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Sample records for assumed cosmic ray-modulated

  1. 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.

  2. Heliospheric Impact on Cosmic Rays Modulation

    NASA Astrophysics Data System (ADS)

    Tiwari, Bhupendra Kumar

    2016-07-01

    Heliospheric Impact on Cosmic RaysModulation B. K. Tiwari Department of Physics, A. P. S. University, Rewa (M.P.), btiwari70@yahoo.com Cosmic rays (CRs) flux at earth is modulated by the heliosphereric magnetic field and the structure of the heliosphere, controls by solar outputs and their variability. Sunspots numbers (SSN) is often treated as a primary indicator of solar activity (SA). GCRs entering the helioshphere are affected by the interplanetary magnetic field (IMF) and solar wind speed, their modulation varies with the varying solar activity. The observation based on data recoded from Omniweb data Centre for solar- interplanetary activity indices and monthly mean count rate of cosmic ray intensity (CRI) data from neutron monitors of different cut-off rigidities(Rc) (Moscow Rc=2.42Gv and Oulu Rc=0.80Gv). During minimum solar activity periodof solar cycle 23/24, the sun is remarkably quiet, weakest strength of the IMF and least dense and slowest, solar wind speed, whereas, in 2003, highest value of yearly averaged solar wind speed (~568 Km/sec) associated with several coronal holes, which generate high speed wind stream has been recorded. It is observed that GCRs fluxes reduces and is high anti-correlated with SSN (0.80) and IMF (0.86). CRI modulation produces by a strong solar flare, however, CME associated solar flare produce more disturbance in the interplanetary medium as well as in geomagnetic field. It is found that count rate of cosmic ray intensity and solar- interplanetary parameters were inverse correlated and solar indices were positive correlated. Keywords- Galactic Cosmic rays (GCRs), Sunspot number (SSN), Solar activity (SA), Coronal Mass Ejection (CME), Interplanetary magnetic field (IMF)

  3. Are cosmic rays modulated beyond the heliopause?

    SciTech Connect

    Kóta, J.; Jokipii, J. R.

    2014-02-10

    We discuss the possible spatial variation of Galactic and anomalous cosmic rays (GCRs and ACRs) at and beyond the heliopause (HP). Remaining within the framework of the Parker transport equation and assuming incompressible plasma in the heliosheath, we consider highly idealized simple-flow models and compare our GCR results with recent publications of Scherer et al. and Strauss et al. First, we discuss an order-of-magnitude estimate and a simple spherical model to demonstrate that the modulation of GCRs beyond the HP must be quite small if the diffusion coefficient beyond the HP is greater than ≈10{sup 26} cm{sup 2} s{sup –1}, a value that is two orders of magnitude smaller than the value of 10{sup 28} cm{sup 2} s{sup –1} determined from observations of GCR composition. Second, we construct a non-spherical model, which allows lateral deflection of the flow and uses different diffusion coefficients parallel and perpendicular to the magnetic field. We find that modulation of GCRs beyond the HP remains small even if the perpendicular diffusion coefficient beyond the HP is quite small (≈10{sup 22} cm{sup 2} s{sup –1}) as long as the parallel diffusion is sufficiently fast. We also consider the case when the parallel diffusion beyond the HP is fast, but the perpendicular diffusion is as small as ≈10{sup 20} cm{sup 2} s{sup –1}; this results in a sharp, almost step-like increase of GCR flux (and decrease of ACRs) at the HP. Possible implications are briefly discussed. We further suggest the possibility that the observed sharp gradient of GCRs at the HP might push the HP closer to the Sun than previously thought.

  4. Are Cosmic Rays Modulated beyond the Heliopause?

    NASA Astrophysics Data System (ADS)

    Kóta, J.; Jokipii, J. R.

    2014-02-01

    We discuss the possible spatial variation of Galactic and anomalous cosmic rays (GCRs and ACRs) at and beyond the heliopause (HP). Remaining within the framework of the Parker transport equation and assuming incompressible plasma in the heliosheath, we consider highly idealized simple-flow models and compare our GCR results with recent publications of Scherer et al. and Strauss et al. First, we discuss an order-of-magnitude estimate and a simple spherical model to demonstrate that the modulation of GCRs beyond the HP must be quite small if the diffusion coefficient beyond the HP is greater than ≈1026 cm2 s-1, a value that is two orders of magnitude smaller than the value of 1028 cm2 s-1 determined from observations of GCR composition. Second, we construct a non-spherical model, which allows lateral deflection of the flow and uses different diffusion coefficients parallel and perpendicular to the magnetic field. We find that modulation of GCRs beyond the HP remains small even if the perpendicular diffusion coefficient beyond the HP is quite small (≈1022 cm2 s-1) as long as the parallel diffusion is sufficiently fast. We also consider the case when the parallel diffusion beyond the HP is fast, but the perpendicular diffusion is as small as ≈1020 cm2 s-1 this results in a sharp, almost step-like increase of GCR flux (and decrease of ACRs) at the HP. Possible implications are briefly discussed. We further suggest the possibility that the observed sharp gradient of GCRs at the HP might push the HP closer to the Sun than previously thought.

  5. Cosmic ray modulation and merged interaction regions

    NASA Technical Reports Server (NTRS)

    Burlaga, L. F.; Goldstein, M. L.; Mcdonald, F. B.

    1985-01-01

    Beyond several AU, interactions among shocks and streams give rise to merged interaction regions in which the magnetic field is turbulent. The integral intensity of . 75 MeV/Nuc cosmic rays at Voyager is generally observed to decrease when a merged interaction region moves past the spacecraft and to increase during the passage of a rarefaction region. When the separation between interaction regions is relatively large, the cosmic ray intensity tends to increase on a scale of a few months. This was the case at Voyager 1 from July 1, 1983 to May 1, 1984, when the spacecraft moved from 16.7 to 19.6 AU. Changes in cosmic ray intensity were related to the magnetic field strength in a simple way. It is estimated that the diffusion coefficient in merged interaction regions at this distance is similar to 0.6 x 10 to the 22nd power sq cm/s.

  6. Cosmic ray modulation over a solar cycle.

    NASA Astrophysics Data System (ADS)

    Ferreira, Stefan; Manuel, Rex; Potgieter, Marius

    2016-07-01

    The time-dependent modulation of galactic cosmic rays in the heliosphere is studied over different polarity cycles by computing 2.5 GV proton intensities using a two-dimensional, time-dependent modulationmodel. By incorporating recent theoretical advances in the relevant transport parameters in the model, we showed in previous work that this approach gave realistic computed intensities over a solar cycle. New in this work is that a time dependence of the solar wind termination shock (TS) position is implemented in our model to study the effect of a dynamic inner heliosheath thickness (the region between the TS and heliopause) on the solar modulation of galactic cosmic rays. The study reveals that changes in the inner heliosheath thickness, arising from a time-dependent shock position, does affect cosmic-ray intensities everywhere in the heliosphere over a solar cycle, with the smallest effect in the innermost heliosphere. A time-dependent TS position causes a phase difference between the solar activity periods and the corresponding intensity periods. The maximum intensities in response to a solarminimum activity period are found to be dependent on the time-dependent TS profile. It is found that changing the width of the inner heliosheath with time over a solar cycle can shift the time of when the maximum or minimum cosmic-ray intensities occur at various distances throughout the heliosphere, but more significantly in the outer heliosphere. The time-dependent extent of the inner heliosheath, as affected by solar activity conditions, is thus an additional time-dependent factor to be considered in the long-term modulation of cosmic rays.

  7. Rigidity Dependence of Cosmic Ray Modulation

    NASA Astrophysics Data System (ADS)

    Agarwal Mishra, Rekha; Mishra, Rajesh Kumar

    2012-07-01

    The various observed harmonics of the cosmic ray variation may be understood on a unified basis if the free space cosmic ray anisotropy is non-sinusoidal in form. The major objective of this paper is to study the first three harmonics of cosmic ray intensity on geo-magnetically quiet days over the period 1965-1990 for Deep River, Goose Bay and Tokyo neutron monitoring stations. The amplitude of first harmonic remains high for Deep River having low cutoff rigidity as compared to Tokyo neutron monitor having high cutoff rigidity on quiet days. The diurnal amplitude significantly decreases in 1987 at Deep River and in 1986 at Tokyo during solar activity minimum years. The diurnal time of maximum significantly shifts to an earlier time as compared to the corotational direction at both the stations 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 i.e. Deep River as compared to the high cut off rigidity station i.e. Tokyo 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 solar wind velocity significantly remains in the range 350 to 425 km/s i.e. being nearly average on quiet days. The amplitude and direction of the anisotropy on quiet days are weakly dependent on high-speed solar wind streams for these neutron monitoring stations of low and high cutoff rigidity threshold. Keywords: cosmic ray, cut off rigidity, quiet days, harmonics.

  8. Galactic cosmic-ray modulation near the heliopause

    SciTech Connect

    Guo, X.; Florinski, V.

    2014-09-20

    We investigate the modulation of galactic cosmic rays in the inner and outer heliosheaths using three-dimensional numerical simulations. The model is based on the Parker transport equation integrated using a stochastic phase-space trajectory method. Integration is performed on a plasma background obtained from a global three-dimensional magnetohydrodynamic simulations. Our results predict a negligible amount of modulation in the outer heliosheath because of weak scattering of cosmic ray ions owing to very low levels of magnetic fluctuation power at wavenumbers relevant to the transport of cosmic rays with MeV to GeV energies. This means that the heliopause may be treated as a Dirichlet-type boundary for the purpose of energetic particle modeling. We present models with and without drift velocity to facilitate comparison with papers published earlier. We also attempt to reproduce the sudden step-like increases of cosmic-ray intensity observed by Voyager 1 before its encounter with the heliopause. Our results indicate that very slow cross-field diffusion in the outer heliosheath could produce a large gradient of cosmic rays inside the heliospheric boundary. The resulting large gradient in cosmic-ray intensity near the heliopause qualitatively agrees with recent Voyager 1 observations.

  9. Drift and observations in cosmic-ray modulation, 2

    NASA Technical Reports Server (NTRS)

    Potgieter, M. S.

    1985-01-01

    The significant effect of drift on the radial and latitudinal dependence of cosmic rays for consecutive solar minimum periods is illustrated. Compared with the integral radial gradient observed in 1976, the calculated value seems too small. A detailed comparison will however have to await the forthcoming solar minimum. The same applies to the latitudinal gradient which is as yet inconclusive about drift effects. Searching the literature for observations related to the IMF polarity reversal, distinct differences were found in neutron monitor response functions for consecutive solar minimum periods, and also in the annual variations of cosmic rays observed before and after polarity reversals. Whether drift is the predominant effect is however not yet clear. Better correlation was found between variations in the cosmic ray intensity and solar activity parameters over a much wider range of heliolatitude during 1970-80 compared to before this period.

  10. Study cosmic ray modulation near the heliopause: A numerical approach

    NASA Astrophysics Data System (ADS)

    Luo, X.; Zhang, M.; Potgieter, M. S.; Feng, X.; Pogorelov, N. V.

    2016-03-01

    By incorporating the MagnetoHydroDynamic (MHD) global heliospheric data into the Parker's cosmic-rays (CRs) transport equation, we constructed a hybrid galactic cosmic ray transport model to study the galactic cosmic-rays (GCR) behaviour near the heliopause(HP). Based on this hybrid model, we found that: (1)By increasing the ratio of the parallel diffusion coefficient to the perpendicular diffusion coefficient in the outer heliosheath (the region near HP and beyond), the simulated radial flux gradient near the HP increases as well. As this ratio multiplying factor reaches 1010, the flux experiences a sudden jump near the HP, similar to what Voyager 1 had observed in 2012. (2)After increasing the ratio of the diffusion coefficients beyond the HP, more pseudo- particles in our numerical approach which have been traced from the upwind nose region exit in the downwind tail region. It is thus possible that they diffuse more directly from the tail region to the nose region.

  11. Cosmic-ray modulation and the heliospheric magnetic field

    NASA Astrophysics Data System (ADS)

    Burger, R. A.

    The heliospheric magnetic field plays a key role in any model for the modulation of cosmic rays. It enters into all diffusion coefficients, and its magnitude, spatial gradient and direction determine drifts patterns of cosmic rays in the heliosphere. While the first axisymmetric model of E.N. Parker proved quite successful to explain in situ measurements in the ecliptic plane, new insight into the origin and the nature of the field, especially at high heliographic latitudes, has led to the development of complex fully-three-dimensional, time-dependent models. In this review, we discuss a selection of models for the heliospheric magnetic field, and discuss how some of the more recent Fisk-type models affect the modulation of cosmic rays.

  12. Observations of cosmic-ray modulations in the fall, 1984

    NASA Technical Reports Server (NTRS)

    Torsti, J. J.; Nieminen, M.; Valtonen, E.; Arvela, H.; Lumme, M.; Peltonen, J.; Vainikka, E.

    1985-01-01

    Modulation of cosmic-ray energy spectrum was studied by using the Turku double neutron monitor. The multiplicity region of detected neutrons produced by cosmic ray hadrons in the monitor was divided into seven categories corresponding to mean energies 0.1, 0.3, 1.0, 3.2, 8.6, 21, and 94 GeV of hadrons at sea level. Based on 24-hour frequencies, a statistical analysis showed that modulation of the intensity in all categories occurred during several periods in the fall 1984. The magnitude of the variation was a few per cent.

  13. A numerical investigation of cosmic ray modulation near the heliopause

    NASA Astrophysics Data System (ADS)

    Luo, Xi; Zhang, Ming; Toit Strauss, Du; Pogorelov, Nikolai; Feng, Xueshang; Potgieter, Marius

    2016-07-01

    A hybrid transport model is used for studying the modulation of galactic cosmic ray in the global heliosphere. This model incorporates the output data of a comprehensive MagnetoHydroDynamics (MHD) model as numerical input for the Parker's transport equation which is solved using a Stochastic Differential Equations (SDE) approach. We use this approach to study the transport of galactic cosmic rays near and beyond the heliopause (HP). We find that: The simulated radial flux near the HP increases when increasing the ratio of the parallel to the perpendicular diffusion coefficients in the interstellar magnetic field of the outer heliosheath. As the multiplying factor of this ratio reaches 10 ^{10}, the radial flux experiences a sudden upwards jump near the HP, similar to what Voyager 1 had observed in 2012. We simulate the cosmic ray radial flux along different directions in the heliosphere. There is not a well-defined thin layer between the solar wind region and interstellar region along the tail and polar directions of the heliosphere. By analysing the radial flux profile along the direction of Voyager 2, together with its trajectory information, the time when the HP may be crossed by Voyager 2 is predicted. We also simulate the cosmic ray radial flux for different energy values along the direction of Voyager 1. We find that there is indeed a modulation region beyond the HP but only of a modest width of about 10 AU, so that Voyager 1 observing the very local interstellar spectra is justified in numerical modelling. We find that after increasing the ratio of the mentioned diffusion coefficients beyond the HP, more pseudo-particles in our SDE approach, which have been traced from the upwind nose region, exit in the downwind tail region. It is thus possible that they diffuse directly from the tail region to the nose region.

  14. GALACTIC COSMIC-RAY MODULATION IN A REALISTIC GLOBAL MAGNETOHYDRODYNAMIC HELIOSPHERE

    SciTech Connect

    Luo, Xi; Zhang, Ming; Rassoul, Hamid K.; Pogorelov, Nikolai V.; Heerikhuisen, Jacob

    2013-02-10

    To understand the behavior of cosmic-ray modulation seen by the two Voyager spacecraft in the region near the termination shock (TS) and in the heliosheath at a distance of >100 AU, a realistic magnetohydrodynamic global heliosphere model is incorporated into our cosmic-ray transport code, so that the detailed effects of the heliospheric boundaries and their plasma/magnetic geometry can be revealed. A number of simulations of cosmic-ray modulation performed with this code result in the following conclusions. (1) Diffusive shock acceleration by the TS can significantly affect the level of cosmic-ray flux and, in particular, its radial gradient profile in the region near the TS and in the inner heliosheath. (2) The radial profile of cosmic-ray flux strongly depends on longitude. There is a slight north-south asymmetry due to an asymmetric TS, but the larger difference in the radial profiles comes from longitudinal variation. Voyager 1 and 2 are separated by {approx} 40 Degree-Sign in longitude. Simulations in these two directions show a large difference in the radial profile of cosmic-ray flux. Thus, it is not appropriate to determine the cosmic-ray radial gradient by directly using the two-point Voyager measurements. Various other simulations are also performed to show how sensitively the modulation level depends on latitude, cosmic-ray energy, and interstellar spectrum.

  15. COSMIC RAY MODULATION BEYOND THE HELIOPAUSE: A HYBRID MODELING APPROACH

    SciTech Connect

    Strauss, R. D.; Potgieter, M. S.; Ferreira, S. E. S.; Fichtner, H.; Scherer, K.

    2013-03-01

    Results from a newly developed hybrid cosmic ray (CR) modulation model are presented. In this approach, the transport of CRs is computed by incorporating the plasma flow from a magnetohydrodynamic model for the heliospheric environment, resulting in representative CR transport. The model is applied to the modulation of CRs beyond the heliopause (HP) and we show that (1) CR modulation persists beyond the HP, so it is unlikely that the Voyager spacecraft will measure the pristine local interstellar spectra of galactic CRs when crossing the HP. (2) CR modulation in the outer heliosheath could maintain solar-cycle-related changes. (3) The modulation of CRs in the outer heliosheath is primarily determined by the ratio of perpendicular to parallel diffusion, so that the value of the individual diffusion coefficients cannot be determined uniquely using this approach. (4) CRs can efficiently diffuse between the nose and tail regions of the heliosphere.

  16. Heliocentric radius of the cosmic ray modulation boundary

    NASA Technical Reports Server (NTRS)

    Randall, B. A.; Van Allen, J. A.

    1986-01-01

    A semiempirical analysis is made of an extensive body of observed cosmic ray intensity data from Pioneers 10 and 11, and related spectral information from other authors, in order to infer the radius R of the modulation region surrounding the sun. During the period 1972-1985, the inferred values of R vary with time systematically and in a manner generally similar to that of sunspot numbers. The range of values of R is from 42 AU at the time of minimum solar activity (circa 1976) to 88 AU about 1.5 yr following the time of maximum solar activity (circa 1980). A specific, testable prediction is that Pioneer 10 will reach the modulation boundary in 1988, and will remain in its vicinity for several years thereafter.

  17. Drift effects on the galactic cosmic ray modulation

    SciTech Connect

    Laurenza, M.; Storini, M.; Carbone, V.

    2014-02-01

    Cosmic ray (CR) modulation is driven by both solar activity and drift effects in the heliosphere, although their role is only qualitatively understood as it is difficult to connect the CR variations to their sources. In order to address this problem, the Empirical Mode Decomposition technique has been applied to the CR intensity, recorded by three neutron monitors at different rigidities (Climax, Rome, and Huancayo-Haleakala (HH)), the sunspot area, as a proxy for solar activity, the heliospheric magnetic field magnitude, directly related to CR propagation, and the tilt angle (TA) of the heliospheric current sheet (HCS), which characterizes drift effects on CRs. A prominent periodicity at ∼six years is detected in all the analyzed CR data sets and it is found to be highly correlated with changes in the HCS inclination at the same timescale. In addition, this variation is found to be responsible for the main features of the CR modulation during periods of low solar activity, such as the flat (peaked) maximum in even (odd) solar cycles. The contribution of the drift effects to the global Galactic CR modulation has been estimated to be between 30% and 35%, depending on the CR particle energy. Nevertheless, the importance of the drift contribution is generally reduced in periods nearing the sunspot maximum. Finally, threshold values of ∼40°, ∼45°, and >55° have been derived for the TA, critical for the CR modulation at the Climax, Rome, and HH rigidity thresholds, respectively.

  18. Galactic Cosmic Ray Modulation near the Heliospheric Current Sheet

    NASA Astrophysics Data System (ADS)

    Thomas, S. R.; Owens, M. J.; Lockwood, M.; Scott, C. J.

    2014-07-01

    Galactic cosmic rays (GCRs) are modulated by the heliospheric magnetic field (HMF) both over decadal time scales (due to long-term, global HMF variations), and over time scales of a few hours (associated with solar wind structures such as coronal mass ejections or the heliospheric current sheet, HCS). Due to the close association between the HCS, the streamer belt, and the band of slow solar wind, HCS crossings are often associated with corotating interaction regions where fast solar wind catches up and compresses slow solar wind ahead of it. However, not all HCS crossings are associated with strong compressions. In this study we categorize HCS crossings in two ways: Firstly, using the change in magnetic polarity, as either away-to-toward (AT) or toward-to-away (TA) magnetic field directions relative to the Sun and, secondly, using the strength of the associated solar wind compression, determined from the observed plasma density enhancement. For each category, we use superposed epoch analyses to show differences in both solar wind parameters and GCR flux inferred from neutron monitors. For strong-compression HCS crossings, we observe a peak in neutron counts preceding the HCS crossing, followed by a large drop after the crossing, attributable to the so-called `snow-plough' effect. For weak-compression HCS crossings, where magnetic field polarity effects are more readily observable, we instead observe that the neutron counts have a tendency to peak in the away magnetic field sector. By splitting the data by the dominant polarity at each solar polar region, we find that the increase in GCR flux prior to the HCS crossing is primarily from strong compressions in cycles with negative north polar fields due to GCR drift effects. Finally, we report on unexpected differences in GCR behavior between TA weak compressions during opposing polarity cycles.

  19. AN AB INITIO MODEL FOR COSMIC-RAY MODULATION

    SciTech Connect

    Engelbrecht, N. E.; Burger, R. A.

    2013-07-20

    A proper understanding of the effects of turbulence on the diffusion and drift of cosmic rays (CRs) is of vital importance for a better understanding of CR modulation in the heliosphere. This study presents an ab initio model for CR modulation, incorporating for the first time the results yielded by a two-component turbulence transport model. This model is solved for solar minimum heliospheric conditions, utilizing boundary values chosen so that model results are in reasonable agreement with spacecraft observations of turbulence quantities in the solar ecliptic plane and along the out-of-ecliptic trajectory of the Ulysses spacecraft. These results are employed as inputs for modeled slab and two-dimensional (2D) turbulence energy spectra. The modeled 2D spectrum is chosen based on physical considerations, with a drop-off at the very lowest wavenumbers. There currently exist no models or observations for the wavenumber where this drop-off occurs, and it is considered to be the only free parameter in this study. The modeled spectra are used as inputs for parallel mean free path expressions based on those derived from quasi-linear theory and perpendicular mean free paths from extended nonlinear guiding center theory. Furthermore, the effects of turbulence on CR drifts are modeled in a self-consistent way, also employing a recently developed model for wavy current sheet drift. The resulting diffusion and drift coefficients are applied to the study of galactic CR protons and antiprotons using a 3D, steady-state CR modulation code, and sample solutions in fair to good agreement with multiple spacecraft observations are presented.

  20. A simplified ab initio cosmic-ray modulation model: construction and predictive capabilities

    NASA Astrophysics Data System (ADS)

    Moloto, Katlego; Burger, Renier; Engelbrecht, Nicholas

    2016-07-01

    A simplified ab initio approach is followed to model cosmic-ray modulation using a steady-state three-dimensional stochastic solver of the Parker transport equation. Standard diffusion coefficients based on Quasilinear Theory (QLT) and Nonlinear Guiding Center Theory (NLGC) are used. The spatial dependence of turbulence quantities required as input for the drift- and diffusion coefficients, follow from parametric fits to results from a turbulence transport model. Effective values are used for the solar wind speed, magnetic field magnitude and tilt angle in the modulation model. The unusually high cosmic-ray intensities observed during the 2009 solar minimum follow naturally from the current model for most of the energies considered. This demonstrates that changes in turbulence contribute significantly to than usual cosmic-ray intensities during the 2009 solar minimum. We also discuss and illustrate how this model can be used to predict future cosmic-ray intensities, and comment on the reliability of such predictions.

  1. Cosmic ray modulation and noise level on the extended multidirectional muons detector telescope installed in south of Brazil: preliminary analysis

    NASA Astrophysics Data System (ADS)

    Braga, C. R.; Savian, J. F.; da Silva, M. R.; da Silva, S. M.; da Silva, C. W.; Dal Lago, A.; Kuwabara, T.; Munakata, K.; Bieber, J. W.; Schuch, N. J.; All

    Because of the large detector mass required to detect high-energy cosmic rays ground-based instruments remain the state-of-the-art method for studying these particles At energies up to 100 GeV primary galactic cosmic rays experience significant variation in response to solar wind disturbances such as interplanetary coronal mass ejections ICMEs In this way ground-based detectors can provide unique information on conditions in the near-earth interplanetary medium Since 2001 a prototype multidirectional high energy 50 GeV cosmic-ray muons detector telescope was operating in the Southern Space Observatory SSO CRSPE INPE - MCT Brazil geomagnetic coordinates 19o 13 S and 16o 30 E In December 2005 an upgrade increased the collection area in 600 becoming two layers of 28 m2 each The objective of this work is to analyze cosmic ray count rates observed by ground-based detector in order to find both variations not associated with interplanetary structures possible associated with the noise from the instrument and decrease rates caused by cosmic ray modulation due to interplanetary structures near Earth We use 1 minute resolution data from the extended telescope collected since January 2006 which is the first data since the update of the instrument on December 2005 We also use the disturbance storm time Dst index from Kyoto plasma and interplanetary magnetic field from the ACE satellite In the future this study will help to separate cosmic ray modulation caused by interplanetary structures from those variations in short periods less than 1 month

  2. Despiking of Spacecraft Energetic Proton Flux to Study Galactic Cosmic-Ray Modulation

    NASA Astrophysics Data System (ADS)

    Qin, G.; Zhao, L.-L.; Chen, H.-C.

    2012-06-01

    Galactic cosmic ray (GCR) is usually assumed as a stable "background," with solar influence considered as a modulation. The violent solar energetic particle (SEP) events associated with solar activities change particle fluxes by several orders of magnitude in a few minutes. Thus, the flux observation of GCR provided by satellites may be heavily contaminated by spurious spikes due to SEPs, and that provided by ground-based neutron monitors (NMs) may be contaminated by the system error spikes and the ground level enhancement effect. To obtain the "pure" background GCR flux for modulation research, the removal of multifarious spikes is necessary. In this article, we use a robust automatic despiking algorithm based on the Poincare map thresholding method provided by Goring and Nikora for "purification" of the time-series GCR flux observations. We can show that the algorithm is good at cleaning up the heavily contaminated GCR intensity rates measured by both spacecraft and NMs without artificial parameters. In addition, using the algorithm to despike the spacecraft observations of relatively lower energetic proton flux, we get both 11 year and 27 day period cycles comparable to the much higher energy GCR flux data measured by the ground-based NMs.

  3. ON COSMIC RAY MODULATION BEYOND THE HELIOPAUSE: WHERE IS THE MODULATION BOUNDARY?

    SciTech Connect

    Scherer, K.; Fichtner, H.; Strauss, R. D.; Ferreira, S. E. S.; Potgieter, M. S.; Fahr, H.-J.

    2011-07-10

    Two of the paradigms in modeling the transport of galactic cosmic rays are that the modulation boundary is the heliopause and that the local interstellar spectra are identical to the galactic cosmic ray spectra. Here we demonstrate that the proton spectrum is already modulated due to an altered interstellar diffusion in the outer heliosheath as a consequence of the heliospheric 'obstacle' in the interstellar flow. The main modulation effect however is adiabatic energy losses during a 'confinement time' of cosmic rays inside the heliosphere.

  4. Where is the cosmic-ray modulation boundary of the heliosphere?

    SciTech Connect

    Zhang, Ming; Luo, Xi; Pogorelov, Nikolai

    2015-09-15

    The intensity of Galactic cosmic rays in the heliosphere is modulated by solar activities. The outer boundary where the solar modulation begins has always been a subject matter of debate in the cosmic-ray and heliophysics community. Various experimental methods and theoretical model calculations have been used to determine the boundary. Although the heliopause was always suspected to be the boundary, it is only until very recently after Voyager 1 had crossed the heliopause did we confirm that the boundary is indeed the heliopause. In this paper, we use a model simulation and detailed Voyager observation of cosmic rays at the heliopause crossing to show that the modulation boundary, in fact, is a fraction of an AU beyond the heliopause. Such a conclusion requires a very low turbulence level of the interstellar magnetic field in the outer heliosheath. According to the quasi-linear theory, a low level of turbulence should result in a very large diffusion coefficient parallel to the magnetic field and a very small perpendicular diffusion coefficient. For the first time, we are confident that Voyager 1 has obtained the truly pristine local interstellar cosmic-ray spectra down to the energies below 1 MeV. The cosmic-ray intensity is rapidly filtered by a thin layer of the interstellar magnetic field immediately outside of the heliopause. Its filtration amount depends on the conditions of magnetic field turbulence on the both sides of the heliopause, thus making it solar-cycle dependent as well.

  5. Long-term variations of interplanetary magnetic field spectra with implications for cosmic ray modulation

    NASA Technical Reports Server (NTRS)

    Bieber, John W.; Chen, Jiasheng; Matthaeus, William H.; Smith, Charles W.; Pomerantz, Martin A.

    1993-01-01

    The paper calculates yearly averaged power spectra of interplanetary magnetic field turbulence at 1 AU over the period 1965-1988 for fluctuations in the frequency range 5.8 x 10 exp -6 to 4.6 x 10 exp -5 Hz, corresponding to periods of 6-48 hr. The amplitudes of the spectra vary with the sunspot cycle and are inversely correlated with the intensity of about 10-GeV cosmic rays. The observed spectra are used to calculate a lower limit to the cosmic ray scattering mean free path employing resonant magnetostatic quasi-linear theory for both 'slab' and isotropic geometries of the turbulence. The mean free paths thus obtained are typically about 0.1 AU in the slab model and about 0.3 AU in the isotropic model, but they are not significantly correlated with the modulated galactic cosmic ray intensity recorded by neutron monitors. It is inferred that the scattering processes described by resonant magnetostatic theory play, at best, a very minor role in the solar modulation of about 10-GeV cosmic rays.

  6. A NUMERICAL SIMULATION OF COSMIC-RAY MODULATION NEAR THE HELIOPAUSE

    SciTech Connect

    Luo, Xi; Feng, Xueshang; Zhang, Ming; Potgieter, Marius; Pogorelov, N. V.

    2015-07-20

    Based on a hybrid galactic cosmic-ray transport model, which incorporated MHD global heliospheric data into Parker’s cosmic-ray transport equation, we studied the behavior of the transport of galactic cosmic rays and the corresponding gradients in their flux near the heliopause (HP). We found that, (1) by increasing the ratio of the parallel diffusion coefficient to the perpendicular diffusion coefficient in the interstellar magnetic field of the outer heliosheath, the simulated radial flux near the HP increases as well. As the ratio multiplying factor reached 10{sup 10}, the radial flux experienced a sudden jump near the HP, similar to what Voyager 1 observed in 2012. (2) The effect of changing the diffusion coefficients’ ratio on the radial flux variation depends on the energy of the cosmic rays, the lower the energy, the more pronounced the effect is. (3) The magnitude of the diffusion coefficients also affect the radial flux near the HP, the modulation beyond the HP varies by adjusting the magnitude multiplying factor.

  7. THE EFFECT OF A DYNAMIC INNER HELIOSHEATH THICKNESS ON COSMIC-RAY MODULATION

    SciTech Connect

    Manuel, R.; Ferreira, S. E. S.; Potgieter, M. S.

    2015-02-01

    The time-dependent modulation of galactic cosmic rays in the heliosphere is studied over different polarity cycles by computing 2.5 GV proton intensities using a two-dimensional, time-dependent modulation model. By incorporating recent theoretical advances in the relevant transport parameters in the model, we showed in previous work that this approach gave realistic computed intensities over a solar cycle. New in this work is that a time dependence of the solar wind termination shock (TS) position is implemented in our model to study the effect of a dynamic inner heliosheath thickness (the region between the TS and heliopause) on the solar modulation of galactic cosmic rays. The study reveals that changes in the inner heliosheath thickness, arising from a time-dependent shock position, does affect cosmic-ray intensities everywhere in the heliosphere over a solar cycle, with the smallest effect in the innermost heliosphere. A time-dependent TS position causes a phase difference between the solar activity periods and the corresponding intensity periods. The maximum intensities in response to a solar minimum activity period are found to be dependent on the time-dependent TS profile. It is found that changing the width of the inner heliosheath with time over a solar cycle can shift the time of when the maximum or minimum cosmic-ray intensities occur at various distances throughout the heliosphere, but more significantly in the outer heliosphere. The time-dependent extent of the inner heliosheath, as affected by solar activity conditions, is thus an additional time-dependent factor to be considered in the long-term modulation of cosmic rays.

  8. Evidence for regions of negligible cosmic-ray modulation in the inner heliosphere ( 10 AU)

    NASA Technical Reports Server (NTRS)

    Roelof, E. C.

    1985-01-01

    Gold and Venkatesan report observations of periods during 1974-1976 when extended regions of heliolongitude that emitted lower than average solar wind velocities at 1 AU also exhibited higher than average cosmic ray intensities as measured by the E 35 MeV CPME anti-coincidence scintillator (28 sq cm omnidirectional geometric factor) on IMP-8. Their observations reproduced by a simple model, based on the observed steady solar wind structure, wherein there is little modulation of cosmic rays in the inner heliosphere until they reach the shocked plasma beyond the stream interactions in the outer heliosphere (similar to 5 to 10 AU). Beyond the interaction boundary, the intensity exhibits a constant radial gradient (similar to 2%/AU). The model also offers an explanation for the irregular behavior of the rotation averaged radial gradients observed by inside 10 AU, as well as the significant, but often ephemeral, latitude gradients observed by Voyagers 1 and 2 and IMP-8.

  9. Further considerations of cosmic ray modulation of infra-red radiation in the atmosphere

    NASA Astrophysics Data System (ADS)

    Aplin, K. L.; Lockwood, M.

    2015-08-01

    Understanding effects of ionisation in the lower atmosphere is a new interdisciplinary area, crossing the traditionally distinct scientific boundaries between astro-particle and atmospheric physics and also requiring understanding of both heliospheric and magnetospheric influences on cosmic rays. Following the paper of Erlykin et al. (2014) we develop further the interpretation of our observed changes in long-wave (LW) radiation, Aplin and Lockwood (2013) by taking account of both cosmic ray ionisation yields and atmospheric radiative transfer. To demonstrate this, we show that the thermal structure of the whole atmosphere needs to be considered along with the vertical profile of ionisation. Allowing for, in particular, ionisation by all components of a cosmic ray shower and not just by the muons, reveals that the effect we have detected is certainly not inconsistent with laboratory observations of the LW absorption cross section. The analysis presented here, although very different from that of Erlykin et al., does come to the same conclusion that the events detected by AL were not caused by individual cosmic ray primaries - not because it is impossible on energetic grounds, but because events of the required energy are too infrequent for the 12 h-1 rate at which they were seen by the AL experiment. The present paper numerically models the effect of three different scenario changes to the primary GCR spectrum which all reproduce the required magnitude of the effect observed by AL. However, they cannot solely explain the observed delay in the peak effect which, if confirmed, would appear to open up a whole new and interesting area in the study of water oligomers and their effects on LW radiation. We argue that a technical artefact in the AL experiment is highly unlikely and that our initial observations merit both a wide-ranging follow-up experiment and more rigorous, self-consistent, three-dimensional radiative transfer modelling.

  10. Study of the Cosmic-Ray Modulation During the Passage of ICMEs and CIRs

    NASA Astrophysics Data System (ADS)

    Badruddin; Kumar, Anand

    2016-02-01

    We compare the cosmic-ray response to interplanetary coronal mass ejections (ICMEs) and corotating interaction regions (CIRs) during their passage in near-Earth space. We study the relative importance of various structures/features identified during the passage of the ICMEs and CIRs observed during Cycle 23 (1995 - 2009). The identified ICME structures are the shock front, the sheath, and the CME ejecta. We isolate the shock arrival time, the passage of the sheath region, the arrival of ejecta, and the end time of their passage. Similarly, we isolate the CIR arrival, the associated forward shock, the stream interface, and the reverse shock during the passage of a CIR. For the cosmic-ray intensity, we utilize the data from high counting rate neutron monitors. In addition to neutron monitor data, we utilize near-simultaneous and same time-resolution data of interplanetary plasma and field, namely the solar-wind velocity, the interplanetary magnetic field (IMF) vector, and its variance. Further, we also utilize some derived interplanetary parameters. We apply the method of the superposed-epoch analysis. As the plasma and field properties are different during the passage of different structures, both in ICMEs and CIRs, we systematically vary the epoch time in our superposed-epoch analysis one by one. In this way, we study the role and effects of each of the identified individual structures/features during the passage of the ICMEs and CIRs. Relating the properties of various structures and the corresponding variations in plasma and field parameters with changes of the cosmic-ray intensity, we identify the relative importance of the plasma/field parameters in influencing the amplitude and time profiles of the cosmic-ray intensity variations during the passage of the ICMEs and CIRs.

  11. Cosmic ray modulation of infra-red radiation in the atmosphere

    NASA Astrophysics Data System (ADS)

    Aplin, Karen; Lockwood, Michael

    2013-04-01

    Cosmic rays produce small charged clusters, known as molecular cluster ions, as they pass through the lower atmosphere. Neutral molecular clusters such as dimers and complexes are expected to make a small contribution to the radiative balance, but atmospheric absorption by charged clusters has not hitherto been observed. Here we describe results from an atmospheric experiment where a thermopile filter radiometer tuned to a 9.15μm absorption band, already associated with infra-red absorption of molecular cluster ions, was used to monitor changes following events identified by a cosmic ray telescope sensitive to high energy (>400MeV) particles, principally muons at the surface. The change in longwave radiation in this absorption band due to molecular cluster ions is 7 mWm-2 for each event recorded by the cosmic ray telescope. The integrated atmospheric energy change for each event is 1.9 Jm-2, whereas the energy density of a typical air shower (40m radius from a 10GeV primary) is estimated to be 10-13 Jm-2, representing a direct amplification factor of 1012. This infra-red absorption from molecular cluster-ions is expected to occur continuously and globally, but calculations suggest that it has only a small effect on climate.

  12. Cosmic ray modulation of infra-red radiation in the atmosphere

    NASA Astrophysics Data System (ADS)

    Aplin, K. L.; Lockwood, M.

    2013-03-01

    Cosmic rays produce molecular cluster ions as they pass through the lower atmosphere. Neutral molecular clusters such as dimers and complexes are expected to make a small contribution to the radiative balance, but atmospheric absorption by charged clusters has not hitherto been observed. In an atmospheric experiment, a narrowband thermopile filter radiometer centred on 9.15 μm, an absorption band previously associated with infra-red absorption of molecular cluster ions, was used to monitor changes following events identified by a cosmic ray telescope sensitive to high-energy (>400 MeV) particles, principally muons. The average change in longwave radiation in this absorption band due to molecular cluster ions is 7 mWm-2. The integrated atmospheric energy density for each event is 2 Jm-2, representing an amplification factor of 1012 compared to the estimated energy density of a typical air shower. This absorption is expected to occur continuously and globally, but calculations suggest that it has only a small effect on climate.

  13. Cosmic Ray Modulation in the Outer Heliosphere During the Minimum of Solar Cycle 23/24

    NASA Technical Reports Server (NTRS)

    Adams, James H., Jr.; Florinski, V.; Washimi, H.; Pogorelov, N. V.

    2011-01-01

    We report a next generation model of galactic cosmic ray (GCR) transport in the three dimensional heliosphere. Our model is based on an accurate three-dimensional representation of the heliospheric interface. This representation is obtained by taking into account the interaction between partially ionized, magnetized plasma flows of the solar wind and the local interstellar medium. Our model reveals that after entering the heliosphere GCRs are stored in the heliosheath for several years. The preferred GCR entry locations are near the nose of the heliopause and at high latitudes. Low-energy (hundreds of MeV) galactic ions observed in the heliosheath have spent, on average, a longer time in the solar wind than those observed in the inner heliosphere, which would explain their cooled-off spectra at these energies. We also discuss radial gradients in the heliosheath and the implications for future Voyager observations.

  14. Interstellar environment change: effects on heliospheric structure, galactic cosmic ray modulation and cosmogenic isotope production.

    NASA Astrophysics Data System (ADS)

    Mueller, H. R.; Florinski, V.; Zank, G. P.

    2005-12-01

    Galactic cosmic ray (GCR) intensity levels in the inner heliosphere over the past million years, preserved in cosmogenic isotope records, display significant variability on virtually all timescales. Here we focus on the variability caused by changes in the interstellar environment of the Sun as it encounters interstellar clouds or low-density regions (supernova bubbles) during its journey through the Galaxy. Three possible environments are compared and the resulting structure of the heliosphere investigated: the tenuous fully ionized Local Bubble, the Local Interstellar Cloud, and a dense cold cloud of pure atomic hydrogen. Using several plausible models of interplanetary turbulence evolution and particle diffusion we investigate the dependence of the cosmic-ray mean free paths and intensities on the size of the modulation region and the pickup ion (PUI) intensities. We show that, while denser clouds usually yield smaller diffusion coefficients due to enhanced PUI turbulence, GCR radiation levels in the inner heliosphere are actually increased due to a reduction in the size of the modulation region. Our results indicate that GCR intensities at Earth can vary by a factor 2 to 7 between 300 MeV and 1 GeV compared to the present intensity. Interestingly, most of the changes are due to a variation in the thickness of the modulation wall in the inner heliosheath. Finally, we calculate cosmogenic isotope production rates in the Earth's atmosphere for the three environments and show that Beryllium-10 concentration could vary between 25% declines in low-density environments to increases in excess of 300% in high density interstellar clouds.

  15. Despiking of energetic proton flux to study galactic cosmic ray modulation

    NASA Astrophysics Data System (ADS)

    Zhao, L.; Qin, G.; Chen, H.

    2011-12-01

    The solar influence on Galactic cosmic ray (GCR) flux can be generally described as the usually stable "background" modulation. The violent Solar Energetic Particle (SEP) events associated with solar activities can cause surging particle flux. Thus, the GCR flux observation from satellites may be heavily contaminated by spurious spikes due to SEPs. And spike may also arise in the long time series count rates data provided by ground-based neutron monitors, e.g., system glitch. To obtain the "pure" background GCR flux for modulation research, the removal of multifarious spikes is necessary. In this article, we present a robust automatic despiking algorithm based on Poincare map thresholding method to "purify" time-series GCR flux. The algorithm is effective and robust for detecting various types of spikes in the GCR count rates of neutron monitors. In addition, after despiking spacecraft observations of relatively lower energy energetic proton flux using our algorithm, we get both 11-year and 27-day period cycles comparable to the much higher energy GCR count rate data from the ground-based neutron monitors.

  16. A study of Forbush Decreases with a full 3-D cosmic ray modulation model

    NASA Astrophysics Data System (ADS)

    Luo, Xi; Zhang, Ming; Potgieter, Marius

    2016-07-01

    We have constructed a 3-D numerical model for studying Forbush Decreases (FDs) in the global heliosphere. It incorporates 3-D propagation barriers, with enhanced cooling inside, into a time-dependent Parker type modulation model using a Stochastic Differential Equation (SDE) approach. This numerical model simultaneously takes into account the effect of solar wind convection with associated adiabatic energy changes; gradient, curvature and current sheet drifts; as well as parallel and perpendicular diffusion. This state-of-the-art numerical model enables us to find and study some new 3-D features for FD type events: 1. The cosmic ray intensity at Earth varies depending on the relative location of the Earth to the current sheet, and is reflected also in the amplitude of the FDs. The local modulation conditions, at a given observational point, determine the total amplitude. 2. The radial, latitudinal and longitudinal extent of a diffusion barrier significantly affects the amplitude of a FD. 3. The recovery time of a FD, at a given observational location, is determined by the modulation conditions which the corresponding propagation barrier encounters as it moves outwards in the heliosphere.

  17. Cosmic Ray Modulation Observed by the Princess Sirindhorn Neutron Monitor at High Rigidity Cutoff

    NASA Astrophysics Data System (ADS)

    Mangeard, Pierre-Simon; Pyle, Roger; Evenson, Paul; Ruffolo, David; Saiz, Alejandro; Clem, John; Madlee, Suttiwat; Nutaro, Tanin

    2016-07-01

    Neutron monitors (NMs) are the premier instruments for precisely tracking time variations in the Galactic cosmic ray (GCR) flux at the GV-range. For more than 60 years, the worldwide NM network has provided continuous measurements of the solar induced variations of the GCR flux impinging Earth and the data cover about six 11-year solar cycles. The recent rise of space exploration, with PAMELA and AMS-02 spacecraft, brings new energy sensitive measurements of GCR fluxes. Moreover since late 2007, the range of sensitivity of the worldwide NM network has been increased with the installation of the Princess Sirindhorn Neutron Monitor (PSNM), at the summit of Doi Inthanon, Thailand's highest mountain (2565 m altitude). PSNM records the GCR flux with the world's highest vertical rigidity cutoff for a fixed station, 16.8 GV. PSNM data now cover the period from the last solar minimum to the recent solar maximum and give us the opportunity to study the effect of the solar modulation at such high rigidity for the first time. We present here the observations of PSNM since 2007. The observed solar modulation is much weaker than predicted by the force field model with φ inferred from NM data at low cutoff. We compare measurements with those from NMs located at low rigidity cutoff and with spacecraft data. We discuss the solar modulation at high rigidity. Partially supported by a postdoctoral fellowship from Mahidol University, the Thailand Research Fund (BRG 5880009), the Science Achievement Scholarship of Thailand, and US National Science Foundation awards PLR-1341562, PLR-1245939, and their predecessors.

  18. Sunspot activity and cosmic ray modulation at 1 a.u. for 1900-2013

    NASA Astrophysics Data System (ADS)

    Ahluwalia, H. S.

    2014-10-01

    The descent of sunspot cycle 23 to an unprecedented minimum of long duration in 2006-2009 led to a prolonged galactic cosmic ray (GCR) recovery to the highest level observed in the instrumental era for a variety of energetic charged particle species on Earth, over a wide range of rigidities. The remarkable GCR increase measured by several ground-based, balloon-borne, and detectors on a satellite is described and discussed. It is accompanied by a decrease in solar wind velocity and interplanetary magnetic field at 1 a.u., reaching the lowest values since measurements of the solar wind began in October 1963; the solar polar field strength (μT) measured at the Wilcox Solar Observatory (WSO) is also significantly reduced compared to prior cycles since the start of the program in 1976, the polar field in the northern hemisphere reversed in June 2012 and again in February 2014, that in the southern hemisphere reversed in July 2013. If updates of WSO data confirm the second reversal in northern solar hemisphere, it would pose a serious challenge to the Dynamo Theory. The long-term change in solar behavior may have begun in 1992, perhaps earlier. The physical underpinnings of these solar changes need to be understood and their effect on GCR modulation processes clarified. The study discusses the recent phenomena in the context of GCR modulation since 1900. These happenings affected our empirical predictions for the key parameters for the next two sunspot cycles (they may be progressively less active than sunspot cycle 24) but it enhanced support for our prediction that solar activity is descending into a Dalton-like grand minimum in the middle of the twentyfirst century, reducing the frequency of the coronal mass ejections; they determine the space weather affecting the quality of life on Earth, radiation dose for hardware and human activities in space as well as the frequency of large Forbush decreases at 1 a.u.

  19. A Numerical Simulation of Cosmic Ray Modulation Near the Heliopause. II. Some Physical Insights

    NASA Astrophysics Data System (ADS)

    Luo, Xi; Potgieter, Marius S.; Zhang, Ming; Pogorelov, Nikolai V.; Feng, Xueshang; du Toit Strauss, R.

    2016-08-01

    Cosmic ray (CR) transport near the heliopause (HP) is studied using a hybrid transport model, with the parameters constrained by observations from the Voyager 1 spacecraft. We simulate the CR radial flux along different directions in the heliosphere. There is no well-defined thin layer between the solar wind region and the interstellar region along the tail and polar directions of the heliosphere. By analyzing the radial flux curve along the direction of Voyager 2, together with its trajectory information, the crossing time of the HP by Voyager 2 is predicted to be in 2017.14. We simulate the CR radial flux for different energy values along the direction of Voyager 1. We find that there is only a modest modulation region of about 10 au wide beyond the HP, so that Voyager 1 observing the Local Interstellar Spectra is justified in numerical modeling. We analyze the heliospheric exit information of pseudo-particles in our stochastic numerical (time-backward) method, conjecturing that they represent the behavior of CR particles, and we find that pseudo-particles that have been traced from the nose region exit in the tail region. This implies that many CR particles diffuse directly from the heliospheric tail region to the nose region near the HP. In addition, when pseudo-particles were traced from the Local Interstellar Medium (LISM), it is found that their exit location (entrance for real particles) from the simulation domain is along the prescribed Interstellar Magnetic Field direction. This indicates that parallel diffusion dominates CR particle transport in the LISM.

  20. Solar Drivers of 11-yr and Long-Term Cosmic Ray Modulation

    NASA Technical Reports Server (NTRS)

    Cliver, E. W.; Richardson, I. G.; Ling, A. G.

    2011-01-01

    In the current paradigm for the modulation of galactic cosmic rays (GCRs), diffusion is taken to be the dominant process during solar maxima while drift dominates at minima. Observations during the recent solar minimum challenge the pre-eminence of drift: at such times. In 2009, the approx.2 GV GCR intensity measured by the Newark neutron monitor increased by approx.5% relative to its maximum value two cycles earlier even though the average tilt angle in 2009 was slightly larger than that in 1986 (approx.20deg vs. approx.14deg), while solar wind B was significantly lower (approx.3.9 nT vs. approx.5.4 nT). A decomposition of the solar wind into high-speed streams, slow solar wind, and coronal mass ejections (CMEs; including postshock flows) reveals that the Sun transmits its message of changing magnetic field (diffusion coefficient) to the heliosphere primarily through CMEs at solar maximum and high-speed streams at solar minimum. Long-term reconstructions of solar wind B are in general agreement for the approx. 1900-present interval and can be used to reliably estimate GCR intensity over this period. For earlier epochs, however, a recent Be-10-based reconstruction covering the past approx. 10(exp 4) years shows nine abrupt and relatively short-lived drops of B to < or approx.= 0 nT, with the first of these corresponding to the Sporer minimum. Such dips are at variance with the recent suggestion that B has a minimum or floor value of approx.2.8 nT. A floor in solar wind B implies a ceiling in the GCR intensity (a permanent modulation of the local interstellar spectrum) at a given energy/rigidity. The 30-40% increase in the intensity of 2.5 GV electrons observed by Ulysses during the recent solar minimum raises an interesting paradox that will need to be resolved.

