Number Density Ratio Research Articles

A Microphysical Interpretation of Radar Reflectivity–Rain Rate Relationships

Abstract The microphysical aspects of the relationship between radar reflectivity Z and rainfall rate R are examined. Various concepts discussed in the literature are integrated into a coherent analytical framework and discussed with a focus on the interpretability of Z–R relations from a microphysical point of view. The forward problem of analytically characterizing the Z–R relationship based on exponential, gamma, and monodisperse raindrop size distributions is highlighted as well as the inverse problem of a microphysical interpretation of empirically obtained Z–R relation coefficients. Three special modes that a Z–R relationship may attain are revealed, depending on whether the variability of the raindrop size distribution is governed by variations of drop number density, drop size, or a coordinated combination thereof with constant ratio of mean drop size and number density. A rain parameter diagram is presented that assists in diagnosing these microphysical modes. The number-controlled case results i...

Cavity ring-down spectroscopy measurements of the concentrations of C 2(X 1Σ g+) radicals in a DC arc jet reactor used for chemical vapour deposition of diamond films

Absorption spectroscopy measurements are reported of the absolute number density (3.0 ± 0.9 × 10 12 cm −3) and vibrational temperature (3000 ± 500 K) of C 2(X 1Σ g +) radicals in a DC arc activated chemical vapour deposition reactor under the standard operating conditions (3.3% CH 4 in H 2 and 6.4 kW discharge) used to grow polycrystalline diamond films. The ratio of number densities of C 2 radicals in their ground (X 1Σ g +) and low-lying electronically excited (a 3Π u) states is close to that expected from a Boltzmann distribution at the measured temperature, despite the more rapid rates of reaction of C 2(X) with H 2 and hydrocarbon molecules.

Effects of Geomagnetic and Solar Activities on the Composition and Position of the Ring Current Ion

AbstractWe study the effects of the solar‐cycle and geomagnetic activities on the ring current ion composition and their maximum positions by using the energetic particle data obtained by MICS instrument on board CRRES satellite and other research results of AMPTE. Observations show that the number density ratio and energy density ratio of O+, He+ + and He+ ions to the total ring current all show an increase during geomagnetic active times, whereas that of H+ ions exhibits an obvious decrease. Compared with AMPTE observations in the solar minimum, the abundance of ring current H+ ions is apparently lower in the solar maximum than that during solar minimum. In contrast, the abundance of both O+ and He+ + ions are higher. CRRES data also show that, in addition to the inward motion of the position of the maximum flux of O+ and He+ during a geomagnetic storm, the location of the maximum number density of the energetic ions is about 0.5 RE lower in solar maximum than that in solar minimum.

Relic Densities for Kaluza–Klein Dark Matter

We consider the lightest Kaluza–Klein particle in universal extra dimensions (UED) to be a possible candidate for cold dark matter (CDM). We compute the relic densities for such Kaluza–Klein dark matter. This is done by first solving Boltzmann equation numerically to obtain freeze-out temperature and the ratio of number density and entropy density, for different masses. The relic densities (Ωh2) are then computed to find their variation with CDM masses. These calculations are performed considering two coannihilation channels namely B1 B1 → e+e- and B1 B1 → qq.

Consequences of the Solar System passage through dense interstellar clouds

Abstract. Several consequences of the passage of the solar system through dense interstellar molecular clouds are discussed. These clouds, dense (more than 100 cm-3), cold (10–50 K) and extended (larger than 1 pc), are characterized by a gas-to-dust mass ratio of about 100, by a specific power grain size spectrum (grain radii usually cover the range 0.001–3 micron) and by an average dust-to-gas number density ratio of about 10-12. Frequently these clouds contain small-scale (10–100 AU) condensations with gas concentrations ranging up to 10 5 cm-3. At their casual passage over the solar system they exert pressures very much enhanced with respect to today’s standards. Under these conditions it will occur that the Earth is exposed directly to the interstellar flow. It is shown first that even close to the Sun, at 1 AU, the cloud’s matter is only partly ionized and should mainly interact with the solar wind by charge exchange processes. Dust particles of the cloud serve as a source of neutrals, generated by the solar UV irradiation of dust grains, causing the evaporation of icy materials. The release of neutral atoms from dust grains is then followed by strong influences on the solar wind plasma flow. The behavior of the neutral gas inflow parameters is investigated by a 2-D hydrodynamic approach to model the interaction processes. Because of a reduction of the heliospheric dimension down to 1 AU, direct influence of the cloud’s matter to the terrestrial environment and atmosphere could be envisaged.Key words. Interplanetary physics (heliopause and solar wind termination; interplanetary dust; interstellar gas)

