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In order to locate the atmospheric origin, direction finding must be used. As direction finding has various types of error, the arrival direction of atmospherics is normally disturbed by these errors. In this paper, using a simple ionospheric model for nighttime, the wave polarization due to the effect of the Earth's magnetic field is calculated for both ELF and VLF bands below 10 kHz and also the behavior of the bearing error is investigated as a function of propagation distance. This paper shows that if the direction finding can be operated at a frequency in the ELF range, there would be two merits in comparison with 10 kHz direction finding.

Hypothetical reaction schemes are frequently used in the interpretation of atmospheric photochemistry, and rate parameters chosen to give a good fit to the observed data. Although the close agreement between the experimental and calculated results gives considerable confidence in the proposed mechanisms, it is clearly more satisfactory if laboratory investigations yield information about reactions and their rates which predicts with some degree of accuracy the atmospheric observations. In this paper, some laboratory studies on the photochemistry of the O3-O2-O system are presented, with particular reference to the participation of O2(1Δg) in the various processes. These studies have permitted the evaluation of atmospheric models, and the relevance of the studies to atmospheric photochemistry will be discussed. Detailed descriptions of the experimental techniques are to be found in the papers to which reference is made.

Numerical solutions of mutually coupled time-dependent equations of continuity, momentum, and energy balance are presented to illustrate the effect of eddy turbulence on the neutral composition and temperature of the lower and upper thermospheres. The procedure adopted in this paper eliminates the necessity of making ad hoc assumptions about the conditions at the turbopause level and allows the study of the two regions in a self-consistent manner. From the illustrative examples comprising parametric changes in the eddy diffusion coefficient the specific roles of eddy turbulence in the development of theoretical models of the thermosphere are discussed.

Magnetic field data from the Goddard Space Flight Center magnetometer experiment on board Ogo 5 are analyzed by the minimum-variance technique for two magnetopause crossings, believed to provide the best evidence presently available of magnetopause rotational discontinuities. Approximate agreement with predictions from MHD and first-order orbit theory is found, but available low-energy electron data suggest the presence of significant non-MHD effects. The paper also illustrates an improved method for data interval selection, a new magnetopause hodogram representation, and the utility of data simulation.

Analyses of the wave spectral amplitude and wave polarization characteristics of magnetic pulsations measured at four magnetometer stations near L=4 on January 5, 1972, demonstrated that the wave properties in selected frequency bands varied with latitude in a systematic way throughout the day. By using an idealized model of the radial profile of the magnetospheric plasma density a theoretical extension is made to the magnetic pulsation model of L. Chen and A. Hasegawa (1974). The latitude dependence of the wave properties is calculated for locations away from the localized wave source. This paper shows that good agreement is obtained between the plasma wave properties measured near L=4 and the theoretical predictions of the Chen and Hasegawa model.

An analysis was performed on 29,574 densities derived from the drag of 10 satellites to determine simultaneously the parameters of the solar-activity effect in the thermosphere on the one hand, and the amplitude and shape of the diurnal-variation curve on the other. This paper reports on the study of the diurnal variation only. Although a considerable amount of smoothing is inherent in the drag method, it seemed useful to see whether any change could be detected in the shape of the diurnal-variation curve with height, latitude and solar activity. None was detected; the curve remains remarkably stable, symmetric, with a maximum at 14 hr 20 min L.S.T. and a minimum at 2 hr 20 min L.S.T. A systematic variation of the temperature range with height is observed when static models are used to derive it.

This paper reports results obtained on ionosphere formation in the Jovian upper atmosphere with special reference to some of the recently available reaction rates, and to recent models of the Jovian neutral atmosphere based on the possibility of a warmer mesopause. In the older models of the Jovian ionosphere, the major ions were H+ which were lost only by pure radiative recombination. This led to high electron densities and practically no diurnal change. In contrast, recent models have relatively much smaller electron densities, especially in lower regions, and may be susceptible to significant diurnal variation.

Observational results on the density in the thermosphere and lower exosphere (i.e., within the altitude range from about 150 to about 1000 km) are discussed in this paper. Most observational results on total gas density were obtained from orbital drag and more recently also from in-situ drag analysis. The primary parameter measured is atmospheric density, with temperature as a secondary structural parameter deduced with the help of theory and/or atmospheric models. Both the merits and shortcomings of the drag analysis method are outlined in view of a comparison of temperature deduced from total density and kinetic gas temperature measured by incoherent scatter. Recent improvements of our knowledge of the known density variations are presented.

