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Sample records for spinning dust radiation

  1. A new spin on primordial hydrogen recombination and a refined model for spinning dust radiation

    NASA Astrophysics Data System (ADS)

    Ali-Haimoud, Yacine

    2011-08-01

    This thesis describes theoretical calculations in two subjects: the primordial recombination of the electron-proton plasma about 400,000 years after the Big Bang and electric dipole radiation from spinning dust grains in the present-day interstellar medium. Primordial hydrogen recombination has recently been the subject of a renewed attention because of the impact of its theoretical uncertainties on predicted cosmic microwave background (CMB) anisotropy power spectra. The physics of the primordial recombination problem can be divided into two qualitatively different aspects. On the one hand, a detailed treatment of the non-thermal radiation field in the optically thick Lyman lines is required for an accurate recombination history near the peak of the visibility function. On the other hand, stimulated recombinations and out-of equilibrium effects are important at late times and a multilevel calculation is required to correctly compute the low-redshift end of the ionization history. Another facet of the problem is the requirement of computational efficiency, as a large number of recombination histories must be evaluated in Markov chains when analyzing CMB data. In this thesis, an effective multilevel atom method is presented, that speeds up multilevel atom computations by more than 5 orders of magnitude. The impact of previously ignored radiative transfer effects is quantified, and explicitly shown to be negligible. Finally, the numerical implementation of a fast and highly accurate primordial recombination code partly written by the author is described. The second part of this thesis is devoted to one of the potential galactic foregrounds for CMB experiments: the rotational emission from small dust grains. The rotational state of dust grains is described, first classically, and assuming that grains are rotating about their axis of greatest inertia. This assumption is then lifted, and a quantum-mechanical calculation is presented for disk-like grains with a

  2. The spin of cosmic dust: Rotational bursting of circumsolar dust in the F corona

    NASA Astrophysics Data System (ADS)

    Misconi, Nebil Y.

    1993-11-01

    This paper will list, investigate, and evaluate the various spin mechanisms for cosmic dust particles that have been suggested in the literature. This evaluation will concentrate on the possibility of particle fragmentation (rotational bursting) of cosmic dust. The importance of partical fragmentation is manifested by the fact that dust particle size distribution will be changed. More importantly, repeated fragmentation of interplanetary dust particles will give rise to some of the observed 'beta meteoroids.' Some of these particles are driven out of the solar system and into interstellar space by solar radiation pressure. If this mass loss mechanism is taking place in stellar systems, then it becomes a source for interstellar dust. This paper also addresses the possibility that massive rotational bursting by circumsolar dust particles is taking place in the F corona region. This rotational bursting of F coronal dust could be taking place because of the classical 'Paddack effect,' along with a similar spin mechanism suggested by the author, and caused by coronal mass ejections.

  3. AKARI and Spinning Dust: A look at microwave dust emission via the Infrared

    NASA Astrophysics Data System (ADS)

    Bell, Aaron Christopher; Onaka, Takashi; Wu, Ronin; Doi, Yasuo

    2015-08-01

    Rapidly spinning dust particles having a permanent electric dipole moment have been shown to be a likely carrier of the anomalous microwave emission (AME), a continuous excess of microwave flux in the 10 to 90 GHz range. Small grains, possibly polycyclic aromatic hydrocarbons (PAHs), are a leading suspect. Due to the overlap frequency overlap with the CMB, the AME is requiring cosmologists to consider the ISM with more care. ISM astronomers are also needing to consider the contribution of cosmological radiation to large-scale dust investigations. We present data from AKARI/Infrared Camera (IRC) due to the effective PAH band coverage of its 9 um survey to investigate PAH emission within 98 AME candidate regions identified by Planck Collaboration et al. (2014). We supplement AKARI data with the four Infrared Astronomical Satellite (IRAS) all-sky maps and complement with the Planck High Frequency Instrument (HFI) bands at 857 and 545GHz to constrain the full dust SED. We sample analyse the SEDs of all 98 regions. We utilize all 7 AKARI photometric bands, as well as the 4 IRAS bands and 2 HFI. We carry out a modified blackbody fitting, and estimate the optical depth of thermal dust at 250 um, and compare this to AME parameters. We also show plots of each band's average intensity for all 98 regions vs. AME parameters. We find a positive trend between the optical depth and AME. In the band-by-band comparison the AKARI 9 um intensity shows a weaker trend with AME. In general, the MIR correlates less strongly with AME than the FIR. The optical depth vs. AME trend improves slightly when looking only at significant AME regions. Scaling the IR intensities by the ISRF strength G0 does not improve the correlations. We cannot offer strong support of a spinning dust model. The results highlight the need for full dust SED modelling, and for a better understanding of the role that magnetic dipole emission from dust grains could play in producing the AME.

  4. Planck early results. XX. New light on anomalous microwave emission from spinning dust grains

    NASA Astrophysics Data System (ADS)

    Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Arnaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Balbi, A.; Banday, A. J.; Barreiro, R. B.; Bartlett, J. G.; Battaner, E.; Benabed, K.; Benoît, A.; Bernard, J.-P.; Bersanelli, M.; Bhatia, R.; Bock, J. J.; Bonaldi, A.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Bucher, M.; Burigana, C.; Cabella, P.; Cappellini, B.; Cardoso, J.-F.; Casassus, S.; Catalano, A.; Cayón, L.; Challinor, A.; Chamballu, A.; Chary, R.-R.; Chen, X.; Chiang, L.-Y.; Chiang, C.; Christensen, P. R.; Clements, D. L.; Colombi, S.; Couchot, F.; Coulais, A.; Crill, B. P.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Gasperis, G.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Delouis, J.-M.; Dickinson, C.; Donzelli, S.; Doré, O.; Dörl, U.; Douspis, M.; Dupac, X.; Efstathiou, G.; Enßlin, T. A.; Eriksen, H. K.; Finelli, F.; Forni, O.; Frailis, M.; Franceschi, E.; Galeotta, S.; Ganga, K.; Génova-Santos, R. T.; Giard, M.; Giardino, G.; Giraud-Héraud, Y.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Hansen, F. K.; Harrison, D.; Helou, G.; Henrot-Versillé, S.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hovest, W.; Hoyland, R. J.; Huffenberger, K. M.; Jaffe, T. R.; Jaffe, A. H.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knox, L.; Kurki-Suonio, H.; Lagache, G.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Laureijs, R. J.; Lawrence, C. R.; Leach, S.; Leonardi, R.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; MacTavish, C. J.; Maffei, B.; Maino, D.; Mandolesi, N.; Mann, R.; Maris, M.; Marshall, D. J.; Martínez-González, E.; Masi, S.; Matarrese, S.; Matthai, F.; Mazzotta, P.; McGehee, P.; Meinhold, P. R.; Melchiorri, A.; Mendes, L.; Mennella, A.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, A.; Naselsky, P.; Natoli, P.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; O'Dwyer, I. J.; Osborne, S.; Pajot, F.; Paladini, R.; Partridge, B.; Pasian, F.; Patanchon, G.; Pearson, T. J.; Peel, M.; Perdereau, O.; Perotto, L.; Perrotta, F.; Piacentini, F.; Piat, M.; Plaszczynski, S.; Platania, P.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Poutanen, T.; Prézeau, G.; Procopio, P.; Prunet, S.; Puget, J.-L.; Reach, W. T.; Rebolo, R.; Reich, W.; Reinecke, M.; Renault, C.; Ricciardi, S.; Riller, T.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rowan-Robinson, M.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Santos, D.; Savini, G.; Scott, D.; Seiffert, M. D.; Shellard, P.; Smoot, G. F.; Starck, J.-L.; Stivoli, F.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Torre, J.-P.; Tristram, M.; Tuovinen, J.; Umana, G.; Valenziano, L.; Varis, J.; Verstraete, L.; Vielva, P.; Villa, F.; Vittorio, N.; Wade, L. A.; Wandelt, B. D.; Watson, R.; Wilkinson, A.; Ysard, N.; Yvon, D.; Zacchei, A.; Zonca, A.

    2011-12-01

    Anomalous microwave emission (AME) has been observed by numerous experiments in the frequency range ~10-60 GHz. Using Planck maps and multi-frequency ancillary data, we have constructed spectra for two known AME regions: the Perseus and ρ Ophiuchi molecular clouds. The spectra are well fitted by a combination of free-free radiation, cosmic microwave background, thermal dust, and electric dipole radiation from small spinning dust grains. The spinning dust spectra are the most precisely measured to date, and show the high frequency side clearly for the first time. The spectra have a peak in the range 20-40 GHz and are detected at high significances of 17.1σ for Perseus and 8.4σ for ρ Ophiuchi. In Perseus, spinning dust in the dense molecular gas can account for most of the AME; the low density atomic gas appears to play a minor role. In ρ Ophiuchi, the ~30 GHz peak is dominated by dense molecular gas, but there is an indication of an extended tail at frequencies 50-100 GHz, which can be accounted for by irradiated low density atomic gas. The dust parameters are consistent with those derived from other measurements. We have also searched the Planck map at 28.5 GHz for candidate AME regions, by subtracting a simple model of the synchrotron, free-free, and thermal dust. We present spectra for two of the candidates; S140 and S235 are bright Hii regions that show evidence for AME, and are well fitted by spinning dust models. Corresponding author: C. Dickinson, Clive.Dickinson@manchester.ac.uk

  5. Re-Evaluation of Dust Radiative Forcing Using Remote Measurements of Dust Absorption

    NASA Technical Reports Server (NTRS)

    Kaufman, Yoram J.; Tanre, Didier; Karnieli, Arnon; Remer, Lorraine A.

    1998-01-01

    Spectral remote observations of dust properties from space and from the ground creates a powerful tool for determination of dust absorption of solar radiation with an unprecedented accuracy. Absorption is a key component in understanding dust impact on climate. We use Landsat spaceborne measurements at 0.47 to 2.2 microns over Senegal with ground based sunphotometers to find that Saharan dust absorption of solar radiation is two to four times smaller than in models. Though dust absorbs in the blue, almost no absorption was found for wavelengths greater 0.6 microns. The new finding increases by 50% recent estimated solar radiative forcing by dust and decreases the estimated dust heating of the lower troposphere. Dust transported from Asia shows slightly higher absorption probably due to the presence of black carbon from populated regions. Large scale application of this method to satellite data from the Earth Observing System can reduce significantly the uncertainty in the dust radiative effects.

  6. OT2_ctibbs_1: Exploring the role of CII in current Spinning Dust Models

    NASA Astrophysics Data System (ADS)

    Tibbs, C.

    2011-09-01

    We propose HIFI observations of the CII fine structure line at 158 micron (1.9THz) in 22 pointings distributed across four Galactic anomalous emission regions (the Perseus cloud, LDN 1780, LDN 675 and LDN 1111). The currently favoured explanation for the observed anomalous microwave emission is that of electric dipole radiation from rapidly rotating small dust grains (PAHs and/or VSGs), commonly referred to as spinning dust. Although this hypothesis predicts that the source of the excess emission is due to dust, the small dust grains are sensitive to the ionisation state of the gas, and hence the spinning dust models have a dependancy on the abundance of the major gas ions. CII observations will enable us to investigate this dependancy, and combining these observations with the available mid- to far-IR observations will permit a complete analysis of the role of both the dust and gas in regions of anomalous emission. We request a total of 14.9 hrs of HIFI observing time.

  7. Sunrise: Radiation transfer through interstellar dust

    NASA Astrophysics Data System (ADS)

    Jonsson, Patrik

    2013-03-01

    Sunrise is a Monte Carlo radiation transfer code for calculating absorption and scattering of light to study the effects of dust in hydrodynamic simulations of interacting galaxies. It uses an adaptive mesh refinement grid to describe arbitrary geometries of emitting and absorbing/scattering media, with spatial dynamical range exceeding 104; it can efficiently generate images of the emerging radiation at arbitrary points in space and spectral energy distributions of simulated galaxies run with the Gadget, Gasoline, Arepo, Enzo or ART codes. In addition to the monochromatic radiative transfer typically used by Monte Carlo codes, Sunrise can propagate a range of wavelengths simultaneously. This "polychromatic" algorithm gives significant improvements in efficiency and accuracy when spectral features are calculated.

  8. Constraint on the Polarization of Electric Dipole Emission from Spinning Dust

    NASA Astrophysics Data System (ADS)

    Hoang, Thiem; Lazarian, A.; Martin, P. G.

    2013-12-01

    Planck results have revealed that the electric dipole emission from polycyclic aromatic hydrocarbons (PAHs) is the most reliable explanation for the anomalous microwave emission that interferes with cosmic microwave background (CMB) radiation experiments. The emerging question is to what extent this emission component contaminates the polarized CMB radiation. We present constraints on polarized dust emission for the model of grain-size distribution and grain alignment that best fits the observed extinction and polarization curves. Two stars with a prominent polarization feature at λ = 2175 Å—HD 197770 and HD 147933-4—are chosen for our study. For HD 197770, we find that the model with aligned silicate grains plus weakly aligned PAHs can successfully reproduce the 2175 Å polarization feature; in contrast, for HD 147933-4, we find that the alignment of only silicate grains can account for that feature. The alignment function of PAHs for the best-fit model to the HD 197770 data is used to constrain polarized spinning dust emission. We find that the degree of polarization of spinning dust emission is about 1.6% at frequency ν ≈ 3 GHz and declines to below 0.9% for ν > 20 GHz. We also predict the degree of polarization of thermal dust emission at 353 GHz to be P em ≈ 11% and 14% for the lines of sight to the HD 197770 and HD 147933-4 stars, respectively.

  9. Quantum dust magnetosonic waves with spin and exchange correlation effects

    SciTech Connect

    Maroof, R.; Qamar, A.; Mushtaq, A.

    2016-01-15

    Dust magnetosonic waves are studied in degenerate dusty plasmas with spin and exchange correlation effects. Using the fluid equations of magnetoplasma with quantum corrections due to the Bohm potential, temperature degeneracy, spin magnetization energy, and exchange correlation, a generalized dispersion relation is derived. Spin effects are incorporated via spin force and macroscopic spin magnetization current. The exchange-correlation potentials are used, based on the adiabatic local-density approximation, and can be described as a function of the electron density. For three different values of angle, the dispersion relation is reduced to three different modes under the low frequency magnetohydrodynamic assumptions. It is found that the effects of quantum corrections in the presence of dust concentration significantly modify the dispersive properties of these modes. The results are useful for understanding numerous collective phenomena in quantum plasmas, such as those in compact astrophysical objects (e.g., the cores of white dwarf stars and giant planets) and in plasma-assisted nanotechnology (e.g., quantum diodes, quantum free-electron lasers, etc.)

  10. Quantum dust magnetosonic waves with spin and exchange correlation effects

    NASA Astrophysics Data System (ADS)

    Maroof, R.; Mushtaq, A.; Qamar, A.

    2016-01-01

    Dust magnetosonic waves are studied in degenerate dusty plasmas with spin and exchange correlation effects. Using the fluid equations of magnetoplasma with quantum corrections due to the Bohm potential, temperature degeneracy, spin magnetization energy, and exchange correlation, a generalized dispersion relation is derived. Spin effects are incorporated via spin force and macroscopic spin magnetization current. The exchange-correlation potentials are used, based on the adiabatic local-density approximation, and can be described as a function of the electron density. For three different values of angle, the dispersion relation is reduced to three different modes under the low frequency magnetohydrodynamic assumptions. It is found that the effects of quantum corrections in the presence of dust concentration significantly modify the dispersive properties of these modes. The results are useful for understanding numerous collective phenomena in quantum plasmas, such as those in compact astrophysical objects (e.g., the cores of white dwarf stars and giant planets) and in plasma-assisted nanotechnology (e.g., quantum diodes, quantum free-electron lasers, etc.).

  11. Axial dissipative dust as a source of gravitational radiation in f(R) gravity

    NASA Astrophysics Data System (ADS)

    Sharif, M.; Siddiqa, Aisha

    2017-03-01

    In this paper, we explore the source of gravitational radiation in the context of f(R) gravity by considering axially symmetric dissipative dust under geodesic condition. We evaluate scalars associated with electric and magnetic parts of the Weyl tensor for both non-spinning (at the center) and spinning (in the surrounding of the center) fluids of the configuration. For this purpose, we use the evolution as well as constraint equations for kinematical quantities and Weyl tensor. Finally, we investigate the existence of gravitational radiation through super-Poynting vector. It is found that the fluid is not gravitationally radiating in the non-spinning case but it is gravitationally radiating for the spinning case.

  12. Active Dust Mitigation Technology for Thermal Radiators for Lunar Exploration

    NASA Technical Reports Server (NTRS)

    Calle, C. I.; Buhler, C. R.; Hogue, M. D.; Johansen, M. R.; Hopkins, J. W.; Holloway, N. M. H.; Connell, J. W.; Chen, A.; Irwin, S. A.; Case, S. O.; hide

    2010-01-01

    Dust accumulation on thermal radiator surfaces planned for lunar exploration will significantly reduce their efficiency. Evidence from the Apollo missions shows that an insulating layer of dust accumulated on radiator surfaces could not be removed and caused serious thermal control problems. Temperatures measured at different locations in the magnetometer on Apollo 12 were 38 C warmer than expected due to lunar dust accumulation. In this paper, we report on the application of the Electrodynamic Dust Shield (EDS) technology being developed in our NASA laboratory and applied to thermal radiator surfaces. The EDS uses electrostatic and dielectrophoretic forces generated by a grid of electrodes running a 2 micro A electric current to remove dust particles from surfaces. Working prototypes of EDS systems on solar panels and on thermal radiators have been successfully developed and tested at vacuum with clearing efficiencies above 92%. For this work EDS prototypes on flexible and rigid thermal radiators were developed and tested at vacuum.

  13. EFFICIENT THREE-DIMENSIONAL NLTE DUST RADIATIVE TRANSFER WITH SKIRT

    SciTech Connect

    Baes, Maarten; Verstappen, Joris; De Looze, Ilse; Fritz, Jacopo; Saftly, Waad; Vidal Perez, Edgardo; Stalevski, Marko; Valcke, Sander

    2011-10-01

    We present an updated version of SKIRT, a three-dimensional (3D) Monte Carlo radiative transfer code developed to simulate dusty galaxies. The main novel characteristics of the SKIRT code are the use of a stellar foam to generate random positions, an efficient combination of eternal forced scattering and continuous absorption, and a new library approach that links the radiative transfer code to the DustEM dust emission library. This approach enables a fast, accurate, and self-consistent calculation of the dust emission of arbitrary mixtures of transiently heated dust grains and polycyclic aromatic hydrocarbons, even for full 3D models containing millions of dust cells. We have demonstrated the accuracy of the SKIRT code through a set of simulations based on the edge-on spiral galaxy UGC 4754. The models we ran were gradually refined from a smooth, two-dimensional, local thermal equilibrium (LTE) model to a fully 3D model that includes non-LTE (NLTE) dust emission and a clumpy structure of the dusty interstellar medium. We find that clumpy models absorb UV and optical radiation less efficiently than smooth models with the same amount of dust, and that the dust in clumpy models is on average both cooler and less luminous. Our simulations demonstrate that, given the appropriate use of optimization techniques, it is possible to efficiently and accurately run Monte Carlo radiative transfer simulations of arbitrary 3D structures of several million dust cells, including a full calculation of the NLTE emission by arbitrary dust mixtures.

  14. Observations of the impact of a major Saharan dust storm on the atmospheric radiation balance

    SciTech Connect

    Slingo, A.; Ackerman, Thomas P.; Allan, R. P.; Kassianov, Evgueni I.; McFarlane, Sally A.; Robinson, G. J.; Barnard, James C.; Miller, Mark; Harries, J. E.; Russell, J. E.; Dewitte, S.

    2006-12-01

    Saharan dust storms transport large quantities of material across the African continent and beyond, causing widespread disruption and hazards to health. The dust may be deposited into the Atlantic Ocean, where it provides an important source of nutrients1, and may be carried as far as the West Indies. Such events may also influence the growth of Atlantic tropical cyclones. Satellite observations have enabled estimates to be made of the effect of the dust on the radiation budget seen from space, but only limited in situ observations have hitherto been made at the surface. Here we present the first simultaneous and continuous observations of the effect of a major dust storm in March 2006 on the radiation budget both at the top of the atmosphere (TOA) and at the surface. We combine data from the Geostationary Earth Radiation Budget (GERB) broadband radiometer and the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) on the Meteosat-8 weather satellite with remote sensing and in situ measurements from a new Mobile Facility located in Niamey, Niger (13{sup o} 29'N, 2{sup o} 10'E), operated by the US Atmospheric Radiation Measurement (ARM) program. We show that the dust produced major perturbations to the radiation budget seen from space and from the surface. By combining the two datasets, we estimate the impact on the radiation budget of the atmosphere itself. Using independent data from the Mobile Facility, we derive the optical properties of the dust and input these and other information into radiation codes to simulate the radiative fluxes. Comparisons with the observed fluxes provides a stringent test of the ability of the codes to represent the radiative properties of this important component of the global aerosol burden.

  15. A Multi-wavelength Investigation of RCW175: An H II Region Harboring Spinning Dust Emission

    NASA Astrophysics Data System (ADS)

    Tibbs, C. T.; Paladini, R.; Compiègne, M.; Dickinson, C.; Alves, M. I. R.; Flagey, N.; Shenoy, S.; Noriega-Crespo, A.; Carey, S.; Casassus, S.; Davies, R. D.; Davis, R. J.; Molinari, S.; Elia, D.; Pestalozzi, M.; Schisano, E.

    2012-08-01

    Using infrared, radio continuum, and spectral observations, we performed a detailed investigation of the H II region RCW175. We determined that RCW175, which actually consists of two separate H II regions, G29.1-0.7 and G29.0-0.6, is located at a distance of 3.2 ± 0.2 kpc. Based on the observations we infer that the more compact G29.0-0.6 is less evolved than G29.1-0.7 and was possibly produced as a result of the expansion of G29.1-0.7 into the surrounding interstellar medium. We compute a star formation rate for RCW175 of (12.6 ± 1.9) × 10-5 M ⊙ yr-1, and identified six possible young stellar object candidates within its vicinity. Additionally, we estimate that RCW175 contains a total dust mass of 215 ± 53 M ⊙. RCW175 has previously been identified as a source of anomalous microwave emission (AME), an excess of emission at centimeter wavelengths often attributed to electric dipole radiation from the smallest dust grains. We find that the AME previously detected in RCW175 is not correlated with the smallest dust grains (polycyclic aromatic hydrocarbons or small carbonaceous dust grains), but rather with the exciting radiation field within the region. This is a similar result to that found in the Perseus molecular cloud, another region which harbors AME, suggesting that the radiation field may play a pivotal role in the production of this new Galactic emission mechanism. Finally, we suggest that these observations may hint at the importance of understanding the role played by the major gas ions in spinning dust models.

  16. Impact of Dust Radiative Forcing upon Climate. Chapter 13

    NASA Technical Reports Server (NTRS)

    Miller, Ronald L.; Knippertz, Peter; Perez Garcia-Pando, Carlos; Perlwitz, Jan P.; Tegan, Ina

    2014-01-01

    Dust aerosols perturb the atmospheric radiative flux at both solar and thermal wavelengths, altering the energy and water cycles. The climate adjusts by redistributing energy and moisture, so that local temperature perturbations, for example, depend upon the forcing over the entire extent of the perturbed circulation. Within regions frequently mixed by deep convection, including the deep tropics, dust particles perturb the surface air temperature primarily through radiative forcing at the top of the atmosphere (TOA). Many models predict that dust reduces global precipitation. This reduction is typically attributed to the decrease of surface evaporation in response to dimming of the surface. A counterexample is presented, where greater shortwave absorption by dust increases evaporation and precipitation despite greater dimming of the surface. This is attributed to the dependence of surface evaporation upon TOA forcing through its influence upon surface temperature and humidity. Perturbations by dust to the surface wind speed and vegetation (through precipitation anomalies) feed back upon the dust aerosol concentration. The current uncertainty of radiative forcing attributed to dust and the resulting range of climate perturbations calculated by models remain a useful test of our understanding of the mechanisms relating dust radiative forcing to the climate response.

  17. Interactive Soil Dust Aerosol Model in the GISS GCM. Part 1; Sensitivity of the Soil Dust Cycle to Radiative Properties of Soil Dust Aerosols

    NASA Technical Reports Server (NTRS)

    Perlwitz, Jan; Tegen, Ina; Miller, Ron L.

    2000-01-01

    The sensitivity of the soil dust aerosol cycle to the radiative forcing by soil dust aerosols is studied. Four experiments with the NASA/GISS atmospheric general circulation model, which includes a soil dust aerosol model, are compared, all using a prescribed climatological sea surface temperature as lower boundary condition. In one experiment, dust is included as dynamic tracer only (without interacting with radiation), whereas dust interacts with radiation in the other simulations. Although the single scattering albedo of dust particles is prescribed to be globally uniform in the experiments with radiatively active dust, a different single scattering albedo is used in those experiments to estimate whether regional variations in dust optical properties, corresponding to variations in mineralogical composition among different source regions, are important for the soil dust cycle and the climate state. On a global scale, the radiative forcing by dust generally causes a reduction in the atmospheric dust load corresponding to a decreased dust source flux. That is, there is a negative feedback in the climate system due to the radiative effect of dust. The dust source flux and its changes were analyzed in more detail for the main dust source regions. This analysis shows that the reduction varies both with the season and with the single scattering albedo of the dust particles. By examining the correlation with the surface wind, it was found that the dust emission from the Saharan/Sahelian source region and from the Arabian peninsula, along with the sensitivity of the emission to the single scattering albedo of dust particles, are related to large scale circulation patterns, in particular to the trade winds during Northern Hemisphere winter and to the Indian monsoon circulation during summer. In the other regions, such relations to the large scale circulation were not found. There, the dependence of dust deflation to radiative forcing by dust particles is probably

  18. Dynamics of Cometary Dust Particles in Electromagnetic Radiation Fields

    NASA Astrophysics Data System (ADS)

    Herranen, Joonas; Markkanen, Johannes; Penttilä, Antti; Muinonen, Karri

    2016-10-01

    The formation of cometary dust tails and comae is based on solar radiation pressure. The pressure effects of electromagnetic radiation were originally conceptualized in Kepler's observations of the tails of comets and formulated mathematically by Maxwell in 1873. Today, the dynamics of cometary dust are known to be governed by gravity, electromagnetic forces, drag, solar wind, and solar radiation pressure.Solar radiation pressure has its roots in absorption, emission, and scattering of electromagnetic radiation. Due to modern advances in so-called integral equation methods in electromagnetics, a new approach of studying the effect of radiation pressure on cometary dust dynamics can be constructed. We solve the forces and torques due to radiation pressure for an arbitrarily shaped dust particle using volume integral equation methods.We then present a framework for solving the equations of motion of cometary dust particles due to radiative interactions. The solution is studied in a simplified cometary environment, where the radiative effects are studied at different orbits. The rotational and translational equations of motion are solved directly using a quaternion-based integrator. The rotational and translational equations of motion affect dust particle alignment and concentration. This is seen in the polarization of the coma. Thus, our direct dynamical approach can be used in modelling the observed imaging photo-polarimetry of the coma.In future studies, the integrator can be further extended to an exemplary comet environment, taking into account the drag, and the electric and magnetic fields. This enables us to study the dynamics of a single cometary dust particle based on fundamental physics.Acknowledgments. Research supported, in part, bythe European Research Council (ERC, grant Nr. 320773).

  19. The Effect of Martian Dust on Radiator Performance

    NASA Technical Reports Server (NTRS)

    Hollingsworth, D. Keith; Witte, Larry C.; Hinke, Jaime; Hulbert, Kathryn

    2004-01-01

    Experiments were performed in which the effective emittance of three types of radiator Coatings was measured as Martian dust simulant was added to the radiator face. The apparatus consisted of multiple radiator coupons on which Carbondale Red Clay dust was deposited. The coupons were powered by electric heaters, using a guard-heating configuration to achieve the accuracy required for acceptable emittance calculations. The apparatus was containing in a vacuum chamber that featured a liquid-nitrogen cooled shroud that simulated the Martian sky temperature. Radiator temperatures ranged from 250 to 350 K with sky temperatures from 185 to 248 K. Results show that as dust was added to the radiator surfaces, the effective emittance of the high - emittance coatings decreased from near 0.9 to a value of about 0.5. A low-emittance control surface, polished aluminum, demonstrated a rise in effective emittance for thin dust layers, and then a decline as the dust layer thickened. This behavior is attributed to the conductive resistance caused by the dust layer.

  20. Degradation of radiator performance on Mars due to dust

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Perez-Davis, Marla E.; Rutledge, Sharon K.; Forkapa, Mark

    1992-01-01

    An artificial mineral of the approximate elemental composition of Martian soil was manufactured, crushed, and sorted into four different size ranges. Dust particles from three of these size ranges were applied to arc-textured Nb-1 percent Zr and Cu radiator surfaces to assess their effect on radiator performance. Particles larger than 75 microns did not have sufficient adhesive forces to adhere to the samples at angles greater than about 27 deg. Pre-deposited dust layers were largely removed by clear wind velocities greater than 40 m/s, or by dust-laden wind velocities as low as 25 m/s. Smaller dust grains were more difficult to remove. Abrasion was found to be significant only in high velocity winds (89 m/s or greater). Dust-laden winds were found to be more abrasive than clear wind. Initially dusted samples abraded less than initially clear samples in dust laden wind. Smaller dust particles of the simulant proved to be more abrasive than large. This probably indicates that the larger particles were in fact agglomerates.

  1. The wavelength dependence of Martian atmospheric dust radiative properties

    NASA Technical Reports Server (NTRS)

    Pollack, J. B.; Ockert-Bell, M. E.; Arvidson, R.; Shepard, M.

    1993-01-01

    One of the key radiative agents in the atmosphere of Mars is the suspended dust particles. A new analysis of two data sets of the Martian atmosphere is being carried out in order to better evaluate the radiative properties of the atmospheric dust particles. The properties of interest are the size distribution, optical constants, and other radiative properties, such as the single-scattering albedo and phase function. Of prime importance is the wavelength dependence of these radiative properties throughout the visible and near-infrared wavelengths. Understanding the wavelength dependence of absorption and scattering characteristics will provide a good definition of the influence that the atmospheric dust has on heating of the atmosphere.

  2. Dust Heating by Ultraviolet Accretion Disk Radiation

    NASA Astrophysics Data System (ADS)

    Lagua, R. O.; Viegas-Aldrovandi, S. M.

    1987-05-01

    ABSTRACT. Since the first observations, the continuum of active galactic nuclei have been represented by a power law (F ). Recently, infrared and ultraviolet observations lead to the of thermal com ponents at these ranges. The Seyfert 2 galaxies show an ultraviolet excess at 10 -2O associated to thermal emission by heated dust (Neugebauer 1978, hq , 17, 149; Neugebauer, Becklin, Oke, and Searle, 1976, Ap. J., 205, 29). The extrapolation of the optical law does not provide enough ioni zing photons neither the necessary ultraviolet luminosity that explains dust heating. In this paper, we analyze the contribution of an ultraviolet accretion disk component (Malkan and Sargent 1982, Ap. J., 254, 22 (Paper I); 1983, Ap. 5., 268, 582) added to the non thermal continuum explaining the observational values of H luminosity, the intensity ratio ( /H ) and the infrared luminosity associated to thermal emission of dust grains heated by the central source. oit : GALAXIES-ACTIVE

  3. Aeolian removal of dust from radiator surfaces on Mars

    SciTech Connect

    Gaier, J.R.; Perez-Davis, M.E.; Rutledge, S.K.; Hotes, D.

    1994-09-01

    Simulated radiator surfaces made of arc-textured copper and niobium-one percent-zirconium, and ion beam textured graphite and carbon-carbon composite were fabricated and their integrated spectral emittance characterized from 300 to 3000 K. A thin layer of aluminum oxide, basalt, or iron (III) oxide dust was then deposited on them, and they were subjected to low pressure winds in the Martian Surface Wind Tunnel. It has been found that dust deposited on simulated radiator surfaces may or may not seriously lower their integrated spectral emittance, depending upon the characteristics of the dust. With Al{sub 2}O{sub 3} there is no appreciable degradation of emittance on a dusted sample, with basaltic dust there is a 10-20 percent degradation, and with Fe{sub 2}O{sub 3} a 20-40 percent degradation. It was also found that very high winds on dusted highly textured surfaces can result in their abrasion. Degradation in emittance due to abrasion was found to vary with radiator material. Arc-textured copper and Nb-1%Zr was found to be more susceptible to emittance degradation than graphite or carbon-carbon composite. The most abrasion occurred at low angles, peaking at the 22.5{degrees} test samples.

  4. Aeolian removal of dust from radiator surfaces on Mars

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Perez-Davis, Marla E.; Rutledge, Sharon K.; Hotes, Deborah

    1990-01-01

    Simulated radiator surfaces made of arc-textured Cu and Nb-1 percent-Zr and ion beam textured graphite and C-C composite were fabricated and their integrated spectral emittance characterized from 300 to 3000 K. A thin layer of aluminum oxide, basalt, or iron (III) oxide dust was then deposited on them, and they were subjected to low pressure winds in the Martian Surface Wind Tunnel. It was found that dust deposited on simulated radiator surfaces may or may not seriously lower their integrated spectral emittance, depending upon the characteristics of the dust. With Al2O3 there is no appreciable degradation of emittance on a dusted sample, with basaltic dust there is a 10 to 20 percent degradation, and with Fe2O3 a 20 to 40 percent degradation. It was also found that very high winds on dusted highly textured surfaces can result in their abrasion. Degradation in emittance due to abrasion was found to vary with radiator material. Arc-textured Cu and Nb-1 percent Zr was found to be more susceptible to emittance degradation than graphite or C-C composite. The most abrasion occurred at low angles, peaking at the 22.5 deg test samples.

  5. ULTRAVIOLET RADIATIVE TRANSFER MODELING OF NEARBY GALAXIES WITH EXTRAPLANAR DUSTS

    SciTech Connect

    Shinn, Jong-Ho; Seon, Kwang-Il

    2015-12-20

    In order to examine their relation to the host galaxy, the extraplanar dusts of six nearby galaxies are modeled, employing a three-dimensional Monte Carlo radiative transfer code. The targets are from the highly inclined galaxies that show dust-scattered ultraviolet halos, and the archival Galaxy Evolution Explorer FUV band images were fitted with the model. The observed images are generally well-reproduced by two dust layers and one light source layer, whose vertical and radial distributions have exponential profiles. We obtained several important physical parameters, such as star formation rate (SFR{sub UV}), face-on optical depth, and scale-heights. Three galaxies (NGC 891, NGC 3628, and UGC 11794) show clear evidence for the existence of an extraplanar dust layer. However, it is found that the remaining three targets (IC 5249, NGC 24, and NGC 4173) do not necessarily need a thick dust disk to model the ultraviolet (UV) halo, because its contribution is too small and the UV halo may be caused by the wing part of the GALEX point spread function. This indicates that the galaxy samples reported to have UV halos may be contaminated by galaxies with negligible extraplanar (halo) dust. The galaxies showing evidence of an extraplanar dust layer fall within a narrow range on the scatter plots between physical parameters such as SFR{sub UV} and extraplanar dust mass. Several mechanisms that could possibly produce the extraplanar dust are discussed. We also found a hint that the extraplanar dust scale-height might not be much different from the polycyclic aromatic hydrocarbon emission characteristic height.

  6. Ultraviolet Radiative Transfer Modeling of Nearby Galaxies with Extraplanar Dusts

    NASA Astrophysics Data System (ADS)

    Shinn, Jong-Ho; Seon, Kwang-Il

    2015-12-01

    In order to examine their relation to the host galaxy, the extraplanar dusts of six nearby galaxies are modeled, employing a three-dimensional Monte Carlo radiative transfer code. The targets are from the highly inclined galaxies that show dust-scattered ultraviolet halos, and the archival Galaxy Evolution Explorer FUV band images were fitted with the model. The observed images are generally well-reproduced by two dust layers and one light source layer, whose vertical and radial distributions have exponential profiles. We obtained several important physical parameters, such as star formation rate (SFRUV), face-on optical depth, and scale-heights. Three galaxies (NGC 891, NGC 3628, and UGC 11794) show clear evidence for the existence of an extraplanar dust layer. However, it is found that the remaining three targets (IC 5249, NGC 24, and NGC 4173) do not necessarily need a thick dust disk to model the ultraviolet (UV) halo, because its contribution is too small and the UV halo may be caused by the wing part of the GALEX point spread function. This indicates that the galaxy samples reported to have UV halos may be contaminated by galaxies with negligible extraplanar (halo) dust. The galaxies showing evidence of an extraplanar dust layer fall within a narrow range on the scatter plots between physical parameters such as SFRUV and extraplanar dust mass. Several mechanisms that could possibly produce the extraplanar dust are discussed. We also found a hint that the extraplanar dust scale-height might not be much different from the polycyclic aromatic hydrocarbon emission characteristic height.

  7. Bipolar charging of dust particles under ultraviolet radiation

    SciTech Connect

    Filippov, A. V. Babichev, V. N.; Fortov, V. E.; Gavrikov, A. V.; Pal', A. F.; Petrov, O. F.; Starostin, A. N.; Sarkarov, N. E.

    2011-05-15

    The photoemission charging of dust particles under ultraviolet radiation from a xenon lamp has been investigated. The velocities of yttrium dust particles with a work function of 3.3 eV and their charges have been determined experimentally; the latter are about 400-500 and about 100 elementary charges per micron of radius for the positively and negatively charged fractions, respectively. The dust particle charging and the dust cloud evolution in a photoemission cell after exposure to an ultraviolet radiation source under the applied voltage have been simulated numerically. The photoemission charging of dust particles has been calculated on the basis of nonlocal and local charging models. Only unipolar particle charging is shown to take place in a system of polydisperse dust particles with the same photoemission efficiency. It has been established that bipolar charging is possible in the case of monodisperse particles with different quantum efficiencies. Polydispersity in this case facilitates the appearance of oppositely charged particles in a photoemission plasma.

  8. Gravitational radiation from collapsing magnetized dust

    SciTech Connect

    Sotani, Hajime; Yoshida, Shijun; Kokkotas, Kostas D.

    2007-04-15

    In this article we study the influence of magnetic fields on the axial gravitational waves emitted during the collapse of a homogeneous dust sphere. We found that while the energy emitted depends weakly on the initial matter perturbations it has strong dependence on the strength and the distribution of the magnetic field perturbations. The gravitational wave output of such a collapse can be up to an order of magnitude larger or smaller calling for detailed numerical 3D studies of collapsing magnetized configurations.

  9. Adaptable radiative transfer innovations for submillimetre telescopes (ARTIST). Dust polarisation module (DustPol)

    NASA Astrophysics Data System (ADS)

    Padovani, M.; Brinch, C.; Girart, J. M.; Jørgensen, J. K.; Frau, P.; Hennebelle, P.; Kuiper, R.; Vlemmings, W. H. T.; Bertoldi, F.; Hogerheijde, M.; Juhasz, A.; Schaaf, R.

    2012-07-01

    We present a new publicly available tool (DustPol) aimed to model the polarised thermal dust emission. The module DustPol, which is publicly available, is part of the ARTIST (Adaptable Radiative Transfer Innovations for Submillimetre Telescopes) package, which also offers tools for modelling the polarisation of line emission together with a model library and a Python-based user interface. DustPol can easily manage analytical as well as pre-gridded models to generate synthetic maps of the Stokes I, Q, and U parameters. These maps are stored in FITS format which is straightforwardly read by the data reduction software used, e.g., by the Atacama Large Millimeter Array (ALMA). This turns DustPol into a powerful engine for the prediction of the expected polarisation features of a source observed with ALMA or the Planck satellite as well as for the interpretation of existing submillimetre observations obtained with other telescopes. DustPol allows the parameterisation of the maximum degree of polarisation and we find that, in a prestellar core, if there is depolarisation, this effect should happen at densities of 106 cm-3 or larger. We compare a model generated by DustPol with the observational polarisation data of the low-mass Class 0 object NGC 1333 IRAS 4A, finding that the total and the polarised emission are consistent.

  10. Spinning dust emission: the effect of rotation around a non-principal axis

    NASA Astrophysics Data System (ADS)

    Silsbee, Kedron; Ali-Haïmoud, Yacine; Hirata, Christopher M.

    2011-03-01

    We investigate the rotational emission from dust grains that rotate around non-principal axes. We argue that in many phases of the interstellar medium, the smallest grains, which dominate spinning dust emission, are likely to have their nutation state (orientation of principal axes relative to the angular momentum vector) randomized during each thermal spike. We recompute the excitation and damping rates associated with rotational emission from the grain permanent dipole, grain-plasma interactions, infrared photon emission and collisions. The resulting spinning dust spectra generally show a shift towards higher emissivities and peak frequencies relative to previous calculations.

  11. Radiative shocks create environments for dust formation in classical novae

    NASA Astrophysics Data System (ADS)

    Derdzinski, Andrea M.; Metzger, Brian D.; Lazzati, Davide

    2017-08-01

    Classical novae commonly show evidence of rapid dust formation within months of the outburst. However, it is unclear how molecules and grains are able to condense within the ejecta, given the potentially harsh environment created by ionizing radiation from the white dwarf. Motivated by the evidence for powerful radiative shocks within nova outflows, we propose that dust formation occurs within the cool, dense shell behind these shocks. We incorporate a simple molecular chemistry network and classical nucleation theory with a model for the thermodynamic evolution of the post-shock gas, in order to demonstrate the formation of both carbon and forsterite (Mg2SiO4) grains. The high densities due to radiative shock compression (n ∼ 1014 cm-3) result in CO saturation and rapid dust nucleation. Grains grow efficiently to large sizes ≳ 0.1 μm, in agreement with IR observations of dust-producing novae, and with total dust masses sufficient to explain massive extinction events such as V705 Cas. As in dense stellar winds, dust formation is CO-regulated, with carbon-rich flows producing carbon-rich grains and oxygen-rich flows primarily forming silicates. CO is destroyed by non-thermal particles accelerated at the shock, allowing additional grain formation at late times, but the efficiency of this process appears to be low. Given observations showing that individual novae produce both carbonaceous and silicate grains, we concur with previous works attributing this bimodality to chemical heterogeneity of the ejecta. Nova outflows are diverse and inhomogeneous, and the observed variety of dust formation events can be reconciled by different abundances, the range of shock properties, and the observer viewing angle. The latter may govern the magnitude of extinction, with the deepest extinction events occurring for observers within the binary equatorial plane.

  12. Gamma radiation resistance of spin Seebeck devices

    NASA Astrophysics Data System (ADS)

    Yagmur, A.; Uchida, K.; Ihara, K.; Ioka, I.; Kikkawa, T.; Ono, M.; Endo, J.; Kashiwagi, K.; Nakashima, T.; Kirihara, A.; Ishida, M.; Saitoh, E.

    2016-12-01

    Thermoelectric devices based on the spin Seebeck effect (SSE) were irradiated with gamma (γ) rays with the total dose of around 3 × 105 Gy in order to investigate the γ-radiation resistance of the devices. To demonstrate this, Pt/Ni0.2Zn0.3Fe2.5O4/Glass and Pt/Bi0.1Y2.9Fe5O12/Gd3Ga5O12 SSE devices were used. We confirmed that the thermoelectric, magnetic, and structural properties of the SSE devices are not affected by the γ-ray irradiation. This result demonstrates that SSE devices are applicable to thermoelectric generation even in high radiation environments.

  13. Direct Radiative Effect of Intense Dust Outbreaks in the Mediterranean

    NASA Astrophysics Data System (ADS)

    Gkikas, A.; Obiso, V.; Basart, S.; Jorba, O.; Pérez García-Pando, C.; Hatzianastassiou, N.; Gassó, S.; Baldasano, J. M.

    2015-12-01

    The broader Mediterranean basin is affected by intense desert dust outbreaks in spring. In the present study, we make use of satellite observations and modelling to investigate dust radiative impacts during three consecutive dust outbreaks occurred over the Mediterranean in the period 9/4-15/4/2008. The direct radiative effect (DRE) is estimated by using two simulations run with the NMMB/BSC-Dust model, where the interaction between dust aerosols and radiation is activated and deactivated, respectively. The simulation domain covers the North Africa, the Middle East and Europe at 0.25ºx0.25° and 40σ-layers. The first outbreak took place over the central and eastern Mediterranean on the 9th reaching aerosol optical depths (AODs) close to 1. The second one, with AODs up to 2, lasted from 10th to 14th affecting mainly the central Mediterranean. The third one, with AODs up to 5, affected the Iberian Peninsula on the 15th. DREs are computed for the outgoing radiation at the top of the atmosphere (TOA), the absorbed radiation into the atmosphere (ATMAB), for the downwelling (SURF) and the absorbed (NETSURF) radiation at surface, for the shortwave (SW), longwave (LW) and NET (SW+LW) radiation. According to our results, it is evident that DREs' spatial patterns are driven by those of AOD. Negative (cooling) instantaneous DRETOA, DRESURF and DRENETSURF values up to -500W/m2, -700W/m2 and -600W/m2, respectively, and positive (warming) instantaneous DREATMAB up to 340W/m2 are found for the SW spectrum, during daytime. Opposite but less pronounced effects are encountered for the LW radiation and during nightime. Due to these perturbations on the radiation field, the surface temperature is reduced locally by up to 8°C during daytime and increased by up to 4°C during nightime. It is found that the regional average NET DREs can be as large as -12W/m2, -45W/m2, -30W/m2 and 27W/m2 for TOA, SURF, NETSURF and ATMAB, respectively. Impacts on atmospheric stability and dust

  14. Solar Spectral Radiative Forcing Due to Dust Aerosol During the Puerto Rico Dust Experiment

    NASA Technical Reports Server (NTRS)

    Pilewskie, P.; Bergstrom, R.; Rabbette, M.; Livingston, J.; Russell, P.; Gore, Warren J. (Technical Monitor)

    2000-01-01

    During the Puerto Rico Dust Experiment (PRIDE) upwelling and downwelling solar spectral irradiance was measured on board the SPAWAR Navajo and downwelling solar spectral flux was measured at a surface site using the NASA Ames Solar Spectral Flux Radiometer. These data will be used to determine the net solar radiative forcing of dust aerosol and to quantify the solar spectral radiative energy budget in the presence of elevated aerosol loading. We will assess the variability in spectral irradiance using formal principal component analysis procedures and relate the radiative variability to aerosol microphysical properties. Finally, we will characterize the sea surface reflectance to improve aerosol optical depth retrievals from the AVHRR satellite and to validate SeaWiFS ocean color products.

  15. Coma morphology and dust-emission pattern of periodic Comet Halley. II - Nucleus spin vector and modeling of major dust features in 1910

    NASA Technical Reports Server (NTRS)

    Sekanina, Z.; Larson, S. M.

    1984-01-01

    The continuous ejection of dust from discrete emission sources on the rotating nucleus of the Comet Halley is modelled in order to explain the evolution of spiral jets which unwind from the nucleus condensation into envelopes or halos in the comet head. The model is applied to digitally processed images of three features of the comet taken from Mount Wilson plates during the 1910 fly-by. The model permits a determination of the motion and spin vector for each emission source, its cometocentric coordinates, and a function relating particle ejection velocity to the solar radiation pressure exerted on the ejecta. It is found that the obliquity of the comet orbit's plane to its equatorial plane is 45 deg, the axis of rotation period of 17.3 days. The derived function of particle ejection velocity to the solar radiation pressure implied no contribution from grains larger than 10 microns in radius. High dust loading of gas flows from the June 1910 emission sources is indicated. It is estimated that because of the favorable approach geometry of the Gioto spacecraft during its 1986 flyby, the likelihood of encountering dense jets of dust is small.

  16. Influence of Dust Loading on Atmospheric Ionizing Radiation on Mars

    NASA Technical Reports Server (NTRS)

    Norman, Ryan B.; Gronoff, Guillaume; Mertens, Christopher J.

    2014-01-01

    Measuring the radiation environment at the surface of Mars is the primary goal of the Radiation Assessment Detector on the NASA Mars Science Laboratory's Curiosity rover. One of the conditions that Curiosity will likely encounter is a dust storm. The objective of this paper is to compute the cosmic ray ionization in different conditions, including dust storms, as these various conditions are likely to be encountered by Curiosity at some point. In the present work, the Nowcast of Atmospheric Ionizing Radiation for Aviation Safety model, recently modified for Mars, was used along with the Badhwar & O'Neill 2010 galactic cosmic ray model. In addition to galactic cosmic rays, five different solar energetic particle event spectra were considered. For all input radiation environments, radiation dose throughout the atmosphere and at the surface was investigated as a function of atmospheric dust loading. It is demonstrated that for galactic cosmic rays, the ionization depends strongly on the atmosphere profile. Moreover, it is shown that solar energetic particle events strongly increase the ionization throughout the atmosphere, including ground level, and can account for the radio blackout conditions observed by the Mars Advanced Radar for Subsurface and Ionospheric Sounding instrument on the Mars Express spacecraft. These results demonstrate that the cosmic rays' influence on the Martian surface chemistry is strongly dependent on solar and atmospheric conditions that should be taken into account for future studies.

  17. Influence of dust loading on atmospheric ionizing radiation on Mars

    NASA Astrophysics Data System (ADS)

    Norman, Ryan B.; Gronoff, Guillaume; Mertens, Christopher J.

    2014-01-01

    Measuring the radiation environment at the surface of Mars is the primary goal of the Radiation Assessment Detector on the NASA Mars Science Laboratory's Curiosity rover. One of the conditions that Curiosity will likely encounter is a dust storm. The objective of this paper is to compute the cosmic ray ionization in different conditions, including dust storms, as these various conditions are likely to be encountered by Curiosity at some point. In the present work, the Nowcast of Atmospheric Ionizing Radiation for Aviation Safety model, recently modified for Mars, was used along with the Badhwar & O'Neill 2010 galactic cosmic ray model. In addition to galactic cosmic rays, five different solar energetic particle event spectra were considered. For all input radiation environments, radiation dose throughout the atmosphere and at the surface was investigated as a function of atmospheric dust loading. It is demonstrated that for galactic cosmic rays, the ionization depends strongly on the atmosphere profile. Moreover, it is shown that solar energetic particle events strongly increase the ionization throughout the atmosphere, including ground level, and can account for the radio blackout conditions observed by the Mars Advanced Radar for Subsurface and Ionospheric Sounding instrument on the Mars Express spacecraft. These results demonstrate that the cosmic rays' influence on the Martian surface chemistry is strongly dependent on solar and atmospheric conditions that should be taken into account for future studies.

  18. Simulation of the Radiative Impact of High Dust Loading during a Dust Storm in March 2012

    NASA Astrophysics Data System (ADS)

    Puthan Purakkal, J.; Kalenderski, S.; Stenchikov, G. L.

    2013-12-01

    We investigated a severe dust storm that developed over vast areas of the Middle East on 18-19 March 2012 and affected Saudi Arabia, Sudan, Egypt, Jordan, United Arab Emirates, Bahrain, Qatar, Oman, Kuwait, Iraq, Iran, Israel, and Pakistan. The visible aerosol optical depth recorded by the AERONET station on the KAUST campus (22.30o N 39.10o E) during the storm reached 4.5, exceeding the average level by an order of magnitude. To quantify the effects of the dust on atmospheric radiation and dynamics, we analyzed available ground-based and satellite observations and conducted numerical simulations using a fully coupled meteorology-chemistry-aerosol model (WRF-Chem). The model was able to reproduce the spatial and temporal patterns of the aerosol optical depths (AOD) observed by airborne and ground-based instruments. The major dust sources included river valleys of lower Tigris and Euphrates in Iraq, desert areas in Kuwait, Iran, United Arab Emirates, central Arabia including Rub' al Khali, An Nafud, and Ad Dahna, as well as the Red Sea coast of the Arabian Peninsula. The total amount of dust generated across the entire domain during the period of the simulation reached 93.76 Mt; 73.04 Mt of dust was deposited within the domain; 6.56 Mt of dust sunk in the adjacent sea waters, including 1.20 Mt that sedimented into the Red Sea. The model predicted a well-mixed boundary layer expanding up to 3.5 km in the afternoon. Some dust plumes were seen above the Planetary Boundary layer. In our simulations, mineral dust heated the lower atmosphere with a maximum heating rate of 9 K/day. The dust storm reduced the downwelling shortwave radiation at the surface to a maximum daily average value of -134 Wm-2 and the daily averaged long-wave forcing at the surface increased to 43 Wm-2. The combined short-wave cooling and long-wave warming effects of dust aerosols caused significant reduction in the surface air temperature -6.7 K at 1200 UTC on 19 March 2013.

  19. The radiation-induced rotation of cosmic dust particles: A feasibility study

    NASA Technical Reports Server (NTRS)

    Misconi, N. Y.; Ratcliff, K. F.

    1981-01-01

    A crossed beam, horizontal optical trap, used to achieve laser levitation of particles in an effort to determine how solar radiation produces high spin rate in interplanetary dust particles, is described. It is suggested that random variations in albedo and geometry give rise to a nonzero effective torque when the influence of a unidrectional source of radiaton (due to the Sun) over the surface of a interplanetary dust particle is averaged. This resultant nonzero torque is characterized by an asymmetry factor which is the ratio of the effective moment arm to the maximum linear dimension of the body and is estimated to be 5 X 10 to the minus four power. It is hoped that this symmetry factor, which stabilizes the nonstatistical response of the particle, can be measured in a future Spacelab experiment.

  20. Dust aerosol-radiation-clouds-precipitation interactions over the Mediterranean

    NASA Astrophysics Data System (ADS)

    Valentini, Chiara; Baró, Rocío; Palacios-Peña, Laura; José Gómez-Navarro, Juan; María López-Romero, José; Montávez, Juan Pedro; Jiménez-Guerrero, Pedro

    2017-04-01

    Dust intrusions from African desert regions have an impact on the whole Mediterranean Basin and its climate. They cause an anomalous increase of aerosol load in the tropospheric column and have the potential to change the energy fluxes in the Earth-atmosphere system by modifying cloud microphysical properties, such as the cloud liquid water path (CLWP), cloud fraction (CFRAC), cloud top temperature (CTT), droplet number concentration (CDNC), or cloud particle size distribution (CPSD). Through aerosol-radiation-cloud interactions, dust can modify convective and large-scale precipitation under certain conditions, thus affecting the hydrological cycle. In this work, desert dust outbreaks occurred in October2010 over the whole Mediterranean Basin has been studied with the objective of quantifying the influence of including dust interactions in a regional on-line coupled climate/chemistry model on several variables: convective precipitation, CLWP, CFRAC and CDNC. The focus is set on characterizing the impacts of aerosol indirect effects on the radiative budget. A set of three WRF-Chem simulations differing only in the inclusion (or not) of aerosol-radiation (ARI) and the aerosol-cloud interactions (ACI) has been carried out. The comparison between simulation results show a satisfying agreement when compared with satellite observations, and supports the skills of the model to estimate the African dust contribution over the Mediterranean. Differences between the ARI+ACI and the base case (not including aerosol-radiation-cloud interactions) suggest variations around +/- 15 mm/day in convective precipitation for several events. For instance, considering ARI+ACI leads to a generalized reduction of the cloud liquid water path (-50 kg/kg over the areas affected by the dust aerosols) and modified patterns of clouds (differences between -65% and +35% in the CFRAC). Also, the low estimated significance of the changes observed between the diverse simulations over certain areas

  1. Exploring the Longwave Radiative Effects of Dust Aerosols

    NASA Technical Reports Server (NTRS)

    Hansell, Richard A., Jr.

    2012-01-01

    Dust aerosols not only affect air quality and visibility where they pose a significant health and safety risk, but they can also play a role in modulating the energy balance of the Earth-atmosphere system by directly interacting with local radiative fields. Consequently, dust aerosols can impact regional climate patterns such as changes in precipitation and the evolution of the hydrological cycle. Assessing the direct effect of dust aerosols at the solar wavelengths is fairly straightforward due in part to the relatively large signal-to-noise ratio in broadband irradiance measurements. The longwave (LW) impacts, on the other hand, are rather difficult to ascertain since the measured dust signal level (10 Wm-2) is on the same order as the instrumental uncertainties. Moreover, compared to the shortwave (SW), limited experimental data on the LW optical properties of dust makes it a difficult challenge for constraining the LW impacts. Owing to the strong absorption features found in many terrestrial minerals (e.g., silicates and clays), the LW effects, although much smaller in magnitude compared to the SW, can still have a sizeable impact on the energetics of the Earth-atmosphere system, which can potentially trigger changes in the heat and moisture surface budgets, and dynamics of the atmosphere. The current endeavor is an integral part of an on-going research study to perform detailed assessments of dust direct aerosol radiative effects (DARE) using comprehensive global datasets from NASA Goddards mobile ground-based facility (cf. http://smartlabs.gsfc.nasa.gov/) during previous field experiments near key dust source regions. Here we examine and compare the results from two of these studies: the 2006 NASA African Monsoon Multidisciplinary Activities and the 2008 Asian Monsoon Years. The former study focused on transported Saharan dust at Sal Island (16.73N, 22.93W), Cape Verde along the west coast of Africa while the latter focused on Asian dust at Zhangye China (39

  2. Geometric doppler effect: spin-split dispersion of thermal radiation.

    PubMed

    Dahan, Nir; Gorodetski, Yuri; Frischwasser, Kobi; Kleiner, Vladimir; Hasman, Erez

    2010-09-24

    A geometric Doppler effect manifested by a spin-split dispersion relation of thermal radiation is observed. A spin-dependent dispersion splitting was obtained in a structure consisting of a coupled thermal antenna array. The effect is due to a spin-orbit interaction resulting from the dynamics of the surface waves propagating along the structure whose local anisotropy axis is rotated in space. The observation of the spin-symmetry breaking in thermal radiation may be utilized for manipulation of spontaneous or stimulated emission.

  3. Dust in Snow in the Colorado River Basin: Spatial Variability in Dust Concentrations, Radiative Forcing, and Snowmelt Rates

    NASA Astrophysics Data System (ADS)

    Skiles, M.; Painter, T.; Deems, J. S.; Landry, C.; Bryant, A.

    2012-12-01

    Since the disturbance of the western US that began with the Anglo settlement in the mid 19th century, the mountain snow cover of the Colorado River Basin (CRB) has been subject to five-fold greater dust loading. This dust deposition accelerates snowmelt through its direct reduction of albedo and its further reduction of albedo by accelerating the growth of snow effective grain size. We have previously quantified the impacts of dust in snow using a 6-year record of dust concentration and energy balance fluxes at the alpine and subalpine towers in the Senator Beck Basin Study Area (SBBSA), San Juan Mountains in southwestern Colorado, USA. Dust loading exhibited interannual variability, and end of year dust concentrations were not necessarily related to the number of dust deposition events. Radiative forcing enhanced springtime melt by 21 to 51 days with the magnitude of advanced loss being linearly related to total dust concentration at the end of snow cover. To expand our understanding of dust on snow deposition patterns we utilize collections of dust concentration at the Colorado Dust on Snow (CODOS) study sites, established in 2009 along the western side of the CRB, to assess spatial variability in dust loading. In situ sampling of dust stratigraphy and concentration occurs twice each season, once over peak snow water equivalent (15 April), and again during melt (15 May). Dust loading occurs at all sites; dust concentrations are always higher in May, vary between sites, and the highest and lowest dust years were 2009 and 2012, respectively. In the absence of regular sampling and energy balance instrumentation these sites do not allow us to quantify the advanced melt due to dust. To facilitate this a new energy balance site, Grand Mesa Study plot (GMSP), was established for water year 2010 in west central Colorado, 150 km north of SBBSA. Back trajectories indicate similar Colorado Plateau dust sources at both SBBSA and GMSP, yet GMSP exhibits slightly lower dust

  4. Numerical modeling of orbit-spin coupling accelerations in a Mars general circulation model: Implications for global dust storm activity

    NASA Astrophysics Data System (ADS)

    Mischna, Michael A.; Shirley, James H.

    2017-07-01

    We employ the MarsWRF general circulation model (GCM) to test the predictions of a new physical hypothesis: a weak coupling of the orbital and rotational angular momenta of extended bodies is predicted to give rise to cycles of intensification and relaxation of circulatory flows within atmospheres. The dynamical core of MarsWRF has been modified to include the orbit-spin coupling accelerations due to solar system dynamics for the years 1920-2030. The modified GCM is subjected to extensive testing and verification. We compare forced and unforced model outcomes for large-scale zonal and meridional flows, and for near-surface wind velocities and surface wind stresses. The predicted cycles of circulatory intensification and relaxation within the modified GCM are observed. Most remarkably, the modified GCM reproduces conditions favorable for the occurrence of perihelion-season global-scale dust storms (GDSs) on Mars in years in which such storms were observed. A strengthening of the meridional overturning circulation during the dust storm season occurs in the GCM in all recorded years with perihelion-season global-scale dust storms. The increased upwelling produced in the southern hemisphere in southern summer may facilitate the transport of dust to high altitudes in the Mars atmosphere during the dust storm season, where radiative heating may further strengthen the circulation. Significantly increased surface winds and surface wind stresses are also obtained. These may locally facilitate dust lifting from the surface. Based on comparison to the historical record, there is a strong likelihood of a perihelion-season GDS in Mars year 33 and/or Mars year 34.

  5. Estimation of diurnal shortwave dust aerosol radiative forcing during PRIDE

    NASA Astrophysics Data System (ADS)

    Christopher, Sundar A.; Wang, Jun; Ji, Qiang; Tsay, Si-Chee

    2003-10-01

    Using measured and derived aerosol properties from the Puerto Rico Dust Experiment (PRIDE), a four-stream broadband radiative transfer model is used to calculate the downward shortwave irradiance (DSWI) at the surface and the shortwave irradiance at the top of atmosphere (TOA). The results of the calculated DSWI are compared against pyranometer measurements from the Surface Measurements For Atmospheric Radiative Transfer (SMART) instrument suite at Roosevelt Road (18.20°N, 65.60°W). Using aerosol optical thickness retrievals from half-hourly geostationary satellite data (GOES 8 imager), the diurnal short wave aerosol forcing (SWARF) of dust aerosols both at the surface and TOA are calculated for the entire study area (14°N ˜ 26°N, 61°W ˜ 73°W). For selected days, the Clouds and the Earth Radiant Energy System (CERES) TOA shortwave irradiance values from Terra are compared with radiative transfer calculations. [2003] show that the satellite derived aerosol optical thickness is in excellent agreement with Aerosol Robotic Network (AERONET) values. Results of this study show that the calculated direct, diffuse and total DSWI are in excellent agreement with the corresponding SMART values with biases of 1.8%, -3.3% and 0.5% respectively, indicating that dust aerosols are well characterized in the radiative transfer model. This is well within the measured uncertainties (1.3%) and the model uncertainties (5%). The monthly mean value and standard deviation of aerosol optical thickness at 670 nm (AOT670) during PRIDE are 0.26 ± 0.13, and the corresponding monthly mean daytime SWARF values are -12.34 ± 9.62 W m-2 at TOA and -18.13 ± 15.81 W m-2 at the surface, respectively. Our results also show that if diurnal changes in aerosol optical thickness are not considered, it leads to uncertainties in SWARF of 4 W m-2 at the surface and 2 W m-2 at the TOA. The CERES TOA short wave irradiance underestimates calculated values by about 10 W m-2 mainly due problems in

  6. The Influence of Dust-radiation-microphysics Processes on Tropical Cyclone Development

    NASA Astrophysics Data System (ADS)

    Chen, S.; Cheng, C.; Chen, J.; Lin, Y.; Lee, H.; Tsai, I.

    2011-12-01

    Saharan dust can modify the Saharan Air Layer (SAL) and its environment by changing the energy budget through direct and indirect radiative forcing. Scattering and absorption of radiation by suspended dust directly modifies the energy budget in the atmosphere and at the surface. Smaller dust particles can remain suspended in the air for prolonged periods and propagate over the Atlantic Ocean along with SAL. These fine particles can reach an altitude of 8-9 km, where they nucleate ice crystals and transform cloud microphysical properties, indirectly changing the energy budget. Thus, the dust within the air mass is likely to affect the evolution of hurricane properties, life cycles, and the corresponding cloud systems through the dust-cloud-radiation interactions. A tracer model based on the Weather Research and Forecasting model (named WRFT) was developed to study the influence of dust-radiation-microphysics effects on hurricane activities. The dust-radiation effects and a two-moment microphysics scheme with dust particles acting as ice nuclei were implemented into WRFT. In this work, two easterly waves, which were precursors of Tropical Storm Debby and Hurricane Ernesto, during 18-25 August 2006 were studied. Four high-resolution numerical experiments were conducted with the combinations of activating/deactivating dust-radiation and/or dust-microphysics processes. Results from these four experiments are compared to investigate the influence of dust-radiation-microphysics processes on these two storm developments.

  7. CARMA observations of Galactic cold cores: searching for spinning dust emission

    NASA Astrophysics Data System (ADS)

    Tibbs, C. T.; Paladini, R.; Cleary, K.; Muchovej, S. J. C.; Scaife, A. M. M.; Stevenson, M. A.; Laureijs, R. J.; Ysard, N.; Grainge, K. J. B.; Perrott, Y. C.; Rumsey, C.; Villadsen, J.

    2015-11-01

    We present the first search for spinning dust emission from a sample of 34 Galactic cold cores, performed using the CARMA interferometer. For each of our cores, we use photometric data from the Herschel Space Observatory to constrain bar{N}H, bar{T}d, bar{n}H, and bar{G}0. By computing the mass of the cores and comparing it to the Bonnor-Ebert mass, we determined that 29 of the 34 cores are gravitationally unstable and undergoing collapse. In fact, we found that six cores are associated with at least one young stellar object, suggestive of their protostellar nature. By investigating the physical conditions within each core, we can shed light on the cm emission revealed (or not) by our CARMA observations. Indeed, we find that only three of our cores have any significant detectable cm emission. Using a spinning dust model, we predict the expected level of spinning dust emission in each core and find that for all 34 cores, the predicted level of emission is larger than the observed cm emission constrained by the CARMA observations. Moreover, even in the cores for which we do detect cm emission, we cannot, at this stage, discriminate between free-free emission from young stellar objects and spinning dust emission. We emphasize that although the CARMA observations described in this analysis place important constraints on the presence of spinning dust in cold, dense environments, the source sample targeted by these observations is not statistically representative of the entire population of Galactic cores.

  8. Exact linearization of the radiation-damped spin system

    PubMed

    Rourke; Augustine

    2000-02-21

    Nonlinear evolution of the Landau-Lifshitz type can be exactly linearized. Special cases include the radiation-damped spin system and the superradiant system in the semiclassical regime, in the presence of time-varying driving fields. For these, the resultant linear system is simply that of a spin 1 / 2 particle, with the radiation damping rate, or superradiant characteristic time, manifested as an imaginary addition to the spin's resonance frequency. Consequently, methods from inverse scattering theory can be used to design driving fields. The behavior of these systems under stochastic excitation can be determined exactly.

  9. Spin-Crossover Materials towards Microwave Radiation Switches

    PubMed Central

    Kucheriv, Olesia I.; Oliynyk, Viktor V.; Zagorodnii, Volodymyr V.; Launets, Vilen L.; Gural’skiy, Il’ya A.

    2016-01-01

    Microwave electromagnetic radiation that ranges from one meter to one millimetre wavelengths is finding numerous applications for wireless communication, navigation and detection, which makes materials able to tune microwave radiation getting widespread interest. Here we offer a new way to tune GHz frequency radiation by using spin-crossover complexes that are known to change their various physical properties under the influence of diverse external stimuli. As a result of electronic re-configuration process, microwave absorption properties differ for high spin and low spin forms of the complex. The evolution of a microwave absorption spectrum for the switchable compound within the region of thermal transition indicates that the high-spin and the low-spin forms are characterized by a different attenuation of electromagnetic waves. Absorption and reflection coefficients were found to be higher in the high-spin state comparing to the low-spin state. These results reveal a considerable potential for the implementation of spin-crossover materials into different elements of microwave signal switching and wireless communication. PMID:27910956

  10. Spin-Crossover Materials towards Microwave Radiation Switches.

    PubMed

    Kucheriv, Olesia I; Oliynyk, Viktor V; Zagorodnii, Volodymyr V; Launets, Vilen L; Gural'skiy, Il'ya A

    2016-12-02

    Microwave electromagnetic radiation that ranges from one meter to one millimetre wavelengths is finding numerous applications for wireless communication, navigation and detection, which makes materials able to tune microwave radiation getting widespread interest. Here we offer a new way to tune GHz frequency radiation by using spin-crossover complexes that are known to change their various physical properties under the influence of diverse external stimuli. As a result of electronic re-configuration process, microwave absorption properties differ for high spin and low spin forms of the complex. The evolution of a microwave absorption spectrum for the switchable compound within the region of thermal transition indicates that the high-spin and the low-spin forms are characterized by a different attenuation of electromagnetic waves. Absorption and reflection coefficients were found to be higher in the high-spin state comparing to the low-spin state. These results reveal a considerable potential for the implementation of spin-crossover materials into different elements of microwave signal switching and wireless communication.

  11. A Search for the Polarization of Spinning Dust in the Dark Cloud LDN 1622

    NASA Astrophysics Data System (ADS)

    Mason, B.; Robishaw, T.; Finkbeiner, D.

    2008-08-01

    Numerous observations have shown that the dark cloud LDN 1622 possesses an anomalous, dust-correlated spectrum of microwave emission. The microwave spectrum is consistent with anomalous spectra observed in other, more diffuse, clouds in the Galaxy and could be caused by electric-dipole emission from small, spinning dust grains. Other mechanisms that have been proposed are magnetic-dipole emission from larger, ferrous grains and hard synchrotron, both of which (unlike electric-dipole emission) would could evince significantly higher levels of polarization. We describe results from an ongoing campaign to measure the polarization of LDN 1622 with the Green Bank Telescope at 8 GHz.

  12. A Comparative Study of Mesoscale Modeling of Smoke and Dust Direct Radiative Effects over Northern Sub-Saharan African Region.

    NASA Astrophysics Data System (ADS)

    Yue, Y.; Wang, J.; Ichoku, C. M.; Zhang, F.

    2014-12-01

    This study aims to investigate the radiative effects of smoke and dust aerosols and of the underlying surface in the Northern Sub-Saharan African (NSSA) region using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem). We performed a yearlong (from September 2009 to September 2010) WRF-Chem simulation using hourly emissions from the Fire Energetics and Emissions Research (FEER) emission dataset derived by multiplying emission coefficients based on aerosol and fire observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments aboard Terra and Aqua with fire radiative energy (FRE) measurements from the geostationary Meteosat Spinning Enhanced Visible and Infrared Imager (SEVIRI). The geographic distribution and vertical profiles of simulated dust and smoke aerosols were evaluated with MODIS true color images and Cloud-Aerosol Lidar data with Orthogonal Polarization (CALIPSO) total attenuated backscatter, aerosol extinction coefficient and depolarization data. We found that simulated aerosol vertical concentration profiles are consistent with the above CALIPSO data. Surface albedo and columnar aerosol optical depth (AOD) sensitivity to smoke and dust simulations are performed with WRF-Chem. The simulated surface albedo and AOD were compared with MODIS albedo product (MODIS43) and AOD measurements from the Aerosol Robotic Network (AERONET). The modeled smoke/dust clear-sky and all-sky radiative impacts were analyzed in this study and reveal interesting results that will be discussed.

  13. OUTWARD MOTION OF POROUS DUST AGGREGATES BY STELLAR RADIATION PRESSURE IN PROTOPLANETARY DISKS

    SciTech Connect

    Tazaki, Ryo; Nomura, Hideko

    2015-02-01

    We study the dust motion at the surface layer of protoplanetary disks. Dust grains in the surface layer migrate outward owing to angular momentum transport via gas-drag force induced by the stellar radiation pressure. In this study we calculate the mass flux of the outward motion of compact grains and porous dust aggregates by the radiation pressure. The radiation pressure force for porous dust aggregates is calculated using the T-Matrix Method for the Clusters of Spheres. First, we confirm that porous dust aggregates are forced by strong radiation pressure even if they grow to be larger aggregates, in contrast to homogeneous and spherical compact grains, for which radiation pressure efficiency becomes lower when their sizes increase. In addition, we find that the outward mass flux of porous dust aggregates with monomer size of 0.1 μm is larger than that of compact grains by an order of magnitude at the disk radius of 1 AU, when their sizes are several microns. This implies that large compact grains like calcium-aluminum-rich inclusions are hardly transported to the outer region by stellar radiation pressure, whereas porous dust aggregates like chondritic-porous interplanetary dust particles are efficiently transported to the comet formation region. Crystalline silicates are possibly transported in porous dust aggregates by stellar radiation pressure from the inner hot region to the outer cold cometary region in the protosolar nebula.

  14. Short and Long Wave Radiative Forcing from Desert Dust and Impacts on Weather and Climate

    NASA Astrophysics Data System (ADS)

    Kallos, G.; Spyrou, C.; Mitsakou, C.

