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Sample records for drift wave stability

  1. Atomic physics effects on dissipative toroidal drift wave stability

    SciTech Connect

    Beer, M.A.; Hahm, T.S.

    1992-02-01

    The effects of atomic physics processes such as ionization, charge exchange, and radiation on the linear stability of dissipative drift waves are investigated in toroidal geometry both numerically and analytically. For typical TFTR and TEXT edge parameters, overall linear stability is determined by the competition between the destabilizing influence of ionization and the stabilizing effect due to the electron temperature gradient. An analytical expression for the linear marginal stability condition, {eta}{sub e}{sup crit}, is derived. The instability is most likely to occur at the extreme edge of tokamaks with a significant ionization source and a steep electron density gradient.

  2. Fast wave stabilization/destabilization of drift waves in a plasma

    SciTech Connect

    Kumar, Pawan; Tripathi, V. K.

    2013-03-15

    Four wave-nonlinear coupling of a large amplitude whistler with low frequency drift wave and whistler wave sidebands is examined. The pump and whistler sidebands exert a low frequency ponderomotive force on electrons introducing a frequency shift in the drift wave. For whistler pump propagating along the ambient magnetic field B{sub s}z-caret with wave number k(vector sign){sub 0}, drift waves of wave number k(vector sign)=k(vector sign){sub Up-Tack }+k{sub ||}z-caret see an upward frequency shift when k{sub Up-Tack }{sup 2}/k{sub 0}{sup 2}>4k{sub ||}/k{sub 0} and are stabilized once the whistler power exceeds a threshold value. The drift waves of low transverse wavelength tend to be destabilized by the nonlinear coupling. Oblique propagating whistler pump with transverse wave vector parallel to k(vector sign){sub Up-Tack} is also effective but with reduced effectiveness.

  3. Drift waves in rotating plasmas

    SciTech Connect

    Horton, W.; Liu, J.

    1983-09-01

    The stability of the electron drift wave is investigated in the presence of E x B plasma rotation typical of the central cell plasma in tandem mirrors. It is shown that a rotationally-driven drift wave may occur at low azimuthal mode numbers. Conditions for rotational instabilities are derived. Quasilinear formulas are given for the anomalous transport associated with the unstable fluctuations.

  4. Collisional Drift Waves in Stellarator Plasmas

    SciTech Connect

    J.L.V. Lewandowski

    2003-10-07

    A computational study of resistive drift waves in the edge plasma of a stellarator with an helical magnetic axis is presented. Three coupled field equations, describing the collisional drift wave dynamics in the linear approximation, are solved as an initial-value problem along the magnetic field line. The magnetohydrodynamic equilibrium is obtained from a three-dimensional local equilibrium model. The use of a local magnetohydrodynamic equilibrium model allows for a computationally efficient systematic study of the impact of the magnetic field structure on drift wave stability.

  5. Drift Wave Turbulence and Magnetic Reconnection

    NASA Astrophysics Data System (ADS)

    Price, L.; Drake, J. F.; Swisdak, M.

    2015-12-01

    An important feature in collisionless magnetic reconnection is the development of sharp discontinuities along the separatrices bounding the Alfvenic outflow. The typical scale length of these features is ρs (the Larmor radius based on the sound speed) for guide field reconnection. Temperature gradients in the inflowing plasma (as might be found in the magnetopause and the magnetotail) can lead to instabilities at these separatrices, specifically drift wave turbulence. We present standalone 2D and 3D PIC simulations of drift wave turbulence to investigate scaling properties and growth rates. We specifically consider stabilization of the lower hybrid drift instability (LHDI) and the development of this instability in the presence of a sheared magnetic field. Further investigations of the relative importance of drift wave turbulence in the development of reconnection will also be considered.

  6. Stability of drift-cyclotron loss-cone waves in H-mode plasmas

    DOE PAGESBeta

    Farmer, W. A.; Morales, G. J.

    2016-05-24

    The drift-cyclotron loss-cone mode was first studied in mirror machines. In such devices, particles with small pitch angles are not confined, creating a hole in the velocity distribution function that is a source of free energy and leads to micro-instabilities in the cyclotron-range of frequencies. In the edge region of tokamak devices operating under H-mode conditions, ion loss also occurs. In this case, gradient drift carries ions moving opposite to the plasma current preferentially into the divertor, creating a one-sided loss cone. A simple analysis shows that for the quiescent H-mode plasmas in DIII-D the critical gradient for instability ismore » exceeded within 2 cm of the separatrix, and the maximum growth rate at the separatrix is 3×107 s-1.« less

  7. Stability of drift-cyclotron loss-cone waves in H-mode plasmas

    NASA Astrophysics Data System (ADS)

    Farmer, W. A.; Morales, G. J.

    2016-06-01

    The drift-cyclotron loss-cone mode was first studied in mirror machines. In such devices, particles with small pitch angles are not confined, creating a hole in the velocity distribution function that is a source of free energy and leads to micro-instabilities in the cyclotron-range of frequencies. In the edge region of tokamak devices operating under H-mode conditions, ion loss also occurs. In this case, gradient drift carries ions moving opposite to the plasma current preferentially into the divertor, creating a one-sided loss cone. A simple analysis shows that for the quiescent H-mode plasmas in DIII-D the critical gradient for instability is exceeded within 2 cm of the separatrix, and the maximum growth rate at the separatrix is 3  ×  107 s‑1.

  8. Electromagnetic drift waves dispersion for arbitrarily collisional plasmas

    SciTech Connect

    Lee, Wonjae Krasheninnikov, Sergei I.; Angus, J. R.

    2015-07-15

    The impacts of the electromagnetic effects on resistive and collisionless drift waves are studied. A local linear analysis on an electromagnetic drift-kinetic equation with Bhatnagar-Gross-Krook-like collision operator demonstrates that the model is valid for describing linear growth rates of drift wave instabilities in a wide range of plasma parameters showing convergence to reference models for limiting cases. The wave-particle interactions drive collisionless drift-Alfvén wave instability in low collisionality and high beta plasma regime. The Landau resonance effects not only excite collisionless drift wave modes but also suppress high frequency electron inertia modes observed from an electromagnetic fluid model in collisionless and low beta regime. Considering ion temperature effects, it is found that the impact of finite Larmor radius effects significantly reduces the growth rate of the drift-Alfvén wave instability with synergistic effects of high beta stabilization and Landau resonance.

  9. Drift waves in helically symmetric stellarators

    SciTech Connect

    Rafiq, T.; Hegna, C.

    2005-11-15

    The local linear stability of electron drift waves and ion temperature gradient modes (ITG) is investigated in a quasihelically symmetric (QHS) stellarator and a conventional asymmetric (Mirror) stellarator. The geometric details of the different equilibria are emphasized. Eigenvalue equations for the models are derived using the ballooning mode formalism and solved numerically using a standard shooting technique in a fully three-dimensional stellarator configuration. While the eigenfunctions have a similar shape in both magnetic geometries, they are slightly more localized along the field line in the QHS case. The most unstable electron drift modes are strongly localized at the symmetry points (where stellarator symmetry is present) and in the regions where normal curvature is unfavorable and magnitude of the local magnetic shear and magnetic field is minimum. The presence of a large positive local magnetic shear in the bad curvature region is found to be destabilizing. Electron drift modes are found to be more affected by the normal curvature than by the geodesic curvature. The threshold of stability of the ITG modes in terms of {eta}{sub i} is found to be 2/3 in this fluid model consistent with the smallest threshold for toroidal geometry with adiabatic electrons. Optimization to favorable drift wave stability has small field line curvature, short connection lengths, the proper combination of geodesic curvature and local magnetic shear, large values of local magnetic shear, and the compression of flux surfaces in the unfavorable curvature region.

  10. Damping of lower hybrid waves by low-frequency drift waves

    NASA Astrophysics Data System (ADS)

    Krall, Nicholas A.

    1989-11-01

    The conditions under which a spectrum of lower hybrid drift waves will decay into low-frequency drift waves (LFD) are calculated. The purpose is to help understand why lower hybrid drift waves are not seen in all field-reversed configuration (FRC) experiments in which they are predicted. It is concluded that if there is in the plasma a LFD wave amplitude above a critical level, lower hybrid waves will decay into low-frequency drift waves. The critical level required to stabilize TRX-2 [Phys. Fluids 30, 1497 (1987)] is calculated and found to be reasonably consistent with theoretical estimates.

  11. On the drift magnetosonic waves in anisotropic low beta plasmas

    SciTech Connect

    Naim, Hafsa; Bashir, M. F.; Murtaza, G.

    2014-10-15

    A generalized dispersion relation of obliquely propagating drift magnetosonic waves is derived by using the gyrokinetic theory for anisotropic low beta plasmas. The stability analysis applicable to a wide range of plasma parameters is performed to understand the stabilization mechanism of the drift magnetosonic instability and the estimation of the growth rate is also presented. It is noted that the growth rate of the drift instability enhances for small anisotropy (A{sub e,i} = T{sub ⊥e,i}/T{sub ∥e,i} < 1) whereas it is suppressed for large anisotropy (A{sub e,i} > 1)

  12. Strange Attractors in Drift Wave Turbulence

    SciTech Connect

    J.L.V. Lewandowski

    2003-04-25

    A multi-grid part-in-cell algorithm for a shearless slab drift wave model with kinetic electrons is presented. The algorithm, which is based on an exact separation of adiabatic and nonadiabatic electron responses, is used to investigate the presence of strange attractors in drift wave turbulence. Although the simulation model has a large number of degrees of freedom, it is found that the strange attractor is low-dimensional and that it is strongly affected by dissipative (collisional) effects.

  13. Stabilization of the lower hybrid drift instability by resonant electrons

    SciTech Connect

    Chen, Y.; Nevins, W.M.; Birdsall, C.K.

    1981-09-16

    The lower hybrid drift instability was studied with a two dimensional electrostatic simulation code. Simulations showed good agreement of the measured local growth rates and frequencies with the results of local theory during the early stage of wave growth. At later times nonlocal effects become important, and a coherent mode structure develops. This normal mode was observed to propagate up the density gradient. At zero plasma beta and zero electron temperature, we found that the lower hybrid drift instability is stabilized by the local current relaxation due to both ion quasilinear diffusion and electron E x B trapping which causes electron heating to occur.

  14. Drift kinetic Alfvén wave in temperature anisotropic plasma

    SciTech Connect

    Naim, Hafsa Bashir, M. F.; Murtaza, G.

    2014-03-15

    By using the gyrokinetic theory, the kinetic Alfvén waves (KAWs) are discussed to emphasize the drift effects through the density inhomogeneity and the temperature anisotropy on their dispersion characteristics. The dependence of stabilization mechanism of the drift-Alfvén wave instability on the temperature anisotropy is highlighted. The estimate of the growth rate and the threshold condition for a wide range of parameters are also discussed.

  15. Spatiotemporal mode structure of nonlinearly coupled drift wave modes

    SciTech Connect

    Brandt, Christian; Grulke, Olaf; Klinger, Thomas; Negrete, Jose Jr.; Bousselin, Guillaume; Brochard, Frederic; Bonhomme, Gerard; Oldenbuerger, Stella

    2011-11-15

    This paper presents full cross-section measurements of drift waves in the linear magnetized plasma of the Mirabelle device. Drift wave modes are studied in regimes of weakly developed turbulence. The drift wave modes develop azimuthal space-time structures of plasma density, plasma potential, and visible light fluctuations. A fast camera diagnostic is used to record visible light fluctuations of the plasma column in an azimuthal cross section with a temporal resolution of 10 {mu}s corresponding approximately to 10% of the typical drift wave period. Mode coupling and drift wave dispersion are studied by spatiotemporal Fourier decomposition of the camera frames. The observed coupling between modes is compared to calculations of nonlinearly coupled oscillators described by the Kuramoto model.

  16. Dust gravitational drift wave in complex plasma under gravity

    SciTech Connect

    Salahshoor, M. Niknam, A. R.

    2014-12-15

    The dispersion relation of electrostatic waves in a complex plasma under gravity is presented. It is assumed that the waves propagate parallel to the external fields. The effects of weak electric field, neutral drag force, and ion drag force are also taken into account. The dispersion relation is numerically examined in an appropriate parameter space in which the gravity plays the dominant role in the dynamics of microparticles. The numerical results show that, in the low pressure complex plasma under gravity, a low frequency drift wave can be developed in the long wavelength limit. The stability state of this wave is switched at a certain critical wavenumber in such a way that the damped mode is transformed into a growing one. Furthermore, the influence of the external fields on the dispersion properties is analyzed. It is shown that the wave instability is essentially due to the electrostatic streaming of plasma particles. It is also found that by increasing the electric field strength, the stability switching occurs at smaller wavenumbers.

  17. Anomalous phase shifts in drift wave fluctuations

    NASA Astrophysics Data System (ADS)

    Diallo, Ahmed; Skiff, Fred

    2003-10-01

    Ion phase space density fluctuation measurements are performed in a linearly magnetized device using Laser Induced Fluorescence(LIF). An ICP source produces an 8cm diameter plasma column that drifts in a cylindrical vessel whose diameter and length are 40 cm and 3 m, respectively. These experiments are performed using a CW singly ionized Argon plasma that is immersed in a 1kG magnetic field along the axis of the cylinder. A density of the order of 10^9 cm-3 is obtained under a regulated neutral background pressure of 2.× 10-4 torr. The electron and ion temperature are respectively 2 eV and 0.1 eV. LIF is carried out by pumping the Ar II metastable (3d^1)^2G_9/2, using a CW tunable laser centered at 611.6653 nm scanned over 6 GHz, to metastable (4p^1)F_7/2, and then detecting the 460nm photons emitted from its transition to (4s^1)^2F_5/2. This collection is made possible using two low f-umber periscopes that are directed to PMTs. Here we present measurements of the complex two-point correlation function < f(v_i_allel),z_1,ω)f(v_i_allel,z_2,ω)> as a function of the spatial separation of two LIF detection systems Δ d = z_2-z_1, the ion parallel velocity v_i_allel and the frequency ω. Preliminary results show ion particle velocity dependent phase shifts at the drift wave frequency.

  18. Drift laws for spiral waves on curved anisotropic surfaces

    NASA Astrophysics Data System (ADS)

    Dierckx, Hans; Brisard, Evelien; Verschelde, Henri; Panfilov, Alexander V.

    2013-07-01

    Rotating spiral waves organize spatial patterns in chemical, physical, and biological excitable systems. Factors affecting their dynamics, such as spatiotemporal drift, are of great interest for particular applications. Here, we propose a quantitative description for spiral wave dynamics on curved surfaces which shows that for a wide class of systems, including the Belousov-Zhabotinsky reaction and anisotropic cardiac tissue, the Ricci curvature scalar of the surface is the main determinant of spiral wave drift. The theory provides explicit equations for spiral wave drift direction, drift velocity, and the period of rotation. Depending on the parameters, the drift can be directed to the regions of either maximal or minimal Ricci scalar curvature, which was verified by direct numerical simulations.

  19. Drift laws for spiral waves on curved anisotropic surfaces.

    PubMed

    Dierckx, Hans; Brisard, Evelien; Verschelde, Henri; Panfilov, Alexander V

    2013-07-01

    Rotating spiral waves organize spatial patterns in chemical, physical, and biological excitable systems. Factors affecting their dynamics, such as spatiotemporal drift, are of great interest for particular applications. Here, we propose a quantitative description for spiral wave dynamics on curved surfaces which shows that for a wide class of systems, including the Belousov-Zhabotinsky reaction and anisotropic cardiac tissue, the Ricci curvature scalar of the surface is the main determinant of spiral wave drift. The theory provides explicit equations for spiral wave drift direction, drift velocity, and the period of rotation. Depending on the parameters, the drift can be directed to the regions of either maximal or minimal Ricci scalar curvature, which was verified by direct numerical simulations. PMID:23944539

  20. Drift wave instability in the Io plasma torus

    NASA Technical Reports Server (NTRS)

    Huang, T. S.; Hill, T. W.

    1991-01-01

    A linear normal mode analysis of the drift wave instability in the Io plasma torus was carried out on the basis of the Richmond (1973) and Huang et al. (1990) analyses of drift waves in the vicinity of the earth's plasmapause. Results indicate that the outer torus boundary is linearly unstable to the growth of electrostatic drift waves. It is shown that the linear growth rate is proportional to the ion drift frequency and to the ratio of the flux tube charge content to the Jovian ionospheric Pedersen conductance. It is also shown that various theoretical models of global radial transport in Jupiter's atmosphere (including corotating convection, interchange diffusion, and transient flux tube convection) can be understood as plausible nonlinear evolutions of electrostatic drift waves.

  1. Surface acoustic wave stabilized oscillators

    NASA Technical Reports Server (NTRS)

    Parker, T. E.

    1978-01-01

    A number of 401.2 MHz surface acoustic wave (SAW) controlled oscillators were built and tested. The performance of these oscillators was evaluated for possible use as stable oscillators in communication systems. A short term frequency stability of better than 1 x 10 to the minus 9th power for one second was measured for the SAW oscillators. Long term frequency drift was measured and was found to be dependent on SAW design and packaging. Drift rates ranging from 15 ppm in twenty weeks to 2.5 ppm in twenty weeks were observed. Some further improvement was required. The temperature dependence of the saw oscillators was evaluated and it was concluded that some form of temperature compensation will be necessary to meet the requirements of some communication systems.

  2. Surface acoustic wave stabilized oscillators

    NASA Technical Reports Server (NTRS)

    Parker, T. E.; Lee, D. L.; Leja, I.

    1979-01-01

    Four areas of surface acoustic wave (SAW) controlled oscillators were investigated and a number of 401.2 MHz oscillators were constructed that showed improved performance. Aging studies on SAW devices packaged in HC36/U cold weld enclosures produced frequency drifts as low as 0.4 ppm in 35 weeks and drift rates well under 0.5 ppm/year. Temperature compensation circuits have substantially improved oscillator temperature stability, with a deviation of + or - 4 ppm observed over the range -45 C to + 40 C. High efficiency amplifiers were constructed for SAW oscillators and a dc to RF efficiency of 44 percent was obtained for an RF output of 25 mW. Shock and vibration tests were made on four oscillators and all survived 500 G shock pulses unchanged. Only when white noise vibration (20 Hz to 2000 Hz) levels of 20 G's rms were applied did some of the devices fail.

  3. Drift wave instability in a nonuniform quantum dusty magnetoplasma

    SciTech Connect

    Salimullah, M.; Jamil, M.; Zeba, I.; Uzma, Ch.; Shah, H. A.

    2009-03-15

    Using the quantum hydrodynamic model of plasmas and with quantum effects arising through the Bohm potential and the Fermi degenerate pressure, the possible drift waves and their instabilities have been investigated in considerable detail in a nonuniform dusty magnetoplasma. It is found that in the presence of a nonuniform ambient magnetic field, the drift waves grow in amplitude by taking energy from the streaming ions and density inhomogeneity. The implication of the drift wave instability for nonthermal electrostatic fluctuations to laboratory and astrophysical environments is also pointed out.

  4. Drift wave transport scalings introduced by varying correlation length

    SciTech Connect

    Weiland, J.; Holod, I.

    2005-01-01

    Scalings of the correlation length of drift wave turbulence with magnetic current q, shear, elongation, and temperature ratio have been introduced into a drift wave transport model. The correlation length is calculated from linear scaling of the fastest growing mode. Such a procedure is supported by previous turbulence simulations with absorbing boundaries for short and long wavelengths. The resulting q and s scalings are now in better agreement with experimental scalings. In particular, the simulation results for transport barrier shots improve.

  5. Propagations of drift waves in toroidal plasma systems

    SciTech Connect

    Yoshikawa, S.; Cheng, C.Z.

    1990-05-01

    Drift wave patterns in toroidal plasmas are studied. The dispersion relation was simplified to retain both the shear and the toroidal coupling effects. Since the dispersion relation does not depend on the toroidal angle, {phi}, the dispersion is solved in the two- dimensional space made up with minor radius and poloidal angle. The dispersion relation can be reduced into second-order, partial differential equations of a hyperbolic type. The one-dimensional convective mode analysis, which was originated in the 1960's, was extended into the two-dimensional analysis. Depending on the strength of the magnetic shear, one can obtain either the convective or the localized solutions. The results show that the plasma is expected to be unstable for large azimuthal mode number and that the plasma instability tends to be more stabilized for large mass ions. 8 refs., 3 figs., 1 tab.

  6. Interactions between Drift-Wave Microturbulence and the Tearing Mode

    NASA Astrophysics Data System (ADS)

    James, S. D.; Brennan, D. P.; Izacard, O.; Holland, C.

    2014-10-01

    Turbulent dynamics are known to be affected by the presence of a magnetic island. The evolution of a magnetic island is also known to be affected by evolving turbulent fields. Capturing this interaction is a challenging computational problem due to the disparate scales involved. Using a Hasegawa-Wakatani model for the small spatial and temporal scale drift-wave microturbulence and coupling it to Ohm's Law for evolving the larger-scale magnetic island we can capture the dynamics of this interaction self-consistently. We have developed a new code, TURBO, to simulate this system using an equilibrium with prescribed turbulent drives and magnetohydrodynamic stability properties. We present progress toward understanding this interaction via comparisons with analytic predictions for a turbulent resistivity and turbulent viscosity. These two transport coefficients are calculated as integrals over the wave spectrum and the scaling with wave number is investigated. An extension to a five-field model including the ion temperature gradient is also presented. Supported in part by US DOE Grant DE-SC0007851

  7. Growth and stabilization of drift-tearing modes in weakly collisional plasmas

    NASA Astrophysics Data System (ADS)

    Grasso\\ad{a}, D.; Ottaviani, M.; Porcelli\\ad{a}, F.

    2002-09-01

    In the limit where the electron drift-wave frequency exceeds the electron-ion collision frequency, drift-tearing modes are found to grow with a linear growth rate independent of resistivity and proportional to the product of the electron inertial skin depth and the ion sound Larmor radius. The stabilization of these modes in collisionless and semi-collisional regimes is investigated. The stabilization mechanism is related to the coupling and propagation of drift-acoustic perturbations away from the reconnecting mode-rational surface. Analytic and numerical solutions of the four-field reduced fluid model in the slab geometry approximation with constant electron temperature and negligible ion temperature are presented. The actual stability threshold can occur at values of the normalized tearing mode stability parameter Δ' as high as 102.\\pacs{52.35.P}} \\fnm{1}{Permanent address: Istituto Nazionale Fisica della Materia, Department of Energetics, Politecnico di Torino, Italy

  8. On the modulational stability of magnetic structures in electron drift turbulence

    SciTech Connect

    Jucker, Martin; Pavlenko, Vladimir P.

    2007-10-15

    The generation of large-scale magnetic fields in magnetic electron drift mode turbulence is investigated. In particular, the mechanism of modulational instability caused by three-wave interactions is elucidated and the explicit increment is calculated. Also, a stability criterion similar to the known Lighthill criterion is found.

  9. Two-fluid MHD Regime of Drift Wave Instability

    NASA Astrophysics Data System (ADS)

    Yang, Shang-Chuan; Zhu, Ping; Xie, Jin-Lin; Liu, Wan-Dong

    2015-11-01

    Drift wave instabilities contribute to the formation of edge turbulence and zonal flows, and thus are believed to play essential roles in the anomalous transport processes in tokamaks. Whereas drift waves are generally assumed to be local and electrostatic, experiments have often found regimes where the spatial scales and the magnetic components of drift waves approach those of magnetohydrodynamic (MHD) processes. In this work we study such a drift wave regime in a cylindrical magnetized plasma using a full two-fluid MHD model implemented in the NIMROD code. The linear dependency of growth rates on resistivity and the dispersion relation found in the NIMROD calculations qualitatively agree with theoretical analysis. As the azimuthal mode number increases, the drift modes become highly localized radially; however, unlike the conventional local approximation, the radial profile of the drift mode tends to shift toward the edge away from the center of the density gradient slope, suggesting the inhomogeneity of two-fluid effects. Supported by National Natural Science Foundation of China Grant 11275200 and National Magnetic Confinement Fusion Science Program of China Grant 2014GB124002.

  10. Antenna excitation of drift wave in a toroidal plasma

    SciTech Connect

    Diallo, A.; Ricci, P.; Fasoli, A.; Furno, I.; Labit, B.; Mueller, S. H.; Podesta, M.; Poli, F. M.; Skiff, F.

    2007-10-15

    In a magnetized toroidal plasma, an antenna tunable in vertical wave number is used to excite density perturbations. Coherent detection is performed by means of Langmuir probes to directly determine both the wave vector and the plasma response induced by the antenna. Comparison between the theoretical density response predicted by the generalized Hasegawa-Wakatani model, and the experimentally determined density response enables us the identification of one peak of the plasma response as a drift wave.

  11. Drift and ion acoustic wave driven vortices with superthermal electrons

    SciTech Connect

    Ali Shan, S.; Haque, Q.

    2012-08-15

    Linear and nonlinear analysis of coupled drift and acoustic mode is presented in an inhomogeneous electron-ion plasma with {kappa}-distributed electrons. A linear dispersion relation is found which shows that the phase speed of both the drift wave and the ion acoustic wave decreases in the presence of superthermal electrons. Several limiting cases are also discussed. In the nonlinear regime, stationary solutions in the form of dipolar and monopolar vortices are obtained. It is shown that the condition for the boundedness of the solution implies that the speed of drift wave driven vortices reduces with increase in superthermality effect. Ignoring density inhomogeniety, it is investigated that the lower and upper limits on the speed of the ion acoustic driven vortices spread with the inclusion of high energy electrons. The importance of results with reference to space plasmas is also pointed out.

  12. Spatiotemporal synchronization of drift waves in a magnetron sputtering plasma

    SciTech Connect

    Martines, E.; Zuin, M.; Cavazzana, R.; Antoni, V.; Serianni, G.; Spolaore, M.; Vianello, N.; Adámek, J.

    2014-10-15

    A feedforward scheme is applied for drift waves control in a magnetized magnetron sputtering plasma. A system of driven electrodes collecting electron current in a limited region of the explored plasma is used to interact with unstable drift waves. Drift waves actually appear as electrostatic modes characterized by discrete wavelengths of the order of few centimeters and frequencies of about 100 kHz. The effect of external quasi-periodic, both in time and space, travelling perturbations is studied. Particular emphasis is given to the role played by the phase relation between the natural and the imposed fluctuations. It is observed that it is possible by means of localized electrodes, collecting currents which are negligible with respect to those flowing in the plasma, to transfer energy to one single mode and to reduce that associated to the others. Due to the weakness of the external action, only partial control has been achieved.

  13. Route to Drift Wave Chaos and Turbulence in a Bounded Low-{beta} Plasma Experiment

    SciTech Connect

    Klinger, T.; Latten, A.; Piel, A.; Bonhomme, G.; Pierre, T.; Dudok de Wit, T.

    1997-11-01

    The transition scenario from stability to drift wave turbulence is experimentally investigated in a magnetized low-{beta} plasma with cylindrical geometry. It is demonstrated that the temporal dynamics is determined by the interaction and destabilization of spatiotemporal patterns, in particular, traveling waves. The analysis of the temporal and the spatiotemporal data shows that the bifurcations sequence towards weakly developed turbulence follows the Ruelle-Takens scenario. {copyright} {ital 1997} {ital The American Physical Society}

  14. Scroll wave drift along steps, troughs, and corners

    NASA Astrophysics Data System (ADS)

    Ke, Hua; Zhang, Zhihui; Steinbock, Oliver

    2015-06-01

    Three-dimensional excitable systems can create nonlinear scroll waves that rotate around one-dimensional phase singularities. Recent theoretical work predicts that these filaments drift along step-like height variations. Here, we test this prediction using experiments with thin layers of the Belousov-Zhabotinsky reaction. We observe that over short distances scroll waves are attracted towards the step and then rapidly commence a steady drift along the step line. The translating filaments always reside on the shallow side of the step near the edge. Accordingly, filaments in the deep domain initially collide with and shorten at the step wall. The drift speeds obey the predicted proportional dependence on the logarithm of the height ratio and the direction depends on the vortex chirality. We also observe drift along the perimeter of rectangular plateaus and find that the filaments perform sharp turns at the corners. In addition, we investigate rectangular troughs for which vortices of equal chirality can drift in different directions. The latter two effects are reproduced in numerical simulations with the Barkley model. The simulations show that narrow troughs instigate scroll wave encounters that induce repulsive interaction and symmetry breaking. Similar phenomena could exist in the geometrically complicated ventricles of the human heart where reentrant vortex waves cause tachycardia and fibrillation.

  15. Nonlinear interaction of drift waves with driven plasma currents

    SciTech Connect

    Brandt, Christian; Grulke, Olaf; Klinger, Thomas

    2010-03-15

    In a cylindrical magnetized plasma, coherent drift wave modes are synchronized by a mode selective drive of plasma currents. Nonlinear effects of the synchronization are investigated in detail. Frequency pulling is observed over a certain frequency range. The dependence of the width of this synchronization range on the amplitude of the driven plasma currents forms Arnold tongues. The transition between complete and incomplete synchronization is indicated by the onset of periodic pulling and phase slippage. Synchronization is observed for driven current amplitudes, which are some percent of the typical value of parallel currents generated by drift waves.

  16. Numerical experiments on the drift wave-zonal flow paradigm for nonlinear saturation

    SciTech Connect

    Waltz, R. E.; Holland, C.

    2008-12-15

    This paper confirms that ExB shearing from toroidally symmetric (toroidal mode number n=0) 'radial modes' provides the dominant nonlinear saturation mechanism for drift wave (n{ne}0) turbulence, which in turn nonlinearly drives the modes. In common usage, this is loosely referred to as the 'drift wave-zonal flow paradigm' for nonlinear saturation despite the fact that radial modes have several components distinguished in this paper: a residual or zero mean frequency 'zonal flow' part and an oscillatory 'geodesic acoustic mode' (GAM) part. Linearly, the zonal flows (and GAMs) are weakly damped only by ion-ion collisions, while the GAMs are strongly Landau damped only at low safety factor q. At high q the Hinton-Rosenbluth residual flow from an impulse vanishes and only the weakly damped GAMs remain. With the linear physics and driving rates of the finite-n transport modes unchanged, this paper argues that GAMs are only somewhat less effective than the residual zonal flows in providing the nonlinear saturation, and in some cases ExB shearing from GAMs (or at least the GAM physics) appears to dominate: transport appears to be nearly linear in the GAM frequency. By deleting the drift wave-drift wave nonlinear coupling, it is found that drift wave-radial mode nonlinear coupling triads account for most of the nonlinear saturation. Furthermore, the ExB shear components of the radial modes nonlinearly stabilize the finite-n modes, while the diamagnetic components nonlinearly destabilize them. Finally, from wave number spectral contour plots of the time average nonlinear entropy transfer function (and rates), it is shown that the peak in entropy generation coincides with the peak in transport production, while entropy dissipation (like Landau damping) is spread equally over all n modes (including n=0). Most of these conclusions appear to hold about equally well for all types of drift wave turbulence.

  17. Drift induced by repeated hydropeaking waves in controlled conditions

    NASA Astrophysics Data System (ADS)

    Maiolini, Bruno; Bruno, M. Cristina; Biffi, Sofia; Cashman, Matthew J.

    2014-05-01

    Repeated hydropeaking events characterize most alpine rivers downstream of power plants fed by high elevation reservoirs. The effects of hydropeaking on the benthic communities are well known, and usually each hydropeaking wave causes an increase in tractive force and changes in temperature and water quality. Simulations of hydropeaking in artificial system can help to disentangle the direct effects of the modified flow regime from impacts associated with other associated physio-chemical changes, and with the effects of river regulation and land-use changes that often accompany water resource development. In September 2013 we conducted a set of controlled simulations in five steel flumes fed by an Alpine stream (Fersina stream, Adige River catchment, Trentino, Italy), where benthic invertebrates can freely colonize the flumes. One flume was used as control with no change in flow, in the other four flumes we simulated an hydropeaking wave lasting six hours, and repeated for five consecutive days. Flow was increased by twice baseflow in two flumes, and three times in the other two. We collected benthic samples before the beginning (morning of day 1) and after the end (afternoon of day 5) of the set of simulations to evaluate changes in the benthic communities due to induced drift migration. During each simulation, we collected drifting organisms at short time intervals to assess the responses to: 1) the initial discharge increase, 2) the persistence of high flows for several hours; 3) the decrease of discharge to the baseflow; 4) the change in drift with each successive day. Preliminary results indicate typical strong increases of catastrophic drift on the onset of each simulated hydropeaking, drift responses proportional to the absolute discharge increase, a decrease in the drift responses over successive days. Different taxa responded with different patterns: taxa which resist tractive force increased in drift only during the periods of baseflow that follow the

  18. Stabilization of the lower-hybrid drift instability by resonant electrons

    SciTech Connect

    Chen, Y.; Nevins, W.M.; Birdsall, C.K.

    1983-09-01

    The lower-hybrid drift instability is studied with a two-dimensional electrostatic simulation code. Simulations show good agreement of the measured local growth rates and frequencies with the results of local theory during the early stage of wave growth. At later times nonlocal effects become important, and a coherent mode structure develops. This normal mode is observed to propagate up the density gradient. At zero plasma beta and zero electron temperature, it is found that the lower-hybrid drift instability is stabilized by the local current relaxation due to both ion quasilinear diffusion and electron E x B trapping which causes electron heating to occur.

  19. Impacts of wave spreading and multidirectional waves on estimating Stokes drift

    NASA Astrophysics Data System (ADS)

    Webb, A.; Fox-Kemper, B.

    2015-12-01

    The Stokes drift, and its leading-order approximation, for a random sea depend upon the interaction of different wave groups and the process of wave spreading. Here Stokes drift direction and magnitude from prescribed spectra, local observational buoy data, and global model WAVEWATCH III output are used to analyze approximations of Stokes drift for directional random seas in deep water. To facilitate analysis, a new approximation is defined to incorporate the systematic effects of wave spreading. Stokes drift is typically overestimated by ignoring these effects or by ignoring directional differences in swell and wind seas. These two errors are differentiated and found to be largely uncorrelated. These errors depend strongly on depth, with deeper Stokes drift favoring narrow-banded swell and shallower Stokes drift favoring wind seas. Results are consistent among the data examined. Mean Stokes drift magnitude reductions from wave spreading and multidirectional wave effects alone are 14-20% and 7-23% respectively, giving a combined reduction of 20-40% versus unidirectional waves, depending on wave age and depth. Approximations that do not include these reductions however, will on average overestimate Stokes drift by 16-26%, 26-43%, and 45-71% respectively. In addition to magnitude, the direction of Stokes drift is also affected and multidirectional waves generate a directional veer with depth: the 30/60/90% confidence intervals are bounded (approximately) by ± 0.12/0.28/0.84 radians (± 7/16/48 deg) at the surface, with smaller intervals at depth. Complementary depth-integrated approximations are also investigated and directional effects are similar with depth-dependent subsurface results. Furthermore, an optimized directional spread correction for the surface is nearly identical for global simulations and a buoy located at Ocean Weather Station P (50°N 145°W), and does not require directional wave spectrum data.

  20. Drift waves and vortices: a dynamical point vortex model

    NASA Astrophysics Data System (ADS)

    Leoncini, Xavier; Verga, Alberto

    2013-10-01

    Interactions of localized vortices with drift waves are investigated using a model of point vortices in the presence of a transverse or longitudinal wave. This simple model shows a rich dynamical behavior including oscillations of a dipole, splitting and merging of two like-circulation vortices, and chaos. The analytical and numerical results of this model have been found to predict under certain conditions, the behavior of more complex systems, such as the vortices of the Charney-Hasegawa-Mima equation, where the presence of waves strongly affects the evolution of large coherent structures.

  1. Drift prediction for a roll-stabilized inertial measurement system

    SciTech Connect

    Bateman, V.I.

    1983-01-01

    A roll-stabilized inertial measurement system is being developed by Sandia National Laboratories. This system will measure three orthogonal-body angular rates and three orthogonal-body accelerations and will calculate three Euler angles for attitude control of small rocket systems and/or large rocket payloads in flight. An analysis of the predicted drift in the Euler angles has been undertaken to aid in the definition of computational hardware characteristics (such as gyro resolution and gyro sample frequency) and to assess the performance of the system over typical trajectories. The method of analysis uses two different techniques to calculate Euler angles and to compare the results. The first technique results in a true Euler angle which is calculated by a Bortz equation (a method to relate vehicle body coordinates to earth coordinates). The second technique simulates the in-flight calculations by including effects of drift from the truncated Bortz algorithm, quantization, and random gyro drift. The comparison results in drift as a function of time for the three Euler angles, roll, pitch, and yaw. Examples of predicted drift over typical trajectories are presented.

  2. Drift waves and chaos in a LAPTAG plasma physics experiment

    NASA Astrophysics Data System (ADS)

    Gekelman, Walter; Pribyl, Patrick; Birge-Lee, Henry; Wise, Joe; Katz, Cami; Wolman, Ben; Baker, Bob; Marmie, Ken; Patankar, Vedang; Bridges, Gabriel; Buckley-Bonanno, Samuel; Buckley, Susan; Ge, Andrew; Thomas, Sam

    2016-02-01

    In a project involving an alliance between universities and high schools, a magnetized plasma column with a steep pressure gradient was established in an experimental device. A two-dimensional probe measured fluctuations in the plasma column in a plane transverse to the background magnetic field. Correlation techniques determined that the fluctuations were that of electrostatic drift waves. The time series data were used to generate the Bandt-Pompe entropy and Jensen-Shannon complexity for the data. These quantities, when plotted against one another, revealed that a combination of drift waves and other background fluctuations were a deterministically chaotic system. Our analysis can be used to tell the difference between deterministic chaos and random noise, making it a potentially useful technique in nonlinear dynamics.

  3. Shock drift acceleration in the presence of waves

    NASA Technical Reports Server (NTRS)

    Decker, R. B.; Vlahos, L.

    1985-01-01

    Attention is given to the initial results of a model designed to study the modification of the scatter-free, shock drift acceleration of energetic test particles by wave activity in the vicinity of a quasi-perpendicular, fast-mode MHD shock. It is emphasized that the concept of magnetic moment conservation is a valid approximation only in the perpendicular and nearly perpendicular regimes, when the angle theta-Bn between the shock normal and the upstream magnetic field vector is in the range from 70 deg to 90 deg. The present investigation is concerned with one step in a program which is being developed to combine the shock drift and diffusive processes at a shock of arbitrary theta-Bn.

  4. Drift-Wave Instabilities and Transport in Non - Tokamak Geometry

    NASA Astrophysics Data System (ADS)

    Hua, Daniel Duc

    Motivated by experimental scaling laws that suggest an improvement in the confinement time of fusion plasmas in tokamaks with elongated cross section, we search theoretically for favorable dependence on elongation for drift-wave instabilities, which may be responsible for anomalous transport in tokamaks. First, using thermodynamic methods, we derive upper bounds on thermal diffusivities for drift-wave instabilities in tokamaks but find no elongation dependence to lowest order. Also, compared with experimentally inferred ion thermal diffusivities from the DIIID tokamak, the thermodynamic bounds are as much as 100 times bigger in the plasma core. Second, utilizing a simulation code to calculate linear growth rates, we obtain mixing-length estimates of ion thermal diffusivities for a specific drift wave, the ion-temperature-gradient (ITG) mode, which becomes unstable only if the temperature gradient exceeds a finite threshold value (whereas the thermodynamic constraints allow instability for any value). We find that the simulation growth rates and the diffusivities estimated from them do decrease for increasing elongation, due to finite Larmor radius effects (which do not explicitly appear in the thermodynamic constraints). Compared with the experimentally inferred diffusivities, the simulation diffusivities are similar near the edge but are 10 times bigger in the core. However, a small adjustment in the temperature profile, within experimental and theoretical uncertainties, would produce good agreement everywhere. Therefore, we suggest that for the DIIID experiments studied, the plasma is actually very close to the ITG instability threshold in the core and farther away from threshold near the edge, but not far enough to induce the full thermodynamic level of diffusivities. This conjecture is supported by model transport calculations that reproduce the experimental diffusivity profile fairly well.

  5. Large-scale drift and Rossby wave turbulence

    NASA Astrophysics Data System (ADS)

    Harper, K. L.; Nazarenko, S. V.

    2016-08-01

    We study drift/Rossby wave turbulence described by the large-scale limit of the Charney–Hasegawa–Mima equation. We define the zonal and meridional regions as Z:= \\{{k} :| {k}y| \\gt \\sqrt{3}{k}x\\} and M:= \\{{k} :| {k}y| \\lt \\sqrt{3}{k}x\\} respectively, where {k}=({k}x,{k}y) is in a plane perpendicular to the magnetic field such that k x is along the isopycnals and k y is along the plasma density gradient. We prove that the only types of resonant triads allowed are M≤ftrightarrow M+Z and Z≤ftrightarrow Z+Z. Therefore, if the spectrum of weak large-scale drift/Rossby turbulence is initially in Z it will remain in Z indefinitely. We present a generalised Fjørtoft’s argument to find transfer directions for the quadratic invariants in the two-dimensional {k}-space. Using direct numerical simulations, we test and confirm our theoretical predictions for weak large-scale drift/Rossby turbulence, and establish qualitative differences with cases when turbulence is strong. We demonstrate that the qualitative features of the large-scale limit survive when the typical turbulent scale is only moderately greater than the Larmor/Rossby radius.

  6. Integrated Study of the Nonlinear Dynamics of Collisional Drift Wave Turbulence

    SciTech Connect

    George R. Tynan

    2012-04-24

    An existing linear magnetized plasma device, the Controlled Shear Decorrelation experiment (CSDX) was used to study the transition from a state of coherent wave like activity to a state of turbulent activity using the magnetic field and thus magnetization of the plasma as the control parameter. The results show the onset of coherent drift waves consistent with linear stability analysis. As the magnetization is raised, at first multiple harmonics appear, consistent with wave steepening. This period is then followed by the beginning of nonlinear interactions between different wave modes, which then results in the formation of narrow frequency but distributed azimuthal wave number fluctuations that are consistent with the formation of long-lived coherent nonlinear structures within the plasmas. These structures, termed quasicoherent modes, persist as the magnetic field is raised. Measurements of turbulent momentum flux indicate that the plasma is also forming an azimuthally symmetric radially sheared fluid flow that is nonlinearly driven by smaller scaled turbulent fluctuations. Further increases in the magnetic field result in the breakup of the quasicoherent mode, and the clear formation of the sheared flow. Numerical simulations of the experiment reproduce the formation of the sheared flow via a vortex merging process, and confirm that the experiment is providing the first clear experimental evidence of the formation of sheared zonal flows from drift turbulent fluctuations in a magnetized plasma.

  7. Drift stabilizer for reciprocating free-piston devices

    DOEpatents

    Ward, William C.; Corey, John A.; Swift, Gregory W.

    2003-05-20

    A free-piston device has a stabilized piston drift. A piston having a frequency of reciprocation over a stroke length and with first and second sides facing first and second variable volumes, respectively, for containing a working fluid defining an acoustic wavelength at the frequency of reciprocation. A bypass tube waveguide connects the first and second variable volumes at all times during reciprocation of the piston. The waveguide has a relatively low impedance for steady flow and a relatively high impedance for oscillating flow at the frequency of reciprocation of the piston, so that steady flow returns fluid leakage from about the piston between the first and second volumes while oscillating flow is not diverted through the waveguide. Thus, net leakage about the piston is returned during each stroke of the piston while oscillating leakage is not allowed and pressure buildup on either the first or second side of the piston is avoided to provide a stable piston location.

  8. Drift-wave fluctuation in an inviscid tokamak plasma

    NASA Astrophysics Data System (ADS)

    Yang, Jian-Rong; Mao, Jie-Jian; Tang, Xiao-Yan

    2013-11-01

    In order to describe the characterization of resistive drift-wave fluctuation in a tokamak plasma, a coupled inviscid two-dimensional Hasegawa—Wakatani model is investigated. Two groups of new analytic solutions with and without phase shift between the fluctuant density and the fluctuant potential are obtained by using the special function transformation method. It is demonstrated that the fluctuant potential shares similar spatio—temporal variations with the density. It is found from the solutions without phase shift that the effect of the diffusion and adiabaticity on the fluctuant density is quite complex, and that the fluctuation may be controlled through the adiabaticity and diffusion. By using the typical parameters in the quasi-adiabatic regime in the solutions with phase shift, it is shown that the density gradient becomes larger as the contours become dense toward the plasma edge and the contours have irregular structures, which reveal the nonuniform distribution in the tokamak edge.

  9. Drift-wave transport in the velocity shear layer

    NASA Astrophysics Data System (ADS)

    Rosalem, K. C.; Roberto, M.; Caldas, I. L.

    2016-07-01

    Particle drift driven by electrostatic wave fluctuations is numerically computed to describe the transport in a gradient velocity layer at the tokamak plasma edge. We consider an equilibrium plasma in large aspect ratio approximation with E × B flow and specified toroidal plasma velocity, electric field, and magnetic field profiles. A symplectic map, previously derived for infinite coherent time modes, is used to describe the transport dependence on the electric, magnetic, and plasma velocity shears. We also show that resonant perturbations and their correspondent islands in the Poincaré maps are much affected by the toroidal velocity profiles. Moreover, shearless transport barriers, identified by extremum values of the perturbed rotation number profiles of the invariant curves, allow chaotic trajectories trapped into the plasma. We investigate the influence of the toroidal plasma velocity profile on these shearless transport barriers.

  10. Impact of ion diamagnetic drift on ideal ballooning mode stability in rotating tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Aiba, N.

    2016-04-01

    Drift magnetohydrodynamic (MHD) equations have been derived in order to investigate the ion diamagnetic drift effect on the stability to ideal MHD modes in rotating plasmas. These drift MHD equations have been simplified with the Frieman-Rotenberg formalism under the incompressible assumption, and a new code, MINERVA-DI, has been developed to solve the derived extended Frieman-Rotenberg equation. Benchmark results of the MINERVA-DI code show good agreements with the analytic theory discussing the stability to an internal kink mode and that to a ballooning mode in static plasmas. The stability analyses of the ballooning mode with respect to toroidal rotation with the ion diamagnetic drift effect have been performed using MINERVA-DI. The stabilizing effect by the ion diamagnetic drift is found to be negligible when the rotation frequency is large compared to the ion diamagnetic drift frequency. The direction of plasma rotation affects the ballooning mode stability when the ion diamagnetic drift effect is taken into account. It is identified that there are two physics mechanisms responsible for the dependence of MHD stability on the rotation direction. One is the correction of the dynamic pressure effect on MHD stability by the ion diamagnetic drift, and the other is the change of the MHD eigenmode structure by the combined effect of plasma rotation and ion diamagnetic drift.

  11. Simulating the coupled evolution of drift-wave turbulence and the tearing mode

    NASA Astrophysics Data System (ADS)

    James, S. D.; Brennan, D. P.; Izacard, O.; Holland, C.

    2015-11-01

    Numerical simulations of turbulence and MHD instabilities such as the tearing mode can be computationally expensive and only recently have simulations begun to address their coupled, self-consistent interactions. The disparate scales involved in simulating the coupled evolution of small-scale turbulence and the larger-scale tearing mode make this a challenging numerical problem. Using the newly developed code, TURBO, we have performed nonlinear simulations of Hasegawa-Wakatani drift-wave turbulence coupled to Ohm's law. An equilibrium with prescribed stability properties and turbulent drives is used to examine the impact of drift-wave turbulence on the stability of the tearing mode and the energy transport between them in the context of a turbulent resistivity and turbulent viscosity. We find that the spatial structure of the density flux and these transport coefficients are asymmetric in the poloidal direction and peaked away from the X-point in the presence of an island in a poloidal flow. Similar effects are seen in simulations of ITG turbulence in the presence of a magnetic island and we discuss the connections to our work. Supported by US DOE Grant DE-SC0007851.

  12. Physical mechanism behind zonal-flow generation in drift-wave turbulence.

    PubMed

    Manz, P; Ramisch, M; Stroth, U

    2009-10-16

    The energetic interaction between drift-wave turbulence and zonal flows is studied experimentally in two-dimensional wave number space. The kinetic energy is found to be transferred nonlocally from the drift waves to the zonal flow. This confirms the theoretical prediction that the parametric-modulational instability is the driving mechanism of zonal flows. The physical mechanism of this nonlocal energetic interaction between and zonal flows and turbulent drift-wave eddies in relation to the suppression of turbulent transport is discussed. PMID:19905704

  13. Electrostatic Drift-Wave Instability in Field-Reversed Configuration

    NASA Astrophysics Data System (ADS)

    Lau, Calvin; Fulton, Daniel; Holod, Ihor; Lin, Zhihong; Binderbauer, Michl; Tajima, Toshiki; Schmitz, Lothar

    2015-11-01

    Recent progress in the C-2 advanced beam-driven field-reversed configuration (FRC) experiment [Binderbauer 2015] at Tri Alpha Energy has led to consistently reproducible plasma lifetimes of 5+ ms, ie. transport regimes. To understand the mechanisms, gyrokinetic particle-in-cell simulations of drift-wave instabilities have been carried out for the FRC [Fulton 2015]. The realistic magnetic geometry is represented in Boozer coordinates in the upgraded gyrokinetic toroidal code (GTC) [Lin 1998]. Radially local simulations find that, in the FRC core, ion scale modes are stable for realistic pressure gradients while the electron scale modes are unstable. On the other hand, in the scrape-off layer (SOL) outside of the separatrix, both ion and electron scale modes are unstable. These findings and linear instability thresholds found in simulation are consistent with the C-2 experimental measurements of density fluctuations [Schmitz 2015]. Collisional effects and instability drive mechanism will be clarified. Nonlocal and nonlinear simulation results will also be reported. supported by TAE.

  14. Rescaling effects on a low-frequency drift wave in dusty plasmas

    NASA Astrophysics Data System (ADS)

    Qiu, Xin; Liu, Sanqiu

    2015-03-01

    The effect of dust on the low-frequency drift wave in inhomogeneous magnetized dusty plasmas is investigated. It is shown that a low-frequency drift wave can be modeled by the Hasegawa-Mima equation (HME) both in mobile and immobile dusty plasmas, which are dust-modified HME and HME in dusty background, respectively. The former is rescaled significantly by the presence of the dust and the space-time scale greatly increases with the increasing density and mass of dust, while the latter is not rescaled, but an additional driving force appears to drive the drift waves.

  15. Spatial localization of resistive drift wave structure in tokamak edge plasmas with an embedded magnetic island

    SciTech Connect

    Hu, Shilin; Qu, Hongpeng; Li, Jiquan; Kishimoto, Y.

    2014-10-15

    Resistive drift wave instability is investigated numerically in tokamak edge plasma confined by sheared slab magnetic field geometry with an embedded magnetic island. The focus is on the structural characteristics of eigenmode inside the island, where the density profile tends to be flattened. A transition of the dominant eigenmode occurs around a critical island width w{sub c}. For thin islands with a width below w{sub c}, two global long wavelength eigenmodes with approximately the same growth rate but different eigenfrequency are excited, which are stabilized by the magnetic island through two-dimensional mode coupling in both x and y (corresponding to radial and poloidal in tokamak) directions. On the other hand, a short wavelength eigenmode, which is destabilized by thick islands with a width above w{sub c}, dominates the edge fluctuation, showing a prominent structural localization in the region between the X-point and the O-point of the magnetic island. The main destabilization mechanism is identified as the mode coupling in the y direction, which is similar to the so-called toroidal coupling in tokamak plasmas. These three eigenmodes may coexist in the drift wave fluctuation for the island with a width around w{sub c}. It is demonstrated that the structural localization results mainly from the quasilinear flattening of density profile inside the magnetic island.

  16. Linear study of the nonmodal growth of drift waves in dusty plasmas

    SciTech Connect

    Manz, P.; Greiner, F.

    2010-06-15

    The main effect of dust on drift wave turbulence is the enhancement of the nonadiabaticity. Previous work found that nonmodal behavior is important in the nonadiabatic regime of the drift wave system. Here, the modal and nonmodal properties of the linear Hasegawa-Wakatani system of dusty plasmas are investigated. The non-normality of the linear evolution operator can lead to enhanced transient growth rates compared to the modal growth rates.

  17. Streamers generation by small-scale drift-Alfvén waves

    SciTech Connect

    Zhao, J. S.; Yu, M. Y.

    2014-10-15

    Excitation of streamers by modulationally unstable small-scale drift-Alfvén wave (SSDAW) is investigated. It is found that the excitation depends strongly on the propagation direction of the SSDAW, and the ion and electron diamagnetic drift waves are both unstable due to the generation of streamers. It is also shown that zonal flows can be effectively excited by the SSDAW with the propagation direction different from that for streamer excitation.

  18. Drift ion acoustic shock waves in an inhomogeneous two-dimensional quantum magnetoplasma

    SciTech Connect

    Masood, W.; Siddiq, M.; Karim, S.; Shah, H. A.

    2009-04-15

    Linear and nonlinear propagation characteristics of drift ion acoustic waves are investigated in an inhomogeneous quantum plasma with neutrals in the background employing the quantum hydrodynamics (QHD) model. In this regard, a quantum Kadomtsev-Petviashvili-Burgers (KPB) equation is derived for the first time. It is shown that the ion acoustic wave couples with the drift wave if the parallel motion of ions is taken into account. Discrepancies in the earlier works on drift solitons and shocks in inhomogeneous plasmas are also pointed out and a correct theoretical framework is presented to study the one-dimensional as well as the two-dimensional propagation of shock waves in an inhomogeneous quantum plasma. Furthermore, the solution of KPB equation is presented using the tangent hyperbolic (tanh) method. The variation of the shock profile with the quantum Bohm potential, collision frequency, and ratio of drift to shock velocity in the comoving frame, v{sub *}/u, are also investigated. It is found that increasing the number density and collision frequency enhances the strength of the shock. It is also shown that the fast drift shock (i.e., v{sub *}/u>0) increases, whereas the slow drift shock (i.e., v{sub *}/u<0) decreases the strength of the shock. The relevance of the present investigation with regard to dense astrophysical environments is also pointed out.

  19. Nonlinear Drift-Kinetic Equation in the Presence of a Circularly Polarized Wave

    NASA Technical Reports Server (NTRS)

    Khazanov, G. V.; Krivorutsky, E. N.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Equations of the single particle motion and nonlinear kinetic equation for plasma in the presence of a circularly polarized wave of arbitrary frequency in the drift approximation are presented. The nonstationarity and inhomogeneity of the plasma-wave system are taken into account.

  20. Nonlinear Drift-Kinetic Equation in the Presence of a Circularly Polarized Wave

    NASA Technical Reports Server (NTRS)

    Khazanov, G. V.; Krivorutsky, E. N.; Six, N. Frank (Technical Monitor)

    2002-01-01

    Equations of the single particle motion and nonlinear kinetic equation for plasma in the presence of a circularly polarized wave of arbitrary frequency in the drift approximation are presented. The nonstationarity and inhomogeneity of the plasma-wave system are taken into account. The time dependent part of the ponderomotive force is discussed.

  1. A Computer Simulation Study of Anatomy Induced Drift of Spiral Waves in the Human Atrium

    PubMed Central

    Kharche, Sanjay R.; Biktasheva, Irina V.; Seemann, Gunnar; Zhang, Henggui; Biktashev, Vadim N.

    2015-01-01

    The interaction of spiral waves of excitation with atrial anatomy remains unclear. This simulation study isolates the role of atrial anatomical structures on spiral wave spontaneous drift in the human atrium. We implemented realistic and idealised 3D human atria models to investigate the functional impact of anatomical structures on the long-term (∼40 s) behaviour of spiral waves. The drift of a spiral wave was quantified by tracing its tip trajectory, which was correlated to atrial anatomical features. The interaction of spiral waves with the following idealised geometries was investigated: (a) a wedge-like structure with a continuously varying atrial wall thickness; (b) a ridge-like structure with a sudden change in atrial wall thickness; (c) multiple bridge-like structures consisting of a bridge connected to the atrial wall. Spiral waves drifted from thicker to thinner regions and along ridge-like structures. Breakthrough patterns caused by pectinate muscles (PM) bridges were also observed, albeit infrequently. Apparent anchoring close to PM-atrial wall junctions was observed. These observations were similar in both the realistic and the idealised models. We conclude that spatially altering atrial wall thickness is a significant cause of drift of spiral waves. PM bridges cause breakthrough patterns and induce transient anchoring of spiral waves. PMID:26587545

  2. Instability of Drift Waves in Two-Component Solid-State Plasma

    SciTech Connect

    Bulgakov, A.A.; Shramkova, O.V.

    2005-09-15

    The instabilities of longitudinal waves in infinite semiconductor plasma containing charge carriers of two types are considered under the assumption that the thermal velocity of electrons slightly exceeds that of holes. The main result of this study is that instability can occur in intrinsic semiconductors if the electron drift velocity is lower than the thermal velocity. Drift wave instabilities are studied in intrinsic semiconductors and semiconductors with identical plasma frequencies of electrons and holes. The influence of dissipation on the instability of these waves is also considered.

  3. Linear and nonlinear coupled drift and ion acoustic waves in collisional pair ion-electron magnetoplasma

    SciTech Connect

    Mushtaq, A.; Saeed, R.; Haque, Q.

    2011-04-15

    Linear and nonlinear coupled electrostatic drift and ion acoustic waves are studied in inhomogeneous, collisional pair ion-electron plasma. The Korteweg-de Vries-Burgers (KdVB) equation for a medium where both dispersion and dissipation are present is derived. An attempt is made to obtain exact solution of KdVB equation by using modified tanh-coth method for arbitrary velocity of nonlinear drift wave. Another exact solution for KdVB is obtained, which gives a structure of shock wave. Korteweg-de Vries (KdV) and Burgers equations are derived in limiting cases with solitary and monotonic shock solutions, respectively. Effects of species density, magnetic field, obliqueness, and the acoustic to drift velocity ratio on the solitary and shock solutions are investigated. The results discussed are useful in understanding of low frequency electrostatic waves at laboratory pair ion plasmas.

  4. Observation of drift compressional waves with a mid-latitude decameter coherent radar

    NASA Astrophysics Data System (ADS)

    Chelpanov, Maksim; Mager, Pavel; Klimushkin, Dmitriy; Berngardt, Oleg; Mager, Olga

    2016-06-01

    Magnetospheric Pc5 pulsations observed on December 26, 2014 are analyzed. They were recorded in the nightside magnetosphere with a mid-latitude coherent decameter radar located near Ekaterinburg. It registers velocity variations in electric drift of ionospheric plasma caused by ULF waves in the magnetosphere. The westward direction of azimuthal propagation of wave coincides with the direction of magnetic drift of protons. A cross-wavelet analysis reveals that the frequency of oscillations depends on the wave number m, and the correlation between them is 0.90. The frequency increase from 2.5 to 5 mHz was followed by an increase in the absolute value m from 20 to 80. These features of the wave under study testify that it should be classified as a drift compressional mode which is typical for the ULF mode in kinetics. Existence conditions for it are the terminal pressure of plasma and its inhomogeneity across magnetic shells.

  5. Up-gradient particle flux in a drift wave-zonal flow system

    SciTech Connect

    Cui, L.; Tynan, G. R.; Thakur, S. C.; Diamond, P. H.; Brandt, C.

    2015-05-15

    We report a net inward, up-gradient turbulent particle flux in a cylindrical plasma when collisional drift waves generate a sufficiently strong sheared azimuthal flow that drives positive (negative) density fluctuations up (down) the background density gradient, resulting in a steepening of the mean density gradient. The results show the existence of a saturation mechanism for drift-turbulence driven sheared flows that can cause up-gradient particle transport and density profile steepening.

  6. Cancellation of drift kinetic effects between thermal and energetic particles on the resistive wall mode stabilization

    NASA Astrophysics Data System (ADS)

    Guo, S. C.; Liu, Y. Q.; Xu, X. Y.; Wang, Z. R.

    2016-07-01

    Drift kinetic stabilization of the resistive wall mode (RWM) is computationally investigated using MHD-kinetic hybrid code MARS-K following the non-perturbative approach (Liu et al 2008 Phys. Plasmas 15 112503), for both reversed field pinch (RFP) and tokamak plasmas. Toroidal precessional drift resonance effects from trapped energetic ions (EIs) and various kinetic resonances between the mode and the guiding center drift motions of thermal particles are included into the self-consistent toroidal computations. The results show cancellation effects of the drift kinetic damping on the RWM between the thermal particles and EIs contributions, in both RFP and tokamak plasmas, even though each species alone can provide damping and stabilize RWM instability by respective kinetic resonances. The degree of cancellation generally depends on the EIs equilibrium distribution, the particle birth energy, as well as the toroidal flow speed of the plasma.

  7. Non-linear Paradigm for Drift Wave - Zonal Flow interplay: coherence, chaos and turbulence

    NASA Astrophysics Data System (ADS)

    Zonca, Fulvio

    2003-10-01

    Non-linear equations for the slow space-time evolution of the radial drift wave (DW) envelope and zonal flow (ZF) amplitude have been self-consistently derived for a model nonuniform tokamak equilibrium within the coherent 4-wave drift wave-zonal flow modulation interaction model of Chen, Lin and White(chen00). For the sake of simplicity, in this work we assume electrostatic fluctuations; but our formalism is readily extended to electromagnetic fluctuations(chen01). In the local limit, i.e. neglecting equilibrium profile variations, the coherent 4-wave DW-ZF modulation interaction model has successfully demonstrated spontaneous generation of ZFs and non-linear DW/ITG-ZF dynamics in toroidal plasmas(chen00). The present work is an extension of previous analyses to allow both (slow) temporal and spatial variations of the DW/ITG radial envelope; thus, it naturally incorporates the effects of equilibrium variations; i.e., turbulence spreading and size-dependence of the saturated wave intensities and transport coefficients(lin99). This approach makes it possible to treat equilibrium profile variations and non-linear interactions on the same footing, assuming that coupling among different DWs on the shortest non-linear time scale is mediated by ZF only. At this level, the competition between linear drive/damping, DW spreading due to finite linear (and nonlinear) group velocity(lin02,chen02,kim02) and non-linear energy transfer between DWs and ZF, determines the saturation levels of the fluctuating fields. Despite the coherence of the underlying non-linear dynamics at this level, this system exhibits both chaotic behavior and intermittency, depending on system size and proximity to marginal stability(chen02). The present model can be further extended to include longer time-scale physics such as 3-wave interactions and collisionless damping of zonal flows. 9 chen00 Liu Chen, Zhihong Lin and Roscoe White, Phys. Plasmas 7, 3129, (2000). chen01 L. Chen, Z. Lin, R.B. White and

  8. Wave-number spectrum of dissipative drift waves and a transition scale

    NASA Astrophysics Data System (ADS)

    Ghantous, K.; Gürcan, Ö. D.

    2015-09-01

    We study the steady state spectrum of the Hasegawa-Wakatani (HW) equations that describe drift wave turbulence. Beyond a critical scale kc, which appears as a balance between the nonlinear time and the parallel conduction time, the adiabatic electron response breaks down nonlinearly and an internal energy density spectrum of the form F (k⊥)∝k⊥-3 , associated with the background gradient, is established. More generally a dual power law spectrum, approximately of the form F (k⊥)∝k⊥-3(kc-2+k⊥-2) is obtained, which captures this transition. Using dimensional analysis, an expression of the form kc∝C /κ is derived for the transition scale, where C and κ are normalized parameters of the HW equations signifying the electron adiabaticity and the density gradient, respectively. The results are numerically confirmed using a shell model developed and used for the Hasegawa-Wakatani system.

  9. Modulation of drift-wave envelopes in a nonuniform quantum magnetoplasma

    SciTech Connect

    Misra, A. P. E-mail: apmisra@gmail.com

    2014-04-15

    We study the amplitude modulation of low-frequency, long-wavelength electrostatic drift-wave envelopes in a nonuniform quantum magnetoplasma consisting of cold ions and degenerate electrons. The effects of tunneling associated with the quantum Bohm potential and the Fermi pressure for nonrelativistic degenerate electrons, as well as the equilibrium density and magnetic field inhomogeneities are taken into account. Starting from a set of quantum magnetohydrodynamic equations, we derive a nonlinear Schrödinger equation (NLSE) that governs the dynamics of the modulated quantum drift-wave packets. The NLSE is used to study the modulational instability (MI) of a Stoke's wave train to a small plane wave perturbation. It is shown that the quantum tunneling effect as well as the scale length of inhomogeneity plays crucial roles for the MI of the drift-wave packets. Thus, the latter can propagate in the form of bright and dark envelope solitons or as drift-wave rogons in degenerate dense magnetoplasmas.

