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Sample records for accelerating cosmic expansion

  1. Nuclear Fusion Drives Present-Day Accelerated Cosmic Expansion

    SciTech Connect

    Ying, Leong

    2010-09-30

    The widely accepted model of our cosmos is that it began from a Big Bang event some 13.7 billion years ago from a single point source. From a twin universe perspective, the standard stellar model of nuclear fusion can account for the Dark Energy needed to explain the mechanism for our present-day accelerated expansion. The same theories can also be used to account for the rapid inflationary expansion at the earliest time of creation, and predict the future cosmic expansion rate.

  2. Cosmic accelerated expansion and the entropy-corrected holographic dark energy

    NASA Astrophysics Data System (ADS)

    Sadjadi, H. Mohseni; Jamil, Mubasher

    2011-06-01

    By considering the logarithmic correction to the energy density, we study the behavior of Hubble parameter in the holographic dark energy model. We assume that the universe is dominated by interacting dark energy and matter and the accelerated expansion of the universe, which may be occurred in the early universe or late time, is studied.

  3. Yang-Mills Gravity in Flat Space-Time II:. Gravitational Radiations and Lee-Yang Force for Accelerated Cosmic Expansion

    NASA Astrophysics Data System (ADS)

    Hsu, Jong-Ping

    Within Yang-Mills gravity with translation group T(4) in flat space-time, the invariant action involving quadratic translation gauge-curvature leads to quadrupole radiations, which are shown to be consistent with experiments. The radiation power turns out to be the same as that in Einstein's gravity to the second-order approximation. We also discuss an interesting physical reason for the accelerated cosmic expansion based on the long-range Lee-Yang force of Ub(1) gauge field associated with the established conservation law of baryon number. We show that the Lee-Yang force can be related to a linear potential ∝ r, provided the gauge field satisfies a fourth-order differential equation in flat space-time. Furthermore, we consider an experimental test of the Lee-Yang force related to the accelerated cosmic expansion. The necessity of generalizing Lorentz transformations for accelerated frames of reference and accelerated Wu-Doppler effects are briefly discussed.

  4. On the emergence of accelerating cosmic expansion in f (R ) theories of gravity

    NASA Astrophysics Data System (ADS)

    Clifton, Timothy; Dunsby, Peter K. S.

    2015-05-01

    We consider cosmological modeling in f (R ) theories of gravity, using both top-down and bottom-up constructions. The top-down models are based on Robertson-Walker geometries, and the bottom-up constructions are built by patching together subhorizon-sized regions of perturbed Minkowski space. Our results suggest that these theories do not provide a theoretically attractive alternative to the standard general relativistic cosmology. We find that the only f (R ) theories that can admit an observationally viable weak-field limit have large-scale expansions that are observationally indistinguishable from the Friedmann solutions of general relativity with Λ . Such theories do not alleviate any of the difficulties associated with Λ , and cannot produce any new behavior in the cosmological expansion without simultaneously destroying the Newtonian approximation to gravity on small scales.

  5. Is cosmic acceleration slowing down?

    SciTech Connect

    Shafieloo, Arman; Sahni, Varun; Starobinsky, Alexei A.

    2009-11-15

    We investigate the course of cosmic expansion in its recent past using the Constitution SN Ia sample, along with baryon acoustic oscillations (BAO) and cosmic microwave background (CMB) data. Allowing the equation of state of dark energy (DE) to vary, we find that a coasting model of the universe (q{sub 0}=0) fits the data about as well as Lambda cold dark matter. This effect, which is most clearly seen using the recently introduced Om diagnostic, corresponds to an increase of Om and q at redshifts z < or approx. 0.3. This suggests that cosmic acceleration may have already peaked and that we are currently witnessing its slowing down. The case for evolving DE strengthens if a subsample of the Constitution set consisting of SNLS+ESSENCE+CfA SN Ia data is analyzed in combination with BAO+CMB data. The effect we observe could correspond to DE decaying into dark matter (or something else)

  6. Cosmic Plasma Wakefield Acceleration

    NASA Astrophysics Data System (ADS)

    Chen, Pisin; Tajima, Toshiki; Takahashi, Yoshiyuki

    2002-10-01

    A cosmic acceleration mechanism is introduced which is based on the wakefields excited by the Alfven shocks in a relativistically flowing plasma. We show that there exists a threshold condition for transparency below which the accelerating particle is collision-free and suffers little energy loss in the plasma medium. The stochastic encounters of the random accelerating-decelerating phases results in a power-law energy spectrum: f([epsilon]) [is proportional to] 1/[epsilon]2. As an example, we discuss the possible production of super-GZK ultra high energy cosmic rays (UHECR) in the atmosphere of gamma ray bursts. The estimated event rate in our model agrees with that from UHECR observations. [copyright] 2002 American Institute of Physics

  7. Cosmic expansion in extended quasidilaton massive gravity

    NASA Astrophysics Data System (ADS)

    Kahniashvili, Tina; Kar, Arjun; Lavrelashvili, George; Agarwal, Nishant; Heisenberg, Lavinia; Kosowsky, Arthur

    2015-02-01

    Quasidilaton massive gravity offers a physically well-defined gravitational theory with nonzero graviton mass. We present the full set of dynamical equations governing the expansion history of the Universe, valid during radiation domination, matter domination, and a late-time self-accelerating epoch related to the graviton mass. The existence of self-consistent solutions constrains the amplitude of the quasidilaton field and the graviton mass, as well as other model parameters. We point out that the effective mass of gravitational waves can be significantly larger than the graviton mass, opening the possibility that a single theory can explain both the late-time acceleration of cosmic expansion and modifications of structure growth leading to the suppression of large-angle correlations observed in the cosmic microwave background.

  8. Accelerated expansion of the Universe as the most powerful source of the energy release in cosmic objects

    NASA Astrophysics Data System (ADS)

    Harutyunian, H. A.

    2014-12-01

    The available data on the expansion effects in the shorter scales are considered. It is mentioned that the prevailing opinion on the gravitationally bound states of the short-scale physical systems like solar system or galaxies is not provable but results from the a priori accepted ideas of their formation due to condensation. On the contrary, a lot of observational data speaks in favor of existence of Hubble expansion for all the scales. Some estimates of gravitational energy accumulation in cosmic objects owing to dark energy physical work are done. These estimates show that a cluster of galaxies could be formed from a pre-cluster via matter ejection during the Hubble time.

  9. Observational probes of cosmic acceleration

    NASA Astrophysics Data System (ADS)

    Weinberg, David H.; Mortonson, Michael J.; Eisenstein, Daniel J.; Hirata, Christopher; Riess, Adam G.; Rozo, Eduardo

    2013-09-01

    The accelerating expansion of the universe is the most surprising cosmological discovery in many decades, implying that the universe is dominated by some form of “dark energy” with exotic physical properties, or that Einstein’s theory of gravity breaks down on cosmological scales. The profound implications of cosmic acceleration have inspired ambitious efforts to understand its origin, with experiments that aim to measure the history of expansion and growth of structure with percent-level precision or higher. We review in detail the four most well established methods for making such measurements: Type Ia supernovae, baryon acoustic oscillations (BAO), weak gravitational lensing, and the abundance of galaxy clusters. We pay particular attention to the systematic uncertainties in these techniques and to strategies for controlling them at the level needed to exploit “Stage IV” dark energy facilities such as BigBOSS, LSST, Euclid, and WFIRST. We briefly review a number of other approaches including redshift-space distortions, the Alcock-Paczynski effect, and direct measurements of the Hubble constant H0. We present extensive forecasts for constraints on the dark energy equation of state and parameterized deviations from General Relativity, achievable with Stage III and Stage IV experimental programs that incorporate supernovae, BAO, weak lensing, and cosmic microwave background data. We also show the level of precision required for clusters or other methods to provide constraints competitive with those of these fiducial programs. We emphasize the value of a balanced program that employs several of the most powerful methods in combination, both to cross-check systematic uncertainties and to take advantage of complementary information. Surveys to probe cosmic acceleration produce data sets that support a wide range of scientific investigations, and they continue the longstanding astronomical tradition of mapping the universe in ever greater detail over ever

  10. Accelerating the loop expansion

    SciTech Connect

    Ingermanson, R.

    1986-07-29

    This thesis introduces a new non-perturbative technique into quantum field theory. To illustrate the method, I analyze the much-studied phi/sup 4/ theory in two dimensions. As a prelude, I first show that the Hartree approximation is easy to obtain from the calculation of the one-loop effective potential by a simple modification of the propagator that does not affect the perturbative renormalization procedure. A further modification then susggests itself, which has the same nice property, and which automatically yields a convex effective potential. I then show that both of these modifications extend naturally to higher orders in the derivative expansion of the effective action and to higher orders in the loop-expansion. The net effect is to re-sum the perturbation series for the effective action as a systematic ''accelerated'' non-perturbative expansion. Each term in the accelerated expansion corresponds to an infinite number of terms in the original series. Each term can be computed explicitly, albeit numerically. Many numerical graphs of the various approximations to the first two terms in the derivative expansion are given. I discuss the reliability of the results and the problem of spontaneous symmetry-breaking, as well as some potential applications to more interesting field theories. 40 refs.

  11. Cosmic acceleration and Brans-Dicke theory

    SciTech Connect

    Sharif, M. Waheed, S.

    2012-10-15

    We study the accelerated expansion of the universe by exploring the Brans-Dicke parameter in different eras. For this, we take the FRW universe model with a viscous fluid (without potential) and the Bianchi type-I universe model with a barotropic fluid (with and without a potential). We evaluate the deceleration parameter and the Brans-Dicke parameter to explore cosmic acceleration. It is concluded that accelerated expansion of the universe can also be achieved for higher values of the Brans-Dicke parameter in some cases.

  12. Cosmic ray antiprotons from nearby cosmic accelerators

    NASA Astrophysics Data System (ADS)

    Joshi, Jagdish C.; Gupta, Nayantara

    2015-05-01

    The antiproton flux measured by PAMELA experiment might have originated from Galactic sources of cosmic rays. These antiprotons are expected to be produced in the interactions of cosmic ray protons and nuclei with cold protons. Gamma rays are also produced in similar interactions inside some of the cosmic accelerators. We consider a few nearby supernova remnants observed by Fermi LAT. Many of them are associated with molecular clouds. Gamma rays have been detected from these sources which most likely originate in decay of neutral pions produced in hadronic interactions. The observed gamma ray fluxes from these SNRs are used to find out their contributions to the observed diffuse cosmic ray antiproton flux near the earth.

  13. Gravitational entropy of cosmic expansion

    NASA Astrophysics Data System (ADS)

    Sussman , R. A.

    2014-09-01

    We apply a recent proposal to define ``gravitational entropy'' to the expansion of cosmic voids within the framework of non-perturbative General Relativity. By considering CDM void configurations compatible with basic observational constraints, we show that this entropy grows from post-inflationary conditions towards a final asymptotic value in a late time fully non-linear regime described by the Lemaître- Tolman-Bondi (LTB) dust models. A qualitatively analogous behavior occurs if we assume a positive cosmological constant consistent with a Λ-CDM background model. However, the Λ term introduces a significant suppression of entropy growth with the terminal equilibrium value reached at a much faster rate.

  14. Hot Spot Cosmic Accelerators

    NASA Astrophysics Data System (ADS)

    2002-11-01

    length of more than 3 million light-years, or no less than one-and-a-half times the distance from the Milky Way to the Andromeda galaxy, this structure is indeed gigantic. The region where the jets collide with the intergalactic medium are known as " hot spots ". Superposing the intensity contours of the radio emission from the southern "hot spot" on a near-infrared J-band (wavelength 1.25 µm) VLT ISAAC image ("b") shows three distinct emitting areas; they are even better visible on the I-band (0.9 µm) FORS1 image ("c"). This emission is obviously associated with the shock front visible on the radio image. This is one of the first times it has been possible to obtain an optical/near-IR image of synchrotron emission from such an intergalactic shock and, thanks to the sensitivity and image sharpness of the VLT, the most detailed view of its kind so far . The central area (with the strongest emission) is where the plasma jet from the galaxy centre hits the intergalactic medium. The light from the two other "knots", some 10 - 15,000 light-years away from the central "hot spot", is also interpreted as synchrotron emission. However, in view of the large distance, the astronomers are convinced that it must be caused by electrons accelerated in secondary processes at those sites . The new images thus confirm that electrons are being continuously accelerated in these "knots" - hence called "cosmic accelerators" - far from the galaxy and the main jets, and in nearly empty space. The exact physical circumstances of this effect are not well known and will be the subject of further investigations. The present VLT-images of the "hot spots" near 3C 445 may not have the same public appeal as some of those beautiful images that have been produced by the same instruments during the past years. But they are not less valuable - their unusual importance is of a different kind, as they now herald the advent of fundamentally new insights into the mysteries of this class of remote and active

  15. Dark before light: testing the cosmic expansion history through the cosmic microwave background

    SciTech Connect

    Linder, Eric V.; Smith, Tristan L. E-mail: tlsmith@berkeley.edu

    2011-04-01

    The cosmic expansion history proceeds in broad terms from a radiation dominated epoch to matter domination to an accelerated, dark energy dominated epoch. We investigate whether intermittent periods of acceleration (from a canonical, minimally coupled scalar field) are possible in the early universe — between Big Bang nucleosynthesis (BBN) and recombination and beyond. We establish that the standard picture is remarkably robust: anisotropies in the cosmic microwave background consistent with ΛCDM will exclude any extra period of accelerated expansion between 1 ≤ z∼<10{sup 5} (corresponding to 5 × 10{sup −4}eV ≤ T∼<25eV)

  16. Magnetic expansion of cosmic plasmas

    NASA Technical Reports Server (NTRS)

    Yang, Wei-Hong

    1995-01-01

    Plasma expansion is common in many astrophysical phenomena. The understanding of the driving mechanism has usually been focused on the gas pressure that implies conversion of thermal energy into flow kinetic energy. However, 'cool' expansions have been indicated in stellar/solar winds and other expanding processes. Magnetic expansion may be the principal driving mechanism. Magnetic energy in the potential form can be converted into kinetic energy during global expansion of magnetized plasmas.

  17. Growth of Cosmic Structure: Probing Dark Energy Beyond Expansion

    SciTech Connect

    Huterer, Dragan; Kirkby, David; Bean, Rachel; Connolly, Andrew; Dawson, Kyle; Dodelson, Scott; Evrard, August; Jain, Bhuvnesh; Jarvis, Michael; Linder, Eric; Mandelbaum, Rachel; May, Morgan; Raccanelli, Alvise; Reid, Beth; Rozo, Eduardo; Schmidt, Fabian; Sehgal, Neelima; Slosar, Anze; Van Engelen, Alex; Wu, Hao-Yi; Zhao, Gongbo

    2014-03-15

    The quantity and quality of cosmic structure observations have greatly accelerated in recent years, and further leaps forward will be facilitated by imminent projects. These will enable us to map the evolution of dark and baryonic matter density fluctuations over cosmic history. The way that these fluctuations vary over space and time is sensitive to several pieces of fundamental physics: the primordial perturbations generated by GUT-scale physics; neutrino masses and interactions; the nature of dark matter and dark energy. We focus on the last of these here: the ways that combining probes of growth with those of the cosmic expansion such as distance-redshift relations will pin down the mechanism driving the acceleration of the Universe.

  18. Hubble's diagram and cosmic expansion

    PubMed Central

    Kirshner, Robert P.

    2004-01-01

    Edwin Hubble's classic article on the expanding universe appeared in PNAS in 1929 [Hubble, E. P. (1929) Proc. Natl. Acad. Sci. USA 15, 168–173]. The chief result, that a galaxy's distance is proportional to its redshift, is so well known and so deeply embedded into the language of astronomy through the Hubble diagram, the Hubble constant, Hubble's Law, and the Hubble time, that the article itself is rarely referenced. Even though Hubble's distances have a large systematic error, Hubble's velocities come chiefly from Vesto Melvin Slipher, and the interpretation in terms of the de Sitter effect is out of the mainstream of modern cosmology, this article opened the way to investigation of the expanding, evolving, and accelerating universe that engages today's burgeoning field of cosmology. PMID:14695886

  19. Cosmic parallax as a probe of late time anisotropic expansion

    SciTech Connect

    Quercellini, Claudia; Cabella, Paolo; Balbi, Amedeo; Amendola, Luca

    2009-09-15

    Cosmic parallax is the change of angular separation between a pair of sources at cosmological distances induced by an anisotropic expansion. An accurate astrometric experiment like Gaia could observe or put constraints on cosmic parallax. Examples of anisotropic cosmological models are Lemaitre-Tolman-Bondi void models for off-center observers (introduced to explain the observed acceleration without the need for dark energy) and Bianchi metrics. If dark energy has an anisotropic equation of state, as suggested recently, then a substantial anisotropy could arise at z < or approx. 1 and escape the stringent constraints from the cosmic microwave background. In this paper we show that such models could be constrained by the Gaia satellite or by an upgraded future mission.

  20. New cosmic accelerating scenario without dark energy

    NASA Astrophysics Data System (ADS)

    Lima, J. A. S.; Basilakos, S.; Costa, F. E. M.

    2012-11-01

    We propose an alternative, nonsingular, cosmic scenario based on gravitationally induced particle production. The model is an attempt to evade the coincidence and cosmological constant problems of the standard model (ΛCDM) and also to connect the early and late time accelerating stages of the Universe. Our space-time emerges from a pure initial de Sitter stage thereby providing a natural solution to the horizon problem. Subsequently, due to an instability provoked by the production of massless particles, the Universe evolves smoothly to the standard radiation dominated era thereby ending the production of radiation as required by the conformal invariance. Next, the radiation becomes subdominant with the Universe entering in the cold dark matter dominated era. Finally, the negative pressure associated with the creation of cold dark matter (CCDM model) particles accelerates the expansion and drives the Universe to a final de Sitter stage. The late time cosmic expansion history of the CCDM model is exactly like in the standard ΛCDM model; however, there is no dark energy. The model evolves between two limiting (early and late time) de Sitter regimes. All the stages are also discussed in terms of a scalar field description. This complete scenario is fully determined by two extreme energy densities, or equivalently, the associated de Sitter Hubble scales connected by ρI/ρf=(HI/Hf)2˜10122, a result that has no correlation with the cosmological constant problem. We also study the linear growth of matter perturbations at the final accelerating stage. It is found that the CCDM growth index can be written as a function of the Λ growth index, γΛ≃6/11. In this framework, we also compare the observed growth rate of clustering with that predicted by the current CCDM model. Performing a χ2 statistical test we show that the CCDM model provides growth rates that match sufficiently well with the observed growth rate of structure.

  1. Matter creation and cosmic acceleration

    NASA Astrophysics Data System (ADS)

    Ramos, Rudnei O.; Vargas dos Santos, Marcelo; Waga, Ioav

    2014-04-01

    We investigate the creation of cold dark matter (CCDM) cosmology as an alternative to explain the cosmic acceleration. Particular attention is given to the evolution of density perturbations and constraints coming from recent observations. By assuming negligible effective sound speed we compare CCDM predictions with redshift-space-distortion based f(z)σ8(z) measurements. We identify a subtle issue associated with which contribution in the density contrast should be used in this test and then show that the CCDM results are the same as those obtained with ΛCDM. These results are then contrasted with the ones obtained at the background level. For the background tests we have used type Ia supernovae data (Union 2.1 compilation) in combination with baryonic acoustic oscillations and cosmic microwave background observations and also measurements of the Hubble parameter at different redshifts. As a consequence of the studies we have performed at both the background and perturbation levels, we explicitly show that CCDM is observationally degenerate with respect to ΛCDM (dark degeneracy). The need to overcome the lack of a fundamental microscopic basis for the CCDM is the major challenge for this kind of model.

  2. When did cosmic acceleration start?

    SciTech Connect

    Melchiorri, Alessandro; Pagano, Luca; Pandolfi, Stefania

    2007-08-15

    A precise determination, and comparison, of the epoch of the onset of cosmic acceleration, at redshift z{sub acc}, and of dark energy domination, at z{sub eq}, provides an interesting measure with which to parametrize dark energy models. By combining several cosmological data sets, we place constraints on the redshift and age of cosmological acceleration. For a {lambda}CDM model, we find the constraint z{sub acc}=0.76{+-}0.10 at 95% C.L., occurring 6.7{+-}0.4 Gyr ago. Allowing a constant equation of state but different from -1 changes the constraint to z{sub acc}=0.81{+-}0.12 (6.9{+-}0.5 Gyr ago), while dynamical models markedly increase the error on the constraint z{sub acc}=0.81{+-}0.30 (6.8{+-}1.4 Gyr ago). Unified dark energy models such as silent quartessence yield z{sub acc}=0.8{+-}0.16 (6.8{+-}0.6 Gyr ago). Interestingly, we find that the best fit z{sub acc} and z{sub eq} are remarkably insensitive to both the cosmological data sets and theoretical dark energy models considered.

  3. Ion acceleration to cosmic ray energies

    NASA Technical Reports Server (NTRS)

    Lee, Martin A.

    1990-01-01

    The acceleration and transport environment of the outer heliosphere is described schematically. Acceleration occurs where the divergence of the solar-wind flow is negative, that is at shocks, and where second-order Fermi acceleration is possible in the solar-wind turbulence. Acceleration at the solar-wind termination shock is presented by reviewing the spherically-symmetric calculation of Webb et al. (1985). Reacceleration of galactic cosmic rays at the termination shock is not expected to be important in modifying the cosmic ray spectrum, but acceleration of ions injected at the shock up to energies not greater than 300 MeV/charge is expected to occur and to create the anomalous cosmic ray component. Acceleration of energetic particles by solar wind turbulence is expected to play almost no role in the outer heliosphere. The one exception is the energization of interstellar pickup ions beyond the threshold for acceleration at the quasi-perpendicular termination shock.

  4. A Simplified Model for the Acceleration of Cosmic Ray Particles

    ERIC Educational Resources Information Center

    Gron, Oyvind

    2010-01-01

    Two important questions concerning cosmic rays are: Why are electrons in the cosmic rays less efficiently accelerated than nuclei? How are particles accelerated to great energies in ultra-high energy cosmic rays? In order to answer these questions we construct a simple model of the acceleration of a charged particle in the cosmic ray. It is not…

  5. Muon acceleration in cosmic-ray sources

    SciTech Connect

    Klein, Spencer R.; Mikkelsen, Rune E.; Becker Tjus, Julia

    2013-12-20

    Many models of ultra-high energy cosmic-ray production involve acceleration in linear accelerators located in gamma-ray bursts, magnetars, or other sources. These transient sources have short lifetimes, which necessitate very high accelerating gradients, up to 10{sup 13} keV cm{sup –1}. At gradients above 1.6 keV cm{sup –1}, muons produced by hadronic interactions undergo significant acceleration before they decay. This muon acceleration hardens the neutrino energy spectrum and greatly increases the high-energy neutrino flux. Using the IceCube high-energy diffuse neutrino flux limits, we set two-dimensional limits on the source opacity and matter density, as a function of accelerating gradient. These limits put strong constraints on different models of particle acceleration, particularly those based on plasma wake-field acceleration, and limit models for sources like gamma-ray bursts and magnetars.

  6. Does electromagnetic radiation accelerate galactic cosmic rays

    NASA Technical Reports Server (NTRS)

    Eichler, D.

    1977-01-01

    The 'reactor' theories of Tsytovich and collaborators (1973) of cosmic-ray acceleration by electromagnetic radiation are examined in the context of galactic cosmic rays. It is shown that any isotropic synchrotron or Compton reactors with reasonable astrophysical parameters can yield particles with a maximum relativistic factor of only about 10,000. If they are to produce particles with higher relativistic factors, the losses due to inverse Compton scattering of the electromagnetic radiation in them outweigh the acceleration, and this violates the assumptions of the theory. This is a critical restriction in the context of galactic cosmic rays, which have a power-law spectrum extending up to a relativistic factor of 1 million.

  7. Cosmic Ray Origin, Acceleration and Propagation

    NASA Technical Reports Server (NTRS)

    Baring, Matthew G.

    2000-01-01

    This paper summarizes highlights of the OG3.1, 3.2 and 3.3 sessions of the 26th International Cosmic Ray Conference in Salt Lake City, which were devoted to issues of origin/composition, acceleration and propagation.

  8. Cosmology with hybrid expansion law: scalar field reconstruction of cosmic history and observational constraints

    SciTech Connect

    Akarsu, Özgür; Kumar, Suresh; Myrzakulov, R.; Sami, M.; Xu, Lixin E-mail: sukuyd@gmail.com E-mail: samijamia@gmail.com

    2014-01-01

    In this paper, we consider a simple form of expansion history of Universe referred to as the hybrid expansion law - a product of power-law and exponential type of functions. The ansatz by construction mimics the power-law and de Sitter cosmologies as special cases but also provides an elegant description of the transition from deceleration to cosmic acceleration. We point out the Brans-Dicke realization of the cosmic history under consideration. We construct potentials for quintessence, phantom and tachyon fields, which can give rise to the hybrid expansion law in general relativity. We investigate observational constraints on the model with hybrid expansion law applied to late time acceleration as well as to early Universe a la nucleosynthesis.

  9. On cosmic acceleration without dark energy

    SciTech Connect

    Kolb, E.W.; Matarrese, S.; Riotto, A.; ,

    2005-06-01

    We elaborate on the proposal that the observed acceleration of the Universe is the result of the backreaction of cosmological perturbations, rather than the effect of a negative-pressure dark energy fluid or a modification of general relativity. Through the effective Friedmann equations describing an inhomogeneous Universe after smoothing, we demonstrate that acceleration in our local Hubble patch is possible even if fluid elements do not individually undergo accelerated expansion. This invalidates the no-go theorem that there can be no acceleration in our local Hubble patch if the Universe only contains irrotational dust. We then study perturbatively the time behavior of general-relativistic cosmological perturbations, applying, where possible, the renormalization group to regularize the dynamics. We show that an instability occurs in the perturbative expansion involving sub-Hubble modes, which indicates that acceleration in our Hubble patch may originate from the backreaction of cosmological perturbations on observable scales.

  10. Cosmic acceleration without dark energy: background tests and thermodynamic analysis

    SciTech Connect

    Lima, J.A.S.; Graef, L.L.; Pavón, D.; Basilakos, Spyros E-mail: leilagraef@usp.br E-mail: svasil@academyofathens.gr

    2014-10-01

    A cosmic scenario with gravitationally induced particle creation is proposed. In this model the Universe evolves from an early to a late time de Sitter era, with the recent accelerating phase driven only by the negative creation pressure associated with the cold dark matter component. The model can be interpreted as an attempt to reduce the so-called cosmic sector (dark matter plus dark energy) and relate the two cosmic accelerating phases (early and late time de Sitter expansions). A detailed thermodynamic analysis including possible quantum corrections is also carried out. For a very wide range of the free parameters, it is found that the model presents the expected behavior of an ordinary macroscopic system in the sense that it approaches thermodynamic equilibrium in the long run (i.e., as it nears the second de Sitter phase). Moreover, an upper bound is found for the Gibbons–Hawking temperature of the primordial de Sitter phase. Finally, when confronted with the recent observational data, the current 'quasi'-de Sitter era, as predicted by the model, is seen to pass very comfortably the cosmic background tests.

  11. Cosmic acceleration without dark energy: background tests and thermodynamic analysis

    NASA Astrophysics Data System (ADS)

    Lima, J. A. S.; Graef, L. L.; Pavón, D.; Basilakos, Spyros

    2014-10-01

    A cosmic scenario with gravitationally induced particle creation is proposed. In this model the Universe evolves from an early to a late time de Sitter era, with the recent accelerating phase driven only by the negative creation pressure associated with the cold dark matter component. The model can be interpreted as an attempt to reduce the so-called cosmic sector (dark matter plus dark energy) and relate the two cosmic accelerating phases (early and late time de Sitter expansions). A detailed thermodynamic analysis including possible quantum corrections is also carried out. For a very wide range of the free parameters, it is found that the model presents the expected behavior of an ordinary macroscopic system in the sense that it approaches thermodynamic equilibrium in the long run (i.e., as it nears the second de Sitter phase). Moreover, an upper bound is found for the Gibbons-Hawking temperature of the primordial de Sitter phase. Finally, when confronted with the recent observational data, the current `quasi'-de Sitter era, as predicted by the model, is seen to pass very comfortably the cosmic background tests.

  12. Growth of cosmic structure: Probing dark energy beyond expansion

    NASA Astrophysics Data System (ADS)

    Huterer, Dragan; Kirkby, David; Bean, Rachel; Connolly, Andrew; Dawson, Kyle; Dodelson, Scott; Evrard, August; Jain, Bhuvnesh; Jarvis, Michael; Linder, Eric; Mandelbaum, Rachel; May, Morgan; Raccanelli, Alvise; Reid, Beth; Rozo, Eduardo; Schmidt, Fabian; Sehgal, Neelima; Slosar, Anže; van Engelen, Alex; Wu, Hao-Yi; Zhao, Gongbo

    2015-03-01

    The quantity and quality of cosmic structure observations have greatly accelerated in recent years, and further leaps forward will be facilitated by imminent projects. These will enable us to map the evolution of dark and baryonic matter density fluctuations over cosmic history. The way that these fluctuations vary over space and time is sensitive to several pieces of fundamental physics: the primordial perturbations generated by GUT-scale physics; neutrino masses and interactions; the nature of dark matter and dark energy. We focus on the last of these here: the ways that combining probes of growth with those of the cosmic expansion such as distance-redshift relations will pin down the mechanism driving the acceleration of the Universe. One way to explain the acceleration of the Universe is invoke dark energy parameterized by an equation of state w. Distance measurements provide one set of constraints on w, but dark energy also affects how rapidly structure grows; the greater the acceleration, the more suppressed the growth of structure. Upcoming surveys are therefore designed to probe w with direct observations of the distance scale and the growth of structure, each complementing the other on systematic errors and constraints on dark energy. A consistent set of results will greatly increase the reliability of the final answer. Another possibility is that there is no dark energy, but that General Relativity does not describe the laws of physics accurately on large scales. While the properties of gravity have been measured with exquisite precision at stellar system scales and densities, within our solar system and by binary pulsar systems, its properties in different environments are poorly constrained. To fully understand if General Relativity is the complete theory of gravity we must test gravity across a spectrum of scales and densities. Rapid developments in gravitational wave astronomy and numerical relativity are directed at testing gravity in the high

  13. Acceleration of cosmic rays in Tycho's SNR.

    NASA Astrophysics Data System (ADS)

    Morlino, G.; Caprioli, D.

    We apply the non-linear diffusive shock acceleration theory in order to describe the properties of SN 1572 (G120.1+1.4, hereafter simply Tycho). By analyzing its multi-wavelength spectrum, we show how Tycho's forward shock (FS) is accelerating protons up to ˜ 500 TeV, channeling into cosmic rays more than 10 per cent of its kinetic energy. We find that the streaming instability induced by cosmic rays is consistent with all the observational evidences indicating a very efficient magnetic field amplification (up to ˜ 300 mu G), in particular the X-ray morphology of the remnant. We are able to explain the gamma-ray spectrum from the GeV up to the TeV band, recently measured respectively by Fermi-LAT and VERITAS, as due to pion decay produced in nuclear collisions by accelerated nuclei scattering against the background gas. We also show that emission due to the accelerated electrons does not play a relevant role in the observed gamma-ray spectrum.

  14. Superdiffusion of cosmic rays: Implications for cosmic ray acceleration

    SciTech Connect

    Lazarian, A.; Yan, Huirong

    2014-03-20

    Diffusion of cosmic rays (CRs) is the key process for understanding their propagation and acceleration. We employ the description of spatial separation of magnetic field lines in magnetohydrodynamic turbulence in Lazarian and Vishniac to quantify the divergence of the magnetic field on scales less than the injection scale of turbulence and show that this divergence induces superdiffusion of CR in the direction perpendicular to the mean magnetic field. The perpendicular displacement squared increases, not as the distance x along the magnetic field, which is the case for a regular diffusion, but as the x {sup 3} for freely streaming CRs. The dependence changes to x {sup 3/2} for the CRs propagating diffusively along the magnetic field. In the latter case, we show that it is important to distinguish the perpendicular displacement with respect to the mean field and to the local magnetic field. We consider how superdiffusion changes the acceleration of CRs in shocks and show how it decreases efficiency of the CRs acceleration in perpendicular shocks. We also demonstrate that in the case when the small-scale magnetic field is generated in the pre-shock region, an efficient acceleration can take place for the CRs streaming without collisions along the magnetic loops.

  15. The influence of gravitational binding energy on cosmic expansion dynamics: new perspectives for cosmology

    NASA Astrophysics Data System (ADS)

    Fahr, Hans-Jörg; Sokaliwska, Michael

    2012-06-01

    Confronted with microwave background observations by WMAP and with consternating supernova locations in the magnitude-redshift diagram modern cosmology feels enforced to call for cosmic vacuum energy as a necessary cosmological ingredient. Most often this vacuum energy is associated with Einstein's cosmological constant Λ or with so-called "dark energy". A positive value of Λ describes an inflationary action on cosmic dynamics which in view of recent cosmological data appears as an absolute need. In this article, however, we question the hypothesis of a constant vacuum energy density since not justifiable on physical grounds. Instead we show that gravitational binding energy of cosmic matter, connected with ongoing structure formation during cosmic expansion, acts similar to vacuum energy, since it reduces the effective gravitating proper mass density. Thus one may be encouraged to believe that actions of cosmic vacuum energy and gravitational binding energy concerning their cosmological effects are closely related to each other, perhaps in some respects even have identical phenomenologies. Based on results presented in this article we propose that the generally wanted action of vacuum energy on cosmic spacetime dynamics inevitably leads to a decay of vacuum energy density. Connected with this decay is a decrease of cosmic binding energy and the generation of new effective gravitating mass in the universe. If this all is adequately taken into account by the energy-momentum tensor of the GR field equations, one is then led to non-standard cosmologies which for the first time can guarantee the conservation of the total energy both in static and expanding universes. We describe the structuring of cosmic matter by a change in time of the 2-point correlation-function. We do show here that cosmic structure formation drives accelerated cosmic expansion and feigns the action of vacuum energy density.

  16. Stephani Cosmological Models with Accelerated Expansion

    NASA Astrophysics Data System (ADS)

    Korkina, M. P.; Kopteva, E. M.; Egurnov, A. A.

    2016-07-01

    Stephani cosmological models are considered which describe spacetimes for a shear-free matter distribution and include Friedmann models as a particular case. The possibility is considered of constructing cosmological models in which a change of sign of the acceleration of the Universe expansion arises only due to curvature.

  17. Constraints on anisotropic cosmic expansion from supernovae

    NASA Astrophysics Data System (ADS)

    Kalus, B.; Schwarz, D. J.; Seikel, M.; Wiegand, A.

    2013-05-01

    Aims: We test the isotropy of the expansion of the Universe by estimating the hemispherical anisotropy of supernova type Ia (SN Ia) Hubble diagrams at low redshifts (z < 0.2). Methods: We compare the best fit Hubble diagrams in pairs of hemispheres and search for the maximal asymmetric orientation. For an isotropic Universe, we expect only a small asymmetry due to noise and the presence of nearby structures. This test does not depend on the assumed content of the Universe, the assumed model of gravity, or the spatial curvature of the Universe. The expectation for possible fluctuations due to large scale structure is evaluated for the Λ cold dark matter (ΛCDM) model and is compared to the supernova data from the Constitution set for four different light curve fitters, thus allowing a study of the systematic effects. Results: The expected order of magnitude of the hemispherical asymmetry of the Hubble expansion agrees with the observed one. The direction of the Hubble asymmetry is established at 95% confidence level (C.L.) using both, the MLCS2k2 and the SALT II light curve fitter. The highest expansion rate is found towards (ℓ,b) ≈ (-35°, -19°), which agrees with directions reported by other studies. Its amplitude is not in contradiction to expectations from the ΛCDM model. The measured Hubble anisotropy is ΔH/H ~ 0.026. With 95% C.L. the expansion asymmetry is ΔH/H < 0.038.

  18. ACCELERATION OF GALACTIC COSMIC RAYS IN THE INTERSTELLAR MEDIUM

    SciTech Connect

    Fisk, L. A.; Gloeckler, G.

    2012-01-10

    Challenges have arisen to diffusive shock acceleration as the primary means to accelerate galactic cosmic rays (GCRs) in the interstellar medium. Diffusive shock acceleration is also under challenge in the heliosphere, where at least the simple application of diffusive shock acceleration cannot account for observations. In the heliosphere, a new acceleration mechanism has been invented-a pump mechanism, driven by ambient turbulence, in which particles are pumped up in energy out of a low-energy core particle population through a series of adiabatic compressions and expansions-that can account for observations not only at shocks but in quiet conditions in the solar wind and throughout the heliosheath. In this paper, the pump mechanism is applied to the acceleration of GCRs in the interstellar medium. With relatively straightforward assumptions about the magnetic field in the interstellar medium, and how GCRs propagate in this field, the pump mechanism yields (1) the overall shape of the GCR spectrum, a power law in particle kinetic energy, with a break at the so-called knee in the GCR spectrum to a slightly steeper power-law spectrum. (2) The rigidity dependence of the H/He ratio observed from the PAMELA satellite instrument.

  19. Holographic dark energy and late cosmic acceleration

    NASA Astrophysics Data System (ADS)

    Pavón, Diego

    2007-06-01

    It has been persuasively argued that the number of effective degrees of freedom of a macroscopic system is proportional to its area rather than to its volume. This entails interesting consequences for cosmology. Here we present a model based on this 'holographic principle' that accounts for the present stage of accelerated expansion of the Universe and significantly alleviates the coincidence problem also for non-spatially flat cosmologies. Likewise, we comment on a recently proposed late transition to a fresh decelerated phase.

  20. Growth of Cosmic Structure: Probing Dark Energy Beyond Expansion

    DOE PAGESBeta

    Huterer, Dragan; Kirkby, David; Bean, Rachel; Connolly, Andrew; Dawson, Kyle; Dodelson, Scott; Evrard, August; Jain, Bhuvnesh; Jarvis, Michael; Linder, Eric; et al

    2014-03-15

    The quantity and quality of cosmic structure observations have greatly accelerated in recent years, and further leaps forward will be facilitated by imminent projects. These will enable us to map the evolution of dark and baryonic matter density fluctuations over cosmic history. The way that these fluctuations vary over space and time is sensitive to several pieces of fundamental physics: the primordial perturbations generated by GUT-scale physics; neutrino masses and interactions; the nature of dark matter and dark energy. We focus on the last of these here: the ways that combining probes of growth with those of the cosmic expansionmore » such as distance-redshift relations will pin down the mechanism driving the acceleration of the Universe.« less

  1. New Kinematical Constraints on Cosmic Acceleration

    SciTech Connect

    Rapetti, David; Allen, Steve W.; Amin, Mustafa A.; Blandford, Roger; /-KIPAC, Menlo Park

    2007-05-25

    We present and employ a new kinematical approach to ''dark energy'' studies. We construct models in terms of the dimensionless second and third derivatives of the scale factor a(t) with respect to cosmic time t, namely the present-day value of the deceleration parameter q{sub 0} and the cosmic jerk parameter, j(t). An elegant feature of this parameterization is that all {Lambda}CDM models have j(t)=1 (constant), which facilitates simple tests for departures from the {Lambda}CDM paradigm. Applying our model to redshift-independent distance measurements, from type Ia supernovae and X-ray cluster gas mass fraction measurements, we obtain clear statistical evidence for a late time transition from a decelerating to an accelerating phase. For a flat model with constant jerk, j(t)=j, we measure q{sub 0}=-0.81 {+-} 0.14 and j=2.16 +0.81 -0.75, results that are consistent with {Lambda}CDM at about the 1{sigma} confidence level. In comparison to dynamical analyses, the kinematical approach uses a different model set and employs a minimum of prior information, being independent of any particular gravity theory. The results obtained with this new approach therefore provide important additional information and we argue that both kinematical and dynamical techniques should be employed in future dark energy studies, where possible.

  2. Cosmic expansion histories in massive bigravity with symmetric matter coupling

    SciTech Connect

    Enander, Jonas; Mörtsell, Edvard; Solomon, Adam R.; Akrami, Yashar E-mail: a.r.solomon@damtp.cam.ac.uk E-mail: edvard@fysik.su.se

    2015-01-01

    We study the cosmic expansion history of massive bigravity with a viable matter coupling which treats both metrics on equal footing. We derive the Friedmann equation for the effective metric through which matter couples to the two metrics, and study its solutions. For certain parameter choices, the background cosmology is identical to that of ΛCDM. More general parameters yield dynamical dark energy, which can still be in agreement with observations of the expansion history. We study specific parameter choices of interest, including minimal models, maximally-symmetric models, and a candidate partially-massless theory.

  3. Differential cosmic expansion and the Hubble flow anisotropy

    NASA Astrophysics Data System (ADS)

    Bolejko, Krzysztof; Nazer, M. Ahsan; Wiltshire, David L.

    2016-06-01

    The Universe on scales 01–100 h‑1Mpc is dominated by a cosmic web of voids, filaments, sheets and knots of galaxy clusters. These structures participate differently in the global expansion of the Universe: from non-expanding clusters to the above average expansion rate of voids. In this paper we characterize Hubble expansion anisotropies in the COMPOSITE sample of 4534 galaxies and clusters. We concentrate on the dipole and quadrupole in the rest frame of the Local Group. These both have statistically significant amplitudes. These anisotropies, and their redshift dependence, cannot be explained solely by a boost of the Local Group in the Friedmann-Lemaitre-Robertson-Walker (FLRW) model which expands isotropically in the rest frame of the cosmic microwave background (CMB) radiation. We simulate the local expansion of the Universe with inhomogeneous Szekeres solutions, which match the standard FLRW model on gtrsim 100 h‑1Mpc scales but exhibit nonkinematic relativistic differential expansion on small scales. We restrict models to be consistent with observed CMB temperature anisotropies, while simultaneously fitting the redshift variation of the Hubble expansion dipole. We include features to account for both the Local Void and the "Great Attractor". While this naturally accounts for the Hubble expansion and CMB dipoles, the simulated quadrupoles are smaller than observed. Further refinement to incorporate additional structures may improve this. This would enable a test of the hypothesis that some large angle CMB anomalies result from failing to treat the relativistic differential expansion of the background geometry; a natural feature of solutions to Einstein's equations not included in the current standard model of cosmology.

  4. Solar Cosmic Ray Acceleration and Propagation

    NASA Astrophysics Data System (ADS)

    Podgorny, I. M.; Podgorny, A. I.

    2016-05-01

    The GOES data for emission of flare protons with the energies of 10 - 100 MeV are analyzed. Proton fluxes of ~1032 accelerated particles take place at the current sheet decay. Proton acceleration in a flare occurs along a singular line of the current sheet by the Lorentz electric field, as in the pinch gas discharge. The duration of proton flux measured on the Earth orbit is by 2 - 3 orders of magnitude longer than the duration of flares. The high energy proton flux from the flares that appear on the western part of the solar disk arrives to Earth with the time of flight. These particles propagate along magnetic lines of the Archimedes spiral connecting the flare with the Earth. Protons from the flare on the eastern part of the solar disk begin to register with a delay of several hours. Such particles cannot get on the magnetic field line connecting the flare with the Earth. These protons reach the Earth, moving across the interplanetary magnetic field. The particles captured by the magnetic field in the solar wind are transported with solar wind and due to diffusion across the magnetic field. The patterns of solar cosmic rays generation demonstrated in this paper are not always observed in the small ('1 cm-2 s-1 ster-1) proton events.

  5. Cosmic ray sources, acceleration and propagation

    NASA Technical Reports Server (NTRS)

    Ptuskin, V. S.

    1986-01-01

    A review is given of selected papers on the theory of cosmic ray (CR) propagation and acceleration. The high isotropy and a comparatively large age of galactic CR are explained by the effective interaction of relativistic particles with random and regular electromagnetic fields in interstellar medium. The kinetic theory of CR propagation in the Galaxy is formulated similarly to the elaborate theory of CR propagation in heliosphere. The substantial difference between these theories is explained by the necessity to take into account in some cases the collective effects due to a rather high density of relativisitc particles. In particular, the kinetic CR stream instability and the hydrodynamic Parker instability is studied. The interaction of relativistic particles with an ensemble of given weak random magnetic fields is calculated by perturbation theory. The theory of CR transfer is considered to be basically completed for this case. The main problem consists in poor information about the structure of the regular and the random galactic magnetic fields. An account is given of CR transfer in a turbulent medium.

  6. Ionisation as indicator for cosmic ray acceleration

    NASA Astrophysics Data System (ADS)

    Schuppan, F.; Röken, C.; Fedrau, N.; Becker Tjus, J.

    2014-06-01

    Astrospheres and wind bubbles of massive stars are believed to be sources of cosmic rays with energies E ≲ 1 TeV. These particles are not directly detectable, but their impact on surrounding matter, in particular ionisation of atomic and molecular hydrogen, can lead to observable signatures. A correlation study of both gamma ray emission, induced by proton-proton interactions of cosmic ray protons with kinetic energies Ep ≥ 280 MeV with ambient hydrogen, and ionisation induced by cosmic ray protons of kinetic energies Ep < 280 MeV can be performed in order to study potential sources of (sub)TeV cosmic rays.

  7. Particle acceleration in cosmic sites. Astrophysics issues in our understanding of cosmic rays

    NASA Astrophysics Data System (ADS)

    Diehl, R. L.

    2009-11-01

    Particles are accelerated in cosmic sites probably under conditions very different from those at terrestrial particle accelerator laboratories. Nevertheless, specific experiments which explore plasma conditions and stimulate particle acceleration carry significant potential to illuminate some aspects of the cosmic particle acceleration process. Here we summarize our understanding of cosmic particle acceleration, as derived from observations of the properties of cosmic ray particles, and through astronomical signatures caused by these near their sources or throughout their journey in interstellar space. We discuss the candidate-source object variety, and what has been learned about their particle-acceleration characteristics. We conclude identifying open issues as they are discussed among astrophysicists. - The cosmic ray differential intensity spectrum across energies from 1010 eV to 1021 eV reveals a rather smooth power-law spectrum. Two kinks occur at the “knee” (≃1015 eV) and at the “ankle” (≃ 3×1018 eV). It is unclear if these kinks are related to boundaries between different dominating sources, or rather related to characteristics of cosmic-ray propagation. Currently we believe that galactic sources dominate up to 1017 eV or even above, and the extragalactic origin of cosmic rays at highest energies merges rather smoothly with galactic contributions throughout the 1015-1018 eV range. Pulsars and supernova remnants are among the prime candidates for galactic cosmic-ray production, while nuclei of active galaxies are considered best candidates to produce ultrahigh-energy cosmic rays of extragalactic origin. The acceleration processes are probably related to shocks formed when matter is ejected into surrounding space from energetic sources such as supernova explosions or matter accreting onto black holes. Details of shock acceleration are complex, as relativistic particles modify the structure of the shock, and simple approximations or perturbation

  8. Conflation: a new type of accelerated expansion

    NASA Astrophysics Data System (ADS)

    Fertig, Angelika; Lehners, Jean-Luc; Mallwitz, Enno

    2016-08-01

    In the framework of scalar-tensor theories of gravity, we construct a new kind of cosmological model that conflates inflation and ekpyrosis. During a phase of conflation, the universe undergoes accelerated expansion, but with crucial differences compared to ordinary inflation. In particular, the potential energy is negative, which is of interest for supergravity and string theory where both negative potentials and the required scalar-tensor couplings are rather natural. A distinguishing feature of the model is that, for a large parameter range, it does not significantly amplify adiabatic scalar and tensor fluctuations, and in particular does not lead to eternal inflation and the associated infinities. We also show how density fluctuations in accord with current observations may be generated by adding a second scalar field to the model. Conflation may be viewed as complementary to the recently proposed anamorphic universe of Ijjas and Steinhardt.

  9. Cosmic-ray acceleration at stellar wind terminal shocks

    NASA Technical Reports Server (NTRS)

    Webb, G. M.; Axford, W. I.; Forman, M. A.

    1985-01-01

    Steady-state spherically symmetric analytic solutions of the cosmic-ray transport equations, applicable to the problem of acceleration of cosmic rays at the terminal shock to a stellar wind, are studied. The spectra, graidents, and flow patterns of particles modulated and accelerated by the stellar wind and shock are investigated by means of monoenergetic-source solutions at finite radius, as well as solutions with monoenergetic and power-law galactic spectra. On the basis of calculations given, early-type stars could supply a significant fraction of the 3 x 10 to the 40th ergs/sec required by galactic cosmic rays.

  10. Cosmic-ray shock acceleration in oblique MHD shocks

    NASA Technical Reports Server (NTRS)

    Webb, G. M.; Drury, L. OC.; Volk, H. J.

    1986-01-01

    A one-dimensional, steady-state hydrodynamical model of cosmic-ray acceleration at oblique MHD shocks is presented. Upstream of the shock the incoming thermal plasma is subject to the adverse pressure gradient of the accelerated particles, the J x B force, as well as the thermal gas pressure gradient. The efficiency of the acceleration of cosmic-rays at the shock as a function of the upstream magnetic field obliquity and upstream plasma beta is investigated. Astrophysical applications of the results are briefly discussed.

  11. Strangelets accelerated by pulsars in galactic cosmic rays

    SciTech Connect

    Cheng, K. S.; Usov, V. V.

    2006-12-15

    It is shown that nuggets of strange quark matter may be extracted from the surface of pulsars and accelerated by strong electric fields to high energies if pulsars are strange stars with the crusts, comprised of nuggets embedded in a uniform electron background. Such high energy nuggets called usually strangelets give an observable contribution into galactic cosmic rays and may be detected by the upcoming cosmic ray experiment Alpha Magnetic Spectrometer AMS-02 on the International Space Station.

  12. Intergalactic shock acceleration and the cosmic gamma-ray background

    NASA Astrophysics Data System (ADS)

    Miniati, Francesco

    2002-11-01

    We investigate numerically the contribution to the cosmic gamma-ray background from cosmic-ray ions and electrons accelerated at intergalactic shocks associated with cosmological structure formation. We show that the kinetic energy of accretion flows in the low-redshift intergalactic medium is thermalized primarily through moderately strong shocks, which allow for an efficient conversion of shock ram pressure into cosmic-ray pressure. Cosmic rays accelerated at these shocks produce a diffuse gamma-ray flux which is dominated by inverse Compton emission from electrons scattering off cosmic microwave background photons. Decay of neutral π mesons generated in p-p inelastic collisions of the ionic cosmic-ray component with the thermal gas contribute about 30 per cent of the computed emission. Based on experimental upper limits on the photon flux above 100 MeV from nearby clusters we constrain the efficiency of conversion of shock ram pressure into relativistic CR electrons to <~1 per cent. Thus, we find that cosmic rays of cosmological origin can generate an overall significant fraction of order 20 per cent and no more than 30 per cent of the measured gamma-ray background.

  13. X-ray Observations of Cosmic Ray Acceleration

    NASA Technical Reports Server (NTRS)

    Petre, Robert

    2012-01-01

    Since the discovery of cosmic rays, detection of their sources has remained elusive. A major breakthrough has come through the identification of synchrotron X-rays from the shocks of supernova remnants through imaging and spectroscopic observations by the most recent generation of X-ray observatories. This radiation is most likely produced by electrons accelerated to relativistic energy, and thus has offered the first, albeit indirect, observational evidence that diffusive shock acceleration in supernova remnants produces cosmic rays to TeV energies, possibly as high as the "knee" in the cosmic ray spectrum. X-ray observations have provided information about the maximum energy to which these shOCks accelerate electrons, as well as indirect evidence of proton acceleration. Shock morphologies measured in X-rays have indicated that a substantial fraction of the shock energy can be diverted into particle acceleration. This presentation will summarize what we have learned about cosmic ray acceleration from X-ray observations of supernova remnants over the past two decades.

  14. A class of effective field theory models of cosmic acceleration

    NASA Astrophysics Data System (ADS)

    Bloomfield, Jolyon K.; Flanagan, Éanna É.

    2012-10-01

    We explore a class of effective field theory models of cosmic acceleration involving a metric and a single scalar field. These models can be obtained by starting with a set of ultralight pseudo-Nambu-Goldstone bosons whose couplings to matter satisfy the weak equivalence principle, assuming that one boson is lighter than all the others, and integrating out the heavier fields. The result is a quintessence model with matter coupling, together with a series of correction terms in the action in a covariant derivative expansion, with specific scalings for the coefficients. After eliminating higher derivative terms and exploiting the field redefinition freedom, we show that the resulting theory contains nine independent free functions of the scalar field when truncated at four derivatives. This is in contrast to the four free functions found in similar theories of single-field inflation, where matter is not present. We discuss several different representations of the theory that can be obtained using the field redefinition freedom. For perturbations to the quintessence field today on subhorizon lengthscales larger than the Compton wavelength of the heavy fields, the theory is weakly coupled and natural in the sense of t'Hooft. The theory admits a regime where the perturbations become modestly nonlinear, but very strong nonlinearities lie outside its domain of validity.

  15. Multiwavelength Signatures of Cosmic Ray Acceleration by Young Supernova Remnants

    SciTech Connect

    Vink, Jacco

    2008-12-24

    An overview is given of multiwavelength observations of young supernova remnants, with a focus on the observational signatures of efficient cosmic ray acceleration. Some of the effects that may be attributed to efficient cosmic ray acceleration are the radial magnetic fields in young supernova remnants, magnetic field amplification as determined with X-ray imaging spectroscopy, evidence for large post-shock compression factors, and low plasma temperatures, as measured with high resolution optical/UV/X-ray spectroscopy. Special emphasis is given to spectroscopy of post-shock plasma's, which offers an opportunity to directly measure the post-shock temperature. In the presence of efficient cosmic ray acceleration the post-shock temperatures are expected to be lower than according to standard equations for a strong shock. For a number of supernova remnants this seems indeed to be the case.

  16. Constraint on electromagnetic acceleration of highest energy cosmic rays.

    PubMed

    Medvedev, Mikhail V

    2003-04-01

    The energetics of electromagnetic acceleration of ultrahigh-energy cosmic rays (UHECRs) is constrained both by confinement of a particle within an acceleration site and by radiative energy losses of the particle in the confining magnetic fields. We demonstrate that the detection of approximately 3 x 10(20) eV events is inconsistent with the hypothesis that compact cosmic accelerators with high magnetic fields can be the sources of UHECRs. This rules out the most popular candidates, namely spinning neutron stars, active galactic nuclei (AGNs). Galaxy clusters and, perhaps, AGN radio lobes and gamma-ray burst blast waves remain the only possible (although not very strong) candidates for UHECR acceleration sites. Our analysis places no limit on linear accelerators. With the data from the future Auger experiment one should be able to answer whether a conventional theory works or some new physics is required to explain the origin of UHECRs. PMID:12786427

  17. Particle acceleration, transport and turbulence in cosmic and heliospheric physics

    NASA Technical Reports Server (NTRS)

    Matthaeus, W.

    1992-01-01

    In this progress report, the long term goals, recent scientific progress, and organizational activities are described. The scientific focus of this annual report is in three areas: first, the physics of particle acceleration and transport, including heliospheric modulation and transport, shock acceleration and galactic propagation and reacceleration of cosmic rays; second, the development of theories of the interaction of turbulence and large scale plasma and magnetic field structures, as in winds and shocks; third, the elucidation of the nature of magnetohydrodynamic turbulence processes and the role such turbulence processes might play in heliospheric, galactic, cosmic ray physics, and other space physics applications.

  18. Characterizing the Sites of Hadronic Cosmic Ray Acceleration

    NASA Astrophysics Data System (ADS)

    Pihlstrom, Ylva; Mesler, R.; Sjouwerman, L.; Frail, D.; Claussen, M.

    2012-01-01

    It has been argued that supernova remnant (SNRs) shocks are the acceleration sites for galactic cosmic rays. While this has been established for electrons, solid evidence for hadrons constituting the bulk of the cosmic rays have been lacking. Models of hadronic cosmic ray acceleration in SNRs predict a gamma-ray flux density depending on parameters like the environment density and distance. Few reliable estimates of those parameters exist. SNRs with cosmic rays interacting with molecular clouds are expected to be bright gamma-ray sources, and these sites can be traced using 1720 MHz OH masers. The masers give information about the density and kinematical distance estimates. Only 10% of galactic SNRs harbor OH masers, and we have therefore searched for a more frequently occurring SNR/cloud interaction tracer. We have detected 36 GHz and 44 GHz methanol masers associated with a few SNRs. Here we report on the result of a search for methanol masers in 21 SNRs, and in particular the details of our detections in Sgr A East. Combining observations and modeling of methanol masers in SNRs, we aim to better constrain the density and distance to SNRs with TeV emission. The goal is to test the hadronic cosmic ray models and to understand the mechanisms of particle acceleration in SNRs. This project is supported under NASA-Fermi grant NNX10A055G.

  19. Method for direct measurement of cosmic acceleration by 21-cm absorption systems.

    PubMed

    Yu, Hao-Ran; Zhang, Tong-Jie; Pen, Ue-Li

    2014-07-25

    So far there is only indirect evidence that the Universe is undergoing an accelerated expansion. The evidence for cosmic acceleration is based on the observation of different objects at different distances and requires invoking the Copernican cosmological principle and Einstein's equations of motion. We examine the direct observability using recession velocity drifts (Sandage-Loeb effect) of 21-cm hydrogen absorption systems in upcoming radio surveys. This measures the change in velocity of the same objects separated by a time interval and is a model-independent measure of acceleration. We forecast that for a CHIME-like survey with a decade time span, we can detect the acceleration of a ΛCDM universe with 5σ confidence. This acceleration test requires modest data analysis and storage changes from the normal processing and cannot be recovered retroactively. PMID:25105607

  20. Acceleration and propagation of solar cosmic rays

    NASA Astrophysics Data System (ADS)

    Podgorny, I. M.; Podgorny, A. I.

    2015-12-01

    Analysis of the solar cosmic ray measurements on the Geostationary Orbital Environmental Satellite (GOES) spacecraft indicated that the duration of solar flare relativistic proton large pulses is comparable with the solar wind propagation duration from the Sun to the Earth. The front of the proton flux from flares on the western solar disk approaches the Earth with a flight time along the Archimedean spiral magnetic field line of 15-20 min. The proton flux from eastern flares is registered in the Earth's orbit 3-5 h after the flare onset. These particles apparently propagate across IMF owing to diffusion.

  1. Cosmic Accelerators: Engines of the Extreme Universe

    SciTech Connect

    Funk, Stefan

    2009-06-23

    The universe is home to numerous exotic and beautiful phenomena, some of which can generate almost inconceivable amounts of energy. While the night sky appears calm, it is populated by colossal explosions, jets from supermassive black holes, rapidly rotating neutron stars, and shock waves of gas moving at supersonic speeds. These accelerators in the sky boost particles to energies far beyond those we can produce on earth. New types of telescopes, including the Fermi Gamma-ray Space Telescope orbiting in space, are now discovering a host of new and more powerful accelerators. Please come and see how these observations are revising our picture of the most energetic phenomena in the universe.

  2. Constraining the efficiency of cosmic ray acceleration by cluster shocks

    NASA Astrophysics Data System (ADS)

    Vazza, F.; Brüggen, M.; Wittor, D.; Gheller, C.; Eckert, D.; Stubbe, M.

    2016-06-01

    We study the acceleration of cosmic rays by collisionless structure formation shocks with ENZO grid simulations. Data from the Fermi satellite enable the use of galaxy clusters as a testbed for particle acceleration models. Based on advanced cosmological simulations that include different prescriptions for gas and cosmic rays physics, we use the predicted γ-ray emission to constrain the shock acceleration efficiency. We infer that the efficiency must be on average ≤10-3 for cosmic shocks, particularly for the M ˜ 2-5 merger shocks that are mostly responsible for the thermalization of the intracluster medium (ICM). These results emerge, both, from non-radiative and radiative runs including feedback from active galactic nuclei, as well as from zoomed resimulations of a cluster resembling MACSJ1752.0+0440. The limit on the acceleration efficiency we report is lower than what has been assumed in the literature so far. Combined with the information from radio emission in clusters, it appears that a revision of the present understanding of shock acceleration in the ICM is unavoidable.

  3. Magnetowave induced plasma wakefield acceleration for ultrahigh energy cosmic rays.

    PubMed

    Chang, Feng-Yin; Chen, Pisin; Lin, Guey-Lin; Noble, Robert; Sydora, Richard

    2009-03-20

    Magnetowave induced plasma wakefield acceleration (MPWA) in a relativistic astrophysical outflow has been proposed as a viable mechanism for the acceleration of cosmic particles to ultrahigh energies. Here we present simulation results that clearly demonstrate the viability of this mechanism for the first time. We invoke the high frequency and high speed whistler mode for the driving pulse. The plasma wakefield obtained in the simulations compares favorably with our newly developed relativistic theory of the MPWA. We show that, under appropriate conditions, the plasma wakefield maintains very high coherence and can sustain high-gradient acceleration over hundreds of plasma skin depths. Invoking active galactic nuclei as the site, we show that MPWA production of ultrahigh energy cosmic rays beyond ZeV (10{21} eV) is possible. PMID:19392185

  4. An overview of cosmic ray research - Composition, acceleration and propagation

    NASA Technical Reports Server (NTRS)

    Wefel, John P.

    1988-01-01

    An overview of cosmic ray (CR) research and its relationship to other areas of high-energy astrophysics is presented. Research being conducted on the composition of cosmic rays (CRs) is examined, including the study of the solar system 'template' for CRs, CR abundances at earth, solar energetic particles, the CR elements beyond zinc, and the study of electrons, positrons, antinuclei, and of isotopic composition of CRs. Research on the CR energy spectrum and anisotropy is briefly reviewed. The study of acceleration processes, particle confinement, and propagation of CRs is addressed. Finally, the investigation of source abundances in CRs is discussed.

  5. Cosmic acceleration and the helicity-0 graviton

    SciTech Connect

    Rham, Claudia de; Heisenberg, Lavinia; Gabadadze, Gregory; Pirtskhalava, David

    2011-05-15

    We explore cosmology in the decoupling limit of a nonlinear covariant extension of Fierz-Pauli massive gravity obtained recently in arXiv:1007.0443. In this limit the theory is a scalar-tensor model of a unique form defined by symmetries. We find that it admits a self-accelerated solution, with the Hubble parameter set by the graviton mass. The negative pressure causing the acceleration is due to a condensate of the helicity-0 component of the massive graviton, and the background evolution, in the approximation used, is indistinguishable from the {Lambda}CDM model. Fluctuations about the self-accelerated background are stable for a certain range of parameters involved. Most surprisingly, the fluctuation of the helicity-0 field above its background decouples from an arbitrary source in the linearized theory. We also show how massive gravity can remarkably screen an arbitrarily large cosmological constant in the decoupling limit, while evading issues with ghosts. The obtained static solution is stable against small perturbations, suggesting that the degravitation of the vacuum energy is possible in the full theory. Interestingly, however, this mechanism postpones the Vainshtein effect to shorter distance scales. Hence, fifth force measurements severely constrain the value of the cosmological constant that can be neutralized, making this scheme phenomenologically not viable for solving the old cosmological constant problem. We briefly speculate on a possible way out of this issue.

  6. Stochastic acceleration of solar cosmic rays in an expanding coronal magnetic bottle

    SciTech Connect

    Mullan, D.J.

    1980-04-01

    Several key features of the coronal propagation of solar cosmic rays have previously been explained by a ''magnetic bottle'' model proposed by Schatten and Mullan. The major apparent difficulty with that model is that expansion of the closed bottle might have a severe cooling effect on the cosmic rays trapped inside. In the present paper, we examine this difficulty by applying the equation for stochastic acceleration to an expanding bottle. Following our earlier suggestion, the scattering centers are taken to be small-scale magnetic inhomogeneities which are present in the corona prior to the flare, and which are set into turbulent motion when a flare-induced shock passes by. We identify the inhomogeneities with the collapsing magnetic neutral sheets discussed by Levine in the context of normal coronal heating. We find that the acceleration efficiencies can indeed be high enough to offset expansive cooling: within the time intervals that are typically available for closed bottle evolution (1000--3000 s), protons can be accelerated from 1 keV to 100 MeV and more. Our results indicate that the flux of particles which are accelerated to (say) 100 MeV is very sensitive to shock speed if this speed is less than about 10/sup 3/ km s/sup -1/.

  7. Accelerated dryland expansion under climate change

    NASA Astrophysics Data System (ADS)

    Huang, Jianping; Yu, Haipeng; Guan, Xiaodan; Wang, Guoyin; Guo, Ruixia

    2016-02-01

    Drylands are home to more than 38% of the total global population and are one of the most sensitive areas to climate change and human activities. Projecting the areal change in drylands is essential for taking early action to prevent the aggravation of global desertification. However, dryland expansion has been underestimated in the Fifth Coupled Model Intercomparison Project (CMIP5) simulations considering the past 58 years (1948-2005). Here, using historical data to bias-correct CMIP5 projections, we show an increase in dryland expansion rate resulting in the drylands covering half of the global land surface by the end of this century. Dryland area, projected under representative concentration pathways (RCPs) RCP8.5 and RCP4.5, will increase by 23% and 11%, respectively, relative to 1961-1990 baseline, equalling 56% and 50%, respectively, of total land surface. Such an expansion of drylands would lead to reduced carbon sequestration and enhanced regional warming, resulting in warming trends over the present drylands that are double those over humid regions. The increasing aridity, enhanced warming and rapidly growing human population will exacerbate the risk of land degradation and desertification in the near future in the drylands of developing countries, where 78% of dryland expansion and 50% of the population growth will occur under RCP8.5.

  8. Cosmic bullets as particle accelerators and radio sources

    NASA Technical Reports Server (NTRS)

    Jones, T. W.; Kang, Hyesung; Tregillis, I. L.