We propose chromospheric models of plages to explain profiles of the Ca ii H, K, λl8498, λ8542, and λ8662 lines described in Paper I. These models are consistent with boundary conditions imposed by the photosphere and the Lyman continuum. We find that increasing emission in these lines is consistent with a picture of increasing temperature gradient in the low chromosphere and the resulting increase in pressure and electron density at similar line optical depths. With this picture we suggest how to empirically determine the distribution of chromospheric parameters across the solar disk directly from Ca ii filtergrams. We also propose that the high density aspects of solar activity are produced by steep temperature gradients in the low chromosphere and thus by the enhanced heating mechanisms that steepen these gradients.

If the atmosphere is simulated by a number of homogeneous sublayers, it was shown (Takashima, 1973a) that the intensity and polarization parameters emerging from any boundary of internal sublayer's field can be determined, provided that the diffuse reflection and transmission matrices of radiation of sublayers are known. Furthermore, if the surface (ground) is assumed to reflect light in accordance with the Lambert law, it is shown in this paper that the internal radiation field at boundary of any sublayer can be also computed in terms of the diffuse radiation matrices of sublayers rather than in terms of that of the entire atmosphere (Sekera, unpublished). The effect of polarization is included.

An Aerobee 170 rocket carried five slitless extreme ultraviolet (XUV) spectroheliographs into the March 7, 1970, solar eclipse. Salt water damage left latent images on 16 exposures of the XUV camera covering the wavelength range from 1390 A to 1945 A. The salt water damage made the absolute calibration of the spectroheliograms uncertain. Therefore, the analysis in this paper is based on a comparison of the extent of flash spectrum crescents from emission lines formed in the chromosphere-corona transition zone with two simple but fundamentally different models describing this region. The observations can be satisfactorily described by an inhomogeneous model where cool spicules are surrounded by a transition zone which has the same temperature and density structure as the chromospheric coronal transition zone customarily used in spherically symmetric models of the quiet Sun.

The phasefront distortion imposed on space signals by fine-grained refractivity variations of the atmosphere is an important consideration in the design of large-aperture antennas, antenna arrays, antenna systems for measuring spacecraft position and position-rate, and radioastronomy systems. The distortion caused by ionospheric and tropospheric refractivity variations imposes fundamental limitations on the capabilities of these antennas and antenna systems, particularly on systems which must operate at low elevation angles. The purpose of this paper is to present numerical estimates of distortion imposed on signals passing through the atmosphere. Atmospheric models based on available literature are selected for this purpose.

The Upper Atmosphere can be examined from many points of view. For example, it can be considered as an aerodynamic, chemical, or electrical medium. This paper tabulates key parameters used in describing various atmospheric models and gives a brief indication of the instrumentation used in their measurement.

In an earlier paper, values of exospheric density were obtained from the orbit of Echo 2 for the years 1964–1965. The results indicated a semi-annual variation in density by a factor of between 2 and 3, considerably larger than predicted by existing atmospheric models. These studies have now been extended to the beginning of 1967, using both Echo 2 and Calsphere 1, to show how the density is responding to increasing solar activity. Variations in density during 1964 have been analysed in more detail. The long-term variation associated with the solar cycle and the short-term variations associated with magnetic and solar disturbances agree with the variations expected on the basis of current models. The semi-annual variation is persisting to higher levels of solar activity, and although its amplitude is diminishing the factor of variation was still 1.6 in 1966.

This paper develops an objective technique for estimating the mass and energy exchange in convection systems corresponding to altocumulus cumulogenitus and cumulonimbus intensities using measurements of the area change of the cirrus outflow on a sequence of satellite cloud photographs obtained at geostationary altitude. The data clearly show that: (1) the technique is able to isolate vigorous and moderate convection regimes on the geostationary satellite cloud photos; and (2) the model-estimated mass and energy are consistent with ground-based measurements such as those of Braham and Brown.

Satellite-measured radiances offer the first opportunity for investigating the total structure of winter stratospheric warmings, a phenomenon whose cause is still unknown despite intensive study since 1952, Vertical temperature profiles inferred from Nimbus III and IV SIRS 15 μ infrared measurements do not appear to be ideally suited for monitoring sudden warmings above the 10-mb level because of increased dependence, in the upper stratosphere, of inverse solutions of the radiative transfer equation on the climatological or “first-guess” profiles employed. In this paper, a temperature model for stratospheric warmings is presented, from which radiance changes are calculated by direct solution of the integral radiative transfer equation. The model is based on a review of past warming events and its construction was guided by stated physical constraints. The radiance changes correspond to changes in the temperature structure from a pre-warming condition to an arbitrary phase of warming. Warmings by ...

