Grain abundance in the primordial atmosphere of the Earth

For models of planetary accumulation in the presence of solar nebular gas, the initial surface temperature of the Earth is controlled by the grain opacity of the atmosphere. The surface temperature in turn controls the quantity of neon dissolved and trapped within the interior of the Earth. To compare accumulation theory with observation calculations have been made of the grain opacity expected to be associated with accumulation in a gaseous nebula. There are two parameters that are in principle determined by the theory, but actually are at present uncertain: the mean eccentricity e of the planetesimal swarm, and the fraction ξ of the accretional energy that is expended in the release of grains into the atmosphere by ablation of the incoming planetesimal. It is found that if the eccentricity of swarm is low (10^?3), rather low values of ξ(10^?5) are required to match the observed neon data. In contrast higher values of ξ are required (10^?1) for the most probable case, intermediate eccentricity (10^?2). For the high eccentricity case (e ～ 0.1) ξ must be >10^?2. The results show that avoidance of excess trapped neon of solar composition places restrictive, but not necessarily impossible, conditions on the parameters of the accumulation theory.     

The evolution of the atmosphere of the earth

Computer simulations of the evolution of the Earth's atmospheric composition and surface temperature have been carried out. The program took into account changes in the solar luminosity, variations in the Earth's albedo, the greenhouse effect, variation in the biomass, and a variety of geochemical processes. Results indicate that prior to two billion years ago the Earth had a partially reduced atmosphere, which included N₂, CO₂, reduced carbon compounds, some NH₃, but no free H₂. Surface temperatures were higher than now, due to a large greenhouse effect. When free O₂ appeared the temperature fell sharply. Had Earth been only slightly further from the Sun, runaway glaciation would have occured at that time. Simulations also indicate that a runaway greenhouse would have occured early in Earth's history had Earth been only a few percent closer to the Sun. It therefore appears that, taking into account the possibilities of either runaway glaciation or a runaway greenhouse effect, the continously habitable zone about a solar-type star is rather narrow, extending only from roughly 0.95 to 1.01 AU.     

Origin of the Moon — Capture by gas drag of the Earth's primordial atmosphere

We propose a new scenario of the lunar origin, which is a natural extension of planetary formation processes studied so far by us in Kyoto. According to these studies, the Earth grew up in a gaseous solar nebula and, consequently, the sphere of its gravitational influence (i.e., the Hill sphere of the Earth) was filled by a gas forming a dense primordial atmosphere of the Earth. In the later stages, this atmosphere as well as the solar nebula was dissipated gradually, owing to strong activities of the early-Sun in a T Tauri-stage.In the present and the subsequent papers, we study a series of dynamical processes where a lowenergy (i.e., slightly unbound) planetisimal is trapped within the terrestrial Hill sphere, under the above-mentioned circumstances that the gas density of the primordial atmosphere is gradually decreasing. It is clear that two conditions must be satisfied for the lunar origin: first, an unbound planetesimal entering the Hill sphere have to dissipate its kinetic energy and come into a bound orbit before it escapes from the Hill sphere and, second, the bound planetisimal never falls onto the surface of the Earth.In this paper we study the first condition by calculating the oribital motion of a planetesimal in the Hill sphere, which is affected both by solar gravity and by atmospheric gas drag. The results show that a low-energy planetisimal with the lunar mass or less can be trapped in the Hill sphere with a high probability, if it enters the Hill sphere at stages before the atmospheric density is decreased to about 1/50 of the initial value.In the subsequent paper, the second condition will be studied and it will be shown that a tidal force, among other forces, is very important for a trapped planetesimal to avoid collision with the Earth and stay eternally in the Hill sphere as a satellite.     

Extraterrestrial particles and the greenhouse effect

We discuss the possibility that a variable atmospheric load of porous 0.1 m-sized dielectric particles of extraterrestrial origin could lead to a fluctuating baseline for the atmospheric temperature near ground level. Global warming has to be reckoned relative to this baseline.     

The effect of primordial non-Gaussianity on the topology of large-scale structure

We study the effect of primordial non-Gaussianity on the development of large-scale cosmic structure using high-resolution N -body simulations. In particular, we focus on the topological properties of the 'cosmic web', quantitatively characterized by the Minkowski functionals (MFs), for models with quadratic non-linearities with different values of the usual non-Gaussianity parameter f _NL. In the weakly non-linear regime (the amplitude of mass density fluctuations σ₀ < 0.1), we find that analytic formulae derived from perturbation theory agree with the numerical results within a few per cent of the amplitude of each MF when | f _NL| < 1000. In the non-linear regime, the detailed behaviour of the MFs as functions of threshold density deviates more strongly from the analytical curves, while the overall amplitude of the primordial non-Gaussian effect remains comparable to the perturbative prediction. When smaller-scale information is included, the influence of primordial non-Gaussianity becomes increasingly significant statistically due to decreasing sample variance. We find that the effect of the primordial non-Gaussianity with  | f _NL| = 50  is comparable to the sample variance of mass density fields with a volume of 0.125( h ⁻¹ Gpc)³ when they are smoothed by Gaussian filter at a scale of 5  h ⁻¹ Mpc. The detectability of this effect in actual galaxy surveys will strongly depend on residual uncertainties in cosmological parameters and galaxy biasing.     