  10. Drift Wave Chaos and Turbulence in a LAPTAG Plasma Physics experiment

    NASA Astrophysics Data System (ADS)

    Katz, Cami; Gekelman, Walter; Pribyl, Patrick; Wise, Joe; Birge-Lee, Henry; Baker, Bob; Marmie, Ken; Thomas, Sam; Buckley-Bonnano, Samuel

    2015-11-01

    Whenever there is a pressure gradient in a magnetized plasma drift waves occur spontaneously. Drift waves have density and electrical potential fluctuations but no self magnetic field. In our experiment the drift waves form spontaneously in a narrow plasma column. (ne = 5 ×1011 cm3 , Te = 5 eV , B = 200 Gauss, dia = 25 cm , L = 1 . 5 m). As the drift waves grow from noise simple averaging techniques cannot be used to map them out in space and time. The ion saturation current Isat n√{Te} is recorded for an ensemble of 50 shots on a fixed probe located on the density gradient and for a movable probe. The probe signals are not sinusoidal and are filtered to calculate the cross-spectral function CSF = ∫ ∑ nshot Ifix, ωr->1 , tImov , ω (r->1 + δr-> , t + τ) dt , which can be used to extract the temporal and spatially varying wave patterns. The dominant wave at 18 kHz is a rotating spiral with m =2. LAPTAG is a university-high school alliance outreach program, which has been in existence for over 20 years. Work done at the BaPSF and supported by NSF/DOE.

  11. Fundamental mode of ultra-low frequency electrostatic dust-cyclotron surface waves in a magnetized complex plasma with drifting ions

    NASA Astrophysics Data System (ADS)

    Lee, Seungjun; Lee, Myoung-Jae

    2012-10-01

    The electrostatic dust-cyclotron (EDC) waves in a magnetized dusty plasma was reported that they could be excited by gravity in a collisional plasma [1]. Rosenberg suggested that EDC waves could be excited by ions drifting along the magnetic field in a collisional plasma containing dust grains with large thermal speeds [2]. The existing investigations, however, focus on EDC volume waves in which the boundary effects are not considered. In this work, we attempt to obtain some physical results concerning the fundamental mode of EDC surface wave and the stability of wave by utilizing a kinetic method. The EDC surface wave is assumed to propagate along an external magnetic field at the interface between the plasma and the vacuum. The plasma is comprised of drifting ions flowing along an external magnetic field. To derive the growth rate of surface waves, we employ the specular reflection boundary conditions. The EDC surface wave is found to be unstable when the ion drift velocity is larger than the phase velocity of the wave. In addition, the wave becomes to be more unstable if dust particles carry more negative charges.[4pt] [1] N. D'Angelo, Phys. Lett. A 323, 445 (2004).[0pt] [2] M. Rosenberg, Phys. Scr. 82, 035505 (2010).

  12. A theory of non-local linear drift wave transport

    SciTech Connect

    Moradi, S.; Anderson, J.; Weyssow, B.

    2011-06-15

    Transport events in turbulent tokamak plasmas often exhibit non-local or non-diffusive action at a distance features that so far have eluded a conclusive theoretical description. In this paper a theory of non-local transport is investigated through a Fokker-Planck equation with fractional velocity derivatives. A dispersion relation for density gradient driven linear drift modes is derived including the effects of the fractional velocity derivative in the Fokker-Planck equation. It is found that a small deviation (a few percent) from the Maxwellian distribution function alters the dispersion relation such that the growth rates are substantially increased and thereby may cause enhanced levels of transport.

  13. Fast scanning cavity offset lock for laser frequency drift stabilization

    NASA Astrophysics Data System (ADS)

    Seymour-Smith, Nicolas; Blythe, Peter; Keller, Matthias; Lange, Wolfgang

    2010-07-01

    We have implemented a compact setup for long-term laser frequency stabilization. Light from a stable reference laser and several slave lasers is coupled into a confocal Fabry-Pérot resonator. By stabilizing the position of the transmission peaks of the slave lasers relative to successive peaks of the master laser as the length of the cavity is scanned over one free spectral range, the long-term stability of the master laser is transferred to the slave lasers. By using fast analog peak detection and low-latency microcontroller-based digital feedback, with a scanning frequency of 3 kHz, we obtain a feedback bandwidth of 380 Hz and a relative stability of better than 10 kHz at timescales longer than 1 s, a significant improvement on previous scanning-cavity stabilization systems.

  14. Dynamics of vortices and drift waves: a point vortex model

    NASA Astrophysics Data System (ADS)

    Leoncini, Xavier; Verga, Alberto

    2013-03-01

    The complex interactions of localized vortices with waves are investigated using a model of point vortices in the presence of a transverse or longitudinal wave. This simple model shows a rich dynamical behavior including oscillations of a dipole, splitting and merging of two like-circulation vortices, and chaos. The analytical and numerical results of this model have been found to predict under certain conditions, the behavior of more complex systems, such as the vortices of the Charney-Hasegawa-Mima equation, where the presence of waves strongly affects the evolution of large coherent structures.

  15. Ionospheric vertical plasma drift perturbations due to the quasi 2 day wave

    NASA Astrophysics Data System (ADS)

    Gu, Sheng-Yang; Liu, Han-Li; Li, Tao; Dou, Xiankang

    2015-05-01

    The thermosphere-ionosphere-mesosphere-electrodynamics-general circulation model is utilized to study the vertical E × B drift perturbations due to the westward quasi 2 day wave with zonal wave numbers 2 and 3 (W2 and W3). The simulations show that both wind components contribute directly and significantly to the vertical drift, which is not merely confined to low latitudes. The vertical drifts at the equator induced by the total wind perturbations of W2 are comparable with that at middle latitudes, while the vertical drifts from W3 are much stronger at middle latitudes than at the equator. The ion drift perturbations induced by the zonal and meridional wind perturbations of W2 are nearly in-phase with each other, whereas the phase discrepancies of the ion drift induced by the individual wind component of W3 are much larger. This is because the wind perturbations of W2 and W3 have different latitudinal structures and phases, which result in different ionospheric responses through wind dynamo.

  16. Lattice Boltzmann model for collisionless electrostatic drift wave turbulence obeying Charney-Hasegawa-Mima dynamics

    NASA Astrophysics Data System (ADS)

    Held, M.; Kendl, A.

    2015-10-01

    A lattice Boltzmann method (LBM) approach to the Charney-Hasegawa-Mima (CHM) model for adiabatic drift wave turbulence in magnetised plasmas is implemented. The CHM-LBM model contains a barotropic equation of state for the potential, a force term including a cross-product analogous to the Coriolis force in quasigeostrophic models, and a density gradient source term. Expansion of the resulting lattice Boltzmann model equations leads to cold-ion fluid continuity and momentum equations, which resemble CHM dynamics under drift ordering. The resulting numerical solutions of standard test cases (monopole propagation, stable drift modes and decaying turbulence) are compared to results obtained by a conventional finite difference scheme that directly discretizes the CHM equation. The LB scheme resembles characteristic CHM dynamics apart from an additional shear in the density gradient direction. The occurring shear reduces with the drift ratio and is ascribed to the compressible limit of the underlying LBM.

  17. On the kinetic stability of magnetic structures in electron drift turbulence

    SciTech Connect

    Jucker, Martin; Pavlenko, Vladimir P.

    2007-03-15

    The generation of large-scale magnetic fields in magnetic electron drift mode turbulence is investigated. The mechanism of magnetic Reynolds stress is elucidated with the help of kinetic theory, and a sufficient criterion in the form of Nyquist's criterion for the generation of zonal magnetic fields is developed. This criterion is then applied to a narrow wave packet, where an amplitude threshold due to finite width of the wave spectrum in k space is found.

  18. Current-Driven Drift Wave Turbulence and Electron Thermal Transport in Tokamaks

    NASA Astrophysics Data System (ADS)

    Lee, C.; Diamond, P. H.; Porkolab, M.

    2009-11-01

    Recent analyses (Y. Lin, M. Porkolab; 2009) have indicated that the ``usual suspects'' for the mechanism of electron thermal transport, such as ITG, ETG, CTEM modes, etc, cannot explain results from modest density, Te>Ti plasmas, in either OH or ECH heating regimes. Interestingly, such plasmas exhibit very large toroidal current drift parameters vd/cs, thus naturally suggesting a re-visitation of current driven drift waves. In this paper, we discuss the linear, quasilinear and non-linear theory of current driven drift waves in tokamaks. Parallel electron velocity scattering, a critical effect beyond the capacity of most, gyrokinetic codes is a major focus of investigations. The coupled transport of current density and heat are considered. Work is ongoing and results will be presented.

  19. A probe array for the investigation of spatio-temporal structures in drift wave turbulence

    SciTech Connect

    Latten, A.; Klinger, T.; Piel, A.; Pierre, T.

    1995-05-01

    A probe array with 64 azimuthally arranged Langmuir probes is presented as a new diagnostic tool for the investigation of drift waves. A parallel data acquisition system provides full spatio-temporal data of azimuthally propagating waves. For both regular and turbulent states of current-driven drift waves, the information provided by such space-time patterns is compared with results obtained from conventional two-point correlation methods. The probe array allows one to directly estimate the time-averaged wave number spectrum. In a turbulent state, the spectrum yields to a power law of {ital S}({ital k}){proportional_to}{ital k}{sup {minus}3.6{plus_minus}0.1}. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  20. Models for electrostatic drift waves with density variations along magnetic field lines

    NASA Astrophysics Data System (ADS)

    Garcia, O. E.; Pécseli, H. L.

    2013-11-01

    Drift waves with vertical magnetic fields in gravitational ionospheres are considered where the unperturbed plasma density is enhanced in a magnetic flux tube. The gravitational field gives rise to an overall decrease of plasma density for increasing altitude. Simple models predict that drift waves with finite vertical wave vector components can increase in amplitude merely due to a conservation of energy density flux of the waves. Field-aligned currents are some of the mechanisms that can give rise to fluctuations that are truly unstable. We suggest a self-consistent generator or "battery" mechanism that in the polar ionospheres can give rise to magnetic field-aligned currents even in the absence of electron precipitation. The free energy here is supplied by steady state electric fields imposed in the direction perpendicular to the magnetic field in the collisional lower parts of the ionosphere or by neutral winds that have similar effects.

  1. Plasma diffusion at the magnetopause - The case of lower hybrid drift waves

    NASA Technical Reports Server (NTRS)

    Treumann, R. A.; Labelle, J.; Pottelette, R.

    1991-01-01

    The diffusion expected from the quasi-linear theory of the lower hybrid drift instability at the earth's magnetopause is recalculated. The resulting diffusion coefficient is marginally large enough to explain the thickness of the boundary layer under quiet conditions, based on observational upper limits for the wave intensities. Thus, one possible model for the boundary layer could involve equilibrium between the diffusion arising from lower hybrid waves and various loss processes.

  2. Theory on excitations of drift Alfvén waves by energetic particles. I. Variational formulation

    SciTech Connect

    Zonca, Fulvio; Chen, Liu

    2014-07-15

    A unified theoretical framework is presented for analyzing various branches of drift Alfvén waves and describing their linear and nonlinear behaviors, covering a wide range of spatial and temporal scales. Nonlinear gyrokinetic quasineutrality condition and vorticity equation, derived for drift Alfvén waves excited by energetic particles in fusion plasmas, are cast in integral form, which is generally variational in the linear limit; and the corresponding gyrokinetic energy principle is obtained. Well known forms of the kinetic energy principle are readily recovered from this general formulation. Furthermore, it is possible to demonstrate that the general fishbone like dispersion relation, obtained within the present theoretical framework, provides a unified description of drift Alfvén waves excited by energetic particles as either Alfvén eigenmodes or energetic particle modes. The advantage of the present approach stands in its capability of extracting underlying linear and nonlinear physics as well as spatial and temporal scales of the considered fluctuation spectrum. For these reasons, this unified theoretical framework can help understanding experimental observations as well as numerical simulation and analytic results with different levels of approximation. Examples and applications are given in Paper II [F. Zonca and L. Chen, “Theory on excitations of drift Alfvén waves by energetic particles. II. The general fishbone-like dispersion relation,” Phys. Plasmas 21, 072121 (2014)].

  3. The Use of the Information Wave Function in a Drift Dependent Option Price: A Simple Example

    SciTech Connect

    Haven, Emmanuel

    2009-03-10

    This paper briefly describes how a drift-dependent option price is obtained, following the work of Tan. We briefly argue how the information wave function concept, which has now been used in various financial settings, can be used in this type of option price.

  4. Dust magneto-gravitational drift wave in g×B configuration

    SciTech Connect

    Salahshoor, M. Niknam, A. R.

    2014-11-15

    The dispersion relation of electrostatic waves in a magnetized complex plasma under gravity is presented. It is assumed that the waves propagate perpendicular to the external fields. The effects of weak electric field, neutral drag force, and ion drag force are also taken into account. The dispersion relation is numerically examined in an appropriate parameter space in which the gravity plays the dominant role in the dynamics of magnetized microparticles. The numerical results show that an unstable low frequency drift wave can be developed in the long wavelength limit. This unstable mode is transformed into an aperiodic stationary structure at a cut-off wavenumber. Furthermore, the influence of the external fields on the dispersion properties is analyzed. It is shown that the instability is essentially due to the E×B drift motion of plasma particles. However, in the absence of weak electric field, the g×B drift motion of microparticles can cause the instability in a wide range of wavenumbers. It is also found that by increasing the magnetic field strength, the wave frequency is first increased and then decreased. This behaviour is explained by the existence of an extremum point in the dust magneto-gravitational drift velocity.

  5. Generation of zonal flows by electrostatic drift waves in electron-positron-ion plasmas

    SciTech Connect

    Kaladze, T. D.; Shad, M.; Tsamalashvili, L. V.

    2010-02-15

    Generation of large-scale zonal flows by comparatively small-scale electrostatic drift waves in electron-positron-ion plasmas is considered. The generation mechanism is based on the parametric excitation of convective cells by finite amplitude drift waves having arbitrary wavelengths (as compared with the ion Larmor radius of plasma ions at the plasma electron temperature). Temperature inhomogeneity of electrons and positrons is taken into account assuming ions to be cold. To describe the generation of zonal flow generalized Hasegawa-Mima equation containing both vector and two scalar (of different nature) nonlinearities is used. A set of coupled equations describing the nonlinear interaction of drift waves and zonal flows is deduced. Explicit expressions for the maximum growth rate as well as for the optimal spatial dimensions of the zonal flows are obtained. Enriched possibilities of zonal flow generation with different growth rates are revealed. The present theory can be used for interpretations of drift wave observations in laboratory and astrophysical plasmas.

  6. The Entropy and Complexity of Drift waves in a LAPTAG Plasma Physics Experiment

    NASA Astrophysics Data System (ADS)

    Birge-Lee, Henry; Gekelman, Walter; Pribyl, Patrick; Wise, Joe; Katz, Cami; Baker, Bob; Marmie, Ken; Thomas, Sam; Buckley-Bonnano, Samuel

    2015-11-01

    Drift waves grow from noise on a density gradient in a narrow (dia = 3 cm, L = 1.5 m) magnetized (Boz = 160G) plasma column. A two-dimensional probe drive measured fluctuations in the plasma column in a plane transverse to the background magnetic field. Correlation techniques determined that the fluctuations were that of electrostatic drift waves. The time series data was used to generate the Bandt-Pompe/Shannon entropy, H, and Jensen-Shannon complexity, CJS. C-H diagrams can be used to tell the difference between deterministic chaos, random noise and stochastic processes and simple waves, which makes it a powerful tool in nonlinear dynamics. The C-H diagram in this experiment, reveal that the combination of drift waves and other background fluctuations is a deterministically chaotic system. The PDF of the time series, the wave spectra the spatial dependence of the entropy wave complexity will be presented. LAPTAG is a university-high school alliance outreach program, which has been in existence for over 20 years. Work done at BaPSF at UCLA and supported by NSF and DOE.

  7. Drift wave model for geomagnetic pulsations in a high. beta. plasma

    SciTech Connect

    Patel, V.L.; Ng, P.H.; Cahill, L.J. Jr.

    1983-07-01

    A dispersion relation for the instability of the coupled drift compressional drift mirror, and shear Alven waves in the magnetospheric plasma is analyzed by numerical method. The analysis is suitable for the storm time plasma conditions in the magnetosphere which usually has gradients in plasma density temperature, magnetic field, and anisotropy in temperature. The effect of high ..beta.. which is characteristic of storm time plasma is included in the model. For a given appropriate set of plasma parameters, and wave parameters of a mode relative wave amplitudes are calculated from the model. A comparison is made of model generated and observed relative wave amplitudes by using two sample wave events observed by Explorer 45 during the August 4--6, 1972, magnetic storm. The quantitative analysis shows good agreement between theory and observations for a gradient-driven Alvenlike instability; however, growth rates are veery small for this mode. The anisotropy-driven drift mirror instability has large growth rates but does not show correlation between theory and observations of relative wave amplitudes.

  8. A Hybrid Statistics/Amplitude Approach to the Theory of Interacting Drift Waves and Zonal Flows

    NASA Astrophysics Data System (ADS)

    Parker, Jeffrey; Krommes, John

    2012-10-01

    An approach to the theory of drift-wave--zonal-flow systems is adopted in which only the DW statistics but the full ZF amplitude are kept. Any statistical description of turbulence must inevitably face the closure problem. A particular closure, the Stochastic Structural Stability Theory (SSST), has been recently studied in plasmafootnotetextB. F. Farrell and P. J. Ioannou, Phys. Plasmas 16, 112903 (2009). as well as atmospheric-science contexts. First, the predictions of the SSST are examined in the weakly inhomogeneous limit, using the generalized Hasegawa--Mima model as a simple example. It is found that the equations do not admit a complete solution, as the characteristic ZF scale cannot be calculated. To address that deficiency, an analysis is performed of a bifurcation from a DW-only state to a DW--ZF state in the Hasegawa--Wakatani model in order to gain analytical insight into a nonlinear DW--ZF equilibrium, including prediction of the charactistic scale. The calculation permits discussion of the relative importance of eddy shearing and coupling to damped eigenmodes for the saturation of the self-consistently regulated turbulence level.

  9. Stability of imploding spherical shock waves

    NASA Astrophysics Data System (ADS)

    Chen, H. B.; Zhang, L.; Panarella, E.

    1995-12-01

    The stability of spherically imploding shock waves is systematically investigated in this letter. The basic state is Guderley and Landau's unsteady self-similar solution of the implosion of a spherical shock wave. The stability analysis is conducted by combining Chandrasekhar's approach to the stability of a viscous liquid drop with Zel'dovich's approach to the stability of spherical flames. The time-dependent amplitudes of the perturbations are obtained analytically by using perturbation method. The relative amplification and decay of the amplitudes of perturbations decides the stability/instability of the spherical imploding shock waves. It is found that the growth rate of perturbations is not in exponential form and near the collapse phase of the shocks, the spherically imploding shock waves are relatively stable.

  10. Stability of imploding spherical shock waves

    SciTech Connect

    Chen, H.B.; Zhang, L.; Panarella, E.

    1995-12-01

    The stability of spherically imploding shock waves is systematically investigated in this letter. The basic state is Guderley and Landau`s unsteady self-similar solution of the implosion of a spherical shock wave. The stability analysis is conducted by combining Chandrasekhar`s approach to the stability of a viscous liquid drop with Zel`dovich`s approach to the stability of spherical flames. The time-dependent amplitudes of the perturbations are obtained analytically by using perturbation method. The relative amplification and decay of the amplitudes of perturbations are obtained analytically by using perturbation method. The relative amplification and decay of the amplitudes of perturbations decides the stability/instability of the spherical imploding shock waves. It is found that the growth rate of perturbations is not in exponential form and near the collapse phase of the shocks, the spherically imploding shock waves are relatively stable. 14 refs., 1 fig.

  11. Long-term stability and zero drift of digital barometric pressure gauges

    NASA Astrophysics Data System (ADS)

    Kojima, M.; Kobata, T.; Fujii, K.

    2015-04-01

    Several digital pressure gauges at the National Metrology Institute of Japan (NMIJ) have been calibrated in the barometric pressure range on a regular basis for over ten years. The long-term stability of the zero and span readings for these pressure gauges was evaluated using their historical calibration data. The evaluation showed that most of the gauges have quite good long-term stabilities for the span readings, but some have large zero drifts with rates of about (10 to 50) Pa yr-1. This paper discusses the causes for this drift: it can be explained by the combination of a small leak and gas emissions from the sensor volume, which are estimated from the typical drift rates. The zero drift of a particular gauge is well-approximated by an exponential function of time; the fitting function may give a good estimation of the zero drift in the future. This indicates that continuous characterization of a pressure gauge may enable appropriate correction of the indication and provide users more reliable data with less calibration work.

  12. The role of coherent vorticity in turbulent transport in resistive drift-wave turbulence

    SciTech Connect

    Bos, W. J. T.; Futatani, S.; Benkadda, S.; Schneider, K.

    2008-07-15

    The coherent vortex extraction method, a wavelet technique for extracting coherent vortices out of turbulent flows, is applied to simulations of resistive drift-wave turbulence in magnetized plasma (Hasegawa-Wakatani system). The aim is to retain only the essential degrees of freedom, responsible for the transport. It is shown that the radial density flux is carried by these coherent modes. In the quasi-hydrodynamic regime, coherent vortices exhibit depletion of the polarization-drift nonlinearity and vorticity strongly dominates strain, in contrast to the quasiadiabatic regime.

  13. Parallel-velocity-shear-modified drift wave in negative ion plasmas

    NASA Astrophysics Data System (ADS)

    Ichiki, R.; Kaneko, T.; Hayashi, K.; Tamura, S.; Hatakeyama, R.

    2009-03-01

    A systematic investigation of the effects of a parallel velocity shear and negative ions on the collisionless drift wave instability has for the first time been realized by simultaneously using a segmented tungsten hot plate of a Q-machine and sulfur hexafluoride (SF6) gas in a magnetized potassium plasma. The parallel velocity shear of the positive ion flow tends to decrease the fluctuation level of the drift wave. The introduction of negative ions first increases the fluctuation level and then starts to decrease it at the negative ion exchange fraction of around 10%, while keeping the above-mentioned shear effect qualitatively. In addition, a simple dispersion relation based on the local model has been calculated to show that it can predict wave characteristics similar to the experimental results. Our findings provide a potential for gaining a more profound insight into the physics of space/circumterrestrial plasmas.

  14. Impurity transport due to electromagnetic drift wave turbulence

    NASA Astrophysics Data System (ADS)

    Moradi, S.; Pusztai, I.; Mollén, A.; Fülöp, T.

    2012-03-01

    Finite β effects on impurity transport are studied through local linear gyrokinetic simulations with GYRO [J. Candy and E. Belli, General Atomics Report No. GA-A26818, 2011]; in particular, we investigate the parametric dependences of the impurity peaking factor (zero-flux density gradient) and the onset of the kinetic ballooning modes (KBMs). We find that electromagnetic effects even at low β can have significant impact on the impurity transport. The KBM instability threshold depends on the plasma parameters, particularly strongly on plasma shape. We have shown that magnetic geometry significantly influences the results, and the commonly used s-α model overestimates the KBM growth rates and ITG stabilization at high β. In the β range, where the KBM is the dominant instability the impurity peaking factor is strongly reduced, with very little dependence on β and the impurity charge.

  15. Asymptotic Linear Stability of Solitary Water Waves

    NASA Astrophysics Data System (ADS)

    Pego, Robert L.; Sun, Shu-Ming

    2016-06-01

    We prove an asymptotic stability result for the water wave equations linearized around small solitary waves. The equations we consider govern irrotational flow of a fluid with constant density bounded below by a rigid horizontal bottom and above by a free surface under the influence of gravity neglecting surface tension. For sufficiently small amplitude waves, with waveform well-approximated by the well-known sech-squared shape of the KdV soliton, solutions of the linearized equations decay at an exponential rate in an energy norm with exponential weight translated with the wave profile. This holds for all solutions with no component in (that is, symplectically orthogonal to) the two-dimensional neutral-mode space arising from infinitesimal translational and wave-speed variation of solitary waves. We also obtain spectral stability in an unweighted energy norm.

  16. Toroidal Alfven wave stability in ignited tokamaks

    SciTech Connect

    Cheng, C.Z.; Fu, G.Y.; Van Dam, J.W.

    1989-01-01

    The effects of fusion-product alpha particles on the stability of global-type shear Alfven waves in an ignited tokamak plasma are investigated in toroidal geometry. Finite toroidicity can lead to stabilization of the global Alfven eigenmodes, but it induces a new global shear Alfven eigenmodes, which is strongly destabilized via transit resonance with alpha particles. 8 refs., 2 figs.

  17. Zonal flow generation and its feedback on turbulence production in drift wave turbulence

    NASA Astrophysics Data System (ADS)

    Pushkarev, Andrey V.; Bos, Wouter J. T.; Nazarenko, Sergey V.

    2013-04-01

    Plasma turbulence described by the Hasegawa-Wakatani equations is simulated numerically for different models and values of the adiabaticity parameter C. It is found that for low values of C turbulence remains isotropic, zonal flows are not generated and there is no suppression of the meridional drift waves and particle transport. For high values of C, turbulence evolves towards highly anisotropic states with a dominant contribution of the zonal sector to the kinetic energy. This anisotropic flow leads to a decrease of turbulence production in the meridional sector and limits the particle transport across the mean isopycnal surfaces. This behavior allows to consider the Hasegawa-Wakatani equations a minimal PDE model, which contains the drift-wave/zonal-flow feedback loop mechanism.

  18. Zonal flow generation and its feedback on turbulence production in drift wave turbulence

    SciTech Connect

    Pushkarev, Andrey V.; Bos, Wouter J. T.; Nazarenko, Sergey V.

    2013-04-15

    Plasma turbulence described by the Hasegawa-Wakatani equations is simulated numerically for different models and values of the adiabaticity parameter C. It is found that for low values of C turbulence remains isotropic, zonal flows are not generated and there is no suppression of the meridional drift waves and particle transport. For high values of C, turbulence evolves towards highly anisotropic states with a dominant contribution of the zonal sector to the kinetic energy. This anisotropic flow leads to a decrease of turbulence production in the meridional sector and limits the particle transport across the mean isopycnal surfaces. This behavior allows to consider the Hasegawa-Wakatani equations a minimal PDE model, which contains the drift-wave/zonal-flow feedback loop mechanism.

  19. A link between nonlinear self-organization and dissipation in drift-wave turbulence

    SciTech Connect

    Manz, P.; Birkenmeier, G.; Stroth, U.; Ramisch, M.

    2012-08-15

    Structure formation and self-organization in two-dimensional drift-wave turbulence show up in many different faces. Fluctuation data from a magnetized plasma are analyzed and three mechanisms transferring kinetic energy to large-scale structures are identified. Beside the common vortex merger, clustering of vortices constituting a large-scale strain field and vortex thinning, where due to the interactions of vortices of different scales larger vortices are amplified by the smaller ones, are observed. The vortex thinning mechanism appears to be the most efficient one to generate large scale structures in drift-wave turbulence. Vortex merging as well as vortex clustering are accompanied by strong energy transfer to small-scale noncoherent fluctuations (dissipation) balancing the negative entropy generation due to the self-organization process.

  20. Shear flow driven drift waves and the counter-rotating vortices

    SciTech Connect

    Haque, Q.; Saleem, H.; Mirza, Arshad M.

    2005-10-01

    It is shown that the drift waves can become unstable due to the shear flow produced by externally applied electric field. The modified Rayleigh instability condition is obtained which is applicable to both electron-ion and electron-positron-ion plasmas. It is proposed that the shear flow driven drift waves can be responsible for large amplitude electrostatic fluctuations in tokamak edges. In the nonlinear regime the stationary structures may appear in electron-positron-ion plasmas as well as electron-ion plasmas. A particular form of the shear flow can give rise to counter-rotating dipole vortices and vortex chains. The speed and amplitude of the structures are affected by the presence of positrons in the electron ion plasma. The relevance of this investigation to laboratory and astrophysical plasmas is pointed out.

  1. Spatiotemporal control and synchronization of flute modes and drift waves in a magnetized plasma column

    SciTech Connect

    Brochard, F.; Bonhomme, G.; Gravier, E.; Oldenbuerger, S.; Philipp, M.

    2006-05-15

    An open-loop spatiotemporal synchronization method is applied to flute modes in a cylindrical magnetized plasma. It is demonstrated that synchronization can be achieved only if the exciter signal rotates in the same direction as the propagating mode. Moreover, the efficiency of the synchronization is shown to depend on the radial properties of the instability under consideration. It is also demonstrated that the control disposition can alternatively be used to produce strongly developed turbulence of drift waves or flute instabilities.

  2. Kinetic vortex chain solution in the drift-wave plasma regime

    PubMed

    Jovanovic; Pegoraro

    2000-01-01

    A fully nonlinear Bernstein-Greene-Kruskal stationary solution is found in the form of a quasi-three-dimensional chain of electron holes coupled to hydrodynamic vortices. This new coherent structure is enabled by the trapping and depletion of resonant particles, and the cyclotron dissipation of the singular current sheets. It is expected to play an important role in the collisionless magnetic field line reconnection in the drift-wave plasma regime, where it represents a plausible saturated state. PMID:11015843

  3. Observation of Quasi-Two-Dimensional Nonlinear Interactions in a Drift-Wave Streamer

    SciTech Connect

    Yamada, T.; Nagashima, Y.; Itoh, S.-I.; Inagaki, S.; Kamataki, K.; Yagi, M.; Fujisawa, A.; Kasuya, N.; Itoh, K.; Arakawa, H.; Kobayashi, T.

    2010-11-26

    A streamer, which is a bunching of drift-wave fluctuations, and its mediator, which generates the streamer by coupling with other fluctuations, have been observed in a cylindrical magnetized plasma. Their radial structures were investigated in detail by using the biphase analysis. Their quasi-two-dimensional structures were revealed to be equivalent with a pair of fast and slow modes predicted by a nonlinear Schroedinger equation based on the Hasegawa-Mima model.

  4. Drifts of a three-axis stabilizer under vibration of the frames and platform with unbalanced dynamically tuned gyroscopes

    NASA Astrophysics Data System (ADS)

    Zbrutskii, A. V.; Sarapulov, S. A.

    1985-10-01

    It is shown that the unbalance of a dynamically tuned gyro, leading to gyro self-excitation through vibration of the platform in a gimball suspension, causes drifts of the stabilizer. The magnitude of the drift depends on the gyro balancing precision, the location of gyros on the platform, and the relationship between the moments of inertia of the suspension elements, the precision of the adjustment, and the ultimate rigidity of the platform. Ways to reduce the drifts of the system are examined.

  5. An analysis of the role of drift waves in equatorial spread F

    NASA Technical Reports Server (NTRS)

    Labelle, J.; Kelley, M. C.; Seyler, C. E.

    1986-01-01

    An account is given of results of rocket measurements of the wave number spectrum of equatorial spread F irregularities, with emphasis on wavelengths less than 100 m. The measurements were made from two sounding rockets launched from Peru as part of Project Condor. The Condor density fluctuation spectra display a break at a wavelength near 100 m, identical to that found in the PLUMEX experiment (Kelley et al., 1982). The Condor data also confirm a subrange in which the density and the wave potential obey the Boltzmann relation - a strong indication of the presence of low-frequency electrostatic waves with finite wavelength parallel to the magnetic field, perhaps low-frequency drift waves as proposed by Kelley et al. The Condor data are also consistent with the previous conjecture that drift waves only exist above 300 km altitude. To investigate the difference in spectra observed over two altitude ranges, the data must be fitted to a form for the power spectrum taken from Keskinen and Ossakow (1981). The fitted spectrum, along with empirically determined growth and dissipation rates, is used to calculate the energy pumped into the spectrum at long wavelengths as well as the energy dissipated at shorter wavelengths. It is found that the energy is balanced by classical collisional effects in the low-altitude case, but energy balance in the high-altitude case requires an enhanced dissipation of about 500 times that due to classical diffusion. The model is consistent with, but does not uniquely imply, an inverse cascade of drift wave turbulence in equatorial spread F.

  6. Anatomy of Drift Ridges Revealed by Shallow Seismic Shear Wave Profiling

    NASA Astrophysics Data System (ADS)

    Phillips, A. C.

    2005-12-01

    Ridges, up to 30 m high and generally oriented NE-SW across the Illinois Episode drift plain in southern Illinois, USA, have been variously interpreted as eskers, crevasse fills, moraines, and kames. The ice contact diamictons and sorted sediments that occur in these ridges are typically Illinois Episode in age and likely record the final melting of the Laurentide Ice Sheet near its southernmost extent in the continental U.S. Shallow shear wave seismic profiles across several of these ridges help reveal their complex origins. Borehole control includes sediment cores with shear wave and natural gamma logs. The shear wave profiles reveal m-scale features of drift and bedrock over a depth range of 1 up to 100 m. Terrapin Ridge overlies a bedrock valley with drift up to 70 m thick. Dipping seismic reflectors on the stoss side are interpreted as imbricated till sheets, whereas horizontal reflectors on the lee side are interpreted as mainly outwash sediments over basal till and glacilacustrine sediment. Although most ridges were probably formed during the Illinois Episode, based on current data, the core of this particular ridge may be a remnant moraine from a pre-Illinois Episode glaciation.

  7. Simulating the effects of stellarator geometry on gyrokinetic drift-wave turbulence

    NASA Astrophysics Data System (ADS)

    Baumgaertel, Jessica Ann

    Nuclear fusion is a clean, safe form of energy with abundant fuel. In magnetic fusion energy (MFE) experiments, the plasma fuel is confined by magnetic fields at very high temperatures and densities. One fusion reactor design is the non-axisymmetric, torus-shaped stellarator. Its fully-3D fields have advantages over the simpler, better-understood axisymmetric tokamak, including the ability to optimize magnetic configurations for desired properties, such as lower transport (longer confinement time). Turbulence in the plasma can break MFE confinement. While turbulent transport is known to cause a significant amount of heat loss in tokamaks, it is a new area of research in stellarators. Gyrokinetics is a good mathematical model of the drift-wave instabilities that cause turbulence. Multiple gyrokinetic turbulence codes that had great success comparing to tokamak experiments are being converted for use with stellarator geometry. This thesis describes such adaptations of the gyrokinetic turbulence code, GS2. Herein a new computational grid generator and upgrades to GS2 itself are described, tested, and benchmarked against three other gyrokinetic codes. Using GS2, detailed linear studies using the National Compact Stellarator Experiment (NCSX) geometry were conducted. The first compares stability in two equilibria with different β=(plasma pressure)/(magnetic pressure). Overall, the higher β case was more stable than the lower β case. As high β is important for MFE experiments, this is encouraging. The second compares NCSX linear stability to a tokamak case. NCSX was more stable with a 20% higher critical temperature gradient normalized by the minor radius, suggesting that the fusion power might be enhanced by ˜ 50%. In addition, the first nonlinear, non-axisymmetric GS2 simulations are presented. Finally, linear stability of two locations in a W7-AS plasma were compared. The experimentally-measured parameters used were from a W7-AS shot in which measured heat fluxes

  8. Observation of anomalous ion heating by broadband drift-wave turbulence.

    PubMed

    Enge, S; Birkenmeier, G; Manz, P; Ramisch, M; Stroth, U

    2010-10-22

    Using laser induced fluorescence and passive spectroscopy on a magnetically confined low-temperature plasma, anomalous ion heating is observed which exceeds collisional heating from the electrons by a factor of up to five. Direct wave heating due to the 2.45 GHz microwave as well as stochastic heating by large-amplitude fluctuations could be ruled out as explanations. Good quantitative agreement is found when comparing the missing power in the ion species with heating power due to the dissipation of drift-wave turbulence. This turbulent energy transfer into the ion channel could have important consequences for the interpretation of transport in fusion plasmas. PMID:21231054

  9. Supersonic Wave Interference Affecting Stability

    NASA Technical Reports Server (NTRS)

    Love, Eugene S.

    1958-01-01

    Some of the significant interference fields that may affect stability of aircraft at supersonic speeds are briefly summarized. Illustrations and calculations are presented to indicate the importance of interference fields created by wings, bodies, wing-body combinations, jets, and nacelles.

  10. Coupled nonlinear drift and ion acoustic waves in dense dissipative electron-positron-ion magnetoplasmas

    SciTech Connect

    Masood, W.; Siddiq, M.; Karim, S.; Shah, H. A.

    2009-11-15

    Linear and nonlinear propagation characteristics of drift ion acoustic waves are investigated in an inhomogeneous electron-positron-ion (e-p-i) quantum magnetoplasma with neutrals in the background using the well known quantum hydrodynamic model. In this regard, Korteweg-de Vries-Burgers (KdVB) and Kadomtsev-Petviashvili-Burgers (KPB) equations are obtained. Furthermore, the solutions of KdVB and KPB equations are presented by using the tangent hyperbolic (tanh) method. The variation in the shock profile with the quantum Bohm potential, collision frequency, and the ratio of drift to shock velocity in the comoving frame, v{sub *}/u, is also investigated. It is found that increasing the positron concentration and collision frequency decreases the strength of the shock. It is also shown that when the localized structure propagates with velocity greater than the diamagnetic drift velocity (i.e., u>v{sub *}), the shock strength decreases. However, the shock strength is observed to increase when the localized structure propagates with velocity less than that of drift velocity (i.e., u

  11. On the onset of surface wind drift at short fetches as observed in a wind wave flume

    NASA Astrophysics Data System (ADS)

    Ocampo-Torres, Francisco J.; Branger, Hubert; Osuna, Pedro; Robles, Lucia

    2014-05-01

    Ocean surface drift is of great relevance to properly model wind waves and specially the early stages of surface waves development and ocean-atmosphere fluxes during incipient wind events and storms. In particular, wave models are not so accurate predicting wave behaviour at short fetches, where wind drift onset might be very important. The onset of surface drift induced by wind and waves is being studied through detailed laboratory measurements in a large wind-wave flume. Wind stress over the water surface, waves and surface drift are measured in the 40m long wind-wave tank at IRPHE, Marseille. While momentum fluxes are estimated directly through the eddy correlation method in a station about the middle of the tank, they provide reference information to the corresponding surface drift onset recorded at rather short non-dimensional fetches. At each experimental run very low wind was on (about 1m/s) for a certain period and suddenly it was constantly accelerated to reach about 13 m/s (as well as 8 and 5 m/s during different runs) in about 15 sec to as long as 600 sec. The wind was kept constant at that high speed for 2 to 10 min, and then suddenly and constantly decelerate to 0. Surface drift values were up to 0.5 cm/s for the highest wind while very distinctive shear was detected in the upper 1.5 cm. Rather linear variation of surface drift was observed with depth. Evolution of the surface drift velocity is analysed and onset behaviour is addressed with particular emphasis in accelerated winds. This work represents a RugDiSMar Project (CONACYT 155793) contribution. The support from ANUIES-ECOS M09-U01 project, CONACYT-187112 Estancia Sabática, and Institute Carnot, is greatly acknowledged.

  12. Stability of post-fertilization traveling waves

    NASA Astrophysics Data System (ADS)

    Flores, Gilberto; Plaza, Ramón G.

    This paper studies the stability of a family of traveling wave solutions to the system proposed by Lane et al. [D.C. Lane, J.D. Murray, V.S. Manoranjan, Analysis of wave phenomena in a morphogenetic mechanochemical model and an application to post-fertilization waves on eggs, IMA J. Math. Appl. Med. Biol. 4 (4) (1987) 309-331], to model a pair of mechanochemical phenomena known as post-fertilization waves on eggs. The waves consist of an elastic deformation pulse on the egg's surface, and a free calcium concentration front. The family is indexed by a coupling parameter measuring contraction stress effects on the calcium concentration. This work establishes the spectral, linear and nonlinear orbital stability of these post-fertilization waves for small values of the coupling parameter. The usual methods for the spectral and evolution equations cannot be applied because of the presence of mixed partial derivatives in the elastic equation. Nonetheless, exponential decay of the directly constructed semigroup on the complement of the zero eigenspace is established. We show that small perturbations of the waves yield solutions to the nonlinear equations decaying exponentially to a phase-modulated traveling wave.

  13. Effects of dust correlations on the marginal stability of ion stream driven dust acoustic waves

    NASA Astrophysics Data System (ADS)

    Shukla, Manish K.; Avinash, K.

    2016-06-01

    The effect of dust–dust correlations on the marginal stability of dust acoustic waves excited by ion drift is studied. The ion drift is driven by the electric field {E}0 which is generally present in the discharge. Correlation effects on marginal stability are studied using augmented Debye–Hückel approximation. The marginal stability boundary is calculated in {E}0-{P}0 (P 0 is the pressure of the neutral gas) space with correlated dust grains. We show that due to dust-dust correlation the stability boundary moves into the unstable region thereby stabilizing the DAW. The effects are significant for smaller values of κ (=a/{λ }d) below unity (a is the mean particle distance and {λ }d is Debye length).

  14. Electrostatic drift waves in a 2D magnetic current sheet - a new kinetic theory

    NASA Astrophysics Data System (ADS)

    Fruit, G.; Louarn, P.; Tur, A.

    2015-12-01

    In the general context of understanding the possible destabilization of the magnetotail before a substorm, a kinetic model for electromagnetic instabilities in resonant interaction with trapped bouncing electrons has been proposed for several years. Fruit et al. 2013 already used it to investigate the possibilities for electrostatic instabilities. Tur et al. 2014 generalizes the model for full electromagnetic perturbations.It turns out that some corrections should be added to the electrostatic version of Fruit et al. 2013. We propose to revist the theory in this present paper.Starting with a modified 2D Harris sheet as equilibrium state, the linearized gyrokinetic Vlasov equation is solved for electrostatic fluctuations with period of the order of the electron bounce period (a few seconds). The particle motion is restricted to its first Fourier component along the magnetic field and this allows the complete time integration of the non local perturbed distribution functions. The dispersion relation for electrostatic modes is finally obtained through the quasineutrality condition.The new feature of the present model is the inclusion of diamagnetic drift effects due to the density gradient in the tail. It is well known in MHD theory that drift waves are driven unstable through collisions or other dissipative effects. Here electrostatic drift waves are revisited in this more complete kinetic model including bouncing electrons and finite Larmor radius effects. A new mode has been found with original propagation proprieties. It is moreover mildly unstable due to electron or ion damping (dissipative instability).

  15. Transition from flute modes to drift waves in a magnetized plasma column

    SciTech Connect

    Brochard, F.; Gravier, E.; Bonhomme, G.

    2005-06-15

    Recent experiments performed on the low {beta} plasma device Mirabelle [T. Pierre, G. Leclert, and F. Braun, Rev. Sci. Instrum. 58, 6 (1987)] using a limiter have shown that transitions between various gradient driven instabilities occurred on increasing the magnetic field strength. New thorough measurements allow to identify unambiguously three instability regimes. At low magnetic field the strong ExB velocity shear drives a Kelvin-Helmholtz instability, whereas at high magnetic field drift waves are only observed. A centrifugal (Rayleigh-Taylor) instability is also observed in between when the ExB velocity is shearless and strong enough. A close connection is made between the ratio {rho}{sub s}/L{sub perpendicular} of the drift parameter to the radial density gradient length and each instability regime.

  16. Kinetic Electron Closures for Electromagnetic Simulation of Drift and Shear-Alfven Waves (II)

    SciTech Connect

    Cohen, B I; Dimits, A M; Nevins, W M; Chen, Y; Parker, S

    2001-10-11

    An electromagnetic hybrid scheme (fluid electrons and gyrokinetic ions) is elaborated in example calculations and extended to toroidal geometry. The scheme includes a kinetic electron closure valid for {beta}{sub e} > m{sub e}/m{sub i} ({beta}{sub e} is the ratio of the plasma electron pressure to the magnetic field energy density). The new scheme incorporates partially linearized ({delta}f) drift-kinetic electrons whose pressure and number density moments are used to close the fluid momentum equation for the electron fluid (Ohm's law). The test cases used are small-amplitude kinetic shear-Alfven waves with electron Landau damping, the ion-temperature-gradient instability, and the collisionless drift instability (universal mode) in an unsheared slab as a function of the plasma {beta}{sub e}. Attention is given to resolution and convergence issues in simulations of turbulent steady states.

  17. Effects of water depth and spectral bandwidth on Stokes drift estimation based on short-term variation of wave conditions

    NASA Astrophysics Data System (ADS)

    Myrhaug, Dag; Wang, Hong; Holmedal, Lars Erik

    2016-04-01

    The Stokes drift represents an important transport component of ocean circulation models. Locally it is responsible for transport of e.g. contaminated ballast water from ships, oil spills, plankton and larvae. It also plays an important role in mixing processes across the interphase between the atmosphere and the ocean. The Stokes drift is the mean Lagrangian velocity obtained from the water particle trajectory in the wave propagation direction; it is maximum at the surface, decreasing rapidly with the depth below the surface. The total mean mass transport is obtained by integrating the Stokes drift over the water depth; this is also referred to as the volume Stokes transport. The paper provides a simple analytical method which can be used to give estimates of the Stokes drift in moderate intermediate water depth based on short-term variation of wave conditions. This is achieved by using a joint distribution of individual wave heights and wave periods together with an explicit solution of the wave dispersion equation. The mean values of the surface Stokes drift and the volume Stokes transport for individual random waves within a sea state are presented, and the effects of water depth and spectral bandwidth parameter are discussed. Furthermore, example of results corresponding to typical field conditions are presented to demonstrate the application of the method, including the Stokes drift profile in the water column beneath the surface. Thus, the present analytical method can be used to estimate the Stokes drift in moderate intermediate water depth for random waves within a sea state based on available wave statistics.

  18. Anomalous electron-ion energy coupling in electron drift wave turbulence

    NASA Astrophysics Data System (ADS)

    Zhao, Lei

    Turbulence is a ubiquitous phenomenon in nature, and it is well known that turbulence couples energy input to dissipation by cascade processes. Plasma turbulence play a critical role in tokamak confinement. Magnetized plasma turbulence is quasi 2D, anisotropic, wave like and two fluid (i.e. electrons and ions) in structure. Thus, weakly collisional plasma turbulence can mediate electron and ion energy transfer. The issue of anomalous electron and ion energy coupling is particularly important for low collisionality, electron heated plasmas, such as ITER. In this work, we reconsider the classic problem of turbulent heating and energy transfer pathways in drift wave turbulence. The total turbulent heating, composed of quasilinear electron cooling, quasilinear ion heating, nonlinear ion heating and zonal flow frictional heating, is analyzed. In Chapter 2, the electron and ion energy exchange via linear wave and particle resonance will be computed. To address net heating, we show the turbulent heating in an annulus arises due to a wave energy flux differential across this region. We show this net heating is proportional to the Reynolds work on the zonal flow. Zonal flow friction heats ions, thus the turbulence and zonal flow interaction enters as an important energy transfer channel. Since zonal flows are nonlinearly generated, it follows that we should apply weak turbulence theory to calculate the nonlinear ion turbulent heating via the virtual mode resonance in the electron drift wave turbulence, which will be discussed in Chapter 3. We defines a new collisionless turbulent energy transfer channel through nonlinear Landau damping in the electron and ion energy coupling process. The result shows that nonlinear ion heating can exceed quasilinear ion heating, so that nonlinear heating becomes the principal collisionless wave energy dissipation channel in electron drift wave turbulence. This follows since the beat mode resonates with the bulk of the ion distribution, in

  19. Anomalous perturbative transport in tokamaks due to drift-Alfven-wave turbulence

    SciTech Connect

    Thoul, A.A. ); Similon, P.L. ); Sudan, R.N. )

    1994-03-01

    The method developed in Thoul, Similon, and Sudan [Phys. Plasmas [bold 1], 579 (1994)] is used to calculate the transport due to drift-Alfven-wave turbulence, in which electromagnetic effects such as the fluttering of the magnetic field lines are important. Explicit expressions are obtained for all coefficients of the anomalous transport matrix relating particle and heat fluxes to density and temperature gradients in the plasma. Although the magnetic terms leave the transport by trapped electrons unaffected, they are important for the transport by circulating electrons.

  20. Stability evaluation of the Panel 1 rooms and the E140 drift at WIPP

    SciTech Connect

    Maleki, H.; Chaturvedi, L.

    1996-08-01

    WIPP, intended for underground permanent disposal of defense transuranic waste, is located 40 km east of Carlsbad at a depth of 655 m in the salt beds of the 600-m thick Permian Salado Formation. It will consist of 56 ``rooms`` each 91.5 m long, 10 m wide, and 4 m high, grouped in 8 ``panels`` of 7 rooms each. About 7.5 km of access drifts will also be provided. Excavation began in 1982 and surface/access/test facilities and one panel were completed by 1988, many years before it could be used. Current plans are to start emplacing waste in WIPP in 1998 and continue for 35 years. The north- south drift E140 is the widest (25 ft) of the four main north-south drifts and is the main north-south passage. Plans to conduct experiments with waste in 1993 were abandoned, and the plan now is to use panel 1 for permanent disposal of waste starting in 1998. The stability evaluation resulted in the conclusion that, while it would be possible to safely use portions of panel 1 for waste emplacement, it would be best to abandon panel 1 and mine a new panel after the decision has been made to use WIPP as a repository and the necessary permits obtained.

  1. Straightforward and accurate technique for post-coupler stabilization in drift tube linac structures

    NASA Astrophysics Data System (ADS)

    Khalvati, Mohammad Reza; Ramberger, Suitbert

    2016-04-01

    The axial electric field of Alvarez drift tube linacs (DTLs) is known to be susceptible to variations due to static and dynamic effects like manufacturing tolerances and beam loading. Post-couplers are used to stabilize the accelerating fields of DTLs against tuning errors. Tilt sensitivity and its slope have been introduced as measures for the stability right from the invention of post-couplers but since then the actual stabilization has mostly been done by tedious iteration. In the present article, the local tilt-sensitivity slope TSn' is established as the principal measure for stabilization instead of tilt sensitivity or some visual slope, and its significance is developed on the basis of an equivalent-circuit diagram of the DTL. Experimental and 3D simulation results are used to analyze its behavior and to define a technique for stabilization that allows finding the best post-coupler settings with just four tilt-sensitivity measurements. CERN's Linac4 DTL Tank 2 and Tank 3 have been stabilized successfully using this technique. The final tilt-sensitivity error has been reduced from ±100 %/MHz down to ±3 %/MHz for Tank 2 and down to ±1 %/MHz for Tank 3. Finally, an accurate procedure for tuning the structure using slug tuners is discussed.

  2. Possible inverse cascade behavior for drift-wave turbulence. [in plasma

    NASA Technical Reports Server (NTRS)

    Fyfe, D.; Montgomery, D.

    1979-01-01

    The turbulent spectral properties of the dynamical equation of Hasegawa and Mima (1978) governing the evolution of the electrostatic potential in drift-wave turbulence is investigated for two formulations of the problem: (1) as a nondissipative initial value problem, with the potential represented by a truncated Fourier series with large number of terms, and (2) as a dissipative problem with a small viscous dissipation at very short spatial scales, and a long wavelength forcing term at longer wavelengths. It is found that Hasegawa and Mima's prediction for the nondissipative, truncated initial value modal problem is accurate, but substantial differences exist for the forced dissipative case between computer results and analytical predictions based on a wave kinetic equation of Kadomtsev. Much better agreement is found with a simple dual-cascade model based on Kraichnan's generalization of Kolmogorov's cascade arguments.

  3. Effect of resonant magnetic perturbations on secondary structures in drift-wave turbulence

    SciTech Connect

    Leconte, M.; Diamond, P. H.

    2011-08-15

    Recent experiments showed a decrease of long range correlations during the application of resonant magnetic perturbations (RMPs) [Y. Xu et al., Nucl. Fusion 51, 063020 (2011)]. This finding suggests that RMPs damp zonal flows. To elucidate the effect of the RMPs on zonal structures in drift wave turbulence, we construct a generalized Hasegawa-Wakatani model including RMP fields. The effect of the RMPs is to induce a linear coupling between the zonal electric field and the zonal density gradient, which drives the system to a state of electron radial force balance for large RMP amplitude. A predator-prey model coupling the primary drift wave dynamics to the zonal modes evolution is derived. This model has both turbulence drive and RMP amplitude as control parameters and predicts a novel type of transport bifurcation in the presence of RMPs. The novel regime has a power threshold which increases with RMP amplitude as {gamma}{sub c}{approx}[({delta}B{sub r}/B)]{sup 2}.

  4. Spontaneous profile self-organization in a simple realization of drift-wave turbulence

    NASA Astrophysics Data System (ADS)

    Cui, L.; Ashourvan, A.; Thakur, S. C.; Hong, R.; Diamond, P. H.; Tynan, G. R.

    2016-05-01

    We report the observation of a transport bifurcation that occurs by spontaneous self-organization of a drift-wave and shear flow system in a linear plasma device. As we increase the magnetic field above a threshold ( BC r = 1200 G), a global transition occurs, with steepening of mean density and ion pressure profiles, onset of strong E ×B shearing, a reduction of turbulence, and improved turbulent radial particle transport. An abrupt transition appears in the graph of turbulent particle flux versus density gradient. Hysteresis in the density gradient further confirms this transport bifurcation. The total Reynolds work on the flow sharply increases above threshold. This correlates with the increase of density steepness, which suggests the Reynolds stress-driven flow that plays an essential role in density steepening and transport bifurcation. A change in turbulence feature from drift waves (DWs) to a mix of DWs and ion temperature gradients also coincides with the transport bifurcation. Interesting phenomena related to the transport bifurcation are also reported; a local inward particle flux, the co-existence of ion and electron features, and a self-sustained axial flow absent momentum input.

  5. Intended motion estimation using fuzzy Kalman filtering for UAV image stabilization with large drifting

    NASA Astrophysics Data System (ADS)

    Xin, Tiantian; Zhao, Hongying; Liu, Sijie; Wang, Lu

    2015-03-01

    Videos from a small Unmanned Aerial Vehicle (UAV) are always unstable because of the wobble of the vehicle and the impact of surroundings, especially when the motion has a large drifting. Electronic image stabilization aims at removing the unwanted wobble and obtaining the stable video. Then estimation of intended motion, which represents the tendency of global motion, becomes the key to image stabilization. It is usually impossible for general methods of intended motion estimation to obtain stable intended motion remaining as much information of video images and getting a path as much close to the real flying path at the same time. This paper proposed a fuzzy Kalman filtering method to estimate the intended motion to solve these problems. Comparing with traditional methods, the fuzzy Kalman filtering method can achieve better effect to estimate the intended motion.

  6. Resolving Structural Isomers of Monosaccharide Methyl Glycosides Using Drift Tube and Traveling Wave Ion Mobility Mass Spectrometry

    PubMed Central

    Li, Hongli; Giles, Kevin; Bendiak, Brad; Kaplan, Kimberly; Siems, William F.; Hill, Herbert H.

    2013-01-01

    Monosaccharide structural isomers including sixteen methyl-D-glycopyranosides and four methyl-N-acetylhexosamines were subjected to ion mobility measurements by electrospray ion mobility mass spectrometry. Two ion mobility-MS systems were employed: atmospheric pressure drift tube ion mobility time-of-flight mass spectrometry and a Synapt G2 HDMS system which incorporates a low pressure traveling wave ion mobility separator. All the compounds were investigated as [M+Na]+ ions in the positive mode. A majority of the monosaccharide structural isomers exhibited different mobility drift times in either system, depending on differences in their anomeric and stereochemical configurations. In general, drift time patterns (relative drift times of isomers) matched between the two instruments. Higher resolving power was observed using the atmospheric pressure drift tube. Collision cross section values of monosaccharide structural isomers were directly calculated from the atmospheric pressure ion mobility experiments and a collision cross section calibration curve was made for the traveling wave ion mobility instrument. Overall, it was demonstrated that ion mobility-mass spectrometry using either drift tube or traveling wave ion mobility is a valuable technique for resolving subtle variations in stereochemistry among the sodium adducts of monosaccharide methyl glycosides. PMID:22339760

  7. Kinetic water-bag model of global collisional drift waves and ion temperature gradient instabilities in cylindrical geometry

    SciTech Connect

    Gravier, E.; Plaut, E.

    2013-04-15

    Collisional drift waves and ion temperature gradient (ITG) instabilities are studied using a linear water-bag kinetic model [P. Morel et al., Phys. Plasmas 14, 112109 (2007)]. An efficient spectral method, already validated in the case of drift waves instabilities [E. Gravier et al., Eur. Phys. J. D 67, 7 (2013)], allows a fast solving of the global linear problem in cylindrical geometry. The comparison between the linear ITG instability properties thus computed and the ones given by the COLUMBIA experiment [R. G. Greaves et al., Plasma Phys. Controlled Fusion 34, 1253 (1992)] shows a qualitative agreement. Moreover, the transition between collisional drift waves and ITG instabilities is studied theoretically as a function of the ion temperature profile.

  8. Reduction effect of neutral density on the excitation of turbulent drift waves in a linear magnetized plasma with flow

    SciTech Connect

    Saitou, Y.; Yonesu, A.; Shinohara, S.; Ignatenko, M. V.; Kasuya, N.; Kawaguchi, M.; Terasaka, K.; Nishijima, T.; Nagashima, Y.; Kawai, Y.; Yagi, M.; Itoh, S.-I.; Azumi, M.; Itoh, K.

    2007-07-15

    The importance of reducing the neutral density to reach strong drift wave turbulence is clarified from the results of the extended magnetohydrodynamics and Monte Carlo simulations in a linear magnetized plasma. An upper bound of the neutral density relating to the ion-neutral collision frequency for the excitation of drift wave instability is shown, and the necessary flow velocity to excite this instability is also estimated from the neutral distributions. Measurements of the Mach number and the electron density distributions using Mach probe in the large mirror device (LMD) of Kyushu University [S. Shinohara et al., Plasma Phys. Control. Fusion 37, 1015 (1995)] are reported as well. The obtained results show a controllability of the neutral density and provide the basis for neutral density reduction and a possibility to excite strong drift wave turbulence in the LMD.

  9. Fast and Ultra-fast Kelvin wave modulations of the equatorial evening F region vertical drift and spread F development.

    NASA Astrophysics Data System (ADS)

    Garnett Marques Brum, C.; Abdu, M. A.; Batista, P. P.; Gurubaran, S.; Pancheva, D.; Bageston, J. V.; Batista, I. S.; Takahashi, H.

    2014-12-01

    In this paper we investigate the role of eastward and upward propagating Fast (FK) and Ultrafast Kelvin (UFK) waves in the day-to-day variability of equatorial evening prereversal vertical drift and post sunset generation of spread F/plasma bubbles irregularities. Meteor wind data from Cariri and Cachoeira Paulista (Brazil) and medium Frequency (MF) radar wind data from Tirunelveli (India) are analyzed together with TIMED/SABER temperature in the 40 km - 100 km region to characterize the zonal and vertical propagations of these waves. Also analyzed are the F region evening vertical drift and spread F (ESF) development features as diagnosed by Digisondes operated at Fortaleza and Sao Luis in Brazil. The SABER temperature data permitted determination of the upward propagation characteristics of the FK (E1) waves with propagation speed in the range of 4 km/day. The radar Mesosphere and Lower Thermosphere (MLT) winds in the widely separated longitude sectors have yielded the eastward phase velocity of the both the FK and UFK waves. The vertical propagation of these waves cause strong oscillation in the F region evening prereversal vertical drift, observed for the first time at both FK and UFK periodicities. A delay of a few (~10) days is observed in the F region vertical drift perturbation with respect to the corresponding FK/UFK zonal wind oscillations, or temperature oscillations in the MLT region, which has permitted a direct identification of the sunset electro dynamic coupling process as responsible for the generation of the FK/UFK induced vertical drift oscillation. The vertical drift oscillations are found to cause significant modulation in the spread F/ plasma bubble irregularity development. The overall results highlight the role of FK/UFK waves in the day-to-day variability of the ESF in its occurrence season.

  10. Fast and ultrafast Kelvin wave modulations of the equatorial evening F region vertical drift and spread F development

    NASA Astrophysics Data System (ADS)

    Abdu, Mangalathayil A.; Brum, Christiano GM; Batista, Paulo P.; Gurubaran, Subramanian; Pancheva, Dora; Bageston, Jose V.; Batista, Inez S.; Takahashi, Hisao

    2015-01-01

    In this paper, we investigate the role of eastward and upward propagating fast (FK) and ultrafast Kelvin (UFK) waves in the day-to-day variability of equatorial evening prereversal vertical drift and post sunset generation of spread F/plasma bubble irregularities. Meteor wind data from Cariri and Cachoeira Paulista (Brazil) and medium frequency (MF) radar wind data from Tirunelveli (India) are analyzed together with Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics/Sounding of the Atmosphere using Broadband Emission Radiometry (TIMED/SABER) temperature in the 40- to 100-km region to characterize the zonal and vertical propagations of these waves. Also analyzed are the F region evening vertical drift and spread F (ESF) development features as diagnosed by Digisonde (Lowell Digisonde International, LLC, Lowell, MA, USA) operated at Fortaleza and Sao Luis in Brazil. The SABER temperature data permitted determination of the upward propagation characteristics of the FK (E1) waves with propagation speed in the range of 4 km/day. The radar mesosphere and lower thermosphere (MLT) winds in the widely separated longitude sectors have yielded the eastward phase velocity of both the FK and UFK waves. The vertical propagation of these waves cause strong oscillation in the F region evening prereversal vertical drift, observed for the first time at both FK and UFK periodicities. A delay of a few (approximately 10) days is observed in the F region vertical drift perturbation with respect to the corresponding FK/UFK zonal wind oscillations, or temperature oscillations in the MLT region, which has permitted a direct identification of the sunset electrodynamic coupling process as being responsible for the generation of the FK/UFK-induced vertical drift oscillation. The vertical drift oscillations are found to cause significant modulation in the spread F/plasma bubble irregularity development. The overall results highlight the role of FK/UFK waves in the day

  11. Seismic architecture and morphology of Neogenic sediment waves and drifts, offshore West Africa

    NASA Astrophysics Data System (ADS)

    Baglioni, Luca; Bonamini, Enrico

    2013-04-01

    The three dimension visualisation softwares of seismic data and the recent development of semi-automatic interpretation tools allow to define the 3D morphology of ancient depositional systems at a resolution never achieved before. This study analyses a Neogenic stratigraphic interval in the deep water of the West African margin. The purpose of the work is the understanding of the sedimentary architectures and the link with the genetic depositional processes. The study is mainly based on the interpretation of seismic geometries and amplitude/isochron maps derived from newly-interpreted seismic horizons. The seismic stratigraphy reveals abrupt changes in depositional styles and sedimentary processes. Transitions between Sediment Drifts (SD), Sediment Waves (SWs) and Mass Transport Complexes (MTCs) are here frequently observed, suggesting that cyclically either bottom-current intensity decreased or gravity-flow input overwhelmed the bottom-current signal. The lower studied interval corresponds to a SD sequence, made up of stacked individual packages and having a maximum thickness of 300 ms. The landward drift morphology is characterized by convex-upward, mounded seismic reflections. Each drift onlaps on a seaward-dipping reflection interpreted as paleo-slope. These contouritic deposits are concentrated near the base of slope, and fade out downdip. The drift appears to be grown from the deeper part of the basin and backstepped up the slope. It is inferred that the deposition of the drifts took place under the influence of a marine current, subparallel to the southern margin of West African coast. The backstepping of the onlapping architecture may have resulted from bottom current acceleration across the ramp. The intermediate studied interval represents a transitional sequence in which SW are alternated with MTDs of minor size (up to 60 ms thick). In this transition interval, onlap relationships and thickness variations suggest that gravity flow deposits preferentially

  12. Collisionless inter-species energy transfer and turbulent heating in drift wave turbulence

    SciTech Connect

    Zhao, L.; Diamond, P. H.

    2012-08-15

    We reconsider the classic problems of calculating 'turbulent heating' and collisionless inter-species transfer of energy in drift wave turbulence. These issues are of interest for low collisionality, electron heated plasmas, such as ITER, where collisionless energy transfer from electrons to ions is likely to be significant. From the wave Poynting theorem at steady state, a volume integral over an annulus r{sub 1}=-S{sub r}|{sub r{sub 1}{sup r{sub 2}}}{ne}0. Here S{sub r} is the wave energy density flux in the radial direction. Thus, a wave energy flux differential across an annular region indeed gives rise to a net heating, in contrast to previous predictions. This heating is related to the Reynolds work by the zonal flow, since S{sub r} is directly linked to the zonal flow drive. In addition to net heating, there is inter-species heat transfer. For collisionless electron drift waves, the total turbulent energy source for collisionless heat transfer is due to quasilinear electron cooling. Subsequent quasilinear ion heating occurs through linear ion Landau damping. In addition, perpendicular heating via ion polarization currents contributes to ion heating. Since at steady state, Reynolds work of the turbulence on the zonal flow must balance zonal flow frictional damping ({approx}{nu}{sub ii}{sup 2}{approx}|(e{phi}(tilde sign)/T)|{sup 4}), it is no surprise that zonal flow friction appears as an important channel for ion heating. This process of energy transfer via zonal flow has not previously been accounted for in analyses of energy transfer. As an application, we compare the rate of turbulent energy transfer in a low collisionality plasma with the rate of the energy transfer by collisions. The result shows that the collisionless turbulent energy transfer is a significant energy coupling process for ITER plasma.