    1994-01-01

    We have simulated in two dimensions the dynamical evolution of dense gas clouds(`cosmic bullets') moving supersonically through a uniform low-density medium. The diffusive shock acceleration of relativistic protons (cosmic rays) and their dynamical feedback on the background flow are included by the two-fluid model for this process. The acceleration of relativistic electrons is approximated by a test-particle model, and a passive magnetic field is followed by a simple advection scheme. Strong bow shocks, with Mach numbers similar to that of a bullet's motion, are the most important particle accelerators in the flow, while tail shocks and shocks inside the bullets do not play generally significant roles in this regard. For our simulation parameters, approximately greater than 10% of the initial bullet kinetic energy is converted to a combination of internal energy of gas and cosmic-ray protons by the time the bullets begin to be disrupted. Characteristically, the cosmic rays gain several percent of the available kinetic energy. Bullet destruction on timescales only a little larger than the ram pressure bullet crushing time begins in response to Kelvin-Helmholtz and especially to Rayleigh-Taylor instabilities along the forward bullet surface. For dense bullets this happens before the bullet is stopped by ram pressure. According to our simple model for synchrotron emission from relativistic electrons accelerated and transported within the flows, that emission increases rapidly as the bullet begins to fragment, when it is strongly dominated by field enhancement in sheared flows. Synchrotron emission from the acceleration region within the bow shock is, by contrast, much weaker.

  9. Cosmic ray acceleration by spiral shocks in the galactic wind

    NASA Astrophysics Data System (ADS)

    Völk, H. J.; Zirakashvili, V. N.

    2004-04-01

    Cosmic ray acceleration by shocks related with Slipping Interaction Regions (SIRs) in the Galactic Wind is considered. SIRs are similar to Solar Wind Corotating Interaction Regions. The spiral structure of our Galaxy results in a strong nonuniformity of the Galactic Wind flow and in SIR formation at distances of 50 to 100 kpc. SIRs are not corotating with the gas and magnetic field because the angular velocity of the spiral pattern differs from that of the Galactic rotation. It is shown that the collective reacceleration of the cosmic ray particles with charge Ze in the resulting shock ensemble can explain the observable cosmic ray spectrum beyond the ``knee'' up to energies of the order of 1017 Z eV. For the reaccelerated particles the Galactic Wind termination shock acts as a reflecting boundary.

  10. Cosmic Ray Acceleration in Force Free Fields

    NASA Astrophysics Data System (ADS)

    Colgate, Stirling; Li, Hui; Kronberg, Philipp

    2002-11-01

    Galactic, extragalactic, and cluster magnetic fields are in apparent pressure equilibrium with the in-fall pressure of matter from the external medium, IGM, onto the Galaxies and clusters, and from the voids onto the galaxy sheets, (walls), implying fields of 5 , 0.5, & 20 μG respectively. Equipartition or minimum energy, implies β_CR=n_CRm_pc^2/(B^2/8π)˜= 1. The total energy in field and CRs is then ˜= 10^55 ergs Galactic and ˜= 4 ot 10^60 ergs per galaxy in the IGM and less within clusters, e.g., radio lobes, synchrotron "glow" in the IGM (Kronberg), and the UHECRs spectrum, Γ =-2.6. CRs escape from the Galaxy to the IGM, τ˜=10^7y, and similarly from the walls to the voids, ˜=10^8y, less than the GZK cut-off time provided B_galaxy>B_IGM>B_voids. The free energy of black hole formation, The Los Alamos model, is just sufficient. The lack of shocks at the boundaries of over pressured radio lobes and the need for high acceleration efficiency suggests eE_allel˜= eη_reconJ_allel, acceleration by reconnection of these force-free fields.

  11. Connecting inflation with late cosmic acceleration by particle production

    NASA Astrophysics Data System (ADS)

    Nunes, Rafael C.

    2016-04-01

    A continuous process of creation of particles is investigated as a possible connection between the inflationary stage with late cosmic acceleration. In this model, the inflationary era occurs due to a continuous and fast process of creation of relativistic particles, and the recent accelerating phase is driven by the nonrelativistic matter creation from the gravitational field acting on the quantum vacuum, which finally results in an effective equation of state (EoS) less than ‑ 1. Thus, explaining recent results in favor of a phantom dynamics without the need of any modifications in the gravity theory has been proposed. Finally, we confront the model with recent observational data of type Ia Supernova, history of the Hubble parameter, baryon acoustic oscillations (BAOs) and the cosmic microwave background (CMB).

  12. SPECTRUM OF GALACTIC COSMIC RAYS ACCELERATED IN SUPERNOVA REMNANTS

    SciTech Connect

    Ptuskin, Vladimir; Zirakashvili, Vladimir; Seo, Eun-Suk

    2010-07-20

    The spectra of high-energy protons and nuclei accelerated by supernova remnant (SNR) shocks are calculated, taking into account magnetic field amplification and Alfvenic drift both upstream and downstream of the shock for different types of SNRs during their evolution. The maximum energy of accelerated particles may reach 5 x 10{sup 18} eV for Fe ions in Type IIb SNRs. The calculated energy spectrum of cosmic rays after propagation through the Galaxy is in good agreement with the spectrum measured at the Earth.

  13. Is Cosmic Acceleration Telling Us Something About Gravity?

    ScienceCinema

    Trodden, Mark [Syracuse University, Syracuse, New York, United States

    2009-09-01

    Among the possible explanations for the observed acceleration of the universe, perhaps the boldest is the idea that new gravitational physics might be the culprit. In this colloquium I will discuss some of the challenges of constructing a sensible phenomenological extension of General Relativity, give examples of some candidate models of modified gravity and survey existing observational constraints on this approach. I will conclude by discussing how we might hope to distinguish between modifications of General Relativity and dark energy as competing hypotheses to explain cosmic acceleration.

  14. Dark matter and cosmic acceleration from Wesson's IMT

    NASA Astrophysics Data System (ADS)

    Israelit, Mark

    2009-12-01

    In the present work a procedure is build up, that allows obtaining dark matter (DM) and cosmic acceleration in our 4D universe embedded in a 5D manifold. Both, DM and the factor causing cosmic acceleration, as well ordinary matter are induced in the 4D space-time by a warped, but empty from matter, 5D bulk. The procedure is carried out in the framework of the Weyl-Dirac version (Israelit, Found Phys 35:1725, 2005; Israelit, Found Phys 35:1769, 2005) of Paul Wesson’s Induced Matter Theory (Wesson, Space-time matter, 1999) enriched by Rosen’s approach (Found Phys 12:213, 1982). Considering chaotically oriented Weyl vector fields, which exist in microscopic cells, we obtain cold dark matter (CDM) consisting of weylons, massive bosons having spin 1. Assuming homogeneity and isotropy at large scale we derive cosmological equations in which luminous matter, CDM and dark energy may be considered separately. Making in the given procedure use of present observational data one can develop a model of the Universe with conventional matter, DM and cosmic acceleration, induced by the 5D bulk.

  15. Cosmic ray drift, shock wave acceleration and the anomalous component of cosmic rays

    NASA Technical Reports Server (NTRS)

    Pesses, M. E.; Jokipii, J. R.; Eichler, D.

    1981-01-01

    A model of the anomalous component of the quiet-time cosmic ray flux is presented in which ex-interstellar neutral particles are accelerated continuously in the polar regions of the solar-wind termination shock, and then drift into the equatorial regions of the inner heliosphere. The observed solar-cycle variations, radial gradient, and apparent latitude gradient of the anomalous component are a natural consequence of this model.

  16. Archimedean-type force in a cosmic dark fluid. II. Qualitative and numerical study of a multistage universe expansion

    SciTech Connect

    Balakin, Alexander B.; Bochkarev, Vladimir V.

    2011-01-15

    In this (second) part of the work we present the results of numerical and qualitative analysis, based on a new model of the Archimedean-type interaction between dark matter and dark energy. The Archimedean-type force is linear in the four-gradient of the dark energy pressure and plays a role of self-regulator of the energy redistribution in a cosmic dark fluid. Because of the Archimedean-type interaction the cosmological evolution is shown to have a multistage character. Depending on the choice of the values of the model-guiding parameters, the Universe expansion is shown to be perpetually accelerated, periodic or quasiperiodic with a finite number of deceleration/acceleration epochs. We distinguished the models, which can be definitely characterized by the inflation in the early Universe, by the late-time accelerated expansion and nonsingular behavior in intermediate epochs, and classified them with respect to a number of transition points. Transition points appear, when the acceleration parameter changes the sign, providing the natural partition of the Universe's history into epochs of accelerated and decelerated expansion. The strategy and results of numerical calculations are advocated by the qualitative analysis of the instantaneous phase portraits of the dynamic system associated with the key equation for the dark energy pressure evolution.

  17. Cosmic acceleration of Earth and the Moon by dark matter

    NASA Technical Reports Server (NTRS)

    Nordtvedt, Kenneth L.

    1994-01-01

    In order to test the hypothesis that the gravitational interaction between our Galaxy's dark matter and the ordinary matter in Earth and the Moon might not fulfill the equivalence principle (universality of free fall), we consider the pertinent perturbation of the lunar orbit -- a sidereal month period range oscillation resulting from a spatially fixed polarization of the orbit. Lunar laser ranging (LLR) data can measure this sidereal perturbation to an accuracy equal to or better than its existing measurement of the synodic month period range oscillation amplitude (+/- 3 cm) which has been used for testing whether Earth and the Moon accelerate at equal rates toward the Sun. Because of the slow precession rate of the Moon's perigree (8.9 yr period), the lunar orbit is particularly sensitive to a cosmic acceleration; the LLR fit of the orbit places an upper limit of 10(exp -13) cm/sq. s for any cosmic differential acceleration between Earth (Fe) and the Moon (silicates). This is 10(exp -5) of the total galactic acceleration of the solar system, of which, it has been suggested, a large portion is produced by dark matter.

  18. Radio emission and nonlinear diffusive shock acceleration of cosmic rays in the supernova SN 1993J

    NASA Astrophysics Data System (ADS)

    Tatischeff, V.

    2009-05-01

    Aims: The extensive observations of the supernova SN 1993J at radio wavelengths make this object a unique target for the study of particle acceleration in a supernova shock. Methods: To describe the radio synchrotron emission we use a model that couples a semianalytic description of nonlinear diffusive shock acceleration with self-similar solutions for the hydrodynamics of the supernova expansion. The synchrotron emission, which is assumed to be produced by relativistic electrons propagating in the postshock plasma, is worked out from radiative transfer calculations that include the process of synchrotron self-absorption. The model is applied to explain the morphology of the radio emission deduced from high-resolution VLBI imaging observations and the measured time evolution of the total flux density at six frequencies. Results: Both the light curves and the morphology of the radio emission indicate that the magnetic field was strongly amplified in the blast wave region shortly after the explosion, possibly via the nonresonant regime of the cosmic-ray streaming instability operating in the shock precursor. The amplified magnetic field immediately upstream from the subshock is determined to be Bu ≈ 50 (t/1 { day})-1 G. The turbulent magnetic field was not damped behind the shock but carried along by the plasma flow in the downstream region. Cosmic-ray protons were efficiently produced by diffusive shock acceleration at the blast wave. We find that during the first 8.5 years after the explosion, about 19% of the total energy processed by the forward shock was converted to cosmic-ray energy. However, the shock remained weakly modified by the cosmic-ray pressure. The high magnetic field amplification implies that protons were rapidly accelerated to energies well above 1015 eV. The results obtained for this supernova support the scenario that massive stars exploding into their former stellar wind are a major source of Galactic cosmic-rays of energies above 1015 eV. We

  19. Cosmic acceleration in a model of fourth order gravity

    NASA Astrophysics Data System (ADS)

    Banerjee, Shreya; Jayswal, Nilesh; Singh, Tejinder P.

    2015-10-01

    We investigate a fourth order model of gravity, having a free length parameter, and no cosmological constant or dark energy. We consider cosmological evolution of a flat Friedmann universe in this model for the case that the length parameter is of the order of the present Hubble radius. By making a suitable choice for the present value of the Hubble parameter, and the value of the third derivative of the scale factor (the jerk), we find that the model can explain cosmic acceleration to the same degree of accuracy as the standard concordance model. If the free length parameter is assumed to be time dependent, and of the order of the Hubble parameter of the corresponding epoch, the model can still explain cosmic acceleration, and provides a possible resolution of the cosmic coincidence problem. We work out the effective equation of state, and its time evolution, in our model. The fourth order correction terms are proportional to the metric, and hence mimic the cosmological constant. We also compare redshift drift in our model, with that in the standard model. The equation of state and the redshift drift serve to discriminate our model from the standard model.

  20. A new limit on the time between the nucleosynthesis and the acceleration of cosmic rays in supernova remnants using the Co/Ni ratio

    NASA Technical Reports Server (NTRS)

    Webber, W. R.; Gupta, M.

    1990-01-01

    Using new cross section measurements of Ni into Co, data on the Co/Ni ratio in cosmic rays from the HEAO C spacecraft have been reinterpreted in terms of the time between nucleosynthesis and the acceleration of cosmic rays, delta t. The observed Co/Ni ratio is now consistent with interstellar fragmentation only, leading to a small or zero source abundance. In terms of the decay of e-process nucleosynthesis nuclides into Co after a supernova explosion, this permits an estimate of delta t = 4-30,000 yr for the time between nucleosynthesis and the acceleration of cosmic rays if supernovae are the direct progenitors of cosmic rays. These age limits are used in conjunction with models of the expansion of supernova remnants (SNRs), to estimate that cosmic rays are accelerated when the radius of these remnants is between 0.1 and 25 pc.

  1. Toward a Direct Measurement of the Cosmic Acceleration

    NASA Astrophysics Data System (ADS)

    Darling, Jeremiah K.

    2013-01-01

    We present precise redshift measurements and place model-free constraints on cosmic acceleration and the acceleration of the Solar System in a universal context. HI 21 cm absorption lines observed over multiple epochs can constrain the secular redshift drift or the proper acceleration, Δv/Δto, with high precision. A comparison of literature analog spectra to contemporary digital spectra shows significant acceleration almost certainly attributable to systematic instrumental or calibration errors. However, robust constraints have been obtained by using digital data from a single telescope, the Green Bank Telescope. An ensemble of 10 objects spanning z = 0.09-0.69 observed over 13.5 years show Δz/Δto = (-1.8 ± 1.2) × 10-8 yr-1 or Δv/Δto = -4.0 ± 3.0 m s-1 yr-1. The best constraint from a single object, 3C286 at = 0.692153275(85), is dz/dto = (1.5 ± 4.7) × 10-8 yr-1 or Δv/Δto = 2.7 ± 8.4 m s-1 yr-1. These measurements are three orders of magnitude larger than the expected acceleration in the concordance dark energy cosmology at z=0.5, Δz/Δto = 2 × 10-11 yr-1 or Δv/Δto = 0.3 cm s-1 yr-1, but they demonstrate a lack of secular redshift drift in absorption line systems and the long-term frequency stability of modern radio telescopes. This measurement likewise constrains the barycentric proper acceleration in a cosmological reference frame (as opposed to the Galactic pulsar-defined reference frame), but currently lacks the precision of quasar proper motion observations. A comparison of rest-frame UV metal absorption lines to the HI 21 cm line places improved constraints on the cosmic variation of physical constants: Δ(α2 gp μ)/(α2 gp μ) = (-3.5 ± 1.4) × 10-6 in the redshift range z=0.24-2.04, consistent with no variation. We estimate that the cosmic acceleration could be directly measured with this technique in about 300 years using modern telescopes or in about 12 years using a Square Kilometer Array, provided that new systematic effects do

  2. Accelerated expansion of the universe à la the Stueckelberg mechanism

    SciTech Connect

    Akarsu, Özgür; Arık, Metin; Katırcı, Nihan; Kavuk, Mehmet E-mail: metin.arik@boun.edu.tr E-mail: mehmet.kavuk@boun.edu.tr

    2014-07-01

    We investigate a cosmological model in which the Stueckelberg fields are non-minimally coupled to the scalar curvature in a gauge invariant manner. We present not only a solution that can be considered in the context of the late time acceleration of the universe but also a solution compatible with the inflationary cosmology. Distinct behaviors of the scalar and vector fields together with the real valued mass gained by the Stueckelberg mechanism lead the universe to go through the two different accelerated expansion phases with a decelerated expansion phase between them. On the other hand, in the solutions we present, if the mass is null then the universe is either static or exhibits a simple power law expansion due to the vector field potential.

  3. Dynamics of rising magnetized cavities and ultrahigh energy cosmic ray acceleration in clusters of galaxies

    NASA Astrophysics Data System (ADS)

    Gourgouliatos, Konstantinos N.; Lyutikov, Maxim

    2012-02-01

    We study the expansion of low-density cavities produced by active galactic nucleus jets in clusters of galaxies. The long-term stability of these cavities requires the presence of linked magnetic fields. We find solutions describing the self-similar expansion of structures containing large-scale electromagnetic fields. Unlike the force-free spheromak-like configurations, these solutions have no surface currents and, thus, are less susceptible to resistive decay. The cavities are internally confined by external pressure, with zero gradient at the surface. If the adiabatic index of the plasma within the cavity is Γ > 4/3, the expansion ultimately leads to the formation of large-scale current sheets. The resulting dissipation of the magnetic field can only partially offset the adiabatic and radiative losses of radio-emitting electrons. We demonstrate that if the formation of large-scale current sheets is accompanied by explosive reconnection of the magnetic field, the resulting reconnection layer can accelerate cosmic rays to ultrahigh energies. We speculate that the enhanced flux of ultrahigh energy cosmic rays towards Centaurus A originates at the cavities due to magnetic reconnection.

  4. A test of the nature of cosmic acceleration using galaxy redshift distortions.

    PubMed

    Guzzo, L; Pierleoni, M; Meneux, B; Branchini, E; Le Fèvre, O; Marinoni, C; Garilli, B; Blaizot, J; De Lucia, G; Pollo, A; McCracken, H J; Bottini, D; Le Brun, V; Maccagni, D; Picat, J P; Scaramella, R; Scodeggio, M; Tresse, L; Vettolani, G; Zanichelli, A; Adami, C; Arnouts, S; Bardelli, S; Bolzonella, M; Bongiorno, A; Cappi, A; Charlot, S; Ciliegi, P; Contini, T; Cucciati, O; de la Torre, S; Dolag, K; Foucaud, S; Franzetti, P; Gavignaud, I; Ilbert, O; Iovino, A; Lamareille, F; Marano, B; Mazure, A; Memeo, P; Merighi, R; Moscardini, L; Paltani, S; Pellò, R; Perez-Montero, E; Pozzetti, L; Radovich, M; Vergani, D; Zamorani, G; Zucca, E

    2008-01-31

    Observations of distant supernovae indicate that the Universe is now in a phase of accelerated expansion the physical cause of which is a mystery. Formally, this requires the inclusion of a term acting as a negative pressure in the equations of cosmic expansion, accounting for about 75 per cent of the total energy density in the Universe. The simplest option for this 'dark energy' corresponds to a 'cosmological constant', perhaps related to the quantum vacuum energy. Physically viable alternatives invoke either the presence of a scalar field with an evolving equation of state, or extensions of general relativity involving higher-order curvature terms or extra dimensions. Although they produce similar expansion rates, different models predict measurable differences in the growth rate of large-scale structure with cosmic time. A fingerprint of this growth is provided by coherent galaxy motions, which introduce a radial anisotropy in the clustering pattern reconstructed by galaxy redshift surveys. Here we report a measurement of this effect at a redshift of 0.8. Using a new survey of more than 10,000 faint galaxies, we measure the anisotropy parameter beta = 0.70 +/- 0.26, which corresponds to a growth rate of structure at that time of f = 0.91 +/- 0.36. This is consistent with the standard cosmological-constant model with low matter density and flat geometry, although the error bars are still too large to distinguish among alternative origins for the accelerated expansion. The correct origin could be determined with a further factor-of-ten increase in the sampled volume at similar redshift. PMID:18235494

  5. TOWARD A DIRECT MEASUREMENT OF THE COSMIC ACCELERATION

    SciTech Connect

    Darling, Jeremy

    2012-12-20

    We present precise H I 21 cm absorption line redshifts observed in multiple epochs to directly constrain the secular redshift drift z-dot or the cosmic acceleration, {Delta}v/{Delta}t{sub circle}. A comparison of literature analog spectra to contemporary digital spectra shows significant acceleration likely attributable to systematic instrumental errors. However, we obtain robust constraints using primarily Green Bank Telescope digital data. Ten objects spanning z = 0.09-0.69 observed over 13.5 years show z-dot = (-2.3 {+-} 0.8) Multiplication-Sign 10{sup -8} yr{sup -1} or {Delta}v/{Delta}t{sub circle} = -5.5 {+-} 2.2 m s{sup -1} yr{sup -1}. The best constraint from a single object, 3C 286 at (z) = 0.692153275(85), is z-dot = (1.6 {+-} 4.7) Multiplication-Sign 10{sup -8} yr{sup -1} or {Delta}v/{Delta}t{sub circle} = 2.8 {+-} 8.4 m s{sup -1} yr{sup -1}. These measurements are three orders of magnitude larger than the theoretically expected acceleration at z = 0.5, z-dot = 2 Multiplication-Sign 10{sup -11} yr{sup -1} or {Delta}v/{Delta}t{sub circle} = 0.3 cm s{sup -1} yr{sup -1}, but they demonstrate the lack of peculiar acceleration in absorption line systems and the long-term frequency stability of modern radio telescopes. A comparison of UV metal absorption lines to the 21 cm line improves constraints on the cosmic variation of physical constants: {Delta}({alpha}{sup 2} g{sub p} {mu})/{alpha}{sup 2} g{sub p} {mu} = (- 1.2 {+-} 1.4) Multiplication-Sign 10{sup -6} in the redshift range z = 0.24-2.04. The linear evolution over the last 10.4 Gyr is (- 0.2 {+-} 2.7) Multiplication-Sign 10{sup -16} yr{sup -1}, consistent with no variation. The cosmic acceleration could be directly measured in {approx}125 years using current telescopes or in {approx}5 years using a Square Kilometer Array, but systematic effects will arise at the 1 cm s{sup -1} yr{sup -1} level.

  6. Acceleration of cosmic rays in supernova-remnants

    NASA Technical Reports Server (NTRS)

    Dorfi, E. A.; Drury, L. O.

    1985-01-01

    It is commonly accepted that supernova-explosions are the dominant source of cosmic rays up to an energy of 10 to the 14th power eV/nucleon. Moreover, these high energy particles provide a major contribution to the energy density of the interstellar medium (ISM) and should therefore be included in calculations of interstellar dynamic phenomena. For the following the first order Fermi mechanism in shock waves are considered to be the main acceleration mechanism. The influence of this process is twofold; first, if the process is efficient (and in fact this is the cas) it will modify the dynamics and evolution of a supernova-remnant (SNR), and secondly, the existence of a significant high energy component changes the overall picture of the ISM. The complexity of the underlying physics prevented detailed investigations of the full non-linear selfconsistent problem. For example, in the context of the energy balance of the ISM it has not been investigated how much energy of a SN-explosion can be transfered to cosmic rays in a time-dependent selfconsistent model. Nevertheless, a lot of progress was made on many aspects of the acceleration mechanism.

  7. Non-minimal Kinetic coupling to gravity and accelerated expansion

    SciTech Connect

    Granda, L.N.

    2010-07-01

    We study a scalar field with kinetic term coupled to itself and to the curvature, as a source of dark energy, and analyze the role of this new coupling in the accelerated expansion at large times. In the case of scalar field dominance, the scalar field and potential giving rise to power-law expansion are found in some cases, and a dynamical equation of state is calculated for a given solution of the field equations. A behavior very close to that of the cosmological constant was found.

  8. Inflation and accelerated expansion tensor-vector-scalar cosmological solutions

    SciTech Connect

    Diaz-Rivera, Luz Maria; Samushia, Lado; Ratra, Bharat

    2006-04-15

    We find exact exponentially expanding and contracting de Sitter solutions of the spatially homogeneous TeVeS cosmological equations of motion in the vacuum TeVeS model and a power law accelerated expanding solution in the presence of an additional ideal fluid with equation of state parameter -5/3<{omega}<-1. A preliminary stability analysis shows that the expanding vacuum solution is stable, while in the ideal fluid case stability depends on model parameter values. These solutions might provide a basis for incorporating early-time inflation or late-time accelerated expansion in TeVeS cosmology.

  9. Nuclear Effects of Supernova-Accelerated Cosmic Rays on Early Solar System Planetary Bodies

    NASA Astrophysics Data System (ADS)

    Meyer, B. S.; The, L.-S.; Johnson, J.

    2008-03-01

    The solar system apparently formed in the neighborhood of massive stars. Supernova explosions of these stars accelerate cosmic rays to 100s of TeVs. These cosmic rays could accelerate the beta decay of certain radioactive species in meteorite parent bodies.

  10. Constraining pre-big-bang nucleosynthesis expansion using cosmic antiprotons

    SciTech Connect

    Schelke, Mia; Catena, Riccardo; Fornengo, Nicolao; Masiero, Antonio; Pietroni, Massimo

    2006-10-15

    A host of dark energy models and nonstandard cosmologies predict an enhanced Hubble rate in the early Universe: perfectly viable models, which satisfy big bang nucleosynthesis (BBN), cosmic microwave background and general relativity tests, may nevertheless lead to enhancements of the Hubble rate up to many orders of magnitude. In this paper we show that strong bounds on the pre-BBN evolution of the Universe may be derived, under the assumption that dark matter is a thermal relic, by combining the dark matter relic density bound with constraints coming from the production of cosmic-ray antiprotons by dark matter annihilation in the Galaxy. The limits we derive apply to the Hubble rate around the temperature of dark matter decoupling. For dark matter masses lighter than 100 GeV, the bound on the Hubble rate enhancement ranges from a factor of a few to a factor of 30, depending on the actual cosmological model, while for a mass of 500 GeV the bound falls in the range 50-500. Uncertainties in the derivation of the bounds and situations where the bounds become looser are discussed. We finally discuss how these limits apply to some specific realizations of nonstandard cosmologies: a scalar-tensor gravity model, kination models and a Randall-Sundrum D-brane model.

  11. Stellar black holes and the origin of cosmic acceleration

    SciTech Connect

    Prescod-Weinstein, Chanda; Afshordi, Niayesh; Balogh, Michael L.

    2009-08-15

    The discovery of cosmic acceleration has presented a unique challenge for cosmologists. As observational cosmology forges ahead, theorists have struggled to make sense of a standard model that requires extreme fine-tuning. This challenge is known as the cosmological constant problem. The theory of gravitational aether is an alternative to general relativity that does not suffer from this fine-tuning problem, as it decouples the quantum field theory vacuum from geometry, while remaining consistent with other tests of gravity. In this paper, we study static black hole solutions in this theory and show that it manifests a UV-IR coupling: Aether couples the space-time metric close to the black hole horizon, to metric at infinity. We then show that using the trans-Planckian ansatz (as a quantum gravity effect) close to the black hole horizon, leads to an accelerating cosmological solution, far from the horizon. Interestingly, this acceleration matches current observations for stellar-mass black holes. Based on our current understanding of the black hole accretion history in the Universe, we then make a prediction for how the effective dark energy density should evolve with redshift, which can be tested with future dark energy probes.

  12. "Espresso" Acceleration of Ultra-high-energy Cosmic Rays

    NASA Astrophysics Data System (ADS)

    Caprioli, Damiano

    2015-10-01

    We propose that ultra-high-energy (UHE) cosmic rays (CRs) above 1018 eV are produced in relativistic jets of powerful active galactic nuclei via an original mechanism, which we dub “espresso” acceleration: “seed” galactic CRs with energies ≲1017 eV that penetrate the jet sideways receive a “one-shot” boost of a factor of ∼Γ2 in energy, where Γ is the Lorentz factor of the relativistic flow. For typical jet parameters, a few percent of the CRs in the host galaxy can undergo this process, and powerful blazars with Γ ≳ 30 may accelerate UHECRs up to more than 1020 eV. The chemical composition of espresso-accelerated UHECRs is determined by that at the Galactic CR knee and is expected to be proton-dominated at 1018 eV and increasingly heavy at higher energies, in agreement with recent observations made at the Pierre Auger Observatory.

  13. A Comprehensive Investigation on the Slowing Down of Cosmic Acceleration

    NASA Astrophysics Data System (ADS)

    Wang, Shuang; Hu, Yazhou; Li, Miao; Li, Nan

    2016-04-01

    Shafieloo et al. first proposed the possibility that the current cosmic acceleration (CA) is slowing down. However, this is rather counterintuitive because a slowing down CA cannot be accommodated in most mainstream cosmological models. In this work, by exploring the evolutionary trajectories of the dark energy equation of state w(z) and deceleration parameter q(z), we present a comprehensive investigation on the slowing down of CA from both the theoretical and the observational sides. For the theoretical side, we study the impact of different w(z) using six parametrization models, and then we discuss the effects of spatial curvature. For the observational side, we investigate the effects of different type Ia supernovae (SNe Ia), baryon acoustic oscillation (BAO), and cosmic microwave background (CMB) data. We find that (1) the evolution of CA is insensitive to the specific form of w(z); in contrast, a non-flat universe favors a slowing down CA more than a flat universe. (2) SNLS3 SNe Ia data sets favor a slowing down CA at a 1σ confidence level, while JLA SNe Ia samples prefer an eternal CA; in contrast, the effects of different BAO data are negligible. (3) Compared with CMB distance prior data, full CMB data favor a slowing down CA more. (4) Due to the low significance, the slowing down of CA is still a theoretical possibility that cannot be confirmed by the current observations.

  14. Ringlike inelastic events in cosmic rays and accelerators

    NASA Technical Reports Server (NTRS)

    Dremin, I. M.; Orlov, A. M.; Tretyakova, M. I.

    1985-01-01

    In cosmic rays and in accelerators there were observed single inelastic processes with densely produced (azimuthally isotropic) groups of particles exhibiting spikes in the pseudorapidity plot of an individual event (i.e. ringlike events). Theoretically the existence of such processes was predicted as a consequence of Cerenkov gluon radiation or, more generally, of deconfinement radiation. Nowadays some tens of such events have been accumulated at 400 GeV and at 150 TeV. Analyzing ringlike events in proton-nucleon interactions at 400 GeV/c it is shown that they exhibit striking irregularity in the positions of pseudorapidity spikes' centers which tend to lie mostly at 55,90 and 125 deg in cms. It implies rather small deconfinement lengths of the order of some fermi.

  15. Cosmic slowing down of acceleration for several dark energy parametrizations

    SciTech Connect

    Magaña, Juan; Cárdenas, Víctor H.; Motta, Verónica E-mail: victor.cardenas@uv.cl

    2014-10-01

    We further investigate slowing down of acceleration of the universe scenario for five parametrizations of the equation of state of dark energy using four sets of Type Ia supernovae data. In a maximal probability analysis we also use the baryon acoustic oscillation and cosmic microwave background observations. We found the low redshift transition of the deceleration parameter appears, independently of the parametrization, using supernovae data alone except for the Union 2.1 sample. This feature disappears once we combine the Type Ia supernovae data with high redshift data. We conclude that the rapid variation of the deceleration parameter is independent of the parametrization. We also found more evidence for a tension among the supernovae samples, as well as for the low and high redshift data.

  16. Hidden Cosmic-Ray Accelerators as an Origin of TeV-PeV Cosmic Neutrinos.

    PubMed

    Murase, Kohta; Guetta, Dafne; Ahlers, Markus

    2016-02-19

    The latest IceCube data suggest that the all-flavor cosmic neutrino flux may be as large as 10^{-7}  GeV cm^{-2} s^{-1} sr^{-1} around 30 TeV. We show that, if sources of the TeV-PeV neutrinos are transparent to γ rays with respect to two-photon annihilation, strong tensions with the isotropic diffuse γ-ray background measured by Fermi are unavoidable, independently of the production mechanism. We further show that, if the IceCube neutrinos have a photohadronic (pγ) origin, the sources are expected to be opaque to 1-100 GeV γ rays. With these general multimessenger arguments, we find that the latest data suggest a population of cosmic-ray accelerators hidden in GeV-TeV γ rays as a neutrino origin. Searches for x-ray and MeV γ-ray counterparts are encouraged, and TeV-PeV neutrinos themselves will serve as special probes of dense source environments. PMID:26943524

  17. Hidden Cosmic-Ray Accelerators as an Origin of TeV-PeV Cosmic Neutrinos

    NASA Astrophysics Data System (ADS)

    Murase, Kohta; Guetta, Dafne; Ahlers, Markus

    2016-02-01

    The latest IceCube data suggest that the all-flavor cosmic neutrino flux may be as large as 10-7 GeV cm-2 s-1 sr-1 around 30 TeV. We show that, if sources of the TeV-PeV neutrinos are transparent to γ rays with respect to two-photon annihilation, strong tensions with the isotropic diffuse γ -ray background measured by Fermi are unavoidable, independently of the production mechanism. We further show that, if the IceCube neutrinos have a photohadronic (p γ ) origin, the sources are expected to be opaque to 1-100 GeV γ rays. With these general multimessenger arguments, we find that the latest data suggest a population of cosmic-ray accelerators hidden in GeV-TeV γ rays as a neutrino origin. Searches for x-ray and MeV γ -ray counterparts are encouraged, and TeV-PeV neutrinos themselves will serve as special probes of dense source environments.

  18. Accelerated expansion from a nonminimal gravitational coupling to matter

    SciTech Connect

    Bertolami, O.; Frazao, P.; Paramos, J.

    2010-05-15

    It is shown that a nonminimal coupling between the scalar curvature and the matter Lagrangian density may account for the accelerated expansion of the Universe and provide, through mimicking, for a viable unification of dark energy and dark matter. An analytical exploration is first performed, and a numerical study is then used to validate the obtained results. The encountered scenario allows for a better grasp of the proposed mechanism, and sets up the discussion for improvements that can lead to a complete agreement with the observational data.

  19. Explaining the accelerated expansion of the Universe by particle creation

    NASA Astrophysics Data System (ADS)

    Singh, Ibotombi N.; Devi, Bembem Y.

    2016-04-01

    A spatially flat FRW Universe in the context of particle creation has been discussed by assuming a variable deceleration parameter which is a function of scale factor. A dust model in which creation of particles giving a negative creation pressure has been studied. Treating the Universe as an open adiabatic system, it is supposed that matter creation takes place out of gravitational energy. In this model, the Universe shows an accelerating phase of its expansion. Total number of particles increases while number of particle density decreases. Some physical implications of this model are investigated.

  20. Effects of cosmic acceleration on black hole thermodynamics

    NASA Astrophysics Data System (ADS)

    Mandal, Abhijit

    2016-07-01

    Direct local impacts of cosmic acceleration upon a black hole are matters of interest. Babichev et. al. had published before that the Friedmann equations which are prevailing the part of fluid filled up in the universe to lead (or to be very specific, `dominate') the other constituents of universe and are forcing the universe to undergo present-day accelerating phase (or to lead to violate the strong energy condition and latter the week energy condition), will themselves tell that the rate of change of mass of the central black hole due to such exotic fluid's accretion will essentially shrink the mass of the black hole. But this is a global impact indeed. The local changes in the space time geometry next to the black hole can be analysed from a modified metric governing the surrounding space time of a black hole. A charged deSitter black hole solution encircled by quintessence field is chosen for this purpose. Different thermodynamic parameters are analysed for different values of quintessence equation of state parameter, ω_q. Specific jumps in the nature of the thermodynamic space near to the quintessence or phantom barrier are noted and physically interpreted as far as possible. Nature of phase transitions and the situations at which these transitions are taking place are also explored. It is determined that before quintessence starts to work (ω_q=-0.33>-1/3) it was preferable to have a small unstable black hole followed by a large stable one. But in quintessence (-1/3>ω_q>-1), black holes are destined to be unstable large ones pre-quelled by stable/ unstable small/ intermediate mass black holes.

  1. The acceleration rate of cosmic rays at cosmic ray modified shocks

    NASA Astrophysics Data System (ADS)

    Saito, Tatsuhiko; Hoshino, Masahiro; Amano, Takanobu

    It is a still controversial matter whether the production efficiency of cosmic rays (CRs) is relatively efficient or inefficient (e.g. Helder et al. 2009; Hughes et al. 2000; Fukui 2013). In upstream region of SNR shocks (the interstellar medium), the energy density of CRs is comparable to a substantial fraction of that of the thermal plasma (e.g. Ferriere 2001). In such a situation, CRs can possibly exert a back-reaction to the shocks and modify the global shock structure. These shocks are called cosmic ray modified shocks (CRMSs). In CRMSs, as a result of the nonlinear feedback, there are almost always up to three steady-state solutions for given upstream parameters, which are characterized by CR production efficiencies (efficient, intermediate and inefficient branch). We evaluate qualitatively the efficiency of the CR production in SNR shocks by considering the stability of CRMS, under the effects of i) magnetic fields and ii) injection, which play significant roles in efficiency of acceleration. By adopting two-fluid model (Drury & Voelk, 1981), we investigate the stability of CRMSs by means of time-dependent numerical simulations. As a result, we show explicitly the bi-stable feature of these multiple solutions, i.e., the efficient and inefficient branches are stable and the intermediate branch is unstable, and the intermediate branch transit to the inefficient one. This feature is independent of the effects of i) shock angles and ii) injection. Furthermore, we investigate the evolution from a hydrodynamic shock to CRMS in a self-consistent manner. From the results, we suggest qualitatively that the CR production efficiency at SNR shocks may be the least efficient.

  2. Cosmic-Ray Accelerators in Milky Way studied with the Fermi Gamma-ray Space Telescope

    SciTech Connect

    Kamae, Tuneyoshi; /SLAC /KIPAC, Menlo Park

    2012-05-04

    High-energy gamma-ray astrophysics is now situated at a confluence of particle physics, plasma physics and traditional astrophysics. Fermi Gamma-ray Space Telescope (FGST) and upgraded Imaging Atmospheric Cherenkov Telescopes (IACTs) have been invigorating this interdisciplinary area of research. Among many new developments, I focus on two types of cosmic accelerators in the Milky-Way galaxy (pulsar, pulsar wind nebula, and supernova remnants) and explain discoveries related to cosmic-ray acceleration.

  3. Studies into the nature of cosmic acceleration: Dark energy or a modification to gravity on cosmological scales

    NASA Astrophysics Data System (ADS)

    Dossett, Jason Nicholas

    Since its discovery more than a decade ago, the problem of cosmic acceleration has become one of the largest in cosmology and physics as a whole. An unknown dark energy component of the universe is often invoked to explain this observation. Mathematically, this works because inserting a cosmic fluid with a negative equation of state into Einstein's equations provides an accelerated expansion. There are, however, alternative explanations for the observed cosmic acceleration. Perhaps the most promising of the alternatives is that, on the very largest cosmological scales, general relativity needs to be extended or a new, modified gravity theory must be used. Indeed, many modified gravity models are not only able to replicate the observed accelerated expansion without dark energy, but are also more compatible with a unified theory of physics. Thus it is the goal of this dissertation to develop and study robust tests that will be able to distinguish between these alternative theories of gravity and the need for a dark energy component of the universe. We will study multiple approaches using the growth history of large-scale structure in the universe as a way to accomplish this task. These approaches include studying what is known as the growth index parameter, a parameter that describes the logarithmic growth rate of structure in the universe, which describes the rate of formation of clusters and superclusters of galaxies over the entire age of the universe. We will explore the effectiveness of this parameter to distinguish between general relativity and modifications to gravity physics given realistic expectations of results from future experiments. Next, we will explore the modified growth formalism wherein deviations from the growth expected in general relativity are parameterized via changes to the growth equations, i.e. the perturbed Einstein's equations. We will also explore the impact of spatial curvature on these tests. Finally, we will study how dark energy

  4. Late time cosmic acceleration from natural infrared cutoff

    NASA Astrophysics Data System (ADS)

    Gorji, Mohammad Ali

    2016-09-01

    In this paper, inspired by the ultraviolet deformation of the Friedmann-Lemaître-Robertson-Walker geometry in loop quantum cosmology, we formulate an infrared-modified cosmological model. We obtain the associated deformed Friedmann and Raychaudhuri equations and we show that the late time cosmic acceleration can be addressed by the infrared corrections. As a particular example, we applied the setup to the case of matter dominated universe. This model has the same number of parameters as ΛCDM, but a dynamical dark energy generates in the matter dominated era at the late time. According to our model, as the universe expands, the energy density of the cold dark matter dilutes and when the Hubble parameter approaches to its minimum, the infrared effects dominate such that the effective equation of state parameter smoothly changes from weff = 0 to weff = - 2. Interestingly and nontrivially, the unstable de Sitter phase with weff = - 1 is corresponding to Ωm =Ωd = 0.5 and the universe crosses the phantom divide from the quintessence phase with weff > - 1 and Ωm >Ωd to the phantom phase with weff < - 1 and Ωm <Ωd which shows that the model is observationally viable. The results show that the universe finally ends up in a big rip singularity for a finite time proportional to the inverse of the minimum of the Hubble parameter. Moreover, we consider the dynamical stability of the model and we show that the universe starts from the matter dominated era at the past attractor with weff = 0 and ends up in a future attractor at the big rip with weff = - 2.

  5. SUPERNOVA REMNANT KES 17: AN EFFICIENT COSMIC RAY ACCELERATOR INSIDE A MOLECULAR CLOUD

    SciTech Connect

    Gelfand, Joseph D.; Castro, Daniel; Slane, Patrick O.; Temim, Tea; Hughes, John P.; Rakowski, Cara E-mail: cara.rakowski@gmail.com

    2013-11-10

    The supernova remnant Kes 17 (SNR G304.6+0.1) is one of a few but growing number of remnants detected across the electromagnetic spectrum. In this paper, we analyze recent radio, X-ray, and γ-ray observations of this object, determining that efficient cosmic ray acceleration is required to explain its broadband non-thermal spectrum. These observations also suggest that Kes 17 is expanding inside a molecular cloud, though our determination of its age depends on whether thermal conduction or clump evaporation is primarily responsible for its center-filled thermal X-ray morphology. Evidence for efficient cosmic ray acceleration in Kes 17 supports recent theoretical work concluding that the strong magnetic field, turbulence, and clumpy nature of molecular clouds enhance cosmic ray production in supernova remnants. While additional observations are needed to confirm this interpretation, further study of Kes 17 is important for understanding how cosmic rays are accelerated in supernova remnants.

  6. Adiabatic expansion of cosmic ray sources and the consequences for secondary antiprotons

    NASA Technical Reports Server (NTRS)

    Mauger, B. G.; Stephens, S. A.

    1983-01-01

    The low-energy antiproton flux measurement of Buffinton et al. (1981) is more than an order of magnitude higher than can be explained by interstellar production. It has been suggested that the excess antiprotons may be created by supernovae in very dense regions of ISM. These sources would provide the additional target material necessary to produce the excess cosmic ray antiprotons; in addition, adiabatic energy losses due to supernova expansion will increase the flux of low-energy antiprotons. The antiproton flux from such sources is examined here, with attention given to the energy loss effects of the adiabatic and collisional losses of both the primary and secondary cosmic ray fluxes. Ionization losses of the antiprotons are also considered.

  7. Pointlike gamma ray sources as signatures of distant accelerators of ultrahigh energy cosmic rays.

    PubMed

    Gabici, Stefano; Aharonian, Felix A

    2005-12-16

    We discuss the possibility of observing distant accelerators of ultrahigh energy cosmic rays in synchrotron gamma rays. Protons propagating away from their acceleration sites produce extremely energetic electrons during photopion interactions with cosmic microwave background photons. If the accelerator is embedded in a magnetized region, these electrons will emit high energy synchrotron radiation. The resulting synchrotron source is expected to be pointlike, steady, and detectable in the GeV-TeV energy range if the magnetic field is at the nanoGauss level. PMID:16384444

  8. High energy neutrinos from astrophysical accelerators of cosmic ray nuclei

    NASA Astrophysics Data System (ADS)

    Anchordoqui, Luis A.; Hooper, Dan; Sarkar, Subir; Taylor, Andrew M.

    2008-02-01

    Ongoing experimental efforts to detect cosmic sources of high energy neutrinos are guided by the expectation that astrophysical accelerators of cosmic ray protons would also generate neutrinos through interactions with ambient matter and/or photons. However, there will be a reduction in the predicted neutrino flux if cosmic ray sources accelerate not only protons but also significant numbers of heavier nuclei, as is indicated by recent air shower data. We consider plausible extragalactic sources such as active galactic nuclei, gamma ray bursts and starburst galaxies and demand consistency with the observed cosmic ray composition and energy spectrum at Earth after allowing for propagation through intergalactic radiation fields. This allows us to calculate the expected neutrino fluxes from the sources, normalized to the observed cosmic ray spectrum. We find that the likely signals are still within reach of next generation neutrino telescopes such as IceCube.PACS95.85.Ry98.70.Rz98.54.Cm98.54.EpReferencesFor a review, see:F.HalzenD.HooperRep. Prog. Phys.6520021025A.AchterbergIceCube CollaborationPhys. Rev. Lett.972006221101A.AchterbergIceCube CollaborationAstropart. Phys.262006282arXiv:astro-ph/0611063arXiv:astro-ph/0702265V.NiessANTARES CollaborationAIP Conf. Proc.8672006217I.KravchenkoPhys. Rev. D732006082002S.W.BarwickANITA CollaborationPhys. Rev. Lett.962006171101V.Van ElewyckPierre Auger CollaborationAIP Conf. Proc.8092006187For a survey of possible sources and event rates in km3 detectors see e.g.,W.BednarekG.F.BurgioT.MontaruliNew Astron. Rev.4920051M.D.KistlerJ.F.BeacomPhys. Rev. D742006063007A. Kappes, J. Hinton, C. Stegmann, F.A. Aharonian, arXiv:astro-ph/0607286.A.LevinsonE.WaxmanPhys. Rev. Lett.872001171101C.DistefanoD.GuettaE.WaxmanA.LevinsonAstrophys. J.5752002378F.A.AharonianL.A.AnchordoquiD.KhangulyanT.MontaruliJ. Phys. Conf. Ser.392006408J.Alvarez-MunizF.HalzenAstrophys. J.5762002L33F.VissaniAstropart. Phys.262006310F.W

  9. Stochastic Acceleration of Galactic Cosmic Rays by Compressible Plasma Fluctuations in Supernova Shells

    NASA Astrophysics Data System (ADS)

    Zhang, Ming

    2015-10-01

    A theory of 2-stage acceleration of Galactic cosmic rays in supernova remnants is proposed. The first stage is accomplished by the supernova shock front, where a power-law spectrum is established up to a certain cutoff energy. It is followed by stochastic acceleration with compressible waves/turbulence in the downstream medium. With a broad \\propto {k}-2 spectrum for the compressible plasma fluctuations, the rate of stochastic acceleration is constant over a wide range of particle momentum. In this case, the stochastic acceleration process extends the power-law spectrum cutoff energy of Galactic cosmic rays to the knee without changing the spectral slope. This situation happens as long as the rate of stochastic acceleration is faster than 1/5 of the adiabatic cooling rate. A steeper spectrum of compressible plasma fluctuations that concentrate their power in long wavelengths will accelerate cosmic rays to the knee with a small bump before its cutoff in the comic-ray energy spectrum. This theory does not require a strong amplification of the magnetic field in the upstream interstellar medium in order to accelerate cosmic rays to the knee energy.

  10. (Re-)Constraining the Cosmic-Ray Acceleration Efficiency and Magnetic Field Strength in the Northeast Rims of RCW 86

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Hiroya

    2014-09-01

    Accurate determination of SNR's shock velocity and magnetic filed is essential to reveal the mechanism of cosmic-ray acceleration. A previous velocity measurement with Chandra for the SNR RCW 86 northeast rim revealed that a substantial fraction of the postshock pressure is produced by the accelerated particles. However, there are disagreement with a H-alpha-measured velocity, and large uncertainty in the X-ray measurement itself, since the observation dates of the two Chandra datasets that were used for the proper motion measurement were not well separated with each other. We thus propose an additional observation of this region to measure the expansion velocity accurately. We will also constrain the magnetic field by searching for short-time variability in the synchrotron X-ray flux.

  11. An absence of neutrinos associated with cosmic-ray acceleration in γ-ray bursts.

    PubMed

    2012-04-19

    Very energetic astrophysical events are required to accelerate cosmic rays to above 10(18) electronvolts. GRBs (γ-ray bursts) have been proposed as possible candidate sources. In the GRB 'fireball' model, cosmic-ray acceleration should be accompanied by neutrinos produced in the decay of charged pions created in interactions between the high-energy cosmic-ray protons and γ-rays. Previous searches for such neutrinos found none, but the constraints were weak because the sensitivity was at best approximately equal to the predicted flux. Here we report an upper limit on the flux of energetic neutrinos associated with GRBs that is at least a factor of 3.7 below the predictions. This implies either that GRBs are not the only sources of cosmic rays with energies exceeding 10(18) electronvolts or that the efficiency of neutrino production is much lower than has been predicted. PMID:22517161

  12. Laboratory laser acceleration and high energy astrophysics: {gamma}-ray bursts and cosmic rays

    SciTech Connect

    Tajima, T.; Takahashi, Y.

    1998-08-20

    Recent experimental progress in laser acceleration of charged particles (electrons) and its associated processes has shown that intense electromagnetic pulses can promptly accelerate charged particles to high energies and that their energy spectrum is quite hard. On the other hand some of the high energy astrophysical phenomena such as extremely high energy cosmic rays and energetic components of {gamma}-ray bursts cry for new physical mechanisms for promptly accelerating particles to high energies. The authors suggest that the basic physics involved in laser acceleration experiments sheds light on some of the underlying mechanisms and their energy spectral characteristics of the promptly accelerated particles in these high energy astrophysical phenomena.

  13. Polytropic dark matter flows illuminate dark energy and accelerated expansion

    NASA Astrophysics Data System (ADS)

    Kleidis, K.; Spyrou, N. K.

    2015-04-01

    Currently, a large amount of data implies that the matter constituents of the cosmological dark sector might be collisional. An attractive feature of such a possibility is that, it can reconcile dark matter (DM) and dark energy (DE) in terms of a single component, accommodated in the context of a polytropic-DM fluid. In fact, polytropic processes in a DM fluid have been most successfully used in modeling dark galactic haloes, thus significantly improving the velocity dispersion profiles of galaxies. Motivated by such results, we explore the time evolution and the dynamical characteristics of a spatially-flat cosmological model, in which, in principle, there is no DE at all. Instead, in this model, the DM itself possesses some sort of fluidlike properties, i.e., the fundamental units of the Universe matter-energy content are the volume elements of a DM fluid, performing polytropic flows. In this case, together with all the other physical characteristics, we also take the energy of this fluid's internal motions into account as a source of the universal gravitational field. This form of energy can compensate for the extra energy, needed to compromise spatial flatness, namely, to justify that, today, the total energy density parameter is exactly unity. The polytropic cosmological model, depends on only one free parameter, the corresponding (polytropic) exponent, Γ. We find this model particularly interesting, because for Γ ≤ 0.541, without the need for either any exotic DE or the cosmological constant, the conventional pressure becomes negative enough so that the Universe accelerates its expansion at cosmological redshifts below a transition value. In fact, several physical reasons, e.g., the cosmological requirement for cold DM (CDM) and a positive velocity-of-sound square, impose further constraints on the value of Γ, which is eventually settled down to the range -0.089 < Γ ≤ 0. This cosmological model does not suffer either from the age problem or from the

  14. Visual phenomena induced by cosmic rays and accelerated particles

    NASA Technical Reports Server (NTRS)

    Tobias, C. A.; Budinger, T. F.; Leith, J. T.; Mamoon, A.; Chapman, P. K.

    1972-01-01

    Experiments, conducted at cyclotrons together with observations by Apollo astronauts, suggest with little doubt that cosmic nuclei interacting with the visual apparatus cause the phenomenon of light flashes seen on translunar and transearth coast over the past four Apollo missions. Other experiments with high and low energy neutrons and a helium ion beam suggest that slow protons and helium ions with a stopping power greater than 10 to the 8th power eV/gram sq cm can cause the phenomenon in the dark adapted eye. It was demonstrated that charged particles induced by neutrons and helium ions can stimulate the visual apparatus. Some approaches to understanding the long term mission effects of galactic cosmic nuclei interacting with man and his nervous system are outlined.

  15. Late time cosmic acceleration from vacuum Brans-Dicke theory in 5D

    NASA Astrophysics Data System (ADS)

    Ponce de Leon, J.

    2010-05-01

    We show that the scalar-vacuum Brans-Dicke equations in 5D are equivalent to Brans-Dicke theory in 4D with a self-interacting potential and an effective matter field. The cosmological implication, in the context of FRW models, is that the observed accelerated expansion of the universe comes naturally from the condition that the scalar field is not a ghost, i.e. ω > -3/2. We find an effective matter-dominated 4D universe which shows accelerated expansion if -3/2 < ω < -1. We study the question of whether accelerated expansion can be made compatible with large values of ω, within the framework of a 5D scalar-vacuum Brans-Dicke theory with variable, instead of constant, parameter ω. In this framework, and based on a general class of solutions of the field equations, we demonstrate that accelerated expansion is incompatible with large values of ω.

  16. A MODEL OF ACCELERATION OF ANOMALOUS COSMIC RAYS BY RECONNECTION IN THE HELIOSHEATH

    SciTech Connect

    Lazarian, A.; Opher, M. E-mail: mopher@gmu.ed

    2009-09-20

    We discuss a model of cosmic ray acceleration that accounts for the observations of anomalous cosmic rays (ACRs) by Voyager 1 and 2. The model appeals to fast magnetic reconnection rather than shocks as the driver of acceleration. The ultimate source of energy is associated with magnetic field reversals that occur in the heliosheath. It is expected that the magnetic field reversals will occur throughout the heliosheath, but especially near the heliopause where the flows slow down and diverge with respect to the interstellar wind and also in the boundary sector in the heliospheric current sheet. While the first-order Fermi acceleration theory within reconnection layers is in its infancy, the predictions do not contradict the available data on ACR spectra measured by the spacecraft. We argue that the Voyager data are one of the first pieces of evidence favoring the acceleration within regions of fast magnetic reconnection, which we believe to be a widely spread astrophysical process.

  17. Generation of mesoscale magnetic fields and the dynamics of Cosmic Ray acceleration

    NASA Astrophysics Data System (ADS)

    Diamond, P. H.; Malkov, M. A.

    The problem of the cosmic ray origin is discussed in connection with their acceleration in supernova remnant shocks. The diffusive shock acceleration mechanism is reviewed and its potential to accelerate particles to the maximum energy of (presumably) galactic cosmic rays (1018eV ) is considered. It is argued that to reach such energies, a strong magnetic field at scales larger than the particle gyroradius must be created as a result of the acceleration process, itself. One specific mechanism suggested here is based on the generation of Alfven wave at the gyroradius scale with a subsequent transfer to longer scales via interaction with strong acoustic turbulence in the shock precursor. The acoustic turbulence in turn, may be generated by Drury instability or by parametric instability of the Alfven waves. The generation mechanism is modulational instability of CR generated Alfven wave packets induced, in turn, by scattering off acoustic fluctuations in the shock precursor which are generated by Drury instability.

  18. Photon damping in cosmic-ray acceleration in active galactic nuclei

    SciTech Connect

    Colgate, S.A.

    1983-04-07

    The usual assumption of the acceleration of ultra high energy cosmic rays, greater than or equal to 10/sup 18/ eV in quasars, Seyfert galaxies and other active galactic nuclei is challenged on the basis of the photon interactions with the accelerated nucleons. This is similar to the effect of the black body radiation on particles > 10/sup 20/ eV for times of the age of the universe except that the photon spectrum is harder and the energy density greater by approx. = 10/sup 15/. Hence, a single traversal, radial or circumferential, of radiation whose energy density is no greater than the emitted flux will damp an ultra high energy. Hence, it is unlikely that any reasonable configuration of acceleration can void disastrous photon energy loss. A different site for ultra high energy cosmic ray acceleration must be found.

  19. A cocoon of freshly accelerated cosmic rays detected by Fermi in the Cygnus superbubble.

    PubMed

    Ackermann, M; Ajello, M; Allafort, A; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Belfiore, A; Bellazzini, R; Berenji, B; Blandford, R D; Bloom, E D; Bonamente, E; Borgland, A W; Bottacini, E; Brigida, M; Bruel, P; Buehler, R; Buson, S; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Cecchi, C; Chekhtman, A; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; de Angelis, A; de Palma, F; Dermer, C D; do Couto E Silva, E; Drell, P S; Dumora, D; Favuzzi, C; Fegan, S J; Focke, W B; Fortin, P; Fukazawa, Y; Fusco, P; Gargano, F; Germani, S; Giglietto, N; Giordano, F; Giroletti, M; Glanzman, T; Godfrey, G; Grenier, I A; Guillemot, L; Guiriec, S; Hadasch, D; Hanabata, Y; Harding, A K; Hayashida, M; Hayashi, K; Hays, E; Jóhannesson, G; Johnson, A S; Kamae, T; Katagiri, H; Kataoka, J; Kerr, M; Knödlseder, J; Kuss, M; Lande, J; Latronico, L; Lee, S-H; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Martin, P; Mazziotta, M N; McEnery, J E; Mehault, J; Michelson, P F; Mitthumsiri, W; Mizuno, T; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Naumann-Godo, M; Nolan, P L; Norris, J P; Nuss, E; Ohsugi, T; Okumura, A; Orlando, E; Ormes, J F; Ozaki, M; Paneque, D; Parent, D; Pesce-Rollins, M; Pierbattista, M; Piron, F; Pohl, M; Prokhorov, D; Rainò, S; Rando, R; Razzano, M; Reposeur, T; Ritz, S; Parkinson, P M Saz; Sgrò, C; Siskind, E J; Smith, P D; Spinelli, P; Strong, A W; Takahashi, H; Tanaka, T; Thayer, J G; Thayer, J B; Thompson, D J; Tibaldo, L; Torres, D F; Tosti, G; Tramacere, A; Troja, E; Uchiyama, Y; Vandenbroucke, J; Vasileiou, V; Vianello, G; Vitale, V; Waite, A P; Wang, P; Winer, B L; Wood, K S; Yang, Z; Zimmer, S; Bontemps, S

    2011-11-25

    The origin of Galactic cosmic rays is a century-long puzzle. Indirect evidence points to their acceleration by supernova shockwaves, but we know little of their escape from the shock and their evolution through the turbulent medium surrounding massive stars. Gamma rays can probe their spreading through the ambient gas and radiation fields. The Fermi Large Area Telescope (LAT) has observed the star-forming region of Cygnus X. The 1- to 100-gigaelectronvolt images reveal a 50-parsec-wide cocoon of freshly accelerated cosmic rays that flood the cavities carved by the stellar winds and ionization fronts from young stellar clusters. It provides an example to study the youth of cosmic rays in a superbubble environment before they merge into the older Galactic population. PMID:22116880

  20. RAISIN: Tracers of Cosmic Expansion with SN Ia in the IR

    NASA Astrophysics Data System (ADS)

    Foley, Ryan; Kirshner, Robert; Challis, Peter; Rest, Armin; Chornock, Ryan; Riess, Adam; Scolnic, Dan; Stubbs, Christopher

    2013-02-01

    Progress on measuring dark energy properties with supernovae (SN) was rapid when the samples were small. However, today, the statistical errors from sample size are no longer dominant. Rather, progress is currently limited by the systematic errors introduced by photometry, light curve fitting, and accounting for dust extinction. Observations of SN Ia in the NIR offer the most promising way forward to a more accurate measurement of cosmic expansion history. We have a large it HST program in Cycle 20 to observe SN Ia in the rest-frame NIR at cosmologically interesting distances. We will find the SN with Pan- STARRS, but we need Gemini to determine the type and age, and measure the SN redshift. The final sample will provide constraints on the nature of dark energy competitive with the best current measurements, but with significantly smaller systematic errors.

  1. RAISIN: Tracers of cosmic expansion with SN IA in the IR

    NASA Astrophysics Data System (ADS)

    Kirshner, Robert

    2012-10-01

    Progress on measuring dark energy properties with supernovae was rapid when the samples were small. However, today, the statistical errors from sample size are not the most important ones. Systematic errors introduced by photometry, light curve fitters, and by dust limit progress. Observations of SN Ia in the IR offer the most promising way forward to a more accurate measurement of cosmic expansion history. Theory predicts and empirical evidence shows that SN Ia are more nearly standard candles in the Y, J, and H bands than in the optical bands. Dust absorption is similarly a much smaller problem in the near IR. The drawback is that precise measurements of the restframe infrared flux from cosmologically interesting supernovae at z ~ 0.3 to 0.5 are not feasible from the ground. HST can solve this problem. By following up the most promising of the flood of SN Ia we are discovering in PanSTARRS fields, WFC3/IR can obtain rest frame IR observations that will lead to precise cosmic distances and the best knowledge of dark energy properties. Once this approach proves its worth, a more extensive sample would provide powerful constraints on dark energy properties and could distinguish between a cosmological constant and more exotic forms of dark energy.

  2. Constraining the Cosmic-ray Acceleration Efficiency in the Supernova Remnant IC 443

    NASA Astrophysics Data System (ADS)

    Ritchey, Adam Michael; Federman, Steven R.; Jenkins, Edward B.; Caprioli, Damiano; Wallerstein, George

    2015-08-01

    Supernova remnants are widely believed to be the sources responsible for the acceleration of Galactic cosmic rays. Over the last several years, observations made with the Fermi Gamma-ray Space Telescope have confirmed that cosmic-ray nuclei are indeed accelerated in some supernova remnants, including IC 443, which is a prototype for supernova remnants interacting with molecular clouds. However, the details concerning the particle acceleration processes in middle aged remnants are not fully understood, in part because the basic model parameters are not always well constrained. Here, we present preliminary results of a Hubble Space Telescope investigation into the physical conditions in diffuse molecular gas interacting with IC 443. We examine high-resolution FUV spectra of two stars, one that probes the interior region of the supernova remnant, and the other located just outside the visible edge of IC 443. With this arrangement, we are able to evaluate the densities and temperatures in neutral gas clumps positioned both ahead of and behind the supernova shock front. From these measurements, we obtain estimates for the post-shock temperature and the shock velocity in the interclump medium. We discuss the efficacy of these results for constraining both the age of IC 443, and also the cosmic-ray acceleration efficiency. Finally, we report the first detection of boron in a supernova remnant, and discuss the usefulness of the B/O ratio in constraining the cosmic-ray content of the gas interacting with IC 443.

  3. Particle acceleration in cosmic plasmas – paradigm change?

    SciTech Connect

    Lytikov, Maxim; Guo, Fan

    2015-07-21

    The presentation begins by considering the requirements on the acceleration mechanism. It is found that at least some particles in high-energy sources are accelerated by magnetic reconnection (and not by shocks). The two paradigms can be distinguished by the hardness of the spectra. Shocks typically produce spectra with p > 2 (relativistic shocks have p ~ 2.2); non-linear shocks & drift acceleration may give p < 2, e.g. p=1.5; B-field dissipation can give p = 1. Then collapse of stressed magnetic X-point in force-free plasma and collapse of a system of magnetic islands are taken up, including Island merger: forced reconnection. Spectra as functions of sigma are shown, and gamma ~ 109 is addressed. It is concluded that reconnection in magnetically-dominated plasma can proceed explosively, is an efficient means of particle acceleration, and is an important (perhaps dominant for some phenomena) mechanism of particle acceleration in high energy sources.

  4. Uncorrelated measurements of the cosmic expansion history and dark energy from supernovae

    SciTech Connect

    Wang Yun; Tegmark, Max

    2005-05-15

    We present a method for measuring the cosmic expansion history H(z) in uncorrelated redshift bins, and apply it to current and simulated type Ia supernova data assuming spatial flatness. If the matter density parameter {omega}{sub m} can be accurately measured from other data, then the dark-energy density history X(z)={rho}{sub X}(z)/{rho}{sub X}(0) can trivially be derived from this expansion history H(z). In contrast to customary 'black box' parameter fitting, our method is transparent and easy to interpret: the measurement of H(z){sup -1} in a redshift bin is simply a linear combination of the measured comoving distances for supernovae in that bin, making it obvious how systematic errors propagate from input to output. We find the Riess et al. (2004) gold sample to be consistent with the vanilla concordance model where the dark energy is a cosmological constant. We compare two mission concepts for the NASA/DOE Joint Dark-Energy Mission (JDEM), the Joint Efficient Dark-energy Investigation (JEDI), and the Supernova Accelaration Probe (SNAP), using simulated data including the effect of weak lensing (based on numerical simulations) and a systematic bias from K corrections. Estimating H(z) in seven uncorrelated redshift bins, we find that both provide dramatic improvements over current data: JEDI can measure H(z) to about 10% accuracy and SNAP to 30%-40% accuracy.

  5. Uncorrelated measurements of the cosmic expansion history and dark energy from supernovae

    NASA Astrophysics Data System (ADS)

    Wang, Yun; Tegmark, Max

    2005-05-01

    We present a method for measuring the cosmic expansion history H(z) in uncorrelated redshift bins, and apply it to current and simulated type Ia supernova data assuming spatial flatness. If the matter density parameter Ωm can be accurately measured from other data, then the dark-energy density history X(z)=ρX(z)/ρX(0) can trivially be derived from this expansion history H(z). In contrast to customary “black box” parameter fitting, our method is transparent and easy to interpret: the measurement of H(z)-1 in a redshift bin is simply a linear combination of the measured comoving distances for supernovae in that bin, making it obvious how systematic errors propagate from input to output. We find the Riess et al. (2004) gold sample to be consistent with the vanilla concordance model where the dark energy is a cosmological constant. We compare two mission concepts for the NASA/DOE Joint Dark-Energy Mission (JDEM), the Joint Efficient Dark-energy Investigation (JEDI), and the Supernova Accelaration Probe (SNAP), using simulated data including the effect of weak lensing (based on numerical simulations) and a systematic bias from K corrections. Estimating H(z) in seven uncorrelated redshift bins, we find that both provide dramatic improvements over current data: JEDI can measure H(z) to about 10% accuracy and SNAP to 30% 40% accuracy.

