Stability of drift waves with the integral eigenmode equation
Chen, L.; Ke, F.J.; Xu, M.J.; Tsai, S.T.; Lee, Y.C.; Antonsen, T.M. Jr.
1981-11-01
An analytical theory on the stability properties of drift-wave eigenmodes in a slab plasma with finite magnetic shear is presented. The corresponding eigenmode equation is the integral equation first given by Coppi, Rosenbluth, and Sagdeev (1967) and rederived here, in a relatively simpler fashion, via the gyrokinetic equation. It is then proved that the universal drift-wave eigenmodes remain absolutely stable and finite electron temperature gradients do not alter the stability.
Drift wave stability and transport in tandem mirrors
NASA Astrophysics Data System (ADS)
Pratt, Jane Lillian
In recent years experimental advances at the GAMMA-10 facility in Tsukuba, Japan have shown that tandem mirrors should remain an important subject for theoretical study. The absence of toroidal curvature and relatively weak internal plasma parallel currents in a tandem mirror gives the mirror system strongly favorable stability and transport properties compared with toroidal systems. GAMMA-10 experiments (T. Cho et al. PRL (97), 2006) demonstrate that sheared plasma rotation suppresses turbulent radial losses by controlling radial potential profiles. Achievements of the GAMMA-10 include 2.5 keV ion confining potentials and electron temperatures approaching 1 keV (T. Cho, Private correspondence, Dec 24th, 2006). Total energy confinement times for the GAMMA-10 experiment are significantly larger than corresponding empirical confinement times in toroidal devices. At the temperatures currently achieved in the GAMMA-10, the end loss rate tau∣∣ ≃ 100 ms so that radial losses determine the energy confinement time tauE, as intended in tandem mirror reactor designs (R. F. Post, T.K. Fowler, et al., Fusion Science and Technology, (47), 2005). The most current measurements of tauE are on the order of 72 ms. Tandem mirrors exhibit a qualitatively different type of drift wave transport than do toroidal devices, as we have shown by developing confinement time scaling predictions (J. Pratt and W. Horton, Phys. Plasmas (13), 2006. W. Horton, J. Pratt, H.L. Berk, M. Hirata. Proceedings of the Open Magnetic Systems For Plasma Confinement Conference. Tsukuba, Japan, July 17-21, 2006). These predictions use a variety of standard transport models, e.g., Bohm, gyro-Bohm, and electron-temperature gradient models. We analyze electrostatic drift wave eigenmodes for the electrostatic potential and the magnetic perturbation in the GAMMA-10. We use teraFLOPS speed, large scale parallel computers to integrate the orbits in models of the drift wave losses in the GAMMA-10. We extrapolate
Fast wave stabilization/destabilization of drift waves in a plasma
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.
Resistive Drift Waves in a Bumpy Torus
J.L.V. Lewandowski
2004-01-12
A computational study of resistive drift waves in the edge plasma of a bumpy torus is presented. 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.
Drift wave stabilized by an additional streaming ion or plasma population.
Bashir, M F; Vranjes, J
2015-03-01
It is shown that the universally unstable kinetic drift wave in an electron-ion plasma can very effectively be suppressed by adding an extra flowing ion (or plasma) population. The effect of the flow of the added ions is essential, their response is of the type (vph-vf0)exp[-(vph-vf0)2], where vf0 is the flow speed and vph is the phase speed parallel to the magnetic field vector. The damping is strong and it is mainly due to this ion exponential term, and this remains so for vf0
Collisional Drift Waves in Stellarator Plasmas
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.
Stability of drift-cyclotron loss-cone waves in H-mode plasmas
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 is exceeded within 2 cm of the separatrix, and the maximum growth rate at the separatrix is 3×10^{7} s^{-1}.
Stability of drift-cyclotron loss-cone waves in H-mode plasmas
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
Electromagnetic drift waves dispersion for arbitrarily collisional plasmas
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.
Drift waves in helically symmetric stellarators
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.
Autoresonant control of drift waves
NASA Astrophysics Data System (ADS)
Shagalov, A. G.; Rasmussen, J. Juul; Naulin, V.
2017-03-01
The control of nonlinear drift waves in a magnetized plasmas column has been investigated. The studies are based on the Hasegawa–Mima model, which is solved on a disk domain with radial inhomogeneity of the plasma density. The system is forced by a rotating potential with varying frequency defined on the boundary. To excite and control the waves we apply the autoresonant effect, taking place when the amplitude of the forcing exceeds a threshold value and the waves are phase-locked with the forcing. We demonstrate that the autoresonant approach is applicable for excitation of a range of steady nonlinear waves of the lowest azimuthal mode numbers and for controlling their amplitudes and phases. We also demonstrate the excitation of zonal flows (m = 0 modes), which are controlled via the forced modes.
On the drift magnetosonic waves in anisotropic low beta plasmas
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)
Finite-beta stabilization of the universal drift instability - Revisited
NASA Technical Reports Server (NTRS)
Huba, J. D.; Gary, S. P.
1982-01-01
A numerical study has been made of the universal drift instability in finite beta plasmas, and a marginal stability curve has been plotted. Several limits have been considered to illustrate the various influences of finite beta. The mode is found to be stable for beta larger than or equal to 0.135; the most difficult waves to stabilize are those that have arbitrarily small wavenumbers. The stabilization mechanism is the ion Landau resonance which is enhanced by the coupling of electrostatic and transverse electromagneticc oscillations.
Rossby wave, drift wave and zonal flow turbulence
NASA Astrophysics Data System (ADS)
Quinn, Brenda E.
An extensive qualitative and quantitative study of Rossby wave, drift wave and zonal flow turbulence in the Charney-Hasegawa-Mima model is presented. This includes details of two generation mechanisms of the zonal flows, evidence of the nonlocal nature of this turbulence and of the energy exchange between the small and large scales. The modulational instability study shows that for strong primary waves the most unstable modes are perpendicular to the primary wave, which corresponds to the generation of a zonal flow if the primary wave is purely meridional. For weak waves, the maximum growth occurs for off-zonal modulations that are close to being in three-wave resonance with the primary wave. Nonlinear jet pinching is observed for all nonlinearity levels but the subsequent dynamics differ between strong and weak primary waves. The jets of the former further roll up into Karman-like vortex streets and saturate, while for the latter, the growth of the unstable mode reverses and the system oscillates between a dominant jet and a dominant primary wave. A critical level of nonlinearity is defined which separates the two regimes. Some of these characteristics are captured by truncated models. Numerical proof of the extra invariant in Rossby and drift wave turbulence is presented. 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 Fjortoft 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 wellknown 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
Lower hybrid drift waves: space observations.
Norgren, Cecilia; Vaivads, Andris; Khotyaintsev, Yuri V; André, Mats
2012-08-03
Lower hybrid drift waves (LHDWs) are commonly observed at plasma boundaries in space and laboratory, often having the strongest measured electric fields within these regions. We use data from two of the Cluster satellites (C3 and C4) located in Earth's magnetotail and separated by a distance of the order of the electron gyroscale. These conditions allow us, for the first time, to make cross-spacecraft correlations of the LHDWs and to determine the phase velocity and wavelength of the LHDWs. Our results are in good agreement with the theoretical prediction. We show that the electrostatic potential of LHDWs is linearly related to fluctuations in the magnetic field magnitude, which allows us to determine the velocity vector through the relation ∫δEdt·v = ϕ(δB)(∥). The electrostatic potential fluctuations correspond to ∼10% of the electron temperature, which suggests that the waves can strongly affect the electron dynamics.
NASA Astrophysics Data System (ADS)
Liu, Chao; Liu, Yue
2015-10-01
> The effect of a parallel viscous force induced damping and the magnetic precessional drift resonance induced damping on the stability of the resistive wall mode (RWM) is numerically investigated for one of the advanced steady-state scenarios in international thermonuclear experimental reactor (ITER). The key element of the investigation is to study how different plasma rotation profiles affect the stability prediction. The single-fluid, toroidal magnetohydrodynamic (MHD) code MARS-F (Liu et al., Phys. Plasmas, vol. 7, 2000, p. 3681) and the MHD-kinetic hybrid code MARS-K (Liu et al., Phys. Plasmas, vol. 15, 2008, 112503) are used for this purpose. Three extreme rotation profiles are considered: (a) a uniform profile with no shear, (b) a profile with negative flow shear at the rational surface ( is the equilibrium safety factor), and (c) a profile with positive shear at . The parallel viscous force is found to be effective for the mode stabilization at high plasma flow speed (about a few percent of the Alfven speed) for the no shear flow profile and the negative shear flow profile, but the stable domain does not appear with the positive shear flow profile. The predicted eigenmode structure is different with different rotation profiles. With a self-consistent inclusion of the magnetic precession drift resonance of thermal particles in MARS-K computations, a lower critical flow speed, i.e. the minimum speed needed for full suppression of the mode, is obtained. Likewise the eigenmode structure is also modified by different rotation profiles in the kinetic results.
Coherent Vortex Evolution in Drift Wave Turbulence
NASA Astrophysics Data System (ADS)
Gatto, R.; Terry, P. W.
1998-11-01
Localized structures in turbulence are subject to loss of coherence by mixing. Phase space structures, such as drift-hole, (P. W. Terry, P. H. Diamond, T. S. Hahm, Phys. Fluids B) 2 9 2048 (1990) possess a self-electric field, which if sufficiently large maintains particle trapping against the tidal deformations of ambient turbulence. We show here that intense vortices in fluid drift wave turbulence avoid mixing by suppressing ambient turbulence with the strong flow shear of the vortex edge. Analysis of turbulence evolution in the vortex edge recovers Rapid Distortion Theory (G. K. Batchelor and I. Proudman, Q. J. Mech. Appl. Math.) 7 83 (1954) as the short time limit and the shear suppression scaling theory (H. Biglari, P. H. Diamond and P. W. Terry, Phys. Fluids B) 2 1 (1990) as the long time limit. Shear suppression leads to an amplitude condition for coherence and delineates the Gaussian core from the non Gaussian tail of the probability distribution function. The amplitude condition of shear suppression is compared with the trapping condition for phase space holes. The possibility of nonlinear vortex growth will be examined by considering electron dynamics in the vortex evolution.
Spatiotemporal mode structure of nonlinearly coupled drift wave modes
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.
Dust gravitational drift wave in complex plasma under gravity
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.
The Development of Drift Wave Turbulence in Magnetic Reconnection
NASA Astrophysics Data System (ADS)
McMurtrie, L.; Drake, J. F.; Swisdak, M. M.
2013-12-01
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) 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. Further investigations of the relative importance of drift wave turbulence in the development of reconnection will also be considered.
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.
Antenna excitation of drift wave in a toroidal plasma
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.
Spatiotemporal synchronization of drift waves in a magnetron sputtering plasma
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.
Asymmetric drift instability of magnetosonic waves in anisotropic plasmas
NASA Astrophysics Data System (ADS)
Bashir, M. F.; Chen, Lunjin
2016-10-01
The general dispersion relation of obliquely propagating magneto-sonic (MS) waves for the inhomogeneous and anisotropic plasmas is analyzed including the effect of wave-particle interaction. The numerical analysis is performed without expanding both the plasma dispersion and the modified Bessel functions to highlight the effects of density inhomogeneity and the temperature anisotropy. The obtained results are compared with the recent work [Naim et al., Phys. Plasmas 22, 062117 (2015)], where only drift mode near the magnetosonic frequency is investigated. In our paper, we additionally analyzed two related modes depicting that the drift effect leads to an asymmetric behavior in the dispersion properties of drift MS waves. The possible application to the solar coronal heating problem has also been discussed.
Drift Wave Test Particle Transport in Reversed Shear Profile
Horton, W.; Park, H.B.; Kwon, J.M.; Stronzzi, D.; Morrison, P.J.; Choi, D.I.
1998-06-01
Drift wave maps, area preserving maps that describe the motion of charged particles in drift waves, are derived. The maps allow the integration of particle orbits on the long time scale needed to describe transport. Calculations using the drift wave maps show that dramatic improvement in the particle confinement, in the presence of a given level and spectrum of E x B turbulence, can occur for q(r)-profiles with reversed shear. A similar reduction in the transport, i.e. one that is independent of the turbulence, is observed in the presence of an equilibrium radial electric field with shear. The transport reduction, caused by the combined effects of radial electric field shear and both monotonic and reversed shear magnetic q-profiles, is also investigated.
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.
Route to Drift Wave Chaos and Turbulence in a Bounded Low-{beta} Plasma Experiment
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}
Strange Attractors in Drift Wave Turbulence
Jerome L.V. Lewandowski
2003-09-03
There are growing experimental, numerical and theoretical evidences that the anomalous transport observed in tokamaks and stellarators is caused by slow, drift-type modes (such as trapped electron modes and ion-temperature gradient-driven modes). Although typical collision frequencies in hot, magnetized fusion plasmas can be quite low in absolute values, collisional effects are nevertheless important since they act as dissipative sinks. As it is well known, dissipative systems with many (strictly speaking more than two) degrees of freedom are often chaotic and may evolve towards a so-called attractor.
Polarization of drifting pairs at decameter waves
NASA Astrophysics Data System (ADS)
Brazhenko, A. I.; Melnik, V. N.; Konovalenko, A. A.; Abranin, E. P.; Dorovskyy, V. V.; Vashchishin, R. V.; Frantsuzenko, A. V.; Rucker, H. O.; Lecacheux, A.
2006-08-01
The results of polarization researches of drifting pairs (DP) observed during Type III bursts storm in July[S:,:S][Author ID2: at Fri Jul 14 10:33:00 2006 ] 11-21, 2002 with radio telescope URAN-2 are presented. The array of the radio telescope consists of 512 broadband cross dipoles, that enables to receive signals of two polarizations, has the area about of 28000 m^2 and works in 9-30 MHz range. Circular polarization measurements were made at frequency 24.75 MHz in frequency band 10 μHz with time resolution 10 ms. Some hundreds bursts, both forward and reverse DPs, which have been registered with radio telescope UTR-2 in the frequency range 18-32 μHz, were analyzed. For the first time we find that DP polarizations strongly depend on the location of the active area associated with these bursts. When an active area is near to the central meridian, polarizations of both DP components have the same signs and their values are up to 30%. In other days in most cases polarizations of both components have opposite signs and only for some bursts polarization reaches 10%. In all cases both DP components have comparable polarization degrees.
Field stability in two-stem drift-tube linacs
Billen, J.H.; Spalek, G.; Shapiro, A.H.
1988-01-01
Drift tubes supported by two stems have been considered for cryogenic drift-tube linacs (DTLs) to reduce vibrations and to minimize drift-tube deflections upon cool down. We investigated rf properties of two-stem DTL structures at room temperature and low power. Even apart is inherently more stable against tuning errors than a similar structure with single stems. The increased stability is higher for DTLs with shorter drift tubes. Ordinary quarter-wavelength-long post couplers actually destabilize the two-stem DTL fields; the extra stem raises the post coupler frequency compared to the frequency of the same post coupler extended beyond the tank wall into coaxial stub tuners. Adjustment of the stub lengths tunes the post-coupler frequencies, but post-coupler lengths in the tank have no effect, which suggests a field pattern different from traditional post couplers. The stabilized DTL resembles multiple-stem DTLs in which the angle between stems is varied to achieve stabilization. Adjusting the coaxial stub length is mechanically simpler than changing the stem azimuth angle. 5 refs., 6 figs., 1 tab.
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.
Transport of parallel momentum by collisionless drift wave turbulence
Diamond, P. H.; McDevitt, C. J.; Guercan, Oe. D.; Hahm, T. S.; Naulin, V.
2008-01-15
This paper presents a novel, unified approach to the theory of turbulent transport of parallel momentum by collisionless drift waves. The physics of resonant and nonresonant off-diagonal contributions to the momentum flux is emphasized, and collisionless momentum exchange between waves and particles is accounted for. Two related momentum conservation theorems are derived. These relate the resonant particle momentum flux, the wave momentum flux, and the refractive force. A perturbative calculation, in the spirit of Chapman-Enskog theory, is used to obtain the wave momentum flux, which contributes significantly to the residual stress. A general equation for mean k{sub parallel} (
NASA Astrophysics Data System (ADS)
Dai, L.; Takahashi, K.; Wygant, J. R.; Chen, L.; Bonnell, J. W.; Cattell, C. A.; Thaller, S. A.; Kletzing, C.; Smith, C. W.; MacDowall, R. J.; Baker, D. N.; Blake, J. B.; Fennell, J. F.; Claudepierre, S. G.; Funsten, H. O.; Reeves, G. D.; Spence, H.
2013-12-01
Charged particles trapped in the magnetosphere undergo a longitudinal drift motion around the Earth induced by the magnetic field curvature and gradient. The resonant wave-particle interaction associated with the drift motion is important for understanding the dynamics of the ring current and radiation belt particles. Using cross-spectral analysis of electric field, magnetic field, and ion flux data from the Van Allen Probe (RBSP) spacecraft, we present direct evidence identifying the generation of a fundamental mode standing poloidal wave through drift-resonance interactions in the inner magnetosphere. Intense azimuthal electric field (E φ ) oscillations as large as 10mV/m are observed associated with radial magnetic field (Br) oscillations in the dawn-noon sector near but south of the magnetic equator at L~5. The observed wave period, Eφ/Br, and the 90 degrees phase lag between Br and Eφ are all consistent with fundamental mode standing poloidal waves. Phase shifts between particle fluxes and wave electric fields clearly demonstrate a drift resonance with ~90 keV ring current ions. The estimated earthward gradient of ion phase space density provides free energy source for wave generation through the drift-resonance instability. To our knowledge, this is the first unambiguous observation of drift-resonance wave-particle interaction driving poloidal wave oscillations in the magnetosphere. Similar drift-resonance process should occur ubiquitously in collisionless plasma systems. One example is the ';fishbone' instability in fusion plasma devices. In addition, our observations have important implications for the long-standing mysterious origin of Giant Pulsations detected on the ground.
Excitation of poloidal standing Alfvén waves through drift resonance wave-particle interaction
NASA Astrophysics Data System (ADS)
Dai, Lei; Takahashi, Kazue; Wygant, John R.; Chen, Liu; Bonnell, John; Cattell, Cynthia A.; Thaller, Scott; Kletzing, Craig; Smith, Charles W.; MacDowall, Robert J.; Baker, Daniel N.; Blake, J. Bernard; Fennell, Joseph; Claudepierre, Seth; Funsten, Herbert O.; Reeves, Geoffrey D.; Spence, Harlan E.
2013-08-01
Drift-resonance wave-particle interaction is a fundamental collisionless plasma process studied extensively in theory. Using cross-spectral analysis of electric field, magnetic field, and ion flux data from the Van Allen Probe (Radiation Belt Storm Probes) spacecraft, we present direct evidence identifying the generation of a fundamental mode standing poloidal wave through drift-resonance interactions in the inner magnetosphere. Intense azimuthal electric field (Eφ) oscillations as large as 10mV/m are observed, associated with radial magnetic field (Br) oscillations in the dawn-noon sector near but south of the magnetic equator at L˜5. The observed wave period, Eφ/Br ratio and the 90° phase lag between Br and Eφ are all consistent with fundamental mode standing Poloidal waves. Phase shifts between particle fluxes and wave electric fields clearly demonstrate a drift resonance with ˜90 keV ring current ions. The estimated earthward gradient of ion phase space density provides a free energy source for wave generation through the drift-resonance instability. A similar drift-resonance process should occur ubiquitously in collisionless plasma systems. One specific example is the "fishbone" instability in fusion plasma devices. In addition, our observations have important implications for the long-standing mysterious origin of Giant Pulsations.
Kinetic instability of drift magnetosonic wave in anisotropic low beta plasmas
NASA Astrophysics Data System (ADS)
Naim, H.; Bashir, M. F.; Vranjes, J.; Murtaza, G.
2015-06-01
The kinetic instability of the obliquely propagating drift magnetosonic wave for temperature anisotropic low beta plasmas is studied by using the gyro-kinetic model. The interplay between the temperature anisotropy and the density inhomogeneity free energy sources is discussed in order to provide stabilization of drift instability by the temperature anisotropy effect. It is shown that the anisotropy suppresses the growth rate when the anisotropy ratio A e , i ( = T ⊥ ( e , i ) / T ∥ ( e , i ) ) is greater than unity, whereas it enhances the growth rate for A e , i < 1 . Comparison of kinetic instability with reactive instability [Naim et al., Phys. Plasmas 21, 102112 (2014)] and the scaling of growth time with the diffusion and the anisotropy relaxation times are presented. Additionally, the stability analysis applicable to a wide range of plasma parameters is also performed.
Scattering of Electromagnetic Waves by Drift Vortex in Plasma
NASA Astrophysics Data System (ADS)
Wang, Dong; Chen, Yinhua; Wang, Ge
2008-02-01
In a quasi-two-dimensional model, the scattering of incident ordinary electromagnetic waves by a dipole-electrostatic drift vortex is studied with first-order Born approximation. The distribution of the scattering cross-section and total cross-section are evaluated analytically in different approximate conditions, and the physical interpretations are discussed. When the wavelength of incident wave is much longer than the vortex radius (kia ll 1), it is found that the angle at which the scattering cross-section reaches its maxim depends significantly on the approximation of the parameters of the vortex used. It is also found that the total scattering cross-section has an affinitive relation with the parameters of the plasma, while it is irrelevant to the frequency of the incident wave in a wide range of parameters of the vortex. In a totally different range of parameters when incident wave is in the radar-frequency range (then kia ll 1, the wavelength of incident wave is much shorter than the vortex radius), the numerical procedure is conducted with computer in order to obtain the distribution and the total expression of the scattering cross-section. Then it is found that the total scattering cross-section in the low frequency range is much larger than that in high frequency range, so the scattering is more effective in the low frequency range than in high frequency range.
Directional change of particles in dissipative drift-wave turbulence
NASA Astrophysics Data System (ADS)
Kadoch, Benjamin; Bos, Wouter J. T.; Schneider, Kai
2016-10-01
We analyze the statistical properties of Lagrangian particle transport in dissipative drift-wave turbulence modeled by the Hasegawa-Wakatani system. The angle between subsequent particle displacement increments is evaluated as a function of the timelag and thus multi-scale geometric statistics can be performed. The evolution of the mean angle with the time lag is studied and the probability density function of the directional change are analyzed for the different flow regimes. By varying the adiabaticity parameter the flow regime can be modified from the hydrodynamic limit to a geostrophic limit, including the quasi adiabatic regime which has some relevance for edge turbulence of fusion plasmas in tokamaks. Support by the French Research Federation for Fusion Studies within the framework of the European Fusion Development Agreement (EFDA) is thankfully acknowledged.
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.
Drift stabilizer for reciprocating free-piston devices
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.
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.
Nonlinear saturation spectra of electric fields and density fluctuations in drift wave turbulence
NASA Technical Reports Server (NTRS)
Kelley, M. C.
1982-01-01
The detection of drift waves in the nonlinear evolution of a space plasma process driven at long wavelengths is considered, adducing measurements of the electric field and density fluctuation power spectra as evidence. Since the driving mechanism is clearly at long wavelengths, the detection of drift waves suggests that they may play an important role in the transfer of wave energy from long to short wavelengths in a low beta plasma. The saturated spectral density is compared with theoretical results in order to estimate the anomalous diffusion rate. The observed spectral form and amplitude is in excellent agreement with drift wave predictions.
Propagation of cylindrical lower hybrid drift solitary wave in an inhomogeneous plasma
Liu Haifeng; Wang Shiqing; Fazhan Yang; Li Kehua; Wang Zhanhe; Zhang Weibing; Wang Zhilong; Qiangxiang; Kaihuang; Yaoliu; Silili; Lanchang
2013-04-15
The nonlinear cylindrical lower hybrid drift solitary wave in an inhomogeneous, magnetized plasma with the combined effects of electron density inhomogeneity and electron temperature inhomogeneity is investigated in a two-fluid model. The amplitude and width of the solitary wave are found to decrease as the electronic density inhomogeneity increases. When the electron temperature inhomogeneity grows, the amplitude of the soliton decays and the width never changes. It is noted that the decrease of diamagnetic drift velocity will strengthen the cylindrical lower hybrid drift solitary wave height and width.
NASA Astrophysics Data System (ADS)
Burston, Robert; Astin, Ivan; Mitchell, Cathryn; Alfonsi, Lucilla; Pedersen, Todd; Skone, Susan
2009-07-01
A model is developed of the gradient drift instability growth rate in the north polar cap ionosphere, utilizing a novel approach employing an ionospheric imaging algorithm. The growth rate values calculated by this model are in turn used to estimate how the amplitudes of actual gradient drift waves vary over time as the plasma drifts and the growth rates change with time. Ionospheric imaging is again used in order to determine plasma drift velocities. The final output from the model is in turn used to assess the linear correlation between the scintillation indices S4 and σ $\\phi$ recorded by several GPS L1 band scintillation receivers stationed in the north polar cap and mean gradient drift wave amplitudes. Four separate magnetic storm periods, totaling 13 days, are analyzed in this way. The results show weak but significant linear correlations between the mean wave amplitudes calculated and the observed scintillation indices at F layer altitudes.
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.
The mean drift forces and yaw moment on multiple-cylinders in waves and current
Kinoshita, Takeshi; Bao, Weiguang; Sunahara, Shunji
1996-12-31
In the present work, the interaction of an assembly of circular cylinders with regular waves and slow current is considered. The interaction among cylinders is represented by additional waves emitting from adjacent cylinders towards the cylinders under consideration. By means of eigenfunction expansion, drift forces, as well as yaw moment, are evaluated by the far field method and the wave drift damping is deduced from these results semi-analytically. The contribution from the second order steady potential which is quadratic in wave amplitude is also considered. Calculated examples are presented in various wave direction. Those results are also compared with experimental measurements to verify the present theory.
Streamers generation by small-scale drift-Alfvén waves
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.
Lower-Hybrid-Drift Wave Turbulence in the Distant Magnetotail
1978-05-01
Timofeev, I963: Freidberg and Gerwin, 1977). The nature of the lower-hybrid-drift instability is twofold. In the presence of strong plasma gradients (L...drift cyclotron instability ( Freidberg and Gerwin, 1977; Gladd and Huba, I978) which has a characteris- 1 tic frequency and growth rate uo ~ in...Instability at (n+-?)/ anc* its Relationship to c Some Satellite Observations, J. Geophys. Res., 76, 53^4, 1971. Freidberg , J. P. and R. A. Gerwin
Tariq, Sabeen; Mirza, Arshad M.; Masood, W.
2010-10-15
The propagation of high and low frequency (in comparison with the cyclotron frequency) electrostatic drift-waves is investigated in a nonuniform, dense magnetoplasma (composed of electrons and ions), in the presence of parallel shear flow, by employing the quantum magnetohydrodynamic (QMHD) model. Using QMHD model, a new set of equations is presented in order to investigate linear properties of electrostatic drift-waves with sheared plasma flows for dense plasmas. In this regard, dispersion relations for coupled electron-thermal and drift-ion acoustic modes are derived and several interesting limiting cases are discussed. For instance, it is found that sheared ion flow parallel to the external magnetic field can drive the quantum drift-ion acoustic wave unstable, etc. The present investigation may have relevance in dense astrophysical environments where quantum effects are significant.
Fluid simulations of nonlocal dissipative drift-wave turbulence
NASA Astrophysics Data System (ADS)
Xu, X. Q.; Cohen, R. H.; Crotinger, J. A.; Shestakov, A. I.
1995-03-01
A two-dimensional [2d(x,y)] fluid code has been developed to explore nonlocal dissipative drift-wave turbulence and anomalous transport. In order to obtain steady-state turbulence, the y-averaged fluctuating density
Instability of Drift Waves in Two-Component Solid-State Plasma
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.
A Computer Simulation Study of Anatomy Induced Drift of Spiral Waves in the Human Atrium
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
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.
Effects of electron drifts on collisionless damping of kinetic Alfvén waves
NASA Astrophysics Data System (ADS)
Tong, Yuguang; Bale, Stuart; Chen, Christopher; Salem, Chadi; Verscharen, Daniel
2015-04-01
Collisionless dissipation of obliquely propogating Alfvén waves has been a promising candidate to solve the solar wind heating problem. Extensive studies have examined kinetic properties of Alfvén waves in simple Maxwellian or Bi-Maxwellian plasmas. However, the solar wind electron velocity distribution function is more complex. A study of Alfvén waves in a plasma, whose electrons consist of two drifting populations in the proton bulk frame, is reported here. We numerically solve the linearized Maxwell-Vlasov equations and find that the damping rate and the proton-electron energy partition for Alfven waves have been significantly modified in such plasmas, comparing to their counterparts without electron drifts. We suggest that electron drift is an important factor to take into account when considering the dissipation of Alfvénic turbulence in the solar wind.
Effects of electron drifts on collisionless damping of Alfvén waves
NASA Astrophysics Data System (ADS)
Tong, Y.; Bale, S. D.; Chen, C. H. K.
2014-12-01
Collisionless dissipation of obliquely propogating Alfvén waves has been a promising candidate to solve the coronal and the solar wind heating problem. Extensive studies have examined kinetic properties of Alfvén waves in simple Maxwellian or Bi-Maxwellian plasmas. However, the solar wind electron velocity distribution function is more complex. A study of Alfvén waves in a plasma, whose electrons consist of two drifting populations in the proton bulk frame, is reported here. By numerically solving the linearized Maxwell-Vlasov equations, we find that the damping rate and the proton-electron energy partition for Alfven waves have been significantly modified in such plasmas, comparing to their counterparts without electron drifts. We suggest that electron drift is an important factor to take into account when considering the dissipation of Alfvénic turbulence in the solar wind.