Low order effect of crand input in the Jovian atmosphere

Modeling of the Jovian atmosphere shows that cosmic ray induced albedo neutron decay is inadequate to account for Pioneer 10 and 11 projected electron levels on Jupiter. High energy solar protons must also be excluded as an important neutron decay source. Analysis of neutron flux data near the top of the Jovian atmosphere can lead to the determination of He/H₂ and³He/⁴He ratios for the Jovian atmosphere.     

Momentum of meteoroids and its effect on the Earth's atmosphere

Recent studies have attributed certain properties of the Earth's atmosphere to excess orbita angular momentum of impinging meteoroids. A realistic analysis of meteor observations does not support the existence of this excess.     

Presence of a primary solar-type atmosphere around the earth: evidence of dissolved noble gas

Recent noble gas data of mantle-derived samples show that there are two end members: PLUME-type and MORB-type. The estimated high ³He and ²²Ne abundances of the PLUME source, possibly representing the lower mantle, should reflect the remnant of dissolved solar-type atmosphere. Calculations of the structure of the primary atmosphere and the noble gas dissolution into the magma ocean of the accreting planet suggest that the high ³He and ²²Ne abundances can be explained if the primary atmosphere persisted until M0.4–0.6 M_E (M_E being the present Earth mass). The PLUME source has higher ³He/⁴He and lower ²¹Ne/²²Ne than the MORB source. This is explained by assuming that the lower mantle was less degassed during magma ocean cooling. The carbon abundance in the mantle can be constrained from the estimated abundance of mantle ³He and C/³He data of the present mantle-derived samples. Dissolved solar-type noble gas might explain high noble gas abundance in the present Venus, if the primary atmosphere persisted until the final stage of accretion under lower dust opacity of the atmosphere.     

The Hanle effect and the diagnostics of turbulent magnetic fields in the solar atmosphere

The theory of the Hanle effect is used to interpret the linear polarization measured in a number of spectral lines on the solar disk near the heliographic north and south poles, in search for a turbulent magnetic field in the solar atmosphere. The Hanle depolarization is separated from a number of other effects, including collisional depolarization and scattering geometry. Although the main aim of the paper is to elucidate the physics of the Hanle effect as applied to the Sun, our results indicate the existence of hidden or turbulent magnetic flux near the temperature minimum of the solar atmosphere, with a field strength between 10 and 100 G. This field is hidden in the sense that it is not seen in measurements of the longitudinal Zeeman effect (solar magnetograms). It carries more total magnetic flux than the kG network fields.     

Estimation of long-term density variations in the upper atmosphere of the earth at minimums of solar activity from evolution of the orbital parameters of the earth’s artificial satellites

Long-term data on the evolution of the parameters of motion of 15 artificial satellites of the Earth in orbits with minimal heights of 400–1100 km were used to study the density variations in the upper atmosphere at minimums of four cycles of solar activity. It was found that the density at these heights considered increased by about 7% at the minimum of solar cycle 20 as compared to solar cycle 19. Later, the density fell rather linearly at the minimums of cycles 21 and 22. The statistical processing of the data for solar cycles 20–22 demonstrated that the density decreased by 4.6% over ten years and by 9.9% over 20 years. Analyzing the density variations during the four cycles of solar activity, we found that the long-term decrease in density observed at the minimums of cycles 20–22 is caused mainly by specific variations of the solar activity parameters (namely, the solar radio flux and the level of geomagnetic disturbance).__________Translated from Astronomicheskii Vestnik, Vol. 39, No. 2, 2005, pp. 177–183.Original Russian Text Copyright © 2005 by Volkov, Suevalov.     