  13. Drift-Alfven wave mediated particle transport in an elongated density depression

    SciTech Connect

    Vincena, Stephen; Gekelman, Walter

    2006-06-15

    Cross-field particle transport due to drift-Alfven waves is measured in an elongated density depression within an otherwise uniform, magnetized helium plasma column. The depression is formed by drawing an electron current to a biased copper plate with cross-field dimensions of 28x0.24 ion sound-gyroradii {rho}{sub s}=c{sub s}/{omega}{sub ci}. The process of density depletion and replenishment via particle flux repeats in a quasiperiodic fashion for the duration of the current collection. The mode structure of the wave density fluctuations in the plane perpendicular to the background magnetic field is revealed using a two-probe correlation technique. The particle flux as a function of frequency is measured using a linear array of Langmuir probes and the only significant transport occurs for waves with frequencies between 15%-25% of the ion cyclotron frequency (measured in the laboratory frame) and with perpendicular wavelengths k{sub perpendicular}{rho}{sub s}{approx}0.7. The frequency-integrated particle flux is in rough agreement with observed increases in density in the center of the depletion as a function of time. The experiments are carried out in the Large Plasma Device (LAPD) [Gekelman et al., Rev. Sci. Instrum. 62, 2875 (1991)] at the Basic Plasma Science Facility located at the University of California, Los Angeles.

  14. A flowing plasma model to describe drift waves in a cylindrical helicon discharge

    NASA Astrophysics Data System (ADS)

    Chang, L.; Hole, M. J.; Corr, C. S.

    2011-04-01

    A two-fluid model developed originally to describe wave oscillations in the vacuum arc centrifuge, a cylindrical, rapidly rotating, low temperature, and confined plasma column, is applied to interpret plasma oscillations in a RF generated linear magnetized plasma [WOMBAT (waves on magnetized beams and turbulence)], with similar density and field strength. Compared to typical centrifuge plasmas, WOMBAT plasmas have slower normalized rotation frequency, lower temperature, and lower axial velocity. Despite these differences, the two-fluid model provides a consistent description of the WOMBAT plasma configuration and yields qualitative agreement between measured and predicted wave oscillation frequencies with axial field strength. In addition, the radial profile of the density perturbation predicted by this model is consistent with the data. Parameter scans show that the dispersion curve is sensitive to the axial field strength and the electron temperature, and the dependence of oscillation frequency with electron temperature matches the experiment. These results consolidate earlier claims that the density and floating potential oscillations are a resistive drift mode, driven by the density gradient. To our knowledge, this is the first detailed physics model of flowing plasmas in the diffusion region away from the RF source. Possible extensions to the model, including temperature nonuniformity and magnetic field oscillations, are also discussed.

  15. A flowing plasma model to describe drift waves in a cylindrical helicon discharge

    SciTech Connect

    Chang, L.; Hole, M. J.; Corr, C. S.

    2011-04-15

    A two-fluid model developed originally to describe wave oscillations in the vacuum arc centrifuge, a cylindrical, rapidly rotating, low temperature, and confined plasma column, is applied to interpret plasma oscillations in a RF generated linear magnetized plasma [WOMBAT (waves on magnetized beams and turbulence)], with similar density and field strength. Compared to typical centrifuge plasmas, WOMBAT plasmas have slower normalized rotation frequency, lower temperature, and lower axial velocity. Despite these differences, the two-fluid model provides a consistent description of the WOMBAT plasma configuration and yields qualitative agreement between measured and predicted wave oscillation frequencies with axial field strength. In addition, the radial profile of the density perturbation predicted by this model is consistent with the data. Parameter scans show that the dispersion curve is sensitive to the axial field strength and the electron temperature, and the dependence of oscillation frequency with electron temperature matches the experiment. These results consolidate earlier claims that the density and floating potential oscillations are a resistive drift mode, driven by the density gradient. To our knowledge, this is the first detailed physics model of flowing plasmas in the diffusion region away from the RF source. Possible extensions to the model, including temperature nonuniformity and magnetic field oscillations, are also discussed.

  16. Anomalous perturbative transport in tokamaks due to drift-wave turbulence

    SciTech Connect

    Thoul, A.A. ); Similon, P.L. ); Sudan, R.N. )

    1994-03-01

    A new method for calculating the anomalous transport in tokamak plasmas is presented. The renormalized nonlinear plasma response function is derived using the direct-interaction approximation (DIA). A complete calculation for the case of electrostatic drift-wave turbulence is presented. Explicit expressions for all coefficients of the anomalous transport matrix relating particle and heat fluxes to density and temperature gradients in the plasma are obtained. The anomalous transport matrix calculated using the DIA does not have the Onsager symmetry. As an example of application, the parameters of the Texas Experimental Tokamak (TEXT) [Nucl. Technol. Fusion [bold 1], 479 (1981)] are used to evaluate all transport coefficients numerically, as well as the spectrum modulation. The relation between the theoretical results and the experimental data is discussed. Although this paper focuses on electron transport for simplicity, the method can also be used to calculate anomalous transport due to ion instabilities, such as the ion-temperature-gradient instability.

  17. Small scale coherent vortex generation in drift wave-zonal flow turbulence

    SciTech Connect

    Guo, Z. B. Hahm, T. S.; Diamond, P. H.

    2015-12-15

    We present a paradigm for the generation of small scale coherent vortex (SSCV) in drift wave-zonal flow (DW-ZF) turbulence. We demonstrate that phases of DWs can couple coherently, mediated by the ZF shearing. A SSCV is formed when the phases of the DWs are “attracted” to form a stable “phase cluster.” We show that the ZF shearing induces asymmetry between “attractive” and “repulsive” phase couplings, so that a net attractive phase coupling results. The turbulent DWs will (partially)synchronize into a stable SSCV at locations, where the attractive phase coupling induced by the ZF shearing exceeds the “detuning” effects by the DW dispersion and random phase scattering. We also discuss the “self-binding” effect of the newly formed SSCV.

  18. A mini-max principle for drift waves and mesoscale fluctuations

    NASA Astrophysics Data System (ADS)

    Itoh, S.-I.; Itoh, K.

    2011-01-01

    A mini-max principle for the system of the drift waves and mesoscale fluctuations (e.g. zonal flows, etc) is studied. For the system of model equations a Lyapunov function is constructed, which takes the minimum when the stationary state is realized. The dynamical evolution describes the access to the state that is realized. The competition between different mesoscale fluctuations is explained. The origins of irreversibility that cause an approach to the stationary state are discussed. A selection rule among fluctuations is derived, and conditions, under which different kinds of mesocale fluctuations coexist, are investigated. An analogy of this minimum principle to the principle of 'minimum Helmholtz free energy' in thermal equilibrium is shown.

  19. ECE Imaging of Temperature Fluctuations and Drift Waves in DIII-D Plasmas

    NASA Astrophysics Data System (ADS)

    Zemedkun, Samuel; Munsat, Tobin; Tobias, Benjamin; Luhmann, Neville; Domier, Calvin

    2012-10-01

    Recent observations of 2-D turbulent structures have been performed with the ECEI instrument on DIII-D. The experiments were performed in NBI and ECH-heated plasmas, over a range of external heating power. Correlation techniques similar to those used in Correlation Electron Cyclotron Emission (CECE) systems are employed, with the advantage that the ECEI system detects a full 2-D array of plasma locations: vertical separation is provided by an optical system and horizontal separation is provided by frequency discrimination in the detection electronics. Among the results are 2-D images of poloidally-propagating drift-waves, and correlation properties of fluctuations (<200 kHz) in both the radial and poloidal directions. Scaling and parameter dependencies on plasma and heating conditions will be presented. In addition to the physics results, the data demonstrates the viability of the ECEI system in the presence of ECH heating, which will also be discussed.

  20. Excitation of kinetic geodesic acoustic modes by drift waves in nonuniform plasmas

    SciTech Connect

    Qiu, Z.; Chen, L.; Zonca, F.

    2014-02-15

    Effects of system nonuniformities and kinetic dispersiveness on the spontaneous excitation of Geodesic Acoustic Mode (GAM) by Drift Wave (DW) turbulence are investigated based on nonlinear gyrokinetic theory. The coupled nonlinear equations describing parametric decay of DW into GAM and DW lower sideband are derived and then solved both analytically and numerically to investigate the effects on the parametric decay process due to system nonuniformities, such as nonuniform diamagnetic frequency, finite radial envelope of DW pump, and kinetic dispersiveness. It is found that the parametric decay process is a convective instability for typical tokamak parameters when finite group velocities of DW and GAM associated with kinetic dispersiveness and finite radial envelope are taken into account. When, however, nonuniformity of diamagnetic frequency is taken into account, the parametric decay process becomes, time asymptotically, a quasi-exponentially growing absolute instability.

  1. Gyroaverage effects on chaotic transport by drift waves in zonal flows

    SciTech Connect

    Martinell, J.; Del-Castillo-Negrete, Diego B

    2013-01-01

    Finite Larmor radius (FLR) effects on E x B test particle chaotic transport in the presence of zonal flows is studied. The FLR effects are introduced by the gyro-average of a simplified E x B guiding center model consisting of the linear superposition of a non-monotonic zonal flow and drift waves. Non-monotonic zonal flows play a critical role on transport because they exhibit robust barriers to chaotic transport in the region(s) where the shear vanishes. In addition, the non-monotonicity gives rise to nontrivial changes in the topology of the orbits of the E x B Hamiltonian due to separatrix reconnection. The present study focuses on the role of FLR effects on these two signatures of non-monotonic zonal flows: shearless transport barriers and separatrix reconnection. It is shown that, as the Larmor radius increases, the effective zonal flow profile bifurcates and multiple shearless regions are created. As a result, the topology of the gyro-averaged Hamiltonian exhibits very complex separatrix reconnection bifurcations. It is also shown that FLR effects tend to reduce chaotic transport. In particular, the restoration of destroyed transport barriers is observed as the Larmor radius increases. A detailed numerical study is presented on the onset of global chaotic transport as function of the amplitude of the drift waves and the Larmor radius. For a given amplitude, the threshold for the destruction of the shearless transport barrier, as function of the Larmor radius, exhibits a fractal-like structure. The FLR effects on a thermal distribution of test particles are also studied. In particular, the fraction of confined particles with a Maxwellian distribution of gyroradii is computed, and an effective transport suppression is found for high enough temperatures.

  2. Gyroaverage effects on chaotic transport by drift waves in zonal flows

    SciTech Connect

    Martinell, Julio J.; Castillo-Negrete, Diego del

    2013-02-15

    Finite Larmor radius (FLR) effects on E Multiplication-Sign B test particle chaotic transport in the presence of zonal flows is studied. The FLR effects are introduced by the gyro-average of a simplified E Multiplication-Sign B guiding center model consisting of the linear superposition of a non-monotonic zonal flow and drift waves. Non-monotonic zonal flows play a critical role on transport because they exhibit robust barriers to chaotic transport in the region(s) where the shear vanishes. In addition, the non-monotonicity gives rise to nontrivial changes in the topology of the orbits of the E Multiplication-Sign B Hamiltonian due to separatrix reconnection. The present study focuses on the role of FLR effects on these two signatures of non-monotonic zonal flows: shearless transport barriers and separatrix reconnection. It is shown that, as the Larmor radius increases, the effective zonal flow profile bifurcates and multiple shearless regions are created. As a result, the topology of the gyro-averaged Hamiltonian exhibits very complex separatrix reconnection bifurcations. It is also shown that FLR effects tend to reduce chaotic transport. In particular, the restoration of destroyed transport barriers is observed as the Larmor radius increases. A detailed numerical study is presented on the onset of global chaotic transport as function of the amplitude of the drift waves and the Larmor radius. For a given amplitude, the threshold for the destruction of the shearless transport barrier, as function of the Larmor radius, exhibits a fractal-like structure. The FLR effects on a thermal distribution of test particles are also studied. In particular, the fraction of confined particles with a Maxwellian distribution of gyroradii is computed, and an effective transport suppression is found for high enough temperatures.

  3. Stability of spherical converging shock wave

    SciTech Connect

    Murakami, M.; Sanz, J.; Iwamoto, Y.

    2015-07-15

    Based on Guderley's self-similar solution, stability of spherical converging shock wave is studied. A rigorous linear perturbation theory is developed, in which the growth rate of perturbation is given as a function of the spherical harmonic number ℓ and the specific heats ratio γ. Numerical calculation reveals the existence of a γ-dependent cut-off mode number ℓ{sub c}, such that all the eigenmode perturbations for ℓ > ℓ{sub c} are smeared out as the shock wave converges at the center. The analysis is applied to partially spherical geometries to give significant implication for different ignition schemes of inertial confinement fusion. Two-dimensional hydrodynamic simulations are performed to verify the theory.

  4. Stability of spherical converging shock wave

    NASA Astrophysics Data System (ADS)

    Murakami, M.; Sanz, J.; Iwamoto, Y.

    2015-07-01

    Based on Guderley's self-similar solution, stability of spherical converging shock wave is studied. A rigorous linear perturbation theory is developed, in which the growth rate of perturbation is given as a function of the spherical harmonic number ℓ and the specific heats ratio γ. Numerical calculation reveals the existence of a γ-dependent cut-off mode number ℓc, such that all the eigenmode perturbations for ℓ > ℓc are smeared out as the shock wave converges at the center. The analysis is applied to partially spherical geometries to give significant implication for different ignition schemes of inertial confinement fusion. Two-dimensional hydrodynamic simulations are performed to verify the theory.

  5. Density-dependence, Drift and Disturbance: Feedbacks and Interactions Between Hydraulics, Bed Stability and Invertebrates in a Sandy Gravel-bed River

    NASA Astrophysics Data System (ADS)

    Gibbins, C. N.; Vericat, D.; Batalla, R.

    2008-12-01

    Whether invertebrate drift is dependent on benthic density or not remains a key but unresolved question in stream ecology. Downstream drift is important not only because voluntary entry into the water column is one of the main ways in which invertebrates can affect their redistribution, but because involuntary drift during floods is a very obvious cause of disturbance to benthic communities. Moreover, drifting invertebrates are an important source of food for many fish and so drift influences wider ecosystem processes. Despite its importance, a number of issues related to drift remain unclear and/or contentious; notable amongst these is the issue of whether drift rates depend on benthic density (i.e. whether drift is density-dependent). In this paper we assess whether channel hydraulics and bed stability affect the density-dependence of drift. We use a portable flume to manipulate hydraulic conditions in a section of river with contrasting sediment sizes, levels of bed stability and benthic densities and assess the drift responses of invertebrates. We describe the interactions and feedbacks between benthic invertebrate density, drift losses and substrate stability, focusing particularly on whether drift changes from being density dependent to independent once bed material is mobilized during flood events. The paper emphasizes the importance of substrate size and stability both for benthic assemblages and the magnitude of drift losses during periods of physical disturbance. It argues that large scale loss of animals from the bed can occur rapidly during small floods and even minor discharge fluctuations, such that exhaustion of the benthic source pool affects subsequent drift losses. Local (within- reach) differences in sediment sizes, bed structure and substrate stability influence the dependence of drift on benthic density.

  6. Selecting, Characterizing, and Acting on Drift Waves and Flute Modes Turbulence in a Low-{beta} Magnetized Plasma Column

    SciTech Connect

    Bonhomme, G.; Brochard, F.; Gravier, E.; Oldenbuerger, S.; Philipp, M.

    2006-01-15

    We report on experiments performed on the low-{beta} plasma device MIRABELLE. Using a limiter, we recently observed that when increasing the magnetic field strength transitions between various gradient driven instabilities occur. New thorough measurements allow to identify unambiguously three instability regimes. At low magnetic field the strong ErxB velocity shear drives a Kelvin-Helmholtz instability, whereas at high magnetic field drift waves are only observed. A centrifugal (Rayleigh-Taylor) instability is also observed in between when the poloidal velocity field is shearless and strong enough. A close connection is made between the ratio {rho}s /L perpendicular of the drift parameter to the radial density gradient length and each instability regime. The transition scenario from regular waves to turbulence was experimentally investigated. As for drift waves the transition from regular state to spatio-temporal chaos and turbulence follows the quasi-periodicity (or Ruelle-Takens-Newhouse) route. Eventually we present new results on the efficiency of control and synchronization methods on Kelvin-Helmholtz and Rayleigh-Taylor spatio-temporal chaos in comparison with drift waves.

  7. Estimates of Lagrangian particle transport by wave groups: forward transport by Stokes drift and backward transport by the return flow

    NASA Astrophysics Data System (ADS)

    van den Bremer, Ton S.; Taylor, Paul H.

    2014-11-01

    Although the literature has examined Stokes drift, the net Lagrangian transport by particles due to of surface gravity waves, in great detail, the motion of fluid particles transported by surface gravity wave groups has received considerably less attention. In practice nevertheless, the wave field on the open sea often has a group-like structure. The motion of particles is different, as particles at sufficient depth are transported backwards by the Eulerian return current that was first described by Longuet-Higgins & Stewart (1962) and forms an inseparable counterpart of Stokes drift for wave groups ensuring the (irrotational) mass balance holds. We use WKB theory to study the variation of the Lagrangian transport by the return current with depth distinguishing two-dimensional seas, three-dimensional seas, infinite depth and finite depth. We then provide dimensional estimates of the net horizontal Lagrangian transport by the Stokes drift on the one hand and the return flow on the other hand for realistic sea states in all four cases. Finally we propose a simple scaling relationship for the transition depth: the depth above which Lagrangian particles are transported forwards by the Stokes drift and below which such particles are transported backwards by the return current.

  8. Precursor wave structure, prereversal vertical drift, and their relative roles in the development of post sunset equatorial spread-F

    NASA Astrophysics Data System (ADS)

    Abdu, Mangalathayil; Sobral, José; alam Kherani, Esfhan; Batista, Inez S.; Souza, Jonas

    2016-07-01

    The characteristics of large-scale wave structure in the equatorial bottomside F region that are present during daytime as precursor to post sunset development of the spread F/plasma bubble irregularities are investigated in this paper. Digisonde data from three equatorial sites in Brazil (Fortaleza, Sao Luis and Cachimbo) for a period of few months at low to medium/high solar activity phases are analyzed. Small amplitude oscillations in the F layer true heights, representing wave structure in polarization electric field, are identified as upward propagating gravity waves having zonal scale of a few hundred kilometers. Their amplitudes undergo amplification towards sunset, and depending on the amplitude of the prereversal vertical drift (PRE) they may lead to post sunset generation of ESF/plasma bubble irregularities. On days of their larger amplitudes they appear to occur in phase coherence on all days, and correspondingly the PRE vertical drift velocities are larger than on days of the smaller amplitudes of the wave structure that appear at random phase on the different days. The sustenance of these precursor waves structures is supported by the relatively large ratio (approaching unity) of the F region-to- total field line integrated Pedersen conductivities as calculated using the SUPIM simulation of the low latitude ionosphere. This study examines the role of the wave structure relative to that of the prereversal vertical drift in the post sunset spread F irregularity development.

  9. Reentrant stability of BEC standing wave patterns

    SciTech Connect

    Kalas, Ryan M; Solenov, Dmitry; Timmermans, Eddy M

    2009-01-01

    We describe standing wave patterns induced by an attractive finite-ranged external potential in a large Bose-Einstein Condensate (BEC). As the potential depth increases, the time independent Gross-Pitaevskii equation develops pairs of solutions that have nodes in their wavefunction. We elucidate the nature of these states and study their dynamical stability. Although we study the problem in a two-dimensional BEC subject to a cylindrically symmetric square-well potential of a radius that is comparable to the coherence length of the BEC, our analysis reveals general trends, valid in two and three dimensions, independent of the symmetry of the localized potential well, and suggestive of the behavior in general, short- and large-range potentials. One set of nodal BEC wavefunctions resembles the single particle n node bound state wavefunction of the potential well, the other wavefunctions resemble the n - 1 node bound-state wavefunction with a kink state pinned by the potential. The second state, though corresponding to the lower free energy value of the pair of n node BEC states, is always unstable, whereas the first can be dynamically stable in intervals of the potential well depth, implying that the standing wave BEC can evolve from a dynamically unstable to stable, and back to unstable status as the potential well is adiabatically deepened, a phenomenon that we refer to as 'reentrant dynamical stability'.

  10. Drift and diffusion of spin and charge density waves in a two-dimensional electron gas

    NASA Astrophysics Data System (ADS)

    Yang, Luyi; Koralek, J. D.; Orenstein, J.; Tibbetts, D. R.; Reno, J. L.; Lilly, M. P.

    2011-03-01

    We use transient grating spectroscopy (TGS) to study the persistent spin helix (PSH) state and electron-hole density wave (EHDW) in a 2D electron gas in the presence of an in-plane electric field parallel to the wavevector of the PSH or EHDW. By directly measuring the phase, we can measure the PSH and EHDW displacement with 10 nm spatial and sub-picosecond time resolution. We obtain both the spin diffusion and mobility and ambipolar diffusion and mobility from the TGS measurements of PSH and EHDW, respectively. The spin transresistivity extracted from the spin diffusion is in excellent agreement with the RPA theory of spin Coulomb drag (SCD). The spin mobility data indicate that SCD may also play a role in the spin wave drifting process. From the ambipolar diffusion and mobility, we obtain the transresistivity of electrons and holes in the same layer, which is much stronger than is typically seen in the conventional Coulomb drag experiments on coupled quantum wells.

  11. Coupled ion acoustic and drift waves in magnetized superthermal electron-positron-ion plasmas

    SciTech Connect

    Adnan, Muhammad; Qamar, Anisa; Mahmood, S.

    2014-09-15

    Linear and nonlinear coupled drift-ion acoustic waves are investigated in a nonuniform magnetoplasma having kappa distributed electrons and positrons. In the linear regime, the role of kappa distribution and positron content on the dispersion relation has been highlighted; it is found that strong superthermality (low value of κ) and addition of positrons lowers the phase velocity via decreasing the fundamental scalelengths of the plasmas. In the nonlinear regime, first, coherent nonlinear structure in the form of dipoles and monopoles are obtained and the boundary conditions (boundedness) in the context of superthermality and positron concentrations are discussed. Second, in case of scalar nonlinearity, a Korteweg–de Vries-type equation is obtained, which admit solitary wave solution. It is found that both compressive and rarefactive solitons are formed in the present model. The present work may be useful to understand the low frequency electrostatic modes in inhomogeneous electron positron ion plasmas, which exist in astrophysical plasma situations such as those found in the pulsar magnetosphere.

  12. Rossby and drift wave turbulence and zonal flows: The Charney-Hasegawa-Mima model and its extensions

    NASA Astrophysics Data System (ADS)

    Connaughton, Colm; Nazarenko, Sergey; Quinn, Brenda

    2015-12-01

    A detailed study of the Charney-Hasegawa-Mima model and its extensions is presented. These simple nonlinear partial differential equations suggested for both Rossby waves in the atmosphere and drift waves in a magnetically-confined plasma, exhibit some remarkable and nontrivial properties, which in their qualitative form, survive in more realistic and complicated models. As such, they form a conceptual basis for understanding the turbulence and zonal flow dynamics in real plasma and geophysical systems. Two idealised scenarios of generation of zonal flows by small-scale turbulence are explored: a modulational instability and turbulent cascades. A detailed study of the generation of zonal flows by the modulational instability reveals that the dynamics of this zonal flow generation mechanism differ widely depending on the initial degree of nonlinearity. The jets in the strongly nonlinear case further roll up into vortex streets and saturate, while for the weaker nonlinearities, the growth of the unstable mode reverses and the system oscillates between a dominant jet, which is slightly inclined to the zonal direction, and a dominant primary wave. A numerical proof is provided for the extra invariant in Rossby and drift wave turbulence-zonostrophy. While the theoretical derivations of this invariant stem from the wave kinetic equation which assumes weak wave amplitudes, it is shown to be relatively well-conserved for higher nonlinearities also. Together with the energy and enstrophy, these three invariants cascade into anisotropic sectors in the k-space as predicted by the Fjørtoft argument. The cascades are characterised by the zonostrophy pushing the energy to the zonal scales. A small scale instability forcing applied to the model has demonstrated the well-known drift wave-zonal flow feedback loop. The drift wave turbulence is generated from this primary instability. The zonal flows are then excited by either one of the generation mechanisms, extracting energy from

  13. Collective behavior of stabilized reaction-diffusion waves.

    PubMed

    Steele, Aaron J; Tinsley, Mark; Showalter, Kenneth

    2008-06-01

    Stabilized wave segments in the photosensitive Belousov-Zhabotinsky reaction are directionally controlled with intensity gradients in the applied illumination. The constant-velocity waves behave like self-propelled particles, and multiple waves interact via an applied interaction potential. Alignment arises from the intrinsic properties of the interacting waves, leading to processional and rotational behavior. PMID:18601510

  14. Early stages of wind wave and drift current generation under non-stationary wind conditions.

    NASA Astrophysics Data System (ADS)

    Robles-Diaz, Lucia; Ocampo-Torres, Francisco J.; Branger, Hubert

    2016-04-01

    Generation and amplification mechanisms of ocean waves are well understood under constant wind speed or limited fetch conditions. Under these situations, the momentum and energy transfers from air to water are also quite well known. However during the wind field evolution over the ocean, we may observe sometime high wind acceleration/deceleration situations (e.g. Mexican Tehuano or Mediterranean Mistral wind systems). The evolution of wave systems under these conditions is not well understood. The purpose of these laboratory experiments is to better understand the early stages of water-waves and surface-drift currents under non-stationary wind conditions and to determine the balance between transfers creating waves and surface currents during non-equilibrium situations. The experiments were conducted in the Institut Pythéas wind-wave facility in Marseille-France. The wave tank is 40 m long, 2.7 m wide and 1 m deep. The air section is 50 m long, 3 m wide and 1.8 m height. We used 11 different resistive wave-gauges located along the tank. The momentum fluxes in the air column were estimated from single and X hot-film anemometer measurements. The sampling frequency for wind velocity and surface displacement measurements was 256 Hz. Water-current measurements were performed with a profiling velocimeter. This device measures the first 3.5 cm of the water column with a frequency rate of 100Hz. During the experiments, the wind intensity was abruptly modified with a constant acceleration and deceleration over time. We observed that wind drag coefficient values for accelerated wind periods are lower than the ones reported in previous studies for constant wind speed (Large and Pond 1981; Ocampo-Torres et al. 2010; Smith 1980; Yelland and Taylor 1996). This is probably because the turbulent boundary layer is not completely developed during the increasing-wind sequence. As it was reported in some theoretical studies (Miles 1957; Phillips 1957; Kahma and Donelan 1988), we

  15. Early stages of wind wave and drift current generation under non-stationary wind conditions.

    NASA Astrophysics Data System (ADS)

    Robles-Diaz, Lucia; Ocampo-Torres, Francisco J.; Branger, Hubert

    2016-04-01

    Generation and amplification mechanisms of ocean waves are well understood under constant wind speed or limited fetch conditions. Under these situations, the momentum and energy transfers from air to water are also quite well known. However during the wind field evolution over the ocean, we may observe sometime high wind acceleration/deceleration situations (e.g. Mexican Tehuano or Mediterranean Mistral wind systems). The evolution of wave systems under these conditions is not well understood. The purpose of these laboratory experiments is to better understand the early stages of water-waves and surface-drift currents under non-stationary wind conditions and to determine the balance between transfers creating waves and surface currents during non-equilibrium situations. The experiments were conducted in the Institut Pythéas wind-wave facility in Marseille-France. The wave tank is 40 m long, 2.7 m wide and 1 m deep. The air section is 50 m long, 3 m wide and 1.8 m height. We used 11 different resistive wave-gauges located along the tank. The momentum fluxes in the air column were estimated from single and X hot-film anemometer measurements. The sampling frequency for wind velocity and surface displacement measurements was 256 Hz. Water-current measurements were performed with a profiling velocimeter. This device measures the first 3.5 cm of the water column with a frequency rate of 100Hz. During the experiments, the wind intensity was abruptly modified with a constant acceleration and deceleration over time. We observed that wind drag coefficient values for accelerated wind periods are lower than the ones reported in previous studies for constant wind speed (Large and Pond 1981; Ocampo-Torres et al. 2010; Smith 1980; Yelland and Taylor 1996). This is probably because the turbulent boundary layer is not completely developed during the increasing-wind sequence. As it was reported in some theoretical studies (Miles 1957; Phillips 1957; Kahma and Donelan 1988), we

  16. Stabilized wave segments in an excitable medium with a phase wave at the wave back

    NASA Astrophysics Data System (ADS)

    Zykov, V. S.; Bodenschatz, E.

    2014-04-01

    The propagation velocity and the shape of a stationary propagating wave segment are determined analytically for excitable media supporting excitation waves with trigger fronts and phase backs. The general relationships between the medium's excitability and the wave segment parameters are obtained in the framework of the free boundary approach under quite usual assumptions. Two universal limits restricting the region of existence of stabilized wave segments are found. The comparison of the analytical results with numerical simulations of the well-known Kessler-Levine model demonstrates their good quantitative agreement. The findings should be applicable to a wide class of systems, such as the propagation of electrical waves in the cardiac muscle or wave propagation in autocatalytic chemical reactions, due to the generality of the free-boundary approach used.

  17. The Influence of Drift Gas Composition on the Separation Mechanism in Traveling Wave Ion Mobility Spectrometry: Insight from Electrodynamic Simulations

    PubMed Central

    May, Jody C.; McLean, John A.

    2013-01-01

    The influence of three different drift gases (helium, nitrogen, and argon) on the separation mechanism in traveling wave ion mobility spectrometry is explored through ion trajectory simulations which include considerations for ion diffusion based on kinetic theory and the electrodynamic traveling wave potential. The model developed for this work is an accurate depiction of a second-generation commercial traveling wave instrument. Three ion systems (cocaine, MDMA, and amphetamine) whose reduced mobility values have previously been measured in different drift gases are represented in the simulation model. The simulation results presented here provide a fundamental understanding of the separation mechanism in traveling wave, which is characterized by three regions of ion motion: (1) ions surfing on a single wave, (2) ions exhibiting intermittent roll-over onto subsequent waves, and (3) ions experiencing a steady state roll-over which repeats every few wave cycles. These regions of ion motion are accessed through changes in the gas pressure, wave amplitude, and wave velocity. Resolving power values extracted from simulated arrival times suggest that momentum transfer in helium gas is generally insufficient to access regions (2) and (3) where ion mobility separations occur. Ion mobility separations by traveling wave are predicted to be effectual for both nitrogen and argon, with slightly lower resolving power values observed for argon as a result of band-broadening due to collisional scattering. For the simulation conditions studied here, the resolving power in traveling wave plateaus between regions (2) and (3), with further increases in wave velocity contributing only minor improvements in separations. PMID:23888124

  18. Note: Autocollimation with ultra-high resolution and stability using telephoto objective together with optical enlargement and beam drift compensation.

    PubMed

    Zhu, Fan; Tan, Xinran; Tan, Jiubin; Fan, Zhigang

    2016-08-01

    An autocollimation (AC) setup with ultra-high resolution and stability for micro-angle measurement is presented. The telephoto objective, which is characterized in long focal length at a compact structure size, and the optical enlargement unit, which can magnify the image displacement to improve its measurement resolution and accuracy, are used to obtain an ultra-high measurement resolution of the AC. The common-path beam drift compensation is used to suppress the drift of measurement results, which is evident in the high-resolution AC, thus to obtain a high measurement stability. Experimental results indicate that an effective resolution of better than 0.0005 arc sec (2.42 nrad) over a measurement range of ±30 arc sec and a 2-h stability of 0.0061 arc sec (29.57 nrad) can be achieved. PMID:27587181

  19. Complete classification of discrete resonant Rossby/drift wave triads on periodic domains

    NASA Astrophysics Data System (ADS)

    Bustamante, Miguel D.; Hayat, Umar

    2013-09-01

    We consider the set of Diophantine equations that arise in the context of the partial differential equation called "barotropic vorticity equation" on periodic domains, when nonlinear wave interactions are studied to leading order in the amplitudes. The solutions to this set of Diophantine equations are of interest in atmosphere (Rossby waves) and Tokamak plasmas (drift waves), because they provide the values of the spectral wavevectors that interact resonantly via three-wave interactions. These wavenumbers come in "triads", i.e., groups of three wavevectors. We provide the full solution to the Diophantine equations in the physically sensible limit when the Rossby deformation radius is infinite. The method is completely new, and relies on mapping the unknown variables via rational transformations, first to rational points on elliptic curves and surfaces, and from there to rational points on quadratic forms of "Minkowski" type (such as the familiar space-time in special relativity). Classical methods invented centuries ago by Fermat, Euler, Lagrange, Minkowski, are used to classify all solutions to our original Diophantine equations, thus providing a computational method to generate numerically all the resonant triads in the system. Computationally speaking, our method has a clear advantage over brute-force numerical search: on a 10,0002 grid, the brute-force search would take 15 years using optimised C codes on a cluster, whereas our method takes about 40 min using a laptop. Moreover, the method is extended to generate so-called quasi-resonant triads, which are defined by relaxing the resonant condition on the frequencies, allowing for a small mismatch. Quasi-resonant triads' distribution in wavevector space is robust with respect to physical perturbations, unlike resonant triads' distribution. Therefore, the extended method is really valuable in practical terms. We show that the set of quasi-resonant triads form an intricate network of connected triads, forming

  20. Nonlinear Trivelpiece-Gould Waves: Frequency, Functional Form, and Stability

    NASA Astrophysics Data System (ADS)

    Dubin, Daniel H. E.

    2015-11-01

    This poster considers the frequency, spatial form, and stability, of nonlinear Trivelpiece- Gould (TG) waves on a cylindrical plasma column of length L and radius rp, treating both traveling and standing waves, and focussing on the regime of experimental interest in which L/rp >> 1. In this regime TG waves are weakly dispersive, allowing strong mode-coupling between Fourier harmonics. The mode coupling implies that linear theory for such waves is a poor approximation even at fairly small amplitudes, and nonlinear theories that include only a small number of harmonics (such as 3-wave parametric resonance theory) fail to fully capture the stability properties of the system. We find that nonlinear standing waves suffer jumps in their functional form as their amplitude is varied continuously. The jumps are caused by nonlinear resonances between the standing wave and nearly linear waves whose frequencies and wave numbers are harmonics of the standing wave. Also, the standing waves are found to be unstable to a multi-wave version of 3-wave parametric resonance, with an amplitude required for instability onset that is much larger than expected from three wave theory. For traveling wave, linearly stability is found for all amplitudes that could be studied, in contradiction to 3-wave theory. Supported by National Science Foundation Grant PHY-1414570, Department of Energy Grants DE-SC0002451and DE-SC0008693.

  1. On wave stability in relativistic cosmic-ray hydrodynamics

    NASA Technical Reports Server (NTRS)

    Webb, G. M.

    1989-01-01

    Wave stability of a two-fluid hydrodynamical model describing the acceleration of cosmic rays by the first-order Fermi mechanism in relativistic, cosmic-ray-modified shocks is investigated. For a uniform background state, the short- and long-wavelength wave speeds are shown to interlace, thus assuring wave stability in this case. A JWKB analysis is performed to investigate the stability of short-wavelength thermal gas sound waves in the smooth, decelerating supersonic flow upstream of a relativistic, cosmic-ray-modified shock. The stability of the waves is assessed both in terms of the fluid velocity and density perturbations, as well as in terms of the wave action. The stability and interaction of the short-wavelength cosmic-ray coherent mode with the background flow is also studied.

  2. Flow topology and Lagrangian conditional statistics in dissipative drift-wave turbulence

    NASA Astrophysics Data System (ADS)

    Kadoch, Benjamin; Del-Castillo-Negrete, Diego; Bos, Wouter J. T.; Schneider, Kai

    2015-11-01

    Lagrangian statistics in drift-wave turbulence, modeled by the Hasegawa-Wakatani system and its modified version, are investigated. The later shows the emergence of pronounced zonal flows. Different values of the adiabaticity parameter are considered. The main goal is to characterize the role of coherent structures (vortices and zonal flows) on the Lagrangian statistics of particles. Computationally intensive simulations following ensembles of test particles over hundreds of eddy turnover times are considered in statistically stationary turbulent flows. The flow topology is characterized using the Lagrangian Okubo-Weiss criterion [Kadoch et al., Phys. Rev. E 83 (2011)], and the flow is thus split into topologically different domains. In elliptic and hyperbolic regions, the probability density functions (pdfs) of the residence time have self-similar algebraic decaying tails. However, in the intermediate regions the pdfs do exhibit exponentially decaying tails. Topologically conditioned pdfs of the Lagrangian velocity and acceleration are also computed. The differences between the classical Hasegawa-Wakatani system and its modified version are assessed.

  3. Impact of resonant magnetic perturbations on nonlinearly driven modes in drift-wave turbulence

    SciTech Connect

    Leconte, M.; Diamond, P. H.

    2012-05-15

    In this work, we study the effects of resonant magnetic perturbations (RMPs) on turbulence, flows, and confinement in the framework of resistive drift wave turbulence. We extend the Hasegawa-Wakatani model to include RMP fields. The effect of the RMPs is to induce a linear coupling between the zonal electric field and the zonal density gradient, which drives the system to a state of electron radial force balance for large ({delta}B{sub r}/B{sub 0}). Both the vorticity flux (Reynolds stress) and particle flux are modulated. We derive an extended predator prey model which couples zonal potential and density dynamics to the evolution of turbulence intensity. This model has both turbulence drive and RMP amplitude as control parameters and predicts a novel type of transport bifurcation in the presence of RMPs. We find states that are similar to the ZF-dominated state of the standard predator-prey model, but for which the power threshold is now a function of the RMP strength. For small RMP amplitude, the energy of zonal flows decreases and the turbulence energy increases with ({delta}B{sub r}/B{sub 0}), corresponding to a damping of zonal flows.

  4. Flow topology, Lagrangian statistics, and transport in resistive drift-wave turbulence

    NASA Astrophysics Data System (ADS)

    Kadoch, B.; Del-Castillo-Negrete, Diego; Bos, W. J. T.; Schneider, K.

    2012-10-01

    Transport is strongly influenced by coherent structures. In particular, trapping in vortices tends to arrest transport and zonal flows can induce large Lagrangian displacements. It is thus of interest to characterize coherent structures from a Lagrangian perspective. For 2-D flows, the Eulerian Weiss criterion provides a tool to partition the flow into topologically different regions: elliptic (vortex dominated), hyperbolic (deformation dominated), and intermediate (turbulent background). In Ref.footnotetextB. Kadoch, D. del-Castillo-Negrete, W.J.T Bos, and K. Schneider, Phys. Rev. E 83, 036314 (2011). we proposed the Lagrangian Weiss criterion (i.e. the Weiss field computed along particle orbits) and applied it to 2-D Navier-Stokes turbulence. Here we apply this criterion to resistive drift-wave turbulence. The probability density functions (pdfs) of residence time in the topologically different regions are computed for ensembles of Lagrangian tracers. It is shown that in elliptic and hyperbolic regions the pdfs have algebraically decaying tails. The pdf of residence time in elliptic regions is proposed as a measure of particle trapping, and the relationship with waiting time statistics in continuous time random walk models of anomalous transport is explored.

  5. Shear flow and drift wave turbulence dynamics in a cylindrical plasma device

    SciTech Connect

    Yan, Z.; Tynan, G. R.; Holland, C.; Xu, M.; Mueller, S. H.; Yu, J. H.

    2010-03-15

    The experimental observations of the dynamics of the coupled drift wave turbulence (DWT)/sheared zonal flow (ZF) system in a cylindrical plasma device using a combination of Langmuir probe and fast-framing imaging measurements are reported. The results show the presence of an azimuthal ZF that exhibits low frequency (approx250 Hz) fluctuations. The envelope of the higher frequency (above 5 kHz) floating potential fluctuations associated with the DWT, the density gradient, and the turbulent radial particle flux are all modulated out of phase with the strength of the ZF. The divergence of the turbulent Reynolds stress is also modulated at the same slow time scale in a phase-coherent manner consistent with a turbulent-driven shear flow sustained against the collisional and viscous damping. The radial turbulence correlation length and cross-field particle transport are reduced during periods of strong flow shear. The results are qualitatively consistent with theoretical expectations for coupled DWT-ZF dynamics.

  6. Effects of drift gas on collision cross sections of a protein standard in linear drift tube and traveling wave ion mobility mass spectrometry.

    PubMed

    Jurneczko, Ewa; Kalapothakis, Jason; Campuzano, Iain D G; Morris, Michael; Barran, Perdita E

    2012-10-16

    There has been a significant increase in the use of ion mobility mass spectrometry (IM-MS) to investigate conformations of proteins and protein complexes following electrospray ionization. Investigations which employ traveling wave ion mobility mass spectrometry (TW IM-MS) instrumentation rely on the use of calibrants to convert the arrival times of ions to collision cross sections (CCS) providing "hard numbers" of use to structural biology. It is common to use nitrogen as the buffer gas in TW IM-MS instruments and to calibrate by extrapolating from CCS measured in helium via drift tube (DT) IM-MS. In this work, both DT and TW IM-MS instruments are used to investigate the effects of different drift gases (helium, neon, nitrogen, and argon) on the transport of multiply charged ions of the protein myoglobin, frequently used as a standard in TW IM-MS studies. Irrespective of the drift gas used, recorded mass spectra are found to be highly similar. In contrast, the recorded arrival time distributions and the derived CCS differ greatly. At low charge states (7 ≤ z ≤ 11) where the protein is compact, the CCS scale with the polarizability of the gas; this is also the case for higher charge states (12 ≤ z ≤ 22) where the protein is more unfolded for the heavy gases (neon, argon, and nitrogen) but not the case for helium. This is here interpreted as a different conformational landscape being sampled by the lighter gas and potentially attributable to increased field heating by helium. Under nanoelectrospray ionization (nESI) conditions, where myoglobin is sprayed from an aqueous solution buffered to pH 6.8 with 20 mM ammonium acetate, in the DT IM-MS instrument, each buffer gas can yield a different arrival time distribution (ATD) for any given charge state. PMID:22974196

  7. Traveling wave solutions of compressible fluid equations and orbital stability

    NASA Astrophysics Data System (ADS)

    Li, Xiang; Zhang, Weiguo; Li, Zhengming

    2015-11-01

    In this paper, we discuss the existence of traveling wave solutions for compressible fluid equations by applying the theory and method of planar dynamical system, and obtain explicit expressions for all bounded traveling wave solutions by undetermined coefficient method, including kink and bell profile traveling wave solutions, as well as periodic wave solutions. We prove the kink profile solitary wave solution, both sides of which asymptotic values are not zero, is orbitally stable by the theory of Grillakis-Shatah-Strauss orbital stability.

  8. Generation of Large-Scale Zonal Structures by Drift Flute Waves in High-Beta HED Plasmas

    NASA Astrophysics Data System (ADS)

    Yasin, Essam; Sotnikov, Vladmir; Kindel, Joseph; Onishchenko, O. G.; Leboeuf, J. N.

    2009-05-01

    Our aim is to develop a more general analysis of nonlinear dynamics of drift-flute waves, applicable to arbitrary plasma beta and arbitrary spatial scales in comparison with the ion Larmor radius. This study is of interest for fundamental plasma theory as well as for the interpretation of Z-pinch and laboratory astrophysics experiments. Description of low-frequency waves and in particular drift flute waves in a high beta plasma, generally speaking, requires a kinetic approach, based on the Vlasov-Maxwell set of equations. In the present work we show that the alternative two-fluid description can adequately describe the ion perturbations with arbitrary ratio of the characteristic spatial scales to the ion Larmor radius in so-called Pade approximation. For this purpose reduced two-fluid hydrodynamic equations which describe nonlinear dynamics of the flute waves with arbitrary spatial scales and arbitrary plasma beta are derived. The linear dispersion relation of the flute waves and the Rayleigh-Taylor instability are analyzed. A general nonlinear dispersion relation which describes generation of large-scale zonal structures by the flute waves is presented and analyzed.

  9. Stabilization of lower hybrid drift modes by finite parallel wavenumber and electron temperature gradients in field-reversed configurations

    NASA Astrophysics Data System (ADS)

    Farengo, R.; Guzdar, P. N.; Lee, Y. C.

    1989-08-01

    The effect of finite parallel wavenumber and electron temperature gradients on the lower hybrid drift instability is studied in the parameter regime corresponding to the TRX-2 device [Fusion Technol. 9, 48 (1986)]. Perturbations in the electrostatic potential and all three components of the vector potential are considered and finite beta electron orbit modifications are included. The electron temperature gradient decreases the growth rate of the instability but, for kz=0, unstable modes exist for ηe(=T'en0/Ten0)>6. Since finite kz effects completely stabilize the mode at small values of kz/ky(≂5×10-3), magnetic shear could be responsible for stabilizing the lower hybrid drift instability in field-reversed configurations.

  10. Stability Design and Response to Waves by Batoids.

    PubMed

    Fish, Frank E; Hoffman, Jessica L

    2015-10-01

    Unsteady flows in the marine environment can affect the stability and locomotor costs of animals. For fish swimming at shallow depths, waves represent a form of unsteady flow. Waves consist of cyclic oscillations, during which the water moves in circular or elliptical orbits. Large gravity waves have the potential to displace fish both cyclically and in the direction of wave celerity for animals floating in the water column or holding station on the bottom. Displacement of a fish can exceed its stability control capability when the size of the wave orbit is equivalent to the size of the fish. Previous research into compensatory behaviors of fishes to waves has focused on pelagic osteichthyan fishes with laterally compressed bodies. However, dorsoventrally compressed batoid rays must also contend with waves. Examination of rays subjected to waves showed differing strategies for stability between pelagic and demersal species. Pelagic cownose rays (Rhinoptera bonasus) would glide through or be transported by waves, maintaining a positive dihedral of the wing-like pectoral fins. Demersal Atlantic stingrays (Dasyatis sabina) and freshwater rays (Potamotrygon motoro) maintained contact with the bottom and performed compensatory fin motions and body postures. The ability to limit displacement due to wave action by the demersal rays was also a function of the bottom texture. The ability of rays to maintain stability due to wave action suggests mechanisms to compensate for the velocity flux of the water impinging on the large projected area of the enlarged pectoral fins of rays. PMID:26060212

  11. Theory on excitations of drift Alfvén waves by energetic particles. II. The general fishbone-like dispersion relation

    SciTech Connect

    Zonca, Fulvio; Chen, Liu

    2014-07-15

    The theoretical framework of the general fishbone-like dispersion relation (GFLDR), presented and discussed in the Companion Paper [Phys. Plasmas 21, 072120 (2014)], is applied to cases of practical interest of shear/drift Alfvén waves (SAWs/DAWs) excited by energetic particles (EPs) in toroidal fusion plasmas. These applications demonstrate that the GFLDR provides a unified approach that allows analytical and numerical calculations of stability properties, as well as mode structures and, in general, nonlinear evolutions, based on different models and with different levels of approximation. They also show the crucial importance of kinetic descriptions, accurate geometries and boundary conditions for predicting linear as well as nonlinear SAW/DAW and EP behaviors in burning plasmas. Thus, the GFLDR unified theoretical framework elevates the interpretative capability for both experimental and numerical simulation results.

  12. A simple model for testing the effects of gravity-wave-produced vertical oscillations of scattering irregularities on spaced-antenna, horizontal drift measurements

    NASA Technical Reports Server (NTRS)

    Meek, C. E.; Reid, I. M.

    1984-01-01

    It has been suggested that the velocities produced by the spaced antenna partial-reflection drift experiment may constitute a measure of the vertical oscillations due to short-period gravity waves rather than the mean horizontal flow. The contention is that the interference between say two scatterers, one of which is traveling upward, and the other down, will create a pattern which sweeps across the ground in the direction (or anti-parallel) of the wave propagation. Since the expected result, viz., spurious drift directions, is seldom, if ever, seen in spaced antenna drift velocities, this speculation is tested in an atmospheric model.

  13. Attribution of ionospheric vertical plasma drift perturbations to large-scale waves and the dependence on solar activity (Invited)

    NASA Astrophysics Data System (ADS)

    Liu, H.; Richmond, A. D.

    2013-12-01

    In this study we quantify the contribution of individual large-scale waves to ionospheric electrodynamics, and examine the dependence of the ionospheric perturbations on solar activity. We focus on migrating diurnal tide (DW1) plus mean winds, migrating semidiurnal tide (SW2), quasi-stationary planetary wave 1 (QSPW1), and nonmigrating semidiurnal westward wave 1 (SW1) under northern winter conditions, when QSPW1 and SW1 are climatologically strong. From TIME-GCM simulations under solar minimum conditions, we calculate equatorial vertical ExB drifts due to mean winds and DW1, SW2, SW1 and QSPW1. In particular, wind components of both SW2 and SW1 become large at mid to high latitudes in the E-region, and kernel functions obtained from numerical experiments reveal that they can significantly affect the equatorial ion drift, likely through modulating the E-region wind dynamo. The most evident changes of total ionospheric vertical drift when solar activity is increased are seen around dawn and dusk, reflecting the more dominant role of large F-region Pedersen conductivity and of the F-region dynamo under high solar activity. Therefore, the lower atmosphere driving of the ionospheric variability is more evident under solar minimum conditions, not only because variability is more identifiable in a quieter background, but also because the E-region wind dynamo is more significant. These numerical experiments also demonstrate that the amplitudes, phases and latitudinal and vertical structures of large-scale waves are important in quantifying the ionospheric responses.

  14. Temporal indications of atmospheric stability affecting off-target spray drift in the midsouth U S

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study was designed to determine atmospheric conditions favorable for long-distance spray drift deleterious to susceptible crops. A tall meteorological monitoring tower equipped with six precision (and periodically calibrated) thermistors at six heights to 27.4 m and wind speed anemometers at fo...

  15. Long-range correlations induced by the self-regulation of zonal flows and drift-wave turbulence

    SciTech Connect

    Manz, P.; Ramisch, M.; Stroth, U.

    2010-11-15

    By means of a unique probe array, the interaction between zonal flows and broad-band drift-wave turbulence has been investigated experimentally in a magnetized toroidal plasma. Homogeneous potential fluctuations on a magnetic flux surface, previously reported as long range correlations, could be traced back to a predator-prey-like interaction between the turbulence and the zonal flow. At higher frequency the nonlocal transfer of energy to the zonal flow is dominant and the low-frequency oscillations are shown to result from the reduced turbulence activity due to this energy loss. This self-regulation process turns out to be enhanced with increased background shear flows.

  16. The stability of Rossby waves in a stratified shear fluid

    NASA Astrophysics Data System (ADS)

    Tan, Benkui

    1990-11-01

    An investigation is undertaken of the stability of linear Rossby waves in a stratified shear fluid by means of a qualitative theory employing ordinary differential equations. It is noted that, while the basic current has no detectable shear, the Rossby waves are always stable. If the basic current possesses only horizontal shear, the unstable criterion for waves takes one form, but it takes entirely another in the case where the basic current possesses only vertical shear.

  17. Hysteresis and drift of spiral waves near heterogeneities: From chemical experiments to cardiac simulations

    NASA Astrophysics Data System (ADS)

    Nakouzi, Elias; Totz, Jan Frederik; Zhang, Zhihui; Steinbock, Oliver; Engel, Harald

    2016-02-01

    Dissipative patterns in excitable reaction-diffusion systems can be strongly affected by spatial heterogeneities. Using the photosensitive Belousov-Zhabotinsky reaction, we show a hysteresis effect in the transition between free and pinned spiral rotation. The latter state involves the rotation around a disk-shaped obstacle with an impermeable and inert boundary. The transition is controlled by changes in light intensity. For permeable heterogeneities of higher excitability, we observe spiral drift along both linear and circular boundaries. Our results confirm recent theoretical predictions and, in the case of spiral drift, are further reproduced by numerical simulations with a modified Oregonator model. Additional simulations with a cardiac model show that orbital motion can also exist in anisotropic and three-dimensional systems.

  18. Hysteresis and drift of spiral waves near heterogeneities: From chemical experiments to cardiac simulations.

    PubMed

    Nakouzi, Elias; Totz, Jan Frederik; Zhang, Zhihui; Steinbock, Oliver; Engel, Harald

    2016-02-01

    Dissipative patterns in excitable reaction-diffusion systems can be strongly affected by spatial heterogeneities. Using the photosensitive Belousov-Zhabotinsky reaction, we show a hysteresis effect in the transition between free and pinned spiral rotation. The latter state involves the rotation around a disk-shaped obstacle with an impermeable and inert boundary. The transition is controlled by changes in light intensity. For permeable heterogeneities of higher excitability, we observe spiral drift along both linear and circular boundaries. Our results confirm recent theoretical predictions and, in the case of spiral drift, are further reproduced by numerical simulations with a modified Oregonator model. Additional simulations with a cardiac model show that orbital motion can also exist in anisotropic and three-dimensional systems. PMID:26986327

  19. On the nonlinear stability of a quasi-two-dimensional drift kinetic model for ion temperature gradient turbulence

    SciTech Connect

    Plunk, G. G.

    2015-04-15

    We study a quasi-two-dimensional electrostatic drift kinetic system as a model for near-marginal ion temperature gradient driven turbulence. A proof is given for the nonlinear stability of this system under conditions of linear stability. This proof is achieved using a transformation that diagonalizes the linear dynamics and also commutes with nonlinear E × B advection. For the case when linear instability is present, a corollary is found that forbids nonlinear energy transfer between appropriately defined sets of stable and unstable modes. It is speculated that this may explain the preservation of linear eigenmodes in nonlinear gyrokinetic simulations. Based on this property, a dimensionally reduced (∞×∞→1) system is derived that may be useful for understanding dynamics around the critical gradient of Dimits.

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

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

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

  1. Laser induced fluorescence measurements of ion velocity in a DC magnetron microdischarge with self-organized drift wave modes propagating in the direction opposite the E x B electron drift velocity

    NASA Astrophysics Data System (ADS)

    Young, Chris; Gascon, Nicolas; Lucca Fabris, Andrea; Cappelli, Mark; Ito, Tsuyohito; Stanford Plasma Physics Laboratory Collaboration; Osaka University CenterAtomic; Molecular Technologies Collaboration

    2015-09-01

    Evidence is presented of rotating azimuthal wave structures in a planar DC magnetron microdischarge operating in argon and xenon. Plasma emission captured using a high frame rate camera reveals waves of varying azimuthal modes propagating in the negative E x B direction. The dominant stable mode structure depends on discharge voltage. The negative drift direction is attributed to a local field reversal arising from strong density gradients that drive excess ions towards the anode. The transition between modes is shown to be consistent with models of gradient drift-wave dispersion in the presence of such a field reversal when the fluid representation includes ambipolar diffusion along the direction parallel to the magnetic field. Time-average and time-synchronized laser induced fluorescence measurements are carried out to elucidate the anode-bound ion dynamics driven by the field reversal. This research is supported by the Air Force Office of Scientific Research.

  2. Orbital stability of solitary waves for Kundu equation

    NASA Astrophysics Data System (ADS)

    Zhang, Weiguo; Qin, Yinghao; Zhao, Yan; Guo, Boling

    In this paper, we consider the Kundu equation which is not a standard Hamiltonian system. The abstract orbital stability theory proposed by Grillakis et al. (1987, 1990) cannot be applied directly to study orbital stability of solitary waves for this equation. Motivated by the idea of Guo and Wu (1995), we construct three invariants of motion and use detailed spectral analysis to obtain orbital stability of solitary waves for Kundu equation. Since Kundu equation is more complex than the derivative Schrödinger equation, we utilize some techniques to overcome some difficulties in this paper. It should be pointed out that the results obtained in this paper are more general than those obtained by Guo and Wu (1995). We present a sufficient condition under which solitary waves are orbitally stable for 2c+sυ<0, while Guo and Wu (1995) only considered the case 2c+sυ>0. We obtain the results on orbital stability of solitary waves for the derivative Schrödinger equation given by Colin and Ohta (2006) as a corollary in this paper. Furthermore, we obtain orbital stability of solitary waves for Chen-Lee-Lin equation and Gerdjikov-Ivanov equation, respectively.

  3. Lower hybrid drift instability with temperature gradient in a perpendicular shock wave

    NASA Technical Reports Server (NTRS)

    Zhou, Y. M.; Wong, H. K.; Wu, C. S.

    1983-01-01

    Finite beta effects and an electron temperature gradient are included in the present study of the perpendicular bow shock geometry's lower hybrid instability, where the flute mode that is stable at the shock for constant electron temperature is destabilized in the case of a sufficiently great temperature gradient. Numerical solutions are given for cases in which the ion distribution is either drifting Maxwellian or consists of two Maxwellians, to represent the effect of reflected ions at the shock. A discussion is presented of the implications of results obtained for ion and electron heating and electron acceleration at the bow shock.

  4. Ion-wave stabilization of an inductively coupled plasma

    SciTech Connect

    Camparo, J.C.; Mackay, R.

    2006-04-24

    Stabilization of the rf power driving an inductively coupled plasma (ICP) has implications for fields ranging from atomic clocks to analytical chemistry to illumination technology. Here, we demonstrate a technique in which the plasma itself acts as a probe of radio wave power, and provides a correction signal for active rf-power control. Our technique takes advantage of the resonant nature of forced ion waves in the plasma, and their observation in the ICP's optical emission.

  5. Stabilized High Power Laser for Advanced Gravitational Wave Detectors

    NASA Astrophysics Data System (ADS)

    Willke, B.; Danzmann, K.; Fallnich, C.; Frede, M.; Heurs, M.; King, P.; Kracht, D.; Kwee, P.; Savage, R.; Seifert, F.; Wilhelm, R.

    2006-03-01

    Second generation gravitational wave detectors require high power lasers with several 100W of output power and with very low temporal and spatial fluctuations. In this paper we discuss possible setups to achieve high laser power and describe a 200W prestabilized laser system (PSL). The PSL noise requirements for advanced gravitational wave detectors will be discussed in general and the stabilization scheme proposed for the Advanced LIGO PSL will be described. Special emphasis will be given to the most demanding power stabilization requiremets and new results (RIN <= 4×10-9/surdHz) will be presented.

  6. Phase change in terahertz waves emitted from differently doped graphite: The role of carrier drift

    SciTech Connect

    Irfan, Muhammad; Yim, Jong-Hyuk; Jho, Young-Dahl; Kim, Changyoung; Wook Lee, Sang

    2013-11-11

    We investigate characteristics of THz waves radiated from differently doped graphite samples excited by femtosecond laser pulses. Between n-type single-crystalline graphite and p-type polycrystalline graphite films, we observe the phase reversal of THz waves regardless of excitation energy variations around K-valley. In addition, variations in other parameters such as excitation fluence and azimuthal angle produce no changes in the phase of THz waves, which correlate well with the opposite dipole polarization between differently doped samples rather than unidirectional diffusive transport.

  7. Coherent vorticity extraction in resistive drift-wave turbulence: Comparison of orthogonal wavelets versus proper orthogonal decomposition

    NASA Astrophysics Data System (ADS)

    Futatani, Shimpei; Bos, Wouter J. T.; del-Castillo-Negrete, Diego; Schneider, Kai; Benkadda, Sadruddin; Farge, Marie

    2011-03-01

    We assess two techniques for extracting coherent vortices out of turbulent flows: the wavelet based Coherent Vorticity Extraction (CVE) and the Proper Orthogonal Decomposition (POD). The former decomposes the flow field into an orthogonal wavelet representation and subsequent thresholding of the coefficients allows one to split the flow into organized coherent vortices with non-Gaussian statistics and an incoherent random part which is structureless. POD is based on the singular value decomposition and decomposes the flow into basis functions which are optimal with respect to the retained energy for the ensemble average. Both techniques are applied to direct numerical simulation data of two-dimensional drift-wave turbulence governed by Hasegawa-Wakatani equation, considering two limit cases: the quasi-hydrodynamic and the quasi-adiabatic regimes. The results are compared in terms of compression rate, retained energy, retained enstrophy and retained radial flux, together with the enstrophy spectrum and higher order statistics.

  8. Spatiotemporal splitting of global eigenmodes due to cross-field coupling via vortex dynamics in drift wave turbulence.

    PubMed

    Brandt, C; Thakur, S C; Light, A D; Negrete, J; Tynan, G R

    2014-12-31

    Spatiotemporal splitting events of drift wave (DW) eigenmodes due to nonlinear coupling are investigated in a cylindrical helicon plasma device. DW eigenmodes in the radial-azimuthal cross section have been experimentally observed to split at radial locations and recombine into the global eigenmode with a time shorter than the typical DW period (t≪fDW(-1)). The number of splits correlates with the increase of turbulence. The observed dynamics can be theoretically reproduced by a Kuramoto-type model of a network of radially coupled azimuthal eigenmodes. Coupling by E×B-vortex convection cell dynamics and ion gyro radii motion leads to cross-field synchronization and occasional mode splitting events. PMID:25615346

  9. On the energetic stability of solitary water waves.

    PubMed

    Mielke, Alexander

    2002-10-15

    We study solutions of the water-wave problem for a fluid layer of finite depth in the presence of gravity and surface tension. We use the canonical Hamiltonian formulation by Zakharov in terms of the surface elevation and the trace of the velocity potential on the surface. With a new continuity result for the Dirichlet-Neumann operator in terms of the surface as a function in H(1)(R), we show conditional energetic stability of the trivial solution in certain regions of the parameter space. In the same region we obtain stability of solitary waves under the additional assumption that the second variation of the energy has only one negative eigenvalue. The latter assumption is shown to be fulfilled for the small-amplitude solitary waves first constructed by Amick & Kirchgässner. PMID:12804235

  10. Two-dimensional bispectral analysis of drift wave turbulence in a cylindrical plasma

    SciTech Connect

    Yamada, T.; Nagashima, Y.; Itoh, S.-I.; Inagaki, S.; Yagi, M.; Fujisawa, A.; Shinohara, S.; Terasaka, K.; Kamataki, K.; Arakawa, H.; Kasuya, N.; Itoh, K.

    2010-05-15

    Bispectral analysis and multichannel measurement are becoming attractive investigation tools in plasma fluctuation studies. In the Large Mirror Device-Upgrade, the measurement of fluctuations in the ion saturation-current with a 64-channel poloidal Langmuir probe array was performed. The two-dimensional (2D) (poloidal wave number and frequency) power spectrum showed a number of pronounced peaks and broadband fluctuations in the poloidal wave number-frequency space. We applied 2D bispectral analysis, which considers both the matching conditions of poloidal wave number and frequency, to the spatiotemporal waveform, and confirmed the nonlinear couplings between coherent-coherent, coherent-broadband, and broadband-broadband fluctuation components. More than ten peaks were revealed to have as their origins only three original parent modes generated in the plasma. Comparison between the theoretical estimate and experimental observation for the bicoherence showed good agreement.

  11. Stability of traveling waves of a diffusive susceptible-infective-removed (SIR) epidemic model

    NASA Astrophysics Data System (ADS)

    Li, Yan; Li, Wan-Tong; Yang, Yun-Rui

    2016-04-01

    This paper is concerned with the stability and uniqueness of traveling waves of a delayed diffusive susceptible-infective-removed (SIR) epidemic model. We first prove the exponential stability of traveling waves by using the weighted energy method, where the traveling waves are allowed to be non-monotone. Then we establish the exact asymptotic behavior of traveling waves at -∞ by using Ikehara's theorem. Finally, the uniqueness of traveling waves is proved by the stability result of traveling waves.

  12. Existence and uniqueness of stabilized propagating wave segments in wave front interaction model

    NASA Astrophysics Data System (ADS)

    Guo, Jong-Shenq; Ninomiya, Hirokazu; Tsai, Je-Chiang

    2010-02-01

    Recent experimental studies of photosensitive Belousov-Zhabotinskii reaction have revealed the existence of propagating wave segments. The propagating wave segments are unstable, but can be stabilized by using a feedback control to continually adjust the excitability of the medium. Experimental studies also indicate that the locus of the size of a stabilized wave segment as a function of the excitability of the medium gives the excitability boundary for the existence of 2D wave patterns with free ends in excitable media. To study the properties of this boundary curve, we use the wave front interaction model proposed by Zykov and Showalter. This is equivalent to study a first order system of three ordinary differential equations which includes a singular nonlinearity. Using two different reduced first order systems of two ordinary differential equations, we first show the existence of wave segments for any given propagating velocity. Then the wave profiles can be classified into two types, namely, convex and non-convex types. More precisely, when the normalized propagating velocity is small, we show that the wave profile is of convex type, while the wave profile is of non-convex type when the normalized velocity is close to 1.

  13. Existence and Stability of Relativistic Solitary Waves in Warm Plasmas

    SciTech Connect

    Maza-Palacios, Marco A.; Herrera-Velazquez, J. Julio E.

    2006-12-04

    A variational mehod for one dimensional relativistic solitons is established, within the two fluid model framework, including finite temperature effects. Our starting point is a Lagrangian for a two species fluid plasma, which allows the deduction of the conserved quantities of the system by means of Noether's theorem, as well as the model equations. At a first stage, travelling wave solutions are studied with the usual shape of envelope solitary waves. It is found that bounded travelling waves (bright solitons) exist for most velocities, if both ions and electrons are assumed to be relativistic, except for a window at small values of v/c. In order to study their stability, we obtain the evolution equations of the solitary wave parameters, along those of radiation.

  14. Effect of the magnetic field curvature on the generation of zonal flows by drift-Alfven waves

    SciTech Connect

    Mikhailovskii, A. B.; Kovalishen, E. A.; Shirokov, M. S.; Tsypin, V. S.; Galvao, R. M. O.