  1. Transient galactic cosmic ray modulation during solar cycle 24: A comparative study of two prominent Forbush decrease events

    NASA Astrophysics Data System (ADS)

    Lingling, Zhao; Huai, Zhang; Hongqing, He

    2016-04-01

    Forbush decrease (FD) events are of great interest for transient galactic cosmic ray modulation study. In this study, we perform statistical analysis of two prominent Forbush events during cycle 24, occurred on 8 March 2012 (Event 1) and 22 June 2015 (Event 2), respectively, utilizing the measurements from the worldwide neutron monitor (NM) network. Despite of their comparable magnitudes, the two Forbush events are distinctly different in terms of evolving GCR energy spectrum and energy dependence of the recovery time. The recovery time of Event 1 is strongly dependent on the median energy, compared to the nearly constant recovery time of Event 2 over the studied energy range. Additionally, while the evolution of the energy spectra during the two FD event exhibit similar variation pattern, the spectrum of Event 2 is very harder, especially at the time of deepest depression. These difference are essentially related to their associated solar wind disturbances. Event 1 is associated with a complicated shock-associated ICME structure of IP/Sheath/MC sequence with large radial extend and limited longitudinal extent (narrow and thick), probably merged from multiple shocks and transient flows. Conversely, Event 2 is accompanied by a relatively simple interplanetary disturbance of IP/Sheath/Ejecta sequence with small radial extend and wide longitudinal departure (wide and thin), possibly evolved from an over expanded CME. Such comparative study may help to clarify the occurrence mechanisms of Forbush events related to different types solar wind structures and provide valuable insight into the transient GCR modulation, especially during the unusual solar cycle 24.

  2. Cosmic ray modulation in three dimensions. [transport theory on particle motion and scattering in the solar wind

    NASA Technical Reports Server (NTRS)

    Quenby, J. J.

    1976-01-01

    A brief critique of spherically symmetric conventional modulation theory is supplied. Estimates are made of the cosmic ray intensity at high solar latitudes. Direct evidence for significant off-ecliptic cosmic ray gradients is reviewed in support of the requirement for an off-ecliptic spacecraft mission. The possibility of measuring the galactic spectrum is discussed. The effect of interplanetary magnetic fields on cosmic ray motion is examined, and calculations (Fokker-Planck equation) are shown.

  3. Cosmic ray modulation at the solar maximum: Ulysses observations during the fast latitude scan of the inner heliosphere*

    NASA Astrophysics Data System (ADS)

    Zhang, M.; McKibben, R. B.; Lopate, C.

    2002-05-01

    Starting at the maximum southern latitude of 80o in November 2000, Ulysses made a fast latitude scan of the inner heliosphere within approximately one year at the time of maximum solar activity. It passed through a perihelion at 1.34 AU near the solar equator in May 2001, and reached its maximum northern latitude in October 2001. The fast latitude scan provides best conditions for the determination of cosmic ray latitudinal gradients because of little expected drift of instrument performance and a small coverage of radial distance (2.2 to 1.34 AU). Although the time period is dominated by solar energetic particle events, measurements from the High-Energy Telescope on the Ulysses COSPIN experiment together with simultaneous measurements from the University of Chicago Charge Particle Telescope on IMP-8 near Earth made during rare solar quiet time periods found that the latitudinal gradient of cosmic ray intensities is essentially zero for all nuclei of energies above 30 MeV/n. Compared to the measurements of small cosmic ray latitude gradients made by Ulysses' first fast latitude scan at the 1994-1995 solar minimum, this observation indicates that the inner heliosphere is more spherically symmetric at the solar maximum. In this paper, we will discuss its implications to the understanding of the structure of heliospheric magnetic fields and the mechanisms of particle transport. * This work was supported in part by NASA Contract JPL-955432 and by NASA Grants NAG5-11036 and NAG5-10888

  4. CMEs, the Tail of the Solar Wind Magnetic Field Distribution, and 11-yr Cosmic Ray Modulation at 1 AU. Revised

    NASA Technical Reports Server (NTRS)

    Cliver, E. W.; Ling, A. G.; Richardson, I. G.

    2003-01-01

    Using a recent classification of the solar wind at 1 AU into its principal components (slow solar wind, high-speed streams, and coronal mass ejections (CMEs) for 1972-2000, we show that the monthly-averaged galactic cosmic ray intensity is anti-correlated with the percentage of time that the Earth is imbedded in CME flows. We suggest that this correlation results primarily from a CME related change in the tail of the distribution function of hourly-averaged values of the solar wind magnetic field (B) between solar minimum and solar maximum. The number of high-B (square proper subset 10 nT) values increases by a factor of approx. 3 from minimum to maximum (from 5% of all hours to 17%), with about two-thirds of this increase due to CMEs. On an hour-to-hour basis, average changes of cosmic ray intensity at Earth become negative for solar wind magnetic field values square proper subset 10 nT.

  5. A 17-year oscillation in cancer mortality birth cohorts on three continents - synchrony to cosmic ray modulations one generation earlier.

    PubMed

    Juckett, David A

    2009-11-01

    Cross-generational effects (grandmother effects) associated with epigenetic imprinting, environmental exposures, and lifestyle choices are beginning to be explored by various investigators. The possibility that low-level background radiation can be a driver of such effects has been suggested previously and is explored further in this study. Age-period-cohort analysis was performed on United States (US), United Kingdom (UK), and Australian (AU) female breast cancer mortality of the twentieth century, as well as on UK female total cancer mortality, to extract the high-frequency oscillations in the birth cohort time series. US fetal and infant congenital mortality were examined to extend the birth cohorts to modern times. A approximately 17-year cycle was detected in all birth cohort series, which spanned approximately 180 years from 1820 to 2000. This suggests a global, environmental cause. To mimic previous work in examining a possible link to cosmic radiation, the 17- to 18-year cycles of the cosmogenic nuclide (14)C, the sunspot double-cycle, neutron monitors, and a compilation of ground-based magnetic field observations were examined in the birth cohort and germ cell cohort time frames. Evidence is presented that optimal alignments with extraterrestrial oscillations occur in the time frame of the germ-cell cohort, one generation before the birth cohorts. Furthermore, the alignment is optimized by accounting for the changes in the maternal age distribution over time. These findings have potential importance to the mechanisms of disease as well as species adaptation and evolution.

  6. Transient Galactic Cosmic-ray Modulation during Solar Cycle 24: A Comparative Study of Two Prominent Forbush Decrease Events

    NASA Astrophysics Data System (ADS)

    Zhao, L.-L.; Zhang, H.

    2016-08-01

    Forbush decrease (FD) events are of great interest for transient galactic cosmic-ray (GCR) modulation study. In this study, we perform comparative analysis of two prominent Forbush events during cycle 24, occurring on 2012 March 8 (Event 1) and 2015 June 22 (Event 2), utilizing the measurements from the worldwide neutron monitor (NM) network. Despite their comparable magnitudes, the two Forbush events are distinctly different in terms of evolving GCR energy spectrum and energy dependence of the recovery time. The recovery time of Event 1 is strongly dependent on the median energy, compared to the nearly constant recovery time of Event 2 over the studied energy range. Additionally, while the evolutions of the energy spectra during the two FD events exhibit similar variation patterns, the spectrum of Event 2 is significantly harder, especially at the time of deepest depression. These difference are essentially related to their associated solar wind disturbances. Event 1 is associated with a complicated shock-associated interplanetary coronal mass ejection (ICME) disturbance with large radial extent, probably formed by the merging of multiple shocks and transient flows, and which delivered a glancing blow to Earth. Conversely, Event 2 is accompanied by a relatively simple halo ICME with small radial extent that hit Earth more head-on.

  7. Studies of Cosmic Ray Modulation and Energetic Particle Propagation in Time-Dependent 3-Dimensional Heliospheric Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Zhang, Ming

    2005-01-01

    The primary goal of this project was to perform theoretical calculations of propagation of cosmic rays and energetic particles in 3-dimensional heliospheric magnetic fields. We used Markov stochastic process simulation to achieve to this goal. We developed computation software that can be used to study particle propagation in, as two examples of heliospheric magnetic fields that have to be treated in 3 dimensions, a heliospheric magnetic field suggested by Fisk (1996) and a global heliosphere including the region beyond the termination shock. The results from our model calculations were compared with particle measurements from Ulysses, Earth-based spacecraft such as IMP-8, WIND and ACE, Voyagers and Pioneers in outer heliosphere for tests of the magnetic field models. We particularly looked for features of particle variations that can allow us to significantly distinguish the Fisk magnetic field from the conventional Parker spiral field. The computer code will eventually lead to a new generation of integrated software for solving complicated problems of particle acceleration, propagation and modulation in realistic 3-dimensional heliosphere of realistic magnetic fields and the solar wind with a single computation approach.

  8. Study of cosmic-ray modulation during the recent deep solar minimum, mini maximum and intervening ascending phase of solar cycle 24

    NASA Astrophysics Data System (ADS)

    Badruddin, B.; Aslam, O. P. M.

    After a prolonged and deep solar minimum at the end of cycle 23, current solar cycle 24 is one of the very low active cycles, weakest cycle in more than 50 years. These two periods of deep minima and mini maxima are separated by a period of increasing solar activity as measured by sunspot numbers. We study the cosmic ray relationship with the solar activity, heliospheric plasma and field parameters including the heliospheric current sheet (HCS), during these three periods (phases) of different level and nature of solar activity; (a) a deep minimum, (b) an increasing period and (c) a ‘mini’ maximum. We utilize the neutron monitor data from stations located around the globe to study the rigidity dependence of modulation during the two extremes, i.e., minima and maxima. We also study the time lag between the GCR intensity and various solar/interplanetary parameters separately during the three activity phases. Using the cosmic ray data of neutron monitors with different cutoff rigidities, we study the rigidity dependence of time lag during individual phases. The role/effectiveness of various parameters, including the HCS tilt, in modulating the GCR intensity during the three different phases has also been studied by correlation analysis. The relative importance of various physical processes during different phases and the implication of these results for modulation models are also discussed.

  9. Cosmic ray modulation by solar wind disturbances

    NASA Astrophysics Data System (ADS)

    Dumbović, M.; Vršnak, B.; Čalogović, J.; Karlica, M.

    2011-07-01

    Aims: We perform a systematic statistical study of the relationship between characteristics of solar wind disturbances, caused by interplanetary coronal mass ejections and corotating interaction regions, and properties of Forbush decreases (FDs). Since the mechanism of FDs is still being researched, this analysis should provide a firm empirical basis for physical interpretations of the FD phenomenon. Methods: The analysis is based on the ground-based neutron monitor data and the solar wind data recorded by the Advanced Composition Explorer, where the disturbances were identified as increases in proton speed, magnetic field, and magnetic field fluctuations. We focus on the relative timing of FDs, as well as on the correlations between various FD and solar wind parameters, paying special attention to the statistical significance of the results. Results: It was found that the onset, the minimum, and the end of FDs are delayed after the onset, the maximum, and the end of the magnetic field enhancement. The t-test shows that at the 95% significance level the average lags have to be longer than 3, 7, and 26 h, respectively. FD magnitude (| FD|) is correlated with the magnetic field strength (B), magnetic field fluctuations (δB), and speed (v), as well as with combined parameters, BtB, Bv, vtB, and BvtB, where tB is the duration of the magnetic field disturbance. In the |FD|(B) dependence, a "branching" effect was observed, i.e., two different trends exist. The analysis of the FD duration and recovery period reveals a correlation with the duration of the magnetic field enhancement. The strongest correlations are obtained for the dependence on combined solar wind parameters of the product of the FD duration and magnitude, implying that combined parameters are in fact true variables themselves, rather than just a product of variables. Conclusions: From the time lags we estimate that "the penetration depth" in the disturbance, at which FD onset becomes recognizable, is on the order of 100 Larmor radii and is comparable to a typical shock-sheath dimension. The results for the FD time profile indicate "shadow effect" of the solar wind disturbance before and after it passes the observer. The importance of reduced parallel diffusion during the passage of the disturbance is discussed, along with the influence of terrestrial effects on the observed "branching effect". Appendices A-C are available in electronic form at http://www.aanda.org

  10. The neutron moderated detector and groundbased cosmic ray modulation studies

    NASA Technical Reports Server (NTRS)

    Stoker, P. H.; Raubenheimer, B. C.

    1985-01-01

    Reports appear on modulation studies with the neutron monitor without lead. Some of these studies cast doubt on the reliability of this detector. The stability of the neutron moderated detector (NMD) at Sanae, Antarctic is discussed. The barometric coeficient of the 4NMD for epoch 1976 appears not to differ statistically from the 0.73%/mb of the 3NM64. The monthly averaged hourly counting rate of our 4NMD and 3NM64 correlates very well (correlation coefficient: 98%) over the years from 1974-1984, with the 4NMD showing a 8% larger long term modulation effect than the 3NM64, indicating a difference in sensitivities of the two detectors. From this difference in sensitivities spectra of ground level solar proton events and modulation functions of Forbush decreases are deduced.

  11. Performance Improvement Assuming Complexity

    ERIC Educational Resources Information Center

    Rowland, Gordon

    2007-01-01

    Individual performers, work teams, and organizations may be considered complex adaptive systems, while most current human performance technologies appear to assume simple determinism. This article explores the apparent mismatch and speculates on future efforts to enhance performance if complexity rather than simplicity is assumed. Included are…

  12. Collaboration: Assumed or Taught?

    ERIC Educational Resources Information Center

    Kaplan, Sandra N.

    2014-01-01

    The relationship between collaboration and gifted and talented students often is assumed to be an easy and successful learning experience. However, the transition from working alone to working with others necessitates an understanding of issues related to ability, sociability, and mobility. Collaboration has been identified as both an asset and a…

  13. Web life: If We Assume

    NASA Astrophysics Data System (ADS)

    2012-10-01

    The title If We Assume refers to physicists' habit of making back-of-the-envelope calculations, but do not let the allusion to assumptions fool you: there are precious few spherical cows rolling around frictionless surfaces in this corner of the Internet.

  14. Calculations of the cosmic ray modulation in interplanetary space taking into account the possible dependence of the transport travel for the scattering of the particles and of the velocity of the solar winds on the angles they make with the helioequator plane: The case of isotropic diffusion

    NASA Technical Reports Server (NTRS)

    Dorman, L. I.; Kobilinski, Z.

    1975-01-01

    The modulation of galactic cosmic rays is studied by the magnetic heterogeneities stream on the assumption that the diffusion coefficient is reduced whereas the solar wind velocity is increased with the growth of the angle between the sun's rotation axis and the direction of solar plasma motion. The stationary plane problem of isotropic diffusion is solved as it applies to two cases: (1) with due account of particle retardation by the antiphermium mechanism; and (2) without an account of the above mechanism. This problem is solved by the grid method in the polar coordinate system. The results of the calculations are followed by a discussion of the method of solution and of the errors.

  15. Galactic cosmic-ray mediation of a spherical solar wind flow. 1: The steady state cold gas hydrodynamical approximation

    NASA Technical Reports Server (NTRS)

    Le Roux, J. A.; Ptuskin, V. S.

    1995-01-01

    Realistic models of the outer heliosphere should consider that the interstellar cosmic-ray pressure becomes comparable to pressures in the solar wind at distances more than 100 AU from the Sun. The cosmic-ray pressure dynamically affects solar wind flow through deceleration. This effect, which occurs over a scale length of the order of the effective diffusion length at large radial distances, has important implications for cosmic-ray modulation and acceleration. As a first step toward solution of this nonlinear problem, a steady state numerical model was developed for a relatively cold spherical solar wind flow which encounters the confining isotropic pressure of the surrounding Galactic medium. This pressure is assumed to be dominated by energetic particles (Galactic cosmic rays). The system of equations, which are solved self-consistently, includes the relevant hydrodynamical equations for the solar wind flow and the spherical cosmic-ray transport equation. To avoid the closure parameter problem of the two-fluid model, the latter equation is solved for the energy-dependent cosmic-ray distribution function.

  16. 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.

  17. 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.

  18. The cosmic ray interplanetary radial gradient from 1972 - 1985

    NASA Technical Reports Server (NTRS)

    Webber, W. R.; Lockwood, J. A.

    1985-01-01

    It is now established that the solar modulation of cosmic rays is produced by turbulent magnetic fields propagated outward by the solar wind. Changes in cosmic ray intensity are not simultaneous throughout the modulation region, thus requiring time dependent theories for the cosmic ray modulation. Fundamental to an overall understanding of this observed time dependent cosmic ray modulation is the behavior of the radial intensity gradient with time and heliocentric distance over the course of a solar modulation cycle. The period from 1977 to 1985 when data are available from the cosmic ray telescopes on Pioneer (P) 10, Voyager (V) 1 and 2, and IMP 8 spacecraft is studied. Additional data from P10 and other IMP satellites for 1972 to 1977 can be used to determine the gradient at the minimum in the solar modulation cycle and as a function of heliocentric distance. All of these telescopes have thresholds for protons and helium nuclei of E 60 MeV/nucleon.

  19. 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

  20. Variations of the cosmic ray general component in Antarctica

    NASA Technical Reports Server (NTRS)

    Charakhchyan, T. N.; Krasotkin, A. F.; Kurguzova, A. I.; Svirzhevsky, N. S.

    1985-01-01

    A cosmic ray variations, zonal cosmic ray modulation, was found in the lower atmosphere from the sonde measurement results. The variations give rise to anomalies in the latitude distributions of the cosmic ray charged component and the anomalous north-south asymmetry. To find the nature of the variations, the cosmic ray general component was measured with the same detectors as in the sonde measurements gas discharge counters and the counter telescopes with 7-mm Al filters detecting the electrons of energy above 200 keV and 5 MeV. The measurement data obtained in Antarctica in the years 1978 to 1983 are presented and discussed.

  1. International Cosmic Ray Conference, 13th, University of Denver, Denver, Colo., August 17-30, 1973, Proceedings. Volume 5

    NASA Technical Reports Server (NTRS)

    1974-01-01

    An X-ray observation of the Norma-Lupus region, charge and isotope measurements of heavy cosmic ray nuclei and their role in the determination of cosmic ray age, and the possibility of a contribution to primary cosmic ray spectra from pulsars are among the topics covered in papers concerned with some of the results of recent cosmic ray research. Other topics covered include multiple scattering of charged particles in magnetic fields, absorption of primary cosmic rays in the atmosphere, and phase lag effects on cosmic ray modulation during a recent solar cycle. Individual items are announced in this issue.

  2. Assumed PDF modeling in rocket combustor simulations

    NASA Astrophysics Data System (ADS)

    Lempke, M.; Gerlinger, P.; Aigner, M.

    2013-03-01

    In order to account for the interaction between turbulence and chemistry, a multivariate assumed PDF (Probability Density Function) approach is used to simulate a model rocket combustor with finite-rate chemistry. The reported test case is the PennState preburner combustor with a single shear coaxial injector. Experimental data for the wall heat flux is available for this configuration. Unsteady RANS (Reynolds-averaged Navier-Stokes) simulation results with and without the assumed PDF approach are analyzed and compared with the experimental data. Both calculations show a good agreement with the experimental wall heat flux data. Significant changes due to the utilization of the assumed PDF approach can be observed in the radicals, e. g., the OH mass fraction distribution, while the effect on the wall heat flux is insignificant.

  3. Assumed modes method and flexible multibody dynamics

    NASA Technical Reports Server (NTRS)

    Tadikonda, S. S. K.; Mordfin, T. G.; Hu, T. G.

    1993-01-01

    The use of assumed modes in flexible multibody dynamics algorithms requires the evaluation of several domain dependent integrals that are affected by the type of modes used. The implications of these integrals - often called zeroth, first and second order terms - are investigated in this paper, for arbitrarily shaped bodies. Guidelines are developed for the use of appropriate boundary conditions while generating the component modal models. The issue of whether and which higher order terms must be retained is also addressed. Analytical results, and numerical results using the Shuttle Remote Manipulator System as the multibody system, are presented to qualitatively and quantitatively address these issues.

  4. Longitudinal distribution of cosmic rays in the heliosphere

    NASA Technical Reports Server (NTRS)

    Gold, R. E.; Venkatesan, D.

    1985-01-01

    The longitudinal distribution of cosmic ray intensity was examined during the years 1974-1976 when the persistent high speed solar wind stream structures produced a well ordered inner heliosphere. Solar wind velocity is mapped back to the Sun and compared with cosmic ray intensity which is represented relative to the solar rotation average. Low solar wind velocity is observed to be a necessary, but not sufficient, condition for the occurrence of higher cosmic ray intensities at 1 AU. These relative enhancements cover a restricted range of heliographic longitudes and persist for several solar rotations. The observed solar wind and cosmic ray intensity relationships are consistent with a simple model suggested here in which cosmic ray modulation is very weak in the inner heliosphere, sunward of the first shock crossing on each field line and more intense in the outer heliosphere.

  5. 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

  6. 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.

  7. Cosmic ray interactions in the ground: Temporal variations in cosmic ray intensities and geophysical studies

    NASA Technical Reports Server (NTRS)

    Lal, D.

    1986-01-01

    Temporal variations in cosmic ray intensity have been deduced from observations of products of interactions of cosmic ray particles in the Moon, meteorites, and the Earth. Of particular interest is a comparison between the information based on Earth and that based on other samples. Differences are expected at least due to: (1) differences in the extent of cosmic ray modulation, and (2) changes in the geomagnetic dipole field. Any information on the global changes in the terrestrial cosmic ray intensity is therefore of importance. In this paper a possible technique for detecting changes in cosmic ray intensity is presented. The method involves human intervention and is applicable for the past 10,000 yrs. Studies of changes over longer periods of time are possible if supplementary data on age and history of the sample are available using other methods. Also discussed are the possibilities of studying certain geophysical processes, e.g., erosion, weathering, tectonic events based on studies of certain cosmic ray-produced isotopes for the past several million years.

  8. 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.

  9. 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

  10. Cosmic string structure at the gravitational radiation scale

    SciTech Connect

    Polchinski, Joseph; Rocha, Jorge V.

    2007-06-15

    We use our model of the small scale structure on cosmic strings to develop further the result of Siemens, Olum, and Vilenkin that the gravitational radiation length scale on cosmic strings is smaller than the previously assumed {gamma}G{mu}t. We discuss some of the properties of cosmic string loops at this cutoff scale, and we argue that recent network simulations point to two populations of cosmic string loops, one near the horizon scale and one near the gravitational radiation cutoff.

  11. 46 CFR 174.075 - Compartments assumed flooded: general.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Units § 174.075 Compartments assumed flooded: general. The individual flooding of each of the... § 174.065 (a). Simultaneous flooding of more than one compartment must be assumed only when indicated...

  12. 46 CFR 174.075 - Compartments assumed flooded: general.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Units § 174.075 Compartments assumed flooded: general. The individual flooding of each of the... § 174.065 (a). Simultaneous flooding of more than one compartment must be assumed only when indicated...

  13. 46 CFR 174.075 - Compartments assumed flooded: general.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Units § 174.075 Compartments assumed flooded: general. The individual flooding of each of the... § 174.065 (a). Simultaneous flooding of more than one compartment must be assumed only when indicated...

  14. The 22-Year Hale Cycle in Cosmic Ray Flux - Evidence for Direct Heliospheric Modulation

    NASA Astrophysics Data System (ADS)

    Thomas, Simon; Owens, Mathew; Lockwood, Mike

    2013-04-01

    The ability to predict times of greater fluxes of galactic cosmic rays is important for reducing the hazards caused by these energetic particles on satellite communications, aviation and astronauts. During the 22-year Hale cycle, we see a difference in shape from a 'flat topped' to a 'spiked topped' peak in cosmic ray flux time series. It is thought that differing drift patterns for when the northern solar pole is predominantly positive (qA>0) to when the northern pole is negative (qA<0) cause this difference in cosmic ray modulation. Here, we demonstrate a link between cosmic ray modulation and properties of the large-scale heliospheric magnetic field during the declining phase of the solar cycle, when the difference between qA>0 and qA<0 cycles is most apparent. The results suggest that drift affects may not be the sole mechanism responsible for the Hale Cycle in cosmic ray flux at Earth. Further to this it is suggested that the Hale cycle in cosmic ray flux may be primarily limited to the grand solar maximum of the space-age.

  15. 24 CFR 234.66 - Free assumability; exceptions.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 24 Housing and Urban Development 2 2010-04-01 2010-04-01 false Free assumability; exceptions. 234... CONDOMINIUM OWNERSHIP MORTGAGE INSURANCE Eligibility Requirements-Individually Owned Units § 234.66 Free assumability; exceptions. For purposes of HUD's policy of free assumability with no restrictions, as...

  16. 24 CFR 234.66 - Free assumability; exceptions.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 24 Housing and Urban Development 2 2011-04-01 2011-04-01 false Free assumability; exceptions. 234... CONDOMINIUM OWNERSHIP MORTGAGE INSURANCE Eligibility Requirements-Individually Owned Units § 234.66 Free assumability; exceptions. For purposes of HUD's policy of free assumability with no restrictions, as...

  17. 24 CFR 234.66 - Free assumability; exceptions.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 24 Housing and Urban Development 2 2013-04-01 2013-04-01 false Free assumability; exceptions. 234... CONDOMINIUM OWNERSHIP MORTGAGE INSURANCE Eligibility Requirements-Individually Owned Units § 234.66 Free assumability; exceptions. For purposes of HUD's policy of free assumability with no restrictions, as...

  18. 24 CFR 234.66 - Free assumability; exceptions.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 24 Housing and Urban Development 2 2012-04-01 2012-04-01 false Free assumability; exceptions. 234... CONDOMINIUM OWNERSHIP MORTGAGE INSURANCE Eligibility Requirements-Individually Owned Units § 234.66 Free assumability; exceptions. For purposes of HUD's policy of free assumability with no restrictions, as...

  19. 24 CFR 234.66 - Free assumability; exceptions.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 24 Housing and Urban Development 2 2014-04-01 2014-04-01 false Free assumability; exceptions. 234... CONDOMINIUM OWNERSHIP MORTGAGE INSURANCE Eligibility Requirements-Individually Owned Units § 234.66 Free assumability; exceptions. For purposes of HUD's policy of free assumability with no restrictions, as...

  20. 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.

  1. Cosmic Flows

    NASA Astrophysics Data System (ADS)

    Tully, Brent; Courtois, Helene; Freedman, Wendy; Jarrett, Tom; Madore, Barry; Persson, Eric; Seibert, Mark; Shaya, Ed

    2011-05-01

    It is astonishing that only 30% of the motion of our Galaxy is understood, a fact that highlights a fundamental deficiency in our understanding of the composition of the Universe. Spitzer Cosmic Flows is the photometric component of a program to map the peculiar motions and large-scale flows of galaxies out to 200 Mpc in order to constrain the distribution of mass. This task requires measuring the peculiar velocity of galaxies, a response to the distribution of both baryonic and dark matter, densely sampled over the full sky. With an independent distance measurement, an observed galaxy redshift can be separated into cosmic expansion and peculiar velocity components. Spitzer Cosmic Flows will use IRAC 3.6 micron imaging to obtain independent distances using the correlation between galaxy luminosity and rotation rate (the mid-IR Tully-Fisher relation). The rotational velocity data is being acquired through the Cosmic Flows Large Program on the NRAO Green Bank Telescope and a complementary program of southern targets with the Parkes Telescope. Spitzer Cosmic Flows consists of five distinct samples totaling 4642 galaxies. New observations are required for 3531 galaxies and archival data exists for 1111 galaxies. Each of the samples serves a distinct purpose and/or domain while overlapping to assure a connectivity over a wide range of distances. The photometry of galaxies directly drives the peculiar velocity accuracy of this program. Spitzer IRAC 3.6 micron imaging provides the ability of a single instrument to perform the required imaging over the full sky with exquisite quality. The mid-IR traces the dominant stellar population with negligible extinction. Most importantly, the backgrounds are low from space enabling surface photometry to be extended to many exponential scale-lengths, capturing essentially all the light from the target.

  2. 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.

  3. Cosmic clocks

    NASA Astrophysics Data System (ADS)

    Jeong, Donghui; Schmidt, Fabian

    2014-02-01

    In a perturbed universe, comoving tracers on a two-dimensional surface of constant observed redshift are at different proper times since the big bang. For tracers whose age is known independently, one can measure these perturbations of the proper time. Examples of such sources include cosmic events which only happen during a short period of cosmic history, as well as evolving standard candles and standard rulers. In this paper, we derive a general gauge-invariant linear expression for this perturbation in terms of spacetime perturbations. We show that this perturbation in general contributes a previously overlooked leading order term to observables such as the magnification (although this contribution is generally small). Further, as an illustrative example, we show that the observed temperature perturbations of the cosmic microwave background on large scales (ℓ≪100) are exactly given by these proper-time perturbations. Together with the six ruler perturbations derived in [F. Schmidt and D. Jeong, Phys. Rev. D 86, 083527 (2012)], this completes the set of independent observables which can be measured with standard rulers and candles.

  4. Cosmic impacts, cosmic catastrophes. II

    NASA Astrophysics Data System (ADS)

    Chapman, C. R.; Morrison, D.

    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.

  5. Cosmic radioactivities

    NASA Astrophysics Data System (ADS)

    Arnould, Marcel; Prantzos, Nikos

    1999-07-01

    Radionuclides with half-lives ranging from some years to billions of years presumably synthesized outside of the solar system are now recorded in "live" or "fossil" form in various types of materials, like meteorites or the galactic cosmic rays. They bring specific astrophysical messages, the deciphering of which is briefly reviewed here, with special emphasis on the contribution of Dave Schramm and his collaborators to this exciting field of research. Short-lived radionuclides are also present in the Universe today, as directly testified by the γ-ray lines emitted by the de-excitation of their daughter products. A short review of recent developments in this field is also presented.

  6. Cosmic Catastrophes

    NASA Astrophysics Data System (ADS)

    Wheeler, J. Craig

    2000-07-01

    In this tour de force of the ultimate and extreme in astrophysics, renowned astrophysicist and author J. Craig Wheeler takes us on a breathtaking journey to supernovae, black holes, gamma-ray bursts and adventures in hyperspace. This is no far-fetched science fiction tale, but an enthusiastic exploration of ideas at the cutting edge of current astrophysics. Wheeler follows the tortuous life of a star from birth to evolution and death, and goes on to consider the complete collapse of a star into a black hole, worm-hole time machines, the possible birth of baby bubble universes, and the prospect of a revolutionary view of space and time in a ten-dimensional string theory. Along the way he offers evidence that suggests the Universe is accelerating and describes recent developments in understanding gamma-ray bursts--perhaps the most catastrophic cosmic events of all. With the use of lucid analogies, simple language and crystal-clear cartoons, Cosmic Catastrophes makes accessible some of the most exciting and mind-bending objects and ideas in the Universe. J. Craig Wheeler is currently Samuel T. and Fern Yanagisawa Regents Professor of Astronomy at the University of Texas at Austin and Vice President of the American Astronomical Society as of 1999.

  7. 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.

  8. Abstraction and Assume-Guarantee Reasoning for Automated Software Verification

    NASA Technical Reports Server (NTRS)

    Chaki, S.; Clarke, E.; Giannakopoulou, D.; Pasareanu, C. S.

    2004-01-01

    Compositional verification and abstraction are the key techniques to address the state explosion problem associated with model checking of concurrent software. A promising compositional approach is to prove properties of a system by checking properties of its components in an assume-guarantee style. This article proposes a framework for performing abstraction and assume-guarantee reasoning of concurrent C code in an incremental and fully automated fashion. The framework uses predicate abstraction to extract and refine finite state models of software and it uses an automata learning algorithm to incrementally construct assumptions for the compositional verification of the abstract models. The framework can be instantiated with different assume-guarantee rules. We have implemented our approach in the COMFORT reasoning framework and we show how COMFORT out-performs several previous software model checking approaches when checking safety properties of non-trivial concurrent programs.

  9. Assume-Guarantee Abstraction Refinement Meets Hybrid Systems

    NASA Technical Reports Server (NTRS)

    Bogomolov, Sergiy; Frehse, Goran; Greitschus, Marius; Grosu, Radu; Pasareanu, Corina S.; Podelski, Andreas; Strump, Thomas

    2014-01-01

    Compositional verification techniques in the assume- guarantee style have been successfully applied to transition systems to efficiently reduce the search space by leveraging the compositional nature of the systems under consideration. We adapt these techniques to the domain of hybrid systems with affine dynamics. To build assumptions we introduce an abstraction based on location merging. We integrate the assume-guarantee style analysis with automatic abstraction refinement. We have implemented our approach in the symbolic hybrid model checker SpaceEx. The evaluation shows its practical potential. To the best of our knowledge, this is the first work combining assume-guarantee reasoning with automatic abstraction-refinement in the context of hybrid automata.

  10. New approach to cosmic ray investigations above the knee

    NASA Astrophysics Data System (ADS)

    Bogdanov, A. G.; Kokoulin, R. P.; Petrukhin, A. A.

    2016-05-01

    It is assumed that at energies around the knee the nucleus-nucleus interaction is drastically changed due to production of blobs of quark-gluon matter with very large orbital momentum. This approach allows explain all so-called unusual events observed in cosmic rays and gives a new connection between results of EAS investigations and energy spectrum and mass composition of primary cosmic rays. To check this approach, the experiments in cosmic rays and at LHC are proposed.

  11. 24 CFR 201.19 - Refinanced and assumed loans.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... TITLE I PROPERTY IMPROVEMENT AND MANUFACTURED HOME LOANS Loan and Note Provisions § 201.19 Refinanced... manufactured home loan may be refinanced without an advance of funds only under the following conditions: (i) A... liability for repayment of the loan at the time the loan was assumed. A lender may not refinance...

  12. 24 CFR 201.19 - Refinanced and assumed loans.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... TITLE I PROPERTY IMPROVEMENT AND MANUFACTURED HOME LOANS Loan and Note Provisions § 201.19 Refinanced... manufactured home loan may be refinanced without an advance of funds only under the following conditions: (i) A... liability for repayment of the loan at the time the loan was assumed. A lender may not refinance...

  13. 46 CFR 174.075 - Compartments assumed flooded: general.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 7 2013-10-01 2013-10-01 false Compartments assumed flooded: general. 174.075 Section 174.075 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SUBDIVISION AND STABILITY SPECIAL RULES PERTAINING TO SPECIFIC VESSEL TYPES Special Rules Pertaining to Mobile Offshore...

  14. 46 CFR 174.075 - Compartments assumed flooded: general.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 7 2010-10-01 2010-10-01 false Compartments assumed flooded: general. 174.075 Section 174.075 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SUBDIVISION AND STABILITY SPECIAL RULES PERTAINING TO SPECIFIC VESSEL TYPES Special Rules Pertaining to Mobile Offshore...

  15. Positron fraction in cosmic rays and models of cosmic-ray propagation

    SciTech Connect

    Cowsik, R.; Burch, B.

    2010-07-15

    The positron fraction observed by PAMELA and other experiments up to {approx}100 GeV is analyzed in terms of models of cosmic-ray propagation. It is shown that generically we expect the positron fraction to reach {approx}0.6 at energies of several TeV, and its energy dependence bears an intimate but subtle connection with that of the boron to carbon ratio in cosmic rays. The observed positron fraction can be fit in a model that assumes a significant fraction of the boron below {approx}10 GeV is generated through spallation of cosmic-ray nuclei in a cocoonlike region surrounding the sources, and the positrons of energy higher than a few GeV are almost exclusively generated through cosmic-ray interactions in the general interstellar medium. Such a model is consistent with the bounds on cosmic-ray anisotropies and other observations.

  16. Automated Assume-Guarantee Reasoning by Abstraction Refinement

    NASA Technical Reports Server (NTRS)

    Pasareanu, Corina S.; Giannakopoulous, Dimitra; Glannakopoulou, Dimitra

    2008-01-01

    Current automated approaches for compositional model checking in the assume-guarantee style are based on learning of assumptions as deterministic automata. We propose an alternative approach based on abstraction refinement. Our new method computes the assumptions for the assume-guarantee rules as conservative and not necessarily deterministic abstractions of some of the components, and refines those abstractions using counter-examples obtained from model checking them together with the other components. Our approach also exploits the alphabets of the interfaces between components and performs iterative refinement of those alphabets as well as of the abstractions. We show experimentally that our preliminary implementation of the proposed alternative achieves similar or better performance than a previous learning-based implementation.

  17. Modeling turbulent/chemistry interactions using assumed pdf methods

    NASA Technical Reports Server (NTRS)

    Gaffney, R. L, Jr.; White, J. A.; Girimaji, S. S.; Drummond, J. P.

    1992-01-01

    Two assumed probability density functions (pdfs) are employed for computing the effect of temperature fluctuations on chemical reaction. The pdfs assumed for this purpose are the Gaussian and the beta densities of the first kind. The pdfs are first used in a parametric study to determine the influence of temperature fluctuations on the mean reaction-rate coefficients. Results indicate that temperature fluctuations significantly affect the magnitude of the mean reaction-rate coefficients of some reactions depending on the mean temperature and the intensity of the fluctuations. The pdfs are then tested on a high-speed turbulent reacting mixing layer. Results clearly show a decrease in the ignition delay time due to increases in the magnitude of most of the mean reaction rate coefficients.

  18. Chemically reacting supersonic flow calculation using an assumed PDF model

    NASA Technical Reports Server (NTRS)

    Farshchi, M.

    1990-01-01

    This work is motivated by the need to develop accurate models for chemically reacting compressible turbulent flow fields that are present in a typical supersonic combustion ramjet (SCRAMJET) engine. In this paper the development of a new assumed probability density function (PDF) reaction model for supersonic turbulent diffusion flames and its implementation into an efficient Navier-Stokes solver are discussed. The application of this model to a supersonic hydrogen-air flame will be considered.

  19. Delayed recombination and cosmic parameters

    SciTech Connect

    Galli, Silvia; Melchiorri, Alessandro; Bean, Rachel; Silk, Joseph

    2008-09-15

    Current cosmological constraints from cosmic microwave background anisotropies are typically derived assuming a standard recombination scheme, however additional resonance and ionizing radiation sources can delay recombination, altering the cosmic ionization history and the cosmological inferences drawn from the cosmic microwave background data. We show that for recent observations of the cosmic microwave background anisotropy, from the Wilkinson microwave anisotropy probe satellite mission (WMAP) 5-year survey and from the arcminute cosmology bolometer array receiver experiment, additional resonance radiation is nearly degenerate with variations in the spectral index, n{sub s}, and has a marked effect on uncertainties in constraints on the Hubble constant, age of the universe, curvature and the upper bound on the neutrino mass. When a modified recombination scheme is considered, the redshift of recombination is constrained to z{sub *}=1078{+-}11, with uncertainties in the measurement weaker by 1 order of magnitude than those obtained under the assumption of standard recombination while constraints on the shift parameter are shifted by 1{sigma} to R=1.734{+-}0.028. From the WMAP5 data we obtain the following constraints on the resonance and ionization sources parameters: {epsilon}{sub {alpha}}<0.39 and {epsilon}{sub i}<0.058 at 95% c.l.. Although delayed recombination limits the precision of parameter estimation from the WMAP satellite, we demonstrate that this should not be the case for future, smaller angular scales measurements, such as those by the Planck satellite mission.

  20. Cosmic censorship and test particles

    SciTech Connect

    Needham, T.

    1980-08-15

    In this paper one unambiguous prediction of cosmic censorship is put to the test, namely that it should be impossible to destroy a black hole (i.e. eliminate its horizon) by injecting test particles into it. Several authors have treated this problem and have not found their conclusions in contradiction with the prediction. Here we prove that if a general charged spinning particle (with parameters very much smaller than the respective hole parameters) is injected in an arbitrary manner into an extreme Kerr-Newman black hole, then cosmic censorship is upheld. As a by-product of the analysis a natural proof is given of the Christodoulou-Ruffini conditions on the injection of a spinless particle which yield a reversible black-hole transformation. Finally we consider the injection of particles with parameters that are not small compared with those of the hole, for which cosmic censorship is apparently violated. By assuming the validity of cosmic censorship we are led to a few conjectures concerning the extent of the particle's interaction with the hole while approaching it.

  1. Delayed recombination and cosmic parameters

    NASA Astrophysics Data System (ADS)

    Galli, Silvia; Bean, Rachel; Melchiorri, Alessandro; Silk, Joseph

    2008-09-01

    Current cosmological constraints from cosmic microwave background anisotropies are typically derived assuming a standard recombination scheme, however additional resonance and ionizing radiation sources can delay recombination, altering the cosmic ionization history and the cosmological inferences drawn from the cosmic microwave background data. We show that for recent observations of the cosmic microwave background anisotropy, from the Wilkinson microwave anisotropy probe satellite mission (WMAP) 5-year survey and from the arcminute cosmology bolometer array receiver experiment, additional resonance radiation is nearly degenerate with variations in the spectral index, ns, and has a marked effect on uncertainties in constraints on the Hubble constant, age of the universe, curvature and the upper bound on the neutrino mass. When a modified recombination scheme is considered, the redshift of recombination is constrained to z*=1078±11, with uncertainties in the measurement weaker by 1 order of magnitude than those obtained under the assumption of standard recombination while constraints on the shift parameter are shifted by 1σ to R=1.734±0.028. From the WMAP5 data we obtain the following constraints on the resonance and ionization sources parameters: γα<0.39 and γi<0.058 at 95% c.l.. Although delayed recombination limits the precision of parameter estimation from the WMAP satellite, we demonstrate that this should not be the case for future, smaller angular scales measurements, such as those by the Planck satellite mission.

  2. An ab initio model for the modulation of galactic cosmic-ray electrons

    SciTech Connect

    Engelbrecht, N. E.; Burger, R. A.

    2013-12-20

    The modulation of galactic cosmic-ray electrons is studied using an ab initio three-dimensional steady state cosmic-ray modulation code in which the effects of turbulence on both the diffusion and drift of these cosmic-rays are treated as self-consistently as possible. A significant refinement is that a recent two-component turbulence transport model is used. This model yields results in reasonable agreement with observations of turbulence quantities throughout the heliosphere. The sensitivity of computed galactic electron intensities to choices of various turbulence parameters pertaining to the dissipation range of the slab turbulence spectrum, and to the choice of model of dynamical turbulence, is demonstrated using diffusion coefficients derived from the quasi-linear and extended nonlinear guiding center theories. Computed electron intensities and latitude gradients are also compared with spacecraft observations.

  3. Effects of particle drift on the transport of cosmic rays. IV - More realistic diffusion coefficients

    NASA Technical Reports Server (NTRS)

    Jokipii, J. R.; Davila, J. M.

    1981-01-01

    Results from numerical simulations of cosmic-ray modulations by the solar wind are presented which show that the scattering mean free path should be larger than the particle gyroradius in the average magnetic field. It is found that the difference between drift and no-drift solutions is not as great as in previous simulations, which violated the mean free path constraint stated. Profound effects are still noted for the drifts, which determine the origin of the bulk of the cosmic rays seen at any given time in the inner solar system. Accordingly, during the 1975 solar minimum, the positively charged cosmic rays seen in the inner solar system came primarily from the outer boundary near the heliospheric poles while negative particles came from the equatorial regions of the boundary.

  4. Cosmic Discovery

    NASA Astrophysics Data System (ADS)

    Harwit, Martin

    1984-04-01

    In the remarkable opening section of this book, a well-known Cornell astronomer gives precise thumbnail histories of the 43 basic cosmic discoveries - stars, planets, novae, pulsars, comets, gamma-ray bursts, and the like - that form the core of our knowledge of the universe. Many of them, he points out, were made accidentally and outside the mainstream of astronomical research and funding. This observation leads him to speculate on how many more major phenomena there might be and how they might be most effectively sought out in afield now dominated by large instruments and complex investigative modes and observational conditions. The book also examines discovery in terms of its political, financial, and sociological context - the role of new technologies and of industry and the military in revealing new knowledge; and methods of funding, of peer review, and of allotting time on our largest telescopes. It concludes with specific recommendations for organizing astronomy in ways that will best lead to the discovery of the many - at least sixty - phenomena that Harwit estimates are still waiting to be found.

  5. 17. Photographic copy of photograph. Location unknown but assumed to ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    17. Photographic copy of photograph. Location unknown but assumed to be uper end of canal. Features no longer extant. (Source: U.S. Department of Interior. Office of Indian Affairs. Indian Irrigation service. Annual Report, Fiscal Year 1925. Vol. I, Narrative and Photographs, Irrigation District #4, California and Southern Arizona, RG 75, Entry 655, Box 28, National Archives, Washington, DC.) Photographer unknown. MAIN (TITLED FLORENCE) CANAL, WASTEWAY, SLUICEWAY, & BRIDGE, 1/26/25. - San Carlos Irrigation Project, Marin Canal, Amhurst-Hayden Dam to Picacho Reservoir, Coolidge, Pinal County, AZ

  6. Plasma expansion into vacuum assuming a steplike electron energy distribution.

    PubMed

    Kiefer, Thomas; Schlegel, Theodor; Kaluza, Malte C

    2013-04-01

    The expansion of a semi-infinite plasma slab into vacuum is analyzed with a hydrodynamic model implying a steplike electron energy distribution function. Analytic expressions for the maximum ion energy and the related ion distribution function are derived and compared with one-dimensional numerical simulations. The choice of the specific non-Maxwellian initial electron energy distribution automatically ensures the conservation of the total energy of the system. The estimated ion energies may differ by an order of magnitude from the values obtained with an adiabatic expansion model supposing a Maxwellian electron distribution. Furthermore, good agreement with data from experiments using laser pulses of ultrashort durations τ(L)assumed.

  7. 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

  8. Cosmic Ray Acceleration in Supernova Remnants and Propagation in Galactic Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Shin, Taeksu

    We propose a detailed study of cosmic ray energy spectra from 1 to 10^6 GeV/nucleon for relativistic nuclei accelerated in different types of supernova remnants. We will also study elemental composition and spectral structure from the knee around 10^6 GeV/nucleon to the energy limit of Galactic sources. This will bring modelling of cosmic ray acceleration and propagation to the level of modern high-accuracy experimental studies. The latter have shown that cosmic ray spectra deviate from simple power laws at 10 to 10^5 GeV/nucleon energies, and they have revealed fine structure in the spectrum above the knee at energies 3x10^6 10^8 GeV. Modeling the interstellar spectra at energies less than 1 GeV/nucleon will also be undertaken in support of cosmic ray modulation studies in the heliosphere. The numerical nonlinear model that we developed earlier for shock acceleration of cosmic rays in supernova remnants with forward and reverse shocks will be employed in this work. The most significant part of the research will be elaboration of a scenario of cosmic ray propagation in the Galaxy that would be compatible with both the modern theory of interstellar magneto- hydrodynamic turbulence and recent observations of cosmic ray spectral composition and anisotropy. This scenario will include the transport of cosmic rays by the galactic wind, and it will allow studies of cosmic ray intensity fluctuations in a galactic wind model. Our model calculations will be compared with the measurements for the interpretation of data. Understanding the nature of cosmic accelerators addresses NASA s 2010 Science Plan for the Science Mission Directorate s Science Goal for Astrophysics, Discover how the universe works, explore how the universe began and evolved, and search for Earth- like planets. Specifically, it addresses the Science Question, How do matter, energy, space and time behave under the extraordinarily diverse conditions of the cosmos?

  9. 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.

  10. Inference of directional selection and mutation parameters assuming equilibrium.

    PubMed

    Vogl, Claus; Bergman, Juraj

    2015-12-01

    In a classical study, Wright (1931) proposed a model for the evolution of a biallelic locus under the influence of mutation, directional selection and drift. He derived the equilibrium distribution of the allelic proportion conditional on the scaled mutation rate, the mutation bias and the scaled strength of directional selection. The equilibrium distribution can be used for inference of these parameters with genome-wide datasets of "site frequency spectra" (SFS). Assuming that the scaled mutation rate is low, Wright's model can be approximated by a boundary-mutation model, where mutations are introduced into the population exclusively from sites fixed for the preferred or unpreferred allelic states. With the boundary-mutation model, inference can be partitioned: (i) the shape of the SFS distribution within the polymorphic region is determined by random drift and directional selection, but not by the mutation parameters, such that inference of the selection parameter relies exclusively on the polymorphic sites in the SFS; (ii) the mutation parameters can be inferred from the amount of polymorphic and monomorphic preferred and unpreferred alleles, conditional on the selection parameter. Herein, we derive maximum likelihood estimators for the mutation and selection parameters in equilibrium and apply the method to simulated SFS data as well as empirical data from a Madagascar population of Drosophila simulans.

  11. Cosmic electrons. [literature review

    NASA Technical Reports Server (NTRS)

    Ramaty, R.

    1974-01-01

    The published literature on cosmic electrons is summarized. The primary and secondary sources of cosmic electrons are discussed, and the propagation of the electrons in the interstellar medium is studied with respect to energy loss mechanisms, age distributions, and spectral modifications during flight. Various portions of the electron and positron spectra are then considered in relation to problems of astrophysics. New information is presented on such topics as the origin of low-energy positrons, the decay kinematics of the pi-mu-e process, the application of age distributions for nuclear cosmic rays to cosmic electrons, and the possibility of nonidentical sources for cosmic electrons and protons.

  12. Cosmic Complexity

    NASA Technical Reports Server (NTRS)

    Mather, John C.

    2012-01-01

    neutrons, liberating a little energy and creating complexity. Then, the expanding universe cooled some more, and neutrons and protons, no longer kept apart by immense temperatures, found themselves unstable and formed helium nuclei. Then, a little more cooling, and atomic nuclei and electrons were no longer kept apart, and the universe became transparent. Then a little more cooling, and the next instability began: gravitation pulled matter together across cosmic distances to form stars and galaxies. This instability is described as a "negative heat capadty" in which extracting energy from a gravitating system makes it hotter -- clearly the 2nd law of thermodynamics does not apply here! (This is the physicist's part of the answer to e e cummings' question: what is the wonder that's keeping the stars apart?) Then, the next instability is that hydrogen and helium nuclei can fuse together to release energy and make stars burn for billions of years. And then at the end of the fuel source, stars become unstable and explode and liberate the chemical elements back into space. And because of that, on planets like Earth, sustained energy flows support the development of additional instabilities and all kinds of complex patterns. Gravitational instability pulls the densest materials into the core of the Earth, leaving a thin skin of water and air, and makes the interior churn incessantly as heat flows outwards. And the heat from the sun, received mostly near the equator and flowing towards the poles, supports the complex atmospheric and oceanic circulations. And because or that, the physical Earth is full of natural chemical laboratories, concentrating elements here, mixing them there, raising and lowering temperatures, ceaselessly experimenting with uncountable events where new instabilities can arise. At least one of them was the new experiment called life. Now that we know that there are at least as many planets as there are stars, it is hard to imagine that nature's ceasess

  13. Cosmic Complexity

    NASA Technical Reports Server (NTRS)

    Mather, John C.