Laboratory simulation experiments on the solid-state greenhouse effect in planetary ices

Icy surfaces like the polar caps of Mars, comets, Edgeworth-Kuiper belt objects or the surface areas of many moons in the outer Solar System behave different than rock and soil surfaces when irradiated by solar light. The latter ones absorb and reflect incoming solar radiation immediately at the surface. In contrast, ices are partially transparent in the visible spectral range and opaque in the infrared. Due to this fact it is possible for the solar radiation to reach a certain depth and increase the temperature of the sub-surface layers directly. This internal temperature rise is called “solid-state greenhouse effect,” in analogy to the classical greenhouse effect in an atmosphere. It may play an important role in the energy balance of various icy bodies in the Solar System. Within the scope of a project conducted at the Space Research Institute of the Austrian Academy of Sciences in Graz the solid-state greenhouse effect was investigated experimentally and theoretically. A number of experiments with diverse materials, focussing mainly on layered samples with a surface cover consisting of transparent H₂O-ice, were performed. The samples were irradiated under cryo-vacuum conditions by a solar simulator. The temperature distributions inside the samples were measured and compared with the results of numerical model calculations. We found that the predicted sub-surface temperature maximum is very clearly measurable in glass beads samples with various particle size distributions, but can also be detected in transparent compact surface ice layers. However, in the latter case it is less distinct than originally expected. Measuring the effect by laboratory methods turned out to be a difficult task due to the shallow depth where the temperature maximum occurs.     

Cosmic rays and the primordial gas

One of the most-outstanding problems in the gravitational collapse scenario of early structure formation is the cooling of primordial gas to allow for small-mass objects to form. As the neutral primordial gas is a poor radiator at temperatures   T ≤ 10⁴ K  , molecular hydrogen is needed for further cooling down to temperatures   T ∼ 100 K  . The formation of molecular hydrogen is catalyzed by the presence of free electrons, which could be provided by the ionization due to an early population of cosmic rays (CRs). In order to investigate this possibility, we developed a code to study the effects of ionizing CRs on the thermal and chemical evolution of primordial gas. We found that CRs can provide enough free electrons needed for the formation of molecular hydrogen, and therefore can increase the cooling ability of such primordial gas under following conditions. A dissociating photon flux with   F < 10⁻¹⁸ erg cm⁻² Hz⁻¹ s⁻¹  , initial temperature of the gas  ∼10³ K  , total gas number densities   n ≥ 1 cm⁻³  , and cosmic-ray sources with     .     

Hawking-Unruh effect associated with primordial black holes and maximum acceleration of elementary particles

Three decades ago an expression for the maximum acceleration of elementary particles was derived using quantum theory. There is no experimental confirmation of this so far. In this paper we study the phenomenon of acceleration of elementary particles by the surface gravity of primordial black holes (PBH) formed in the early universe and the associated Hawking-Unruh effect. From a heuristic theory we find that every elementary particle can be associated with a PBH of unique mass and Hawking temperature. This implies a unique Hawking-Unruh acceleration for each elementary particle. The inferred values of maximum acceleration from our theory range from 6.24 × 10³³ m/s² for top quarks to 1.85 × 10²⁸ m/s² for electrons. These values can be considered to be the maximum acceleration given by the general expression $\frac{m{c}^3}{2h}$ of elementary particles of given rest mass (m) due to the force of gravity. Elementary particles with the maximum Compton wavelength (${10}^{-4}$ m) and an inferred mass of 0.0185 eV (possibly neutrinos) are found to be associated with a PBH whose Hawking temperature is identical to the cosmic microwave background temperature of the present Universe.     

Null Variance Altitudes for the photolysis rate constants of species with barometric distribution: Illustration on Titan upper atmosphere modeling

The precision of the rates of the photolysis processes initiating the complex chemistry of Titan’s upper atmosphere conditions strongly the predictivity of photochemical models. Recent studies in sensitivity analysis of such models point out photolysis rate constants as key parameters. However, they have been treated approximately so far. We deal here directly with uncertainty in the absorption cross-sections to derive the uncertain altitude-dependent photolysis rate constants. We observe that the uncertainty on the photolysis rate constants of the major species, N₂ and CH₄, varies strongly with altitude and rather surprisingly vanishes at specific altitudes. We propose a simple model to interpret these features and we demonstrate that they are transferable to any major absorber distributed barometrically in an atmosphere.     

The effect of the atmosphere and ionosphere on long period magnetospheric micropulsations

A study is made of the screening effect of the atmosphere and ionosphere which lets only part of a magnetospheric micropulsation signal reach the ground. We obtain analytical expressions relating the magnetic field in the magnetosphere to that on the ground, which are confirmed by computing a full solution. Only the part of the signal with no vertical current will be seen on the ground; this agrees with previous work. Using this result, we find that the reflection condition of a transverse hydromagnetic wave incident on the top of the ionosphere indicates a ‘fixed-end’ boundary condition for the field line. To a first approximation, micropulsation polarisations observed on the ground must be rotated through a right angle to obtain those in the magnetosphere. The strength of the electric field predicted in the ionosphere agrees with radio aurorae observations.     