Since the barometer measures the weight of the overlying atmosphere, it follows by the law of Gladstone and Dale that the height integral∫(n#x2212;1) of the atmospheric refractivity for light, taken from ground level up to the top of the atmosphere, is directly proportional to ground pressure. The refractivity integral, therefore, can be determined without detailed knowledge of the height distribution of the refractive index, which not only simplifies the derivation of refraction formulas in which atmospheric models have been used hitherto, but also improves their accuracy. For zenith distances not exceeding about 75 degrees, the correction for astronomical refraction will be given by the standard formula $$\begin{gathered} \Delta z''_0 = 16''.271 tan z\left[ {1 + 0.0000394 tan^2 z\left( {\frac{{p - 0.156e}}{T}} \right)} \right]\left( {\frac{{p - 0.156e}}{T}} \right) - \hfill \\ - 0''.0749 (tan^3 z + tan z)\left( {\frac{p}{{1000}}} \right) \hfill \\ \end{gathered} $$ wherez is the apparent zenith distance,p is the total pressure ande is the partial pressure of water vapour, both in millibars, andT is the absolute temperature in degrees Kelvin Part II of the paper contains further applications of the theory to refraction problems in satellite geodesy, including the photogrammetric refraction and the atmospheric corrections in the ranging of artificial satellites.

Previous work on the excitation of large-scale oscillations in an atmosphere on a rotating globe is extended to include a unified treatment for both gravitational and thermal forcing functions and is applied to the solar and lunar semi-diurnal pressure variation, that is, S2 and L2, respectively. It is assumed that the heating is applied only at the base of the atmosphere and that the temperature gradient is constant in this region as in the actual troposphere. The solution of the problem consists of the usual Bessel's functions characteristic of a purely gravitational forcing function found by Pekeris [see 1 of “References” at end of paper], plus a particular integral found by the method of variation of parameters. The total resonant amplification is obtained for the various atmospheric models used by Jacchia and Kopal [2]. The hitherto neglected phase of the dynamical tidal oscillation is included in a treatment where complex variables are systematically employed to represent the magnitude and phase of observables. It is found that current atmospheric models favor the conclusion that thermal effects are far more important than the gravitational in producing the S2 variation (≃15) as compared with Chapman's [3] 1924 conclusion that they are of nearly equal importance. However, if one assumes, as did Chapman, that eddy motion at the ground is the only heating source, then our conclusion is at odds with observed values of eddy conductivity found by Eiffel Tower measurements. A possible resolution of this paradox is the consideration of other heating sources. Balloon observations by Riehl and the analysis of Haurwitz [4] are cited in support of this possibility.

In this paper we treat the multiple scattering theory of radiative transfer in plane-parallel inhomogeneous atmospheres. The treatment presented here may be adopted to model atmospheres characterized by an optical depth dependent coherent scattering phase function. For the purpose of illustration we consider the semi-infinite medium in which the absorption property of the atmosphere is characterized by an exponential function. The methodology employed here is the extension of the case treated previously by the author for homogeneous atmospheres.

This paper presents a stratospheric aerosol model and infers its effects on terrestrial radiation. Composition of the aerosol is assumed to be concentrated sulfuric acid. An appropriate size distribution has been determined from available size distribution measurements of other investigators. Aerosols composed of concentrated sulfuric acid emit energy in the atmospheric window region of the infrared spectrum, 8-13 microns. Laboratory measurements of optical constant data obtained at room temperature are presented for 75 and 90% aqueous sulfuric acid. Calculations of an aerosol extinction coefficient are then performed by using the above data. Effects of changes in aerosol phase and temperature are discussed but not resolved.

This paper presents particle data obtained from synchronous altitudes and attempts to evaluate the origin and nature of particle flux variations observed during substorms. The correlated particle intensities, time variations, and energy spectrums are compared between the equatorial and auroral zones. The correlated particle and field observations during substorms are tied together and a model of magnetospheric substorms is derived. Among the features predicted by the model is the poleward expansion of visual auroras observed at the onset of magnetospheric substorms. The model also explains how substorms are triggered in a few minutes time scale during sudden commencements.

In this paper we obtain an approximate expression for the temperature structure of a stellar atmosphere heated by an external flux of soft X-rays. Allowance is made for reradiation in both the soft X-ray and optical regions. As may be expected our results indicate that the temperature structure will be drastically changed from the grey T-T relation, particularly at low optical depths. The stronger lines should appear in emission with the possibility of a central absorption in certain circumstances. The present results are in general agreement with those of Strittmatter (1974).

Since the early work of Dungey, Axford and Hines, and Piddington, the concept of magnetospheric convection has become more and more widely accepted as the fundamental driving force for magnetospheric processes. Although the early convection theories have been modified to include the effects of magnetospheric-ionospheric coupling, the original steady large-scale convection models remain largely intact. This paper discusses a variety of recent magnetospheric measurements which support the basic convection model. These measurements include the dynamics of thermal plasma, the drift patterns of medium-energy protons and electrons, and the direct measurement of magnetospheric electric fields by satellites and balloons. All of these measurements have added significantly to our understanding of convection processes, and taken collectively, they offer a fairly unified picture of magnetospheric convection.