Disintegration of planar liquid film impacted by two-dimensional gas jets

The distortion and break-up of a thin planar liquid film impacted by two gas jets while discharging from a twin-fluid atomizer is studied numerically. The gas momentum vector has components normal and parallel to the liquid stream. Viscosity and compressibility are neglected in both the liquid phase and the gas phase. The reduced-dimension (lubrication) approximation is employed to describe the nonlinear distortion and breakup of the thin film. The gas-phase dynamics are modelled by using a boundary-element-method formulation. For the considered parameter range and for a given energy expenditure, direct modulation of liquid-phase velocities at the nozzle exit is found to be more effective in causing film rupture than indirect modulation via adjacent impacting gas jets. In the former case, dilational film modulation results in shorter breakup lengths than sinuous modulation. On the other hand, for gas-jet modulated films, sinuous mode forcing is more effective than dilational forcing for the same energy input. Co-flowing gas streams significantly alter wavelengths and amplitudes of film disturbances generated by direct film modulation. Large ratios of gas-jet momentum to liquid-film momentum result in “immediate” film rupture in response to the dynamics of the impacting gas jets, whereas for lower ratios films disintegration occurs further downstream after continuous growth of the initial disturbances. Film distortion is characterized by the formation of fluid blobs or long band-like films depending on Weber number values and density ratio.

Polyelectrolytes at Charged Particles: Particle Number Density, Molecular Weight, and Charge Ratio Effects

The effect of molecular weight, particle number density, and charge ratio on the colloidal behavior of positively charged polystyrene particles (PSA) in the presence of the natural polyanion carboxymethyl cellulose (CMC) was investigated by zeta potential and light scattering measurements. For low ionic strength, a phase diagram with three distinct regimes was proposed. Flocculation is favored for R values close to 1, where R is the ratio of the total negative charge (Ntn) to the total positive charge (Ntp). Colloidal stabilization is achieved in the R range of 2.5−200 and with polyelectrolytes chain length smaller than the critical chain length (Lcrit), which is the contour length corresponding to the particle mean perimeter. For R values larger than 200, isolated particles and/or doublets are present in the dispersion and with polyelectrolytes chain length smaller than Lcrit, whereas doublets and/or aggregates are observed when the polyelectrolytes chain length is larger than Lcrit. The effect of the particle number density on the colloidal stabilization was weak. The adsorption behavior of CMC onto PSA particles was not comparable to that of CMC onto PSA films.

HiNarrow Self‐Absorption in Dark Clouds

We have used the Arecibo telescope to carry out a survey of 31 dark clouds in the Taurus/Perseus region for narrow absorption features in H I (21 cm) and OH (1667 and 1665 MHz) emission. We detected H I narrow self-absorption (HINSA) in 77% of the clouds that we observed. HINSA and OH emission, observed simultaneously, are remarkably well correlated. Spectrally, they have the same nonthermal line width and the same line centroid velocity. Spatially, they both peak at the optically selected central position of each cloud, and both fall off toward the cloud edges. Sources with clear HINSA features have also been observed in transitions of CO, 13CO, C18O, and C I. HINSA exhibits better correlation with molecular tracers than with C I. The line width of the absorption feature, together with analyses of the relevant radiative transfer, provides upper limits to the kinetic temperature of the gas producing the HINSA. Some sources must have a temperature close to or lower than 10 K. The correlation of column densities and line widths of HINSA with those characteristics of molecular tracers suggests that a significant fraction of the atomic hydrogen is located in the cold, well-shielded portions of molecular clouds and is mixed with the molecular gas. The average number density ratio [H I]/[H2] is 1.5 × 10-3. The inferred H I density appears consistent with, but slightly higher than, the value expected in steady state equilibrium between formation of H I via cosmic-ray destruction of H2 and destruction via formation of H2 on grain surfaces. The distribution and abundance of atomic hydrogen in molecular clouds are critical tests of dark cloud chemistry and structure, including the issues of grain surface reaction rates, PDRs, circulation, and turbulent diffusion.