    2007-05-15

    The generation of zonal flows by drift-Alfven waves is studied with allowance for magnetic curvature effects. The basic plasmadynamic equations relating the electrostatic potential, vector potential, and perturbed plasma density are the vorticity equation, longitudinal Ohm's law, and continuity equation. The basic equations are analyzed by applying a parametric formalism similar to that used in the theory of the generation of convective cells. In contrast to most previous investigations on the subject, consideration is given to primary modes having an arbitrary spectrum rather than to an individual monochromatic wave packet. The parametric approach so modified makes it possible to reveal a new class of instabilities of zonal flows that are analogous to two-stream instabilities in linear theory. It is shown that, in the standard theory of zonal flows, the zonal components of the vector potential and perturbed density are not excited. It is pointed out that zonal flows can be generated both in the case of a magnetic hill and in the case of a magnetic well. In the first case, the instabilities of zonal flows are analogous to negative-mass instabilities in linear theory, and, in the second case, they are analogous to two-stream instabilities.

  15. Natural Analoges as a Check of Predicted Drift Stability at Yucca Mountain, Nevada

    SciTech Connect

    J. Stuckless

    2006-03-10

    Calculations made by the U.S. Department of Energy's Yucca Mountain Project as part of the licensing of a proposed geologic repository (in southwestern Nevada) for the disposal of high-level radioactive waste, predict that emplacement tunnels will remain open with little collapse long after ground support has disintegrated. This conclusion includes the effects of anticipated seismic events. Natural analogues cannot provide a quantitative test of this conclusion, but they can provide a reasonableness test by examining the natural and anthropogenic examples of stability of subterranean openings. Available data from a variety of sources, combined with limited observations by the author, show that natural underground openings tend to resist collapse for millions of years and that anthropogenic subterranean openings have remained open from before recorded history through today. This stability is true even in seismically active areas. In fact, the archaeological record is heavily skewed toward preservation of underground structures relative to those found at the surface.

  16. Analogues as a check of predicted drift stability at Yucca Mountain, Nevada

    USGS Publications Warehouse

    Stuckless, J.S.

    2006-01-01

    Calculations made by the U.S. Department of Energy's Yucca Mountain Project as part of the licensing of a proposed geologic repository in southwestern Nevada for the disposal of high-level radioactive waste, predict that emplacement tunnels will remain open with little collapse long after ground support has disintegrated. This conclusion includes the effects of anticipated seismic events. Natural analogues cannot provide a quantitative test of this conclusion, but they can provide a reasonableness test by examining the naturally occuring and anthropogenic examples of stability of subterranean openings. Available data from a variety of sources, combined with limited observations by the author, show that natural underground openings tend to resist collapse for millions of years and that anthropogenic subterranean openings have remained open from before recorded history through today. This stability is true even in seismically active areas. In fact, the archaeological record is heavily skewed toward preservation of underground structures relative to those found at the surface.

  17. Evolution of a reassortant North American gull influenza virus lineage: drift, shift and stability

    PubMed Central

    2013-01-01

    Background The role of gulls in the ecology of avian influenza (AI) is different than that of waterfowl. Different constellations of subtypes circulate within the two groups of birds and AI viruses isolated from North American gulls frequently possess reassortant genomes with genetic elements from both North America and Eurasian lineages. A 2008 isolate from a Newfoundland Great Black-backed Gull contained a mix of North American waterfowl, North American gull and Eurasian lineage genes. Methods We isolated, sequenced and phylogenetically compared avian influenza viruses from 2009 Canadian wild birds. Results We analyzed six 2009 virus isolates from Canada and found the same phylogenetic lineage had persisted over a larger geographic area, with an expanded host range that included dabbling and diving ducks as well as gulls. All of the 2009 virus isolates contained an internal protein coding set of genes of the same Eurasian lineage genes except PB1 that was from a North American lineage, and these genes continued to evolve by genetic drift. We show evidence that the 2008 Great Black-backed Gull virus was derived from this lineage with a reassortment of a North American PA gene into the more stable core set of internal protein coding genes that has circulated in avian populations for at least 2 years. From this core, the surface glycoprotein genes have switched several times creating H13N6, H13N2, and H16N3 subtypes. These gene segments were from North American lineages except for the H16 and N3 vRNAs. Conclusions This process appears similar to genetic shifts seen with swine influenza where a stable “triple reassortant internal gene” core has circulated in swine populations with genetic shifts occurring with hemaggluttinin and neuraminidase proteins getting periodically switched. Thus gulls may serve as genetic mixing vessels for different lineages of avian influenza, similar to the role of swine with regards to human influenza. These findings illustrate the

  18. Evolution of a reassortant North American gull influenza virus lineage: drift, shift and stability

    USGS Publications Warehouse

    Hall, Jeffrey S.; TeSlaa, Joshua L.; Nashold, Sean W.; Halpin, Rebecca A.; Stockwell, Timothy; Wentworth, David E.; Dugan, Vivien; Ip, Hon S.

    2013-01-01

    Background: The role of gulls in the ecology of avian influenza (AI) is different than that of waterfowl. Different constellations of subtypes circulate within the two groups of birds and AI viruses isolated from North American gulls frequently possess reassortant genomes with genetic elements from both North America and Eurasian lineages. A 2008 isolate from a Newfoundland Great Black-backed Gull contained a mix of North American waterfowl, North American gull and Eurasian lineage genes. Methods: We isolated, sequenced and phylogenetically compared avian influenza viruses from 2009 Canadian wild birds. Results: We analyzed six 2009 virus isolates from Canada and found the same phylogenetic lineage had persisted over a larger geographic area, with an expanded host range that included dabbling and diving ducks as well as gulls. All of the 2009 virus isolates contained an internal protein coding set of genes of the same Eurasian lineage genes except PB1 that was from a North American lineage, and these genes continued to evolve by genetic drift. We show evidence that the 2008 Great Black-backed Gull virus was derived from this lineage with a reassortment of a North American PA gene into the more stable core set of internal protein coding genes that has circulated in avian populations for at least 2 years. From this core, the surface glycoprotein genes have switched several times creating H13N6, H13N2, and H16N3 subtypes. These gene segments were from North American lineages except for the H16 and N3 vRNAs. Conclusions: This process appears similar to genetic shifts seen with swine influenza where a stable "triple reassortant internal gene" core has circulated in swine populations with genetic shifts occurring with hemaggluttinin and neuraminidase proteins getting periodically switched. Thus gulls may serve as genetic mixing vessels for different lineages of avian influenza, similar to the role of swine with regards to human influenza. These findings illustrate the

  19. Regulation of ion drifts and anisotropies by parametrically unstable finite-amplitude Alfvén-cyclotron waves in the fast solar wind

    SciTech Connect

    Maneva, Y. G.; Araneda, J. A.; Marsch, E.

    2014-03-10

    We study the preferential heating and differential acceleration of minor ions by dissipation of ion-acoustic waves (IAWs) generated by parametric instabilities of a finite-amplitude monochromatic Alfvén-cyclotron pump wave. We consider the associated kinetic effects of Landau damping and nonlinear pitch-angle scattering of protons and α particles in the tenuous plasma of coronal holes and the fast solar wind. Various data collected by Wind spacecraft show signatures for a local transverse heating of the minor ions, presumably by Alfvén-cyclotron wave dissipation, and an unexpected parallel heating by a so far unknown mechanism. Here, we present the results from a set of 1.5 dimensional hybrid simulations in search for a plausible explanation for the observed field-aligned kinetic features in the fast solar wind minor ions. We investigate the origin and regulation of ion relative drifts and temperature anisotropies in low plasma β, fast solar wind conditions. Depending on their initial drifts, both ion species can heat up not only transversely through cyclotron resonance and non-resonant wave-particle interactions, but also strongly in the parallel direction by Landau damping of the daughter IAWs. We discuss the dependence of the relative ion drifts and temperature anisotropies on the plasma β of the individual species and we describe the effect of the pump wave amplitude on the ion heating and acceleration.

  20. The effects of nonthermal electron distributions on ion-temperature-gradient driven drift-wave instabilities in electron-ion plasma

    SciTech Connect

    Batool, Nazia; Masood, W.; Mirza, Arshad M.

    2012-08-15

    The effects of nonthermal electron distributions on electrostatic ion-temperature-gradient (ITG) driven drift-wave instabilities in the presence of equilibrium density, temperature, and magnetic field gradients are investigated here. By using Braginskii's transport equations for ions and Cairns as well as Kappa distribution for electrons, the coupled mode equations are derived. The modified ITG driven modes are derived, and it is found both analytically as well as numerically that the nonthermal distribution of electrons significantly modify the real frequencies as well as the growth rate of the ITG driven drift wave instability. The growth rate of ion-temperature-gradient driven instability is found to be maximum for Cairns, intermediate for Kappa, and minimum for the Maxwellian distributed electron case. The results of present investigation might be helpful to understand several wave phenomena in space and laboratory plasmas in the presence of nonthermal electrons.

  1. Thermal Rossby waves in a rotating annulus. Their stability.

    PubMed

    Pino, D; Net, M; Sánchez, J; Mercader, I

    2001-05-01

    Nonlinear thermal convection in a fast rotating annulus about its axis, with slightly inclined ends, radial gravity and heating, is studied numerically for a fluid of Prandtl number sigma=0.7 and different values of the radius ratio and rotation rate. The properties of the rotating waves that appear after the Hopf bifurcation of the conductive state are analyzed. Near the critical Rayleigh number, different types of solutions with the same wave number coexist, and they are classified as a function of their connection with the two types of modes identified in the linear analysis for this Prandtl number. For different rotation rates, the stability of the primary solutions as a function of the radius ratio is also studied. The shape of the stability regions and the type of dominant disturbances that limit these regions are very sensitive to the proximity to the value of the radius ratio for which the type of dominant mode changes. PMID:11415011

  2. Stability of strong electromagnetic waves in overdense plasmas

    NASA Astrophysics Data System (ADS)

    Romeiras, F. J.

    1982-04-01

    The paper considers the stability against small perturbations of a class of exact wave solutions of the equations that describe an unmagnetized relativistic cold electron plasma. The main feature of these nonlinear waves is a transverse circularly polarized electric field with periodic amplitude modulation in the longitudinal direction. Floquet's theory of linear differential equations with periodic coefficients is used to solve the perturbation equations and obtain the instability growth rates. Both an approximate solution for small modulation depth and a numerical treatment for arbitrary depth are presented. It is shown that the well-known small-wavenumber instability of the purely transverse circularly polarized waves of constant amplitude is reduced as the modulation depth increases from zero to its maximum allowed value.

  3. Drift Mode Calculations in Nonaxisymmetric Geometry

    SciTech Connect

    G. Rewoldt; L.-P. Ku; W.A. Cooper; W.M. Tang

    1999-07-01

    A fully kinetic assessment of the stability properties of toroidal drift modes has been obtained for nonaxisymmetric (stellarator) geometry, in the electrostatic limit. This calculation is a comprehensive solution of the linearized gyrokinetic equation, using the lowest-order ''ballooning representation'' for high toroidal mode number instabilities, with a model collision operator. Results for toroidal drift waves destabilized by temperature gradients and/or trapped particle dynamics are presented, using three-dimensional magnetohydrodynamic equilibria generated as part of a design effort for a quasiaxisymmetric stellarator. Comparisons of these results with those obtained for typical tokamak cases indicate that the basic trends are similar.

  4. Stability theory for the synchronized waving of marine grass

    NASA Astrophysics Data System (ADS)

    Singh, Ravi; Mahadevan, Amala; Mandre, Shreyas; Mahadevan, L. M.

    2014-11-01

    Synchronized waving of grass blades in the presence of fluid flow has been observed in cases such as wheat field in wind, marine grass in tidal currents. The synchronous motion can have important environmental and ecological impact via mixing of fluid due to waving. When the hydrodynamic and elastic time scales are well separated, this waving is thought to be due to Kelvin-Helmholtz instability resulting from an inflection point in the flow profile. We find that the inflection point is located near the tip of grass canopy. We extend the Orr-Sommerfeld equation for the stability of a shear flow to include a continuum mean-field approximation for the vegetation, thus capturing the essential ingredients for flow instability leading to coherent waving. Our linear stability analysis shows that the flow in presence of grass become unstable not only through a mechanism of Kelvin-Helmholtz instability but also through shear instability of flow above grass. We also find that flow with low submergence ratio of grass becomes unstable due to Kelvin-Helmholtz instability whereas flow high submergence ratio becomes unstable due to shear instability of flow above the grass. Numerical results demonstrating these instability mechanism will also be presented.

  5. Nonlinear electrostatic drift waves in dense electron-positron-ion plasmas

    SciTech Connect

    Haque, Q.; Mahmood, S.; Mushtaq, A.

    2008-08-15

    The Korteweg-de Vries-Burgers (KdVB)-type equation is obtained using the quantum hydrodynamic model in an inhomogeneous electron-positron-ion quantum magnetoplasma with neutral particles in the background. The KdV-type solitary waves, Burgers-type monotonic, and oscillatory shock like solutions are discussed in different limits. The quantum parameter is also dependent on the positron concentration in dense multicomponent plasmas. It is found that both solitary hump and dip are formed and their amplitude and width are dependent on percentage presence of positrons in electron-ion plasmas. The height of the monotonic shock is decreased with the increase of positron concentration and it is independent of the quantum parameter in electron-positron-ion magnetized quantum plasmas. However, the amplitude of the oscillatory shock is dependent on positron concentration and quantum parameter in electron-positron-ion plasmas.

  6. Theory and simulation of a high-frequency magnetic drift wave

    NASA Technical Reports Server (NTRS)

    Huba, J. D.

    1991-01-01

    The equilibrium of a nonneutral plasma in a toroidal vessel with a toroidal magnetic field is analyzed. In the zero inertia limit it is heuristically shown from force balance considerations that there is an electrostatic hoop force and a force due to diamagnetism along the major radius. The problem of equilibrium is formulated in terms of solutions of a 2D partial difference equation. This equation is solved in the large-aspect-ratio limit and a general expression for the shift of the potential axis is obtained which shows that the shift is approximately epsilon and that it depends solely on the internal capacitance of the cloud. The simulation study is based upon the modified MHD equations and the nonlocal nature of the mode is investigated. Applications to sub-Alfvenic plasma expansions, electromagnetic waves in the earth's magnetosphere, and plasma switches are discussed.

  7. Phase stability of transition metal dichalcogenide by competing ligand field stabilization and charge density wave

    NASA Astrophysics Data System (ADS)

    C, Santosh K.; Zhang, Chenxi; Hong, Suklyun; Wallace, Robert M.; Cho, Kyeongjae

    2015-09-01

    Transition metal dichalcogenides (TMDs) have been investigated extensively for potential application as device materials in recent years. TMDs are found to be stable in trigonal prismatic (H), octahedral (T), or distorted octahedral (Td) coordination of the transition metal. However, the detailed understanding of stabilities of TMDs in a particular phase is lacking. In this work, the detailed TMD phase stability using first-principles calculations based on density functional theory (DFT) has been investigated to clarify the mechanism of phase stabilities of TMDs, consistent with the experimental observation. Our results indicate that the phase stability of TMDs can be explained considering the relative strength of two competing mechanisms: ligand field stabilization of d-orbitals corresponding to transition metal coordination geometry, and charge density wave (CDW) instability accompanied by a periodic lattice distortion (PLD) causing the phase transition in particular TMDs.

  8. Coherent vorticity extraction in resistive drift-wave turbulence: Comparison of orthogonal wavelets versus proper orthogonal decomposition

    SciTech Connect

    Futatani, S.; Bos, W.J.T.; Del-Castillo-Negrete, Diego B; Schneider, Kai; Benkadda, S.; Farge, Marie

    2011-01-01

    We assess two techniques for extracting coherent vortices out of turbulent flows: the wavelet based Coherent Vorticity Extraction (CVE) and the Proper Orthogonal Decomposition (POD). The former decomposes the flow field into an orthogonal wavelet representation and subsequent thresholding of the coefficients allows one to split the flow into organized coherent vortices with non-Gaussian statistics and an incoherent random part which is structureless. POD is based on the singular value decomposition and decomposes the flow into basis functions which are optimal with respect to the retained energy for the ensemble average. Both techniques are applied to direct numerical simulation data of two-dimensional drift-wave turbulence governed by Hasegawa Wakatani equation, considering two limit cases: the quasi-hydrodynamic and the quasi-adiabatic regimes. The results are compared in terms of compression rate, retained energy, retained enstrophy and retained radial flux, together with the enstrophy spectrum and higher order statistics. (c) 2010 Published by Elsevier Masson SAS on behalf of Academie des sciences.

  9. On the stability of lumps and wave collapse in water waves.

    PubMed

    Akylas, T R; Cho, Yeunwoo

    2008-08-13

    In the classical water-wave problem, fully localized nonlinear waves of permanent form, commonly referred to as lumps, are possible only if both gravity and surface tension are present. While much attention has been paid to shallow-water lumps, which are generalizations of Korteweg-de Vries solitary waves, the present study is concerned with a distinct class of gravity-capillary lumps recently found on water of finite or infinite depth. In the near linear limit, these lumps resemble locally confined wave packets with envelope and wave crests moving at the same speed, and they can be approximated in terms of a particular steady solution (ground state) of an elliptic equation system of the Benney-Roskes-Davey-Stewartson (BRDS) type, which governs the coupled evolution of the envelope along with the induced mean flow. According to the BRDS equations, however, initial conditions above a certain threshold develop a singularity in finite time, known as wave collapse, due to nonlinear focusing; the ground state, in fact, being exactly at the threshold for collapse suggests that the newly discovered lumps are unstable. In an effort to understand the role of this singularity in the dynamics of lumps, here we consider the fifth-order Kadomtsev-Petviashvili equation, a model for weakly nonlinear gravity-capillary waves on water of finite depth when the Bond number is close to one-third, which also admits lumps of the wave packet type. It is found that an exchange of stability occurs at a certain finite wave steepness, lumps being unstable below but stable above this critical value. As a result, a small-amplitude lump, which is linearly unstable and according to the BRDS equations would be prone to wave collapse, depending on the perturbation, either decays into dispersive waves or evolves into an oscillatory state near a finite-amplitude stable lump. PMID:18487123

  10. Standardized F1: a consistent measure of strength of modulation of visual responses to sine-wave drifting gratings.

    PubMed

    Wypych, M; Wang, C; Nagy, A; Benedek, G; Dreher, B; Waleszczyk, W J

    2012-11-01

    The magnitude of spike-responses of neurons in the mammalian visual system to sine-wave luminance-contrast-modulated drifting gratings is modulated by the temporal frequency of the stimulation. However, there are serious problems with consistency and reliability of the traditionally used methods of assessment of strength of such modulation. Here we propose an intuitive and simple tool for assessment of the strength of modulations in the form of standardized F1 index, zF1. We define zF1 as the ratio of the difference between the F1 (component of amplitude spectrum of the spike-response at temporal frequency of stimulation) and the mean value of spectrum amplitudes to standard deviation along all frequencies in the spectrum. In order to assess the validity of this measure, we have: (1) examined behavior of zF1 using spike-responses to optimized drifting gratings of single neurons recorded from four 'visual' structures (area V1 of primary visual cortex, superior colliculus, suprageniculate nucleus and caudate nucleus) in the brain of commonly used visual mammal - domestic cat; (2) compared the behavior of zF1 with that of classical statistics commonly employed in the analysis of steady-state responses; (3) tested the zF1 index on simulated spike-trains generated with threshold-linear model. Our analyses indicate that zF1 is resistant to distortions due to the low spike count in responses and therefore can be particularly useful in the case of recordings from neurons with low firing rates and/or low net mean responses. While most V1 and a half of caudate neurons exhibit high zF1 indices, the majorities of collicular and suprageniculate neurons exhibit low zF1 indices. We conclude that despite the general shortcomings of measuring strength of modulation inherent in the linear system approach, zF1 can serve as a sensitive and easy to interpret tool for detection of modulation and assessment of its strength in responses of visual neurons. PMID:23000273

  11. Hurricane-induced ocean waves and stokes drift and their impacts on surface transport and dispersion in the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Curcic, Milan; Chen, Shuyi S.; Özgökmen, Tamay M.

    2016-03-01

    Hurricane Isaac induced large surface waves and a significant change in upper ocean circulation in the Gulf of Mexico before making landfall at the Louisiana coast on 29 August 2012. Isaac was observed by 194 surface drifters during the Grand Lagrangian Deployment (GLAD). A coupled atmosphere-wave-ocean model was used to forecast hurricane impacts during GLAD. The coupled model and drifter observations provide an unprecedented opportunity to study the impacts of hurricane-induced Stokes drift on ocean surface currents. The Stokes drift induced a cyclonic (anticyclonic) rotational flow on the left (right) side of the hurricane and accounted for up to 20% of the average Lagrangian velocity. In a significant deviation from drifter measurements prior to Isaac, the scale-dependent relative diffusivity is estimated to be 6 times larger during the hurricane, which represents a deviation from Okubo's (1971) canonical results for lateral dispersion in nonhurricane conditions at the ocean surface.

  12. Mesoscopic stability and sedimentation waves in settling periodic arrays.

    PubMed

    Felderhof, B U

    2003-11-01

    The stability of a periodic array of particles settling in a viscous incompressible fluid under the influence of gravity is investigated in the framework of the point sedimentation model. The simple cubic array is unstable, but the body-centered and face-centered cubic arrays with gravity directed along one of the crystal axes are mesoscopically stable, i.e., they are stable except for very long wavelength in a certain domain of directions of the wave vector. In such mesoscopically stable arrays the instability is suppressed in periodic boundary conditions for systems smaller than a maximum size. In a stable finite system the particles perform small motions about the positions of the regular array, and sedimentation waves propagate through the system. PMID:14682796

  13. Equilibrium and stability in vortex and wave flows

    NASA Astrophysics Data System (ADS)

    Luzzatto-Fegiz, Paolo

    This dissertation focuses on the development of theoretical and numerical methodologies to study equilibrium and stability in conservative fluid flows. These techniques include: a bifurcation-diagram approach to obtain the stability properties of families of steady flows; a theory of Hamiltonian resonance for vortex arrays; an efficient numerical method for computing vortices with arbitrary symmetry; and a variational principle for compressible, barotropic or baroclinic flows. We employ these theoretical and numerical approaches to obtain new results regarding the structure and stability of several fundamental vortex and wave flows. The applications that we examine involve simple representations of fundamental fluid problems, which may be regarded as prototypical of flows associated with transport and mixing in the ocean and in the atmosphere, with aquatic animal propulsion, and with the dynamics of vortices in quantum condensates. We address two issues affecting the use of a variational argument to determine stability of families of steady flows. By building on ideas from bifurcation theory, we link turning points in a velocity-impulse diagram to gains or losses of stability. We introduce concepts from imperfection theory into these problems, enabling us to reveal hidden solution branches. The resulting methodology detects exchanges of stability through an "imperfect velocity-impulse" (IVI) diagram. We apply the IVI diagram approach to wide variety of vortex and wave flows. These examples include elliptical vortices, translating and rotating vortex pairs, single and double vortex rows, distributed vortices, as well as steep gravity waves. For a few of the flows considered, our work yields the first available stability boundaries. In addition, the IVI diagram methodology leads us to the discovery of several new families of steady flows, which exhibit lower symmetry. We next examine conditions for the development of an oscillatory instability in two

  14. Heterodyne laser frequency stabilization for long baseline optical interferometry in space-based gravitational wave detectors

    NASA Astrophysics Data System (ADS)

    Eichholz, Johannes; Tanner, David B.; Mueller, Guido

    2015-07-01

    The European Space Agency (ESA) selected the gravitational universe as the science theme for L3, a large space mission with a planned launch in 2034. NASA expressed a strong interest in joining ESA as a junior partner. The goal of the mission is the detection of gravitational waves of frequencies between 0.1 mHz and 0.1 Hz, where many long-lived sources are expected to be steady emitters of gravitational waves. Most likely, the mission design will evolve out of the earlier Laser Interferometer Space Antenna (LISA) concept. The interferometric heterodyne phase readout in LISA is performed by phase meters developed specifically to handle the low light powers and Doppler-drift of laser frequencies that appear as complications in the mission baseline. LISA requires the frequency noise of its seed lasers to be below 300 Hz /√{Hz } throughout the measurement band due to uncertainties in the absolute interferometer arm lengths. We have developed and successfully demonstrated Heterodyne Stabilization (HS), a novel cavity-laser frequency stabilization method that integrates well into the LISA mission baseline due to similar component demand. The cavities for the test setup were assembled with Clearceram-Z spacers, an ultralow thermal expansion coefficient material with potential applicability in interferometric space missions. Using HS, we were able to suppress the frequency noise of two lasers in a bench-top experiment to a level that meets the LISA requirement, suggesting both HS and Clearceram-Z can be considered in future mission concepts.

  15. Exact traveling wave solutions and L1 stability for the shallow water wave model of moderate amplitude

    NASA Astrophysics Data System (ADS)

    Wang, Ying; Guo, Yunxi

    2016-07-01

    In this paper, we developed, for the first time, the exact expressions of several periodic travelling wave solutions and a solitary wave solution for a shallow water wave model of moderate amplitude. Then, we present the existence theorem of the global weak solutions. Finally, we prove the stability of solution in L1(R) space for the Cauchy problem of the equation.

  16. Stability of stagnation via an expanding accretion shock wave

    NASA Astrophysics Data System (ADS)

    Velikovich, A. L.; Murakami, M.; Taylor, B. D.; Giuliani, J. L.; Zalesak, S. T.; Iwamoto, Y.

    2016-05-01

    Stagnation of a cold plasma streaming to the center or axis of symmetry via an expanding accretion shock wave is ubiquitous in inertial confinement fusion (ICF) and high-energy-density plasma physics, the examples ranging from plasma flows in x-ray-generating Z pinches [Maron et al., Phys. Rev. Lett. 111, 035001 (2013)] to the experiments in support of the recently suggested concept of impact ignition in ICF [Azechi et al., Phys. Rev. Lett. 102, 235002 (2009); Murakami et al., Nucl. Fusion 54, 054007 (2014)]. Some experimental evidence indicates that stagnation via an expanding shock wave is stable, but its stability has never been studied theoretically. We present such analysis for the stagnation that does not involve a rarefaction wave behind the expanding shock front and is described by the classic ideal-gas Noh solution in spherical and cylindrical geometry. In either case, the stagnated flow has been demonstrated to be stable, initial perturbations exhibiting a power-law, oscillatory or monotonic, decay with time for all the eigenmodes. This conclusion has been supported by our simulations done both on a Cartesian grid and on a curvilinear grid in spherical coordinates. Dispersion equation determining the eigenvalues of the problem and explicit formulas for the eigenfunction profiles corresponding to these eigenvalues are presented, making it possible to use the theory for hydrocode verification in two and three dimensions.

  17. Reexamination of dynamical stabilization of matter-wave solitons

    SciTech Connect

    Itin, Alexander; Morishita, Toru; Watanabe, Shinichi

    2006-09-15

    We consider dynamical stabilization of Bose-Einstein condensates by time-dependent modulation of the scattering length. The problem has been studied before by several methods: Gaussian variational approximation, the method of moments, the method of modulated Townes soliton, and the direct averaging of the Gross-Pitaevskii equation. We summarize these methods and find that the numerically obtained stabilized solution has a different configuration than that assumed by the theoretical methods (in particular a phase of the wave function is not quadratic with r). We show that there is presently no clear evidence for stabilization in a strict sense, because in the numerical experiments only metastable (slowly decaying) solutions have been obtained. In other words, neither numerical nor mathematical evidence for a new kind of soliton solutions has been revealed so far. The existence of the metastable solutions is nevertheless an interesting and complicated phenomenon on its own. We try some non-Gaussian variational trial functions to obtain better predictions for the critical nonlinearity g{sub cr} for metastabilization but other dynamical properties of the solutions remain difficult to predict.

  18. Design of stabilization system for medium wave infrared laser power

    NASA Astrophysics Data System (ADS)

    Ding, Zhong-kui; Wang, Lin; Shi, Xue-shun; Xu, Jun

    2013-12-01

    The 3~5um Medium Wave Infrared(MWIR) laser has gained a lot of attention for its important application values in remote sensing, medical, military and many other fields. However, there are many technical difficulties to fabricate those kind lasers, and the performance of their output power stabilities remain to be improved. In a practical application, the MWIR's output power will be instability when the temperature changes and the current varies. So a system of reducing MWIR power fluctuation should be established. In this paper, a photoelectric system of stabilizing the output power of He-Ne laser is developed, which is designed based on the theory of feedback control. Some primary devices and technologies are presented and the functions of each module are described in detail. Among of those, an auxiliary visible light path is designed to aid to adjust WMIR optical system. A converging lens as spatial filter is employed to eliminate stray light well. Dewar temperature control equipment is also used to reduce circuit noise in IR detector. The power supply of AD conversion circuit is independently designed to avoid the crosstalk caused by the analog section and digital section. Then the system has the advantages of good controllability, stability and high precision after above designation. Finally, the measurement precision of the system is also analyzed and verified.

  19. Jupiter's winds and Arnol'd's second stability theorem: Slowly moving waves and neutral stability

    NASA Technical Reports Server (NTRS)

    Stamp, Andrew P.; Dowling, Timothy E.

    1993-01-01

    Since the Voyager encounters in 1979, it has been known that Jupiter's cloud-top zonal winds violate the barotropic stability criterion. A vortex-tube stretching analysis of the Voyager wind data indicates that the more general Charney-Stern stability criterion is also violated. On the other hand, the zonal winds determined by tracking cloud features in Hubble Space Telescope images taken in 1991 precisely match the zonal winds determined by tracking cloud features in Voyager images, and it is hard to understand how a complicated zonal wind profile like Jupiter's could be unstable and yet not change at all in 12 years. In fact, there are at least two unknown ways to violate the Charney-Stern stability criterion and still have a stable flow. The better known of these is called Fjortoft's theorem, or Arnol'd's 1st theorem for the case of large-amplitude perturbations. Although the Fjortoft-Arnol'd theorem has been extended from the quasi-geostrophic equations to the primitive equations, the basic requirement that the potential vorticity be an increasing function of streamfunction is opposite to the case found in Jupiter, where the Voyager data indicate that the potential vorticity is a decreasing function of streamfunction. But this second case is precisely that which is covered by Arnol'd's 2nd stability theorem. In fact, the Voyager data suggest that Jupiter's zonal winds are neutrally stable with respect to Arnol'd's 2nd stability theorem. Here, we analyze the linear stability problem of a one-parameter family of sinusoidal zonal wind profiles that are close to neutral stability with respect to Arnol'd's 2nd stability theorem. We find numerically that the most unstable mode is always stationary, which may help to explain the slowly moving mode 10 waves observed on Jupiter. We find that violation of Arnol'd's 2nd stability theorem is both necessary and sufficient for instability of sinusoidal profiles. However, there appears to be no simple extension of Arnol'd's 2

  20. Stabilization of three-wave vortex beams in the waveguide

    NASA Astrophysics Data System (ADS)

    Gammal, Arnaldo; Malomed, Boris A.

    2015-04-01

    We consider two-dimensional (2D) localized vortical modes in the three-wave system with the quadratic ({{χ }(2)}) nonlinearity, alias nondegenerate second-harmonic (SH)-generating system, guided by the isotropic harmonic-oscillator (alias parabolic) confining potential. In addition to the straightforward realization in optics, the system models mixed atomic-molecular Bose-Einstein condensates. The main issue is stability of the vortex modes, which is investigated through computation of instability growth rates for eigenmodes of small perturbations, and by means of direct simulations. The threshold of parametric instability for single-color beams, represented solely by the SH with zero vorticity, is found in an analytical form with the help of the variational approximation. Trapped states with vorticities ≤ft( +1,-1,0 \\right) in the two fundamental-frequency components and the SH one (the so-called hidden-vorticity modes) are completely unstable. Also unstable are semi-vortices, with component vorticities ≤ft( 1,0,1 \\right). However, full vortices, with charges ≤ft( 1,1,2 \\right), have a well-defined stability region. Unstable full vortices feature regions of robust dynamical behavior, where they periodically split and recombine, keeping their vortical content.

  1. Stability of periodic traveling waves in the Aliev-Panfilov reaction-diffusion system

    NASA Astrophysics Data System (ADS)

    Gani, M. Osman; Ogawa, Toshiyuki

    2016-04-01

    We study the two-component Aliev-Panfilov reaction-diffusion system of cardiac excitation. It is known that the model exhibits spiral wave instability in two-dimensional spatial domains. In order to describe the spiral wave instability, it is important to understand periodic traveling wave instability resulting from the model. We determine the existence and stability of periodic traveling waves in the model. In addition, we calculate the stability boundary between stable and unstable periodic traveling waves in a two-dimensional parameter plane. It is observed that the periodic traveling waves express instability by a stability change of Eckhaus type. As a result, a stable wave bifurcates to an oscillating periodic traveling wave. We describe these phenomena by calculating the essential spectra of the waves. Furthermore, we study the stability of the waves as a function of the gaps between two nullclines. In two dimensions, we determine the spiral wave instability based on the stability boundary of the periodic traveling waves.

  2. Stability of capillary-gravity interfacial waves between two bounded fluids

    NASA Astrophysics Data System (ADS)

    Christodoulides, Paul; Dias, Frédéric

    1995-12-01

    Two-dimensional periodic capillary-gravity waves at the interface between two bounded fluids of different densities are considered. Based on a variational formulation, the relation between wave frequency and wave amplitude is obtained through a weakly nonlinear analysis. All classes of space-periodic waves are studied: traveling and standing waves as well as a degenerate class of mixed waves. As opposed to water waves, mixed interfacial waves exist even for pure gravity waves. The stability of traveling and standing waves with respect to three-dimensional modulations is then studied. By using the method of multiple scales, Davey-Stewartson-type equations are obtained. A detailed stability analysis is performed in three cases: pure gravity waves, capillary-gravity waves when one layer is infinitely deep, and capillary-gravity waves when both layers are infinitely deep. The main results for oblique (i.e., combined longitudinal and transverse) modulations reveal a mostly stabilizing effect of the density ratio for traveling waves and a destabilizing effect for standing waves.

  3. Initial Results of DC Electric Fields, Associated Plasma Drifts, Magnetic Fields, and Plasma Waves Observed on the C/NOFS Satellite

    NASA Technical Reports Server (NTRS)

    Pfaff, R.; Freudenreich, H.; Bromund, K.; Klenzing, J.; Rowland, D.; Maynard, N.

    2010-01-01

    Initial results are presented from the Vector Electric Field Investigation (VEFI) on the Air Force Communication/Navigation Outage Forecasting System (C/NOFS) satellite, a mission designed to understand, model, and forecast the presence of equatorial ionospheric irregularities. The VEFI instrument includes a vector DC electric field detector, a fixed-bias Langmuir probe operating in the ion saturation regime, a flux gate magnetometer, an optical lightning detector, and associated electronics including a burst memory. Compared to data obtained during more active solar conditions, the ambient DC electric fields and their associated E x B drifts are variable and somewhat weak, typically < 1 mV/m. Although average drift directions show similarities to those previously reported, eastward/outward during day and westward/downward at night, this pattern varies significantly with longitude and is not always present. Daytime vertical drifts near the magnetic equator are largest after sunrise, with smaller average velocities after noon. Little or no pre-reversal enhancement in the vertical drift near sunset is observed, attributable to the solar minimum conditions creating a much reduced neutral dynamo at the satellite altitude. The nighttime ionosphere is characterized by larger amplitude, structured electric fields, even where the plasma density appears nearly quiescent. Data from successive orbits reveal that the vertical drifts and plasma density are both clearly organized with longitude. The spread-F density depletions and corresponding electric fields that have been detected thus far have displayed a preponderance to appear between midnight and dawn. Associated with the narrow plasma depletions that are detected are broad spectra of electric field and plasma density irregularities for which a full vector set of measurements is available for detailed study. Finally, the data set includes a wide range of ELF/VLF/HF oscillations corresponding to a variety of plasma waves

  4. Quantification of the Effect of Pressure Wire Drift on the Diagnostic Performance of Fractional Flow Reserve, Instantaneous Wave-Free Ratio, and Whole-Cycle Pd/Pa

    PubMed Central

    Ahmad, Yousif; Shun-Shin, Matthew J.; Nijjer, Sukhjinder; Petraco, Ricardo; Al-Lamee, Rasha; Mayet, Jamil; Francis, Darrel P.; Sen, Sayan; Davies, Justin E.

    2016-01-01

    Background— Small drifts in intracoronary pressure measurements (±2 mm Hg) can affect stenosis categorization using pressure indices. This has not previously been assessed for fractional flow reserve (FFR), instantaneous wave-free ratio (iFR), and whole-cycle distal pressure/proximal pressure (Pd/Pa) indices. Methods and Results—Four hundred forty-seven stenoses were assessed with FFR, iFR, and whole-cycle Pd/Pa. Cut point values for significance were predefined as ≤0.8, <0.90, and <0.93, respectively. Pressure wire drift was simulated by offsetting the distal coronary pressure trace by ±2 mm Hg. FFR, iFR, and whole-cycle Pd/Pa indices were recalculated and stenosis misclassification quantified. Median (±median absolute deviation) values for FFR, iFR, and whole-cycle Pd/Pa were 0.81 (±0.11), 0.90 (±0.07), and 0.93 (±0.06), respectively. For the cut point of FFR, iFR, and whole-cycle Pd/Pa, 34.6% (155), 50.1% (224), and 62.2% (278) of values, respectively, lay within ±0.05 U. With ±2 mm Hg pressure wire drift, 21% (94), 25% (110), and 33% (148) of the study population were misclassified with FFR, iFR, and whole-cycle Pd/Pa, respectively. Both FFR and iFR had significantly lower misclassification than whole-cycle Pd/Pa (P<0.001). There was no statistically significant difference between the diagnostic performance of FFR and iFR (P=0.125). Conclusions— In a substantial proportion of cases, small amounts of pressure wire drift are enough to cause stenoses to change classification. Whole-cycle Pd/Pa is more vulnerable to such reclassification than FFR and iFR. PMID:27076571

  5. Stability of shock waves for multi-dimensional hyperbolic-parabolic conservation laws

    NASA Astrophysics Data System (ADS)

    Li, Dening

    1988-01-01

    The uniform linear stability of shock waves is considerd for quasilinear hyperbolic-parabolic coupled conservation laws in multi-dimensional space. As an example, the stability condition and its dynamic meaning for isothermal shock wave in radiative hydrodynamics are analyzed.

  6. The complex mixed Wentzel–Kramers–Brillouin-full-wave approach and its application to the two dimensional mode structure analysis of ion temperature gradient/collisionless trapped electron mode drift waves

    SciTech Connect

    Lu, Z. X.

    2015-05-15

    The complex mixed Wentzel–Kramers–Brillouin (WKB)-full-wave approach is applied to the 2D mode structure analysis of ion temperature gradient/collisionless trapped electron mode drift waves in tokamak plasmas. The parallel mode structure is calculated with the full-wave approach, while the radial envelope is calculated with the complex WKB method. The tilting of the global mode structure along radius is demonstrated analytically. The effects of the phase and amplitude variation of the radial envelope on the parallel mode structure are included in terms of a complex radial wave vector in the parallel mode equation. It is shown that the radial equilibrium non-uniformity leads to the asymmetry of the parallel mode structure not only in configuration space but also in spectrum space. The mixed approach provides a practical way to analyze the asymmetric component of the global mode structure due to radial equilibrium non-uniformity.

  7. The complex mixed Wentzel-Kramers-Brillouin-full-wave approach and its application to the two dimensional mode structure analysis of ion temperature gradient/collisionless trapped electron mode drift waves

    NASA Astrophysics Data System (ADS)

    Lu, Z. X.

    2015-05-01

    The complex mixed Wentzel-Kramers-Brillouin (WKB)-full-wave approach is applied to the 2D mode structure analysis of ion temperature gradient/collisionless trapped electron mode drift waves in tokamak plasmas. The parallel mode structure is calculated with the full-wave approach, while the radial envelope is calculated with the complex WKB method. The tilting of the global mode structure along radius is demonstrated analytically. The effects of the phase and amplitude variation of the radial envelope on the parallel mode structure are included in terms of a complex radial wave vector in the parallel mode equation. It is shown that the radial equilibrium non-uniformity leads to the asymmetry of the parallel mode structure not only in configuration space but also in spectrum space. The mixed approach provides a practical way to analyze the asymmetric component of the global mode structure due to radial equilibrium non-uniformity.

  8. Stability of negative solitary waves for an integrable modified Camassa-Holm equation

    SciTech Connect

    Yin Jiuli; Tian Lixin; Fan Xinghua

    2010-05-15

    In this paper, we prove that the modified Camassa-Holm equation is Painleve integrable. We also study the orbital stability problem of negative solitary waves for this integrable equation. It is shown that the negative solitary waves are stable for arbitrary wave speed of propagation.

  9. On the Stability of Self-Similar Solutions to Nonlinear Wave Equations

    NASA Astrophysics Data System (ADS)

    Costin, Ovidiu; Donninger, Roland; Glogić, Irfan; Huang, Min

    2016-04-01

    We consider an explicit self-similar solution to an energy-supercritical Yang-Mills equation and prove its mode stability. Based on earlier work by one of the authors, we obtain a fully rigorous proof of the nonlinear stability of the self-similar blowup profile. This is a large-data result for a supercritical wave equation. Our method is broadly applicable and provides a general approach to stability problems related to self-similar solutions of nonlinear wave equations.

  10. The influence of genetic drift on the formation and stability of polymorphisms arising from negative frequency-dependent selection.

    PubMed

    Zhao, Lei; Waxman, David

    2016-02-21

    We consider the simplest form of negative frequency-dependent selection in a biallelic haploid population, where the selection coefficient of a mutant allele is a linear function of the allele's frequency, and changes from positive to negative as the frequency is increased. In an effectively infinite population this behaviour leads to a stable polymorphism. We present a theoretical investigation of what occurs in a finite population, where a long-lived polymorphism may be formed, but which fluctuates and ultimately disappears due to random genetic drift. We model the dynamics as a branching process and explicitly take into account differences between the census population size and the effective population size, which play different roles in the dynamics. We characterise the behaviour of the population in terms of three distinct timescales associated with: (i) early loss of mutant alleles, (ii) achievement of the long-lived polymorphism, (iii) disappearance of the polymorphism. Timescales (i) and (iii) depend on the effective population size and are, as a consequence, affected by random genetic drift, while timescale (ii) depends primarily on the census size and is relatively insensitive to genetic drift. Analysis and simulations of the branching process clarify the different influences of the census and effective population sizes. One substantial quantitative difference, between populations where the effective and census population sizes coincide and where they differ, lies in the number of mutant alleles in the long-lived polymorphism. This number is approximately proportional to the census size. Thus assuming the census size equals a much smaller effective population size predicts a much smaller number of mutants in the long-lived polymorphism. PMID:26656188

  11. Stability of a superposition of shock waves with contact discontinuities for systems of viscous conservation laws

    NASA Astrophysics Data System (ADS)

    Zeng, Huihui

    In this paper, we show the large time asymptotic nonlinear stability of a superposition of viscous shock waves with viscous contact waves for systems of viscous conservation laws with small initial perturbations, provided that the strengths of these viscous waves are small with the same order. The results are obtained by elementary weighted energy estimates based on the underlying wave structure and a new estimate on the heat equation.

  12. Slosh wave excitation and stability of spacecraft fluid systems

    NASA Technical Reports Server (NTRS)

    Hung, R. J.; Lee, C. C.; Leslie, F. W.

    1990-01-01

    The instability of liquid and gas interface can be induced by the pressure of longitudinal and lateral accelerations, vehicle vibration, and rotational fields of spacecraft in a microgravity environment. Characteristics of slosh waves excited by the restoring force field of gravity jitters have been investigated. Results show that lower frequency gravity jitters excite slosh waves with higher ratio of maximum amplitude to wave length than that of the slosh waves generated by the higher frequency gravity jitters.

  13. On the stability of the moments of the maximum entropy wind wave spectrum

    SciTech Connect

    Pena, H.G.

    1983-03-01

    The stability of some current wind wave parameters as a function of high-frequency cut-off and degrees of freedom of the spectrum has been numerically investigated when computed in terms of the moments of the wave energy spectrum. From the Pierson-Moskovitz wave spectrum type, a sea surface profile is simulated and its wave energy spectrum is estimated by the Maximum Entropy Method (MEM). As the degrees of freedom of the MEM spectral estimation are varied, the results show a much better stability of the wave parameters as compared to the classical periodogram and correlogram spectral approaches. The stability of wave parameters as a function of high-frequency cut-off has the same result as obtained by the classical techniques.

  14. Drift mode calculations for the Large Helical Device

    SciTech Connect

    G. Rewoldt; L.-P. Ku; W.M. Tang; H. Sugama; N. Nakajima; K.Y. Watanabe; S. Murakami; H. Yamada; W.A. Cooper

    2000-06-08

    A fully kinetic assessment of the stability properties of toroidal drift modes has been obtained for a case for the Large Helical Device (LHD) [A.Iiyoshi, et al., Plasma Physics and Controlled Nuclear Fusion Research, 1998, Nucl.Fusion 39, 1245 (1999)]. This calculation retains the important effects in the linearized gyrokinetic equation, using the lowest-order ''ballooning representation'' for high toroidal mode number instabilities in the electrostatic limit. Results for toroidal drift waves destabilized by trapped particle dynamics and ion temperature gradients are presented, using three-dimensional magnetohydrodynamics equilibria reconstructed from experimental measurements. The effects of helically-trapped particles and helical curvature are investigated.

  15. Global transition from drift wave dominated regimes to multi-instability plasma dynamics and simultaneous formation of a radial transport barrier in helicon plasma

    NASA Astrophysics Data System (ADS)

    Chakraborty Thakur, Saikat; Cui, Lang; Gosselin, Jordan; Vaezi, Payam; Holland, Chris; Tynan, George

    2014-10-01

    Recent studies in CSDX reported a sharp global transition in the plasma dynamics during the route to turbulence. For B <140 mT, the plasma is dominated by density gradient driven drift waves [DW]. For B >140 mT, a new global equilibrium is achieved with simultaneous existence of three radially separated plasma instabilities: coherent Rayleigh Taylor [RT] modes at the center, DW at the density gradient and turbulent, shear driven Kelvin-Helmholtz [KH] instabilities at the edge. Only the RT modes rotate in the ion diamagnetic drift direction. The radial particle flux is directed outward for small radii and inward for large radii, forming a radial particle transport barrier leading to stiff profiles and increased core density. Simultaneously the core Ar-II light emission increases (×10) forming a very bright blue core. The radial extent of the inner RT mode and the blue core coincides with the radial location of the particle transport barrier. This equilibrium with simultaneous RT-DW-KH instabilities shows very rich plasma dynamics including intermittency, blob formation and propagation, inward particle flux against density gradients etc. We report detailed studies of azimuthal momentum balance and time resolved dynamics leading to the transition using Langmuir probes, fast imaging, spectroscopy, laser induced fluorescence etc.

  16. Stabilized high-power laser system for the gravitational wave detector advanced LIGO.

    PubMed

    Kwee, P; Bogan, C; Danzmann, K; Frede, M; Kim, H; King, P; Pöld, J; Puncken, O; Savage, R L; Seifert, F; Wessels, P; Winkelmann, L; Willke, B

    2012-05-01

    An ultra-stable, high-power cw Nd:YAG laser system, developed for the ground-based gravitational wave detector Advanced LIGO (Laser Interferometer Gravitational-Wave Observatory), was comprehensively characterized. Laser power, frequency, beam pointing and beam quality were simultaneously stabilized using different active and passive schemes. The output beam, the performance of the stabilization, and the cross-coupling between different stabilization feedback control loops were characterized and found to fulfill most design requirements. The employed stabilization schemes and the achieved performance are of relevance to many high-precision optical experiments. PMID:22565688

  17. Stability and Asymptotic Behavior of Periodic Traveling Wave Solutions of Viscous Conservation Laws in Several Dimensions

    NASA Astrophysics Data System (ADS)

    Oh, Myunghyun; Zumbrun, Kevin

    2010-04-01

    Under natural spectral stability assumptions motivated by previous investigations of the associated spectral stability problem, we determine sharp L p estimates on the linearized solution operator about a multidimensional planar periodic wave of a system of conservation laws with viscosity, yielding linearized L 1 ∩ L p → L p stability for all {p ≥q 2} and dimensions {d ≥q 1} and nonlinear L 1 ∩ H s → L p ∩ H s stability and L 2-asymptotic behavior for {p≥q 2} and {d≥q 3} . The behavior can in general be rather complicated, involving both convective (that is, wave-like) and diffusive effects.

  18. Stability of a family of travelling wave solutions in a feedforward chain of phase oscillators

    NASA Astrophysics Data System (ADS)

    Lanford, O. E., III; Mintchev, S. M.

    2015-01-01

    Travelling waves are an important class of signal propagation phenomena in extended systems with a preferred direction of information flow. We study the generation of travelling waves in unidirectional chains of coupled oscillators communicating via a phase-dependent pulse-response interaction borrowed from mathematical neuroscience. Within the context of such systems, we develop a widely applicable, jointly numerical and analytical methodology for deducing existence and stability of periodic travelling waves. We provide careful numerical studies that support the existence of a periodic travelling wave solution as well as the asymptotic relaxation of a single oscillator to the wave when it is forced with the wave profile. Using this evidence as an assumption, we analytically prove global stability of waves in the infinite chain, with respect to initial perturbations of downstream sites. This rigorous stability result suggests that asymptotic relaxation to the travelling wave occurs even when the forcing is perturbed from the wave profile, a property of the motivating system that is supported by previous work as well as the convergence of the more sophisticated numerical algorithm that we propose in order to compute a high-precision approximation to the solution. We provide additional numerical studies that show that the wave is part of a one-parameter family, and we illustrate the structural robustness of this family with respect to changes in the coupling strength.

  19. Stability of periodic waves generated by long-wavelength instabilities in isotropic and anisotropic systems

    NASA Astrophysics Data System (ADS)

    Bar, Doron E.; Nepomnyashchy, Alexander A.

    1999-08-01

    We consider spontaneous generation of long waves in the presence of a conservation law in both cases of isotropic systems (e.g., Bénard-Marangoni waves) and anisotropic systems (e.g., waves in a film on an inclined plane). We found that near the instability threshold the problem is governed by the dissipation-modified Kadomtsev-Petviashvili equation in the former case and by the anisotropic dissipation-modified Korteweg-de Vries equation in the latter case. In frames of the derived 2+1-dimensional amplitude equations, we investigate the stability of one-dimensional waves. In isotropic systems the one-dimensional waves turned out to be always unstable with respect to a long-wave transverse modulation of the front. In anisotropic systems, only the one-dimensional periodic waves moving in the most preferred direction are found to be stable. Any deviation from this direction leads to instability of such an oblique wave.

  20. Surface drift in the upper centimetres of the water column in short fetches and the behaviour of the diffusive sub-layer from experiments in a wind wave flume

    NASA Astrophysics Data System (ADS)

    Ocampo-Torres, Francisco J.; Branger, Hubert; Osuna, Pedro; Robles, Lucia

    2015-04-01

    Ocean surface drift is of great relevance to properly model exchange processes between the ocean and the atmosphere. It is also important to better understand the early stages of surface waves development and their implications in the momentum transfer across the sea surface. In this work we study the the onset of surface drift induced by wind and waves through detailed laboratory measurements in a large wind-wave flume. Momentum transfer through the water surface, waves and surface drift were being measured in the 40m long wind-wave tank at IRPHE, Marseille. In a station in the middle of the tank momentum fluxes were estimated directly through the eddy correlation method to provide reference information for the corresponding surface drift onset recorded at very short fetch. During each experimental run very low wind was set on (about 1m/s) for a certain period and suddenly it was constantly accelerated to reach about 13 m/s (as well as 8 and 5 m/s during different runs) in about 15 sec to as long as 600 sec. The wind was kept constant at that high speed for 2 to 10 min, and then suddenly and constantly decelerate to 0 at the end of each experiment. The 3-d velocity vertical profile is measured with an acoustic sensor (Nortek Vectrino Profiler), with a vertical resolution of 0.1 cm and sampling rate of 100 Hz, over a column of 3.5 cm in length. Under the highest wind conditions a very distinctive shear was detected in the upper 1.5 cm while the strongest surface drift was recorded as about 0.5 cm/s. A rather linear variation of surface drift was observed with depth under cases of low to moderate wind speed. Evolution of the surface drift velocity is analysed and onset behaviour is addressed with particular emphasis in accelerated winds. A strong surface drift is expected to play a major role in the early stages of surface wave spectrum development, which is to be addressed in terms of frequency spectra estimated from a capacitance gauge deployed in the vicinity of

  1. Doppler effect in a solid medium: Spin wave emission by a precessing domain wall drifting in spin current

    NASA Astrophysics Data System (ADS)

    Xia, Hong; Chen, Jie; Zeng, Xiaoyan; Yan, Ming

    2016-04-01

    The Doppler effect is a fundamental physical phenomenon observed for waves propagating in vacuum or various media, commonly gaseous or liquid. Here, we report on the occurrence of a Doppler effect in a solid medium. Instead of a real object, a topological soliton, i.e., a magnetic domain wall (DW) traveling in a current-carrying ferromagnetic nanowire, plays the role of the moving wave source. The Larmor precession of the DW in an external field stimulates emission of monochromatic spin waves (SWs) during its motion, which show a significant Doppler effect, comparable to the acoustic one of a train whistle. This process involves two prominent spin-transfer-torque effects simultaneously, the current-driven DW motion and the current-induced SW Doppler shift. The latter gives rise to an interesting feature, i.e., the observed SW Doppler effect appears resulting from a stationary source and a moving observer, contrary to the laboratory frame.

  2. Linear stability of multiple internal solitary waves in fluids of great depth

    NASA Astrophysics Data System (ADS)

    Matsuno, Y.; Kaup, D. J.

    1997-02-01

    The linear stability of the multiple solitary wave solution of the Benjamin-Ono (BO) equation is studied analytically. By establishing the completeness relation for the eigenfunctions of the BO equation linearized about multisoliton solutions, we solve the initial value problem for this system. We find that the wave under consideration is stable against infinitesimal perturbations.

  3. Stability of the kinetic Alfven wave in a current-less plasma

    NASA Astrophysics Data System (ADS)

    Sreekala, G.; Sebastian, Sijo; Michael, Manesh; Abraham, Noble P.; Renuka, G.; Venugopal, Chandu

    2015-06-01

    The two potential theory of Hasegawa has been used to derive the dispersion relation for the kinetic Alfven wave (KAW) in a plasma composed of hydrogen, oxygen and electrons. All three components have been modeled by ring distributions (obtained by subtracting two Maxwellian distributions with different temperatures) with the hydrogen and electrons drifting, respectively, with velocities VdH and Vde. For the most general case, the dispersion relation is a polynomial equation of order five; it reduces to a relation which supports only one mode when VdH = 0. For typical parameters at comet Halley, we find that both VdH and Vde can drive the wave unstable; the KAW is thus driven unstable in a current-less plasma. Such an instability was found for the ion acoustic wave by Vranjes et al. (2009).

  4. Stability of the kinetic Alfven wave in a current-less plasma

    NASA Astrophysics Data System (ADS)

    Abraham, Noble P.; C, Venugopal; Sebastian, Sijo; Renuka, G.; Balan, Nanan; Sreekala, G.

    The two potential theory of Hasegawa has been used to derive the dispersion relation for the kinetic Alfven wave (KAW) in a plasma composed of hydrogen, oxygen and electrons. All three components have been modeled by ring distributions (obtained by subtracting two Maxwellian distributions with different temperatures) with the hydrogen and electrons drifting, respectively, with velocities V_{dH} and V_{de}. For the most general case, the dispersion equation is a polynomial equation of order five; it reduces to a relation which supports only one mode when V_{dH}=0. For typical parameters at comet Halley, we find that both V_{dH} and V_{de} can drive the wave unstable; the KAW is thus driven unstable in a current-less plasma. Such an instability was found for the ion acoustic wave by Vranjes et al.

  5. A proof for the mode stability of a self-similar wave map

    NASA Astrophysics Data System (ADS)

    Costin, O.; Donninger, R.; Xia, X.

    2016-08-01

    We study the fundamental self-similar solution to the SU(2) sigma model, found by Shatah and Turok–Spergel. We give a rigorous proof for its mode stability. Based on earlier results by the second author, the present paper constitutes the last building block for a completely rigorous proof of the nonlinear stability of the Shatah–Turok–Spergel wave map.

  6. Stability of the solitary wave solutions to a coupled BBM system

    NASA Astrophysics Data System (ADS)

    Chen, Hongqiu; Wang, Xiaojun

    2016-07-01

    In this work, we present a stability criteria for the solitary wave solutions to a BBM system that contains coupled nonlinear terms. Using the idea by Bona, Chen and Karakashian [5] and exploiting the accurate point spectrum information of the associated Schrödinger operator, we improve the stability results previously gotten by Pereira [15].

  7. Effect of a backward wave on the stability of an ultrahigh gain gyrotron traveling-wave amplifier

    SciTech Connect

    Du Chaohai; Liu Pukun; Xue Qianzhong; Wang Minghong

    2008-12-15

    A systematic stability analysis method using theoretical tools combining linear and self-consistent nonlinear theory is presented to analyze an ultrahigh gain gyrotron traveling-wave (gyro-TWT) amplifier operated in the fundamental TE{sub 11} mode in the Ka-band. It characterizes the role that the backward-wave component plays in the internal feedback physical processes of two major kinds of self-induced oscillations associated with TE{sub 11}{sup (1)} absolute instability and TE{sub 21}{sup (2)} gyrobackward-wave oscillation. For the first time, self-induced constriction in TE{sub 11}{sup (1)} absolute instability caused by a strong backward-wave component is revealed through simulation. Both the thickness and resistivity of the distributed wall loss loaded on the inside of the interaction waveguide have obvious effects on stabilizing both kinds of oscillations. Following the stability analysis, a multistage interaction circuit is proposed by nonlinear analysis which shortens the length of the entire structure and enables the ultrahigh gain gyro-TWT to operate with high stability and wide bandwidth.

  8. Asymptotic nonlinear stability of traveling waves to conservation laws arising from chemotaxis

    NASA Astrophysics Data System (ADS)

    Li, Tong; Wang, Zhi-An

    In this paper, we establish the existence and the nonlinear stability of traveling wave solutions to a system of conservation laws which is transformed, by a change of variable, from the well-known Keller-Segel model describing cell (bacteria) movement toward the concentration gradient of the chemical that is consumed by the cells. We prove the existence of traveling fronts by the phase plane analysis and show the asymptotic nonlinear stability of traveling wave solutions without the smallness assumption on the wave strengths by the method of energy estimates.

  9. S-parameter characterization and lumped-element modelling of millimeter-wave single-drift impact-ionization avalanche transit-time diode

    NASA Astrophysics Data System (ADS)

    Zhang, Wogong; Yamamoto, Yuji; Oehme, Michael; Matthies, Klaus; Raju, Ashraful I.; Senthil Srinivasan, V. S.; Körner, Roman; Gollhofer, Martin; Bechler, Stefan; Funk, Hannes; Tillack, Bernd; Kasper, Erich; Schulze, Jörg

    2016-04-01

    Five silicon (Si) p++-n--n++ samples were grown at various doping concentrations (1.0 × 1017-2.2 × 1017 cm-3) in an n- layer by using the reduced-pressure CVD technique. By using these samples, 30 × 2 µm2 single-drift (SD) impact-ionization avalanche transit-time (IMPATT) diodes were processed with Si-based monolithic millimeter-wave integrated circuit (SIMMWIC) technology.1 , 2 ) The samples within a small process window exhibited a large negative differential resistance at approximately the avalanche frequency, as confirmed by small-signal S-parameter characterization. A model based on depletion width was given to explain the conditions for the appearance of the negative differential IMPATT resistance, which is the basis of millimeter-wave amplifier and oscillator applications. Furthermore, a measurement-based small-signal lumped-element model was established to describe the IMPATT functionality from the circuit component aspect. This lumped-element model shows a negative differential resistance within a well-defined range in the given element parameters, which can explain the experimental observations.

  10. Uniqueness and stability of traveling waves for cellular neural networks with multiple delays

    NASA Astrophysics Data System (ADS)

    Yu, Zhi-Xian; Mei, Ming

    2016-01-01

    In this paper, we investigate the properties of traveling waves to a class of lattice differential equations for cellular neural networks with multiple delays. Following the previous study [38] on the existence of the traveling waves, here we focus on the uniqueness and the stability of these traveling waves. First of all, by establishing the a priori asymptotic behavior of traveling waves and applying Ikehara's theorem, we prove the uniqueness (up to translation) of traveling waves ϕ (n - ct) with c ≤c* for the cellular neural networks with multiple delays, where c* < 0 is the critical wave speed. Then, by the weighted energy method together with the squeezing technique, we further show the global stability of all non-critical traveling waves for this model, that is, for all monotone waves with the speed c waves, when the initial perturbations around the monotone traveling waves decay exponentially at far fields, but can be arbitrarily large in other locations.

  11. Drift of Scroll Wave Filaments in an Anisotropic Model of the Left Ventricle of the Human Heart

    PubMed Central

    Pravdin, Sergei; Dierckx, Hans; Markhasin, Vladimir S.; Panfilov, Alexander V.

    2015-01-01

    Scroll waves are three-dimensional vortices which occur in excitable media. Their formation in the heart results in the onset of cardiac arrhythmias, and the dynamics of their filaments determine the arrhythmia type. Most studies of filament dynamics were performed in domains with simple geometries and generic description of the anisotropy of cardiac tissue. Recently, we developed an analytical model of fibre structure and anatomy of the left ventricle (LV) of the human heart. Here, we perform a systematic study of the dynamics of scroll wave filaments for the cases of positive and negative tension in this anatomical model. We study the various possible shapes of LV and different degree of anisotropy of cardiac tissue. We show that, for positive filament tension, the final position of scroll wave filament is mainly determined by the thickness of the myocardial wall but, however, anisotropy attracts the filament to the LV apex. For negative filament tension, the filament buckles, and for most cases, tends to the apex of the heart with no or slight dependency on the thickness of the LV. We discuss the mechanisms of the observed phenomena and their implications for cardiac arrhythmias. PMID:26539486

  12. Orbital stability of periodic traveling-wave solutions for the regularized Schamel equation

    NASA Astrophysics Data System (ADS)

    de Andrade, Thiago Pinguello; Pastor, Ademir

    2016-03-01

    In this work we study the orbital stability of periodic traveling-wave solutions for dispersive models. The study of traveling waves started in the mid-18th century when John S. Russel established that the flow of water waves in a shallow channel has constant evolution. In recent years, the general strategy to obtain orbital stability consists in proving that the traveling wave in question minimizes a conserved functional restricted to a certain manifold. Although our method can be applied to other models, we deal with the regularized Schamel equation, which contains a fractional nonlinear term. We obtain a smooth curve of periodic traveling-wave solutions depending on the Jacobian elliptic functions and prove that such solutions are orbitally stable in the energy space. In our context, instead of minimizing the augmented Hamiltonian in the natural codimension two manifold, we minimize it in a "new" manifold, which is suitable to our purposes.

  13. 3-dimensional Oil Drift Simulations

    NASA Astrophysics Data System (ADS)

    Wettre, C.; Reistad, M.; Hjøllo, B.Å.

    Simulation of oil drift has been an ongoing activity at the Norwegian Meteorological Institute since the 1970's. The Marine Forecasting Centre provides a 24-hour service for the Norwegian Pollution Control Authority and the oil companies operating in the Norwegian sector. The response time is 30 minutes. From 2002 the service is extended to simulation of oil drift from oil spills in deep water, using the DeepBlow model developed by SINTEF Applied Chemistry. The oil drift model can be applied both for instantaneous and continuous releases. The changes in the mass of oil and emulsion as a result of evaporation and emulsion are computed. For oil spill at deep water, hydrate formation and gas dissolution are taken into account. The properties of the oil depend on the oil type, and in the present version 64 different types of oil can be simulated. For accurate oil drift simulations it is important to have the best possible data on the atmospheric and oceanic conditions. The oil drift simulations at the Norwegian Meteorological Institute are always based on the most updated data from numerical models of the atmosphere and the ocean. The drift of the surface oil is computed from the vectorial sum of the surface current from the ocean model and the wave induced Stokes drift computed from wave energy spectra from the wave prediction model. In the new model the current distribution with depth is taken into account when calculating the drift of the dispersed oil droplets. Salinity and temperature profiles from the ocean model are needed in the DeepBlow model. The result of the oil drift simulations can be plotted on sea charts used for navigation, either as trajectory plots or particle plots showing the situation at a given time. The results can also be sent as data files to be included in the user's own GIS system.

  14. Experimental Evaluation of Journal Bearing Stability and New Gas Wave Bearing Materials

    NASA Technical Reports Server (NTRS)

    Keith, Theo G., Jr.; Dimofte, Florin

    1998-01-01

    A gas journal bearing, with a wavy surfaces was tested in a range of speeds up to 18,000 RPM to determine its stability in an unloaded condition as a function of the wave amplitude. The bearing, was 50 mm in diameter, 58 mm long and had 0.01 65 mm radial clearance. Three waves were created on the inner surface by deforming the bearing sleeve. The ratio of the wave amplitude to the radial clearance (the wave amplitude ratio) was varied from zero to 0.3.

  15. Sensitivity of the stability of a waste emplacement drift to variation in assumed rock joint parameters in welded tuff

    SciTech Connect

    Christianson, M.