    2009-04-01

    The presence of desert dust in the atmosphere has considerable impacts on radiative transfer, clouds and precipitation. Desert dust is a considerable climate modifier. The impacts of desert dust to land and marine ecosystems are considerable as well in humans. Modeling tools have been developed for studying the dust cycle in both global and regional scales. The uncertainties associated with the dust production, transport and deposition processes are still high for various reasons. Most of them are associated with the surface properties and dust production as well as with the radiative forcing parameterization. Modeling the impacts on radiation and cloud is a complicated task that is either oversimplified or absent in most of the dust models. Radiative transfer corrections due to the presence of dust particles for the incoming solar radiation can be applied (shading effects) by utilizing look up tables in the calculation of Aerosol Optical Depth (AOD). The impacts of dust on long wave radiation transfer are more complicated. A new version of the SKIRON/Dust modeling system incorporates the Rapid Radiative Transfer Model - RRTM for both short and long wave radiation. The new radiative transfer scheme has many properties that allow the partitioning of both short and long wave radiation according to the dust concentration and size distribution. In this presentation we discuss the new model characteristics and especially the dust radiative properties as described by both: lookup tables and empirical formulation as well as the new approach by utilizing RRTM. Several cases with dust outbreaks in the Mediterranean and Europe have been analyzed. Heating rates of 2-10 degrees K/day (or even higher in cases of a strong episode) have been calulated within the dust layer. The model results are compared with soundings, lidar and AERONET observations. As it was found, the dust cloud has as a result the surface cooling of 50-80 Wm-2 in remote locations. Near the source areas is

  15. Higher-spin currents and thermal flux from Hawking radiation

    SciTech Connect

    Iso, Satoshi; Morita, Takeshi; Umetsu, Hiroshi

    2007-06-15

    Quantum fields near black hole horizons can be described in terms of an infinite set of d=2 conformal fields. In this paper, by investigating transformation properties of general higher-spin currents under a conformal transformation, we reproduce the thermal distribution of Hawking radiation in both cases of bosons and fermions. As a by-product, we obtain a generalization of the Schwarzian derivative for higher-spin currents.

  16. Hawking radiation via higher-spin gauge anomalies

    SciTech Connect

    Iso, Satoshi; Morita, Takeshi; Umetsu, Hiroshi

    2008-02-15

    We give a higher-spin generalization of the anomaly method for the Hawking radiation from black holes. In the paper [S. Iso, T. Morita, and H. Umetsu, arXiv:0710.0453.] higher-spin generalizations of the gauge (and gravitational) anomalies in d=2 were obtained. By applying these anomalies to black hole physics, we derive the higher moments of the Hawking fluxes. We also give a higher-spin generalization of the trace anomaly method by Christensen and Fulling [S. Christensen and S. Fulling, Phys. Rev. D 15, 2088 (1977).].

  17. The Evolution of Dust and Infrared Radiation in HII Regions

    NASA Astrophysics Data System (ADS)

    Topchieva, A.; Wiebe, D.; Kirsanova, M.; Krushinsky, V.

    2017-06-01

    Regions of ionized hydrogen are often observed in infrared (IR) emission as ring-like nebulae. IR emission presumably comes from hot dust embedded in ionized gas and surrounding the ionized gas. The dust within these regions is believed to be partially blown away by the action of both the stellar wind and radiation pressure from young massive stars. We investigate trends in morphology of IR ring nebulae representing HII regions. Archival data from VLA New GPS 20 cm survey as well as from Spitzer GLIMPSE and MIPSGAL surveys at 8 and 24 micron are utilized to select visually objects with more or less regular shapes. We have identified 92 HII regions surrounded by closed or nearly closed IR rings. Shapes of these rings are characterized by fitting ellipses in order to estimate their orientation and oblateness. From our catalogue of 92 objects we have selected 27 objects with eccentricities of fitted ellipses less than 0.3. These objects are suggested as prototype targets for 1D hydrodynamic modeling.

  18. Sensitivity simulations with direct shortwave radiative forcing by aeolian dust during glacial cycles

    NASA Astrophysics Data System (ADS)

    Bauer, E.; Ganopolski, A.

    2014-07-01

    Possible feedback effects between aeolian dust, climate and ice sheets are studied for the first time with an Earth system model of intermediate complexity over the late Pleistocene period. Correlations between climate and dust deposition records suggest that aeolian dust potentially plays an important role for the evolution of glacial cycles. Here climatic effects from the dust direct radiative forcing (DRF) caused by absorption and scattering of solar radiation are investigated. Key elements controlling the dust DRF are the atmospheric dust distribution and the absorption-scattering efficiency of dust aerosols. Effective physical parameters in the description of these elements are varied within uncertainty ranges known from available data and detailed model studies. Although the parameters can be reasonably constrained, the simulated dust DRF spans a~wide uncertainty range related to the strong nonlinearity of the Earth system. In our simulations, the dust DRF is highly localized. Medium-range parameters result in negative DRF of several watts per square metre in regions close to major dust sources and negligible values elsewhere. In the case of high absorption efficiency, the local dust DRF can reach positive values and the global mean DRF can be insignificantly small. In the case of low absorption efficiency, the dust DRF can produce a significant global cooling in glacial periods, which leads to a doubling of the maximum glacial ice volume relative to the case with small dust DRF. DRF-induced temperature and precipitation changes can either be attenuated or amplified through a feedback loop involving the dust cycle. The sensitivity experiments suggest that depending on dust optical parameters, dust DRF has the potential to either damp or reinforce glacial-interglacial climate changes.

  19. Mineral dust radiative effect on snow in European Alps

    NASA Astrophysics Data System (ADS)

    Di Mauro, Biagio; Fava, Francesco; Ferrero, Luca; Garzonio, Roberto; Baccolo, Giovanni; Delmonte, Barbara; Colombo, Roberto

    2015-04-01

    Mineral Dust (MD) is known to increase the absorption of solar radiation when deposited on snow and ice. This process causes a decrease in the albedo and may enhance snow melting, resulting in a positive radiative forcing (RF) in climate system. The RF from MD on snow can assume high values (~100-200 W/m2) after depositional events altering snow and ice radiative balance and hydrological cycle. In this study, we analyzed a significant MD transport happened during spring in 2014 and in particular its impact on snow optical properties. The dust plume was entrained in the troposphere over the Saharan desert (North African Grand Erg Oriental) during the passage of a cold front, and then transported NE over the Mediterranean by cyclonic atmospheric conditions. MD reached the European Alps where it was deposited by snowfall. We conducted a field proximal sensing survey in 10 plots (2x2 meters) at the Artavaggio plains (Lecco, Italy) with a hyperspectral radiometer (ASD Field-spec pro) collecting reflected radiance of snow in a spectral range between 350 and 2500 nm. Surface snow samples were collected and analyzed in clean room with microparticle counter in order to determine the size distribution and the concentration of MD in each sample. In addition, total mass of insoluble material was also measured by filtering the melted snow. Observed spectra were compared to those simulated by parameterizing the Snow, Ice, and Aerosol Radiation (SNICAR) radiative transfer model with observed variables such as snow grain size, snow density and size distribution of MD. We defined a novel spectral index, the Snow Darkening Index (SDI) to combine red and green wavelengths showing nonlinear correlation with measured MD concentration. Instantaneous radiative forcing was then estimated as the spectral difference between upwelling irradiance of plot containing MD and pure snow plots. MD concentration was up to 107 ppm and total mass of insoluble material up to 325 ppm. Measured RF values

  20. The Mars Dust Cycle: Investigating the Effects of Radiatively Active Water Ice Clouds on Surface Stresses and Dust Lifting Potential with the NASA Ames Mars General Circulation Model

    NASA Technical Reports Server (NTRS)

    Kahre, Melinda A.; Hollingsworth, Jeffery

    2012-01-01

    The dust cycle is a critically important component of Mars' current climate system. Dust is present in the atmosphere of Mars year-round but the dust loading varies with season in a generally repeatable manner. Dust has a significant influence on the thermal structure of the atmosphere and thus greatly affects atmospheric circulation. The dust cycle is the most difficult of the three climate cycles (CO2, water, and dust) to model realistically with general circulation models. Until recently, numerical modeling investigations of the dust cycle have typically not included the effects of couplings to the water cycle through cloud formation. In the Martian atmosphere, dust particles likely provide the seed nuclei for heterogeneous nucleation of water ice clouds. As ice coats atmospheric dust grains, the newly formed cloud particles exhibit different physical and radiative characteristics. Thus, the coupling between the dust and water cycles likely affects the distributions of dust, water vapor and water ice, and thus atmospheric heating and cooling and the resulting circulations. We use the NASA Ames Mars GCM to investigate the effects of radiatively active water ice clouds on surface stress and the potential for dust lifting. The model includes a state-of-the-art water ice cloud microphysics package and a radiative transfer scheme that accounts for the radiative effects of CO2 gas, dust, and water ice clouds. We focus on simulations that are radiatively forced by a prescribed dust map, and we compare simulations that do and do not include radiatively active clouds. Preliminary results suggest that the magnitude and spatial patterns of surface stress (and thus dust lifting potential) are substantial influenced by the radiative effects of water ice clouds.

  1. The impact of mineral dust particles on radiation and cloud formation during a Saharan dust event over Western Europe

    NASA Astrophysics Data System (ADS)

    Bangert, M.; Nenes, A.; Vogel, B.; Vogel, H.; Barahona, D.; Kumar, P.; Blahak, U.; Seifert, A.

    2010-12-01

    Dust, through their action as cloud condensation nuclei (CCN) and ice nuclei (IN), has long been hypothesized to impact clouds and the hydrological cycle. This effect is particularly strong during dust outbreaks. Europe, being adjacent to the Sahara, is susceptible to the effects of dust storms; a quantitative assessment remains elusive and is the subject of this study. This talk focuses on one major dust event that occurred in May 2008. Its origin was in the Sahara and from there mineral dust particles were transported over the western Mediterranean, covering large areas of Western Europe. During the episode, high aerosol concentrations were observed throughout Europe; ice nuclei concentrations significantly increased (compared to pre-event levels) at Kleiner Feldberg, Germany (Bingemer et al. 2009). During this time, traditional weather forecast models (which currently neglect aerosol impacts on atmospheric processes) exhibited poor prediction skill. The impacts of dust on atmospheric state is studied with the regional scale online coupled model system COSMO-ART (Vogel et al., 2009) that accounts for feedbacks between chemistry, aerosols, radiation, and clouds. A two-moment cloud microphysics scheme (Seifert & Beheng 2001) is coupled together with comprehensive parameterisations for aerosol activation (Kumar et al. 2009; Barahona et al. 2010) and ice nucleation (Barahona and Nenes 2009) to simulate the impact of the various aerosol particles on the cloud microphysics and therefore on cloud properties and precipitation. The sensitivity of predicted atmospheric state to the dust amount, properties (hygroscopicity) and parameterization is thoroughly studied.

  2. Sensitivity simulations with direct radiative forcing by aeolian dust during glacial cycles

    NASA Astrophysics Data System (ADS)

    Bauer, E.; Ganopolski, A.

    2014-01-01

    Possible feedback effects between aeolian dust, climate and ice sheets are studied for the first time with an Earth system model of intermediate complexity over the late Pleistocene period. Correlations between climate variables and dust deposits suggest that aeolian dust potentially plays an important role for the evolution of glacial cycles. Here climatic effects from the dust direct radiative forcing (DRF) caused by absorption and scattering of solar radiation are investigated. Key factors controlling the dust DRF are the atmospheric dust distribution and the absorption-scattering efficiency of dust aerosols. Effective physical parameters in the description of these factors are varied within uncertainty ranges known from available data and detailed model studies. Although the parameters are reasonably constrained by use of these studies, the simulated dust DRF spans a wide uncertainty range related to nonlinear dependencies. In our simulations, the dust DRF is highly localized. Medium-range parameters result in negative DRF of several W m-2 in regions close to major dust sources and negligible values elsewhere. In case of high absorption efficiency, the local dust DRF can reach positive values and the global mean DRF can be insignificantly small. In case of low absorption efficiency, the dust DRF can produce a significant global cooling in glacial periods which leads to a doubling of the maximum glacial ice volume relative to the case with small dust DRF. DRF-induced temperature and precipitation changes can either be attenuated or amplified through a feedback loop involving the dust cycle. The sensitivity experiments suggest that depending on dust optical parameters the DRF has the potential to either damp or reinforce glacial-interglacial climate changes.

  3. Effects of dust accumulation and removal on radiator surfaces on Mars

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Perez-Davis, Marla E.; Rutledge, Sharon K.; Hotes, Deborah; Olle, Raymond

    1991-01-01

    Tests were carried out to assess the impact of wind blown dust accumulation and abrasion on radiator surfaces on Mars. High emittance arc-textured copper and niobium-1 percent-zirconium samples were subjected to basaltic dust laden wind at Martian pressure (1000 Pa) at speeds varying from 19 to 97 m/s in the Martian Surface Wind Tunnel. The effect of accumulated dust was also observed by pre-dusting some of the samples before the test. Radiator degradation was determined by measuring the change in the emittance after dust was deposited and/or removed. The principle mode of degradation was abrasion. Arc textured Nb-1 percent-Zr proved to be more susceptible to degradation than Cu, and pre-dusting appeared to have lessened the abrasion.

  4. Effects of dust accumulation and removal on radiators surfaces on Mars

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Perez-Davis, Marla E.; Rutledge, Sharon K.; Hotes, Deborah; Olle, Raymond M.

    1991-01-01

    Tests were carried out to assess the impact of wind blown dust accumulation and abrasion on radiator surfaces on Mars. High emittance arc-textured copper and niobium-1 percent-zirconium samples were subjected to basaltic dust laden wind at Martian pressure (1000 Pa) at speeds varying from 19 to 97 m/s in the Martian Surface Wind Tunnel. The effect of accumulated dust was also observed by pre-dusting some of the samples before the test. Radiator degradation was determined by measuring the change in the emittance after dust was deposited and/or removed. The principle mode of degradation was abrasion. Arc textured Nb-1 percent-Zr proved to be more susceptible to degradation than Cu, and pre-dusting appeared to have lessened the abrasion.

  5. Effects of dust accumulation and removal on radiator surfaces on Mars

    SciTech Connect

    Gaier, J.R.; Perez-Davis, M.E.; Rutledge, S.K.; Hotes, D.; Olle, R.

    1991-01-01

    Tests were carried out to assess the impact of wind blown dust accumulation and abrasion on radiator surfaces on Mars. High emittance arc-textured copper (Cu) and niobium-1%-zirconium (Nb-1%Zr) samples were subjected to basaltic dust laden wind at Martian pressure (1000 Pa) at speeds varying from 19 to 97 m/s in the Martian Surface Wind Tunnel at NASA Ames Research Center. The effect of accumulated dust was also observed by pre-dusting some of the samples before the test. Radiator degradation was determined by measuring the change in the emittance after dust was deposited and/or removed. The principal mode of degradation was abrasion. Arc-textured Nb-1%Zr proved to be more susceptible to degradation than Cu, and pre-dusting appeared to have lessened the abrasion.

  6. Uniform Dust Distributor for Testing Radiative Emittance of Dust-Coated Surfaces

    NASA Technical Reports Server (NTRS)

    Hurlbert, Kathryn Miller; Witte, Larry C.; Hollingsworth, D. Keith

    2012-01-01

    This apparatus distributes dust (typical of the Martian surface) in a uniform fashion on the surface of multiple samples simultaneously. The primary innovation is that the amount of dust deposited on the multiple surfaces can be controlled by the time that the apparatus operates, and each sample will be subject to the same amount of dust deposition. The exact weight of dust that is added per unit of sample area is determined by the use of slides that can be removed sequentially after each dusting.

  7. Undulator radiation carrying spin and orbital angular momentum.

    SciTech Connect

    Sasaki, S.; McNulty, I.; Dejus, R.; X-Ray Science Division

    2007-11-11

    We show that the radiation from a helical undulator not only carries spin angular momentum (circular polarization) but also orbital angular momentum. This exotic property of the undulator radiation may be useful in coherent X-ray imaging and scattering experiments and to probe electronic transitions in matter by orbital dichroism spectroscopy. Also, we present that a new magnet configuration, similar to the structure of Figure-8 undulator or the PERA undulator, may generate right- and left-hand circularly polarized off-axis radiation simultaneously.

  8. Impact of Asian Dust on Global Surface Air Quality and Radiation Budget

    NASA Technical Reports Server (NTRS)

    Chin, Mian; Diehl, Thomas; Yu, Hongbin; Ginoux, Paul

    2006-01-01

    Dust originating from Asian deserts and desertification areas can be transported regionally and globally to affect surface air quality, visibility, and radiation budget not only at immediate downwind locations (e.g., eastern Asia) but also regions far away from the sources (e.g., North America). Deposition of Asian dust to the North Pacific Ocean basin influences the ocean productivity. In this study, we will use the Goddard Chemistry Aerosol Radiation and Transport (GOCART) model, remote sensing data form satellite and from the ground-based network, and in-situ data from aircraft and surface observations to address the following questions: - What are the effects of Asian dust on the surface air quality and visibility over Asia and North America? - What are the seasonal and spatial variations of dust deposition to the North Pacific Ocean? How does the Asian dust affect surface radiation budget?

  9. Impact of Asian Dust on Global Surface Air Quality and Radiation Budget

    NASA Technical Reports Server (NTRS)

    Chin, Mian; Diehl, Thomas; Yu, Hongbin; Ginoux, Paul

    2006-01-01

    Dust originating from Asian deserts and desertification areas can be transported regionally and globally to affect surface air quality, visibility, and radiation budget not only at immediate downwind locations (e.g., eastern Asia) but also regions far away from the sources (e.g., North America). Deposition of Asian dust to the North Pacific Ocean basin influences the ocean productivity. In this study, we will use the Goddard Chemistry Aerosol Radiation and Transport (GOCART) model, remote sensing data form satellite and from the ground-based network, and in-situ data from aircraft and surface observations to address the following questions: - What are the effects of Asian dust on the surface air quality and visibility over Asia and North America? - What are the seasonal and spatial variations of dust deposition to the North Pacific Ocean? How does the Asian dust affect surface radiation budget?

  10. Estimation of Asian Dust Aerosol Effect on Cloud Radiation Forcing Using Fu-Liou Radiative Model and CERES Measurements

    NASA Technical Reports Server (NTRS)

    Su, Jing; Huang, Jianping; Fu, Qiang; Minnis, Patrick; Ge, Jinming; Bi, Jianrong

    2008-01-01

    The impact of Asian dust on cloud radiative forcing during 2003-2006 is studied by using the Earth's Radiant Energy Budget Scanner (CERES) data and the Fu-Liou radiative transfer model. Analysis of satellite data shows that the dust aerosol significantly reduced the cloud cooling effect at TOA. In dust contaminated cloudy regions, the 4-year mean values of the instantaneous shortwave, longwave and net cloud radiative forcing are -138.9, 69.1, and -69.7 Wm(sup -2), which are 57.0, 74.2, and 46.3%, respectively, of the corresponding values in more pristine cloudy regions. The satellite-retrieved cloud properties are significantly different in the dusty regions and can influence the radiative forcing indirectly. The contributions to the cloud radiation forcing by the dust direct, indirect and semi-direct effects are estimated using combined satellite observations and Fu-Liou model simulation. The 4-year mean value of combination of indirect and semi-direct shortwave radiative forcing (SWRF) is 82.2 Wm(sup -2), which is 78.4% of the total dust effect. The direct effect is only 22.7 Wm(sup -2), which is 21.6% of the total effect. Because both first and second indirect effects enhance cloud cooling, the aerosol-induced cloud warming is mainly the result of the semi-direct effect of dust.

  11. Interannual Variability in Dust Deposition, Radiative Forcing, and Snowmelt Rates in the Colorado River Basin

    NASA Astrophysics Data System (ADS)

    Skiles, M.; Painter, T. H.; Deems, J. S.; Barrett, A. P.

    2011-12-01

    Dust in snow accelerates snowmelt through its direct reduction of albedo and its further reduction of albedo by accelerating the growth of snow effective grain size. Since the Anglo expansion and disturbance of the western US that began in the mid 19th century, the mountain snow cover of the Colorado River Basin has been subject to five-fold greater dust loading. Here we present the impacts of dust deposition onto alpine snow cover using a 7-year energy balance record at the alpine and subalpine towers in the Senator Beck Basin Study Area (SBBSA), San Juan Mountains in southwestern Colorado, USA. We assess the radiative and hydrologic impacts with a two-layer point snow energy balance snowmelt model that calculates snowmelt and predicts point runoff using measured inputs of energy exchanges and snow properties. By removing the radiative forcing due to dust, we can determine snowmelt under observed dusty and modeled clean conditions. Additionally, we model the relative response of melt rates to simulated increases in air temperature. Our modeling results indicate that the number of days that dust advances retreat of snow cover and cumulative radiative forcing are linearly related to total dust concentration. The greatest dust radiative impact occurred in 2009, when the highest observed end of year dust concentrations reduced visible albedo to less than 0.35 during the last three weeks of snowcover and snow cover duration was shortened by 50 days. This work also shows that dust radiative forcing has a markedly greater impact on snow cover duration than increases in temperature in terms of acceleration of snowmelt. We have completed the same analysis over a 2-year energy balance record at the Grand Mesa Study plot (GMSP) in west central Colorado, 150 km north of SBBSA. This new location allows us to assess site variability. For example, at SBBSA 2010 and 2011 were the second and third highest dust deposition years, respectively, but 2010 was a larger year with 3

  12. Mineral Dust Impact on Short- and Long-Wave Radiation and Comparison with Ceres Measurements

    NASA Astrophysics Data System (ADS)

    Romano, Salvatore; Perrone, Maria Rita

    2016-06-01

    Clear-sky downward and upward radiative flux measurements both in the short- and in the long-wave spectral range have been used to estimate and analyze the radiation changes at the surface due to the mineral dust advection at a Central Mediterranean site. Then, short- and long-wave radiative fluxes retrieved from the CERES (Clouds and the Earth's Radiant Energy System) radiometer sensors operating on board the EOS (Earth Observing System) AQUA and TERRA platforms have been used to evaluate the mineral dust radiative impact at the top of the atmosphere. Satellite-derived radiative fluxes at the surface have been compared with corresponding ground-based flux measurements, collocated in space and time, to better support and understand the desert dust radiative impact. Results referring to the year 2012 are reported.

  13. Regional Modeling of Dust Mass Balance and Radiative Forcing over East Asia using WRF-Chem

    SciTech Connect

    Chen, Siyu; Zhao, Chun; Qian, Yun; Leung, Lai-Yung R.; Huang, J.; Huang, Zhongwei; Bi, Jianrong; Zhang, Wu; Shi, Jinsen; Yang, Lei; Li, Deshuai; Li, Jinxin

    2014-12-01

    The Weather Research and Forecasting model with Chemistry (WRF-Chem) is used to investigate the seasonal and annual variations of mineral dust over East Asia during 2007-2011, with a focus on the dust mass balance and radiative forcing. A variety of measurements from in-stu and satellite observations have been used to evaluate simulation results. Generally, WRF-Chem reproduces not only the column variability but also the vertical profile and size distribution of mineral dust over and near the dust source regions of East Asia. We investigate the dust lifecycle and the factors that control the seasonal and spatial variations of dust mass balance and radiative forcing over the seven sub-regions of East Asia, i.e. source regions, the Tibetan Plateau, Northern China, Southern China, the ocean outflow region, and Korea-Japan regions. Results show that, over the source regions, transport and dry deposition are the two dominant sinks. Transport contributes to ~30% of the dust sink over the source regions. Dust results in a surface cooling of up to -14 and -10 W m-2, atmospheric warming of up to 20 and 15 W m-2, and TOA cooling of -5 and -8 W m-2 over the two major dust source regions of East Asia, respectively. Over the Tibetan Plateau, transport is the dominant source with a peak in summer. Over identified outflow regions, maximum dust mass loading in spring is contributed by the transport. Dry and wet depositions are the comparably dominant sinks, but wet deposition is larger than dry deposition over the Korea-Japan region, particularly in spring (70% versus 30%). The WRF-Chem simulations can generally capture the measured features of dust aerosols and its radaitve properties and dust mass balance over East Asia, which provides confidence for use in further investigation of dust impact on climate over East Asia.

  14. Saharan Dust Event Impacts on Cloud Formation and Radiation over Western Europe

    NASA Technical Reports Server (NTRS)

    Bangert, M.; Nenes, A.; Vogel, B.; Vogel, H.; Barahona, D.; Karydis, V. A.; Kumar, P.; Kottmeier, C.; Blahak, U.

    2013-01-01

    We investigated the impact of mineral dust particles on clouds, radiation and atmospheric state during a strong Saharan dust event over Europe in May 2008, applying a comprehensive online-coupled regional model framework that explicitly treats particle-microphysics and chemical composition. Sophisticated parameterizations for aerosol activation and ice nucleation, together with two-moment cloud microphysics are used to calculate the interaction of the different particles with clouds depending on their physical and chemical properties. The impact of dust on cloud droplet number concentration was found to be low, with just a slight increase in cloud droplet number concentration for both uncoated and coated dust. For temperatures lower than the level of homogeneous freezing, no significant impact of dust on the number and mass concentration of ice crystals was found, though the concentration of frozen dust particles reached up to 100 l-1 during the ice nucleation events. Mineral dust particles were found to have the largest impact on clouds in a temperature range between freezing level and the level of homogeneous freezing, where they determined the number concentration of ice crystals due to efficient heterogeneous freezing of the dust particles and modified the glaciation of mixed phase clouds. Our simulations show that during the dust events, ice crystals concentrations were increased twofold in this temperature range (compared to if dust interactions are neglected). This had a significant impact on the cloud optical properties, causing a reduction in the incoming short-wave radiation at the surface up to -75Wm-2. Including the direct interaction of dust with radiation caused an additional reduction in the incoming short-wave radiation by 40 to 80Wm-2, and the incoming long-wave radiation at the surface was increased significantly in the order of +10Wm-2. The strong radiative forcings associated with dust caused a reduction in surface temperature in the order of -0

  15. The Effect of Asian Dust Aerosols on Cloud Properties and Radiative Forcing from MODIS and CERES

    NASA Technical Reports Server (NTRS)

    Huang, Jianping; Minnis, Patrick; Lin, Bing; Wang, Tianhe; Yi, Yuhong; Hu, Yongxiang; Sun-Mack, Sunny; Ayers, Kirk

    2005-01-01

    The effects of dust storms on cloud properties and radiative forcing are analyzed over northwestern China from April 2001 to June 2004 using data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) and Clouds and the Earth's Radiant Energy System (CERES) instruments on the Aqua and Terra satellites. On average, ice cloud effective particle diameter, optical depth and ice water path of the cirrus clouds under dust polluted conditions are 11%, 32.8%, and 42% less, respectively, than those derived from ice clouds in dust-free atmospheric environments. The humidity differences are larger in the dusty region than in the dust-free region, and may be caused by removal of moisture by wet dust precipitation. Due to changes in cloud microphysics, the instantaneous net radiative forcing is reduced from -71.2 W/m2 for dust contaminated clouds to -182.7 W/m2 for dust-free clouds. The reduced cooling effects of dusts may lead to a net warming of 1 W/m2, which, if confirmed, would be the strongest aerosol forcing during later winter and early spring dust storm seasons over the studied region.

  16. Orbit-spin coupling and the interannual variability of global-scale dust storm occurrence on Mars

    NASA Astrophysics Data System (ADS)

    Shirley, James H.; Mischna, Michael A.

    2017-05-01

    A new physical hypothesis predicts that a weak coupling of the orbital and rotational motions of extended bodies may give rise to a modulation of circulatory flows within their atmospheres. Driven cycles of intensification and relaxation of large-scale circulatory flows are predicted, with the phasing of these changes linked directly to the rate of change of the orbital angular momentum, dL/dt, with respect to inertial frames. We test the hypothesis that global-scale dust storms (GDS) on Mars may occur when periods of circulatory intensification (associated with positive and negative extrema of the dL/dt waveform) coincide with the southern summer dust storm season on Mars. The orbit-spin coupling hypothesis additionally predicts that the intervening 'transitional' periods, which are characterized by the disappearance and subsequent sign change of dL/dt, may be unfavorable for the occurrence of GDS, when they occur during the southern summer dust storm season. These hypotheses are strongly supported by comparisons between calculated dynamical time series of dL/dt and historic observations. All of the nine known global-scale dust storms on Mars took place during Mars years when circulatory intensification during the dust storm season is 'retrodicted' under the orbit-spin coupling hypothesis. None of the historic global-scale dust storms of our catalog occurred during transitional intervals. Orbit-spin coupling appears to play an important role in the excitation of the interannual variability of the atmospheric circulation of Mars.

  17. The spatial distribution of mineral dust and its shortwave radiative forcing over North Africa. Modeling sensitivities to dust emissions and aerosol size treatments

    SciTech Connect

    Zhao, Chun; Liu, Xiaohong; Leung, Lai-Yung R.; Johnson, Ben; McFarlane, Sally A.; Gustafson, William I.; Fast, Jerome D.; Easter, Richard C.

    2010-09-20

    A fully coupled meteorology-chemistry-aerosol model (WRF-Chem) with the implementation of two dust emission schemes (GOCART and DUSTRAN) into two aerosol models (MADE/SORGAM and MOSAIC) is applied over North Africa to investigate the modeling sensitivities to dust emissions and aerosol size treatments in simulating mineral dust and its shortwave (SW) radiative forcing. Model results of the spatial distribution of mineral dust and its radiative forcing are evaluated using measurements from the AMMA SOP0 campaign in January and February of 2006 over North Africa. Our study suggests that the size distribution of emitted dust can result in significant differences (up to 100%) in simulating mineral dust and its SW radiative forcing. With the same dust emission and dry deposition processes, two aerosol models, MADE/SORGAM and MOSAIC, can yield large difference in size distributions of dust particles due to their different aerosol size treatments using modal and sectional approaches respectively. However, the difference between the two aerosol models in simulating the mass concentrations and the SW radiative forcing of mineral dust is small (< 10%). The model simulations show that mineral dust increases AOD by a factor of 2, heats the lower atmosphere (1-3 km) with a maximum rate of 0.7±0.5 K day-1 below 1 km, and reduces the downwelling SW radiation by up to 25 W m-2 on 24-hour average at surface, highlighting the importance of including dust radiative impact in understanding the regional climate of North Africa. When compared to the available measurements, WRF-Chem simulations can generally capture the measured features of mineral dust and its radiative properties over North Africa, suggesting that the model can be used to perform more extensive simulations of regional climate over North Africa.

  18. Dust Transport, Deposition and Radiative Effects Observed from MODIS

    NASA Technical Reports Server (NTRS)

    Kaufman, Y. J.; Koren, I.; Remer, L. A.; Tanre, D.; Ginoux, P.; Fan, S.

    2003-01-01

    Carlson (1977) used satellite (AVHRR) observation of dust episodes 3 estimate that 90 tg of dust are emitted from Africa (0-30 N) to the Atlantic Ocean between June and August. MODIS systematic measurements of aerosol optical thickness (AOT) and the fraction of the AOT (f) due to the fine mode (see Remer et al abstract), are used to derive the column concentration, flux and deposition of African dust over the Atlantic Ocean. The main data set is for 2001 but the results are consistent with MODIS measurements from 2002. The analysis first determines the properties of maritime baseline aerosol (AOT=0.06, f=0.5); followed by linear scaling of the dust AOT and the anthropogenic AOT, based on MODIS measured values of the fraction "f" being 0.9 for anthropogenic aerosol and 0.5 for dust. NCEP winds are used in the analysis and are evaluated against observed dust movements between the Terra and Aqua passes (see Koren et al. abstract). Monthly values of dust transport and deposition are calculated. Preliminary results show that 280 tg of dust are emitted annually from Africa to the Atlantic Ocean between 20s and 30N, with 40 tg returning to Africa and Europe between 30N and 50N. 85 tg reach the Americas, with 130-150 tg are deposited in the Atlantic Ocean. The results are compared with dust transport models that indicate 110-230 tg of dust being deposited in the Ocean. It is interesting to note that the early estimates of Carlson (1977) and Carlson & Prosper0 (1972) are very close to our estimate from MODIS of 100 tg for the same latitude range and monthly period.

  19. CONSTRAINING SPINNING DUST PARAMETERS WITH THE WMAP FIVE-YEAR DATA

    SciTech Connect

    Dobler, Gregory; Finkbeiner, Douglas P.; Draine, Bruce

    2009-07-10

    We characterize spinning dust emission in the warm ionized medium (WIM) by comparing templates of Galactic dust and H{alpha} with the five-year maps from the Wilkinson Microwave Anisotropy Probe (WMAP). The H{alpha}-correlated microwave emission deviates from the thermal bremsstrahlung (free-free) spectrum expected for ionized gas, exhibiting an additional broad bump peaked at {approx}40 GHz which provides {approx}20% of the peak intensity. We confirm that the bump is consistent with a modified Draine and Lazarian spinning dust model, though the peak frequency of the emission is somewhat lower than the 50 GHz previously claimed. This frequency shift results from systematic errors in the large-scale modes of the three-year WMAP data which have been corrected in the five-year data release. We show that the bump is not the result of errors in the H{alpha} template by analyzing regions of high free-free intensity, where the WMAP K-band map may be used as the free-free template. We rule out a pure free-free spectrum for the H{alpha}-correlated emission at high confidence: {approx}27{sigma} for the nearly full-sky fit, even after marginalizing over the cosmic microwave background cross-correlation bias. We also extend the previous analysis by searching the parameter space of the Draine and Lazarian model but letting the amplitude float. The best fit for reasonable values of the characteristic electric dipole moment and density requires an amplitude factor of {approx}0.3. This suggests that small polycyclic aromatic hydrocarbons in the WIM are depleted by a factor of {approx}3.

  20. Uncertainty in Modeling Dust Mass Balance and Radiative Forcing from Size Parameterization

    SciTech Connect

    Zhao, Chun; Chen, Siyu; Leung, Lai-Yung R.; Qian, Yun; Kok, Jasper; Zaveri, Rahul A.; Huang, J.

    2013-11-05

    This study examines the uncertainties in simulating mass balance and radiative forcing of mineral dust due to biases in the aerosol size parameterization. Simulations are conducted quasi-globally (180oW-180oE and 60oS-70oN) using the WRF24 Chem model with three different approaches to represent aerosol size distribution (8-bin, 4-bin, and 3-mode). The biases in the 3-mode or 4-bin approaches against a relatively more accurate 8-bin approach in simulating dust mass balance and radiative forcing are identified. Compared to the 8-bin approach, the 4-bin approach simulates similar but coarser size distributions of dust particles in the atmosphere, while the 3-mode pproach retains more fine dust particles but fewer coarse dust particles due to its prescribed og of each mode. Although the 3-mode approach yields up to 10 days longer dust mass lifetime over the remote oceanic regions than the 8-bin approach, the three size approaches produce similar dust mass lifetime (3.2 days to 3.5 days) on quasi-global average, reflecting that the global dust mass lifetime is mainly determined by the dust mass lifetime near the dust source regions. With the same global dust emission (~6000 Tg yr-1), the 8-bin approach produces a dust mass loading of 39 Tg, while the 4-bin and 3-mode approaches produce 3% (40.2 Tg) and 25% (49.1 Tg) higher dust mass loading, respectively. The difference in dust mass loading between the 8-bin approach and the 4-bin or 3-mode approaches has large spatial variations, with generally smaller relative difference (<10%) near the surface over the dust source regions. The three size approaches also result in significantly different dry and wet deposition fluxes and number concentrations of dust. The difference in dust aerosol optical depth (AOD) (a factor of 3) among the three size approaches is much larger than their difference (25%) in dust mass loading. Compared to the 8-bin approach, the 4-bin approach yields stronger dust absorptivity, while the 3-mode

  1. Dust size parameterization in RegCM4: Impact on aerosol burden and radiative forcing

    NASA Astrophysics Data System (ADS)

    Tsikerdekis, A.; Zanis, P.; Steiner, A. L.; Solmon, F.; Amiridis, V.; Marinou, E.; Katragkou, E.; Karacostas, T.; Foret, G.

    2015-12-01

    We investigate the sensitivity of two dust parameterizations of the regional climate model RegCM4, for the period 2008-2012, over a large domain focused on the Sahara and the Mediterranean. We implement two size bin distributions: 1) a 4-bin approach, where each bin is delimited using an isolog approach and every size group has equal ranges in logarithmic scale according to the diameter of the dust particles, and 2) a 12-bin approach with each bin defined according to an isogradient method, where the size ranges are dependent on the dry deposition velocity of dust particles. Increasing the number of the transported dust size bin improves the representation of the physical properties of dust particles that belong on the same group. Thus, more size bins minimize the error and improve the simulation of atmospheric processes. The emission, deposition and transport of dust are evaluated combined for each experiment to determine the impact of dust size bin partition. The radiative effects of dust over the area are also discussed and evaluated with the CALIPSO Aerosol Optical Depth (AOD) pure dust product. Techniques for the discrimination of the dust component from other aerosol types have been recently developed in the framework of the LIVAS (LIdar climatology of Vertical Aerosol Structure for space-based lidar simulation studies- http://lidar.space.noa.gr:8080/livas/).

  2. Hydrological and ecological implications of radiative forcing by dust in snow

    NASA Astrophysics Data System (ADS)

    Painter, T.; Bryant, A. C.; Deems, J. S.; Skiles, M.

    2012-12-01

    The runoff from the Colorado River supplies water to over 30 million people in seven US states and Mexico. Climate change projections suggest that this runoff will decrease in the next 50 years by 7-20% due to increases in evapotranspiration and decreases in the ratio of snowfall to rain. Such scenarios challenge the sustainability of the freshwater supply to the southwest US. Recent research however has shown that radiative forcing by dust in snow has been shortening snow cover duration by several weeks due to a 5-7-fold increase in dust loading relative to prior to the European-settlement of the western US in the mid-1800s. In the mountains of the Upper Colorado River, the absolute dust radiative forcing across the period ranges from 30 to 75 W m-2, in turn shortening snow cover duration by 21 to 51 days. Extended to the scale of the Upper Colorado River Basin, this impact has brought peak normalized runoff at Lee's Ferry, AZ (Lake Powell) more than three weeks earlier and reduced the total annual runoff by an average of ~5%. In this region, earlier snowmelt forced by dust radiative forcing impacts alpine vegetation by increasing synchronicity in phenology across the alpine landscape with increasingly earlier snowmelt. Whereas reduced dust load results in topographically-sensitive melt and loss of snow cover, the more spatially-uniform snowmelt from dust radiative forcing leads to synchronized growth and flowering across the landscape. Water managers in the Upper Colorado basin now seek detailed real-time knowledge of dust presence, radiative forcing, and its potential to accelerate snowmelt, as well as understanding its implications for water supply under current conditions and in a changed climate. Likewise, water stakeholder groups, water conservation districts, and state and federal agencies are discussing efforts to restabilize soil surfaces in the dust-emitting regions to mitigate impacts of dust on snowmelt and runoff. However, as these policy

  3. Impact of Radiatively Interactive Dust Aerosols in the NASA GEOS-5 Climate Model: Sensitivity to Dust Particle Shape and Refractive Index

    NASA Technical Reports Server (NTRS)

    Colarco, Peter R.; Nowottnick, Edward Paul; Randles, Cynthia A.; Yi, Bingqi; Yang, Ping; Kim, Kyu-Myong; Smith, Jamison A.; Bardeen, Charles D.

    2013-01-01

    We investigate the radiative effects of dust aerosols in the NASA GEOS-5 atmospheric general circulation model. GEOS-5 is improved with the inclusion of a sectional aerosol and cloud microphysics module, the Community Aerosol and Radiation Model for Atmospheres (CARMA). Into CARMA we introduce treatment of the dust and sea salt aerosol lifecycle, including sources, transport evolution, and sinks. The aerosols are radiatively coupled to GEOS-5, and we perform a series of multi-decade AMIP-style simulations in which dust optical properties (spectral refractive index and particle shape distribution) are varied. Optical properties assuming spherical dust particles are from Mie theory, while those for non-spherical shape distributions are drawn from a recently available database for tri-axial ellipsoids. The climatologies of the various simulations generally compare well to data from the MODIS, MISR, and CALIOP space-based sensors, the ground-based AERONET, and surface measurements of dust deposition and concentration. Focusing on the summertime Saharan dust cycle we show significant variability in our simulations resulting from different choices of dust optical properties. Atmospheric heating due to dust enhances surface winds over important Saharan dust sources, and we find a positive feedback where increased dust absorption leads to increased dust emissions. We further find that increased dust absorption leads to a strengthening of the summertime Hadley cell circulation, increasing dust lofting to higher altitudes and strengthening the African Easterly Jet. This leads to a longer atmospheric residence time, higher altitude, and generally more northward transport of dust in simulations with the most absorbing dust optical properties. We find that particle shape, although important for radiance simulations, is a minor effect compared to choices of refractive index, although total atmospheric forcing is enhanced by greater than 10 percent for simulations incorporating a

  4. Dust plumes over the Pacific, Indian, and Atlantic oceans: Climatology and radiative impact

    NASA Astrophysics Data System (ADS)

    Zhu, Aihua; Ramanathan, V.; Li, Fang; Kim, Dohyeong

    2007-08-01

    Multiple satellite data sets in conjunction with the Monte Carlo Aerosol-Cloud-Radiation (MACR) model are employed to determine climatological distributions and radiative impacts of dust plumes over the Pacific, Indian, and Atlantic oceans. Three target regions, namely the Yellow Sea (YS), Arabian Sea (AS), and Saharan Coast (SC), are examined for quantitative comparisons of dust properties and their impacts on climate. Twenty year averaged Advanced Very High Resolution Radiometer (AVHRR) aerosol optical depth (AOD) data clearly show the peak dust season for the three target regions, March-April-May for YS and June-July-August for AS and SC. Georgia Institute of Technology-Goddard Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) modeled dust AOD fraction and Moderate Imaging Spectroradiometer (MODIS) large-mode AOD ratio are adopted to evaluate the dust fraction estimate. Stratospheric Aerosol and Gas Experiment (SAGE) II aerosol extinction coefficient data are used to define the vertical distribution of dust. The elevated dust plumes are detected by subtracting the non-dust-season values from dust season values of SAGE II data, showing extinction peak around ˜4 km over AS and SC. Over YS, dust plumes are found presenting multilayered structure. The shortwave (SW) forcing of dust, although moderated by the longwave (LW) effect, dominates the net effects (SW + LW) of dust plumes. Under clear-sky (i.e., cloudless) conditions, dust plumes reduce about 5.9 W m-2, 17.8 W m-2, and 14.2 W m-2 regional and seasonal mean radiative flux reaching the surface over YS, AS, and SC, respectively. Of the three regions, dust plumes over AS have the largest effect on atmospheric heating owing to a lower single-scattering albedo and the relatively large dust loading. The maximum SW heating occurs over AS with the value around +0.5 K/day inside the dust layer at ˜4 km. The LW effect results in strong cooling throughout the dust layer and moderate heating below the

  5. Dust radiative forcing in snow of the Upper Colorado River Basin: 1. A 6 year record of energy balance, radiation, and dust concentrations

    NASA Astrophysics Data System (ADS)

    Painter, Thomas H.; Skiles, S. Mckenzie; Deems, Jeffrey S.; Bryant, Ann C.; Landry, Christopher C.

    2012-07-01

    Dust in snow accelerates snowmelt through its direct reduction of snow albedo and its further indirect reduction of albedo by accelerating the growth of snow grains. Since the westward expansion of the United States that began in the mid-19th century, the mountain snow cover of the Colorado River Basin has been subject to five-fold greater dust loading, largely from the Colorado Plateau and Great Basin. Radiative forcing of snowmelt by dust is not captured by conventional micrometeorological measurements, and must be monitored by a more comprehensive suite of radiation instruments. Here we present a 6 year record of energy balance and detailed radiation measurements in the Senator Beck Basin Study Area, San Juan Mountains, Colorado, USA. Data include broadband irradiance, filtered irradiance, broadband reflected flux, filtered reflected flux, broadband and visible albedo, longwave irradiance, wind speed, relative humidity, and air temperatures. The gradient of the snow surface is monitored weekly and used to correct albedo measurements for geometric effects. The snow is sampled weekly for dust concentrations in plots immediately adjacent to each tower over the melt season. Broadband albedo in the last weeks of snow cover ranged from 0.33 to 0.55 across the 6 years and two sites. Total end of year dust concentration in the top 3 cm of the snow column ranged from 0.23 mg g-1 to 4.16 mg g-1. These measurements enable monitoring and modeling of dust and climate-driven snowmelt forcings in the Upper Colorado River Basin.

  6. Longwave radiative effects of Saharan dust during the ICE-D campaign

    NASA Astrophysics Data System (ADS)

    Brooke, Jennifer; Havemann, Stephan; Ryder, Claire; O'Sullivan, Debbie

    2017-04-01

    The Havemann-Taylor Fast Radiative Transfer Code (HT-FRTC) is a fast radiative transfer model based on Principal Components. Scattering has been incorporated into HT-FRTC which allows simulations of aerosol as well as clear-sky atmospheres. This work evaluates the scattering scheme in HT-FRTC and investigates dust-affected brightness temperatures using in-situ observations from Ice in Clouds Experiment - Dust (ICE-D) campaign. The ICE-D campaign occurred during August 2015 and was based from Cape Verde. The ICE-D campaign is a multidisciplinary project which achieved measurements of in-situ mineral dust properties of the dust advected from the Sahara, and on the aerosol-cloud interactions using the FAAM BAe-146 research aircraft. ICE-D encountered a range of low (0.3), intermediate (0.8) and high (1.3) aerosol optical depths, AODs, and therefore provides a range of atmospheric dust loadings in the assessment of dust scattering in HT-FRTC. Spectral radiances in the thermal infrared window region (800 - 1200 cm-1) are sensitive to the presence of mineral dust; mineral dust acts to reduce the upwelling infrared radiation caused by the absorption and re-emission of radiation by the dust layer. ARIES (Airborne Research Interferometer Evaluation System) is a nadir-facing interferometer, measuring infrared radiances between 550 and 3000 cm-1. The ARIES spectral radiances are converted to brightness temperatures by inversion of the Planck function. The mineral dust size distribution is important for radiative transfer applications as it provides a measure of aerosol scattering. The longwave spectral mineral dust optical properties including the mass extinction coefficients, single scattering albedos and the asymmetry parameter have been derived from the mean ICE-D size distribution. HT-FRTC scattering simulations are initialised with vertical mass fractions which can be derived from extinction profiles from the lidar along with the specific extinction coefficient, kext (m2

  7. Spinning mode acoustic radiation from the flight inlet

    NASA Technical Reports Server (NTRS)

    Moss, W. F.

    1983-01-01

    A mathematical model was developed for spinning mode acoustic radiation from a thick wall duct without flow. This model is based on a series of experiments (with and without flow). A nearly pure azimuthal spinning mode was isolated and then reflection coefficients and far field pressure (amplitude and phase) were measured. In our model the governing boundary value problem for the Helmholtz equation is first converted into an integral equation for the unknown acoustic pressure over a disk, S1, near the mouth of the duct and over the exterior surface, S2, of the duct. Assuming a pure azimuthal mode excitation, the azimuthal dependence is integrated out which yields an integral equation over the generator C1 of S1 and the generator C2 of S2. The sound pressure on C1 was approximated by a truncated modal expansion of the interior acoustic pressure. Piecewise linear spline approximation on C2 was used.

  8. The new surface and radiative transfer parameterization in the SKIRON/Dust modeling System

    NASA Astrophysics Data System (ADS)

    Kallos, G.; Spyrou, C.; Mitsakou, C.; Vlastou, G.

    2008-12-01

    Major contributors of PM in the atmosphere are the dust areas and mainly Sahara. The impacts of dust in the atmosphere are many and especially in radiation, clouds and precipitation. It is a considerable climate modifier. The impacts to land and marine ecosystems are considerable as well in humans. Modeling the dust cycle in the atmosphere at the University of Athens started in the mid-nineties with the development of the SKIRON/Dust atmospheric modeling system. The main purpose was the development of an analysis and forecasting tool that will provide early warning of Saharan dust outbreaks. The dust cycle module is directly coupled with the meteorological model and in its early development was called DREAM. Continuous development of the entire system led to a model version where inaccuracies have been reduced and extra features have been added. Some of these are log-normal particle size distribution (eight bins), calculation of Aerosol Optical Depth (AOD), radiative transfer corrections by utilizing look up tables (shading effect), new dust source identification and utilization of rocky soil characterization, replacement of the dry and wet deposition schemes with more accurate ones, in-cloud scavenging, etc. The new model version replaced the previous four-size bins system in the operations of the University of Athens. Recently, the old radiative transfer scheme from GFDL has been replaced by the Rapid Radiative Transfer Model - RRTM for both short and long wave radiation. The new radiative transfer scheme has many properties that allow the description of dust impacts in the atmosphere on a more accurate way. Mid and low tropospheric warming by dust is one of the new features that the model can describe. In this presentation we discuss the new model characteristics and especially the dust radiative properties as described by both: lookup tables and empirical formulation as well as the new approach by utilizing RRTM. The model results are compared with lidar and

  9. What happens when spins meet for ionizing radiation dosimetry?

    NASA Astrophysics Data System (ADS)

    Pavoni, Juliana F.; Neves-Junior, Wellington F. P.; Baffa, Oswaldo

    2016-07-01

    Electron spin resonance (ESR) and magnetic resonance imaging (MRI) can be used to measure radiation dose deposited in different milieu through its effects. Radiation can break chemical bonds and if they produce stable free radicals, ESR can measure their concentration through their spins and a dose can be inferred. Ionizing radiation can also promote polymerization and in this case proton relaxation times can be measured and an image weighed by T2 can be produced giving spatial information about dose. A review of the basics of these applications is presented concluding with an end-to-end test using a composite Gel-Alanine phantom to validate 3-dimensionally dose distribution delivered in a simulation of Volume Modulated Arch Therapy on the simultaneous treatment of multiple brain metastases. The results obtained with the gel and alanine dosimeters are consistent with the expected by the treatment planning system, showing the potential of this multidosimetric approach and validating dosimetrically the multiple brain metastases treatment using VMAT.

  10. What happens when spins meet for ionizing radiation dosimetry?

    SciTech Connect

    Pavoni, Juliana F.; Baffa, Oswaldo; Neves-Junior, Wellington F. P.

    2016-07-07

    Electron spin resonance (ESR) and magnetic resonance imaging (MRI) can be used to measure radiation dose deposited in different milieu through its effects. Radiation can break chemical bonds and if they produce stable free radicals, ESR can measure their concentration through their spins and a dose can be inferred. Ionizing radiation can also promote polymerization and in this case proton relaxation times can be measured and an image weighed by T2 can be produced giving spatial information about dose. A review of the basics of these applications is presented concluding with an end-to-end test using a composite Gel-Alanine phantom to validate 3-dimensionally dose distribution delivered in a simulation of Volume Modulated Arch Therapy on the simultaneous treatment of multiple brain metastases. The results obtained with the gel and alanine dosimeters are consistent with the expected by the treatment planning system, showing the potential of this multidosimetric approach and validating dosimetrically the multiple brain metastases treatment using VMAT.

  11. Direct radiative effects induced by intense desert dust outbreaks over the broader Mediterranean basin

    NASA Astrophysics Data System (ADS)

    Gkikas, Antonis; Obiso, Vincenzo; Vendrell, Lluis; Basart, Sara; Jorba, Oriol; Pérez Garcia-Pando, Carlos; Hatzianastassiou, Nikos; Gassó, Santiago; Baldasano, Jose Maria

    2016-04-01

    Throughout the year, under favorable conditions, massive loads of mineral particles originating in the northern African and Middle East deserts are transported over the Mediterranean basin. Due to their composition and size, dust aerosols perturb the Earth-Atmosphere system's energy budget interacting directly with the shortwave (SW) and longwave (LW) radiation. The present study aims to compute the Mediterranean dust outbreaks' direct radiative effects (DREs) as well as to assess the effect of including dust DREs in numerical simulations of a regional model. To this aim, 20 intense dust outbreaks have been selected based on their spatial coverage and intensity. Their identification, over the period 2000-2013, has been achieved through an objective and dynamic algorithm which utilizes as inputs daily satellite retrievals derived by the MODIS-Terra, EP-TOMS and OMI-Aura sensors. For each outbreak, two simulations of the NMMB/BSC-Dust model were made for a forecast period of 84 hours, with the model initialized at 00 UTC of the day when the dust outbreak was ignited, activating (RADON) and deactivating (RADOFF) dust-radiation interactions. The simulation domain covers the northern Africa, the Middle East and Europe at 0.25° x 0.25° horizontal resolution, for 40 hybrid sigma pressure levels up to 50 hPa. The instantaneous and regional DREs have been calculated at the top of the atmosphere (TOA), into the atmosphere (ATMAB), and at surface, for the downwelling (SURF) and the absorbed (NETSURF) radiation, for the SW, LW and NET (SW+LW) radiation. The interaction between dust aerosols and NET radiation, locally leads to an atmospheric warming (DREATMAB) by up to 150 Wm-2, a surface cooling (DRENETSURF) by up to 250 Wm-2 and a reduction of the downwelling radiation at the surface (DRESURF) by up to 300 Wm-2. At TOA, DREs are mainly negative (down to -150 Wm-2) indicating a cooling of the Earth-Atmosphere system, although positive values (up to 50 Wm-2) are encountered

  12. Orbit-Spin Coupling Accelerations and Global Dust Storm Intermittency on Mars

    NASA Astrophysics Data System (ADS)

    Mischna, M. A.; Shirley, J. H.

    2015-12-01

    The occurrence of global dust storms (GDS) in some Mars years and not in others is recognized as an outstanding unsolved problem of atmospheric physics. While GDS exhibit a clear seasonality as to when they occur (centered loosely around Mars' perihelion), prior efforts to replicate GDS phenomena using general circulation models (GCMs) have not been entirely successful. A recently developed non-tidal orbit-spin coupling hypothesis predicts that variations in the orbital angular momentum of Mars may give rise to instantaneously small but cumulatively significant changes in the circulation of the Mars atmosphere. Through the use of the MarsWRF GCM, we are able to quantify the time-varying magnitude of this 'coupling term acceleration' (CTA) and relate it to changes in the martian atmospheric circulation and subsequently to observations of the presence or absence of a GDS in particular Mars years. The MarsWRF output shows interannual variability that is derived largely from year-to-year differences in the CTA magnitude and direction, which varies significantly with time and exhibits variable phasing with respect to Mars' annual insolation cycle. A record of the definitive occurrence or non-occurrence of GDS on Mars dating back to 1924 is used in this study. Conditions favorable for the occurrence of GDS, specifically including a constructive strengthening of the overturning meridional circulation, and an enhancement of near-surface wind speed and surface stress, are reproduced by the GCM in all of the Mars years in which a solstice-season GDS was positively identified. In a majority of the Mars years lacking GDS, CTA during the southern summer season are found to be small or nonexistent, or interfere destructively with the meridional overturning circulation, thereby inhibiting GDS initiation. We continue to explore the relationships between the CTA and the martian dust cycle and the modulation of large-scale circulatory flows on Mars due to orbit-spin coupling.

  13. The Impact of the Dust-Shortwave Radiation Effect on Atlantic Hurricane Activity in 2007

    NASA Astrophysics Data System (ADS)

    Isik, A. G.; Chen, S. H.

    2016-12-01

    Mineral dust particles play a vital role in climate and the Earth's energy budget and can have impact on weather as well. This research is to investigate the dust-radiation effect on Atlantic tropical cyclone (TC) activities. The first objective of the research is to follow the development of knowledge about the Saharan air layer (SAL). To investigate how the SAL and Saharan dust affect Atlantic tropical activities, tropical cyclone activities in 2005 and 2007 were studied and connected to environmental conditions, such as sea surface temperature (SST) anomaly, vertical wind shear, and aerosol optical depth (AOD). The 2005 hurricane season was very active, while the 2007 was a normal year. Compared to the normal year 2007, the 2005 hurricane season had a lower dust load, weaker deep shear and warm SST anomaly. The second objective of the research is to study the dust-radiation interaction on Atlantic seasonal TC activity in 2007 using a dust numerical model. Two numerical experiments were conducted. The dust short-wave radiation interaction was activated in one simulation (ON) and deactivated in the other one (OFF). Nine TCs formed in the ON experiment, while only two TCs formed in the OFF experiment through July to September. The results show that for a normal year the dust-radiation interaction reduces vertical wind shear over West Atlantic and thus increases the TC development over region, which is more comparable to observations. It is unfortunate that the model did not produce any TC over the main developing region in both experiments, while five TCs formed in reality.

  14. Spin radiative corrections to the radiation probability and power in classical and quantum electrodynamics

    NASA Astrophysics Data System (ADS)

    Lebedev, S. L.

    2016-04-01

    Spin radiative effects in a one-particle sector of QED have a dual nature and can be understood with the Frenkel classical rotating-electron model. In the region of parameters under study γ⊥ 2 ≫ 1 (γ⊥ 2 = 1 + p ⊥ 2/ m 2) and χ ≪ 1 (χ = {{√ {{{( {e{F_{μ v}}{p_v}} )}^2}} } {/ {{√ ( {e{F_{μ v}}{p_v}} )}^2}} {m^3}, the imaginary part of the mass shift and radiation power contain two types of spin contributions. The contributions of the first type are related to the intrinsic magnetic moment of a fermion representing an additional source of electromagnetic radiation. The contributions of the second type have the opposite sign and are caused by a small change in the electron acceleration appearing due to the Frenkel addition to the particle mass. Contributions of the second type dominate, which explains the "wrong" sign of total spin corrections. We show that not only the sign but also the values of coefficients can be explained with specified accuracy using classical electrodynamics if corrections to the mass shift (action) and radiation power are calculated in canonical variables, i.e., for fixed velocity and momentum values, respectively. The results can be treated as a demonstration of the correspondence principle in the field of radiative spin effects, in addition to correspondence between classical and quantum theories at the tree (in the external filed) level. For a e ≡ ( g-2)/2 ≲ χ ≪ 1, equations of the Frenkel model lead to generalization of the system of Lorentz-BMT (Bargmann-Michel-Telegdi) equations taking into account the Frenkel addition to mass. Some features of experimental observations of the spin light are discussed.

  15. Radiative transfer in dusty nebulae. III - The effects of dust albedo

    NASA Technical Reports Server (NTRS)

    Petrosian, V.; Dana, R. A.

    1980-01-01

    The effects of an albedo of internal dust, such as ionization structure and temperature of dust grain, were studied by the quasi-diffusion method with an iterative technique for solving the radiative heat transfer equations. It was found that the generalized on-the-spot approximation solution is adequate for most astrophysical applications for a zero albedo; for a nonzero albedo, the Eddington approximation is more accurate. The albedo increases the average energy of the diffuse photons, increasing the ionization level of hydrogen and heavy elements if the Eddington approximation is applied; the dust thermal gradient is reduced so that the infrared spectrum approaches blackbody spectrum with an increasing albedo.

  16. Radiative transfer in dusty nebulae. III - The effects of dust albedo

    NASA Technical Reports Server (NTRS)

    Petrosian, V.; Dana, R. A.

    1980-01-01

    The effects of an albedo of internal dust, such as ionization structure and temperature of dust grain, were studied by the quasi-diffusion method with an iterative technique for solving the radiative heat transfer equations. It was found that the generalized on-the-spot approximation solution is adequate for most astrophysical applications for a zero albedo; for a nonzero albedo, the Eddington approximation is more accurate. The albedo increases the average energy of the diffuse photons, increasing the ionization level of hydrogen and heavy elements if the Eddington approximation is applied; the dust thermal gradient is reduced so that the infrared spectrum approaches blackbody spectrum with an increasing albedo.

  17. 3D radiative transfer of intrinsically polarized dust emission based on aligned aspherical grains

    NASA Astrophysics Data System (ADS)

    Bertrang, G. H.-M.; Wolf, S.

    2017-08-01

    (Sub-)millimetre observations of the polarized emission of aligned aspherical dust grains enable us to study the magnetic fields within protoplanetary disc. However, the interpretation of these observations is complex. One must consider the various effects that alter the measured polarized signal, such as the shape of dust grains, the efficiency of grain alignment, the magnetic field properties and the projection of the signal along the line of sight. We aim at analysing observations of the polarized dust emission by disentangling the effects on the polarization signal in the context of 3D radiative transfer simulations. For this purpose, we developed a code capable of simulating dust grain alignment of aspherical grains and intrinsical polarization of thermal dust emission. We find that the influence of thermal polarization and dust grain alignment on the polarized emission displayed as spatially resolved polarization map or as spectral energy distribution trace disc properties that are not traced in total (unpolarized) emission such as the magnetic field topology. The radiative transfer simulations presented in this work enable the 3D analysis of intrinsically polarized dust emission - observed with e.g. Atacama Large Millimeter/submillimeter Array (ALMA) - which is essential to constrain magnetic field properties.

  18. The Impact of Desert Dust Aerosol Radiative Forcing on Global and West African Precipitation

    NASA Astrophysics Data System (ADS)

    Jordan, A.; Zaitchik, B. F.; Gnanadesikan, A.; Dezfuli, A. K.

    2015-12-01

    Desert dust aerosols exert a radiative forcing on the atmosphere, influencing atmospheric temperature structure and modifying radiative fluxes at the top of the atmosphere (TOA) and surface. As dust aerosols perturb radiative fluxes, the atmosphere responds by altering both energy and moisture dynamics, with potentially significant impacts on regional and global precipitation. Global Climate Model (GCM) experiments designed to characterize these processes have yielded a wide range of results, owing to both the complex nature of the system and diverse differences across models. Most model results show a general decrease in global precipitation, but regional results vary. Here, we compare simulations from GFDL's CM2Mc GCM with multiple other model experiments from the literature in order to investigate mechanisms of radiative impact and reasons for GCM differences on a global and regional scale. We focus on West Africa, a region of high interannual rainfall variability that is a source of dust and that neighbors major Sahara Desert dust sources. As such, changes in West African climate due to radiative forcing of desert dust aerosol have serious implications for desertification feedbacks. Our CM2Mc results show net cooling of the planet at TOA and surface, net warming of the atmosphere, and significant increases in precipitation over West Africa during the summer rainy season. These results differ from some previous GCM studies, prompting comparative analysis of desert dust parameters across models. This presentation will offer quantitative analysis of differences in dust aerosol parameters, aerosol optical properties, and overall particle burden across GCMs, and will characterize the contribution of model differences to the uncertainty of forcing and climate response affecting West Africa.

  19. TRUST. I. A 3D externally illuminated slab benchmark for dust radiative transfer

    NASA Astrophysics Data System (ADS)

    Gordon, K. D.; Baes, M.; Bianchi, S.; Camps, P.; Juvela, M.; Kuiper, R.; Lunttila, T.; Misselt, K. A.; Natale, G.; Robitaille, T.; Steinacker, J.

    2017-07-01

    Context. The radiative transport of photons through arbitrary three-dimensional (3D) structures of dust is a challenging problem due to the anisotropic scattering of dust grains and strong coupling between different spatial regions. The radiative transfer problem in 3D is solved using Monte Carlo or Ray Tracing techniques as no full analytic solution exists for the true 3D structures. Aims: We provide the first 3D dust radiative transfer benchmark composed of a slab of dust with uniform density externally illuminated by a star. This simple 3D benchmark is explicitly formulated to provide tests of the different components of the radiative transfer problem including dust absorption, scattering, and emission. Methods: The details of the external star, the slab itself, and the dust properties are provided. This benchmark includes models with a range of dust optical depths fully probing cases that are optically thin at all wavelengths to optically thick at most wavelengths. The dust properties adopted are characteristic of the diffuse Milky Way interstellar medium. This benchmark includes solutions for the full dust emission including single photon (stochastic) heating as well as two simplifying approximations: One where all grains are considered in equilibrium with the radiation field and one where the emission is from a single effective grain with size-distribution-averaged properties. A total of six Monte Carlo codes and one Ray Tracing code provide solutions to this benchmark. Results: The solution to this benchmark is given as global spectral energy distributions (SEDs) and images at select diagnostic wavelengths from the ultraviolet through the infrared. Comparison of the results revealed that the global SEDs are consistent on average to a few percent for all but the scattered stellar flux at very high optical depths. The image results are consistent within 10%, again except for the stellar scattered flux at very high optical depths. The lack of agreement between

  20. Impact of dust size parameterizations on aerosol burden and radiative forcing in RegCM4

    NASA Astrophysics Data System (ADS)

    Tsikerdekis, Athanasios; Zanis, Prodromos; Steiner, Allison L.; Solmon, Fabien; Amiridis, Vassilis; Marinou, Eleni; Katragkou, Eleni; Karacostas, Theodoros; Foret, Gilles

    2017-01-01

    We investigate the sensitivity of aerosol representation in the regional climate model RegCM4 for two dust parameterizations for the period 2007-2014 over the Sahara and the Mediterranean. We apply two discretization methods of the dust size distribution keeping the total mass constant: (1) the default RegCM4 4-bin approach, where the size range of each bin is calculated using an equal, logarithmic separation of the total size range of dust, using the diameter of dust particles, and (2) a newly implemented 12-bin approach with each bin defined according to an isogradient method where the size ranges are dependent on the dry deposition velocity of dust particles. Increasing the number of transported dust size bins theoretically improves the representation of the physical properties of dust particles within the same size bin. Thus, more size bins improve the simulation of atmospheric processes. The radiative effects of dust over the area are discussed and evaluated with the CALIPSO dust optical depth (DOD). This study is among the first studies evaluating the vertical profile of simulated dust with a pure dust product. Reanalysis winds from ERA-Interim and the total precipitation flux from the Climate Research Unit (CRU) observational gridded database are used to evaluate and explain the discrepancies between model and observations. The new dust binning approach increases the dust column burden by 4 and 3 % for fine and coarse particles, respectively, which increases DOD by 10 % over the desert and the Mediterranean. Consequently, negative shortwave radiative forcing (RF) is enhanced by more than 10 % at the top of the atmosphere and by 1 to 5 % on the surface. Positive longwave RF locally increases by more than 0.1 W m-2 in a large portion of the Sahara, the northern part of the Arabian Peninsula and the Middle East. The four-bin isolog method is to some extent numerically efficient, nevertheless our work highlights that the simplified representation of the four

  1. Characterisation of mineral dust emission in the Middle EAST using the Spinning Enhanced Visible and Infrared Imager (SEVIRI)

    NASA Astrophysics Data System (ADS)

    Hennen, M.; Shahgedanova, M.; White, K.

    2015-12-01

    Using the Spinning Enhanced Visual and InfraRed Imager (SEVIRI) on-board Meteosat's second generation satellite (MSG), mineral dust emissions from the Middle East were observed at a high temporal and spatial resolution between the years 2006 and 2013. This research provides a subjective derivation of mineral dust source locations in the Middle East using the thermal infrared Dust RGB product. Focusing on the brightness temperature difference around 10.8 µm channel and their spectral contrast with clear sky conditions, the Dust RGB product has been recognised as a major asset in detecting dust. While the product has already been used to map dust emissions in Sahara and south Africa, this research is the first to map dust emissions in the Middle East using SEVIRI, one of the dustiest regions in the world second only to the Sahara Desert. For every dust storm activation within the Middle East, the point of first emission is derived from visual inspection of each 15 minute image, these points were then recorded in a dust source climatology (DSC) database, along with time and direction of dust movement. To take account of potential errors inherent in this subjective detection method, a degree of confidence is associated with each data point with relevance to time of day (which has a strong effect on ability to detect dust in these products) and weather conditions, in particular presence of clouds. These results are compared with an automated retrieval using Aerosol Optical Depth (AOD) measurements form the Moderate Resolution Image Spectrometer (MODIS); which, due to its sun-synchronous orbit allows a measurement of dust in the atmosphere once a day. Differences in the spatial distribution of SEVIRI dust sources and MODIS inferred dust source regions can be explained by inherent transport bias in the latter's low sampling rate and prevailing wind conditions. This database will provide an important tool in further understanding dust emission processes in the region

  2. Longwave Radiative Forcing of Saharan Dust Aerosols Estimated from MODIS, MISR and CERES Observations on Terra

    NASA Technical Reports Server (NTRS)

    Zhang, Jiang-Long; Christopher, Sundar A.

    2003-01-01

    Using observations from the Multi-angle Imaging Spectroradiometer (MISR), the Moderate Resolution Imaging Spectroradiometer (MODIS), and the Clouds and the Earth's Radiant Energy System (CERES) instruments onboard the Terra satellite; we present a new technique for studying longwave (LW) radiative forcing of dust aerosols over the Saharan desert for cloud-free conditions. The monthly-mean LW forcing for September 2000 is 7 W/sq m and the LW forcing efficiency' (LW(sub eff)) is 15 W/sq m. Using radiative transfer calculations, we also show that the vertical distribution of aerosols and water vapor are critical to the understanding of dust aerosol forcing. Using well calibrated, spatially and temporally collocated data sets, we have combined the strengths of three sensors from the same satellite to quantify the LW radiative forcing, and show that dust aerosols have a "warming" effect over the Saharan desert that will counteract the shortwave "cooling effect" of aerosols.

  3. Analysis of the radiated information in spinning sound fields.

    PubMed

    Carley, Michael

    2010-10-01

    The information content of a spinning sound field is analyzed using a combination of exact and asymptotic results, in order to set limits on how accurately source identification can be carried out. Using a transformation of the circular source to an exactly equivalent set of line source modes, given by Chebyshev polynomials, it is found that the line source modes of order greater than the source wavenumber generate exponentially small fields. Asymptotic analysis shows that the remaining, lower order, modes radiate efficiently only into a region around the source plane, with this region shrinking as the mode order is increased. The results explain the ill-conditioning of source identification methods; the successful use of low order models in active noise control; and the low radiation efficiency of subsonic jets.

  4. Direct Radiative Forcing from Saharan Mineral Dust Layers from In-situ Measurements and Satellite Retrievals

    NASA Astrophysics Data System (ADS)

    Sauer, D. N.; Vázquez-Navarro, M.; Gasteiger, J.; Chouza, F.; Weinzierl, B.

    2016-12-01

    Mineral dust is the major species of airborne particulate matter by mass in the atmosphere. Each year an estimated 200-3000 Tg of dust are emitted from the North African desert and arid regions alone. A large fraction of the dust is lifted into the free troposphere and gets transported in extended dust layers westward over the Atlantic Ocean into the Caribbean Sea. Especially over the dark surface of the ocean, those dust layers exert a significant effect on the atmospheric radiative balance though aerosol-radiation interactions. During the Saharan Aerosol Long-range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE) in summer 2013 airborne in-situ aerosol measurements on both sides of the Atlantic Ocean, near the African coast and the Caribbean were performed. In this study we use data about aerosol microphysical properties acquired between Cabo Verde and Senegal to derive the aerosol optical properties and the resulting radiative forcing using the radiative transfer package libRadtran. We compare the results to values retrieved from MSG/SEVIRI data using the RRUMS algorithm. The RRUMS algorithm can derive shortwave and longwave top-of-atmosphere outgoing fluxes using only information issued from the narrow-band MSG/SEVIRI channels. A specific calibration based on collocated Terra/CERES measurements ensures a correct retrieval of the upwelling flux from the dust covered pixels. The comparison of radiative forcings based on in-situ data to satellite-retrieved values enables us to extend the radiative forcing estimates from small-scale in-situ measurements to large scale satellite coverage over the Atlantic Ocean.

  5. Dust and Black Carbon Radiative Forcing Controls on Snowmelt in the Colorado River Basin

    NASA Astrophysics Data System (ADS)

    Skiles, Sara McKenzie

    Light absorbing impurities (LAIs), like dust and black carbon (BC), initiate powerful albedo feedbacks when deposited on snow cover, yet due to a scarcity of observations radiative forcing by LAIs is often neglected, or poorly constrained, in climate and hydrological models. This has important consequences for regions like the Colorado River Basin, where dust deposition to mountain snow cover frequently occurs in the upper basin in the springtime, a relatively new phenomenon since western expansion of the US. Previous work showed that dust on snow (DOS) enhances snowmelt by 3-7 weeks, shifts timing and intensity of runoff, and reduces total water yield. Here, advanced methods are presented to measure, model, and monitor DOS in the hydrologically sensitive Colorado River Basin. A multi-year multi-site spatial variability analysis indicates the heaviest dust loading comes from point sources in the southern Colorado Plateau, but also shows that lower levels of dust loading from diffuse sources still advances melt by 3-4 weeks. A high-resolution snow property dataset, including vertically resolved measurements of snow optical grain size and dust/BC concentrations, confirms that impurity layers remain in the layer in which they are deposited and converge at the surface as snow melts: influencing snow properties, rapidly reducing snow albedo, and increasing snowmelt rates. The optical properties of deposited impurities, which are mainly dust, are determined using an inversion technique from measurements of hemispherical reflectance and particle size distributions. Using updated optical properties in the snow+aerosols radiative transfer model SNICAR improves snow albedo modeling over a more general dust characterization, reducing errors by 50% across the full range of snow reflectance. Radiative forcing by LAIs in the CRB, estimated directly from measurements and updated optical properties, is most strongly controlled by dust concentrations in the uppermost surface layer

  6. Modelling ripples in Orion with coupled dust dynamics and radiative transfer

    NASA Astrophysics Data System (ADS)

    Hendrix, T.; Keppens, R.; Camps, P.

    2015-03-01

    Aims: In light of the recent detection of direct evidence for the formation of Kelvin-Helmholtz instabilities in the Orion nebula, we expand upon previous modelling efforts by numerically simulating the shear-flow driven gas and dust dynamics in locations where the Hii region and the molecular cloud interact. We aim to directly confront the simulation results with the infrared observations. Methods: To numerically model the onset and full nonlinear development of the Kelvin-Helmholtz instability we take the setup proposed to interpret the observations, and adjust it to a full 3D hydrodynamical simulation that includes the dynamics of gas as well as dust. A dust grain distribution with sizes between 5-250 nm is used, exploiting the gas+dust module of the MPI-AMRVAC code, in which the dust species are represented by several pressureless dust fluids. The evolution of the model is followed well into the nonlinear phase. The output of these simulations is then used as input for the SKIRT dust radiative transfer code to obtain infrared images at several stages of the evolution, which can be compared to the observations. Results: We confirm that a 3D Kelvin-Helmholtz instability is able to develop in the proposed setup, and that the formation of the instability is not inhibited by the addition of dust. Kelvin-Helmholtz billows form at the end of the linear phase, and synthetic observations of the billows show striking similarities to the infrared observations. It is pointed out that the high density dust regions preferentially collect on the flanks of the billows. To get agreement with the observed Kelvin-Helmholtz ripples, the assumed geometry between the background radiation, the billows and the observer is seen to be of critical importance.