Up-gradient particle flux in a drift wave-zonal flow system
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.
Eddy, drift wave and zonal flow dynamics in a linear magnetized plasma
Arakawa, H.; Inagaki, S.; Sasaki, M.; Kosuga, Y.; Kobayashi, T.; Kasuya, N.; Nagashima, Y.; Yamada, T.; Lesur, M.; Fujisawa, A.; Itoh, K.; Itoh, S.-I.
2016-01-01
Turbulence and its structure formation are universal in neutral fluids and in plasmas. Turbulence annihilates global structures but can organize flows and eddies. The mutual-interactions between flow and the eddy give basic insights into the understanding of non-equilibrium and nonlinear interaction by turbulence. In fusion plasma, clarifying structure formation by Drift-wave turbulence, driven by density gradients in magnetized plasma, is an important issue. Here, a new mutual-interaction among eddy, drift wave and flow in magnetized plasma is discovered. A two-dimensional solitary eddy, which is a perturbation with circumnavigating motion localized radially and azimuthally, is transiently organized in a drift wave – zonal flow (azimuthally symmetric band-like shear flows) system. The excitation of the eddy is synchronized with zonal perturbation. The organization of the eddy has substantial impact on the acceleration of zonal flow. PMID:27628894
Eddy, drift wave and zonal flow dynamics in a linear magnetized plasma
NASA Astrophysics Data System (ADS)
Arakawa, H.; Inagaki, S.; Sasaki, M.; Kosuga, Y.; Kobayashi, T.; Kasuya, N.; Nagashima, Y.; Yamada, T.; Lesur, M.; Fujisawa, A.; Itoh, K.; Itoh, S.-I.
2016-09-01
Turbulence and its structure formation are universal in neutral fluids and in plasmas. Turbulence annihilates global structures but can organize flows and eddies. The mutual-interactions between flow and the eddy give basic insights into the understanding of non-equilibrium and nonlinear interaction by turbulence. In fusion plasma, clarifying structure formation by Drift-wave turbulence, driven by density gradients in magnetized plasma, is an important issue. Here, a new mutual-interaction among eddy, drift wave and flow in magnetized plasma is discovered. A two-dimensional solitary eddy, which is a perturbation with circumnavigating motion localized radially and azimuthally, is transiently organized in a drift wave – zonal flow (azimuthally symmetric band-like shear flows) system. The excitation of the eddy is synchronized with zonal perturbation. The organization of the eddy has substantial impact on the acceleration of zonal flow.
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.
Modulation of drift-wave envelopes in a nonuniform quantum magnetoplasma
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.
Drift wave turbulence in the edge region of MST reversed field pinch plasmas
NASA Astrophysics Data System (ADS)
Thuecks, D. J.; Almagri, A. F.; Sarff, J. S.; Terry, P. W.
2016-10-01
Measurements of electric field fluctuations reveal activity consistent with drift waves in the edge region of standard-confinement MST plasmas. The fluctuations are broadband and strongly anisotropic, with a power spectral index that is steeper in the direction parallel to the mean magnetic field direction than it is in the perpendicular direction. The power in the fluctuating kinetic energy, 1/2 minivẼ×B0 2 , exceeds the power in magnetic fluctuation energy for frequencies above 80 kHz. At lower frequencies (20-40 kHz), magnetic energy associated with unstable global tearing modes dominates. A lack of equipartition in the turbulent cascade coincides with measured signatures of independent fluctuation activity broadly consistent with drift-wave fluctuations. Statistical coherence measurements reveal mode activity at high frequencies (>=80 kHz) that is compressive, has high coherence in regions of the plasma with strong density gradients, and has a phase speed comparable to the electron drift speed. Elevated coherency associated with this fluctuation feature of the drift wave fluctuations return more quickly following magnetic reconnection events than corresponding coherence associated with the tearing activity. This suggests the drift-wave fluctuations may be excited by the large edge-localized thermal pressure gradient, but they could also be excited nonlinearly in a turbulent cascade driven by the tearing modes. Work supported by DOE and NSF.
Studying the interaction mechanisms of the tearing mode and drift-wave turbulence
NASA Astrophysics Data System (ADS)
James, S. D.; Brennan, D. P.; Holland, C.; Izacard, O.
2016-10-01
Understanding the mechanisms through which turbulence and MHD instabilities interact is vital to the success of magnetically confined fusion. Simulating the self-consistent evolution of turbulence and MHD instabilities is a challenging numerical problem due to the disparate scales involved. We use a newly developed code, TURBO, to perform nonlinear simulations of a three-field model which couples the evolution of drift-wave turbulence to Ohm's Law. TURBO evolves the density, vorticity, and magnetic flux in a slab geometry using an equilibrium with prescribed stability properties and turbulent drives. By imposing a propagating boundary condition on the magnetic flux we examine the dependence of an asymmetry in the density flux on the propagation velocity of the boundary condition. We present results showing the influence of the turbulence on the stability of the tearing mode and the energy transport between them via a turbulent resistivity. For the case of a static island in a poloidal flow, results indicate that the energy transport and density flux display a spatial asymmetry in the poloidal direction and are peaked away from the X-point. A recent study of ITG turbulence in the presence of a magnetic island found analogous effects and we discuss the relation to our work. Supported by US DOE Grant DE-SC0007851.
Resonant drift of spiral waves in the complex ginzburg-landau equation.
Biktasheva, I V; Elkin, Y E; Biktashev, V N
1999-06-01
Weak periodic external perturbations of an autowave medium can cause large-distance directed motion of the spiral wave. This happens when the period of the perturbation coincides with, or is close to the rotation period of a spiral wave, or its multiple. Such motion is called resonant or parametric drift. It may be used for low-voltage defibrillation of heart tissue. Theory of the resonant drift exists, but so far was used only qualitatively. In this paper, we show good quantitative agreement of the theory with direct numerical simulations. This is done for Complex Ginzburg-Landau Equation, one of the simplest autowave models.
Shear driven electromagnetic drift-waves in a nonuniform dense magnetoplasma
Tariq, Sabeen; Mirza, Arshad M.; Masood, Waqas
2011-08-15
Linear characteristic properties of high- and low-frequency (in comparison with the cyclotron frequency) electromagnetic drift-waves are studied in a nonuniform, dense magnetoplasma (composed of electrons and ions), in the presence of parallel (magnetic field-aligned) velocity shear, by using quantum magnetohydrodynamic model. By applying the drift-approximation (viz., |{partial_derivative} {sub t}|<<{omega}{sub ci}<<{omega}{sub ce}) to the quantum momentum equations, together with the continuity equations and the Poisson equation, we derive the governing equations for electromagnetic drift-waves with the shear flow. These linear equations are then Fourier transformed to obtain the dispersion relation in both high-frequency and low-frequency regimes. The dispersion relations are then discussed under various limiting cases.
A probe array for the investigation of spatio-temporal structures in drift wave turbulence
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}.
Regulating drift-wave plasma turbulence into spatiotemporal patterns by pinning coupling.
Liu, Panpan; Yang, Lei; Deng, Zhigang; Wang, Xingang
2011-07-01
Using the technique of pinning coupling in chaos control, we investigate how the two-dimensional drift-wave plasma turbulence described by the Hasegawa-Mima equation can be regulated into different spatiotemporal patterns. It is shown both analytically and numerically that, depending on the pattern structure of the target, the pinning strength necessary for regulating the turbulence could have a large variation. More specifically, with the increase of the wave number of the target, the critical pinning strength is found to be increased by a power-law scaling. Moreover, in both the transition and transient process of the pinning regulation, the modes of the turbulence are found to be suppressed in a hierarchical fashion, that is, by the sequence of mode wave number. The findings give insight into the dynamics of drift-wave turbulence, as well as indicative to the design of new control techniques for real-world turbulence.
Dust magneto-gravitational drift wave in g×B configuration
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.
The Use of the Information Wave Function in a Drift Dependent Option Price: A Simple Example
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.
Dynamics of Zonal FLow Instability and Saturation in Drift Wave Turbulence
NASA Astrophysics Data System (ADS)
Katt, S. T.; Kim, E.; Diamond, P. H.
2001-10-01
We study generalized Kelvin-Helmholtz (GKH) instability as a saturation mechanism for a collisionless zonal flow in the background of drift waves. By treating drift waves as adiabatically modified by GKH, we investigate the modulation instability of drift waves due to GKH modes as well as the linear inflection-type instability of zonal flow. In the case where zonal flows evolve on the time scale much larger than GKH mode, GKH mode is shown to become destabilized not only by the linear instability of zonal flow but also by coupling to drift waves, with a growth rate which is enhanced over the linear value. Furthermore, the nonlinear (modulational) generation of a zonal flow is estimated to dominate over that of GKH. Our results indicate that GKH may not play an important role in a collisionless saturation of zonal flow, in contrast to [1] and [2]. The effect of temperature fluctuation will be discussed. [1] B.N. Rogers, W. Dorland, and M. Kotschenreuther, PRL, 85, 5336, (2000). [2] Y. Idomura, M. Wakatani, and S. Tokuda, PoP, 7, 3551, (2000).
Theory on excitations of drift Alfvén waves by energetic particles. I. Variational formulation
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)].
Theory on excitations of drift Alfvén waves by energetic particles. I. Variational formulation
NASA Astrophysics Data System (ADS)
Zonca, Fulvio; Chen, Liu
2014-07-01
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)].
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.
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.
Experimental quiescent drifting dusty plasmas and temporal dust acoustic wave growth
Heinrich, J. R.; Kim, S.-H.; Meyer, J. K.; Merlino, R. L.
2011-11-15
We report on dust acoustic wave growth rate measurements taken in a dc (anode glow) discharge plasma device. By introducing a mesh with a variable bias 12-17 cm from the anode, we developed a technique to produce a drifting dusty plasma. A secondary dust cloud, free of dust acoustic waves, was trapped adjacent to the anode side of the mesh. When the mesh was returned to its floating potential, the secondary cloud was released and streamed towards the anode and primary dust cloud, spontaneously exciting dust acoustic waves. The amplitude growth of the excited dust acoustic waves was measured directly along with the wavelength and Doppler shifted frequency. These measurements were compared to fluid and kinetic dust acoustic wave theories. As the wave growth saturated a transition from linear to nonlinear waves was observed. The merging of the secondary and primary dust clouds was also observed.
Lion roars and nonoscillatory drift mirror waves in the magnetosheath
Tsurutani, B.T.; Smith, E.J.; Anderson, R.R.; Ogilvie, K.W.; Scudder, J.D.; Baker, D.N.; Bame, S.J.
1982-08-01
A complete set of ISEE plasma wave, plasma, and field data are used to identify the plasma instability responsible for the generation of extremely low frequency (ELF) electromagnetic lion roars. Lion roars detected close to the magnetopause are generated by the cyclotron instability of anisotropic (T/sup -//sub perpendicular//T/sup -//sub parallel/approx. =1.2) thermal electrons when the local plasma critical energy, E/sub M/ = B/sup 2//8..pi..N, falls to values (E/sub M/ approx.10--30 eV) close to or below the electron thermal energy, 25 eV, as a result of decreases in B. The lion roars are terminated by increases in the ambient magnetic field magnitude and consequential increases in E/sub M/ to values greater than 100 eV. Because there are few resonant particles at these high energies, the growth rate decreases by 3 orders of magnitude and measurable growth ceases. The value of the absolute upper limit of the frequency of unstable waves predicted by theory, ..omega../sub max/ = A/sup -/..cap omega../sup -//(A/sup -/+1), is compared with observations. The predictions and observations are found to be in general, but not exact, agreement. Several possible explanations are explored. The quasi-periodic, approx.20-s magnetic and plasma oscillations which cause the variations in E/sub M/ and hence alternately drive the cyclotron waves unstable and then stable are also investigated.
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.
NASA Astrophysics Data System (ADS)
Tao, Xie; Shang-Zhuo, Zhao; William, Perrie; He, Fang; Wen-Jin, Yu; Yi-Jun, He
2016-06-01
To study the electromagnetic backscattering from a one-dimensional drifting fractal sea surface, a fractal sea surface wave-current model is derived, based on the mechanism of wave-current interactions. The numerical results show the effect of the ocean current on the wave. Wave amplitude decreases, wavelength and kurtosis of wave height increase, spectrum intensity decreases and shifts towards lower frequencies when the current occurs parallel to the direction of the ocean wave. By comparison, wave amplitude increases, wavelength and kurtosis of wave height decrease, spectrum intensity increases and shifts towards higher frequencies if the current is in the opposite direction to the direction of ocean wave. The wave-current interaction effect of the ocean current is much stronger than that of the nonlinear wave-wave interaction. The kurtosis of the nonlinear fractal ocean surface is larger than that of linear fractal ocean surface. The effect of the current on skewness of the probability distribution function is negligible. Therefore, the ocean wave spectrum is notably changed by the surface current and the change should be detectable in the electromagnetic backscattering signal. Project supported by the National Natural Science Foundation of China (Grant No. 41276187), the Global Change Research Program of China (Grant No. 2015CB953901), the Priority Academic Development Program of Jiangsu Higher Education Institutions (PAPD), Program for the Innovation Research and Entrepreneurship Team in Jiangsu Province, China, the Canadian Program on Energy Research and Development, and the Canadian World Class Tanker Safety Service.
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.
NASA Astrophysics Data System (ADS)
van Compernolle, Bart; Morales, George; Maggs, James; Sydora, Richard
2016-10-01
Results of a basic heat transport experiment involving an off-axis heat source are presented. Experiments are performed in the Large Plasma Device (LAPD) at UCLA. A ring-shaped electron beam source injects low energy electrons (below ionization energy) along a strong magnetic field into a preexisting, large and cold plasma. The injected electrons are thermalized by Coulomb collisions within a short distance and provide an off-axis heat source that results in a long, hollow, cylindrical region of elevated plasma pressure embedded in a colder plasma, and far from the machine walls. The off-axis source is active for a period long compared to the density decay time, i.e. as time progresses the power per particle increases. Two distinct regimes are observed to take place, an initial regime dominated by avalanches, identified as sudden intermittent rearrangements of the pressure profile, and a second regime dominated by sustained drift-Alfvén wave activity. The transition between the two regimes is sudden, affects the full radial profile and is preceded by the growth of drift Alfvén waves. Langmuir probe data will be shown on the evolution of the density, temperature and flow profiles during the transition. The character of the sustained drift wave activity will also be presented. Work supported by NSF/DOE Grant 1619505, and performed at the Basic Plasma Science Facility, sponsored jointly by DOE and NSF.
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.
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.
Effects of thin film and Stokes drift on the generation of vorticity by surface waves
NASA Astrophysics Data System (ADS)
Parfenyev, V. M.; Vergeles, S. S.; Lebedev, V. V.
2016-11-01
Recently a theoretical scheme explaining the vorticity generation by surface waves in liquids was developed [Phys. Rev. Lett. 116, 054501 (2016), 10.1103/PhysRevLett.116.054501]. Here we study how a thin (monomolecular) film presented on the surface of liquid affects the generated vorticity. We demonstrate that the vorticity becomes parametrically larger than for the case of liquid with a free surface, and the parameter is the quality factor of surface waves up to numerical factor. We also discuss the PIV experimental scheme intended to observe the generated vorticity and find that Stokes drift influences the measured velocity field. Explicit expression for the vertical vorticity was obtained.
Ambipolar potential effect on a drift-wave mode in a tandem-mirror plasma
Mase, A.; Jeong, J.H.; Itakura, A.; Ishii, K.; Inutake, M.; Miyoshi, S. )
1990-05-07
The {bold k}-{omega} spectra of low-frequency waves which exist in a tandem-mirror plasma are observed by using the Fraunhofer-diffraction method. The observed dispersion relations are in good agreement with those of drift waves including a Doppler shift due to {bold E}{times}{bold B} rotation velocity. The fluctuation level is observed to depend sensitively on the radial profile of a plasma potential. It has a maximum value when a slightly negative electric field is formed, and decreases with increase in an electric field regardless of its sign.
Asymptotic Linear Stability of Solitary Water Waves
NASA Astrophysics Data System (ADS)
Pego, Robert L.; Sun, Shu-Ming
2016-12-01
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.
Finite system size effects on drift wave stability
Militello, F.; Wynn, A.
2014-02-15
Unstable electrostatic resistive modes, driven by density gradients, are identified in a bounded sheared slab. The boundary conditions play a crucial role and are shown to change the nature of the problem, which is related to so called “universal” mode. The dispersion relation and the structure of the eigenmodes of the instability are derived and are shown to depend on a limited set of dimensionless parameters. The occurrence and possible impact of these modes on numerical simulations and actual plasmas are discussed.
The Stabilization of Postoperative Exo-drift in Intermittent Exotropia after Surgical Treatment
Park, Hoon; Kim, Won Jae
2016-01-01
Purpose To investigate the long-term clinical course of intermittent exotropia after surgical treatment to determine whether and when postoperative exo-drift stabilizes, and the required postsurgery follow-up duration in cases of intermittent exotropia. Methods We retrospectively reviewed the medical records of patients diagnosed with intermittent exotropia who underwent surgical treatment between January 1992 and January 2006 at Yeungnam University Hospital and postoperatively performed regular follow-up examinations for up to 7 years. We also analyzed the difference in exo-drift stabilization, according to surgical procedure. Results A total of 101 patients were enrolled in the study. Thirty-one patients underwent lateral rectus recession and medial rectus resection (R&R) and 70 patients underwent bilateral lateral rectus recession (BLR). The postoperative angles of deviation increased significantly during the initial 36 months, but no subsequent significant changes were observed for up to 84 months. Follow-ups for 7 years revealed that more than 50% of the total amount of exo-drift was observed within the first postoperative year. In addition, the angles of deviation at 1 year correlated with those at 7 years postoperatively (Pearson correlation coefficient r = 0.517, p < 0.001). No significant exo-drift was observed after 36 months in patients who underwent BLR, whereas after 18 months in patients who underwent R&R. Conclusions The minimum postoperative follow-up required after surgical treatment to ensure stable results is 36 months. In particular, careful follow-up is necessary during the first postoperative year to detect rapid exo-drift. Patients who underwent BLR required a longer follow-up than those who underwent R&R to ensure stable postoperative alignment. PMID:26865805
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.
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).
Transition from flute modes to drift waves in a magnetized plasma column
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.
Kinetic Electron Closures for Electromagnetic Simulation of Drift and Shear-Alfven Waves (II)
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.
NASA Astrophysics Data System (ADS)
Shaukat, Muzzamal I.; Masood, W.; Shah, H. A.; Iqbal, M. J.; Mirza, Arshad M.
2016-10-01
In the present investigation, linear and nonlinear electrostatic drift waves in the presence of trapped electrons with quantizing magnetic field and finite electron temperature effects in dense plasmas have been studied. The linear dispersion relation of the ion drift wave has been derived and it has been found that the Landau quantization and finite temperature effects significantly alter the linear propagation characteristics of the wave under consideration. Employing the Sagdeev potential approach, the formation of finite amplitude drift solitary structures has been investigated in the presence of a quantizing magnetic field for both fully and partially degenerate plasmas. Both compressive and rarefactive drift solitary structures have been obtained for different values of quantizing magnetic field and finite electron temperature effects. The theoretical results obtained have been analyzed numerically for the parameters typically found in white dwarfs.
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.
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
Impact of ion diamagnetic drift on MHD stability at edge pedestal in JT-60U rotating plasmas
NASA Astrophysics Data System (ADS)
Aiba, N.; Honda, M.; Kamiya, K.
2017-02-01
The effect of ion diamagnetic drift on the stability of peeling-ballooning modes in rotating tokamak plasmas has been analyzed numerically. The results show that plasma toroidal rotation can not only destabilize the peeling-ballooning mode but also can reduce the ion diamagnetic drift effect on the mode stability, even though the ion diamagnetic drift effect stabilizes the mode in a static plasma. Plasma poloidal rotation can also destabilize the mode and cancel the ion diamagnetic drift effect, even when the rotation frequency is much smaller than the toroidal one. These impacts of the rotation on the stability can resolve the discrepancy between the result of the numerical stability analysis and the experimental result in type-I ELMy H-mode plasmas in JT-60U. The reduction of the ion diamagnetic drift effect on ELM stability due to plasma rotation is shown to depend on the direction of the rotation, so that the ion diamagnetic drift effect becomes negligible only when the JT-60U plasma rotates in the direction counter to the plasma current.
Suppression of drift wave instability due to sheared field-aligned flow and negative ions
NASA Astrophysics Data System (ADS)
Ichiki, Ryuta; Hayashi, Kenichiro; Kaneko, Toshiro; Hatakeyama, Rikizo
2006-10-01
Sheared field-aligned plasma flow is a significant topic in space/circumterrestrial plasmas. Taking into account negative ions or dust grains will make the space plasma physics more general and accurate. Using the QT-Upgrade Machine, we have conducted laboratory experiments to examine negative ion effects on shear-modified drift waves. Field-aligned K^+ ion flow and its shear strength are controlled with a concentrically segmented W hot plate. Negative ions SF6^- are produced by introducing SF6 gas in the plasma. The drift wave shows a gradual monotonic decrease in amplitude as the shear strength is increased from zero. However, as the shear strength is decreased from zero to negative values, the amplitude increases up to a certain shear strength and rapidly decreases after the peaking. The negative ion introduction, in general, suppresses this instability while retaining the dependence of the amplitude on the shear. These wave characteristics are interpreted using the theories of current-driven (kinetic) and of D’Angelo (fluid) instabilities.
Predator prey oscillations in a simple cascade model of drift wave turbulence
Berionni, V.; Guercan, Oe. D.
2011-11-15
A reduced three shell limit of a simple cascade model of drift wave turbulence, which emphasizes nonlocal interactions with a large scale mode, is considered. It is shown to describe both the well known predator prey dynamics between the drift waves and zonal flows and to reduce to the standard three wave interaction equations. Here, this model is considered as a dynamical system whose characteristics are investigated. The analytical solutions for the purely nonlinear limit are given in terms of the Jacobi elliptic functions. An approximate analytical solution involving Jacobi elliptic functions and exponential growth is computed using scale separation for the case of unstable solutions that are observed when the energy injection rate is high. The fixed points of the system are determined, and the behavior around these fixed points is studied. The system is shown to display periodic solutions corresponding to limit cycle oscillations, apparently chaotic phase space orbits, as well as unstable solutions that grow slowly while oscillating rapidly. The period doubling route to transition to chaos is examined.
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.
Anomalous perturbative transport in tokamaks due to drift-Alfven-wave turbulence
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.
Anomalous perturbative transport in tokamaks due to drift-Alfvén-wave turbulence
NASA Astrophysics Data System (ADS)
Thoul, Anne A.; Similon, P. L.; Sudan, R. N.
1994-03-01
The method developed in Thoul, Similon, and Sudan [Phys. Plasmas 1, 579 (1994)] is used to calculate the transport due to drift-Alfvén-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.
Drift and breakup of spiral waves in reaction-diffusion-mechanics systems.
Panfilov, A V; Keldermann, R H; Nash, M P
2007-05-08
Rotating spiral waves organize excitation in various biological, physical, and chemical systems. They underpin a variety of important phenomena, such as cardiac arrhythmias, morphogenesis processes, and spatial patterns in chemical reactions. Important insights into spiral wave dynamics have been obtained from theoretical studies of the reaction-diffusion (RD) partial differential equations. However, most of these studies have ignored the fact that spiral wave rotation is often accompanied by substantial deformations of the medium. Here, we show that joint consideration of the RD equations with the equations of continuum mechanics for tissue deformations (RD-mechanics systems), yield important effects on spiral wave dynamics. We show that deformation can induce the breakup of spiral waves into complex spatiotemporal patterns. We also show that mechanics leads to spiral wave drift throughout the medium approaching dynamical attractors, which are determined by the parameters of the model and the size of the medium. We study mechanisms of these effects and discuss their applicability to the theory of cardiac arrhythmias. Overall, we demonstrate the importance of RD-mechanics systems for mathematics applied to life sciences.
Stability evaluation of the Panel 1 rooms and the E140 drift at WIPP
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.
NASA Astrophysics Data System (ADS)
Khazanov, G. V.; Boardsen, S.; Krivorutsky, E. N.; Engebretson, M. J.; Sibeck, D.; Chen, S.; Breneman, A.
2017-01-01
We analyze a wave event that occurred near noon between 07:03 and 07:08 UT on 23 February 2014 detected by the Van Allen Probes B spacecraft, where waves in the lower hybrid frequency range (LHFR) and electromagnetic ion cyclotron (EMIC) waves are observed to be highly correlated, with Pearson correlation coefficient of 0.86. We assume that the correlation is the result of LHFR wave generation by the ions' polarization drift in the electric field of the EMIC waves. To check this assumption the drift velocities of electrons and H+, He+, and O+ ions in the measured EMIC wave electric field were modeled. Then the LHFR wave linear instantaneous growth rates for plasma with these changing drift velocities and different plasma compositions were calculated. The time distribution of these growth rates, their frequency distribution, and the frequency dependence of the ratio of the LHFR wave power spectral density (PSD) parallel and perpendicular to the ambient magnetic field to the total PSD were found. These characteristics of the growth rates were compared with the corresponding characteristics of the observed LHFR activity. Reasonable agreement between these features and the strong correlation between EMIC and LHFR energy densities support the assumption that the LHFR wave generation can be caused by the ions' polarization drift in the electric field of an EMIC wave.
Effects of thin film and Stokes drift on the generation of vorticity by surface waves.
Parfenyev, V M; Vergeles, S S; Lebedev, V V
2016-11-01
Recently a theoretical scheme explaining the vorticity generation by surface waves in liquids was developed [Phys. Rev. Lett. 116, 054501 (2016)PRLTAO0031-900710.1103/PhysRevLett.116.054501]. Here we study how a thin (monomolecular) film presented on the surface of liquid affects the generated vorticity. We demonstrate that the vorticity becomes parametrically larger than for the case of liquid with a free surface, and the parameter is the quality factor of surface waves up to numerical factor. We also discuss the PIV experimental scheme intended to observe the generated vorticity and find that Stokes drift influences the measured velocity field. Explicit expression for the vertical vorticity was obtained.
Effect of resonant magnetic perturbations on secondary structures in drift-wave turbulence
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}.
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.
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
Solar Microwave Drifting Spikes and Solitary Kinetic Alfvén Waves
NASA Astrophysics Data System (ADS)
Wu, D. J.; Huang, J.; Tang, J. F.; Yan, Y. H.
2007-08-01
Mechanisms driving eruptive phenomena and elementary processes occurring at the smallest coherent scales have been outstanding problems in solar physics. In this Letter, a novel kind of fine structures of solar radio bursts, ``solar microwave drifting spikes'' (SMDSs), is reported. Our analysis shows that the SMDSs can be produced by a group of ``solitary kinetic Alfvén waves'' (SKAWs) with small cross-field scales, in which the electrons in the SKAWs are accelerated self-consistently by the SKAW electric fields to tens of keV and trapped within the SKAW potential wells. It is these trapped electrons that trigger the SMDSs. And the frequency drifts of the SMDSs are attributed to the SKAW propagation along the magnetic field. The SKAWs are exact solutions of two-fluid equations for a low-β plasma and have been experimentally verified in the magnetosphere, where they accelerate auroral electrons to several keV. We believe the SMDSs represent a new observational signature of SKAWs in the solar atmosphere.
Drift-Alfven wave mediated particle transport in an elongated density depression
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.
Plasma diffusion at the magnetopause? The case of lower hybrid drift waves
NASA Technical Reports Server (NTRS)
Treumann, R. A.; Labelle, J.; Pottelette, R.; Gary, S. P.
1990-01-01
The diffusion expected from the quasilinear theory of the lower hybrid drift instability at the Earth's magnetopause is recalculated. The resulting diffusion coefficient is in principle just 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 low processes. However, some recent data and simulations seems to indicate that the magnetopause is not consistent with such a soft diffusive equilibrium model. Furthermore, investigation of the nonlinear equations for the lower hybrid waves for magnetopause parameters indicates that the quasilinear state may never arise because coalescence to large wavelengths, followed by collapse once a critical wavelengths is reached, occur on a time scale faster than the quasilinear diffusion. In this case, an inhomogeneous boundary layer is to be expected. More simulations are required over longer time periods to explore whether this nonlinear evolution really takes place at the magnetopause.
Anomalous perturbative transport in tokamaks due to drift-wave turbulence
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.
Excitation of kinetic geodesic acoustic modes by drift waves in nonuniform plasmas
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.