    1989-04-01

    This report presents the results of a numerical analysis to determine the effects of variation of rock joint parameters on stability of waste disposal rooms for vertical emplacement. Conditions and parameters used were taken from the Nevada Nuclear Waste Storage Investigation (NNWSI) Project Site Characterization Plan Conceptual Design report (MacDougall et al., 1987). Mechanical results are presented which illustrate the predicted distribution of stress, joint slip, and room deformations for times of initial excavation and after 50 years heating. 82 refs., 93 figs.

  16. Stability of spiral wave vortex filaments with phase twists

    NASA Astrophysics Data System (ADS)

    Nam, Keeyeol; Ott, Edward; Guzdar, Parvez N.; Gabbay, Michael

    1998-08-01

    In this paper we investigate the stability of a straight vortex filament with phase twist described by the three-dimensional complex Ginzburg-Landau equation (CGLE). The results of the linear stability analysis show that the straight filament is stable in a limited region of the two parameter space of the CGLE. The stable region is dependent on the phase twist imposed on the filament and shrinks in size as the phase twist is increased. It is also shown numerically that the nonlinear evolution of an unstable initial straight filament can lead to a helical filament.

  17. First results of the high-resolution multibeam ULF wave experiment at the Ekaterinburg SuperDARN radar: Ionospheric signatures of coupled poloidal Alfvén and drift-compressional modes

    NASA Astrophysics Data System (ADS)

    Mager, Pavel N.; Berngardt, Oleg I.; Klimushkin, Dmitri Yu.; Zolotukhina, Nina A.; Mager, Olga V.

    2015-08-01

    A continuous experiment was carried out at the Ekaterinburg (EKB) stereoradar of the Russian segment of SuperDARN in order to examine the spatio-temporal characteristics of radar-detected magnetospheric ULF waves. The study of magnetospheric oscillations is based on analysis of scattering from field-aligned F-layer irregularities. Their E × B drift Doppler velocity at F-layer heights is associated with the background electric field in the ionosphere. During the experiment one of the radar channels operates in 0-2 beam scanning, with an integration time of 6 s, which corresponds to the total 18-s time resolution at each beam. This allows detecting magnetospheric ULF waves with periods of 40 s and up. Beam 0 is along the 132 magnetic meridian, so the registered velocity oscillations correspond to the wave electric field azimuthal component. Operation of the radar in this mode was started in December 2013. The first ULF wave events observed in the experiment and presented here occurred on 14 December 2013 and 2 January 2014 in the nightside magnetosphere during two geomagnetic disturbances classified as small magnetic storms and associated with high speed streams from coronal holes. Both the ULF events occurred after substorm-like auroral disturbances. The ULF waves observed during these events are classified as Pc5 geomagnetic pulsations. Two oscillation branches were observed, the higher and the lower frequency ones. As the azimuthal wave numbers m increase, the branches converge and merge into a single oscillation branch at some critical azimuthal wave number value m⋆. This ω(m) dependence is characteristic of the coupled Alfvén and drift-compressional waves which according to theory merge if the azimuthal wave number exceeds some critical value. This merged single oscillation branch represents an unstable drift ballooning coupling mode. Thus, the following interpretation of the observed events can be suggested; at m

  18. Stability of matter-wave solitons in optical lattices

    NASA Astrophysics Data System (ADS)

    Ali, Sk. Golam; Roy, S. K.; Talukdar, B.

    2010-08-01

    We consider localized states of both single- and two-component Bose-Einstein condensates (BECs) confined in a potential resulting from the superposition of linear and nonlinear optical lattices and make use of Vakhitov-Kolokolov criterion to investigate the effect of nonlinear lattice on the stability of the soliton solutions in the linear optical lattice (LOL). For the single-component case we show that a weak nonlinear lattice has very little effect on the stability of such solitons while sufficiently strong nonlinear optical lattice (NOL) squeezes them to produce narrow bound states. For two-component condensates we find that when the strength of the NOL (γ1) is less than that of the LOL (V0) a relatively weak intra-atomic interaction (IAI) has little effect on the stability of the component solitons. This is true for both attractive and repulsive IAI. A strong attractive IAI, however, squeezes the BEC solitons while a similar repulsive IAI makes the component solitons wider. For γ1 > V0, only a strong attractive IAI squeezes the BEC solitons but the squeezing effect is less prominent than that found for γ1 < V0. We make useful checks on the results of our semianalytical stability analysis by solving the appropriate Gross-Pitaevskii equations numerically.

  19. Gyrotron Frequency Stabilization by a Weak Reflected Wave

    NASA Astrophysics Data System (ADS)

    Glyavin, M. Yu.; Denisov, G. G.; Kulygin, M. L.; Mel'nikova, M. M.; Novozhilova, Yu. V.; Ryskin, N. M.

    2016-02-01

    The possibility of reducing the radiation frequency fluctuations by a factor of 3-5 using a nonresonant or highly resonant weakly reflecting load for the gyrotrons employed in controlled-fusion facilities is shown. The ranges of system parameters where the frequency stabilization is most effective were identified both analytically and numerically.

  20. Atomic physics effects on tokamak edge drift-tearing modes

    SciTech Connect

    Hahm, T.S.

    1993-03-01

    The effects of ionization and charge exchange on the linear stability of drift-tearing modes are analytically investigated. In particular, the linear instability threshold {Delta}{sup Th}, produced by ion sound wave coupling is modified. In the strongly collisional regime, the ionization breaks up the near cancellation of the perturbed electric field and the pressure gradient along the magnetic field, and increases the threshold. In the semi-collisional regime, both ionization and charge exchange act as drag on the ion parallel velocity, and consequently decrease the threshold by reducing the effectiveness of ion sound wave propagation.

  1. Atomic physics effects on tokamak edge drift-tearing modes

    SciTech Connect

    Hahm, T.S.

    1993-03-01

    The effects of ionization and charge exchange on the linear stability of drift-tearing modes are analytically investigated. In particular, the linear instability threshold [Delta][sup Th], produced by ion sound wave coupling is modified. In the strongly collisional regime, the ionization breaks up the near cancellation of the perturbed electric field and the pressure gradient along the magnetic field, and increases the threshold. In the semi-collisional regime, both ionization and charge exchange act as drag on the ion parallel velocity, and consequently decrease the threshold by reducing the effectiveness of ion sound wave propagation.

  2. Stability and waves of transonic laboratory and space plasmas

    NASA Astrophysics Data System (ADS)

    Goedbloed, J. P.

    2003-04-01

    The properties of magnetohydrodynamic waves and instabilities of laboratory and space plasmas are determined by the overall magnetic confinement geometry and by the detailed distributions of the density, pressure, magnetic field, and background velocity of the plasma. Consequently, measurement of the spectrum of MHD waves (MHD spectroscopy) gives direct information on the internal state of the plasma, provided a theoretical model is available to solve the forward as well as the inverse spectral problems. This terminology entails a program, viz. to improve the accuracy of our knowledge of plasmas, both in the laboratory and in space. Here, helioseismology (which could be considered as one of the forms of MHD spectroscopy) may serve as a luminous example. The required study of magnetohydrodynamic waves and instabilities of both laboratory and space plasmas has been conducted for many years starting from the assumption of static equilibrium. Recently, there is a outburst of interest for plasma states where this assumption is violated. In fusion research, this interest is due to the importance of neutral beam heating and pumped divertor action for the extraction of heat and exhaust needed in future tokamak reactors. Both result in rotation of the plasma with speeds that do not permit the assumption of static equilibrium anymore. In astrophysics, observations in the full range of electromagnetic radiation has revealed the primary importance of plasma flows in such diverse situations as coronal flux tubes, stellar winds, rotating accretion disks, and jets emitted from radio galaxies. These flows have speeds which substantially influence the background stationary equilibrium state, if such a state exists at all. Consequently, it is important to study both the stationary states of magnetized plasmas with flow and the waves and instabilities they exhibit. We will present new results along these lines, extending from the discovery of gaps in the continuous spectrum and low

  3. Analytical and numerical treatment of drift-tearing and resistive drift instabilities in plasma slab

    NASA Astrophysics Data System (ADS)

    Mirnov, V. V.; Hegna, C. C.; Sauppe, J. P.; Sovinec, C. R.

    2015-11-01

    We consider modification to linear resistive MHD instability theory in a slab due to two categories of non-MHD effects: (1) electron and ion diamagnetic flows caused by equilibrium pressure gradients and (2) electron and ion decoupling on short scales associated with kinetic Alfven and whistler waves. The relationship between the expected stabilizing response due to the effects (1) and the destabilizing contribution caused by the dispersive waves (2) is investigated. An analytic solution combining the effect of diamagnetic flows and the ion-sound gyroradius contribution is derived using a perturbative approach. Linear numerical simulations using the NIMROD code are performed with cold ions and hot electrons in plasma slab with a doubly periodic box bounded by two perfectly conducting walls. Configurations with magnetic shear are unstable to current-driven drift-tearing instability. A second linearly unstable resistive drift type mode with largely electrostatic perturbations is also observed in simulations. The resistive-drift mode is suppressed by magnetic shear in unbounded domains but can remain unstable in the simulations with finite slab thickness and perfectly conducting wall. Additionally, the growth rate is sensitive to the magnetic shear length. We analyze whether these modes can be unstable in cylindrical configurations with magnetic shear typical for reversed field pinches. The material is based on work supported by the U.S. DOE and NSF.

  4. Surface drift prediction in the Adriatic Sea using hyper-ensemble statistics on atmospheric, ocean and wave models: Uncertainties and probability distribution areas

    USGS Publications Warehouse

    Rixen, M.; Ferreira-Coelho, E.; Signell, R.

    2008-01-01

    Despite numerous and regular improvements in underlying models, surface drift prediction in the ocean remains a challenging task because of our yet limited understanding of all processes involved. Hence, deterministic approaches to the problem are often limited by empirical assumptions on underlying physics. Multi-model hyper-ensemble forecasts, which exploit the power of an optimal local combination of available information including ocean, atmospheric and wave models, may show superior forecasting skills when compared to individual models because they allow for local correction and/or bias removal. In this work, we explore in greater detail the potential and limitations of the hyper-ensemble method in the Adriatic Sea, using a comprehensive surface drifter database. The performance of the hyper-ensembles and the individual models are discussed by analyzing associated uncertainties and probability distribution maps. Results suggest that the stochastic method may reduce position errors significantly for 12 to 72??h forecasts and hence compete with pure deterministic approaches. ?? 2007 NATO Undersea Research Centre (NURC).

  5. Time interval measurement device based on surface acoustic wave filter excitation, providing 1 ps precision and stability

    NASA Astrophysics Data System (ADS)

    Panek, Petr; Prochazka, Ivan

    2007-09-01

    This article deals with the time interval measurement device, which is based on a surface acoustic wave (SAW) filter as a time interpolator. The operating principle is based on the fact that a transversal SAW filter excited by a short pulse can generate a finite signal with highly suppressed spectra outside a narrow frequency band. If the responses to two excitations are sampled at clock ticks, they can be precisely reconstructed from a finite number of samples and then compared so as to determine the time interval between the two excitations. We have designed and constructed a two-channel time interval measurement device which allows independent timing of two events and evaluation of the time interval between them. The device has been constructed using commercially available components. The experimental results proved the concept. We have assessed the single-shot time interval measurement precision of 1.3ps rms that corresponds to the time of arrival precision of 0.9ps rms in each channel. The temperature drift of the measured time interval on temperature is lower than 0.5ps/K, and the long term stability is better than ±0.2ps/h. These are to our knowledge the best values reported for the time interval measurement device. The results are in good agreement with the error budget based on the theoretical analysis.

  6. Time interval measurement device based on surface acoustic wave filter excitation, providing 1 ps precision and stability.

    PubMed

    Panek, Petr; Prochazka, Ivan

    2007-09-01

    This article deals with the time interval measurement device, which is based on a surface acoustic wave (SAW) filter as a time interpolator. The operating principle is based on the fact that a transversal SAW filter excited by a short pulse can generate a finite signal with highly suppressed spectra outside a narrow frequency band. If the responses to two excitations are sampled at clock ticks, they can be precisely reconstructed from a finite number of samples and then compared so as to determine the time interval between the two excitations. We have designed and constructed a two-channel time interval measurement device which allows independent timing of two events and evaluation of the time interval between them. The device has been constructed using commercially available components. The experimental results proved the concept. We have assessed the single-shot time interval measurement precision of 1.3 ps rms that corresponds to the time of arrival precision of 0.9 ps rms in each channel. The temperature drift of the measured time interval on temperature is lower than 0.5 ps/K, and the long term stability is better than +/-0.2 ps/h. These are to our knowledge the best values reported for the time interval measurement device. The results are in good agreement with the error budget based on the theoretical analysis. PMID:17902964

  7. Stabilization of three-dimensional scroll waves and suppression of spatiotemporal chaos by heterogeneities.

    PubMed

    Spreckelsen, Florian; Hornung, Daniel; Steinbock, Oliver; Parlitz, Ulrich; Luther, Stefan

    2015-10-01

    Scroll waves in a three-dimensional medium with negative filament tension may break up and display spatiotemporal chaos. The presence of heterogeneities can influence the evolution of the medium, in particular scroll waves may pin to such heterogeneities. We show that as a result the medium may be stabilized by heterogeneities of a suitably chosen geometry. Thin rodlike heterogeneities suppress otherwise developing spatiotemporal chaos and additionally clear out already existing chaotic excitation patterns. PMID:26565317

  8. Global stability of travelling wave fronts for non-local diffusion equations with delay

    NASA Astrophysics Data System (ADS)

    Wang, X.; Lv, G.

    2014-04-01

    This paper is concerned with the global stability of travelling wave fronts for non-local diffusion equations with delay. We prove that the non-critical travelling wave fronts are globally exponentially stable under perturbations in some exponentially weighted L^\\infty-spaces. Moreover, we obtain the decay rates of \\sup_{x\\in{R}}\\vert u(x,t)-\\varphi(x+ct)\\vert using weighted energy estimates.

  9. Scale effect of spherical projectiles for stabilization of oblique detonation waves

    NASA Astrophysics Data System (ADS)

    Maeda, S.; Sumiya, S.; Kasahara, J.; Matsuo, A.

    2015-03-01

    Oblique detonation waves (ODWs) were stabilized by launching a spherical projectile with 1.2-1.4 times the Chapman-Jouguet (C-J) velocity into detonable mixtures at rest. We used smaller projectiles (3.18 mm diameter) than those (4.76 mm diameter) in our previous studies and investigated the effect of the projectile scale on the stabilization of ODWs. We carried out high time resolution schlieren visualization using a high-speed camera. The detonable mixtures used were stoichiometric oxygen mixtures with acetylene, ethylene or hydrogen. They were diluted with argon with a 50 % volumetric fraction, and a dilute mixture containing 75 % argon was also tested for the acetylene/oxygen mixture. Here, we discuss the detonation stability in terms of the curvature effect arising from the three-dimensional nature of a stabilized ODW around a projectile. The curvature effect attenuated the detonation wave to below its C-J velocity in the vicinity of the projectile before the wave velocity asymptotically reached the C-J velocity in the far field. Our previous study showed that the propagation limit of the curvature effect is responsible for the stabilizing criticality of detonation waves. By obtaining detailed distributions of the wave propagation velocity and radius of curvature at the stabilizing criticality, we showed that the radius of curvature at the local minimum point of the wave propagation velocity represents the critical radius of curvature required for curved self-sustained detonation. In this study, we focused on this critical mode of the stabilized ODW for a small projectile (3.18 mm diameter). Distributions of the wave velocity and radius of curvature were obtained in the critical mode of the stabilized ODW. We compare these distributions with those for a larger projectile (4.76 mm diameter) and discuss the stabilizing criticality. For the small projectile, the observed combustion regimes had qualitatively the same trend for the initial pressure of the mixture

  10. Asymptotic stability of Riemann waves for conservation laws

    NASA Astrophysics Data System (ADS)

    Chen, G.-Q.; Frid, H.; Marta

    We are concerned with the asymptotic behavior of entropy solutions of conservation laws. A new notion about the asymptotic stability of Riemann solutions is introduced, and corresponding analytical frameworks are developed. The correlation between the asymptotic problem and many important topics in conservation laws and nonlinear analysis is recognized and analyzed, such as zero dissipation limits, uniqueness of entropy solutions, entropy analysis, and divergence-measure fields in L∞ . Then this theory is applied to understanding the asymptotic behavior of entropy solutions for many important systems of conservation laws.

  11. Frontal Wave Stability during Moist Deformation Frontogenesis. Part I: Linear Wave Dynamics.

    NASA Astrophysics Data System (ADS)

    Bishop, Craig H.; Thorpe, Alan J.

    1994-03-01

    It has been shown that lower tropospheric potential vorticity zones formed during moist deformation frontogenesis will support growing waves if at some time the frontogenesis ceases. In this paper, the ways in which these waves are affected by the frontogenetic process are identified.Observations show that fronts in the eastern Atlantic commonly feature saturated ascent regions characterized by zero moist potential vorticity. Furthermore, in many cases the horizontal temperature gradient in the lowest one to two kilometers of the atmosphere is rather weak. These features are incorporated in an analytical archetype. The dynamical implications of saturated ascent in conditions of zero moist potential vorticity are represented in the model by assuming that adiabatic temperature changes are precisely balanced by diabatic tendencies. The observed small temperature gradient at low levels is represented in the model by taking it to be zero in the lowest two kilometers. Consequently, the forcing of the low-level moist ageostrophic vortex stretching that strengthens the low-level potential vorticity anomaly is confined to middle and upper levels.A semianalytical initial value solution for the linear development of waves on the evolving low-level potential vorticity anomaly is obtained. The waves approximately satisfy the inviscid primitive equations whenever the divergent part of the perturbation is negligible relative to the rotational part. The range of nonmodal wave developments supported by the front is summarized using RT phase diagrams. This analysis shows that the most dramatic effects of frontogenesis on frontal wave growth are due to (a) the increase in time of the potential vorticity and hence potential instability of the flow and (b) the increase in time of the alongfront wavelength relative to the width of the strip. An optimally growing streamfunction wave is described. Finally, a diagnostic technique suitable for identifying small amplitude frontal waves in

  12. Existence and stability of traveling wave solutions for multilayer cellular neural networks

    NASA Astrophysics Data System (ADS)

    Hsu, Cheng-Hsiung; Lin, Jian-Jhong; Yang, Tzi-Sheng

    2015-08-01

    The purpose of this article is to investigate the existence and stability of traveling wave solutions for one-dimensional multilayer cellular neural networks. We first establish the existence of traveling wave solutions using the truncated technique. Then we study the asymptotic behaviors of solutions for the Cauchy problem of the neural model. Applying two kinds of comparison principles and the weighed energy method, we show that all solutions of the Cauchy problem converge exponentially to the traveling wave solutions provided that the initial data belong to a suitable weighted space.

  13. Stabilities of Superfluid and Density Wave States in Fermionic Mass Imbalanced Optical Lattices

    NASA Astrophysics Data System (ADS)

    Takemori, Nayuta; Koga, Akihisa

    We study the attractive Hubbard model with different masses by means of dynamical mean-field theory with continuous-time quantum Monte Carlo simulation. Calculating the internal energy and density of states, we discuss how the interaction affects the stabilities of superfluid and density wave states at half-filling. It is found that the density wave and superfluid states are almost degenerate in a certain region. On the other hand, the genuine density wave state is stable in a wide parameter space.

  14. Linear stability of internal wave solitons in a deep stratified fluid

    NASA Astrophysics Data System (ADS)

    Chen, H. H.; Kaup, D. J.

    1980-02-01

    The linear stability problem of the internal wave solitons described by the Benjamin-Ono equation has been solved. The wave functions corresponding to the continuum spectrum are stable, showing no reflection and no phase shift. There are two bound states associated with the soliton symmetries. The one associated with the translational invariance shows no growth; the other one associated with the scale invariance shows a secular instability growing linearly with time. The closure is also proven and, therefore, the completeness of these wave functions.

  15. PROPAGATION AND STABILITY OF SUPERLUMINAL WAVES IN PULSAR WINDS

    SciTech Connect

    Mochol, Iwona; Kirk, John G. E-mail: john.kirk@mpi-hd.mpg.de

    2013-07-01

    Nonlinear electromagnetic waves with superluminal phase velocity can propagate in the winds around isolated pulsars, and around some pulsars in binary systems. Using a short-wavelength approximation, we find and analyze an integrable system of equations that govern their evolution in spherical geometry. A confined mode is identified that stagnates to finite pressure at large radius and can form a precursor to the termination shock. Using a simplified criterion, we find this mode is stable for most isolated pulsars, but may be unstable if the external pressure is high, such as in the pulsar wind nebulae in starburst galaxies and in W44. Pulsar winds in eccentric binary systems, such as PSR 1259-63, may go through phases with stable and unstable electromagnetic precursors, as well as phases in which the density is too high for these modes to propagate.

  16. The structure and stability of mode-2 internal solitary-like waves

    NASA Astrophysics Data System (ADS)

    Carr, Magda; Davies, Peter; Hoebers, Ruud

    2015-04-01

    Recent observational examples of Mode-2 internal solitary-like waves (ISWs) in the ocean (e.g. Yang et al., 2009; Schroyer et al., 2010) have motivated modelling studies. The present laboratory study investigates the structure and stability of mode-2 ISWs. A rank-ordered train of mode-2 ISWs is generated using a lock release configuration. The pycnocline is centred either on the mid-depth of the water column (the 0% offset case) or it is offset in the positive vertical direction by a fraction of 5%, 10% or 20% of the total fluid depth. It is found that offsetting the pycnocline has little effect on the basic wave properties but it does significantly affect wave stability. Instability takes the form of small K-H-like billows in the rear of the wave and small scale overturning in the core of the wave. In the 0% offset case, instability occurs on both the upper and lower interfaces of the pycnocline and is similar in extent and vigour over the two interfaces. As the offset percentage is increased, however, instability is more pronounced on the lower interface with little or no evidence of instability being observed on the upper interface. In the 20% offset case a mode-1 tail is associated with the wave and the wave characteristics resemble qualitatively the recent field observations of Shroyer et al., (2010).

  17. A Stability Analysis for a Hydrodynamic Three-Wave Journal Bearing

    NASA Technical Reports Server (NTRS)

    Ene, Nicoleta M.; Dimofte, Florin; Keith, Theo G., Jr.

    2007-01-01

    The influence of the wave amplitude and oil supply pressure on the dynamic behavior of a hydrodynamic three-wave journal bearing is presented. Both, a transient and a small perturbation technique, were used to predict the threshold to fractional frequency whirl (FFW). In addition, the behavior of the rotor after FFW appeared was determined from the transient analysis. The turbulent effects were also included in the computations. Bearings having a diameter of 30 mm, a length of 27.5 mm, and a clearance of 35 microns were analyzed. Numerical results were compared to experimental results obtained at the NASA GRC. Numerical and experimental results showed that the above-mentioned wave bearing with a wave amplitude ratio of 0.305 operates stably at rotational speeds up to 60,000 rpm, regardless of the oil supply pressure. For smaller wave amplitude ratios, a threshold of stability was found. It was observed that the threshold of stability for lower wave amplitude strongly depends on the oil supply pressure and on the wave amplitude. When the FFW occurs, the journal center maintains its trajectory inside the bearing clearance and therefore the rotor can be run safely without damaging the bearing surfaces.

  18. Stability of steady rotational water-waves of finite amplitude on arbitrary shear currents

    NASA Astrophysics Data System (ADS)

    Seez, William; Abid, Malek; Kharif, Christian

    2016-04-01

    A versatile solver for the two-dimensional Euler equations with an unknown free-surface has been developed. This code offers the possibility to calculate two-dimensional, steady rotational water-waves of finite amplitude on an arbitrary shear current. Written in PYTHON the code incorporates both pseudo-spectral and finite-difference methods in the discretisation of the equations and thus allows the user to capture waves with large steepnesses. As such it has been possible to establish that, in a counter-flowing situation, the existence of wave solutions is not guaranteed and depends on a pair of parameters representing mass flux and vorticity. This result was predicted, for linear solutions, by Constantin. Furthermore, experimental comparisons, both with and without vorticity, have proven the precision of this code. Finally, waves propagating on top of highly realistic shear currents (exponential profiles under the surface) have been calculated following current profiles such as those used by Nwogu. In addition, a stability analysis routine has been developed to study the stability regimes of base waves calculated with the two-dimensional code. This linear stability analysis is based on three dimensional perturbations of the steady situation which lead to a generalised eigenvalue problem. Common instabilities of the first and second class have been detected, while a third class of wave-instability appears due to the presence of strong vorticity. {1} Adrian Constantin and Walter Strauss. {Exact steady periodic water waves with vorticity}. Communications on Pure and Applied Mathematics, 57(4):481-527, April 2004. Okey G. Nwogu. {Interaction of finite-amplitude waves with vertically sheared current fields}. Journal of Fluid Mechanics, 627:179, May 2009.

  19. Stability analysis of an interactive system of wave equation and heat equation with memory

    NASA Astrophysics Data System (ADS)

    Zhang, Qiong

    2014-10-01

    This paper is devoted to the stability analysis of an interaction system comprised of a wave equation and a heat equation with memory, where the hereditary heat conduction is due to Gurtin-Pipkin law or Coleman-Gurtin law. First, we show the strong asymptotic stability of solutions to this system. Then, the exponential stability of the interaction system is obtained when the hereditary heat conduction is of Gurtin-Pipkin type. Further, we show the lack of uniform decay of the interaction system when the heat conduction law is of Coleman-Gurtin type.

  20. Nonlinear stability of surface waves in magnetic fluids: effect of a periodic tangential magnetic field

    NASA Astrophysics Data System (ADS)

    El-Dib, Yusry O.

    1993-04-01

    Nonlinear wave propagation on the surface between two superposed magnetic fluids stressed by a tangential periodic magnetic field is investigated using the method of multiple scales. A stability analysis reveals the existence of both nonresonant and resonant cases. From the solvability conditions, three types of nonlinear Schrodinger equation are obtained. The necessary and sufficient conditions for stability are obtained in each case. Formulae for the surface elevation are also obtained in both the non-resonant and the resonant cases. It is found from the numerical calculation that the tangential periodic magnetic field plays a dual role in the stability criterion, while the field frequency has a destabilizing influence.

  1. Nonlinear stability of overcompresive shock waves in a rotationally invariant system of viscous conservation laws

    NASA Astrophysics Data System (ADS)

    Freistühler, Heinrich; Liu, Tai-Ping

    1993-04-01

    This paper proves that certain non-classical shock waves in a rotationally invariant system of viscous conservation laws posses nonlinear large-time stability against sufficiently small perturbations. The result applies to small intermediate magnetohydrodynamic shocks in the presence of dissipation.

  2. Propagation of Curved Detonation Waves Stabilized in Annular Channels with a Rectangular Cross-section

    NASA Astrophysics Data System (ADS)

    Nakayama, Hisahiro; Takahiro Moriya; Kasahara, Jiro; Matsuo, Akiko; Sasamoto, Yuya; Funaki, Ikkoh

    Visualization experiments employing rectangular cross-section curved channels were performed in order to examine the fundamental characteristics of a curved detonation wave propagating stably through an annular channel. A stoichiometric ethylene-oxygen mixture gas and five types of curved channels with different inner radii of curvature were used. The detonation waves propagating in the curved channels were curved due to the expansion waves from the inner walls of the curved channels. The ratio of the inner radius of curved channel (ri) to the normal detonation cell width (λ) was an important factor determining the stability of the curved detonation waves. The detonation propagation mode in the curved channels transitioned from unstable to stable in the range 14 ≤ ri/λ ≤ 26. The normal detonation velocity (Dn) of the curved detonation wave propagating stably in a curved channel was approximately formulated. The approximated Dn given by the formula agreed well with the experimental results. The front shock shape of the curved detonation wave could be reconstructed accurately using the formula. The value of Dn nondimensionalized by the Chapman-Jouguet detonation velocity became a function of the local curvature of the curved detonation wave (κ) nondimensionalized by λ regardless of the shape of curved channel. The front shock shapes of the detonation waves in the stable mode became similar to each other under constant ri/λ conditions.

  3. Topics in Lagrangian and Hamiltonian fluid dynamics: Relabeling symmetry and ion-acoustic wave stability

    NASA Astrophysics Data System (ADS)

    Padhye, Nikhil Subhash

    1998-12-01

    Relabeling symmetries of the Lagranian action are found for the ideal, compressible fluid and magnetohydrodynamics (MHD). These give rise to conservation laws of potential vorticity (Ertel's theorem) and helicity in the ideal fluid, cross helicity in MHD, and a conservation law for an ideal fluid with three thermodynamic variables. The symmetry that gives rise to Ertel's theorem is generated by an infinite parameter group, and leads to a generalized Bianchi identity. The existence of a more general symmetry is also shown, with dependence on time and space derivatives of the fields, and corresponds to a family of conservation laws associated with the potential vorticity. In the Hamiltonian formalism, Casimir invariants of the noncanonical formulation are directly constructed from the symmetries of the reduction map from Lagrangian to Eulerian variables. Casimir invariants of MHD include a gauge-dependent family of invariants that incorporates magnetic helicity as a special case. Novel examples of finite dimensional, noncanonical Hamiltonian dynamics are also presented: the equations for a magnetic field line flow with a symmetry direction, and Frenet formulas that describe a curve in 3-space. In the study of Lyapunov stability of ion-acoustic waves, existence of negative energy perturbations is found at short wavelengths. The effect of adiabatic, ionic pressure on ion-acoustic waves is investigated, leading to explicit solitary and nonlinear periodic wave solutions for the adiabatic exponent γ = 3. In particular, solitary waves are found to exist at any wave speed above Mach number one, without an upper cutoff speed. Negative energy perturbations are found to exist despite the addition of pressure, which prevents the establishment of Lyapunov stability, however the stability of ion-acoustic waves is established in the KdV limit, in a manner far simpler than the proof of KdV soliton stability. It is also shown that the KdV free energy (Benjamin, 1972) is recovered

  4. Linear stability analysis and the speed of gravitational waves in dynamical Chern-Simons modified gravity

    SciTech Connect

    Garfinkle, David; Pretorius, Frans; Yunes, Nicolas

    2010-08-15

    We perform a linear stability analysis of dynamical Chern-Simons modified gravity in the geometric optics approximation and find that it is linearly stable on the backgrounds considered. Our analysis also reveals that gravitational waves in the modified theory travel at the speed of light in Minkowski spacetime. However, on a Schwarzschild background the characteristic speed of propagation along a given direction splits into two modes, one subluminal and one superluminal. The width of the splitting depends on the azimuthal components of the propagation vector, is linearly proportional to the mass of the black hole, and decreases with the third inverse power of the distance from the black hole. Radial propagation is unaffected, implying that as probed by gravitational waves the location of the event horizon of the spacetime is unaltered. The analysis further reveals that when a high frequency, pure gravitational wave is scattered from a black hole, a scalar wave of comparable amplitude is excited, and vice versa.

  5. In vivo estimation of elastic wave parameters using phase-stabilized swept source optical coherence elastography

    NASA Astrophysics Data System (ADS)

    Manapuram, Ravi Kiran; Aglyamov, Salavat R.; Monediado, Floredes M.; Mashiatulla, Maleeha; Li, Jiasong; Emelianov, Stanislav Y.; Larin, Kirill V.

    2012-10-01

    We report a highly sensitive method based on phase-stabilized swept source optical coherence elastography (PhS-SSOCE) to measure elastic wave propagation in soft tissues in vivo. The waves were introduced using a mechanical stimulus and were assessed using the phase response of the swept source optical coherence tomography signal. The technique was utilized to measure age-related changes in elastic flexural wave velocity and attenuation in mice cornea in vivo. Results demonstrate that the wave velocity increases with animal age, supporting previous observations that stiffness of mice cornea gradually increases with age. Our studies suggest that the PhS-SSOCE technique could potentially be used to obtain biomechanical properties of ocular tissues in vivo.

  6. Stability of magneto-acoustic waves in a thermally conducting compressible fluid

    NASA Astrophysics Data System (ADS)

    Antia, H. M.; Chitre, S. M.

    1980-03-01

    The stability of magneto-acoustic waves in an inviscid, perfectly conducting isothermal fluid, stratified under constant gravity and subjected to a horizontal magnetic field is investigated, where mathematically tractable equations are provided. Both an isothermal atmosphere and a polytropic fluid are considered in the presence of thermal dissipation, with the magnetic field having pressure proportional to the gas pressure. It is found that, for both cases, the fluid can be convectively unstable for all values of gamma (the ratio of specific heats) and GB in the case of waves with small wave number or waves travelling in a direction nearly perpendicular to the magnetic field. The oscillatory modes, however, are overstable when the temperature gradient is superadiabatic.

  7. Drift-tearing magnetic islands in tokamak plasmas

    SciTech Connect

    Fitzpatrick, R.; Waelbroeck, F. L.

    2008-01-15

    A systematic fluid theory of nonlinear magnetic island dynamics in conventional low-{beta}, large aspect-ratio, circular cross-section tokamak plasmas is developed using an extended magnetohydrodynamics model that incorporates diamagnetic flows, ion gyroviscosity, fast parallel electron heat transport, the ion sound wave, the drift wave, and average magnetic field-line curvature. The model excludes the compressible Alfven wave, geodesic field-line curvature, neoclassical effects, and ion Landau damping. A collisional closure is used for plasma dynamics parallel to the magnetic field. Two distinct branches of island solutions are found, namely the 'sonic' and 'hypersonic' branches. Both branches are investigated analytically, using suitable ordering schemes, and in each case the problem is reduced to a relatively simple set of nonlinear differential equations that can be solved numerically via iteration. The solution determines the island phase velocity, relative to the plasma, and the effect of local currents on the island stability. Sonic islands are relatively wide, flatten both the temperature and density profiles, and tend to propagate close to the local ion fluid velocity. Hypersonic islands, on the other hand, are relatively narrow, only flatten the temperature profile, radiate drift-acoustic waves, and tend to propagate close to the local electron fluid velocity. The hypersonic solution branch ceases to exist above a critical island width. Under normal circumstances, both types of island are stabilized by local ion polarization currents.

  8. Stability analysis for acoustic wave propagation in tilted TI media by finite differences

    NASA Astrophysics Data System (ADS)

    Bakker, Peter M.; Duveneck, Eric

    2011-05-01

    Several papers in recent years have reported instabilities in P-wave modelling, based on an acoustic approximation, for inhomogeneous transversely isotropic media with tilted symmetry axis (TTI media). In particular, instabilities tend to occur if the axis of symmetry varies rapidly in combination with strong contrasts of medium parameters, which is typically the case at the foot of a steeply dipping salt flank. In a recent paper, we have proposed and demonstrated a P-wave modelling approach for TTI media, based on rotated stress and strain tensors, in which the wave equations reduce to a coupled set of two second-order partial differential equations for two scalar stress components: a normal component along the variable axis of symmetry and a lateral component of stress in the plane perpendicular to that axis. Spatially constant density is assumed in this approach. A numerical discretization scheme was proposed which uses discrete second-derivative operators for the non-mixed second-order derivatives in the wave equations, and combined first-derivative operators for the mixed second-order derivatives. This paper provides a complete and rigorous stability analysis, assuming a uniformly sampled grid. Although the spatial discretization operator for the TTI acoustic wave equation is not self-adjoint, this operator still defines a complete basis of eigenfunctions of the solution space, provided that the solution space is somewhat restricted at locations where the medium is elliptically anisotropic. First, a stability analysis is given for a discretization scheme, which is purely based on first-derivative operators. It is shown that the coefficients of the central difference operators should satisfy certain conditions. In view of numerical artefacts, such a discretization scheme is not attractive, and the non-mixed second-order derivatives of the wave equation are discretized directly by second-derivative operators. It is shown that this modification preserves

  9. Stability of relativistic electron trapping by strong whistler or electromagnetic ion cyclotron waves

    NASA Astrophysics Data System (ADS)

    Artemyev, A. V.; Mourenas, D.; Agapitov, O. V.; Vainchtein, D. L.; Mozer, F. S.; Krasnoselskikh, V.

    2015-08-01

    In the present paper, we investigate the trapping of relativistic electrons by intense whistler-mode waves or electromagnetic ion cyclotron waves in the Earth's radiation belts. We consider the non-resonant impact of additional, lower amplitude magnetic field fluctuations on the stability of electron trapping. We show that such additional non-resonant fluctuations can break the adiabatic invariant corresponding to trapped electron oscillations in the effective wave potential. This destruction results in a diffusive escape of electrons from the trapped regime of motion and thus can lead to a significant reduction of the efficiency of electron acceleration. We demonstrate that when energetic electrons are trapped by intense parallel or very oblique whistler-mode waves, non-resonant magnetic field fluctuations in the whistler-mode frequency range with moderate amplitudes around 3 -15 pT (much less intense than the primary waves) can totally disrupt the trapped motion. However, the trapping of relativistic electrons by electromagnetic ion cyclotron waves is noticeably more stable. We also discuss how the proposed approach can be used to estimate the effects of wave amplitude modulations on the motion of trapped particles.

  10. Stability of solitary waves in the nonlinear Dirac equation with arbitrary nonlinearity.

    PubMed

    Shao, Sihong; Quintero, Niurka R; Mertens, Franz G; Cooper, Fred; Khare, Avinash; Saxena, Avadh

    2014-09-01

    We consider the nonlinear Dirac equation in 1 + 1 dimension with scalar-scalar self interaction g(2)/κ+1(̅ΨΨ)(κ+1) and with mass m. Using the exact analytic form for rest frame solitary waves of the form Ψ(x,t)=ψ(x)e(-iωt) for arbitrary κ, we discuss the validity of various approaches to understanding stability that were successful for the nonlinear Schrödinger equation. In particular we study the validity of a version of Derrick's theorem and the criterion of Bogolubsky as well as the Vakhitov-Kolokolov criterion, and find that these criteria yield inconsistent results. Therefore, we study the stability by numerical simulations using a recently developed fourth-order operator splitting integration method. For different ranges of κ we map out the stability regimes in ω. We find that all stable nonlinear Dirac solitary waves have a one-hump profile, but not all one-hump waves are stable, while all waves with two humps are unstable. We also find that the time t(c), it takes for the instability to set in, is an exponentially increasing function of ω and t(c) decreases monotonically with increasing κ. PMID:25314512

  11. An Evans-function approach to spectral stability of internal solitary waves in stratified fluids

    NASA Astrophysics Data System (ADS)

    Klaiber, Andreas

    2015-11-01

    Frequently encountered in nature, internal solitary waves in stratified fluids have been investigated experimentally, theoretically, and numerically. Mathematically, these waves are exact solutions of the incompressible 2D Euler equations. Contrasting with a rich existence theory and the development of methods for their computation, their stability analysis has hardly received attention at a rigorous mathematical level. This paper proposes a new approach to the investigation of stability of internal solitary waves in a continuously stratified fluid and carries out the following four steps of this approach: (I) to formulate the eigenvalue problem as an infinite-dimensional spatial-dynamical system, (II) to introduce finite-dimensional truncations of the spatial-dynamics description, (III) to demonstrate that each truncation, of any order, permits a well-defined Evans function, (IV) to prove absence of small zeros of the Evans function in the small-amplitude limit. The latter notably implies the low-frequency spectral stability of small-amplitude waves to arbitrarily high truncation order.

  12. Drift reduction with drift control adjuvants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Numerous drift reduction adjuvants and spray deposition aids are available to applicators of crop production and protection chemicals. Performance of many of the newly introduced drift control adjuvants has not been well documented for aerial application. Five new drift control adjuvants were sele...

  13. Drift reduction with drift control adjuvants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Numerous drift reduction adjuvants and spray deposition aids are available to applicators of crop production and protection chemicals. Performance of many of the newly introduced drift control adjuvants has not been well documented for aerial application. Four new drift control adjuvants were sele...

  14. Beam instabilities stabilization as a result of strong nonlinear interaction between waves

    SciTech Connect

    Soloshenko, I.A.; Taranov, V.B.; Tsyolko, V.V.; Shamrai, K.P.; Shulzhenko, P.M. )

    1990-01-01

    It is shown that the nonlinear interaction between unstable low-frequency ion waves and high-frequency electron waves growing in an ion beam plasma can result in stabilization of one of the modes if the level of the other is sufficiently high. A theoretical model of the phenomenon has been developed, and its predictions are in reasonable agreement with experimental results. The suppression mechanism is considered, and appears to be essentially nonlinear. The effect of this mutual suppression of ion beam instabilities may be important for improved ion beam transport.

  15. Stability analysis for two-dimensional ion-acoustic waves in quantum plasmas

    SciTech Connect

    Seadawy, A. R.

    2014-05-15

    The quantum hydrodynamic model is applied to two-dimensional ion-acoustic waves in quantum plasmas. The two-dimensional quantum hydrodynamic model is used to obtain a deformed Kortewegde Vries (dKdV) equation by reductive perturbation method. By using the solution of auxiliary ordinary equations, a extended direct algebraic method is described to construct the exact solutions for nonlinear quantum dKdV equation. The present results are describing the generation and evolution of such waves, their interactions, and their stability.

  16. Nonlinear Stability Analysis with Decay Rates of Two Classes of Waves for Conservation Laws.

    NASA Astrophysics Data System (ADS)

    Zingano, Paulo Ricardo

    1990-08-01

    We study in this work the decay rate of disturbances to certain elementary waves for conservation laws when their initial profile is perturbed. In the first problem, rarefaction waves for the scalar equation u_ {t}+f(u)_{x}=u_{xx }, f convex, are considered, and we show that disturbances decay in the L^2 -norm as O(t^{-1/4+mu }), for mu > 0 arbitrarily small, provided they belong to the space L^1cap H^1 initially. The second problem concerns the stability of weak shock waves of a certain class of hyperbolic systems with relaxation, disturbances in this case are shown to decay in L ^2 at certain algebraic rates which depend on how fast they die off as x to +/- infty at initial time, provided they are sufficiently weak. This behavior is due to the compressibility of such waves with respect to the dynamic characteristics governing the propagation of disturbances, a basic feature of shock waves. This result is in vivid contrast to the corresponding one for rarefaction waves, where the decay is ultimately governed by diffusion processes which impose a limit on the overall rate. In both problems treated here, the analysis is based on the derivation of suitable energy inequalities with appropriate decay rates.

  17. Note: silicon carbide telescope dimensional stability for space-based gravitational wave detectors.

    PubMed

    Sanjuán, J; Korytov, D; Mueller, G; Spannagel, R; Braxmaier, C; Preston, A; Livas, J

    2012-11-01

    Space-based gravitational wave detectors are conceived to detect gravitational waves in the low frequency range by measuring the distance between proof masses in spacecraft separated by millions of kilometers. One of the key elements is the telescope which has to have a dimensional stability better than 1 pm Hz(-1/2) at 3 mHz. In addition, the telescope structure must be light, strong, and stiff. For this reason a potential telescope structure consisting of a silicon carbide quadpod has been designed, constructed, and tested. We present dimensional stability results meeting the requirements at room temperature. Results at -60 °C are also shown although the requirements are not met due to temperature fluctuations in the setup. PMID:23206114

  18. Note: Silicon Carbide Telescope Dimensional Stability for Space-based Gravitational Wave Detectors

    NASA Technical Reports Server (NTRS)

    Sanjuah, J.; Korytov, D.; Mueller, G.; Spannagel, R.; Braxmaier, C.; Preston, A.; Livas, J.

    2012-01-01

    Space-based gravitational wave detectors are conceived to detect gravitational waves in the low frequency range by measuring the distance between proof masses in spacecraft separated by millions of kilometers. One of the key elements is the telescope which has to have a dimensional stability better than 1 pm Hz(exp -1/2) at 3 mHz. In addition, the telescope structure must be light, strong, and stiff. For this reason a potential telescope structure consisting of a silicon carbide quadpod has been designed, constructed, and tested. We present dimensional stability results meeting the requirements at room temperature. Results at -60 C are also shown although the requirements are not met due to temperature fluctuations in the setup.

  19. Electrostatic wave structures and their stability analysis in nonextensive magnetised electron-positron-ion plasma

    NASA Astrophysics Data System (ADS)

    Gill, T. S.; Bala, Parveen; Bains, A. S.

    2015-05-01

    A rigorous theoretical study based on Zakharov Kuznetsov (ZK) equation of ion-acoustic solitary waves (IASWs), their stability analysis in a magnetized e- p- i plasma is presented. The plasma model consists of inertial ions, magnetic field, electrons and positrons obeying q-nonextensive velocity distribution. Reductive perturbation method is used to derive ZK equation. The solitary wave structures are dependent on chosen plasma model, whose parameters influence the solitary characteristics. Particularly, nonextensivity, proportion of positron concentration, magnetic field and difference between electron and positron temperatures play crucial role in the solitary structures. The present work is also extended to give stability analysis and parametric ranges for the existence of stable and unstable solitons. This research work may be useful to understand the physics of nonlinear electrostatic excitations in different astrophysical and cosmic scenarios like stellar polytropes, hadron matter and quark-gluon plasma.

  20. Stability of the unique continuation for the wave operator via Tataru inequality and applications

    NASA Astrophysics Data System (ADS)

    Bosi, Roberta; Kurylev, Yaroslav; Lassas, Matti

    2016-04-01

    In this paper we study the stability of the unique continuation in the case of the wave equation with variable coefficients independent of time. We prove a logarithmic estimate in an arbitrary domain of R n + 1, where all the parameters are calculated explicitly in terms of the C1-norm of the coefficients and on the other geometric properties of the problem. We use the Carleman-type estimate proved by Tataru in 1995 and an iteration of the local stability. We apply the result to the case of a wave equation with data on a cylinder and we get a stable estimate for any positive time, also after the first conjugate point associated with the geodesics of the metric of the variable coefficients.

  1. A quasioptically stabilized resonant-tunneling-diode oscillator for the millimeter- and submillimeter-wave regions

    NASA Technical Reports Server (NTRS)

    Brown, Elliott R.; Parker, Christopher D.; Molvar, Karen M.; Stephan, Karl D.

    1992-01-01

    A semiconfocal open-cavity resonator has been used to stabilize a resonant-tunneling-diode waveguide oscillator at frequencies near 100 GHz. The high quality factor of the open cavity resulted in a linewidth of approximately 10 kHz at 10 dB below the peak, which is about 100 times narrower than the linewidth of an unstabilized waveguide oscillator. This technique is well suited for resonant-tunneling-diode oscillators in the submillimeter-wave region.

  2. Equilibrium and stability properties of detonation waves in the hydrodynamic limit of a kinetic model

    NASA Astrophysics Data System (ADS)

    Marques, Wilson, Jr.; Jacinta Soares, Ana; Pandolfi Bianchi, Miriam; Kremer, Gilberto M.

    2015-06-01

    A shock wave structure problem, like the one which can be formulated for the planar detonation wave, is analyzed here for a binary mixture of ideal gases undergoing the symmetric reaction {{A}1}+{{A}1}\\rightleftharpoons {{A}2}+{{A}2}. The problem is studied at the hydrodynamic Euler limit of a kinetic model of the reactive Boltzmann equation. The chemical rate law is deduced in this frame with a second-order reaction rate, in a chemical regime such that the gas flow is not far away from the chemical equilibrium. The caloric and the thermal equations of state for the specific internal energy and temperature are employed to close the system of balance laws. With respect to other approaches known in the kinetic literature for detonation problems with a reversible reaction, this paper aims to improve some aspects of the wave solution. Within the mathematical analysis of the detonation model, the equation of the equilibrium Hugoniot curve of the final states is explicitly derived for the first time and used to define the correct location of the equilibrium Chapman-Jouguet point in the Hugoniot diagram. The parametric space is widened to investigate the response of the detonation solution to the activation energy of the chemical reaction. Finally, the mathematical formulation of the linear stability problem is given for the wave detonation structure via a normal-mode approach, when bidimensional disturbances perturb the steady solution. The stability equations with their boundary conditions and the radiation condition of the considered model are explicitly derived for small transversal deviations of the shock wave location. The paper shows how a second-order chemical kinetics description, derived at the microscopic level, and an analytic deduction of the equilibrium Hugoniot curve, lead to an accurate picture of the steady detonation with reversible reaction, as well as to a proper bidimensional linear stability analysis.

  3. Stability of standing spin wave in permalloy thin film studied by anisotropic magnetoresistance effect

    SciTech Connect

    Yamanoi, K.; Yokotani, Y.; Cui, X.; Yakata, S.; Kimura, T.

    2015-12-21

    We have investigated the stability for the resonant spin precession under the strong microwave magnetic field by a specially developed detection method using the anisotropic magnetoresistance effect. The electrically separated excitation and detection circuits enable us to investigate the influence of the heating effect and the nonuniform spin dynamics independently. The large detecting current is found to induce the field shift of the resonant spectra because of the Joule heating. From the microwave power dependence, we found that the linear response regime for the standing spin wave is larger than that for the ferromagnetic resonance. This robust characteristic of the standing spin wave is an important advantage for the high power operation of the spin-wave device.

  4. On stability of parametric resonances of nonlinear surface waves propagating between two superposed electrified fluids

    NASA Astrophysics Data System (ADS)

    El-Dib, Yusry O.

    1995-10-01

    Resonances of interfacial waves in a nonlinear interfacial instability of two superposed electrified fluids stressed by a time-dependent electric field are studied. Two subharmonic resonances have been distinguished and investigated. Based on the method of multiple-scale expansion, for a small amplitude of periodic field, two parametric nonlinear Schrodinger equations are derived to describe the propagation of capillary waves on the fluid interface in the resonance cases. A classical nonlinear Schrodinger equation is derived in the nonresonant case. A temporal solution for a travelling wave is obtained analytically. The necessary and sufficient conditions for stability are obtained. It is found that the stability criteria are significantly affected by the amplitude of the temporal solution. Further the formula for the surface elevation is obtained in each case. Numerical calculations show that the constant electric field plays a dual role in the stability analysis. It is observed that the field frequency changes the mechanism due to the dual role of the electric field.

  5. Continuation and stability of convective modulated rotating waves in spherical shells

    NASA Astrophysics Data System (ADS)

    Garcia, F.; Net, M.; Sánchez, J.

    2016-01-01

    Modulated rotating waves (MRW), bifurcated from the thermal-Rossby waves that arise at the onset of convection of a fluid contained in a rotating spherical shell, and their stability, are studied. For this purpose, Newton-Krylov continuation techniques are applied. Nonslip boundary conditions, an Ekman number E =10-4 , and a low Prandtl number fluid Pr=0.1 in a moderately thick shell of radius ratio η =0.35 , differentially heated, are considered. The MRW are obtained as periodic orbits by rewriting the equations of motion in the rotating frame of reference where the rotating waves become steady states. Newton-Krylov continuation allows us to obtain unstable MRW that cannot be found by using only time integrations, and identify regions of multistability. For instance, unstable MRW without any azimuthal symmetry have been computed. It is shown how they become stable in a small Rayleigh-number interval, in which two branches of traveling waves are also stable. The study of the stability of the MRW helps to locate and classify the large sequence of bifurcations, which takes place in the range analyzed. In particular, tertiary Hopf bifurcations giving rise to three-frequency stable solutions are accurately determined.

  6. Continuation and stability of convective modulated rotating waves in spherical shells.

    PubMed

    Garcia, F; Net, M; Sánchez, J

    2016-01-01

    Modulated rotating waves (MRW), bifurcated from the thermal-Rossby waves that arise at the onset of convection of a fluid contained in a rotating spherical shell, and their stability, are studied. For this purpose, Newton-Krylov continuation techniques are applied. Nonslip boundary conditions, an Ekman number E=10^{-4}, and a low Prandtl number fluid Pr=0.1 in a moderately thick shell of radius ratio η=0.35, differentially heated, are considered. The MRW are obtained as periodic orbits by rewriting the equations of motion in the rotating frame of reference where the rotating waves become steady states. Newton-Krylov continuation allows us to obtain unstable MRW that cannot be found by using only time integrations, and identify regions of multistability. For instance, unstable MRW without any azimuthal symmetry have been computed. It is shown how they become stable in a small Rayleigh-number interval, in which two branches of traveling waves are also stable. The study of the stability of the MRW helps to locate and classify the large sequence of bifurcations, which takes place in the range analyzed. In particular, tertiary Hopf bifurcations giving rise to three-frequency stable solutions are accurately determined. PMID:26871166

  7. Nondestructive evaluation of orthopaedic implant stability in THA using highly nonlinear solitary waves

    NASA Astrophysics Data System (ADS)

    Yang, Jinkyu; Silvestro, Claudio; Sangiorgio, Sophia N.; Borkowski, Sean L.; Ebramzadeh, Edward; De Nardo, Luigi; Daraio, Chiara

    2012-01-01

    We propose a new biomedical sensing technique based on highly nonlinear solitary waves to assess orthopaedic implant stability in a nondestructive and efficient manner. We assemble a granular crystal actuator consisting of a one-dimensional tightly packed array of spherical particles, to generate acoustic solitary waves. Via direct contact with the specimen, we inject acoustic solitary waves into a biomedical prosthesis, and we nondestructively evaluate the mechanical integrity of the bone-prosthesis interface, studying the properties of the waves reflected from the contact zone between the granular crystal and the implant. The granular crystal contains a piezoelectric sensor to measure the travelling solitary waves, which allows it to function also as a sensor. We perform a feasibility study using total hip arthroplasty (THA) samples made of metallic stems implanted in artificial composite femurs using polymethylmethacrylate for fixation. We first evaluate the sensitivity of the proposed granular crystal sensor to various levels of prosthesis insertion into the composite femur. Then, we impose a sequence of harsh mechanical loading on the THA samples to degrade the mechanical integrity at the stem-cement interfaces, using a femoral load simulator that simulates aggressive, accelerated physiological loading. We investigate the implant stability via the granular crystal sensor-actuator during testing. Preliminary results suggest that the reflected waves respond sensitively to the degree of implant fixation. In particular, the granular crystal sensor-actuator successfully detects implant loosening at the stem-cement interface following violent cyclic loading. This study suggests that the granular crystal sensor and actuator has the potential to detect metal-cement defects in a nondestructive manner for orthopaedic applications.

  8. Plasmon-soliton waves in planar slot waveguides. II. Results for stationary waves and stability analysis

    NASA Astrophysics Data System (ADS)

    Walasik, Wiktor; Renversez, Gilles; Ye, Fangwei

    2016-01-01

    We describe the results of the two methods we developed to calculate the stationary nonlinear solutions in one-dimensional plasmonic slot waveguides made of a finite-thickness nonlinear dielectric core surrounded by metal regions. These two methods are described in detail in the preceding article [Walasik and Renversez, preceding paper, Phys. Rev. A 93, 013825 (2016)], 10.1103/PhysRevA.93.013825. For symmetric waveguides, we provide the nonlinear dispersion curves obtained using the two methods and compare them. We describe the well-known low-order modes and higher modes that were not described before. All the modes are classiffied into two families: modes with or without nodes. We also compare nonlinear modes with nodes with the linear modes in similar linear slot waveguides with a homogeneous core. We recover the symmetry breaking Hopf bifurcation of the first symmetric nonlinear mode toward an asymmetric mode and we show that some of the higher modes also exhibit a bifurcation. We study the behavior of the bifurcation of the fundamental mode as a function of the permittivities of the metal cladding and of the nonlinear core. We demonstrate that the bifurcation can be obtained at low power levels in structures with optimized parameters. Moreover, we provide the dispersion curves for asymmetric nonlinear slot waveguides. Finally, we give results concerning the stability of the fundamental symmetric mode and the asymmetric mode that bifurcates from it using both theoretical argument and numerical propagation simulations from two different full-vector methods. We also investigate the stability properties of the first antisymmetric mode using our two numerical propagation methods.

  9. Gravitational waves and stability of cosmological solutions in the theory with anomaly-induced corrections

    SciTech Connect

    Fabris, Júlio C.; Pelinson, Ana M.; Salles, Filipe de O.; Shapiro, Ilya L. E-mail: ana.pelinson@gmail.com E-mail: shapiro@fisica.ufjf.br

    2012-02-01

    The dynamics of metric perturbations is explored in the gravity theory with anomaly-induced quantum corrections. Our first purpose is to derive the equation for gravitational waves in this theory on the general homogeneous and isotropic background, and then verify the stability of such background with respect to metric perturbations. The problem under consideration has several interesting applications. Our first purpose is to explore the stability of the classical cosmological solutions in the theory with quantum effects taken into account. There is an interesting literature about stability of Minkowski and de Sitter spaces and here we extend the consideration also to the radiation and matter dominated cosmologies. Furthermore, we analyze the behavior of metric perturbations during inflationary period, in the stable phase of the Modified Starobinsky inflation.

  10. Robust control based on feedback linearization for roll stabilizing of autonomous underwater vehicle under wave disturbances

    NASA Astrophysics Data System (ADS)

    Pan, Li-Xin; Jin, Hong-Zhang; Wang, Lin-Lin

    2011-06-01

    In the case of Autonomous Underwater Vehicle (AUV) navigating with low speed near water surface, a new method for design of roll motion controller is proposed in order to restrain wave disturbance effectively and improve roll stabilizing performance. Robust control is applied, which is based on uncertain nonlinear horizontal motion model of AUV and the principle of zero speed fin stabilizer. Feedback linearization approach is used to transform the complex nonlinear system into a comparatively simple linear system. For parameter uncertainty of motion model, the controller is designed with mixed-sensitivity method based on H-infinity robust control theory. Simulation results show better robustness improved by this control method for roll stabilizing of AUV navigating near water surface.

  11. The stability of freely-propagating ion acoustic waves in 2D systems

    NASA Astrophysics Data System (ADS)

    Chapman, Thomas; Berger, Richard; Banks, Jeffrey; Brunner, Stephan

    2014-10-01

    The stability of a freely-propagating ion acoustic wave (IAW) is a basic science problem that is made difficult by the need to resolve electron kinetic effects over a timescale that greatly exceeds the IAW period during numerical simulation. Recent results examining IAW stability using a 1D+1V Vlasov-Poisson solver indicate that instability is a fundamental property of IAWs that occurs over most if not all of the parameter space of relevance to ICF experiments. We present here new results addressing the fundamental question of IAW stability across a broad range of plasma conditions in a 2D+2V system using LOKI, ranging from a regime of relatively weak to a regime of relatively strong ion kinetic effects. Work performed under the auspices of the U.S. DOE by LLNL (DE-AC52-07NA27344) and funded by the LDRD Program at LLNL (12-ERD-061).

  12. MHD Stability Analysis Using an X-ray Wave Array Diagnostic on the PEGASUS Toroidal Experiment*

    NASA Astrophysics Data System (ADS)

    Wilson, C.; Fonck, R.; Intrator, T.; Thorson, T.

    1998-11-01

    Tearing mode instabilities during plasma current ramp-up are important for extremely low aspect ratio devices. Fast current ramping, aided by the low internal inductance of low aspect ratio plasmas, induces skin currents. The resulting hollow current profile may produce double tearing modes, which allows for reconnection and current penetration. Another area of interest for MHD stability studies in the first phase of operation of the P EGASUS Experiment is the nature of the plasma stability boundary as the edge-q is lowered at extremely low aspect ratio. This boundary plays a major role in the accessibility to stable operation at very low toroidal field. P EGASUS will employ an X-ray diode (XRD) detector array to diagnose the internal plasma MHD structure. We are designing and installing a vertical 20 channel radially viewing pinhole array of XRD's for >= 50 eV photon measurement. Each channel will have a vertical resolution of 2 cm and an upper frequency limit of 100 kHz. The lithium drifted XRD's have a large surface area of 90 mm^2, thereby being quite sensitive and suited to a low temperature start-up plasma. The expected signal-to-noise ratio due to photon noise is < 0.1% for P EGASUS plasmas. * *Supported by U.S. DoE grant No. DE-FG02-96ER54375

  13. Multi-stability of circadian phase wave within early postnatal suprachiasmatic nucleus.

    PubMed

    Jeong, Byeongha; Hong, Jin Hee; Kim, Hyun; Choe, Han Kyoung; Kim, Kyungjin; Lee, Kyoung J

    2016-01-01

    The suprachiasmatic nucleus (SCN) is a group of cells that functions as a biological master clock. In different SCN cells, oscillations of biochemical markers such as the expression-level of clock genes, are not synchronized but instead form slow circadian phase waves propagating over the whole cell population spatio-temporal struc- ture is a fixed property set by the anatomy of a given SCN. Here, we show that this is not the case in early postnatal SCN. Earlier studies presumed that their Based on bioluminescence imaging experiments with Per2-Luciferase mice SCN cultures which guided computer simulations of a realistic model of the SCN, we demonstrate that the wave is not unique but can be in various modes including phase- coherent oscillation, crescent-shaped wave, and most notably, a rotating pinwheel wave that conceptually resembles a wall clock with a rotating hand. Furthermore, mode transitions can be induced by a pulse of 38.5 °C temperature perturbation. Importantly, the waves support a significantly different period, suggesting that neither a spatially-fixed phase ordering nor a specialized pacemaker having a fixed period exist in these studied SCNs. These results lead to new important questions of what the observed multi-stability means for the proper function of an SCN and its arrhythmia. PMID:26891917

  14. Multi-stability of circadian phase wave within early postnatal suprachiasmatic nucleus

    PubMed Central

    Jeong, Byeongha; Hong, Jin Hee; Kim, Hyun; Choe, Han Kyoung; Kim, Kyungjin; Lee, Kyoung J.

    2016-01-01

    The suprachiasmatic nucleus (SCN) is a group of cells that functions as a biological master clock. In different SCN cells, oscillations of biochemical markers such as the expression-level of clock genes, are not synchronized but instead form slow circadian phase waves propagating over the whole cell population spatio-temporal struc- ture is a fixed property set by the anatomy of a given SCN. Here, we show that this is not the case in early postnatal SCN. Earlier studies presumed that their Based on bioluminescence imaging experiments with Per2-Luciferase mice SCN cultures which guided computer simulations of a realistic model of the SCN, we demonstrate that the wave is not unique but can be in various modes including phase- coherent oscillation, crescent-shaped wave, and most notably, a rotating pinwheel wave that conceptually resembles a wall clock with a rotating hand. Furthermore, mode transitions can be induced by a pulse of 38.5 °C temperature perturbation. Importantly, the waves support a significantly different period, suggesting that neither a spatially-fixed phase ordering nor a specialized pacemaker having a fixed period exist in these studied SCNs. These results lead to new important questions of what the observed multi-stability means for the proper function of an SCN and its arrhythmia. PMID:26891917

  15. Formation mechanism of steep wave front in magnetized plasmas

    SciTech Connect

    Sasaki, M. Kasuya, N.; Itoh, S.-I.; Kobayashi, T.; Arakawa, H.; Itoh, K.; Fukunaga, K.; Yamada, T.; Yagi, M.

    2015-03-15

    Bifurcation from a streamer to a solitary drift wave is obtained in three dimensional simulation of resistive drift waves in cylindrical plasmas. The solitary drift wave is observed in the regime where the collisional transport is important as well as fluctuation induced transport. The solitary drift wave forms a steep wave front in the azimuthal direction. The phase of higher harmonic modes are locked to that of the fundamental mode, so that the steep wave front is sustained for a long time compared to the typical time scale of the drift wave oscillation. The phase entrainment between the fundamental and second harmonic modes is studied, and the azimuthal structure of the stationary solution is found to be characterized by a parameter which is determined by the deviation of the fluctuations from the Boltzmann relation. There are two solutions of the azimuthal structures, which have steep wave front facing forward and backward in the wave propagation direction, respectively. The selection criterion of these solutions is derived theoretically from the stability of the phase entrainment. The simulation result and experimental observations are found to be consistent with the theoretical prediction.

  16. IK1 heterogeneity affects genesis and stability of spiral waves in cardiac myocyte monolayers

    PubMed Central

    Sekar, Rajesh B.; Kizana, Eddy; Cho, Hee C.; Molitoris, Jared M.; Hesketh, Geoffrey G.; Eaton, Brett P.; Marbán, Eduardo; Tung, Leslie

    2009-01-01

    Previous studies have postulated an important role for the inwardly rectifying potassium current (IK1) in controlling the dynamics of electrophysiological spiral waves responsible for ventricular tachycardia and fibrillation. In this study, we developed a novel tissue model of cultured neonatal rat ventricular myocytes (NRVMs) with uniform or heterogeneous Kir2.1 expression achieved by lentiviral transfer to elucidate the role of IK1 in cardiac arrhythmogenesis. Kir2.1-overexpressed NRVMs showed increased IK1 density, hyperpolarized resting membrane potential and increased action potential upstroke velocity compared with GFP-transduced NRVMs. Opposite results were observed in Kir2.1-suppressed NRVMs. Optical mapping of uniformly Kir2.1 gene-modified monolayers showed altered conduction velocity (CV) and action potential duration (APD) compared with non-transduced and empty vector-transduced monolayers, but functional reentrant waves could not be induced. In monolayers with an island of altered Kir2.1 expression, CV and APD of the locally transduced and non-transduced regions were similar to those of the uniformly transduced and non-transduced monolayers, respectively, and functional reentrant waves could be induced. The waves were anchored to islands of Kir2.1 overexpression and remained stable, but dropped in frequency and meandered away from islands of Kir2.1 suppression. In monolayers with an inverse pattern of IK1 heterogeneity, stable high frequency spiral waves were present with IK1 overexpression, whereas lower frequency, meandering spiral waves were observed with IK1 suppression. Our study provides direct evidence for the contribution of IK1 heterogeneity and level to the genesis and stability of spiral waves and highlights the potential importance of IK1 as an anti-arrhythmia target. PMID:19122180

  17. A case study of global stability of strong rarefaction waves for 2×2 hyperbolic conservation laws with artificial viscosity

    NASA Astrophysics Data System (ADS)

    Duan, Ran; Ma, Xuan; Zhao, Huijiang

    This paper is concerned with the global stability of strong rarefaction waves for a class of 2×2 hyperbolic conservation laws with artificial viscosity, i.e., the p-system with artificial viscosity {

  18. Forecast of iceberg ensemble drift

    SciTech Connect

    El-Tahan, M.S.; El-Tahan, H.W.; Venkatesh, S.

