Science.gov

Sample records for plasma epoch theory

  1. Plasma Sterilization: New Epoch in Medical Textiles

    NASA Astrophysics Data System (ADS)

    Senthilkumar, P.; Arun, N.; Vigneswaran, C.

    2015-04-01

    Clothing is perceived to be second skin to the human body since it is in close contact with the human skin most of the times. In hospitals, use of textile materials in different forms and sterilization of these materials is an essential requirement for preventing spread of germs. The need for appropriate disinfection and sterilization techniques is of paramount importance. There has been a continuous demand for novel sterilization techniques appropriate for use on various textile materials as the existing sterilization techniques suffer from various technical and economical drawbacks. Plasma sterilization is the alternative method, which is friendlier and more effective on the wide spectrum of prokaryotic and eukaryotic microorganisms. Basically, the main inactivation factors for cells exposed to plasma are heat, UV radiation and various reactive species. Plasma exposure can kill micro-organisms on a surface in addition to removing adsorbed monolayer of surface contaminants. Advantages of plasma surface treatment are removal of contaminants from the surface, change in the surface energy and sterilization of the surface. Plasma sterilization aims to kill and/or remove all micro-organisms which may cause infection of humans or animals, or which can cause spoilage of foods or other goods. This review paper emphasizes necessity for sterilization, essentials of sterilization, mechanism of plasma sterilization and the parameters influencing it.

  2. Superposed Epoch Analysis of Ring Current Geoeffectiveness Related to Solar Wind and Plasma Sheet Drivers

    NASA Technical Reports Server (NTRS)

    Liemohm, M. W.; Kozyra, J. U.; Thomsen, M. F.; Borovsky, J. E.; Gahurthakurta, Madulika (Technical Monitor)

    2004-01-01

    The goal of that proposal was to examine the relationship between solar wind drivers and ring current dynamics through data analysis and numerical simulations. The data analysis study was a statistical examination (via superposed epoch analyses) of a solar cycle's worth of storm data. Solar wind data, geophysical indices, and geosynchronous plasma data were collected for every time period with Dst< -50 nT from 1989 through 2002, and the storm list now exceeds 400 entries. This work was first conducted by a summer undergraduate student, Mr. John Vann (University of Kansas), with funding from the NSF Research Experience for Undergraduates program. It was then continued by a University of Michigan graduate student, Mr. Jichun Zhang. Mr. Zhang is now in his fourth year at U-M and is progressing very well toward a PhD in space science. His dissertation will be based on his data analysis and modeling efforts using this geomagnetic storm database. The results of the data analysis study have been the focus of several conference presentations, and the first manuscript has just been published. Two additional papers are presently being prepared, one on average (superposed) solar wind features for various storm subsets (e.g., intense storms at solar maximum), and another on geosynchronous plasma features for these same storm subsets. The latter result was highlighted by the TR&T program director in his presentation at the COSPAR meeting this summer.

  3. Superposed epoch analysis of pressure and magnetic field configuration changes in the plasma sheet

    NASA Technical Reports Server (NTRS)

    Kistler, L. M.; Baumjohann, W.; Nagai, T.; Mobius, E.

    1993-01-01

    Using data from 41 substorm events in the near-Earth magnetotail, we have combined plasma, energetic ion, and magnetic field data from the AMPTE/IRM spacecraft to perform a superposed epoch analysis of changes in the total pressure and in the magnetic field configuration as a function of time relative to substorm onset. Unloading is evident in the total pressure profile; the pressure decreases by about 20 percent. Pressure changes during the growth phase are not as uniform for the different substorms as the pressure changes during the expansion phase. To study changes in the magnetic field configuration, we have determined the development of the plasma pressure profiles in z for an average of data from 15 to 19 R(E). At substorm onset, the field line dipolarization begins on the innermost field lines and then progresses to the outer field lines. The field lines map the closest to the Earth about 45 min after substorm onset, and then begin to stretch out again during the recovery phase of the substorm.

  4. Theory of the unmagnetized plasma.

    NASA Technical Reports Server (NTRS)

    Montgomery, D. C.

    1971-01-01

    The Vlasov mathematical model of a plasma, which has come to be thought more useful than any other in describing the dynamical behavior of the majority of plasmas of interest, is first examined. Macroscopic variables and moment equations; linear electrostatics solutions; plasma oscillations, ion acoustic waves, and linear instabilities are treated, as well as external fields, 'test' charges, and nonlinear Vlasov phenomena. Plasmas are statistically described, and attention is given to the kinetic theory of the stable, uniform plasma and the Balescu-Lenard equation; two-time ensemble averages and fluctuation spectra in stable plasmas; the kinetic theory of the unstable plasma; and ensembles of Vlasov plasmas. Some illustrative experiments are described. Four appendixes deal with the electrostatic approximation and transverse waves; solution of the linearized Vlasov equation in a magnetic field; estimates of correlation functions from thermal equilibrium; and equivalence of spatially uniform BBGKY and Klimontovich correlations.

  5. A consistent understanding of the ribbon structure for the Io plasma torus at the Voyager 1, 1991 ground-based, and Galileo J0 epochs

    NASA Astrophysics Data System (ADS)

    Smyth, William H.; Peterson, Charles A.; Marconi, Max L.

    2011-07-01

    A new four-dimensional (three spatial and local time) empirical model for the Io plasma torus is presented that includes several System III longitude asymmetries and a dawn-dusk electric field with variable direction and magnitude. The model is used to analyze and compare observations for the peak density structure of the plasma torus acquired at the 1979 Voyager 1, the 1991 ground-based, and the 1995 Galileo J0 epochs. The mean magnitude of the dawn-dusk electric field is determined to be much smaller at the 1991 ground-based epoch than at the Voyager 1 and Galileo J0 epochs. A consistent understanding of the radial structure for the density peaks in the plasma torus may then be achieved for these epochs if the dawn-dusk electric field departs by ˜20° from the true dawn-dusk direction and if account is taken of absolute density changes. The ratio of the electron density in the inner and outer plasma torus varies significantly for the three epochs and indicates different temporal evolutions in the balance of the plasma torus production and loss processes. The undisturbed electron density at Io's position in the plasma torus is calculated and has significantly different values at the three epochs; it is shown for each epoch to undergo large variations as Io changes its location in heliocentric phase angle and System III longitude. These large variations provide a wide variety of changing upstream plasma conditions for Io's atmospheric formation, local aurora and distant footprint emissions, and electrodynamic interaction.

  6. Plasma theory and simulation research

    SciTech Connect

    Birdsall, C.K.

    1989-01-01

    Our research group uses both theory and simulation as tools in order to increase the understanding of instabilities, heating, diffusion, transport and other phenomena in plasmas. We also work on the improvement of simulation, both theoretically and practically. Our focus has been more and more on the plasma edge (the sheath''), interactions with boundaries, leading to simulations of whole devices (someday a numerical tokamak).

  7. Fusion Plasma Theory project summaries

    SciTech Connect

    Not Available

    1993-10-01

    This Project Summary book is a published compilation consisting of short descriptions of each project supported by the Fusion Plasma Theory and Computing Group of the Advanced Physics and Technology Division of the Department of Energy, Office of Fusion Energy. The summaries contained in this volume were written by the individual contractors with minimal editing by the Office of Fusion Energy. Previous summaries were published in February of 1982 and December of 1987. The Plasma Theory program is responsible for the development of concepts and models that describe and predict the behavior of a magnetically confined plasma. Emphasis is given to the modelling and understanding of the processes controlling transport of energy and particles in a toroidal plasma and supporting the design of the International Thermonuclear Experimental Reactor (ITER). A tokamak transport initiative was begun in 1989 to improve understanding of how energy and particles are lost from the plasma by mechanisms that transport them across field lines. The Plasma Theory program has actively-participated in this initiative. Recently, increased attention has been given to issues of importance to the proposed Tokamak Physics Experiment (TPX). Particular attention has been paid to containment and thermalization of fast alpha particles produced in a burning fusion plasma as well as control of sawteeth, current drive, impurity control, and design of improved auxiliary heating. In addition, general models of plasma behavior are developed from physics features common to different confinement geometries. This work uses both analytical and numerical techniques. The Fusion Theory program supports research projects at US government laboratories, universities and industrial contractors. Its support of theoretical work at universities contributes to the office of Fusion Energy mission of training scientific manpower for the US Fusion Energy Program.

  8. Theory of Space Dusty Plasma

    NASA Astrophysics Data System (ADS)

    Mendis, A.

    2012-12-01

    Ionized gases, contaminated with fine (nanometer to micrometer-sized) charged dust, loosely referred to a dusty plasmas, occur in a wide variety of cosmic and laboratory environments. In this topical review I will discuss the underlying theory of such plasmas, with emphasis on the space environment. Central to the discussion is the electrostatic charging of the dust grains by the various currents that they experience in the plasma and radiative environment in which they are immersed. This charging could lead to both physical and dynamical consequences for the dust as well as for the plasma. Among the physical effects for the dust are electrostatic disruption and electrostatic levitation from charged surfaces. The dynamics of the charged dust is affected by the Lorentz force they experience, since space plasmas are generally magnetized. The physical effects for plasma result from the fact that the dust can act both as a sink and as a source of electrons in different space environments. The dynamical effects on the plasma arise from the fact that the charged dust can alter the phase velocity of normal wave modes (e.g., the Ion acoustic mode) by changing the charge equilibrium in the plasma. Additionally the charged dust can also participate in the wave dynamics, leading, for example, to the very low frequency, novel, "dust-acoustic" wave that has been observed in the laboratory. Finally the possibility that charged dust in a space plasma, may indirectly influence the propagation of electromagnetic radiation through it, will also be, briefly, discussed.

  9. Perspectives in Space Plasma Theory

    NASA Astrophysics Data System (ADS)

    Treumann, R. A.

    The past half century has been characterized by the birth of space plasma physics and its rise to maturity which has led into a certain mood of satisfaction and partial saturation with its achievements. Indeed, on the global scale our knowledge about the magnetosphere, the solar wind from the Sun out to its boundaries, even of the condition on the surface and in the atmosphere of the Sun and the Sun's interior has to a high degree become complete. The degree of completion is indeed such that it allows predicting up to a certain precision their behaviour. New names like Solar Seismology, Solar Meteorology, and Space Weather have been coined indicating the transition of some of the sub-field of Space Plasma Physics into the domain of an industry of monitoring and prediction in the interest of the needs of a general society. This is an entirely healthy evolution of a scientific field that is on the way of completion. Still there is a large number of questions which should and can hopefully be answered by space plasma theory. Some of them will be listed here in view of what has been achieved and in which direction future theory could contribute to their resolution when addressing the already operating and the new upcoming space missions like Cluster, MMS and others, most of which are designed to become multi-spacecraft enterprises and also in view of the new theoretical and computational techniques and methods that have been developed during the past decades. These directions reach from the detailed understanding of the processes in the solar atmosphere and solar wind through the detailed physics of the formation of collisionless shocks, magnetosheaths and turbulence, the microphysics of reconnection and particle acceleration, the substorm mechanism to the detailed understanding of planetary magnetospheres and the heliospheric termination shock, heliosheath and boundary layer. All this research though already in flow is by far not completed. It requires new efforts as

  10. Perspectives in space plasma theory

    NASA Astrophysics Data System (ADS)

    Treumann, R. A.

    The past half century has been characterized by the birth of space plasma physics and its rise to maturity which has led into a certain mood of satisfaction and partial saturation with its achievements. Indeed, on the global scale our knowledge about the magnetosphere, the solar wind from the Sun out to its boundaries, even of the conditions on the surface and in the atmosphere of the Sun and the Sun’s interior has to a high degree become complete. The degree of completion is indeed such that it allows predicting up to a certain precision their behavior. New names like solar seismology, solar meteorology, and space weather have been coined indicating the transition of some of the sub-field of Space Plasma Physics into the domain of an industry of monitoring and predicting in the interest of the needs of a general society. This is an entirely healthy evolution of a scientific field that is on the path of completion. Still there is a large number of questions which should and can hopefully be answered by space plasma theory. Some of them will be listed here in view of what has been achieved and in which direction future theory could proceed in order to contribute to their resolution when addressing the already operating and the new and upcoming space missions like Cluster, the planned Magnetospheric Multi-Scale mission MMS and others, respectively, most of which are designed to become multi-spacecraft enterprizes and also in view of the new theoretical and computational techniques and methods that have been developed during the past decades. These directions reach from the detailed understanding of the processes in the solar atmosphere and solar wind through the detailed physics of the formation of collisionless shocks, magnetosheaths and turbulence, the microphysics of reconnection and particle acceleration, and the substorm mechanism to the detailed understanding of planetary magnetospheres, the outer heliosphere with its heliospheric termination shock

  11. Theory for Plasma Rocket Propulsion

    NASA Astrophysics Data System (ADS)

    Grabbe, Crockett

    2009-11-01

    Electrical propulsion of rockets is developing potentially into the use of 3 different thrusters for future long-distance space missions that primarily involve plasma dynamics. These are the Magnetoplasmadynamic (MPD) Thruster, the Plasma Induction Thruster (PID), and the VASIMIR Thruster. The history of the development of electrical propulsion into these prospects and the current research of particularly the VASIMIR Thruster are reviewed. Theoretical questions that need to be addressed in that development are explored.

  12. The quantum epoché.

    PubMed

    Pylkkänen, Paavo

    2015-12-01

    The theme of phenomenology and quantum physics is here tackled by examining some basic interpretational issues in quantum physics. One key issue in quantum theory from the very beginning has been whether it is possible to provide a quantum ontology of particles in motion in the same way as in classical physics, or whether we are restricted to stay within a more limited view of quantum systems, in terms of complementary but mutually exclusive phenomena. In phenomenological terms we could describe the situation by saying that according to the usual interpretation of quantum theory (especially Niels Bohr's), quantum phenomena require a kind of epoché (i.e. a suspension of assumptions about reality at the quantum level). However, there are other interpretations (especially David Bohm's) that seem to re-establish the possibility of a mind-independent ontology at the quantum level. We will show that even such ontological interpretations contain novel, non-classical features, which require them to give a special role to "phenomena" or "appearances", a role not encountered in classical physics. We will conclude that while ontological interpretations of quantum theory are possible, quantum theory implies the need of a certain kind of epoché even for this type of interpretations. While different from the epoché connected to phenomenological description, the "quantum epoché" nevertheless points to a potentially interesting parallel between phenomenology and quantum philosophy. PMID:26276464

  13. BOOK REVIEW: Kinetic theory of plasma waves, homogeneous plasmas

    NASA Astrophysics Data System (ADS)

    Porkolab, Miklos

    1998-11-01

    The linear theory of plasma waves in homogeneous plasma is arguably the most mature and best understood branch of plasma physics. Given the recently revised version of Stix's excellent Waves in Plasmas (1992), one might ask whether another book on this subject is necessary only a few years later. The answer lies in the scope of this volume; it is somewhat more detailed in certain topics than, and complementary in many fusion research relevant areas to, Stix's book. (I am restricting these comments to the homogeneous plasma theory only, since the author promises a second volume on wave propagation in inhomogeneous plasmas.) This book is also much more of a theorist's approach to waves in plasmas, with the aim of developing the subject within the logical framework of kinetic theory. This may indeed be pleasing to the expert and to the specialist, but may be too difficult to the graduate student as an `introduction' to the subject (which the author explicitly states in the Preface). On the other hand, it may be entirely appropriate for a second course on plasma waves, after the student has mastered fluid theory and an introductory kinetic treatment of waves in a hot magnetized `Vlasov' plasma. For teaching purposes, my personal preference is to review the cold plasma wave treatment using the unified Stix formalism and notation (which the author wisely adopts in the present book, but only in Chapter 5). Such an approach allows one to deal with CMA diagrams early on, as well as to provide a framework to discuss electromagnetic wave propagation and accessibility in inhomogeneous plasmas (for which the cold plasma wave treatment is perfectly adequate). Such an approach does lack some of the rigour, however, that the author achieves with the present approach. As the author correctly shows, the fluid theory treatment of waves follows logically from kinetic theory in the cold plasma limit. I only question the pedagogical value of this approach. Otherwise, I welcome this

  14. Stability theory of Knudsen plasma diodes

    SciTech Connect

    Kuznetsov, V. I. Ender, A. Ya.

    2015-11-15

    A stability theory is developed for a plasma diode in which an electron beam supplied from the emitter propagates without collisions in the self-consistent electric field against the immobile ion background. An integral equation for the amplitude of the perturbed field is deduced using the Q,G method for the regime without electron reflection from a potential barrier. Analytic solutions to this equation are obtained for a number of important particular cases, and the plasma dispersion properties are examined.

  15. Statistical theory of plasma-molecular systems

    NASA Astrophysics Data System (ADS)

    Klimontovich, Yu. L.; Wilhelmsson, H.; Yakimenko, I. P.; Zagorodny, A. G.

    1989-04-01

    The basic principles of kinetic theory are formulated for combined plasma-molecular systems consisting of both free and bound charged particles. The description of the subsystem of bound particles is bassed on the classical model of atomic oscillators (this makes it impossible to take into account ionization and recombination processes, byt the general formalism is still quite useful). In the framework of such a model, collective electromagnetic processes in infinite and bounded plasma-molecular matter are studied. The influence of boundaries on the collision integrals, on the kinetic coefficients and on the space distributions of particles is investigated in detail. The theory of electromagnetic fluctuations in bounded plasma-molecular systems is developed as well. This theory is used to obtain the correlation functions of electron density fluctuations and spontaneous emission spectra. A numerical analysis of spontaneous emission spectra is presented for systems with plane-parallel boundaries. The generalization of the fluctuation theory of bremsstrahlung radiation in a plasma to the case of plasma-molecular matter is also discussed.

  16. Neutral Vlasov kinetic theory of magnetized plasmas

    SciTech Connect

    Tronci, Cesare; Camporeale, Enrico

    2015-02-15

    The low-frequency limit of Maxwell equations is considered in the Maxwell-Vlasov system. This limit produces a neutral Vlasov system that captures essential features of plasma dynamics, while neglecting radiation effects. Euler-Poincaré reduction theory is used to show that the neutral Vlasov kinetic theory possesses a variational formulation in both Lagrangian and Eulerian coordinates. By construction, the new model recovers all collisionless neutral models employed in plasma simulations. Then, comparisons between the neutral Vlasov system and hybrid kinetic-fluid models are presented in the linear regime.

  17. Kinetic theory of relativistic plasmas

    NASA Technical Reports Server (NTRS)

    Gould, R. J.

    1981-01-01

    The thermalization of particle kinetic motion by binary collisions is considered for a plasma with a Boltzmann constant-temperature product approximately equal to 10 to 100 times the product of the electron mass with the square of the speed of light. At this temperature, the principal mechanism for relaxation of electron motion is via radiationless electron-electron collisions (Moller scattering). Ions are nonrelativistic, but are energetic enough so that their Coulomb scattering can be treated in the Born approximation. Relaxation times are computed and Boltzmann-equation Fokker-Planck operators are derived for the various binary-collision processes. The expression for the rate of kinetic energy exchange between electron and ion gases is derived for the case where the gases are at different temperatures.

  18. Weak turbulence theory for collisional plasmas

    NASA Astrophysics Data System (ADS)

    Yoon, P. H.; Ziebell, L. F.; Kontar, E. P.; Schlickeiser, R.

    2016-03-01

    Plasma is an ionized gas in which the collective behavior dominates over the individual particle interactions. For this reason, plasma is often treated as collisionless or collision-free. However, the discrete nature of the particles can be important, and often, the description of plasmas is incomplete without properly taking the discrete particle effects into account. The weak turbulence theory is a perturbative nonlinear theory, whose essential formalism was developed in the late 1950s and 1960s and continued on through the early 1980s. However, the standard material found in the literature does not treat the discrete particle effects and the associated fluctuations emitted spontaneously by thermal particles completely. Plasma particles emit electromagnetic fluctuations in all frequencies and wave vectors, but in the standard literature, the fluctuations are approximately treated by considering only those frequency-wave number regimes corresponding to the eigenmodes (or normal modes) satisfying the dispersion relations, while ignoring contributions from noneigenmodes. The present paper shows that the noneigenmode fluctuations modify the particle kinetic equation so that the generalized equation includes the Balescu-Lénard-Landau collision integral and also modify the wave kinetic equation to include not only the collisional damping term but also a term that depicts the bremsstrahlung emission of plasma normal modes.

  19. Theory and Simulations of Solar System Plasmas

    NASA Technical Reports Server (NTRS)

    Goldstein, Melvyn L.

    2011-01-01

    "Theory and simulations of solar system plasmas" aims to highlight results from microscopic to global scales, achieved by theoretical investigations and numerical simulations of the plasma dynamics in the solar system. The theoretical approach must allow evidencing the universality of the phenomena being considered, whatever the region is where their role is studied; at the Sun, in the solar corona, in the interplanetary space or in planetary magnetospheres. All possible theoretical issues concerning plasma dynamics are welcome, especially those using numerical models and simulations, since these tools are mandatory whenever analytical treatments fail, in particular when complex nonlinear phenomena are at work. Comparative studies for ongoing missions like Cassini, Cluster, Demeter, Stereo, Wind, SDO, Hinode, as well as those preparing future missions and proposals, like, e.g., MMS and Solar Orbiter, are especially encouraged.

  20. Recent Advances in Plasma Edge Physics Theory

    NASA Astrophysics Data System (ADS)

    Stacey, W. M.

    2015-11-01

    This presentation summarizes recent theory developments for interpreting plasma edge physics experiments in DIII-D. i) Radial and poloidal moment balance require that the radial particle flux be of a pinch-diffusive nature with the pinch representing the electromagnetic forces and external momentum input. Ion radial particle fluxes in experiment are found to be a smaller difference between large outward diffusion fluxes and inward pinch fluxes. When the pinch-diffusion relation is used in the continuity equation a new diffusion theory that preserves momentum balance is obtained. ii) The majority of thermalized ions and their energy cross the LCFS on ion loss orbits and are deposited in the SOL near the outboard midplane. The lost ions are predominantly ctr-current, producing a co-current intrinsic rotation of the remaining ions in the edge plasma. iii) While the contribution of the leading order parallel viscosity to toroidal momentum damping vanishes identically in axisymmetric plasmas, non-axisymmetric radial B-fields in the edge plasma enable parallel viscosity to enhance the damping of toroidal rotation. Work supported by the US DOE under DE-FG02-00ER54538, DE-FC02-04ER54698.

  1. Plasmas as Antennas - Theory, Experiment and Applications

    NASA Astrophysics Data System (ADS)

    Borg, Gerard

    1999-11-01

    A variety of antennas are employed in telecommunications and radar systems. Some applications pose special problems. Large structures are easily detected by hostile radar. The performance of multi-element HF-VHF arrays is complicated by mutual coupling between large radiating elements. High speed data communications and radar can be limited by signal decay and ringing. A novel solution is an antenna made of plasma that can be made to disappear on microsecond time scales. Recent experiments at the Australian National University (G.G. Borg et. al. App. Phys. Letts. Vol. 74, 3272-3274 [1999]), have shown that highly efficient (25 - 50radiating elements for the range 3 - 300 MHz can be formed using low power (10 - 50 W average) plasma surface waves launched at one end of a tube containing a suitable gas. Only a single capacitive coupler is needed to launch the waves - there is no electrical connection to the other end of the tube. The regimes of wave propagation correlate with expectations from plasma surface wave theory. Actual communications experiments have shown that these plasma antennas can have surprisingly low noise provided they are excited by the rf surface waves and not by a low frequency or DC ohmic current. Applications to HF-VHF communications and radar are being developed. These include both single ruggedised plasma elements and multi-element arrays.

  2. Geometric Gyrokinetic Theory for Edge Plasma

    SciTech Connect

    Qin, H; Cohen, R H; Nevins, W M; Xu, X Q

    2007-01-18

    It turns out that gyrokinetic theory can be geometrically formulated as special cases of a geometrically generalized Vlasov-Maxwell system. It is proposed that the phase space of the spacetime is a 7-dimensional fiber bundle P over the 4-dimensional spacetime M, and that a Poincare-Cartan-Einstein 1-form {gamma} on the 7-dimensional phase space determines particles worldlines in the phase space. Through Liouville 6-form {Omega} and fiber integral, the 1-form {gamma} also uniquely defines a geometrically generalized Vlasov-Maxwell system as a field theory for the collective electromagnetic field. The geometric gyrokinetic theory is then developed as a special case of the geometrically generalized Vlasov-Maxwell system. In its most general form, gyrokinetic theory is about a symmetry, called gyro-symmetry, for magnetized plasmas, and the 1-form {gamma} again uniquely defines the gyro-symmetry. The objective is to decouple the gyro-phase dynamics from the rest of particle dynamics by finding the gyro-symmetry in {gamma}. Compared with other methods of deriving the gyrokinetic equations, the advantage of the geometric approach is that it allows any approximation based on mathematical simplification or physical intuition to be made at the 1-form level, and yet the field theories still have the desirable exact conservation properties such as phase space volume conservation and energy-momentum conservation if the 1-form does not depend on the spacetime coordinate explicitly. A set of generalized gyrokinetic equations valid for the edge plasmas is then derived using this geometric method. This formalism allows large-amplitude, time-dependent background electromagnetic fields to be developed fully nonlinearly in addition to small-amplitude, short-wavelength electromagnetic perturbations. The fact that we adopted the geometric method in the present study does not necessarily imply that the major results reported here can not be achieved using classical methods. What the

  3. Kinetic theory of partially ionized complex (dusty) plasmas

    SciTech Connect

    Tsytovich, V.N.; De Angelis, U.; Ivlev, A.V.; Morfill, G.E.

    2005-08-15

    The general approach to the kinetic theory of complex (dusty) plasmas [Tsytovich and de Angelis, Phys. Plasmas 6, 1093 (1999)], which was formulated with the assumption of a regular (nonfluctuating) source of plasma particles, is reformulated to include ionization by electron impact on neutrals as the plasma source and the effects of collisions of ions and dust particles with neutrals.

  4. Theory and simulation of plasma sheath waves

    SciTech Connect

    Xu, X.Q.; DiPeso, G.; Vahedi, V.; Birdsall, C.K.

    1992-12-15

    Sheath waves have been investigated analytically and with particle simulation for an unmagnetized two dimensional plasma slab with periodic boundary conditions in y and conducting walls at x = 0, L{sub x}. Analytically treating the sheath as a vacuum layer, the sheath wave bears a resemblance to plasma vacuum surface waves. The simulations are in agreement with the theory for both bulk Bohm Grow waves and edge sheath waves, with some unanswered questions. Some waves that were expected did not show up, at least, where we thought they should be. Hence, improvements were made in the initialization (a better quiet start), in the diagnostics (especially the spectra in frequency), and in the excitation (ability to pulse). It has become clear that this problem, seeking both sheath (or surface) and body waves in a bounded system, needs far more attention, in analysis (non-uniform density included) and in simulation, especially in diagnostics. Hence, this report is to be treated as a start on the problem. The problem is not dropped, as the understanding of such waves (in 2d and 3d) is very important, for both basic sheath understanding and for applications, such as plasma control via excitation of sheath or pre-sheath waves.

  5. Hydrodynamic gradient expansion in gauge theory plasmas.

    PubMed

    Heller, Michal P; Janik, Romuald A; Witaszczyk, Przemysław

    2013-05-24

    We utilize the fluid-gravity duality to investigate the large order behavior of hydrodynamic gradient expansion of the dynamics of a gauge theory plasma system. This corresponds to the inclusion of dissipative terms and transport coefficients of very high order. Using the dual gravity description, we calculate numerically the form of the stress tensor for a boost-invariant flow in a hydrodynamic expansion up to terms with 240 derivatives. We observe a factorial growth of gradient contributions at large orders, which indicates a zero radius of convergence of the hydrodynamic series. Furthermore, we identify the leading singularity in the Borel transform of the hydrodynamic energy density with the lowest nonhydrodynamic excitation corresponding to a 'nonhydrodynamic' quasinormal mode on the gravity side. PMID:23745858

  6. Theory of correlation effects in dusty plasmas

    SciTech Connect

    Avinash, K.

    2015-03-15

    A theory of correlation effects in dusty plasmas based on a suitably augmented Debye Huckel approximation is proposed. A model which takes into account the confinement of the dust within the plasma (by external fields) is considered. The dispersion relation of compressional modes with correlation effects is obtained. Results show that strong coupling effects may be subdominant even when Γ ≫ 1. Thus, in the limit Γ→0 and/or κ → ∞, one obtains the weakly coupled dust thermal mode. In the range of values of Γ ≫ 1, the strong coupling effects scale with κ instead of Γ; increasing Γ increases the dust acoustic waves phase velocity C{sub DAW} in this regime. In the limit Γ≫1,κ≪1, one obtains the weakly coupled dust acoustic wave. Only in the limit Γ≫1,κ≥1, one obtains strong coupling effects, e.g., the dust lattice waves (κ=a/λ{sub d}, a is the mean particle distance and λ{sub d} is the Debye length). Observations from a number of experiments are explained.

  7. Theory of plasma contactors for electrodynamic tethered satellite systems

    NASA Technical Reports Server (NTRS)

    Parks, D. E.; Katz, I.

    1987-01-01

    Recent data from ground and space experiments indicate that plasma releases from an object dramatically reduce the sheath impedance between the object and the ambient plasma surrounding it. Available data is in qualitative accord with the theory developed to quantify the flow of current in the sheath. Electron transport in the theory is based on a fluid model of a collisionless plasma with an effective collision frequency comparable to frequencies of plasma oscillations. The theory leads to low effective impedances varying inversely with the square root of the injected plasma density. To support such a low impedance mode of operation using an argon plasma source, for example, requires that only one argon ion be injected for each thirty electrons extracted from the ambient plasma. The required plasma flow rates are quite low; to extract one ampere of electron current requires a mass flow rate of about one gram of argon per day.

  8. Plasma transport theory spanning weak to strong coupling

    SciTech Connect

    Daligault, Jérôme; Baalrud, Scott D.

    2015-06-29

    We describe some of the most striking characteristics of particle transport in strongly coupled plasmas across a wide range of Coulomb coupling strength. We then discuss the effective potential theory, which is an approximation that was recently developed to extend conventional weakly coupled plasma transport theory into the strongly coupled regime in a manner that is practical to evaluate efficiently.

  9. Dust in fusion plasmas: theory and modeling

    SciTech Connect

    Smirnov, R. D.; Pigarov, A. Yu.; Krasheninnikov, S. I.; Mendis, D. A.; Rosenberg, M.; Rudakov, D.; Tanaka, Y.; Rognlien, T. D.; Soboleva, T. K.; Shukla, P. K.; Bray, B. D.; West, W. P.; Roquemore, A. L.; Skinner, C. H.

    2008-09-07

    Dust may have a large impact on ITER-scale plasma experiments including both safety and performance issues. However, the physics of dust in fusion plasmas is very complex and multifaceted. Here, we discuss different aspects of dust dynamics including dust-plasma, and dust-surface interactions. We consider the models of dust charging, heating, evaporation/sublimation, dust collision with material walls, etc., which are suitable for the conditions of fusion plasmas. The physical models of all these processes have been incorporated into the DUST Transport (DUSTT) code. Numerical simulations demonstrate that dust particles are very mobile and accelerate to large velocities due to the ion drag force (cruise speed >100 m/s). Deep penetration of dust particles toward the plasma core is predicted. It is shown that DUSTT is capable of reproducing many features of recent dust-related experiments, but much more work is still needed.

  10. Theory for explosive ideal magnetohydrodynamic instabilities in plasmas.

    PubMed

    Wilson, H R; Cowley, S C

    2004-04-30

    Flux tubes confined in tokamaks are observed to erupt explosively in some plasma disruptions and edge localized modes. Similar eruptions occur in astrophysical plasmas, for example, in solar flares and magnetospheric substorms. A single unifying nonlinear evolution equation describing such behavior in both astrophysical and tokamak plasmas is derived. This theory predicts that flux tubes rise explosively, narrow, and twist to pass through overlying magnetic field lines without reconnection. PMID:15169163

  11. Final Report on The Theory of Fusion Plasmas

    SciTech Connect

    Steven C. Cowley

    2008-06-17

    Report describes theoretical research in the theory of fusion plasmas funded under grant DE-FG02-04ER54737. This includes work on: explosive instabilities, plasma turbulence, Alfven wave cascades, high beta (pressure) tokamaks and magnetic reconnection. These studies have lead to abetter understanding of fusion plasmas and in particular the future behavior of ITER. More than ten young researchers were involved in this research -- some were funded under the grant.

  12. Experiments and Theory of Dusty Plasmas

    SciTech Connect

    Shukla, P. K.

    2011-11-29

    The purpose of this paper is to present the most important theoretical and experimental discoveries that have been made in the area of dusty plasma physics. We describe the physics and observations of the well celebrated dust acoustic wave (DAW) and the dust ion-acoustic wave (DIAW) in dusty plasmas with weakly coupled dust grains, as well as the dust Coulomb crystal and dust lattice oscillations (DLOs) in dusty plasmas with strongly coupled dust grains. In dusty plasmas, the dust charge fluctuation is a dynamical variable, which provides a novel collisionless damping of the DA and DIA waves. The latter and the DLOs are excited by external sources, which are here discussed. Besides the Debye-Hueckel short-range repulsive force between like charged dust grains, there are novel attractive forces (e.g. due to dipole-dipole dust particle interactions, overlapping Debye spheres, ion focusing and ion wakefields, dipole magnetic moments etc.), which provide unique possibilities for attracting charged dust particles of similar polarity. The dust particle attraction is responsible for the formation of dust Coulomb crystals in laboratory dusty plasmas, as well as for the formation of planets and large astrophysical bodies in the Milky Way galaxy and in interstellar media. Furthermore, the nonlinear DAW, DIAW, and DLOs also appear in the form of solitary and shock waves, the physics and observations of which are briefly discussed. Finally, we discuss possible applications of dust-in-plasmas and dusty plasmas in laboratory and space.

  13. Testing THEMIS wave measurements against the cold plasma theory

    NASA Astrophysics Data System (ADS)

    Taubenschuss, Ulrich; Santolik, Ondrej; Le Contel, Olivier; Bonnell, John

    2016-04-01

    The THEMIS (Time History of Events and Macroscale Interactions during Substorms) mission records a multitude of electromagnetic waves inside Earth's magnetosphere and provides data in the form of high-resolution electric and magnetic waveforms. We use multi-component measurements of whistler mode waves and test them against the theory of wave propagation in a cold plasma. The measured ratio cB/E (c is speed of light in vacuum, B is magnetic wave amplitude, E is electric wave amplitude) is compared to the same quantity calculated from cold plasma theory over linearized Faraday's law. The aim of this study is to get estimates for measurement uncertainties, especially with regard to the electric field and the cold plasma density, as well as evaluating the validity of cold plasma theory inside Earth's radiation belts.

  14. Pliocene geomagnetic polarity epochs

    USGS Publications Warehouse

    Dalrymple, G.B.; Cox, A.; Doell, Richard R.; Gromme, C.S.

    1967-01-01

    A paleomagnetic and K-Ar dating study of 44 upper Miocene and Pliocene volcanic units from the western United States suggests that the frequency of reversals of the earth's magnetic field during Pliocene time may have been comparable with that of the last 3.6 m.y. Although the data are too limited to permit the formal naming of any new polarity epochs or events, four polarity transitions have been identified: the W10 R/N boundary at 3.7 ?? 0.1 m.y., the A12 N/R boundary at 4.9 ?? 0.1 m.y., the W32 N/R boundary at 9.0 ?? 0.2m.y., and the W36 R/N boundary at 10.8 ?? 0.3 - 1.0 m.y. The loss of absolute resolution of K-Ar dating in older rocks indicates that the use of well defined stratigraphic successions to identify and date polarity transitions will be important in the study of Pliocene and older reversals. ?? 1967.

  15. Geometric perturbation theory and plasma physics

    SciTech Connect

    Omohundro, S.M.

    1985-04-04

    Modern differential geometric techniques are used to unify the physical asymptotics underlying mechanics, wave theory and statistical mechanics. The approach gives new insights into the structure of physical theories and is suited to the needs of modern large-scale computer simulation and symbol manipulation systems. A coordinate-free formulation of non-singular perturbation theory is given, from which a new Hamiltonian perturbation structure is derived and related to the unperturbed structure. The theory of perturbations in the presence of symmetry is developed, and the method of averaging is related to reduction by a circle group action. The pseudo-forces and magnetic Poisson bracket terms due to reduction are given a natural asymptotic interpretation. Similar terms due to changing reference frames are related to the method of variation of parameters, which is also given a Hamiltonian formulation. These methods are used to answer a question about nearly periodic systems. The answer leads to a new secular perturbation theory that contains no ad hoc elements. Eikonal wave theory is given a Hamiltonian formulation that generalizes Whitham's Lagrangian approach. The evolution of wave action density on ray phase space is given a Hamiltonian structure using a Lie-Poisson bracket. The relationship between dissipative and Hamiltonian systems is discussed. A new type of attractor is defined which attracts both forward and backward in time and is shown to occur in infinite-dimensional Hamiltonian systems with dissipative behavior. The theory of Smale horseshoes is applied to gyromotion in the neighborhood of a magnetic field reversal and the phenomenon of reinsertion in area-preserving horseshoes is introduced. The central limit theorem is proved by renormalization group techniques. A natural symplectic structure for thermodynamics is shown to arise asymptotically from the maximum entropy formalism.

  16. Nonlinear theory of a plasma Cherenkov maser

    SciTech Connect

    Choi, J.S.; Heo, E.G.; Choi, D.I.

    1995-12-31

    The nonlinear saturation state in a plasma Cherenkov maser (PCM) propagating the intense relativistic electron beam through a circular waveguide partially filled with a dense annular plasma, is analyzed from the nonlinear formulation based on the cold fluid-Maxwell equations. We obtain the nonlinear efficiency and the final operation frequency under consideration of the effects of the beam current, the beam energy and the slow wave structure. We show that the saturation mechanism of a PCM instablity is a close correspondence in that of the relativistic two stream instability by the coherent trapping of electrons in a single most-ustable wave. And the optimal conditions in PCM operation are also obtained from performing our nonliear analysis together with computer simulations.

  17. Microwave Plasma Window Theory and Experiments

    NASA Astrophysics Data System (ADS)

    McKelvey, Andrew; Zheng, Peng; Franzi, Matthew; Lau, Y. Y.; Gilgenbach, Ronald; Plasma, Pulsed Power,; Microwave Laboratory Team

    2011-10-01

    The microwave plasma window is an experiment designed to promote RF breakdown in a controlled vacuum-gas environment using a DC bias. Experimental data has shown that this DC bias will significantly reduce the RF power required to yield breakdown, a feature also shown in recent simulation. The cross-polarized conducting array is biased at (100's V) DC on the surface of a Lucite vacuum window. Microwave power is supplied to the window's surface by a single 1-kW magnetron operating at 2.45 GHz CW. The goal of this project is to establish controllable characteristics relating vacuum pressure, DC bias, RF power required for surface breakdown, as well as RF transmission after the formation of plasma. Experimental data will be compared with multipactor susceptibility curves generated using a Monte Carlo simulation which incorporates an applied DC bias and finite pressures of air and argon. Research supported by an AFOSR grant on the Basic Physics of Distributed Plasma Discharge, AFRL, L-3 Communications, and Northrop Grumman.

  18. Plasma confinement theory and transport simulation

    SciTech Connect

    Ross, D.W.

    1993-02-01

    The objectives continue to be: (1) to advance the transport studies of tokamaks, including development and maintenance of the Magnetic Fusion Energy Database, and (2) to provide theoretical interpretation, modeling and equilibrium and stability for TEXT-Upgrade. Recent publications and reports, and conference presentations of the Fusion Research Center theory group are listed.

  19. Theory of current-drive in plasmas

    SciTech Connect

    Fisch, N.J.

    1986-12-01

    The continuous operation of a tokamak fusion reactor requires, among other things, a means of providing continuous toroidal current. Such operation is preferred to the conventional pulsed operation, where the plasma current is induced by a time-varying magnetic field. A variety of methods has been proposed to provide continuous current, including methods which utilize particle beams or radio frequency waves in any of several frequency regimes. Currents as large as half a mega-amp have now been produced in the laboratory by such means, and experimentation in these techniques has now involved major tokamak facilities worldwide.

  20. Elements of Neoclassical Theory and Plasma Rotation in a Tokamak

    NASA Astrophysics Data System (ADS)

    Smolyakov, A.

    2015-12-01

    The following sections are included: * Introduction * Quasineutrality condition * Diffusion in fully ionized magnetized plasma and automatic ambipolarity * Toroidal geometry and neoclassical diffusion * Diffusion and ambipolarity in toroidal plasmas * Ambipolarity and equilibrium poloidal rotation * Ambipolarity paradox and damping of poloidal rotation * Neoclassical plasma inertia * Oscillatory modes of poloidal plasma rotation * Dynamics of the toroidal momentum * Momentum diffusion in strongly collisional, short mean free path regime * Diffusion of toroidal momentum in the weak collision (banana) regime * Toroidal momentum diffusion and momentum damping from drift-kinetic theory and fluid moment equations * Comments on non-axisymmetric effects * Summary * Acknowledgments * Appendix: Trapped (banana) particles and collisionality regimes in a tokamak * Appendix: Hierarchy of moment equations * Appendix: Plasma viscosity tensor in the magnetic field: parallel viscosity, gyroviscosity, and perpendicular viscosity * Appendix: Closure relations for the flux surface averaged parallel viscosity in neoclassical (banana and plateau) regimes * References

  1. A First-Principle Kinetic Theory of Meteor Plasma Formation

    NASA Astrophysics Data System (ADS)

    Dimant, Yakov; Oppenheim, Meers

    2015-11-01

    Every second millions of tiny meteoroids hit the Earth from space, vast majority too small to observe visually. However, radars detect the plasma they generate and use the collected data to characterize the incoming meteoroids and the atmosphere in which they disintegrate. This diagnostics requires a detailed quantitative understanding of formation of the meteor plasma. Fast-descending meteoroids become detectable to radars after they heat due to collisions with atmospheric molecules sufficiently and start ablating. The ablated material then collides into atmospheric molecules and forms plasma around the meteoroid. Reflection of radar pulses from this plasma produces a localized signal called a head echo. Using first principles, we have developed a consistent collisional kinetic theory of the near-meteoroid plasma. This theory shows that the meteoroid plasma develops over a length-scale close to the ion mean free path with a non-Maxwellian velocity distribution. The spatial distribution of the plasma density shows significant deviations from a Gaussian law usually employed in head-echo modeling. This analytical model will serve as a basis for more accurate quantitative interpretation of the head echo radar measurements. Work supported by NSF Grant 1244842.

  2. Kinetic theory of nonlinear transport phenomena in complex plasmas

    SciTech Connect

    Mishra, S. K.; Sodha, M. S.

    2013-03-15

    In contrast to the prevalent use of the phenomenological theory of transport phenomena, a number of transport properties of complex plasmas have been evaluated by using appropriate expressions, available from the kinetic theory, which are based on Boltzmann's transfer equation; in particular, the energy dependence of the electron collision frequency has been taken into account. Following the recent trend, the number and energy balance of all the constituents of the complex plasma and the charge balance on the particles is accounted for; the Ohmic loss has also been included in the energy balance of the electrons. The charging kinetics for the complex plasma comprising of uniformly dispersed dust particles, characterized by (i) uniform size and (ii) the Mathis, Rumpl, and Nordsieck power law of size distribution has been developed. Using appropriate expressions for the transport parameters based on the kinetic theory, the system of equations has been solved to investigate the parametric dependence of the complex plasma transport properties on the applied electric field and other plasma parameters; the results are graphically illustrated.

  3. Thermoemission (dust-electron) plasmas: theory of neutralizing charges.

    PubMed

    Vishnyakov, V I; Dragan, G S

    2006-09-01

    Thermoemission plasma--i.e., a system consisting of dust grains and electrons--is studied. In the proposed model, it is assumed that the major part of the electronic gas is uniformly distributed in space and the spatial inhomogeneities of electronic density exist only near the dust grains. The experimental data, well described by the proposed theory, are given. PMID:17025751

  4. Theory for neoclassical toroidal plasma viscosity in tokamaks

    NASA Astrophysics Data System (ADS)

    Shaing, K. C.; Chu, M. S.; Hsu, C. T.; Sabbagh, S. A.; Seol, Jae Chun; Sun, Y.

    2012-12-01

    Error fields and magnetohydrodynamic modes break toroidal symmetry in tokamaks. The broken symmetry enhances the toroidal plasma viscosity, which results in a steady-state toroidal plasma flow. A theory for neoclassical toroidal plasma viscosity in the low-collisionality regimes is developed. It extends stellarator transport theory to include multiple modes and to allow for |m - nq| ˜ 1. Here, m is the poloidal mode number, n is the toroidal mode number and q is the safety factor. The bounce averaged drift kinetic equation is solved in several asymptotic limits to obtain transport fluxes. These fluxes depend non-linearly on the radial electric field except for those in the 1/ν regime. Here, ν is the collision frequency. The theory is refined to include the effects of the superbanana plateau resonance at the phase space boundary and the finite ∇B drift on the collisional boundary layer fluxes. Analytical expressions that connect all asymptotic limits are constructed and are in good agreement with the numerical results. The flux-force relations that relate transport fluxes to forces are used to illustrate the roles of transport fluxes in the momentum equation. It is shown that the ambipolar state is reached when the momentum equation is relaxed. It is also shown that the origin of the momentum for plasma flow generated without momentum sources is the local unbalance of particles' momenta and is diamagnetic in nature regardless of the details of the theory.

  5. Theories of radio emissions and plasma waves. [in Jupiter magnetosphere

    NASA Technical Reports Server (NTRS)

    Goldstein, M. L.; Goertz, C. K.

    1983-01-01

    The complex region of Jupiter's radio emissions at decameter wavelengths, the so-called DAM, is considered, taking into account the basic theoretical ideas which underly both the older and newer theories and models. Linear theories are examined, giving attention to direct emission mechanisms, parallel propagation, perpendicular propagation, and indirect emission mechanisms. An investigation of nonlinear theories is also conducted. Three-wave interactions are discussed along with decay instabilities, and three-wave up-conversio. Aspects of the Io and plasma torus interaction are studied, and a mechanism by which Io can accelerate electrons is reviewed.

  6. Propagation of radiation in fluctuating multiscale plasmas. I. Kinetic theory

    SciTech Connect

    Tyshetskiy, Yu.; Pal Singh, Kunwar; Thirunavukarasu, A.; Robinson, P. A.; Cairns, Iver H.

    2012-11-15

    A theory for propagation of radiation in a large scale plasma with small scale fluctuations is developed using a kinetic description in terms of the probability distribution function of the radiation in space, time, and wavevector space. Large scale effects associated with spatial variations in the plasma density and refractive index of the plasma wave modes and small scale effects such as scattering of radiation by density clumps in fluctuating plasma, spontaneous emission, damping, and mode conversion are included in a multiscale kinetic description of the radiation. Expressions for the Stokes parameters in terms of the probability distribution function of the radiation are used to enable radiation properties such as intensity and polarization to be calculated.

  7. Cold plasma heating in the plasma sheet boundary layer - Theory and simulations

    NASA Technical Reports Server (NTRS)

    Schriver, David; Ashour-Abdalla, Maha

    1990-01-01

    Satellite observations in recent years have confirmed that the plasma sheet boundary layer is a permanent feature of the earth's magnetotail located between the lobe and central plasma sheet during both quiet and active magnetic periods. Distinct features of the boundary layer include field aligned ion beams and intense electrostatic emissions known as broadband electrostatic noise. Since the plasma sheet boundary layer is a spatial feature of the magnetotail, within it will occur thermal mixing of the resident warm boundary layer plasma with inflowing (convecting) cold ionospheric plasma. A theoretical study involving linear theory and nonlinear numerical particle simulations is presented which examines ion beam instabilities in the presence of a thermally mixed hot and cold background plasma. It is found that the free energy in the ion beams can heat the cool ionospheric plasma to ambient plasma sheet boundary layer temperatures via broadband electrostatic noise. These results, along with recent observational reports that ionospheric outflow can account for measured plasma sheet densities, suggest that the ionospheric role in plasma sheet dynamics and content may be as large as the solar wind.

  8. Nonlinear theory of slow dissipative layers in anisotropic plasmas

    SciTech Connect

    Ballai, I.; Ruderman, M.S.; Erdelyi, R.

    1998-01-01

    The solar coronal plasma is a well-known example of a plasma with strongly anisotropic dissipative coefficients. The main dissipative processes in the solar corona are strongly anisotropic thermal conductivity and viscosity. Ruderman and Goossens [Astrophys. J. {bold 471}, 1015 (1996)] developed a linear theory of driven slow resonant waves in plasmas with strongly anisotropic viscosity and thermal conductivity. Linear theory shows that in the slow dissipative layer the amplitudes of oscillations become very large for high Reynolds and Pecklet numbers, so that nonlinearity may be important. In the present paper the nonlinear behavior of driven magnetohydrodynamic waves in the slow dissipative layer in plasmas with strongly anisotropic viscosity and thermal conductivity is studied. The nonlinear governing equation for wave variables in the dissipative layer is derived. The nonlinear connection formulae, which are extensions of the linear connection formulae first introduced in the theory of resonant magnetohydrodynamic waves by Sakurai, Goossens, and Hollweg [Solar Phys. {bold 133}, 127 (1991)], are derived. {copyright} {ital 1998 American Institute of Physics.}

  9. Hydrodynamic theory of diffusion in two-temperature multicomponent plasmas

    SciTech Connect

    Ramshaw, J.D.; Chang, C.H.

    1995-12-31

    Detailed numerical simulations of multicomponent plasmas require tractable expressions for species diffusion fluxes, which must be consistent with the given plasma current density J{sub q} to preserve local charge neutrality. The common situation in which J{sub q} = 0 is referred to as ambipolar diffusion. The use of formal kinetic theory in this context leads to results of formidable complexity. We derive simple tractable approximations for the diffusion fluxes in two-temperature multicomponent plasmas by means of a generalization of the hydrodynamical approach used by Maxwell, Stefan, Furry, and Williams. The resulting diffusion fluxes obey generalized Stefan-Maxwell equations that contain driving forces corresponding to ordinary, forced, pressure, and thermal diffusion. The ordinary diffusion fluxes are driven by gradients in pressure fractions rather than mole fractions. Simplifications due to the small electron mass are systematically exploited and lead to a general expression for the ambipolar electric field in the limit of infinite electrical conductivity. We present a self-consistent effective binary diffusion approximation for the diffusion fluxes. This approximation is well suited to numerical implementation and is currently in use in our LAVA computer code for simulating multicomponent thermal plasmas. Applications to date include a successful simulation of demixing effects in an argon-helium plasma jet, for which selected computational results are presented. Generalizations of the diffusion theory to finite electrical conductivity and nonzero magnetic field are currently in progress.

  10. Kinetic theory of Jeans instability of a dusty plasma.

    PubMed

    Pandey, B P; Lakhina, G S; Krishan, V

    1999-12-01

    A kinetic theory of the Jeans instability of a dusty plasma has been developed in the present work. The effect of grain charge fluctuations due to the attachment of electrons and ions to the grain surface has been considered in the framework of Krook's collisional model. We demonstrate that the grain charge fluctuations alter the growth rate of the gravitational collapse of the dusty plasma. The Jeans length has been derived under limiting cases, and its dependence on the attachment frequency is shown. In the absence of gravity, we see that the damping rate of the dust acoustic mode is proportional to the electron-dust collision frequency. PMID:11970688

  11. Third and fourth quarter progress report on plasma theory and simulation, July 1-December 31, 1986

    SciTech Connect

    Birdsall, C.K.

    1987-01-01

    Our group uses theory and simulation as tools in order to increase the understanding of plasma instabilities, heating, transport, plasma-wall interactions, and large potentials in plasmas. We also work on the improvement of simulation both theoretically and practically.

  12. Theory components of the VASIMR plasma propulsion concept

    NASA Astrophysics Data System (ADS)

    Arefiev, Alexey

    2003-10-01

    The talk presents a selection of theoretical problems all motivated by the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) concept [1]. The focus of the talk is on fundamental physics aspects of VASIMR operation, which are formulated as standalone physics problems. The VASIMR device has a magnetic mirror configuration and consists of three main components: a low energy helicon plasma source; an ion cyclotron-resonance heating (ICRH) section; and a magnetic nozzle, which forms a superalfvenic outgoing plasma flow. The ICRH conditions in VASIMR are fundamentally different from the conventional ICRH, because 1) each ion passes the resonance only once; 2) the ion motion is collisionless; 3) the ion energy gain in a single pass significantly exceeds ion energy in the incoming flow. A self-consistent nonlinear model for the rf-power deposition in the ion cyclotron frequency range into a steady-state plasma flow has been developed [3], which generalizes the linear magnetic beach problem solved by T. Stix. Despite the fact that helicon sources are routinely used for plasma production, the underlying physics mechanism is yet to be established. The talk presents a first-principle theory for light-gas helicon plasma sources with a self-consistent treatment of the particle balance [4], power balance, and rf-field structure [2]. A separation of scales among the particle confinement time, the energy confinement time, and the wave period allows one to consider all three constituents separately prior to combining them into an integrated description. The theory addresses the mystery of the high efficiency of helicon sources at frequencies below the typical helicon frequency. The magnetic nozzle transforms the ion rotational motion into the longitudinal motion and it also ensures plasma detachment from the rocket. The detachment occurs when the energy density of the magnetic field drops below the kinetic energy density of the plasma flow. Then the plasma breaks free

  13. Thought analysis on self-organization theories of MHD plasma

    NASA Astrophysics Data System (ADS)

    Kondoh, Yoshiomi; Sato, Tetsuya

    1992-08-01

    A thought analysis on the self-organization theories of dissipative MHD plasmas is presented to lead to three groups of theories that lead to the same relaxed state of del x B = lambda(B), in order to find an essential physical picture embedded in the self-organization phenomena due to nonlinear and dissipative processes. The self-organized relaxed state due to the dissipation by the Ohm loss is shown to be formulated generally as the state such that yields the minimum dissipation rate of global auto- and/or cross-correlations between two quantities in j, B, and A for their own instantaneous values of the global correlations.

  14. Kinetic theory of electromagnetic ion waves in relativistic plasmas

    SciTech Connect

    Marklund, Mattias; Shukla, Padma K.

    2006-09-15

    A kinetic theory for electromagnetic ion waves in a cold relativistic plasma is derived. The kinetic equation for the broadband electromagnetic ion waves is coupled to the slow density response via an acoustic equation driven by a ponderomotive force-like term linear in the electromagnetic field amplitude. The modulational instability growth rate is derived for an arbitrary spectrum of waves. The monochromatic and random phase cases are studied.

  15. Information Epochs and Human Society.

    ERIC Educational Resources Information Center

    Masuda, Yoneji

    1982-01-01

    Mankind has experienced three societal transformations in the course of history. A new information epoch has served as a precondition for social change. The current information society is post-industrial and will lead to change in the socioeconomic structure and in social values. (KC)

  16. Basic plasma and fusion theory and computer simulations survey

    SciTech Connect

    Kawakami, I.; Nishikawa, K.

    1983-12-01

    The College of Science and Technology at Nihon University and the Institute for Fusion Theory at Hiroshima University discuss the history of the role of theory and simulation in fusion-oriented research. Recent activities include a one-dimensional tokamak transport code at Nagoya University and three-dimensional resistive MHD simulation studies of spheromaks. Other recent activities discussed include the tokamak computer code system TRITON, transport flux in currentless ECH-produced plasma in Heliotron-E, and thermal electron transport in the presence of a steep temperature gradient. The Japan-U.S. Joint Institute for Fusion Theory's present activities are discussed, including subject areas in three-dimensional simulation studies, nonequilibrium statistical physics, anaomalous transport and drift wave turbulence and hot-electron physics.

  17. Relativistic warm plasma theory of nonlinear laser-driven electron plasma waves

    SciTech Connect

    Schroeder, Carl B.; Esarey, Eric

    2010-06-30

    A relativistic, warm fluid model of a nonequilibrium, collisionless plasma is developed and applied to examine nonlinear Langmuir waves excited by relativistically-intense, short-pulse lasers. Closure of the covariant fluid theory is obtained via an asymptotic expansion assuming a non-relativistic plasma temperature. The momentum spread is calculated in the presence of an intense laser field and shown to be intrinsically anisotropic. Coupling between the transverse and longitudinal momentum variances is enabled by the laser field. A generalized dispersion relation is derived for langmuir waves in a thermal plasma in the presence of an intense laser field. Including thermal fluctuations in three velocity-space dimensions, the properties of the nonlinear electron plasma wave, such as the plasma temperature evolution and nonlinear wavelength, are examined, and the maximum amplitude of the nonlinear oscillation is derived. The presence of a relativistically intense laser pulse is shown to strongly influence the maximum plasma wave amplitude for non-relativistic phase velocities owing to the coupling between the longitudinal and transverse momentum variances.

  18. Relativistic warm plasma theory of nonlinear laser-driven electron plasma waves.

    PubMed

    Schroeder, C B; Esarey, E

    2010-05-01

    A relativistic, warm fluid model of a nonequilibrium, collisionless plasma is developed and applied to examine nonlinear Langmuir waves excited by relativistically intense, short-pulse lasers. Closure of the covariant fluid theory is obtained via an asymptotic expansion assuming a nonrelativistic plasma temperature. The momentum spread is calculated in the presence of an intense laser field and shown to be intrinsically anisotropic. Coupling between the transverse and longitudinal momentum variances is enabled by the laser field. A generalized dispersion relation is derived for Langmuir waves in a thermal plasma in the presence of an intense laser field. Including thermal fluctuations in three-velocity-space dimensions, the properties of the nonlinear electron plasma wave, such as the plasma temperature evolution and nonlinear wavelength, are examined and the maximum amplitude of the nonlinear oscillation is derived. The presence of a relativistically intense laser pulse is shown to strongly influence the maximum plasma wave amplitude for nonrelativistic phase velocities owing to the coupling between the longitudinal and transverse momentum variances. PMID:20866340

  19. Laser/plasma theory for microwave modeling experiments. Final report

    SciTech Connect

    Thomson, J J; Divergilio, W F

    1980-01-01

    During the last year, we have carried out theoretical investigations of microwave-plasma interactions in support of both the UCLA program, and the TRW program. The UCLA program concentrated on experimental studies of Stimulated Brillouin Scattering (SBS). We derived a theory which successfully explained the basic features of their experiment. The TRW program was originally conceived of as an investigation of electron heating and thermal transport; however, the subject was later changed to the interaction of SBS and self focusing. The experimental program has not yet started; however, we have developed a theoretical description of the expected interaction.

  20. Effects of the g Factor in Semiclassical Kinetic Plasma Theory

    SciTech Connect

    Brodin, Gert; Marklund, Mattias; Zamanian, Jens; Ericsson, Aasa; Mana, Piero L.

    2008-12-12

    A kinetic theory for spin plasmas is put forward, generalizing those of previous authors. In the model, the ordinary phase space is extended to include the spin degrees of freedom. Together with Maxwell's equations, the system is shown to be energy conserving. Analyzing the linear properties, it is found that new types of wave-particle resonances are possible that depend directly on the anomalous magnetic moment of the electron. As a result, new wave modes, not present in the absence of spin, appear. The implications of our results are discussed.

  1. Diamagnetic boundary layers - A kinetic theory. [for collisionless magnetized plasmas

    NASA Technical Reports Server (NTRS)

    Lemaire, J.; Burlaga, L. F.

    1976-01-01

    A kinetic theory is presented for boundary layers associated with MHD tangential 'discontinuities' in a collisionless magnetized plasma, such as those observed in the solar wind. The theory consists of finding self-consistent solutions of Vlasov's equation and Maxwell's equation for stationary one-dimensional boundary layers separating two Maxwellian plasma states. Layers in which the current is carried by electrons are found to have a thickness of the order of a few electron gyroradii, but the drift speed of the current-carrying electrons is found to exceed the Alfven speed, and accordingly such layers are not stable. Several types of layers in which the current is carried by protons are discussed; in particular, cases are considered in which the magnetic-field intensity, direction, or both, changed across the layer. In every case, the thickness was of the order of a few proton gyroradii, and the field changed smoothly, although the characteristics depended somewhat on the boundary conditions. The drift speed was always less than the Alfven speed, consistent with stability of such structures. These results are consistent with observations of boundary layers in the solar wind near 1 AU.

  2. Some improvements in the theory of plasma relaxation

    SciTech Connect

    Hameiri, Eliezer

    2014-04-15

    Taylor's relaxation theory is extended to plasmas with mass flow by using the cross helicity as a conserved quantity, similar to the magnetic helicity. Indeed, it is shown that the conservation of the cross helicity in magnetohydrodynamics is the result of the conservation of two magnetic-like helicities in two-fluid plasmas. In addition, the usually ignored toroidal flux is also held to be conserved. We also view plasma relaxation as attaining a maximum entropy state rather than Taylor's minimum energy state, but prove that maximizing the entropy subject to a given amount of energy is equivalent to minimizing the energy subject to a given amount of entropy. The resulting relaxed state is similar to the one discussed by Finn and Antonsen [Phys. Fluids 26, 3540 (1983)], and involves flow parallel to the magnetic field and constant temperature, but non-constant pressure. We show how to construct an asymptotic solution to the relaxed state based on the smallness of the Alfven Mach number of the flow.

  3. Theory of interparticle correlations in dense, high-temperature plasmas. V - Electric and thermal conductivities

    NASA Technical Reports Server (NTRS)

    Ichimaru, S.; Tanaka, S.

    1985-01-01

    Ichimaru et al. (1985) have developed a general theory in which the interparticle correlations in dense, high-temperature multicomponent plasmas were formulated systematically over a wide range of plasma parameters. The present paper is concerned with an extension of this theory, taking into account the problems of the electronic transport in such high-density plasmas. It is shown that the resulting theory is capable of describing the transport coefficients accurately over a wide range of the density and temperature parameters. Attention is given to electric and thermal conductivities, generalized Coulomb logarithms, a comparison of the considered theory with other theories, and a comparison of the theory with experimental results.

  4. Plasma theory and simulation. Quarterly progress report I, II, January 1-June 30, 1984

    SciTech Connect

    Birdsall, C.K.

    1984-01-01

    Our group uses theory and simulation as tools in order to increase the understanding of instabilities, heating, transport, and other phenomena in plasmas. We also work on the improvement of simulation both theoretically and practically. Research in plasma theory and simulation has centered on the following: (1) electron Bernstein wave investigations; (2) simulation of plasma-sheath region, including ion reflection; (3) single ended plasma device, general behavior dc or ac; (4) single ended plasma device, unstable states; (5) corrections to time-independent Q-machine equilibria; (6) multifluid derivation of the Alfven ion-cyclotron linear dispersion relation; and (7) potential barrier between hot and cool plasmas.

  5. Perturbation theory of a classical one-component plasma

    SciTech Connect

    Lee, J.W.; Ree, F.H.

    1988-12-01

    We have extended a recent perturbation theory (J. Chem. Phys. 82, 414 (1985); 84, 4547 (1986)) for nonionic systems to the one-component plasma (OCP). Characteristic features of the theory are its ability to handle both fluids and solids and the use of a reference potential whose repulsive range shrinks with density. Based on the computed thermodynamic data, we have developed a simple alternative (optimized hard-sphere) model, whose Helmholtz free energy is a sum of the Helmholtz free energy of the hard-sphere reference system and the Madelung energy of a fcc lattice. Comparison with available Monte Carlo and other theoretical results shows that the optimized hard-sphere model gives reliable solid (fcc) and fluid properties. The theory predicts that the fcc solid will melt at the Coulomb coupling parameter GAMMAsub m/ = 208 versus Helfer et al.'s (J. Stat. Phys. 37, 577 (1984)) Monte Carlo value of 196. This difference is due to a small difference (0.1%) in the computed excess free energy. The computed internal energy can be accurately fitted by an analytic form. Its two leading terms (for the fluid) are -0.899488GAMMA1.272 97GAMMAsup 1/4/, in close agreement with Slattery et al.'s (Phys. Rev. A 21, 2087 (1980); 26, 2255 (1982)) empirical fit to their Monte Carlo data. We conclude that the hard-sphere perturbation theory is applicable to a long-range repulsive system, such as the OCP, so long as the hard-sphere diameter is judiciously chosen by using a density-dependent reference potential.

  6. Kinetic theory of weak turbulence in magnetized plasmas: Perpendicular propagation

    SciTech Connect

    Yoon, Peter H.

    2015-08-15

    The present paper formulates a weak turbulence theory in which electromagnetic perturbations are assumed to propagate in directions perpendicular to the ambient magnetic field. By assuming that all wave vectors lie in one direction transverse to the ambient magnetic field, the linear solution and second-order nonlinear solutions to the equation for the perturbed distribution function are obtained. Nonlinear perturbed current from the second-order nonlinearity is derived in general form, but the limiting situation of cold plasma temperature is taken in order to derive an explicit nonlinear wave kinetic equation that describes three-wave decay/coalescence interactions among X and Z modes. A potential application of the present formalism is also discussed.

  7. A survey of problems in divertor and edge plasma theory

    SciTech Connect

    Boozer, A. ); Braams, B.; Weitzner, H. . Courant Inst. of Mathematical Sciences); Cohen, R. ); Hazeltine, R. . Inst. for Fusion Studies); Hinton, F. ); Houlberg, W. (Oak

    1992-12-22

    Theoretical physics problems related to divertor design are presented, organized by the region in which they occur. Some of the open questions in edge physics are presented from a theoretician's point of view. After a cursory sketch of the fluid models of the edge plasma and their numerical realization, the following topics are taken up: time-dependent problems, non-axisymmetric effects, anomalous transport in the scrape-off layer, edge kinetic theory, sheath effects and boundary conditions in divertors, electric field effects, atomic and molecular data issues, impurity transport in the divertor region, poloidally localized power dissipation (MARFEs and dense gas targets), helium ash removal, and neutral transport. The report ends with a summary of selected problems of particular significance and a brief bibliography of survey articles and related conference proceedings.

  8. A survey of problems in divertor and edge plasma theory

    SciTech Connect

    Boozer, A.; Braams, B.; Weitzner, H.; Cohen, R.; Hazeltine, R.; Hinton, F.; Houlberg, W.; Oktay, E.; Sadowski, W.; Post, D.; Sigmar, D.; Wootton, A.

    1992-12-22

    Theoretical physics problems related to divertor design are presented, organized by the region in which they occur. Some of the open questions in edge physics are presented from a theoretician`s point of view. After a cursory sketch of the fluid models of the edge plasma and their numerical realization, the following topics are taken up: time-dependent problems, non-axisymmetric effects, anomalous transport in the scrape-off layer, edge kinetic theory, sheath effects and boundary conditions in divertors, electric field effects, atomic and molecular data issues, impurity transport in the divertor region, poloidally localized power dissipation (MARFEs and dense gas targets), helium ash removal, and neutral transport. The report ends with a summary of selected problems of particular significance and a brief bibliography of survey articles and related conference proceedings.

  9. Wakes in complex plasmas: A self-consistent kinetic theory

    NASA Astrophysics Data System (ADS)

    Kompaneets, Roman; Morfill, Gregor E.; Ivlev, Alexei V.

    2016-06-01

    In ground-based experiments with complex (dusty) plasmas, charged microparticles are levitated against gravity by an electric field, which also drives ion flow in the parent gas. Existing analytical approaches to describe the electrostatic interaction between microparticles in such conditions generally ignore the field and ion-neutral collisions, assuming free ion flow with a certain approximation for the ion velocity distribution function (usually a shifted Maxwellian). We provide a comprehensive analysis of our previously proposed self-consistent kinetic theory including the field, ion-neutral collisions, and the corresponding ion velocity distribution. We focus on various limiting cases and demonstrate how the interplay of these factors results in different forms of the shielding potential.

  10. Wakes in complex plasmas: A self-consistent kinetic theory.

    PubMed

    Kompaneets, Roman; Morfill, Gregor E; Ivlev, Alexei V

    2016-06-01

    In ground-based experiments with complex (dusty) plasmas, charged microparticles are levitated against gravity by an electric field, which also drives ion flow in the parent gas. Existing analytical approaches to describe the electrostatic interaction between microparticles in such conditions generally ignore the field and ion-neutral collisions, assuming free ion flow with a certain approximation for the ion velocity distribution function (usually a shifted Maxwellian). We provide a comprehensive analysis of our previously proposed self-consistent kinetic theory including the field, ion-neutral collisions, and the corresponding ion velocity distribution. We focus on various limiting cases and demonstrate how the interplay of these factors results in different forms of the shielding potential. PMID:27415371

  11. Hyper-resistivity Theory in a Cylindrical Plasma

    SciTech Connect

    Berk, H L; Fowler, T K; LoDestro, L L; Pearlstein, L D

    2001-02-27

    A model is presented for determining the hyper-resistivity coefficient that arises due to the presence of magnetic structures that appear in plasma configurations such as the reversed field pinch and spheromak. Emphasis is placed on modeling cases where magnetic islands pass from non-overlap to overlap regimes. Earlier works have shown that a diffusion-based model can give realistic transport scalings when magnetic islands are isolated, and this formalism is extended to apply to the hyper-resistivity problem. In this case electrons may either be in long or short mean-free-path regimes and intuitively-based arguments are presented of how to extend previous theories to incorporate this feature in the presence of magnetic structures that pass from laminar to moderately chaotic regimes.

  12. Toward the Theory of Turbulence in Magnetized Plasmas

    SciTech Connect

    Boldyrev, Stanislav

    2013-07-26

    The goal of the project was to develop a theory of turbulence in magnetized plasmas at large scales, that is, scales larger than the characteristic plasma microscales (ion gyroscale, ion inertial scale, etc.). Collisions of counter-propagating Alfven packets govern the turbulent cascade of energy toward small scales. It has been established that such an energy cascade is intrinsically anisotropic, in that it predominantly supplies energy to the modes with mostly field-perpendicular wave numbers. The resulting energy spectrum of MHD turbulence, and the structure of the fluctuations were studied both analytically and numerically. A new parallel numerical code was developed for simulating reduced MHD equations driven by an external force. The numerical setting was proposed, where the spectral properties of the force could be varied in order to simulate either strong or weak turbulent regimes. It has been found both analytically and numerically that weak MHD turbulence spontaneously generates a “condensate”, that is, concentration of magnetic and kinetic energy at small k{sub {parallel}}. A related topic that was addressed in the project is turbulent dynamo action, that is, generation of magnetic field in a turbulent flow. We were specifically concentrated on the generation of large-scale magnetic field compared to the scales of the turbulent velocity field. We investigate magnetic field amplification in a turbulent velocity field with nonzero helicity, in the framework of the kinematic Kazantsev-Kraichnan model.