    2012-01-01

    neutrons, liberating a little energy and creating complexity. Then, the expanding universe cooled some more, and neutrons and protons, no longer kept apart by immense temperatures, found themselves unstable and formed helium nuclei. Then, a little more cooling, and atomic nuclei and electrons were no longer kept apart, and the universe became transparent. Then a little more cooling, and the next instability began: gravitation pulled matter together across cosmic distances to form stars and galaxies. This instability is described as a "negative heat capadty" in which extracting energy from a gravitating system makes it hotter -- clearly the 2nd law of thermodynamics does not apply here! (This is the physicist's part of the answer to e e cummings' question: what is the wonder that's keeping the stars apart?) Then, the next instability is that hydrogen and helium nuclei can fuse together to release energy and make stars burn for billions of years. And then at the end of the fuel source, stars become unstable and explode and liberate the chemical elements back into space. And because of that, on planets like Earth, sustained energy flows support the development of additional instabilities and all kinds of complex patterns. Gravitational instability pulls the densest materials into the core of the Earth, leaving a thin skin of water and air, and makes the interior churn incessantly as heat flows outwards. And the heat from the sun, received mostly near the equator and flowing towards the poles, supports the complex atmospheric and oceanic circulations. And because or that, the physical Earth is full of natural chemical laboratories, concentrating elements here, mixing them there, raising and lowering temperatures, ceaselessly experimenting with uncountable events where new instabilities can arise. At least one of them was the new experiment called life. Now that we know that there are at least as many planets as there are stars, it is hard to imagine that nature's ceasess

  14. The effect of cosmic rays on thunderstorm electricity

    NASA Technical Reports Server (NTRS)

    Bragin, Y. A.

    1975-01-01

    The inflow of charges of small ions, formed by cosmic rays, into thunderstorm cells is estimated on the basis of rocket measurements of ionic concentrations below 90 km. Out of the two processes that form the thunderstorm charge (generation and separation of charges), the former is supposed to be caused by cosmic rays, and the nature of separation is assumed to be the same as in other thunderstorm theories.

  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 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)

  17. An ab initio approach to the anisotropic perpendicular diffusion of galactic cosmic rays

    NASA Astrophysics Data System (ADS)

    Engelbrecht, Nicholas; Richardson, John; Burger, Renier

    2016-07-01

    The assumption that cosmic-ray diffusion perpendicular to the background magnetic field is anisotropic has been made in many numerical modulation studies. This was done in order to reproduce spacecraft observations of, for example, lower than expected latitude gradients of galactic protons. This assumption is usually justified in terms of observations of non-axisymmetric turbulent magnetic fluctuations, but is often implemented in a completely ad hoc manner. This study implements anisotropic perpendicular diffusion coefficients in an ab initio cosmic ray modulation model in a self-consistent manner, employing perpendicular mean free path expressions derived for the case where transverse magnetic fluctuations are non-axisymmetric. Voyager magnetic field observations are analysed to ascertain the nature of this non-axisymmetry, and modulation model solutions for various assumptions as to the spatial dependence of this non-axisymmetry, also taking into account the Voyager observations, are presented.

  18. The abundances of the heavier elements in the cosmic radiation

    NASA Technical Reports Server (NTRS)

    Binns, W. R.; Israel, M. H.; Klarmann, J.; Garrard, T. L.; Stone, E. C.

    1989-01-01

    Current work on the abundances of the ultraheavy elements in the cosmic radiation, i.e., those with Z greater than 30 is reviewed. Those abundances are compared with predictions based on propagation and fractionation of elemental abundances from various assumed sources of the cosmic rays. Striking similarities are found between the solar system and the cosmic ray source abundances for those elements with Z values between 32 and 60. For elements with Z greater than 60, there appears to be a substantial enhancement in the abundances of elements synthesized in the r-process.

  19. Steady state and dynamical structure of a cosmic-ray-modified termination shock

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    A hydrodynamic model is developed for the structure of a cosmic-ray-modified termination shock. The model is based on the two-fluid equations of diffuse shock acceleration (Drury and Volk, 1981). Both the steady state structure of the shock and its interaction with outer heliospheric disturbances are considered. Under the assumption that the solar wind is decelerated by diffusing interstellar cosmic rates, it is shown that the natural state of the termination shock is a gradual deceleration and compression, followed by a discontinuous jump to a downstream state which is dominated by the pressure contribution of the cosmic rays. A representative model is calculated for the steady state which incorporates both interstellar cosmic ray mediation and diffusively accelerated anomalous ions through a proposed thermal leakage mechanism. The interaction of large-scale disturbances with the equilibrium termination shock model is shown to result in some unusual downstream structure, including transmitted shocks and cosmic-ray-modified contact discontinuities. The structure observed may be connected to the 2-kHz outer heliospheric radio emission (Cairns et al., 1992a, b). The time-dependent simulations also demonstrate that interaction with solar wind compressible turbulence (e.g., traveling interplanetary shocks, etc.) could induce the termination shock to continually fluctuate between cosmic-ray-dominated and gas-dynamic states. This fluctuation may represent a partial explanation of the galactic cosmic ray modulation effect and illustrates that the Pioneer and Voyager satellites will encounter an evolving shock whose structure and dynamic properties are strongly influence by the mediation of interstellar and anomalous cosmic rays.

  20. 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…

  1. 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.

  2. 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…

  3. 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.

  4. 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.

  5. 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.

  6. Determination of galactic cosmic ray latitudinal gradient using Earth based detectors

    NASA Technical Reports Server (NTRS)

    BADRUDDIN; Yadav, R. S.

    1985-01-01

    Using cosmic ray intensity data from the Deep River Neutron monitor and the relation between solar wind velocity and heliomagnetic latitude, an attempt is made to evaluate quantitatively the latitudinal gradient of cosmic ray intensity during the periods dominated by a two sector pattern. Assuming a constant orientation of the heliospheric current sheet on a time scale of the order of a year, a relationship is determined between cosmic ray intensity and heliomagnetic latitude.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  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. 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

  13. 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

  14. 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.

  15. The dependence of solar modulation on the sign of the cosmic ray particle charge

    NASA Technical Reports Server (NTRS)

    Garcia-Munoz, M.; Meyer, P.; Pyle, K. R.; Simpson, J. A.; Evenson, P.

    1986-01-01

    ISEE-3 spacecraft cosmic ray telescope data on the modulation of cosmic ray electrons are compared with IMP-8 spacecraft data on low energy He atoms to evaluate the effects of solar maxima on cosmic ray modulation. The investigation is constrained to the modulation of 70-95 MeV He-4 nuclei and 600-1000 MeV electrons over the period 1965-1984, an interval covering solar maxima in 1970 and 1981. It is shown that the occurrences of solar maxima are associated with magnetic field polarity reversals. When the interplanetary magnetic field reverses polarity, oppositely charged particles flow in different directions, thereby permitting studies of drift effects and modulation. Data on the recovery periods after the solar maxima show that the He-4 nuclei recovered before the electron population in 1970, while the situation was reversed in 1981. Actual flux ratio reversals were recorded in the years surrounding the maxima. Although the data support a connection between modulation of cosmic rays and the sign of charged particles, current models cannot account for the deviation of electron intensities from the nuclei intensities.

  16. Anisotropy of TeV Galactic cosmic rays

    NASA Astrophysics Data System (ADS)

    Zhang, Ming; Pogorelov, Nikolai; Desiati, Paolo; DuVernois, Michael

    2016-07-01

    TeV cosmic rays are significantly deflected by the magnetic field of the heliosphere, and they gain or lose energies in heliospheric electric field that in the meantime drives the motion of plasma. These propagation mechanisms will cause the map of TeV cosmic rays seen at the Earth to look different from the map seen in the local interstellar medium without the presence of the heliosphere. We have developed a method of using Liouville's theorem to map out particle distribution function to Earth from the local interstellar medium, where we assume that the cosmic rays have small pitch-angle anisotropy harmonics up to the second order and a small uniform spatial density gradient. The amount of heliospheric distortion can be determined by tracing the trajectories of cosmic rays propagating through the heliosphere. In this paper, we apply this method to TeV cosmic ray propagation through a MHD-kinetic model of the heliosphere and try to fit observations from Tibet ASgamma and IceCube experiments. We are able to locate features in the TeV cosmic ray anisotropy that are associated with the interstellar magnetic field, hydrogen deflection plane, heliotail, and solar corona. Some of the features are also slightly affected by the solar cycle and interstellar magnetic turbulence. The results provide us powerful tools to explore large-scale heliospheric structures as well as to determine the cosmic ray distribution in the local interstellar medium.

  17. Statistical Comparison of Anomalous Cosmic Rays and Galactic Cosmic Rays during the Recently Consecutive Unusual Solar Cycles

    NASA Astrophysics Data System (ADS)

    Zhao, L.; Zhang, H.

    2014-12-01

    Anomalous cosmic rays (ACRs) carry crucial information on the coupling between solar wind and interstellar medium, as well as cosmic ray modulation within the heliosphere. Due to the distinct origins and modulation processes, the spectra and abundance of ACRs are significantly different from that of galactic cosmic rays (GCRs). Since the launch of NASA's ACE spacecraft in 1997, its CRIS and SIS instruments have continuously recorded GCR and ACR intensities of several elemental heavy-ions, spanning the whole cycle 23 and the cycle 24 maximum. Here we present a statistical comparison of ACR and GCR observed by ACE spacecraft and their possible relation to solar activity. While the differential flux of ACR also exhibits apparent anti-correlation with solar activity level, the flux of the latest prolonged solar minimum (year 2009) is approximately 5% lower than its previous solar minimum (year 1997). And the minimal level of ACR flux appears in year 2004, instead of year 2001 with the strongest solar activities. The negative indexes of the power law spectra within the energy range from 5 to 30 MeV/nuc also vary with time. The spectra get harder during the solar minimum but softer during the solar maximum. The approaching solar minimum of cycle 24 is believed to resemble the Dalton or Gleissberg Minimum with extremely low solar activity (Zolotova and Ponyavin, 2014). Therefore, the different characteristics of ACRs between the coming solar minimum and the previous minimum are also of great interest. Finally, we will also discuss the possible solar-modulation processes which is responsible for different modulation of ACR and GCR, especially the roles played by diffusion and drifts. The comparative analysis will provide valuable insights into the physical modulation process within the heliosphere under opposite solar polarity and variable solar activity levels.

  18. Pulsars, supernovae, and ultrahigh energy cosmic rays

    NASA Astrophysics Data System (ADS)

    Kotera, K.; Fang, K.; Olinto, A. V.; Phinney, E. S.

    2012-12-01

    The acceleration of ultrahigh energy nuclei in fast spinning newborn pulsars can explain the observed spectrum of ultrahigh energy cosmic rays and the trend towards heavier nuclei for energies above 10^{19} eV as indicated by air shower studies reported by the Auger Observatory. By assuming a normal distribution of pulsar birth periods centered at 300 ms, we show that the contribution of extragalactic pulsar births to the ultrahigh energy cosmic ray spectrum naturally gives rise to a contribution to very high energy cosmic rays (VHECRs, between 10^{16} and 10^{18} eV) by Galactic pulsar births. The required injected composition to fit the observed spectrum depends on the absolute energy scale, differing considerably between the energy scale used by Auger and that used by the Telescope Array. Depending on the composition of the cosmic rays that escape the supernova remnant and the diffusion behavior of VHECRs in the Galaxy, the contribution of Galactic pulsar births can also bridge the gap between predictions for cosmic ray acceleration in supernova remnants and the observed spectrum below the ankle. Fast spinning newborn pulsars that could produce UHECRs would be born in supernovae that could present interesting specific radiative features, due to the interaction of the pulsar wind with the surrounding ejecta. The resulting supernova lightcurves could present a high luminosity plateau over a few years, and a bright X-ray and gamma-ray peak around one or two years after the onset of the explosion. If such signatures were observed, they could have important implications both for UHECR astrophysics and for the understanding of core-collapse supernovae.

  19. Preliminary Study of the 400-Year Geomagnetic Cutoff Rigidity Changes, Cosmic Rays and Possible Climate Changes

    NASA Astrophysics Data System (ADS)

    Shea, Margaret Ann; Smart, D. F.

    2003-07-01

    The studies of Friis-Christensen and Svensmark reported a variation of 34% in the global cloud cover between 1980 and 1995 that appeared to be correlated with the change in galactic cosmic radiation flux over the solar cycle. Using world grids of vertical cutoff rigidities calculated over a 400-year interval and assuming constant solar modulation over that period, we find that the cosmic ray flux over the glob e has increased by 18 percent. This change is equivalent to the cosmic ray flux at high latitude locations over a solar cycle. We also find that the change in the cosmic ray flux over the 400-year interval is not uniformly distributed. We suggest that the long-term change in the cosmic radiation impinging at the top of the atmosphere at specific locations on the glob e should be considered in studies of possible relationships between cosmic radiation and climate.

  20. Angular correlation of cosmic neutrinos with ultrahigh-energy cosmic rays and implications for their sources

    SciTech Connect

    Moharana, Reetanjali; Razzaque, Soebur E-mail: srazzaque@uj.ac.za

    2015-08-01

    Cosmic neutrino events detected by the IceCube Neutrino Observatory with energy 0∼> 3 TeV have poor angular resolutions to reveal their origin. Ultrahigh-energy cosmic rays (UHECRs), with better angular resolutions at 0>6 EeV energies, can be used to check if the same astrophysical sources are responsible for producing both neutrinos and UHECRs. We test this hypothesis, with statistical methods which emphasize invariant quantities, by using data from the Pierre Auger Observatory, Telescope Array and past cosmic-ray experiments. We find that the arrival directions of the cosmic neutrinos are correlated with 0≥ 10 EeV UHECR arrival directions at confidence level ≈ 90%. The strength of the correlation decreases with decreasing UHECR energy and no correlation exists at energy 0∼ 6 EeV . A search in astrophysical databases within 3{sup o} of the arrival directions of UHECRs with energy 0≥ 10 EeV, that are correlated with the IceCube cosmic neutrinos, resulted in 18 sources from the Swift-BAT X-ray catalog with redshift z≤ 0.06. We also found 3 objects in the Kühr catalog of radio sources using the same criteria. The sources are dominantly Seyfert galaxies with Cygnus A being the most prominent member. We calculate the required neutrino and UHECR fluxes to produce the observed correlated events, and estimate the corresponding neutrino luminosity (25 TeV–2.2 PeV) and cosmic-ray luminosity (500 TeV–180 EeV), assuming the sources are the ones we found in the Swift-BAT and Kühr catalogs. We compare these luminosities with the X-ray luminosity of the corresponding sources and discuss possibilities of accelerating protons to 0∼> 10 EeV and produce neutrinos in these sources.

  1. 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.

  2. 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.

  3. FORCE: FORtran for Cosmic Errors

    NASA Astrophysics Data System (ADS)

    Colombi, Stéphane; Szapudi, István

    We review the theory of cosmic errors we have recently developed for count-in-cells statistics. The corresponding FORCE package provides a simple and useful way to compute cosmic covariance on factorial moments and cumulants measured in galaxy catalogs.

  4. Gamma-ray emitting supernova remnants as the origin of Galactic cosmic rays?

    NASA Astrophysics Data System (ADS)

    Becker Tjus, Julia; Eichmann, Björn; Kroll, Mike; Nierstenhöfer, Nils

    2016-08-01

    The origin of cosmic rays is one of the long-standing mysteries in physics and astrophysics. Simple arguments suggest that a scenario of supernova remnants (SNRs) in the Milky Way as the dominant sources for the cosmic ray population below the knee could work: a generic calculation indicates that these objects can provide the energy budget necessary to explain the observed flux of cosmic rays. However, this argument is based on the assumption that all sources behave in the same way, i.e. they all have the same energy budget, spectral behavior and maximum energy. In this paper, we investigate if a realistic population of SNRs is capable of producing the cosmic ray flux as it is observed below the knee. We use 21 SNRs that are well-studied from radio wavelengths up to gamma-ray energies and derive cosmic ray spectra under the assumption of hadronic emission. The cosmic ray spectra show a large variety in their energy budget, spectral behavior and maximum energy. These sources are assumed to be representative for the total class of SNRs, where we assume that about 100-200 cosmic ray emitting SNRs should be present today. Finally, we use these source spectra to simulate the cosmic ray transport from individual SNRs in the Galaxy with the GALPROP code for cosmic ray propagation. We find that the cosmic ray budget can be matched well for these sources. We conclude that gamma-ray emitting SNRs can be a representative sample of cosmic ray emitting sources. In the future, experiments like CTA and HAWC will help to distinguish hadronic from leptonic sources and to further constrain the maximum energy of the sources and contribute to producing a fully representative sample in order to further investigate the possibility of SNRs being the dominant sources of cosmic rays up to the knee.

  5. Solar induced long- and short-term variations of the cosmic ray intensity in the past, and predictions and opportunities for the future

    NASA Astrophysics Data System (ADS)

    McCracken, K. G.; McDonald, F. B.; Beer, J.

    2009-12-01

    The cosmogenic radionuclide data from the past 10,000 years, and the instrumental cosmic ray data since 1936 provide detailed information on the possible consequences of the present long and deep solar minimum. Furthermore, the cosmic ray transport equation has been used to estimate the strength of the interplanetary magnetic field (IMF) throughout the past 10,000 years. This paper presents a series of figures that document the behavior of both the cosmic radiation and the IMF at Earth in the past. In particular, the 11-year cycles in both quantities for the past 600 years are displayed; and estimates given of the cosmic ray spectrum at Earth for situations that history tells us may occur in the near future. Over the longer term, a minimum of the Hallstatt cycle (2200 yr periodicity) of solar activity occurred ~500 years ago and the Sun is now on a steadily rising plane of activity. The historic record shows that the cosmic ray intensity has decreased extremely rapidly after earlier prolonged deep minima and this suggests rapid and large changes in the heliospheric conditions that we may see replicated. The paper will also display data from the deep, isolated solar minimum of 1956 that exhibited unusual low energy cosmic ray fluxes, and a highly anomalous cosmic ray gradient in the inner heliosphere. Paleo-cosmic ray evidence will also be displayed of an episode of intense solar energetic particle (SEP) events in the interval of reduced solar activity, 1892-1900, that may possibly be repeated. If the present long, deep solar minimum is a precursor to a “Grand Minimum” such as the Dalton minimum, it will provide a much improved insight into the spectrum of the cosmic radiation in interstellar space, and to the cosmic ray modulation process in the heliosphere. With this in mind, the paper suggests key measurements, and speculates on experimental conditions that may be markedly different from those encountered in the instrumental era.

  6. 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.

  7. 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.

  8. 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.

  9. Cosmic microwave background polarization signals from tangled magnetic fields.

    PubMed

    Seshadri, T R; Subramanian, K

    2001-09-01

    Tangled, primordial cosmic magnetic fields create small rotational velocity perturbations on the last scattering surface of the cosmic microwave background radiation. For fields which redshift to a present value of B0 = 3 x 10(-9) G, these vector modes are shown to generate polarization anisotropies of order 0.1-4 microK on small angular scales (500assuming delta function or a power law spectra with n = -1. About 200 times larger signals result for n = 2 spectra. Unlike inflation generated, scalar modes, these signals are dominated by the odd parity, B-type polarization, which could help in their detection.

  10. Distortion of the cosmic background radiation by superconducting strings

    NASA Technical Reports Server (NTRS)

    Ostriker, J. P.; Thompson, C.

    1987-01-01

    Superconducting cosmic strings can be significant energy sources, keeping the universe ionized past the commonly assumed epoch of recombination. As a result, the spectrum of the cosmic background radiation is distorted in the presence of heated primordial gas via the Suniaev-Zel'dovich effect. Thiis distortion can be relatively large: the Compton y parameter attains a maximum in the range 0.001-0.005, with these values depending on the mass scale of the string. A significant contribution to y comes from loops decaying at high redshift when the universe is optically thick to Thomson scattering. Moreover, the isotropic spectral distortion is large compared to fluctuations at all angular scales.

  11. Bosonic condensates in realistic supersymmetric GUT cosmic strings

    NASA Astrophysics Data System (ADS)

    Allys, Erwan

    2016-04-01

    We study the realistic structure of F-term Nambu-Goto cosmic strings forming in a general supersymmetric Grand Unified Theory implementation, assuming standard hybrid inflation. Examining the symmetry breaking of the unification gauge group down to the Standard Model, we discuss the minimal field content necessary to describe abelian cosmic strings appearing at the end of inflation. We find that several fields will condense in most theories, questioning the plausible occurrence of associated currents (bosonic and fermionic). We perturbatively evaluate the modification of their energy per unit length due to the condensates. We provide a criterion for comparing the usual abelian Higgs approximation used in cosmology to realistic situations.

  12. 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…

  13. 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.

  14. Recombination clumping factor during cosmic reionization

    SciTech Connect

    Kaurov, Alexander A.; Gnedin, Nickolay Y. E-mail: gnedin@fnal.gov

    2014-06-01

    We discuss the role of recombinations in the intergalactic medium, and the related concept of the clumping factor, during cosmic reionization. The clumping factor is, in general, a local quantity that depends on both the local overdensity and the scale below which the baryon density field can be assumed smooth. That scale, called the filtering scale, depends on over-density and local thermal history. We present a method for building a self-consistent analytical model of inhomogeneous reionization, assuming the linear growth rate of the density fluctuation, which simultaneously accounts for these effects. We show that taking into account the local clumping factor introduces significant corrections to the total recombination rate, compared to the model with a globally uniform clumping factor.

  15. Radiative Feedback Effects during Cosmic Reionization

    NASA Astrophysics Data System (ADS)

    Sullivan, David; Iliev, Ilian T.

    2016-10-01

    We present coupled radiation hydrodynamical simulations of the epoch of reionization, aimed at probing self-feedback on galactic scales. Unlike previous works, which assume a (quasi) homogeneous UV background, we self-consistently evolve both the radiation field and the gas to model the impact of previously unresolved processes such as spectral hardening and self-shielding. We find that the characteristic halo mass with a gas fraction half the cosmic mean, Mc (z), a quantity frequently used in semi-analytical models of galaxy formation, is significantly larger than previously assumed. While this results in an increased suppression of star formation in the early Universe, our results are consistent with the extrapolated stellar abundance matching models from Moster et al. 2013.

  16. 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)

  17. The Unusual Time History of Galactic and Anomalous Cosmic Rays at 1 AU over the Solar Minimum of Cycle 23

    NASA Astrophysics Data System (ADS)

    McDonald, F. B.; Webber, W. R.; Reames, D. V.

    2008-12-01

    Studies of the galactic cosmic rays temporal variations (GCRs) over the "Modern Era" (from 1950s) establish the existence of a 22-year cosmic ray modulation cycle that is dominated by the 11-year solar activity cycle but is significantly influenced by gradient and curvature drifts in the interplanetary magnetic field (IPB) in association with changes in the tilt of the heliospheric neutral current sheet over the heliomagnetic cycle. In qA<0 epochs (when positive ions flow in along the neutral sheet and out over the solar poles), the solar minimum cosmic rays intensity is peaked over a period of several months (1965, 1987) in contrast to the 3 - 4 year plateau periods for qA>0 minima when the flow pattern is reversed. However, for 200 MeV/n GCR HE at 1 AU there is a quasi-plateau region for the cycle 23 solar minimum that now extends over some 12 months. The intensity level of this component is essentially the same as that of 1965 and 1987, as is the large depression of anomalous cosmic ray ACR He (10 - 40 MeV/n) relative to the qA>0 minima. There appears to be two different solar effects, the current sheet tilt in 2007 is less than in 1987 while the magnitude of the 1P B field is at its lowest value since essentially continuous measurements began in 1963. These will have off-setting effects on the GCR intensity. 10 Be and 14 C studies have shown that previous epochs of low solar activity [Oort (1050 AD); Spoerer (1420-1540); and Maunder (1615-1715)] have been marked by high cosmic ray intensity. There were other periods of reduced solar activity [Wolf (1320) and Dalton (1810)] which were associated with more moderate enhancements of the GCR intensity. Studies using data from the Cosmic Ray Network [IMP, ACE, neutron monitors at 1 AU, and Pioneer, Voyager, and Ulysses at greater heliocentric distances] are providing a better understanding of the solar phenomena that produce the cosmic ray modulation and should lead to an understanding of the solar changes in the

  18. 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

  19. 76 FR 4933 - Environmental Review Procedures for Entities Assuming HUD Environmental Review Responsibilities...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-27

    ... Responsibilities; Notice of Proposed Information Collection: Comment Request AGENCY: Office of the Assistant...: Environmental Review Procedures for Entities Assuming HUD Environmental Responsibilities. OMB Control...

  20. Cosmic Rays, the Black Pole and Extreme Climate.

    NASA Astrophysics Data System (ADS)

    Ely, J.

    2001-04-01

    The Magnetic Coupling Model predicts many climate anomalies due to solar oscillations (from gravitational torque impulses), galactic cosmic ray modulations, etc, back thru the Pleistocene. A major process in this era is Hale cycle reconnection of solar and galactic B, causing strong recurring "Cirrus Holes." These: shift pressure centers, making drought cycles, record floods, etc; disguised global warming (causing disunity on its reality) by high contrast (deglaciating) climate in the northern hemisphere in alternate sunspot cycles. Fossil fuel CO2 ended major ice ages and risks imminent rapid (decade) CO2 runaway via sea surface exchange (see refs: Ely, Session A8, APS Mtg March 2001; Bette Hileman, Chem Eng News 9, Apr 24, 2000; Ely, Proc. IEEE Conf. Oceans '91, 3: 1658-1665, 1991) Polar regions warm much more in summer than the global averages and now, having lost snow cover, in the Arctic radiate as a black body in winter becoming extremely cold. Hence, altho the record highest average first quarter year US temperature was in April 2000, the most severe US winter ever recorded began in Nov, due to polar breakthrough. Using fossil fuel to survive the winter, hastens the 6m sea level rise.

  1. Pre-Service Teachers' Personal Epistemic Beliefs and the Beliefs They Assume Their Pupils to Have

    ERIC Educational Resources Information Center

    Rebmann, Karin; Schloemer, Tobias; Berding, Florian; Luttenberger, Silke; Paechter, Manuela

    2015-01-01

    In their workaday life, teachers are faced with multiple complex tasks. How they carry out these tasks is also influenced by their epistemic beliefs and the beliefs they assume their pupils hold. In an empirical study, pre-service teachers' epistemic beliefs and those they assume of their pupils were investigated in the setting of teacher…

  2. Estimating Treatment Effects and Precision for Quasi-Experiments Assuming Differential Group and Individual Growth Patterns.

    ERIC Educational Resources Information Center

    Olejnik, Stephen F.; Porter, Andrew C.

    The statistical properties of two methods of estimating gain scores for groups in quasi-experiments are compared: (1) gains in scores standardized separately for each group; and (2) analysis of covariance with estimated true pretest scores. The fan spread hypothesis is assumed for groups but not necessarily assumed for members of the groups.…

  3. 39 CFR 3060.40 - Calculation of the assumed Federal income tax.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 39 Postal Service 1 2010-07-01 2010-07-01 false Calculation of the assumed Federal income tax... Federal income tax. (a) The assumed Federal income tax on competitive products income shall be based on... income tax on competitive products income shall be September 30. (c) The calculation of the...

  4. 39 CFR 3060.40 - Calculation of the assumed Federal income tax.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 39 Postal Service 1 2011-07-01 2011-07-01 false Calculation of the assumed Federal income tax... Federal income tax. (a) The assumed Federal income tax on competitive products income shall be based on... income tax on competitive products income shall be September 30. (c) The calculation of the...

  5. 13 CFR 120.1718 - SBA's right to assume Seller's responsibilities.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 13 Business Credit and Assistance 1 2010-01-01 2010-01-01 false SBA's right to assume Seller's... LOANS Establishment of SBA Secondary Market Guarantee Program for First Lien Position 504 Loan Pools § 120.1718 SBA's right to assume Seller's responsibilities. SBA may, in its sole discretion,...

  6. 41 CFR 102-78.55 - For which properties must Federal agencies assume historic preservation responsibilities?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... must Federal agencies assume historic preservation responsibilities? 102-78.55 Section 102-78.55 Public... MANAGEMENT REGULATION REAL PROPERTY 78-HISTORIC PRESERVATION Historic Preservation § 102-78.55 For which properties must Federal agencies assume historic preservation responsibilities? Federal agencies must...

  7. 41 CFR 102-78.55 - For which properties must Federal agencies assume historic preservation responsibilities?

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... must Federal agencies assume historic preservation responsibilities? 102-78.55 Section 102-78.55 Public... MANAGEMENT REGULATION REAL PROPERTY 78-HISTORIC PRESERVATION Historic Preservation § 102-78.55 For which properties must Federal agencies assume historic preservation responsibilities? Federal agencies must...

  8. 41 CFR 102-78.55 - For which properties must Federal agencies assume historic preservation responsibilities?

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... must Federal agencies assume historic preservation responsibilities? 102-78.55 Section 102-78.55 Public... MANAGEMENT REGULATION REAL PROPERTY 78-HISTORIC PRESERVATION Historic Preservation § 102-78.55 For which properties must Federal agencies assume historic preservation responsibilities? Federal agencies must...

  9. 41 CFR 102-78.55 - For which properties must Federal agencies assume historic preservation responsibilities?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... must Federal agencies assume historic preservation responsibilities? 102-78.55 Section 102-78.55 Public... MANAGEMENT REGULATION REAL PROPERTY 78-HISTORIC PRESERVATION Historic Preservation § 102-78.55 For which properties must Federal agencies assume historic preservation responsibilities? Federal agencies must...

  10. 41 CFR 102-78.55 - For which properties must Federal agencies assume historic preservation responsibilities?

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... must Federal agencies assume historic preservation responsibilities? 102-78.55 Section 102-78.55 Public... MANAGEMENT REGULATION REAL PROPERTY 78-HISTORIC PRESERVATION Historic Preservation § 102-78.55 For which properties must Federal agencies assume historic preservation responsibilities? Federal agencies must...

  11. 39 CFR 3060.40 - Calculation of the assumed Federal income tax.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 39 Postal Service 1 2014-07-01 2014-07-01 false Calculation of the assumed Federal income tax... Federal income tax. (a) The assumed Federal income tax on competitive products income shall be based on... income tax on competitive products income shall be September 30. (c) The calculation of the...

  12. 39 CFR 3060.40 - Calculation of the assumed Federal income tax.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 39 Postal Service 1 2013-07-01 2013-07-01 false Calculation of the assumed Federal income tax... Federal income tax. (a) The assumed Federal income tax on competitive products income shall be based on... income tax on competitive products income shall be September 30. (c) The calculation of the...

  13. 39 CFR 3060.40 - Calculation of the assumed Federal income tax.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 39 Postal Service 1 2012-07-01 2012-07-01 false Calculation of the assumed Federal income tax... Federal income tax. (a) The assumed Federal income tax on competitive products income shall be based on... income tax on competitive products income shall be September 30. (c) The calculation of the...

  14. The Motivation of Teachers to Assume the Role of Cooperating Teacher

    ERIC Educational Resources Information Center

    Jonett, Connie L. Foye

    2009-01-01

    The Motivation of Teachers to Assume the Role of Cooperating Teacher This study explored a phenomenological understanding of the motivation and influences that cause experienced teachers to assume pedagogical training of student teachers through the role of cooperating teacher. The research question guiding the study was what motivates teachers to…

  15. 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.

  16. The effects of magnetic field modifications on the solar modulation of cosmic rays with a SDE-based model

    NASA Astrophysics Data System (ADS)

    Raath, J. L.; Potgieter, M. S.; Strauss, R. D.; Kopp, A.

    2016-05-01

    A numerical model for the solar modulation of cosmic rays, based on the solution of a set of stochastic differential equations (SDEs), is used to illustrate the effects of modifying the heliospheric magnetic field, particularly in the polar regions of the heliosphere. SDE-based models are well suited for such studies so that new insights are gained. To this end, the differences in the modulation brought about by each of three choices for the heliospheric magnetic field, i.e. the unmodified Parker field, the Smith-Bieber modified field, and the Jokipii-Kóta modified field, are studied as typical well-known cases. It is illustrated that although both these modifications change the Parker field satisfactorily in the polar regions of the heliosphere, the Smith-Bieber modification is more effective in reducing cosmic ray drift effects in these regions. The features of these two modifications, as well as the effects on the solar modulation of cosmic rays, are illustrated qualitatively and quantitatively. In particular, it is shown how the Smith-Bieber modified field is applied in a cosmic ray modulation model to reproduce observational proton spectra from the PAMELA mission during the solar minimum of 2006-2009. These SDE-based results are compared with those obtained in previous studies of this unusual solar minimum activity period and found to be in good qualitative agreement.

  17. 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.

  18. Modeling cosmic void statistics

    NASA Astrophysics Data System (ADS)

    Hamaus, Nico; Sutter, P. M.; Wandelt, Benjamin D.

    2016-10-01

    Understanding the internal structure and spatial distribution of cosmic voids is crucial when considering them as probes of cosmology. We present recent advances in modeling void density- and velocity-profiles in real space, as well as void two-point statistics in redshift space, by examining voids identified via the watershed transform in state-of-the-art ΛCDM n-body simulations and mock galaxy catalogs. The simple and universal characteristics that emerge from these statistics indicate the self-similarity of large-scale structure and suggest cosmic voids to be among the most pristine objects to consider for future studies on the nature of dark energy, dark matter and modified gravity.

  19. 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.

  20. 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

  1. Cosmic microwave background theory.

    PubMed

    Bond, J R

    1998-01-01

    A long-standing goal of theorists has been to constrain cosmological parameters that define the structure formation theory from cosmic microwave background (CMB) anisotropy experiments and large-scale structure (LSS) observations. The status and future promise of this enterprise is described. Current band-powers in -space are consistent with a DeltaT flat in frequency and broadly follow inflation-based expectations. That the levels are approximately (10(-5))2 provides strong support for the gravitational instability theory, while the Far Infrared Absolute Spectrophotometer (FIRAS) constraints on energy injection rule out cosmic explosions as a dominant source of LSS. Band-powers at 100 suggest that the universe could not have re-ionized too early. To get the LSS of Cosmic Background Explorer (COBE)-normalized fluctuations right provides encouraging support that the initial fluctuation spectrum was not far off the scale invariant form that inflation models prefer: e.g., for tilted Lambda cold dark matter sequences of fixed 13-Gyr age (with the Hubble constant H0 marginalized), ns = 1.17 +/- 0.3 for Differential Microwave Radiometer (DMR) only; 1.15 +/- 0.08 for DMR plus the SK95 experiment; 1.00 +/- 0.04 for DMR plus all smaller angle experiments; 1.00 +/- 0.05 when LSS constraints are included as well. The CMB alone currently gives weak constraints on Lambda and moderate constraints on Omegatot, but theoretical forecasts of future long duration balloon and satellite experiments are shown which predict percent-level accuracy among a large fraction of the 10+ parameters characterizing the cosmic structure formation theory, at least if it is an inflation variant.

  2. The cosmic microwave background

    NASA Technical Reports Server (NTRS)

    Silk, Joseph

    1989-01-01

    Recent observational and theoretical investigations of the cosmic microwave background radiation (CMBR) are reviewed. Particular attention is given to spectral distortions and CMBR temperature anisotropies at large, intermediate, and small angular scales. The implications of the observations for inflationary cosmological models with curvature fluctuation are explored, and it is shown that the limits determined for intermediate-scale CMBR anisotropy almost rule out a baryon-dominated cosmology.

  3. 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.

  4. 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)

  5. Web life: Cosmic Diary

    NASA Astrophysics Data System (ADS)

    2009-03-01

    What is it? Cosmic Diary brings together a smorgasbord of blogging astronomers from around the world, with more than 50 contributors commenting on new discoveries and long-standing questions in astronomy - as well as offering insights into their ordinary working lives and outside interests. The site is sponsored by the International Astronomical Union and UNESCO, and it is one of 11 "cornerstone projects" of the International Year of Astronomy 2009 (IYA2009).

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Effect of Assumed Damage and Location on the Delamination Onset Predictions for Skin-Stiffener Debonding

    NASA Technical Reports Server (NTRS)

    Paris, Isabelle L.; Krueger, Ronald; OBrien, T. Kevin

    2004-01-01

    The difference in delamination onset predictions based on the type and location of the assumed initial damage are compared in a specimen consisting of a tapered flange laminate bonded to a skin laminate. From previous experimental work, the damage was identified to consist of a matrix crack in the top skin layer followed by a delamination between the top and second skin layer (+45 deg./-45 deg. interface). Two-dimensional finite elements analyses were performed for three different assumed flaws and the results show a considerable reduction in critical load if an initial delamination is assumed to be present, both under tension and bending loads. For a crack length corresponding to the peak in the strain energy release rate, the delamination onset load for an assumed initial flaw in the bondline is slightly higher than the critical load for delamination onset from an assumed skin matrix crack, both under tension and bending loads. As a result, assuming an initial flaw in the bondline is simpler while providing a critical load relatively close to the real case. For the configuration studied, a small delamination might form at a lower tension load than the critical load calculated for a 12.7 mm (0.5") delamination, but it would grow in a stable manner. For the bending case, assuming an initial flaw of 12.7 mm (0.5") is conservative, the crack would grow unstably.

  11. A Concept Analysis: Assuming Responsibility for Self-Care among Adolescents with Type 1 Diabetes

    PubMed Central

    Hanna, Kathleen M.; Decker, Carol L.

    2009-01-01

    Purpose This concept analysis clarifies “assuming responsibility for self-care” by adolescents with type 1 diabetes. Methods Walker and Avant’s (2005) methodology guided the analysis. Results Assuming responsibility for self-care was defined as a process specific to diabetes within the context of development. It is daily, gradual, individualized to person, and unique to task. The goal is ownership that involves autonomy in behaviors and decision-making. Practice Implications Adolescents with type 1 diabetes need to be assessed for assuming responsibility for self-care. This achievement has implications for adolescents’ diabetes management, short- and long-term health, and psychosocial quality of life. PMID:20367781

  12. The atmospheric cosmic- and solar energetic particle radiation environment at aircraft altitudes.

    PubMed

    O'Brien, K; Friedberg, W; Smart, D F; Sauer, H H

    1998-01-01

    Galactic cosmic rays interact with the solar wind, the earth's magnetic field and hadron, lepton and photon fields at aircraft altitudes. In addition to cosmic rays, energetic particles generated by solar activity bombard the earth from time to time. These particles, while less energetic than cosmic rays, also produce radiation fields at aircraft altitudes which have qualitatively the same properties as atmospheric cosmic rays. We have used a code based on transport theory to calculate atmospheric cosmic-ray quantities and compared them with experimental data. Agreement with these data is seen to be good. We have then used this code to calculate equivalent doses to aircraft crews. We have also used the code to calculate radiation doses from several large solar energetic particle events which took place in 1989, including the very large event that occurred on September 29th and 30th of that year. The spectra incident on the atmosphere were determined assuming diffusive shock theory.

  13. The relationship between the galactic matter distribution, cosmic ray dynamics, and gamma ray production

    NASA Technical Reports Server (NTRS)

    Kniffen, D. A.; Fichtel, C. E.; Thompson, D. J.

    1976-01-01

    Theoretical considerations and analysis of the results of gamma ray astronomy suggest that the galactic cosmic rays are dynamically coupled to the interstellar matter through the magnetic fields, and hence the cosmic ray density should be enhanced where the matter density is greatest on the scale of galactic arms. This concept has been explored in a galactic model using recent 21 cm radio observations of the neutral hydrogen and 2.6 mm observations of carbon monoxide, which is considered to be a tracer of molecular hydrogen. The model assumes: (1) cosmic rays are galactic and not universal; (2) on the scale of galactic arms, the cosmic ray column (surface) density is proportional to the total interstellar gas column density; (3) the cosmic ray scale height is significantly larger than the scale height of the matter; and (4) ours is a spiral galaxy characterized by an arm to interarm density ratio of about 3:1.

  14. 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.

  15. Cosmic ray driven Galactic winds

    NASA Astrophysics Data System (ADS)

    Recchia, S.; Blasi, P.; Morlino, G.

    2016-11-01

    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 determines 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.

  16. The Origin of Cosmic Rays

    ScienceCinema

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

    2016-07-12

    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.

  17. 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.

  18. 25 CFR 117.5 - Procedure for hearings to assume supervision of expenditure of allowance funds.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... INDIANS WHO DO NOT HAVE CERTIFICATES OF COMPETENCY § 117.5 Procedure for hearings to assume supervision of... not having certificates of competency, including amounts paid for each minor, shall, in case...

  19. Atmospheric cosmic rays and solar energetic particles at aircraft altitudes.

    PubMed

    O'Brien, K; Friedberg, W; Sauer, H H; Smart, D F

    1996-01-01

    Galactic cosmic rays, which are thought to be produced and accelerated by a variety of mechanisms in the Milky Way galaxy, interact with the solar wind, the earth's magnetic field, and its atmosphere to produce hadron, lepton, and photon fields at aircraft altitudes that are quite unlike anything produced in the laboratory. The energy spectra of these secondary particles extend from the lowest possible energy to energies over an EeV. In addition to cosmic rays, energetic particles, generated on the sun by solar flares or coronal mass ejections, bombard the earth from time to time. These particles, while less energetic than cosmic rays, also produce radiation fields at aircraft altitudes which have qualitatively the same properties as cosmic rays. The authors have calculated atmospheric cosmic-ray angular fluxes, spectra, scalar fluxes, and ionization, and compared them with experimental data. Agreement with these data is seen to be good. These data have been used to calculate equivalent doses in a simplified human phantom at aircraft altitudes and the estimated health risks to aircraft crews. The authors have also calculated the radiation doses from several large solar energetic particle events (known as GLEs, or Ground Level Events), which took place in 1989, including the very large event known as GLE 42, which took place on September 29th and 30th of that year. The spectra incident on the atmosphere were determined assuming diffusive shock theory. Unfortunately, there are essentially no experimental data with which to compare these calculations.

  20. 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.

  1. 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.

  2. Inverse problem for extragalactic transport of ultra-high energy cosmic rays

    SciTech Connect

    Ptuskin, V.S.; Rogovaya, S.I.; Zirakashvili, V.N. E-mail: rogovaya@izmiran.ru

    2015-03-01

    The energy spectra and composition of ultra-high energy cosmic rays are changing in a course of propagation in the expanding Universe filled with background radiation. We developed a numerical code for solution of inverse problem for cosmic-ray transport equations that allows the determination of average source spectra of different nuclei from the cosmic ray spectra observed at the Earth. Employing this approach, the injection spectra of protons and Iron nuclei in extragalactic sources are found assuming that only these species are accelerated at the source. The data from the Auger experiment and the combined data from the Telescope Array + HiRes experiments are used to illustrate the method.

  3. Anomalous Cosmic Rays Acceleration By the Termination Shock

    NASA Astrophysics Data System (ADS)

    Qin, G.; Zhang, L.

    2014-12-01

    When crossing the termination shock (TS), Voyager 1 and 2 observed Anomalous Cosmic Rays (ACRs) different as expected by diffusive shock acceleration. In this work, we study the ACRs acceleration by analyzing test particles trajectories fromnumerical solution of Newton-Lorentz equation. As a preliminary work, simple toy models of plasma, magnetic field, and TS are assumed. In addition, our modeling results of ACRs spectra will be compared with Voyager 1 and 2 observations.

  4. 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.

  5. 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

  6. Cosmic bubble collisions

    NASA Astrophysics Data System (ADS)

    Kleban, Matthew

    2011-10-01

    I briefly review the physics of cosmic bubble collisions in false-vacuum eternal inflation. My purpose is to provide an introduction to the subject for readers unfamiliar with it, focussing on recent work related to the prospects for observing the effects of bubble collisions in cosmology. I will attempt to explain the essential physical points as simply and concisely as possible, leaving most technical details to the references. I make no attempt to be comprehensive or complete. I also present a new solution to Einstein's equations that represents a bubble universe after a collision, containing vacuum energy and ingoing null radiation with an arbitrary density profile.

  7. 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.

  8. The Cosmic Background Explorer

    NASA Technical Reports Server (NTRS)

    Gulkis, Samuel; Lubin, Philip M.; Meyer, Stephan S.; Silverberg, Robert F.

    1990-01-01

    The Cosmic Background Explorer (CBE), NASA's cosmological satellite which will observe a radiative relic of the big bang, is discussed. The major questions connected to the big bang theory which may be clarified using the CBE are reviewed. The satellite instruments and experiments are described, including the Differential Microwave Radiometer, which measures the difference between microwave radiation emitted from two points on the sky, the Far-Infrared Absolute Spectrophotometer, which compares the spectrum of radiation from the sky at wavelengths from 100 microns to one cm with that from an internal blackbody, and the Diffuse Infrared Background Experiment, which searches for the radiation from the earliest generation of stars.

  9. Wormhole cosmic censorship

    NASA Astrophysics Data System (ADS)

    Matos, Tonatiuh; Ureña-López, L. Arturo; Miranda, Galaxia

    2016-05-01

    We analyze the properties of a Kerr-like wormhole supported by phantom matter, which is an exact solution of the Einstein-phantom field equations. It is shown that the solution has a naked ring singularity which is unreachable to null geodesics falling freely from the outside. Similarly to Roger Penrose's cosmic censorship, that states that all naked singularities in the Universe must be protected by event horizons, here we conjecture from our results that a naked singularity can also be fully protected by the intrinsic properties of a wormhole's throat.

  10. Characteristics of cosmic time

    NASA Astrophysics Data System (ADS)

    Salopek, D. S.

    1995-11-01

    The nature of cosmic time is illuminated using Hamilton-Jacobi theory for general relativity. For problems of interest to cosmology, one may solve for the phase of the wave functional by using a line integral in superspace. Each contour of integration corresponds to a particular choice of time hypersurface, and each yields the same answer. In this way, one can construct a covariant formalism where all time hypersurfaces are treated on an equal footing. Using the method of characteristics, explicit solutions for an inflationary epoch with several scalar fields are given. The theoretical predictions of double inflation are compared with recent galaxy data and large angle microwave background anistropies.

  11. The cosmic microwave background

    NASA Technical Reports Server (NTRS)

    Silk, Joseph

    1991-01-01

    Recent limits on spectral distortions and angular anisotropies in the cosmic microwave background are reviewed. The various backgrounds are described, and the theoretical implications are assessed. Constraints on inflationary cosmology dominated by cold dark matter (CDM) and on open cosmological models dominated by baryonic dark matter (BDM), with, respectively, primordial random phase scale-invariant curvature fluctuations or non-gaussian isocurvature fluctuations are described. More exotic theories are addressed, and I conclude with the 'bottom line': what theorists expect experimentalists to be measuring within the next two to three years without having to abandon their most cherished theories.

  12. Dynamical evolution of cosmic strings

    SciTech Connect

    Bouchet, F.R.

    1988-05-11

    The author have studied by means of numerical simulations the dynamical evolution of a network of cosmic strings, both in the radiation and matter era. Our basic conclusion is that a scaling solution exists, i.e., the string energy density evolves as t/sup -2/. This means that the process by which long strings dump their energy into closed loops (which can gravitationally radiate away) is efficient enough to prevent the string domination over other forms of energy. This conclusion does not depend on the initial string energy density, nor on the various numerical parameters. On the other hand, the generated spectrum of loop sizes does depend on the value of our numerical lower cutoff (i.e., the minimum length of loop we allow to be chopped off the network). Furthermore, the network evolution is very different from what was assumed before), namely the creation of a few horizon sized loops per horizon volume and per hubble time, which subsequently fragment into about 10 smaller daughter loops. Rather, many tiny loops are directly cut from the network of infinite strings, and it appears that the only fundamental scale (the horizon) has been lost. This is probably because a fundamental ingredient had been overlooked, namely the kinks. These kinks are created in pairs at each intercommutation, and very rapidly, the long strings appear to be very kinky. Thus the number of long strings per horizon is still of the order of a few, but their total length is fairly large. Furthermore, a large number of kinks favors the formation of small loops, and their sizes might well be governed by the kink density along the long strings. Finally, we computed the two-point correlation function of the loops and found significant differences from the work of Turok.

  13. Cosmic Ray Neutron Flux Measurements

    NASA Astrophysics Data System (ADS)

    Dayananda, Mathes

    2009-11-01

    Cosmic rays are high-energetic particles originating from outer space that bombard the upper atmosphere of the Earth. Almost 90% of cosmic ray particles consist of protons, electrons and heavy ions. When these particles hit the Earth's atmosphere, cascade of secondary particles are formed. The most abundant particles reach to the surface of the Earth are muons, electrons and neutrons. In recent years many research groups are looking into potential applications of the effects of cosmic ray radiation at the surface of the Earth [1, 2]. At Georgia State University we are working on a long-term measurement of cosmic ray flux distribution. This study includes the simultaneous measurement of cosmic ray muons, neutrons and gamma particles at the Earth surface in downtown Atlanta. The initial effort is focusing on the correlation studies of the cosmic ray particle flux distribution and the atmospheric weather conditions. In this presentation, I will talk about the development of a cosmic ray detector using liquid scintillator and the preliminary results. [4pt] [1] K.Borozdin, G.Hogan, C.Morris, W.Priedhorsky, A.Saunders, L.Shultz, M.Teasdale, ``Radiographic imaging with cosmic-ray muons'', Nature, Vol.422, p.277, Mar.2003[0pt] [2] Svensmark Henrik, Physical Review 81, 3, (1998)

  14. Testing Galactic Cosmic Ray Models

    NASA Technical Reports Server (NTRS)

    Adams, James H., Jr.

    2009-01-01

    Models of the Galactic Cosmic Ray Environment are used for designing and planning space missions. The existing models will be reviewed. Spectral representations from these models will be compared with measurements of galactic cosmic ray spectra made on balloon flights and satellite flights over a period of more than 50 years.

  15. Testing Galactic Cosmic Ray Models

    NASA Technical Reports Server (NTRS)

    Adams, James H., Jr.