    1983-05-01

    The objectives of the study are to gain a better understanding of the characteristics of iceberg motion and the factors controlling iceberg drift, and to develop an iceberg ensemble drift forecast system to be operated by the Canadian Atmospheric Environment Service. An extensive review of field and theoretical studies on iceberg behaviour, and the factors controlling iceberg motion has been carried out. Long term and short term behaviour of icebergs are critically examined. A quantitative assessment of the effects of the factors controlling iceberg motion is presented. The study indicated that wind and currents are the primary driving forces. Coriolis Force and ocean surface slope also have significant effects. As for waves, only the higher waves have a significant effect. Iceberg drift is also affected by iceberg size characteristics. Based on the findings of the study a comprehensive computerized forecast system to predict the drift of iceberg ensembles off Canada's east coast has been designed. The expected accuracy of the forecast system is discussed and recommendations are made for future improvements to the system.

  19. Experiments on the structure and stability of mode-2 internal solitary-like waves propagating on an offset pycnocline

    NASA Astrophysics Data System (ADS)

    Carr, M.; Davies, P. A.; Hoebers, R. P.

    2015-04-01

    The structure and stability of mode-2 internal solitary-like waves is investigated experimentally. A rank-ordered train of mode-2 internal solitary waves is generated using a lock release configuration. The pycnocline is centred either on the mid-depth of the water column (the 0% offset case) or it is offset in the positive vertical direction by a fraction of 5%, 10%, or 20% of the total fluid depth. It is found that offsetting the pycnocline has little effect on the basic wave properties (e.g., wave speed, wave amplitude, and wavelength) but it does significantly affect wave stability. Instability takes the form of small K-H-like billows in the rear of the wave and small scale overturning in the core of the wave. In the 0% offset case, instability occurs on both the upper and lower interfaces of the pycnocline and is similar in extent and vigour over the two interfaces. As the offset percentage is increased, however, instability is more pronounced on the lower interface with little or no evidence of instability being observed on the upper interface. In the 20% offset case, a mode-1 tail is associated with the wave and the wave characteristics resemble qualitatively the recent field observations of Shroyer et al. ["Mode 2 waves on the continental shelf: Ephemeral components of the nonlinear internal wavefield," J. Geophys. Res. 115, C07001, doi:10.1029/2009JC005605 (2010)].

  20. Wave-Activity Conservation Laws and Stability Theorems for Semi-Geostrophic Dynamics.

    NASA Astrophysics Data System (ADS)

    Kushner, Paul Joel

    Our understanding of the role that large-scale eddies play in the atmospheric general circulation is largely based on theoretical results developed using quasi-geostrophic (QG) dynamics. This dissertation represents part of an overall effort to extend these important results to more accurate dynamical models than the seriously limited QG model. In this dissertation, a body of QG theory, concerning the evolution of disturbances to prescribed basic states, is systematically generalized to the semi-geostrophic (SG) model. This body of theory consists of wave-activity conservation laws, linear and nonlinear stability theorems for parallel and non-parallel basic states, and wave-zonal-mean-flow interaction theory. The generalization exploits the two key features of Hamiltonian structure and balanced dynamics that SG and QG dynamics share. The abovementioned theory arises from the conservation of finite-amplitude pseudomomentum and pseudoenergy wave -activity invariants. In an introductory review, these invariants are derived for QG dynamics and shown to yield the body of QG theory, including an apparently novel finite -amplitude generalization of the QG wave-zonal-mean-flow interaction theory. The same procedure is then carried out first for f-plane Boussinesq and then for beta-plane compressible SG dynamics. The body of SG theory is analogous to the QG one and reduces to it in the small-Rossby-number limit. Two important differences between SG and QG dynamics complicate the generalization but yield novel insights and results. First, the transformation to isentropic and geostrophic coordinates in the SG model simplifies the dynamics to a 'potential-vorticity-invertible' form free of explicit ageostrophic advection terms but introduces complex boundary variability in the transformed space. Boundary contributions are here incorporated explicitly into the wave-activity and stability results, yielding novel lateral -boundary stabilty criteria. Second, the SG invertibility

  1. Stability analysis of the Gyroscopic Power Take-Off wave energy point absorber

    NASA Astrophysics Data System (ADS)

    Nielsen, Søren R. K.; Zhang, Zili; Kramer, Morten M.; Olsen, Jan

    2015-10-01

    The Gyroscopic Power Take-Off (GyroPTO) wave energy point absorber consists of a float rigidly connected to a lever. The operational principle is somewhat similar to that of the so-called gyroscopic hand wrist exercisers, where the rotation of the float is brought forward by the rotational particle motion of the waves. At first, the equations of motion of the system are derived based on analytical rigid body dynamics. Next, assuming monochromatic waves simplified equations are derived, valid under synchronisation of the ring of the gyro to the angular frequency of the excitation. Especially, it is demonstrated that the dynamics of the ring can be described as an autonomous nonlinear single-degree-of-freedom system, affected by three different types of point attractors. One where the ring vibrations are attracted to a static equilibrium point indicating unstable synchronisation and two types of attractors where the ring is synchronised to the wave angular frequency, either rotating in one or the opposite direction. Finally, the stability conditions and the basins of attraction to the point attractors defining the synchronised motion are determined.

  2. Amplification of Reynolds number dependent processes by wave distortion. [liquid fuel combustor stability

    NASA Technical Reports Server (NTRS)

    Ventrice, M.

    1979-01-01

    The amplification of a Reynolds number dependent process by wave distortion and the possibility of applying the results to other similar Reynolds number dependent processes were investigated. The process investigated was that associated with the operation of a constant-temperature hot-wire anemometer. The application of vaporization limited combustion, the type of combustion typically associated with liquid propellant rocket engines, was studied. A series of experiments were carried out to determine the effect of wave distortion on a Reynolds number dependent process and to establish the analogy between the anemometer process and the combustion process. Parametric trends, behavior common to different chamber geometries, and stability boundaries were identified. The results indicate a high degree of similarity between the two processes and the possibility of using the anemometer system to investigate combustion instability. The nonlinear aspects of a Reynolds number dependent process appear to be the dominant mechanisms controlling instability.

  3. Four-wave mixing stability in hybrid photonic crystal fibers with two zero-dispersion wavelengths.

    PubMed

    Sévigny, Benoit; Vanvincq, Olivier; Valentin, Constance; Chen, Na; Quiquempois, Yves; Bouwmans, Géraud

    2013-12-16

    The four-wave mixing process in optical fibers is generally sensitive to dispersion uniformity along the fiber length. However, some specific phase matching conditions show increased robustness to longitudinal fluctuations in fiber dimensions, which affect the dispersion, even for signal and idler wavelengths far from the pump. In this paper, we present the method by which this point is found, how the fiber design characteristics impact on the stable point and demonstrate the stability through propagation simulations using the non-linear Schrödinger equation. PMID:24514659

  4. Neogenin recruitment of the WAVE regulatory complex maintains adherens junction stability and tension

    PubMed Central

    Lee, Natalie K.; Fok, Ka Wai; White, Amanda; Wilson, Nicole H.; O'Leary, Conor J.; Cox, Hayley L.; Michael, Magdalene; Yap, Alpha S.; Cooper, Helen M.

    2016-01-01

    To maintain tissue integrity during epithelial morphogenesis, adherens junctions (AJs) must resist the mechanical stresses exerted by dynamic tissue movements. Junctional stability is dependent on actomyosin contractility within the actin ring. Here we describe a novel function for the axon guidance receptor, Neogenin, as a key component of the actin nucleation machinery governing junctional stability. Loss of Neogenin perturbs AJs and attenuates junctional tension. Neogenin promotes actin nucleation at AJs by recruiting the Wave regulatory complex (WRC) and Arp2/3. A direct interaction between the Neogenin WIRS domain and the WRC is crucial for the spatially restricted recruitment of the WRC to the junction. Thus, we provide the first example of a functional WIRS–WRC interaction in epithelia. We further show that Neogenin regulates cadherin recycling at the AJ. In summary, we identify Neogenin as a pivotal component of the AJ, where it influences both cadherin dynamics and junctional tension. PMID:27029596

  5. Numerical solution of wave equations for the stability of the inner cometo-sheath

    NASA Technical Reports Server (NTRS)

    Srivastava, Krishna M.; Tsurutani, Bruce T.; Goldstein, Bruce E.

    1993-01-01

    Numerical solution of the MHD wave equations for stability of the cometary sheath determined by the balance between the inward Lorentz body force and the outward ion-neutral drag force is obtained by using a two-point boundary value method. The eigenvalues and the eigenfunctions are obtained numerically by treating the cometary inner sheath as a layer of finite thickness, bounded by the contact surface, i.e., the diamagnetic cavity boundary. The magnetic field structure discovered in the ionosphere of Comets Halley and Giacobini-Zinner is found to be unstable. The effects of finite plasma pressure, dissociative recombination, and mass loading due to photoionization are found to be stabilizing but are unable to quench the instability completely. It is also found that the higher the neutral production rate the lesser is the growth rate for the instability.

  6. Locking the Advanced LIGO Gravitational Wave Detector: with a focus on the Arm Length Stabilization Technique

    NASA Astrophysics Data System (ADS)

    Staley, Alexa

    2015-11-01

    This thesis begins with an introduction on the theory of general relativity and gravitational waves. Common astrophysical sources are described in Chapter 2. Chapter 3 begins with a description of the installed instrument. A discussion on the detector design sensitivity, limiting noise sources, and estimated detection rates is also given. At the end of Chapte 3, the complications of lock acquisition are highlighted. The arm length stabilization system was introduced to Advanced LIGO as a partial way to solve the difficulties of locking. Chapter 4 discusses the motivation for the use of this scheme and explains the methodology. A detailed discussion on the arm length stabilization model is given, along with the noise budget in Chapters 5 and 6 respectively. The full lock sequence is described in Chapter 7. The thesis concludes with the current status of the interferometers. (Abstract shortened by UMI.).

  7. Study on interfacial stability and internal flow of a droplet levitated by ultrasonic wave.

    PubMed

    Abe, Yutaka; Yamamoto, Yuji; Hyuga, Daisuke; Awazu, Shigeru; Aoki, Kazuyoshi

    2009-04-01

    For a microgravity environment, new and high-quality material is expected to be manufactured. However, the effect of surface instability and the internal flow become significant when the droplet becomes large. Elucidation of internal flow and surface instability on a levitated droplet is required for the quality improvement of new material manufacturing in a microgravity environment. The objectives of this study are to clarify the interfacial stability and internal flow of a levitated droplet. Surface instability and internal flow are investigated with a large droplet levitated by the ultrasonic acoustic standing wave. The experiment with a large droplet is conducted both under normal gravity and microgravity environments. In the experiment, at first, the characteristics of the levitated droplet are investigated; that is, the relationships among the levitated droplet diameter, the droplet aspect ratio, the displacement of the antinode of the standing wave, and the sound pressure are experimentally measured. As a result, it is clarified that the levitated droplet tends to be located at an optimal position with an optimal shape and diameter. Second, the border condition between the stable and the unstable levitation of the droplet is evaluated by using the existing stability theory. The experimental results qualitatively agree with the theory. It is suggested that the stability of the droplet can be evaluated with the stability theory. Finally, multidimensional visual measurement is conducted to investigate the internal flow structure in a levitated droplet. It is suggested that complex flow with the vortex is generated in the levitated droplet. Moreover, the effect of physical properties of the test fluid on the internal flow structure of the levitated droplet is investigated. As a result, the internal flow structure of the levitated droplet is affected by the surface tension and viscosity. PMID:19426319

  8. Notes on drift theory

    NASA Technical Reports Server (NTRS)

    Burger, R. A.; Moraal, H.; Webb, G. M.

    1985-01-01

    It is shown that there is a simpler way to derive the average guiding center drift of a distribution of particles than via the so-called single particle analysis. Based on this derivation it is shown that the entire drift formalism can be considerably simplified, and that results for low order anisotropies are more generally valid than is usually appreciated. This drift analysis leads to a natural alternative derivation of the drift velocity along a neutral sheet.

  9. Drift of dislocation tripoles under ultrasound influence.

    PubMed

    Murzaev, R T; Bachurin, D V; Nazarov, A A

    2016-01-01

    Numerical simulations of dynamics of different stable dislocation tripoles under influence of monochromatic standing sound wave were performed. The basic conditions necessary for the drift and mutual rearrangements between dislocation structures were investigated. The dependence of the drift velocity of the dislocation tripoles as a function of the frequency and amplitude of the external influence was obtained. The results of the work can be useful in analysis of motion and self-organization of dislocation structure under ultrasound influence. PMID:26278625

  10. Transient chaotic transport in dissipative drift motion

    NASA Astrophysics Data System (ADS)

    Oyarzabal, R. S.; Szezech, J. D.; Batista, A. M.; de Souza, S. L. T.; Caldas, I. L.; Viana, R. L.; Sanjuán, M. A. F.

    2016-04-01

    We investigate chaotic particle transport in magnetised plasmas with two electrostatic drift waves. Considering dissipation in the drift motion, we verify that the removed KAM surfaces originate periodic attractors with their corresponding basins of attraction. We show that the properties of the basins depend on the dissipation and the space-averaged escape time decays exponentially when the dissipation increases. We find positive finite time Lyapunov exponents in dissipative drift motion, consequently the trajectories exhibit transient chaotic transport. These features indicate how the transient plasma transport depends on the dissipation.

  11. Ground Control for Emplacement Drifts for LA

    SciTech Connect

    Y. Sun

    2004-07-09

    The purpose of this calculation is to analyze the stability of repository emplacement drifts during the preclosure period, and to provide a final ground support method for emplacement drifts for the License Application (LA). The scope of the work includes determination of input parameter values and loads, selection of appropriate process and methods for the calculation, application of selected methods, such as empirical or analytical, to the calculation, development and execution of numerical models, and evaluation of results. Results from this calculation are limited to use for design of the emplacement drifts and the final ground support system installed in these drifts. The design of non-emplacement openings and their ground support systems is covered in the ''Ground Control for Non-Emplacement Drifts for LA'' (BSC 2004c).

  12. Stability analysis of a coaxial-waveguide gyrotron traveling-wave amplifier

    SciTech Connect

    Hung, C.L.; Yeh, Y.S.

    2005-10-01

    The gyrotron traveling-wave tube (gyro-TWT) amplifier is known to be highly susceptible to spurious oscillations. This study develops a simulation approach to analyze the stability of a coaxial-waveguide gyro-TWT with distributed wall losses. The interplay among the absolute instabilities, the gyrotron backward-wave oscillations, and the circuit parameters is analyzed. Simulation results reveal that the distributed wall losses effectively stabilize spurious oscillations in the coaxial gyro-TWT. Furthermore, the wall resistivity of the center conductor is shown to be an additional effective mechanism for suppressing oscillations. Under stable operation conditions, the coaxial gyro-TWT with distributed losses is predicted to generate 435 kW in the Ka band with 31% efficiency, a saturated gain of 45 dB, and a bandwidth of 1.86 GHz ({approx_equal}5.8%) for a 70 kV, 20 A electron beam with an {alpha}(={nu}{sub perpendicular})/{nu}{sub z})=1.0 and an axial velocity spread of {delta}{nu}{sub z}/{nu}{sub z}=5%.

  13. Asymptotic stability of traveling waves for scalar viscous conservation laws with non-convex nonlinearity

    NASA Astrophysics Data System (ADS)

    Matsumura, Akitaka; Nishihara, Kenji

    1994-10-01

    The asymptotic stability of traveling wave solutions with shock profile is considered for scalar viscous conservation laws u t + f(u) x = μu xx with the initial data u 0 which tend to the constant states u ± as x→±∞. Stability theorems are obtained in the absence of the convexity of f and in the allowance of s (shock speed)= f'( u ±). Moreover, the rate of asymptotics in time is investigated. For the case f'(u+) wave at the corresponding rate as t→∞. This rate seems to be almost optimal compared with the rate in the case f= u 2/2 for which an explicit form of the solution exists. The rate is also obtained in the case f'( u ± =s under some additional conditions. Proofs are given by applying an elementary weighted energy method to the integrated equation of the original one. The selection of the weight plays a crucial role in those procedures.

  14. Transient characteristics and stability analysis of standing wave thermoacoustic-piezoelectric harvesters.

    PubMed

    Nouh, Mostafa; Aldraihem, Osama; Baz, Amr

    2014-02-01

    Standing wave thermoacoustic-piezoelectric (TAP) energy harvesters convert thermal energy, such as solar or waste heat energy, directly into electrical energy without the need for any moving components. The input thermal energy generates a steep temperature gradient along a porous medium called "stack." At a critical threshold of the temperature gradient, self-sustained acoustic waves are developed inside an acoustic resonator. The associated pressure fluctuations impinge on a piezoelectric diaphragm, placed at the end of the resonator, to generate electricity. The behavior of this multi-field system is modeled using the electrical analogy approach. The developed model combines the descriptions of the acoustic resonator and the stack with the characteristics of the piezoelectric diaphragm. The equivalent electric network is analyzed to determine the system's stability and predict the temperature gradient necessary to developing self-sustained oscillations inside the harvester. The developed network is utilized also to investigate the transient performance of the harvester by employing the network theory and Simulation Program with Integrated Circuit Emphasis software package. The established stability boundaries are validated against the predictions of the root locus technique. Furthermore, the obtained results are compared with experimental results extracted from testing a prototype of the harvester. The developed approach presents an innovative tool for the design of TAP energy harvesters. PMID:25234876

  15. On the orbital stability of Gaussian solitary waves in the log-KdV equation

    NASA Astrophysics Data System (ADS)

    Carles, Rémi; Pelinovsky, Dmitry

    2014-12-01

    We consider the logarithmic Korteweg-de Vries (log-KdV) equation, which models solitary waves in anharmonic chains with Hertzian interaction forces. By using an approximating sequence of global solutions of the regularized generalized KdV equation in H^1({R}) with conserved L2 norm and energy, we construct a weak global solution of the log-KdV equation in a subset of H^1({R}) . This construction yields conditional orbital stability of Gaussian solitary waves of the log-KdV equation, provided that uniqueness and continuous dependence of the constructed solution holds. Furthermore, we study the linearized log-KdV equation at the Gaussian solitary wave and prove that the associated linearized operator has a purely discrete spectrum consisting of simple purely imaginary eigenvalues in addition to the double zero eigenvalue. The eigenfunctions, however, do not decay like Gaussian functions but have algebraic decay. Using numerical approximations, we show that the Gaussian initial data do not spread out but produce visible radiation at the left slope of the Gaussian-like pulse in the time evolution of the linearized log-KdV equation.

  16. Dust-acoustic waves and stability in the permeating dusty plasma. II. Power-law distributions

    SciTech Connect

    Gong Jingyu; Du Jiulin; Liu Zhipeng

    2012-08-15

    The dust-acoustic waves and the stability theory for the permeating dusty plasma with power-law distributions are studied by using nonextensive q-statistics. In two limiting physical cases, when the thermal velocity of the flowing dusty plasma is much larger than, and much smaller than the phase velocity of the waves, we derived the dust-acoustic wave frequency, the instability growth rate, and the instability critical flowing velocity. As compared with the formulae obtained in part I [Gong et al., Phys. Plasmas 19, 043704 (2012)], all formulae of the present cases and the resulting plasma characteristics are q-dependent, and the power-law distribution of each plasma component of the permeating dusty plasma has a different q-parameter and thus has a different nonextensive effect. Further, we make numerical analyses of an example that a cometary plasma tail is passing through the interplanetary space dusty plasma and we show that these power-law distributions have significant effects on the plasma characteristics of this kind of plasma environment.

  17. Shape stability and violent collapse of microbubbles interacting with acoustic waves and shocks

    NASA Astrophysics Data System (ADS)

    Calvisi, Michael Louis

    This dissertation elucidates the effect of nonspherical perturbations on the energy-focusing properties of bubble collapses driven by acoustic and shock wave forcing. First, the influence of acoustic forcing on shape stability is explored and two models of bubble breakup---one based on perturbation analysis and the other based on numerical solution of the Laplace equation---are compared, showing remarkably good agreement. The Laplace equation for axisymmetric geometry is solved through use of a Boundary Integral Method that can efficiently model highly deformed; even toroidal bubble geometries. This model is based on the work of previous researchers but is significantly augmented for our purposes to simulate extremely violent, acoustically-driven collapses. Our numerical model based on the Boundary Integral Method is then used to explore the effect of shape stability on energy concentration in the bubble interior by comparing the peak temperatures and pressures of spherical to nonspherical bubble collapses. It is demonstrated that for very intense collapses, nonspherical bubbles do not focus the energy as efficiently as spherical collapses due to the conversion of some of the incident acoustic energy into kinetic energy of a liquid jet that pierces the bubble near the point of minimum volume. This is clarified by a calculation of the (gas) thermal equivalent of this liquid kinetic energy. Finally, the effect of shock wave forcing on bubbles is analyzed in the vicinity of a rigid boundary. Through calculation of quantities such as kinetic energy and Kelvin impulse of the surrounding liquid, the physics of shock-bubble interaction near a wall is illuminated. A key finding is that reflection of the incident shock wave enhances the intensity of bubble collapse in the near region due to constructive interference between the incident and reflected shock waves. Conversely, destructive interference suppresses the intensity of such collapses further away from the surface

  18. Forced generation of solitary waves in a rotating fluid and their stability

    NASA Astrophysics Data System (ADS)

    Choi, Wooyoung

    The primary objective of this graduate research is to study forced generation of solitary waves in a rotating fluid and their stability properties. For axisymmetric flow of a non-uniformly rotating fluid within a long cylindrical tube, an analysis is presented to predict the periodic generation of upstream-advancing vortex solitons by axisymmetric disturbance steadily moving with a transcritical velocity as a forcing agent. The phenomenon is simulated using the forced Korteweg-de Vries (fKdV) equation to model the amplitude function of the Stokes stream function for describing this family of rotating flows of an inviscid and incompressible fluid. The numerical results for the weakly nonlinear and weakly dispersive wave motion show that a sequence of well-defined axisymmetrical recirculating eddies is periodically produced and emitted to radiate upstream of the disturbance, soon becoming permanent in the form as a procession of vortex solitons, which we call vortons. Two primary flows, the Rankine vortex and the Burgers vortex, are adopted to exhibit in detail the process of producing the upstream vortons by the critical motion of a slender body moving along the central axis, with the Burgers vortex being found the more effective of the two in the generation of vortons. To investigate the evolution of free or forced waves within a tube of non-uniform radius, a new forced KdV equation is derived which models the variable geometry with variable coefficients. A set of section-mean conservation laws is derived specially for this class of rotational tube flows of an inviscid and incompressible fluid, in both differential and integral forms. A new aspect of stability theory is analyzed for possible instabilities of the axisymmetric solitary waves subject to non-axisymmetric disturbances. The present linear analysis based on the model equation involving the bending mode shows that the axisymmetric solitary wave is neutrally stable with respect to small bending mode

  19. Analytical modelling of wave refraction and convergence on coral reef platforms: Implications for island formation and stability

    NASA Astrophysics Data System (ADS)

    Mandlier, Philipp Georg; Kench, Paul Simon

    2012-07-01

    An analytical model was constructed to simulate the refraction of waves on coral reef platforms comprising an idealised bathymetry of uniform depth and vertical reef faces. Model simulations were conducted to investigate the influence of key parameters such as reef shape and depth as well as wave period on the propagation behaviour of incident waves. Results of the refraction analysis demonstrate that different reef shapes produce characteristic patterns of wave convergence on reef surfaces. The location and stability of focal zones and hence wave convergence is largely controlled by the shape of platforms. Platform configuration further controls the distribution of wave energy across platform surfaces and determines the influence of incident wave forcing on different reef sections. Results have significant implications for sedimentation processes and hence the formation and stability of islands on reef platforms. Wave propagation patterns define sediment transport vectors and subsequently control the transport and deposition of different sized material. Platforms which promote marked wave convergence behaviour, such as elliptical and circular reefs, are more likely to retain sediment on reef surfaces, whereas narrow linear structures have a higher potential for the off-reef evacuation of sediment over leeward reef margins and the subsequent infill of deeper lagoonal areas. The study provides a physical basis for future investigations of reef hydrodynamics and platform sedimentation processes.

  20. Linear stability analysis for travelling waves of second order in time PDE's

    NASA Astrophysics Data System (ADS)

    Stanislavova, Milena; Stefanov, Atanas

    2012-09-01

    We study travelling waves φc of second order in time PDE's u_{tt}+{ L} u+N(u)=0 . The linear stability analysis for these models is reduced to the question of the stability of quadratic pencils in the form \\lambda^2Id+2c\\lambda \\partial_x+{ H}_c , where { H}_c=c^2 \\partial_{xx}+{ L}+N'(\\varphi_c) . If { H}_c is a self-adjoint operator, with a simple negative eigenvalue and a simple eigenvalue at zero, then we completely characterize the linear stability of φc. More precisely, we introduce an explicitly computable index \\omega^*({ H}_c)\\in (0, \\infty] , so that the wave φc is stable if and only if |c|\\geq \\omega^*({ H}_c) . The results are applicable both in the periodic case and in the whole line case. The method of proof involves a delicate analysis of a function { G} , associated with { H} , whose positive zeros are exactly the positive (unstable) eigenvalues of the pencil \\lambda^2Id+2c\\lambda \\partial_x+{ H} . We would like to emphasize that the function { G} is not the Evans function for the problem, but rather a new object that we define herein, which fits the situation rather well. As an application, we consider three classical models—the ‘good’ Boussinesq equation, the Klein-Gordon-Zakharov (KGZ) system and the fourth order beam equation. In the whole line case, for the Boussinesq case and the KGZ system (and as a direct application of the main results), we compute explicitly the set of speeds which give rise to linearly stable travelling waves (and for all powers of p in the case of Boussinesq). This result is new for the KGZ system, while it generalizes the results of Alexander et al (2012, personal communication) and Alexander and Sachs (1995 Nonlinear World 2 471-507), which apply to the case p = 2. For the beam equation, we provide an implicit formula (depending only on the function \\|\\varphi_c'\\|_{L^2}) , which works for all p and for both the periodic and the whole line cases. Our results complement (and exactly match

  1. Experimental Investigation of Hexagon Stability in Two Frequency Forced Faraday Waves

    NASA Astrophysics Data System (ADS)

    Ding, Yu; Umbanhowar, Paul

    2003-03-01

    We have conducted experiments on a deep layer of silicone oil vertically oscillated with an acceleration a(t) = Am sin(m ω t + φ_m) + An sin(n ω t + φ_n). The stability of hexagonal surface wave patterns is investigated as a function of the overall acceleration, the ratio m:n, and the phase of the two rationally related driving frequencies. When the ratio A_m/An is chosen so the system is near a co-dimension two point, the stability of hexagons above onset is determined by the acceleration amplitude and the relative phase. Recent results by Porter and Silver (J. Porter and M. Silber, Phys. Rev. Lett. 084501, 2002) predicts that the range of pattern stability above onset as a function of acceleration is determined by cos(Φ), where Φ = π/4 - m φn / 2- n φm /2. We have tested this prediction for a number of m:n ratios and for various values of the dimensionless damping coefficient γ. We find that the patterns exhibit the predicted functional dependence on s(Φ) but with an additional phase offset. We measure the phase offset as a function of m:n and γ for varying frequency ω and fluid viscosity 5 cS <= ν <= 30 cS.

  2. Active laser frequency stabilization and resolution enhancement of interferometers for the measurement of gravitational waves in space

    NASA Astrophysics Data System (ADS)

    Herz, Markus

    2005-09-01

    Laser frequency stabilization is notably one of the major challenges on the way to a space-borne gravitational wave observatory. The proposed Laser Interferometer Space Antenna (LISA) is presently under development in an ESA, NASA collaboration. We present a novel method for active laser stabilization and phase noise suppression in such a gravitational wave detector. The proposed approach is a further evolution of the "arm-locking" method, which in essence consists of using an interferometer arm as an optical cavity, exploiting the extreme long-run stability of the cavity size in the frequency band of interest. We extend this method by using the natural interferometer arm length differences and existing interferometer signals as additional information sources for the reconstruction and active suppression of the quasi-periodic laser frequency noise, enhancing the resolution power of space-borne gravitational wave detectors.

  3. Exploring the stability and dynamics of dipolar matter-wave dark solitons

    NASA Astrophysics Data System (ADS)

    Edmonds, M. J.; Bland, T.; O'Dell, D. H. J.; Parker, N. G.

    2016-06-01

    We study the stability, form, and interaction of single and multiple dark solitons in quasi-one-dimensional dipolar Bose-Einstein condensates. The solitons are found numerically as stationary solutions in the moving frame of a nonlocal Gross Pitaevskii equation and characterized as a function of the key experimental parameters, namely the ratio of the dipolar atomic interactions to the van der Waals interactions, the polarization angle, and the condensate width. The solutions and their integrals of motion are strongly affected by the phonon and roton instabilities of the system. Dipolar matter-wave dark solitons propagate without dispersion and collide elastically away from these instabilities, with the dipolar interactions contributing an additional repulsion or attraction to the soliton-soliton interaction. However, close to the instabilities, the collisions are weakly dissipative.

  4. Stability of Solitary Waves and Vortices in a 2D Nonlinear Dirac Model

    NASA Astrophysics Data System (ADS)

    Cuevas-Maraver, Jesús; Kevrekidis, Panayotis G.; Saxena, Avadh; Comech, Andrew; Lan, Ruomeng

    2016-05-01

    We explore a prototypical two-dimensional massive model of the nonlinear Dirac type and examine its solitary wave and vortex solutions. In addition to identifying the stationary states, we provide a systematic spectral stability analysis, illustrating the potential of spinor solutions to be neutrally stable in a wide parametric interval of frequencies. Solutions of higher vorticity are generically unstable and split into lower charge vortices in a way that preserves the total vorticity. These conclusions are found not to be restricted to the case of cubic two-dimensional nonlinearities but are found to be extended to the case of quintic nonlinearity, as well as to that of three spatial dimensions. Our results also reveal nontrivial differences with respect to the better understood nonrelativistic analogue of the model, namely the nonlinear Schrödinger equation.

  5. Invariant manifolds and the stability of traveling waves in scalar viscous conservation laws

    NASA Astrophysics Data System (ADS)

    Beck, Margaret; Wayne, C. Eugene

    The stability of traveling wave solutions of scalar viscous conservation laws is investigated by decomposing perturbations into three components: two far-field components and one near-field component. The linear operators associated to the far-field components are the constant coefficient operators determined by the asymptotic spatial limits of the original operator. Scaling variables can be applied to study the evolution of these components, allowing for the construction of invariant manifolds and the determination of their temporal decay rate. The large time evolution of the near-field component is shown to be governed by that of the far-field components, thus giving it the same temporal decay rate. We also give a discussion of the relationship between this geometric approach and previous results, which demonstrate that the decay rate of perturbations can be increased by requiring that initial data lie in appropriate algebraically weighted spaces.

  6. Stability of Solitary Waves and Vortices in a 2D Nonlinear Dirac Model.

    PubMed

    Cuevas-Maraver, Jesús; Kevrekidis, Panayotis G; Saxena, Avadh; Comech, Andrew; Lan, Ruomeng

    2016-05-27

    We explore a prototypical two-dimensional massive model of the nonlinear Dirac type and examine its solitary wave and vortex solutions. In addition to identifying the stationary states, we provide a systematic spectral stability analysis, illustrating the potential of spinor solutions to be neutrally stable in a wide parametric interval of frequencies. Solutions of higher vorticity are generically unstable and split into lower charge vortices in a way that preserves the total vorticity. These conclusions are found not to be restricted to the case of cubic two-dimensional nonlinearities but are found to be extended to the case of quintic nonlinearity, as well as to that of three spatial dimensions. Our results also reveal nontrivial differences with respect to the better understood nonrelativistic analogue of the model, namely the nonlinear Schrödinger equation. PMID:27284659

  7. Study of electric and magnetic field fluctuations from lower hybrid drift instability waves in the terrestrial magnetotail with the fully kinetic, semi-implicit, adaptive multi level multi domain method

    NASA Astrophysics Data System (ADS)

    Innocenti, M. E.; Norgren, C.; Newman, D.; Goldman, M.; Markidis, S.; Lapenta, G.

    2016-05-01

    The newly developed fully kinetic, semi-implicit, adaptive multi-level multi-domain (MLMD) method is used to simulate, at realistic mass ratio, the development of the lower hybrid drift instability (LHDI) in the terrestrial magnetotail over a large wavenumber range and at a low computational cost. The power spectra of the perpendicular electric field and of the fluctuations of the parallel magnetic field are studied at wavenumbers and times that allow to appreciate the onset of the electrostatic and electromagnetic LHDI branches and of the kink instability. The coupling between electric and magnetic field fluctuations observed by Norgren et al. ["Lower hybrid drift waves: Space observations," Phys. Rev. Lett. 109, 055001 (2012)] for high wavenumber LHDI waves in the terrestrial magnetotail is verified. In the MLMD simulations presented, a domain ("coarse grid") is simulated with low resolution. A small fraction of the entire domain is then simulated with higher resolution also ("refined grid") to capture smaller scale, higher frequency processes. Initially, the MLMD method is validated for LHDI simulations. MLMD simulations with different levels of grid refinement are validated against the standard semi-implicit particle in cell simulations of domains corresponding to both the coarse and the refined grid. Precious information regarding the applicability of the MLMD method to turbulence simulations is derived. The power spectra of MLMD simulations done with different levels of refinements are then compared. They consistently show a break in the magnetic field spectra at k⊥di˜30 , with di the ion skin depth and k⊥ the perpendicular wavenumber. The break is observed at early simulated times, Ωcit <6 , with Ωci the ion cyclotron frequency. It is due to the initial decoupling of electric and magnetic field fluctuations at intermediate and low wavenumbers, before the development of the electromagnetic LHDI branch. Evidence of coupling between electric and magnetic

  8. Transient-induced climate drift

    SciTech Connect

    Johansson, A.; Reinhold, B.; Saha, S. )

    1993-05-01

    The climate drift of various quantities associated with deep, planetary-scale, equilibrated, transient Rossby waves are estimated for the Southern Hemisphere extratropical summer as revealed by the DERF II (Dynamical Extended Range Forecasting) dataset. It is found that the vertical structures of these waves systematically become too baroclinic during the course of integration. There are two time scales associated with this climate drift. There is one very short time scale, estimated to be of the order of one day, when the waves become more barotropic. It is followed by a period when the wave baroclinicity monotonically increases, and after roughly 10 days the model structures appear to have reached their statistically equilibrated state. In the meantime, the kinetic energy of the transient waves decreases substantially to roughly half the observed value. After this initial drop, however, the transient kinetic energy increases again, and it is not clear if an equilibrium value has been reached after 30 days, which is the limit of the DERF II dataset. This third time scale is not found in the quantities directly associated with the vertical structures per se, but it is hypothesized to be a consequence of these errors. A theory is utilized that in a simplified way takes into account the processes that determine the vertical structure of baroclinic waves as well as their robustness as a means of understanding the processes leading to these errors. The implications from this theory are that the formulation and magnitude of the dissipative and diffusive processes in the model are the most likely problem, but there are other possibilities. 37 refs., 10 figs.

  9. Stability, Causality, and Shock Waves in the Israel - Theory of Relativistic Dissipative Fluids.

    NASA Astrophysics Data System (ADS)

    Olson, Timothy Scott

    1990-08-01

    The stability, causality, and hyperbolicity properties were analyzed for the Israel-Stewart theory of relativistic dissipative fluids formulated in the energy frame. The equilibria of the theory which are stable for small perturbations were found by constructing a Liapunov functional. The conditions which guarantee that small perturbations about equilibrium will propagate with velocities less than the speed of light and will obey a system of hyperbolic differential equations were determined by calculating the characteristic velocities. It was shown that the stability conditions are equivalent to the causality and hyperbolicity conditions. The behavior of the theory far from equilibrium was studied by considering the plane symmetric motions of an inviscid ultrarelativistic Boltzmann gas. The theory was shown to be hyperbolic for large deviations from equilibrium, and acausality implies instability in this example. The plane steady shock wave solutions were also studied for the Israel-Stewart theory formulated in the Eckart frame. The theory was shown to fail to adequately describe the structure of strong shock waves. Physically acceptable solutions do not exist above a maximum upstream Mach number in any thermally nonconducting and viscous fluid described by the theory because the solutions become multiple-valued when the characteristic velocity is exceeded. It was also proven that physically acceptable solutions do not exist for thermally conducting and viscous fluids above either a maximum upstream Mach number, or else below a minimum downstream Mach number (or both). These limiting Mach numbers again correspond to the characteristic velocities of the fluid. Only extremely weak plane steady shock solutions can be single-valued in the Israel-Stewart theory for the ultrarelativistic Boltzmann gas or for the degenerate free Fermi gas.

  10. Dike/Drift Interactions

    SciTech Connect

    E. Gaffiney

    2004-11-23

    This report presents and documents the model components and analyses that represent potential processes associated with propagation of a magma-filled crack (dike) migrating upward toward the surface, intersection of the dike with repository drifts, flow of magma in the drifts, and post-magma emplacement effects on repository performance. The processes that describe upward migration of a dike and magma flow down the drift are referred to as the dike intrusion submodel. The post-magma emplacement processes are referred to as the post-intrusion submodel. Collectively, these submodels are referred to as a conceptual model for dike/drift interaction. The model components and analyses of the dike/drift interaction conceptual model provide the technical basis for assessing the potential impacts of an igneous intrusion on repository performance, including those features, events, and processes (FEPs) related to dike/drift interaction (Section 6.1).

  11. Structure and stability of wave-theoretic kernels in the ocean.

    PubMed

    Dzieciuch, Matthew A; Cornuelle, Bruce D; Skarsoulis, Emmanuel K

    2013-10-01

    Wave-theoretic modeling can be applied to obtain travel-time sensitivity kernels (TSKs) representing the amount ray travel times are affected by sound-speed variations anywhere in the medium. This work explores the spatial frequency content of the TSK compared to expected ocean variability. It also examines the stability of the TSK in environments that produce strong sensitivity of ray paths to initial conditions. The conclusion is that the linear TSK model is an effective predictor of travel-time changes and that the rays perform nearly as well as the full-wave kernel. The TSK is examined in physical space and in wavenumber space, and it is found that this is the key to understanding how the travel time reacts to ocean perturbations. There are minimum vertical and horizontal length scales of ocean perturbations that are required for the travel time to be affected. The result is that the correspondence between true travel times and those calculated from the kernel is high for large-scale perturbations and somewhat less for the small scales. This demonstrates the validity of ray-based inversion of travel time observations for the cases under study. PMID:24116526

  12. Propagation and stability of quantum dust-ion-acoustic shock waves in planar and nonplanar geometry

    SciTech Connect

    Masood, W.; Siddiq, M.; Nargis, Shahida; Mirza, Arshad M.

    2009-01-15

    Dust-ion-acoustic (DIA) shock waves are studied in an unmagnetized quantum plasma consisting of electrons, ions, and dust by employing the quantum hydrodynamic (QHD) model. In this context, a Korteweg-deVries-Burger (KdVB) equation is derived by employing the small amplitude perturbation expansion method. The dissipation is introduced by taking into account the kinematic viscosity among the plasma constituents. It is found that the strength of the quantum DIA shock wave is maximum for spherical, intermediate for cylindrical, and minimum for the planar geometry. The effects of quantum Bohm potential, dust concentration, and kinematic viscosity on the quantum DIA shock structure are also investigated. The temporal evolution of DIA KdV solitons and Burger shocks are also studied by putting the dissipative and dispersive coefficients equal to zero, respectively. The effects of the quantum Bohm potential on the stability of the DIA shock is also investigated. The present investigation may be beneficial to understand the dissipative and dispersive processes that may occur in the quantum dusty plasmas found in microelectronic devices as well as in astrophysical plasmas.

  13. Modeling the time-dependent water wave stability of human hair.

    PubMed

    Wortmann, F-J; Stapels, M; Chandra, L

    2010-01-01

    The viscoelastic bending recovery of human hair is described by a hydro-rheologically complex, two-phase model, where the humidity dependence of the pertinent parameters as well as the effects of physical aging are known. Model calculations are conducted to assess the consequences of the time- and humidity-dependent bending recovery of human hair for the formation and the stability of the water wave. It is shown that a hair fiber that has been set in bending will achieve at 65% RH a recovery of about 50% after about ten times its storage time prior to release, if it is a non-aging material. However, aging drastically slows the recovery process so that it approaches an apparent "equilibrium," final recovery value of about 60%. The values of final recovery decrease linearly with water content, vanishing as expected at maximum water content, where the hair fiber is above its glass transition. The calculations further show that damage to the elastic modulus, attributed to the intermediate filaments, is expected to reduce recovery and thus enhance fiber set. The calculations demonstrate that it is in fact the phenomenon of physical aging that makes water waving a feasible and practically successful process for hair styling. PMID:20211115

  14. Stability of the train of N solitary waves for the two-component Camassa-Holm shallow water system

    NASA Astrophysics Data System (ADS)

    Liu, Xingxing

    2016-06-01

    Considered herein is the integrable two-component Camassa-Holm shallow water system derived in the context of shallow water theory, which admits blow-up solutions and the solitary waves interacting like solitons. Using modulation theory, and combining the almost monotonicity of a local version of energy with the argument on the stability of a single solitary wave, we prove that the train of N solitary waves, which are sufficiently decoupled, is orbitally stable in the energy space H1 (R) ×L2 (R).

  15. Avoiding Tokamak Disruptions by Applying Static Magnetic Fields That Align Locked Modes with Stabilizing Wave-Driven Currents.

    PubMed

    Volpe, F A; Hyatt, A; La Haye, R J; Lanctot, M J; Lohr, J; Prater, R; Strait, E J; Welander, A

    2015-10-23

    Nonrotating ("locked") magnetic islands often lead to complete losses of confinement in tokamak plasmas, called major disruptions. Here locked islands were suppressed for the first time, by a combination of applied three-dimensional magnetic fields and injected millimeter waves. The applied fields were used to control the phase of locking and so align the island O point with the region where the injected waves generated noninductive currents. This resulted in stabilization of the locked island, disruption avoidance, recovery of high confinement, and high pressure, in accordance with the expected dependencies upon wave power and relative phase between the O point and driven current. PMID:26551119

  16. The stability of the dust acoustic waves under transverse perturbations in a magnetized and collisionless dusty plasma

    NASA Astrophysics Data System (ADS)

    Gao, Dong-Ning; Qi, Xin; Hong, Xue-Ren; Yang, Xue; Duan, Wen-Shan; Yang, Lei; Yang

    2014-06-01

    Numerical and theoretical investigations are carried out for the stability of the dust acoustic waves (DAWs) under the transverse perturbation in a two-ion temperature magnetized and collisionless dusty plasma. The Zakharov-Kuznetsov (ZK) equation, modified ZK equation, and Extended ZK (EZK) equation of the DAWs are given by using the reductive perturbation technique. The cut-off frequency is obtained by applying higher-order transverse perturbations to the soliton solution of the EZK equation. The propagation velocity of solitary waves, the real cut-off frequency, as well as the growth rate of the higher-order perturbation to the solitary wave are obtained.

  17. Avoiding Tokamak Disruptions by Applying Static Magnetic Fields That Align Locked Modes with Stabilizing Wave-Driven Currents

    NASA Astrophysics Data System (ADS)

    Volpe, F. A.; Hyatt, A.; La Haye, R. J.; Lanctot, M. J.; Lohr, J.; Prater, R.; Strait, E. J.; Welander, A.

    2015-10-01

    Nonrotating ("locked") magnetic islands often lead to complete losses of confinement in tokamak plasmas, called major disruptions. Here locked islands were suppressed for the first time, by a combination of applied three-dimensional magnetic fields and injected millimeter waves. The applied fields were used to control the phase of locking and so align the island O point with the region where the injected waves generated noninductive currents. This resulted in stabilization of the locked island, disruption avoidance, recovery of high confinement, and high pressure, in accordance with the expected dependencies upon wave power and relative phase between the O point and driven current.

  18. THERMAL TEST ALCOVE HEATED DRIFT GROUND SUPPORT ANALYSIS

    SciTech Connect

    S. Bonabian

    1996-10-03

    The main purpose and objective of this analysis is to analyze the stability of the Thermal Test Facility Heated Drift and to design a ground support system. The stability of the Heated Drift is analyzed considering in situ, seismic, and thermal loading conditions. A ground support system is recommended to provide a stable opening for the Heated Drift. This report summarizes the results of the analyses and provides the details of the recommended ground support system for the Heated Drift. The details of the ground support system are then incorporated into the design output documents for implementation in the field.

  19. Effect of anisotropic dust pressure and superthermal electrons on propagation and stability of dust acoustic solitary waves

    SciTech Connect

    Bashir, M. F.; Behery, E. E.; El-Taibany, W. F.

    2015-06-15

    Employing the reductive perturbation technique, Zakharov–Kuznetzov (ZK) equation is derived for dust acoustic (DA) solitary waves in a magnetized plasma which consists the effects of dust anisotropic pressure, arbitrary charged dust particles, Boltzmann distributed ions, and Kappa distributed superthermal electrons. The ZK solitary wave solution is obtained. Using the small-k expansion method, the stability analysis for DA solitary waves is also discussed. The effects of the dust pressure anisotropy and the electron superthermality on the basic characteristics of DA waves as well as on the three-dimensional instability criterion are highlighted. It is found that the DA solitary wave is rarefactive (compressive) for negative (positive) dust. In addition, the growth rate of instability increases rapidly as the superthermal spectral index of electrons increases with either positive or negative dust grains. A brief discussion for possible applications is included.

  20. Dike/Drift Interactions

    SciTech Connect

    E.S. Gaffney

    2003-10-08

    This report documents the model of events associated with a potential intrusion of magma from a volcanic dike into a drift or drifts in the Yucca Mountain Nuclear Waste Repository. The following topics are included in this report: (1) A discussion of dike propagation, which provides the basis for describing the path that a representative dike, or swarm of dikes, would follow during an event. (2) A discussion of magma flow, which evaluates the interaction at the junction of the propagating dike with the drift and the movement of magmatic products into and down drifts and, potentially, through a drift to the surface by way of access drift or a secondary dike opened up along the drift. (3) A discussion of gas flow and conductive cooling of a magma-filled drift, describing how an adjacent drift that has not been intersected by a dike could be affected by post-intrusion phenomena. Note that a gas flow analysis is also addressed in ''Igneous Intrusion Impacts on Waste Form and Waste Packages'' (BSC 2003 [DIRS 161810]), and those results are consistent with the results presented in this report.

  1. Free Drifting Buoys

    NASA Technical Reports Server (NTRS)

    1974-01-01

    Information was exchanged between people directly involved with the development, use, and/or potential use of free drifting buoys. Tracking systems and techniques, where methods and accuracy of optical, radio, radar, satellite, and sonic tracking of free-drifting buoys were discussed. Deployment and retrieval covering methods currently used or planned in the deployment and retrieval of free-drifting buoys from boats, ships, helicopters, fixed platforms, and fixed-wing aircraft were reported. Simulation, sensors, and data emphasizing the status of water circulation modeling, and sensors useful on free-drifting buoys, and data display and analysis were described.

  2. Hypersonic drift-tearing magnetic islands in tokamak plasmas

    SciTech Connect

    Fitzpatrick, R.; Waelbroeck, F. L.

    2007-12-15

    A two-fluid theory of long wavelength, hypersonic, drift-tearing magnetic islands in low-collisionality, low-{beta} plasmas possessing relatively weak magnetic shear is developed. The model assumes both slab geometry and cold ions, and neglects electron temperature and equilibrium current gradient effects. The problem is solved in three asymptotically matched regions. The 'inner region' contains the island. However, the island emits electrostatic drift-acoustic waves that propagate into the surrounding 'intermediate region', where they are absorbed by the plasma. Since the waves carry momentum, the inner region exerts a net force on the intermediate region, and vice versa, giving rise to strong velocity shear in the region immediately surrounding the island. The intermediate region is matched to the surrounding 'outer region', in which ideal magnetohydrodynamic holds. Isolated hypersonic islands propagate with a velocity that lies between those of the unperturbed local ion and electron fluids, but is much closer to the latter. The ion polarization current is stabilizing, and increases with increasing island width. Finally, the hypersonic branch of isolated island solutions ceases to exist above a certain critical island width. Hypersonic islands whose widths exceed the critical width are hypothesized to bifurcate to the so-called 'sonic' solution branch.

  3. Inhibition of intercellular coupling stabilizes spiral-wave reentry, whereas enhancement of the coupling destabilizes the reentry in favor of early termination.

    PubMed

    Takemoto, Yoshio; Takanari, Hiroki; Honjo, Haruo; Ueda, Norihiro; Harada, Masahide; Kato, Sara; Yamazaki, Masatoshi; Sakuma, Ichiro; Opthof, Tobias; Kodama, Itsuo; Kamiya, Kaichiro

    2012-09-01

    Spiral-wave (SW) reentry is a major organizing principle of ventricular tachycardia/fibrillation (VT/VF). We tested a hypothesis that pharmacological modification of gap junction (GJ) conductance affects the stability of SW reentry in a two-dimensional (2D) epicardial ventricular muscle layer prepared by endocardial cryoablation of Langendorff-perfused rabbit hearts. Action potential signals were recorded and analyzed by high-resolution optical mapping. Carbenoxolone (CBX; 30 μM) and rotigaptide (RG, 0.1 μM) were used to inhibit and enhance GJ coupling, respectively. CBX decreased the space constant (λ) by 36%, whereas RG increased it by 22-24% (n = 5; P < 0.01). During centrifugal propagation, there was a linear relationship between the wavefront curvature (κ) and local conduction velocity (LCV): LCV = LCV(0) - D·κ (D, diffusion coefficient; LCV(0), LCV at κ = 0). CBX decreased LCV(0) and D by 27 ± 3 and 57 ± 3%, respectively (n = 5; P < 0.01). RG increased LCV(0) and D by 18 ± 3 and 54 ± 5%, respectively (n = 5, P < 0.01). The regression lines with and without RG crossed, resulting in a paradoxical decrease of LCV with RG at κ > ~60 cm(-1). SW reentry induced after CBX was stable, and the incidence of sustained VTs (>30 s) increased from 38 ± 4 to 85 ± 4% after CBX (n = 18; P < 0.01). SW reentry induced after RG was characterized by decremental conduction near the rotation center, prominent drift and self-termination by collision with the anatomical boundaries, and the incidence of sustained VTs decreased from 40 ± 5 to 17 ± 6% after RG (n = 13; P < 0.05). These results suggest that decreased intercellular coupling stabilizes SW reentry in 2D cardiac muscle, whereas increased coupling facilitates its early self-termination. PMID:22707561

  4. A combined wave distribution function and stability analysis of Viking particle and low-frequency wave data

    SciTech Connect

    Oscarsson, T.E.; Roennmark, K.G. )

    1990-12-01

    In this paper the authors present an investigation of low-frequency waves observed on auroral field lines below the acceleration region by the Swedish satellite Viking. The measured frequency spectra are peaked at half the local proton gyrofrequency, and the waves are observed in close connection with precipitating electrons. In order to obtain information about the distribution of wave energy in wave vector space, they reconstruct the wave distribution function (WDF) from observed spectral densities. They use a new scheme that allows them to reconstruct simultaneously the WDF over a broad frequency band. The method also makes it possible to take into account available particle observations as well as Doppler shifts caused by the relative motion between the plasma and the satellite. The distribution of energy in wave vector space suggested by the reconstructed WDF is found to be consistent with what is expected from a plasma instability driven by the observed precipitating electrons. Furthermore, by using UV images obtained on Viking, they demonstrate that the wave propagation directions indicated by the reconstructed WDFs are consistent with a simple model of the presumed wave source in the electron precipitation region.

  5. Personality Types in Adolescence: Change and Stability and Links with Adjustment and Relationships--A Five-Wave Longitudinal Study

    ERIC Educational Resources Information Center

    Meeus, Wim; Van de Schoot, Rens; Klimstra, Theo; Branje, Susan

    2011-01-01

    We examined change and stability of the 3 personality types identified by Block and Block (1980) and studied their links with adjustment and relationships. We used data from a 5-wave study of 923 early-to-middle and 390 middle-to-late adolescents, thereby covering the ages of 12-20 years. In Study 1, systematic evidence for personality change was…

  6. Stability analysis of a tidally excited internal gravity wave near the centre of a solar-type star

    NASA Astrophysics Data System (ADS)

    Barker, Adrian J.; Ogilvie, Gordon I.

    2011-10-01

    We perform a stability analysis of a tidally excited non-linear internal gravity wave near the centre of a solar-type star in two-dimensional cylindrical geometry. The motivation is to understand the tidal interaction between short-period planets and their slowly rotating solar-type host stars, which involves the launching of internal gravity waves at the top of the radiation zone that propagate towards the centre of the star. Studying the instabilities of these waves near the centre, where non-linearities are most important, is essential, since it may have implications for the survival of short-period planets orbiting solar-type stars. When these waves have sufficient amplitude to overturn the stratification, they break and form a critical layer, which efficiently absorbs subsequent ingoing wave angular momentum, and can result in the planet spiralling into the star. However, in previous simulations the waves have not been observed to undergo instability for smaller amplitudes. Here we perform a stability analysis of a non-linear standing internal gravity wave in the central regions of a solar-type star. This work has two aims: to determine any instabilities that set in for small-amplitude waves, and to further understand the breaking process for large-amplitude waves that overturn the stratification. Our results are compared with the stability of a plane internal gravity wave in a uniform stratification, and with previous work by Kumar & Goodman on a similar problem to our own. Our main result is that the waves undergo parametric instabilities for any amplitude (in the absence of viscosity and thermal conduction). However, because the non-linearity is spatially localized in the innermost wavelengths, the growth rates of these instabilities tend to be sufficiently small that they do not result in astrophysically important tidal dissipation. Indeed, we estimate that the modified tidal quality factors of the star that result are Q'★≳ 107, and possibly much

  7. Nonlinear stability of periodic traveling wave solutions of systems of viscous conservation laws in the generic case

    NASA Astrophysics Data System (ADS)

    Johnson, Mathew A.; Zumbrun, Kevin

    Extending previous results of Oh-Zumbrun and Johnson-Zumbrun, we show that spectral stability implies linearized and nonlinear stability of spatially periodic traveling wave solutions of viscous systems of conservation laws for systems of generic type, removing a restrictive assumption that wave speed be constant to first order along the manifold of nearby periodic solutions. Key to our analysis is a nonlinear cancellation estimate observed by Johnson and Zumbrun, along with a detailed understanding of the Whitham averaged system. The latter motivates a careful analysis of the Bloch perturbation expansion near zero frequency and suggests factoring out an appropriate translational modulation of the underlying wave, allowing us to derive the sharpened low-frequency estimates needed to close the nonlinear iteration arguments.

  8. Booktalking: Avoiding Summer Drift

    ERIC Educational Resources Information Center

    Whittingham, Jeff; Rickman, Wendy A.

    2015-01-01

    Summer drift, otherwise known as loss of reading comprehension skills or reading achievement, has been a well-known and well-documented phenomenon of public education for decades. Studies from the late twentieth century to the present have demonstrated a slowdown in summer drift attributed to specific summer reading programs addressing motivation…

  9. On the Stability of Wave Disturbances in Non-Pressure Round-Cylindrical Channels

    NASA Astrophysics Data System (ADS)

    Gagoshidze, Shalva

    2015-04-01

    In hydraulic engineering practice, is well know of and take into account the fact that for a nearly fully filled gravity-flow tunnel with a circular cross section the water flows with shocks, i.e. unstable. Such a phenomenon also occurs when emptying a bottle, but no mathematical confirmation has so far been found for it. In the paper, the estimate of the flow stability is obtained for two limiting cases: - when the channel of circular cross-section is nearly fully filled with water and when it is nearly empty, i.e. the water flow in the channel has a small depth as compared with the radius of the water conduit. Wave equations written in a cylindrical system of coordinates x,r,θ where the x- axis coincides with the axis of the channel; r is the radius vector, θ is the angle counted off from the equatorial plane of the channel upward (with sign "+') and downward (with sign "-') are simplified by neglecting the change of the polar angle (π 2 -θ)in limit of a small width of the free surface of the flow. As a result of this simplification the Helmholtz equation for the wave potential reduces to a Bessel equation with respect to the function ψ(r) not depending on the angle θ and its asymptotic solution will be expressed by the relation ° -- R0 ψ(r) = C -r-cosh k(R0 - r). (1) Dispersion relations will take the form σ = kU0 ± i°gk-tanh-k(R0--h) (2) - for channels with nearly full filling, and ° -------- σ = kU0 ± gktanhk(R0 - h) (3) - for round-cylindrical channels with a small water depth. In these relations, R0 is the radius of the channel, U0 is the stationary water flow velocity, i is the imaginary unit, h is the distance between the horizontal axis and the water level in the channel, σ is the wave disturbance frequency, k is the wave number, C is an arbitrary constant. In the first case, the relation (2) indicates the occurrence of Helmholtz instability of wave disturbances independently of a velocity value of stationary water flow. This result fully

  10. Two-dimensional s-polarized solitary waves in plasmas. II. Stability, collisions, electromagnetic bursts, and post-soliton evolution

    SciTech Connect

    Sanchez-Arriaga, G.; Lefebvre, E.

    2011-09-15

    The dynamics of two-dimensional s-polarized solitary waves is investigated with the aid of particle-in-cell (PIC) simulations. Instead of the usual excitation of the waves with a laser pulse, the PIC code was directly initialized with the numerical solutions from the fluid plasma model. This technique allows the analysis of different scenarios including the theoretical problems of the solitary wave stability and their collision as well as features already measured during laser-plasma experiments such as the emission of electromagnetic bursts when the waves reach the plasma-vacuum interface, or their expansion on the ion time scale, usually named post-soliton evolution. Waves with a single density depression are stable whereas multihump solutions decay to several waves. Contrary to solitons, two waves always interact through a force that depends on their relative phases, their amplitudes, and the distance between them. On the other hand, the radiation pattern at the plasma-vacuum interface was characterized, and the evolution of the diameter of different waves was computed and compared with the ''snow plow'' model.

  11. Two-dimensional s-polarized solitary waves in plasmas. II. Stability, collisions, electromagnetic bursts, and post-soliton evolution.

    PubMed

    Sánchez-Arriaga, G; Lefebvre, E

    2011-09-01

    The dynamics of two-dimensional s-polarized solitary waves is investigated with the aid of particle-in-cell (PIC) simulations. Instead of the usual excitation of the waves with a laser pulse, the PIC code was directly initialized with the numerical solutions from the fluid plasma model. This technique allows the analysis of different scenarios including the theoretical problems of the solitary wave stability and their collision as well as features already measured during laser-plasma experiments such as the emission of electromagnetic bursts when the waves reach the plasma-vacuum interface, or their expansion on the ion time scale, usually named post-soliton evolution. Waves with a single density depression are stable whereas multihump solutions decay to several waves. Contrary to solitons, two waves always interact through a force that depends on their relative phases, their amplitudes, and the distance between them. On the other hand, the radiation pattern at the plasma-vacuum interface was characterized, and the evolution of the diameter of different waves was computed and compared with the "snow plow" model. PMID:22060510

  12. Abstraction of Drift Seepage

    SciTech Connect

    J.T. Birkholzer

    2004-11-01

    This model report documents the abstraction of drift seepage, conducted to provide seepage-relevant parameters and their probability distributions for use in Total System Performance Assessment for License Application (TSPA-LA). Drift seepage refers to the flow of liquid water into waste emplacement drifts. Water that seeps into drifts may contact waste packages and potentially mobilize radionuclides, and may result in advective transport of radionuclides through breached waste packages [''Risk Information to Support Prioritization of Performance Assessment Models'' (BSC 2003 [DIRS 168796], Section 3.3.2)]. The unsaturated rock layers overlying and hosting the repository form a natural barrier that reduces the amount of water entering emplacement drifts by natural subsurface processes. For example, drift seepage is limited by the capillary barrier forming at the drift crown, which decreases or even eliminates water flow from the unsaturated fractured rock into the drift. During the first few hundred years after waste emplacement, when above-boiling rock temperatures will develop as a result of heat generated by the decay of the radioactive waste, vaporization of percolation water is an additional factor limiting seepage. Estimating the effectiveness of these natural barrier capabilities and predicting the amount of seepage into drifts is an important aspect of assessing the performance of the repository. The TSPA-LA therefore includes a seepage component that calculates the amount of seepage into drifts [''Total System Performance Assessment (TSPA) Model/Analysis for the License Application'' (BSC 2004 [DIRS 168504], Section 6.3.3.1)]. The TSPA-LA calculation is performed with a probabilistic approach that accounts for the spatial and temporal variability and inherent uncertainty of seepage-relevant properties and processes. Results are used for subsequent TSPA-LA components that may handle, for example, waste package corrosion or radionuclide transport.

  13. Flight and Stability of a Laser Inertial Fusion Energy Target in the Drift Region between Injection and the Reaction Chamber with Computational Fluid Dynamics

    SciTech Connect

    Mitori, T.

    2013-12-01

    A Laser Inertial Fusion Energy (LIFE) target’s flight through a low Reynolds number and high Mach number regime was analyzed with computational fluid dynamics software. This regime consisted of xenon gas at 1,050 K and approximately 6,670 Pa. Simulations with similar flow conditions were performed with a sphere and compared with experimental data and published correlations for validation purposes. Transient considerations of the developing flow around the target were explored. Simulations of the target at different velocities were used to determine correlations for the drag coefficient and Nusselt number as functions of the Reynolds number. Simulations with different angles of attack were used to determine the aerodynamic coefficients of drag, lift, Magnus moment, and overturning moment as well as target stability. The drag force, lift force, and overturning moment changed minimally with spin. Above an angle of attack of 15°, the overturning moment would be destabilizing. At low angles of attack (less than 15°), the overturning moment would tend to decrease the target’s angle of attack, indicating the lack of a need for spin for stability at small angles. This stabilizing moment would cause the target to move in a mildly damped oscillation about the axis parallel to the free-stream velocity vector through the target’s center of gravity.

  14. Linear and nonlinear stability of hydrothermal waves in planar liquid layers driven by thermocapillarity

    NASA Astrophysics Data System (ADS)

    Sáenz, P. J.; Valluri, P.; Sefiane, K.; Karapetsas, G.; Matar, O. K.

    2013-09-01

    A shallow planar layer of liquid bounded from above by gas is set into motion via the thermocapillary effect resulting from a thermal gradient applied along its interface. Depending on the physical properties of the liquid and the strength of the gradient, the system is prone to departure from its equilibrium state and to the consequent development of an oscillatory regime. This problem is numerically investigated for the first time by means of two-phase direct numerical simulations fully taking into account the presence of a deformable interface. Obliquely travelling hydrothermal waves (HTWs), similar to those first described by Smith and Davis [J. Fluid Mech. 132, 119-144 (1983)], 10.1017/S0022112083001512, are reported presenting good agreement with linear stability theory and experiments. The nonlinear spatiotemporal growth of the instabilities is discussed extensively along with the final bulk flow for both the liquid and gas phases. Our study reveals the presence of interface deformations which accompany the HTWs pattern with a certain time-delay. The local interface heat fluxes are found to be significantly affected by the transient nature of the HTWs, contradicting the results of previous single-phase studies.

  15. High frequency stability oscillator for surface acoustic wave-based gas sensor

    NASA Astrophysics Data System (ADS)

    Wang, Wen; He, Shitang; Li, Shunzhou; Pan, Yong

    2006-12-01

    This paper presents a 158 MHz surface acoustic wave (SAW) oscillator used for a gas sensor. As the oscillator element, a SAW delay line on ST-X quartz substrate with low insertion loss (<8 dB) and single mode selection capability was developed. Low insertion loss was achieved by an electrode width control single phase unidirectional transducer (EWC/SPUDT) configuration. Single mode selection was simply accomplished by a comb transducer which is a means of combining the frequency selectivity of two interdigital transducers (IDTs). Coupling of modes (COM) simulation was performed to predict device performance prior to fabrication. The measured frequency response S12 showed a good agreement with simulated results. The effect of the oscillator circuit system temperature shift upon frequency stability was observed in detail. The experimental results showed that the baseline noise was typically up to ~0.7 × 10-7 in a laboratory environment with temperature control. The oscillator was successfully applied to a gas sensor coated self-assembled composite monolayer as a sensor material for dimethyl-methyl-phosphonate (DMMP). The sensitivity for low DMMP concentration detection was evaluated as ~25 Hz mg-1 m-3, and the threshold detection limit was up to 0.5 mg m-3.