  13. Plasma stability theory including the resistive wall effects

    NASA Astrophysics Data System (ADS)

    Pustovitov, V. D.

    2015-12-01

    > Plasma stabilization due to a nearby conducting wall can provide access to better performance in some scenarios in tokamaks. This was proved by experiments with an essential gain in and demonstrated as a long-lasting effect at sufficiently fast plasma rotation in the DIII-D tokamak (see, for example, Strait et al., Nucl. Fusion, vol. 43, 2003, pp. 430-440). The rotational stabilization is the central topic of this review, though eventually the mode rotation gains significance. The analysis is based on the first-principle equations describing the energy balance with dissipation in the resistive wall. The method emphasizes derivation of the dispersion relations for the modes which are faster than the conventional resistive wall modes, but slower than the ideal magnetohydrodynamics modes. Both the standard thin wall and ideal-wall approximations are not valid in this range. Here, these are replaced by an approach incorporating the skin effect in the wall. This new element in the stability theory makes the energy sink a nonlinear function of the complex growth rate. An important consequence is that a mode rotating above a critical level can provide a damping effect sufficient for instability suppression. Estimates are given and applications are discussed.

  14. Experiments and Theory of Ablation Plasma Ion Implantation

    NASA Astrophysics Data System (ADS)

    Gilgenbach, R. M.; Qi, B.; Lau, Y. Y.; Johnston, M. D.; Doll, G. L.; Lazarides, A.

    2000-10-01

    Research is underway to accelerate laser ablation plume ions for implantation into substrates. Ablation plasma ion implantation (APII) biases the deposition substrate to a large negative voltage. APII has the advantages of direct acceleration and implantation of ions from metals or any other solid targets. This process is environmentally friendly because it avoids the use of toxic gaseous precursors. Initial experiments are directed towards the implantation of iron ions into silicon substrates at negative voltages from 2-10 kV. A KrF laser ablates iron targets at pulse energies up to 600 mJ and typical repetition rates of 10 Hz. Parameters which can be varied include laser fluence, relative timing of laser and high voltage pulse, and target-to-substrate distance. Spectroscopic diagnostics yield Fe plasma plume electron temperatures up to about 10 eV. Analysis of films will compare surface morphology, hardness and adhesion between deposited Vs accelerated-implanted plumes. A simple one dimensional theory is developed [1] to calculate the implanted ion current, extracted from the ion matrix sheath, as a function of time for various substrate-plume separations. This model accurately recovers Lieberman's classic results when the plume front is initially in contact with the substrate. [1] B. Qi, Y. Y. Lau, and R. M. Gilgenbach, Appl. Phys. Lett. (to be published). * This research is supported by the National Science Foundation.

  15. Plasma theory and simulation: Third and fourth quarterly progress report, July 1, 1986-December 31, 1986

    SciTech Connect

    Birdsall, C.K.

    1986-01-01

    Our group uses theory and simulation as tools in order to increase the understanding of plasma instabilities, heating, transport, plasma-wall interactions, and large potentials in plasmas. We also work on the improvement of simulation both theoretically and practically. Two separate papers are included in this report.

  16. Kinetic theory of magnetized dusty plasmas with dust particles charged by collisional processes and by photoionization

    SciTech Connect

    Galvao, R. A.; Ziebell, L. F.

    2012-09-15

    In this work, we detail the derivation of a plasma kinetic theory leading to the components of the dielectric tensor for a magnetized dusty plasma with variable charge on the dust particles, considering that the dust component of the plasma contains spherical dust particles with different sizes, which are charged both by inelastic collisions of electrons and ions and by photoionization.

  17. Effect of Electron Energy Distribution on the Hysteresis of Plasma Discharge: Theory, Experiment, and Modeling

    PubMed Central

    Lee, Hyo-Chang; Chung, Chin-Wook

    2015-01-01

    Hysteresis, which is the history dependence of physical systems, is one of the most important topics in physics. Interestingly, bi-stability of plasma with a huge hysteresis loop has been observed in inductive plasma discharges. Despite long plasma research, how this plasma hysteresis occurs remains an unresolved question in plasma physics. Here, we report theory, experiment, and modeling of the hysteresis. It was found experimentally and theoretically that evolution of the electron energy distribution (EED) makes a strong plasma hysteresis. In Ramsauer and non-Ramsauer gas experiments, it was revealed that the plasma hysteresis is observed only at high pressure Ramsauer gas where the EED deviates considerably from a Maxwellian shape. This hysteresis was presented in the plasma balance model where the EED is considered. Because electrons in plasmas are usually not in a thermal equilibrium, this EED-effect can be regarded as a universal phenomenon in plasma physics. PMID:26482650

  18. Effect of Electron Energy Distribution on the Hysteresis of Plasma Discharge: Theory, Experiment, and Modeling

    NASA Astrophysics Data System (ADS)

    Lee, Hyo-Chang; Chung, Chin-Wook

    2015-10-01

    Hysteresis, which is the history dependence of physical systems, is one of the most important topics in physics. Interestingly, bi-stability of plasma with a huge hysteresis loop has been observed in inductive plasma discharges. Despite long plasma research, how this plasma hysteresis occurs remains an unresolved question in plasma physics. Here, we report theory, experiment, and modeling of the hysteresis. It was found experimentally and theoretically that evolution of the electron energy distribution (EED) makes a strong plasma hysteresis. In Ramsauer and non-Ramsauer gas experiments, it was revealed that the plasma hysteresis is observed only at high pressure Ramsauer gas where the EED deviates considerably from a Maxwellian shape. This hysteresis was presented in the plasma balance model where the EED is considered. Because electrons in plasmas are usually not in a thermal equilibrium, this EED-effect can be regarded as a universal phenomenon in plasma physics.

  19. Spherical crystals in dusty plasmas - Simulation and theory

    NASA Astrophysics Data System (ADS)

    Bonitz, M.; Henning, C.; Golubnychiy, V.; Baumgartner, H.; Ludwig, P.; Arp, O.; Block, D.; Piel, A.; Melzer, A.; Kraeft, W. D.

    2006-10-01

    Coulomb crystals in spherically symmetric traps have been found in trapped cold ions and, recently, in dusty plasmas at room temperature [1] allowing for precision measurements, including individual particle positions and trajectories. Thus, for the first time, strong correlation phenomena can be studied directly on the microscopic level which allows for detailed comparisons with theoretical results and computer simulations. We present molecular dynamics and Monte Carlo simulations of Coulomb crystals in the range from 10 to 10,000 particles which agree very well with the measurements [3]. The results include the ground state shell configurations and symmetry properties [2,3], the crystal stability and melting behavior. Finally, a thermodynamic theory is developed and compared to simpler models, such as shell models [4]. [1] O. Arp, D. Block, A. Piel, and A. Melzer, Phys. Rev. Lett. 93, 165004 (2004). [2] P. Ludwig, S. Kosse, and M. Bonitz, Phys. Rev. E 71, 046403 (2005). [3] M. Bonitz, D. Block, O. Arp, V. Golubnychiy, H. Baumgartner, P. Ludwig, A. Piel, and A. Filinov, Phys. Rev. Lett. 96, 075001 (2006). [4] C. Henning et al., submitted for publication.

  20. Plasma theory and simulation: Quarterly progress report Nos. 3 and 4, July 1, 1985-December 31, 1985

    SciTech Connect

    Birdsall, C.K.

    1985-01-01

    Our group uses theory and simulation as tools in order to increase the understanding of plasma instabilities, heating, transport, plasma-wall interaction an large potentials in plasmas. We also work on the improvement of simulation both theoretically and practically.

  1. Theory of electromagnetic fluctuations for magnetized multi-species plasmas

    SciTech Connect

    Navarro, Roberto E. Muñoz, Víctor; Araneda, Jaime; Moya, Pablo S.; Viñas, Adolfo F.; Valdivia, Juan A.

    2014-09-15

    Analysis of electromagnetic fluctuations in plasma provides relevant information about the plasma state and its macroscopic properties. In particular, the solar wind persistently sustains a small but detectable level of magnetic fluctuation power even near thermal equilibrium. These fluctuations may be related to spontaneous electromagnetic fluctuations arising from the discreteness of charged particles. Here, we derive general expressions for the plasma fluctuations in a multi-species plasma following arbitrary distribution functions. This formalism, which generalizes and includes previous works on the subject, is then applied to the generation of electromagnetic fluctuations propagating along a background magnetic field in a plasma of two proton populations described by drifting bi-Maxwellians.

  2. On the theory of Langmuir waves in a quantum plasma

    SciTech Connect

    Kuzelev, M. V.

    2010-04-15

    Nonlinear quantum-mechanical equations are derived for Langmuir waves in an isotropic electron collisionless plasma. A general analysis of dispersion relations is carried out for complex spectra of Langmuir waves and van Kampen waves in a quantum plasma with an arbitrary electron momentum distribution. Quantum nonlinear collisionless Landau damping in Maxwellian and degenerate plasmas is studied. It is shown that collisionless damping of Langmuir waves (including zero sound) occurs in collisionless plasmas due to quantum correction in the Cherenkov absorption condition, which is a purely quantum effect. Solutions to the quantum dispersion equation are obtained for a degenerate plasma.

  3. Comparison of Theory with Rotation Measurements in JET ICRH Plasmas

    SciTech Connect

    R.V. Budny; C.S. Chang; C. Giroud; R.J. Goldston; D. McCune; J. Ongena; F.W. Perkins; R.B. White; K.-D. Zastrow; and contributors to the EFDA-JET work programme

    2001-06-27

    Plasma rotation appears to improve plasma performance by increasing the E x B flow shearing rate, thus decreasing radial correlations in the microturbulence. Also, plasma rotation can increase the stability to resistive MHD modes. In the Joint European Torus (JET), toroidal rotation rates omega (subscript ''tor'') with high Mach numbers are generally measured in NBI-heated plasmas (since the neutral beams aim in the co-plasma current direction). They are considerably lower with only ICRH (and Ohmic) heating, but still surprisingly large considering that ICRH appears to inject relatively small amounts of angular momentum. Either the applied torques are larger than naively expected, or the anomalous transport of angular momentum is smaller than expected. Since ICRH is one of the main candidates for heating next-step tokamaks, and for creating burning plasmas in future tokamak reactors, this paper attempts to understand ICRH-induced plasma rotation.

  4. Study on longitudinal dispersion relation in one-dimensional relativistic plasma: Linear theory and Vlasov simulation

    SciTech Connect

    Zhang, H.; Wu, S. Z.; Zhou, C. T.; He, X. T.; Key Laboratory of HEDP of the Ministry of Education, CAPT, Peking University, Beijing 100871 ; Zhu, S. P.

    2013-09-15

    The dispersion relation of one-dimensional longitudinal plasma waves in relativistic homogeneous plasmas is investigated with both linear theory and Vlasov simulation in this paper. From the Vlasov-Poisson equations, the linear dispersion relation is derived for the proper one-dimensional Jüttner distribution. Numerically obtained linear dispersion relation as well as an approximate formula for plasma wave frequency in the long wavelength limit is given. The dispersion of longitudinal wave is also simulated with a relativistic Vlasov code. The real and imaginary parts of dispersion relation are well studied by varying wave number and plasma temperature. Simulation results are in agreement with established linear theory.

  5. Extended neoclassical transport theory for incompressible tokamak plasmas

    SciTech Connect

    Shaing, K.C.

    1997-09-01

    Conventional neoclassical transport theory is extended to include the effects of orbit squeezing, and to allow the effective poloidal Mach number U{sub pM}=[(V{sub {parallel}}/v{sub t})+(V{sub E}B/v{sub t}B{sub p})] of the order of unity for incompressible tokamak plasmas. Here, V{sub {parallel}} is the parallel mass flow, v{sub t} is the ion thermal speed, V{sub E} is the poloidal {bold E{times}B} drift speed, B is the magnetic field strength, and B{sub p} is the poloidal magnetic field strength. It is found that ion thermal conductivity is reduced from its conventional neoclassical value in both banana and plateau regimes if U{sub pM}{gt}1 and S{gt}1. Here, S=[1+cI{sup 2}{Phi}{sup {prime}{prime}}/({Omega}{sub 0}B{sub 0})] is the orbit squeezing factor with c the speed of light, I=RB{sub t}, R the major radius, {Phi} the electrostatic potential, B{sub 0} the magnetic field strength on the axis, {Omega}{sub 0}=eB{sub 0}/Mc, M the ion mass, e the ion charge, {Phi}{sup {prime}{prime}}=d{sup 2}{Phi}/d{psi}{sup 2}, and {psi} the poloidal flux function. However, there is an irreducible minimum for the ion thermal conductivity in the banana-plateau regime set by the conventional Pfirsch{endash}Schl{umlt u}ter transport. {copyright} {ital 1997 American Institute of Physics.}

  6. Linear Covariance Analysis and Epoch State Estimators

    NASA Technical Reports Server (NTRS)

    Markley, F. Landis; Carpenter, J. Russell

    2012-01-01

    This paper extends in two directions the results of prior work on generalized linear covariance analysis of both batch least-squares and sequential estimators. The first is an improved treatment of process noise in the batch, or epoch state, estimator with an epoch time that may be later than some or all of the measurements in the batch. The second is to account for process noise in specifying the gains in the epoch state estimator. We establish the conditions under which the latter estimator is equivalent to the Kalman filter.

  7. Linear Covariance Analysis and Epoch State Estimators

    NASA Technical Reports Server (NTRS)

    Markley, F. Landis; Carpenter, J. Russell

    2014-01-01

    This paper extends in two directions the results of prior work on generalized linear covariance analysis of both batch least-squares and sequential estimators. The first is an improved treatment of process noise in the batch, or epoch state, estimator with an epoch time that may be later than some or all of the measurements in the batch. The second is to account for process noise in specifying the gains in the epoch state estimator. We establish the conditions under which the latter estimator is equivalent to the Kalman filter.

  8. Theory of semicollisional drift-interchange modes in cylindrical plasmas

    SciTech Connect

    Hahm, T.S.; Chen, L.

    1985-01-01

    Resistive interchange instabilities in cylindrical plasmas are studied, including the effects of electron diamagnetic drift, perpendicular resistivity, and plasma compression. The analyses are pertinent to the semicollisional regime where the effective ion gyro-radius is larger than the resistive layer width. Both analytical and numerical results show that the modes can be completely stabilized by the perpendicular plasma transport. Ion sound effects, meanwhile, are found to be negligible in the semicollisional regime.

  9. A theory of MHD instability of an inhomogeneous plasma jet

    NASA Astrophysics Data System (ADS)

    Leonovich, Anatoly S.

    2011-06-01

    A problem of the stability of an inhomogeneous axisymmetric plasma jet in a parallel magnetic field is solved. The jet boundary becomes, under certain conditions, unstable relative to magnetosonic oscillations (Kelvin-Helmholtz instability) in the presence of a shear flow at the jet boundary. Because of its internal inhomogeneity the plasma jet has resonance surfaces, where conversion takes place between various modes of plasma magnetohydrodynamic (MHD) oscillations. Propagating in inhomogeneous plasma, fast magnetosonic waves drive the Alfven and slow magnetosonic (SMS) oscillations, tightly localized across the magnetic shells, on the resonance surfaces. MHD oscillation energy is absorbed in the neighbourhood of these resonance surfaces. The resonance surfaces disappear for the eigenmodes of SMS waves propagating in the jet waveguide. The stability of the plasma MHD flow is determined by competition between the mechanisms of shear flow instability on the boundary and wave energy dissipation because of resonant MHD-mode coupling. The problem is solved analytically, in the Wentzel, Kramers, Brillouin (WKB) approximation, for the plasma jet with a boundary in the form of a tangential discontinuity over the radial coordinate. The Kelvin-Helmholtz instability develops if plasma flow velocity in the jet exceeds the maximum Alfven speed at the boundary. The stability of the plasma jet with a smooth boundary layer is investigated numerically for the basic modes of MHD oscillations, to which the WKB approximation is inapplicable. A new 'unstable mode of MHD oscillations has been discovered which, unlike the Kelvin-Helmholtz instability, exists for any, however weak, plasma flow velocities.

  10. On Kraichnan's 'direct interaction approximation' and Kolmogoroff's theory in two-dimensional plasma turbulence

    SciTech Connect

    Kulsrud, R.M.; Sudan, R.N.

    1981-04-01

    The nonlinear damping in a strongly turbulent convecting plasma computed by Kraichnan's modified direct inteaction approximation and the power spectrum are rederived in a physically transparent form using Kolmogoroff's theory of turbulence.

  11. Hollow cathodes as electron emitting plasma contactors Theory and computer modeling

    NASA Technical Reports Server (NTRS)

    Davis, V. A.; Katz, I.; Mandell, M. J.; Parks, D. E.

    1987-01-01

    Several researchers have suggested using hollow cathodes as plasma contactors for electrodynamic tethers, particularly to prevent the Shuttle Orbiter from charging to large negative potentials. Previous studies have shown that fluid models with anomalous scattering can describe the electron transport in hollow cathode generated plasmas. An improved theory of the hollow cathode plasmas is developed and computational results using the theory are compared with laboratory experiments. Numerical predictions for a hollow cathode plasma source of the type considered for use on the Shuttle are presented, as are three-dimensional NASCAP/LEO calculations of the emitted ion trajectories and the resulting potentials in the vicinity of the Orbiter. The computer calculations show that the hollow cathode plasma source makes vastly superior contact with the ionospheric plasma compared with either an electron gun or passive ion collection by the Orbiter.

  12. Orbital-motion-limited theory of dust charging and plasma response

    SciTech Connect

    Tang, Xian-Zhu Luca Delzanno, Gian

    2014-12-15

    The foundational theory for dusty plasmas is the dust charging theory that provides the dust potential and charge arising from the dust interaction with a plasma. The most widely used dust charging theory for negatively charged dust particles is the so-called orbital motion limited (OML) theory, which predicts the dust potential and heat collection accurately for a variety of applications, but was previously found to be incapable of evaluating the dust charge and plasma response in any situation. Here, we report a revised OML formulation that is able to predict the plasma response and hence the dust charge. Numerical solutions of the new OML model show that the widely used Whipple approximation of dust charge-potential relationship agrees with OML theory in the limit of small dust radius compared with plasma Debye length, but incurs large (order-unity) deviation from the OML prediction when the dust size becomes comparable with or larger than plasma Debye length. This latter case is expected for the important application of dust particles in a tokamak plasma.

  13. Plasma theory and simulation research. Final technical report, January 1, 1986--October 31, 1989

    SciTech Connect

    Birdsall, C.K.

    1989-12-31

    Our research group uses both theory and simulation as tools in order to increase the understanding of instabilities, heating, diffusion, transport and other phenomena in plasmas. We also work on the improvement of simulation, both theoretically and practically. Our focus has been more and more on the plasma edge (the ``sheath``), interactions with boundaries, leading to simulations of whole devices (someday a numerical tokamak).

  14. Energy branching in the Io plasma torus - The failure of neutral cloud theory

    NASA Technical Reports Server (NTRS)

    Shemansky, D. E.

    1988-01-01

    Model calculations are used to explore the energy source characteristics of the energy branching of the hot Io plasma torus. It is assumed that the energy is derived from the kinetic energy acquired by ions created in the rotating planetary magnetic field, and that Coulomb collisions with the electron gas control the flow of energy to the ionizing and radiative processes. The results show that neutral cloud theory is qualitatively inadequate. It is shown that neutral cloud theory can only support a dominantly singly ionized system (at the measured electron densities in the plasma torus) and that it fails to predict observed plasma properties relative to variations in number density.

  15. A theory of the plasma torch for waste-treatment

    SciTech Connect

    Uhm, H.S.; Hong, S.H.

    1997-12-31

    Arc-plasma technology has broad applications to waste treatment processing including the safe disposal of hazardous and low-level radioactive wastes. The plasma torch could be useful to the development of an efficient, compact, lightweight, clean burning incinerator for industrial and municipal waste disposal in an environmentally beneficial way. The authors therefore develop a simple theoretical model describing physics of the plasma torch plume in connection with its applications to the arc-plasma waste-treatment system. The theoretical analysis is carried out by making use of Bernoulli`s pressure-balance equation, which provides a stable equilibrium solution of the gas density in the plume ejected from the torch into a high-pressure reactor chamber with 4{var_epsilon} < 1. The pressure depression parameter {var_epsilon} is proportional to the gas temperature and inversely proportional to the square of the chamber pressure. In a low-pressure chamber, characterized by 4{var_epsilon} > 1, there is no stable equilibrium solution satisfying Bernoulli`s equation. Therefore, it is expected that the observable plasma data may change abruptly as the chamber pressure crosses the borderline defined by 4{var_epsilon} = 1. Indeed most of the plasma data measured in an experiment change abruptly at the pressure borderline of 4{var_epsilon} = 1.

  16. Spin Kinetic Models of Plasmas - Semiclassical and Quantum Mechanical Theory

    SciTech Connect

    Brodin, Gert; Marklund, Mattias; Zamanian, Jens

    2009-11-10

    In this work a recently published semiclassical spin kinetic model, generalizing those of previous authors are discussed. Some previously described properties are reviewed, and a new example illustrating the theory is presented. The generalization to a fully quantum mechanical description is discussed, and the main features of such a theory is outlined. Finally, the main conclusions are presented.

  17. Validating Laser-Induced Birefringence Theory with Plasma Interferometry

    SciTech Connect

    Chen, Cecilia

    2015-09-02

    Intense laser beams crossing paths in plasma is theorized to induce birefringence in the medium, resulting from density and refractive index modulations that affect the polarization of incoming light. The goal of the associated experiment, conducted on Janus at Lawrence Livermore’s Jupiter Laser Facility, was to create a tunable laser-plasma waveplate to verify the relationship between dephasing angle and beam intensity, plasma density, plasma temperature, and interaction length. Interferometry analysis of the plasma channel was performed to obtain a density map and to constrain temperature measured from Thomson scattering. Various analysis techniques, including Fast Fourier transform (FFT) and two variations of fringe-counting, were tried because interferograms captured in this experiment contained unusual features such as fringe discontinuity at channel edges, saddle points, and islands. The chosen method is flexible, semi-automated, and uses a fringe tracking algorithm on a reduced image of pre-traced synthetic fringes. Ultimately, a maximum dephasing angle of 49.6° was achieved using a 1200 μm interaction length, and the experimental results appear to agree with predictions.

  18. Quasilinear theory of general electromagnetic fluctuations in unmagnetized plasmas

    SciTech Connect

    Schlickeiser, R. E-mail: yoonp@umd.edu; Yoon, P. H. E-mail: yoonp@umd.edu

    2014-09-15

    The general quasilinear Fokker-Planck kinetic equation for the plasma particle distribution functions in unmagnetized plasmas is derived, making no restrictions on the frequency of the electromagnetic fluctuations. The derived kinetic particle equation complements our earlier study of the general fluctuation's kinetic equation. For collective plasma eigenmodes and gyrotropic particle distribution functions, the two coupled kinetic equations describe the self-consistent dynamical evolution of the plasma. The limit of weakly damped collective modes correctly reproduces the well-known textbook kinetic particle equation with longitudinal Langmuir and ion-acoustic fluctuations, demonstrating, in particular, the resonant nature of parallel momentum diffusion of particles. In the limit of aperiodic modes, the Fokker-Planck equation contains the nonresonant diffusion of particles in momentum and the parallel and perpendicular momentum drag coefficients. As an application these drag and diffusion coefficients are calculated for extragalactic cosmic ray particles propagating in the unmagnetized intergalactic medium. Whereas for all cosmic rays, the perpendicular momentum diffusion in intergalactic aperiodic fluctuations is negligibly small; cosmic ray protons with energies below 10{sup 5 }GeV are affected by the plasma drag.

  19. Beyond the Plasma Analogy: Collective Field Theory for Quantum Hall States

    NASA Astrophysics Data System (ADS)

    Can, Tankut; Laskin, Michael; Wiegmann, Paul

    We develop a quantum field theory of collective coordinates describing fractional quantum Hall (FQH) states. We show that the familiar properties of Laughlin states are captured by a Gaussian free field theory with a background charge. Gradient corrections to the Gaussian theory arise from ultraviolet regularization, and go beyond the celebrated plasma analogy. They give rise to a gravitational anomaly described by the Liouville theory of 2D quantum gravity. The field theory simplifies the computation of correlation functions in FQH states and makes manifest the effect of quantum anomalies. This talk is based on the preprint arXiv:1412.8716.

  20. Extending plasma transport theory to strong coupling through the concept of an effective interaction potential

    SciTech Connect

    Baalrud, Scott D.; Daligault, Jérôme

    2014-05-15

    A method for extending traditional plasma transport theories into the strong coupling regime is presented. Like traditional theories, this is based on a binary scattering approximation, but where physics associated with many body correlations is included through the use of an effective interaction potential. The latter is simply related to the pair-distribution function. Modeling many body effects in this manner can extend traditional plasma theory to orders of magnitude stronger coupling. Theoretical predictions are tested against molecular dynamics simulations for electron-ion temperature relaxation as well as diffusion in one component systems. Emphasis is placed on the connection with traditional plasma theory, where it is stressed that the effective potential concept has precedence through the manner in which screening is imposed. The extension to strong coupling requires accounting for correlations in addition to screening. Limitations of this approach in the presence of strong caging are also discussed.

  1. Nonlinear gyrokinetic theory for finite-BETA plasmas

    SciTech Connect

    Hahm, T.S.; Lee, W.W.; Brizard, A.

    1988-02-01

    A self-consistent and energy-conserving set of nonlinear gyrokinetic equations, consisting of the averaged Vlasov and Maxwell's equations for finite-..beta.. plasmas, is derived. The method utilized in the present investigation is based on the Hamiltonian formalism and Lie transformation. The resulting formation is valid for arbitrary values of k/perpendicular//rho//sub i/ and, therefore, is most suitable for studying linear and nonlinear evolution of microinstabilities in tokamak plasmas as well as other areas of plasma physics where the finite Larmor radius effects are important. Because the underlying Hamiltonian structure is preserved in the present formalism, these equations are directly applicable to numerical studies based on the existing gyrokinetic particle simulation techniques. 31 refs.

  2. Electromagnetic fluctuations in magnetized plasmas. I. The rigorous relativistic kinetic theory

    SciTech Connect

    Schlickeiser, R. E-mail: yoonp@umd.edu; Yoon, P. H. E-mail: yoonp@umd.edu

    2015-07-15

    Using the system of the Klimontovich and Maxwell equations, the general linear fluctuation theory for magnetized plasmas is developed. General expressions for the electromagnetic fluctuation spectra (electric and magnetic fields) from uncorrelated plasma particles in plasmas with a uniform magnetic field are derived, which are covariantly correct within the theory of special relativity. The general fluctuation spectra hold for plasmas of arbitrary composition, arbitrary momentum dependences of the plasma particle distribution functions, and arbitrary orientations of the wave vector with respect to the uniform magnetic field. Moreover, no restrictions on the values of the real and the imaginary parts of the frequency are made. The derived fluctuation spectra apply to both non-collective fluctuations and collective plasma eigenmodes in magnetized plasmas. In the latter case, kinetic equations for the components of fluctuating electric and magnetic fields in magnetized plasmas are derived that include the effect of spontaneous emission and absorption. In the limiting case of an unmagnetized plasmas, the general fluctuation spectra correctly reduce to the unmagnetized fluctuation spectra derived before.

  3. Theory and application of maximum magnetic energy in toroidal plasmas

    SciTech Connect

    Chu, T.K.

    1992-02-01

    The magnetic energy in an inductively driven steady-state toroidal plasma is a maximum for a given rate of dissipation of energy (Poynting flux). A purely resistive steady state of the piecewise force-free configuration, however, cannot exist, as the periodic removal of the excess poloidal flux and pressure, due to heating, ruptures the static equilibrium of the partitioning rational surfaces intermittently. The rupture necessitates a plasma with a negative q{prime}/q (as in reverse field pinches and spheromaks) to have the same {alpha} in all its force-free regions and with a positive q{prime}/q (as in tokamaks) to have centrally peaked {alpha}'s.

  4. Theory and application of maximum magnetic energy in toroidal plasmas

    SciTech Connect

    Chu, T.K.

    1992-02-01

    The magnetic energy in an inductively driven steady-state toroidal plasma is a maximum for a given rate of dissipation of energy (Poynting flux). A purely resistive steady state of the piecewise force-free configuration, however, cannot exist, as the periodic removal of the excess poloidal flux and pressure, due to heating, ruptures the static equilibrium of the partitioning rational surfaces intermittently. The rupture necessitates a plasma with a negative q{prime}/q (as in reverse field pinches and spheromaks) to have the same {alpha} in all its force-free regions and with a positive q{prime}/q (as in tokamaks) to have centrally peaked {alpha}`s.

  5. On the theory of dynamics of dust grain in plasma

    SciTech Connect

    Stepanenko, A. A.; Krasheninnikov, S. I.

    2013-03-15

    The dynamics of rotationally symmetric dust grains in plasma embedded in a magnetic field are of concern. The general expressions for forces and torques acting on dust are found. It is shown that dust spinning is determined by torques related to both the Lorentz force (dominant for relatively small grains) and the gyro-motion of plasma particles impinging the grain (which prevails for large grains). The stability of grain spinning is analyzed and it is shown that, for some cases (e.g., oblate spheroid), there is no stable dynamic equilibrium of grain spinning.

  6. TOWARD A THEORY OF ASTROPHYSICAL PLASMA TURBULENCE AT SUBPROTON SCALES

    SciTech Connect

    Boldyrev, Stanislav; Horaites, Konstantinos; Xia, Qian; Perez, Jean Carlos

    2013-11-01

    We present an analytical study of subproton electromagnetic fluctuations in a collisionless plasma with a plasma beta of the order of unity. In the linear limit, a rigorous derivation from the kinetic equation is conducted focusing on the role and physical properties of kinetic-Alfvén and whistler waves. Then, nonlinear fluid-like equations for kinetic-Alfvén waves and whistler modes are derived, with special emphasis on the similarities and differences in the corresponding plasma dynamics. The kinetic-Alfvén modes exist in the lower-frequency region of phase space, ω << k v{sub Ti} , where they are described by the kinetic-Alfvén system. These modes exist both below and above the ion-cyclotron frequency. The whistler modes, which are qualitatively different from the kinetic-Alfvén modes, occupy a different region of phase space, k v{sub Ti} << ω << k{sub z}v{sub Te} , and they are described by the electron magnetohydrodynamics (MHD) system or the reduced electron MHD system if the propagation is oblique. Here, k{sub z} and k are the wavenumbers along and transverse to the background magnetic field, respectively, and v{sub Ti} and v{sub Te} are the ion and electron thermal velocities, respectively. The models of subproton plasma turbulence are discussed and the results of numerical simulations are presented. We also point out possible implications for solar-wind observations.

  7. Exact kinetic theory for the instability of an electron beam in a hot magnetized plasma

    SciTech Connect

    Timofeev, I. V.; Annenkov, V. V.

    2013-09-15

    Efficiency of collective beam-plasma interaction strongly depends on the growth rates of dominant instabilities excited in the system. Nevertheless, exact calculations of the full unstable spectrum in the framework of relativistic kinetic theory for arbitrary magnetic fields and particle distributions were unknown until now. In this paper, we give an example of such a calculation answering the question whether the finite thermal spreads of plasma electrons are able to suppress the fastest growing modes in the beam-plasma system. It is shown that nonrelativistic temperatures of Maxwellian plasmas can stabilize only the oblique instabilities of relativistic beam. On the contrary, non-Maxwellian tails typically found in laboratory beam-plasma experiments are able to substantially reduce the growth rate of the dominant longitudinal modes affecting the efficiency of turbulent plasma heating.

  8. Geomagnetic polarity epochs: Sierra Nevada II

    USGS Publications Warehouse

    Cox, A.; Doell, Richard R.; Brent, Dalrymple G.

    1963-01-01

    Ten new determinations on volcanic extrusions in the Sierra Nevada with potassium-argon ages of 3.1 million years or less indicate that the remanent magnetizations fall into two groups, a normal group in which the remanent magnetization is directed downward and to the north, and a reversed group magnetized up and to the south. Thermomagnetic experiments and mineralogic studies fail to provide an explanation of the opposing polarities in terms of mineralogic control, but rather suggest that the remanent magnetization reflects reversals of the main dipole field of the earth. All available radiometric ages are consistent with this field-reversal hypothesis and indicate that the present normal polarity epoch (N1) as well as the previous reversed epoch (R1) are 0.9 to 1.0 million years long, whereas the previous normal epoch (N2) was at least 25 percent longer.

  9. Geomagnetic Polarity Epochs: Sierra Nevada II.

    PubMed

    Cox, A; Doell, R R; Dalrymple, G B

    1963-10-18

    Ten new determinations on volcanic extrusions in the Sierra Nevada with potassium-argon ages of 3.1 million years or less indicate that the remanent magnetizations fall into two groups, a normal group in which the remanent magnetization is directed downward and to the north, and a reversed group magnetized up and to the south. Thermomagnetic experiments and mineralogic studies fail to provide an explanation of the opposing polarities in terms of mineralogic control, but rather suggest that the remanent magnetization reflects reversals of the main dipole field of the earth. All available radiometric ages are consistent with this field-reversal hypothesis and indicate that the present normal polarity epoch (N1) as well as the previous reversed epoch (R1) are 0.9 to 1.0 million years long, whereas the previous normal epoch (N2) was at least 25 percent longer. PMID:17799480

  10. Synchronization Phenomena and Epoch Filter of Electroencephalogram

    NASA Astrophysics Data System (ADS)

    Matani, Ayumu

    Nonlinear electrophysiological synchronization phenomena in the brain, such as event-related (de)synchronization, long distance synchronization, and phase-reset, have received much attention in neuroscience over the last decade. These phenomena contain more electrical than physiological keywords and actually require electrical techniques to capture with electroencephalography (EEG). For instance, epoch filters, which have just recently been proposed, allow us to investigate such phenomena. Moreover, epoch filters are still developing and would hopefully generate a new paradigm in neuroscience from an electrical engineering viewpoint. Consequently, electrical engineers could be interested in EEG once again or from now on.

  11. Theory and observation of a dynamically evolviong negative ion plasma

    SciTech Connect

    Mendillo, M.; Forbes, J.

    1982-10-01

    As part of the Project Firefly ionospheric modification campaigns conducted during the early 1960's, sulfur hexafluoride (SF/sub 6/) was used to study the creation and consequences of artificially-induced electron depletion regions via the attachment process (SF/sub 6/+e..-->..SF/sub 6/). Since those early experiments, a great many advances have occurred in theoretical, laboratory, and diagnostic techniques related to negative ion plasmas. This study examines the full range of negative ion chemistry in the upper ionosphere by using current reaction rate data to investigate the many chemical paths SF/sub 6/ type injections might take in an F region environment. Particular attention is given to the conditions required to create heavy negative ions that persist long enough to affect the dynamical properties of the F region. The ambipolar diffusion characteristics of a three component plasma (O/sup +/, e/sup -/, SF/sub 6//sup -/) are described, and estimates of the incoherent scatter spectra obtained from such a plasma are presented. Model calculations using a first order chemical code are defined and tested to investigate the actual types of negative ion plasmas capable of being created under nighttime conditions. A versatile model for diffusion in an exponential atmosphere ws used to simulate the evolution of 10/sup 26/SF/sub 6/ molecules released at 222 km during a 1962 Firefly experiment. When examined in conjunction with the chemical model calculatins, the results suggest that the ionospheric perturbations recorded at the time probably resulted more from molecular and atomic ion neutralizations involving SF/sub 6//sup -/, SF/sub 5//sup +/, O/sup -/, O/sup +/, and epsilon/sup -/, rather than simple electron attachments, as had been expected. A similar use of SF/sub 6/ diffusion scenarios for high-altitude releases (h = 350-500 km) indicates that large-scale, long-lived negative ion plasmas could be produced by modest rocket or Shuttle-borne payloads to study

  12. Kinetic theory of plasma adiabatic major radius compression in tokamaks

    NASA Astrophysics Data System (ADS)

    Gorelenkova, M. V.; Gorelenkov, N. N.; Azizov, E. A.; Romannikov, A. N.; Herrmann, H. W.

    1998-05-01

    In order to understand the individual charged particle behavior as well as plasma macroparameters (temperature, density, etc.) during the adiabatic major radius compression (R-compression) in a tokamak, a kinetic approach is used. The perpendicular electric field from the Ohm's law at zero resistivity is made use of in order to describe particle motion during the R-compression. Expressions for both passing and trapped particle energy and pitch angle change are derived for a plasma with high aspect ratio and circular magnetic surfaces. The particle behavior near the passing trapped boundary during the compression is studied to simulate the compression-induced collisional losses of alpha particles. Qualitative agreement is obtained with the alphas loss measurements in deuterium-tritium (D-T) experiments in the Tokamak Fusion Test Reactor (TFTR) [World Survey of Activities in Controlled Fusion Research [Nucl. Fusion special supplement (1991)] (International Atomic Energy Agency, Vienna, 1991)]. The plasma macroparameters evolution at the R-compression is calculated by solving the gyroaveraged drift kinetic equation.

  13. Gyrokinetic stability theory of electron-positron plasmas

    NASA Astrophysics Data System (ADS)

    Helander, P.; Connor, J. W.

    2016-06-01

    > The linear gyrokinetic stability properties of magnetically confined electron-positron plasmas are investigated in the parameter regime most likely to be relevant for the first laboratory experiments involving such plasmas, where the density is small enough that collisions can be ignored and the Debye length substantially exceeds the gyroradius. Although the plasma beta is very small, electromagnetic effects are retained, but magnetic compressibility can be neglected. The work of a previous publication (Helander, Phys. Rev. Lett., vol. 113, 2014a, 135003) is thus extended to include electromagnetic instabilities, which are of importance in closed-field-line configurations, where such instabilities can occur at arbitrarily low pressure. It is found that gyrokinetic instabilities are completely absent if the magnetic field is homogeneous: any instability must involve magnetic curvature or shear. Furthermore, in dipole magnetic fields, the stability threshold for interchange modes with wavelengths exceeding the Debye radius coincides with that in ideal magnetohydrodynamics. Above this threshold, the quasilinear particle flux is directed inward if the temperature gradient is sufficiently large, leading to spontaneous peaking of the density profile.

  14. Kinetic studies of microinstabilities in toroidal plasmas: Simulation and theory

    SciTech Connect

    Lee, W.W.; Haham, T.S.; Parker, S.E.; Perkins, F.W.; Rath, S.; Rewoldt, G.; Reynders, J.V.W.; Santoro, R.A.; Tang, W.M.

    1992-12-01

    A comprehensive program for the development and use of particle simulation techniques for solving the gyrokinetic Vlasov-Maxwell equations on massively parallel computers has been carried out at Princeton Plasma Physics Laboratory. This is a key element of our ongoing theoretical efforts to systematically investigate physics issues vital to understanding tokamak plasmas. In this paper, our focus is on spatial-gradient-driven microinstabilities. Their importance is supported by the recent progress in achieving a physics-based understanding of anomalous transport in toroidal systems which has been based on the proposition that these drift-type electrostatic modes dependent on ion temperature gradient (ITG) and trapped particle effects are dominant in the bulk ( confinement'') region. Although their presence is consistent with a number of significant confinement trends, results from high temperature tokamaks such as TFTR have highlighted the need for better insight into the nonlinear properties of such instabilities in long-mean-free-path plasmas. In addressing this general issue, we report important new results including (i) the first fully toroidal 3D gyrokinetic simulation of ITG modes and (ii) realistic toroidal eigenmode calculations demonstrating the unique capability to deal with large scale kinetic behavior extending over many rational surfaces. The effects of ITG modes (iii) on the inward pinch of impurities in 3D slab geometry and (iv) on the existence of microtearing modes in 2D slab are also discussed. Finally, (v) sheared toroidal flow effects on trapped-particle modes are presented.

  15. Kinetic studies of microinstabilities in toroidal plasmas: Simulation and theory

    SciTech Connect

    Lee, W.W.; Haham, T.S.; Parker, S.E.; Perkins, F.W.; Rath, S.; Rewoldt, G.; Reynders, J.V.W.; Santoro, R.A.; Tang, W.M.

    1992-12-01

    A comprehensive program for the development and use of particle simulation techniques for solving the gyrokinetic Vlasov-Maxwell equations on massively parallel computers has been carried out at Princeton Plasma Physics Laboratory. This is a key element of our ongoing theoretical efforts to systematically investigate physics issues vital to understanding tokamak plasmas. In this paper, our focus is on spatial-gradient-driven microinstabilities. Their importance is supported by the recent progress in achieving a physics-based understanding of anomalous transport in toroidal systems which has been based on the proposition that these drift-type electrostatic modes dependent on ion temperature gradient (ITG) and trapped particle effects are dominant in the bulk (``confinement``) region. Although their presence is consistent with a number of significant confinement trends, results from high temperature tokamaks such as TFTR have highlighted the need for better insight into the nonlinear properties of such instabilities in long-mean-free-path plasmas. In addressing this general issue, we report important new results including (i) the first fully toroidal 3D gyrokinetic simulation of ITG modes and (ii) realistic toroidal eigenmode calculations demonstrating the unique capability to deal with large scale kinetic behavior extending over many rational surfaces. The effects of ITG modes (iii) on the inward pinch of impurities in 3D slab geometry and (iv) on the existence of microtearing modes in 2D slab are also discussed. Finally, (v) sheared toroidal flow effects on trapped-particle modes are presented.

  16. An effective field theory approach to the stabilization of 8Be in a QED plasma

    NASA Astrophysics Data System (ADS)

    Yao, Xiaojun; Mehen, Thomas; Müller, Berndt

    2016-07-01

    We use effective field theory to study the α –α resonant scattering in a finite-temperature QED plasma. The static plasma screening effect causes the resonance state 8Be to live longer and eventually leads to the formation of a bound state when {m}{{D}}≳ 0.3 {{MeV}}. We speculate that this effect may have implications on the rates of cosmologically and astrophysically relevant nuclear reactions involving α particles.

  17. Kinetic Theory of Meteor Plasma in the Earth's atmosphere: Implications for Radar Head Echo

    NASA Astrophysics Data System (ADS)

    Dimant, Y. S.; Oppenheim, M. M.

    2015-12-01

    Every second millions of tiny meteoroids hit the Earth from space, vast majority too small to be observed visually. However, radars detect the plasma they generate and use the collected data to characterize the incoming meteoroids and the atmosphere in which they disintegrate. This diagnostics requires a detailed quantitative understanding of formation of the meteor plasma and how it interacts with the Earth's atmosphere. Fast-descending meteoroids become detectable to radars after they heat due to collisions with atmospheric molecules sufficiently and start ablating. The ablated material then collides into atmospheric molecules and forms plasma around the meteoroid. Reflection of radar pulses from this plasma produces a localized signal called a head echo often accompanied by a much longer non-specular trail (see the Figure). Using first principles, we have developed a consistent collisional kinetic theory of the near-meteoroid plasma responsible for the radar head echo. This theory produces analytic expressions describing the ion and neutral velocity distributions along with the detailed 3-D spatial structure of the near-meteoroid plasma. These expressions predict a number of unexpected features such as shell-like velocity distributions. This theory shows that the meteoroid plasma develops over a length-scale close to the ion mean free path with a strongly non-Maxwellian velocity distribution. The spatial distribution of the plasma density shows significant deviations from a Gaussian law usually employed in head-echo modeling. This analytical model will serve as a basis for a more accurate quantitative interpretation of radar measurements, estimates of the ionization efficiency, and should help calculate meteoroid and atmosphere parameters from radar head-echo observations. This theory could also help clarify the physical nature of electromagnetic pulses observed during recent meteor showers and associated with the passage of fast-moving meteors through the

  18. Thermoemission (dust-electron) plasmas: Theory of neutralizing charges

    NASA Astrophysics Data System (ADS)

    Vishnyakov, V. I.; Dragan, G. S.

    2006-09-01

    Thermoemission plasma—i.e., a system consisting of dust grains and electrons—is studied. In the proposed model, it is assumed that the major part of the electronic gas is uniformly distributed in space and the spatial inhomogeneities of electronic density exist only near the dust grains. The experimental data, well described by the proposed theory, are given.

  19. Theory of coupled whistler-electron temperature gradient mode in high beta plasma: Application to linear plasma device

    SciTech Connect

    Singh, S. K.; Awasthi, L. M.; Singh, R.; Kaw, P. K.; Jha, R.; Mattoo, S. K.

    2011-10-15

    This paper presents a theory of coupled whistler (W) and electron temperature gradient (ETG) mode using two-fluid model in high beta plasma. Non-adiabatic ion response, parallel magnetic field perturbation ({delta}B{sub z}), perpendicular magnetic flutter ({delta}B{sub perpendicular}), and electron collisions are included in the treatment of theory. A linear dispersion relation for whistler-electron temperature gradient (W-ETG) mode is derived. The numerical results obtained from this relation are compared with the experimental results observed in large volume plasma device (LVPD) [Awasthi et al., Phys. Plasma 17, 42109 (2010)]. The theory predicts that the instability grows only where the temperature gradient is finite and the density gradient flat. For the parameters of the experiment, theoretically estimated frequency and wave number of W-ETG mode match with the values corresponding to the peak in the power spectrum observed in LVPD. By using simple mixing length argument, estimated level of fluctuations of W-ETG mode is in the range of fluctuation level observed in LVPD.

  20. Hydrodynamic Theory of Atomic Mixing in Multicomponent Gases and Plasmas

    SciTech Connect

    Ramshaw, J D

    2001-08-22

    Atomic mixing in multicomponent gases and plasmas is usually described as a diffusional process. The diffusional description is an approximation to a more general dynamical description in which the motion of each individual species or material is governed by its own momentum equation, with appropriate coupling terms to represent the exchange of momentum between different species. These equations are not new, but they are scattered in the literature. Here we summarize the form of these species momentum equations, and the coupling coefficients therein, in sufficient detail to facilitate their inclusion and use to simulate atomic mixing in hydrodynamics codes.

  1. Hydrodynamic theory for ion structure and stopping power in quantum plasmas.

    PubMed

    Shukla, P K; Akbari-Moghanjoughi, M

    2013-04-01

    We present a theory for the dynamical ion structure factor (DISF) and ion stopping power in an unmagnetized collisional quantum plasma with degenerate electron fluids and nondegenerate strongly correlated ion fluids. Our theory is based on the fluctuation dissipation theorem and the quantum plasma dielectric constant that is deduced from a linearized viscoelastic quantum hydrodynamical (LVQHD) model. The latter incorporates the essential physics of quantum forces, which are associated with the quantum statistical pressure, electron-exchange, and electron-correlation effects, the quantum electron recoil effect caused by the dispersion of overlapping electron wave functions that control the dynamics of degenerate electron fluids, and the viscoelastic properties of strongly correlated ion fluids. Both degenerate electrons and nondegenerate strongly correlated ions are coupled with each other via the space charge electric force. Thus, our LVQHD theory is valid for a collisional quantum plasma at atomic scales with a wide range of the ion coupling parameter, the plasma composition, and plasma number densities that are relevant for compressed plasmas in laboratories (inertial confinement fusion schemes) and in astrophysical environments (e.g., warm dense matter and the cores of white dwarf stars). It is found that quantum electron effects and viscoelastic properties of strongly correlated ions significantly affect the features of the DISF and the ion stopping power (ISP). Unlike previous theories, which have studied ion correlations in terms of the ion coupling parameter, by neglecting the essential physics of collective effects that are competing among each other, we have here developed a method to evaluate the dependence of the plasma static and dynamical features in terms of individual parameters, like the Wigner-Seitz radius, the ion atomic number, and the ion temperature. It is found that due to the complex nature of charge screening in quantum plasmas, the ion

  2. Theory and Observations of High Frequency Alfven Eigenmodes in Low Aspect Ratio Plasma

    SciTech Connect

    N.N. Gorelenkov; E. Fredrickson; E. Belova; C.Z. Cheng; D. Gates; S. Kaye; R. White

    2003-06-27

    New observations of sub-cyclotron frequency instability in low aspect ratio plasma in National Spherical Torus Experiments (NSTX) are reported. The frequencies of observed instabilities correlate with the characteristic Alfven velocity of the plasma. A theory of localized Compressional Alfven Eigenmodes (CAE) and Global shear Alfven Eigenmodes (GAE) in low aspect ratio plasma is presented to explain the observed high frequency instabilities. CAE's/GAE's are driven by the velocity space gradient of energetic super-Alfvenic beam ions via Doppler shifted cyclotron resonances. One of the main damping mechanisms of GAE's, the continuum damping, is treated perturbatively within the framework of ideal MHD. Properties of these cyclotron instabilities ions are presented.

  3. Microscopic nonlinear relativistic quantum theory of absorption of powerful x-ray radiation in plasma.

    PubMed

    Avetissian, H K; Ghazaryan, A G; Matevosyan, H H; Mkrtchian, G F

    2015-10-01

    The microscopic quantum theory of plasma nonlinear interaction with the coherent shortwave electromagnetic radiation of arbitrary intensity is developed. The Liouville-von Neumann equation for the density matrix is solved analytically considering a wave field exactly and a scattering potential of plasma ions as a perturbation. With the help of this solution we calculate the nonlinear inverse-bremsstrahlung absorption rate for a grand canonical ensemble of electrons. The latter is studied in Maxwellian, as well as in degenerate quantum plasma for x-ray lasers at superhigh intensities and it is shown that one can achieve the efficient absorption coefficient in these cases. PMID:26565352

  4. Kinetic theory of a two-dimensional magnetized plasma. II - Balescu-Lenard limit.

    NASA Technical Reports Server (NTRS)

    Vahala, G.

    1972-01-01

    The kinetic theory of a two-dimensional one-species plasma in a uniform dc magnetic field is investigated in the small plasma parameter limit. The plasma consists of charged rods interacting through the logarithmic Coulomb potential. Vahala and Montgomery earlier (1971) derived a Fokker-Planck equation for this system, but it contained a divergent integral, which had to be cut off on physical grounds. This cutoff is compared to the standard cutoff introduced in the two-dimensional unmagnetized Fokker-Planck equation. In the small plasma parameter limit, it is shown that the Balescu-Lenard collision term is zero in the long time average limit if only two-body interactions are considered. The energy transfer from a test particle to an equilibrium plasma is discussed and is also shown to be zero in the long time average limit. This supports the unexpected result of zero Balescu-Lenard collision term.

  5. Fokker Planck and Krook theory of energetic electron transport in a laser produced plasma

    SciTech Connect

    Manheimer, Wallace; Colombant, Denis

    2015-09-15

    Various laser plasma instabilities, such as the two plasma decay instability and the stimulated Raman scatter instability, produce large quantities of energetic electrons. How these electrons are transported and heat the plasma are crucial questions for laser fusion. This paper works out a Fokker Planck and Krook theory for such transport and heating. The result is a set of equations, for which one can find a simple asymptotic approximation for the solution, for the Fokker Planck case, and an exact solution for the Krook case. These solutions are evaluated and compared with one another. They give rise to expressions for the spatially dependent heating of the background plasma, as a function of the instantaneous laser and plasma parameters, in either planar or spherical geometry. These formulas are simple, universal (depending weakly only on the single parameter Z, the charge state), and can be easily be incorporated into a fluid simulation.

  6. Fokker Planck and Krook theory of energetic electron transport in a laser produced plasma

    NASA Astrophysics Data System (ADS)

    Manheimer, Wallace; Colombant, Denis

    2015-09-01

    Various laser plasma instabilities, such as the two plasma decay instability and the stimulated Raman scatter instability, produce large quantities of energetic electrons. How these electrons are transported and heat the plasma are crucial questions for laser fusion. This paper works out a Fokker Planck and Krook theory for such transport and heating. The result is a set of equations, for which one can find a simple asymptotic approximation for the solution, for the Fokker Planck case, and an exact solution for the Krook case. These solutions are evaluated and compared with one another. They give rise to expressions for the spatially dependent heating of the background plasma, as a function of the instantaneous laser and plasma parameters, in either planar or spherical geometry. These formulas are simple, universal (depending weakly only on the single parameter Z, the charge state), and can be easily be incorporated into a fluid simulation.

  7. Scale-free transport in fusion plasmas: theory and applications

    SciTech Connect

    Sanchez, R.; Mier, J. A.; Garcia, L.; Newman, D. E.; Carreras, B. A.; Leboeuf, J. N.; Decyk, V.

    2008-11-01

    A novel approach to detect the existence of scale-free transport in turbulent flows, based on the characterization of its Lagrangian characteristics, is presented and applied to two situations relevant for tokamak plasmas. The first one, radial transport in the presence of near-critical turbulence, has been known for quite some time to yield scale-free, superdiffusive transport. We use it to test the method and illustrate its robustness with respect to other approaches. The second situation, radial transport across radially-sheared poloidal zonal flows driven by turbulence via the Reynold stresses, is examined for the first time in this manner. The result is rather surprising and different from the traditionally assumed diffusive behavior. Instead, radial transport behaves instead in a scale-free, subdiffusive manner, which may have implications for the modeling of transport across transport barriers.

  8. Scale-free transport in fusion plasmas: theory and applications

    SciTech Connect

    Sanchez, Raul; Mier, Jose Angel; Newman, David E; Carreras, Benjamin A; Garcia, Luis; Leboeuf, Jean-Noel; Decyk, Viktor

    2008-01-01

    A novel approach to detect the existence of scale-free transport in turbulent flows, based on the characterization of its Lagrangian characteristics, is presented and applied to two situations relevant for tokamak plasmas. The first one, radial transport in the presence of near-critical turbulence, has been known for quite some time to yield scale-free, superdiffusive transport. We use it to test the method and illustrate its robustness with respect to other approaches. The second situation, radial transport across radially-sheared poloidal zonal flows driven by turbulence via the Reynold stresses, is examined for the first time in this manner. The result is rather surprising and different from the traditionally assumed diffusive behavior. Instead, radial transport behaves instead in a scale-free, subdiffusive manner, which may have implications for the modeling of transport across transport barriers.

  9. Kinetic theory of a two-dimensional magnetized plasma.

    NASA Technical Reports Server (NTRS)

    Vahala, G.; Montgomery, D.

    1971-01-01

    Several features of the equilibrium and nonequilibrium statistical mechanics of a two-dimensional plasma in a uniform dc magnetic field are investigated. The charges are assumed to interact only through electrostatic potentials. The problem is considered both with and without the guiding-center approximation. With the guiding-center approximation, an appropriate Liouville equation and BBGKY hierarchy predict no approach to thermal equilibrium for the spatially uniform case. For the spatially nonuniform situation, a guiding-center Vlasov equation is discussed and solved in special cases. For the nonequilibrium, nonguiding-center case, a Boltzmann equation, and a Fokker-Planck equation are derived in the appropriate limits. The latter is more tractable than the former, and can be shown to obey conservation laws and an H-theorem, but contains a divergent integral which must be cut off on physical grounds. Several unsolved problems are posed.

  10. CONFERENCE DESCRIPTION Theory of Fusion Plasmas: Varenna-Lausanne International Workshop

    NASA Astrophysics Data System (ADS)

    Garbet, X.; Sauter, O.

    2010-12-01

    The Joint Varenna-Lausanne international workshop on Theory of Fusion Plasmas takes place every other year in a place particularly favourable for informal and in-depth discussions. Invited and contributed papers present state-of-the-art research in theoretical plasma physics, covering all domains relevant to fusion plasmas. This workshop always welcomes a fruitful mix of experienced researchers and students, to allow a better understanding of the key theoretical physics models and applications. Theoretical issues related to burning plasmas Anomalous Transport (Turbulence, Coherent Structures, Microinstabilities) RF Heating and Current Drive Macroinstabilities Plasma-Edge Physics and Divertors Fast particles instabilities Further details: http://Varenna-Lausanne.epfl.ch The conference is organized by: Centre de Recherches en Physique des Plasmas, Ecole Polytechnique Fédérale de Lausanne, Association EURATOM - Confédération Suisse 'Piero Caldirola' International Centre for the Promotion of Science and International School of Plasma Physics Istituto di Fisica del Plasma del CNR, Milano Editors: X Garbet (CEA, Cadarache, France) and O Sauter (CRPP-EPFL, Lausanne, Switzerland)

  11. Theory of spatially non-symmetric kinetic equilibria for collisionless plasmas

    SciTech Connect

    Cremaschini, Claudio; Tessarotto, Massimo

    2013-01-15

    The problem posed by the possible existence/non-existence of spatially non-symmetric kinetic equilibria has remained unsolved in plasma theory. For collisionless magnetized plasmas, this involves the construction of stationary solutions of the Vlasov-Maxwell equations. In this paper, the issue is addressed for non-relativistic plasmas both in astrophysical and laboratory contexts. The treatment is based on a Lagrangian variational description of single-particle dynamics. Starting point is a non-perturbative formulation of gyrokinetic theory, which allows one to construct 'a posteriori' with prescribed order of accuracy an asymptotic representation for the magnetic moment. In terms of the relevant particle adiabatic invariants generalized bi-Maxwellian equilibria are proved to exist. These are shown to recover, under suitable assumptions, a Chapman-Enskog form which permits an analytical treatment of the corresponding fluid moments. In particular, the constrained posed by the Poisson and the Ampere equations are analyzed, both for quasi-neutral and non-neutral plasmas. The conditions of existence of the corresponding non-symmetric kinetic equilibria are investigated. As a notable feature, both astrophysical and laboratory plasmas are shown to exhibit, under suitable conditions, a kinetic dynamo, whereby the equilibrium magnetic field can be self-generated by the equilibrium plasma currents.

  12. Quantum theory of the dielectric constant of a magnetized plasma and astrophysical applications. I.

    NASA Technical Reports Server (NTRS)

    Canuto, V.; Ventura, J.

    1972-01-01

    A quantum mechanical treatment of an electron plasma in a constant and homogeneous magnetic field is considered, with the aim of (1) defining the range of validity of the magnetoionic theory (2) studying the deviations from this theory, in applications involving high densities, and intense magnetic field. While treating the magnetic field exactly, a perturbation approach in the photon field is used to derive general expressions for the dielectric tensor. Numerical estimates on the range of applicability of the magnetoionic theory are given for the case of the 'one-dimensional' electron gas, where only the lowest Landau level is occupied.

  13. Very high Mach number shocks - Theory. [in space plasmas

    NASA Technical Reports Server (NTRS)

    Quest, Kevin B.

    1986-01-01

    The theory and simulation of collisionless perpendicular supercritical shock structure is reviewed, with major emphasis on recent research results. The primary tool of investigation is the hybrid simulation method, in which the Newtonian orbits of a large number of ion macroparticles are followed numerically, and in which the electrons are treated as a charge neutralizing fluid. The principal results include the following: (1) electron resistivity is not required to explain the observed quasi-stationarity of the earth's bow shock, (2) the structure of the perpendicular shock at very high Mach numbers depends sensitively on the upstream value of beta (the ratio of the thermal to magnetic pressure) and electron resistivity, (3) two-dimensional turbulence will become increasingly important as the Mach number is increased, and (4) nonadiabatic bulk electron heating will result when a thermal electron cannot complete a gyrorbit while transiting the shock.

  14. Electronics Research Laboratory, Plasma Theory and Simulation Group annual progress report, January 1, 1989--December 31, 1989

    SciTech Connect

    Birdsall, C.K.

    1989-12-31

    This is a brief progress report, covering our research in general plasma theory and simulation, plasma-wall physics theory and simulation, and code development. Reports written in this period are included with this mailing. A publications list plus abstracts for two major meetings are included.

  15. Geomagnetic reversal in brunhes normal polarity epoch.

    PubMed

    Smith, J D; Foster, J H

    1969-02-01

    The magnetic stratigraphly of seven cores of deep-sea sediment established the existence of a short interval of reversed polarity in the upper part of the Brunches epoch of normal polarity. The reversed zone in the cores correlates well with paleontological boundaries and is named the Blake event. Its boundaries are estimated to be 108,000 and 114,000 years ago +/- 10 percent. PMID:17750890

  16. Theory and Fluid Simulations of Boundary Plasma Fluctuations

    SciTech Connect

    Cohen, R H; LaBombard, B; LoDestro, L L; Rognlien, T D; Ryutov, D D; Terry, J L; Umansky, M V; Xu, X Q; Zweben, S

    2007-01-09

    Theoretical and computational investigations are presented of boundary plasma microturbulence that take into account important effects of the geometry of diverted tokamaks--in particular, the effect of x-point magnetic shear and the termination of field lines on divertor plates. We first generalize our previous 'heuristic boundary condition' which describes, in a lumped model, the closure of currents in the vicinity of the x-point region to encompass three current-closure mechanisms. We then use this boundary condition to derive the dispersion relation for low-beta flute-like modes in the divertor-leg region under the combined drives of curvature, sheath impedance, and divertor tilt effects. The results indicate the possibility of strongly growing instabilities, driven by sheath boundary conditions, and localized in either the private or common flux region of the divertor leg depending on the radial tilt of divertor plates. We re-visit the issue of x-point effects on blobs, examining the transition from blobs terminated by x-point shear to blobs that extend over both the main SOL and divertor legs. We find that, for a main-SOL blob, this transition occurs without a free-acceleration period as previously thought, with x-point termination conditions applying until the blob has expanded to reach the divertor plate. We also derive propagation speeds for divertor-leg blobs. Finally, we present fluid simulations of the C-Mod tokamak from the BOUT edge fluid turbulence code, which show main-SOL blob structures with similar spatial characteristics to those observed in the experiment, and also simulations which illustrate the possibility of fluctuations confined to divertor legs.

  17. Kinetic theory of low-frequency cross-field instability in a weakly ionized plasma. II

    SciTech Connect

    Dimant, Y.S.; Sudan, R.N.

    1995-04-01

    The consistent kinetic approach developed in Paper I [Ya. S. Dimant and R. N. Sudan, Phys. Plasmas {bold 2}, 1157 (1995)] is applied to obtain the general dispersion relation of the two-stream {bold E}{times}{bold B} instability in collisionally dominated weakly ionized plasmas for wave frequencies small compared to the ion--neutral collision frequency. This dispersion relation covers the whole low-frequency band from the asymptotic short-wave limit studied in Paper I to the long-wave limit. Previous theories employing simplified kinetic theory or fluid equations for electron behavior are only correct in the long-wave limit. The principal new results are that the threshold conditions for this instability and the growth rates are altered from those predicted by earlier simplified theories. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  18. A tutorial introduction to the statistical theory of turbulent plasmas, a half-century after Kadomtsev's Plasma Turbulence and the resonance-broadening theory of Dupree and Weinstock

    NASA Astrophysics Data System (ADS)

    Krommes, John A.

    2015-12-01

    > In honour of the 50th anniversary of the influential review/monograph on plasma turbulence by B. B. Kadomtsev as well as the seminal works of T. H. Dupree and J. Weinstock on resonance-broadening theory, an introductory tutorial is given about some highlights of the statistical-dynamical description of turbulent plasmas and fluids, including the ideas of nonlinear incoherent noise, coherent damping, and self-consistent dielectric response. The statistical closure problem is introduced. Incoherent noise and coherent damping are illustrated with a solvable model of passive advection. Self-consistency introduces turbulent polarization effects that are described by the dielectric function . Dupree's method of using to estimate the saturation level of turbulence is described; then it is explained why a more complete theory that includes nonlinear noise is required. The general theory is best formulated in terms of Dyson equations for the covariance and an infinitesimal response function , which subsumes . An important example is the direct-interaction approximation (DIA). It is shown how to use Novikov's theorem to develop an -space approach to the DIA that is complementary to the original -space approach of Kraichnan. A dielectric function is defined for arbitrary quadratically nonlinear systems, including the Navier-Stokes equation, and an algorithm for determining the form of in the DIA is sketched. The independent insights of Kadomtsev and Kraichnan about the problem of the DIA with random Galilean invariance are described. The mixing-length formula for drift-wave saturation is discussed in the context of closures that include nonlinear noise (shielded by ). The role of in the calculation of the symmetry-breaking (zonostrophic) instability of homogeneous turbulence to the generation of inhomogeneous mean flows is addressed. The second-order cumulant expansion and the stochastic structural stability theory are also discussed in that context. Various historical

  19. First and second quarter progress report 1987 on plasma theory and simulation, January 1-June 30, 1987

    SciTech Connect

    Birdsall, C.K.

    1987-01-01

    This paper contains papers on general plasma theory and plasma-wall physics. Specific titles enclosed are as follows: ion acceleration in a source sheath with an initial velocity; collector and source sheaths of a finite ion temperature plasma; effects of secondary electron emission on the collector and source sheaths of a finite ion temperature plasma; effects of ion reflection on the collector and source sheaths of a finite ion temperature plasma; and vortex dynamics and transport to the wall in a crossed field plasma sheath.

  20. Profile of a low-Mach-number shock in two-fluid plasma theory

    NASA Astrophysics Data System (ADS)

    Gedalin, M.; Kushinsky, Y.; Balikhin, M.

    2015-08-01

    Magnetic profiles of low-Mach-number collisionless shocks in space plasmas are studied within the two-fluid plasma theory. Particular attention is given to the upstream magnetic oscillations generated at the ramp. By including weak resistive dissipation in the equations of motion for electrons and protons, the dependence of the upstream wave train features on the ratio of the dispersion length to the dissipative length is established quantitatively. The dependence of the oscillation amplitude and spatial damping scale on the shock normal angle θ is found.

  1. Theory of "clumps" in drift-wave turbulence in tokamak plasma

    NASA Astrophysics Data System (ADS)

    Wang, Xiaogang; Qiu, Xiaoming; X, M. Qhiu

    1986-08-01

    Basing on the new method of trajectory stochastic treatment advanced by one of the authors of this paper, the theory of "clumps" in driftwave turbulence in tokamak plasmas has been developed. It is shown that, as a longer time behaviour, plasmas in tokamaks will have the same "clumps" effects as those in uniform magnetic fields, although the diffusion crossing magnetic field lines in tokamaks will be enhanced. The influence of the non-uniformity of the magnetic field, such as curvature, shear, etc., on the transverse diffusion and the "clump" life-time is discussed.

  2. Administering an epoch initiated for remote memory access

    SciTech Connect

    Blocksome, Michael A; Miller, Douglas R

    2014-03-18

    Methods, systems, and products are disclosed for administering an epoch initiated for remote memory access that include: initiating, by an origin application messaging module on an origin compute node, one or more data transfers to a target compute node for the epoch; initiating, by the origin application messaging module after initiating the data transfers, a closing stage for the epoch, including rejecting any new data transfers after initiating the closing stage for the epoch; determining, by the origin application messaging module, whether the data transfers have completed; and closing, by the origin application messaging module, the epoch if the data transfers have completed.

  3. Administering an epoch initiated for remote memory access

    DOEpatents

    Blocksome, Michael A; Miller, Douglas R

    2012-10-23

    Methods, systems, and products are disclosed for administering an epoch initiated for remote memory access that include: initiating, by an origin application messaging module on an origin compute node, one or more data transfers to a target compute node for the epoch; initiating, by the origin application messaging module after initiating the data transfers, a closing stage for the epoch, including rejecting any new data transfers after initiating the closing stage for the epoch; determining, by the origin application messaging module, whether the data transfers have completed; and closing, by the origin application messaging module, the epoch if the data transfers have completed.

  4. Administering an epoch initiated for remote memory access

    DOEpatents

    Blocksome, Michael A.; Miller, Douglas R.

    2013-01-01

    Methods, systems, and products are disclosed for administering an epoch initiated for remote memory access that include: initiating, by an origin application messaging module on an origin compute node, one or more data transfers to a target compute node for the epoch; initiating, by the origin application messaging module after initiating the data transfers, a closing stage for the epoch, including rejecting any new data transfers after initiating the closing stage for the epoch; determining, by the origin application messaging module, whether the data transfers have completed; and closing, by the origin application messaging module, the epoch if the data transfers have completed.

  5. Radar probing of ionospheric plasmas precisely confirms linear kinetic plasma theory (Hannes Alfvén Medal Lecture)

    NASA Astrophysics Data System (ADS)

    Farley, Donald

    2010-05-01

    In 1958 W. E. Gordon first suggested that huge radars could probe the ionosphere via scattering from independent electrons, even though the radar cross section of a single electron is only 10-28 m2. This suggestion quickly led to the construction of two enormous radars in the early 1960s, one near Lima, Peru, and one near Arecibo, Puerto Rico. It soon became apparent that the theory of this scatter was more complicated than originally envisaged by Gordon. Although the new theory was more complicated, it was much richer: by measuring the detailed shape of the Doppler frequency spectrum (or alternatively the signal autocorrelation function, the ACF), a radar researcher could determine many, if not most, of the parameters of interest of the plasma. There is now a substantial network of major radar facilities scattered from the magnetic equator (Peru) to the high arctic latitudes (Svalbard and Resolute Bay), all doing important ionospheric research. The history of what is now called Incoherent Scatter (even though it is not truly incoherent) is fascinating, and I will touch on a few highlights. The sophisticated radar and data processing techniques that have been developed are also impressive. In this talk, however, I want to focus mainly on the details of the theory and on how the radar observations have confirmed the predictions of classical linear plasma kinetic theory to an amazingly high degree of precision, far higher than has any other technique that I am aware of. The theory can be, and has been, developed from two very different points of view. One starts with 'dressed particles,' or Coulomb 'clouds' around ions and electrons moving with a Maxwellian velocity distribution; the second starts by considering all the charged particles to be made up of a spectrum of density plane waves and then invokes a generalized version of the Nyquist Noise Theorem to calculate the thermal amplitudes of the waves. Both approaches give exactly the same results, results that

  6. Experimental Measurements and Density Functional Theory Calculations of Continuum Lowering in Strongly Coupled Plasmas

    NASA Astrophysics Data System (ADS)

    Vinko, Sam

    2014-10-01

    An accurate description of the ionization potential depression (IPD) of ions in plasmas due to their interaction with the environment is a fundamental problem in plasma physics, playing a key role in determining the ionization balance, charge state distribution, opacity and plasma equation of state. Here I present the first experimental investigation of the IPD as a function of ionic charge state in a range of dense Mg, Al and Si plasmas, using the Linac Coherent Light Source X-ray free-electron laser. The measurements show significantly larger IPDs than are predicted by the most commonly used models, such as that of Stewart-Pyatt, or the ion-sphere model of Zimmerman-More. Instead, plasma simulations using finite-temperature density functional theory with excited-state projector augmented-wave potentials show excellent agreement with the experimental results and explain the stronger-than-expected continuum lowering through the electronic structure of the valence states in these strong-coupling conditions, which retain much of their atomic characteristics close to the ion core regions. These results have a profound impact on the understanding and modelling of plasmas over a wide range of warm- and hot-dense matter conditions.