Modeling studies of transport bifurcation phenomena in a collisional drift wave turbulence
NASA Astrophysics Data System (ADS)
Hajjar, Rima; Diamond, Patrick; Tynan, Georges; Ashourvan, Arash
2016-10-01
Self-organization of drift wave turbulence via particle transport and Reynolds stresses is a mechanism for turbulence suppression and reduction of cross field transport. This energy transfer mechanism between microscale drift waves and mesoscale zonal flows can create a transport bifurcation and trigger the formation of an internal transport barrier. We report here on studies investigating transport bifurcation dynamics in the CSDX linear device using a 1D reduced turbulence and mean field evolution model. This two-mixing scale Hasegawa-Wakatani based model evolves spatio-temporal variations of three plasma fields: the mean density n, the mean vorticity u and the turbulent potential enstrophy e. The model adopts inhomogeneous potential vorticity mixing on a mixing length the expression of which is related to the Rhines' scale and to the mode scale (i.e. is ∇n and ∇u dependent). The model is based on expressions for turbulent fluxes of n, u and e derived from mixing length concepts. Turbulent particle and enstrophy transport are written as diffusive, but a residual stress part is included in the expression for the vorticity flux. Mixed boundary conditions are used at both ends of the domain and an external boundary fueling source is added. Simulation results show a steepening in the particle density profiles with B along with the formation of a net flow shear layer resulting from the vorticity mixing. These results suggest that the system dynamic is capable of sustaining the plasma core by means of a purely diffusive particle flux, without any explicit inward particle pinch.
Gyroaverage effects on chaotic transport by drift waves in zonal flows
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.
Gyroaverage effects on chaotic transport by drift waves in zonal flows
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.
Effects of Electron Drifts on the Collisionless Damping of Kinetic Alfvén Waves in the Solar Wind
NASA Astrophysics Data System (ADS)
Tong, Yuguang; Bale, Stuart D.; Chen, Christopher H. K.; Salem, Chadi S.; Verscharen, Daniel
2015-05-01
The collisionless dissipation of anisotropic Alfvénic turbulence is a promising candidate to solve the solar wind heating problem. Extensive studies examined the kinetic properties of Alfvén waves in simple Maxwellian or bi-Maxwellian plasmas. However, the observed electron velocity distribution functions in the solar wind are more complex. In this study, we analyze the properties of kinetic Alfvén waves (KAWs) in a plasma with two drifting electron populations. We numerically solve the linearized Maxwell-Vlasov equations and find that the damping rate and the proton-electron energy partition for KAWs are significantly modified in such plasmas, compared to plasmas without electron drifts. We suggest that electron drift is an important factor to take into account when considering the dissipation of Alfvénic turbulence in the solar wind or other β ˜ 1 astrophysical plasmas.
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.
NASA Astrophysics Data System (ADS)
Crabbe, R. S.; McCooeye, M.; Mickle, R. E.
1994-04-01
Measurements of drift cloud mass from 11 cases selected from a study of wind-borne droplet drift from ultra low-volume aerial spray applications over northern Ontario forests are presented as a function of atmospheric stability. Six swaths were overlaid onto a flight line in 30 min to obtain ensemble-averaged data from rotary atomizer emissions from an agricultural spray plane flying at about 21 and 26 m above ground level. The estimated volume median diameters of the spray were 100 µm for the 21-m height and 70 µm for the 26-m height. The mass of spray material in the drift cloud was measured at 400, 1200, and 2200 m downwind of the (crosswind) flight line using Rotorods' suspended from tethered blimps. Wind speed at aircraft height varied from 2 to 5 m s1 and meteorological conditions varied from moderately stable to moderately unstable.Analysis of the data revealed that 35% more drift occurred in stable than in unstable conditions. The lowest drift was measured when the aircraft was flown in the morning mixing layer beneath a low capping inversion. Under thee conditions, only 18% of the emission drifted put 400 m downwind and 10% past 1200 m. The highest drift occurred in moderately stable flow, 71% past 400 m and 50% past 2200 m in 3 m s1 wind speeds and, in slightly stable flow, 77% past 400 m and 27% past 2200 m in 5 m s1 wind speeds.Within experimental error, little difference was observed between wind drift of the 100-µm-diameter droplets and the 70-µm-diameter droplets past 400 m downwind although farther downwind, drift from the larger-droplet emission was less. This difference is discussed in terms of the descent rate of the aircraft vortex wake in stable conditions.
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.
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
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
Effect of Resonant Magnetic Perturbations on secondary structures in Drift-Wave turbulence
NASA Astrophysics Data System (ADS)
Leconte, Michael
2011-10-01
In this work, we study the effects of RMPs on turbulence, flows and confinement, in the framework of two paradigmatic models, resistive ballooning and resistive drift waves. For resistive ballooning turbulence, we use 3D global numerical simulations, including RMP fields and (externally-imposed) sheared rotation profile. Without RMPs, relaxation oscillations of the pressure profile occur. With RMPs, results show that long-lived convection cells are generated by the combined effects of pressure modulation and toroidal curvature coupling. These modify the global structure of the turbulence and eliminate relaxation oscillations. This effect is due mainly to a modification of the pressure profile linked to the presence of residual magnetic island chains. Hence convection-cell generation increases for increasing δBr/B0. For RMP effect on zonal flows in 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 δBr/B0. 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 a novel set of system states that are similar to the Hmode-like 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 and low collisionality, both the ambient turbulence and zonal flow energy increase with δBr/B0. For larger RMP strength, the turbulence energy increases, but the energy of zonal flows decreases with δBr/B0, corresponding to a damping of zonal flows. At high
Reentrant stability of BEC standing wave patterns
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'.
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.
Comparison of Collisional Drift-Wave Simulation with CSDX Experimental Results
NASA Astrophysics Data System (ADS)
Vaezi, Payam; Holland, Christopher; Tynan, George; Thakur, Saikat; Brandt, Christian; Dudson, Benjamin; Friedman, Brett; Carter, Troy
2013-10-01
Recent upgrades to the linear Controlled Shear Decorrelation Experiment (CSDX) [Burin et al., PoP 2005] at UCSD (maximum Bz from 1 kG to 2.4 kG, increase of helicon source diameter from 10 cm to 15 cm) have revealed a rich array of turbulence dynamics at previously inaccessible conditions. We report initial comparisons of linear and nonlinear collisional drift-wave physics made using analytic theory and the BOUT + + code [Dudson et al., CPC 2009] against these observations, focusing upon the transition from nonlinearly coupled but distinct eigenmodes at 0.9 kG to fully developed broadband turbulence at 2.4 kG. Comparisons of predicted linear eigenmode structures, frequencies, and density-potential cross-phases to measurement are presented, as well as predictions for nonlinear frequency power spectra and saturated fluctuation levels. We also report progress on the development and implementation of synthetic Langmuir probe and fast framing camera diagnostics for improving the fidelity of our model-experiment comparisons.
Self-regulating Drift wave -- Zonal Flow turbulence in a linear plasma device
NASA Astrophysics Data System (ADS)
Xie, Jinlin; Chen, Ran; Hu, Guanghai; Jin, Xiaoli; Li, Hong; Liu, Wandong; Yu, Changxuan
2012-10-01
Here we report new and interesting results about the DW-ZF system in a linear plasma device with much better control environments to illustrate important Zonal flow physics: (1) The three-dimensional spectral features of the LFZF have been provided. In particular, it is identified that the LFZF damping is dominated by ion-neutral collision in our case. Also experimental evidence of the shearing effect of ZF on DW has been given. (2) A zonal flow dominated state of the DW-ZF system has been achieved. Theoretically, it has been predicted that a significant portion of the turbulence energy can be stored in the Zonal Flows for the case of low collisionality plasmas. In our experiments we achieve a zonal flow dominated state, in which the maximum ratio of the ZF energy to the total turbulence energy is about 80%, which seems to support the hypothesis of zonostropic state in geostrophic turbulence. (3) The self-regulating dynamics in the DW-ZF system is clearly elucidated. The evolution of the energy partition ratio of drift-wave turbulence and zonal flow is investigated with varying magnetic field strength, which is found consistent with the general prey-predator model.
Impact of resonant magnetic perturbations on nonlinearly driven modes in drift-wave turbulence
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.
Dynamics of zonal flow saturation in strong collisionless drift wave turbulence
NASA Astrophysics Data System (ADS)
Kim, Eun-jin; Diamond, P. H.
2002-11-01
Generalized Kelvin-Helmholtz (GKH) instability is examined as a mechanism for the saturation of zonal flows in the collisionless regime. By focusing on strong turbulence regimes, GKH instability is analyzed in the presence of a background of finite-amplitude drift waves. A detailed study of a simple model with cold ions shows that nonlinear excitation of GKH modes via modulational instability can be comparable to their linear generation. Furthermore, it is demonstrated that zonal flows are likely to grow faster than GKH mode near marginality, with insignificant turbulent viscous damping by linear GKH. The effect of finite ion temperature fluctuations is incorporated in a simple toroidal ion temperature gradient model, within which both zonal flow and temperature are generated by modulational instability. The phase between the two is calculated self-consistently and shown to be positive. Furthermore, the correction to nonlinear generation of GKH modes appears to be small, being of order O(ρi2k2). Thus, the role of linear GKH instability in the saturation of collisionless zonal flows, in general, seems dubious.
NASA Astrophysics Data System (ADS)
Tang, Jun; Jia, Ya; Ma, Jun; Yi, Ming
2009-05-01
Based on the Tang-Othmer Ca2+ model, the drift behavior of intracellular Ca2+ spiral waves under the influence of weak electric field is investigated. Numerical results show that the dependence of drift velocity of the spiral tip on dc electric field is similar to experimental observations in BZ system. When an ac electric field is applied, interesting resonant-drift phenomenon is observed with ω = 2Ω0. All results can be explained analytically using a proximate method.
NASA Technical Reports Server (NTRS)
Fung, Shing
2007-01-01
By analyzing CRRES and GOES observations on Aug. 27 1991, Tan et al. [2004] reported evidence of magnetospheric relativistic electron acceleration by resonant interactions with PC5 ULF waves. The event showed strong ULF wave activities after a storm sudden commencement (SSC) and energetic electron fluxes were enhanced in 2 hours. The electron flux peak observed in energy channels (0.6 - 1.1 MeV) were modulated by local electric field observed by CRRES. In this study, we set up a drift-resonant interaction model between ULF wave and magnetospheric relativistic electrons to model the observed electron flux in the event. In this model, the poloidal mode wave is concentrated in the dayside and the toroidal mode wave is concentrated in two flanks. The toroidal mode waves in the dawn and dusk flanks are in anti-phase. We found that electron can be accelerated jointly by the poloidal wave in the dayside and toroidal wave in flanks. The dayside poloidal wave serves as the dominant source of electron acceleration. The simulated electron flux variations agree well with observations both in fine details and long period behavior. These agreements in electron behavior indicate that the ULF wave plays an important role in accelerating MeV relativistic electrons around the geosynchronous orbit.
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.
Parsa, Behnoosh; Terekhov, Alexander; Zatsiorsky, Vladimir M; Latash, Mark L
2017-02-01
We address the nature of unintentional changes in performance in two papers. This first paper tested a hypothesis that unintentional changes in performance variables during continuous tasks without visual feedback are due to two processes. First, there is a drift of the referent coordinate for the salient performance variable toward the actual coordinate of the effector. Second, there is a drift toward minimum of a cost function. We tested this hypothesis in four-finger isometric pressing tasks that required the accurate production of a combination of total moment and total force with natural and modified finger involvement. Subjects performed accurate force-moment production tasks under visual feedback, and then visual feedback was removed for some or all of the salient variables. Analytical inverse optimization was used to compute a cost function. Without visual feedback, both force and moment drifted slowly toward lower absolute magnitudes. Over 15 s, the force drop could reach 20% of its initial magnitude while moment drop could reach 30% of its initial magnitude. Individual finger forces could show drifts toward both higher and lower forces. The cost function estimated using the analytical inverse optimization reduced its value as a consequence of the drift. We interpret the results within the framework of hierarchical control with referent spatial coordinates for salient variables at each level of the hierarchy combined with synergic control of salient variables. The force drift is discussed as a natural relaxation process toward states with lower potential energy in the physical (physiological) system involved in the task.
NASA Astrophysics Data System (ADS)
Zonca, Fulvio; Chen, Liu
2014-07-01
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.
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.
NASA Technical Reports Server (NTRS)
Pfaff, R. F.; Kelley, M. C.; Kudeki, E.; Fejer, B. G.; Baker, K. D.
1987-01-01
The results of electric field and plasma density measurements in the strongly driven daytime equatorial electrojet over Peru, made during the March 1983 Condor electrojet experiment from Punta Lobos, Peru, are discussed together with the rocket instrumentation used for the measurements and the pertinent payload dynamics. The overall characteristics of the irregularity layer observed in situ in the electrojet are described. Special consideration is given to the waves generated by the gradient drift instability (observed between 90 and 106.5 km) and to primary and secondary two-stream waves detected by the two probes on the topside between 103 and 111 km, where the electron current was considered to be strongest.
Stability Design and Response to Waves by Batoids.
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.
Boie, R.A.; Radeka, V.; Rehak, P.; Xi, D.M.
1980-11-01
The feasibility of using an anode wire and surrounding electrodes in drift chambers as a transmission line for second coordinate readout has been studied. The method is based on propagation of the electromagnetic wave along the anode wire is determined by measurement, in an optimized electronic readout system, of the time difference between the arrivals of the signal to the ends of the wire. The resolution obtained on long wires (approx. 2 meters) is about 2 cm FWHM for minimum ionizing particles at a gas gain of approx. = 10/sup 5/.
Long-range correlations induced by the self-regulation of zonal flows and drift-wave turbulence
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.
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...
Inertialess multilayer film flow with surfactant: Stability and traveling waves
NASA Astrophysics Data System (ADS)
Thompson, J.; Blyth, M. G.
2016-10-01
Multilayer film flow down an inclined plane in the presence of an insoluble surfactant is investigated with particular emphasis on determining flow stability and investigating the possibility of traveling-wave solutions. The investigation is conducted for two or three layers under conditions of Stokes flow and, separately, on the basis of a long-wave assumption. A normal mode linear stability analysis for Stokes flow shows that adding surfactant to one of the film surfaces can destabilize an otherwise stable flow configuration. For the long-wave system, periodic traveling-wave branches are detected and traced, revealing solutions with pulselike solitary waves on each film surface traveling in phase with each other, traveling waves with capillary ridge structures, and solutions with two of the film surfaces almost in contact. Time-periodic traveling-wave solutions are also found. The stability of the traveling waves is determined by solving initial-value problems and by computing eigenvalue spectra. Boundary element simulations for Stokes flow confirm the existence of traveling waves outside the long-wave regime.
NASA Astrophysics Data System (ADS)
Leconte, M.; Diamond, P. H.; Xu, Y.
2014-01-01
We study the effects of resonant magnetic perturbations (RMPs) on turbulence, flows and confinement in the framework of resistive drift-wave turbulence. This work was motivated, in parts, by experiments reported at the IAEA 2010 conference (Xu et al 2011 Nucl. Fusion 51 062030) which showed a decrease of long-range correlations during the application of RMPs. We derive and apply a zero-dimensional predator-prey model coupling the drift-wave-zonal-mode system (Leconte and Diamond 2012 Phys. Plasmas 19 055903) to the evolution of mean quantities. This model has both density-gradient drive and RMP amplitude as control parameters and predicts a novel type of transport bifurcation in the presence of RMPs. This model allows a description of the full L-H transition evolution with RMPs, including the mean sheared flow evolution. The key results are the following: (i) the L-I and I-H power thresholds both increase with RMP amplitude |\\tilde b_x| , the relative increase of the L-I threshold scales as \\Delta P_LI \\propto |\\tilde b_x|^2 \
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.
NASA Technical Reports Server (NTRS)
Winckler, J. R.; Erickson, K. N.; Abe, Y.; Steffen, J. E.; Malcolm, P. R.
1985-01-01
Orthogonal probes on a free-flying plasma diagnostics payload are used to study ELF electric disturbances in the auroral ionosphere that are due to the injection of powerful electron beams. Frequency spectrograms are presented for various pitch angles, pulsing characteristics, and other properties of the injected beams; the large scale DC ionospheric convection electric field is measured, together with auroral particle precipitation, visual auroral forms, and ionospheric parameters. In view of the experimental results obtained, it is postulated that the observed ELF waves are in the Alfven and drift modes, and are generated by the positive vehicle potential during beam injection.
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.
NASA Astrophysics Data System (ADS)
Carrasco, Ana; Semedo, Alvaro; Behrens, Arno; Weisse, Ralf; Breivik, Øyvind; Saetra, Øyvind; Håkon Christensen, Kai
2016-04-01
The global wave-induced current (the Stokes Drift - SD) is an important feature of the ocean surface, with mean values close to 10 cm/s along the extra-tropical storm tracks in both hemispheres. Besides the horizontal displacement of large volumes of water the SD also plays an important role in the ocean mix-layer turbulence structure, particularly in stormy or high wind speed areas. The role of the wave-induced currents in the ocean mix-layer and in the sea surface temperature (SST) is currently a hot topic of air-sea interaction research, from forecast to climate ranges. The SD is mostly driven by wind sea waves and highly sensitive to changes in the overlaying wind speed and direction. The impact of climate change in the global wave-induced current climate will be presented. The wave model WAM has been forced by the global climate model (GCM) ECHAM5 wind speed (at 10 m height) and ice, for present-day and potential future climate conditions towards the end of the end of the twenty-first century, represented by the Intergovernmental Panel for Climate Change (IPCC) CMIP3 (Coupled Model Inter-comparison Project phase 3) A1B greenhouse gas emission scenario (usually referred to as a ''medium-high emissions'' scenario). Several wave parameters were stored as output in the WAM model simulations, including the wave spectra. The 6 hourly and 0.5°×0.5°, temporal and space resolution, wave spectra were used to compute the SD global climate of two 32-yr periods, representative of the end of the twentieth (1959-1990) and twenty-first (1969-2100) centuries. Comparisons of the present climate run with the ECMWF (European Centre for Medium-Range Weather Forecasts) ERA-40 reanalysis are used to assess the capability of the WAM-ECHAM5 runs to produce realistic SD results. This study is part of the WRCP-JCOMM COWCLIP (Coordinated Ocean Wave Climate Project) effort.
Stability for line solitary waves of Zakharov-Kuznetsov equation
NASA Astrophysics Data System (ADS)
Yamazaki, Yohei
2017-04-01
In this paper, we consider the stability for line solitary waves of the two dimensional Zakharov-Kuznetsov equation on R ×TL which is one of a high dimensional generalization of Korteweg-de Vries equation, where TL is the torus with the 2 πL period. The orbital and asymptotic stability of the one soliton of Korteweg-de Vries equation on the energy space was proved by Benjamin [2], Pego and Weinstein [41] and Martel and Merle [30]. We regard the one soliton of Korteweg-de Vries equation as a line solitary wave of Zakharov-Kuznetsov equation on R ×TL. We prove the stability and the transverse instability of the line solitary waves of Zakharov-Kuznetsov equation by applying the method of Evans' function and the argument of Rousset and Tzvetkov [44]. Moreover, we prove the asymptotic stability for orbitally stable line solitary waves of Zakharov-Kuznetsov equation by using the argument of Martel and Merle [30-32] and a Liouville type theorem. If L is the critical period with respect to a line solitary wave, the line solitary wave is orbitally stable. However, since this line solitary wave is a bifurcation point of the stationary equation, the linearized operator of the stationary equation is degenerate. Because of the degeneracy of the linearized operator, we can not show the Liouville type theorem for the line solitary wave by using the usual virial type estimate. To show the Liouville type theorem for the line solitary wave, we modify a virial type estimate.
NASA Astrophysics Data System (ADS)
Mathias, A. C.; Viana, R. L.; Kroetz, T.; Caldas, I. L.
2017-03-01
Chaotic dynamics in open Hamiltonian dynamical systems typically presents a number of fractal structures in phase space derived from the interwoven structure of invariant manifolds and the corresponding chaotic saddle. These structures are thought to play an important role in the transport properties related to the chaotic motion. Such properties can explain some aspects of the non-uniform nature of the anomalous transport observed in magnetically confined plasmas. Accordingly we consider a theoretical model for the interaction of charged test particles with drift waves. We describe the exit basin structure of the corresponding chaotic orbit in phase space and interpret it in terms of the invariant manifold structure underlying chaotic dynamics. As a result, the exit basin boundary is shown to be a fractal curve, by direct calculation of its box-counting dimension. Moreover, when there are more than two basins, we verify the existence of the Wada property, an extreme form of fractality.
Furukawa, M.; Tokuda, S.
2012-10-15
A matching method using a finite-width inner region is extended for stability analysis of magnetohydrodynamic mode including diamagnetic drift effect. The inclusion of the diamagnetic drift effect is accomplished by a newly developed ordering scheme in the outer region. The ordering scheme enables us to derive a hierarchy of generalized Newcomb equations. Higher-order equations give us correction of outer solution due to the diamagnetic drift effect as well as inertia and resistivity. By this correction, the accuracy of the dispersion relation is improved. Several numerical results are presented to demonstrate good performance of the matching method. Dropping the diamagnetic drift effect in the outer region leads to less accurate results.
Ion-wave stabilization of an inductively coupled plasma
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.
Note on the stability of viscous roll waves
NASA Astrophysics Data System (ADS)
Barker, Blake; Johnson, Mathew A.; Noble, Pascal; Rodrigues, Luis Miguel; Zumbrun, Kevin
2017-02-01
In this note, we announce a complete classification of the stability of periodic roll-wave solutions of the viscous shallow water equations, from their onset at Froude number F ≈ 2 up to the infinite Froude limit. For intermediate Froude numbers, we obtain numerically a particularly simple power-law relation between F and the boundaries of the region of stable periods, which appears potentially useful in hydraulic engineering applications. In the asymptotic regime F → 2 (onset), we provide an analytic expression of the stability boundaries, whereas in the limit F → ∞, we show that roll waves are always unstable.
SUNWARD PROPAGATING ALFVÉN WAVES IN ASSOCIATION WITH SUNWARD DRIFTING PROTON BEAMS IN THE SOLAR WIND
He, Jiansen; Pei, Zhongtian; Wang, Linghua; Tu, Chuanyi; Zhang, Lei; Marsch, Eckart; Salem, Chadi
2015-06-01
Using measurements from the WIND spacecraft, here we report the observation of sunward propagating Alfvén waves (AWs) in solar wind that is magnetically disconnected from the Earth's bow shock. In the sunward magnetic field sector, we find a period lasting for more than three days in which there existed (during most time intervals) a negative correlation between the flow velocity and magnetic field fluctuations, thus indicating that the related AWs are mainly propagating sunward. Simultaneous observations of counter-streaming suprathermal electrons suggest that these sunward AWs may not simply be due to the deflection of an open magnetic field line. Moreover, no interplanetary coronal mass ejection appears to be associated with the counter-streaming suprathermal electrons. As the scale goes from the magnetohydrodynamic down to the ion kinetic regime, the wave vector of magnetic fluctuations usually becomes more orthogonal to the mean magnetic field direction, and the fluctuations become increasingly compressible, which are both features consistent with quasi-perpendicular kinetic AWs. However, in the case studied here, we find clear signatures of quasi-parallel sunward propagating ion-cyclotron waves. Concurrently, the solar wind proton velocity distribution reveals a sunward field-aligned beam that drifts at about the local Alfvén speed. This beam is found to run in the opposite direction of the normally observed (anti-sunward) proton beam, and is apparently associated with sunward propagating Alfvén/ion-cyclotron waves. The results and conclusions of this study enrich our knowledge of solar wind turbulence and foster our understanding of proton heating and acceleration within a complex magnetic field geometry.
Stability of Waves in Semiconductor-Ferrite-Metamaterials Waveguide Structure
NASA Astrophysics Data System (ADS)
Shabat, M. M.; Hamada, M. S.; El-Astal, A. H.; Mohammad, H. A. H.
In recent years, the properties of electromagnetic waves propagating in various waveguide structures containing metamaterials have attracted increasing and growing attention. In this paper, the propagation of electromagnetic waves in a layered structure consisting of ferrite film bounded by a semiconductor cover and a metamaterial substrate was analyzed and discussed. The stability of magnetostatic surface waves through mentioned three waveguide structures has been obtained by implementing the perturbation method and the lighthill criteria has also been checked to find out the possibility of existence of magnetostatic envelope Solitons.
Stability of a steady, large amplitude whistler wave.
NASA Technical Reports Server (NTRS)
Palmadesso, P. J.; Schmidt, G.
1972-01-01
Study of the behavior of weak electrostatic waves in a collisionless magnetoplasma supporting a steady large amplitude whistler wave. All waves are assumed to propagate parallel to a uniform background magnetic field B sub zero. In the presence of the whistler wave fields each particle executes an oscillatory motion parallel to B sub zero, in addition to a translation along B sub zero and transverse motions. This oscillation causes the Landau resonance to be replaced by a series of new resonances between particles and the electrostatic modes. A distribution function for the perturbed plasma is constructed by solving the Vlasov equation, linearized in the electrostatic wave amplitudes. A dispersion relation is obtained and solved approximately for the growth/damping rate of the perturbations. Growing electrostatic modes are found to be approximately uncoupled. Trapped particles have a strong influence on the stability of the system.
Effect of the magnetic field curvature on the generation of zonal flows by drift-Alfven waves
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.
A tunable low-drift laser stabilized to an atomic reference
NASA Astrophysics Data System (ADS)
Leopold, T.; Schmöger, L.; Feuchtenbeiner, S.; Grebing, C.; Micke, P.; Scharnhorst, N.; Leroux, I. D.; López-Urrutia, J. R. Crespo; Schmidt, P. O.
2016-09-01
We present a laser system with a linewidth and long-term frequency stability at the 50 kHz level. It is based on a Ti:Sapphire laser emitting radiation at 882 nm which is referenced to an atomic transition. For this, the length of an evacuated transfer cavity is stabilized to a reference laser at 780 nm locked to the ^{85}Rb D_2-line via modulation transfer spectroscopy. Gapless frequency tuning of the spectroscopy laser is realized using the sideband-locking technique to the transfer cavity. In this configuration , the linewidth of the spectroscopy laser is derived from the transfer cavity, while the long-term stability is derived from the atomic resonance. Using an optical frequency comb, the frequency stability and linewidth of both lasers are characterized by comparison against an active hydrogen maser frequency standard and an ultra-narrow linewidth laser, respectively. The laser system presented here will be used for spectroscopy of the 1s22s22p 2P_{1/2} - 2P_{3/2} transition in sympathetically cooled Ar^{13+} ions at 441 nm after frequency doubling.
Analogues as a check of predicted drift stability at Yucca Mountain, Nevada
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.
Natural Analoges as a Check of Predicted Drift Stability at Yucca Mountain, Nevada
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.
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.
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.
Evolution of a reassortant North American gull influenza virus lineage: drift, shift and stability
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
Longitudinal stability in multiharmonic standing wave linacs
NASA Astrophysics Data System (ADS)
Carver, L. R.; Jones, R. M.; Jiang, Y.; Hirshfield, J. L.
2016-09-01
Accelerating cavities that excite multiple modes at integer harmonics of the fundamental frequency have the potential to be used to suppress the onset of rf breakdown and reduce the pulsed surface heating at high accelerating gradients. Understanding the effect of an additional harmonic cavity mode on the longitudinal beam dynamics is important to their development and use. A Hamiltonian that describes the longitudinal motion of a particle as it traverses a chain of multiharmonic cavities has been derived and is applied to the case of a second harmonic cavity. The Hamiltonian is based upon formalisms found in literature for the fundamental harmonic and is extended to include different longitudinal field distributions and harmonic frequencies. The study initially explores the longitudinal motion for moderate accelerating gradients with high-β protons, as this will allow fundamental properties of the stable region (acceptance and shape of the rf bucket) to be determined. High accelerating gradients are also investigated but the focus will be on phase stability throughout. This work concludes by considering the longitudinal dynamics of a modified European Spallation Source accelerator, comprised of multiharmonic cavities that has specifications broadly consistent with the accelerator.
Gas scintillation drift chambers with wave shifter read-out for hard X-ray astronomy
NASA Technical Reports Server (NTRS)
Sadoulet, Bernard; Lin, Robert P.; Weiss, Steven C.
1987-01-01
A major improvement in hard X-ray and gamma ray astrophysics could be provided by high pressure xenon time projection chambers where gas scintillation is used both for the measurement of the time of interaction and for the detection of the extracted electrons. This allows three dimensional imaging of naturally complex events (photoelectric interaction with escape photon, Compton scatter, and pair production). A novel read-out system based on wave shifter fibers, which is well suited to the high pressures and large areas required of a hard X-ray telescope is proposed. Expected performances are computed, potential problems are outlined, and the experimental effort to solve these problems are described.
Stability of traveling wave solutions to the Whitham equation
NASA Astrophysics Data System (ADS)
Sanford, Nathan; Kodama, Keri; Carter, John D.; Kalisch, Henrik
2014-06-01
The Whitham equation was proposed as an alternate model equation for the simplified description of unidirectional wave motion at the surface of an inviscid fluid. An advantage of the Whitham equation over the KdV equation is that it provides a more faithful description of short waves of small amplitude. Recently, Ehrnström and Kalisch [19] established that the Whitham equation admits periodic traveling-wave solutions. The focus of this work is the stability of these solutions. The numerical results presented here suggest that all large-amplitude solutions are unstable, while small-amplitude solutions with large enough wavelength L are stable. Additionally, periodic solutions with wavelength smaller than a certain cut-off period always exhibit modulational instability. The cut-off wavelength is characterized by kh0=1.145, where k=2π/L is the wave number and h0 is the mean fluid depth.
Drift Mode Calculations in Nonaxisymmetric Geometry
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.