In this introductory paper, no attempt will be made to describe any particular model or to compare different models. Emphasis will be given to the physical phenomena occurring in the terrestrial upper atmosphere.

An attempt is made to integrate and interpret various polar and magnetospheric substorm phenomena as consequences of the acceleration process of auroral particles which could result from the diversion of a part of the magnetotail current to the night side of the auroral oval. Thus, this paper is not intended to be a literature survey, but to present a way along which magnetospheric substorms might be studied in the future.

It has become clear in recent years through the work of Collins (1963, 1965, 1966), Collins and Harrington (1966), Hardorp and Strittmatter (1968a, b) and Roxburgh and Strittmatter (1965) how seriously the spectrum of a star may be affected by rotation. However, before atmospheric models for rotating stars can be computed, the results of corresponding interior models have to be available. For polytropic configurations a great many rotating interior models have been constructed (Chandrasekhar, 1933; James, 1964; Stoeckly, 1965; Monaghan and Roxburgh, 1965; and Anand, 1968), but for rotating main-sequence stars few computations exist (Sweet and Roy, 1953; Roxburgh et al, 1965; Ostriker and Mark, 1968; Faulkner et al., 1968). In fact for B- and Be-type stars for which the most rapid rotation along the main sequence is observed, not a single interior model has yet been computed except in this conference reported by Kippenhahn and Thomas (1970). It is this gap that the present paper attempts to close.

Attainable accuracy of short-term prediction of atmosphere density for operational determination and prediction of close Earth satellite orbits is estimated in this paper. Using available atmospheric models short-term variations of atmospheric parameters are represented generally as a function of the 10.7 cm solar flux F 10.7 and the planetary geomagnetic index a p (or A p ). Using such models the accuracy of description of atmosphere density changes within the interval of AES orbit determination and prediction depends considerably on the accuracy of predicted quantities F 10.7, a p or A p . Various methods of prediction are considered here and their accuracies are compared. Errors of atmosphere density prediction are recalculated from errors of predicted quantities F 10.7, a p and A p . In this case empirical relationships between variations of the quantities F 10.7, a p , A p and corresponding atmospheric density changes calculated from AES drag data are used. The prediction intervals considered are from some hours up to three days. Some tables and diagrams given allow estimation of the accuracy obtainable of atmosphere density calculations for the altitudes of 150–350 km.

I an earlier paper, the author has calculated the downward atmospheric radiation fluxes, for several Martian atmospheric models, incident on a horizontal plate located on the Martian surface. These calculations have been extended to the case of a plate inclined to the horizontal using updated Martian atmospheric models which reflect the data obtained from Mariners 6 and 7. Elsasser's approach to atmospheric radiation calculations was extended to include inclined plates, and radiation tables were prepared for several inclination angles. Effective Martian sky temperatures, defined as the temperature of a black hemisphere with the same total emittance as the atmosphere, were calculated as previously. The effective sky temperatures were calculated for the five model atmospheres of the Viking 75 Project Mars Engineering Model and for the Jet Propulsion Laboratory (JPL) Lower Atmosphere Model I for four surface temperatures. The Viking Project atmospheres include the results of the measurements made dy Mariners 6 and 7; however, the older JPL atmosphere does not. All of these atmospheric models were developed primarily for preliminary design purposes. It should be emphasized that the assumptions of the various atmospheric models vary considerably, and this should be taken into account when comparing their respective sky temperatures. The atmospheric composition, surface pressures and temperatrues, and the effective sky temperatures for plate inclinations of 0°, 30° 60°, 75°, and 90° are presented in Tables 1 and 2. In addition, effective sky temperatures were computed for several surface altitudes for the Viking Project atmospheres, Table 3.

Recent studies have used the superposition principle (extended Huygens-Fresnel principle) to characterize completely the statistics of a field that has propagated through a thick slab of turbulent air in terms of the statistics for spherical-wave sources. In this paper, we consider the normal-mode decomposition associated with this linear system propagation model. In particular, we use the statistics of the atmospheric impulse response (Green's function) to show that the atmospheric mode decomposition exhibits far-field and near-field regimes very similar to those of free-space propagation. The significance of these results for optical communication through the atmosphere is briefly discussed.

The escape of atomic hydrogen from the high regions of the earth's atmosphere plays a fundamental role in determining the altitude distribution of this gas. The rate of escape is well known to be a very sensitive function of temperature, with the result that, if hydrogen gas responded instantaneously to diurnal exospheric temperature variations, a day-night asymmetry as high as 20 in the concentration of hydrogen might be expected. Studies during the last few years have shown, however, that lateral flow of hydrogen gas in the exosphere will cause a considerable reduction in the magnitude of this asymmetry, a ratio of the order of 2 being much more likely. In this paper the results of earlier work will be reviewed and updated by more recent studies.