  7. Plasma theory and simulation. Quarterly progress report Nos. 1 and 2, 1 January-30 June 1985

    SciTech Connect

    Birdsall, C.K.

    1985-06-01

    Partial contents include: (1) The Alfven Ion Cyclotron Instability: Simulation Theory and Techniques; (2) Transport of particle and energy fluxes through the plasma-sheath region, including ion reflection. The time-independent theory developed is very nearly verified by the average of the time-dependent simulations, with some exceptions; (3) Thermionic emission I-V paradox. The problem is described (Longo's 1/J observations) and conjectures are offered on the causes; (4) POLY: A hybrid scheme for the solution of the Vlasov equation. One component is modeled by linearized fluid equations and the other component(s) by the full Vlasov equation(s).

  8. Plasma theory and simulation. Quarterly progress report Nos. 3 and 4, 1 July-30 December 1984

    SciTech Connect

    Birdsall, C.K.

    1984-12-31

    Contents include: oblique-electron Bernstein-wave investigations; simulation of the effect of large-amplitude rf waves on the interchange instability-supporting theory; one-beam Alfven ion-cyclotron instabilities of multiple-ion distribution functions; linear-mode coupling in simulations of the Alfven ion-cyclotron instability; simulation of the plasma-sheath region including ion reflection; planar magnetron discharges; partial simulations of the low-alpha Pierce diode; theory and simulation of ion-acoustic double layers; and uniform-number generation for quiet starts.

  9. Application of linear response theory to magnetotransport properties of dense plasmas

    SciTech Connect

    Adams, J. R.; Redmer, R.; Reinholz, H.

    2010-03-15

    Linear response theory, as developed within the Zubarev formalism, is a quantum statistical approach for describing systems out of but close to equilibrium, which has been successfully applied to a wide variety of plasmas in an external electric field and/or containing a temperature gradient. We present here an extension of linear response theory to include the effects of an external magnetic field. General expressions for the complete set of relevant transport properties are given. In particular, the Hall effect and the influence of a magnetic field on the dc electrical conductivity are discussed. Low-density limits including electron-electron scattering are presented as well as results for arbitrary degeneracy.

  10. Theory of the jitter radiation in a magnetized plasma accompanying a temperature gradient

    NASA Astrophysics Data System (ADS)

    Hattori, Makoto; Fujiki, Kazushiro

    2016-04-01

    The linear stability of a magnetized plasma accompanying a temperature gradient is reexamined by using plasma kinetic theory. We propose that the anisotropic velocity distribution function should be decomposed into two components. One is proportional to the temperature gradient parallel to the background magnetic field. The other is proportional to the temperature gradient perpendicular to the background magnetic field. Since the amplitude of the anisotropic velocity distribution function is proportional to the heat conductivity, and the heat conductivity perpendicular to the magnetic field is strongly reduced, the first component of the anisotropic velocity distribution function is predominant. The anisotropic velocity distribution function induced by the temperature gradient along the background magnetic field drives plasma kinetic instability and circular polarized magnetic plasma waves are excited. We show that the instability is almost identical to the Weibel instability in the weakly magnetized plasma. However, in the case of the instability caused by the temperature gradient, whether wave vectors of modes are parallel to or antiparallel to the background magnetic field, the growth rate of one mode is suppressed and the growth rate of the other mode is enhanced due to the background magnetic field. In the strongly magnetized plasma, one mode is stabilized and only one of the modes remains unstable. The formulae for the jitter radiation spectrum emitted by relativistic electrons when they travel through the magnetized plasma with the plasma waves driven by the instability are deduced at the first time. We show that the synchrotron emission and the jitter radiation are simultaneously emitted from the same relativistic electron. The jitter radiation is expected to be circularly polarized but with a very small polarization degree since almost the same amounts of left-handed and right-handed circular polarized magnetic waves are excited by the instability.

  11. Current-driven plasma acceleration versus current-driven energy dissipation. I - Wave stability theory

    NASA Technical Reports Server (NTRS)

    Kelly, A. J.; Jahn, R. G.; Choueiri, E. Y.

    1990-01-01

    The dominant unstable electrostatic wave modes of an electromagnetically accelerated plasma are investigated. The study is the first part of a three-phase program aimed at characterizing the current-driven turbulent dissipation degrading the efficiency of Lorentz force plasma accelerators such as the MPD thruster. The analysis uses a kinetic theory that includes magnetic and thermal effects as well as those of an electron current transverse to the magnetic field and collisions, thus combining all the features of previous models. Analytical and numerical solutions allow a detailed description of threshold criteria, finite growth behavior, destabilization mechanisms and maximized-growth characteristics of the dominant unstable modes. The lower hybrid current-driven instability is implicated as dominant and was found to preserve its character in the collisional plasma regime.

  12. Theory of optical phase conjugation via four-wave mixing in laser plasmas

    SciTech Connect

    Lahiri, J.; Sinha, B.K.

    1995-05-01

    Theoretical studies of optical phase conjugation via four-wave mixing in a two-temperature laser produced carbon plasma are reported. Starting from Maxwell equations and using the theory of parametric decay instability, analytical expressions of the phase conjugate reflectivity for a steady-state probe have been obtained and numerically evaluated for the case of the laser plasma formed by irradiating a carbon slab target with a Nd:Glass laser operating at {lambda}{sub 0}=1.06 {mu}. The variation of reflectivity as a function of frequency and angular mismatch between the pump and probe waves has been considered. It is observed that the reflectivity peaks occur under the situation of resonance when the frequency mismatch equals the ion-acoustic frequency of the plasma. The detailed numerical results are graphically reported and discussed. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  13. COSMIC-RAY TRANSPORT THEORY IN PARTIALLY TURBULENT SPACE PLASMAS WITH COMPRESSIBLE MAGNETIC TURBULENCE

    SciTech Connect

    Casanova, S.; Schlickeiser, R.

    2012-02-01

    Recently, a new transport theory of cosmic rays in magnetized space plasmas extending the quasilinear approximation to the particle orbit has been developed for the case of an axisymmetric incompressible magnetic turbulence. Here, we generalize the approach to the important physical case of a compressible plasma. As previously obtained in the case of an incompressible plasma, we allow arbitrary gyrophase deviations from the unperturbed spiral orbits in the uniform magnetic field. For the case of quasi-stationary and spatially homogeneous magnetic turbulence we derive, in the small Larmor radius approximation, gyrophase-averaged cosmic-ray Fokker-Planck coefficients. Upper limits for the perpendicular and pitch-angle Fokker-Planck coefficients and for the perpendicular and parallel spatial diffusion coefficients are presented.

  14. Theory of type 3b solar radio bursts. [plasma interaction and electron beams

    NASA Technical Reports Server (NTRS)

    Smith, R. A.; Delanoee, J.

    1975-01-01

    During the initial space-time evolution of an electron beam injected into the corona, the strong beam-plasma interaction occurs at the head of the beam, leading to the amplification of a quasi-monochromatic large-amplitude plasma wave that stabilizes by trapping the beam particles. Oscillation of the trapped particles in the wave troughs amplifies sideband electrostatic waves. The sidebands and the main wave subsequently decay to observable transverse electromagnetic waves through the parametric decay instability. This process gives rise to the elementary striation bursts. Owing to velocity dispersion in the beam and the density gradient of the corona, the entire process may repeat at a finite number of discrete plasma levels, producing chains of elementary bursts. All the properties of the type IIIb bursts are accounted for in the context of the theory.

  15. Fully kinetic plasma-sheath theory for a cold-electron emitting surface

    NASA Astrophysics Data System (ADS)

    Ordonez, C. A.

    1992-04-01

    The fully kinetic, one-dimensional, plasma-sheath theory by Schwager and Birdsall [Phys. Fluids B 2, 1057 (1990)] is further developed. A cold-electron emitting surface is included and a three-dimensional plasma is considered. The sheath potential is not assumed to equal the floating potential so that the theory applies to a current-carrying sheath. Appropriate values are found for higher-order moments of the velocity distribution which depend on the three-dimensional velocity distribution width. Distribution functions in terms of energy and angle are derived. The (effective) temperature, the total energy flux, and the heat flux are evaluated in terms of exact analytic functions. The normalized magnitude of the floating potential for a deuterium plasma with equal ion and electron temperatures is calculated to be ψf=3.2 for δ=0 and ψf=1.8 for δ=0.75 where δ is the electron emission coefficient. The normalized magnitude of the sheath potential for the same plasma (with δ=0) is calculated to be ψs=3.9 for γ=0.02 and ψs=2.8 for γ=-0.02 where γ is the normalized current density. A self-consistent integral solution for the electrostatic potential profile within the sheath is derived.

  16. Neoclassical transport theory in a tokamak plasma with large spatial gradients

    SciTech Connect

    Chang, C.S.

    1996-12-31

    Usual neoclassical theories assumed that the spatical inhomogeneity of the plasma was weak. Specifically, this included the following two strong assumptions: banana width was negligible compared to the radial gradient scale length and variation of any physical quantity along the field line was small. This led to the simplification that the spatial inhomogeneity itself did not affect the fundamental transport processes. However, there have been many experimental suggestions that the spatial inhomogeneity may not be small. Firstly, both H-mode and ERS mode experiments have indicated that the finite banana width effect may be important to understand the plasma transport processes. Secondly, the RF and auxiliary heating processes may be sufficiently localized in space so that we may need to consider a strongly inhomogeneous heating effect along the field lines. In the present work we develop a modified neoclassical theory, in parallel with the old theories, which can include the finite banana width effect and the inhomogeneous heating effect. Several new and significant transport terms have been identified, which can play important roles in the understanding of the fundamental transport processes in a tokamak plasma.

  17. Kinetic Theory in Hot Plasmas and Neutral Gases Applications to the Computation of the transport coefficients

    SciTech Connect

    Bendib, A.

    2008-09-23

    The conference is devoted to the study of systems consisting of a large number of particles by using the kinetic theory. In a first part, we present a general overview of the kinetic theory. In particular, the role of the correlations between particles is shown and discussed through the main models reported in the literature. In a second part, we present three applications to the transport properties in plasmas and neutral gases. The first application is devoted to the transport in hot plasmas perturbed with respect to the global equilibrium. The quasi-static and collisionless distribution function and transport coefficients are established. The influence of relativistic effects is also discussed. The second application deals with strongly inhomogeneous magnetized plasmas. The transport coefficients of Braginskii are calculated numerically in the local and the weakly nonlocal approximations. New nonlocal transport coefficients are emphasized. Finally, we apply the kinetic theory to the neutral gases by calculating the semi-collisional dispersion relation of acoustic waves. In particular, the dispersion and the damping of these waves in rarefied gases are highlighted. The method used to solve the kinetic equations is compared with the conventional method of Chapman-Enskog.

  18. Theory and observations of Alfvén solitons in the finite beta magnetospheric plasma

    NASA Astrophysics Data System (ADS)

    Patel, V. L.; Dasgupta, Brahmananda

    1987-08-01

    A nonlinear Schrödinger equation which governs the nonlinear evolution of Alfvén wave in a hot, two-fluid plasma, is derived by using a modified version of reductive perturbation theory. The effect of coupling with the density fluctuation is taken into account in the calculation of nonlinear frequency shift. The theory is applied to explain recent observations of the solitary Alfvén waves in space plasma. For the observational analysis, an extensive search was conducted by analyzing magnetic field data from geostationary satellites GOES 2, 3, and 5 in the earth's magnetosphere at 6.6 earth radii. In data covering a period of August 1979-January 1984, we have found occurrence of 292 solitary wave events. Out of these events, 108 events are classified as Alfvénic solitons (perturbations perpendicular to the ambient field) and 184 mixed mode solitons (perturbations perpendicular and parallel to the ambient field.) No event for compressional mode soliton was found. We believe, this is the first time, such analysis and observations of solitary waves in space plasma have been performed. A statistical analysis has been carried out to compare the results of theory and observations. A range of unstable wave numbers has been determined for the Alfvénic soliton in the magnetosphere. Permanent address: Saha Institute of Nuclear Physics, 92 Acharya P.C. Road, Calcutta, 700009 India.

  19. Geomagnetic polarity epochs: Nunivak Island, Alaska

    USGS Publications Warehouse

    Cox, A.; Dalrymple, G.B.

    1967-01-01

    New paleomagnetic and potassium-argon dating measurements have been made of basalt flows from Nunivak Island, Alaska, with the following results. (1) The best estimate of the age of the Brunhes/Matuyama polarity epoch boundary is found to be 0.694 m.y. (2) The best estimate of the age of the Gauss/Gilbert boundary is 3.32 m.y. (3) Three normally magnetized flows with ages from 0.93 to 0.88 m.y. are in accord with previous estimates of the age and duration of the Jaramillo normal event. (4) One normally magnetized flow with an age of 1.65 ?? 0.09 m.y. supplies additional evidence for the Gilsa?? normal event. (5) Two new normal events are identified within the Gilbert reversed epoch, the "Cochiti normal event" with an age of 3.7 m.y. and the "Nunivak normal event" with an age of 4.1 m.y. ?? 1967.

  20. On the Threshold of the Reionization Epoch

    NASA Astrophysics Data System (ADS)

    Djorgovski, S. G.; Castro, S.; Stern, D.; Mahabal, A. A.

    2001-10-01

    Discovery of the cosmic reionization epoch would represent a significant milestone in cosmology. We present Keck spectroscopy of the quasar SDSS 1044-0125, at z=5.73. The spectrum shows a dramatic increase in the optical depth at observed wavelengths λ>~7550 Å, corresponding to zabs>~5.2. Only a few small, narrow transmission regions are present in the spectrum beyond that point and out to the redshifts where the quasar signal begins. We interpret this result as a signature of the trailing edge of the cosmic reionization epoch, which we estimate to occur around ~6 (as indeed confirmed by subsequent observations by Becker et al.) and extending down to z~5.2. This behavior is expected in the modern theoretical models of the reionization era, which predict a patchy and gradual onset of reionization. The remaining transmission windows we see may correspond to the individual reionization bubbles (Strömgren spheres) embedded in a still largely neutral intergalactic medium, intersected by the line of sight to the quasar. Future spectroscopic observations of quasars at comparable or larger redshifts will provide a more detailed insight into the structure and extent of the reionization era. Based on the observations obtained at the W. M. Keck Observatory, which is operated by the California Association for Research in Astronomy, a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration.

  1. Multi-Epoch XMM Observations of NGC4258

    NASA Technical Reports Server (NTRS)

    Greenhill, Lincoln J.

    2004-01-01

    The goal of this project was detection of variability in the X-ray absorption column of the AGN in NGC4258 through monitoring with the XMM satellite. We have accomplished this goal and submitted the results to ApJ for publication in a paper entitled, "X-ray Luminosity and Absorption Column Fluctuations in the H2O Maser Galaxy NGC4258 from Weeks to Years," by Fruscione, A., Greenhill, L.J., Filippedco, A.V., Moran, J.M., Hermstein, J.R., and Galle, E. We have received a favorable referee report and expect the article will appear in 2005. To complete the project, we reduced our four epochs of XMM data for NGC4258, one archival XMM observation, and all existing Chandra datasets for NGC4258 (with the latest calibration tables and a grid of corrections for pileup). Self-consistent reduction of all these data permitted detailed comparison that could not have been accomplished simply by taking published model fits that appear in the literature. To accumulate a broader monitoring record, we combined the Chandra and XMM results with those published for SAX and ASCA. We modeled the Chandra and XMM data self-consistently with partially absorbed, hard power-law, soft thermal plasmas, and soft power-law components. Over nine years, the photo-electric absorbing column exhibited a 40% drop between two ASCA epochs separated by 3 years and a 60% rise between two XMM epochs separated by just 5 months. In contract, uncorrelated factor of of 2-3 changes were seen in absorbed flux on te timescale of years, which suggests intrinsic variability of the central engine. The warped disk that is a known source of H2O maser emission in 4258 is believed to cross the line of sight to the central engine. We have proposed that the variations in absorbing column arise from inhomogeneities in the rotating disk, as they sweep across the line of sight. We estimate from the XMM data that the inhomogeneities are about 1E+15 cm in size at radii greater than 0.27 pc. This is consistent with the estimated

  2. The applications of Complexity Theory and Tsallis Non-extensive Statistics at Solar Plasma Dynamics

    NASA Astrophysics Data System (ADS)

    Pavlos, George

    2015-04-01

    As the solar plasma lives far from equilibrium it is an excellent laboratory for testing complexity theory and non-equilibrium statistical mechanics. In this study, we present the highlights of complexity theory and Tsallis non extensive statistical mechanics as concerns their applications at solar plasma dynamics, especially at sunspot, solar flare and solar wind phenomena. Generally, when a physical system is driven far from equilibrium states some novel characteristics can be observed related to the nonlinear character of dynamics. Generally, the nonlinearity in space plasma dynamics can generate intermittent turbulence with the typical characteristics of the anomalous diffusion process and strange topologies of stochastic space plasma fields (velocity and magnetic fields) caused by the strange dynamics and strange kinetics (Zaslavsky, 2002). In addition, according to Zelenyi and Milovanov (2004) the complex character of the space plasma system includes the existence of non-equilibrium (quasi)-stationary states (NESS) having the topology of a percolating fractal set. The stabilization of a system near the NESS is perceived as a transition into a turbulent state determined by self-organization processes. The long-range correlation effects manifest themselves as a strange non-Gaussian behavior of kinetic processes near the NESS plasma state. The complex character of space plasma can also be described by the non-extensive statistical thermodynamics pioneered by Tsallis, which offers a consistent and effective theoretical framework, based on a generalization of Boltzmann - Gibbs (BG) entropy, to describe far from equilibrium nonlinear complex dynamics (Tsallis, 2009). In a series of recent papers, the hypothesis of Tsallis non-extensive statistics in magnetosphere, sunspot dynamics, solar flares, solar wind and space plasma in general, was tested and verified (Karakatsanis et al., 2013; Pavlos et al., 2014; 2015). Our study includes the analysis of solar plasma time

  3. Into the Epoch of Galaxy Formation

    NASA Astrophysics Data System (ADS)

    2000-02-01

    Infrared VLT Observations Identify Hidden Galaxies in the Early Universe Working with the ESO Very Large Telescope (VLT) at the Paranal Observatory , a group of European astronomers [1] has just obtained one of the deepest looks into the distant Universe ever made by an optical telescope. These observations were carried out in the near-infrared spectral region and are part of an attempt to locate very distant galaxies that have so far escaped detection in the visual bands. The first results are very promising and some concentrations of galaxies at very large distances were uncovered. Some early galaxies may be in hiding Current theories hypothesize that more than 80% of all stars ever formed were assembled in galaxies during the latter half of the elapsed lifetime of the Universe, i.e., during the past 7-8 billion years. However, doubts have arisen about these ideas. There are now observational indications that a significant number of those galaxies that formed during the first 20% of the age of the Universe, i.e. within about 3 billion years after the Big Bang, may not be visible to optical telescopes. In some cases, we do not see them, because their light is obscured by dust. Other distant galaxies may escape detection by optical telescopes because star formation in them has ceased and their light is mainly emitted in the red and infrared spectral bands. This is because, while very young galaxies mostly contain hot and blue stars, older galaxies have substantial numbers of cool and red stars. They are then dominated by an older, "evolved" stellar population that is cooler and redder. The large cosmic velocities of these galaxies further enhance this effect by causing their light to be "redshifted" towards longer wavelengths, i.e. into the near-infrared spectral region. Observations in the infrared needed Within the present programme, long exposures in near-infrared wavebands were made with the Infrared Spectrometer And Array Camera (ISAAC) , mounted on ANTU , the

  4. Derivations and Comparisons of Three Groups ofSelf-Organization Theories for Magnetohydrodynamic Plasmas

    NASA Astrophysics Data System (ADS)

    Kondoh, Yoshiomi; Sato, Tetsuya

    1994-04-01

    A theoretical investigation on self-organization theories ofdissipative MHD plasmas is presented to derive three groups oftheories that lead to the same relaxed state of ∇ × B=λ B, in order to find more essential physicalpicture embedded in self-organization phenomena due to nonlinear anddissipative processes. Comparisons among all of the theories treatedand derived here suggest that a theory standing upon spectrumspreadings and selective dissipations of eigenmodes for thedissipative operator -∇ ×η j and leading toself-organized relaxed states of ∇ ×ηj=α B/2 with the minimum dissipation rate is the most agreeable to various results obtained by experiments and by 3-D MHD simulations reported so far.

  5. Hydrogen Epoch of Reionization Array (HERA)

    NASA Astrophysics Data System (ADS)

    DeBoer, David R.; HERA

    2015-01-01

    The Hydrogen Epoch of Reionization Arrays (HERA - reionization.org) roadmap uses the unique properties of the neutral hydrogen (HI) 21cm line to probe our cosmic dawn: from the birth of the first stars and black holes, through the full reionization of the primordial intergalactic medium (IGM). HERA is a collaboration between the Precision Array Probing the Epoch of Reionization (PAPER - eor.berkeley.edu), the US-based Murchison Widefield Array (MWA - mwatelescope.org), and MIT Epoch of Reionization (MITEOR) teams along with the South African SKA-SA, University of KwaZulu Natal and the University of Cambridge Cavendish Laborabory. HERA has recently been awarded a National Science Foundation Mid-Scale Innovation Program grant to begin the next phase.HERA leverages the operation of the PAPER and MWA telescopes to explore techniques and designs required to detect the primordial HI signal in the presence of systematics and radio continuum foreground emission some four orders of magnitude brighter. With this understanding, we are now able to remove foregrounds to the limits of our sensitivity, culminating in the first physically meaningful upper limits. A redundant calibration algorithm from MITEOR improves the sensitivity of the approach.Building on this, the next stage of HERA incorporates a 14m diameter antenna element that is optimized both for sensitivity and for minimizing foreground systematics. Arranging these elements in a compact hexagonal grid yields an array that facilitates calibration, leverages proven foreground removal techniques, and is scalable to large collecting areas. HERA will be located in the radio quiet environment of the SKA site in the Karoo region of South Africa (where PAPER is currently located). It will have a sensitivity close to two orders of magnitude better than PAPER and the MWA to ensure a robust detection. With its sensitivity and broader frequency coverage, HERA can paint an uninterrupted picture through reionization, back to the

  6. KINETIC THEORY OF EQUILIBRIUM AXISYMMETRIC COLLISIONLESS PLASMAS IN OFF-EQUATORIAL TORI AROUND COMPACT OBJECTS

    SciTech Connect

    Cremaschini, Claudio; Kovář, Jiří; Slaný, Petr; Stuchlík, Zdeněk; Karas, Vladimír

    2013-11-01

    The possible occurrence of equilibrium off-equatorial tori in the gravitational and electromagnetic fields of astrophysical compact objects has been recently proved based on non-ideal magnetohydrodynamic theory. These stationary structures can represent plausible candidates for the modeling of coronal plasmas expected to arise in association with accretion disks. However, accretion disk coronae are formed by a highly diluted environment, and so the fluid description may be inappropriate. The question is posed of whether similar off-equatorial solutions can also be determined in the case of collisionless plasmas for which treatment based on kinetic theory, rather than a fluid one, is demanded. In this paper the issue is addressed in the framework of the Vlasov-Maxwell description for non-relativistic, multi-species axisymmetric plasmas subject to an external dominant spherical gravitational and dipolar magnetic field. Equilibrium configurations are investigated and explicit solutions for the species kinetic distribution function are constructed, which are expressed in terms of generalized Maxwellian functions characterized by isotropic temperature and non-uniform fluid fields. The conditions for the existence of off-equatorial tori are investigated. It is proved that these levitating systems are admitted under general conditions when both gravitational and magnetic fields contribute to shaping the spatial profiles of equilibrium plasma fluid fields. Then, specifically, kinetic effects carried by the equilibrium solution are explicitly provided and identified here with diamagnetic energy-correction and electrostatic contributions. It is shown that these kinetic terms characterize the plasma equation of state by introducing non-vanishing deviations from the assumption of thermal pressure.

  7. Kinetic theory of quasi-stationary collisionless axisymmetric plasmas in the presence of strong rotation phenomena

    SciTech Connect

    Cremaschini, Claudio; Stuchlík, Zdeněk; Tessarotto, Massimo

    2013-05-15

    The problem of formulating a kinetic treatment for quasi-stationary collisionless plasmas in axisymmetric systems subject to the possibly independent presence of local strong velocity-shear and supersonic rotation velocities is posed. The theory is developed in the framework of the Vlasov-Maxwell description for multi-species non-relativistic plasmas. Applications to astrophysical accretion discs arising around compact objects and to plasmas in laboratory devices are considered. Explicit solutions for the equilibrium kinetic distribution function (KDF) are constructed based on the identification of the relevant particle adiabatic invariants. These are shown to be expressed in terms of generalized non-isotropic Gaussian distributions. A suitable perturbative theory is then developed which allows for the treatment of non-uniform strong velocity-shear/supersonic plasmas. This yields a series representation for the equilibrium KDF in which the leading-order term depends on both a finite set of fluid fields as well as on the gradients of an appropriate rotational frequency. Constitutive equations for the fluid number density, flow velocity, and pressure tensor are explicitly calculated. As a notable outcome, the discovery of a new mechanism for generating temperature and pressure anisotropies is pointed out, which represents a characteristic feature of plasmas considered here. This is shown to arise as a consequence of the canonical momentum conservation and to contribute to the occurrence of temperature anisotropy in combination with the adiabatic conservation of the particle magnetic moment. The physical relevance of the result and the implications of the kinetic solution for the self-generation of quasi-stationary electrostatic and magnetic fields through a kinetic dynamo are discussed.

  8. Unification of Plasma Fluid and Kinetic Theory via Gaussian Radial Basis Functions

    NASA Astrophysics Data System (ADS)

    Candy, J. M.

    2015-11-01

    A fundamental macroscopic description of a magnetized plasma is the Vlasov equation supplemented by the nonlinear inverse-square force Fokker-Planck collision operator [Rosenbluth et al., Phys. Rev. 107, 1957]. The Vlasov part describes advection in a six-dimensional phase space whereas the collision operator contains friction and diffusion coefficients that are weighted velocity-space integrals of the particle distribution function. The Fokker-Planck collision operator is an integro-differential, nonlinear (bilinear) operator. Numerical discretization of the operator, in particular for collisions of unlike species, is extremely challenging. In this work, we describe a new approach to discretize the entire kinetic system based on an expansion in Gaussian Radial Basis functions (RBFs). This approach is particularly well-suited to treat the collision operator because the friction and diffusion coefficients can be analytically calculated. Although the RBF method is known to be a powerful scheme for the interpolation of scattered multidimensional data, Gaussian RBFs also have a deep physical interpretation in statistical mechanics and plasma physics as local thermodynamic equilibria. We outline the general theory, highlight the connection to plasma fluid theories, and also give 2D and 3D numerical solutions of the nonlinear Fokker-Planck equation. A broad spectrum of applications for the new method is anticipated in both astrophysical and laboratory plasmas. In particular, we believe that the RBF method may provide a new bridge between fluid and kinetic descriptions of magnetized plasma. Work supported in part by US DOE under DE-FG02-08ER54963.

  9. PREFACE: Theory of Fusion Plasmas, 13th Joint Varenna-Lausanne International Workshop (2012)

    NASA Astrophysics Data System (ADS)

    Garbet, Xavier; Sauter, Olivier

    2012-12-01

    The 2012 joint Varenna-Lausanne international workshop on the theory of fusion plasmas has been very fruitful. A broad variety of topics were addressed, as usual covering turbulence, MHD, edge physic, RF wave heating and a taste of astrophysics. Moreover the scope of the meeting was extended this year to include the physics of materials and diagnostics for burning plasmas. This evolution reflects the complexity of problems at hand in fusion, in particular in the context of ITER construction. Long-standing problems without immediate consequences have sometimes become an urgent matter in that context. One may quote for instance the choice of plasma facing components or the design of control systems. Another characteristic of the meeting is the interplay between various domains of plasma physics. For instance MHD modes are now currently investigated with gyrokinetic codes, kinetic effects are more and more included in MHD stability analysis, and turbulence is now accounted for in wave propagation problems. This is the proof of cross-fertilization and it is certainly a healthy sign in our community. Finally introducing some novelty in the programme does not prevent us from respecting the traditions of the meeting. As usual a good deal of the presentations were dedicated to numerical simulations. Combining advanced numerical techniques with elaborated analytical theory is certainly a trademark of the Varenna-Lausanne conference, which was respected again this year. The quality and size of the scientific production is illustrated by the 26 papers which appear in the present volume of Journal of Physics: Conference Series, all refereed. We would also like to mention another set of 20 papers to be published in Plasma Physics and Controlled Fusion. We hope the readers will enjoy this special issue of JPCS and the one to come in PPCF. Xavier Garbet and Olivier Sauter October 26, 2012

  10. Non-linear theory of a cavitated plasma wake in a plasma channel for special applications and control

    NASA Astrophysics Data System (ADS)

    Thomas, Johannes; Kostyukov, Igor Yu.; Pronold, Jari; Golovanov, Anton; Pukhov, Alexander

    2016-05-01

    We introduce a complete semi-analytical model for a cavitated electron wake driven by an electron beam in a radially inhomogeneous plasma. The electron response to the driver, dynamics of electrons in a thin sheath surrounding the cavity, as well as accelerating and focusing fields inside the cavity are calculated in the quasistatic approximation. Our theory holds for arbitrary radial density profiles and reduces to known models in the limit of a homogeneous plasma. A free-propagating blow-out in an evacuated channel experiences longitudinal squeezing, qualitatively the same as observed in particle-in-cell simulations for the laser pulse-driven case [Pukhov et al., Phys. Rev. Lett. 113, 245003 (2014)]. Our model also permits qualitative interpretation of the earlier observed cancellation of the focusing gradient in the cavity [Pukhov et al., Phys. Rev. Lett. 113, 245003 (2014)]. In this work, we show the underlying mechanism that causes the radial fields in the vacuum part of a channel to become defocussing.

  11. LEDDB: LOFAR Epoch of Reionization Diagnostic Database

    NASA Astrophysics Data System (ADS)

    Martinez-Rubi, O.; Veligatla, V. K.; de Bruyn, A. G.; Lampropoulos, P.; Offringa, A. R.; Jelic, V.; Yatawatta, S.; Koopmans, L. V. E.; Zaroubi, S.

    2013-10-01

    One of the key science projects of the Low-Frequency Array (LOFAR) is the detection of the cosmological signal coming from the Epoch of Reionization (EoR). Here we present the LOFAR EoR Diagnostic Database (LEDDB) that is used in the storage, management, processing and analysis of the LOFAR EoR observations. It stores referencing information of the observations and diagnostic parameters extracted from their calibration. These stored data are used to ease the pipeline processing, monitor the performance of the telescope, and visualize the diagnostic parameters which facilitates the analysis of the several contamination effects on the signals. It is implemented with PostgreSQL and accessed through the psycopg2 Python module. We have developed a very flexible query engine, which is used by a web user interface to access the database, and a very extensive set of tools for the visualization of the diagnostic parameters through all their multiple dimensions.

  12. Modeling the Extragalactic Epoch of Reionization Foreground

    NASA Astrophysics Data System (ADS)

    Carroll, Patricia A.

    The Epoch of Reionization represents a largely unexplored yet fundamental chapter of the early universe. During this period, spanning several hundred million years, the first stars and galaxies formed and the Hydrogen-dominated intergalactic medium transitioned from a predominantly neutral to ionized state. Modern efforts to study exactly when and how reionization occurred are largely focused on the distribution of neutral Hydrogen gas and its evolution in response to the increasing abundance of luminous objects and ionizing flux. The Murchison Widefield Array is a low frequency radio interferometer designed as a first generation EoR experiment. The predominant systematic difficulty in making a detection of the primordial HI signal is the overwhelmingly bright emission from the intervening foreground galaxies and quasars. This thesis presents novel survey methods used to create a highly precise and reliable catalog of discrete extragalactic sources for the purposes of both calibration and foreground removal.

  13. Orion: The Final Epoch (OrionTFE)

    NASA Astrophysics Data System (ADS)

    Megeath, Tom; Allen, Tom; Arce, Hector; Booker, Joseph; Calvet, Nuria; Flaherty, Kevin; Furlan, Elise; Fischer, Will; Gonzales, Beatriz; Gutermuth, Rob; Hartman, Lee; Henning, Thomas; Hora, Joe; Karnath, Nicole; Kim, Kyoung Hee; Kounkel, Marina; Mazur, Brian; Offner, Stella; Osorio, Mayra; Pillitteri, Ignazio; Pipher, Judy; Prchlik, Jakub; Rebull, Luisa; Terebey, Susan; Tobin, John; Stanke, Thomas; Stutz, Amelia; Watson, Dan; Wolk, Scott

    2016-08-01

    The Orion molecular clouds are an essential laboratory for studying low mass star formation over the broad range of environments in which they form. Starting with the Spitzer survey of Orion in 2004, more than a decade of observations with Spitzer, WISE, HST and Herschel, have accumulated an unparalleled characterization of the young stellar object population in Orion. We propose a final epoch of observations divided into two separate, complementary observations: A repeat of the entire Orion molecular cloud survey to 1.) identify ejected stars from clusters, 2.) measure the bulk proper motions of groups and clusters of stars, 3.) constrain the rate of luminous, accretion driven outbursts from both protostars and pre-main sequence stars with disks and 4.) use proper motions of IR Herbig-Haro knots as a fossil record of previous accretion events. A high cadence variability survey of the L1641 cloud extending the YSOVAR variability survey of the Orion Nebula Cluster across the Orion A cloud with the goals of 1.) constraining the star formation history of Orion A, 2.) studying the evolution of mid-IR variability from the protostellar to pre-main sequence phase, 3.) searching for periodicities in (nearly) edge-on protostars and disks due to orbiting clumps and structures from orbiting planets, and 4.) assessing whether inner disk processes - as traced by variability - are affected by their birth environment. This program completes an unparalleled, > 12 year multi-epoch, mid-IR study of the nearest large molecular cloud complex with both a wide spatial coverage and a uniformity that will not be exceeded in the forseeable future. It will place unique constraints on the highly dynamic processes that control low mass star formation, serve as a pathfinder to molecular cloud surveys of WFIRST, and provide well characterized targets needed to study mass accretion and planet formation around young low mass stars with SOFIA and JWST.

  14. Towards a Lunar Epoch of Reionization Telescope

    NASA Astrophysics Data System (ADS)

    Jones, Dayton L.; Lazio, J.; MacDowall, R.; Weiler, K.; Burns, J.

    2007-05-01

    Low-frequency radio astronomy is recognized as one of the few areas of astronomy that would clearly benefit from lunar basing. This is particularly true for locations on the far side of the Moon, a unique location because it provides simultaneous shielding from terrestrial interference and from strong solar radio bursts (half of the time). All lunar based instruments are also free of the serious effects of Earth's ionosphere, which is opaque at frequencies below 20-30 MHz and introduces large phase errors below 100 MHz. As a first step, a relatively small radio array on the near side of the Moon (ROLSS, the Radio Observatory for Lunar Sortie Science) has been proposed to NASA's Lunar Sortie Science Opportunity program. ROLSS will be able to image radio emission from coronal mass ejections (type II radio bursts) and fast electron streams (type III bursts), and will also produce the first high-resolution images of the sky at low frequencies. It is possible that solar observations below a few MHz may be limited by the transient lunar ionosphere; a simple experiments to monitor the lunar ionosphere with riometry (LAPS, the Lunar Array Precursor Station), has also been proposed to the Lunar Sortie Science program. Finally, the lunar far side is the best location for large radio arrays designed to produce the highest quality images of redshifted neutral Hydrogen before and during the epoch of reionization. This is an area of fundamental importance, and will require a large number of array antenna elements. One concept for this far-future array is MERIT, the Moon-based Epoch of Reionization Imaging Telescope), which is partly based on technologies to be demonstrated by ROLSS. This work has been carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

  15. The applications of Complexity Theory and Tsallis Non-extensive Statistics at Solar Plasma Dynamics

    NASA Astrophysics Data System (ADS)

    Pavlos, George

    2015-04-01

    As the solar plasma lives far from equilibrium it is an excellent laboratory for testing complexity theory and non-equilibrium statistical mechanics. In this study, we present the highlights of complexity theory and Tsallis non extensive statistical mechanics as concerns their applications at solar plasma dynamics, especially at sunspot, solar flare and solar wind phenomena. Generally, when a physical system is driven far from equilibrium states some novel characteristics can be observed related to the nonlinear character of dynamics. Generally, the nonlinearity in space plasma dynamics can generate intermittent turbulence with the typical characteristics of the anomalous diffusion process and strange topologies of stochastic space plasma fields (velocity and magnetic fields) caused by the strange dynamics and strange kinetics (Zaslavsky, 2002). In addition, according to Zelenyi and Milovanov (2004) the complex character of the space plasma system includes the existence of non-equilibrium (quasi)-stationary states (NESS) having the topology of a percolating fractal set. The stabilization of a system near the NESS is perceived as a transition into a turbulent state determined by self-organization processes. The long-range correlation effects manifest themselves as a strange non-Gaussian behavior of kinetic processes near the NESS plasma state. The complex character of space plasma can also be described by the non-extensive statistical thermodynamics pioneered by Tsallis, which offers a consistent and effective theoretical framework, based on a generalization of Boltzmann - Gibbs (BG) entropy, to describe far from equilibrium nonlinear complex dynamics (Tsallis, 2009). In a series of recent papers, the hypothesis of Tsallis non-extensive statistics in magnetosphere, sunspot dynamics, solar flares, solar wind and space plasma in general, was tested and verified (Karakatsanis et al., 2013; Pavlos et al., 2014; 2015). Our study includes the analysis of solar plasma time

  16. Theory of the plasma thruster based on the rotating electromagnetic field

    NASA Astrophysics Data System (ADS)

    Kolesnichenko, Ya. I.; Lutsenko, V. V.; Rudenko, T. S.

    2015-04-01

    A theory of electrodeless electric propulsion systems (EEPS) based on the use of the solenoid magnetic field and the rotating electromagnetic field produced by antennas is developed, which includes a study of the plasma acceleration by the Radio Frequency (RF) field and the concomitant thrust. It was assumed that the frequency of the RF field exceeds the lower hybrid frequency but is much less than the electron gyrofrequency. Relations for the thrust are obtained and analyzed. It is shown that thrust gain is significant only when the RF-induced drift velocity well exceeds the fluid velocity of the injected plasma. It is revealed that the curvature of the magnetic field lines and the plasma acceleration in the region outside the solenoid are the factors which can considerably increase the thrust. On the other hand, it is found that the axial inhomogeneity of the plasma and some other factors are unfavorable for the thrust. The obtained results can be used for the optimization of particular experiments aimed to create a new thruster for long-time space missions.

  17. Gyrotropic guiding-center fluid theory for turbulent inhomogeneous magnetized plasma

    SciTech Connect

    Jasperse, John R.; Basu, Bamandas; Lund, Eric J.; Bouhram, Mehdi

    2006-07-15

    In this paper, a new fluid theory is given in the guiding-center and gyrotropic approximation which is derivable from the Vlasov-Maxwell equations. The theory includes the effect of wave-particle interactions for the weakly turbulent, weakly inhomogeneous, nonuniformly magnetized plasma, and it is applicable to a variety of space and laboratory plasmas. It is assumed that the turbulence is random and electrostatic, and that the velocity-space Fokker-Planck operator can be used to calculate the correlation functions that describe the wave-particle interactions. Conservation laws are derived that relate the low-order velocity moments of the particle distributions to the turbulence. The theory is based on the work of Hubbard [Proc. R. Soc. London, Ser. A 260, 114 (1961)] and Ichimaru and Rosenbluth [Phys. Fluids 13, 2778 (1970)]. In the work presented here, the idea is proposed that the fluid equations can be solved (1) by using measurements of the turbulence to specify the electric-field fluctuations; and (2) by using measurements of the low-order velocity moments to specify the initial and boundary conditions.

  18. Introduction to Gyrokinetic Theory with Applications in Magnetic Confinement Research in Plasma Physics

    SciTech Connect

    W.M. Tang

    2005-01-03

    The present lecture provides an introduction to the subject of gyrokinetic theory with applications in the area of magnetic confinement research in plasma physics--the research arena from which this formalism was originally developed. It was presented as a component of the ''Short Course in Kinetic Theory within the Thematic Program in Partial Differential Equations'' held at the Fields Institute for Research in Mathematical Science (24 March 2004). This lecture also discusses the connection between the gyrokinetic formalism and powerful modern numerical simulations. Indeed, simulation, which provides a natural bridge between theory and experiment, is an essential modern tool for understanding complex plasma behavior. Progress has been stimulated in particular by the exponential growth of computer speed along with significant improvements in computer technology. The advances in both particle and fluid simulations of fine-scale turbulence and large-scale dynamics have produced increasingly good agreement between experimental observations and computational modeling. This was enabled by two key factors: (i) innovative advances in analytic and computational methods for developing reduced descriptions of physics phenomena spanning widely disparate temporal and spatial scales and (ii) access to powerful new computational resources.

  19. Nonlinear theory of ion-acoustic waves in an electron-positron-ion plasma

    SciTech Connect

    Dubinov, A. E.; Sazonkin, M. A.

    2009-01-15

    An analytical nonlinear gasdynamic theory of ion-acoustic waves in an e-p-i plasma is developed for the case in which all the plasma components in the wave undergo polytropic compression and rarefaction. An exact solution to the basic equations is found and analyzed by the Bernoulli pseudopotential method. The parameter range in which periodic waves can propagate and the range in which solitary waves (solitons) exist are determined. It is shown that the propagation velocity of a solitary is always higher than the linear ion sound velocity. The profiles of all the physical quantities in both subsonic and supersonic waves are calculated. The results obtained agree well with both the data from other papers and particular limiting cases.

  20. Ionic and electronic transport properties in dense plasmas by orbital-free density functional theory.

    PubMed

    Sjostrom, Travis; Daligault, Jérôme

    2015-12-01

    We validate the application of our recent orbital-free density functional theory (DFT) approach [Phys. Rev. Lett. 113, 155006 (2014);] for the calculation of ionic and electronic transport properties of dense plasmas. To this end, we calculate the self-diffusion coefficient, the viscosity coefficient, the electrical and thermal conductivities, and the reflectivity coefficient of hydrogen and aluminum plasmas. Very good agreement is found with orbital-based Kohn-Sham DFT calculations at lower temperatures. Because the computational costs of the method do not increase with temperature, we can produce results at much higher temperatures than is accessible by the Kohn-Sham method. Our results for warm dense aluminum at solid density are inconsistent with the recent experimental results reported by Sperling et al. [Phys. Rev. Lett. 115, 115001 (2015)]. PMID:26764850

  1. Ionic and electronic transport properties in dense plasmas by orbital-free density functional theory

    NASA Astrophysics Data System (ADS)

    Sjostrom, Travis; Daligault, Jérôme

    2015-12-01

    We validate the application of our recent orbital-free density functional theory (DFT) approach [Phys. Rev. Lett. 113, 155006 (2014), 10.1103/PhysRevLett.113.155006;] for the calculation of ionic and electronic transport properties of dense plasmas. To this end, we calculate the self-diffusion coefficient, the viscosity coefficient, the electrical and thermal conductivities, and the reflectivity coefficient of hydrogen and aluminum plasmas. Very good agreement is found with orbital-based Kohn-Sham DFT calculations at lower temperatures. Because the computational costs of the method do not increase with temperature, we can produce results at much higher temperatures than is accessible by the Kohn-Sham method. Our results for warm dense aluminum at solid density are inconsistent with the recent experimental results reported by Sperling et al. [Phys. Rev. Lett. 115, 115001 (2015), 10.1103/PhysRevLett.115.115001].

  2. Kinetic theory of the filamentation instability in a collisional current-driven plasma with nonextensive distribution

    SciTech Connect

    Khorashadizadeh, S. M. Rastbood, E.; Niknam, A. R.

    2015-07-15

    The evolution of filamentation instability in a weakly ionized current-carrying plasma with nonextensive distribution was studied in the diffusion frequency region, taking into account the effects of electron-neutral collisions. Using the kinetic theory, Lorentz transformation formulas, and Bhatnagar-Gross-Krook collision model, the generalized dielectric permittivity functions of this plasma system were achieved. By obtaining the dispersion relation of low-frequency waves, the possibility of filamentation instability and its growth rate were investigated. It was shown that collisions can increase the maximum growth rate of instability. The analysis of temporal evolution of filamentation instability revealed that the growth rate of instability increased by increasing the q-parameter and electron drift velocity. Finally, the results of Maxwellian and q-nonextensive velocity distributions were compared and discussed.

  3. A theory of two-beam acceleration of charged particles in a plasma waveguide

    SciTech Connect

    Ostrovsky, A.O.

    1993-11-01

    The progress made in recent years in the field of high-current relativistic electron beam (REB) generation has aroused a considerable interest in studying REB potentialities for charged particle acceleration with a high acceleration rate T = 100MeV/m. It was proposed, in particular, to employ high-current REB in two-beam acceleration schemes (TBA). In these schemes high current REB (driving beam) excites intense electromagnetic waves in the electrodynamic structure which, in their turn, accelerate particles of the other beam (driven beam). The TBA schemes can be divided into two groups. The first group includes the schemes, where the two beams (driving and driven) propagate in different electrodynamic structures coupled with each other through the waveguides which ensure the microwave power transmission to accelerate driven beam particles. The second group includes the TBA schemes, where the driving and driven beams propagate in one electrodynamic structure. The main aim of this work is to demonstrate by theory the possibility of realizing effectively the TBA scheme in the plasma waveguide. The physical model of the TBA scheme under study is formulated. A set of equations describing the excitation of RF fields by a high-current REB and the acceleration of driven beam electrons is also derived. Results are presented on the the linear theory of plasma wave amplification by the driving beam. The range of system parameters, at which the plasma-beam instability develops, is defined. Results of numerical simulation of the TBA scheme under study are also presented. The same section gives the description of the dynamics of accelerated particle bunching in the high-current REB-excited field. Estimates are given for the accelerating field intensities in the plasma and electron acceleration rates.

  4. Theory of Collisional Two-Stream Plasma Instabilities in the Solar Chromosphere

    NASA Astrophysics Data System (ADS)

    Madsen, Chad Allen; Dimant, Yakov; Oppenheim, Meers; Fontenla, Juan

    2014-06-01

    The solar chromosphere experiences intense heating just above its temperature minimum. The heating increases the electron temperature in this region by over 2000 K. Furthermore, it exhibits little time variation and appears widespread across the solar disk. Although semi-empirical models, UV continuum observations, and line emission measurements confirm the existence of the heating, its source remains unexplained. Potential heating sources such as acoustic shocks, resistive dissipation, and magnetic reconnection via nanoflares fail to account for the intensity, persistence, and ubiquity of the heating. Fontenla (2005) suggested turbulence from a collisional two-stream plasma instability known as the Farley-Buneman instability (FBI) could contribute significantly to the heating. This instability is known to heat the plasma of the E-region ionosphere which bears many similarities to the chromospheric plasma. However, the ionospheric theory of the FBI does not account for the diverse ion species found in the solar chromosphere. This work develops a new collisional, two-stream instability theory appropriate for the chromospheric plasma environment using a linear fluid analysis to derive a new dispersion relationship and critical E x B drift velocity required to trigger the instability. Using a 1D, non-local thermodynamic equilibrium, radiative transfer model and careful estimates of collision rates and magnetic field strengths, we calculate the trigger velocities necessary to induce the instability throughout the chromosphere. Trigger velocities as low as 4 km s^-1 are found near the temperature minimum, well below the local neutral acoustic speed in that region. From this, we expect the instability to occur frequently, converting kinetic energy contained in neutral convective flows from the photosphere into thermal energy via turbulence. This could contribute significantly to chromospheric heating and explain its persistent and ubiquitous nature.

  5. Linearized kinetic theory of spin-1/2 particles in magnetized plasmas

    SciTech Connect

    Lundin, J.; Brodin, G.

    2010-11-15

    We have considered linear kinetic theory, including the electron-spin properties in a magnetized plasma. The starting point is a mean-field Vlasov-like equation, derived from a fully quantum-mechanical treatment, where effects from the electron-spin precession and the magnetic dipole force are taken into account. The general conductivity tensor is derived, including both the free current contribution and the magnetization current associated with the spin contribution. We conclude the paper with an extensive discussion of the quantum-mechanical boundary where we list parameter conditions that must be satisfied for various quantum effects to be influential.

  6. Higher-order paraxial theory of the propagation of ring rippled laser beam in plasma: Relativistic ponderomotive regime

    SciTech Connect

    Purohit, Gunjan Rawat, Priyanka; Chauhan, Prashant; Mahmoud, Saleh T.

    2015-05-15

    This article presents higher-order paraxial theory (non-paraxial theory) for the ring ripple formation on an intense Gaussian laser beam and its propagation in plasma, taking into account the relativistic-ponderomotive nonlinearity. The intensity dependent dielectric constant of the plasma has been determined for the main laser beam and ring ripple superimposed on the main laser beam. The dielectric constant of the plasma is modified due to the contribution of the electric field vector of ring ripple. Nonlinear differential equations have been formulated to examine the growth of ring ripple in plasma, self focusing of main laser beam, and ring rippled laser beam in plasma using higher-order paraxial theory. These equations have been solved numerically for different laser intensities and plasma frequencies. The well established experimental laser and plasma parameters are used in numerical calculation. It is observed that the focusing of the laser beams (main and ring rippled) becomes fast in the nonparaxial region by expanding the eikonal and other relevant quantities up to the fourth power of r. The splitted profile of laser beam in the plasma is observed due to uneven focusing/defocusing of the axial and off-axial rays. The growths of ring ripple increase when the laser beam intensity increases. Furthermore, the intensity profile of ring rippled laser beam gets modified due to the contribution of growth rate.

  7. Molecular hydrogen in the cosmic recombination epoch

    SciTech Connect

    Alizadeh, Esfandiar; Hirata, Christopher M.

    2011-10-15

    The advent of precise measurements of the CMB anisotropies has motivated correspondingly precise calculations of the cosmic recombination history. Cosmic recombination proceeds far out of equilibrium because of a ''bottleneck'' at the n=2 level of hydrogen: atoms can only reach the ground state via slow processes--two-photon decay or Lyman-{alpha} resonance escape. However, even a small primordial abundance of molecules could have a large effect on the interline opacity in the recombination epoch and lead to an additional route for hydrogen recombination. Therefore, this paper computes the abundance of the H{sub 2} molecule during the cosmic recombination epoch. Hydrogen molecules in the ground electronic levels X{sup 1}{Sigma}{sub g}{sup +} can either form from the excited H{sub 2} electronic levels B{sup 1}{Sigma}{sub u}{sup +} and C{sup 1}{Pi}{sub u} or through the charged particles H{sub 2}{sup +}, HeH{sup +}, and H{sup -}. We follow the transitions among all of these species, resolving the rotational and vibrational sublevels. Since the energies of the X{sup 1}{Sigma}{sub g}{sup +}-B{sup 1}{Sigma}{sub u}{sup +} (Lyman band) and X{sup 1}{Sigma}{sub g}{sup +}-C{sup 1}{Pi}{sub u} (Werner band) transitions are near the Lyman-{alpha} energy, the distortion of the CMB spectrum caused by escaped H Lyman-line photons accelerates both the formation and the destruction of H{sub 2} due to this channel relative to the thermal rates. This causes the populations of H{sub 2} molecules in X{sup 1}{Sigma}{sub g}{sup +} energy levels to deviate from their thermal equilibrium abundances. We find that the resulting H{sub 2} abundance is 10{sup -17} at z=1200 and 10{sup -13} at z=800, which is too small to have any significant influence on the recombination history.

  8. Theory Issues for Induced Plasma Convection Experiments in the Divertor of the MAST Spherical Tokamak

    SciTech Connect

    Cohen, R H; Fielding, S; Helander, P; Ryutov, D D

    2001-09-05

    This paper surveys theory issues associated with inducing convective cells through divertor tile biasing in a tokamak to broaden the scrape-off layer (SOL). The theory is applied to the Mega-Ampere Spherical Tokamak (MAST), where such experiments are planned in the near future. Criteria are presented for achieving strong broadening and for exciting shear-flow turbulence in the SOL; these criteria are shown to be attainable in practice. It is also shown that the magnetic shear present in the vicinity of the X-point is likely to confine the potential perturbations to the divertor region below the X-point, leaving the part of the SOL that is in direct contact with the core plasma intact. The current created by the biasing and the associated heating power are found to be modest.

  9. Theory of waves in pair-ion plasmas: Natural explanation of backward modes

    SciTech Connect

    Kono, M.; Vranjes, J.; Batool, N.

    2013-12-15

    Backward waves observed in the experiments by Oohara and Hatakeyama (Phys. Rev. Lett. 91, 205005 (2003)) are identified to be ion cyclotron harmonic waves inherent to the kinetic theory. The derived dispersion equation is based on exact solutions of the characteristic equations of the Vlasov equation in a bounded cylindrical coordinate system; it is different from its counterpart in unbounded plasmas, and it provides all the branches of the dispersion relations observed in the experiment. Positive and negative ions respond to a potential in the same time scale and cooperate to expose kinetic orbital behaviors to the macroscopic propagation characteristics. In addition, the experimental setting of the large Larmor radius makes higher harmonic ion cyclotron backward/forward waves observable. The large Larmor radius effects are naturally treated by a kinetic theory.

  10. Theory for large-amplitude electrostatic ion shocks in quantum plasmas.

    PubMed

    Akbari-Moghanjoughi, M; Shukla, P K

    2012-12-01

    We present a generalized nonlinear theory for large-amplitude electrostatic (ES) ion shocks in collisional quantum plasmas composed of mildly coupled degenerate electron fluid of arbitrary degeneracy and nondegenerate strongly correlated ion fluid with arbitrary atomic number. For our purposes, we use the inertialess electron momentum equation including the electrostatic force, pressure gradient, and relevant quantum forces, as well as a generalized viscoelastic ion momentum (GVIM) equation for strongly correlated nondegenerate ions. The ion continuity equation, in the quasineutral approximation, then closes our nonlinear system of equations. When the electric field force is eliminated from the GVIM equation by using the inertialess electron momentum equation, we then obtain a GVIM and ion continuity equations, which exhibit nonlinear couplings between the ion number density and the ion fluid velocity. The pair of nonlinear equations is numerically solved to study the dynamics of arbitrarily-large-amplitude planar and nonplanar ES shocks arising from a balance between harmonic generation nonlinearities and the ion fluid viscosity for a wide range of plasma mass densities and ion atomic numbers that are relevant for the cores of giant planets (viz., Jupiter) and compact stars (viz., white dwarfs). Our numerical results reveal that the ES shock density profiles strongly depend on the plasma number density and composition (the atomic-number) parameters. Furthermore, ion density perturbations propagate with Mach numbers which significantly depend on the studied plasma fractional parameters. It is concluded that the dynamics of the ES shocks in the superdense degenerate plasma is quite different in the core of a white dwarf star from that in the lower density crust region. PMID:23368053

  11. Theory of plasma contactors in ground-based experiments and low Earth orbit

    NASA Technical Reports Server (NTRS)

    Gerver, M. J.; Hastings, Daniel E.; Oberhardt, M. R.

    1990-01-01

    Previous theoretical work on plasma contactors as current collectors has fallen into two categories: collisionless double layer theory (describing space charge limited contactor clouds) and collisional quasineutral theory. Ground based experiments at low current are well explained by double layer theory, but this theory does not scale well to power generation by electrodynamic tethers in space, since very high anode potentials are needed to draw a substantial ambient electron current across the magnetic field in the absence of collisions (or effective collisions due to turbulence). Isotropic quasineutral models of contactor clouds, extending over a region where the effective collision frequency upsilon sub e exceeds the electron cyclotron frequency omega sub ce, have low anode potentials, but would collect very little ambient electron current, much less than the emitted ion current. A new model is presented, for an anisotropic contactor cloud oriented along the magnetic field, with upsilon sub e less than omega sub ce. The electron motion along the magnetic field is nearly collisionless, forming double layers in that direction, while across the magnetic field the electrons diffuse collisionally and the potential profile is determined by quasineutrality. Using a simplified expression for upsilon sub e due to ion acoustic turbulence, an analytic solution has been found for this model, which should be applicable to current collection in space. The anode potential is low and the collected ambient electron current can be several times the emitted ion current.

  12. Parallax Results from Urat Epoch Data

    NASA Astrophysics Data System (ADS)

    Finch, Charlie T.; Zacharias, Norbert

    2016-06-01

    We present 1103 trigonometric parallaxes and proper motions from the United States Naval Observatory Robotic Astrometric Telescope (URAT) observations taken at the Naval Observatory Flagstaff Station (NOFS) over a three-year period from 2012 April to 2015 June covering the entire sky north of about -10^\\circ decl. We selected two samples: previously suspected nearby stars from known photometric distances and stars showing a large, significant parallax signature in URAT epoch data without any prior selection criteria. All systems presented in this paper have an observed parallax ≥40 mas with no previous published trigonometric parallax. The formal errors on these weighted parallax solutions are mostly between 4 and 10 mas. This sample gives a significant (of the order of 50%) increase to the number of known systems having a trigonometric parallax to be within 25 pc of the Sun (without applying Lutz–Kelker bias corrections). A few of these are found to be within 10 pc. Many of these new nearby stars display a total proper motion of less than 200 mas yr‑1. URAT parallax results have been verified against Hipparcos and Yale data for stars in common. The publication of all signifigant parallax observations from URAT data is in preparation for CDS.

  13. Kinetic theory of low-frequency cross-field instability in a weakly ionized plasma. I

    SciTech Connect

    Dimant, Y.S.; Sudan, R.N.

    1995-04-01

    A consistent kinetic theory is developed for the description of electrons under conditions of a low-frequency two-stream {bold E}{times}{bold B} instability in collisionally dominated, weakly ionized plasmas. Starting from the Boltzmann collision integral, a simplified kinetic equation for the electron distribution function has been derived, which takes into account strong pitch-angle scattering of electrons by neutrals, velocity dependence of the electron--neutral collision frequency, etc. Linearized equations describing small oscillations of the electron distribution function and ion density are presented. For the asymptotic case of short waves, the dispersion relation of the {bold E}{times}{bold B} instability has been obtained and analyzed under conditions typical for the lower ionosphere. Under certain conditions, the rigorous kinetic consideration yields substantial changes in results compared to previous theories. The general approach may be applied to other linear and nonlinear low-frequency processes in a weakly ionized plasma. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  14. Energy branching in the Io plasma torus - The failure of neutral cloud theory

    NASA Astrophysics Data System (ADS)

    Shemansky, D. E.

    1988-03-01

    The energy branching of the hot Io plasma torus using model calculations which include all of the significant physical chemistry that affects the system has been examined in order to study energy source characteristics. Most theoretical discussions of the energetics of the torus assume that the system is maintained against radiative and other losses by the interaction of the plasma with neutral atomic clouds. The energy in this theory is derived from the kinetic energy acquired by ions created in the rotating planetary magnetic field. Coulomb collisions with the electron gas control the flow of energy to the ionizing and radiative processes. The energetics of this theoretical system is defined by fixing the electron density, the diffusive loss time, and the relative volumetric rates of injection of the major neutral constituents, oxygen and sulfur. On the basis of calculations of this kind in comparison with the characteristics of the observed system, the conclusion has been drawn that neutral cloud theory is qualitatively inadequate. Two possibilities for energy sources involving a particular interaction with an Io atmosphere and a heterogeneous source of energetic electrons are discussed.

  15. Plasma theory and simulation. Quarterly progress report Nos. 3-4, 1 July-31 December 1987

    SciTech Connect

    Birdsall, C.K.

    1987-12-31

    A magnetized plasma next to an absorbing wall is simulated, showing positive wall charging causing a large E-field near the wall, then a large ExB drift, then a Kevlin-Helmholtz instability, vortices, and coalescence. Particle transport to the walls is Bohm-like for Omega sub pl > Omega sub ci. A kinetic theory, allowing finite ion Larmor radii, general magnetic-field geometries and plasma equilibria, was developed for hydromagnetic Alfven waves excited within the Earth's magnetosphere by the storm-time energetic ring-current particles. Multi-time and space scaling for bounded plasmas is being developed using an implicit method. It is found that, using large time steps, (Omega sub ce) (Delta t > 1) provides reliable guiding-center motions for single particles. Electron-neutral elastic scattering is added to ES1 readily. Runs with initial beam verify predictions. RF heating (ECRH) is shown to work well with PIC simulations, providing results very similar to a Monte Carlo RF heating code.

  16. Theory of isolated, small-scale magnetic islands in a high temperature tokamak plasma

    SciTech Connect

    Connor, J.W.; Wilson, H.R.

    1995-12-01

    A theory for the existence of noninteracting small-scale, ``drift`` magnetic islands in a high temperature tokamak plasma is presented. This situation contrasts with that discussed by Rebut and Hugon [Plasma Phys. Controlled Fusion {bold 33}, 1085 (1991)] which involves a background ``sea`` of magnetic turbulence caused by island overlap. The islands are driven by the effect of finite ion Larmor radius on the particle drifts and they propagate with a velocity comparable to the diamagnetic velocity. In contrast with the work of Smolyakov [Plasma Phys. Controlled Fusion {bold 35}, 657 (1993)] collisions are assumed to be rare. Although the saturated island size is independent of the collision frequency in the model discussed here, collisions play a crucial role in determining the frequency of the magnetic islands. An estimate is made of the anomalous heat transport which results from the fluctuations in the electrostatic potential associated with these magnetic islands. The predicted thermal diffusivity has several, but not all, of the characteristics of the Rebut--Lallia--Watkins transport model. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  17. Variational theory of average-atom and superconfigurations in quantum plasmas

    SciTech Connect

    Blenski, T.

    2007-05-15

    Models of screened ions in equilibrium plasmas with all quantum electrons are important in opacity and equation of state calculations. Although such models have to be derived from variational principles, up to now existing models have not been fully variational. In this paper a fully variational theory respecting virial theorem is proposed--all variables are variational except the parameters defining the equilibrium, i.e., the temperature T, the ion density n{sub i} and the atomic number Z. The theory is applied to the quasiclassical Thomas-Fermi (TF) atom, the quantum average atom (QAA), and the superconfigurations (SC) in plasmas. Both the self-consistent-field (SCF) equations for the electronic structure and the condition for the mean ionization Z* are found from minimization of a thermodynamic potential. This potential is constructed using the cluster expansion of the plasma free energy from which the zero and the first-order terms are retained. In the zero order the free energy per ion is that of the quantum homogeneous plasma of an unknown free-electron density n{sub 0}=Z*n{sub i} occupying the volume 1/n{sub i}. In the first order, ions submerged in this plasma are considered and local neutrality is assumed. These ions are considered in the infinite space without imposing the neutrality of the Wigner-Seitz (WS) cell. As in the Inferno model, a central cavity of a radius R is introduced, however, the value of R is unknown a priori. The charge density due to noncentral ions is zero inside the cavity and equals en{sub 0} outside. The first-order contribution to free energy per ion is the difference between the free energy of the system 'central ion+infinite plasma' and the free energy of the system 'infinite plasma'. An important part of the approach is an 'ionization model' (IM), which is a relation between the mean ionization charge Z* and the first-order structure variables. Both the IM and the local neutrality are respected in the minimization procedure

  18. Variational theory of average-atom and superconfigurations in quantum plasmas.

    PubMed

    Blenski, T; Cichocki, B

    2007-05-01

    Models of screened ions in equilibrium plasmas with all quantum electrons are important in opacity and equation of state calculations. Although such models have to be derived from variational principles, up to now existing models have not been fully variational. In this paper a fully variational theory respecting virial theorem is proposed-all variables are variational except the parameters defining the equilibrium, i.e., the temperature T, the ion density ni and the atomic number Z. The theory is applied to the quasiclassical Thomas-Fermi (TF) atom, the quantum average atom (QAA), and the superconfigurations (SC) in plasmas. Both the self-consistent-field (SCF) equations for the electronic structure and the condition for the mean ionization Z* are found from minimization of a thermodynamic potential. This potential is constructed using the cluster expansion of the plasma free energy from which the zero and the first-order terms are retained. In the zero order the free energy per ion is that of the quantum homogeneous plasma of an unknown free-electron density n0 = Z* ni occupying the volume 1/ni. In the first order, ions submerged in this plasma are considered and local neutrality is assumed. These ions are considered in the infinite space without imposing the neutrality of the Wigner-Seitz (WS) cell. As in the Inferno model, a central cavity of a radius R is introduced, however, the value of R is unknown a priori. The charge density due to noncentral ions is zero inside the cavity and equals en0 outside. The first-order contribution to free energy per ion is the difference between the free energy of the system "central ion+infinite plasma" and the free energy of the system "infinite plasma." An important part of the approach is an "ionization model" (IM), which is a relation between the mean ionization charge Z* and the first-order structure variables. Both the IM and the local neutrality are respected in the minimization procedure. The correct IM in the TF case

  19. Into the Epoch of Galaxy Formation

    NASA Astrophysics Data System (ADS)

    2000-02-01

    Infrared VLT Observations Identify Hidden Galaxies in the Early Universe Working with the ESO Very Large Telescope (VLT) at the Paranal Observatory , a group of European astronomers [1] has just obtained one of the deepest looks into the distant Universe ever made by an optical telescope. These observations were carried out in the near-infrared spectral region and are part of an attempt to locate very distant galaxies that have so far escaped detection in the visual bands. The first results are very promising and some concentrations of galaxies at very large distances were uncovered. Some early galaxies may be in hiding Current theories hypothesize that more than 80% of all stars ever formed were assembled in galaxies during the latter half of the elapsed lifetime of the Universe, i.e., during the past 7-8 billion years. However, doubts have arisen about these ideas. There are now observational indications that a significant number of those galaxies that formed during the first 20% of the age of the Universe, i.e. within about 3 billion years after the Big Bang, may not be visible to optical telescopes. In some cases, we do not see them, because their light is obscured by dust. Other distant galaxies may escape detection by optical telescopes because star formation in them has ceased and their light is mainly emitted in the red and infrared spectral bands. This is because, while very young galaxies mostly contain hot and blue stars, older galaxies have substantial numbers of cool and red stars. They are then dominated by an older, "evolved" stellar population that is cooler and redder. The large cosmic velocities of these galaxies further enhance this effect by causing their light to be "redshifted" towards longer wavelengths, i.e. into the near-infrared spectral region. Observations in the infrared needed Within the present programme, long exposures in near-infrared wavebands were made with the Infrared Spectrometer And Array Camera (ISAAC) , mounted on ANTU , the

  20. Theory of ballooning-mirror instabilities for anisotropic pressure plasmas in the magnetosphere

    SciTech Connect

    Cheng, C.Z.; Qian, Q.

    1993-09-01

    This paper deals with a kinetic-MHD eigenmode stability analysis of low frequency ballooning-mirror instabilities for anisotropic pressure plasmas in the magnetosphere. The ballooning mode is a dominant transverse wave driven unstable by pressure gradient in the bad curvature region. The mirror mode with a dominant compressional magnetic field perturbation is excited when the product of plasma beta and pressure anisotropy is large. The field-aligned eigenmode equations take into account the coupling of the transverse and compressional components of the perturbed magnetic field and describe the coupled ballooning-mirror mode. Because the energetic trapped ions precess very rapidly across the {rvec B} field, their motion becomes very rigid with respect to low frequency MHD perturbations with symmetric structure of parallel perturbed magnetic field {delta}B{sub {parallel}} and electrostatic potential {Phi} along the north-south ambient magnetic field, and the symmetric ballooning-mirror mode is shown to be stable. On the other hand, the ballooning-mirror mode with antisymmetric {delta}B{sub {parallel}}, and {Phi} structure along the north-south ambient magnetic field is only weakly influenced by energetic trapped particle kinetic effects due to rapid trapped particle bounce motion and has the lowest instability threshold determined by MHD theory. With large plasma beta ({beta}{sub {parallel}} {ge} O(1)) and pressure anisotropy (P{sub {perpendicular}}/P{sub {parallel}} > 1) at equator the antisymmetric ballooning-mirror mode structures resemble the field-aligned wave structures of the multisatellite observations of a long lasting compressional Pc 5 wave event during November 14--15, 1979 [Takahashi et al.]. The study provides the theoretical basis for identifying the internal excitation mechanism of ULF (Pc 4-5) waves by comparing the plasma stability parameters computed from the satellite particle data with the theoretical values.