    2010-01-01

    Models of the Galactic Cosmic Ray Environment are used for designing and planning space missions. The exising models will be reviewed. Spectral representations from these models will be compared with measurements of galactic cosmic ray spectra made on balloon flights and satellite flights over a period of more than 50 years.

  16. Cosmic Rays and Experiment CZELTA

    SciTech Connect

    Smolek, Karel; Nyklicek, Michal

    2007-11-26

    This paper gives a review of the physics of cosmic rays with emphasis on the methods of detection and study. A summary is given of the Czech project CZELTA which is part of a multinational program to study cosmic rays with energies above 10{sup 14} eV.

  17. Does a cosmic censor exist?

    NASA Astrophysics Data System (ADS)

    Israel, W.

    1984-11-01

    A distinction is drawn between the event horizon conjecture (EHC), the conjecture that an event horizon forms in a gravitational collapse, and cosmic censorship, the idea that every singularity which develops in the course of collapse must be enclosed within a horizon. It is argued that a body of circumstantial evidence seems to favor EHC, but cosmic censorship seems contraindicated.

  18. Does a cosmic censor exist

    SciTech Connect

    Israel, W.

    1984-11-01

    A distinction is drawn between the event horizon conjecture (EHC), the conjecture that an event horizon forms in a gravitational collapse, and cosmic censorship, the idea that every singularity which develops in the course of collapse must be enclosed within a horizon. It is argued that a body of circumstantial evidence seems to favor EHC, but cosmic censorship seems contraindicated.

  19. Flat wormholes from cosmic strings.

    NASA Astrophysics Data System (ADS)

    Clement, G.

    1997-11-01

    The author describes the analytical extension of certain cylindrical multi-cosmic string metrics to wormhole spacetimes with only one region at spatial infinity, and investigates in detail the geometry of asymptotically Minkowskian wormhole spacetimes generated by one or two cosmic strings. It is found that such wormholes tend to lengthen rather than shorten space travel. Possible signatures of these wormholes are briefly discussed.

  20. The Resurgence of Cosmic Storytellers.

    ERIC Educational Resources Information Center

    Swimme, Brian T.

    1998-01-01

    Argues that children and society as a whole have an inherent need for a cosmic story whose purpose is to provide insight into people's place in the universe. Describes the importance, role, and place for a cosmic storyteller in modern society. (SD)

  1. Monopole annihilation in cosmic necklaces

    SciTech Connect

    Blanco-Pillado, Jose J.; Olum, Ken D. E-mail: kdo@cosmos.phy.tufts.edu

    2010-05-01

    A sequence of two symmetry breaking transitions in the early universe may produce monopoles whose flux is confined into two strings each, which thus assemble into ''necklaces'' with monopoles as beads. Such ''cosmic necklaces'' have been proposed as a source of ultra-high-energy cosmic rays. We analyze the evolution of these systems and show that essentially all monopoles annihilate or leave the string at early times, after which cosmic necklaces evolve in a similar way to a network of ordinary cosmic strings. We investigate several modifications to the basic picture, but in nearly all cases we find that too few monopoles remain on the necklaces to produce any observable cosmic rays. There may be a small window for superconducting condensates to prevent annihilations, but only if both the string and the condensate scale are very high.

  2. COSMIC monthly progress report

    NASA Technical Reports Server (NTRS)

    1993-01-01

    Activities of the Computer Software Management and Information Center (COSMIC) are summarized for the month of August, 1993. Tables showing the current inventory of programs available from COSMIC are presented and program processing and evaluation activities are discussed. Ten articles were prepared for publication in the NASA Tech Brief Journal. These articles (included in this report) describe the following software items: (1) MOM3D - A Method of Moments Code for Electromagnetic Scattering (UNIX Version); (2) EM-Animate - Computer Program for Displaying and Animating the Steady-State Time-Harmonic Electromagnetic Near Field and Surface-Current Solutions; (3) MOM3D - A Method of Moments Code for Electromagnetic Scattering (IBM PC Version); (4) M414 - MIL-STD-414 Variable Sampling Procedures Computer Program; (5) MEDOF - Minimum Euclidean Distance Optimal Filter; (6) CLIPS 6.0 - C Language Integrated Production System, Version 6.0 (Macintosh Version); (7) CLIPS 6.0 - C Language Integrated Production System, Version 6.0 (IBM PC Version); (8) CLIPS 6.0 - C Language Integrated Production System, Version 6.0 (UNIX Version); (9) CLIPS 6.0 - C Language Integrated Production System, Version 6.0 (DEC VAX VMS Version); and (10) TFSSRA - Thick Frequency Selective Surface with Rectangular Apertures. Activities in the areas of marketing, customer service, benefits identification, maintenance and support, and dissemination are also described along with a budget summary.

  3. 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 May 1994. Tables showing the current inventory of programs available from COSMIC are presented and program processing and evaluation activities are summarized. Nine articles were prepared for publication in the NASA Tech Brief Journal. These articles (included in this report) describe the following software items: (1) WFI - Windowing System for Test and Simulation; (2) HZETRN - A Free Space Radiation Transport and Shielding Program; (3) COMGEN-BEM - Composite Model Generation-Boundary Element Method; (4) IDDS - Interactive Data Display System; (5) CET93/PC - Chemical Equilibrium with Transport Properties, 1993; (6) SDVIC - Sub-pixel Digital Video Image Correlation; (7) TRASYS - Thermal Radiation Analyzer System (HP9000 Series 700/800 Version without NASADIG); (8) NASADIG - NASA Device Independent Graphics Library, Version 6.0 (VAX VMS Version); and (9) NASADIG - NASA Device Independent Graphics Library, Version 6.0 (UNIX Version). Activities in the areas of marketing, customer service, benefits identification, maintenance and support, and dissemination are also described along with a budget summary.

  4. 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.

  5. Three dimensional potential and current distributions in a Hall generator with assumed velocity profiles

    NASA Technical Reports Server (NTRS)

    Stankiewicz, N.; Palmer, R. W.

    1972-01-01

    Three-dimensional potential and current distributions in a Faraday segmented MHD generator operating in the Hall mode are computed. Constant conductivity and a Hall parameter of 1.0 is assumed. The electric fields and currents are assumed to be coperiodic with the electrode structure. The flow is assumed to be fully developed and a family of power-law velocity profiles, ranging from parabolic to turbulent, is used to show the effect of the fullness of the velocity profile. Calculation of the square of the current density shows that nonequilibrium heating is not likely to occur along the boundaries. This seems to discount the idea that the generator insulating walls are regions of high conductivity and are therefore responsible for boundary-layer shorting, unless the shorting is a surface phenomenon on the insulating material.

  6. Assuming a Pharmacy Organization Leadership Position: A Guide for Pharmacy Leaders.

    PubMed

    Shay, Blake; Weber, Robert J

    2015-11-01

    Important and influential pharmacy organization leadership positions, such as president, board member, or committee chair, are volunteer positions and require a commitment of personal and professional time. These positions provide excellent opportunities for leadership development, personal promotion, and advancement of the profession. In deciding to assume a leadership position, interested individuals must consider the impact on their personal and professional commitments and relationships, career planning, employer support, current and future department projects, employee support, and personal readiness. This article reviews these factors and also provides an assessment tool that leaders can use to determine their readiness to assume leadership positions. By using an assessment tool, pharmacy leaders can better understand their ability to assume an important and influential leadership position while achieving job and personal goals. PMID:27621512

  7. Assuming a Pharmacy Organization Leadership Position: A Guide for Pharmacy Leaders.

    PubMed

    Shay, Blake; Weber, Robert J

    2015-11-01

    Important and influential pharmacy organization leadership positions, such as president, board member, or committee chair, are volunteer positions and require a commitment of personal and professional time. These positions provide excellent opportunities for leadership development, personal promotion, and advancement of the profession. In deciding to assume a leadership position, interested individuals must consider the impact on their personal and professional commitments and relationships, career planning, employer support, current and future department projects, employee support, and personal readiness. This article reviews these factors and also provides an assessment tool that leaders can use to determine their readiness to assume leadership positions. By using an assessment tool, pharmacy leaders can better understand their ability to assume an important and influential leadership position while achieving job and personal goals.

  8. Cosmic-ray exposure ages of chondrules

    NASA Astrophysics Data System (ADS)

    Roth, Antoine S. G.; Metzler, Knut; Baumgartner, Lukas P.; Leya, Ingo

    2016-07-01

    If chondrules were exposed to cosmic rays prior to meteorite compaction, they should retain an excess of cosmogenic noble gases. Beyersdorf-Kuis et al. (2015) showed that such excesses can be detected provided that the chemical composition of each individual chondrule is precisely known. However, their study was limited to a few samples as they had to be irradiated in a nuclear reactor for instrumental neutron activation analysis. We developed a novel analytical protocol that combines the measurements of He and Ne isotopic concentrations with a fast method to correct for differences in chemical composition using micro X-ray computed tomography. Our main idea is to combine noble gas, nuclear track, and petrography data for numerous chondrules to understand the precompaction exposure history of the chondrite parent bodies. Here, we report our results for a total of 77 chondrules and four matrix samples from NWA 8276 (L3.00), NWA 8007 (L3.2), and Bjurböle (L/LL4). All chondrules from the same meteorite have within uncertainty identical 21Ne exposure ages, and all chondrules from Bjurböle have within uncertainty identical 3He exposure ages. However, most chondrules from NWA 8276 and a few from NWA 8007 show small but resolvable differences in 3He exposure age that we attribute to matrix contamination and/or gas loss. The finding that none of the chondrules has noble gas excesses is consistent with the uniform track density found for each meteorite. We conclude that the studied chondrules did not experience a precompaction exposure longer than a few Ma assuming present-day flux of galactic cosmic rays. A majority of chondrules from L and LL chondrites thus rapidly accreted and/or was efficiently shielded from cosmic rays in the solar nebula.

  9. Optimal Control for TB disease with vaccination assuming endogeneous reactivation and exogeneous reinfection

    NASA Astrophysics Data System (ADS)

    Anggriani, N.; Wicaksono, B. C.; Supriatna, A. K.

    2016-06-01

    Tuberculosis (TB) is one of the deadliest infectious disease in the world which caused by Mycobacterium tuberculosis. The disease is spread through the air via the droplets from the infectious persons when they are coughing. The World Health Organization (WHO) has paid a special attention to the TB by providing some solution, for example by providing BCG vaccine that prevent an infected person from becoming an active infectious TB. In this paper we develop a mathematical model of the spread of the TB which assumes endogeneous reactivation and exogeneous reinfection factors. We also assume that some of the susceptible population are vaccinated. Furthermore we investigate the optimal vaccination level for the disease.

  10. CMB ISW-lensing bispectrum from cosmic strings

    SciTech Connect

    Yamauchi, Daisuke; Sendouda, Yuuiti; Takahashi, Keitaro E-mail: sendouda@cc.hirosaki-u.ac.jp

    2014-02-01

    We study the effect of weak lensing by cosmic (super-)strings on the higher-order statistics of the cosmic microwave background (CMB). A cosmic string segment is expected to cause weak lensing as well as an integrated Sachs-Wolfe (ISW) effect, the so-called Gott-Kaiser-Stebbins (GKS) effect, to the CMB temperature fluctuation, which are thus naturally cross-correlated. We point out that, in the presence of such a correlation, yet another kind of the post-recombination CMB temperature bispectra, the ISW-lensing bispectra, will arise in the form of products of the auto- and cross-power spectra. We first present an analytic method to calculate the autocorrelation of the temperature fluctuations induced by the strings, and the cross-correlation between the temperature fluctuation and the lensing potential both due to the string network. In our formulation, the evolution of the string network is assumed to be characterized by the simple analytic model, the velocity-dependent one scale model, and the intercommutation probability is properly incorporated in order to characterize the possible superstringy nature. Furthermore, the obtained power spectra are dominated by the Poisson-distributed string segments, whose correlations are assumed to satisfy the simple relations. We then estimate the signal-to-noise ratios of the string-induced ISW-lensing bispectra and discuss the detectability of such CMB signals from the cosmic string network. It is found that in the case of the smaller string tension, Gμ << 10{sup -7}, the ISW-lensing bispectrum induced by a cosmic string network can constrain the string-model parameters even more tightly than the purely GKS-induced bispectrum in the ongoing and future CMB observations on small scales.

  11. Universal density profile for cosmic voids.

    PubMed

    Hamaus, Nico; Sutter, P M; Wandelt, Benjamin D

    2014-06-27

    We present a simple empirical function for the average density profile of cosmic voids, identified via the watershed technique in ΛCDM N-body simulations. This function is universal across void size and redshift, accurately describing a large radial range of scales around void centers with only two free parameters. In analogy to halo density profiles, these parameters describe the scale radius and the central density of voids. While we initially start with a more general four-parameter model, we find two of its parameters to be redundant, as they follow linear trends with the scale radius in two distinct regimes of the void sample, separated by its compensation scale. Assuming linear theory, we derive an analytic formula for the velocity profile of voids and find an excellent agreement with the numerical data as well. In our companion paper [Sutter et al., arXiv:1309.5087 [Mon. Not. R. Astron. Soc. (to be published)

  12. Universal Density Profile for Cosmic Voids

    NASA Astrophysics Data System (ADS)

    Hamaus, Nico; Sutter, P. M.; Wandelt, Benjamin D.

    2014-06-01

    We present a simple empirical function for the average density profile of cosmic voids, identified via the watershed technique in ΛCDM N-body simulations. This function is universal across void size and redshift, accurately describing a large radial range of scales around void centers with only two free parameters. In analogy to halo density profiles, these parameters describe the scale radius and the central density of voids. While we initially start with a more general four-parameter model, we find two of its parameters to be redundant, as they follow linear trends with the scale radius in two distinct regimes of the void sample, separated by its compensation scale. Assuming linear theory, we derive an analytic formula for the velocity profile of voids and find an excellent agreement with the numerical data as well. In our companion paper [Sutter et al., arXiv:1309.5087 [Mon. Not. R. Astron. Soc. (to be published)

  13. Interplanetary diffusion coefficients for cosmic rays

    NASA Technical Reports Server (NTRS)

    Cummings, A. C.; Stone, E. C.; Vogt, R. E.

    1974-01-01

    Information on the cosmic-ray diffusion coefficient, kappa, derived from near-earth observations of the solar modulation of galactic electron fluxes and from the near-earth power spectra of the interplanetary magnetic field, has been used to study the heliocentric radial dependence of kappa, and to derive limits on the spatial extent of the solar modulation region. Representing kappa, as a separable function of radius r and rigidity, and assumming kappa(r) proportional to r to the n-th power, we can place a limit on the power law exponent, n not greater than 1.2. The distance of the modulation boundary is a function of n, and, e.g., for n = 0, falls into the range of 6-25 AU.

  14. Cosmic ray anisotropies at high energies

    NASA Technical Reports Server (NTRS)

    Martinic, N. J.; Alarcon, A.; Teran, F.

    1986-01-01

    The directional anisotropies of the energetic cosmic ray gas due to the relative motion between the observers frame and the one where the relativistic gas can be assumed isotropic is analyzed. The radiation fluxes formula in the former frame must follow as the Lorentz invariance of dp/E, where p, E are the 4-vector momentum-energy components; dp is the 3-volume element in the momentum space. The anisotropic flux shows in such a case an amplitude, in a rotating earth, smaller than the experimental measurements from say, EAS-arrays for primary particle energies larger than 1.E(14) eV. Further, it is shown that two consecutive Lorentz transformations among three inertial frames exhibit the violation of dp/E invariance between the first and the third systems of reference, due to the Wigner rotation. A discussion of this result in the context of the experimental anisotropic fluxes and its current interpretation is given.

  15. 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

  16. A Model for Teacher Effects from Longitudinal Data without Assuming Vertical Scaling

    ERIC Educational Resources Information Center

    Mariano, Louis T.; McCaffrey, Daniel F.; Lockwood, J. R.

    2010-01-01

    There is an increasing interest in using longitudinal measures of student achievement to estimate individual teacher effects. Current multivariate models assume each teacher has a single effect on student outcomes that persists undiminished to all future test administrations (complete persistence [CP]) or can diminish with time but remains…

  17. The Ability to Assume the Upright Position in Blind and Sighted Children.

    ERIC Educational Resources Information Center

    Gipsman, Sandra Curtis

    To investigate the ability of 48 blind and partially sighted children (8 to 10 and 12 to 14 years old) to assume the upright position, Ss were given six trials in which they were requested to move themselves from a tilted starting position in a specially constructed chair to an upright position. No significant differences were found between three…

  18. Cosmic Dawn Science Interest Group

    NASA Astrophysics Data System (ADS)

    Lazio, T. Joseph W.; Cosmic Origins Program Analysis Group

    2016-01-01

    Cosmic Dawn was identified as one of the three science objectives for this decade in the _New Worlds, New Horizons_ Decadal report, and it will likely continue to be a research focus well into the next decade. Cosmic Dawn refers to the interval during which the Universe transitioned from a nearly completely neutral state back to a nearly fully ionized state and includes the time during which the first stars formed and the first galaxies assembled.The Cosmic Dawn Science Interest Group (SIG) was formed recently under the auspices of the Cosmic Origins Program Analysis Group (COPAG). The Cosmic Dawn SIG focusses on the science cases, observations, and technology development needed to address the "great mystery" of Cosmic Origins. The reach of this SIG is broad, involving the nature of the first stars and the detectability of gamma-ray bursts at high redshifts, the extent to which the first galaxies and first supermassive black holes grew together, and the technology required to pursue these questions.For further information, consult the Cosmic Dawn SIG Web site http://cd-sig.jpl.nasa.gov/ and join the mailing list (by contacting the author).Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

  19. WINDS, CLUMPS, AND INTERACTING COSMIC RAYS IN M82

    SciTech Connect

    Yoast-Hull, Tova M.; Everett, John E.; Zweibel, Ellen G.; Gallagher, J. S. III

    2013-05-01

    We construct a family of models for the evolution of energetic particles in the starburst galaxy M82 and compare them to observations to test the calorimeter assumption that all cosmic ray energy is radiated in the starburst region. Assuming constant cosmic ray acceleration efficiency with Milky Way parameters, we calculate the cosmic-ray proton and primary and secondary electron/positron populations as a function of energy. Cosmic rays are injected with Galactic energy distributions and electron-to-proton ratio via Type II supernovae at the observed rate of 0.07 yr{sup -1}. From the cosmic ray spectra, we predict the radio synchrotron and {gamma}-ray spectra. To more accurately model the radio spectrum, we incorporate a multiphase interstellar medium in the starburst region of M82. Our model interstellar medium is highly fragmented with compact dense molecular clouds and dense photoionized gas, both embedded in a hot, low density medium in overall pressure equilibrium. The spectra predicted by this one-zone model are compared to the observed radio and {gamma}-ray spectra of M82. {chi}{sup 2} tests are used with radio and {gamma}-ray observations and a range of model predictions to find the best-fit parameters. The best-fit model yields constraints on key parameters in the starburst zone of M82, including a magnetic field strength of {approx}250 {mu}G and a wind advection speed in the range of 300-700 km s{sup -1}. We find that M82 is a good electron calorimeter but not an ideal cosmic-ray proton calorimeter and discuss the implications of our results for the astrophysics of the far-infrared-radio correlation in starburst galaxies.

  20. Cosmic Ray Scattering Radiography

    NASA Astrophysics Data System (ADS)

    Morris, C. L.

    2015-12-01

    Cosmic ray muons are ubiquitous, are highly penetrating, and can be used to measure material densities by either measuring the stopping rate or by measuring the scattering of transmitted muons. The Los Alamos team has studied scattering radiography for a number of applications. Some results will be shown of scattering imaging for a range of practical applications, and estimates will be made of the utility of scattering radiography for nondestructive assessments of large structures and for geological surveying. Results of imaging the core of the Toshiba Nuclear Critical Assembly (NCA) Reactor in Kawasaki, Japan and simulations of imaging the damaged cores of the Fukushima nuclear reactors will be presented. Below is an image made using muons of a core configuration for the NCA reactor.

  1. Collision of cosmic superstrings

    SciTech Connect

    Copeland, E. J.; Firouzjahi, H.; Kibble, T. W. B.; Steer, D. A.

    2008-03-15

    We study the formation of three-string junctions between (p,q)-cosmic superstrings, and collisions between such strings and show that kinematic constraints analogous to those found previously for collisions of Nambu-Goto strings apply here too, with suitable modifications to take account of the additional requirements of flux conservation. We examine in detail several examples involving collisions between strings with low values of p and q, and also examine the rates of growth or shrinkage of strings at a junction. Finally, we briefly discuss the formation of junctions for strings in a warped space, specifically with a Klebanov-Strassler throat, and show that similar constraints still apply with changes to the parameters taking account of the warping and the background flux.

  2. Cosmic Light EDU kit

    NASA Astrophysics Data System (ADS)

    Doran, Rosa

    2015-08-01

    In 2015 we celebrate the International Year of Light, a great opportunity to promote awareness about the importance of light coming from the Cosmos and what messages it is bringing to mankind. In parallel a unique moment to attract the attention of stakeholders on the dangers of light pollution and its impact in our lives and our pursuit of more knowledge. In this presentation I want to present one of the conrnerstones of IYL2015, a partnership between the Galileo Teacher Training Program, Universe Awareness and Globe at Night, the Cosmic Light EDU kit. The aim of this project is to assemble a core set of tools and resources representing our basic knowledge pilars about the Universe and simple means to preserve our night sky.

  3. The Cosmic Origins Spectrograph

    NASA Technical Reports Server (NTRS)

    Green, James C.; Froning, Cynthia S.; Osterman, Steve; Ebbets, Dennis; Heap, Sara H.; Leitherer, Claus; Linsky, Jeffrey L.; Savage, Blair D.; Sembach, Kenneth; Shull, J. Michael; Siegmund, Oswald H. W.; Snow, Theodore P.; Spencer, John; Stern, S. Alan; Stocke, John; Welsh, Barry; Beland, Stephane; Burgh, Eric B.; Danforth, Charles; France, Kevin; Keeney, Brian; McPhate, Jason; Penton, Steven V; Andrews, John; Morse, Jon

    2010-01-01

    The Cosmic Origins Spectrograph (COS) is a moderate-resolution spectrograph with unprecedented sensitivity that was installed into the Hubble Space Telescope (HST) in May 2009, during HST Servicing Mission 4 (STS-125). We present the design philosophy and summarize the key characteristics of the instrument that will be of interest to potential observers. For faint targets, with flux F(sub lambda) approximates 1.0 X 10(exp -14) ergs/s/cm2/Angstrom, COS can achieve comparable signal to noise (when compared to STIS echelle modes) in 1-2% of the observing time. This has led to a significant increase in the total data volume and data quality available to the community. For example, in the first 20 months of science operation (September 2009 - June 2011) the cumulative redshift pathlength of extragalactic sight lines sampled by COS is 9 times that sampled at moderate resolution in 19 previous years of Hubble observations. COS programs have observed 214 distinct lines of sight suitable for study of the intergalactic medium as of June 2011. COS has measured, for the first time with high reliability, broad Lya absorbers and Ne VIII in the intergalactic medium, and observed the HeII reionization epoch along multiple sightlines. COS has detected the first CO emission and absorption in the UV spectra of low-mass circumstellar disks at the epoch of giant planet formation, and detected multiple ionization states of metals in extra-solar planetary atmospheres. In the coming years, COS will continue its census of intergalactic gas, probe galactic and cosmic structure, and explore physics in our solar system and Galaxy.

  4. THE COSMIC ORIGINS SPECTROGRAPH

    SciTech Connect

    Green, James C.; Michael Shull, J.; Snow, Theodore P.; Stocke, John; Froning, Cynthia S.; Osterman, Steve; Beland, Stephane; Burgh, Eric B.; Danforth, Charles; France, Kevin; Ebbets, Dennis; Heap, Sara H.; Leitherer, Claus; Sembach, Kenneth; Linsky, Jeffrey L.; Savage, Blair D.; Siegmund, Oswald H. W.; Spencer, John; Alan Stern, S.; Welsh, Barry; and others

    2012-01-01

    The Cosmic Origins Spectrograph (COS) is a moderate-resolution spectrograph with unprecedented sensitivity that was installed into the Hubble Space Telescope (HST) in 2009 May, during HST Servicing Mission 4 (STS-125). We present the design philosophy and summarize the key characteristics of the instrument that will be of interest to potential observers. For faint targets, with flux F{sub {lambda}} Almost-Equal-To 1.0 Multiplication-Sign 10{sup -14} erg cm{sup -2} s{sup -1} A{sup -1}, COS can achieve comparable signal to noise (when compared to Space Telescope Imaging Spectrograph echelle modes) in 1%-2% of the observing time. This has led to a significant increase in the total data volume and data quality available to the community. For example, in the first 20 months of science operation (2009 September-2011 June) the cumulative redshift pathlength of extragalactic sight lines sampled by COS is nine times than sampled at moderate resolution in 19 previous years of Hubble observations. COS programs have observed 214 distinct lines of sight suitable for study of the intergalactic medium as of 2011 June. COS has measured, for the first time with high reliability, broad Ly{alpha} absorbers and Ne VIII in the intergalactic medium, and observed the He II reionization epoch along multiple sightlines. COS has detected the first CO emission and absorption in the UV spectra of low-mass circumstellar disks at the epoch of giant planet formation, and detected multiple ionization states of metals in extra-solar planetary atmospheres. In the coming years, COS will continue its census of intergalactic gas, probe galactic and cosmic structure, and explore physics in our solar system and Galaxy.

  5. Cosmic rays in the heliosphere

    NASA Technical Reports Server (NTRS)

    Webber, William R.

    1987-01-01

    The different types of cosmic ray particles and their role in the heliosphere are briefly described. The rates of various energetic particles were examined as a function of time and used to derive various differential energy gradients. The Pioneer and Voyager cosmic ray observations throughout the heliosphere are indeed giving a perspective on the three-dimensional character and size of the heliosphere. Most clearly the observations are emphasizing the role that transient variations in the outer heliosphere, and most likely the heliospheric boundary shock, play in the 11 year solar cycle modulation of cosmic rays.

  6. Cosmic sparks from superconducting strings.

    PubMed

    Vachaspati, Tanmay

    2008-10-01

    We investigate cosmic sparks from cusps on superconducting cosmic strings in light of the recently discovered millisecond radio burst by Lorimer et al.. We find that the observed duration, fluence, spectrum, and event rate can be reasonably explained by grand unification scale superconducting cosmic strings that carry currents approximately 10{5} GeV. The superconducting string model predicts an event rate that falls off only as S{-1/2}, where S is the energy flux, and hence predicts a population of very bright bursts. Other surveys, with different observational parameters, are shown to impose tight constraints on the superconducting string model. PMID:18851517

  7. Cosmic Sparks from Superconducting Strings

    SciTech Connect

    Vachaspati, Tanmay

    2008-10-03

    We investigate cosmic sparks from cusps on superconducting cosmic strings in light of the recently discovered millisecond radio burst by Lorimer et al.. We find that the observed duration, fluence, spectrum, and event rate can be reasonably explained by grand unification scale superconducting cosmic strings that carry currents {approx}10{sup 5} GeV. The superconducting string model predicts an event rate that falls off only as S{sup -1/2}, where S is the energy flux, and hence predicts a population of very bright bursts. Other surveys, with different observational parameters, are shown to impose tight constraints on the superconducting string model.

  8. Cosmic-Ray Injection from Star-Forming Regions.

    PubMed

    Carlson, Eric; Profumo, Stefano; Linden, Tim

    2016-09-01

    At present, all physical models of diffuse Galactic γ-ray emission assume that the distribution of cosmic-ray sources traces the observed populations of either OB stars, pulsars, or supernova remnants. However, since H_{2}-rich regions host significant star formation and numerous supernova remnants, the morphology of observed H_{2} gas (as traced by CO line surveys) should also provide a physically motivated, high-resolution tracer for cosmic-ray injection. We assess the impact of utilizing H_{2} as a tracer for cosmic-ray injection on models of diffuse Galactic γ-ray emission. We employ state-of-the-art 3D particle diffusion and gas density models, along with a physical model for the star-formation rate based on global Schmidt laws. Allowing a fraction, f_{H_{2}}, of cosmic-ray sources to trace the observed H_{2} density, we find that a theoretically well-motivated value f_{H_{2}}∼0.20-0.25 (i) provides a significantly better global fit to the diffuse Galactic γ-ray sky and (ii) highly suppresses the intensity of the residual γ-ray emission from the Galactic center region. Specifically, in models utilizing our best global fit values of f_{H_{2}}∼0.20-0.25, the spectrum of the galactic center γ-ray excess is drastically affected, and the morphology of the excess becomes inconsistent with predictions for dark matter annihilation. PMID:27661675

  9. Cosmic-Ray Injection from Star-Forming Regions.

    PubMed

    Carlson, Eric; Profumo, Stefano; Linden, Tim

    2016-09-01

    At present, all physical models of diffuse Galactic γ-ray emission assume that the distribution of cosmic-ray sources traces the observed populations of either OB stars, pulsars, or supernova remnants. However, since H_{2}-rich regions host significant star formation and numerous supernova remnants, the morphology of observed H_{2} gas (as traced by CO line surveys) should also provide a physically motivated, high-resolution tracer for cosmic-ray injection. We assess the impact of utilizing H_{2} as a tracer for cosmic-ray injection on models of diffuse Galactic γ-ray emission. We employ state-of-the-art 3D particle diffusion and gas density models, along with a physical model for the star-formation rate based on global Schmidt laws. Allowing a fraction, f_{H_{2}}, of cosmic-ray sources to trace the observed H_{2} density, we find that a theoretically well-motivated value f_{H_{2}}∼0.20-0.25 (i) provides a significantly better global fit to the diffuse Galactic γ-ray sky and (ii) highly suppresses the intensity of the residual γ-ray emission from the Galactic center region. Specifically, in models utilizing our best global fit values of f_{H_{2}}∼0.20-0.25, the spectrum of the galactic center γ-ray excess is drastically affected, and the morphology of the excess becomes inconsistent with predictions for dark matter annihilation.

  10. A 4-node assumed-stress hybrid shell element with rotational degrees of freedom

    NASA Technical Reports Server (NTRS)

    Aminpour, Mohammad A.

    1990-01-01

    An assumed-stress hybrid/mixed 4-node quadrilateral shell element is introduced that alleviates most of the deficiencies associated with such elements. The formulation of the element is based on the assumed-stress hybrid/mixed method using the Hellinger-Reissner variational principle. The membrane part of the element has 12 degrees of freedom including rotational or drilling degrees of freedom at the nodes. The bending part of the element also has 12 degrees of freedom. The bending part of the element uses the Reissner-Mindlin plate theory which takes into account the transverse shear contributions. The element formulation is derived from an 8-node isoparametric element. This process is accomplished by assuming quadratic variations for both in-plane and out-of-plane displacement fields and linear variations for both in-plane and out-of-plane rotation fields along the edges of the element. In addition, the degrees of freedom at midside nodes are approximated in terms of the degrees of freedom at corner nodes. During this process the rotational degrees of freedom at the corner nodes enter into the formulation of the element. The stress field are expressed in the element natural-coordinate system such that the element remains invariant with respect to node numbering.

  11. The impact of assumed knowledge entry standards on undergraduate mathematics teaching in Australia

    NASA Astrophysics Data System (ADS)

    King, Deborah; Cattlin, Joann

    2015-10-01

    Over the last two decades, many Australian universities have relaxed their selection requirements for mathematics-dependent degrees, shifting from hard prerequisites to assumed knowledge standards which provide students with an indication of the prior learning that is expected. This has been regarded by some as a positive move, since students who may be returning to study, or who are changing career paths but do not have particular prerequisite study, now have more flexible pathways. However, there is mounting evidence to indicate that there are also significant negative impacts associated with assumed knowledge approaches, with large numbers of students enrolling in degrees without the stated assumed knowledge. For students, there are negative impacts on pass rates and retention rates and limitations to pathways within particular degrees. For institutions, the necessity to offer additional mathematics subjects at a lower level than normal and more support services for under-prepared students impacts on workloads and resources. In this paper, we discuss early research from the First Year in Maths project, which begins to shed light on the realities of a system that may in fact be too flexible.

  12. Cosmic instability from radiation pressure

    NASA Technical Reports Server (NTRS)

    Hogan, Craig J.

    1990-01-01

    The Cosmic Background Explorer has recently confirmed the blackbody character of the microwave background to high accuracy (Mather et al., 1990), and will have the capability to detect other cosmic backgrounds throughout the infrared. A detection of cosmic background radiation dating from the pregalactic era would have important consequences for theories of cosmic structure. During the creation of such a background the pressure of the radiation itself causes an instability which leads inevitably to the growth of large-scale structure in the matter distribution. In contrast to conventional gravitational-instability models, the statistical properties of this structure are determined primarily by the self-organizing dynamics of the instability rather than details of cosmological initial conditions. The behavior of the instability is described here.

  13. Cosmic rays, clouds, and climate.

    PubMed

    Carslaw, K S; Harrison, R G; Kirkby, J

    2002-11-29

    It has been proposed that Earth's climate could be affected by changes in cloudiness caused by variations in the intensity of galactic cosmic rays in the atmosphere. This proposal stems from an observed correlation between cosmic ray intensity and Earth's average cloud cover over the course of one solar cycle. Some scientists question the reliability of the observations, whereas others, who accept them as reliable, suggest that the correlation may be caused by other physical phenomena with decadal periods or by a response to volcanic activity or El Niño. Nevertheless, the observation has raised the intriguing possibility that a cosmic ray-cloud interaction may help explain how a relatively small change in solar output can produce much larger changes in Earth's climate. Physical mechanisms have been proposed to explain how cosmic rays could affect clouds, but they need to be investigated further if the observation is to become more than just another correlation among geophysical variables.

  14. Cosmic ray studies at CERN

    SciTech Connect

    Fernandez T, Arturo

    2006-09-25

    The use of the sophisticated and large underground detectors at CERN for cosmic ray studies has been considered by several groups, e.g. UA1, LEP and LHC detectors. They offer the opportunity to provide large sensitivity area with magnetic analysis which allow a precise determination of the direction of cosmic ray muons as well as their momentum up to the order of some TeV. The aim of this article is to review the observation of high energy cosmic ray muons using precise spectrometers at CERN, mainly LEP detectors as well as the possibility of improve those measurements with LHC apparatus, giving special emphasis to the ACORDE-ALICE cosmic ray physics program.

  15. 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

  16. Coherent scattering of cosmic neutrinos

    NASA Technical Reports Server (NTRS)

    Opher, R.

    1974-01-01

    It is shown that cosmic neutrino scattering can be non-negligible when coherence effects previously neglected are taken into account. The coherent neutrino scattering cross section is derived and the neutrino index of refraction evaluated. As an example of coherent neutrino scattering, a detector using critical reflection is described which in principle can detect the low energy cosmic neutrino background allowed by the measured cosmological red shift.

  17. Blast waves with cosmic rays

    NASA Astrophysics Data System (ADS)

    Arbutina, B.

    2015-04-01

    Blast waves appear in many astrophysical phenomena, such as supernovae. In this paper we discuss blast waves with cosmic rays, i.e., with a component with a power-law number density distribution function N( p) ∝ p -Γ that may be particulary important in describing the evolution of supernova remnants. We confirm some previous findings that a significant amount of cosmic ray energy is deposited towards the center of a remnant.

  18. Cosmic string induced CMB maps

    SciTech Connect

    Landriau, M.; Shellard, E. P. S.

    2011-02-15

    We compute maps of CMB temperature fluctuations seeded by cosmic strings using high resolution simulations of cosmic strings in a Friedmann-Robertson-Walker universe. We create full-sky, 18 deg. and 3 deg. CMB maps, including the relevant string contribution at each resolution from before recombination to today. We extract the angular power spectrum from these maps, demonstrating the importance of recombination effects. We briefly discuss the probability density function of the pixel temperatures, their skewness, and kurtosis.

  19. Revisit of cosmic age problem

    SciTech Connect

    Wang Shuang; Li Xiaodong; Li Miao

    2010-11-15

    We investigate the cosmic age problem associated with 9 extremely old globular clusters in M31 galaxy and 1 very old high-z quasar automatic plate-measuring machine 08279+5255 at z=3.91. These 9 globular clusters have not been used to study the cosmic age problem in the previous literature. By evaluating the age of the Universe in the {Lambda} cold dark matter model with the observational constraints from the Type Ia supernovae, the baryon acoustic oscillations, the cosmic microwave background, and the independent H{sub 0} measurements, we find that the existence of 5 globular clusters and 1 high-z quasar are in tension (over 2{sigma} confidence level) with the current cosmological observations. So if the age estimates of these objects are correct, the cosmic age puzzle still remains in the standard cosmology. Moreover, we extend our investigations to the cases of the interacting dark energy models. It is found that although the introduction of the interaction between dark sectors can give a larger cosmic age, the interacting dark energy models still have difficulty to pass the cosmic age test.

  20. Are gamma-ray bursts the sources of ultra-high energy cosmic rays?

    NASA Astrophysics Data System (ADS)

    Baerwald, Philipp; Bustamante, Mauricio; Winter, Walter

    2015-03-01

    We reconsider the possibility that gamma-ray bursts (GRBs) are the sources of the ultra-high energy cosmic rays (UHECRs) within the internal shock model, assuming a pure proton composition of the UHECRs. For the first time, we combine the information from gamma-rays, cosmic rays, prompt neutrinos, and cosmogenic neutrinos quantitatively in a joint cosmic ray production and propagation model, and we show that the information on the cosmic energy budget can be obtained as a consequence. In addition to the neutron model, we consider alternative scenarios for the cosmic ray escape from the GRBs, i.e., that cosmic rays can leak from the sources. We find that the dip model, which describes the ankle in UHECR observations by the pair production dip, is strongly disfavored in combination with the internal shock model because (a) unrealistically high baryonic loadings (energy in protons versus energy in electrons/gamma-rays) are needed for the individual GRBs and (b) the prompt neutrino flux easily overshoots the corresponding neutrino bound. On the other hand, GRBs may account for the UHECRs in the ankle transition model if cosmic rays leak out from the source at the highest energies. In that case, we demonstrate that future neutrino observations can efficiently test most of the parameter space - unless the baryonic loading is much larger than previously anticipated.

  1. Nonthermal cosmic neutrino background

    NASA Astrophysics Data System (ADS)

    Chen, Mu-Chun; Ratz, Michael; Trautner, Andreas

    2015-12-01

    We point out that, for Dirac neutrinos, in addition to the standard thermal cosmic neutrino background (C ν B ), there could also exist a nonthermal neutrino background with comparable number density. As the right-handed components are essentially decoupled from the thermal bath of standard model particles, relic neutrinos with a nonthermal distribution may exist until today. The relic density of the nonthermal (nt) background can be constrained by the usual observational bounds on the effective number of massless degrees of freedom Neff and can be as large as nν nt≲0.5 nγ. In particular, Neff can be larger than 3.046 in the absence of any exotic states. Nonthermal relic neutrinos constitute an irreducible contribution to the detection of the C ν B and, hence, may be discovered by future experiments such as PTOLEMY. We also present a scenario of chaotic inflation in which a nonthermal background can naturally be generated by inflationary preheating. The nonthermal relic neutrinos, thus, may constitute a novel window into the very early Universe.

  2. Revealing cosmic rotation

    NASA Astrophysics Data System (ADS)

    Yadav, Amit P. S.; Shimon, Meir; Keating, Brian G.

    2012-10-01

    Cosmological Birefringence, a rotation of the polarization plane of radiation coming to us from distant astrophysical sources, may reveal parity violation in either the electromagnetic or gravitational sectors of the fundamental interactions in nature. Until only recently this phenomenon could be probed with only radio observations or observations at UV wavelengths. Recently, there is a substantial effort to constrain such nonstandard models using observations of the rotation of the polarization plane of cosmic microwave background (CMB) radiation. This can be done via measurements of the B-modes of the CMB or by measuring its TB and EB correlations which vanish in the standard model. In this paper we show that EB correlations-based estimator is the best for upcoming polarization experiments. The EB-based estimator surpasses other estimators because it has the smallest noise and of all the estimators is least affected by systematics. Current polarimeters are optimized for the detection of B-mode polarization from either primordial gravitational waves or by large-scale structures via gravitational lensing. In the paper we also study the optimization of CMB experiments for the detection of cosmological birefringence, in the presence of instrumental systematics, which by themselves are capable of producing EB correlations, potentially mimicking cosmological birefringence.

  3. The Cosmic Century

    NASA Astrophysics Data System (ADS)

    Longair, Malcolm S.

    2006-06-01

    Part I. Stars and Stellar Evolution up to the Second World War: 1. The legacy of the nineteenth century; 2. The classification of stellar spectra; 3. Stellar structure and evolution; 4. The end points of stellar evolution; Part II. The Large-Scale Structure of the Universe, 1900-1939: 5. The Galaxy and the nature of spiral nebulae; 6. The origins of astrophysical cosmology; Part III. The Opening up of the Electromagnetic Spectrum: 7. The opening up of the electromagnetic spectrum and the new astronomies; Part IV. The Astrophysics of Stars and Galaxies since 1945: 8. Stars and stellar evolution; 9. The physics of the interstellar medium; 10. The physics of galaxies and clusters of galaxies; 11. High-energy astrophysics; Part V. Astrophysical Cosmology since 1945: 12. Astrophysical cosmology; 13. The determination of cosmological parameters; 14. The evolution of galaxies and active galaxies with cosmic epoch; 15. The origin of galaxies and the large-scale structure of the Universe; 16. The very early Universe; References; Name index; Object index; Subject index.

  4. The Cosmic Century

    NASA Astrophysics Data System (ADS)

    Longair, Malcolm S.

    2013-04-01

    Part I. Stars and Stellar Evolution up to the Second World War: 1. The legacy of the nineteenth century; 2. The classification of stellar spectra; 3. Stellar structure and evolution; 4. The end points of stellar evolution; Part II. The Large-Scale Structure of the Universe, 1900-1939: 5. The Galaxy and the nature of spiral nebulae; 6. The origins of astrophysical cosmology; Part III. The Opening up of the Electromagnetic Spectrum: 7. The opening up of the electromagnetic spectrum and the new astronomies; Part IV. The Astrophysics of Stars and Galaxies since 1945: 8. Stars and stellar evolution; 9. The physics of the interstellar medium; 10. The physics of galaxies and clusters of galaxies; 11. High-energy astrophysics; Part V. Astrophysical Cosmology since 1945: 12. Astrophysical cosmology; 13. The determination of cosmological parameters; 14. The evolution of galaxies and active galaxies with cosmic epoch; 15. The origin of galaxies and the large-scale structure of the Universe; 16. The very early Universe; References; Name index; Object index; Subject index.

  5. Cosmic string wakes

    NASA Technical Reports Server (NTRS)

    Stebbins, Albert; Veeraraghavan, Shoba; Silk, Joseph; Brandenberger, Robert; Turok, Neil

    1987-01-01

    Accretion of matter onto wakes left behind by horizon-sized pieces of cosmic string is investigated, and the effects of wakes on the large-scale structure of the universe are determined. Accretion of cold matter onto wakes, the effects of a long string on fluids with finite velocity dispersion or sound speeds, the interactions between loops and wakes, and the conditions for wakes to survive disruption by loops are discussed. It is concluded that the most important wakes are those which were formed at the time of equal matter and radiation density. This leads to sheetlike overdense regions of galaxies with a mean separation in agreement with the scale of the bubbles of de Lapparent, Geller, and Huchra (1986). However, for the value of G(mu) favored from galaxy formation considerations in a universe with cold dark matter, a wake accretes matter from a distance of only about 1.5 Mpc, which is much less than the distance between the wakes.

  6. Bosonic structure of realistic SO(10) supersymmetric cosmic strings

    NASA Astrophysics Data System (ADS)

    Allys, Erwan

    2016-05-01

    We study the bosonic structure of F -term Nambu-Goto cosmic strings forming in a realistic SO(10) implementation, assuming standard hybrid inflation. We describe the supersymmetric grand unified theory, and its spontaneous symmetry breaking scheme in parallel with the inflationary process. We also write the explicit tensor formulation of its scalar sector, focusing on the subrepresentations singlet under the standard model, which is sufficient to describe the string structure. We then introduce an ansatz for Abelian cosmic strings, discussing in details the hypothesis, and write down the field equations and boundary conditions. Finally, after doing a perturbative study of the model, we present and discuss the results obtained with numerical solutions of the string structure.

  7. 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.

  8. Virgo cluster as a high energy cosmic rays source

    NASA Technical Reports Server (NTRS)

    Karakula, S.; Tkaczyk, W.

    1985-01-01

    The extragalactic charged particles are reflecting from the Galaxy by its magnetic field. Assuming magnetic field in the Galaxy as quasilongitudinal, the mean transparency of Galaxy has been evaluated for extragalactic protons defined as a fraction of particles at a given energy from a given direction passing by the galactic plane. The anisotropy caused by the Galactic magnetic field reflection of protons can explain observed arrival directions of extensive air showers at large angle to the galactic plane. Our analysis shows that the increase with energy observed in sin b sup 11 is self-consistent with changing in the cosmic ray energy spectrum at high energy (E 10 to the 19th power eV) in the case when extragalactic cosmic ray source with spectral index -2.2 is at the position of the Virgo Cluster.

  9. CMOS RAM cosmic-ray-induced-error-rate analysis

    NASA Technical Reports Server (NTRS)

    Pickel, J. C.; Blandford, J. T., Jr.

    1981-01-01

    A significant number of spacecraft operational anomalies are believed to be associated with cosmic-ray-induced soft errors in the LSI memories. Test programs using a cyclotron to simulate cosmic rays have established conclusively that many common commercial memory types are vulnerable to heavy-ion upset. A description is given of the methodology and the results of a detailed analysis for predicting the bit-error rate in an assumed space environment for CMOS memory devices. Results are presented for three types of commercially available CMOS 1,024-bit RAMs. It was found that the HM6508 is susceptible to single-ion induced latchup from argon and krypton ions. The HS6508 and HS6508RH and the CDP1821 apparently are not susceptible to single-ion induced latchup.

  10. Constraining warm dark matter with cosmic shear power spectra

    SciTech Connect

    Markovic, Katarina; Weller, Jochen; Bridle, Sarah; Slosar, Anže E-mail: sarah.bridle@ucl.ac.uk E-mail: jochen.weller@usm.lmu.de

    2011-01-01

    We investigate potential constraints from cosmic shear on the dark matter particle mass, assuming all dark matter is made up of light thermal relic particles. Given the theoretical uncertainties involved in making cosmological predictions in such warm dark matter scenarios we use analytical fits to linear warm dark matter power spectra and compare (i) the halo model using a mass function evaluated from these linear power spectra and (ii) an analytical fit to the non-linear evolution of the linear power spectra. We optimistically ignore the competing effect of baryons for this work. We find approach (ii) to be conservative compared to approach (i). We evaluate cosmological constraints using these methods, marginalising over four other cosmological parameters. Using the more conservative method we find that a Euclid-like weak lensing survey together with constraints from the Planck cosmic microwave background mission primary anisotropies could achieve a lower limit on the particle mass of 2.5 keV.

  11. Constraining invisible neutrino decays with the cosmic microwave background

    SciTech Connect

    Hannestad, Steen; Raffelt, Georg G.

    2005-11-15

    Precision measurements of the acoustic peaks of the cosmic microwave background indicate that neutrinos must be freely streaming at the photon decoupling epoch when T{approx_equal}0.3 eV. This requirement implies restrictive limits on 'secret neutrino interactions', notably on neutrino Yukawa couplings with hypothetical low-mass (pseudo)scalars {phi}. For diagonal couplings in the neutrino mass basis we find g < or approx. 1x10{sup -7}, comparable to limits from supernova 1987A. For the off-diagonal couplings and assuming hierarchical neutrino masses we find g < or approx. 1x10{sup -11}(0.05 eV/m){sup 2} where m is the heavier mass of a given neutrino pair connected by g. This stringent limit excludes that the flavor content of high-energy neutrinos from cosmic-ray sources is modified by {nu}{yields}{nu}{sup '}+{phi} decays on their way to Earth.

  12. A simulation of high energy cosmic ray propagation 1

    NASA Technical Reports Server (NTRS)

    Honda, M.; Kifune, T.; Matsubara, Y.; Mori, M.; Nishijima, K.; Teshima, M.

    1985-01-01

    High energy cosmic ray propagation of the energy region 10 to the 14.5 power - 10 to the 18th power eV is simulated in the inter steller circumstances. In conclusion, the diffusion process by turbulent magnetic fields is classified into several regions by ratio of the gyro-radius and the scale of turbulence. When the ratio becomes larger then 10 to the minus 0.5 power, the analysis with the assumption of point scattering can be applied with the mean free path E sup 2. However, when the ratio is smaller than 10 to the minus 0.5 power, we need a more complicated analysis or simulation. Assuming the turbulence scale of magnetic fields of the Galaxy is 10-30pc and the mean magnetic field strength is 3 micro gauss, the energy of cosmic ray with that gyro-radius is about 10 to the 16.5 power eV.

  13. Comparison of symbolic and numerical integration methods for an assumed-stress hybrid shell element

    NASA Technical Reports Server (NTRS)

    Rengarajan, Govind; Knight, Norman F., Jr.; Aminpour, Mohammad A.

    1993-01-01

    Hybrid shell elements have long been regarded with reserve by the commercial finite element developers despite the high degree of reliability and accuracy associated with such formulations. The fundamental reason is the inherent higher computational cost of the hybrid approach as compared to the displacement-based formulations. However, a noteworthy factor in favor of hybrid elements is that numerical integration to generate element matrices can be entirely avoided by the use of symbolic integration. In this paper, the use of the symbolic computational approach is presented for an assumed-stress hybrid shell element with drilling degrees of freedom and the significant time savings achieved is demonstrated through an example.

  14. Federal and state management of inland wetlands: Are states ready to assume control?

    NASA Astrophysics Data System (ADS)

    Glubiak, Peter G.; Nowka, Richard H.; Mitsch, William J.

    1986-03-01

    As inland wetlands face increasing pressure for development, both the federal government and individual states have begun reevaluating their respective wetland regulatory schemes. This article focuses first on the effectiveness of the past, present, and proposed federal regulations, most notably the Section 404, Dredge and Fill Permit Program, in dealing with shrinking wetland resources. The article then addresses the status of state involvement in this largely federal area, as well as state preparedness to assume primacy should federal priorities change. Finally, the subject of comprehensive legislation for wetland protection is investigated, and the article concludes with some procedural suggestions for developing a model law.