  6. Cosmic microwave background anisotropy from nonlinear structures in accelerating universes

    SciTech Connect

    Sakai, Nobuyuki; Inoue, Kaiki Taro

    2008-09-15

    We study the cosmic microwave background (CMB) anisotropy due to spherically symmetric nonlinear structures in flat universes with dust and a cosmological constant. By modeling a time-evolving spherical compensated void/lump by Lemaitre-Tolman-Bondi spacetimes, we numerically solve the null geodesic equations with the Einstein equations. We find that a nonlinear void redshifts the CMB photons that pass through it regardless of the distance to it. In contrast, a nonlinear lump blueshifts (or redshifts) the CMB photons if it is located near (or sufficiently far from) us. The present analysis comprehensively covers previous works based on a thin-shell approximation and a linear/second-order perturbation method and the effects of shell thickness and full nonlinearity. Our results indicate that, if quasilinear and large (> or approx.100 Mpc) voids/lumps would exist, they could be observed as cold or hot spots with temperature variance > or approx. 10{sup -5} K in the CMB sky.

  7. Magnetowave Induced Plasma Wakefield Acceleration for Ultra High Energy Cosmic Rays

    SciTech Connect

    Chang, Feng-Yin; Chen, Pisin; Lin, Guey-Lin; Noble, Robert; Sydora, Richard; /Alberta U.

    2009-10-17

    Magnetowave induced plasma wakefield acceleration (MPWA) in a relativistic astrophysical outflow has been proposed as a viable mechanism for the acceleration of cosmic particles to ultrahigh energies. Here we present simulation results that clearly demonstrate the viability of this mechanism for the first time. We invoke the high frequency and high speed whistler mode for the driving pulse. The plasma wakefield obtained in the simulations compares favorably with our newly developed relativistic theory of the MPWA. We show that, under appropriate conditions, the plasma wakefield maintains very high coherence and can sustain high-gradient acceleration over hundreds of plasma skin depths. Invoking active galactic nuclei as the site, we show that MPWA production of ultrahigh energy cosmic rays beyond ZeV (10{sup 21} eV) is possible.

  8. Spontaneous excitation of a uniformly accelerated atom in the cosmic string spacetime

    NASA Astrophysics Data System (ADS)

    Zhou, Wenting; Yu, Hongwei

    2016-04-01

    We study, in the cosmic string spacetime, the average rate of change of energy for an atom coupled to massless scalar fields and uniformly accelerated in a direction parallel to the string in vacuum. We find that both the noninertial motion and the nontrivial global spacetime topology affect the atomic transition rates, so an accelerated atom (an Unruh detector) does feel the string contrary to claims in the literature. We demonstrate that the equivalence between the effect of uniform acceleration and that of thermal radiation on the transition rates of the atom, which is valid in the Minkowski spacetime, holds only on the string.

  9. Probing cosmic-ray acceleration and propagation with H{sub 3}{sup +} observations

    SciTech Connect

    Indriolo, Nick; Fields, Brian D.; McCall, Benjamin J.

    2015-01-22

    As cosmic rays traverse the interstellar medium (ISM) they interact with the ambient gas in various ways. These include ionization of atoms and molecules, spallation of nuclei, excitation of nuclear states, and production of pions among others. All of these interactions produce potential observables which may be used to trace the flux of cosmic rays. One such observable is the molecular ion H{sub 3}{sup +}-produced via the ionization of an H{sub 2} molecule and its subsequent collision with another H{sub 2}-which can be identified by absorption lines in the 3.5-4 μm spectral region. We have detected H{sub 3}{sup +} in several Galactic diffuse cloud sight lines and used the derived column densities to infer ζ{sub 2}, the cosmic-ray ionization rate of H{sub 2}. Ionization rates determined in this way vary from about 7×10{sup −17} s{sup −1} to about 8×10{sup −16} s{sup −1}, and suggest the possibility of discrete sources producing high local fluxes of low-energy cosmic rays. Theoretical calculations of the ionization rate from postulated cosmic-ray spectra also support this possibility. Our recent observations of H{sub 3}{sup +} near the supernova remnant IC 443 (a likely site of cosmic-ray acceleration) point to even higher ionization rates, on the order of 10{sup −15} s{sup −1}. Together, all of these results can further our understanding of the cosmic-ray spectrum both near the acceleration source and in the general Galactic ISM.

  10. Cosmic-ray acceleration during the impact of shocks on dense clouds

    NASA Technical Reports Server (NTRS)

    Jones, T. W.; Kang, Hyesung

    1993-01-01

    In order to elucidate the properties of diffusive shock acceleration in nonuniform environments, an extensive set of simulations of the dynamical interactions between plane nonradiative shocks and dense gas clouds was carried out initially in static equilibrium with their environments. These time-dependent calculations are based on the two-fluid model for diffusive cosmic ray transport, and include the dynamically active energetic proton component of the cosmic rays as well as passive electron and magnetic field components. Except when the incident shock is itself already dominated by cosmic ray pressure, it is found that the presence of the cloud adds little to the net acceleration efficiency of the original shock and can, in fact, reduce slightly the net amount of energy transferred to cosmic rays after a given time. It is found that, in 2D cloud simulations, the always-weak bow shock and the shock inside the cloud are less important to acceleration during the interaction than the tail shock.

  11. Influence of Reverse Expansion of Laser Plasma on Ions Acceleration

    NASA Astrophysics Data System (ADS)

    Sysoev, Alexander A.; Gracheva, O. I.; Karpov, A. V.

    Effect of laser plasma reverse extension is described in this paper. Influence of the effect on ion acceleration in a laser ion source is researched. This effect leads to sedimentation of ions on metal target, which significantly impacts acceleration time of other ions. In this case, the ions also tend to travel major part of their path with constant velocity. This allows one to consider movement of the ions in plasma drift space, when optimizing time focusing ability of the TOF analyzer.

  12. Fab 5: noncanonical kinetic gravity, self tuning, and cosmic acceleration

    SciTech Connect

    Appleby, Stephen A.; Linder, Eric V.; Felice, Antonio De E-mail: adefelic@gmail.com

    2012-10-01

    We investigate circumstances under which one can generalize Horndeski's most general scalar-tensor theory of gravity. Specifically we demonstrate that a nonlinear combination of purely kinetic gravity terms can give rise to an accelerating universe without the addition of extra propagating degrees of freedom on cosmological backgrounds, and exhibit self tuning to bring a large cosmological constant under control. This nonlinear approach leads to new properties that may be instructive for exploring the behaviors of gravity.

  13. Cosmic ray acceleration at perpendicular shocks in supernova remnants

    SciTech Connect

    Ferrand, Gilles; Danos, Rebecca J.; Shalchi, Andreas; Safi-Harb, Samar; Edmon, Paul; Mendygral, Peter

    2014-09-10

    Supernova remnants (SNRs) are believed to accelerate particles up to high energies through the mechanism of diffusive shock acceleration (DSA). Except for direct plasma simulations, all modeling efforts must rely on a given form of the diffusion coefficient, a key parameter that embodies the interactions of energetic charged particles with magnetic turbulence. The so-called Bohm limit is commonly employed. In this paper, we revisit the question of acceleration at perpendicular shocks, by employing a realistic model of perpendicular diffusion. Our coefficient reduces to a power law in momentum for low momenta (of index α), but becomes independent of the particle momentum at high momenta (reaching a constant value κ{sub ∞} above some characteristic momentum p {sub c}). We first provide simple analytical expressions of the maximum momentum that can be reached at a given time with this coefficient. Then we perform time-dependent numerical simulations to investigate the shape of the particle distribution that can be obtained when the particle pressure back-reacts on the flow. We observe that for a given index α and injection level, the shock modifications are similar for different possible values of p {sub c}, whereas the particle spectra differ markedly. Of particular interest, low values of p {sub c} tend to remove the concavity once thought to be typical of non-linear DSA, and result in steep spectra, as required by recent high-energy observations of Galactic SNRs.

  14. Some clues to understand MOND and the accelerated expansion of the universe

    NASA Astrophysics Data System (ADS)

    Tank, Hasmukh K.

    2011-12-01

    This letter points out that the values of `critical-acceleration' of MOND, and the `accelerated-expansion' of the universe are just two of the fourteen strikingly equal values of accelerations recurring in different physical situations. Some of them could be explained by a new law of equality of potential-energy and energy-of-mass of reasonably-independent systems (Tank in Astrophys. Space Sci. 330:203-205, 2010; Tank in Adv. Stud. Theor. Phys. 5:45-55, 2011). This new conservation-law, of equality of potential-energy, energy-of-mass and `kinetic-energy' may be a clue to understand MOND, and the `accelerated-expansion' of the universe. Alternative expressions for the cosmological red-shift, the `critical-acceleration' of MOND and Newton's law of universal gravitation are also presented for comparison of three different accelerations.

  15. Local expansion flows of galaxies: quantifying acceleration effect of dark energy

    NASA Astrophysics Data System (ADS)

    Chernin, A. D.; Teerikorpi, P.

    2013-08-01

    The nearest expansion flow of galaxies observed around the Local group is studied as an archetypical example of the newly discovered local expansion flows around groups and clusters of galaxies in the nearby Universe. The flow is accelerating due to the antigravity produced by the universal dark energy background. We introduce a new acceleration measure of the flow which is the dimensionless ``acceleration parameter" Q (x) = x - x-2 depending on the normalized distance x only. The parameter is zero at the zero-gravity distance x = 1, and Q(x) ∝ x, when x ≫ 1. At the distance x = 3, the parameter Q = 2.9. Since the expansion flows have a self-similar structure in normalized variables, we expect that the result is valid as well for all the other expansion flows around groups and clusters of galaxies on the spatial scales from ˜ 1 to ˜ 10 Mpc everywhere in the Universe.

  16. The Evolution of the Acceleration Mechanisms of Cosmic Rays and Relativistic Electrons in Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Tsvyk, N.

    There are estimated an efficacy for different acceleration mechanisms of e- and p-cosmic rays (CRs) in radio galaxies, using an evolution model for jet gaps and shock fronts with a turbulence. It is shown that diffusion shock acceleration of the CRs is the most efficient mechanism in the FR II radio galaxies (RGs). At the same time, there are a break-pinch mechanism (for a short-term at a jet gap moment), and a stochastic turbulent mechanism (for an all time when RG exist), that to play a grate part in acceleration of the CRs (give to 10-50 % of the all acceleration efficiency). It is predicted what properties of radio emission spectra give us to recognize a type of acceleration mechanisms of e-CR in the RG.

  17. A 6% measurement of the Hubble parameter at z~0.45: direct evidence of the epoch of cosmic re-acceleration

    NASA Astrophysics Data System (ADS)

    Moresco, Michele; Pozzetti, Lucia; Cimatti, Andrea; Jimenez, Raul; Maraston, Claudia; Verde, Licia; Thomas, Daniel; Citro, Annalisa; Tojeiro, Rita; Wilkinson, David

    2016-05-01

    Deriving the expansion history of the Universe is a major goal of modern cosmology. To date, the most accurate measurements have been obtained with Type Ia Supernovae (SNe) and Baryon Acoustic Oscillations (BAO), providing evidence for the existence of a transition epoch at which the expansion rate changes from decelerated to accelerated. However, these results have been obtained within the framework of specific cosmological models that must be implicitly or explicitly assumed in the measurement. It is therefore crucial to obtain measurements of the accelerated expansion of the Universe independently of assumptions on cosmological models. Here we exploit the unprecedented statistics provided by the Baryon Oscillation Spectroscopic Survey (BOSS, [1-3]) Data Release 9 to provide new constraints on the Hubble parameter H(z) using the cosmic chronometers approach. We extract a sample of more than 130000 of the most massive and passively evolving galaxies, obtaining five new cosmology-independent H(z) measurements in the redshift range 0.3 < z < 0.5, with an accuracy of ~11–16% incorporating both statistical and systematic errors. Once combined, these measurements yield a 6% accuracy constraint of H(z = 0.4293) = 91.8 ± 5.3 km/s/Mpc. The new data are crucial to provide the first cosmology-independent determination of the transition redshift at high statistical significance, measuring zt = 0.4 ± 0.1, and to significantly disfavor the null hypothesis of no transition between decelerated and accelerated expansion at 99.9% confidence level. This analysis highlights the wide potential of the cosmic chronometers approach: it permits to derive constraints on the expansion history of the Universe with results competitive with standard probes, and most importantly, being the estimates independent of the cosmological model, it can constrain cosmologies beyond—and including—the ΛCDM model.

  18. A cocoon of freshly accelerated cosmic rays detected by Fermi in the Cygnus superbubble

    NASA Astrophysics Data System (ADS)

    Grenier, Isabelle A.; Tibaldo, Luigi; Fermi-LAT Collaboration

    2013-02-01

    Conspicuous stellar clusters, with high densities of massive stars, powerful stellar winds, and intense UV flux, have formed over the past few million years in the large molecular clouds of the Cygnus X region, 1.4 kpc away from the Sun. By capturing the gamma-ray signal of young cosmic rays spreading in the interstellar medium surrounding the clusters, the Fermi Large Area Telescope (LAT) has confirmed the long-standing hypothesis that massive-star forming regions host cosmic-ray factories. The 50-pc wide cocoon of energetic particles appears to fill the interstellar cavities carved by the stellar activity. The cocoon provides a first test case to study the impact of wind-powered turbulence on the early phases of cosmic-ray diffusion (between the sources and the Galaxy at large) and to study the acceleration potential of this type of superbubble environment for in-situ cosmic-ray production or to energize Galactic cosmic rays passing by.

  19. Late decaying dark matter, bulk viscosity, and the cosmic acceleration

    SciTech Connect

    Mathews, G. J.; Kolda, C.; Lan, N. Q.

    2008-08-15

    We discuss a cosmology in which cold dark matter begins to decay into relativistic particles at a recent epoch (z<1). We show that the large entropy production and associated bulk viscosity from such decays leads to an accelerating cosmology as required by observations. We investigate the effects of decaying cold dark matter in a {lambda}=0, flat, initially matter dominated cosmology. We show that this model satisfies the cosmological constraint from the redshift-distance relation for type Ia supernovae. The age in such models is also consistent with the constraints from the oldest stars and globular clusters. Possible candidates for this late decaying dark matter are suggested along with additional observational tests of this cosmological paradigm.

  20. Inflationary Expansions Generated by a Physically Real Kinematic Acceleration

    NASA Astrophysics Data System (ADS)

    Savickas, David

    2010-02-01

    A repulsive cosmological acceleration is shown to exist that exhibits a behavior very similar to that found in both inflationary models at the time of origin of the universe, and also in the repulsive acceleration found in present-day cosmological observations. It is able to describe an inflationary model of a radiation universe in considerable numerical detail. It is based on a method that defines the Hubble parameter H, and consequently inertial systems themselves, directly in terms of the positions and velocities of mass particles in a universe. This makes it possible to describe a mass particle's motion relative to other particles in the universe, rather than relative to inertial systems. Because of this, the repulsive acceleration is a real kinematic effect existing in the present-day universe. This definition of H cannot include the use of photon positions or velocities because H determines the velocities of receding inertial systems of galaxies, and the velocity of a photon in a distant inertial system then depends on the definition of H itself. Therefore, at the time of its origin the magnitude of H in a radiation dominated universe would be solely determined by the behavior of the relatively few mass particles that it contained while allowing for a near balance with the gravitation of the Friedmann-Lemaître model. )

  1. Acceleration of cosmic rays by turbulence during reconnection events

    NASA Astrophysics Data System (ADS)

    Drake, Jim

    2007-05-01

    A Fermi-like model for energetic electron production during magnetic reconnection is described that converts a substantial fraction of released magnetic energy into energetic electrons [1]. Magnetic reconnection with a guide field leads to the growth and dynamics of multiple magnetic islands rather than a single large x-line. Electrons trapped within islands gain energy as they reflect from ends of contracting magnetic islands. The resulting rate of energy gain dominates that from parallel electric fields. The pressure from energetic electrons rises rapidly until the rate of electron energy gain balances the rate of magnetic energy release, establishing for the first time a link between the energy gain of electrons and the released magnetic energy. The energetic particle pressure therefore throttles the rate of reconnection. A transport equation for the distribution of energetic particles, including their feedback on island contraction, is obtained by averaging over the particle interaction with many islands. The steady state solutions in reconnection geometry result from convective losses balancing the Fermi drive. At high energy distribution functions take the form of a powerlaw whose spectral index depends only on the initial electron β, lower (higher) β producing harder (softer) spectra. The spectral index matches that seen in recent Wind spacecraft observations in the Earth's magnetotail. Harder spectra are predicted for the low β conditions of the solar corona or other astrophysical systems. Ions can be similarly accelerated if they are above an energy threshold. 1. J. F. Drake, M. Swisdak, H. Che and M. Shay, Nature 443, 553, 2006.

  2. Power requirements for cosmic ray propagation models involving re-acceleration and a comment on second-order Fermi acceleration theory

    NASA Astrophysics Data System (ADS)

    Thornbury, Andrew; Drury, Luke O'C.

    2014-08-01

    We derive an analytic expression for the power transferred from interstellar turbulence to the Galactic cosmic rays in propagation models which include re-acceleration. This is used to estimate the power required in such models and the relative importance of the primary acceleration as against re-acceleration. The analysis provides a formal mathematical justification for Fermi's heuristic account of second-order acceleration in his classic 1949 paper.

  3. Spatial Assortment of Mixed Propagules Explains the Acceleration of Range Expansion

    PubMed Central

    Ramanantoanina, Andriamihaja; Ouhinou, Aziz; Hui, Cang

    2014-01-01

    Range expansion of spreading organisms has been found to follow three types: (i) linear expansion with a constant rate of spread; (ii) bi-phase expansion with a faster linear expansion following a slower linear expansion; and (iii) accelerating expansion with a continuously increasing rate of spread. To date, no overarching formula exists that can be applied to all three types of range expansion. We investigated how propagule pressure, i.e., the initial number of individuals and their composition in terms of dispersal ability, affects the spread of a population. A system of integrodifference equations was then used to model the spatiotemporal dynamics of the population. We studied the dynamics of dispersal ability as well as the instantaneous and asymptotic rate of spread. We found that individuals with different dispersal abilities were spatially sorted with the stronger dispersers situated at the expanding range front, causing the velocity of expansion to accelerate. The instantaneous rate of spread was found to be fully determined by the growth and dispersal abilities of the population at the advancing edge of the invasion. We derived a formula for the asymptotic rate of spread under different scenarios of propagule pressure. The results suggest that data collected from the core of the invasion may underestimate the spreading rate of the population. Aside from better managing of invasive species, the derived formula could conceivably also be applied to conservation management of relocated, endangered or extra-limital species. PMID:25105414

  4. Accelerated expansion of the Universe in Gauss-Bonnet gravity

    SciTech Connect

    Dehghani, M.H.

    2004-09-15

    We show that in Gauss-Bonnet gravity with negative Gauss-Bonnet coefficient and without a cosmological constant, one can explain the acceleration of the expanding Universe. We first introduce a solution of the Gauss-Bonnet gravity with negative Gauss-Bonnet coefficient and no cosmological constant term in an empty (n+1)-dimensional bulk. This solution can generate a de Sitter spacetime with curvature n(n+1)/{l_brace}(n-2)(n-3) vertical bar {alpha} vertical bar {r_brace}. We show that an (n-1)-dimensional brane embedded in this bulk can have an expanding feature with acceleration. We also considered a four-dimensional brane world in a five-dimensional empty space with zero cosmological constant and obtain the modified Friedmann equations. The solution of these modified equations in matter-dominated era presents an expanding Universe with negative deceleration and positive jerk which is consistent with the recent cosmological data. We also find that for this solution, the 'n' th derivative of the scale factor with respect to time can be expressed only in terms of Hubble and deceleration parameters.

  5. VERITAS observations of supernova remnants for studies of cosmic ray acceleration

    NASA Astrophysics Data System (ADS)

    Park, Nahee

    Supernova remnants (SNRs) have been suggested as the main sites for acceleration of cosmic rays (CRs) with energies up to the knee region ( 10(15) eV). Gamma-ray emission from SNRs can provide a unique window to observe the cosmic ray acceleration and to test existing acceleration models in these objects. The Very Energetic Radiation Imaging Telescope Array System (VERITAS) is an array of atmospheric Cherenkov telescopes that measures gamma rays with energies higher than 100 GeV. Located in Arizona, USA, VERITAS has observed several SNRs in the northern hemisphere since the beginning of operations in 2007. These include two young SNRs of different types (Cassiopeia A and Tycho), as well as middle- to old-aged remnants with nearby target material such as molecular clouds. Gamma-ray data from different types of SNRs in different evolutionary stages are important to study SNRs as CR accelerators. Here we present a summary of VERITAS results on Galactic SNRs including Tycho, and discuss what these observations have taught us.

  6. Acceleration of High Energy Cosmic Rays in the Nonlinear Shock Precursor

    NASA Astrophysics Data System (ADS)

    Derzhinsky, F.; Diamond, P. H.; Malkov, M. A.

    2006-10-01

    The problem of understanding acceleration of very energetic cosmic rays to energies above the 'knee' in the spectrum at 10^15-10^16eV remains one of the great challenges in modern physics. Recently, we have proposed a new approach to understanding high energy acceleration, based on exploiting scattering of cosmic rays by inhomogenities in the compressive nonlinear shock precursor, rather than by scattering across the main shock, as is conventionally assumed. We extend that theory by proposing a mechanism for the generation of mesoscale magnetic fields (krg<1, where rg is the cosmic ray gyroradius). The mechanism is the decay or modulational instability of resonantly generated Alfven waves scattering off ambient density perturbations in the precursors. Such perturbations can be produced by Drury instability. This mechanism leads to the generation of longer wavelength Alfven waves, thus enabling the confinement of higher energy particles. A simplified version of the theory, cast in the form of a Fokker-Planck equation for the Alfven population, will also be presented. This process also limits field generation on rg scales.

  7. Constraining the expansion history of the universe from the red shift evolution of cosmic shear

    SciTech Connect

    Levy, Daniel; Brustein, Ram E-mail: ramyb@bgu.ac.il

    2010-09-01

    We present a quantitative analysis of the constraints on the total equation of state parameter that can be obtained from measuring the red shift evolution of the cosmic shear. We compare the constraints that can be obtained from measurements of the spin two angular multipole moments of the cosmic shear to those resulting from the two dimensional and three dimensional power spectra of the cosmic shear. We find that if the multipole moments of the cosmic shear are measured accurately enough for a few red shifts the constraints on the dark energy equation of state parameter improve significantly compared to those that can be obtained from other measurements.

  8. COLLISIONLESS SHOCKS IN A PARTIALLY IONIZED MEDIUM. III. EFFICIENT COSMIC RAY ACCELERATION

    SciTech Connect

    Morlino, G.; Blasi, P.; Bandiera, R.; Amato, E.; Caprioli, D.

    2013-05-10

    In this paper, we present the first formulation of the theory of nonlinear particle acceleration in collisionless shocks in the presence of neutral hydrogen in the acceleration region. The dynamical reaction of the accelerated particles, the magnetic field amplification, and the magnetic dynamical effects on the shock are also included. The main new aspect of this study, however, consists of accounting for charge exchange and the ionization of a neutral hydrogen, which profoundly change the structure of the shock, as discussed in our previous work. This important dynamical effect of neutrals is mainly associated with the so-called neutral return flux, namely the return of hot neutrals from the downstream region to upstream, where they deposit energy and momentum through charge exchange and ionization. We also present the self-consistent calculation of Balmer line emission from the shock region and discuss how to use measurements of the anomalous width of the different components of the Balmer line to infer cosmic ray acceleration efficiency in supernova remnants showing Balmer emission: the broad Balmer line, which is due to charge exchange of hydrogen atoms with hot ions downstream of the shock, is shown to become narrower as a result of the energy drainage into cosmic rays, while the narrow Balmer line, due to charge exchange in the cosmic-ray-induced precursor, is shown to become broader. In addition to these two well-known components, the neutral return flux leads to the formation of a third component with an intermediate width: this too contains information on ongoing processes at the shock.

  9. Ultraintense laser interaction with nanoscale target: a simple model for layer expansion and ion acceleration

    SciTech Connect

    Albright, Brian J; Yin, Lin; Hegelich, Bjoorn M; Bowers, Kevin J; Huang, Chengkun; Fernandez, Juan C; Flippo, Kirk A; Gaillard, Sandrine; Kwan, Thomas J T; Henig, Andreas; Yan, Xue Q; Tajima, Toshi; Habs, Dieter

    2009-01-01

    A simple model has been derived for the expansion of a thin (up to 100s of nm thickness), solid-density target driven by an u.ltraintense laser. In this regime, new ion acceleration mechanisms, such as the Break-Out Afterburner (BOA) [1], emerge with the potential to dramatically improve energy, efficiency, and energy spread of laser-driven ion beams. Such beams have been proposed [2] as drivers for fast ignition inertial confinement fusion [3]. Analysis of kinetic simulations of the BOA shows two dislinct times that bound the period of enhanced acceleration: t{sub 1}, when the target becomes relativistically transparent to the laser, and t{sub 2}, when the target becomes classically underdense and the enhanced acceleration terminates. A silllple dynamical model for target expansion has been derived that contains both the early, one-dimensional (lD) expansion of the target as well as three-dimensional (3D) expansion of the plasma at late times, The model assumes that expansion is slab-like at the instantaneous ion sound speed and requires as input target composition, laser intensity, laser spot area, and the efficiency of laser absorption into electron thermal energy.

  10. Ultraintense laser interaction with nanoscale targets: a simple model for layer expansion and ion acceleration

    NASA Astrophysics Data System (ADS)

    Albright, B. J.; Yin, L.; Hegelich, B. M.; Bowers, K. J.; Huang, C.; Henig, A.; Fernández, J. C.; Flippo, K. A.; Gaillard, S. A.; Kwan, T. J. T.; Yan, X. Q.; Tajima, T.; Habs, D.

    2010-08-01

    A simple model has been derived for expansion of a thin (up to 100s of nm thickness) target initially of solid density irradiated by an ultraintense laser. In this regime, ion acceleration mechanisms, such as the Break-Out Afterburner (BOA) [1], emerge with the potential for dramatically improved energy, efficiency, and energy spread. Ion beams have been proposed [2] as drivers for fast ignition inertial confinement fusion [3]. Analysis of kinetic simulations of the BOA shows the period of enhanced acceleration occurs between times t1, when the target becomes relativistically transparent to the laser, and t2, when the target becomes classically underdense and the enhanced acceleration terminates. A simple model for target expansion has been derived that contains early, one-dimensional (1D) expansion of the target and three-dimensional (3D) expansion at late times. The model assumes expansion is slab-like at the instantaneous ion sound speed and requires as input target composition, laser intensity, laser spot area, and the efficiency of laser absorption into electron thermal energy.

  11. Evidence of the accelerated expansion of the Universe from weak lensing tomography with COSMOS

    NASA Astrophysics Data System (ADS)

    Schrabback, T.; Hartlap, J.; Joachimi, B.; Kilbinger, M.; Simon, P.; Benabed, K.; Bradač, M.; Eifler, T.; Erben, T.; Fassnacht, C. D.; High, F. William; Hilbert, S.; Hildebrandt, H.; Hoekstra, H.; Kuijken, K.; Marshall, P. J.; Mellier, Y.; Morganson, E.; Schneider, P.; Semboloni, E.; van Waerbeke, L.; Velander, M.

    2010-06-01

    We present a comprehensive analysis of weak gravitational lensing by large-scale structure in the Hubble Space Telescope Cosmic Evolution Survey (COSMOS), in which we combine space-based galaxy shape measurements with ground-based photometric redshifts to study the redshift dependence of the lensing signal and constrain cosmological parameters. After applying our weak lensing-optimized data reduction, principal-component interpolation for the spatially, and temporally varying ACS point-spread function, and improved modelling of charge-transfer inefficiency, we measured a lensing signal that is consistent with pure gravitational modes and no significant shape systematics. We carefully estimated the statistical uncertainty from simulated COSMOS-like fields obtained from ray-tracing through the Millennium Simulation, including the full non-Gaussian sampling variance. We tested our lensing pipeline on simulated space-based data, recalibrated non-linear power spectrum corrections using the ray-tracing analysis, employed photometric redshift information to reduce potential contamination by intrinsic galaxy alignments, and marginalized over systematic uncertainties. We find that the weak lensing signal scales with redshift as expected from general relativity for a concordance ΛCDM cosmology, including the full cross-correlations between different redshift bins. Assuming a flat ΛCDM cosmology, we measure σ_8(Ω_m/0.3)0.51 = 0.75±0.08 from lensing, in perfect agreement with WMAP-5, yielding joint constraints Ω_m = 0.266+0.025-0.023, σ_8 = 0.802+0.028-0.029 (all 68.3% conf.). Dropping the assumption of flatness and using priors from the HST Key Project and Big-Bang nucleosynthesis only, we find a negative deceleration parameter q0 at 94.3% confidence from the tomographic lensing analysis, providing independent evidence of the accelerated expansion of the Universe. For a flat wCDM cosmology and prior w ∈ [-2,0], we obtain w <-0.41 (90% conf.). Our dark energy

  12. Particle acceleration and turbulence in cosmic Ray shocks: possible pathways beyond the Bohm limit

    NASA Astrophysics Data System (ADS)

    Malkov, M. A.; Diamond, P. H.

    2007-08-01

    Diffusive shock acceleration is discussed in terms of its potential to accelerate cosmic rays (CR) to 1018 eV (beyond the ``knee,'' as observations suggest) and in terms of the related observational signatures (spectral features). One idea to reach this energy is to resonantly generate a turbulent magnetic field via accelerated particles much in excess of the background field. We identify difficulties with this scenario and suggest two separate mechanisms that can work in concert with one another leading to a significant acceleration enhancement. The first mechanism is based on a nonlinear modification of the flow ahead of the shock supported by particles already accelerated to some specific (knee) momentum. The particles gain energy by bouncing off converging magnetic irregularities frozen into the flow in the shock precursor and not so much by re-crossing the shock itself. The acceleration rate is determined by the gradient of the flow velocity and turns out to be formally independent of the particle mean free path. The velocity gradient is set by the knee-particles. The acceleration rate of particles above the knee does not decrease with energy, unlike in the linear acceleration regime. The knee (spectrum steepening) forms because particles above it are effectively confined to the shock only if they are within limited domains in the momentum space, while other particles fall into ``loss-islands'', similar to the ``loss-cone'' of magnetic traps. This also maintains the steep velocity gradient and high acceleration rate. The second mechanism is based on the generation of Alfven waves at the gyroradius scale at the background field level, with a subsequent transfer to longer scales via interaction with strong acoustic turbulence in the shock precursor. The acoustic turbulence in turn, may be generated by Drury instability or by parametric instability of the Alfven (A) waves.

  13. Tanshinon IIA Injection Accelerates Tissue Expansion by Reducing the Formation of the Fibrous Capsule

    PubMed Central

    Yang, Mei; Zhu, Ming; Huang, Xiaolu; Li, Qingfeng

    2014-01-01

    The tissue expansion technique has been applied to obtain new skin tissue to repair large defects in clinical practice. The implantation of tissue expander could initiate a host response to foreign body (FBR), which leads to fibrotic encapsulation around the expander and prolongs the period of tissue expansion. Tanshinon IIA (Tan IIA) has been shown to have anti-inflammation and immunoregulation effect. The rat tissue expansion model was used in this study to observe whether Tan IIA injection systematically could inhibit the FBR to reduce fibrous capsule formation and accelerate the process of tissue expansion. Forty-eight rats were randomly divided into the Tan IIA group and control group with 24 rats in each group. The expansion was conducted twice a week to maintain a capsule pressure of 60 mmHg. The expansion volume and expanded area were measured. The expanded tissue in the two groups was harvested, and histological staining was performed; proinflammatory cytokines such as tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and interleukin-1β (IL-1β) and transforming growth factor-β (TGF-β) were examined. The expansion volume and the expanded area in the Tan IIA group were greater than that of the control group. The thickness of the fibrous capsule in the Tan IIA group was reduced with no influence on the normal skin regeneration. Decreased infiltration of macrophages, lower level of TNF-α, IL-6, IL-1β and TGF-β, less proliferating myofibroblasts and enhanced neovascularization were observed in the Tan IIA group. Our findings indicated that the Tan IIA injection reduced the formation of the fibrous capsule and accelerated the process of tissue expansion by inhibiting the FBR. PMID:25157742

  14. Improved constraints on the expansion rate of the Universe up to z ∼ 1.1 from the spectroscopic evolution of cosmic chronometers

    SciTech Connect

    Moresco, M.; Cimatti, A.; Jimenez, R.; Verde, L.; Pozzetti, L.; Zamorani, G.; Bolzonella, M.; Mignoli, M.; Zucca, E.; Dunlop, J.; Pearce, H.; Lamareille, F.; Contini, T.; Rosati, P.; Mainieri, V.; Stern, D.; Carollo, C.M.; Lilly, S.J.; Kneib, J.-P.; Fèvre, O. Le; and others

    2012-08-01

    We present new improved constraints on the Hubble parameter H(z) in the redshift range 0.15 < z < 1.1, obtained from the differential spectroscopic evolution of early-type galaxies as a function of redshift. We extract a large sample of early-type galaxies ( ∼ 11000) from several spectroscopic surveys, spanning almost 8 billion years of cosmic lookback time (0.15 < z < 1.42). We select the most massive, red elliptical galaxies, passively evolving and without signature of ongoing star formation. Those galaxies can be used as standard cosmic chronometers, as firstly proposed by Jimenez and Loeb (2002), whose differential age evolution as a function of cosmic time directly probes H(z). We analyze the 4000 Å break (D4000) as a function of redshift, use stellar population synthesis models to theoretically calibrate the dependence of the differential age evolution on the differential D4000, and estimate the Hubble parameter taking into account both statistical and systematical errors. We provide 8 new measurements of H(z), and determine its change in H(z) to a precision of 5–12% mapping homogeneously the redshift range up to z ∼ 1.1; for the first time, we place a constraint on H(z) at z≠0 with a precision comparable with the one achieved for the Hubble constant (about 5–6% at z ∼ 0.2), and covered a redshift range (0.5 < z < 0.8) which is crucial to distinguish many different quintessence cosmologies. These measurements have been tested to best match a ΛCDM model, clearly providing a statistically robust indication that the Universe is undergoing an accelerated expansion. This method shows the potentiality to open a new avenue in constrain a variety of alternative cosmologies, especially when future surveys (e.g. Euclid) will open the possibility to extend it up to z ∼ 2.

  15. Origin of cosmic rays. II. The cosmic-ray distribution and the spiral structure of NGC 3310. III. Particle acceleration by global spiral shocks

    SciTech Connect

    Duric, N.

    1986-05-01

    The optical and radio continuum properties of the spiral arms of NGC 3310 are analyzed and intercompared. The likely presence of a strong density wave in NGC 3310 is demonstrated, and a number of observational results constraining the relationship between synchrotron emission, emission line radiation, and starlight are developed. The role of supernova remnants in the production of relativistic particles is investigated and found to be inconsistent with the constraints. The generation of cosmic rays by global spiral shocks via a Fermi-type shock acceleration process is shown to agree with all the major constraints, suggesting that the rotation of the galaxy powers the acceleration of particles to cosmic ray energies. A medium with temperature of 10,000 K, partially to fully ionized, is shown to support the diffusive shock acceleration mechanism. 57 references.

  16. Relativistic cosmic ray spectra in the full non-linear theory of shock acceleration

    NASA Technical Reports Server (NTRS)

    Eichler, D.; Ellison, D. C.

    1985-01-01

    The non-linear theory of shock acceleration was generalized to include wave dynamics. In the limit of rapid wave damping, it is found that a finite ave velocity tempers the acceleration of high Mach number shocks and limits the maximum compression ratio even when energy loss is important. For a given spectrum, the efficiency of relativistic particle production is essentially independent of v sub Ph. For the three families shown, the percentage of kinetic energy flux going into relativistic particles is (1) 72%, 2) 44%, and (3) 26% (this includes the energy loss at the upper energy cuttoff). Even small v sub ph, typical of the HISM, produce quasi-universal spectra that depend only weakly on the acoustic Mach number. These spectra should be close enough to e(-2) to satisfy cosmic ray source requirements.

  17. Acceleration and propagation of high Z cosmic rays in a pulsar environment

    NASA Technical Reports Server (NTRS)

    Balasubrahmanyan, V. K.; Ormes, J. F.; Ryan, M. J.

    1971-01-01

    The survival of high Z nuclei in the X-ray photon field of a pulsar is investigated. For heavy nuclei with energies greater than or equal to 100 GeV/nucleon, 100 keV X-ray photons have sufficient energy to cause photodisintegration with cross sections of approximately 10 to the minus 25th power sq cm. Using the observed properties of the Crab pulsar, extrapolation back to epochs when the pulsar was more active indicates that the photon field is sufficiently dense to prevent the acceleration of heavy nuclei within the velocity of light cylinder. On this model, the upper limit on the energy of the escaping nuclei varies with time. The models for cosmic ray acceleration in supernova explosions or by pulsars will be related to experimental observations.

  18. The solar wind structures associated with cosmic ray decreases and particle acceleration in 1978-1982

    NASA Technical Reports Server (NTRS)

    Cane, H. V.; Richardson, I. G.; Vonrosenvinge, T. T.

    1992-01-01

    The time histories of particles in the energy range 1 MeV to 1 GeV at times of all greater than 3 percent cosmic ray decreases in the years 1978 to 1982 are studied. Essentially all 59 of the decreases commenced at or before the passages of interplanetary shocks, the majority of which accelerated energetic particles. We use the intensity-time profiles of the energetic particles to separate the cosmic ray decreases into four classes which we subsequently associate with four types of solar wind structures. Decreases in class 1 (15 events) and class 2 (26 events) can be associated with shocks which are driven by energetic coronal mass ejections. For class 1 events the ejecta is detected at 1 AU whereas this is not the case for class 2 events. The shock must therefore play a dominant role in producing the depression of cosmic rays in class 2 events. In all class 1 and 2 events (which comprise 69 percent of the total) the departure time of the ejection from the sun (and hence the location) can be determined from the rapid onset of energetic particles several days before the shock passage at Earth. The class 1 events originate from within 50 deg of central meridian. Class 3 events (10 decreases) can be attributed to less energetic ejections which are directed towards the Earth. In these events the ejecta is more important than the shock in causing a depression in the cosmic ray intensity. The remaining events (14 percent of the total) can be attributed to corotating streams which have ejecta material embedded in them.

  19. Ion acceleration - A phenomenon characteristic of the 'expansion of plasma into a vacuum'

    NASA Technical Reports Server (NTRS)

    Samir, Uri; Wright, K. H., Jr.; Stone, N. H.

    1986-01-01

    The physics of the complex process by which plasma expands across a strong density gradient is briefly discussed with particular emphasis on the resulting ion acceleration. The results from a laboratory experiment that addresses the steady-state expansion of a collisionless, streaming plasma into the wake of a body are presented. The experimental results are in good qualitative agreement with theoretical predictions, thereby demonstrating the equivalence of expansion with distance in the flow direction to time in the one-dimensional theory. On this basis, the potential application of the plasma process in space plasma physics is mentioned.

  20. Cosmic-ray acceleration in supernova remnants: non-linear theory revised

    SciTech Connect

    Caprioli, Damiano

    2012-07-01

    A rapidly growing amount of evidences, mostly coming from the recent gamma-ray observations of Galactic supernova remnants (SNRs), is seriously challenging our understanding of how particles are accelerated at fast shocks. The cosmic-ray (CR) spectra required to account for the observed phenomenology are in fact as steep as E{sup −2.2}–E{sup −2.4}, i.e., steeper than the test-particle prediction of first-order Fermi acceleration, and significantly steeper than what expected in a more refined non-linear theory of diffusive shock acceleration. By accounting for the dynamical back-reaction of the non-thermal particles, such a theory in fact predicts that the more efficient the particle acceleration, the flatter the CR spectrum. In this work we put forward a self-consistent scenario in which the account for the magnetic field amplification induced by CR streaming produces the conditions for reversing such a trend, allowing — at the same time — for rather steep spectra and CR acceleration efficiencies (about 20%) consistent with the hypothesis that SNRs are the sources of Galactic CRs. In particular, we quantitatively work out the details of instantaneous and cumulative CR spectra during the evolution of a typical SNR, also stressing the implications of the observed levels of magnetization on both the expected maximum energy and the predicted CR acceleration efficiency. The latter naturally turns out to saturate around 10-30%, almost independently of the fraction of particles injected into the acceleration process as long as this fraction is larger than about 10{sup −4}.

  1. Current and Prospective Constraints on Cosmic Acceleration using X-ray Galaxy Clusters and Supernovae

    NASA Astrophysics Data System (ADS)

    Rapetti, David A.; Allen, S. W.; Amin, M. A.; Blandford, R. D.

    2006-09-01

    We employ both a standard dynamical approach and a new kinematical approach to constrain cosmic acceleration using the three best available sets of redshift-independent distance measurements, from type Ia supernovae and X-ray cluster gas mass fraction measurements. The standard `dynamical' analysis employs the Friedmann equations and models dark energy as a fluid with an equation of state parameter, w. From a purely kinematical point of view, however, we can also construct models in terms of the dimensionless second and third derivatives of the scale factor a(t) with respect to cosmic time t, namely the present-day value of the deceleration parameter q_0 and the cosmic jerk parameter, j(t). A convenient feature of this parameterization is that all LambdaCDM models have j(t)=1 (constant), which facilitates simple tests for departures from the LambdaCDM paradigm. We obtain clear statistical evidence for a late time transition from a decelerating to an accelerating phase. For a flat model with constant jerk j(t)=j, we measure q_0=-0.81+-0.14 and j=2.16+0.81-0.75. For a dynamical model with constant w we measure Omega_m=0.306+0.042-0.040 and w=-1.15+0.14-0.18. Both kinematical and dynamical results are consistent with LambdaCDM at the 1sigma level. In comparison to dynamical analyses, the kinematical approach uses a different model set and employs a minimum of prior information, being independent of any particular gravity theory. We argue that both kinematical and dynamical techniques should be employed in future dark energy studies, where possible. Finally, we discuss the potential for future experiments including Constellation-X, which will constrain dark energy with comparable accuracy and in a beautifully complementary manner to the best other techniques available circa 2018.

  2. EVIDENCE FOR PARTICLE ACCELERATION TO THE KNEE OF THE COSMIC RAY SPECTRUM IN TYCHO'S SUPERNOVA REMNANT

    SciTech Connect

    Eriksen, Kristoffer A.; Hughes, John P.; Badenes, Carles; Fesen, Robert; Ghavamian, Parviz; Moffett, David; Plucinksy, Paul P.; Slane, Patrick; Rakowski, Cara E.; Reynoso, Estela M.

    2011-02-20

    Supernova remnants (SNRs) have long been assumed to be the source of cosmic rays (CRs) up to the 'knee' of the CR spectrum at 10{sup 15} eV, accelerating particles to relativistic energies in their blast waves by the process of diffusive shock acceleration (DSA). Since CR nuclei do not radiate efficiently, their presence must be inferred indirectly. Previous theoretical calculations and X-ray observations show that CR acceleration significantly modifies the structure of the SNR and greatly amplifies the interstellar magnetic field. We present new, deep X-ray observations of the remnant of Tycho's supernova (SN 1572, henceforth Tycho), which reveal a previously unknown, strikingly ordered pattern of non-thermal high-emissivity stripes in the projected interior of the remnant, with spacing that corresponds to the gyroradii of 10{sup 14}-10{sup 15} eV protons. Spectroscopy of the stripes shows the plasma to be highly turbulent on the (smaller) scale of the Larmor radii of TeV energy electrons. Models of the shock amplification of magnetic fields produce structure on the scale of the gyroradius of the highest energy CRs present, but they do not predict the highly ordered pattern we observe. We interpret the stripes as evidence for acceleration of particles to near the knee of the CR spectrum in regions of enhanced magnetic turbulence, while the observed highly ordered pattern of these features provides a new challenge to models of DSA.

  3. ENTROPY AT THE OUTSKIRTS OF GALAXY CLUSTERS AS IMPLICATIONS FOR COSMOLOGICAL COSMIC-RAY ACCELERATION

    SciTech Connect

    Fujita, Yutaka; Ohira, Yutaka; Yamazaki, Ryo

    2013-04-10

    Recently, gas entropy at the outskirts of galaxy clusters has attracted much attention. We propose that the entropy profiles could be used to study cosmic-ray (CR) acceleration around the clusters. If the CRs are effectively accelerated at the formation of clusters, the kinetic energy of infalling gas is consumed by the acceleration and the gas entropy should decrease. As a result, the entropy profiles become flat at the outskirts. If the acceleration is not efficient, the entropy should continue to increase outward. By comparing model predictions with X-ray observations with Suzaku, which show flat entropy profiles, we find that the CRs have carried {approx}< 7% of the kinetic energy of the gas away from the clusters. Moreover, the CR pressure at the outskirts can be {approx}< 40% of the total pressure. On the other hand, if the entropy profiles are not flat at the outskirts, as indicated by combined Plank and ROSAT observations, the carried energy and the CR pressure should be much smaller than the above estimations.

  4. Simulation of Cosmic Ray Acceleration, Propagation And Interaction in SNR Environment

    SciTech Connect

    Lee, S.H.; Kamae, T.; Ellison, D.C.; /North Carolina State U.

    2007-10-15

    Recent studies of young supernova remnants (SNRs) with Chandra, XMM, Suzaku and HESS have revealed complex morphologies and spectral features of the emission sites. The critical question of the relative importance of the two competing gamma-ray emission mechanisms in SNRs; inverse-Compton scattering by high-energy electrons and pion production by energetic protons, may be resolved by GLAST-LAT. To keep pace with the improved observations, we are developing a 3D model of particle acceleration, diffusion, and interaction in a SNR where broad-band emission from radio to multi-TeV energies, produced by shock accelerated electrons and ions, can be simulated for a given topology of shock fronts, magnetic field, and ISM densities. The 3D model takes as input, the particle spectra predicted by a hydrodynamic simulation of SNR evolution where nonlinear diffusive shock acceleration is coupled to the remnant dynamics. We will present preliminary models of the Galactic Ridge SNR RX J1713-3946 for selected choices of SNR parameters, magnetic field topology, and ISM density distributions. When constrained by broad-band observations, our models should predict the extent of coupling between spectral shape and morphology and provide direct information on the acceleration efficiency of cosmic-ray electrons and ions in SNRs.

  5. Simulation of Cosmic Ray Acceleration, Propagation and Interaction in SNR Environment

    NASA Astrophysics Data System (ADS)

    Lee, S. H.; Kamae, T.; Ellison, D. C.

    2007-07-01

    Recent studies of young supernova remnants (SNRs) with Chandra, XMM, Suzaku and HESS have revealed complex morphologies and spectral features of the emission sites. The critical question of the relative importance of the two competing gamma-ray emission mechanisms in SNRs; inverse-Compton scattering by high-energy electrons and pion production by energetic protons, may be resolved by GLAST-LAT. To keep pace with the improved observations, we are developing a 3D model of particle acceleration, diffusion, and interaction in a SNR where broad-band emission from radio to multi-TeV energies, produced by shock accelerated electrons and ions, can be simulated for a given topology of shock fronts, magnetic field, and ISM densities. The 3D model takes as input, the particle spectra predicted by a hydrodynamic simulation of SNR evolution where nonlinear diffusive shock acceleration is coupled to the remnant dynamics (e.g., Ellison, Decourchelle & Ballet; Ellison & Cassam-Chenai Ellison, Berezhko & Baring). We will present preliminary models of the Galactic Ridge SNR RX J1713-3946 for selected choices of SNR parameters, magnetic field topology, and ISM density distributions. When constrained by broad-band observations, our models should predict the extent of coupling between spectral shape and morphology and provide direct information on the acceleration efficiency of cosmic-ray electrons and ions in SNRs.

  6. Evidence for Particle Acceleration to the Knee of the Cosmic Ray Spectrum in Tycho's Supernova Remnant

    NASA Astrophysics Data System (ADS)

    Eriksen, Kristoffer A.; Hughes, John P.; Badenes, Carles; Fesen, Robert; Ghavamian, Parviz; Moffett, David; Plucinksy, Paul P.; Rakowski, Cara E.; Reynoso, Estela M.; Slane, Patrick

    2011-02-01

    Supernova remnants (SNRs) have long been assumed to be the source of cosmic rays (CRs) up to the "knee" of the CR spectrum at 1015 eV, accelerating particles to relativistic energies in their blast waves by the process of diffusive shock acceleration (DSA). Since CR nuclei do not radiate efficiently, their presence must be inferred indirectly. Previous theoretical calculations and X-ray observations show that CR acceleration significantly modifies the structure of the SNR and greatly amplifies the interstellar magnetic field. We present new, deep X-ray observations of the remnant of Tycho's supernova (SN 1572, henceforth Tycho), which reveal a previously unknown, strikingly ordered pattern of non-thermal high-emissivity stripes in the projected interior of the remnant, with spacing that corresponds to the gyroradii of 1014-1015 eV protons. Spectroscopy of the stripes shows the plasma to be highly turbulent on the (smaller) scale of the Larmor radii of TeV energy electrons. Models of the shock amplification of magnetic fields produce structure on the scale of the gyroradius of the highest energy CRs present, but they do not predict the highly ordered pattern we observe. We interpret the stripes as evidence for acceleration of particles to near the knee of the CR spectrum in regions of enhanced magnetic turbulence, while the observed highly ordered pattern of these features provides a new challenge to models of DSA.

  7. Ongoing cosmic ray acceleration in the supernova remnant W51C revealed with the MAGIC telescopes

    NASA Astrophysics Data System (ADS)

    Krause, J.; Reichardt, I.; Carmona, E.; Gozzini, S. R.; Jankowski, F.; MAGIC Collaboration

    2012-12-01

    The supernova remnant (SNR) W51C interacts with the molecular clouds of the star-forming region W51B, making the W51 complex one of the most promising targets to study cosmic ray acceleration. Gamma-ray emission from this region was discovered by Fermi/LAT and H.E.S.S., although its location was compatible with the SNR shell, the molecular cloud (MC) and a pulsar wind nebula (PWN) candidate. The modeling of the spectral energy distribution presented by the Fermi/LAT collaboration suggests a hadronic emission mechanism. Furthermore indications of an enhanced flux of low energy cosmic rays in the interaction region between SNR and MC have been reported based on ionization measurements in the mm regime. MAGIC conducted deep observations of W51, yielding a detection of an extended emission with more than 11 standard deviations. We extend the spectrum from the highest Fermi/LAT energies to ~5 TeV and find that it follows a single power law with an index of 2.58+/-0.07stat+/-0.22syst. We restrict the main part of the emission region to the zone where the SNR interacts with the molecular clouds. We also find a tail extending towards the PWN candidate CXO J192318.5+140305, possibly contributing up to 20% of the total flux. The broad band spectral energy distribution can be explained with a hadronic model that implies proton acceleration at least up to 50 TeV. This result, together with the morphology of the source, suggests that we observe ongoing acceleration of ions in the interaction zone between the SNR and the cloud.

  8. Is the acceleration of anomalous cosmic rays affected by the geometry of the termination shock?

    SciTech Connect

    Senanayake, U. K.; Florinski, V. E-mail: vaf0001@uah.edu

    2013-12-01

    Historically, anomalous cosmic rays (ACRs) were thought to be accelerated at the solar-wind termination shock (TS) by the diffusive shock acceleration process. When Voyager 1 crossed the TS in 2004, the measured ACR spectra did not match the theoretical prediction of a continuous power law, and the source of the high-energy ACRs was not observed. When the Voyager 2 crossed the TS in 2007, it produced similar results. Several possible explanations have since appeared in the literature, but we follow the suggestion that ACRs are still accelerated at the shock, only away from the Voyager crossing points. To investigate this hypothesis closer, we study ACR acceleration using a three-dimensional, non-spherical model of the heliosphere that is axisymmetric with respect to the interstellar flow direction. We then compare the results with those obtained for a spherical TS. A semi-analytic model of the plasma and magnetic field backgrounds is developed to permit an investigation over a wide range of parameters under controlled conditions. The model is applied to helium ACRs, whose phase-space trajectories are stochastically integrated backward in time until a pre-specified, low-energy boundary, taken to be 0.5 MeV n{sup –1} (the so-called injection energy), is reached. Our results show that ACR acceleration is quite efficient on the heliotail-facing part of the TS. For small values of the perpendicular diffusion coefficient, our model yields a positive intensity gradient between the TS and about midway through the heliosheath, in agreement with the Voyager observations.

  9. On ultra-high energy cosmic ray acceleration at the termination shock of young pulsar winds

    NASA Astrophysics Data System (ADS)

    Lemoine, Martin; Kotera, Kumiko; Pétri, Jérôme

    2015-07-01

    Pulsar wind nebulae (PWNe) are outstanding accelerators in Nature, in the sense that they accelerate electrons up to the radiation reaction limit. Motivated by this observation, this paper examines the possibility that young pulsar wind nebulae can accelerate ions to ultra-high energies at the termination shock of the pulsar wind. We consider here powerful PWNe, fed by pulsars born with ~ millisecond periods. Assuming that such pulsars exist, at least during a few years after the birth of the neutron star, and that they inject ions into the wind, we find that protons could be accelerated up to energies of the order of the Greisen-Zatsepin-Kuzmin cut-off, for a fiducial rotation period P ~ 1 msec and a pulsar magnetic field Bstar ~ 1013 G, implying a fiducial wind luminosity Lp ~ 1045 erg/s and a spin-down time tsd ~ 3× 107 s. The main limiting factor is set by synchrotron losses in the nebula and by the size of the termination shock; ions with Z>= 1 may therefore be accelerated to even higher energies. We derive an associated neutrino flux produced by interactions in the source region. For a proton-dominated composition, our maximum flux lies slightly below the 5-year sensitivity of IceCube-86 and above the 3-year sensitivity of the projected Askaryan Radio Array. It might thus become detectable in the next decade, depending on the exact level of contribution of these millisecond pulsar wind nebulae to the ultra-high energy cosmic ray flux.

  10. Shock waves and cosmic ray acceleration in the outskirts of galaxy clusters

    SciTech Connect

    Hong, Sungwook E.; Ryu, Dongsu; Kang, Hyesung; Cen, Renyue E-mail: ryu@canopus.cnu.ac.kr E-mail: cen@astro.princeton.edu

    2014-04-20

    The outskirts of galaxy clusters are continuously disturbed by mergers and gas infall along filaments, which in turn induce turbulent flow motions and shock waves. We examine the properties of shocks that form within r {sub 200} in sample galaxy clusters from structure formation simulations. While most of these shocks are weak and inefficient accelerators of cosmic rays (CRs), there are a number of strong, energetic shocks which can produce large amounts of CR protons via diffusive shock acceleration. We show that the energetic shocks reside mostly in the outskirts and a substantial fraction of them are induced by infall of the warm-hot intergalactic medium from filaments. As a result, the radial profile of the CR pressure in the intracluster medium is expected to be broad, dropping off more slowly than that of the gas pressure, and might be even temporarily inverted, peaking in the outskirts. The volume-integrated momentum spectrum of CR protons inside r {sub 200} has the power-law slope of 4.25-4.5, indicating that the average Mach number of the shocks of main CR production is in the range of {sub CR} ≈ 3-4. We suggest that some radio relics with relatively flat radio spectrum could be explained by primary electrons accelerated by energetic infall shocks with M{sub s} ≳ 3 induced in the cluster outskirts.

  11. High energy neutrinos from primary cosmic rays accelerated in the cores of active galaxies

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.; Done, C.; Salamon, M. H.; Sommers, P.

    1991-01-01

    The spectra and high-energy neutrino fluxes are calculated from photomeson production in active galactic nuclei (AGN) such as quasars and Seyfert galaxies using recent UV and X-ray observations to define the photon fields and an accretion-disk shock-acceleration model for producing ultrahigh-energy cosmic rays in the AGN. Collectively AGN should produce the dominant isotropic neutrino background between 10 exp 4 and 10 exp 10 GeV. Measurement of this background could be critical in determining the energy-generation mechanism, evolution, and distribution of AGN. High-energy background spectra and spectra from bright AGN such as NGC4151 and 3C273 are predicted which should be observable with present detectors. High energy AGN nus should produce a sphere of stellar disruption around their cores which could explain their observed broad-line emission regions.

  12. Dark Energy Models and Cosmic Acceleration with Anisotropic Universe in f(T) Gravity

    NASA Astrophysics Data System (ADS)

    Sharif, M.; Sehrish, Azeem

    2014-04-01

    This paper is devoted to studing the accelerated expansion of the universe in context of f(T) theory of gravity. For this purpose, we construct different f(T) models and investigate their cosmological behavior through equation of state parameter by using holographic, new agegraphic and their power-law entropy corrected dark energy models. We discuss the graphical behavior of this parameter versus redshift for particular values of constant parameters in Bianchi type I universe model. It is shown that the universe lies in different forms of dark energy, namely quintessence, phantom, and quintom corresponding to the chosen scale factors, which depend upon the constant parameters of the models.

  13. A no-go for no-go theorems prohibiting cosmic acceleration in extra dimensional models

    SciTech Connect

    Koster, Rik; Postma, Marieke E-mail: mpostma@nikhef.nl

    2011-12-01

    A four-dimensional effective theory that arises as the low-energy limit of some extra-dimensional model is constrained by the higher dimensional Einstein equations. Steinhardt and Wesley use this to show that accelerated expansion in our four large dimensions can only be transient in a large class of Kaluza-Klein models that satisfy the (higher dimensional) null energy condition [1]. We point out that these no-go theorems are based on a rather ad-hoc assumption on the metric, without which no strong statements can be made.

  14. Mimosoid legume plastome evolution: IR expansion, tandem repeat expansions, and accelerated rate of evolution in clpP

    PubMed Central

    Dugas, Diana V.; Hernandez, David; Koenen, Erik J.M.; Schwarz, Erika; Straub, Shannon; Hughes, Colin E.; Jansen, Robert K.; Nageswara-Rao, Madhugiri; Staats, Martijn; Trujillo, Joshua T.; Hajrah, Nahid H.; Alharbi, Njud S.; Al-Malki, Abdulrahman L.; Sabir, Jamal S. M.; Bailey, C. Donovan

    2015-01-01

    The Leguminosae has emerged as a model for studying angiosperm plastome evolution because of its striking diversity of structural rearrangements and sequence variation. However, most of what is known about legume plastomes comes from few genera representing a subset of lineages in subfamily Papilionoideae. We investigate plastome evolution in subfamily Mimosoideae based on two newly sequenced plastomes (Inga and Leucaena) and two recently published plastomes (Acacia and Prosopis), and discuss the results in the context of other legume and rosid plastid genomes. Mimosoid plastomes have a typical angiosperm gene content and general organization as well as a generally slow rate of protein coding gene evolution, but they are the largest known among legumes. The increased length results from tandem repeat expansions and an unusual 13 kb IR-SSC boundary shift in Acacia and Inga. Mimosoid plastomes harbor additional interesting features, including loss of clpP intron1 in Inga, accelerated rates of evolution in clpP for Acacia and Inga, and dN/dS ratios consistent with neutral and positive selection for several genes. These new plastomes and results provide important resources for legume comparative genomics, plant breeding, and plastid genetic engineering, while shedding further light on the complexity of plastome evolution in legumes and angiosperms. PMID:26592928

  15. Mimosoid legume plastome evolution: IR expansion, tandem repeat expansions, and accelerated rate of evolution in clpP.

    PubMed

    Dugas, Diana V; Hernandez, David; Koenen, Erik J M; Schwarz, Erika; Straub, Shannon; Hughes, Colin E; Jansen, Robert K; Nageswara-Rao, Madhugiri; Staats, Martijn; Trujillo, Joshua T; Hajrah, Nahid H; Alharbi, Njud S; Al-Malki, Abdulrahman L; Sabir, Jamal S M; Bailey, C Donovan

    2015-01-01

    The Leguminosae has emerged as a model for studying angiosperm plastome evolution because of its striking diversity of structural rearrangements and sequence variation. However, most of what is known about legume plastomes comes from few genera representing a subset of lineages in subfamily Papilionoideae. We investigate plastome evolution in subfamily Mimosoideae based on two newly sequenced plastomes (Inga and Leucaena) and two recently published plastomes (Acacia and Prosopis), and discuss the results in the context of other legume and rosid plastid genomes. Mimosoid plastomes have a typical angiosperm gene content and general organization as well as a generally slow rate of protein coding gene evolution, but they are the largest known among legumes. The increased length results from tandem repeat expansions and an unusual 13 kb IR-SSC boundary shift in Acacia and Inga. Mimosoid plastomes harbor additional interesting features, including loss of clpP intron1 in Inga, accelerated rates of evolution in clpP for Acacia and Inga, and dN/dS ratios consistent with neutral and positive selection for several genes. These new plastomes and results provide important resources for legume comparative genomics, plant breeding, and plastid genetic engineering, while shedding further light on the complexity of plastome evolution in legumes and angiosperms. PMID:26592928

  16. Model experiment of cosmic ray acceleration due to an incoherent wakefield induced by an intense laser pulse

    SciTech Connect

    Kuramitsu, Y.; Sakawa, Y.; Takeda, K.; Tampo, M.; Takabe, H.; Nakanii, N.; Kondo, K.; Tsuji, K.; Kimura, K.; Fukumochi, S.; Kashihara, M.; Tanimoto, T.; Nakamura, H.; Ishikura, T.; Kodama, R.; Mima, K.; Tanaka, K. A.; Mori, Y.; Miura, E.; Kitagawa, Y.

    2011-01-15

    The first report on a model experiment of cosmic ray acceleration by using intense laser pulses is presented. Large amplitude light waves are considered to be excited in the upstream regions of relativistic astrophysical shocks and the wakefield acceleration of cosmic rays can take place. By substituting an intense laser pulse for the large amplitude light waves, such shock environments were modeled in a laboratory plasma. A plasma tube, which is created by imploding a hollow polystyrene cylinder, was irradiated by an intense laser pulse. Nonthermal electrons were generated by the wakefield acceleration and the energy distribution functions of the electrons have a power-law component with an index of {approx}2. The maximum attainable energy of the electrons in the experiment is discussed by a simple analytic model. In the incoherent wakefield the maximum energy can be much larger than one in the coherent field due to the momentum space diffusion or the energy diffusion of electrons.

  17. Accelerating expansion or inhomogeneity? II. Mimicking acceleration with the energy function in the Lemaître-Tolman model

    NASA Astrophysics Data System (ADS)

    Krasiński, Andrzej

    2014-07-01

    This is a continuation of the paper published in Phys. Rev. D 89, 023520 (2014). Here we investigate how the luminosity distance-redshift relation DL(z) of the ΛCDM model is duplicated in the Lemaître-Tolman (L-T) model with Λ =0, constant bang-time function tB and the energy function E(r) mimicking accelerated expansion on the observer's past light cone (r is a uniquely defined comoving radial coordinate). Numerical experiments show that E>0 necessarily. The functions z(r) and E(r) are numerically calculated from the initial point at the observer's position, then backward from the initial point at the apparent horizon (AH). Reconciling the results of the two calculations allows one to determine the values of E/r2 at r=0 and at the AH. The problems connected with continuing the calculation through the AH are discussed in detail and solved. Then z(r) and E(r) are continued beyond the AH, up to the numerical crash that signals the contact of the light cone with the big bang. Similarly, the light cone of the L-T model is calculated by proceeding from the two initial points, and compared with the ΛCDM light cone. The model constructed here contains shell crossings, but they can be removed by matching the L-T region to a Friedmann background, without causing any conflict with the type Ia supernovae observations. The mechanism of imitating the accelerated expansion by the E(r) function is explained in a descriptive way.

  18. Calibrating the cosmic distance scale ladder: the role of the sound-horizon scale and the local expansion rate as distance anchors

    NASA Astrophysics Data System (ADS)

    Cuesta, Antonio J.; Verde, Licia; Riess, Adam; Jimenez, Raul

    2015-04-01

    We exploit cosmological model-independent measurements of the expansion history of the Universe to provide a cosmic distance ladder. These are supernovae Type Ia used as standard candles (at redshift between 0.01 and 1.3) and baryon acoustic oscillations (at redshifts between 0.1 and 0.8) as standard rulers. We calibrate (anchor) the ladder in two ways: first using the local H0 value as an anchor at z = 0 (effectively calibrating the standard candles) and secondly using the cosmic microwave background-inferred sound-horizon scale as an anchor (giving the standard ruler length) as an inverse distance ladder. Both methods are consistent, but the uncertainty in the expansion history H(z) is smaller if the sound-horizon scale is used. We present inferred values for the sound horizon at radiation drag rd which do not rely on assumptions about the early expansion history nor on cosmic microwave background measurements but on the cosmic distance ladder and baryon acoustic oscillations measurements. We also present derived values of H0 from the inverse distance ladder and we show that they are in very good agreement with the extrapolated value in a Λ cold dark matter model from Planck cosmic microwave background data.