  1. Dusty plasmas over the Moon: theory research in support of the upcoming lunar missions

    NASA Astrophysics Data System (ADS)

    Popel, Sergey; Zelenyi, Lev; Zakharov, Alexander; Izvekova, Yulia; Dolnikov, Gennady; Dubinskii, Andrey; Kopnin, Sergey; Golub, Anatoly

    The future Russian lunar missions Luna 25 and Luna 27 are planned to be equipped with instruments for direct detection of nano- and microscale dust particles and determination of plasma properties over the surface of the Moon. Lunar dust over the Moon is usually considered as a part of a dusty plasma system. Here, we present the main our theory results concerning the lunar dusty plasmas. We start with the description of the observational data on dust particles on and over the surface of the Moon. We show that the size distribution of dust on the lunar surface is in a good agreement with the Kolmogorov distribution, which is the size distribution of particles in the case of multiple crushing. We discuss the role of adhesion which has been identified as a significant force in the dust particle launching process. We evaluate the adhesive force for lunar dust particles with taking into account the roughness and adsorbed molecular layers. We show that dust particle launching can be explained if the dust particles rise at a height of about dozens of nanometers owing to some processes. This is enough for the particles to acquire charges sufficient for the dominance of the electrostatic force over the gravitational and adhesive forces. The reasons for the separation of the dust particles from the surface of the Moon are, in particular, their heating by solar radiation and cooling. We consider migration of free protons in regolith from the viewpoint of the photoemission properties of the lunar soil. Finally, we develop a model of dusty plasma system over the Moon and show that it includes charged dust, photoelectrons, and electrons and ions of the solar wind. We determine the distributions of the photoelectrons and find the characteristics of the dust which rise over the lunar regolith. We show that there are no significant constraints on the Moon landing sites for future lunar missions that will study dusty plasmas in the surface layer of the Moon. We discuss also waves in

  2. Refinement of the semiclassical theory of the Stark broadening of hydrogen spectral lines in plasmas

    NASA Astrophysics Data System (ADS)

    Oks, Eugene

    2015-02-01

    Stark broadening (SB) of hydrogen, deuterium, and tritium lines (H-lines) is an important diagnostic tool for many applications. The most "user-friendly" are semiclassical theories of the SB of H-lines: their results can be expressed analytically in a relatively simple form for any H-line. The simplest semiclassical theory is the so-called Conventional Theory (CT), which is frequently referred to as Griem's theory. While by now there are several significantly more advanced semiclassical "non-CT" theories of the SB, Griem's CT is still used by a number of groups performing laboratory experiments or astrophysical observations for the comparison with their experimental or observational results. In the present study we engage unexplored capabilities of the CT for creating analytically a more accurate CT. First, we take into account that the perturbing electrons actually do not move as free particles: rather they move in a dipole potential V=·r/r3, where r is the radius-vector of the perturbing electrons and is the mean value of the radius vector of the atomic electron. Second, Griem's definition of the so-called Weisskopf radius was not quite accurate. Third, in his book of year 1974, Griem suggested changing so-called strong collision constant without changing the Weisskopf radius, while in reality the choices of the Weisskopf radius and of the strong collision constant are interrelated. We show that the above refinements of the CT increase the electron broadening - especially for warm dense plasmas emitting H-lines. By comparison with benchmark experiments concerning the Hα line we demonstrate that the effect of the ion dynamics (neglected in any CT) might be slightly smaller than previously thought, while the effect of the acceleration of perturbing electrons by the ion field in the vicinity of the radiating atom (neglected in any CT) might be greater than previously thought.

  3. The effect of epoch length on estimated EEG functional connectivity and brain network organisation

    NASA Astrophysics Data System (ADS)

    Fraschini, Matteo; Demuru, Matteo; Crobe, Alessandra; Marrosu, Francesco; Stam, Cornelis J.; Hillebrand, Arjan

    2016-06-01

    Objective. Graph theory and network science tools have revealed fundamental mechanisms of functional brain organization in resting-state M/EEG analysis. Nevertheless, it is still not clearly understood how several methodological aspects may bias the topology of the reconstructed functional networks. In this context, the literature shows inconsistency in the chosen length of the selected epochs, impeding a meaningful comparison between results from different studies. Approach. The aim of this study was to provide a network approach insensitive to the effects that epoch length has on functional connectivity and network reconstruction. Two different measures, the phase lag index (PLI) and the amplitude envelope correlation (AEC) were applied to EEG resting-state recordings for a group of 18 healthy volunteers using non-overlapping epochs with variable length (1, 2, 4, 6, 8, 10, 12, 14 and 16 s). Weighted clustering coefficient (CCw), weighted characteristic path length (L w) and minimum spanning tree (MST) parameters were computed to evaluate the network topology. The analysis was performed on both scalp and source-space data. Main results. Results from scalp analysis show a decrease in both mean PLI and AEC values with an increase in epoch length, with a tendency to stabilize at a length of 12 s for PLI and 6 s for AEC. Moreover, CCw and L w show very similar behaviour, with metrics based on AEC more reliable in terms of stability. In general, MST parameters stabilize at short epoch lengths, particularly for MSTs based on PLI (1–6 s versus 4–8 s for AEC). At the source-level the results were even more reliable, with stability already at 1 s duration for PLI-based MSTs. Significance. The present work suggests that both PLI and AEC depend on epoch length and that this has an impact on the reconstructed network topology, particularly at the scalp-level. Source-level MST topology is less sensitive to differences in epoch length, therefore enabling the comparison of

  4. New Insight into the Cosmic Renaissance Epoch

    NASA Astrophysics Data System (ADS)

    2003-08-01

    VLT Discovers a Group of Early Inhabitants and Find Signs of Many More [1] Summary Using the ESO Very Large Telescope (VLT) , two astronomers from Germany and the UK [2] have discovered some of the most distant galaxies ever seen . They are located about 12,600 million light-years away. It has taken the light now recorded by the VLT about nine-tenths of the age of the Universe to traverse this huge distance. We therefore observe those galaxies as they were at a time when the Universe was very young, less than about 10% of its present age . At this time, the Universe was emerging from a long period known as the "Dark Ages" , entering the luminous "Cosmic Renaissance" epoch. Unlike previous studies which resulted in the discovery of a few, widely dispersed galaxies at this early epoch, the present study found at least six remote citizens within a small sky area, less than five per cent the size of the full moon! This allowed understanding the evolution of these galaxies and how they affect the state of the Universe in its youth. In particular, the astronomers conclude on the basis of their unique data that there were considerably fewer luminous galaxies in the Universe at this early stage than 500 million years later. There must therefore be many less luminous galaxies in the region of space that they studied, too faint to be detected in this study. It must be those still unidentified galaxies that emit the majority of the energetic photons needed to ionise the hydrogen in the Universe at that particularly epoch. PR Photo 25a/03 : Colour-composite of the sky field with the distant galaxies. PR Photo 25b/03 : Close-Up images of some of the most distant galaxies known in the Universe. PR Photo 25c/03 : Spectra of these galaxies. From the Big Bang to the Cosmic Renaissance Nowadays, the Universe is pervaded by energetic ultraviolet radiation, produced by quasars and hot stars. The short-wavelength photons liberate electrons from the hydrogen atoms that make up the

  5. Investigation of the epoch state filter. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Edwards, J. A.

    1972-01-01

    A navigation filtering technique has been formulated using as state variables the initial or epoch position and velocity of the spacecraft. The estimate of this initial state is then improved by filtering new measurements. The current state may be obtained by a conic extrapolation of the epoch state. Results of a digital computer simulation of the epoch state filter show that this formulation of the navigational problem results in less computer run time and less computer storage space than conventional techniques. The errors produced by this technique have been demonstrated to be comparable to those obtained by conventional maximum-likelihood filtering.

  6. Kinetic theory of dust ion acoustic waves in a kappa-distributed plasma

    NASA Astrophysics Data System (ADS)

    Baluku, T. K.; Hellberg, M. A.

    2015-08-01

    Using a kinetic theory approach, dust ion acoustic (DIA) waves are investigated in an unmagnetized collisionless plasma with kappa-distributed electrons and ions, and Maxwellian dust grains of constant charge. Both analytical and numerical results, the latter following from the full solution of the associated dispersion relation, are presented, and a comparison is made. The effects of the ion and electron spectral indices, as well as the species' density ( ne/ni ) and temperature ( Te/Ti ) ratios, on the dispersion and damping of the waves are considered. In the long wavelength regime, increases in both the electron spectral index (κe) and the dust density fraction (reduced f =ne/ni ) lead to an increase in phase velocity. The range in wavelength over which modes are weakly damped increases with an increase in Te/Ti . However, the ion spectral index, κi, does not have a significant effect on the dispersion or damping of DIA waves.

  7. Sub-Daily Earth Rotation During Epoch '92

    NASA Technical Reports Server (NTRS)

    Freedman, A. P.; Ibanez-Meier, R.; Dickey, J. O.; Lichten, S. M.; Herring, T. A.

    1994-01-01

    Earth rotation data were obtained with GPS during the EPOCH '92 campaign in the summer of 1992. About 10 days of data were acquired from 25 globally distributed stations and a constellation of 17 GPS satellites.

  8. Rotation of the Universe at different cosmological epochs

    NASA Astrophysics Data System (ADS)

    Chechin, L. M.

    2016-06-01

    A step-by-step foundation for the differential character of the Universe's rotation is presented. First, invoking the concept of spacetime foam with spin, it is reasonable to assume that the very early Universe can be described by the Dirac equation. Second, it is shown using the Ehrenfest theorem that, from a classical point of view, the early Universe can be described by the Papapetrou equations. Third, it is stressed that our Universe can perform only rotational motion. It is shown based on the spin part of the Papapetrou equations that the Universe's rotation depends appreciably on the physical properties of a specific cosmological epoch. The rotational angular velocity is calculated for three basic cosmological epochs: the matter-dominated epoch, the transition period (from domination of matter to domination of vacuum), and the vacuum-dominated epoch.

  9. Propagation of high power electromagnetic beams in overdense plasmas: Higher order paraxial theory

    SciTech Connect

    Sodha, Mahendra Singh; Faisal, Mohammad

    2008-03-15

    This article presents the paraxial theory of the propagation of an initially Gaussian electromagnetic beam in an inhomogeneous plasma with an overdense region; in contrast to earlier work on penetration in overdense plasma, higher order terms (up to r{sup 4}) in the expansion of the dielectric function and the eikonal have been taken into account. Three types of nonlinearities, viz., collisional, ponderomotive, and relativistic, have been considered. As expected the higher order terms do not affect the critical curves, corresponding to initial propagation without convergence or divergence. It is seen that the inclusion of higher order terms does significantly affect the dependence of the beam width on the distance of propagation. Corresponding to the case of ponderomotive nonlinearity numerical results for the dependence of beam width parameter and the axial dielectric function on the distance of propagation have been presented for specific values of the initial beam width and axial irradiance and specific spatial dependence of the electron density in the absence of the beam. Both the situations, viz., formation of bright or dark rings in the transverse irradiation pattern, have been considered. From a parametric analysis the dependence of the maximum penetration (when the axial dielectric function tends to zero) on the axial irradiance and an inhomogeneity parameter has been graphically illustrated.

  10. DYNAMICS AND STAGNATION IN THE MALTHUSIAN EPOCH

    PubMed Central

    Ashraf, Quamrul; Galor, Oded

    2013-01-01

    This paper examines the central hypothesis of the influential Malthusian theory, according to which improvements in the technological environment during the pre-industrial era had generated only temporary gains in income per capita, eventually leading to a larger, but not significantly richer, population. Exploiting exogenous sources of cross-country variations in land productivity and the level of technological advancement the analysis demonstrates that, in accordance with the theory, technological superiority and higher land productivity had significant positive effects on population density but insignificant effects on the standard of living, during the time period 1–1500 CE. PMID:25506082

  11. Theory and Simulation of Magnetohydrodynamic Dynamos and Faraday Rotation for Plasmas of General Composition

    NASA Astrophysics Data System (ADS)

    Park, Kiwan

    2013-03-01

    Many astrophysical phenomena depend on the underlying dynamics of magnetic fields. The observations of accretion disks and their jets, stellar coronae, and the solar corona are all best explained by models where magnetic fields play a central role. Understanding these phenomena requires studying the basic physics of magnetic field generation, magnetic energy transfer into radiating particles, angular momentum transport, and the observational implications of these processes. Each of these topics comprises a large enterprise of research. However, more practically speaking, the nonlinearity in large scale dynamo is known to be determined by magnetic helicity(>), the topological linked number of knotted magnetic field. Magnetic helicity, which is also observed in solar physics, has become an important tool for observational and theoretical study. The first part of my work addresses one aspect of the observational implications of magnetic fields, namely Faraday rotation. It is shown that plasma composition affects the interpretation of Faraday rotation measurements of the field, and in turn how this can be used to help constrain unknown plasma composition. The results are applied to observations of astrophysical jets. The thesis then focuses on the evolution of magnetic fields. In particular, the dynamo amplification of large scale magnetic fields is studied with an emphasis on the basic physics using both numerical simulations and analytic methods. In particular, without differential rotation, a two and three scale mean field (large scale value + fluctuation scales) dynamo theory and statistical methods are introduced. The results are compared to magnetohydrodynamic (MHD) simulations of the Pencil code, which utilizes high order finite difference methods. Simulations in which the energy is initially driven into the system in the form of helical kinetic energy (via kinetic helicity) or helical magnetic energy (via magnetic helicity) reveal the exponential growth of

  12. [Demographic transition at the epoch of industrialization].

    PubMed

    Billig, W

    1984-01-01

    The relationship between the early stages of industrialization and population factors in the United Kingdom, France, and the United States is analyzed from a Marxist perspective. The author attempts to associate successive phases of industrialization with phases of the demographic transition. He concludes that no comprehensive general theory concerning this relationship has been established. (summary in ENG, RUS) PMID:12266382

  13. Shear viscosity of the quark-gluon plasma in a kinetic theory approach

    SciTech Connect

    Puglisi, A.; Plumari, S.; Scardina, F.; Greco, V.

    2014-05-09

    One of the main results of heavy ions collision (HIC) at relativistic energy experiments is the very small shear viscosity to entropy density ratio of the Quark-Gluon Plasma, close to the conjectured lower bound η/s=1/4π for systems in the infinite coupling limit. Transport coefficients like shear viscosity are responsible of non-equilibrium properties of a system: Green-Kubo relations give us an exact expression to compute these coefficients. We compute shear viscosity numerically using Green-Kubo relation in the framework of Kinetic Theory solving the relativistic transport Boltzmann equation in a finite box with periodic boundary conditions. We investigate a system of particles interacting via anisotropic and energy dependent cross-section in the range of temperature of interest for HIC. Green-Kubo results are in agreement with Chapman-Enskog approximation while Relaxation Time approximation can underestimates the viscosity of a factor 2. The correct analytic formula for shear viscosity can be used to develop a transport theory with a fixed η/s and have a comparison with physical observables like elliptic flow.

  14. BRIGHTEST CLUSTER GALAXIES AT THE PRESENT EPOCH

    SciTech Connect

    Lauer, Tod R.; Postman, Marc; Strauss, Michael A.; Graves, Genevieve J.; Chisari, Nora E.

    2014-12-20

    We have obtained photometry and spectroscopy of 433 z ≤ 0.08 brightest cluster galaxies (BCGs) in a full-sky survey of Abell clusters to construct a BCG sample suitable for probing deviations from the local Hubble flow. The BCG Hubble diagram over 0 < z < 0.08 is consistent to within 2% of the Hubble relation specified by a Ω {sub m} = 0.3, Λ = 0.7 cosmology. This sample allows us to explore the structural and photometric properties of BCGs at the present epoch, their location in their hosting galaxy clusters, and the effects of the cluster environment on their structure and evolution. We revisit the L{sub m} -α relation for BCGs, which uses α, the log-slope of the BCG photometric curve of growth, to predict the metric luminosity in an aperture with 14.3 kpc radius, L{sub m} , for use as a distance indicator. Residuals in the relation are 0.27 mag rms. We measure central stellar velocity dispersions, σ, of the BCGs, finding the Faber-Jackson relation to flatten as the metric aperture grows to include an increasing fraction of the total BCG luminosity. A three-parameter ''metric plane'' relation using α and σ together gives the best prediction of L{sub m} , with 0.21 mag residuals. The distribution of projected spatial offsets, r{sub x} of BCGs from the X-ray-defined cluster center is a steep γ = –2.33 power law over 1 < r{sub x} < 10{sup 3} kpc. The median offset is ∼10 kpc, but ∼15% of the BCGs have r{sub x} > 100 kpc. The absolute cluster-dispersion normalized BCG peculiar velocity |ΔV {sub 1}|/σ {sub c} follows an exponential distribution with scale length 0.39 ± 0.03. Both L{sub m} and α increase with σ {sub c}. The α parameter is further moderated by both the spatial and velocity offset from the cluster center, with larger α correlated with the proximity of the BCG to the cluster mean velocity or potential center. At the same time, position in the cluster has little effect on L{sub m} . Likewise, residuals from the metric plane

  15. 'Black universe' epoch in string cosmology

    SciTech Connect

    Buchel, Alex; Kofman, Lev

    2008-10-15

    String theory compactification involves manifolds with multiple warp factors. For cosmological applications, we often introduce a short, high-energy inflationary throat, and a long, low-energy standard model (SM) throat. It is assumed that at the end of inflation, the excited Kaluza-Klein modes from the inflationary throat tunnel to the SM throat and reheat standard model degrees of freedom, which are attached to probe brane(s). However, the huge hierarchy of energy scales can result in a highly dynamic transition of the throat geometry. We point out that in such a cosmological scenario the standard model throat (together with SM brane) will be cloaked by a Schwarzschild horizon, produced by the Kaluza-Klein modes tunneling from the short throat. The black brane formation is dual to the first order chiral phase transition of the cascading gauge theory. We calculate the critical energy density corresponding the formation of the black hole (BH) horizon in the long throat. We discuss the duality between 'black universe' cosmology and an expanding universe driven by the hot gauge theory radiation. We address the new problem of the hierarchical multiple-throat scenarios: SM brane disappearance after the decay of the BH horizon.

  16. Plasma theory and simulation: Quarterly progress report Nos. 1 and 2, January 1, 1986-June 30, 1986

    SciTech Connect

    Birdsall, C.K.

    1986-06-30

    This quarterly report deals with General Plasma Theory and Simulation. Computer simulation of bounded plasma systems, with external circuits, is discussed in considerable detail. Artificial cooling of trapped electrons in bounded simulations was observed and is now attributed to noiseless injection; the cooling does not occur if random injection is used. This report also deals with Plasma-Wall Physics and Simulation. The collector and source sheaths at the boundaries of warm plasma are treated in detail, including ion reflection and secondary electron emission at the collector. The Kelvin-Helmholtz instability is observed in a self-consistent magnetized sheath, producing long-lived vortices which increase the particle transport to the wall dramatically.

  17. A two-dimensional theory of plasma contactor clouds used in the ionosphere with an electrodynamic tether

    NASA Technical Reports Server (NTRS)

    Hastings, D. E.; Gatsonis, N. A.; Rivas, D. A.

    1988-01-01

    Plasma contactors have been proposed as a means of making good electrical contact between biased surfaces such as found at the ends of an electrodynamic tether and the space environment. A plasma contactor is a plasma source which emits a plasma cloud which facilitates the electrical connection. The physics of this plasma cloud is investigated for contactors used as electron collectors and it is shown that contactor clouds in space will consist of a spherical core possibly containing a shock wave. Outside of the core the cloud will expand anisotropically across the magnetic field leading to a turbulent cigar shape structure along the field. This outer region is itself divided into two regions by the ion response to the electric field. A two-dimensional theory of the motion of the cloud across the magnetic field is developed. The current voltage characteristic of an Argon plasma contactor cloud is estimated for several ion currents in the range of 1-100 Amperes. It is shown that small ion current contactors are more efficient than large ion current contactors. This suggests that if a plasma contactor is used on an electrodynamic tether then a miltiple tether array will be more efficient than a single tether.

  18. Thin current sheet embedded within a thicker plasma sheet: Self-consistent kinetic theory

    NASA Astrophysics Data System (ADS)

    Sitnov, M. I.; Zelenyi, L. M.; Malova, H. V.; Sharma, A. S.

    2000-06-01

    A self-consistent theory of thin current sheets, where the magnetic field line tension is balanced by the ion inertia rather than by the pressure gradient, is presented. Assuming that ions are the main current carriers and their dynamics is quasi-adiabatic, the Maxwell-Vlasov equations are reduced to the nonlocal analogue of the Grad-Shafranov equation using a new set of integrals of motion, namely, the particle energy and the sheet invariant of the quasi-adiabatic motion. It is shown that for a drifting Maxwellian distribution of ions outside the sheet the equilibrium equation can be reduced in the limits of strong and weak anisotropy to universal equations that determine families of equilibria with similar profiles of the magnetic field. In the region Bn/B0>1) the self-consistent current sheet equilibrium may also exist with no indications of the catastrophe reported earlier by Burkhart et al. [1992a]. On the contrary, it is found that in this limit the magnetic field profiles again become similar to each other with the characteristic thickness ~ρ0. The profiles of plasma and current densities as well as the components of the pressure tensor are calculated for arbitrary ion anisotropy outside the sheet. It is shown that the thin current sheet for the equilibrium considered here is usually embedded into a much thicker plasma sheet. Moreover, in the case of weak anisotropy the perturbation of the plasma density inside the sheet is shown to be proportional to the parameter vD/vT, and as a result the electrostatic effects should be small, consistent with observations. This model of the thin current sheet

  19. Trapped Electron Instability of Electron Plasma Waves: Vlasov simulations and theory

    NASA Astrophysics Data System (ADS)

    Berger, Richard; Chapman, Thomas; Brunner, Stephan

    2013-10-01

    The growth of sidebands of a large-amplitude electron plasma wave is studied with Vlasov simulations for a range of amplitudes (. 001 < eϕ0 /Te < 1) and wavenumbers (0 . 25 theory. Despite the simplicity of the dispersion relation, growth rates found with the Kruer-Dawson-Sudan model [Kruer et al. PRL 23, 838 (1969)] agree quite well with the numerical results. The most unstable modes with frequency and wavenumber ω , k satisfy the relation, ω - k .vph = +/-ωbe , where vph =ω0 /k0 and ωbe is the bounce frequency of a deeply trapped electron. In 2D simulations, we find that the instability persists and co-exists with the filamentation instability. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and funded by the Laboratory Research and Development Program at LLNL under project tracking code 12-ERD.

  20. Kinetic theory of electromagnetic plane wave obliquely incident on bounded plasma slab

    SciTech Connect

    Angus, J. R.; Krasheninnikov, S. I.; Smolyakov, A. I.

    2010-10-15

    The effects of electromagnetic plane waves obliquely incident on a warm bounded plasma slab of finite length L are studied by solving the coupled Vlasov-Maxwell set of equations. It is shown that the solution can be greatly simplified in the limit where thermal effects are most important by expanding in small parameters and introducing self-similar variables. These solutions reveal that the coupling of thermal effects with the angle of incidence is negligible in the region of bounce resonance and anomalous skin effect. In the region of the anomalous skin effect, the heating is shown to scale linearly with the anomalous skin depth {delta}{sub a} when {delta}{sub a}<>L, the heating is shown to decay with 1/{delta}{sub a}{sup 3}. The transmission is found to be exponentially larger than that predicted from a local theory in the appropriate region of the anomalous skin effect.

  1. A New Cosmic Ray Transport Theory in Partially Turbulent Space Plasmas: Extending the Quasilinear Approach

    NASA Astrophysics Data System (ADS)

    Schlickeiser, R.

    2011-05-01

    A new transport theory of cosmic rays in magnetized space plasmas with axisymmetric incompressible magnetic turbulence is developed extending the quasilinear approximation to the particle orbit. Arbitrary gyrophase deviations from the unperturbed spiral orbits in the uniform magnetic field are allowed. For quasi-stationary and spatially homogeneous magnetic turbulence, we derive the small Larmor radius approximation gyrophase-averaged cosmic ray Fokker-Planck coefficients. The generalized Fokker-Planck coefficients correctly reduce to their known quasilinear values in the corresponding limit. New forms of the quasilinear Fokker-Planck coefficients in axisymmetric turbulence are derived which no longer involve infinite sums of products of Bessel functions, which facilitate their numerical computation for specified turbulence field correlation tensors. The Fokker-Planck coefficients for arbitrary phase orbits of the cosmic ray particles provide strict upper limits for the perpendicular and pitch-angle Fokker-Planck coefficients, which in turn yield strict upper and lower limits for the perpendicular and parallel spatial diffusion coefficients, respectively, describing the spatial diffusion of the isotropic part of the cosmic ray phase space density. For the associated mean free paths, we find for this general case that the product of the minimum parallel mean free path with the sum of the maximum perpendicular mean free paths equals R 2 L , where RL denotes the cosmic ray gyroradius.

  2. Alpha Particle-Driven Toroidal Alfven Eigenmodes in Tokamak Fusion Test Reactor Deuterium-Tritium Plasmas: Theory and Experiments

    SciTech Connect

    Budny, R.; Chang, Z.; Fu, G.Y.; Nazikian, R.

    1998-07-09

    The toroidal Alfvén eigenmodes (TAE) in the Tokamak Fusion Test Reactor [K. Young, et al., Plasma Phys. Controlled Fusion 26, 11 (1984)]deuterium-tritium plasmas are analyzed using the NOVA-K code [C.Z. Cheng, Phys. Reports 211, 1 (1992)]. The theoretical results are compared with the experimental measurements in detail. In most cases, the theory agrees with the observations in terms of mode frequency, mode structure, and mode stability. However, one mode with toroidal mode number n = 2 is observed to be poloidally localized on the high field side of the magnetic axis with a mode frequency substantially below the TAE frequency.

  3. Will nonlinear peculiar velocity and inhomogeneous reionization spoil 21 cm cosmology from the epoch of reionization?

    PubMed

    Shapiro, Paul R; Mao, Yi; Iliev, Ilian T; Mellema, Garrelt; Datta, Kanan K; Ahn, Kyungjin; Koda, Jun

    2013-04-12

    The 21 cm background from the epoch of reionization is a promising cosmological probe: line-of-sight velocity fluctuations distort redshift, so brightness fluctuations in Fourier space depend upon angle, which linear theory shows can separate cosmological from astrophysical information. Nonlinear fluctuations in ionization, density, and velocity change this, however. The validity and accuracy of the separation scheme are tested here for the first time, by detailed reionization simulations. The scheme works reasonably well early in reionization (≲40% ionized), but not late (≳80% ionized). PMID:25167246

  4. Declinations in the Almagest: accuracy, epoch, and observers

    NASA Astrophysics Data System (ADS)

    Brandt, John C.; Zimmer, Peter; Jones, Patricia B.

    2014-11-01

    Almagest declinations attributed to Timocharis, Aristyllos, Hipparchus, and Ptolemy are investigated through comparisons of the reported declinations with the declinations computed from modern positions translated to the earlier epochs. Consistent results indicate an observational accuracy of ≈ 0.1° and epochs of: Timocharis, c. 298 BC; Aristyllos, c. 256 BC, and Hipparchus, c. 128 BC.The ≈ 42-year difference between Aristyllos and Timocharis is confirmed to be statistically significant. The declinations attributed to Ptolemy were likely two distinct groups—observations taken c. AD 57 and observations taken c. AD 128. The later observations could have been taken by Ptolemy himself.

  5. Equilibrium Plasma Position Control for a Large Tokamak Using Modern Control Theory

    NASA Astrophysics Data System (ADS)

    Fukunishi, Kohyu; Saito, Seiji; Ogata, Atsushi; Ninomiya, Hiromasa

    1980-09-01

    Optimal control techniques are applied to maintain the plasma in its equilibrium position in a large tokamak. The application of the state space equation to plasma position control is also discussed. Optimal controls with states, which are plasma current, OH coil current and vertical field current, and integrated plasma displacement feedbacks are formulated as linear, time invariant expressions with quadratic performance indices. Effective plasma position control was obtained with integral state feedback in computer simulations for the JT-60. These control techniques will be applied to the JT-60.

  6. Theory of the pulse response from a small antenna in a magnetized plasma

    NASA Technical Reports Server (NTRS)

    Grabbe, Crockett L.

    1989-01-01

    The electrostatic plasma response to a small pulsed antenna in a magnetic field is analyzed. The ringing of the plasma at three discrete frequencies--the upper-hybrid frequency and two resonance cone branch frequencies--is evidenced, and the amplitudes of these frequency responses is determined as a function of the characteristic plasma frequencies, the angle of observation with respect to the magnetic field, and the pulse length. Applications to plasma diagnostics are discussed. It is shown that the upper hybrid response and the response at either of the resonance cone branch frequencies is adequate information to determine the plasma density, and the magnetic field magnitude and angle.

  7. Multiple solutions in the theory of direct current glow discharges: Effect of plasma chemistry and nonlocality, different plasma-producing gases, and 3D modelling

    SciTech Connect

    Almeida, P. G. C.; Benilov, M. S.

    2013-10-15

    The work is aimed at advancing the multiple steady-state solutions that have been found recently in the theory of direct current (DC) glow discharges. It is shown that an account of detailed plasma chemistry and non-locality of electron transport and kinetic coefficients results in an increase of the number of multiple solutions but does not change their pattern. Multiple solutions are shown to exist for discharges in argon and helium provided that discharge pressure is high enough. This result indicates that self-organization in DC glow microdischarges can be observed not only in xenon, which has been the case until recently, but also in other plasma-producing gases; a conclusion that has been confirmed by recent experiments. Existence of secondary bifurcations can explain why patterns of spots grouped in concentric rings, observed in the experiment, possess in many cases higher number of spots in outer rings than in inner ones.

  8. The Utility of Shorter Epochs in Direct Motion Monitoring

    ERIC Educational Resources Information Center

    Dorsey, Karen; Herrin, Jeph; Krumholz, Harlan; Irwin, Melinda

    2009-01-01

    This cross-sectional study using direct motion monitoring evaluated whether short epochs increased estimates of moderate or vigorous physical activity (MPA or VPA) and enhanced differences in daily VPA comparing overweight (OW) and nonoverweight (NOW) children. Seventy-seven children (ages 8-10 years) wore accelerometers for 7 days. We calculated…

  9. Sub-Daily Polar Motion During Epoch '92 with GPS

    NASA Technical Reports Server (NTRS)

    Ibanez-Meier, R.; Freedman, A. P.; Lichten, S. M.; Lindqwister, U. J.; Gross, R. S.; Herring, T. A.

    1994-01-01

    Data from a worldwide Global Positioning System (GPS) tracking network spanning six days during the EPOCH '92 campaign are used to estimate variations of the Earth's pole position every 30 minutes. The resulting polar motion time series is compared with estimates derived from very long baseline interferometry (VLBI) observations.

  10. Kinetic theory of transport processes in partially ionized reactive plasma, I: General transport equations

    NASA Astrophysics Data System (ADS)

    Zhdanov, V. M.; Stepanenko, A. A.

    2016-03-01

    In this paper we derive the set of general transport equations for multicomponent partially ionized reactive plasma in the presence of electric and magnetic fields taking into account the internal degrees of freedom and electronic excitation of plasma particles. Our starting point is a generalized Boltzmann equation with the collision integral in the Wang-Chang and Uhlenbeck form and a reactive collision integral. We obtain a set of conservation equations for such plasma and employ a linearized variant of Grad's moment method to derive the system of moment (or transport) equations for the plasma species nonequilibrium parameters. Full and reduced transport equations, resulting from the linearized system of moment equations, are presented, which can be used to obtain transport relations and expressions for transport coefficients of electrons and heavy plasma particles (molecules, atoms and ions) in partially ionized reactive plasma.

  11. 2012 Joint Varenna-Lausanne International Workshop on the theory of fusion plasmas (Varenna, Italy, 27-31 August 2012)

    NASA Astrophysics Data System (ADS)

    Gabet, Xavier; Sauter, Olivier

    2013-07-01

    The 2012 Joint Varenna-Lausanne International Workshop on the theory of fusion plasmas was very fruitful. A broad variety of topics was addressed, covering turbulence, magnetohydrodynamics (MHD), edge physics, and radio frequency (RF) wave heating. Moreover, the scope of the meeting was extended this year to include the physics of materials and diagnostics for burning plasmas. This evolution reflects the complexity of problems at hand in fusion, some of them triggered by the construction of ITER and JT-60SA. Long-standing problems without immediate consequences have sometimes become an urgent matter in that context. One may refer to, for instance, the choice of plasma facing components or the design of control systems. Another characteristic of these workshops is the interplay between various domains of plasma physics. For instance, MHD modes are currently investigated with gyrokinetic codes, kinetic effects are included in MHD stability analysis more and more, and turbulence is now accounted for in wave propagation problems. This is proof of cross-fertilization and is certainly a healthy sign for our community. Finally, introducing some novelty in the programme does not prevent from us respecting old traditions. As usual, many presentations were dedicated to numerical simulations. Combining advanced numerical techniques with elaborated analytical theory is certainly a trademark of the Varenna-Lausanne Workshop, which was respected again this year. The quality and size of the scientific output from this workshop is shown in this special issue of Plasma Physics and Controlled Fusion; a further 26 papers have already appeared in Journal of Physics: Conference Series in December 2012. We hope the readers will enjoy this special issue, and find therein knowledge and inspiration.

  12. Superposed epoch analysis of ion temperatures during CIR/HSS-driven storms

    NASA Astrophysics Data System (ADS)

    Keesee, A. M.; Scime, E. E.

    2013-05-01

    Ion temperatures in the plasma sheet influence the development of the ring current. The variation of ion temperatures in the magnetosphere during geomagnetic storms depends on the storm driver. While the magnitude of storms driven by corotating interaction regions and the associated high speed streams (CIR/HSS), as measured by Dst index, tends to be smaller than that for CME-driven storms, significant ion heating occurs during these storms. The TWINS Mission provides a global view of the magnetosphere with continuous temporal coverage provided by two satellites. Ion temperature images with spatial and temporal resolution can be calculated from the energetic neutral atom (ENA) data provided by the satellites. Using this technique, we have found that ion temperatures increase throughout the recovery phase of CIR/HSS-driven storms. Denton and Borovsky [2008] performed a superposed epoch analysis of CIR/HSS-driven storms and found that ion heating begins at convection onset, as measured by the midnight boundary index (MBI). We present superposed epoch analysis results of ion temperature evolution during CIR/HSS-driven storms using both the minimum in the Sym-H index and the MBI for comparison.

  13. The big contradiction between the perturbation theory and the chaotic state. A detailed mathematical analysis indicates when the plasma is stable or unstable

    NASA Astrophysics Data System (ADS)

    Xaplanteris, C. L.; Xaplanteris, S. C.

    2016-05-01

    In the present manuscript enough observations and interpretations of three issues of Plasma Physics are presented. The first issue is linked to the common experimental confirmation of plasma waves which appear to be repeated in a standard way while there are also cases where plasma waves change to an unstable state or even to chaotic state. The second issue is associated with a mathematical analysis of the movement of a charged particle using the perturbation theory; which could be used as a guide for new researchers on similar issues. Finally, the suitability and applicability of the perturbation theory or the chaotic theory is presented. Although this study could be conducted on many plasma phenomena (e.g. plasma diffusion) or plasma quantities (e.g. plasma conductivity), here it was decided this study to be conducted on plasma waves and particularly on drift waves. This was because of the significance of waves on the plasmatic state and especially their negative impact on the thermonuclear fusion, but also due to the long-time experience of the plasma laboratory of Demokritos on drift waves.

  14. A non-linear theory of the parallel firehose and gyrothermal instabilities in a weakly collisional plasma

    NASA Astrophysics Data System (ADS)

    Rosin, M. S.; Schekochihin, A. A.; Rincon, F.; Cowley, S. C.

    2011-05-01

    Weakly collisional magnetized cosmic plasmas have a dynamical tendency to develop pressure anisotropies with respect to the local direction of the magnetic field. These anisotropies trigger plasma instabilities at scales just above the ion Larmor radius ρi and much below the mean free path λmfp. They have growth rates of a fraction of the ion cyclotron frequency, which is much faster than either the global dynamics or even local turbulence. Despite their microscopic nature, these instabilities dramatically modify the transport properties and, therefore, the macroscopic dynamics of the plasma. The non-linear evolution of these instabilities is expected to drive pressure anisotropies towards marginal stability values, controlled by the plasma beta βi. Here this non-linear evolution is worked out in an ab initio kinetic calculation for the simplest analytically tractable example - the parallel (k⊥= 0) firehose instability in a high-beta plasma. An asymptotic theory is constructed, based on a particular physical ordering and leading to a closed non-linear equation for the firehose turbulence. In the non-linear regime, both the analytical theory and the numerical solution predict secular (∝t) growth of magnetic fluctuations. The fluctuations develop a k-3∥ spectrum, extending from scales somewhat larger than ρi to the maximum scale that grows secularly with time (∝t1/2); the relative pressure anisotropy (p⊥-p∥)/p∥ tends to the marginal value -2/βi. The marginal state is achieved via changes in the magnetic field, not particle scattering. When a parallel ion heat flux is present, the parallel firehose mutates into the new gyrothermal instability (GTI), which continues to exist up to firehose-stable values of pressure anisotropy, which can be positive and are limited by the magnitude of the ion heat flux. The non-linear evolution of the GTI also features secular growth of magnetic fluctuations, but the fluctuation spectrum is eventually dominated by

  15. Theory of Filamentary Plasma Array Formation in Microwave Breakdown at Near-Atmospheric Pressure

    SciTech Connect

    Nam, Sang Ki; Verboncoeur, John P.

    2009-07-31

    Recently reported observations of filamentation during high power microwaves breakdown of near-atmospheric pressure gas are explained using a one-dimensional fluid model coupled to a theoretical wave-plasma model. This self-consistent treatment allows for time-dependent effects, plasma growth and diffusion, and partial absorption and reflection of waves. Simulation results, consistent with experiments, show the evolution of the plasma filaments spaced less than one-quarter wavelength, the sequential discrete light emission propagating back toward the source, and the diffusion and decay of the plasma. The model allows examination of many features not easily obtained experimentally, including dependence on field strength and frequency, pressure, and gas composition, which influence the breakdown and emission properties, including the spacing and speed of propagation of the filaments.

  16. Theory and Experimental Program for p-B11 Fusion with the Dense Plasma Focus

    NASA Astrophysics Data System (ADS)

    Lerner, Eric J.; Krupakar Murali, S.; Haboub, A.

    2011-10-01

    Lawrenceville Plasma Physics Inc. has initiated a 2-year-long experimental project to test the scientific feasibility of achieving controlled fusion using the dense plasma focus (DPF) device with hydrogen-boron (p-B11) fuel. The goals of the experiment are: first, to confirm the achievement of high ion and electron energies observed in previous experiments from 2001; second, to greatly increase the efficiency of energy transfer into the plasmoid where the fusion reactions take place; third, to achieve the high magnetic fields (>1 GG) needed for the quantum magnetic field effect, which will reduce cooling of the plasma by X-ray emission; and finally, to use p-B11 fuel to demonstrate net energy gain. The experiments are being conducted with a newly constructed dense plasma focus in Middlesex, NJ which is expected to generate peak currents in excess of 2 MA. Some preliminary results are reported.

  17. Theory of filamentary plasma array formation in microwave breakdown at near-atmospheric pressure.

    PubMed

    Nam, Sang Ki; Verboncoeur, John P

    2009-07-31

    Recently reported observations of filamentation during high power microwaves breakdown of near-atmospheric pressure gas are explained using a one-dimensional fluid model coupled to a theoretical wave-plasma model. This self-consistent treatment allows for time-dependent effects, plasma growth and diffusion, and partial absorption and reflection of waves. Simulation results, consistent with experiments, show the evolution of the plasma filaments spaced less than one-quarter wavelength, the sequential discrete light emission propagating back toward the source, and the diffusion and decay of the plasma. The model allows examination of many features not easily obtained experimentally, including dependence on field strength and frequency, pressure, and gas composition, which influence the breakdown and emission properties, including the spacing and speed of propagation of the filaments. PMID:19792510

  18. Epoch-based Entropy for Early Screening of Alzheimer's Disease.

    PubMed

    Houmani, N; Dreyfus, G; Vialatte, F B

    2015-12-01

    In this paper, we introduce a novel entropy measure, termed epoch-based entropy. This measure quantifies disorder of EEG signals both at the time level and spatial level, using local density estimation by a Hidden Markov Model on inter-channel stationary epochs. The investigation is led on a multi-centric EEG database recorded from patients at an early stage of Alzheimer's disease (AD) and age-matched healthy subjects. We investigate the classification performances of this method, its robustness to noise, and its sensitivity to sampling frequency and to variations of hyperparameters. The measure is compared to two alternative complexity measures, Shannon's entropy and correlation dimension. The classification accuracies for the discrimination of AD patients from healthy subjects were estimated using a linear classifier designed on a development dataset, and subsequently tested on an independent test set. Epoch-based entropy reached a classification accuracy of 83% on the test dataset (specificity = 83.3%, sensitivity = 82.3%), outperforming the two other complexity measures. Furthermore, it was shown to be more stable to hyperparameter variations, and less sensitive to noise and sampling frequency disturbances than the other two complexity measures. PMID:26560459

  19. Fluid and drift-kinetic description of a magnetized plasma with low collisionality and slow dynamics orderings. I. Electron theory

    SciTech Connect

    Ramos, J. J.

    2010-08-15

    A closed theoretical model to describe slow, macroscopic plasma processes in a fusion-relevant collisionality regime is set forward. This formulation is a hybrid one, with fluid conservation equations for particle number, momentum and energy, and drift-kinetic closures. Intended for realistic application to the core of a high-temperature tokamak plasma, the proposed approach is unconventional in that the ion collisionality is ordered lower than in the ion banana regime of neoclassical theory. The present first part of a two-article series concerns the electron system, which is still equivalent to one based on neoclassical electron banana orderings. This system is derived such that it ensures the precise compatibility among the complementary fluid and drift-kinetic equations, and the rigorous treatment of the electric field and the Fokker-Planck-Landau collision operators. As an illustrative application, the special limit of an axisymmetric equilibrium is worked out in detail.

  20. Modified theory of secondary electron emission from spherical particles and its effect on dust charging in complex plasma

    SciTech Connect

    Misra, Shikha; Mishra, S. K.; Sodha, M. S.

    2013-01-15

    The authors have modified Chow's theory of secondary electron emission (SEE) to take account of the fact that the path length of a primary electron in a spherical particle varies between zero to the diameter or x{sub m} the penetration depth depending on the distance of the path from the centre of the particle. Further by including this modified expression for SEE efficiency, the charging kinetics of spherical grains in a Maxwellian plasma has been developed; it is based on charge balance over dust particles and number balance of electrons and ionic species. It is seen that this effect is more pronounced for smaller particles and higher plasma temperatures. Desirable experimental work has also been discussed.

  1. Kinetic theory of current and density drift instabilities with weak charged-neutral collisions. [in space plasmas

    NASA Technical Reports Server (NTRS)

    Gary, S. P.

    1984-01-01

    This paper describes the linear kinetic theory of electrostatic instabilities driven by a density gradient drift and a magnetic-field-aligned current in a plasma with weak charged neutral collisions. The configuration is that of a uniform magnetic field B, a weak, uniform density gradient in the x direction and a weak, uniform electric field in the z direction. Collisions are represented by the BGK model. The transition from the (kinetic) universal density drift instability to the (fluidlike) current convective instability is studied in detail, and the short wavelength properties of the latter mode are investigated.

  2. Structure and Characteristics of a Spherical Plasma Focus: Theory and Simulation

    NASA Astrophysics Data System (ADS)

    Ay, Yasar; Abdal-Halim, Mohamed A.; Bourham, Mohamed

    2014-10-01

    Most studies of dense plasma focus devices use cylindrical coaxial shapes, however, a spherical shape is investigated herein. Snow plow model and shock wave equations are coupled with the circuit equations to model the spherical plasma focus. Of interest in spherical plasma focus is to have both sheath expansion and the magnetic pressure changing rate for the rundown phase instead of the constant sheath only for the cylindrical case. The developed model is compared to published experimental results for validation and good agreement was obtained. Hydrogen and its isotopes were separately used for investigating the effect of the different molecular weights on plasma parameters. The gas pressure and discharge voltage were varied for these gases to study their effect on the plasma parameters. The study predicts a peak discharge current of 1.5 MA for tritium with 0.92 MA dip discharge current, and less for deuterium and hydrogen. The current drop for tritium indicates focus action. It indicates that the sheath velocity for heavy gases is lower than lighter gases. Predicted maximum temperature variation is about 11.1 eV for hydrogen, 14.6 eV for deuterium, 15.9 eV for DT mixture and 17eV for pure tritium; which indicates higher temperature with heavier gasses.

  3. Phase-space description of plasma waves. Part 1. Linear theory

    NASA Astrophysics Data System (ADS)

    Biro, T.; Rönnmark, K.

    1992-06-01

    We develop an (r, k) phase-space description of waves in plasmas by introducing Gaussian window functions to separate short-scale oscillations from long-scale modulations of the wave fields and variations in the plasma parameters. To obtain a wave equation that unambiguously separates conservative dynamics from dissipation in an inhomogeneous and time-varying background plasma, we first discuss the proper form of the current response function. In analogy with the particle distribution function f(v, r, t), we introduce a wave density N(k, r, t) on phase space. This function is proved to satisfy a simple continuity equation. Dissipation is also included, and this allows us to describe the damping or growth of wave density along rays. Problems involving geometric optics of continuous media often appear simpler when viewed in phase space, since the flow of N in phase space is incompressible.

  4. Plasma theory and simulation. Quarterly progress report Nos. 1 and 2, 1 January-30 June 1986

    SciTech Connect

    Birdsall, C.K.

    1986-06-30

    Computer simulation of bounded plasma systems, with external circuits, is discussed in considerable detail; artificial cooling of trapped electrons in bounded simulations was observed and is now attributed to noiseless injection: the cooling does not occur if random injection is used; the collector and source sheaths at the boundaries of warm plasma are treated in detail, including ion reflection and secondary-electron emission at the collector; the kelvin-Helmholtz instability is observed in a self-consistent magnetized sheath, producing long-lived vortices which increase the particle transport to the wall dramatically; the ES2 user's manual - Version 1 has been issued; addition of electron-neutral elastic collisions is introduced; implicit particle simulation of velocity space transport and self-consistent electric potentials in magnetized plasmas (TESS code) is described in detail; and dynamic dimensioning with heap management is described in detail.

  5. Theory of plasma contactors in ground-based experiments and low earth orbit

    NASA Astrophysics Data System (ADS)

    Gerver, M. J.; Hastings, D. E.; Oberhardt, M. R.

    1990-08-01

    An examination of several models of electron collection by plasma contactors leads to a definition of the range of validity and applicability for each model. It is noted that most present ground-based experiments are of limited relevance to space applications of plasma contactors, since they operate in a regime where the magnetic field and effective collisions are at most only marginally important. An exception is the experiment of Stenzel and Urrutia (1986), which examined a plasma whose electron Larmor radius was small by comparison to the scale of the potential, and in which the anomalous transport of electrons across the magnetic field was important. The enhanced electron current was not continuous in time, but occurred in periodic bursts as the instabilities periodically emerged, saturated, and decayed.

  6. Theory of plasma contactors in ground-based experiments and low earth orbit

    NASA Technical Reports Server (NTRS)

    Gerver, M. J.; Hastings, D. E.; Oberhardt, M. R.

    1990-01-01

    An examination of several models of electron collection by plasma contactors leads to a definition of the range of validity and applicability for each model. It is noted that most present ground-based experiments are of limited relevance to space applications of plasma contactors, since they operate in a regime where the magnetic field and effective collisions are at most only marginally important. An exception is the experiment of Stenzel and Urrutia (1986), which examined a plasma whose electron Larmor radius was small by comparison to the scale of the potential, and in which the anomalous transport of electrons across the magnetic field was important. The enhanced electron current was not continuous in time, but occurred in periodic bursts as the instabilities periodically emerged, saturated, and decayed.

  7. Theory of coherent transition radiation generated at a plasma-vacuum interface

    SciTech Connect

    Schroeder, Carl B.; Esarey, Eric; van Tilborg, Jeroen; Leemans, Wim P.

    2003-06-26

    Transition radiation generated by an electron beam, produced by a laser wakefield accelerator operating in the self-modulated regime, crossing the plasma-vacuum boundary is considered. The angular distributions and spectra are calculated for both the incoherent and coherent radiation. The effects of the longitudinal and transverse momentum distributions on the differential energy spectra are examined. Diffraction radiation from the finite transverse extent of the plasma is considered and shown to strongly modify the spectra and energy radiated for long wavelength radiation. This method of transition radiation generation has the capability of producing high peak power THz radiation, of order 100 (mu)J/pulse at the plasma-vacuum interface, which is several orders of magnitude beyond current state-of-the-art THz sources.

  8. Theory and observation of a dynamically evolving negative ion plasma. [in F region

    NASA Technical Reports Server (NTRS)

    Mendillo, M.; Forbes, J.

    1982-01-01

    The study described here examines the full range of negative-ion chemistry in the upper ionosphere by using current reaction rate data to investigate the many chemical paths SF6-type injections might take in an F region environment. Special attention is given to the conditions required to create heavy negative ions that persist long enough to affect the dynamical properties of the F region. The ambipolar diffusion characteristics of a three-component plasma are described, and estimates are given of the incoherent scatter spectra obtained from such a plasma. Model calculations using a first-order chemical code are defined and tested in order to investigate the actual types of negative-ion plasma capable of being created under nighttime conditions.

  9. Theory of coherent transition radiation generated at a plasma-vacuum interface.

    PubMed

    Schroeder, C B; Esarey, E; Van Tilborg, J; Leemans, W P

    2004-01-01

    Transition radiation generated by an electron beam, produced by a laser wakefield accelerator operating in the self-modulated regime, crossing the plasma-vacuum boundary is considered. The angular distributions and spectra are calculated for both the incoherent and the coherent radiation. The effects of the longitudinal and transverse momentum distributions on the differential energy spectra are examined. Diffraction radiation from the finite transverse extent of the plasma is considered and shown to strongly modify the spectra and energy radiated for long-wavelength radiation. This method of transition radiation generation has the capability of producing high peak power terahertz radiation, of order 100 microJ/pulse at the plasma-vacuum interface, which is several orders of magnitude beyond current state-of-the-art terahertz sources. PMID:14995729

  10. Saliva versus plasma pharmacokinetics: theory and application of a salivary excretion classification system.

    PubMed

    Idkaidek, Nasir; Arafat, Tawfiq

    2012-08-01

    The aims of this work were to study pharmacokinetics of randomly selected drugs in plasma and saliva samples in healthy human volunteers, and to introduce a Salivary Excretion Classification System. Saliva and plasma samples were collected for 3-5 half-life values of sitagliptin, cinacalcet, metformin, montelukast, tolterodine, hydrochlorothiazide (HCT), lornoxicam, azithromycin, diacerhein, rosuvastatin, cloxacillin, losartan and tamsulosin after oral dosing. Saliva and plasma pharmacokinetic parameters were calculated by noncompartmental analysis using the Kinetica program. Effective intestinal permeability (Peff) values were estimated by the Nelder-Mead algorithm of the Parameter Estimation module using the SimCYP program. Peff values were optimized to predict the actual average plasma profile of each drug. All other physicochemical factors were kept constant during the minimization processes. Sitagliptin, cinacalcet, metformin, tolterodine, HCT, azithromycin, rosuvastatin and cloxacillin had salivary excretion with correlation coefficients of 0.59-0.99 between saliva and plasma concentrations. On the other hand, montelukast, lornoxicam, diacerhein, losartan and tamsulosin showed no salivary excretion. Estimated Peff ranged 0.16-44.16 × 10(-4) cm/s, while reported fraction unbound to plasma proteins (fu) ranged 0.01-0.99 for the drugs under investigation. Saliva/plasma concentrations ratios ranged 0.11-13.4, in agreement with drug protein binding and permeability. A Salivary Excretion Classification System (SECS) was suggested based on drug high (H)/low (L) permeability and high (H)/low (L) fraction unbound to plasma proteins, which classifies drugs into 4 classes. Drugs that fall into class I (H/H), II (L/H) or III (H/L) are subjected to salivary excretion, while those falling into class IV (L/L) are not. Additional data from literature was also analyzed, and all results were in agreement with the suggested SECS. Moreover, a polynomial relationship with

  11. Plasma theory and simulation. Quarterly progress report Nos. 3 and 4, 1 July-31 December 1985

    SciTech Connect

    Birdsall, C.K.

    1985-12-31

    Contents include: linear magnetized plasma response to an oblique electrostatic wave; limits of linear response of a Vlasov distribution; saturation and post-saturation behavior of the Alfven ion-cyclotron instability: a simulation study; stabilizing effects of finite-amplitude r-f waves on the interchange instability; effect of large amplitude perpendicularly-propagating rf waves on the interchange instability; numerical simulations of turbulent trapping in the weak beam plasma instability: study of the growth rates; planar magnetron discharge simulations; planar magnetron discharges: mechanisms for instability, and numerical study of equilibrium; ES2: an electrostatic 2-D bounded simulation code with injection and external circuit; and energy conserving reflection algorithm.

  12. Long wavelength gradient drift instability in Hall plasma devices. I. Fluid theory

    SciTech Connect

    Frias, Winston; Smolyakov, Andrei I.; Kaganovich, Igor D.; Raitses, Yevgeny

    2012-07-15

    The problem of long wavelength instabilities in Hall thruster plasmas is revisited. A fluid model of the instabilities driven by the E{sub 0} Multiplication-Sign B drift in plasmas with gradients of density, electron temperature, and magnetic field is proposed. It is shown that full account of compressibility of the electron flow in inhomogeneous magnetic field leads to quantitative modifications of earlier obtained instability criteria and characteristics of unstable modes. Modification of the stability criteria due to finite temperature fluctuations is investigated.

  13. Physics of laser fusion. Vol. I. Theory of the coronal plasma in laser-fusion targets

    SciTech Connect

    Max, C.E.

    1981-12-01

    This monograph deals with the physics of the coronal region in laser fusion targets. The corona consists of hot plasma which has been evaporated from the initially solid target during laser heating. It is in the corona that the laser light is absorbed by the target, and the resulting thermal energy is conducted toward cold high-density regions, where ablation occurs. The topics to be discussed are theoretical mechanisms for laser light absorption and reflection, hot-electron production, and the physics of heat conduction in laser-produced plasmas. An accompanying monograph by H. Ahlstrom (Vol.II) reviews the facilities, diagnostics, and data from recent laser fusion experiments.

  14. Theory of a Stationary Current-Free Double Layer in a Collisionless Plasma

    SciTech Connect

    Ahedo, Eduardo; Martinez Sanchez, Manuel

    2009-09-25

    Current-free double layers can develop in a collisionless, inertia-controlled plasma with two electron populations, expanding in a convergent-divergent nozzle. The double layer characteristics depend on whether they develop at the nozzle divergent side, convergent side, or throat. The divergent-geometry double layer describes faithfully the Hairapetian-Stenzel experiment [Phys. Rev. Lett. 65, 175 (1990)], whereas the two other types correspond with those studied in self-similar expansions and wall-collection models of similar plasmas.

  15. Tests of Transport Theory and Reduced Impurity Influx with Highly Radiative Plasmas in TFTR

    NASA Astrophysics Data System (ADS)

    Hill, K. W.

    1997-11-01

    The electron and ion temperature profiles in beam-heated plasmas were observed to be remarkably invariant when radiative losses were increased significantly through gas puffing of high-Z impurities (argon, krypton, xenon) in the Tokamak Fusion Test Reactor. Without impurity puffing, radiative losses accounted for typically only ~ 25\\char'45 of the input power and the radiation profile was strongly peaked at the plasma edge, where the dominant carbon impurity was not fully stripped. At central electron temperatures, T_eo, of ~ 6 keV, trace concentrations of krypton and xenon (n_z/ne ~ 10-3) generated flat and centrally peaked radiation profiles respectively, and a significant fraction of the input power (45-100\\char'45 ) was lost through radiation. This loss provided a nearly ideal technique for studying local heat transport in tokamaks because it perturbed the net heating profile strongly and in a measureable way, with little effect on the density and the beam deposition profiles. In supershot plasmas, Ti >> T_e, the ion temperature profile remained constant, or even increased modestly, as the radiated power fraction was increased to 75-90\\char'45 with krypton and xenon. This observation is surprising because ion-electron coupling is the dominant power loss term for the ions in the core of supershot plasmas, and the central Ti would have decreased a factor of two if the local ion thermal diffusivity had remained constant at its value without impurity puffing. In L-mode plasmas where ion-electron power coupling is a smaller term in the power balance, the electron temperature during impurity puffing also changed only ~ 10-15\\char'45 even as the net power flow through the electrons was decreased by a factor of ~ 3. The ``stiffness" of the temperature profiles to net input power is supportive of transport mechanisms which have a marginal-stability character. Preliminary comparisons of the temperature changes with predictions of the IFS/PPPL transport model

  16. Weakly relativistic quantum kinetic theory for electrostatic wave modes in magnetized plasmas

    SciTech Connect

    Hussain, Azhar; Stefan, Martin; Brodin, Gert

    2014-03-15

    We have derived the electrostatic dispersion relation in a magnetized plasma using a recently developed quantum kinetic model based on the Dirac equation. The model contains weakly relativistic spin effects such as Thomas precession, the polarization currents associated with the spin and the spin-orbit coupling. It turns out that for strictly electrostatic perturbations the non-relativistic spin effects vanish, and the modification of the classical dispersion relation is solely associated with the relativistic terms. Several new wave modes appear due the electron spin effects, and an example for astrophysical plasmas are given.

  17. Electrodynamics of the Plasma Environment Induced around Spacecraft in Low Earth Orbit: Three-Dimensional Theory and Numerical Modeling.

    NASA Astrophysics Data System (ADS)

    Gatsonis, Nikolaos Achilleas

    A study is presented of the electrodynamic interactions within the plasma environment induced around spacecraft in Low Earth Orbit. A fully three-dimensional theory and a computational model is developed for an artificial plasma cloud created by spacecraft with the potential of releasing neutrals and/or plasma into the ambient ionosphere. A fluid model for the plasma transport is derived. The forces included in the momentum balance are due to electric fields, pressure, gravity, drag due to collisions and perturbative inertia terms. The Flux Corrected Transport (FCT) scheme is used for the numerical solution of the hyperbolic continuity equations. This approach limits the artificial dissipation or dispersion arising in the numerical solution. The 3D -FCT algorithm, and the stability characteristics of the high and low order schemes used in the FCT are discussed. The equation for the electrostatic potential is a three-dimensional nonself-adjoint elliptic equation with highly dissimilar coefficients. The numerical solution of the resulting large, sparse, asymmetric system of equations is discussed. Initial time numerical simulations are performed. A water-bag plasma cloud model is used to demonstrate the current coupling process. For neutral densities higher than the ambient the plasma cloud develops a transverse drift of the order of the orbital velocity. Simulations of typical spacecraft operations are performed and the created water plasma cloud is studied. It is shown that the flow of neutrals is in the free molecular regime. The effects of altitude of the release, orientation of the thrust vector with regard to the magnetic field, and latitude are considered. It is shown that a large water ion cloud is formed with densities of the order of the ambient oxygen ions. The ultraviolet radiation emission is shown to modify the signature of the spacecraft. The model predicts qualitatively most of the observations. Quantitatively predictions are within the measured

  18. Phase-space description of plasma waves: Linear and nonlinear theory

    NASA Astrophysics Data System (ADS)

    Biro, Thomas

    1992-11-01

    A (r,k) phase description of waves in plasmas is developed by introducing Gaussian window functions to separate short scale oscillations from long scale modulations of the wave fields and variations in the plasma parameters. To obtain a wave equation that unambiguously separates conservative dynamics from dissipation also in an inhomogeneous and time varying background plasma, the proper form of the current response function, is discussed. On the analogy of the particle distribution function f(v,r,t), a wave density N(k,r,t) is introduced on phase space. This function is proven to satisfy a simple continuity equation. Dissipation is also included, and this allows the damping or growth of wave density along rays to be described. Problems involving geometric optics of continuous media often appear simpler when viewed in phase space, since the flow of N in phase space is incompressible. Within the phase space representation, a very general formula for the second order nonlinear current is obtained in terms of the vector potential. This formula is a convenient starting point for studies of coherent as well as turbulent nonlinear processes. Kinetic equations for weakly inhomogeneous and turbulent plasmas are derived, including the effects of inhomogeneous turbulence, wave convection and refraction.

  19. Phenomenological Theory of the Kink Instability in a Slender Plasma Column

    SciTech Connect

    Ryutov, D D; Furno, I; Intrator, T P; Abbate, S; Madziwa-Nussinov, T

    2005-11-18

    When one deals with a plasma column whose radius a is much smaller than its length L, one can think of it as of a thin filament whose kink instability can be adequately described simply by a 2D displacement vector, {xi}{sub x} = {xi}{sub s}(z,t); {xi}{sub y} = {xi}{sub y}(z,t). Details of the internal structure of the column such as the current, density, and axial flow velocity distribution would be lumped into some phenomenological parameters. This approach is particularly efficient in the problems with non-ideal (sheath) boundary conditions (BC) at the end electrodes, with the finite plasma resistivity, and with a substantial axial flow. With the sheath BC imposed at one of the end-plates, we find instability in the domain well below the classical Kruskal-Shafranov limit. The presence of an axial flow causes the onset of rotation of the kink and strong axial ''skewness'' of the eigenfunction, with the perturbation amplitude increasing in the flow direction. We consider the limitations of the phenomenological approach and find that they are related to the steepness with which the plasma resistivity increases at the plasma boundary with vacuum.

  20. Plasma theory and simulation. Quarterly progress report Nos. 1-2, 1 January-30 June 1988

    SciTech Connect

    Birdsall, C.K.

    1988-06-30

    A magnetized plasma next to an absorbing wall is simulated, showing positive wall charging causing a large E-field near the wall, than a large ExB drift, then a Kelvin-Helmholtz instability, vortices, and coalescence. Particle transport to the walls is Bohm-like, for omega sub pi > omega sub ci. Plasma transport across B/sub O/ to a wall is studied without and with an active antenna buried in the wall. Particle losses are increased appreciably by the fields of the antenna. Small-angle Coulomb collisions produce a drag force and diffusion tensor, which are calculated self-consistently. This produces a FP-PIC method. An example is shown for a beam scattering off fixed ions. Implicit particle simulations are discussed for bounded plasma. The effect of source distribution on the sheath potential is discussed. Initiation of an effort to simulate a traveling-wave tube is discussed. Substantial progress was made in making the authors standard periodic code ES1 work efficiently on a fast PC. A plasma sheath reference listing is discussed.

  1. Theory of coherent electron-scale magnetic structures in space plasma turbulence

    NASA Astrophysics Data System (ADS)

    Jovanović, Dušan; Alexandrova, Olga; Maksimović, Milan

    2015-08-01

    Recent spacecraft observations in the solar wind and in the Earth’s magnetosheath indicate that the dissipation range of magnetic turbulence probably takes place at electron scales. Here, we derive nonlinear electron magnetohydrodynamic (EMHD) equations for warm plasma, i.e. with the ratio of thermodynamic and magnetic pressures, β ∼ 1. This model describes plasma turbulence under the solar wind and magnetosheath conditions on the electron spatial scales and with the characteristic frequency that does not exceed the electron gyrofrequency. We show that at electron scales and in the presence of a sufficiently large temperature anisotropy {T}{e\\perp }/{T}{e\\parallel }\\gt 1, there exist self-organized, coherent, nonlinear dipole vortex structures associated with obliquely propagating whistler waves. These can be visualized as pairs of counterstreaming helicoidal currents that produce both the compressional and torsional perturbations of the magnetic field. In contrast to the previously known long-range EMHD dipolar vortices in a cold plasma, this novel solution is an evanescent mode, strongly localized in space (with wave numbers {k}\\perp \\gg {k}\\parallel ). It can constitute a building block for the plasma turbulence at short scales and provide a possible scenario of turbulence dissipation at electron scales.

  2. Phenomenological theory of the kink instability in a slender plasma column

    NASA Astrophysics Data System (ADS)

    Ryutov, D. D.; Furno, I.; Intrator, T. P.; Abbate, S.; Madziwa-Nussinov, T.

    2006-03-01

    In this paper we are concerned with the kink instability of a current-carrying plasma column whose radius a is much smaller than its length L. In the limit a ≪L, one can consider the column as a thin filament whose kinking can be adequately described simply by a two dimensional 2D displacement vector, ξx=ξx(z,t); ξy=ξy(z,t). Details of the internal structure of the column such as the radial distribution of the current, density, and axial flow can be lumped into some phenomenological parameters. This approach is particularly efficient in the problems with nonideal (sheath) boundary conditions (BC) at the end electrodes, with the finite plasma resistivity, and with a substantial axial flow. With the sheath BC imposed at one of the endplates, we find instability in the domain well below the classical Kruskal-Shafranov limit. The presence of an axial flow causes the onset of rotation of the kink and strong axial "skewness" of the eigenfunction, with the perturbation amplitude increasing in the flow direction. The limitations of the phenomenological approach are analyzed and are related to the steepness with which the plasma resistivity increases at the plasma boundary with vacuum.

  3. Phenomenological theory of the kink instability in a slender plasma column

    NASA Astrophysics Data System (ADS)

    Ryutov, D. D.; Furno, I.

    2005-10-01

    When one deals with a plasma column whose radius a is much smaller than its length L, one can think of it as of a thin filament whose kink instability can be adequately described simply by a 2D displacement vector, x=x(z,t); y=y(z,t). Details of the internal structure of the column such as the current, density, and axial flow velocity distribution would be lumped into some phenomenological parameters. This approach is particularly efficient in the problems with non-ideal (sheath) boundary conditions at the end electrodes, the finite plasma resistivity, and the case of a substantial axial flow. For the non-ideal situation, we find instability in the domain well below the classical Kruskal-Shafranov limit. The presence of an axial flow causes the onset of a rotation of the kink and strong axial ``skewness'' of the eigenfunction. We consider the limitations of the phenomenological approach and find that they are related to the steepness with which the plasma resistivity increases at the plasma boundary with vacuum. Work performed for US DOE by UC LLNL under contract #W-7405-Eng-48.

  4. Asymptotic theory of double layer and shielding of electric field at the edge of illuminated plasma

    SciTech Connect

    Benilov, M. S.; Thomas, D. M.

    2014-04-15

    The method of matched asymptotic expansions is applied to the problem of a collisionless plasma generated by UV illumination localized in a central part of the plasma in the limiting case of small Debye length λ{sub D}. A second-approximation asymptotic solution is found for the double layer positioned at the boundary of the illuminated region and for the un-illuminated plasma for the plane geometry. Numerical calculations for different values of λ{sub D} are reported and found to confirm the asymptotic results. The net integral space charge of the double layer is asymptotically small, although in the plane geometry it is just sufficient to shield the ambipolar electric field existing in the illuminated region and thus to prevent it from penetrating into the un-illuminated region. The double layer has the same mathematical nature as the intermediate transition layer separating an active plasma and a collisionless sheath, and the underlying physics is also the same. In essence, the two layers represent the same physical object: a transonic layer.

  5. Nonlinear theory of ionic sound waves in a hot quantum-degenerate electron-positron-ion plasma

    SciTech Connect

    Dubinov, A. E. Sazonkin, M. A.

    2010-11-15

    A collisionless nonmagnetized e-p-i plasma consisting of quantum-degenerate gases of ions, electrons, and positrons at nonzero temperatures is considered. The dispersion equation for isothermal ionic sound waves is derived and analyzed, and an exact expression is obtained for the linear velocity of ionic sound. Analysis of the dispersion equation has made it possible to determine the ranges of parameters in which nonlinear solutions in the form of solitons should be sought. A nonlinear theory of isothermal ionic sound waves is developed and used for obtaining and analyzing the exact solution to the system of initial equations. Analysis has been carried out by the method of the Bernoulli pseudopotential. The ranges of phase velocities of periodic ionic sound waves and soliton velocities are determined. It is shown that in the plasma under investigation, these ranges do not overlap and that the soliton velocity cannot be lower than the linear velocity of ionic sound. The profiles of physical quantities in a periodic wave and in a soliton are constructed, as well as the dependences of the velocity of sound and the critical velocity on the ionic concentration in the plasma. It is shown that these velocities increase with the ion concentration.

  6. From liquid crystal models to the guiding-center theory of magnetized plasmas

    NASA Astrophysics Data System (ADS)

    Tronci, Cesare

    2016-08-01

    Upon combining Northrop's picture of charged particle motion with modern liquid crystal theories, this paper provides a new description of guiding center dynamics (to lowest order). This new perspective is based on a rotation gauge field (gyrogauge) that encodes rotations around the magnetic field. In liquid crystal theory, an analogue rotation field is used to encode the rotational state of rod-like molecules. Instead of resorting to sophisticated tools (e.g. Hamiltonian perturbation theory and Lie series expansions) that still remain essential in higher-order gyrokinetics, the present approach combines the WKB method with a simple kinematical ansatz, which is then replaced into the charged particle Lagrangian. The latter is eventually averaged over the gyrophase to produce the guiding-center equations. A crucial role is played by the vector potential for the gyrogauge field. A similar vector potential is related to liquid crystal defects and is known as wryness tensor in Eringen's micropolar theory.

  7. Hollow cathode theory and experiment. I. Plasma characterization using fast miniature scanning probes

    SciTech Connect

    Goebel, Dan M.; Jameson, Kristina K.; Watkins, Ron M.; Katz, Ira; Mikellides, Ioannis G.

    2005-12-01

    A detailed study of the spatial variation of plasma density, temperature, and potential in hollow cathodes using miniature fast scanning probes has been undertaken in order to better understand the cathode operation and to provide benchmark data for the modeling of the cathode performance and life described in a companion paper. Profiles are obtained throughout the discharge and in the very high-density orifice region by pneumatically driven Langmuir probes, which are inserted directly into the hollow cathode orifice from either the upstream insert region inside the hollow cathode or from the downstream anode-plasma region. A fast transverse-scanning probe is also used to provide radial profiles of the cathode plume as a function of position from the cathode exit. The probes are extremely small to avoid perturbing the plasma; the ceramic tube insulator is 0.05 cm in diameter with a probe tip area of 0.002 cm{sup 2}. A series of current-voltage characteristics are obtained by applying a rapid sawtooth voltage wave form to the probe as it is scanned through the plasma at speeds of up to 2 m/s to produce the profiles with a spatial resolution of about 0.05 cm. At discharge currents of 10-25 A from the 1.5-cm-diameter hollow cathode, the plasma density inside the cathode is found to exceed 10{sup 14} cm{sup -3}, with the peak density occurring upstream of the orifice. The plasma potentials on axis inside the cathode are found to be in the 10-20 V range with electron temperatures of 2-5 eV, depending on the discharge current and gas flow rate. A potential discontinuity or double layer of less than 10 V is observed in the orifice region, and under certain conditions appears in the bright 'plasma ball' in front of the cathode. This structure tends to change location and magnitude with discharge current, gas flow, and orifice size. A potential maximum proposed in the literature to exist in or near the cathode orifice is not observed. Instead, the plasma potential increases

  8. Thermal fluctuation levels of magnetic and electric fields in unmagnetized plasma: The rigorous relativistic kinetic theory

    SciTech Connect

    Yoon, P. H. E-mail: rsch@tp4.rub.de; Schlickeiser, R. E-mail: rsch@tp4.rub.de; Kolberg, U. E-mail: rsch@tp4.rub.de

    2014-03-15

    Any fully ionized collisionless plasma with finite random particle velocities contains electric and magnetic field fluctuations. The fluctuations can be of three different types: weakly damped, weakly propagating, or aperiodic. The kinetics of these fluctuations in general unmagnetized plasmas, governed by the competition of spontaneous emission, absorption, and stimulated emission processes, is investigated, extending the well-known results for weakly damped fluctuations. The generalized Kirchhoff radiation law for both collective and noncollective fluctuations is derived, which in stationary plasmas provides the equilibrium energy densities of electromagnetic fluctuations by the ratio of the respective spontaneous emission coefficient and the true absorption coefficient. As an illustrative example, the equilibrium energy densities of aperiodic transverse collective electric and magnetic fluctuations in an isotropic thermal electron-proton plasmas of density n{sub e} are calculated as |δB|=√((δB){sup 2})=2.8(n{sub e}m{sub e}c{sup 2}){sup 1/2}g{sup 1/2}β{sub e}{sup 7/4} and |δE|=√((δE){sup 2})=3.2(n{sub e}m{sub e}c{sup 2}){sup 1/2}g{sup 1/3}β{sub e}{sup 2}, where g and β{sub e} denote the plasma parameter and the thermal electron velocity in units of the speed of light, respectively. For densities and temperatures of the reionized early intergalactic medium, |δB|=6·10{sup −18}G and |δE|=2·10{sup −16}G result.