Effect of geometric anisotropy on optical nonlinearity enhancement for periodic composites

The effect of geometric anisotropy on the optical nonlinearity enhancement for the composites with metal or semiconductor spheriodal-shaped particles periodically in an insulating host is investigated. The frequency dependences of effective nonlinear susceptibility are calculated with the Stroud-Hui relation and a series expression of space-dependent electric field in periodic composites. The results show that for both metal-insulator (MI) and semiconductor-insulator (SI) composites, nonlinearity enhancement increases almost to its maximum when the percolation networks of the inclusion phase form. The nonlinearity enhancement increases to its maximum when the composites are transformed into the Boyd-Sipe layered composites. The behavior of the nonlinearity enhancement near the percolation threshold is also investigated. A local minimum appears in the nonlinear optical responses at the percolation threshold for the MI composites. For the SI composites the local minimum appears when the ratio of the bound-electron number density to the effective mass of the electron is large.

Optical nonlinearity enhancement of a periodic array of semiconductor elliptical cylinders

We investigate the effect of geometric anisotropy on optical nonlinearity enhancement for composites with semiconductor elliptical cylinders in an insulating host in a square lattice. The frequency dependences of the effective nonlinear susceptibility are calculated, and the optical nonlinearity of the composites near the percolation threshold are studied. The calculations are based on the Stroud–Hui relation and a series expression of the space-dependent electric field in periodic composites. The results show that, analogous to metal–insulator composites, a local minimum appears in the nonlinear optical responses near the percolation threshold for two-dimensional percolating semiconductor–insulator composites with geometric anisotropy when the ratio of the bound-electron number density to the effective mass of the electron is large. The results also show that the nonlinearity enhancement increases almost to its maximum when a structure with layers of fluctuating thicknesses forms, and there are no further obvious increases of the enhancement when the thickness fluctuation of the layers decreases. We compare the results of our calculation with those calculated by use of the Boyd–Sipe relation in layered composites, and we conclude that the nonlinearity enhancement reaches its maximum when composites with elliptic cylinders are transformed into Boyd–Sipe-type layered composites.

Baryogenesis via lepton number violation and family replicated gauge group

We developed a previous model fitting all quark and lepton—including neutrino quantities in the region of the Large Mixing Angle-MSW solar solution—order of magnitudewise by only six adjustable parameters (Higgs vacuum expectation values) to also give an agreeing prediction for the amount of baryogenesis produced in the early time of cosmology. We use Fukugita–Yanagida scheme and take into account now also the effect of the remormalisation equation for the Dirac neutrino sector from Planck scale to the see-saw scale. The present version of our model with many approximately conserved (gauge) charges distinguishing various left- and right-Weyl particles has the largest matrix element of the mass matrix for the three flavour see-saw neutrinos being the off-diagonal elements associated with the second- and third-proto-flavour and gives the ratio of baryon number density to the entropy density to 2.59 +17.0 −2.25×10 −11 which agrees perfectly well as do also all the fermion masses and their mixing angles order of magnitudewise.

AN UNSTEADY CONDUCTION AND TWO-PHASE RADIATION IN A 2-D RECTANGULAR ENCLOSURE WITH GAS AND PARTICLES

A problem of combined conductive and two-phase radiative heat transfer in a two-dimensional rectangular enclosure with two-phase (gas-particles) media is analyzed. A two-phase radiative transfer equation (RTE) considering radiation by both gas and particles is studied. Its nonlinear integrodifferential RTE is solved using the discrete ordinates method (DOM, or so-called S N method). To validate the program, we compare the solution in a two-dimensional rectangular black enclosure with others. The DOM is then applied to the unsteady thermal development in two-phase media contained in a rectangular enclosure. A parametric study is performed by changing the gas and particle absorption coefficients, particle number density, particle emissivity, wall emissivity, and aspect ratio of the enclosure. The results confirm a significant effect of the two-phase radiation on the thermal development in the geometry. However, it is found that the conduction is predominant near the hot wall.

The Measurement of Condensation Coefficient of Methanol Vapor in Nonequilibrium States by a Temperature-Controllable Shock Tube.

A shock tube available in a state from initially normal to high temperatures is made and it is used for the measurement of the growth of a liquid film formed on the endwall surface of the tube in a shock wave reflection region. It is found that the shock tube satisfies requirements for the experiment and the liquid film grows uniformly on the wall surface at an initially high temperature. The condensation coefficient of methanol vapor is determined from the growth of liquid films at initially normal temperatures (286.3 K∼299.6 K) and higher ones (323.3 K∼324.4 K). It is clarified that the condensation coefficient is strongly dependent on both by the ratio of vapor and liquid temperatures and by the ratio of number densities of vapor and saturated vapor at the vapor/liquid interface. For the same temperature and number density ratios, the higher is the liquid temperature, the smaller becomes the condensation coefficient, and it decreases with the increase of the number density ratio.