  15. Traction free finite elements with the assumed stress hybrid model. M.S. Thesis, 1981

    NASA Technical Reports Server (NTRS)

    Kafie, Kurosh

    1991-01-01

    An effective approach in the finite element analysis of the stress field at the traction free boundary of a solid continuum was studied. Conventional displacement and assumed stress finite elements were used in the determination of stress concentrations around circular and elliptical holes. Specialized hybrid elements were then developed to improve the satisfaction of prescribed traction boundary conditions. Results of the stress analysis indicated that finite elements which exactly satisfy the free stress boundary conditions are the most accurate and efficient in such problems. A general approach for hybrid finite elements which incorporate traction free boundaries of arbitrary geometry was formulated.

  16. Aseismic Slips Preceding Ruptures Assumed for Anomalous Seismicities and Crustal Deformations

    NASA Astrophysics Data System (ADS)

    Ogata, Y.

    2007-12-01

    If aseismic slips occurs on a fault or its deeper extension, both seismicity and geodetic records around the source should be affected. Such anomalies are revealed to have occurred during the last several years leading up to the October 2004 Chuetsu Earthquake of M6.8, the March 2007 Noto Peninsula Earthquake of M6.9, and the July 2007 Chuetsu-Oki Earthquake of M6.8, which occurred successively in the near-field, central Japan. Seismic zones of negative and positive increments of the Coulomb failure stress, assuming such slips, show seismic quiescence and activation, respectively, relative to the predicted rate by the ETAS model. These are further supported by transient crustal movement around the source preceding the rupture. Namely, time series of the baseline distance records between a numbers of the permanent GPS stations deviated from the predicted trend, with the trend of different slope that is basically consistent with the horizontal displacements of the stations due to the assumed slips. References Ogata, Y. (2007) Seismicity and geodetic anomalies in a wide area preceding the Niigata-Ken-Chuetsu Earthquake of October 23, 2004, central Japan, J. Geophys. Res. 112, in press.

  17. Children's Everyday Learning by Assuming Responsibility for Others: Indigenous Practices as a Cultural Heritage Across Generations.

    PubMed

    Fernández, David Lorente

    2015-01-01

    This chapter uses a comparative approach to examine the maintenance of Indigenous practices related with Learning by Observing and Pitching In in two generations--parent generation and current child generation--in a Central Mexican Nahua community. In spite of cultural changes and the increase of Western schooling experience, these practices persist, to different degrees, as a Nahua cultural heritage with close historical relations to the key value of cuidado (stewardship). The chapter explores how children learn the value of cuidado in a variety of everyday activities, which include assuming responsibility in many social situations, primarily in cultivating corn, raising and protecting domestic animals, health practices, and participating in family ceremonial life. The chapter focuses on three main points: (1) Cuidado (assuming responsibility for), in the Nahua socio-cultural context, refers to the concepts of protection and "raising" as well as fostering other beings, whether humans, plants, or animals, to reach their potential and fulfill their development. (2) Children learn cuidado by contributing to family endeavors: They develop attention and self-motivation; they are capable of responsible actions; and they are able to transform participation to achieve the status of a competent member of local society. (3) This collaborative participation allows children to continue the cultural tradition and to preserve a Nahua heritage at a deeper level in a community in which Nahuatl language and dress have disappeared, and people do not identify themselves as Indigenous. PMID:26955923

  18. An assumed-stress hybrid 4-node shell element with drilling degrees of freedom

    NASA Technical Reports Server (NTRS)

    Aminpour, M. A.

    1992-01-01

    An assumed-stress hybrid/mixed 4-node quadrilateral shell element is introduced that alleviates most of the deficiencies associated with such elements. The formulation of the element is based on the assumed-stress hybrid/mixed method using the Hellinger-Reissner variational principle. The membrane part of the element has 12 degrees of freedom including rotational or 'drilling' degrees of freedom at the nodes. The bending part of the element also has 12 degrees of freedom. The bending part of the element uses the Reissner-Mindlin plate theory which takes into account the transverse shear contributions. The element formulation is derived from an 8-node isoparametric element by expressing the midside displacement degrees of freedom in terms of displacement and rotational degrees of freedom at corner nodes. The element passes the patch test, is nearly insensitive to mesh distortion, does not 'lock', possesses the desirable invariance properties, has no hidden spurious modes, and for the majority of test cases used in this paper produces more accurate results than the other elements employed herein for comparison.

  19. Perceiving others' personalities: examining the dimensionality, assumed similarity to the self, and stability of perceiver effects.

    PubMed

    Srivastava, Sanjay; Guglielmo, Steve; Beer, Jennifer S

    2010-03-01

    In interpersonal perception, "perceiver effects" are tendencies of perceivers to see other people in a particular way. Two studies of naturalistic interactions examined perceiver effects for personality traits: seeing a typical other as sympathetic or quarrelsome, responsible or careless, and so forth. Several basic questions were addressed. First, are perceiver effects organized as a global evaluative halo, or do perceptions of different traits vary in distinct ways? Second, does assumed similarity (as evidenced by self-perceiver correlations) reflect broad evaluative consistency or trait-specific content? Third, are perceiver effects a manifestation of stable beliefs about the generalized other, or do they form in specific contexts as group-specific stereotypes? Findings indicated that perceiver effects were better described by a differentiated, multidimensional structure with both trait-specific content and a higher order global evaluation factor. Assumed similarity was at least partially attributable to trait-specific content, not just to broad evaluative similarity between self and others. Perceiver effects were correlated with gender and attachment style, but in newly formed groups, they became more stable over time, suggesting that they grew dynamically as group stereotypes. Implications for the interpretation of perceiver effects and for research on personality assessment and psychopathology are discussed. PMID:20175628

  20. Children's Everyday Learning by Assuming Responsibility for Others: Indigenous Practices as a Cultural Heritage Across Generations.

    PubMed

    Fernández, David Lorente

    2015-01-01

    This chapter uses a comparative approach to examine the maintenance of Indigenous practices related with Learning by Observing and Pitching In in two generations--parent generation and current child generation--in a Central Mexican Nahua community. In spite of cultural changes and the increase of Western schooling experience, these practices persist, to different degrees, as a Nahua cultural heritage with close historical relations to the key value of cuidado (stewardship). The chapter explores how children learn the value of cuidado in a variety of everyday activities, which include assuming responsibility in many social situations, primarily in cultivating corn, raising and protecting domestic animals, health practices, and participating in family ceremonial life. The chapter focuses on three main points: (1) Cuidado (assuming responsibility for), in the Nahua socio-cultural context, refers to the concepts of protection and "raising" as well as fostering other beings, whether humans, plants, or animals, to reach their potential and fulfill their development. (2) Children learn cuidado by contributing to family endeavors: They develop attention and self-motivation; they are capable of responsible actions; and they are able to transform participation to achieve the status of a competent member of local society. (3) This collaborative participation allows children to continue the cultural tradition and to preserve a Nahua heritage at a deeper level in a community in which Nahuatl language and dress have disappeared, and people do not identify themselves as Indigenous.

  1. Factors that affect action possibility judgments: the assumed abilities of other people.

    PubMed

    Welsh, Timothy N; Wong, Lokman; Chandrasekharan, Sanjay

    2013-06-01

    Judging what actions are possible and impossible to complete is a skill that is critical for planning and executing movements in both individual and joint actions contexts. The present experiments explored the ability to adapt action possibility judgments to the assumed characteristics of another person. Participants watched alternating pictures of a person's hand moving at different speeds between targets of different indexes of difficulty (according to Fitts' Law) and judged whether or not it was possible for individuals with different characteristics to maintain movement accuracy at the presented speed. Across four studies, the person in the pictures and the background information about the person were manipulated to determine how and under what conditions participants adapted their judgments. Results revealed that participants adjusted their possibility judgments to the assumed motor capabilities of the individual they were judging. However, these adjustments only occurred when participants were instructed to take the other person into consideration suggesting that the adaption process is a voluntary process. Further, it was observed that the slopes of the regression equations relating movement time and index of difficulty did not differ across conditions. All differences between conditions were in the y-intercept of the regression lines. This pattern of findings suggests that participants formed the action possibility judgments by first simulating their own performance, and then adjusted the "possibility" threshold by adding or subtracting a correction factor to determine what is and is not possible for the other person to perform.

  2. The combined oral contraceptive pill and the assumed 28-day cycle.

    PubMed

    Dowse, M St Leger; Gunby, A; Moncad, R; Fife, C; Smerdon, G; Bryson, P

    2007-07-01

    Some studies involving women taking the combined oral contraceptive pill (COCP) have on occasion assumed the COCP group to have a rigid 28-day pharmaceutically driven cycle. Anecdotal evidence suggests otherwise, with many women adjusting their COCP usage to alter the time between break-through bleeds for sporting and social reasons. A prospective field study involving 533 scuba diving females allowed all menstrual cycle lengths (COCP and non-COCP) to be observed for up to three consecutive years (St Leger Dowse et al. 2006). A total of 29% of women were COCP users who reported 3,241 cycles. Of these cycles, only 42% had a rigid 28-day cycle, with the remainder varying in length from 21 to 60 days. When performing studies involving the menstrual cycle, it should not be assumed that COCP users have a rigid confirmed 28-day cycle and careful consideration should be given to data collection and analysis. The effects of differing data interpretations are shown.

  3. Factors that affect action possibility judgments: the assumed abilities of other people.

    PubMed

    Welsh, Timothy N; Wong, Lokman; Chandrasekharan, Sanjay

    2013-06-01

    Judging what actions are possible and impossible to complete is a skill that is critical for planning and executing movements in both individual and joint actions contexts. The present experiments explored the ability to adapt action possibility judgments to the assumed characteristics of another person. Participants watched alternating pictures of a person's hand moving at different speeds between targets of different indexes of difficulty (according to Fitts' Law) and judged whether or not it was possible for individuals with different characteristics to maintain movement accuracy at the presented speed. Across four studies, the person in the pictures and the background information about the person were manipulated to determine how and under what conditions participants adapted their judgments. Results revealed that participants adjusted their possibility judgments to the assumed motor capabilities of the individual they were judging. However, these adjustments only occurred when participants were instructed to take the other person into consideration suggesting that the adaption process is a voluntary process. Further, it was observed that the slopes of the regression equations relating movement time and index of difficulty did not differ across conditions. All differences between conditions were in the y-intercept of the regression lines. This pattern of findings suggests that participants formed the action possibility judgments by first simulating their own performance, and then adjusted the "possibility" threshold by adding or subtracting a correction factor to determine what is and is not possible for the other person to perform. PMID:23644579

  4. Effects of assumed tow architecture on the predicted moduli and stresses in woven composites

    NASA Technical Reports Server (NTRS)

    Chapman, Clinton Dane

    1994-01-01

    This study deals with the effect of assumed tow architecture on the elastic material properties and stress distributions of plain weave woven composites. Specifically, the examination of how a cross-section is assumed to sweep-out the tows of the composite is examined in great detail. The two methods studied are extrusion and translation. This effect is also examined to determine how sensitive this assumption is to changes in waviness ratio. 3D finite elements were used to study a T300/Epoxy plain weave composite with symmetrically stacked mats. 1/32nd of the unit cell is shown to be adequate for analysis of this type of configuration with the appropriate set of boundary conditions. At low waviness, results indicate that for prediction of elastic properties, either method is adequate. At high waviness, certain elastic properties become more sensitive to the method used. Stress distributions at high waviness ratio are shown to vary greatly depending on the type of loading applied. At low waviness, both methods produce similar results.

  5. Cosmic ray exposure ages of iron meteorites, complex irradiation and the constancy of cosmic ray flux in the past

    NASA Technical Reports Server (NTRS)

    Marti, K.; Lavielle, B.; Regnier, S.

    1984-01-01

    While previous calculations of potassium ages assumed a constant cosmic ray flux and a single stage (no change in size) exposure of iron meteorites, present calculations relaxed these constancy assumptions and the results reveal multistage irradiations for some 25% of the meteorites studied, implying multiple breakup in space. The distribution of exposure ages suggests several major collisions (based on chemical composition and structure), although the calibration of age scales is not yet complete. It is concluded that shielding-corrected (corrections which depend on size and position of sample) production rates are consistent for the age bracket of 300 to 900 years. These production rates differ in a systematic way from those calculated for present day fluxes of cosmic rays (such as obtained for the last few million years).

  6. Cosmic ray Implications for Human Health

    NASA Astrophysics Data System (ADS)

    Shea, M. A.; Smart, D. F.

    2000-07-01

    There appears to be concern among some people about the possible effects of cosmic radiation on everyday life. The amount of cosmic radiation that reaches the Earth and its environment is a function of solar cycle, altitude and latitude. The possible effect of naturally occurring cosmic radiation on airplane crews and space flight personal is a subject of current study. This paper discusses the variables controlling the cosmic ray flux in the atmosphere and describes models and software that have been developed that provide quantitative information about the cosmic radiation exposure at flight altitudes. The discussion is extended to include the cosmic radiation exposure to manned spacecraft.

  7. POLARBEAR constraints on cosmic birefringence and primordial magnetic fields

    NASA Astrophysics Data System (ADS)

    Ade, Peter A. R.; Arnold, Kam; Atlas, Matt; Baccigalupi, Carlo; Barron, Darcy; Boettger, David; Borrill, Julian; Chapman, Scott; Chinone, Yuji; Cukierman, Ari; Dobbs, Matt; Ducout, Anne; Dunner, Rolando; Elleflot, Tucker; Errard, Josquin; Fabbian, Giulio; Feeney, Stephen; Feng, Chang; Gilbert, Adam; Goeckner-Wald, Neil; Groh, John; Hall, Grantland; Halverson, Nils W.; Hasegawa, Masaya; Hattori, Kaori; Hazumi, Masashi; Hill, Charles; Holzapfel, William L.; Hori, Yasuto; Howe, Logan; Inoue, Yuki; Jaehnig, Gregory C.; Jaffe, Andrew H.; Jeong, Oliver; Katayama, Nobuhiko; Kaufman, Jonathan P.; Keating, Brian; Kermish, Zigmund; Keskitalo, Reijo; Kisner, Theodore; Kusaka, Akito; Le Jeune, Maude; Lee, Adrian T.; Leitch, Erik M.; Leon, David; Li, Yun; Linder, Eric; Lowry, Lindsay; Matsuda, Frederick; Matsumura, Tomotake; Miller, Nathan; Montgomery, Josh; Myers, Michael J.; Navaroli, Martin; Nishino, Haruki; Okamura, Takahiro; Paar, Hans; Peloton, Julien; Pogosian, Levon; Poletti, Davide; Puglisi, Giuseppe; Raum, Christopher; Rebeiz, Gabriel; Reichardt, Christian L.; Richards, Paul L.; Ross, Colin; Rotermund, Kaja M.; Schenck, David E.; Sherwin, Blake D.; Shimon, Meir; Shirley, Ian; Siritanasak, Praween; Smecher, Graeme; Stebor, Nathan; Steinbach, Bryan; Suzuki, Aritoki; Suzuki, Jun-ichi; Tajima, Osamu; Takakura, Satoru; Tikhomirov, Alexei; Tomaru, Takayuki; Whitehorn, Nathan; Wilson, Brandon; Yadav, Amit; Zahn, Alex; Zahn, Oliver; Polarbear Collaboration

    2015-12-01

    We constrain anisotropic cosmic birefringence using four-point correlations of even-parity E -mode and odd-parity B -mode polarization in the cosmic microwave background measurements made by the POLARization of the Background Radiation (POLARBEAR) experiment in its first season of observations. We find that the anisotropic cosmic birefringence signal from any parity-violating processes is consistent with zero. The Faraday rotation from anisotropic cosmic birefringence can be compared with the equivalent quantity generated by primordial magnetic fields if they existed. The POLARBEAR nondetection translates into a 95% confidence level (C.L.) upper limit of 93 nanogauss (nG) on the amplitude of an equivalent primordial magnetic field inclusive of systematic uncertainties. This four-point correlation constraint on Faraday rotation is about 15 times tighter than the upper limit of 1380 nG inferred from constraining the contribution of Faraday rotation to two-point correlations of B -modes measured by Planck in 2015. Metric perturbations sourced by primordial magnetic fields would also contribute to the B -mode power spectrum. Using the POLARBEAR measurements of the B -mode power spectrum (two-point correlation), we set a 95% C.L. upper limit of 3.9 nG on primordial magnetic fields assuming a flat prior on the field amplitude. This limit is comparable to what was found in the Planck 2015 two-point correlation analysis with both temperature and polarization. We perform a set of systematic error tests and find no evidence for contamination. This work marks the first time that anisotropic cosmic birefringence or primordial magnetic fields have been constrained from the ground at subdegree scales.

  8. Angular distribution of cosmic rays in the interplanetary magnetic field

    NASA Astrophysics Data System (ADS)

    Fedorov, Yu. I.

    2001-08-01

    Cosmic ray propagation in the interplanetary medium is considered on the basis of kinetic equation describing the scattering of charged particles by magnetic irregularities and their focusing by regular interplanetary magnetic field. The relationship between cosmic ray distribution function and parameters of particle scattering in the interplanetary medium is investigated. Obtained results are applied to the analyses of solar proton events and galactic cosmic ray anisotropy. 1 COSMIC RAY DISTRIBUTION FUNCTION Angular distribution of energetic charged particles contains valuable information about particle scattering in the heliosphere and the geometry of interplanetary magnetic field (IMF) (Bieber and Pomerantz, 1983; Beeck and Wibberenz,1986; Wibberenz and Green, 1988; Hatzky and Wibberenz, 1997). In the present paper the relationship between the distribution function of cosmic rays (CR) and parameters of particle scattering is investigated. The kinetic equation describing CR propagation in the interplanetary medium, can be written as (Earl,1981; Toptygin,1985) ∂f ∂t + vµ ∂f ∂z + v 2ζ (1 - µ2 ) ∂f ∂µ - ∂ ∂µ Dµµ ∂f ∂µ = Q, (1) where f is CR distribution function, Dµµ is the diffusion coefficient in angular space, µ = cos θ and θ is the pitch angle, ς is the focusing length, and z is a coordinate directed along regular magnetic field. The particle source is included in the right hand side of Eq(1). One can present the distribution function as a superposition of isotropic f0 and anisotropic δf(µ) components f(z, µ, t) = 1 2 f0(z, t) + δf(z, µ, t). (2) Assuming that the particle source Q is isotropic and subtracting from Eq.(1) averaged over µ equation, we obtain

  9. Cosmic Microwave Background spectral distortions from cosmic string loops

    NASA Astrophysics Data System (ADS)

    Anthonisen, Madeleine; Brandenberger, Robert; Laguë, Alex; Morrison, Ian A.; Xia, Daixi

    2016-02-01

    Cosmic string loops contain cusps which decay by emitting bursts of particles. A significant fraction of the released energy is in the form of photons. These photons are injected non-thermally and can hence cause spectral distortions of the Cosmic Microwave Background (CMB). Under the assumption that cusps are robust against gravitational back-reaction, we compute the fractional energy density released as photons in the redshift interval where such non-thermal photon injection causes CMB spectral distortions. Whereas current constraints on such spectral distortions are not strong enough to constrain the string tension, future missions such as the PIXIE experiment will be able to provide limits which rule out a range of string tensions between G μ ~ 10-15 and G μ ~ 10-12, thus ruling out particle physics models yielding these kind of intermediate-scale cosmic strings.

  10. Fitting cosmic microwave background data with cosmic strings and inflation.

    PubMed

    Bevis, Neil; Hindmarsh, Mark; Kunz, Martin; Urrestilla, Jon

    2008-01-18

    We perform a multiparameter likelihood analysis to compare measurements of the cosmic microwave background (CMB) power spectra with predictions from models involving cosmic strings. Adding strings to the standard case of a primordial spectrum with power-law tilt ns, we find a 2sigma detection of strings: f10=0.11+/-0.05, where f10 is the fractional contribution made by strings in the temperature power spectrum (at l=10). CMB data give moderate preference to the model ns=1 with cosmic strings over the standard zero-strings model with variable tilt. When additional non-CMB data are incorporated, the two models become on a par. With variable ns and these extra data, we find that f10<0.11, which corresponds to Gmicro<0.7x10(-6) (where micro is the string tension and G is the gravitational constant). PMID:18232848

  11. A Cosmic Searchlight

    NASA Technical Reports Server (NTRS)

    2002-01-01

    A Cosmic Searchlight Streaming out from the center of the galaxy M87 like a cosmic searchlight is one of nature's most amazing phenomena, a black-hole- powered jet of electrons and other sub-atomic particles traveling at nearly the speed of light. In this NASA Hubble Space Telescope image, the blue of the jet contrasts with the yellow glow from the combined light of billions of unseen stars and the yellow, point-like globular clusters that make up this galaxy. At first glance, M87 (also known as NGC 4486) appears to be an ordinary giant elliptical galaxy; one of many ellipticals in the nearby Virgo cluster of galaxies. However, as early as 1918, astronomer H.D. Curtis noted a 'curious straight ray' protruding from M87. In the 1950s when the field of radio was blossoming, one of the brightest radio sources in the sky, Virgo A, was discovered to be associated with M87 and its jet. After decades of study, prompted by these discoveries, the source of this incredible amount of energy powering the jet has become clear. Lying at the center of M87 is a supermassive black hole, which has swallowed up a mass equivalent to 2 billion times the mass of our Sun. The jet originates in the disk of superheated gas swirling around this black hole and is propelled and concentrated by the intense, twisted magnetic fields trapped within this plasma. The light that we see (and the radio emission) is produced by electrons twisting along magnetic field lines in the jet, a process known as synchrotron radiation, which gives the jet its bluish tint. M87 is one of the nearest and is the most well-studied extragalactic jet, but many others exist. Wherever a massive black hole is feeding on a particularly rich diet of disrupted stars, gas, and dust, the conditions are right for the formation of a jet. Interestingly, a similar phenomenon occurs around young stars, though at much smaller scales and energies. At a distance of 50 million light-years, M87 is too distant for Hubble to discern

  12. Nearest Cosmic Mirage

    NASA Astrophysics Data System (ADS)

    2003-07-01

    Discovery of quadruply lensed quasar with Einstein ring Summary Using the ESO 3.6-m telescope at La Silla (Chile), an international team of astronomers [1] has discovered a complex cosmic mirage in the southern constellation Crater (The Cup). This "gravitational lens" system consists of (at least) four images of the same quasar as well as a ring-shaped image of the galaxy in which the quasar resides - known as an "Einstein ring". The more nearby lensing galaxy that causes this intriguing optical illusion is also well visible. The team obtained spectra of these objects with the new EMMI camera mounted on the ESO 3.5-m New Technology Telescope (NTT), also at the La Silla observatory. They find that the lensed quasar [2] is located at a distance of 6,300 million light-years (its "redshift" is z = 0.66 [3]) while the lensing elliptical galaxy is rougly halfway between the quasar and us, at a distance of 3,500 million light-years (z = 0.3). The system has been designated RXS J1131-1231 - it is the closest gravitationally lensed quasar discovered so far . PR Photo 20a/03 : Image of the gravitational lens system RXS J1131-1231 (ESO 3.6m Telescope). PR Photo 20b/03 : Spectra of two lensed images of the source quasar and the lensing galaxy. Cosmic mirages The physical principle behind a "gravitational lens" (also known as a "cosmic mirage") has been known since 1916 as a consequence of Albert Einstein's Theory of General Relativity . The gravitational field of a massive object curves the local geometry of the Universe, so light rays passing close to the object are bent (like a "straight line" on the surface of the Earth is necessarily curved because of the curvature of the Earth's surface). This effect was first observed by astronomers in 1919 during a total solar eclipse. Accurate positional measurements of stars seen in the dark sky near the eclipsed Sun indicated an apparent displacement in the direction opposite to the Sun, about as much as predicted by Einstein

  13. A Cosmic Magnifying Glass

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Scanning the heavens for the first time since the successful December 1999 servicing mission, NASA's Hubble Space Telescope imaged a giant, cosmic magnifying glass, a massive cluster of galaxies called Abell 2218. This 'hefty' cluster resides in the constellation Draco, some 2 billion light-years from Earth. The cluster is so massive that its enormous gravitational field deflects light rays passing through it, much as an optical lens bends light to form an image. This phenomenon, called gravitational lensing, magnifies, brightens, and distorts images from faraway objects. The cluster's magnifying powers provides a powerful 'zoom lens' for viewing distant galaxies that could not normally be observed with the largest telescopes. The picture is dominated by spiral and elliptical galaxies. Resembling a string of tree lights, the biggest and brightest galaxies are members of the foreground cluster. Researchers are intrigued by a tiny red dot just left of top center. This dot may be an extremely remote object made visible by the cluster's magnifying powers. Further investigation is needed to confirm the object's identity. The color picture already reveals several arc-shaped features that are embedded in the cluster and cannot be easily seen in the black-and- white image. The colors in this picture yield clues to the ages, distances, and temperatures of stars, the stuff of galaxies. Blue pinpoints hot young stars. The yellow-white color of several of the galaxies represents the combined light of many stars. Red identifies cool stars, old stars, and the glow of stars in distant galaxies. This view is only possible by combining Hubble's unique image quality with the rare lensing effect provided by the magnifying cluster.

  14. Theoretical cosmic Type Ia supernova rates

    NASA Astrophysics Data System (ADS)

    Valiante, R.; Matteucci, F.; Recchi, S.; Calura, F.

    2009-10-01

    The purpose of this work is the computation of the cosmic Type Ia supernova rates, namely the frequency of Type Ia supernovae per unit time in a unitary volume of the Universe. Our main goal in this work is to predict the Type Ia supernova rates at very high redshifts and to check whether it is possible to select the best delay time distribution model, on the basis of the available observations of Type Ia supernovae. We compute the cosmic Type Ia supernova rates in different scenarios for galaxy formation and predict the expected number of explosions at high redshift ( z⩾2). Moreover, we adopt various progenitor models in order to compute the Type Ia supernova rate in typical elliptical galaxies of initial luminous masses of 1010M⊙,1011M⊙ and 1012M⊙, and compute the total amount of iron produced by Type Ia supernovae in each case. In this analysis we assume that Type Ia supernovae are caused by thermonuclear explosions of C-O white dwarfs in binary systems and we consider the most popular frameworks: the single degenerate and the double degenerate scenarios. The two competing schemes for the galaxy formation, namely the monolithic collapse and the hierarchical clustering, are also taken into account, by considering the histories of star formation increasing and decreasing with redshift, respectively. We calculate the Type Ia supernova rates through an analytical formulation which rests upon the definition of the SN Ia rate following an instantaneous burst of star formation as a function of the time elapsed from the birth of the progenitor system to its explosion as a Type Ia supernova (i.e. the delay time). What emerges from this work is that: (i) we confirm the result of previous papers that it is not easy to select the best delay time distribution scenario from the observational data and this is because the cosmic star formation rate dominates over the distribution function of the delay times; (ii) the monolithic collapse scenario for galaxy formation

  15. 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

  16. Cosmic logic: a computational model

    NASA Astrophysics Data System (ADS)

    Vanchurin, Vitaly

    2016-02-01

    We initiate a formal study of logical inferences in context of the measure problem in cosmology or what we call cosmic logic. We describe a simple computational model of cosmic logic suitable for analysis of, for example, discretized cosmological systems. The construction is based on a particular model of computation, developed by Alan Turing, with cosmic observers (CO), cosmic measures (CM) and cosmic symmetries (CS) described by Turing machines. CO machines always start with a blank tape and CM machines take CO's Turing number (also known as description number or Gödel number) as input and output the corresponding probability. Similarly, CS machines take CO's Turing number as input, but output either one if the CO machines are in the same equivalence class or zero otherwise. We argue that CS machines are more fundamental than CM machines and, thus, should be used as building blocks in constructing CM machines. We prove the non-computability of a CS machine which discriminates between two classes of CO machines: mortal that halts in finite time and immortal that runs forever. In context of eternal inflation this result implies that it is impossible to construct CM machines to compute probabilities on the set of all CO machines using cut-off prescriptions. The cut-off measures can still be used if the set is reduced to include only machines which halt after a finite and predetermined number of steps.

  17. The microphysics and macrophysics of cosmic rays

    SciTech Connect

    Zweibel, Ellen G.

    2013-05-15

    This review paper commemorates a century of cosmic ray research, with emphasis on the plasma physics aspects. Cosmic rays comprise only ∼10{sup −9} of interstellar particles by number, but collectively their energy density is about equal to that of the thermal particles. They are confined by the Galactic magnetic field and well scattered by small scale magnetic fluctuations, which couple them to the local rest frame of the thermal fluid. Scattering isotropizes the cosmic rays and allows them to exchange momentum and energy with the background medium. I will review a theory for how the fluctuations which scatter the cosmic rays can be generated by the cosmic rays themselves through a microinstability excited by their streaming. A quasilinear treatment of the cosmic ray–wave interaction then leads to a fluid model of cosmic rays with both advection and diffusion by the background medium and momentum and energy deposition by the cosmic rays. This fluid model admits cosmic ray modified shocks, large scale cosmic ray driven instabilities, cosmic ray heating of the thermal gas, and cosmic ray driven galactic winds. If the fluctuations were extrinsic turbulence driven by some other mechanism, the cosmic ray background coupling would be entirely different. Which picture holds depends largely on the nature of turbulence in the background medium.

  18. the Origin of Cosmic Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Kulsrud, Russell

    1996-05-01

    It is proposed that the origin of our galactic magnetic field occurred during the protogalactic formation phase of our galaxy. It is assumed that prior to the formation there was no cosmic field at all. It is shown that as the protogalaxy formed the thermoelectric currents in cosmic plasma increased the magnetic field from zero by the Biermann battery mechanism up to a value of order 10-20 gauss. From numerical simulations, it is found that there there is very strong Kolmogoroff turbulence present in the protogalaxy. This turbulence acts on the magnetic field resulting from the Biermann battery and amplifies it at a rate γ = (k_max/k_min )^2/3 × 10-16 sec-1 where k_min and k_max are the minimum and maximum wave numbers for the turbulence. The value of k_min is found to be of order 1 megaparsec-1 , but the value of k_max lies below the grid resolution of the numerical simulation and must be determined by the physics of the cosmic plasma on small scales. During a Hubble time there is plenty of time to amplify the magnetic field from 10-20 gauss to a value that would serve as a seed field for the galactic field. The question that arises is will this field be coherent on large scales or will all the energy be concentrated in small scales. This question is addressed in this talk. the important consideration is that the cosmic plasma at this stage is very hot and has a very low density. As a result, the mean free path is extremely long of order a sizable fraction of the entire size of the protogalaxy. Therefore, it is necessary to treat the effect of the turbulent motions of the cosmic magnetic field by a semicollionless theory on scales shorter than the mean free path. It turns out that as long as the ion gyroradius is small the magnetic field controls the motion of ions through the magnetic mirror effect. this is true even if the magnetic energy is tiny compared to the thermal or kinetic energy of the plasma. As a result of this process the magnetic energy is

  19. Analysis of an object assumed to contain “Red Mercury”

    NASA Astrophysics Data System (ADS)

    Obhođaš, Jasmina; Sudac, Davorin; Blagus, Saša; Valković, Vladivoj

    2007-08-01

    After having been informed about an attempt of illicit trafficking, the Organized Crime Division of the Zagreb Police Authority confiscated in November 2003 a hand size metal cylinder suspected to contain "Red Mercury" (RM). The sample assumed to contain RM was analyzed with two nondestructive analytical methods in order to obtain information about the nature of the investigated object, namely, activation analysis with 14.1 MeV neutrons and EDXRF analysis. The activation analysis with 14.1 MeV neutrons showed that the container and its contents were characterized by the following chemical elements: Hg, Fe, Cr and Ni. By using EDXRF analysis, it was shown that the elements Fe, Cr and Ni were constituents of the capsule. Therefore, it was concluded that these three elements were present in the capsule only, while the content of the unknown material was Hg. Antimony as a hypothetical component of red mercury was not detected.

  20. Distance fields on unstructured grids: Stable interpolation, assumed gradients, collision detection and gap function

    PubMed Central

    Wolff, Sebastian; Bucher, Christian

    2013-01-01

    This article presents a novel approach to collision detection based on distance fields. A novel interpolation ensures stability of the distances in the vicinity of complex geometries. An assumed gradient formulation is introduced leading to a C1-continuous distance function. The gap function is re-expressed allowing penalty and Lagrange multiplier formulations. The article introduces a node-to-element integration for first order elements, but also discusses signed distances, partial updates, intermediate surfaces, mortar methods and higher order elements. The algorithm is fast, simple and robust for complex geometries and self contact. The computed tractions conserve linear and angular momentum even in infeasible contact. Numerical examples illustrate the new algorithm in three dimensions. PMID:23888088

  1. Challenging residents to assume maximal responsibilities in homes for the aged.

    PubMed

    Rodstein, M

    1975-07-01

    A program for activating residents of homes for the aged to assume maximal responsibilities is described. Promoting maximal physical and mental health through various modalities including activity programs, appropriate exercise and participation in democratic self-government mechanisms, will result in a happier, healthier population of residents in institutions for the aged. The increased demands on staff time and patience will be compensated for by relief of the too-frequent feelings of hopelessness and boredom endemic among the staff of long-term care facilities. Such programs demand constant effort by all staff members, patients, volunteers and relatives because if they succumb to the usual human dislike of persistency, short-term gains can easily be lost. PMID:1141631

  2. An assumed pdf approach for the calculation of supersonic mixing layers

    NASA Technical Reports Server (NTRS)

    Baurle, R. A.; Drummond, J. P.; Hassan, H. A.

    1992-01-01

    In an effort to predict the effect that turbulent mixing has on the extent of combustion, a one-equation turbulence model is added to an existing Navier-Stokes solver with finite-rate chemistry. To average the chemical-source terms appearing in the species-continuity equations, an assumed pdf approach is also used. This code was used to analyze the mixing and combustion caused by the mixing layer formed by supersonic coaxial H2-air streams. The chemistry model employed allows for the formation of H2O2 and HO2. Comparisons are made with recent measurements using laser Raman diagnostics. Comparisons include temperature and its rms, and concentrations of H2, O2, N2, H2O, and OH. In general, good agreement with experiment was noted.

  3. Estimating option values of solar radiation management assuming that climate sensitivity is uncertain.

    PubMed

    Arino, Yosuke; Akimoto, Keigo; Sano, Fuminori; Homma, Takashi; Oda, Junichiro; Tomoda, Toshimasa

    2016-05-24

    Although solar radiation management (SRM) might play a role as an emergency geoengineering measure, its potential risks remain uncertain, and hence there are ethical and governance issues in the face of SRM's actual deployment. By using an integrated assessment model, we first present one possible methodology for evaluating the value arising from retaining an SRM option given the uncertainty of climate sensitivity, and also examine sensitivities of the option value to SRM's side effects (damages). Reflecting the governance challenges on immediate SRM deployment, we assume scenarios in which SRM could only be deployed with a limited degree of cooling (0.5 °C) only after 2050, when climate sensitivity uncertainty is assumed to be resolved and only when the sensitivity is found to be high (T2x = 4 °C). We conduct a cost-effectiveness analysis with constraining temperature rise as the objective. The SRM option value is originated from its rapid cooling capability that would alleviate the mitigation requirement under climate sensitivity uncertainty and thereby reduce mitigation costs. According to our estimates, the option value during 1990-2049 for a +2.4 °C target (the lowest temperature target level for which there were feasible solutions in this model study) relative to preindustrial levels were in the range between $2.5 and $5.9 trillion, taking into account the maximum level of side effects shown in the existing literature. The result indicates that lower limits of the option values for temperature targets below +2.4 °C would be greater than $2.5 trillion.

  4. Estimating option values of solar radiation management assuming that climate sensitivity is uncertain.

    PubMed

    Arino, Yosuke; Akimoto, Keigo; Sano, Fuminori; Homma, Takashi; Oda, Junichiro; Tomoda, Toshimasa

    2016-05-24

    Although solar radiation management (SRM) might play a role as an emergency geoengineering measure, its potential risks remain uncertain, and hence there are ethical and governance issues in the face of SRM's actual deployment. By using an integrated assessment model, we first present one possible methodology for evaluating the value arising from retaining an SRM option given the uncertainty of climate sensitivity, and also examine sensitivities of the option value to SRM's side effects (damages). Reflecting the governance challenges on immediate SRM deployment, we assume scenarios in which SRM could only be deployed with a limited degree of cooling (0.5 °C) only after 2050, when climate sensitivity uncertainty is assumed to be resolved and only when the sensitivity is found to be high (T2x = 4 °C). We conduct a cost-effectiveness analysis with constraining temperature rise as the objective. The SRM option value is originated from its rapid cooling capability that would alleviate the mitigation requirement under climate sensitivity uncertainty and thereby reduce mitigation costs. According to our estimates, the option value during 1990-2049 for a +2.4 °C target (the lowest temperature target level for which there were feasible solutions in this model study) relative to preindustrial levels were in the range between $2.5 and $5.9 trillion, taking into account the maximum level of side effects shown in the existing literature. The result indicates that lower limits of the option values for temperature targets below +2.4 °C would be greater than $2.5 trillion. PMID:27162346

  5. Cosmic Rays and Global Warming

    SciTech Connect

    Sloan, T.; Wolfendale, A. W.

    2008-01-24

    Some workers have claimed that the observed temporal correlations of (low level) terrestrial cloud cover with the cosmic ray intensity changes, due to solar modulation, are causal. The possibility arises, therefore, of a connection between cosmic rays and Global Warming. If true, the implications would be very great. We have examined this claim in some detail. So far, we have not found any evidence in support and so our conclusions are to doubt it. From the absence of corroborative evidence we estimate that less than 15% at the 95% confidence level, of the 11-year cycle warming variations are due to cosmic rays and less than 2% of the warming over the last 43 years is due to this cause. The origin of the correlation itself is probably the cycle of solar irradiance although there is, as yet, no certainty.

  6. Efficacy of Cosmic Ray Shields

    NASA Astrophysics Data System (ADS)

    Rhodes, Nicholas

    2015-10-01

    This research involved testing various types of shielding with a self-constructed Berkeley style cosmic ray detector, in order to evaluate the materials of each type of shielding's effectiveness at blocking cosmic rays and the cost- and size-efficiency of the shields as well. The detector was constructed, then tested for functionality and reliability. Following confirmation, the detector was then used at three different locations to observe it altitude or atmospheric conditions had any effect on the effectiveness of certain shields. Multiple types of shielding were tested with the detector, including combinations of several shields, primarily aluminum, high-iron steel, polyethylene plastic, water, lead, and a lead-alternative radiation shield utilized in radiology. These tests regarding both the base effectiveness and the overall efficiency of shields is designed to support future space exploratory missions where the risk of exposure to possibly lethal amounts of cosmic rays for crew and the damage caused to unshielded electronics are of serious concern.

  7. 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)

  8. Cosmic Ray Origins: An Introduction

    NASA Astrophysics Data System (ADS)

    Blandford, Roger; Simeon, Paul; Yuan, Yajie

    2014-11-01

    Physicists have pondered the origin of cosmic rays for over a hundred years. However the last few years have seen an upsurge in the observation, progress in the theory and a genuine increase in the importance attached to the topic due to its intimate connection to the indirect detection of evidence for dark matter. The intent of this talk is to set the stage for the meeting by reviewing some of the basic features of the entire cosmic ray spectrum from GeV to ZeV energy and some of the models that have been developed. The connection will also be made to recent developments in understanding general astrophysical particle acceleration in pulsar wind nebulae, relativistic jets and gamma ray bursts. The prospects for future discoveries, which may elucidate the origin of cosmic rays, are bright.

  9. Number of cosmic string loops

    NASA Astrophysics Data System (ADS)

    Blanco-Pillado, Jose J.; Olum, Ken D.; Shlaer, Benjamin

    2014-01-01

    Using recent simulation results, we provide the mass and speed spectrum of cosmic string loops. This is the quantity of primary interest for many phenomenological signatures of cosmic strings, and it can be accurately predicted using recently acquired detailed knowledge of the loop production function. We emphasize that gravitational smoothing of long strings plays a negligible role in determining the total number of existing loops. We derive a bound on the string tension imposed by recent constraints on the stochastic gravitational wave background from pulsar timing arrays, finding Gμ ≤2.8×10-9. We also provide a derivation of the Boltzmann equation for cosmic string loops in the language of differential forms.

  10. Cosmic necklaces from string theory

    SciTech Connect

    Leblond, Louis; Wyman, Mark

    2007-06-15

    We present the properties of a cosmic superstring network in the scenario of flux compactification. An infinite family of strings, the (p,q) strings, are allowed to exist. The flux compactification leads to a string tension that is periodic in p. Monopoles, appearing here as beads on a string, are formed in certain interactions in such networks. This allows bare strings to become cosmic necklaces. We study network evolution in this scenario, outlining what conditions are necessary to reach a cosmologically viable scaling solution. We also analyze the physics of the beads on a cosmic necklace, and present general conditions for which they will be cosmologically safe, leaving the network's scaling undisturbed. In particular, we find that a large average loop size is sufficient for the beads to be cosmologically safe. Finally, we argue that loop formation will promote a scaling solution for the interbead distance in some situations.

  11. The Heliosphere and Galactic Cosmic Rays

    NASA Video Gallery

    The heliosphere deflects galactic cosmic rays from entering the system. Galactic cosmic rays are a very high energy form of particle radiation that are extremely difficult to shield against and are...

  12. Evaluation of Galactic Cosmic Ray Models

    NASA Technical Reports Server (NTRS)

    Adams, James H., Jr.; Heiblim, Samuel; Malott, Christopher

    2009-01-01

    Models of the galactic cosmic ray spectra have been tested by comparing their predictions to an evaluated database containing more than 380 measured cosmic ray spectra extending from 1960 to the present.

  13. Cosmic microwave background radiation anisotropies in brane worlds.

    PubMed

    Koyama, Kazuya

    2003-11-28

    We propose a new formulation to calculate the cosmic microwave background (CMB) spectrum in the Randall-Sundrum two-brane model based on recent progress in solving the bulk geometry using a low energy approximation. The evolution of the anisotropic stress imprinted on the brane by the 5D Weyl tensor is calculated. An impact of the dark radiation perturbation on the CMB spectrum is investigated in a simple model assuming an initially scale-invariant adiabatic perturbation. The dark radiation perturbation induces isocurvature perturbations, but the resultant spectrum can be quite different from the prediction of simple mixtures of adiabatic and isocurvature perturbations due to Weyl anisotropic stress.

  14. Translational invariance and the anisotropy of the cosmic microwave background

    SciTech Connect

    Carroll, Sean M.; Tseng, C.-Y.; Wise, Mark B.

    2010-04-15

    Primordial quantum fluctuations produced by inflation are conventionally assumed to be statistically homogeneous, a consequence of translational invariance. In this paper we quantify the potentially observable effects of a small violation of translational invariance during inflation, as characterized by the presence of a preferred point, line, or plane. We explore the imprint such a violation would leave on the cosmic microwave background anisotropy, and provide explicit formulas for the expected amplitudes of the spherical-harmonic coefficients.

  15. Relativistic Landau levels in the rotating cosmic string spacetime

    NASA Astrophysics Data System (ADS)

    Cunha, M. S.; Muniz, C. R.; Christiansen, H. R.; Bezerra, V. B.

    2016-09-01

    In the spacetime induced by a rotating cosmic string we compute the energy levels of a massive spinless particle coupled covariantly to a homogeneous magnetic field parallel to the string. Afterwards, we consider the addition of a scalar potential with a Coulomb-type and a linear confining term and completely solve the Klein-Gordon equations for each configuration. Finally, assuming rigid-wall boundary conditions, we find the Landau levels when the linear defect is itself magnetized. Remarkably, our analysis reveals that the Landau quantization occurs even in the absence of gauge fields provided the string is endowed with spin.

  16. Search for Linear Polarization of the Cosmic Background Radiation

    DOE R&D Accomplishments Database

    Lubin, P. M.; Smoot, G. F.

    1978-10-01

    We present preliminary measurements of the linear polarization of the cosmic microwave background (3 deg K blackbody) radiation. These ground-based measurements are made at 9 mm wavelength. We find no evidence for linear polarization, and set an upper limit for a polarized component of 0.8 m deg K with a 95% confidence level. This implies that the present rate of expansion of the Universe is isotropic to one part in 10{sup 6}, assuming no re-ionization of the primordial plasma after recombination

  17. The Cosmic Shoreline

    NASA Technical Reports Server (NTRS)

    Zahnle, Kevin J.; Catling, D. C.

    2013-01-01

    in 2004 when there were just two transiting exoplanets to consider. The trend was well-defined by late 2007. Figure 1 shows how matters stood in Dec 2012 with approx.240 exoplanets. The figure shows that the boundary between planets with and without active volatiles - the cosmic shoreline, as it were - is both well-defined and follows a power law.

  18. Cosmic microwave background images

    NASA Astrophysics Data System (ADS)

    Herranz, D.; Vielva, P.

    2010-01-01

    Cosmology concerns itself with the fundamental questions about the formation, structure, and evolution of the Universe as a whole. Cosmic microwave background (CMB) radiation is one of the foremost pillars of physical cosmology. Joint analyses of CMB and other astronomical observations are able to determine with ever increasing precision the value of the fundamental cosmological parameters and to provide us with valuable insight about the dynamics of the Universe in evolution. The CMB radiation is a relic of the hot and dense first moments of the Universe: a extraordinarily homogeneous and isotropic blackbody radiation, which shows small temperature anisotropies that are the key for understanding the conditions of the primitive Universe, testing cosmological models and probing fundamental physics at the very dawn of time. CMB observations are obtained by imaging of the sky at microwave wavelengths. However, the CMB signal is mixed with other astrophysical signals of both Galactic and extragalactic origin. To properly exploit the cosmological information contained in CMB images, they must be cleansed of these other astrophysical emissions first. Blind source separation (BSS) has been a very active field in the last few years. Conversely, the term "compact sources" is often used in the CMB literature referring to spatially bounded, small features in the images, such as galaxies and galaxy clusters. Compact sources and diffuse sources are usually treated separately in CMB image processing. We devote this tutorial to the case of compact sources. Many of the compact source-detection techniques that are widespread inmost fields of astronomy are not easily applicable to CMB images. In this tutorial, we present an overview of the fundamentals of compact object detection theory keeping in mind at every moment these particularities. Throughout the article, we briefly consider Bayesian object detection, model selection, optimal linear filtering, nonlinear filtering, and

  19. 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

  20. 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.

  1. The Cosmic Web: Geometric Analysis

    NASA Astrophysics Data System (ADS)

    van de Weygaert, R.; Schaap, W.

    The spatial cosmic matter distribution on scales of a few up to more than a hundred megaparsec displays a salient and pervasive foam-like pattern. Revealed through the painstaking efforts of redshift survey campaigns, it has completely revised our view of the matter distribution on these cosmological scales. The web-like spatial arrangement of galaxies and mass into elongated filaments, sheet-like walls and dense compact clusters, the existence of large near-empty void regions and the hierarchical nature of this mass distribution - marked by substructure over a wide range of scales and densities - are three major characteristics we have come to know as the cosmic web.

  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. Evolution of cosmic string networks

    NASA Technical Reports Server (NTRS)

    Albrecht, Andreas; Turok, Neil

    1989-01-01

    Results on cosmic strings are summarized including: (1) the application of non-equilibrium statistical mechanics to cosmic string evolution; (2) a simple one scale model for the long strings which has a great deal of predictive power; (3) results from large scale numerical simulations; and (4) a discussion of the observational consequences of our results. An upper bound on G mu of approximately 10(-7) emerges from the millisecond pulsar gravity wave bound. How numerical uncertainties affect this are discussed. Any changes which weaken the bound would probably also give the long strings the dominant role in producing observational consequences.

  4. Evolution of cosmic string networks

    SciTech Connect

    Albrecht, A.; Turok, N.

    1989-06-01

    We summarize our new results on cosmic strings. These results include: the application of non-equilibrium statistical mechanics to cosmic string evolution, a simple ''one scale'' model for the long strings which has a great deal of predictive power, results from large scale numerical simulations, and a discussion of the observational consequences of our results. An upper bond on G/mu/ of approximately 10/sup /minus/7/ emerges from the millisecond pulsar gravity wave bound. We discuss how numerical uncertainties affect this. Any changes which weaken the bound would probably also give the long strings the dominant role in producing observational consequences. 22 refs.

  5. The distinction between gamma-quanta spectra from both local sources and cosmic rays, and the formation of a uniform cosmic ray spectrum

    NASA Astrophysics Data System (ADS)

    Nikolsky, S. I.; Sinitsyna, V. G.

    2003-07-01

    The experimental data about gamma-quanta sources with energy > 1 TeV are characterised by the fact that the observed metagalactic sources (active galactic nuclei) are 106 - 107 times more powerful than the galactic ones, but they do not differ in energy spectrum (F(> Eγ)~Eγ-1.3+/-0.15). The power of metagalactic sources and their unlimited number puts into doubt the assumption about the galactic origin of the observable cosmic ray flux. It is possible to assume, that the uniform cosmic ray spectrum is formed (by ``braking'') in an ``infinite'' number of elastic (or inelastic) collisions with relict photons in intergalactic space. Thus, the observable spectral distribution of protons and cosmic ray nuclei with index of (2.72+/-0.02) = 2.718... (the Nipper's number) is the consequence of such ``braking'' warming up the relict photons. RFBR, FNP, GNTP

  6. Cosmic strings and ultra-high energy cosmic rays

    NASA Technical Reports Server (NTRS)

    Bhattacharjee, Pijushpani

    1989-01-01

    The flux is calculated of ultrahigh energy protons due to the process of cusp evaporation from cosmic string loops. For the standard value of the dimensionless cosmic string parameter epsilon is identical to G(sub mu) approx. = 10(exp -6), the flux is several orders of magnitude below the observed cosmic ray flux of ultrahigh energy protons. However, the flux at any energy initially increases as the value of epsilon is decreased. This at first suggests that there may be a lower limit on the value of epsilon, which would imply a lower limit on the temperature of a cosmic string forming phase transition in the early universe. However, the calculation shows that this is not the case -- the particle flux at any energy reaches its highest value at epsilon approx. = 10(exp -15) and it then decreases for further decrease of the value of epsilon. This is due to the fact that for too small values of epsilon (less than 10(exp -15)), the energy loss of the loops through the cusp evaporation process itself (rather than gravitational energy loss of the loops) becomes the dominant factor that controls the behavior of the number density of the loops at the relevant times of emission of the particles. The highest flux at any energy remains at least four orders of magnitude below the observed flux. There is thus no lower limit on epsilon.