  9. New Release of the BSM Epoch Photometry Database

    NASA Astrophysics Data System (ADS)

    Henden, A.

    2016-06-01

    (Abstract only) The Bright Star Monitor (BSM) Epoch Photometry Database (EPD) is a searchable catalog of all observations made by one of the AAVSO's five BSM systems. The newest release of this database contains some 100 million datasets, from both northern and southern hemispheres, taken over the last six years. These have been calibrated by both nightly visits to Landolt standard fields as well as through the use of the Tycho2 photometric catalog. The paper will describe how the observations were made, how to access the catalog, and the limitations to the photometric accuracy. Some examples of well-studied fields will be shown.

  10. The joint US/UK 1990 epoch world magnetic model

    NASA Technical Reports Server (NTRS)

    Quinn, John M.; Coleman, Rachel J.; Peck, Michael R.; Lauber, Stephen E.

    1991-01-01

    A detailed summary of the data used, analyses performed, modeling techniques employed, and results obtained in the course of the 1990 Epoch World Magnetic Modeling effort are given. Also, use and limitations of the GEOMAG algorithm are presented. Charts and tables related to the 1990 World Magnetic Model (WMM-90) for the Earth's main field and secular variation in Mercator and polar stereographic projections are presented along with useful tables of several magnetic field components and their secular variation on a 5-degree worldwide grid.

  11. Multi-Epoch Observations of Dust Formed around WR140

    NASA Astrophysics Data System (ADS)

    Sakon, I.; Ohsawa, R.; Asano, K.; Mori, T. I.; Onaka, T.; Nozawa, T.; Kozasa, T.; Fujiyoshi, T.

    2012-08-01

    We present results of the mid-infrared multi-epoch observations of periodically dust-making Wolf-Rayet binary WR140 with Subaru/COMICS. Based on the N- and Q-bands photometric observations, the mass evolution of dust in the expanding concentric arc structures formed during the 2001 and 2009 periastron events is investigated. Our results show that at most 1.0×10-8M⊙ of dust survives per periastron later than an orbital phase, suggesting that such WR binary systems may not be the major dust budget in the early universe unless the grain growth later on should not take place.

  12. Multi-epoch Multi-frequency Observations of Double Pulsar using GMRT at lower radio frequencies

    NASA Astrophysics Data System (ADS)

    Joshi, Bhal Chandra

    The double pulsar system, J0737-3039, (Burgay et al. 2003; Lyne et al. 2004) with two radio pulsars in a tight edge-on mildly eccentric orbit with a significant advance of angle of periastron (orbital period Pb = 2.4 hr, orbital inclination angle i = 87.7 deg, eccentricity 0.09, ω = ˙ 17 deg) continues to display interesting and changing phenomenology. The timing observations and this phenomenology has been very useful to test theories of gravity (Kramer and Stairs 2009). We report on last seven years of monitoring of these pulsars at 325 and 235 MHz using GMRT and compare the variation in the phenomenology of the pulsars as a function of observation epoch with that at higher frequencies.

  13. Kinetic theory of alpha particles production in a dense and strongly magnetized plasma

    NASA Astrophysics Data System (ADS)

    Cereceda, Carlo; Deutsch, Claude; De Peretti, Michel; Sabatier, Michel; Basko, Mikhail M.; Kemp, Andreas; Meyer-ter-Vehn, Jurgend

    2000-11-01

    In connection with fundamental issues relevant to magnetized target fusion, the distribution function of thermonuclear alpha particles produced in situ in a dense, hot, and strongly magnetized hydrogenic plasma considered fully ionized in a cylindrical geometry is investigated. The latter is assumed in local thermodynamic equilibrium with Maxwellian charged particles. The approach is based on the Fokker-Planck equation with isotropic source S and loss s terms, which may be taken arbitrarily under the proviso that they remain compatible with a steady state. A novel and general expression is then proposed for the isotropic and stationary distribution f(v). Its time-dependent extension is worked out numerically. The solutions are valid for any particle velocity v and plasma temperature T. Higher order magnetic and collisional corrections are also obtained for electron gyroradius larger than Debye length. f(v) moments provide particle diffusion coefficient and heat thermal conductivity. Their scaling on collision time departs from Braginski's.

  14. Microwave N{sub 2}-Ar plasma torch. II. Experiment and comparison with theory

    SciTech Connect

    Henriques, J.; Tatarova, E.; Dias, F. M.; Ferreira, C. M.

    2011-01-15

    Spatially resolved emission spectroscopy techniques have been used to determine the gas temperature, the electron, and N{sub 2}{sup +} ion densities and the relative emission intensities of radiative species in a microwave (2.45 GHz) plasma torch driven by a surface wave. The experimental results have been analyzed in terms of a two-dimensional theoretical model based on a self-consistent treatment of particles kinetics, gas dynamics, and wave electrodynamics. The measured spatial variations in the various quantities agree well with the model predictions. The radially averaged gas temperature is around 3000 K and varies only slowly along the discharge zone of the source but it drops sharply down to about 400 K in the postdischarge. The experimental wave dispersion characteristics nearly follow the theoretical ones, thus confirming that this plasma source is driven by a surface wave.

  15. Microwave heating power distribution in electron-cyclotron resonance processing plasmas, experiment and theory

    SciTech Connect

    Douglass, S.R.; Eddy, C. Jr.; Lampe, M.; Joyce, G.; Slinker, S.; Weber, B.V.

    1995-12-31

    The authors are currently investigating the mechanisms of microwave power absorption in an ECR plasma. The microwave electric field is detected with an antenna at the end of a shielded co-ax cable, connected to a bolometer for power measurements. Initial measurements have been 1-D along the axis of the plasma chamber. Later, 3-D profiles will be made of the microwave heating power distribution. A comparison of the experimental results with the theoretical microwave absorption are presented. A ray tracing analysis of the propagating right hand wave are given, including both collisional and collisionless absorption. Mode conversion effects are studied to explain why most of the power is absorbed at the entry window, especially the L wave power.

  16. Plasma irregularities associated with a morning discrete auroral arc - Radar interferometer observations and theory

    NASA Technical Reports Server (NTRS)

    Providakes, J.; Farley, D. T.; Swartz, W. E.; Riggin, D.

    1985-01-01

    A description is given of E region auroral plasma irregularities associated with an intense auroral morning arc observed over Fort Churchill by radar. The observations are compared with data from an all-sky camera (ASC) operated at Fort Churchill by the National Research Council of Canada. The particular event described was chosen because of the rapid variation in structure and motion of the arc as it traveled through the radar beam. The horizontal vector electron drift velocity and electric field along the poleward boundary of the morning discrete auroral arc was successfully measured with a radar interferometer. This instrument provided information concerning the temporal and spatial structure of the electrostatic plasma turbulence in the arc. The observations are described.

  17. Comment on 'Nonlinear gyrokinetic theory with polarization drift' [Phys. Plasmas 17, 082304 (2010)

    SciTech Connect

    Leerink, S.; Parra, F. I.; Heikkinen, J. A.

    2010-12-15

    In this comment, we show that by using the discrete particle distribution function the changes of the phase-space volume of gyrocenter coordinates due to the fluctuating ExB velocity do not explicitly appear in the Poisson equation and the [Sosenko et al., Phys. Scr. 64, 264 (2001)] result is recovered. It is demonstrated that there is no contradiction between the work presented by Sosenko et al. and the work presented by [Wang et al., Phys. Plasmas 17, 082304 (2010)].

  18. Plasma theory and simulation. Third and fourth quarter progress report, July 1-December 31, 1984

    SciTech Connect

    Birdsall, C.K.

    1984-01-01

    Several theoretical investigations are reported. These topics include: (1) oblique electron Bernstein waves; (2) the effect of large amplitude rf waves on the interchange instability; (3) one-beam Alfven ion-cyclotron instabilities of multibeam ion distribution; (4) linear mode coupling in simulations of the Alfven ion-cyclotron instability; (5) plasma-sheath region; (6) planar magnetron discharges; (7) low-alpha Pierce diode; and (8) ion-acoustic double layers. 8 refs., 37 figs.

  19. Self-consistent theory of high-order harmonic generation by relativistic plasma mirror.

    PubMed

    Debayle, A; Sanz, J; Gremillet, L

    2015-11-01

    We present a self-consistent semianalytical model of the relativistic plasma mirror, based on the exact computation of the laser-driven electron surface oscillations within the cold-fluid approximation. Valid for arbitrary solid densities, laser incidence angle, and a large set of laser intensities (10(18)-10(21) W/cm(2)), the model unravels different regimes of harmonic generation. In particular, it is found that efficient conversion of p-polarized laser pulses into high-order harmonics well above the plasma frequency requires either high laser intensities, low plasma densities, or incidence angles larger than a threshold value. This critical angle corresponds to a transition between a regime where the electron surface dynamics is mostly governed by the laser J×B force and a "cyclotron Brunel" regime, where electrons perform many cyclotron gyrations when moving into the vacuum. Under conditions relevant to current laser experiments, the latter regime gives rise to nonmonotonic variations of the harmonic yield with the laser field. Our predictions are supported by an extensive parametric study performed with highly resolved one-dimensional particle-in-cell simulations. PMID:26651803

  20. Self-consistent theory of high-order harmonic generation by relativistic plasma mirror

    NASA Astrophysics Data System (ADS)

    Debayle, A.; Sanz, J.; Gremillet, L.

    2015-11-01

    We present a self-consistent semianalytical model of the relativistic plasma mirror, based on the exact computation of the laser-driven electron surface oscillations within the cold-fluid approximation. Valid for arbitrary solid densities, laser incidence angle, and a large set of laser intensities (1018-1021W/cm2 ), the model unravels different regimes of harmonic generation. In particular, it is found that efficient conversion of p -polarized laser pulses into high-order harmonics well above the plasma frequency requires either high laser intensities, low plasma densities, or incidence angles larger than a threshold value. This critical angle corresponds to a transition between a regime where the electron surface dynamics is mostly governed by the laser J ×B force and a "cyclotron Brunel" regime, where electrons perform many cyclotron gyrations when moving into the vacuum. Under conditions relevant to current laser experiments, the latter regime gives rise to nonmonotonic variations of the harmonic yield with the laser field. Our predictions are supported by an extensive parametric study performed with highly resolved one-dimensional particle-in-cell simulations.

  1. Multicomponent theory of buoyancy instabilities in magnetized plasmas: the case of magnetic field parallel to gravity

    NASA Astrophysics Data System (ADS)

    Nekrasov, A. K.; Shadmehri, Mohsen

    2011-06-01

    We investigate electromagnetic buoyancy instabilities of the electron-ion plasma with the heat flux based on not the magnetohydrodynamic (MHD) equations, but using the multicomponent plasma approach when the momentum equations are solved for each species. We consider a geometry in which the background magnetic field, gravity, and stratification are directed along one axis. The nonzero background electron thermal flux is taken into account. Collisions between electrons and ions are included in the momentum equations. No simplifications usual for the one-fluid MHD-approach in studying these instabilities are used. We derive a simple dispersion relation, which shows that the thermal flux perturbation generally stabilizes an instability for the geometry under consideration. This result contradicts to conclusion obtained in the MHD-approach. We show that the reason of this contradiction is the simplified assumptions used in the MHD analysis of buoyancy instabilities and the role of the longitudinal electric field perturbation which is not captured by the ideal MHD equations. Our dispersion relation also shows that the medium with the electron thermal flux can be unstable, if the temperature gradients of ions and electrons have the opposite signs. The results obtained can be applied to the weakly collisional magnetized plasma objects in laboratory and astrophysics.

  2. A new fluid scheme for weakly collisional plasmas: 1. General theory

    NASA Astrophysics Data System (ADS)

    Chiuderi, C.; Pietrini, P.; Torricelli-Ciamponi, G.

    2011-04-01

    We present a new approach to the study of two-fluid hydrodynamics of weakly collisional plasma systems, such as those frequently encountered in the astrophysical context. Our starting point is the novel procedure developed in past years by Chen, Rao, and Spiegel (CRS) for the fluid description of semicollisional neutral monoatomic gases. The new system of fluid equations that include viscous and conductive effects has been successfully tested. However, the extension of such a procedure to plasmas is not a straightforward one. We have to deal with (at least) two components, with vastly different values of the masses, and the nature of collisions between charged particles is substantially different from the neutral particle case. We perform a preliminary careful examination of the basic requirements of the CRS method and identify the conditions under which an extension of such method is indeed possible. We then derive the system of fluid equations appropriate to the description of a weakly collisional two-component plasma in the new scheme and discuss the differences with respect to the more familiar Navier-Stokes approach. This paper is therefore of a general theoretical nature. However, we also point out that solar wind is a good testing ground for the newly derived system of fluid equations. This application will be the subject of a subsequent paper.

  3. Flow-Induced New Channels of Energy Exchange in Multi-Scale Plasma Dynamics – Revisiting Perturbative Hybrid Kinetic-MHD Theory

    PubMed Central

    Shiraishi, Junya; Miyato, Naoaki; Matsunaga, Go

    2016-01-01

    It is found that new channels of energy exchange between macro- and microscopic dynamics exist in plasmas. They are induced by macroscopic plasma flow. This finding is based on the kinetic-magnetohydrodynamic (MHD) theory, which analyses interaction between macroscopic (MHD-scale) motion and microscopic (particle-scale) dynamics. The kinetic-MHD theory is extended to include effects of macroscopic plasma flow self-consistently. The extension is realised by generalising an energy exchange term due to wave-particle resonance, denoted by δ WK. The first extension is generalisation of the particle’s Lagrangian, and the second one stems from modification to the particle distribution function due to flow. These extensions lead to a generalised expression of δ WK, which affects the MHD stability of plasmas. PMID:27160346

  4. Flow-Induced New Channels of Energy Exchange in Multi-Scale Plasma Dynamics – Revisiting Perturbative Hybrid Kinetic-MHD Theory

    NASA Astrophysics Data System (ADS)

    Shiraishi, Junya; Miyato, Naoaki; Matsunaga, Go

    2016-05-01

    It is found that new channels of energy exchange between macro- and microscopic dynamics exist in plasmas. They are induced by macroscopic plasma flow. This finding is based on the kinetic-magnetohydrodynamic (MHD) theory, which analyses interaction between macroscopic (MHD-scale) motion and microscopic (particle-scale) dynamics. The kinetic-MHD theory is extended to include effects of macroscopic plasma flow self-consistently. The extension is realised by generalising an energy exchange term due to wave-particle resonance, denoted by δ WK. The first extension is generalisation of the particle’s Lagrangian, and the second one stems from modification to the particle distribution function due to flow. These extensions lead to a generalised expression of δ WK, which affects the MHD stability of plasmas.

  5. Flow-Induced New Channels of Energy Exchange in Multi-Scale Plasma Dynamics - Revisiting Perturbative Hybrid Kinetic-MHD Theory.

    PubMed

    Shiraishi, Junya; Miyato, Naoaki; Matsunaga, Go

    2016-01-01

    It is found that new channels of energy exchange between macro- and microscopic dynamics exist in plasmas. They are induced by macroscopic plasma flow. This finding is based on the kinetic-magnetohydrodynamic (MHD) theory, which analyses interaction between macroscopic (MHD-scale) motion and microscopic (particle-scale) dynamics. The kinetic-MHD theory is extended to include effects of macroscopic plasma flow self-consistently. The extension is realised by generalising an energy exchange term due to wave-particle resonance, denoted by δ WK. The first extension is generalisation of the particle's Lagrangian, and the second one stems from modification to the particle distribution function due to flow. These extensions lead to a generalised expression of δ WK, which affects the MHD stability of plasmas. PMID:27160346

  6. Physics of the Intergalactic Medium During the Epoch of Reionization

    NASA Astrophysics Data System (ADS)

    Lidz, Adam

    A major goal of observational and theoretical cosmology is to observe the largely unexplored time period in the history of our universe when the first galaxies form, and to interpret these measurements. Early galaxies dramatically impacted the gas around them in the surrounding intergalactic medium (IGM) by photoionzing the gas during the "Epoch of Reionization" (EoR). This epoch likely spanned an extended stretch in cosmic time: ionized regions formed and grew around early generations of galaxies, gradually filling a larger and larger fraction of the volume of the universe. At some time—thus far uncertain, but within the first billion years or so after the big bang—essentially the entire volume of the universe became filled with ionized gas. The properties of the IGM provide valuable information regarding the formation time and nature of early galaxy populations, and many approaches for studying the first luminous sources are hence based on measurements of the surrounding intergalactic gas. The prospects for improved reionization-era observations of the IGM and early galaxy populations over the next decade are outstanding. Motivated by this, we review the current state of models of the IGM during reionization. We focus on a few key aspects of reionization-era phenomenology and describe: the redshift evolution of the volume-averaged ionization fraction, the properties of the sources and sinks of ionizing photons, along with models describing the spatial variations in the ionization fraction, the ultraviolet radiation field, the temperature of the IGM, and the gas density distribution.

  7. Moon-based Epoch of Reionization Imaging Telescope (MERIT)

    NASA Astrophysics Data System (ADS)

    Jones, D. L.; MacDowall, R. J.; Bale, S. D.; Demaio, L.; Kasper, J. C.; Weiler, K. W.

    2005-05-01

    Radio observations of emission and absorption from neutral Hydrogen during the Epoch of Reionization (EoR) can reveal how structure leading to the first stars, galaxies, and black holes formed in the intergalactic medium between redshifts of about 6 and at least 20. Ground-based low frequency radio arrays are under construction (LOFAR, PAST) or development (LWA, MWA) to detect and eventually image the EoR signal. The Moon-based Epoch of Reionization Imaging Telescope (MERIT) is a mission concept that is intended to extend ground-based observations of the EoR to the highest possible dynamic range and image fidelity. This can be accomplished by locating the MERIT array on the far side of the moon. The array is composed of 10-12 radial arms, each 1-2 km in length. Each arm has several hundred dipole antennas and feedlines printed on a very thin sheet of kapton with a total mass of about 300 kg. This provides a convenient way to deploy thousands of individual antennas, and a centrally condensed distribution of array baselines. The lunar farside provides shielding from terrestrial natural and technological radio interference, shielding (half the time) from strong solar radio emissions, and freedom from the corrupting influence of Earth's ionosphere. Various options for array deployment and data transmission to Earth will be described is this paper. Part of this work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

  8. Multi-epoch optical velocities of bright carbon stars

    NASA Astrophysics Data System (ADS)

    Barnbaum, Cecilia

    1992-10-01

    Cross-correlated optical radial velocities are presented of 87 bright carbon stars, 67 with multiple epochs, as well as the velocities of atomic transitions of K I, Li I, and Mg I. The mean optical velocity variation is about 3 km/s for SR and Lb variables and 8.7 km/s for Miras. The spread in velocities among atomic lines at a given epoch is significantly greater in Miras than in SR and Lb variables. Although Li I shows significant velocity variation in Miras, K I is more stable. Thirteen of 33 carbon stars with H-alpha emission also show bright Mg I emission in a type of inverse P-Cygni profile, and each of these 13 stars shows a clear splitting of the K I resonance line. Only two stars, R For and CL Mon, show K I as P-Cygni profile. J-type carbon stars have deeper Li absorption profiles than other carbon stars in the sample.

  9. A tutorial introduction to the statistical theory of turbulent plasmas, a half-century after Kadomtsev’s Plasma Turbulence and the resonance-broadening theory of Dupree and Weinstock

    DOE PAGESBeta

    Krommes, John A.

    2015-09-21

    In honour of the 50th anniversary of the influential review/monograph on plasma turbulence by B. B. Kadomtsev as well as the seminal works of T. H. Dupree and J. Weinstock on resonance-broadening theory, an introductory tutorial is given about some highlights of the statistical–dynamical description of turbulent plasmas and fluids, including the ideas of nonlinear incoherent noise, coherent damping, and self-consistent dielectric response. The statistical closure problem is introduced. Incoherent noise and coherent damping are illustrated with a solvable model of passive advection. Self-consistency introduces turbulent polarization effects that are described by the dielectric functionmore » $${\\mathcal{D}}$$. Dupree’s method of using$${\\mathcal{D}}$$to estimate the saturation level of turbulence is described; then it is explained why a more complete theory that includes nonlinear noise is required. The general theory is best formulated in terms of Dyson equations for the covariance$C$and an infinitesimal response function$R$, which subsumes$${\\mathcal{D}}$$. An important example is the direct-interaction approximation (DIA). It is shown how to use Novikov’s theorem to develop an$$\\boldsymbol{x}$$-space approach to the DIA that is complementary to the original$$\\boldsymbol{k}$$-space approach of Kraichnan. A dielectric function is defined for arbitrary quadratically nonlinear systems, including the Navier–Stokes equation, and an algorithm for determining the form of$${\\mathcal{D}}$$in the DIA is sketched. The independent insights of Kadomtsev and Kraichnan about the problem of the DIA with random Galilean invariance are described. The mixing-length formula for drift-wave saturation is discussed in the context of closures that include nonlinear noise (shielded by$${\\mathcal{D}}$$). The role of$R$in the calculation of the symmetry-breaking (zonostrophic) instability of homogeneous turbulence to the generation of inhomogeneous mean flows is

  10. A theory for the radiation at the third to fifth harmonics of the plasma frequency upstream from the earth's bow shock

    NASA Technical Reports Server (NTRS)

    Cairns, Iver H.

    1988-01-01

    A theory involving the process L + T' - T is proposed for the observed third to fifth harmonics of the plasma frequency observed upstream from the earth's bow shock. The conditions for which the theory may explain the observed radiation are determined, and the viability of the theory is discussed. The theory is found to require L waves with temperature between about 10 to the 21st and 10 to the 22nd K in the source regions to account for the levels and number of harmonics of the observed radiation. Such L wave temperatures are theoretically possible in the foreshock, but are not consistent with the most intense observed L waves.

  11. Plasma confinement theory and transport simulation. Technical progress report, May 1, 1992--April 30, 1993

    SciTech Connect

    Ross, D.W.

    1993-02-01

    The objectives continue to be: (1) to advance the transport studies of tokamaks, including development and maintenance of the Magnetic Fusion Energy Database, and (2) to provide theoretical interpretation, modeling and equilibrium and stability for TEXT-Upgrade. Recent publications and reports, and conference presentations of the Fusion Research Center theory group are listed.

  12. Nonlocal theory of electromagnetic wave decay into two electromagnetic waves in a rippled density plasma channel

    SciTech Connect

    Sati, Priti; Tripathi, V. K.

    2012-12-15

    Parametric decay of a large amplitude electromagnetic wave into two electromagnetic modes in a rippled density plasma channel is investigated. The channel is taken to possess step density profile besides a density ripple of axial wave vector. The density ripple accounts for the momentum mismatch between the interacting waves and facilitates nonlinear coupling. For a given pump wave frequency, the requisite ripple wave number varies only a little w.r.t. the frequency of the low frequency decay wave. The radial localization of electromagnetic wave reduces the growth rate of the parametric instability. The growth rate decreases with the frequency of low frequency electromagnetic wave.

  13. Kinetic theory and simulation of multi-species plasmas in tokamaks excited with ICRF microwaves

    SciTech Connect

    Kerbel, G.D.; McCoy, M.G.

    1984-12-21

    This paper presents a description of a bounce-averaged Fokker-Planck quasilinear model for the kinetic description of tokamak plasmas. The non-linear collision and quasilinear resonant diffusion operators are represented in a form conducive to numerical solution with specific attention to the treatment of the boundary layer separating trapped and passing orbit regions of velocity space. The numerical techniques employed are detailed in so far as they constitute significant departure from those used in the conventional uniform magnetic field case. Examples are given to illustrate the combined effects of collisional and resonant diffusion.

  14. Relativistic theory for localized electrostatic excitations in degenerate electron-ion plasmas.

    PubMed

    Mc Kerr, Michael; Haas, Fernando; Kourakis, Ioannis

    2014-09-01

    A self-consistent relativistic two-fluid model is proposed for electron-ion plasma dynamics. A one-dimensional geometry is adopted. Electrons are treated as a relativistically degenerate fluid, governed by an appropriate equation of state. The ion fluid is also allowed to be relativistic, but is cold, nondegenerate, and subject only to an electrostatic potential. Exact stationary-profile solutions are sought, at the ionic scale, via the Sagdeev pseudopotential method. The analysis provides the pulse existence region, in terms of characteristic relativistic parameters, associated with the (ultrahigh) particle density. PMID:25314552

  15. Comment on 'Turbulent equipartition theory of toroidal momentum pinch' [Phys. Plasmas 15, 055902 (2008)

    SciTech Connect

    Peeters, A. G.; Angioni, C.; Strintzi, D.

    2009-03-15

    The comment addresses questions raised on the derivation of the momentum pinch velocity due to the Coriolis drift effect [A. G. Peeters et al., Phys. Rev. Lett. 98, 265003 (2007)]. These concern the definition of the gradient, and the scaling with the density gradient length. It will be shown that the turbulent equipartition mechanism is included within the derivation using the Coriolis drift, with the density gradient scaling being the consequence of drift terms not considered in [T. S. Hahm et al., Phys. Plasmas 15, 055902 (2008)]. Finally the accuracy of the analytic models is assessed through a comparison with the full gyrokinetic solution.

  16. Superposed epoch analysis of CIRs at 0. 3 and 1. 0 AU: A comparative study

    SciTech Connect

    Richter, A.K.; Luttrell, A.H.

    1986-05-01

    Applying the superposed epoch analysis technique to 16 and to 31 well-defined, nonshock-associated stream-stream interaction regions observed by the Helios spacecraft in the distance ranges 0.3 to 0.4 AU and 0.9 to 1.0 AU, respectively, we obtain the average azimuthal variation in the solar wind density, velocity and temperature, in the magnetic field strength, and in the total proton plasma plus magnetic field pressure across CIRs at these two radial distances separately. For the radial evolution of these interaction regions we find by comparison: (1) due to compressional and rarefactional effects the amplitudes of all parameters in question taken along the leading as well as along the trailing part of the CIR are steadily increasing with the most pronounced increase in the pressure; (2) at the same time even the leading portion of the velocity profile steepens; (3) simultaneously, the positions in azimuth of the overall maximum values of the solar wind density and temperature, of the magnetic field strength and of the plasma plus magnetic field pressure are getting steadily lined up in longitude; (4) at the same time the leading portions of all profiles are steepening into discontinuous, shocklike structures. Thus, this analysis provides observational evidence for the following results obtained earlier from numerical simulation studies. Stream steepening does occur within 1 AU, and the probability of corotating shocks to form is, on average, much higher beyond than at or within 1 AU.

  17. USU center of excellence in theory and analysis of the geo-plasma environment

    NASA Astrophysics Data System (ADS)

    Schunk, Robert W.

    1992-05-01

    A team of ten Ph.D. scientists and several graduate students were assembled at USU to work in close collaboration with scientists at the Air Force Geophysics Laboratory on a number of problems that are relevant to Air Force systems, including OTH radars, communications, and orbiting space structures. The overall goal of the research is to obtain a better understanding of the basic chemical and physical processes operating in the geoplasma environment, including the ionosphere, thermosphere, and magnetosphere. Some of our specific tasks include the following: (1) studies of ionospheric structure and irregularities; (2) study of the feasibility of developing better operational ionospheric models; (3) conduct model/data comparisons in order to validate the ionospheric models; (4) study plasma electrodynamics in the high latitude ionosphere; (5) study magnetosphere-ionosphere coupling problems; (6) continue the development of our thermospheric circulation model; (7) study plasmasphere refilling problems; (8) study OTH ray tracing problems at high latitudes; and (9) study certain spacecraft-environment interaction problems, including those related to high-voltage power sources, spacecraft outgassing, artificial plasma cloud expansion, and spacecraft charging at LEO altitudes.

  18. USU center of excellence in theory and analysis of the geo-plasma environment

    NASA Astrophysics Data System (ADS)

    Schunk, Robert W.

    1993-02-01

    A team of ten Ph.D. scientists and several graduate students was assembled at USU to work in close collaboration with scientists at the Air Force Geophysics Laboratory on a number of problems that are relevant to Air Force systems, including OTH radars, communications, and orbiting space structures. The overall goal of the research was to obtain a better understanding of the basic chemical and physical processes operating in the geoplasma environment, including the ionosphere, thermosphere, and magnetosphere. Some of the specific tasks included the following: (1) studies of ionospheric structure and irregularities; (2) study the feasibility of developing better operational ionospheric models; (3) conduct model/data comparisons in order to validate the ionospheric models; (4) study plasma electrodynamics in the high latitude ionosphere; (5) study magnetosphere-ionosphere coupling problems; (6) continue the development of a thermospheric circulation model; (7) study plasmasphere refilling problems; (8) study OTH ray tracing problems at high latitudes; and (9) study certain spacecraft-environment interaction problems, including those related to high-voltage power sources, spacecraft outgassing, artificial plasma cloud expansion, and spacecraft charging at LEO altitudes.

  19. Analytic theory for betatron radiation from relativistic electrons in ion plasma channels with magnetic field

    SciTech Connect

    Lee, H. C.; Jiang, T. F.

    2010-11-15

    We analytically solve the relativistic equation of motion for an electron in ion plasma channels and calculate the corresponding trajectory as well as the synchrotron radiation. The relativistic effect on a trajectory is strong, i.e., many high-order harmonic terms in the trajectory, when the ratio of the initial transverse velocity (v{sub x0}) to the longitudinal velocity (v{sub z0}) of the electron injected to ion plasma channels is high. Interestingly, these high-order harmonic terms result in a quite broad and intense radiation spectrum, especially at an oblique angle, in contrast to an earlier understanding. As the initial velocity ratio (v{sub x0}:v{sub z0}) decreases, the relativistic effect becomes weak; only the first and second harmonic terms remain in the transverse and longitudinal trajectories, respectively, which coincides with the result of Esarey et al. [Phys. Rev. E 65, 056505 (2002)]. Our formalism also allows the description of electron's trajectory in the presence of an applied magnetic field. Critical magnetic fields for cyclotron motions are figured out and compared with semiclassical results. The cyclotron motion leads to more high-order harmonic terms than the trajectory without magnetic fields and causes an immensely broad spectrum with vastly large radiation amplitude for high initial velocity ratios (v{sub x0}:v{sub z0}). The radiation from hard x-ray to gamma-ray regions can be generated with a broad radiation angle, thus available for applications.

  20. Repeated-cascade theory of strong turbulence in a magnetized plasma

    NASA Technical Reports Server (NTRS)

    Tchen, C. M.

    1976-01-01

    A two-dimensional Navier-Stokes equation of vorticity in fluid turbulence is used to model drift turbulence in a plasma with a strong constant magnetic field and a constant mean density gradient. The nonlinear eddy diffusivity is described by a time-integrated Lagrangian correlation of velocities, and the repeated-cascade method is employed to choose the rank accounting for nearest-neighbor interactions, to calculate the Lagrangian correlation, and to close the correlation hierarchy. As a result, the diffusivity becomes dependent on the plasma's induced diffusion and is represented by a memory chain that is cut off by similarity and inertial randomization. Spectral laws relating the kinetic-energy spectrum to the -5, -5/2, -3, and -11 powers of wavenumber are derived for the velocity subranges of production, approach to inertia, inertia, and dissipation, respectively. It is found that the diffusivity is proportional to some inverse power of the magnetic field, that power being 1, 2/3, 5/6, and 2, respectively, for the four velocity subranges.

  1. Multi-epoch Doppler tomography and polarimetry of QQ Vul

    NASA Astrophysics Data System (ADS)

    Schwope, Axel D.; Catalán, Maria S.; Beuermann, Klaus; Metzner, André; Smith, Robert Connon; Steeghs, Danny

    2000-04-01

    We present multi-epoch high-resolution spectroscopy and photoelectric polarimetry of the long-period polar (AM Herculis star) QQ Vul. The blue emission lines show several distinct components, the sharpest of which can unequivocally be assigned to the illuminated hemisphere of the secondary star and used to trace its orbital motion. This narrow emission line can be used in combination with Nai absorption lines from the photosphere of the companion to build a stable long-term ephemeris for the star: inferior conjunction of the companion occurs at HJD=2448446.4710(5)+Ex0.15452011 day (11). The polarization curves are dissimilar at different epochs, thus supporting the idea of fundamental changes of the accretion geometry, e.g., between one- and two-pole accretion modes. The linear polarization pulses display a random scatter by 0.2 phase units and are not suitable for the determination of the binary period. The polarization data suggest that the magnetic (dipolar) axis has a colatitude of 23 deg, an azimuth of -50 deg, and an orbital inclination between 50 deg and 70 deg. Doppler images of blue emission and red absorption lines show a clear separation between the illuminated and non-illuminated hemispheres of the secondary star. The absorption lines on their own can be used to determine the mass ratio of the binary by Doppler tomography with an accuracy of 15-20 per cent. The narrow emission lines of different atomic species show remarkably different radial velocity amplitudes: K=85-130kms-1. Emission lines from the most highly ionized species, Heii, originate closest to the inner Lagrangian point L1. We can discern two kinematic components within the accretion stream; one is associated with the ballistic part, and the other with the magnetically threaded part of the stream. The location of the emission component associated with the ballistic accretion stream appears displaced between different epochs. Whether this displacement indicates a dislocation of the ballistic

  2. Multicomponent Theory of Buoyancy Instabilities in Astrophysical Plasma Objects: The Case of Magnetic Field Perpendicular to Gravity

    NASA Astrophysics Data System (ADS)

    Nekrasov, Anatoly K.; Shadmehri, Mohsen

    2010-12-01

    We develop a general theory of buoyancy instabilities in the electron-ion plasma with the electron heat flux based not upon magnetohydrodynamic (MHD) equations, but using a multicomponent plasma approach in which the momentum equation is solved for each species. We investigate the geometry in which the background magnetic field is perpendicular to the gravity and stratification. General expressions for the perturbed velocities are given without any simplifications. Collisions between electrons and ions are taken into account in the momentum equations in a general form, permitting us to consider both weakly and strongly collisional objects. However, the electron heat flux is assumed to be directed along the magnetic field, which implies a weakly collisional case. Using simplifications justified for an investigation of buoyancy instabilities with electron thermal flux, we derive simple dispersion relations for both collisionless and collisional cases for arbitrary directions of the wave vector. Our dispersion relations considerably differ from that obtained in the MHD framework and conditions of instability are similar to Schwarzschild's criterion. This difference is connected with simplified assumptions used in the MHD analysis of buoyancy instabilities and with the role of the longitudinal electric field perturbation which is not captured by the ideal MHD equations. The results obtained can be applied to clusters of galaxies and other astrophysical objects.

  3. Satellite- and Epoch Differenced Precise Point Positioning Based on a Regional Augmentation Network

    PubMed Central

    Li, Haojun; Chen, Junping; Wang, Jiexian; Wu, Bin

    2012-01-01

    Precise Point Positioning (PPP) has been demonstrated as a simple and effective approach for user positioning. The key issue in PPP is how to shorten convergence time and improve positioning efficiency. Recent researches mainly focus on the ambiguity resolution by correcting residual phase errors at a single station. The success of this approach (referred to hereafter as NORM-PPP) is subject to how rapidly one can fix wide-lane and narrow-lane ambiguities to achieve the first ambiguity-fixed solution. The convergence time of NORM-PPP is receiver type dependent, and normally takes 15–20 min. Different from the general algorithm and theory by which the float ambiguities are estimated and the integer ambiguities are fixed, we concentrate on a differential PPP approach: the satellite- and epoch differenced (SDED) approach. In general, the SDED approach eliminates receiver clocks and ambiguity parameters and thus avoids the complicated residual phase modeling procedure. As a further development of the SDED approach, we use a regional augmentation network to derive tropospheric delay and remaining un-modeled errors at user sites. By adding these corrections and applying the Robust estimation, the weak mathematic properties due to the ED operation is much improved. Implementing this new approach, we need only two epochs of data to achieve PPP positioning converging to centimeter-positioning accuracy. Using seven days of GPS data at six CORS stations in Shanghai, we demonstrate the success rate, defined as the case when three directions converging to desired positioning accuracy of 10 cm, reaches 100% when the interval between the two epochs is longer than 15 min. Comparing the results of 15 min' interval to that of 10 min', it is observed that the position RMS improves from 2.47, 3.95, 5.78 cm to 2.21, 3.93, 4.90 cm in the North, East and Up directions, respectively. Combining the SDED coordinates at the starting point and the ED relative coordinates thereafter, we

  4. Investigating the earliest epochs of the Milky Way halo

    NASA Astrophysics Data System (ADS)

    Starkenburg, Else; Starkenburg

    2016-08-01

    Resolved stellar spectroscopy can obtain knowledge about chemical enrichment processes back to the earliest times, when the oldest stars were formed. In this contribution I will review the early (chemical) evolution of the Milky Way halo from an observational perspective. In particular, I will discuss our understanding of the origin of the peculiar abundance patterns in various subclasses of extremely metal-poor stars, taking into account new data from our abundance and radial velocity monitoring programs, and their implications for our understanding of the formation and early evolution of both the Milky Way halo and the satellite dwarf galaxies therein. I conclude by presenting the ``Pristine'' survey, a program on the Canada-France-Hawaii Telescope to study this intriguing epoch much more efficiently.

  5. Primary Effusion Lymphoma: Is Dose-Adjusted-EPOCH Worthwhile Therapy?

    PubMed

    Jessamy, Kegan; Ojevwe, Fidelis O; Doobay, Ravi; Naous, Rana; Yu, John; Lemke, Sheila M

    2016-01-01

    Primary effusion lymphoma (PEL) is a rare condition, which accounts for approximately 4% of all human immunodeficiency virus (HIV)-associated non-Hodgkin lymphomas. PEL has a predilection for body cavities and occurs in the pleural space, pericardium, and peritoneum. Without treatment, the median survival is approximately 2-3 months, and with chemotherapy, the median survival is approximately 6 months. We describe the case of a 47-year-old male with HIV and Kaposi's sarcoma who presented with complaints of abdominal pain and distension and was subsequently diagnosed with PEL. Despite limited clinical data being available, chemotherapy with dose-adjusted etoposide, prednisone, vincristine, cyclophosphamide, and doxorubicin (EPOCH) has proven to increase survival rates in patients with this condition. PMID:27462227

  6. An ionospheric occultation inversion technique based on epoch difference

    NASA Astrophysics Data System (ADS)

    Lin, Jian; Xiong, Jing; Zhu, Fuying; Yang, Jian; Qiao, Xuejun

    2013-09-01

    Of the ionospheric radio occultation (IRO) electron density profile (EDP) retrievals, the Abel based calibrated TEC inversion (CTI) is the most widely used technique. In order to eliminate the contribution from the altitude above the RO satellite, it is necessary to utilize the calibrated TEC to retrieve the EDP, which introduces the error due to the coplanar assumption. In this paper, a new technique based on the epoch difference inversion (EDI) is firstly proposed to eliminate this error. The comparisons between CTI and EDI have been done, taking advantage of the simulated and real COSMIC data. The following conclusions can be drawn: the EDI technique can successfully retrieve the EDPs without non-occultation side measurements and shows better performance than the CTI method, especially for lower orbit mission; no matter which technique is used, the inversion results at the higher altitudes are better than those at the lower altitudes, which could be explained theoretically.

  7. Multi-Epoch Spectroscopy of Hydrogen-Poor Superluminous Supernovae

    NASA Astrophysics Data System (ADS)

    Quimby, Robert; De Cia, Annalisa; Gal-Yam, Avishay; Leloudas, Giorgos; Lunnan, Ragnhild; Perley, Daniel A.; Vreeswijk, Paul; Yan, Lin

    2016-06-01

    A growing sample of intrinsically rare supernovae is being uncovered by wide-field synoptic surveys, such as the Palomar Transient Factory (PTF). A fraction of these events have been labeled "superluminous supernovae" due to their peak luminosities, which can exceed normal supernovae by factors of 10 to 100. The power sources for these events and thus their connection to normal luminosity supernovae remains uncertain. Here we present results from 134 spectroscopic observations of 17 hydrogen-poor superluminous supernovae (SLSN-I) discovered by PTF. We select our targets from the full PTF sample using only spectroscopic information; we do not employ the traditional cut in absolute magnitude (e.g. M < -21) to avoid potential bias. Using our multi-epoch observations, we identify the ion species contributing to the spectroscopic features, and we perform parametric modeling to estimate photospheric velocities. Finally we discuss the physical insights into the nature of these explosions offered by this unique dataset.

  8. Primary Effusion Lymphoma: Is Dose-Adjusted-EPOCH Worthwhile Therapy?

    PubMed Central

    Jessamy, Kegan; Ojevwe, Fidelis O.; Doobay, Ravi; Naous, Rana; Yu, John; Lemke, Sheila M.

    2016-01-01

    Primary effusion lymphoma (PEL) is a rare condition, which accounts for approximately 4% of all human immunodeficiency virus (HIV)-associated non-Hodgkin lymphomas. PEL has a predilection for body cavities and occurs in the pleural space, pericardium, and peritoneum. Without treatment, the median survival is approximately 2–3 months, and with chemotherapy, the median survival is approximately 6 months. We describe the case of a 47-year-old male with HIV and Kaposi's sarcoma who presented with complaints of abdominal pain and distension and was subsequently diagnosed with PEL. Despite limited clinical data being available, chemotherapy with dose-adjusted etoposide, prednisone, vincristine, cyclophosphamide, and doxorubicin (EPOCH) has proven to increase survival rates in patients with this condition. PMID:27462227

  9. Doppler imaging of AR Lacertae at three epochs

    NASA Technical Reports Server (NTRS)

    Walter, Frederick M.; Neff, James E.; Linsky, Jeffrey L.; Rodono, Marcello

    1988-01-01

    Observations from IUE were used to study the structure of the lower chromosphere of AR Lacertae in the light of Mg II k. Sequences of LWR/P-HI images distributed around the binary period at three epochs were obtained. Discrete plage-like regions of enhanced Mg II surface flux in this system are identified. There are temporal variations in the Mg II flux on timescales of hours as well as substantial changes in chromospheric morphology on timescales of years. Even with the limited S/N attainable with the IUE, one can map the gross structures of active stellar atmospheres. With such information, one can begin to study the true 3-D structure of the atmospheres of late-type stars.

  10. High Energy Neutrino Signals from the Epoch of Reionization

    SciTech Connect

    Iocco, F.; Murase, K.; Nagataki, S.; Serpico, P.D.

    2007-07-06

    In this paper we perform a new estimate of the high energy neutrinos expected from GRBs associated with the first generation of stars in light of new models and constraints on the epoch of reionization and a more detailed evaluation of the neutrino emission yields. We also compare the diffuse high energy neutrino background from Population III stars with the one from ''ordinary stars'' (Population II), as estimated consistently within the same cosmological and astrophysical assumptions. In disagreement with previous literature, we find that high energy neutrinos from Population III stars will not be observable with current or near future neutrino telescopes, falling below both IceCube sensitivity and atmospheric neutrino background under the most extreme assumptions for the GRB rate. This rules them out as a viable diagnostic tool for these still elusive metal-free stars.

  11. Subdaily Earth rotation during the Epoch '92 campaign

    NASA Technical Reports Server (NTRS)

    Freedman, A. P.; Ibanez-Meier, R.; Herring, T. A.; Lichten, S. M.; Dickey, J. O.

    1994-01-01

    Global Positioning System (GPS) data were used to estimate Earth rotation variations over an 11-day period during the Epoch '92 campaign in the summer of 1992. Earth orientation was measured simultaneously by several very long baseline interferometry (VLBI) networks. GPS and VLBI estimates of UT1 with 3-hour time resolution were then compared and analyzed. The high frequency behavior of both data sets is similar, although drifts between the two series of approximately 0.1 ms over 2-5 days are evident. The geodetic results were also compared with models for UT1 fluctuations at tidal periods and with estimates of atmospheric angular momentum made at 6-hour intervals. Most of the geodetic signal in the diurnal and semidiurnal frequency bands can be attributed to tidal processes, whereas UT1 variations over a few days are mostly atmospheric in origin.

  12. Sub-Daily Earth Rotation during the Epoch '92 Campaign

    NASA Technical Reports Server (NTRS)

    Freedman, A. P.; Ibanez-Meier, R.; Lichten, S. M.; Dickey, J. O.; Herring, T. A.

    1993-01-01

    Earth rotation measurements were obtained using Global Positioning System (GPS) data for 11 days during the Epoch '92 campaign in the Summer of 1992. Earth orientation was measured simultaneously with several very long baseline interferornetry (VLBI) networks. These data were processed to yield both GPS and VLBI estimates of UT1 with 3-hour time resolution, which were then compared and analyzed. The high frequency behavior of both data sets is similar, although drifts between the two series of approx.0,1 ms over 2-5 days are evident, Models for tidally induced UT1 variations and estimates of atmospheric angular momentum (AAM) at 6-hour intervals were also compared with the geodetic data, These studies indicate that most of the geodetic signal in the diurnal and semidiurnal frequency bands can be attributed to tidal processes, and that UT1 variations over a few days are mostly atmospheric in origin.

  13. Neutral Hydrogen in Galaxies at the Present Epoch

    NASA Astrophysics Data System (ADS)

    Rao, Sandhya; Briggs, Frank

    1993-12-01

    The evolution of the neutral hydrogen content of galaxies as a function of time is an important constraint on processes in galactic evolution. We present a comprehensive, statistical description of the H I content and distribution within galaxies at the present epoch and compare these statistics with the properties of H I associated with "damped Lyα" absorption systems at high redshift that are observed in the spectra of QSOs. ΩH I(z = 0), the H I mass density at the present epoch relative to the present critical mass density, is found to be (2.5±0.6) × 10-4h-175, consistent with the decreasing trend of the H I content with time deduced from QSO absorption line statistics for redshifts from about 4 to 0.5 (Lanzetta 1993). Spiral galaxies contain an overwhelming 89% of this neutral hydrogen mass. The rest is contained in irregulars, SOs, and ellipticals Spirals also offer the largest cross section to line-of-sight absorption of light from QSOs By considering nearby spirals as potential absorbers, the interception probability as a function of the H I column density, N(H I), is derived for comparison with the cross sections inferred from observations of damped Lyman-alpha systems. The comparison shows that the damped Lyα lines are created by absorbers that subtend larger cross sections than present-day spirals by a factor of 5 implying that galaxies were either larger or more numerous at z ˜ 2.5.

  14. Bifurcation Theory of the Transition to Collisionless Ion-temperature-gradient-driven Plasma Turbulence

    SciTech Connect

    Kolesnikov, R.A.; Krommes, J.A.

    2005-09-22

    The collisionless limit of the transition to ion-temperature-gradient-driven plasma turbulence is considered with a dynamical-systems approach. The importance of systematic analysis for understanding the differences in the bifurcations and dynamics of linearly damped and undamped systems is emphasized. A model with ten degrees of freedom is studied as a concrete example. A four-dimensional center manifold (CM) is analyzed, and fixed points of its dynamics are identified and used to predict a ''Dimits shift'' of the threshold for turbulence due to the excitation of zonal flows. The exact value of that shift in terms of physical parameters is established for the model; the effects of higher-order truncations on the dynamics are noted. Multiple-scale analysis of the CM equations is used to discuss possible effects of modulational instability on scenarios for the transition to turbulence in both collisional and collisionless cases.

  15. On the theory of MHD waves in a shear flow of a magnetized turbulent plasma

    NASA Astrophysics Data System (ADS)

    Mishonov, Todor M.; Maneva, Yana G.; Dimitrov, Zlatan D.; Hristov, Tihomir S.

    The set of equations for magnetohydrodynamic (MHD) waves in a shear flow is consecutively derived. This investigation is devoted on the wave heating of space plasmas. The proposed scenario involves the presence of a self-sustained turbulence and magnetic field. In the framework of Langevin--Burgers approach the influence of the turbulence is described by an additional external random force in the MHD system. Kinetic equation for the spectral density of the slow magnetosonic (Alfvénic) mode is derived in the short wavelength (WKB) approximation. The results show a pressing need for conduction of numerical Monte Carlo (MC) simulations with a random driver to take into account the influence of the long wavelength modes and to give a more precise analytical assessment of the short ones. Realistic MC calculations for the heating rate and shear stress tensor should give an answer to the perplexing problem for the missing viscosity in accretion disks and reveal why the quasars are the most powerful sources of light in the universe. It is supposed that the heating mechanism by alfvén waves absorption is common for many kinds of space plasmas from solar corona to active galactic nuclei and the solution of these longstanding puzzles deserves active interdisciplinary research. The work is illustrated by typical solutions of MHD equations and their spectral densities obtained by numerical calculations or by analytical solutions with the help of Heun functions. The amplification coefficient of slow magnetosonic wave in shear flow is analytically calculated. Pictorially speaking, if in WKB approximation we treat Alfvén waves as particles -- this amplification is effect of ``lasing of alfvons.''

  16. Plasma Streaming and Explosive Events in the Solar Transition Region: Theory and Observations

    NASA Astrophysics Data System (ADS)

    Ryutova, M.; Tarbell, T.

    1999-05-01

    As shown by Tarbell et al. (ApJ, 514, L47, 1999 ) a sporadic excess of temperature and wide variety of plasma jets observed in the chromosphere and transition region overlying quiet sun regions may be explained by hydrodynamic cumulation resulted from the acoustic shocks generated by the reconnecting small scale network magnetic elements in the solar photosphere. Here we study magneto-hydrodynamic cumulation resulted from post-reconnection MHD shocks generated in complex magnetic field geometries typical to upper chromosphere and low corona. We present the results for the observed regularities obtained from simultaneous measurements taken by TRACE in chromospheric, transition region and coronal images and MDI on SOHO showing time series of high resolution magnetograms. We find that (1) All the essential features of the hydrodynamic cumulation remain in place: the MHD shocks driven by the post-reconnection sling-shot effect and self-focusing of these shocks lead to several well observed signatures of the energy release. (2) The evolution of generated flows depends on the geometry of intermittent magnetic fields and the height of jet formation. In regions of open magnetic structures plasma flows have tendency to accelerate and reach supersonic and super-Alfvenic velocities. Due to linear KH instability such flows may generate high frequency Alfven waves propagating along the magnetic structures. (3) In those regions where cumulative effects result in the predominant heating which is accompanied by generation of "moderate" (sub-Alfvenic) velocity jets, there are conditions when high velocity explosive events are driven. Our theoretical model shows that the explosive events proceeded by appearance of the bright transients are caused by the development of shear flow dissipative (nonlinear) instabilities. We also suggest that "non-bright"explosive events may be driven by rare effect of the cylindrical focusing of the MHD shocks (the Guderley's effect).

  17. THE IMPACT OF POINT-SOURCE SUBTRACTION RESIDUALS ON 21 cm EPOCH OF REIONIZATION ESTIMATION

    SciTech Connect

    Trott, Cathryn M.; Wayth, Randall B.; Tingay, Steven J.

    2012-09-20

    Precise subtraction of foreground sources is crucial for detecting and estimating 21 cm H I signals from the Epoch of Reionization (EoR). We quantify how imperfect point-source subtraction due to limitations of the measurement data set yields structured residual signal in the data set. We use the Cramer-Rao lower bound, as a metric for quantifying the precision with which a parameter may be measured, to estimate the residual signal in a visibility data set due to imperfect point-source subtraction. We then propagate these residuals into two metrics of interest for 21 cm EoR experiments-the angular power spectrum and two-dimensional power spectrum-using a combination of full analytic covariant derivation, analytic variant derivation, and covariant Monte Carlo simulations. This methodology differs from previous work in two ways: (1) it uses information theory to set the point-source position error, rather than assuming a global rms error, and (2) it describes a method for propagating the errors analytically, thereby obtaining the full correlation structure of the power spectra. The methods are applied to two upcoming low-frequency instruments that are proposing to perform statistical EoR experiments: the Murchison Widefield Array and the Precision Array for Probing the Epoch of Reionization. In addition to the actual antenna configurations, we apply the methods to minimally redundant and maximally redundant configurations. We find that for peeling sources above 1 Jy, the amplitude of the residual signal, and its variance, will be smaller than the contribution from thermal noise for the observing parameters proposed for upcoming EoR experiments, and that optimal subtraction of bright point sources will not be a limiting factor for EoR parameter estimation. We then use the formalism to provide an ab initio analytic derivation motivating the 'wedge' feature in the two-dimensional power spectrum, complementing previous discussion in the literature.

  18. Experimental validation of Mueller-Stokes theory and investigation of the influence of the Cotton-Mouton effect on polarimetry in a magnetized fusion plasma

    SciTech Connect

    Zhang, J.; Peebles, W. A.; Crocker, N. A.; Carter, T. A.; Doyle, E. J.; Rhodes, T. L.; Wang, G.; Zeng, L.; Hyatt, A. W.

    2013-10-15

    Mueller-Stokes theory can be used to calculate the polarization evolution of an electromagnetic (EM) wave as it propagates through a magnetized plasma. Historically, the theory has been used to interpret polarimeter signals from systems operating on fusion plasmas. These interpretations have mostly employed approximations of Mueller-Stokes theory in regimes where either the Faraday rotation (FR) or the Cotton-Mouton (CM) effect is dominant. The current paper presents the first systematic comparison of polarimeter measurements with the predictions of full Mueller-Stokes theory where conditions transition smoothly from a FR-dominant (i.e., weak CM effect) plasma to one where the CM effect plays a significant role. A synthetic diagnostic code, based on Mueller-Stokes theory accurately reproduces the trends evident in the experimentally measured polarimeter phase over this entire operating range, thereby validating Mueller-Stokes theory. The synthetic diagnostic code is then used to investigate the influence of the CM effect on polarimetry measurements. As expected, the measurements are well approximated by the FR effect when the CM effect is predicted to be weak. However, the code shows that as the CM effect increases, it can compete with the FR effect in rotating the polarization of the EM-wave. This results in a reduced polarimeter response to the FR effect, just as observed in the experiment. The code also shows if sufficiently large, the CM effect can even reverse the handedness of a wave launched with circular polarization. This helps to understand the surprising experimental observations that the sensitivity to the FR effect can be nearly eliminated at high enough B{sub T} (2.0 T). The results also suggest that the CM effect on the plasma midplane can be exploited to potentially measure magnetic shear in tokamak plasmas. These results establish increased confidence in the use of such a synthetic diagnostic code to guide future polarimetry design and interpret

  19. Theory of field line resonances of standing shear Alfven waves in three-dimensional inhomogeneous plasmas

    SciTech Connect

    Schulze-Berge, S.; Crowley, S.; Chen, Liu.

    1991-05-01

    We have analyzed field line resonances of Alfven waves in a rectangular box model with a straight uniform magnetic field but three dimensionally varying density. Field line resonances are shown to exist even with this three-dimensional nonuniformity. For a given wave frequency, we can construct the surface on which the resonance occurs and derive the local form of the singular solution. Magnetic perturbations are found to lie predominantly in the resonant surface. In the presence of azimuthal inhomogeneities, the present theory could explain why some satellite measurements show geomagnetic pulsations of comparable magnitude in radial and azimuthal components. 5 refs.

  20. Theory of field line resonances of standing shear Alfven waves in three-dimensional inhomogeneous plasmas

    SciTech Connect

    Schulze-Berge, S.; Cowley, S.; Liu Chen )

    1992-03-01

    The authors have analyzed field line resonances of Alfven waves in a rectangular box model with a straight uniform magnetic field but three-dimensionally varying density. Field line resonances are shown to exist even with this three-dimensional uniformity. For a given wave frequency they can construct the surface on which the resonance occurs and derive the local form of the singular solution. Magnetic perturbations are found to lie predominantly in the resonant surface. In the presence of azimuthal inhomogeneous the present theory could explain why some satellite measurements show geomagnetic pulsations of comparable magnitude in radial and azimuthal components.

  1. Renormalized theory of ion temperature gradient instability of the magnetic-field-aligned plasma shear flow with hot ions

    SciTech Connect

    Mikhailenko, V. V. Mikhailenko, V. S.; Lee, Hae June

    2015-10-15

    The developed kinetic theory for the stability of a magnetic-field-aligned (parallel) shear flow with inhomogeneous ion temperature [Mikhailenko et al., Phys. Plasmas 21, 072117 (2014)] predicted that a kinetic instability arises from the coupled reinforcing action of the flow velocity shear and ion temperature gradient in the cases where comparable ion and electron temperatures exist. In the present paper, the nonlinear theory was developed for the instability caused by the combined effects of ion-temperature-gradient and shear-flow (ITG–SF). The level of the electrostatic turbulence is determined for the saturation state of the instability on the basis of the nonlinear dispersion equation, which accounts for a nonlinear scattering of ions by the developed turbulence in a sheared flow. The renormalized quasilinear equation for the ion distribution function, which accounts for the turbulent scattering of ions by ITG–SF driven turbulence, was derived and employed for the estimation of the turbulent ion viscosity, the anomalous ion thermal conductivity, and anomalous ion heating rate at the saturation state of the instability.

  2. Renormalization Group Theory Technique and Subgrid Scale Closure for Fluid and Plasma Turbulence.

    NASA Astrophysics Data System (ADS)

    Zhou, Ye.

    Renormalization group theory is applied to incompressible three-dimension Navier-Stokes turbulence so as to eliminate unresolvable small scales. The renormalized Navier-Stokes equation includes a triple nonlinearity with the eddy viscosity exhibiting a mild cusp behavior, in qualitative agreement with the test-field model results of Kraichnan. For the cusp behavior to arise, not only is the triple nonlinearity necessary but the effects of pressure must be incorporated in the triple term. Renormalization group theory is also applied to a model Alfven wave turbulence equation. In particular, the effect of small unresolvable subgrid scales on the large scales is computed. It is found that the removal of the subgrid scales leads to a renormalized response function. (i) This response function can be calculated analytically via the difference renormalization group technique. Strong absorption can occur around the Alfven frequency for sharply peaked subgrid frequency spectra. (ii) With the epsilon - expansion renormalization group approach, the Lorenzian wavenumber spectrum of Chen and Mahajan can be recovered for finite epsilon , but the nonlinear coupling constant still remains small, fully justifying the neglect of higher order nonlinearities introduced by the renormalization group procedure.

  3. Theory of resistivity-gradient-driven turbulence in a differentially rotating plasma

    SciTech Connect

    Kim, Y.B.; Diamond, P.H.; Biglari, H. ); Terry, P.W. )

    1990-09-01

    The effects of a radially sheared poloidal flow on the structure of resistivity-gradient-driven turbulence in tokamak edge plasmas are self-consistently investigated. Sheared flow induces a coupling between turbulent radial diffusion and poloidal shearing, which results in enhanced decorrelation and a concomitant reduction in the size of the turbulent convection cells. These effects result in the suppression of resistivity-gradient-driven turbulence in the presence of strongly sheared poloidal flows. While the effects of sheared rotation are ultimately more pronounced at high {ital k}{sub {theta}}, the onset of enhanced decorrelation occurs first for low {ital k}{sub {theta}} modes. In addition to the trivial rotation-induced Doppler shift, sheared poloidal flows also induce a mode frequency that is comparable in size to the enhanced turbulent decorrelation rate, and whose sign varies with the sign of the flow shear. The mode frequency and flow shear can effectively render the turbulent diffusion nonresonant. The implications of these results for this and other models of edge turbulence are discussed.

  4. Further testing of anisotropic plasma turbulence theory with spacecraft observations of the solar wind

    NASA Astrophysics Data System (ADS)

    Summerlin, E. J.; Wicks, R.; Forman, M. A.; Salem, C. S.; Roberts, D. A.

    2014-12-01

    We use magnetic field observations from the fast solar wind made by the Ulysses, Wind, and Cluster spacecraft to measure the anisotropic scaling of the full power-spectra-tensor of inertial range turbulence in the solar wind. We use the results to make the most rigorous test of anisotropic turbulence theories thus far by solar wind observations. We compare the diagonal and off-diagonal terms of the tensor at different scales to reveal the different effects of sampling causing the projection of the anisotropic spectrum into the spacecraft observation frame. There is clear indication of anisotropy similar to "critical balance" in the inertial range, but the most striking result is the departure from the inertial range behavior observed at smaller scales in the "dissipation range".

  5. Introduction to statistical field theory: from a toy model to a one-component plasma

    NASA Astrophysics Data System (ADS)

    Frydel, Derek

    2015-11-01

    Working with a toy model whose partition function consists of a discrete summation, we introduce the statistical field theory methodology by transforming a partition function via a formal Gaussian integral relation (the Hubbard-Stratonovich transformation). We then consider Gaussian-type approximations, wherein correlational contributions enter as harmonic fluctuations around the saddle-point solution. This work focuses on how to arrive at a self-consistent, non-perturbative approximation without recourse to a standard variational construction based on the Gibbs-Bogolyubov-Feynman inequality that is inapplicable to a complex action. To address this problem, we propose a construction based on selective satisfaction of a set of exact relations generated by considering a dual representation of a partition function, in its original and transformed form.

  6. A tutorial introduction to the statistical theory of turbulent plasmas, a half-century after Kadomtsev’s Plasma Turbulence and the resonance-broadening theory of Dupree and Weinstock

    SciTech Connect

    Krommes, John A.

    2015-09-21

    In honour of the 50th anniversary of the influential review/monograph on plasma turbulence by B. B. Kadomtsev as well as the seminal works of T. H. Dupree and J. Weinstock on resonance-broadening theory, an introductory tutorial is given about some highlights of the statistical–dynamical description of turbulent plasmas and fluids, including the ideas of nonlinear incoherent noise, coherent damping, and self-consistent dielectric response. The statistical closure problem is introduced. Incoherent noise and coherent damping are illustrated with a solvable model of passive advection. Self-consistency introduces turbulent polarization effects that are described by the dielectric function${\\mathcal{D}}$. Dupree’s method of using${\\mathcal{D}}$to estimate the saturation level of turbulence is described; then it is explained why a more complete theory that includes nonlinear noise is required. The general theory is best formulated in terms of Dyson equations for the covariance$C$and an infinitesimal response function$R$, which subsumes${\\mathcal{D}}$. An important example is the direct-interaction approximation (DIA). It is shown how to use

  7. A tutorial introduction to the statistical theory of turbulent plasmas, a half-century after Kadomtsev’s Plasma Turbulence and the resonance-broadening theory of Dupree and Weinstock

    SciTech Connect

    Krommes, John A.

    2015-09-21

    In honour of the 50th anniversary of the influential review/monograph on plasma turbulence by B. B. Kadomtsev as well as the seminal works of T. H. Dupree and J. Weinstock on resonance-broadening theory, an introductory tutorial is given about some highlights of the statistical–dynamical description of turbulent plasmas and fluids, including the ideas of nonlinear incoherent noise, coherent damping, and self-consistent dielectric response. The statistical closure problem is introduced. Incoherent noise and coherent damping are illustrated with a solvable model of passive advection. Self-consistency introduces turbulent polarization effects that are described by the dielectric function${\\mathcal{D}}$. Dupree’s method of using${\\mathcal{D}}$to estimate the saturation level of turbulence is described; then it is explained why a more complete theory that includes nonlinear noise is required. The general theory is best formulated in terms of Dyson equations for the covariance$C$and an infinitesimal response function$R$, which subsumes${\\mathcal{D}}$. An important example is the direct-interaction approximation (DIA). It is shown how to use

  8. Residual fluctuations in the matter and radiation distribution after the decoupling epoch. [of early universe

    NASA Technical Reports Server (NTRS)

    Silk, J.; Wilson, M. L.

    1980-01-01

    The residual spectra of matter and radiation fluctuations in the early universe are investigated, and the evolution of primordial adiabatic and isothermal fluctuations through the decoupling epoch is studied. Amplification of adiabatic density fluctuations during decoupling, or velocity 'overshoot', is largely suppressed by Compton drag. Consequently, the amplitude of density fluctuations entering the horizon prior to decoupling is larger than hitherto assumed in the adiabatic theory. Damping of primordial adiabatic density fluctuations by an order of magnitude occurs on mass-scales of 3 x 10 to the 13th solar masses (Omega = 1) or 10 to the 14th solar masses (Omega = 0.2). Comparison of the residual radiation fluctuations with observational limits indicates that the adiabatic theory is only acceptable if re-ionization of the intergalactic medium results in additional scattering of the radiation after decoupling. Primordial isothermal fluctuations are found to yield radiation fluctuations which are insensitive to the assumed spectrum and lie a factor of about 5 below current limits

  9. Do Newton's G and Milgrom's a{sub 0} vary with cosmological epoch?

    SciTech Connect

    Bekenstein, Jacob D.; Sagi, Eva

    2008-05-15

    In the scalar-tensor gravitational theories Newton's constant G{sub N} evolves in the expanding universe. Likewise, it has been speculated that the acceleration scale a{sub 0} in Milgrom's modified Newtonian dynamics is tied to the scale of the cosmos, and must thus evolve. With the advent of relativistic implementations of the modified dynamics, one can address the issue of variability of the two gravitational 'constants' with some confidence. Using TeVeS, the tensor-vector-scalar gravitational theory, as an implementation of Milgrom's modified Newtonian dynamics, we calculate the dependence of G{sub N} and a{sub 0} on the TeVeS parameters and the coeval cosmological value of its scalar field, {phi}{sub c}. We find that G{sub N}, when expressed in atomic units, is strictly nonevolving, a result fully consistent with recent empirical limits on the variation of G{sub N}. By contrast, we find that a{sub 0} depends on {phi}{sub c} and may thus vary with cosmological epoch. However, for the brand of TeVeS which seems most promising, a{sub 0} variation occurs on a time scale much longer than Hubble's, and should be imperceptible back to redshift unity or even beyond it. This is consistent with emergent data on the rotation curves of disk galaxies at significant redshifts.

  10. Vlasov Theory of the Equilibrium Structure of Tangential Discontinuities in Space Plasmas

    NASA Astrophysics Data System (ADS)

    Roth, M.; de Keyser, J.; Kuznetsova, M. M.

    1996-05-01

    Extensive theoretical work has been performed on the equilibrium structure of tangential discontinuities (TDs) in collisionless plasmas. This paper reviews kinetic models based on steady-state solutions of the Vlasov equation. It is shown that most of the existing models are special cases of a generalized multi-species model. In this generalized model all particle populations -from both outer regions and from inside the layer — are described using a unique formalism for the velocity distribution functions. Because of their historical importance, the Harris and Sestero models are reviewed and deduced from the generalized model. The Lee and Kan model is also a special case of the generalized model. The generalized model, however, is also able to describe TDs with velocity shear and large angles of magnetic field rotation. Such a multi-species model with a large number of free parameters and different gradient scales illustrates many observable features of TDs, including their multiscale fine structure. Particular attention is paid to the magnetopause. Observed magnetopause crossings are simulated. The effects of the relative flow velocity and asymmetrical magnetic field profiles on the structure of the magnetopause and on its stability with respect to tearing perturbations are discussed. We also present calculations that demonstrate the potential of the generalized model in explaining the origin of discrete auroral arcs. Numerical simulations of solar wind TDs with heavy ions and a large spectrum of thicknesses are also feasible. This indicates that such a model is of fundamental importance for understanding the detailed structure of solar wind TDs, like those observed by the interplanetary spacecraft ULYSSES. The problems associated with the one-dimensional, time-independent Vlasov approach are discussed and a variational principle is suggested to reduce the arbitrariness resulting from the large number of free parameters.

  11. Correlation theory of a two-dimensional plasma turbulence with shear flow

    NASA Astrophysics Data System (ADS)

    Zhang, Y. Z.; Mahajan, S. M.

    1993-07-01

    When the ion sound effect is neglected, a wide class of electrostatic plasma turbulence can be modeled by a two-dimensional equation for the generalized enstrophy Ψ, an inviscid constant of motion along the turbulent orbits. Under the assumption of a Gaussian stochastic electrostatic potential, an averaged Green's function method is used to rigorously derive equations for the N-particle correlation functions for a dissipative and sheared flow. This approach is equivalent to the cumulant expansion method [T. H. Dupree, Phys. Fluids 15, 334 (1972); 21, 783 (1978)] used to study the Vlasov-Poisson system. For various cases of interest, appropriate equations are solved to obtain the absolute level as well as the detailed structure of the two-point correlation function C(r), and its Fourier transform, the enstrophy spectral function I(k). Uniformly valid analytical expressions are derived for the dissipative but shearless case resulting in a ``fluctuation-dissipation'' theorem relating the total spectral intensity to classical viscosity. These self-consistent results show a strong logarithmic modification of the mixing length estimates for the turbulence levels. For the extremely important and interesting problem of a sheared flow, the suppression of turbulence is demonstrated by using asymptotic analytical techniques in the inviscid range, and uniformly valid numerical methods for the dissipative system. The current asymptotic methods reproduce the results obtained in the orbit picture [Y. Z. Zhang and S. M. Mahajan, Phys. Fluids B 4, 1385 (1992)], but provide much clearer physical perspective and a better definition of crucial parameters like the decorrelation time. The uniformly valid numerical approach allows the determination of the change in spectral shape and intensity due to the presence of shear. It is found that the suppression is more effective for longer wavelengths as compared to the shorter wavelengths. This and other relevant issues, concerning the role

  12. Epochs of intrusion-related copper mineralization in the Andes

    NASA Astrophysics Data System (ADS)

    Sillitoe, R. H.