Ion composition aspects of magnetotail plasma flows

Recent archiving of energetic (<18 keV/e) ion composition data from the ISEE 1 satellite has created a 4.5‐year World Wide Web based set well suited for statistical investigations of magnetospheric plasmas inside of 23 RE, especially with regard to signatures of solar (He++) or terrestrial (O+) origins. This is an application that investigates tail ion flows in the 10–23 RE radial range, specifically the (spacecraft spin plane) GSE x and y flows of H+, He++, and O+ ions in the 0.1–16 keV/e energy range. The plasma sheet is divided into (1) “high,” (2) “intermediate,” and (3) “low” latitude regions based on magnetic field GSE elevation angle λ and ion beta (sum of H+, He++, He+, and O+ ions), such that regions 1 and 2 both have , , with region 1 being at β < 0.1 and region 2 being at β > 0.1, and region 3 has and β > 0.1. A fourth region has remaining plasma sheet samples (30%). In region 1 the most common drift is within ±30° of the tailward magnetic field direction for all ions, including, somewhat surprisingly, the He++ ions (about half the time). Tailward drift speeds (<100 km s−1) are substantially smaller than thermal speeds (∼500 km s−1) for both He++ and H+ ions. Only the O+ ions have a net field‐aligned (and tailward) distribution . On average, the He++/H+ number density and mean energy ratios are ∼4% and ∼4, respectively, indicating a mostly solar origin of both species. The second most common drift of He++ and H+ ions (∼20%) is aligned near the earthward field direction and has the largest speeds (>100 km s−1). It also has velocity dispersion, however, and seems to be associated with the leading edge of intermittent bursts of ions expanding earthward from the downtail plasma sheet. Superimposed on these drifts is E × B drift of varying speed and direction, which has a net average of the order of 10 km s−1 toward local midnight, away from the tail flanks. Comparing times (2‐hour intervals) of northward and southward interplanetary magnetic field, drift speeds are some 50% larger in the southward case, and thermal speeds are 10–20% larger. In region 2, drifts are more random in direction and somewhat slower, whereas thermal speeds are 30–50% larger than in region 1. Only the O+ ions maintain dominantly tailward (field‐aligned) drift. The average E × B drift is reversed, away from local midnight, but still of the order of 10 km s−1. In region 3, average E × B drift is sunward and away from midnight. Sunward drift occurs ∼2.5 times more often than tailward drift with northward interplanetary magnetic field and almost 8 times more often with southward interplanetary magnetic field. Comparing all four regions, tailward flows of H+ and He++ ions in region 1 can account for some but only part (≤30%) of the sunward flows at lower latitude, implying that solar ions enter the plasma sheet both tailward and sunward of the ISEE 1.

Observation Examples of the Neutral Atmos‐Phere Lifting in the Thermosphere During Period of Magnetic Storms

AbstractUsing neutral atmospheric data from the satellite AE‐D, number density ratios of n(He)/n(N2), n(O)/n(N2) and n(Ar)/n(N2), and their variations during magnetic storms in November, 1975 are analyzed. The results indicate that the response of atmospheric compositions to the geomagnetic heating is basically coincided with that expected from related theory. The lifting of the neutral atmosphere with higher proportion of heavier compositions (such as N2 and Ar) will lead to a relative decreasing of the concentration of lighter compositions (such as He and O), meanwhile the volume percentage of heavier ones will increase largely. During strong storms, the ratio of n(He)/n(N2) decreases larger than one order of magnitude at 140‐160 km and the value of n(Ar)/n(N2) increases more evidently, as compared with that during magnetic quiet days. The variation amplitude of the ratios varies with altitude, but their developing tendencies as function of storm time are keeping similar at different heights.

Effects of Dust on Amplitude Modulation of Kinetic Alfvén Waves

Effects of dust on the amplitude modulation of two possible types of kinetic Alfvén waves, modified and dust kinetic Alfvén waves, in a magnetized dusty plasma have been investigated. The appropriate nonlinear dispersion relations of the amplitude modulation predict that the carrier kinetic Alfvén waves are modulationally unstable for long wave-length perturbations. It has been found that the parameter σ plays a significant role on the amplitude modulation of the waves, where σ is the ratio of the equilibrium number densities of the ions and the electrons and is a measure of the charge carried by the dust component. The maximum growth rate of the modulational instability increases with the parameter σ, whereas, the range of the perpendicular component of the modulation wavenumber K⊥ of the unstable wave remains almost constant for the case of dust kinetic Alfvén waves. On the other hand, the maximum growth rate is almost constant with σ, while the range of K⊥ of the unstable wave drastically decreases for the case of modified kinetic Alfvén waves.