  7. Accelerated Radiation-Damping for Increased Spin Equilibrium (ARISE)

    PubMed Central

    Huang, Susie Y.; Witzel, Thomas; Wald, Lawrence L.

    2008-01-01

    Control of the longitudinal magnetization in fast gradient echo sequences is an important factor enabling the high efficiency of balanced Steady State Free Precession (bSSFP) sequences. We introduce a new method for accelerating the return of the longitudinal magnetization to the +z-axis that is independent of externally applied RF pulses and shows improved off-resonance performance. The Accelerated Radiation damping for Increased Spin Equilibrium (ARISE) method uses an external feedback circuit to strengthen the Radiation Damping (RD) field. The enhanced RD field rotates the magnetization back to the +z-axis at a rate faster than T1 relaxation. The method is characterized in gradient echo phantom imaging at 3T as a function of feedback gain, phase, and duration and compared with results from numerical simulations of the Bloch equations incorporating RD. A short period of feedback (10ms) during a refocused interval of a crushed gradient echo sequence allowed greater than 99% recovery of the longitudinal magnetization when very little T2 relaxation has time to occur. Appropriate applications might include improving navigated sequences. Unlike conventional flip-back schemes, the ARISE “flip-back” is generated by the spins themselves, thereby offering a potentially useful building block for enhancing gradient echo sequences. PMID:18956463

  8. Dust, Elemental Carbon and Other Impurities on Central Asian Glaciers: Origin and Radiative Forcing

    NASA Astrophysics Data System (ADS)

    Schmale, J.; Flanner, M.; Kang, S.; Sprenger, M.; Zhang, Q.; Li, Y.; Guo, J.; Schwikowski, M.

    2015-12-01

    In Central Asia, more than 60 % of the population depends on water stored in glaciers and mountain snow. While temperature, precipitation and dynamic processes are key drivers of glacial change, deposition of light absorbing impurities such as mineral dust and black carbon can lead to accelerated melting through surface albedo reduction. Here, we discuss the origin of deposited mineral dust and black carbon and their impacts on albedo change and radiative forcing (RF). 218 snow samples were taken from 13 snow pits on 4 glaciers, Abramov (Pamir), Suek, Glacier No. 354 and Golubin (Tien Shan), representing deposition between summer 2012 and 2014. They were analyzed for elemental and organic carbon by a thermo-optical method, mineral dust by gravimetry, and iron by ICP-MS. Back trajectory ensembles were released every 6 hours with the Lagranto model for the covered period at all sites. Boundary layer "footprints" were calculated to estimate general source regions and combined with MODIS fire counts for potential fire contributions. Albedo reduction due to black carbon and mineral dust was calculated with the Snow-Ice-Aerosol-Radiative model (SNICAR), and surface spectral irradiances were derived from atmospheric radiative transfer calculations to determine the RF under clear-sky and all sky conditions using local radiation measurements. Dust contributions came from Central Asia, the Arabian Peninsula, the Sahara and partly the Taklimakan. Fire contributions were higher in 2014 and generally came from the West and North. We find that EC exerts roughly 3 times more RF than mineral dust in fresh and relatively fresh snow (~5 W/m2) and up to 6 times more in snow that experienced melting (> 10 W/m2) even though EC concentrations (average per snow pit from 90 to 700 ng/g) were up to two orders of magnitude lower than mineral dust (10 to 140 μg/g).

  9. Radiation dose to workers due to the inhalation of dust during granite fabrication.

    PubMed

    Zwack, L M; McCarthy, W B; Stewart, J H; McCarthy, J F; Allen, J G

    2014-03-01

    There has been very little research conducted to determine internal radiation doses resulting from worker exposure to ionising radiation in granite fabrication shops. To address this issue, we estimated the effective radiation dose of granite workers in US fabrication shops who were exposed to the maximum respirable dust and silica concentrations allowed under current US regulations, and also to concentrations reported in the literature. Radiation doses were calculated using standard methods developed by the International Commission on Radiological Protection. The calculated internal doses were very low, and below both US occupational standards (50 mSv yr(-1)) and limits applicable to the general public (1 mSv yr(-1)). Workers exposed to respirable granite dust concentrations at the US Occupational Safety and Health Administration (OSHA) respirable dust permissible exposure limit (PEL) of 5 mg m(-3) over a full year had an estimated radiation dose of 0.062 mSv yr(-1). Workers exposed to respirable granite dust concentrations at the OSHA silica PEL and at the American Conference of Governmental Industrial Hygienists Threshold Limit Value for a full year had expected radiation doses of 0.007 mSv yr(-1) and 0.002 mSv yr(-1), respectively. Using data from studies of respirable granite dust and silica concentrations measured in granite fabrication shops, we calculated median expected radiation doses that ranged from <0.001 to 0.101 mSv yr(-1).

  10. Estimation of top-altitude of Asian Dust from Satellite Observations of Backscattered UV Radiation

    NASA Astrophysics Data System (ADS)

    Choi, S.; Kim, J.; Lee, J.

    2008-12-01

    Asian dust (Hwangsa in Korean), which is a typical example of mineral dust aerosol, frequently occurs in the desert and loess plateau in northern China and Mongolia during the spring season (Park and Lee 2004). In particular, they mainly originate from the arid area above 1500m from sea level (Wang et al. 2000) and some of them affect to North Pacific Ocean and North America (Husar et al. 2001). In addition, UV-absorbing aerosols such as mineral dust have a strong altitude dependence in the near UV region that is a low surface reflectivity and nearly constant over land and water ( Herman et al. 1997; Torres et al. 1998). Thus, in this study, we concentrate on estimation of top-altitude for UV-absorbing aerosol like a mineral dust by using weather charts and radiative transfer model (RTM) and satellite data. To estimate the top-altitude of Asian dust using multiple satellite data, in the first, we investigate the source regions of Asian dust based on results of HYSPLIT backward trajectory for the period from Jan 2001 to May 2008 and analyze qualitative synoptic weather patterns associated with the long-range transport. Next, assuming that vertical profile of Asian dust is similar to Gaussian distribution from surface to maximum altitude, we select a sensitive wavelength for Asian dust from RTM test. Then, we evaluate the top-altitude of Asian dust estimated from the satellite data, MODIS, OMI, CALIOP and Rstar5b model. Rstar5b inputs are generated by MODIS-AOD and OMI geometry information, which is located in minimum distance from CALIOP data pixel. At last, we compare altitude calculated from Rstar5b with that retrieved from CALIOP using radiance of simulated Rstar5b and measured OMI. This simultaneous approach of multi-satellite platform and RTM is expected to contribute to the comprehension of the mechanism as well as the estimation of the altitude for Asian dust.

  11. Attenuation of Ultraviolet Radiation by Dust in Interstellar Clouds

    NASA Astrophysics Data System (ADS)

    Escalante, V.

    1994-07-01

    Se han obtenido soluciones de la ecuación de transporte para la dispersión coherente, no conservativa y anisotrópica para estimar la precisión de métodos aproximados, usados en modelos de nubes en que la luz es atenuada principalmente por el polvo. En los cálculos se ha aplicado el metodo de armónicos esféricos para distintos parámetros del polvo. Se ha explorado la posibilidad de descubrir cambios en las caracterísiticas del polvo mediante observaciones de regiones fotodisociadas. Se muestra que para altos valores del albedo de dispersión simple y del parametro de asimetria de Ia función de fase que son adecuados para el polvo galáctico, no es posible determinar variaciones de más de un factor de 2 en el cociente de gas a polvo. Solutions to the transfer equation for coherent, non-conservative, anisotropic scattering have been obtained in order to estimate the accuracy of approximate methods used in models of clouds where light is attenuated mostly by dust. In the calculations the spherical harmonic method has been applied for different grain parameters. The possibility of discovering changes of dust characteristics through observations of photodissociation regions has been considered. It is shown that for the high values of the single scattering albedo and the asymmetry parameter of the phase function for redistribution that appear to be appropriate for galactic dust, it is not possible to determine variations of more than a factor of 2 in the gas to dust ratio.

  12. Radiation Pressure Measurements on Micron-Size Individual Dust Grains

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Craven, P. D.; Spann, J. F.; Witherow, W. K.; West, E. A.; Gallagher, D. L.; Adrian, M. L.; Fishman, G. J.; Tankosic, D.; LeClair, A.

    2003-01-01

    Measurements of electromagnetic radiation pressure have been made on individual silica (SiO2) particles levitated in an electrodynamic balance. These measurements were made by inserting single charged particles of known diameter in the 0.2- to 6.82-micron range and irradiating them from above with laser radiation focused to beam widths of approximately 175- 400 microns at ambient pressures particle due to the radiation force is balanced by the electrostatic force indicated by the compensating dc potential applied to the balance electrodes, providing a direct measure of the radiation force on the levitated particle. Theoretical calculations of the radiation pressure with a least-squares fit to the measured data yield the radiation pressure efficiencies of the particles, and comparisons with Mie scattering theory calculations provide the imaginary part of the refractive index of SiO2 and the corresponding extinction and scattering efficiencies.

  13. Radiation Pressure Measurements on Micron-Size Individual Dust Grains

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Craven, P. D.; Spann, J. F.; Witherow, W. K.; West, E. A.; Gallagher, D. L.; Adrian, M. L.; Fishman, G. J.; Tankosic, D.; LeClair, A.

    2003-01-01

    Measurements of electromagnetic radiation pressure have been made on individual silica (SiO2) particles levitated in an electrodynamic balance. These measurements were made by inserting single charged particles of known diameter in the 0.2- to 6.82-micron range and irradiating them from above with laser radiation focused to beam widths of approximately 175- 400 microns at ambient pressures particle due to the radiation force is balanced by the electrostatic force indicated by the compensating dc potential applied to the balance electrodes, providing a direct measure of the radiation force on the levitated particle. Theoretical calculations of the radiation pressure with a least-squares fit to the measured data yield the radiation pressure efficiencies of the particles, and comparisons with Mie scattering theory calculations provide the imaginary part of the refractive index of SiO2 and the corresponding extinction and scattering efficiencies.

  14. Radiative impact of mineral dust on monsoon precipitation variability over West Africa

    SciTech Connect

    Zhao, Chun; Liu, Xiaohong; Leung, Lai-Yung R.; Hagos, Samson M.

    2011-03-01

    The radiative forcing of dust and its impact on precipitation over the West Africa monsoon (WAM) region is simulated using a coupled meteorology and aerosol/chemistry model (WRF-Chem). During the monsoon season, dust is a dominant contributor to AOD over West Africa. In the standard simulation, on 24-hour domain average, dust has a cooling effect (-6.11 W/m2) at the surface, a warming effect (6.94 W/m2) in the atmosphere, and a relatively small TOA forcing (0.83 W/m2). Dust modifies the surface energy budget and atmospheric diabatic heating and hence causes lower atmospheric cooling in the daytime but warming in the nighttime. As a result, atmospheric stability is increased in the daytime and reduced in the nighttime, leading to a reduction of late afternoon precipitation by up to 0.14 mm/hour (30%) and an increase of nocturnal and early morning precipitation by up to 0.04 mm/hour (23%) over the WAM region. Dust-induced reduction of diurnal precipitation variation improves the simulated diurnal cycle of precipitation when compared to measurements. However, daily precipitation is only changed by a relatively small amount (-0.14 mm/day or -4%). On the other hand, sensitivity simulations show that, for weaker-to-stronger absorbing dust, dust longwave warming effect in the nighttime surpasses its shortwave cooling effect in the daytime at the surface, leading to a less stable atmosphere associated with more convective precipitation in the nighttime. As a result, the dust-induced change of daily WAM precipitation varies from a significant reduction of -0.40 mm/day (-12%, weaker absorbing dust) to a small increase of 0.05 mm/day (1%, stronger absorbing dust). This variation originates from the competition between dust impact on daytime and nighttime precipitation, which depends on dust shortwave absorption. Dust reduces the diurnal variation of precipitation regardless of its absorptivity, but more reduction is associated with stronger absorbing dust.

  15. Radiative Energetics of Mineral Dust Aerosols from Ground-Based Measurements

    NASA Technical Reports Server (NTRS)

    Tsay, Si-Chee; Hansell, Richard A.

    2011-01-01

    Airborne dust aerosols worldwide contribute a significant part to air quality problems and, to some extent, regional climatic issues (e.g., radiative forcing, hydrological cycle, and primary biological productivity in oceans). Evaluating the direct solar radiative effect of dust aerosols is relatively straightforward due in part to the relatively large SIN ratio in broadband irradiance measurements. The longwave (LW) impact, on the other hand, is rather difficult to ascertain since the measured dust signal level (approx.10 W/sq m) is on the same order as the instrumental uncertainties. Although the magnitude of the LW impact is much smaller than that of the shortwave (SW), it can still have a noticeable influence on the energy distribution of Earth-atmosphere system, particularly due to the strong light-absorptive properties commonly found in many terrestrial minerals. The current effort is part of an ongoing research study to perform a global assessment of dust direct aerosol radiative effects (DARE) during major field deployments of key dust source regions worldwide. In this work we present results stemming from two previous field deployments: the 2006 NASA African Monsoon Multidisciplinary Activities and the 2008 Asian Monsoon Years, both utilizing NASA Goddard's mobile ground-based facility. The former study focused on transported Saharan dust at Sal (16.73degN, 22.93degW), Cape Verde along the west coast of Africa while the latter focused on Asian dust at Zhangye (39.082degN, 100.276degE), China near the source between the Taklimakan and Gobi deserts. Due to the compelling variability in spatial and temporal scale of dust properties during field experiments, a deterministic I-D radiative transfer model constrained by local measurements (i.e., spectral photometry/interferometry and lidar for physical/microphysical, mineralogy, and single-scattering properties) is employed to evaluate dust's local instantaneous SW/LW DARE both at the surface and at the top of

  16. Radiative transfer with POLARIS. I. Analysis of magnetic fields through synthetic dust continuum polarization measurements

    NASA Astrophysics Data System (ADS)

    Reissl, S.; Wolf, S.; Brauer, R.

    2016-09-01

    Aims: We present POLARIS (POLArized RadIation Simulator), a newly developed three-dimensional Monte-Carlo radiative transfer code. POLARIS was designed to calculate dust temperature, polarization maps, and spectral energy distributions. It is optimized to handle data that results from sophisticated magneto-hydrodynamic simulations. The main purpose of the code is to prepare and analyze multi-wavelength continuum polarization measurements in the context of magnetic field studies in the interstellar medium. An exemplary application is the investigation of the role of magnetic fields in star formation processes. Methods: We combine currently discussed state-of-the-art grain alignment theories with existing dust heating and polarization algorithms. We test the POLARIS code on multiple scales in complex astrophysical systems that are associated with different stages of star formation. POLARIS uses the full spectrum of dust polarization mechanisms to trace the underlying magnetic field morphology. Results: Resulting temperature distributions are consistent with the density and position of radiation sources resulting from magneto-hydrodynamic (MHD) - collapse simulations. The calculated layers of aligned dust grains in the considered cirumstellar disk models are in excellent agreement with theoretical predictions. Finally, we compute unique patterns in synthetic multi-wavelength polarization maps that are dependent on applied dust-model and grain-alignment theory in analytical cloud models.

  17. Laboratory investigation of electric charging of dust particles by electrons, ions, and UV radiation

    NASA Technical Reports Server (NTRS)

    Svestka, Jiri; Pinter, S.; Gruen, E.

    1989-01-01

    In many cosmic environments electric charging of dust particles occurs by electrons, ions, and UV radiation. In case of interstellar dust particles the value of their electric charge can have, for instance, very important consequences for their destruction rate in supernova remnant's shock waves and can globally influence the overall life cycle of dust particles in galaxies. For experimental simulation of charging processes a vacuum chamber was used in which the particles fall through an electron or ion beam of energies up to 10 KeV. The aim of the experiments was to attain maximum charge of dust particles. Furthermore the influence of the rest gas was also determined because electrons and ions produced by collisional ionization of the rest gas can result in significant effects. For measurement particles from 1 to 100 microns from glass, carbon, Al, Fe, MgO, and very loosely bound conglomerates of Al2O3 were used.

  18. The Martian polar cap - Radiative effects of ozone, clouds, and airborne dust

    NASA Technical Reports Server (NTRS)

    Lindner, Bernhard Lee

    1990-01-01

    The solar and thermal flux striking the polar cap of Mars is computed for various ozone, dust, and cloud abundances and for three solar zenith angles. Ozone does not significantly affect the total energy budget of the polar cap. Hence the observed hemispherical asymmetry in ozone abundance causes only an insignificant hemispherical asymmetry in the polar caps. Vertical optical depths of dust and cloud ranging from zero to 1 cause little change in the total flux absorbed by the polar cap near its edge but increase the absorbed flux significantly as one travels poleward. Hemispherical asymmetries in dust abundance, cloud cover, and surface pressure combine to cause a significant hemispherical asymmetry in the total flux absorbed by the residual polar caps, which helps to explain the dichotomy in the residual polar caps on Mars. Other processes which affect the energy budget of the polar cap are proposed and reviewed, particularly with respect to their interaction with the radiative effects of clouds and dust.

  19. The Martian polar CAP - Radiative effects of ozone, clouds, and airborne dust

    NASA Astrophysics Data System (ADS)

    Lindner, B. L.

    1990-02-01

    The solar and thermal flux striking the polar cap of Mars is computed for various ozone, dust, and cloud abundances and for three solar zenith angles. Ozone does not significantly affect the total energy budget of the polar cap. Hence the observed hemispherical asymmetry in ozone abundance causes only an insignificant hemispherical asymmetry in the polar caps. Vertical optical depths of dust and cloud ranging from zero to 1 cause little change in the total flux absorbed by the polar cap near its edge but increase the absorbed flux significantly as one travels poleward. Hemispherical asymmetries in dust abundance, cloud cover, and surface pressure combine to cause a significant hemispherical asymmetry in the total flux absorbed by the residual polar caps, which helps to explain the dichotomy in the residual polar caps on Mars. Other processes which affect the energy budget of the polar cap are proposed and reviewed, particularly with respect to their interaction with the radiative effects of clouds and dust.

  20. Photoproduction and radiative decay of spin 1/2 and 3/2 pentaquarks

    SciTech Connect

    He Xiaogang; Li Tong; Li Xueqian; Lih, C.-C.

    2005-01-01

    We study photoproduction and radiative decays of pentaquarks paying particular attention to the differences between spin-1/2 and spin-3/2, positive and negative parities of pentaquarks. Detailed study of these processes can not only give crucial information about the spin, but also the parity of pentaquarks.

  1. Response of the Water Cycle of West Africa and Atlantic to Radiative Forcing by Saharan Dust

    NASA Technical Reports Server (NTRS)

    Lau, K. M.; Kim, Kyu-Myong; Sud, Yogesh C.; Walker, Gregory L.

    2010-01-01

    The responses of the atmospheric water cycle and climate of West Africa and the Atlantic to radiative forcing of Saharan dust are studied using the NASA finite volume general circulation model (fvGCM), coupled to a mixed layer ocean. We find evidence in support of the "elevated heat pump" (EHP) mechanism that underlines the responses of the atmospheric water cycle to dust forcing as follow. During the boreal summer, as a result of large-scale atmospheric feed back triggered by absorbing dust aerosols, rainfall and cloudiness are enhanced over the West Africa/Easter Atlantic ITCZ, and suppressed over the West Atlantic and Caribbean. region. Shortwave radiation absorption by dust warms the atmosphere and cools the surface, while long wave has the opposite response. The elevated dust layer warms the air over Nest Africa and the eastern Atlantic. The condensation heating associated with the induced deep convection drives and maintains an anomalous large-scale east-west overturning circulation with rising motion over West Africa/eastern Atlantic, and sinking motion over the Caribbean region. The response also includes a strengthening of the West African monsoon, manifested in northward shift of the West Africa precipitation over land, increased low-level westerlies flow over West Africa at the southern edge of the dust layer, and a near surface energy fluxes, resulting in cooling of the Nest African land and the eastern Atlantic, and a warming in the West Atlantic and Caribbean. The EHP effect is most effective for moderate to highly absorbing dusts, and becomes minimized for reflecting dust with single scattering albedo at 0.95 or higher.

  2. Determination of Radiative Forcing of Saharan Dust using Combined TOMS and ERBE Data

    NASA Technical Reports Server (NTRS)

    Hsu, N. Christina; Herman, Jay R.; Weaver, Clark

    1999-01-01

    The direct radiative forcing of Saharan dust aerosols has been determined by combining aerosol information derived from Nimbus-7 TOMS with radiation measurements observed at the top of atmosphere (TOA) by NOAA-9 ERBE made during February-July 1985. Cloud parameters and precipitable water derived from the NOAA-9 HIRS2 instrument were used to aid in screening for clouds and water vapor in the analyses. Our results indicate that under "cloud-free" and "dry" conditions there is a good correlation between the ERBE TOA outgoing longwave fluxes and the TOMS aerosol index measurements over both land and ocean in areas under the influence of airborne Saharan dust. The ERBE TOA outgoing shortwave fluxes were also found to correlate well with the dust loading derived from TOMS over ocean. However, the calculated shortwave forcing of Saharan dust aerosols is very weak and noisy over land for the range of solar zenith angle viewed by the NOAA-9 ERBE in 1985. Sensitivity factors of the TOA outgoing fluxes to changes in aerosol index were estimated using a linear regression fit to the ERBE and TOMS measurements. The ratio of the shortwave-to-longwave response to changes in dust loading over the ocean is found to be roughly 2 to 3, but opposite in sign. The monthly averaged "clear-sky" TOA direct forcing of airborne Saharan dust was also calculated by multiplying these sensitivity factors by the TOMS monthly averaged "clear-sky" aerosol index. Both the observational and theoretical analyses indicate that the dust layer height, ambient moisture content as well as the presence of cloud all play an important role in determining the TOA direct radiative forcing due to mineral aerosols.

  3. Spin-down of Pulsars, and Their Electromagnetic and Gravitational Wave Radiations

    NASA Astrophysics Data System (ADS)

    Yue-zhu, Zhang; Yan-yan, Fu; Yi-huan, Wei; Cheng-min, Zhang; Shao-hua, Yu; Yuan-yue, Pan; Yuan-qi, Guo; De-hua, Wang

    2016-04-01

    Pulsars posses extremely strong magnetic fields, and their magnetic axis does not coincide with their rotation axis, this causes the pulsars to emit electromagnetic radiations. Pulsars rely on their rotational energy to compensate for the energy loss caused by the electromagnetic radiation, which leads to the gradually decelerated spin of pulsars. According to the theoretical deduction, we have calculated the initial period of the Crab Nebula pulsar, and derived the period evolution of the pulsar at any time in the future under the effect of the electromagnetic radiation. Considered the possible existence of quadrupole moment in the mass distribution of a pulsar, the gravitational wave radiation will also make the pulsar spin down, hence the variation of spin period of the Crab pulsar under the effect of gravitational wave radiation is further analyzed. Finally, combining the two kinds of radiation mechanisms, the evolution of spin period of the Crab pulsar under the joint action of these two kinds of radiation mechanisms is analyzed.

  4. Dust aerosol radiative effect and influence on urban atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Chen, M.; Li, L.

    2007-11-01

    An 1.5-level-closure and 3-D non-stationary atmospheric boundary layer (ABL) model and a radiation transfer model with the output of Weather Research and Forecast (WRF) Model and lidar AML-1 are employed to simulate the dust aerosol radiative effect and its influence on ABL in Beijing for the period of 23-26 January 2002 when a dust storm occurred. The simulation shows that daytime dust aerosol radiative effect heats up the ABL at the mean rate of about 0.68 K/h. The horizontal wind speed from ground to 900 m layer is also overall increased, and the value changes about 0.01 m/s at 14:00 LT near the ground. At night, the dust aerosol radiative effect cools the ABL at the mean rate of -0.21 K/h and the wind speed lowers down at about -0.19 m/s at 02:00 LT near the ground.

  5. Frame-dragging fields and spin 1 gravitomagnetic radiation

    NASA Astrophysics Data System (ADS)

    Tolstoy, Ivan

    2012-12-01

    Experimental results published in 2004 (Ciufolini and Pavlis in Nature 431:958-960, 2004) and 2011 (Everitt et al. in Phys Rev Lett 106:221101, 1-5, 2011) have confirmed the frame-dragging phenomenon for a spinning earth predicted by Einstein's field equations. Since this is observed as a precession caused by the gravitomagnetic (GM) field of the rotating body, these experiments may be viewed as measurements of a GM field. The effect is encapsulated in the classic steady state solution for the vector potential field ζ of a spinning sphere-a solution applying to a sphere with angular momentum J and describing a field filling space for all time (Weinberg in Gravitation and Cosmology, Wiley, New York, 1972). In a laboratory setting one may visualise the case of a sphere at rest (ζ =0, { t}<0), being spun up by an external torque at { t}=0 to the angular momentum J: the ζ field of the textbook solution cannot establish itself instantaneously over all space at { t}=0, but must propagate with the velocity c, implying the existence of a travelling GM wave field yielding the textbook ζ field for large enough t (Tolstoy in Int J Theor Phys 40(5):1021-1031, 2001). The linearized GM field equations of the post-Newtonian approximation being isomorphic with Maxwell's equations (Braginsky et al. in Phys Rev D 15(6):2047-2060, 1977), such GM waves are dipole waves of spin 1. It is well known that in purely gravitating systems conservation of angular momentum forbids the existence of dipole radiation (Misner et al. in Gravitation, Freeman & Co., New York, 1997); but this rule does not prohibit the insertion of angular momentum into the system from an external source-e.g., by applying a torque to our laboratory sphere.

  6. Understanding the direct radiative effect of dust aerosols on transport pathways using the NASA GEOS-5 AGCM

    NASA Astrophysics Data System (ADS)

    Nowottnick, E. P.; Colarco, P. R.; Lau, W. K.; Kim, K.

    2012-12-01

    African dust aerosols are transported across the Atlantic Ocean to the Caribbean by the easterly trade winds.While in transport, dust aerosols interact with the Earth system in various ways, ranging from influencing the local radiation balance to serving as a nutrient for tropical ecosystems.However, our current understanding of these processes is incomplete and serves as a source of uncertainty in Earth system modeling.Here, we focus on understanding the direct radiative impacts of African dust aerosols on the atmosphere using the NASA GEOS-5 atmospheric general circulation model that simulates aerosols with an online version of the GOCART model. For this study, we compare a high resolution GEOS-5 climate simulation where aerosols have been radiatively coupled to the atmosphere to one where aerosols are treated as passive tracers for June - September, 2009. Utilizing streamfunction and velocity potentials of the simulated dust mass flux, we isolate differences in dust transport pathways caused by the direct radiative effect of dust by comparing the rotational and divergent components of the dust flow in the horizontal and vertical on various timescales.Additionally, we pay special attention to the influence of dust aerosols on African Easterly Jet (AEJ) position and strength, as well as temperature profiles, cloudiness, and precipitation to gain further insight into the direct radiative effect of dust aerosols on the atmosphere

  7. Energetic Radiation from Rapidly Spinning Pulsars. II. VELA and Crab

    NASA Astrophysics Data System (ADS)

    Cheng, K. S.; Ho, C.; Ruderman, M.

    1986-01-01

    The growth of charge-depleted regions (gaps) in the outer magnetosphere of rapidly spinning magnetized neutron stars is limited by e± production. In the Vela pulsar a pair of e+ and e- created within the gap (primaries) are accelerated in opposite directions to extreme relativistic energies. The primary e-/e+ produce primary γ-rays through inverse Compton scattering on IR photons. Primary γ-rays are sufficiently energetic to produce (secondary) e± pairs in collisions with this same IR photon flux. Secondary synchrotron radiation by these pairs gives crossed fan beams of γ-rays and weaker ones of X-rays. Collisions of the hard secondary γ-rays with the secondary crossed beam soft X-rays give a large flux of lower energy e± (tertiary) pairs which fill much of the outer magnetosphere. It is the (tertiary) IR synchrotron radiation from tertiary pairs through the outer gap which initiates the entire series of pair production processes. For Vela, the calculated observable consequences include (a) twin cusped γ-ray pulses with photon spectrum F(ω) ≍ ω-3/2 ln (3 GeV/hω) from 3 GeV to about 102 KeV; (b) total fan beam radiated power 10-2 the pulsar spin-down energy loss rate; (c) an X-ray spectrum F(ω) ≍ ω-2/3 below 102 KeV; (d) weak, more closely spaced twin optical pulses from the tertiary radiation with power 10-5 that of the secondary γ-rays; (e) and e± outflow of 1036 s-1; (f) a double pulse of 1012 - 1013 eV γ-rays with about 10-2 the γ-ray power. Model Crab pulsar emissions are considered with emphasis on differences from those of Vela. Crab primary outer gap e+/e- lose most of their energy to curvature γ-rays, which convert to e± pairs in collisions with X-rays. These X-rays come from the synchrotron (secondary) emission from such (secondary) pairs created beyond the gap boundary. Inverse Compton scattering of secondary e± on the secondary X-rays boosts a fraction to γ-rays. The combination of secondary synchrotron and inverse Compton

  8. Radiation Pressure Measurements on Micron Size Individual Dust Grains

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Craven, P.D.; Spann, J. F.; Tankosic, D.; Witherow, W. K.; LeClair, A.; West, E.; Sheldon, R.; Gallagher, D. L.; Adrian, M. L.

    2003-01-01

    Measurements of electromagnetic radiation pressure have been made on individual silica (SiO2) particles levitated in an electrodynamic balance. These measurements were made by inserting single charged particles of known diameter in the 0.2 micron to 6.82 micron range and irradiating them from above with laser radiation focused to beam-widths of approx. 175-400 micron, at ambient pressures approx. 10(exp -3) to 10(exp -4) torr. The downward displacement of the particle due to the radiation force is balanced by the electrostatic force indicated by the compensating dc potential applied to the balance electrodes, providing a direct measure of the radiation force on the levitated particle. Theoretical calculations of the radiation pressure with a least-squares fit to the measured data yield the radiation pressure efficiencies of the particles, and comparisons with Mie scattering theory calculations provide the imaginary part of the refractive index of silica and the corresponding extinction and scattering efficiencies.

  9. Radiation Pressure Measurements on Micron Size Individual Dust Grains

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Craven, P.D.; Spann, J. F.; Tankosic, D.; Witherow, W. K.; LeClair, A.; West, E.; Sheldon, R.; Gallagher, D. L.; Adrian, M. L.

    2003-01-01

    Measurements of electromagnetic radiation pressure have been made on individual silica (SiO2) particles levitated in an electrodynamic balance. These measurements were made by inserting single charged particles of known diameter in the 0.2 micron to 6.82 micron range and irradiating them from above with laser radiation focused to beam-widths of approx. 175-400 micron, at ambient pressures approx. 10(exp -3) to 10(exp -4) torr. The downward displacement of the particle due to the radiation force is balanced by the electrostatic force indicated by the compensating dc potential applied to the balance electrodes, providing a direct measure of the radiation force on the levitated particle. Theoretical calculations of the radiation pressure with a least-squares fit to the measured data yield the radiation pressure efficiencies of the particles, and comparisons with Mie scattering theory calculations provide the imaginary part of the refractive index of silica and the corresponding extinction and scattering efficiencies.

  10. The Importance of Physical Models for Deriving Dust Masses and Grain Size Distributions in Supernova Ejecta. I. Radiatively Heated Dust in the Crab Nebula

    NASA Technical Reports Server (NTRS)

    Temim, Tea; Dwek, Eli

    2013-01-01

    Recent far-infrared (IR) observations of supernova remnants (SNRs) have revealed significantly large amounts of newly condensed dust in their ejecta, comparable to the total mass of available refractory elements. The dust masses derived from these observations assume that all the grains of a given species radiate at the same temperature, regardless of the dust heating mechanism or grain radius. In this paper, we derive the dust mass in the ejecta of the Crab Nebula, using a physical model for the heating and radiation from the dust. We adopt a power-law distribution of grain sizes and two different dust compositions (silicates and amorphous carbon), and calculate the heating rate of each dust grain by the radiation from the pulsar wind nebula. We find that the grains attain a continuous range of temperatures, depending on their size and composition. The total mass derived from the best-fit models to the observed IR spectrum is 0.019-0.13 Solar Mass, depending on the assumed grain composition. We find that the power-law size distribution of dust grains is characterized by a power-law index of 3.5-4.0 and a maximum grain size larger than 0.1 micron. The grain sizes and composition are consistent with what is expected for dust grains formed in a Type IIP supernova (SN). Our derived dust mass is at least a factor of two less than the mass reported in previous studies of the Crab Nebula that assumed more simplified two-temperature models. These models also require a larger mass of refractory elements to be locked up in dust than was likely available in the ejecta. The results of this study show that a physical model resulting in a realistic distribution of dust temperatures can constrain the dust properties and affect the derived dust masses. Our study may also have important implications for deriving grain properties and mass estimates in other SNRs and for the ultimate question of whether SNe are major sources of dust in the Galactic interstellar medium and in

  11. THE IMPORTANCE OF PHYSICAL MODELS FOR DERIVING DUST MASSES AND GRAIN SIZE DISTRIBUTIONS IN SUPERNOVA EJECTA. I. RADIATIVELY HEATED DUST IN THE CRAB NEBULA

    SciTech Connect

    Temim, Tea; Dwek, Eli

    2013-09-01

    Recent far-infrared (IR) observations of supernova remnants (SNRs) have revealed significantly large amounts of newly condensed dust in their ejecta, comparable to the total mass of available refractory elements. The dust masses derived from these observations assume that all the grains of a given species radiate at the same temperature, regardless of the dust heating mechanism or grain radius. In this paper, we derive the dust mass in the ejecta of the Crab Nebula, using a physical model for the heating and radiation from the dust. We adopt a power-law distribution of grain sizes and two different dust compositions (silicates and amorphous carbon), and calculate the heating rate of each dust grain by the radiation from the pulsar wind nebula. We find that the grains attain a continuous range of temperatures, depending on their size and composition. The total mass derived from the best-fit models to the observed IR spectrum is 0.019-0.13 M{sub Sun }, depending on the assumed grain composition. We find that the power-law size distribution of dust grains is characterized by a power-law index of 3.5-4.0 and a maximum grain size larger than 0.1 {mu}m. The grain sizes and composition are consistent with what is expected for dust grains formed in a Type IIP supernova (SN). Our derived dust mass is at least a factor of two less than the mass reported in previous studies of the Crab Nebula that assumed more simplified two-temperature models. These models also require a larger mass of refractory elements to be locked up in dust than was likely available in the ejecta. The results of this study show that a physical model resulting in a realistic distribution of dust temperatures can constrain the dust properties and affect the derived dust masses. Our study may also have important implications for deriving grain properties and mass estimates in other SNRs and for the ultimate question of whether SNe are major sources of dust in the Galactic interstellar medium and in

  12. Gravitational radiation from a spinning compact object around a supermassive Kerr black hole in circular orbit

    SciTech Connect

    Han Wenbiao

    2010-10-15

    The gravitational waves and energy radiation from a spinning compact object with stellar mass in a circular orbit in the equatorial plane of a supermassive Kerr black hole are investigated in this paper. The effect of how the spin acts on energy and angular moment fluxes is discussed in detail. The calculation results indicate that the spin of a small body should be considered in waveform-template production for the upcoming gravitational wave detections. It is clear that when the direction of spin axes is the same as the orbitally angular momentum ('positive' spin), spin can decrease the energy fluxes which radiate to infinity. For antidirection spin ('negative'), the energy fluxes to infinity can be enlarged. And the relations between fluxes (both infinity and horizon) and spin look like quadratic functions. From frequency shift due to spin, we estimate the wave-phase accumulation during the inspiraling process of the particle. We find that the time of particle inspiral into the black hole is longer for positive spin and shorter for negative compared with the nonspinning particle. Especially, for extreme spin value, the energy radiation near the horizon of the extreme Kerr black hole is much more than that for the nonspinning one. And consequently, the maximum binging energy of the extreme spinning particle is much larger than that of the nonspinning particle.

  13. High-resolution 3D dust radiative transfer in galaxies with DART-Ray

    NASA Astrophysics Data System (ADS)

    Natale, Giovanni; Popescu, Cristina C.; Tuffs, Richard. J.; Debattista, Victor P.; Grootes, Meiert W.

    2015-02-01

    DART-Ray is a 3D ray-tracing dust radiative transfer (RT) code that can be used to derive stellar and dust emission maps of galaxy models and simulations with arbitrary geometries. In addition to the previously published RT algorithm, we have now included in DART-Ray the possibility of calculating the stocastically heated dust emission from each volume element within a galaxy. To show the capabilities of the code, we performed a high-resolution (26 pc) RT calculation for a galaxy N-body+SPH simulation. The simulated galaxy we considered is characterized by a nuclear disc and a flocculent spiral structure. We analysed the derived galaxy maps for the global and local effects of dust on the galaxy attenuation as well as the contribution of scattered radiation to the predicted observed emission. In addition, by performing an additional RT calculation including only the stellar volume emissivity due to young stellar populations (SPs), we derived the contribution to the total dust emission powered by young and old SPs. Full details of this work will be presented in a forthcoming publication.

  14. Observation and simulation of dust aerosol cycle and impact on radiative fluxes during the FENNEC campaign in summer 2011

    NASA Astrophysics Data System (ADS)

    Minvielle, Fanny; Derimian, Yevgeny; Pere, Jean-Christophe; Flamant, Cyrille; Brogniez, Gérard

    2013-04-01

    The Sahara desert is one of the principal worldwide sources of dust aerosol emissions that play significant role in the climatic system. In the framework of the FENNEC campaign, conducted during the summer 2011, we focus on dust radiative effect and impact on the atmospheric dynamics and profile structure. We study the variability of the measured radiative parameters and model atmospheric dynamics during dust plume observations at the FENNEC sites, therefore, trying to understand the link between the Saharan heat low system and dust aerosols. Due to its large size the airborne dust can absorb and scatter not only solar, but also thermal infrared radiation, which requires consideration of both spectral ranges. Analysis of AERONET and other optical observations during the period of intensive campaign in summer 2011 provides information on variability of aerosol optical characteristics and perturbation of solar and TIR flux. We use these observations in conjunction with the meso-scale model RAMS to understand the impact of the dust plumes on the atmospheric dynamics. We also simulate the dust cycle in order to find the contribution of the different emission sources and identify structure of transport over an extended domain. Then, coupling the radiative code (GAME) we calculate the radiative forcing of dust and compare it to the radiative flux observed and computed based on the AERONET observations. Validation of simulations is made using measurements from space-borne CALIOP lidar, SEVIRI and OMI satellites, AERONET ground-based stations and observations acquired onboard the SAFIRE Falcon 20 research aircraft.

  15. Efficient spin resolved spectroscopy observation machine at Hiroshima Synchrotron Radiation Center

    SciTech Connect

    Okuda, Taichi; Miyamaoto, Koji; Namatame, Hirofumi; Miyahara, Hirokazu; Kuroda, Kenta; Kimura, Akio; Taniguchi, Masaki

    2011-10-15

    Highly efficient spin- and angle-resolved photoelectron spectrometer named ESPRESSO (Efficient SPin REsolved SpectroScopy Observation) machine has been developed at the beamline BL-9B in Hiroshima Synchrotron Radiation Center. Combination of high-resolution hemispherical electron analyzer and the high-efficient spin detector based on very low energy electron diffraction by the ferromagnetic target makes the high-energy resolution and angular resolution compatible with spin- and angle-resolved photoemission (SARPES) measurement. 7.5 meV in energy and {+-}0.18 deg. in angular resolution have been achieved with spin resolution. The ESPRESSO machine, combination of quick energy-band dispersion measurement and Fermi surface mapping by two-dimensional electron detector for the spin integrated ARPES and the high-efficient spin analysis by the efficient spin detector realizes the comprehensive investigation of spin electronic structure of materials.

  16. Radiative Energetics of Mineral Dust Aerosol over Zhangye China during the AMY 2008 Field Campaign

    NASA Astrophysics Data System (ADS)

    Hansell, R. A.; Tsay, S.; Ji, Q.; Hsu, C.; Bell, S.; Li, C.; Wang, C.

    2010-12-01

    In support of the DOE ARM program, NASA Goddard’s mobile ground-based laboratories (SMART-COMMIT) were deployed to Zhangye China (39.082°N; 100.276°E) from April-June 2008 as an ARM Ancillary Facility (AAF) to support the Asian Monsoon Year (AMY) field study. The primary objective at Zhangye, a semi-arid region located between the Taklimakan and Gobi deserts, was to both capture and characterize dust aerosol near the source region and to determine its direct aerosol radiative effects (DARE). To facilitate this study, the AAF’s Atmospheric Emitted Radiance Interferometer (AERI), a key instrument for spectrally characterizing the thermal IR, is employed to retrieve the daytime/nighttime dust IR aerosol optical thickness (AOT) for several notable dust events. Regional dust microphysical and mineralogy measurements are also used for developing a representative aerosol optical model of dust single-scattering properties. The retrieved AOT are then inputted into a 1-D radiative transfer model constrained by local measurements to evaluate dust’s local instantaneous shortwave (SW) and longwave (LW) DARE at the surface and top of the atmosphere (TOA) along with the heating rate profiles under cloud-free atmospheres. Comparisons of the SW DARE are made with a previous study over the same area using broadband data from thermal dome effect corrected pyranometers and the significance of the LW effects relative to the SW is examined. This study is part of an on-going effort to complete a global assessment of dust DARE for the major dust source regions of the world.

  17. Dust aerosol radiative effect and forcing over West Africa : A case study from the AMMA SOP

    NASA Astrophysics Data System (ADS)

    Lemaître, C.; Flamant, C.; Pelon, J.; Cuesta, J.; Chazette, P.; Raut, J. C.

    2009-04-01

    The massive transport of arid dust by the African easterly jet (AEJ) can impact the dynamic of the AEJ and modify the development of westerly African waves through modifications of horizontal temperature gradient. Hence, it is important to evaluate the radiative impact of dust and their effect on thermodynamical properties of the AEJ. In this presentation, the impact of aerosol on solar and infra-red fluxes and the heating rate due to dust over West Africa are investigated using the radiative code STREAMER, as well as space-borne and airborne lidars (CALIPSO and LEANDRE 2, respectively) as well as dropsonde observations acquired during the African Monsoon Multidisciplinary Analysis Special Observing Period. Aircraft operations were conducted on 13 and 14 June 2006, over Benin and Niger. On these days the dust observed over Benin and Niger originated from the Bodélé depression and from West Sudan. In this study, we use aerosol extinction coefficient derived from lidar, as well as temperature, pressure and water vapour profiles derived from dropsondes as inputs to STREAMER. The surface albedo is obtained with MODIS. A series of runs was carried out on 13 and 14 June 2006, around mid-day, to investigate the dust radiative forcing as a function of latitude, from 6°N to 15°N, i.e. between the vegetated coast of the Guinea Gulf and the arid Sahel. In the solar spectrum, the maximum heating rate associated with the dust plume on these days was comprised between 1.5 K/day and 3 K/day, depending on the aerosol load, over the entire Sudanian and Sahel regions as inferred from CALIPSO. Sensitivity studies to surface albedo, aerosol backscatter-to-extinction ratio, temperature and water vapor mixing ratio profiles were also conducted.

  18. The radiative effects of Saharan dust layer on the marine atmospheric layer

    NASA Astrophysics Data System (ADS)

    Abed, Mohammed

    2017-04-01

    The North African Saharan desert is one of the main sources of atmospheric dust. Since dust can be transported by winds for thousands of miles, reaching the Americas and extending across vast expanses of the tropical Atlantic Ocean, it is important to understand the influence that dust has on the radiative properties and the thermodynamic structure of the atmosphere. For climate models it is important that this is represented since the structure of the atmosphere can have important influences downwind on the development of convection, clouds, storms, precipitation and consequently radiative properties. In this study, we aim to understand the dynamic and thermodynamic properties of Saharan dust on the atmospheric structure of marine environment and to investigate the causes of the observed regions of well-mixed potential temperatures of the marine atmosphere in the presence of Saharan dust layers. We compare the influence of dust to other potentially important influences such as wind shear and air mass. To investigate this, we simulated the marine atmosphere in the presence and absence of dust using the UK Met Office Large Eddy Model (LEM) based the BOMEX case-study that is provided with the LEM and updated with observation taken during the FENNEC experiments of June 2011 and 2012. We performed LEM simulations with and without dust heating rates for an eight-hour time period. Data for meteorological profiles were used from the FENNEC aircraft measurements taken over the Atlantic Ocean near the Canary Islands. Our LEM results show that using a stratified (typical of non-dusty) atmosphere and then apply a dust heating rate the profile of potential temperature tends towards a well-mixed layer where the heating rates were applied and consistent with the observational cases. While LEM simulations for wind shear showed very little difference in the potential temperature profile and it was clear the well-mixed layer would not result. LEM simulations using dust heating

  19. Spherically symmetric cosmological spacetimes with dust and radiation — numerical implementation

    SciTech Connect

    Lim, Woei Chet; Regis, Marco; Clarkson, Chris E-mail: regis@to.infn.it

    2013-10-01

    We present new numerical cosmological solutions of the Einstein Field Equations. The spacetime is spherically symmetric with a source of dust and radiation approximated as a perfect fluid. The dust and radiation are necessarily non-comoving due to the inhomogeneity of the spacetime. Such a model can be used to investigate non-linear general relativistic effects present during decoupling or big-bang nucleosynthesis, as well as for investigating void models of dark energy with isocurvature degrees of freedom. We describe the full evolution of the spacetime as well as the redshift and luminosity distance for a central observer. After demonstrating accuracy of the code, we consider a few example models, and demonstrate the sensitivity of the late time model to the degree of inhomogeneity of the initial radiation contrast.

  20. Radiative transfer in spherical dust shells using a generalized two-stream Eddington approximation

    NASA Technical Reports Server (NTRS)

    Haisch, B. M.

    1979-01-01

    Application of a generalized two-stream Eddington approximation to the problem of radiative transfer in extended, spherically symmetric dust shells is presented. It is assumed that the radiation field can be characterized by the mean intensity, the flux, and a positionally dependent direction cosine specifying the division into two solid-angle ranges. The direction cosine is not specified a priori and is a function of the geometry, opacity, and emissivity in the dust shell. A multiple-grain-size multiple-temperature-distribution dust shell is postulated in which isotropic and anisotropic scattering as well as absorption and thermal reemission are allowed. A program has been developed that solves for the multiple temperature distributions by applying the constraint of radiative equilibrium to each grain size, and then calculates emergent fluxes. Results of one such calculation are presented for a model dust shell having a maximum optical depth (approximately 41) in the visible, clearly showing large optical extinction and a moderate infrared excess.

  1. Solar and thermal radiative effects during the 2011 extreme desert dust episode over Portugal

    NASA Astrophysics Data System (ADS)

    Valenzuela, A.; Costa, M. J.; Guerrero-Rascado, J. L.; Bortoli, D.; Olmo, F. J.

    2017-01-01

    This paper analyses the influence of the extreme Saharan desert dust (DD) event on shortwave (SW) and longwave (LW) radiation at the EARLINET/AERONET Évora station (Southern Portugal) from 4 up to 7 April 2011. There was also some cloud occurrence in the period. In this context, it is essential to quantify the effect of cloud presence on aerosol radiative forcing. A radiative transfer model was initialized with aerosol optical properties, cloud vertical properties and meteorological atmospheric vertical profiles. The intercomparison between the instantaneous TOA shortwave and longwave fluxes derived using CERES and those calculated using SBDART, which was fed with aerosol extinction coefficients derived from the CALIPSO and lidar-PAOLI observations, varying OPAC dataset parameters, was reasonably acceptable within the standard deviations. The dust aerosol type that yields the best fit was found to be the mineral accumulation mode. Therefore, SBDART model constrained with the CERES observations can be used to reliably determine aerosol radiative forcing and heating rates. Aerosol radiative forcings and heating rates were derived in the SW (ARFSw, AHRSw) and LW (ARFLw, AHRLw) spectral ranges, considering a cloud-aerosol free reference atmosphere. We found that AOD at 440 nm increased by a factor of 5 on 6 April with respect to the lower dust load on 4 April. It was responsible by a strong cooling radiative effect pointed out by the ARFSw value (-99 W/m2 for a solar zenith angle of 60°) offset by a warming radiative effect according to ARFLw value (+21.9 W/m2) at the surface. Overall, about 24% and 12% of the dust solar radiative cooling effect is compensated by its longwave warming effect at the surface and at the top of the atmosphere, respectively. Hence, larger aerosol loads could enhance the response between the absorption and re-emission processes increasing the ARFLw with respect to those associated with moderate and low aerosol loads. The unprecedented

  2. Radiative Effects of Aerosols Generated from Biomass Burning, Dust Storms, and Forest Fires

    NASA Technical Reports Server (NTRS)

    Christopher Sundar A.; Vulcan, Donna V.; Welch, Ronald M.

    1996-01-01

    Atmospheric aerosol particles, both natural and anthropogenic, are important to the earth's radiative balance. They scatter the incoming solar radiation and modify the shortwave reflective properties of clouds by acting as Cloud Condensation Nuclei (CCN). Although it has been recognized that aerosols exert a net cooling influence on climate (Twomey et al. 1984), this effect has received much less attention than the radiative forcings due to clouds and greenhouse gases. The radiative forcing due to aerosols is comparable in magnitude to current anthropogenic greenhouse gas forcing but opposite in sign (Houghton et al. 1990). Atmospheric aerosol particles generated from biomass burning, dust storms and forest fires are important regional climatic variables. A recent study by Penner et al. (1992) proposed that smoke particles from biomass burning may have a significant impact on the global radiation balance. They estimate that about 114 Tg of smoke is produced per year in the tropics through biomass burning. The direct and indirect effects of smoke aerosol due to biomass burning could add up globally to a cooling effect as large as 2 W/sq m. Ackerman and Chung (1992) used model calculations and the Earth Radiation Budget Experiment (ERBE) data to show that in comparison to clear days, the heavy dust loading over the Saudi Arabian peninsula can change the Top of the Atmosphere (TOA) clear sky shortwave and longwave radiant exitance by 40-90 W/sq m and 5-20 W/sq m, respectively. Large particle concentrations produced from these types of events often are found with optical thicknesses greater than one. These aerosol particles are transported across considerable distances from the source (Fraser et al. 1984). and they could perturb the radiative balance significantly. In this study, the regional radiative effects of aerosols produced from biomass burning, dust storms and forest fires are examined using the Advanced Very High Resolution Radiometer (AVHRR) Local Area

  3. Implications of particle composition and shape to dust radiative effect: A case study from the Great Indian Desert

    NASA Astrophysics Data System (ADS)

    Mishra, S. K.; Dey, Sagnik; Tripathi, S. N.

    2008-12-01

    The assessment of direct radiative forcing (DRF) of aerosol is uncertain, particularly where the natural dust particles mix with the anthropogenic components. One of the sources of such uncertainty is the assumption of morphology (size and shape) and composition of pure dust particles. Recently Mishra and Tripathi [2008] have computationally assessed the effect of particle morphology on optical properties over the Great Indian Desert. As a continuation of the previous study, in this paper, we have further examined the effects on dust radiative properties. Non-spherical pure dust particles show large variations in the optical and radiative properties from spherical pure dust particles, however, particle composition is found to have greater influence than particle shape on the radiative properties. Among the various shapes, sharp-edged particles show larger difference than smooth-shaped particles. Although the overall atmospheric absorption monotonically increases with increase in hematite content, maximum effect of particle non-sphericity at 4% hematite content implies that non-sphericity should be considered to minimize the uncertainty of regional estimates of aerosol DRF, as most of the global dusts contain that much hematite. However the difference in radiative properties for two different background dust cases due to particle morphology is low. Our results show that ignoring non-sphericity will lead to under-estimation of the regional warming and dust-absorption efficiency.

  4. Quantifying the climatological cloud-free shortwave direct radiative forcing of mineral dust aerosol over the Red Sea

    NASA Astrophysics Data System (ADS)

    Stenchikov, G. L.; Brindley, H. E.; Osipov, S.; Bantges, R. J.; Smirnov, A.; Prakash, P. J.

    2014-12-01

    While there have been a number of campaigns designed to probe dust-climate interactions over much of the world, relatively little attention has been paid to the Red Sea. Because of the remoteness of the area, satellite retrievals provide a crucial tool for assessing aerosol loading over the Sea. However, agreement between aerosol properties inferred from measurements from different instruments, and even in some cases from the same measurements using different retrieval algorithms can be poor, particularly in the case of mineral dust. Ground based measurements, which can be used to evaluate retrievals, are thus highly desirable. Here we take advantage of ship-based hand-held sun-photometer (microtops) observations gathered within the framework of NASA Aerosol Maritime Network from a series of cruises, which took place across the Red Sea during 2011 and 2013. To our knowledge these data represent the first set of detailed aerosol measurements from the Sea. They thus provide a unique opportunity to assess the performance of satellite retrieval algorithms in this region. Here we used the microtops measurements to evaluate the performance of co-located satellite retrievals from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) and the MODerate Imaging Spectrometer (MODIS). Both algorithms show good agreement with the ship-based measurements and with each other, although it appears that the MODIS cloud detection scheme in particular is rather conservative. The stand alone Rapid Radiative Transfer Model (RRTM) driven by reanalysis meteorological fields is used to estimate the cloud-free aerosol direct radiative effect at the surface and TOA along the ship tracks. The TOA effects are compared to co-located measurements from the Geostationary Earth Radiation Budget (GERB) instrument. Having evaluated both the quality of the retrievals and the ability of the model to capture the associated radiative effect, we will present a climatology of aerosol loading over the

  5. An evaluation of radiation and dust hazards at a mineral sand processing plant.

    PubMed

    Johnston, G

    1991-06-01

    This three-part article discusses the results of a 2-y study on radiation and dust hazards in a mineral sand processing plant involving: (1) evaluation of external gamma radiation levels and determination of isotopic composition of the different sand products; (2) evaluation of radiation carried in long-lived radioactive dust (LLRD) particles; (3) evaluation of Rn gas concentrations within the working environs of the plant. Gamma radiation levels had a mean value of approximately 40 nSv h-1, and monazite sand returned the highest activity concentrations of 0.16% and 3.4% for 238U and 232Th, respectively. Low volume gross respirable dust sampling revealed an average long-lived airborne alpha activity concentration of 0.07 +/- 0.02 Bq m-3 and an average dust mass concentration of 3.3 +/- 2 mg m-3. Gamma spectroscopy applied to high-volume air samples showed average airborne 232Th and 238U activities of 0.012 +/- 0.004 Bq m-3 and 0.005 +/- 0.002 Bq m-3, respectively, giving an airborne 232Th: 238U ratio of 2.4:1. Air sampling using a high volume, five-stage cascade impactor indicated an average activity median aerodynamic diameter (AMAD) of 3.2 microns with an associated average geometric standard deviation (GSD) of 2.8. Average radiation dose arising from the inhalation of LLRD was estimated to be 7 mSv per annum. CR-39 (polycarbonate plastic) nuclear track detectors indicated that Rn gas concentrations in the environs of the processing plant dry mill and main product warehouse ranged from 30 Bq m-3 to 220 Bq m-3, with an average value of 100 Bq m-3, which presents a possible inhaled dose from Rn daughters of 1.5 mSv y-1 (assuming an equilibrium ratio of 0.5).

  6. Dust scattering and the radiation pressure force in the M82 superwind

    SciTech Connect

    Coker, Carl T.; Thompson, Todd A.; Martini, Paul E-mail: thompson@astronomy.ohio-state.edu

    2013-11-20

    Radiation pressure on dust grains may be an important physical mechanism driving galaxy-wide superwinds in rapidly star-forming galaxies. We calculate the combined dust and gas Eddington ratio (Γ) for the archetypal superwind of M82. By combining archival Galaxy Evolution Explorer data, a standard dust model, Monte Carlo dust scattering calculations, and the Herschel map of the dust surface density distribution, the observed far-UV/near-UV surface brightness in the outflow constrains both the total UV luminosity escaping from the starburst along its minor axis (L {sub *,UV}) and the flux-mean opacity, thus allowing a calculation of Γ. We find that L {sub *,UV} ≈ (1-6) × 10{sup 42} erg s{sup –1}, ∼2-12 times greater than the UV luminosity observed from our line of sight. On a scale of 1-3 kpc above the plane of M82, we find that Γ ∼ 0.01-0.06. On smaller scales (∼0.25-0.5 kpc), where the enclosed mass decreases, our calculation of L {sub *,UV} implies that Γ ∼ 0.1 with factor of few uncertainties. Within the starburst itself, we estimate the single-scattering Eddington ratio to be of order unity. Thus, although radiation pressure is weak compared to gravity on kpc scales above the plane of M82, it may yet be important in launching the observed outflow. We discuss the primary uncertainties in our calculation, the sensitivity of Γ to the dust grain size distribution, and the time evolution of the wind following M82's recent starburst episodes.

  7. Characterization and radiative impact of dust aerosols over northwestern part of India: a case study during a severe dust storm

    NASA Astrophysics Data System (ADS)

    Singh, Atinderpal; Tiwari, Shani; Sharma, Deepti; Singh, Darshan; Tiwari, Suresh; Srivastava, Atul Kumar; Rastogi, Neeraj; Singh, A. K.

    2016-12-01

    The present study focused on examining the impact of a severe dust storm (DS) on aerosol properties over Patiala (30.33°N, 76.4°E), a site located in the northwestern part of India during 20th-23rd March, 2012. On 20th March, average PM10 mass concentration increased abruptly from 182 to 817 µg m-3 along with significant increase in the number density of coarser particles (diameter >0.45 µm). During DS, spectral aerosol optical depth (AOD) increases significantly with more increase at longer wavelengths resulting in weak wavelength dependence (AOD at 380 nm increases by 210 % and at 870 nm by 270 % on 20th March). Significant decrease in Ångström exponent (AE; α 380-870) from 0.56 to 0.11 and fine-mode fraction (FMF; PM2.5/PM10) from 0.49 to 0.25 indicates dominance of coarser particles over the station. Net short wave (SW) radiation flux has been decreased by 20 % and single scattering albedo (SSA675) has been increased from 0.86 (19th March) to 0.90 (20th March). This observation is attributed to additional loading of scattering type aerosols on arrival of DS. Wavelength dependence of SSA reverses during DS and it increases with wavelength due to dominance of coarse-mode particles. Atmospheric aerosol radiative forcing (ATM ARF) during DS ranged from +45 to +77 W m-2, consequently heating the lower atmosphere up to 2.2 K day-1. Significant atmospheric heating rate due to severe dust storm may affect the regional atmospheric dynamics and hence the climate system.

  8. Radiative Effects of African Dust and Smoke Observed from CERES and CALIOP Data

    NASA Technical Reports Server (NTRS)

    Yorks, John E.; McGill, Matt; Rodier, Sharon; Vaughan, Mark; Xu, Yongxiang; Hlavka, Dennis

    2009-01-01

    Cloud and aerosol effects have a significant impact on the atmospheric radiation budget in the Tropical Atlantic because of the spatial and temporal extent of desert dust and smoke from biomass burning in the atmosphere. The influences of African dust and smoke aerosols on cloud radiative properties over the Tropical Atlantic Ocean were analyzed for the month of July for three years (2006-2008) using collocated data collected by the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and Clouds and the Earth s Radiant Energy System (CERES) instruments on the CALIPSO and Aqua satellites. Aerosol layer height and type can be more accurately determined using CALIOP data, through parameters such as cloud and aerosol layer height, optical depth and depolarization ratio, than data from atmospheric imagers used in previous cloud-aerosol interaction studies. On average, clouds below 5 km had a daytime instantaneous shortwave (SW) radiative flux of 270.2 +/- 16.9 W/sq m and thin cirrus clouds had a SW radiative flux of 208.0 +/- 12.7 W/sq m. When dust aerosols interacted with clouds below 5 km, as determined from CALIPSO, the SW radiative flux decreased to 205.4 +/- 13.0 W/sq m. Similarly, smoke aerosols decreased the SW radiative flux of low clouds to a value of 240.0 +/- 16.6 W/sq m. These decreases in SW radiative flux were likely attributed to the aerosol layer height and changes in cloud microphysics. CALIOP lidar observations, which more accurately identify aerosol layer height than passive instruments, appear essential for better understanding of cloud-aerosol interactions, a major uncertainty in predicting the climate system.

  9. The heating of diffuse dust at large scale in AGNs: a radiative transfer model study

    NASA Astrophysics Data System (ADS)

    Fritz, Jacopo; De Looze, Ilse; Baes, Maarten; Camps, Peter; Saftly, Waad; Pérez Villegas, Angeles; Rivaz-Sánchez, Mariana; Stalevski, Marko; Hatziminaoglou, Evanthia

    2016-08-01

    The panchromatic, broad-band, spectral energy distribution (SED) of galaxies is usually modelled by combining together the theoretical spectra of its emission components: stars in the optical/near-infrared, and thermal emission by dust -heated by the stellar radiation field- in the infrared. SED fitting codes such as MAGPHYS and CIGALE are capable to automatically fit observed multiwavelength data of galaxies, providing a set of galactic properties as a result. The situation gets somehow complicated when Active Galaxies (both local, low-luminosity Seyferts, and the bright QSOs) are considered. Very often, in fact, their observed near- and mid-infrared (NIR and MIR, respectively) SED is dominated by the emission of hot dust located close to the supermassive, active black hole which powers the bulk of their luminosity. Hence, a third component must be added to the set of theoretical SEDs: that of the molecular torus which surrounds the disk of gas accreting onto the supermassive black hole. The standard way to do it, is to simply add such models to the observed SED, until the MIR gap is filled. This implicitly assumes that the AGN has no influence whatsoever on the dust properties on scales larger than that of the torus (~few pc). I am investigating whether this assumption is valid, in which cases, and under which circumstances the AGN provides a non negligible contribution to the interstellar radiation field heating the diffuse dust in galaxies. This is accomplished by means of radiative transfer models which take into account the most relevant characteristics of the problem: the relative dust-stars distribution and the very wide range of spatial scales involved.

  10. Global mountain snow and ice loss driven by dust and black carbon radiative forcing

    NASA Astrophysics Data System (ADS)

    Painter, T. H.

    2014-12-01

    Changes in mountain snow and glaciers have been our strongest indicators of the effects of changing climate. Earlier melt of snow and losses of glacier mass have perturbed regional water cycling, regional climate, and ecosystem dynamics, and contributed strongly to sea level rise. Recent studies however have revealed that in some regions, the reduction of albedo by light absorbing impurities in snow and ice such as dust and black carbon can be distinctly more powerful than regional warming at melting snow and ice. In the Rocky Mountains, dust deposition has increased 5 to 7 fold in the last 150 years, leading to ~3 weeks earlier loss of snow cover from forced melt. In absolute terms, in some years dust radiative forcing there can shorten snow cover duration by nearly two months. Remote sensing retrievals are beginning to reveal powerful dust and black carbon radiative forcing in the Hindu Kush through Himalaya. In light of recent ice cores that show pronounced increases in loading of dust and BC during the Anthropocene, these forcings may have contributed far more to glacier retreat than previously thought. For example, we have shown that the paradoxical end of the Little Ice Age in the European Alps beginning around 1850 (when glaciers began to retreat but temperatures continued to decline and precipitation was unchanged) very likely was driven by the massive increases in deposition to snow and ice of black carbon from industrialization in surrounding nations. A more robust understanding of changes in mountain snow and ice during the Anthropocene requires that we move past simplistic treatments (e.g. temperature-index modeling) to energy balance approaches that assess changes in the individual forcings such as the most powerful component for melt - net solar radiation. Remote sensing retrievals from imaging spectrometers and multispectral sensors are giving us more powerful insights into the time-space variation of snow and ice albedo.

  11. A case study of dust aerosol radiative properties over Lanzhou, China

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Cao, X.; Bao, J.; Zhou, B.; Huang, J.; Shi, J.; Bi, J.

    2010-02-01

    The vertical distribution of dust aerosol and its radiative properties are analysed using the data measured by the micropulse lidar, profiling microwave radiometer, sunphotometer, particulate monitor, and nephelometer at the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) during a dust storm from 27 March to 29 March 2007. The analysis shows that the dust aerosol mainly exists below 2 km in height, and the dust aerosol extinction coefficient decreases with height. The temporal evolution of aerosol optical depth (AOD) during the dust storm is characterized by a sub-maximum at 22:00 (Beijing Time) on 27 March and a maximum at 12:00 on 28 March. The AOD derived by lidar is compared with that obtained by sunphotometer, and shows a good consistency. The PM10 concentration and aerosol scattering coefficient share identical variation trends, and their maximums both appear at 22:00 on 27 March. The aerosol extinction coefficient and relative humidity have the same trends and their maximums appear at identical heights, showing a correlation between extinction coefficient and relative humidity known as aerosol hygroscopicity. Nevertheless, the correlation between aerosol extinction coefficient and temperature cannot be obviously seen. The aerosol extinction coefficient, scattering coefficient, and PM10 concentration present good linear correlations. The correlation coefficients of the aerosol scattering coefficient and PM10 concentration, of aerosol extinction coefficient and PM10 concentration, and of aerosol extinction and scattering coefficient are respectively 0.98, 0.94, and 0.96.

  12. Asian Dust particles impacts on air quality and radiative forcing over Korea

    NASA Astrophysics Data System (ADS)

    Kim, Y. J.; Noh, Y. M.; Song, C. H.; Yoon, S. C.; Han, J. S.

    2009-03-01

    Asian Dust particles originated from the deserts and loess areas of the Asian continent are often transported over Korea, Japan, and the North Pacific Ocean during spring season. Major air mass pathway of Asian dust storm to Korea is from either north-western Chinese desert regions or north-eastern Chinese sandy areas. The local atmospheric environment condition in Korea is greatly impacted by Asian dust particles transported by prevailing westerly wind. Since these Asian dust particles pass through heavily populated urban and industrial areas in China before it reach Korean peninsular, their physical, chemical and optical properties vary depending on the atmospheric conditions and air mass pathway characteristics. An integrated system approach has been adopted at the Advanced Environment Monitoring Research Center (ADEMRC), Gwangju Institute Science and Technology (GIST), Korea for effective monitoring of atmospheric aerosols utilizing various in-situ and optical remote sensing methods, which include a multi-channel Raman LIDAR system, sunphotometer, satellite, and in-situ instruments. Results from recent studies on impacts of Asian dust particles on local air quality and radiative forcing over Korea are summarized here.

  13. Response of Colorado river runoff to dust radiative forcing in snow

    USGS Publications Warehouse

    Painter, T.H.; Deems, J.S.; Belnap, J.; Hamlet, A.F.; Landry, C.C.; Udall, B.

    2010-01-01

    The waters of the Colorado River serve 27 million people in seven states and two countries but are overallocated by more than 10% of the river's historical mean. Climate models project runoff losses of 7-20% from the basin in this century due to human-induced climate change. Recent work has shown however that by the late 1800s, decades prior to allocation of the river's runoff in the 1920s, a fivefold increase in dust loading from anthropogenically disturbed soils in the southwest United States was already decreasing snow albedo and shortening the duration of snow cover by several weeks. The degree to which this increase in radiative forcing by dust in snow has affected timing and magnitude of runoff from the Upper Colorado River Basin (UCRB) is unknown. Hereweuse the Variable Infiltration Capacity model with postdisturbance and predisturbance impacts of dust on albedo to estimate the impact on runoff from the UCRB across 1916-2003. We find that peak runoff at Lees Ferry, Arizona has occurred on average 3 wk earlier under heavier dust loading and that increases in evapotranspiration from earlier exposure of vegetation and soils decreases annual runoff by more than 1.0 billion cubic meters or ???5% of the annual average. The potential to reduce dust loading through surface stabilization in the deserts and restore more persistent snow cover, slow runoff, and increase water resources in the UCRB may represent an important mitigation opportunity to reduce system management tensions and regional impacts of climate change.

  14. Foehn-induced effects on local dust pollution, frontal clouds and solar radiation in the Dead Sea valley

    NASA Astrophysics Data System (ADS)

    Kishcha, Pavel; Starobinets, Boris; Savir, Amit; Alpert, Pinhas; Kaplan, Michael

    2017-03-01

    Despite the long history of investigation of foehn phenomena, there are few studies of the influence of foehn winds on air pollution and none in the Dead Sea valley. For the first time the foehn phenomenon and its effects on local dust pollution, frontal cloudiness and surface solar radiation were analyzed in the Dead Sea valley, as it occurred on 22 March 2013. This was carried out using both numerical simulations and observations. The foehn winds intensified local dust emissions, while the foehn-induced temperature inversion trapped dust particles beneath this inversion. These two factors caused extreme surface dust concentration in the western Dead Sea valley. The dust pollution was transported by west winds eastward, to the central Dead Sea valley, where the speed of these winds sharply decreased. The transported dust was captured by the ascending airflow contributing to the maximum aerosol optical depth (AOD) over the central Dead Sea valley. On the day under study, the maximum surface dust concentration did not coincide with the maximum AOD: this being one of the specific effects of the foehn phenomenon on dust pollution in the Dead Sea valley. Radar data showed a passage of frontal cloudiness through the area of the Dead Sea valley leading to a sharp drop in noon solar radiation. The descending airflow over the downwind side of the Judean Mountains led to the formation of a cloud-free band followed by only the partial recovery of solar radiation because of the extreme dust pollution caused by foehn winds.

  15. Deflection of the local interstellar dust flow by solar radiation pressure.

    PubMed

    Landgraf, M; Augustsson, K; Grün, E; Gustafson, B A

    1999-12-17

    Interstellar dust grains intercepted by the dust detectors on the Ulysses and Galileo spacecrafts at heliocentric distances from 2 to 4 astronomical units show a deficit of grains with masses from 1 x 10(-17) to 3 x 10(-16) kilograms relative to grains intercepted outside 4 astronomical units. To divert grains out of the 2- to 4-astronomical unit region, the solar radiation pressure must be 1.4 to 1.8 times the force of solar gravity. These figures are consistent with the optical properties of spherical or elongated grains that consist of astronomical silicates or organic refractory material. Pure graphite grains with diameters of 0.2 to 0.4 micrometer experience a solar radiation pressure force as much as twice the force of solar gravity.

  16. Hydromagnetic transport of dust particles in gas flow over an inclined plane with thermal radiation

    NASA Astrophysics Data System (ADS)

    Mehmood, Obaid Ullah; Maskeen, Muhammad Muddassar; Zeeshan, Ahmad

    In present article, hydromagnetic transport of dust particles in gas flow over an inclined plane is examined under the influence of thermal radiation and viscous dissipation. The Rosseland diffusion flux model is utilized for thermal radiation effects. The resulting non-linear ordinary differential equations are converted into similar forms via suitable similarity transforms and then tackled numerically by bvp4c built in code of Matlab software. The influences of numerous emergent parameters on flow features like velocities, temperature distributions and Nusselt number are depicted graphically and discussed in detail.

  17. Transport, vertical structure and radiative properties of dust events in southeast China determined from ground and space sensors

    SciTech Connect

    Liu, Jianjun; Zheng, Y.; Li, Zhanqing; Flynn, Connor J.; Welton, Ellsworth J.; Cribb, Maureen

    2011-11-01

    Two dust events were detected over the Yangtze Delta region of China during March 14-17 and April 25-26 in 2009 where such dust events are uncommon. The transport behavior, spatio-temporal evolution, vertical structure, direct radiative effects, as well as induced heating rates, are investigated using a combination of ground-based and satellite-based measurements, a back-trajectory analysis, an aerosol model and a radiative transfer model.

  18. Dust Propagation and Radiation In the Presence of a Low-level Jet in Central China on March 17, 2010

    NASA Astrophysics Data System (ADS)

    McDowell, B. K.; Chen, S. H.

    2014-12-01

    Suspended dust in the air can directly change the energy budget in the atmosphere and at the surface through scattering and absorption of radiation. Thus, dust can potentially modify the development of weather systems. To explore the dust-radiation effects on weather systems, a dust model was developed based on the Weather Research and Forecasting (WRF) model. The calculations of dust processes in the WRF dust model include emission, advection, boundary layer mixing, cumulus mixing, dust-radiation interaction, wet scavenging, and sedimentation. Due to a high vertical spatial resolution near the surface a time splitting method was applied to the calculation of dust sedimentation to relax the numerical time step. The "Hexi Corridor" is the historical name given to a string of oases along the northern slope of the Tibetan Plateau that formed a relatively easy transportation route between eastern China and central Asia. As trade developed over the centuries, this route became known as the Silk Road. This corridor also marks the transition from the relatively flat Gobi desert area in northern China to the elevated mountains of the Tibetan Plateau. These mountains present a southern barrier to the paths of dust storms that develop during spring outbreaks of the Mongolian Cyclone. In March of 2010, a series of dust storms developed in the Gobi Desert north of the Hexi Corridor that transported massive amounts of dust eastward to central and northeastern China, Korea and Japan. On March 17 during this event, a low-level jet developed along the northern perimeter of the Plateau, in alignment with upper level winds and the Hexi Corridor. Over the course of the day, a well-defined short-duration dust plume was emitted in the southern Gobi desert area and was transported over 1300 km in a southeast direction, over the Loess Plateau and into the Gansu Province. In this study, the interactions of synoptic conditions with regional topography that led to the development of the low

  19. Spin-polarized photoemission spectroscopy of magnetic surfaces using undulator radiation

    NASA Astrophysics Data System (ADS)

    Johnson, P. D.; Brookes, N. B.; Hulbert, S. L.; Klaffky, R.; Clarke, A.; Sinković, B.; Smith, N. V.; Celotta, R.; Kelly, M. H.; Pierce, D. T.; Scheinfein, M. R.; Waclawski, B. J.; Howells, M. R.