    Seventy-four copper deposits and prospects related intimately to intrusive activity in the Andes have been dated radiometrically during the last 18 years by many different investigators, most of whom used the KAr method. The results are summarized and some of their local and regional implications are reviewed. A number of copper deposits, mainly of the porphyry type, were emplaced in, or near to, premineral volcanic sequences and (or) equigranular plutons. Such precursor volcanism lasted for as long as 9 Ma, and preceded mineralization by intervals of from less than 1 Ma to as much as 9 Ma. Precursor plutons were emplaced no more than 2 to 3 Ma prior to mineralization at several localities in Chile, but possibly as long as 10 to 30 Ma earlier in parts of Colombia and Peru. The time separating emplacement of progenitor stocks and hydrothermal alteration and accompanying copper mineralization, and the duration of alteration-mineralization sequences generally are both less than the analytical uncertainty of the KAr method. However, on the basis of a detailed study of the Julcani vein system in Peru and less clearcut evidence from elsewhere, it may be concluded that alteration and copper mineralization followed stock or dome emplacement by substantially less than 1 Ma and lasted for 0.5 to 2 Ma and, locally, possibly as long as 3 Ma. At several localities, post-mineral magmatic activity could not be separated by the KAr method from the preceding alteration-mineralization events. As many as nine epochs of copper mineralization, ranging in age from late Paleozoic to late Pliocene-Pleistocene, are recognizable in the central Andes of Chile, Peru, Bolivia, and Argentina, and at least four somewhat different epochs characterize the northern Andes of Colombia. Each epoch coincides with a discrete linear sub-belt, some of which extend for more than 2000 km along the length of the orogen. More than 90% of Andean copper resources, mainly as porphyry deposits, are

  13. Numerical study of chiral plasma instability within the classical statistical field theory approach

    NASA Astrophysics Data System (ADS)

    Buividovich, P. V.; Ulybyshev, M. V.

    2016-07-01

    We report on a numerical study of real-time dynamics of electromagnetically interacting chirally imbalanced lattice Dirac fermions within the classical statistical field theory approach. Namely, we perform exact simulations of the real-time quantum evolution of fermionic fields coupled to classical electromagnetic fields, which are in turn coupled to the vacuum expectation value of the fermionic electric current. We use Wilson-Dirac Hamiltonian for fermions, and noncompact action for the gauge field. In general, we observe that the backreaction of fermions on the electromagnetic field prevents the system from acquiring chirality imbalance. In the case of chirality pumping in parallel electric and magnetic fields, the electric field is screened by the produced on-shell fermions and the accumulation of chirality is hence stopped. In the case of evolution with initially present chirality imbalance, axial charge tends to transform to helicity of the electromagnetic field. By performing simulations on large lattices we show that in most cases this decay process is accompanied by the inverse cascade phenomenon, which transfers energy from short-wavelength to long-wavelength electromagnetic fields. In some simulations, however, we observe a very clear signature of inverse cascade for the helical magnetic fields that is not accompanied by the axial charge decay. This suggests that the relation between the inverse cascade and axial charge decay is not as straightforward as predicted by the simplest form of anomalous Maxwell equations.

  14. Accelerometry to Assess Preschooler's Free-Play: Issues with Count Thresholds and Epoch Durations

    ERIC Educational Resources Information Center

    Oliver, Melody; Schofield, Grant M.; Schluter, Philip J.

    2009-01-01

    This study examines the utility of current accelerometer threshold definitions and epoch durations for physical activity intensity classification in preschool-aged children. Using video footage of children engaged in active play, directly observed 1-sec epoch physical activity intensity scores were derived from a modified version of the Children's…

  15. GRB 150101B/ Swift J123205.1-105602: Second epoch Chandra observations

    NASA Astrophysics Data System (ADS)

    Levan, A. J.; Hjorth, J.; Tanvir, N. R.; van der Horst, A. J.

    2015-02-01

    We obtained a second epoch of observations of the very short GRB 150101B/ Swift J123205.1-105602 (Cummings et al. GCN 17267) with Chandra. Observations began on 10 Feb 2015, 39 days after the burst, and 32 days after the first epoch of observations.

  16. A dusty, normal galaxy in the epoch of reionization

    NASA Astrophysics Data System (ADS)

    Watson, Darach; Christensen, Lise; Knudsen, Kirsten Kraiberg; Richard, Johan; Gallazzi, Anna; Michałowski, Michał Jerzy

    2015-03-01

    Candidates for the modest galaxies that formed most of the stars in the early Universe, at redshifts z > 7, have been found in large numbers with extremely deep restframe-ultraviolet imaging. But it has proved difficult for existing spectrographs to characterize them using their ultraviolet light. The detailed properties of these galaxies could be measured from dust and cool gas emission at far-infrared wavelengths if the galaxies have become sufficiently enriched in dust and metals. So far, however, the most distant galaxy discovered via its ultraviolet emission and subsequently detected in dust emission is only at z = 3.2 (ref. 5), and recent results have cast doubt on whether dust and molecules can be found in typical galaxies at z >= 7. Here we report thermal dust emission from an archetypal early Universe star-forming galaxy, A1689-zD1. We detect its stellar continuum in spectroscopy and determine its redshift to be z = 7.5 +/- 0.2 from a spectroscopic detection of the Lyman-α break. A1689-zD1 is representative of the star-forming population during the epoch of reionization, with a total star-formation rate of about 12 solar masses per year. The galaxy is highly evolved: it has a large stellar mass and is heavily enriched in dust, with a dust-to-gas ratio close to that of the Milky Way. Dusty, evolved galaxies are thus present among the fainter star-forming population at z > 7.

  17. Observing the Epoch of Reionization with the Cosmic Microwave Background

    NASA Astrophysics Data System (ADS)

    Reichardt, Christian L.

    We review the observable consequences of the epoch of reionization (EoR) on the cosmic microwave background (CMB), and the resulting constraints on the EoR. We discuss how Thomson scattering with the free electrons produced during EoR equates to an optical depth for CMB photons. The optical depth measurements from the WMAP and Planck satellites, using large-scale CMB polarization power spectra, are one of the few current constraints on the timing of cosmic reionization. We also present forecasts for the precision with which the optical depth will be measured by future satellite missions. Second, we consider the kinematic Sunyaev-Zel'dovich (kSZ) effect, and how the kSZ power spectrum depends on the duration of reionization. We review current measurements of the kSZ power and forecasts for future experiments. Finally, we mention proposals to look for spectral distortions in the CMB that are related to the electron temperature at EoR, and ideas to map the variations in the optical depth across the sky.

  18. The “Anthropocene” epoch: Scientific decision or political statement?

    USGS Publications Warehouse

    Finney, Stanley C.; Edwards, Lucy E.

    2016-01-01

    The proposal for the “Anthropocene” epoch as a formal unit of the geologic time scale has received extensive attention in scientific and public media. However, most articles on the Anthropocene misrepresent the nature of the units of the International Chronostratigraphic Chart, which is produced by the International Commission on Stratigraphy (ICS) and serves as the basis for the geologic time scale. The stratigraphic record of the Anthropocene is minimal, especially with its recently proposed beginning in 1945; it is that of a human lifespan, and that definition relegates considerable anthropogenic change to a “pre-Anthropocene.” The utility of the Anthropocene requires careful consideration by its various potential users. Its concept is fundamentally different from the chronostratigraphic units that are established by ICS in that the documentation and study of the human impact on the Earth system are based more on direct human observation than on a stratigraphic record. The drive to officially recognize the Anthropocene may, in fact, be political rather than scientific.

  19. Second Epoch VLBA Calibrator Survey Observations: VCS-II

    NASA Astrophysics Data System (ADS)

    Gordon, David; Jacobs, Christopher; Beasley, Anthony; Peck, Alison; Gaume, Ralph; Charlot, Patrick; Fey, Alan; Ma, Chopo; Titov, Oleg; Boboltz, David

    2016-06-01

    Six very successful Very Long Baseline Array (VLBA) calibrator survey campaigns were run between 1994 and 2007 to build up a large list of compact radio sources with positions precise enough for use as very long baseline interferometry (VLBI) phase reference calibrators. We report on the results of a second epoch VLBA Calibrator Survey campaign (VCS-II) in which 2400 VCS sources were re-observed in the X and S bands in order to improve the upcoming third realization of the International Celestial Reference Frame (ICRF3) as well as to improve their usefulness as VLBI phase reference calibrators. In this survey, some 2062 previously detected sources and 324 previously undetected sources were detected and revised positions are presented. Average position uncertainties for the re-observed sources were reduced from 1.14 and 1.98 mas to 0.24 and 0.41 mas in R.A. and decl., respectively, or by nearly a factor of 5. Minimum detected flux values were approximately 15 and 28 mJy in the X and S bands, respectively, and median total fluxes are approximately 230 and 280 mJy. The vast majority of these sources are flat-spectrum sources, with ∼82% having spectral indices greater than ‑0.5.

  20. Tangled magnetic fields and CMBR signal from reionization epoch

    SciTech Connect

    Gopal, Rajesh; Sethi, Shiv K.

    2005-11-15

    We compute the secondary cosmic microwave background radiation (CMBR) anisotropy signal from the reionization of the Universe in the presence of tangled magnetic fields. We consider the tangled-magnetic-field-induced scalar, vector, and tensor modes for our analysis. The most interesting signal for l < or approx. 100 arises from tensor perturbations. In particular, we show that the enhancement observed by Wilkinson microwave anisotropy probe (WMAP) in the TE cross-correlation signal for l < or approx. 10 could be explained by tensor TE cross correlation from tangled magnetic fields generated during the inflationary epoch for magnetic field strength B{sub 0}{approx_equal}4.5x10{sup -9} G and magnetic field power spectrum spectral index n{approx_equal}-2.9. Alternatively, a mixture of tensor mode signal with primordial scalar modes gives weaker bounds on the value of the optical depth to the reionization surface, {tau}{sub reion}: {tau}{sub reion}=0.11{+-}0.02. This analysis can also be translated to a limit on magnetic field strength of {approx_equal}5x10{sup -9} G for wave numbers < or approx. 0.05 Mpc{sup -1}.

  1. Revisiting The First Galaxies: The Epoch of Population III Stars

    NASA Astrophysics Data System (ADS)

    Muratov, Alexander; Gnedin, O. Y.; Gnedin, N. Y.; Zemp, M. K.

    2013-01-01

    We study the formation of the first galaxies using new hydrodynamic cosmological simulations with the ART code. Our simulations feature a recently developed model for dust-based formation of molecular gas. Here, we develop and implement a new recipe for the formation of metal-free Pop III stars. We reach a spatial resolution of 2 pc at z=10 and resolve star-forming galaxies with the masses above 10^6 solar masses. We find the epoch during which Pop III stars dominate the energy and metal budget of the universe to be short-lived. While these stars seed their host galaxies with metals, they cannot drive significant outflows to enrich the IGM in our simulations. Feedback from pair instability supernovae causes Pop III star formation to self-terminate within their host galaxies, but is not strong enough to suppress star formation in external galaxies. Within any individual galaxy, Pop II stars overtake Pop III stars within ~50-150 Myr. A threshold of M = 3 * 10^6 solar masses separates galaxies that lose a significant fraction of their baryons due to Pop III feedback from those that do not. Understanding the nature of the transition between Pop III and Pop II star formation is of key importance for studying the dawn of galaxy formation.

  2. Observations of the first light and the epoch of reionization

    NASA Astrophysics Data System (ADS)

    Fan, Xiaohui

    2012-08-01

    Studying the first generation of stars, galaxies and supermassive black holes as well as the epoch of reionization is one of the fundamental questions of modern astrophysics. The last few years have witnessed the first confirmation of the discoveries of galaxies, quasars and Gamma-Ray Bursts at z > 7, with possible detections at z ~ 10. There is also mounting evidence that cosmic reionization is a prolonged process that peaks around z ~ 10 and ends at z ~ 6-7. Observations of the highest redshift intergalactic medium and the most metal-poor stars in the Galaxy begin to constrain the earliest chemical enrichment processes in the Universe. These observations provide a glimpse of cosmic history over the first billion years after the Big Bang. In this review, we will present recent results on the observations of the high-redshift Universe over the past decade, highlight key challenges and uncertainties in these observations, and preview what is possible with the next generation facilities in studying the first light and mapping the history of reionization.

  3. Phase-compensated averaging for analyzing electroencephalography and magnetoencephalography epochs.

    PubMed

    Matani, Ayumu; Naruse, Yasushi; Terazono, Yasushi; Iwasaki, Taro; Fujimaki, Norio; Murata, Tsutomu

    2010-05-01

    Stimulus-locked averaging for electroencephalography and/or megnetoencephalography (EEG/MEG) epochs cancels out ongoing spontaneous activities by treating them as noise. However, such spontaneous activities are the object of interest for EEG/MEG researchers who study phase-related phenomena, e.g., long-distance synchronization, phase-reset, and event-related synchronization/desynchronization (ERD/ERS). We propose a complex-weighted averaging method, called phase-compensated averaging, to investigate phase-related phenomena. In this method, any EEG/MEG channel is used as a trigger for averaging by setting the instantaneous phases at the trigger timings to 0 so that cross-channel averages are obtained. First, we evaluated the fundamental characteristics of this method by performing simulations. The results showed that this method could selectively average ongoing spontaneous activity phase-locked in each channel; that is, it evaluates the directional phase-synchronizing relationship between channels. We then analyzed flash evoked potentials. This method clarified the directional phase-synchronizing relationship from the frontal to occipital channels and recovered another piece of information, perhaps regarding the sequence of experiments, which is lost when using only conventional averaging. This method can also be used to reconstruct EEG/MEG time series to visualize long-distance synchronization and phase-reset directly, and on the basis of the potentials, ERS/ERD can be explained as a side effect of phase-reset. PMID:20172813

  4. Exploring a Massive Starburst in the Epoch of Reionization

    NASA Astrophysics Data System (ADS)

    Marrone, Daniel; Aravena, M.; Chapman, S.; De Breuck, C.; Gonzalez, A.; Hezavehe, S.; Litke, K.; Ma, J.; Malkan, M.; Spilker, J.; Stalder, B.; Stark, D.; Strandet, M.; Tang, M.; Vieira, J.; Weiss, A.; Welikala, N.

    2016-08-01

    We request deep multi-band imaging of a unique dusty galaxy in the Epoch of Reionization (EoR), selected via its millimeter-wavelength dust emission in the 2500-square-degree South Pole Telescope survey. Spectroscopically confirmed to lie at z=6.900, this galaxy has a large dust mass and is likely one of the most rapidly star-forming objects in the EoR. Using Gemini-S, we have identified z-band emission from this object that could be UV continuum emission at z=6.9 or from a foreground lens. Interpretation of this object, and a complete understanding of its meaning for the census of star formation in the EoR, requires that we establish the presence or absence of gravitational lensing. The dust mass observed in this source is also unexpectedly large for its era, and measurements of the assembled stellar population, through the UV-continuum slope and restframe optical color, will help characterize the stellar mass and dust properties in this very early galaxy, the most spectacular galaxy yet discovered by the SPT.

  5. Stable warm tropical climate through the Eocene Epoch

    NASA Astrophysics Data System (ADS)

    Pearson, Paul N.; van Dongen, Bart E.; Nicholas, Christopher J.; Pancost, Richard D.; Schouten, Stefan; Singano, Joyce M.; Wade, Bridget S.

    2007-03-01

    Earth's climate cooled from a period of extreme warmth in the early Eocene Epoch (ca. 50 Ma) to the early Oligocene (ca. 33 Ma), when a large ice cap first appeared on Antarctica. Evidence from the planktonic foraminifer oxygen isotope record in deep-sea cores has suggested that tropical sea-surface temperatures declined by 5-10 degrees over this interval, eventually becoming much cooler than modern temperatures. Here we present paleotemperature estimates from foraminifer isotopes and the membrane lipids of marine Crenarcheota from new drill cores in Tanzania that indicate a warm and generally stable tropical climate over this period. We reinterpret the previously published isotope records in the light of comparative textural analysis of the deep-sea foraminifer shells, which shows that in contrast to the Tanzanian material, they have been diagenetically recrystallized. We suggest that increasingly severe alteration of the deep-sea plankton shells through the Eocene produced a diagenetic overprint on their oxygen isotope ratios that imparts the false appearance of a tropical sea-surface cooling trend. This implies that the long-term Eocene climatic cooling trend occurred mainly at the poles and had little effect at lower latitudes.

  6. PROBING THE EPOCH OF PRE-REIONIZATION BY CROSS-CORRELATING COSMIC MICROWAVE AND INFRARED BACKGROUND ANISOTROPIES

    SciTech Connect

    Atrio-Barandela, F.; Kashlinsky, A. E-mail: Alexander.Kashlinsky@nasa.gov

    2014-12-20

    The epoch of first star formation and the state of the intergalactic medium (IGM) at that time are not directly observable with current telescopes. The radiation from those early sources is now part of the cosmic infrared background (CIB) and, as these sources ionize the gas around them, the IGM plasma would produce faint temperature anisotropies in the cosmic microwave background (CMB) via the thermal Sunyaev-Zeldovich (TSZ) effect. While these TSZ anisotropies are too faint to be detected, we show that the cross-correlation of maps of source-subtracted CIB fluctuations from Euclid, with suitably constructed microwave maps at different frequencies, can probe the physical state of the gas during reionization and test/constrain models of the early CIB sources. We identify the frequency-combined, CMB-subtracted microwave maps from space- and ground-based instruments to show that they can be cross-correlated with the forthcoming all-sky Euclid CIB maps to detect the cross-power at scales ∼5'-60' with signal-to-noise ratios (S/Ns) of up to S/N ∼ 4-8 depending on the contribution to the Thomson optical depth during those pre-reionization epochs (Δτ ≅ 0.05) and the temperature of the IGM (up to ∼10{sup 4} K). Such a measurement would offer a new window to explore the emergence and physical properties of these first light sources.

  7. Atlas Basemaps in Web 2.0 Epoch

    NASA Astrophysics Data System (ADS)

    Chabaniuk, V.; Dyshlyk, O.

    2016-06-01

    The authors have analyzed their experience of the production of various Electronic Atlases (EA) and Atlas Information Systems (AtIS) of so-called "classical type". These EA/AtIS have been implemented in the past decade in the Web 1.0 architecture (e.g., National Atlas of Ukraine, Atlas of radioactive contamination of Ukraine, and others). One of the main distinguishing features of these atlases was their static nature - the end user could not change the content of EA/AtIS. Base maps are very important element of any EA/AtIS. In classical type EA/AtIS they were static datasets, which consisted of two parts: the topographic data of a fixed scale and data of the administrative-territorial division of Ukraine. It is important to note that the technique of topographic data production was based on the use of direct channels of topographic entity observation (such as aerial photography) for the selected scale. Changes in the information technology of the past half-decade are characterized by the advent of the "Web 2.0 epoch". Due to this, in cartography appeared such phenomena as, for example, "neo-cartography" and various mapping platforms like OpenStreetMap. These changes have forced developers of EA/AtIS to use new atlas basemaps. Our approach is described in the article. The phenomenon of neo-cartography and/or Web 2.0 cartography are analysed by authors using previously developed Conceptual framework of EA/AtIS. This framework logically explains the cartographic phenomena relations of three formations: Web 1.0, Web 1.0x1.0 and Web 2.0. Atlas basemaps of the Web 2.0 epoch are integrated information systems. We use several ways to integrate separate atlas basemaps into the information system - by building: weak integrated information system, structured system and meta-system. This integrated information system consists of several basemaps and falls under the definition of "big data". In real projects it is already used the basemaps of three strata: Conceptual

  8. THE GALAXY LUMINOSITY FUNCTION DURING THE REIONIZATION EPOCH

    SciTech Connect

    Trenti, M.; Shull, J. M.; Stiavelli, M.; Bradley, L. D.; Bouwens, R. J.; Illingworth, G. D.; Oesch, P.; Carollo, C. M.

    2010-05-10

    The new Wide Field Camera 3/IR observations on the Hubble Ultra-Deep Field (HUDF) started investigating the properties of galaxies during the reionization epoch. To interpret these observations, we present a novel approach inspired by the conditional luminosity function method. We calibrate our model to observations at z = 6 and assume a non-evolving galaxy luminosity versus halo mass relation. We first compare model predictions against the luminosity function (LF) measured at z = 5 and z = 4. We then predict the LF at z {>=} 7 under the sole assumption of evolution in the underlying dark-matter halo mass function. Our model is consistent with the observed z {approx_gt} 7 galaxy number counts in the HUDF survey and suggests a possible steepening of the faint-end slope of the LF: {alpha}(z {approx_gt} 8) {approx_lt} -1.9 compared to {alpha} = -1.74 at z = 6. Although we currently see only the brightest galaxies, a hidden population of lower luminosity objects (L/L {sub *} {approx_gt} 10{sup -4}) might provide {approx_gt}75% of the total reionizing flux. Assuming escape fraction f {sub esc} {approx} 0.2, clumping factor C {approx} 5, top-heavy initial mass function (IMF), and low metallicity, galaxies below the detection limit produce complete reionization at z {approx_gt} 8. For solar metallicity and normal stellar IMF, reionization finishes at z {approx_gt} 6, but a smaller C/f {sub esc} is required for an optical depth consistent with the Wilkinson Microwave Anisotropy Probe measurement. Our model highlights that the star formation rate in sub-L {sub *} galaxies has a quasi-linear relation to dark-matter halo mass, suggesting that radiative and mechanical feedback were less effective at z {>=} 6 than today.

  9. The Galaxy UV Luminosity Function before the Epoch of Reionization

    NASA Astrophysics Data System (ADS)

    Mason, Charlotte A.; Trenti, Michele; Treu, Tommaso

    2015-11-01

    We present a model for the evolution of the galaxy ultraviolet (UV) luminosity function (LF) across cosmic time where star formation is linked to the assembly of dark matter halos under the assumption of a mass-dependent, but redshift-independent, efficiency. We introduce a new self-consistent treatment of the halo star formation history, which allows us to make predictions at z > 10 (lookback time ≲500 Myr), when growth is rapid. With a calibration at a single redshift to set the stellar-to-halo mass ratio, and no further degrees of freedom, our model captures the evolution of the UV LF over all available observations (0 ≲ z ≲ 10). The significant drop in luminosity density of currently detectable galaxies beyond z ˜ 8 is explained by a shift of star formation toward less massive, fainter galaxies. Assuming that star formation proceeds down to atomic cooling halos, we derive a reionization optical depth τ ={0.056}-0.010+0.007, fully consistent with the latest Planck measurement, implying that the universe is fully reionized at z={7.84}-0.98+0.65. In addition, our model naturally produces smoothly rising star formation histories for galaxies with L ≲ L* in agreement with observations and hydrodynamical simulations. Before the epoch of reionization at z > 10 we predict the LF to remain well-described by a Schechter function, but with an increasingly steep faint-end slope (α ˜ -3.5 at z ˜ 16). Finally, we construct forecasts for surveys with James Webb Space Telescope (JWST) and Wide-field Infrared Survey Telescope (WFIRST) and predict that galaxies out to z ˜ 14 will be observed. Galaxies at z > 15 will likely be accessible to JWST and WFIRST only through the assistance of strong lensing magnification.

  10. Seeking the epoch of maximum luminosity for dusty quasars

    SciTech Connect

    Vardanyan, Valeri; Weedman, Daniel; Sargsyan, Lusine E-mail: dweedman@isc.astro.cornell.edu

    2014-08-01

    Infrared luminosities νL{sub ν}(7.8 μm) arising from dust reradiation are determined for Sloan Digital Sky Survey (SDSS) quasars with 1.4 10{sup 46.6} erg s{sup –1} for all 2 epoch when quasars first reached their maximum luminosity has not yet been identified at any redshift below 5. The most ultraviolet luminous quasars, defined by rest frame νL{sub ν}(0.25 μm), have the largest values of the ratio νL{sub ν}(0.25 μm)/νL{sub ν}(7.8 μm) with a maximum ratio at z = 2.9. From these results, we conclude that the quasars most luminous in the ultraviolet have the smallest dust content and appear luminous primarily because of lessened extinction. Observed ultraviolet/infrared luminosity ratios are used to define 'obscured' quasars as those having >5 mag of ultraviolet extinction. We present a new summary of obscured quasars discovered with the Spitzer Infrared Spectrograph and determine the infrared luminosity function of these obscured quasars at z ∼ 2.1. This is compared with infrared luminosity functions of optically discovered, unobscured quasars in the SDSS and in the AGN and Galaxy Evolution Survey. The comparison indicates comparable numbers of obscured and unobscured quasars at z ∼ 2.1 with a possible excess of obscured quasars at fainter luminosities.

  11. Estimating Asteroid Thermal Inertia from Multi-epoch Observations

    NASA Astrophysics Data System (ADS)

    MacLennan, Eric M.; Emery, Joshua P.

    2014-11-01

    Granular material, or regolith, is observed to be ubiquitous on asteroid surfaces. To date, two feasible mechanisms of regolith generation have been proposed: recurrent impacts and thermal fracturing. By combining thermal infrared observations and a thermophysical model (TPM), the thermal inertia of an asteroid surface can be used to infer its physical properties, including the average regolith grain size. With the regolith properties of a large population of diverse asteroids (i.e. different spectral class, size, rotation period etc.), information regarding the details of regolith generation can be inferred.Traditional thermal inertia determination methods use a TPM with a previously derived asteroid shape model and spin axis for constraining the observed surface temperature distribution. TPMs invoke the heat diffusion equation to calculate surface temperatures for a rotating asteroid. An asteroid spin axis provide the boundary condition needed to calculate the surface energy balance in a TPM. However the limited amount of objects with a shape model and thermal infrared observations inhibit the number of thermal inertias that can potentially be calculated. Here, a technique using WISE (12 & 22 μm) observations taken before or after opposition is employed to derive thermal inertias of asteroids without using a shape model. By gathering thermal infrared data at multiple viewing geometries the temperature distribution, thus thermal inertia, is constrained.We first demonstrate the validity of this method on objects with a previously determined shape model and spin axis from the DAMIT website. Our analyses show that not knowing an asteroid’s shape does not significantly affect the resulting thermal inertia estimates. Additionally, we apply our TPM to WISE multi-epoch thermal observations to place estimates for the thermal inertia for more than 100 objects. The set of objects used samples many sizes, spectral classes and rotation periods, which may be important

  12. A dusty, normal galaxy in the epoch of reionization.

    PubMed

    Watson, Darach; Christensen, Lise; Knudsen, Kirsten Kraiberg; Richard, Johan; Gallazzi, Anna; Michałowski, Michał Jerzy

    2015-03-19

    Candidates for the modest galaxies that formed most of the stars in the early Universe, at redshifts z > 7, have been found in large numbers with extremely deep restframe-ultraviolet imaging. But it has proved difficult for existing spectrographs to characterize them using their ultraviolet light. The detailed properties of these galaxies could be measured from dust and cool gas emission at far-infrared wavelengths if the galaxies have become sufficiently enriched in dust and metals. So far, however, the most distant galaxy discovered via its ultraviolet emission and subsequently detected in dust emission is only at z = 3.2 (ref. 5), and recent results have cast doubt on whether dust and molecules can be found in typical galaxies at z ≥ 7. Here we report thermal dust emission from an archetypal early Universe star-forming galaxy, A1689-zD1. We detect its stellar continuum in spectroscopy and determine its redshift to be z = 7.5 ± 0.2 from a spectroscopic detection of the Lyman-α break. A1689-zD1 is representative of the star-forming population during the epoch of reionization, with a total star-formation rate of about 12 solar masses per year. The galaxy is highly evolved: it has a large stellar mass and is heavily enriched in dust, with a dust-to-gas ratio close to that of the Milky Way. Dusty, evolved galaxies are thus present among the fainter star-forming population at z > 7. PMID:25731171

  13. The epoch of reionization in the Rh = ct universe

    NASA Astrophysics Data System (ADS)

    Melia, Fulvio; Fatuzzo, Marco

    2016-03-01

    The measured properties of the epoch of reionization (EoR) show that reionization probably began around z ˜ 12-15 and ended by z = 6. In addition, a careful analysis of the fluctuations in the cosmic microwave background indicate a scattering optical depth τ ˜ 0.066 ± 0.012 through the EoR. In the context of Λ cold dark matter, galaxies at intermediate redshifts and dwarf galaxies at higher redshifts now appear to be the principal sources of UV ionizing radiation, but only for an inferred (ionizing) escape fraction fion ˜ 0.2, which is in tension with other observations that suggest a value as small as ˜0.05. In this paper, we examine how reionization might have progressed in the alternative Friedmann-Robertson Walker cosmology known as the Rh = ct universe, and determine the value of fion required with this different rate of expansion. We find that Rh = ct accounts quite well for the currently known properties of the EoR, as long as its fractional baryon density falls within the reasonable range 0.026 ≲ Ωb ≲ 0.037. This model can also fit the EoR data with fion ˜ 0.05, but only if the Lyman continuum photon production is highly efficient and Ωb ˜ 0.037. These results are still preliminary, however, given their reliance on a particular form of the star formation rate density, which is still uncertain at very high redshifts. It will also be helpful to reconsider the EoR in Rh = ct when complete structure formation models become available.

  14. On the Detection of Spectral Ripples from the Recombination Epoch

    NASA Astrophysics Data System (ADS)

    Sathyanarayana Rao, Mayuri; Subrahmanyan, Ravi; Udaya Shankar, N.; Chluba, Jens

    2015-09-01

    Photons emitted during cosmological hydrogen (500≲ z≲ 1600) and helium recombination (1600≲ z≲ 3500 for He ii \\to He i, 5000≲ z≲ 8000 for He iii \\to He ii) are predicted to appear as broad, weak spectral distortions of the cosmic microwave background. We present a feasibility study for a ground-based detection of these recombination lines, which would uniquely probe astrophysical cosmology beyond the last scattering surface and provide observational constraints on the thermal history of the universe. We find that including sufficient signal spectral structure and maximizing signal-to-noise ratio, an octave band in the 2-6 GHz window is optimal; in this band the predicted signal appears as an additive quasi-sinusoidal component with amplitude about 8 nK embedded in a sky spectrum some nine orders of magnitude brighter. We discuss algorithms to detect these tiny spectral fluctuations in the sky spectrum by foreground modeling and introduce a maximally smooth function capable of describing the foreground spectrum and distinguishing the signal of interest. We conclude that detection is in principle feasible in realistic observing times provided that radio frequency interference and instrument bandpass calibration are controlled in this band at the required level; using Bayesian tests and mock data, we show that 90% confidence detection is possible with an array of 128 radiometers observing for 255 days of effective integration time. We propose APSERa—Array of Precision Spectrometers for the Epoch of Recombination—a dedicated radio telescope to detect these recombination lines.

  15. Seeking the Epoch of Maximum Luminosity for Dusty Quasars

    NASA Astrophysics Data System (ADS)

    Vardanyan, Valeri; Weedman, Daniel; Sargsyan, Lusine

    2014-08-01

    Infrared luminosities νL ν(7.8 μm) arising from dust reradiation are determined for Sloan Digital Sky Survey (SDSS) quasars with 1.4 ~ 3 with maximum luminosity νL ν(7.8 μm) >~ 1047 erg s-1 luminosity functions show one quasar Gpc-3 having νL ν(7.8 μm) > 1046.6 erg s-1 for all 2 epoch when quasars first reached their maximum luminosity has not yet been identified at any redshift below 5. The most ultraviolet luminous quasars, defined by rest frame νL ν(0.25 μm), have the largest values of the ratio νL ν(0.25 μm)/νL ν(7.8 μm) with a maximum ratio at z = 2.9. From these results, we conclude that the quasars most luminous in the ultraviolet have the smallest dust content and appear luminous primarily because of lessened extinction. Observed ultraviolet/infrared luminosity ratios are used to define "obscured" quasars as those having >5 mag of ultraviolet extinction. We present a new summary of obscured quasars discovered with the Spitzer Infrared Spectrograph and determine the infrared luminosity function of these obscured quasars at z ~ 2.1. This is compared with infrared luminosity functions of optically discovered, unobscured quasars in the SDSS and in the AGN and Galaxy Evolution Survey. The comparison indicates comparable numbers of obscured and unobscured quasars at z ~ 2.1 with a possible excess of obscured quasars at fainter luminosities.

  16. RACLETTE: a model for evaluating the thermal response of plasma facing components to slow high power plasma transients. Part I: Theory and description of model capabilities

    NASA Astrophysics Data System (ADS)

    Raffray, A. René; Federici, Gianfranco

    1997-04-01

    RACLETTE (Rate Analysis Code for pLasma Energy Transfer Transient Evaluation), a comprehensive but relatively simple and versatile model, was developed to help in the design analysis of plasma facing components (PFCs) under 'slow' high power transients, such as those associated with plasma vertical displacement events. The model includes all the key surface heat transfer processes such as evaporation, melting, and radiation, and their interaction with the PFC block thermal response and the coolant behaviour. This paper represents part I of two sister and complementary papers. It covers the model description, calibration and validation, and presents a number of parametric analyses shedding light on and identifying trends in the PFC armour block response to high plasma energy deposition transients. Parameters investigated include the plasma energy density and deposition time, the armour thickness and the presence of vapour shielding effects. Part II of the paper focuses on specific design analyses of ITER plasma facing components (divertor, limiter, primary first wall and baffle), including improvements in the thermal-hydraulic modeling required for better understanding the consequences of high energy deposition transients in particular for the ITER limiter case.

  17. Recent Developments in Reconnection Theory: the Plasmoid Instability, Self-Generated Turbulence, and Implications for Laboratory and Space Plasmas

    NASA Astrophysics Data System (ADS)

    Bhattacharjee, Amitava

    2015-11-01

    In recent years, new developments in reconnection theory have challenged classical nonlinear reconnection models. One of these developments is the so-called plasmoid instability of thin current sheets that grows at super-Alfvenic growth rates. Within the resistive MHD model, this instability alters qualitatively the predictions of the Sweet-Parker model, leading to a new nonlinear regime of fast reconnection in which the reconnection rate itself becomes independent of S. This regime has also been seen in Hall MHD as well as fully kinetic simulations, and thus appears to be a universal feature of thin current sheet dynamics, including applications to reconnection forced by the solar wind in the heliosphere and spontaneously unstable sawtooth oscillations in tokamaks. Plasmoids, which can grow by coalescence to large sizes, provide a powerful mechanism for coupling between global and kinetic scales as well as an efficient accelerator of particles to high energies. In two dimensions, the plasmoids are characterized by power-law distribution functions followed by exponential tails. In three dimensions, the instability produces self-generated and strongly anisotropic turbulence in which the reconnection rate for the mean-fields remain approximately at the two-dimensional value, but the energy spectra deviate significantly from anisotropic strong MHD turbulence phenomenology. A new phase diagram of fast reconnection has been proposed, guiding the design of future experiments in magnetically confined and high-energy-density plasmas, and have important implications for explorations of the reconnection layer in the recently launched Magnetospheric Multiscale (MMS) mission. This research is supported by DOE, NASA, and NSF.

  18. Superposed epoch study of ICME sub-structures near Earth and their effects on Galactic cosmic rays

    NASA Astrophysics Data System (ADS)

    Masías-Meza, J. J.; Dasso, S.; Démoulin, P.; Rodriguez, L.; Janvier, M.

    2016-08-01

    Context. Interplanetary coronal mass ejections (ICMEs) are the interplanetary manifestations of solar eruptions. The overtaken solar wind forms a sheath of compressed plasma at the front of ICMEs. Magnetic clouds (MCs) are a subset of ICMEs with specific properties (e.g. the presence of a flux rope). When ICMEs pass near Earth, ground observations indicate that the flux of Galactic cosmic rays (GCRs) decreases. Aims: The main aims of this paper are to find common plasma and magnetic properties of different ICME sub-structures and which ICME properties affect the flux of GCRs near Earth. Methods: We used a superposed epoch method applied to a large set of ICMEs observed in situ by the spacecraft ACE, between 1998 and 2006. We also applied a superposed epoch analysis on GCRs time series observed with the McMurdo neutron monitors. Results: We find that slow MCs at 1 AU have on average more massive sheaths. We conclude that this is because they are more effectively slowed down by drag during their travel from the Sun. Slow MCs also have a more symmetric magnetic field and sheaths expanding similarly as their following MC, while in contrast, fast MCs have an asymmetric magnetic profile and a sheath in compression. In all types of MCs, we find that the proton density and the temperature and the magnetic fluctuations can diffuse within the front of the MC due to 3D reconnection. Finally, we derive a quantitative model that describes the decrease in cosmic rays as a function of the amount of magnetic fluctuations and field strength. Conclusions: The obtained typical profiles of sheath, MC and GCR properties corresponding to slow, middle, and fast ICMEs, can be used for forecasting or modelling these events, and to better understand the transport of energetic particles in ICMEs. They are also useful for improving future operative space weather activities.

  19. The Observatory for Multi-Epoch Gravitational Lens Astrophysics (OMEGA)

    NASA Astrophysics Data System (ADS)

    Moustakas, Leonidas A.; Bolton, Adam J.; Booth, Jeffrey T.; Bullock, James S.; Cheng, Edward; Coe, Dan; Fassnacht, Christopher D.; Gorjian, Varoujan; Heneghan, Cate; Keeton, Charles R.; Kochanek, Christopher S.; Lawrence, Charles R.; Marshall, Philip J.; Metcalf, R. Benton; Natarajan, Priyamvada; Nikzad, Shouleh; Peterson, Bradley M.; Wambsganss, Joachim

    2008-07-01

    Dark matter in a universe dominated by a cosmological constant seeds the formation of structure and is the scaffolding for galaxy formation. The nature of dark matter remains one of the fundamental unsolved problems in astrophysics and physics even though it represents 85% of the mass in the universe, and nearly one quarter of its total mass-energy budget. The mass function of dark matter "substructure" on sub-galactic scales may be enormously sensitive to the mass and properties of the dark matter particle. On astrophysical scales, especially at cosmological distances, dark matter substructure may only be detected through its gravitational influence on light from distant varying sources. Specifically, these are largely active galactic nuclei (AGN), which are accreting super-massive black holes in the centers of galaxies, some of the most extreme objects ever found. With enough measurements of the flux from AGN at different wavelengths, and their variability over time, the detailed structure around AGN, and even the mass of the super-massive black hole can be measured. The Observatory for Multi-Epoch Gravitational Lens Astrophysics (OMEGA) is a mission concept for a 1.5-m near-UV through near-IR space observatory that will be dedicated to frequent imaging and spectroscopic monitoring of ~100 multiply-imaged active galactic nuclei over the whole sky. Using wavelength-tailored dichroics with extremely high transmittance, efficient imaging in six channels will be done simultaneously during each visit to each target. The separate spectroscopic mode, engaged through a flip-in mirror, uses an image slicer spectrograph. After a period of many visits to all targets, the resulting multidimensional movies can then be analyzed to a) measure the mass function of dark matter substructure; b) measure precise masses of the accreting black holes as well as the structure of their accretion disks and their environments over several decades of physical scale; and c) measure a

  20. Second Epoch Hubble Space Telescope Imaging of Kepler's Supernova Remnant

    NASA Astrophysics Data System (ADS)

    Sankrit, Ravi; Blair, William P.; Borkowski, Kazimierz J.; Long, Knox S.; Patnaude, Daniel; Raymond, John C.; Reynolds, Stephen P.; Williams, Brian J.

    2015-01-01

    We have obtained new HST/WFC3 images of Kepler's supernova remnant in H-alpha (F656N) and [N II] (F658N) emission line filters. The bright radiative shocks in dense clumps are detected in both filters, while non-radiative shocks are seen as faint filaments only in the H-alpha image. Most of these Balmer filaments lie around the periphery of the remnant where the blast wave encounters partially neutral interstellar gas. We compare the new images with HST/ACS images taken nearly 10 years previously, and find that these filaments tracing the forward shock have moved 0.6"-0.9" between the two epochs. Assuming a distance of 4 kpc to the remnant, these proper motions correspond to shock velocities of 1160-1740 km/s, which are consistent with the published values, 1550-2000 km/s (e.g. Blair et al. 1991, ApJ 366, 484). We also find a few Balmer filaments with highly non-radial proper motions. In one particularly interesting case in the projected interior of the remnant, SE of the center, the shock appears to have wrapped around a sharp density enhancement and moved about 0.3" in the period between the observations.The images allow us to study the evolution of the shock around an ejecta knot, which is punching through the remnant boundary in the northwest. The forward shock, visible as an arcuate Balmer filament, has moved about 1". At the trailing edges, the system of radiative knots formed by Rayleigh-Taylor instabilities have undergone significant changes - some knots have disappeared, new ones have appeared, and many have changed in brightness. Elsewhere in the remnant we find changes in the relative intensities of many small, bright knots over the 10 year baseline, indicating the short radiative lifetimes of these features.This work has been supported in part by grant HST-GO-12885 to the Universities Space Research Association.

  1. Faint Blue Galaxies and the Epoch of Dwarf Galaxy Formation

    NASA Astrophysics Data System (ADS)

    Babul, Arif; Ferguson, Henry C.

    1996-02-01

    Several independent lines of reasoning, both theoretical and observational, suggest that the very faint (B ≳ 24) galaxies seen in deep images of the sky are small low-mass galaxies that experienced a short starburst at redshifts 0.5 ≲ z ≲ 1 and have since faded into low-luminosity, low surface brightness (LSB) objects. We examine this hypothesis in detail in order to determine whether a model incorporating such dwarfs can account for the observed wavelength-dependent number counts, as well as redshift, color, and size distributions. Low-mass galaxies generically arise in large numbers in hierarchical clustering scenarios with realistic initial conditions. Generally, these galaxies are expected to form at high redshifts. Babul & Rees have argued that the formation epoch of these galaxies is, in fact, delayed until z ≲ 1 due to the photoionization of the gas by the metagalactic UV radiation at high redshifts. We combine these two elements, along with simple heuristic assumptions regarding star formation histories and efficiency, to construct our bursting dwarf model. The slope and the normalization of the mass function of the dwarf galaxies are derived from the initial conditions and are not adjusted to fit the data. We further augment the model with a phenomenological prescription for the formation and evolution of the locally observed population of galaxies (E, S0, Sab, Sbc, and Sdm types). We use spectral synthesis and Monte Carlo methods to generate realistic model galaxy catalogs for comparison with observations. We find that for reasonable choices of the star formation histories for the dwarf galaxies, the model results are in very good agreement with the results of the deep galaxy surveys. Such a dwarf-dominated model is also qualitatively supported by recent studies of faint galaxy gravitational lensing and clustering, by galaxy size distributions measured with the Hubble Space Telescope, and by the evidence for very modest evolution in regular galaxy

  2. Discovery of a Giant Lya Emitter Near the Reionization Epoch

    SciTech Connect

    Ouchi, Masami; Ono, Yoshiaki; Egami, Eiichi; Saito, Tomoki; Oguri, Masamune; McCarthy, Patrick J.; Farrah, Duncan; Kashikawa, Nobunari; Momcheva, Ivelina; Shimasaku, Kazuhiro; Nakanishi, Kouichiro; Furusawa, Hisanori; Akiyama, Masayuki; Dunlop, James S.; Mortier, Angela M.J.; Okamura, Sadanori; Hayashi, Masao; Cirasuolo, Michele; Dressler, Alan; Iye, Masanori; Jarvis, Matt.J.

    2008-08-01

    We report the discovery of a giant Ly{alpha} emitter (LAE) with a Spitzer/IRAC counterpart near the reionization epoch at z = 6.595. The giant LAE is found from the extensive 1 deg{sup 2} Subaru narrow-band survey for z = 6.6 LAEs in the Subaru/XMM-Newton Deep Survey (SXDS) field, and subsequently identified by deep spectroscopy of Keck/DEIMOS and Magellan/IMACS. Among our 207 LAE candidates, this LAE is not only the brightest narrow-band object with L(Ly{alpha}) = 3.9 {+-} 0.2 x 10{sup 43} erg s{sup -1} in our survey volume of 10{sup 6} Mpc{sup 3}, but also a spatially extended Ly{alpha} nebula with the largest isophotal area whose major axis is at least {approx_equal} 3-inches. This object is more likely to be a large Ly{alpha} nebula with a size of {approx}> 17-kpc than to be a strongly-lensed galaxy by a foreground object. Our Keck spectrum with medium-high spectral and spatial resolutions suggests that the velocity width is v{sub FWHM} = 251 {+-} 21 km s{sup -1}, and that the line-center velocity changes by {approx_equal} 60 km s{sup -1} in a 10-kpc range. The stellar mass and star-formation rate are estimated to be 0.9-5.0 x 10{sup 10}M{sub {circle_dot}} and > 34 M{sub {circle_dot}}yr{sup -1}, respectively, from the combination of deep optical to infrared images of Subaru, UKIDSS-Ultra Deep Survey, and Spitzer/IRAC. Although the nature of this object is not yet clearly understood, this could be an important object for studying cooling clouds accreting onto a massive halo, or forming-massive galaxies with significant outflows contributing to cosmic reionization and metal enrichment of inter-galactic medium.

  3. Organic Chemostratigraphic Markers Characteristic of the (Informally Designated) Anthropocene Epoch

    NASA Astrophysics Data System (ADS)

    Kruge, M. A.

    2008-12-01

    Recognizing the tremendous collective impact of humans on the environment in the industrial age, the proposed designation of the current time period as the Anthropocene Epoch has considerable merit. One of the signature activities during this time continues to be the intensive extraction, processing, and combustion of fossil fuels. While fossil fuels themselves are naturally-occurring, they are most often millions of years old and associated with deeply buried strata. They may be found at the surface, for example, as natural oil seeps or coal seam outcrops, but these are relatively rare occurrences. Fossil fuels and their myriad by- products become the source of distinctive organic chemostratigraphic marker compounds for the Anthropocene when they occur out of their original geological context, i.e., as widespread contaminants in sediments and soils. These persistent compounds have high long-term preservation potential, particularly when deposited under low oxygen conditions. Fossil fuels can occur as environmental contaminants in raw form (e.g., crude petroleum spilled during transport) or as manufactured products (e.g., diesel oil from a leaking storage facility, coal tar from a manufactured gas plant, plastic waste in a landfill, pesticides from petroleum feedstock in agricultural soils). Distinctive assemblages of hydrocarbon marker compounds including acyclic isoprenoids, hopanes, and steranes can be readily detected by gas chromatography/mass spectrometric analysis of surface sediments and soils. Polycyclic aromatic hydrocarbons (PAHs), along with sulfur-, oxygen-, and nitrogen-containing aromatic compounds, are also characteristic of fossil fuels and are readily detectable as well. More widespread is the airfall deposition of fossil fuel combustion products from vehicular, domestic and industrial sources. These occur in higher concentrations in large urban centers, but are also detected in remote areas. Parent (nonmethylated) PAHs such as phenanthrene

  4. A Superposed Epoch Analysis of Geomagnetic Storms over a Solar Cycle: Geomagnetic and Solar Wind Data, Radar Backscatter & Auroral Imagery

    NASA Astrophysics Data System (ADS)

    Hutchinson, J. A.; Wright, D. M.; Milan, S. E.; Grocott, A.

    2010-12-01

    Geomagnetic storms - episodes of intense solar wind-magnetosphere coupling usually associated with extreme conditions in the solar wind such as coronal mass ejections (CMEs) or co-rotating interaction regions (CIRs) - cause large global disturbances in the Earth’s magnetosphere. During such storms, large amounts of energy are deposited in the magnetotail and inner magnetosphere, producing an enhanced ring current and energising plasma to relativistic levels by as yet unknown excitation mechanisms. By exploiting data from the Advanced Composition Explorer (ACE) spacecraft in conjunction with space- and ground-based measurements of geospace over the last solar cycle, a database of geomagnetic storms has been compiled and analysed. Here we present some statistical findings from a superposed epoch analysis of 143 events identified from the global SYM-H index. We find that the duration of the main phase of storms decreases for increasing storm size, as defined by the maximum negative excursion of SYM-H, contrary to the results of previous studies. We also discuss a comparison of CME and CIR driven storms in terms of storm size, phase duration and evolution, and the associated solar wind-magnetosphere coupling. Initial work has successfully identified characteristic radar backscatter observed by the Super Dual Auoral Radar Network (SuperDARN) and, in particular, the new lower-latitude StormDARN radar network during these storm-time conditions. Here we present early findings of a superposed epoch analysis of auroral imagery from the IMAGE spacecraft and ionospheric convection maps from the SuperDARN radar network. This work further illustrates the storm-time coupling between the solar wind and magnetosphere, and develops the relationship between auroral oval radius and the evolution of the storm-time SYM-H index first reported by Milan et al., (2009). Once completed, this will be the most complete superposed epoch analyses of storms to date, combining multiple datasets

  5. Nonlinear frequency shift of electrostatic waves in general collisionless plasma: Unifying theory of fluid and kinetic nonlinearities

    SciTech Connect

    Liu, Chang; Dodin, Ilya Y.

    2015-08-15

    The nonlinear frequency shift is derived in a transparent asymptotic form for intense Langmuir waves in general collisionless plasma. The formula describes both fluid and kinetic effects simultaneously. The fluid nonlinearity is expressed, for the first time, through the plasma dielectric function, and the kinetic nonlinearity accounts for both smooth distributions and trapped-particle beams. Various known limiting scalings are reproduced as special cases. The calculation avoids differential equations and can be extended straightforwardly to other nonlinear plasma waves.

  6. Trajectory of the cosmic plasma through the quark matter phase diagram

    NASA Astrophysics Data System (ADS)

    McInnes, Brett

    2016-02-01

    Experimental studies of the quark-gluon plasma (QGP) focus on two, in practice distinct, regimes: one in which the baryonic chemical potential μB is essentially zero, the other in which it is of the same order of magnitude as the temperature. The cosmic QGP which dominates the early universe after reheating is normally assumed to be of the first kind, but recently it has been suggested that it might well be of the second: this is the case in the theory of "little inflation." If that is so, then it becomes a pressing issue to fix the trajectory of the Universe, as it cools, through the quark matter phase diagram: in particular, one wishes to know where in that diagram the plasma epoch ends, so that the initial conditions of the hadronic epoch can be determined. Here we combine various tools from strongly coupled QGP theory (the latest lattice results, together with gauge-gravity duality) in order to constrain that trajectory, assuming that little inflation did occur.

  7. Nonlinear and three-dimensional theory for cross-magnetic field propagation of short-pulse lasers in underdense plasmas

    NASA Astrophysics Data System (ADS)

    Ren, C.; Mori, W. B.

    2004-05-01

    The nonlinear and finite spot size effects for short laser pulses propagating in a plasma across a constant magnetic field (ordinary and extraordinary modes) have been studied. Starting from a fluid Lagrangian for magnetized plasmas with immobile ions, we derive the envelope equation for the laser and also the equation for the plasma wake in a three-dimensional geometry. The derived equations reveal that the external magnetic field reduces the strength of ponderomotive self-focusing, causes astigmatic self-focusing, and leads to the possibility of deflecting a short and narrow laser pulse in a magnetized plasma.

  8. Spectrotemporal receptive fields during spindling and non-spindling epochs in cat primary auditory cortex.

    PubMed

    Britvina, T; Eggermont, J J

    2008-07-17

    It was often thought that synchronized rhythmic epochs of spindle waves disconnect thalamo-cortical system from incoming sensory signals. The present study addresses this issue by simultaneous extracellular action potential and local field potential (LFP) recordings from primary auditory cortex of ketamine-anesthetized cats during spindling activity. We compared cortical spectrotemporal receptive fields (STRF) obtained during spindling and non-spindling epochs. The basic spectro-temporal parameters of "spindling" and "non-spindling" STRFs were similar. However, the peak-firing rate at the best frequency was significantly enhanced during spindling epochs. This enhancement was mainly caused by the increased probability of a stimulus to evoke spikes (effectiveness of stimuli) during spindling as compared with non-spindling epochs. Augmented LFPs associated with effective stimuli and increased single-unit pair correlations during spindling epochs suggested higher synchrony of thalamo-cortical inputs during spindling that resulted in increased effectiveness of stimuli presented during spindling activity. The neuronal firing rate, both stimulus-driven and spontaneous, was higher during spindling as compared with non-spindling epochs. Overall, our results suggests that thalamic cells during spindling respond to incoming stimuli-related inputs and, moreover, cause more powerful stimulus-related or spontaneous activation of the cortex. PMID:18515012

  9. Kinetic description of a degenerate, rotating, non-neutral electron plasma in external magnetic fields in the framework of the Thomas-Fermi-Dirac theory

    NASA Astrophysics Data System (ADS)

    Molinari, V. G.; Rocchi, F.; Sumini, M.

    2002-01-01

    Aim of this work is to extend the results obtained in a previous study on the magnetic confinement and stability of a quantum degenerate non-neutral fermion plasma. This extension consists in the inclusion in the previously set up model of the effects of the exchange forces, and generalises the Thomas-Fermi (TF) approach used in the referenced work towards a Thomas-Fermi-Dirac (TFD) statistical description. The TF model has not only been used extensively and with success in these years to study atomic, nuclear and molecular properties, or to evaluate features of matter in extreme conditions such as low temperatures and/or high densities typical of astrophysics and inertial confinement fusion experiments, but also to found hydrodynamic theories for the diffusion and stability of fermion plasmas, one component non-neutral degenerate fluids, plasmas etc. In this paper an equation for density profiles in cylindrical symmetry is found, from the semiclassical kinetic theory of quantum gases, which takes into account the effects of temperature, average velocity, external magnetic field and quantum exchange. Numerical solutions of this equation for the case of complete quantum degeneracy are given and comparisons with the previous results are carried out.

  10. Basis of the quasi-steady plasma accelerator theory in the presence of a longitudinal magnetic field

    NASA Astrophysics Data System (ADS)

    Kozlov, Andrey N.

    2008-04-01

    The analytic and numerical approaches to the investigation of the two-dimensional steady-state plasma flows are analyzed and compared with reference to a plasma accelerator channel in the presence of a longitudinal magnetic field. The present study continues a cycle of research into the plasma flows in the coaxial channels with the traditional azimuthal magnetic field. The additional longitudinal field opens new possibilities for controlling the dynamic processes and achieving the transonic flows. The research is based on the magnetohydrodynamic equations.

  11. Ginzburg-Landau theory for the solid-liquid interface of bcc elements. II - Application to the classical one-component plasma, the Wigner crystal, and He-4

    NASA Technical Reports Server (NTRS)

    Zeng, X. C.; Stroud, D.

    1989-01-01

    The previously developed Ginzburg-Landau theory for calculating the crystal-melt interfacial tension of bcc elements to treat the classical one-component plasma (OCP), the charged fermion system, and the Bose crystal. For the OCP, a direct application of the theory of Shih et al. (1987) yields for the surface tension 0.0012(Z-squared e-squared/a-cubed), where Ze is the ionic charge and a is the radius of the ionic sphere. Bose crystal-melt interface is treated by a quantum extension of the classical density-functional theory, using the Feynman formalism to estimate the relevant correlation functions. The theory is applied to the metastable He-4 solid-superfluid interface at T = 0, with a resulting surface tension of 0.085 erg/sq cm, in reasonable agreement with the value extrapolated from the measured surface tension of the bcc solid in the range 1.46-1.76 K. These results suggest that the density-functional approach is a satisfactory mean-field theory for estimating the equilibrium properties of liquid-solid interfaces, given knowledge of the uniform phases.

  12. Evolution of neutral gas at high redshift: implications for the epoch of galaxy formation

    NASA Astrophysics Data System (ADS)

    Storrie-Lombardi, L. J.; McMahon, R. G.; Irwin, M. J.

    1996-12-01

    Although observationally rare, damped Lyalpha absorption systems dominate the mass density of neutral gas in the Universe. 11 high-redshift damped Lyalpha systems covering 2.8<=z<=4.4 were discovered in 26 QSOs from the APMz<~4 QSO survey, extending these absorption system surveys to the highest redshifts currently possible. Combining our new data set with previous surveys, we find that the cosmological mass density in neutral gas, Omega_g, does not rise as steeply prior to z~2 as indicated by previous studies. There is evidence in the observed Omega_g for a flattening at z~2 and a possible turnover at z~3. When combined with the decline at z<~3.5 in number density per unit redshift of damped systems with column densities log N_HI>=21 atom cm^-2, these results point to an epoch at z>~3 prior to which the highest column density damped systems are still forming. We find that, over the redshift range 2theories of galaxy formation.

  13. Axion-induced oscillations of cooperative electric field in a cosmic magneto-active plasma

    NASA Astrophysics Data System (ADS)

    Balakin, Alexander B.; Muharlyamov, Ruslan K.; Zayats, Alexei E.

    2014-06-01

    We consider one cosmological application of an axionic extension of the Maxwell-Vlasov theory, which describes axionically induced oscillatory regime in the state of global magnetic field evolving in the anisotropic expanding (early) universe. We show that the cooperative electric field in the relativistic plasma, being coupled to the pseudoscalar (axion) and global magnetic fields, plays the role of a regulator in this three-level system; in particular, the cooperative (Vlasov) electric field converts the regime of anomalous growth of the pseudoscalar field, caused by the axion-photon coupling at the inflationary epoch of the universe expansion, into an oscillatory regime with finite density of relic axions. We analyze solutions to the dispersion equations for the axionically induced cooperative oscillations of the electric field in the relativistic plasma.

  14. The pulsar B2224+65 and its jets: a two epoch X-ray analysis

    NASA Astrophysics Data System (ADS)

    Johnson, S. P.; Wang, Q. D.

    2010-10-01

    We present an X-ray morphological and spectroscopic study of the pulsar B2224+65 and its apparent jet-like X-ray features based on two epoch Chandra observations. The main X-ray feature, which shows a large directional offset from the ram-pressure confined pulsar wind nebula (Guitar nebula), is broader in apparent width and shows evidence for spectral hardening (at 95 per cent confidence) in the second epoch compared to the first. Furthermore, the sharp leading edge of the feature is found to have a proper motion consistent with that of the pulsar (~180 mas yr-1). The combined data set also provides evidence for the presence of a counter feature, albeit substantially fainter and shorter than the main one. Additional spectral trends along the major and minor axes of the feature are only marginally detected in the two epoch data, including softening counter to the direction of proper motion. Possible explanations for the X-ray features include diffuse energetic particles being confined by an organized ambient magnetic field as well as a simple ballistic jet interpretation; however, the former may have difficulty in explaining observed spectral trends between epochs and along the feature's major axis, whereas the latter may struggle to elucidate its linearity. Given the low counting statistics available in the two epoch observations, it remains difficult to determine a physical production scenario for these enigmatic X-ray emitting features with any certainty.

  15. A comparison of weak-turbulence and particle-in-cell simulations of weak electron-beam plasma interaction

    SciTech Connect

    Ratcliffe, H. Brady, C. S.; Che Rozenan, M. B.; Nakariakov, V. M.

    2014-12-15

    Quasilinear theory has long been used to treat the problem of a weak electron beam interacting with plasma and generating Langmuir waves. Its extension to weak-turbulence theory treats resonant interactions of these Langmuir waves with other plasma wave modes, in particular, ion-sound waves. These are strongly damped in plasma of equal ion and electron temperatures, as sometimes seen in, for example, the solar corona and wind. Weak turbulence theory is derived in the weak damping limit, with a term describing ion-sound wave damping then added. In this paper, we use the EPOCH particle-in-cell code to numerically test weak turbulence theory for a range of electron-ion temperature ratios. We find that in the cold ion limit, the results agree well, but for increasing ion temperature the three-wave resonance becomes broadened in proportion to the ion-sound wave damping rate. Additionally, we establish lower limits on the number of simulation particles needed to accurately reproduce the electron and wave distributions in their saturated states and to reproduce their intermediate states and time evolution. These results should be taken into consideration in, for example, simulations of plasma wave generation in the solar corona of Type III solar radio bursts from the corona to the solar wind and in weak turbulence investigations of ion-acoustic lines in the ionosphere.

  16. Rydberg gas theory of a glow discharge plasma: II. Electrode kinetics (probe theory) and the thermal rate constant for Symmetrical charge transfer involving Rydberg atoms of Ar.

    PubMed

    Mason, Rod S

    2010-04-21

    A steady state chemical kinetic model is developed to describe the conduction of electrical current between two probes, of relatively large surface area, immersed in a fast flowing plasma by the mechanism of charge transfer through a gas of Rydberg atoms. It correctly predicts the shape of current-voltage profiles which are similar to those of Langmuir, or floating double probe measurements. The difference is that the plateau current at the probe reflects the transport limited ion current at the cathodic electrode, even when the probe is being scanned in the anodic region. The sharp gradient leading up to the plateau of the I-V curve is associated with the field dependence of the efficiency of Rydberg atom ionisation, not the electron temperature. This approach gives a good qualitative explanation of experimental behaviour over a wide range of probe bias voltages and includes the occurrence of electron impact ionisation at the anode. It also gives a value for the thermal rate coefficient of symmetrical charge transfer between Rydberg atoms of Ar (8.2 x 10(-7) molecule(-1) cm(3) s(-1), at 313 K; plasma density approximately = 10(10) atoms cm(-3), total pressure = 2.7 mbar). PMID:20358036

  17. Scientists Debate Whether the Anthropocene Should Be a New Geological Epoch

    NASA Astrophysics Data System (ADS)

    Showstack, Randy

    2013-01-01

    By about 2017 or 2018, scientists probably will have determined whether or not the Earth has entered into the "Anthropocene" epoch. Although many people are convinced that we are already living in the Anthropocene, that's the estimate for when a scientific review process could culminate in officially designating this potential new epoch of the Quaternary Period (roughly the past 2.6 million years) signified by profound human alteration to geological conditions and processes. The epoch would encompass—for the time being—a sliver of geological time separate rom the Holocene (roughly 12,000 years ago to the present), starting from perhaps the beginning of the Industrial Revolution, the end of World War II, or some other date determined to be a good marker to designate the beginning of the Anthropocene.

  18. Sub-Proton Scale Magnetic Holes: Turbulence Simulations, Theory and Cluster Observations in the Earth's Plasma Sheet.

    NASA Astrophysics Data System (ADS)

    Haynes, C. T.; Burgess, D.; Camporeale, E.; Sundberg, T.

    2014-12-01

    We investigate the properties of a new type of nonlinear coherent structure, called electron vortex magnetic holes (EVMHs) discovered during 2-D full particle realistic mass ratio simulations of turbulence. These structures form via the interaction of magnetic depletions and the local electron population in the plasma. They are characterised by local depressions in the magnetic field strength with circular cross-sections. We use PIC and test particle simulations to show that the magnetic structure is maintained by a current carried by an electron vortex which is due to a population of electrons with pitch angles close to 90 degrees in trapped, or quasi-trapped, non-adiabatic orbits. We then compare these results to Cluster observations of electron-scale magnetic holes (MH) in the Earth's plasma sheet. MHs in the solar wind are often explained in terms of the mirror mode instability. Here, in the plasma sheet, we show MH events in mirror stable environments, with high electron perpendicular temperature anisotropy, which cannot be explained in terms of a standard mirror mode growth. We show that EVMHs may provide a theoretical explanation for a majority of the MHs observed in the plasma sheet at scales less than the proton thermal gyroradius.

  19. On the luminosity distance and the epoch of acceleration

    NASA Astrophysics Data System (ADS)

    Sutherland, Will; Rothnie, Paul

    2015-02-01

    Standard cosmological models based on general relativity (GR) with dark energy predict that the Universe underwent a transition from decelerating to accelerating expansion at a moderate redshift zacc ˜ 0.7. Clearly, it is of great interest to directly measure this transition in a model-independent way, without the assumption that GR is the correct theory of gravity. We explore to what extent supernova (SN) luminosity distance measurements provide evidence for such a transition: we show that, contrary to intuition, the well-known `turnover' in the SN distance residuals Δμ relative to an empty (Milne) model does not give firm evidence for such a transition within the redshift range spanned by SN data. The observed turnover in that diagram is predominantly due to the negative curvature in the Milne model, not the deceleration predicted by Λ cold dark matter and relatives. We show that there are several advantages in plotting distance residuals against a flat, non-accelerating model (w = -1/3), and also remapping the z-axis to u = ln (1 + z); we outline a number of useful and intuitive properties of this presentation. We conclude that there are significant complementarities between SNe and baryon acoustic oscillations (BAOs): SNe offer high precision at low redshifts and give good constraints on the net amount of acceleration since z ˜ 0.7, but are weak at constraining zacc; while radial BAO measurements are probably superior for placing direct constraints on zacc.

  20. Analytical theory of a current sheet formed between the magnetized and nonmagnetized plasmas with arbitrary energy distribution of particles

    NASA Astrophysics Data System (ADS)

    Martyanov, Vladimir; Kocharovsky, Vladimir; Kocharovsky, Vitaly

    We present analytical description of a self-consistent stationary boundary layer formed between the magnetized and nonmagnetized collisionless plasmas with arbitrary energy distribution of particles. Various spatial profiles of the current and respective particle distributions in the neutral current sheets are found on the basis of the self-consistency equation of the Grad-Shafranov type, which takes into account a homogeneous external magnetic field. The solutions are obtained due to development of the method of invariants of particle motion (Astron. Lett. 36, 396 (2010)) and provide, for the first time, a detailed description of various transition domains in the magnetospheres of stars and planets, in particular, boundary regions formed by an interaction of a solar wind with an interstellar medium or Earth magnetosphere. We restrict ourselves to the shearless magnetic field configurations and consider four special dependencies of particle distribution function on momentum parallel to current direction, which make it possible to detail the relations between the magnetic field profile, plasma density, and particle anisotropy gradient, including both thin and thick (with respect to a particle gyroradius) layers. Special attention is paid to the cases of an utmost sharp boundary between the magnetized and nonmagnetized plasmas and to the cases where there are sections of a boundary current sheet with magnetic field energy density exceeding kinetic energy density of plasma particles. The kinetic instabilities and reconnection phenomena are also discussed, especially the ones related to the Weibel instability in the weakly magnetized parts of the boundary layer. These analytical results are applied to the analysis of the spacecraft observations of the magnetized-nonmagnetized boundaries in cosmic plasma.

  1. Comparing Theory and Experiment for Analyte Transport in the First Vacuum Stage of the Inductively Coupled Plasma Mass Spectrometer

    NASA Astrophysics Data System (ADS)

    Zachreson, Matthew R.

    The inductively coupled plasma mass spectrometer (ICP-MS) has been used in laboratories for many years. The majority of the improvements to the instrument have been done empirically through trial and error. A few fluid models have been made, which have given a general description of the flow through the mass spectrometer interface. However, due to long mean free path effects and other factors, it is very difficult to simulate the flow details well enough to predict how changing the interface design will change the formation of the ion beam. Towards this end, Spencer et al. developed FENIX, a direct simulation Monte Carlo algorithm capable of modeling this transitional flow through the mass spectrometer interface, the transitional flow from disorganized plasma to focused ion beam. Their previous work describes how FENIX simulates the neutral ion flow. While understanding the argon flow is essential to understanding the ICP-MS, the true goal is to improve its analyte detection capabilities. In this work, we develop a model for adding analyte to FENIX and compare it to previously collected experimental data. We also calculate how much ambipolar fields, plasma sheaths, and electron-ion recombination affect the ion beam formation. We find that behind the sampling interface there is no evidence of turbulent mixing. The behavior of the analyte seems to be described simply by convection and diffusion. Also, ambipolar field effects are small and do not significantly affect ion beam formation between the sampler and skimmer cones. We also find that the plasma sheath that forms around the sampling cone does not significantly affect the analyte flow downstream from the skimmer. However, it does thermally insulate the electrons from the sampling cone, which reduces ion-electron recombination. We also develop a model for electron-ion recombination. By comparing it to experimental data, we find that significant amounts of electron-ion recombination occurs just downstream from the

  2. Theory and simulation of quasilinear transport from external magnetic field perturbations in a DIII-D plasma

    NASA Astrophysics Data System (ADS)

    Waltz, R. E.; Ferraro, N. M.

    2015-04-01

    The linear response profiles for the 3D perturbed magnetic fields, currents, ion velocities, plasma density, pressures, and electric potential from low-n external resonant magnetic field perturbations (RMPs) are obtained from the collisional two-fluid M3D-C1 code [N. M. Ferraro and S. C. Jardin, J. Comput. Phys. 228, 7742 (2009)]. A newly developed post-processing RMPtran code computes the resulting quasilinear E×B and magnetic (J×B) radial transport flows with respect to the unperturbed flux surfaces in all channels. RMPtran simulations focus on ion (center of mass) particle and transient non-ambipolar current flows, as well as the toroidal angular momentum flow. The paper attempts to delineate the RMP transport mechanisms that might be responsible for the RMP density pump-out seen in DIII-D [M. A. Mahdavi and J. L. Luxon, Fusion Sci. Technol. 48, 2 (2005)]. Experimentally, the starting high toroidal rotation does not brake to a significantly lower rotation after the pump-out suggesting that convective and E×B transport mechanisms dominate. The direct J×B torque from the transient non-ambipolar radial current expected to accelerate plasma rotation is shown to cancel much of the Maxwell stress J×B torque expected to brake the plasma rotation. The dominant E×B Reynolds stress accelerates rotation at the top of the pedestal while braking rotation further down the pedestal.

  3. Probing the Epoch Reionization at Redshifts 6 to 12 with MWA, PAPER and HERA

    NASA Astrophysics Data System (ADS)

    Jacobs, Daniel; HERA Collaboration

    2016-03-01

    Direct observation of cosmological hydrogen throughout cosmic time is possible via the 21cm line and is now being pursued as a new cosmological and astrophysical probe. Multiple experimental low frequency radio arrays have worked towards detection and characterization of this spectral line signal through many different epochs of cosmic time. The Epoch of Reionization (EoR), when the first stars ionized the primordial hydrogen half a billion years after the big bang, thought to occur between redshifts 6 and 12 is a period of intense interest. The Precision Array for Probing the Epoch of Reionization (PAPER) has placed a series of ever more sensitive limits on the 21cm power spectrum while the Murchison Widefield Array (MWA) has pioneered imaging of structure in the presence of foregrounds. Here we present the latest results from these experiments and introduce the next generation Hydrogen Epoch of Reionization Array (HERA) which will yield 20 times the sensitivity of first generation arrays and provide new constraints on the nature of the first stars, the evolution of primordial galaxies, and significant new constraints on fundamental cosmological parameters.

  4. The Influence of Epoch Length on Physical Activity Patterns Varies by Child's Activity Level

    ERIC Educational Resources Information Center

    Nettlefold, Lindsay; Naylor, P. J.; Warburton, Darren E. R.; Bredin, Shannon S. D.; Race, Douglas; McKay, Heather A.