Stability of steep gravity capillary solitary waves in deep water
NASA Astrophysics Data System (ADS)
Calvo, David C.; Akylas, T. R.
2002-02-01
The stability of steep gravity capillary solitary waves in deep water is numerically investigated using the full nonlinear water-wave equations with surface tension. Out of the two solution branches that bifurcate at the minimum gravity capillary phase speed, solitary waves of depression are found to be stable both in the small-amplitude limit when they are in the form of wavepackets and at finite steepness when they consist of a single trough, consistent with observations. The elevation-wave solution branch, on the other hand, is unstable close to the bifurcation point but becomes stable at finite steepness as a limit point is passed and the wave profile features two well-separated troughs. Motivated by the experiments of Longuet-Higgins & Zhang (1997), we also consider the forced problem of a localized pressure distribution applied to the free surface of a stream with speed below the minimum gravity capillary phase speed. We find that the finite-amplitude forced solitary-wave solution branch computed by Vanden-Broeck & Dias (1992) is unstable but the branch corresponding to Rayleigh’s linearized solution is stable, in agreement also with a weakly nonlinear analysis based on a forced nonlinear Schrödinger equation. The significance of viscous effects is assessed using the approach proposed by Longuet-Higgins (1997): while for free elevation waves the instability predicted on the basis of potential-flow theory is relatively weak compared with viscous damping, the opposite turns out to be the case in the forced problem when the forcing is strong. In this régime, which is relevant to the experiments of Longuet-Higgins & Zhang (1997), the effects of instability can easily dominate viscous effects, and the results of the stability analysis are used to propose a theoretical explanation for the persistent unsteadiness of the forced wave profiles observed in the experiments.
A Kinetic Approach to Propagation and Stability of Detonation Waves
NASA Astrophysics Data System (ADS)
Monaco, R.; Bianchi, M. Pandolfi; Soares, A. J.
2008-12-01
The problem of the steady propagation and linear stability of a detonation wave is formulated in the kinetic frame for a quaternary gas mixture in which a reversible bimolecular reaction takes place. The reactive Euler equations and related Rankine-Hugoniot conditions are deduced from the mesoscopic description of the process. The steady propagation problem is solved for a Zeldovich, von Neuman and Doering (ZND) wave, providing the detonation profiles and the wave thickness for different overdrive degrees. The one-dimensional stability of such detonation wave is then studied in terms of an initial value problem coupled with an acoustic radiation condition at the equilibrium final state. The stability equations and their initial data are deduced from the linearized reactive Euler equations and related Rankine-Hugoniot conditions through a normal mode analysis referred to the complex disturbances of the steady state variables. Some numerical simulations for an elementary reaction of the hydrogen-oxygen chain are proposed in order to describe the time and space evolution of the instabilities induced by the shock front perturbation.
On the dependence of travelling wave stability on basic state wave phase speed
NASA Technical Reports Server (NTRS)
Manney, Gloria L.
1991-01-01
The dependence of stability on basic state wave phase speed is examined in a nondivergent barotropic model on a sphere for planetary scale waves with phase speeds typical of waves observed in the atmosphere. Triad interactions are examined analytically and compared to numerical results from a full spectral model. A number of triads may result in growth of the perturbation components for each basic state wave; for each triad there is a basic state wave phase speed where it is resonant, identified as the point where the critical amplitude for instability to that perturbation becomes zero. Critical amplitudes for instability obtained using the full spectral model generally agree well with triad results. Since the basic state wave phase speed determines which triad will grow, spatial structure and critical amplitudes for instability for the growing disturbances depend strongly on basic state wave phase speed. The results of this idealized study suggest that phase speed may be an important factor in determining the stability of planetary scale waves in the atmosphere.
A statistical study of gyro-averaging effects in a reduced model of drift-wave transport
Fonseca, Julio; Del-Castillo-Negrete, Diego B.; Sokolov, Igor M.; Caldas, Ibere L.
2016-08-25
Here, a statistical study of finite Larmor radius (FLR) effects on transport driven by electrostatic driftwaves is presented. The study is based on a reduced discrete Hamiltonian dynamical system known as the gyro-averaged standard map (GSM). In this system, FLR effects are incorporated through the gyro-averaging of a simplified weak-turbulence model of electrostatic fluctuations. Formally, the GSM is a modified version of the standard map in which the perturbation amplitude, K_{0}, becomes K_{0}J_{0}($\\hat{p}$), where J_{0} is the zeroth-order Bessel function and $\\hat{p}$ s the Larmor radius. Assuming a Maxwellian probability density function (pdf) for $\\hat{p}$ , we compute analytically and numerically the pdf and the cumulative distribution function of the effective drift-wave perturba- tion amplitude K_{0}J_{0}($\\hat{p}$). Using these results, we compute the probability of loss of confinement (i.e., global chaos), P_{c} provides an upper bound for the escape rate, and that P_{t }rovides a good estimate of the particle trapping rate. Lastly. the analytical results are compared with direct numerical Monte-Carlo simulations of particle transport.
A statistical study of gyro-averaging effects in a reduced model of drift-wave transport
Fonseca, Julio; Del-Castillo-Negrete, Diego B.; Sokolov, Igor M.; ...
2016-08-25
Here, a statistical study of finite Larmor radius (FLR) effects on transport driven by electrostatic driftwaves is presented. The study is based on a reduced discrete Hamiltonian dynamical system known as the gyro-averaged standard map (GSM). In this system, FLR effects are incorporated through the gyro-averaging of a simplified weak-turbulence model of electrostatic fluctuations. Formally, the GSM is a modified version of the standard map in which the perturbation amplitude, K0, becomes K0J0(more » $$\\hat{p}$$), where J0 is the zeroth-order Bessel function and $$\\hat{p}$$ s the Larmor radius. Assuming a Maxwellian probability density function (pdf) for $$\\hat{p}$$ , we compute analytically and numerically the pdf and the cumulative distribution function of the effective drift-wave perturba- tion amplitude K0J0($$\\hat{p}$$). Using these results, we compute the probability of loss of confinement (i.e., global chaos), Pc provides an upper bound for the escape rate, and that Pt rovides a good estimate of the particle trapping rate. Lastly. the analytical results are compared with direct numerical Monte-Carlo simulations of particle transport.« less
NASA Astrophysics Data System (ADS)
Paraskevov, A. V.; Zendrikov, D. K.
2017-04-01
We show that in model neuronal cultures, where the probability of interneuronal connection formation decreases exponentially with increasing distance between the neurons, there exists a small number of spatial nucleation centers of a network spike, from where the synchronous spiking activity starts propagating in the network typically in the form of circular traveling waves. The number of nucleation centers and their spatial locations are unique and unchanged for a given realization of neuronal network but are different for different networks. In contrast, if the probability of interneuronal connection formation is independent of the distance between neurons, then the nucleation centers do not arise and the synchronization of spiking activity during a network spike occurs spatially uniform throughout the network. Therefore one can conclude that spatial proximity of connections between neurons is important for the formation of nucleation centers. It is also shown that fluctuations of the spatial density of neurons at their random homogeneous distribution typical for the experiments in vitro do not determine the locations of the nucleation centers. The simulation results are qualitatively consistent with the experimental observations.
Carniel, S; Umgiesser, G; Sclavo, M; Kantha, L H; Monti, S
2002-01-01
This paper describes the use of numerical models to infer the path of a floating human body in the Ligurian Sea (north-west Mediterranean) during the month of January 2001. The prevailing oceanic currents were obtained from a state-of-the-art real-time nowcast/forecast ocean circulation model, while the sea state was inferred from a numerical model of the surface gravity waves, both driven by regional atmospheric models. The surface currents (from the ocean model) and the drift ones at the ocean surface, as inferred from the wave model, were used to drive a Lagrangian model of the drifting body to deduce its plausible trajectory along the Ligurian coast. The inferred path is reasonably consistent with location and time of the discovery on the French coast. This note illustrates the utility of numerical prediction models at the disposal of modern forensic science in the fields of ocean sciences.
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.
Local stability analysis for a planar shock wave
NASA Technical Reports Server (NTRS)
Salas, M. D.
1984-01-01
A procedure to study the local stability of planar shock waves is presented. The procedure is applied to a Rankine-Hugoniot shock in a divergent/convergent nozzle, to an isentropic shock in a divergent/convergent nozzle, and to Rankine-Hugoniot shocks attached to wedges and cones. It is shown that for each case, the equation governing the shock motion is equivalent to the damped harmonic oscillator equation.
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.
Stability analysis for extended models of gap solitary waves
Schollmann; Mayer
2000-05-01
A numerical linear stability analysis has been carried out for stationary spatially localized solutions of several systems of coupled nonlinear partial differential equations (PDE's) with two and more complex variables. These coupled PDE's have recently been discussed in the literature, mostly in the context of physical systems with a frequency gap in the dispersion relation of their linear excitations, and they are extensions of the Mills-Trullinger gap soliton model. Translational and oscillatory instabilities are identified, and their associated growth rates are computed as functions of certain parameters characterizing the solitary waves.
NASA Technical Reports Server (NTRS)
Abraham-Shrauner, B.
1986-01-01
Upper hybrid drift waves are found as a special solution to a Vlasov-Maxwell plasma which has a longitudinal electric field and a perpendicular uniform magnetic field. A single-species plasma with a constant-density mobile neutralizing background supports spatially varying disturbances that oscillate at the upper hybrid frequency. The general functional dependences of the electric field, the plasma number density, and the one-particle distribution function for the special case are found from more general Vlasov-Maxwell equations invariant under a Lie group point transformation. The one-particle distribution function for the plasma is a function of the Liouville invariant, which is the energy in the generalized Bernstein-Greene-Kruskal (BGK) reference frame, and the momentum in the drift direction.
NASA Astrophysics Data System (ADS)
Golfinopoulos, Theodore
2013-10-01
Experiments indicate that short-wavelength, k⊥ρs ~ 0 . 1 , drift-Alfvénic turbulence plays an important role in C-Mod edge plasma transport. A Quasi-Coherent Mode (QCM, 50 < f < 150 kHz, k⊥ ~ 1 . 5 cm-1) regulates particle and impurity transport in C-Mod's EDA H-modes. A Weakly Coherent Mode (WCM, 150 < f < 500 kHz, k⊥ ~ 1 . 5 cm-1) plays a similar role in I-mode discharges, suppressing the formation of a density pedestal while maintaining a temperature pedestal. ELMs are not present in either confinement regime. With the idea of exciting, probing, and perhaps exploiting this transport behavior, we have developed a novel antenna system to excite drift-Alfvén-like modes at the outer midplane. A winding with a ``shoelace'' geometry is placed ~ 3 - 5 mm from the LCFS. The principal design parameters, k⊥ = 1 . 5 +/- 0 . 1 cm-1 and 45 < f < 300 kHz, match the QCM and WCM properties, so that the antenna induces parallel currents in the boundary plasma that mimic those observed for the intrinsic modes. Phase-locking to intrinsic modes is also accomplished via a custom circuit. The antenna produces perturbations in density and field comparable to amplitudes of the intrinsic QCM. The plasma response exhibits a resonance near the natural QCM frequency, which generally satisfies the drift wave dispersion relation. While a driven B~θ fluctuation is visible throughout the discharge, the driven ñe is only observed during H-mode, though it precedes the onset of the intrinsic QCM. Like the QCM, the driven mode propagates in the electron diamagnetic drift direction and is approximately field-aligned. Recent mirror probe measurements show the intrinsic QCM structure is predominantly drift-Alfvénic, and we might expect the same of the driven mode. However, the induced perturbation is not global, but is localized to field lines which map to the antenna, suggesting a damped response, and direct measurements of the damping rate indicate γ /ω0 ~ 5 %. If the antenna
Stability of shock waves in high temperature plasmas
Das, Madhusmita; Bhattacharya, Chandrani; Menon, S. V. G.
2011-10-15
The Dyakov-Kontorovich criteria for spontaneous emission of acoustic waves behind shock fronts are investigated for high temperature aluminum and beryllium plasmas. To this end, the Dyakov and critical stability parameters are calculated from Rankine-Hugoniot curves using a more realistic equation of state (EOS). The cold and ionic contributions to the EOS are obtained via scaled binding energy and mean field theory, respectively. A screened hydrogenic model, including l-splitting, is used to calculate the bound electron contribution to the electronic EOS. The free electron EOS is obtained from Fermi-Dirac statistics. Predictions of the model for ionization curves and shock Hugoniot are found to be in excellent agreement with available experimental and theoretical data. It is observed that the electronic EOS has significant effect on the stability of the planar shock front. While the shock is stable for low temperatures and pressures, instability sets in as temperature rises. The basic reason is ionization of electronic shells and consequent increase in electronic specific heat. The temperatures and densities of the unstable region correspond to those where electronic shells get ionized. With the correct modeling of bound electrons, we find that shock instability for Al occurs at a compression ratio {approx}5.4, contrary to the value {approx}3 reported in the literature. Free electrons generated in the ionization process carry energy from the shock front, thereby giving rise to spontaneously emitted waves, which decay the shock front.
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.
Tsai, Je-Chiang; Sneyd, James
2007-04-01
Traveling waves of calcium are widely observed under the condition that the free cytosolic calcium is buffered. Thus it is of physiological interest to determine how buffers affect the properties of calcium waves. Here we summarise and extend previous results on the existence, uniqueness and stability of traveling wave solutions of the buffered bistable equation, which is the simplest possible model of the upstroke of a calcium wave. Taken together, the results show that immobile buffers do not change the existence, uniqueness or stability of the traveling wave, while mobile buffers can eliminate a traveling wave. However, if a wave exists in the latter case, it remains unique and stable.
Reexamination of dynamical stabilization of matter-wave solitons
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.
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
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
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
Stability of Brillouin Flow in Slow-Wave Structures
NASA Astrophysics Data System (ADS)
Simon, David; Lau, Y. Y.; Greening, Geoffrey; Wong, Patrick; Gilgenbach, Ronald; Hoff, Brad
2016-10-01
For the first time, we include a slow-wave structure (SWS) to study the stability of Brillouin flow in the conventional, planar, and inverted magnetron geometry. The resonant interaction of the SWS circuit mode and the corresponding smooth-bore diocotron-like mode is found to be the dominant cause for instability, overwhelming the intrinsic negative (positive) mass property of electrons in the inverted (conventional) magnetron geometry. It severely restricts the wavenumber for instability to the narrow range in which the cold tube frequency of the SWS is within a few percent of the corresponding smooth bore diocotron-like mode in the Brillouin flow. This resonant interaction is absent in a smooth bore magnetron. Work supported by ONR N00014-13-1-0566 and N00014-16-1-2353, AFOSR FA9550-15-1-0097, and L-3 Communications Electron Device Division.
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.
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.
Dewhurst, J. M.; Hnat, B.; Dendy, R. O.
2009-07-15
The extended Hasegawa-Wakatani equations generate fully nonlinear self-consistent solutions for coupled density n and vorticity {nabla}{sup 2}{phi}, where {phi} is electrostatic potential, in a plasma with background density inhomogeneity {kappa}=-{partial_derivative} ln n{sub 0}/{partial_derivative}x and magnetic field strength inhomogeneity C=-{partial_derivative} ln B/{partial_derivative}x. Finite C introduces interchange effects and {nabla}B drifts into the framework of drift turbulence through compressibility of the ExB and diamagnetic drifts. This paper addresses the direct computation of the radial ExB density flux {gamma}{sub n}=-n{partial_derivative}{phi}/{partial_derivative}y, tracer particle transport, the statistical properties of the turbulent fluctuations that drive {gamma}{sub n} and tracer motion, and analytical underpinnings. Systematic trends emerge in the dependence on C of the skewness of the distribution of pointwise {gamma}{sub n} and in the relative phase of density-velocity and density-potential pairings. It is shown how these effects, together with conservation of potential vorticity {pi}={nabla}{sup 2}{phi}-n+({kappa}-C)x, account for much of the transport phenomenology. Simple analytical arguments yield a Fickian relation {gamma}{sub n}=({kappa}-C)D{sub x} between the radial density flux {gamma}{sub n} and the radial tracer diffusivity D{sub x}, which is shown to explain key trends in the simulations.
Stability of ion acoustic nonlinear waves and solitons in magnetized plasmas
NASA Astrophysics Data System (ADS)
Goldstein, Piotr; Infeld, Eryk
2016-12-01
Early results concerning the shape and stability of ion acoustic waves are generalized to propagation at an angle to the magnetic field lines. Each wave has a critical angle for stability. Known soliton results are recovered as special cases. A historical overview of the problem concludes the paper.
Drift mode calculations for the Large Helical Device
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.
Stability of negative solitary waves for an integrable modified Camassa-Holm equation
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.
Sharp wave ripples during learning stabilize the hippocampal spatial map.
Roux, Lisa; Hu, Bo; Eichler, Ronny; Stark, Eran; Buzsáki, György
2017-04-10
Cognitive representation of the environment requires a stable hippocampal map, but the mechanisms maintaining a given map are unknown. Because sharp wave-ripples (SPW-R) orchestrate both retrospective and prospective spatial information, we hypothesized that disrupting neuronal activity during SPW-Rs affects spatial representation. Mice learned new sets of three goal locations daily in a multiwell maze. We used closed-loop SPW-R detection at goal locations to trigger optogenetic silencing of a subset of CA1 pyramidal neurons. Control place cells (nonsilenced or silenced outside SPW-Rs) largely maintained the location of their place fields after learning and showed increased spatial information content. In contrast, the place fields of SPW-R-silenced place cells remapped, and their spatial information remained unaltered. SPW-R silencing did not impact the firing rates or proportions of place cells. These results suggest that interference with SPW-R-associated activity during learning prevents stabilization and refinement of hippocampal maps.
NASA Astrophysics Data System (ADS)
Xaplanteris, Constantine L.
2011-06-01
A suitable modification on the plasma production device makes the plasma column length changeable; the axially propagating wave strikes on the movable circular base of the cavity and the reflected wave is affected enough. A tightening on the azimouthally propagating wave makes the amplitude measurements precarious, and the previous experimental results for fixed cavity length are valid. A strong boundaries' influence on the instability's reinforcement makes clear the need to extend even more the thermonuclear reactor's dimensions. In the present paper, an extended research of plasma parameters has been carried out, a corresponding theoretical model is developed to explain the phenomena and the comparison to the simulated results has been confirmed.
NASA Astrophysics Data System (ADS)
Rixen, M.; Ferreira-Coelho, E.; Signell, Richard
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.
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.
On the stability of the moments of the maximum entropy wind wave spectrum
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.
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
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.
Stabilized high-power laser system for the gravitational wave detector advanced LIGO.
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
2012-05-07
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.
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.
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.
Spectral stability of periodic waves in the generalized reduced Ostrovsky equation
NASA Astrophysics Data System (ADS)
Geyer, Anna; Pelinovsky, Dmitry E.
2017-02-01
We consider stability of periodic travelling waves in the generalized reduced Ostrovsky equation with respect to co-periodic perturbations. Compared to the recent literature, we give a simple argument that proves spectral stability of all smooth periodic travelling waves independent of the nonlinearity power. The argument is based on the energy convexity and does not use coordinate transformations of the reduced Ostrovsky equations to the semi-linear equations of the Klein-Gordon type.
Drift of Scroll Wave Filaments in an Anisotropic Model of the Left Ventricle of the Human Heart
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
NASA Technical Reports Server (NTRS)
Manney, G. L.; Elson, L. S.; Mechoso, C. R.; Farrara, J. D.
1991-01-01
A barotropic stability model linearized about a zonally symmetric flow is used to examine the stability characteristics of horizontal zonal-mean flow profiles representative of the Southern Hemisphere middle stratosphere during winter and early spring, with emphasis on periods when planetary wave growth appears confined to the stratosphere. Unstable modes of eastward-travelling waves 2 and 3 are found to have period sand spatial structures, similar to observations. Wave-2 and wave-3 momentum fluxes are similar in observations and model results and are consistent with the transfer of kinetic energy from the zonal-mean flow to the wave. When a barotropic model with a zonally symmetric basic flow is used, wave 3 is usually most unstable. Including a stationary wave 1 in the basic flow destabilizes both wave 2 and wave 3, but has little effect on their periods or spatial structures. The similarity between observed fields and model results in a number of cases when wave 2 appears to grow within the stratosphere suggests that in situ instabilities play a role in the evolution of the eastward-traveling wave-2 characteristic of the Southern Hemisphere winter and early spring stratosphere.
Wave Propagation and Stability for Finite Difference Schemes.
1982-05-01
DISSERTATION SUBMITTED TO THE DEPARTMENT OF COMPUTER SCIENCE AND THE COMMITTEE ON GRADUATE STUDIES OF STANFORD UNIVERSITY IN PARTIAL FULFILLMENT OF THE REQUIRE...numerical errors, ror both smooth and parasitic waves. The reflection and transmission of waves at boundaries and interfaces are then studied at length. The...together this group and for guiding our work with patience and good 1.1 Dispersion relations and modified equatios ... 13 natue. he the stdens inolvd hve
Co-periodic stability of periodic waves in some Hamiltonian PDEs
NASA Astrophysics Data System (ADS)
Benzoni-Gavage, S.; Mietka, C.; Rodrigues, L. M.
2016-10-01
The stability of periodic traveling wave solutions to dispersive PDEs with respect to ‘arbitrary’ perturbations is still widely open. The focus is put here on stability with respect to perturbations of the same period as the wave, for KdV-like systems of one-dimensional Hamiltonian PDEs. Stability criteria are derived and investigated first in a general abstract framework, and then applied to three basic examples that are very closely related, and ubiquitous in mathematical physics, namely, a quasilinear version of the generalized Korteweg-de Vries equation (qKdV), and the Euler-Korteweg system in both Eulerian coordinates (EKE) and in mass Lagrangian coordinates (EKL). Those criteria consist of a necessary condition for spectral stability, and of a sufficient condition for orbital stability. Both are expressed in terms of a single function, the abbreviated action integral along the orbits of waves in the phase plane, which is the counterpart of the solitary waves moment of instability introduced by Boussinesq. Regarding solitary waves, the celebrated Grillakis-Shatah-Strauss stability criteria amount to looking for the sign of the second derivative of the moment of instability with respect to the wave speed. For periodic waves, the most striking results obtained here can be summarized as: an odd value for the difference between N—the size of the PDE system—and the negative signature of the Hessian of the action implies spectral instability, whereas a negative signature of the same Hessian being equal to N implies orbital stability. Since these stability criteria are merely encoded by the negative signature of matrices, they can at least be checked numerically. Various numerical experiments are presented, which clearly discriminate between stable cases and unstable cases for (qKdV), (EKE) and (EKL).
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].
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
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.
The stability of freak waves with regard to external impact and perturbation of initial data
NASA Astrophysics Data System (ADS)
Smirnova, Anna; Shamin, Roman
2014-05-01
We investigate solutions of the equations, describing freak waves, in perspective of stability with regard to external impact and perturbation of initial data. The modeling of freak waves is based on numerical solution of equations describing a non-stationary potential flow of the ideal fluid with a free surface. We consider the two-dimensional infinitely deep flow. For waves modeling we use the equations in conformal variables. The variant of these equations is offered in [1]. Mathematical correctness of these equations was discussed in [2]. These works establish the uniqueness of solutions, offer the effective numerical solution calculation methods, prove the numerical convergence of these methods. The important aspect of numerical modeling of freak waves is the stability of solutions, describing these waves. In this work we study the questions of stability with regards to external impact and perturbation of initial data. We showed the stability of freak waves numerical model, corresponding to the external impact. We performed series of computational experiments with various freak wave initial data and random external impact. This impact means the power density on free surface. In each experiment examine two waves: the wave that was formed by external impact and without one. In all the experiments we see the stability of equation`s solutions. The random external impact practically does not change the time of freak wave formation and its form. Later our work progresses to the investigation of solution's stability under perturbations of initial data. We take the initial data that provide a freak wave and get the numerical solution. In common we take the numerical solution of equation with perturbation of initial data. The computing experiments showed that the freak waves equations solutions are stable under perturbations of initial data.So we can make a conclusion that freak waves are stable relatively external perturbation and perturbation of initial data both. 1
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.
The Structure and Stability of Three Dimensional Detonation Waves
1990-04-30
stability - a paradigm for flickering diffusion flames’. J. Buckmaster and N. Peters. Proceedings of the 21st (International) Symposium on Combustion...stability of flame-balls: a NEF analysis’ C. J. Lee and J. Buckmaster. 6 Abstracts of Technical Reports. TR1. Diffusion flames on tube burners flicker at...necessary in the age of the supercomputer. The three problems are: the lifting of turbulent diffusion flames; hydrogen flame bubbles (TR7); and nonlinear
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).
Stability of Three-Wave Simplex Estimates of Reliability.
ERIC Educational Resources Information Center
Coenders, Germa; Saris, Willem E.; Batista-Foguet, Joan M.; Andreenkova, Anna
1999-01-01
Illustrates that sampling variance can be very large when a three-wave quasi simplex model is used to obtain reliability estimates. Also shows that, for the reliability parameter to be identified, the model assumes a Markov process. These problems are evaluated with both real and Monte Carlo data. (SLD)
Stability of Viscous St. Venant Roll Waves: From Onset to Infinite Froude Number Limit
NASA Astrophysics Data System (ADS)
Barker, Blake; Johnson, Mathew A.; Noble, Pascal; Rodrigues, L. Miguel; Zumbrun, Kevin
2017-02-01
We study the spectral stability of roll wave solutions of the viscous St. Venant equations modeling inclined shallow water flow, both at onset in the small Froude number or "weakly unstable" limit F→ 2^+ and for general values of the Froude number F, including the limit F→ +∞ . In the former, F→ 2^+, limit, the shallow water equations are formally approximated by a Korteweg-de Vries/Kuramoto-Sivashinsky (KdV-KS) equation that is a singular perturbation of the standard Korteweg-de Vries (KdV) equation modeling horizontal shallow water flow. Our main analytical result is to rigorously validate this formal limit, showing that stability as F→ 2^+ is equivalent to stability of the corresponding KdV-KS waves in the KdV limit. Together with recent results obtained for KdV-KS by Johnson-Noble-Rodrigues-Zumbrun and Barker, this gives not only the first rigorous verification of stability for any single viscous St. Venant roll wave, but a complete classification of stability in the weakly unstable limit. In the remainder of the paper, we investigate numerically and analytically the evolution of the stability diagram as Froude number increases to infinity. Notably, we find transition at around F=2.3 from weakly unstable to different, large- F behavior, with stability determined by simple power-law relations. The latter stability criteria are potentially useful in hydraulic engineering applications, for which typically 2.5≤ F≤ 6.0.
NASA Astrophysics Data System (ADS)
Bocian, Mateusz; Burn, Jeremy F.; Macdonald, John H. G.; Brownjohn, James M. W.
2017-03-01
The subject of this paper pertains to the contentious issue of synchronisation of walking pedestrians to lateral structural motion, which is the mechanism most commonly purported to cause lateral dynamic instability. Tests have been conducted on a custom-built experimental setup consisting of an instrumented treadmill laterally driven by a hydraulic shaking table. The experimental setup can accommodate adaptive pedestrian behaviour via a bespoke speed feedback control mechanism that allows automatic adjustment of the treadmill belt speed to that of the walker. 15 people participated in a total of 137 walking tests during which the treadmill underwent lateral sinusoidal motion. The amplitude of this motion was set from 5 to 15 mm and the frequency was set from 0.54 to 1.1 Hz. A variety of stepping behaviours are identified in the kinematic data obtained using a motion capture system. The most common behaviour is for the timing of footsteps to be essentially unaffected by the structural motion, but a few instances of synchronisation are found. A plausible mechanism comprising an intermediate state between unsynchronised and synchronised pedestrian and structural motion is observed. This mechanism, characterised by a weak form of modulation of the timing of footsteps, could possibly explain the under-estimation of negative damping coefficients in models and laboratory trials compared with previously reported site measurements. The results from tests conducted on the setup for which synchronisation is identified are evaluated in the context of structural stability and related to the predictions of the inverted pendulum model, providing insight into fundamental relations governing pedestrian behaviour on laterally oscillating structures.
Modeling the influence of storms on sand wave formation: A linear stability approach
NASA Astrophysics Data System (ADS)
Campmans, G. H. P.; Roos, P. C.; de Vriend, H. J.; Hulscher, S. J. M. H.
2017-04-01
We present an idealized process-based morphodynamic model to study the effect of storms on sand wave formation. To this end, we include wind waves, wind-driven flow and, in addition to bed load transport, suspended load sediment transport. A linear stability analysis is applied to systematically study the influence of wave and wind conditions on growth and migration rates of small-amplitude wavy bed undulations. The effects of the wind and waves of various magnitudes and directions are investigated. Waves turn out to decrease the growth rate of sand waves, because their effect on the downhill gravitational transport component is stronger than their growth-enhancing effect. The wind wave effect is strongest for wind waves perpendicular to the tidal current. In the case of a symmetrical tidal current, wind-driven flow tends to breach the symmetry, thus causing sand wave migration. Wind effects on sand wave behavior are strongly influenced by the Coriolis effect, in magnitude as well as direction. Stirring due to wind waves enhances sand wave migration. Next to bed load transport, suspended load also has a growing and a decaying mechanism, being the perturbed flow and the perturbed suspended sediment concentration respectively. The decaying mechanism outcompetes the growing mechanism for bed forms with shorter wavelengths, resulting in an increase in the preferred wavelength. Wind waves increase the growth rate due to suspended load, but this is outcompeted by the reduction in growth rate by wind waves due to bed load transport. We conclude that storms significantly influence sand wave dynamics in their formation stage.