    1992-03-01

    A beamline has been established at the National Synchrotron Light Source to perform angle-resolved photoemission experiments on magnetic surfaces with spin sensitivity. The system has two novel features: it uses a miniature electron-spin polarization analyzer and it also uses synchrotron radiation from an undulator rather than a bending magnet.

  20. Radiative Transfer Model of Dust Attenuation Curves in Clumpy, Galactic Environments

    NASA Astrophysics Data System (ADS)

    Seon, Kwang-Il; Draine, Bruce T.

    2016-12-01

    The attenuation of starlight by dust in galactic environments is investigated through models of radiative transfer in a spherical, clumpy interstellar medium (ISM). We show that the attenuation curves are primarily determined by the wavelength dependence of absorption rather than by the underlying extinction (absorption+scattering) curve; the observationally derived attenuation curves cannot constrain a unique extinction curve unless the absorption or scattering efficiency is specified. Attenuation curves consistent with the “Calzetti curve” are found by assuming the silicate-carbonaceous dust model for the Milky Way (MW), but with the 2175 Å bump suppressed or absent. The discrepancy between our results and previous work that claimed the Small Magellanic Cloud dust to be the origin of the Calzetti curve is ascribed to the difference in adopted albedos; we use the theoretically calculated albedos, whereas the previous works adopted albedos derived empirically from observations of reflection nebulae. It is found that the attenuation curves calculated with the MW dust model are well represented by a modified Calzetti curve with a varying slope and UV bump strength. The strong correlation between the slope and UV bump strength, as found in star-forming galaxies at 0.5\\lt z\\lt 2.0, is well reproduced when the abundance of the UV bump carriers is assumed to be 30%-40% of that of the MW dust; radiative transfer effects lead to shallower attenuation curves with weaker UV bumps as the ISM is more clumpy and dustier. We also argue that some local starburst galaxies have a UV bump in their attenuation curves, albeit very weak.

  1. Aerosol radiative effects during two desert dust events in August 2012 over the Southwestern Iberian Peninsula

    NASA Astrophysics Data System (ADS)

    Obregón, M. A.; Pereira, S.; Salgueiro, V.; Costa, M. J.; Silva, A. M.; Serrano, A.; Bortoli, D.

    2015-02-01

    This study provides an analysis of desert dust aerosol radiative effects in the shortwave solar spectrum. For this purpose, the aerosol radiative forcing (ARF) at the earth's surface was calculated during two desert dust events that occurred during August 2012 over Badajoz (Spain) and Évora (Portugal), both stations are located in southwestern Iberian Peninsula. Aerosol properties from these two AERONET stations have been employed to feed the libRadtran model used to simulate irradiances in the shortwave range at the surface under cloud-free conditions. In addition, simulated irradiances for Évora have been compared with Eppley pyranometer measurements. Simulated irradiance values have been used to calculate ARF values at both sites. The overall mean simulated ARF values for Évora and Badajoz during the first event are - 43.03 and - 43.76 W m- 2, respectively, while, for the second event, the overall mean values are - 19.73 and - 26.07 W m- 2, respectively, indicating that the first event has a greater regional radiative impact than the second one, causing a more pronounced radiate cooling at the surface. The ARF per unit of aerosol optical depth (AOD), called the aerosol radiative forcing efficiency (ARFE), is also evaluated for this shortwave spectral range. The ARFE values obtained for Évora and Badajoz during the first event are - 112.93 ± 6.60 W m- 2 and - 101.63 ± 10.73 W m- 2 per unit of AOD (500 nm), respectively, and, for the second event, - 92.44 ± 9.82 W m- 2 and - 87.85 ± 10.19 W m- 2 per unit of AOD (500 nm), respectively. These values also confirm the previous results, i.e., the first event causes a greater radiate cooling than the second one in both stations, although the second desert dust event is more intense, i.e., with higher aerosol optical depth and PM10 aerosol mass concentration. The presence of absorbing aerosols, together with dust, near the surface during the first event may explain the greater efficiency of this aerosol mixture

  2. Radiative transfer modeling of dust-coated Pancam calibration target materials: Laboratory visible/near-infrared spectrogoniometry

    USGS Publications Warehouse

    Johnson, J. R.; Sohl-Dickstein, J.; Grundy, W.M.; Arvidson, R. E.; Bell, J.F.; Christensen, P.R.; Graff, T.; Guinness, E.A.; Kinch, K.; Morris, Robert; Shepard, M.K.

    2006-01-01

    Laboratory visible/near-infrared multispectral observations of Mars Exploration Rover Pancam calibration target materials coated with different thicknesses of Mars spectral analog dust were acquired under variable illumination geometries using the Bloomsburg University Goniometer. The data were fit with a two-layer radiative transfer model that combines a Hapke formulation for the dust with measured values of the substrate interpolated using a He-Torrance approach. We first determined the single-scattering albedo, phase function, opposition effect width, and amplitude for the dust using the entire data set (six coating thicknesses, three substrates, four wavelengths, and phase angles 3??-117??). The dust exhibited single-scattering albedo values similar to other Mars analog soils and to Mars Pathfinder dust and a dominantly forward scattering behavior whose scattering lobe became narrower at longer wavelengths. Opacity values for each dust thickness corresponded well to those predicted from the particles sizes of the Mars analog dust. We then restricted the number of substrates, dust thicknesses, and incidence angles input to the model. The results suggest that the dust properties are best characterized when using substrates whose reflectances are brighter and darker than those of the deposited dust and data that span a wide range of dust thicknesses. The model also determined the dust photometric properties relatively well despite limitations placed on the range of incidence angles. The model presented here will help determine the photometric properties of dust deposited on the MER rovers and to track the multiple episodes of dust deposition and erosion that have occurred at both landing sites. Copyright 2006 by the American Geophysical Union.

  3. Dust Radiative Transfer Modeling of the Infrared Ring around the Magnetar SGR 1900+14

    NASA Astrophysics Data System (ADS)

    Natale, G.; Rea, N.; Lazzati, D.; Perna, R.; Torres, D. F.; Girart, J. M.

    2017-03-01

    A peculiar infrared ring-like structure was discovered by Spitzer around the strongly magnetized neutron star SGR 1900+14. This infrared (IR) structure was suggested to be due to a dust-free cavity, produced by the Soft Gamma-ray Repeaters (SGRs) Giant Flare occurring in 1998, and kept illuminated by surrounding stars. Using a 3D dust radiative transfer code, we aimed to reproduce the emission morphology and the integrated emission flux of this structure assuming different spatial distributions and densities for the dust, and different positions for the illuminating stars. We found that a dust-free ellipsoidal cavity can reproduce the shape, flux, and spectrum of the ring-like IR emission, provided that the illuminating stars are inside the cavity and that the interstellar medium has high gas density (n H ∼ 1000 cm‑3). We further constrain the emitting region to have a sharp inner boundary and to be significantly extended in the radial direction, possibly even just a cavity in a smooth molecular cloud. We discuss possible scenarios for the formation of the dustless cavity and the particular geometry that allows it to be IR-bright.

  4. Modelling direct radiative effect of mineral dust with the NMMB/BSC-CTM for dust outbreak events over the Mediterranean in summer 2012

    NASA Astrophysics Data System (ADS)

    Obiso, Vincezo; Jorba, Oriol; Basart, Sara; Baldasano, Jose M.; Nabat, Pierre

    2014-05-01

    Aerosols interact with the atmospheric system scattering and absorbing solar radiation, with a significant impact on atmospheric energy and hydrologic processes. Radiative forcing associated with these perturbations affects climate and meteorology. In this contribution, we analyse model results of the Direct Radiative Effect (DRE) of mineral dust over the western-Mediterranean during summer 2012. For that, the NMMB/BSC Chemical Transport Model (NMMB/BSC-CTM) is applied on a regional domain at 0.1º horizontal resolution. The NMMB/BSC-CTM is a new on-line chemical weather prediction system coupling atmospheric and chemistry processes. In the radiation module of the model mineral dust is treated as a radiatively active substance interacting both short and longwave radiation. The impact of the mineral dust outbreaks on meteorology is discussed by comparing model forecasts with atmospheric analysis and meteorological observations. The analysis focuses in the vertical structure of the atmosphere and the resulting surface meteorological conditions. The authors acknowledge the support from the grant SEV-2011-00067 of Severo Ochoa Program, awarded by the Spanish Government.

  5. SKIRT: An advanced dust radiative transfer code with a user-friendly architecture

    NASA Astrophysics Data System (ADS)

    Camps, P.; Baes, M.

    2015-03-01

    We discuss the architecture and design principles that underpin the latest version of SKIRT, a state-of-the-art open source code for simulating continuum radiation transfer in dusty astrophysical systems, such as spiral galaxies and accretion disks. SKIRT employs the Monte Carlo technique to emulate the relevant physical processes including scattering, absorption and emission by the dust. The code features a wealth of built-in geometries, radiation source spectra, dust characterizations, dust grids, and detectors, in addition to various mechanisms for importing snapshots generated by hydrodynamical simulations. The configuration for a particular simulation is defined at run-time through a user-friendly interface suitable for both occasional and power users. These capabilities are enabled by careful C++ code design. The programming interfaces between components are well defined and narrow. Adding a new feature is usually as simple as adding another class; the user interface automatically adjusts to allow configuring the new options. We argue that many scientific codes, like SKIRT, can benefit from careful object-oriented design and from a friendly user interface, even if it is not a graphical user interface.

  6. Polarization in Monte Carlo radiative transfer and dust scattering polarization signatures of spiral galaxies

    NASA Astrophysics Data System (ADS)

    Peest, C.; Camps, P.; Stalevski, M.; Baes, M.; Siebenmorgen, R.

    2017-05-01

    Polarization is an important tool to further the understanding of interstellar dust and the sources behind it. In this paper we describe our implementation of polarization that is due to scattering of light by spherical grains and electrons in the dust Monte Carlo radiative transfer code SKIRT. In contrast to the implementations of other Monte Carlo radiative transfer codes, ours uses co-moving reference frames that rely solely on the scattering processes. It fully supports the peel-off mechanism that is crucial for the efficient calculation of images in 3D Monte Carlo codes. We develop reproducible test cases that push the limits of our code. The results of our program are validated by comparison with analytically calculated solutions. Additionally, we compare results of our code to previously published results. We apply our method to models of dusty spiral galaxies at near-infrared and optical wavelengths. We calculate polarization degree maps and show them to contain signatures that trace characteristics of the dust arms independent of the inclination or rotation of the galaxy.

  7. Retrieval of Martian dust properties by surface observations and radiative transfer models

    NASA Astrophysics Data System (ADS)

    Kemppinen, O.; Merikallio, S.; Crisp, D.; Harri, A.

    2013-12-01

    We present the investigations of the properties of Martian dust based on observed changes in atmospheric opacity and surface temperature by using fast and accurate radiative transfer models. We utilize large amounts of atmospheric data, such as the data from Viking Landers recently re-processed by Finnish Meteorological Institute, and select periods of time when there are sudden changes in the observed atmospheric opacity. Then, we will automatically fine-tune the dust and other optical parameters in a radiative transfer model and other models to reproduce the observed effect in the atmospheric temperature. This will result in a large number of required computations, which dictates that the models need to be computationally fast, while also being accurate and flexible. Due to these restrictions, we will be using the SMART model developed by Dr. David Crisp. As is usual for inverse problems with several free parameters, there will likely be an infinite number of possible solutions. We hope to limit the valid solution space by using a large amount of separate instances of opacity changes. We will also utilize a priori information based on the current knowledge of Martian dust to achieve additional accuracy on top of the purely computational approach.

  8. Emission, transport, and radiative effects of mineral dust from the Taklimakan and Gobi deserts: comparison of measurements and model results

    NASA Astrophysics Data System (ADS)

    Chen, Siyu; Huang, Jianping; Kang, Litai; Wang, Hao; Ma, Xiaojun; He, Yongli; Yuan, Tiangang; Yang, Ben; Huang, Zhongwei; Zhang, Guolong

    2017-02-01

    The Weather Research and Forecasting Model with chemistry (WRF-Chem model) was used to investigate a typical dust storm event that occurred from 18 to 23 March 2010 and swept across almost all of China, Japan, and Korea. The spatial and temporal variations in dust aerosols and the meteorological conditions over East Asia were well reproduced by the WRF-Chem model. The simulation results were used to further investigate the details of processes related to dust emission, long-range transport, and radiative effects of dust aerosols over the Taklimakan Desert (TD) and Gobi Desert (GD). The results indicated that weather conditions, topography, and surface types in dust source regions may influence dust emission, uplift height, and transport at the regional scale. The GD was located in the warm zone in advance of the cold front in this case. Rapidly warming surface temperatures and cold air advection at high levels caused strong instability in the atmosphere, which strengthened the downward momentum transported from the middle and low troposphere and caused strong surface winds. Moreover, the GD is located in a relatively flat, high-altitude region influenced by the confluence of the northern and southern westerly jets. Therefore, the GD dust particles were easily lofted to 4 km and were the primary contributor to the dust concentration over East Asia. In the dust budget analysis, the dust emission flux over the TD was 27.2 ± 4.1 µg m-2 s-1, which was similar to that over the GD (29 ± 3.6 µg m-2 s-1). However, the transport contribution of the TD dust (up to 0.8 ton d-1) to the dust sink was much smaller than that of the GD dust (up to 3.7 ton d-1) because of the complex terrain and the prevailing wind in the TD. Notably, a small amount of the TD dust (PM2.5 dust concentration of approximately 8.7 µg m-3) was lofted to above 5 km and transported over greater distances under the influence of the westerly jets. Moreover, the direct radiative forcing induced by dust

  9. Desert dust transported over Europe: Lidar observations and model evaluation of the radiative impact

    NASA Astrophysics Data System (ADS)

    Pitari, Giovanni; Di Genova, Glauco; Coppari, Eleonora; De Luca, Natalia; Di Carlo, Piero; Iarlori, Marco; Rizi, Vincenzo

    2015-04-01

    Three years of measurements of aerosol vertical profiles (2007-2009) made at the lidar station of L'Aquila, a site in central Italy that is part of the European Aerosol Research Lidar Network, are studied by means of well-tested radiative transfer models to analyze the radiative impact of mineral dust aerosols transported from the Sahara desert. Sixteen major episodes of desert dust transport are considered; the radiative analysis is conducted in terms of diurnal averages of the top-of-atmosphere radiative flux changes (TOARFC) with respect to a reference "clean" aerosol profile not perturbed by long-range transported desert particles. The aerosol size distribution, needed as an input parameter for the Mie scattering program to obtain single-scattering albedo, asymmetry parameter, and extinction scaling over the whole wavelength spectrum, is obtained from simultaneous surface measurements with a multichannel aerosol spectrometer. The calculated average net TOARFC is +2.3 and +3.0 W/m2 in clear- and total-sky conditions, respectively. Solar, planetary components account for -0.42 and +2.7 W/m2 in clear-sky conditions and +0.93 and +2.1 W/m2 in total-sky conditions, respectively. The large effective radius of these coarse mode soil dust particles (reff = 1.5 µm) makes the longwave planetary component of the TOARFC dominant over the solar component, at least for typical continental surface albedo values (0.18 on average, at L'Aquila). The solar component, however, shows a pronounced sensitivity to the surface albedo and becomes dominant over the longwave component for both an ocean albedo (0.07) and a typical surface-snow albedo (0.4), with TOARFC values of -6.3 and +10.6 W/m2, respectively.

  10. Effect of polyfunctional monomers on properties of radiation crosslinked EPDM/waste tire dust blend

    NASA Astrophysics Data System (ADS)

    Yasin, Tariq; Khan, Sajid; Nho, Young-Chang; Ahmad, Rashid

    2012-04-01

    In this study, waste tire dust is recycled as filler and blended with ethylene-propylene diene monomer (EPDM) rubber. Three different polyfuntional monomers (PFMs) are incorporated into the standard formulation and irradiated under electron beam at different doses up to maximum of 100 kGy. The combined effects of PFMs and absorbed dose on the physical properties of EPDM/WTD blend are measured and compared with sulfur crosslinked formulation. Thermogravimetric analysis showed that radiation developed better crosslinked network with higher thermal stability than sulfur crosslinked structure. The physical properties of radiation crosslinked blend are similar to the sulfur crosslinked blend. The absence of toxic chemicals/additives in radiation crosslinked blends made them an ideal candidate for many applications such as roof sealing sheets, water retention pond, playground mat, sealing profile for windows etc.

  11. Aerosol chemical and radiative properties in the tropical Atlantic trade winds: The importance of African mineral dust

    NASA Astrophysics Data System (ADS)

    Li-Jones, Xu

    This dissertation presents results relevant to aerosol radiative forcing. The focus of this dissertation is the role of mineral dust in atmospheric radiative processes over the tropical Atlantic Ocean. The aerosol mass and light scattering data concurrently measured over the tropical North Atlantic ocean yield a dust mass scattering efficiency of 0.77 m2/g, about a quarter of that measured for non-sea-salt sulfate (nss SO4=) in the North Atlantic marine boundary layer. Because of the high concentration of mineral dust relative to nss SO4= over the tropical North Atlantic, the total scattering by mineral dust is about four times that by nss SO4 = aerosol in this region. On an annual basis, aerosol optical depth is apportioned to: mineral dust 71%, nss- SO4 = 16% and sea salt 13%. The coarse-particle fraction (CPF) (aerodynamic diameter > 1 μm) of nss SO4= varied from about 21% to 73%, with the highest CPF values associated with African dust events. The CPF nss SO 4= was believed to be a result of the heterogeneous reactions of SO2 (presumably from European sources) with dust particles suspended in the air over North Africa. This study provides the first direct evidence that confirms the importance of dust in sulfate production and resulting the coarse particle sulfate in the tropical Atlantic Ocean region. An important implication is that dust particles may reduce the effectiveness of sulfate aerosol as a radiative forcing agent in many regions where dust events are frequent and where dust concentrations are high. The aerosol scattering coefficient (ASC) measured during this experiment increased by a factor of 1.13 to 1.69 when RH was increased from about 40% to 80%. Through chemical apportioning of ASC, the HGF for sea-salt was found to be 1.8 +/- 0.2, while that of mineral dust was close to unity. This study shows that climate studies must consider the effect of mineral dust not only because of its direct effects on the radiation balance but also because of its

  12. Response of Colorado River runoff to dust radiative forcing in snow

    PubMed Central

    Painter, Thomas H.; Deems, Jeffrey S.; Belnap, Jayne; Hamlet, Alan F.; Landry, Christopher C.; Udall, Bradley

    2010-01-01

    The waters of the Colorado River serve 27 million people in seven states and two countries but are overallocated by more than 10% of the river’s historical mean. Climate models project runoff losses of 7–20% from the basin in this century due to human-induced climate change. Recent work has shown however that by the late 1800s, decades prior to allocation of the river’s runoff in the 1920s, a fivefold increase in dust loading from anthropogenically disturbed soils in the southwest United States was already decreasing snow albedo and shortening the duration of snow cover by several weeks. The degree to which this increase in radiative forcing by dust in snow has affected timing and magnitude of runoff from the Upper Colorado River Basin (UCRB) is unknown. Here we use the Variable Infiltration Capacity model with postdisturbance and predisturbance impacts of dust on albedo to estimate the impact on runoff from the UCRB across 1916–2003. We find that peak runoff at Lees Ferry, Arizona has occurred on average 3 wk earlier under heavier dust loading and that increases in evapotranspiration from earlier exposure of vegetation and soils decreases annual runoff by more than 1.0 billion cubic meters or ∼5% of the annual average. The potential to reduce dust loading through surface stabilization in the deserts and restore more persistent snow cover, slow runoff, and increase water resources in the UCRB may represent an important mitigation opportunity to reduce system management tensions and regional impacts of climate change. PMID:20855581

  13. Response of Colorado River runoff to dust radiative forcing in snow.

    PubMed

    Painter, Thomas H; Deems, Jeffrey S; Belnap, Jayne; Hamlet, Alan F; Landry, Christopher C; Udall, Bradley

    2010-10-05

    The waters of the Colorado River serve 27 million people in seven states and two countries but are overallocated by more than 10% of the river's historical mean. Climate models project runoff losses of 7-20% from the basin in this century due to human-induced climate change. Recent work has shown however that by the late 1800s, decades prior to allocation of the river's runoff in the 1920s, a fivefold increase in dust loading from anthropogenically disturbed soils in the southwest United States was already decreasing snow albedo and shortening the duration of snow cover by several weeks. The degree to which this increase in radiative forcing by dust in snow has affected timing and magnitude of runoff from the Upper Colorado River Basin (UCRB) is unknown. Here we use the Variable Infiltration Capacity model with postdisturbance and predisturbance impacts of dust on albedo to estimate the impact on runoff from the UCRB across 1916-2003. We find that peak runoff at Lees Ferry, Arizona has occurred on average 3 wk earlier under heavier dust loading and that increases in evapotranspiration from earlier exposure of vegetation and soils decreases annual runoff by more than 1.0 billion cubic meters or ∼5% of the annual average. The potential to reduce dust loading through surface stabilization in the deserts and restore more persistent snow cover, slow runoff, and increase water resources in the UCRB may represent an important mitigation opportunity to reduce system management tensions and regional impacts of climate change.

  14. A case study of dust aerosol radiative properties over Lanzhou, China

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Cao, X.; Bao, J.; Zhou, B.; Huang, J.; Shi, J.; Bi, J.

    2010-05-01

    The vertical distribution of dust aerosol and its radiative properties are analysed using the data measured by the micropulse lidar, profiling microwave radiometer, sunphotometer, particulate monitor, and nephelometer at the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) during a dust storm from 27 March to 29 March 2007. The analysis shows that the dust aerosol mainly exists below 2 km in height, and the dust aerosol extinction coefficient decreases with height. The temporal evolution of aerosol optical depth (AOD) during the dust storm is characterized by a sub-maximum at 22:00 (Beijing Time), 27 March and a maximum at 12:00, 28 March. The AOD respectively derived by lidar and sunphotometer shows a good consistency. The PM10 concentration and aerosol scattering coefficient share similar variation trends, and their maximums both appear at 22:00, 27 March. The aerosol extinction coefficient and relative humidity have the similar trends and their maximums almost appear at the same heights, which presents a correlation between extinction coefficient and relative humidity known as aerosol hygroscopicity. The relative humidity is related with temperature, and then the temperature will affect the aerosol extinction properties by modifying the relative humidity condition. The aerosol extinction coefficient, scattering coefficient, and PM10 concentration present good linear correlations. The correlation coefficients of the aerosol scattering coefficients of 450, 520, and 700 nm and PM10 concentration, of aerosol extinction coefficient retrieved by lidar at 532 nm and PM10 concentration, and of aerosol extinction and scattering coefficient are respectively 0.98, 0.94, and 0.96.

  15. The Herschel Exploitation of Local Galaxy Andromeda (HELGA). VII. A SKIRT radiative transfer model and insights on dust heating

    NASA Astrophysics Data System (ADS)

    Viaene, S.; Baes, M.; Tamm, A.; Tempel, E.; Bendo, G.; Blommaert, J. A. D. L.; Boquien, M.; Boselli, A.; Camps, P.; Cooray, A.; De Looze, I.; De Vis, P.; Fernández-Ontiveros, J. A.; Fritz, J.; Galametz, M.; Gentile, G.; Madden, S.; Smith, M. W. L.; Spinoglio, L.; Verstocken, S.

    2017-03-01

    The radiation from stars heats dust grains in the diffuse interstellar medium and in star-forming regions in galaxies. Modelling this interaction provides information on dust in galaxies, a vital ingredient for their evolution. It is not straightforward to identify the stellar populations heating the dust, and to link attenuation to emission on a sub-galactic scale. Radiative transfer models are able to simulate this dust-starlight interaction in a realistic, three-dimensional setting. We investigate the dust heating mechanisms on a local and global galactic scale, using the Andromeda galaxy (M 31) as our laboratory. We have performed a series of panchromatic radiative transfer simulations of Andromeda with our code SKIRT. The high inclination angle of M 31 complicates the 3D modelling and causes projection effects. However, the observed morphology and flux density are reproduced fairly well from UV to sub-millimeter wavelengths. Our model reveals a realistic attenuation curve, compatible with previous, observational estimates. We find that the dust in M 31 is mainly (91% of the absorbed luminosity) heated by the evolved stellar populations. The bright bulge produces a strong radiation field and induces non-local heating up to the main star-forming ring at 10 kpc. The relative contribution of unevolved stellar populations to the dust heating varies strongly with wavelength and with galactocentric distance. The dust heating fraction of unevolved stellar populations correlates strongly with NUV-r colour and specific star formation rate. These two related parameters are promising probes for the dust heating sources at a local scale. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  16. POLARIZATION OF MAGNETIC DIPOLE EMISSION AND SPINNING DUST EMISSION FROM MAGNETIC NANOPARTICLES

    SciTech Connect

    Hoang, Thiem; Lazarian, Alex

    2016-04-20

    Magnetic dipole emission (MDE) from interstellar magnetic nanoparticles is potentially an important Galactic foreground in the microwave frequencies, and its polarization level may pose great challenges for achieving reliable measurements of cosmic microwave background B-mode signal. To obtain realistic predictions for the polarization of MDE, we first compute the degree of alignment of big silicate grains incorporated with magnetic inclusions. We find that thermally rotating big grains with magnetic inclusions are weakly aligned and can achieve alignment saturation when the magnetic alignment rate becomes much faster than the rotational damping rate. We then compute the degree of alignment for free-flying magnetic nanoparticles, taking into account various interaction processes of grains with the ambient gas and radiation field, including neutral collisions, ion collisions, and infrared emission. We find that the rotational damping by infrared emission can significantly decrease the degree of alignment of small particles from the saturation level, whereas the excitation by ion collisions can enhance the alignment of ultrasmall particles. Using the computed degrees of alignment, we predict the polarization level of MDE from free-flying magnetic nanoparticles to be rather low. Such a polarization level is within the upper limits measured for anomalous microwave emission (AME), which indicates that MDE from free-flying iron particles may not be ruled out as a source of AME. We also quantify rotational emission from free-flying iron nanoparticles with permanent magnetic moments and find that its emissivity is about one order of magnitude lower than that from spinning polycyclic aromatic hydrocarbons.

  17. INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Properties of the interaction of laser radiation with a gaseous dust medium

    NASA Astrophysics Data System (ADS)

    Glova, A. F.; Lysikov, A. Yu; Zverev, M. M.

    2009-06-01

    It is found that upon irradiation of a mixture of the atmospheric air and carbon particles of size 30-300 μm at a concentration of ~102 cm-3 by a cw CO2 laser, the active combustion of particles in the mixture appears when the radiation intensity in the focal region achieves ~103 W cm-2. The dependences of the threshold radiation intensity for the evaporation of particles on their radius are obtained for a gaseous dust medium in the form of a free vertical jet of spherical aluminium and carbon microparticles in nitrogen. It is shown that particles of size ~10 μm can be completely evaporated in a focused cw laser beam of power ~102 W.

  18. Radiation Fields in Blazars - a Possible Extension of the Small Scale Symbiosis (Disk/Jet) into a Large Scale (Dust/Dust) Symbiosis

    NASA Astrophysics Data System (ADS)

    Donea, Alina-C.; Protheroe, Raymond J.

    In blazar models both protons and electrons may be efficiently accelerated in jets and produce γ-rays. Here we discuss the interactions of these γ-rays with different radiation fields. The external radiation fields within a few parsecs from the black hole involved in such interactions could be the direct radiation from the accretion disk coupled with the jet, the infrared radiation from a dusty torus, and the emission line radiation from the broad line region surrounding the accretion disk. The optical thickness for absorption of γ-ray photons in the external radiation fields is analysed for blazars and quasars. Based on the unification theory of active galactic nuclei we briefly review the evidence for the existence of small scale dust tori in blazars/FR I. We propose that the existing jet-accretion disk symbiosis extrapolates to a large scale symbiosis between other important dusty constituents of the blazar/FR I family.

  19. Direct Radiative Effect of Mineral Dust on the Development of African Easterly Waves in Late Summer, 2003-07

    SciTech Connect

    Ma, Po-Lun; Zhang, Kai; Shi, Jainn Jong; Matsui, Toshihisa; Arking, Albert

    2012-12-19

    Episodic events of both Saharan dust outbreaks and African easterly waves (AEWs) are observed to move westward over the eastern tropical Atlantic Ocean. The relationship between the warm, dry, and dusty Saharan air layer on the nearby storms has been the subject of considerable debate. In this study, the Weather Research and Forecasting model is used to investigate the radiative effect of dust on the development of AEWs during August and September, the months of maximumtropical cyclone activity, in years 2003–07. The simulations show that dust radiative forcing enhances the convective instability of the environment. As a result, mostAEWsintensify in the presence of a dust layer. The Lorenz energy cycle analysis reveals that the dust radiative forcing enhances the condensational heating, which elevates the zonal and eddy available potential energy. In turn, available potential energy is effectively converted to eddy kinetic energy, in which local convective overturning plays the primary role. The magnitude of the intensification effect depends on the initial environmental conditions, including moisture, baroclinity, and the depth of the boundary layer. The authors conclude that dust radiative forcing, albeit small, serves as a catalyst to promote local convection that facilitates AEW development.

  20. Direct Radiative Effect of Mineral Dust on the Development of African Easterly Wave in Late Summer, 2003-2007

    NASA Technical Reports Server (NTRS)

    Ma, Po-Lun; Zhang, Kai; Shi, Jainn Jong; Matsui, Toshihisa; Arking, Albert

    2012-01-01

    Episodic events of both Saharan dust outbreaks and African Easterly Waves (AEWs) are observed to move westward over the eastern tropical Atlantic Ocean. The relationship between the warm, dry, and dusty Saharan Air Layer (SAL) on the nearby storms has been the subject of considerable debate. In this study, the Weather Research and Forecasting (WRF) model is used to investigate the radiative effect of dust on the development of AEWs during August and September, the months of maximum tropical cyclone activity, in years 2003-2007. The simulations show that dust radiative forcing enhances the convective instability of the environment. As a result, most AEWs intensify in the presence of a dust layer. The Lorenz energy cycle analysis reveals that the dust radiative forcing enhances the condensational heating, which elevates the zonal and eddy available potential energy. In turn, available potential energy is effectively converted to eddy kinetic energy, in which local convective overturning plays the primary role. The magnitude of the intensification effect depends on the initial environmental conditions, including moisture, baroclinity, and the depth of the boundary layer. We conclude that dust radiative forcing, albeit small, serves as a catalyst to promote local convection that facilitates AEW development.

  1. Thermal IR radiative properties of mixed mineral dust and biomass aerosol during SAMUM-2

    NASA Astrophysics Data System (ADS)

    Köhler, Claas H.; Trautmann, Thomas; Lindermeir, Erwin; Vreeling, Willem; Lieke, Kirsten; Kandler, Konrad; Weinzierl, Bernadett; Groß, Silke; Tesche, Matthias; Wendisch, Manfred

    2011-09-01

    Ground-based high spectral resolution measurements of downwelling radiances from 800 to 1200 cm-1 were conducted between 20 January and 6 February 2008 within the scope of the SAMUM-2 field experiment. We infer the spectral signature of mixed biomass burning/mineral dust aerosols at the surface from these measurements and at top of the atmosphere from IASI observations. In a case study for a day characterized by the presence of high loads of both dust and biomass we attempt a closure with radiative transfer simulations assuming spherical particles. A detailed sensitivity analysis is performed to investigate the effect of uncertainties in the measurements ingested into the simulation on the simulated radiances. Distinct deviations between modelled and observed radiances are limited to a spectral region characterized by resonance bands in the refractive index. A comparison with results obtained during recent laboratory studies and field experiments reveals, that the deviations could be caused by the aerosol particles' non-sphericity, although an unequivocal discrimination from measurement uncertainties is not possible. Based on radiative transfer simulations we estimate the aerosol's direct radiative effect in the atmospheric window region to be 8 W m-2 at the surface and 1 W m-2 at top of the atmosphere.

  2. GPU-BASED MONTE CARLO DUST RADIATIVE TRANSFER SCHEME APPLIED TO ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Heymann, Frank; Siebenmorgen, Ralf

    2012-05-20

    A three-dimensional parallel Monte Carlo (MC) dust radiative transfer code is presented. To overcome the huge computing-time requirements of MC treatments, the computational power of vectorized hardware is used, utilizing either multi-core computer power or graphics processing units. The approach is a self-consistent way to solve the radiative transfer equation in arbitrary dust configurations. The code calculates the equilibrium temperatures of two populations of large grains and stochastic heated polycyclic aromatic hydrocarbons. Anisotropic scattering is treated applying the Heney-Greenstein phase function. The spectral energy distribution (SED) of the object is derived at low spatial resolution by a photon counting procedure and at high spatial resolution by a vectorized ray tracer. The latter allows computation of high signal-to-noise images of the objects at any frequencies and arbitrary viewing angles. We test the robustness of our approach against other radiative transfer codes. The SED and dust temperatures of one- and two-dimensional benchmarks are reproduced at high precision. The parallelization capability of various MC algorithms is analyzed and included in our treatment. We utilize the Lucy algorithm for the optical thin case where the Poisson noise is high, the iteration-free Bjorkman and Wood method to reduce the calculation time, and the Fleck and Canfield diffusion approximation for extreme optical thick cells. The code is applied to model the appearance of active galactic nuclei (AGNs) at optical and infrared wavelengths. The AGN torus is clumpy and includes fluffy composite grains of various sizes made up of silicates and carbon. The dependence of the SED on the number of clumps in the torus and the viewing angle is studied. The appearance of the 10 {mu}m silicate features in absorption or emission is discussed. The SED of the radio-loud quasar 3C 249.1 is fit by the AGN model and a cirrus component to account for the far-infrared emission.

  3. [Evaluation of working environment in the textile industry. IV. Dust concentration in the air of the flax spinning and weaving plants].

    PubMed

    Gościcki, J; Wiecek, E; Matecki, W; Bielichowska, G

    1980-01-01

    Evaluation of dust concentration in the air of spinning and weaving rooms was made by gravimetric sampling of dust in 3 flax plants, where short flax fibres (flax--tow) and long flax fibres were manufactured. Besides, the dispersion of dusts and concentration of free silica were determined. The highest concentration of dust (10 mg/m3) was found in hackling room, mixing mill, and the one where spreading machines are operated, while in the carding room it was - 7.0 mg/m3. In other shops the concentration was - 5.5 mg/m3. The dust in the air of spinning rooms contained 2.3% of free silica and 53% of its particles were smaller than 5 micrometers. In the weaving rooms it contained 1.6% of free silica and 57% particles were smaller than 5 micrometers. The geometric mean of dust concentration higher than MAC for vegetable dusts (4 mg/m3) was found in hackling mill, mixing mill and the one where spreading machines are operated.

  4. Heating rate profiles and radiative forcing due to a dust storm in the Western Mediterranean using satellite observations

    NASA Astrophysics Data System (ADS)

    Peris-Ferrús, C.; Gómez-Amo, J. L.; Marcos, C.; Freile-Aranda, M. D.; Utrillas, M. P.; Martínez-Lozano, J. A.

    2017-07-01

    We analyze the vertically-resolved radiative impact due to a dust storm in the Western Mediterranean. The dust plume travels around 3-5 km altitude and the aerosol optical depth derived by MODIS at 550 nm ranges from 0.33 to 0.52 at the overpass time (13:05 UT). The aerosol radiative forcing (ARF), forcing efficiency (FE) and heating rate profile (AHR) are determined throughout the dust trajectory in shortwave (SW) and longwave (LW) ranges. To do this, we integrate different satellite observations (CALIPSO and MODIS) and detailed radiative transfer modeling. The combined (SW + LW) effect of the dust event induces a net cooling in the studied region. On average, the FE at 22.4° solar zenith angle is -190.3 W m-2 and -38.1 W m-2, at surface and TOA, respectively. The corresponding LW/SW offset is 14% and 38% at surface and TOA, respectively. Our results at TOA are sensitive to the surface albedo in the SW and surface temperature in the LW. The absolute value of FE decrease (increase) in the SW (LW) with the surface albedo, resulting in an increasing LW/SW offset, up to 76%. The AHR profiles show a net warming within the dust layer, with a maximum value of 3.3 Kd-1. The ARF, FE and AHR are also highly sensitive to the dust optical properties in SW and LW. We evaluate this sensitivity by comparing the results obtained using two set of dust properties as input in our simulations: a) the prescribed dust model by Optical Properties of Aerosols and Clouds (OPAC) and; b) the dust optical properties derived from measurements of the size distribution and refractive index. Experimentally derived dust properties present larger SSA and asymmetry parameter in the SW than OPAC dust. Conversely, OPAC dust presents higher AOD in the LW range. These parameters drive the FE and AHR sensitivities in the SW and LW ranges, respectively. Therefore, when measured dust properties are used in our simulations: the ARF in the LW substantially reduces at surface and TOA (up to 57%); the

  5. Light Absorbing Impurities in Snow in the Western US: Partitioning Radiative Impacts from Mineral Dust and Black Carbon

    NASA Astrophysics Data System (ADS)

    Skiles, M.; Painter, T. H.

    2013-12-01

    Melt of annual mountain snow cover dominates water resources in the western United States. Recent studies in the Upper Colorado River Basin have shown that radiative forcing by light absorbing impurities (LAIs) in mountain snow cover has accelerated snowmelt, impacted runoff timing and magnitude, and reduced annual flow. However, these studies have assumed that LAIs are primarily mineral dust, and have not quantified the radiative contribution by carbonaceous particles from bio and fossil fuel (industrial and urban) sources. Here we quantify both dust and black carbon (BC) content and assess the unique BC radiative forcing contribution in this dust dominated impurity regime using a suite of advanced field, lab, and modeling techniques. Daily measurements of surface spectral albedo and optical grain radius were collected with a field spectrometer over the 2013 spring melt season in Senator Beck Basin Study Area in the San Juan Mountains, CO, Southwestern US. Coincident snow samples were collected daily and processed for; (1) dust and BC content (2) impurity particle size, and (3) impurity optical properties. Measured snow and impurity properties were then used to drive the Snow, Ice, and Aerosol Radiation (SNICAR) model. Partitioning the unique radiative contribution from each constituents is achieved through unique model runs for clean snow, dust only, and BC only.

  6. Laboratory Experiments on Rotation and Alignment of the Analogs of Interstellar Dust Grains by Radiation

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Craven, P. D.; Spann, J. F.; Tankosic, D.; LeClair, A.; Gallagher, D. L.; West, E. A.; Weingartner, J. C.; Witherow, W. K.; Tielens, A. G. G. M.

    2004-01-01

    The processes and mechanisms involved in the rotation and alignment of interstellar dust grains have been of great interest in astrophysics ever since the surprising discovery of the polarization of starlight more than half a century ago. Numerous theories, detailed mathematical models and numerical studies of grain rotation and alignment with respect to the Galactic magnetic field have been presented in the literature. In particular, the subject of grain rotation and alignment by radiative torques has been shown to be of particular interest in recent years. However, despite many investigations, a satisfactory theoretical understanding of the processes involved in grain rotation and alignment has not been achieved. As there appears to be no experimental data available on this subject, we have carried out some unique experiments to illuminate the processes involved in rotation of dust grains in the interstellar medium. In this paper we present the results of some preliminary laboratory experiments on the rotation of individual micron/submicron size nonspherical dust grains levitated in an electrodynamic balance evacuated to pressures of approximately 10(exp -3) to 10(exp -5) torr. The particles are illuminated by laser light at 5320 Angstroms, and the grain rotation rates are obtained by analyzing the low frequency (approximately 0-100 kHz) signal of the scattered light detected by a photodiode detector. The rotation rates are compared with simple theoretical models to retrieve some basic rotational parameters. The results are examined in the light of the current theories of alignment.

  7. Laboratory Experiments on Rotation and Alignment of the Analogs of Interstellar Dust Grains by Radiation

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Craven, P. D.; Spann, J. F.; Tankosic, D.; LeClair, A.; Gallagher, D. L.; West, E. A.; Weingartner, J. C.; Witherow, W. K.; Tielens, A. G. G. M.

    2004-01-01

    The processes and mechanisms involved in the rotation and alignment of interstellar dust grains have been of great interest in astrophysics ever since the surprising discovery of the polarization of starlight more than half a century ago. Numerous theories, detailed mathematical models, and numerical studies of grain rotation and alignment with respect to the Galactic magnetic field have been presented in the literature. In particular, the subject of grain rotation and alignment by radiative torques has been shown to be of particular interest in recent years. However, despite many investigations, a satisfactory theoretical understanding of the processes involved in subject, we have carried out some unique experiments to illuminate the processes involved in the rotation of dust grains in the interstellar medium. In this paper we present the results of some preliminary laboratory experiments on the rotation of individual micron/submicron-sized, nonspherical dust grains levitated in an electrodynamic balance evacuated to pressures of approximately 10(exp -3) to 10(exp -5) torr. The particles are illuminated by laser light at 5320 A, and the grain rotation rates are obtained by analyzing the low-frequency (approximately 0 - 100 kHz) signal of the scattered light detected by a photodiode detector. The rotation rates are compared with simple theoretical models to retrieve some basic rotational parameters. The results are examined in light of the current theories of alignment.

  8. Laboratory Experiments on Rotation of Micron Size Cosmic Dust Grains with Radiation

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Craven, P. D.; Spann, J. F.; Tankosic, D.; LeClair, A.; Gallagher, D. L.; West, E.; Weingartner, J.; Witherow, W. K.

    2004-01-01

    The processes and mechanisms involved in the rotation and alignment of interstellar dust grains have been of great interest in astrophysics ever since the surprising discovery of the polarization of starlight more than half a century ago. Numerous theories, detailed mathematical models and numerical studies of grain rotation and alignment along the Galactic magnetic field have been presented in the literature. In particular, the subject of grain rotation and alignment by radiative torques has been shown to be of particular interest in recent years. However, despite many investigations, a satisfactory theoretical understanding of the processes involved in grain rotation and alignment has not been achieved. As there appears to be no experimental data available on this subject, we have carried out some unique experiments to illuminate the processes involved in rotation of dust grains in the interstellar medium. In this paper we present the results of some preliminary laboratory experiments on the rotation of individual micron/submicron size nonspherical dust grains levitated in an electrodynamic balance evacuated to pressures of approx. 10(exp -3) to 10(exp -5) torr. The particles are illuminated by laser light at 5320 A, and the grain rotation rates are obtained by analyzing the low frequency (approx. 0-100 kHz) signal of the scattered light detected by a photodiode detector. The rotation rates are compared with simple theoretical models to retrieve some basic rotational parameters. The results are examined in the light of the current theories of alignment.

  9. Laboratory Experiments on Rotation of Micron Size Cosmic Dust Grains with Radiation

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Craven, P. D.; Spann, J. F.; Tankosic, D.; LeClair, A.; Gallagher, D. L.; West, E.; Weingartner, J.; Witherow, W. K.

    2004-01-01

    The processes and mechanisms involved in the rotation and alignment of interstellar dust grains have been of great interest in astrophysics ever since the surprising discovery of the polarization of starlight more than half a century ago. Numerous theories, detailed mathematical models and numerical studies of grain rotation and alignment along the Galactic magnetic field have been presented in the literature. In particular, the subject of grain rotation and alignment by radiative torques has been shown to be of particular interest in recent years. However, despite many investigations, a satisfactory theoretical understanding of the processes involved in grain rotation and alignment has not been achieved. As there appears to be no experimental data available on this subject, we have carried out some unique experiments to illuminate the processes involved in rotation of dust grains in the interstellar medium. In this paper we present the results of some preliminary laboratory experiments on the rotation of individual micron/submicron size nonspherical dust grains levitated in an electrodynamic balance evacuated to pressures of approx. 10(exp -3) to 10(exp -5) torr. The particles are illuminated by laser light at 5320 A, and the grain rotation rates are obtained by analyzing the low frequency (approx. 0-100 kHz) signal of the scattered light detected by a photodiode detector. The rotation rates are compared with simple theoretical models to retrieve some basic rotational parameters. The results are examined in the light of the current theories of alignment.

  10. Laboratory Experiments on Rotation and Alignment of the Analogs of Interstellar Dust Grains by Radiation

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Craven, P. D.; Spann, J. F.; Tankosic, D.; LeClair, A.; Gallagher, D. L.; West, E. A.; Weingartner, J. C.; Witherow, W. K.; Tielens, A. G. G. M.

    2004-01-01

    The processes and mechanisms involved in the rotation and alignment of interstellar dust grains have been of great interest in astrophysics ever since the surprising discovery of the polarization of starlight more than half a century ago. Numerous theories, detailed mathematical models and numerical studies of grain rotation and alignment with respect to the Galactic magnetic field have been presented in the literature. In particular, the subject of grain rotation and alignment by radiative torques has been shown to be of particular interest in recent years. However, despite many investigations, a satisfactory theoretical understanding of the processes involved in grain rotation and alignment has not been achieved. As there appears to be no experimental data available on this subject, we have carried out some unique experiments to illuminate the processes involved in rotation of dust grains in the interstellar medium. In this paper we present the results of some preliminary laboratory experiments on the rotation of individual micron/submicron size nonspherical dust grains levitated in an electrodynamic balance evacuated to pressures of approximately 10(exp -3) to 10(exp -5) torr. The particles are illuminated by laser light at 5320 Angstroms, and the grain rotation rates are obtained by analyzing the low frequency (approximately 0-100 kHz) signal of the scattered light detected by a photodiode detector. The rotation rates are compared with simple theoretical models to retrieve some basic rotational parameters. The results are examined in the light of the current theories of alignment.

  11. Laboratory Experiments on Rotation and Alignment of the Analogs of Interstellar Dust Grains by Radiation

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Craven, P. D.; Spann, J. F.; Tankosic, D.; LeClair, A.; Gallagher, D. L.; West, E. A.; Weingartner, J. C.; Witherow, W. K.; Tielens, A. G. G. M.

    2004-01-01

    The processes and mechanisms involved in the rotation and alignment of interstellar dust grains have been of great interest in astrophysics ever since the surprising discovery of the polarization of starlight more than half a century ago. Numerous theories, detailed mathematical models, and numerical studies of grain rotation and alignment with respect to the Galactic magnetic field have been presented in the literature. In particular, the subject of grain rotation and alignment by radiative torques has been shown to be of particular interest in recent years. However, despite many investigations, a satisfactory theoretical understanding of the processes involved in subject, we have carried out some unique experiments to illuminate the processes involved in the rotation of dust grains in the interstellar medium. In this paper we present the results of some preliminary laboratory experiments on the rotation of individual micron/submicron-sized, nonspherical dust grains levitated in an electrodynamic balance evacuated to pressures of approximately 10(exp -3) to 10(exp -5) torr. The particles are illuminated by laser light at 5320 A, and the grain rotation rates are obtained by analyzing the low-frequency (approximately 0 - 100 kHz) signal of the scattered light detected by a photodiode detector. The rotation rates are compared with simple theoretical models to retrieve some basic rotational parameters. The results are examined in light of the current theories of alignment.

  12. Response of the water cycle of West Africa and Atlantic to radiative forcing by Saharan dust (Invited)

    NASA Astrophysics Data System (ADS)

    Lau, W. K.; Kim, K.

    2010-12-01

    The responses of the atmospheric water cycle and climate of West Africa and the Atlantic toradiative forcing of Saharan dust are studied using the NASA finite volume general circulation model (fvGCM), coupled to a mixed layer ocean. We find evidence in support of the “elevated heat pump” (EHP) mechanism that underlines the responses of the atmospheric water cycle to dust forcing as follow. During the boreal summer, as a result of large-scale atmospheric feedback triggered by absorbing dust aerosols, rainfall and cloudiness are enhanced over the West Africa/Eastern Atlantic ITCZ, and suppressed over the West Atlantic and Caribbean region. Shortwave radiation absorption by dust warms the atmosphere and cools the surface, while longwave has the opposite response. The elevated dust layer warms the air over West Africa and the eastern Atlantic. As the warm air rises, it spawns a large-scale onshore flow carrying the moist air from the eastern Atlantic and the Gulf of Guinea. The onshore flow in turn enhances the deep convection over West Africa land, and the eastern Atlantic. The condensation heating associated with the induced deep convection drives and maintains an anomalous large-scale east-west overturning circulation with rising motion over West Africa/eastern Atlantic, and sinking motion over the Caribbean region. The response also includes a strengthening of the West African monsoon, manifested in a northward shift of the West Africa precipitation over land, increased low-level westerlies flow over West Africa at the southern edge of the dust layer, and a near surface westerly jet underneath the dust layer over the Sahara. The dust radiative forcing also leads to significant changes in surface energy fluxes, resulting in cooling of the West African land and the eastern Atlantic, and warming in the West Atlantic and Caribbean. The EHP effect is most effective for moderate to highly absorbing dusts, and becomes minimized for reflecting dust with single

  13. The contrasting roles of water and dust in controlling daily variations in radiative heating of the summertime Saharan heat low

    NASA Astrophysics Data System (ADS)

    Marsham, John H.; Parker, Douglas J.; Todd, Martin C.; Banks, Jamie R.; Brindley, Helen E.; Garcia-Carreras, Luis; Roberts, Alexander J.; Ryder, Claire L.

    2016-03-01

    The summertime Sahara heat low (SHL) is a key component of the West African monsoon (WAM) system. Considerable uncertainty remains over the relative roles of water vapour and dust aerosols in controlling the radiation budget over the Sahara and therefore our ability to explain variability and trends in the SHL, and in turn, the WAM. Here, new observations from Fennec supersite-1 in the central Sahara during June 2011 and June 2012, together with satellite retrievals from GERB, are used to quantify how total column water vapour (TCWV) and dust aerosols (from aerosol optical depth, AOD) control day-to-day variations in energy balance in both observations and ECWMF reanalyses (ERA-I). The data show that the earth-atmosphere system is radiatively heated in June 2011 and 2012. Although the empirical analysis of observational data cannot completely disentangle the roles of water vapour, clouds and dust, the analysis demonstrates that TCWV provides a far stronger control on TOA net radiation, and so the net heating of the earth-atmosphere system, than AOD does. In contrast, variations in dust provide a much stronger control on surface heating, but the decreased surface heating associated with dust is largely compensated by increased atmospheric heating, and so dust control on net TOA radiation is weak. Dust and TCWV are both important for direct atmospheric heating. ERA-I, which assimilated radiosondes from the Fennec campaign, captures the control of TOA net flux by TCWV, with a positive correlation (r = 0.6) between observed and modelled TOA net radiation, despite the use of a monthly dust climatology in ERA-I that cannot capture the daily variations in dustiness. Variations in surface net radiation, and so the vertical profile of radiative heating, are not captured in ERA-I, since it does not capture variations in dust. Results show that ventilation of the SHL by cool moist air leads to a radiative warming, stabilising the SHL with respect to such perturbations. It is

  14. Properties of a local dust storm on Mars' Atlantis Chaos by means of radiative transfer modeling.

    NASA Astrophysics Data System (ADS)

    Oliva, Fabrizio; Altieri, Francesca; Geminale, Anna; Bellucci, Giancarlo; D'Aversa, Emiliano; Carrozzo, Giacomo; Sindoni, Giuseppe; Grassi, Davide

    2017-04-01

    In this study we present the analysis of the dust properties in a local storm imaged in the Atlantis Chaos region on Mars by the OMEGA spectrometer (Bibring et al., 2004) on March 2nd 2005 (ORB1441_5). By means of an inverse radiative transfer code we study the dust properties across the region and try to infer the connection be-tween the local storm dynamics and the orography. OMEGA is a visible and near-IR mapping spectrometer, operating in the spectral range 0.38-5.1 μm with three separate channels with different spectral resolution. The instrument's IFOV is 1.2 mrad. To analyze the storm properties we have used the inverse radiative transfer model MITRA (Oliva et al., 2016; Sindoni et al., 2013) to retrieve the effective radius reff, the optical depth at 880 nm τ880 and the top pressure tp of the dust layer. We used the Mars Climate Database (MCD, Forget et al., 1999) to obtain the atmospheric properties of the studied region to be used as input in our model. Moreover we used the optical constants from Wolff et al. (2009) to describe the dust composition. The properties from the surface have been obtained by ap-plying the SAS method (Geminale et al., 2015) to observations of the same region relatively clear from dust. All retrievals have been performed in the spectral range 500 ÷ 2500 nm. Here we describe the result from our analysis carried out on selected regions of the storm and characterized by a different optical depth of the dust. Aknowledgements: This study has been performed within the UPWARDS project and funded in the context of the European Union's Horizon 2020 Programme (H2020-Compet-08-2014), grant agreement UPWARDS-633127. References: Bibring, J-P. et al., 2004. OMEGA: Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité. Mars Express: the scientific payload, Ed. by Andrew Wilson, scientific coordination: Agustin Chicarro. ESA SP-1240, Noordwijk, Netherlands: ESA Publications Division, ISBN 92-9092-556-6, 2004, p. 37 - 49. Forget

  15. Bioprocess of Kosa bioaerosols: effect of ultraviolet radiation on airborne bacteria within Kosa (Asian dust).

    PubMed

    Kobayashi, Fumihisa; Maki, Teruya; Kakikawa, Makiko; Yamada, Maromu; Puspitasari, Findya; Iwasaka, Yasunobu

    2015-05-01

    Kosa (Asian dust) is a well-known weather phenomenon in which aerosols are carried by the westerly winds from inland China to East Asia. Recently, the frequency of this phenomenon and the extent of damage caused have been increasing. The airborne bacteria within Kosa are called Kosa bioaerosols. Kosa bioaerosols have affected ecosystems, human health and agricultural productivity in downwind areas. In order to develop a new and useful bacterial source and to identify the source region of Kosa bioaerosols, sampling, isolation, identification, measurement of ultraviolet (UV) radiation tolerance and experimental simulation of UV radiation conditions were performed during Kosa bioaerosol transportation. We sampled these bioaerosols using a Cessna 404 airplane and a bioaerosol sampler at an altitude of approximately 2900 m over the Noto Peninsula on March 27, 2010. The bioaerosol particles were isolated and identified as Bacillus sp. BASZHR 1001. The results of the UV irradiation experiment showed that the UV radiation tolerance of Kosa bioaerosol bacteria was very high compared with that of a soil bacterium. Moreover, the UV radiation tolerance of Kosa bioaerosol spores was higher than that of soil bacterial spores. This suggested that Kosa bioaerosols are transported across the atmosphere as living spores. Similarly, by the experimental simulation of UV radiation conditions, the limited source region of this Kosa bioaerosol was found to be southern Russia and there was a possibility of transport from the Kosa source area.

  16. Electronic and spin structures of solids investigated by means of synchrotron radiation photoemission

    NASA Astrophysics Data System (ADS)

    Taniguchi, M.; Iwasawa, H.; Miyamoto, K.; Okuda, T.

    2013-12-01

    Recent progress in research on electronic and spin structures of solids and instrumentation on spin-resolved photoemission at Hiroshima Synchrotron Radiation Center are reported. The fine details of electron dynamics of a typical multiband superconductor Sr2RuO4 were uncovered by high-resolution angle-resolved photoemission spectroscopy (ARPES) with tunable polarizations, and the surface of W(1 1 0) was found to have a Dirac-corn-like state of d character with nearly massless energy dispersion by high-resolution ARPES and spin-resolved ARPES (SARPES). The SARPES system with very low energy electron diffraction spin detector and modified VG-SCIENTA R4000 electron analyzer brought a breakthrough in spin detection efficiency as well as energy and angular resolution, and enables precise SARPES measurements for materials that require high energy and angular resolution.

  17. Translational anisotropy in the cosmic microwave background radiation and far-infrared emission by galactic dust clouds

    NASA Technical Reports Server (NTRS)

    Forman, M. A.

    1977-01-01

    The predicted emission spectrum of galactic dust at about 10 K is compared with the spectrum of 2.8-K universal blackbody radiation and with the spectrum of the anisotropy expected in the 2.8-K radiation due to motion of earth with respect to the coordinate system in which the radiation was last scattered. The extremely anisotropic galactic-dust emission spectrum may contribute a significant background to anisotropy measurements which scan through the galactic plane. The contamination would appear in an 8-mm scan around the celestial equator, for example, as a spurious 200 km/s velocity toward declination 0 deg, right ascension 19 hr, if predictions are correct. The predicted spectrum of dust emission in the galactic plane at longitudes not exceeding about 30 deg falls below the total 2.8-K cosmic background intensity at wavelengths of at least 1 mm.

  18. Comparison of Radiative Forcing Calculations Due to Mineral Dust from a Transport Model, Satellite Measurements and an Assimilation System

    NASA Technical Reports Server (NTRS)

    Weaver, Clark J.; Ginoux, Paul; Hsu, Christina; Joiner, Joanna; Chou, Ming-Dah

    1999-01-01

    This study uses information on mineral aerosol from a transport model to calculate global radiative forcing values. The transport model is driven by assimilated meteorology and outputs three-dimensional dust spatial information for various size ranges. The dust fields are input to an off-line radiative transfer calculation to obtain the direct radiative forcing due to the dust fields. During June, July and August of 1988 presence of dust 1) reduces the global net incoming radiation at the top of atmosphere (TOA) by 0.3 to 0.7 W/sq m and 2) reduces net incoming radiation at the earth's surface by 1.3 to 2.0 W/sq m. Over Africa our estimates of the reduction of radiation at the top of atmosphere compare well with TOA reductions derived from ERBE and TOMS satellite data. However, our heating rates are not consistent with analysis temperature increments produced by the assimilation system over regions of high aerosol loading. These increments are based on differences between temperature observations and temperatures from the assimilation general circulation model. One explanation is that the lower tropospheric temperatures retrieved by TOVS are being contaminated by mineral aerosol.

  19. An Assessment of the Surface Longwave Direct Radiative Effect of Airborne Saharan Dust During the NAMMA Field Campaign

    NASA Technical Reports Server (NTRS)

    Hansell, R. A.; Tsay, S. C.; Ji, Q.; Hsu, N. C.; Jeong, M. J.; Wang, S. H.; Reid, J. S.; Liou, K. N.; Ou, S. C.

    2010-01-01

    In September 2006, NASA Goddard s mobile ground-based laboratories were deployed to Sal Island in Cape Verde (16.73degN, 22.93degW) to support the NASA African Monsoon Multidisciplinary Analysis (NAMMA) field study. The Atmospheric Emitted Radiance Interferometer (AERI), a key instrument for spectrally characterizing the thermal IR, was used to retrieve the dust IR aerosol optical depths (AOTs) in order to examine the diurnal variability of airborne dust with emphasis on three separate dust events. AERI retrievals of dust AOT are compared with those from the coincident/collocated multifilter rotating shadow-band radiometer (MFRSR), micropulse lidar (MPL), and NASA Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) sensors. The retrieved AOTs are then inputted into the Fu-Liou 1D radiative transfer model to evaluate local instantaneous direct longwave radiative effects (DRE(sub LW)) of dust at the surface in cloud-free atmospheres and its sensitivity to dust microphysical parameters. The top-of-atmosphere DRE(sub LW) and longwave heating rate profiles are also evaluated. Instantaneous surface DRE(sub LW) ranges from 2 to 10 W/sq m and exhibits a strong linear dependence with dust AOT yielding a DRE(sub LW) of 16 W/sq m per unit dust AOT. The DRE(sub LW) is estimated to be approx.42% of the diurnally averaged direct shortwave radiative effect at the surface but of opposite sign, partly compensating for the shortwave losses. Certainly nonnegligible, the authors conclude that DRE(sub LW) can significantly impact the atmospheric energetics, representing an important component in the study of regional climate variation.

  20. Alteration of Organic Compounds in Small Bodies and Cosmic Dusts by Cosmic Rays and Solar Radiation

    NASA Astrophysics Data System (ADS)

    Kobayashi, Kensei; Kaneko, Takeo; Mita, Hajime; Obayashi, Yumiko; Takahashi, Jun-ichi; Sarker, Palash K.; Kawamoto, Yukinori; Okabe, Takuto; Eto, Midori; Kanda, Kazuhiro

    2012-07-01

    A wide variety of complex organic compounds have been detected in extraterrestrial bodies like carbonaceous chondrites and comets, and their roles in the generation of terrestrial life are discussed. It was suggested that organics in small bodies were originally formed in ice mantles of interstellar dusts in dense cloud. Irradiation of frozen mixture of possible interstellar molecules including CO (or CH _{3}OH), NH _{3} and H _{2}O with high-energy particles gave complex amino acid precursors with high molecular weights [1]. Such complex organic molecules were taken in planetesimals or comets in the early solar system. In prior to the generation of the terrestrial life, extraterrestrial organics were delivered to the primitive Earth by such small bodies as meteorites, comets and space dusts. These organics would have been altered by cosmic rays and solar radiation (UV, X-rays) before the delivery to the Earth. We examined possible alteration of amino acids, their precursors and nucleic acid bases in interplanetary space by irradiation with high energy photons and heavy ions. A mixture of CO, NH _{3} and H _{2}O was irradiated with high-energy protons from a van de Graaff accelerator (TIT, Japan). The resulting products (hereafter referred to as CAW) are complex precursors of amino acids. CAW, amino acids (dl-Isovaline, glycine), hydantoins (amino acid precursors) and nucleic acid bases were irradiated with continuous emission (soft X-rays to IR; hereafter referred to as soft X-rays irradiation) from BL-6 of NewSUBARU synchrotron radiation facility (Univ. Hyogo). They were also irradiated with heavy ions (eg., 290 MeV/u C ^{6+}) from HIMAC accelerator (NIRS, Japan). After soft X-rays irradiation, water insoluble materials were formed. After irradiation with soft X-rays or heavy ions, amino acid precursors (CAW and hydantoins) gave higher ratio of amino acids were recovered after hydrolysis than free amino acids. Nucleic acid bases showed higher stability than free

  1. Aerosol radiative forcing over the Indo-Gangetic plains during major dust storms

    NASA Astrophysics Data System (ADS)

    Prasad, Anup K.; Singh, Sachchidanand; Chauhan, S. S.; Srivastava, Manoj K.; Singh, Ramesh P.; Singh, Risal

    Indo-Gangetic (IG) alluvial plains, one of the largest river basins in the world, suffers from the long range transport of mineral dust from the western arid and desert regions of Africa, Arabia and Rajasthan during the summer (pre-monsoon season, April-June). These dust storms influence the aerosol optical depth (AOD) across the IG plains. The Kanpur AERONET (Aerosol Robotic Network) station and Moderate Resolution Imaging Spectro-radiometer (MODIS) data show pronounced effect on the aerosol optical properties and aerosol size distribution during major dust storm events over the IG plains that have significant effect on the aerosol radiative forcing (ARF). The multi-band AOD, from AERONET and MODIS, show contrasting changes in wavelength dependency over dust affected regions. A time collocated (±30 min) validation of AERONET AOD with MODIS Terra (level 2 swath product) over Kanpur, at a common wavelength of 550 nm for the period 2001-2005 show moderate correlation ( R2˜0.6) during the summer season. The average surface forcing is found to change by -23 W m -2 during dust events and the top of the atmosphere (TOA) forcing change by -11 W m -2 as compared to the non-dusty clear-sky days. A strong correlation is found between AOD at 500 nm and the ARF. At surface, the correlation coefficient between AOD and ARF is found to be high ( R2=0.925) and is found to be moderate ( R2=0.628) at the TOA. The slope of the regression line gives the aerosol forcing efficiency at 500 nm of about -46±2.6 W m -2 and -17±2.5 W m -2 at the surface and the TOA, respectively. The ARF is found to increase with the advance of the dry season in conjunction with the gradual rise in AOD (at 500 nm) from April (0.4-0.5) to June (0.6-0.7) over the IG plains.

  2. Evidence for dust-driven, radial plasma transport in Saturn's inner radiation belts

    NASA Astrophysics Data System (ADS)

    Roussos, E.; Krupp, N.; Kollmann, P.; Paranicas, C.; Mitchell, D. G.; Krimigis, S. M.; Andriopoulou, M.

    2016-08-01

    A survey of Cassini MIMI/LEMMS data acquired between 2004 and 2015 has led to the identification of 13 energetic electron microsignatures that can be attributed to particle losses on one of the several faint rings of the planet. Most of the signatures were detected near L-shells that map between the orbits of Mimas and Enceladus or near the G-ring. Our analysis indicates that it is very unlikely for these signatures to have originated from absorption on Mimas, Enceladus or unidentified Moons and rings, even though most were not found exactly at the L-shells of the known rings of the saturnian system (G-ring, Methone, Anthe, Pallene). The lack of additional absorbers is apparent in the L-shell distribution of MeV ions which are very sensitive for tracing the location of weakly absorbing material permanently present in Saturn's radiation belts. This sensitivity is demonstrated by the identification, for the first time, of the proton absorption signatures from the asteroid-sized Moons Pallene, Anthe and/or their rings. For this reason, we investigate the possibility that the 13 energetic electron events formed at known saturnian rings and the resulting depletions were later displaced radially by one or more magnetospheric processes. Our calculations indicate that the displacement magnitude for several of those signatures is much larger than the one that can be attributed to radial flows imposed by the recently discovered noon-to-midnight electric field in Saturn's inner magnetosphere. This observation is consistent with a mechanism where radial plasma velocities are enhanced near dusty obstacles. Several possibilities are discussed that may explain this observation, including a dust-driven magnetospheric interchange instability, mass loading by the pick-up of nanometer charged dust grains and global magnetospheric electric fields induced by perturbed orbits of charged dust due to the act of solar radiation pressure. Indirect evidence for a global scale interaction

  3. Measuring the momentum distribution of the unpaired spin electrons in ferromagnets using synchrotron radiation

    SciTech Connect

    Mills, D.M.

    1988-12-01

    The dominant term in the x-ray Compton cross-section of an electron is the interaction of the photon and the electron's charge. Platzman and Tsoar many years ago pointed out that there is also an interaction between an x-ray and the electron's spin and in principle this interaction can give information on the momentum distribution of the unpaired spin electrons in the solid. Unfortunately, the spin sensitive term is not only small compared to the charge term, but in addition couples to the photons in first order only with that components of the x-ray beam that is circularly polarized. A lack of intense sources of circularly polarized x-rays combined with the relative small size of the spin sensitive term makes measurements of the momentum distributions of unpaired spin electrons difficult, resulting in little experiment progress initially made in spin or magnetic Compton scattering. In the past several years, interest in spin sensitive Compton scattering has been revived due in large part to the availability of intense beams of high energy photons from synchrotron radiation sources. The radiation from storage ring sources has well defined polarization states; highly linearly polarized in the orbital plane and elliptically polarized above and below the plane of the orbit of the circulating particles. The high flux and unique polarization properties of synchrotron radiation sources have greatly facilitated measurements of the momentum distributions of the unpaired spin electrons in ferromagnetic solids. Recent results of the work of several groups will be presented, along with some thoughts on the impact that the next generation of storage rings, such as the Advanced Photon Source, and insertion devices specifically designed to produce circularly polarized x-ray beams will have on the field of magnetic Compton scattering. 21 refs., 6 figs.

  4. Design for CubeSat-based dust and radiation studies at Europa

    NASA Astrophysics Data System (ADS)

    Goel, Ashish; Krishnamoorthy, Siddharth; Swenson, Travis; West, Stephen; Li, Alan; Crew, Alexander; Phillips, Derek James; Screve, Antoine; Close, Sigrid

    2017-07-01

    Europa is one of the icy moons of Jupiter and the possibility of an ocean of liquid water beneath its icy crust makes it one of the most fascinating destinations for exploration in the solar system. NASA's Europa Multiple Flyby Mission (EMFM, formerly Europa Clipper) is slated to visit the icy moon in a timeframe near the year 2022 to study the habitability of Europa. CubeSats carried along by the primary mission can supplement the measurements made, at a relatively low cost, and with the added benefits of involving students at universities in this challenging endeavor. Further, such a mission holds the key to extending the applicability of CubeSats to interplanetary missions. In this paper, we present the design of the Europa Radiation and Dust Observation Satellite (ERDOS), a 3U CubeSat designed to be deployed by the Europa Multiple Flyby Mission to carry out measurements of the radiation and dust environment, before impacting Europa's surface. We present a detailed design for a CubeSat-based secondary mission, and discuss the science goals that may be accomplished by such a mission. Further, we discuss results from a comprehensive analysis of various engineering challenges associated with an interplanetary CubeSat mission, such as radiation shielding and thermal environment control. Our results show that a short duration CubeSat-based flyby mission is feasible when the CubeSat is carried on board the primary mission until the Jovian system is reached. Such a flyby mission can provide important supplementary information to the primary mission about Europa's environment at a closer range and lead to a substantial increase in scientific knowledge about surface processes on Europa.

  5. Modeling dust as component minerals in the Community Atmosphere Model: development of framework and impact on radiative forcing

    DOE PAGES

    Scanza, Rachel; Mahowald, N.; Ghan, Steven J.; ...

    2015-01-01

    The mineralogy of desert dust is important due to its effect on radiation, clouds and biogeochemical cycling of trace nutrients. This study presents the simulation of dust radiative forcing as a function of both mineral composition and size at the global scale, using mineral soil maps for estimating emissions. Externally mixed mineral aerosols in the bulk aerosol module in the Community Atmosphere Model version 4 (CAM4) and internally mixed mineral aerosols in the modal aerosol module in the Community Atmosphere Model version 5.1 (CAM5) embedded in the Community Earth System Model version 1.0.5 (CESM) are speciated into common mineral componentsmore » in place of total dust. The simulations with mineralogy are compared to available observations of mineral atmospheric distribution and deposition along with observations of clear-sky radiative forcing efficiency. Based on these simulations, we estimate the all-sky direct radiative forcing at the top of the atmosphere as + 0.05 Wm⁻² for both CAM4 and CAM5 simulations with mineralogy. We compare this to the radiative forcing from simulations of dust in release versions of CAM4 and CAM5 (+0.08 and +0.17 Wm⁻²) and of dust with optimized optical properties, wet scavenging and particle size distribution in CAM4 and CAM5, -0.05 and -0.17 Wm⁻², respectively. The ability to correctly include the mineralogy of dust in climate models is hindered by its spatial and temporal variability as well as insufficient global in situ observations, incomplete and uncertain source mineralogies and the uncertainties associated with data retrieved from remote sensing methods.« less

  6. On realistic size equivalence and shape of spheroidal Saharan mineral dust particles applied in solar and thermal radiative transfer calculations

    NASA Astrophysics Data System (ADS)

    Otto, S.; Trautmann, T.; Wendisch, M.

    2011-05-01

    Realistic size equivalence and shape of Saharan mineral dust particles are derived from in-situ particle, lidar and sun photometer measurements during SAMUM-1 in Morocco (19 May 2006), dealing with measured size- and altitude-resolved axis ratio distributions of assumed spheroidal model particles. The data were applied in optical property, radiative effect, forcing and heating effect simulations to quantify the realistic impact of particle non-sphericity. It turned out that volume-to-surface equivalent spheroids with prolate shape are most realistic: particle non-sphericity only slightly affects single scattering albedo and asymmetry parameter but may enhance extinction coefficient by up to 10 %. At the bottom of the atmosphere (BOA) the Saharan mineral dust always leads to a loss of solar radiation, while the sign of the forcing at the top of the atmosphere (TOA) depends on surface albedo: solar cooling/warming over a mean ocean/land surface. In the thermal spectral range the dust inhibits the emission of radiation to space and warms the BOA. The most realistic case of particle non-sphericity causes changes of total (solar plus thermal) forcing by 55/5 % at the TOA over ocean/land and 15 % at the BOA over both land and ocean and enhances total radiative heating within the dust plume by up to 20 %. Large dust particles significantly contribute to all the radiative effects reported. They strongly enhance the absorbing properties and forward scattering in the solar and increase predominantly, e.g., the total TOA forcing of the dust over land.

  7. On Influence of Neutrals on Dust Particle Charging in Complex Plasmas in the Presence of Electromagnetic Radiation

    SciTech Connect

    Kopnin, S. I.; Morzhakova, A. A.; Popel, S. I.; Shukla, P. K.

    2011-11-29

    Effects associated with neutral component of complex (dusty) ionospheric plasmas which affect dust particle charging are studied. Microscopic ion currents on dust particles with taking into account ion-neutral interaction are presented. Calculations are performed both for the case of negative charges of dust particles, when the influence of Solar radiation on dust particle charging processes is negligible, and for the case of positive charges which is realized in the presence of sufficiently intensive UV or X-ray radiation. We also carry out investigation of the electron heating due to the photoelectric effect. We show that the efficiency of electron heating depends on the density of neutral component of the plasma. As result, we determine altitudes where the influence of the neutral plasma component on dust particle charging processes as well as the electron heating effect are significant and should be taken into account under consideration of the ionospheric complex plasmas. In particular, we show that the effects considered could be important for the description of noctilucent clouds, polar mesosphere summer echoes, and some other physical phenomena associated with dust particles in the ionosphere.