    2016-01-01

    Purpose: Patterns of physical activity (PA) and sedentary time, including volume of bouted activity, are important health indicators. However, the effect of accelerometer epoch length on measurement of these patterns and associations with health outcomes in children remain unknown. Method: We measured activity patterns in 308 children (52% girls,…

  5. The Corporate University's Role in Managing an Epoch in Learning Organisation Innovation

    ERIC Educational Resources Information Center

    Dealtry, Richard

    2006-01-01

    Purpose: The purpose of this paper is to set the scene for some radical epochal thinking about the approach and future strategic directions in the management of organisational learning, following the author's earlier editorial theme concerning the need for exploration and innovation in organisational learning management.…

  6. ATLAS limits on explosion epoch of SN2016bau in NGC3631

    NASA Astrophysics Data System (ADS)

    Tonry, J.; Denneau, L.; Stalder, B.; Heinze, A.; Sherstyuk, A.; Rest, A.; Smith, K. W.; Smartt, S. J.

    2016-03-01

    Following the discovery of SN2016bau in NGC3631 at 13Mpc by Ron Arbour (TNS Astronomical Transient Report No. 1487) and the spectroscopic confirmation of Granata et al. (ATel #8818, Asiago Transient Classification Program) as a young type Ib supernova, we report limits on the explosion epoch.

  7. Response to ``Comment on `Scaling of asymmetric magnetic reconnection: General theory and collisional simulations' '' [Phys. Plasmas 16, 034701 (2009)

    NASA Astrophysics Data System (ADS)

    Cassak, P. A.; Shay, M. A.

    2009-03-01

    The comment by Semenov et al. has called into question our derivation of the outflow velocity in asymmetric magnetic reconnection. We present three reasons that the analysis presented in the comment is incorrect. Most importantly, the authors of the comment have incorrectly applied results from one-dimensional shock theory to the problem of conservation through a two-dimensional dissipation region. For completeness, we compare their predictions to numerical simulation results, finding that their theory does not describe the data. We conclude the analysis in the comment is without merit.

  8. Unmatter Plasma

    NASA Astrophysics Data System (ADS)

    Smarandache, Florentin

    2015-11-01

    ``Unmatter Plasma'' is a novel form of plasma, exclusively made of matter and its antimatter counterpart. An experiment (2015) on matter-antimatter plasma [or unmatter plasma] was recently successful at the Astra Gemini laser facility at the Rutherford Appleton Laboratory, Oxford, United Kingdom. The experiment that was made has produced electron-positron plasma. The positron is the antimatter of the electron, having an opposite charge of the electron, but the other properties are the same. Unmatter is considered as a combination of matter and antimatter. For example electron-positron is a type of unmatter. We coined the word ``unmatter'' (2004) that means neither matter nor antimatter, but something in between. Besides matter and antimatter there may exist unmatter (as a new form of matter) in accordance with the neutrosophy theory that between an entity and its opposite there exist intermediate entities.

  9. STAR FORMATION IN ORION'S L1630 CLOUD: AN INFRARED AND MULTI-EPOCH X-RAY STUDY

    SciTech Connect

    Principe, David A.; Kastner, J. H.; Richmond, Michael; Grosso, Nicolas; Hamaguchi, Kenji

    2014-07-01

    X-ray emission is characteristic of young stellar objects (YSOs) and is known to be highly variable. We investigate, via an infrared and multi-epoch X-ray study of the L1630 dark cloud, whether and how X-ray variability in YSOs is related to protostellar evolutionary state. We have analyzed 11 Chandra X-Ray Observatory observations, obtained over the course of four years and totaling ∼240 ks exposure time, targeting the eruptive Class I YSO V1647 Ori in L1630. We used Two Micron All Sky Survey and Spitzer data to identify and classify IR counterparts to L1630 X-ray sources and identified a total of 52 X-ray-emitting YSOs with IR counterparts, including four Class I sources and one Class 0/I source. We have detected cool (<3 MK) plasma, possibly indicative of accretion shocks, in three classical T Tauri stars. A subsample of 27 X-ray-emitting YSOs were covered by 9 of the 11 Chandra observations targeting V1647 Ori and the vicinity. For these 27 YSOs, we have constructed X-ray light curves spanning approximately four years. These light curves highlight the variable nature of pre-main-sequence X-ray-emitting young stars; many of the L1630 YSOs vary by orders of magnitude in count rate between observations. We discuss possible scenarios to explain apparent trends between various X-ray spectral properties, X-ray variance, and YSO classification.

  10. Redshift-space distortion of the 21-cm background from the epoch of reionization - I. Methodology re-examined

    NASA Astrophysics Data System (ADS)

    Mao, Yi; Shapiro, Paul R.; Mellema, Garrelt; Iliev, Ilian T.; Koda, Jun; Ahn, Kyungjin

    2012-05-01

    The peculiar velocity of the intergalactic gas responsible for the cosmic 21-cm background from the epoch of reionization and beyond introduces an anisotropy in the three-dimensional power spectrum of brightness temperature fluctuations. Measurement of this anisotropy by future 21-cm surveys is a promising tool for separating cosmology from 21-cm astrophysics. However, previous attempts to model the signal have often neglected peculiar velocity or only approximated it crudely. This paper re-examines the effects of peculiar velocity on the 21-cm signal in detail, improving upon past treatment and addressing several issues for the first time. (1) We show that even the angle-averaged power spectrum, P(k), is affected significantly by the peculiar velocity. (2) We re-derive the brightness temperature dependence on atomic hydrogen density, spin temperature, peculiar velocity and its gradient and redshift to clarify the roles of thermal versus velocity broadening and finite optical depth. (3) We show that properly accounting for finite optical depth eliminates the unphysical divergence of the 21-cm brightness temperature in overdense regions of the intergalactic medium found by previous work that employed the usual optically thin approximation. (4) We find that the approximation made previously to circumvent the diverging brightness temperature problem by capping the velocity gradient can misestimate the power spectrum on all scales. (5) We further show that the observed power spectrum in redshift space remains finite even in the optically thin approximation if one properly accounts for the redshift-space distortion. However, results that take full account of finite optical depth show that this approximation is only accurate in the limit of high spin temperature. (6) We also show that the linear theory for redshift-space distortion widely employed to predict the 21-cm power spectrum results in a ˜30 per cent error in the observationally relevant wavenumber range k˜ 0

  11. Non-modal theory of the kinetic ion temperature gradient driven instability of plasma shear flows across the magnetic field

    NASA Astrophysics Data System (ADS)

    Mikhailenko, V. V.; Mikhailenko, V. S.; Lee, Hae June

    2016-06-01

    The temporal evolution of the kinetic ion temperature gradient driven instability and of the related anomalous transport of the ion thermal energy of plasma shear flow across the magnetic field is investigated analytically. This instability develops in a steady plasma due to the inverse ion Landau damping and has the growth rate of the order of the frequency when the ion temperature is equal to or above the electron temperature. The investigation is performed employing the non-modal methodology of the shearing modes which are the waves that have a static spatial structure in the frame of the background flow. The solution of the governing linear integral equation for the perturbed potential displays that the instability experiences the non-modal temporal evolution in the shearing flow during which the unstable perturbation becomes very different from a canonical modal form. It transforms into the non-modal structure with vanishing frequency and growth rate with time. The obtained solution of the nonlinear integral equation, which accounts for the random scattering of the angle of the ion gyro-motion due to the interaction of ions with ensemble of shearing waves, reveals similar but accelerated process of the transformations of the perturbations into the zero frequency structures. It was obtained that in the shear flow the anomalous ion thermal conductivity decays with time. It is a strictly non-modal effect, which originates from the temporal evolution of the shearing modes turbulence.

  12. Trapped-electron effects on time-independent negative-bias states of a collisionless single-emitter plasma device: Theory and simulation

    SciTech Connect

    Crystal, T.L.; Gray, P.C.; Lawson, W.S.; Birdsall, C.K.; Kuhn, S. )

    1991-01-01

    Time-average values from particle simulations of a collisionless, single-emitter plasma device modeling single-ended {ital Q} machines or thermionic converters with a negatively biased collector are presented. These results quantitatively confirm the predictions of collisionless, kinetic plane-diode theory for spatial potential profiles that decrease monotonically. However, simulations of negative-bias potential profiles with a single internal maximum differ significantly from previous theoretical predictions which assumed electron phase space to have either (i) no trapped electrons or (ii) trapped electrons isothermal with the passing electrons. A more general class of trapped-electron model distributions is introduced from which new equilibrium potential values can be recovered that closely match the simulations. These simulations clearly demonstrate the sensitive role that trapped electrons play in shaping the potential profiles of the equilibrium (or slowly evolving) states of the simulated systems. The trapped-electron distributions in these simulations are themselves shown to be controlled critically by fluctuations whose levels are varied by the choice of particle injection scheme. These effects, although found and discussed here in the context of a particular model, are believed to be important in many bounded plasma systems where electrons can be trapped in potential wells.

  13. Effects of solar wind high-speed streams on the high-latitude ionosphere: Superposed epoch study

    NASA Astrophysics Data System (ADS)

    Grandin, M.; Aikio, A. T.; Kozlovsky, A.; Ulich, T.; Raita, T.

    2015-12-01

    Solar wind high-speed streams (HSSs) are the most important source of geomagnetic disturbances during the declining phase of the solar cycle. Their ionospheric response, especially at high latitudes, is not fully understood yet. We carried out a phase-locked superposed epoch analysis to study the effects of HSSs on the high-latitude ionospheric F region, using data from the Sodankylä ionosonde (L = 5.25) during 2006-2008. We found that the F layer critical frequency foF2 decreases between 12 and 23 magnetic local time (MLT) in summer and around equinoxes for several days. Our interpretation, supported by numerical estimations, is that increased electric fields in the evening sector of the auroral and subauroral regions create ion-neutral frictional heating. Frictional heating will increase the loss rate of O+ due to two reasons. The first one is neutral heating producing thermal expansion of the atmosphere and enhancing N2 and O2 contents at the F region peak. The second one is ion heating which may occur under strong enough electric fields (about 50-60 mV/m), leading to enhancement of the reaction coefficients. An increase in foF2 is observed in two different MLT sectors. First, a short-lived foF2 increase is visible during all seasons near noon on the first day after the arrival of the HSS, possibly triggered by the compressed solar wind plasma pressure pulse, which may produce particle precipitation from the dayside central plasma sheet. Second, foF2 is enhanced for several days in the morning sector during equinoxes and in winter. We suggest that this is caused by the low-energy tail of particle precipitation.

  14. Extension of the flow-rate-of-strain tensor formulation of plasma rotation theory to non-axisymmetric tokamaks

    NASA Astrophysics Data System (ADS)

    Stacey, W. M.; Bae, C.

    2015-06-01

    A systematic formalism for the calculation of rotation in non-axisymmetric tokamaks with 3D magnetic fields is described. The Braginskii Ω τ -ordered viscous stress tensor formalism, generalized to accommodate non-axisymmetric 3D magnetic fields in general toroidal flux surface geometry, and the resulting fluid moment equations provide a systematic formalism for the calculation of toroidal and poloidal rotation and radial ion flow in tokamaks in the presence of various non-axisymmetric "neoclassical toroidal viscosity" mechanisms. The relation among rotation velocities, radial ion particle flux, ion orbit loss, and radial electric field is discussed, and the possibility of controlling these quantities by producing externally controllable toroidal and/or poloidal currents in the edge plasma for this purpose is suggested for future investigation.

  15. USU (Utah State University) Center of Excellence in Theory and Analysis of the Geo-Plasma Environment

    NASA Astrophysics Data System (ADS)

    Schunk, Robert W.

    1987-10-01

    The overall goal of the research is to obtain a better understanding of the basic chemical and physical processes operating in the geoplasma environment, including the ionosphere, thermosphere, and magnetosphere. Some of the specific tasks include the following: (1) Studies of ionospheric structure and irregularities; (2) Study the feasibility of developing better operational ionospheric models for the Air Force; (3) Conduct model/data comparisons in order to validate the ionospheric models; (4) Study plasma convection characteristics in the high-latitude ionosphere; (5) Study magnetosphere-ionosphere coupling problems; (6) Construct a thermospheric general circulation model; (7) Develop a 3D, time-dependent model of the outer plasmasphere; (8) Develop a 3D, time-dependent MHD model of the earth's magnetosphere; (9) Conduct satellite drag studies; and (10) Study certain spacecraft-environment interaction problems, including those related to high-voltage power sources, spacecraft outgassing, and spacecraft charging at LEO altitudes.

  16. Alfvén wave collisions, the fundamental building block of plasma turbulence. III. Theory for experimental design

    SciTech Connect

    Howes, G. G.; Nielson, K. D.; Schroeder, J. W. R.; Skiff, F.; Kletzing, C. A.; Drake, D. J.; Carter, T. A.

    2013-07-15

    Turbulence in space and astrophysical plasmas is governed by the nonlinear interactions between counterpropagating Alfvén waves. Here, we present the theoretical considerations behind the design of the first laboratory measurement of an Alfvén wave collision, the fundamental interaction underlying Alfvénic turbulence. By interacting a relatively large-amplitude, low-frequency Alfvén wave with a counterpropagating, smaller-amplitude, higher-frequency Alfvén wave, the experiment accomplishes the secular nonlinear transfer of energy to a propagating daughter Alfvén wave. The predicted properties of the nonlinearly generated daughter Alfvén wave are outlined, providing a suite of tests that can be used to confirm the successful measurement of the nonlinear interaction between counterpropagating Alfvén waves in the laboratory.

  17. Extension of the flow-rate-of-strain tensor formulation of plasma rotation theory to non-axisymmetric tokamaks

    SciTech Connect

    Stacey, W. M.; Bae, C.

    2015-06-15

    A systematic formalism for the calculation of rotation in non-axisymmetric tokamaks with 3D magnetic fields is described. The Braginskii Ωτ-ordered viscous stress tensor formalism, generalized to accommodate non-axisymmetric 3D magnetic fields in general toroidal flux surface geometry, and the resulting fluid moment equations provide a systematic formalism for the calculation of toroidal and poloidal rotation and radial ion flow in tokamaks in the presence of various non-axisymmetric “neoclassical toroidal viscosity” mechanisms. The relation among rotation velocities, radial ion particle flux, ion orbit loss, and radial electric field is discussed, and the possibility of controlling these quantities by producing externally controllable toroidal and/or poloidal currents in the edge plasma for this purpose is suggested for future investigation.

  18. Solar-wind turbulence and shear: a superposed-epoch analysis of corotating interaction regions at 1 AU

    SciTech Connect

    Borovsky, Joseph E; Denton, Michael H

    2009-01-01

    A superposed-epoch analysis of ACE and OMNI2 measurements is performed on 27 corotating interaction regions (CIRs) in 2003-2008, with the zero epoch taken to be the stream interface as determined by the maximum of the plasma vorticity. The structure of CIRs is investigated. When the flow measurements are rotated into the local-Parker-spiral coordinate system the shear is seen to be abrupt and intense, with vorticities on the order of 10{sup -5}-10{sup -4} sec{sup -1}. Converging flows perpendicular to the stream interface are seen in the local-Parker-spiral coordinate system and about half of the CIRs show a layer of divergent rebound flow away from the stream interface. Arguments indicate that any spreading of turbulence away from the region where it is produced is limited to about 10{sup 6} km, which is very small compared with the thickness of a CrR. Analysis of the turbulence across the CrRs is performed. When possible, the effects of discontinuities are removed from the data. Fluctuation amplitudes, the Alfvenicity, and the level of Alfvenic correlations all vary smoothly across the CrR. The Alfven ratio exhibits a decrease at the shear zone of the stream interface. Fourier analysis of 4.5-hr subintervals of ACE data is performed and the results are superposed averaged as an ensemble of realizations. The spectral slopes of the velocity, magnetic-field, and total-energy fluctuations vary smoothly across the CIR. The total-energy spectral slope is {approx} 3/2 in the slow and fast wind and in the CrRs. Analysis of the Elsasser inward-outward fluctuations shows a smooth transition across the CrR from an inward-outward balance in the slow wind to an outward dominance in the fast wind. A number of signatures of turbulence driving at the shear zone are sought (entropy change, turbulence amplitude, Alfvenicity, Alfven ratio, spectral slopes, in-out nature): none show evidence of driving of turbulence by shear.

  19. Fundamentals of Plasma Physics

    NASA Astrophysics Data System (ADS)

    Bellan, Paul M.

    2008-07-01

    Preface; 1. Basic concepts; 2. The Vlasov, two-fluid, and MHD models of plasma dynamics; 3. Motion of a single plasma particle; 4. Elementary plasma waves; 5. Streaming instabilities and the Landau problem; 6. Cold plasma waves in a magnetized plasma; 7. Waves in inhomogeneous plasmas and wave energy relations; 8. Vlasov theory of warm electrostatic waves in a magnetized plasma; 9. MHD equilibria; 10. Stability of static MHD equilibria; 11. Magnetic helicity interpreted and Woltjer-Taylor relaxation; 12. Magnetic reconnection; 13. Fokker-Planck theory of collisions; 14. Wave-particle nonlinearities; 15. Wave-wave nonlinearities; 16. Non-neutral plasmas; 17. Dusty plasmas; Appendix A. Intuitive method for vector calculus identities; Appendix B. Vector calculus in orthogonal curvilinear coordinates; Appendix C. Frequently used physical constants and formulae; Bibliography; References; Index.

  20. Distinct Biological Epochs in the Reproductive Life of Female Drosophila melanogaster

    PubMed Central

    Rogina, Blanka; Wolverton, Tom; Bross, Tyson G.; Chen, Kun; Müller, Hans-Georg; Carey, James R.

    2008-01-01

    Mating alters the physiology and behavior of female Drosophila melanogaster resulting in a surge of egg laying, a decrease in receptivity to other males, and a decrease in life span. Here, we show striking differences in patterns of Drosophila egg laying and mortality rate dependent upon mating history. Our data reveal previously unreported epochs in the reproductive life of females: optimal, vulnerable and declining-terminal. During the optimal period, mating induces females to respond with a surge in egg laying and has a reversible effect on mortality rate. In contrast, during the vulnerable period, mating does not induce females to respond with a surge in egg laying and causes an irreversible increase in mortality rate. The terminal period was always observed several days before death, irrespective of the chronological age, and is marked by sharp reductions in egg laying. The presence of these distinctive biological epochs may reflect increased female sensitivity to mating due to age-related decline. PMID:17681363

  1. The Effects of Polarized Foregrounds on 21 cm Epoch of Reionization Power Spectrum Measurements

    NASA Astrophysics Data System (ADS)

    Moore, David F.; Aguirre, James E.; Parsons, Aaron R.; Jacobs, Daniel C.; Pober, Jonathan C.

    2013-06-01

    Experiments aimed at detecting highly-redshifted 21 cm emission from the epoch of reionization (EoR) are plagued by the contamination of foreground emission. A potentially important source of contaminating foregrounds may be Faraday-rotated, polarized emission, which leaks into the estimate of the intrinsically unpolarized EoR signal. While these foregrounds' intrinsic polarization may not be problematic, the spectral structure introduced by the Faraday rotation could be. To better understand and characterize these effects, we present a simulation of the polarized sky between 120 and 180 MHz. We compute a single visibility, and estimate the three-dimensional power spectrum from that visibility using the delay spectrum approach presented in Parsons et al. Using the Donald C. Backer Precision Array to Probe the Epoch of Reionization as an example instrument, we show the expected leakage into the unpolarized power spectrum to be several orders of magnitude above the expected 21 cm EoR signal.

  2. THE EFFECTS OF POLARIZED FOREGROUNDS ON 21 cm EPOCH OF REIONIZATION POWER SPECTRUM MEASUREMENTS

    SciTech Connect

    Moore, David F.; Aguirre, James E.; Parsons, Aaron R.; Pober, Jonathan C.; Jacobs, Daniel C.

    2013-06-01

    Experiments aimed at detecting highly-redshifted 21 cm emission from the epoch of reionization (EoR) are plagued by the contamination of foreground emission. A potentially important source of contaminating foregrounds may be Faraday-rotated, polarized emission, which leaks into the estimate of the intrinsically unpolarized EoR signal. While these foregrounds' intrinsic polarization may not be problematic, the spectral structure introduced by the Faraday rotation could be. To better understand and characterize these effects, we present a simulation of the polarized sky between 120 and 180 MHz. We compute a single visibility, and estimate the three-dimensional power spectrum from that visibility using the delay spectrum approach presented in Parsons et al. Using the Donald C. Backer Precision Array to Probe the Epoch of Reionization as an example instrument, we show the expected leakage into the unpolarized power spectrum to be several orders of magnitude above the expected 21 cm EoR signal.

  3. Solar wind conditions leading to efficient radiation belt electron acceleration: A superposed epoch analysis

    SciTech Connect

    Li, W.; Thorne, R. M.; Bortnik, J.; Baker, D. N.; Reeves, G. D.; Kanekal, S. G.; Spence, H. E.; Green, J. C.

    2015-09-07

    In this study by determining preferential solar wind conditions leading to efficient radiation belt electron acceleration is crucial for predicting radiation belt electron dynamics. Using Van Allen Probes electron observations (>1 MeV) from 2012 to 2015, we identify a number of efficient and inefficient acceleration events separately to perform a superposed epoch analysis of the corresponding solar wind parameters and geomagnetic indices. By directly comparing efficient and inefficient acceleration events, we clearly show that prolonged southward Bz, high solar wind speed, and low dynamic pressure are critical for electron acceleration to >1 MeV energies in the heart of the outer radiation belt. We also evaluate chorus wave evolution using the superposed epoch analysis for the identified efficient and inefficient acceleration events and find that chorus wave intensity is much stronger and lasts longer during efficient electron acceleration events, supporting the scenario that chorus waves play a key role in MeV electron acceleration.

  4. Energy Dissipation of Energetic Electrons in the Inhomogeneous Intergalactic Medium during the Epoch of Reionization

    NASA Astrophysics Data System (ADS)

    Kaurov, Alexander A.

    2016-06-01

    We explore a time-dependent energy dissipation of the energetic electrons in the inhomogeneous intergalactic medium (IGM) during the epoch of cosmic reionization. In addition to the atomic processes, we take into account the inverse Compton (IC) scattering of the electrons on the cosmic microwave background photons, which is the dominant channel of energy loss for electrons with energies above a few MeV. We show that: (1) the effect on the IGM has both local (atomic processes) and non-local (IC radiation) components; (2) the energy distribution between hydrogen and helium ionizations depends on the initial energy of an electron; (3) the local baryon overdensity significantly affects the fractions of energy distributed in each channel; and (4) the relativistic effect of the atomic cross-section becomes important during the epoch of cosmic reionization. We release our code as open source for further modification by the community.

  5. Observations and Analysis of Three Field RR Lyrae Stars Selected Using Single-epoch SDSS Data

    NASA Astrophysics Data System (ADS)

    Powell, W. L., Jr.; Jameson, S. N.; De lee, N.; Wilhelm, R. J.

    2015-08-01

    We present the results of our Johnson B and V observations of three RR Lyrae candidate stars that we identified as likely variable stars using SDSS data. The stars were selected based upon a single epoch of photometry and spectroscopy. The stars were observed at McDonald Observatory to obtain full light curves. We present full light curves, measured periods, and amplitudes, as well as the results of our Fourier analysis of the light curves.

  6. The Time Evolution of HH 1 from Four Epochs of HST Images

    NASA Astrophysics Data System (ADS)

    Raga, A. C.; Reipurth, B.; Esquivel, A.; Bally, J.

    2016-05-01

    We present an analysis of four epochs of Hα and [S ii] λλ 6716/6731 Hubble Space Telescope (HST) images of HH 1. For determining proper motions, we explore a new method based on the analysis of spatially degraded images obtained convolving the images with wavelet functions of chosen widths. With this procedure, we are able to generate maps of proper motion velocities along and across the outflow axis, as well as (angularly integrated) proper motion velocity distributions. From the four available epochs, we find the time evolution of the velocities, intensities, and spatial distribution of the line emission. We find that over the last two decades HH 1 shows a clear acceleration. Also, the Hα and [S ii] intensities first dropped and then recovered in the more recent (2014) images. Finally, we show a comparison between the two available HST epochs of [O iii] λ 5007 (1994 and 2014), in which we see a clear drop in the value of the [O iii]/Hα ratio.

  7. The Reel Deal: Interpreting HST Multi-Epoch Movies of YSO Jets.

    NASA Astrophysics Data System (ADS)

    Frank, Adam

    2010-09-01

    The goal of this proposal is to bring the theoretical interpretation of Young Stellar Object jets and their environments to a new level of realism. We propose to build on the results of a successful Cycle 16 observing proposal that has obtained 3rd epoch images of HH jets. We will use Adaptive Mesh Refinement MHD simulations {developed by our team} to carry forward a detailed program of modeling and interpretation of the time-dependent behavior revealed in the new, extended multi-epoch data set. Only with the third epoch observations can we explore forces: i.e. accelerations, decelerations and structural changes to develop an accurate understanding of physical processes occurring in hypersonic, magnetized jet flows. Our studies will allow us to characterize the jets and, therefore, make the crucial link with jet central engines. We note an innovative feature of our project is its link with laboratory astrophysical experiments of jets. Our analysis of the observations will be used to determine future laboratory experiments which will explore A?clumpyA? jet propagation issues.

  8. Use of Apollo 17 Epoch Neutron Spectrum as a Benchmark in Testing LEND Collimated Sensor

    NASA Technical Reports Server (NTRS)

    Chin, Gordon; Sagdeev, R.; Milikh, G.

    2011-01-01

    The Apollo 17 neutron experiment LPNE provided a unique set of data on production of neutrons in the Lunar soil bombarded by Galactic Cosmic Rays (GCR). It serves as valuable "ground-truth" in the age of orbital remote sensing. We used the neutron data attributed to Apollo 17 epoch as a benchmark for testing the LEND's collimated sensor, as introduced by the geometry of collimator and efficiency of He3 counters. The latter is defined by the size of gas counter and pressure inside it. The intensity and energy spectrum of neutrons escaping the lunar surface are dependent on incident flux of Galactic Cosmic Rays (GCR) whose variability is associated with Solar Cycle and its peculiarities. We obtain first the share of neutrons entering through the field of view of collimator as a fraction of the total neutron flux by using the angular distribution of neutron exiting the Moon described by our Monte Carlo code. We computed next the count rate of the 3He sensor by using the neutron energy spectrum from McKinney et al. [JGR, 2006] and by consider geometry and gas pressure of the LEND sensor. Finally the neutron count rate obtained for the Apollo 17 epoch characterized by intermediate solar activity was adjusted to the LRO epoch characterized by low solar activity. It has been done by taking into account solar modulation potential, which affects the GCR flux, and in turn changes the neutron albedo flux.

  9. Fossil wood from the Miocene and Oligocene epoch: chemistry and morphology.

    PubMed

    Bardet, Michel; Pournou, Anastasia

    2015-01-01

    Fossil wood is the naturally preserved remain of the secondary xylem of plants that lived before the Holocene epoch. Typically, fossil wood is preserved as coalified or petrified and rarely as mummified tissue. The process of fossilization is very complex and it is still unknown why in the same fossil record, wood can be found in different fossilisation forms. In 2007, a fossil forest was found in the Bükkábrány open-pit coal mine in Hungary. The non-petrified forest is estimated to be 7 million years old (Miocene epoch) and its trees were found standing in an upright position. This fossil assemblage is exceptionally rare because wood has been preserved as soft waterlogged tissue. This study aimed to investigate this remarkable way of fossil wood preservation, by examining its chemistry with (13)C CPMAS NMR and its morphology with light and electron microscopy. For comparison reasons, a petrified wood trunk from the Oligocene epoch (30 Myr) found in 2001 at Porrentruy region in Switzerland and two fresh wood samples of the modern equivalents of the Miocene sample were also examined. The results obtained showed that the outstanding preservation state of the Miocene fossil is not owed to petrification or coalification. Mummification is a potential mechanism that could explain Bükkábrány trunks' condition, however this fossilisation process is not well studied and therefore this hypothesis needs to be further investigated. PMID:25294390

  10. Theory of hysteresis during electron heating of electromagnetic wave scattering by self-organized dust structures in complex plasmas

    SciTech Connect

    Tsytovich, Vadim; Gusein-zade, Namik; Ignatov, Alexander

    2015-07-15

    Dust structuring is a natural and universal process in complex plasmas. The scattering of electromagnetic waves by dust structures is governed by the factor of coherency, i.e., the total number of coherent electrons in a single structure. In the present paper, we consider how the factor of coherency changes due to additional pulse electron heating and show that it obeys a hysteresis. After the end of the pulse heating, the scattering intensity differs substantially from that before heating. There are three necessary conditions for scattering hysteresis: first, the radiation wavelength should be larger than the pattern (structure) size; second, the total number of coherent electrons confined by the structure should be large; and third, the heating pulse duration should be shorter than the characteristic time of dust structure formation. We present the results of numerical calculations using existing models of self-consistent dust structures with either positively or negatively charged dust grains. It is shown that, depending on the grain charge and the ionization rate, two types of hysteresis are possible: one with a final increase of the scattering and the other with a final decrease of the scattering. It is suggested that the hysteresis of coherent scattering can be used as a tool in laboratory experiments and that it can be a basic mechanism explaining the observed hysteresis in radar scattering by noctilucent clouds during active experiments on electron heating in mesosphere.

  11. Plasma Physics: An Introductory Course

    NASA Astrophysics Data System (ADS)

    Dendy, R. O.

    1995-03-01

    Preface; Introduction R. O. Dendy; 1. Plasma particle dynamics R. J. Hastie; 2. Plasma kinetic theory J. A. Elliott; 3. Waves in plasmas J. P. Doughtery; 4. Magnetohydrodynamics K. I. Hopcraft; 5. Turbulence in fluids and fusion plasmas F. A. Haas; 6. Finite-dimensional dynamics and chaos T. J. Mullin; 7. Computational plasma physics J. W. Eastwood; 8. Tokomak experiments D. C. Robinson and M. R. O'Brien; 9. Magnetospheric plasmas: Part I Basic processes in the solar system D. A. Bryant; Part II Microprocesses R. L. Bingham; 10. Solar plasmas R. A. Hood; 11. Gravitational plasmas J. J. Binney; 12. Laser plasmas A. R. Bell; 13. Industrial plasmas P. C. Johnson; 14. Transport in magnetically confined plasmas T. E. Stringer; 15. Radio-frequency plasma heating R. A. Cairns; 16. Boundary plasmas G. McCracken; 17. How to build a tokomak T. N. Todd; 18. Survey of fusion plasma physics R. S. Pease; Index.

  12. Poleward leaping auroras, the substorm expansive and recovery phases and the recovery of the plasma sheet

    SciTech Connect

    Hones, E.W.

    1992-01-01

    The auroral motions and geomagnetic changes the characterize the substorm's expansive phase, maximum epoch, and recovery phase are discussed in the context of their possible associations with the dropout and, especially, the recovery of the magnetotail plasma sheet. The evidence that there may be an inordinately sudden large poleward excursion or displacement (a poleward leap) of the electrojet and the auroras at the expansive phase-recovery phase transition is described. The close temporal association of these signatures with the recovery of the plasma sheet, observed on many occasions, suggests a causal relationship between substorm maximum epoch and recovery phase on the one hand and plasma sheet recovery on the other.

  13. Poleward leaping auroras, the substorm expansive and recovery phases and the recovery of the plasma sheet

    SciTech Connect

    Hones, E.W.

    1992-05-01

    The auroral motions and geomagnetic changes the characterize the substorm`s expansive phase, maximum epoch, and recovery phase are discussed in the context of their possible associations with the dropout and, especially, the recovery of the magnetotail plasma sheet. The evidence that there may be an inordinately sudden large poleward excursion or displacement (a poleward leap) of the electrojet and the auroras at the expansive phase-recovery phase transition is described. The close temporal association of these signatures with the recovery of the plasma sheet, observed on many occasions, suggests a causal relationship between substorm maximum epoch and recovery phase on the one hand and plasma sheet recovery on the other.

  14. Plasma-based accelerator structures

    SciTech Connect

    Schroeder, Carl B.

    1999-12-01

    Plasma-based accelerators have the ability to sustain extremely large accelerating gradients, with possible high-energy physics applications. This dissertation further develops the theory of plasma-based accelerators by addressing three topics: the performance of a hollow plasma channel as an accelerating structure, the generation of ultrashort electron bunches, and the propagation of laser pulses is underdense plasmas.

  15. 21 cm line bispectrum as a method to probe cosmic dawn and epoch of reionization

    NASA Astrophysics Data System (ADS)

    Shimabukuro, Hayato; Yoshiura, Shintaro; Takahashi, Keitaro; Yokoyama, Shuichiro; Ichiki, Kiyotomo

    2016-05-01

    Redshifted 21 cm signal is a promising tool to investigate the state of intergalactic medium (IGM) in the cosmic dawn (CD) and epoch of reionization (EoR). In our previous work, we studied the variance and skewness of the 21 cm fluctuations to give a clear interpretation of the 21 cm power spectrum and found that skewness is a good indicator of the epoch when X-ray heating becomes effective. Thus, the non-Gaussian feature of the spatial distribution of the 21 cm signal is expected to be useful to investigate the astrophysical effects in the CD and EoR. In this paper, in order to investigate such a non-Gaussian feature in more detail, we focus on the bispectrum of the 21 cm signal. It is expected that the 21 cm brightness temperature bispectrum is produced by non-Gaussianity due to the various astrophysical effects such as the Wouthuysen-Field effect, X-ray heating and reionization. We study the various properties of 21 cm bispectrum such as scale dependence, shape dependence and redshift evolution. And also we study the contribution from each component of 21 cm bispectrum. We find that the contribution from each component has characteristic scale-dependent feature. In particular, we find that the bulk of the 21 cm bispectrum at z = 20 comes from the matter fluctuations, while in other epochs it is mainly determined by the spin and/or neutral fraction fluctuations and it is expected that we could obtain more detailed information on the IGM in the CD and EoR by using the 21 cm bispectrum in the future experiments, combined with the power spectrum and skewness.

  16. Experimental challenge to nucleosynthesis in core-collapse supernovae - Very early epoch of type II SNe -

    NASA Astrophysics Data System (ADS)

    Kubono, S.; Binh, Dam N.; Hayakawa, S.; Hashimoto, T.; Kahl, D. M.; Yamaguchi, H.; Wakabayashi, Y.; Teranishi, T.; Iwasa, N.; Komatsubara, T.; Kato, S.; Chen, A.; Cherubini, S.; Choi, S. H.; Hahn, I. S.; He, J. J.; Khiem, Le H.; Lee, C. S.; Kwon, Y. K.; Wanajo, S.; Janka, H.-T.

    2013-05-01

    Nucleosynthesis is one of the keys in studying the mechanism of core-collapse supernovae, which is an interesting challenge for modern science. The νp-process, which is similar to an explosive hydrogen burning process, has been proposed as the most probable process in the very early epoch of type II supernovae. Here, we discuss our experimental efforts for the νp-process, the first extensive direct measurements of the (α,p) reactions on bottle-neck proto-rich nuclei in light mass regions. Other challenges for the νp-process study are also discussed.

  17. Joint US/UK Epoch World Magnetic Model 1995. Technical report

    SciTech Connect

    Quinn, J.M.; Coleman, R.J.; Shiel, D.L.

    1995-04-01

    This report contains a detailed summary of the data used, analyses performed, modeling techniques employed, and results obtained during the course of the 1995 Epoch World Magnetic Modeling effort. This report also contains the GEOMAG algorithm and describes its uses and limitations. Charts derived from the WMM-95 model and the GEOMAG algorithm for both the main geomagnetic field components and their secular variations are presented on Mercator and polar stereographic projections. Additionally, the numerical values of the main geomagnetic field components and their secular variations are tabulated on a 5-degree worldwide grid.

  18. Lithographed spectrometers for tomographic line mapping of the Epoch of Reionization

    NASA Astrophysics Data System (ADS)

    O'Brient, R.; Bock, J. J.; Bradford, C. M.; Crites, A.; Duan, R.; Hailey-Dunsheath, S.; Hunacek, J.; LeDuc, R.; Shirokoff, E.; Staniszewski, Z.; Turner, A.; Zemcov, M.

    2014-08-01

    The Tomographic Ionized carbon Mapping Experiment (TIME) is a multi-phased experiment that will topographically map [CII] emission from the Epoch of Reionization. We are developing lithographed spectrometers that couple to TES bolometers in anticipation of the second generation instrument. Our design intentionally mirrors many features of the parallel SuperSpec project, inductively coupling power from a trunk-line microstrip onto half-wave resonators. The resonators couple to a rat-race hybrids that feeds TES bolometers. Our 25 channel prototype shows spectrally positioned lines roughly matching design with a receiver optical efficiency of 15-20%, a level that is dominated by loss in components outside the spectrometer.

  19. The First Billion Years: The Growth of Galaxies in the Reionization Epoch

    NASA Astrophysics Data System (ADS)

    Illingworth, Garth

    2015-08-01

    Detection and measurement of the earliest galaxies in the first billion years only became possible after the Hubble Space Telescope was updated in 2009 with the infrared WFC3/IR camera during Shuttle servicing mission SM4. The first billion years is a fascinating epoch, not just because of the earliest galaxies known from about 450 Myr after the Big Bang, but also because it encompasses the reionization epoch that peaked around z~9, as Planck has recently shown, and ended around redshift z~6 at 900 Myr. Before 2009 just a handful of galaxies were known in the reionization epoch at z>6. But within the last 5 years, with the first HUDF09 survey, the HUDF12, CANDELS and numerous other surveys on the GOODS and CANDELS fields, as well as detections from the cluster lensing programs like CLASH and the Frontier Fields, the number of galaxies at redshifts 7-10 has exploded, with some 700 galaxies being found and characterized. The first billion years was a period of extraordinary growth in the galaxy population with rapid growth in the star formation rate density and global mass density in galaxies. Spitzer observations in the infrared of these Hubble fields are establishing masses as well as giving insights into the nature and timescales of star formation from the very powerful emission lines being revealed by the Spitzer IRAC data. I will discuss what we understand about the growth of galaxies in this epoch from the insights gained from remarkable deep fields like the XDF, as well as the wide-area GOODS/CANDELS fields, the detection of unexpectedly luminous galaxies at redshifts 8-10, the impact of early galaxies on reionization, confirmation of a number of galaxies at z~7-8 from ground-based spectroscopic measurements, and the indications of a change in the growth of the star formation rate around 500 Myr. The first billion years was a time of dramatic growth and change in the early galaxy population.

  20. Simulating matched filter detection of ionized bubble around a quasar in the epoch of reionization

    NASA Astrophysics Data System (ADS)

    Majumdar, Suman; Bharadwaj, Somnath; Choudhury, Tirthankar Roy

    2012-12-01

    The recent discovery of the z = 7.085 quasar has opened up a new window to peep into the inter galactic medium during the epoch of reionization (EoR). The detection of the ionized region around such a high redshift quasar is in principle capable of constraining the neutral fraction of the IGM and the quasar's age. Here we present the possibility of detection of such an ionized region around a quasar at z = 8 using redshifted 21-cm observations of the neutral hydrogen and possible ways to constrain IGM neutral fraction and quasar's age through this detection.

  1. The epoch state navigation filter. [for maximum likelihood estimates of position and velocity vectors

    NASA Technical Reports Server (NTRS)

    Battin, R. H.; Croopnick, S. R.; Edwards, J. A.

    1977-01-01

    The formulation of a recursive maximum likelihood navigation system employing reference position and velocity vectors as state variables is presented. Convenient forms of the required variational equations of motion are developed together with an explicit form of the associated state transition matrix needed to refer measurement data from the measurement time to the epoch time. Computational advantages accrue from this design in that the usual forward extrapolation of the covariance matrix of estimation errors can be avoided without incurring unacceptable system errors. Simulation data for earth orbiting satellites are provided to substantiate this assertion.

  2. Study of the star catalogue (epoch AD 1396.0) recorded in ancient Korean astronomical almanac

    NASA Astrophysics Data System (ADS)

    Jeon, Junhyeok; Lee, Yong Bok; Lee, Yong-Sam

    2015-11-01

    The study of old star catalogues provides important astrometric data. Most of the researches based on the old star catalogues were manuscript published in Europe and from Arabic/Islam. However, the old star catalogues published in East Asia did not get attention. Therefore, among the East Asian star catalogues we focus on a particular catalogue recorded in a Korean almanac. Its catalogue contains 277 stars that are positioned in a region within 10° of the ecliptic plane. The stars in the catalogue were identified using the modern Hipparcos catalogue. We identified 274 among 277 stars, which is a rate of 98.9 per cent. The catalogue records the epoch of the stars' positions as AD 1396.0. However, by using all of the identified stars we found that the initial epoch of the catalogue is AD 1363.1 ± 3.2. In conclusion, the star catalogue was compiled and edited from various older star catalogues. We assume a correlation with the Almagest by Ptolemaios. This study presents newly analysed results from the historically important astronomical data discovered in East Asia. Therefore, this star catalogue will become important data for comparison with the star catalogues published in Europe and from Arabic/Islam.

  3. OPENING THE 21 cm EPOCH OF REIONIZATION WINDOW: MEASUREMENTS OF FOREGROUND ISOLATION WITH PAPER

    SciTech Connect

    Pober, Jonathan C.; Parsons, Aaron R.; Ali, Zaki; Aguirre, James E.; Moore, David F.; Bradley, Richard F.; Carilli, Chris L.; DeBoer, Dave; Dexter, Matthew; MacMahon, Dave; Gugliucci, Nicole E.; Jacobs, Daniel C.; Klima, Patricia J.; Manley, Jason; Walbrugh, William P.; Stefan, Irina I.

    2013-05-10

    We present new observations with the Precision Array for Probing the Epoch of Reionization with the aim of measuring the properties of foreground emission for 21 cm epoch of reionization (EoR) experiments at 150 MHz. We focus on the footprint of the foregrounds in cosmological Fourier space to understand which modes of the 21 cm power spectrum will most likely be compromised by foreground emission. These observations confirm predictions that foregrounds can be isolated to a {sup w}edge{sup -}like region of two-dimensional (k , k{sub Parallel-To })-space, creating a window for cosmological studies at higher k{sub Parallel-To} values. We also find that the emission extends past the nominal edge of this wedge due to spectral structure in the foregrounds, with this feature most prominent on the shortest baselines. Finally, we filter the data to retain only this ''unsmooth'' emission and image its specific k{sub Parallel-To} modes. The resultant images show an excess of power at the lowest modes, but no emission can be clearly localized to any one region of the sky. This image is highly suggestive that the most problematic foregrounds for 21 cm EoR studies will not be easily identifiable bright sources, but rather an aggregate of fainter emission.

  4. The Environment Changes in the Southwestern Taiwan Since the Last Glacial Maximum Epoch

    NASA Astrophysics Data System (ADS)

    Yang, Yung-Jan; Chen, Wen-Shan

    2015-04-01

    We use 31 boreholes to reconstruct the depositional environments in the southwestern Taiwan. Based on the sedimentary structures, it is divided into eight facies associations that is important to reconstruct depositional environment. Based on the depositional environment, sequence stratigraphy and radiocarbon dating data, it can be implied significant environment and shoreline changes. (1) The southwestern Taiwan is characterized by a subaerial environment and formed two incised valleys during the sea-level fall in the last glacial maximum epoch. (2) The shoreline was migrated to the landward and close to the frontal foothills, and the environment changed deepen into tidal flat and lagoon during 18,000-10,000 years ago. (3) The area occurred the deepest environment from shoreface to offshore transition during 8,000-7,000 years ago. (4) The shoreline was retreated to the seaward. The environment changed shallowen into barrier island, lagoon, and coastal plain since 7,000 years ago. This study confirm the decreasing accommodation space in this area result from huge sediment inputs and decreased eustatic sea-level rise, which cause the maximum flooding epoch appear earlier.

  5. The Hydrogen Epoch of Reionization Array Dish. I. Beam Pattern Measurements and Science Implications

    NASA Astrophysics Data System (ADS)

    Neben, Abraham R.; Bradley, Richard F.; Hewitt, Jacqueline N.; DeBoer, David R.; Parsons, Aaron R.; Aguirre, James E.; Ali, Zaki S.; Cheng, Carina; Ewall-Wice, Aaron; Patra, Nipanjana; Thyagarajan, Nithyanandan; Bowman, Judd; Dickenson, Roger; Dillon, Joshua S.; Doolittle, Phillip; Egan, Dennis; Hedrick, Mike; Jacobs, Daniel C.; Kohn, Saul A.; Klima, Patricia J.; Moodley, Kavilan; Saliwanchik, Benjamin R. B.; Schaffner, Patrick; Shelton, John; Taylor, H. A.; Taylor, Rusty; Tegmark, Max; Wirt, Butch; Zheng, Haoxuan

    2016-08-01

    The Hydrogen Epoch of Reionization Array (HERA) is a radio interferometer aiming to detect the power spectrum of 21 cm fluctuations from neutral hydrogen from the epoch of reionization (EOR). Drawing on lessons from the Murchison Widefield Array and the Precision Array for Probing the EOR, HERA is a hexagonal array of large (14 m diameter) dishes with suspended dipole feeds. The dish not only determines overall sensitivity, but also affects the observed frequency structure of foregrounds in the interferometer. This is the first of a series of four papers characterizing the frequency and angular response of the dish with simulations and measurements. In this paper, we focus on the angular response (i.e., power pattern), which sets the relative weighting between sky regions of high and low delay and thus apparent source frequency structure. We measure the angular response at 137 MHz using the ORBCOMM beam mapping system of Neben et al. We measure a collecting area of 93 m2 in the optimal dish/feed configuration, implying that HERA-320 should detect the EOR power spectrum at z ˜ 9 with a signal-to-noise ratio of 12.7 using a foreground avoidance approach with a single season of observations and 74.3 using a foreground subtraction approach. Finally, we study the impact of these beam measurements on the distribution of foregrounds in Fourier space.

  6. Multi-redshift limits on the Epoch of Reionization 21cm power spectrum from PAPER

    NASA Astrophysics Data System (ADS)

    Jacobs, Danny; Pober, Jonathan; Parsons, Aaron; Paper Team

    2015-01-01

    The epoch of reionization hydrogen power spectrum is expected to vary strongly with redshift with cosmic history as star formation progressively ionizes the pervasive intergalactic hydrogen. We present an analysis of observations from the Donald C. Backer Precision Array for Probing the Epoch of Reionization (PAPER) telescope which place new limits on the HI power spectrum over the redshift range of 7.5

  7. Solar wind conditions leading to efficient radiation belt electron acceleration: A superposed epoch analysis

    DOE PAGESBeta

    Li, W.; Thorne, R. M.; Bortnik, J.; Baker, D. N.; Reeves, G. D.; Kanekal, S. G.; Spence, H. E.; Green, J. C.

    2015-09-07

    In this study by determining preferential solar wind conditions leading to efficient radiation belt electron acceleration is crucial for predicting radiation belt electron dynamics. Using Van Allen Probes electron observations (>1 MeV) from 2012 to 2015, we identify a number of efficient and inefficient acceleration events separately to perform a superposed epoch analysis of the corresponding solar wind parameters and geomagnetic indices. By directly comparing efficient and inefficient acceleration events, we clearly show that prolonged southward Bz, high solar wind speed, and low dynamic pressure are critical for electron acceleration to >1 MeV energies in the heart of the outermore » radiation belt. We also evaluate chorus wave evolution using the superposed epoch analysis for the identified efficient and inefficient acceleration events and find that chorus wave intensity is much stronger and lasts longer during efficient electron acceleration events, supporting the scenario that chorus waves play a key role in MeV electron acceleration.« less

  8. Opening the 21 cm Epoch of Reionization Window: Measurements of Foreground Isolation with PAPER

    NASA Astrophysics Data System (ADS)

    Pober, Jonathan C.; Parsons, Aaron R.; Aguirre, James E.; Ali, Zaki; Bradley, Richard F.; Carilli, Chris L.; DeBoer, Dave; Dexter, Matthew; Gugliucci, Nicole E.; Jacobs, Daniel C.; Klima, Patricia J.; MacMahon, Dave; Manley, Jason; Moore, David F.; Stefan, Irina I.; Walbrugh, William P.

    2013-05-01

    We present new observations with the Precision Array for Probing the Epoch of Reionization with the aim of measuring the properties of foreground emission for 21 cm epoch of reionization (EoR) experiments at 150 MHz. We focus on the footprint of the foregrounds in cosmological Fourier space to understand which modes of the 21 cm power spectrum will most likely be compromised by foreground emission. These observations confirm predictions that foregrounds can be isolated to a "wedge"-like region of two-dimensional (k , k ∥)-space, creating a window for cosmological studies at higher k ∥ values. We also find that the emission extends past the nominal edge of this wedge due to spectral structure in the foregrounds, with this feature most prominent on the shortest baselines. Finally, we filter the data to retain only this "unsmooth" emission and image its specific k ∥ modes. The resultant images show an excess of power at the lowest modes, but no emission can be clearly localized to any one region of the sky. This image is highly suggestive that the most problematic foregrounds for 21 cm EoR studies will not be easily identifiable bright sources, but rather an aggregate of fainter emission.

  9. The Impact of Peculiar Velocity and Reionization Patchiness on 21cm Cosmology from the Epoch of Reionization

    NASA Astrophysics Data System (ADS)

    Mao, Yi; Shapiro, P. R.; Iliev, I. T.; Mellema, G.; Ahn, K.; Datta, K.

    2012-01-01

    Neutral hydrogen atoms in the intergalactic medium at high redshift contribute a diffuse background of redshifted 21cm radiation which encodes information about the physical conditions in the early universe at z>6 during and before the epoch of reionization (EOR). Tomography of this 21cm background has emerged as a promising cosmological probe. The assumption that cosmological information in the 21cm signal can be separated from astrophysical information (i.e. that fluctuations in the total matter density can be measured separately from the dependence on patchy reionization and spin temperature) is based on linear perturbation theory and the anisotropy introduced by peculiar velocity. While it is true that fluctuations in the matter density at such high redshift are likely to be of linear amplitude on the large scales which correspond to the beam- and bandwidths of upcoming experiments, the nonlinearity of smaller scale structure in density, velocity and reionization patchiness can leave its imprint on the signal, which might then spoil the linear separation scheme. We have built a robust and efficient computational scheme to predict the 21cm background in observer redshift space, given real-space simulation data, which accounts for peculiar velocity in every detail. We apply this to the results of new state-of-the-art large-scale reionization simulations which combine large-box, high-resolution N-body simulations of the LCDM universe (with up to 165 billion particles in comoving boxes up to 607 Mpc on a side in present units) with radiative transfer simulations of reionization, to test the validity of using 21cm background measurements for cosmology and characterize the predicted signal for upcoming radio surveys. This work was supported in part by NSF grants AST-0708176 and AST-1009799, NASA grants NNX07AH09G, NNG04G177G and NNX11AE09G, and Chandra grant SAO TM8-9009X.

  10. Signals from the epoch of cosmological recombination (Karl Schwarzschild Award Lecture 2008)

    NASA Astrophysics Data System (ADS)

    Sunyaev, R. A.; Chluba, J.

    2009-07-01

    The physical ingredients to describe the epoch of cosmological recombination are amazingly simple and well-understood. This fact allows us to take into account a very large variety of physical processes, still finding potentially measurable consequences for the energy spectrum and temperature anisotropies of the Cosmic Microwave Background (CMB). In this contribution we provide a short historical overview in connection with the cosmological recombination epoch and its connection to the CMB. Also we highlight some of the detailed physics that were studied over the past few years in the context of the cosmological recombination of hydrogen and helium. The impact of these considerations is two-fold: The associated release of photons during this epoch leads to interesting and unique deviations of the Cosmic Microwave Background (CMB) energy spectrum from a perfect blackbody, which, in particular at decimeter wavelength and the Wien part of the CMB spectrum, may become observable in the near future. Despite the fact that the abundance of helium is rather small, it still contributes a sizeable amount of photons to the full recombination spectrum, leading to additional distinct spectral features. Observing the spectral distortions from the epochs of hydrogen and helium recombination, in principle would provide an additional way to determine some of the key parameters of the Universe (e.g. the specific entropy, the CMB monopole temperature and the pre-stellar abundance of helium). Also it permits us to confront our detailed understanding of the recombination process with direct observational evidence. In this contribution we illustrate how the theoretical spectral template of the cosmological recombination spectrum may be utilized for this purpose. We also show that because hydrogen and helium recombine at very different epochs it is possible to address questions related to the thermal history of our Universe. In particular the cosmological recombination radiation may

  11. Environmental Profile of a Community's Health (EPOCH): An Instrument to Measure Environmental Determinants of Cardiovascular Health in Five Countries

    PubMed Central

    Chow, Clara K.; Lock, Karen; Madhavan, Manisha; Corsi, Daniel J.; Gilmore, Anna B.; Subramanian, S. V.; Li, Wei; Swaminathan, Sumathi; Lopez-Jaramillo, Patricio; Avezum, Alvaro; Lear, Scott A.; Dagenais, Gilles; Teo, Koon; McKee, Martin; Yusuf, Salim

    2010-01-01

    Background The environment in which people live is known to be important in influencing diet, physical activity, smoking, psychosocial and other risk factors for cardiovascular (CV) disease. However no instrument exists that evaluates communities for these multiple environmental factors and is suitable for use across different communities, regions and countries. This report describes the design and reliability of an instrument to measure environmental determinants of CV risk factors. Method/Principal Findings The Environmental Profile of Community Health (EPOCH) instrument comprises two parts: (I) an assessment of the physical environment, and (II) an interviewer-administered questionnaire to collect residents' perceptions of their community. We examined the inter-rater reliability amongst 3 observers from each region of the direct observation component of the instrument (EPOCH I) in 93 rural and urban communities in 5 countries (Canada, Colombia, Brazil, China and India). Data collection using the EPOCH instrument was feasible in all communities. Reliability of the instrument was excellent (Intraclass Correlation Coefficient - ICC>0.75) for 24 of 38 items and fair to good (ICC 0.4–0.75) for 14 of 38 items. Conclusion This report shows data collection with the EPOCH instrument is feasible and direct observation of community measures reliable. The EPOCH instrument will enable further research on environmental determinants of health for population studies from a broad range of settings. PMID:21170320

  12. Plasma scale-length effects on electron energy spectra in high-irradiance laser plasmas

    NASA Astrophysics Data System (ADS)

    Culfa, O.; Tallents, G. J.; Rossall, A. K.; Wagenaars, E.; Ridgers, C. P.; Murphy, C. D.; Dance, R. J.; Gray, R. J.; McKenna, P.; Brown, C. D. R.; James, S. F.; Hoarty, D. J.; Booth, N.; Robinson, A. P. L.; Lancaster, K. L.; Pikuz, S. A.; Faenov, A. Ya.; Kampfer, T.; Schulze, K. S.; Uschmann, I.; Woolsey, N. C.

    2016-04-01

    An analysis of an electron spectrometer used to characterize fast electrons generated by ultraintense (1020W cm-2 ) laser interaction with a preformed plasma of scale length measured by shadowgraphy is presented. The effects of fringing magnetic fields on the electron spectral measurements and the accuracy of density scale-length measurements are evaluated. 2D EPOCH PIC code simulations are found to be in agreement with measurements of the electron energy spectra showing that laser filamentation in plasma preformed by a prepulse is important with longer plasma scale lengths (>8 μ m ).

  13. Research in solar plasma theory

    NASA Technical Reports Server (NTRS)

    Vanhoven, Gerard

    1992-01-01

    The main thrust and significance of our research results are presented. The topics covered include: (1) coronal structure and dynamics; (2) coronal heating; (3) filament formation; and (4) flare energy release.

  14. Plasma probe characteristics in low density hydrogen pulsed plasmas

    NASA Astrophysics Data System (ADS)

    Astakhov, D. I.; Goedheer, W. J.; Lee, C. J.; Ivanov, V. V.; Krivtsun, V. M.; Zotovich, A. I.; Zyryanov, S. M.; Lopaev, D. V.; Bijkerk, F.

    2015-10-01

    Probe theories are only applicable in the regime where the probe’s perturbation of the plasma can be neglected. However, it is not always possible to know, a priori, that a particular probe theory can be successfully applied, especially in low density plasmas. This is especially difficult in the case of transient, low density plasmas. Here, we applied probe diagnostics in combination with a 2D particle-in-cell model, to an experiment with a pulsed low density hydrogen plasma. The calculations took into account the full chamber geometry, including the plasma probe as an electrode in the chamber. It was found that the simulations reproduce the time evolution of the probe IV characteristics with good accuracy. The disagreement between the simulated and probe measured plasma density is attributed to the limited applicability of probe theory to measurements of low density pulsed plasmas on a similarly short time scale as investigated here. Indeed, in the case studied here, probe measurements would lead to, either a large overestimate, or underestimate of the plasma density, depending on the chosen probe theory. In contrast, the simulations of the plasma evolution and the probe characteristics do not suffer from such strict applicability limits. These studies show that probe theory cannot be justified through probe measurements. However, limiting cases of probe theories can be used to estimate upper and lower bounds on plasma densities. These theories include and neglect orbital motion, respectively, with different collisional terms leading to intermediate estimates.

  15. Light-cone anisotropy in the 21 cm signal from the epoch of reionization

    NASA Astrophysics Data System (ADS)

    Zawada, Karolina; Semelin, Benoît; Vonlanthen, Patrick; Baek, Sunghye; Revaz, Yves

    2014-04-01

    Using a suite of detailed numerical simulations, we estimate the level of anisotropy generated by the time evolution along the light cone of the 21 cm signal from the epoch of reionization. Our simulations include the physics necessary to model the signal during both the late emission regime and the early absorption regime, namely X-ray and Lyman band 3D radiative transfer in addition to the usual dynamics and ionizing UV transfer. The signal is analysed using correlation functions perpendicular and parallel to the line of sight. We reproduce general findings from previous theoretical studies: the overall amplitude of the correlations and the fact that the light-cone anisotropy is visible only on large scales (100 comoving Mpc). However, the detailed behaviour is different. We find that, at three different epochs, the amplitudes of the correlations along and perpendicular to the line of sight differ from each other, indicating anisotropy. We show that these three epochs are associated with three events of the global reionization history: the overlap of ionized bubbles, the onset of mild heating by X-rays in regions around the sources, and the onset of efficient Lyman α coupling in regions around the sources. We find that a 20 × 20 deg2 survey area may be necessary to mitigate sample variance when we use the directional correlation functions. On a 100 Mpc (comoving) scale, we show that the light-cone anisotropy dominates over the anisotropy generated by peculiar velocity gradients computed in the linear regime. By modelling instrumental noise and limited resolution, we find that the anisotropy should be easily detectable by the Square Kilometre Array, assuming perfect foreground removal, the limiting factor being a large enough survey size. In the case of the Low-Frequency Array for radio astronomy, it is likely that only one anisotropy episode (ionized bubble overlap) will fall in the observing frequency range. This episode will be detectable only if sample

  16. Massachusetts Institute of Technology Plasma Fusion Center 1992-1993 report to the President

    NASA Astrophysics Data System (ADS)

    1993-07-01

    This report discusses research being conducted at MIT's plasma fusion center. Some of the areas covered are: plasma diagnostics, RF plasma heating, gyrotron research, treatment of solid waste by arc plasma, divertor experiments, tokamak studies, and plasma and fusion theory.

  17. Detection of an oxygen emission line from a high-redshift galaxy in the reionization epoch

    NASA Astrophysics Data System (ADS)

    Inoue, Akio K.; Tamura, Yoichi; Matsuo, Hiroshi; Mawatari, Ken; Shimizu, Ikkoh; Shibuya, Takatoshi; Ota, Kazuaki; Yoshida, Naoki; Zackrisson, Erik; Kashikawa, Nobunari; Kohno, Kotaro; Umehata, Hideki; Hatsukade, Bunyo; Iye, Masanori; Matsuda, Yuichi; Okamoto, Takashi; Yamaguchi, Yuki

    2016-06-01

    The physical properties and elemental abundances of the interstellar medium in galaxies during cosmic reionization are important for understanding the role of galaxies in this process. We report the Atacama Large Millimeter/submillimeter Array detection of an oxygen emission line at a wavelength of 88 micrometers from a galaxy at an epoch about 700 million years after the Big Bang. The oxygen abundance of this galaxy is estimated at about one-tenth that of the Sun. The nondetection of far-infrared continuum emission indicates a deficiency of interstellar dust in the galaxy. A carbon emission line at a wavelength of 158 micrometers is also not detected, implying an unusually small amount of neutral gas. These properties might allow ionizing photons to escape into the intergalactic medium.

  18. Superposed epoch analysis of the ionospheric convection evolution during substorms: onset latitude dependence

    NASA Astrophysics Data System (ADS)

    Grocott, A.; Wild, J. A.; Milan, S. E.; Yeoman, T. K.

    2008-12-01

    Using data from the Super Dual Auroral Radar Network (SuperDARN) we investigate the ionospheric convection response to magnetospheric substorms. Substorms were identified using the Far Ultraviolet (FUV) instrument on board the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft, and were then grouped according to the magnetic latitude of their onset. A superposed epoch analysis of the ionospheric convection patterns for each latitude group was then performed using radar data for the interval 60 minutes before onset to 90 minutes after. It is found that lower latitude onset substorms are associated with generally more enhanced convection than the higher latitude substorms, although they suffer from the most significant localised suppression of the flow in the midnight sector during the expansion phase. On the other hand, the higher-latitude events are associated with a significant and rapid increase in the nightside convection following substorm onset. These results suggest differences in the electrodynamics associated with substorms occurring at different latitudes.

  19. The Mars water cycle at other epochs: History of the polar caps and layered terrain

    NASA Technical Reports Server (NTRS)

    Jakosky, Bruce M.; Henderson, Bradley G.; Mellon, Michael T.

    1992-01-01

    The atmospheric water cycle at the present epoch involves summertime sublimation of water from the north polar cap, transport of water through the atmosphere, and condensation on one or both winter CO2 caps. Exchange with the regolith is important seasonally, but the water content of the atmosphere appears to be controlled by the polar caps. The net annual transport through the atmosphere, integrated over long timescales, must be the driving force behind the long-term evolution of the polar caps; clearly, this feeds back into the evolution of the layered terrain. We have investigated the behavior of the seasonal water cycle and the net integrated behavior at the pole for the last 10 exp 7 years. Our model of the water cycle includes the solar input, CO2 condensation and sublimation, and summertime water sublimation through the seasonal cycles, and incorporates the long-term variations in the orbital elements describing the Martian orbit.

  20. Commissioning and Science Forecasts for the Hydrogen Epoch of Reionization Array (HERA)

    NASA Astrophysics Data System (ADS)

    Parsons, Aaron; HERA Collaboration

    2016-01-01

    The HERA is a low-frequency radio interferometer aiming to make precise measurements of the power spectrum of fluctuations in 21cm emission from the Epoch of Reionization at z=13—6. This project was recently awarded development funding under the 2014 cycle of the National Science Foundation's Mid-Scale Innovations Program (MSIP). We present initial results from the commissioning and testing of the 19-element HERA prototype in South Africa, including measurements of the performance of HERA's 14-m dish and feed via reflectometry, beam mapping, and on-sky commissioning tests. We then forecast the science results that HERA will deliver once it reaches its full size of 352 elements. These forecasts include constraints on the 21cm power spectrum, the impact of these constraints on parametrized models of ionization, and their relevance to cosmological models. Construction of HERA-352 is pending the outcome of the 2016 NSF MSIP cycle.

  1. A Lyman Break Galaxy in the Epoch of Reionization from Hubble Space Telescope (HST) Grism Spectroscopy

    NASA Technical Reports Server (NTRS)

    Rhoads, James E.; Malhotra, Sangeeta; Stern, Daniel K.; Gardner, Jonathan P.; Dickinson, Mark; Pirzkal, Norbert; Spinrad, Hyron; Reddy, Naveen; Dey, Arjun; Hathi, Nimish; Grogin, Norman; Koekemoer, Anton; Peth, Michael A.; Cohen, Seth; Budavari, Tamas; Ferreras, Ignacio; Gronwall, Caryl; Haiman, Zoltan; Meurer, Gernhardt; Straughn, Amber N.

    2013-01-01

    Slitless grism spectroscopy from space offers dramatic advantages for studying high redshift galaxies: high spatial resolution to match the compact sizes of the targets, a dark and uniform sky background, and simultaneous observation over fields ranging from five square arcminutes (HST) to over 1000 square arcminutes (Euclid). Here we present observations of a galaxy at z = 6.57 the end of the reioinization epoch identified using slitless HST grism spectra from the PEARS survey (Probing Evolution And Reionization Spectroscopically) and reconfirmed with Keck + DEIMOS. This high redshift identification is enabled by the depth of the PEARS survey. Substantially higher redshifts are precluded for PEARS data by the declining sensitivity of the ACS grism at greater than lambda 0.95 micrometers. Spectra of Lyman breaks at yet higher redshifts will be possible using comparably deep observations with IR-sensitive grisms.

  2. Relativistic jet models for the BL Lacertae object Mrk 421 during three epochs of observation

    NASA Technical Reports Server (NTRS)

    Mufson, S. L.; Hutter, D. J.; Kondo, Y.; Wisniewski, W. Z.

    1988-01-01

    Coordinated observation of the nearby BL Lacertae object Mrk 421 obtained during May 1980, January 1984, and March 1984 are described. These observations give a time-frozen picture of the continuous spectrum of Mrk 421 at X-ray, ultraviolet, optical, and radio wavelengths. The observed spectra have been fitted to an inhomogeneous relativistic jet model. In general, the models reproduce the data well. Many of the observed differences during the three epochs can be attributed to variations in the opening angle of the jet and in the angle that the jet makes to the line of sight. The jet models obtained here are compared with the homogeneous, spherically symmetric, synchrotron self-Compton models for this source. The models are also compared with the relativistic jet models obtained for other active galactic nuclei.

  3. The Influence of Indian Ocean Atmospheric Circulation on Warm Pool Hydroclimate During the Holocene Epoch

    NASA Technical Reports Server (NTRS)

    Tierney, J.E.; Oppo, D. W.; LeGrande, A. N.; Huang, Y.; Rosenthal, Y.; Linsley, B. K.

    2012-01-01

    Existing paleoclimate data suggest a complex evolution of hydroclimate within the Indo-Pacific Warm Pool (IPWP) during the Holocene epoch. Here we introduce a new leaf wax isotope record from Sulawesi, Indonesia and compare proxy water isotope data with ocean-atmosphere general circulation model (OAGCM) simulations to identify mechanisms influencing Holocene IPWP hydroclimate. Modeling simulations suggest that orbital forcing causes heterogenous changes in precipitation across the IPWP on a seasonal basis that may account for the differences in time-evolution of the proxy data at respective sites. Both the proxies and simulations suggest that precipitation variability during the September-November (SON) season is important for hydroclimate in Borneo. The preeminence of the SON season suggests that a seasonally lagged relationship between the Indian monsoon and Indian Ocean Walker circulation influences IPWP hydroclimatic variability during the Holocene.

  4. Lyman horizons in the early phases of the epoch of reionization

    NASA Astrophysics Data System (ADS)

    Vonlanthen, P.; Semelin, B.

    2011-12-01

    It has been shown that the radial profile of the Lyman-α flux around light sources emitting in the Lyman band during the early phases of the epoch of reionization is characterized by a series of step-like discontinuities. This property originates in the fact that the neutral intergalactic medium is optically thick at the frequencies of all the Lyman-series lines. We show that, through unsaturated Wouthuysen-Field coupling, these spherical discontinuities are also present in the redshifted 21 cm signal of neutral hydrogen. We use realistic 3D numerical simulations with full radiative transfer calculation in the first five Lyman lines in order to study the properties of these discontinuities and the possibility for detection with the future Square Kilometre Array. Although challenging, these observations could provide a diagnostic tool to disentangle the cosmological signal and residuals from imperfect foreground removal.

  5. Detection of an oxygen emission line from a high-redshift galaxy in the reionization epoch.

    PubMed

    Inoue, Akio K; Tamura, Yoichi; Matsuo, Hiroshi; Mawatari, Ken; Shimizu, Ikkoh; Shibuya, Takatoshi; Ota, Kazuaki; Yoshida, Naoki; Zackrisson, Erik; Kashikawa, Nobunari; Kohno, Kotaro; Umehata, Hideki; Hatsukade, Bunyo; Iye, Masanori; Matsuda, Yuichi; Okamoto, Takashi; Yamaguchi, Yuki

    2016-06-24

    The physical properties and elemental abundances of the interstellar medium in galaxies during cosmic reionization are important for understanding the role of galaxies in this process. We report the Atacama Large Millimeter/submillimeter Array detection of an oxygen emission line at a wavelength of 88 micrometers from a galaxy at an epoch about 700 million years after the Big Bang. The oxygen abundance of this galaxy is estimated at about one-tenth that of the Sun. The nondetection of far-infrared continuum emission indicates a deficiency of interstellar dust in the galaxy. A carbon emission line at a wavelength of 158 micrometers is also not detected, implying an unusually small amount of neutral gas. These properties might allow ionizing photons to escape into the intergalactic medium. PMID:27312046

  6. Direct detection of projectile relics from the end of the lunar basin-forming epoch.

    PubMed

    Joy, Katherine H; Zolensky, Michael E; Nagashima, Kazuhide; Huss, Gary R; Ross, D Kent; McKay, David S; Kring, David A

    2012-06-15

    The lunar surface, a key proxy for the early Earth, contains relics of asteroids and comets that have pummeled terrestrial planetary surfaces. Surviving fragments of projectiles in the lunar regolith provide a direct measure of the types and thus the sources of exogenous material delivered to the Earth-Moon system. In ancient [>3.4 billion years ago (Ga)] regolith breccias from the Apollo 16 landing site, we located mineral and lithologic relics of magnesian chondrules from chondritic impactors. These ancient impactor fragments are not nearly as diverse as those found in younger (3.4 Ga to today) regolith breccias and soils from the Moon or that presently fall as meteorites to Earth. This suggests that primitive chondritic asteroids, originating from a similar source region, were common Earth-Moon-crossing impactors during the latter stages of the basin-forming epoch. PMID:22604725

  7. The Latitude and Epoch for the Origin of the Astronomical Lore of Eudoxus

    NASA Astrophysics Data System (ADS)

    Schaefer, B. E.