Analysis of a Stabilized CNLF Method with Fast Slow Wave Splittings for Flow Problems
Jiang, Nan; Tran, Hoang A.
2015-04-01
In this work, we study Crank-Nicolson leap-frog (CNLF) methods with fast-slow wave splittings for Navier-Stokes equations (NSE) with a rotation/Coriolis force term, which is a simplification of geophysical flows. We propose a new stabilized CNLF method where the added stabilization completely removes the method's CFL time step condition. A comprehensive stability and error analysis is given. We also prove that for Oseen equations with the rotation term, the unstable mode (for which u(n+1) + u(n-1) equivalent to 0) of CNLF is asymptotically stable. Numerical results are provided to verify the stability and the convergence of the methods.
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.
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.
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.
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.
PROPAGATION AND STABILITY OF SUPERLUMINAL WAVES IN PULSAR WINDS
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.
Gradient Drift Instabilities in Two Dimensional Hybrid Hall Thruster Simulations
NASA Astrophysics Data System (ADS)
Aley, Jacob; Dowdy, Caleb; Fernandez, Eduardo
2014-10-01
Instabilities triggered by a variety of mechanisms have been theoretically predicted for Hall thruster plasmas. Experimentally, fluctuations spanning a wide range of frequencies and wave numbers have been observed. Perhaps more importantly, fluctuations have been postulated to play a role in regulating cross-field electron transport in Hall thrusters. However, a clear understanding of what instabilities are responsible for such transport is presently lacking. In this work we focus on analysis of long wavelength gradient drift instability in the Hall thruster via two dimensional hybrid fluid-PIC simulations that resolve azimuthal dynamics. Recent theoretical analysis by Frias et al. shows that previous stability criteria for drift instabilities are modified due to compressibility of the electron flow. In our simulations, we test this improved criterion by examining the transient waves that emerge in the simulation from a smooth initial condition. The simulations give good agreement with the theory, both in the frequency/growth rate characteristics of the waves as well as the region of the thruster where such disturbances are predicted to emerge. These results suggest that gradient drift instabilities play a significant role in Hall thruster plasmas. Jacob Aley, Caleb Dowdy, and Eduardo Fernandez are supported by a grant from the II-VI Foundation.
Nonlinear electrostatic drift Kelvin-Helmholtz instability
NASA Technical Reports Server (NTRS)
Sharma, Avadhesh C.; Srivastava, Krishna M.
1993-01-01
Nonlinear analysis of electrostatic drift Kelvin-Helmholtz instability is performed. It is shown that the analysis leads to the propagation of the weakly nonlinear dispersive waves, and the nonlinear behavior is governed by the nonlinear Burger's equation.
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.
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...
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...
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.
Study of a harmonic mode lock stability under external continuous-wave injection
NASA Astrophysics Data System (ADS)
Semaan, Georges; Komarov, Andrey; Salhi, Mohamed; Sanchez, François
2017-03-01
In this paper, we investigate experimentally the effect of an injected continuous external optical laser in a stable passive harmonic mode-locked fiber laser operating in the anomalous dispersion regime. Under specific conditions, the continuous-wave significantly increases the stability of the harmonic mode-locked regime. This occurs for a discrete set of wavelengths and below a critical injected power.
Effects of Mechano-Electric Feedback on Scroll Wave Stability in Human Ventricular Fibrillation
Hu, Yuxuan; Gurev, Viatcheslav; Constantino, Jason; Bayer, Jason D.; Trayanova, Natalia A.
2013-01-01
Recruitment of stretch-activated channels, one of the mechanisms of mechano-electric feedback, has been shown to influence the stability of scroll waves, the waves that underlie reentrant arrhythmias. However, a comprehensive study to examine the effects of recruitment of stretch-activated channels with different reversal potentials and conductances on scroll wave stability has not been undertaken; the mechanisms by which stretch-activated channel opening alters scroll wave stability are also not well understood. The goals of this study were to test the hypothesis that recruitment of stretch-activated channels affects scroll wave stability differently depending on stretch-activated channel reversal potential and channel conductance, and to uncover the relevant mechanisms underlying the observed behaviors. We developed a strongly-coupled model of human ventricular electromechanics that incorporated human ventricular geometry and fiber and sheet orientation reconstructed from MR and diffusion tensor MR images. Since a wide variety of reversal potentials and channel conductances have been reported for stretch-activated channels, two reversal potentials, −60 mV and −10 mV, and a range of channel conductances (0 to 0.07 mS/µF) were implemented. Opening of stretch-activated channels with a reversal potential of −60 mV diminished scroll wave breakup for all values of conductances by flattening heterogeneously the action potential duration restitution curve. Opening of stretch-activated channels with a reversal potential of −10 mV inhibited partially scroll wave breakup at low conductance values (from 0.02 to 0.04 mS/µF) by flattening heterogeneously the conduction velocity restitution relation. For large conductance values (>0.05 mS/µF), recruitment of stretch-activated channels with a reversal potential of −10 mV did not reduce the likelihood of scroll wave breakup because Na channel inactivation in regions of large stretch led to conduction block, which
Waves and linear stability of magnetoconvection in a rotating cylindrical annulus
NASA Astrophysics Data System (ADS)
Hori, K.; Takehiro, S.; Shimizu, H.
2014-11-01
Magnetohydrodynamic (MHD) waves in a rapidly rotating planetary core can cause the magnetic secular variation. To strengthen our understanding of the physical basis, we revisit the linear stability analyses of thermal convection in a quasi-geostrophic rotating cylindrical annulus with an applied toroidal magnetic field, and we extend the investigation of the oscillatory modes to a broader range of the parameters. Particular attention is paid to influence of thermal boundary conditions, either fixed temperature or heat-flux conditions. While the non-dissipative approximation yields a slow wave propagating retrograde, termed as a Magnetic-Coriolis (MC) Rossby wave, dissipative effects produce a variety of waves. When magnetic diffusion is stronger than thermal diffusion, this can cause a very slow wave propagating prograde. Retrograde-traveling slow waves appear when magnetic diffusion is weaker. Emergence of the slow modes allows convection to occur at lower critical Rayleigh numbers than in the nonmagnetic case. When magnetic diffusion is strong, the onset of the convection occurs with the prograde-propagating slow wave, whereas when it is weak, a slow MC-Rossby mode yields the critical convection. Fixed heat-flux boundary conditions have profound effects on the marginal curves, which monotonically increase with the azimuthal wavenumber, and favor larger length scales at the onset of the convection, provided there is sufficient field strength that the Coriolis force is balanced with the Lorentz force. The effect, however, becomes less clear as magnetic diffusion is weakened and various MHD waves emerge.
Stability of position control of traveling waves in reaction-diffusion systems
NASA Astrophysics Data System (ADS)
Löber, Jakob
2014-06-01
We consider the stability of position control of traveling waves in reaction-diffusion systems as proposed in Löber and Engel [Phys. Rev. Lett. 112, 148305 (2014), 10.1103/PhysRevLett.112.148305]. Instead of analyzing the controlled reaction-diffusion system, stability is studied on the reduced level of the equation of motion for the position over time of perturbed traveling waves. We find an interval of perturbations of initial conditions for which position control is stable. This interval can be interpreted as a localized region where traveling waves are susceptible to perturbations. For stationary solutions of reaction-diffusion systems with reflection symmetry, this region does not exist. Analytical results are in qualitative agreement with numerical simulations of the controlled Schlögl model.
The refined inviscid stability condition and cellular instability of viscous shock waves
NASA Astrophysics Data System (ADS)
Zumbrun, Kevin
2010-07-01
Combining the work of Serre and Zumbrun, Benzoni-Gavage, Serre, and Zumbrun, and Texier and Zumbrun, we propose as a mechanism for the onset of cellular instability of viscous shock and detonation waves in a finite-cross-section duct, the violation of the refined planar stability condition of Zumbrun-Serre, a viscous correction of the inviscid planar stability condition of Majda. More precisely, we show for a model problem involving flow in a rectangular duct with artificial periodic boundary conditions that transition to multidimensional instability through violation of the refined stability condition of planar viscous shock waves on the whole space generically implies for a duct of sufficiently large cross-section, a cascade of Hopf bifurcations involving more and more complicated cellular instabilities. The refined condition is numerically calculable as described by Benzoni-Gavage-Serre-Zumbrun.
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
Linear stability of free planetary waves in the presence of radiative-photochemical feedbacks
NASA Technical Reports Server (NTRS)
Nathan, Terrence R.; Li, Long
1991-01-01
The diabatic effects of Newtonian cooling and ozone-dynamics interaction on the linear stability of free planetary waves in the atmosphere have been studied using a simple beta-plane model. The model couples radiative transfer, ozone advection, and ozone photochemistry with the quasi-geostrophic dynamical circulation. An analytical expression is derived which demonstrates the following: (1) the influence of meridional ozone advection on wave growth or decay depends on the wave and basic state vertical structures; and (2) photochemically accelerated cooling, which predominates in the upper stratosphere, augments the Newtonian cooling rate and is stabilizing. Attention is also given to the 1D linear stability problem which is numerically solved for a Charney basic state and for zonal mean basic states. It is shown that ozone heating generated by ozone-dynamics interaction in the stratosphere can reduce (enhance) the damping rates due to Newtonian cooling by as much as 50 percent for planetary waves of large vertical scale and maximum amplitude in the stratosphere.
Stability analysis for two-dimensional ion-acoustic waves in quantum plasmas
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.
Forecast of iceberg ensemble drift
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.
The stabilization of unstable detonation waves for the mixture of nitromethane/methanol
NASA Astrophysics Data System (ADS)
Utkin, A. V.; Koldunov, S. A.; Mochalova, V. M.; Torunov, S. I.; Lapin, S. M.
2015-11-01
Using a laser interferometer VISAR the measurements of the particle velocity profiles in detonation waves for nitromethane/methanol mixtures with additions of a sensitizer diethylenetriamine were conducted. It is shown that the detonation front in a mixture of nitromethane/methanol is unstable and sensitizer is an effective method for the flow stabilization. If the diluent concentration is less than 10%, the detonation front is stabilized by adding of 1% diethylenetriamine. At higher concentrations of methanol, the sensitizer does not reject instability, but the amplitude of oscillations decreases in several times. An increase of the limit concentration of methanol at the addition of diethylenetriamine to the mixture was found.
Formation mechanism of steep wave front in magnetized plasmas
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.
Stability of Steep Gravity--Capillary Solitary Waves in Deep Water
NASA Astrophysics Data System (ADS)
Akylas, T. R.; Calvo, D. C.
2000-11-01
The stability of steep gravity--capillary solitary waves in deep water is numerically investigated using the full nonlinear water-wave equations with surface tension. As was found in prior work based on model equations for small-amplitude solitary waves in shallow water, out of the two solution branches that bifurcate at the minimum gravity--capillary phase speed, solitary waves of depression again turn out to be stable while those of elevation are unstable to small disturbances. Motivated by the experiments of Longuet-Higgins & Zhang (Phys. Fluids 9:1963--1968, 1997), we also consider the forced problem of a localised pressure distribution applied to the free surface of a stream with speed below the minimum gravity--capillary phase speed. We find that the finite-amplitude forced solitary-wave solution branch computed by Vanden-Broeck & Dias (J. Fluid Mech. 240:549--557, 1992) is unstable but the branch corresponding to Rayleigh's linearised solution is stable. The significance of viscous effects is assessed; the effects of instability in steep waves generally are comparable to, and in some cases greater than, those of dissipation. These findings are discussed in connection with the experimental observations of Longuet-Higgins & Zhang.
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.
Note: silicon carbide telescope dimensional stability for space-based gravitational wave detectors.
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.
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.
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).
The generalized drift flux approach: Identification of the void-drift closure law
NASA Technical Reports Server (NTRS)
Boure, J. A.
1989-01-01
The main characteristics and the potential advantages of generalized drift flux models are presented. In particular it is stressed that the issue on the propagation properties and on the mathematical nature (hyperbolic or not) of the model and the problem of closure are easier to tackle than in two fluid models. The problem of identifying the differential void-drift closure law inherent to generalized drift flux models is then addressed. Such a void-drift closure, based on wave properties, is proposed for bubbly flows. It involves a drift relaxation time which is of the order of 0.25 s. It is observed that, although wave properties provide essential closure validity tests, they do not represent an easily usable source of quantitative information on the closure laws.
Multi-stability of circadian phase wave within early postnatal suprachiasmatic nucleus.
Jeong, Byeongha; Hong, Jin Hee; Kim, Hyun; Choe, Han Kyoung; Kim, Kyungjin; Lee, Kyoung J
2016-02-19
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 structure 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.
Multi-stability of circadian phase wave within early postnatal suprachiasmatic nucleus
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
Zhao, Guangyu; Ruan, Shigui
2011-06-01
We study the existence, uniqueness, and asymptotic stability of time periodic traveling wave solutions to a periodic diffusive Lotka-Volterra competition system. Under certain conditions, we prove that there exists a maximal wave speed c(*) such that for each wave speed c ≤ c(*), there is a time periodic traveling wave connecting two semi-trivial periodic solutions of the corresponding kinetic system. It is shown that such a traveling wave is unique modulo translation and is monotone with respect to its co-moving frame coordinate. We also show that the traveling wave solutions with wave speed c < c(*) are asymptotically stable in certain sense. In addition, we establish the nonexistence of time periodic traveling waves for nonzero speed c > c(*).
Zhao, Guangyu; Ruan, Shigui
2011-01-01
We study the existence, uniqueness, and asymptotic stability of time periodic traveling wave solutions to a periodic diffusive Lotka-Volterra competition system. Under certain conditions, we prove that there exists a maximal wave speed c* such that for each wave speed c ≤ c*, there is a time periodic traveling wave connecting two semi-trivial periodic solutions of the corresponding kinetic system. It is shown that such a traveling wave is unique modulo translation and is monotone with respect to its co-moving frame coordinate. We also show that the traveling wave solutions with wave speed c < c* are asymptotically stable in certain sense. In addition, we establish the nonexistence of time periodic traveling waves for nonzero speed c > c*. PMID:21572575
Interaction between a drifting spiral and defects
Zou, X.; Levine, H. ); Kessler, D.A. )
1993-02-01
Spiral waves, a type of reentrant excitation,'' are believed to be associated with the most dangerous cardiac arrhythmias, including ventricular tachycardia and fibrillation. Recent experimental findings have implicated defective regions as a means of trapping spirals which would otherwise drift and (eventually) disappear. Here, we model the myocardium as a simple excitable medium and study via simulation the interaction between a drifting spiral and one or more such defects. We interpret our results in terms of a criterion for the transition between trapped and untrapped drifting spirals.
Geometric phase in the Hopf bundle and the stability of non-linear waves
NASA Astrophysics Data System (ADS)
Grudzien, Colin J.; Bridges, Thomas J.; Jones, Christopher K. R. T.
2016-11-01
We develop a stability index for the traveling waves of non-linear reaction-diffusion equations using the geometric phase induced on the Hopf bundle S 2 n - 1 ⊂Cn. This can be viewed as an alternative formulation of the winding number calculation of the Evans function, whose zeros correspond to the eigenvalues of the linearization of reaction-diffusion operators about the wave. The stability of a traveling wave can be determined by the existence of eigenvalues of positive real part for the linear operator. Our method of geometric phase for locating and counting eigenvalues is inspired by the numerical results in Way's Dynamics in the Hopf bundle, the geometric phase and implications for dynamical systems Way (2009). We provide a detailed proof of the relationship between the phase and eigenvalues for dynamical systems defined on C2 and sketch the proof of the method of geometric phase for Cn and its generalization to boundary-value problems. Implementing the numerical method, modified from Way (2009), we conclude with open questions inspired from the results.
Ground Control for Emplacement Drifts for LA
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).
Dynamics and stability of relativistic gamma-ray-bursts blast waves
NASA Astrophysics Data System (ADS)
Meliani, Z.; Keppens, R.
2010-09-01
Aims: In gamma-ray-bursts (GRBs), ultra-relativistic blast waves are ejected into the circumburst medium. We analyse in unprecedented detail the deceleration of a self-similar Blandford-McKee blast wave from a Lorentz factor 25 to the nonrelativistic Sedov phase. Our goal is to determine the stability properties of its frontal shock. Methods: We carried out a grid-adaptive relativistic 2D hydro-simulation at extreme resolving power, following the GRB jet during the entire afterglow phase. We investigate the effect of the finite initial jet opening angle on the deceleration of the blast wave, and identify the growth of various instabilities throughout the coasting shock front. Results: We find that during the relativistic phase, the blast wave is subject to pressure-ram pressure instabilities that ripple and fragment the frontal shock. These instabilities manifest themselves in the ultra-relativistic phase alone, remain in full agreement with causality arguments, and decay slowly to finally disappear in the near-Newtonian phase as the shell Lorentz factor drops below 3. From then on, the compression rate decreases to levels predicted to be stable by a linear analysis of the Sedov phase. Our simulations confirm previous findings that the shell also spreads laterally because a rarefaction wave slowly propagates to the jet axis, inducing a clear shell deformation from its initial spherical shape. The blast front becomes meridionally stratified, with decreasing speed from axis to jet edge. In the wings of the jetted flow, Kelvin-Helmholtz instabilities occur, which are of negligible importance from the energetic viewpoint. Conclusions: Relativistic blast waves are subject to hydrodynamical instabilities that can significantly affect their deceleration properties. Future work will quantify their effect on the afterglow light curves.
An, Z.G.
1982-01-01
Four topics are presented in this dissertation. In chapter one, the electromagnetic cyclotron instabilities occurring in a relativistic electron beam propagating in an external magnetic field are studied by considering the electron motions inside the self-consistent electromagnetic field. When the number of electrons in a subgroup is greater than two, or when the phases are random, the linear dispersion relation obtained agrees with that of Chu et al. for a gyrotron in a ring model. The effects of plasma waves on the electron runaway production rate are studied in chapter two. For a wave packet with a one-dimensional spectrum directed along the electric field and with phase velocity range containing the critical velocity v/sub c/ for runaway, the runaway production rate is found to be enhanced by many orders of magnitude. In chapter three the effect of ion waves on the runaway ion production is studied by solving a Fokker-Planck equation with a quasi-linear diffusion operator. It is shown that the presence of a wave packet with a one-dimensional spectrum can considerably enhance the population of the energetic runaway ions. The cylindrical spheromak, an optimal force-free cylindrical plasma configuration, having internal toroidal and poloidal fields and external poloidal field, is analyzed in chapter four for its equilibrium and stability properties.
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.
High Stability Low Scatter Telescope for a Space-based Gravitational Wave Observatory
NASA Astrophysics Data System (ADS)
Livas, Jeffrey; Sankar, Shannon
2017-01-01
A laser interferometer space-based gravitational wave observatory requires an optical telescope to efficiently transfer laser light between pairs of widely-separated sciencecraft. The application is precision interferometric metrology, and therefore requires the telescope to have high optical pathlength stability, and low scattered light performance. We discuss the expected on-orbit environment and present the latest design, including materials choice trades, surface roughness and cleanliness requirements, and an optical prescription optimized to reduce scattered light. We will also discuss some of the remaining system-level trades. This work is supported by NASA Strategic Astrophysics Technology grant 14-SAT14-0014.
Four-wave mixing stability in hybrid photonic crystal fibers with two zero-dispersion wavelengths.
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.
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
The advanced cosmic microwave explorer - A millimeter-wave telescope and stabilized platform
NASA Technical Reports Server (NTRS)
Meinhold, P. R.; Chingcuanco, A. O.; Gundersen, J. O.; Schuster, J. A.; Seiffert, M. D.; Lubin, P. M.; Morris, D.; Villela, T.
1993-01-01
We have developed and flown a 1 m diameter Gregorian telescope system for measurements of anisotropy in the Cosmic Background Radiation (CBR). The telescope is incorporated in a balloon-borne stabilized platform with arcminute stabilization capability. To date, the system has flown four times and observed from the ground at the South Pole twice. The telescope has used both coherent and incoherent detectors. We describe the development of the telescope, pointing platform, and one of the receivers employed in making measurements of the CBR. Performance of the system during the first flight and operation on the ground at the South Pole are described, and the quality of the South Pole as a millimeter wave observing site is discussed.
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.
Ballooning instability and structure of diamagnetic hydromagnetic waves in a model magnetosphere
Miura, A.; Ohtani, S.; Tamao, T. )
1989-11-01
A linear eigenmode analysis of ballooning instability of an Alfven wave and a drift-Alfven wave is performed for a curved magnetic field line configuration in finite-{beta} plasma to examine stability of the tail plasma sheet and to find a generation mechanism of diamagnetic storm time Pc 5 pulsations, which are characterized by a large azimuthal mode number (m>50). Only fundamental mode is unstable to the ballooning instability, which is driven by the pressure gradient combined with the unfavorable magnetic field line curvature, while higher harmonic modes are stable. The eigenfunction of the unstable wave (fundamental mode) is evanescent or decaying exponential toward the ionosphere along the field line and strongly confined near the equator with its plasma pressure and magnetic pressure being out of phase. The stable higher harmonic modes, on the other hand, have standing Alfven mode structures along the field line and have frequencies determined by oscillation periods of the standing Alfven modes. In the absence of the coupling to the drift wave, the unstable fundamental wave is aperiodic with zero real frequency. When the unstable fundamental wave is coupled to the drift wave; however, the unstable wave (drift-Alfven wave) has a real frequency determined by an ion diamagnetic drift speed. The obtained oscillation period of a few hundred seconds for the unstable drift-Alfven wave with an azimuthal number m = 50, its westward propagation, diamagnetic relationship between the perturbed magnetic and plasma pressures, and strong spatial confinement of the unstable wave near the equator suggest of the authors that the unstable drift-Alfven wave destabilized by the ballooning instability is a strong candidate mechanism for explaining the observed storm time Pc 5 pulsations.
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).
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.
NASA Astrophysics Data System (ADS)
Grasso, Francesco; Paoli, Roberto
1999-11-01
Shock wave reflections in steady flows have been widely studied in the last decades for their importance in many aerospace applications, such as supersonic intakes and wind tunnel technologies. One of the yet unresolved problems is the understanding of the physical mechanism responsible for the transition between regular and Mach reflections and the hysteresis phenomenon (i.e. the attainement of different shock configurations for the same incident shock angle) as well as the stability of shock wave configurations. In the present paper we study the influence of thermochemical relaxation phenomena on shock reflections by means of a two-temperature model for the thermal nonequilibrium and the reduced Park's model for finite rate chemistry. Stable shock wave configurations are characterized by invoking Prigogine minimum entropy production principle. For that purpose we formulate the entropy budget for nonequilibrium flows and identify the different contributions to the evolution of entropy due to translational and vibrational heat conduction and species diffusion, as well as dissociation reactions and translational vibrational energy exchanges. A study of shock reflection transition is carried out at two Mach numbers (M=7.5 and M=9.8) both for air and nitrogen. In order to identify the controlling mechanisms that affect the transition and the hysteresis we also carry out simulations assuming an ideal gas behaviour.
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
Tofan-Lazar, Julia; Situm, Arthur; Al-Abadleh, Hind A
2013-10-10
Surface water plays a crucial role in facilitating or inhibiting surface reactions in atmospheric aerosols. However, little is known about the role of surface water in the complexation of organic acid molecules to transition metals in multicomponent aerosol systems. We report herein results from real time DRIFTS experiments that show in situ complexation of catechol to Fe(III) under humid conditions. Catechol was schosen as a simple model for humic-like substances (HULIS) in aerosols and aged polyaromatic hydrocarbons (PAH). It was also detected in secondary organic aerosols (SOA) formed from the reaction of hydroxyl radicals with benzene. Given the importance of the iron content in aerosols and its biogeochemistry, our studies were conducted using FeCl3. For comparison, these surface-sensitive studies were complemented with bulk aqueous ATR-FTIR, UV-vis, and HPLC measurements for structural, quantitative, and qualitative information about complexes in the bulk, and potential degradation products in the dark. Under dry conditions, DRIFTS spectra show that gas phase catechol adsorbs molecularly and is fully protonated on samples containing FeCl3 with no evidence of complexation to Fe(III). Upon increasing the relative humidity to a value below the deliquescence of FeCl3, surface water facilitates ionic mobility resulting in the formation of monodentate catechol-Fe complexes. These complexes are stable at the gas/solid interface and do not undergo any further degradation in the dark as shown from bulk UV-vis and HPLC experiments. The implications of our studies on understanding interfacial and condensed phase chemistry relevant to multicomponent aerosols, water thin films on buildings, and ocean surfaces containing transition metals are discussed.
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
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.
THERMAL TEST ALCOVE HEATED DRIFT GROUND SUPPORT ANALYSIS
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.
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.
Gomberoff, L.
2008-02-15
It has been shown that a large amplitude Alfven wave can stabilize linear magnetosonic instabilities triggered by an ion beam. This phenomenon occurs for large amplitude waves above a threshold value. Here the effect of a second ion beam on the threshold amplitude for stabilization of the magnetosonic instability is studied. It is shown that the second beam modifies the threshold amplitude behavior for complete saturation of the magnetosonic instability. The effect of the second beam on the properties of purely electrostatic nonlinear instabilities triggered by the finite amplitude wave is also studied. Apart from the changes induced by the second beam on the threshold amplitude behavior, it is shown that in some cases there are two regimes of the nonlinear ion-acousticlike instability. These results should be of importance in those environments where the interplay of the two beams should not be ignored like, e.g., in the fast solar wind.
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.
Stability of Solitary Waves and Vortices in a 2D Nonlinear Dirac Model.
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.
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.
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.
NASA Astrophysics Data System (ADS)
Chomaz, Jean-Marc; Ortiz, Sabine; Lerisson, Gaétan
2016-11-01
Triadic instability is a very generic mechanism by which a primary wave of finite amplitude is destabilized by two secondary (daugther) waves forming a resonant triad. For gravity wave in the ocean, as shown by Phillips, O.M. (CUP, 1967) the resonant triads form several continuous family that may be represented in twodimension (2D) as resonant lines in the 2D wave vector space of the secondary wave. We show here that the crossing of two od these branches may results in a double triadic instability where the instability is reduced. Building on McEwan, A.D. & Plumb, R.A. (Dyn. Atm. & Oceans, 1977) we show that this double triadic instability stabilization domain expends from a singular point to a finite significant region when the amplitude of the primary wave is increased. Comparison with direct computation of the instability branches shows that, from very small to order unity primary wave amplitude, the theoretical prediction stay valid and is able to explain the strong departure from the classical triadic instability theory. Support by DGA is acknowledged.
Propagation and stability of quantum dust-ion-acoustic shock waves in planar and nonplanar geometry
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.
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.
Stability of Brillouin flow in the presence of slow-wave structure
NASA Astrophysics Data System (ADS)
Simon, D. H.; Lau, Y. Y.; Greening, G.; Wong, P.; Hoff, B.; Gilgenbach, R. M.
2016-09-01
Including a slow-wave structure (SWS) on the anode in the conventional, planar, and inverted magnetron, we systematically study the linear stability of Brillouin flow, which is the prevalent flow in crossed-field devices. The analytic treatment is fully relativistic and fully electromagnetic, and it incorporates the equilibrium density profile, flow profile, and electric field and magnetic field profiles in the linear stability analysis. Using parameters similar to the University of Michigan's recirculating planar magnetron, the numerical data show that the resonant interaction of the vacuum circuit mode and the corresponding smooth-bore diocotron-like mode is the dominant cause for instability. This resonant interaction is far more important than the intrinsic negative (positive) mass property of electrons in the inverted (conventional) magnetron geometry. It is absent in either the smooth-bore magnetron or under the electrostatic assumption, one or both of which was almost always adopted in prior analytical formulation. This resonant interaction severely restricts the wavenumber for instability to the narrow range in which the cold tube frequency of the SWS is within a few percent of the corresponding smooth bore diocotron-like mode in the Brillouin flow.
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.
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…
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.
A Numerical Study of the Stability of Solitary Waves of the Bona-Smith Family of Boussinesq Systems
NASA Astrophysics Data System (ADS)
Dougalis, V. A.; Durán, A.; López-Marcos, M. A.; Mitsotakis, D. E.
2007-12-01
In this paper we study, from a numerical point of view, some aspects of stability of solitary-wave solutions of the Bona-Smith systems of equations. These systems are a family of Boussinesq-type equations and were originally proposed for modelling the two-way propagation of one-dimensional long waves of small amplitude in an open channel of water of constant depth. We study numerically the behavior of solitary waves of these systems under small and large perturbations with the aim of illuminating their long-time asymptotic stability properties and, in the case of large perturbations, examining, among other, phenomena of possible blow-up of the perturbed solutions in finite time.
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
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.
Continental drift before 1900.
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.
NASA Astrophysics Data System (ADS)
Majumder, D. P.; Dhar, A. K.