In situ observations of aerosol properties above ice saturation in the polar tropopause region

In the polar winter tropopause region (T≅ 200 K, p = 200 hPa) over northern Europe, the occurrence of a haze‐mode aerosol in the diameter range 0.75 μm <D < 10 μm was frequently observed during airborne in situ measurements of aerosol properties. In ascending air parcels the haze mode was detected as soon as a water saturation ratio Swν = 0.5 (Sice ≅ 1.0) was exceeded. Larger cirrus particles with size D > 10 μm where found in regions with Swν > 0.57 (Sice ≥ 1.17). Hence, a range of Swν values existed between 0.5 and 0.57, where the haze mode was present outside of cirrus clouds. The ratio of number densities of haze‐mode particles to Aitken‐mode particles reached ∼1.25% inside and <0.3% outside of ice‐supersaturated regions. In descending air parcels a continuous decrease in the number density of haze‐mode particles was observed. This suggests a deliquescence transition in rising air parcels and evaporation of liquid haze droplets without recrystallization in sinking air parcels. Consideration of the possible chemical composition, phase, and growth timescales of the haze‐mode particles leads to the conclusion that they are likely to contain ammoniated sulfates in the liquid phase. On the basis of measured particle sizes and calculated extinction values, the observed haze mode may be a candidate for subvisible cirrus cloud particles.

Variation of mesospheric ozone during the highly relativistic electron event in May 1992 as measured by the High Resolution Doppler Imager instrument on UARS

Highly relativistic electron precipitation events (HREs) include long‐lived enhancements of the flux of electrons with E > 1 MeV into the Earth's atmosphere. HREs also contain increased fluxes of electrons with energies above 100 keV that have been predicted to cause large depletions of mesospheric ozone. For some of the measured instantaneous values of the electron fluxes during the HRE of May 1992, relative depletions greater than 22% were predicted to occur between altitudes of 55 and 80 km, where HOx reactions cause local minima in both the ozone number density and mixing ratio altitude profiles. These ozone depletions should follow the horizontal distribution of the electron precipitation, having a distinct boundary equatorward of the L = 3 magnetic shell. To search for these effects, we have analyzed ozone data from the High Resolution Doppler Imager (HRDI) instrument on UARS. Owing to the multiple, off‐track viewing angles of HRDI, observations in the region affected by the electrons are taken at similar local solar times before, during, and after the electron flux increase. Our analysis limits the relative ozone depletion to values < 10% during the very intense May 1992 HRE. We do observe decreases in the ozone mixing ratio at several points in the diurnal cycle that may be associated with the transport of water vapor into the mesosphere during May 1992. This masking of the precipitating electron effects by the seasonal variations in water vapor can complicate the detection of those effects.

A possible steady state kinetic model for the atomization and excitation processes during inductively coupled plasma atomic emission spectrometry: application to interference effects of lithium on calcium.

A possible steady state kinetic model is presented for the atomization and excitation processes during inductively coupled plasma atomic emission spectrometry. The model takes into account the relative rates of (a) thermal dissociation of analyte salt, (b) recombination of counter atom and analyte atoms, (c) charge transfer between analyte and interferent species, (d) charge transfer between analyte and argon species, and (e) ion/electron collisional de-ionization. Number density ratio data, n(u)'/n(u), where n(u) denotes the excited state and the prime denotes the presence of an interferent element, are presented showing that the predictions of the model are consistent with the signal enhancement observed at low analyte concentrations when Ca is determined by ICP in the presence of excess Li.

Partitioning of Alkane and Alcohol Solutes between Water and (Dry or Wet) 1-Octanol

Configurational-bias Monte Carlo simulations in the Gibbs ensemble using the OPLS (optimized potentials for liquid simulations) force field were performed to study the partitioning of normal alkane and primary alcohol solutes between water, neat or water-saturated 1-octanol, and helium vapor phases. Precise values of the Gibbs free energy of transfer were calculated directly from the ratio of the solute number densities in the two co-existing phases. It is observed that the OPLS force field yields Gibbs free energies of transfer that are in qualitative, albeit not quantitative, agreement with experimental results. Comparison of the partitioning between a helium vapor and dry or wet 1-octanol phases established that water saturation affects mostly the partitioning of polar solutes, while differences for alkane partitioning were found to be negligible. In addition, the analysis of radial distribution functions of alcohol solutes in wet 1-octanol shows preferential partitioning into water-rich regions of the...