  8. Dust Emission at 8 and 24 μm as Diagnostics of H ii Region Radiative Transfer

    NASA Astrophysics Data System (ADS)

    Oey, M. S.; López-Hernández, J.; Kellar, J. A.; Pellegrini, E. W.; Gordon, K. D.; Jameson, K. E.; Li, A.; Madden, S. C.; Meixner, M.; Roman-Duval, J.; Bot, C.; Rubio, M.; Tielens, A. G. G. M.

    2017-07-01

    We use the Spitzer Surveying the Agents of Galaxy Evolution (SAGE) survey of the Magellanic Clouds to evaluate the relationship between the 8 μm polycyclic aromatic hydrocarbon (PAH) emission, 24 μm hot dust emission, and H ii region radiative transfer. We confirm that in the higher-metallicity Large Magellanic Cloud, PAH destruction is sensitive to optically thin conditions in the nebular Lyman continuum: objects identified as optically thin candidates based on nebular ionization structure show six times lower median 8 μm surface brightness (0.18 mJy arcsec-2) than their optically thick counterparts (1.2 mJy arcsec-2). The 24 μm surface brightness also shows a factor of three offset between the two classes of objects (0.13 versus 0.44 mJy arcsec-2, respectively), which is driven by the association between the very small dust grains and higher density gas found at higher nebular optical depths. In contrast, PAH and dust formation in the low-metallicity Small Magellanic Cloud is strongly inhibited such that we find no variation in either 8 μm or 24 μm emission between our optically thick and thin samples. This is attributable to extremely low PAH and dust production together with high, corrosive UV photon fluxes in this low-metallicity environment. The dust mass surface densities and gas-to-dust ratios determined from dust maps using Herschel HERITAGE survey data support this interpretation.

  9. Universality, maximum radiation, and absorption in high-energy collisions of black holes with spin.

    PubMed

    Sperhake, Ulrich; Berti, Emanuele; Cardoso, Vitor; Pretorius, Frans

    2013-07-26

    We explore the impact of black hole spins on the dynamics of high-energy black hole collisions. We report results from numerical simulations with γ factors up to 2.49 and dimensionless spin parameter χ=+0.85, +0.6, 0, -0.6, -0.85. We find that the scattering threshold becomes independent of spin at large center-of-mass energies, confirming previous conjectures that structure does not matter in ultrarelativistic collisions. It has further been argued that in this limit all of the kinetic energy of the system may be radiated by fine tuning the impact parameter to threshold. On the contrary, we find that only about 60% of the kinetic energy is radiated for γ=2.49. By monitoring apparent horizons before and after scattering events we show that the "missing energy" is absorbed by the individual black holes in the encounter, and moreover the individual black-hole spins change significantly. We support this conclusion with perturbative calculations. An extrapolation of our results to the limit γ→∞ suggests that about half of the center-of-mass energy of the system can be emitted in gravitational radiation, while the rest must be converted into rest-mass and spin energy.

  10. Foehn-induced effects on dust pollution, frontal clouds and solar radiation in the Dead Sea valley

    NASA Astrophysics Data System (ADS)

    Kishcha, Pavel; Starobinets, Boris; Alpert, Pinhas; Kaplan, Michael

    2017-04-01

    The significant drying up of the Dead Sea over the past 40 years has led to an increase in an exposed area contributing to local dust pollution. Measurements show that, sometimes, in the Dead Sea valley, dust pollution can reach extreme concentrations up to several thousands of micrograms per cubic meters. Our analysis of a meteorological situation shows that a foehn phenomenon can be a causal factor for the aforementioned extreme local dust concentration. This foehn phenomenon creates strong warm and dry winds, which are accompanied by air turbulence and temperature inversion. In our study, foehn-induced effects on dust pollution, frontal clouds and solar radiation were analyzed over the Judean Mountains ( 1000 m) and over the Dead Sea valley (-420 m), using high-resolution numerical simulations and in-situ observations at meteorological stations located across the mountain ridge. An extreme dust episode occurring on March 22, 2013, was analyzed, which was characterized by measured surface dust concentrations of up to 7000 µg m-3 in the Dead Sea valley. We simulated this foehn phenomenon with the 3-km resolution COSMO-ART model. Our analysis has shown that the foehn phenomenon could be observed even over the relatively low Judean Mountains. This analysis was based on various meteorological, pyranometer, radar, and aerosol measurements together with high-resolution model data. In the Dead Sea valley, the maximum aerosol optical depth (AOD) did not coincide with the maximum surface dust concentration. This lack of coincidence indicates difficulties in using satellite-based AOD for initializing dust concentration within numerical forecast systems over this region with complex terrain. In the western Dead Sea valley, strong foehn winds of over 20 m/s were accompanied by maximal air turbulence leading to maximal local dust emissions. Thus, the model showed that, by creating significant turbulence, the foehn phenomenon intensified the saltation (bombardment) mechanism

  11. Benchmarking the calculation of stochastic heating and emissivity of dust grains in the context of radiative transfer simulations

    NASA Astrophysics Data System (ADS)

    Camps, Peter; Misselt, Karl; Bianchi, Simone; Lunttila, Tuomas; Pinte, Christophe; Natale, Giovanni; Juvela, Mika; Fischera, Joerg; Fitzgerald, Michael P.; Gordon, Karl; Baes, Maarten; Steinacker, Jürgen

    2015-08-01

    Context. Thermal emission by stochastically heated dust grains (SHGs) plays an important role in the radiative transfer (RT) problem for a dusty medium. It is therefore essential to verify that RT codes properly calculate the dust emission before studying the effects of spatial distribution and other model parameters on the simulated observables. Aims: We define an appropriate problem for benchmarking dust emissivity calculations in the context of RT simulations, specifically including the emission from SHGs. Our aim is to provide a self-contained guide for implementors of such functionality and to offer insight into the effects of the various approximations and heuristics implemented by the participating codes to accelerate the calculations. Methods: The benchmark problem definition includes the optical and calorimetric material properties and the grain size distributions for a typical astronomical dust mixture with silicate, graphite, and PAH components. It also includes a series of analytically defined radiation fields to which the dust population is to be exposed and instructions for the desired output. We processed this problem using six RT codes participating in this benchmark effort and compared the results to a reference solution computed with the publicly available dust emission code DustEM. Results: The participating codes implement different heuristics to keep the calculation time at an acceptable level. We study the effects of these mechanisms on the calculated solutions and report on the level of (dis)agreement between the participating codes. For all but the most extreme input fields, we find agreement within 10% across the important wavelength range 3 μm ≤ λ ≤ 1000 μm. Conclusions: We conclude that the relevant modules in RT codes can and do produce fairly consistent results for the emissivity spectra of SHGs. This work can serve as a reference for implementors of dust RT codes, and it will pave the way for a more extensive benchmark effort

  12. Modeling the Spin Equilibrium of Neutron Stars in LMXBs Without Gravitational Radiation

    NASA Technical Reports Server (NTRS)

    Andersson, N.; Glampedakis, K.; Haskell, B.; Watts, A. L.

    2004-01-01

    In this paper we discuss the spin-equilibrium of accreting neutron stars in LMXBs. We demonstrate that, when combined with a naive spin-up torque, the observed data leads to inferred magnetic fields which are at variance with those of galactic millisecond radiopulsars. This indicates the need for either additional spin-down torques (eg. gravitational radiation) or an improved accretion model. We show that a simple consistent accretion model can be arrived at by accounting for radiation pressure in rapidly accreting systems (above a few percent of the Eddington accretion rate). In our model the inner disk region is thick and significantly sub-Keplerian, and the estimated equilibrium periods are such that the LMXB neutron stars have properties that accord well with the galactic millisecond radiopulsar sample. The implications for future gravitational-wave observations are also discussed briefly.

  13. Modeling the Spin Equilibrium of Neutron Stars in LMXBs Without Gravitational Radiation

    NASA Technical Reports Server (NTRS)

    Andersson, N.; Glampedakis, K.; Haskell, B.; Watts, A. L.

    2004-01-01

    In this paper we discuss the spin-equilibrium of accreting neutron stars in LMXBs. We demonstrate that, when combined with a naive spin-up torque, the observed data leads to inferred magnetic fields which are at variance with those of galactic millisecond radiopulsars. This indicates the need for either additional spin-down torques (eg. gravitational radiation) or an improved accretion model. We show that a simple consistent accretion model can be arrived at by accounting for radiation pressure in rapidly accreting systems (above a few percent of the Eddington accretion rate). In our model the inner disk region is thick and significantly sub-Keplerian, and the estimated equilibrium periods are such that the LMXB neutron stars have properties that accord well with the galactic millisecond radiopulsar sample. The implications for future gravitational-wave observations are also discussed briefly.

  14. Comparison of the electron-spin force and radiation reaction force

    NASA Astrophysics Data System (ADS)

    Mahajan, Swadesh M.; Asenjo, Felipe A.; Hazeltine, Richard D.

    2015-02-01

    It is shown that the forces that originate from the electron-spin interacting with the electromagnetic field can play, along with the Lorentz force, a fundamentally important role in determining the electron motion in a high energy density plasma embedded in strong high-frequency radiation, a situation that pertains to both laser-produced and astrophysical systems. These forces, for instance, dominate the standard radiation reaction force as long as there is a `sufficiently' strong ambient magnetic field for affecting spin alignment. The inclusion of spin forces in any advanced modelling of electron dynamics pertaining to high energy density systems (for instance in particle-in-cell codes), therefore, is a must.

  15. Effect of Mineral Dust on Ocean Color Retrievals From Space: A Radiative Transfer Simulation Study

    NASA Astrophysics Data System (ADS)

    Ahmad, Z.; Franz, B. A.

    2016-02-01

    In this paper we examine the effect of mineral aerosols (dust) on the retrieval of ocean colors from space. Mineral aerosols are one of the major components of all aerosols found in the earth's atmosphere. These are mainly soil particles that originate from arid and semiarid regions of the world and are blown away by winds thousands of kilometers away from their source regions. The radii of these aerosols are between 0.1 and 1.0 μm and their resident time in the atmosphere is about 21 days. The primary focus of this paper is to estimate the remote sensing reflectance (Rrs) errors in the presence of absorbing aerosols over ocean. The present study is based on radiative transfer (RT) simulations, and it is particularly relevant to ocean color retrievals from sensors like MODIS, MERIS, VIIRS, and the future PACE/OCI. In the simulations, we have used mineralogy to determine the spectral dependence of aerosol refractive index, and modeled the aerosols to represent dust over Cape Verde (Sal Island). As a part of this study, we will present the results for retrieved aerosol optical thickness (τ), Angstrom exponent (α), and remote sensing reflectance (Rrs) and compare them with similar results for non-absorbing aerosols. In addition, we will show how aerosol layer height affects the ocean color retrievals.

  16. DUST DESTRUCTION IN A NON-RADIATIVE SHOCK IN THE CYGNUS LOOP SUPERNOVA REMNANT

    SciTech Connect

    Sankrit, Ravi; Gaetz, Terrance J.; Raymond, John C.; Blair, William P.; Ghavamian, Parviz; Long, Knox S.

    2010-04-01

    We present 24 {mu}m and 70 {mu}m images of a non-radiative shock in the Cygnus Loop supernova remnant, obtained with the Multiband Imaging Photometer for Spitzer on board the Spitzer Space Telescope. The post-shock region is resolved in these images. The ratio of the 70 {mu}m to the 24 {mu}m flux rises from about 14 at a distance 0.'1 behind the shock front to about 22 in a zone 0.'75 further downstream, as grains are destroyed in the hot plasma. Models of dust emission and destruction using post-shock electron temperatures between 0.15 keV and 0.30 keV and post-shock densities, n{sub H}{approx} 2.0 cm{sup -3}, predict flux ratios that match the observations. Non-thermal sputtering (i.e., sputtering due to bulk motion of the grains relative to the gas) contributes significantly to the dust destruction under these shock conditions. From the model calculations, we infer that about 35% by mass of the grains are destroyed over a 0.14 pc region behind the shock front.

  17. Aerosol radiative forcing during African desert dust events (2005-2010) over Southeastern Spain

    NASA Astrophysics Data System (ADS)

    Valenzuela, A.; Olmo, F. J.; Lyamani, H.; Antón, M.; Quirantes, A.; Alados-Arboledas, L.

    2012-11-01

    The daily (24 h) averages of the aerosol radiative forcing (ARF) at the surface and the top of the atmosphere (TOA) were calculated during desert dust events over Granada (southeastern Spain) from 2005 to 2010. A radiative transfer model (SBDART) was utilized to simulate the solar irradiance values (0.31-2.8 μm) at the surface and TOA, using as input aerosol properties retrieved from CIMEL sun photometer measurements via an inversion methodology that uses the sky radiance measurements in principal plane configuration and a spheroid particle shape approximation. This inversion methodology was checked by means of simulated data from aerosol models, and the derived aerosol properties were satisfactorily compared against well-known AERONET products. Good agreement was found over a common spectral interval (0.2-4.0 μm) between the simulated SBDART global irradiances at surface and those provided by AERONET. In addition, simulated SBDART solar global irradiances at the surface have been successfully validated against CM-11 pyranometer measurements. The comparison indicates that the radiative transfer model slightly overestimates (mean bias of 3%) the experimental solar global irradiance. These results show that the aerosol optical properties used to estimate ARF represent appropriately the aerosol properties observed during desert dust outbreak over the study area. The ARF mean monthly values computed during desert dust events ranged from -13 ± 8 W m-2 to -34 ± 15 W m-2 at surface, from -4 ± 3 W m-2 to -13 ± 7 W m-2 at TOA and from +6 ± 4 to +21 ± 12 W m-2 in the atmosphere. We have checked if the differences found in aerosol optical properties among desert dust sectors translate to differences in ARF. The mean ARF at surface (TOA) were -20 ± 12 (-5 ± 5) W m-2, -21 ± 9 (-7 ± 5) W m-2 and -18 ± 9 (-6 ± 5) W m-2 for sector A (northern Morocco; northwestern Algeria), sector B (western Sahara, northwestern Mauritania and southwestern Algeria), and sector C

  18. Electron Spin Resonance and Radiation Effects in MOS Devices

    DTIC Science & Technology

    1990-10-01

    I. Solomon, D. Biegelsen, and J. C. Knights , Solid State Comm. 22, 505 (1977). 21 22 APPENDIX B SPIN DEPENDENT RECOMBINATION AT THE SILICON/ SILICON...1952) 387. 10 D.J. Lepine, Phys. Rev. B, 6 (1972) 436. 11 I. Solomon, Solid-State Commun., 20 (1976) 215. 12 I. Solomon, D. Bieglesen and J.C. Knights ...ATTN: YAR CAPT STAPANIAN ALLIED-SIGNAL, INC ATTN: DOCUMENT CONTROL SPACE DIVISION/YD ATTN: YD AMPEX CORP ATTN: B RICKARD SPACE DIVISION/YE ATTN: YE

  19. Modeling dust as component minerals in the Community Atmosphere Model: development of framework and impact on radiative forcing

    DOE PAGES

    Scanza, R. A.; Mahowald, N.; Ghan, S.; ...

    2014-07-02

    The mineralogy of desert dust is important due to its effect on radiation, clouds and biogeochemical cycling of trace nutrients. This study presents the simulation of dust radiative forcing as a function of both mineral composition and size at the global scale using mineral soil maps for estimating emissions. Externally mixed mineral aerosols in the bulk aerosol module in the Community Atmosphere Model version 4 (CAM4) and internally mixed mineral aerosols in the modal aerosol module in the Community Atmosphere Model version 5.1 (CAM5) embedded in the Community Earth System Model version 1.0.5 (CESM) are speciated into common mineral componentsmore » in place of total dust. The simulations with mineralogy are compared to available observations of mineral atmospheric distribution and deposition along with observations of clear-sky radiative forcing efficiency. Based on these simulations, we estimate the all-sky direct radiative forcing at the top of the atmosphere as +0.05 W m−2 for both CAM4 and CAM5 simulations with mineralogy and compare this both with simulations of dust in release versions of CAM4 and CAM5 (+0.08 and +0.17 W m−2) and of dust with optimized optical properties, wet scavenging and particle size distribution in CAM4 and CAM5, −0.05 and −0.17 W m−2, respectively. The ability to correctly include the mineralogy of dust in climate models is hindered by its spatial and temporal variability as well as insufficient global in-situ observations, incomplete and uncertain source mineralogies and the uncertainties associated with data retrieved from remote sensing methods.« less

  20. Vertical distribution and radiative effects of mineral dust and biomass burning aerosol over West Africa during DABEX

    SciTech Connect

    Johnson, Ben; Heese, B.; McFarlane, Sally A.; Chazette, P.; Jones, A.; Bellouin, N.

    2008-09-12

    This paper presents measurements of the vertical distribution of aerosol extinction coefficient over West Africa, during the Dust and Biomass burning aerosol Experiment (DABEX) / African Monsoon Multidisciplinary Analysis dry season Special Observing period zero (AMMA-SOP0). In situ aircraft measurements from the UK FAAM aircraft are compared with two ground based lidars (POLIS and ARM MPL) and an airborne lidar on an ultra-light aircraft. In general mineral dust was observed at low altitudes (up to 2km) and a mixture of biomass burning aerosol and dust was observed at altitudes of 2-5km. The study exposes difficulties associated with spatial and temporal variability when inter-comparing aircraft and ground measurements. Averaging over many profiles provided a better means of assessing consistent errors and biases associated with in situ sampling instruments and retrievals of lidar ratios. Shortwave radiative transfer calculations and a 3-year simulation with the HadGEM2-A climate model show that the radiative effect of biomass burning aerosol is somewhat sensitive to the vertical distribution of aerosol. Results show a 15% increase in absorption of solar radiation by elevated biomass burning aerosol when the observed low-level dust layer is included as part of the background atmospheric state in the model. This illustrates that the radiative forcing of anthropogenic absorbing aerosol is sensitive to the treatment of other aerosol species and that care is needed in simulating natural aerosols assumed to exist in the pre-industrial, or natural state of the atmosphere.

  1. Aerosol's optical and physical characteristics and direct radiative forcing during a shamal dust storm, a case study

    NASA Astrophysics Data System (ADS)

    Saeed, T. M.; Al-Dashti, H.; Spyrou, C.

    2014-04-01

    Dust aerosols are analyzed for their optical and physical properties during an episode of a dust storm that blew over Kuwait on 26 March 2003 when the military Operation Iraqi Freedom was in full swing. The intensity of the dust storm was such that it left a thick suspension of dust throughout the following day, 27 March. The synoptic sequence leading to the dust storm and the associated wind fields are discussed. Ground-based measurements of aerosol optical thickness reached 3.617 and 4.17 on 26 and 27 March respectively while the Ångstrom coefficient, α870/440, dropped to -0.0234 and -0.0318. Particulate matter concentration of 10 μm diameter or less, PM10, peaked at 4800 μg m-3 during dust storm hours of 26 March. Moderate Resolution Imaging Spectroradiometer (MODIS) retrieved aerosol optical depth (AOD) by Deep Blue algorithm and Total Ozone Mapping Spectrometer (TOMS) aerosol index (AI) exhibited high values. Latitude-longitude maps of AOD and AI were used to deduce source regions of dust transport over Kuwait. The vertical profile of the dust layer was simulated using the SKIRON atmospheric model. Instantaneous net direct radiative forcing is calculated at top of atmosphere (TOA) and surface level. The thick dust layer of 26 March resulted in cooling the TOA by -60 Wm-2 and surface level by -175 Wm-2 for a surface albedo of 0.35. Slightly higher values were obtained for 27 March due to the increase in aerosol optical thickness. Radiative heating/cooling rates in the shortwave and longwave bands were also examined. Shortwave heating rate reached a maximum value of 2 K day-1 between 3 and 5 km, dropped to 1.5 K day-1 at 6 km and diminished at 8 km. Longwave radiation initially heated the lower atmosphere by a maximum value of 0.2 K day-1 at surface level, declined sharply at increasing altitude and diminished at 4 km. Above 4 km longwave radiation started to cool the atmosphere slightly reaching a maximum rate of -0.1 K day-1 at 6 km.

  2. Composition, size distribution, optical properties, and radiative effects of laboratory-resuspended PM10 from geological dust of the Rome area, by electron microscopy and radiative transfer modelling

    NASA Astrophysics Data System (ADS)

    Pietrodangelo, A.; Salzano, R.; Bassani, C.; Pareti, S.; Perrino, C.

    2015-11-01

    In this work, new information has been gained on the laboratory-resuspended PM10 fraction from geological topsoil and outcropped rocks representative of the Rome area (Latium). Mineralogical composition, size distribution, optical properties and the surface radiative forcing efficiency (RFE) of dust types representing the compositional end members of this geological area have been addressed. A multi-disciplinary approach was used, based on chamber resuspension of raw materials and sampling of the PM10 fraction, to simulate field sampling at dust source, scanning electron microscopy/X-ray energy-dispersive microanalysis (SEM XEDS) of individual mineral particles, X-ray diffraction (XRD) analysis of bulk dust samples, building of number and volume size distribution (SD) from microanalysis data of mineral particles and fitting to a log-normal curve, and radiative transfer modelling (RTM) to retrieve optical properties and radiative effects of the compositional end-member dust samples. The mineralogical composition of Rome lithogenic PM10 varies between an end-member dominated by silicate minerals (from volcanics lithotypes), and one mostly composed of calcite (from travertine or limestones). Lithogenic PM10 with intermediate composition derives mainly from siliciclastic rocks or marlstones. Size and mineral species of PM10 particles of silicate-dominated dust types are tuned mainly by rock weathering and, to lesser extent, by debris formation or crystallization; chemical precipitation of CaCO3 plays a major role in calcite-dominated types. These differences are reflected in the diversity of volume distributions, either within dust types or mineral species. Differences are also observed between volume distributions of calcite from travertine (natural source; SD unimodal at 5 μm a.d.) and from road dust (anthropic source; SD bimodal at 3.8 and 1.8 μm a.d.). The volcanics and travertine dusts differently affect the single scattering albedo (SSA) and the asymmetry

  3. Aerosols optical and physical characteristics and direct radiative forcing during a "Shamal" dust storm, a case study

    NASA Astrophysics Data System (ADS)

    Saeed, T. M.; Al-Dashti, H.; Spyrou, C.

    2013-09-01

    Dust aerosols are analyzed for their optical and physical properties during an episode of dust storm that hit Kuwait on 26 March 2003 when "Iraqi Freedom" military operation was in full swing. The intensity of the dust storm was such that it left a thick suspension of dust throughout the following day, 27 March, resulting in a considerable cooling effect at the surface on both days. Ground-based measurements of aerosol optical thickness reached 3.617 and 4.17 on 26-27 March respectively while Ångstrom coefficient, α870/440, dropped to -0.0234 and -0.0318. Particulate matter concentration of diameter 10 μm or less, PM10, peaked at 4800 μg m-3 during dust storm hours of 26 March. Moderate resolution imaging spectrometer (MODIS) retrieved optical and physical characteristics that exhibited extreme values as well. The synoptic of the dust storm is presented and source regions are identified using total ozone mapping spectrometer (TOMS) aerosol index retrieved images. The vertical profile of the dust layer was simulated using SKIRON atmospheric model. Instantaneous net direct radiative forcing is calculated at top of atmosphere (TOA) and surface level. The thick dust layer of 26 March resulted in cooling the TOA by -60 Wm-2 and surface level by -175 Wm-2 for a surface albedo of 0.35. Slightly higher values were obtained for 27 March due to the increase in aerosol optical thickness. The large reduction in the radiative flux at the surface level had caused a drop in surface temperature by approximately 6 °C below its average value. Radiative heating/cooling rates in the shortwave and longwave bands were also examined. Shortwave heating rate reached a maximum value of 2 °K day-1 between 3 and 5 km, dropped to 1.5 °K day-1 at 6 km and diminished at 8 km. Longwave radiation initially heated the lower atmosphere by a maximum value of 0.2 °K day-1 at surface level, declined sharply at increasing altitude and diminished at 4 km. Above 4 km longwave radiation started to

  4. Role of sea surface temperature and Saharan dust radiative forcing on the multi-decadal variation of rainfall over West Africa and northern Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Kim, K. M.; Lau, W. K. M.; Colarco, P. R.

    2015-12-01

    Under the Second West African Monsoon Model Evaluation Experiments project (WAMME-2), we have carried out model experiments to investigate multi-decadal variation of sea surface temperature (SST), and Saharan dust radiative forcing on the West Africa Monsoon (WAM), and associated dust emission and transport of. Comparing experiments with prescribed SST during the 1980s to the 1950s, we find that SST forcing significant alter the large-scale circulation, rainfall, and the dust emissions and transport during these two decades. Colder SST over northern Atlantic Ocean in 1980s strengthened the subtropical high and expanded it southwestward, compared to the 1950's. As a result, the rain band over the tropical Atlantic Ocean and Sahel moves southward, and rainfall is reduced over the Sahel. Stronger surface winds associated with enhanced surface temperature gradients increase dust emission in the southern Saharan desert and northern Sahel. Combined with circulation changes induced by strengthening the subtropical high and reduced wet deposition, dust transport is increased in the deep tropics (10-20N), but relatively reduced in the northern path (20-30N) To examine the role of the increased dust aerosol radiative forcing, additional experiments are conducted with reduced dust shortwave absorption. With reduced atmospheric heating by dust aerosol, model still simulates aforementioned contrast between 1980s and 1950s, but the anomalies of Sahel drought and dust transports is weaker. The atmospheric heating due to shortwave absorption by dust provides additional buoyance and lifts dust particles to higher altitudes. Dust radiative forcing also increases meridional temperature gradients and strengthens the African Easterly Jet, resulting in an increased residence time of dust and farther westward transport. Increased dust loading and lifetime further enhance dryness over the Sahel, but bring more rain to the south of the dust region.

  5. Electrons in strong electromagnetic fields: spin effects and radiation reaction (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Bauke, Heiko; Wen, Meng; Keitel, Christoph H.

    2017-05-01

    Various different classical models of electrons including their spin degree of freedom are commonly applied to describe the coupled dynamics of relativistic electron motion and spin precession in strong electromagnetic fields. The spin dynamics is usually governed by the Thomas-Bargmann-Michel-Telegdi equation [1, 2] in these models, while the electron's orbital motion follows the (modified) Lorentz force and a spin-dependent Stern-Gerlach force. Various classical models can lead to different or even contradicting predictions how the spin degree of freedom modifies the electron's orbital motion when the electron moves in strong electromagnetic fields. This discrepancy is rooted in the model-specific energy dependency of the spin induced relativistic Stern-Gerlach force acting on the electron. The Frenkel model [3, 4] and the classical Foldy-Wouthuysen model 5 are compared exemplarily against each other and against the quantum mechanical Dirac equation in order to identify parameter regimes where these classical models make different predictions [6, 7]. Our theoretical results allow for experimental tests of these models. In the setup of the longitudinal Stern-Gerlach effect, the Frenkel model and classical Foldy-Wouthuysen model lead in the relativistic limit to qualitatively different spin effects on the electron trajectory. Furthermore, it is demonstrated that in tightly focused beams in the near infrared the effect of the Stern-Gerlach force of the Frenkel model becomes sufficiently large to be potentially detectable in an experiment. Among the classical spin models, the Frenkel model is certainly prominent for its long history and its wide application. Our results, however, suggest that the classical Foldy-Wouthuysen model is superior as it is qualitatively in better agreement with the quantum mechanical Dirac equation. In ultra strong laser setups at parameter regimes where effects of the Stern-Gerlach force become relevant also radiation reaction effects are

  6. Spin-flip processes and radiative decay of dark intravalley excitons in transition metal dichalcogenide monolayers

    NASA Astrophysics Data System (ADS)

    Slobodeniuk, A. O.; Basko, D. M.

    2016-09-01

    We perform a theoretical study of radiative decay of dark intravalley excitons in transition metal dichalcogenide monolayers. This decay necessarily involves an electronic spin flip. The intrinsic decay mechanism due to interband spin-flip dipole moment perpendicular to the monolayer plane, gives a rate about 100-1000 times smaller than that of bright excitons. However, we find that this mechanism also introduces an energy splitting due to a local field effect, and the whole oscillator strength is contained in the higher-energy component, while the lowest-energy state remains dark and needs an extrinsic spin-flip mechanism for the decay. Rashba effect due to a perpendicular electric field or a dielectric substrate, gives a negligible radiative decay rate (about 107 times slower than that of bright excitons). Spin flip due to Zeeman effect in a sufficiently strong in-plane magnetic field can give a decay rate comparable to that due to the intrinsic interband spin-flip dipole.

  7. Effects of Spin on High-energy Radiation from Accreting Black Holes

    NASA Astrophysics Data System (ADS)

    O' Riordan, Michael; Pe'er, Asaf; McKinney, Jonathan C.

    2016-11-01

    Observations of jets in X-ray binaries show a correlation between radio power and black hole spin. This correlation, if confirmed, points toward the idea that relativistic jets may be powered by the rotational energy of black holes. In order to examine this further, we perform general relativistic radiative transport calculations on magnetically arrested accretion flows, which are known to produce powerful jets via the Blandford-Znajek (BZ) mechanism. We find that the X-ray and γ-ray emission strongly depend on spin and inclination angle. Surprisingly, the high-energy power does not show the same dependence on spin as the BZ jet power, but instead can be understood as a redshift effect. In particular, photons observed perpendicular to the spin axis suffer little net redshift until originating from close to the horizon. Such observers see deeper into the hot, dense, highly magnetized inner disk region. This effect is largest for rapidly rotating black holes due to a combination of frame dragging and decreasing horizon radius. While the X-ray emission is dominated by the near horizon region, the near-infrared (NIR) radiation originates at larger radii. Therefore, the ratio of X-ray to NIR power is an observational signature of black hole spin.

  8. Quantum Suppression of Alignment in Ultrasmall Grains: Microwave Emission from Spinning Dust will be Negligibly Polarized

    NASA Astrophysics Data System (ADS)

    Draine, B. T.; Hensley, Brandon S.

    2016-11-01

    The quantization of energy levels in small, cold, free-flying nanoparticles suppresses dissipative processes that convert grain rotational kinetic energy into heat. For interstellar grains small enough to have ˜GHz rotation rates, the suppression of dissipation can be extreme. As a result, alignment of such grains is suppressed. This applies both to alignment of the grain body with its angular momentum {\\boldsymbol{J}}, and to alignment of {\\boldsymbol{J}} with the local magnetic field {\\boldsymbol{B}} 0. If the anomalous microwave emission is rotational emission from spinning grains, then it will be negligibly polarized at GHz frequencies, with P ≲ 10-6 at ν > 10 GHz.

  9. Effects on surface meteorological parameters and radiation levels of a heavy dust storm occurred in Central Arabian Peninsula

    NASA Astrophysics Data System (ADS)

    Maghrabi, A. H.; Al-Dosari, A. F.

    2016-12-01

    On 24 April 2015 a severe dust storm event arrived at Riyadh causing various problems. The quantitative impact of this dusty event on solar ultraviolet radiation UVA and UVB, global solar radiation component, downward and outgoing long-wave radiation, and some meteorological variables, was investigated and presented. The results showed significant changes in all of these parameters due to this event. Shortly after the storm arrived, UVA, UVB, global radiation, and air temperature rapidly decrease by 83%, 86%, 57.5%, and 9.4%, respectively. Atmospheric pressure increased by 4 mbar, relative humidly increased from 8% to 16%, and wind direction became northerly with wind speed increasing to a maximum of 6.3 m/s. Outgoing long-wave radiation decreased by 19 W/m2 and downward long-wave radiation increased by 41 W/m2. The dust storm caused the atmosphere to emit radiation that resembled that of a black body. The daily average of the atmospheric pressure showed no changes compared to a non-dusty day. Apart from the relative humidity (which increased by about 32%), the remainder of the variables have shown significant reduction, with different magnitudes, in their daily values due to the dust event compared to the values of a non-disturbed reference day. For instance, the daily mean values of the UVA radiation, air temperature, and outgoing long-wave radiation, decreased in the dusty day by 15.6%, 30.8% and 11.4%, respectively, as compared to the clear day.

  10. Spin observables in deuteron proton radiative capture at intermediate energies

    NASA Astrophysics Data System (ADS)

    Mehmandoost-Khajeh-Dad, A. A.; Amir-Ahmadi, H. R.; Bacelar, J. C. S.; van den Berg, A. M.; Castelijns, R.; Deltuva, A.; van Garderen, E. D.; Glöckle, W.; Golak, J.; Kalantar-Nayestanaki, N.; Kamada, H.; Kiš, M.; Koohi-Fayegh-Dehkordi, R.; Löhner, H.; Mahjour-Shafiei, M.; Mardanpour, H.; Messchendorp, J. G.; Nogga, A.; Sauer, P.; Shende, S. V.; Skibinski, R.; Witała, H.; Wörtche, H. J.

    2005-06-01

    A radiative deuteron-proton capture experiment was carried out at KVI using polarized-deuteron beams at incident energies of 55, 66.5, and 90 MeV/nucleon. Vector and tensor-analyzing powers were obtained for a large angular range. The results are interpreted with the help of Faddeev calculations, which are based on modern two- and three-nucleon potentials. Our data are described well by the calculations, and disagree significantly with the observed tensor anomaly at RCNP.

  11. Effect of ion radiative cooling on Jeans instability of partially ionized dusty plasma with dust charge fluctuation

    NASA Astrophysics Data System (ADS)

    Sharma, Prerana; Patidar, Archana

    2017-01-01

    In this paper, the effect of ion radiative cooling on the gravitational instability of dusty plasma is studied, incorporating dust charge fluctuation with dust-neutral, neutral-ion, and ion-neutral collisions. The basic equations are linearized using normal mode analysis to obtain a general dispersion relation. The general dispersion relation is analytically and numerically discussed to explain the role of ion radiative cooling in the structure formation through gravitational instability. The Jeans collapse criteria are found to be modified due to ion and electron radiative cooling, dust charge fluctuations, and collisions effects. It is determined from the analytical and numerical calculations that the support of radiative cooling of ions drives thermal fluctuations and gives instability to the system. The electron cooling effect remains dominating over ion cooling effect, and thus, it enhances the collapse more efficiently than ion cooling effect. Although the radiative cooling is slow, it may precede the collapse in molecular cloud, which further leads to the structure formation. The present work is relevance for the structure formation in the molecular cloud.

  12. Post-Newtonian gravitational radiation and equations of motion via direct integration of the relaxed Einstein equations. III. Radiation reaction for binary systems with spinning bodies

    SciTech Connect

    Will, Clifford M.

    2005-04-15

    Using post-Newtonian equations of motion for fluid bodies that include radiation-reaction terms at 2.5 and 3.5 post-Newtonian (PN) order (O[(v/c){sup 5}] and O[(v/c){sup 7}] beyond Newtonian order), we derive the equations of motion for binary systems with spinning bodies. In particular we determine the effects of radiation reaction coupled to spin-orbit effects on the two-body equations of motion, and on the evolution of the spins. For a suitable definition of spin, we reproduce the standard equations of motion and spin-precession at the first post-Newtonian order. At 3.5 PN order, we determine the spin-orbit induced reaction effects on the orbital motion, but we find that radiation damping has no effect on either the magnitude or the direction of the spins. Using the equations of motion, we find that the loss of total energy and total angular momentum induced by spin-orbit effects precisely balances the radiative flux of those quantities calculated by Kidder et al. The equations of motion may be useful for evolving inspiraling orbits of compact spinning binaries.

  13. Numerical simulation of spatial-temporal distribution of dust aerosol and its direct radiative effects on East Asian climate

    NASA Astrophysics Data System (ADS)

    Sun, Hui; Pan, Zaitao; Liu, Xiaodong

    2012-07-01

    The latest regional climate model version 4 (RegCM4) coupled with a dust module developed at the International Center for Theoretical Physics (ICTP, Italy) is used to simulate the spatial-temporal distribution of dust aerosol and its climatic impact through direct radiative forcing over East Asia. Dust coupled and uncoupled experiments are carried out for the past decade (2000-2009). Comparison with satellite observed aerosol optical depth (AOD) shows that the coupled RegCM4 better reproduces spatial distribution of Asian dust loading that has been poorly resolved by general circulation models (GCM), capturing three surface dust concentration (SDC) centers in the Taklimakan desert, western Inner Mongolia, and northern Xinjiang respectively, with maximum values greater than 1000μg m-3 in spring. The negative surface shortwave (SW) irradiance is strongest in spring over East Asia. Its -20 W m-2 forcing near dust source centers results in surface temperature cooling by 0.8°C from spring through summer. SW irradiance at the top of the atmosphere (TOA) is also negative with a minimum value of up to -8 W m-2in North China. Dust aerosol induced cooling leads to the formation of a cyclonic circulation in the lower troposphere in Northwest China that further excites downstream an anticyclonic circulation (the Yellow River Loop) and a cyclonic circulation (East China Sea, ECS). The northeasterly flow in southern China straddled by the anticyclone and cyclone acts to weaken the southwest monsoon in southeastern China and the surrounding sea. Supported by the dust-induced circulations, precipitation increases in cyclonic regions in Northwest China and ECS and decreases in the anticyclonic north-central China.

  14. Ion-neutral collisions and dust grain charging in the presence of electromagnetic radiation in the Earth's Ionosphere

    NASA Astrophysics Data System (ADS)

    Kopnin, Sergey; Popel, Sergey; Morzhakova, Anastasia

    2010-05-01

    Ion-neutral collisions in dust particle charging process in the presence of electromagnetic radiation in Earth's "dusty" ionosphere are taken into account. These collisions can result in a charge exchange between a fast ion and a slow neutral. The slow neutrals become slow positively charged ions which interact effectively with positively charged dust grains. As a result a microscopic ion current on the dust grains decreases in comparison with the case when ion-neutral collisions are not taken into account in the dust grain charging process. The microscopic ion current on the positively charged dust grains is derived. A condition on neutral density is obtained for which the influence of ion-neutral collisions on dust particle charging process is important. It is shown that the effect of ion-neutral collisions should be taken into account when considering the charging of nano- and microsize dust grains in Noctilucent Clouds, Polar Mesosphere Summer Echoes, meteoritic dust, active geophysical rocket experiments such as Fluxus 1 and 2. We discuss also the effect of electrons with energies of the order of 1 eV which are produced as a result of photoelectric effect during the charging process, which can result in an increase of the electron temperature in plasmas. The most important effect resulting in cooling of such electrons is that of electron-ion collisions. We found a condition on the neutral density when the electron temperature in Earth's "dusty" ionosphere can become of the order of 1 eV. The importance of this effect for ionospheric plasmas is discussed. This work was supported by the Russian Foundation for Basic Research, project no. 06-05-64826-а. S.I.P. acknowledges financial support of the Dynasty Foundation.

  15. An assessment of the quality of aerosol retrievals over the Red Sea and evaluation of the climatological cloud-free dust direct radiative effect in the region

    NASA Astrophysics Data System (ADS)

    Brindley, H.; Osipov, S.; Bantges, R.; Smirnov, A.; Banks, J.; Levy, R.; Jish Prakash, P.; Stenchikov, G.

    2015-10-01

    Ground-based and satellite observations are used in conjunction with the Rapid Radiative Transfer Model (RRTM) to assess climatological aerosol loading and the associated cloud-free aerosol direct radiative effect (DRE) over the Red Sea. Aerosol optical depth (AOD) retrievals from the Moderate Resolution Imaging Spectroradiometer and Spinning Enhanced Visible and InfraRed Imager (SEVIRI) instruments are first evaluated via comparison with ship-based observations. Correlations are typically better than 0.9 with very small root-mean-square and bias differences. Calculations of the DRE along the ship cruises using RRTM also show good agreement with colocated estimates from the Geostationary Earth Radiation Budget instrument if the aerosol asymmetry parameter is adjusted to account for the presence of large particles. A monthly climatology of AOD over the Red Sea is then created from 5 years of SEVIRI retrievals. This shows enhanced aerosol loading and a distinct north to south gradient across the basin in the summer relative to the winter months. The climatology is used with RRTM to estimate the DRE at the top and bottom of the atmosphere and the atmospheric absorption due to dust aerosol. These climatological estimates indicate that although longwave effects can reach tens of W m-2, shortwave cooling typically dominates the net radiative effect over the Sea, being particularly pronounced in the summer, reaching 120 W m-2 at the surface. The spatial gradient in summertime AOD is reflected in the radiative effect at the surface and in associated differential heating by aerosol within the atmosphere above the Sea. This asymmetric effect is expected to exert a significant influence on the regional atmospheric and oceanic circulation.

  16. The Continuous Monitoring of Desert Dust using an Infrared-based Dust Detection and Retrieval Method

    NASA Technical Reports Server (NTRS)

    Duda, David P.; Minnis, Patrick; Trepte, Qing; Sun-Mack, Sunny

    2006-01-01

    Airborne dust and sand are significant aerosol sources that can impact the atmospheric and surface radiation budgets. Because airborne dust affects visibility and air quality, it is desirable to monitor the location and concentrations of this aerosol for transportation and public health. Although aerosol retrievals have been derived for many years using visible and near-infrared reflectance measurements from satellites, the detection and quantification of dust from these channels is problematic over bright surfaces, or when dust concentrations are large. In addition, aerosol retrievals from polar orbiting satellites lack the ability to monitor the progression and sources of dust storms. As a complement to current aerosol dust retrieval algorithms, multi-spectral thermal infrared (8-12 micron) data from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Meteosat-8 Spinning Enhanced Visible and Infrared Imager (SEVIRI) are used in the development of a prototype dust detection method and dust property retrieval that can monitor the progress of Saharan dust fields continuously, both night and day. The dust detection method is incorporated into the processing of CERES (Clouds and the Earth s Radiant Energy System) aerosol retrievals to produce dust property retrievals. Both MODIS (from Terra and Aqua) and SEVERI data are used to develop the method.

  17. Composition of dust deposited to snow cover in the Wasatch Range (Utah, USA): Controls on radiative properties of snow cover and comparison to some dust-source sediments

    USGS Publications Warehouse

    Reynolds, Richard L.; Goldstein, Harland L.; Moskowitz, Bruce M.; Bryant, Ann C.; Skiles, S. McKenzie; Kokaly, Raymond F.; Flagg, Cody B.; Yauk, Kimberly; Berquó, Thelma S.; Breit, George N.; Ketterer, Michael; Fernandez, Daniel; Miller, Mark E.; Painter, Thomas H.

    2014-01-01

    Dust layers deposited to snow cover of the Wasatch Range (northern Utah) in 2009 and 2010 provide rare samples to determine the relations between their compositions and radiative properties. These studies are required to comprehend and model how such dust-on-snow (DOS) layers affect rates of snow melt through changes in the albedo of snow surfaces. We evaluated several constituents as potential contributors to the absorption of solar radiation indicated by values of absolute reflectance determined from bi-conical reflectance spectroscopy. Ferric oxide minerals and carbonaceous matter appear to be the primary influences on lowering snow-cover albedo. Techniques of reflectance and Mössbauer spectroscopy as well as rock magnetism provide information about the types, amounts, and grain sizes of ferric oxide minerals. Relatively high amounts of ferric oxide, indicated by hard isothermal remanent magnetization (HIRM), are associated with relatively low average reflectance (<0.25) across the visible wavelengths of the electromagnetic spectrum. Mössbauer spectroscopy indicates roughly equal amounts of hematite and goethite, representing about 35% of the total Fe-bearing phases. Nevertheless, goethite (α-FeOOH) is the dominant ferric oxide found by reflectance spectroscopy and thus appears to be the main iron oxide control on absorption of solar radiation. At least some goethite occurs as nano-phase grain coatings less than about 50 nm thick. Relatively high amounts of organic carbon, indicating as much as about 10% organic matter, are also associated with lower reflectance values. The organic matter, although not fully characterized by type, correlates strongly with metals (e.g., Cu, Pb, As, Cd, Mo, Zn) derived from distal urban and industrial settings, probably including mining and smelting sites. This relation suggests anthropogenic sources for at least some of the carbonaceous matter, such as emissions from transportation and industrial activities. The composition

  18. Composition of dust deposited to snow cover in the Wasatch Range (Utah, USA): Controls on radiative properties of snow cover and comparison to some dust-source sediments

    NASA Astrophysics Data System (ADS)

    Reynolds, Richard L.; Goldstein, Harland L.; Moskowitz, Bruce M.; Bryant, Ann C.; Skiles, S. McKenzie; Kokaly, Raymond F.; Flagg, Cody B.; Yauk, Kimberly; Berquó, Thelma; Breit, George; Ketterer, Michael; Fernandez, Daniel; Miller, Mark E.; Painter, Thomas H.

    2014-12-01

    Dust layers deposited to snow cover of the Wasatch Range (northern Utah) in 2009 and 2010 provide rare samples to determine the relations between their compositions and radiative properties. These studies are required to comprehend and model how such dust-on-snow (DOS) layers affect rates of snow melt through changes in the albedo of snow surfaces. We evaluated several constituents as potential contributors to the absorption of solar radiation indicated by values of absolute reflectance determined from bi-conical reflectance spectroscopy. Ferric oxide minerals and carbonaceous matter appear to be the primary influences on lowering snow-cover albedo. Techniques of reflectance and Mössbauer spectroscopy as well as rock magnetism provide information about the types, amounts, and grain sizes of ferric oxide minerals. Relatively high amounts of ferric oxide, indicated by hard isothermal remanent magnetization (HIRM), are associated with relatively low average reflectance (<0.25) across the visible wavelengths of the electromagnetic spectrum. Mössbauer spectroscopy indicates roughly equal amounts of hematite and goethite, representing about 35% of the total Fe-bearing phases. Nevertheless, goethite (α-FeOOH) is the dominant ferric oxide found by reflectance spectroscopy and thus appears to be the main iron oxide control on absorption of solar radiation. At least some goethite occurs as nano-phase grain coatings less than about 50 nm thick. Relatively high amounts of organic carbon, indicating as much as about 10% organic matter, are also associated with lower reflectance values. The organic matter, although not fully characterized by type, correlates strongly with metals (e.g., Cu, Pb, As, Cd, Mo, Zn) derived from distal urban and industrial settings, probably including mining and smelting sites. This relation suggests anthropogenic sources for at least some of the carbonaceous matter, such as emissions from transportation and industrial activities. The composition of

  19. Composition of Dust Deposited on Snow Cover in the Wasatch Range (Utah, USA): Controls on Radiative Properties of Snow Cover and Comparison to Some Dust-Source Sediments

    NASA Astrophysics Data System (ADS)

    Reynolds, R. L.; Goldstein, H.; Painter, T.; Moskowitz, B. M.; Yauk, K.; Flagg, C.; Kokaly, R. F.; Miller, M. E.; Ketterer, M. E.

    2012-12-01

    Dust layers deposited on snow cover of the Wasatch Range (northern Utah) in 2009 and 2010 provide rare samples to determine the relations between their compositions and radiative properties. These studies are required to comprehend and model how such dust-on-snow (DOS) layers affect rates of snow melt through changes in the albedo of snow surfaces. We evaluated several constituents as potential contributors to the absorption of solar radiation indicated by values of absolute reflectance determined from bi-directional reflectance spectroscopy. Ferric oxide minerals and organic matter appear to be the primary influences on lowering snow-cover albedo. Techniques of reflectance and Mössbauer spectroscopy as well as rock magnetism provide information about the types, amounts, and grain sizes of ferric oxide minerals. Relatively high amounts of ferric oxide, indicated by hard isothermal remanent magnetization (HIRM), are associated with relatively low average reflectance (0.1702-0.3160) within the visible part of the solar radiation spectrum. Mössbauer spectroscopy indicates roughly equal amounts of hematite and goethite, representing about 35% of the total Fe-bearing phases. Nevertheless, goethite (FeOOH) is the dominant ferric oxide found by reflectance spectroscopy and thus appears to be the main iron oxide control on absorption of solar energy. At least some goethite probably occurs as nano-phase grain coatings less than about 50 nm thick. Relatively high amounts of organic carbon, indicating as much as 9 % organic matter, are also associated with lower reflectance values. The organic matter correlates strongly with metals (e.g., Cu, Pb, As, Cd, Mo, Zn) derived from far-distant urban and industrial settings (including mining and smelting sites). This relation suggests anthropogenic sources for at least some of the organic matter, such as emissions from transportation and industrial activities. The composition of the DOS samples can be compared with sediments in a

  20. Vortex viscosity in magnetic superconductors due to radiation of spin waves.

    PubMed

    Shekhter, A; Bulaevskii, L N; Batista, C D

    2011-01-21

    In type-II superconductors that contain a lattice of magnetic moments, vortices polarize the magnetic system inducing additional contributions to the vortex mass, vortex viscosity, and vortex-vortex interaction. Extra magnetic viscosity is caused by radiation of spin waves by a moving vortex. Like in the case of Cherenkov radiation, this effect has a characteristic threshold behavior and the resulting vortex viscosity may be comparable to the well-known Bardeen-Stephen contribution. The threshold behavior leads to an anomaly in the current-voltage characteristics, and a drop in dissipation for a current interval that is determined by the magnetic excitation spectrum.

  1. Hawking radiation of spin-1 particles from a three-dimensional rotating hairy black hole

    SciTech Connect

    Sakalli, I.; Ovgun, A.

    2015-09-15

    We study the Hawking radiation of spin-1 particles (so-called vector particles) from a three-dimensional rotating black hole with scalar hair using a Hamilton–Jacobi ansatz. Using the Proca equation in the WKB approximation, we obtain the tunneling spectrum of vector particles. We recover the standard Hawking temperature corresponding to the emission of these particles from a rotating black hole with scalar hair.

  2. Synchrotron radiation macromolecular crystallography: science and spin-offs

    PubMed Central

    Helliwell, John R.; Mitchell, Edward P.

    2015-01-01

    A current overview of synchrotron radiation (SR) in macromolecular crystallography (MX) instrumentation, methods and applications is presented. Automation has been and remains a central development in the last decade, as have the rise of remote access and of industrial service provision. Results include a high number of Protein Data Bank depositions, with an increasing emphasis on the successful use of microcrystals. One future emphasis involves pushing the frontiers of using higher and lower photon energies. With the advent of X-ray free-electron lasers, closely linked to SR developments, the use of ever smaller samples such as nanocrystals, nanoclusters and single molecules is anticipated, as well as the opening up of femtosecond time-resolved diffraction structural studies. At SR sources, a very high-throughput assessment for the best crystal samples and the ability to tackle just a few micron and sub-micron crystals will become widespread. With higher speeds and larger detectors, diffraction data volumes are becoming long-term storage and archiving issues; the implications for today and the future are discussed. Together with the rise of the storage ring to its current pre-eminence in MX data provision, the growing tendency of central facility sites to offer other centralized facilities complementary to crystallography, such as cryo-electron microscopy and NMR, is a welcome development. PMID:25866664

  3. On the Role of Flash Floods for Dust Emission over North Africa: Alluvial Sediments acting as Dust Source

    NASA Astrophysics Data System (ADS)

    Schepanski, K.; Klueser, L.; Tegen, I.

    2014-12-01

    Studies analyzing satellite dust products show that numerous dust sources are located in the foothills of arid and semi-arid mountain regions. There, alluvial sediments deposited on valley bottoms and flood plains are very susceptible to wind erosion and frequently serve as dust source. This study focuses on the spatio-temporal distribution of dust source activation events over the mountain foothills and flood plains over North Africa. Satellite dust retrievals with sub-daily resolution such as from Meteosat Second Generation (MSG) Spinning Enhanced Visible and InfraRed Imager (SEVIRI) and METOP A/B Infrared Atmospheric Sounding Interferometer (IASI) instruments are used to identify dust source regions. Identified dust source regions are then linked to soil properties and land type classification data sets. Information on the mineralogical composition of transported dust inferred from IASI observation are used (a) to investigate the impact of different source geomorphologies and thus different radiative properties of airborne dust particles, and (b) to estimate the contribution of dust uplift from alluvial sediments compared to dust emission from non-hydrological sources. Ultimately, this study contributes to the understanding of controlling mechanism on the interannual variability of dust source activation and will improve current dust emission modules coupled to atmosphere models.

  4. Application of a New Method to Study the Spin Equilibrium of Aql X–1: The Possibility of Gravitational Radiation

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, Sudip

    2017-09-01

    Accretion via disks can make neutron stars in low-mass X-ray binaries (LMXBs) fast spinning, and some of these stars are detected as millisecond pulsars. Here we report a practical way to find out if a neutron star in a transient LMXB has reached the spin equilibrium by disk–magnetosphere interaction alone, and if not, to estimate this spin equilibrium frequency. These can be done using specific measurable source luminosities, such as the luminosity corresponding to the transition between the accretion and propeller phases, and the known stellar spin rate. Such a finding can be useful to test if the spin distribution of millisecond pulsars, as well as an observed upper cutoff of their spin rates, can be explained using disk–magnetosphere interaction alone, or additional spin-down mechanisms, such as gravitational radiation, are required. Applying our method, we find that the neutron star in the transient LMXB Aql X–1 has not yet reached the spin equilibrium by disk–magnetosphere interaction alone. We also perform numerical computations, with and without gravitational radiation, to study the spin evolution of Aql X–1 through a series of outbursts and to constrain its properties. While we find that the gravitational wave emission from Aql X–1 cannot be established with certainty, our numerical results show that the gravitational radiation from Aql X–1 is possible, with a 1.6× {10}37 g cm2 upper limit of the neutron star misaligned mass quadrupole moment.

  5. The Impact of Aerosols Generated from Biomass Burning, Dust Storms, and Volcanoes Upon the Earth's Radiative Energy Budget

    NASA Technical Reports Server (NTRS)

    Christopher, Sundar A.

    1997-01-01

    A new technique for detecting aerosols from biomass burning and dust is developed. The radiative forcing of aerosols is estimated over four major ecosystems in South America. A new smoke and fire detection scheme is developed for biomass burning aerosols over South America. Surface shortware irradiance calculations are developed in the presence of biomass burning aerosols during the SCAR-B experiment. This new approach utilizes ground based, aircraft, and satellite measurements.

  6. Modeling the effects of the dust rings and plasma waves on the electron radiation belts of Jupiter

    NASA Astrophysics Data System (ADS)

    Nénon, Quentin; Sicard-Piet, Angélica; Girard, Julien N.; Zarka, Philippe

    2016-04-01

    ONERA has been modeling radiation belts since the 90's through the 3D physical model Salammbô. The model requires a good knowledge and modeling of the interactions between the trapped particles and the inner magnetosphere environment. Here we report on the investigations that have been performed about the roles of the dust rings and plasma waves around Jupiter on the electron radiation belts. Prior to this work, the surface potential of the dust grains have been argued to deflect the electrons, so that there are no collisions between electrons and dust grains. We dismiss the previous argument, the possible surface potentials being negligible compared to the relativistic kinetic energies of the trapped electrons. The dust grain size distribution was then constrained by the normal optical depth of "large" particles measured by the Galileo NIMS experiment. We will show that this constraint and the Pioneer 11 electron flux measurements indicate that "very large" grains (radius >10mm) are not likely to exist. It leads to the conclusion that electrons with energies higher than a few MeV are not influenced by the rings. The Galileo PWS data has been used to determine representative characteristics (localization and frequency spectrum) of the plasma waves that can be encountered between the orbit of Io (6 Rj) and the numerical box limit of Salammbô (9.5 Rj). We then benefited from the experience ONERA has in modeling the effects of waves on the Earth radiation belts. In particular, the WAPI (WAve-Particle Interaction) code, that uses the quasi-linear theory to compute the pitch angle and energy diffusion coefficients, has been adapted to the Jupiter environment. Finally, Salammbô has been used to investigate the influence of each process on observation data: electron fluxes measured by the Pioneer 10, 11 and Galileo missions and synchrotron radiation images obtained by the VLA (at 5000 and 1424 MHz in May 1997) and LOFAR (127-172 MHz in November 2011).

  7. Composition, size distribution, optical properties and radiative effects of re-suspended local mineral dust of Rome area by individual-particle microanalysis and radiative transfer modelling

    NASA Astrophysics Data System (ADS)

    Pietrodangelo, A.; Salzano, R.; Bassani, C.; Pareti, S.; Perrino, C.

    2015-05-01

    New information on the PM10 mineral dust from site-specific (Rome area, Latium) outcropped rocks, and on the microphysics, optical properties and radiative effects of mineral dust at local level were gained in this work. A multi-disciplinary approach was used, based on individual-particle scanning electron microscopy with X-ray energy-dispersive microanalysis (SEM XEDS), X-ray diffraction (XRD) analysis of dust, size distribution of mineral particles, and radiative transfer modelling (RTM).The mineral composition of Rome lithogenic PM10 varies between an end-member dominated by silicate minerals and one exclusively composed of calcite. The first is obtained from volcanic lithotypes, the second from travertine or limestones; lithogenic PM10 with intermediate composition derives mainly from siliciclastic rocks or marlstones of Rome area. Size and mineral species of PM10 particles of silicate-dominated dust types are tuned mainly by weathering and, to lesser extent, by debris formation or crystallization; chemical precipitation of CaCO3 plays a major role in calcite-dominated types. These differences are evidenced by the diversity of volume distributions, within either dust types, or mineral species. Further differences are observed between volume distributions of calcite from travertine (natural source) and from road dust (anthropic source), specifically on the width, shape and enrichment of the fine fraction (unimodal at 5 μm a.d. for travertine, bimodal at 3.8 and 1.8 μm a.d. for road dust). Log-normal probability density functions of volcanics and travertine dusts affect differently the single scattering albedo (SSA) and the asymmetry parameter (g) in the VISible and Near Infrared (NIR) regions, depending also on the absorbing/non-absorbing character of volcanics and travertine, respectively. The downward component of the BOA solar irradiance simulated by RTM for a volcanics-rich or travertine-rich atmosphere shows that volcanics contribution to the solar

  8. Dust radiative effects on atmospheric thermodynamics and tropical cyclogenesis over the Atlantic Ocean using WRF-Chem coupled with an AOD data assimilation system

    NASA Astrophysics Data System (ADS)

    Chen, Dan; Liu, Zhiquan; Davis, Chris; Gu, Yu

    2017-06-01

    This study investigated the dust radiative effects on atmospheric thermodynamics and tropical cyclogenesis over the Atlantic Ocean using the Weather Research and Forecasting Model with Chemistry (WRF-Chem) coupled with an aerosol data assimilation (DA) system. MODIS AOD (aerosol optical depth) data were assimilated with the Gridpoint Statistical Interpolation (GSI) three-dimensional variational (3DVAR) DA scheme to depict the Saharan dust outbreak events in the 2006 summer. Comparisons with Ozone Monitoring Instrument (OMI), AErosol RObotic NETwork (AERONET), and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) observations showed that the system was capable of reproducing the dust distribution. Two sets of 180 h forecasts were conducted with the dust radiative effects activated (RE_ON) and inactivated (RE_OFF) respectively. Differences between the RE_ON and RE_OFF forecasts showed that low-altitude (high-altitude) dust inhibits (favors) convection owing to changes in convective inhibition (CIN). Heating in dust layers immediately above the boundary layer increases inhibition, whereas sufficiently elevated heating allows cooling above the boundary layer that reduces convective inhibition. Semi-direct effects in which clouds are altered by thermodynamic changes are also noted, which then alter cloud-radiative temperature (T) changes. The analysis of a tropical cyclone (TC) suppression case on 5 September shows evidence of enhanced convective inhibition by direct heating in dust, but it also suggests that the low-predictability dynamics of moist convection reduces the determinism of the effects of dust on timescales of TC development (days).

  9. Accounting for particle non-sphericity in modeling of mineral dust radiative properties in the thermal infrared

    NASA Astrophysics Data System (ADS)

    Legrand, M.; Dubovik, O.; Lapyonok, T.; Derimian, Y.

    2014-12-01

    Spectral radiative parameters (extinction optical depth, single scattering albedo, asymmetry factor) of spheroids of mineral dust composed of quartz and clays have been simulated at wavelengths between 7.0 and 10.2 μm using a T-matrix code. In spectral intervals with high values of complex index of refraction and for large particles, the parameters cannot be fully calculated with the code. Practically, the calculations are stopped at a truncation radius over which the particles contribution cannot thus be taken into account. To deal with this issue, we have developed and applied an accurate corrective technique of T-matrix Size Truncation Compensation (TSTC). For a mineral dust described by its AERONET standard aspect ratio (AR) distribution, the full error margin when applying the TSTC is within 0.3% (or ±0.15%), whatever the radiative parameter and the wavelength considered, for quartz (the most difficult case). Large AR values limit also the possibilities of calculation with the code. The TSTC has been able to complete the calculations of the T-matrix code for a modified AERONET AR distribution with a maximum AR of 4.7 instead of 3 for the standard distribution. Comparison between the simulated properties of spheroids and of spheres of same volume confirms, in agreement with the literature, that significant differences are observed in the vicinity of the mineral resonant peaks (λ ca. 8.3-8.7 μm for quartz, ca. 9.3-9.5 μm for clays) and that they are due to absorption by the small particles. This is a favorable circumstance for the TSTC, which is concerned with the contribution of the largest particles. This technique of numerical calculation improves the accuracy of the simulated radiative parameters of mineral dust, which must lead to a progress in view of applications such as remote sensing or determination of energy balance of dust in the thermal infrared (TIR), incompletely investigated so far.

  10. Improvement in Clouds and the Earth's Radiant Energy System/Surface and Atmosphere Radiation Budget Dust Aerosol Properties, Effects on Surface Validation of Clouds and Radiative Swath

    SciTech Connect

    Rutan, D.; Rose, F.; Charlock, T.P.

    2005-03-18

    Within the Clouds and the Earth's Radiant Energy System (CERES) science team (Wielicki et al. 1996), the Surface and Atmospheric Radiation Budget (SARB) group is tasked with calculating vertical profiles of heating rates, globally, and continuously, beneath CERES footprint observations of Top of Atmosphere (TOA) fluxes. This is accomplished using a fast radiative transfer code originally developed by Qiang Fu and Kuo-Nan Liou (Fu and Liou 1993) and subsequently highly modified by the SARB team. Details on the code and its inputs can be found in Kato et al. (2005) and Rose and Charlock (2002). Among the many required inputs is characterization of the vertical column profile of aerosols beneath each footprint. To do this SARB combines aerosol optical depth information from the moderate-resolution imaging spectroradiometer (MODIS) instrument along with aerosol constituents specified by the Model for Atmosphere and Chemical Transport (MATCH) of Collins et al. (2001), and aerosol properties (e.g. single scatter albedo and asymmetry parameter) from Tegen and Lacis (1996) and OPAC (Hess et al. 1998). The publicly available files that include these flux profiles, called the Clouds and Radiative Swath (CRS) data product, available from the Langley Atmospheric Sciences Data Center (http://eosweb.larc.nasa.gov/). As various versions of the code are completed, publishable results are named ''Editions.'' After CRS Edition 2A was finalized it was found that dust aerosols were too absorptive. Dust aerosols have subsequently been modified using a new set of properties developed by Andy Lacis and results have been released in CRS Edition 2B. This paper discusses the effects of changing desert dust aerosol properties, which can be significant for the radiation budget in mid ocean, a few thousand kilometers from the source regions. Resulting changes are validated via comparison of surface observed fluxes from the Saudi Solar Village surface site (Myers et al. 1999), and the E13 site

  11. Role of dust direct radiative effect on the tropical rain belt over Middle East and North Africa: A high-resolution AGCM study

    NASA Astrophysics Data System (ADS)

    Bangalath, Hamza Kunhu; Stenchikov, Georgiy

    2015-05-01

    To investigate the influence of direct radiative effect of dust on the tropical summer rain belt across the Middle East and North Africa (MENA), the present study utilizes the high-resolution capability of an Atmospheric General Circulation Model, the High-Resolution Atmospheric Model. Ensembles of Atmospheric Model Intercomparison Project style simulations have been conducted with and without dust radiative impacts, to differentiate the influence of dust on the tropical rain belt. The analysis focuses on summer season. The results highlight the role of dust-induced responses in global- and regional-scale circulations in determining the strength and the latitudinal extent of the tropical rain belt. A significant response in the strength and position of the local Hadley circulation is predicted in response to meridionally asymmetric distribution of dust and the corresponding radiative effects. Significant responses are also found in regional circulation features such as African Easterly Jet and West African Monsoon circulation. Consistent with these dynamic responses at various scales, the tropical rain belt across MENA strengthens and shifts northward. Importantly, the summer precipitation over the semiarid strip south of Sahara, including Sahel, increases up to 20%. As this region is characterized by the "Sahel drought," the predicted precipitation sensitivity to the dust loading over this region has a wide range of socioeconomic implications. Overall, the study demonstrates the extreme importance of incorporating dust radiative effects and the corresponding circulation responses at various scales, in the simulations and future projections of this region's climate.

  12. Surface spin-polarized currents generated in topological insulators by circularly polarized synchrotron radiation and their photoelectron spectroscopy indication

    NASA Astrophysics Data System (ADS)

    Shikin, A. M.; Klimovskikh, I. I.; Filyanina, M. V.; Rybkina, A. A.; Pudikov, D. A.; Kokh, K. A.; Tereshchenko, O. E.

    2016-08-01

    A new method for generating spin-polarized currents in topological insulators has been proposed and investigated. The method is associated with the spin-dependent asymmetry of the generation of holes at the Fermi level for branches of topological surface states with the opposite spin orientation under the circularly polarized synchrotron radiation. The result of the generation of holes is the formation of compensating spin-polarized currents, the value of which is determined by the concentration of the generated holes and depends on the specific features of the electronic and spin structures of the system. The indicator of the formed spin-polarized current can be a shift of the Fermi edge in the photoelectron spectra upon photoexcitation by synchrotron radiation with the opposite circular polarization. The topological insulators with different stoichiometric compositions (Bi1.5Sb0.5Te1.8Se1.2 and PbBi2Se2Te2) have been investigated. It has been found that there is a correlation in the shifts and generated spin-polarized currents with the specific features of the electronic spin structure. Investigations of the graphene/Pt(111) system have demonstrated the possibility of using this method for other systems with a spin-polarized electronic structure.

  13. The impact of Dust Storms on both Solar Radiation and Sky temperature in Tabouk Saudi Arabia, theoretical Investigations

    NASA Astrophysics Data System (ADS)

    Maghrabi, Abdullrahman

    2016-04-01

    Dust particles affect both solar and terrestrial radiation by scattering and absorption and are therefore considered to be a significant climate-forcing factor. Dust storms are a very frequent phenomenon in Saudi Arabia. Several dust storm events occurred in Tabouk, northern region of Saudi Arabia, during the period between 2014-2015. In this study, simulations using the SMART model were conducted to investigate how the dusty conditions affected the solar irradiances during these events. Additionally, theoretical simulations were carried out using MODTRAN program to examine the changes in the infrared sky temperature during dusty conditions. The Atmospheric Optical Depth (AOD) measurements at (500 nm) were used as an input into both programs. The analysis showed that the dusty conditions significantly decrease the global and direct irradiances and increase the diffuse component compared with clear sky days. Also it was found that the dust storms increase the sky temperature in the atmospheric window (8-14 μm) such that the window emissions resembled those of a blackbody and the atmospheric window was almost closed.

  14. Spectroscopy of diffuse light in dust clouds. Scattered light and the solar neighbourhood radiation field

    NASA Astrophysics Data System (ADS)

    Lehtinen, K.; Mattila, K.

    2013-01-01

    Context. The optical surface brightness of dark nebulae is mainly due to scattering of integrated starlight by classical dust grains. It contains information on the impinging interstellar radiation field, cloud structure, and grain scattering properties. We have obtained spectra of the scattered light from 3500 to 9000 Å in two globules, the Thumbprint Nebula and DC 303.8-14.2. Aims. We use observations of the scattered light to study the impinging integrated starlight spectrum as well as the scattered Hα and other line emissions from all over the sky. We search also for the presence of other than scattered light in the two globules. Methods. We obtained long-slit spectra encompassing the whole globule plus adjacent sky in a one-slit setting, thus enabling efficient elimination of airglow and other foreground sky components. We calculated synthetic integrated starlight spectra for the solar neighbourhood using HIPPARCOS-based stellar distributions and the spectral library of Pickles. Results. Spectra are presented separately for the bright rims and dark cores of the globules. The continuum spectral energy distributions and absorption line spectra can be well modelled with the synthetic integrated starlight spectra. Emission lines of Hα +[N II], Hβ, and [S II] are detected and are interpreted in terms of scattered light plus an in situ warm ionized medium component behind the globules. We detected an excess of emission over the wavelength range 5200-8000 Å in DC 303.8-14.2 but the nature of this emission remains open. Based on observations collected at the European Southern Observatory, Chile, under programme ESO No. 073.C-0239(A). Appendix A is available in electronic form at http://www.aanda.org.

  15. The thermal structure of the atmospheric surface boundary layer on Mars as modified by the radiative effect of aeolian dust

    NASA Technical Reports Server (NTRS)

    Pallmann, A. J.

    1983-01-01

    A computational simulation, based on Mariner 9 data, was performed for the thermal characteristics of the Martian atmospheric surface boundary layer in clear and dust-filled conditions. A radiative transfer model consisting of the atmospheric enthalpy rate equation, the radiative flux integrated over the 0.2-50 microns, the solid angle interval, and 0.50 km altitudes, broken into 52 levels. Mariner 9 IR data for CO2 absorption lines were included in the form of a temperture-dependent equation, while the line-widths were interpreted in terms of the pressure dependene as well as temperature. The lines covered the regions from 1-50 microns and varying conditions of dust content in the atmosphere. Attention was given to the thermal coupling between the ground and the atmosphere. It was found that convective heat exchange develops quickly due to radiative heating of the Martian desert surface, but does not cool the surface because of the attenuated atmosphere. The model predictd the 100 K temperature variations in the dusty atmosphere, as observed by the Viking thermal mapper. It is suggested that radiative flux convergence is as important as convection at equivalent efficiencies.

  16. Experimental determination of short- and long-wave dust radiative effects in the Central Mediterranean and comparison with model results

    NASA Astrophysics Data System (ADS)

    Romano, S.; Burlizzi, P.; Perrone, M. R.

    2016-05-01

    Downward and upward irradiance measurements, in the short-wave (SW) and long-wave (LW) spectral range, have been used in combination with simultaneous aerosol optical depths (AODs) to experimentally determine the instantaneous and clear-sky aerosol Direct Radiative Forcing (DRF) at the surface, during a desert dust outbreak which affected the Central Mediterranean from 9 to 13 July 2012. AODs were retrieved from AERONET (AErosol RObotic NETwork) sun/sky photometer measurements collocated in space and time. The importance of downward and upward radiative flux measurements to properly account for both the surface albedo dependence on the solar zenith angle, and the land surface temperature (TLS) has been highlighted. Measured radiative fluxes were in reasonable agreement with the CERES (Clouds and the Earth's Radiant Energy System) and AERONET corresponding ones collocated in space and time. SW and LW downward fluxes at the surface decreased up to 9% and increased up to 13%, respectively, as a consequence of a factor 5 increase of the AOD at 675 nm (AOD675). This is due to the cooling and warming effect of desert dust in the SW and LW spectral range, respectively. In fact, we have also found that the TLS increased at a rate of about 250 K per unit increase of the AOD675. The aerosol DRF at the surface varied from - 8 to - 74 W m- 2 and from + 1.2 to + 9.6 W m- 2 in the SW and LW spectral domains, respectively. In particular, we have found that the LW-DRF on average offsets 14% of the related SW component. It is shown that a two-stream radiative transfer model can reproduce the experimental findings at the surface by replacing the refractive indices typical of dust particles with the ones obtained for a mixture made of dust and soot particles. The dust contamination by anthropogenic particles during its transport to the monitoring site located several hundred kilometers away from the source region was responsible for this last result. We have also found by model

  17. Modeling Mineral Dust and Accessing Its Impact on Radiative Forcing over East Asia

    NASA Astrophysics Data System (ADS)

    Dong, X.

    2015-12-01

    East Asia dust storm has been investigated with revised WRF/CMAQ modeling system in this study. Taklamkan and Gobi deserts in China and Mongolia are the major contributors for East Asia dust storm, which significantly affect air quality and regional climate over downwind areas in China, Japan and Korea. Understanding the mixing of dust and intensive anthropogenic emissions would require a regional chemistry transport model which can simulate both the emission and transport of the natural and anthropogenic particles, and also their chemical interactions as well as the particles evolutions. In this study, we conducted model development of the WRF/CMAQ modeling system by revising the dust emission scheme and implementing source-dependent speciation profiles of dust aerosol and heterogeneous chemistry. With the revised modeling system, East Asia dust impact on atmospheric chemistry and regional climate has been investigated for the period of March and April from 2006 to 2010. The revised modeling system has been demonstrated to greatly improve model's capability of reproducing dust emission and transport over East Asia by comparing with surface measurements and satellite observations.

  18. Mineral composition of TALDICE aeolian ice core dust by means of synchrotron radiation XAS and XRF techniques

    NASA Astrophysics Data System (ADS)

    Marcelli, A.; Cibin, G.; Sala, M.; Hampai, D.; Maggi, V.; Marino, F.; Delmonte, B.