    2003-12-01

    The earliest presentation of the ancient Greek constellations that survives to today is the poem titled Phaenomena by Aratus which is a reasonable copy of a book of the same name by Eudoxus (c. 366 BC) which has not survived. Hipparchus' sole surviving work (his Commentaries) also gives many direct quotes from Eudoxus' book. Eudoxus reports on many astronomical lore items such as that the head of Draco skims the northern horizon and that Orion sets when Scorpius rises. Many of these lore items have their validity depend on the latitude and epoch of the observations on which the lore is based, so for example the two lore items just quoted will each yield rather fuzzy simultaneous constraints on the latitude and epoch of the observer. In all, I have found 172 useful constraints for Eudoxus' lore, and the large number can be used to greatly increase the accuracy of the final joint constraint. My results are; (1) All lore reported by Eudoxus were based on observations from the year 1130 ± 80 BC and at a latitude of 36.0 ± 0.9 degrees north. (2) My derived date and latitude correspond only to the peak of the Assyrian culture. (3) The typical accuracy of the lore is 4-8 degrees, even though 1 degree accuracy is easy to be gotten by primitive methods. (4) About half the rise/set pairs recorded in the Mesopotamian MUL.APIN tablets are also given in Eudoxus' lore. (5) The MUL.APIN tablets have been independently determined to be based on observations from roughly 1000 BC at a latitude of 36 degrees north, which is consistent within uncertainties to my results for Eudoxus. Given the close match in date/latitude/content, I conclude that both Eudoxus' lore and MUL.APIN were derived from the same old Assyrian observations. This research was made possible with the support of the Herbert C. Pollack Award from the Dudley Observatory.

  8. Accuracy assessment of single and double difference models for the single epoch GPS compass

    NASA Astrophysics Data System (ADS)

    Chen, Wantong; Qin, Honglei; Zhang, Yanzhong; Jin, Tian

    2012-02-01

    The single epoch GPS compass is an important field of study, since it is a valuable technique for the orientation estimation of vehicles and it can guarantee a total independence from carrier phase slips in practical applications. To achieve highly accurate angular estimates, the unknown integer ambiguities of the carrier phase observables need to be resolved. Past researches focus on the ambiguity resolution for single epoch; however, accuracy is another significant problem for many challenging applications. In this contribution, the accuracy is evaluated for the non-common clock scheme of the receivers and the common clock scheme of the receivers, respectively. We focus on three scenarios for either scheme: single difference model vs. double difference model, single frequency model vs. multiple frequency model and optimal linear combinations vs. traditional triple-frequency least squares. We deduce the short baseline precision for a number of different available models and analyze the difference in accuracy for those models. Compared with the single or double difference model of the non-common clock scheme, the single difference model of the common clock scheme can greatly reduce the vertical component error of baseline vector, which results in higher elevation accuracy. The least squares estimator can also reduce the error of fixed baseline vector with the aid of the multi-frequency observation, thereby improving the attitude accuracy. In essence, the "accuracy improvement" is attributed to the difference in accuracy for different models, not a real improvement for any specific model. If all noise levels of GPS triple frequency carrier phase are assumed the same in unit of cycles, it can be proved that the optimal linear combination approach is equivalent to the traditional triple-frequency least squares, no matter which scheme is utilized. Both simulations and actual experiments have been performed to verify the correctness of theoretical analysis.

  9. Multi-epoch observations of extremely high-velocity emergent broad absorption

    NASA Astrophysics Data System (ADS)

    Rogerson, Jesse A.; Hall, Patrick B.; Rodríguez Hidalgo, Paola; Pirkola, Patrik; Brandt, William N.; Filiz Ak, Nur

    2016-03-01

    We present the discovery of the highest velocity C IV broad absorption line to date in the z = 2.47 quasar SDSS J023011.28+005913.6, hereafter J0230. In comparing the public DR7 and DR9 spectra of J0230, we discovered an emerging broad absorption trough outflowing at ˜60 000 km s-1, which we refer to as trough A. In pursuing follow up observations of trough A, we discovered a second emergent C IV broad absorption trough outflowing at ˜40 000 km s-1, namely trough B. In total, we collected seven spectral epochs of J0230 that demonstrate emergent and rapidly (˜10 d in the rest-frame) varying broad absorption. We investigate two possible scenarios that could cause these rapid changes: bulk motion and ionization variability. Given our multi-epoch data, we were able to rule out some simple models of bulk motion, but have proposed two more realistic models to explain the variability of both troughs. Trough A is likely an augmented `crossing disc' scenario with the absorber moving at 10 000 < v(km s-1) < 18 000. Trough B can be explained by a flow-tube feature travelling across the emitting region at 8000 < v(km s-1) < 56 000. If ionization variability is the cause for the changes observed, trough A's absorber has ne ≥ 724 cm-3 and is at requal ≥ 2.00 kpc, or is at r < 2.00 kpc with no constraint on the density; trough B's absorber either has ne ≥ 1540 cm-3 and is at requal ≥ 1.37 kpc, or is at r < 1.37 kpc with no constraint on the density.

  10. A Flux Scale for Southern Hemisphere 21 cm Epoch of Reionization Experiments

    NASA Astrophysics Data System (ADS)

    Jacobs, Daniel C.; Parsons, Aaron R.; Aguirre, James E.; Ali, Zaki; Bowman, Judd; Bradley, Richard F.; Carilli, Chris L.; DeBoer, David R.; Dexter, Matthew R.; Gugliucci, Nicole E.; Klima, Pat; MacMahon, Dave H. E.; Manley, Jason R.; Moore, David F.; Pober, Jonathan C.; Stefan, Irina I.; Walbrugh, William P.

    2013-10-01

    We present a catalog of spectral measurements covering a 100-200 MHz band for 32 sources, derived from observations with a 64 antenna deployment of the Donald C. Backer Precision Array for Probing the Epoch of Reionization (PAPER) in South Africa. For transit telescopes such as PAPER, calibration of the primary beam is a difficult endeavor and errors in this calibration are a major source of error in the determination of source spectra. In order to decrease our reliance on an accurate beam calibration, we focus on calibrating sources in a narrow declination range from -46° to -40°. Since sources at similar declinations follow nearly identical paths through the primary beam, this restriction greatly reduces errors associated with beam calibration, yielding a dramatic improvement in the accuracy of derived source spectra. Extrapolating from higher frequency catalogs, we derive the flux scale using a Monte Carlo fit across multiple sources that includes uncertainty from both catalog and measurement errors. Fitting spectral models to catalog data and these new PAPER measurements, we derive new flux models for Pictor A and 31 other sources at nearby declinations; 90% are found to confirm and refine a power-law model for flux density. Of particular importance is the new Pictor A flux model, which is accurate to 1.4% and shows that between 100 MHz and 2 GHz, in contrast with previous models, the spectrum of Pictor A is consistent with a single power law given by a flux at 150 MHz of 382 ± 5.4 Jy and a spectral index of -0.76 ± 0.01. This accuracy represents an order of magnitude improvement over previous measurements in this band and is limited by the uncertainty in the catalog measurements used to estimate the absolute flux scale. The simplicity and improved accuracy of Pictor A's spectrum make it an excellent calibrator in a band important for experiments seeking to measure 21 cm emission from the epoch of reionization.

  11. Chiral plasma instabilities.

    PubMed

    Akamatsu, Yukinao; Yamamoto, Naoki

    2013-08-01

    We study the collective modes in relativistic electromagnetic or quark-gluon plasmas with an asymmetry between left- and right-handed chiral fermions, based on the recently formulated kinetic theory with Berry curvature corrections. We find that there exists an unstable mode, signaling the presence of a plasma instability. We argue the fate of this "chiral plasma instability" including the effect of collisions, and briefly discuss its relevance in heavy ion collisions and compact stars. PMID:23952387

  12. Atoms in dense plasmas

    SciTech Connect

    More, R.M.

    1986-01-01

    Recent experiments with high-power pulsed lasers have strongly encouraged the development of improved theoretical understanding of highly charged ions in a dense plasma environment. This work examines the theory of dense plasmas with emphasis on general rules which govern matter at extreme high temperature and density. 106 refs., 23 figs.

  13. Generalized Brans-Dicke theories

    SciTech Connect

    De Felice, Antonio; Tsujikawa, Shinji E-mail: shinji@rs.kagu.tus.ac.jp

    2010-07-01

    In Brans-Dicke theory a non-linear self interaction of a scalar field φ allows a possibility of realizing the late-time cosmic acceleration, while recovering the General Relativistic behavior at early cosmological epochs. We extend this to more general modified gravitational theories in which a de Sitter solution for dark energy exists without using a field potential. We derive a condition for the stability of the de Sitter point and study the background cosmological dynamics of such theories. We also restrict the allowed region of model parameters from the demand for the avoidance of ghosts and instabilities. A peculiar evolution of the field propagation speed allows us to distinguish those theories from the ΛCDM model.

  14. HIGH-RESOLUTION VLBA OBSERVATIONS OF THREE 7 mm SiO MASERS TOWARD VX Sgr AT FIVE EPOCHS

    SciTech Connect

    Su, J. B.; Shen, Z.-Q.; Chen, X.; Jiang, D. R.; Yi Jiyune; Yun, Y. J.

    2012-07-20

    VX Sgr is a red supergiant at an adopted distance of 1.6 kpc with intense 43 GHz SiO maser emission. In this paper, we present the high-resolution very long baseline interferometry (VLBI) observations of SiO masers toward VX Sgr at five epochs. We used the Very Long Baseline Array to map the J = 1{yields}0 (v = 1, 2) {sup 28}SiO masers and confirmed a ring-like structure. In the first two epochs, the v = 1 masers form a ring, but v = 2 maser spots residing only in the southern and northern regions do not form a complete ring. In the third epoch, the two masers are distributed in a ring structure and the v = 2 masers are a bit closer to the central star. In the last two epochs, many new maser spots appear and overlap each other. These overlapping maser spots can be related to the shock waves and reflect the collisional pumping. We compare the observations with the pumping models and speculate that the real pumping mechanism may be complex in VX Sgr and vary with time. The J = 1{yields}0 (v = 0) {sup 29}SiO line emission is also detected, but is too weak to produce any VLBI map.

  15. 78 FR 48421 - Publication of North American Datum of 1983 (2011) Epoch 2010.00, North American Datum of 1983...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-08

    ..., 54 FR 25318, June 14, 1989). DATES: Individuals or organizations wishing to submit comments on the...) Epoch 2010.00 AGENCY: National Geodetic Survey (NGS), National Ocean Service (NOS), National Oceanic and... Geodetic Survey (NGS) has finalized the publication of new realizations of three geodetic references...

  16. Bianchi class A models in Sàez-Ballester's theory

    NASA Astrophysics Data System (ADS)

    Socorro, J.; Espinoza-García, Abraham

    2012-08-01

    We apply the Sàez-Ballester (SB) theory to Bianchi class A models, with a barotropic perfect fluid in a stiff matter epoch. We obtain exact classical solutions à la Hamilton for Bianchi type I, II and VIh=-1 models. We also find exact quantum solutions to all Bianchi Class A models employing a particular ansatz for the wave function of the universe.

  17. On the theory of global population growth

    NASA Astrophysics Data System (ADS)

    Kapitza, Sergei P.

    2010-12-01

    Ours is an epoch of global demographic revolution, a time of a rapid transition from explosive population growth to a low reproduction level. This, possibly the most momentous change ever witnessed by humankind has, first and foremost, important implications for the dynamics of population. But it also affects billions of people in all aspects of their lives, and it is for this reason that demographic processes have grown into a vast problem, both globally and in Russia. Their fundamental understanding will to a large extent impact the present, the short-term future following the current critical epoch, the stable and uniform global development and its priorities, and indeed global security. Quantitative treatment of historical processes is reached using the phenomenological theory of mankind's population growth. This theory relies on the concepts and methods of physics and its conclusions should take into account the ideas of economics and genetics.

  18. Prediction in Real Time of the 2000 July 14 Heliospheric Shock Wave and its Companions During the `Bastille' Epoch*

    NASA Astrophysics Data System (ADS)

    Dryer, M.; Fry, C. D.; Sun, W.; Deehr, C.; Smith, Z.; Akasofu, S.-I.; Andrews, M. D.

    2001-12-01

    Prediction of solar-generated disturbances and their three-dimensional propagation through interplanetary space continues to present a vitally important operational space weather forecasting objective. This paper presents the first successful real-time prediction of a series of major heliospheric shock waves at Earth, including the one from the 14 July 2000 (`Bastille Day') flare. An ensemble of three models and their predictions were distributed to a world-wide group of interested scientists as part of an informal Internet space weather forecast research program. Two of the models, STOA (Shock Time of Arrival) and ISPM (Interplanetary Shock Propagation Model), presently in operation by the US Air Force Weather Agency, provided predictions of shock arrival time (SAT) that were, respectively, 0.5 hours after and 3.7 hours before the observed arrival. The third model, HAFv.2 (Hakamada Akasofu Fry version 2.0) predicted a time 0.3 hours after the observed shock arrival time (14:37 UT, 15 July 2000). Of primary interest to this study is the third model, firstly in terms of its capability of propagating shocks through non-uniform solar wind conditions, and secondly, in terms of its ability to integrate multiple solar events and display them graphically along with the background solar wind. This latter capability was brought to bear on ten real-time-reported flares, some with CMEs (coronal mass ejections) that took place as companions to the Bastille flare during the period 7 15 July 2000. Some limited statistics are given regarding the three models' shock arrival prediction capability at Earth, as an extension of our earlier studies with this three model ensemble in the prediction of SAT. HAFv.2, however, was able to describe not only the ten events and their interaction as measured at Earth, but also at the spacecraft NEAR (orbiting the asteroid, Eros, at 1.8 AU), and CASSINI (en route, at 4.0 AU, to Saturn). Several important points are noted: (1) this epoch

  19. Modelling of dust around the symbiotic Mira RR Telescopii during obscuration epochs

    NASA Astrophysics Data System (ADS)

    Jurkic, T.; Kotnik-Karuza, D.

    2012-08-01

    Context. Symbiotic Miras represent a class of peculiar binaries whose nature is still not well understood. Physical properties of the circumstellar dust and associated physical mechanisms play an important role in understanding the evolution of symbiotic binaries and the interaction between their components. We present a model of inner dust regions around the cool Mira component of the symbiotic nova RR Tel based on the near-IR terrestrial photometry and infrared ISO spectra. Aims: Our goal is to find a comprehensive and consistent model of the circumstellar inner dust regions around the Mira component that can explain the observed photometric and spectroscopic features in the near- and mid-infrared. Methods: Available JHKL photometric observations from South African Astronomical Observatory were collected and corrected for Mira pulsations as well as for interstellar reddening to follow temporal changes of the near-infrared colours. Spectral energy distributions (SEDs) from 1 to 13 μm during obscuration epoch were reconstructed with the simultaneously available ISO/SWS spectra and JHKL magnitudes. The dust properties were determined by modelling both the reconstructed SEDs and the near-IR colours using the DUSTY numerical code. This 1D code solves radiative transfer through the circumstellar dust by calculating the dust temperature profile assuming spherical symmetry. Results: The Mira pulsation period of 387 days was found and confirmed with two independent fitting methods. A long-term variation of ~7000 days, which cannot be attributed to orbital motion, was obtained from the analysis of the near-IR magnitudes. Reconstructed infrared SEDs were modelled successfully by a single dust shell with dust distribution enhanced by radiatively driven stellar winds. Mira temperature, dust sublimation temperature, grain diameter, density distribution, and optical depth have been obtained. Our model shows a maximum dust grain diameter of 4 μm, which is larger than expected

  20. Distinctive rings in the 21 cm signal of the epoch of reionization

    NASA Astrophysics Data System (ADS)

    Vonlanthen, P.; Semelin, B.; Baek, S.; Revaz, Y.

    2011-08-01

    Context. It is predicted that sources emitting UV radiation in the Lyman band during the epoch of reionization show a series of discontinuities in their Lyα flux radial profile as a consequence of the thickness of the Lyman-series lines in the primeval intergalactic medium. Through unsaturated Wouthuysen-Field coupling, these spherical discontinuities are also present in the 21 cm emission of the neutral IGM. Aims: We study the effects that these discontinuities have on the differential brightness temperature of the 21 cm signal of neutral hydrogen in a realistic setting that includes all other sources of fluctuations. We focus on the early phases of the epoch of reionization, and we address the question of the detectability by the planned Square Kilometre Array (SKA). Such a detection would be of great interest because these structures could provide an unambiguous diagnostic tool for the cosmological origin of the signal that remains after the foreground cleaning procedure. These structures could also be used as a new type of standard rulers. Methods: We determine the differential brightness temperature of the 21 cm signal in the presence of inhomogeneous Wouthuysen-Field effect using simulations that include (hydro)dynamics as well as ionizing and Lyman lines 3D radiative transfer with the code LICORICE. We include radiative transfer for the higher-order Lyman-series lines and consider also the effect of backreaction from recoils and spin diffusivity on the Lyα resonance. Results: We find that the Lyman horizons are difficult to indentify using the power spectrum of the 21 cm signal but are clearly visible in the maps and radial profiles around the first sources of our simulations, if only for a limited time interval, typically Δz ≈ 2 at z ~ 13. Stacking the profiles of the different sources of the simulation at a given redshift results in extending this interval to Δz ≈ 4. When we take into account the implementation and design planned for the SKA

  1. A FLUX SCALE FOR SOUTHERN HEMISPHERE 21 cm EPOCH OF REIONIZATION EXPERIMENTS

    SciTech Connect

    Jacobs, Daniel C.; Bowman, Judd; Parsons, Aaron R.; Ali, Zaki; Pober, Jonathan C.; Aguirre, James E.; Moore, David F.; Bradley, Richard F.; Carilli, Chris L.; DeBoer, David R.; Dexter, Matthew R.; MacMahon, Dave H. E.; Gugliucci, Nicole E.; Klima, Pat; Manley, Jason R.; Walbrugh, William P.; Stefan, Irina I.

    2013-10-20

    We present a catalog of spectral measurements covering a 100-200 MHz band for 32 sources, derived from observations with a 64 antenna deployment of the Donald C. Backer Precision Array for Probing the Epoch of Reionization (PAPER) in South Africa. For transit telescopes such as PAPER, calibration of the primary beam is a difficult endeavor and errors in this calibration are a major source of error in the determination of source spectra. In order to decrease our reliance on an accurate beam calibration, we focus on calibrating sources in a narrow declination range from –46° to –40°. Since sources at similar declinations follow nearly identical paths through the primary beam, this restriction greatly reduces errors associated with beam calibration, yielding a dramatic improvement in the accuracy of derived source spectra. Extrapolating from higher frequency catalogs, we derive the flux scale using a Monte Carlo fit across multiple sources that includes uncertainty from both catalog and measurement errors. Fitting spectral models to catalog data and these new PAPER measurements, we derive new flux models for Pictor A and 31 other sources at nearby declinations; 90% are found to confirm and refine a power-law model for flux density. Of particular importance is the new Pictor A flux model, which is accurate to 1.4% and shows that between 100 MHz and 2 GHz, in contrast with previous models, the spectrum of Pictor A is consistent with a single power law given by a flux at 150 MHz of 382 ± 5.4 Jy and a spectral index of –0.76 ± 0.01. This accuracy represents an order of magnitude improvement over previous measurements in this band and is limited by the uncertainty in the catalog measurements used to estimate the absolute flux scale. The simplicity and improved accuracy of Pictor A's spectrum make it an excellent calibrator in a band important for experiments seeking to measure 21 cm emission from the epoch of reionization.

  2. THE LICK AGN MONITORING PROJECT: RECALIBRATING SINGLE-EPOCH VIRIAL BLACK HOLE MASS ESTIMATES

    SciTech Connect

    Park, Daeseong; Woo, Jong-Hak; Treu, Tommaso; Bennert, Vardha N.; Barth, Aaron J.; Walsh, Jonelle; Bentz, Misty C.; Canalizo, Gabriela; Filippenko, Alexei V.; Gates, Elinor; Greene, Jenny E.; Malkan, Matthew A.

    2012-03-01

    We investigate the calibration and uncertainties of black hole (BH) mass estimates based on the single-epoch (SE) method, using homogeneous and high-quality multi-epoch spectra obtained by the Lick Active Galactic Nucleus (AGN) Monitoring Project for nine local Seyfert 1 galaxies with BH masses <10{sup 8} M{sub Sun }. By decomposing the spectra into their AGNs and stellar components, we study the variability of the SE H{beta} line width (full width at half-maximum intensity, FWHM{sub H{beta}} or dispersion, {sigma}{sub H{beta}}) and of the AGN continuum luminosity at 5100 A (L{sub 5100}). From the distribution of the 'virial products' ({proportional_to} FWHM{sub H{beta}}{sup 2} L{sup 0.5}{sub 5100} or {sigma}{sub H{beta}}{sup 2} L{sup 0.5}{sub 5100}) measured from SE spectra, we estimate the uncertainty due to the combined variability as {approx}0.05 dex (12%). This is subdominant with respect to the total uncertainty in SE mass estimates, which is dominated by uncertainties in the size-luminosity relation and virial coefficient, and is estimated to be {approx}0.46 dex (factor of {approx}3). By comparing the H{beta} line profile of the SE, mean, and root-mean-square (rms) spectra, we find that the H{beta} line is broader in the mean (and SE) spectra than in the rms spectra by {approx}0.1 dex (25%) for our sample with FWHM{sub H{beta}} <3000 km s{sup -1}. This result is at variance with larger mass BHs where the difference is typically found to be much less than 0.1 dex. To correct for this systematic difference of the H{beta} line profile, we introduce a line-width dependent virial factor, resulting in a recalibration of SE BH mass estimators for low-mass AGNs.

  3. Zirconium-titanium placers of the Voronezh Anteclise: Types, epochs and factors of formation, and forecast

    NASA Astrophysics Data System (ADS)

    Savko, A. D.; Zvonarev, A. E.; Ivanov, D. A.

    2012-02-01

    The early and late Frasnian, Barremian-Aptian, Cenomanian, early Santonian, early Campanian, and Oligocene-Miocene epochs of the formation of various types of zirconium-titanium placers are distinguished in the Voronezh Anteclise. The factors of their formation are considered, and a forecast of prospecting has been made. Lower Frasnian sedimentary rocks occur in the southeast, where the placers are related to the ilmenite-bearing volcanosedimentary rocks of the Yastrebovo Sequence. The upper Frasnian productive quartz sand of the Petino Sequence occurs in the central part of the Voronezh Anteclise. The Barremian-Aptian productive quartz sand and kaolinite clay occur in the northern and northeastern parts of the anteclise (Ryazan and Lipetsk oblasts). The placers formed in the Cenomanian are known in the Tambov oblast in the northeast of the Voronezh Anteclise and are related to phosphate-bearing glauconite-quartz sand. The early Campanian phosphorite-glauconite-quartz formation is widespread in the northwest of the Voronezh Anteclise at the junction with the northeastern wall of the Dnieper-Donets Basin (Bryansk oblast). The Oligocene-Miocene epoch was characterized by quartz sands abundant in the northwestern and south-western areas. The formation of zirconium-titanium placers is controlled by structural-tectonic, facies, volcanic, paleogeographic, stratigraphic, and evolutional factors. The indispensable condition for heavy mineral concentration is existence of positive forms of underwater topography. These are mostly structural elements of the third and fourth orders on the slopes of the Voronezh Anteclise at the boundaries of the adjacent negative structures. As concerns the facies factor, the occurrence of coastal and shallow-water marine facies with alternating and medium hydrodynamic activity and predominance of sand fractions 0.25-0.05 mm are criteria of elevated concentration of heavy minerals in sand. One of the conditions providing concentration of heavy

  4. Plasma heating power dissipation in low temperature hydrogen plasmas

    SciTech Connect

    Komppula, J. Tarvainen, O.

    2015-10-15

    A theoretical framework for power dissipation in low temperature plasmas in corona equilibrium is developed. The framework is based on fundamental conservation laws and reaction cross sections and is only weakly sensitive to plasma parameters, e.g., electron temperature and density. The theory is applied to low temperature atomic and molecular hydrogen laboratory plasmas for which the plasma heating power dissipation to photon emission, ionization, and chemical potential is calculated. The calculated photon emission is compared to recent experimental results.

  5. Beam-Plasma Interactions

    SciTech Connect

    Cairns, R. A.; Vorgul, I.; Bingham, R.; Ronald, K.; Speirs, D. C.; Phelps, A. D. R.; McConville, S. L.; Gillespie, K. M.; Cross, A. W.; Robertson, C. W.; Whyte, C. G.; Kellett, B. J.

    2009-11-10

    We describe the theory of a cyclotron maser instability which appears to be a likely source of auroral kilometric radiation and its generation in a laboratory experiment. We then outline plans for future development of the experiment to investigate a wider range of instabilities resulting from the existence of electron beams in a plasma. The basic theory theory underlying a few of these is then discussed.

  6. GNSS Single Frequency, Single Epoch Reliable Attitude Determination Method with Baseline Vector Constraint.

    PubMed

    Gong, Ang; Zhao, Xiubin; Pang, Chunlei; Duan, Rong; Wang, Yong

    2015-01-01

    For Global Navigation Satellite System (GNSS) single frequency, single epoch attitude determination, this paper proposes a new reliable method with baseline vector constraint. First, prior knowledge of baseline length, heading, and pitch obtained from other navigation equipment or sensors are used to reconstruct objective function rigorously. Then, searching strategy is improved. It substitutes gradually Enlarged ellipsoidal search space for non-ellipsoidal search space to ensure correct ambiguity candidates are within it and make the searching process directly be carried out by least squares ambiguity decorrelation algorithm (LAMBDA) method. For all vector candidates, some ones are further eliminated by derived approximate inequality, which accelerates the searching process. Experimental results show that compared to traditional method with only baseline length constraint, this new method can utilize a priori baseline three-dimensional knowledge to fix ambiguity reliably and achieve a high success rate. Experimental tests also verify it is not very sensitive to baseline vector error and can perform robustly when angular error is not great. PMID:26633413

  7. Superposed epoch analysis of the ionospheric convection evolution during substorms: onset latitude dependence

    NASA Astrophysics Data System (ADS)

    Grocott, A.; Wild, J. A.; Milan, S. E.; Yeoman, T. K.

    2009-02-01

    Using data from the Super Dual Auroral Radar Network (SuperDARN) we investigate the ionospheric convection response to magnetospheric substorms. Substorms were identified using the Far Ultraviolet (FUV) instrument on board the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft, and were then binned according to the magnetic latitude of their onset. A superposed epoch analysis of the ionospheric convection patterns for each onset-latitude bin was then performed using radar data for the interval 60 min before onset to 90 min after. It is found that lower onset-latitude substorms are associated with generally more enhanced convection than the higher latitude substorms, although they suffer from a significant localised reduction of the flow in the midnight sector during the expansion phase. Higher-latitude substorms are associated with a significant and rapid increase in the nightside convection following substorm onset, with all onset-latitude bins showing an enhancement over onset values by ~60 min into the expansion phase. A rudimentary inspection of the concurrent auroral evolution suggests that the duration of the flow reduction following substorm onset is dependent on the strength and duration of the expansion phase aurora and its associated conductivity enhancement.

  8. The Mars water cycle at other epochs: Recent history of the polar caps and layered terrain

    NASA Technical Reports Server (NTRS)

    Jakosky, Bruce M.; Henderson, Bradley G.; Mellon, Michael T.

    1992-01-01

    The Martian polar caps and layered terrain presumably evolves by the deposition and removal of small amounts of water and dust each year, the current cap attributes therefore represent the incremental transport during a single year as integrated over long periods of time. The role was studied of condensation and sublimation of water ice in this process by examining the seasonal water cycle during the last 10(exp 7) yr. In the model, axial obliquity, eccentricity, and L sub s of perihelion vary according to dynamical models. At each epoch, the seasonal variations in temperature are calculated at the two poles, keeping track of the seasonal CO2 cap and the summertime sublimation of water vapor into the atmosphere; net exchange of water between the two caps is calculated based on the difference in the summertime sublimation between the two caps (or on the sublimation from one cap if the other is covered with CO2 frost all year). Results from the model can help to explain (1) the apparent inconsistency between the timescales inferred for layer formation and the much older crater retention age of the cap and (2) the difference in sizes of the two residual caps, with the south being smaller than the north.

  9. GNSS Single Frequency, Single Epoch Reliable Attitude Determination Method with Baseline Vector Constraint

    PubMed Central

    Gong, Ang; Zhao, Xiubin; Pang, Chunlei; Duan, Rong; Wang, Yong

    2015-01-01

    For Global Navigation Satellite System (GNSS) single frequency, single epoch attitude determination, this paper proposes a new reliable method with baseline vector constraint. First, prior knowledge of baseline length, heading, and pitch obtained from other navigation equipment or sensors are used to reconstruct objective function rigorously. Then, searching strategy is improved. It substitutes gradually Enlarged ellipsoidal search space for non-ellipsoidal search space to ensure correct ambiguity candidates are within it and make the searching process directly be carried out by least squares ambiguity decorrelation algorithm (LAMBDA) method. For all vector candidates, some ones are further eliminated by derived approximate inequality, which accelerates the searching process. Experimental results show that compared to traditional method with only baseline length constraint, this new method can utilize a priori baseline three-dimensional knowledge to fix ambiguity reliably and achieve a high success rate. Experimental tests also verify it is not very sensitive to baseline vector error and can perform robustly when angular error is not great. PMID:26633413

  10. Performance improvement of GPS single frequency, single epoch attitude determination with poor satellite visibility

    NASA Astrophysics Data System (ADS)

    Chen, Wantong; Sun, Xingli

    2016-07-01

    Similar to global positioning system (GPS) positioning in urban canyons, a fast and successful attitude determination with limited satellite visibility is very significant. For land vehicles, the possible attitude candidates can be treated as a spherical zone with the center at the reference antenna and the baseline as the radius. This provides an important constraint, which can be exploited to improve the reliability of GPS single frequency and single epoch attitude determination in the case of poor satellite reception. First, we fully integrate the spherical zone constraint into the estimation procedure of ambiguity resolution, but not in the validation procedure. Combining both the coordinate domain search and the ambiguity domain search, allows development of a global minimizer of the fixed ambiguity objective function. This scheme also improves the precision of the float ambiguity solution, thus avoiding the problem of search halting. The performance of the new ambiguity resolution method was analyzed by means of several experimental tests, using simulated as well as actual GPS data in urban environments. The experimental results showed that this new, proposed method can utilize a priori spherical zone knowledge to improve the reliability of ambiguity resolution in difficult environments.

  11. Constraints on the Star Formation Efficiency of Galaxies During the Epoch of Reionization

    NASA Astrophysics Data System (ADS)

    Sun, G.; Furlanetto, S. R.

    2016-04-01

    Reionization is thought to have occurred in the redshift range of 6 < z < 9, which is now being probed by both deep galaxy surveys and CMB observations. Using halo abundance matching over the redshift range 5 < z < 8 and assuming smooth, continuous gas accretion, we develop a model for the star formation efficiency f⋆ of dark matter halos at z > 6 that matches the measured galaxy luminosity functions at these redshifts. We find that f⋆ peaks at ˜30% at halo masses M ˜ 1011-1012 M⊙, in qualitative agreement with its behavior at lower redshifts. We then investigate the cosmic star formation histories and the corresponding models of reionization for a range of extrapolations to small halo masses. We use a variety of observations to further constrain the characteristics of the galaxy populations, including the escape fraction of UV photons. Our approach provides an empirically-calibrated, physically-motivated model for the properties of star-forming galaxies sourcing the epoch of reionization. In the case where star formation in low-mass halos is maximally efficient, an average escape fraction ˜0.1 can reproduce the optical depth reported by Planck, whereas inefficient star formation in these halos requires either about twice as many UV photons to escape, or an escape fraction that increases towards higher redshifts. Our models also predict how future observations with JWST can improve our understanding of these galaxy populations.

  12. Constraining Neutrino mass using the large scale HI distribution in the Post-reionization epoch

    NASA Astrophysics Data System (ADS)

    Pal, Ashis Kumar; Guha Sarkar, Tapomoy

    2016-04-01

    The neutral intergalactic medium in the post reionization epoch allows us to study cosmological structure formation through the observation of the redshifted 21 cm signal and the Lyman-alpha forest. We investigate the possibility of measuring the total neutrino mass through the suppression of power in the matter power spectrum. We investigate the possibility of measuring the neutrino mass through its imprint on the cross-correlation power spectrum of the 21-cm signal and the Lyman-alpha forest. We consider a radio-interferometric measurement of the 21 cm signal with a SKA1-mid like radio telescope and a BOSS like Lyman-alpha forest survey. A Fisher matrix analysis shows that at the fiducial redshift z = 2.5, a 10,000 hrs 21-cm observation distributed equally over 25 radio pointings and a Lyman-alpha forest survey with 30 quasars lines of sights in 1deg2, allows us to measure Ων at a 3.25% level. A total of 25,000 hrs radio-interferometric observation distributed equally over 25 radio pointings and a Lyman-alpha survey with n¯ = 60deg-2 will allow Ων to be measured at a 2.26% level. This corresponds to an idealized measurement of ∑mν at the precision of (100 ± 2.26meV and fν = Ων/Ωm at 2.49% level.

  13. Study of redshifted H I from the epoch of reionization with drift scan

    SciTech Connect

    Paul, Sourabh; Sethi, Shiv K.; Subrahmanyan, Ravi; Shankar, N. Udaya; Dwarakanath, K. S.; Deshpande, Avinash A.; Bernardi, Gianni; Bowman, Judd D.; Briggs, Frank; Gaensler, Bryan M.; Cappallo, Roger J.; Corey, Brian E.; Goeke, Robert F.; Emrich, David; Greenhill, Lincoln J.; Kasper, Justin C.; Hazelton, Bryna J.; Hewitt, Jacqueline N.; Johnston-Hollitt, Melanie; Kaplan, David L. E-mail: sethi@rri.res.in; and others

    2014-09-20

    Detection of the epoch of reionization (EoR) in the redshifted 21 cm line is a challenging task. Here, we formulate the detection of the EoR signal using the drift scan strategy. This method potentially has better instrumental stability compared to the case where a single patch of sky is tracked. We demonstrate that the correlation time between measured visibilities could extend up to 1-2 hr for an interferometer array such as the Murchison Widefield Array, which has a wide primary beam. We estimate the EoR power based on a cross-correlation of visibilities over time and show that the drift scan strategy is capable of detecting the EoR signal with a signal to noise that is comparable/better compared to the tracking case. We also estimate the visibility correlation for a set of bright point sources and argue that the statistical inhomogeneity of bright point sources might allow their separation from the EoR signal.

  14. Late middle Eocene epoch of Libya yields earliest known radiation of African anthropoids.

    PubMed

    Jaeger, Jean-Jacques; Beard, K Christopher; Chaimanee, Yaowalak; Salem, Mustafa; Benammi, Mouloud; Hlal, Osama; Coster, Pauline; Bilal, Awad A; Duringer, Philippe; Schuster, Mathieu; Valentin, Xavier; Marandat, Bernard; Marivaux, Laurent; Métais, Eddy; Hammuda, Omar; Brunet, Michel

    2010-10-28

    Reconstructing the early evolutionary history of anthropoid primates is hindered by a lack of consensus on both the timing and biogeography of anthropoid origins. Some prefer an ancient (Cretaceous) origin for anthropoids in Africa or some other Gondwanan landmass, whereas others advocate a more recent (early Cenozoic) origin for anthropoids in Asia, with subsequent dispersal of one or more early anthropoid taxa to Africa. The oldest undoubted African anthropoid primates described so far are three species of the parapithecid Biretia from the late middle Eocene Bir El Ater locality of Algeria and the late Eocene BQ-2 site in the Fayum region of northern Egypt. Here we report the discovery of the oldest known diverse assemblage of African anthropoids from the late middle Eocene Dur At-Talah escarpment in central Libya. The primate assemblage from Dur At-Talah includes diminutive species pertaining to three higher-level anthropoid clades (Afrotarsiidae, Parapithecidae and Oligopithecidae) as well as a small species of the early strepsirhine primate Karanisia. The high taxonomic diversity of anthropoids at Dur At-Talah indicates either a much longer interval of anthropoid evolution in Africa than is currently documented in the fossil record or the nearly synchronous colonization of Africa by multiple anthropoid clades at some time during the middle Eocene epoch. PMID:20981098

  15. THE DOMINANT EPOCH OF STAR FORMATION IN THE MILKY WAY FORMED THE THICK DISK

    SciTech Connect

    Snaith, Owain N.; Haywood, Misha; Di Matteo, Paola; Katz, David; Gómez, Ana; Lehnert, Matthew D.; Combes, Françoise

    2014-02-01

    We report the first robust measurement of the Milky Way star formation history using the imprint left on chemical abundances of long-lived stars. The formation of the Galactic thick disk occurs during an intense star formation phase between 9.0 (z ∼ 1.5) and 12.5 Gyr (z ∼ 4.5) ago and is followed by a dip (at z ∼ 1.1) lasting about 1 Gyr. Our results imply that the thick disk is as massive as the Milky Way's thin disk, suggesting a fundamental role of this component in the genesis of our Galaxy, something that had been largely unrecognized. This new picture implies that huge quantities of gas necessary to feed the building of the thick disk must have been present at these epochs, in contradiction with the long-term infall assumed by chemical evolution models in the last two decades. These results allow us to fit the Milky Way within the emerging features of the evolution of disk galaxies in the early universe.

  16. Coarse Initial Orbit Determination for a Geostationary Satellite Using Single-Epoch GPS Measurements

    PubMed Central

    Kim, Ghangho; Kim, Chongwon; Kee, Changdon

    2015-01-01

    A practical algorithm is proposed for determining the orbit of a geostationary orbit (GEO) satellite using single-epoch measurements from a Global Positioning System (GPS) receiver under the sparse visibility of the GPS satellites. The algorithm uses three components of a state vector to determine the satellite’s state, even when it is impossible to apply the classical single-point solutions (SPS). Through consideration of the characteristics of the GEO orbital elements and GPS measurements, the components of the state vector are reduced to three. However, the algorithm remains sufficiently accurate for a GEO satellite. The developed algorithm was tested on simulated measurements from two or three GPS satellites, and the calculated maximum position error was found to be less than approximately 40 km or even several kilometers within the geometric range, even when the classical SPS solution was unattainable. In addition, extended Kalman filter (EKF) tests of a GEO satellite with the estimated initial state were performed to validate the algorithm. In the EKF, a reliable dynamic model was adapted to reduce the probability of divergence that can be caused by large errors in the initial state. PMID:25835299

  17. Neural correlates of rules and conflict in medial prefrontal cortex during decision and feedback epochs

    PubMed Central

    Bissonette, Gregory B.; Roesch, Matthew R.

    2015-01-01

    The ability to properly adjust behavioral responses to cues in a changing environment is crucial for survival. Activity in the medial Prefrontal Cortex (mPFC) is thought to both represent rules to guide behavior as well as detect and resolve conflicts between rules in changing contingencies. However, while lesion and pharmacological studies have supported a crucial role for mPFC in this type of set-shifting, an understanding of how mPFC represents current rules or detects and resolves conflict between different rules is unclear. Here, we directly address the role of rat mPFC in shifting rule based behavioral strategies using a novel behavioral task designed to tease apart neural signatures of rules, conflict and direction. We demonstrate that activity of single neurons in rat mPFC represent distinct rules. Further, we show increased firing on high conflict trials in a separate population of mPFC neurons. Reduced firing in both populations of neurons was associated with poor performance. Moreover, activity in both populations increased and decreased firing during the outcome epoch when reward was and was not delivered on correct and incorrect trials, respectively. In addition, outcome firing was modulated by the current rule and the degree of conflict associated with the previous decision. These results promote a greater understanding of the role that mPFC plays in switching between rules, signaling both rule and conflict to promote improved behavioral performance. PMID:26500516

  18. Superposed epoch analysis of storm time response of the ionosphere-thermosphere (IT) system

    NASA Astrophysics Data System (ADS)

    Oliveira, D. M.; Zesta, E.; Connor, H.; Su, Y. J.; Sutton, E. K.; Huang, C. Y.; Ober, D. M.; Delay, S. H.; Schuck, P. W.

    2015-12-01

    The thermosphere-ionosphere system response to energy input by Joule heating via Poynting flux and auroral precipitation is strongly intensified during times with high geomagnetic activity or during geomagnetic storms. The most dramatic thermospheric response is the intensification and upwelling of the thermospheric mass density. The neutral mass density is not only a key parameter to understanding the solar wind - IT coupling, but also plays an important role in understanding satellite orbital drag, which in turn impacts satellite position predictions. Results of numerical simulations and satellite observations (CHAMP and GRACE) have shown that the neutral mass density is rapidly intensified (within minutes) after the initial storm shock impact and also after the onset of storm main phase. This almost immediate response is typical of CME-driven storms in which the neutral density is enhanced first in the dayside polar cap and the intensification subsequently spreads out to all magnetic local time regions and lower latitude regions. We perform a superposed epoch analysis using CHAMP and GRACE satellite data as well as DMSP data to study the spatial and temporal distribution of the measured Poynting flux and neutral density response during the main phase of storms of different intensity. We also examine the correlation characteristics between Poynting flux and neutral density response, in space and time during the storm.

  19. Epochs in the depressor/pressor balance of the renin-angiotensin system.

    PubMed

    Colafella, Katrina M Mirabito; Hilliard, Lucinda M; Denton, Kate M

    2016-05-01

    The renin-angiotensin system (RAS) plays a commanding role in the regulation of extracellular fluid homoeostasis. Tigerstadt and Bergman first identified the RAS more than two centuries ago. By the 1980s a voyage of research and discovery into the mechanisms and actions of this system led to the development of drugs that block the RAS, which have become the mainstay for the treatment of cardiovascular and renal disease. In the last 25 years new components of the RAS have come to light, including the angiotensin type 2 receptor (AT2R) and the angiotensin-converting enzyme 2 (ACE2)/angiotensin-(1-7) [Ang(1-7)]/Mas receptor (MasR) axis. These have been shown to counter the classical actions of angiotensin II (AngII) at the predominant angiotensin type 1 receptor (AT1R). Our studies, and those of others, have demonstrated that targeting these depressor RAS pathways may be therapeutically beneficial. It is apparent that the evolution of both the pressor and depressor RAS pathways is distinct throughout life and that the depressor/pressor balance of the RAS vary between the sexes. These temporal patterns of expression suggest that therapies targeting the RAS could be optimized for discrete epochs in life. PMID:27128801

  20. Power spectrum extraction for redshifted 21-cm Epoch of Reionization experiments: the LOFAR case

    NASA Astrophysics Data System (ADS)

    Harker, Geraint; Zaroubi, Saleem; Bernardi, Gianni; Brentjens, Michiel A.; de Bruyn, A. G.; Ciardi, Benedetta; Jelić, Vibor; Koopmans, Leon V. E.; Labropoulos, Panagiotis; Mellema, Garrelt; Offringa, André; Pandey, V. N.; Pawlik, Andreas H.; Schaye, Joop; Thomas, Rajat M.; Yatawatta, Sarod

    2010-07-01

    One of the aims of the Low Frequency Array (LOFAR) Epoch of Reionization (EoR) project is to measure the power spectrum of variations in the intensity of redshifted 21-cm radiation from the EoR. The sensitivity with which this power spectrum can be estimated depends on the level of thermal noise and sample variance, and also on the systematic errors arising from the extraction process, in particular from the subtraction of foreground contamination. We model the extraction process using realistic simulations of the cosmological signal, the foregrounds and noise, and so estimate the sensitivity of the LOFAR EoR experiment to the redshifted 21-cm power spectrum. Detection of emission from the EoR should be possible within 360 h of observation with a single station beam. Integrating for longer, and synthesizing multiple station beams within the primary (tile) beam, then enables us to extract progressively more accurate estimates of the power at a greater range of scales and redshifts. We discuss different observational strategies which compromise between depth of observation, sky coverage and frequency coverage. A plan in which lower frequencies receive a larger fraction of the time appears to be promising. We also study the nature of the bias which foreground fitting errors induce on the inferred power spectrum and discuss how to reduce and correct for this bias. The angular and line-of-sight power spectra have different merits in this respect, and we suggest considering them separately in the analysis of LOFAR data.

  1. Toward Epoch of Reionization Measurements with Wide-Field Radio Observations

    NASA Astrophysics Data System (ADS)

    Morales, Miguel F.; Hewitt, Jacqueline

    2004-11-01

    This paper explores the potential for statistical epoch of reionization (EOR) measurements using wide-field radio observations. New developments in low-frequency radio instrumentation and signal processing allow very sensitive EOR measurements, and the analysis techniques enabled by these advances offer natural ways of separating the EOR signal from the residual foreground emission. This paper introduces the enabling technologies and proposes an analysis technique designed to make optimal use of the capabilities of next-generation low-frequency radio arrays. The observations we propose can directly observe the power spectrum of the EOR using relatively short observations and are significantly more sensitive than other techniques that have been discussed in the literature. For example, in the absence of foreground contamination the measurements we propose would produce five 3 σ power spectrum points in 100 hr of observation with only 4 MHz bandwidth with LOFAR for simple models of the high-redshift 21 cm emission. The challenge of residual foreground removal may be addressed by the symmetries in the three-dimensional (two spatial frequencies and radio frequency) radio interferometric data. These symmetries naturally separate the EOR signal from most classes of residual unsubtracted foreground contamination, including all foreground continuum sources and radio line emission from the Milky Way.

  2. An improved model of H II bubbles during the epoch of reionization

    NASA Astrophysics Data System (ADS)

    Paranjape, Aseem; Choudhury, T. Roy

    2014-08-01

    The size distribution of ionized regions during the epoch of reionization - a key ingredient in understanding the H I power spectrum observable by 21 cm experiments - can be modelled analytically using the excursion set formalism of random walks in the smoothed initial density field. To date, such calculations have been based on simplifying assumptions carried forward from the earliest excursion set models of two decades ago. In particular, these models assume that the random walks have uncorrelated steps and that haloes can form at arbitrary locations in the initial density field. We extend these calculations by incorporating recent technical developments that allow us to (a) include the effect of correlations in the steps of the walks induced by a realistic smoothing filter and (b) more importantly, account for the fact that dark matter haloes preferentially form near peaks in the initial density. A comparison with previous calculations shows that including these features, particularly the peaks constraint on halo locations, has large effects on the size distribution of the H II bubbles surrounding these haloes. For example, when comparing models at the same value of the globally averaged ionized volume fraction, the typical bubble sizes predicted by our model are more than a factor of 2 larger than earlier calculations. Our results can potentially have a significant impact on estimates of the observable H I power spectrum.

  3. The Intricate Role of Cold Gas and Dust in Galaxy Evolution at Early Cosmic Epochs

    NASA Astrophysics Data System (ADS)

    Riechers, Dominik A.; Capak, Peter L.; Carilli, Christopher L.

    Cold molecular and atomic gas plays a central role in our understanding of early galaxy formation and evolution. It represents the component of the interstellar medium (ISM) that stars form out of, and its mass, distribution, excitation, and dynamics provide crucial insight into the physical processes that support the ongoing star formation and stellar mass buildup. We here present results that demonstrate the capability of the Atacama Large (sub-)Millimeter Array (ALMA) to detect the cold ISM and dust in ``normal'' galaxies at redshifts z=5-6. We also show detailed studies of the ISM in massive, dust-obscured starburst galaxies out to z>6 with ALMA, the Combined Array for Research in Millimeter-wave Astronomy (CARMA), the Plateau de Bure Interferometer (PdBI), and the Karl G. Jansky Very Large Array (VLA). These observations place some of the most direct constraints on the dust-obscured fraction of the star formation history of the universe at z>5 to date, showing that ``typical'' galaxies at these epochs have low dust content, but also that highly-enriched, dusty starbursts already exist within the first billion years after the Big Bang.

  4. On the latitudinal distribution of Titan's haze at the Voyager epoch

    NASA Astrophysics Data System (ADS)

    Negrao, A.; Roos-Serote, M.; Rannou, P.; Rages, K.; McKay, C.

    2002-09-01

    In this work, we re-analyse a total of 10 high phase angle images of Titan (2 from Voyager 1 and 8 from Voyager 2). The images were acquired in different filters of the Voyager Imaging Sub System in 1980 - 1981. We apply a model, developed and used by Rannou etal. (1997) and Cabane etal. (1992), that calculates the vertical (1-D) distribution of haze particles and the I/F radial profiles as a function of a series of parameters. Two of these parameters, the haze particle production rate (P) and imaginary refractive index (xk), are used to obtain fits to the observed I/F profiles at different latitudes. Differerent from previous studies is that we consider all filters simultaneously, in an attempt to better fix the parameter values. We also include the filter response functions, not considered previously. The results show that P does not change significantly as a function of latitude, eventhough somewhat lower values are found at high northern latitudes. xk seems to increase towards southern latitudes. We will compare our results with GCM runs, that can give the haze distribution at the epoch of the observations. Work financed by portuguese Foundation for Science and Tecnology (FCT), contract ESO/PRO/40157/2000

  5. ARE OUTFLOWS BIASING SINGLE-EPOCH C IV BLACK HOLE MASS ESTIMATES?

    SciTech Connect

    Denney, K. D.

    2012-11-01

    We use a combination of reverberation mapping data and single-epoch (SE) spectra of the C IV emission line in a sample of both low- and high-redshift active galactic nuclei to investigate sources of the discrepancies between C IV- and H{beta}-based SE black hole (BH) mass estimates. We find that for all reverberation mapped sources, there is a component of the line profile that does not reverberate, and the velocity characteristics of this component vary from object to object. The differing strength and properties of this non-variable component are responsible for much of the scatter in C IV-based BH masses compared to H{beta} masses. The C IV mass bias introduced by this non-variable component is correlated with the shape of the C IV line, allowing us to make an empirical correction to the BH mass estimates. Using this correction and accounting for other sources of scatter, such as poor data quality and data inhomogeneity, reduces the scatter between the C IV and H{beta} masses in our sample by a factor of {approx}2, to only {approx}0.2 dex. We discuss the possibility that this non-variable C IV component originates in an orientation-dependent outflow from either the proposed broad-line region disk wind or the intermediate-line region, a high-velocity inner extension of the narrow-line region.

  6. Constraints on the star formation efficiency of galaxies during the epoch of reionization

    NASA Astrophysics Data System (ADS)

    Sun, G.; Furlanetto, S. R.

    2016-07-01

    Reionization is thought to have occurred in the redshift range of 6 < z < 9, which is now being probed by both deep galaxy surveys and CMB observations. Using halo abundance matching over the redshift range 5 < z < 8 and assuming smooth, continuous gas accretion, we develop a model for the star formation efficiency f⋆ of dark matter haloes at z > 6 that matches the measured galaxy luminosity functions at these redshifts. We find that f⋆ peaks at ˜30 per cent at halo masses M ˜ 1011-1012 M⊙, in qualitative agreement with its behaviour at lower redshifts. We then investigate the cosmic star formation histories and the corresponding models of reionization for a range of extrapolations to small halo masses. We use a variety of observations to further constrain the characteristics of the galaxy populations, including the escape fraction of UV photons. Our approach provides an empirically calibrated, physically motivated model for the properties of star-forming galaxies sourcing the epoch of reionization. In the case where star formation in low-mass haloes is maximally efficient, an average escape fraction ˜0.1 can reproduce the optical depth reported by Planck, whereas inefficient star formation in these haloes requires either about twice as many UV photons to escape, or an escape fraction that increases towards higher redshifts. Our models also predict how future observations with James Webb Space Telescope can improve our understanding of these galaxy populations.

  7. Studying populations of eclipsing binaries using large scale multi-epoch photometric surveys

    NASA Astrophysics Data System (ADS)

    Mowlavi, Nami; Barblan, Fabio; Holl, Berry; Rimoldini, Lorenzo; Lecoeur-Taïbi, Isabelle; Süveges, Maria; Eyer, Laurent; Guy, Leanne; Nienartowicz, Krzysztof; Ordonez, Diego; Charnas, Jonathan; Jévardat de Fombelle, Grégory

    2015-08-01

    Large scale multi-epoch photometric surveys provide unique opportunities to study populations of binary stars through the study of eclipsing binaries, provided the basic properties of binary systems can be derived from their light curves without the need to fully model the binary system. Those systems can then be classified into various types from, for example, close to wide systems, from circular to highly elliptical systems, or from systems with similar components to highly asymmetric systems. The challenge is to extract physically relevant information from the light curve geometry.In this contribution, we present the study of eclipsing binaries in the Large Magellanic Clouds (LMC) from the OGLE-III survey. The study is based on the analysis of the geometry of their light curves parameterized using a two-Gaussian model. We show what physical parameters could be extracted from such an analysis, and the results for the LMC eclipsing binaries. The method is very well adapted to process large-scale surveys containing millions of eclipsing binaries, such as is expected from the current Gaia mission or the future LSST survey.

  8. FIVE NEW TRANSIT EPOCHS OF THE EXOPLANET OGLE-TR-111b

    SciTech Connect

    Hoyer, S.; Rojo, P.; Lopez-Morales, M.; DIaz, R. F.; Chambers, J.; Minniti, D. E-mail: pato@das.uchile.cl E-mail: diaz@iap.fr E-mail: dante@astro.puc.cl

    2011-05-20

    We report five new transit epochs of the extrasolar planet OGLE-TR-111b, observed in the v-HIGH and Bessell I bands with the FORS1 and FORS2 at the ESO Very Large Telescope between 2008 April and May. The new transits have been combined with all previously published transit data for this planet to provide a new transit timing variations (TTVs) analysis of its orbit. We find no TTVs with amplitudes larger than 1.5 minutes over a four-year observation time baseline, in agreement with the recent result by Adams et al. Dynamical simulations fully exclude the presence of additional planets in the system with masses greater than 1.3, 0.4, and 0.5 M{sub +} at the 3:2, 1:2, and 2:1 resonances, respectively. We also place an upper limit of about 30 M{sub +} on the mass of potential second planets in the region between the 3:2 and 1:2 mean-motion resonances.

  9. Thermokarst, mantling and Late Amazonian Epoch periglacial-revisions in the Argyre region, Mars

    NASA Astrophysics Data System (ADS)

    Soare, R. J.; Baoini, D.; Conway, S. J.; Dohm, J. M.; Kargel, J. S.

    2015-10-01

    Thermokarst, mantling and Late Amazonian Epoch periglacial-revisions in the Argyre region, Mars R.J. Soare(1), D. Baioni(2), S.J. Conway (3), J.M. Dohm(4)and J.S. Kargel (5)(1) Geography Department, Dawson College, Montreal, Canada H3Z 1A4 rsoare@dawsoncollege.qc.ca.(2) Dipartimento di Scienze della Terra,della Vita e Ambiente, Università di Urbino "Carlo Bo", Campus SOGESTA, 61029 Urbino (PU) Italy. (3) Department of Physical Sciences, Open University, Milton Keynes, United Kingdom, MK7 6AA. (4) The University Museum, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-, Japan.(5) Department of Hydrology & Water Resources, University of Arizona, Tucson, Arizona, USA 85719.1.Introduction Metre to decametre-deep depressions that are rimless, relatively flat-floored, polygonised and scallop-shaped have been widely observed in Utopia Planitia (UP) [e.g. 1-5] and Malea Planum (MP) [6-8]. Although there is some debate about whether the depressions formed by means of sublimation or evaporation, it is commonly believed that the terrain in which the depressions occur is ice-rich.Moreover, most workers assume that this "ice-richness" is derived of a bi-hemispheric, latitudinally-dependent and atmospherically-precipitated mantle that is metres thick [2,4,6-10].

  10. Second Epoch Hubble Space Telescope Observations of Kepler's Supernova Remnant: The Proper Motions of Balmer Filaments

    NASA Astrophysics Data System (ADS)

    Sankrit, Ravi; Raymond, John C.; Blair, William P.; Long, Knox S.; Williams, Brian J.; Borkowski, Kazimierz J.; Patnaude, Daniel J.; Reynolds, Stephen P.

    2016-01-01

    We report on the proper motions of Balmer-dominated filaments in Kepler’s supernova remnant using high resolution images obtained with the Hubble Space Telescope at two epochs separated by about 10 years. We use the improved proper motion measurements and revised values of shock velocities to derive a distance to Kepler of {5.1}-0.7+0.8 kpc. The main shock around the northern rim of the remnant has a typical speed of 1690 km s-1 and is encountering material with densities of about 8 cm-3. We find evidence for the variation of shock properties over small spatial scales, including differences in the driving pressures as the shock wraps around a curved cloud surface. We find that the Balmer filaments ahead of the ejecta knot on the northwest boundary of the remnant are becoming fainter and more diffuse. We also find that the Balmer filaments associated with circumstellar material in the interior regions of the remnant are due to shocks with significantly lower velocities and that the brightness variations among these filaments trace the density distribution of the material, which may have a disk-like geometry. Based on observations made with the Hubble Space Telescope.

  11. Diverse properties of interstellar medium embedding gamma-ray bursts at the epoch of reionization

    SciTech Connect

    Cen, Renyue; Kimm, Taysun

    2014-10-10

    Analysis is performed on ultra-high-resolution large-scale cosmological radiation-hydrodynamic simulations to quantify, for the first time, the physical environment of long-duration gamma-ray bursts (GRBs) at the epoch of reionization. We find that, on parsec scales, 13% of GRBs remain in high-density (≥10{sup 4} cm{sup –3}) low-temperature star-forming regions, whereas 87% of GRBs occur in low-density (∼10{sup –2.5} cm{sup –3}) high-temperature regions heated by supernovae. More importantly, the spectral properties of GRB afterglows, such as the neutral hydrogen column density, total hydrogen column density, dust column density, gas temperature, and metallicity of intervening absorbers, vary strongly from sight line to sight line. Although our model explains extant limited observationally inferred values with respect to circumburst density, metallicity, column density, and dust properties, a substantially larger sample of high-z GRB afterglows would be required to facilitate a statistically solid test of the model. Our findings indicate that any attempt to infer the physical properties (such as metallicity) of the interstellar medium (ISM) of the host galaxy based on a very small number (usually one) of sight lines would be precarious. Utilizing high-z GRBs to probe the ISM and intergalactic medium should be undertaken properly, taking into consideration the physical diversities of the ISM.

  12. H I absorption from the epoch of reionization and primordial magnetic fields

    SciTech Connect

    Vasiliev, Evgenii O.; Sethi, Shiv K.

    2014-05-10

    We study the impact of primordial magnetic fields on the H I absorption from the epoch of reionization. The presence of these fields results in two distinct effects: (1) the heating of the halos from the decay of the magnetic fields owing to ambipolar diffusion, and (2) an increase in the number of halos owing to additional matter fluctuations induced by magnetic fields. We analyze both of these effects and show that the latter is potentially observable because the number of halos along of line of sight can increase by many orders of magnitude. While this effect is not strongly dependent on the magnetic field strength in the range 0.3-0.6 nG, it is extremely sensitive to the magnetic field power spectral index for the near scale-free models. Therefore, the detection of such absorption features could be a sensitive probe of the primordial magnetic field and its power spectrum. We discuss the detectability of these features with the ongoing and future radio interferometers. In particular, we show that LOFAR might be able to detect these absorption features at z ≅ 10 in less than 10 hr of integration if the flux of the background source is 400 mJy.

  13. ARECIBO MULTI-EPOCH H I ABSORPTION MEASUREMENTS AGAINST PULSARS: TINY-SCALE ATOMIC STRUCTURE

    SciTech Connect

    Stanimirovic, S.; Weisberg, J. M.; Pei, Z.; Tuttle, K.; Green, J. T.

    2010-09-01

    We present results from multi-epoch neutral hydrogen (H I) absorption observations of six bright pulsars with the Arecibo telescope. Moving through the interstellar medium (ISM) with transverse velocities of 10-150 AU yr{sup -1}, these pulsars have swept across 1-200 AU over the course of our experiment, allowing us to probe the existence and properties of the tiny-scale atomic structure (TSAS) in the cold neutral medium (CNM). While most of the observed pulsars show no significant change in their H I absorption spectra, we have identified at least two clear TSAS-induced opacity variations in the direction of B1929+10. These observations require strong spatial inhomogeneities in either the TSAS clouds' physical properties themselves or else in the clouds' galactic distribution. While TSAS is occasionally detected on spatial scales down to 10 AU, it is too rare to be characterized by a spectrum of turbulent CNM fluctuations on scales of 10{sup 1}-10{sup 3} AU, as previously suggested by some work. In the direction of B1929+10, an apparent correlation between TSAS and interstellar clouds inside the warm Local Bubble (LB) indicates that TSAS may be tracing the fragmentation of the LB wall via hydrodynamic instabilities. While similar fragmentation events occur frequently throughout the ISM, the warm medium surrounding these cold cloudlets induces a natural selection effect wherein small TSAS clouds evaporate quickly and are rare, while large clouds survive longer and become a general property of the ISM.

  14. The Hubble Expansion is Isotropic in the Epoch of Dark Energy

    NASA Astrophysics Data System (ADS)

    Darling, Jeremy

    2015-01-01

    The isotropy of the universal Hubble expansion is a fundamental tenet of physical cosmology, but it has not been precisely tested during the current epoch, when dark energy is dominant. Anisotropic expansion will produce a shearing velocity field, causing objects to stream toward directions of faster expansion and away from directions of slower expansion. This work tests the basic cosmological assumption of isotropic expansion and thus the isotropy of dark energy. The simplest anisotropy will manifest as a quadrupolar curl-free proper motion vector field. We derive this theoretical signature using a tri-axial expanding metric with a flat geometry (Bianchi I model), generalizing and correcting previous work. We then employ the best current data, the Titov & Lambert [1] proper motion catalog of 429 objects, to measure the isotropy of universal expansion. We demonstrate that the Hubble expansion is isotropic to 7% (1 sigma), corresponding to streaming motions of 1 microarcsecond per year, in the best-constrained directions (-19% and +17% in the least-constrained directions) and does not significantly deviate from isotropy in any direction. The Gaia mission, which is expected to obtain proper motions for 500,000 quasars, will likely constrain the anisotropy below 1%, but this is still orders of magnitude larger than the history-integrated anisotropy constraint provided by the cosmic microwave background.We acknowledge support from the NSF grant AST-1411605.[1] Titov, O. & Lambert, S. 2013, A&A, 559, A95

  15. MULTI-EPOCH OBSERVATIONS OF THE RED WING EXCESS IN THE SPECTRUM OF 3C 279

    SciTech Connect

    Punsly, Brian E-mail: brian.punsly@comdev-usa.com

    2013-01-10

    It has been previously determined that there is a highly significant correlation between the spectral index from 10 GHz to 1350 A and the amount of excess luminosity in the red wing of quasar C IV {lambda}1549 broad emission lines (BELs). Ostensibly, the prominence of the red excess is associated with the radio jet emission mechanism and is most pronounced for lines of sight close to the jet axis. Studying the scant significant differences in the UV spectra of radio-loud and radio-quiet quasars might provide vital clues to the origin of the unknown process that creates powerful relativistic jets that appear in only about 10% of quasars. In this study, the phenomenon is explored with multi-epoch observations of the Mg II {lambda}2798 broad line in 3C 279 which has one of the largest known red wing excesses in a quasar spectrum. The amount of excess that is detected appears to be independent of all directly observed optical continuum, radio, or submillimeter properties (fluxes or polarizations). The only trend that occurs in this sparse data is: the stronger the BEL, the larger the fraction of flux that resides in the red wing. It is concluded that more monitoring is needed and spectropolarimetry with a large telescope is essential during low states to understand more.

  16. Foreground contamination in Lyα intensity mapping during the epoch of reionization

    SciTech Connect

    Gong, Yan; Cooray, Asantha; Silva, Marta; Santos, Mario G.

    2014-04-10

    The intensity mapping of Lyα emission during the epoch of reionization will be contaminated by foreground emission lines from lower redshifts. We calculate the mean intensity and the power spectrum of Lyα emission at z ∼ 7 and estimate the uncertainties according to the relevant astrophysical processes. We find that the low-redshift emission lines from 6563 Å Hα, 5007 Å [O III], and 3727 Å [O II] will be strong contaminants on the observed Lyα power spectrum. We make use of both the star formation rate and luminosity functions to estimate the mean intensity and power spectra of the three foreground lines at z ∼ 0.5 for Hα, z ∼ 0.9 for [O III], and z ∼ 1.6 for [O II], as they will contaminate the Lyα emission at z ∼ 7. The [O II] line is found to be the strongest. We analyze the masking of the bright survey pixels with a foreground line above some line intensity threshold as a way to reduce the contamination in an intensity mapping survey. We find that the foreground contamination can be neglected if we remove pixels with fluxes above 1.4 × 10{sup –20} W m{sup –2}.

  17. A LYMAN BREAK GALAXY IN THE EPOCH OF REIONIZATION FROM HUBBLE SPACE TELESCOPE GRISM SPECTROSCOPY

    SciTech Connect

    Rhoads, James E.; Malhotra, Sangeeta; Cohen, Seth; Zheng Zhenya; Stern, Daniel; Dickinson, Mark; Pirzkal, Norbert; Grogin, Norman; Koekemoer, Anton; Peth, Michael A.; Spinrad, Hyron; Reddy, Naveen; Hathi, Nimish; Budavari, Tamas; Ferreras, Ignacio; Gardner, Jonathan P.; Gronwall, Caryl; Haiman, Zoltan; Kuemmel, Martin; Meurer, Gerhardt; and others

    2013-08-10

    We present observations of a luminous galaxy at z = 6.573-the end of the reionization epoch-which has been spectroscopically confirmed twice. The first spectroscopic confirmation comes from slitless Hubble Space Telescope Advanced Camera for Surveys grism spectra from the PEARS survey (Probing Evolution And Reionization Spectroscopically), which show a dramatic continuum break in the spectrum at rest frame 1216 A. The second confirmation is done with Keck + DEIMOS. The continuum is not clearly detected with ground-based spectra, but high wavelength resolution enables the Ly{alpha} emission line profile to be determined. We compare the line profile to composite line profiles at z = 4.5. The Ly{alpha} line profile shows no signature of a damping wing attenuation, confirming that the intergalactic gas is ionized at z = 6.57. Spectra of Lyman breaks at yet higher redshifts will be possible using comparably deep observations with IR-sensitive grisms, even at redshifts where Ly{alpha} is too attenuated by the neutral intergalactic medium to be detectable using traditional spectroscopy from the ground.

  18. Analysis of short single rest/activation epoch fMRI by self-organizing map neural network

    NASA Astrophysics Data System (ADS)

    Erberich, Stephan G.; Dietrich, Thomas; Kemeny, Stefan; Krings, Timo; Willmes, Klaus; Thron, Armin; Oberschelp, Walter

    2000-04-01

    Functional magnet resonance imaging (fMRI) has become a standard non invasive brain imaging technique delivering high spatial resolution. Brain activation is determined by magnetic susceptibility of the blood oxygen level (BOLD effect) during an activation task, e.g. motor, auditory and visual tasks. Usually box-car paradigms have 2 - 4 rest/activation epochs with at least an overall of 50 volumes per scan in the time domain. Statistical test based analysis methods need a large amount of repetitively acquired brain volumes to gain statistical power, like Student's t-test. The introduced technique based on a self-organizing neural network (SOM) makes use of the intrinsic features of the condition change between rest and activation epoch and demonstrated to differentiate between the conditions with less time points having only one rest and one activation epoch. The method reduces scan and analysis time and the probability of possible motion artifacts from the relaxation of the patients head. Functional magnet resonance imaging (fMRI) of patients for pre-surgical evaluation and volunteers were acquired with motor (hand clenching and finger tapping), sensory (ice application), auditory (phonological and semantic word recognition task) and visual paradigms (mental rotation). For imaging we used different BOLD contrast sensitive Gradient Echo Planar Imaging (GE-EPI) single-shot pulse sequences (TR 2000 and 4000, 64 X 64 and 128 X 128, 15 - 40 slices) on a Philips Gyroscan NT 1.5 Tesla MR imager. All paradigms were RARARA (R equals rest, A equals activation) with an epoch width of 11 time points each. We used the self-organizing neural network implementation described by T. Kohonen with a 4 X 2 2D neuron map. The presented time course vectors were clustered by similar features in the 2D neuron map. Three neural networks were trained and used for labeling with the time course vectors of one, two and all three on/off epochs. The results were also compared by using a

  19. Effects of Varying Epoch Lengths, Wear Time Algorithms, and Activity Cut-Points on Estimates of Child Sedentary Behavior and Physical Activity from Accelerometer Data

    PubMed Central

    Banda, Jorge A.; Haydel, K. Farish; Davila, Tania; Desai, Manisha; Haskell, William L.; Matheson, Donna; Robinson, Thomas N.

    2016-01-01

    Objective To examine the effects of accelerometer epoch lengths, wear time (WT) algorithms, and activity cut-points on estimates of WT, sedentary behavior (SB), and physical activity (PA). Methods 268 7–11 year-olds with BMI ≥ 85th percentile for age and sex wore accelerometers on their right hips for 4–7 days. Data were processed and analyzed at epoch lengths of 1-, 5-, 10-, 15-, 30-, and 60-seconds. For each epoch length, WT minutes/day was determined using three common WT algorithms, and minutes/day and percent time spent in SB, light (LPA), moderate (MPA), and vigorous (VPA) PA were determined using five common activity cut-points. ANOVA tested differences in WT, SB, LPA, MPA, VPA, and MVPA when using the different epoch lengths, WT algorithms, and activity cut-points. Results WT minutes/day varied significantly by epoch length when using the NHANES WT algorithm (p < .0001), but did not vary significantly by epoch length when using the ≥ 20 minute consecutive zero or Choi WT algorithms. Minutes/day and percent time spent in SB, LPA, MPA, VPA, and MVPA varied significantly by epoch length for all sets of activity cut-points tested with all three WT algorithms (all p < .0001). Across all epoch lengths, minutes/day and percent time spent in SB, LPA, MPA, VPA, and MVPA also varied significantly across all sets of activity cut-points with all three WT algorithms (all p < .0001). Conclusions The common practice of converting WT algorithms and activity cut-point definitions to match different epoch lengths may introduce significant errors. Estimates of SB and PA from studies that process and analyze data using different epoch lengths, WT algorithms, and/or activity cut-points are not comparable, potentially leading to very different results, interpretations, and conclusions, misleading research and public policy. PMID:26938240

  20. Beam-Plasma Interaction and Nonlinear Effects

    SciTech Connect

    Yoon, Peter H.

    2009-11-10

    This paper presents a survey of perturbative nonlinear plasma theory known as the weak turbulence theory. After the basic concepts and methodology of the weak turbulence theory are outlined in sufficient detail, numerical solutions of the weak turbulence theory obtained in the context of the beam-plasma interaction are compared against particle-in-cell (PIC) numerical simulations. It is demonstrated that theory and PIC simulation are in excellent agreement.