Interannual variability of regional climate and its change due to the greenhouse effect

Interannual variability of regional climate was investigated on a seasonal basis. Observations and two global climate model (GCM) simulations were intercompared to identify model biases and climate change signals due to the enhanced greenhouse effect. Observed record length varies from 40 to 100 years, while the model output comes from two 100-year equilibrium climate simulations corresponding to atmospheric greenhouse gas concentrations at observed 1990 and projected 2050 levels. The GCM includes an atmosphere based on the NCAR CCM1 with the addition of the radiative effects of CH₄, N₂O and CFCs, a bulk layer land surface and a mixed-layer ocean with thermodynamic sea-ice and fixed meridional oceanic heat transport.Because comparisons of interannual variability are sensitive to the time period chosen, a climate ensemble technique has been developed. This technique provides comparisons between variance ratios of two time series for all possible contiguous sub-periods of a fixed length. The time autocorrelation is thus preserved within each sub-period. The optimal sub-period length was found to be 30 years, based on which robust statistics of the ensemble were obtained to identify substantial differences in interannual variability that are both physically important and statistically significant.Several aspects of observed interannual variability were reproduced by the GCM. These include: global surface air temperature; Arctic sea-ice extent; and regional variability of surface air temperature, sea level pressure and 500 mb height over about one quarter of the observed data domains. Substantial biases, however, exist over broad regions, where strong seasonality and systematic links between variables were identified. For instance, during summer substantially greater model variability was found for both surface air temperature and sea-level pressure over land areas between 20–50°N, while this tendency was confined to 20–30°N in other seasons. When greenhouse gas concentrations increase, atmospheric moisture variability is substantially larger over areas that experience the greatest surface warming. This corresponds to an intensified hydrologic cycle and, hence, regional increases in precipitation variability. Surface air temperature variability increases where hydrologic processes vary greatly or where mean soil moisture is much reduced. In contrast, temperature variability decreases substantially where sea-ice melts completely. These results indicate that regional changes in interannual variability due to the enhanced greenhouse effect are associated with mechanisms that depend on the variable and season.     

Life-bearing primordial planets in the solar vicinity

The space density of life-bearing primordial planets in the solar vicinity may amount to ～8.1×10⁴?pc^?3 giving total of ～10¹⁴ throughout the entire galactic disk. Initially dominated by H₂ these planets are stripped of their hydrogen mantles when the ambient radiation temperature exceeds 3?K as they fall from the galactic halo to the mid-plane of the galaxy. The zodiacal cloud in our solar system encounters a primordial planet once every 26 My (on our estimate) thus intercepting an average mass of 10³ tonnes of interplanetary dust on each occasion. If the dust included microbial material that originated on Earth and was scattered via impacts or cometary sublimation into the zodiacal cloud, this process offers a way by which evolved genes from Earth life could become dispersed through the galaxy.     

The neutrino in the primordial magnetic field

We discuss the evolution of the massive Dirac particle in the cosmic magnetic field. The magnetic field makes the space metric anisotropic. By solving the Dirac equation we obtain the apparent magnetic moment of the neutrino in the cosmic magnetic field.     

Laboratory measurements of the microwave opacity of gaseous Ammonia (NH3) under simulated conditions for the Jovian atmosphere

Gaseous ammonia (NH₃) has long been recognized as a primary source of microwave opacity in the atmosphere of Jupiter. In order to more accurately infer the abundance and distribution of ammonia from radio emission measurements in the 1 to 20-cm wavelength range and radio occultation measurements at 3.6 and 13 cm, we have made measurements of the microwave opacity from gaseous ammonia under simulated conditions for the Jovian atmosphere. Measurements of ammonia absorptivity were made at five frequencies from 1.62 to 21.7 GHz (wavelengths from 18.5 to 1.38 cm), at temperatures from 178 to 300°K, and at pressures from 1 to 6 atm, in a 90% hydrogen/10% helium atmosphere. The results of these measurements show that in the 1.38- to 18.5-cm wavelength range, the absorption from gaseous ammonia is correctly expressed by the modified Ben-Reuven lineshape as per G.L. Berge and S. Gulkis (1976, Earth-based radio observations of Jupiter: Millimeter to meter wavelengths. In Jupiter (T. Gehrels, Ed.), pp. 621–692, Univ. of Arizona Press, Tucson). When applied to the microwave opacity measured by radio occultation measurements, or the microwave opacity inferred from radio emmission measurements, these results suggest that either an abundance of ammonia 1.5 to 2.0 times greater than the solar abundance must exist at levels below the 1- to 2-bar pressure range, or that some other microwave absorber must be present.We conclude by suggesting further laboratory measurements of other potential microwave-absorbing constituents and additional investigation of the microwave absorption from ammonia in the 10- to 20-cm wavelength range and at wavelengths shortward of 1 cm.