2015-12-01
A nonlinear spectral transport equation for the narrow band Gaussian random surface wave trains is derived from a fourth order nonlinear evolution equation, which is a good starting point for the study of nonlinear water waves. The effect of randomness on the stability of deep water capillary gravity waves in the presence of air flowing over water is investigated. The stability is then considered for an initial homogenous wave spectrum having a simple normal form to small oblique long wave length perturbations for a range of spectral widths. An expression for the growth rate of instability is obtained; in which a higher order contribution comes from the fourth order term in the evolution equation, which is responsible for wave induced mean flow. This higher order contribution produces a decrease in the growth rate. The growth rate of instability is found to decrease with the increase of spectral width and the instability disappears if the spectral width increases beyond a certain critical value, which is not influenced by the fourth order term in the evolution equation.
NASA Astrophysics Data System (ADS)
Mochalova, V.; Utkin, A.
2014-05-01
Instability of detonation front in the nitromethane/acetone (NM/A) solution was observed in our previous work: at 10% of acetone the amplitude of heterogeneities was about 20 microns and at 20% of acetone this size was 50 microns. It is known that small additions of diethylenetriamine (DETA) considerably increase the initial rate of chemical reaction in detonation waves for NM. It was expected that DETA would influence the stability of detonation waves in the NM/A solution too. To investigate this phenomenon the laser interferometer VISAR was used for the recording of particle velocity profiles in detonation waves for NM/A. It was found that at the addition of 0.5% DETA to NM/A 90/10 the oscillations in the velocity profile decreased several times over. At the addition of 1% DETA the profile is smooth, i.e. the heterogeneities disappear and detonation wave becomes steady-state. In NM/A 80/20 at the addition of 5% DETA the heterogeneities size is reduced by the order. The increase of detonation wave velocity of NM/A grater than 1% was observed at small concentrations of DETA. Thus it was found that small additions of DETA to the NM/A solution with an unstable detonation front resulted not only in the decrease of heterogeneities size but in their disappearance and stabilization of detonation waves.
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.
NASA Astrophysics Data System (ADS)
Golovato, S. N.; Brau, K.; Casey, J.; Gerver, M. J.; Horne, S.; Irby, J.; Kesner, J.; Lane, B.; Machuzak, J.; Myer, R.; Post, R. S.; Sevillano, E.; Wang, L.
1989-04-01
The stability of plasmas produced by radio-frequency heating in the ion cyclotron frequency range (ICRF) has been studied in the central cell of the Tara tandem mirror [Nucl. Fusion 22, 549 (1982); Plasma Physics and Controlled Nuclear Fusion Research 1986, Proceedings of the 11th International Conference, Kyoto (IAEA, Vienna, 1987), Vol. II, p. 251]. Ion cyclotron wave excitation by a slot antenna provided stability against macroscopic plasma motions in an axisymmetric configuration. The maintenance of macroscopic stability depended on the ICRF power, gas fueling rate, ion cyclotron resonance location, and ω/ωci at the antenna location. The ICRF ponderomotive force model is consistent with many of the observed stability features and predicts that the E+ component of the ion cyclotron wave was responsible for the stabilization. The Alfvén ion cyclotron microinstability was observed when the plasma β⊥ and anisotropy were sufficiently high. Magnetic probe measurements of the unstable mode identified it as an ion cyclotron wave and the instability threshold was within a factor of 2 of the theoretical value.
Investigations of SPS Orbit Drifts
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.
Effects of Fault Displacement on Emplacement Drifts
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.
Dynamical Stability Limit for the Charge Density Wave in K0.3MoO3
NASA Astrophysics Data System (ADS)
Mankowsky, R.; Liu, B.; Rajasekaran, S.; Liu, H. Y.; Mou, D.; Zhou, X. J.; Merlin, R.; Först, M.; Cavalleri, A.
2017-03-01
We study the response of the one-dimensional charge density wave in K0.3MoO3 to different types of excitation with femtosecond optical pulses. We compare direct excitation of the lattice at midinfrared frequencies with injection of quasiparticles across the low energy charge density wave gap and with charge transfer excitation in the near infrared. For all three cases, we observe a fluence threshold above which the amplitude-mode oscillation frequency is softened and the mode becomes increasingly damped. We show that all the data can be collapsed onto a universal curve in which the melting of the charge density wave occurs abruptly at a critical lattice excursion. These data highlight the existence of a universal stability limit for a charge density wave, reminiscent of the Lindemann criterion for the melting of a crystal lattice.
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.
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
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.
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
Ground Control for Non-Emplacement Drifts for LA
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.
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
Spiral silicon drift detectors
Rehak, P.; Gatti, E.; Longoni, A.; Sampietro, M.; Holl, P.; Lutz, G.; Kemmer, J.; Prechtel, U.; Ziemann, T.
1988-01-01
An advanced large area silicon photodiode (and x-ray detector), called Spiral Drift Detector, was designed, produced and tested. The Spiral Detector belongs to the family of silicon drift detectors and is an improvement of the well known Cylindrical Drift Detector. In both detectors, signal electrons created in silicon by fast charged particles or photons are drifting toward a practically point-like collection anode. The capacitance of the anode is therefore kept at the minimum (0.1pF). The concentric rings of the cylindrical detector are replaced by a continuous spiral in the new detector. The spiral geometry detector design leads to a decrease of the detector leakage current. In the spiral detector all electrons generated at the silicon-silicon oxide interface are collected on a guard sink rather than contributing to the detector leakage current. The decrease of the leakage current reduces the parallel noise of the detector. This decrease of the leakage current and the very small capacities of the detector anode with a capacitively matched preamplifier may improve the energy resolution of Spiral Drift Detectors operating at room temperature down to about 50 electrons rms. This resolution is in the range attainable at present only by cooled semiconductor detectors. 5 refs., 10 figs.
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.
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.
NASA Astrophysics Data System (ADS)
Shalaby, M.; EL-Labany, S. K.; EL-Shamy, E. F.; El-Taibany, W. F.; Khaled, M. A.
2009-12-01
Obliquely propagating dust ion acoustic solitary waves (DIASWs) are investigated in hot adiabatic magnetized dusty plasmas consisting of hot adiabatic inertial ions, hot adiabatic inertialess electrons, and negatively/positively charged static dust grains. Using a reductive perturbation method, a nonlinear Zakharov-Kuznetsov equation is derived. The effects of the concentration of negatively/positively charged dust particles and ion-neutral collision on the basic characteristics of DIASWs are studied. The three-dimensional stability of these waves is examined by the use of small-k (long wavelength plane wave) perturbation expansion technique. It is shown that the instability criterion and their growth rate depend on external magnetic field, obliqueness, the concentration of charged dust grains, ion-neutral, and ion-dust collisions.
NASA Astrophysics Data System (ADS)
Selima, Ehab S.; Seadawy, Aly R.; Yao, Xiaohua
2016-12-01
The three-dimensional (3-D) nonlinear and dispersive PDEs system for surface waves propagating at undisturbed water surface under the gravity force and surface tension effects are studied. By applying the reductive perturbation method, we derive the (2 + 1) -dimensions form of the Davey-Stewartson (DS) system for the modulation of 2-D harmonic waves. By using the simplest equation method, we find exact traveling wave solutions and a general form of the multiple-soliton solution of the DS model. The dispersion analysis as well as the conservation law of the DS system are discussed. It is revealed that the consistency of the results with the conservation of the potential energy increases with increasing Ursell parameter. Also, the stability of the ODEs form of the DS system is presented by using the phase portrait method.
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.
High resolution drift chambers
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.
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.
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.
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.
Stability of giant sand waves in eastern Long Island Sound, U.S.A.
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.
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.
Observation of Up-gradient Particle Flux in Collisional Drift-ITG Turbulence
NASA Astrophysics Data System (ADS)
Cui, Lang
2015-11-01
We report the observation of a net inward, up-gradient turbulent particle flux from two independent diagnostics in collisional drift-ITG plasma turbulence. At low magnetic fields (B <= 1.0 kG), particle transport is outward at all radii and the predominantly collisional electron drift wave turbulence drives a sheared ExB zonal flow. As the magnetic field is further increased (B >= 1.2 kG) the drift-waves persist, an up-gradient inward particle flux develops, fluctuations propagating in the ion diamagnetic drift direction develop and a pronounced steepening of the ion temperature and mean density gradients occurs. The two different types of fluctuation features modulate and compete with each other and dominate in different radial location and magnetic field region. Linear stability analyses show that a robust ITG instability is excited for these conditions. The onset of net inward flux also coincides with the development of a strong intrinsic parallel flow shear that can drive an inward pinch when it is coupled with grad-Ti. However, we find that the ITG-driven inward pinch is more dominant in our experiments. This basic experiment provides for a detailed examination of turbulent-driven particle pinches and up-gradient fluxes in the presence of multiple free-energy sources. Moreover, the coexistence and competition of DWs and ITG have been observed to influence tokamak transport and remains a topic of interest for both magnetically confined fusion plasmas and space plasma systems. A detailed experimental study complemented by theory and linear and nonlinear simulations of these experiments is used to elucidate the physics of up-gradient particle transport. Supported by DOE (DE- SC0001961).
Diogene pictorial drift chamber
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).
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.
Novel stability diagrams for continuous-wave solid-state laser resonators
De Silvestri, S.; Laporta, P.; Magni, V.
1986-08-01
Two novel stability diagrams are proposed, which provide a clear understanding of the behavior of solid-state laser resonators with focusing rods. By means of this graphic analysis, information on the stability boundaries, dynamic stability, misalignment sensitivity, and spot size in the rod can be obtained. On the basis of these diagrams the complicated experimental output power curves of a cw Nd:YAG laser have been easily interpreted.
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.
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.
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.
A theoretical model of asymmetric wave ripples.
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.
Two-stream instability with time-dependent drift velocity
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.
NASA Astrophysics Data System (ADS)
Oberleithner, Kilian; Rukes, Lothar; Paschereit, Oliver; Soria, Julio
2014-11-01
We report on a number of experimental and theoretical investigations of shear flow instabilities in jet flows. In these studies, linear stability analysis is employed to the time-averaged flow taken from experiments, contrasting the ``classic'' stability approach that is based on a stationary base flow. The eigenmodes of the time-averaged flow are considered as models for the nonlinearly saturated state of the instability waves. The accuracy of these models is validated through a detailed comparison with experiments. In this talk we outline the potential and limitation of these flow models for convectively and globally unstable jet flows. The first author was supported by a fellowship within the Postdoc-Program of the German Academic Exchange Service (DAAD). The support of the Australian Research Council (ARC) and the German Research Foundation (DFG) is greatfully acknowledged.
Long-term wavelength drift compensation of tunable pulsed dye laser for sodium detection lidar
NASA Astrophysics Data System (ADS)
Xia, Yuan; Cheng, Xuewu; Li, Faquan; Wang, Jihong; Yang, Yong; Lin, Xin; Gong, Shunsheng
2015-11-01
Wavelength stabilization for a pulsed laser presents more challenges than that of continuous wave laser. We have developed a simple and efficient long-term wavelength drifts compensation technique for tunable pulsed dye lasers (PDL) applied in sodium detection lidar system. Wavelength calibration and locking are implemented by using optogalvanic (OG) spectroscopy in a Na hollow cathode lamp (HCL) in conjunction with a digital control software. Optimization of OG signals for better laser wavelength discrimination and feedback control is performed. Test results indicate that locking the multimode broadband PDL to the Na atomic transition corresponding to 589.158 nm is well achieved although the temperature in the laboratory is unstable. Through active compensation, the maximum wavelength drift is reduced from over 5 pm to 0.42 pm in 10 h and the maximum wavelength drift rate of the PDL is improved from 3.3 pm/h to 0.3 pm/h. It has been used to efficient sodium resonance fluorescence lidar detection. This technique is economical and easy to implement, and it provides flexible wavelength control and allows generalization for some other applications which require the wavelength of tunable pulsed lasers to be fixed at an atomic resonance transition references.
Price, Rebecca M; Andrews, Tessa C; McElhinny, Teresa L; Mead, Louise S; Abraham, Joel K; Thanukos, Anna; Perez, Kathryn E
2014-01-01
Understanding genetic drift is crucial for a comprehensive understanding of biology, yet it is difficult to learn because it combines the conceptual challenges of both evolution and randomness. To help assess strategies for teaching genetic drift, we have developed and evaluated the Genetic Drift Inventory (GeDI), a concept inventory that measures upper-division students' understanding of this concept. We used an iterative approach that included extensive interviews and field tests involving 1723 students across five different undergraduate campuses. The GeDI consists of 22 agree-disagree statements that assess four key concepts and six misconceptions. Student scores ranged from 4/22 to 22/22. Statements ranged in mean difficulty from 0.29 to 0.80 and in discrimination from 0.09 to 0.46. The internal consistency, as measured with Cronbach's alpha, ranged from 0.58 to 0.88 across five iterations. Test-retest analysis resulted in a coefficient of stability of 0.82. The true-false format means that the GeDI can test how well students grasp key concepts central to understanding genetic drift, while simultaneously testing for the presence of misconceptions that indicate an incomplete understanding of genetic drift. The insights gained from this testing will, over time, allow us to improve instruction about this key component of evolution.
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.
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.
Drift mode growth rates and associated transport
Redd, A.J.; Kritz, A.H.; Bateman, G.; Rewoldt, G.; Tang, W.M.
1999-04-01
Drift mode linear growth rates and quasilinear transport are investigated using the FULL kinetic stability code [Rewoldt {ital et al.}, Phys. Plasmas {bold 5}, 1815 (1998)] and a version of the Weiland transport model [Strand {ital et al.}, Nucl. Fusion {bold 38}, 545 (1998)]. It is shown that the drift mode growth rates (as well as the marginal stability temperature gradient) obtained using the FULL code are dependent on the accuracy of the equilibrium employed. In particular, when an approximate equilibrium model is utilized by the FULL code, the results can differ significantly from those obtained using a more accurate numerical equilibrium. Also investigated are the effects of including full electron physics. It is shown, using both the FULL code and the Weiland model, that the nonadiabatic (e.g., trapped) electron response produces a significant increase in the linear growth rate of the ion-temperature-gradient (ITG) driven branch of the drift instability. Other consequences of the nonadiabatic electron response include a reduction in the marginal temperature gradient for the onset of the ITG mode and an additional contribution to transport due to the excitation of the Trapped Electron Mode (TEM). Physical explanations are given for the sensitivity of the mode growth rates to the equilibrium and the nonadiabatic electron response. Finally, linear growth rates for the ITG mode computed using the FULL code are compared with growth rates obtained using the Weiland model. {copyright} {ital 1999 American Institute of Physics.}
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).
Passive appendages generate drift through symmetry breaking
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
NASA Astrophysics Data System (ADS)
Sund, Richard; Scharer, John
2002-11-01
We examine a new method for generating sheared flows in advanced tokamak D-T reactors with the goal of creating and controlling internal transport barriers. Ion-Bernstein waves (IBWs) have the recognized capacity to create internal transport barriers through sheared plasma flows resulting from ion absorption. Under reactor conditions, the IBW can be generated by mode conversion of a fast magnetosonic wave incident from the high-field side (HFS) on the second harmonic resonance of a minority hydrogen component, with near 100200 MHz) minimizes parasitic absorption and permits the converted IBW to approach the fifth tritium harmonic. It also facilitates compact antennas and feeds, and efficient fast wave launch. Placement of the 5T absorption layer on the HFS is advantageous for shear production. The scheme is applicable to reactors with aspect ratio < 3 such that the conversion and absorption layers are both on the high field side of the magnetic axis. Various factors (adequate separation of the mode conversion layer from the magnetic axis, concentration of the fast wave near the midplane, large machine size, and plasma elongation) minimize poloidal field effects in the conversion zone and permit a slab analysis. We use a 1-D full-wave code to analyze the conversion and absorption. A 2-D ray-tracing code incorporating poloidal magnetic fields is used to follow the IBW for various equilibria. Within this analysis a weak bean shape appears most favorable. This is an attractive scheme for future advanced tokamak reactors. *Research supported by the Univ. of Wisconsin, Madison
Role of long waves in the stability of the plane wake
NASA Astrophysics Data System (ADS)
Scarsoglio, Stefania; Tordella, Daniela; Criminale, William O.
2010-03-01
This work is directed toward investigating the fate of three-dimensional long perturbation waves in a plane incompressible wake. The analysis is posed as an initial-value problem in space. More specifically, input is made at an initial location in the downstream direction and then tracing the resulting behavior further downstream subject to the restriction of finite kinetic energy. This presentation follows the outline given by Criminale and Drazin [W. O. Criminale and P. G. Drazin, Stud. Appl. Math. 83, 123 (1990)] that describes the system in terms of perturbation vorticity and velocity. The analysis is based on large scale waves and expansions using multiscales and multitimes for the partial differential equations. The multiscaling is based on an approach where the small parameter is linked to the perturbation property independently from the flow control parameter. Solutions of the perturbative equations are determined numerically after the introduction of a regular perturbation scheme analytically deduced up to the second order. Numerically, the complete linear system is also integrated. Since the results relevant to the complete problem are in very good agreement with the results of the first-order analysis, the numerical solution at the second order was deemed not necessary. The use for an arbitrary initial-value problem will be shown to contain a wealth of information for the different transient behaviors associated to the symmetry, angle of obliquity, and spatial decay of the long waves. The amplification factor of transversal perturbations never presents the trend—a growth followed by a long damping—usually seen in waves with wave number of order one or less. Asymptotical instability is always observed.
Drift-Scale Radionuclide Transport
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
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.
Drift-scale thermomechanical analysis for the retrievability systems study
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.
Detecting the Drift of Quantum Sources: Not the de Finetti Theorem
NASA Astrophysics Data System (ADS)
Schwarz, Lucia; van Enk, S. J.
2011-05-01
We propose and analyze a method to detect and characterize the drift of a nonstationary quantum source. It generalizes a standard measurement for detecting phase diffusion of laser fields to quantum systems of arbitrary Hilbert space dimension, qubits in particular. We distinguish diffusive and systematic drifts, and examine how quickly one can determine that a source is drifting. We show that for single-photon wave packets our measurement is implemented by the Hong-Ou-Mandel effect.
Detecting the drift of quantum sources: not the de Finetti theorem.
Schwarz, Lucia; van Enk, S J
2011-05-06
We propose and analyze a method to detect and characterize the drift of a nonstationary quantum source. It generalizes a standard measurement for detecting phase diffusion of laser fields to quantum systems of arbitrary Hilbert space dimension, qubits in particular. We distinguish diffusive and systematic drifts, and examine how quickly one can determine that a source is drifting. We show that for single-photon wave packets our measurement is implemented by the Hong-Ou-Mandel effect.
Repository Drift Backfilling Demonstrator
Londe, I.; Dubois, J.Ph.; Bauer, C.
2008-07-01
The 'Backfilling Demonstrator' is one of the technological demonstrators developed by ANDRA in the framework of the feasibility studies for a geological repository for high-level long-lived (HL-LL waste) within a clay formation. The demonstrator concerns the standard and supporting backfills as defined in Andra's 2005 design. The standard backfill is intended to fill up almost all drifts of the underground repository in order to limit any deformation of the rock after the degradation of the drift lining. The supporting backfill only concerns a small portion of the volume to be backfilled in order to counter the swelling pressure of the swelling clay contained in the sealing structures. The first objective of the demonstrator was to show the possibility of manufacturing a satisfactory backfill, in spite of the exiguity of the underground structures, and of reusing as much as possible the argillite muck. For the purpose of this experiment, the argillite muck was collected on Andra's work-site for the implementation of an underground research laboratory. Still ongoing, the second objective is to follow up the long-term evolution of the backfill. Approximately 200 m{sup 3} of compacted backfill material have been gathered in a large concrete tube simulating a repository drift. The standard backfill was manufactured exclusively with argillite. The supporting backfill was made by forming a mixture of argillite and sand. Operations were carried out mostly at Richwiller, close to Mulhouse, France. The objectives of the demonstrator were met: an application method was tested and proven satisfactory. The resulting dry densities are relatively high, although the moduli of deformation do not always reach the set goal. The selected objective for the demonstrator was a dry density corresponding to a relatively high compaction level (95% of the standard Proctor optimum [SPO]), for both pure argillite and the argillite-sand mixture. The plate-percussion compaction technique was
Drift-induced Benjamin-Feir instabilities
NASA Astrophysics Data System (ADS)
Di Patti, F.; Fanelli, D.; Carletti, T.
2016-06-01
A modified version of the Ginzburg-Landau equation is introduced which accounts for asymmetric couplings between neighbors sites on a one-dimensional lattice, with periodic boundary conditions. The drift term which reflects the imposed microscopic asymmetry seeds a generalized class of instabilities, reminiscent of the Benjamin-Feir type. The uniformly synchronized solution is spontaneously destabilized outside the region of parameters classically associated to the Benjamin-Feir instability, upon injection of a nonhomogeneous perturbation. The ensuing patterns can be of the traveling wave type or display a patchy, colorful mosaic for the modulus of the complex oscillators amplitude.
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.
Drift-Alfven eigenmodes in inhomogeneous plasma
Vranjes, J.; Poedts, S.
2006-03-15
A set of three nonlinear equations describing drift-Alfven waves in a nonuniform magnetized plasma is derived and discussed both in linear and nonlinear limits. In the case of a cylindric radially bounded plasma with a Gaussian density distribution in the radial direction the linearized equations are solved exactly yielding general solutions for modes with quantized frequencies and with radially dependent amplitudes. The full set of nonlinear equations is also solved yielding particular solutions in the form of rotating radially limited structures. The results should be applicable to the description of electromagnetic perturbations in solar magnetic structures and in astrophysical column-like objects including cosmic tornados.
NASA Astrophysics Data System (ADS)
De Basabe, Jonás D.; Sen, Mrinal K.
2010-04-01
We investigate the stability of some high-order finite element methods, namely the spectral element method and the interior-penalty discontinuous Galerkin method (IP-DGM), for acoustic or elastic wave propagation that have become increasingly popular in the recent past. We consider the Lax-Wendroff method (LWM) for time stepping and show that it allows for a larger time step than the classical leap-frog finite difference method, with higher-order accuracy. In particular the fourth-order LWM allows for a time step 73 per cent larger than that of the leap-frog method; the computational cost is approximately double per time step, but the larger time step partially compensates for this additional cost. Necessary, but not sufficient, stability conditions are given for the mentioned methods for orders up to 10 in space and time. The stability conditions for IP-DGM are approximately 20 and 60 per cent more restrictive than those for SEM in the acoustic and elastic cases, respectively.
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.
NASA Astrophysics Data System (ADS)
Balázs, Csaba; Fowlie, Andrew; Mazumdar, Anupam; White, Graham A.
2017-02-01
A new gauge singlet scalar field can undergo a strongly first-order phase transition (PT) leading to gravitational waves (GW) potentially observable at aLIGO and stabilizes the electroweak vacuum at the same time by ensuring that the Higgs quartic coupling remains positive up to at least the grand unification (GUT) scale. aLIGO (O5) is potentially sensitive to cosmological PTs at 1 07- 1 08 GeV , which coincides with the requirement that the singlet scale is less than the standard model (SM) vacuum instability scale, which is between 1 08 GeV and 1 014 GeV . After sampling its parameter space, we identify three benchmark points with a PT at about T ≈1 07 GeV in a gauge singlet extension of the SM. We calculate the nucleation temperature, order parameter, characteristic time scale, and peak amplitude and frequency of GW from bubble collisions during the PT for the benchmarks and find that, in an optimistic scenario, GW from such a PT may be in reach of aLIGO (O5). We confirm that the singlet stabilizes the electroweak vacuum while remaining consistent with zero-temperature phenomenology as well. Thus, this scenario presents an intriguing possibility that aLIGO may detect traces of fundamental physics motivated by vacuum stability at an energy scale that is well above the reach of any other experiment.
Stability of Flame-Shock Coupling in Detonation Waves: 1D Dynamics (Preprint)
2011-09-01
much sharper; however, the non-linear procedure necessary for sharpening CDs may also artificially sharpen the gradients in acoustic and entropy waves...approach, commonly chosen in funda- mental studies of detonation dynamics, is a 1-step model, in which the entire chemistry is described by the evolution of...better description is obtained with the 2-step model [12], where the heat release is associated with a second progress vari- able, whose evolution can
NASA Astrophysics Data System (ADS)
Beretta, Elena; de Hoop, Maarten V.; Francini, Elisa; Vessella, Sergio; Zhai, Jian
2017-03-01
We consider the inverse problem of determining the Lamé parameters and the density of a three-dimensional elastic body from the local time-harmonic Dirichlet-to-Neumann map. We prove uniqueness and Lipschitz stability of this inverse problem when the Lamé parameters and the density are assumed to be piecewise constant on a given domain partition.
Ground Control for Emplacement Drifts for SR
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
Progress in semiconductor drift detectors
Rehak, P.; Walton, J.; Gatti, E.; Longoni, A.; Sanpietro, M.; Kemmer, J.; Dietl, H.; Holl, P.; Klanner, R.; Lutz, G.
1985-01-01
Progress in testing semiconductor drift detectors is reported. Generally better position and energy resolutions were obtained than resolutions published previously. The improvement is mostly due to new electronics better matched to different detectors. It is shown that semiconductor drift detectors are becoming versatile and reliable detectors for position and energy measurements.
CURVATURE-DRIFT INSTABILITY FAILS TO GENERATE PULSAR RADIO EMISSION
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.
CTF Void Drift Validation Study
Salko, Robert K.; Gosdin, Chris; Avramova, Maria N.; Gergar, Marcus
2015-10-26
This milestone report is a summary of work performed in support of expansion of the validation and verification (V&V) matrix for the thermal-hydraulic subchannel code, CTF. The focus of this study is on validating the void drift modeling capabilities of CTF and verifying the supporting models that impact the void drift phenomenon. CTF uses a simple turbulent-diffusion approximation to model lateral cross-flow due to turbulent mixing and void drift. The void drift component of the model is based on the Lahey and Moody model. The models are a function of two-phase mass, momentum, and energy distribution in the system; therefore, it is necessary to correctly model the ow distribution in rod bundle geometry as a first step to correctly calculating the void distribution due to void drift.
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.
Effect of ultrasonic waves on the stability of all-trans lutein and its degradation kinetics.
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.
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.
Flexible 2D Crystals of Polycyclic Aromatics Stabilized by Static Distortion Waves
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
Effects of drift angle on model ship flow
NASA Astrophysics Data System (ADS)
Longo, J.; Stern, F.
The effects of drift angle on model ship flow are investigated through towing tank tests for the Series 60 CB=0.6 cargo/container model ship. Resistance, side force, drift moment, sinkage, trim, and heel data are procured for a range of drift angles β and Froude numbers (Fr) and the model free condition. Detailed free-surface and mean velocity and pressure flow maps are procured for high and low Fr=0.316 and 0.16 and β=5° and 10° (free surface) and β=10° (mean velocity and pressure) for the model fixed condition (i.e. fixed with zero sinkage, trim, and heel). Comparison of results at high and low Fr and previous data for β=0° enables identification of important free-surface and drift effects. Geometry, conditions, data, and uncertainty analysis are documented in sufficient detail so as to be useful as a benchmark for computational fluid dynamics (CFD) validation. The resistance increases linearly with β with same slope for all Fr, whereas the increases in the side force, drift moment, sinkage, trim, and heel with β are quadratic. The wave profile is only affected near the bow, i.e. the bow wave amplitude increases/decreases on the windward/leeward sides, whereas the wave elevations are affected throughout the entire wave field. However, the wave envelope angle on both sides is nearly the same as β=0°, i.e. the near-field wave pattern rotates with the hull and remains within a similar wave envelope as β=0°. The wave amplitudes are significantly increased/decreased on the windward/leeward sides. The wake region is also asymmetric with larger wedge angle on the leeward side. The boundary layer and wake are dominated by the hull vortex system consisting of fore body keel, bilge, and wave-breaking vortices and after body bilge and counter-rotating vortices. The occurrence of a wave-breaking vortex for breaking bow waves has not been previously documented in the literature. The trends for the maximum vorticity, circulation, minimum axial velocity, and
NASA Astrophysics Data System (ADS)
LeFloch, Philippe G.; Ma, Yue
2016-09-01
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.
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.
Pilot-wave dynamics in a harmonic potential: Quantization and stability of circular orbits.
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.
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.
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.
Stability of coda wave attenuation during the Loma Prieta, California, earthquake sequence
NASA Astrophysics Data System (ADS)
Beroza, Gregory C.; Cole, Alex T.; Ellsworth, William L.
1995-03-01
The Loma Prieta, California, earthquake occurred in a densely instrumented region with a history of microearthquake recording beginning more than a decade before the October 1989 mainshock. This affords an unprecedented opportunity to detect changes in seismic wave propagation in the Earth's crust associated with a major earthquake. In this study we use pairs of nearly identical earthquakes (doublets) to search for temporal changes of coda attenuation in the vicinity of the Loma Prieta earthquake. We analyze 21 earthquake doublets recorded from 1978 to 1991 that span the preseismic, coseismic, and postseismic intervals and measure the change in coda Q using a running window ratio of the doublet spectral amplitudes in three frequency bands from 2 to 15 Hz. This method provides an estimate of changes in coda Q that is insensitive to other factors that influence coda amplitudes.
Hemoglobin Drift after Cardiac Surgery
George, Timothy J.; Beaty, Claude A.; Kilic, Arman; Haggerty, Kara A.; Frank, Steven M.; Savage, William J.; Whitman, Glenn J.