  16. Bifurcation and Stability of the Traveling-Wave Convection in a Binary Fluid Mixture

    NASA Astrophysics Data System (ADS)

    Yahata, Hideo

    2002-08-01

    The Rayleigh-Bénard convection of a binary fluid mixture in a horizontal layer is considered for a moderate negative value of the separation ratio S for which the spatio-temporal structure of fully-developed periodic convection rolls is known to take either the stationary overturning convection (SOC) or the traveling-wave (TW) convection state depending on the values of the Rayleigh number. Numerical solutions for the SOC and the TW states are computed using the 2D MAC and the 2D spectral simulations of the governing equations of motion in the finite difference and the Galerkin form respectively. In addition to these, a method for finding their solutions as the steady-state problem of the Galerkin system using the Newton iterative method is presented and the computed results are compared with those obtained previously by others. Linear stability analysis of the linearized dynamical system shows that the transition between the SOC and TW states is involved by the real-mode instability.

  17. Dodging the Drifts

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This image taken by NASA's Mars Exploration Rover Opportunity is a portion of a mosaic acquired by the panoramic camera. The picture highlights the light-toned outcrop on the rim of 'Erebus Crater' and large, dark, wind-deposited drifts that have filled the center of the crater. Opportunity took this image on the rover's 608th sol (Oct. 9, 2005). The rover is driving west, avoiding the large drifts and crossing the low ripples and outcrop to the right. After traversing to the north of the large drift on the horizon (near the center of the image), Opportunity will drive south to the western rim of the crater.

  18. A Challenging Solar Eruptive Event of 18 November 2003 and the Causes of the 20 November Geomagnetic Superstorm. II. CMEs, Shock Waves, and Drifting Radio Bursts

    NASA Astrophysics Data System (ADS)

    Grechnev, V. V.; Uralov, A. M.; Chertok, I. M.; Slemzin, V. A.; Filippov, B. P.; Egorov, Y. I.; Fainshtein, V. G.; Afanasyev, A. N.; Prestage, N. P.; Temmer, M.

    2014-04-01

    We continue our study (Grechnev et al., 2013, doi:10.1007/s11207-013-0316-6; Paper I) on the 18 November 2003 geoffective event. To understand possible impact on geospace of coronal transients observed on that day, we investigated their properties from solar near-surface manifestations in extreme ultraviolet, LASCO white-light images, and dynamic radio spectra. We reconcile near-surface activity with the expansion of coronal mass ejections (CMEs) and determine their orientation relative to the earthward direction. The kinematic measurements, dynamic radio spectra, and microwave and X-ray light curves all contribute to the overall picture of the complex event and confirm an additional eruption at 08:07 - 08:20 UT close to the solar disk center presumed in Paper I. Unusual characteristics of the ejection appear to match those expected for a source of the 20 November superstorm but make its detection in LASCO images hopeless. On the other hand, none of the CMEs observed by LASCO seem to be a promising candidate for a source of the superstorm being able to produce, at most, a glancing blow on the Earth's magnetosphere. Our analysis confirms free propagation of shock waves revealed in the event and reconciles their kinematics with "EUV waves" and dynamic radio spectra up to decameters.

  19. Stability Dust-Ion-Acoustic Wave In Dusty Plasmas With Stream -Influence Of Charge Fluctuation Of Dust Grains

    SciTech Connect

    Atamaniuk, Barbara; Zuchowski, Krzysztof

    2006-01-15

    There is a quickly increasing wealth of experimental data on so-called dusty plasmas i. e. ionized gases or usual plasmas that contain micron sized charged particles. Interest in these structures is driven both by their importance in many astrophysical as well as commercial situations. Among them are linear and nonlinear wave phenomena. We consider the influence of dust charge fluctuations on stability of the ion-acoustic waves when the stream of particles is present. It is assumed that all grains of dust have equal masses but charges are not constant in time-they may fluctuate in time. The dust charges are not really independent of the variations of the plasma potentials. All modes will influence the charging mechanism, and feedback will lead to several new interesting and unexpected phenomena. The charging of the grains depends on local plasma characteristics. If the waves disturb these characteristic, then charging of the grains is affected and the grain charge is modified, with a resulting feedback on the wave mode. In case considering here, when temperature of electrons is much greater then the temperature of the ions and temperature of electrons is not great enough for further ionization of the ions, we show that stability of the acoustic wave depends only one phenomenological coefficient.

  20. Asymptotic Stability of Rarefaction Wave for the Navier-Stokes Equations for a Compressible Fluid in the Half Space

    NASA Astrophysics Data System (ADS)

    Kawashima, Shuichi; Zhu, Peicheng

    2009-10-01

    This paper is concerned with the asymptotic stability towards a rarefaction wave of the solution to an outflow problem for the Navier-Stokes equations in a compressible fluid in the Eulerian coordinate in the half space. This is the second one of our series of papers on this subject. In this paper, firstly we classify completely the time-asymptotic states, according to some parameters, that is the spatial-asymptotic states and boundary conditions, for this initial boundary value problem, and some pictures for the classification of time-asymptotic states are drawn in the state space. In order to prove the stability of the rarefaction wave, we use the solution to Burgers’ equation to construct a suitably smooth approximation of the rarefaction wave and establish some time-decay estimates in L p -norm for the smoothed rarefaction wave. We then employ the L 2-energy method to prove that the rarefaction wave is non-linearly stable under a small perturbation, as time goes to infinity.

  1. Stability and accuracy analysis of some fully-discrete algorithms for the one-dimensional second-order wave equation

    NASA Technical Reports Server (NTRS)

    Hughes, T. J. R.; Tezduyar, T. E.

    1984-01-01

    The present investigation is concerned with some basic results for a predictor-multicorrector algorithm applied to the one-dimensional wave equation, giving particular attention to so-called 2-pass explicit schemes in which both lumped and coupled mass matrices are employed. In an assessment of the accuracy and stability properties of the algorithms, use is made of the one-dimensional, second-order wave equation. The maximum stable time step of the lumped right-hand-side mass, 2-pass explicit algorithm is twice that of the 1-pass explicit algorithm. Improved accuracy is obtained by employing higher-order, or consistent, right-hand-side, mass.

  2. Stability of Microturbulent Drift Modes during Internal Transport Barrier Formation in the Alcator C-Mod Radio Frequency Heated H-mode

    SciTech Connect

    M.H. Redi; C.L. Fiore; W. Dorland; D.R. Mikkelsen; G. Rewoldt; P.T. Bonoli; D.R. Ernst; J.E. Rice; S.J. Wukitch

    2003-11-20

    Recent H-mode experiments on Alcator C-Mod [I.H. Hutchinson, et al., Phys. Plasmas 1 (1994) 1511] which exhibit an internal transport barrier (ITB), have been examined with flux tube geometry gyrokinetic simulations, using the massively parallel code GS2 [M. Kotschenreuther, G. Rewoldt, and W.M. Tang, Comput. Phys. Commun. 88 (1995) 128]. The simulations support the picture of ion/electron temperature gradient (ITG/ETG) microturbulence driving high xi/ xe and that suppressed ITG causes reduced particle transport and improved ci on C-Mod. Nonlinear calculations for C-Mod confirm initial linear simulations, which predicted ITG stability in the barrier region just before ITB formation, without invoking E x B shear suppression of turbulence. Nonlinear fluxes are compared to experiment, which both show low heat transport in the ITB and higher transport within and outside of the barrier region.

  3. Lithium drifted germanium system

    NASA Technical Reports Server (NTRS)

    Fjarlie, E. J.

    1969-01-01

    General characteristics of the lithium-drifted germanium photodiode-Dewar-preamplifier system and particular operating instructions for the device are given. Information is included on solving operational problems.

  4. A mesoscale gravity-wave event observed during CCOPE. IV - Stability analysis and Doppler-derived wave vertical structure

    NASA Technical Reports Server (NTRS)

    Koch, Steven E.; Einaudi, F.; Dorian, Paul B.; Lang, Stephen; Heymsfield, Gerald M.

    1993-01-01

    A summary of the results of a detailed study of the vertical structure of mesoscale gravity waves conducted during the Cooperative Convective Precipitation Experiment (CCOPE) is presented. Pressure perturbation fields derived from the Doppler wind fields are compared with the vertical structure of eigenfunctions resulting from a solution to the Taylor-Goldstein linear wave equation for an atmosphere whose mean state is described by vertical profiles obtained from a representative CCOPE sounding. An analysis of the potential for shear instability is also performed on all of the soundings taken on this day to assess the representativeness of the one chosen for the linear theoretical analysis.

  5. Investigations of SPS Orbit Drifts

    SciTech Connect

    Drøsdal, Lene; Bracco, Chiara; Cornelis, Karel; Goddard, Brennan; Kain, Verena; Meddahi, Malika; Wenninger, Jorg; Gianfelice-Wendt, Eliana

    2014-07-01

    The LHC is filled from the last pre-injector, the Super Proton Synchrotron (SPS), via two 3 km long transfer lines, TI 2 and TI 8. Over the LHC injection processes, a drift of the beam trajectories has been observed in TI 2 and TI 8, requiring regular correction of the trajectories, in order to ensure clean injection into the LHC. Investigations of the trajectory variations in the transfer lines showed that the main source of short term trajectory drifts are current variations of the SPS extraction septa (MSE). The stability of the power converters has been improved, but the variations are still present and further improvements are being investigated. The stability over a longer period of time cannot be explained by this source alone. The analysis of trajectory variations shows that there are also slow variations in the SPS closed orbit at extraction. A set of SPS orbit measurements has been saved and analysed. These observations will be used together with simulations and observed field errors to locate the second source of variations.

  6. Gravity jitter effected slosh waves and the stability of a rotating bubble under microgravity

    NASA Technical Reports Server (NTRS)

    Hung, R. J.; Lee, C. C.; Leslie, F. W.

    1991-01-01

    The instability of liquid and gas interface can be induced by the pressure of longitudinal and lateral accelerations, vehicle vibration, and rotational fields of spacecraft in a microgravity environment. Characteristics of slosh waves excited by the restoring force field of gravity jitters have been investigated. Results show that lower frequency gravity jitters excite slosh wave with higher ratio of maximum amplitude to wave length than that of the slosh waves generated by the higher frequency gravity jitters.

  7. Effects of Fault Displacement on Emplacement Drifts

    SciTech Connect

    F. Duan

    2000-04-25

    The purpose of this analysis is to evaluate potential effects of fault displacement on emplacement drifts, including drip shields and waste packages emplaced in emplacement drifts. The output from this analysis not only provides data for the evaluation of long-term drift stability but also supports the Engineered Barrier System (EBS) process model report (PMR) and Disruptive Events Report currently under development. The primary scope of this analysis includes (1) examining fault displacement effects in terms of induced stresses and displacements in the rock mass surrounding an emplacement drift and (2 ) predicting fault displacement effects on the drip shield and waste package. The magnitude of the fault displacement analyzed in this analysis bounds the mean fault displacement corresponding to an annual frequency of exceedance of 10{sup -5} adopted for the preclosure period of the repository and also supports the postclosure performance assessment. This analysis is performed following the development plan prepared for analyzing effects of fault displacement on emplacement drifts (CRWMS M&O 2000). The analysis will begin with the identification and preparation of requirements, criteria, and inputs. A literature survey on accommodating fault displacements encountered in underground structures such as buried oil and gas pipelines will be conducted. For a given fault displacement, the least favorable scenario in term of the spatial relation of a fault to an emplacement drift is chosen, and the analysis is then performed analytically. Based on the analysis results, conclusions are made regarding the effects and consequences of fault displacement on emplacement drifts. Specifically, the analysis will discuss loads which can be induced by fault displacement on emplacement drifts, drip shield and/or waste packages during the time period of postclosure.

  8. Deterministic drift instability and stochastic thermal perturbations of magnetic dissipative droplet solitons

    NASA Astrophysics Data System (ADS)

    Wills, P.; Iacocca, E.; Hoefer, M. A.

    2016-04-01

    The magnetic dissipative droplet is a strongly nonlinear wave structure that can be stabilized in a thin film ferromagnet exhibiting perpendicular magnetic anisotropy by use of spin transfer torque. These structures have been observed experimentally at room temperature, showcasing their robustness against noise. Here, we quantify the effects of thermal noise by deriving stochastic equations of motion for a droplet based on soliton perturbation theory. First, it is found that deterministic droplets are linearly unstable at large bias currents, subject to a drift instability. When the droplet is linearly stable, our framework allows us to analytically compute the droplet's generation linewidth and center variance. Additionally, we study the influence of nonlocal and Oersted fields with micromagnetic simulations, providing insight into their effect on the generation linewidth. These results motivate detailed experiments on the current and temperature-dependent linewidth as well as drift instability statistics of droplets, which are important figures-of-merit in the prospect of droplet-based applications.

  9. Stability of dust ion acoustic solitary waves in a collisionless unmagnetized nonthermal plasma in presence of isothermal positrons

    NASA Astrophysics Data System (ADS)

    Sardar, Sankirtan; Bandyopadhyay, Anup; Das, K. P.

    2016-07-01

    A three-dimensional KP (Kadomtsev Petviashvili) equation is derived here describing the propagation of weakly nonlinear and weakly dispersive dust ion acoustic wave in a collisionless unmagnetized plasma consisting of warm adiabatic ions, static negatively charged dust grains, nonthermal electrons, and isothermal positrons. When the coefficient of the nonlinear term of the KP-equation vanishes an appropriate modified KP (MKP) equation describing the propagation of dust ion acoustic wave is derived. Again when the coefficient of the nonlinear term of this MKP equation vanishes, a further modified KP equation is derived. Finally, the stability of the solitary wave solutions of the KP and the different modified KP equations are investigated by the small-k perturbation expansion method of Rowlands and Infeld [J. Plasma Phys. 3, 567 (1969); 8, 105 (1972); 10, 293 (1973); 33, 171 (1985); 41, 139 (1989); Sov. Phys. - JETP 38, 494 (1974)] at the lowest order of k, where k is the wave number of a long-wavelength plane-wave perturbation. The solitary wave solutions of the different evolution equations are found to be stable at this order.

  10. Interactions of delta shock waves and stability of Riemann solutions for nonlinear chromatography equations

    NASA Astrophysics Data System (ADS)

    Zhang, Qingling

    2016-03-01

    This paper is devoted to studying the simplified nonlinear chromatography equations by introducing the change of state variables. The Riemann solutions containing delta shock waves are presented. In order to study wave interactions of delta shock waves with elementary waves, the global structure of solutions is constructed completely when the initial data are taken as three pieces of constants and the delta shock waves are included. In particular, the strength of delta shock wave is expressed explicitly and the delta contact discontinuity is discovered during the process of wave interactions. Moreover, by analyzing the limits of the solutions as the middle region vanishes, we observe that the Riemann solutions are stable for such a local small perturbation of the Riemann initial data.

  11. Drift Scale THM Model

    SciTech Connect

    J. Rutqvist

    2004-10-07

    This model report documents the drift scale coupled thermal-hydrological-mechanical (THM) processes model development and presents simulations of the THM behavior in fractured rock close to emplacement drifts. The modeling and analyses are used to evaluate the impact of THM processes on permeability and flow in the near-field of the emplacement drifts. The results from this report are used to assess the importance of THM processes on seepage and support in the model reports ''Seepage Model for PA Including Drift Collapse'' and ''Abstraction of Drift Seepage'', and to support arguments for exclusion of features, events, and processes (FEPs) in the analysis reports ''Features, Events, and Processes in Unsaturated Zone Flow and Transport and Features, Events, and Processes: Disruptive Events''. The total system performance assessment (TSPA) calculations do not use any output from this report. Specifically, the coupled THM process model is applied to simulate the impact of THM processes on hydrologic properties (permeability and capillary strength) and flow in the near-field rock around a heat-releasing emplacement drift. The heat generated by the decay of radioactive waste results in elevated rock temperatures for thousands of years after waste emplacement. Depending on the thermal load, these temperatures are high enough to cause boiling conditions in the rock, resulting in water redistribution and altered flow paths. These temperatures will also cause thermal expansion of the rock, with the potential of opening or closing fractures and thus changing fracture permeability in the near-field. Understanding the THM coupled processes is important for the performance of the repository because the thermally induced permeability changes potentially effect the magnitude and spatial distribution of percolation flux in the vicinity of the drift, and hence the seepage of water into the drift. This is important because a sufficient amount of water must be available within a

  12. Ionospheric vertical drift response at a mid-latitude station

    NASA Astrophysics Data System (ADS)

    Kouba, Daniel; Koucká Knížová, Petra

    2016-07-01

    equinox. In general, the detected values of the observed vertical drift are of lower magnitudes compare to low latitudes. Drift data in midlatitudes seems to be more influenced by the atmospheric waves than data in lower latitudes.

  13. Craton Development and Stabilization: Insights from SE Canada using P and S Wave Tomography

    NASA Astrophysics Data System (ADS)

    Boyce, A.; Bastow, I. D.; Darbyshire, F. A.; Gilligan, A.; Ellwood, A.; Levin, V. L.; Menke, W. H.

    2015-12-01

    Cratons, the ancient cores of the continents, are the longest-lived parts of Earth's surface that have survived thermal and mechanical erosion during multiple Wilson cycles. They are visible in tomographic images due to their thick (>200km), seismically fast keels or roots. The Laurentian keel beneath North America is intriguing since its root is thought to extend beneath both the Archean Superior craton and the Proterozoic Grenville province thus implying that keel formation may not have been restricted to Archean times. In order to address this issue we present a P and S wave relative arrival-time tomographic study using data from seismograph networks in SE Canada and the NE US, stretching from the southern tip of Hudson Bay within the Superior craton to the coastal Phanerozoic Appalachian terranes. The tomographic images display three broad zones of increasing mantle wavespeed from globally "slow" in the Appalachian terranes, to a "fast" Grenville Province and "extremely fast" Superior craton. We observe a linear low-velocity feature resulting from modification of the Laurentian keel by the passage of the Great Meteor hotspot. This feature is progressively offset southwestward with depth, potentially due to viscous coupling with mantle flow. No major plate-scale underthrusting during the Grenville Orogeny is apparent, which contradicts the inferred results from crustal seismic reflection and refraction studies. Our results therefore may have fundamental implications for the nature of the Grenville orogenic collision and cratonic stabilization of North America. The results also support the developing consensus that keels form in two stages: a chemically depleted core of Archean age followed by a thermally developed, less-depleted lithosphere during Proterozoic times, highlighted by an abrupt wavespeed contrast in the tomographic images.

  14. Spin-wave spectra and stability of the in-plane vortex state in two-dimensional magnetic nanorings

    SciTech Connect

    Mamica, S.

    2013-12-21

    We study theoretically two-dimensional nanorings assumed to have the in-plane vortex magnetic configuration. Using a discrete dipole model we examine the spectrum of normal spin-wave modes vs. the dipolar-to-exchange interaction ratio. We systematize the spin-wave excitations by their azimuthal and radial wave numbers. The lowest-frequency mode, the fundamental (quasiuniform) mode, and the mode hybridization are analyzed; the discussion of the influence of effective pinning at the ring boundaries is provided as well. We study the stability of the in-plane vortex state and discuss the role of the size of the ring and the type of lattice arrangement of the magnetic moments within it. To facilitate comparison with our results we provide the relationships between microscopic parameters, used in our model, and those used in the case of continuous medium.

  15. Stability of thermocapillary convection and regimes of a fluid flow acted upon by a standing surface wave

    NASA Astrophysics Data System (ADS)

    Feonychev, A. I.

    2007-09-01

    It has been established that, in the case where a standing surface wave acts on a thermocapillary-convection flow in a cylindrical volume, there arises an oscillating-convection zone between the laminar and turbulent regimes of flow. It is shown that the boundary between these regimes is determined by the amplitude δ and the number of periods n of the standing wave and is practically independent of the Marangoni number and the oscillation frequency of this wave. At n = 2, in the range 0.004 < δ < 0.006, the parameters of the fluid cease to oscillate. The mechanisms by which the thermocapillary convection in closed volumes loses its stability are discussed.

  16. Stability analysis of a two-stage tapered gyrotron traveling-wave tube amplifier with distributed losses

    SciTech Connect

    Hung, C. L.; Lian, Y. H.; Cheng, N. H.; Yeh, Y. S.; Chang, T. H.

    2012-11-15

    The two-stage tapered gyrotron traveling-wave tube (gyro-TWT) amplifier has achieved wide bandwidth in the millimeter wave range. However, possible oscillations in each stage limit this amplifier's operating beam current and thus its output power. To further enhance the amplifier's stability, distributed losses are applied to the interaction circuit of the two-stage tapered gyro-TWT. A self-consistent particle-tracing code is used for analyzing the beam-wave interactions. The stability analysis includes the effects of the wall losses and the length of each stage on the possible oscillations. Simulation results reveal that the distributed-loss method effectively stabilizes all the oscillations in the two stages. Under stable operating conditions, the device is predicted to produce a peak power of 60 kW with an efficiency of 29% and a saturated gain of 52 dB in the Ka-band. The 3-dB bandwidth is 5.7 GHz, which is approximately 16% of the center frequency.

  17. Quantum Computation with Phase Drift Errors

    NASA Astrophysics Data System (ADS)

    Miquel, César; Paz, Juan Pablo; Zurek, Wojciech Hubert

    1997-05-01

    We numerically simulate the evolution of an ion trap quantum computer made out of 18 ions subject to a sequence of nearly 15 000 laser pulses in order to find the prime factors of N = 15. We analyze the effect of random and systematic phase drift errors arising from inaccuracies in the laser pulses which induce over (under) rotation of the quantum state. Simple analytic estimates of the tolerance for the quality of driving pulses are presented. We examine the use of watchdog stabilization to partially correct phase drift errors concluding that, in the regime investigated, it is rather inefficient.

  18. The Drifting Star

    NASA Astrophysics Data System (ADS)

    2008-04-01

    By studying in great detail the 'ringing' of a planet-harbouring star, a team of astronomers using ESO's 3.6-m telescope have shown that it must have drifted away from the metal-rich Hyades cluster. This discovery has implications for theories of star and planet formation, and for the dynamics of our Milky Way. ESO PR Photo 09a/08 ESO PR Photo 09a/08 Iota Horologii The yellow-orange star Iota Horologii, located 56 light-years away towards the southern Horologium ("The Clock") constellation, belongs to the so-called "Hyades stream", a large number of stars that move in the same direction. Previously, astronomers using an ESO telescope had shown that the star harbours a planet, more than 2 times as large as Jupiter and orbiting in 320 days (ESO 12/99). But until now, all studies were unable to pinpoint the exact characteristics of the star, and hence to understand its origin. A team of astronomers, led by Sylvie Vauclair from the University of Toulouse, France, therefore decided to use the technique of 'asteroseismology' to unlock the star's secrets. "In the same way as geologists monitor how seismic waves generated by earthquakes propagate through the Earth and learn about the inner structure of our planet, it is possible to study sound waves running through a star, which forms a sort of large, spherical bell," says Vauclair. The 'ringing' from this giant musical instrument provides astronomers with plenty of information about the physical conditions in the star's interior. And to 'listen to the music', the astronomers used one of the best instruments available. The observations were conducted in November 2006 during 8 consecutive nights with the state-of-the-art HARPS spectrograph mounted on the ESO 3.6-m telescope at La Silla. Up to 25 'notes' could be identified in the unique dataset, most of them corresponding to waves having a period of about 6.5 minutes. These observations allowed the astronomers to obtain a very precise portrait of Iota Horologii: its

  19. Ground Control for Non-Emplacement Drifts for LA

    SciTech Connect

    D. Tang

    2004-02-26

    The purpose of this calculation is to analyze the stability of repository non-emplacement drifts during the preclosure period, and to provide a final ground support method for non-emplacement drifts for the License Application (LA). This calculation will provide input for the development of LA documents. The scope of this calculation is limited to the non-emplacement drifts including access mains, ramps, exhaust mains, turnouts, intersections between access mains and turnouts, and intersections between exhaust mains and emplacement drifts, portals, TBM launch chambers, observation drift and test alcove in the performance confirmation (PC) facilities, etc. The calculation is limited to the non-emplacement drifts subjected to a combined loading of in-situ stress, seismic stress, and/or thermal stress. Other effects such as hydrological and chemical effects are not considered in this analysis.

  20. Stabilization of the potential multi-steady-state absolute instabilities in a gyrotron traveling-wave amplifier

    SciTech Connect

    Du Chaohai; Liu Pukun

    2009-10-15

    The problem of spurious oscillations induced by absolute instabilities is the most challenging one that hinders the development of the millimeter-wave gyrotron traveling-wave amplifiers (gyro-TWTs). A spurious oscillation exists as a high order axial mode (HOAM) in the interaction circuit. This paper is devoted to demonstrating the complicated steady states of these HOAMs and exploring corresponding techniques to stabilize these potential multi-steady-state absolute instabilities. The stability-oriented design principle is conveyed in a start-to-end design flow of a Ka-band TE{sub 11} mode gyro-TWT. Strong magnetic tapering near the downstream port, which is capable of cutting short the effective interaction circuit of a spurious oscillation and simultaneously boosting the amplification performance, is for the first time proposed to further improve the system stability. It is also found that an ideal prebunched electron beam in the linear stage is the necessary condition to efficient amplification in the nonlinear stage, suggesting that it is feasible to design a stable prebunching stage to replace the distributed-loss-loaded linear stage. The stability-oriented design principle provides more explicit reference for future design of a zero-drive stable gyro-TWT.

  1. Stability study of a gyrotron-traveling-wave amplifier based on a lossy dielectric-loaded mode-selective circuit

    SciTech Connect

    Du Chaohai; Liu Pukun

    2009-07-15

    The millimeter microwave source of gyrotron-traveling-wave amplifier (gyro-TWT) is capable of generating high power coherent radiation in a broad bandwidth, while its performance is severely deteriorated by the stability problems. This paper focuses on modeling and the stability analysis of the Naval Research Laboratory (NRL) Ka-band TE{sub 01} mode gyro-TWT based on an interaction circuit alternately loaded with lossy ceramic shells and metal rings. The propagation characteristics of the interaction circuit is analyzed first, based on which the boundary impedance method is employed to build an equivalent uniform lossy circuit. Then the stability of the interaction system is studied using linear and nonlinear theories. The analysis reveals that, due to the special waveguide structure and the dielectric loss, the propagation characteristics of the complex waveguide are similar to that of a uniform lossy circuit. The analysis of the absolute instabilities characterizes the roles the forward-backward-wave components played. The study indicates that the lowest threshold current of the absolute instabilities is higher than the operating current, which brings the system high stability. The reliability of the analysis is proved by the consistency between the analysis and the NRL experimental results.

  2. Dynamics and stability of stationary states for the spin-1 Bose-Einstein condensates in a standing light wave

    NASA Astrophysics Data System (ADS)

    Wang, Deng-Shan; Han, Wei; Shi, Yuren; Li, Zaidong; Liu, Wu-Ming

    2016-07-01

    The spin-1 Bose-Einstein condensates trapped in a standing light wave can be described by three coupled Gross-Pitaevskii equations with a periodic potential. In this paper, nine families of stationary solutions without phase structures in the form of Jacobi elliptic functions are proposed, and their stabilities are analyzed by both linear stability analysis and dynamical evolutions. Taking the ferromagnetic 87Rb atoms and antiferromagnetic (polar) 23Na atoms as examples, we investigate the stability regions of the nine stationary solutions, which are given in term of elliptic modulus k. It is shown that for the same stationary solution the stability regions of condensates with antiferromagnetic (polar) spin-dependent interactions are larger than that of the condensates with ferromagnetic ones. The dn-dn-dn stationary solution is the most stable solution among the nine families of stationary solutions. Moreover, in the same standing light wave, the spin-1 Bose-Einstein condensates are more stable than the scalar Bose-Einstein condensate.

  3. Drift Degradation Analysis

    SciTech Connect

    D. Kicker

    2004-09-16

    Degradation of underground openings as a function of time is a natural and expected occurrence for any subsurface excavation. Over time, changes occur to both the stress condition and the strength of the rock mass due to several interacting factors. Once the factors contributing to degradation are characterized, the effects of drift degradation can typically be mitigated through appropriate design and maintenance of the ground support system. However, for the emplacement drifts of the geologic repository at Yucca Mountain, it is necessary to characterize drift degradation over a 10,000-year period, which is well beyond the functional period of the ground support system. This document provides an analysis of the amount of drift degradation anticipated in repository emplacement drifts for discrete events and time increments extending throughout the 10,000-year regulatory period for postclosure performance. This revision of the drift degradation analysis was developed to support the license application and fulfill specific agreement items between the U.S. Nuclear Regulatory Commission (NRC) and the U.S. Department of Energy (DOE). The earlier versions of ''Drift Degradation Analysis'' (BSC 2001 [DIRS 156304]) relied primarily on the DRKBA numerical code, which provides for a probabilistic key-block assessment based on realistic fracture patterns determined from field mapping in the Exploratory Studies Facility (ESF) at Yucca Mountain. A key block is defined as a critical block in the surrounding rock mass of an excavation, which is removable and oriented in an unsafe manner such that it is likely to move into an opening unless support is provided. However, the use of the DRKBA code to determine potential rockfall data at the repository horizon during the postclosure period has several limitations: (1) The DRKBA code cannot explicitly apply dynamic loads due to seismic ground motion. (2) The DRKBA code cannot explicitly apply loads due to thermal stress. (3) The DRKBA

  4. Orbital stability of periodic waves in the class of reduced Ostrovsky equations

    NASA Astrophysics Data System (ADS)

    Johnson, Edward R.; Pelinovsky, Dmitry E.

    2016-09-01

    Periodic travelling waves are considered in the class of reduced Ostrovsky equations that describe low-frequency internal waves in the presence of rotation. The reduced Ostrovsky equations with either quadratic or cubic nonlinearities can be transformed to integrable equations of the Klein-Gordon type by means of a change of coordinates. By using the conserved momentum and energy as well as an additional conserved quantity due to integrability, we prove that small-amplitude periodic waves are orbitally stable with respect to subharmonic perturbations, with period equal to an integer multiple of the period of the wave. The proof is based on construction of a Lyapunov functional, which is convex at the periodic wave and is conserved in the time evolution. We also show numerically that convexity of the Lyapunov functional holds for periodic waves of arbitrary amplitudes.

  5. SAA drift: Experimental results

    NASA Astrophysics Data System (ADS)

    Grigoryan, O. R.; Romashova, V. V.; Petrov, A. N.

    According to the paleomagnetic analysis there are variations of Earth’s magnetic field connected with magnetic moment changing. These variations affect on the South Atlantic Anomaly (SAA) location. Indeed different observations approved the existence of the SAA westward drift rate (0.1 1.0 deg/year) and northward drift rate (approximately 0.1 deg/year). In this work, we present the analysis of experimental results obtained in Scobeltsyn Institute of Nuclear Physics, Moscow State University (SINP MSU) onboard different Earth’s artificial satellites (1972 2003). The fluxes of protons with energy >50 MeV, gamma quanta with energy >500 keV and neutrons with energy 0.1 1.0 MeV in the SAA region have been analyzed. The mentioned above experimental data were obtained onboard the orbital stations Salut-6 (1979), MIR (1991, 1998) and ISS (2003) by the similar experimental equipment. The comparison of the data obtained during these two decades of investigations confirms the fact that the SAA drifts westward. Moreover the analysis of fluxes of electrons with energy about hundreds keV (Cosmos-484 (1972) and Active (Interkosmos-24, 1991) satellites) verified not only the SAA westward drift but northward drift also.

  6. Plasma drifts deduced from resonance cone asymmetries: II. Evaluation of COREX data

    NASA Astrophysics Data System (ADS)

    Piel, A.; Rohde, V.; Thiemann, H.; Oyama, K. I.

    The data from the COREX instrument are discussed with respect to non-reciprocities in resonance cones for opposing wave propagation directions. The shift of the maxima has a different symmetry from the case of field aligned drifts. Using a generalized drift model the magnitude and direction of the drift is evaluated. Velocities of the order of up to 38 km/s are found. The drift direction is nearly perpendicular to the magnetic field.

  7. Sawtooth-Control Mechanism using Toroidally Propagating Ion-Cyclotron-Resonance Waves in Tokamaks

    SciTech Connect

    Graves, J. P.; Coda, S.; Chapman, I.

    2009-02-13

    The sawtooth control mechanism in plasmas employing off-axis toroidally propagating ion cyclotron resonance waves in tokamaks is reinvestigated. The radial drift excursion of energetic passing ions distributed asymmetrically in the velocity parallel to the magnetic field determines stability when the rational q=1 surface resides within a narrow region centered about the shifted fundamental cyclotron resonance.

  8. Asymptotic Stability of Planar Rarefaction Waves for the Relaxation Approximation of Conservation Laws in Several Dimensions

    NASA Astrophysics Data System (ADS)

    Luo, Tao

    1997-01-01

    This paper concerns the large time behavior toward planar rarefaction waves of solutions for the relaxation approximation of conservation laws in several dimensions. It is shown that a planar rarefaction wave is nonlinear stable in the sense that it is an asymptotic attractor for the relaxation approximation of conservation laws.

  9. Stability of giant sand waves in eastern Long Island Sound, U.S.A.

    USGS Publications Warehouse

    Fenster, M.S.; FitzGerald, D.M.; Bohlen, W.F.; Lewis, R.S.; Baldwin, C.T.

    1990-01-01

    A combination of a highly accurate bathymetric surveying technique and in-situ submersible observations and measurements were used to assess the migrational trends and morphological changes of large sand waves (Ht ??? 17 m) in eastern Long Island Sound. Although residing in a high-energy tidal environment characterized by a net westward sediment flux, the large bedforms are relatively stable over the short term. Over a 7 month period, 55.1% of a total 2942 m of sand wave crestline lengths migrated less than the horizontal accuracy limits of navigation (2 m). Approximately 35% of the remaining sand wave crests migrated less than 4 m. Net migration of the sand wave crests in the study area was 0.2 m. In addition, the bulk form (center of area in profile view) or the base of the sand waves showed little, if any, movement. These data, in conjunction with flow data within the sand wave field, suggest that net migration rates are greater than the time span of this study and/or the sand waves move in response to large residual flows created by high-energy, aperiodic storm events. The latter scenerio suggests that day to day processes only serve to rework and modify the sand waves. ?? 1990.

  10. Complex plasma in g ×B configurations: Stability switching and stationary structure

    NASA Astrophysics Data System (ADS)

    Salahshoor, M.; Niknam, A. R.

    2015-08-01

    In a low-pressure magneto-gravitated complex plasma, the stability state of dust gravitational drift wave is switched at a critical wavenumber and the propagating dust magneto-gravitational drift wave is transformed into an aperiodic stationary structure at a cut-off wavenumber. In this paper, two analytical formulas have been derived for the critical wavenumber of stability switching and the cut-off wavenumber of stationary structure. The critical wavenumber is equal to the ratio of ion plasma frequency to ion streaming velocity and the cut-off wavenumber is proportional to the ratio of dust plasma frequency to dust g ×B drift velocity. These scaling formulas are in excellent agreement with exact numerical solutions of dispersion relations. These scenarios are expected to be observed in fully magnetized dusty plasma experiments as the next frontier for complex plasma research.

  11. Theoretical Studies of Drift-Alfven and Energetic Particle Physics in Fusion Plasmas

    SciTech Connect

    Liu Chen

    2005-07-06

    Nonlinear equations for the slow space-time evolution of the radial drift-wave envelope and zonal flow amplitude have been self-consistently derived for a model nonuniform tokamak equilibrium within the coherent four-wave drift wave-zonal flow modulation interaction model of Chen, Lin, and White [Phys. Plasmas 7, 3129 (2000)]. Solutions clearly demonstrate turbulence spreading due to nonlinearly dispersiveness and, consequently, the device-size dependence of the saturated wave intensities and transport coefficients.

  12. Time-stepping stability of continuous and discontinuous finite-element methods for 3-D wave propagation

    NASA Astrophysics Data System (ADS)

    Mulder, W. A.; Zhebel, E.; Minisini, S.

    2014-02-01

    We analyse the time-stepping stability for the 3-D acoustic wave equation, discretized on tetrahedral meshes. Two types of methods are considered: mass-lumped continuous finite elements and the symmetric interior-penalty discontinuous Galerkin method. Combining the spatial discretization with the leap-frog time-stepping scheme, which is second-order accurate and conditionally stable, leads to a fully explicit scheme. We provide estimates of its stability limit for simple cases, namely, the reference element with Neumann boundary conditions, its distorted version of arbitrary shape, the unit cube that can be partitioned into six tetrahedra with periodic boundary conditions and its distortions. The Courant-Friedrichs-Lewy stability limit contains an element diameter for which we considered different options. The one based on the sum of the eigenvalues of the spatial operator for the first-degree mass-lumped element gives the best results. It resembles the diameter of the inscribed sphere but is slightly easier to compute. The stability estimates show that the mass-lumped continuous and the discontinuous Galerkin finite elements of degree 2 have comparable stability conditions, whereas the mass-lumped elements of degree one and three allow for larger time steps.

  13. Drift solitons and shocks in inhomogeneous quantum magnetoplasmas

    SciTech Connect

    Haque, Q.; Mahmood, S.

    2008-03-15

    Linear and nonlinear drift waves are studied in inhomogeneous electron-ion quantum magnetoplasma with neutrals in the background. The Korteweg-de Vries-Burgers equation is derived by using the quantum hydrodynamic model for nonlinear drift waves with quantum corrections. Both soliton and shock solutions are obtained in different limits. It is noticed that the width of the solitary hump is decreased with the increase in the quantum parameter. However this effect is reversed for the solitary dip case. It is also found that oscillatory shock wave is dependent on the quantum parameter. However, the monotonic shock formation is independent of the quantum parameter.

  14. Continental drift before 1900.

    PubMed

    Rupke, N A

    1970-07-25

    The idea that Francis Bacon and other seventeenth and eighteenth century thinkers first conceived the notion of continental drift does not stand up to close scrutiny. The few authors who expressed the idea viewed the process as a catastrophic event. PMID:16057953

  15. High resolution drift chambers

    SciTech Connect

    Va'vra, J.

    1985-07-01

    High precision drift chambers capable of achieving less than or equal to 50 ..mu..m resolutions are discussed. In particular, we compare so called cool and hot gases, various charge collection geometries, several timing techniques and we also discuss some systematic problems. We also present what we would consider an ''ultimate'' design of the vertex chamber. 50 refs., 36 figs., 6 tabs.

  16. IN DRIFT CORROSION PRODUCTS

    SciTech Connect

    D.M. Jolley

    1999-12-02

    As directed by a written development plan (CRWMS M&O 1999a), a conceptual model for steel and corrosion products in the engineered barrier system (EBS) is to be developed. The purpose of this conceptual model is to assist Performance Assessment Operations (PAO) and its Engineered Barrier Performance Department in modeling the geochemical environment within a repository drift, thus allowing PAO to provide a more detailed and complete in-drift geochemical model abstraction and to answer the key technical issues (KTI) raised in the NRC Issue Resolution Status Report (IRSR) for the Evolution of the Near-Field Environment (NFE) Revision 2 (NRC 1999). This document provides the conceptual framework for the in-drift corrosion products sub-model to be used in subsequent PAO analyses including the EBS physical and chemical model abstraction effort. This model has been developed to serve as a basis for the in-drift geochemical analyses performed by PAO. However, the concepts discussed within this report may also apply to some near and far-field geochemical processes and may have conceptual application within the unsaturated zone (UZ) and saturated zone (SZ) transport modeling efforts.

  17. Modulational stability of weakly nonlinear wave-trains in media with small- and large-scale dispersions

    NASA Astrophysics Data System (ADS)

    Nikitenkova, S.; Singh, N.; Stepanyants, Y.

    2015-12-01

    In this paper, we revisit the problem of modulation stability of quasi-monochromatic wave-trains propagating in a media with the double dispersion occurring both at small and large wavenumbers. We start with the shallow-water equations derived by Shrira [Izv., Acad. Sci., USSR, Atmos. Ocean. Phys. (Engl. Transl.) 17, 55-59 (1981)] which describes both surface and internal long waves in a rotating fluid. The small-scale (Boussinesq-type) dispersion is assumed to be weak, whereas the large-scale (Coriolis-type) dispersion is considered as without any restriction. For unidirectional waves propagating in one direction, only the considered set of equations reduces to the Gardner-Ostrovsky equation which is applicable only within a finite range of wavenumbers. We derive the nonlinear Schrödinger equation (NLSE) which describes the evolution of narrow-band wave-trains and show that within a more general bi-directional equation the wave-trains, similar to that derived from the Ostrovsky equation, are also modulationally stable at relatively small wavenumbers k < kc and unstable at k > kc, where kc is some critical wavenumber. The NLSE derived here has a wider range of applicability: it is valid for arbitrarily small wavenumbers. We present the analysis of coefficients of the NLSE for different signs of coefficients of the governing equation and compare them with those derived from the Ostrovsky equation. The analysis shows that for weakly dispersive waves in the range of parameters where the Gardner-Ostrovsky equation is valid, the cubic nonlinearity does not contribute to the nonlinear coefficient of NLSE; therefore, the NLSE can be correctly derived from the Ostrovsky equation.

  18. The influence of oceanic internal waves on the phase stability of broadband acoustic transmission at long range

    NASA Astrophysics Data System (ADS)

    Viechnicki, John Thomas

    1999-12-01

    Instantaneous phase stability in acoustic wavefields measured during the 1994 Acoustic Engineering Test (AET) is examined. AET is one of several preliminary Acoustic Thermometry of Ocean Climate (ATOC) experiments conducted in the past several years. Internal waves are assumed to be the mechanism responsible for phase decorrelation over time scales of ten to thirty minutes. The AET experiment had a center frequency of 75 Hz and a 3 megameter path length. Comparison of numerical simulations to experimental results provide insight into how internal waves scatter sound and can be used to constrain statistical descriptors of realistic deep ocean internal wave fields. Ray-based wavefield simulations are performed using both Deterministic Ray Theory (DRT) and Stochastic Ray Theory (SRT), while full wave simulations are performed using the co insensitive parabolic equation model. This work complements recent similar inference studies of Colosi et al. (1994) and Heaney (1997) on other preliminary ATOC experiments. Working within the framework of the Garrett- Munk internal wave spectrum, phase coherence time, which was observed to be roughly ten to fifteen minutes in the AET experiment, is found to be dependent on the vertically integrated potential energy density, ɛ, and the bounds on the horizontal wavenumber spectrum, k min and kmax. Results suggest that phase coherence is insensitive to mode number cutoff, jmax . Two manifestations of the phase decorrelation observed in simulations are studied. Temporal wavefront wander as defined by Flatté et al. (1979) is examined over the decorrelation period as a function of the horizontal wavenumber spectrum. Intermittent structure that appears and disappears throughout the wavefront on time scales of ten to thirty minutes is examined. This intermittent structure is observed in both full wave modeling and DRT but not SRT.

  19. Modulational stability of weakly nonlinear wave-trains in media with small- and large-scale dispersions.

    PubMed

    Nikitenkova, S; Singh, N; Stepanyants, Y

    2015-12-01

    In this paper, we revisit the problem of modulation stability of quasi-monochromatic wave-trains propagating in a media with the double dispersion occurring both at small and large wavenumbers. We start with the shallow-water equations derived by Shrira [Izv., Acad. Sci., USSR, Atmos. Ocean. Phys. (Engl. Transl.) 17, 55-59 (1981)] which describes both surface and internal long waves in a rotating fluid. The small-scale (Boussinesq-type) dispersion is assumed to be weak, whereas the large-scale (Coriolis-type) dispersion is considered as without any restriction. For unidirectional waves propagating in one direction, only the considered set of equations reduces to the Gardner-Ostrovsky equation which is applicable only within a finite range of wavenumbers. We derive the nonlinear Schrödinger equation (NLSE) which describes the evolution of narrow-band wave-trains and show that within a more general bi-directional equation the wave-trains, similar to that derived from the Ostrovsky equation, are also modulationally stable at relatively small wavenumbers k < kc and unstable at k > kc, where kc is some critical wavenumber. The NLSE derived here has a wider range of applicability: it is valid for arbitrarily small wavenumbers. We present the analysis of coefficients of the NLSE for different signs of coefficients of the governing equation and compare them with those derived from the Ostrovsky equation. The analysis shows that for weakly dispersive waves in the range of parameters where the Gardner-Ostrovsky equation is valid, the cubic nonlinearity does not contribute to the nonlinear coefficient of NLSE; therefore, the NLSE can be correctly derived from the Ostrovsky equation. PMID:26723152

  20. Dike Propagation Near Drifts

    SciTech Connect

    NA

    2002-03-04

    The purpose of this Analysis and Model Report (AMR) supporting the Site Recommendation/License Application (SR/LA) for the Yucca Mountain Project is the development of elementary analyses of the interactions of a hypothetical dike with a repository drift (i.e., tunnel) and with the drift contents at the potential Yucca Mountain repository. This effort is intended to support the analysis of disruptive events for Total System Performance Assessment (TSPA). This AMR supports the Process Model Report (PMR) on disruptive events (CRWMS M&O 2000a). This purpose is documented in the development plan (DP) ''Coordinate Modeling of Dike Propagation Near Drifts Consequences for TSPA-SR/LA'' (CRWMS M&O 2000b). Evaluation of that Development Plan and the work to be conducted to prepare Interim Change Notice (ICN) 1 of this report, which now includes the design option of ''Open'' drifts, indicated that no revision to that DP was needed. These analyses are intended to provide reasonable bounds for a number of expected effects: (1) Temperature changes to the waste package from exposure to magma; (2) The gas flow available to degrade waste containers during the intrusion; (3) Movement of the waste package as it is displaced by the gas, pyroclasts and magma from the intruding dike (the number of packages damaged); (4) Movement of the backfill (Backfill is treated here as a design option); (5) The nature of the mechanics of the dike/drift interaction. These analyses serve two objectives: to provide preliminary analyses needed to support evaluation of the consequences of an intrusive event and to provide a basis for addressing some of the concerns of the Nuclear Regulatory Commission (NRC) expressed in the Igneous Activity Issue Resolution Status Report.

  1. Asymptotic stability of stationary states in the wave equation coupled to a nonrelativistic particle

    NASA Astrophysics Data System (ADS)

    Kopylova, E. A.; Komech, A. I.

    2016-01-01

    We consider the Hamiltonian system consisting of a scalar wave field and a single particle coupled in a translation invariant manner. The point particle is subjected to an external potential. The stationary solutions of the system are a Coulomb type wave field centered at those particle positions for which the external force vanishes. It is assumed that the charge density satisfies the Wiener condition, which is a version of the "Fermi Golden Rule." We prove that in the large time approximation, any finite energy solution, with the initial state close to the some stable stationary solution, is a sum of this stationary solution and a dispersive wave which is a solution of the free wave equation.

  2. Influence of standing surface waves on thermocapillary convection stability and crystal growth in weightlessness

    NASA Astrophysics Data System (ADS)

    Feonychev, A. I.

    Numerical investigation of thermocapillary flows and crystal growth by the floating zone method had been carried out in the case what free fluid surface oscillates in the form of standing wave by vibration. Two sorts of standing waves were considered. First, it is inertia-capillary standing waves due to vibration motion of fluid column as unit. These waves had been discovered under numerical investigation of problem /1/. Analytical model and the characteristic properties of these waves are described in /2/. Secondly, usual capillary waves generated by vibration of growing crystal were also considered. The effects of these surface waves on fluid flow and heat and mass transfer in process of crystal growth had been investigated over the wide ranges of dimensionless parameters for the Prandtl number is less than 1. The Marangoni number was varied from 140 to 2500, the range of cyclic frequency was between 200 and 76000. Transition from laminar thermocapillary convection to regime of flow with high oscillations (turbulent convection) happens very sharply when dimensionless amplitude (scale for linear dimensions is radius of fluid column) of standing wave reached 0.01112/n, where n is number of standing wave periods are along the length of fluid zone. If configuration of standing wave correlates with thermocapillary flow pattern two specific regimes of flow had been discovered. Flow with small oscillations is located in the range of standing wave amplitude between 0.0028 and 0.00418. In this area, radial macrosegregation of dopant is lowered by the factor of 3-6 depending on the Marangoni number. Next is an area with practically stable flow, in particular is identical to laminar flow without vibration. This area ends very sharply in the boundary of turbulent flow. All the mentioned boundaries are independent of the Marangoni number and frequency of oscillation of standing wave. For oscillatory thermocapillary convection (the Marangoni number is more than 2000

  3. Stability and slosh wave for rotating bubble due to gravity-jitters under microgravity

    NASA Technical Reports Server (NTRS)

    Hung, R. J.; Lee, C. C.; Leslie, F. W.

    1990-01-01

    Time-dependent fluid behaviors in microgravity environments are examined with particular attention given to the dynamics of bubble configurations. The initial bubble profiles, computed from the steady-state formulation, are used as the initial input for the time dependent computation. The parameters considered are liquid density and its kinematic viscosity, gas density and its kinematic viscosity, surface tension coefficient, angular velocity, and gravity environment. This computer algorithm can be used to simulate the fluid behavior in a microgravity environment, in particular the excitation of slosh waves due to different frequencies of gravity jitters. Results show that lower-frequency gravity jitters excite slosh waves with a higher ratio of maximum amplitude to wave length than that of the slosh waves generated by the higher frequency gravity jitters.

  4. Magnetosheath plasma stability and ULF wave occurrence as a function of location in the magnetosheath and upstream bow shock parameters

    NASA Astrophysics Data System (ADS)

    Soucek, Jan; Escoubet, C. Philippe; Grison, Benjamin

    2015-04-01

    We present the results of a statistical study of the distribution of mirror and Alfvén-ion cyclotron (AIC) waves in the magnetosheath together with plasma parameters important for the stability of ULF waves, specifically ion temperature anisotropy and ion beta. Magnetosheath crossings registered by Cluster spacecraft over the course of 2 years served as a basis for the statistics. For each observation we used bow shock, magnetopause, and magnetosheath flow models to identify the relative position of the spacecraft with respect to magnetosheath boundaries and local properties of the upstream shock crossing. A strong dependence of both plasma parameters and mirror/AIC wave occurrence on upstream ΘBn and MA is identified. We analyzed a joint dependence of the same parameters on ΘBn and fractional distance between shock and magnetopause, zenith angle, and length of the flow line. Finally, the occurrence of mirror and AIC modes was compared against the respective instability thresholds. We noted that AIC waves occurred nearly exclusively under mirror stable conditions. This is interpreted in terms of different characters of nonlinear saturation of the two modes.

  5. Stability and evolution of wave packets in strongly coupled degenerate plasmas.

    PubMed

    Misra, A P; Shukla, P K

    2012-02-01

    We study the nonlinear propagation of electrostatic wave packets in a collisional plasma composed of strongly coupled ions and relativistically degenerate electrons. The equilibrium of ions is maintained by an effective temperature associated with their strong coupling, whereas that of electrons is provided by the relativistic degeneracy pressure. Using a multiple-scale technique, a (3 + 1)-dimensional coupled set of nonlinear Schrödinger-like equations with nonlocal nonlinearity is derived from a generalized viscoelastic hydrodynamic model. These coupled equations, which govern the dynamics of wave packets, are used to study the oblique modulational instability of a Stoke's wave train to a small plane-wave perturbation. We show that the wave packets, though stable to the parallel modulation, become unstable against oblique modulations. In contrast to the long-wavelength carrier modes, the wave packets with short wavelengths are shown to be stable in the weakly relativistic case, whereas they can be stable or unstable in the ultrarelativistic limit. Numerical simulation of the coupled equations reveals that a steady-state solution of the wave amplitude exists together with the formation of a localized structure in (2 + 1) dimensions. However, in the (3 + 1)-dimensional evolution, a Gaussian wave beam self-focuses after interaction and blows up in a finite time. The latter is, however, arrested when the dispersion predominates over the nonlinearities. This occurs when the Coulomb coupling strength is higher or a choice of obliqueness of modulation, or a wavelength of excitation is different. Possible application of our results to the interior as well as in an outer mantle of white dwarfs are discussed. PMID:22463339

  6. Asymptotic stability of rarefaction waves for 2 ∗ 2 viscous hyperbolic conservation laws

    NASA Astrophysics Data System (ADS)

    Xin, Zhouping

    This paper concerns the asymptotic behavior toward rarefaction waves of the solution of a general 2 × 2 hyperbolic conservation laws with positive viscosity. We prove that if the initial data is close to a constant state and its values at ±∞ lie on the kth rarefaction curve for the corresponding hyperbolic conservation laws, then the solution tends as t → ∞ to the rarefaction wave determined by these states.

  7. Stability of two-dimensional ion-acoustic wave packets in quantum plasmas

    SciTech Connect

    Misra, A. P.; Marklund, M.; Brodin, G.; Shukla, P. K.

    2011-04-15

    The nonlinear propagation of two-dimensional (2D) quantum ion-acoustic waves (QIAWs) is studied in a quantum electron-ion plasma. By using a 2D quantum hydrodynamic model and the method of multiple scales, a new set of coupled nonlinear partial differential equations is derived which governs the slow modulation of the 2D QIAW packets. The oblique modulational instability (MI) is then studied by means of a corresponding nonlinear Schroedinger equation derived from the coupled nonlinear partial differential equations. It is shown that the quantum parameter H (ratio of the plasmon energy density to Fermi energy) shifts the MI domains around the k{theta} -plane, where k is the carrier wave number and {theta} is the angle of modulation. In particular, the ion-acoustic wave (IAW), previously known to be stable under parallel modulation in classical plasmas, is shown to be unstable in quantum plasmas. The growth rate of the MI is found to be quenched by the obliqueness of modulation. The modulation of 2D QIAW packets along the wave vector k is shown to be described by a set of Davey-Stewartson-like equations. The latter can be studied for the 2D wave collapse in dense plasmas. The predicted results, which could be important to look for stable wave propagation in laboratory experiments as well as in dense astrophysical plasmas, thus generalize the theory of MI of IAW propagations both in classical and quantum electron-ion plasmas.

  8. Numerical Simulation of Waves Driven by Plasma Currents Generated by Low-Frequency Alfven Waves in a Multi-Ion Plasma

    NASA Technical Reports Server (NTRS)

    Singh, Nagendra; Khazanov, George

    2004-01-01

    When multi-ion plasma consisting of heavy and light ions is permeated by a low-frequency Alfven (LFA) wave, the crossed-electric-and-magnetic field (E x B), and the polarization drifts of the different ion species and the electrons could be quite different. The relative drifts between the charged-particle species drive waves, which energize the plasma. Using 2.5-dimensional (2.5-D) particle-in-cell simulations, we study this process of wave generation and its nonlinear consequences in terms of acceleration and heating plasma. Specifically, we study the situation for LFA wave frequency being lower than the heavy-ion cyclotron frequency in a multi-ion plasma. We impose such a wave to the plasma assuming that its wavelength is much larger than that of the waves generated by the relative drifts. For better understanding, the LFA-wave driven simulations are augmented by those driven by initialized ion beams. The driven high-frequency (HF) wave modes critically depend on the heavy ion density nh; for small values of nh, the lower hybrid (LH) waves dominate. On the other hand, for large nh a significantly enhanced level of waves occurs over a much broader frequency spectrum below the LH frequency and such waves are interpreted here as the ion Bernstein (IB) mode near the light ion cyclotron harmonics. Irrespective of the driven wave modes, both the light and heavy ions undergo significant transverse acceleration, but for the large heavy-ion densities, even the electrons are significantly accelerated in the parallel direction by the waves below the LH frequency. Even when the LFA wave drive is maintained, the ion heating leads to the cessation of HF wave excitation just after a few cycles of the former wave. On the basis of marginal stability seen in the simulations, an empirical relation for LFA wave amplitude, frequency and ion temperature is given.

  9. Adiabatic Transformation of Gravitational Stabilization Waves of the Crystalline Vacuum Space Into Baryons at the Big Bang

    NASA Astrophysics Data System (ADS)

    Montemayor-Aldrete, J. A.; Morones-Ibarra, J. R.; Morales-Mori, A.; Ugalde-Velez, P.; Mendoza-Allende, A.; Cabrera-Bravo, E.; Montemayor-Varela, A.

    2013-03-01

    It is shown that the entropy of the low density monochromatic gravitational waves which stabilize gravitationally the crystalline structure of vacuum cosmic space varies with the volume in the same way as the entropy of an ideal gas formed by particles. This implies that close enough to the local Big-Bang event the energy of all the gravitational waves which stabilizes the crystalline structure of vacuum space behaves thermodynamically as though it is consisted of a number of independent energy or matter quanta (neutrons). Also it is shown that the diminishing in the gravitational energy of the waves which stabilize the crystalline vacuum space structure is the source of energy required to produce the electromagnetic radiation which is responsible for the hot matter expansion through a preexisting infinite cosmic space. Matter and antimatter is produced in equal quantities at the Big Bang region and there are no annihilation events between them during their initial stage of expansion through vacuum cosmic space due to the gravitational stress gradient pattern existing around the source region which has zero gravitational stress all the matter travels globally in one direction (For instance pointing to the long range tension gravitational stress cell-region) and all the antimatter corresponding to the contiguous compressed cell-region travels in the opposite direction. The obtained expression for the volumetric electromagnetic energy density resembles the classical one proportional to , obtained for the black body radiation in equilibrium conditions at temperature ; and at thermal equilibrium with baryons for the decoupling temperature between photons and matter, , electromagnetic energy of radiation has a value of photons per baryon. Also the evaluation of the Gibbs ´s free energy for the adiabatic compression process of transformation of gravitational stabilization waves of the crystalline vacuum space into baryons at the Big Bang gives a value of zero for the

  10. Exponential Stability of the Energy of the Wave Equation with Variable Coefficients and a Boundary Distributed Delay

    NASA Astrophysics Data System (ADS)

    Liu, Wenjun

    2014-11-01

    In this paper, we consider a wave equation with space variable coefficients. Due to physical considerations, a distributed delay damping is acted on the part of the boundary. Under suitable assumptions, we prove the exponential stability of the energy based on the use of Riemannian geometry method, the perturbed energy argument, and some observability inequalities. From the applications point of view, our results may provide some qualitative analysis and intuition for the researchers in fields such as engineering, biophysics, and mechanics. And the method is rather general and can be adapted to other evolution systems with variable coefficients (e. g. elasticity plates) as well.

  11. Wave-activity conservation laws and stability theorems for semi-geostrophic dynamics. Part 1. Pseudomomentum-based theory

    NASA Astrophysics Data System (ADS)

    Kushner, Paul J.; Shepherd, Theodore G.

    1995-05-01

    A body theory based on quasi-geostatic (QG) dynamics is central to the understanding of large-scale atmospheric and oceanic dynamics. This paper treats the f-plane Boussinesq form of semi-geostatic (SG) dynamics, and its recent extension to beta -plane, compressible flow by Magnusdottir & Schubert. In the limit of small Rossby number, the results reduce to their respective QG forms. Novel features particular to SG dynamic include apparently unnoticed lateral boundary stability criteria and the necessity of including additional zonal-mean eddy correlation terms besides the zonal-mean potential vorticity fluxes wave-mean-flow balance.

  12. Instrumentation system for determination and compensation of electro-optic modulator transfer function drift

    NASA Astrophysics Data System (ADS)

    Thanh Bui, Dang; Thanh Nguyen, Chi; Ledoux-Rak, Isabelle; Zyss, Joseph; Journet, Bernard

    2011-12-01

    This paper presents an instrumentation system developed to improve the operation of an electro-optic modulator (EOM). During their operating time, EOM are subject to a drift of the optical transfer function; therefore the initial tuning of the bias point no longer corresponds to the best characteristics of the device. Because of this drift the EOM no longer behaves linearly and there is degradation during time of the performances of the system in which the EOM is included. To determine the drift, a low frequency modulation signal (at 500 Hz) is applied to the EOM and the second harmonic component at 1 kHz is detected. A new criterion is introduced for estimating the nonlinearity and for compensating the drift of the transfer function, keeping the optical bias point at the quadrature position. Temperature changes significantly influence the EOM characteristics. Thus, the instrumentation system has to be simultaneously developed with temperature control and drift compensation of the optical transfer function. The design is based on PSOC microcontrollers for tuning the different parameters, for data acquisition and regulation process. By setting the temperature to some specific values, it is possible to test the behaviour of the modulator. Finally, by using both temperature and bias point control, a significant reduction of the nonlinearity can be obtained during 2 h of experiment: the biasing point at the quadrature point of the transfer function which corresponds to the most linear behaviour can be stabilized within ±0.22% of the half-wave voltage. All the works presented here were carried out with a Mach-Zehnder intensity modulator made of lithium niobate, but it is also possible to apply this method to other kinds of material, for example polymer material.

  13. Introduction to Drift Wave Turbulence Modeling

    SciTech Connect

    Garbet, X.

    2004-03-15

    This tutorial presents the techniques that are used to build a transport model from turbulence simulations. Achievements and limitations are reviewed. The main mechanisms leading to an improved confinement are also addressed. The results of turbulence modelling regarding this issue are assessed.

  14. Unconventional ballooning structures for toroidal drift waves

    SciTech Connect

    Xie, Hua-sheng Xiao, Yong

    2015-09-15

    With strong gradients in the pedestal of high confinement mode (H-mode) fusion plasmas, gyrokinetic simulations are carried out for the trapped electron and ion temperature gradient modes. A broad class of unconventional mode structures is found to localize at arbitrary poloidal positions or with multiple peaks. It is found that these unconventional ballooning structures are associated with different eigen states for the most unstable mode. At weak gradient (low confinement mode or L-mode), the most unstable mode is usually in the ground eigen state, which corresponds to a conventional ballooning mode structure peaking in the outboard mid-plane of tokamaks. However, at strong gradient (H-mode), the most unstable mode is usually not the ground eigen state and the ballooning mode structure becomes unconventional. This result implies that the pedestal of H-mode could have better confinement than L-mode.

  15. Unconventional ballooning structures for toroidal drift waves

    NASA Astrophysics Data System (ADS)

    Xie, Hua-sheng; Xiao, Yong

    2015-09-01

    With strong gradients in the pedestal of high confinement mode (H-mode) fusion plasmas, gyrokinetic simulations are carried out for the trapped electron and ion temperature gradient modes. A broad class of unconventional mode structures is found to localize at arbitrary poloidal positions or with multiple peaks. It is found that these unconventional ballooning structures are associated with different eigen states for the most unstable mode. At weak gradient (low confinement mode or L-mode), the most unstable mode is usually in the ground eigen state, which corresponds to a conventional ballooning mode structure peaking in the outboard mid-plane of tokamaks. However, at strong gradient (H-mode), the most unstable mode is usually not the ground eigen state and the ballooning mode structure becomes unconventional. This result implies that the pedestal of H-mode could have better confinement than L-mode.

  16. Insights into Volcanic Tremor: A Linear Stability Analysis of Waves Propagating Along Fluid-Filled Cracks

    NASA Astrophysics Data System (ADS)

    Lipovsky, B.; Dunham, E. M.

    2012-12-01

    Crack waves are guided waves along fluid-filled cracks that propagate with phase velocity less than the sound wave speed. Chouet (JGR, 1986) and Ferrazzini and Aki (JGR, 1977) have shown that such waves could explain volcanic tremor in terms of the resonant modes of a finite length magma-filled crack. Based on an idealized lumped-parameter model, Julian (JGR, 1994) further proposed that the steady flow of a viscous magma in a volcanic conduit is unstable to perturbations, leading to self-excited oscillations of the conduit walls and radiation of seismic waves. Our objective is to evaluate the possibility of self-excited oscillations within a rigorous, continuum framework. Our specific focus has been on basaltic fissure eruptions. In a typical basaltic fissure system, the magnitudes of the wave restoring forces, fluid compressibility and wall elasticity, are highly depth dependent. Because of the elevated fluid compressibility from gas exsolution at shallow depths, fluid pressure perturbations in this regime propagate as acoustic waves with effectively rigid conduit walls. Below the exsolution depth, the conduit walls are more compliant relative to the magma compressibility and perturbations propagate as dispersive crack waves. Viscous magma flow through such a fissure will evolve to a fully developed state characterized by a parabolic velocity profile in several to tens of seconds. This time scale is greater than harmonic tremor periods, typically 0.1 to 1 second. A rigorous treatment of the wave response to pressure perturbations therefore requires a general analysis of conduit flow that is not in a fully developed state. We present a linearized analysis of the coupled fluid and elastic response to general flow perturbations. We assume that deformation of the wall is linear elastic. As our focus is on wavelengths greatly exceeding the crack width, fluid flow is described by a quasi-one dimensional, or width-averaged, model. We account for conservation of magma

  17. Modulated spin helicity stabilized by incommensurate orbital density waves in a quadruple perovskite manganite

    NASA Astrophysics Data System (ADS)

    Johnson, R. D.; Khalyavin, D. D.; Manuel, P.; Bombardi, A.; Martin, C.; Chapon, L. C.; Radaelli, P. G.