    2009-04-01

    In this work we present the first accurate non-destructive comparison of the mineral composition of atmospheric dusts contained in a deep ice core from Antarctica using synchrotron radiation. Different mineral assemblages reaching glaciated areas could be correlated to sources areas starting from the knowledge of the dust composition. In this investigation we demonstrate the possibility to characterize with SR the mineral composition of the dust in order to perform its geochemical characterization and to understand the pattern of the transport and the trajectories of the aerosol. This study has been focused on the elemental characterization and the identification of the iron oxidation state of aeolian Antarctic dust by means of synchrotron radiation X-Ray Fluorescence and X-Ray Absorption Spectroscopy. A set of twelve ice samples from the TALDICE (TD, 72˚ 46'S, 159˚ 04'E, 2316 m a.s.l., mean accumulation rate 80 kg*m-2*yr-1) ice core, corresponding to the warm climatic period, Holocene, and to the cold climatic period, Marine Isotopic Stage 3 (MIS 3) have been measured. To obtain both the elemental composition and the iron oxidation state of the mineral dust we performed experiments on specially prepared samples at the Stanford Synchrotron Radiation Lightsource (SSRL) laboratory in the framework of the Proposal N.3082B. Actually, melted ice samples were filtered and then mineral particles were deposited onto Nuclepore polycarbonate membranes in a 1000 class clean room under a 100 class laminar flow bench for both XRF and XAS experiments. A dedicated HV experimental chamber, that allows performing different type of experimental technique on very low absorber concentration samples was developed and tested in Italy. The original experimental setup, including an in-vacuum sample micromanipulator and a special alignment and docking sample system was installed at the beamline 10-2 at SSRL. For the x-ray detection a 7 mm2 high sensitive Silicon Drift Detector was

  19. Mariner-9 based simulation of radiative convective temperature changes in the Martian dust-laden atmosphere-soil system

    NASA Technical Reports Server (NTRS)

    Dannevik, W. P.; Pallmann, A. J.

    1974-01-01

    A numerical simulation of radiative, conductive, and convective heat transfer of the Martian dust-laden atmosphere-soil system is presented with particular emphasis given to heating/cooling in regions of sharp variation in temperature or absorption and its resultant impact on outgoing planetary spectral radiance, as measured by the Mariner 9 IRIS. Thermal coupling between the ground and atmospheric subsystems is modeled by the total heat flux balance at the interface. In the simulation procedure, local thermodynamic equilibrium (LTE) is assumed, and a combined strong-weak line transmission function permits short- and long-range exchanges of energy from the surface toward space. Direct absorption of insolation in the near-IR bands by both silicate dust and CO2 is incorporated.

  20. Iron oxide minerals in dust-source sediments from the Bodélé Depression, Chad: Implications for radiative properties and Fe bioavailability of dust plumes from the Sahara

    NASA Astrophysics Data System (ADS)

    Moskowitz, Bruce M.; Reynolds, Richard L.; Goldstein, Harland L.; Berquó, Thelma S.; Kokaly, Raymond F.; Bristow, Charlie S.

    2016-09-01

    Atmospheric mineral dust can influence climate and biogeochemical cycles. An important component of mineral dust is ferric oxide minerals (hematite and goethite) which have been shown to influence strongly the optical properties of dust plumes and thus affect the radiative forcing of global dust. Here we report on the iron mineralogy of dust-source samples from the Bodélé Depression (Chad, north-central Africa), which is estimated to be Earth's most prolific dust producer and may be a key contributor to the global radiative budget of the atmosphere as well as to long-range nutrient transport to the Amazon Basin. By using a combination of magnetic property measurements, Mössbauer spectroscopy, reflectance spectroscopy, chemical analysis, and scanning electron microscopy, we document the abundance and relative amounts of goethite, hematite, and magnetite in dust-source samples from the Bodélé Depression. The partition between hematite and goethite is important to know to improve models for the radiative effects of ferric oxide minerals in mineral dust aerosols. The combination of methods shows (1) the dominance of goethite over hematite in the source sediments, (2) the abundance and occurrences of their nanosize components, and (3) the ubiquity of magnetite, albeit in small amounts. Dominant goethite and subordinate hematite together compose about 2% of yellow-reddish dust-source sediments from the Bodélé Depression and contribute strongly to diminution of reflectance in bulk samples. These observations imply that dust plumes from the Bodélé Depression that are derived from goethite-dominated sediments strongly absorb solar radiation. The presence of ubiquitous magnetite (0.002-0.57 wt%) is also noteworthy for its potentially higher solubility relative to ferric oxide and for its small sizes, including PM < 0.1 μm. For all examined samples, the average iron apportionment is estimated at about 33% in ferric oxide minerals, 1.4% in magnetite, and 65% in

  1. Iron oxide minerals in dust-source sediments from the Bodélé Depression, Chad: Implications for radiative properties and Fe bioavailability of dust plumes from the Sahara

    USGS Publications Warehouse

    Moskowitz, Bruce M; Reynolds, Richard; Goldstein, Harland; Beroquo, Thelma; Kokaly, Raymond; Bristow, Charlie S

    2016-01-01

    Atmospheric mineral dust can influence climate and biogeochemical cycles. An important component of mineral dust is ferric oxide minerals (hematite and goethite) which have been shown to influence strongly the optical properties of dust plumes and thus affect the radiative forcing of global dust. Here we report on the iron mineralogy of dust-source samples from the Bodélé Depression (Chad, north-central Africa), which is estimated to be Earth’s most prolific dust producer and may be a key contributor to the global radiative budget of the atmosphere as well as to long-range nutrient transport to the Amazon Basin. By using a combination of magnetic property measurements, Mössbauer spectroscopy, reflectance spectroscopy, chemical analysis, and scanning electron microscopy, we document the abundance and relative amounts of goethite, hematite, and magnetite in dust-source samples from the Bodélé Depression. The partition between hematite and goethite is important to know to improve models for the radiative effects of ferric oxide minerals in mineral dust aerosols. The combination of methods shows (1) the dominance of goethite over hematite in the source sediments, (2) the abundance and occurrences of their nanosize components, and (3) the ubiquity of magnetite, albeit in small amounts. Dominant goethite and subordinate hematite together compose about 2% of yellow-reddish dust-source sediments from the Bodélé Depression and contribute strongly to diminution of reflectance in bulk samples. These observations imply that dust plumes from the Bodélé Depression that are derived from goethite-dominated sediments strongly absorb solar radiation. The presence of ubiquitous magnetite (0.002–0.57 wt%) is also noteworthy for its potentially higher solubility relative to ferric oxide and for its small sizes, including PM < 0.1 μm. For all examined samples, the average iron apportionment is estimated at about 33% in ferric oxide minerals, 1.4% in magnetite, and 65

  2. Earth radiation budget measurement from a spinning satellite: Conceptual design of detectors

    NASA Technical Reports Server (NTRS)

    Sromovsky, L. A.; Revercomb, H. E.; Suomi, V. E.

    1975-01-01

    The conceptual design, sensor characteristics, sensor performance and accuracy, and spacecraft and orbital requirements for a spinning wide-field-of-view earth energy budget detector were investigated. The scientific requirements for measurement of the earth's radiative energy budget are presented. Other topics discussed include the observing system concept, solar constant radiometer design, plane flux wide FOV sensor design, fast active cavity theory, fast active cavity design and error analysis, thermopile detectors as an alternative, pre-flight and in-flight calibration plane, system error summary, and interface requirements.

  3. Spin zero Hawking radiation for non-zero-angular momentum mode

    SciTech Connect

    Ngampitipan, Tritos; Bonserm, Petarpa; Visser, Matt

    2015-05-15

    Black hole greybody factors carry some quantum black hole information. Studying greybody factors may lead to understanding the quantum nature of black holes. However, solving for exact greybody factors in many black hole systems is impossible. One way to deal with this problem is to place some rigorous analytic bounds on the greybody factors. In this paper, we calculate rigorous bounds on the greybody factors for spin zero hawking radiation for non-zero-angular momentum mode from the Kerr-Newman black holes.

  4. Radiative forcing by dust and black carbon in snow of High Mountain Asia: Implications for glaciers and water resources

    NASA Astrophysics Data System (ADS)

    Painter, Thomas; Qian, Yun

    2017-04-01

    Snow and ice of High Mountain Asia provide critical freshwater supply to over a billion people and provide climate influence through higher albedo and lower thermal conductivity. High Mountain Asia holds the greatest amount of ice outside of Earth's polar region and as such has great potential to contribute to sea level rise. Snow cover and glaciers have been in general negative trend across the Anthropocene, yet there are large uncertainties in the scale of that retreat, the magnitude of the resulting contribution to sea-level rise, and in particular the causes. Our overarching science goal is to better understand the physical processes that are driving changes in High Mountain Asia snow and ice. Here, we present analysis of our NASA remote sensing retrievals of radiative forcing by dust and black carbon in snow and ice from MODIS, VIIRS, and Landsat 8 in the study domain of the NASA High Mountain Asia program. We also evaluate the simulations of radiative forcing by impurities in snow from the Weather Research and Forecasting (WRF) model coupled with its chemistry component (Chem), the land surface scheme of the Community Land Model (CLM), and the snow, ice, and aerosol radiative transfer model SNICAR. The unique suite of remote sensing products are (1) the MODIS Snow Covered Area and Grain size (MODSCAG) from which we calculate fractional snow covered area and the spatial bulk surface snow grain size of that fractional cover, and (2) the MODIS Dust Radiative Forcing in Snow (MODDRFS) from which we calculate clear-sky radiative forcing by impurities in snow. The analysis will be cast in context of our understanding of at-surface radiative forcing by anomalies in greenhouse gases and give us insight into the controls on snow and glacier retreat.

  5. Influence of the vertical absorption profile of mixed Asian dust plumes on aerosol direct radiative forcing over East Asia

    NASA Astrophysics Data System (ADS)

    Noh, Young Min; Lee, Kwonho; Kim, Kwanchul; Shin, Sung-Kyun; Müller, Detlef; Shin, Dong Ho

    2016-08-01

    We estimate the aerosol direct radiative forcing (ADRF) and heating rate profiles of mixed East Asian dust plumes in the solar wavelength region ranging from 0.25 to 4.0 μm using the Santa Barbara Discrete Ordinate Atmospheric Radiative Transfer (SBDART) code. Vertical profiles of aerosol extinction coefficients and single-scattering albedos (SSA) were derived from measurements with a multi-wavelength Raman lidar system. The data are used as input parameters for our radiative transfer calculations. We considered four cases of radiative forcing in SBDART: 1. dust, 2. pollution, 3. mixed dust plume and the use of vertical profiles of SSA, and 4. mixed dust plumes and the use of column-averaged values of SSA. In our sensitivity study we examined the influence of SSA and aerosol layer height on our results. The ADRF at the surface and in the atmosphere shows a small dependence on the specific shape of the aerosol extinction vertical profile and its light-absorption property for all four cases. In contrast, at the top of the atmosphere (TOA), the ADRF is largely affected by the vertical distribution of the aerosols extinction. This effect increases if the light-absorption capacity (decrease of SSA) of the aerosols increases. We find different radiative effects in situations in which two layers of aerosols had different light-absorption properties. The largest difference was observed at the TOA for an absorbing aerosol layer at high altitude in which we considered in one case the vertical profile of SSA and in another case the column-averaged SSA only. The ADRF at the TOA increases when the light-absorbing aerosol layer is located above 3 km altitude. The differences between height-resolved SSA, which can be obtained from lidar data, and total layer-mean SSA indicates that the use of a layer-mean SSA can be rather misleading as it can induce a large error in the calculation of the ADRF at the TOA, which in turn may cause errors in the vertical profiles of heating rates.

  6. A GCM study of the response of the atmospheric water cycle of West Africa and the Atlantic to Saharan dust radiative forcing

    NASA Astrophysics Data System (ADS)

    Lau, K. M.; Kim, K. M.; Sud, Y. C.; Walker, G. K.

    2009-10-01

    The responses of the atmospheric water cycle and climate of West Africa and the Atlantic to radiative forcing of Saharan dust are studied using the NASA finite volume general circulation model (fvGCM), coupled to a mixed layer ocean. We find evidence of an "elevated heat pump" (EHP) mechanism that underlines the responses of the atmospheric water cycle to dust forcing as follow. During the boreal summer, as a result of large-scale atmospheric feedback triggered by absorbing dust aerosols, rainfall and cloudiness are enhanced over the West Africa/Eastern Atlantic ITCZ, and suppressed over the West Atlantic and Caribbean region. Shortwave radiation absorption by dust warms the atmosphere and cools the surface, while longwave has the opposite response. The elevated dust layer warms the air over West Africa and the eastern Atlantic. As the warm air rises, it spawns a large-scale onshore flow carrying the moist air from the eastern Atlantic and the Gulf of Guinea. The onshore flow in turn enhances the deep convection over West Africa land, and the eastern Atlantic. The condensation heating associated with the ensuing deep convection drives and maintains an anomalous large-scale east-west overturning circulation with rising motion over West Africa/eastern Atlantic, and sinking motion over the Caribbean region. The response also includes a strengthening of the West African monsoon, manifested in a northward shift of the West Africa precipitation over land, increased low-level westerly flow over West Africa at the southern edge of the dust layer, and a near surface westerly jet underneath the dust layer over the Sahara. The dust radiative forcing also leads to significant changes in surface energy fluxes, resulting in cooling of the West African land and the eastern Atlantic, and warming in the West Atlantic and Caribbean. The EHP effect is most effective for moderate to highly absorbing dusts, and becomes minimized for reflecting dust with single scattering albedo at 0

  7. A GCM Study of Responses of the Atmospheric Water Cycle of West Africa and the Atlantic to Saharan Dust Radiative Forcing

    NASA Technical Reports Server (NTRS)

    Lau, K. M.; Kim, K. M.; Sud, Y. C.; Walker, G. K.

    2009-01-01

    The responses of the atmospheric water cycle and climate of West Africa and the Atlantic to radiative forcing of Saharan dust are studied using the NASA finite volume general circulation model (fvGCM), coupled to a mixed layer ocean. We find evidence of an "elevated heat pump" (EHP) mechanism that underlines the responses of the atmospheric water cycle to dust forcing as follow. During the boreal summerr, as a result of large-scale atmospheric feedback triggered by absorbing dust aerosols, rainfall and cloudiness are ehanIed over the West Africa/Eastern Atlantic ITCZ, and suppressed over the West Atlantic and Caribbean region. Shortwave radiation absorption by dust warms the atmosphere and cools the surface, while longwave has the opposite response. The elevated dust layer warms the air over West Africa and the eastern Atlantic. As the warm air rises, it spawns a large-scale onshore flow carrying the moist air from the eastern Atlantic and the Gulf of Guinea. The onshore flow in turn enhances the deep convection over West Africa land, and the eastern Atlantic. The condensation heating associated with the ensuing deep convection drives and maintains an anomalous large-scale east-west overturning circulation with rising motion over West Africa/eastern Atlantic, and sinking motion over the Caribbean region. The response also includes a strengthening of the West African monsoon, manifested in a northward shift of the West Africa precipitation over land, increased low-level westerlies flow over West Africa at the southern edge of the dust layer, and a near surface westerly jet underneath the dust layer overr the Sahara. The dust radiative forcing also leads to significant changes in surface energy fluxes, resulting in cooling of the West African land and the eastern Atlantic, and warming in the West Atlantic and Caribbean. The EHP effect is most effective for moderate to highly absorbing dusts, and becomes minimized for reflecting dust with single scattering albedo at0

  8. Modeling the Transport and Radiative Forcing of Taklimakan Dust over the Tibetan Plateau: A case study in the summer of 2006

    SciTech Connect

    Chen, Siyu; Huang, J.; Zhao, Chun; Qian, Yun; Leung, Lai-Yung R.; Yang, Ben

    2013-01-30

    The Weather Research and Forecasting model with chemistry (WRF-Chem) is used to investigate an intense dust storm event during 26 to 30 July 2006 that originated over the Taklimakan Desert (TD) and transported to the northern slope of Tibetan Plateau (TP). The dust storm is initiated by the approach of a strong cold frontal system over the TD. In summer, the meridional transport of TD dust to the TP is favored by the thermal effect of the TP and the weakening of the East Asian westerly winds. During this dust storm, the transport of TD dust over the TP is further enhanced by the passage of the cold front. As a result, TD dust breaks through the planetary boundary layer and extends to the upper troposphere over the northern TP. TD dust flux arrived at the TP with a value of 6.6 Gg/day in this 5 day event but decays quickly during the southward migration over the TP due to dry deposition. The simulations show that TD dust cools the atmosphere near the surface and heats the atmosphere above with a maximum heating rate of 0.11 K day-1 at ~7 km over the TP. The event-averaged net radiative forcings of TD dust over the TP are -3.97, 1.61, and -5.58 Wm-2 at the top of the atmosphere (TOA), in the atmosphere, and at the surface, respectively. The promising performance of WRF-Chem in simulating dust and its radiative forcing provides confidence for use in further investigation of climatic impact of TD dust over the TP.

  9. Saharan Desert Dust Radiative Impact On The Evolution of The Vertical Thermal Characteristics of The Atmosphere Over The Mediterranean

    NASA Astrophysics Data System (ADS)

    Iori, C.; Liberti, G. L.

    The passage of Saharan dust over the Mediterranean basin, represents the most in- tense and relatively frequent event for what concerns the tropospheric aerosols in that region. Transport of the crustal dusts from the Saharan surface to the mean Mediter- ranean troposphere happens inside air volumes belonging to the superficial layers of the Sahara desert. As a consequence, it is associated with anomalies both in the verti- cal thermodynamic structure as well as in the composition. The first one is due to the avvection of air volumes geographically and vertically belonging to a different region. The second one is due to the composition of the air volumes (water vapour, ozone and aerosol) different from the one of the unperturbed status. Due to the occurence of such anomalies a perturbation in the radiative balance is also expected, because of the in- teraction of water vapour, ozone and aerosol with the atmospheric radiation field and hence with the radiative balance of earth-atmosphere system. This study examine the relative contribution of radiative processes in the evolution of the vertical structure of the atmosphere during the occurence of a desert dust transport event (18-5-1999). In order to do that radiosoundings from a set of stations around the Mediterranean Sea as well as in the source area have been analysed for the spring 1999 to define a mean sta- tus and succesively characterize quantitatively the anomaly associated with the event. In parallel detailed description of vertical properties of the aerosols as well as of the other parameters of interest, available from the PAUR II campaign [Kourtidis et al., 2000], has been employed for computing with the CLIRAD RTM [Chou and Suarez 1999; Chou and Suarez 2001] the heating/cooling rate profiles. Computation have been performed for a day in presence of aerosol as well as for a relatively clear day in order to evaluate the desert dust contribution on the overall radiative effects. A detailed analysis of the

  10. An Assessment of the Surface Longwave Direct Radiative Effect of Airborne Dust in Zhangye China During the Asian Monsoon Year Field Experiment (2008)

    NASA Technical Reports Server (NTRS)

    Hansell, Richard A.; Tsay, Si-Chee; Hsu, N. Christina; Ji, Qiang; Bell, Shaun W.; Holben, Brent N.; Ellsworth, Welton J.; Roush, Ted L.; Zhang, Wu; Huang, J.; hide

    2012-01-01

    Tiny suspensions of solid particles or liquid droplets, called aerosols, hover in earth's atmosphere and can be found over just about anywhere including oceans, deserts, vegetated areas, and other global regions. Aerosols come in a variety of sizes, shapes, and compositions which depend on such factors as their origin and how long they have been in the atmosphere (i.e., their residence time). Some of the more common types of aerosols include mineral dust and sea salt which get lifted from the desert and ocean surfaces, respectively by mechanical forces such as strong winds. Depending on their size, aerosols will either fall out gravitationally, as in the case of larger particles, or will remain resident in the atmosphere where they can undergo further change through interactions with other aerosols and cloud particles. Not only do aerosols affect air quality where they pose a health risk, they can also perturb the distribution of radiation in the earth-atmosphere system which can inevitably lead to changes in our climate. One aerosol that has been in the forefront of many recent studies, particularly those examining its radiative effects, is mineral dust. The large spatial coverage of desert source regions and the fact that dust can radiatively interact with such a large part of the electromagnetic spectrum due to its range in particle size, makes it an important aerosol to study. Dust can directly scatter and absorb solar and infrared radiation which can subsequently alter the amount of radiation that would otherwise be present in the absence of dust at any level of the atmosphere like the surface. This is known as radiative forcing. At the surface dust can block incoming solar energy, however at infrared wavelengths, dust acts to partially compensate the solar losses. Evaluating the solar radiative effect of dust aerosols is relatively straightforward due in part to the relatively large signal-to-noise ratio in the measurements. At infrared wavelengths, on the

  11. Earth Reflected Solar Radiation Incident upon an Arbitrarily Oriented Spinning Flat Plate

    NASA Technical Reports Server (NTRS)

    Cunningham, Fred G.

    1963-01-01

    A general derivation is given for the earth reflected solar radiation input to a flat plate--a solar cell paddle, for example--which is spinning about an axis coincident with the axis of symmetry of the satellite to which it is affixed. The resulting equations are written for the general case so that arbitrary orientations of the spin axis with respect to the earth-satellite line and arbitrary orientations of the normal to the plate with respect to the spin axis can be treated. No attempt is made to perform the resulting integrations because of the complexity of the equations; nor is there any attempt to delineate the integration limits for the general case. However, the equations governing these limits are given. The appendixes contain: the results, in graphical form, of two representative examples; the general computer program for the calculation is given in Fortran notation; and the results of a calculation of the distribution of albedo energy on the proposed Echo II satellite. The value of the mean solar constant used is 1.395 times 10 (sup 4) ergs per centimeters-squared per second; the mean albedo of the earth is assumed to be 0.34; and the earth is assumed to be a diffuse reflector.

  12. Assessment of Clear Sky Radiative Forcing in the Caribbean Region Using an Aerosol Dispersion Model and Ground Radiometry During Puerto Rico Dust Experiment

    NASA Technical Reports Server (NTRS)

    Gasso, Santiago; Qi, Qiang; Westpthal, Douglas; Reid, Jeffery; Tsay, Si-Chee

    2004-01-01

    This study investigates the surface and top of the atmosphere solar radiative forcing by long-range transport of Saharan dust. The calculations of radiative forcing are based on measurements collected in the Puerto Rico Dust Experiment (PRIDE) carried out during July, 2000. The purpose of the experiment was the characterization of the Saharan dust plume, which frequently reaches the Caribbean region during the summer. The experiment involved the use of three approaches to study the plume: space and ground based remote sensing, airborne and ground based in-situ measurements and aerosol dispersion modeling. The diversity of measuring platforms provides an excellent opportunity for determination of the direct effect of dust on the clear sky radiative forcing. Specifically, comparisons of heating rates, surface and TOA fluxes derived from the Navy global aerosol dispersion model NAAPS (NRL Aerosol Analysis and Prediction System) and actual measurements of fluxes from ground and space based platforms are shown. In addition, the direct effect of dust on the clear sky radiative forcing is modeled. The extent and time of evolution of the radiative properties of the plume are computed with the aerosol concentrations modeled by NAAPS. Standard aerosol parameterizations, as well as in-situ composition and size distributions measured during PRIDE, are utilized to compute the aerosol optical depth, single scattering albedo and asymmetry factor. Radiative transfer computations are done with an in-house modified spectral radiative transfer code (Fu-Liou). The code includes gas absorption and cloud particles (ice and liquid phase) and it allows the input of meteorological data. The code was modified to include modules for the aerosols contribution to the calculated fluxes. This comparison study helps to narrow the current uncertainty in the dust direct radiative forcing, as recently reported in the 2001 IPCC assessment.

  13. Assessment of Clear Sky Radiative Forcing in the Caribbean Region Using an Aerosol Dispersion Model and Ground Radiometry During Puerto Rico Dust Experiment

    NASA Technical Reports Server (NTRS)

    Gasso, Santiago; Qi, Qiang; Westpthal, Douglas; Reid, Jeffery; Tsay, Si-Chee

    2004-01-01

    This study investigates the surface and top of the atmosphere solar radiative forcing by long-range transport of Saharan dust. The calculations of radiative forcing are based on measurements collected in the Puerto Rico Dust Experiment (PRIDE) carried out during July, 2000. The purpose of the experiment was the characterization of the Saharan dust plume, which frequently reaches the Caribbean region during the summer. The experiment involved the use of three approaches to study the plume: space and ground based remote sensing, airborne and ground based in-situ measurements and aerosol dispersion modeling. The diversity of measuring platforms provides an excellent opportunity for determination of the direct effect of dust on the clear sky radiative forcing. Specifically, comparisons of heating rates, surface and TOA fluxes derived from the Navy global aerosol dispersion model NAAPS (NRL Aerosol Analysis and Prediction System) and actual measurements of fluxes from ground and space based platforms are shown. In addition, the direct effect of dust on the clear sky radiative forcing is modeled. The extent and time of evolution of the radiative properties of the plume are computed with the aerosol concentrations modeled by NAAPS. Standard aerosol parameterizations, as well as in-situ composition and size distributions measured during PRIDE, are utilized to compute the aerosol optical depth, single scattering albedo and asymmetry factor. Radiative transfer computations are done with an in-house modified spectral radiative transfer code (Fu-Liou). The code includes gas absorption and cloud particles (ice and liquid phase) and it allows the input of meteorological data. The code was modified to include modules for the aerosols contribution to the calculated fluxes. This comparison study helps to narrow the current uncertainty in the dust direct radiative forcing, as recently reported in the 2001 IPCC assessment.

  14. Physical and Radiative Properties of Aerosol Particles in the Caribbean: Influence of African Dust and Soufriere Volcanic Ash

    NASA Astrophysics Data System (ADS)

    Villanueva-Birriel, C. M.; Mayol-Bracero, O. L.; Sheridan, P.; Ogren, J. A.

    2007-12-01

    Atmospheric particles such as dust and volcanic ash have the potential of influencing the earth's radiative budget directly by scattering or absorbing solar radiation in the atmosphere and indirectly by affecting cloud condensation nuclei (CCN) concentrations and, therefore, cloud albedo. The radiatively-important properties of atmospheric particles are determined at the most fundamental level by their chemical composition and size distributions; therefore, the importance of studying the chemical, physical, and optical aerosol properties. Over the summer months, the island of Puerto Rico receives African dust incursions that reduce visibility and have an impact on public health, ecosystem, and climate. Visibility is also negatively affected when the island receives south-east winds and the Soufriere volcano (Montserrat Island) has been active. Here we present preliminary results of measurements performed during 2006 and 2007 at Cape San Juan, a ground-based station located at the northeastern tip of Puerto Rico. The cases investigated showed three possible types of air masses: clean (C), with African Dust (AD), and with volcanic ash (VA) from the Soufriere. We used a condensation particle counter to determine the particle number concentration, a sunphotometer (part of the AERONET) to determine volume size distributions and aerosol optical thickness (AOT), a 3-wavelength nephelometer to determine the scattering coefficients, and a 3-wavelength particle/soot absorption photometer (PSAP) for the absorption coefficients. The particle number concentrations were higher for AD and VA periods (up to about 700 cm-3 on average for both cases) in contrast to ~400 cm-3 for the C period. Volume size distributions showed bimodal distributions for the three cases with a greater influence of the coarse fraction for the C and VA periods and an increase in the fine particles for the AD period. The total scattering coefficient showed higher values for the AD (30 Mm-1) and the VA (26

  15. Radiative Lifetime for Nuclear Spin Conversion of Water-Ion H_2O^+

    NASA Astrophysics Data System (ADS)

    Tanaka, Keiichi; Harada, Kensuke; Oka, Takeshi

    2013-06-01

    Nuclear spin conversion interaction of the water ion, H_2O^+, has been studied to derive the spontaneous emission lifetime between the ortho- and para-levels. The H_2O^+ ion is a radical with ^2 B _1 electronic ground state and the off-diagonal electron spin-nuclear spin interaction term, T_{ab} (S_aΔ I_b + S_bΔ I_a), connects para and ortho levels, because Δ {I} = {I}_1 - {I}_2 has nonvanishing matrix elements between I = 0 and 1. The T_{ab} coupling constant, derived by an ab initio calculation in MRD-CI/Bk level to be 72 MHz, is larger than that of H_2O by 4 orders of magnitude, makes the ortho to para conversion of H_2O^+ faster than that of H_2O by 8 orders of magnitude and possibly competitive with other astrophysical processes. Last year we reported ortho and para coupling channels below 900 cm^{-1} caused by accidental near degeneracy of rotational levels. For example, hyperfine components of the 4_{2,2}(o) and 3_{3,0}(p) levels mix each other by 1.2 x 10^{-3} due to the near degeneracy (Δ E = 0.417 cm^{-1}), but the lower lying 1_{0,1}(p) and 1_{1,1}(o) levels mix only by 8.9 x 10^{-5} because of their large separation (Δ E = 16.27 cm^{-1}). In the present study, we solved the radiative rate equations including all the rotational levels below 900 cm^{-1} to give the o-p conversion lifetime to be 0.451, 3.27, 398 and 910 years for the equilibrium o/p ratio of 3.00, 3.00, 4.52, and 406 when the radiation temperature T_r is 100, 60, 20 and 5 K. These results qualitatively help to understand the observed high o/p ratio of 4.8 ± 0.5 (corresponding to the nuclear spin temperature of 21 K) toward Sgr B2, but they are too slow to compete with the reaction by collision unless the number of density of H_2 in the region is very low (n˜1 cm^{-3}) or the radiative temperature is very high (T_r > 50K). K. Tanaka, K. Harada, and T. Oka, the 67th OSU Symposium MG06, 2012. P. Schilke, et al., A&A 521, L11 (2010). K. Tanaka, K. Harada, and T. Oka, J. Phys. Chem. A

  16. Mergers of Non-spinning Black-hole Binaries: Gravitational Radiation Characteristics

    NASA Technical Reports Server (NTRS)

    Baker, John G.; Boggs, William D.; Centrella, Joan; Kelly, Bernard J.; McWilliams, Sean T.; vanMeter, James R.

    2008-01-01

    We present a detailed descriptive analysis of the gravitational radiation from black-hole binary mergers of non-spinning black holes, based on numerical simulations of systems varying from equal-mass to a 6:1 mass ratio. Our primary goal is to present relatively complete information about the waveforms, including all the leading multipolar components, to interested researchers. In our analysis, we pursue the simplest physical description of the dominant features in the radiation, providing an interpretation of the waveforms in terms of an implicit rotating source. This interpretation applies uniformly to the full wavetrain, from inspiral through ringdown. We emphasize strong relationships among the l = m modes that persist through the full wavetrain. Exploring the structure of the waveforms in more detail, we conduct detailed analytic fitting of the late-time frequency evolution, identifying a key quantitative feature shared by the l = m modes among all mass-ratios. We identify relationships, with a simple interpretation in terms of the implicit rotating source, among the evolution of frequency and amplitude, which hold for the late-time radiation. These detailed relationships provide sufficient information about the late-time radiation to yield a predictive model for the late-time waveforms, an alternative to the common practice of modeling by a sum of quasinormal mode overtones. We demonstrate an application of this in a new effective-one-body-based analytic waveform model.

  17. A spin dependent recombination study of radiation induced defects at and near the Si/SiO sub 2 interface

    SciTech Connect

    Jupina, M.A.; Lenahan, P.M. )

    1989-12-01

    A new electron spin resonance technique, spin dependent recombination (SDR) permits extremely rapid, high signal to noise ratio electron spin resonance (ESR) measurements of electrically active radiation damage centers in (relatively) hard MOS transistors in integrated circuits. Using SDR the authors observe the radiation induced buildup of Pbo and E' centers at relatively low concentration in individual MOSFETs in integrated circuits with (100) silicon surface orientation. Earlier ESR studies of extremely large ({approximately}1 cm{sup 2}) capacitor structures have identified Pb and E' centers as the dominant radiation induced defects in MOS devices. The authors discuss how their results extend and confirm these earlier results and at least qualitatively answer objections to the earlier work related to the relevance of large capacitor studies to transistors in an integrated circuit.

  18. A spin label study of the effects of asbestos, quartz, and titanium dioxide dusts on the bovine erythrocyte membrane.

    PubMed

    Leyko, W; Gendek, E

    1985-04-01

    The effects of five UICC asbestos samples, titanium dioxide, and quartz on the bovine red cell membrane have been studied in erythrocyte ghosts by the spin labelling technique. Analysis of the electron paramagnetic resonance (EPR) spectra of two sulphydryl reactive spin labels and one fatty acid spin label in red cell ghosts showed modifications in membrane protein after asbestos treatment but no alterations in membrane lipids. In experiments with quartz no membrane changes were noted but titanium dioxide altered the proteins bound with the protein reactive spin label used in the present study. The possible mechanism for these effects is discussed.

  19. Modeling the Dust Properties of z ~ 6 Quasars with ART2—All-Wavelength Radiative Transfer with Adaptive Refinement Tree

    NASA Astrophysics Data System (ADS)

    Li, Yuexing; Hopkins, Philip F.; Hernquist, Lars; Finkbeiner, Douglas P.; Cox, Thomas J.; Springel, Volker; Jiang, Linhua; Fan, Xiaohui; Yoshida, Naoki

    2008-05-01

    The detection of large quantities of dust in z ~ 6 quasars by infrared and radio surveys presents puzzles for the formation and evolution of dust in these early systems. Previously, Li et al. showed that luminous quasars at zgtrsim 6 can form through hierarchical mergers of gas-rich galaxies, and that these systems are expected to evolve from starburst through quasar phases. Here, we calculate the dust properties of simulated quasars and their progenitors using a three-dimensional Monte Carlo radiative transfer code, ART2 (All-wavelength Radiative Transfer with Adaptive Refinement Tree). ART2 incorporates a radiative equilibrium algorithm which treats dust emission self-consistently, an adaptive grid method which can efficiently cover a large dynamic range in both spatial and density scales, a multiphase model of the interstellar medium which accounts for the observed scaling relations of molecular clouds, and a supernova-origin model for dust which can explain the existence of dust in cosmologically young objects. By applying ART2 to the hydrodynamic simulations of Li et al., we reproduce the observed spectral energy distribution (SED) and inferred dust properties of SDSS J1148+5251, the most distant Sloan quasar. We find that the dust and infrared emission are closely associated with the formation and evolution of the quasar host. The system evolves from a cold to a warm ultraluminous infrared galaxy (ULIRG) owing to heating and feedback from stars and the active galactic nucleus (AGN). Furthermore, the AGN activity has significant implications for the interpretation of observation of the hosts. Our results suggest that vigorous star formation in merging progenitors is necessary to reproduce the observed dust properties of z ~ 6 quasars, supporting a merger-driven origin for luminous quasars at high redshifts and the starburst-to-quasar evolutionary hypothesis.

  20. The relative importance of water vapour and dust in controlling the variability in radiative heating of the summertime Saharan heat low

    NASA Astrophysics Data System (ADS)

    Marsham, John H.; Parker, Douglas J.; Todd, Martin C.; Banks, Jamie R.; Brindley, Helen E.; Garcia-Carreras, Luis; Roberts, Alexander J.; Ryder, Claire L.

    2017-04-01

    The summertime Sahara heat low (SHL) is a key component of the West African monsoon (WAM) system but is a key source of uncertainty in global models. There is considerable uncertainty over the relative importance of water vapour and dust concentrations in controlling the radiation budget over the Sahara. This limits our ability to explain the variability and trends in the SHL and WAM systems, and so hampers our ability to reduce model biases. Here we use in situ observations from Fennec supersite-1 in the central Sahara from June 2011 and 2012, as well as satellite retrievals from GERB, to quantify how total column water vapour (TCWV) and dust aerosols control day-to-day variability in the energy balance in observations and ECMWF reanalyses (ERA-I). Results show that the earth-atmosphere system is radiatively heated in June 2011 and 2012. While we are not able to completely disentangle the roles of water vapour, clouds and dust from the observations, the analysis demonstrates that TCWV provides a far stronger control on TOA net radiation, and so the net heating of the earth-atmosphere system, than AOD does. Variations in dust provide a much stronger control on surface heating, but the reduction in surface heating associated with high dust loadings are largely compensated by associated increases in atmospheric heating, and so dust control on net TOA radiation is weak. Dust and TCWV are both important for direct atmospheric heating. ERA-I assimilated radiosondes from the Fennec campaign but uses a monthly dust climatology, and so cannot capture the impact of daily variations in dustiness. Despite this, ERA-I managed to capture the control of TOA net flux by TCWV, with a positive correlation (r = 0.6) between observed and modelled TOA net radiation. Variations in surface net radiation, and so the vertical profile of radiative heating, are not captured in ERA-I, given it does not capture variations in dust. Results show that ventilation of the SHL by cool moist air

  1. Motion of dust in a planetary magnetosphere - Orbit-averaged equations for oblateness, electromagnetic, and radiation forces with application to Saturn's E ring

    NASA Technical Reports Server (NTRS)

    Hamilton, Douglas P.

    1993-01-01

    The orbital dynamics of micrometer-sized dust grains is explored numerically and analytically, treating the strongest perturbation forces acting on close circumplanetary dust grains: higher-order gravity, radiation pressure, and the electromagnetic force. The appropriate orbit-average equations are derived and applied to the E ring. Arguments are made for the existence of azimuthal and vertical asymmetries in the E ring. New understanding of the dynamics of E ring dust grains is applied to problems of the ring's breadth and height. The possibility for further ground-based and spacecraft observations is considered.

  2. Motion of dust in a planetary magnetosphere - Orbit-averaged equations for oblateness, electromagnetic, and radiation forces with application to Saturn's E ring

    NASA Technical Reports Server (NTRS)

    Hamilton, Douglas P.

    1993-01-01

    The orbital dynamics of micrometer-sized dust grains is explored numerically and analytically, treating the strongest perturbation forces acting on close circumplanetary dust grains: higher-order gravity, radiation pressure, and the electromagnetic force. The appropriate orbit-average equations are derived and applied to the E ring. Arguments are made for the existence of azimuthal and vertical asymmetries in the E ring. New understanding of the dynamics of E ring dust grains is applied to problems of the ring's breadth and height. The possibility for further ground-based and spacecraft observations is considered.

  3. Electrostatic charging of acoustically suspended dust grains by ultraviolet radiation and by plasma

    SciTech Connect

    Dyer, T.W.

    1992-01-01

    An experimental apparatus was developed for the study of dust grain charging by photoemission and by immersion in plasma. The technique used to do this involved acoustically suspending the dust grains against gravity while they are exposed to the charging influences. The apparatus consisted of a terminated acoustic plane-wave tube coupled to an assembly of microwave equipment for use in the plasma charging studies. The origin of the acoustic force used to levitate the dust grains is a nonlinear dependence of fluid drag on an object with the flow velocity past the object. The effectiveness of the resulting force for the levitation of dust grains against gravity was inversely proportional to both grain radius and grain density. Grains of various materials including metals and silica with diameters ranging from 5 to 90[mu]m were readily levitated in krypton gas at 100 torr. These dust grain parameters and background gas conditions were standard for all of the grain charging. The interaction between a high intensity traveling acoustic wave with a highly collisional microwave producted plasma was investigated. The dominant effect of the acoustic wave on the plasma occurred in the plasma production rate. The resulting audio frequency plasma density fluctuations then propagated away from the production region in both directions as the plasma diffused out from this region against the background gas. In the dust grain charging studies, the steady state charge acquired by the grains was set by a condition on the electrostatic potential of the grains. This was true in both the photoemission charging experiments and the plasma charging studies. All of the grain charge measurements were made by observing the electrophoresis of the grains through the background gas in an externally applied electric field. The mobility of spherical grains varies proportionally with the ratio q/r. The mobility was independent of radius observed in the experiments.

  4. Seasonal and Elevational Variations of Black Carbon and Dust in Snow and Ice in the Solu-Khumbu, Nepal and Estimated Radiative Forcings

    NASA Astrophysics Data System (ADS)

    Kaspari, S.; Painter, T. H.; Gysel, M.; Skiles, M.; Schwikowski, M.

    2014-12-01

    Black carbon (BC) and dust deposited on snow and glacier surfaces can reduce the surface albedo, accelerate melt, and trigger albedo feedback. Assessing BC and dust concentrations in snow and ice in the Himalaya is of interest because this region borders large BC and dust sources, and seasonal snow and glacier ice in this region are an important source of water resources. Snow and ice samples were collected from crevasse profiles and snowpits at elevations between 5400 and 6400 m asl from Mera glacier located in the Solu-Khumbu region of Nepal. The samples were measured for Fe concentrations (used as a dust proxy) via ICP-MS, total impurity content gravimetrically, and BC concentrations using a Single Particle Soot Photometer (SP2). BC and Fe concentrations are substantially higher at elevations < 6000 m due to post-depositional processes including melt and sublimation and greater loading in the lower troposphere. Because the largest areal extent of snow and ice resides at elevations < 6000 m, the higher BC and dust concentrations at these elevations can reduce the snow and glacier albedo over large areas, accelerating melt, affecting glacier mass-balance and water resources, and contributing to a positive climate forcing. Radiative transfer modeling constrained by measurements at 5400 m at Mera La indicates that BC concentrations in the winter-spring snow/ice horizons are sufficient to reduce albedo by 6-10% relative to clean snow, corresponding to localized instantaneous radiative forcings of 75-120 W m-2. The other bulk impurity concentrations, when treated separately as dust, reduce albedo by 40-42% relative to clean snow and give localized instantaneous radiative forcings of 488 to 525 W m-2. Adding the BC absorption to the other impurities results in additional radiative forcings of 3 W m-2. While these results suggest that the snow albedo and radiative forcing effect of dust is considerably greater than BC, there are several sources of uncertainty.

  5. Restoration and Reexamination of Data from the Apollo 11, 12, 14, and 15 Dust, Thermal and Radiation Engineering Measurements Experiments

    NASA Technical Reports Server (NTRS)

    McBride, Marie J.; Williams, David R.; Kent, H.; Turner, Niescja

    2012-01-01

    As part of an effort by the Lunar Data Node (LDN) we are restoring data returned by the Apollo Dust, Thermal, and Radiation Engineering Measurements (DTREM) packages emplaced on the lunar surface by the crews of Apollo 11, 12, 14, and 15. Also commonly known as the Dust Detector experiments, the DTREM packages measured the outputs of exposed solar cells and thermistors over time. They operated on the surface for up to nearly 8 years, returning data every 54 seconds. The Apollo 11 DTREM was part of the Early Apollo Surface Experiments Package (EASEP), and operated for a few months as planned following emplacement in July 1969. The Apollo 12, 14, and 15 DTREMs were mounted on the central station as part of the Apollo Lunar Surface Experiments Package (ALSEP) and operated from deployment until ALSEP shutdown in September 1977. The objective of the DTREM experiments was to determine the effects of lunar and meteoric dust, thermal stresses, and radiation exposure on solar cells. The LDN, part of the Geosciences Node of the Planetary Data System (PDS), operates out of the National Space Science Data Center (NSSDC) at Goddard Space Flight Center. The goal of the LDN is to extract lunar data stored on older media and/or in obsolete formats, restore the data into a usable digital format, and archive the data with PDS and NSSDC. For the DTREM data we plan to recover the raw telemetry, translate the raw counts into appropriate output units, and then apply calibrations. The final archived data will include the raw, translated, and calibrated data and the associated conversion tables produced from the microfilm, as well as ancillary supporting data (metadata) packaged in PDS format.

  6. Maps of Dust Infrared Emission for Use in Estimation of Reddening and Cosmic Microwave Background Radiation Foregrounds

    NASA Astrophysics Data System (ADS)

    Schlegel, David J.; Finkbeiner, Douglas P.; Davis, Marc

    1998-06-01

    standard reddening law and use the colors of elliptical galaxies to measure the reddening per unit flux density of 100 μm emission. We find consistent calibration using the B-R color distribution of a sample of the 106 brightest cluster ellipticals, as well as a sample of 384 ellipticals with B-V and Mg line strength measurements. For the latter sample, we use the correlation of intrinsic B-V versus Mg2 index to tighten the power of the test greatly. We demonstrate that the new maps are twice as accurate as the older Burstein-Heiles reddening estimates in regions of low and moderate reddening. The maps are expected to be significantly more accurate in regions of high reddening. These dust maps will also be useful for estimating millimeter emission that contaminates cosmic microwave background radiation experiments and for estimating soft X-ray absorption. We describe how to access our maps readily for general use.

  7. Quantum Čerenkov Radiation: Spectral Cutoffs and the Role of Spin and Orbital Angular Momentum

    NASA Astrophysics Data System (ADS)

    Kaminer, Ido; Mutzafi, Maor; Levy, Amir; Harari, Gal; Herzig Sheinfux, Hanan; Skirlo, Scott; Nemirovsky, Jonathan; Joannopoulos, John D.; Segev, Mordechai; Soljačić, Marin

    2016-01-01

    We show that the well-known Čerenkov effect contains new phenomena arising from the quantum nature of charged particles. The Čerenkov transition amplitudes allow coupling between the charged particle and the emitted photon through their orbital angular momentum and spin, by scattering into preferred angles and polarizations. Importantly, the spectral response reveals a discontinuity immediately below a frequency cutoff that can occur in the optical region. Near this cutoff, the intensity of the conventional Čerenkov radiation (ČR) is very small but still finite, while our quantum calculation predicts exactly zero intensity above the cutoff. Below that cutoff, with proper shaping of electron beams (ebeams), we predict that the traditional ČR angle splits into two distinctive cones of photonic shockwaves. One of the shockwaves can move along a backward cone, otherwise considered impossible for conventional ČR in ordinary matter. Our findings are observable for ebeams with realistic parameters, offering new applications including novel quantum optics sources, and opening a new realm for Čerenkov detectors involving the spin and orbital angular momentum of charged particles.

  8. Mineral dust impact on snow radiative properties in the European Alps combining ground, UAV, and satellite observations

    NASA Astrophysics Data System (ADS)

    Di Mauro, B.; Fava, F.; Ferrero, L.; Garzonio, R.; Baccolo, G.; Delmonte, B.; Colombo, R.

    2015-06-01

    In this paper, we evaluate the impact of mineral dust (MD) on snow radiative properties in the European Alps at ground, aerial, and satellite scale. A field survey was conducted to acquire snow spectral reflectance measurements with an Analytical Spectral Device (ASD) Field Spec Pro spectroradiometer. Surface snow samples were analyzed to determine the concentration and size distribution of MD in each sample. An overflight of a four-rotor Unmanned Aerial Vehicle (UAV) equipped with an RGB digital camera sensor was carried out during the field operations. Finally, Landsat 8 Operational Land Imager (OLI) data covering the central European Alps were analyzed. Observed reflectance evidenced that MD strongly reduced the spectral reflectance of snow, in particular, from 350 to 600 nm. Reflectance was compared with that simulated by parameterizing the Snow, Ice, and Aerosol Radiation radiative transfer model. We defined a novel spectral index, the Snow Darkening Index (SDI), that combines different wavelengths showing nonlinear correlation with measured MD concentrations (R2 = 0.87, root-mean-square error = 0.037). We also estimated a positive instantaneous radiative forcing that reaches values up to 153 W/m2 for the most concentrated sampling area. SDI maps at local scale were produced using the UAV data, while regional SDI maps were generated with OLI data. These maps show the spatial distribution of MD in snow after a natural deposition from the Saharan desert. Such postdepositional experimental data are fundamental for validating radiative transfer models and global climate models that simulate the impact of MD on snow radiative properties.

  9. Techniques for carrying out radiative transfer calculations for the Martian atmospheric dust

    NASA Technical Reports Server (NTRS)

    Aronson, J. R.; Emslie, A. G.; Strong, P. F.

    1974-01-01

    A description is given of the modification of a theory on the reflectance of particulate media so as to apply it to analysis of the infrared spectra obtained by the IRIS instrument on Mariner 9. With the aid of this theory and the optical constants of muscovite mica, quartz, andesite, anorthosite, diopside pyroxenite, and dunite, modeling calculations were made to refine previous estimates of the mineralogical composition of the Martian dust particles. These calculations suggest that a feldspar rich mixture is a very likely composition for the dust particles. The optical constants used for anorthosite and diopside pyroxenite were derived during this program from reflectance measurements. Those for the mica were derived from literature reflectance data. Finally, a computer program was written to invert the measured radiance data so as to obtain the absorption coefficient spectrum which should then be independent of the temperature profile and gaseous component effects.

  10. The radiative impact of desert dust on orographic rain in the Cevennes-Vivarais area: a case study from HyMeX

    NASA Astrophysics Data System (ADS)

    Flamant, C.; Chaboureau, J.-P.; Chazette, P.; Di Girolamo, P.; Bourrianne, T.; Totems, J.; Cacciani, M.

    2015-08-01

    The study is focused on Intensive Observation Period (IOP) 14 of the Hydrology Cycle in the Mediterranean Experiment first Special Observing Period (HyMeX SOP 1) that took place from 17 to 19 October and was dedicated to the study of orographic rain in the Cevennes Vivarais (CV) target area. During this IOP a dense dust plume originating from North Africa (Maghreb and Sahara) was observed to be transported over the Balearic Islands towards the south of France. The plume was characterized by an aerosol optical depth between 0.2 and 0.8 at 550 nm, highly variable in time and space over the Western Mediterranean basin. The impact of this dust plume, the biggest event observed during the 2 month long HyMeX SOP 1, on the precipitation over the CV area has been analyzed using high resolution simulations from the convection permitting mesoscale model Meso-NH validated against measurements obtained from numerous instruments deployed specifically during SOP 1 (ground-based/airborne water vapor and aerosol lidars, airborne microphysics probes) as well as space-borne aerosol products. The 4 day simulation reproduced realistically the temporal and spatial variability (incl. vertical distribution) of the dust. The dust radiative impact led to an average 0.6 K heating at the altitude of the dust layer in the CV area (and up to +3 K locally) and an average 100 J kg-1 increase of most unstable convective available potential energy (and up to +900 J kg-1 locally) with respect to a simulation without prescribed dust aerosols. The rainfall amounts and location were only marginally affected by the dust radiative effect, even after 4 days of simulation. The transient nature of this radiative effect in dynamical environments such as those found in the vicinity of heavy precipitation events in the Mediterranean is not sufficient to impact 24 h accumulated rainfall in the dusty simulation.

  11. Dynamics of CO2- radiation defects in natural calcite studied by ESR, electron spin echo and electron spin relaxation

    NASA Astrophysics Data System (ADS)

    Wencka, M.; Lijewski, S.; Hoffmann, S. K.

    2008-06-01

    ESR spectra were recorded in the X-band (9.6 GHz) and in the W-band (94 GHz) and electron spin relaxation was measured by electron spin echo (ESE) in the temperature range 4.2-300 K for radicals in natural calcite samples obtained from a cave stalactite and a dripstone layer. Four types of carbonate radical spectra and two sulfate radical spectra were identified and high accuracy g-factors were derived. Time and temperature behaviour of the spectra show that the dominating CO2- radicals are rigidly bonded or undergo free reorientations, whereas CO3-, SO2- and SO3- only undergo free reorientations. Below 200 K the free reorientations of CO2- are suppressed and a hindered rotation around single local axis appears. The ESE detected spectrum proves that the lines of free rotating radicals are homogeneously broadened, thus they cannot participate in electron spin echo formation. Spin-lattice relaxation data show that CO2- radicals are decoupled from lattice phonons and relax via local mode tunnelling motion between inequivalent oxygen positions of CO2- molecules. The tunnelling appears in two excited vibrational states of energy 71 and 138 cm-1. Librational motions of CO2- molecules were detected by electron spin echo decay (phase relaxation) with energy 153 cm-1. Two kinds of impurity hydrogen atoms were distinguished from ESEEM: in-water inclusions and water coordinated to the calcium ions.

  12. The effects of the diffuse radiation fields due to multiple scattering and thermal reradiation by dust on the dynamics and thermodynamics of a dusty cometary atmosphere

    NASA Technical Reports Server (NTRS)

    Marconi, M. L.; Mendis, D. A.

    1984-01-01

    A self-consistent model of a dirty, clathrate cometary nucleus is extended to account for diffuse radiation fields caused by multiple scattering and thermal reradiation of the solar continuum by dust. The model is configured to fit conditions expected for the various spacecraft which will encounter Halley's comet at 0.89 AU. The atmosphere is assumed a chemically reactive dust-gas mixture in quasi-steady spherically symmetric expansion. The effect of electron-neutral ion collisions is accounted for, along with rate constants of the various species of clathrate ice particles and radiative transfer of the solar input in the UV, visible and near-IR intervals. The opacity of the circumnuclear dust is projected to be an order of magnitude greater than previous estimates, which severely impacts the potential visibility of the nucleus to the cameras of the flyby satellites.

  13. Seasonal and elevational variations of black carbon and dust in snow and ice in the Solu-Khumbu, Nepal and estimated radiative forcings

    NASA Astrophysics Data System (ADS)

    Kaspari, S.; Painter, T. H.; Gysel, M.; Skiles, S. M.; Schwikowski, M.

    2014-08-01

    Black carbon (BC) and dust deposited on snow and glacier surfaces can reduce the surface albedo, accelerate snow and ice melt, and trigger albedo feedback. Assessing BC and dust concentrations in snow and ice in the Himalaya is of interest because this region borders large BC and dust sources, and seasonal snow and glacier ice in this region are an important source of water resources. Snow and ice samples were collected from crevasse profiles and snow pits at elevations between 5400 and 6400 m a.s.l. from Mera glacier located in the Solu-Khumbu region of Nepal during spring and fall 2009, providing the first observational data of BC concentrations in snow and ice from the southern slope of the Himalaya. The samples were measured for Fe concentrations (used as a dust proxy) via ICP-MS, total impurity content gravimetrically, and BC concentrations using a Single Particle Soot Photometer (SP2). Measured BC concentrations underestimate actual BC concentrations due to changes to the sample during storage and loss of BC particles in the ultrasonic nebulizer; thus, we correct for the underestimated BC mass. BC and Fe concentrations are substantially higher at elevations < 6000 m due to post-depositional processes including melt and sublimation and greater loading in the lower troposphere. Because the largest areal extent of snow and ice resides at elevations < 6000 m, the higher BC and dust concentrations at these elevations can reduce the snow and glacier albedo over large areas, accelerating melt, affecting glacier mass balance and water resources, and contributing to a positive climate forcing. Radiative transfer modeling constrained by measurements at 5400 m at Mera La indicates that BC concentrations in the winter-spring snow/ice horizons are sufficient to reduce albedo by 6-10% relative to clean snow, corresponding to localized instantaneous radiative forcings of 75-120 W m-2. The other bulk impurity concentrations, when treated separately as dust, reduce albedo by

  14. Radiative Transfer Modeling of the Mid-IR/Far-IR Dust Emissions of the Symbiotic Mira, V* R Aqr

    NASA Astrophysics Data System (ADS)

    Omelian, Eric B.; Sankrit, Ravi; Helton, L. Andrew; Gorti, Uma; Wagner, R. Mark

    2017-01-01

    We present RADMC-3D models of the symbiotic system V* R Aqr, which consists of a Mira variable and white dwarf. Thermal radiative transfer modeling is performed using RADMC-3D to characterize the mid-IR/far-IR Spectral Energy Distributions (SEDs) of the system at two different phases of the visible light curve. Near maximum visible light (Mira phase of 1.0), we utilize the Infrared Space Observatory (ISO) Short Wave Spectrometer/Long Wave Spectrometer observations (2.3 - 197 mu-m) and contrast them to the recently obtained near minimum visible light (~0.4 Mira phase) observations from the Stratospheric Observatory for Infrared Astronomy (SOFIA)/Faint Object infraRed CAmera for the SOFIA Telescope (FORCAST) (6.4 - 37.1 mu-m). Initial spectra and photometry from the SOFIA/FORCAST observations of the central Mira indicate that flux values are about 50% of that measured by the ISO SWS/LWS observations. Dust models utilizing a spherical shell and amorphous silicates are used to generate synthetic SEDs, which are compared with the ISO and FORCAST observations in order to constrain the properties of the shell (such as its dust mass and temperature) at different phases of the Mira variability. Our proposed monitoring of the V* R Aqr system will establish a characterization baseline of the SEDs as the system approaches its upcoming eclipse and periastron passage.

  15. [The influence of the triterpenoid from the weeping birch (Betula Pendula) on the changed reactivity of an organism exposed to action of the dust-radiating factor].

    PubMed

    Il'derbaev, O Z; Il'derbaeva, G O

    2011-01-01

    The obtained data testify about immunmodulating properties of the given medicine. Influence of "Be phytomedicine on organism, which undergoes dust-radiation factor leads to positive dynamics in humoral and cellular parts of immunity, also to increasing immunological reactivity of an organism.

  16. On the radiation driven alignment of dust grains: Detection of the polarization hole in a starless core

    NASA Astrophysics Data System (ADS)

    Alves, F. O.; Frau, P.; Girart, J. M.; Franco, G. A. P.; Santos, F. P.; Wiesemeyer, H.

    2014-09-01

    Aims: We aim to investigate the polarization properties of a starless core in an early evolutionary stage. Linear polarization data reveal the properties of the dust grains in the distinct phases of the interstellar medium. Our goal is to investigate how the polarization degree and angle correlate with the cloud and core gas. Methods: We use optical, near infrared, and submillimeter polarization observations on the starless object Pipe-109 in the Pipe nebula. Our data cover a physical scale range of 0.08 to 0.4 pc, comprising the dense gas, envelope, and the surrounding cloud. Results: The cloud polarization is well traced by the optical data. The near infrared polarization is produced by a mixed population of grains from the core border and the cloud gas. The optical and near infrared polarization toward the cloud reaches the maximum possible value and saturates with respect to the visual extinction. The core polarization is predominantly traced by the submillimeter data and has a steep decrease with respect to the visual extinction. Modeling of the submillimeter polarization indicates a magnetic field main direction projected onto the plane-of-sky and loss of grain alignment for densities higher than 6 × 104 cm-3 (or AV> 30 mag). Conclusions: The object is immersed in a magnetized medium with a very ordered magnetic field. The absence of internal source of radiation significantly affects the polarization efficiencies in the core, creating a polarization hole at the center of the starless core. This result supports the theory of dust grain alignment via radiative torques Based on data acquired with the Atacama Pathfinder Experiment (APEX) and the 1.6 m telescope at Observatorio do Pico dos Dias (LNA/MCTI).The data are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/569/L1

  17. Electrodynamic Dust Shield Technology for Thermal Radiators Used in Lunar Exploration

    NASA Technical Reports Server (NTRS)

    Calle, Carlos I.; Hogue, Michael D.; Snyder, Sarah J.; Clements, Sidney J.; Johansen, Michael R.; Chen, Albert

    2011-01-01

    Two general types of thermal radiators are being considered for lunar missions: coated metallic surfaces and Second Surface Mirrors. Metallic surfaces are coated with a specially formulated white paint that withstands the space environment and adheres well to aluminium, the most common metal used in space hardware. AZ-93 White Thermal Control Paint, developed for the space program, is an electrically conductive inorganic coating that offers thermal control for spacecraft. It is currently in use on satellite surfaces (Fig 1). This paint withstands exposure to atomic oxygen, charged particle radiation, and vacuum ultraviolet radiation form 118 nm to 170 nm while reflecting 84 to 85% of the incident solar radiation and emitting 89-93% of the internal heat generated inside the spacecraft.

  18. Vertical distribution of aerosols and shortwave radiative forcing over the Indo-Gangetic Basin during three major dust storms of 2010

    NASA Astrophysics Data System (ADS)

    Kumar, Sarvan; Singh, Abhay Kumar

    Abstract: The present study aims to analyze the Aerosol Radiative Forcing (ARF) and vertical distribution of aerosols over Kanpur (located in central Indo-Gangetic Basin; IGB) during the three (20 April, 28 May and 2 June, 2010) intense dust-storm events in the pre-monsoon season, using the synergy of ground and satellite observations and SBDART simulation. The analysis reveals considerable changes in the aerosol vertical profiles and ARF during the dust-storm events highlighting the important role of dust in the aerosol load and ARF properties over the IGB. The CALIOP-derived aerosol properties show vertically elevated aerosol profiles (up to 4 km altitude), majorly consisting of dust particles during the dust event. The maximum daily average top of the atmosphere (TOA), atmosphere (ATM) and surface (SRF) forcing is found to be -40.95, 60.65 W/m2 and -101.59W/m2 during the dust events respectively. A strong correlation is found between AOD at 500 nm and the ARF. The correlation coefficient (R2) between AOD and ARF is found to be 0.74, 0.46 and 0.84 at TOA, ATM and SRF respectively. The slope of the regression line gives the aerosol forcing efficiency at 500nm of about 24.29, -19.85 and -44.15 W/m2 at the ATM, TOA and SRF respectively. The ARF is found to increase with the advance of the dry season. Keywords: Dust Storms, Aerosol properties, AERONET, Satellites, Indo-Gangetic Basin, Aerosol Radiative Forcing (ARF).

  19. Light Dust Devil Tracks

    NASA Technical Reports Server (NTRS)

    2004-01-01

    14 October 2004 Many Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) images exhibit wild patterns of dark streaks thought to have formed by the passage of many dust devils. The dust devils disrupt the dust coating the martian surface, leaving behind a streak. However, not all dust devils make streaks, and not all dust devil streaks are dark. Some are light---it simply depends upon which is darker, the substrate or the dust that the spinning vortex disrupts. The example of light-toned dust devil streaks shown here is located in southern Schiaparelli Basin near 5.3oS, 343.3oW. The image covers an area about 3 km (1.9 mi) across; sunlight illuminates the scene from the left/upper left.

  20. Galaxy formation by dust

    NASA Technical Reports Server (NTRS)

    Wang, Boqi; Field, Goerge B.

    1989-01-01

    It has been known since the early 1940's that radiation can cause an instability in the interstellar medium. Absorbing dust particles in an isotropic radiation field shadow each other by a solid angle which is inversely proportional to the square of the distance between the two particles, leading to an inverse-square attractive force - mock gravity. The effect is largest in an optically thin medium. Recently Hogan and White (HW, hereafter) proposed that if the pre-galactic universe contained suitable sources of radiation and dust, instability in the dust distribution caused by mock gravity may have led to the formation of galaxies and galaxy clusters. In their picture of a well-coupled dust-gas medium, HW show that mock gravity begins to dominate gravitational instability when the perturbation becomes optically thin, provided that the radiation field at the time is strong enough. The recent rocket observation of the microwave background at submillimeter wavelengths by Matsumoto et al. might be from pre-galactic stars, the consequence of the absorption of ultraviolet radiation by dust, and infrared reemission which is subsequently redshifted. HW's analysis omits radiative drag, incomplete collisional coupling of gas and dust, finite dust albedo, and finite matter pressure. These effects could be important. In a preliminary calculation including them, the authors have confirmed that mock gravitational instability is effective if there is a strong ultraviolet radiation at the time, but any galaxies that form would be substantially enriched in heavy elements because the contraction of the dust is more rapid than that of the gas. Moreover, since the dust moves with supersonic velocity through the gas soon after the perturbation becomes optically thin, the sputtering of dust particles by gas is significant, so the dust could disappear before the instability develops significantly. They conclude that the mock gravity by dust is not important in galaxy formations.

  1. Radiation losses and dark mode for spin-wave propagation through a discrete magnetic micro-waveguide

    NASA Astrophysics Data System (ADS)

    Barabanenkov, Yuri; Osokin, Sergey; Kalyabin, Dmitry; Nikitov, Sergey

    2016-11-01

    This paper presents the quantum mechanical type T -scattering operator approach to studying the forward volume magnetostatic spin-wave multiple scattering by a finite ensemble of cylindrical magnetic inclusions in a ferromagnetic thin film. The approach is applied to the problem of spin-wave excitation transfer along a linear chain of inclusions. The substantial results are deriving the optical theorem for the T -scattering operator and, as a consequence, deriving a formula for collective extinction cross section of inclusion ensemble, where only the first inclusion of the chain is irradiated by an incident narrow spin-wave beam. From this formula it can be shown that only irradiated inclusion makes a direct contribution in the collective extinction cross section of the total number of inclusions. In this case the direct summarized contribution of all the other inclusions from the chain into the spin-wave scattering is invisible; we call such phenomenon the dark mode. Applying a one-multipole and closest neighbor coupling approximation, we reveal a regime of distant resonant transfer for spin-wave excitation along the linear chain of an essentially big but finite number of particles with the dark mode. Because we also found a resonant mechanism of filtering this mode from radiation losses, the revealed regime shows that at resonant conditions the linear chain of magnetic inclusions can play the role of a spin-wave micro-waveguide, which transfers a signal over a big distance in a form of the dark mode, where the controllable level of radiation losses can tend to reach nearly zero values.

  2. Local geological dust in the area of Rome (Italy): linking mineral composition, size distribution and optical properties to radiative transfer modelling

    NASA Astrophysics Data System (ADS)

    Pietrodangelo, Adriana; Salzano, Roberto; Bassani, Cristiana; Pareti, Salvatore; Perrino, Cinzia

    2015-04-01

    Airborne mineral dust plays a key role in the energy balance of the Earth - atmosphere coupled system. The microphysical and optical properties of dust drive the direct radiative effects and are in turn influenced by the dust mineralogical composition. The latter varies largely, depending on the geology of the source region. Knowledge gaps still exist about relationships between the scattering and absorption of solar and terrestrial radiation by mineral dust and its mineralogical, size distribution and particle morphology features; this also affects the reliability of radiative transfer (RT) modelling estimates (Hansell et al., 2011). In this study, these relationships were investigated focusing on the crustal suspended PM10 dust, sourced from outcropping rocks of the local geological domains around Rome (Latium, Italy). The mineral composition variability of the Latium rocks ranges from the silicate-dominated (volcanics domain) to the calcite-dominated (travertine), through lithological materials composed in different proportions by silicates, silica and calcite, mainly (limestone series, siliciclastic series) (Cosentino et al., 2009). This peculiarity of the Latium region was thus exploited to investigate the behavior of the size distribution, optical properties and radiative transfer at BOA (Bottom Of Atmosphere) of the suspended dust PM10 fraction with the variability of mineral composition. Elemental source profiles of the same dust samples were previously determined (Pietrodangelo et al., 2013). A multi-faceted analysis was performed, and outcomes from the following approaches were merged: individual-particle scanning electron microscopy combined with X-ray energy-dispersive microanalysis (SEM XEDS), bulk mineralogical analysis by X-ray diffraction (XRD), size distribution fit of the individual-particle data set and modelling of the dust optical and radiative properties. To this aim, the 6SV atmospheric radiative transfer code (Kotchenova et al., 2008

  3. The radiative impact of desert dust on orographic rain in the Cévennes-Vivarais area: a case study from HyMeX

    NASA Astrophysics Data System (ADS)

    Flamant, C.; Chaboureau, J.-P.; Chazette, P.; Di Girolamo, P.; Bourrianne, T.; Totems, J.; Cacciani, M.

    2015-11-01

    The study is focused on Intensive Observation Period (IOP) 14 of the Hydrological Cycle in the Mediterranean Experiment first Special Observing Period (HyMeX SOP 1) that took place from 17 to 19 October 2012 and was dedicated to the study of orographic rain in the Cévennes-Vivarais (CV) target area. During this IOP a dense dust plume originating from northern Africa (the Maghreb and Sahara) was observed to be transported over the Balearic Islands towards the south of France. The plume was characterized by an aerosol optical depth between 0.2 and 0.8 at 550 nm, highly variable in time and space over the western Mediterranean Basin. The impact of this dust plume, the biggest event observed during the 2-month-long HyMeX SOP 1, on the precipitation over the CV area has been analyzed using high-resolution simulations from the convection permitting mesoscale model Meso-NH (mesoscale non-hydrostatic model) validated against measurements obtained from numerous instruments deployed specifically during SOP 1 (ground-based/airborne water vapor and aerosol lidars, airborne microphysics probes) as well as space-borne aerosol products. The 4-day simulation reproduced realistically the temporal and spatial variability (including the vertical distribution) of the dust. The dust radiative impact led to an average 0.6 K heating at the altitude of the dust layer in the CV area (and up to +3 K locally) and an average 100 J kg-1 increase of most unstable convective available potential energy (and up to +900 J kg-1 locally) with respect to a simulation without prescribed dust aerosols. The rainfall amounts and location were only marginally affected by the dust radiative effect, even after 4 days of simulation. The transient nature of this radiative effect in dynamical environments such as those found in the vicinity of heavy precipitation events in the Mediterranean is not sufficient to impact 24 h of accumulated rainfall in the dust simulation.

  4. Variability of the infrared complex refractive index of African mineral dust: experimental estimation and implications for radiative transfer and satellite remote sensing

    NASA Astrophysics Data System (ADS)

    Di Biagio, C.; Boucher, H.; Caquineau, S.; Chevaillier, S.; Cuesta, J.; Formenti, P.

    2014-10-01

    radiative transfer (mass extinction efficiency, kext, single scattering albedo, ω, and asymmetry factor, g) have been calculated, by using the Mie theory, based on the estimated refractive index and measured particle size distribution. The optical properties show a large sample-to-sample variability, with kext, ω, and g varying in the range 0.05-0.35, 0.25-1.0, and 0.05-0.75. This variability is expected to significantly impact satellite retrievals of atmospheric and surface parameters (e.g. from the Infrared Atmospheric Sounding Interferometer, IASI) and estimates of the dust radiative forcing.

  5. Martian thermal boundary layers: Subhourly variations induced by radiative-conductive heat transfer within the dust-laden atmosphere-ground system

    NASA Technical Reports Server (NTRS)

    Pallmann, A. J.; Dannevik, W. P.; Frisella, S. P.

    1973-01-01

    Radiative-conductive heat transfer has been investigated for the ground-atmosphere system of the planet Mars. The basic goal was the quantitative determination of time dependent vertical distributions of temperature and static stability for Southern-Hemispheric summer season and middle and polar latitudes, for both dust-free and dust-laden atmospheric conditions. The numerical algorithm which models at high spatial and temporal resolution the thermal energy transports in the dual ground-atmosphere system, is based on solution of the applicable heating rate equation, including radiative and molecular-conductive heat transport terms. The two subsystems are coupled by an internal thermal boundary condition applied at the ground-atmosphere interface level. Initial data and input parameters are based on Mariner 4, 6, 7, and 9 measurements and the JPL Mars Scientific Model. Numerical experiments were run for dust-free and dust-laden conditions in the midlatitudes, as well as ice-free and ice-covered polar regions. Representative results and their interpretation are presented. Finally, the theoretical framework of the generalized problem with nonconservative Mie scattering and explicit thermal-convective heat transfer is formulated, and applicable solution algorithms are outlined.

  6. Radiative transfer modelling of dust in IRAS 18333-2357: the only planetary nebula in the metal-poor globular cluster M22

    NASA Astrophysics Data System (ADS)

    Muthumariappan, C.; Parthasarathy, M.; Ita, Y.

    2013-10-01

    We report results from our 1D radiative transfer modelling of dust in the hydrogen-deficient planetary nebula IRAS 18333-2357 located in the globular cluster M22. A spectral energy distribution was constructed from archival UV, optical and IR data including Akari photometry at its 18, 65, 90, 140 and 160 μm bands. An archival Spitzer spectrum shows several aromatic infrared bands indicating a carbon-rich dust shell. The spectral energy distribution is well fitted by a model which considers a modified Mathis-Rumpl-Nordsieck grain size distribution and a radial density function which includes compression of the nebula by its interaction with the Galactic halo gas. The model indicates that a significant amount of cold dust, down to a temperature of 50 K, is present at the outer edge of the nebula. At the inner edge, the dust temperature is 97 K. The dust shell has a size of 26 ± 6.3 arcsec. We find a large amount of excess emission, over the emission from thermal equilibrium dust, in the mid-IR region. This excess emission may have originated from the thermally fluctuating dust grains with size ˜12 Å in the UV field of the hot central star. These grains, however, come from the same population and conditions as the thermal equilibrium grains. The dust mass of this grain population is (1.2 ± 0.73) × 10-3 M⊙ and for the thermal equilibrium grains it is (1.4 ± 0.60) × 10-4 M⊙, leading to a total dust mass of (1.3 ± 0.91) × 10-3 M⊙. The derived dust-to-gas mass ratio is 0.3 ± 0.21. For a derived bolometric luminosity of (1700 ± 1230) L⊙ and an assumed central star mass of (0.55 ± 0.02) M⊙, the surface gravity is derived to be log g = 4.6 ± 0.24. We propose that the progenitor of IRAS 18333-2357 had possibly evolved from an early stellar merger case and the hydrogen-deficient nebula results from a late thermal pulse. The hydrogen-rich nebula, which was ejected by the progenitor during its normal asymptotic giant branch evolution, might have been

  7. Fast radiative transfer of dust reprocessing in semi-analytic models with artificial neural networks

    NASA Astrophysics Data System (ADS)

    Silva, Laura; Fontanot, Fabio; Granato, Gian Luigi

    2012-06-01

    A serious concern for semi-analytical galaxy formation models, aiming to simulate multiwavelength surveys and to thoroughly explore the model parameter space, is the extremely time-consuming numerical solution of the radiative transfer of stellar radiation through dusty media. To overcome this problem, we have implemented an artificial neural network (ANN) algorithm in the radiative transfer code GRASIL, in order to significantly speed up the computation of the infrared (IR) spectral energy distribution (SED). The ANN we have implemented is of general use, in that its input neurons are defined as those quantities effectively determining the shape of the IR SED. Therefore, the training of the ANN can be performed with any model and then applied to other models. We made a blind test to check the algorithm, by applying a net trained with a standard chemical evolution model (i.e. CHE_EVO) to a mock catalogue extracted from the semi-analytic model MORGANA, and compared galaxy counts and evolution of the luminosity functions in several near-IR to sub-millimetre (sub-mm) bands, and also the spectral differences for a large subset of randomly extracted models. The ANN is able to excellently approximate the full computation, but with a gain in CPU time by ˜2 orders of magnitude. It is only advisable that the training covers reasonably well the range of values of the input neurons in the application. Indeed in the sub-mm at high redshift, a tiny fraction of models with some sensible input neurons out of the range of the trained net cause wrong answer by the ANN. These are extreme starbursting models with high optical depths, favourably selected by sub-mm observations, and are difficult to predict a priori.