  19. Rapid analysis of scattering from periodic dielectric structures using accelerated Cartesian expansions

    SciTech Connect

    Baczewski, Andrew David; Miller, Nicholas C.; Shanker, Balasubramaniam

    2012-03-22

    Here, the analysis of fields in periodic dielectric structures arise in numerous applications of recent interest, ranging from photonic bandgap structures and plasmonically active nanostructures to metamaterials. To achieve an accurate representation of the fields in these structures using numerical methods, dense spatial discretization is required. This, in turn, affects the cost of analysis, particularly for integral-equation-based methods, for which traditional iterative methods require Ο(Ν2) operations, Ν being the number of spatial degrees of freedom. In this paper, we introduce a method for the rapid solution of volumetric electric field integral equations used in the analysis of doubly periodic dielectric structures. The crux of our method is the accelerated Cartesian expansion algorithm, which is used to evaluate the requisite potentials in Ο(Ν) cost. Results are provided that corroborate our claims of acceleration without compromising accuracy, as well as the application of our method to a number of compelling photonics applications.

  20. Accelerated Cartesian expansions for the rapid solution of periodic multiscale problems

    DOE PAGESBeta

    Baczewski, Andrew David; Dault, Daniel L.; Shanker, Balasubramaniam

    2012-07-03

    We present an algorithm for the fast and efficient solution of integral equations that arise in the analysis of scattering from periodic arrays of PEC objects, such as multiband frequency selective surfaces (FSS) or metamaterial structures. Our approach relies upon the method of Accelerated Cartesian Expansions (ACE) to rapidly evaluate the requisite potential integrals. ACE is analogous to FMM in that it can be used to accelerate the matrix vector product used in the solution of systems discretized using MoM. Here, ACE provides linear scaling in both CPU time and memory. Details regarding the implementation of this method within themore » context of periodic systems are provided, as well as results that establish error convergence and scalability. In addition, we also demonstrate the applicability of this algorithm by studying several exemplary electrically dense systems.« less

  1. Accelerated Cartesian expansions for the rapid solution of periodic multiscale problems

    SciTech Connect

    Baczewski, Andrew David; Dault, Daniel L.; Shanker, Balasubramaniam

    2012-07-03

    We present an algorithm for the fast and efficient solution of integral equations that arise in the analysis of scattering from periodic arrays of PEC objects, such as multiband frequency selective surfaces (FSS) or metamaterial structures. Our approach relies upon the method of Accelerated Cartesian Expansions (ACE) to rapidly evaluate the requisite potential integrals. ACE is analogous to FMM in that it can be used to accelerate the matrix vector product used in the solution of systems discretized using MoM. Here, ACE provides linear scaling in both CPU time and memory. Details regarding the implementation of this method within the context of periodic systems are provided, as well as results that establish error convergence and scalability. In addition, we also demonstrate the applicability of this algorithm by studying several exemplary electrically dense systems.

  2. Effects of Nonlinear Inhomogeneity on the Cosmic Expansion with Numerical Relativity.

    PubMed

    Bentivegna, Eloisa; Bruni, Marco

    2016-06-24

    We construct a three-dimensional, fully relativistic numerical model of a universe filled with an inhomogeneous pressureless fluid, starting from initial data that represent a perturbation of the Einstein-de Sitter model. We then measure the departure of the average expansion rate with respect to this homogeneous and isotropic reference model, comparing local quantities to the predictions of linear perturbation theory. We find that collapsing perturbations reach the turnaround point much earlier than expected from the reference spherical top-hat collapse model and that the local deviation of the expansion rate from the homogeneous one can be as high as 28% at an underdensity, for an initial density contrast of 10^{-2}. We then study, for the first time, the exact behavior of the backreaction term Q_{D}. We find that, for small values of the initial perturbations, this term exhibits a 1/a scaling, and that it is negative with a linearly growing absolute value for larger perturbation amplitudes, thereby contributing to an overall deceleration of the expansion. Its magnitude, on the other hand, remains very small even for relatively large perturbations. PMID:27391711

  3. Effects of Nonlinear Inhomogeneity on the Cosmic Expansion with Numerical Relativity

    NASA Astrophysics Data System (ADS)

    Bentivegna, Eloisa; Bruni, Marco

    2016-06-01

    We construct a three-dimensional, fully relativistic numerical model of a universe filled with an inhomogeneous pressureless fluid, starting from initial data that represent a perturbation of the Einstein-de Sitter model. We then measure the departure of the average expansion rate with respect to this homogeneous and isotropic reference model, comparing local quantities to the predictions of linear perturbation theory. We find that collapsing perturbations reach the turnaround point much earlier than expected from the reference spherical top-hat collapse model and that the local deviation of the expansion rate from the homogeneous one can be as high as 28% at an underdensity, for an initial density contrast of 10-2. We then study, for the first time, the exact behavior of the backreaction term QD. We find that, for small values of the initial perturbations, this term exhibits a 1 /a scaling, and that it is negative with a linearly growing absolute value for larger perturbation amplitudes, thereby contributing to an overall deceleration of the expansion. Its magnitude, on the other hand, remains very small even for relatively large perturbations.

  4. Diffusive Cosmic-ray Acceleration at Relativistic Shock Waves with Magnetostatic Turbulence

    NASA Astrophysics Data System (ADS)

    Schlickeiser, R.

    2015-08-01

    The analytical theory of diffusive cosmic-ray acceleration at parallel stationary shock waves with magnetostatic turbulence is generalized to arbitrary shock speeds {V}{{s}}={β }1c, including, in particular, relativistic speeds. This is achieved by applying the diffusion approximation to the relevant Fokker-Planck particle transport equation formulated in the mixed comoving coordinate system. In this coordinate system, the particle's momentum coordinates p and μ ={p}\\parallel /p are taken in the rest frame of the streaming plasma, whereas the time and space coordinates are taken in the observer's system. For magnetostatic slab turbulence, the diffusion-convection transport equation for the isotropic (in the rest frame of the streaming plasma) part of the particle's phase space density is derived. For a step-wise shock velocity profile, the steady-state diffusion-convection transport equation is solved. For a symmetric pitch-angle scattering Fokker-Planck coefficient, {D}μ μ (-μ )={D}μ μ (μ ), the steady-state solution is independent of the microphysical scattering details. For nonrelativistic mono-momentum particle injection at the shock, the differential number density of accelerated particles is a Lorentzian-type distribution function, which at large momenta approaches a power-law distribution function N(p≥slant {p}c)\\propto {p}-ξ with the spectral index ξ ({β }1)=1+[3/({{{Γ }}}1\\sqrt{{r}2-{β }12}-1)(1+3{β }12)]. For nonrelativistic ({β }1\\ll 1) shock speeds, this spectral index agrees with the known result ξ ({β }1\\ll 1)≃ (r+2)/(r-1), whereas for ultrarelativistic ({{{Γ }}}1\\gg 1) shock speeds the spectral index value is close to unity.

  5. Issues for Simulation of Galactic Cosmic Ray Exposures for Radiobiological Research at Ground-Based Accelerators.

    PubMed

    Kim, Myung-Hee Y; Rusek, Adam; Cucinotta, Francis A

    2015-01-01

    For radiobiology research on the health risks of galactic cosmic rays (GCR) ground-based accelerators have been used with mono-energetic beams of single high charge, Z and energy, E (HZE) particles. In this paper, we consider the pros and cons of a GCR reference field at a particle accelerator. At the NASA Space Radiation Laboratory (NSRL), we have proposed a GCR simulator, which implements a new rapid switching mode and higher energy beam extraction to 1.5 GeV/u, in order to integrate multiple ions into a single simulation within hours or longer for chronic exposures. After considering the GCR environment and energy limitations of NSRL, we performed extensive simulation studies using the stochastic transport code, GERMcode (GCR Event Risk Model) to define a GCR reference field using 9 HZE particle beam-energy combinations each with a unique absorber thickness to provide fragmentation and 10 or more energies of proton and (4)He beams. The reference field is shown to well represent the charge dependence of GCR dose in several energy bins behind shielding compared to a simulated GCR environment. However, a more significant challenge for space radiobiology research is to consider chronic GCR exposure of up to 3 years in relation to simulations with animal models of human risks. We discuss issues in approaches to map important biological time scales in experimental models using ground-based simulation, with extended exposure of up to a few weeks using chronic or fractionation exposures. A kinetics model of HZE particle hit probabilities suggests that experimental simulations of several weeks will be needed to avoid high fluence rate artifacts, which places limitations on the experiments to be performed. Ultimately risk estimates are limited by theoretical understanding, and focus on improving knowledge of mechanisms and development of experimental models to improve this understanding should remain the highest priority for space radiobiology research. PMID:26090339

  6. Issues for Simulation of Galactic Cosmic Ray Exposures for Radiobiological Research at Ground-Based Accelerators

    PubMed Central

    Kim, Myung-Hee Y.; Rusek, Adam; Cucinotta, Francis A.

    2015-01-01

    For radiobiology research on the health risks of galactic cosmic rays (GCR) ground-based accelerators have been used with mono-energetic beams of single high charge, Z and energy, E (HZE) particles. In this paper, we consider the pros and cons of a GCR reference field at a particle accelerator. At the NASA Space Radiation Laboratory (NSRL), we have proposed a GCR simulator, which implements a new rapid switching mode and higher energy beam extraction to 1.5 GeV/u, in order to integrate multiple ions into a single simulation within hours or longer for chronic exposures. After considering the GCR environment and energy limitations of NSRL, we performed extensive simulation studies using the stochastic transport code, GERMcode (GCR Event Risk Model) to define a GCR reference field using 9 HZE particle beam–energy combinations each with a unique absorber thickness to provide fragmentation and 10 or more energies of proton and 4He beams. The reference field is shown to well represent the charge dependence of GCR dose in several energy bins behind shielding compared to a simulated GCR environment. However, a more significant challenge for space radiobiology research is to consider chronic GCR exposure of up to 3 years in relation to simulations with animal models of human risks. We discuss issues in approaches to map important biological time scales in experimental models using ground-based simulation, with extended exposure of up to a few weeks using chronic or fractionation exposures. A kinetics model of HZE particle hit probabilities suggests that experimental simulations of several weeks will be needed to avoid high fluence rate artifacts, which places limitations on the experiments to be performed. Ultimately risk estimates are limited by theoretical understanding, and focus on improving knowledge of mechanisms and development of experimental models to improve this understanding should remain the highest priority for space radiobiology research. PMID:26090339

  7. ASSESSING THE FEASIBILITY OF COSMIC-RAY ACCELERATION BY MAGNETIC TURBULENCE AT THE GALACTIC CENTER

    SciTech Connect

    Fatuzzo, M.; Melia, F. E-mail: fmelia@email.arizona.edu

    2012-05-01

    The presence of relativistic particles at the center of our Galaxy is evidenced by the diffuse TeV emission detected from the inner {approx}2 Degree-Sign of the Galaxy. Although it is not yet entirely clear whether the origin of the TeV photons is due to hadronic or leptonic interactions, the tight correlation of the intensity distribution with the distribution of molecular gas along the Galactic ridge strongly points to a pionic-decay process involving relativistic protons. In previous work, we concluded that point-source candidates, such as the supermassive black hole Sagittarius A* (identified with the High-Energy Stereoscopic System (HESS) source J1745-290) or the pulsar wind nebulae dispersed along the Galactic plane, could not account for the observed diffuse TeV emission from this region. Motivated by this result, we consider here the feasibility that the cosmic rays populating the Galactic center region are accelerated in situ by magnetic turbulence. Our results indicate that even in a highly conductive environment, this mechanism is efficient enough to energize protons within the intercloud medium to the {approx}>TeV energies required to produce the HESS emission.

  8. Cosmology of a Friedmann-Lamaître-Robertson-Walker 3-brane, late-time cosmic acceleration, and the cosmic coincidence.

    PubMed

    Doolin, Ciaran; Neupane, Ishwaree P

    2013-04-01

    A late epoch cosmic acceleration may be naturally entangled with cosmic coincidence--the observation that at the onset of acceleration the vacuum energy density fraction nearly coincides with the matter density fraction. In this Letter we show that this is indeed the case with the cosmology of a Friedmann-Lamaître-Robertson-Walker (FLRW) 3-brane in a five-dimensional anti-de Sitter spacetime. We derive the four-dimensional effective action on a FLRW 3-brane, from which we obtain a mass-reduction formula, namely, M(P)(2) = ρ(b)/|Λ(5)|, where M(P) is the effective (normalized) Planck mass, Λ(5) is the five-dimensional cosmological constant, and ρ(b) is the sum of the 3-brane tension V and the matter density ρ. Although the range of variation in ρ(b) is strongly constrained, the big bang nucleosynthesis bound on the time variation of the effective Newton constant G(N) = (8πM(P)(2))(-1) is satisfied when the ratio V/ρ ≳ O(10(2)) on cosmological scales. The same bound leads to an effective equation of state close to -1 at late epochs in accordance with astrophysical and cosmological observations. PMID:25166976

  9. REVIEWS OF TOPICAL PROBLEMS: Cosmic vacuum

    NASA Astrophysics Data System (ADS)

    Chernin, Artur D.

    2001-11-01

    Recent observational studies of distant supernovae have suggested the existence of cosmic vacuum whose energy density exceeds the total density of all the other energy components in the Universe. The vacuum produces the field of antigravity that causes the cosmological expansion to accelerate. It is this accelerated expansion that has been discovered in the observations. The discovery of cosmic vacuum radically changes our current understanding of the present state of the Universe. It also poses new challenges to both cosmology and fundamental physics. Why is the density of vacuum what it is? Why do the densities of the cosmic energy components differ in exact value but agree in order of magnitude? On the other hand, the discovery made at large cosmological distances of hundreds and thousands Mpc provides new insights into the dynamics of the nearby Universe, the motions of galaxies in the local volume of 10 - 20 Mpc where the cosmological expansion was originally discovered.

  10. Rapid analysis of scattering from periodic dielectric structures using accelerated Cartesian expansions

    DOE PAGESBeta

    Baczewski, Andrew David; Miller, Nicholas C.; Shanker, Balasubramaniam

    2012-03-22

    Here, the analysis of fields in periodic dielectric structures arise in numerous applications of recent interest, ranging from photonic bandgap structures and plasmonically active nanostructures to metamaterials. To achieve an accurate representation of the fields in these structures using numerical methods, dense spatial discretization is required. This, in turn, affects the cost of analysis, particularly for integral-equation-based methods, for which traditional iterative methods require Ο(Ν2) operations, Ν being the number of spatial degrees of freedom. In this paper, we introduce a method for the rapid solution of volumetric electric field integral equations used in the analysis of doubly periodic dielectricmore » structures. The crux of our method is the accelerated Cartesian expansion algorithm, which is used to evaluate the requisite potentials in Ο(Ν) cost. Results are provided that corroborate our claims of acceleration without compromising accuracy, as well as the application of our method to a number of compelling photonics applications.« less

  11. ANALYTIC SOLUTION FOR SELF-REGULATED COLLECTIVE ESCAPE OF COSMIC RAYS FROM THEIR ACCELERATION SITES

    SciTech Connect

    Malkov, M. A.; Diamond, P. H.; Sagdeev, R. Z.; Aharonian, F. A.; Moskalenko, I. V. E-mail: pdiamond@ucsd.edu

    2013-05-01

    Supernova remnants (SNRs), as the major contributors to the galactic cosmic rays (CRs), are believed to maintain an average CR spectrum by diffusive shock acceleration regardless of the way they release CRs into the interstellar medium (ISM). However, the interaction of the CRs with nearby gas clouds crucially depends on the release mechanism. We call into question two aspects of a popular paradigm of the CR injection into the ISM, according to which they passively and isotropically diffuse in the prescribed magnetic fluctuations as test particles. First, we treat the escaping CR and the Alfven waves excited by them on an equal footing. Second, we adopt field-aligned CR escape outside the source, where the waves become weak. An exact analytic self-similar solution for a CR ''cloud'' released by a dimmed accelerator strongly deviates from the test-particle result. The normalized CR partial pressure may be approximated as P(p,z,t)=2[|z|{sup 5/3}+z{sub dif}{sup 5/3}(p,t)]{sup -3/5} exp[-z{sup 2}/4D{sub ISM}(p)t], where p is the momentum of CR particle, and z is directed along the field. The core of the cloud expands as z{sub dif}{proportional_to}{radical}(D{sub NL}(p)t) and decays in time as p{proportional_to}2z{sup -1}{sub dif}(t). The diffusion coefficient D{sub NL} is strongly suppressed compared to its background ISM value D{sub ISM}: D{sub NL} {approx} D{sub ISM}exp (- {Pi}) << D{sub ISM} for sufficiently high field-line-integrated CR partial pressure, {Pi}. When {Pi} >> 1, the CRs drive Alfven waves efficiently enough to build a transport barrier (p Almost-Equal-To 2/ Divides z Divides -{sup p}edestal{sup )} that strongly reduces the leakage. The solution has a spectral break at p = p{sub br}, where p{sub br} satisfies the equation D{sub NL}(p{sub br}) {approx_equal} z {sup 2}/t.

  12. Non Parametric Determination of Acceleration Characteristics in Supernova Shocks Based on Spectra of Cosmic Rays and Remnant Radiation

    NASA Astrophysics Data System (ADS)

    Petrosian, Vahe

    2016-07-01

    We have developed an inversion method for determination of the characteristics of the acceleration mechanism directly and non-parametrically from observations, in contrast to the usual forward fitting of parametric model variables to observations. This is done in the frame work of the so-called leaky box model of acceleration, valid for isotropic momentum distribution and for volume integrated characteristics in a finite acceleration site. We consider both acceleration by shocks and stochastic acceleration where turbulence plays the primary role to determine the acceleration, scattering and escape rates. Assuming a knowledge of the background plasma the model has essentially two unknown parameters, namely the momentum and pitch angle scattering diffusion coefficients, which can be evaluated given two independent spectral observations. These coefficients are obtained directly from the spectrum of radiation from the supernova remnants (SNRs), which gives the spectrum of accelerated particles, and the observed spectrum of cosmic rays (CRs), which are related to the spectrum of particles escaping the SNRs. The results obtained from application of this method will be presented.

  13. Rayleigh-Taylor instabilities in Type Ia supernova remnants undergoing cosmic ray particle acceleration - low adiabatic index solutions

    NASA Astrophysics Data System (ADS)

    Wang, Chih-Yueh

    2011-07-01

    This study investigates the evolution of Rayleigh-Taylor (R-T) instabilities in Type Ia supernova remnants that are associated with a low adiabatic index γ, where γ < 5/3, which reflects the expected change in the supernova shock structure as a result of cosmic ray particle acceleration. Extreme cases, such as the case with the maximum compression ratio that corresponds to γ= 1.1, are examined. As γ decreases, the shock compression ratio rises, and an increasingly narrow intershock region with a more pronounced initial mixture of R-T unstable gas is produced. Consequently, the remnant outline may be perturbed by small-amplitude, small-wavelength bumps. However, as the instability decays over time, the extent of convective mixing in terms of the ratio of the radius of the R-T fingers to the blast wave does not strongly depend on the value of γ for γ≥ 1.2. As a result of the age of the remnant, the unstable gas cannot extend sufficiently far to form metal-enriched filaments of ejecta material close to the periphery of Tycho's supernova remnant. The consistency of the dynamic properties of Tycho's remnant with the adiabatic model γ= 5/3 reveals that the injection of cosmic rays is too weak to alter the shock structure. Even with very efficient acceleration of cosmic rays at the shock, significantly enhanced mixing is not expected in Type Ia supernova remnants.

  14. Late cosmic acceleration in a vector-Gauss-Bonnet gravity model

    NASA Astrophysics Data System (ADS)

    Oliveros, A.; Solis, Enzo L.; Acero, Mario A.

    2016-12-01

    In this work, we study a general vector-tensor model of dark energy (DE) with a Gauss-Bonnet term coupled to a vector field and without explicit potential terms. Considering a spatially flat Friedmann-Robertson-Walker (FRW) type universe and a vector field without spatial components, the cosmological evolution is analyzed from the field equations of this model considering two sets of parameters. In this context, we have shown that it is possible to obtain an accelerated expansion phase of the universe since the equation state parameter w satisfies the restriction - 1 < w < -1/3 (for suitable values of model parameters). Further, analytical expressions for the Hubble parameter H, equation state parameter w and the invariant scalar ϕ are obtained. We also find that the square of the speed of sound is negative for all values of redshift, therefore, the model presented here shows a sign of instability under small perturbations. We finally perform an analysis using H(z) observational data and we find that for the free parameter ξ in the interval (-23.9,-3.46) × 10-5, at 99.73% C.L. (and fixing η = -1 and ω = 1/4), the model has a good fit to the data.

  15. FRW Like Cosmological Model and Accelerated Expansion of the Universe from Non Commutative Seiberg-Witten Geometry

    NASA Astrophysics Data System (ADS)

    Aissaoui, H.; Mebarki, N.; Bouhalouf, H.

    2010-10-01

    An FRW like cosmological model in the non commutative Seiberg-Witten space-time is proposed. The pure NCG dynamical apparent horizon and Hawking temperature are obtained and explicit expressions of the scale factor, Hubble and deceleration parameters are derived. The accelerated expansion of the universe scenario is also discussed.

  16. ON THE e{sup +}e{sup -} EXCESSES AND THE KNEE OF THE COSMIC RAY SPECTRA-HINTS OF COSMIC RAY ACCELERATION IN YOUNG SUPERNOVA REMNANTS

    SciTech Connect

    Hu Hongbo; Yuan Qiang; Wang Bo; Fan Chao; Zhang Jianli; Bi Xiaojun

    2009-08-01

    Supernova remnants (SNRs) have long been regarded as sources of the Galactic cosmic rays (CRs) up to petaelectronvolts, but convincing evidence is still lacking. In this work we explore the common origin of the subtle features of the CR spectra, such as the knee of CR spectra and the excesses of electron/positron fluxes recently observed by ATIC, H.E.S.S., Fermi-LAT, and PAMELA. Numerical calculation shows that those features of CR spectra can be well reproduced in a scenario with e{sup +}e{sup -} pair production by interactions between high-energy CRs and background photons in an environment similar to the young SNR. The success of such a coherent explanation serves in turn as evidence that at least a portion of CRs might be accelerated in young SNRs.

  17. Cosmic Rays: "A Thin Rain of Charged Particles."

    ERIC Educational Resources Information Center

    Friedlander, Michael

    1990-01-01

    Discussed are balloons and electroscopes, understanding cosmic rays, cosmic ray paths, isotopes and cosmic-ray travel, sources of cosmic rays, and accelerating cosmic rays. Some of the history of the discovery and study of cosmic rays is presented. (CW)

  18. On a phenomenology of the accelerated expansion with a varying ghost dark energy

    NASA Astrophysics Data System (ADS)

    Khurshudyan, M. Z.; Makarenko, A. N.

    2016-06-01

    Subject of our study it is the accelerated expansion of the large scale universe, where a varying ghost dark energy can take the role of the dark energy. The model of the varying ghost dark energy considered in this work it is a phenomenological modification of the ghost dark energy. Recently, three other phenomenological models of the varying ghost dark energy have been suggested and the model considered in this work will complete the logical chain of considered modifications. The best fit of the theoretical results to the luminosity distance, has been used to obtain preliminary constraints on the parameters of the models. This does help us to reduce the amount of discussion. On the other hand, detailed comparison of the theoretical results with observational data has been left as a subject of another discussion elsewhere. Moreover, a look to considered models via Om and statefinder hierarchy analysis are presented and discussed for different forms of interaction between the varying ghost dark energy and cold dark matter.

  19. TWO-STEP ACCELERATION MODEL OF COSMIC RAYS AT MIDDLE-AGED SUPERNOVA REMNANTS: UNIVERSALITY IN SECONDARY SHOCKS

    SciTech Connect

    Inoue, Tsuyoshi; Yamazaki, Ryo; Inutsuka, Shu-ichiro

    2010-11-01

    Recent gamma-ray observations of middle-aged supernova remnants revealed a mysterious broken power-law spectrum. Using three-dimensional magnetohydrodynamic simulations, we show that the interaction between a supernova blast wave and interstellar clouds formed by thermal instability generates multiple reflected shocks. The typical Mach numbers of the reflected shocks are shown to be M{approx_equal} 2 depending on the density contrast between the diffuse intercloud gas and clouds. These secondary shocks can further energize cosmic-ray particles originally accelerated at the blast-wave shock. This 'two-step' acceleration scenario reproduces the observed gamma-ray spectrum and predicts the high-energy spectral index ranging approximately from 3 to 4.

  20. Coronal and interplanetary propagation, interplanetary acceleration, cosmic-ray observations by deep space network and anomalous component

    NASA Technical Reports Server (NTRS)

    Ng, C. K.

    1986-01-01

    The purpose is to provide an overview of the contributions presented in sessions SH3, SH1.5, SH4.6 and SH4.7 of the 19th International Cosmic Ray Conference. These contributed papers indicate that steady progress continues to be made in both the observational and the theoretical aspects of the transport and acceleration of energetic charged particles in the heliosphere. Studies of solar and interplanetary particles have placed emphasis on particle directional distributions in relation to pitch-angle scattering and magnetic focusing, on the rigidity and spatial dependence of the mean free path, and on new propagation regimes in the inner and outer heliosphere. Coronal propagation appears in need of correlative multi-spacecraft studies in association with detailed observation of the flare process and coronal magnetic structures. Interplanetary acceleration has now gone into a consolidation phase, with theories being worked out in detail and checked against observation.

  1. Two-step Acceleration Model of Cosmic Rays at Middle-aged Supernova Remnants: Universality in Secondary Shocks

    NASA Astrophysics Data System (ADS)

    Inoue, Tsuyoshi; Yamazaki, Ryo; Inutsuka, Shu-ichiro

    2010-11-01

    Recent gamma-ray observations of middle-aged supernova remnants revealed a mysterious broken power-law spectrum. Using three-dimensional magnetohydrodynamic simulations, we show that the interaction between a supernova blast wave and interstellar clouds formed by thermal instability generates multiple reflected shocks. The typical Mach numbers of the reflected shocks are shown to be Msime 2 depending on the density contrast between the diffuse intercloud gas and clouds. These secondary shocks can further energize cosmic-ray particles originally accelerated at the blast-wave shock. This "two-step" acceleration scenario reproduces the observed gamma-ray spectrum and predicts the high-energy spectral index ranging approximately from 3 to 4.

  2. Studies of charge neutral FCC Lattice Gas with Yukawa Interaction and Accelerated Cartesian Expansion method

    NASA Astrophysics Data System (ADS)

    Huang, He

    In this thesis, I present the results of studies of the structural properties and phase transition of a charge neutral FCC Lattice Gas with Yukawa Interaction and discuss a novel fast calculation algorithm---Accelerated Cartesian Expansion (ACE) method. In the first part of my thesis, I discuss the results of Monte Carlo simulations carried out to understand the finite temperature (phase transition) properties and the ground state structure of a Yukawa Lattice Gas (YLG) model. In this model the ions interact via the potential q iqjexp(-kappar> ij)/rij where qi,j are the charges of the ions located at the lattice sites i and j with position vectors R i and Rj; rij = Ri-Rj, kappa is a measure of the range of the interaction and is called the screening parameter. This model approximates an interesting quaternary system of great current thermoelectric interest called LAST-m, AgSbPbmTem+2. I have also developed rapid calculation methods for the potential energy calculation in a lattice gas system with periodic boundary condition bases on the Ewald summation method and coded the algorithm to compute the energies in MC simulation. Some of the interesting results of the MC simulations are: (i) how the nature and strength of the phase transition depend on the range of interaction (Yukawa screening parameter kappa) (ii) what is the degeneracy of the ground state for different values of the concentration of charges, and (iii) what is the nature of two-stage disordering transition seen for certain values of x. In addition, based on the analysis of the surface energy of different nano-clusters formed near the transition temperature, the solidification process and the rate of production of these nano-clusters have been studied. In the second part of my thesis, we have developed two methods for rapidly computing potentials of the form R-nu. Both these methods are founded on addition theorems based on Taylor expansions. Taylor's series has a couple of inherent advantages: (i) it

  3. Cosmic ray decreases and particle acceleration in 1978-1982 and the associated solar wind structures

    NASA Technical Reports Server (NTRS)

    Cane, H. V.; Richardson, I. G.; Von Rosenvinge, T. T.

    1993-01-01

    Results of a study of the time histories of particles in the energy range 1 MeV to 1 GeV at the times of greater than 3-percent cosmic ray decreases in the years 1978-1982 are presented. The intensity-time profiles of the particles are used to separate the cosmic ray decreases into four classes which are subsequently associated with three types of solar wind structures. Decreases in class 1 (15 events) and class 2 (26 events) are associated with shocks driven by energetic coronal mass ejections. For class 1 events, the ejecta are detected at 1 AU, whereas this is not usually the case for class 2 events. The shock must therefore play a dominant role in producing the cosmic ray depression in class 2 events. It is argued that since energetic particles (from MEV to GeV energies) seen at earth may respond to solar wind structures which are not detected at earth, consideration of particle observations over a wide range of energies is necessary for a full understanding of cosmic ray decreases.

  4. OBJECTS APPEAR SMALLER AS THEY RECEDE: HOW PROPER MOTIONS CAN DIRECTLY REVEAL THE COSMIC EXPANSION, PROVIDE GEOMETRIC DISTANCES, AND MEASURE THE HUBBLE CONSTANT

    SciTech Connect

    Darling, Jeremy

    2013-11-10

    Objects and structures gravitationally decoupled from the Hubble expansion will appear to shrink in angular size as the universe expands. Observations of extragalactic proper motions can thus directly reveal the cosmic expansion. Relatively static structures such as galaxies or galaxy clusters can potentially be used to measure the Hubble constant, and test masses in large scale structures can measure the overdensity. Since recession velocities and angular separations can be precisely measured, apparent proper motions can also provide geometric distance measurements to static structures. The apparent fractional angular compression of static objects is 15 μas yr{sup –1} in the local universe; this motion is modulated by the overdensity in dynamic expansion-decoupled structures. We use the Titov et al. quasar proper motion catalog to examine the pairwise proper motion of a sparse network of test masses. Small-separation pairs (<200 Mpc comoving) are too few to measure the expected effect, yielding an inconclusive 8.3 ± 14.9 μas yr{sup –1}. Large-separation pairs (200-1500 Mpc) show no net convergence or divergence for z < 1, –2.7 ± 3.7 μas yr{sup –1}, consistent with pure Hubble expansion and significantly inconsistent with static structures, as expected. For all pairs a 'null test' gives –0.36 ± 0.62 μas yr{sup –1}, consistent with Hubble expansion and excludes a static locus at ∼5-10σ significance for z ≅ 0.5-2.0. The observed large-separation pairs provide a reference frame for small-separation pairs that will significantly deviate from the Hubble flow. The current limitation is the number of small-separation objects with precise astrometry, but Gaia will address this and will likely detect the cosmic recession.

  5. A New Mechanism of Magnetic Field Generation in Supernova Shock Waves and its Implication for Cosmic Ray Acceleration

    NASA Astrophysics Data System (ADS)

    Diamond, Patrick

    2005-10-01

    SNR shocks are the most probable source of galactic cosmic rays. We discuss the diffusive acceleration mechanism in terms of its potential to accelerate CRs to 10^18 eV, as observations imply. One possibility, currently discussed in the literature, is to resonantly generate a turbulent magnetic field via accelerated particles in excess of the background field. We indicate some difficulties of this scenario and suggest a different possibility, which is based on the generation of Alfven waves at the gyroradius scale at the background field level, with a subsequent transfer to longer scales via interaction with strong acoustic turbulence in the shock precursor. The acoustic turbulence in turn, may be generated by Drury instability or by parametric instability of the Alfven (A) waves. The essential idea is an A-->A+S decay instability process, where one of the interacting scatterers (i.e. the sound, or S-waves) are driven by the Drury instability process. This rapidly generates longer wavelength Alfven waves, which in turn resonate with high energy CRs thus binding them to the shock and enabling their further acceleration.

  6. Exploring a matter-dominated model with bulk viscosity to drive the accelerated expansion of the Universe

    SciTech Connect

    Avelino, Arturo; Nucamendi, Ulises E-mail: ulises@ifm.umich.mx

    2010-08-01

    We explore the viability of a bulk viscous matter-dominated Universe to explain the present accelerated expansion of the Universe. The model is composed by a pressureless fluid with bulk viscosity of the form ζ = ζ{sub 0}+ζ{sub 1}H where ζ{sub 0} and ζ{sub 1} are constants and H is the Hubble parameter. The pressureless fluid characterizes both the baryon and dark matter components. We study the behavior of the Universe according to this model analyzing the scale factor as well as some curvature scalars and the matter density. On the other hand, we compute the best estimated values of ζ{sub 0} and ζ{sub 1} using the type Ia Supernovae (SNe Ia) probe. We find that from all the possible scenarios for the Universe, the preferred one by the best estimated values of (ζ{sub 0},ζ{sub 1}) is that of an expanding Universe beginning with a Big-Bang, followed by a decelerated expansion at early times, and with a smooth transition in recent times to an accelerated expansion epoch that is going to continue forever. The predicted age of the Universe is a little smaller than the mean value of the observational constraint coming from the oldest globular clusters but it is still inside of the confidence interval of this constraint. A drawback of the model is the violation of the local second law of thermodynamics in redshifts z∼>1. However, when we assume ζ{sub 1} = 0, the simple model ζ = ζ{sub 0} evaluated at the best estimated value for ζ{sub 0} satisfies the local second law of thermodynamics, the age of the Universe is in perfect agreement with the constraint of globular clusters, and it also has a Big-Bang, followed by a decelerated expansion with the smooth transition to an accelerated expansion epoch in late times, that is going to continue forever.

  7. Direct Acceleration of Pickup Ions at The Solar Wind Termination Shock: The Production of Anomalous Cosmic Rays

    NASA Technical Reports Server (NTRS)

    Ellison, Donald C.; Jones, Frank C.; Baring, Matthew G.

    1998-01-01

    We have modeled the injection and acceleration of pickup ions at the solar wind termination shock and investigated the parameters needed to produce the observed Anomalous Cosmic Ray (ACR) fluxes. A non-linear Monte Carlo technique was employed, which in effect solves the Boltzmann equation and is not restricted to near-isotropic particle distribution functions. This technique models the injection of thermal and pickup ions, the acceleration of these ions, and the determination of the shock structure under the influence of the accelerated ions. The essential effects of injection are treated in a mostly self-consistent manner, including effects from shock obliquity, cross- field diffusion, and pitch-angle scattering. Using recent determinations of pickup ion densities, we are able to match the absolute flux of hydrogen in the ACRs by assuming that pickup ion scattering mean free paths, at the termination shock, are much less than an AU and that modestly strong cross-field diffusion occurs. Simultaneously, we match the flux ratios He(+)/H(+) or O(+)/H(+) to within a factor approx. 5. If the conditions of strong scattering apply, no pre-termination-shock injection phase is required and the injection and acceleration of pickup ions at the termination shock is totally analogous to the injection and acceleration of ions at highly oblique interplanetary shocks recently observed by the Ulysses spacecraft. The fact that ACR fluxes can be modeled with standard shock assumptions suggests that the much-discussed "injection problem" for highly oblique shocks stems from incomplete (either mathematical or computer) modeling of these shocks rather than from any actual difficulty shocks may have in injecting and accelerating thermal or quasi-thermal particles.

  8. Modeling Focused Acceleration of Cosmic-Ray Particles by Stochastic Methods

    NASA Astrophysics Data System (ADS)

    Armstrong, C. K.; Litvinenko, Yuri E.; Craig, I. J. D.

    2012-10-01

    Schlickeiser & Shalchi suggested that a first-order Fermi mechanism of focused particle acceleration could be important in several astrophysical applications. In order to investigate focused acceleration, we express the Fokker-Planck equation as an equivalent system of stochastic differential equations. We simplify the system for a set of physically motivated parameters, extend the analytical theory, and determine the evolving particle distribution numerically. While our numerical results agree with the focused acceleration rate of Schlickeiser & Shalchi for a weakly anisotropic particle distribution, we establish significant limitations of the analytical approach. Momentum diffusion is found to be more significant than focused acceleration at early times. Most critically, the particle distribution rapidly becomes anisotropic, leading to a much slower momentum gain rate. We discuss the consequences of our results for the role of focused acceleration in astrophysics.

  9. Generation of the cosmic rays flux variations due to surfatron acceleration of charges by electromagnetic waves in space plasma

    NASA Astrophysics Data System (ADS)

    Erokhin, Nikolay; Loznikov, Vladimir; Shkevov, Rumen; Zolnikova, Nadezhda; Mikhailovskaya, Ludmila

    2016-07-01

    The analysis of experimental data on the spectra of cosmic rays (CR) has shown their variability on time scales of a few years, in particular, CR variations observed in E / Z range from TeV to 10000 TeV, where E is the energy of the particle, Z is its charge number. Consequently, the source of these variations must be located at a distance of no more than 1 parsec from the sun in the closest local interstellar clouds. As a mechanism of such variations appearance it is considered the surfatron acceleration of CR particles by electromagnetic wave in a relatively quiet space plasma. On the basis of developed model the numerical calculations were performed for particle capture dynamics (electrons, protons, helium and iron nuclei) in the wave effective potential well with a following growth their energy by 3-6 orders of magnitude. Optimal conditions for the implementation of charged particles surfatron acceleration in space plasma, the rate of trapped particles energy growth, the dynamics of wave phase on the captured particle trajectory, a temporal dynamics of components for charge impulse momentum and speed were studied. It is indicated that the capture of a small fraction of particles by wave for energies about TeV and less followed by their surfatron acceleration to an energy of about 10000 TeV will lead to a significant increase in the CR flux at such high energies. Thus CL flow variations are conditioned by changes in the space weather parameters

  10. Ion acceleration and plasma jet formation in ultra-thin foils undergoing expansion and relativistic transparency

    NASA Astrophysics Data System (ADS)

    King, M.; Gray, R. J.; Powell, H. W.; MacLellan, D. A.; Gonzalez-Izquierdo, B.; Stockhausen, L. C.; Hicks, G. S.; Dover, N. P.; Rusby, D. R.; Carroll, D. C.; Padda, H.; Torres, R.; Kar, S.; Clarke, R. J.; Musgrave, I. O.; Najmudin, Z.; Borghesi, M.; Neely, D.; McKenna, P.

    2016-09-01

    At sufficiently high laser intensities, the rapid heating to relativistic velocities and resulting decompression of plasma electrons in an ultra-thin target foil can result in the target becoming relativistically transparent to the laser light during the interaction. Ion acceleration in this regime is strongly affected by the transition from an opaque to a relativistically transparent plasma. By spatially resolving the laser-accelerated proton beam at near-normal laser incidence and at an incidence angle of 30°, we identify characteristic features both experimentally and in particle-in-cell simulations which are consistent with the onset of three distinct ion acceleration mechanisms: sheath acceleration; radiation pressure acceleration; and transparency-enhanced acceleration. The latter mechanism occurs late in the interaction and is mediated by the formation of a plasma jet extending into the expanding ion population. The effect of laser incident angle on the plasma jet is explored.

  11. Mass entrainment and turbulence-driven acceleration of ultra-high energy cosmic rays in Centaurus A

    NASA Astrophysics Data System (ADS)

    Wykes, Sarka; Croston, Judith H.; Hardcastle, Martin J.; Eilek, Jean A.; Biermann, Peter L.; Achterberg, Abraham; Bray, Justin D.; Lazarian, Alex; Haverkorn, Marijke; Protheroe, Ray J.; Bromberg, Omer

    2013-10-01

    Observations of the FR I radio galaxy Centaurus A in radio, X-ray, and gamma-ray bands provide evidence for lepton acceleration up to several TeV and clues about hadron acceleration to tens of EeV. Synthesising the available observational constraints on the physical conditions and particle content in the jets, inner lobes and giant lobes of Centaurus A, we aim to evaluate its feasibility as an ultra-high-energy cosmic-ray source. We apply several methods of determining jet power and affirm the consistency of various power estimates of ~1 × 1043 erg s-1. Employing scaling relations based on previous results for 3C 31, we estimate particle number densities in the jets, encompassing available radio through X-ray observations. Our model is compatible with the jets ingesting ~3 × 1021 g s-1 of matter via external entrainment from hot gas and ~7 × 1022 g s-1 via internal entrainment from jet-contained stars. This leads to an imbalance between the internal lobe pressure available from radiating particles and magnetic field, and our derived external pressure. Based on knowledge of the external environments of other FR I sources, we estimate the thermal pressure in the giant lobes as 1.5 × 10-12 dyn cm-2, from which we deduce a lower limit to the temperature of ~1.6 × 108 K. Using dynamical and buoyancy arguments, we infer ~440-645 Myr and ~560 Myr as the sound-crossing and buoyancy ages of the giant lobes respectively, inconsistent with their spectral ages. We re-investigate the feasibility of particle acceleration via stochastic processes in the lobes, placing new constraints on the energetics and on turbulent input to the lobes. The same "very hot" temperatures that allow self-consistency between the entrainment calculations and the missing pressure also allow stochastic UHECR acceleration models to work.

  12. Onion-shell model of cosmic ray acceleration in supernova remnants

    NASA Technical Reports Server (NTRS)

    Bogdan, T. J.; Volk, H. J.

    1983-01-01

    A method is devised to approximate the spatially averaged momentum distribution function for the accelerated particles at the end of the active lifetime of a supernova remnant. The analysis is confined to the test particle approximation and adiabatic losses are oversimplified, but unsteady shock motion, evolving shock strength, and non-uniform gas flow effects on the accelerated particle spectrum are included. Monoenergetic protons are injected at the shock front. It is found that the dominant effect on the resultant accelerated particle spectrum is a changing spectral index with shock strength. High energy particles are produced in early phases, and the resultant distribution function is a slowly varying power law over several orders of magnitude, independent of the specific details of the supernova remnant.

  13. Kinetic studies of wave-particle interactions in cosmic-ray acceleration

    NASA Astrophysics Data System (ADS)

    Pohl, Martin; Niemiec, Jacek; Stroman, Thomas; Bret, Antoine; Roeken, Christian

    Shock acceleration relies on the presence of magnetic-field fluctuations that can scatter rela-tivistic charged particles in both the upstream and downstream regions of the shock. We report on kinetic particle-in-cell simulations of the non-linear evolution of magnetic turbulence that arises upstream of the shock as well as at the shock itself. We will in particular address the relation between modes seen in the simulations and waves expected on the grounds of a linear instability analysis, the efficiency of small-scale turbulence in scattering relativistic particles, and the influence of accelerated particles on the formation of the shock itself.

  14. Magnetic field amplification in nonlinear diffusive shock acceleration including resonant and non-resonant cosmic-ray driven instabilities

    SciTech Connect

    Bykov, Andrei M.; Osipov, Sergei M.; Ellison, Donald C.; Vladimirov, Andrey E. E-mail: osm2004@mail.ru E-mail: avenovo@gmail.com

    2014-07-10

    We present a nonlinear Monte Carlo model of efficient diffusive shock acceleration where the magnetic turbulence responsible for particle diffusion is calculated self-consistently from the resonant cosmic-ray (CR) streaming instability, together with non-resonant short- and long-wavelength CR-current-driven instabilities. We include the backpressure from CRs interacting with the strongly amplified magnetic turbulence which decelerates and heats the super-Alfvénic flow in the extended shock precursor. Uniquely, in our plane-parallel, steady-state, multi-scale model, the full range of particles, from thermal (∼eV) injected at the viscous subshock to the escape of the highest energy CRs (∼PeV) from the shock precursor, are calculated consistently with the shock structure, precursor heating, magnetic field amplification, and scattering center drift relative to the background plasma. In addition, we show how the cascade of turbulence to shorter wavelengths influences the total shock compression, the downstream proton temperature, the magnetic fluctuation spectra, and accelerated particle spectra. A parameter survey is included where we vary shock parameters, the mode of magnetic turbulence generation, and turbulence cascading. From our survey results, we obtain scaling relations for the maximum particle momentum and amplified magnetic field as functions of shock speed, ambient density, and shock size.

  15. Complete cosmic scenario from inflation to late time acceleration: Nonequilibrium thermodynamics in the context of particle creation

    NASA Astrophysics Data System (ADS)

    Chakraborty, Subenoy; Saha, Subhajit

    2014-12-01

    The paper deals with the mechanism of particle creation in the framework of irreversible thermodynamics. The second order nonequilibrium thermodynamical prescription of Israel and Stewart has been presented with particle creation rate, treated as the dissipative effect. In the background of a flat Friedmann-Robertson-Walker (FRW) model, we assume the nonequilibrium thermodynamical process to be isentropic so that the entropy per particle does not change and consequently the dissipative pressure can be expressed linearly in terms of the particle creation rate. Here the dissipative pressure behaves as a dynamical variable having a nonlinear inhomogeneous evolution equation and the entropy flow vector satisfies the second law of thermodynamics. Further, using the Friedmann equations and by proper choice of the particle creation rate as a function of the Hubble parameter, it is possible to show (separately) a transition from the inflationary phase to the radiation era and also from the matter dominated era to late time acceleration. Also, in analogy to analytic continuation, it is possible to show a continuous cosmic evolution from inflation to late time acceleration by adjusting the parameters. It is found that in the de Sitter phase, the comoving entropy increases exponentially with time, keeping entropy per particle unchanged. Subsequently, the above cosmological scenarios have been described from a field theoretic point of view by introducing a scalar field having self-interacting potential. Finally, we make an attempt to show the cosmological phenomenon of particle creation as Hawking radiation, particularly during the inflationary era.

  16. The Role of Cosmic-Ray Pressure in Accelerating Galactic Outflows

    NASA Astrophysics Data System (ADS)

    Simpson, Christine M.; Pakmor, Rüdiger; Marinacci, Federico; Pfrommer, Christoph; Springel, Volker; Glover, Simon C. O.; Clark, Paul C.; Smith, Rowan J.

    2016-08-01

    We study the formation of galactic outflows from supernova (SN) explosions with the moving-mesh code AREPO in a stratified column of gas with a surface density similar to the Milky Way disk at the solar circle. We compare different simulation models for SN placement and energy feedback, including cosmic rays (CRs), and find that models that place SNe in dense gas and account for CR diffusion are able to drive outflows with similar mass loading as obtained from a random placement of SNe with no CRs. Despite this similarity, CR-driven outflows differ in several other key properties including their overall clumpiness and velocity. Moreover, the forces driving these outflows originate in different sources of pressure, with the CR diffusion model relying on non-thermal pressure gradients to create an outflow driven by internal pressure and the random-placement model depending on kinetic pressure gradients to propel a ballistic outflow. CRs therefore appear to be non-negligible physics in the formation of outflows from the interstellar medium.

  17. Acceleration of solar cosmic rays in a flare current sheet and their propagation in interplanetary space

    NASA Astrophysics Data System (ADS)

    Podgorny, A. I.; Podgorny, I. M.

    2015-09-01

    Analyses of GOES spacecraft data show that the prompt component of high-energy protons arrive at the Earth after a time corresponding to their generation in flares in the western part of the solar disk, while the delayed component is detected several hours later. All protons in flares are accelerated by a single mechanism. The particles of the prompt component propagate along magnetic lines of the Archimedean spiral connectng the flare with the Earth. The prompt component generated by flares in the eastern part of the solar disk is not observed at the Earth, since particles accelerated by these flares do not intersect magnetic-field lines connecting the flare with the Earth. These particles arrive at the Earth via their motion across the interplanetary magnetic field. These particles are trapped by the magnetic field and transported by the solar wind, since the interplanetary magnetic field is frozen in the wind plasma, and these particles also diffuse across the field. The duration of the delay reaches several days.

  18. Cosmology with cosmic shear observations: a review.

    PubMed

    Kilbinger, Martin

    2015-07-01

    Cosmic shear is the distortion of images of distant galaxies due to weak gravitational lensing by the large-scale structure in the Universe. Such images are coherently deformed by the tidal field of matter inhomogeneities along the line of sight. By measuring galaxy shape correlations, we can study the properties and evolution of structure on large scales as well as the geometry of the Universe. Thus, cosmic shear has become a powerful probe into the nature of dark matter and the origin of the current accelerated expansion of the Universe. Over the last years, cosmic shear has evolved into a reliable and robust cosmological probe, providing measurements of the expansion history of the Universe and the growth of its structure. We review here the principles of weak gravitational lensing and show how cosmic shear is interpreted in a cosmological context. Then we give an overview of weak-lensing measurements, and present the main observational cosmic-shear results since it was discovered 15 years ago, as well as the implications for cosmology. We then conclude with an outlook on the various future surveys and missions, for which cosmic shear is one of the main science drivers, and discuss promising new weak cosmological lensing techniques for future observations. PMID:26181770

  19. Using Dark Matter Haloes to Learn about Cosmic Acceleration: A New Proposal for a Universal Mass Function

    NASA Technical Reports Server (NTRS)

    Prescod-Weinstein, Chanda; Afshordi, Niayesh

    2011-01-01

    Structure formation provides a strong test of any cosmic acceleration model because a successful dark energy model must not inhibit or overpredict the development of observed large-scale structures. Traditional approaches to studies of structure formation in the presence of dark energy or a modified gravity implement a modified Press-Schechter formalism, which relates the linear overdensities to the abundance of dark matter haloes at the same time. We critically examine the universality of the Press-Schechter formalism for different cosmologies, and show that the halo abundance is best correlated with spherical linear overdensity at 94% of collapse (or observation) time. We then extend this argument to ellipsoidal collapse (which decreases the fractional time of best correlation for small haloes), and show that our results agree with deviations from modified Press-Schechter formalism seen in simulated mass functions. This provides a novel universal prescription to measure linear density evolution, based on current and future observations of cluster (or dark matter) halo mass function. In particular, even observations of cluster abundance in a single epoch will constrain the entire history of linear growth of cosmological of perturbations.

  20. K-essence model from the mechanical approach point of view: coupled scalar field and the late cosmic acceleration

    NASA Astrophysics Data System (ADS)

    Bouhmadi-López, Mariam; Sravan Kumar, K.; Marto, João; Morais, João; Zhuk, Alexander

    2016-07-01

    In this paper, we consider the Universe at the late stage of its evolution and deep inside the cell of uniformity. At these scales, we can consider the Universe to be filled with dust-like matter in the form of discretely distributed galaxies, a K-essence scalar field, playing the role of dark energy, and radiation as matter sources. We investigate such a Universe in the mechanical approach. This means that the peculiar velocities of the inhomogeneities (in the form of galaxies) as well as the fluctuations of the other perfect fluids are non-relativistic. Such fluids are designated as coupled because they are concentrated around the inhomogeneities. In the present paper, we investigate the conditions under which the K-essence scalar field with the most general form for its action can become coupled. We investigate at the background level three particular examples of the K-essence models: (i) the pure kinetic K-essence field, (ii) a K-essence with a constant speed of sound and (iii) the K-essence model with the Lagrangian bX+cX2‑V(phi). We demonstrate that if the K-essence is coupled, all these K-essence models take the form of multicomponent perfect fluids where one of the component is the cosmological constant. Therefore, they can provide the late-time cosmic acceleration and be simultaneously compatible with the mechanical approach.

  1. Cosmic flows and the expansion of the local Universe from non-linear phase-space reconstructions

    NASA Astrophysics Data System (ADS)

    Heß, Steffen; Kitaura, Francisco-Shu

    2016-03-01

    In this work, we investigate the impact of cosmic flows and density perturbations on Hubble constant H0 measurements using non-linear phase-space reconstructions of the Local Universe (LU). In particular, we rely on a set of 25 precise constrained N-body simulations based on Bayesian initial conditions reconstructions of the LU using the Two-Micron Redshift Survey galaxy sample within distances of about 90 h-1 Mpc. These have been randomly extended up to volumes enclosing distances of 360 h-1 Mpc with augmented Lagrangian perturbation theory (750 simulations in total), accounting in this way for gravitational mode coupling from larger scales, correcting for periodic boundary effects, and estimating systematics of missing attractors (σlarge = 134 s-1 km). We report on Local Group (LG) speed reconstructions, which for the first time are compatible with those derived from cosmic microwave background-dipole measurements: |vLG| = 685 ± 137 s-1 km. The direction (l, b) = (260.5° ± 13.3°, 39.1 ± 10.4°) is found to be compatible with the observations after considering the variance of large scales. Considering this effect of large scales, our local bulk flow estimations assuming a Λ cold dark matter model are compatible with the most recent estimates based on velocity data derived from the Tully-Fisher relation. We focus on low-redshift supernova measurements out to 0.01 < z < 0.025, which have been found to disagree with probes at larger distances. Our analysis indicates that there are two effects related to cosmic variance contributing to this tension. The first one is caused by the anisotropic distribution of supernovae, which aligns with the velocity dipole and hence induces a systematic boost in H0. The second one is due to the inhomogeneous matter fluctuations in the LU. In particular, a divergent region surrounding the Virgo Supercluster is responsible for an additional positive bias in H0. Taking these effects into account yields a correction of ΔH0 = -1

  2. The Accelerating Universe: Infinite Expansion, the Cosmological Constant, and the Beauty of the Cosmos

    NASA Astrophysics Data System (ADS)

    Livio, Mario

    2000-12-01

    Advance Praise for The Accelerating Universe "The Accelerating Universe is not only an informative book about modern cosmology. It is rich storytelling and, above all, a celebration of the human mind in its quest for beauty in all things." -Alan Lightman, author of Einstein's Dreams "This is a wonderfully lucid account of the extraordinary discoveries that have made the last years a golden period for observational cosmology. But Mario Livio has not only given the reader one clear explanation after another of what astronomers are up to, he has used them to construct a provocative argument for the importance of aesthetics in the development of science and for the inseparability of science, art, and culture." -Lee Smolin, author of The Life of the Cosmos "What a pleasure to read! An exciting, simple account of the universe revealed by modern astronomy. Beautifully written, clearly presented, informed by scientific and philosophical insights." -John Bahcall, Institute for Advanced Study "A book with charm, beauty, elegance, and importance. As authoritative a journey as can be taken through modern cosmology." -Allan Sandage, Observatories of the Carnegie Institution of Washington

  3. Constraining the cosmic deceleration-acceleration transition with type Ia supernova, BAO/CMB and H(z) data

    NASA Astrophysics Data System (ADS)

    Vargas dos Santos, M.; Reis, R. R. R.; Waga, I.

    2016-02-01

    We revisit the kink-like parametrization of the deceleration parameter q(z) [1], which considers a transition, at redshift zt, from cosmic deceleration to acceleration. In this parametrization the initial, at z gg zt, value of the q-parameter is qi, its final, z=-1, value is qf and the duration of the transition is parametrized by τ. By assuming a flat space geometry we obtain constraints on the free parameters of the model using recent data from type Ia supernovae (SN Ia), baryon acoustic oscillations (BAO), cosmic microwave background (CMB) and the Hubble parameter H(z). The use of H(z) data introduces an explicit dependence of the combined likelihood on the present value of the Hubble parameter H0, allowing us to explore the influence of different priors when marginalizing over this parameter. We also study the importance of the CMB information in the results by considering data from WMAP7, WMAP9 (Wilkinson Microwave Anisotropy Probe—7 and 9 years) and Planck 2015. We show that the contours and best fit do not depend much on the different CMB data used and that the considered new BAO data is responsible for most of the improvement in the results. Assuming a flat space geometry, qi=1/2 and expressing the present value of the deceleration parameter q0 as a function of the other three free parameters, we obtain zt=0.67+0.10-0.08, τ=0.26+0.14-0.10 and q0=-0.48+0.11-0.13, at 68% of confidence level, with an uniform prior over H0. If in addition we fix qf=-1, as in flat ΛCDM, DGP and Chaplygin quartessence that are special models described by our parametrization, we get zt=0.66+0.03-0.04, τ=0.33+0.04-0.04 and q0=-0.54+0.05-0.07, in excellent agreement with flat ΛCDM for which τ=1/3. We also obtain for flat wCDM, another dark energy model described by our parametrization, the constraint on the equation of state parameter -1.22 < w < -0.78 at more than 99% confidence level.

  4. Java Based Tool To Explore The Discovery Of Dark Energy And The Accelerated Expansion Of The Universe

    NASA Astrophysics Data System (ADS)

    Mijic, Milan; Lim, R.; Hu, Z.; Park, D.; Wells, D.; Wong, F.; Perrault, S.; Shvarts, E.; Levitin, S.; Rios, M.; Kang, E. Y. E.; Longson, T.

    2008-05-01

    The discovery of the accelerated expansion of the universe through observations of High-Redshift supernovae and its implication for the existence of Dark Energy as the dominant component of our universe, surely counts as one of the most important moments in the entire history of physics and astronomy. This discovery has great appeal to the general public, both because of the heroic lore to observe distant supernovae and because of the strange relativistic properties of the Dark Energy. To bring this development to the non-professionals, the Cal State L.A. Science Visualization project developed an easy to use Java based tool, which may be used in college, pre-college or public science education. The tool utilizes multimedia presentations, such as graphs or images, to simulate the search for and observations of high-redshift supernovae, and interactively leads to the discovery of the created universe fluid content. Model universes are selected in a semi-random manner, which displays range of interesting possibilities for the effective equation of state, the shape of the Hubble diagram, or the nature of the expansion. The Java-based tool is deployed through Java webstart for both high-end and low-end terminal users across platforms.

  5. The acoustic signatures of ground acceleration, gas expansion, and spall fallback in experimental volcanic explosions

    NASA Astrophysics Data System (ADS)

    Bowman, Daniel C.; Taddeucci, Jacopo; Kim, Keehoon; Anderson, Jacob F.; Lees, Jonathan M.; Graettinger, Alison H.; Sonder, Ingo; Valentine, Greg A.

    2014-03-01

    Infrasound and high-speed imaging during a series of field-scale buried explosions suggest new details about the generation and radiation patterns of acoustic waves from volcanic eruptions. We recorded infrasound and high-speed video from a series of subsurface explosions with differing burial depths and charge sizes. Joint observations and modeling allow the extraction of acoustic energy related to the magnitude of initial ground deformation, the contribution of gas breakout, and the timing of the fallback of displaced material. The existence and relative acoustic amplitudes of these three phases depended on the size and depth of the explosion. The results motivate a conceptual model that relates successive contributions from ground acceleration, gas breakout, and spall fallback to the acoustic amplitude and waveform characteristics of buried explosions. We place the literature on infrasound signals at Santiaguito Volcano, Guatemala, and Sakurajima and Suwonosejima Volcanoes, Japan, in the context of this model.

  6. Accelerating Atomic Orbital-based Electronic Structure Calculation via Pole Expansion plus Selected Inversion

    SciTech Connect

    Lin, Lin; Chen, Mohan; Yang, Chao; He, Lixin

    2012-02-10

    We describe how to apply the recently developed pole expansion plus selected inversion (PEpSI) technique to Kohn-Sham density function theory (DFT) electronic structure calculations that are based on atomic orbital discretization. We give analytic expressions for evaluating charge density, total energy, Helmholtz free energy and atomic forces without using the eigenvalues and eigenvectors of the Kohn-Sham Hamiltonian. We also show how to update the chemical potential without using Kohn-Sham eigenvalues. The advantage of using PEpSI is that it has a much lower computational complexity than that associated with the matrix diagonalization procedure. We demonstrate the performance gain by comparing the timing of PEpSI with that of diagonalization on insulating and metallic nanotubes. For these quasi-1D systems, the complexity of PEpSI is linear with respect to the number of atoms. This linear scaling can be observed in our computational experiments when the number of atoms in a nanotube is larger than a few hundreds. Both the wall clock time and the memory requirement of PEpSI is modest. This makes it even possible to perform Kohn-Sham DFT calculations for 10,000-atom nanotubes on a single processor. We also show that the use of PEpSI does not lead to loss of accuracy required in a practical DFT calculation.

  7. Stability of bellows used as expansion joints between superconducting magnets in accelerators

    SciTech Connect

    Shutt, R.P.; Rehak, M.L.

    1991-01-01

    For superconducting magnets, one needs many bellows for connection of various helium cooling transfer lines. There could be approximately 20,000 magnet interconnection bellows in the SSC exposed to an internal pressure. When axially compressed, internally pressurized, or insufficiently supported at their ends, bellows can become unstable, leading to gross distortion or complete failure. If several bellows are contained in a magnet assembly, failure modes might interact. If designed properly large bellows can be used to connect the large tubular shells that support the magnet iron yokes and superconducting coils and contain supercritical helium for magnet cooling. We investigate here bellows design features and end supports to insure that instabilities will not occur in the bellows pressure operating region, including some margin. A model of three superconducting accelerator magnets connected by two large bellows is analyzed in order to ascertain that support requirements are satisfied and in order to study interaction effects between the two bellows. Specific details of large and small bellows design and reliability for our application will be addressed.

  8. Mass varying neutrinos, quintessence, and the accelerating expansion of the Universe

    SciTech Connect

    Chitov, Gennady Y.; August, Tyler; Natarajan, Aravind; Kahniashvili, Tina

    2011-02-15

    We analyze the mass varying neutrino scenario. We consider a minimal model of massless Dirac fermions coupled to a scalar field, mainly in the framework of finite-temperature quantum field theory. We demonstrate that the mass equation we find has nontrivial solutions only for special classes of potentials, and only within certain temperature intervals. We give most of our results for the Ratra-Peebles dark energy (DE) potential. The thermal (temporal) evolution of the model is analyzed. Following the time arrow, the stable, metastable, and unstable phases are predicted. The model predicts that the present Universe is below its critical temperature and accelerates. At the critical point, the Universe undergoes a first-order phase transition from the (meta)stable oscillatory regime to the unstable rolling regime of the DE field. This conclusion agrees with the original idea of quintessence as a force making the Universe roll towards its true vacuum with a zero {Lambda} term. The present mass varying neutrino scenario is free from the coincidence problem, since both the DE density and the neutrino mass are determined by the scale M of the potential. Choosing M{approx}10{sup -3} eV to match the present DE density, we can obtain the present neutrino mass in the range m{approx}10{sup -2}-1 eV and consistent estimates for other parameters of the Universe.

  9. First-order Fermi acceleration in the two-stream limit. [for cosmic rays at relativistic and non-relativistic shocks

    NASA Technical Reports Server (NTRS)

    Bogdan, T. J.; Webb, G. M.

    1987-01-01

    A study of the first-order Fermi mechanism for accelerating cosmic-rays at relativistic and nonrelativistic shocks is carried out by using the two-stream approximation. Exact steady-state analytic solutions illustrating the shock acceleration process in the test-particle limit in which monoenergetic (relativistic) seed particles enter the shock through an upstream free-escape boundary are obtained. The momentum spectrum of the shock accelerated particles consists of a series of Dirac delta distributions corresponding to particles that have undergone an integral number of acceleration cycles. Since particles in the model have a finite fixed escape probability from the shock and the particle momenta p are equally spaced in log p, the envelope of the delta functions series is a power law in momentum. The solutions are used to discuss time-dependent aspects of the shock acceleration process in terms of the finite cycle time, escape probability, and momentum change per cycle that can be deduced from the steady-state model. The length-scale over which the accelerated particles extend upstream of the shock is shown to depend upon the particle energy, with the higher energy particles extending further upstream. This effect is shown to be intimately related to the kinematic threshold requirement that the particle speed exceed the fluid speed in order for particles to swim upstream of the shock and participate in the shock acceleration process.

  10. Surrogate accelerated sampling of reservoir models with complex structures using sparse polynomial chaos expansion

    NASA Astrophysics Data System (ADS)

    Bazargan, Hamid; Christie, Mike; Elsheikh, Ahmed H.; Ahmadi, Mohammad

    2015-12-01

    Markov Chain Monte Carlo (MCMC) methods are often used to probe the posterior probability distribution in inverse problems. This allows for computation of estimates of uncertain system responses conditioned on given observational data by means of approximate integration. However, MCMC methods suffer from the computational complexities in the case of expensive models as in the case of subsurface flow models. Hence, it is of great interest to develop alterative efficient methods utilizing emulators, that are cheap to evaluate, in order to replace the full physics simulator. In the current work, we develop a technique based on sparse response surfaces to represent the flow response within a subsurface reservoir and thus enable efficient exploration of the posterior probability density function and the conditional expectations given the data. Polynomial Chaos Expansion (PCE) is a powerful tool to quantify uncertainty in dynamical systems when there is probabilistic uncertainty in the system parameters. In the context of subsurface flow model, it has been shown to be more accurate and efficient compared with traditional experimental design (ED). PCEs have a significant advantage over other response surfaces as the convergence to the true probability distribution when the order of the PCE is increased can be proved for the random variables with finite variances. However, the major drawback of PCE is related to the curse of dimensionality as the number of terms to be estimated grows drastically with the number of the input random variables. This renders the computational cost of classical PCE schemes unaffordable for reservoir simulation purposes when the deterministic finite element model is expensive to evaluate. To address this issue, we propose the reduced-terms polynomial chaos representation which uses an impact factor to only retain the most relevant terms of the PCE decomposition. Accordingly, the reduced-terms polynomial chaos proxy can be used as the pseudo

  11. Sostdc1 deficiency accelerates fracture healing by promoting the expansion of periosteal mesenchymal stem cells.

    PubMed

    Collette, Nicole M; Yee, Cristal S; Hum, Nicholas R; Murugesh, Deepa K; Christiansen, Blaine A; Xie, LiQin; Economides, Aris N; Manilay, Jennifer O; Robling, Alexander G; Loots, Gabriela G

    2016-07-01

    Loss of Sostdc1, a growth factor paralogous to Sost, causes the formation of ectopic incisors, fused molars, abnormal hair follicles, and resistance to kidney disease. Sostdc1 is expressed in the periosteum, a source of osteoblasts, fibroblasts and mesenchymal progenitor cells, which are critically important for fracture repair. Here, we investigated the role of Sostdc1 in bone metabolism and fracture repair. Mice lacking Sostdc1 (Sostdc1(-/-)) had a low bone mass phenotype associated with loss of trabecular bone in both lumbar vertebrae and in the appendicular skeleton. In contrast, Sostdc1(-/-) cortical bone measurements revealed larger bones with higher BMD, suggesting that Sostdc1 exerts differential effects on cortical and trabecular bone. Mid-diaphyseal femoral fractures induced in Sostdc1(-/-) mice showed that the periosteal population normally positive for Sostdc1 rapidly expands during periosteal thickening and these cells migrate into the fracture callus at 3days post fracture. Quantitative analysis of mesenchymal stem cell (MSC) and osteoblast populations determined that MSCs express Sostdc1, and that Sostdc1(-/-) 5day calluses harbor >2-fold more MSCs than fractured wildtype controls. Histologically a fraction of Sostdc1-positive cells also expressed nestin and α-smooth muscle actin, suggesting that Sostdc1 marks a population of osteochondral progenitor cells that actively participate in callus formation and bone repair. Elevated numbers of MSCs in D5 calluses resulted in a larger, more vascularized cartilage callus at day 7, and a more rapid turnover of cartilage with significantly more remodeled bone and a thicker cortical shell at 21days post fracture. These data support accelerated or enhanced bone formation/remodeling of the callus in Sostdc1(-/-) mice, suggesting that Sostdc1 may promote and maintain mesenchymal stem cell quiescence in the periosteum. PMID:27102547

  12. Cosmic Inhomogeneities and Averaged Cosmological Dynamics

    NASA Astrophysics Data System (ADS)

    Paranjape, Aseem; Singh, T. P.