    2016-05-01

    Through a combination of neutron diffraction and Landau theory we describe the spin ordering in the ground state of the quadruple perovskite manganite CaMn7O12 —a magnetic multiferroic supporting an incommensurate orbital density wave that onsets above the magnetic ordering temperature, TN 1=90 K. The multi-k magnetic structure in the ground state was found to be a nearly-constant-moment helix with modulated spin helicity, which oscillates in phase with the orbital occupancies on the Mn3 + sites via trilinear magneto-orbital coupling. Our phenomenological model also shows that, above TN 2=48 K, the primary magnetic order parameter is locked into the orbital wave by an admixture of helical and collinear spin density wave structures. Furthermore, our model naturally explains the lack of a sharp dielectric anomaly at TN 1 and the unusual temperature dependence of the electrical polarization.

  18. Stability and interactions of nanocolloids at fluid interfaces: effects of capillary waves and line tensions

    NASA Astrophysics Data System (ADS)

    Lehle, H.; Oettel, M.

    2008-10-01

    We analyze the effective potential for nanoparticles trapped at a fluid interface within a simple model which incorporates surface and line tensions as well as a thermal average over interface fluctuations (capillary waves). For a single colloid, a reduced steepness of the potential well hindering movements out of the interface plane compared to rigid interface models is observed, and an instability of the capillary wave partition sum in the case of negative line tensions is pointed out. For two colloids, averaging over the capillary waves leads to an effective Casimir-type interaction which is long ranged, power-like in the inverse distance, but whose power sensitively depends on possible restrictions of the colloid degrees of freedom. A nonzero line tension leads to changes in the magnitude but not in the functional form of the effective potential asymptotics.

  19. Diogene pictorial drift chamber

    SciTech Connect

    Gosset, J.

    1984-01-01

    A pictorial drift chamber, called DIOGENE, has been installed at Saturne in order to study central collisions of high energy heavy ions. It has been adapted from the JADE internal detector, with two major differences to be taken into account. First, the center-of-mass of these collisions is not identical to the laboratory reference frame. Second, the energy loss and the momentum ranges of the particles to be detected are different from the ones in JADE. It was also tried to keep the cost as small as possible, hence the choice of minimum size and minimum number of sensitive wires. Moreover the wire planes are shifted from the beam axis: this trick helps very much to quickly reject the bad tracks caused by the ambiguity of measuring drift distances (positive or negative) through times (always positive).

  20. Evolution and stability of shock waves in dissipative gases characterized by activated inelastic collisions.

    PubMed

    Sirmas, N; Radulescu, M I

    2015-02-01

    Previous experiments have revealed that shock waves driven through dissipative gases may become unstable, for example, in granular gases and in molecular gases undergoing strong relaxation effects. The mechanisms controlling these instabilities are not well understood. We successfully isolated and investigated this instability in the canonical problem of piston-driven shock waves propagating into a medium characterized by inelastic collision processes. We treat the standard model of granular gases, where particle collisions are taken as inelastic, with a constant coefficient of restitution. The inelasticity is activated for sufficiently strong collisions. Molecular dynamic simulations were performed for 30,000 particles. We find that all shock waves investigated become unstable, with density nonuniformities forming in the relaxation region. The wavelength of these fingers is found to be comparable to the characteristic relaxation thickness. Shock Hugoniot curves for both elastic and inelastic collisions were obtained analytically and numerically. Analysis of these curves indicates that the instability is not of the Bethe-Zeldovich-Thompson or D'yakov-Kontorovich type. Analysis of the shock relaxation rates and rates for clustering in a convected fluid element with the same thermodynamic history ruled out the clustering instability of a homogeneous granular gas. Instead, wave reconstruction of the early transient evolution indicates that the onset of instability occurs during repressurization of the gas following the initial relaxation of the medium behind the lead shock. This repressurization gives rise to internal pressure waves in the presence of strong density gradients. This indicates that the mechanism of instability is more likely of the vorticity-generating Richtmyer-Meshkov type, relying on the action of the inner pressure wave development during the transient relaxation. PMID:25768593

  1. Narrowband frequency-drift structures in solar type IV bursts

    NASA Astrophysics Data System (ADS)

    Nishimura, Yukio; Ono, Takayuki; Tsuchiya, Fuminori; Misawa, Hiroaki; Kumamoto, Atsushi; Katoh, Yuto; Masuda, Satoshi; Miyoshi, Yoshizumi

    2013-12-01

    We have established the Zao Solar Radiospectrograph (ZSR), a new solar radio observation system, at the Zao observatory of Tohoku University, Japan. We observed narrowband fine structures with type IV bursts with ZSR on 2 and 3 November 2008. The observed fine structures are similar to fiber bursts in terms of the drift rates and the existence of emission and absorption stripes. Statistical analysis of the drift rates, however, shows that the observed fine structures are different from the ordinary fiber bursts as regards the sense and the magnitude of their drift rates. First, the observed drift rates include both positive and negative rates, whereas ordinary fiber bursts are usually characterized by negative drift rates. Second, the absolute values of the observed drift rates are tens of MHz s-1, whereas the typical drift rate of fiber bursts at 325 MHz is approximately -9 MHz s-1. In addition, all fine structures analyzed have narrow emission bands of less than 17 MHz. We also show that the observed narrowband emission features with drift rates of approximately 40 MHz s-1 can be interpreted as the propagation of whistler-mode waves, which is the same process as that underlying fiber bursts.

  2. A theoretical model of asymmetric wave ripples

    PubMed Central

    Blondeaux, P.; Foti, E.; Vittori, G.

    2015-01-01

    The time development of ripples under sea waves is investigated by means of the weakly nonlinear stability analysis of a flat sandy bottom subjected to the viscous oscillatory flow that is present in the boundary layer at the bottom of propagating sea waves. Second-order effects in the wave steepness are considered, to take into account the presence of the steady drift generated by the surface waves. Hence, the work of Vittori & Blondeaux (1990 J. Fluid Mech. 218, 19–39 (doi:10.1017/S002211209000091X)) is extended by considering steeper waves and/or less deep waters. As shown by the linear analysis of Blondeaux et al. (2000 Eur. J. Mech. B 19, 285–301 (doi:10.1016/S0997-7546(90)00106-I)), because of the presence of a steady velocity component in the direction of wave propagation, ripples migrate at a constant rate that depends on sediment and wave characteristics. The weakly nonlinear analysis shows that the ripple profile is no longer symmetric with respect to ripple crests and troughs and the symmetry index is computed as a function of the parameters of the problem. In particular, a relationship is determined between the symmetry index and the strength of the steady drift. A fair agreement between model results and laboratory data is obtained, albeit further data and analyses are necessary to determine the behaviour of vortex ripples and to be conclusive. PMID:25512587

  3. A theoretical model of asymmetric wave ripples.

    PubMed

    Blondeaux, P; Foti, E; Vittori, G

    2015-01-28

    The time development of ripples under sea waves is investigated by means of the weakly nonlinear stability analysis of a flat sandy bottom subjected to the viscous oscillatory flow that is present in the boundary layer at the bottom of propagating sea waves. Second-order effects in the wave steepness are considered, to take into account the presence of the steady drift generated by the surface waves. Hence, the work of Vittori & Blondeaux (1990 J. Fluid Mech. 218, 19-39 (doi:10.1017/S002211209000091X)) is extended by considering steeper waves and/or less deep waters. As shown by the linear analysis of Blondeaux et al. (2000 Eur. J. Mech. B 19, 285-301 (doi:10.1016/S0997-7546(90)00106-I)), because of the presence of a steady velocity component in the direction of wave propagation, ripples migrate at a constant rate that depends on sediment and wave characteristics. The weakly nonlinear analysis shows that the ripple profile is no longer symmetric with respect to ripple crests and troughs and the symmetry index is computed as a function of the parameters of the problem. In particular, a relationship is determined between the symmetry index and the strength of the steady drift. A fair agreement between model results and laboratory data is obtained, albeit further data and analyses are necessary to determine the behaviour of vortex ripples and to be conclusive. PMID:25512587

  4. Personality types in adolescence: change and stability and links with adjustment and relationships: a five-wave longitudinal study.

    PubMed

    Meeus, Wim; Van de Schoot, Rens; Klimstra, Theo; Branje, Susan

    2011-07-01

    We examined change and stability of the 3 personality types identified by Block and Block (1980) and studied their links with adjustment and relationships. We used data from a 5-wave study of 923 early-to-middle and 390 middle-to-late adolescents, thereby covering the ages of 12-20 years. In Study 1, systematic evidence for personality change was found, in that the number of overcontrollers and undercontrollers decreased, whereas the number of resilients increased. Undercontrol, in particular, was found to peak in early-to-middle adolescence. We also found substantial stability of personality types, because 73.5% of the adolescents had the same personality type across the 5 waves. Personality change was mainly characterized by 2 transitions: overcontrol → resiliency and undercontrol → resiliency. The transitional analyses implied that the resilient type serves more often as the end point of personality development in adolescence than do overcontrol and undercontrol. Analyses of the personality type trajectories also revealed that the majority of adolescents who change personality type across 5 years made only 1 transition. Study 2 revealed systematic differences between resilients and overcontrollers in anxiety. Stable resilients were less anxious over time than were stable overcontrollers. Further, change from overcontrol to the resilient type was accompanied by decreases in anxiety, whereas change from the resilient type to overcontrol was accompanied by an increase in anxiety. Similarly, systematic differences between personality types were found in the formation of intimate relationships. PMID:21639626

  5. The axisymmetric long-wave interfacial stability of core-annular flow of power-law fluid with surfactant

    NASA Astrophysics Data System (ADS)

    Sun, Xue-Wei; Peng, Jie; Zhu, Ke-Qin

    2012-02-01

    The long wave stability of core-annular flow of power-law fluids with an axial pressure gradient is investigated at low Reynolds number. The interface between the two fluids is populated with an insoluble surfactant. The analytic solution for the growth rate of perturbation is obtained with long wave approximation. We are mainly concerned with the effects of shear-thinning/thickening property and interfacial surfactant on the flow stability. The results show that the influence of shear-thinning/thickening property accounts to the change of the capillary number. For a clean interface, the shear-thinning property enhances the capillary instability when the interface is close to the pipe wall. The converse is true when the interface is close to the pipe centerline. For shear-thickening fluids, the situation is reversed. When the interface is close to the pipe centerline, the capillary instability can be restrained due to the influence of surfactant. A parameter set can be found under which the flow is linearly stable.

  6. Laboratory Course on Drift Chambers

    NASA Astrophysics Data System (ADS)

    García-Ferreira, Ix-B.; García-Herrera, J.; Villaseñor, L.

    2006-09-01

    Drift chambers play an important role in particle physics experiments as tracking detectors. We started this laboratory course with a brief review of the theoretical background and then moved on to the the experimental setup which consisted of a single-sided, single-cell drift chamber. We also used a plastic scintillator paddle, standard P-10 gas mixture (90% Ar, 10% CH4) and a collimated 90Sr source. During the laboratory session the students performend measurements of the following quantities: a) drift velocities and their variations as function of the drift field; b) gas gains and c) diffusion of electrons as they drifted in the gas.

  7. Concentration of Laplace Eigenfunctions and Stabilization of Weakly Damped Wave Equation

    NASA Astrophysics Data System (ADS)

    Burq, N.; Zuily, C.

    2016-08-01

    In this article, we prove some universal bounds on the speed of concentration on small (frequency-dependent) neighbourhoods of sub-manifolds of L 2-norms of quasi modes for Laplace operators on compact manifolds. We deduce new results on the rate of decay of weakly damped wave equations.

  8. Phase stability of a standing-wave free-electron laser

    SciTech Connect

    Sharp, W.M.; Rangarajan, G.; Sessler, A.M.; Wurtele, J.S.

    1991-01-01

    The standing-wave free-electron laser (FEL) differs from a conventional linear-wiggler microwave FEL in using irises along the wiggler to form a series of standing-wave cavities and in reaccelerating the beam between cavities to maintain the average energy. The device has been proposed for use in a two-beam accelerator because microwave power can be extracted more effectively than from a traveling-wave FEL. A simplified numerical simulation indicates that, with appropriate prebunching, the standing-wave FEL can produce an output signal that is effectively the same in all cavities. However, changes in the beam energy of less than 1% are found to introduce unacceptably large fluctuations of signal phase along the device. Analytic calculations and single-particle simulations are used here to show that the phase fluctuations result from beam synchrotron motion in the initial signal field, and an approximate analytic expression for the signal phase is derived. Numerical simulations are used to illustrate the dependence of phase fluctuations on the beam prebunching, the beam-current axial profile, and the initial signal amplitude.

  9. Boundary conditions and stability of a perfectly matched layer for the elastic wave equation in first order form

    NASA Astrophysics Data System (ADS)

    Duru, Kenneth; Kozdon, Jeremy E.; Kreiss, Gunilla

    2015-12-01

    In computations, it is now common to surround artificial boundaries of a computational domain with a perfectly matched layer (PML) of finite thickness in order to prevent artificially reflected waves from contaminating a numerical simulation. Unfortunately, the PML does not give us an indication about appropriate boundary conditions needed to close the edges of the PML, or how those boundary conditions should be enforced in a numerical setting. Terminating the PML with an inappropriate boundary condition or an unstable numerical boundary procedure can lead to exponential growth in the PML which will eventually destroy the accuracy of a numerical simulation everywhere. In this paper, we analyze the stability and the well-posedness of boundary conditions terminating the PML for the elastic wave equation in first order form. First, we consider a vertical modal PML truncating a two space dimensional computational domain in the horizontal direction. We freeze all coefficients and consider a left half-plane problem with linear boundary conditions terminating the PML. The normal mode analysis is used to study the stability and well-posedness of the resulting initial boundary value problem (IBVP). The result is that any linear well-posed boundary condition yielding an energy estimate for the elastic wave equation, without the PML, will also lead to a well-posed IBVP for the PML. Second, we extend the analysis to the PML corner region where both a horizontal and vertical PML are simultaneously active. The challenge lies in constructing accurate and stable numerical approximations for the PML and the boundary conditions. Third, we develop a high order accurate finite difference approximation of the PML subject to the boundary conditions. To enable accurate and stable numerical boundary treatments for the PML we construct continuous energy estimates in the Laplace space for a one space dimensional problem and two space dimensional PML corner problem. We use summation

  10. Nonlinear EHD stability of the travelling and standing waves of two superposed dielectric bounded fluids in relative motion

    NASA Astrophysics Data System (ADS)

    El-Sayed, M. F.

    2001-03-01

    The nonlinear modulation of the interfacial waves of two superposed dielectric fluids with uniform depths and rigid horizontal boundaries, under the influence of constant normal electric fields and uniform horizontal velocities, is investigated using the multiple-time scales method. It is found that the quasi-monochromatic travelling waves can be described by a nonlinear Schrödinger equation in a frame of reference moving with the group velocity. The stability of uniform and periodic solution of the nonlinear Schrödinger equation is tested by means of three-mode model, involving the interaction of a finite number of Fourier components. A set of coupled differential equations is obtained, describing the effect of sideband modulations. The Benjamin-Feir instability appears clearly related to the linearized technique, and is the first stage of the nonlinear recurrence phenomenon. On the other hand, the complex amplitude of quasi-monochromatic standing waves near the cut-off wavenumber is governed by a similar type of nonlinear Schrödinger equation in which the roles of time and space are interchanged. This equation makes it possible to estimate the nonlinear effect on the linear cut-off wavenumber.

  11. Drift Resonance in High Density Nonneutral Plasmas

    NASA Astrophysics Data System (ADS)

    Kaup, D. J.

    2005-10-01

    Theoretical studies of the operation of crossed-field electron vacuum devices, such as magnetrons and crossed-field amplifiers (CFA), have usually centered on their initial growth, taking this as an indication of their operating modes. In such an analysis, one solves the equations for the density profile and other features of these devices. However what one actually obtains are only the conditions for the initial operation of the device. Eventually the rf fields will saturate, at which time, an operating device will settle into a stationary operating regime, called the ``saturation stage,'' which is where the device simply delivers rf power. Here there is a different set of physical interactions occuring. The amplitudes have saturated and the ponderomotive forces and nonlinear diffusion of the initiation stage have vanished. In this saturation stage, we now find three new rf modes appearing, in addition to the two modes of the initiation stage. These three new modes have very fast oscillations in the vertical direction: one fast mode corresponds to a plasma drift wave, while the other two fast modes are cyclotron-like modes. In this presentation, we will describe how the fast plasma drift wave interacts with the slow modes at the diocotron resonance. In particular, we will determine the conversion coefficients for the crossing of the drift mode with the slow modes at the diocotron resonance.

  12. Two-stream instability with time-dependent drift velocity

    SciTech Connect

    Qin, Hong; Davidson, Ronald C.

    2014-06-15

    The classical two-stream instability driven by a constant relative drift velocity between two plasma components is extended to the case with time-dependent drift velocity. A solution method is developed to rigorously define and calculate the instability growth rate for linear perturbations relative to the time-dependent unperturbed two-stream motions. Stability diagrams for the oscillating two-stream instability are presented over a large region of parameter space. It is shown that the growth rate for the classical two-stream instability can be significantly reduced by adding an oscillatory component to the relative drift velocity.

  13. Two-stream instability with time-dependent drift velocity

    DOE PAGESBeta

    Qin, Hong; Davidson, Ronald C.

    2014-06-26

    The classical two-stream instability driven by a constant relative drift velocity between two plasma components is extended to the case with time-dependent drift velocity. A solution method is developed to rigorously define and calculate the instability growth rate for linear perturbations relative to the time-dependent unperturbed two-stream motions. The stability diagrams for the oscillating two-stream instability are presented over a large region of parameter space. It is shown that the growth rate for the classical two-stream instability can be significantly reduced by adding an oscillatory component to the relative drift velocity.

  14. Roll stability catastrophe mechanism of a flooded ship on regular sea waves

    NASA Astrophysics Data System (ADS)

    Liu, Yu-Liang

    2014-04-01

    Based on a typical one-free-degree ship roll motion equation, the cusp catastrophe model is built including the bifurcation set equation, splitting factor ‘u’ and regular factor ‘v’, where both ‘u’ and ‘v’ are further expressed with typical flooded ship parameters. Then, the roll catastrophe mechanism is analyzed mainly by means ‘u’, under the given parameters of a typical trawler boat. The aim of this research is to reveal the mutagenic mechanism of the roll stability and provide a reference for improving ship roll stability.

  15. Stability analysis of numerical solutions of wave propagation when pseudoviscosity is replaced by real viscosity

    NASA Astrophysics Data System (ADS)

    Fanget, A.

    1996-05-01

    The artificial viscocity method was originally introduced by Von Neuman and Richtmeyer [R.D. Richtmeyer and K. W. Morton, in Difference methods for Initial Value Problem (Interscience, New York, 1967)] to spread the shock over several cells of the mesh. This method is useful if the physical phenomena present in the shock front are not of interest. In some cases, such as for polymers, the amount of viscosity is large enough to spread the front shock naturally. In our problem, pseudoviscosity is ignored. A stability analysis shows that time step restrictions for stability can be less stringent than with pseudoviscosity.

  16. Influence of atmospheric static stability and meridional temperature gradient on the growth in amplitude of synoptic-scale unstable waves

    NASA Astrophysics Data System (ADS)

    Soldatenko, S. A.

    2014-11-01

    Observations and results of numerical experiments with climate models under different green-house-gas emission scenarios point to a reconstruction of the thermal and circulation atmospheric regime induced by global climate changes. In particular, an increase in atmospheric static stability, a poleward shift of midlatitude storm tracks, a decrease in the frequency of extratropical cyclones, and a change in their intensity are found at tropical and middle latitudes. This paper, using a simplified idealized model of baroclinic instability, investigates the influence of small variations in the basic atmospheric parameters governing the development of baroclinic instability, namely, static stability and the vertical quasi-zonal flow velocity shear induced by a meridional temperature gradient, on variations in the growth rate of the amplitude of synopticscale unstable waves. Analytical expressions are derived for absolute and relative sensitivity functions to estimate the absolute and relative contribution of variations in the static stability and the vertical flow velocity shear to a change in the growth rate of the amplitude of unstable modes.

  17. Numerical proof of stability of roll waves in the small-amplitude limit for inclined thin film flow

    NASA Astrophysics Data System (ADS)

    Barker, Blake

    2014-10-01

    We present a rigorous numerical proof based on interval arithmetic computations categorizing the linearized and nonlinear stability of periodic viscous roll waves of the KdV-KS equation modeling weakly unstable flow of a thin fluid film on an incline in the small-amplitude KdV limit. The argument proceeds by verification of a stability condition derived by Bar-Nepomnyashchy and Johnson-Noble-Rodrigues-Zumbrun involving inner products of various elliptic functions arising through the KdV equation. One key point in the analysis is a bootstrap argument balancing the extremely poor sup norm bounds for these functions against the extremely good convergence properties for analytic interpolation in order to obtain a feasible computation time. Another is the way of handling analytic interpolation in several variables by a two-step process carving up the parameter space into manageable pieces for rigorous evaluation. These and other general aspects of the analysis should serve as blueprints for more general analyses of spectral stability.

  18. A class of reduced-order models in the theory of waves and stability

    PubMed Central

    Sorokin, S. V.

    2016-01-01

    This paper presents a class of approximations to a type of wave field for which the dispersion relation is transcendental. The approximations have two defining characteristics: (i) they give the field shape exactly when the frequency and wavenumber lie on a grid of points in the (frequency, wavenumber) plane and (ii) the approximate dispersion relations are polynomials that pass exactly through points on this grid. Thus, the method is interpolatory in nature, but the interpolation takes place in (frequency, wavenumber) space, rather than in physical space. Full details are presented for a non-trivial example, that of antisymmetric elastic waves in a layer. The method is related to partial fraction expansions and barycentric representations of functions. An asymptotic analysis is presented, involving Stirling's approximation to the psi function, and a logarithmic correction to the polynomial dispersion relation. PMID:27118895

  19. Stability and Instability of the KDV Solitary Wave Under the KP-I Flow

    NASA Astrophysics Data System (ADS)

    Rousset, Frederic; Tzvetkov, Nikolay

    2012-07-01

    We consider the KP-I and gKP-I equations in {{{R}} × ({{R}}/2π{{Z}})}. We prove that the KdV soliton with subcritical speed 0 < c < c* is orbitally stable under the global KP-I flow constructed by Ionescu and Kenig (Ann Math Stud 163:181-211, 2007). For supercritical speeds c > c*, in the spirit of the work by Duyckaerts and Merle (GAFA 18:1787-1840, 2009), we sharpen our previous instability result and construct a global solution which is different from the solitary wave and its translates and which converges to the solitary wave as time goes to infinity. This last result also holds for the gKP-I equation.

  20. Long-wave linear stability theory for two-fluid channel flow including compressibility effects

    NASA Astrophysics Data System (ADS)

    Segin, Tetyana M.; Kondic, Lou; Tilley, Burt S.

    2006-10-01

    We present the linear stability of the laminar flow of an immiscible system of a compressible gas and incompressible liquid separated by an interface with large surface tension in a thin inclined channel. The flow is driven by an applied pressure drop and gravity. Following the air-water case, which is found in a variety of engineering systems, the ratio of the characteristic values of the gas and liquid densities and viscosities are assumed to be disparate. Under the lubrication approximation, and assuming ideal gas behaviour and isothermal conditions, this approach leads to a coupled non-linear system of partial differential equations describing the evolution of the interface between the gas and the liquid and the streamwise density distribution of the gas. This system also includes the effects of viscosity stratification, inertia, shear and capillarity. A linear stability analysis that allows for physically relevant non-zero pressure-drop base state is then performed. In contrast to the zero-pressure drop case which is amenable to the classical normal-mode approach, this configuration requires numerically solving a boundary-value problem for the gas density and interfacial deviations from the base state in the streamwise coordinate. We find that the effect of the gas compressibility on the interfacial stability in the limit of vanishingly small wavenumber is destabilizing, even for Stokes flow in the liquid. However, for finite wavenumber disturbances, compressibility may have stabilizing effects. In this regime, sufficient shear is required to destabilize the flow.

  1. Analysis of hydrogen maser frequency drift due to possible drifts in load VSWR and phase angle of reflection coefficient

    NASA Technical Reports Server (NTRS)

    Beatty, R. W.; Otosh, T. Y.

    1978-01-01

    Theoretical equations are derived for calculating the effects of local VSWR and reflection coefficient phase angle drifts on hydrogen maser frequency stability. Sample calculations made for a typical JPL maser show that under special load conditions, a VSWR drift of 0.000075/h or phase angle drive of 0.01 deg/h can produce a frequency drift of (10 to the -14th power f sub 0) Hz/h where f sub 0 is the maser frequency of approximately 1.42 x 10 to the 9th power Hz.

  2. Non-Neutral Drift Resonance in Magnetrons

    NASA Astrophysics Data System (ADS)

    Kaup, D. J.

    2005-04-01

    We study the features of the RF fields in a magnetron, when the RF amplitude has saturated, in the nonrelativistic, electrostatic limit. In this saturated stage, the linear RF equations can be reduced to a fifth-order set of ordinary differential equations. Two modes of which are fast cyclotron modes, one mode is a fast drift wave, and the other two modes are the usual, well-known, slow magnetron modes. Here, we will study the interaction between the fast drift mode (diocotron mode) and the slow magnetron modes, at the diocotron resonance. We will also show that the fast cyclotron modes can be ignored at this resonance, and thereby can reduce the system to a third- order set of ordinary differential equations. Using multiscale techniques, we will then obtain solutions for the inner and the outer regions at the diocotron resonance, and thereby obtain the conversion and transmission rates between these three modes at the diocotron resonance.

  3. Drift in toroidal configurations

    NASA Astrophysics Data System (ADS)

    Evangelidis, E. A.

    1990-12-01

    This paper considers possible mechanisms involved in amplifying the drift velocity of plasma particles, under conditions of toroidal geometry. It is shown that particles constrained to move on an axisymmetric circular spheroidal surface, develop a sinusoidal motion with a characteristic frequency which depends on the energy of the particles, the value of the isoflux surface, and the value of the general momentum. It is also shown that the incorporation of the effects of toroidal geometry in the Lorentz equation produces a nonambipolar charge-dependent particle flux amplified by a factor 2(q/epsilon) squared.

  4. Spaced antenna drift

    NASA Technical Reports Server (NTRS)

    Royrvik, O.

    1983-01-01

    It has been suggested that the spaced antenna drift (SAD) technique could be successfully used by VHF radars and that it would be superior to a Doppler-beam-swinging (DBS) technique because it would take advantage of the aspect sensitivity of the scattered signal, and might also benefit from returns from single meteors. It appears, however, that the technique suffers from several limitations. On the basis of one SAD experiment performed at the very large Jicamarca radar, it is concluded that the SAD technique can be compared in accuracy to the DBS technique only if small antenna dimensions are used.

  5. Arabidopsis BRICK1/HSPC300 is an essential WAVE-complex subunit that selectively stabilizes the Arp2/3 activator SCAR2.

    PubMed

    Le, Jie; Mallery, Eileen L; Zhang, Chunhua; Brankle, Steven; Szymanski, Daniel B

    2006-05-01

    The actin cytoskeleton dynamically reorganizes the cytoplasm during cell morphogenesis. The actin-related protein (Arp)2/3 complex is a potent nucleator of actin filaments that controls a variety of endomembrane functions including the endocytic internalization of plasma membrane , vacuole biogenesis , plasma-membrane protrusion in crawling cells , and membrane trafficking from the Golgi . Therefore, Arp2/3 is an important signaling target during morphogenesis. The evolutionarily conserved Rac-WAVE-Arp2/3 pathway links actin filament nucleation to cell morphogenesis . WAVE translates Rac-GTP signals into Arp2/3 activation by regulating the stability and/or localization of the activator subunit Scar/WAVE . The WAVE complex includes Sra1/PIR121/CYFIP1, Nap1/NAP125, Abi-1/Abi-2, Brick1(Brk1)/HSPC300, and Scar/WAVE : Defining the in vivo function of each subunit is an important step toward understanding this complicated signaling pathway. Brk1/HSPC300 has been the most recalcitrant WAVE-complex protein and has no known function. In this paper, we report that Arabidopsis brick1 (brk1) is a member of the "distorted group" of trichome morphology mutants, a group that defines a WAVE-ARP2/3 morphogenesis pathway . In this paper we provide the first strong genetic and biochemical evidence that BRK1 is a critical WAVE-complex subunit that selectively stabilizes the Arp2/3 activator SCAR2. PMID:16584883

  6. Stability of the subseismic wave equation for the Earth's fluid core

    NASA Astrophysics Data System (ADS)

    Friedlander, Susan

    The effects of compressibility on the stability of internal oscillations in the Earth's fluid core are examined in the context of the subseismic approximation for the equations of motion describing a rotating, stratified, self-gravitating, compressible fluid in a thick shell. It is shown that in the case of a bounded fluid the results are closely analogous to those derived under the Boussinesq approximation.

  7. On the stabilization of neoclassical tearing modes by electron cyclotron waves

    NASA Astrophysics Data System (ADS)

    Ramponi, G.; Lazzaro, E.; Nowak, S.

    1999-09-01

    The control of neoclassical tearing modes in tokamaks by means of electron cyclotron current drive and heating is investigated. The nonlinear evolution of the amplitude in absence and in presence of the stabilizing terms of an auxiliary current inside the island and of the associate heating is solved self-consistently with the evolution of the rotation frequency for International Thermonuclear Experimental Reactor (ITER) reference magnetic equilibrium [ITER-JCT and Home Teams, Plasma Phys. Controlled Fusion 37, A19 (1995)]. It is shown that, unless the wall braking torque is neutralized by external means, neoclassical tearing modes in ITER will be locked in a very short time. On the other hand, for rotating islands, the beneficial effect of modulating the current source in phase with the island rotation is pointed out, after an analysis of the time scales of the relevant phenomena (time response of the driven current, island rotation frequency, power pulse duration, and inductive response of the plasma). Consideration is given to different effects that may reduce the efficiency of the control of the flux reconnection rate and to the benefits of wall stabilization associated to the island rotation frequency. A quantitative assessment of the EC (electron cyclotron) power required to keep the island width at a reasonable level is given, both in absence and in presence of wall stabilization.

  8. Effect of ultrasonic waves on the stability of all-trans lutein and its degradation kinetics.

    PubMed

    Song, Jiang-Feng; Li, Da-Jing; Pang, Hui-Li; Liu, Chun-Quan

    2015-11-01

    Ultrasound treatment has been widely applied in the extraction of biologically active compounds including carotenoids. However, there are few reports on their effects on the stability of these compounds. In the present study, the stability of all-trans lutein, one of the carotenoids, was investigated under the action of ultrasound. Results showed that ultrasound induced the isomerization of all-trans lutein to its isomers, namely to 13-cis lutein, 13'-cis lutein, 9-cis lutein and 9'-cis lutein as analyzed by HPLC coupled with DAD and LC-MS; and the percentage of the isomerization increased with increasing both ultrasonic frequency and power. The stability of all-trans lutein in dichloromethane was worst among multiple kinds of solvents. Interestingly, the retention rate of all-trans lutein improved as the temperature increased, which runs counter to the Arrhenius law. Under ultrasound irradiation, the degradation mechanism might be different with various temperatures, the degradation of all-trans lutein followed first-order kinetics at 20°C, while second-order kinetics was followed at 30-50°C. As the ultrasonic reaction time prolonged, lutein epoxidation nearly occurred. Those results presented here emphasized that UAE techniques should be carefully used in the extraction of all-trans lutein. PMID:25934130

  9. Wave propagation in and stability of geomaterials with negative stiffness inclusions

    NASA Astrophysics Data System (ADS)

    Esin, Maxim; Dyskin, Arcady; Pasternak, Elena

    2015-04-01

    The effects of negative stiffness are some times observed in the behaviour of geomaterials, for instance, in the form of post-peak softening. Locally the negative stiffness can be caused by rotations of non-spherical blocks, fragments or grains and can be interpreted as negative shear modulus. While the negative stiffness materials are inherently unstable, materials with negative stiffness inclusions can still be stable as long as the concentration of the inclusions does not exceed a critical one. As the concentration of negative stiffness increases and approaching the critical value the effective shear modulus can both increase or decrease compared to the matrix value. Correspondingly the wave velocities can increase or decrease thus providing a monitoring tool to predict the approaching instability stage and possibly failure. In order to investigate the mechanism of instability in detail we model geomaterials as discrete mass-spring systems with normal, shear and rotating springs between point masses in one-, two- and three-dimensions. By analysing the equations of motion of such a system we established that systems with certain number of negative stiffness inclusions could be stable and permit wave propagation. For example a finite, one-dimensional mass-spring system with normal and shear springs is stable if not more than one normal and one shear springs are of negative stiffness. Furthermore, the presence of negative stiffness springs increases the stiffness of the system and enhances the damping. These findings open a way to construct the discrete models of geomaterials with negative stiffness inclusions that fit the observed peculiarities of the wave propagation.

  10. Surface waves and stability of tangential velocity discontinuity on a solid-fluid boundary

    NASA Astrophysics Data System (ADS)

    Simonov, I. V.

    1981-05-01

    Solutions of the Rayleigh-wave type on the boundary of an elastic half-space and a moving layer of ideal fluid are obtained. The limiting cases of zero flow velocity and a tangential velocity discontinuity in the fluid were investigated in [1 3]. In [4] the order of magnitude of the critical flow velocity was estimated. An increase in the velocity scales used in engineering and experimental practice (see [5], for instance) has aroused interest in a more thorough analysis of the effect.

  11. Fingermark ridge drift.

    PubMed

    De Alcaraz-Fossoul, Josep; Roberts, Katherine A; Feixat, Carme Barrot; Hogrebe, Gregory G; Badia, Manel Gené

    2016-01-01

    Distortions of the fingermark topography are usually considered when comparing latent and exemplar fingerprints. These alterations are characterized as caused by an extrinsic action, which affects entire areas of the deposition and alters the overall flow of a series of contiguous ridges. Here we introduce a novel visual phenomenon that does not follow these principles, named fingermark ridge drift. An experiment was designed that included variables such as type of secretion (eccrine and sebaceous), substrate (glass and polystyrene), and degrees of exposure to natural light (darkness, shade, and direct light) indoors. Fingermarks were sequentially visualized with titanium dioxide powder, photographed and analyzed. The comparison between fresh and aged depositions revealed that under certain environmental conditions an individual ridge could randomly change its original position regardless of its unaltered adjacent ridges. The causes of the drift phenomenon are not well understood. We believe it is exclusively associated with intrinsic natural aging processes of latent fingermarks. This discovery will help explain the detection of certain dissimilarities at the minutiae/ridge level; determine more accurate "hits"; identify potentially erroneous corresponding points; and rethink identification protocols, especially the criteria of "no single minutiae discrepancy" for a positive identification. PMID:26646735

  12. Approximate Stokes Drift Profiles and their use in Ocean Modelling

    NASA Astrophysics Data System (ADS)

    Breivik, Oyvind; Bidlot, Jea-Raymond; Janssen, Peter A. E. M.; Mogensen, Kristian

    2016-04-01

    Deep-water approximations to the Stokes drift velocity profile are explored as alternatives to the monochromatic profile. The alternative profiles investigated rely on the same two quantities required for the monochromatic profile, viz the Stokes transport and the surface Stokes drift velocity. Comparisons against parametric spectra and profiles under wave spectra from the ERA-Interim reanalysis and buoy observations reveal much better agreement than the monochromatic profile even for complex sea states. That the profiles give a closer match and a more correct shear has implications for ocean circulation models since the Coriolis-Stokes force depends on the magnitude and direction of the Stokes drift profile and Langmuir turbulence parameterizations depend sensitively on the shear of the profile. Of the two Stokes drift profiles explored here, the profile based on the Phillips spectrum is by far the best. In particular, the shear near the surface is almost identical to that influenced by the f‑5 tail of spectral wave models. The NEMO general circulation ocean model was recently extended to incorporate the Stokes-Coriolis force along with two other wave-related effects. The ECWMF coupled atmosphere-wave-ocean ensemble forecast system now includes these wave effects in the ocean model component (NEMO).

  13. Passive appendages generate drift through symmetry breaking

    NASA Astrophysics Data System (ADS)

    Lācis, U.; Brosse, N.; Ingremeau, F.; Mazzino, A.; Lundell, F.; Kellay, H.; Bagheri, S.

    2014-10-01

    Plants and animals use plumes, barbs, tails, feathers, hairs and fins to aid locomotion. Many of these appendages are not actively controlled, instead they have to interact passively with the surrounding fluid to generate motion. Here, we use theory, experiments and numerical simulations to show that an object with a protrusion in a separated flow drifts sideways by exploiting a symmetry-breaking instability similar to the instability of an inverted pendulum. Our model explains why the straight position of an appendage in a fluid flow is unstable and how it stabilizes either to the left or right of the incoming flow direction. It is plausible that organisms with appendages in a separated flow use this newly discovered mechanism for locomotion; examples include the drift of plumed seeds without wind and the passive reorientation of motile animals.

  14. Chandra Optical Axis, Aimpoint and Their Drifts

    NASA Astrophysics Data System (ADS)

    Zhao, Ping

    2014-08-01

    Chandra X-ray Observatory revolutionized the X-ray astronomy as being the first, and so far the only, X-ray telescope achieving sub-arcsecond resolution. Chandra comprises of three principal elements: the High Resolution Mirror Assembly (HRMA), Pointing Control and Aspect Determination (PCAD) system, and the Science Instrument Module (SIM). To achieve and retain the unprecedented imaging quality, it is critical that these three principal elements stay rigid and stable for the entire life time of the Chandra operation. Measuring and tracking the telescope optical axis and aimpoint positions are the key to understand the stability of the telescope and to maintain the optimal Chandra operation. The study shows that both the optical axis and the aimpoint has been drifting since Chandra launch. I will review the history and current status of these drift and their impact to the Chandra operation, as well as the steps we took to ensure the Chandra science returns.

  15. Passive appendages generate drift through symmetry breaking.

    PubMed

    Lācis, U; Brosse, N; Ingremeau, F; Mazzino, A; Lundell, F; Kellay, H; Bagheri, S

    2014-01-01

    Plants and animals use plumes, barbs, tails, feathers, hairs and fins to aid locomotion. Many of these appendages are not actively controlled, instead they have to interact passively with the surrounding fluid to generate motion. Here, we use theory, experiments and numerical simulations to show that an object with a protrusion in a separated flow drifts sideways by exploiting a symmetry-breaking instability similar to the instability of an inverted pendulum. Our model explains why the straight position of an appendage in a fluid flow is unstable and how it stabilizes either to the left or right of the incoming flow direction. It is plausible that organisms with appendages in a separated flow use this newly discovered mechanism for locomotion; examples include the drift of plumed seeds without wind and the passive reorientation of motile animals. PMID:25354545

  16. Passive appendages generate drift through symmetry breaking

    PubMed Central

    Lācis, U.; Brosse, N.; Ingremeau, F.; Mazzino, A.; Lundell, F.; Kellay, H.; Bagheri, S.

    2014-01-01

    Plants and animals use plumes, barbs, tails, feathers, hairs and fins to aid locomotion. Many of these appendages are not actively controlled, instead they have to interact passively with the surrounding fluid to generate motion. Here, we use theory, experiments and numerical simulations to show that an object with a protrusion in a separated flow drifts sideways by exploiting a symmetry-breaking instability similar to the instability of an inverted pendulum. Our model explains why the straight position of an appendage in a fluid flow is unstable and how it stabilizes either to the left or right of the incoming flow direction. It is plausible that organisms with appendages in a separated flow use this newly discovered mechanism for locomotion; examples include the drift of plumed seeds without wind and the passive reorientation of motile animals. PMID:25354545

  17. Effect of solenoidal magnetic field on drifting laser plasma

    NASA Astrophysics Data System (ADS)

    Takahashi, Kazumasa; Okamura, Masahiro; Sekine, Megumi; Cushing, Eric; Jandovitz, Peter

    2013-04-01

    An ion source for accelerators requires to provide a stable waveform with a certain pulse length appropriate to the application. The pulse length of laser ion source is easy to control because it is expected to be proportional to plasma drifting distance. However, current density decay is proportional to the cube of the drifting distance, so large current loss will occur under unconfined drift. We investigated the stability and current decay of a Nd:YAG laser generated copper plasma confined by a solenoidal field using a Faraday cup to measure the current waveform. It was found that the plasma was unstable at certain magnetic field strengths, so a baffle was introduced to limit the plasma diameter at injection and improve the stability. Magnetic field, solenoid length, and plasma diameter were varied in order to find the conditions that minimize current decay and maximize stability.

  18. Uniformity of spherical shock wave dynamically stabilized by two successive laser profiles in direct-drive inertial confinement fusion implosions

    NASA Astrophysics Data System (ADS)

    Temporal, M.; Canaud, B.; Garbett, W. J.; Ramis, R.

    2015-10-01

    The implosion uniformity of a directly driven spherical inertial confinement fusion capsule is considered within the context of the Laser Mégajoule configuration. Two-dimensional (2D) hydrodynamic simulations have been performed assuming irradiation with two laser beam cones located at 49° and 131° with respect to the axis of symmetry. The laser energy deposition causes an inward shock wave whose surface is tracked in time, providing the time evolution of its non-uniformity. The illumination model has been used to optimize the laser intensity profiles used as input in the 2D hydro-calculations. It is found that a single stationary laser profile does not maintain a uniform shock front over time. To overcome this drawback, it is proposed to use two laser profiles acting successively in time, in order to dynamically stabilize the non-uniformity of the shock front.

  19. Uniformity of spherical shock wave dynamically stabilized by two successive laser profiles in direct-drive inertial confinement fusion implosions

    SciTech Connect

    Temporal, M.; Canaud, B.; Garbett, W. J.; Ramis, R.

    2015-10-15

    The implosion uniformity of a directly driven spherical inertial confinement fusion capsule is considered within the context of the Laser Mégajoule configuration. Two-dimensional (2D) hydrodynamic simulations have been performed assuming irradiation with two laser beam cones located at 49° and 131° with respect to the axis of symmetry. The laser energy deposition causes an inward shock wave whose surface is tracked in time, providing the time evolution of its non-uniformity. The illumination model has been used to optimize the laser intensity profiles used as input in the 2D hydro-calculations. It is found that a single stationary laser profile does not maintain a uniform shock front over time. To overcome this drawback, it is proposed to use two laser profiles acting successively in time, in order to dynamically stabilize the non-uniformity of the shock front.

  20. Drift-scale thermomechanical analysis for the retrievability systems study

    SciTech Connect

    Tsai, F.C.

    1996-04-01

    A numerical method was used to estimate the stability of potential emplacement drifts without considering a ground support system as a part of the Thermal Loading Systems Study for the Yucca Mountain Site Characterization Project. The stability of the drift is evaluated with two variables: the level of thermal loading and the diameter of the emplacement drift. The analyses include the thermomechanical effects generated by the excavation of the drift, subsequently by the thermal loads from heat-emitting waste packages, and finally by the thermal reduction resulting from rapid cooling ventilation required for the waste retrieval if required. The Discontinuous Deformation Analysis (DDA) code was used to analyze the thermomechanical response of the rock mass of multiple blocks separated by joints. The result of this stability analysis is used to discuss the geomechanical considerations for the advanced conceptual design (ACD) with respect to retrievability. In particular, based on the rock mass strength of the host rock described in the current version of the Reference Information Base, the computed thermal stresses, generated by 111 MTU/acre thermal loads in the near field at 100 years after waste emplacement, is beyond the criterion for the rock mass strength used to predict the stability of the rock mass surrounding the emplacement drift.

  1. Flexible 2D Crystals of Polycyclic Aromatics Stabilized by Static Distortion Waves

    PubMed Central

    2016-01-01

    The epitaxy of many organic films on inorganic substrates can be classified within the framework of rigid lattices which helps to understand the origin of energy gain driving the epitaxy of the films. Yet, there are adsorbate–substrate combinations with distinct mutual orientations for which this classification fails and epitaxy cannot be explained within a rigid lattice concept. It has been proposed that tiny shifts in atomic positions away from ideal lattice points, so-called static distortion waves (SDWs), are responsible for the observed orientational epitaxy in such cases. Using low-energy electron diffraction and scanning tunneling microscopy, we provide direct experimental evidence for SDWs in organic adsorbate films, namely hexa-peri-hexabenzocoronene on graphite. They manifest as wave-like sub-Ångström molecular displacements away from an ideal adsorbate lattice which is incommensurate with graphite. By means of a density-functional-theory based model, we show that, due to the flexibility in the adsorbate layer, molecule–substrate energy is gained by straining the intermolecular bonds and that the resulting total energy is minimal for the observed domain orientation, constituting the orientational epitaxy. While structural relaxation at an interface is a common assumption, the combination of the precise determination of the incommensurate epitaxial relation, the direct observation of SDWs in real space, and their identification as the sole source of epitaxial energy gain constitutes a comprehensive proof of this effect. PMID:27014920

  2. Flexible 2D Crystals of Polycyclic Aromatics Stabilized by Static Distortion Waves.

    PubMed

    Meissner, Matthias; Sojka, Falko; Matthes, Lars; Bechstedt, Friedhelm; Feng, Xinliang; Müllen, Klaus; Mannsfeld, Stefan C B; Forker, Roman; Fritz, Torsten

    2016-07-26

    The epitaxy of many organic films on inorganic substrates can be classified within the framework of rigid lattices which helps to understand the origin of energy gain driving the epitaxy of the films. Yet, there are adsorbate-substrate combinations with distinct mutual orientations for which this classification fails and epitaxy cannot be explained within a rigid lattice concept. It has been proposed that tiny shifts in atomic positions away from ideal lattice points, so-called static distortion waves (SDWs), are responsible for the observed orientational epitaxy in such cases. Using low-energy electron diffraction and scanning tunneling microscopy, we provide direct experimental evidence for SDWs in organic adsorbate films, namely hexa-peri-hexabenzocoronene on graphite. They manifest as wave-like sub-Ångström molecular displacements away from an ideal adsorbate lattice which is incommensurate with graphite. By means of a density-functional-theory based model, we show that, due to the flexibility in the adsorbate layer, molecule-substrate energy is gained by straining the intermolecular bonds and that the resulting total energy is minimal for the observed domain orientation, constituting the orientational epitaxy. While structural relaxation at an interface is a common assumption, the combination of the precise determination of the incommensurate epitaxial relation, the direct observation of SDWs in real space, and their identification as the sole source of epitaxial energy gain constitutes a comprehensive proof of this effect. PMID:27014920

  3. Variational properties and orbital stability of standing waves for NLS equation on a star graph

    NASA Astrophysics Data System (ADS)

    Adami, Riccardo; Cacciapuoti, Claudio; Finco, Domenico; Noja, Diego

    2014-11-01

    We study standing waves for a nonlinear Schrödinger equation on a star graph G, i.e. N halflines joined at a vertex. At the vertex an interaction occurs described by a boundary condition of delta type with strength α⩽0. The nonlinearity is of focusing power type. The dynamics is given by an equation of the form iddtΨt=HΨt-|2μΨt, where H is the Hamiltonian operator which generates the linear Schrödinger dynamics. We show the existence of several families of standing waves for every sign of the coupling at the vertex for every ω>α2N2. Furthermore, we determine the ground states, as minimizers of the action on the Nehari manifold, and order the various families. Finally, we show that the ground states are orbitally stable for every allowed ω if the nonlinearity is subcritical or critical, and for ω<ω* otherwise.

  4. Stability and efficacy of synthetic cationic antimicrobial peptides nebulized using high frequency acoustic waves.

    PubMed

    Wang, Ying; Rezk, Amgad R; Khara, Jasmeet Singh; Yeo, Leslie Y; Ee, Pui Lai Rachel

    2016-05-01

    Surface acoustic wave (SAW), a nanometer amplitude electroelastic wave generated and propagated on low-loss piezoelectric substrates (such as LiNbO3), is an extremely efficient solid-fluid energy transfer mechanism. The present study explores the use of SAW nebulization as a solution for effective pulmonary peptide delivery. In vitro deposition characteristics of the nebulized peptides were determined using a Next Generation Cascade Impactor. 70% of the peptide-laden aerosols generated were within a size distribution favorable for deep lung distribution. The integrity of the nebulized peptides was found to be retained, as shown via mass spectrometry. The anti-mycobacterial activity of the nebulized peptides was found to be uncompromised compared with their non-nebulized counterparts, as demonstrated by the minimum inhibition concentration and the colony forming inhibition activity. The peptide concentration and volume recoveries for the SAW nebulizer were significantly higher than 90% and found to be insensitive to variation in the peptide sequences. These results demonstrate the potential of the SAW nebulization platform as an effective delivery system of therapeutic peptides through the respiratory tract to the deep lung. PMID:27375820

  5. Drift-Scale Radionuclide Transport

    SciTech Connect

    J. Houseworth

    2004-09-22

    The purpose of this model report is to document the drift scale radionuclide transport model, taking into account the effects of emplacement drifts on flow and transport in the vicinity of the drift, which are not captured in the mountain-scale unsaturated zone (UZ) flow and transport models ''UZ Flow Models and Submodels'' (BSC 2004 [DIRS 169861]), ''Radionuclide Transport Models Under Ambient Conditions'' (BSC 2004 [DIRS 164500]), and ''Particle Tracking Model and Abstraction of Transport Process'' (BSC 2004 [DIRS 170041]). The drift scale radionuclide transport model is intended to be used as an alternative model for comparison with the engineered barrier system (EBS) radionuclide transport model ''EBS Radionuclide Transport Abstraction'' (BSC 2004 [DIRS 169868]). For that purpose, two alternative models have been developed for drift-scale radionuclide transport. One of the alternative models is a dual continuum flow and transport model called the drift shadow model. The effects of variations in the flow field and fracture-matrix interaction in the vicinity of a waste emplacement drift are investigated through sensitivity studies using the drift shadow model (Houseworth et al. 2003 [DIRS 164394]). In this model, the flow is significantly perturbed (reduced) beneath the waste emplacement drifts. However, comparisons of transport in this perturbed flow field with transport in an unperturbed flow field show similar results if the transport is initiated in the rock matrix. This has led to a second alternative model, called the fracture-matrix partitioning model, that focuses on the partitioning of radionuclide transport between the fractures and matrix upon exiting the waste emplacement drift. The fracture-matrix partitioning model computes the partitioning, between fractures and matrix, of diffusive radionuclide transport from the invert (for drifts without seepage) into the rock water. The invert is the structure constructed in a drift to provide the floor of the

  6. Pilot-wave dynamics in a harmonic potential: Quantization and stability of circular orbits.

    PubMed

    Labousse, M; Oza, A U; Perrard, S; Bush, J W M

    2016-03-01

    We present the results of a theoretical investigation of the dynamics of a droplet walking on a vibrating fluid bath under the influence of a harmonic potential. The walking droplet's horizontal motion is described by an integro-differential trajectory equation, which is found to admit steady orbital solutions. Predictions for the dependence of the orbital radius and frequency on the strength of the radial harmonic force field agree favorably with experimental data. The orbital quantization is rationalized through an analysis of the orbital solutions. The predicted dependence of the orbital stability on system parameters is compared with experimental data and the limitations of the model are discussed. PMID:27078462

  7. Exponential stabilization of magnetoelastic waves in a Mindlin-Timoshenko plate by localized internal damping

    NASA Astrophysics Data System (ADS)

    Grobbelaar-Van Dalsen, Marié

    2015-08-01

    This article is a continuation of our earlier work in Grobbelaar-Van Dalsen (Z Angew Math Phys 63:1047-1065, 2012) on the polynomial stabilization of a linear model for the magnetoelastic interactions in a two-dimensional electrically conducting Mindlin-Timoshenko plate. We introduce nonlinear damping that is effective only in a small portion of the interior of the plate. It turns out that the model is uniformly exponentially stable when the function , that represents the locally distributed damping, behaves linearly near the origin. However, the use of Mindlin-Timoshenko plate theory in the model enforces a restriction on the region occupied by the plate.

  8. Pilot-wave dynamics in a harmonic potential: Quantization and stability of circular orbits

    NASA Astrophysics Data System (ADS)

    Labousse, M.; Oza, A. U.; Perrard, S.; Bush, J. W. M.

    2016-03-01

    We present the results of a theoretical investigation of the dynamics of a droplet walking on a vibrating fluid bath under the influence of a harmonic potential. The walking droplet's horizontal motion is described by an integro-differential trajectory equation, which is found to admit steady orbital solutions. Predictions for the dependence of the orbital radius and frequency on the strength of the radial harmonic force field agree favorably with experimental data. The orbital quantization is rationalized through an analysis of the orbital solutions. The predicted dependence of the orbital stability on system parameters is compared with experimental data and the limitations of the model are discussed.

  9. The Global Nonlinear Stability of Minkowski Space for Self-gravitating Massive Fields - The Wave-Klein-Gordon Model

    NASA Astrophysics Data System (ADS)

    LeFloch, Philippe G.; Ma, Yue

    2016-01-01

    The Hyperboloidal Foliation Method (introduced by the authors in 2014) is extended here and applied to the Einstein equations of general relativity. Specifically, we establish the nonlinear stability of Minkowski spacetime for self-gravitating massive scalar fields, while existing methods only apply to massless scalar fields. First of all, by analyzing the structure of the Einstein equations in wave coordinates, we exhibit a nonlinear wave-Klein-Gordon model defined on a curved background, which is the focus of the present paper. For this model, we prove here the existence of global-in-time solutions to the Cauchy problem, when the initial data have sufficiently small Sobolev norms. A major difficulty comes from the fact that the class of conformal Killing fields of Minkowski space is significantly reduced in the presence of a massive scalar field, since the scaling vector field is not conformal Killing for the Klein-Gordon operator. Our method relies on the foliation (of the interior of the light cone) of Minkowski spacetime by hyperboloidal hypersurfaces and uses Lorentz-invariant energy norms. We introduce a frame of vector fields adapted to the hyperboloidal foliation and we establish several key properties: Sobolev and Hardy-type inequalities on hyperboloids, as well as sup-norm estimates, which correspond to the sharp time decay for the wave and the Klein-Gordon equations. These estimates allow us to control interaction terms associated with the curved geometry and the massive field by distinguishing between two levels of regularity and energy growth and by a successive use of our key estimates in order to close a bootstrap argument.

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

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

  11. Photonic generation of millimeter and terahertz waves with high phase stability.

    PubMed

    Sun, Dongning; Dong, Yi; Yi, Lilin; Wang, Siwei; Shi, Hongxiao; Xia, Zongyang; Xie, Weilin; Hu, Weisheng

    2014-03-15

    Optical generation of highly stable millimeter and terahertz waves is proposed and experimentally demonstrated. The optical-fiber-path-induced phase fluctuation is identically transferred to a 40 MHz intermediate frequency by using dual-heterodyne phase error transfer, then canceled by a phase-locked loop. Based on the scheme, highly stable signals within the frequency range from 25 GHz to 1 THz are generated, and the phase jitter is decreased from 2.05 rad to 4.7 mrad in the frequency range from 0.01 Hz to 1 MHz. For 1 THz, the residual phase noise reaches -60  dBc/Hz at 1 Hz frequency offset from the carrier, and the relative timing jitter is reduced to 0.7 fs. PMID:24690821

  12. MAGSAT anomaly map and continental drift

    NASA Technical Reports Server (NTRS)

    Lemouel, J. L. (Principal Investigator); Galdeano, A.; Ducruix, J.

    1981-01-01

    Anomaly maps of high quality are needed to display unambiguously the so called long wave length anomalies. The anomalies were analyzed in terms of continental drift and the nature of their sources is discussed. The map presented confirms the thinness of the oceanic magnetized layer. Continental magnetic anomalies are characterized by elongated structures generally of east-west trend. Paleomagnetic reconstruction shows that the anomalies found in India, Australia, and Antarctic exhibit a fair consistency with the African anomalies. It is also shown that anomalies are locked under the continents and have a fixed geometry.

  13. Adiabatic-drift-loss modification of the electromagnetic loss-cone instability for anisotropic plasma

    NASA Astrophysics Data System (ADS)

    Juhl, B.; Treumann, R. A.

    1980-09-01

    Observation of the adiabatic behavior of energetic particle pitch-angle distributions in the magnetosphere in the past indicated the development of pronounced minima or drift-loss cones on the pitch-angle distributions centered at angles between particle velocity and magnetic field of approximately 90 deg in connection with storm-time changes in magnetospheric convection and magnetic field. Using a model of a drift-modified loss-cone distribution (MLCD) of the butterfly type, the linear stability of electromagnetic whistler or ion-cyclotron waves propagating parallel to the magnetic field has been investigated. The instability is shown to be quenched at high frequencies less than the marginally stable frequency, which is equal to A/(A + 1), where A is the thermal anisotropy. This quenching becomes stronger the higher are the respective parallel hot particle thermal velocity and cold plasma density. Particles around pitch-angles of approximately 90 deg are identified as generating electromagnetic cyclotron waves near the marginally stable frequency. It is concluded that the absence of electromagnetic VLF and ELF noise during times when MLCD develops is the result of the shift of the unstable spectrum to low frequencies.

  14. Ground Control for Emplacement Drifts for SR

    SciTech Connect

    Y. Sun

    2000-04-07

    This analysis demonstrates that a satisfactory ground control system can be designed for the Yucca Mountain site, and provides the technical basis for the design of ground support systems to be used in repository emplacement and non-emplacement drifts. The repository ground support design was based on analytical methods using acquired computer codes, and focused on the final support systems. A literature review of case histories, including the lessons learned from the design and construction of the ESF, the studies on the seismic damages of underground openings, and the use of rock mass classification systems in the ground support design, was conducted (Sections 6.3.4 and 6.4). This review provided some basis for determining the inputs and methodologies used in this analysis. Stability of the supported and unsupported emplacement and non-emplacement drifts was evaluated in this analysis. The excavation effects (i.e., state of the stress change due to excavation), thermal effects (i.e., due to heat output from waste packages), and seismic effects (i.e., from potential earthquake events) were evaluated, and stress controlled modes of failure were examined for two in situ stress conditions (k_0=0.3 and 1.0) using rock properties representing rock mass categories of 1 and 5. Variation of rock mass units such as the non-lithophysal (Tptpmn) and lithophysal (Tptpll) was considered in the analysis. The focus was on the non-lithophysal unit because this unit appears to be relatively weaker and has much smaller joint spacing. Therefore, the drift stability and ground support needs were considered to be controlled by the design for this rock unit. The ground support systems for both emplacement and non-emplacement drifts were incorporated into the models to assess their performance under in situ, thermal, and seismic loading conditions. Both continuum and discontinuum modeling approaches were employed in the analyses of the rock mass behavior and in the evaluation of the

  15. Existence, stability and dynamics of discrete solitary waves in a binary waveguide array

    NASA Astrophysics Data System (ADS)

    Shen, Y.; Kevrekidis, P. G.; Srinivasan, G.; Aceves, A. B.

    2016-07-01

    Recent work has explored binary waveguide arrays in the long-wavelength, near-continuum limit, here we examine the opposite limit, namely the vicinity of the so-called anti-continuum limit. We provide a systematic discussion of states involving one, two and three excited waveguides, and provide comparisons that illustrate how the stability of these states differ from the monoatomic limit of a single type of waveguide. We do so by developing a general theory which systematically tracks down the key eigenvalues of the linearized system. When we find the states to be unstable, we explore their dynamical evolution through direct numerical simulations. The latter typically illustrate, for the parameter values considered herein, the persistence of localized dynamics and the emergence for the duration of our simulations of robust quasi-periodic states for two excited sites. As the number of excited nodes increases, the unstable dynamics feature less regular oscillations of the solution’s amplitude.

  16. Dissolution enhancement of gliclazide using ultrasound waves and stabilizers in liquid anti-solvent precipitation.

    PubMed

    Al-Nimry, S S; Qandil, A M; Salem, M S

    2014-12-01

    The absorption rate of gliclazide is slow and variable among subjects probably due to poor dissolution from the dosage form. The objective of this study was to enhance the dissolution rate of gliclazide by reducing the particle size. Gliclazide was precipitated from an acetone solution by adding an antisolvent (water) containing stabilizers. A combination of jets (flow rate of 20 ml/min), ultrasound, HPMC 4000, and sodium dodecyl sulfate was used to control particle size and particle size distribution. The effects of concentration of stabilizers, initial drug concentration in solution, time of insonation, antisolvent-to-solvent ratio, and ultrasound power on particle size and particle size distribution were studied. Precipitated drug particles were characterized by laser diffraction particle size analysis, SEM, FTIR spectroscopy, DSC, powder x-ray diffraction and in-vitro dissolution. With increasing almost all the studied parameters, the particle size of gliclazide initially decreased, exhibited a minimum, and then increased. Drug particles of glicazide with a mean particle size of 1.56 ± 0.09 μm and a narrow size distribution (d10/d50/d90 = 0.67/1.67/2.26) were precipitated as compared to unprocessed gliclazide with a mean particle size of 10.67 ± 0.04 μm and a wide size distribution (d10/ds50/d90 = 4.53/9.88/18.03). SEM images indicated changes in the particle morphology. Powder x-ray diffraction patterns and DSC curves indicated no changes in the chemical properties but only decrease in crystallinity and/or particle size. The dissolution rate was enhanced 2.55-fold. In conclusion, drug particles with small size and narrow size distribution were precipitated by selecting favorable process conditions, and dissolution was enhanced several folds. PMID:25951659

  17. Development of a low-drift integrator system on the HL-2A tokamak.

    PubMed

    Xu, Yuan; Ji, Xiaoquan; Yang, Qingwei; Sun, Tengfei; Yuan, Baoshan; Liang, Shaoyong; Ren, Leilei; Zhou, Jian

    2016-02-01

    In this work, we developed a new integrator system with low-drift and small integration time constant less than 1 ms, which applies to the weak signals from magnetic measurements. This integrator system is designed on the basis of the analog drift compensation and the real-time digital correction of residual drift. The analog drift compensation is achieved by the subtraction between two integrators and the digital correction method is available due to the stability of integral drift in short time scale. The algorithm of the residual drift calculation and correction is implemented by the field programmable gate array. The integral drift can be well compensated within 10 mV/10 s at RC = 0.5 ms and meet the requirements of magnetic diagnostic on HL-2A. PMID:26931849

  18. CURVATURE-DRIFT INSTABILITY FAILS TO GENERATE PULSAR RADIO EMISSION

    SciTech Connect

    Kaganovich, Alexander; Lyubarsky, Yuri

    2010-10-01

    The curvature-drift instability has long been considered as a viable mechanism for pulsar radio emission. We reconsidered this mechanism by finding an explicit solution describing the propagation of short electromagnetic waves in a plasma flow along curved magnetic field lines. We show that even though the waves could be amplified, the amplification factor remains very close to unity; therefore, this mechanism is unable to generate high brightness temperature emission from initial weak fluctuations.

  19. Stability analysis of the Biot/squirt models for wave propagation in saturated porous media

    NASA Astrophysics Data System (ADS)

    Liu, Jiawei; Yong, Wen-An

    2016-01-01

    This work is concerned with the Biot/squirt (BISQ) models for wave propagation in saturated porous media. We show that the models allow exponentially exploding solutions, as time goes to infinity, when the characteristic squirt-flow coefficient is negative or has a non-zero imaginary part. We also show that the squirt-flow coefficient does have non-zero imaginary parts for some experimental parameters or for low angular frequencies. Because the models are linear, the existence of such exploding solutions indicates instability of the BISQ models. This result, for the first time, provides a theoretical explanation of the well-known empirical observation that BISQ model is not reliable (not consistent with Gassmann's formula) at low frequencies. It calls on a reconsideration of the widely used BISQ theory. On the other hand, we demonstrate that the 3-D isotropic BISQ model is stable when the squirt-flow coefficient is positive. In particular, the original Biot model is unconditionally stable where the squirt-flow coefficient is 1.

  20. Drift mode accelerometry for spaceborne gravity measurements

    NASA Astrophysics Data System (ADS)

    Conklin, John W.

    2015-11-01

    A drift mode accelerometer is a precision instrument for spacecraft that overcomes much of the acceleration noise and readout dynamic range limitations of traditional electrostatic accelerometers. It has the potential of achieving acceleration noise performance similar to that of drag-free systems over a restricted frequency band without the need for external drag-free control or continuous spacecraft propulsion. Like traditional accelerometers, the drift mode accelerometer contains a high-density test mass surrounded by an electrode housing, which can control and sense all six degrees of freedom of the test mass. Unlike traditional accelerometers, the suspension system is operated with a low duty cycle so that the limiting suspension force noise only acts over brief, known time intervals, which can be neglected in the data analysis. The readout is performed using a laser interferometer which is immune to the dynamic range limitations of even the best voltage references typically used to determine the inertial acceleration of electrostatic accelerometers. The drift mode accelerometer is a novel offshoot of the like-named operational mode of the LISA Pathfinder spacecraft, in which its test mass suspension system is cycled on and off to estimate the acceleration noise associated with the front-end electronics. This paper presents the concept of a drift mode accelerometer, describes the operation of such a device, develops models for its performance with respect to non-drag-free satellite geodesy and gravitational wave missions, and discusses plans for testing the performance of a prototype sensor in the laboratory using torsion pendula.