  8. THE MOST MASSIVE ACTIVE BLACK HOLES AT z ∼ 1.5-3.5 HAVE HIGH SPINS AND RADIATIVE EFFICIENCIES

    SciTech Connect

    Trakhtenbrot, Benny

    2014-07-01

    The radiative efficiencies (η) of 72 luminous unobscured active galactic nuclei at z ∼ 1.5-3.5, powered by some of the most massive black holes (BHs), are constrained. The analysis is based on accretion disk (AD) models, which link the continuum luminosity at rest-frame optical wavelengths and the BH mass (M {sub BH}) to the accretion rate through the AD, M-dot {sub AD}. The data are gathered from several literature samples with detailed measurements of the Hβ emission line complex, observed at near-infrared bands. When coupled with standard estimates of bolometric luminosities (L {sub bol}), the analysis suggests high radiative efficiencies, with most of the sources showing η > 0.2, that is, higher than the commonly assumed value of 0.1, and the expected value for non-spinning BHs (η = 0.057). Even under more conservative assumptions regarding L {sub bol} (i.e., L {sub bol} = 3 × L {sub 5100}), most of the extremely massive BHs in the sample (i.e., M {sub BH} ≳ 3 × 10{sup 9} M {sub ☉}) show radiative efficiencies which correspond to very high BH spins (a {sub *}), with typical values well above a {sub *} ≅ 0.7. These results stand in contrast to the predictions of a ''spin-down'' scenario, in which a series of randomly oriented accretion episodes leads to a {sub *} ∼ 0. Instead, the analysis presented here strongly supports a ''spin-up'' scenario, which is driven by either prolonged accretion or a series of anisotropically oriented accretion episodes. Considering the fact that these extreme BHs require long-duration or continuous accretion to account for their high masses, it is argued that the most probable scenario for the super-massive black holes under study is that of an almost continuous sequence of randomly yet not isotropically oriented accretion episodes.

  9. Reinterpretation of Mariner 9 IRIS data on the basis of a simulation of radiative-conductive convective transfer in the dust laden Martian atmosphere

    NASA Technical Reports Server (NTRS)

    Pallman, A. J.

    1974-01-01

    Time dependent vertical distributions of atmospheric temperature and static stability were determined by a radiative-convective-conductive heat transfer model attuned to Mariner 9 IRIS radiance data. Of particular interest were conditions of both the dust-laden and dust-free atmosphere in the middle latitudes on Mars during the late S.H. summer season. The numerical model simulates at high spatial and temporal resolution (52 atmospheric and 30 subsurface levels; with a time-step of 7.5 min.) the heat transports in the ground-atmosphere system. The algorithm is based on the solution of the appropriate heating rate equation which includes radiative, molecular-conductive and convective heat transfer terms. Ground and atmosphere are coupled by an internal thermal boundary condition.

  10. Electric Dust Devils and Dust Storms

    NASA Astrophysics Data System (ADS)

    Renno, N. O.; Yana, C.

    2004-12-01

    Electrical fields measurements in terrestrial dust devils show that they maintain tremendous charge separation and that their electric fields exceeds the breakdown potential (~10 kV/m) of the Martian atmosphere (Farrell et al., 2002, 2003; Krauss et al., 2002; Renno et al., 2004). Typical Martian dust devils are be up to 100 times larger and much stronger than the small terrestrial analogues. Martian dust devils have higher dust content and may produce even stronger electrical fields. Indeed, the dust devils observed in the Pathfinder images have about 700 times the dust content of the local background atmosphere (Metzger et al., 1999). Thus, strong charge separations and electric-field breakdown are likely to occur on Martian dust devils and dust storms. Our theory (Renno et al., 2004) and laboratory experiments in a Mars chamber shows that collisions between sand and dust particles produce non-thermal microwave radiation. The non-thermal microwave emission allows not only the indirect detection of electric activity but also the determination of the physical properties of Martian sand and dust by remote sensing. Besides being geologically important, electrically charged Martian dust devils and dust storms are potential hazards to Landers and will be dangerous to future astronauts exploring its surface. Indeed, the design of adequate mechanical and electrical systems for these Landers cannot progress effectively without a better understanding of Martian dust devils and dust storms. Moreover, ancillary phenomena associated with electrically charged vortices can ionize atmospheric gases and might have important implications for atmosphere chemistry and even habitability.

  11. Simulating Black Carbon and Dust and their Radiative Forcing in Seasonal Snow: A Case Study over North China with Field Campaign Measurements

    SciTech Connect

    Zhao, Chun; Hu, Zhiyuan; Qian, Yun; Leung, Lai-Yung R.; Huang, J.; Huang, Maoyi; Jin, Jiming; Flanner, M. G.; Zhang, Rudong; Wang, Hailong; Yan, Huiping; Lu, Zifeng; Streets, D. G.

    2014-10-30

    A state-of-the-art regional model, WRF-Chem, is coupled with the SNICAR model that includes the sophisticated representation of snow metamorphism processes available for climate study. The coupled model is used to simulate the black carbon (BC) and dust concentrations and their radiative forcing in seasonal snow over North China in January-February of 2010, with extensive field measurements used to evaluate the model performance. In general, the model simulated spatial variability of BC and dust mass concentrations in the top snow layer (hereafter BCS and DSTS, respectively) are quantitatively or qualitatively consistent with observations. The model generally moderately underestimates BCS in the clean regions but significantly overestimates BCS in some polluted regions. Most model results fall into the uncertainty ranges of observations. The simulated BCS and DSTS are highest with >5000 ng g-1 and up to 5 mg g-1, respectively, over the source regions and reduce to <50 ng g-1 and <1 μg g-1, respectively, in the remote regions. BCS and DSTS introduce similar magnitude of radiative warming (~10 W m-2) in snowpack, which is comparable to the magnitude of surface radiative cooling due to BC and dust in the atmosphere. This study represents the first effort in using a regional modeling framework to simulate BC and dust and their direct radiative forcing in snow. Although a variety of observational datasets have been used to attribute model biases, some uncertainties in the results remain, which highlights the need for more observations, particularly concurrent measurements of atmospheric and snow aerosols and the deposition fluxes of aerosols, in future campaigns.

  12. Variability of the infrared complex refractive index of African mineral dust: experimental estimation and implications for radiative transfer and satellite remote sensing

    NASA Astrophysics Data System (ADS)

    Di Biagio, C.; Boucher, H.; Caquineau, S.; Chevaillier, S.; Cuesta, J.; Formenti, P.

    2014-04-01

    Experimental estimations of the infrared refractive index of African mineral dust have been retrieved from laboratory measurements of particle transmission spectra in the wavelength range 2.5-25 μm. Five dust samples collected at Banizoumbou (Niger) and Tamanrasset (Algeria) during dust events originated from different Western Saharan and Sahelian areas have been investigated. The obtained real (n) and imaginary (k) parts of the refractive index for the different dust cases vary in the range 1.1-2.7 and 0.05-1.0, respectively, and appear to be strongly sensitive to the mineralogical composition of the particles, especially in the 8-12 μm and 17-25 μm spectral intervals. Dust absorption is controlled mainly by clays, and, in minor fraction, by quartz and Ca-rich minerals. Size distribution, and the coarse fraction in particular, plays also a role in determining the refractive index. Significant differences are obtained when comparing our results with existing experimental estimations available in the literature, and with the values of the OPAC (Optical Properties of Aerosols and Clouds) database. The different datasets appear comparable in magnitude, with our values of n and k falling in the range of variability of past studies. However, literature data fail in accurately reproducing the spectral signatures of main minerals, in particular clays, and they significantly overestimate the contribution of quartz. We also found that the real and the imaginary parts of the refractive index from part of literature studies do not verify Kramers-Kronig relations, thus resulting theoretically incorrect. The comparison between our results, from Western Africa, and literature data, from different locations in Europe, Africa, and the Caribbean, nonetheless, confirms the expected large variability of the infrared refractive index of dust, thus highlighting the necessity for an extended systematic investigation. Aerosol intensive optical properties relevant to radiative transfer

  13. The Evidence of Radio Polarization Induced by the Radiative Grain Alignment and Self-scattering of Dust Grains in a Protoplanetary Disk

    NASA Astrophysics Data System (ADS)

    Kataoka, Akimasa; Tsukagoshi, Takashi; Pohl, Adriana; Muto, Takayuki; Nagai, Hiroshi; Stephens, Ian W.; Tomisaka, Kohji; Momose, Munetake

    2017-07-01

    The mechanisms causing millimeter-wave polarization in protoplanetary disks are under debate. To disentangle the polarization mechanisms, we observe the protoplanetary disk around HL Tau at 3.1 mm with the Atacama Large Millimeter/submillimeter Array (ALMA), which had the polarization detected with CARMA at 1.3 mm. We successfully detect the ring-like azimuthal polarized emission at 3.1 mm. This indicates that dust grains are aligned with the major axis being in the azimuthal direction, which is consistent with the theory of radiative alignment of elongated dust grains, where the major axis of dust grains is perpendicular to the radiation flux. Furthermore, the morphology of the polarization vectors at 3.1 mm is completely different from those at 1.3 mm. We interpret the polarization at 3.1 mm to be dominated by the grain alignment with the radiative flux producing azimuthal polarization vectors, while the self-scattering dominates at 1.3 mm and produces the polarization vectors parallel to the minor axis of the disk. By modeling the total polarization fraction with a single grain population model, the maximum grain size is constrained to be 100 μ {{m}}, which is smaller than the previous predictions based on the spectral index between ALMA at 3 mm and the Very Large Array at 7 mm.

  14. Spitzer characterization of dust in an anomalous emission region: the Perseus cloud

    NASA Astrophysics Data System (ADS)

    Tibbs, C. T.; Flagey, N.; Paladini, R.; Compiègne, M.; Shenoy, S.; Carey, S.; Noriega-Crespo, A.; Dickinson, C.; Ali-Haïmoud, Y.; Casassus, S.; Cleary, K.; Davies, R. D.; Davis, R. J.; Hirata, C. M.; Watson, R. A.

    2011-12-01

    Anomalous microwave emission is known to exist in the Perseus cloud. One of the most promising candidates to explain this excess of emission is electric dipole radiation from rapidly rotating very small dust grains, commonly referred to as spinning dust. Photometric data obtained with the Spitzer Space Telescope have been reprocessed and used in conjunction with the dust emission model DUSTEM to characterize the properties of the dust within the cloud. This analysis has allowed us to constrain spatial variations in the strength of the interstellar radiation field (χISRF), the mass abundances of the polycyclic aromatic hydrocarbons (PAHs) and the very small grains (VSGs) relative to the big grains (YPAH and YVSG), the column density of hydrogen (NH) and the equilibrium dust temperature (Tdust). The parameter maps of YPAH, YVSG and χISRF are the first of their kind to be produced for the Perseus cloud, and we used these maps to investigate the physical conditions in which anomalous emission is observed. We find that in regions of anomalous emission the strength of the ISRF, and consequently the equilibrium temperature of the dust, is enhanced while there is no significant variation in the abundances of the PAHs and the VSGs or the column density of hydrogen. We interpret these results as an indication that the enhancement in χISRF might be affecting the properties of the small stochastically heated dust grains resulting in an increase in the spinning dust emission observed at 33 GHz. This is the first time that such an investigation has been performed, and we believe that this type of analysis creates a new perspective in the field of anomalous emission studies, and represents a powerful new tool for constraining spinning dust models.

  15. Dust Mitigation Vehicle

    NASA Technical Reports Server (NTRS)

    Cardiff, Eric H.

    2011-01-01

    A document describes the development and demonstration of an apparatus, called a dust mitigation vehicle, for reducing the amount of free dust on the surface of the Moon. The dust mitigation vehicle would be used to pave surfaces on the Moon to prevent the dust from levitating or adhering to surfaces. The basic principle of operation of these apparatuses is to use a lens or a dish mirror to concentrate solar thermal radiation onto a small spot to heat lunar regolith. In the case of the prototype dust mitigation vehicle, a Fresnel lens was used to heat a surface layer of regolith sufficiently to sinter or melt dust grains into a solid mass. The prototype vehicle has demonstrated paving rates up to 1.8 square meters per day. The proposed flight design of the dust mitigation vehicle is also described.

  16. An assessment of the surface longwave direct radiative effect of airborne dust in Zhangye, China, during the Asian Monsoon Years field experiment (2008)

    NASA Astrophysics Data System (ADS)

    Hansell, Richard A.; Tsay, Si-Chee; Hsu, N. Christina; Ji, Qiang; Bell, Shaun W.; Holben, Brent N.; Welton, Ellsworth J.; Roush, Ted L.; Zhang, W.; Huang, J.; Li, Zhanqing; Chen, H.

    2012-08-01

    In April-June 2008, NASA Goddard's ground-based mobile laboratories (SMART-COMMIT) were deployed to Zhangye China (39.0°N; 101°W) to support the Asian Monsoon Years field experiment and the East Asian Study of Tropospheric Aerosols and Impact on Regional Climate. One of the primary objectives at Zhangye, a semi-arid region located between the Taklimakan and Gobi Deserts, was to capture and characterize dust aerosols near the source and to quantify their direct radiative effects (DRE). A regional dust optical model was constructed by combining previously measured soil mineralogy data at Zhangye with COMMIT's particle microphysical measurements. During a 2-week period of heightened dust activity, retrieved longwave (LW) aerosol optical thickness (τ) from SMART's Atmospheric Emitted Radiance Interferometer was used in the Fu-Liou radiative transfer model to derive LW instantaneous DRE (DRELW) at the surface, top of atmosphere, and heating rate profiles for cloud-free conditions. Conservatively, surface instantaneous DRELW and LW forcing efficiency range from about 2-20 Wm-2 and 31-35 Wm-2τ-1 (0 ≤ τ ≤ 0.83), respectively. The significance of DRELWrelative to its shortwave counterpart was estimated to be between 51 and 58%, but of opposite sign, partly compensating shortwave surface cooling. Compared to Saharan dust observed during the NAMMA-2006 field experiment at Cape Verde, dust LW forcing efficiency for this study was found to be a factor of two larger stemming from differences in environmental and surface conditions, aerosol absorption, and Zhangye's close proximity to major desert sources. Relative to observed and modeled ranges in surface DRELW for clouds (˜30-80 Wm-2) and greenhouse gases (˜2 Wm-2), this study's upper range in DRELW represents a significant perturbation to the climate system with important implications for better understanding regional changes in surface temperatures and moisture budgets.

  17. Spin-orbit and rotational couplings in radiative association of C(3P) and N(4S) atoms.

    PubMed

    Antipov, Sergey V; Gustafsson, Magnus; Nyman, Gunnar

    2011-11-14

    The role of spin-orbit and rotational couplings in radiative association of C((3)P) and N((4)S) atoms is investigated. Couplings among doublet electronic states of the CN radical are considered, giving rise to a 6-state model of the process. The solution of the dynamical problem is based on the L(2) method, where a complex absorbing potential is added to the Hamiltonian operator in order to treat continuum and bound levels in the same manner. Comparison of the energy-dependent rate coefficients calculated with and without spin-orbit and rotational couplings shows that the couplings have a strong effect on the resonance structure and low-energy baseline of the rate coefficient.

  18. Rotational bursting of interplanetary dust particles

    NASA Technical Reports Server (NTRS)

    Paddack, S. J.; Rhee, J. W.

    1974-01-01

    Solar radiation pressure is discussed as a cause of rotational bursting, and of eventual elimination of asymmetric dust particles from the solar system, by a windmill effect. The predicted life span with this process for metallic particles with radii of 0.00001 to 0.01 cm ranges from 10 to 10,000 years. The effects of magnetic spin damping were considered. This depletion mechanism works faster than the traditional Poynting-Robertson effect by approximately one order of magnitude for metallic particles and about two orders of magnitude for nonmetallic particles.

  19. Dust and Planetary Rings

    NASA Astrophysics Data System (ADS)

    Siddiqui, Muddassir

    ABSTRACT Space is not empty it has comic radiations (CMBR), dust etc. Cosmic dust is that type of dust which is composed of particles in space which vary from few molecules to 0.1micro metres in size. This type of dust is made up of heavier atoms born in the heart of stars and supernova. Mainly it contains dust grains and when these dust grains starts compacting then it turns to dense clouds, planetary ring dust and circumstellar dust. Dust grains are mainly silicate particles. Dust plays a major role in our solar system, for example in zodiacal light, Saturn's B ring spokes, planetary rings at Jovian planets and comets. Observations and measurements of cosmic dust in different regions of universe provide an important insight into the Universe's recycling processes. Astronomers consider dust in its most recycled state. Cosmic dust have radiative properties by which they can be detected. Cosmic dusts are classified as intergalactic dusts, interstellar dusts and planetary rings. A planetary ring is a ring of cosmic dust and other small particles orbiting around a planet in flat disc shape. All of the Jovian planets in our solar system have rings. But the most notable one is the Saturn's ring which is the brightest one. In March 2008 a report suggested that the Saturn's moon Rhea may have its own tenuous ring system. The ring swirling around Saturn consists of chunks of ice and dust. Most rings were thought to be unstable and to dissipate over course of tens or hundreds of millions of years but it now appears that Saturn's rings might be older than that. The dust particles in the ring collide with each other and are subjected to forces other than gravity of its own planet. Such collisions and extra forces tend to spread out the rings. Pluto is not known to have any ring system but some Astronomers believe that New Horizons probe might find a ring system when it visits in 2015.It is also predicted that Phobos, a moon of Mars will break up and form into a planetary ring

  20. Effective mie-scattering and CO2 absorption in the dust-laden Martian atmosphere and its impact on radiative-convective temperature changes in the lower scale heights

    NASA Technical Reports Server (NTRS)

    Pallmann, A. J.

    1976-01-01

    A time dependent computer model of radiative-convective-conductive heat transfer in the Martian ground-atmosphere system was refined by incorporating an intermediate line strength CO2 band absorption which together with the strong-and weak-line approximation closely simulated the radiative transmission through a vertically inhomogeneous stratification. About 33,000 CO2 lines were processed to cover the spectral range of solar and planetary radiation. Absorption by silicate dust particulates, was taken into consideration to study its impact on the ground-atmosphere temperature field as a function of time. This model was subsequently attuned to IRIS, IR-radiometric and S-band occultation data. Satisfactory simulations of the measured IRIS spectra were accomplished for the dust-free condition. In the case of variable dust loads, the simulations were sufficiently fair so that some inferences into the effect of dust on temperature were justified.

  1. Direct, Longwave Radiative Forcing of Mineral Dust: Improvement of its Estimation by Means of Tools Recently Developed by the EARLINET Community

    NASA Astrophysics Data System (ADS)

    Sicard, Michaël; Muñoz-Porcar, Constantino; Comerón, Adolfo; Rodriguez, Alejandro; Rocadenbosch, Francesc; Barragan, Ruben

    2016-06-01

    The objective of this work is to investigate how the knowledge of the vertically-resolved fine and coarse mode aerosol optical depth modifies the longwave radiative forcing. Since relatively little the EARLINET (European Aerosol Research Lidar Network) community has developed codes that combine sun-photometer and lidar data to retrieve a set of parameters vertically-resolved related to the size distribution (fine and coarse mode extinction coefficients, fine and coarse mode volumetric concentrations, etc.). We concentrate on the case of mineral dust whose size distribution is often dominated by the coarse mode. This work demonstrates that the knowledge of the vertically-resolved fine and coarse mode aerosol optical depth modifies the LW RF as compared to the classical approach with a unique profile of total aerosol optical depth. The results show that when the coarse mode predominates the classical approach underestimates the dust longwave radiative forcing by 10 to 20 % at the surface. The effect at the top of the atmosphere is not systematic because of the predominance of fine particles near the top of the dust layer.

  2. Optical colours and spectral indices of z = 0.1 eagle galaxies with the 3D dust radiative transfer code skirt

    NASA Astrophysics Data System (ADS)

    Trayford, James W.; Camps, Peter; Theuns, Tom; Baes, Maarten; Bower, Richard G.; Crain, Robert A.; Gunawardhana, Madusha L. P.; Schaller, Matthieu; Schaye, Joop; Frenk, Carlos S.

    2017-09-01

    We present mock optical images, broad-band and H α fluxes, and D4000 spectral indices for 30 145 galaxies from the eagle hydrodynamical simulation at redshift z = 0.1, modelling dust with the skirt Monte Carlo radiative transfer code. The modelling includes a subgrid prescription for dusty star-forming regions, with both the subgrid obscuration of these regions and the fraction of metals in diffuse interstellar dust calibrated against far-infrared fluxes of local galaxies. The predicted optical colours as a function of stellar mass agree well with observation, with the skirt model showing marked improvement over a simple dust-screen model. The orientation dependence of attenuation is weaker than observed because eagle galaxies are generally puffier than real galaxies, due to the pressure floor imposed on the interstellar medium (ISM). The mock H α luminosity function agrees reasonably well with the data, and we quantify the extent to which dust obscuration affects observed H α fluxes. The distribution of D4000 break values is bimodal, as observed. In the simulation, 20 per cent of galaxies deemed 'passive' for the skirt model, i.e. exhibiting D4000 >1.8, are classified 'active' when ISM dust attenuation is not included. The fraction of galaxies with stellar mass greater than 1010 M⊙ that are deemed passive is slightly smaller than observed, which is due to low levels of residual star formation in these simulated galaxies. Colour images, fluxes and spectra of eagle galaxies are to be made available through the public eagle data base.

  3. High Radiation Pressure on Interstellar Dust Computed by Light-scattering Simulation on Fluffy Agglomerates of Magnesium-silicate Grains with Metallic-iron Inclusions

    NASA Astrophysics Data System (ADS)

    Kimura, Hiroshi

    2017-04-01

    Recent space missions have provided information on the physical and chemical properties of interstellar grains such as the ratio β of radiation pressure to gravity acting on the grains in addition to the composition, structure, and size distribution of the grains. Numerical simulation on the trajectories of interstellar grains captured by Stardust and returned to Earth constrained the β ratio for the Stardust samples of interstellar origin. However, recent accurate calculations of radiation pressure cross-sections for model dust grains have given conflicting stories in the β ratio of interstellar grains. The β ratio for model dust grains of so-called “astronomical silicate” in the femto-kilogram range lies below unity, in conflict with β ˜ 1 for the Stardust interstellar grains. Here, I tackle this conundrum by re-evaluating the β ratio of interstellar grains on the assumption that the grains are aggregated particles grown by coagulation and composed of amorphous MgSiO3 with the inclusion of metallic iron. My model is entirely consistent with the depletion and the correlation of major rock-forming elements in the Local Interstellar Cloud surrounding the Sun and the mineralogical identification of interstellar grains in the Stardust and Cassini missions. I find that my model dust particles fulfill the constraints on the β ratio derived from not only the Stardust mission but also the Ulysses and Cassini missions. My results suggest that iron is not incorporated into silicates but exists as metal, contrary to the majority of interstellar dust models available to date.

  4. Dust Formation and Destruction

    NASA Astrophysics Data System (ADS)

    Wiebe, Dmitry

    Recent infrared and sub-millimeter observations have opened up a new window in dust evolution studies. High angular resolution of Spitzer and Herschel space telescopes from near to far-infrared wavelengths allows observing dust emission in galactic and extragalactic star-forming complexes, covering a broad range of metallicities, radiation field properties, etc. A wide-scale picture of dust evolution starts to arise from these observations. In my contribution I will try to cover major recent advances in studies of dust formation and destruction, including such topics as a diverse role of supernovae in dust evolution, possibility of dust formation and/or growth in molecular clouds, and VSG and PAH evolution in HII regions and complexes.

  5. Physicochemical Processes on Ice Dust Towards Deuterium Enrichment

    NASA Astrophysics Data System (ADS)

    Watanabe, Naoki

    2017-06-01

    Water and some organic molecules were found to be deuterium enriched toward various astronomical targets. Understanding the deuterium-fractionation process pertains directly to know how and when molecules are created. Although gas phase chemistry is certainly important for deuterium enrichment, the role of physicochemical processes on the dust surfaces should be also considered. In fact, the extreme deuterium enrichment of formaldehyde and methanol requires the dust grain-surface process. In this context, we have performed a series of experiments on the formation of deuterated species of water and simple organic molecules. From the results of these experiments and related works, I will discuss the key processes for the deuterium enrichment on dust. For deuterium chemistry, another important issue is the ortho-to-para ratio (OPR) of H_{2}, which is closely related to the formation of H_{2}D^{+} and thus the deuterium fractionation of molecules in the gas phase. Because the radiative nuclear spin conversion of H_{2} is forbidden, the ortho-para conversion is very slow in the gas phase. In contrast, it was not obvious how the nuclear spins behave on cosmic dust. Therefore, it is desirable to understand how the OPR of H_{2} is determined on the dust surfaces. We have tackled this issue experimentally. Using experimental techniques of molecular beam, photostimulated-desorption, and resonance-enhanced multiphoton ionization, we measured the OPRs of H_{2} photodesorbed from amorphous solid water at around 10 K, which is an ice dust analogue. It was first demonstrated that the rate of spin conversion from ortho to para drastically increases from 2.4 × 10^{-4} to 1.7 × 10^{-3} s^{-1} within the very narrow temperature window of 9.2 to16 K. The observed strong temperature cannot be explained by solely state-mixing models ever proposed but by the energy dissipation model via two phonon process. I will present our recent experiments regarding this.

  6. Seasonal and elevational variations of black carbon and dust in snow and ice in the Solu-Khumbu, Nepal and estimated radiative forcings

    NASA Astrophysics Data System (ADS)

    Kaspari, S.; Painter, T. H.; Gysel, M.; Schwikowski, M.

    2013-12-01

    Black carbon (BC) and dust deposited on snow and glacier surfaces can reduce the surface albedo, accelerate snow and ice melt, and trigger albedo feedback. Assessing BC concentrations in snow and ice in the Himalaya is of interest because this region borders large BC sources, and seasonal snow and glacier ice in this region are an important source of water resources. Snow and ice samples were collected from crevasse profiles and snowpits at elevations between 5400 and 6400 m a.s.l. from Mera glacier located in the Solu-Khumbu region of Nepal on the southern slope of the Himalaya during spring and fall 2009. The samples were measured for Fe concentrations (used as a dust proxy) via ICP-MS, total impurity content gravimetrically, and BC concentrations using a Single Particle Soot Photometer (SP2). Measured BC concentrations underestimate actual BC concentrations due to changes to the sample during storage, and loss of BC particles in the ultrasonic nebulizer. BC and Fe concentrations peak during the winter-spring, and are substantially higher at elevations <6000 m due to post-depositional processes including melt and sublimation and greater loading in the lower troposphere. Because the largest areal extent of snow and ice resides at elevations <6000 m, the higher BC and dust concentrations at these elevations can reduce the snow and glacier albedo over large areas, accelerating melt, affecting glacier mass-balance and water resources, and contributing to a positive climate forcing. Radiative transfer modeling constrained by measurements indicates that BC concentrations in the winter-spring snow/ice horizons are sufficient to reduce albedo by 6-10% relative to clean snow, corresponding to instantaneous radiative forcings of 75-120 W m-2. The other bulk impurity concentrations, when treated separately as dust, reduce albedo by 40-42% relative to clean snow and give instantaneous radiative forcings of 490 to 520 W m-2. Adding the BC absorption to the other impurities

  7. Stochastic Circumplanetary Dynamics of Rotating Non-Spherical Dust Particles

    NASA Astrophysics Data System (ADS)

    Makuch, Martin; Brilliantov, N. V.; Sremcevic, M.; Spahn, F.; Krivov, A. V.

    2006-12-01

    Influence of stochastically fluctuating radiation pressure on the dynamics of dust grains on circumplanetary orbits was studied. Stochasticity stems from the permanent change of the particle cross-section due to rotation of nonspherical grains, exposed to the solar radiation. We found that stochasticity depends on the characteristic angular velocity of particles which, according to our estimates, spins very fast on the time scale of the orbital motion. According to this we modelled the stochastic part of the radiation pressure by a Gaussian white noise. Gauss perturbation equations with the radiation pressure being a sum of the deterministic and stochastic component have been used. We observed monotonous increasing standard deviation of the orbital elements, that is, the diffusive-like behaviour of the ensemble, which results in a spatial spreading of initially confined set of particles. By linear approximation we obtained expression for the effective diffusion coefficients and estimate their dependence on the geometrical characteristics of particles and their spin. Teoretical results were compared with numerical simulations performed for the putative dust tori of Mars. Our theory agrees fairly well with simulations for the initial period of the system evolution. The agreement however deteriorates with increasing time where impact of the non-linear terms of the perturbation equations becomes important. Analysis shows that the theoretical results may estimate the low boundary of the time-dependent standard deviation of the orbital elements. In the case of dust ejected from Martian moon Deimos we observed a change of orbital elements up to 10% of their initial values during the first 1000 years of orbital evolution. Our results indicate that the stochastic modulation of the radiation pressure can play an important role in the circumplanetary dynamics of dust and may, together with further noise sources (shadow, planetary bowshock, charge fluctuations, etc

  8. Three-dimensional Monte Carlo dust radiative transfer study of the H-poor planetary nebula IRAS 18333-2357 located in M22

    NASA Astrophysics Data System (ADS)

    Muthumariappan, C.

    2017-09-01

    We analyse the characteristics of dust and its distribution in the planetary nebula IRAS 18333-2357 located in M22 using a three-dimensional radiative transfer code Hochunk3D. The spectral energy distribution was constructed using ultraviolet, optical and infrared archival data. We also have used Spitzer 8-μm and Wide-field Infrared Survey Explorer (WISE) 22-μm images for our study. Taking into account that the dust shell is carbon-rich, models are presented for amorphous carbon and graphite grains. The spectral energy distribution and the thermal images are fit better by the amorphous carbon model than the graphite model. The stellar photospheric temperature is (50 000 ± 3000) K. IRAS 18333-2357 has a (40 ± 2)° inclined equatorial disc and a thin spherical shell around it, similar to the inner geometry of the born-again planetary nebula A30. Disc inner and outer radii are (2.8 ± 0.1) and (6.0 ± 0.6) arcsec, respectively. The inner and outer radii of the shell are (13.3 ± 1.5) and (25 ± 4) arcsec, respectively. Incorporating a very small grain population, we explain the excess emission in the region of 3-12 μm. The stellar bolometric luminosity is (2460 ± 800) L⊙ and the luminosity reprocessed by dust is (630 ± 200) L⊙. The masses of very small grain population and the classical dust grains are (9.4 ± 0.75) × 10-4 M⊙ and (3.1 ± 0.24) × 10-3 M⊙, respectively, resulting in a total dust mass of (4.1 ± 0.31)× 10-3 M⊙. The derived gas-to-dust mass ratio is 7 ± 1. We discuss a possible origin of IRAS 18333-2357 from a born-again event. The faint envelope seen in the WISE 22-μm image may contain H-rich matter ejected before the H-deficient nebula.

  9. Model simulations and satellite observations of radiative effects of lower stratospheric aerosol from volcanoes, air pollution and desert dust in the period 2002 to 2011

    NASA Astrophysics Data System (ADS)

    Brühl, Christoph; Schallock, Jennifer; Lelieveld, Jos; Klingmüller, Klaus

    2017-04-01

    Decadal simulation in the framework of SPARC/SSIRC with the atmospheric chemistry - general circulation model EMAC, with modal interactive aerosol, shows that sulfate particles from about 230 volcanic eruptions dominate the interannual variability of aerosol extinction in the lower stratosphere and of radiative forcing at the tropopause. The EMAC model simulates sulphate from 3D volcanic SO2 plumes based mostly on observations by MIPAS on ENVISAT. To explain the total stratospheric optical depth observed by satellites (including GOMOS on ENVISAT), desert dust and organic and black carbon, transported to the lowermost stratosphere by the Asian summer monsoon and tropical convection, need to be accounted for. In the upper troposphere and lower stratosphere over the Asian summer monsoon air pollution from road traffic appears to be the largest contributor to black carbon. Absorbing aerosol dominates the local radiative heating. We show the contributions by different aerosol types and in different spectral regions.

  10. Genomic analysis of lung cell lines exposures to space radiation and the effect of lunar dust on selected fibrosis gene using RT2 PCR Array

    NASA Astrophysics Data System (ADS)

    Yeshitla, Samrawit

    In the United States (U.S.), lung cancer is the number one cause of cancer death among men and women. Previous studies on human and animal epithelial lung cells showed that ionizing radiation and certain environmental pollutants are carcinogens. The surface area of the lungs and the slow turnover rate of the epithelial cells are suggested to play a role in the vulnerability of the cells, which lead to increase in the progenitor cell of the lung. It has been proposed that these progenitor cells, when exposed to radiation undergo multiple alterations that cause the cells to become cancerous. The current thought is that the lungs contain several facultative progenitor cells that are situated throughout the lung epithelium and are regionally restricted in their regenerative capacity. In this study, normal Human Bronchial Epithelial Cells (HBECs) were immortalized through the expression of Cdk4 and hTERT and evaluated for the effects radiation using in vitro study. The HBECs retained its novel multipotent capacity in vitro and represented unrestricted progenitor cells of the adult lungs, which resemble an embryonic progenitor. Analysis of the transformed clones of human bronchial epithelial cell line, HEBC3KT exposed to Fe ions and gamma rays revealed chromosomal abnormality, which was detected with the Multi-color Fluorescent In Situ Hybridization (mFish). In Part two of this study the F344 rats exposed to lunar dust, for 4 weeks (6h/d; 5d/wk.) in nose-only inhalation chambers at concentrations of 0 (control air), 2.1, 6.8, 20.8, and 61 mg/m3 of lunar dust, were used to determine the lunar dust toxicity on the lung tissues and total RNA were prepared from the tissues and used for gene expression. Analysis of gene expression data using Ingenuity Pathway Analysis tool identified multiple pathways of which fibrosis was one of the pathways. The Rat Fibrosis RT 2 Profile PCR Array was used to profile the expression of 84 genes that are relevant to fibrosis in the lung

  11. An anomalous African dust event and its impact on aerosol radiative forcing on the Southwest Atlantic coast of Europe in February 2016.

    PubMed

    Sorribas, M; Adame, J A; Andrews, E; Yela, M

    2017-04-01

    A desert dust (DD) event that had its origin in North Africa occurred on the 20th-23rd of February 2016. The dust transport phenomenon was exceptional because of its unusual intensity during the coldest season. A historical dataset (2006-2015) of February meteorological scenarios using ECMWF fields, meteorological parameters, aerosol optical properties, surface O3 and AOD retrieved from MODIS at the El Arenosillo observatory (southwestern Spain) were analysed and compared with the levels during the DD event to highlight its exceptionality. Associated with a low-pressure system in western North Africa, flows transported air from the Sahel to Algeria and consequently increased temperatures from the surface to 700hPa by up to 7-9°C relative to the last decade. These conditions favoured the formation of a Saharan air layer. Dust was transported to the north and reached the Western Mediterranean Basin and the Iberian Peninsula. The arrival of the DD event at El Arenosillo did not affect the surface weather conditions or ozone but did impact the aerosol radiative forcing at the top of atmosphere (RFTOA). Aerosol radiative properties did not change relative to historical; however, the particle size and the amount of the aerosol were significantly higher. The DD event caused an increase (in absolute terms) of the mean aerosol RFTOA to a value of -8.1Wm(-2) (long-term climatological value ~-1.5Wm(-2)). The aerosol RFTOA was not very large relative other DD episodes; however, our analysis of the historical data concluded that the importance of this DD event lay in the month of occurrence. European phenological datasets related to extreme atmospheric events predominantly reflect changes that are probably associated with climate change. This work is an example of this phenomenon, showing an event that occurred in a hotspot, the Saharan desert, and its impact two thousand km away.

  12. The effects of smoke and dust aerosols on UV-B radiation in Australia from ground-based and satellite measurements

    NASA Astrophysics Data System (ADS)

    Kalashnikova, Olga V.; Mills, Franklin P.; Eldering, Annmarie; Anderson, Don; Mitchell, Ross

    2005-08-01

    An understanding of the effect of aerosols on biologically- and photochemically-active UV radiation reaching the Earth's surface is important for many ongoing climate, biophysical, and air pollution studies. In particular, estimates of the UV characteristics of the most common Australian aerosols will be valuable inputs to UV Index forecasts, air quality studies, and assessments of the impact of regional environmental changes. Based on MODIS fire maps and MISR aerosol property retrievals, we have analyzed the climatological distributions of Australian dust and smoke particles and have identified sites where collocated ground-based UV-B and ozone measurements were available during episodes of relatively high aerosol activity. Since at least June 2003, overhead ozone and surface UV spectra (285-450 nm) have been measured routinely at Darwin and Alice Springs in Australia by the Australian Bureau of Meteorology (BoM). Using collocated AERONET sunphotometer measurements at Darwin and collocated BoM sunphotometer measurements at Darwin and Alice Springs, we identified several episodes of relatively high aerosol activity that could be used to study the effects of dust and smoke on the UV-B solar irradiance at the Earth's surface. To assess smoke effect we compared the measured UV irradiances at Darwin with irradiancies simulated with the LibRadtran radiative transfer model for aerosol-free conditions. We found that for otherwise similar atmospheric conditions, aerosols reduced the UVB irradiance by 50% near the fire source and up to 15% downwind. We also found the effect of smoke particles to be 5 to 10% larger in the UV-B part of the spectrum. For the selected period at Darwin, changes in the aerosol loadings gave larger variations in the surface UV irradiances than previously reported changes seen in the ozone column. We are continuing similar investigations for the Alice Springs site to assess spectral differences between smoke and dust aerosols.

  13. Stochastic circumplanetary Dynamics of rotating non-spherical Dust Particles

    NASA Astrophysics Data System (ADS)

    Makuch, M.; Brilliantov, N. V.; Sremcevic, M.; Spahn, F.; Krivov, A. V.

    We investigate the influence of stochastically fluctuating radiation pressure on the dynamics of dust grains on circumplanetary orbits. The stochasticity stems from the permanent change of the particle cross-section exposed to the solar radiation due to rotation of nonspherical grains. Therefore, the stochastic properties of the radiation pressure are related to the ensemble-averaged characteristics of rotating particles, such as orientational time-correlation function of an individual grain. We evaluate this function and observe that it depends on the characteristic angular velocity of particles, which according to our estimates, spin very fast on the time scale of the orbital motion. This allows to model the stochastic part of the radiation pressure by a Gaussian white noise. The parameters of the noise are expressed in terms of the particle's geometric properties and their characteristic spin. In our analytical approach we use the Gauss perturbation equations with the radiation pressure being a sum of the deterministic and stochastic component and analyse the dynamics of a grains ensemble. We observe a steadily increasing standard deviation of the orbital elements, that is, the diffusive-like behaviour of the ensemble, which results in a spatial spreading of initially confined set of particles. In the linear approximation we obtain analytical expression for the effective diffusion coefficients and estimate their dependence on the geometrical characteristics of particles and their spin. The results of our analytical theory were compared with extensive numerical simulations performed for a specific dust complex, the putative dust tori of Mars. We found that our theory agrees fairly well with simulations for the initial period of the system evolution. The agreement however deteriorates at later time when the impact of the non-linear terms of the perturbation equations, neglected in our theory, becomes important. Nevertheless, the analysis shows that the theoretical

  14. Cesium Speciation in Dust from Municipal Solid Waste and Sewage Sludge Incineration by Synchrotron Radiation Micro-X-ray Analysis.

    PubMed

    Shiota, Kenji; Takaoka, Masaki; Fujimori, Takashi; Oshita, Kazuyuki; Terada, Yasuko

    2015-11-17

    The chemical behavior of Cs in waste incineration processes is important to consider when disposing of radionuclide-contaminated waste from the Fukushima Daiichi nuclear power plant accident in Japan. To determine the speciation of Cs, we attempted the direct speciation of trace amounts of stable Cs in the dust from municipal solid waste incineration (MSWI) and sewage sludge incineration (SSI) by micro-X-ray fluorescence (μ-XRF) and micro-X-ray absorption fine structure (μ-XAFS) at the SPring-8 facility. The μ-XRF results revealed that locally produced Cs was present in MSWI and SSI dust within the cluster size range of 2-10 μm. The μ-XAFS analysis confirmed that the speciation of Cs in MSWI dust was similar to that of CsCl, while in SSI dusts it was similar to pollucite. The solubility of Cs was considered to be influenced by the exact Cs species present in incineration residue.

  15. Classification of aerosol radiative properties during African desert dust intrusions over southeastern Spain by sector origins and cluster analysis

    NASA Astrophysics Data System (ADS)

    Valenzuela, A.; Olmo, F. J.; Lyamani, H.; Antón, M.; Quirantes, A.; Alados-Arboledas, L.

    2012-03-01

    The main goal of this study is to analyze the dependence of columnar aerosol optical and microphysical properties on source region and transport pathways during desert dust intrusions over Granada (Spain) from January 2005 to December 2010. Columnar aerosol properties have been derived from a non-spherical inversion code using the solar extinction measurements and sky radiances in the principal plane. Two classification methods of the African air masses ending at the study location were used by means of the HYSPLIT back-trajectories analysis. The first one, based on desert dust origin sources, discriminated the optical properties only for sector B (corresponding to western Sahara, northwest Mauritania and southwest Algeria). The particles present marked absorbing properties (low value of single scattering albedo at all wavelengths) during the desert dust events when the air masses were transported from sector A (north Morocco, northwest Algeria). This result may be related to the mixing of desert dust with anthropogenic pollutants from North African industrial areas in addition to the mixing with local anthropogenic aerosol and pollutants transported from European and Mediterranean areas. The second classification method was based on a statistics technique called cluster classification which allows grouping the air masses back trajectories with similar speed and direction of the trajectory. This method showed slight differences in the optical properties between the several transport pathways of air masses. High values of the aerosol optical depth and low mean values of the Angström parameter were associated with longer transport pathways over desert dust sources and slowly moving air masses. Both classification methods showed that the fine mode was mixed with coarse mode, being the fine mode fraction smaller than 55%.

  16. Electron spin resonance of ultraviolet radiation induced defects in ZnO thermal control coating pigment.

    NASA Technical Reports Server (NTRS)

    Mookherji, T.

    1972-01-01

    Electron spin resonance measurements on variously treated zinc oxide powders reveal that the resonance signal at g = 1.956 is due to one electron trapped oxygen ion vacancy level, at a depth of (0.31 plus or minus 0.02) eV below the conduction band. The electrons at this level are delocalized. Schottky barrier influences nearly the entire bulk of the powder sample, and the bending of the bands caused by chemisorbed oxygen puts the vacancy level above the Fermi level almost through the entire bulk.

  17. Nonlinear Interactions between Laser Radiation and Spin-Aligned Carriers in Semiconductors.

    DTIC Science & Technology

    1980-11-25

    functions, u - exp(k*.), must satisfy the Schrodinger equation : bk + V + i K.1 + mti (VV x u) o Ub , [E - U2b2 2m m k p 4m2c- b, 2mI=, (4.2.1) In the...scattering rates with spin flip. Equations (4.3.2) are obviously too formidable for any kind of general solutions . By making certain simpifying...scattering processes by simple relaxation times TRC -rpin fli rLOetc. A general solution to the rate equations obtained is formdable nd conclu- sions

  18. Electron spin resonance of ultraviolet radiation induced defects in ZnO thermal control coating pigment.

    NASA Technical Reports Server (NTRS)

    Mookherji, T.

    1972-01-01

    Electron spin resonance measurements on variously treated zinc oxide powders reveal that the resonance signal at g = 1.956 is due to one electron trapped oxygen ion vacancy level, at a depth of (0.31 plus or minus 0.02) eV below the conduction band. The electrons at this level are delocalized. Schottky barrier influences nearly the entire bulk of the powder sample, and the bending of the bands caused by chemisorbed oxygen puts the vacancy level above the Fermi level almost through the entire bulk.

  19. Bispectrum speckle interferometry observations and radiative transfer modelling of the red supergiant NML Cyg. Multiple dust-shell structures evidencing previous superwind phases

    NASA Astrophysics Data System (ADS)

    Blöcker, T.; Balega, Y.; Hofmann, K.-H.; Weigelt, G.

    2001-04-01

    NML Cyg is a highly evolved OH/IR supergiant, one of the most prominent infrared objects due to its strong obscuration by dust, and supposed to be among the most luminous supergiants in the galaxy. We present the first diffraction-limited 2.13 mu m observations of NML Cyg with 73 mas resolution. The speckle interferograms were obtained with the 6 m telescope at the Special Astrophysical Observatory, and the image reconstruction is based on the bispectrum speckle-interferometry method. The visibility function declines towards the diffraction limit to ~ 0.6. Radiative transfer calculations have been carried out to model the spectral energy distribution, given by ground-based photometry and ISO spectroscopy, and our 2.13 mu m visibility function. Additionally, mid-infrared visibility functions at 11 mu m were considered. The observed dust shell properties do not appear to be in accordance with standard single-shell (uniform outflow) models but seem to require multiple components. Considering previous periods of enhanced mass-loss, various density enhancements in the dust shell were taken into account. An extensive grid of models was calculated for different locations and strenghts of such superwind regions in the dust shell. To match the observations from the optical to the sub-mm domain requires at least two superwind regions embedded in the shell. The best model includes a dust shell with a temperature of 1000 K at its inner radius of 6.2 R*, a close embedded superwind shell extending from 15.5 R* to 21.7 R* with an amplitude (factor of density enhancement) of 10, and a far-out density enhancement at 186 R* with an amplitude of 5. The angular diameters of the central star and of the inner rim of the dust shell amount to 16.2 mas and 105 mas, resp. The diameter of the embedded close superwind region extends from 263 mas to 368 mas, and the inner boundary of the distant superwind region has a diameter of 3\\farcs 15. In the near-infrared the dust condensation zone is

  20. Dust storms: recent developments.

    PubMed

    Goudie, Andrew S

    2009-01-01

    Dust storms have a number of impacts upon the environment including radiative forcing, and biogeochemical cycling. They transport material over many thousands of kilometres. They also have a range of impacts on humans, not least on human health. In recent years the identification of source areas for dust storms has been an important area or research, with the Sahara (especially Bodélé) and western China being recognised as the strongest sources globally. Another major development has been the recognition of the degree to which dust storm activity has varied at a range of time scales, millennial, century, decadal, annual and seasonal.

  1. Spin- and phase transition in the spin crossover complex [Fe(ptz) 6](BF 4) 2 studied by nuclear inelastic scattering of synchrotron radiation and by DFT calculations

    NASA Astrophysics Data System (ADS)

    Böttger, Lars H.; Chumakov, Aleksandr I.; Matthias Grunert, C.; Gütlich, Philipp; Kusz, Joachim; Paulsen, Hauke; Ponkratz, Ulrich; Rusanov, Ventzislav; Trautwein, Alfred X.; Wolny, Juliusz A.

    2006-09-01

    Nuclear inelastic scattering (NIS) spectra of [Fe(ptz) 6](BF 4) 2 (ptz = 1- n-propyl-tetrazole) have been measured for five phases differing in spin state and crystallographic structure. Different spectral patterns have been found for the low-spin and high-spin phases and are described in terms of normal coordinate analysis of the complex molecule. For both low-spin and high-spin phases the conversion from ordered to disordered phase results in splitting of the observed NIS bands. Packing becomes visible in the NIS spectra via coupling of the Fe-N stretching vibrations with those of the terminal n-propyl groups. The DFT-based normal coordinate analysis also reveals the character of Raman markers.

  2. Inverse method predicting spinning modes radiated by a ducted fan from free-field measurements.

    PubMed

    Lewy, Serge

    2005-02-01

    In the study the inverse problem of deducing the modal structure of the acoustic field generated by a ducted turbofan is addressed using conventional farfield directivity measurements. The final objective is to make input data available for predicting noise radiation in other configurations that would not have been tested. The present paper is devoted to the analytical part of that study. The proposed method is based on the equations governing ducted sound propagation and free-field radiation. It leads to fast computations checked on Rolls-Royce tests made in the framework of previous European projects. Results seem to be reliable although the system of equations to be solved is generally underdetermined (more propagating modes than acoustic measurements). A limited number of modes are thus selected according to any a priori knowledge of the sources. A first guess of the source amplitudes is obtained by adjusting the calculated maximum of radiation of each mode to the measured sound pressure level at the same angle. A least squares fitting gives the final solution. A simple correction can be made to take account of the mean flow velocity inside the nacelle which shifts the directivity patterns. It consists of modifying the actual frequency to keep the cut-off ratios unchanged.

  3. A public code for general relativistic, polarised radiative transfer around spinning black holes

    NASA Astrophysics Data System (ADS)

    Dexter, Jason

    2016-10-01

    Ray tracing radiative transfer is a powerful method for comparing theoretical models of black hole accretion flows and jets with observations. We present a public code, GRTRANS, for carrying out such calculations in the Kerr metric, including the full treatment of polarised radiative transfer and parallel transport along geodesics. The code is written in FORTRAN 90 and efficiently parallelises with OPENMP, and the full code and several components have PYTHON interfaces. We describe several tests which are used for verifiying the code, and we compare the results for polarised thin accretion disc and semi-analytic jet problems with those from the literature as examples of its use. Along the way, we provide accurate fitting functions for polarised synchrotron emission and transfer coefficients from thermal and power-law distribution functions, and compare results from numerical integration and quadrature solutions of the polarised radiative transfer equations. We also show that all transfer coefficients can play an important role in predicted images and polarisation maps of the Galactic centre black hole, Sgr A*, at submillimetre wavelengths.

  4. Electric Activity in Dust Devils and Dust Storms

    NASA Astrophysics Data System (ADS)

    Renno, R. O.; Yana, C.; Covert, A.; Renno, K.; Wilson, J.

    2005-12-01

    Terrestrial dust devils produce charge separation and electric fields that exceeds the breakdown potential of the thin Martian atmosphere (Farrell et al., 2002, 2003; Krauss et al., 2002; Renno et al., 2004). Typical Martian dust devils are wider, taller and have larger dust content than terrestrial vortices. Thus, charge separation and electric-field breakdown are likely to occur in Martian dust devils and dust storms. We show that theory, laboratory experiments, and field measurements in Arizona suggests that collisions between sand and dust particles at the bottom of dust devils produce non-thermal microwave radiation. The non-thermal microwave emission allows not only the indirect detection of electric activity but could also allow the determination of the physical properties of Martian sand and dust by remote sensing. Besides being geologically important, electrically charged Martian dust devils and dust storms are potential hazards to Landers and at minimum would be an annoyance to future astronauts exploring the planet. Indeed, the design of adequate mechanical and electrical systems for these Landers cannot progress effectively without a better understanding of Martian dust devils and dust storms. Moreover, ancillary phenomena associated with electrically charged vortices can ionize atmospheric gases and might have important implications for atmosphere chemistry and even habitability.

  5. The Martian Dust Cycle: Observations and Modeling

    NASA Technical Reports Server (NTRS)

    Kahre, Melinda A.

    2013-01-01

    The dust cycle is critically important for Mars' current climate system. Suspended atmospheric dust affects the radiative balance of the atmosphere, and thus greatly influences the thermal and dynamical state of the atmosphere. Evidence for the presence of dust in the Martian atmosphere can be traced back to yellow clouds telescopically observed as early as the early 19th century. The Mariner 9 orbiter arrived at Mars in November of 1971 to find a planet completely enshrouded in airborne dust. Since that time, the exchange of dust between the planet's surface and atmosphere and the role of airborne dust on Mars' weather and climate has been studied using observations and numerical models. The goal of this talk is to give an overview of the observations and to discuss the successes and challenges associated with modeling the dust cycle. Dust raising events on Mars range in size from meters to hundreds of kilometers. During some years, regional storms merge to produce hemispheric or planet encircling dust clouds that obscure the surface and raise atmospheric temperatures by tens of kelvin. The interannual variability of planet encircling dust storms is poorly understood. Although the occurrence and season of large regional and global dust storms are highly variable from one year to the next, there are many features of the dust cycle that occur year after year. A low-level dust haze is maintained during northern spring and summer, while elevated levels of atmospheric dust occur during northern autumn and winter. During years without global-scale dust storms, two peaks in total dust loading are generally observed: one peak occurs before northern winter solstice and one peak occurs after northern winter solstice. Numerical modeling studies attempting to interactively simulate the Martian dust cycle with general circulation models (GCMs) include the lifting, transport, and sedimentation of radiatively active dust. Two dust lifting processes are commonly represented in

  6. Particle-gas temperature differentials resulting from time-dependent radiative-conductive heat flux divergences in the tenuous dust-laden atmosphere of mars

    NASA Astrophysics Data System (ADS)

    Bellaire, Paul J., Jr.

    For an aerosol atmosphere, disparities in gas temperature,g, and particle temperature,g, may arise over the diurnal cycle. A radiative-conductive- convective heat transfer simulation of the dusty atmosphere of Mars was developed to quantify the temporal and spatial character of the temperature difference (p -g). This program computed thermal energy fluxes in the temporal and vertical domains in a 51-layer, vertically inhomogeneous , plane-parallel model atmosphere, with a 30 layer simulated ground structure. Observations from Mariner and Viking spacecraft were used in conjunction with other research findings to provide model input and set the boundary and initial conditions for the simulation. Temperature fields within the atmosphere were inferred from radiative-conductive-convective flux fields by means of enthalpy rate principles, while the radiation laws of Kirchoff and Planck were applied to the flux fields to determine aerosol temperatures. Several independent methods of validation were sucessfully applied to the model output, including comparisons with distinct spacecraft observations and the separate computation of dust heating effects outside the model.

  7. Powerful radiative jets in supercritical accretion discs around non-spinning black holes

    NASA Astrophysics Data System (ADS)

    Sądowski, Aleksander; Narayan, Ramesh

    2015-11-01

    We describe a set of simulations of supercritical accretion on to a non-rotating supermassive black hole (BH). The accretion flow takes the form of a geometrically thick disc with twin low-density funnels around the rotation axis. For accretion rates {gtrsim } 10 dot{M}_Edd, there is sufficient gas in the funnel to make this region optically thick. Radiation from the disc first flows into the funnel, after which it accelerates the optically thick funnel gas along the axis. The resulting jet is baryon loaded and has a terminal density-weighted velocity ≈0.3c. Much of the radiative luminosity is converted into kinetic energy by the time the escaping gas becomes optically thin. These jets are not powered by BHrotation or magnetic driving, but purely by radiation. Their characteristic beaming angle is ˜0.2 rad. For an observer viewing down the axis, the isotropic equivalent luminosity of total energy is as much as 1048 erg s- 1 for a 107 M⊙ BH accreting at 103 Eddington. Therefore, energetically, the simulated jets are consistent with observations of the most powerful tidal disruption events, e.g. Swift J1644. The jet velocity is, however, too low to match the Lorentz factor γ > 2 inferred in J1644. There is no such conflict in the case of other tidal disruption events. Since favourably oriented observers see isotropic equivalent luminosities that are highly super-Eddington, the simulated models can explain observations of ultraluminous X-ray sources, at least in terms of luminosity and energetics, without requiring intermediate-mass BHs.

  8. Spin modulation periods detected in Saturnian kilometric radiation and inner magnetic field

    NASA Astrophysics Data System (ADS)

    Galopeau, P. H. M.

    2012-09-01

    A few years ago, observations performed by the radio and plasma wave science (RPWS) experiment on board the Cassini spacecraft revealed two distinct and variable rotation periods, at 10.6 hours and 10.8 hours, in Saturn's radio emissions. These two periods correspond to SKR produced in the northern and southern hemispheres respectively. The main time modulation of planetary radio emissions has always been attributed to the effect on the inner magnetosphere of the internal magnetic field which rigidly rotates with the deep interior of the planet. As a consequence, the magnetospheric plasma, which is supposed to be frozen in the magnetic field, should rotate (or sub-rotate) with a unique spin period and such a north/south asymmetry in the radio period should never be observed. However, contrary to the other magnetized planets, Saturn presents a very particular magnetic field since its dipolar moment is nearly aligned with the rotation axis of the planet. This alignment could bring out some phenomena developing in the internal structure which are probably masked in the case of the planets the magnetic dipole of which is significantly tilted. We propose to interpret the existence of the two separated and slowly varying periods in the saturnian magnetic field as the signature of the inner dynamo.

  9. The Role of Charge and Spin Migration in DNA Radiation Damage

    NASA Astrophysics Data System (ADS)

    Becker, David; Adhikary, Amitava; Sevilla, Michael D.

    High energy radiation damage to DNA results in direct ionization of DNA and its immediate surroundings. Holes are generated throughout the DNA and its first hydration layer in accord with the electron density and the electrons produced add randomly to the DNA bases. Within a short time frame the holes move to the most stable site, the guanine base, or react by deprotonation thus localizing the damage. Electrons rapidly transfer to the DNA bases of highest electron affinity, thymine and cytosine. From these initial events the major products of radiation damage to DNA result. In Chap. 7, Becker, Adhikary and Sevilla have reviewed the recent efforts that have elucidated hole and electron transfer processes within DNA and from its hydration layer. In addition recent results are presented and discussed in this chapter. demonstrating that visible light induces hole transfer to other bases, as well as, most significantly, to the sugar phosphate backbone resulting in sugar radicals and ultimately strand breaks, i.e. a significant DNA damage.

  10. On the rotational bursting of interplanetary dust particles

    NASA Technical Reports Server (NTRS)

    Misconi, N. Y.

    1976-01-01

    A model of the zodiacal cloud is used to evaluate the effects of rotational bursting on interplanetary dust particles caused by the interaction of solar radiation pressure with the irregular surface geometry of the particles. The effectiveness of this mechanism is evaluated using several values for the effective moment arm and tensile strength of the particles. Due to repeated bursting, it is shown that particles spiraling in from the asteroid belt by the Poynting-Robertson effect do not penetrate inside 1.2 AU. Spin rate stabilization under the effect of magnetic damping is found to depend critically on the initial heliocentric distance of the particle and on its radius.

  11. Reduced radiative conductivity of low spin FeO6-octahedra in FeCO3 at high pressure and temperature

    NASA Astrophysics Data System (ADS)

    Lobanov, Sergey S.; Holtgrewe, Nicholas; Goncharov, Alexander F.

    2016-09-01

    The ability of Earth's mantle to conduct heat by radiation is determined by optical properties of mantle phases. Optical properties of mantle minerals at high pressure are accessible through diamond anvil cell experiments, but because of the intense thermal radiation at T > 1000 K such studies are limited to lower temperatures. Accordingly, radiative thermal conductivity at mantle conditions has been evaluated with the assumption of the temperature-independent optical properties. Particularly uncertain is the temperature-dependence of optical properties of lower mantle minerals across the spin transition, as the spin state itself is a strong function of temperature. Here we use laser-heated diamond anvil cells combined with a pulsed ultra-bright supercontinuum laser probe and a synchronized time-gated detector to examine optical properties of high and low spin ferrous iron at 45-73 GPa up to 1600 K in an octahedral crystallographic unit (FeO6), one of the most abundant building blocks in the mantle. Siderite (FeCO3) is used as a model for FeO6-octahedra as it contains no ferric iron and exhibits a sharp optically apparent pressure-induced spin transition at 44 GPa, simplifying data interpretation. We find that the optical absorbance of low spin FeO6 increases with temperature due to the partially lifted Laporte selection rule. The temperature-induced low-to-high spin transition, however, results in a dramatic drop in absorbance of the FeO6 unit in siderite. The absorption edge (Fe-O charge transfer) red-shifts (∼1 cm-1/K) with increasing temperature and at T > 1600 K and P > 70 GPa becomes the dominant absorption mechanism in the visible range, suggesting its superior role in reducing the ability of mantle minerals to conduct heat by radiation. This implies that the radiative thermal conductivity of analogous FeO6-bearing minerals such as ferropericlase, the second most abundant mineral in the Earth's lower mantle, is substantially reduced approaching the core

  12. Melatonin and a spin-trap compound block radiofrequency electromagnetic radiation-induced DNA strand breaks in rat brain cells.

    PubMed

    Lai, H; Singh, N P

    1997-01-01

    Effects of in vivo microwave exposure on DNA strand breaks, a form of DNA damage, were investigated in rat brain cells. In previous research, we have found that acute (2 hours) exposure to pulsed (2 microseconds pulses, 500 pps) 2450-MHz radiofrequency electromagnetic radiation (RFR) (power density 2 mW/cm2, average whole body specific absorption rate 1.2 W/kg) caused an increase in DNA single- and double-strand breaks in brain cells of the rat when assayed 4 hours post exposure using a microgel electrophoresis assay. In the present study, we found that treatment of rats immediately before and after RFR exposure with either melatonin (1 mg/kg/injection, SC) or the spin-trap compound N-tert-butyl-alpha-phenylnitrone (PBN) (100 mg/kg/injection, i.p.) blocks this effects of RFR. Since both melatonin and PBN are efficient free radical scavengers it is hypothesized that free radicals are involved in RFR-induced DNA damage in the brain cells of rats. Since cumulated DNA strand breaks in brain cells can lead to neurodegenerative diseases and cancer and an excess of free radicals in cells has been suggested to be the cause of various human diseases, data from this study could have important implications for the health effects of RFR exposure.

  13. Smaller desert dust cooling effect estimated from analysis of dust size and abundance

    NASA Astrophysics Data System (ADS)

    Kok, Jasper F.; Ridley, David A.; Zhou, Qing; Miller, Ron L.; Zhao, Chun; Heald, Colette L.; Ward, Daniel S.; Albani, Samuel; Haustein, Karsten

    2017-03-01

    Desert dust aerosols affect Earth's global energy balance through direct interactions with radiation, and through indirect interactions with clouds and ecosystems. But the magnitudes of these effects are so uncertain that it remains unclear whether atmospheric dust has a net warming or cooling effect on global climate. Consequently, it is still uncertain whether large changes in atmospheric dust loading over the past century have slowed or accelerated anthropogenic climate change, or what the effects of potential future changes in dust loading will be. Here we present an analysis of the size and abundance of dust aerosols to constrain the direct radiative effect of dust. Using observational data on dust abundance, in situ measurements of dust optical properties and size distribution, and climate and atmospheric chemical transport model simulations of dust lifetime, we find that the dust found in the atmosphere is substantially coarser than represented in current global climate models. As coarse dust warms the climate, the global dust direct radiative effect is likely to be less cooling than the ~-0.4 W m-2 estimated by models in a current global aerosol model ensemble. Instead, we constrain the dust direct radiative effect to a range between -0.48 and +0.20 W m-2, which includes the possibility that dust causes a net warming of the planet.

  14. Cosmic dust

    NASA Technical Reports Server (NTRS)

    Brownlee, Donald E.; Sandford, Scott A.

    1992-01-01

    Dust is a ubiquitous component of our galaxy and the solar system. The collection and analysis of extraterrestrial dust particles is important to exobiology because it provides information about the sources of biogenically significant elements and compounds that accumulated in distant regions of the solar nebula and that were later accreted on the planets. The topics discussed include the following: general properties of interplanetary dust; the carbonaceous component of interplanetary dust particles; and the presence of an interstellar component.

  15. Evaluating NCEP Global Dust Forecasts using VIIRS Dust Mask Index and VIIRS Aerosol Observations

    NASA Astrophysics Data System (ADS)

    Lu, C. H.; Ciren, P.; Kondragunta, S.; Wang, J.; Bhattacharjee, P. S.

    2014-12-01

    NOAA/NCEP recently implemented NASA's Goddard Global Ozone Chemistry Aerosol Radiation and Transport model (GOCART) into Global Forecast System (GFS) and the resulting global aerosol forecasting system (called NGAC) has the capability to simulate dust, sulfate, sea salt, and carbonaceous aerosols. A real-time dust-only NGAC has been operational since September 2012. Evaluation of NGAC dust forecast for the summer 2013 utilizes Visible Infrared Imaging Radiometer Suite (VIIRS) AOD retrievals and VIIRS dust mask index. While AOD retrievals are quantitative indicating column atmospheric aerosol loading, dust mask index is a qualitative flag indicating the presence of dust and dust intensity in the atmosphere. The combination of dust flag and AOD from VIIRS enables the comparison between NGAC dust AOD versus VIIRS dust AOD. The performance NGAC will be evaluated with these comparisons on a global and regional scales near and downwind of dust sources.

  16. Dust Storm

    Atmospheric Science Data Center

    2013-04-16

    article title:  Massive Dust Storm over Australia     View ... at JPL September 22, 2009 - Massive dust storm over Australia. project:  MISR category:  ... Sep 22, 2009 Images:  Dust Storm location:  Australia and New Zealand ...

  17. Experimental assessment of gold nanoparticle-mediated dose enhancement in radiation therapy beams using electron spin resonance dosimetry

    NASA Astrophysics Data System (ADS)

    Wolfe, T.; Guidelli, E. J.; Gómez, J. A.; Baffa, O.; Nicolucci, P.

    2015-06-01

    In this work, we aim to experimentally assess increments of dose due to nanoparticle-radiation interactions via electron spin resonance (ESR) dosimetry performed with a biological-equivalent sensitive material. We employed 2-Methyl-Alanine (2MA) in powder form to compose the radiation sensitive medium embedding gold nanoparticles (AuNPs) 5 nm in diameter. Dosimeters manufactured with 0.1% w/w of AuNPs or no nanoparticles were irradiated with clinically utilized 250 kVp orthovoltage or 6 MV linac x-rays in dosimetric conditions. Amplitude peak-to-peak (App) at the central ESR spectral line was used for dosimetry. Dose-response curves were obtained for samples with or without nanoparticles and each energy beam. Dose increments due to nanoparticles were analyzed in terms of absolute dose enhancements (DEs), calculated as App ratios for each dose/beam condition, or relative dose enhancement factors (DEFs) calculated as the slopes of the dose-response curves. Dose enhancements were observed to present an amplified behavior for small doses (between 0.1-0.5 Gy), with this effect being more prominent with the kV beam. For doses between 0.5-5 Gy, dose-independent trends were observed for both beams, stable around (2.1   ±   0.7) and (1.3   ±   0.4) for kV and MV beams, respectively. We found DEFs of (1.62   ±   0.04) or (1.27   ±   0.03) for the same beams. Additionally, we measured no interference between AuNPs and the ESR apparatus, including the excitation microwaves, the magnetic fields and the paramagnetic radicals. 2MA was demonstrated to be a feasible paramagnetic radiation-sensitive material for dosimetry in the presence of AuNPs, and ESR dosimetry a powerful experimental method for further verifications of increments in nanoparticle-mediated doses of biological interest. Ultimately, gold nanoparticles can cause significant and detectable dose enhancements in biological-like samples irradiated at both

  18. Hierarchical data-driven approach to fitting numerical relativity data for nonprecessing binary black holes with an application to final spin and radiated energy

    NASA Astrophysics Data System (ADS)

    Jiménez-Forteza, Xisco; Keitel, David; Husa, Sascha; Hannam, Mark; Khan, Sebastian; Pürrer, Michael

    2017-03-01

    Numerical relativity is an essential tool in studying the coalescence of binary black holes (BBHs). It is still computationally prohibitive to cover the BBH parameter space exhaustively, making phenomenological fitting formulas for BBH waveforms and final-state properties important for practical applications. We describe a general hierarchical bottom-up fitting methodology to design and calibrate fits to numerical relativity simulations for the three-dimensional parameter space of quasicircular nonprecessing merging BBHs, spanned by mass ratio and by the individual spin components orthogonal to the orbital plane. Particular attention is paid to incorporating the extreme-mass-ratio limit and to the subdominant unequal-spin effects. As an illustration of the method, we provide two applications, to the final spin and final mass (or equivalently: radiated energy) of the remnant black hole. Fitting to 427 numerical relativity simulations, we obtain results broadly consistent with previously published fits, but improving in overall accuracy and particularly in the approach to extremal limits and for unequal-spin configurations. We also discuss the importance of data quality studies when combining simulations from diverse sources, how detailed error budgets will be necessary for further improvements of these already highly accurate fits, and how this first detailed study of unequal-spin effects helps in choosing the most informative parameters for future numerical relativity runs.

  19. Lunar Dust Mitigation Screens

    NASA Astrophysics Data System (ADS)

    Knutson, Shawn; Holloway, Nancy

    With plans for the United States to return to the moon, and establish a sustainable human presence on the lunar surface many issues must be successfully overcome. Lunar dust is one of a number of issues with the potential to create a myriad of problems if not adequately addressed. Samples of dust brought back from Apollo missions show it to be soft, yet sharp and abrasive. The dust consists of a variety of morphologies including spherical, angular blocks, shards, and a number of irregular shapes. One of the main issues with lunar dust is its attraction to stick to anything it comes in contact with (i.e. astronauts, equipment, habitats, etc.). Ionized radiation from the sun strikes the moon's surface and creates an electrostatic charge on the dust. Further, the dust harbors van der Waals forces making it especially difficult to separate once it sticks to a surface. During the Apollo missions, it was discovered that trying to brush the lunar dust from spacesuits was not effective, and rubbing it caused degradation of the suit material. Further, when entering the lunar module after moonwalks, the astronauts noted that the dust was so prolific inside the cabin that they inhaled and ingested it, causing at least one of them, Harrison "Jack" Schmidt, to report irritation of the throat and lungs. It is speculated that the dust could also harm an astronaut's nervous and cardiovascular systems, especially during an extended stay. In addition to health issues, the dust can also cause problems by scouring reflective coatings off of thermal blankets, and roughening surfaces of windows and optics. Further, panels on solar cells and photovoltaics can also be compromised due to dust sticking on the surfaces. Lunar dust has the capacity to penetrate seals, interfere with connectors, as well as mechanisms on digging machines, all of which can lead to problems and failure. To address lunar dust issues, development of electrostatic screens to mitigate dust on sur-faces is currently

  20. Electron spin resonance studies of radiation damage to DNA and to proteins

    NASA Astrophysics Data System (ADS)

    Symons, Martyn C. R.

    1995-06-01

    Exposure of biopolymers to ionising radiation in dilute aqueous solution results in damage to water and resulting radicals attack the solute molecules in various ways. This form of damage is usually described as "indirect". However, in cellular systems "direct" damage is more frequent, especially to nuclear DNA, where the concentration of water may be quite low. In this review, I am primarily concerned with direct damage. The intial chemical consequence of direct damage is electron-ejection followed by electron-capture. ESR studies have established that electron-loss is fixed in the purine bases (mainly as G- +) whilst electron-capture occurs mainly at the pyrimidine bases (C- - and T- -). Almost certainly, these centres are stabilized by proton-loss and proton-gain. These results indicate that even electron-loss must occur initially from all regions of the DNA, including the phosphate and sugar units, it moves rapidly into the stacked base system. Similarly, the ejected electrons fail to react with phosphate and react preferentially witht the bases. Also, the electron-hole and electron-gain centres are well separated, since radical-pairs (triplet-states) have never been detected by ESR spectroscopy. A similar situation arises for direct damage to proteins. Electron-loss initially be mainly from the amide backbone and the ESR results suggest that this is rapidly trapped by loss of an N—H proton to give amido radicals. However, electrons are not trapped by the protein backbone, unless there are no electron-affinic groups present. In many cases, the results establish that these electrons move through large distances before being specifically trapped at unique sites.

  1. Coupling Mars' Dust and Water Cycles: Effects on Dust Lifting Vigor, Spatial Extent and Seasonality

    NASA Technical Reports Server (NTRS)

    Kahre, M. A.; Hollingsworth, J. L.; Haberle, R. M.; Montmessin, F.

    2012-01-01

    The dust cycle is an important component of Mars' current climate system. Airborne dust affects the radiative balance of the atmosphere, thus greatly influencing the thermal and dynamical state of the atmosphere. Dust raising events on Mars occur at spatial scales ranging from meters to planet-wide. Although the occurrence and season of large regional and global dust storms are highly variable from one year to the next, there are many features of the dust cycle that occur year after year. Generally, a low-level dust haze is maintained during northern spring and summer, while elevated levels of atmospheric dust occur during northern autumn and winter. During years without global-scale dust storms, two peaks in total dust loading were observed by MGS/TES: one peak occurred before northern winter solstice at Ls 200-240, and one peak occurred after northern winter solstice at L(sub s) 305-340. These maxima in dust loading are thought to be associated with transient eddy activity in the northern hemisphere, which has been observed to maximize pre- and post-solstice. Interactive dust cycle studies with Mars General Circulation Models (MGCMs) have included the lifting, transport, and sedimentation of radiatively active dust. Although the predicted global dust loadings from these simulations capture some aspects of the observed dust cycle, there are marked differences between the simulated and observed dust cycles. Most notably, the maximum dust loading is robustly predicted by models to occur near northern winter solstice and is due to dust lifting associated with down slope flows on the flanks of the Hellas basin. Thus far, models have had difficulty simulating the observed pre- and post- solstice peaks in dust loading. Interactive dust cycle studies typically have not included the formation of water ice clouds or their radiative effects. Water ice clouds can influence the dust cycle by scavenging dust from atmosphere and by interacting with solar and infrared radiation

  2. Circumstellar dust

    NASA Technical Reports Server (NTRS)

    Dwek, E.

    1986-01-01

    The presence of dust in the general interstellar medium is inferred from the extinction, polarization, and scattering of starlight; the presence of dark nebulae; interstellar depletions; the observed infrared emission around certain stars and various types of interstellar clouds. Interstellar grains are subject to various destruction mechanisms that reduce their size or even completely destroy them. A continuous source of newly formed dust must therefore be present for dust to exist in the various phases of the interstellar medium (ISM). The working group has the following goals: (1) review the evidences for the formation of dust in the various sources; (2) examine the clues to the nature and composition of the dust; (3) review the status of grain formation theories; (4) examine any evidence for the processing of the dust prior to its injection into the interstellar medium; and (5) estimate the relative contribution of the various sources to the interstellar dust population.