  7. Cosmic Ray elimination using the Wavelet Transform

    NASA Astrophysics Data System (ADS)

    Orozco-Aguilera, M. T.; Cruz, J.; Altamirano, L.; Serrano, A.

    2009-11-01

    In this work, we present a method for the automatic cosmic ray elimination in a single CCD exposure using the Wavelet Transform. The proposed method can eliminate cosmic rays of any shape or size. With this method we can eliminate over 95% of cosmic rays in a spectral image.

  8. Defining modeling parameters for juniper trees assuming pleistocene-like conditions at the NTS

    SciTech Connect

    Tarbox, S.R.; Cochran, J.R.

    1994-12-31

    This paper addresses part of Sandia National Laboratories` (SNL) efforts to assess the long-term performance of the Greater Confinement Disposal (GCD) facility located on the Nevada Test Site (NTS). Of issue is whether the GCD site complies with 40 CFR 191 standards set for transuranic (TRU) waste burial. SNL has developed a radionuclide transport model which can be used to assess TRU radionuclide movement away from the GCD facility. An earlier iteration of the model found that radionuclide uptake and release by plants is an important aspect of the system to consider. Currently, the shallow-rooted plants at the NTS do not pose a threat to the integrity of the GCD facility. However, the threat increases substantially it deeper-rooted woodland species migrate to the GCD facility, given a shift to a wetter climate. The model parameters discussed here will be included in the next model iteration which assumes a climate shift will provide for the growth of juniper trees at the GCD facility. Model parameters were developed using published data and wherever possible, data were taken from juniper and pinon-juniper studies that mirrored as many aspects of the GCD facility as possible.

  9. Radial diffusion in Saturn's radiation belts - A modeling analysis assuming satellite and ring E absorption

    NASA Technical Reports Server (NTRS)

    Hood, L. L.

    1983-01-01

    A modeling analysis is carried out of six experimental phase space density profiles for nearly equatorially mirroring protons using methods based on the approach of Thomsen et al. (1977). The form of the time-averaged radial diffusion coefficient D(L) that gives an optimal fit to the experimental profiles is determined under the assumption that simple satellite plus Ring E absorption of inwardly diffusing particles and steady-state radial diffusion are the dominant physical processes affecting the proton data in the L range that is modeled. An extension of the single-satellite model employed by Thomsen et al. to a model that includes multisatellite and ring absorption is described, and the procedures adopted for estimating characteristic satellite and ring absorption times are defined. The results obtained in applying three representative solid-body absorption models to evaluate D(L) in the range where L is between 4 and 16 are reported, and a study is made of the sensitivity of the preferred amplitude and L dependence for D(L) to the assumed model parameters. The inferred form of D(L) is then compared with that which would be predicted if various proposed physical mechanisms for driving magnetospheric radial diffusion are operative at Saturn.

  10. Epidemiology of child pedestrian casualty rates: can we assume spatial independence?

    PubMed

    Hewson, Paul J

    2005-07-01

    Child pedestrian injuries are often investigated by means of ecological studies, yet are clearly part of a complex spatial phenomena. Spatial dependence within such ecological analyses have rarely been assessed, yet the validity of basic statistical techniques rely on a number of independence assumptions. Recent work from Canada has highlighted the potential for modelling spatial dependence within data that was aggregated in terms of the number of road casualties who were resident in a given geographical area. Other jurisdictions aggregate data in terms of the number of casualties in the geographical area in which the collision took place. This paper contrasts child pedestrian casualty data from Devon County UK, which has been aggregated by both methods. A simple ecological model, with minimally useful covaraties relating to measures of child deprivation, provides evidence that data aggregated in terms of the casualty's home location cannot be assumed to be spatially independent and that for analysis of these data to be valid there must be some accounting for spatial auto-correlation within the model structure. Conversely, data aggregated in terms of the collision location (as is usual in the UK) was found to be spatially independent. Whilst the spatial model is clearly more complex it provided a superior fit to that seen with either collision aggregated or non-spatial models. Of more importance, the ecological level association between deprivation and casualty rate is much lower once the spatial structure is accounted for, highlighting the importance using appropriately structured models.

  11. Assumed--stress hybrid elements with drilling degrees of freedom for nonlinear analysis of composite structures

    NASA Technical Reports Server (NTRS)

    Knight, Norman F., Jr. (Principal Investigator)

    1996-01-01

    The goal of this research project is to develop assumed-stress hybrid elements with rotational degrees of freedom for analyzing composite structures. During the first year of the three-year activity, the effort was directed to further assess the AQ4 shell element and its extensions to buckling and free vibration problems. In addition, the development of a compatible 2-node beam element was to be accomplished. The extensions and new developments were implemented in the Computational Structural Mechanics Testbed COMET. An assessment was performed to verify the implementation and to assess the performance of these elements in terms of accuracy. During the second and third years, extensions to geometrically nonlinear problems were developed and tested. This effort involved working with the nonlinear solution strategy as well as the nonlinear formulation for the elements. This research has resulted in the development and implementation of two additional element processors (ES22 for the beam element and ES24 for the shell elements) in COMET. The software was developed using a SUN workstation and has been ported to the NASA Langley Convex named blackbird. Both element processors are now part of the baseline version of COMET.

  12. Langevin equation modeling of convective boundary layer dispersion assuming homogeneous, skewed turbulence

    SciTech Connect

    Hasstrom, J.S.; Ermak, D.L.

    1997-10-01

    Vertical dispersion of material in the convective boundary layer, CBL, is dramatically different than in natural or stable boundary layers, as has been shown by field and laboratory experiments. Lagrangian stochastic modeling based on the Langevin equation has been shown to be useful for simulating vertical dispersion in the CBL. This modeling approach can account for the effects of the long Lagrangian time scales (associated with large-scale turbulent structures), skewed vertical velocity distributions, and vertically inhomogeneous turbulent properties found in the CBL. It has been recognized that simplified Langevin equation models that assume skewed but homogeneous velocity statistics can capture the important aspects of dispersion from sources the the CBL. The assumption of homogeneous turbulence has a significant practical advantage, specifically, longer time steps can be used in numerical simulations. In this paper, we compare two Langevin equations models that use the homogeneous turbulence assumption. We also compare and evaluate three reflection boundary conditions, the method for determining a new velocity for a particle that encounters a boundary. Model results are evaluated using data from Willis and Deardorff`s laboratory experiments for three different source heights.

  13. Assume-Guarantee Verification of Source Code with Design-Level Assumptions

    NASA Technical Reports Server (NTRS)

    Giannakopoulou, Dimitra; Pasareanu, Corina S.; Cobleigh, Jamieson M.

    2004-01-01

    Model checking is an automated technique that can be used to determine whether a system satisfies certain required properties. To address the 'state explosion' problem associated with this technique, we propose to integrate assume-guarantee verification at different phases of system development. During design, developers build abstract behavioral models of the system components and use them to establish key properties of the system. To increase the scalability of model checking at this level, we have developed techniques that automatically decompose the verification task by generating component assumptions for the properties to hold. The design-level artifacts are subsequently used to guide the implementation of the system, but also to enable more efficient reasoning at the source code-level. In particular we propose to use design-level assumptions to similarly decompose the verification of the actual system implementation. We demonstrate our approach on a significant NASA application, where design-level models were used to identify; and correct a safety property violation, and design-level assumptions allowed us to check successfully that the property was presented by the implementation.

  14. Molecular relativistic corrections determined in the framework where the Born-Oppenheimer approximation is not assumed.

    PubMed

    Stanke, Monika; Adamowicz, Ludwik

    2013-10-01

    In this work, we describe how the energies obtained in molecular calculations performed without assuming the Born-Oppenheimer (BO) approximation can be augmented with corrections accounting for the leading relativistic effects. Unlike the conventional BO approach, where these effects only concern the relativistic interactions between the electrons, the non-BO approach also accounts for the relativistic effects due to the nuclei and due to the coupling of the coupled electron-nucleus motion. In the numerical sections, the results obtained with the two approaches are compared. The first comparison concerns the dissociation energies of the two-electron isotopologues of the H2 molecule, H2, HD, D2, T2, and the HeH(+) ion. The comparison shows that, as expected, the differences in the relativistic contributions obtained with the two approaches increase as the nuclei become lighter. The second comparison concerns the relativistic corrections to all 23 pure vibrational states of the HD(+) ion. An interesting charge asymmetry caused by the nonadiabatic electron-nucleus interaction appears in this system, and this effect significantly increases with the vibration excitation. The comparison of the non-BO results with the results obtained with the conventional BO approach, which in the lowest order does not describe the charge-asymmetry effect, reveals how this effect affects the values of the relativistic corrections. PMID:23679131

  15. Automated Assume-Guarantee Reasoning for Omega-Regular Systems and Specifications

    NASA Technical Reports Server (NTRS)

    Chaki, Sagar; Gurfinkel, Arie

    2010-01-01

    We develop a learning-based automated Assume-Guarantee (AG) reasoning framework for verifying omega-regular properties of concurrent systems. We study the applicability of non-circular (AGNC) and circular (AG-C) AG proof rules in the context of systems with infinite behaviors. In particular, we show that AG-NC is incomplete when assumptions are restricted to strictly infinite behaviors, while AG-C remains complete. We present a general formalization, called LAG, of the learning based automated AG paradigm. We show how existing approaches for automated AG reasoning are special instances of LAG.We develop two learning algorithms for a class of systems, called infinite regular systems, that combine finite and infinite behaviors. We show that for infinity-regular systems, both AG-NC and AG-C are sound and complete. Finally, we show how to instantiate LAG to do automated AG reasoning for infinite regular, and omega-regular, systems using both AG-NC and AG-C as proof rules

  16. On the assumed impact of germanium doping on void formation in Czochralski-grown silicon

    NASA Astrophysics Data System (ADS)

    Vanhellemont, Jan; Zhang, Xinpeng; Xu, Wubing; Chen, Jiahe; Ma, Xiangyang; Yang, Deren

    2010-12-01

    The assumed impact of Ge doping on void formation during Czochralski-growth of silicon single crystals, is studied using scanning infrared microscopy. It has been reported that Ge doping leads to a reduction in the flow pattern defect density and of the crystal originated particle size, both suggesting an effect of Ge on vacancy concentration and void formation during crystal growth. The present study however reveals only a marginal-if any-effect of Ge doping on grown-in single void size and density. Double and multiple void formation might however be suppressed partially by Ge doping leading to the observed decrease in flow pattern defect density. The limited effect of Ge doping on single void formation is in agreement with earlier findings that Ge atoms are only a weak trap for vacancies at higher temperatures and therefor should have a smaller impact on the vacancy thermal equilibrium concentration and on single void nucleation than, e.g., interstitial oxygen and nitrogen.

  17. Wetware, Hardware, or Software Incapacitation: Observational Methods to Determine When Autonomy Should Assume Control

    NASA Technical Reports Server (NTRS)

    Trujillo, Anna C.; Gregory, Irene M.

    2014-01-01

    Control-theoretic modeling of human operator's dynamic behavior in manual control tasks has a long, rich history. There has been significant work on techniques used to identify the pilot model of a given structure. This research attempts to go beyond pilot identification based on experimental data to develop a predictor of pilot behavior. Two methods for pre-dicting pilot stick input during changing aircraft dynamics and deducing changes in pilot behavior are presented This approach may also have the capability to detect a change in a subject due to workload, engagement, etc., or the effects of changes in vehicle dynamics on the pilot. With this ability to detect changes in piloting behavior, the possibility now exists to mediate human adverse behaviors, hardware failures, and software anomalies with autono-my that may ameliorate these undesirable effects. However, appropriate timing of when au-tonomy should assume control is dependent on criticality of actions to safety, sensitivity of methods to accurately detect these adverse changes, and effects of changes in levels of auto-mation of the system as a whole.

  18. Cardiovascular Responses during Head-Down Crooked Kneeling Position Assumed in Muslim Prayers

    PubMed Central

    Ahmad Rufa’i, Adamu; Hamu Aliyu, Hadeezah; Yunoos Oyeyemi, Adetoyeje; Lukman Oyeyemi, Adewale

    2013-01-01

    Background: Movement dysfunction may be expressed in terms of symptoms experienced in non-physiological postures, and head-down crooked kneeling (HDCK) is a posture frequently assumed by Muslims during prayer activities. The purpose of this study was to investigate the cardiovascular responses in the HDCK posture. Methods: Seventy healthy volunteers, comprising 35 males and 35 females, participated in the study. Cardiovascular parameters of blood pressure and pulse rate of the participants were measured in rested sitting position and then at one and three minutes into the HDCK posture. Two-way ANOVA was used to determine the differences between cardiovascular responses at rest and in the HDCK posture, and the Student t test was utilized to determine gender difference in cardiovascular responses at rest and at one and three minutes into the HDCK posture. Results: The study showed a significant decrease in systolic and diastolic blood pressures at one minute into the HDCK posture and an increase in pulse rate at one and three minutes into the HDCK posture, as compared to the resting values. Rate pressure product also rose at one minute into the HDCK posture, whereas pulse pressure increased at one and three minutes into the HDCK posture, as compared with the resting values. However, no significant change was observed in the mean arterial pressure values. Conclusion: The findings from this study suggest that no adverse cardiovascular event can be expected to occur for the normal duration of this posture during Muslim prayer activities. PMID:24031108

  19. Magnetic fields and the distribution of cosmic rays in the Galaxy

    NASA Technical Reports Server (NTRS)

    Jokipii, J. R.

    1973-01-01

    If a galactic origin for the bulk of cosmic-ray particles is assumed, it is the magnetic field which regulates the propagation and escape of the particles from the Galaxy. Questions of the anisotropy of the cosmic-ray flux are considered together with magnetic-field models which can confine the particles and produce low anisotropies. In one standard approach it is postulated that the particles random walk through the presumably irregular magnetic field. In view of the difficulties associated with a diffusion hypothesis other confinement mechanisms have been proposed.

  20. Cosmology: The oldest cosmic light

    NASA Astrophysics Data System (ADS)

    Spergel, David; Keating, Brian

    2015-02-01

    The cosmic microwave background is a faint glow of light left over from the Big Bang. It fills the entire sky and records the Universe's early history. Two independent experts outline what we know about this ancient light, both theoretically and observationally.

  1. The Resurgence of Cosmic Storytellers

    ERIC Educational Resources Information Center

    Swimme, Brian

    2013-01-01

    Brian Swimme's insights about the Story of the Universe look to the unifying impact of a "cosmic story" that speaks to all cultures and nations. Swimme suggests that humans are now able, through science and narrative, to present a story which will make us all a "cohesive tribe" while answering the universal questions of…

  2. Art and the Cosmic Connection

    ERIC Educational Resources Information Center

    Cobb, Whitney H.; Aiello, Monica Petty; Macdonald, Reeves; Asplund, Shari

    2014-01-01

    The interdisciplinary unit described in this article utilizes "Art and the Cosmic Connection," a free program conceived of by artists Monica and Tyler Aiello and developed by the artists, scientists, and educators through NASA's Discovery and New Frontiers Programs, to inspire learners to explore mysterious worlds in our solar…

  3. The Cosmic Ray Electron Excess

    NASA Technical Reports Server (NTRS)

    Chang, J.; Adams, J. H.; Ahn, H. S.; Bashindzhagyan, G. L.; Christl, M.; Ganel, O.; Guzik, T. G.; Isbert, J.; Kim, K. C.; Kuznetsov, E. N.; Panasyuk, M. I.; Panov, A. D.; Schmidt, W. K. H.; Seo, E. S.; Sokolskaya, N. V.; Watts, J. W.; Wefel, J. P.; Wu, J.; Zatsepin, V. I.

    2008-01-01

    This slide presentation reviews the possible sources for the apparent excess of Cosmic Ray Electrons. The presentation reviews the Advanced Thin Ionization Calorimeter (ATIC) instrument, the various parts, how cosmic ray electrons are measured, and shows graphs that review the results of the ATIC instrument measurement. A review of Cosmic Ray Electrons models is explored, along with the source candidates. Scenarios for the excess are reviewed: Supernova remnants (SNR) Pulsar Wind nebulae, or Microquasars. Each of these has some problem that mitigates the argument. The last possibility discussed is Dark Matter. The Anti-Matter Exploration and Light-nuclei Astrophysics (PAMELA) mission is to search for evidence of annihilations of dark matter particles, to search for anti-nuclei, to test cosmic-ray propagation models, and to measure electron and positron spectra. There are slides explaining the results of Pamela and how to compare these with those of the ATIC experiment. Dark matter annihilation is then reviewed, which represent two types of dark matter: Neutralinos, and kaluza-Kline (KK) particles, which are next explained. The future astrophysical measurements, those from GLAST LAT, the Alpha Magnetic Spectrometer (AMS), and HEPCAT are reviewed, in light of assisting in finding an explanation for the observed excess. Also the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) could help by revealing if there are extra dimensions.

  4. Cosmic censorship and the dilaton

    SciTech Connect

    Horne, J.H. ); Horowitz, G.T. )

    1993-12-15

    We investigate extremal electrically charged black holes in Einstein-Maxwell-dilaton theory with a cosmological constant inspired by string theory. These solutions are not static, and a timelike singularity eventually appears which is not surrounded by an event horizon. This suggests that cosmic censorship may be violated in this theory.

  5. Cosmic Censorship for Gowdy Spacetimes

    NASA Astrophysics Data System (ADS)

    Ringström, Hans

    2010-04-01

    Due to the complexity of Einstein's equations, it is often natural to study a question of interest in the framework of a restricted class of solutions. One way to impose a restriction is to consider solutions satisfying a given symmetry condition. There are many possible choices, but the present article is concerned with one particular choice, which we shall refer to as Gowdy symmetry. We begin by explaining the origin and meaning of this symmetry type, which has been used as a simplifying assumption in various contexts, some of which we shall mention. Nevertheless, the subject of interest here is strong cosmic censorship. Consequently, after having described what the Gowdy class of spacetimes is, we describe, as seen from the perspective of a mathematician, what is meant by strong cosmic censorship. The existing results on cosmic censorship are based on a detailed analysis of the asymptotic behavior of solutions. This analysis is in part motivated by conjectures, such as the BKL conjecture, which we shall therefore briefly describe. However, the emphasis of the article is on the mathematical analysis of the asymptotics, due to its central importance in the proof and in the hope that it might be of relevance more generally. The article ends with a description of the results that have been obtained concerning strong cosmic censorship in the class of Gowdy spacetimes.

  6. Propagation of UH cosmic ray nuclei in a leaky box

    NASA Astrophysics Data System (ADS)

    Waddington, C. Jake

    1997-05-01

    A weighted slab approximation to a leaky box model has been developed to study the influence of various parameters and cross sections on the propagation of Z > 28 ultraheavy (UH) cosmic ray nuclei from the source to earth. This model starts with nuclei of a given charge and energy and then follows them as they lose energy, fragment and escape. It is possible to vary the path length distribution, the escape length and the energy dependent cross sections of all the nuclei generated during the propagation. By combining the results for different nuclei and energies it is possible to compare any assumed source abundance distribution with that predicted at earth. This paper specifically considers the effects introduced when the cross sections are adjusted to take account of radioactive decays in flight, and shows that they are generally rather minor. Some predictions are made as to which elements will provide the best discriminators between various assumed sources.

  7. The effects of magnetic field modifications on the solar modulation of cosmic rays with a SDE-based model

    NASA Astrophysics Data System (ADS)

    Raath, Jan-Louis; Toit Strauss, Du; Kopp, Andreas; Potgieter, Marius

    2016-07-01

    The effects of modifying the heliospheric magnetic field, particularly in the polar regions of the heliosphere, are illustrated by utilizing a numerical model based on the solution of a set of stochastic differential equations (SDEs). Because SDE-based models are especially well suited for such studies, we are able to gain new insights into this subject. The differences in the modulation brought about by each of three choices for the heliospheric magnetic field are studied as typical well-known cases; they are the unmodified Parker field, and the Smith-Bieber and Jokipii-Kóta modified fields. It is illustrated that both these modifications change the Parker field satisfactorily in the heliospheric polar regions, but that the modification of Smith and Bieber affects a larger reduction in cosmic ray drift effects in these regions. The general features of these two modifications are illustrated and the Smith-Bieber modified field is applied in a cosmic ray modulation model to reproduce observational proton spectra from the PAMELA mission during the solar minimum of 2006 - 2009. These SDE-based results are compared to the results from other studies and found to be in good qualitative agreement.

  8. Landau quantization in the spinning cosmic string spacetime

    SciTech Connect

    Muniz, C.R.; Bezerra, V.B.; Cunha, M.S.

    2014-11-15

    We analyze the quantum phenomenon arising from the interaction of a spinless charged particle with a rotating cosmic string, under the action of a static and uniform magnetic field parallel to the string. We calculate the energy levels of the particle in the non-relativistic approach, showing how these energies depend on the parameters involved in the problem. In order to do this, we solve the time independent Schrödinger equation in the geometry of the spinning cosmic string, taking into account that the coupling between the rotation of the spacetime and the angular momentum of the particle is very weak, such that makes sense to apply the Schrödinger equation in a curved background whose metric has an off diagonal term which involves time and space. It is also assumed that the particle orbits sufficiently far from the boundary of the region of closed timelike curves which exist around this topological defect. Finally, we find the Landau levels of the particle in the presence of a spinning cosmic string endowed with internal structure, i.e., having a finite width and uniformly filled with both material and vacuum energies. - Highlights: • Solution of the wave equation characterizing the problem. • Energy levels of the particle in spacetime of the structureless string. • Expression for an analogous of the quadratic Zeeman effect. • Energy levels of the particle in spacetime of the string with internal structure. • Evidence of the string structure by the internal existence of the vacuum energy.

  9. The Effects on Tsunami Hazard Assessment in Chile of Assuming Earthquake Scenarios with Spatially Uniform Slip

    NASA Astrophysics Data System (ADS)

    Carvajal, Matías; Gubler, Alejandra

    2016-06-01

    We investigated the effect that along-dip slip distribution has on the near-shore tsunami amplitudes and on coastal land-level changes in the region of central Chile (29°-37°S). Here and all along the Chilean megathrust, the seismogenic zone extends beneath dry land, and thus, tsunami generation and propagation is limited to its seaward portion, where the sensitivity of the initial tsunami waveform to dislocation model inputs, such as slip distribution, is greater. We considered four distributions of earthquake slip in the dip direction, including a spatially uniform slip source and three others with typical bell-shaped slip patterns that differ in the depth range of slip concentration. We found that a uniform slip scenario predicts much lower tsunami amplitudes and generally less coastal subsidence than scenarios that assume bell-shaped distributions of slip. Although the finding that uniform slip scenarios underestimate tsunami amplitudes is not new, it has been largely ignored for tsunami hazard assessment in Chile. Our simulations results also suggest that uniform slip scenarios tend to predict later arrival times of the leading wave than bell-shaped sources. The time occurrence of the largest wave at a specific site is also dependent on how the slip is distributed in the dip direction; however, other factors, such as local bathymetric configurations and standing edge waves, are also expected to play a role. Arrival time differences are especially critical in Chile, where tsunamis arrive earlier than elsewhere. We believe that the results of this study will be useful to both public and private organizations for mapping tsunami hazard in coastal areas along the Chilean coast, and, therefore, help reduce the risk of loss and damage caused by future tsunamis.

  10. A Sensitivity Study of the Importance of the Assumed Vertical Distribution Of Lightning NOx

    NASA Astrophysics Data System (ADS)

    Labrador, L.; Lawrence, M. G.; von Kuhlmann, R.

    2001-12-01

    A series of sensitivity runs aimed at studying the vertical distribution of lightning-produced NOx and its effects on atmospheric chemistry have been carried out using the Model for Atmospheric Transport and Chemistry (MATCH). The model uses the Prince and Rind (1992, 1994) parameterization for lightning and the Zhang/McFarlane/Hack convection scheme. We consider two classes of runs, one with a simplified lightning-NOx tracer which is released like normal lightning NOx, but has a constant exponential decay loss with a decay lifetime of two days, and another set involving the full non-methane hydrocarbon version of the model. The vertical distribution of lightning NOx generation, as treated in previous versions of the model, rests on three basic assumptions: 1) Intracloud flashes outnumber cloud-to-ground flashes; 2) Cloud-to-ground flashes, on the other hand, are about 2-10 times more energetic than intracloud flashes; and 3) Lightning-NOx production depends linearly on the ambient pressure, as well as being proportional to the energy of the flash. The first two assumptions will tend to cancel each other out to an extent in the model. Thus, due to the pressure weighting, NOx is assumed to be released as an even mixing ratio throughout the convective column. The sensitivity runs examine other possible scenarios regarding the placement of lightning-NOx within the convective events; e.g., lightning-NOx only in the uppermost layers of the convective column. The results with the simplified NOx tracer show substantial differences for the various runs. The NMHC-chemistry runs are currently underway and will also be reported on.

  11. Hyporheic Temperature Dynamics: Predicting Hyporheic Temperatures Based on Travel Time Assuming Instantaneous Water-Sediment Conduction

    NASA Astrophysics Data System (ADS)

    Kraseski, K. A.

    2015-12-01

    Recently developed conceptual frameworks and new observations have improved our understanding of hyporheic temperature dynamics and their effects on channel temperatures. However, hyporheic temperature models that are both simple and useful remain elusive. As water moves through hyporheic pathways, it exchanges heat with hyporheic sediment through conduction, and this process dampens the diurnal temperature wave of the water entering from the channel. This study examined the mechanisms underlying this behavior, and utilized those findings to create two simple models that predict temperatures of water reentering the channel after traveling through hyporheic pathways for different lengths of time. First, we developed a laboratory experiment to represent this process and determine conduction rates for various sediment size classes (sand, fine gravel, coarse gravel, and a proportional mix of the three) by observing the time series of temperature changes between sediment and water of different initial temperatures. Results indicated that conductions rates were near-instantaneous, with heat transfer being completed on the scale of seconds to a few minutes of the initial interaction. Heat conduction rates between the sediment and water were therefore much faster than hyporheic flux rates, rendering reasonable an assumption of instantaneous conduction. Then, we developed two simple models to predict time series of hyporheic water based on the initial diurnal temperature wave and hyporheic travel distance. The first model estimates a damping coefficient based on the total water-sediment heat exchange through each diurnal cycle. The second model solves the heat transfer equation assuming instantaneous conduction using a simple finite difference algorithm. Both models demonstrated nearly complete damping of the sine wave over the distance traveled in four days. If hyporheic exchange is substantial and travel times are long, then hyporheic damping may have large effects on

  12. Reconsideration of pressure anisotropy thresholds in the solar wind assuming bi-kappa distributions

    NASA Astrophysics Data System (ADS)

    Astfalk, P.; Jenko, F.; Görler, T.

    2015-12-01

    Recent space observations revealed that pressure anisotropies in the solar wind are restricted to a clearly constrained parameter space. The observed constraints are believed to stem from kinetic plasma instabilities which feed on the free energy supplied by the pressure anisotropies. E.g., if the parallel pressure sufficiently exceeds the perpendicular pressure, a plasma eventually becomes subject to the parallel and the oblique firehose instability. The nonlinear saturation mechanisms of both instabilities are expected to shape the upper boundary of the pressure anisotropies observed in the solar wind, in the regime pparallel > pperp. However, it is still an open question which instability dominates this process. Despite the nonlinear nature of the saturation process, the linear instability threshold is expected to be of major importance, since it sets the limit for marginal stability. Only recently, first attempts were made to study the linear growth of the parallel firehose instability assuming more realistic bi-kappa velocity distributions instead of traditionally used bi-Maxwellians. We apply a newly developed, fully kinetic dispersion solver to numerically derive the instability thresholds for both firehose instabilities. In contrast to former findings, we observe that suprathermal particle populations lead to an enhancement of the parallel firehose instability close to the threshold, implying a lowering of the threshold especially for low beta setups. This is supposedly due to enhanced cyclotron resonance. For the first time ever, we also look at the oblique firehose threshold and find a contrary picture. Here, the presence of suprathermal particles leads to an increase of the instability threshold. Our findings deepen the understanding of the competition of both instabilities in the solar wind and call for a critical re-examination of existing models.

  13. A genome-wide search for genes predisposing to manic-depression, assuming autosomal dominant inheritance

    SciTech Connect

    Coon, H.; Jensen, S.; Hoff, M.; Holik, J.; Plaetke, R.; Reimherr, F.; Wender, P.; Leppert, M.; Byerley, W. )

    1993-06-01

    Manic-depressive illness (MDI), also known as [open quotes]bipolar affective disorder[close quotes], is a common and devastating neuropsychiatric illness. Although pivotal biochemical alterations underlying the disease are unknown, results of family, twin, and adoption studies consistently implicate genetic transmission in the pathogenesis of MDI. In order to carry out linkage analysis, the authors ascertained eight moderately sized pedigrees containing multiple cases of the disease. For a four-allele marker mapping at 5 cM from the disease gene, the pedigree sample has >97% power to detect a dominant allele under genetic homogeneity and has >73% power under 20% heterogeneity. To date, the eight pedigrees have been genotyped with 328 polymorphic DNA loci throughout the genome. When autosomal dominant inheritance was assumed, 273 DNA markers gave lod scores <[minus]2.0 at [theta] = .05, and 4 DNA marker loci yielded lod scores >1 (chromosome 5 -- D5S39, D5S43, and D5S62; chromosome 11 -- D11S85). Of the markers giving lod scores >1, only D5S62 continued to show evidence for linkage when the affected-pedigree-member method was used. The D5S62 locus maps to distal 5q, a region containing neurotransmitter-receptor genes for dopamine, norepinephrine, glutamate, and gamma-aminobutyric acid. Although additional work in this region may be warranted, the linkage results should be interpreted as preliminary data, as 68 unaffected individuals are not past the age of risk. 72 refs., 2 tabs.

  14. 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.

  15. A COSMIC MICROWAVE BACKGROUND LENSING MASS MAP AND ITS CORRELATION WITH THE COSMIC INFRARED BACKGROUND

    SciTech Connect

    Holder, G. P.; De Haan, T.; Dobbs, M. A.; Dudley, J.; Viero, M. P.; Bock, J.; Zahn, O.; Aird, K. A.; Benson, B. A.; Bhattacharya, S.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Crawford, T. M.; Crites, A. T.; Brodwin, M.; Cho, H-M.; Conley, A.; George, E. M.; Halverson, N. W.; and others

    2013-07-01

    We use a temperature map of the cosmic microwave background (CMB) obtained using the South Pole Telescope at 150 GHz to construct a map of the gravitational convergence to z {approx} 1100, revealing the fluctuations in the projected mass density. This map shows individual features that are significant at the {approx}4{sigma} level, providing the first image of CMB lensing convergence. We cross-correlate this map with Herschel/SPIRE maps covering 90 deg{sup 2} at wavelengths of 500, 350, and 250 {mu}m. We show that these submillimeter (submm) wavelength maps are strongly correlated with the lensing convergence map, with detection significances in each of the three submm bands ranging from 6.7{sigma} to 8.8{sigma}. We fit the measurement of the cross power spectrum assuming a simple constant bias model and infer bias factors of b = 1.3-1.8, with a statistical uncertainty of 15%, depending on the assumed model for the redshift distribution of the dusty galaxies that are contributing to the Herschel/SPIRE maps.

  16. Cosmic Ray Observatories for Space Weather Studies.

    NASA Astrophysics Data System (ADS)

    González, Xavier

    2016-07-01

    The Mexican Space Weather Service (SCiESMEX) was created in October 2014. Some observatories measure data for the service at different frequencies and particles. Two cosmic ray observatories detect the particle variations attributed to solar emissions, and are an important source of information for the SCiESMEX. The Mexico City Cosmic Ray Observatory consists of a neutron monitor (6-NM-64) and a muon telescope, that detect the hadronic and hard component of the secondary cosmic rays in the atmosphere. It has been in continous operation since 1990. The Sierra Negra Cosmic Ray Observatory consists of a solar neutron telescope and the scintillator cosmic ray telescope. These telescopes can detect the neutrons, generated in solar flares and the hadronic and hard components of the secondary cosmic rays. It has been in continous operation since 2004. We present the two observatories and the capability to detect variations in the cosmic rays, generated by the emissions of the solar activity.

  17. Research in cosmic and gamma ray astrophysics

    NASA Technical Reports Server (NTRS)

    Stone, Edward C.; Mewaldt, Richard A.; Prince, Thomas A.

    1992-01-01

    Discussed here is research in cosmic ray and gamma ray astrophysics at the Space Radiation Laboratory (SRL) of the California Institute of Technology. The primary activities discussed involve the development of new instrumentation and techniques for future space flight. In many cases these instrumentation developments were tested in balloon flight instruments designed to conduct new investigations in cosmic ray and gamma ray astrophysics. The results of these investigations are briefly summarized. Specific topics include a quantitative investigation of the solar modulation of cosmic ray protons and helium nuclei, a study of cosmic ray positron and electron spectra in interplanetary and interstellar space, the solar modulation of cosmic rays, an investigation of techniques for the measurement and interpretation of cosmic ray isotopic abundances, and a balloon measurement of the isotopic composition of galactic cosmic ray boron, carbon, and nitrogen.

  18. Production of Magnetic Turbulence by Cosmic Rays Drifting Upstream of Supernova Remnant Shocks

    NASA Technical Reports Server (NTRS)

    Stroman, Thomas; Niemiec, Jacek; Pohl, Martin; Nishikawa, Ken-ichi

    2008-01-01

    I will present results of our recent two- and three-dimensional Particle-In-Cell simulations of magnetic-turbulence production by cosmic-ray ions drifting upstream of supernova remnant shocks. These studies' aim is twofold: test recent predictions of strong amplification in short wavelength, non-resonant wave modes, and study the subsequent evolution of the magnetic turbulence, including its backreaction on cosmic-ray trajectories. We confirm that the drifting cosmic rays give rise to a turbulent magnetic field, but show that an oblique filamentary mode grows more rapidly than the non-resonant parallel modes found in analytical theory. The field perturbations grow more slowly than estimated using a quasi-linear analytical approach for the parallel plane-wave mode, and saturate in amplitude at deltaB/B approximately equal to 1. The backreaction of the magnetic turbulence on the particles leads to an alignment of the bulk-flow velocities of the cosmic rays and the background medium. This is an essential characteristic of cosmic ray-modified shocks: the upstream flow speed is continuously changed by the cosmic rays. The reduction of relative drift between cosmic rays and background medium accounts for the saturation of the instability at only moderate magnetic-field amplitudes. It is possible that the prolonged magnetic field growth observed in recent MHD simulations results from a cosmic-ray current assumed to be constant and thus immune to the backreaction from the turbulent field. We speculate that the parallel plane-wave mode found in analytical treatments very quickly leads co filamentation, which we observe in our PIC modeling and is also apparent in the MHD simulations.

  19. 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

  20. Solar radiative effects of a Saharan dust plume observed during SAMUM assuming spheroidal model particles

    NASA Astrophysics Data System (ADS)

    Otto, Sebastian; Bierwirth, Eike; Weinzierl, Bernadett; Kandler, Konrad; Esselborn, Michael; Tesche, Matthias; Schladitz, Alexander; Wendisch, Manfred; Trautmann, Thomas

    2009-02-01

    ABSTRACT The solar optical properties of Saharan mineral dust observed during the Saharan Mineral Dust Experiment (SAMUM) were explored based on measured size-number distributions and chemical composition. The size-resolved complex refractive index of the dust was derived with real parts of 1.51-1.55 and imaginary parts of 0.0008-0.006 at 550nm wavelength. At this spectral range a single scattering albedo ωo and an asymmetry parameter g of about 0.8 were derived. These values were largely determined by the presence of coarse particles. Backscatter coefficients and lidar ratios calculated with Mie theory (spherical particles) were not found to be in agreement with independently measured lidar data. Obviously the measured Saharan mineral dust particles were of non-spherical shape. With the help of these lidar and sun photometer measurements the particle shape as well as the spherical equivalence were estimated. It turned out that volume equivalent oblate spheroids with an effective axis ratio of 1:1.6 matched these data best. This aspect ratio was also confirmed by independent single particle analyses using a scanning electron microscope. In order to perform the non-spherical computations, a database of single particle optical properties was assembled for oblate and prolate spheroidal particles. These data were also the basis for simulating the non-sphericity effects on the dust optical properties: ωo is influenced by up to a magnitude of only 1% and g is diminished by up to 4% assuming volume equivalent oblate spheroids with an axis ratio of 1:1.6 instead of spheres. Changes in the extinction optical depth are within 3.5%. Non-spherical particles affect the downwelling radiative transfer close to the bottom of the atmosphere, however, they significantly enhance the backscattering towards the top of the atmosphere: Compared to Mie theory the particle non-sphericity leads to forced cooling of the Earth-atmosphere system in the solar spectral range for both dust over

  1. Internal Structure and Mineralogy of Differentiated Asteroids Assuming Chondritic Bulk Composition: The Case of Vesta

    NASA Technical Reports Server (NTRS)

    Toplis, M. J.; Mizzon, H.; Forni, O.; Monnereau, M.; Prettyman, T. H.; McSween, H. Y.; McCoy, T. J.; Mittlefehldt, D. W.; DeSanctis, M. C.; Raymond, C. A.; Russell, C. T.

    2012-01-01

    Bulk composition (including oxygen content) is a primary control on the internal structure and mineralogy of differentiated asteroids. For example, oxidation state will affect core size, as well as Mg# and pyroxene content of the silicate mantle. The Howardite-Eucrite-Diogenite class of meteorites (HED) provide an interesting test-case of this idea, in particular in light of results of the Dawn mission which provide information on the size, density and differentiation state of Vesta, the parent body of the HED's. In this work we explore plausible bulk compositions of Vesta and use mass-balance and geochemical modelling to predict possible internal structures and crust/mantle compositions and mineralogies. Models are constrained to be consistent with known HED samples, but the approach has the potential to extend predictions to thermodynamically plausible rock types that are not necessarily present in the HED collection. Nine chondritic bulk compositions are considered (CI, CV, CO, CM, H, L, LL, EH, EL). For each, relative proportions and densities of the core, mantle, and crust are quantified. Considering that the basaltic crust has the composition of the primitive eucrite Juvinas and assuming that this crust is in thermodynamic equilibrium with the residual mantle, it is possible to calculate how much iron is in metallic form (in the core) and how much in oxidized form (in the mantle and crust) for a given bulk composition. Of the nine bulk compositions tested, solutions corresponding to CI and LL groups predicted a negative metal fraction and were not considered further. Solutions for enstatite chondrites imply significant oxidation relative to the starting materials and these solutions too are considered unlikely. For the remaining bulk compositions, the relative proportion of crust to bulk silicate is typically in the range 15 to 20% corresponding to crustal thicknesses of 15 to 20 km for a porosity-free Vesta-sized body. The mantle is predicted to be largely

  2. Voids and the Cosmic Web: cosmic depression & spatial complexity

    NASA Astrophysics Data System (ADS)

    van de Weygaert, Rien

    2016-10-01

    Voids form a prominent aspect of the Megaparsec distribution of galaxies and matter. Not only do theyrepresent a key constituent of the Cosmic Web, they also are one of the cleanest probesand measures of global cosmological parameters. The shape and evolution of voids are highly sensitive tothe nature of dark energy, while their substructure and galaxy population provides a direct key to thenature of dark matter. Also, the pristine environment of void interiors is an important testing groundfor our understanding of environmental influences on galaxy formation and evolution. In this paper, we reviewthe key aspects of the structure and dynamics ofvoids, with a particular focus on the hierarchical evolution of the void population. We demonstratehow the rich structural pattern of the Cosmic Web is related to the complex evolution and buildupof voids.

  3. Research in cosmic and gamma ray astrophysics: Cosmic physics portion

    NASA Technical Reports Server (NTRS)

    Stone, Edward C.; Mewaldt, Richard A.; Schindler, Stephen

    1993-01-01

    Research in particle astrophysics at the Space Radiation Laboratory (SRL) of the California Institute of Technology is supported under NASA Grant NAGW-1919. A three-year proposal for continuation of support was submitted a year ago and put into effect 1 October 1992. This report is the combined progress report and continuation application called for under the Federal Demonstration Project. Gamma-ray Astrophysics at SRL is separately supported under NAGW-1919 and will be separately summarized and proposed. This report will document progress and plans for our particle spectroscopy activities and for related data analysis, calibration, and community service activities. A bibliography and a budget will be attached as appendices. The Caltech SRL research program includes a heavy emphasis on elemental and isotopic spectroscopy of energetic particles in the cosmic radiation; in solar, interplanetary, and anomalous 'cosmic' radiation; and in planetary magnetospheres as discussed.

  4. A SIMPLE GRAVITATIONAL LENS MODEL FOR COSMIC VOIDS

    SciTech Connect

    Chen, Bin; Kantowski, Ronald; Dai, Xinyu

    2015-05-10

    We present a simple gravitational lens model to illustrate the ease of using the embedded lensing theory when studying cosmic voids. It confirms the previously used repulsive lensing models for deep voids. We start by estimating magnitude fluctuations and weak-lensing shears of background sources lensed by large voids. We find that sources behind large (∼90 Mpc) and deep voids (density contrast about −0.9) can be magnified or demagnified with magnitude fluctuations of up to ∼0.05 mag and that the weak-lensing shear can be up to the ∼10{sup −2} level in the outer regions of large voids. Smaller or shallower voids produce proportionally smaller effects. We investigate the “wiggling” of the primary cosmic microwave background (CMB) temperature anisotropies caused by intervening cosmic voids. The void-wiggling of primary CMB temperature gradients is of the opposite sign to that caused by galaxy clusters. Only extremely large and deep voids can produce wiggling amplitudes similar to galaxy clusters, ∼15 μK by a large void of radius ∼4° and central density contrast −0.9 at redshift 0.5 assuming a CMB background gradient of ∼10 μK arcmin{sup −1}. The dipole signal is spread over the entire void area, and not concentrated at the lens center as it is for clusters. Finally, we use our model to simulate CMB sky maps lensed by large cosmic voids. Our embedded theory can easily be applied to more complicated void models and used to study gravitational lensing of the CMB, to probe dark matter profiles, to reduce the lensing-induced systematics in supernova Hubble diagrams, and to study the integrated Sachs–Wolfe effect.

  5. Studies on Cosmic Ray Sidereal Anisotropy with the Multidirectional Muon Telescope at Ooty

    NASA Astrophysics Data System (ADS)

    Kojima, H.; Fujimoto, K.; Gupta, S. K.; Hayashi, Y.; Ishida, Y.; Ito, N.; Jain, A.; Kawakami, S.; Nonaka, T.; Oshima, A.; Sivaprasad, K.; Tamaki, S.; Tanaka, H.; Tonwar, S. C.; Yoshikoshi, T.

    2003-07-01

    We have developed a multidirectional telescope capable of recording individual muons with angular accuracy of about 5 degrees. This muon telescope consists of ˜ 3000 proportional counters with total area of ˜ 420 m2 with threshold energy > 1 GeV. The telescope is a component of the GRAPES-3 experiment at Ooty in southern India (N 11.4, E 76.7 and 2200m altitude). The very large muon counting rate ˜ 1.8 × 108 per hour, achieved due to the very large area of the telescope, gives us great advantage for cosmic ray modulation studies. The analysis of data with such high statistics enables us to have a sensitive measurement of sidereal variation within a single year of observation. Further, since our telescope is located near the Equator, we are able to observe both the Northern and the Southern hemispheres simultaneously. We present here the results on the sidereal variation obtained with this multidirectional muon telescope for the observational period, 2000-2001. We report here on Tail-in and Loss-corn anisotropies through detailed analysis. We also discuss other possible explanations for the present observations.

  6. 42 CFR 423.908. - Phased-down State contribution to drug benefit costs assumed by Medicare.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 42 Public Health 3 2013-10-01 2013-10-01 false Phased-down State contribution to drug benefit costs assumed by Medicare. 423.908. Section 423.908. Public Health CENTERS FOR MEDICARE & MEDICAID... General Payment Provisions § 423.908. Phased-down State contribution to drug benefit costs assumed...

  7. 42 CFR 423.908. - Phased-down State contribution to drug benefit costs assumed by Medicare.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 42 Public Health 3 2012-10-01 2012-10-01 false Phased-down State contribution to drug benefit costs assumed by Medicare. 423.908. Section 423.908. Public Health CENTERS FOR MEDICARE & MEDICAID... General Payment Provisions § 423.908. Phased-down State contribution to drug benefit costs assumed...

  8. 42 CFR 423.908. - Phased-down State contribution to drug benefit costs assumed by Medicare.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 42 Public Health 3 2011-10-01 2011-10-01 false Phased-down State contribution to drug benefit costs assumed by Medicare. 423.908. Section 423.908. Public Health CENTERS FOR MEDICARE & MEDICAID... Provisions § 423.908. Phased-down State contribution to drug benefit costs assumed by Medicare. This...

  9. 42 CFR 423.908. - Phased-down State contribution to drug benefit costs assumed by Medicare.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 3 2010-10-01 2010-10-01 false Phased-down State contribution to drug benefit costs assumed by Medicare. 423.908. Section 423.908. Public Health CENTERS FOR MEDICARE & MEDICAID... Provisions § 423.908. Phased-down State contribution to drug benefit costs assumed by Medicare. This...

  10. 42 CFR 423.908. - Phased-down State contribution to drug benefit costs assumed by Medicare.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 42 Public Health 3 2014-10-01 2014-10-01 false Phased-down State contribution to drug benefit costs assumed by Medicare. 423.908. Section 423.908. Public Health CENTERS FOR MEDICARE & MEDICAID... General Payment Provisions § 423.908. Phased-down State contribution to drug benefit costs assumed...

  11. 42 CFR 137.292 - How do Self-Governance Tribes assume environmental responsibilities for construction projects...

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...-Governance Tribes assume environmental responsibilities for construction projects under section 509 of the... 42 Public Health 1 2010-10-01 2010-10-01 false How do Self-Governance Tribes assume environmental responsibilities for construction projects under section 509 of the Act ? 137.292 Section 137.292 Public...

  12. 42 CFR 137.291 - May Self-Governance Tribes carry out construction projects without assuming these Federal...

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... projects without assuming these Federal environmental responsibilities? 137.291 Section 137.291 Public...-Governance Tribes carry out construction projects without assuming these Federal environmental... construction projects, or phases of construction projects, under other legal authorities (see § 137.272)....

  13. 42 CFR 137.292 - How do Self-Governance Tribes assume environmental responsibilities for construction projects...

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...-Governance Tribes assume environmental responsibilities for construction projects under section 509 of the... 42 Public Health 1 2011-10-01 2011-10-01 false How do Self-Governance Tribes assume environmental responsibilities for construction projects under section 509 of the Act ? 137.292 Section 137.292 Public...

  14. 42 CFR 137.291 - May Self-Governance Tribes carry out construction projects without assuming these Federal...

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... projects without assuming these Federal environmental responsibilities? 137.291 Section 137.291 Public...-Governance Tribes carry out construction projects without assuming these Federal environmental... construction projects, or phases of construction projects, under other legal authorities (see § 137.272)....

  15. 25 CFR 224.64 - How may a tribe assume management of development of different types of energy resources?

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... Requirements § 224.64 How may a tribe assume management of development of different types of energy resources... 25 Indians 1 2010-04-01 2010-04-01 false How may a tribe assume management of development of different types of energy resources? 224.64 Section 224.64 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT...

  16. Simultaneous Analysis of Recurrent Jovian Electron Increases and Galactic Cosmic Ray Decreases

    NASA Astrophysics Data System (ADS)

    Kühl, P.; Dresing, N.; Dunzlaff, P.; Fichtner, H.; Gieseler, J.; Gomez-Herrero, R.; Heber, B.; Klassen, A.; Kleimann, J.; Kopp, A.; Potgieter, M. S.; Scherer, K.; Strauss, D. R.

    2012-12-01

    Since the early 1970's the magnetosphere of Jupiter is known to be a strong source of relativistic electrons. These Jovian electrons are released quasi-continuously from the magnetosphere. Due to Jupiter's favorable orbit, they offer a unique opportunity for studies of the transport of energetic particles in the heliosphere, in which the Jovian magnetosphere acts as a source of "quit time" electron increase. Of central importance for the propagation of Jovian electrons is the solar wind flow and the structure of the embedded heliospheric magnetic field. The solar wind defines the transport environment for the particles as soon as they have left the Jovian magnetosphere. They enter the solar wind flow close to the ecliptic plane and are immediately subject to the processes of spatial diffusion, convection, and adiabatic deceleration in the expanding solar wind plasma. On the time-scale of a solar rotation, especially during the rising and declining phases of the solar cycle the variability is caused mainly by corotating interaction regions. Due to the changing propagation conditions in the intermediate heliosphere, corotating interaction regions, however, can cause recurrent galactic cosmic ray modulation. A detailed analysis of recurrent Jovian electron events and galactic cosmic ray decreases measured by SOHO EPHIN is presented here, clearly showing a change of phase between both phenomena during a year. This phase shift has been analyzed by calculating the correlation coefficient between the galactic component and the Jovian electrons. Furthermore, the data can be ordered such that the 27-day Jovian electron variation vanishes in the sector which does not connect the Earth with Jupiter using observed solar wind speeds.; Electron intensity dependent on the longitudinal angle between SOHO and Jupiter. Jovian electron increases can only be observed in regions, which are magnetically connected to Jupiter via observed solar wind speeds.

  17. Very high energy antineutrinos from photo-disintegration of cosmic ray nuclei

    NASA Astrophysics Data System (ADS)

    Gupta, Nayantara

    2016-02-01

    The photo-disintegration of cosmic ray nuclei by starlight leads to the production of secondary antineutrinos. We have assumed that the flux of the ultrahigh energy cosmic ray nuclei near the Galactic plane region is the same as that observed near the earth and calculated the antineutrino flux produced from their photo-disintegration. The IceCube detector has measured the neutrino/antineutrino flux in the TeV-PeV energy range. Our calculated secondary antineutrino flux in the energy range of 10-100 TeV is found to be much less compared to the flux detected by the IceCube collaboration. The upper limit on the intensity of the radiation field in the extragalactic medium is much lower than that near the Galactic center. If we extend our formalism to the extragalactic medium the contribution from the photo-disintegration of ultrahigh energy cosmic ray heavy nuclei remains insignificant due to their very low flux.