    2008-10-01

    If general relativity (GR) describes the expansion of the Universe, the observed cosmic acceleration implies the existence of a “dark energy.” However, while the Universe is on average homogeneous on large scales, it is inhomogeneous on smaller scales. While GR governs the dynamics of the inhomogeneous Universe, the averaged homogeneous Universe obeys modified Einstein equations. Can such modifications alone explain the acceleration? For a simple generic model with realistic initial conditions, we show the answer to be “no.” Averaging effects negligibly influence the cosmological dynamics.

  13. Can a matter-dominated model with constant bulk viscosity drive the accelerated expansion of the universe?

    SciTech Connect

    Avelino, Arturo; Nucamendi, Ulises E-mail: ulises@ifm.umich.mx

    2009-04-15

    We test a cosmological model which the only component is a pressureless fluid with a constant bulk viscosity as an explanation for the present accelerated expansion of the universe. We classify all the possible scenarios for the universe predicted by the model according to their past, present and future evolution and we test its viability performing a Bayesian statistical analysis using the SCP ''Union'' data set (307 SNe Ia), imposing the second law of thermodynamics on the dimensionless constant bulk viscous coefficient {zeta}-tilde and comparing the predicted age of the universe by the model with the constraints coming from the oldest globular clusters. The best estimated values found for {zeta}-tilde and the Hubble constant H{sub 0} are: {zeta}-tilde = 1.922{+-}0.089 and H{sub 0} = 69.62{+-}0.59 (km/s)Mpc{sup -1} with a {chi}{sup 2}{sub min} = 314 ({chi}{sup 2}{sub d.o.f} = 1.031). The age of the universe is found to be 14.95{+-}0.42 Gyr. We see that the estimated value of H{sub 0} as well as of {chi}{sup 2}{sub d.o.f} are very similar to those obtained from {Lambda}CDM model using the same SNe Ia data set. The estimated age of the universe is in agreement with the constraints coming from the oldest globular clusters. Moreover, the estimated value of {zeta}-tilde is positive in agreement with the second law of thermodynamics (SLT). On the other hand, we perform different forms of marginalization over the parameter H{sub 0} in order to study the sensibility of the results to the way how H{sub 0} is marginalized. We found that it is almost negligible the dependence between the best estimated values of the free parameters of this model and the way how H{sub 0} is marginalized in the present work. Therefore, this simple model might be a viable candidate to explain the present acceleration in the expansion of the universe.

  14. Simulating the formation of cosmic structure.

    PubMed

    Frenk, C S

    2002-06-15

    A timely combination of new theoretical ideas and observational discoveries has brought about significant advances in our understanding of cosmic evolution. Computer simulations have played a key role in these developments by providing the means to interpret astronomical data in the context of physical and cosmological theory. In the current paradigm, our Universe has a flat geometry, is undergoing accelerated expansion and is gravitationally dominated by elementary particles that make up cold dark matter. Within this framework, it is possible to simulate in a computer the emergence of galaxies and other structures from small quantum fluctuations imprinted during an epoch of inflationary expansion shortly after the Big Bang. The simulations must take into account the evolution of the dark matter as well as the gaseous processes involved in the formation of stars and other visible components. Although many unresolved questions remain, a coherent picture for the formation of cosmic structure is now beginning to emerge. PMID:12804279

  15. Accelerated Cartesian expansion (ACE) based framework for the rapid evaluation of diffusion, lossy wave, and Klein-Gordon potentials

    DOE PAGESBeta

    Baczewski, Andrew David; Vikram, Melapudi; Shanker, Balasubramaniam; Kempel, Leo

    2010-08-27

    Diffusion, lossy wave, and Klein–Gordon equations find numerous applications in practical problems across a range of diverse disciplines. The temporal dependence of all three Green’s functions are characterized by an infinite tail. This implies that the cost complexity of the spatio-temporal convolutions, associated with evaluating the potentials, scales as O(Ns2Nt2), where Ns and Nt are the number of spatial and temporal degrees of freedom, respectively. In this paper, we discuss two new methods to rapidly evaluate these spatio-temporal convolutions by exploiting their block-Toeplitz nature within the framework of accelerated Cartesian expansions (ACE). The first scheme identifies a convolution relation inmore » time amongst ACE harmonics and the fast Fourier transform (FFT) is used for efficient evaluation of these convolutions. The second method exploits the rank deficiency of the ACE translation operators with respect to time and develops a recursive numerical compression scheme for the efficient representation and evaluation of temporal convolutions. It is shown that the cost of both methods scales as O(NsNtlog2Nt). Furthermore, several numerical results are presented for the diffusion equation to validate the accuracy and efficacy of the fast algorithms developed here.« less

  16. Accelerated Cartesian expansion (ACE) based framework for the rapid evaluation of diffusion, lossy wave, and Klein-Gordon potentials

    SciTech Connect

    Baczewski, Andrew David; Vikram, Melapudi; Shanker, Balasubramaniam; Kempel, Leo

    2010-08-27

    Diffusion, lossy wave, and Klein–Gordon equations find numerous applications in practical problems across a range of diverse disciplines. The temporal dependence of all three Green’s functions are characterized by an infinite tail. This implies that the cost complexity of the spatio-temporal convolutions, associated with evaluating the potentials, scales as O(Ns2Nt2), where Ns and Nt are the number of spatial and temporal degrees of freedom, respectively. In this paper, we discuss two new methods to rapidly evaluate these spatio-temporal convolutions by exploiting their block-Toeplitz nature within the framework of accelerated Cartesian expansions (ACE). The first scheme identifies a convolution relation in time amongst ACE harmonics and the fast Fourier transform (FFT) is used for efficient evaluation of these convolutions. The second method exploits the rank deficiency of the ACE translation operators with respect to time and develops a recursive numerical compression scheme for the efficient representation and evaluation of temporal convolutions. It is shown that the cost of both methods scales as O(NsNtlog2Nt). Furthermore, several numerical results are presented for the diffusion equation to validate the accuracy and efficacy of the fast algorithms developed here.

  17. Cosmic jets

    NASA Technical Reports Server (NTRS)

    Rees, M. J.

    1986-01-01

    The evidence that active galactic nuclei produce collimated plasma jets is summarised. The strongest radio galaxies are probably energised by relativistic plasma jets generated by spinning black holes interacting with magnetic fields attached to infalling matter. Such objects can produce e(+)-e(-) plasma, and may be relevant to the acceleration of the highest-energy cosmic ray primaries. Small-scale counterparts of the jet phenomenon within our own galaxy are briefly reviewed.

  18. Accelerator Measurements of Magnetically Induced Radio Emission from Particle Cascades with Applications to Cosmic-Ray Air Showers

    NASA Astrophysics Data System (ADS)

    Belov, K.; Mulrey, K.; Romero-Wolf, A.; Wissel, S. A.; Zilles, A.; Bechtol, K.; Borch, K.; Chen, P.; Clem, J.; Gorham, P. W.; Hast, C.; Huege, T.; Hyneman, R.; Jobe, K.; Kuwatani, K.; Lam, J.; Liu, T. C.; Nam, J.; Naudet, C.; Nichol, R. J.; Rauch, B. F.; Rotter, B.; Saltzberg, D.; Schoorlemmer, H.; Seckel, D.; Strutt, B.; Vieregg, A. G.; Williams, C.; T-510 Collaboration

    2016-04-01

    For 50 years, cosmic-ray air showers have been detected by their radio emission. We present the first laboratory measurements that validate electrodynamics simulations used in air shower modeling. An experiment at SLAC provides a beam test of radio-frequency (rf) radiation from charged particle cascades in the presence of a magnetic field, a model system of a cosmic-ray air shower. This experiment provides a suite of controlled laboratory measurements to compare to particle-level simulations of rf emission, which are relied upon in ultrahigh-energy cosmic-ray air shower detection. We compare simulations to data for intensity, linearity with magnetic field, angular distribution, polarization, and spectral content. In particular, we confirm modern predictions that the magnetically induced emission in a dielectric forms a cone that peaks at the Cherenkov angle and show that the simulations reproduce the data within systematic uncertainties.

  19. Accelerator Measurements of Magnetically Induced Radio Emission from Particle Cascades with Applications to Cosmic-Ray Air Showers.

    PubMed

    Belov, K; Mulrey, K; Romero-Wolf, A; Wissel, S A; Zilles, A; Bechtol, K; Borch, K; Chen, P; Clem, J; Gorham, P W; Hast, C; Huege, T; Hyneman, R; Jobe, K; Kuwatani, K; Lam, J; Liu, T C; Nam, J; Naudet, C; Nichol, R J; Rauch, B F; Rotter, B; Saltzberg, D; Schoorlemmer, H; Seckel, D; Strutt, B; Vieregg, A G; Williams, C

    2016-04-01

    For 50 years, cosmic-ray air showers have been detected by their radio emission. We present the first laboratory measurements that validate electrodynamics simulations used in air shower modeling. An experiment at SLAC provides a beam test of radio-frequency (rf) radiation from charged particle cascades in the presence of a magnetic field, a model system of a cosmic-ray air shower. This experiment provides a suite of controlled laboratory measurements to compare to particle-level simulations of rf emission, which are relied upon in ultrahigh-energy cosmic-ray air shower detection. We compare simulations to data for intensity, linearity with magnetic field, angular distribution, polarization, and spectral content. In particular, we confirm modern predictions that the magnetically induced emission in a dielectric forms a cone that peaks at the Cherenkov angle and show that the simulations reproduce the data within systematic uncertainties. PMID:27104694

  20. Transient acceleration in f(T) gravity

    NASA Astrophysics Data System (ADS)

    Qi, Jing-Zhao; Yang, Rong-Jia; Zhang, Ming-Jian; Liu, Wen-Biao

    2016-02-01

    Recently an f(T) gravity based on the modification of teleparallel gravity was proposed to explain the accelerated expansion of the universe. We use observational data from type Ia supernovae, baryon acoustic oscillations, and cosmic microwave background to constrain this f(T) theory and reconstruct the effective equation of state and the deceleration parameter. We obtain the best-fit values of parameters and find an interesting result that the constrained f(T) theory allows for the accelerated Hubble expansion to be a transient effect.

  1. A simple model of universe describing the early inflation and the late accelerated expansion in a symmetric manner

    SciTech Connect

    Chavanis, Pierre-Henri

    2013-07-23

    We construct a simple model of universe which 'unifies' vacuum energy and radiation on the one hand, and matter and dark energy on the other hand in the spirit of a generalized Chaplygin gas model. Specifically, the phases of early inflation and late accelerated expansion are described by a generalized equation of state p/c{sup 2} = αρ+kρ{sup 1+1/n} having a linear component p = αρc{sup 2} and a polytropic component p = kρ{sup 1+1/n}c{sup 2}. For α= 1/3, n= 1 and k=−4/(3ρ{sub P}), where ρ{sub P}= 5.1610{sup 99} g/m{sup 3} is the Planck density, this equation of state describes the transition between the vacuum energy era and the radiation era. For t≥ 0, the universe undergoes an inflationary expansion that brings it from the Planck size l{sub P}= 1.6210{sup −35} m to a size a{sub 1}= 2.6110{sup −6} m on a timescale of about 23.3 Planck times t{sub P}= 5.3910{sup −44} s (early inflation). When t > t{sub 1}= 23.3t{sub P}, the universe decelerates and enters in the radiation era. We interpret the transition from the vacuum energy era to the radiation era as a second order phase transition where the Planck constant ℏ plays the role of finite size effects (the standard Big Bang theory is recovered for ℏ= 0). For α= 0, n=−1 and k=−ρ{sub Λ}, where ρ{sub Λ}= 7.0210{sup −24} g/m{sup 3} is the cosmological density, the equation of state p/c{sup 2} = αρ+kρ{sup 1+1/n} describes the transition from a decelerating universe dominated by pressureless matter (baryonic and dark matter) to an accelerating universe dominated by dark energy (late inflation). This transition takes place at a size a{sub 2}= 0.204l{sub Λ}. corresponding to a time t{sub 2}= 0.203t{sub Λ} where l{sub Λ}= 4.38 10{sup 26} m is the cosmological length and t{sub Λ}= 1.46 10{sup 18} s the cosmological time. The present universe turns out to be just at the transition between these two periods (t{sub 0}∼t{sub 2}). Our model gives the same results as the standard

  2. A simple model of universe describing the early inflation and the late accelerated expansion in a symmetric manner

    NASA Astrophysics Data System (ADS)

    Chavanis, Pierre-Henri

    2013-07-01

    We construct a simple model of universe which "unifies" vacuum energy and radiation on the one hand, and matter and dark energy on the other hand in the spirit of a generalized Chaplygin gas model. Specifically, the phases of early inflation and late accelerated expansion are described by a generalized equation of state p/c2 = αρ+kρ1+1/n having a linear component p = αρc2 and a polytropic component p = kρ1+1/nc2. For α = 1/3, n = 1 and k = -4/(3ρP), where ρP = 5.161099 g/m3 is the Planck density, this equation of state describes the transition between the vacuum energy era and the radiation era. For t >= 0, the universe undergoes an inflationary expansion that brings it from the Planck size lP = 1.6210-35 m to a size a1 = 2.6110-6 m on a timescale of about 23.3 Planck times tP = 5.3910-44 s (early inflation). When t > t1 = 23.3tP, the universe decelerates and enters in the radiation era. We interpret the transition from the vacuum energy era to the radiation era as a second order phase transition where the Planck constant ℏ plays the role of finite size effects (the standard Big Bang theory is recovered for ℏ = 0). For α = 0, n = -1 and k = -ρΛ, where ρΛ = 7.0210-24 g/m3 is the cosmological density, the equation of state p/c2 = αρ+kρ1+1/n describes the transition from a decelerating universe dominated by pressureless matter (baryonic and dark matter) to an accelerating universe dominated by dark energy (late inflation). This transition takes place at a size a2 = 0.204lΛ. corresponding to a time t2 = 0.203tΛ where lΛ = 4.38 1026 m is the cosmological length and tΛ = 1.46 1018 s the cosmological time. The present universe turns out to be just at the transition between these two periods (t0 ~ t2). Our model gives the same results as the standard ΛCDM model for t >> tP and completes it by incorporating a phase of early inflation for t < 23.3tP in a very natural manner. Furthermore, it reveals a nice "symmetry" between the early and the late

  3. Testing Cosmic Inflation

    NASA Technical Reports Server (NTRS)

    Chuss, David

    2010-01-01

    The Cosmic Microwave Background (CMB) has provided a wealth of information about the history and physics of the early Universe. Much progress has been made on uncovering the emerging Standard Model of Cosmology by such experiments as COBE and WMAP, and ESA's Planck Surveyor will likely increase our knowledge even more. Despite the success of this model, mysteries remain. Currently understood physics does not offer a compelling explanation for the homogeneity, flatness, and the origin of structure in the Universe. Cosmic Inflation, a brief epoch of exponential expansion, has been posted to explain these observations. If inflation is a reality, it is expected to produce a background spectrum of gravitational waves that will leave a small polarized imprint on the CMB. Discovery of this signal would give the first direct evidence for inflation and provide a window into physics at scales beyond those accessible to terrestrial particle accelerators. I will briefly review aspects of the Standard Model of Cosmology and discuss our current efforts to design and deploy experiments to measure the polarization of the CMB with the precision required to test inflation.

  4. A critical shock mach number for particle acceleration in the absence of pre-existing cosmic rays: M=√5

    SciTech Connect

    Vink, Jacco

    2014-01-10

    It is shown that, under some generic assumptions, shocks cannot accelerate particles unless the overall shock Mach number exceeds a critical value M>√5. The reason is that for M≤√5 the work done to compress the flow in a particle precursor requires more enthalpy flux than the system can sustain. This lower limit applies to situations without significant magnetic field pressure. In case that the magnetic field pressure dominates the pressure in the unshocked medium, i.e., for low plasma beta, the resistivity of the magnetic field makes it even more difficult to fulfill the energetic requirements for the formation of shock with an accelerated particle precursor and associated compression of the upstream plasma. We illustrate the effects of magnetic fields for the extreme situation of a purely perpendicular magnetic field configuration with plasma beta β = 0, which gives a minimum Mach number of M = 5/2. The situation becomes more complex, if we incorporate the effects of pre-existing cosmic rays, indicating that the additional degree of freedom allows for less strict Mach number limits on acceleration. We discuss the implications of this result for low Mach number shock acceleration as found in solar system shocks, and shocks in clusters of galaxies.

  5. Constraining dark energy through the stability of cosmic structures

    SciTech Connect

    Pavlidou, V.; Tetradis, N.; Tomaras, T.N. E-mail: ntetrad@phys.uoa.gr

    2014-05-01

    For a general dark-energy equation of state, we estimate the maximum possible radius of massive structures that are not destabilized by the acceleration of the cosmological expansion. A comparison with known stable structures constrains the equation of state. The robustness of the constraint can be enhanced through the accumulation of additional astrophysical data and a better understanding of the dynamics of bound cosmic structures.

  6. Genesis and propagation of cosmic rays

    SciTech Connect

    Shapiro, M.M.; Wefel, J.P.

    1988-01-01

    This book presents a panorama of contemporary state-of-the-art knowledge on the origin of cosmic rays and how they propagate through space. Twenty-eight articles cover such topics as objects which generate cosmic rays, processes which accelerate particles to cosmic ray energies, the interaction of cosmic rays with their environment, elementary particles in cosmic rays, how to detect cosmic rays and future experiments to measure highly energetic particles.

  7. The cosmic-ray pathlength distribution at low energy - A new probe of the source/acceleration regions

    NASA Technical Reports Server (NTRS)

    Guzik, T. G.; Wefel, J. P.

    1984-01-01

    Compiled measurements of secondary to primary ratios covering the charge range Z = 3-26 and the energy range 0.05 - 50 GeV/nucleon are analyzed in energy dependent galactic propagation plus solar modulation calculations. The cosmic ray pathlength distribution is shown to consist of two energy dependent components interpreted as representing confinement in the galaxy and confinement in the 'source' regions.

  8. Relaxation of the accelerating-gas boundary layer to the test-gas boundary layer on a flat plate in an expansion tube

    NASA Technical Reports Server (NTRS)

    Gupta, R. N.; Trimpi, R. L.

    1973-01-01

    An analytic investigation of the relaxation of the accelerating-gas boundary layer to the test-gas boundary layer over a flat plate mounted in an expansion tube has been conducted. In this treatment, nitrogen has been considered as the test gas and helium as the accelerating gas. The problem is analyzed in two conically similar limits: (1) when the time lag between the arrival of the shock and the interface at the leading edge of the plate is very large, and (2) when this time lag is negligible. The transient laminar boundary-layer equations of a perfect binary-gas mixture are taken as the flow governing equations. These coupled equations have been solved numerically by Gauss-Seidel line-relaxation method. The results predict the transient behavior as well as the time required for an all-helium accelerating-gas boundary layer to relax to an all-nitrogen boundary layer.

  9. INTEGRAL IGR J18135-1751 = HESS J1813-178: A New Cosmic High-Energy Accelerator from keV to TeV Energies

    NASA Astrophysics Data System (ADS)

    Ubertini, P.; Bassani, L.; Malizia, A.; Bazzano, A.; Bird, A. J.; Dean, A. J.; De Rosa, A.; Lebrun, F.; Moran, L.; Renaud, M.; Stephen, J. B.; Terrier, R.; Walter, R.

    2005-08-01

    We report the discovery of a soft gamma-ray source, namely, IGR J18135-1751, detected with IBIS, the Imager on Board the INTEGRAL Satellite. The source is persistent and has a 20-100 keV luminosity of ~5.7× 1034 ergs s-1 (assuming a distance of 4 kpc). This source is coincident with one of the eight unidentified objects recently reported by the HESS collaboration as part of the first TeV survey of the inner part of the Galaxy. Two of these new sources found along the Galactic plane, HESS J1813-178 and HESS J1614-518, have no obvious lower energy counterparts, a fact that motivated the suggestion that they might be dark cosmic ray accelerators. HESS J1813-178 has a strongly absorbed X-ray counterpart, the ASCA source AGPS 273.4-17.8, showing a power-law spectrum with photon index ~1.8 and a total (Galactic plus intrinsic) absorption corresponding to NH~5×1022 cm-2. We hypothesize that the source is a pulsar wind nebula embedded in its supernova remnant. The lack of X-ray or gamma-ray variability, the radio morphology, and the ASCA spectrum are all compatible with this interpretation. In any case we rule out the hypothesis that HESS J1813-178 belongs to a new class of TeV objects or that it is a cosmic ``dark particle'' accelerator. Based on observations with INTEGRAL, an ESA project with instruments and science data center funded by ESA member states (especially the PI countries: Denmark, France, Germany, Italy, Switzerland, Spain), the Czech Republic, and Poland and with the participation of Russia and the US.

  10. Acceleration of ions and electrons to near-cosmic ray energies in a perpendicular shock: The January 6, 1978 event

    NASA Technical Reports Server (NTRS)

    Krimigis, S. M.; Sarris, E. T.

    1985-01-01

    Acceleration of energetic ions to approx 200 MeV and electrons to approx 2 MeV were detected by the Low Energy Charged Particle (LECP) instrument on Voyager 2 in association with a quasiperpendicular shock of theta sub Bn - 87.5 deg at 1.9 AU. The measurments, obtained at a time resolution of approx. 1.2 sec, reveal structure of the energetic particle intensity enhancements down to a scale of the order of the particle gyroradius, and suggest that acceleration takes place within a gyrodiameter of the shock. The observations are consistent with the prediction of the shock drift acceleration (SDA) mechanism. The absence of any fluctuations in the magnetic field during the shock passage suggest that turbulence is not essential to the shock acceleration process in the interplanetary medium.

  11. On the Origin of Ultra High Energy Cosmic Rays

    SciTech Connect

    Fowler, T; Colgate, S; Li, H

    2009-07-01

    Turbulence-driven plasma accelerators produced by magnetized accretion disks around black holes are proposed as the mechanism mainly responsible for observed cosmic ray protons with ultra high energies 10{sup 19}-10{sup 21} eV. The magnetized disk produces a voltage comparable to these cosmic ray energies. Here we present a Poynting model in which this voltage provides all of the energy to create the jet-like structures observed to be ejected from accretion disks, and this voltage also accelerates ions to high energies at the top of the expanding structure. Since the inductive electric field E = -v x B driving expansion has no component parallel to the magnetic field B, ion acceleration requires plasma wave generation - either a coherent wave accelerator as recently proposed, or instability-driven turbulence. We find that turbulence can tap the full inductive voltage as a quasi-steady accelerator, and even higher energies are produced by transient events on this structure. We find that both MHD modes due to the current and ion diffusion due to kinetic instability caused by the non-Maxwellian ion distribution contribute to acceleration. We apply our results to extragalactic giant radiolobes, whose synchrotron emissions serve to calibrate the model, and we discuss extrapolating to other astrophysical structures. Approximate calculations of the cosmic ray intensity and energy spectrum are in rough agreement with data and serve to motivate more extensive MHD and kinetic simulations of turbulence that could provide more accurate cosmic ray and synchrotron spectra to be compared with observations. A distinctive difference from previous models is that the cosmic ray and synchrotron emissions arise from different parts of the magnetic structure, thus providing a signature for the model.

  12. Variations of the relative abundances of He, (C,N,O) and Fe-group nuclei in solar cosmic rays and their relationship to solar particle acceleration

    NASA Technical Reports Server (NTRS)

    Bertsch, D. L.; Biswas, S.; Fichtel, C. E.; Pellerin, C. J.; Reames, D. V.

    1973-01-01

    Measurements of the flux of helium nuclei in the 24 January 1971 event and of helium and (C,N,O) nuclei in the 1 September 1971 event are combined with previous measurements to obtain the relative abundances of helium, (C,N,O), and Fe-group nuclei in these events. These data are then summarized together with previously reported results to show that, even when the same detector system using a dE/dx plus range technique is used, differences in the He/(C,N,O) value in the same energy/nucleon interval are observed in solar cosmic ray events. Further, when the He/(C,N,O) value is lower the He/(Fe-group nuclei) value is also systematically lower in these large events. When solar particle acceleration theory is analyzed, it is seen that the results suggest that, for large events, Coulomb energy loss probably does not play a major role in determining solar particle composition at higher energies (10 MeV). The variations in multicharged nuclei composition are more likely due to partial ionization during the acceleration phase.

  13. Protostars: Forges of cosmic rays?

    NASA Astrophysics Data System (ADS)

    Padovani, M.; Marcowith, A.; Hennebelle, P.; Ferrière, K.

    2016-05-01

    Context. Galactic cosmic rays are particles presumably accelerated in supernova remnant shocks that propagate in the interstellar medium up to the densest parts of molecular clouds, losing energy and their ionisation efficiency because of the presence of magnetic fields and collisions with molecular hydrogen. Recent observations hint at high levels of ionisation and at the presence of synchrotron emission in protostellar systems, which leads to an apparent contradiction. Aims: We want to explain the origin of these cosmic rays accelerated within young protostars as suggested by observations. Methods: Our modelling consists of a set of conditions that has to be satisfied in order to have an efficient cosmic-ray acceleration through diffusive shock acceleration. We analyse three main acceleration sites (shocks in accretion flows, along the jets, and on protostellar surfaces), then we follow the propagation of these particles through the protostellar system up to the hot spot region. Results: We find that jet shocks can be strong accelerators of cosmic-ray protons, which can be boosted up to relativistic energies. Other promising acceleration sites are protostellar surfaces, where shocks caused by impacting material during the collapse phase are strong enough to accelerate cosmic-ray protons. In contrast, accretion flow shocks are too weak to efficiently accelerate cosmic rays. Though cosmic-ray electrons are weakly accelerated, they can gain a strong boost to relativistic energies through re-acceleration in successive shocks. Conclusions: We suggest a mechanism able to accelerate both cosmic-ray protons and electrons through the diffusive shock acceleration mechanism, which can be used to explain the high ionisation rate and the synchrotron emission observed towards protostellar sources. The existence of an internal source of energetic particles can have a strong and unforeseen impact on the ionisation of the protostellar disc, on the star and planet formation

  14. Cosmokinetics: a joint analysis of standard candles, rulers and cosmic clocks

    SciTech Connect

    Nair, Remya; Jhingan, Sanjay; Jain, Deepak E-mail: sjhingan@jmi.ac.in

    2012-01-01

    We study the accelerated expansion of the Universe by using the kinematic approach. In this context, we parameterize the deceleration parameter, q(z), in a model independent way. Assuming three simple parameterizations we reconstruct q(z). We do the joint analysis with combination of latest cosmological data consisting of standard candles (Supernovae Union2 sample), standard ruler (CMB/BAO), cosmic clocks (age of passively evolving galaxies) and Hubble (H(z)) data. Our results support the accelerated expansion of the Universe.

  15. Separable projection integrals for higher-order correlators of the cosmic microwave sky: Acceleration by factors exceeding 100

    NASA Astrophysics Data System (ADS)

    Briggs, J. P.; Pennycook, S. J.; Fergusson, J. R.; Jäykkä, J.; Shellard, E. P. S.

    2016-04-01

    We present a case study describing efforts to optimise and modernise "Modal", the simulation and analysis pipeline used by the Planck satellite experiment for constraining general non-Gaussian models of the early universe via the bispectrum (or three-point correlator) of the cosmic microwave background radiation. We focus on one particular element of the code: the projection of bispectra from the end of inflation to the spherical shell at decoupling, which defines the CMB we observe today. This code involves a three-dimensional inner product between two functions, one of which requires an integral, on a non-rectangular domain containing a sparse grid. We show that by employing separable methods this calculation can be reduced to a one-dimensional summation plus two integrations, reducing the overall dimensionality from four to three. The introduction of separable functions also solves the issue of the non-rectangular sparse grid. This separable method can become unstable in certain scenarios and so the slower non-separable integral must be calculated instead. We present a discussion of the optimisation of both approaches. We demonstrate significant speed-ups of ≈100×, arising from a combination of algorithmic improvements and architecture-aware optimisations targeted at improving thread and vectorisation behaviour. The resulting MPI/OpenMP hybrid code is capable of executing on clusters containing processors and/or coprocessors, with strong-scaling efficiency of 98.6% on up to 16 nodes. We find that a single coprocessor outperforms two processor sockets by a factor of 1.3× and that running the same code across a combination of both microarchitectures improves performance-per-node by a factor of 3.38×. By making bispectrum calculations competitive with those for the power spectrum (or two-point correlator) we are now able to consider joint analysis for cosmological science exploitation of new data.

  16. Model-independent tests of cosmic gravity.

    PubMed

    Linder, Eric V

    2011-12-28

    Gravitation governs the expansion and fate of the universe, and the growth of large-scale structure within it, but has not been tested in detail on these cosmic scales. The observed acceleration of the expansion may provide signs of gravitational laws beyond general relativity (GR). Since the form of any such extension is not clear, from either theory or data, we adopt a model-independent approach to parametrizing deviations to the Einstein framework. We explore the phase space dynamics of two key post-GR functions and derive a classification scheme, and an absolute criterion on accuracy necessary for distinguishing classes of gravity models. Future surveys will be able to constrain the post-GR functions' amplitudes and forms to the required precision, and hence reveal new aspects of gravitation. PMID:22084288

  17. Future evolution and finite-time singularities in F(R) gravity unifying inflation and cosmic acceleration

    SciTech Connect

    Nojiri, Shin'ichi; Odintsov, Sergei D.

    2008-08-15

    We study the future evolution of quintessence/phantom-dominated epoch in modified F(R) gravity which unifies the early-time inflation with late-time acceleration and which is consistent with observational tests. Using the reconstruction technique it is demonstrated that there are models where any known (big rip, II, III, or IV type) singularity may classically occur. From another side, in Einstein frame (scalar-tensor description) only IV type singularity occurs. Near the singularity the classical description breaks up, and it is demonstrated that quantum effects act against the singularity and may prevent its appearance. The realistic F(R) gravity which is future singularity free is proposed. We point out that additional modification of any F(R) gravity by the terms relevant at the early universe is possible, in such a way that future singularity does not occur even classically.

  18. Inflation and late-time cosmic acceleration in non-minimal Maxwell-F(R) gravity and the generation of large-scale magnetic fields

    SciTech Connect

    Bamba, Kazuharu; Odintsov, Sergei D E-mail: odintsov@aliga.ieec.uab.es

    2008-04-15

    We study inflation and late-time acceleration in the expansion of the universe in non-minimal electromagnetism, in which the electromagnetic field couples to the scalar curvature function. It is shown that power-law inflation can be realized due to the non-minimal gravitational coupling of the electromagnetic field, and that large-scale magnetic fields can be generated due to the breaking of the conformal invariance of the electromagnetic field through its non-minimal gravitational coupling. Furthermore, it is demonstrated that both inflation and the late-time acceleration of the universe can be realized in a modified Maxwell-F(R) gravity which is consistent with solar-system tests and cosmological bounds and free of instabilities. At small curvature typical for the current universe the standard Maxwell theory is recovered. We also consider the classically equivalent form of non-minimal Maxwell-F(R) gravity, and propose the origin of the non-minimal gravitational coupling function based on renormalization-group considerations.

  19. The Early Universe: Searching for Evidence of Cosmic Inflation

    NASA Technical Reports Server (NTRS)

    Chuss, David T.

    2012-01-01

    In the past two decades, our understanding of the evolution and fate of the universe has increased dramatically. This "Age of Precision Cosmology" has been ushered in by measurements that have both elucidated the details of the Big Bang cosmology and set the direction for future lines of inquiry. Our universe appears to consist of 5% baryonic matter; 23% of the universe's energy content is dark matter which is responsible for the observed structure in the universe; and 72% of the energy density is so-called "dark energy" that is currently accelerating the expansion of the universe. In addition, our universe has been measured to be geometrically flat to 1 %. These observations and related details of the Big Bang paradigm have hinted that the universe underwent an epoch of accelerated expansion known as "inflation" early in its history. In this talk, I will review the highlights of modern cosmology, focusing on the contributions made by measurements of the cosmic microwave background, the faint afterglow of the Big Bang. I will also describe new instruments designed to measure the polarization of the cosmic microwave background in order to search for evidence of cosmic inflation.

  20. Anisotropic modified holographic Ricci dark energy cosmological model with hybrid expansion law

    NASA Astrophysics Data System (ADS)

    Das, Kanika; Sultana, Tazmin

    2015-11-01

    Here in this paper we present a locally rotationally symmetric Bianchi type-II metric filled with dark matter and anisotropic modified holographic Ricci dark energy. To solve the Einstein's field equations we have taken the hybrid expansion law (HEL) which exhibits a cosmic transition of the universe from decelerating to accelerating phase. We have investigated the physical and geometrical properties of the model. It is observed that the anisotropy of the universe and that of the modified holographic Ricci dark energy tends to zero at later times and the universe becomes homogeneous, isotropic and flat. We have also studied the cosmic jerk parameter.

  1. EFFICIENT COSMIC RAY ACCELERATION, HYDRODYNAMICS, AND SELF-CONSISTENT THERMAL X-RAY EMISSION APPLIED TO SUPERNOVA REMNANT RX J1713.7-3946

    SciTech Connect

    Ellison, Donald C.; Patnaude, Daniel J.; Slane, Patrick; Raymond, John

    2010-03-20

    We model the broadband emission from supernova remnant (SNR) RX J1713.7-3946 including, for the first time, a consistent calculation of thermal X-ray emission together with non-thermal emission in a nonlinear diffusive shock acceleration model. Our model tracks the evolution of the SNR including the plasma ionization state between the forward shock and the contact discontinuity. We use a plasma emissivity code to predict the thermal X-ray emission spectrum assuming the initially cold electrons are heated either by Coulomb collisions with the shock-heated protons (the slowest possible heating), or come into instant equilibration with the protons. For either electron heating model, electrons reach {approx}>10{sup 7} K rapidly and the X-ray line emission near 1 keV is more than 10 times as luminous as the underlying thermal bremsstrahlung continuum. Since recent Suzaku observations show no detectable line emission, this places strong constraints on the unshocked ambient medium density and on the relativistic electron-to-proton ratio. For the uniform circumstellar medium (CSM) models that we consider, the low densities and high relativistic electron-to-proton ratios required to match the Suzaku X-ray observations definitively rule out pion decay as the emission process producing GeV-TeV photons. We show that leptonic models, where inverse-Compton scattering against the cosmic background radiation dominates the GeV-TeV emission, produce better fits to the broadband thermal and non-thermal observations in a uniform CSM.

  2. Time-dependent evolution of cosmic-ray-modified shock structure: Transition to steady state

    NASA Technical Reports Server (NTRS)

    Donohue, D. J.; Zank, G. P.; Webb, G. M.

    1994-01-01

    Steady state solutions to the two-fluid equations of cosmic-ray-modified shock structure were investigated first by Drury and Volk (1981). Their analysis revealed, among other properties, that there exist regions of upstream parameter space where the equations possess three different downstream solutions for a given upstream state. In this paper we investigate whether or not all these solutions can occur as time-asymptotic states in a physically realistic evolution. To do this, we investigate the time-dependent evolution of the two-fluid cosmic-ray equations in going from a specified initial condition to a steady state. Our results indicate that the time-asymptotic solution is strictly single-valued, and it undergoes a transition from weakly to strongly cosmic-ray-modified at a critical value of the upstream cosmic ray energy density. The expansion of supernova remnant shocks is considered as an example, and it is shown that the strong to weak transition is in fact more likely. The third intermediate solution is shown to influence the time-dependent evolution of the shock, but it is not found to be a stable time-asymptotic state. Timescales for convergence to these states and their implications for the efficiency of shock acceleration are considered. We also investigate the effects of a recently introduced model for the injection of seed particles into the shock accelerated cosmic-ray population. The injection is found to result in a more strongly cosmic-ray-dominated shock, which supports our conclusion that for most classes of intermediate and strong cosmic-ray-modified shocks, the downstream cosmic-ray pressure component is at least as large as the thermal gas pressure, independent of the upstream state. As a result, cosmic rays almost always play a significant role in determining the shock structure and dissipation and they cannot be regarded as test particles.

  3. Time-dependent evolution of cosmic-ray-modified shock structure: Transition to steady state

    NASA Astrophysics Data System (ADS)

    Donohue, D. J.; Zank, G. P.; Webb, G. M.

    1994-03-01

    Steady state solutions to the two-fluid equations of cosmic-ray-modified shock structure were investigated first by Drury and Volk (1981). Their analysis revealed, among other properties, that there exist regions of upstream parameter space where the equations possess three different downstream solutions for a given upstream state. In this paper we investigate whether or not all these solutions can occur as time-asymptotic states in a physically realistic evolution. To do this, we investigate the time-dependent evolution of the two-fluid cosmic-ray equations in going from a specified initial condition to a steady state. Our results indicate that the time-asymptotic solution is strictly single-valued, and it undergoes a transition from weakly to strongly cosmic-ray-modified at a critical value of the upstream cosmic ray energy density. The expansion of supernova remnant shocks is considered as an example, and it is shown that the strong to weak transition is in fact more likely. The third intermediate solution is shown to influence the time-dependent evolution of the shock, but it is not found to be a stable time-asymptotic state. Timescales for convergence to these states and their implications for the efficiency of shock acceleration are considered. We also investigate the effects of a recently introduced model for the injection of seed particles into the shock accelerated cosmic-ray population. The injection is found to result in a more strongly cosmic-ray-dominated shock, which supports our conclusion that for most classes of intermediate and strong cosmic-ray-modified shocks, the downstream cosmic-ray pressure component is at least as large as the thermal gas pressure, independent of the upstream state. As a result, cosmic rays almost always play a significant role in determining the shock structure and dissipation and they cannot be regarded as test particles.

  4. Cosmic Rays Across the Universe

    NASA Astrophysics Data System (ADS)

    Gould Zweibel, Ellen

    2016-01-01

    Cosmic rays play an important role in the dynamics, energetics, and chemisry of gas inside and outside galaxies. It has long been recognized that gamma ray astronomy is a powerful probe of cosmic ray acceleration and propagation, and that gamma ray data, combined with other observations of cosmic rays and of the host medium and with modeling, can provide an integrated picture of cosmic rays and their environments. I will discuss the plasma physics underlying this picture, where it has been successful, and where issues remain.

  5. The Origin of Cosmic Rays

    ScienceCinema

    Blasi, Pasquale [INAF/Arcetri-Italy and Fermilab, Italy

    2010-01-08

    Cosmic Rays reach the Earth from space with energies of up to more than 1020 eV, carrying information on the most powerful particle accelerators that Nature has been able to assemble. Understanding where and how cosmic rays originate has required almost one century of investigations, and, although the last word is not written yet, recent observations and theory seem now to fit together to provide us with a global picture of the origin of cosmic rays of unprecedented clarity. Here we will describe what we learned from recent observations of astrophysical sources (such as supernova remnants and active galaxies) and we will illustrate what these observations tell us about the physics of particle acceleration and transport. We will also discuss the ?end? of the Galactic cosmic ray spectrum, which bridges out attention towards the so called ultra high energy cosmic rays (UHECRs). At ~1020 eV the gyration scale of cosmic rays in cosmic magnetic fields becomes large enough to allow us to point back to their sources, thereby allowing us to perform ?cosmic ray astronomy?, as confirmed by the recent results obtained with the Pierre Auger Observatory. We will discuss the implications of these observations for the understanding of UHECRs, as well as some questions which will likely remain unanswered and will be the target of the next generation of cosmic ray experiments.

  6. Acceleration of black hole universe

    NASA Astrophysics Data System (ADS)

    Zhang, T. X.; Frederick, C.

    2014-01-01

    Recently, Zhang slightly modified the standard big bang theory and developed a new cosmological model called black hole universe, which is consistent with Mach's principle, governed by Einstein's general theory of relativity, and able to explain all observations of the universe. Previous studies accounted for the origin, structure, evolution, expansion, and cosmic microwave background radiation of the black hole universe, which grew from a star-like black hole with several solar masses through a supermassive black hole with billions of solar masses to the present state with hundred billion-trillions of solar masses by accreting ambient matter and merging with other black holes. This paper investigates acceleration of the black hole universe and provides an alternative explanation for the redshift and luminosity distance measurements of type Ia supernovae. The results indicate that the black hole universe accelerates its expansion when it accretes the ambient matter in an increasing rate. In other words, i.e., when the second-order derivative of the mass of the black hole universe with respect to the time is positive . For a constant deceleration parameter , we can perfectly explain the type Ia supernova measurements with the reduced chi-square to be very close to unity, χ red˜1.0012. The expansion and acceleration of black hole universe are driven by external energy.

  7. Cosmic Dawn

    NASA Astrophysics Data System (ADS)

    Zaldarriaga, Matias

    The following sections are included: * Rapporteur Talk by R. Ellis: Massive Black Holes: Evidence, Demographics and Cosmic Evolution * Rapporteur Talk by S. Furlanetto: The Cosmic Dawn: Theoretical Models and the Future

  8. Cosmic Complexity

    NASA Technical Reports Server (NTRS)

    Mather, John C.

    2012-01-01

    What explains the extraordinary complexity of the observed universe, on all scales from quarks to the accelerating universe? My favorite explanation (which I certainty did not invent) ls that the fundamental laws of physics produce natural instability, energy flows, and chaos. Some call the result the Life Force, some note that the Earth is a living system itself (Gaia, a "tough bitch" according to Margulis), and some conclude that the observed complexity requires a supernatural explanation (of which we have many). But my dad was a statistician (of dairy cows) and he told me about cells and genes and evolution and chance when I was very small. So a scientist must look for me explanation of how nature's laws and statistics brought us into conscious existence. And how is that seemll"!gly Improbable events are actually happening a!1 the time? Well, the physicists have countless examples of natural instability, in which energy is released to power change from simplicity to complexity. One of the most common to see is that cooling water vapor below the freezing point produces snowflakes, no two alike, and all complex and beautiful. We see it often so we are not amazed. But physlc!sts have observed so many kinds of these changes from one structure to another (we call them phase transitions) that the Nobel Prize in 1992 could be awarded for understanding the mathematics of their common features. Now for a few examples of how the laws of nature produce the instabilities that lead to our own existence. First, the Big Bang (what an insufficient name!) apparently came from an instability, in which the "false vacuum" eventually decayed into the ordinary vacuum we have today, plus the most fundamental particles we know, the quarks and leptons. So the universe as a whole started with an instability. Then, a great expansion and cooling happened, and the loose quarks, finding themselves unstable too, bound themselves together into today's less elementary particles like protons and

  9. Cosmic Complexity

    NASA Technical Reports Server (NTRS)

    Mather, John C.

    2012-01-01

    What explains the extraordinary complexity of the observed universe, on all scales from quarks to the accelerating universe? My favorite explanation (which I certainty did not invent) ls that the fundamental laws of physics produce natural instability, energy flows, and chaos. Some call the result the Life Force, some note that the Earth is a living system itself (Gaia, a "tough bitch" according to Margulis), and some conclude that the observed complexity requires a supernatural explanation (of which we have many). But my dad was a statistician (of dairy cows) and he told me about cells and genes and evolution and chance when I was very small. So a scientist must look for me explanation of how nature's laws and statistics brought us into conscious existence. And how is that seemll"!gly Improbable events are actually happening a!1 the time? Well, the physicists have countless examples of natural instability, in which energy is released to power change from simplicity to complexity. One of the most common to see is that cooling water vapor below the freezing point produces snowflakes, no two alike, and all complex and beautiful. We see it often so we are not amazed. But physlc!sts have observed so many kinds of these changes from one structure to another (we call them phase transitions) that the Nobel Prize in 1992 could be awarded for understanding the mathematics of their common features. Now for a few examples of how the laws of nature produce the instabilities that lead to our own existence. First, the Big Bang (what an insufficient name!) apparently came from an instability, in which the "false vacuum" eventually decayed into the ordinary vacuum we have today, plus the most fundamental particles we know, the quarks and leptons. So the universe as a whole started with an instability. Then, a great expansion and cooling happened, and the loose quarks, finding themselves unstable too, bound themselves together into today's less elementary particles like protons and

  10. TOWARD UNDERSTANDING THE COSMIC-RAY ACCELERATION AT YOUNG SUPERNOVA REMNANTS INTERACTING WITH INTERSTELLAR CLOUDS: POSSIBLE APPLICATIONS TO RX J1713.7-3946

    SciTech Connect

    Inoue, Tsuyoshi; Yamazaki, Ryo; Inutsuka, Shu-ichiro; Fukui, Yasuo

    2012-01-01

    Using three-dimensional magnetohydrodynamic simulations, we investigate general properties of a blast wave shock interacting with interstellar clouds. The pre-shock cloudy medium is generated as a natural consequence of the thermal instability that simulates realistic clumpy interstellar clouds and their diffuse surrounding. The shock wave that sweeps the cloudy medium generates a turbulent shell through the vorticity generations that are induced by shock-cloud interactions. In the turbulent shell, the magnetic field is amplified as a result of turbulent dynamo action. The energy density of the amplified magnetic field can locally grow comparable to the thermal energy density, particularly at the transition layers between clouds and the diffuse surrounding. In the case of a young supernova remnant (SNR) with a shock velocity {approx}> 10{sup 3} km s{sup -1}, the corresponding strength of the magnetic field is approximately 1 mG. The propagation speed of the shock wave is significantly stalled in the clouds because of the high density, while the shock maintains a high velocity in the diffuse surrounding. In addition, when the shock wave hits the clouds, reflection shock waves are generated that propagate back into the shocked shell. From these simulation results, many observational characteristics of the young SNR RX J1713.7-3946 that is suggested to be interacting with molecular clouds can be explained as follows. The reflection shocks can accelerate particles in the turbulent downstream region where the magnetic field strength reaches 1 mG, which causes short-time variability of synchrotron X-rays. Since the shock velocity is stalled locally in the clouds, the temperature in the shocked cloud is suppressed far below 1 keV. Thus, thermal X-ray line emission would be faint even if the SNR is interacting with molecular clouds. We also find that the photon index of the {pi}{sup 0}-decay gamma rays generated by cosmic-ray protons can be 1.5 (corresponding energy flux

  11. Toward Understanding the Cosmic-Ray Acceleration at Young Supernova Remnants Interacting with Interstellar Clouds: Possible Applications to RX J1713.7-3946

    NASA Astrophysics Data System (ADS)

    Inoue, Tsuyoshi; Yamazaki, Ryo; Inutsuka, Shu-ichiro; Fukui, Yasuo

    2012-01-01

    Using three-dimensional magnetohydrodynamic simulations, we investigate general properties of a blast wave shock interacting with interstellar clouds. The pre-shock cloudy medium is generated as a natural consequence of the thermal instability that simulates realistic clumpy interstellar clouds and their diffuse surrounding. The shock wave that sweeps the cloudy medium generates a turbulent shell through the vorticity generations that are induced by shock-cloud interactions. In the turbulent shell, the magnetic field is amplified as a result of turbulent dynamo action. The energy density of the amplified magnetic field can locally grow comparable to the thermal energy density, particularly at the transition layers between clouds and the diffuse surrounding. In the case of a young supernova remnant (SNR) with a shock velocity >~ 103 km s-1, the corresponding strength of the magnetic field is approximately 1 mG. The propagation speed of the shock wave is significantly stalled in the clouds because of the high density, while the shock maintains a high velocity in the diffuse surrounding. In addition, when the shock wave hits the clouds, reflection shock waves are generated that propagate back into the shocked shell. From these simulation results, many observational characteristics of the young SNR RX J1713.7-3946 that is suggested to be interacting with molecular clouds can be explained as follows. The reflection shocks can accelerate particles in the turbulent downstream region where the magnetic field strength reaches 1 mG, which causes short-time variability of synchrotron X-rays. Since the shock velocity is stalled locally in the clouds, the temperature in the shocked cloud is suppressed far below 1 keV. Thus, thermal X-ray line emission would be faint even if the SNR is interacting with molecular clouds. We also find that the photon index of the π0-decay gamma rays generated by cosmic-ray protons can be 1.5 (corresponding energy flux is νF νvpropν0.5) because

  12. Supernova and cosmic rays

    NASA Technical Reports Server (NTRS)

    Wefel, J. P.

    1981-01-01

    A general overview of supernova astronomy is presented, followed by a discussion of the relationship between SN and galactic cosmic rays. Pre-supernova evolution is traced to core collapse, explosion, and mass ejection. The two types of SN light curves are discussed in terms of their causes, and the different nucleosynthetic processes inside SNs are reviewed. Physical events in SN remnants are discussed. The three main connections between cosmic rays and SNs, the energy requirement, the acceleration mechanism, and the detailed composition of CR, are detailed.

  13. Galactic cosmic rays

    NASA Astrophysics Data System (ADS)

    Blasi, Pasquale

    2015-12-01

    The multi-facet nature of the origin of cosmic rays is such that some of the problems currently met in our path to describing available data are due to oversimplified models of CR acceleration and transport, and others to lack of knowledge of the physical processes at work in certain conditions. On the other hand, the phenomenology of cosmic rays, as arising from better observations, is getting so rich that it makes sense to try to distinguish the problems that derive from too simple views of Nature and those that are challenging the very foundations of the existing paradigms. Here I will briefly discuss some of these issues.

  14. Static gas expansion cooler

    DOEpatents

    Guzek, J.C.; Lujan, R.A.

    1984-01-01

    Disclosed is a cooler for television cameras and other temperature sensitive equipment. The cooler uses compressed gas ehich is accelerated to a high velocity by passing it through flow passageways having nozzle portions which expand the gas. This acceleration and expansion causes the gas to undergo a decrease in temperature thereby cooling the cooler body and adjacent temperature sensitive equipment.

  15. The Isotopic Composition of Cosmic-Ray Iron and Nickel

    NASA Technical Reports Server (NTRS)

    Wiedenbeck, M.; Binns, W.; Christian, E.; Cummings, A.; George, J.; Hink, P.; Klarmann, J.; Leske, R.; Lijowski, M.; Mewaldt, R.; Stone, E.; Rosenvinge, T. von

    2000-01-01

    Observations from the Cosmic Ray Isotope Spectrometer (CRIS) on ACE have been used to derive contraints on the locations, physical conditions, and time scales for cosmic-ray acceleration and transport.

  16. Nineteenth International Cosmic Ray Conference. OG Sessions, Volume 3

    NASA Technical Reports Server (NTRS)

    Jones, F. C. (Compiler)

    1985-01-01

    Papers submitted for presentation at the 19th International Cosmic Ray Conference are compiled. This volume addresses cosmic ray sources and acceleration, interstellar propagation and nuclear interactions, and detection techniques and instrumentation.

  17. Fundamental constants and cosmic vacuum: The micro and macro connection

    NASA Astrophysics Data System (ADS)

    Fritzsch, Harald; Solà, Joan

    2015-06-01

    The idea that the vacuum energy density ρΛ could be time-dependent is a most reasonable one in the expanding Universe; in fact, much more reasonable than just a rigid cosmological constant for the entire cosmic history. Being ρΛ = ρΛ(t) dynamical, it offers a possibility to tackle the cosmological constant problem in its various facets. Furthermore, for a long time (most prominently since Dirac’s first proposal on a time variable gravitational coupling) the possibility that the fundamental “constants” of Nature are slowly drifting with the cosmic expansion has been continuously investigated. In the last two decades, and specially in recent times, mounting experimental evidence attests that this could be the case. In this paper, we consider the possibility that these two groups of facts might be intimately connected, namely that the observed acceleration of the Universe and the possible time variation of the fundamental constants are two manifestations of the same underlying dynamics. We call it: the “micro and macro connection”, and on its basis we expect that the cosmological term in Einstein’s equations, Newton’s coupling and the masses of all the particles in the Universe, both the dark matter (DM) particles and the ordinary baryons and leptons, should all drift with the cosmic expansion. Here, we discuss specific cosmological models realizing such possibility in a way that preserves the principle of covariance of general relativity (GR).

  18. Cosmic-Rays and Gamma Ray Bursts

    NASA Astrophysics Data System (ADS)

    Meli, A.

    2013-07-01

    Cosmic-rays are subatomic particles of energies ranging between a few eV to hundreds of TeV. These particles register a power-law spectrum, and it seems that most of them originate from astrophysical galactic and extragalactic sources. The shock acceleration in superalfvenic astrophysical plasmas, is believed to be the main mechanism responsible for the production of the non-thermal cosmic-rays. Especially, the importance of the very high energy cosmic-ray acceleration, with its consequent gamma-ray radiation and neutrino production in the shocks of the relativistic jets of Gamma Ray Bursts, is a favourable theme of study. I will discuss the cosmic-ray shock acceleration mechanism particularly focusing on simulation studies of cosmic-ray acceleration occurring in the relativistic shocks of GRB jets.

  19. Cosmic web and environmental dependence of screening: Vainshtein vs. chameleon

    NASA Astrophysics Data System (ADS)

    Falck, Bridget; Koyama, Kazuya; Zhao, Gong-Bo

    2015-07-01

    Theories which modify general relativity to explain the accelerated expansion of the Universe often use screening mechanisms to satisfy constraints on Solar System scales. We investigate the effects of the cosmic web and the local environmental density of dark matter halos on the screening properties of the Vainshtein and chameleon screening mechanisms. We compare the cosmic web morphology of dark matter particles, mass functions of dark matter halos, mass and radial dependence of screening, velocity dispersions and peculiar velocities, and environmental dependence of screening mechanisms in f(R) and nDGP models. Using the ORIGAMI cosmic web identification routine we find that the Vainshtein mechanism depends on the cosmic web morphology of dark matter particles, since these are defined according to the dimensionality of their collapse, while the chameleon mechanism shows no morphology dependence. The chameleon screening of halos and their velocity dispersions depend on halo mass, and small halos and subhalos can be environmentally screened in the chameleon mechanism. On the other hand, the screening of halos in the Vainshtein mechanism does not depend on mass nor environment, and their velocity dispersions are suppressed. The peculiar velocities of halos in the Vainshtein mechanism are enhanced because screened objects can still feel the fifth force generated by external fields, while peculiar velocities of chameleon halos are suppressed when the halo centers are screened.

  20. Exploding Stars and the Accelerating Universe

    NASA Astrophysics Data System (ADS)

    Kirshner, Robert P.

    2012-01-01

    Supernovae are exceptionally interesting astronomical objects: they punctuate the end of stellar evolution, create the heavy elements, and blast the interstellar gas with energetic shock waves. By studying supernovae, we can learn how these important aspects of cosmic evolution take place. Over the decades, we have learned that some supernovae are produced by gravitational collapse, and others by thermonuclear explosions. By understanding what supernovae are, or at least learning how they behave, supernovae explosions have been harnessed for the problem of measuring cosmic distances with some astonishing results. Carefully calibrated supernovae provide the best extragalactic distance indicators to probe the distances to galaxies and to measure the Hubble constant. Even more interesting is the evidence from supernovae that cosmic expansion has been speeding up over the last 5 billion years. We attribute this acceleration to a mysterious dark energy whose effects are clear, but whose nature is obscure. Combining the cosmic expansion history traced by supernovae with clues from galaxy clustering and cosmic geometry from the microwave background has produced today's standard, but peculiar, picture of a universe that is mostly dark energy, braked (with diminishing effect) by dark matter, and illuminated by a pinch of luminous baryons. In this talk, I will show how the attempt to understand supernovae, facilitated by ever-improving instruments, has led to the ability to measure the properties of dark energy. Looking ahead, the properties of supernovae as measured at infrared wavelengths seem to hold the best promise for more precise and accurate distances to help us understand the puzzle of dark energy. My own contribution to this work has been carried out in joyful collaboration with many excellent students, postdocs, and colleagues and with generous support from the places I have worked, the National Science Foundation, and from NASA.

  1. Cosmic impacts, cosmic catastrophes. I

    NASA Technical Reports Server (NTRS)

    Chapman, Clark R.; Morrison, David

    1989-01-01

    The discovery of cosmic impacts and their effects on the earth's surface are discussed. The manner in which the object impacts with the earth is described. The formation of crytovolcanic structures by craters is examined. Examples of cosmic debris collisions with earth, in particular the Tunguska explosion of 1908 and the Meteor Crater in Arizona, are provided.

  2. Origin of high energy Galactic cosmic rays

    NASA Technical Reports Server (NTRS)

    Gaisser, T. K.

    1990-01-01

    The flux of cosmic ray antiprotons and the chemical composition in the region of the 'knee' of the cosmic ray energy spectrum are discussed. The importance of a direct determination of the energy spectrum of each major component of cosmic radiation through the knee region is stressed, and the necessary kinds of experiments are described. It is emphasized that antiprotons are a unique probe of acceleration and propagation of energetic particles in the galaxy because of the high threshold for their production.

  3. Space science: Cosmic rays beyond the knees

    NASA Astrophysics Data System (ADS)

    Taylor, Andrew M.

    2016-03-01

    The development of a radio technique for detecting cosmic rays casts fresh light on the origins of some of these accelerated particles, and suggests that they might have travelled much farther than was previously thought. See Letter p.70

  4. Cosmic superstrings.

    PubMed

    Sakellariadou, Mairi

    2008-08-28

    Cosmic superstrings are expected to be formed at the end of brane inflation, within the context of brane-world cosmological models inspired from string theory. By studying the properties of cosmic superstring networks and comparing their phenomenological consequences against observational data, we aim to pin down the successful and natural inflationary model and get an insight into the stringy description of our Universe. PMID:18534932

  5. Cosmic Rays Astrophysics: The Discipline, Its Scope, and Its Applications

    NASA Technical Reports Server (NTRS)

    Barghouty, A. F.

    2009-01-01

    This slide presentation gives an overview of the discipline surrounding cosmic ray astrophysics. It includes information on recent assertions surrounding cosmic rays, exposure levels, and a short history with specific information on the origin, acceleration, transport, and modulation of cosmic rays.

  6. Cosmological cosmic strings

    NASA Technical Reports Server (NTRS)

    Gregory, Ruth

    1988-01-01

    The effect of an infinite cosmic string on a cosmological background is investigated. It is found that the metric is approximately a scaled version of the empty space string metric, i.e., conical in nature. Results are used to place bounds on the amount of cylindrical gravitational radiation currently emitted by such a string. The gravitational radiation equations are then analyzed explicitly and it is shown that even initially large disturbances are rapidly damped as the expansion proceeds. The implications of the gravitational radiation background and the limitations of the quadrupole formula are discussed.

  7. Numerical Cosmic-Ray Hydrodynamics

    NASA Astrophysics Data System (ADS)

    Miniati, F.

    2009-04-01

    We present a numerical method for integrating the equations describing a system made of a fluid and cosmic-rays. We work out the modified characteristic equations that include the CR dynamical effects in smooth flows. We model the energy exchange between cosmic-rays and the fluid, due to diffusive processes in configuration and momentum space, with a flux conserving method. For a specified shock acceleration efficiency as a function of the upstream conditions and shock Mach number, we modify the Riemann solver to take into account the cosmic-ray mediation at shocks without resolving the cosmic-ray induced substructure. A self-consistent time-dependent shock solution is obtained by using our modified solver with Glimm's method. Godunov's method is applied in smooth parts of the flow.

  8. Tomography from the next generation of cosmic shear experiments for viable f(R) models

    SciTech Connect

    Camera, Stefano; Diaferio, Antonaldo; Cardone, Vincenzo F. E-mail: diaferio@ph.unito.it

    2011-07-01

    We present the cosmic shear signal predicted by two viable cosmological models in the framework of modified-action f(R) theories. We use f(R) models where the current accelerated expansion of the Universe is a direct consequence of the modified gravitational Lagrangian rather than Dark Energy (DE), either in the form of vacuum energy/cosmological constant or of a dynamical scalar field (e.g. quintessence). We choose Starobinsky's (St) and Hu and Sawicki's (HS) f(R) models, which are carefully designed to pass the Solar System gravity tests. In order to further support — or rule out — f(R) theories as alternative candidates to the DE hypothesis, we exploit the power of weak gravitational lensing, specifically of cosmic shear. We calculate the tomographic shear matrix as it would be measured by the upcoming ESA Cosmic Vision Euclid satellite. We find that in the St model the cosmic shear signal is almost completely degenerate with ΛCDM, but it is easily distinguishable in the HS model. Moreover, we compute the corresponding Fisher matrix for both the St and HS models, thus obtaining forecasts for their cosmological parameters. Finally, we show that the Bayes factor for cosmic shear will definitely favour the HS model over ΛCDM if Euclid measures a value larger than ∼ 0.02 for the extra HS parameter n{sub HS}.

  9. High-energy cosmic ray interactions

    SciTech Connect

    Engel, Ralph; Orellana, Mariana; Reynoso, Matias M.; Vila, Gabriela S.

    2009-04-30

    Research into hadronic interactions and high-energy cosmic rays are closely related. On one hand--due to the indirect observation of cosmic rays through air showers--the understanding of hadronic multiparticle production is needed for deriving the flux and composition of cosmic rays at high energy. On the other hand the highest energy particles from the universe allow us to study the characteristics of hadronic interactions at energies far beyond the reach of terrestrial accelerators. This is the summary of three introductory lectures on our current understanding of hadronic interactions of cosmic rays.

  10. Cosmic Rays at Earth

    NASA Astrophysics Data System (ADS)

    Grieder, P. K. F.

    In 1912 Victor Franz Hess made the revolutionary discovery that ionizing radiation is incident upon the Earth from outer space. He showed with ground-based and balloon-borne detectors that the intensity of the radiation did not change significantly between day and night. Consequently, the sun could not be regarded as the sources of this radiation and the question of its origin remained unanswered. Today, almost one hundred years later the question of the origin of the cosmic radiation still remains a mystery. Hess' discovery has given an enormous impetus to large areas of science, in particular to physics, and has played a major role in the formation of our current understanding of universal evolution. For example, the development of new fields of research such as elementary particle physics, modern astrophysics and cosmology are direct consequences of this discovery. Over the years the field of cosmic ray research has evolved in various directions: Firstly, the field of particle physics that was initiated by the discovery of many so-called elementary particles in the cosmic radiation. There is a strong trend from the accelerator physics community to reenter the field of cosmic ray physics, now under the name of astroparticle physics. Secondly, an important branch of cosmic ray physics that has rapidly evolved in conjunction with space exploration concerns the low energy portion of the cosmic ray spectrum. Thirdly, the branch of research that is concerned with the origin, acceleration and propagation of the cosmic radiation represents a great challenge for astrophysics, astronomy and cosmology. Presently very popular fields of research have rapidly evolved, such as high-energy gamma ray and neutrino astronomy. In addition, high-energy neutrino astronomy may soon initiate as a likely spin-off neutrino tomography of the Earth and thus open a unique new branch of geophysical research of the interior of the Earth. Finally, of considerable interest are the biological

  11. A transition from a decelerated to an accelerated phase of the universe expansion from the simplest non-trivial polynomial function of T in the f(R,T) formalism

    NASA Astrophysics Data System (ADS)

    Moraes, P. H. R. S.; Ribeiro, G.; Correa, R. A. C.

    2016-07-01

    In this work we present cosmological solutions from the simplest non-trivial polynomial function of T in f(R,T) theory of gravity, with R and T standing for the Ricci scalar and trace of the energy-momentum tensor, respectively. Although such an approach yields a highly non-linear differential equation for the scale factor, we show that it is possible to obtain analytical solutions for the cosmological parameters. For some values of the free parameters, the model is able to predict a transition from a decelerated to an accelerated expansion of the universe and the values of the deceleration parameter agree with observation.

  12. Expansion of Pannes

    EPA Science Inventory

    For the Long Island, New Jersey, and southern New England region, one facet of marsh drowning as a result of accelerated sea level rise is the expansion of salt marsh ponds and pannes. Over the past century, marsh ponds and pannes have formed and expanded in areas of poor drainag...

  13. High energy physics in cosmic rays

    SciTech Connect

    Jones, Lawrence W.

    2013-02-07

    In the first half-century of cosmic ray physics, the primary research focus was on elementary particles; the positron, pi-mesons, mu-mesons, and hyperons were discovered in cosmic rays. Much of this research was carried out at mountain elevations; Pic du Midi in the Pyrenees, Mt. Chacaltaya in Bolivia, and Mt. Evans/Echo Lake in Colorado, among other sites. In the 1960s, claims of the observation of free quarks, and satellite measurements of a significant rise in p-p cross sections, plus the delay in initiating accelerator construction programs for energies above 100 GeV, motivated the Michigan-Wisconsin group to undertake a serious cosmic ray program at Echo Lake. Subsequently, with the succession of higher energy accelerators and colliders at CERN and Fermilab, cosmic ray research has increasingly focused on cosmology and astrophysics, although some groups continue to study cosmic ray particle interactions in emulsion chambers.

  14. Cosmic strings

    NASA Technical Reports Server (NTRS)

    Bennett, David P.