  3. Modeling the dust size distribution in comets with dust fragmentation

    NASA Technical Reports Server (NTRS)

    Konno, Ichishiro; Huebner, Walter F.

    1990-01-01

    A hydrodynamic model was developed of a spherically symmetric dusty gas flow in a cometary atmosphere assuming a single fluid, inviscid, perfect gas. The hydrodynamics for gas and dust, which involves the gas drag force (momentum transfer), heat exchange between gas and dust, photodissociation energy for H2O gas, and radiative heating and cooling terms for dust particles, are solved using the Gear method for stiff, coupled differential equations. Calculations were done with a dust size distribution for radii alpha = 0.01 micron to 10 cm with densities variable with the size. A nucleus size of 4.0 km radius with a density of 0.5 g/cu cm and a total dust-to-gas mass ratio chi = 1 was adopted. There are indications from in situ observations that dust particle fragment into smaller ones. Fragmentation of dust particles was incorporated into the model. This is done by adding source and sink terms in the continuity equations for the dust. Lifetimes for the decay of dust particles were assumed as a function of particle size. It is also assumed that dust particles always fragment only into the next smaller size.

  4. A Case Against Spinning PAHs as the Source of the Anomalous Microwave Emission

    NASA Astrophysics Data System (ADS)

    Hensley, Brandon S.; Draine, B. T.; Meisner, Aaron M.

    2016-08-01

    We employ an all-sky map of the anomalous microwave emission (AME) produced by component separation of the microwave sky to study correlations between the AME and Galactic dust properties. We find that while the AME is highly correlated with all tracers of dust emission, the best predictor of the AME strength is the dust radiance. Fluctuations in the AME intensity per dust radiance are uncorrelated with fluctuations in the emission from polycyclic aromatic hydrocarbons (PAHs), casting doubt on the association between AME and PAHs. The PAH abundance is strongly correlated with the dust optical depth and dust radiance, consistent with PAH destruction in low density regions. We find that the AME intensity increases with increasing radiation field strength, at variance with predictions from the spinning dust hypothesis. Finally, the temperature dependence of the AME per dust radiance disfavors the interpretation of the AME as thermal emission. A reconsideration of other AME carriers, such as ultrasmall silicates, and other emission mechanisms, such as magnetic dipole emission, is warranted.

  5. Saharan Dust Export towards the Caribbean: Dust Sources and Atmospheric Circulation over North Africa

    NASA Astrophysics Data System (ADS)

    Schepanski, Kerstin; Heinold, Bernd; Groß, Silke; Schäfler, Andreas; Weinzierl, Bernadett; Sauer, Daniel; Walser, Adrian; Tegen, Ina

    2015-04-01

    Studies analysing satellite observations illustrate the spatial and temporal distribution of emitting dust sources. Results show that high surface wind speeds related to the break-down of the nocturnal low-level jet (LLJ) occurring during the morning hours are frequent driving mechanism for dust uplift in the Sahara desert. Here, we present a study investigating atmospheric circulation pattern over North Africa favouring (a) dust entrainment into the boundary layer and (b) dust export towards the Caribbean Sea. Satellite-based information on the spatio-temporal distribution of dust source activation (DSA) events inferred from 15-minute Meteosat Second Generation (MSG) Spinning Enhanced Visible and InfraRed Imager (SEVIRI) dust observations are linked to atmospheric circulation regimes over North Africa. By means of air-mass trajectories, which map the dust export from North Africa toward the SALTRACE ground observation site at Barbados, cases are selected which link DSA regions with dust events observed at Barbados. These cases are then examined with regard to the atmospheric conditions during dust emission and geomorphologic dust source characteristic. Dust properties inferred from LIDAR observation using the POLIS system and measurements taken during Falcon research flights are compared to the different dust source locations and atmospheric conditions during dust emission. Altogether, the results from this study aim at illustrating the relevance of knowing the dust source locations in concert with the atmospheric circulation. Ultimately, this study addresses the question of what is finally transported across the Atlantic towards the Caribbean from which dust source region.

  6. Nano-Dust Analyzer

    NASA Astrophysics Data System (ADS)

    Gruen, E.; Horanyi, M.; Moebius, E.; Sternovsky, Z.; Auer, S.; Srama, R.; Juhasz, A.

    2010-12-01

    Recently, the STEREO WAVES instruments recorded a large number of intense electric field signals, which were interpreted as impacts from nanometer sized particles striking the spacecraft with velocities of about the solar wind speed [1]. This high flux and strong spatial and/or temporal variations of nanometer sized dust grains at low latitude appears to be uncorrelated with the solar wind properties. Early dust instruments onboard Pioneer 8 and 9 and Helios spacecraft detected a flow of submicron sized dust particles coming from the direction of the Sun. These particles originate in the inner solar system from mutual collisions among meteoroids and move on hyperbolic orbits that leave the Solar System under the prevailing radiation pressure force [2]. The observed fluxes of inner-source pickup ions also point to the existence of a much enhanced dust population in the nanometer size range [3]. A new highly sensitive instrument is being developed within NASA's Heliophysics Program to confirm the existence of the so-called nano-dust particles, characterize their impact parameters, and measure their chemical composition. The instrument is based on the Cassini Dust Analyzer (CDA) that has analyzed the composition of nanometer sized dust particles emanating from the Jovian and Saturnian systems but could not be pointed towards the Sun. By applying technologies implemented in solar wind instruments and coronagraphs a highly sensitive dust analyzer will be developed and tested in the laboratory. The measurements will enable us to identify the source of the dust by comparing their elemental composition with that of larger micrometeoroid particles of cometary and asteroid origin and will reveal interaction of nano-dust with the interplanetary medium by investigating the relation of the dust flux with solar wind and IMF properties. [1] Meyer-Vernet, N. et al., Solar Physics, 256, 463, 2009 [2] Zook, H.A. and Berg, O.E.: A source for hyperbolic cosmic dust particles

  7. The sources of the unusual dust jets seen in Comet 103P/Hartley 2

    NASA Astrophysics Data System (ADS)

    Belton, Michael J. S.

    2013-02-01

    We show that the unusual behavior of dust jets seen embedded in the sunward coma of 103P/Hartley 2 originate in active regions migrating over the two lobes of the nucleus following the Sun. The slowly changing orientation of the jets and their rapid changes in brightness is due to the shape and local topography of the nucleus coupled with the complex spin state. The intermittent appearance of a second jet is due to periodic deviations in the direction of the ejection of dust from the small lobe of the nucleus. The release of dust into the structures is likely due to the sublimation of H2O. The jets are characterized by injection speeds from the nucleus of 50-210 m/s, a radiation pressure parameter 0.08 < β < 1, and a particle life-time near 7 h. Within the jets, the average particle size decreases and the injection speed increases with distance from the nucleus.

  8. Spin dependent recombination; A sup 29 Si hyperfine study of radiation-induced P sub b centers at the Si/SiO sub 2 interface

    SciTech Connect

    Jupina, M.A.; Lenahan, P.M. )

    1990-12-01

    The spin dependent recombination (SDR) technique is used to observe the {sup 29}Si hyperfine spectra of radiation-induced P{sub b} centers at the Si/SiO{sub 2} interface in a MOSFET. The P{sub b} center is a paramagnetic, trivalent silicon defect that is the dominant radiation-induced interface state. The {sup 29}Si hyperfine spectra give detailed atomic scale information about the P{sub b} center. The authors' SDR results show that the {sup 29}Si hyperfine spectra vary with surface potential. This result indicates that differences in the defect's local geometry lead to substantial differences in the defect's energy level. However, the {sup 29}Si hyperfine spectra are found to be relatively independent of the ionizing radiation dosage.

  9. Dust Growth in Astrophysical Plasmas

    NASA Astrophysics Data System (ADS)

    Bingham, R.; Tsytovich, V. N.

    2002-12-01

    Dust formation in space is important in diverse environments such as dust molecular clouds, proto-planetary nebulae, stellar outbursts, and supernova explosions. The formation of dust proceeds the formation of stellar objects and planets. In all these environments the dust particles interact with both neutral and plasma particles as well as with (ultraviolet) radiation and cosmic rays. The conventional view of grain growth is one based on accretion by the Van der Waals and chemical forces [Watson and Salpeter [14] considered in detail both theoretically and numerically (Kempf at all [6],Meaking [7]( and confirmed recently by micro-gravity experiments Blum et all [2]). The usual point of view is that the dust grow is occurring in dust molecular clouds at very low temperatures ~ (10 - 30)° K and is a slow process - dust grows to a size of about 0.1 μm in 106 - 109 years. This contradicts recent observations of dust growing in winds of C-stars in about 10 years and behind the supernova SN1987A shock in about 500 days. Also recent observation of star formation at the edge of irradiated dust clouds suggests that new plasma mechanism operates in star formation. Dusty plasma mechanisms of agglomeration are analyzed as an explanation of the new astrophysical observation. New micro-gravity experiments are proposed for observing the plasma mechanisms of dust agglomeration at gas pressures substantially higher than used in ([2]. Calculations for the growth rates of dust agglomeration due to plasma mechanisms are presented. It is shown that at large neutral gas densities the dust plasma attraction provides an explanation of dust grow in about 10 days observed in H-star winds. Ionization by cosmic rays and by radioactive dust can provide the dust attraction necessary for forming dust clumping observed in molecular clouds and the fractal plasma clumping can enhance the time to reach the gravitational contraction phase operating at the final stage of star formation. A new

  10. The Dust Content and Radiation Fields of Sample of Galaxies in the ELAIS-N1 Field

    NASA Astrophysics Data System (ADS)

    Shalima, P.; Gogoi, Rupjyoti; Pathak, Amit; Misra, Ranjeev; Gupta, Ranjan; Vaidya, D. B.

    2015-08-01

    The Mid-IR colors ($F_{8}/F_{24}$) of galaxies together with their IR-UV luminosity correlations can be used to get some insight into the relative abundance of the different dust grain populations present in them. The ELAIS-N1 field contains thousands of galaxies which do not have optical spectra but have been observed in the Mid-IR by {\\it Spitzer} and UV by {\\it GALEX} making it ideal for these studies. As part of this work we have selected a sample of galaxies from the ELAIS-N1 field which have photometric observations in the MIR and UV as well as photometric redshifts from the SDSS database. We put the constraint that the redshifts are $\\le$ 0.1, thereby giving us a total of 309 galaxies. We find that the majority of the galaxies in the sample are PAH dominated due to their high MIR flux ratio. We also find a reasonable correlation between the Mid-IR and the UV luminosities out of which the Mid-IR emission from PAHs at 8 $\\mu$m is marginally better correlated than the 24 $\\mu$m VSG emission with the UV luminosities. However, if we divide the sample based on their $F_{8}/F_{24}$ ratios which is also an indicator of metallicity, the MIR-UV correlation seems to increase with the $F_{8}/F_{24}$ ratio. But the MIR-UV correlations are not very different for the PAHs and the VSG population within the individual metallicity groups.

  11. Dust-magnetospheric interactions

    NASA Technical Reports Server (NTRS)

    Mendis, D. A.

    1979-01-01

    The important processes controlling the electrical potentials of dust grains in planetary magnetospheres are considered, and the quasi-equilibrium electric potentials acquired by them in the different plasma and radiative environments encountered are evaluated. The orbital dynamics of such charged grains is discussed, and their interaction with satellites within the planetary magnetospheres is considered. The possibility of magneto-gravitational capture of these gains by magnetospheres, to form dust rings around the planets, is also discussed. Finally, the possible break-up of grains charged to large electrical potentials and its consequences are briefly addressed.

  12. Protoplanetary Dust

    NASA Astrophysics Data System (ADS)

    Apai, D.´niel; Lauretta, Dante S.

    2014-02-01

    Preface; 1. Planet formation and protoplanetary dust Daniel Apai and Dante Lauretta; 2. The origins of protoplanetary dust and the formation of accretion disks Hans-Peter Gail and Peter Hope; 3. Evolution of protoplanetary disk structures Fred Ciesla and Cornelius P. Dullemond; 4. Chemical and isotopic evolution of the solar nebula and protoplanetary disks Dmitry Semenov, Subrata Chakraborty and Mark Thiemens; 5. Laboratory studies of simple dust analogs in astrophysical environments John R. Brucato and Joseph A. Nuth III; 6. Dust composition in protoplanetaty dust Michiel Min and George Flynn; 7. Dust particle size evolution Klaus M. Pontoppidan and Adrian J. Brearly; 8. Thermal processing in protoplanetary nebulae Daniel Apai, Harold C. Connolly Jr. and Dante S. Lauretta; 9. The clearing of protoplanetary disks and of the protosolar nebula Ilaira Pascucci and Shogo Tachibana; 10. Accretion of planetesimals and the formation of rocky planets John E. Chambers, David O'Brien and Andrew M. Davis; Appendixes; Glossary; Index.

  13. Studies of magnetism and exchange scattering in solids using synchroton radiation and spin-polarized photoemission. Progress report, June 1, 1982-May 31, 1983

    SciTech Connect

    Rothberg, G.M.

    1983-01-01

    Some of the experiments necessary for proving the existence of Spin Polarized EXAFS (SPEXAFS) and for establishing it as a useful techncique for studying magnetism in solids have been carried out at the Stanford Synchrotron Radiation Laboratory (SSRL) and the National Synchrotron Light Source (NSLS). Transmission EXAFS, which does not depend on electron spin, has been measured in several manganese compounds. The 3s photopeaks of Mn/sup 2 +/ in MnF/sub 2/ have been shown to display EXAFS-like oscillations. The pin dependence of these oscillations will next be studied. Observations of the 3p photopeaks of iron metal on a palladium substrate have shown anomalous intensity variations with varying photon energy. This phenomenon will also be studied further. The existence of Cooper minima in the iron 3s and 3p photoabsorption cross sections has been sought, and this investigation will continue.

  14. Spin-orbit and rotational couplings in radiative association of C({sup 3}P) and N({sup 4}S) atoms

    SciTech Connect

    Antipov, Sergey V.; Gustafsson, Magnus; Nyman, Gunnar

    2011-11-14

    The role of spin-orbit and rotational couplings in radiative association of C({sup 3}P) and N({sup 4}S) atoms is investigated. Couplings among doublet electronic states of the CN radical are considered, giving rise to a 6-state model of the process. The solution of the dynamical problem is based on the L{sup 2} method, where a complex absorbing potential is added to the Hamiltonian operator in order to treat continuum and bound levels in the same manner. Comparison of the energy-dependent rate coefficients calculated with and without spin-orbit and rotational couplings shows that the couplings have a strong effect on the resonance structure and low-energy baseline of the rate coefficient.

  15. Experiments on Dust Grain Charging

    NASA Technical Reports Server (NTRS)

    Abbas, M. N.; Craven, P. D.; Spann, J. F.; Tankosic, D.; LeClair, A.; West, E. A.

    2004-01-01

    Dust particles in various astrophysical environments are charged by a variety of mechanisms generally involving collisional processes with other charged particles and photoelectric emission with UV radiation from nearby sources. The sign and the magnitude of the particle charge are determined by the competition between the charging processes by UV radiation and collisions with charged particles. Knowledge of the particle charges and equilibrium potentials is important for understanding of a number of physical processes. The charge of a dust grain is thus a fundamental parameter that influences the physics of dusty plasmas, processes in the interplanetary medium and interstellar medium, interstellar dust clouds, planetary rings, cometary and outer atmospheres of planets etc. In this paper we present some results of experiments on charging of dust grains carried out on a laboratory facility capable levitating micron size dust grains in an electrodynamic balance in simulated space environments. The charging/discharging experiments were carried out by exposing the dust grains to energetic electron beams and UV radiation. Photoelectric efficiencies and yields of micron size dust grains of SiO2, and lunar simulates obtained from NASA-JSC will be presented.

  16. Experiments on Dust Grain Charging

    NASA Technical Reports Server (NTRS)

    Abbas, M. N.; Craven, P. D.; Spann, J. F.; Tankosic, D.; LeClair, A.; West, E. A.

    2004-01-01

    Dust particles in various astrophysical environments are charged by a variety of mechanisms generally involving collisional processes with other charged particles and photoelectric emission with UV radiation from nearby sources. The sign and the magnitude of the particle charge are determined by the competition between the charging processes by UV radiation and collisions with charged particles. Knowledge of the particle charges and equilibrium potentials is important for understanding of a number of physical processes. The charge of a dust grain is thus a fundamental parameter that influences the physics of dusty plasmas, processes in the interplanetary medium and interstellar medium, interstellar dust clouds, planetary rings, cometary and outer atmospheres of planets etc. In this paper we present some results of experiments on charging of dust grains carried out on a laboratory facility capable levitating micron size dust grains in an electrodynamic balance in simulated space environments. The charging/discharging experiments were carried out by exposing the dust grains to energetic electron beams and UV radiation. Photoelectric efficiencies and yields of micron size dust grains of SiO2, and lunar simulates obtained from NASA-JSC will be presented.

  17. High concentration dust monitor

    NASA Astrophysics Data System (ADS)

    Lilienfeld, P.

    1981-06-01

    The development, design, fabrication, and testing of a portable, self-contained prototype monitoring instrument capable of detecting and measuring airborne coal dust levels as concentrations in the range of 20 to 500 g/cu m is described. The output of the high concentration dust monitor is essentially independent of particle size and composition, with a response time of 10 seconds. Direct concentration readout as well as internal memory or recording capabilities are incorporated in the device. The operation of the instrument is based on direct sensing of the mass concentration of airborne dust by air-path beta radiation attenuation. The monitor is battery operated and incorporates a microprocessor that controls periodic automatic zero referencing, executes the mass computations, records the data for subsequent playback, and performs internal diagnostic checks.

  18. Estimation of high altitude Martian dust parameters

    NASA Astrophysics Data System (ADS)

    Pabari, Jayesh; Bhalodi, Pinali

    2016-07-01

    Dust devils are known to occur near the Martian surface mostly during the mid of Southern hemisphere summer and they play vital role in deciding background dust opacity in the atmosphere. The second source of high altitude Martian dust could be due to the secondary ejecta caused by impacts on Martian Moons, Phobos and Deimos. Also, the surfaces of the Moons are charged positively due to ultraviolet rays from the Sun and negatively due to space plasma currents. Such surface charging may cause fine grains to be levitated, which can easily escape the Moons. It is expected that the escaping dust form dust rings within the orbits of the Moons and therefore also around the Mars. One more possible source of high altitude Martian dust is interplanetary in nature. Due to continuous supply of the dust from various sources and also due to a kind of feedback mechanism existing between the ring or tori and the sources, the dust rings or tori can sustain over a period of time. Recently, very high altitude dust at about 1000 km has been found by MAVEN mission and it is expected that the dust may be concentrated at about 150 to 500 km. However, it is mystery how dust has reached to such high altitudes. Estimation of dust parameters before-hand is necessary to design an instrument for the detection of high altitude Martian dust from a future orbiter. In this work, we have studied the dust supply rate responsible primarily for the formation of dust ring or tori, the life time of dust particles around the Mars, the dust number density as well as the effect of solar radiation pressure and Martian oblateness on dust dynamics. The results presented in this paper may be useful to space scientists for understanding the scenario and designing an orbiter based instrument to measure the dust surrounding the Mars for solving the mystery. The further work is underway.

  19. Electron spin resonance analysis of tooth enamel does not indicate exposures to large radiation doses in a large proportion of distally-exposed A-bomb survivors.

    PubMed

    Hirai, Yuko; Kodama, Yoshiaki; Cullings, Harry M; Miyazawa, Chuzo; Nakamura, Nori

    2011-01-01

    The atomic bombs in Hiroshima and Nagasaki led to two different types of radiation exposure; one was direct and brief and the other was indirect and persistent. The latter (so-called exposure to residual radiation) resulted from the presence of neutron activation products in the soil, or from fission products present in the fallout. Compared with the doses from direct exposures, estimations of individual doses from residual radiation have been much more complicated, and estimates vary widely among researchers. The present report bases its conclusions on radiation doses recorded in tooth enamel from survivors in Hiroshima. Those survivors were present at distances of about 3 km or greater from the hypocenter at the time of the explosion, and have DS02 estimated doses (direct exposure doses) of less than 5 mGy (and are regarded as control subjects). Individual doses were estimated by measuring CO(2)(-) radicals in tooth enamel with the electron spin resonance (ESR; or electron paramagnetic resonance, EPR) method. The results from 56 molars donated by 49 survivors provided estimated doses which vary from -200 mGy to 500 mGy, and the median dose was 17 mGy (25% and 75% quartiles are -54 mGy and 137 mGy, respectively) for the buccal parts and 13 mGy (25% and 75% quartiles: -49 mGy and 87 mGy, respectively) for the lingual parts of the molars. Three molars had ESR-estimated doses of 300 to 400 mGy for both the buccal and lingual parts, which indicates possible exposures to excess doses of penetrating radiation, although the origin of such radiation remains to be determined. The results did not support claims that a large fraction of distally-exposed survivors received large doses (e.g. 1 Gy) of external penetrating radiation resulting from residual radiation.

  20. China Dust

    Atmospheric Science Data Center

    2013-04-16

    ... SpectroRadiometer (MISR) nadir-camera images of eastern China compare a somewhat hazy summer view from July 9, 2000 (left) with a ... arid and sparsely vegetated surfaces of Mongolia and western China pick up large quantities of yellow dust. Airborne dust clouds from the ...

  1. Andromeda's dust

    SciTech Connect

    Draine, B. T.; Aniano, G.; Krause, Oliver; Groves, Brent; Sandstrom, Karin; Klaas, Ulrich; Linz, Hendrik; Rix, Hans-Walter; Schinnerer, Eva; Schmiedeke, Anika; Walter, Fabian; Braun, Robert; Leroy, Adam E-mail: ganiano@ias.u-psud.fr

    2014-01-10

    Spitzer Space Telescope and Herschel Space Observatory imaging of M31 is used, with a physical dust model, to construct maps of dust surface density, dust-to-gas ratio, starlight heating intensity, and polycyclic aromatic hydrocarbon (PAH) abundance, out to R ≈ 25 kpc. The global dust mass is M {sub d} = 5.4 × 10{sup 7} M {sub ☉}, the global dust/H mass ratio is M {sub d}/M {sub H} = 0.0081, and the global PAH abundance is (q {sub PAH}) = 0.039. The dust surface density has an inner ring at R = 5.6 kpc, a maximum at R = 11.2 kpc, and an outer ring at R ≈ 15.1 kpc. The dust/gas ratio varies from M {sub d}/M {sub H} ≈ 0.026 at the center to ∼0.0027 at R ≈ 25 kpc. From the dust/gas ratio, we estimate the interstellar medium metallicity to vary by a factor ∼10, from Z/Z {sub ☉} ≈ 3 at R = 0 to ∼0.3 at R = 25 kpc. The dust heating rate parameter (U) peaks at the center, with (U) ≈ 35, declining to (U) ≈ 0.25 at R = 20 kpc. Within the central kiloparsec, the starlight heating intensity inferred from the dust modeling is close to what is estimated from the stars in the bulge. The PAH abundance reaches a peak q {sub PAH} ≈ 0.045 at R ≈ 11.2 kpc. When allowance is made for the different spectrum of the bulge stars, q {sub PAH} for the dust in the central kiloparsec is similar to the overall value of q {sub PAH} in the disk. The silicate-graphite-PAH dust model used here is generally able to reproduce the observed dust spectral energy distribution across M31, but overpredicts 500 μm emission at R ≈ 2-6 kpc, suggesting that at R = 2-6 kpc, the dust opacity varies more steeply with frequency (with β ≈ 2.3 between 200 and 600 μm) than in the model.

  2. Sensitivity test of GOCI dust aerosol index with aerosol absorptivity by using radiative transfer simulation and comparison with AERONET aerosol optical properties

    NASA Astrophysics Data System (ADS)

    Choi, M.; Kim, J.; Lee, J.; Park, Y. J.

    2016-12-01

    For the monitoring of aerosol properties in East Asia using the Geostationary Ocean Color Imager (GOCI), the GOCI Yonsei aerosol retrieval (YAER) algorithm was developed and has been improved continuously since 2011. GOCI YAER algorithm contains several aerosol models consisted of various optical properties such as aerosol optical depth (AOD), fine-mode fraction (FMF), and single scattering albedo (SSA) for assuming every possible aerosol status. Then, AOD at 550 nm is retrieved from selected aerosol models which show least difference between observed top-of-atmosphere (TOA) reflectance and simulated TOA reflectance in terms of spectral AODs. Current inversion method is optimized for spectral AODs, especially AOD at 550 nm. Therefore, GOCI YAER AOD, FMF, and Angstrom exponent show reliable accuracy with ground-based AERONET and satellite-based MODIS and VIIRS products. However, SSA shows least accuracy (R = 0.2) with AERONET SSA, which is different from AOD, FMF, and AE. To improve accuracy of SSA retrieval, the inversion method should reflect a characteristic of aerosol absorptivity well, not only in the aerosol model construction as forward modeling. UV aerosol index from TOMS and OMI measurements, calculated by using 354 and 388 nm, provides the extent of aerosol absorptivity, which can be used for the improvement of aerosol model quality between absorbing and non-absorbing aerosol model. Instead of UV index, a dust aerosol index (DAI) can be calculated using two visible channels such as 412 and 443 (or 490) nm. Heavy dust plume, which is coarse and absorbing aerosol, in 47 April 2012 show DAI of 5, but heavy haze plume, which is fine and non-absorbing aerosol, in 6 May 2012 shows DAI close to 0. To find relationship between DAI and aerosol absorptivity properties, sensitivity is tested by using radiative transfer model (RTM), and retrieved GOCI DAI from observed TOA reflectance is compared with ground-based AERONET SSA and other optical properties. Both of

  3. Single--Spin Asymmetries in the Bethe--Heitler Process e{sup -} + p {yields} e{sup -} + {gamma} + p from QED Radiative Corrections

    SciTech Connect

    Andrei Afanasev; M.I. Konchatnij; N.P. Merenkov

    2005-06-01

    We derived analytic formulae for the polarization single--spin asymmetries (SSA) in the Bethe--Heitler process e{sup -} + p {yields} e{sup -} + {gamma} + p. The asymmetries arise due to one-loop QED radiative corrections to the leptonic part of the interaction and present a systematic correction for the studies of virtual Compton Scattering on a proton through interference with the Bethe-Heitler amplitude. Considered are SSA with either longitudinally polarized electron beam or a polarized proton target. The computed effect appears to be small, not exceeding 0.1 percent for kinematics of current virtual Compton scattering experiments.

  4. Estimation of mineral dust direct radiative forcing at the European Aerosol Research Lidar NETwork site of Lecce, Italy, during the ChArMEx/ADRIMED summer 2013 campaign: Impact of radiative transfer model spectral resolutions

    NASA Astrophysics Data System (ADS)

    Barragan, Ruben; Romano, Salvatore; Sicard, Michaël.; Burlizzi, Pasquale; Perrone, Maria Rita; Comeron, Adolfo

    2016-09-01

    A field campaign took place in the western and central Mediterranean basin on June-July 2013 in the framework of the ChArMEx (Chemistry-Aerosol Mediterranean Experiment, http://charmex.lsce.ipsl.fr/)/ADRIMED (Aerosol Direct Radiative Impact on the regional climate in the MEDiterranean region, http://adrimed.sedoo.fr/) project to characterize the aerosol direct radiative forcing (DRF) over the Mediterranean. This work focuses on the aerosol DRF estimations at Lecce (40.33°N; 18.11°E; 30 m above sea level) during the Saharan dust outbreak that affected southern Italy from 20 to 24 June 2013. The Global Atmospheric Model (GAME) and the Two-Stream (TS) model were used to calculate the instantaneous aerosol DRF in the short-wave (SW) and long-wave (LW) spectral ranges, at the surface and at the top of the atmosphere (TOA). The main differences between the two models were due to the different numerical methods to solve the radiative transfer (RT) equations and to the more detailed spectral resolution of GAME compared to that of TS. 167 and 115 subbands were used by GAME in the 0.3-4 and 4-37 µm spectral ranges, respectively. Conversely, the TS model used 8 and 11 subbands in the same spectral ranges, respectively. We found on 22 June that the SW-DRFs from the two models were in good agreement, both at the TOA and at the surface. The instantaneous SW-DRFs at the surface and at the TOA varied from -50 to -34 W m-2 and from -6 to +8 W m-2, respectively, while the surface and TOA LW-DRFs ranged between +3.5 and +8.0 W m-2 and between +1.7 and +6.9 W m-2, respectively. In particular, both models provided positive TOA SW-DRFs at solar zenith angles smaller than 25° because of the mixing of the desert dust with anthropogenic pollution during its transport to the study site. In contrast, the TS model overestimated the GAME LW-DRF up to about 5 and 7.5 times at the surface and at the TOA, respectively, when the dust particle contribution was largest. The low spectral

  5. Let There Be Dust

    NASA Astrophysics Data System (ADS)

    McKee, Christopher F.

    2011-09-01

    Most of the ordinary matter in the universe is hydrogen and helium. In galaxies such as ours, heavier elements make up only about 1% of the mass, and about half of this is tied up in small particles, termed dust grains, that range in size from a nanometer to a fraction of a micrometer. Interstellar dust contains an appreciable fraction of the carbon and most of the refractory elements, such as magnesium, silicon, and iron. Because these particles are comparable in size to the wavelength of light, they are very effective at absorbing it. As a result, the Milky Way is much fainter in the night sky than it would otherwise be. This absorbed light is reradiated, but because the dust in the interstellar medium is so cold - about 20° above absolute zero - it is radiated at very long wavelengths, at around 200 μm. Such radiation can be observed only from space, and the European Space Agency's Herschel Space Observatory was designed to do just that. On page 1258 of this issue, Matsuura et al. (1) present Herschel observations showing that substantial amounts of dust are created in the aftermath of a supernova, the titanic explosion that terminates the life of a massive star.

  6. MISR Browse Images: Puerto Rico Dust Experiment (PRiDE)

    Atmospheric Science Data Center

    2013-04-02

    MISR Browse Images: Puerto Rico Dust Experiment (PRiDE) These MISR Browse images provide ... overview of the region observed during the Puerto Rico Dust Experiment (PRiDE) field campaign. PRiDE was a study of the radiative, ...

  7. Optimal control of the signal-to-noise ratio per unit time of a spin 1/2 particle: the crusher gradient and the radiation damping cases.

    PubMed

    Lapert, M; Assémat, E; Glaser, S J; Sugny, D

    2015-01-28

    We show to which extent the signal to noise ratio per unit time of a spin 1/2 particle can be maximized. We consider a cyclic repetition of experiments made of a measurement followed by a radio-frequency magnetic field excitation of the system, in the case of unbounded amplitude. In the periodic regime, the objective of the control problem is to design the initial state of the system and the pulse sequence which leads to the best signal to noise performance. We focus on two specific issues relevant in nuclear magnetic resonance, the crusher gradient and the radiation damping cases. Optimal control techniques are used to solve this non-standard control problem. We discuss the optimality of the Ernst angle solution, which is commonly applied in spectroscopic and medical imaging applications. In the radiation damping situation, we show that in some cases, the optimal solution differs from the Ernst one.

  8. Optimal control of the signal-to-noise ratio per unit time of a spin 1/2 particle: The crusher gradient and the radiation damping cases

    SciTech Connect

    Lapert, M.; Glaser, S. J.; Assémat, E.; Sugny, D.

    2015-01-28

    We show to which extent the signal to noise ratio per unit time of a spin 1/2 particle can be maximized. We consider a cyclic repetition of experiments made of a measurement followed by a radio-frequency magnetic field excitation of the system, in the case of unbounded amplitude. In the periodic regime, the objective of the control problem is to design the initial state of the system and the pulse sequence which leads to the best signal to noise performance. We focus on two specific issues relevant in nuclear magnetic resonance, the crusher gradient and the radiation damping cases. Optimal control techniques are used to solve this non-standard control problem. We discuss the optimality of the Ernst angle solution, which is commonly applied in spectroscopic and medical imaging applications. In the radiation damping situation, we show that in some cases, the optimal solution differs from the Ernst one.

  9. Diagnostics for Dust Monitoring in Tokamak Environment

    SciTech Connect

    Rosanvallon, S.; Grisolia, C.; Hong, S. H.; Worms, J.

    2008-03-12

    During ITER lifetime, dusts and flakes will be produced due to the interaction of plasmas with the in-vessel materials or due to maintenance. They will be made of carbon, beryllium and tungsten and will be activated, tritiated and chemically reactive and toxic. Safety limits have been set in order to reduce dust hazards. Thus dust diagnostics and removal methods need to be developed for ITER within the constraints linked to magnetic field, radiation, vacuum and temperature. This paper reviews potential diagnostics to monitor the dust content using techniques already used for erosion or deposition monitoring or techniques specially developed for measuring dust in suspension.

  10. Semidirect Dynamical and Radiative Impact of North African Dust Transport on Lower Tropospheric Clouds over the Subtropical North Atlantic in CESM 1.0

    SciTech Connect

    DeFlorio, Mike; Ghan, Steven J.; Singh, Balwinder; Miller, Arthur J.; Cayan, Dan; Russell, Lynn M.; Somerville, Richard C.

    2014-07-16

    This study uses a century length pre-industrial climate simulation by the Community Earth System Model (CESM 1.0) to explore statistical relationships between dust, clouds and atmospheric circulation, and to suggest a dynamical, rather than microphysical, mechanism linking subtropical North Atlantic lower tropospheric cloud cover with North African dust transport. The length of the run allows us to account for interannual variability of dust emissions and transport downstream of North Africa in the model. CESM’s mean climatology and probability distribution of aerosol optical depth in this region agrees well with available AERONET observations. In addition, CESM shows strong seasonal cycles of dust burden and lower tropospheric cloud fraction, with maximum values occurring during boreal summer, when a strong correlation between these two variables exists downstream of North Africa over the subtropical North Atlantic. Calculations of Estimated Inversion Strength (EIS) and composites of EIS on high and low downstream North Africa dust months during boreal summer reveal that dust is likely increasing inversion strength over this region due to both solar absorption and reflection. We find no evidence for a microphysical link between dust and lower tropospheric clouds in this region. These results yield new insight over an extensive period of time into the complex relationship between North African dust and lower tropospheric clouds over the open ocean, which has previously been hindered by spatiotemporal constraints of observations. Our findings lay a framework for future analyses using sub-monthly data over regions with different underlying dynamics.

  11. Mixtures of pollution, dust, sea salt, and volcanic aerosol during ACE-Asia: Radiative properties as a function of relative humidity

    NASA Astrophysics Data System (ADS)

    Carrico, Christian M.; Kus, Pinar; Rood, Mark J.; Quinn, Patricia K.; Bates, Timothy S.

    2003-12-01

    The Ron Brown cruise during ACE-Asia (March-April 2001) encountered complex aerosol that at times was dominated by marine, polluted, volcanic, and dust aerosols. Average total light scattering coefficients (σsp for Dp <10 μm, relative humidity (RH) = 19%, and λ = 550 nm) ranged from 23 (marine) to 181 Mm-1 (dust). Aerosol hygroscopicity ranged from deliquescent with hysteresis (marine frequently and polluted variably) to hygroscopic without hysteresis (volcanic) to nearly hygrophobic (dust-dominated). Average deliquescence and crystallization RH were 77 ± 2% and 42 ± 3%, respectively. The ambient aerosol was typically on the upper branch of the hysteresis loop for marine and polluted air masses and the lower branch for dust-dominated aerosols. Average f(RH = ambient), defined as σsp (RH = ambient)/σsp (RH = 19%), ranged from 1.25 (dust) to 2.88 (volcanic). Average h(RH ˜60%), defined as f(RH)upper branch/f(RH)lower branch, were 1.6, 1.3, 1, and 1.25 for marine, polluted, volcanic, and dust, demonstrating an importance of hysteresis to optical properties. Hemispheric backscatter fraction (b) at ambient RH ranged from 0.077 (marine) to 0.111 (dust), while single scattering albedo (ω) at ambient RH ranged from 0.94 (dust and polluted) to 0.99 (marine).

  12. Planetary Magnetosphere Probed by Charged Dust Particles

    NASA Astrophysics Data System (ADS)

    Sternovsky, Z.; Horanyi, M.; Gruen, E.; Srama, R.; Auer, S.; Kempf, S.; Krueger, H.

    2010-12-01

    In-situ and remote sensing observations combined with theoretical and numerical modeling greatly advanced our understanding planetary magnetospheres. Dust is an integral component of the Saturnian and Jovian magnetospheres where it can act as a source/sink of plasma particles (dust particles are an effective source for plasma species like O2, OH, etc. through sputtering of ice particles, for example); its distribution is shaped by electrodynamic forces coupled radiation pressure, plasma, and neutral drag, for example. The complex interaction can lead to unusual dust dynamics, including the transport, capture, and ejection of dust grains. The study of the temporal and spatial evolution of fine dust within or outside the magnetosphere thus provides a unique way to combine data from a large number of observations: plasma, plasma wave, dust, and magnetic field measurements. The dust detectors on board the Galileo and Cassini spacecrafts lead to major discoveries, including the jovian dust stream originating from Io or the in-situ sampling and analysis of the plumes of Enceladus. Recent advancement in dust detector technology enables accurate measurement of the dust trajectory and elemental composition that can greatly enhance the understanding of dust magnetorspheric interaction and indentify the source of the dust with high precision. The capabilities of a modern dust detector thus can provide support for the upcoming Europa Jupiter System Mission.

  13. Cycloidal Dust Devil Track

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-382, 5 June 2003

    The spiraling feature near the center of this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image is known as a cycloidal marking. Patterns like this can also occur on Earth. On Mars, the cycloidalpattern--and all of the other dark streaks in this picture--are thought to have been formed by passing dust devils. On Earth, cycloidal markings have been observed to result from some tornadoes. The pattern is created when more than one vortex (spinning column of air) is traveling, and spinning, together. This picture is near 62.9oS, 234.7oW. Sunlight illuminates the scene from the upper left.

  14. Cycloidal Dust Devil Track

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-382, 5 June 2003

    The spiraling feature near the center of this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image is known as a cycloidal marking. Patterns like this can also occur on Earth. On Mars, the cycloidalpattern--and all of the other dark streaks in this picture--are thought to have been formed by passing dust devils. On Earth, cycloidal markings have been observed to result from some tornadoes. The pattern is created when more than one vortex (spinning column of air) is traveling, and spinning, together. This picture is near 62.9oS, 234.7oW. Sunlight illuminates the scene from the upper left.

  15. Circumstellar dust in symbiotic novae

    NASA Astrophysics Data System (ADS)

    Jurkic, Tomislav; Kotnik-Karuza, Dubravka

    2015-08-01

    Physical properties of the circumstellar dust and associated physical mechanisms play an important role in understanding evolution of symbiotic binaries. We present a model of inner dust regions around the cool Mira component of the two symbiotic novae, RR Tel and HM Sge, based on the long-term near-IR photometry, infrared ISO spectra and mid-IR interferometry. Pulsation properties and long-term variabilities were found from the near-IR light curves. The dust properties were determined using the DUSTY code which solves the radiative transfer. No changes in pulsational parameters were found, but a long-term variations with periods of 20-25 years have been detected which cannot be attributed to orbital motion.Circumstellar silicate dust shell with inner dust shell temperatures between 900 K and 1300 K and of moderate optical depth can explain all the observations. RR Tel showed the presence of an optically thin CS dust envelope and an optically thick dust region outside the line of sight, which was further supported by the detailed modelling using the 2D LELUYA code. Obscuration events in RR Tel were explained by an increase in optical depth caused by the newly condensed dust leading to the formation of a compact dust shell. HM Sge showed permanent obscuration and a presence of a compact dust shell with a variable optical depth. Scattering of the near-IR colours can be understood by a change in sublimation temperature caused by the Mira variability. Presence of large dust grains (up to 4 µm) suggests an increased grain growth in conditions of increased mass loss. The mass loss rates of up to 17·10-6 MSun/yr were significantly higher than in intermediate-period single Miras and in agreement with longer-period O-rich AGB stars.Despite the nova outburst, HM Sge remained enshrouded in dust with no significant dust destruction. The existence of unperturbed dust shell suggests a small influence of the hot component and strong dust shielding from the UV flux. By the use

  16. Exozodiacal dust

    NASA Astrophysics Data System (ADS)

    Kuchner, Marc Jason

    Besides the sun, the most luminous feature of the solar system is a cloud of "zodiacal" dust released by asteroids and comets that pervades the region interior to the asteroid belt. Similar clouds of dust around other stars---exozodiacal clouds---may be the best tracers of the habitable zones of extra-solar planetary systems. This thesis discusses three searches for exozodiacal dust: (1) We observed six nearby main-sequence stars with the Keck telescope at 11.6 microns, correcting for atmosphere-induced wavefront aberrations and deconvolving the point spread function via classical speckle analysis. We compare our data to a simple model of the zodiacal dust in our own system based on COBE DIRBE observations and place upper limits on the density of exozodiacal dust in these systems. (2) We observed Sirius, Altair, and Procyon with the NICMOS Coronagraph on the Hubble Space Telescope to look for scattered light from exozodiacal dust and faint companions within 10 AU from these stars. (3) The planned nulling capability of the Keck Interferometer should allow it to probe the region <200 milliarcsecond from a bright star and to suppress on-axis starlight by factors of 10 -3 to reveal faint circumstellar material. We model the response of the Keck Interferometer to hypothetical exozodiacal clouds to derive detection limits that account for the effects of stellar leakage, photon noise, noise from null depth fluctuations, and the fact that the cloud's shape is not known a priori. We also discuss the interaction of dust with planets. We used the COBE DIRBE Sky and Zodi Atlas and the IRAS Sky Survey Atlas to search for dynamical signatures of three different planets in the solar system dust complex: (1) We searched the COBE DIRBE Sky and Zodi Atlas for a wake of dust trailing Mars. We compare the DIRBE images to a model Mars wake based on the empirical model of the Earth's wake as seen by the DIRBE. (2) We searched the COBE DIRRE Sky and Zodi Atlas for Tiojan dust near

  17. Properties of interstellar dust in reflection nebulae

    NASA Technical Reports Server (NTRS)

    Sellgren, Kristin

    1988-01-01

    Observations of interstellar dust in reflection nebulae are the closest analog in the interstellar medium to studies of cometary dust in our solar system. The presence of a bright star near the reflection nebula dust provides the opportunity to study both the reflection and emission characteristics of interstellar dust. At 0.1 to 1 micrometer, the reflection nebula emission is due to starlight scattered by dust. The albedo and scattering phase function of the dust is determined from observations of the scattered light. At 50 to 200 micrometers, thermal emission from the dust in equilibrium with the stellar radiation field is observed. The derived dust temperature determines the relative values of the absorption coefficient of the dust at wavelengths where the stellar energy is absorbed and at far infrared wavelengths where the absorbed energy is reradiated. These emission mechanisms directly relate to those seen in the near and mid infrared spectra of comets. In a reflection nebula the dust is observed at much larger distances from the star than in our solar system, so that the equilibrium dust temperature is 50 K rather than 300 K. Thus, in reflection nebulae, thermal emission from dust is emitted at 50 to 200 micrometer.

  18. The retrieval of optical properties from terrestrial dust devil vortices

    NASA Astrophysics Data System (ADS)

    Mason, Jonathon P.; Patel, Manish R.; Lewis, Stephen R.

    2014-03-01

    The retrieval of the optical properties of desert aerosols in suspension within terrestrial dust devils is presented with possible future application for martian dust devils. The transmission of light through dust devil vortices was measured in situ to obtain the wavelength-dependent attenuation by the aerosols. A Monte Carlo model was applied to each dust devil with the retrieved optical properties corresponding to the set of parameters which lead to the best model representation of the observed transmission spectra. The retrieved optical properties agree well with single scattering theory and are consistent with previous studies of dust aerosols. The enhanced absorption observed for dust devils with a higher tangential wind speed, and in comparison to atmospheric aerosol studies, suggests that larger dust particles are lofted and suspended around dust devil vortices. This analysis has shown that the imaginary refractive indices (and thus the optical properties of the suspended dust) are generally overestimated when these larger dust grains entrained by dust devils are neglected. This will lead to an overestimation of the amount of solar radiation absorbed by the small particles that remain in suspension after the dust devil terminates. It is also demonstrated that a 10% uncertainty in the particle size distribution of the dust entrained in the dust devils can result in a 50% increase in the predicted amount of incident solar radiation absorbed by the dust particles once the dust devil has terminated. The method used here provides the capability to retrieve the optical properties of the dust entrained in martian dust devils by taking advantage of transits over surface spacecraft which are capable of making optical measurements at ultraviolet and visible wavelengths. Our results suggest that we would observed higher absorption at all wavelengths for dust particles entrained in dust devil vortices compared to the ubiquitous dust haze.

  19. Physical and Radiative Properties of Aerosol Particles across the Caribbean Basin: A Comparison between Clean and Perturbed African Dust and Volcanic Ash Air Masses

    NASA Astrophysics Data System (ADS)

    Rivera, H.; Ogren, J. A.; Sheridan, P. J.; Mayol-Bracero, O.

    2009-12-01

    Aerosol’s optical and physical properties were measured during year 2007 at Cape San Juan, a ground-based station located at the northeastern tip of Puerto Rico. The three cases investigated were classified according to the origin of the air masses: clean (C), African dust (AD), and volcanic ash (VA). The instrumentation used included a sunphotometer to determine volume size distributions and aerosol optical thickness (AOT), a 3-wavelength nephelometer to determine the scattering coefficient (σsp), and a 3-wavelength particle/soot absorption photometer (PSAP) to measure the absorption coefficient (σap). The average volume size distributions were trimodal for the C (peaks at 0.14, 0.99 and 4.25 µm radius) and AD (peaks at 0.11, 1.30 and 2.00 µm radius) cases and bimodal for the VA (peaks at 0.19 and 2.75 µm radius) case. Fine and coarse modes maxima for AD occurred at radii smaller than for VA, confirming the different origins of those particles. The average values for the total σsp were higher for AD (82.9 Mm-1) and VA (33.7 Mm-1) compared to C (16.6 Mm-1). The same happened for the AOT maximum values at 500 nm with 0.92, 0.30, and 0.06 for AD, VA, and C, respectively. The observed increase in the values of the Angstrom exponent (å) is indicative of a decrease in the size of the particles associated to VA (å= 0.27) and AD (å =0.89) when compared to C (å =0.24). The volume size distributions and thus the mass were dominated by the coarse mode (> 1.0 µm) especially for the AD case. Results have shown that AD as well as VA has a significant impact on the physical and radiative properties across Puerto Rico and the Caribbean. Additional results on the AOT wavelength dependence and on the annual variability of the properties under study will be presented.

  20. Numerical Prediction of Dust. Chapter 10

    NASA Technical Reports Server (NTRS)

    Benedetti, Angela; Baldasano, J. M.; Basart, S.; Benincasa, F.; Boucher, O.; Brooks, M.; Chen, J. P.; Colarco, P. R.; Gong, S.; Huneeus, N.; Jones, L; Lu, S.; Menut, L.; Mulcahy, J.; Nickovic, S.; Morcrette, J.-J.; Perez, C.; Reid, J. S.; Sekiyama, T. T.; Tanaka, T.; Terradellas, E.; Westphal, D. L.; Zhang, X.-Y.; Zhou, C.-H.

    2013-01-01

    Covers the whole breadth of mineral dust research, from a scientific perspective Presents interdisciplinary work including results from field campaigns, satellite observations, laboratory studies, computer modelling and theoretical studies Explores the role of dust as a player and recorder of environmental change This volume presents state-of-the-art research about mineral dust, including results from field campaigns, satellite observations, laboratory studies, computer modelling and theoretical studies. Dust research is a new, dynamic and fast-growing area of science and due to its multiple roles in the Earth system, dust has become a fascinating topic for many scientific disciplines. Aspects of dust research covered in this book reach from timescales of minutes (as with dust devils, cloud processes, and radiation) to millennia (as with loess formation and oceanic sediments), making dust both a player and recorder of environmental change. The book is structured in four main parts that explore characteristics of dust, the global dust cycle, impacts of dust on the Earth system, and dust as a climate indicator. The chapters in these parts provide a comprehensive, detailed overview of this highly interdisciplinary subject. The contributions presented here cover dust from source to sink and describe all the processes dust particles undergo while travelling through the atmosphere. Chapters explore how dust is lifted and transported, how it affects radiation, clouds, regional circulations, precipitation and chemical processes in the atmosphere, and how it deteriorates air quality. The book explores how dust is removed from the atmosphere by gravitational settling, turbulence or precipitation, how iron contained in dust fertilizes terrestrial and marine ecosystems, and about the role that dust plays in human health. We learn how dust is observed, simulated using computer models and forecast. The book also details the role of dust deposits for climate reconstructions

  1. Spin supplementary conditions for spinning compact binaries

    NASA Astrophysics Data System (ADS)

    Mikóczi, Balázs

    2017-03-01

    We consider different spin supplementary conditions (SSC) for a spinning compact binary with the leading-order spin-orbit (SO) interaction. The Lagrangian of the binary system can be constructed, but it is acceleration-dependent in two cases of SSC. We rewrite the generalized Hamiltonian formalism proposed by Ostrogradsky and compute the conserved quantities and the dissipative part of relative motion during the gravitational radiation of each SSC. We give the orbital elements and observed quantities of the SO dynamics, for instance, the energy and the orbital angular momentum losses and waveforms, and discuss their SSC dependence.

  2. Wormhole shadows in rotating dust

    NASA Astrophysics Data System (ADS)

    Ohgami, Takayuki; Sakai, Nobuyuki

    2016-09-01

    As an extension of our previous work, which investigated the shadows of the Ellis wormhole surrounded by nonrotating dust, in this paper we study wormhole shadows in a rotating dust flow. First, we derive steady-state solutions of slowly rotating dust surrounding the wormhole by solving relativistic Euler equations. Solving null geodesic equations and radiation transfer equations, we investigate the images of the wormhole surrounded by dust for the above steady-state solutions. Because the Ellis wormhole spacetime possesses unstable circular orbits of photons, a bright ring appears in the image, just as in Schwarzschild spacetime. The bright ring looks distorted due to rotation. Aside from the bright ring, there appear weakly luminous complex patterns by the emission from the other side of the throat. These structure could be detected by high-resolution very-long-baseline-interferometry observations in the near future.

  3. High-Pressure-Hydrogen-Induced Spin Reconfiguration in GdFe2 Observed by 57Fe-Polarized Synchrotron Radiation Mössbauer Spectroscopy with Nuclear Bragg Monochromator

    NASA Astrophysics Data System (ADS)

    Mitsui, Takaya; Imai, Yasuhiko; Hirao, Naohisa; Matsuoka, Takahiro; Nakamura, Yumiko; Sakaki, Kouji; Enoki, Hirotoshi; Ishimatsu, Naoki; Masuda, Ryo; Seto, Makoto

    2016-12-01

    57Fe-polarized synchrotron radiation Mössbauer spectroscopy (PSRMS) with an X-ray phase plate and a nuclear Bragg monochromator was used to study ferrimagnetic GdFe2 in high-pressure hydrogen. The pressure-dependent spectra clearly showed a two-step magnetic transition of GdFe2. 57Fe-PSRMS with circular polarization gave direct evidence that the Fe moment was directed parallel to the net magnetization of the GdFe2 hydride at 20 GPa. This spin configuration was opposite to that of the initial GdFe2, suggesting an extreme weakening of the antiferromagnetic interaction between Fe and Gd. 57Fe-PSRMS enables the characterization of the nonuniform properties of iron-based polycrystalline powder alloys. The excellent applicability of 57Fe-PSRMS covers a wide range of scientific fields.

  4. [Weak coherent radiation of OH and ortho- H2O space masers as a carrier in biocommunication: the ortho/para-conversion of H2O spin isomers?].

    PubMed

    Pershin, S M

    2010-01-01

    A conception of biocommunication based on the principle of radiophysics stating that the carrier modulation takes place at the resonance frequency in the transmission-receiver system has been substantiated and proved. The coherent radiation of space OH-masers (1.6-1.7 GHz) and ortho-H2O-maser (22.3 GHz) is proposed as a source of the carrier frequency. The narrow lines of rotational transition of H2O and OH molecules in liquid water were proposed to be considered as an analog of selective resonances of transmitter and receiver in radiocommunication. The possibility of the ortho-para conversion of H2O spin isomers, induced by weak electromagnetic fields, is discussed.

  5. A Test of Dust Grain Alignment via Far-Infrared Polarization

    NASA Astrophysics Data System (ADS)

    Vaillancourt, John E.; Andersson, B.-G.

    2015-01-01

    Interstellar dust grains are aligned with their physical and spin axes parallel to the ambient magnetic field. This fact is supported by polarization observations from ultraviolet to millimeter wavelengths. The radiative torque (RT) mechanism, by which the grains become aligned, has recently survived a number of specific observational tests. One such observation is the relation between the alignment efficiency and the angle between the magnetic field and the radiation responsible for the RTs. The interaction of light with irregularly shaped grains results in a net torque and spin-up of the grain, while magnetization arising within a spinning grain results in precession of the spin axis about the magnetic field. The combination of these two effects leads to alignment of the grain with the field and predicts a correlation between alignment efficiency and the angle between the radiation- and magnetic- field directions. Andersson et al. (2011, A&A, 534, A19) showed that the alignment efficiency, centered on the star HD 97300, varied with angle about the star with a 180-degree period, consistent with theory. While the geometry towards HD 97300 provides a strong test of the RT-vs.-angle prediction, finding such simple geometries for further tests is difficult. Here we identify a similar geometry towards the Becklin-Neugebauer/Kleinmann-Low (BNKL) object in the Orion molecular cloud. Using polarized emission at 100, 350, and 850 micron we find a clear periodic signal in polarization vs. azimuth centered on BNKL, again, in agreement with RT theory predictions. Additionally, the signal is stronger at shorter wavelengths, as would be expected if the same photons providing the RTs are also heating the dust grains.The authors acknowledge support for this work from the National Science Foundation grant AST 11-09469.

  6. Spin foams without spins

    NASA Astrophysics Data System (ADS)

    Hnybida, Jeff

    2016-10-01

    We formulate the spin foam representation of discrete SU(2) gauge theory as a product of vertex amplitudes each of which is the spin network generating function of the boundary graph dual to the vertex. In doing so the sums over spins have been carried out. The boundary data of each n-valent node is explicitly reduced with respect to the local gauge invariance and has a manifest geometrical interpretation as a framed polyhedron of fixed total area. Ultimately, sums over spins are traded for contour integrals over simple poles and recoupling theory is avoided using generating functions.

  7. Status and Future of Dust Storm Forecasting

    NASA Astrophysics Data System (ADS)

    Westphal, D. L.

    2002-12-01

    In recent years, increased attention has been given to the large amounts of airborne dust derived from the deserts and desertified areas of the world and transported over scales ranging from local to global. This dust can have positive and negative impacts on human activities and the environment, including modifying cloud formation, fertilizing the ocean, degrading air quality, reducing visibility, transporting pathogens, and inducing respiratory problems. The atmospheric radiative forcing by the dust has implications for global climate change and presently is one of the largest unknowns in climate models. These uncertainties have lead to much of the funding for research into the sources, properties, and fate of atmospheric dust. As a result of advances in numerical weather prediction over the past decades and the recent climate research, we are now in a position to produce operational dust storm forecasts. International organizations and national agencies are developing programs for dust forecasting. The approaches and applications of dust detection and forecasting are as varied as the nations that are developing the models. The basic components of a dust forecasting system include atmospheric forcing, dust production, and dust microphysics. The forecasting applications include air and auto traffic safety, shipping, health, national security, climate and weather. This presentation will summarize the methods of dust storm forecasting and illustrate the various applications. The major remaining uncertainties (e.g. sources and initialization) will be discussed as well as approaches for solving those problems.

  8. Dust and the Dust Bowl: Connections between 1930's drought and dust

    NASA Astrophysics Data System (ADS)

    O'Brien, T. A.; Sloan, L. C.; Solmon, F.; Snyder, M. A.

    2007-12-01

    There have been a number of investigations into the causes and physical mechanisms of the 1930's Dust Bowl, and together they provide a reasonable explanation of the drought in terms of its length and severity. However no published investigations have considered the possible climatic effects caused by the considerable amount of airborne dust that was generated as a consequence of poor land use management in the late 19th and early 20th centuries. In order to investigate the effects of airborne dust on North American climate during the 1930's, we have performed a climate model sensitivity study that isolates the effects of dust on climate in a regional climate model. The results of the study show that an essentially permanent dust cloud existed over North America through the duration of the drought. The dust cloud, which we show was quite thick over its center in the Midwest, blocked enough solar radiation to reduce surface temperatures by about 1 K. In addition, we show that a complex feedback between dust and drought caused a spatial redistribution of precipitation, in which various regions gained or lost an average of about 1 mm/day of precipitation.

  9. The electrodynamics of charged dust in the cometary environment

    NASA Technical Reports Server (NTRS)

    Horanyi, M.; Mendis, D. A.

    1991-01-01

    Dust in the plasma and radiative environment of a comet is necessarily electrically charged. This charging has both physical and dynamical effects on the dust, being particularly important on the smallest particles observed in the dust size spectrum. In this paper, these dynamical effects are reviewed and the pertinent observations are discussed.

  10. Progress in our understanding of cometary dust tails

    NASA Technical Reports Server (NTRS)

    Sekanina, Z.

    1976-01-01

    Various analytical techniques are employed to analyze observations on the character, composition, and size distribution of solid particles in cometary dust tails. Emphasized is the mechanical theory that includes solar gravitational attraction and solar radiation pressure to explain dust particle motions in cometary tails, as well as interactions between dust and plasma.

  11. Precession of cylindrical dust particles in the plasma sheath

    SciTech Connect

    Banu, N.; Ticoş, C. M.

    2015-10-15

    The vertical precession of cylindrical dust particles levitated in the sheath of an rf plasma is experimentally investigated. Typically, the dust particles have two equilibrium positions depending on the orientation of their longitudinal axis: horizontal and vertical. A transition between these two states is induced by rapidly increasing the neutral gas pressure in the plasma chamber. During this transition, the cylindrical dust particles make an angle with the horizontal and rotate about their center of mass. The rotation speed increases as the dust rods aligned with the vertical axis. All dust particles will eventually end up in the vertical state while spinning fast about their longitudinal axis. Dust-dust interaction and the attracting ion wakes are possible mechanisms for inducing the observed dust precession.

  12. Dust Devils and Convective Vortices on Mars

    NASA Astrophysics Data System (ADS)

    Ordonez-Etxeberria, I.; Hueso, R.; Sánchez-Lavega, A.

    2017-03-01

    Dust devils are low pressure convective vortices able to lift dust from the surface of a planet. They are a common feature on Mars and they can also be found on desertic locations on Earth. On Mars they are considered an important part of the atmospheric dust cycle. Dust in Mars is an essential ingredient of the atmosphere where it affects the radiative balance of the planet. Here we review observations of these dusty vortices from orbit, from in situ measurements on the surface of Mars and some of the models developed to simulate them.

  13. Electro-gravity spin density waves

    NASA Astrophysics Data System (ADS)

    Syromyatnikov, A. G.

    dimension N) under the Conformal Gauge Theory of Gravity (CGTG), here is considered an exact cosmological solution with Friedman’s asymptotic in the form of conformal flat Fock’s metrics at large times, describing the stage of decay on a cold dust-like medium of do-not-interacting-among-themselves particles and a light-like isotropic radiation. It is shown that at high times, indeed, the process of enlarging the space-time in the model metrics Friedman conformal is equivalent to Minkowski space with a gradient torsion trace in the CGTG Newtonian limit, accompanied by a polarization effect separation of electric charges induced by an electric field E⇀F is manifested in the formation of plasma-like medium with a zero complete electric charge, that in the later stages of evolution is identical to the Fock’s model of a cold dust-like medium of do-not-interacting-among-themselves particles moving here with the same speed. The trace of torsion on the CGTG formula is freezing into an electromagnetic field spin tensor trace density and E⇀F defined inside a spherical surface, moving at the speed of light, on which experiencing a gap. Therefore, this decision takes the form of an electro-gravity spin density wave, as performed in kinematic and dynamic close connection conditions for theorems on spin shock waves with spin flip at the front of the wave, moving at the speed of light in a vacuum. The theoretical dependence of electro-gravity wave energy output from the size of the emitting object is received. When applied to GRBs, this can give a new mechanism of nonthermal gamma rays production.

  14. Numerical inverse method predicting acoustic spinning modes radiated by a ducted fan from free-field test data.

    PubMed

    Lewy, Serge

    2008-07-01

    Spinning modes generated by a ducted turbofan at a given frequency determine the acoustic free-field directivity. An inverse method starting from measured directivity patterns is interesting in providing information on the noise sources without requiring tedious spinning-mode experimental analyses. According to a previous article, equations are based on analytical modal splitting inside a cylindrical duct and on a Rayleigh or a Kirchhoff integral on the duct exit cross section to get far-field directivity. Equations are equal in number to free-field measurement locations and the unknowns are the propagating mode amplitudes (there are generally more unknowns than equations). A MATLAB procedure has been implemented by using either the pseudoinverse function or the backslash operator. A constraint comes from the fact that squared modal amplitudes must be positive which involves an iterative least squares fitting. Numerical simulations are discussed along with several examples based on tests performed by Rolls-Royce in the framework of a European project. It is assessed that computation is very fast and it well fits the measured directivities, but the solution depends on the method and is not unique. This means that the initial set of modes should be chosen according to any known physical property of the acoustic sources.

  15. Radiation

    NASA Image and Video Library

    Outside the protective cocoon of Earth's atmosphere, the universe is full of harmful radiation. Astronauts who live and work in space are exposed not only to ultraviolet rays but also to space radi...

  16. Dusty spin plasmas

    SciTech Connect

    Brodin, G.; Marklund, M.; Zamanian, J.

    2008-09-07

    A fluid model is derived, taking into account the effect of spin magnetization of electrons as well as of magnetized dust grains. The model is analyzed, and it is found that both the acoustic velocity and the Alfven velocity is decreased due to the magnetization effects. Furthermore, for low-temperature high density plasmas, it is found that the linear wave modes can be unstable, due to the magnetic attraction of individual fluid elements. The significance of our results are discussed.

  17. Dust-rainfall feedbacks in the West African Sahel

    NASA Astrophysics Data System (ADS)

    Hui, Wanching Jacquie; Cook, Benjamin I.; Ravi, Sujith; Fuentes, José D.; D'Odorico, Paolo

    2008-05-01

    Dust aerosols can suppress rainfall by increasing the number of cloud condensation nuclei in warm clouds and affecting the surface radiation budget and boundary layer instability. The extent to which atmospheric dust may affect precipitation yields and the hydrologic cycle in semiarid regions remains poorly understood. We investigate the relationship between dust aerosols and rainfall in the West African Sahel where the dust-rainfall feedback has been speculated to contribute to sustained droughts. We find that the amount of dust loadings is negatively correlated with rainfall values, suggesting that dust entrained in the atmosphere can significantly inhibit rainfall in this region.

  18. Studying the spatial distribution of interstellar dust

    NASA Technical Reports Server (NTRS)

    Walker, Helen J.; Werner, Michael W.; Allen, C.; Henry, R. C.; Kimble, R.; Wofford, J.; Murthy, Jayant

    1989-01-01

    The spacial distribution of interstellar dust reflects both interstellar dynamics and the processes which form and destroy dust in the interstellar medium (ISM). The IRAS survey, because of its high sensitivity to thermal emission from dust in the IR, provides new approaches to determining the spatial distribution of dust. The initial results are reported of an attempt to use the IRAS data to probe the spatial distribution of dust - by searching for thermal emission from dust in the vicinity of bright stars. These results show that this technique (which relies on finding IR emission associated with randomly selected stars) can ultimately be used to study the distribution of dust in the ISM. The density of the cloud producing the IR emission may be derived by assuming that the dust is at its projected distance from the star and that the heating is due to the star's (known) radiation field. The heating radiation is folded into a grain model, and the number of emitting grains adjusted to reproduce the observed energy distribution. It is noted that this technique is capable in principle of detecting dust densities much lower than those typical of the cirrus clouds.

  19. Migration of Asteroidal Dust

    NASA Technical Reports Server (NTRS)

    Ipatov, S. I.; Mather, J. C.

    2003-01-01

    Using the Bulirsh Stoer method of integration, we investigated the migration of dust particles under the gravitational influence of all planets, radiation pressure, Poynting Robertson drag and solar wind drag for equal to 0.01, 0.05, 0.1, 0.25, and 0.4. For silicate particles such values of correspond to diameters equal to about 40, 9, 4, 2, and 1 microns, respectively [1]. The relative error per integration step was taken to be less than 10sup-8. Initial orbits of the particles were close to the orbits of the first numbered mainbelt asteroids.

  20. Migration of Asteroidal Dust

    NASA Technical Reports Server (NTRS)

    Ipatov, S. I.; Mather, J. C.

    2003-01-01

    Using the Bulirsh Stoer method of integration, we investigated the migration of dust particles under the gravitational influence of all planets, radiation pressure, Poynting Robertson drag and solar wind drag for equal to 0.01, 0.05, 0.1, 0.25, and 0.4. For silicate particles such values of correspond to diameters equal to about 40, 9, 4, 2, and 1 microns, respectively [1]. The relative error per integration step was taken to be less than 10sup-8. Initial orbits of the particles were close to the orbits of the first numbered mainbelt asteroids.

  1. Lunar Dust and Dusty Plasma Physics

    NASA Technical Reports Server (NTRS)

    Wilson, Thomas L.

    2009-01-01

    In the plasma and radiation environment of space, small dust grains from the Moon s surface can become charged. This has the consequence that their motion is determined by electromagnetic as well as gravitational forces. The result is a plasma-like condition known as "dusty plasmas" with the consequence that lunar dust can migrate and be transported by magnetic, electric, and gravitational fields into places where heavier, neutral debris cannot. Dust on the Moon can exhibit unusual behavior, being accelerated into orbit by electrostatic surface potentials as blow-off dust, or being swept away by moving magnetic fields like the solar wind as pick-up dust. Hence, lunar dust must necessarily be treated as a dusty plasma subject to the physics of magnetohydrodynamics (MHD). A review of this subject has been given before [1], but a synopsis will be presented here to make it more readily available for lunar scientists.

  2. Distribution of Dust from Kuiper Belt Objects

    NASA Technical Reports Server (NTRS)

    Gorkavyi, Nick N.; Ozernoy, Leonid; Taidakova, Tanya; Mather, John C.; Fisher, Richard (Technical Monitor)

    2000-01-01

    Using an efficient computational approach, we have reconstructed the structure of the dust cloud in the Solar system between 0.5 and 100 AU produced by the Kuiper belt objects. Our simulations offer a 3-D physical model of the 'kuiperoidal' dust cloud based on the distribution of 280 dust particle trajectories produced by 100 known Kuiper belt objects; the resulting 3-D grid consists of 1.9 x 10' cells containing 1.2 x 10" particle positions. The following processes that influence the dust particle dynamics are taken into account: 1) gravitational scattering on the eight planets (neglecting Pluto); 2) planetary resonances; 3) radiation pressure; and 4) the Poynting-Robertson (P-R) and solar wind drags. We find the dust distribution highly non-uniform: there is a minimum in the kuiperoidal dust between Mars and Jupiter, after which both the column and number densities of kuiperoidal dust sharply increase with heliocentric distance between 5 and 10 AU, and then form a plateau between 10 and 50 AU. Between 25 and 45 AU, there is an appreciable concentration of kuiperoidal dust in the form of a broad belt of mostly resonant particles associated with Neptune. In fact, each giant planet possesses its own circumsolar dust belt consisting of both resonant and gravitationally scattered particles. As with the cometary belts simulated in our related papers, we reveal a rich and sophisticated resonant structure of the dust belts containing families of resonant peaks and gaps. An important result is that both the column and number dust density are more or less flat between 10 and 50 AU, which might explain the surprising data obtained by Pioneers 10 & 11 and Voyager that the dust number density remains approximately distance-independent in this region. The simulated kuiperoidal dust, in addition to asteroidal and cometary dust, might represent a third possible source of the zodiacal light in the Solar system.

  3. Glacial to Holocene changes in trans-Atlantic Saharan dust transport and dust-climate feedbacks.

    PubMed

    Williams, Ross H; McGee, David; Kinsley, Christopher W; Ridley, David A; Hu, Shineng; Fedorov, Alexey; Tal, Irit; Murray, Richard W; deMenocal, Peter B

    2016-11-01

    Saharan mineral dust exported over the tropical North Atlantic is thought to have significant impacts on regional climate and ecosystems, but limited data exist documenting past changes in long-range dust transport. This data gap limits investigations of the role of Saharan dust in past climate change, in particular during the mid-Holocene, when climate models consistently underestimate the intensification of the West African monsoon documented by paleorecords. We present reconstructions of African dust deposition in sediments from the Bahamas and the tropical North Atlantic spanning the last 23,000 years. Both sites show early and mid-Holocene dust fluxes 40 to 50% lower than recent values and maximum dust fluxes during the deglaciation, demonstrating agreement with records from the northwest African margin. These quantitative estimates of trans-Atlantic dust transport offer important constraints on past changes in dust-related radiative and biogeochemical impacts. Using idealized climate model experiments to investigate the response to reductions in Saharan dust's radiative forcing over the tropical North Atlantic, we find that small (0.15°C) dust-related increases in regional sea surface temperatures are sufficient to cause significant northward shifts in the Atlantic Intertropical Convergence Zone, increased precipitation in the western Sahel and Sahara, and reductions in easterly and northeasterly winds over dust source regions. Our results suggest that the amplifying feedback of dust on sea surface temperatures and regional climate may be significant and that accurate simulation of dust's radiative effects is likely essential to improving model representations of past and future precipitation variations in North Africa.

  4. Rocket dust storms and detached dust layers in the Martian atmosphere

    NASA Astrophysics Data System (ADS)

    Spiga, Aymeric; Faure, Julien; Madeleine, Jean-Baptiste; Määttänen, Anni; Forget, François

    2013-04-01

    Airborne dust is the main climatic agent in the Martian environment. Local dust storms play a key role in the dust cycle; yet their life cycle is poorly known. Here we use mesoscale modeling that includes the transport of radiatively active dust to predict the evolution of a local dust storm monitored by OMEGA on board Mars Express. We show that the evolution of this dust storm is governed by deep convective motions. The supply of convective energy is provided by the absorption of incoming sunlight by dust particles, rather than by latent heating as in moist convection on Earth. We propose to use the terminology "rocket dust storm," or conio-cumulonimbus, to describe those storms in which rapid and efficient vertical transport takes place, injecting dust particles at high altitudes in the Martian troposphere (30-50 km). Combined to horizontal transport by large-scale winds, rocket dust storms produce detached layers of dust reminiscent of those observed with Mars Global Surveyor and Mars Reconnaissance Orbiter. Since nighttime sedimentation is less efficient than daytime convective transport, and the detached dust layers can convect during the daytime, these layers can be stable for several days. The peak activity of rocket dust storms is expected in low-latitude regions at clear seasons (late northern winter to late northern summer), which accounts for the high-altitude tropical dust maxima unveiled by Mars Climate Sounder. Dust-driven deep convection has strong implications for the Martian dust cycle, thermal structure, atmospheric dynamics, cloud microphysics, chemistry, and robotic and human exploration.

  5. High sensitivity of Indian summer monsoon to Middle East dust absorptive properties

    PubMed Central

    Jin, Qinjian; Yang, Zong-Liang; Wei, Jiangfeng

    2016-01-01

    The absorptive properties of dust aerosols largely determine the magnitude of their radiative impacts on the climate system. Currently, climate models use globally constant values of dust imaginary refractive index (IRI), a parameter describing the dust absorption efficiency of solar radiation, although it is highly variable. Here we show with model experiments that the dust-induced Indian summer monsoon (ISM) rainfall differences (with dust minus without dust) change from −9% to 23% of long-term climatology as the dust IRI is changed from zero to the highest values used in the current literature. A comparison of the model results with surface observations, satellite retrievals, and reanalysis data sets indicates that the dust IRI values used in most current climate models are too low, tending to significantly underestimate dust radiative impacts on the ISM system. This study highlights the necessity for developing a parameterization of dust IRI for climate studies. PMID:27465689

  6. High sensitivity of Indian summer monsoon to Middle East dust absorptive properties.

    PubMed

    Jin, Qinjian; Yang, Zong-Liang; Wei, Jiangfeng

    2016-07-28

    The absorptive properties of dust aerosols largely determine the magnitude of their radiative impacts on the climate system. Currently, climate models use globally constant values of dust imaginary refractive index (IRI), a parameter describing the dust absorption efficiency of solar radiation, although it is highly variable. Here we show with model experiments that the dust-induced Indian summer monsoon (ISM) rainfall differences (with dust minus without dust) change from -9% to 23% of long-term climatology as the dust IRI is changed from zero to the highest values used in the current literature. A comparison of the model results with surface observations, satellite retrievals, and reanalysis data sets indicates that the dust IRI values used in most current climate models are too low, tending to significantly underestimate dust radiative impacts on the ISM system. This study highlights the necessity for developing a parameterization of dust IRI for climate studies.

  7. Dust deposition fluxes and particle size of Saharan dust across the Atlantic Ocean, from 2012 - 2014

    NASA Astrophysics Data System (ADS)

    van der Does, Michelle; Korte, Laura; Brummer, Geert-Jan; Stuut, Jan-Berend

    2017-04-01

    Every year, an estimated 140 million tons of Saharan dust are deposited in the Atlantic Ocean, which can have several d