  18. Lead, platinum and other heavy elements in the primary cosmic radiation: HEAO-3 results

    NASA Technical Reports Server (NTRS)

    Waddington, C. J.; Binns, W. R.; Brewster, N. R.; Fixsen, D. J.; Garrard, T. L.; Israel, M. H.; Klarmann, J.; Newport, B. J.; Stone, E. C.

    1986-01-01

    An observation of the abundances of cosmic-ray lead and platinum-group nuclei using data from the HEAO-3 Heavy Nuclei Experiment (HNE) which consisted of ion chambers mounted on both sides of a plastic Cherenkov counter (Binns et al., 1981) is reported. Further analysis with more stringent selections, inclusion of additional data, and a calibration at the LBL Bevalac, have allowed the determination of the abundance ratio of lead and the platinum group of elements for particles that had a cutoff rigidity R(c) 5 GV. The observed ratio for Pb/Pt is distinctly lower than that predicted by any of the standard models for cosmic ray sources. It is possible that the difference is not an indication that the cosmic ray source composition is greatly different from that of the solar system, but rather that there is less Pb in the solar system and in the r-process than is assumed in the standard models.

  19. Cosmic physics data analysis program

    NASA Technical Reports Server (NTRS)

    Wilkes, R. Jeffrey

    1993-01-01

    A data analysis program was carried out to investigate the intensity, propagation, and origin of primary Cosmic Ray Galactic electrons. Scanning was carried out on two new balloon flight experiments as well as the border area of previous experiments. The identification and evaluation of the energies of the primary electrons were carried out. A new analysis of these data were incorporated into an overall evaluation of the roll of electrons in the problem of the origin of cosmic rays. Recent measurements indicate that the earth may be within the expanding Geminga supernova shock wave which is expected to have a major effect upon the propagation and the energy spectrum of galactic electrons. Calculations with the Geminga model indicate that the cut-off energy may be very close to the observed highest energy electrons in our analysis.

  20. Antiprotons in the cosmic radiation

    NASA Technical Reports Server (NTRS)

    Protheroe, R. J.

    1983-01-01

    Cosmic ray antiprotons were first detected three years ago by Golden et al. (1979) and Bogomolov et al. (1979). The measured flux at about 10 GeV was found to be a factor of 5 to 10 higher than expected in the leaky box model. More recently, an unexpected high antiproton flux has been measured by Buffington et al. (1981) at about 200 MeV, well below a low energy cut-off in the spectrum expected if the antiprotons are secondary. This paper briefly reviews calculations of the flux of secondary antiprotons expected for different models of cosmic ray propagation and discusses some of the primary origin hypotheses which have been proposed to account for the data.

  1. 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.

  2. Characterising CCDs with cosmic rays

    SciTech Connect

    Fisher-Levine, M.; Nomerotski, A.

    2015-08-06

    The properties of cosmic ray muons make them a useful probe for measuring the properties of thick, fully depleted CCD sensors. The known energy deposition per unit length allows measurement of the gain of the sensor's amplifiers, whilst the straightness of the tracks allows for a crude assessment of the static lateral electric fields at the sensor's edges. The small volume in which the muons deposit their energy allows measurement of the contribution to the PSF from the diffusion of charge as it drifts across the sensor. In this work we present a validation of the cosmic ray gain measurement technique by comparing with radioisotope gain measurments, and calculate the charge diffusion coefficient for prototype LSST sensors.

  3. COSMIC/NASTRAN-PATRAN Interface

    NASA Technical Reports Server (NTRS)

    Libby, D. H.

    1985-01-01

    A three dimensional solid modeling and finite element pre and postprocessing program, PATRAN, uses the latest interactive computer graphics technology, provides a visual means to define a finite element model and its environment, and reviews its resultant model behavior. The capabilities provided by the PATRAN-COSMIC/NASTRAN interface are discussed. While the translator capabilities give some indication of the interface quality between the two programs, there are other attributes to be considered. The ideal interface would be a user transparent union of the two programs so that the engineer could move from one program to the other fluently and naturally. Hence, a valid assessment of the interface completeness must consider how close the current capabilities are to the idealized case. An example problem is presented to demonstrate how COSMIC/NASTRAN and PATRAN can be used together to meet the requirements of an actual engineering application.

  4. Characterising CCDs with cosmic rays

    DOE PAGES

    Fisher-Levine, M.; Nomerotski, A.

    2015-08-06

    The properties of cosmic ray muons make them a useful probe for measuring the properties of thick, fully depleted CCD sensors. The known energy deposition per unit length allows measurement of the gain of the sensor's amplifiers, whilst the straightness of the tracks allows for a crude assessment of the static lateral electric fields at the sensor's edges. The small volume in which the muons deposit their energy allows measurement of the contribution to the PSF from the diffusion of charge as it drifts across the sensor. In this work we present a validation of the cosmic ray gain measurementmore » technique by comparing with radioisotope gain measurments, and calculate the charge diffusion coefficient for prototype LSST sensors.« less

  5. 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.

  6. Antiprotons in the Cosmic Rays

    NASA Astrophysics Data System (ADS)

    Nutter, Scott

    1999-10-01

    The HEAT (High Energy Antimatter Telescope) collaboration flew in May 1999 a balloon-borne instrument to measure the relative abundance of antiprotons and protons in the cosmic rays to kinetic energies of 30 GeV. The instrument uses a multiple energy loss technique to measure the Lorentz factor of through-going cosmic rays, a magnet spectrometer to measure momentum, and several scintillation counters to determine particle charge and direction (up or down in the atmosphere). The antiproton/proton abundance ratio as a function of energy is a probe of the propagation environment of protons through the galaxy. Existing measurements indicate a higher than expected value at both high and low energies. A confirming measurement could indicate peculiar antiproton sources, such as WIMPs or supersymmetric darkmatter candidates. A description of the instrument, details of the flight and instrument performance, and status of the data analysis will be given.

  7. Cosmic microwave background theory

    PubMed Central

    Bond, J. Richard

    1998-01-01

    A long-standing goal of theorists has been to constrain cosmological parameters that define the structure formation theory from cosmic microwave background (CMB) anisotropy experiments and large-scale structure (LSS) observations. The status and future promise of this enterprise is described. Current band-powers in ℓ-space are consistent with a ΔT flat in frequency and broadly follow inflation-based expectations. That the levels are ∼(10−5)2 provides strong support for the gravitational instability theory, while the Far Infrared Absolute Spectrophotometer (FIRAS) constraints on energy injection rule out cosmic explosions as a dominant source of LSS. Band-powers at ℓ ≳ 100 suggest that the universe could not have re-ionized too early. To get the LSS of Cosmic Background Explorer (COBE)-normalized fluctuations right provides encouraging support that the initial fluctuation spectrum was not far off the scale invariant form that inflation models prefer: e.g., for tilted Λ cold dark matter sequences of fixed 13-Gyr age (with the Hubble constant H0 marginalized), ns = 1.17 ± 0.3 for Differential Microwave Radiometer (DMR) only; 1.15 ± 0.08 for DMR plus the SK95 experiment; 1.00 ± 0.04 for DMR plus all smaller angle experiments; 1.00 ± 0.05 when LSS constraints are included as well. The CMB alone currently gives weak constraints on Λ and moderate constraints on Ωtot, but theoretical forecasts of future long duration balloon and satellite experiments are shown which predict percent-level accuracy among a large fraction of the 10+ parameters characterizing the cosmic structure formation theory, at least if it is an inflation variant. PMID:9419321

  8. Diffuse Cosmic Infrared Background Radiation

    NASA Technical Reports Server (NTRS)

    Dwek, Eli

    2002-01-01

    The diffuse cosmic infrared background (CIB) consists of the cumulative radiant energy released in the processes of structure formation that have occurred since the decoupling of matter and radiation following the Big Bang. In this lecture I will review the observational data that provided the first detections and limits on the CIB, and the theoretical studies explaining the origin of this background. Finally, I will also discuss the relevance of this background to the universe as seen in high energy gamma-rays.

  9. Charged Cosmic Rays and Neutrinos

    NASA Astrophysics Data System (ADS)

    Kachelrieß, M.

    2013-04-01

    High-energy neutrino astronomy has grown up, with IceCube as one of its main experiments having sufficient sensitivity to test "vanilla" models of astrophysical neutrinos. I review predictions of neutrino fluxes as well as the status of cosmic ray physics. I comment also briefly on an improvement of the Fermi-LAT limit for cosmogenic neutrinos and on the two neutrino events presented by IceCube first at "Neutrino 2012".

  10. Neutrino mass without cosmic variance

    NASA Astrophysics Data System (ADS)

    LoVerde, Marilena

    2016-05-01

    Measuring the absolute scale of the neutrino masses is one of the most exciting opportunities available with near-term cosmological data sets. Two quantities that are sensitive to neutrino mass, scale-dependent halo bias b (k ) and the linear growth parameter f (k ) inferred from redshift-space distortions, can be measured without cosmic variance. Unlike the amplitude of the matter power spectrum, which always has a finite error, the error on b (k ) and f (k ) continues to decrease as the number density of tracers increases. This paper presents forecasts for statistics of galaxy and lensing fields that are sensitive to neutrino mass via b (k ) and f (k ). The constraints on neutrino mass from the auto- and cross-power spectra of spectroscopic and photometric galaxy samples are weakened by scale-dependent bias unless a very high density of tracers is available. In the high-density limit, using multiple tracers allows cosmic variance to be beaten, and the forecasted errors on neutrino mass shrink dramatically. In practice, beating the cosmic-variance errors on neutrino mass with b (k ) will be a challenge, but this signal is nevertheless a new probe of neutrino effects on structure formation that is interesting in its own right.

  11. On the Energy Spectra of GeV/TeV Cosmic Ray Leptons

    SciTech Connect

    Stawarz, Lukasz; Petrosian, Vahe; Blandford, Roger D.; /KIPAC, Menlo Park

    2011-08-19

    Recent observations of cosmic ray electrons from several instruments have revealed various degrees of deviation in the measured electron energy distribution from a simple power-law, in a form of an excess around 0.1 to 1 TeV energies. An even more prominent deviation and excess has been observed in the fraction of cosmic ray positrons around 10 and 100 GeV energies. These observations have received considerable attention and many theoretical models have been proposed to explain them. The models rely on either dark matter annihilation/decay or specific nearby astrophysical sources, and involve several additional assumptions regarding the dark matter distribution or particle acceleration. In this paper we show that the observed excesses in the electron spectrum may be easily reproduced without invoking any unusual sources other than the general diffuse Galactic components of cosmic rays. The model presented here assumes a power-law injection of electrons (and protons) by supernova remnants, and evaluates their expected energy spectrum based on a simple kinetic equation describing the propagation of charged particles in the interstellar medium. The primary physical effect involved is the Klein-Nishina suppression of the electron cooling rate around TeV energies. With a very reasonable choice of the model parameters characterizing the local interstellar medium, we can reproduce the most recent observations by Fermi and HESS experiments. Interestingly, in our model the injection spectral index of cosmic ray electrons becomes comparable to, or even equal to that of cosmic ray protons. The Klein-Nishina effect may also affect the propagation of the secondary e{sup {+-}} pairs, and therefore modify the cosmic ray positron-to-electron ratio. We have explored this possibility by considering two mechanisms for production of e{sup {+-}} pairs within the Galaxy. The first is due to the decay of {pi}{sup {+-}}'s produced by interaction of cosmic ray nuclei with ambient protons

  12. Cosmic Connections:. from Cosmic Rays to Gamma Rays, Cosmic Backgrounds and Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Kusenko, Alexander

    2013-12-01

    Combined data from gamma-ray telescopes and cosmic-ray detectors have produced some new surprising insights regarding intergalactic and galactic magnetic fields, as well as extragalactic background light. We review some recent advances, including a theory explaining the hard spectra of distant blazars and the measurements of intergalactic magnetic fields based on the spectra of distant sources. Furthermore, we discuss the possible contribution of transient galactic sources, such as past gamma-ray bursts and hypernova explosions in the Milky Way, to the observed ux of ultrahigh-energy cosmicrays nuclei. The need for a holistic treatment of gamma rays, cosmic rays, and magnetic fields serves as a unifying theme for these seemingly unrelated phenomena.

  13. SAS-2 gamma-ray results from the galactic plane and their implications for galactic structure and galactic cosmic-ray dynamics

    NASA Technical Reports Server (NTRS)

    Fichtel, C. E.; Kniffen, D. A.; Thompson, D. J.

    1977-01-01

    The final SAS-2 results related to high energy galactic gamma-ray emission show a strong correlation with galactic structural features seen at other wavelenghts, when the known gamma-ray sources are subtracted. Theoretical considerations and analysis of the gamma-ray data suggest that the galactic cosmic rays are dynamically coupled to the interstellar matter through the magnetic fields, and hence the cosmic ray density is enhanced where the matter density is greatest on the scale of the galactic arms. This concept has been explored in a galactic model that assumes: (1) cosmic rays are galactic and not universal; (2)on the scale of the galactic arms, the cosmic ray column (surface) density is proportional to the total interstellar gas column density; (3)the cosmic ray scale height is significantly larger than the scale height to the matter; and (4) ours is a spiral galaxy characterized by an arm to interarm density ratio of over 2:1.

  14. High-energy galactic gamma radiation from cosmic rays concentrated in spiral arms

    NASA Technical Reports Server (NTRS)

    Bignami, G. F.; Fichtel, C. E.; Kniffen, D. A.; Thompson, D. J.

    1975-01-01

    A model for the emission of high-energy (exceeding 100 Mev) gamma-rays from the galactic disk has been developed and compared with recent SAS-2 observations. In the calculation, it is assumed that (1) the high energy galactic gamma-rays result primarily from the interaction of cosmic rays with galactic matter, (2) the cosmic-ray density is proportional to the matter density on the scale of galactic arms, and (3) the matter in the Galaxy is distributed in a spiral pattern consistent with density-wave theory and experimental data on the matter distribution that is available, including the 21-cm H I line emission, continuum emission from H II regions, and data currently being used to estimate the H2 density. The calculated galactic-longitude distribution of gamma rays is in good agreement with the SAS-2 observations in relative shape and absolute flux. As a corollary, the nonuniform cosmic-ray distribution of this model tends to support the galactic origin of the fraction of cosmic rays which is important in the production of high-energy photons. Modifications of the basic model show that the gamma-ray flux is relatively sensitive to large variations of the assumed distribution of molecular hydrogen in the Galaxy.

  15. Cloud chamber visualization of primary cosmic rays

    SciTech Connect

    Earl, James A.

    2013-02-07

    From 1948 until 1963, cloud chambers were carried to the top of the atmosphere by balloons. From these flights, which were begun by Edward P. Ney at the University of Minnesota, came the following results: discovery of heavy cosmic ray nuclei, development of scintillation and cherenkov detectors, discovery of cosmic ray electrons, and studies of solar proton events. The history of that era is illustrated here by cloud chamber photographs of primary cosmic rays.

  16. Cosmic rays: the highest-energy messengers.

    PubMed

    Olinto, Angela V

    2007-01-01

    The origin of the most energetic particles ever observed, cosmic rays, will begin to be revealed in the next few years. Newly constructed ultrahigh-energy cosmic ray observatories together with high-energy gamma-ray and neutrino observatories are well positioned to unveil this mystery before the centenary of their discovery in 2012. Cosmic ray sources are likely to involve the most energetic phenomena ever witnessed in the universe.

  17. The pregalactic cosmic gravitational wave background

    NASA Technical Reports Server (NTRS)

    Matzner, Richard A.

    1989-01-01

    An outline is given that estimates the expected gravitational wave background, based on plausible pregalactic sources. Some cosmologically significant limits can be put on incoherent gravitational wave background arising from pregalactic cosmic evolution. The spectral region of cosmically generated and cosmically limited radiation is, at long periods, P greater than 1 year, in contrast to more recent cosmological sources, which have P approx. 10 to 10(exp -3).

  18. The elemental abundance ratios of interstellar secondary and primary cosmic rays

    NASA Technical Reports Server (NTRS)

    Brown, J. W.; Stone, E. C.; Vogt, R. E.

    1974-01-01

    We report new observations of abundances in the charge range (Z) between 2 and 10, which were obtained with a dE/dx-Cerenkov detector launched into a polar orbit on OGO-6 as part of the Caltech Solar and Galactic Cosmic Ray Experiment. Integral rigidity spectra of all the elements observed have shapes similar to that of the helium spectrum in the rigidity range of 2 to 14 GV, approaching a power law with exponent -1.6 above 8 GV. Calculations of interstellar propagation assuming a steady-state model and including the presence of interstellar helium and the effects of solar modulation predict a variation with rigidity of ratios such as Be-O and B/O, which is not observed. The data can be explained by assuming a rigidity-dependent confinement of cosmic rays within the Galaxy.

  19. 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.

  20. Diffuse fluxes of cosmic high energy neutrinos

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.

    1978-01-01

    Production spectra of high-energy neutrinos from galactic cosmic ray interactions with interstellar gas and extragalactic ultrahigh energy cosmic-ray interactions with microwave black-body photons are presented and discussed. These production processes involve the decay of charged pions and are thus related to the production of cosmic gamma-rays from the decay of neutral pions. Estimates of the neutrino fluxes from various diffuse cosmic sources are then made and the reasons fro significant differences with previous estimates are discussed. Predicted event rates for a DUMAND type detection system are significantly lower than early estimates indicated.

  1. Propagation of cosmic rays in the galaxy

    NASA Technical Reports Server (NTRS)

    Daniel, R. R.; Stephens, S. A.

    1974-01-01

    The characteristics of a model for analyzing the propagation of cosmic rays are discussed. The requirements for analyzing the relevant observational data on cosmic rays are defines as: (1) the chemical and isotopic composition of cosmic rays as a function of energy, (2) the flux and energy spectrum of the individual nucleonic components, (3) the flux and energy spectrum of the electronic component, (4) the cosmic ray prehistory, and (5) the degree of isotropy in their arrival directions as a function of energy. It is stated that the model which has been able to bring to pass the greatest measure of success is the galactic confinement model.

  2. Are cosmic strings gravitationally stable topological defects?

    NASA Astrophysics Data System (ADS)

    Gleiser, Reinaldo; Pullin, Jorge

    1989-08-01

    A possible mechanism for the dissapearance of an open cosmic string into gravitational radiation is described. This involves the splitting of an infinite straight cosmic string into two pieces whose ends are traveling outward at the speed of light with the associated emission of a gravitational shock wave. This model can also be used to describe the following situations: (1) the development of a growing region of different string tension within a cosmic string, and (2) the creation of a cosmic string in an otherwise flat background.

  3. Topics in Cosmic Acceleration and Braneworlds

    NASA Astrophysics Data System (ADS)

    West, Eric J.

    Cosmic acceleration has come to be a standard, and perhaps required, ingredient in our current understanding of the universe. In the early universe, under the name of inflation, a phase of accelerated expansion is used to solve many problems with the standard Hot Big Bang cosmology. In the late universe, cosmic acceleration seems to best explain a wide variety of observations. In both cases, we lack a complete theory of what drives cosmic acceleration. In this thesis I discuss some open issues in our understanding of cosmic acceleration, both in the early and late universe.

  4. High Energy Cosmic Electrons: Messengers from Nearby Cosmic Ray Sources or Dark Matter?

    NASA Technical Reports Server (NTRS)

    Moiseev, Alexander

    2011-01-01

    This slide presentation reviews the recent discoveries by the Large Area Telescope (LAT) and the Gamma-ray Burst Monitor (GBM) on board the Fermi Gamma-Ray Telescope in reference to high energy cosmic electrons, and whether their source is cosmic rays or dark matter. Specific interest is devoted to Cosmic Ray electrons anisotropy,

  5. Cosmic ray diffusion: Report of the Workshop in Cosmic Ray Diffusion Theory

    NASA Technical Reports Server (NTRS)

    Birmingham, T. J.; Jones, F. C.

    1975-01-01

    A workshop in cosmic ray diffusion theory was held at Goddard Space Flight Center on May 16-17, 1974. Topics discussed and summarized are: (1) cosmic ray measurements as related to diffusion theory; (2) quasi-linear theory, nonlinear theory, and computer simulation of cosmic ray pitch-angle diffusion; and (3) magnetic field fluctuation measurements as related to diffusion theory.

  6. On the large-scale structures formed by wakes of open cosmic strings

    NASA Technical Reports Server (NTRS)

    Hara, Tetsuya; Morioka, Shoji; Miyoshi, Shigeru

    1990-01-01

    Large-scale structures of the universe have been variously described as sheetlike, filamentary, cellular, bubbles or spongelike. Recently cosmic strings became one of viable candidates for a galaxy formation scenario, and some of the large-scale structures seem to be simply explained by the open cosmic strings. According to this scenario, sheets are wakes which are traces of moving open cosmic strings where dark matter and baryonic matter have accumulated. Filaments are intersections of such wakes and high density regions are places where three wakes intersect almost orthogonally. The wakes formed at t sub eq become the largest surface density among all wakes, where t sub eq is the epoch when matter density equals to radiation density. If we assume that there is one open cosmic string per each horizon, then it can be explained that the typical distances among wakes, filaments and clusters are also approx. 10(exp 2) Mpc. This model does not exclude a much more large scale structure. Open cosmic string may move even now and accumulate cold dark matter after its traces. However, the surface density is much smaller than the ones formed at t sub eq. From this model, it is expected that the typical high density region will have extended features such as six filaments and three sheets and be surrounded by eight empty regions (voids). Here, the authors are mainly concerned with such structures and have made numerical simulations for the formation of such large scale structures.

  7. Detectability and Parameter Estimation of Gravitational Waves from Cosmic String with Ground-Based Detectors

    NASA Astrophysics Data System (ADS)

    Yuzurihara, Hirotaka; Kanda, Nobuyuki

    Cosmic string is one dimensional topological defects which might be formed at the phase transition in the early universe. Gravitational Wave (GW) waveform and its power spectrum from structure in closed cosmic string loop that is called as "cusp" are theoretically predicted. Cosmic string is thought to be described with two characteristic parameters: string tension μ and initial loop size α. We demonstrate numerical simulation for GWs from closed comic string loops to study detectability and parameter decision with ground-based detectors, such as KAGRA, advanced LIGO, advanced Virgo and LIGO-India. We employ characteristic parameters 10 - 13 < Gμ < 10 - 7 and 10 - 16 < α < 10 - 1, assuming uniform distribution of cosmic string in isotropic direction, at time epochs of loop forming and GW emission according to the universe model. We calculate waveform numerically in time domain of each GW from these distributed cosmic strings, and superpose waveforms to generate continuously observational signal on the ground-based GW detectors, including detector responses. We consider data analysis for stochastic background type gravitational wave signatures in the observation.

  8. Ultrahigh energy cosmic ray nuclei from extragalactic pulsars and the effect of their Galactic counterparts

    NASA Astrophysics Data System (ADS)

    Fang, Ke; Kotera, Kumiko; Olinto, Angela V.

    2013-03-01

    The acceleration of ultrahigh energy nuclei in fast spinning newborn pulsars can explain the observed spectrum of ultrahigh energy cosmic rays and the trend towards heavier nuclei for energies above 1019 eV as reported by the Auger Observatory. Pulsar acceleration implies a hard injection spectrum ( ~ E-1) due to pulsar spin down and a maximum energy Emax ~ Z 1019 eV due to the limit on the spin rate of neutron stars. We have previously shown that the escape through the young supernova remnant softens the spectrum, decreases slightly the maximum energy, and generates secondary nuclei. Here we show that the distribution of pulsar birth periods and the effect of propagation in the interstellar and intergalactic media modifies the combined spectrum of all pulsars. By assuming a normal distribution of pulsar birth periods centered at 300 ms, we show that the contribution of extragalactic pulsar births to the ultrahigh energy cosmic ray spectrum naturally gives rise to a contribution to very high energy cosmic rays (VHECRs, between 1016 and 1018 eV) by Galactic pulsar births. The required injected composition to fit the observed spectrum depends on the absolute energy scale, which is uncertain, differing between Auger Observatory and Telescope Array. The contribution of Galactic pulsar births can also bridge the gap between predictions for cosmic ray acceleration in supernova remnants and the observed spectrum just below the ankle, depending on the composition of the cosmic rays that escape the supernova remnant and the diffusion behavior of VHECRs in the Galaxy.

  9. Violation of the Greisen-Zatsepin-Kuzmin Cutoff: A Tempest in a (Magnetic) Teapot? Why Cosmic Ray Energies above 1020 eV May Not Require New Physics

    NASA Astrophysics Data System (ADS)

    Farrar, Glennys R.; Piran, Tsvi

    2000-04-01

    The apparent lack of suitable astrophysical sources for the observed highest energy cosmic rays within ~20 Mpc is the ``Greisen-Zatsepin-Kuzmin (GZK) paradox.'' We constrain representative models of the extragalactic magnetic field structure by Faraday rotation measurements; limits are at the μG level rather than the nG level usually assumed. In such fields, even the highest energy cosmic rays experience large deflections. This allows nearby active galactic nuclei (possibly quiet today) or gamma ray bursts to be the source of ultrahigh energy cosmic rays without contradicting the GZK distance limit.

  10. Evolution of the cosmic web

    NASA Astrophysics Data System (ADS)

    Cautun, Marius; van de Weygaert, Rien; Jones, Bernard J. T.; Frenk, Carlos S.

    2014-07-01

    The cosmic web is the largest scale manifestation of the anisotropic gravitational collapse of matter. It represents the transitional stage between linear and non-linear structures and contains easily accessible information about the early phases of structure formation processes. Here we investigate the characteristics and the time evolution of morphological components. Our analysis involves the application of the NEXUS Multiscale Morphology Filter technique, predominantly its NEXUS+ version, to high resolution and large volume cosmological simulations. We quantify the cosmic web components in terms of their mass and volume content, their density distribution and halo populations. We employ new analysis techniques to determine the spatial extent of filaments and sheets, like their total length and local width. This analysis identifies clusters and filaments as the most prominent components of the web. In contrast, while voids and sheets take most of the volume, they correspond to underdense environments and are devoid of group-sized and more massive haloes. At early times the cosmos is dominated by tenuous filaments and sheets, which, during subsequent evolution, merge together, such that the present-day web is dominated by fewer, but much more massive, structures. The analysis of the mass transport between environments clearly shows how matter flows from voids into walls, and then via filaments into cluster regions, which form the nodes of the cosmic web. We also study the properties of individual filamentary branches, to find long, almost straight, filaments extending to distances larger than 100 h-1 Mpc. These constitute the bridges between massive clusters, which seem to form along approximatively straight lines.

  11. Cosmic radiation in commercial aviation.

    PubMed

    Bagshaw, Michael

    2008-05-01

    This paper reviews the current knowledge of cosmic radiation and its applicability to commercial aviation. Galactic cosmic radiation emanates from outside the solar system, while occasionally a disturbance in the suns' atmosphere leads to a surge in radiation particles. Protection is provided by the suns' magnetic field, the earths' magnetic field, and the earths' atmosphere. Dose rates are dependent on the altitude, the geomagnetic latitude and the solar cycle. For occupational exposure to ionising radiation, which includes aircrew, the International Commission on Radiological Protection recommends maximum mean body effective dose limits of 20mSv/yr (averaged over 5 years, with a maximum in any 1 year of 50mSv). Radiation doses can be measured during flight or may be calculated using a computer-modelling program such as CARI, EPCARD, SIEVERT or PCAIRE. Mean ambient equivalent dose rates are consistently reported in the region of 4-5microSv/h for long-haul pilots and 1-3microSv/h for short-haul, giving an annual mean effective exposure of the order 2-3mSv for long-haul and 1-2mSv for short-haul pilots. Epidemiological studies of flight crew have not shown conclusive evidence for any increase in cancer mortality or cancer incidence directly attributable to ionising radiation exposure. Whilst there is no level of radiation exposure below which effects do not occur, current evidence indicates that the probability of airline crew or passengers suffering adverse health effects as a result of exposure to cosmic radiation is very low. PMID:18486066

  12. Cosmic radiation in commercial aviation.

    PubMed

    Bagshaw, Michael

    2008-05-01

    This paper reviews the current knowledge of cosmic radiation and its applicability to commercial aviation. Galactic cosmic radiation emanates from outside the solar system, while occasionally a disturbance in the suns' atmosphere leads to a surge in radiation particles. Protection is provided by the suns' magnetic field, the earths' magnetic field, and the earths' atmosphere. Dose rates are dependent on the altitude, the geomagnetic latitude and the solar cycle. For occupational exposure to ionising radiation, which includes aircrew, the International Commission on Radiological Protection recommends maximum mean body effective dose limits of 20mSv/yr (averaged over 5 years, with a maximum in any 1 year of 50mSv). Radiation doses can be measured during flight or may be calculated using a computer-modelling program such as CARI, EPCARD, SIEVERT or PCAIRE. Mean ambient equivalent dose rates are consistently reported in the region of 4-5microSv/h for long-haul pilots and 1-3microSv/h for short-haul, giving an annual mean effective exposure of the order 2-3mSv for long-haul and 1-2mSv for short-haul pilots. Epidemiological studies of flight crew have not shown conclusive evidence for any increase in cancer mortality or cancer incidence directly attributable to ionising radiation exposure. Whilst there is no level of radiation exposure below which effects do not occur, current evidence indicates that the probability of airline crew or passengers suffering adverse health effects as a result of exposure to cosmic radiation is very low.

  13. Evolution of cosmic string networks

    NASA Technical Reports Server (NTRS)

    Albrecht, Andreas; Turok, Neil

    1989-01-01

    A discussion of the evolution and observable consequences of a network of cosmic strings is given. A simple model for the evolution of the string network is presented, and related to the statistical mechanics of string networks. The model predicts the long string density throughout the history of the universe from a single parameter, which researchers calculate in radiation era simulations. The statistical mechanics arguments indicate a particular thermal form for the spectrum of loops chopped off the network. Detailed numerical simulations of string networks in expanding backgrounds are performed to test the model. Consequences for large scale structure, the microwave and gravity wave backgrounds, nucleosynthesis and gravitational lensing are calculated.

  14. The cosmic microwave background radiation

    NASA Technical Reports Server (NTRS)

    Silk, Joseph

    1992-01-01

    A review the implications of the spectrum and anisotropy of the cosmic microwave background for cosmology. Thermalization and processes generating spectral distortions are discussed. Anisotropy predictions are described and compared with observational constraints. If the evidence for large-scale power in the galaxy distribution in excess of that predicted by the cold dark matter model is vindicated, and the observed structure originated via gravitational instabilities of primordial density fluctuations, the predicted amplitude of microwave background anisotropies on angular scales of a degree and larger must be at least several parts in 10 exp 6.

  15. Cosmic ray heliospheric transport study with neutron monitor data

    NASA Astrophysics Data System (ADS)

    Ahluwalia, H. S.; Ygbuhay, R. C.; Modzelewska, R.; Dorman, L. I.; Alania, M. V.

    2015-10-01

    Determining transport coefficients for galactic cosmic ray (GCR) propagation in the turbulent interplanetary magnetic field (IMF) poses a fundamental challenge in modeling cosmic ray modulation processes. GCR scattering in the solar wind involves wave-particle interaction, the waves being Alfven waves which propagate along the ambient field (B). Empirical values at 1 AU are determined for the components of the diffusion tensor for GCR propagation in the heliosphere using neutron monitor (NM) data. At high rigidities, particle density gradients and mean free paths at 1 AU in B can only be computed from the solar diurnal anisotropy (SDA) represented by a vector A (components Ar, Aϕ, and Aθ) in a heliospherical polar coordinate system. Long-term changes in SDA components of NMs (with long track record and the median rigidity of response Rm ~ 20 GV) are used to compute yearly values of the transport coefficients for 1963-2013. We confirm the previously reported result that the product of the parallel (to B) mean free path (λ||) and radial density gradient (Gr) computed from NM data exhibits a weak Schwabe cycle (11y) but strong Hale magnetic cycle (22y) dependence. Its value is most depressed in solar activity minima for positive (p) polarity intervals (solar magnetic field in the Northern Hemisphere points outward from the Sun) when GCRs drift from the polar regions toward the helioequatorial plane and out along the heliospheric current sheet (HCS), setting up a symmetric gradient Gθs pointing away from HCS. Gr drives all SDA components and λ|| Gr contributes to the diffusive component (Ad) of the ecliptic plane anisotropy (A). GCR transport is commonly discussed in terms of an isotropic hard sphere scattering (also known as billiard-ball scattering) in the solar wind plasma. We use it with a flat HCS model and the Ahluwalia-Dorman master equations to compute the coefficients α (=λ⊥/λ∥) and ωτ (a measure of turbulence in the solar wind) and transport

  16. Contributions to the 19th International Cosmic Ray Conference

    NASA Technical Reports Server (NTRS)

    1985-01-01

    Various aspects of cosmic radiation, its measurements and their patterns are presented. Measurement techniques and variations in solar cosmic ray patterns and calculations of elemental abundances are reviewed.

  17. 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.

  18. Cosmic rays: a review for astrobiologists.

    PubMed

    Ferrari, Franco; Szuszkiewicz, Ewa

    2009-05-01

    Cosmic rays represent one of the most fascinating research themes in modern astronomy and physics. Significant progress is being made toward an understanding of the astrophysics of the sources of cosmic rays and the physics of interactions in the ultrahigh-energy range. This is possible because several new experiments in these areas have been initiated. Cosmic rays may hold answers to a great number of fundamental questions, but they also shape our natural habitat and influence the radiation environment of our planet Earth. The importance of the study of cosmic rays has been acknowledged in many fields, including space weather science and astrobiology. Here, we concentrate on the astrobiological aspects of cosmic rays with regard to the enormous amount of new data available, some of which may, in fact, improve our knowledge about the radiation of cosmic origin on Earth. We focus on fluxes arriving at Earth and doses received, and will guide the reader through the wealth of scientific literature on cosmic rays. We have prepared a concise and self-contained source of data and recipes useful for performing interdisciplinary research in cosmic rays and their effects on life on Earth.

  19. Early history of cosmic rays at Chicago

    NASA Astrophysics Data System (ADS)

    Yodh, Gaurang B.

    2013-02-01

    Cosmic ray studies at the University of Chicago were started by Arthur Compton during the late 1920s. The high points of cosmic ray studies at Chicago under Compton and Marcel Schein are the focus of this report, which summarizes the research done at Chicago up to the end of World War II.

  20. Nano-Particles in Cosmic Plasma Environments

    SciTech Connect

    Mann, Ingrid

    2008-09-07

    Astronomical observations and in-situ measurements point to the existence of cosmic nano-particles, but in most cases their material composition and structure are not known. Nano-dust interacts differently than larger dust with the cosmic radiation and plasma environment. Its dynamics and behavior upon collision is not well studied.

  1. Cosmic strings from supersymmetric flat directions

    SciTech Connect

    Cui Yanou; Morrissey, David E.; Martin, Stephen P.; Wells, James D.

    2008-02-15

    Flat directions are a generic feature of the scalar potential in supersymmetric gauge field theories. They can arise, for example, from D-terms associated with an extra Abelian gauge symmetry. Even when supersymmetry is broken softly, there often remain directions in the scalar field space along which the potential is almost flat. Upon breaking a gauge symmetry along one of these almost-flat directions, cosmic strings may form. Relative to the standard cosmic string picture based on the Abelian Higgs model, these flat-direction cosmic strings have the extreme type-I properties of a thin gauge core surrounded by a much wider scalar field profile. We perform a comprehensive study of the microscopic, macroscopic, and observational characteristics of this class of strings. We find many differences from the standard string scenario, including stable higher winding-mode strings, the dynamical formation of higher mode strings from lower ones, and a resultant multitension scaling string network in the early universe. These strings are only moderately constrained by current observations, and their gravitational wave signatures may be detectable at future gravity wave detectors. Furthermore, there is the interesting but speculative prospect that the decays of cosmic string loops in the early universe could be a source of ultrahigh-energy cosmic rays or nonthermal dark matter. We also compare the observational signatures of flat-direction cosmic strings with those of ordinary cosmic strings as well as (p,q) cosmic strings motivated by superstring theory.

  2. Ultra heavy nuclei in the cosmic radiation

    NASA Technical Reports Server (NTRS)

    Binns, W. Robert

    1988-01-01

    This paper describes the measurements of the ultraheavy cosmic ray abundances obtained by the Heavy Nuclei Experiment aboard the NASA High Energy Astronomy Observatory-3. It is found that the cosmic ray abundances are in broad agreement with solar system abundances with a step-FIP fractionation model applied although in detail there are some differences. In particular, Ge and Pb appear to be underabundant in the cosmic radiation. Although the platinum/lead ratio and the actinides are consistent with some r-process enhancement, the cosmic ray source is not dominated by the r-process up through the 50s as evidenced by the Sr/Rb ratio and by the abundance of Sn and Ba. The actinides are not greatly enhanced, ruling out freshly synthesized r-process production as the primary source of the heavy cosmic rays.

  3. 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.

  4. Gamma rays, cosmic rays, and galactic structure

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.

    1977-01-01

    Observations of cosmic and gamma radiation by SAS-2 satellite are summarized and analyzed to determine processes responsible for producing observed galactic radiation. In addition to the production of gamma rays in discrete galactic objects such as pulsars, there are three main mechanisms by which high-energy (greater than 100 MeV) radiation is produced by high-energy interactions involving cosmic rays in interstellar space. These processes, which produce what may be called diffuse galactic gamma-rays, are: (1) the decay of pi mesons produced by interactions of cosmic ray nucleons with interstellar gas nuclei; (2) the bremsstrahlung radiation produced by cosmic ray electrons interacting in the Coulomb fields of nuclei of interstellar gas atoms; and (3) Compton interactions between cosmic ray electrons and low-energy photons in interstellar space.

  5. Cosmic vacuum and galaxy formation

    NASA Astrophysics Data System (ADS)

    Chernin, A. D.

    2006-04-01

    It is demonstrated that the protogalactic perturbations must enter the nonlinear regime before the red shift z≈ 1; otherwise they would be destroyed by the antigravity of the vacuum dark energy at the subsequent epoch of the vacuum domination. At the zrrV={M/[(8π/3)ρV]}1/3, where M is the mass of a given over-density and ρV is the vacuum density. The criterion provides a new relation between the largest mass condensations and their spatial scales. All the real large-scale systems follow this relation definitely. It is also shown that a simple formula is possible for the key quantity in the theory of galaxy formation, namely the initial amplitude of the perturbation of the gravitational potential in the protogalactic structures. The amplitude is time independent and given in terms of the Friedmann integrals, which are genuine physical characteristics of the cosmic energies. The results suggest that there is a strong correspondence between the global design of the Universe as a whole and the cosmic structures of various masses and spatial scales.

  6. [Cosmic Microwave Background (CMB) Anisotropies

    NASA Astrophysics Data System (ADS)

    Silk, Joseph

    1998-01-01

    One of the main areas of research is the theory of cosmic microwave background (CMB) anisotropies and analysis of CMB data. Using the four year COBE data we were able to improve existing constraints on global shear and vorticity. We found that, in the flat case (which allows for greatest anisotropy), (omega/H)0 less than 10-7, where omega is the vorticity and H is the Hubble constant. This is two orders of magnitude lower than the tightest, previous constraint. We have defined a new set of statistics which quantify the amount of non-Gaussianity in small field cosmic microwave background maps. By looking at the distribution of power around rings in Fourier space, and at the correlations between adjacent rings, one can identify non-Gaussian features which are masked by large scale Gaussian fluctuations. This may be particularly useful for identifying unresolved localized sources and line-like discontinuities. Levin and collaborators devised a method to determine the global geometry of the universe through observations of patterns in the hot and cold spots of the CMB. We have derived properties of the peaks (maxima) of the CMB anisotropies expected in flat and open CDM models. We represent results for angular resolutions ranging from 5 arcmin to 20 arcmin (antenna FWHM), scales that are relevant for the MAP and COBRA/SAMBA space missions and the ground-based interferometer. Results related to galaxy formation and evolution are also discussed.

  7. Cosmic radioactivity and INTEGRAL results

    SciTech Connect

    Diehl, Roland

    2014-05-02

    Gamma-ray lines from radioactive decay of unstable isotopes co-produced by nucleosynthesis in massive stars and supernova have been measured since more than thirty years. Over the past ten years, INTEGRAL complemented the first sky survey made by COMPTEL. The {sup 26}A1 isotope with 1 My decay time had been first direct proof of currently-ongoing nucleosynthesis in our Galaxy. This has now become a tool to study the ∼My history of specific source regions, such as massive-star groups and associations in nearby regions which can be discriminated from the galactic-plane background, and the inner Galaxy, where Doppler shifted lines add to the astronomical information about bar and spiral structure. Recent findings suggest that superbubbles show a remarkable asymmetry, on average, in the spiral arms of our galaxy. {sup 60}Fe is co-produced by the sources of {sup 26}A1, and the isotopic ratio from their nucleosynthesis encodes stellar-structure information. Annihilation gamma-rays from positrons in interstellar space show a puzzling bright and extended source region central to our Galaxy, but also may be partly related to nucleosynthesis. {sup 56}Ni and {sup 44}Ti isotope gamma-rays have been used to constrain supernova explosion mechanisms. Here we report latest results using the accumulated multi-year database of INTEGRAL observations, and discuss their astrophysical interpretations, connecting to other traces of cosmic radioactivity and to other cosmic messengers.

  8. Improving cosmic string network simulations

    NASA Astrophysics Data System (ADS)

    Hindmarsh, Mark; Rummukainen, Kari; Tenkanen, Tuomas V. I.; Weir, David J.

    2014-08-01

    In real-time lattice simulations of cosmic strings in the Abelian Higgs model, the broken translational invariance introduces lattice artifacts; relativistic strings therefore decelerate and radiate. We introduce two different methods to construct a moving string on the lattice, and study in detail the lattice effects on moving strings. We find that there are two types of lattice artifact: there is an effective maximum speed with which a moving string can be placed on the lattice, and a moving string also slows down, with the deceleration approximately proportional to the exponential of the velocity. To mitigate this, we introduce and study an improved discretization, based on the tree-level Lüscher-Weisz action, which is found to reduce the deceleration by an order of magnitude, and to increase the string speed limit by an amount equivalent to halving the lattice spacing. The improved algorithm is expected to be very useful for 3D simulations of cosmic strings in the early Universe, where one wishes to simulate as large a volume as possible.

  9. [Cosmic Microwave Background (CMB) Anisotropies

    NASA Technical Reports Server (NTRS)

    Silk, Joseph

    1998-01-01

    One of the main areas of research is the theory of cosmic microwave background (CMB) anisotropies and analysis of CMB data. Using the four year COBE data we were able to improve existing constraints on global shear and vorticity. We found that, in the flat case (which allows for greatest anisotropy), (omega/H)0 less than 10(exp -7), where omega is the vorticity and H is the Hubble constant. This is two orders of magnitude lower than the tightest, previous constraint. We have defined a new set of statistics which quantify the amount of non-Gaussianity in small field cosmic microwave background maps. By looking at the distribution of power around rings in Fourier space, and at the correlations between adjacent rings, one can identify non-Gaussian features which are masked by large scale Gaussian fluctuations. This may be particularly useful for identifying unresolved localized sources and line-like discontinuities. Levin and collaborators devised a method to determine the global geometry of the universe through observations of patterns in the hot and cold spots of the CMB. We have derived properties of the peaks (maxima) of the CMB anisotropies expected in flat and open CDM models. We represent results for angular resolutions ranging from 5 arcmin to 20 arcmin (antenna FWHM), scales that are relevant for the MAP and COBRA/SAMBA space missions and the ground-based interferometer. Results related to galaxy formation and evolution are also discussed.

  10. Nexus of the Cosmic Web

    NASA Astrophysics Data System (ADS)

    Cautun, Marius; van de Weygaert, Rien; Jones, Bernard J. T.; Frenk, Carlos S.; Hellwing, Wojciech A.

    2015-01-01

    One of the important unknowns of current cosmology concerns the effects of the large scale distribution of matter on the formation and evolution of dark matter haloes and galaxies. One main difficulty in answering this question lies in the absence of a robust and natural way of identifying the large scale environments and their characteristics. This work summarizes the NEXUS+ formalism which extends and improves our multiscale scale-space MMF method. The new algorithm is very successful in tracing the Cosmic Web components, mainly due to its novel filtering of the density in logarithmic space. The method, due to its multiscale and hierarchical character, has the advantage of detecting all the cosmic structures, either prominent or tenuous, without preference for a certain size or shape. The resulting filamentary and wall networks can easily be characterized by their direction, thickness, mass density and density profile. These additional environmental properties allows to us to investigate not only the effect of environment on haloes, but also how it correlates with the environment characteristics.

  11. What Are You Assuming?

    ERIC Educational Resources Information Center

    Kennedy, Nadia Stoyanova

    2012-01-01

    Students are often encouraged to work on problems "like mathematicians"--to be persistent, to investigate different approaches, and to evaluate solutions. This behavior, regarded as problem solving, is an essential component of mathematical practice. Some crucial aspects of problem solving include defining and interpreting problems, working with…

  12. Cosmic rays and space weather

    NASA Astrophysics Data System (ADS)

    Dorman, L. I.

    2003-04-01

    It is well known that in periods of great FEP (Flare Energetic Particle), fluxes can be so big that memory of computers and other electronics in space may be destroyed, satellites and spacecrafts became dead (each year insurance companies paid more than 500,000,000 dollars for these failures). In these periods is necessary to switch off some part of electronics for short time to protect computer memories. These periods are also dangerous for astronauts on space-ships, and passengers and crew in commercial jets (especially during S5 radiation storms according to classification of NOAA). The problem is how to forecast exactly these dangerous phenomena. We show that exact forecast can be made by using high-energy particles (about 5-10 GeV/nucleon and higher) which transportation from the Sun is characterized by much bigger diffusion coefficient than for small and middle energy particles. Therefore high energy particles came from the Sun much more early (8-20 minutes after acceleration and escaping into solar wind) than main part of smaller energy particles caused dangerous situation for electronics and people health (about 30-60 minutes later). We describe here principles and experience of automatically working programs "FEP-Search-1 min", "FEP-Search-2 min","FEP-Search-5 min", developed and checked in the Emilio Segre' Observatory of Israel Cosmic Ray Center (2025 m above sea level, cut-off rigidity 10.8 GV). The second step is automatically determination of flare energetic particle spectrum, and then automatically determination of diffusion coefficient in the interplanetary space, time of ejection and energy spectrum of FEP in source; forecasting of expected FEP flux and radiation hazard for space-probes in space, satellites in the magnetosphere, jets and various objects in the atmosphere and on the ground. We will describe also the theory and experience of high energy cosmic ray using for forecasting of major geomagnetic storms accompanied by Forbush-effects (what

  13. The first three microseconds: Cosmic strings, axions and magnetic fields

    NASA Astrophysics Data System (ADS)

    Quashnock, Jean Maurice

    The dynamics of local cosmic strings are discussed in chapter one. The gravitational back-reaction problem and its relevance to kinks and cusps, as well as its implications for cosmic string networks, gravitational radiation and large-scale structure formation, are treated in depth. Cusps survive the backreaction. The decay time of a kink of size l, t(l)decay is found to be approximately ((gamma kink(G)(mu)) exp(-1))l where gamma kink is approximately 50. Kink decay times together with millisecond pulsar timing measurements yield an upper limit to the string tension, namely, G mu is less than 6 x 10 -5. This is far from ruling out the cosmic string scenario of galaxy formation. The issue of divergences in global strings is resolved in chapter two, using a renormalization technique similar to that first used by Dirac for the classical electron. It is found that the motion of large global strings is very similar to that of local strings, and that as a consequence the axion mass is greater than 10-3 eV. This lower bound is marginally inconsistent with an upper bound derived from SN1987a constraints; effectively the axion is ruled out as a cosmologically important dark matter candidate. The electrodynamics of the quantum chromodynamics (QCD) phase transition are dealt with in chapter three, which is assumed to be first order. Because of temperature gradients during the nucleation of hadron bubbles in the quark-gluon plasma, a thermoelectric Biermann battery is created during the transition. It is found that magnetic fields of size 10-17 gauss will be present on A.U. scales during the epoch of galaxy formation. These fields may be the seeds required by dynamo theories of galactic magnetic fields.

  14. The first three microseconds: Cosmic strings, axions and magnetic fields

    SciTech Connect

    Quashnock, J.M.

    1990-01-01

    The dynamics of local cosmic strings are discussed in chapter one. The gravitational back-reaction problem and its relevance to kinks and cusps, as well as its implications for cosmic string networks, gravitational radiation and large-scale structure formation, are treated in depth. Cusps survive the backreaction. The decay time of a kink of size l, t(l)(sub decay) is found to be approximately ((gamma (sub kink)(G)(mu)) exp(-1))l where gamma (sub kink) is approximately 50. Kink decay times together with millisecond pulsar timing measurements yield an upper limit to the string tension, namely, G mu is less than 6 x 10 (exp -5). This is far from ruling out the cosmic string scenario of galaxy formation. The issue of divergences in global strings is resolved in chapter two, using a renormalization technique similar to that first used by Dirac for the classical electron. It is found that the motion of large global strings is very similar to that of local strings, and that as a consequence the axion mass is greater than 10(exp -3) eV. This lower bound is marginally inconsistent with an upper bound derived from SN1987a constraints; effectively the axion is ruled out as a cosmologically important dark matter candidate. The electrodynamics of the quantum chromodynamics (QCD) phase transition are dealt with in chapter three, which is assumed to be first order. Because of temperature gradients during the nucleation of hadron bubbles in the quark-gluon plasma, a thermoelectric Biermann battery is created during the transition. It is found that magnetic fields of size 10(exp -17) gauss will be present on A.U. scales during the epoch of galaxy formation. These fields may be the seeds required by dynamo theories of galactic magnetic fields.

  15. A Synthesis Of Cosmic X-ray And Infrared Background

    NASA Astrophysics Data System (ADS)

    Shi, Yong; Helou, G.; Armus, L.; Stierwalt, S.