2013-01-01
Introduction Recent literature suggests that a restrictive approach to red blood cell transfusions is associated with improved outcomes in cardiac surgery (CS) patients. Even in the absence of bleeding, intravascular fluid shifts cause hemoglobin levels to drift postoperatively, possibly confounding the decision to transfuse. We undertook this study to define the natural progression of hemoglobin levels in postoperative CS patients. Methods We included all CS patients from 10/10-03/11 who did not receive a postoperative transfusion. Primary stratification was by intraoperative transfusion status. Change in hemoglobin was evaluated relative to the initial postoperative hemoglobin. Maximal drift was defined as the maximum minus the minimum hemoglobin for a given hospitalization. Final drift was defined as the difference between initial and discharge hemoglobin. Results Our final cohort included 199 patients, 71(36%) received an intraoperative transfusion while 128(64%) did not. The average initial and final hemoglobin for all patients were 11.0±1.4g/dL and 9.9±1.3g/dL, respectively, an final drift of 1.1±1.4g/dL. The maximal drift was 1.8±1.1g/dL and was similar regardless of intraoperative transfusion status(p=0.9). Although all patients’ hemoglobin initially dropped, 79% of patients reached a nadir and experienced a mean recovery of 0.7±0.7g/dL by discharge. On multivariable analysis, increasing CPB time was significantly associated with total hemoglobin drift(Coefficient/hour: 0.3[0.1–0.5]g/dL, p=0.02). Conclusions In this first report of hemoglobin drift following CS, although all postoperative patients experienced downward hemoglobin drift, 79% of patients exhibited hemoglobin recovery prior to discharge. Physicians should consider the eventual upward hemoglobin drift prior to administering red cell transfusions. PMID:22609121
Surface stability of an encapsulated bubble subjected to an ultrasonic pressure wave
NASA Astrophysics Data System (ADS)
Liu, Yunqiao; Sugiyama, Kazuyasu; Takagi, Shu; Matsumoto, Yoichiro
2010-11-01
A theoretical study on the shape stability of a nearly spherical bubble encapsulated by a hyperelastic membrane in an ultrasound field is performed. To describe the dynamic balance on the bubble surface, the membrane effects of the in-plane stress and the bending moment are incorporated into the equation set for the perturbed spherical flow of viscous incompressible fluid (Prosperetti, 1977). The spherical motion of the bubble is numerically obtained by solving the Rayleigh-Plesset equation with the elastic stress. The deflection therefrom is linearized and expanded with respect to the Legendre polynomial. Two amplitudes for each shape mode are introduced since the membrane has mobilities not only in the radial direction but also in the tangential direction. The eigenvalue analysis on the system determines the higher-order natural frequency. The derived system is applied to the temporal evolution of the higher-order shape mode. Stability diagrams for the higher-order shape mode are mapped out in the driving amplitude versus driving frequency phase space for various elastic moduli of the membrane. The most unstable driving frequency is found to be approximately integer multiples of the higher-order natural frequency.
Bifurcations of rotating waves in rotating spherical shell convection.
Feudel, F; Tuckerman, L S; Gellert, M; Seehafer, N
2015-11-01
The dynamics and bifurcations of convective waves in rotating and buoyancy-driven spherical Rayleigh-Bénard convection are investigated numerically. The solution branches that arise as rotating waves (RWs) are traced by means of path-following methods, by varying the Rayleigh number as a control parameter for different rotation rates. The dependence of the azimuthal drift frequency of the RWs on the Ekman and Rayleigh numbers is determined and discussed. The influence of the rotation rate on the generation and stability of secondary branches is demonstrated. Multistability is typical in the parameter range considered.
Faltens, A.
2004-10-25
The pulsed drift-tube accelerator (DTA) concept was revived by Joe Kwan and John Staples and is being considered for the HEDP/WDM application. It could be used to reach the full energy or as an intermediate accelerator between the diode and a high gradient accelerator such as multi-beam r.f. In the earliest LBNL HIF proposals and conceptual drivers it was used as an extended injector to reach energies where an induction linac with magnetic quadrupoles is the best choice. For HEDP, because of the very short pulse duration, the DTA could provide an acceleration rate of about 1MV/m. This note is divided into two parts: the first, a design based on existing experience; the second, an optimistic extrapolation. The first accelerates 16 parallel K{sup +} beams at a constant line charge density of 0.25{micro} C/m per beam to 10 MeV; the second uses a stripper and charge selector at around 4MeV followed by further acceleration to reach 40 MeV. Both benefit from more compact sources than the present 2MV injector source, although that beam is the basis of the first design and is a viable option. A pulsed drift-tube accelerator was the first major HIF experiment at LBNL. It was designed to produce a 2{micro}s rectangular 1 Ampere C{sub s}{sup +} beam at 2MeV. It ran comfortably at 1.6MeV for several years, then at lower voltages and currents for other experiments, and remnants of that experiment are in use in present experiments, still running 25 years later. The 1A current, completely equivalent to 1.8A K{sup +}, was chosen to be intermediate between the beamlets appropriate for a multi-beam accelerator, and a single beam of, say, 10A, at injection energies. The original driver scenarios using one large beam on each side of the reactor rapidly fell out of favor because of the very high transverse and longitudinal fields from the beam space charge, circa 1MV/cm and 250 kV/cm respectively, near the chamber and because of aberrations in focusing a large diameter beam down to a 1
Toroidal universal drift instability: A global gyrokinetic study
Chowdhury, J.; Ganesh, R.; Brunner, S.; Vaclavik, J.; Villard, L.
2010-10-15
An electron density gradient driven instability identified as the toroidal branch of the universal drift instability is studied using a global gyrokinetic model treating both electrons and ions fully nonadiabatically and valid at all orders in the ratio of the Larmor radius to the wavelength. The physics of the magnetic drift resonance, Landau resonance and transit resonance, which are considered to be important for the toroidal universal mode, are kept for both species. A systematic parametric study is carried out for the mode. The toroidal universal drift mode is observed to sustain finite temperature gradient and can thus coexist with the temperature gradient driven modes and may contribute to the observed particle transport along with other drift modes. Especially at intermediate scales between the ion temperature gradient driven mode and electron temperature gradient driven mode, this branch of the drift instability can also be a plausible candidate for the observed particle loss. The effect of magnetic fluctuations on the mode is also investigated. In contrast to the slab mode, the toroidal branch of the universal drift mode is found to be strongly stabilized by electromagnetic effects at finite plasma {beta}. Finally, the effect of trapped electrons on the universal mode is studied and compared with the other possible modes in the same parameter regime, namely, ion temperature gradient mode in the presence of trapped electrons and pure trapped electron modes.
The Geodiversity in Drift Sand Landscapes of The Netherlands
NASA Astrophysics Data System (ADS)
van den Ancker, Hanneke; Jungerius, Pieter Dirk; Riksen, Michel
2015-04-01
The authors carried out detailed field studies of more than twelve drift sand landscapes in The Netherlands. The objective of these studies was to restore Natura-2000 values by restoring the wind activity. Active drift sands occur almost exclusively in The Netherlands, Natura 2000 habitat 2330 'Inland dunes with open Corynephorus and Agrostis grasslands', for which reason our country is largely responsible for this European landscape. Active drift sands had almost disappeared for two reasons: first, the stabilization of the drift sands by air pollution, mainly nitrogen, which stimulates the growth of algae and grasses that initiate soil formation, and second, by the growth of forests surrounding the sands, which decreases the wind force. The restoration studies revealed differences in the geodiversity between and within the drift sand areas. Whereas the drift sands on geological and soil maps show as almost homogenous areas, they have in fact highly variable geo-conditions of which examples will be given. These geodiversity aspects concern differences in geomorphological structure, origin, sediments and age of the drift sands. Differences in wind and water erosion, trampling and soil formation add to the geodiversity within the drift sand areas. Especially in the primary stages of succession the differences in geodiversity are relevant for the Natura-2000 values. We discerned three main types of active sands. Firstly, the impressive drift sands with large parabolic dune structures, often consisting of series of interlocking parabolic dunes. They developed from the northeast towards the southwest, against the direction of the dominant wind, and must have taken centuries to develop. Small parts of these systems are still active, other parts show different degrees of soil formation. Their origin is still unclear but probably dates from medieval times (Heidinga, 1985, Jungerius & Riksen, 2008). Second are the drift sand areas with irregular hills from 0.5 to about 2
Time-dependent drift Hamiltonian
Boozer, A.H.
1983-03-01
The lowest-order drift equations are given in a canonical magnetic coordinate form for time-dependent magnetic and electric fields. The advantages of the canonical Hamiltonian form are also discussed.
Extended-MHD modeling of diamagnetic-drift tearing instabilities
NASA Astrophysics Data System (ADS)
King, Jacob; Kruger, Scott
2012-03-01
We use analytics and computations with the NIMROD code to examine tearing stability in large-guide-field slab cases with a nonzero equilibrium pressure gradient. A well known result from drift-reduced MHD is the diamagnetic drift associated with the pressure gradient has a stabilizing influence were the dispersion relation becomes (γ+iφ*e)^3γ(γ+iφ*i)=γrMHD^5 [1]. Here φ*i and φ*e are the ion- and electron-diamagnetic frequencies and γrMHD is the tearing growth rate with a resistive-MHD model. Preliminary computational results with an unreduced extended-MHD model do not produce the expected drift-reduced result. For moderate values of φ*i (φ*i<=3γrMHD), the computations follow the dispersion relation that would result if the ∇pe term were not included in the drift-reduced parallel Ohm's law: (γ+iφ*e)^4(γ+iφ*i)=γrMHD^5. Analytics, guided by computational diagnostics, are used to examine the significant terms in the flux evolution equation and investigate the discrepancy with the drift-reduced result.[4pt] [1] For example Coppi, PoF 7, 1501 (1964); Biskamp, NF 18, 1059 (1978).
Stabilized platform for tethered balloon soundings of broadband long- and short-wave radiation
Alzheimer, J.M.; Anderson, G.A.; Whiteman, C.D.
1993-01-01
Changes in the composition of trace gases in the earth`s atmosphere have been reported by many observers, and a general concern has been expressed regarding possible changes to the earth`s climate that may be caused by radiatively active gases introduced into the earth`s atmosphere by man`s activities. Radiatively active trace gases produce temperature changes in the earth`s atmosphere through changes in radiative flux divergence. Our knowledge of and means of measuring radiative flux divergence is very limited. A few observations of vertical radiative flux divergences have been reported from aircraft from radiometersondes from towers and from large tethered balloons. These measurement techniques suffers from one or more drawbacks, including shallow sounding depths (towers), high cost (aircraft), complicated logistics (large tethered balloons), and limitation to nighttime hours (radiometersondes). Changes in radiative flux divergence caused by anthropogenic trace gases are expected to be quite small, and will be difficult to measure with existing broadband radiative flux instruments. The emphasis of present research in global climate change is thus being focused on improving radiative transfer algorithms in global climate models. The radiative parameterizations in these models are at an early stage of development and information is needed regarding their performance, especially in cloudy conditions. The impetus for the research reported in this paper is the need for a device that can supplement existing means of measuring vertical profiles of long- and short-wave irradiance and radiative flux divergence. We have designed a small tethered-balloon-based system that can make radiometric soundings through the atmospheric boundary layer. This paper discusses the concept, the design considerations, and the design and construction of this sounding system. The performance of the system will be tested in a series of balloon flights scheduled for the fall and winter of 1992.
Stabilized platform for tethered balloon soundings of broadband long- and short-wave radiation
Alzheimer, J.M.; Anderson, G.A.; Whiteman, C.D.
1993-01-01
Changes in the composition of trace gases in the earth's atmosphere have been reported by many observers, and a general concern has been expressed regarding possible changes to the earth's climate that may be caused by radiatively active gases introduced into the earth's atmosphere by man's activities. Radiatively active trace gases produce temperature changes in the earth's atmosphere through changes in radiative flux divergence. Our knowledge of and means of measuring radiative flux divergence is very limited. A few observations of vertical radiative flux divergences have been reported from aircraft from radiometersondes from towers and from large tethered balloons. These measurement techniques suffers from one or more drawbacks, including shallow sounding depths (towers), high cost (aircraft), complicated logistics (large tethered balloons), and limitation to nighttime hours (radiometersondes). Changes in radiative flux divergence caused by anthropogenic trace gases are expected to be quite small, and will be difficult to measure with existing broadband radiative flux instruments. The emphasis of present research in global climate change is thus being focused on improving radiative transfer algorithms in global climate models. The radiative parameterizations in these models are at an early stage of development and information is needed regarding their performance, especially in cloudy conditions. The impetus for the research reported in this paper is the need for a device that can supplement existing means of measuring vertical profiles of long- and short-wave irradiance and radiative flux divergence. We have designed a small tethered-balloon-based system that can make radiometric soundings through the atmospheric boundary layer. This paper discusses the concept, the design considerations, and the design and construction of this sounding system. The performance of the system will be tested in a series of balloon flights scheduled for the fall and winter of 1992.
Landslide stability: Role of rainfall-induced, laterally propagating, pore-pressure waves
Priest, G.R.; Schulz, W.H.; Ellis, W.L.; Allan, J.A.; Niem, A.R.; Niem, W.A.
2011-01-01
The Johnson Creek Landslide is a translational slide in seaward-dipping Miocene siltstone and sandstone (Astoria Formation) and an overlying Quaternary marine terrace deposit. The basal slide plane slopes sub-parallel to the dip of the Miocene rocks, except beneath the back-tilted toe block, where it slopes inland. Rainfall events raise pore-water pressure in the basal shear zone in the form of pulses of water pressure traveling laterally from the headwall graben down the axis of the slide at rates of 1-6 m/hr. Infiltration of meteoric water and vertical pressure transmission through the unsaturated zone has been measured at ~50 mm/hr. Infiltration and vertical pressure transmission were too slow to directly raise head at the basal shear zone prior to landslide movement. Only at the headwall graben was the saturated zone shallow enough for rainfall events to trigger lateral pulses of water pressure through the saturated zone. When pressure levels in the basal shear zone exceeded thresholds defined in this paper, the slide began slow, creeping movement as an intact block. As pressures exceeded thresholds for movement in more of the slide mass, movement accelerated, and differential displacement between internal slide blocks became more pronounced. Rainfall-induced pore-pressure waves are probably a common landslide trigger wherever effective hydraulic conductivity is high and the saturated zone is located near the surface in some part of a slide. An ancillary finding is apparently greater accuracy of grouted piezometers relative to those in sand packs for measurement of pore pressures at the installed depth.
Generalized lower-hybrid-drift instability. [of plasma
NASA Technical Reports Server (NTRS)
Hsia, J. B.; Chiu, S. M.; Hsia, M. F.; Chou, R. L.; Wu, C. S.
1979-01-01
The theory of lower-hybrid-drift instability is extended to include a finite value of the component of wave vector parallel to the ambient magnetic field so that the analysis bridges the usual lower-hybrid-drift instability of flute modes and the modified-two-stream instability. The present theory also includes electromagnetic and ambient magnetic field-gradient effects. It is found that in the cold-electron limit the density and magnetic gradients can qualitatively modify the conclusion obtained in the early theory of the modified-two-stream instability. For example, even if the relative drift far exceeds the Alfven speed of the plasma, the instability may still persist. This result is in contrast to that established in the literature. When the electron temperature is finite, the problem is complicated. Numerical solutions are obtained for a number of cases.
Drift Kelvin-Helmholtz instabilities in space plasmas
NASA Technical Reports Server (NTRS)
Sharma, Avadhesh C.; Srivastava, Krishna M.
1992-01-01
Drift Kelvin-Helmholtz instabilities of a finite-beta plasma in equilibrium electric and magnetic fields which are perpendicular to each other are studied using two fluid equations. Three types of these instabilities are considered including the magnetosonic instability of a finite beta-homogeneous plasma, the electrostatic drift instability of an inhomogeneous low-beta plasma, and the magneto-acoustic instability of a high-beta inhomogeneous isothermal plasma. It is shown that the electric field has either stabilizing or destabilizing effect depending on conditions under consideration.
The US Navy Coupled Ocean-Wave Prediction System
2014-09-01
Stokes drift to be the dominant wave effect and that it increased surface drift speeds by 35% and veered the current in the direction of the wind...important for the prediction of the dispersion of contaminants as well as the projected path of a drifting mine field. Several regional modeling systems...ocean model has been modified to incorporate the effect of the Stokes drift current, wave radiation stresses due to horizontal gradients of the momentum
Drift-Scale Radionuclide Transport
P.R. Dixon
2004-02-17
The purpose of this Model Report is to document two models for drift-scale radionuclide transport. This has been developed in accordance with ''Technical Work Plan for: Performance Assessment Unsaturated Zone'' (Bechtel SAIC Company, LLC (BSC) 2002 [160819]), which includes planning documents for the technical work scope, content, and management of this Model Report in Section 1.15, Work Package AUZM11, ''Drift-Scale Radionuclide Transport.'' The technical work scope for this Model Report calls for development of a process-level model and an abstraction model representing diffusive release from the invert to the rocks, partitioned between fracture and matrix, as compared to the fracture-release approach used in the Site Recommendation. The invert is the structure constructed in a drift to provide the floor of that drift. The plan for validation of the models documented in this Model Report is given in Section I-5 of Attachment I in BSC (2002 [160819]). Note that the model validation presented in Section 7 deviates from the technical work plan (BSC 2002 [160819], Section I-5) in that an independent technical review specifically for model validation has not been conducted, nor publication in a peer-reviewed journal. Model validation presented in Section 7 is based on corroboration with alternative mathematical models, which is also called out by the technical work plan (BSC 2002 [160819], Section I-5), and is sufficient based on the requirements of AP-SIII.10Q for model validation. See Section 7 for additional discussion. The phenomenon of flow and transport in the vicinity of the waste emplacement drift are evaluated in this model report under ambient thermal, chemical, and mechanical conditions. This includes the effects of water diversion around an emplacement drift and the flow and transport behavior expected in a fractured rock below the drift. The reason for a separate assessment of drift-scale transport is that the effects of waste emplacement drifts on flow
Wang, Wei-Bo; Chen, De-Ying; Fan, Rong-Wei; Xia, Yuan-Qin
2010-02-01
The effects of the stability of dye laser on the signal to noise ratio in degenerate four-wave mixing (DFWM) were first investigated in iodine vapor using forward geometries. Frequency-doubled outputs from a multi-mode Nd : YAG laser pumped dye laser with laser dye PM580 dissolved in ethanol was used. With the help of forward compensated beam-split technique and imaging detecting system, the saturation intensity of DFWM spectrum in the iodine vapor at 5 554.013 nm was first measured to be 290 microJ under the condition of atmospheric pressure and room temperature. The features of the dye laser such as wavelength ranges, beam quality and energy conversion efficiency decreased gradually with increasing pumping service use, pulse number and intensity. Additionally, with the comparison of the stable and unstable dye laser output, it was found that the instability of dye laser output had greatly influenced the DFWM signal and decreased the signal to background noise ratio. Shot to shot jitter and the broadening in the output frequency leads to an effective broadening of the recorded spectrum and loss of the DFWM signal to noise ratio under the same pumping intensity at different time. The study is of importance to the detection of trace atom, molecule and radical in combustion diagnosis.
Influence of channel subunit composition on L-type Ca2+ current kinetics and cardiac wave stability.
Gudzenko, Vadim; Shiferaw, Yohannes; Savalli, Nicoletta; Vyas, Roshni; Weiss, James N; Olcese, Riccardo
2007-09-01
Previous studies have demonstrated that the slope of the function relating the action potential duration (APD) and the diastolic interval, known as the APD restitution curve, plays an important role in the initiation and maintenance of ventricular fibrillation. Since the APD restitution slope critically depends on the kinetics of the L-type Ca(2+) current, we hypothesized that manipulation of the subunit composition of these channels may represent a powerful strategy to control cardiac arrhythmias. We studied the kinetic properties of the human L-type Ca(2+) channel (Ca(v)1.2) coexpressed with the alpha(2)delta-subunit alone (alpha(1C) + alpha(2)delta) or in combination with beta(2a), beta(2b), or beta(3) subunits (alpha(1C) + alpha(2)delta + beta), using Ca(2+) as the charge carrier. We then incorporated the kinetic properties observed experimentally into the L-type Ca(2+) current mathematical model of the cardiac action potential to demonstrate that the APD restitution slope can be selectively controlled by altering the subunit composition of the Ca(2+) channel. Assuming that beta(2b) most closely resembles the native cardiac L-type Ca(2+) current, the absence of beta, as well as the coexpression of beta(2a), was found to flatten restitution slope and stabilize spiral waves. These results imply that subunit modification of L-type Ca(2+) channels can potentially be used as an antifibrillatory strategy.
In-Drift Microbial Communities
D. Jolley
2000-11-09
As directed by written work direction (CRWMS M and O 1999f), Performance Assessment (PA) developed a model for microbial communities in the engineered barrier system (EBS) as documented here. The purpose of this model is to assist Performance Assessment and its Engineered Barrier Performance Section in modeling the geochemical environment within a potential repository drift for TSPA-SR/LA, thus allowing PA to provide a more detailed and complete near-field geochemical model 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 model and its predecessor (the in-drift microbial communities model as documented in Chapter 4 of the TSPA-VA Technical Basis Document, CRWMS M and O 1998a) was developed to respond to the applicable KTIs. Additionally, because of the previous development of the in-drift microbial communities model as documented in Chapter 4 of the TSPA-VA Technical Basis Document (CRWMS M and O 1998a), the M and O was effectively able to resolve a previous KTI concern regarding the effects of microbial processes on seepage and flow (NRC 1998). This document supercedes the in-drift microbial communities model as documented in Chapter 4 of the TSPA-VA Technical Basis Document (CRWMS M and O 1998a). This document provides the conceptual framework of the revised in-drift microbial communities model to be used in subsequent performance assessment (PA) analyses.
SAA drift:experimental results
NASA Astrophysics Data System (ADS)
Grigoryan, O. R.; Kudela, K.; Romashova, V. V.; Drozdov, A. Yu.
According to the paleomagnetic analysis there are variations of Earth's magnetic field connected with magnetic momentum changing. Besides these variations affects on the trapped belt South Atlantic Anomaly (SAA) location. Indeed different observations including Space Shuttle short-time flights approved the existence SAA westward drift with speed 0.1-1.0 (deg/year) and northward drift with speed approximately 0.1 (deg/year). In this work we present the analysis of experimental results obtained in SINP MSU in 1972-2003 from different satellites. There were analyzed the fluxes of protons with energy > 50 MeV, gamma quanta with energy > 500 keV and neutrons with energy 0.1-1.0 MeV in SAA area and their maxima location. The data about fluxes were obtained onboard the orbital stations ``Salut-6'' (1979), MIR (1991, 1998) and ISS (2003) by the identical experimental equipment. The comparison of the data obtained during these two decades of investigations confirms the fact of the SAA westward drift. Moreover the same analysis of maximum flux location of electrons with hundreds keV energy (satellites ``Kosmos-484'' (1972), ``Interkosmos-17'' (1977) and ``Activny'' (``Interkosmos-24'', 1991)) confirmed not only the SAA westward drift but northward drift also.
Surface Drift of RAFOS Floats in the California Current System
NASA Astrophysics Data System (ADS)
Gates, D. C.; Collins, C. A.; Margolina, T.
2011-12-01
The patterns of surface drift of ninety RAFOS floats in the California Current System have been studied. The floats were launched in the California Undercurrent during 1992-2010 and were tracked by the ARGOS system when they surfaced at the end of their subsurface mission. The float hulls were glass cylinders which were 8.6 cm wide by 1.52 m long and floated with the upper 30 cm of the hull above water. The surface drift of these floats was typically equatorward in the California Current. However, some floats would flow poleward, others would drift westward into the North Pacific Gyre, and others with orbital cyclonic and/or anti-cyclonic motions. The duration of surface trajectories varied from as short as a period of days to approximately ten months. Forces on the floats included wind stress on the exposed hull and the drag of ocean currents on the subsurface hull. The latter included the Stokes drift associated with surface wind waves, Ekman flow caused by the stress of the wind on the ocean surface, and the currents associated with the general circulation of the ocean. Surface currents can be explained by calculating current direction and velocity from wind stress data. As a first step, the relationship between observed wind stress and the motion of the float is determined by assuming Ekman balance. Mesoscale effects, including eddies, are also considered in explaining the surface drift of the floats.
Drift effects on electromagnetic geodesic acoustic modes
Sgalla, R. J. F.
2015-02-15
A two fluid model with parallel viscosity is employed to derive the dispersion relation for electromagnetic geodesic acoustic modes (GAMs) in the presence of drift (diamagnetic) effects. Concerning the influence of the electron dynamics on the high frequency GAM, it is shown that the frequency of the electromagnetic GAM is independent of the equilibrium parallel current but, in contrast with purely electrostatic GAMs, significantly depends on the electron temperature gradient. The electromagnetic GAM may explain the discrepancy between the f ∼ 40 kHz oscillation observed in tokamak TCABR [Yu. K. Kuznetsov et al., Nucl. Fusion 52, 063044 (2012)] and the former prediction for the electrostatic GAM frequency. The radial wave length associated with this oscillation, estimated presently from this analytical model, is λ{sub r} ∼ 25 cm, i.e., an order of magnitude higher than the usual value for zonal flows (ZFs)
Floating body second order slow drift force spectrum
Aranha, J.A.P.; Fernandes, A.C.
1996-12-31
In this paper it is shown that the slow drift force spectrum of a floating body, obtained from the quadratic transfer function, can be approximated, in the range of interest ({mu} {much_lt} 1) by a white noise of the form S{sub F}({mu}) = S{sub F}(0) + O({mu}{sup 2}) where S{sub F}(0) can be computed from the known drift force coefficient in harmonic waves and the wave energy spectrum. It is also shown here that a special and normally used form of Newman`s approximation represents the spectrum S{sub F}({mu}) with an error [1 + O({mu}{sup 2})] in the low frequency regime. It is also shown that a well chosen Newman`s Approximations may be O({mu}{sup 2}) instead of only O({mu}).
Rolland, A; Loas, G; Brunel, M; Frein, L; Vallet, M; Alouini, M
2011-09-12
We propose an optoelectronic phase-locked loop concept which enables to stabilize optical beat notes at high frequencies in the mm-wave domain. It relies on the use of a nonlinear-response Mach-Zehnder modulator. This concept is demonstrated at 100 GHz using a two-axis dual-frequency laser turned into a voltage controlled oscillator by means of an intracavity electrooptic crystal. A relative frequency stability better than 10⁻¹¹ is reported. This approach of optoelectronic down conversion opens the way to the realization of continuously tunable ultra-narrow linewidth THz radiation.
Kuklik, Pawel; Sanders, Prashanthan; Szumowski, Lukasz; Żebrowski, Jan J
2013-01-01
Various forms of heart disease are associated with remodeling of the heart muscle, which results in a perturbation of cell-to-cell electrical coupling. These perturbations may alter the trajectory of spiral wave drift in the heart muscle. We investigate the effect of spatially extended inhomogeneity of transverse cell coupling on the spiral wave trajectory using a simple active media model. The spiral wave was either attracted or repelled from the center of inhomogeneity as a function of cell excitability and gradient of the cell coupling. High levels of excitability resulted in an attraction of the wave to the center of inhomogeneity, whereas low levels resulted in an escape and termination of the spiral wave. The spiral wave drift velocity was related to the gradient of the coupling and the initial position of the wave. In a diseased heart, a region of altered transverse coupling corresponds with local gap junction remodeling that may be responsible for stabilization-destabilization of spiral waves and hence reflect potentially important targets in the treatment of heart arrhythmias.
Precise Measurement of Drift Velocities in Active-Target Detectors
NASA Astrophysics Data System (ADS)
Jensen, Louis
2016-09-01
Nuclear experiments with radioactive beams are needed to improve our understanding of nuclei structure far from stability. Radioactive beams typically have low beam rates, but active-target detectors can compensate for these low beam rates. In active-target detectors that are also Time-Projection Chambers (TPC), ionized electrons drift through an electric fieldto a detection device to imagethe trajectory of charged-particle ionization tracks within the chamber's gas volume. The measurement of the ionized electrons' drift velocity is crucial for the accurate imaging of these tracks. In order to measure this drift velocity, we will use a UV laser and photo-sensitive foil in a the ND-Cubedetector we are developing, periodically releasingelectrons from the foil at a known timesand a known distance from the electron detector, thereby precisely measuring the drift velocity in situ. We have surveyed several materials to find a material that will work well with typical solid-state UV lasers on the market. We plan to determine the best material and thickness of the foil to maximize the number of photoelectrons. The precision that will be afforded by this measurement of the drift velocity will allow us to eliminate a source of systematic uncertainty.
Agrochemical spray drift; assessment and mitigation--a review.
Felsot, Allan S; Unsworth, John B; Linders, Jan B H J; Roberts, Graham; Rautman, Dirk; Harris, Caroline; Carazo, Elizabeth
2011-01-01
During application of agrochemicals spray droplets can drift beyond the intended target to non-target receptors, including water, plants and animals. Factors affecting this spray drift include mode of application, droplet size, which can be modified by the nozzle types, formulation adjuvants, wind direction, wind speed, air stability, relative humidity, temperature and height of released spray relative to the crop canopy. The rate of fall of spray droplets depends upon the size of the droplets but is modified by entrainment in a mobile air mass and is also influenced by the rate of evaporation of the liquid constituting the aerosol. The longer the aerosol remains in the air before falling to the ground (or alternatively striking an object above ground) the greater the opportunity for it to be carried away from its intended target. In general, all size classes of droplets are capable of movement off target, but the smallest are likely to move the farthest before depositing on the ground or a non-target receptor. It is not possible to avoid spray drift completely but it can be minimized by using best-management practices. These include using appropriate nozzle types, shields, spray pressure, volumes per area sprayed, tractor speed and only spraying when climatic conditions are suitable. Field layout can also influence spray drift, whilst crop-free and spray-free buffer zones and windbreak crops can also have a mitigating effect. Various models are available to estimate the environmental exposure from spray drift at the time of application.
