.5 ± 0.3}$. The overall rate constant for the reaction is 3.8 ± 0.3 × 10^?9 cm³/sec. This reaction may lead to the formation of hydrocarbon ions in the lower ionosphere of Jupiter, and the significance of this process for formation of hydrocarbons and HCN in the atmosphere of Jupiter is discussed.     

New high-speed photometry of EH Lib and a binary interpretation of its period change

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

$\text{T}{}_{\max }\text{= T}{}_0\text{+P}{}_0\text{E+}\text{1}\text{2}\text{βE}{}^2\text{+A}\text{sin}\text{2π}\text{EP}{}_0\text{E}{}_0$

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

$\text{f(m)=}\text{m}{}^3{}_2\text{sin}{}^3\text{i}\text{(m}{}_1\text{m}{}_2\text{)}{}^2\text{=}\text{(a}\text{sin}\text{i)}{}^3\text{E}{}^2{}_0\text{=6 x 10}{}^{\mathrm{?5}}\text{M}{}_{\mathrm{\odot }}$

     

Laboratory measurements of the microwave opacity of sulfur dioxide and other cloud-related gases under simulated conditions for the middle atmosphere of Venus

Recent papers attributing the observed microwave opacity of the middle atmosphere of Venus to gaseous sulfur dioxide (SO₂) and other cloud-related gases have motivated laboratory measurements of their microwave absorbing properties under simulated conditions for this region. In the pressure range from 1 to 5 atmospheres and in the temperature range from 297 to 355°K, the absorption of SO₂ in a carbon dioxide (CO₂) atmosphere, at 2.257 and 8.342 GHz, has been found to be approximately 50% larger than that calculated from Van Vleck-Weisskopf theory. The measured absorption is about $\text{25 × 10}{}^6\text{q?}{}^2\text{p}{}^{1.20}\text{T}{}^{\mathrm{?3.1}}\text{(}\text{dB km}{}^{\mathrm{?1}}\text{)}$, where q is the sulfur dioxide number mixing ratio, ? is frequency in gigahertz, p is pressure in atmospheres, and T is temperature in degrees Kelvin. This represents the best-fit expression to the observed pressure dependence, while theoretical values of frequency and temperature dependence are accepted as being consistent with the measurements. Another cloud-related gas, sulfur trioxide (SO₃), was also tested in a CO₂ atmosphere and found to be relatively transparent. These results reduce the amount of SO₂ in the Venus middle atmosphere required to explain the opacity measured by radio occulatation, but this amount still exceeds the abundance measured in situ by atmospheric probes, suggesting that there must be another important source of opacity. Preliminary measurements of the 13-cm absorptivity of gaseous sulfuric acid (H₂SO₄) show it to be a strong microwave absorber, and thus likely to be responsible for a significant and possibly major part of the observed opacity.     

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.     

On the exponential decay of western hemisphere solar particle events

Numerical solutions of the Fokker-Planck equation governing the transport of solar protons are obtained in three dimensions (time t, radial distance r, energy T) with the diffusion coefficient represented by κ = κ₀r^bT^a. The October 4, 1968, solar flare particle event is re-examined, and the rise and decay of the proton flux profiles for > 10, ;30 and > 60 MeV particles can be reasonably well reproduced with an instantaneous injection and a distant (10 AU) free escape boundary. The best fit is achieved with a diffusion coefficient $\text{κ = 1.4 × 10}{}^{20}\text{r}{}^{0.5}\text{T}{}^{0.75}\text{cm}{}^2\text{sec}$ where r is in AU and T in MeV.     

Empirical model of the E-region electron temperature around noon and at low magnetic activity

Electron temperature measurements made with Langmuir probes at E-region heights together with deviative absorption data show that the electrons are not in thermal equilibrium with the neutrals. Moreover, for very quiet days (A_p ? 7, K_p ? 1⁺ throughout the whole day) and hours close to noon the quotients between the electron and neutral gas temperature profiles have a similar behaviour. In this paper T_e profiles measured in situ with Langmuir probes and T_n, profiles given by neutral atmosphere models, both in the specified ionospheric conditions, are used to compute $\text{T}{}_{\mathrm{e}}\text{T}{}_{\mathrm{n}}$ profiles. Each of the profiles thus obtained is fitted by a Lorentzian curve and the variation with F_10.7 of its parameters is also fitted by simple mathematical expressions.     