    1988-01-01

    Cosmic strings are linear topological defects which are predicted by some grand unified theories to form during a spontaneous symmetry breaking phase transition in the early universe. They are the basis for the only theories of galaxy formation aside from quantum fluctuations from inflation based on fundamental physics. In contrast to inflation, they can also be observed directly through gravitational lensing and their characterisitc microwave background anisotropy. It was recently discovered that details of cosmic string evolution are very differnt from the so-called standard model that was assumed in most of the string-induced galaxy formation calculations. Therefore, the details of galaxy formation in the cosmic string models are currently very uncertain.

  15. Cosmic strings

    SciTech Connect

    Bennett, D.P.

    1988-07-01

    Cosmic strings are linear topological defects that are predicted by some grand unified theories to form during a spontaneous symmetry breaking phase transition in the early universe. They are the basis for the only theories of galaxy formation aside from quantum fluctuations from inflation that are based on fundamental physics. In contrast to inflation, they can also be observed directly through gravitational lensing and their characteristic microwave background anistropy. It has recently been discovered by F. Bouchet and myself that details of cosmic string evolution are very different from the so-called ''standard model'' that has been assumed in most of the string induced galaxy formation calculations. Therefore, the details of galaxy formation in the cosmic string models are currently very uncertain. 29 refs., 9 figs.

  16. Low-Energy Cosmic Rays

    NASA Astrophysics Data System (ADS)

    Wiedenbeck, M. E.; ACE/CRIS Collaboration

    2002-12-01

    Cosmic rays with energies below about 10 GeV/nucleon have been measured with high precision as a result of experiments on the HEAO, Ulysses, and ACE spacecrafts. The observations provide energy spectra, elemental abundances, and isotopic composition for elements up through Z=30. They include both stable and radioactive nuclides that are synthesized in stars or are produced by nuclear fragmentation during diffusion at high energies through interstellar medium. From these data one obtains a rather detailed picture of the origin of low-energy cosmic rays. For refractory species, the cosmic-ray source composition closely resembles that of the Sun, suggesting that cosmic rays are accelerated from a well-mixed sample of interstellar matter. A chemical fractionation process has depleted the abundances of volatile elements relative to refractories. Using various radioactive clock isotopes it has been shown that particle acceleration occurs at least 105 years after supernova nucleosynthesis and that the accelerated particles diffuse in the Galaxy for approximately 15 Myr after acceleration. Energy spectra and secondary-to-primary ratios are reasonably well accounted for by models in which particles gain the bulk of their energy in a single encounter with a strong shock. Among the large number of species that have been measured, 22Ne stands out as the only nuclide with an abundance that is clearly much different than solar. To test models proposed to account for this anomaly, the data are being analyzed for predicted smaller effects on abundances of other nuclides. In addition to providing a detailed understanding of the origin and acceleration of low-energy cosmic rays, these data are providing constraints on the chemical evolution of interstellar matter. This work was supported by NASA at Caltech (under grant NAG5-6912), JPL, NASA/GSFC, and Washington U.

  17. Anisotropic Expansion of the Black Hole Universe

    NASA Astrophysics Data System (ADS)

    Zhang, Tianxi

    2009-01-01

    Recently, Zhang proposed a new cosmological model called black hole universe. According to this model, the universe originated from a hot star-like black hole with several solar masses, and grew up through a supermassive black hole with billion solar masses to the present state of temperature and density with hundred billion-trillion solar masses due to continuously inhaling matter from its outside. The structure of the entire space is similarly hierarchical or layered and the evolution is iterative. In each of iteration a universe passes through birth, growth, and death. The entire life of a universe roughly divides into three periods with different rates of expansion: slowly growing child universe, fast expanding adult universe, and gradually dying aged universe. When one universe expands to die out, a new universe grows up from its inside. On the AAS 211th meeting, the black hole universe model was shown to be consistent with Mach's principle, observations, and Einstein's general relativity. This new cosmological model can explain the cosmic microwave background radiation, quasars, and element abundances with the well-developed physics. Dark energy is not required for the universe to accelerate. Inflation is not necessary because the black hole universe does not have the horizon problem. In this presentation, the author will explain why the expansion of the universe is anisotropic as shown by the observed anisotropy of the Hubble constant. He will also compare the significant differences between the black hole universe and the big bang cosmology.

  18. Models of Cosmic-Ray Origin

    NASA Astrophysics Data System (ADS)

    Shapiro, M. M.

    2001-08-01

    Two models of cosmic-ray genesis are compared: (a) the author s red-dwarf hypothesis requiring the injection of seed particles from coronal mass ejections (CME) prior to shock acceleration, and (b) the direct acceleration of thermal ions and of grains in the ISM, proposed by Meyer, Drury and Ellison. Both models agree that shocks in the expanding envelopes of supernova remnants are principally responsible for acceleration to cosmic-ray energies. Both are designed to overcome the mismatch between the source composition of the Galactic cosmic rays (GCR) and the composition of the thermal ISM gas. Model (a) utilizes the prolific emissions of energetic particles from active dMe and dKe stars via their CME as the agents of seed-particle injection into the ISM. The composition of these seed particles is governed by the FIP (first-ionization potential) selection mechanism that operates for both Galactic cosmic rays and solar energetic particles. Hence it is consistent with the cosmic-ray source composition. Model (b) relies on the sputtering and acceleration of grains in the ISM (along with acceleration of thermal ions) to provide the known source composition. This model considers the FIP ordering of GCR abundances as purely coincidental, and it attributes the relative source abundances to selection according to volatility. Recent cosmic-ray observations in favor of each model are cited.

  19. Cosmic Balloons

    ERIC Educational Resources Information Center

    El Abed, Mohamed

    2014-01-01

    A team of French high-school students sent a weather balloon into the upper atmosphere to recreate Viktor Hess's historical experiment that demonstrated the existence of ionizing radiation from the sky--later called cosmic radiation. This discovery earned him the Nobel Prize for Physics in 1936.

  20. Cosmic balloons

    NASA Astrophysics Data System (ADS)

    El Abed, Mohamed

    2014-11-01

    A team of French high-school students sent a weather balloon into the upper atmosphere to recreate Viktor Hess’s historical experiment that demonstrated the existence of ionizing radiation from the sky—later called cosmic radiation. This discovery earned him the Nobel Prize for Physics in 1936.

  1. Preconditioning Therapy with Lentiviral Vector-Programmed Dendritic Cells Accelerates the Homeostatic Expansion of Antigen-Reactive Human T Cells in NOD.Rag1−/−.IL-2rγc−/− mice

    PubMed Central

    Salguero, Gustavo; Sundarasetty, Bala Sai; Borchers, Sylvia; Wedekind, Dirk; Eiz-Vesper, Britta; Velaga, Sarvari; Jirmo, Adan C.; Behrens, Georg; Warnecke, Gregor; Knöfel, Ann-Kathrin; Blasczyk, Rainer; Mischak-Weissinger, Eva; Ganser, Arnold

    2011-01-01

    Abstract Dendritic cell (DC)-based immunization is a potent strategy to direct prompt and durable immune responses against viral reactivations after transplantations. Here, we show that overnight lentiviral vector (LV) gene transfer into human monocytes co-expressing granulocyte-macrophage colony stimulating factor and interleukin (IL)-4 induced self-differentiated DCs (SMART-DCs) with stable DC immunophenotype over weeks in culture and secreted several inflammatory cytokines. SMART-DCs injected subcutaneously in immunodeficient NOD.Rag1−/−.IL2rγ−/− (NRG) mice 1 day after LV transduction were stable for a month in vivo. “Conventional” DCs (cDCs) and SMART-DCs were compared with regard to their potency to accelerate the expansion, biodistribution, and antigenic stimulation of autologous human T cells. Peripheral blood cells obtained from human cytomegalovirus (hCMV)-reactive donors and full-length hCMV pp65 antigenic protein or peptides were used. DCs loaded with pp65 were administered subcutaneously into NRG mice as a preconditioning treatment a week prior to intravenous infusion with T cells. Optical imaging analyses demonstrated that in mice preconditioned with SMART-DC-pp65, T cells were directly recruited to the immunization site and subsequently spread to the spleen and other organs. A dramatic expansion of both human CD8+ and CD4+ T cells could be observed within a few days after infusion, and this was associated with consistent measurable CD8+ effector memory T-cell responses against different pp65 epitopes. Thus, this mouse model demonstrates the proof-of-principle for SMART-DCs to accelerate expansion of human lymphocytes, resulting in poly-functional and antigen-specific immune responses against hCMV-pp65. PMID:21574869

  2. Aligned interactions in cosmic rays

    NASA Astrophysics Data System (ADS)

    Kempa, J.

    2015-12-01

    The first clean Centauro was found in cosmic rays years many ago at Mt Chacaltaya experiment. Since that time, many people have tried to find this type of interaction, both in cosmic rays and at accelerators. But no one has found a clean cases of this type of interaction.It happened finally in the last exposure of emulsion at Mt Chacaltaya where the second clean Centauro has been found. The experimental data for both the Centauros and STRANA will be presented and discussed in this paper. We also present our comments to the intriguing question of the existence of a type of nuclear interactions at high energy with alignment.

  3. Aligned interactions in cosmic rays

    SciTech Connect

    Kempa, J.

    2015-12-15

    The first clean Centauro was found in cosmic rays years many ago at Mt Chacaltaya experiment. Since that time, many people have tried to find this type of interaction, both in cosmic rays and at accelerators. But no one has found a clean cases of this type of interaction.It happened finally in the last exposure of emulsion at Mt Chacaltaya where the second clean Centauro has been found. The experimental data for both the Centauros and STRANA will be presented and discussed in this paper. We also present our comments to the intriguing question of the existence of a type of nuclear interactions at high energy with alignment.

  4. Constraints on kinematic model from recent cosmic observations: SN Ia, BAO and observational Hubble data

    SciTech Connect

    Xu, Lixin; Li, Wenbo; Lu, Jianbo E-mail: liwenbo10@yahoo.com.cn

    2009-07-01

    In this paper, linear first order expansion of deceleration parameter q(z) = q{sub 0}+q{sub 1}(1−a) (M{sub 1}), constant jerk j = j{sub 0} (M{sub 2}) and third order expansion of luminosity distance (M{sub 3}) are confronted with cosmic observations: SCP 307 SN Ia, BAO and observational Hubble data (OHD). Likelihood is implemented to find the best fit model parameters. All these models give the same prediction of the evolution of the universe which is undergoing accelerated expansion currently and experiences a transition from decelerated expansion to accelerated expansion. But, the transition redshift depends on the concrete parameterized form of the model assumed. M{sub 1} and M{sub 2} give value of transition redshift about z{sub t} ∼ 0.6. M{sub 3} gives a larger one, say z{sub t} ∼ 1. The χ{sup 2}/dof implies almost the same goodness of the models. But, for its badness of evolution of deceleration parameter at high redshift z > 1, M{sub 3} can not be reliable. M{sub 1} and M{sub 2} are compatible with ΛCDM model at the 2σ and 1σ confidence levels respectively. M{sub 3} is not compatible with ΛCDM model at 2σ confidence level. From M{sub 1} and M{sub 2} models, one can conclude that the cosmic data favor a cosmological model having j{sub 0} < −1.

  5. Acceleration in astrophysics

    SciTech Connect

    Colgate, S.A.

    1993-12-31

    The origin of cosmic rays and applicable laboratory experiments are discussed. Some of the problems of shock acceleration for the production of cosmic rays are discussed in the context of astrophysical conditions. These are: The presumed unique explanation of the power law spectrum is shown instead to be a universal property of all lossy accelerators; the extraordinary isotropy of cosmic rays and the limited diffusion distances implied by supernova induced shock acceleration requires a more frequent and space-filling source than supernovae; the near perfect adiabaticity of strong hydromagnetic turbulence necessary for reflecting the accelerated particles each doubling in energy roughly 10{sup 5} to {sup 6} scatterings with negligible energy loss seems most unlikely; the evidence for acceleration due to quasi-parallel heliosphere shocks is weak. There is small evidence for the expected strong hydromagnetic turbulence, and instead, only a small number of particles accelerate after only a few shock traversals; the acceleration of electrons in the same collisionless shock that accelerates ions is difficult to reconcile with the theoretical picture of strong hydromagnetic turbulence that reflects the ions. The hydromagnetic turbulence will appear adiabatic to the electrons at their much higher Larmor frequency and so the electrons should not be scattered incoherently as they must be for acceleration. Therefore the electrons must be accelerated by a different mechanism. This is unsatisfactory, because wherever electrons are accelerated these sites, observed in radio emission, may accelerate ions more favorably. The acceleration is coherent provided the reconnection is coherent, in which case the total flux, as for example of collimated radio sources, predicts single charge accelerated energies much greater than observed.

  6. Cosmic Topology

    NASA Astrophysics Data System (ADS)

    Luminet, Jean-Pierre

    2015-08-01

    Cosmic Topology is the name given to the study of the overall shape of the universe, which involves both global topological features and more local geometrical properties such as curvature. Whether space is finite or infinite, simply-connected or multi-connected like a torus, smaller or greater than the portion of the universe that we can directly observe, are questions that refer to topology rather than curvature. A striking feature of some relativistic, multi-connected "small" universe models is to create multiples images of faraway cosmic sources. While the most recent cosmological data fit the simplest model of a zero-curvature, infinite space model, they are also consistent with compact topologies of the three homogeneous and isotropic geometries of constant curvature, such as, for instance, the spherical Poincaré Dodecahedral Space, the flat hypertorus or the hyperbolic Picard horn. After a "dark age" period, the field of Cosmic Topology has recently become one of the major concerns in cosmology, not only for theorists but also for observational astronomers, leaving open a number of unsolved issues.

  7. Universal Expansion.

    ERIC Educational Resources Information Center

    McArdle, Heather K.

    1997-01-01

    Describes a week-long activity for general to honors-level students that addresses Hubble's law and the universal expansion theory. Uses a discrepant event-type activity to lead up to the abstract principles of the universal expansion theory. (JRH)

  8. Cosmic impacts, cosmic catastrophes. II

    SciTech Connect

    Chapman, C.R.; Morrison, D. NASA, Ames Research Center, Moffett Field, CA )

    1990-02-01

    The role of extraterrestrial impacts in shaping the earth's history is discussed, arguing that cosmic impacts represent just one example of a general shift in thinking that has made the idea of catastrophes respectable in science. The origins of this view are presented and current catastrophic theory is discussed in the context of modern debate on the geological formation of the earth. Various conflicting theories are reviewed and prominent participants in the ongoing scientific controversy concerning catastrophism are introduced.

  9. Cosmic impacts, cosmic catastrophes. II

    NASA Technical Reports Server (NTRS)

    Chapman, Clark R.; Morrison, David

    1990-01-01

    The role of extraterrestrial impacts in shaping the earth's history is discussed, arguing that cosmic impacts represent just one example of a general shift in thinking that has made the idea of catastrophes respectable in science. The origins of this view are presented and current catastrophic theory is discussed in the context of modern debate on the geological formation of the earth. Various conflicting theories are reviewed and prominent participants in the ongoing scientific controversy concerning catastrophism are introduced.

  10. Elemental advances of ultraheavy cosmic rays

    NASA Technical Reports Server (NTRS)

    1984-01-01

    The elemental composition of the cosmic-ray source is different from that which has been generally taken as the composition of the solar system. No general enrichment of products of either r-process or s-process nucleosynthesis accounts for the differences over the entire range of ultraheavy (Z 30) elements; specific determination of nucleosynthetic contributions to the differences depends upon an understanding of the nature of any acceleration fractionation. Comparison between the cosmic-ray source abundances and the abundances of C1 and C2 chondritic meteorites suggests that differences between the cosmic-ray source and the standard (C1) solar system may not be due to acceleration fractionation of the cosmic rays, but rather to a fractionation of the C1 abundances with respect to the interstellar abundances.

  11. Unveiling the Origin of Cosmic Rays

    NASA Astrophysics Data System (ADS)

    Olinto, Angela V.

    2015-04-01

    The origin of cosmic rays, relativistic particles that range from below GeVs to hundreds of EeVs, is a century old mystery. Extremely energetic phenomena occurring over a wide range of scales, from the Solar System to distant galaxies, are needed to explain the non-thermal particle spectrum that covers over 12 orders of magnitude. Space Missions are the most effective platforms to study the origin and history of these cosmic particles. Current missions probe particle acceleration and propagation in the Solar System and in our Galaxy. This year ISS-CREAM and CALET join AMS in establishing the International Space Station as the most active site for studying the origin of Galactic cosmic rays. These missions will study astrophysical cosmic ray accelerators as well as other possible sources of energetic particles such as dark matter annihilation or decay. In the future, the ISS may also be the site for studying extremely high-energy extragalactic cosmic rays with JEM-EUSO. We review recent results in the quest for unveiling the sources of energetic particles with balloons and space payloads and report on activities of the Cosmic ray Science Interest Group (CosmicSIG) under the Physics of the Cosmos Program Analysis Group (PhysPAG).

  12. Cosmic ray transport in astrophysical plasmas

    NASA Astrophysics Data System (ADS)

    Schlickeiser, R.

    2015-09-01

    Since the development of satellite space technology about 50 years ago the solar heliosphere is explored almost routinely by several spacecrafts carrying detectors for measuring the properties of the interplanetary medium including energetic charged particles (cosmic rays), solar wind particle densities, and electromagnetic fields. In 2012, the Voyager 1 spacecraft has even left what could be described as the heliospheric modulation region, as indicated by the sudden disappearance of low energy heliospheric cosmic ray particles. With the available in-situ measurements of interplanetary turbulent electromagnetic fields and of the momentum spectra of different cosmic ray species in different interplanetary environments, the heliosphere is the best cosmic laboratory to test our understanding of the transport and acceleration of cosmic rays in space plasmas. I review both the historical development and the current state of various cosmic ray transport equations. Similarities and differences to transport theories for terrestrial fusion plasmas are highlighted. Any progress in cosmic ray transport requires a detailed understanding of the electromagnetic turbulence that is responsible for the scattering and acceleration of these particles.

  13. Cosmic ray transport in astrophysical plasmas

    SciTech Connect

    Schlickeiser, R.

    2015-09-15

    Since the development of satellite space technology about 50 years ago the solar heliosphere is explored almost routinely by several spacecrafts carrying detectors for measuring the properties of the interplanetary medium including energetic charged particles (cosmic rays), solar wind particle densities, and electromagnetic fields. In 2012, the Voyager 1 spacecraft has even left what could be described as the heliospheric modulation region, as indicated by the sudden disappearance of low energy heliospheric cosmic ray particles. With the available in-situ measurements of interplanetary turbulent electromagnetic fields and of the momentum spectra of different cosmic ray species in different interplanetary environments, the heliosphere is the best cosmic laboratory to test our understanding of the transport and acceleration of cosmic rays in space plasmas. I review both the historical development and the current state of various cosmic ray transport equations. Similarities and differences to transport theories for terrestrial fusion plasmas are highlighted. Any progress in cosmic ray transport requires a detailed understanding of the electromagnetic turbulence that is responsible for the scattering and acceleration of these particles.

  14. Cosmic strings and superconducting cosmic strings

    NASA Technical Reports Server (NTRS)

    Copeland, Edmund

    1988-01-01

    The possible consequences of forming cosmic strings and superconducting cosmic strings in the early universe are discussed. Lecture 1 describes the group theoretic reasons for and the field theoretic reasons why cosmic strings can form in spontaneously broken gauge theories. Lecture 2 discusses the accretion of matter onto string loops, emphasizing the scenario with a cold dark matter dominated universe. In lecture 3 superconducting cosmic strings are discussed, as is a mechanism which leads to the formation of structure from such strings.

  15. Cosmological Expansion

    ERIC Educational Resources Information Center

    Linton, J. O.

    2012-01-01

    As teachers, we want to encourage our students to ask searching questions on topics like how old the Universe is, how much of the Universe we can actually see and how far away the cosmic microwave background radiation is. But how many of us can honestly say we know the answers? And, even if we know the answers, how are we going to respond to the…

  16. Ultrahigh Energy Cosmic Rays: Old Physics or New Physics?

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.

    2004-01-01

    We consider the advantages of and the problems associated with hypotheses to explain the origin of ultrahigh energy cosmic rays (UHECR: E greater than 10 EeV) and the "trans-GZK" cosmic rays (TGZK: E greater than 100 EeV) both through "old physics" (acceleration in cosmic sources) and "new physics" (new particles, topological defects, fat neutrino cross sections, Lorentz invariance violation).

  17. From cosmic ray source to the Galactic pool

    NASA Astrophysics Data System (ADS)

    Schure, K. M.; Bell, A. R.

    2014-01-01

    The Galactic cosmic ray spectrum is a remarkably straight power law. Our current understanding is that the dominant sources that accelerate cosmic rays up to the knee (3 × 1015 eV) or perhaps even the ankle (3 × 1018 eV), are young Galactic supernova remnants. In theory, however, there are various reasons why the spectrum may be different for different sources, and may not even be a power law if non-linear shock acceleration applies during the most efficient stages of acceleration. We show how the spectrum at the accelerator translates to the spectrum that makes up the escaping cosmic rays that replenish the Galactic pool of cosmic rays. We assume that cosmic ray confinement, and thus escape, is linked to the level of magnetic field amplification, and that the magnetic field is amplified by streaming cosmic rays according to the non-resonant hybrid or resonant instability. When a fixed fraction of the energy is transferred to cosmic rays, it turns out that a source spectrum that is flatter than E-2 will result in an E-2 escape spectrum, whereas a steeper source spectrum will result in an escape spectrum with equal steepening. This alleviates some of the concern that may arise from expected flat or concave cosmic ray spectra associated with non-linear shock modification.

  18. Origin of the high energy cosmic neutrino background.

    PubMed

    Dado, Shlomo; Dar, Arnon

    2014-11-01

    The diffuse background of very high energy extraterrestrial neutrinos recently discovered with IceCube is compatible with that expected from cosmic ray interactions in the Galactic interstellar medium plus that expected from hadronic interactions near the source and in the intergalactic medium of the cosmic rays which have been accelerated by the jets that produce gamma ray bursts. PMID:25415894

  19. Ninteenth International Cosmic Ray Conference. SH Sessions, Volume 4

    NASA Technical Reports Server (NTRS)

    Jones, F. C. (Compiler)

    1985-01-01

    Papers submitted for presentation at the 19th International Cosmic Ray Conference are compiled. This volume covers solar and heliospheric phenomena, specifically, particle acceleration; cosmic ray compsotion, spectra, and anisotropy; propagation of solar and interplanetary energetic particles; solar-cycle modulation; and propagation of galactic particles in the heliosphere.

  20. Cosmic pioneers scoop Nobel prize

    NASA Astrophysics Data System (ADS)

    Banks, Michael

    2011-11-01

    The 2011 Nobel Prize for Physics has been awarded to Saul Perlmutter from the Lawrence Berkeley National Laboratory, US, Adam Riess at Johns Hopkins University in Baltimore and Brian Schmidt from the Australian National University, Weston Creek, "for the discovery of the accelerating expansion of the universe through observations of distant supernovae".

  1. BICEP's acceleration

    SciTech Connect

    Contaldi, Carlo R.

    2014-10-01

    The recent Bicep2 [1] detection of, what is claimed to be primordial B-modes, opens up the possibility of constraining not only the energy scale of inflation but also the detailed acceleration history that occurred during inflation. In turn this can be used to determine the shape of the inflaton potential V(φ) for the first time — if a single, scalar inflaton is assumed to be driving the acceleration. We carry out a Monte Carlo exploration of inflationary trajectories given the current data. Using this method we obtain a posterior distribution of possible acceleration profiles ε(N) as a function of e-fold N and derived posterior distributions of the primordial power spectrum P(k) and potential V(φ). We find that the Bicep2 result, in combination with Planck measurements of total intensity Cosmic Microwave Background (CMB) anisotropies, induces a significant feature in the scalar primordial spectrum at scales k∼ 10{sup -3} Mpc {sup -1}. This is in agreement with a previous detection of a suppression in the scalar power [2].

  2. Fun Times with Cosmic Rays

    NASA Technical Reports Server (NTRS)

    Wanjek, Christopher

    2003-01-01

    Who would have thought cosmic rays could be so hip? Although discovered 90 years ago on death-defying manned balloon flights hip even by twenty-first-century extremesport standards cosmic rays quickly lost popularity as way-cool telescopes were finding way-too-cool phenomena across the electromagnetic spectrum. Yet cosmic rays are back in vogue, boasting their own set of superlatives. Scientists are tracking them down with new resolve from the Arctic to Antarctica and even on the high western plains of Argentina. Theorists, too, now see cosmic rays as harbingers of funky physics. Cosmic rays are atomic and subatomic particles - the fastest moving bits of matter in the universe and the only sample of matter we have from outside the solar system (with the exception of interstellar dust grains). Lower-energy cosmic rays come from the Sun. Mid-energy particles come from stellar explosions - either spewed directly from the star like shrapnel, or perhaps accelerated to nearly the speed of light by shock waves. The highest-energy cosmic rays, whose unequivocal existence remains one of astronomy's greatest mysteries, clock in at a staggering 10(exp 19) to 10(exp 22) electron volts. This is the energy carried in a baseball pitch; seeing as how there are as many atomic particles in a baseball as there are baseballs in the Moon, that s one powerful toss. No simple stellar explosion could produce them. At a recent conference in Albuquerque, scientists presented the first observational evidence of a possible origin for the highest-energy variety. A team led by Elihu Boldt at NASA s Goddard Space Flight Center found that five of these very rare cosmic rays (there are only a few dozen confirmed events) come from the direction of four 'retired' quasar host galaxies just above the arm of the Big Dipper, all visible with backyard telescopes: NGC 3610, NGC 3613, NGC 4589, and NGC 5322. These galaxies are billions of years past their glory days as the brightest beacons in the universe

  3. Cosmic jets

    SciTech Connect

    Blandford, R.D.; Begelman, M.C.; Rees, M.J.

    1982-05-01

    Observations with radio telescopes have revealed that the center of many galaxies is a place of violent activity. This activity is often manifested in the production of cosmic jets. Each jet is a narrow stream of plasma that appears to squirt out of the center of a galaxy emitting radiowaves as it does so. New techniques in radio astronomy have shown how common jets are in the universe. These jets take on many different forms. The discovery of radio jets has helped in the understanding of the double structure of the majority of extragalactic radio sources. The morphology of some jets and explanations of how jets are fueled are discussed. There are many difficulties plaguing the investigation of jets. Some of these difficulties are (1) it is not known how much power the jets are radiating, (2) it is hard to tell whether a jet delieated by radio emission is identical to the region where ionized gas is flowing, and (3) what makes them. (SC)

  4. Cosmic vacuum energy decay and creation of cosmic matter.

    PubMed

    Fahr, Hans-Jörg; Heyl, Michael

    2007-09-01

    In the more recent literature on cosmological evolutions of the universe, the cosmic vacuum energy has become a nonrenouncable ingredient. The cosmological constant Lambda, first invented by Einstein, but later also rejected by him, presently experiences an astonishing revival. Interestingly enough, it acts like a constant vacuum energy density would also do. Namely, it has an accelerating action on cosmic dynamics, without which, as it appears, presently obtained cosmological data cannot be conciliated with theory. As we are going to show in this review, however, the concept of a constant vacuum energy density is unsatisfactory for very basic reasons because it would claim for a physical reality that acts upon spacetime and matter dynamics without itself being acted upon by spacetime or matter. PMID:17457553

  5. Relativistic transport theory for cosmic-rays

    NASA Technical Reports Server (NTRS)

    Webb, G. M.

    1985-01-01

    Various aspects of the transport of cosmic-rays in a relativistically moving magnetized plasma supporting a spectrum of hydromagnetic waves that scatter the cosmic-rays are presented. A local Lorentz frame moving with the waves or turbulence scattering the cosmic-rays is used to specify the individual particle momentum. The comoving frame is in general a noninertial frame in which the observer's volume element is expanding and shearing, geometric energy change terms appear in the cosmic-ray transport equation which consist of the relativistic generalization of the adiabatic deceleration term and a further term involving the acceleration vector of the scatterers. A relativistic version of the pitch angle evolution equation, including the effects of adiabatic focussing, pitch angle scattering, and energy changes is presented.

  6. A class of transient acceleration models consistent with Big Bang cosmology

    NASA Astrophysics Data System (ADS)

    Zu, Tian-Long; Chen, Jie-Wen; Zhang, Yang

    2014-02-01

    Is it possible that the current cosmic accelerating expansion will turn into a decelerating one? Can this transition be realized by some viable theoretical model that is consistent with the standard Big Bang cosmology? We study a class of phenomenological models with a transient acceleration, based on a dynamical dark energy with a very general form of equation of state pde = βρde - βρdem. It mimics the cosmological constant ρde → const for a small scale factor a, and behaves as a barotropic gas with ρde → a-3(α+1) with α >= 0 for large a. The cosmic evolution of four models in the class has been examined in detail, and all yield a smooth transient acceleration. Depending on the specific model, the future universe may be dominated by either dark energy or by matter. In two models, the dynamical dark energy can be explicitly realized by a scalar field with an analytical potential V(φ). Moreover, a statistical analysis shows that the models can be as robust as ΛCDM in confronting the observational data of Type Ia supernovae, cosmic microwave background (CMB) and baryon acoustic oscillation. As improvements over previous studies, our models overcome the problem of over-abundance of dark energy during early eras, and satisfy the constraints on dark energy from WMAP observations of CMB.

  7. Galactic Cosmic Rays and the Light Elements

    NASA Astrophysics Data System (ADS)

    Parizot, Etienne

    2001-10-01

    The study of the light elements abundances in low metallicity stars offers a unique way to learn about the past content of our Galaxy in energetic particles (EPs). This study teaches us that either the light elements are not produced by cosmic rays interactions in the interstellar medium (ISM), as has been thought for 30 years, or the cosmic rays are not what one usually thinks they are, namely standard interstellar material accelerated by the shock waves generated by supernova explosions. In any case, we have to revise our understanding of the EPs in the Galaxy. Relying on the observational evidence about Li, Be and B Galactic evolution as well as about the distribution of massive stars, we show that most of the EPs responsible for the production of light elements must be accelerated inside superbubbles, as is probably the case for the standard Galactic cosmic rays as well.

  8. Galactic Cosmic Rays: From Earth to Sources

    NASA Technical Reports Server (NTRS)

    Brandt, Theresa J.

    2012-01-01

    For nearly 100 years we have known that cosmic rays come from outer space, yet proof of their origin, as well as a comprehensive understanding of their acceleration, remains elusive. Direct detection of high energy (up to 10(exp 15)eV), charged nuclei with experiments such as the balloon-born, antarctic Trans-Iron Galactic Element Recorder (TIGER) have provided insight into these mysteries through measurements of cosmic ray abundances. The abundance of these rare elements with respect to certain intrinsic properties suggests that cosmic rays include a component of massive star ejecta. Supernovae and their remnants (SNe & SNRs), often occurring at the end of a massive star's life or in an environment including massive star material, are one of the most likely candidates for sources accelerating galactic comic ray nuclei up to the requisite high energies. The Fermi Gamma-ray Space Telescope Large Area Detector (Fermi LAT) has improved our understanding of such sources by widening the window of observable energies and thus into potential sources' energetic processes. In combination with multiwavelength observations, we are now better able to constrain particle populations (often hadron-dominated at GeV energies) and environmental conditions, such as the magnetic field strength. The SNR CTB 37A is one such source which could contribute to the observed galactic cosmic rays. By assembling populations of SNRs, we will be able to more definitively define their contribution to the observed galactic cosmic rays, as well as better understand SNRs themselves. Such multimessenger studies will thus illuminate the long-standing cosmic ray mysteries, shedding light on potential sources, acceleration mechanisms, and cosmic ray propagation.

  9. Cosmic statistics of statistics

    NASA Astrophysics Data System (ADS)

    Szapudi, István; Colombi, Stéphane; Bernardeau, Francis

    1999-12-01

    The errors on statistics measured in finite galaxy catalogues are exhaustively investigated. The theory of errors on factorial moments by Szapudi & Colombi is applied to cumulants via a series expansion method. All results are subsequently extended to the weakly non-linear regime. Together with previous investigations this yields an analytic theory of the errors for moments and connected moments of counts in cells from highly non-linear to weakly non-linear scales. For non-linear functions of unbiased estimators, such as the cumulants, the phenomenon of cosmic bias is identified and computed. Since it is subdued by the cosmic errors in the range of applicability of the theory, correction for it is inconsequential. In addition, the method of Colombi, Szapudi & Szalay concerning sampling effects is generalized, adapting the theory for inhomogeneous galaxy catalogues. While previous work focused on the variance only, the present article calculates the cross-correlations between moments and connected moments as well for a statistically complete description. The final analytic formulae representing the full theory are explicit but somewhat complicated. Therefore we have made available a fortran program capable of calculating the described quantities numerically (for further details e-mail SC at colombi@iap.fr). An important special case is the evaluation of the errors on the two-point correlation function, for which this should be more accurate than any method put forward previously. This tool will be immensely useful in the future for assessing the precision of measurements from existing catalogues, as well as aiding the design of new galaxy surveys. To illustrate the applicability of the results and to explore the numerical aspects of the theory qualitatively and quantitatively, the errors and cross-correlations are predicted under a wide range of assumptions for the future Sloan Digital Sky Survey. The principal results concerning the cumulants ξ, Q3 and Q4 is that

  10. A model for the proton spectrum and cosmic ray anisotropy

    NASA Technical Reports Server (NTRS)

    Xu, C.

    1985-01-01

    The problem of the origin of the cosmic rays is still uncertain. As a theory, it should explain the support of particles and energy, the mechanism of acceleration and propagation as well as some important features obtained directly from cosmic ray experiments, such as the power spectrum and the knee. There are two kinds of models for interpreting the knee of the cosmic ray spectrum. One is the leaky box model. Another model suggests that the cut-off rigidity of the main sources causes the knee. The present paper studies the spectrum and the anisotropy of cosmic rays in an isotropic diffuse model with explosive discrete sources in an infinite galaxy.

  11. Testing Gravity using Cosmic Voids

    NASA Astrophysics Data System (ADS)

    Falck, Bridget

    2016-01-01

    Though general relativity is well-tested on small (Solar System) scales, the late-time acceleration of the Universe provides strong motivation to test GR on cosmological scales. The difference between the small and large scale behavior of gravity is determined by the screening mechanism in modified gravity theories. Dark matter halos are often screened in these models, especially in models with Vainshtein screening, motivating a search for signatures of modified gravity in cosmic voids. We explore density, force, and velocity profiles of voids found in N-body simulations, using both dark matter particles and dark matter halos to identify the voids. The prospect of testing gravity using cosmic voids may be limited by the sparsity of halos as tracers of the density field.

  12. Cosmic Ray research in Armenia

    NASA Astrophysics Data System (ADS)

    Chilingarian, A.; Mirzoyan, R.; Zazyan, M.

    2009-11-01

    Cosmic Ray research on Mt. Aragats began in 1934 with the measurements of East-West anisotropy by the group from Leningrad Physics-Technical Institute and Norair Kocharian from Yerevan State University. Stimulated by the results of their experiments in 1942 Artem and Abraham Alikhanyan brothers organized a scientific expedition to Aragats. Since that time physicists were studying Cosmic Ray fluxes on Mt. Aragats with various particle detectors: mass spectrometers, calorimeters, transition radiation detectors, and huge particle detector arrays detecting protons and nuclei accelerated in most violent explosions in Galaxy. Latest activities at Mt. Aragats include Space Weather research with networks of particle detectors located in Armenia and abroad, and detectors of Space Education center in Yerevan.

  13. Diffusive Shock Acceleration

    NASA Astrophysics Data System (ADS)

    Baring, Matthew

    2003-04-01

    The process of diffusive acceleration of charged particles in shocked plasmas is widely invoked in astrophysics to account for the ubiquitous presence of signatures of non-thermal relativistic electrons and ions in the universe. This statistical energization mechanism, manifested in turbulent media, was first posited by Enrico Fermi in 1949 to explain the observed cosmic ray population, which exhibits an almost power-law distribution in rigidity. The absence of a momentum scale is a key characteristic of diffusive shock acceleration, and astrophysical systems generally only impose scales at the injection (low energy) and loss (high energy) ends of the particle spectrum. The existence of structure in the cosmic ray spectrum (the "knee") at around 3000 TeV has promoted contentions that there are at least two origins for cosmic rays, a galactic one supplying those up to the knee, and perhaps an extragalactic one that can explain even the ultra-high energy cosmic rays (UHECRs) seen at 1-300 EeV. Accounting for the UHECRs with familiar astrophysical sites of acceleration has historically proven difficult due to the need to assume high magnetic fields in order to reduce the shortest diffusive acceleration timescale, the ion gyroperiod, to meaningful values. Yet active galaxies and gamma-ray bursts remain strong and interesting candidate sources for UHECRs, turning the theoretical focus to relativistic shocks. This review summarizes properties of diffusive shock acceleration that are salient to the issue of UHECR generation. These include spectral indices, anisotropies, acceleration efficencies and timescales, as functions of the shock speed and mean field orientation, and also the degree of field turbulence. Astrophysical sites for UHECR production are also critiqued.

  14. Can f(T) gravity theories mimic ΛCDM cosmic history

    SciTech Connect

    Setare, M.R.; Mohammadipour, N. E-mail: N.Mohammadipour@uok.ac.ir

    2013-01-01

    Recently the teleparallel Lagrangian density described by the torsion scalar T has been extended to a function of T. The f(T) modified teleparallel gravity has been proposed as the natural gravitational alternative for dark energy to explain the late time acceleration of the universe. In order to reconstruct the function f(T) by demanding a background ΛCDM cosmology we assume that, (i) the background cosmic history provided by the flat ΛCDM (the radiation ere with ω{sub eff} = (1/3), matter and de Sitter eras with ω{sub eff} = 0 and ω{sub eff} = −1, respectively) (ii) the radiation dominate in the radiation era with Ω{sub 0r} = 1 and the matter dominate during the matter phases when Ω{sub 0m} = 1. We find the cosmological dynamical system which can obey the ΛCDM cosmic history. In each era, we find a critical lines that, the radiation dominated and the matter dominated are one points of them in the radiation and matter phases, respectively. Also, we drive the cosmologically viability condition for these models. We investigate the stability condition with respect to the homogeneous scalar perturbations in each era and we obtain the stability conditions for the fixed points in each eras. Finally, we reconstruct the function f(T) which mimics cosmic expansion history.

  15. Cosmic ray nuclei from extragalactic and galactic pulsars

    NASA Astrophysics Data System (ADS)

    Fang, Ke

    2013-02-01

    In an extragalactic newly-born pulsar, nuclei striped off the star surface can be accelerated to extreme energies and leave the source through dense supernova surroundings. The escaped ultrahigh energy cosmic rays can explain both UHE energy spectral and atmospheric depth observations. In addition, assuming that Galactic pulsars accelerate cosmic rays with the same injection composition, very high energy cosmic rays from local pulsars can meet the flux measurements from above the knee to the ankle, and at the same time, agree with the detected composition trend.

  16. The cosmic-ray shock structure problem for relativistic shocks

    NASA Technical Reports Server (NTRS)

    Webb, G. M.

    1985-01-01

    The time asymptotic behaviour of a relativistic (parallel) shock wave significantly modified by the diffusive acceleration of cosmic-rays is investigated by means of relativistic hydrodynamical equations for both the cosmic-rays and thermal gas. The form of the shock structure equation and the dispersion relation for both long and short wavelength waves in the system are obtained. The dependence of the shock acceleration efficiency on the upstream fluid spped, long wavelength Mach number and the ratio N = P sub co/cP sub co+P sub go)(Psub co and P sub go are the upstream cosmic-ray and thermal gas pressures respectively) are studied.

  17. Cosmic rays and hadronic interactions

    NASA Astrophysics Data System (ADS)

    Lipari, Paolo

    2015-08-01

    The study of cosmic rays, and more in general of the "high energy universe" is at the moment a vibrant field that, thanks to the observations by several innovative detectors for relativistic charged particles, gamma-rays, and neutrinos continue to generate surprising and exciting results. The progress in the field is rapid but many fundamental problems remain open. There is an intimate relation between the study of the high energy universe and the study of the properties of hadronic interactions. High energy cosmic rays can only be studied detecting the showers they generate in the atmosphere, and for the interpretation of the data one needs an accurate modeling of the collisions between hadrons. Also the study of cosmic rays inside their sources and in the Galaxy requires a precise description of hadronic interactions. A program of experimental studies at the LHC and at lower energy, designed to address the most pressing problems, could significantly reduce the existing uncertainties and is very desirable. Such an experimental program would also have a strong intrinsic scientific interest, allowing the broadening and deepening of our understanding of Quantum Chromo Dynamics in the non-perturbative regime, the least understood sector of the Standard Model of particle physics. It should also be noted that the cosmic ray spectrum extends to particles with energy E ˜ 1020 eV, or a nucleon-nucleon c.m. energy √s ≃ 430 TeV, 30 times higher than the current LHC energy. Cosmic ray experiments therefore offer the possibility to perform studies on the properties of hadronic interactions that are impossible at accelerators.

  18. COSMIC program documentation experience

    NASA Technical Reports Server (NTRS)

    Kalar, M. C.

    1970-01-01

    A brief history of COSMIC as it relates to the handling of program documentation is summarized; the items that are essential for computer program documentation are also discussed. COSMIC documentation and program standards handbook is appended.

  19. Cosmic Interactions

    NASA Astrophysics Data System (ADS)

    2008-01-01

    An image based on data taken with ESO's Very Large Telescope reveals a triplet of galaxies intertwined in a cosmic dance. ESO PR Photo 02/08 ESO PR Photo 02/08 NGC 7173, 7174, and 7176 The three galaxies, catalogued as NGC 7173 (top), 7174 (bottom right) and 7176 (bottom left), are located 106 million light-years away towards the constellation of Piscis Austrinus (the 'Southern Fish'). NGC 7173 and 7176 are elliptical galaxies, while NGC 7174 is a spiral galaxy with quite disturbed dust lanes and a long, twisted tail. This seems to indicate that the two bottom galaxies - whose combined shape bears some resemblance to that of a sleeping baby - are currently interacting, with NGC 7176 providing fresh material to NGC 7174. Matter present in great quantity around the triplet's members also points to the fact that NGC 7176 and NGC 7173 have interacted in the past. Astronomers have suggested that the three galaxies will finally merge into a giant 'island universe', tens to hundreds of times as massive as our own Milky Way. ESO PR Photo 02/08 ESO PR Photo 02b/08 NGC 7173, 7174, and 7176 The triplet is part of a so-called 'Compact Group', as compiled by Canadian astronomer Paul Hickson in the early 1980s. The group, which is the 90th entry in the catalogue and is therefore known as HCG 90, actually contains four major members. One of them - NGC 7192 - lies above the trio, outside of this image, and is another peculiar spiral galaxy. Compact groups are small, relatively isolated, systems of typically four to ten galaxies in close proximity to one another. Another striking example is Robert's Quartet. Compact groups are excellent laboratories for the study of galaxy interactions and their effects, in particular the formation of stars. As the striking image reveals, there are many other galaxies in the field. Some are distant ones, while others seem to be part of the family. Studies made with other telescopes have indeed revealed that the HCG 90 group contains 16 members

  20. Cosmic rays from cosmic strings with condensates

    SciTech Connect

    Vachaspati, Tanmay

    2010-02-15

    We revisit the production of cosmic rays by cusps on cosmic strings. If a scalar field ('Higgs') has a linear interaction with the string world sheet, such as would occur if there is a bosonic condensate on the string, cusps on string loops emit narrow beams of very high energy Higgses which then decay to give a flux of ultrahigh energy cosmic rays. The ultrahigh energy flux and the gamma to proton ratio agree with observations if the string scale is {approx}10{sup 13} GeV. The diffuse gamma ray and proton fluxes are well below current bounds. Strings that are lighter and have linear interactions with scalars produce an excess of direct and diffuse cosmic rays and are ruled out by observations, while heavier strings ({approx}10{sup 15} GeV) are constrained by their gravitational signatures. This leaves a narrow window of parameter space for the existence of cosmic strings with bosonic condensates.

  1. Cosmic Rays and Their Radiative Processes in Numerical Cosmology

    NASA Technical Reports Server (NTRS)

    Ryu, Dongsu; Miniati, Francesco; Jones, Tom W.; Kang, Hyesung

    2000-01-01

    A cosmological hydrodynamic code is described, which includes a routine to compute cosmic ray acceleration and transport in a simplified way. The routine was designed to follow explicitly diffusive, acceleration at shocks, and second-order Fermi acceleration and adiabatic loss in smooth flows. Synchrotron cooling of the electron population can also be followed. The updated code is intended to be used to study the properties of nonthermal synchrotron emission and inverse Compton scattering from electron cosmic rays in clusters of galaxies, in addition to the properties of thermal bremsstrahlung emission from hot gas. The results of a test simulation using a grid of 128 (exp 3) cells are presented, where cosmic rays and magnetic field have been treated passively and synchrotron cooling of cosmic ray electrons has not been included.

  2. Quantum stabilization of cosmic strings

    NASA Astrophysics Data System (ADS)

    Weigel, H.; Quandt, M.; Graham, N.

    2015-07-01

    In the standard model, stabilization of a classically unstable cosmic string may occur through the quantum fluctuations of a heavy fermion doublet. We review numerical results from a semiclassical expansion in a reduced version of the standard model. In this expansion, the leading quantum corrections emerge at one loop level for many internal degrees of freedom. The resulting vacuum polarization energy and the binding energies of occupied fermion energy levels are of the same order, and must therefore be treated on equal footing. Populating these bound states lowers the total energy compared to the same number of free fermions and assigns a charge to the string. Charged strings are already stabilized for a fermion mass only somewhat larger than the top quark mass. Though obtained in a reduced version, these results suggest that neither extraordinarily large fermion masses nor unrealistic couplings are required to bind a cosmic string in the standard model. Furthermore, we also review results for a quantum stabilization mechanism that prevents closed Nielsen-Olesen-type strings from collapsing.

  3. Monopole annihilation and highest energy cosmic rays

    SciTech Connect

    Bhattacharjee, P. Indian Institute of Astrophysics, Sarjapur Road, Koramangala, Bangalore 560 034 ); Sigl, G. NASA/Fermilab Astrophysics Center, Fermi National Accelerator Laboratory, Batavia, Illinois 60510-0500 )

    1995-04-15

    Cosmic rays with energies exceeding 10[sup 20] eV have been detected. The origin of these highest energy cosmic rays remains unknown. Established astrophysical acceleration mechanisms encounter severe difficulties in accelerating particles to these energies. Alternative scenarios where these particles are created by the decay of cosmic topological defects have been suggested in the literature. In this paper we study the possibility of producing the highest energy cosmic rays through a process that involves the formation of metastable magnetic monopole-antimonopole bound states and their subsequent collapse. The annihilation of the heavy monopole-antimonopole pairs constituting the monopolonia can produce energetic nucleons, [gamma] rays, and neutrinos whose expected flux we estimate and discuss in relation to experimental data so far available. The monopoles we consider are the ones that could be produced in the early Universe during a phase transition at the grand unification energy scale. We find that observable cosmic ray fluxes can be produced with monopole abundances compatible with present bounds.

  4. PARSEC: PARametrized Simulation Engine for Cosmic rays

    NASA Astrophysics Data System (ADS)

    Bretz, Hans-Peter; Erdmann, Martin; Schiffer, Peter; Walz, David; Winchen, Tobias

    2015-02-01

    PARSEC (PARametrized Simulation Engine for Cosmic rays) is a simulation engine for fast generation of ultra-high energy cosmic ray data based on parameterizations of common assumptions of UHECR origin and propagation. Implemented are deflections in unstructured turbulent extragalactic fields, energy losses for protons due to photo-pion production and electron-pair production, as well as effects from the expansion of the universe. Additionally, a simple model to estimate propagation effects from iron nuclei is included. Deflections in the Galactic magnetic field are included using a matrix approach with precalculated lenses generated from backtracked cosmic rays. The PARSEC program is based on object oriented programming paradigms enabling users to extend the implemented models and is steerable with a graphical user interface.

  5. Cosmic ray produced isotopes in terrestrial systems.

    NASA Astrophysics Data System (ADS)

    Lal, D.

    1998-12-01

    Continuing improvements in the sensitivity of measurement of cosmic ray produced isotopes in environmental samples have progressively broadened the scope of their applications to characterise and quantify a wide variety of processes in Earth and planetary sciences. In this article, the author concentrates on the new developments in the field of nuclear geophysics, based on isotopic changes produced by cosmic rays in the terrestrial systems. This field, which is best described as cosmic ray geophysics, has roots with the discovery of cosmogenic 14C on the Earth by Willard Libby in 1948, and grew rapidly at first, but slowed down during the '60s and '70s. In the '80s, there was a renaissance in cosmic ray produced isotope studies, thanks mainly to the developments of the accelerator mass spectrometry technique capable of measuring minute amounts of radioactivity in terrestrial samples. This technological advance has considerably enhanced the applications of cosmic ray produced isotopes and today one finds them being used to address diverse problems in Earth and planetary sciences. The author discusses the present scope of the field of cosmic ray geophysics with an emphasis on geomorphology. It is stressed that this is the decade in which this field, which has been studied passionately by geographers, geomorphologists and geochemists for more than five decades, has at its service nuclear methods to introduce numeric time controls in the range of centuries to millions of years.

  6. Cosmic ray interactions in starbursting galaxies

    NASA Astrophysics Data System (ADS)

    Yoast-Hull, Tova M.

    High quality gamma-ray and radio observations of nearby galaxies offer an unprecedented opportunity to quantitatively study the properties of their cosmic ray populations. Accounting for various interactions and energy losses, I developed a multi-component, single-zone model of the cosmic ray populations in the central molecular zones of star-forming galaxies. Using observational knowledge of the interstellar medium and star formation, I successfully predicted the radio, gamma-ray, and neutrino spectra for nearby starbursts. Using chi-squared tests to compare the models with observational radio and gamma-ray data, I placed constraints on magnetic field strengths, cosmic ray energy densities, and galactic wind (advection) speeds. The initial models were applied to and tested on the prototypical starburst galaxy M82. To further test the model and to explore the differences in environment between starbursts and active galactic nuclei, I studied NGC 253 and NGC 1068, both nearby giant spiral galaxies which have been detected in gamma-rays. Additionally, I demonstrated that the excess GeV energy gamma-ray emission in the Galactic Center is likely not diffuse emission from an additional population of cosmic rays accelerated in supernova remnants. Lastly, I investigated cosmic ray populations in the starburst nuclei of Arp 220, a nearby ultraluminous infrared galaxy which displays a high-intensity mode of star formation more common in young galaxies, and I showed that the nuclei are efficient cosmic-ray proton calorimeters.

  7. Expansion Microscopy

    PubMed Central

    Chen, Fei; Tillberg, Paul W.; Boyden, Edward S.

    2014-01-01

    In optical microscopy, fine structural details are resolved by using refraction to magnify images of a specimen. Here we report the discovery that, by synthesizing a swellable polymer network within a specimen, it can be physically expanded, resulting in physical magnification. By covalently anchoring specific labels located within the specimen directly to the polymer network, labels spaced closer than the optical diffraction limit can be isotropically separated and optically resolved, a process we call expansion microscopy (ExM). Thus, this process can be used to perform scalable super-resolution microscopy with diffraction-limited microscopes. We demonstrate ExM with effective ~70 nm lateral resolution in both cultured cells and brain tissue, performing three-color super-resolution imaging of ~107 μm3 of the mouse hippocampus with a conventional confocal microscope. PMID:25592419

  8. The origin of galactic cosmic rays

    NASA Astrophysics Data System (ADS)

    Blasi, Pasquale

    2013-11-01

    One century ago Viktor Hess carried out several balloon flights that led him to conclude that the penetrating radiation responsible for the discharge of electroscopes was of extraterrestrial origin. One century from the discovery of this phenomenon seems to be a good time to stop and think about what we have understood about Cosmic Rays. The aim of this review is to illustrate the ideas that have been and are being explored in order to account for the observable quantities related to cosmic rays and to summarize the numerous new pieces of observation that are becoming available. In fact, despite the possible impression that development in this field is somewhat slow, the rate of new discoveries in the last decade or so has been impressive, and mainly driven by beautiful pieces of observation. At the same time scientists in this field have been able to propose new, fascinating ways to investigate particle acceleration inside the sources, making use of multifrequency observations that range from the radio, to the optical, to X-rays and gamma rays. These ideas can now be confronted with data. I will mostly focus on supernova remnants as the most plausible sources of Galactic cosmic rays, and I will review the main aspects of the modern theory of diffusive particle acceleration at supernova remnant shocks, with special attention for the dynamical reaction of accelerated particles on the shock and the phenomenon of magnetic field amplification at the shock. Cosmic-ray escape from the sources is discussed as a necessary step to determine the spectrum of cosmic rays at the Earth. The discussion of these theoretical ideas will always proceed parallel to an account of the data being collected especially in X-ray and gamma-ray astronomy. In the end of this review I will also discuss the phenomenon of cosmic-ray acceleration at shocks propagating in partially ionized media and the implications of this phenomenon in terms of width of the Balmer line emission. This field of

  9. Early developments: Particle physics aspects of cosmic rays

    NASA Astrophysics Data System (ADS)

    Grupen, Claus

    2014-01-01

    Cosmic rays is the birthplace of elementary particle physics. The 1936 Nobel prize was shared between Victor Hess and Carl Anderson. Anderson discovered the positron in a cloud chamber. The positron was predicted by Dirac several years earlier. In subsequent cloud chamber investigations Anderson and Neddermeyer saw the muon, which for some time was considered to be a candidate for the Yukawa particle responsible for nuclear binding. Measurements with nuclear emulsions by Lattes, Powell, Occhialini and Muirhead clarified the situation by the discovery of the charged pions in cosmic rays. The cloud chamber continued to be a powerful instrument in cosmic ray studies. Rochester and Butler found V's, which turned out to be shortlived neutral kaons decaying into a pair of charged pions. Also Λ's, Σ's, and Ξ's were found in cosmic rays. But after that accelerators and storage rings took over. The unexpected renaissance of cosmic rays started with the search for solar neutrinos and the observation of the supernova 1987A. Cosmic ray neutrino results were best explained by the assumption of neutrino oscillations opening a view beyond the standard model of elementary particles. After 100 years of cosmic ray research we are again at the beginning of a new era, and cosmic rays may contribute to solve the many open questions, like dark matter and dark energy, by providing energies well beyond those of accelerators.

  10. Thermal Expansion

    NASA Astrophysics Data System (ADS)

    Ventura, Guglielmo; Perfetti, Mauro

    All solid materials, when cooled to low temperatures experience a change in physical dimensions which called "thermal contraction" and is typically lower than 1 % in volume in the 4-300 K temperature range. Although the effect is small, it can have a heavy impact on the design of cryogenic devices. The thermal contraction of different materials may vary by as much as an order of magnitude: since cryogenic devices are constructed at room temperature with a lot of different materials, one of the major concerns is the effect of the different thermal contraction and the resulting thermal stress that may occur when two dissimilar materials are bonded together. In this chapter, theory of thermal contraction is reported in Sect. 1.2 . Section 1.3 is devoted to the phenomenon of negative thermal expansion and its applications.

  11. Anomalous isotopic composition of cosmic rays

    SciTech Connect

    Woosley, S.E.; Weaver, T.A.

    1980-06-20

    Recent measurements of nonsolar isotopic patterns for the elements neon and (perhaps) magnesium in cosmic rays are interpreted within current models of stellar nucleosynthesis. One possible explanation is that the stars currently responsible for cosmic-ray synthesis in the Galaxy are typically super-metal-rich by a factor of two to three. Other possibilities include the selective acceleration of certain zones or masses of supernovas or the enhancement of /sup 22/Ne in the interstellar medium by mass loss from red giant stars and planetary nebulas. Measurements of critical isotopic ratios are suggested to aid in distinguishing among the various possibilities. Some of these explanations place significant constraints on the fraction of cosmic ray nuclei that must be fresh supernova debris and the masses of the supernovas involved. 1 figure, 3 tables.

  12. The structure of cosmic ray shocks

    NASA Astrophysics Data System (ADS)

    Axford, W. I.; Leer, E.; McKenzie, J. F.

    1982-07-01

    The acceleration of cosmic rays by steady shock waves has been discussed in brief reports by Leer et al. (1976) and Axford et al. (1977). This paper presents a more extended version of this work. The energy transfer and the structure of the shock wave is discussed in detail, and it is shown that even for moderately strong shock waves most of the upstream energy flux in the background gas is transferred to the cosmic rays. This holds also when the upstream cosmic ray pressure is very small. For an intermediate Mach-number regime the overall shock structure is shown to consist of a smooth transition followed by a gas shock (cf. Drury and Voelk, 1980).

  13. Microphysics of Cosmic Ray Driven Plasma Instabilities

    NASA Astrophysics Data System (ADS)

    Bykov, A. M.; Brandenburg, A.; Malkov, M. A.; Osipov, S. M.

    2013-10-01

    Energetic nonthermal particles (cosmic rays, CRs) are accelerated in supernova remnants, relativistic jets and other astrophysical objects. The CR energy density is typically comparable with that of the thermal components and magnetic fields. In this review we discuss mechanisms of magnetic field amplification due to instabilities induced by CRs. We derive CR kinetic and magnetohydrodynamic equations that govern cosmic plasma systems comprising the thermal background plasma, comic rays and fluctuating magnetic fields to study CR-driven instabilities. Both resonant and non-resonant instabilities are reviewed, including the Bell short-wavelength instability, and the firehose instability. Special attention is paid to the longwavelength instabilities driven by the CR current and pressure gradient. The helicity production by the CR current-driven instabilities is discussed in connection with the dynamo mechanisms of cosmic magnetic field amplification.

  14. Microphysics of Cosmic Ray Driven Plasma Instabilities

    NASA Astrophysics Data System (ADS)

    Bykov, A. M.; Brandenburg, A.; Malkov, M. A.; Osipov, S. M.

    Energetic nonthermal particles (cosmic rays, CRs) are accelerated in supernova remnants, relativistic jets and other astrophysical objects. The CR energy density is typically comparable with that of the thermal components and magnetic fields. In this review we discuss mechanisms of magnetic field amplification due to instabilities induced by CRs. We derive CR kinetic and magnetohydrodynamic equations that govern cosmic plasma systems comprising the thermal background plasma, comic rays and fluctuating magnetic fields to study CR-driven instabilities. Both resonant and non-resonant instabilities are reviewed, including the Bell short-wavelength instability, and the firehose instability. Special attention is paid to the longwavelength instabilities driven by the CR current and pressure gradient. The helicity production by the CR current-driven instabilities is discussed in connection with the dynamo mechanisms of cosmic magnetic field amplification.

  15. Cosmic Superstrings Revisited

    SciTech Connect

    Polchinski, Joseph

    2004-12-10

    It is possible that superstrings, as well as other one-dimensional branes, could have been produced in the early universe and then expanded to cosmic size today. I discuss the conditions under which this will occur, and the signatures of these strings. Such cosmic superstrings could be the brightest objects visible in gravitational wave astronomy, and might be distinguishable from gauge theory cosmic strings by their network properties.

  16. The cosmic neutrino background

    NASA Technical Reports Server (NTRS)

    Dar, Arnon

    1991-01-01

    The cosmic neutrino background is expected to consist of relic neutrinos from the big bang, of neutrinos produced during nuclear burning in stars, of neutrinos released by gravitational stellar collapse, and of neutrinos produced by cosmic ray interactions with matter and radiation in the interstellar and intergalactic medium. Formation of baryonic dark matter in the early universe, matter-antimatter annihilation in a baryonic symmetric universe, and dark matter annihilation could have also contributed significantly to the cosmic neutrino background. The purpose of this paper is to review the properties of these cosmic neutrino backgrounds, the indirect evidence for their existence, and the prospects for their detection.

  17. The Cosmic Background Explorer.

    ERIC Educational Resources Information Center

    Gulkis, Samuel; And Others

    1990-01-01

    Outlines the Cosmic Background Explorer (COBE) mission to measure celestial radiation. Describes the instruments used and experiments involving differential microwave radiometers, and a far infrared absolute spectrophotometer. (YP)

  18. Primary cosmic ray positrons and galactic annihilation radiation

    NASA Technical Reports Server (NTRS)

    Lingenfelter, R. E.; Ramaty, R.

    1980-01-01

    The observation (Leventhal et al, 1978) of positron annihilation radiation at 0.511 MeV from the direction of the Galactic Center is reexamined, suggesting the possibility of a primary positron component of the cosmic rays. The observed 0.511 MeV emission requires a positron production rate nearly two orders of magnitude greater than the production rate of secondary cosmic ray positrons from pion decay produced in cosmic ray interactions. Possible sources of positrons are reviewed with both supernovae and pulsars appearing to be the more likely candidates. If only about 1% of these positrons were accelerated along with the cosmic ray nucleons and electrons to energies not less than 100 MeV, it is believed that these primary positrons would be comparable in intensity to those secondary positrons resulting from pion decay. Some observational evidence for the existence of primary positrons in the cosmic rays is also discussed.

  19. Maria Montessori's Cosmic Vision, Cosmic Plan, and Cosmic Education

    ERIC Educational Resources Information Center

    Grazzini, Camillo

    2013-01-01

    This classic position of the breadth of Cosmic Education begins with a way of seeing the human's interaction with the world, continues on to the grandeur in scale of time and space of that vision, then brings the interdependency of life where each growing human becomes a participating adult. Mr. Grazzini confronts the laws of human nature in…

  20. Report of the cosmic and heliospheric panel

    NASA Technical Reports Server (NTRS)

    Mewaldt, Richard A.; Mason, Glenn M.; Barnes, Aaron; Binns, W. Robert; Burlaga, Leonard F.; Cherry, Michael L.; Holzer, Thomas E.; Jokipii, J. R.; Jones, Vernon; Ling, James C.

    1991-01-01

    The Cosmic and Heliospheric Branch proposes a bold new program for the years 1995 to 2010 that is centered on the following two themes: (1) the global heliosphere and interstellar space; and (2) cosmic particle acceleration and the evolution of matter. Within these major themes are more specific goals that have been studied and continue to be examined for a better understanding of their processes. These include: origin, structure, and evolution of the solar wind; interaction of the heliosphere, the solar wind, and the interstellar medium; fundamental microscopic and macroscopic plasma processes; acceleration and transport of energetic particles; and the origin and evolution of matter. Finally, the report summarizes a wide variety of proposed small and large space missions.

  1. Accelerators for Intensity Frontier Research

    SciTech Connect

    Derwent, Paul; /Fermilab

    2012-05-11

    In 2008, the Particle Physics Project Prioritization Panel identified three frontiers for research in high energy physics, the Energy Frontier, the Intensity Frontier, and the Cosmic Frontier. In this paper, I will describe how Fermilab is configuring and upgrading the accelerator complex, prior to the development of Project X, in support of the Intensity Frontier.

  2. Particle Acceleration in Relativistic Outflows

    NASA Technical Reports Server (NTRS)

    Bykov, Andrei; Gehrels, Neil; Krawczynski, Henric; Lemoine, Martin; Pelletier, Guy; Pohl, Martin

    2012-01-01

    In this review we confront the current theoretical understanding of particle acceleration at relativistic outflows with recent observational results on various source classes thought to involve such outflows, e.g. gamma-ray bursts, active galactic nuclei, and pulsar wind nebulae. We highlight the possible contributions of these sources to ultra-high-energy cosmic rays.

  3. Heliospheric Energetic Particles and Galactic Cosmic Ray Modulation

    NASA Astrophysics Data System (ADS)

    Malandraki, Olga

    2015-08-01

    The paper presents an overview of the SH ‘Solar and Heliospheric cosmic rays’ session of the 24th European Cosmic Ray Symposium (ECRS), Kiel, Germany, 2014. It covers the topics of Solar Energetic Particle (SEP) origin, acceleration and transport at the Sun and in the interplanetary medium, also from the aspect of multi-spacecraft observations, as well as the Galactic Cosmic Ray (GCR) short- and long-term variations and the Jovian electron variations in the heliosphere. Relevant instruments and methods presented are also covered by this review. The paper is written from a personal perspective, emphasizing those results that the author found most interesting.

  4. Global modulation of cosmic rays in the heliosphere

    NASA Astrophysics Data System (ADS)

    Potgieter, Marius

    2016-07-01

    It is possible, now for the first time, to describe the total, global modulation of cosmic rays in the heliosphere using Voyager observations from the Earth to the heliopause and from the PAMELA space mission at the Earth, in comparison with comprehensive numerical models. The very local interstellar spectra for several cosmic ray species have become much better known so that together with knowledge of where the heliopause is located, comprehensive modelling has taken a huge step forward. New and exciting observations, with ample challenges to theoretical and modelling approaches to the acceleration, transport and modulation of cosmic rays in the heliosphere will be reviewed in this presentation.

  5. Cosmic ray studies with an Interstellar Probe

    NASA Technical Reports Server (NTRS)

    Mewaldt, R. A.; Stone, E. C.

    1990-01-01

    Among the NASA mission concepts that have been suggested for the 21st century is an Interstellar Probe that might be accelerated to a velocity of about 10 to 20 AU/yr, allowing it to leave the heliosphere, ultimately reaching a radial distance of about 500 to 1000 AU in about 50 years. Previous studies of such a mission, and its potential significance for cosmic ray studies, both within the heliosphere, and beyond, in interstellar space are discussed.

  6. Cosmic ray isotopes

    NASA Technical Reports Server (NTRS)

    Stone, E. C.

    1973-01-01

    The isotopic composition of cosmic rays is studied in order to develop the relationship between cosmic rays and stellar processes. Cross section and model calculations are reported on isotopes of H, He, Be, Al and Fe. Satellite instrument measuring techniques separate only the isotopes of the lighter elements.