    2012-01-01

    We present a synthesis model of cosmic IR and X-ray background, with the goal to derive a complete census of cosmic evolution of star formation (SF) and black-hole (BH) growth by complementing advantages of X-ray and IR surveys to each other. By assuming that individual galaxies are experiencing both SF and BH accretion, our model decomposes the total IR LF into SF and BH components while taking into account the luminosity-dependent SED and its dispersion of the SF component, and the extinction-dependent SED of the BH component. The best-fit parameters are derived by fitting to the number counts and redshift distributions at X-ray including both hard and soft bands, and mid-IR to submm bands including IRAS, Spitzer, Herschel, SCUBA, Aztec and MAMBO. Based on the fit result, our models provide a series of predictions on galaxy evolution and black-hole growth. For evolution of infrared galaxies, the model predicts that the total infrared luminosity function is best described through evolution in both luminosity and density. For evolution of AGN populations, the model predicts that the evolution of X-ray LF also shows luminosity and density dependent, that the type-1/type-2 AGN fraction is a function of both luminosity and redshift, and that the Compton-thick AGN number density evolves strongly with redshift, contributing about 20% to the total cosmic BH growth. For BH growth in IR galaxies, the model predicts that the majority of BH growth at z>1 occurs in infrared luminous galaxies and the AGN fraction as a function of IR survey is a strong function of the survey depth, ranging from >50% at bright end to below 10% at faint end. We also evaluates various AGN selection techniques at X-ray and IR wavelengths and offer predictions for future missions at X-ray and IR.

  16. Stochastic gravitational wave background from light cosmic strings

    SciTech Connect

    DePies, Matthew R.; Hogan, Craig J.

    2007-06-15

    Spectra of the stochastic gravitational wave backgrounds from cosmic strings are calculated and compared with present and future experimental limits. Motivated by theoretical expectations of light cosmic strings in superstring cosmology, improvements in experimental sensitivity, and recent demonstrations of large, stable loop formation from a primordial network, this study explores a new range of string parameters with masses lighter than previously investigated. A standard 'one-scale' model for string loop formation is assumed. Background spectra are calculated numerically for dimensionless string tensions G{mu}/c{sup 2} between 10{sup -7} and 10{sup -18}, and initial loop sizes as a fraction of the Hubble radius {alpha} from 0.1 to 10{sup -6}. The spectra show a low frequency power-law tail, a broad spectral peak due to loops decaying at the present epoch (including frequencies higher than their fundamental mode, and radiation associated with cusps), and a flat (constant energy density) spectrum at high frequencies due to radiation from loops that decayed during the radiation-dominated era. The string spectrum is distinctive and unlike any other known source. The peak of the spectrum for light strings appears at high frequencies, significantly affecting predicted signals. The spectra of the cosmic string backgrounds are compared with current millisecond pulsar limits and Laser Interferometer Space Antenna (LISA) sensitivity curves. For models with large stable loops ({alpha}=0.1), current pulsar-timing limits exclude G{mu}/c{sup 2}>10{sup -9}, a much tighter limit on string tension than achievable with other techniques, and within the range of current models based on brane inflation. LISA may detect a background from strings as light as G{mu}/c{sup 2}{approx_equal}10{sup -16}, corresponding to field theory strings formed at roughly 10{sup 11} GeV.

  17. Direct observation of cosmic strings via their strong gravitational lensing effect - II. Results from the HST/ACS image archive

    NASA Astrophysics Data System (ADS)

    Morganson, Eric; Marshall, Phil; Treu, Tommaso; Schrabback, Tim; Blandford, Roger D.

    2010-08-01

    We have searched 4.5deg2 of archival Hubble Space Telescope/Advanced Camera for Surveys (HST/ACS) images for cosmic strings, identifying close pairs of similar, faint galaxies and selecting groups whose alignment is consistent with gravitational lensing by a long, straight string. We find no evidence for cosmic strings in five large-area HST treasury surveys (covering a total of 2.22deg2) or in any of 346 multifilter guest observer images (1.18deg2). Assuming that simulations accurately predict the number of cosmic strings in the Universe, this non-detection allows us to place upper limits on the dimensionless Universal cosmic string tension of Gμ/c2 < 2.3 × 10-6 and cosmic string density of Ωs < 2.1 × 10-5 at the 95per cent confidence level (marginalizing over the other parameter in each case). We find four dubious cosmic string candidates in 318 single-filter guest observer images (1.08deg2), which we are unable to conclusively eliminate with existing data. The confirmation of any of these candidates as cosmic strings would imply Gμ/c2 ~ 10-6 and Ωs ~ 10-5. However, we estimate that there is at least a 92per cent chance that these string candidates are random alignments of galaxies. If we assume that these candidates are indeed false detections, our final limits on Gμ/c2 and Ωs fall to 6.5 × 10-7 and 7.3 × 10-6, respectively. Due to the extensive sky coverage of the HST/ACS image archive, the above limits are universal. They are quite sensitive to the number of fields being searched and could be further reduced by more than a factor of 2 using forthcoming HST data.

  18. Search for Cosmic Strings in Cosmic Microwave BackgroundAnisotropies

    SciTech Connect

    Jeong, E.; Smoot, GF

    2004-06-01

    We have searched the 1st-year WMAP W-Band CMB anisotropy map for evidence of cosmic strings. We have set a limit of delta = 8 pi G mu/ c2 < 8.2 times 10-6 at 95 percent CL for statistical search for a significant number of strings in the map. We also have set a limit using the uniform distribution of strings model in the WMAP data with delta = 8pi G mu/c2 < 7.34 times 10-5 at 95 percent CL. And the pattern search technique we developed here set a limit delta = 8 pi G mu/c2 < 1.54 times 10-5 at 95 percent CL.

  19. Possible origin of the anomalous component of cosmic rays

    NASA Technical Reports Server (NTRS)

    Biswas, S.; Durgaprasad, N.; Singh, R. K.; Vahia, M. N.; Yadav, J. S.

    1985-01-01

    The possible origin of the anomalous cosmic rays (ACR) are studied in terms of stellar wind injection from O type stars and their acceleration in shock fronts of SNR's. It is assumed that a fraction of heavy ions will encounter interstellar shock fronts of SNR's and these are accelerated to about 5 to 100 MeV/N and give rise to ACR's. Typically these ions would travel a distance of the order of a few 1000 pc. Therefore it is estimated that O type stars in a volume of radius of a few Kpc around the solar system are contributing to the intensity of ACR in the local ISM. From observational data, the intensity of ACR in the local ISM is estimated. It is suggested that these ACR ions enter the solar system along the solar dipole field lines connected to the interplanetary magnetic field lines.

  20. Self-organization of cosmic radiation pressure instability

    NASA Technical Reports Server (NTRS)

    Hogan, Craig J.

    1991-01-01

    Under some circumstances the absorption of radiation momentum by an absorbing medium opens the possibility of a dynamical instability, sometimes called 'mock gravity'. Here, a simplified abstract model is studied in which the radiation source is assumed to remain spatially uniform, there is no reabsorption or reradiated light, and no forces other than radiative pressure act on the absorbing medium. It is shown that this model displays the unique feature of being not only unstable, but also self-organizing. The structure approaches a statistical dynamical steady state which is almost independent of initial conditions. In this saturated state the absorbers are concentrated in thin walls around empty bubbles; as the instability develops the big bubbles get bigger and the small ones get crushed and disappear. A linear analysis shows that to first order the thin walls are indeed stable structures. It is speculated that this instability may play a role in forming cosmic large-scale structure.

  1. High energy galactic gamma radiation from cosmic rays concentrated in spiral arms. [using SAS-B satellite

    NASA Technical Reports Server (NTRS)

    Bignami, G. F.; Fichtel, C. E.; Thompson, D. J.; Kniffen, D. A.

    1974-01-01

    A model for the emission of high energy ( 100 MeV) gamma rays from the galactic disk was developed and compared to recent SAS-2 observations. In the calculation, it is assumed that (1) the high energy galactic gamma rays result primarily from the interaction of cosmic rays with galactic matter; (2) on the basis of theoretical and experimental arguments the cosmic ray density is proportional to the matter density on the scale of galactic arms; and (3) the matter in the galaxy, atomic and molecular, is distributed in a spiral pattern consistent with density wave theory and the experimental data on the matter distribution.

  2. Space Weather Observations by GNSS Radio Occultation: From FORMOSAT-3/COSMIC to FORMOSAT-7/COSMIC-2

    PubMed Central

    Yue, Xinan; Schreiner, William S; Pedatella, Nicholas; Anthes, Richard A; Mannucci, Anthony J; Straus, Paul R; Liu, Jann-Yenq

    2014-01-01

    The joint Taiwan-United States FORMOSAT-3/COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate) mission, hereafter called COSMIC, is the first satellite constellation dedicated to remotely sense Earth's atmosphere and ionosphere using a technique called Global Positioning System (GPS) radio occultation (RO). The occultations yield abundant information about neutral atmospheric temperature and moisture as well as space weather estimates of slant total electron content, electron density profiles, and an amplitude scintillation index, S4. With the success of COSMIC, the United States and Taiwan are moving forward with a follow-on RO mission named FORMOSAT-7/COSMIC-2 (COSMIC-2), which will ultimately place 12 satellites in orbit with two launches in 2016 and 2019. COSMIC-2 satellites will carry an advanced Global Navigation Satellite System (GNSS) RO receiver that will track both GPS and Russian Global Navigation Satellite System signals, with capability for eventually tracking other GNSS signals from the Chinese BeiDou and European Galileo system, as well as secondary space weather payloads to measure low-latitude plasma drifts and scintillation at multiple frequencies. COSMIC-2 will provide 4–6 times (10–15X in the low latitudes) the number of atmospheric and ionospheric observations that were tracked with COSMIC and will also improve the quality of the observations. In this article we focus on COSMIC/COSMIC-2 measurements of key ionospheric parameters. PMID:26213514

  3. 24 CFR 1000.24 - If an Indian tribe assumes environmental review responsibility, how will HUD assist the Indian...

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 24 Housing and Urban Development 4 2010-04-01 2010-04-01 false If an Indian tribe assumes environmental review responsibility, how will HUD assist the Indian tribe in performing the environmental review? 1000.24 Section 1000.24 Housing and Urban Development Regulations Relating to Housing and Urban Development (Continued) OFFICE OF...

  4. 12 CFR Appendix L to Part 226 - Assumed Loan Periods for Computations of Total Annual Loan Cost Rates

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Annual Loan Cost Rates L Appendix L to Part 226 Banks and Banking FEDERAL RESERVE SYSTEM (CONTINUED) BOARD OF GOVERNORS OF THE FEDERAL RESERVE SYSTEM TRUTH IN LENDING (REGULATION Z) Pt. 226, App. L Appendix L to Part 226—Assumed Loan Periods for Computations of Total Annual Loan Cost Rates (a)...

  5. Beyond an Assumed Mother-Child Symbiosis in Nutritional Guidelines: The Everyday Reasoning behind Complementary Feeding Decisions

    ERIC Educational Resources Information Center

    Nielsen, Annemette; Michaelsen, Kim F.; Holm, Lotte

    2014-01-01

    Researchers question the implications of the way in which "motherhood" is constructed in public health discourse. Current nutritional guidelines for Danish parents of young children are part of this discourse. They are shaped by an assumed symbiotic relationship between the nutritional needs of the child and the interest and focus of the…

  6. 9 CFR 72.15 - Owners assume responsibility; must execute agreement prior to dipping or treatment waiving all...

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... CATTLE § 72.15 Owners assume responsibility; must execute agreement prior to dipping or treatment waiving all claims against United States. When the cattle are to be dipped under APHIS supervision the owner of the cattle, offered for shipment, or his agent duly authorized thereto, shall first execute...

  7. 9 CFR 72.15 - Owners assume responsibility; must execute agreement prior to dipping or treatment waiving all...

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... CATTLE § 72.15 Owners assume responsibility; must execute agreement prior to dipping or treatment waiving all claims against United States. When the cattle are to be dipped under APHIS supervision the owner of the cattle, offered for shipment, or his agent duly authorized thereto, shall first execute...

  8. 9 CFR 72.15 - Owners assume responsibility; must execute agreement prior to dipping or treatment waiving all...

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... CATTLE § 72.15 Owners assume responsibility; must execute agreement prior to dipping or treatment waiving all claims against United States. When the cattle are to be dipped under APHIS supervision the owner of the cattle, offered for shipment, or his agent duly authorized thereto, shall first execute...

  9. 42 CFR 137.300 - Since Federal environmental responsibilities are new responsibilities, which may be assumed by...

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... Federal environmental responsibilities assumed by the Self-Governance Tribe. ... 42 Public Health 1 2010-10-01 2010-10-01 false Since Federal environmental responsibilities are... additional funds available to Self-Governance Tribes to carry out these formerly inherently...

  10. 12 CFR Appendix L to Part 226 - Assumed Loan Periods for Computations of Total Annual Loan Cost Rates

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 12 Banks and Banking 3 2011-01-01 2011-01-01 false Assumed Loan Periods for Computations of Total Annual Loan Cost Rates L Appendix L to Part 226 Banks and Banking FEDERAL RESERVE SYSTEM (CONTINUED) BOARD OF GOVERNORS OF THE FEDERAL RESERVE SYSTEM TRUTH IN LENDING (REGULATION Z) Pt. 226, App....

  11. 9 CFR 72.15 - Owners assume responsibility; must execute agreement prior to dipping or treatment waiving all...

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ....15 Animals and Animal Products ANIMAL AND PLANT HEALTH INSPECTION SERVICE, DEPARTMENT OF AGRICULTURE INTERSTATE TRANSPORTATION OF ANIMALS (INCLUDING POULTRY) AND ANIMAL PRODUCTS TEXAS (SPLENETIC) FEVER IN... 9 Animals and Animal Products 1 2010-01-01 2010-01-01 false Owners assume responsibility;...

  12. 42 CFR 137.286 - Do Self-Governance Tribes become Federal agencies when they assume these Federal environmental...

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 42 Public Health 1 2012-10-01 2012-10-01 false Do Self-Governance Tribes become Federal agencies... HEALTH AND HUMAN SERVICES TRIBAL SELF-GOVERNANCE Construction Nepa Process § 137.286 Do Self-Governance... Self-Governance Tribes are required to assume Federal environmental responsibilities for projects...

  13. 42 CFR 137.286 - Do Self-Governance Tribes become Federal agencies when they assume these Federal environmental...

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 1 2010-10-01 2010-10-01 false Do Self-Governance Tribes become Federal agencies... HEALTH AND HUMAN SERVICES TRIBAL SELF-GOVERNANCE Construction Nepa Process § 137.286 Do Self-Governance... Self-Governance Tribes are required to assume Federal environmental responsibilities for projects...

  14. 42 CFR 137.291 - May Self-Governance Tribes carry out construction projects without assuming these Federal...

    Code of Federal Regulations, 2014 CFR

    2014-10-01

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  15. 42 CFR 137.286 - Do Self-Governance Tribes become Federal agencies when they assume these Federal environmental...

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 42 Public Health 1 2011-10-01 2011-10-01 false Do Self-Governance Tribes become Federal agencies... HEALTH AND HUMAN SERVICES TRIBAL SELF-GOVERNANCE Construction Nepa Process § 137.286 Do Self-Governance... Self-Governance Tribes are required to assume Federal environmental responsibilities for projects...

  16. 42 CFR 137.286 - Do Self-Governance Tribes become Federal agencies when they assume these Federal environmental...

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 42 Public Health 1 2014-10-01 2014-10-01 false Do Self-Governance Tribes become Federal agencies... HEALTH AND HUMAN SERVICES TRIBAL SELF-GOVERNANCE Construction Nepa Process § 137.286 Do Self-Governance... Self-Governance Tribes are required to assume Federal environmental responsibilities for projects...

  17. 42 CFR 137.291 - May Self-Governance Tribes carry out construction projects without assuming these Federal...

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 42 Public Health 1 2012-10-01 2012-10-01 false May Self-Governance Tribes carry out construction... OF HEALTH AND HUMAN SERVICES TRIBAL SELF-GOVERNANCE Construction Nepa Process § 137.291 May Self-Governance Tribes carry out construction projects without assuming these Federal...

  18. 42 CFR 137.286 - Do Self-Governance Tribes become Federal agencies when they assume these Federal environmental...

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 42 Public Health 1 2013-10-01 2013-10-01 false Do Self-Governance Tribes become Federal agencies... HEALTH AND HUMAN SERVICES TRIBAL SELF-GOVERNANCE Construction Nepa Process § 137.286 Do Self-Governance... Self-Governance Tribes are required to assume Federal environmental responsibilities for projects...

  19. 42 CFR 137.291 - May Self-Governance Tribes carry out construction projects without assuming these Federal...

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 42 Public Health 1 2013-10-01 2013-10-01 false May Self-Governance Tribes carry out construction... OF HEALTH AND HUMAN SERVICES TRIBAL SELF-GOVERNANCE Construction Nepa Process § 137.291 May Self-Governance Tribes carry out construction projects without assuming these Federal...

  20. 42 CFR 137.292 - How do Self-Governance Tribes assume environmental responsibilities for construction projects...

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... responsibilities for construction projects under section 509 of the Act ? 137.292 Section 137.292 Public Health...-Governance Tribes assume environmental responsibilities for construction projects under section 509 of the...-Governance Tribe; and (b) Entering into a construction project agreement under section 509 of the Act ....

  1. 42 CFR 137.292 - How do Self-Governance Tribes assume environmental responsibilities for construction projects...

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... responsibilities for construction projects under section 509 of the Act ? 137.292 Section 137.292 Public Health...-Governance Tribes assume environmental responsibilities for construction projects under section 509 of the...-Governance Tribe; and (b) Entering into a construction project agreement under section 509 of the Act ....

  2. 42 CFR 137.292 - How do Self-Governance Tribes assume environmental responsibilities for construction projects...

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... responsibilities for construction projects under section 509 of the Act ? 137.292 Section 137.292 Public Health...-Governance Tribes assume environmental responsibilities for construction projects under section 509 of the...-Governance Tribe; and (b) Entering into a construction project agreement under section 509 of the Act ....

  3. Periodic X-ray Modulation and its Possible Relation with Eccentricity in Black Hole Binaries : Long-Term Swift/BAT and RXTE/ASM Data Analysis

    NASA Astrophysics Data System (ADS)

    Ghosh, Arindam; Chakrabarti, Sandip Kumar

    2016-07-01

    X-ray binary orbits are expected to have some eccentricity, albeit small. Stellar companion of a black hole orbiting in an eccentric orbit will experience modulating tidal force with a periodicity same as that of the orbital period which will result in a modulation of accretion rates, seed photon flux, and flux of inverse Comptonized harder X-rays as well. Timing analysis of long-term X-ray data (1.5-12 keV) of RXTE/ASM and all sky survey data (15-50 keV) of Swift/BAT satellites reveal this periodicity in several black hole candidates. If this modulation is assumed to be solely due to tidal effects (without taking other effects, such as eclipses, reflection from winds, super-hump phenomena etc. into account), the RMS-value of the peak in power density spectrum allows us to estimate eccentricities of these orbits. We present these very interesting results. We show that our results generally agree with independent studies of these parameters.

  4. 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.

  5. Interactions of cosmic rays with the venusian atmosphere during different periods of solar activity

    NASA Astrophysics Data System (ADS)

    Plainaki, Christina; Paschalis, Pavlos; Grassi, Davide; Mavromichalaki, Helen; Andriopoulou, Maria

    2016-04-01

    Interactions of the galactic and solar cosmic ray particles with the atmosphere of Venus result in extensive nuclear and electromagnetic cascades that can affect cloud formation and chemistry in deep atmospheric layers. Variability in the energy spectrum of the cosmic ray particles and in their integrated flux and direction would have possible effects in the local neutral densities, particle ionization and escape. It is therefore of significant importance to understand and quantify such space weather phenomena at Venus, in the context of future mission preparation and also data interpretations of previous missions (e.g. Venus Express). In this paper, we perform a calculation of the atmosphere ionization and ion production rates caused by cosmic rays, as a function of depth in the Venusian atmosphere. We examine the interactions of the planet's atmosphere with galactic and solar cosmic rays (during solar energetic particle events). The latter scenario was studied for two paradigm cases: the very energetic solar event in October 1989 and the recent, less energetic, solar event in May 2012, assuming that the directional and energy properties of the solar particles allowed their arrival and penetration to the Venusian atmosphere. For the event in 2012, we considered the solar particle properties (integrated flux and spectrum) obtained by the NMBANGLE PPOLA model (Plainaki et al., 2010; 2014) applied previously for the Earth case, scaled to the distance of Venus (i.e. 0.72 AU from the Sun). In order to simulate the actual cascade in the atmosphere initiated by the incoming cosmic ray fluxes we use a Monte Carlo modeling technique based on the Geant4 software, previously applied for the Earth case (Paschalis et al., 2014), namely DYASTIMA. Our predictions are afterwards compared to other estimations derived from previous studies. The current method is furthermore proposed as a paradigm for studying cosmic ray-atmosphere interactions in the terrestrial planets possessing

  6. Einsteinian Revolution's Wrong Turn: Lumpy Interacting Cosmos Assumed as Smooth Perfect Fluid, no Dark Energy, Eternal Universe?

    NASA Astrophysics Data System (ADS)

    Mitra, Abhas

    2014-03-01

    Newtonian Cosmology involving a smooth fluid was plagued with the problem of indefiniteness, and General Relativity gave the novel concept of a finite yet unbounded Einstein's Static Universe (ESU). Later, Big Bang model (BBM) essentially incorporated non-static versions of ESU. Also, the concept of a Cosmological Constant (Λ) got reinstated through "Inflation" and "Dark Energy". We dismantle this edifice by presenting several exact proofs showing that Λ = 0 and both ESU & deSitter metrics are just the Minkowski vacuum. More importantly, by using the Schwarzschild form of the FRW metric (Mitra, Grav. Cosmology 2013), we show that FRW metric too is actually the Minkowski vacuum! It is suggested that physical universe is quasi-Newtonian where for any given galaxy, finite gravitational potential is due to interaction of nearest neighbors while the infinite background forces cancel due to symmetry (Chandrasekhar, ApJ 1941). Such an universe is likely to have a fractal structure as suggested by observations. The cosmic redshift might arise due to asymmetric spread of wave packets associated with line emissions from distant galaxies. The cosmic background radiation might be due to thermalization of star lights in an eternal universe as suggested by Hoyle. The compact objects in quasars are ultracompact radiation pressure supported stars which may synthesize light elements and whose explosions & flares infuse fresh plasma for a recycled eternal universe. While these are possibilities, there is indeed no robust alternative cosmology. Though BBM appears to be the best bet, it turns out to be vacuous. In the absence of the BBM singularity, the rationale for "Quantum Gravity" vanishes. It is predicted that there are no primordial Gravitational Waves contrary to BBM suggestion. The fact that the farthest galaxy (z = 7.5) is rich in metals (Finkelstein et al., Nature, 502, 524, 2013) contradicts BBM, and suggests cosmos might be eternal and static.

  7. The cosmic microwave background radiation

    NASA Technical Reports Server (NTRS)

    Silk, J.

    1981-01-01

    Because angular anisotropies and spectral distortions of the cosmic microwave background radiation are judged to be inevitable at some level, in a realistic cosmological model, the evidence for spectral distortions and its theoretical implications are described. The evidence for anisotropy is then discussed, and theoretical predictions of radiation anisotropy are summarized and compared with the data available. It is found that spectral distortions at the 3-sigma level near the peak of the blackbody spectrum, although inconsistent with the predicted distortions due to Compton scattering in the early universe, are elegantly interpreted in terms of radiation from an early, pregalactic generation of massive stars which had been thermalized by a modest amount of dust at high redshift. The quadrupole anisotropy at the 4-sigma level is most simply interpreted in terms of the large-scale structure of the universe.

  8. Quantum bounce and cosmic recall.

    PubMed

    Corichi, Alejandro; Singh, Parampreet

    2008-04-25

    Loop quantum cosmology predicts that, in simple models, the big bang is replaced by a quantum bounce. A natural question is whether the universe retains, after the bounce, its memory about the previous epoch. More precisely, does the Universe retain various properties of the state after evolving unitarily through the bounce, or does it suffer from recently suggested cosmic amnesia? We show that this issue can be answered unambiguously at least within an exactly solvable model. A semiclassical state at late times on one side of the bounce, peaked on a pair of canonically conjugate variables, strongly bounds the fluctuations on the other side, implying semiclassicality. For a model universe growing to 1 megaparsec, the change in relative fluctuation across the bounce is less than 10(-56) (becoming smaller for larger universes). The universe maintains (an almost) total recall. PMID:18518182

  9. Electric currents in cosmic plasmas

    NASA Technical Reports Server (NTRS)

    Alfven, H.

    1977-01-01

    It is suggested that dualism is essential for the physics of cosmic plasmas, that is, that some phenomena should be described by a magnetic field formalism, and others by an electric current formalism. While in earlier work the magnetic field aspect has dominated, at present there is a systematic exploration of the particle (or current) aspect. A number of phenomena which can be understood only from the particle aspect are surveyed. Topics include the formation of electric double layers, the origin of 'explosive' events like magnetic substorms and solar flares, and the transfer of energy from one region to another. A method for exploring many of these phenomena is to draw the electric circuit in which the current flows and then study its properties. A number of simple circuits are analyzed in this way.

  10. Quantum Bounce and Cosmic Recall

    NASA Astrophysics Data System (ADS)

    Corichi, Alejandro; Singh, Parampreet

    2008-04-01

    Loop quantum cosmology predicts that, in simple models, the big bang is replaced by a quantum bounce. A natural question is whether the universe retains, after the bounce, its memory about the previous epoch. More precisely, does the Universe retain various properties of the state after evolving unitarily through the bounce, or does it suffer from recently suggested cosmic amnesia? We show that this issue can be answered unambiguously at least within an exactly solvable model. A semiclassical state at late times on one side of the bounce, peaked on a pair of canonically conjugate variables, strongly bounds the fluctuations on the other side, implying semiclassicality. For a model universe growing to 1 megaparsec, the change in relative fluctuation across the bounce is less than 10-56 (becoming smaller for larger universes). The universe maintains (an almost) total recall.

  11. Shielding against galactic cosmic rays

    NASA Technical Reports Server (NTRS)

    Schimmerling, W.; Wilson, J. W.; Nealy, J. E.; Thibeault, S. A.; Cucinotta, F. A.; Shinn, J. L.; Kim, M.; Kiefer, R.

    1996-01-01

    Ions of galactic origin are modified but not attenuated by the presence of shielding materials. Indeed, the number of particles and the absorbed energy behind most shield materials increases as a function of shield thickness. The modification of the galactic cosmic ray composition upon interaction with shielding is the only effective means of providing astronaut protection. This modification is intimately conntected with the shield transport porperties and is a strong function of shield composition. The systematic behavior of the shield properites in terms of microscopic energy absorption events will be discussed. The shield effectiveness is examined with respect to convectional protection practice and in terms of a biological endpoint: the efficiency for reduction of the probability of transformation of shielded C3H1OT1/2 mouse cells. The relative advantage of developing new shielding technologies is discussed in terms of a shield performance as related to biological effect and the resulting uncertainty in estimating astronaut risk.

  12. Cosmic Ultraviolet Polarimetric Imaging Device

    NASA Astrophysics Data System (ADS)

    Burgh, Eric B.; Nordsieck, Kenneth H.; Jaehnig, Kurt P.; Harris, Walter M.; Bershady, Matthew A.

    The Cosmic Ultraviolet Polarimetric Imaging Device (CUPID) is a suborbital sounding rocket payload designed to perform wide-field, polarimetric imaging of the extragalactic ultraviolet background. In doing so, it will also measure the contribution to the UV background from the diffuse Galactic light (DGL), starlight from the Milky Way scattered off of dust. Current uncertanties in the contribution of the DGL to the UV background are due almost entirely to a poor knowledge of the optical properties of the dust in the diffuse ISM at ultraviolet wavelengths. The polarization of the scattered light is sensitive to scattering angle and thus CUPID imaging may help to constrain the spatial distribution and scattering properties of Galactic dust.

  13. Cosmic string induced peculiar velocities

    NASA Technical Reports Server (NTRS)

    Van Dalen, Anthony; Schramm, David N.

    1988-01-01

    This paper considers the scenario of a flat universe with a network of heavy cosmic strings as the primordial fluctuation spectrum. The joint probability of finding streaming velocities of at least 600 km/s on large scales and local peculiar velocities of less than 800 km/s is calculated. It is shown how the effects of loops breaking up and being born with a spectrum of sizes can be estimated. It is found that to obtain large-scale streaming velocities of at least 600 km/s, it is necessary that either a large value for beta G mu exist or the effect of loop fissioning and production details be considerable.

  14. SLAC Cosmic Ray Telescope Facility

    SciTech Connect

    Va'vra, J.

    2010-02-15

    SLAC does not have a test beam for the HEP detector development at present. We have therefore created a cosmic ray telescope (CRT) facility, which is presently being used to test the FDIRC prototype. We have used it in the past to debug this prototype with the original SLAC electronics before going to the ESA test beam. Presently, it is used to test a new waveform digitizing electronics developed by the University of Hawaii, and we are also planning to incorporate the new Orsay TDC/ADC electronics. As a next step, we plan to put in a full size DIRC bar box with a new focusing optics, and test it together with a final SuberB electronics. The CRT is located in building 121 at SLAC. We anticipate more users to join in the future. This purpose of this note is to provide an introductory manual for newcomers.

  15. Consistency of cosmic-ray source abudances with explosive nucleosynthesis

    NASA Technical Reports Server (NTRS)

    Kozlovsky, B.; Ramaty, R.

    1973-01-01

    A model was examined in which the cosmic ray abundances of elements from C to Fe are consistent with explosive nucleosynthesis. The observed abundance of cosmic rays near the earth, cosmic ray source abundance, and solar system abundance are discussed along with the ratios of cosmic ray sources to the solar system abundances.

  16. 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…

  17. Symbols of a cosmic order

    NASA Astrophysics Data System (ADS)

    Madjid, F. Hadi; Myers, John M.

    2016-10-01

    The world runs on networks over which signals communicate sequences of symbols, e.g. numerals. Examining both engineered and natural communications networks reveals an unsuspected order that depends on contact with an unpredictable entity. This order has three roots. The first is a proof within quantum theory that no evidence can ever determine its explanation, so that an agent choosing an explanation must do so unpredictably. The second root is the showing that clocks that step computers do not "tell time" but serve as self-adjusting symbol-handling agents that regulate "logically synchronized" motion in response to unpredictable disturbances. Such a clock-agent has a certain independence as well as the capacity to communicate via unpredictable symbols with other clock-agents and to adjust its own tick rate in response to that communication. The third root is the noticing of unpredictable symbol exchange in natural systems, including the transmission of symbols found in molecular biology. We introduce a symbol-handling agent as a role played in some cases by a person, for example a physicist who chooses an explanation of given experimental outcomes, and in other cases by some other biological entity, and in still other cases by an inanimate device, such as a computer-based detector used in physical measurements. While we forbear to try to explain the propensity of agents at all levels from cells to civilizations to form and operate networks of logically synchronized symbol-handling agents, we point to this propensity as an overlooked cosmic order, an order structured by the unpredictability ensuing from the proof. Appreciating the cosmic order leads to a conception of agency that replaces volition by unpredictability and reconceives the notion of objectivity in a way that makes a place for agency in the world as described by physics. Some specific implications for physics are outlined.

  18. 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.

  19. Cosmic Convergence: Art and Science

    NASA Astrophysics Data System (ADS)

    Mayo, Elizabeth A.; Zisholtz, E.; Hilton, H.

    2010-01-01

    The I.P. Stanback Museum and Planetarium is a major educational and teaching resource for South Carolina State University, K-12 schools, other universities and the community of Orangeburg and well beyond. The concept of creating a museum with a planetarium on the campus of SC State was ahead of its time. Today scholars are writing about the unity of creative disciplines. Through its integration of the arts, humanities and sciences, the Stanback, the only art museum with a planetarium at any of the Historically Black Colleges and Universities and one of the few in the nation, stands in the forefront of modern thinking. Cosmic Convergence: Art and Science, opening at the I.P. Stanback Museum and Planetarium in February 2010, will feature the works of Mildred Thompson (1936-2003), a prominent African American artist who worked in the media of painting, drawing, print making, sculpture, and photography. Thompson’s artwork shows the strong influences of her interest in physics, astronomy, and metaphysics as well as music and spiritualism. “My work in the visual arts is, and has always been, a continuous search for understanding. It is an expression of purpose and reflects a personal interpretation of the Universe.” Cosmic Convergence will explore the meeting of Art and Science through Mildred Thompson's work and the scientific basis of that work. The paintings and sculptures of the exhibit will be combined with astronomical images showing both the reality and interpretation of the surrounding Universe. Support for this work was provided by the NSF PAARE program to South Carolina State University under award AST-0750814.

  20. Radiation from cosmic string standing waves

    PubMed

    Olum; Blanco-Pillado

    2000-05-01

    We have simulated large-amplitude standing waves on an Abelian-Higgs cosmic string in classical lattice field theory. The radiation rate falls exponentially with wavelength, as one would expect from the field profile around a gauge string. Our results agree with those of Moore and Shellard, but not with those of Vincent, Antunes, and Hindmarsh. The radiation rate falls too rapidly to sustain a scaling solution via direct radiation of particles from string length. There is thus reason to doubt claims of strong constraints on cosmic string theories from cosmic ray observations.

  1. Spectral distortions of the cosmic microwave background

    NASA Technical Reports Server (NTRS)

    Adams, Fred C.; Mcdowell, Jonathan C.; Freese, Katherine; Levin, Janna

    1989-01-01

    Recent experiments indicate that the spectrum of the cosmic microwave background deviates from a pure blackbody; here, spectral distortions produced by cosmic dust are considered. The main result is that cosmic dust in conjunction with an injected radiation field (perhaps produced by an early generation of very massive stars) can explain the observed spectral distortions without violating existing cosmological constraints. In addition, it is shown that Compton y-distortions can also explain the observed spectral shape, but the energetic requirements are more severe.

  2. Antiparticles in the extragalactic cosmic radiation

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.; Wolfendale, A. W.

    1985-01-01

    It may be possible to account for a previously puzzling feature - a bump in the energy range 10 to the 14th power eV to 10 to the 15th power - of the cosmic ray spectrum by hypothesizing a primary extragalactic origin for the bulk of the observed cosmic ray antiprotons, although such an explanation is not unique. In this model, most of the cosmic rays above 10 to the 15th power eV are extragalactic. A method is described of testing this hypothesis experimentally.

  3. The isotopic composition of cosmic ray chlorine

    NASA Technical Reports Server (NTRS)

    Wiedenbeck, M. E.

    1985-01-01

    The isotopic composition of galactic cosmic ray chlorine (approx. = 225 MeV/amu) has been studied using the high energy cosmic ray experiment on the International Sun Earth Explorer 3 (ISEE-3) spacecraft. The abundances of 35C1 and 37C1 are found to be consistent with the secondary production expected from a propagation model developed to account for both light and subiron secondaries. An upper limit on the abundance of the radioactive isotope 36C1 (halflife approx. = 0.3 Myr) is used to set a lower limit on the confinement time of cosmic rays of approximately 1 Myr.

  4. Cosmic Rays Variations and Human Physiological State

    NASA Astrophysics Data System (ADS)

    Dimitrova, S.

    2009-12-01

    It was obtained in our previous investigations that geomagnetic activity as an indirect indicator of solar activity correlates with some human physiological and psycho-physiological parameters. A lot of studies indicate that other parameters of space weather like cosmic rays Forbush decreases affect myocardial infarction, brain stroke, car accidents, etc. The purpose of that work was to study the effect of cosmic rays variations on human physiological status. It was established that the decrease in cosmic rays intensity was related to an increase in systolic and diastolic blood pressure and reported subjective psycho-physiological complaints in healthy volunteers.

  5. D-term inflation without cosmic strings.

    PubMed

    Urrestilla, J; Achúcarro, A; Davis, A C

    2004-06-25

    We present a superstring-inspired version of D-term inflation that does not lead to cosmic string formation and appears to satisfy the current cosmic microwave background constraints. It differs from minimal D-term inflation by a second pair of charged superfields that makes the strings nontopological (semilocal). The strings are also Bogomol'nyi-Prasad-Sommerfield strings, so the scenario is expected to survive supergravity corrections. The second pair of charged superfields arises naturally in several brane and conifold scenarios, but its effect on cosmic string formation had not been noticed so far. PMID:15244993

  6. Cosmic string lensing and closed timelike curves

    NASA Astrophysics Data System (ADS)

    Shlaer, Benjamin; Tye, S.-H. Henry

    2005-08-01

    In an analysis of the gravitational lensing by two relativistic cosmic strings, we argue that the formation of closed timelike curves proposed by Gott is unstable in the presence of particles (e.g. the cosmic microwave background radiation). Because of the attractorlike behavior of the closed timelike curve, we argue that this instability is very generic. A single graviton or photon in the vicinity, no matter how soft, is sufficient to bend the strings and prevent the formation of closed timelike curves. We also show that the gravitational lensing due to a moving cosmic string is enhanced by its motion, not suppressed.

  7. D-term inflation, cosmic strings, and consistency with cosmic microwave background measurements.

    PubMed

    Rocher, Jonathan; Sakellariadou, Mairi

    2005-01-14

    Standard D-term inflation is studied in the framework of supergravity. D-term inflation produces cosmic strings; however, it can still be compatible with cosmic microwave background (CMB) measurements without invoking any new physics. The cosmic strings contribution to the CMB data is not constant, nor dominant, contrary to some previous results. Using current CMB measurements, the free parameters (gauge and superpotential couplings, as well as the Fayet-Iliopoulos term) of D-term inflation are constrained. PMID:15698061

  8. Is it reasonable to assume a uniformly distributed cooling-rate along the microslide of a directional solidification stage?

    PubMed

    Rabin

    2000-10-01

    It is commonly assumed that the cooling-rate along the microslide of a directional solidification stage is uniformly distributed, an assumption which is typically applied in low cooling-rates studies. A new directional solidification stage has recently been presented, which is specified to achieve high cooling-rates of up to 1.8 x 104 degrees C min-1, where cooling-rates are still assumed to be uniformly distributed. The current study presents a closed-form solution to the temperature distribution and to the cooling-rate in the microslide. Thermal analysis shows that the cooling-rate is by no means uniformly distributed and can vary by several hundred percent along the microslide in some cases. Therefore, the mathematical solution presented in this study is essential for experimental planning of high cooling-rate experiments.

  9. Detection of the earth with the SETI microwave observing system assumed to be operating out in the Galaxy

    NASA Technical Reports Server (NTRS)

    Billingham, John; Tarter, Jill

    1989-01-01

    The maximum range is calculated at which radar signals from the earth could be detected by a search system similar to the NASA SETI Microwave Observing Project (SETI MOP) assumed to be operating out in the Galaxy. Figures are calculated for the Targeted Search and for the Sky Survey parts of the MOP, both planned to be operating in the 1990s. The probability of detection is calculated for the two most powerful transmitters, the planetary radar at Arecibo (Puerto Rico) and the ballistic missile early warning systems (BMEWSs), assuming that the terrestrial radars are only in the eavesdropping mode. It was found that, for the case of a single transmitter within the maximum range, the highest probability is for the sky survey detecting BMEWSs; this is directly proportional to BMEWS sky coverage and is therefore 0.25.

  10. Active Galactic Nuclei, Neutrinos, and Interacting Cosmic Rays in NGC 253 and NGC 1068

    NASA Astrophysics Data System (ADS)

    Yoast-Hull, Tova M.; Gallagher, J. S., III; Zweibel, Ellen G.; Everett, John E.

    2014-01-01

    The galaxies M82, NGC 253, NGC 1068, and NGC 4945 have been detected in γ-rays by Fermi. Previously, we developed and tested a model for cosmic-ray interactions in the starburst galaxy M82. Now, we aim to explore the differences between starburst and active galactic nucleus (AGN) environments by applying our self-consistent model to the starburst galaxy NGC 253 and the Seyfert galaxy NGC 1068. Assuming a constant cosmic-ray acceleration efficiency by supernova remnants with Milky Way parameters, we calculate the cosmic-ray proton and primary and secondary electron/positron populations, predict the radio and γ-ray spectra, and compare with published measurements. We find that our models easily fit the observed γ-ray spectrum for NGC 253 while constraining the cosmic-ray source spectral index and acceleration efficiency. However, we encountered difficultly modeling the observed radio data and constraining the speed of the galactic wind and the magnetic field strength, unless the gas mass is less than currently preferred values. Additionally, our starburst model consistently underestimates the observed γ-ray flux and overestimates the radio flux for NGC 1068 these issues would be resolved if the AGN is the primary source of γ-rays. We discuss the implications of these results and make predictions for the neutrino fluxes for both galaxies.

  11. Active galactic nuclei, neutrinos, and interacting cosmic rays in NGC 253 and NGC 1068

    SciTech Connect

    Yoast-Hull, Tova M.; Zweibel, Ellen G.; Gallagher III, J. S.; Everett, John E.

    2014-01-10

    The galaxies M82, NGC 253, NGC 1068, and NGC 4945 have been detected in γ-rays by Fermi. Previously, we developed and tested a model for cosmic-ray interactions in the starburst galaxy M82. Now, we aim to explore the differences between starburst and active galactic nucleus (AGN) environments by applying our self-consistent model to the starburst galaxy NGC 253 and the Seyfert galaxy NGC 1068. Assuming a constant cosmic-ray acceleration efficiency by supernova remnants with Milky Way parameters, we calculate the cosmic-ray proton and primary and secondary electron/positron populations, predict the radio and γ-ray spectra, and compare with published measurements. We find that our models easily fit the observed γ-ray spectrum for NGC 253 while constraining the cosmic-ray source spectral index and acceleration efficiency. However, we encountered difficultly modeling the observed radio data and constraining the speed of the galactic wind and the magnetic field strength, unless the gas mass is less than currently preferred values. Additionally, our starburst model consistently underestimates the observed γ-ray flux and overestimates the radio flux for NGC 1068; these issues would be resolved if the AGN is the primary source of γ-rays. We discuss the implications of these results and make predictions for the neutrino fluxes for both galaxies.

  12. Natural radiation doses for cosmic and terrestrial components in Costa Rica.

    PubMed

    Mora, Patricia; Picado, Esteban; Minato, Susumu

    2007-01-01

    A study of external natural radiation, cosmic and terrestrial components, was carried out with in situ measurements using NaI scintillation counters while driving along the roads in Costa Rica for the period July 2003-July 2005. The geographical distribution of the terrestrial air-absorbed dose rates and the total effective dose rates (including cosmic) are represented on contour maps. Information on the population density of the country permitted the calculation of the per capita doses. The average effective dose for the total cosmic component was 46.88+/-18.06 nSvh(-1) and the average air-absorbed dose for the terrestrial component was 29.52+/-14.46 nGyh(-1). The average total effective dose rate (cosmic plus terrestrial components) was 0.60+/-0.18 mSv per year. The effective dose rate per capita was found to be 83.97 nSvh(-1) which gives an annual dose of 0.74 mSv. Assuming the world average for the internal radiation component, the natural radiation dose for Costa Rica will be 2.29 mSv annually.

  13. Analytical model for CMB temperature angular power spectrum from cosmic (super-)strings

    SciTech Connect

    Yamauchi, Daisuke; Yoo, Chul-Moon; Sasaki, Misao; Takahashi, Keitaro; Sendouda, Yuuiti

    2010-09-15

    We present a new analytical method to calculate the small angle cosmic microwave background (CMB) temperature angular power spectrum due to cosmic (super-)string segments. In particular, using our method, we clarify the dependence on the intercommuting probability P. We find that the power spectrum is dominated by Poisson-distributed string segments. The power spectrum for a general value of P has a plateau on large angular scales and shows a power-law decrease on small angular scales. The resulting spectrum in the case of conventional cosmic strings is in very good agreement with the numerical result obtained by Fraisse et al.. Then we estimate the upper bound on the dimensionless tension of the string for various values of P by assuming that the fraction of the CMB power spectrum due to cosmic (super-)strings is less than ten percent at various angular scales up to l=2000. We find that the amplitude of the spectrum increases as the intercommuting probability. As a consequence, strings with smaller intercommuting probabilities are found to be more tightly constrained.

  14. Interaction of cosmic and solar flare radiations with the Martian atmosphere and their biological implications.

    PubMed

    Yagoda, H

    1964-01-01

    Assuming a constant interplanetary flux of galactic cosmic radiation and a model planetary atmosphere, it is possible to evaluate the magnitude of secondary ionization phenomena therein from parameters measured on Earth. The Martian atmosphere is of particular interest as its total air mass, estimated between 354 and 109 g cm-2, is in the vicinity of the Pfotzer cosmic ray maximum. Assuming the absence of a magnetic field on Mars the maximum neutron production would occur at an atmospheric depth of 75 +/- 5 g cm-2. With the lower air mass limit the surface flux of neutrons reaching the Martian surface could be about 240 times greater than observed at Earth's sea level. Surface minerals containing nuclei with large capture cross sections for slow neutrons, such as Li6, B10 and U235, could thus serve as valuable indicators for the age of the Martian crust. In general, the tenuous Martian atmosphere would result in greater surface radiation dose rates, particularly during times of relativistic solar flares. If the surface air mass is as low as 109 g cm-2 then the rate of nuclear disintegrations due to galactic cosmic radiation would exceed that on Earth's sea level approximately 1000-fold. The tenuous Martian atmosphere would not be a complete shield for heavy primary nuclei and about 1 percent of the incident flux could reach the surface.

  15. Interaction of cosmic and solar flare radiations with the Martian atmosphere and their biological implications.

    PubMed

    Yagoda, H

    1964-01-01

    Assuming a constant interplanetary flux of galactic cosmic radiation and a model planetary atmosphere, it is possible to evaluate the magnitude of secondary ionization phenomena therein from parameters measured on Earth. The Martian atmosphere is of particular interest as its total air mass, estimated between 354 and 109 g cm-2, is in the vicinity of the Pfotzer cosmic ray maximum. Assuming the absence of a magnetic field on Mars the maximum neutron production would occur at an atmospheric depth of 75 +/- 5 g cm-2. With the lower air mass limit the surface flux of neutrons reaching the Martian surface could be about 240 times greater than observed at Earth's sea level. Surface minerals containing nuclei with large capture cross sections for slow neutrons, such as Li6, B10 and U235, could thus serve as valuable indicators for the age of the Martian crust. In general, the tenuous Martian atmosphere would result in greater surface radiation dose rates, particularly during times of relativistic solar flares. If the surface air mass is as low as 109 g cm-2 then the rate of nuclear disintegrations due to galactic cosmic radiation would exceed that on Earth's sea level approximately 1000-fold. The tenuous Martian atmosphere would not be a complete shield for heavy primary nuclei and about 1 percent of the incident flux could reach the surface. PMID:11881641

  16. Mn-53 and Al-26 evidence for solar cosmic ray constancy - An improved model for interpretation

    NASA Technical Reports Server (NTRS)

    Russ, G. P., III; Emerson, M. T.

    1980-01-01

    A general, numerical method for calculating activities of solar cosmic ray produced radionuclides at any point within an irregularly shaped lunar rock of known surface contour and lunar surface orientation is described. This method is then used to predict the activities of Mn-53 andAl-26 as a function of postion within lunar rock 68815 for various assumed values of solar cosmic ray flux (J), rigidity (R sub 0), and rock erosion rate (ER). The predicted activities agree with the measured activities of Kohl et al. (1978) when values of R sub 0 = 100 MV, J = 70 p/sq cm-sec (4 pi, E greater than 10 MeV), ER not greater than 1 mm/m.y. and a total exposure time of 2 m.y. are assumed. These values are in agreement with those found for rocks exposed for not less than 10 m.y. and provide no evidence for variation of the average solar cosmic ray parameters between the last 2 and 10 m.y. intervals. When interpreted with the improved model the activity vs. depth profiles for three faces of 68815 show no evidence of SCR anisotropy or differential erosion.

  17. Detection of the Earth with the SETI microwave observing system assumed to be operating out in the galaxy

    NASA Technical Reports Server (NTRS)

    Billingham, J.; Tarter, J.

    1992-01-01

    This paper estimates the maximum range at which radar signals from the Earth could be detected by a search system similar to the NASA Search for Extraterrestrial Intelligence Microwave Observing Project (SETI MOP) assumed to be operating out in the galaxy. Figures are calculated for the Targeted Search, and for the Sky Survey parts of the MOP, both operating, as currently planned, in the second half of the decade of the 1990s. Only the most powerful terrestrial transmitters are considered, namely, the planetary radar at Arecibo in Puerto Rico, and the ballistic missile early warning systems (BMEWS). In each case the probabilities of detection over the life of the MOP are also calculated. The calculation assumes that we are only in the eavesdropping mode. Transmissions intended to be detected by SETI systems are likely to be much stronger and would of course be found with higher probability to a greater range. Also, it is assumed that the transmitting civilization is at the same level of technological evolution as ours on Earth. This is very improbable. If we were to detect another technological civilization, it would, on statistical grounds, be much older than we are and might well have much more powerful transmitters. Both factors would make detection by the NASA MOP a much more likely outcome.

  18. Smooth halos in the cosmic web

    NASA Astrophysics Data System (ADS)

    Gaite, José

    2015-04-01

    Dark matter halos can be defined as smooth distributions of dark matter placed in a non-smooth cosmic web structure. This definition of halos demands a precise definition of smoothness and a characterization of the manner in which the transition from smooth halos to the cosmic web takes place. We introduce entropic measures of smoothness, related to measures of inequality previously used in economy and with the advantage of being connected with standard methods of multifractal analysis already used for characterizing the cosmic web structure in cold dark matter N-body simulations. These entropic measures provide us with a quantitative description of the transition from the small scales portrayed as a distribution of halos to the larger scales portrayed as a cosmic web and, therefore, allow us to assign definite sizes to halos. However, these ``smoothness sizes'' have no direct relation to the virial radii. Finally, we discuss the influence of N-body discreteness parameters on smoothness.

  19. 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.

  20. Development of the cosmic ray techniques

    NASA Technical Reports Server (NTRS)

    Rossi, B.

    1982-01-01

    It has been found that most advances of cosmic-ray physics have been directly related to the development of observational techniques. The history of observational techniques is discussed, taking into account ionization chambers, refinements applied to ionization chambers to make them suitable for an effective use in the study of cosmic radiation, the Wulf-type electrometer, the electrometer designed by Millikan and Neher, the Geiger-Mueller counter, the experiment of Bothe and Kolhoerster, the coincidence circuit, and a cosmic-ray 'telescope'. Attention is given to a magnetic lens for cosmic rays, a triangular arrangement of Geiger-Mueller counters used to demonstrate the production of a secondary radiation, a stereoscopic cloud-chamber photograph of showers, the cloud-chamber picture which provided the first evidence of the positive electron, and arrangements for studying photon components, mu-mesons, and air showers.