Magnetic ordering of the polar airglow

The visible airglow experiment on the Atmosphere Explorer-C satellite has gathered sufficient data over the Earth's polar regions to allow one to map the geographic distribution of particle precipitation using emissions at 3371 and 5200 Å. Both of these features exhibit large variations in space and time. The 3371 Å emission of N₂(C³π), excited by low energy electrons, indicates substantial energy inputs on the dayside in the vicinity of the polar cusp. More precipitation occurs in the morning than evening for the sample reported here, while the entire night sector between magnetic latitudes 65° and 77.5° is subjected to particle fluxes. Regions of enhanced 5200 Å emission from $\text{N}\text{(}{}^2\text{D)}$ are larger in horizontal extent than those at 3371 Å. This smearing effect is due to ionospheric motions induced by magnetospheric convection.     

Direct measurement of conjugate photoelectrons and predawn 630 nm airglow

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.     

Cosmic ray ionization of the Jovian atmosphere

An approximate form of the Boltzmann equation has been used to obtain local ionization rates due to the absorption of galactic cosmic rays in the Jovian atmosphere. It is shown that the muon flux component of the cosmic ray-induced cascade may be especially importannt in ionizing the atmosphere at levels where the total number density exceeds 10¹⁹ cm^?3 (well below the ionospheric layers produced by solar euv). A model containing both positive and negative ion reactions has been employed to compute equilibrium electron and ion number densities. Peak electron number densities on the order of 10³ cm^?3 may be expected even at relatively low magnetic latitudes. The dominant positive ions are NH₄⁺ and C_nH_m⁺ cluster ions, with n ? 2; it is suggested that the absorption of galactic cosmic ray energy at such relatively high pressures in the Jovian atmosphere $\text{(M ? 10}{}^{18}\text{to}\text{10}{}^{20}\text{cm}{}^{\mathrm{?3}}\text{)}$ and the subsequent chemical reactions may be instrumental in the local formation of complex hydrocarbons.     

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

Measurements of N₂⁺ and supporting data made on the Atmosphere Explorer-C satellite in the ionosphere are used to study the charge exchange process

$\text{O}{}^{\mathrm{+}}\text{(}{}^2\text{D}\text{)+}\text{N}{}_2\text{→}\text{k}\text{N}{}^{\mathrm{+}}{}_2\text{+}\text{O}$

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.     

Ion composition in the E- and lower F- region above kiruna during sunset and sunrise

A magnetic type mass spectrometer has been flown on two ESRO sounding rockets from ESRANGE (Kiruna 68°N) on February 25 and 26, 1970. The first launch was at sunset (16:33 UT) and the second the next morning, during sunrise (04:47 UT). For both flights the solar zenith angle was approximately 98°. The instrument was measuring simultaneously the neutral gas and positive ion composition and the total ion density. In this paper the results of the ion composition measurements are presented. For both flights the main ion constituents measured between approximately 110–220 km were O⁺, NO⁺ and O₂⁺. Only at sunset were N⁺ and N₂⁺ detected above 200 km. In spite of the identical solar UV-radiation, pronounced sunset/sunrise variations in the positive ion composition were found. The total ion densities at sunrise were between 5×10³ and 5 × 10⁴ ions cm^?3 and therefore too high to be explained without a night-time ionization by precipitated particles. At sunrise the NO⁺ and O₂⁺ profiles show a correlated wavelike structure with three pronounced almost equally spaced layers in the E-region. Only the highest layer is present in the O⁺ profile. Locally enhanced field aligned ionization originated by particle precipitation and an E × B instability are the most likely source for this structure. In the E- and lower F-regions the $\text{NO}{}^{\mathrm{+}}\text{O}{}_2{}^{\mathrm{+}}$ ration increased overnight from values around 7 at sunset to 15 at sunrise, correlated with an increase of the local magnetic activity index K from 0⁺ to 2°. This could be explained if the NO density and magnetic activity are correlated.     

Auroral recombination of N and O: A possible source for emission in the γ and δ bands of NO

Radiative recombination of N and O provides a significant source for auroral emission in the γ and δ bands of NO with selective population of vibrational levels in the A²Σ⁺ and C²Π states. This mechanism may account for emissions detected near 2150 Å. Models are derived for the auroral ionosphere and include estimates for the concentrations of N and NO. The concentration of NO is estimated to have a value of about 10⁸ cm^?1 near 140 km in an IBC III aurora. The corresponding density for N is about 5 × 10⁷cm^?3 and the concentration ratio $\text{NO}{}^{\mathrm{+}}\text{O}{}_2{}^{\mathrm{+}}$ has a value of about 5.5.