  7. Interactions of cosmic superstrings

    SciTech Connect

    Jackson, Mark G.; /Fermilab

    2007-06-01

    We develop methods by which cosmic superstring interactions can be studied in detail. These include the reconnection probability and emission of radiation such as gravitons or small string loops. Loop corrections to these are discussed, as well as relationships to (p; q)-strings. These tools should allow a phenomenological study of string models in anticipation of upcoming experiments sensitive to cosmic string radiation.

  8. Deepening Cosmic Education

    ERIC Educational Resources Information Center

    Leonard, Gerard

    2013-01-01

    This article is a special blend of research, theory, and practice, with clear insight into the origins of Cosmic Education and cosmic task, while recalling memories of student explorations in botany, in particular, episodes from Mr. Leonard's teaching. Mr. Leonard speaks of a storytelling curriculum that eloquently puts perspective into dimensions…

  9. Light from cosmic strings

    SciTech Connect

    Steer, Daniele A.; Vachaspati, Tanmay

    2011-02-15

    The time-dependent metric of a cosmic string leads to an effective interaction between the string and photons--the ''gravitational Aharonov-Bohm'' effect--and causes cosmic strings to emit light. We evaluate the radiation of pairs of photons from cosmic strings and find that the emission from cusps, kinks and kink-kink collisions occurs with a flat spectrum at all frequencies up to the string scale. Further, cusps emit a beam of photons, kinks emit along a curve, and the emission at a kink-kink collision is in all directions. The emission of light from cosmic strings could provide an important new observational signature of cosmic strings that is within reach of current experiments for a range of string tensions.

  10. Our Cosmic Insignificance

    PubMed Central

    Kahane, Guy

    2014-01-01

    The universe that surrounds us is vast, and we are so very small. When we reflect on the vastness of the universe, our humdrum cosmic location, and the inevitable future demise of humanity, our lives can seem utterly insignificant. Many philosophers assume that such worries about our significance reflect a banal metaethical confusion. They dismiss the very idea of cosmic significance. This, I argue, is a mistake. Worries about cosmic insignificance do not express metaethical worries about objectivity or nihilism, and we can make good sense of the idea of cosmic significance and its absence. It is also possible to explain why the vastness of the universe can make us feel insignificant. This impression does turn out to be mistaken, but not for the reasons typically assumed. In fact, we might be of immense cosmic significance—though we cannot, at this point, tell whether this is the case. PMID:25729095

  11. Unveiling the Synchrotron Cosmic Web: Pilot Study

    NASA Astrophysics Data System (ADS)

    Brown, Shea; Rudnick, Lawrence; Pfrommer, Christoph; Jones, Thomas

    2010-04-01

    The overall goal of this project is to challenge our current theoretical understanding of the relativistic particle populations in the inter-galactic medium (IGM) through deep 1.4 GHz observations of 13 massive, high-redshift clusters of galaxies. Designed to compliment/extend the GMRT radio halo survey (Venturi et al. 2007), these observations will attempt to detect the peaks of the purported synchrotron cosmic-web, and place serious limits on models of CR acceleration and magnetic field amplification during large-scale structure formation. The primary goals of this survey are: 1) Confirm the bi-modal nature of the radio halo population, which favors turbulent re-acceleration of cosmic-ray electrons (CRe) during cluster mergers as the source of the diffuse radio emission; 2) Directly test hadronic secondary models which predict the presence of cosmic-ray protons (CRp) in the cores of massive X-ray clusters; 3) Search in polarization for shock structures, a potential source of CR acceleration in the IGM.

  12. Unveiling the Synchrotron Cosmic Web: Pilot Study

    NASA Astrophysics Data System (ADS)

    Brown, Shea; Rudnick, Lawrence; Pfrommer, Christoph; Jones, Thomas

    2011-10-01

    The overall goal of this project is to challenge our current theoretical understanding of the relativistic particle populations in the inter-galactic medium (IGM) through deep 1.4 GHz observations of 13 massive, high-redshift clusters of galaxies. Designed to compliment/extend the GMRT radio halo survey (Venturi et al. 2007), these observations will attempt to detect the peaks of the purported synchrotron cosmic-web, and place serious limits on models of CR acceleration and magnetic field amplification during large-scale structure formation. The primary goals of this survey are: 1) Confirm the bi-modal nature of the radio halo population, which favors turbulent re-acceleration of cosmic-ray electrons (CRe) during cluster mergers as the source of the diffuse radio emission; 2) Directly test hadronic secondary models which predict the presence of cosmic-ray protons (CRp) in the cores of massive X-ray clusters; 3) Search in polarization for shock structures, a potential source of CR acceleration in the IGM.

  13. Anomalous Transport of High Energy Cosmic Rays in Galactic Superbubbles

    NASA Technical Reports Server (NTRS)

    Barghouty, Nasser F.

    2014-01-01

    High-energy cosmic rays may exhibit anomalous transport as they traverse and are accelerated by a collection of supernovae explosions in a galactic superbubble. Signatures of this anomalous transport can show up in the particles' evolution and their spectra. In a continuous-time-random- walk (CTRW) model assuming standard diffusive shock acceleration theory (DSA) for each shock encounter, and where the superbubble (an OB stars association) is idealized as a heterogeneous region of particle sources and sinks, acceleration and transport in the superbubble can be shown to be sub-diffusive. While the sub-diffusive transport can be attributed to the stochastic nature of the acceleration time according to DSA theory, the spectral break appears to be an artifact of transport in a finite medium. These CTRW simulations point to a new and intriguing phenomenon associated with the statistical nature of collective acceleration of high energy cosmic rays in galactic superbubbles.

  14. Cosmic Rays in the Heliosphere: Requirements for Future Observations

    NASA Astrophysics Data System (ADS)

    Mewaldt, R. A.

    2013-06-01

    Since the publication of Cosmic Rays in the Heliosphere in 1998 there has been great progress in understanding how and why cosmic rays vary in space and time. This paper discusses measurements that are needed to continue advances in relating cosmic ray variations to changes in solar and interplanetary activity and variations in the local interstellar environment. Cosmic ray acceleration and transport is an important discipline in space physics and astrophysics, but it also plays a critical role in defining the radiation environment for humans and hardware in space, and is critical to efforts to unravel the history of solar activity. Cosmic rays are measured directly by balloon-borne and space instruments, and indirectly by ground-based neutron, muon and neutrino detectors, and by measurements of cosmogenic isotopes in ice cores, tree-rings, sediments, and meteorites. The topics covered here include: what we can learn from the deep 2008-2009 solar minimum, when cosmic rays reached the highest intensities of the space era; the implications of 10Be and 14C isotope archives for past and future solar activity; the effects of variations in the size of the heliosphere; opportunities provided by the Voyagers for discovering the origin of anomalous cosmic rays and measuring cosmic-ray spectra in interstellar space; and future space missions that can continue the exciting exploration of the heliosphere that has occurred over the past 50 years.

  15. Source composition of cosmic rays

    SciTech Connect

    Silberberg, R.; Tsao, C.H. ); Shapiro, M.M. )

    1990-03-20

    A theory is developed that yields great improvement in deriving the cosmic-ray source abundances for energies below 10{sup 12} eV/u. In addition, based on the acceleration theory of Voelk and Biermann and on nucleosynthesis processes in pre-supernova stars, a theory is presented for the source composition at 10{sup 12}--10{sup 15} eV/u. The strong shock wave of young supernova remnant accelerates the wind particles of the pre-supernova red, blue supergiant stars and Wolf-Rayet (WR) stars to energies up to 10{sup 15} eV/u. They contain the nucleosynthesis products of the CNO cycle and of He-burning. They accelerate the flare particles in interstellar space. The composition below 10{sup 12} eV/u differs from that of the general stellar photosphere by: (1) Suppression of elements with a large FIP ({gt}10 eV) by a factor of 4; (2) The depletion of light nuclei (Z{le}10); (3) A large contribution of WC stars to {sup 12}C, {sup 16}O and {sup 22}Ne, with renormalization of the initial (Z{gt}2)/(Z{le}2) abundances of Prantzos et al., based on general elemental abundances.

  16. The origins of cosmic rays and quantum effects on gravity

    NASA Technical Reports Server (NTRS)

    Tomozawa, Y.

    1985-01-01

    The energy spectrum of primary cosmic rays is explained by particles emitted during a thermal expansion of explosive objects inside and near the galaxy, remnants of which may be supernova and/or active talaxies, or even stars or galaxies that disappeared from our sight after the explosion. A power law energy spectrum for cosmic rays, E to the (-alpha -1, is obtained from an expansion rate T is proportional to R to the alpha. Using the solution of the Einstein equation, we obtain a spectrum which agrees very well with experimental data. The implication of an inflationary early universe on the cosmic ray spectrum is also discussed. It is also suggested that the conflict between this model and the singularity theorem in classical general relativity may be eliminated by quantum effects.

  17. Linear Accelerators

    NASA Astrophysics Data System (ADS)

    Sidorin, Anatoly

    2010-01-01

    In linear accelerators the particles are accelerated by either electrostatic fields or oscillating Radio Frequency (RF) fields. Accordingly the linear accelerators are divided in three large groups: electrostatic, induction and RF accelerators. Overview of the different types of accelerators is given. Stability of longitudinal and transverse motion in the RF linear accelerators is briefly discussed. The methods of beam focusing in linacs are described.

  18. Linear Accelerators

    SciTech Connect

    Sidorin, Anatoly

    2010-01-05

    In linear accelerators the particles are accelerated by either electrostatic fields or oscillating Radio Frequency (RF) fields. Accordingly the linear accelerators are divided in three large groups: electrostatic, induction and RF accelerators. Overview of the different types of accelerators is given. Stability of longitudinal and transverse motion in the RF linear accelerators is briefly discussed. The methods of beam focusing in linacs are described.

  19. The Origin of Cosmic Rays: What can GLAST Say?

    NASA Technical Reports Server (NTRS)

    Ormes, Jonathan F.; Digel, Seith; Moskalenko, Igor V.; Moiseev, Alexander; Williamson, Roger

    2000-01-01

    Gamma rays in the band from 30 MeV to 300 GeV, used in combination with direct measurements and with data from radio and X-ray bands, provide a powerful tool for studying the origin of Galactic cosmic rays. Gamma-ray Large Area Space Telescope (GLAST) with its fine 10-20 arcmin angular resolution will be able to map the sites of acceleration of cosmic rays and their interactions with interstellar matter, It will provide information that is necessary to study the acceleration of energetic particles in supernova shocks, their transport in the interstellar medium and penetration into molecular clouds.

  20. Interpretation of Voyager 1 data on low energy cosmic rays in galactic wind model

    NASA Astrophysics Data System (ADS)

    Ptuskin, V. S.; Seo, E. S.; Zirakashvili, V. N.

    2015-08-01

    The local interstellar energy spectra of galactic cosmic rays down to a few MeV/nucleon were directly measured in the experiment on the board of the Voyager 1 spacecraft. We suggest interpretation of these data based on our models of cosmic ray acceleration in supernova remnants and the diffusion in galactic wind where diffusion coefficient is determined by the cosmic ray streaming instability. The dependence of wind velocity on distance above the Galactic disk is determined.

  1. The History of Cosmic Ray Studies after Hess

    NASA Astrophysics Data System (ADS)

    Grupen, Claus

    2013-06-01

    The discovery of cosmic rays by Victor Hess was confirmed with balloon flights at higher altitudes by Kolhörster. Soon the interest turned into questions about the nature of cosmic rays: gamma rays or particles? Subsequent investigations have established cosmic rays as the birthplace of elementary particle physics. The 1936 Nobel prize was shared between Victor Hess and Carl Anderson. Anderson discovered the positron in a cloud chamber. The positron was predicted by Dirac several years earlier. Many new results came now from studies with cloud chambers and nuclear emulsions. Anderson and Neddermeyer saw the muon, which for some time was considered to be a candidate for the Yukawa particle responsible for nuclear binding. Lattes, Powell, Occhialini and Muirhead clarified the situation by the discovery of the charged pions in cosmic rays. Rochester and Butler found V's, which turned out to be short-lived neutral kaons decaying into a pair of charged pions. Λ's, Σ's and Ξ's were found in cosmic rays using nuclear emulsions. After that period, accelerators and storage rings took over. The unexpected renaissance of cosmic rays started with the search for solar neutrinos and the observation of the supernova 1987A and other accelerators in the sky. With the observation of neutrino oscillations one began to look beyond the standard model of elementary particles. After 100 years of cosmic ray research we are again at the beginning of a new era, and cosmic rays may contribute to solve the many open questions, like dark matter and dark energy, by providing energies well beyond those of earth-bound accelerators.

  2. Eleventh European Cosmic Ray Symposium

    NASA Astrophysics Data System (ADS)

    1988-08-01

    The biannual Symposium includes all aspects of cosmic ray research. The scientific program was organized under three main headings: cosmic rays in the heliosphere, cosmic rays in the interstellar and extragalactic space, and properties of high-energy interactions as studied by cosmic rays. Selected short communications out of 114 contributed papers were indexed separately for the INIS database.

  3. Tycho's Remnant Provides Shocking Evidence for Cosmic Rays

    NASA Astrophysics Data System (ADS)

    2005-09-01

    miles per hour. This rapid expansion has created two X-ray emitting shock waves - one moving outward into the interstellar gas, and another moving inward into the stellar debris. These shock waves, analogous to the sonic boom produced by supersonic motion of an airplanes, produce sudden, large changes in pressure, and temperature behind the wave. According to the standard theory, the outward-moving shock should be about two light-years ahead of the stellar debris (that's half the distance from our sun to the nearest star). What Chandra found instead is that the stellar debris has kept pace with the outer shock and is only about half a light-year behind. "The most likely explanation for this behavior is that a large fraction of the energy of the outward-moving shock wave is going into the acceleration of atomic nuclei to speeds approaching the speed of light," said Jessica Warren, also of Rutgers University, and the lead author of the report in the Astrophysical Journal. Previous observations with radio and X-ray telescopes had established that the shock wave in Tycho's remnant was accelerating electrons to high energies. However, since high-speed atomic nuclei produce very weak radio and X-ray emission also, it was not known whether the shock wave was accelerating nuclei as well. The Chandra observations provide the strongest evidence yet that nuclei are indeed accelerated, and that the energy contained in high-speed nuclei is about 100 times that in the electrons. Hughes also pointed out that the Chandra result for Tycho's remnant significantly changes astronomers' view of the evolution of supernova remnants. A large component of cosmic ray nuclei alters the dynamics of the shock wave, and may require changing the way that astronomers estimate the explosive energy of a supernova from the properties of its remnant. NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for the agency's Science Mission Directorate. The Smithsonian

  4. The accelerating universe

    NASA Astrophysics Data System (ADS)

    Blandford, Roger

    2013-02-01

    From keV electrons in the aurorae to Ultra High Energy Cosmic Rays in unidentified "Zevatrons", the cosmos shows a perverse, yet pervasive, proclivity to select a tiny minority of particles and boost them to high energy. The mechanisms involved can be traced back to the ideas of Faraday, Fermi and Alfvén though we are learning that the details are idiosyncratic to the many environments that we have explored. Much can be learned from comparing and contrasting particle acceleration in laboratory, interplanetary, interstellar and intergalactic locations. As it celebrates its centenary, cosmic ray physics, has assumed a new importance in solving one of the greatest problems consuming its illustrious scion - elementary particle physics - namely the nature of dark matter.

  5. Cosmic-ray astrochemistry.

    PubMed

    Indriolo, Nick; McCall, Benjamin J

    2013-10-01

    Gas-phase chemistry in the interstellar medium is driven by fast ion-molecule reactions. This, of course, demands a mechanism for ionization, and cosmic rays are the ideal candidate as they can operate throughout the majority of both diffuse and dense interstellar clouds. Aside from driving interstellar chemistry via ionization, cosmic rays also interact with the interstellar medium in ways that heat the ambient gas, produce gamma rays, and produce light element isotopes. In this paper we review the observables generated by cosmic-ray interactions with the interstellar medium, focusing primarily on the relevance to astrochemistry. PMID:23812538

  6. Supermassive cosmic string compactifications

    SciTech Connect

    Blanco-Pillado, Jose J.; Reina, Borja; Sousa, Kepa; Urrestilla, Jon E-mail: borja.reina@ehu.es E-mail: jon.urrestilla@ehu.es

    2014-06-01

    The space-time dimensions transverse to a static straight cosmic string with a sufficiently large tension (supermassive cosmic strings) are compact and typically have a singularity at a finite distance form the core. In this paper, we discuss how the presence of multiple supermassive cosmic strings in the 4d Abelian-Higgs model can induce the spontaneous compactification of the transverse space and explicitly construct solutions where the gravitational background becomes regular everywhere. We discuss the embedding of this model in N = 1 supergravity and show that some of these solutions are half-BPS, in the sense that they leave unbroken half of the supersymmetries of the model.

  7. Testing the Role of Cosmic Ray Reacceleration in the Galaxy

    NASA Astrophysics Data System (ADS)

    Connell, J. J.; Simpson, J. A.

    1999-05-01

    Cosmic rays constitute a super-thermal gas of charged particles magnetically confined within the Galaxy. While propagating though the interstellar medium (ISM), cosmic ray nuclei undergo nuclear spallation reactions, producing both stable (i.e., Be and B) and unstable secondary nuclei. Consistent cosmic ray confinement times of ~ 20 Myr have been reported from measurements of the radioactive secondary isotopes (10) Be, (26) Al, (36) Cl and (54) Mn using data from the High Energy Telescope (HET) on the Ulysses spacecraft. It is generally accepted that Galactic cosmic rays of energy less than ~ 10(14) eV are accelerated by supernova shocks in the ISM. Reacceleration of existing cosmic rays in the ISM is implicit in interstellar shock acceleration models, but whether reacceleration plays a significant role in cosmic ray production and interstellar propagation is largely unknown. The abundances of secondary electron-capture isotopes provide a crucial test of cosmic ray reacceleration. Electron-capture is suppressed during interstellar propagation because cosmic ray nuclei are essentially stripped of their electrons. If, however, cosmic rays experience significant reacceleration, nuclei will have spent time at lower energies where electron pick-up, and hence electron capture, is more likely than at higher energies. Thus, electron capture secondary isotopes would be less abundant (and their daughters, more abundant) than otherwise predicted. The abundance ratio of (49) V to (51) V is a particularly sensitive test of this effect. The latest Ulysses HET data is used to address this problem. This research was supported in part by NASA/JPL Contract 955432 and NASA Grant NAG5-5179.

  8. Cosmic expansion and structure formation in running vacuum cosmologies

    NASA Astrophysics Data System (ADS)

    Basilakos, Spyros

    2015-06-01

    We investigate the dynamics of the Friedmann-Lemaître-Robertson-Walker (FLRW) flat cosmological models in which the vacuum energy varies with redshift. A particularly well-motivated model of this type is the so-called quantum field vacuum, in which both kind of terms H2 and constant appear in the effective dark energy (DE) density affecting the evolution of the main cosmological functions at the background and perturbation levels. Specifically, it turns out that the functional form of the quantum vacuum endows the vacuum energy of a mild dynamical evolution which could be observed nowadays and appears as dynamical DE. Interestingly, the low-energy behavior is very close to the usual Lambda cold dark matter (ΛCDM) model, but it is by no means identical. Finally, within the framework of the quantum field vacuum we generalize the large scale structure properties, namely growth of matter perturbations, cluster number counts and spherical collapse model.

  9. A dynamical model of the local cosmic expansion

    NASA Astrophysics Data System (ADS)

    Peñarrubia, Jorge; Ma, Yin-Zhe; Walker, Matthew G.; McConnachie, Alan

    2014-09-01

    We combine the equations of motion that govern the dynamics of galaxies in the local volume with Bayesian techniques in order to fit orbits to published distances and velocities of galaxies within 3 Mpc. We find a Local Group (LG) mass 2.3 ± 0.7 × 1012 M⊙ that is consistent with the combined dynamical masses of M31 and the Milky Way, and a mass ratio 0.54^{+0.23}_{-0.17} that rules out models where our Galaxy is more massive than M31 with ˜95 per cent confidence. The Milky Way's circular velocity at the solar radius is relatively high, 245 ± 23 km s-1, which helps to reconcile the mass derived from the local Hubble flow with the larger value suggested by the `timing argument'. Adopting Planck's bounds on ΩΛ yields a (local) Hubble constant H0 = 67 ± 5 km s-1 Mpc-1 which is consistent with the value found on cosmological scales. Restricted N-body experiments show that substructures tend to fall on to the LG along the Milky Way-M31 axis, where the quadrupole attraction is maximum. Tests against mock data indicate that neglecting this effect slightly overestimates the LG mass without biasing the rest of model parameters. We also show that both the time dependence of the LG potential and the cosmological constant have little impact on the observed local Hubble flow.

  10. Paradigm transition in cosmic plasma physics

    NASA Technical Reports Server (NTRS)

    Alfven, H.

    1982-01-01

    New discoveries in cosmic plasma physics are described, and their applications to solar, interstellar, galactic, and cosmological problems are discussed. The new discoveries include the existence of double layers in magnetized plasmas and in the low magnetosphere, and energy transfer by electric current in the auroral circuit. It is argued that solar flares and the solar wind-magnetosphere interaction should not be interpreted in terms of magnetic merging theories, and that electric current needs to be explicitly taken account of in understanding these phenomena. The filamentary structure of cosmic plasmas may be caused by electric currents in space, and the pinch effect may have a central role to play in the evolutionary history of interstellar clouds, stars, and solar systems. Space may have a cellular structure, with the cell walls formed by thin electric current layers. Annihilation may be the source of energy for quasars and the Hubble expansion, and the big bang cosmology may well be wrong.

  11. Cosmic x ray physics

    NASA Technical Reports Server (NTRS)

    Mccammon, Dan; Cox, D. P.; Kraushaar, W. L.; Sanders, W. T.

    1990-01-01

    The annual progress report on Cosmic X Ray Physics is presented. Topics studied include: the soft x ray background, proportional counter and filter calibrations, the new sounding rocket payload: X Ray Calorimeter, and theoretical studies.

  12. Cosmic x ray physics

    NASA Technical Reports Server (NTRS)

    Mccammon, Dan; Cox, D. P.; Kraushaar, W. L.; Sanders, W. T.

    1991-01-01

    The annual progress report on Cosmic X Ray Physics for the period 1 Jan. to 31 Dec. 1990 is presented. Topics studied include: soft x ray background, new sounding rocket payload: x ray calorimeter, and theoretical studies.

  13. Getting around cosmic variance

    SciTech Connect

    Kamionkowski, M.; Loeb, A.

    1997-10-01

    Cosmic microwave background (CMB) anisotropies probe the primordial density field at the edge of the observable Universe. There is a limiting precision ({open_quotes}cosmic variance{close_quotes}) with which anisotropies can determine the amplitude of primordial mass fluctuations. This arises because the surface of last scatter (SLS) probes only a finite two-dimensional slice of the Universe. Probing other SLS{close_quote}s observed from different locations in the Universe would reduce the cosmic variance. In particular, the polarization of CMB photons scattered by the electron gas in a cluster of galaxies provides a measurement of the CMB quadrupole moment seen by the cluster. Therefore, CMB polarization measurements toward many clusters would probe the anisotropy on a variety of SLS{close_quote}s within the observable Universe, and hence reduce the cosmic-variance uncertainty. {copyright} {ital 1997} {ital The American Physical Society}

  14. A COSMIC VARIANCE COOKBOOK

    SciTech Connect

    Moster, Benjamin P.; Rix, Hans-Walter; Somerville, Rachel S.; Newman, Jeffrey A. E-mail: rix@mpia.de E-mail: janewman@pitt.edu

    2011-04-20

    Deep pencil beam surveys (<1 deg{sup 2}) are of fundamental importance for studying the high-redshift universe. However, inferences about galaxy population properties (e.g., the abundance of objects) are in practice limited by 'cosmic variance'. This is the uncertainty in observational estimates of the number density of galaxies arising from the underlying large-scale density fluctuations. This source of uncertainty can be significant, especially for surveys which cover only small areas and for massive high-redshift galaxies. Cosmic variance for a given galaxy population can be determined using predictions from cold dark matter theory and the galaxy bias. In this paper, we provide tools for experiment design and interpretation. For a given survey geometry, we present the cosmic variance of dark matter as a function of mean redshift z-bar and redshift bin size {Delta}z. Using a halo occupation model to predict galaxy clustering, we derive the galaxy bias as a function of mean redshift for galaxy samples of a given stellar mass range. In the linear regime, the cosmic variance of these galaxy samples is the product of the galaxy bias and the dark matter cosmic variance. We present a simple recipe using a fitting function to compute cosmic variance as a function of the angular dimensions of the field, z-bar , {Delta}z, and stellar mass m{sub *}. We also provide tabulated values and a software tool. The accuracy of the resulting cosmic variance estimates ({delta}{sigma}{sub v}/{sigma}{sub v}) is shown to be better than 20%. We find that for GOODS at z-bar =2 and with {Delta}z = 0.5, the relative cosmic variance of galaxies with m{sub *}>10{sup 11} M{sub sun} is {approx}38%, while it is {approx}27% for GEMS and {approx}12% for COSMOS. For galaxies of m{sub *} {approx} 10{sup 10} M{sub sun}, the relative cosmic variance is {approx}19% for GOODS, {approx}13% for GEMS, and {approx}6% for COSMOS. This implies that cosmic variance is a significant source of uncertainty at z

  15. A Cosmic Variance Cookbook

    NASA Astrophysics Data System (ADS)

    Moster, Benjamin P.; Somerville, Rachel S.; Newman, Jeffrey A.; Rix, Hans-Walter

    2011-04-01

    Deep pencil beam surveys (<1 deg2) are of fundamental importance for studying the high-redshift universe. However, inferences about galaxy population properties (e.g., the abundance of objects) are in practice limited by "cosmic variance." This is the uncertainty in observational estimates of the number density of galaxies arising from the underlying large-scale density fluctuations. This source of uncertainty can be significant, especially for surveys which cover only small areas and for massive high-redshift galaxies. Cosmic variance for a given galaxy population can be determined using predictions from cold dark matter theory and the galaxy bias. In this paper, we provide tools for experiment design and interpretation. For a given survey geometry, we present the cosmic variance of dark matter as a function of mean redshift \\bar{z} and redshift bin size Δz. Using a halo occupation model to predict galaxy clustering, we derive the galaxy bias as a function of mean redshift for galaxy samples of a given stellar mass range. In the linear regime, the cosmic variance of these galaxy samples is the product of the galaxy bias and the dark matter cosmic variance. We present a simple recipe using a fitting function to compute cosmic variance as a function of the angular dimensions of the field, \\bar{z}, Δz, and stellar mass m *. We also provide tabulated values and a software tool. The accuracy of the resulting cosmic variance estimates (δσ v /σ v ) is shown to be better than 20%. We find that for GOODS at \\bar{z}=2 and with Δz = 0.5, the relative cosmic variance of galaxies with m *>1011 M sun is ~38%, while it is ~27% for GEMS and ~12% for COSMOS. For galaxies of m * ~ 1010 M sun, the relative cosmic variance is ~19% for GOODS, ~13% for GEMS, and ~6% for COSMOS. This implies that cosmic variance is a significant source of uncertainty at \\bar{z}=2 for small fields and massive galaxies, while for larger fields and intermediate mass galaxies, cosmic variance is

  16. The origin of cosmic rays and TeV gamma-ray astronomy

    NASA Astrophysics Data System (ADS)

    Maier, Gernot

    2013-06-01

    Cosmic rays are accelerated to high energies in Galactic and extragalactic objects like Supernova remnants (SNR) and active galactic nuclei (AGN). How these accelerators work and how efficient they accelerate different types of particles to energies of 1015 eV or beyond, is 100 years after the discovery of cosmic rays by Victor Hess, still unknown. Gamma rays trace cosmic rays at their site of acceleration and give crucial information on the nature and inner workings of these extreme objects. Gamma rays can be used to find the sources of cosmic rays and to determine their type, age and dynamics. We review in these proceedings the observational techniques and recent findings on gamma-ray emission from Supernova remnants.

  17. The Cosmic Labyrinth

    NASA Astrophysics Data System (ADS)

    Atkinson, M.

    2011-06-01

    This paper discusses the intertwined relationship between the terrestrial and celestial using the labyrinth as a metaphor referencing sources from art, gardens and Australian Indigenous culture. Including the Morning Star with the labyrinthine mortuary ritual in Arnhem Land, the cosmic plan garden at Auschwitz and Marea Atkinson's art project undertaken at the Villa Garzoni garden in Italy to create The Cosmic Labyrinth installation exhibited at Palazzo Franchetti, Venice, during the sixth conference on the Inspiration of Astronomical Phenomena.

  18. Cosmic Ray Dosimetry

    NASA Astrophysics Data System (ADS)

    Si Belkhir, F.; Attallah, R.

    2010-10-01

    Radiation levels at aircraft cruising altitudes are twenty times higher than at sea level. Thus, on average, a typical airline pilot receives a larger annual radiation dose than some one working in nuclear industry. The main source of this radiation is from galactic cosmic radiation, high energy particles generated by exploding stars within our own galaxy. In this work we study cosmic rays dosimetry at various aviation altitudes using the PARMA model.

  19. COSMIC monthly progress report

    NASA Technical Reports Server (NTRS)

    1994-01-01

    Activities of the Computer Software Management and Information Center (COSMIC) are summarized for the month of January 1994. Tables showing the current inventory of programs available from COSMIC are presented and program processing and evaluation activities are discussed. Marketing and customer service activities in this period are presented as is the progress report of NASTRAN maintenance and support. Tables of disseminations and budget summary conclude the report.

  20. Cosmic Ray Observation for Nuclear Astrophysics:. Corona Program

    NASA Astrophysics Data System (ADS)

    Hasebe, Nobuyuki; Kobayashi, M. N.

    2003-04-01

    Cosmic Ray Observation for Nuclei Astrophysics (CORONA) program is a large-scaled spacecraft or space station approach for nuclear composition of relativistic cosmic rays 10 ≦ Z ≦ 92 and of low-energy isotopes 1 ≦ Z ≦ 58 in space. A large area Spectrometer for Ultraheavy Nuclear Composition (SUNC) and a Large Isotope Telescope Array (LITA) are proposed in this program. CORONA program focuses on the composition of elements beyond the iron-peak nuclei (Z > 60) and the isotopic composition of ultraheavy particles (Z > 30) in galactic cosmic rays as well as solar and interplanetary particles. The observation of nuclear composition covers a wide range of scientific themes including studies of nucleosynthesis of cosmic ray sources, chemical evolution of galactic material, the characteristic time of cosmic rays, heating and acceleration mechanism of cosmic ray particles. Observation of solar particle events also make clear the physical process of transient solar events emitting wide range of radio, X-ray/gamma-ray, plasma and energetic particle radiation, and particle acceleration mechanism driven by CME.

  1. High Energy Cosmic Rays and Neutrinos from Newborn Pulsars

    NASA Astrophysics Data System (ADS)

    Fang, Ke; Kotera, Kumiko; Olinto, Angela

    2013-04-01

    Newborn pulsars offer favorable sites for cosmic ray acceleration and interaction. Particles could be striped off the star surface and accelerated in the pulsar wind up to PeV-100 EeV energies, depending on the pulsar's birth period and magnetic field strength. Once accelerated, the cosmic rays interact with the surrounding supernova ejecta until they escape the source. By assuming a normal distribution of pulsar birth periods centered at 300,ms, we find the combined contribution of extragalactic pulsars produce ultrahigh energy cosmic rays that agree with both the observed energy spectrum and composition trend reported by the Auger Observatory. Meanwhile, we point out their Galactic counterparts naturally give rise to a cosmic ray flux peaked at very high energies (VHE, between 10^16 and 10^18 ,eV), which can bridge the gap between predictions of cosmic rays produced by supernova remnants and the observed spectrum and composition just below the ankle. Young pulsars in the universe would also contribute to a diffuse neutrino background due to the photomeson interactions, whose detectability and typical neutrino energy are discussed. Lastly, we predict a neutrino emission level for the future birth of a nearby pulsar.

  2. CHEMICAL COMPOSITION AND MAXIMUM ENERGY OF GALACTIC COSMIC RAYS

    SciTech Connect

    Shibata, M.; Katayose, Y.; Huang, J.; Chen, D.

    2010-06-20

    A model of the cosmic-ray energy spectrum is proposed that assumes various acceleration limits at multiple sources. The model describes the broken power-law energy spectrum of cosmic rays by superposition of multiple sources; a diffusive shock acceleration mechanism plays an essential role. The maximum energy of galactic cosmic rays is discussed based on a comparison of experimental data with calculations done using the proposed model. The model can describe the energy spectrum at very high energies of up to several times 10{sup 18} eV, but the observed highest-energy cosmic rays deviate from the model predictions, indicating a different origin, such as an extragalactic source. This model describes the steepening of the power index at the so-called knee. However, it was found that additional assumptions are needed to explain the sharpness of the knee. Two possible explanations for the structure of the knee are discussed in terms of nearby source(s) and the hard energy spectrum suggested by nonlinear effects of cosmic-ray acceleration mechanisms.

  3. Can Accelerators Accelerate Learning?

    NASA Astrophysics Data System (ADS)

    Santos, A. C. F.; Fonseca, P.; Coelho, L. F. S.

    2009-03-01

    The 'Young Talented' education program developed by the Brazilian State Funding Agency (FAPERJ) [1] makes it possible for high-schools students from public high schools to perform activities in scientific laboratories. In the Atomic and Molecular Physics Laboratory at Federal University of Rio de Janeiro (UFRJ), the students are confronted with modern research tools like the 1.7 MV ion accelerator. Being a user-friendly machine, the accelerator is easily manageable by the students, who can perform simple hands-on activities, stimulating interest in physics, and getting the students close to modern laboratory techniques.

  4. PARTICLE ACCELERATOR

    DOEpatents

    Teng, L.C.

    1960-01-19

    ABS>A combination of two accelerators, a cyclotron and a ring-shaped accelerator which has a portion disposed tangentially to the cyclotron, is described. Means are provided to transfer particles from the cyclotron to the ring accelerator including a magnetic deflector within the cyclotron, a magnetic shield between the ring accelerator and the cyclotron, and a magnetic inflector within the ring accelerator.

  5. Super-alfvenic propagation of cosmic rays: The role of streaming modes

    NASA Technical Reports Server (NTRS)

    Morrison, P. J.; Scott, J. S.; Holman, G. D.; Ionson, J. A.

    1980-01-01

    Numerous cosmic ray propagation and acceleration problems require knowledge of the propagation speed of relativistic particles through an ambient plasma. Previous calculations indicated that self-generated turbulence scatters relativistic particles and reduces their bulk streaming velocity to the Alfven speed. This result was incorporated into all currently prominent theories of cosmic ray acceleration and propagation. It is demonstrated that super-Alfvenic propagation is indeed possible for a wide range of physical parameters. This fact dramatically affects the predictions of these models.

  6. Search for the Cosmic Neutrino Background

    NASA Astrophysics Data System (ADS)

    Faessler, A.; Hodak, R.; Kovalenko, S.; Simkovic, F.

    2015-02-01

    One expects three Cosmic Backgrounds: (1) The Cosmic Microwave Background (CMB) originated 380000 years after the Big Bang (BB). (2) The Neutrino Background decoupled about one second after the BB, while (3) the Cosmic Gravitational Wave Background created by the inflationary expansion decoupled directly after the BB. Only the Cosmic Microwave Background (CMB) has been detected and is well studied. Its spectrum follows Planck's black body radiation formula and shows a remarkable constant temperature of T0γ ≈ 2.7 K independent of the direction. The present photon density is about 370 photons per cm3. The size of the hot spots, which deviates only in the fifth decimal of the temperature from the average value, tells us, that the universe is flat. About 380 000 years after the Big Bang at a temperature of T0γ = 3000 K already in the matter dominated era the electrons combine with the protons and 4He and the photons move freely in the neutral universe and form the CMB. So the temperature and distribution of the photons give us information of the universe 380 000 years after the Big Bang. The Cosmic Neutrino Background (CνB) decoupled from matter already one second after the BB at a temperature of about 1010 K. Today their temperature is ~ 1.95 K and the average density is 56 electron-neutrinos and the total density of all neutrinos about 336 per cm3. Measurement of these neutrinos is an extremely challenging experimental problem which can hardly be solved with the present technologies. On the other hand it represents a tempting opportunity to check one of the key elements of the Big Bang Cosmology and to probe the early stages of the universe. The search for the CνB with the induced beta decay νe+3H → 3He + e- using KATRIN (KArlsruhe TRItium Neutrino experiment) is the topic of this contribution.

  7. Nonlinear Transport of Cosmic Rays in Turbulent Magnetic Field

    NASA Astrophysics Data System (ADS)

    Yan, H.; Xu, S.

    2014-09-01

    Recent advances in both the MHD turbulence theory and cosmic ray observations call for revisions in the paradigm of cosmic ray transport. We use the models of magnetohydrodynamic turbulence that were tested in numerical simulations, in which turbulence is injected at large scale and cascades to small scales. We shall present the nonlinear results for cosmic ray transport, in particular, the cross field transport of CRs. We demonstrate that the concept of cosmic ray subdiffusion in general does not apply and the perpendicular motion is well described by normal diffusion with M A4 dependence. Moreover, on scales less than the injection scale of turbulence, CRs' transport becomes super-diffusive. Quantitative predictions for both the normal diffusion on large scale and super diffusion on small scale are confirmed with recent numerical simulations. Implication for shock acceleration is briefly discussed.

  8. Plans for Extreme Energy Cosmic Ray Observations from Space

    NASA Technical Reports Server (NTRS)

    Adams, James H., Jr.

    2004-01-01

    Cosmic rays have been detected at energies beyond 10(exp 20) eV, where Universe is predicted to become opaque to protons. The acceleration of cosmic rays to such extreme energies in known astrophysical objects has also proven difficult to understand, leading to many suggestions that new physics may be required to explain their existence. This has prompted the construction of new experiments designed to detect cosmic rays with fluxes below 1 particle/km/century and follow their spectrum to even higher energies. To detect large numbers of these particles, the next generation of these experiments must be performed on space-based platforms that look on very large detection volumes in the Earth's atmosphere. The talk will review the experimental and theoretical investigations of extreme energy cosmic rays and discuss the present and planned experiments to extend measurements beyond 10(exp 21) eV.

  9. On the level of the cosmic ray sea flux

    SciTech Connect

    Casanova, S.; Aharonian, F. A.; Gabici, S.; Torii, K.; Fukui, Y.; Onishi, T.; Yamamoto, H.; Kawamura, A.

    2009-04-08

    The study of Galactic diffuse {gamma} radiation combined with the knowledge of the distribution of the molecular hydrogen in the Galaxy offers a unique tool to probe the cosmic ray flux in the Galaxy. A methodology to study the level of the cosmic ray 'sea' and to unveil target-accelerator systems in the Galaxy, which makes use of the data from the high resolution survey of the Galactic molecular clouds performed with the NANTEN telescope and of the data from {gamma}-ray instruments, has been developed. Some predictions concerning the level of the cosmic ray 'sea' and the {gamma}-ray emission close to cosmic ray sources for instruments such as Fermi and Cherenkov Telescope Array are presented.

  10. Cosmic rays and the birth of particle physics

    NASA Astrophysics Data System (ADS)

    Friedlander, Michael

    2013-02-01

    Twenty years after the discovery of cosmic rays, the methods of research and resulting discoveries were dramatically changed by the introduction of experimental methods that made visible the passage of individual particles. Between 1932 and 1955, tracks of cosmic rays were found in cloud chambers and special photographic emulsions. From measurements of the ionization produced along these tracks, the mass, charge and energy of a single relativistic particle could be determined. The dynamics of decays and collisions could be analyzed. Positrons and then electron-positron pairs were discovered, followed by muons and pions and then the inhabitants of the 'particle zoo'. Fundamental concepts were challenged. From the mid- 1950s, larger accelerators began to produce many of the 'new' particles, displacing cosmic rays from their prime role in particle studies. But without the initial discoveries in cosmic rays, there might well not be the modern industrial-scale particle physics research.

  11. On wave stability in relativistic cosmic-ray hydrodynamics

    NASA Technical Reports Server (NTRS)

    Webb, G. M.

    1989-01-01

    Wave stability of a two-fluid hydrodynamical model describing the acceleration of cosmic rays by the first-order Fermi mechanism in relativistic, cosmic-ray-modified shocks is investigated. For a uniform background state, the short- and long-wavelength wave speeds are shown to interlace, thus assuring wave stability in this case. A JWKB analysis is performed to investigate the stability of short-wavelength thermal gas sound waves in the smooth, decelerating supersonic flow upstream of a relativistic, cosmic-ray-modified shock. The stability of the waves is assessed both in terms of the fluid velocity and density perturbations, as well as in terms of the wave action. The stability and interaction of the short-wavelength cosmic-ray coherent mode with the background flow is also studied.

  12. Summary for astrophysics and non-accelerator physics

    SciTech Connect

    Kahana, S.H.

    1988-01-01

    This paper summarizes the presentations at the astrophysics and non-accelerator physics conference. Discussed in this paper are: supernovae, neutrinos, x-rays, gamma rays, cosmic rays, monopoles and primordial nucleosynthesis. 15 refs. (LSP)

  13. Galactic Cosmic Ray Simulator at the NASA Space Radiation Laboratory

    NASA Technical Reports Server (NTRS)

    Norbury, John W.; Slaba, Tony C.; Rusek, Adam

    2015-01-01

    The external Galactic Cosmic Ray (GCR) spectrum is significantly modified when it passes through spacecraft shielding and astronauts. One approach for simulating the GCR space radiation environment is to attempt to reproduce the unmodified, external GCR spectrum at a ground based accelerator. A possibly better approach would use the modified, shielded tissue spectrum, to select accelerator beams impinging on biological targets. NASA plans for implementation of a GCR simulator at the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory will be discussed.

  14. WIND/EPACT observations of anomalous cosmic rays

    NASA Astrophysics Data System (ADS)

    Reames, D. V.; Barbier, L. M.; von Rosenvinge, T. T.

    1997-05-01

    The Energetic Particles, Acceleration, Composition and Transport (EPACT) Experiment on the WIND spacecraft, and especially its large-geometry Low Energy Matrix Telescope (LEMT), is capable of sensitive measurements of ions of the anomalous cosmic-ray (ACR) component above 2 MeV/amu. We report on the energy spectra of He, C, N, O, Ne, S, and Ar and estimate element abundances at the acceleration site.

  15. A comparison of models for supernova remnants including cosmic rays

    NASA Astrophysics Data System (ADS)

    Kang, Hyesung; Drury, L. O'C.

    1992-11-01

    A simplified model which can follow the dynamical evolution of a supernova remnant including the acceleration of cosmic rays without carrying out full numerical simulations has been proposed by Drury, Markiewicz, & Voelk in 1989. To explore the accuracy and the merits of using such a model, we have recalculated with the simplified code the evolution of the supernova remnants considered in Jones & Kang, in which more detailed and accurate numerical simulations were done using a full hydrodynamic code based on the two-fluid approximation. For the total energy transferred to cosmic rays the two codes are in good agreement, the acceleration efficiency being the same within a factor of 2 or so. The dependence of the results of the two codes on the closure parameters for the two-fluid approximation is also qualitatively similar. The agreement is somewhat degraded in those cases where the shock is smoothed out by the cosmic rays.

  16. UHECR acceleration at GRB internal shocks

    NASA Astrophysics Data System (ADS)

    Globus, N.; Allard, D.; Mochkovitch, R.; Parizot, E.

    2015-07-01

    Recent results from the Pierre Auger Observatory suggest that nuclei heavier than protons might be present in significant amounts among ultrahigh-energy cosmic rays (UHECRs). It is therefore interesting to investigate the acceleration both protons and nuclei in relativistic jets. We calculate the acceleration of a mixed composition of cosmic rays at Gamma-ray burst (GRB) internal shocks, taking into account the relevant energy loss processes. 3D trajectories during the relativistic Fermi cycles are simulated following previous works by Niemiec & Ostrowski. We use the internal shock model of Daigne & Mochkovitch to derive the evolution of the relevant physical quantities (magnetic fields, baryon and photon densities, shock velocity). We consider different phenomenological hypotheses about the sharing of the dissipated energy between accelerated cosmic rays, electrons and the magnetic field. For various choices of the parameters, we calculate the spectrum of cosmic rays escaping from the GRB environment as well as secondary particles produced either during the acceleration or extragalactic propagation of UHECRs. Only models where (i) the prompt emission represents only a small fraction of the energy dissipated at internal shocks and (ii) most of this dissipated energy is communicated to cosmic rays, are able to reproduce the magnitude of the UHECR flux observed on Earth. For these models, however, the observed shape of the UHECR spectrum can be well reproduced above the ankle, with an evolution of the composition compatible with the trend suggested by Auger, and associated diffuse fluxes of secondary particles which do not violate current observational limits.

  17. Sensitivity of a search for cosmic ray sources including magnetic field effects

    NASA Astrophysics Data System (ADS)

    Erdmann, Martin; Müller, Gero; Urban, Martin

    2016-05-01

    We analyze the sensitivity of a new method investigating correlations between ultra-high energy cosmic rays and extragalactic sources taking into account deflections in the galactic magnetic field. In comparisons of expected and simulated arrival directions of cosmic rays we evaluate the directional characteristics and magnitude of the field. We show that our method is capable of detecting an anisotropy in data sets with a low signal fraction. It also reveals directions with increased probability for sources of cosmic rays, and therefore opens new possibilities for investigating cosmic particle origin and acceleration.

  18. ENERGY SPECTRUM AND CHEMICAL COMPOSITION OF ULTRAHIGH ENERGY COSMIC RAYS FROM SEMI-RELATIVISTIC HYPERNOVAE

    SciTech Connect

    Liu Ruoyu; Wang Xiangyu

    2012-02-10

    It has been suggested that hypernova remnants, with a substantial amount of energy in semi-relativistic ejecta, can accelerate intermediate mass or heavy nuclei to ultrahigh energies and provide a sufficient amount of energy in cosmic rays to account for the observed flux. We here calculate the expected energy spectrum and chemical composition of ultrahigh energy cosmic rays from such semi-relativistic hypernovae. With a chemical composition equal to that of the hypernova ejecta and a flat or hard spectrum for cosmic rays at the sources, the spectrum and composition of the propagated cosmic rays observed at the Earth can be compatible with the measurements by the Pierre Auger Observatory.

  19. A Cerenkov-delta E-Cerenkov detector for high energy cosmic ray isotopes and an accelerator study of Ar-40 and Fe-56 fragmentation. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Lau, K. H.

    1985-01-01

    A high energy cosmic ray detector--the High Energy Isotope Spectrometer Telescope (HEIST) is described. It is a large area (0.25 m(swp 2) SR) balloon borne isotope spectrometer designed to make high resolution measurements of isotopes in the element range from neon to nickel (10 Z 28) at energies of about 2 GeV/nucleon. HEIST determines the mass of individual nuclei by measuring both the change in the Lorentz factor (delta gamma) that results from traversing the NaI stack, and the energy loss (delta E) in the stack. Since the total energy of an isotope is given by E = (gamma M), the mass M can be determined by M = delta E/delta, gamma. The instrument is designed to achieve a typical mass resolution of 0.2 amu. The isotopic composition of the fragments from the breakup of high energy An-40 and Fe-56 nuclei are measured experimentally. Isotope yields are compared with calculated yields based on semi-empirical cross-section formulae.

  20. Cosmic questions: an introduction.

    PubMed

    Primack, J R; Abrams, N E

    2001-12-01

    This introductory talk at the Cosmic Questions conference sponsored by the AAAS summarizes some earlier pictures of the universe and some pictures based on modern physics and cosmology. The uroboros (snake swallowing its tail) is an example of a traditional picture. The Biblical flat-earth picture was very different from the Greek spherical earth-centered picture, which was the standard view until the end of the Middle Ages. Many people incorrectly assume that the Newtonian picture of stars scattered through otherwise empty space is still the prevailing view. Seeing Earth from space shows the power of a new picture. The Hubble Space Telescope can see all the bright galaxies, all the way to the cosmic Dark Ages. We are at the center of cosmic spheres of time: looking outward is looking backward in time. All the matter and energy in the universe can be represented as a cosmic density pyramid. The laws of physics only allow the material objects in the universe to occupy a wedge-shaped region on a diagram of mass versus size. All sizes--from the smallest size scale, the Planck scale, to the entire visible universe--can be represented on the Cosmic Uroboros. There are interesting connections across this diagram, and the human scale lies in the middle. PMID:11797741

  1. Nineteenth International Cosmic Ray Conference. Conference Papers: Invited Rapporteur, Highlight, Miscellaneous, Volume 9

    NASA Technical Reports Server (NTRS)

    Jones, F. C. (Compiler)

    1986-01-01

    Invited talks, rapporteur talks, and highlight talks are included. Topics of the invited and highlight talks include astrophysical jets, gamma-ray line astronomy, cosmic rays and gamma rays in astrophysics, the early universe, elementary particle physics, solar flares and acceleration of energetic particles, cosmogenic nuclei, extragalactic astronomy, composition of solar flare particles, very high energy gamma ray sources, gamma-ray bursts, shock acceleration in the solar wind, cosmic rays in deep underground detectors, spectrum of cosmic rays at 10 to the 19th power eV, and nucleus-nucleus interactions.

  2. Measuring Cosmic Distances with Stellar Heart Beats

    NASA Astrophysics Data System (ADS)

    2004-10-01

    this particular type and bright enough to be easily seen with the unaided eye. In 1912, American astronomer Henrietta Leavitt observed 20 variable stars of the Cepheid-type in the Small Magellanic Cloud (SMC), one of the closest galaxies to the Milky Way. For all purposes, these stars are all at the same distance (the size of the SMC is negligible compared to its much larger distance from us). Apparently brighter stars in this group are thus also intrinsically brighter (more luminous). Henrietta Leavitt discovered a basic relation between the intrinsic brightness and the pulsation period of Cepheid variable stars in the SMC and showed that intrinsically brighter Cepheids have longer periods. This relation is now known as the "Period-Luminosity relation" and is an important way to derive the distance to stars of this type. By measuring the period of a Cepheid star, its intrinsic brightness can be deduced and from the observed apparent brightness, the distance may then be calculated. In this way, Cepheid stars are used by astronomers as one of the "standard candles" in the Universe. They act either as distance indicators themselves or are used to calibrate other distance indicators. The Cepheid stars have taken on an even more important role since the Hubble Space Telescope Key Project on the extragalactic distance scale relies completely on them for the calibration of distance indicators to reach cosmologically large distances. In other words, if the calibration of the Cepheid Period-Luminosity relation were wrong, the entire extragalactic distance scale and with it, the rate of cosmic expansion and the related acceleration, as well as the estimated age of the Universe, would also be off. A main problem is thus to calibrate as accurately as possible the Period-Luminosity relation for nearby Cepheids. This requires measuring their distances with the utmost precision, a truly daunting task. And this is where interferometry now enters the picture. The Baade

  3. Ultrahigh-energy particles from cosmic strings

    SciTech Connect

    Bhattacharjee, P. . Astronomy and Astrophysics Center Fermi National Accelerator Lab., Batavia, IL )

    1991-02-01

    The idea of production of ultrahigh-energy particles in the present universe due to annihilation or collapse of topological defects is discussed. Topological defects, formed in symmetry-breaking phase transitions in the early universe, can survive till today owing to their topological stability. However, under certain circumstances, topological defects may be physically destroyed. When topological defects are destroyed, the energy contained in the defects can be released in the form of massive gauge- and Higgs bosons of the underlying spontaneously broken gauge theory. Subsequent decay of these massive particles can give rise to energetic particles ranging up to an energy on the order of the mass of the original particles released from the defects. This may give us a natural'' mechanism of production of extremely energetic cosmic ray particles in the universe today, without the need for any acceleration mechanism. To illustrate this idea, I describe in detail the calculation of the expected ultrahigh-energy proton spectrum due to a specific process which involves collapse or multiple self-intersections of a class of closed cosmic string loops formed in a phase transition at a grand unification energy scale. I discuss the possibility that some of the highest-energy cosmic ray particles are of this origin. By comparing with the observational results on the ultrahigh-energy cosmic rays, we derive an upper limit to the average fraction of the total energy in all primary'' cosmic string loops that may be released in the form of particles due to collapse or multiple self-intersections of these loops. No nuclei such as {alpha}'s or Fe's are in the spectrum. 43 refs., 3 figs.

  4. Supernova Remnants, Cosmic Rays, and GLAST

    SciTech Connect

    Reynolds, Steve

    2006-02-13

    The shock waves of supernova remnants (SNRs) are the traditional sources of Galactic cosmic rays, at least up to about 3000 TeV (the 'knee' energy in the cosmic-ray spectrum). In the last decade or so, X-ray observations have confirmed in a few SNRs the presence of synchrotron-X-ray-emitting electrons with energies of order 100 TeV. TeV photons from SNRs have been observed with ground-based air Cerenkov telescopes as well, but it is still unclear whether they are due to hadronic processes (inelastic p-p scattering of cosmic-ray protons from thermal gas, with secondary neutral pions decaying to gamma rays), or to leptonic processes (inverse-Compton upscattering of cosmic microwave background photons, or bremsstrahlung). The spatial structure of synchrotron X-rays as observed with the Chandra X-ray Observatory suggests the remarkable possibility that magnetic fields are amplified by orders of magnitude in strong shock waves. The electron spectra inferred from X-rays reach 100 TeV, but at that energy are cutting off steeply, well below the 'knee' energy. Are the cutoff processes due only to radiative losses so that ion spectra might continue unsteepened? Can we confirm the presence of energetic ions in SNRs at all? Are typical SNRs capable of supplying the pool of Galactic cosmic rays? Is strong magnetic-field amplification a property of strong astrophysical shocks in general? These major questions require the next generation of observational tools. I shall outline the theoretical and observational framework of particle acceleration to high energies in SNRs, and shall describe how GLAST will advance this field.

  5. Supernova Remnants, Cosmic Rays, and GLAST

    SciTech Connect

    Reynolds, Steve

    2006-02-13

    The shock waves of supernova remnants (SNRs) are the traditional sources of Galactic cosmic rays, at least up to about 3000 TeV (the "knee" energy in the cosmic-ray spectrum). In the last decade or so, X-ray observations have confirmed in a few SNRs the presence of synchrotron-X-ray-emitting electrons with energies of order 100 TeV. TeV photons from SNRs have been observed with ground-based air Cerenkov telescopes as well, but it is still unclear whether they are due to hadronic processes (inelastic p-p scattering of cosmic-ray protons from thermal gas, with secondary neutral pions decaying to gamma rays), or to leptonic processes (inverse-Compton upscattering of cosmic microwave background photons, or bremsstrahlung). The spatial structure of synchrotron X-rays as observed with the Chandra X-ray Observatory suggests the remarkable possibility that magnetic fields are amplified by orders of magnitude in strong shock waves. The electron spectra inferred from X-rays reach 100 TeV, but at that energy are cutting off steeply, well below the "knee" energy. Are the cutoff processes due only to radiative losses so that ion spectra might continue unsteepened? Can we confirm the presence of energetic ions in SNRs at all? Are typical SNRs capable of supplying the pool of Galactic cosmic rays? Is strong magnetic-field amplification a property of strong astrophysical shocks in general? These major questions require the next generation of observational tools. I shall outline the theoretical and observational framework of particle acceleration to high energies in SNRs, and shall describe how GLAST will advance this field.

  6. Ultra high energy gamma rays, cosmic rays and neutrinos from accreting degenerate stars

    NASA Technical Reports Server (NTRS)

    Brecher, K.; Chanmugam, G.

    1985-01-01

    Super-Eddington accretion for a recently proposed unipolar induction model of cosmic ray acceleration in accreting binary star systems containing magnetic white dwarfs or neutron stars is considered. For sufficiently high accretion rates and low magnetic fields, the model can account for: (1) acceleration of cosmic ray nuclei up to energies of 10 to the 19th power eV; (2) production of more or less normal solar cosmic ray composition; (3) the bulk of cosmic rays observed with energies above 1 TeV, and probably even down to somewhat lower energies as well; and (4) possibly the observed antiproton cosmic ray flux. It can also account for the high ultra high energy (UHE) gamma ray flux observed from several accreting binary systems (including Cygnus X-3), while allowing the possibility of an even higher neutrino flux from these sources, with L sub nu/L sub gamma is approximately 100.

  7. Discovery of cosmic rays

    NASA Astrophysics Data System (ADS)

    Carlson, Per

    2013-02-01

    The mysterious invisible radiation that ionized air was studied a century ago by many scientists. Finally, on 7 August 1912, Victor Hess in his seventh balloon flight that year, reached an altitude of about 5000 m. With his electroscopes on board the hydrogen-filled balloon he observed that the ionization instead of decreasing with altitude increased significantly. Hess had discovered cosmic rays, a discovery that gave him the 1936 Nobel Prize in physics. When research resumed after World War I focus was on understanding the nature of the cosmic radiation. Particles or radiation? Positive or negative? Electrons, positrons or protons? Progress came using new instruments like the Geiger-Muller tube and around 1940 it was clear that cosmic rays were mostly protons.

  8. Semilocal cosmic string networks

    SciTech Connect

    Achucarro, Ana; Salmi, Petja; Urrestilla, Jon

    2007-06-15

    We report on a large-scale numerical study of networks of semilocal cosmic strings in flat space in the parameter regime in which they are perturbatively stable. We find a population of segments with an exponential length distribution and indications of a scaling network without significant loop formation. Very deep in the stability regime strings of superhorizon size grow rapidly and ''percolate'' through the box. We believe these should lead at late times to a population of infinite strings similar to topologically stable strings. However, the strings are very light; scalar gradients dominate the energy density, and the network has thus a global texturelike signature. As a result, the observational constraints, at least from the temperature power spectrum of the cosmic microwave background, on models predicting semilocal strings should be closer to those on global textures or monopoles, rather than on topologically stable gauged cosmic strings.

  9. FERMI BUBBLE γ-RAYS AS A RESULT OF DIFFUSIVE INJECTION OF GALACTIC COSMIC RAYS

    SciTech Connect

    Thoudam, Satyendra

    2013-11-20

    Recently, the Fermi Space Telescope discovered two large γ-ray emission regions, the so-called Fermi bubbles, that extend up to ∼50° above and below the Galactic center (GC). The γ-ray emission from the bubbles is found to follow a hard spectrum with no significant spatial variation in intensity and spectral shape. The origin of the emission is still not clearly understood. Suggested explanations include the injection of cosmic-ray (CR) nuclei from the GC by high-speed Galactic winds, electron acceleration by multiple shocks, and stochastic electron acceleration inside the bubbles. In this Letter, it is proposed that the γ-rays may be the result of diffusive injection of Galactic CR protons during their propagation through the Galaxy. Considering that the bubbles are slowly expanding, and CRs undergo much slower diffusion inside the bubbles than in the average Galaxy and at the same time suffer losses due to adiabatic expansion and inelastic collisions with the bubble plasma, this model can explain the observed intensity profile, the emission spectrum and the measured luminosity without invoking any additional particle production processes, unlike other existing models.

  10. Constraints on cold dark matter accelerating cosmologies and cluster formation

    SciTech Connect

    Basilakos, S.; Lima, J. A. S.

    2010-07-15

    We discuss the properties of homogeneous and isotropic flat cosmologies in which the present accelerating stage is powered only by the gravitationally induced creation of cold dark matter (CCDM) particles ({Omega}{sub m}=1). For some matter creation rates proposed in the literature, we show that the main cosmological functions such as the scale factor of the universe, the Hubble expansion rate, the growth factor, and the cluster formation rate are analytically defined. The best CCDM scenario has only one free parameter and our joint analysis involving baryonic acoustic oscillations + cosmic microwave background (CMB) + SNe Ia data yields {Omega}-tilde{sub m}=0.28{+-}0.01 (1{sigma}), where {Omega}-tilde{sub m} is the observed matter density parameter. In particular, this implies that the model has no dark energy but the part of the matter that is effectively clustering is in good agreement with the latest determinations from the large-scale structure. The growth of perturbation and the formation of galaxy clusters in such scenarios are also investigated. Despite the fact that both scenarios may share the same Hubble expansion, we find that matter creation cosmologies predict stronger small scale dynamics which implies a faster growth rate of perturbations with respect to the usual {Lambda}CDM cosmology. Such results point to the possibility of a crucial observational test confronting CCDM with {Lambda}CDM scenarios through a more detailed analysis involving CMB, weak lensing, as well as the large-scale structure.

  11. Hot atoms in cosmic chemistry.

    PubMed

    Rossler, K; Jung, H J; Nebeling, B

    1984-01-01

    High energy chemical reactions and atom molecule interactions might be important for cosmic chemistry with respect to the accelerated species in solar wind, cosmic rays, colliding gas and dust clouds and secondary knock-on particles in solids. "Hot" atoms with energies ranging from a few eV to some MeV can be generated via nuclear reactions and consequent recoil processes. The chemical fate of the radioactive atoms can be followed by radiochemical methods (radio GC or HPLC). Hot atom chemistry may serve for laboratory simulation of the reactions of energetic species with gaseous or solid interstellar matter. Due to the effective measurement of 10(8)-10(10) atoms only it covers a low to medium dose regime and may add to the studies of ion implantation which due to the optical methods applied are necessarily in the high dose regime. Experimental results are given for the systems: C/H2O (gas), C/H2O (solid, 77 K), N/CH4 (solid, 77K) and C/NH3 (solid, 77 K). Nuclear reactions used for the generation of 2 to 3 MeV atoms are: N(p,alpha) 11C, 16O(p,alpha pn) 11C and 12C(d,n) 13N with 8 to 45 MeV protons or deuterons from a cyclotron. Typical reactions products are: CO, CO2, CH4, CH2O, CH3OH, HCOOH, NH3, CH3NH2, cyanamide, formamidine, guanidine etc. Products of hot reactions in solids are more complex than in corresponding gaseous systems, which underlines the importance of solid state reactions for the build-up of precursors for biomolecules in space. As one of the major mechanisms for product formation, the simultaneous or fast consecutive reactions of a hot carbon with two target molecules (reaction complex) is discussed. PMID:11537799

  12. Heterotic cosmic strings

    SciTech Connect

    Becker, Katrin; Becker, Melanie; Krause, Axel

    2006-08-15

    We show that all three conditions for the cosmological relevance of heterotic cosmic strings, the right tension, stability and a production mechanism at the end of inflation, can be met in the strongly coupled M-theory regime. Whereas cosmic strings generated from weakly coupled heterotic strings have the well-known problems posed by Witten in 1985, we show that strings arising from M5-branes wrapped around 4-cycles (divisors) of a Calabi-Yau in heterotic M-theory compactifications solve these problems in an elegant fashion.

  13. The Formation of Solid Particles from their Gas-Phase Molecular Precursors in Cosmic Environments with NASA Ames' COSmIC Facility

    NASA Technical Reports Server (NTRS)

    Salama, Farid

    2014-01-01

    We present and discuss the unique characteristics and capabilities of the laboratory facility, COSmIC, that was developed at NASA Ames to generate, process and analyze interstellar, circumstellar and planetary analogs in the laboratory. COSmIC stands for Cosmic Simulation Chamber and is dedicated to the study of molecules and ions under the low temperature and high vacuum conditions that are required to simulate interstellar, circumstellar and planetary physical environments in space. COSmIC integrates a variety of state-of-the-art instruments that allow forming, processing and monitoring simulated space conditions for planetary, circumstellar and interstellar materials in the laboratory. COSmIC is composed of a Pulsed Discharge Nozzle (PDN) expansion that generates a free jet supersonic expansion coupled to two ultrahigh-sensitivity, complementary in situ diagnostics: a Cavity Ring Down Spectroscopy (CRDS) system for photonic detection and a Reflectron Time-Of-Flight Mass Spectrometer (ReTOF-MS) for mass detection. Recent, unique, laboratory astrophysics results that were obtained using the capabilities of COSmIC will be discussed, in particular the progress that have been achieved in monitoring in the laboratory the formation of solid gains from their gas-phase molecular precursors in environments as varied as stellar/circumstellar outflow and planetary atmospheres. Plans for future, next generation, laboratory experiments on cosmic molecules and grains in the growing field of laboratory astrophysics will also be addressed as well as the implications of these studies for current and upcoming space missions.

  14. Extensive Air Showers and Cosmic Ray Physics above 1017 eV

    NASA Astrophysics Data System (ADS)

    Bertaina, Mario

    2016-07-01

    Cosmic Rays above 1017 eV allow studying hadronic interactions at energies that can not be attained at accelerators yet. At the same time hadronic interaction models have to be applied to the cosmic-ray induced air-shower cascades in atmosphere to infer the nature of cosmic rays. The reliability of air-shower simulations has become the source of one of the largest systematic uncertainty in the interpretation of cosmic-ray data due to the uncertainties in modeling the hadronic interaction driving the air-shower development. This paper summarises in the first part the recent results on the cosmic ray energy spectrum, composition and anisotropy from the knee region to the GZK cutoff [1, 2] of the spectrum by means of ground-based experiments. Most of the information reported in this contribution is taken from [3-5]. Aspects interconnecting cosmic ray and particle physics are reviewed in the second part of the paper.

  15. A review and interpretation of recent cosmic ray beryllium isotope measurements

    NASA Technical Reports Server (NTRS)

    Buffington, A.

    1978-01-01

    Beryllium-10 is of interest for cosmic ray propagation, because its radioactive decay half-life is well matched to the expected cosmic ray age. Recent beryllium isotope measurements from satellites and balloon covered an energy range from about 30 to 300 MeV/nucleon. At the lowest energies, most of the Be-10 is absent, indicating a cosmic ray lifetime of order 2 x 10 to the 7th power years and the rather low average density of 0.2 atoms/cc traversed by the cosmic rays. At higher energies, a greater propagation of Be-10 is observed, indicating a somewhat shorter lifetime. These experiments will be reviewed and then compared with a new experiment covering from 100 to 1000 MeV/nucleon. Although improved experiments will be necessary to realize the full potential of cosmic ray beryllium isotope measurements, these first results are already disclosing interesting and unexpected facts about cosmic ray acceleration and propagation.

  16. Galactic cosmic rays and nucleosynthesis

    SciTech Connect

    Kiener, Juergen

    2010-03-01

    The nucleosynthesis of the light elements Li, Be and B by galactic cosmic rays is presented. Observations of cosmic rays and the nuclear reactions responsible for Li, Be and B nucleosynthesis are described, followed by some words on propagation. At the end, some open questions concerning galactic cosmic rays are discussed.

  17. The evolution of cosmic-ray-mediated magnetohydrodynamic shocks: A two-fluid approach

    NASA Technical Reports Server (NTRS)

    Jun, Byung-Il; Clarke, David A.; Norman, Michael L.

    1994-01-01

    We study the shock structure and acceleration efficiency of cosmic-ray mediated Magnetohydrodynamic (MHD) shocks both analytically and numerically by using a two-fluid model. Our model includes the dynamical effect of magnetic fields and cosmic rays on a background thermal fluid. The steady state solution is derived by following the technique of Drury & Voelk (1981) and compared to numerical results. We explore the time evolution of plane-perpendicular, piston-driven shocks. From the results of analytical and numerical studies, we conclude that the mean magnetic field plays an important role in the structure and acceleration efficiency of cosmic-ray mediated MHD shocks. The acceleration of cosmic-ray particles becomes less efficient in the presence of strong magnetic pressure since the field makes the shock less compressive. This feature is more prominent at low Mach numbers than at high Mach numbers.

  18. The evolution of cosmic-ray-mediated magnetohydrodynamic shocks: A two-fluid approach

    NASA Astrophysics Data System (ADS)

    Jun, Byung-Il; Clarke, David A.; Norman, Michael L.

    1994-07-01

    We study the shock structure and acceleration efficiency of cosmic-ray mediated Magnetohydrodynamic (MHD) shocks both analytically and numerically by using a two-fluid model. Our model includes the dynamical effect of magnetic fields and cosmic rays on a background thermal fluid. The steady state solution is derived by following the technique of Drury & Voelk (1981) and compared to numerical results. We explore the time evolution of plane-perpendicular, piston-driven shocks. From the results of analytical and numerical studies, we conclude that the mean magnetic field plays an important role in the structure and acceleration efficiency of cosmic-ray mediated MHD shocks. The acceleration of cosmic-ray particles becomes less efficient in the presence of strong magnetic pressure since the field makes the shock less compressive. This feature is more prominent at low Mach numbers than at high Mach numbers.

  19. The galactic origin of cosmic rays. I

    NASA Astrophysics Data System (ADS)

    Colgate, S. A.

    The theoretical basis for the supernova envelope shock origin of cosmic rays is reviewed. The theoretical explanation of the SN Type I light curve requires the ejection of a relativistic mass fraction. The criterion of the adiabatic deceleration by Alfven wave trapping neither applies in theory, when beta is greater than 1, or practice, as in the Starfish high-altitude nuclear explosion experiment. Arguments of delayed acceleration due to K-capture are not applicable to SN ejecta because a period of prompt recombination exists before subsequent stripping in propagation.

  20. Global MHD simulations of cosmic ray driven galactic winds

    NASA Astrophysics Data System (ADS)

    Ruszkowski, Mateusz; Yang, Hsiang-Yi Karen; Gould Zweibel, Ellen

    2016-04-01

    Galactic outflows play an important role in galactic evolution. Despite their importance, a detailed understanding of the physical mechanisms responsible for the driving of these winds is lacking. In an effort to gain more insight into the nature of these flows, we perform global three-dimensional magneto-hydrodynamical simulations of an isolated starbursting galaxy. We focus on the dynamical role of cosmic rays injected by supernovae, and specifically on the impact of the streaming and anisotropic diffusion of cosmic rays along the magnetic fields. We find that these microphysical effects can have a significant effect on the wind launching and mass loading factors depending on the details of the plasma physics. Cosmic rays stream away from the densest regions near the galactic disk along partially ordered magnetic fields and, in the process, accelerate more tenuous gas away from the galaxy. For cosmic ray acceleration efficiencies broadly consistent with the observational constraints, cosmic rays are likely to have a notable impact on the wind launching.

  1. Modified non-linear Burgers' equations and cosmic ray shocks

    NASA Technical Reports Server (NTRS)

    Zank, G. P.; Webb, G. M.; Mckenzie, J. F.

    1988-01-01

    A reductive perturbation scheme is used to derive a generalized non-linear Burgers' equation, which includes the effects of dispersion, in the long wavelength regime for the two-fluid hydrodynamical model used to describe cosmic ray acceleration by the first-order Fermi process in astrophysical shocks. The generalized Burger's equation is derived for both relativistic and non-relativistic cosmic ray shocks, and describes the time evolution of weak shocks in the theory of diffusive shock acceleration. The inclusion of dispersive effects modifies the phase velocity of the shock obtained from the lower order non-linear Burger's equation through the introduction of higher order terms from the long wavelength dispersion equation. The travelling wave solution of the generalized Burgers' equation for a single shock shows that larger cosmic ray pressures result in broader shock transitions. The results for relativistic shocks show a steepening of the shock as the shock speed approaches the relativistic cosmic ray sound speed. The dependence of the shock speed on the cosmic ray pressure is also discussed.

  2. Our Cosmic Connection

    ERIC Educational Resources Information Center

    Young, Donna L.

    2005-01-01

    To help students understand the connection that Earth and the solar system have with the cosmic cycles of stellar evolution, and to give students an appreciation of the beauty and elegance of celestial phenomena, the Chandra X-Ray Center (CXC) educational website contains a stellar evolution module that is available free to teachers. In this…

  3. Heavy cosmic strings

    SciTech Connect

    Donaire, M.; Rajantie, A.

    2006-03-15

    We argue that cosmic strings with high winding numbers generally form in first-order gauge symmetry breaking phase transitions, and we demonstrate this using computer simulations. These strings are heavier than single-winding strings and therefore more easily observable. Their cosmological evolution may also be very different.

  4. Plasma accelerators

    SciTech Connect

    Ruth, R.D.; Chen, P.

    1986-03-01

    In this paper we discuss plasma accelerators which might provide high gradient accelerating fields suitable for TeV linear colliders. In particular we discuss two types of plasma accelerators which have been proposed, the Plasma Beat Wave Accelerator and the Plasma Wake Field Accelerator. We show that the electric fields in the plasma for both schemes are very similar, and thus the dynamics of the driven beams are very similar. The differences appear in the parameters associated with the driving beams. In particular to obtain a given accelerating gradient, the Plasma Wake Field Accelerator has a higher efficiency and a lower total energy for the driving beam. Finally, we show for the Plasma Wake Field Accelerator that one can accelerate high quality low emittance beams and, in principle, obtain efficiencies and energy spreads comparable to those obtained with conventional techniques.

  5. Program and charts for determining shock tube, and expansion tunnel flow quantities for real air

    NASA Technical Reports Server (NTRS)

    Miller, C. G., III; Wilder, S. E.

    1975-01-01

    A computer program in FORTRAN 4 language was written to determine shock tube, expansion tube, and expansion tunnel flow quantities for real-air test gas. This program permits, as input data, a number of possible combinations of flow quantities generally measured during a test. The versatility of the program is enhanced by the inclusion of such effects as a standing or totally reflected shock at the secondary diaphragm, thermochemical-equilibrium flow expansion and frozen flow expansion for the expansion tube and expansion tunnel, attenuation of the flow in traversing the acceleration section of the expansion tube, real air as the acceleration gas, and the effect of wall boundary layer on the acceleration section air flow. Charts which provide a rapid estimation of expansion tube performance prior to a test are included.

  6. Ultra-heavy cosmic rays: Theoretical implications of recent observations

    NASA Technical Reports Server (NTRS)

    Blake, J. B.; Hainebach, K. L.; Schramm, D. N.; Anglin, J. D.

    1977-01-01

    Extreme ultraheavy cosmic ray observations (Z greater or equal 70) are compared with r-process models. A detailed cosmic ray propagation calculation is used to transform the calculated source distributions to those observed at the earth. The r-process production abundances are calculated using different mass formulae and beta-rate formulae; an empirical estimate based on the observed solar system abundances is used also. There is the continued strong indication of an r-process dominance in the extreme ultra-heavy cosmic rays. However it is shown that the observed high actinide/Pt ratio in the cosmic rays cannot be fit with the same r-process calculation which also fits the solar system material. This result suggests that the cosmic rays probably undergo some preferential acceleration in addition to the apparent general enrichment in heavy (r-process) material. As estimate also is made of the expected relative abundance of superheavy elements in the cosmic rays if the anomalous heavy xenon in carbonaceous chondrites is due to a fissioning superheavy element.

  7. Ultraheavy cosmic rays - Theoretical implications of recent observations

    NASA Technical Reports Server (NTRS)

    Blake, J. B.; Hainebach, K. L.; Schramm, D. N.; Anglin, J. D.

    1978-01-01

    The recent extreme ultraheavy cosmic-ray observations (Z greater than or equal to 70) are compared with r-process models. A detailed cosmic ray propagation calculation is used to transform the calculated source distributions to those observed at the earth. The r-process production abundances are calculated using different mass formulae and beta-rate formulae; an empirical estimate based on the observed solar-system abundances is also used. There is the continued strong indication of an r-process dominance in the extreme ultraheavy cosmic rays. It is shown that the observed high actinide/Pt ratio in the cosmic rays cannot be fitted with the same r-process calculation which also fits the solar-system material. This result suggests that the cosmic rays probably undergo some preferential acceleration in addition to the apparent general enrichment in heavy (r-process) material. An estimate is also made of the expected relative abundance of superheavy elements in the cosmic rays if the anomalous heavy xenon in carbonaceous chondrites is due to a fissioning superheavy element.

  8. Cosmic-ray modulation at solar maximum: modeling

    NASA Astrophysics Data System (ADS)

    Kota, J.; Jokipii, J.

    The modulation of the galactic and anomalous cosmic rays is a result of the energy loss cosmic rays suffer during their passage through the heliospheric magnetic and electric fields. By contrast with the years of quiet heliosphere, which can be described with a tilted dipole model that remains stable for several solar rotations, cosmic-ray modulation during the periods of the active Sun is thought to be dominated by transient events. Propagating disturbances forming global merged interaction regions (GMIRs) act as propagating barriers. The heliospheric current sheet (HCS) dividing the opposite polarities of the heliospheric magnetic field (HMF) becomes highly tilted and may contain a significant quadrupole component, leading to a warped current sheet with a profound north-south asymmetry. We present numerical simulations to model cosmic-ray transport and acceleration in the heliosphere during solar maximum. Our 2-D and 3-D codes are extended to include several transients. We consider various complex configurations of the HMF, as well as a dynamical variation of the tilted current sheet, involving meridional field components. We discuss the effects of GMIRs on galactic and anomalous cosmic rays, and compare the time evolution of the two different species, as the disturbance propagates outward through the termination shock (TS) into the heliosheath. Some aspects of cosmic-ray modulation beyond the TS, in the subsonic heliosheath will also be addressed.

  9. Acceleration of the universe: a reconstruction of the effective equation of state

    NASA Astrophysics Data System (ADS)

    Mukherjee, Ankan

    2016-04-01

    The present work is based upon a parametric reconstruction of the effective or total equation of state in a model for the universe with accelerated expansion. The constraints on the model parameters are obtained by maximum likelihood analysis using the supernova distance modulus data, observational Hubble data, baryon acoustic oscillation data and cosmic microwave background shift parameter data. For statistical comparison, the same analysis has also been carried out for the wCDM dark energy model. Different model selection criteria (Akaike information criterion (AIC)) and (Bayesian Information Criterion (BIC)) give the clear indication that the reconstructed model is well consistent with the wCDM model. Then both the models (weff(z) model and wCDM model) have also been presented through (q0,j0) parameter space. Tighter constraint on the present values of dark energy equation of state parameter (wDE(z = 0)) and cosmological jerk (j0) have been achieved for the reconstructed model.

  10. Acceleration of the universe: a reconstruction of the effective equation of state

    NASA Astrophysics Data System (ADS)

    Mukherjee, Ankan

    2016-07-01

    The present work is based upon a parametric reconstruction of the effective or total equation of state in a model for the universe with accelerated expansion. The constraints on the model parameters are obtained by maximum likelihood analysis using the supernova distance modulus data, observational Hubble data, baryon acoustic oscillation data and cosmic microwave background shift parameter data. For statistical comparison, the same analysis has also been carried out for the wCDM dark energy model. Different model selection criteria (Akaike information criterion (AIC)) and (Bayesian Information Criterion (BIC)) give the clear indication that the reconstructed model is well consistent with the wCDM model. Then both the models (w_{eff}(z) model and wCDM model) have also been presented through (q_0 ,j_0 ) parameter space. Tighter constraint on the present values of dark energy equation of state parameter (w_{DE}(z = 0)) and cosmological jerk (j_0) have been achieved for the reconstructed model.

  11. Effects of nonthermal electrons on plasma expansion into vacuum

    SciTech Connect

    Bennaceur-Doumaz, D. Bara, D.; Benkhelifa, E.; Djebli, M.

    2015-01-28

    The expansion of semi-infinite plasma into vacuum is analyzed with a hydrodynamic model for cold ions assuming electrons modelled by a kappa-type distribution. Similarly to Mora study of a plasma expansion into vacuum [P. Mora, Phys. Rev. Lett. 90, 185002 (2003)], we formulated empirical expressions for the electric field strength, velocity, and position of the ion front in one-dimensional nonrelativistic, collisionless isothermally expanding plasma. Analytic expressions for the maximum ion energy and the spectrum of the accelerated ions in the plasma were derived and discussed to highlight the electron nonthermal effects on enhancing the ion acceleration in plasma expansion into vacuum.

  12. FinnCRack, a cosmic muon telescope for detector studies

    NASA Astrophysics Data System (ADS)

    Mäenpää, T.; Moilanen, H.; Ungaro, D.

    2009-06-01

    The Finnish Cosmic Rack (FinnCRack) is a position-sensitive telescope measuring the tracks of cosmic particles. The FinnCRack is based on silicon strip detectors and CERN CMS tracker data acquisition electronics. We present the FinnCRack as a reference tracker suitable for the characterization of novel detectors. The FinnCRack is unencumbered by accelerator beam time availability but suffers from a low tracking rate. The resolution of the reference tracks is 18.5μm.

  13. On particle acceleration in astrophysical relativistic jets

    NASA Astrophysics Data System (ADS)

    Medvedev, Mikhail

    2015-11-01

    Relativistic jets, e.g., in active galactic nuclei, are believed to be accelerators of high-energy cosmic rays. This is a lore but no justification of it exists. We investigate this problem from the first principles and present arguments that ``no-jets'' are better accelerators than the jets themselves. Supported by grant DOE grant DE-FG02-07ER54940 and NSF grant AST-1209665.

  14. Accelerator Test of an Imaging Calorimeter

    NASA Technical Reports Server (NTRS)

    Christl, Mark J.; Adams, James H., Jr.; Binns, R. W.; Derrickson, J. H.; Fountain, W. F.; Howell, L. W.; Gregory, J. C.; Hink, P. L.; Israel, M. H.; Kippen, R. M.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    The Imaging Calorimeter for ACCESS (ICA) utilizes a thin sampling calorimeter concept for direct measurements of high-energy cosmic rays. The ICA design uses arrays of small scintillating fibers to measure the energy and trajectory of the produced cascades. A test instrument has been developed to study the performance of this concept at accelerator energies and for comparison with simulations. Two test exposures have been completed using a CERN test beam. Some results from the accelerator tests are presented.

  15. Introduction to Particle Acceleration in the Cosmos

    NASA Technical Reports Server (NTRS)

    Gallagher, D. L.; Horwitz, J. L.; Perez, J.; Quenby, J.

    2005-01-01

    Accelerated charged particles have been used on Earth since 1930 to explore the very essence of matter, for industrial applications, and for medical treatments. Throughout the universe nature employs a dizzying array of acceleration processes to produce particles spanning twenty orders of magnitude in energy range, while shaping our cosmic environment. Here, we introduce and review the basic physical processes causing particle acceleration, in astrophysical plasmas from geospace to the outer reaches of the cosmos. These processes are chiefly divided into four categories: adiabatic and other forms of non-stochastic acceleration, magnetic energy storage and stochastic acceleration, shock acceleration, and plasma wave and turbulent acceleration. The purpose of this introduction is to set the stage and context for the individual papers comprising this monograph.

  16. On the Origin of Ultra High Energy Cosmic Rays II

    SciTech Connect

    Fowler, T K; Colgate, S; Li, H; Bulmer, R H; Pino, J

    2011-03-08

    We show that accretion disks around Active Galactic Nuclei (AGNs) could account for the enormous power in observed ultra high energy cosmic rays {approx}10{sup 20} eV (UHEs). In our model, cosmic rays are produced by quasi-steady acceleration of ions in magnetic structures previously proposed to explain jets around Active Galactic Nuclei with supermassive black holes. Steady acceleration requires that an AGN accretion disk act as a dynamo, which we show to follow from a modified Standard Model in which the magnetic torque of the dynamo replaces viscosity as the dominant mechanism accounting for angular momentum conservation during accretion. A black hole of mass M{sub BH} produces a steady dynamo voltage V {proportional_to} {radical}M{sub BH} giving V {approx} 10{sup 20} volts for M{sub BH} {approx} 10{sup 8} solar masses. The voltage V reappears as an inductive electric field at the advancing nose of a dynamo-driven jet, where plasma instability inherent in collisionless runaway acceleration allows ions to be steadily accelerated to energies {approx} V, finally ejected as cosmic rays. Transient events can produce much higher energies. The predicted disk radiation is similar to the Standard Model. Unique predictions concern the remarkable collimation of jets and emissions from the jet/radiolobe structure. Given MBH and the accretion rate, the model makes 7 predictions roughly consistent with data: (1) the jet length; (2) the jet radius; (3) the steady-state cosmic ray energy spectrum; (4) the maximum energy in this spectrum; (5) the UHE cosmic ray intensity on Earth; (6) electron synchrotron wavelengths; and (7) the power in synchrotron radiation. These qualitative successes motivate new computer simulations, experiments and data analysis to provide a quantitative verification of the model.

  17. Current and Future Measurements of Ultra-Heavy Galactic Cosmic Rays

    NASA Astrophysics Data System (ADS)

    Link, Jason; Supertiger Collaboration

    2016-03-01

    There is strong evidence from recent experiments that suggest a source of galactic cosmic rays is in superbubble regions and that particles here are accelerated through the shocks from supernova explosions. Through further study of ultra-heavy cosmic-rays, those particles with a Z >26, we can verify and explore the particle source and acceleration process of cosmic-rays. Measuring these particles is a challenge due to their low flux and high interaction cross section, requiring extremely large detectors flown on balloons and in space. In this talk we will discuss how past and recent ultra-heavy cosmic ray measurements have shaped our understanding of the cosmic-ray source and acceleration process and what we hope to learn from future measurements. We will present results on the abundances of ultra-heavy cosmic rays in the charge range 26 <= Z <= 40 from the SuperTIGER Antarctic balloon flight and compare these with previous results from ACE-CRIS and TIGER. We will also review the current status of active missions to measure ultra-heavy cosmic rays and discuss future possibilities.

  18. Development of low thermal expansion superalloy

    NASA Astrophysics Data System (ADS)

    Sato, K.; Ohno, T.

    1993-08-01

    Alloy 903 and Alloy 909 are well-known Fe-Co-Ni-Al-Ti-Nb alloys with controlled low thermal expan-sion, but they have some properties that can be improved. To improve stress-accelerated grain boundary oxidation embrittlement of Alloy 903 and instability of the γ phase of alloy 909, two new alloys with good stress-rupture ductility, high creep-rupture strength, high tensile strength at high temperature, and good controlled thermal expansion were developed. These property improvements were accomplished by the combination of optimizing the Fe-Co-Ni ratio of the matrix and stabilizing the γ phase with the addition of aluminum.

  19. COSMIC-RAY HELIUM HARDENING

    SciTech Connect

    Ohira, Yutaka; Ioka, Kunihito

    2011-03-01

    Recent observations by the CREAM and ATIC-2 experiments suggest that (1) the spectrum of cosmic-ray (CR) helium is harder than that of CR protons below the knee energy, 10{sup 15}eV, and (2) all CR spectra become hard at {approx}>10{sup 11}eV nucleon{sup -1}. We propose a new idea, that higher energy CRs are generated in a more helium-rich region, to explain the hardening without introducing different sources for CR helium. The helium-to-proton ratio at {approx}100 TeV exceeds the Big Bang abundance Y = 0.25 by several times, and the different spectrum is not reproduced within the diffusive shock acceleration theory. We argue that CRs are produced in a chemically enriched region, such as a superbubble, and the outward-decreasing abundance naturally leads to the hard spectrum of CR helium if CRs escape from the supernova remnant shock in an energy-dependent way. We provide a simple analytical spectrum that also fits well the hardening due to the decreasing Mach number in the hot superbubble with {approx}10{sup 6} K. Our model predicts hard and concave spectra for heavier CR elements.

  20. σCDM coupled to radiation: Dark energy and Universe acceleration

    NASA Astrophysics Data System (ADS)

    Abbyazov, Renat R.; Chervon, Sergey V.; Müller, Volker

    2015-07-01

    Recently, the Chiral Cosmological Model (CCM) coupled to cold dark matter (CDM) has been investigated as σCDM model to study the observed accelerated expansion of the Universe. Dark sector fields (as Dark Energy content) coupled to cosmic dust were considered as the source of Einstein gravity in Friedmann-Robertson-Walker (FRW) cosmology. Such model had a beginning at the matter-dominated era. The purposes of our present investigation are two-fold: To extend “life” of the σCDM for earlier times to radiation-dominated era and to take into account variation of the exponential potential V = V0exp -λ φ MP + V0exp -λ χ MP via variation of the interaction parameter λ. We use Markov Chain Monte Carlo (MCMC) procedure to investigate possible values of initial conditions constrained by the measured amount of the dark matter, dark energy and radiation component today. Our analysis includes dark energy contribution to critical density, the ratio of the kinetic and potential energies, deceleration parameter, effective equation of state (EoS) and evolution of DE EoS with variation of coupling constant λ. A comparison with the ΛCDM model was performed. A new feature of the model is the existence of some values of potential coupling constant, leading to a σCDM solution without transition into accelerated expansion epoch.

  1. Parametrized energy spectrum of cosmic-ray protons with kinetic energies down to 1 GeV

    NASA Technical Reports Server (NTRS)

    Tan, L. C.

    1985-01-01

    A new estimation of the interstellar proton spectrum is made in which the source term of primary protons is taken from shock acceleration theory and the cosmic ray propagation calculation is based on a proposed nonuniform galactic disk model.

  2. On Cosmic Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Florido, E.; Battaner, E.

    2010-12-01

    Magnetic fields are present in all astrophysical media. However, many models and interpretations of observations often ignore them, because magnetic fields are difficult to handle and because they produce complicated morphological features. Here we will comment on the basic intuitive properties, which even if not completely true, provide a first guiding insight on the physics of a particular astrophysical problem. These magnetic properties are not mathematically demonstrated here. How magnetic fields evolve and how they introduce dynamical effects are considered, also including a short comment on General Relativity Magnetohydrodynamics. In a second part we consider some audacious and speculative matters. They are answers to three questions: a) How draw a cube without lifting the pencil from the paper so that when the pen passes through the same side do in the same direction? B) Are MILAGRO anisotropies miraculous? C) Do cosmic magnetic lenses exist?. The last two questions deal with issues related with the interplay between magnetic fields and cosmic ray propagation.

  3. Stable Charged Cosmic Strings

    SciTech Connect

    Weigel, H.; Quandt, M.; Graham, N.

    2011-03-11

    We study the quantum stabilization of a cosmic string by a heavy fermion doublet in a reduced version of the standard model. We show that charged strings, obtained by populating fermionic bound state levels, become stable if the electroweak bosons are coupled to a fermion that is less than twice as heavy as the top quark. This result suggests that extraordinarily large fermion masses or unrealistic couplings are not required to bind a cosmic string in the standard model. Numerically we find the most favorable string profile to be a simple trough in the Higgs vacuum expectation value of radius {approx_equal}10{sup -18} m. The vacuum remains stable in our model, because neutral strings are not energetically favored.

  4. Stable charged cosmic strings.

    PubMed

    Weigel, H; Quandt, M; Graham, N

    2011-03-11

    We study the quantum stabilization of a cosmic string by a heavy fermion doublet in a reduced version of the standard model. We show that charged strings, obtained by populating fermionic bound state levels, become stable if the electroweak bosons are coupled to a fermion that is less than twice as heavy as the top quark. This result suggests that extraordinarily large fermion masses or unrealistic couplings are not required to bind a cosmic string in the standard model. Numerically we find the most favorable string profile to be a simple trough in the Higgs vacuum expectation value of radius ≈10(-18)  m. The vacuum remains stable in our model, because neutral strings are not energetically favored. PMID:21469786

  5. COSMIC monthly progress report

    NASA Technical Reports Server (NTRS)

    1994-01-01

    Activities of the Computer Software Management and Information Center (COSMIC) are summarized for the month of April 1994. Tables showing the current inventory of programs available from COSMIC are presented and program processing and evaluation activities are summarized. Five articles were prepared for publication in the NASA Tech Brief Journal. These articles (included in this report) describe the following software items: GAP 1.0 - Groove Analysis Program, Version 1.0; SUBTRANS - Subband/Transform MATLAB Functions for Image Processing; CSDM - COLD-SAT Dynamic Model; CASRE - Computer Aided Software Reliability Estimation; and XOPPS - OEL Project Planner/Scheduler Tool. Activities in the areas of marketing, customer service, benefits identification, maintenance and support, and disseminations are also described along with a budget summary.

  6. GroundBIRD: Observing Cosmic Microwave Polarization at Large Angular Scale with Kinetic Inductance Detectors and High-Speed Rotating Telescope

    NASA Astrophysics Data System (ADS)

    Oguri, S.; Choi, J.; Damayanthi, T.; Hattori, M.; Hazumi, M.; Ishitsuka, H.; Karatsu, K.; Mima, S.; Minowa, M.; Nagasaki, T.; Otani, C.; Sekimoto, Y.; Tajima, O.; Tomita, N.; Yoshida, M.; Won, E.

    2016-08-01

    Cosmic microwave background (CMB) is an important source of information about the origin of our universe. In particular, odd-parity large angular scale patterns in the CMB polarization, the primordial B-modes, are strong evidence for an inflationary universe, related to the accelerating expansion of the metric. We are developing a unique telescope, GroundBIRD, to take CMB polarization measurements. The telescope combines novel techniques: high-speed rotation scanning, cold optics, and microwave kinetic inductance detectors (MKIDs). We evaluated the response of MKIDs on the rotation stage. Method of shielding from the geo-magnetic field is established. We have also developed a receiver cryostat. We are able to maintain a sufficient cold status for observations on the optical configuration. We plan to start commissioning the system by observing CMB in Japan in 2015-2016. We will then deploy GroundBIRD in the Canary Islands for further scientific observations.

  7. Galactic cosmic ray composition

    NASA Technical Reports Server (NTRS)

    Meyer, J. P.

    1986-01-01

    An assessment is given of the galactic cosmic ray source (GCRS) elemental composition and its correlation with first ionization potential. The isotopic composition of heavy nuclei; spallation cross sections; energy spectra of primary nuclei; electrons; positrons; local galactic reference abundances; comparison of solar energetic particles and solar coronal compositions; the hydrogen; lead; nitrogen; helium; and germanium deficiency problems; and the excess of elements are among the topics covered.

  8. Carl Sagan's Cosmic Connection

    NASA Astrophysics Data System (ADS)

    Sagan, Carl; Agel, Jerome

    2000-08-01

    Foreword Freeman Dyson; Personal reflections Ann Druyan; Preface; Part I. Cosmic Perspective: 1. A transitional animal; 2. The Unicorn of Cetus; 3. A message from earth; 4. A message to earth; 5. Experiments in utopias; 6. Chauvinism; 7. Space exploration as a human enterprise I. The scientific interest; 8. Space exploration as a human enterprise II. The public interest; 9. Space exploration as a human enterprise III. The historical interest; Part II. The Solar System: 10. On teaching the first grade; 11. 'The ancient and legendary Gods of old'; 12. The Venus detective story; 13. Venus is hell; 14. Science and 'intelligence'; 15. The moons of Barsoom; 16. The mountains of Mars I. Observations from earth; 17. The mountains of Mars II. Observations from space; 18. The canals of Mars; 19. The lost pictures of Mars; 20. The Ice Age and the cauldron; 21. Beginnings and ends of the Earth; 22. Terraforming the plants; 23. The exploration and utlization of the solar system; Part III. Beyond the Solar System: 24. Some of my best friends are dolphins; 25. 'Hello, central casting? Send me twenty extraterrestrials'; 26. The cosmic connection; 27. Extraterrestrial life: an idea whose time has come; 28. Has the Earth been visited?; 29. A search strategy for detecting extraterrestrial intelligence; 30. If we succeed 31. Cables, drums, and seashells; 32. The night freight to the stars; 33. Astroengineering; 34. Twenty questions: a classification of cosmic civilisations; 35. Galactic cultural exchanges; 36. A passage to elsewhere; 37. Starfolk I. A Fable; 38. Starfolk II. A future; 39. Starfolk III. The cosmic Cheshire cats; Epilog David Morrison; Index.

  9. A Warped Cosmic String

    SciTech Connect

    Slagter, R. J.

    2010-06-23

    We present a cosmic string solution in Einstein-Yang-Mills Gauss-Bonnet theory on a warped 5 dimensional space-time conform the Randall-Sundrum-2 theory. In a simplipied model, we find an exact solutions with exponential decreasing or periodic warp function. In a more general setting, where the metric- and Yang-Mills components depend on both scales and one of the YM components resides in the bulk, we find a time dependent numerical solution.

  10. Cosmic Rays in Thunderstorms

    NASA Astrophysics Data System (ADS)

    Buitink, Stijn; Scholten, Olaf; van den Berg, Ad; Ebert, Ute

    2013-04-01

    Cosmic Rays in Thunderstorms Cosmic rays are protons and heavier nuclei that constantly bombard the Earth's atmosphere with energies spanning a vast range from 109 to 1021 eV. At typical altitudes up to 10-20 km they initiate large particle cascades, called extensive air showers, that contain millions to billions of secondary particles depending on their initial energy. These particles include electrons, positrons, hadrons and muons, and are concentrated in a compact particle front that propagates at relativistic speed. In addition, the shower leaves behind a trail of lower energy electrons from ionization of air molecules. Under thunderstorm conditions these electrons contribute to the electrical and ionization processes in the cloud. When the local electric field is strong enough the secondary electrons can create relativistic electron run-away avalanches [1] or even non-relativistic avalanches. Cosmic rays could even trigger lightning inception. Conversely, strong electric fields also influence the development of the air shower [2]. Extensive air showers emit a short (tens of nanoseconds) radio pulse due to deflection of the shower particles in the Earth's magnetic field [3]. Antenna arrays, such as AERA, LOFAR and LOPES detect these pulses in a frequency window of roughly 10-100 MHz. These systems are also sensitive to the radiation from discharges associated to thunderstorms, and provide a means to study the interaction of cosmic ray air showers and the electrical processes in thunderstorms [4]. In this presentation we discuss the involved radiation mechanisms and present analyses of thunderstorm data from air shower arrays [1] A. Gurevich et al., Phys. Lett. A 165, 463 (1992) [2] S. Buitink et al., Astropart. Phys. 33, 1 (2010) [3] H. Falcke et al., Nature 435, 313 (2005) [4] S. Buitink et al., Astron. & Astrophys. 467, 385 (2007)

  11. Cosmic ray modulation

    NASA Astrophysics Data System (ADS)

    Agarwal Mishra, Rekha; Mishra, Rajesh Kumar

    2016-07-01

    Propagation of cosmic rays to and inside the heliosphere, encounter an outward moving solar wind with cyclic magnetic field fluctuation and turbulence, causing convection and diffusion in the heliosphere. Cosmic ray counts from the ground ground-based neutron monitors at different cut of rigidity show intensity changes, which are anti-correlated with sunspot numbers. They also lose energy as they propagate towards the Earth and experience various types of modulations due to different solar activity indices. In this work, we study the first three harmonics of cosmic ray intensity on geo-magnetically quiet days over the period 1965-2014 for Beijing, Moscow and Tokyo neutron monitoring stations located at different cut off rigidity. The amplitude of first harmonic remains high for low cutoff rigidity as compared to high cutoff rigidity on quiet days. The diurnal amplitude significantly decreases during solar activity minimum years. The diurnal time of maximum significantly shifts to an earlier time as compared to the corotational direction having different cutoff rigidities. The time of maximum for first harmonic significantly shifts towards later hours and for second harmonic it shifts towards earlier hours at low cutoff rigidity station as compared to the high cut off rigidity station on quiet days. The amplitude of second/third harmonics shows a good positive correlation with solar wind velocity, while the others (i.e. amplitude and phase) have no significant correlation on quiet days. The amplitude and direction of the anisotropy on quiet days does not show any significant dependence on high-speed solar wind streams for these neutron monitoring stations of different cutoff rigidity threshold. Keywords: cosmic ray, cut off rigidity, quiet days, harmonics, amplitude, phase.

  12. FORMOSAT-3/COSMIC Mission

    NASA Astrophysics Data System (ADS)

    Cheng, F. C.; Cheng, C.

    2006-12-01

    Six identical micro-satellites of the FORMOSAT-3/COSMIC mission were successfully launched on April 14, 2006 US time. The mission is a Taiwan-US collaborative project jointly carried out by the National Space Organization (NSPO) in Taiwan and the University Corporation for Atmospheric Research (UCAR) in the United States. Each satellite carries three science payloads: a Global Positioning System (GPS) receiver which measures the amplitude and phase of GPS signals, a Tri-Band Beacon (TBB) transmitter which emits three coherent frequencies at 150 MHz, 400 MHz and 1066.7 MHz, and a Tiny Ionospheric Photometer (TIP) which measures photon emission at 135.6 nm wavelength. The FORMOSAT-3/COSMIC mission provides the first satellite constellation to obtain vertical profiles in near-real time of temperature, pressure, and water vapor in the neutral atmosphere and electron density in the ionosphere. Using the GPS radio occultation (RO) technique, the satellite constellation will take at least 2,500 measurements of vertical profiles of atmospheric air density, temperature and water vapor and ionospheric electron density every 24 hours around the globe, filling in current atmospheric data gaps over the oceans and the polar region. Combining the GPS RO data with the data from TIP and ground TBB receivers, the 3D global distribution of electron density and scintillation in the ionosphere can be obtained for space weather monitoring and modeling. Taiwan science teams are conducting an Intensive Observation Period (IOP) campaign to cross validate RO data with other observations (ground based radiosonde, weather satellites, and balloons, radars, ionosondes, etc.), and to assess the impact of FORMOSAT-3/COSMIC observations on predictions of typhoon intensity and track over eastern Asia as well as ionospheric response to storms and substorms. Highlights of early results from the FORMOSAT- 3/COSMIC mission will be presented.

  13. The cosmic background explorer

    SciTech Connect

    Gulkis, G. ); Lubin, P.M. ); Meyer, S.S. ); Silverberg, R.F.

    1990-01-01

    Late last year the National Aeronautics and Space Administration launched its first satellite dedicated to the study of phenomena related to the origins of the universe. The satellite, called the Cosmic Background Explorer (COBE), carries three complementary detectors that will make fundamental measurements of the celestial radiation. Part of that radiation is believed to have originated in processes that occurred at the very dawn of the universe. By measuring the remnant radiation at wavelengths from one micrometer to one centimeter across the entire sky, scientists hope to be able to solve many mysteries regarding the origin and evolution of the early universe. Unfortunately, these radiative relics of the early universe are weak and veiled by local astrophysical and terrestrial sources of radiation. The wavelengths of the various cosmic components may also overlap, thereby making the understanding of the diffuse celestial radiation a challenge. Nevertheless, the COBE instruments, with their full-sky coverage, high sensitivity to a wide range of wavelengths and freedom from interference from the earth's atmosphere, will constitute for astrophysicists an observatory of unprecedented sensitivity and scope. The interesting cosmic signals will then be separated from one another and from noncosmic radiation sources by a comprehensive analysis of the data.

  14. Relativistic heavy cosmic rays

    NASA Technical Reports Server (NTRS)

    Mewaldt, R. A.; Fernandez, J. I.; Israel, M. H.; Klarmann, J.; Binns, W. R.

    1972-01-01

    During three balloon flights of a 1 sq m sr ionization chamber/Cerenkov counter detector system, measurements were made of the atmospheric attenuation, flux, and charge composition of cosmic ray nuclei with 16 is less than or = Z is less than or = 30 and rigidity greater than 4.5 GV. The attenuation mean free path in air of VH (20 less than or = Z less than or = 30) nuclei is found to be 19.7 + or - 1.6 g/sq cm, a value somewhat greater than the best previous measurement. The attenuation mean free path of iron is found to be 15.6 + or - 2.2 g/sq cm, consistent with predictions of geometric cross-section formulae. An absolute flux of VH nuclei 10 to 20% higher than earlier experiments at similar geomagnetic cutoff and level of solar activity was measured. The relative abundances of even-charged nuclei are found to be in good agreement with results of other recent high resolution counter experiments. The observed cosmic ray chemical composition implies relative abundances at the cosmic ray source of Ca/Fe = 0.12 + or - 0.04 and S/Fe = 0.14 + or - 0.05.

  15. Searching for Cosmic Strings in the Cosmic Microwave Background:

    NASA Astrophysics Data System (ADS)

    Wu, Jiun-Huei Proty

    The role of cosmic defects in cosmology is entering its new phase—as a test for several fundamental physics, including unification theories and inflation. We discuss how to use the Cosmic Microwave Background (CMB) to detect cosmic strings, a type of cosmic defects, and how to use this result to constrain the underlying physics. In particular, we use the simulations for the Array for Microwave Background Anisotropy (AMiBA) to demonstrate the power of this approach. The required resolution and sensitivity in such a method are discussed, and so is the possible scientific impact.

  16. Towards a formal description of the collapse approach to the inflationary origin of the seeds of cosmic structure

    SciTech Connect

    Diez-Tejedor, Alberto; Sudarsky, Daniel E-mail: sudarsky@nucleares.unam.mx

    2012-07-01

    Inflation plays a central role in our current understanding of the universe. According to the standard viewpoint, the homogeneous and isotropic mode of the inflaton field drove an early phase of nearly exponential expansion of the universe, while the quantum fluctuations (uncertainties) of the other modes gave rise to the seeds of cosmic structure. However, if we accept that the accelerated expansion led the universe into an essentially homogeneous and isotropic space-time, with the state of all the matter fields in their vacuum (except for the zero mode of the inflaton field), we can not escape the conclusion that the state of the universe as a whole would remain always homogeneous and isotropic. It was recently proposed in [A. Perez, H. Sahlmann and D. Sudarsky, {sup O}n the quantum origin of the seeds of cosmic structure{sup ,} Class. Quant. Grav. 23 (2006) 2317–2354] that a collapse (representing physics beyond the established paradigm, and presumably associated with a quantum-gravity effect à la Penrose) of the state function of the inflaton field might be the missing element, and thus would be responsible for the emergence of the primordial inhomogeneities. Here we will discuss a formalism that relies strongly on quantum field theory on curved space-times, and within which we can implement a detailed description of such a process. The picture that emerges clarifies many aspects of the problem, and is conceptually quite transparent. Nonetheless, we will find that the results lead us to argue that the resulting picture is not fully compatible with a purely geometric description of space-time.

  17. Effects of anisotropic dynamics on cosmic strings

    SciTech Connect

    Kunze, Kerstin E.

    2011-08-01

    The dynamics of cosmic strings is considered in anisotropic backgrounds. In particular, the behaviour of infinitely long straight cosmic strings and of cosmic string loops is determined. Small perturbations of a straight cosmic string are calculated. The relevance of these results is discussed with respect to the possible observational imprints of an anisotropic phase on the behaviour of a cosmic string network.

  18. Cosmic microwave background snapshots: pre-WMAP and post-WMAP.

    PubMed

    Bond, J Richard; Contaldi, Carlo; Pogosyan, Dmitry

    2003-11-15

    We highlight the remarkable evolution in the cosmic microwave background (CMB) power spectrum C(l) as a function of multipole l over the past few years, and in the cosmological parameters for minimal inflation models derived from it: from anisotropy results before 2000; in 2000 and 2001 from Boomerang, Maxima and the Degree Angular Scale Interferometer (DASI), extending l to approximately 1000; and in 2002 from the Cosmic Background Imager (CBI), Very Small Array (VSA), ARCHEOPS and Arcminute Cosmology Bolometer Array Receiver (ACBAR), extending l to approximately 3000, with more from Boomerang and DASI as well. Pre-WMAP (pre-Wilkinson Microwave Anisotropy Probe) optimal band powers are in good agreement with each other and with the exquisite one-year WMAP results, unveiled in February 2003, which now dominate the l less, similar 600 bands. These CMB experiments significantly increased the case for accelerated expansion in the early Universe (the inflationary paradigm) and at the current epoch (dark energy dominance) when they were combined with "prior" probabilities on the parameters. The minimal inflation parameter set, [omega(b), omega(cdm), Omega(tot), Omega(Lambda), n(s), tau(C), sigma(8)], is applied in the same way to the evolving data. C(l) database and Monte Carlo Markov Chain (MCMC) methods are shown to give similar values, which are highly stable over time and for different prior choices, with the increasing precision best characterized by decreasing errors on uncorrelated "parameter eigenmodes". Priors applied range from weak ones to stronger constraints from the expansion rate (HST-h), from cosmic acceleration from supernovae (SN1) and from galaxy clustering, gravitational lensing and local cluster abundance (LSS). After marginalizing over the other cosmic and experimental variables for the weak + LSS prior, the pre-WMAP data of January 2003 compared with the post-WMAP data of March 2003 give Omega(tot) = 1.03(-0.04)(+0.05) compared with 1

  19. ORIGIN OF THE COSMIC-RAY SPECTRAL HARDENING

    SciTech Connect

    Tomassetti, Nicola

    2012-06-10

    Recent data from ATIC, CREAM, and PAMELA indicate that the cosmic-ray energy spectra of protons and nuclei exhibit a remarkable hardening at energies above 100 GeV nucleon{sup -1}. We propose that the hardening is an interstellar propagation effect that originates from a spatial change of the cosmic-ray transport properties in different regions of the Galaxy. The key hypothesis is that the diffusion coefficient is not separable into energy and space variables as usually assumed. Under this scenario, we can reproduce the observational data well. Our model has several implications for cosmic-ray acceleration/propagation physics and can be tested by ongoing experiments such as the Alpha Magnetic Spectrometer or Fermi-LAT.

  20. Cosmic superstrings and primordial magnetogenesis

    SciTech Connect

    Davis, Anne-Christine; Dimopoulos, Konstantinos

    2005-08-15

    Cosmic superstrings are produced at the end of brane inflation. Their properties are similar to cosmic strings arising in grand unified theories. Like cosmic strings they can give rise to a primordial magnetic field, as a result of vortical motions stirred in the ionized plasma by the gravitational pull of moving string segments. The resulting magnetic field is both strong enough and coherent enough to seed the galactic dynamo and explain the observed magnetic fields of the galaxies.

  1. Cosmic strings and galaxy formation

    NASA Technical Reports Server (NTRS)

    Bertschinger, Edmund

    1989-01-01

    The cosmogonical model proposed by Zel'dovich and Vilenkin (1981), in which superconducting cosmic strings act as seeds for the origin of structure in the universe, is discussed, summarizing the results of recent theoretical investigations. Consideration is given to the formation of cosmic strings, the microscopic structure of strings, gravitational effects, cosmic string evolution, and the formation of galaxies and large-scale structure. Simulation results are presented in graphs, and several outstanding issues are listed and briefly characterized.

  2. Cosmic ray driven Galactic winds

    NASA Astrophysics Data System (ADS)

    Recchia, S.; Blasi, P.; Morlino, G.

    2016-08-01

    The escape of cosmic rays from the Galaxy leads to a gradient in the cosmic ray pressure that acts as a force on the background plasma, in the direction opposite to the gravitational pull. If this force is large enough to win against gravity, a wind can be launched that removes gas from the Galaxy, thereby regulating several physical processes, including star formation. The dynamics of these cosmic ray driven winds is intrinsically non-linear in that the spectrum of cosmic rays determines the characteristics of the wind (velocity, pressure, magnetic field) and in turn the wind dynamics affects the cosmic ray spectrum. Moreover, the gradient of the cosmic ray distribution function causes excitation of Alfvén waves, that in turn determine the scattering properties of cosmic rays, namely their diffusive transport. These effects all feed into each other so that what we see at the Earth is the result of these non-linear effects. Here we investigate the launch and evolution of such winds, and we determine the implications for the spectrum of cosmic rays by solving together the hydrodynamical equations for the wind and the transport equation for cosmic rays under the action of self-generated diffusion and advection with the wind and the self-excited Alfvén waves.

  3. The Cosmic Microwave Background & Inflation, Then & Now

    NASA Astrophysics Data System (ADS)

    Bond, J. Richard; Contaldi, Carlo; Pogosyan, Dmitry; Mason, Brian; Myers, Steve; Pearson, Tim; Pen, Ue-Li; Prunet, Simon; Readhead, Tony; Sievers, Jonathan

    2002-12-01

    The most recent results from the Boomerang, Maxima, DASI, CBI and VSA CMB experiments significantly increase the case for accelerated expansion in the early universe (the inflationary paradigm) and at the current epoch (dark energy dominance). This is especially so when combined with data on high redshift supernovae (SN1) and large scale structure (LSS), encoding information from local cluster abundances, galaxy clustering, and gravitational lensing. There are ``7 pillars of Inflation'' that can be shown with the CMB probe, and at least 5, and possibly 6, of these have already been demonstrated in the CMB data: (1) the effects of a large scale gravitational potential, demonstrated with COBE/DMR in 1992-96 (2) acoustic peaks/dips in the angular power spectrum of the radiation, which tell about the geometry of the Universe, with the large first peak convincingly shown with Boomerang and Maxima data in 2000, a multiple peak/dip pattern shown in data from Boomerang and DASI (2nd, 3rd peaks, first and 2nd dips in 2001) and from CBI (2nd, 3rd, 4th, 5th peaks, 3rd, 4th dips at 1-sigma in 2002) (3) damping due to shear viscosity and the width of the region over which hydrogen recombination occurred when the universe was 400000 years old (CBI 2002) (4) the primary anisotropies should have a Gaussian distribution (be maximally random) in almost all inflationary models, the best data on this coming from Boomerang; (5) secondary anisotropies associated with nonlinear phenomena subsequent to 400000 years, which must be there and may have been detected by CBI and another experiment, BIMA. Showing the 5 ``pillars'' involves detailed confrontation of the experimental data with theory; e.g., (5) compares the CBI data with predictions from two of the largest cosmological hydrodynamics simulations ever done. DASI, Boomerang and CBI in 2002, AMiBA in 2003, and many other experiments have the sensitivity to demonstrate the next pillar, (6) polarization, which must be there at the ~ 7

  4. Observation of Energy-Dependent Electron-Capture Decay in Secondary Galactic Cosmic Rays

    NASA Astrophysics Data System (ADS)

    Niebur, S. M.; Binns, W. R.; Hink, P. L.; Israel, M. H.; Klarmann, J.; Lijowski, M.; Christian, E. R.; von Rosenvinge, T. T.; Cummings, A. C.; George, J. S.; Leske, R. A.; Mewaldt, R. A.; Stone, E. C.; Wiedenbeck, M. E.; Yanasak, N. E.

    2000-04-01

    Secondary galactic cosmic rays are produced at cosmic ray energies by fragmentation of primary cosmic rays during propagation through the interstellar medium; these nuclei carry a signature of the energy at which they were produced. Although electron-capture decay is inhibited at most of the energies typical of cosmic rays, decay is possible at the lower energies for isotopes such as 51Cr and 49V. We have analyzed Titanium, Vanadium, and Chromium isotopic data from the Cosmic Ray Isotope Spectrometer on ACE and found evidence of electron-capture decay at lower energies. We will present a comparison of secondary electron-capture decay isotope abundances and abundances of their decay products with results from improved propagation models in order to discuss the amount of electron-capture decay and subsequent acceleration that may have occurred during propagation.

  5. Electron capture decay of cosmic rays: A model of the inhomogeneous interstellar medium

    NASA Technical Reports Server (NTRS)

    Letaw, J. R.; Silberberg, R.; Tsao, C. H.

    1985-01-01

    Traditional analyses of cosmic ray composition seek to identify the sources through a determination of a the isotopic abundances of these nuclei prior to acceleration. At the same time, it is both necessary and interesting to understand the nature of the medium through which cosmic rays pass before arriving at detectors. In fact, only within a model of the interstellar medium (ISM) sampled by cosmic rays can a refined estimate of source composition be made. An elaboration of the traditional model of the ISM used in studying cosmic ray propagation is explored. Inhomogeneity of the ISM is accomodated in this model. Within this model it is found that the abundances of some electron apture isotopes, are very sensitive to density inhomogeneities which might be expected in the ISM. These nuclei therefore measure the penetration of heavy cosmic rays into interstellar clouds.

  6. Evading the pulsar constraints on the cosmic string tension in supergravity inflation

    SciTech Connect

    Kamada, Kohei; Miyamoto, Yuhei; Yokoyama, Jun'ichi E-mail: miyamoto@resceu.s.u-tokyo.ac.jp

    2012-10-01

    The cosmic string is a useful probe of the early Universe and may give us a clue to physics at high energy scales which particle accelerators cannot reach. Although the most promising tool to observe it is the cosmic microwave background (CMB), the constraint from gravitational waves is becoming so stringent that detecting its signatures in CMB may be impossible. In this paper, we construct a scenario that contains cosmic strings observable in the cosmic microwave background while evading the constraint imposed by the recent pulsar timing data. We argue that cosmic strings with relatively large tension are allowed by diluting loops contributing to the relevant frequency range of the gravitational wave background. We also present a particle physics model to realize such dilution in the context of chaotic inflation in supergravity, where the phase transition occurs during inflation due to the time-dependence of the Hubble induced mass.

  7. The Accelerating Universe

    SciTech Connect

    Blandford, Roger

    2013-05-15

    From keV electrons in terrestrial aurorae to Ultra High Energy Cosmic Rays from unidentified "Zevatrons", the cosmos shows a plutocratic proclivity to concentrate energy in a tiny minority of suprathermal particles. The mechanisms involved can be traced back to the ideas of Faraday, Fermi and Alfvén though we are learning that the details are idiosyncratic to the many environments that we have observed and that much can be learned from comparing and contrasting particle acceleration in laboratory and diverse astronomical locations. It will be argued that new mechanisms are required to account for recent observations of galactic nuclei, pulsar wind nebulae and interplanetary, interstellar and intergalactic media and some candidates will be discussed.

  8. Ultra-High Energy Cosmic Rays

    NASA Astrophysics Data System (ADS)

    Colon, Rafael Antonio; Moncada, Roberto; Guerra, Juan; Anchordoqui, Luis

    2016-01-01

    The search for the origin(s) of ultra-high energy (UHE) cosmic rays (CR) remains one of the cornerstones of high energy astrophysics. The previously proposed sources of acceleration for these UHECRs were gamma-ray bursts (GRB) and active galactic nuclei (AGN) due to their energetic activity and powerful jets. However, a problem arises between the acceleration method and the observed CR spectrum. The CRs from GRBs or AGN jets are assumed to undergo Fermi acceleration and a source injection spectrum proportional to E^-2 is expected. However, the most recent fits to the spectrum and nuclear composition suggest an injection spectrum proportional to E^-1. It is well known that such a hard spectrum is characteristic of unipolar induction of rotating compact objects. When this method is applied to the AGN cores, they prove to be much too luminous to accelerate CR nuclei without photodisintegrating, thus creating significant energy losses. Instead, here we re-examine the possibility of these particles being accelerated around the much less luminous quasar remnants, or dead quasars. We compare the interaction times of curvature radiation and photodisintegration, the two primary energy loss considerations with the acceleration time scale. We show that the energy losses at the source are not significant enough as to prevent these CRs from reaching the maximum observed energies. Using data from observatories in the northern and southern sky, the Telescope Array and the Pierre Auger Observatory respectively, two hotspots have been discerned which have some associated quasar remnants that help to motivate our study.

  9. On Becoming a Cosmic Educator. Spotlight: Cosmic Education.

    ERIC Educational Resources Information Center

    Maier, Biff

    2002-01-01

    Discusses Maria Montessori's five pedagogical guidelines for her Cosmic Education concept: starting with the larger context; treating planet Earth as a cosmic organism; stressing similarities among seemingly different groups of people, organisms, or objects; showing chains of interdependence among all things; and examining behavior from a cosmic…

  10. The Emergence of Cosmic Education. Spotlight: Cosmic Education.

    ERIC Educational Resources Information Center

    Trudeau, Sr. Christina Marie

    2002-01-01

    Discusses the influence of Hindu, Moslem, and Buddhist metaphysics on Maria Montessori's own pedagogical philosophy of Cosmic Education, which she regarded as the core of all learning experiences, after her visit to India. Considers the relationship between Montessori's ideas of child development and Cosmic Education, and the effect of Indian…

  11. Phantom Cosmic Ray Decreases and their Extraterrestrial Origins

    NASA Astrophysics Data System (ADS)

    Thomas, Simon; Owens, Mathew; Lockwood, Mike; Scott, Chris

    2014-05-01

    Galactic cosmic rays are extremely high energy charged particles accelerated at extra-solar sources such as supernovae, active galactic nuclei, quasars, and gamma-ray bursts. Upon arrival at Earth's atmosphere, they collide with air molecules to produce a shower of secondary particles. One product of this air shower is energetic neutrons, which can be detected at the Earth's surface. Neutron monitors have been routinely operating for more than half a century and have shown that the cosmic ray flux at the top of the atmosphere is modulated by the heliospheric magnetic field (HMF), both at solar cycle time scales and due to shorter-term HMF variations, such as result from coronal mass ejections (CMEs). When a CME passes over the Earth, the neutron monitor counts are reduced sharply and suddenly (in a matter of hours) due to the modulation of cosmic rays by the enhancement in the heliospheric magnetic field (HMF). Such a drop in neutron counts is known as a Forbush Decrease. We present examples of unusual Forbush Decreases where there is no disturbance in the HMF at Earth at the time, which we name 'Phantom Cosmic Ray Decreases' (PCRDs). For recent PCRD events, we examine STEREO in-situ data and in each case, we find a large CME in either STEREO-A or -B. We also study neutron counts for each event from a number of neutron monitors at different longitudes. Differences between the size of the cosmic ray decreases at different longitudes are shown to give information on the location of the cosmic ray modulation source. We thus propose that these PCRDs are caused by CMEs which have missed Earth but which are large and intense enough to block out galactic cosmic rays on trajectories toward Earth.

  12. Cosmic Dawn with WFIRST

    NASA Astrophysics Data System (ADS)

    Rhoads, James

    Central objectives: WFIRST-AFTA has tremendous potential for studying the epoch of "Cosmic Dawn" the period encompassing the formation of the first galaxies and quasars, and their impact on the surrounding universe through cosmological reionization. Our goal is to ensure that this potential is realized through the middle stages of mission planning, culminating in designs for both WFIRST and its core surveys that meet the core objectives in dark energy and exoplanet science, while maximizing the complementary Cosmic Dawn science. Methods: We will consider a combined approach to studying Cosmic Dawn using a judicious mixture of guest investigator data analysis of the primary WFIRST surveys, and a specifically designed Guest Observer program to complement those surveys. The Guest Observer program will serve primarily to obtain deep field observations, with particular attention to the capabilities of WFIRST for spectroscopic deep fields using the WFI grism. We will bring to bear our years of experience with slitless spectroscopy on the Hubble Space Telescope, along with an expectation of JWST slitless grism spectroscopy. We will use this experience to examine the implications of WFIRST’s grism resolution and wavelength coverage for deep field observations, and if appropriate, to suggest potential modifications of these parameters to optimize the science return on WFIRST. We have assembled a team of experts specializing in (1) Lyman Break Galaxies at redshifts higher than 7 (2) Quasars at high redshifts (3) Lyman-alpha galaxies as probes of reionization (4) Theoretical simulations of high-redshift galaxies (5) Simulations of grism observations (6) post-processing analysis to find emission line galaxies and high redshift galaxies (7) JWST observations and calibrations. With this team we intend to do end-to-end simulations starting with halo populations and expected spectra of high redshift galaxies and finally extracting what we can learn about (a) reionization

  13. The Energetic Trans-Iron Cosmic-ray Experiment (ENTICE)

    NASA Technical Reports Server (NTRS)

    Binns, W. R.; Adams. J. H.; Barghouty, A. F.; Christian, E. R.; Cummings, A. C.; Hams, T.; Israel, M. H.; Labrador, A. W.; Leske, R. A.; Link, J. T.; Mewwaldt, R. A.; Mitchell, J. W.; De Nolfo, G. A.; Sasaki, M.; Stone, E. C.; Waddington, C. J.; Wiedenbeck, M. E.

    2009-01-01

    The ENTICE experiment is one of two instruments that comprise the "Orbiting Astrophysical Spectrometer in Space (OASIS)", which is presently undergoing a NASA "Astrophysics Strategic Mission Concept Study". ENTICE is designed to make high precision measurements of the abundances of individual elements from neon through the actinides and, in addition, will search for possible superheavy nuclei in the galactic cosmic rays. The ENTICE instrument utilizes silicon detectors, aerogel and acrylic Cherenkov counters, and a scintillating optical fiber hodoscope to measure the charge and energy of these ultra-heavy nuclei for energies greater than 0.5 GeV/nucleon. It is a large instrument consisting of four modules with a total effective geometrical factor of approx.20 sq m sr. Measurements made in space for a period of three years with ENTICE will enable us to determine if cosmic rays include a component of recently synthesized transuranic elements (Pu-94 and Cm-96), to measure the age of that component, and to test the model of the OB association origin of galactic cosmic rays. Additionally, these observations will enable us to study how diffusive shock acceleration of cosmic rays operates differently on interstellar grains and gas. Keywords: cosmic rays Galaxy:abundances

  14. Actinides in the Source of Cosmic Rays and the Present Interstellar Medium

    NASA Technical Reports Server (NTRS)

    Lingenfelter, R. E.; Higdon, J. C.; Kratz, K. -L.

    2003-01-01

    The abundances of the actinide elements in the cosmic rays can provide critical constraints on the major sites of their acceleration. Using recent calculations of the r-process yields in core collapse supernovae, we have determined the actinide abundances averaged over various assumed time intervals for their supernova generation and their cosmic-ray acceleration. Using standard Galactic chemical evolution models, we have also determined the expected actinide abundances in the present interstellar medium. From these two components, we have calculated the U/Th and other actinide abundances expected in the supernova-active cores of superbubbles, as a function of their ages and mean metallicity resulting from dilution with interstellar cloud debris. Then, using observations of the fractions of Galactic supernovae that occur in superbubbles and in the rest of the interstellar medium, we calculate the expected actinide abundances in cosmic rays accelerated by Galactic supernovae. We find that the current measurements of actinide/Pt-group and preliminary estimates of the UPuCm/Th ratio in cosmic rays are all consistent with the expected values if superbubble cores have mean metallicities of around 3 times solar. Such metallicities are quite comparable to the superbubble core metallicities inferred from other cosmic-ray observations. Future, more precise measurements of these ratios with experiments such as ECCO are needed to provide a better measure of the mean source metallicity sampled by the local Galactic cosmic rays. Measurements of the cosmic- ray actinide abundances have been favorably compared with the protosolar ratio, inferred from present solar system abundances, to infer that the cosmic rays are accelerated from the general interstellar medium. We suggest, however, that such an inference is not valid because the expected actinide abundances in the present interstellar medium are very different from the protosolar values, which sampled the interstellar medium

  15. CosmicSIG science and plans

    NASA Astrophysics Data System (ADS)

    Olinto, Angela V.

    2014-03-01

    Recent activities of the Cosmic Ray Science Interest Group (CosmicSIG) of the Physics of the Cosmos PAG will be reviewed. CosmicSIG was formed to provide an assessment to NASA HQ and the PCOS program office of the status of current and future missions in the area of cosmic-ray astrophysics. CosmicSIG also strives to act as a focal point and forum for the cosmic ray community.

  16. NASA's Chandra Reveals Origin of Key Cosmic Explosions

    NASA Astrophysics Data System (ADS)

    2010-02-01

    WASHINGTON -- New findings from NASA's Chandra X-ray Observatory have provided a major advance in understanding a type of supernova critical for studying the dark energy that astronomers think pervades the universe. The results show mergers of two dense stellar remnants are the likely cause of many of the supernovae that have been used to measure the accelerated expansion of the universe. These supernovae, called Type Ia, serve as cosmic mile markers to measure expansion of the universe because they can be seen at large distances, and they follow a reliable pattern of brightness. However, until now, scientists have been unsure what actually causes the explosions. "These are such critical objects in understanding the universe," said Marat Gilfanov of the Max Planck Institute for Astrophysics in Germany and lead author of the study that appears in the Feb. 18 edition of the journal Nature. "It was a major embarrassment that we did not know how they worked. Now we are beginning to understand what lights the fuse of these explosions." Most scientists agree a Type Ia supernova occurs when a white dwarf star -- a collapsed remnant of an elderly star -- exceeds its weight limit, becomes unstable and explodes. Scientists have identified two main possibilities for pushing the white dwarf over the edge: two white dwarfs merging or accretion, a process in which the white dwarf pulls material from a sun-like companion star until it exceeds its weight limit. "Our results suggest the supernovae in the galaxies we studied almost all come from two white dwarfs merging," said co-author Akos Bogdan, also of Max Planck. "This is probably not what many astronomers would expect." The difference between these two scenarios may have implications for how these supernovae can be used as "standard candles" -- objects of a known brightness -- to track vast cosmic distances. Because white dwarfs can come in a range of masses, the merger of two could result in explosions that vary somewhat in

  17. The composition of cosmic rays at high energies

    NASA Technical Reports Server (NTRS)

    Muller, Dietrich

    1989-01-01

    Measurements of the composition of the cosmic rays at high energies, and of the energy spectra of the individual components provide the basis for the understanding of the sources, of the acceleration mechanism, and of the galactic containment of these particles. A brief review of the presently available information and a recent measurement performed on the Space Shuttle to substantially extend the range of energies in which the elemental composition is known are described. Results, and recent data on the electron component of cosmic rays are discussed and summarized. The body of data now available contains several features that are difficult to explain within current models of galactic shock acceleration and 'leakly box' containment. The need for further measurements is emphasized and possible opportunities for future work are briefly discussed.

  18. Spallation processes and nuclear interaction products of cosmic rays

    NASA Technical Reports Server (NTRS)

    Silberberg, R.; Tsao, C. H.

    1990-01-01

    Most cosmic-ray nuclei heavier than helium have suffered nuclear collisions in the interstellar gas, with transformation of nuclear composition. The isotopic and elemental composition at the sources has to be inferred from the observed composition near the Earth. The source composition permits tests of current ideas on sites of origin, nucleosynthesis in stars, evolution of stars, the mixing and composition of the interstellar medium and injection processes prior to acceleration. The effects of nuclear spallation, production of radioactive nuclides and the time dependence of their decay provide valuable information on the acceleration and propagation of cosmic rays, their nuclear transformations, and their confinement time in the Galaxy. The formation of spallation products that only decay by electron capture and are relatively long-lived permits an investigation of the nature and density fluctuations (like clouds) of the interstellar medium. Since nuclear collisions yield positrons, antiprotons, gamma rays and neutrinos, we shall discuss these topics briefly.

  19. Structure Shocks as a Source of Cosmic Rays in Clusters

    NASA Astrophysics Data System (ADS)

    Jones, T. W.; Miniati, F.; Ryu, D.; Kang, H.; Hallman, E. J.

    Shocks are a ubiquitous consequence of cosmic structure formation, and they play an essential role in heating galaxy cluster media. Virtually all of the gas in clusters has been processed by one or more shocks of at least moderate strength. These are collisionless shocks, so likely sites for diffusive shock acceleration of high energy particles. We have carried out numerical simulations of cosmic structure formation that directly include acceleration and transport of nonthermal protons, as well as primary and secondary electrons. Nonthermal emissions have also been computed from the resulting particle spatial and energy distributions. Here we outline some of our current findings, showing that nonthermal protons may contribute a significant pressure in cluster media, and that expected radio, X-ray and $\\gamma$-ray emissions from these populations should be important cluster diagnostics.

  20. Cosmic Microwave Background Polarization and Inflation

    NASA Technical Reports Server (NTRS)

    Chuss, David T.

    2011-01-01

    Measurements of the cosmic microwave background (CMB) offer a means to explore the universe at a very early epoch. Specifically, if the universe went through a brief period of exponential expansion called inflation as current data suggest, gravitational waves from this period would polarize the CMB in a specific pattern. At GSFC, we are currently working towards two experiments that work in concert to measure this polarization pattern in search of evidence for inflation. The Cosmology Large Angular Scale Surveyor (CLASS) will measure the polarization at frequencies between 40 and 150 GHz from the Atacama Desert in Chile. The Primordial Inflation Polarization Explorer (PIPER) is a balloon-borne experiment that will make similar measurements at frequencies between 200 and 600 GHz.