Gupta, D. N. Yadav, Pinki; Avinash, K.; Jang, D. G.; Suk, H.; Hur, M. S.
2015-05-15
Stimulated Raman scattering of a laser in plasmas with energetic drifting electrons was investigated by analyzing the growth of interacting waves during the Raman scattering process. The Langmuir wave and scattered electromagnetic sideband wave grow initially and are dampened after attaining a maximum level that indicates a periodic exchange of energy between the pump wave and the daughter waves. The presence of energetic drifting electrons in the laser-produced plasma influences the stimulated Raman scattering process. The plasma wave generated by Raman scattering may be influenced by the energetic electrons, which enhance the growth rate of the instability. Our results show that the presence of energetic (hot) drifting electrons in a plasma has an important effect on the evolution of the interacting waves. This phenomenon is modeled via two-dimensional particle-in-cell simulations of the propagation and interaction of the laser under Raman instability.
Stabilization of the spin density wave structure with rare-earth substitution in Ca3Co2O6
NASA Astrophysics Data System (ADS)
Jain, Anil; Yusuf, S. M.; Meena, S. S.; Ritter, Clemens
2013-03-01
We report the structural and magnetic properties of rare-earth substituted spin-chain compounds Ca2.75R0.25Co2O6 (R = Dy and Lu). The Rietveld refinement of neutron and x-ray powder diffraction patterns confirms the single-phase formation of both compounds in the rhombohedral structure (space group R3¯c). The derived values (from the analysis of the neutron diffraction patterns at 50 K) of the bond-valence sum indicate a reduction in the oxidation state of the cobalt ions at the trigonal prism (TP) site (6a) with R substitution, which is further supported by low temperature neutron diffraction [where a zero value of the ordered moment at the 6b site and a reduction in the values of the maximum ordered moment at the TP site have been observed] and dc magnetization studies. In the neutron diffraction patterns, additional Bragg peaks appear for both compounds below Néel temperature (TN) of ˜16 K, indicating the onset of an antiferromagnetic ordering of cobalt spin chains on the triangular lattice. The magnetic structure corresponds to a spin density wave (SDW) structure [with a propagation vector k={0,0,1.02}], having c axis as a direction of both moment and modulation. For both compounds, the refined values of the ordered moment at the 18e, 6b, and 6a sites are ˜0.03(2),0.02(2), and 4.2 (2) μB, respectively. Unlike the parent compound Ca3Co2O6, no temperature dependence as well as no time dependence in the intensity of the strongest antiferromagnetic reflection (10 τ), corresponding to the propagation vector k = {0, 0, 1.02}, has been observed down to 1.5 K confirming that the SDW structure is stabilized by the substitution with rare-earth ions. The stabilization of the SDW structure and the observed decrease in the values of TN could be due to a decrease in the value of positive FM intrachain exchange interaction J with the rare-earth substitution in a system with competing intrachain and interchain exchange interactions.
1980-01-01
Experiment Station, CE, Vicksburg, Miss. Carver, R. D., and Davidson, D. D. 1976. "Stability of Rubble-Mound Breakwater, Jubail Harbor, Saudi Arabia ...types of armor units were tested: smooth quarrystones (basalt), rough quarry- stones ( granite ), tetrapods, quadripods, tribars, modified cubes, hexa...electrical output of the wave gages was directly proportional to their submergence depth. Materials used 23. Rough granite stone (W ) with an average
Drift Hamiltonian in magnetic coordinates
White, R.B.; Boozer, A.H.; Hay, R.
1982-02-01
A Hamiltonian formulation of the guiding-center drift in arbitrary, steady state, magnetic and electric fields is given. The canonical variables of this formulation are simply related to the magnetic coordinates. The modifications required to treat ergodic magnetic fields using magnetic coordinates are explicitly given in the Hamiltonian formulation.
NASA Astrophysics Data System (ADS)
Ryder, N. C.; Hamilton, P.; Huffman, B. T.; Teng, P. K.; Weidberg, A. R.; Issever, C.
2011-10-01
High Luminosity LHC (HL-LHC) Inner Tracker designs may include the sharing of Timing, Trigger and Control (TTC) signals between several tracker modules. This is possible because the highest frequency signals are common to all modules. Such designs are an attractive option because they reduce the number of optical links required and hence the cost. These designs will require optical signal splitters that are radiation hard up to high doses and capable of operating in cold temperatures. Optical splitters are available as either fused-fibre splitters or Planar Light-wave Circuit (PLC) splitters. PLC splitters are preferable because they are smaller than fused-fibre splitters. A selection of PLC splitters from different manufacturers and of two different technologies (silica and glass based) have been tested for radiation hardness up to a dose of 500 kGy(Si) and for temperature stability. All the tested splitters displayed small increases in insertion losses ( < 0.1 dB) in reducing the operating temperature from 25°C to -25°C. The silica based splitters from all manufacturers did not exhibit significant radiation induced insertion losses, despite the high dose they were exposed to. The glass based sample, however, had a per channel radiation induced insertion loss of up to 1.16 dB. Whilst the silica based splitters can be considered as qualified for HL-LHC use with regards to radiation hardness, the glass technology would require further testing at a lower, more realistic, dose to also be considered as a potential component for HL-LHC upgrade designs.
Quan, Wei; Lv, Lin; Liu, Baiqi
2014-11-01
In order to improve the atom spin gyroscope's operational accuracy and compensate the random error caused by the nonlinear and weak-stability characteristic of the random atomic spin gyroscope (ASG) drift, the hybrid random drift error model based on autoregressive (AR) and genetic programming (GP) + genetic algorithm (GA) technique is established. The time series of random ASG drift is taken as the study object. The time series of random ASG drift is acquired by analyzing and preprocessing the measured data of ASG. The linear section model is established based on AR technique. After that, the nonlinear section model is built based on GP technique and GA is used to optimize the coefficients of the mathematic expression acquired by GP in order to obtain a more accurate model. The simulation result indicates that this hybrid model can effectively reflect the characteristics of the ASG's random drift. The square error of the ASG's random drift is reduced by 92.40%. Comparing with the AR technique and the GP + GA technique, the random drift is reduced by 9.34% and 5.06%, respectively. The hybrid modeling method can effectively compensate the ASG's random drift and improve the stability of the system.
Modeling and optimizing of the random atomic spin gyroscope drift based on the atomic spin gyroscope
Quan, Wei; Lv, Lin Liu, Baiqi
2014-11-15
In order to improve the atom spin gyroscope's operational accuracy and compensate the random error caused by the nonlinear and weak-stability characteristic of the random atomic spin gyroscope (ASG) drift, the hybrid random drift error model based on autoregressive (AR) and genetic programming (GP) + genetic algorithm (GA) technique is established. The time series of random ASG drift is taken as the study object. The time series of random ASG drift is acquired by analyzing and preprocessing the measured data of ASG. The linear section model is established based on AR technique. After that, the nonlinear section model is built based on GP technique and GA is used to optimize the coefficients of the mathematic expression acquired by GP in order to obtain a more accurate model. The simulation result indicates that this hybrid model can effectively reflect the characteristics of the ASG's random drift. The square error of the ASG's random drift is reduced by 92.40%. Comparing with the AR technique and the GP + GA technique, the random drift is reduced by 9.34% and 5.06%, respectively. The hybrid modeling method can effectively compensate the ASG's random drift and improve the stability of the system.
Evolution: drift will tear us apart.
Maderspacher, Florian
2012-11-06
That the widely scattered geographical distribution of some animals could be due to continental drift is a neat idea. Now, cave animals provide evidence for extreme long-term persistence on continents drifting apart.
1988-09-01
decomposed into a series of associated aperiodic solitary waves, as can be achieved for solutions of the KdV equation [11], is still under investigation. 3...The organization of the paper is as follows: In Section 2, we discuss aperiodic and periodic solitary wave solutions of a model equation with...Periodic Solitary Wave Solutions of the Nonlinear Klein Gordon Equation without Dispersion We shall take, as our model equation , the nonlinear Klein
Theory of semicollisional drift-interchange modes in cylindrical plasmas
Hahm, T.S.; Chen, L.
1985-01-01
Resistive interchange instabilities in cylindrical plasmas are studied, including the effects of electron diamagnetic drift, perpendicular resistivity, and plasma compression. The analyses are pertinent to the semicollisional regime where the effective ion gyro-radius is larger than the resistive layer width. Both analytical and numerical results show that the modes can be completely stabilized by the perpendicular plasma transport. Ion sound effects, meanwhile, are found to be negligible in the semicollisional regime.
A Pascalian lateral drift sensor
NASA Astrophysics Data System (ADS)
Jansen, H.
2016-09-01
A novel concept of a layer-wise produced semiconductor sensor for precise particle tracking is proposed herein. In contrast to common semiconductor sensors, local regions with increased doping concentration deep in the bulk termed charge guides increase the lateral drift of free charges on their way to the read-out electrode. This lateral drift enables charge sharing independent of the incident position of the traversing particle. With a regular grid of charge guides the lateral charge distribution resembles a normalised Pascal's triangle for particles that are stopped in depths lower than the depth of the first layer of the charge guides. For minimum ionising particles a sum of binomial distributions describes the lateral charge distribution. This concept decouples the achievable sensor resolution from the pitch size as the characteristic length is replaced by the lateral distance of the charge guides.
Random drift and culture change.
Bentley, R. Alexander; Hahn, Matthew W.; Shennan, Stephen J.
2004-01-01
We show that the frequency distributions of cultural variants, in three different real-world examples--first names, archaeological pottery and applications for technology patents--follow power laws that can be explained by a simple model of random drift. We conclude that cultural and economic choices often reflect a decision process that is value-neutral; this result has far-reaching testable implications for social-science research. PMID:15306315
Abstraction of Seepage into Drifts
M.L. Wilson; C.K. Ho
2000-09-26
A total-system performance assessment (TSPA) for a potential nuclear-waste repository requires an estimate of the amount of water that might contact waste. This paper describes the model used for part of that estimation in a recent TSPA for the Yucca Mountain site. The discussion is limited to estimation of how much water might enter emplacement drifts; additional considerations related to flow within the drifts, and how much water might actually contact waste, are not addressed here. The unsaturated zone at Yucca Mountain is being considered for the potential repository, and a drift opening in unsaturated rock tends to act as a capillary barrier and divert much of the percolating water around it. For TSPA, the important questions regarding seepage are how many waste packages might be subjected to water flow and how much flow those packages might see. Because of heterogeneity of the rock and uncertainty about the future (how the climate will evolve, etc.), it is not possible to predict seepage amounts or locations with certainty. Thus, seepage is treated as a stochastic quantity in TSPA simulations, with the magnitude and spatial distribution of seepage sampled from uncertainty distributions. The distillation of the essential components of process modeling into a form suitable for use in TSPA simulations is referred to as abstraction. In the following sections, seepage process models and abstractions will be summarized and then some illustrative results are presented.
Shear wall ultimate drift limits
Duffey, T.A.; Goldman, A.; Farrar, C.R.
1994-04-01
Drift limits for reinforced-concrete shear walls are investigated by reviewing the open literature for appropriate experimental data. Drift values at ultimate are determined for walls with aspect ratios ranging up to a maximum of 3.53 and undergoing different types of lateral loading (cyclic static, monotonic static, and dynamic). Based on the geometry of actual nuclear power plant structures exclusive of containments and concerns regarding their response during seismic (i.e.,cyclic) loading, data are obtained from pertinent references for which the wall aspect ratio is less than or equal to approximately 1, and for which testing is cyclic in nature (typically displacement controlled). In particular, lateral deflections at ultimate load, and at points in the softening region beyond ultimate for which the load has dropped to 90, 80, 70, 60, and 50 percent of its ultimate value, are obtained and converted to drift information. The statistical nature of the data is also investigated. These data are shown to be lognormally distributed, and an analysis of variance is performed. The use of statistics to estimate Probability of Failure for a shear wall structure is illustrated.
Grain Size of the North-Atlantic Drifts Sediments: is the Gloria Drift a Contourite Drift?
NASA Astrophysics Data System (ADS)
Dorokhova, E.; Sivkov, V.; Bashirova, L.
2015-12-01
Mean size of mineral particles of 10-63 fraction, so-called sortable silt mean size (SS) (McCave, 1995) and modes of grain-size distribution were used as proxies for reconstruction of paleocurrents intensity variations in the North Atlantic. It was assumed that the first mode (3-8 μm) is formed as the result of normal pelagic sedimentation and the second mode (10-30 μm) appears under the bottom currents influence. The sediments with bimodal grain-size distribution (the second mode varies from 10 to 28 μm) correlate with increased SS (up to 18-23 μm) in the Hatton and Snorry Drifts, indicating an increase in contour currents intensity during MIS 1, 3 and 5e. In contrast, there are no any relationships between grain size distribution (high SS values, appearance of bimodal distributions) and climatic cyclicity of variations in contour currents intensity at the Gloria Drift. Moreover, the Gloria Drift sediments differ from the contourite sediments of the Snorry and Hatton Drifts by shifting of the second mode toward the coarse particles (25-40 μm), higher sedimentation rates and higher IRD content. This evidence puts in doubt the contourite origin of the Gloria Drift. At the same time, we have identified the similarity between the Gloria Drift sediments and IRD-containing hemiturbidites of Labrador Sea (Hesse and Khodabakhsh, 2006). Fine-grained sediment lofting has been inferred for ice marginal regions of the northwest Labrador Sea. Sediment failure on the Labrador Slope predominantly produces muddy turbidity currents, because the slope sediments are mud-dominated. Their deposits are the indicative muddy spill-over turbidites of the NAMOC levees and the levees of the tributaries to the NAMOC. Dispersal of the IRD throughout the graded mud layers is evidence that the two processes, ice rafting and the delivery of the fines by lofting, occurred simultaneously. This work was supported by Russian Scientific Fund (grant No. 14-50-00095).
Sheared Flow Driven Drift Instability and Vortices in Dusty Plasmas with Opposite Polarity
NASA Astrophysics Data System (ADS)
Mushtaq, A.; Shah, AttaUllah; Ikram, M.; Clark, R. E. H.
2016-02-01
Low-frequency electrostatic drift waves are studied in an inhomogeneous dust magnetoplasma containing dust with components of opposite polarity. The drift waves are driven by the magnetic-field-aligned (parallel) sheared flows in the presence of electrons and ions. Due to sheared flow in the linear regime, the electrostatic dust drift waves become unstable. The conditions of mode instability, with the effects of dust streaming and opposite polarity, are studied. These are excited modes which gain large amplitudes and exhibit interactions among themselves. The interaction is governed by the Hasegawa-Mima (HM) nonlinear equation with vector nonlinearity. The stationary solutions of the HM equation in the form of a vortex chain and a dipolar vortex, including effects of dust polarity and electron (ion) temperatures, are studied. The relevance of the present work to space and laboratory four component dusty plasmas is noted.
NASA Technical Reports Server (NTRS)
Spencer, B., Jr.; Fournier, R. H.
1973-01-01
An investigation has been made at Mach numbers from 1.50 to 4.63 to determine systematically the effects of the addition and position of outboard stabilizers and vertical- and vee-tail configurations on the performance and stability characteristics of a low-wave-drag elliptical body. The basic body shape was a zero-lift hypersonic minimum-wave-drag body as determined for the geometric constraints of length and volume. The elliptical cross section had an axis ratio of 2 (major axis horizontal) and an equivalent fineness ratio of 6.14. Base-mounted outboard stabilizers were at various dihedral angles from 90 deg to minus 90 deg with and without a single center-line vertical tail or a vee-tail. The angle of attack was varied from about minus 6 to 27 deg at sideslip angles of 0 and 5 deg and a constant Reynolds number of 4.58 x one million (based on body length).
NASA Technical Reports Server (NTRS)
Lerche, I.
1978-01-01
One-dimensional self-similar isothermal flow behind a blast wave propagating in a medium whose density varies with distance is investigated for the cases of one-dimensional and two-dimensional flow. The isothermal flow model is adopted as an alternative to adiabatic models of self-similar flow, which neglect heat flux. The topology of the one-dimensional flow solutions, the singularities, and the influence of boundary conditions are discussed; the instability of the isothermal blast waves against nonself-similar perturbations is also considered. The number of critical points in the two-dimensional solutions is found to vary from the number in the one-dimensional problem.
Charge injectors of ALICE Silicon Drift Detector
NASA Astrophysics Data System (ADS)
Rashevsky, A.; Batigne, G.; Beole, S.; Coli, S.; Crescio, E.; Deremigis, P.; Giraudo, G.; Mazza, G.; Prino, F.; Riccati, L.; Rivetti, A.; Toscano, L.; Tosello, F.; Vacchi, A.; Wheadon, R.; Zampa, G.
2007-03-01
Large area, 7.25×8.76 cm2, Silicon Drift Detector (SDD) has been developed for the ALICE experiment at CERN [A. Vacchi, et al., Nucl. Instr. and Meth. A 306 (1991) 187; A. Rashevsky, et al., Nucl. Instr. and Meth. A 461 (2001) 133-138; A. Rashevsky, et al., Nucl. Instr. and Meth. A 485 (2002) 54; P. Burger, C. Piemonte, A. Rashevsky, A. Roncastri, A. Vacchi, INFN/TC-02/07; C. Piemonte, A. Rashevsky, INFN/TC-02/08; C. Piemonte, A. Rashevsky, D. Nouais, INFN/TC-00/04. C. Piemonte, A. Rashevsky, A. Vacchi, ALICE-INT-2002-15, 2002; Inner Tracking System, CERN/LHCC, June 1999]. SDDs form two out of six cylindrical layers of the ALICE inner tracking system. The 260 high-quality SDDs needed to equip these two layers have been selected. One of the detector design elements devoted to allow controlled operating conditions is the on-board arrays of point-like charge injectors [D. Nouais, et al., CERN-ALICE-PUB-99-31; V. Bonvicini, et al., Il Nuovo Cimento 112AN (1-2) (1999) 137-146]. In the case of an SDD they are essential to trace, with the required frequency and precision, the changes in drift velocity induced by temperature variations. In order to ensure operating stability during the 10 years of the ALICE experiment the bias scheme of the charge injectors exploits the electrical properties not only of a detector itself, but also those of the cables mounted onto it, thus constituting a module. Computer simulations of the equivalent circuit revealed a significant improvement of the injection efficiency. Subsequent experimental tests of the first assembled modules confirmed the predicted performances. We report the layout of the charge injectors integrated in the ALICE SDD, as well as test results.
NASA Astrophysics Data System (ADS)
Hou, Hao; Wang, Xuanze; Zhai, Zhongsheng
2016-01-01
A circuit processing method is present to restrain DC drift after analyzing the traditional signal processing method of interferometry for micro vibration measurement. At first, the circuit diagram is designed and its mathematical model is built, then the theoretical equations of the output signal are derived with the practical parameters. By using SIMULINK simulation, the process for restraining DC drift is present on the conditions of the variations of background intensity. The validity of feedback circuit was verified through analyzing the real experiment data. Theoretical predictions match simulation results, showing that this method effectively restrains DC drift for interferometry of micro vibration measurement and it greatly improves the system's stability.
Ohmae, Noriaki; Moriwaki, Shigenori; Mio, Norikatsu
2010-07-01
Second-generation gravitational wave detectors require a highly stable laser with an output power greater than 100 W to attain their target sensitivity. We have developed a frequency stabilization system for a 100-W injection-locked Nd:YAG (yttrium aluminum garnet) laser. By placing an external wideband electro-optic modulator used as a fast-frequency actuator in the optical path of the slave output, we can circumvent a phase delay in the frequency control loop originating from the pole of an injection-locked slave cavity. Thus, we have developed an electro-optic modulator made of a MgO-doped stoichiometric LiNbO(3) crystal. Using this modulator, we achieve a frequency control bandwidth of 800 kHz and a control gain of 180 dB at 1 kHz. These values satisfy the requirement for a laser frequency control loop in second-generation gravitational wave detectors.
NASA Astrophysics Data System (ADS)
Ohmae, Noriaki; Moriwaki, Shigenori; Mio, Norikatsu
2010-07-01
Second-generation gravitational wave detectors require a highly stable laser with an output power greater than 100 W to attain their target sensitivity. We have developed a frequency stabilization system for a 100-W injection-locked Nd:YAG (yttrium aluminum garnet) laser. By placing an external wideband electro-optic modulator used as a fast-frequency actuator in the optical path of the slave output, we can circumvent a phase delay in the frequency control loop originating from the pole of an injection-locked slave cavity. Thus, we have developed an electro-optic modulator made of a MgO-doped stoichiometric LiNbO3 crystal. Using this modulator, we achieve a frequency control bandwidth of 800 kHz and a control gain of 180 dB at 1 kHz. These values satisfy the requirement for a laser frequency control loop in second-generation gravitational wave detectors.
A Stokes drift approximation based on the Phillips spectrum
NASA Astrophysics Data System (ADS)
Breivik, Øyvind; Bidlot, Jean-Raymond; Janssen, Peter A. E. M.
2016-04-01
A new approximation to the Stokes drift velocity profile based on the exact solution for the Phillips spectrum is explored. The profile is compared with the monochromatic profile and the recently proposed exponential integral profile. ERA-Interim spectra and spectra from a wave buoy in the central North Sea are used to investigate the behavior of the profile. It is found that the new profile has a much stronger gradient near the surface and lower normalized deviation from the profile computed from the spectra. Based on estimates from two open-ocean locations, an average value has been estimated for a key parameter of the profile. Given this parameter, the profile can be computed from the same two parameters as the monochromatic profile, namely the transport and the surface Stokes drift velocity.
Test particle study of ion transport in drift type turbulence
Vlad, M.; Spineanu, F.
2013-12-15
Ion transport regimes in drift type turbulence are determined in the frame of a realistic model for the turbulence spectrum based on numerical simulations. The model includes the drift of the potential with the effective diamagnetic velocity, turbulence anisotropy, and dominant waves. The effects of the zonal flow modes are also analyzed. A semi-analytical method that is able to describe trajectory stochastic trapping or eddying is used for obtaining the transport coefficients as function of the parameters of the turbulence. Analytical approximations of the transport coefficients are derived from the results. They show the transition from Bohm to gyro-Bohm scaling as plasma size increases in very good agreement with the numerical simulations.
Karpitschka, Stefan; Riegler, Hans
2012-08-10
Capillarity always favors drop fusion. Nevertheless, sessile drops from different but completely miscible liquids often do not fuse instantaneously upon contact. Rather, intermediate noncoalescence is observed. Two separate drop bodies, connected by a thin liquid neck, move over the substrate. Supported by new experimental data, a thin film hydrodynamic analysis of this state is presented. Presumably advective and diffusive volume fluxes in the neck region establish a localized and temporarily stable surface tension gradient. This induces a local surface (Marangoni) flow that stabilizes a traveling wave, i.e., the observed moving twin drop configuration. The theoretical predictions are in excellent agreement with the experimental findings.
NASA Astrophysics Data System (ADS)
Makarov, D. V.; Uleysky, M. Yu.
2017-02-01
Binary discrete nonlinear Schrödinger equation is used to describe dynamics of two-species Bose-Einstein condensate loaded into an optical lattice. Linear inter-species coupling leads to Rabi transitions between the species. In the regime of strong nonlinearity, a wavepacket corresponding to condensate separates into localized and ballistic fractions. Localized fraction is predominantly formed by immiscible solitons consisted of only one species. Immiscible solitons are formed from initially non-separated states after transient chaotic regime. We calculate the finite-time Lyapunov exponent as a rate of wavepacket divergence in the Hilbert space. Appearance of immiscible solitons to spontaneous self-stabilization of the wavepacket. It is found that onset of chaos is accompanied by fast variations of interaction energy and energy of inter-site tunneling. Crossover to self-stabilization is accompanied by reduction of condensate density due to emittance of ballistically propagating waves.
Spiral biasing adaptor for use in Si drift detectors and Si drift detector arrays
Li, Zheng; Chen, Wei
2016-07-05
A drift detector array, preferably a silicon drift detector (SDD) array, that uses a low current biasing adaptor is disclosed. The biasing adaptor is customizable for any desired geometry of the drift detector single cell with minimum drift time of carriers. The biasing adaptor has spiral shaped ion-implants that generate the desired voltage profile. The biasing adaptor can be processed on the same wafer as the drift detector array and only one biasing adaptor chip/side is needed for one drift detector array to generate the voltage profiles on the front side and back side of the detector array.
NASA Astrophysics Data System (ADS)
Alaïs, Mazières; Hervé, Gillet; Bruno, Castelle; Corentin, Guyot; Cyril, Mallet
2013-04-01
the canyon. (3) The hydrodynamic modelling shows that for low- to moderate-energy wave conditions wave-driven circulations cannot transport beach sediment towards the canyon's head as a northward current is observed due to offshore wave refraction across the canyon. When wave energy exceeds a threshold, the rotational nature of surf zone circulations changes of sign and wave-induced currents have the potential to transport massive quantities of beach sands in the canyon's head. (4) The morphological evolution between 1998 and 2012 is significant. The bottom of the head of the canyon has been substantially reworked by numerous sediment destabilizations and the south rim was strongly eroded. Conversely, the proximal ramp, closer to the coast, appears to be relatively stable over the past 14 years. In this highly dynamic environment, the littoral drift sediment supply appears as a potential stabilizer of disturbing retrogressive erosion that is going on in the head of the canyon. To explain the presence of more muddy sediments in the canyon head, we must consider in further study the contribution of the Ardour river muddy plume.
Remarkable Stability of Charge Density Wave Order in La1.875 Ba0.125 CuO4
NASA Astrophysics Data System (ADS)
Chen, X. M.; Thampy, V.; Mazzoli, C.; Barbour, A. M.; Miao, H.; Gu, G. D.; Cao, Y.; Tranquada, J. M.; Dean, M. P. M.; Wilkins, S. B.
2016-10-01
The occurrence of charge-density-wave (CDW) order in underdoped cuprates is now well established, although the precise nature of the CDW and its relationship with superconductivity is not. Theoretical proposals include contrasting ideas such as that pairing may be driven by CDW fluctuations or that static CDWs may intertwine with a spatially modulated superconducting wave function. We test the dynamics of CDW order in La1.825 Ba0.125 CuO4 by using x-ray photon correlation spectroscopy at the CDW wave vector, detected resonantly at the Cu L3 edge. We find that the CDW domains are strikingly static, with no evidence of significant fluctuations up to 2 ¾ h . We discuss the implications of these results for some of the competing theories.
Remarkable Stability of Charge Density Wave Order in La_{1.875}Ba_{0.125}CuO_{4}.
Chen, X M; Thampy, V; Mazzoli, C; Barbour, A M; Miao, H; Gu, G D; Cao, Y; Tranquada, J M; Dean, M P M; Wilkins, S B
2016-10-14
The occurrence of charge-density-wave (CDW) order in underdoped cuprates is now well established, although the precise nature of the CDW and its relationship with superconductivity is not. Theoretical proposals include contrasting ideas such as that pairing may be driven by CDW fluctuations or that static CDWs may intertwine with a spatially modulated superconducting wave function. We test the dynamics of CDW order in La_{1.825}Ba_{0.125}CuO_{4} by using x-ray photon correlation spectroscopy at the CDW wave vector, detected resonantly at the Cu L_{3} edge. We find that the CDW domains are strikingly static, with no evidence of significant fluctuations up to 2 ¾ h. We discuss the implications of these results for some of the competing theories.
Remarkable Stability of Charge Density Wave Order in La1.875Ba0.125CuO4
Chen, X. M.; Thampy, V.; Mazzoli, C.; ...
2016-10-11
The occurrence of charge-density-wave (CDW) order in underdoped cuprates is now well established, although the precise nature of the CDW and its relationship with superconductivity is not. Theoretical proposals include contrasting ideas such as that pairing may be driven by CDW uctuations or that static CDWs may intertwine with a spatially-modulated superconducting wave function. We test the dynamics of CDW order in La1.875Ba0.125CuO4 by using x-ray photon correlation spectroscopy (XPCS) at the CDW wave vector, detected resonantly at the Cu L3-edge. We nd that the CDW domains are strikingly static, with no evidence of signi cant uctuations up to 2more » 3/4 hours. We discuss the implications of these results for some of the competing theories.« less
NASA Astrophysics Data System (ADS)
Andreas, Edgar L.
2011-12-01
A common parametrization over snow-covered surfaces that are undergoing saltation is that the aerodynamic roughness length for wind speed ( z 0) scales as {α u_ast^2/g}, where u * is the friction velocity, g is the acceleration of gravity, and α is an empirical constant. Data analyses seem to support this scaling: many published plots of z 0 measured over snow demonstrate proportionality to {u_ast^2 }. In fact, I show similar plots here that are based on two large eddy-covariance datasets: one collected over snow-covered Arctic sea ice; another collected over snow-covered Antarctic sea ice. But in these and in most such plots from the literature, the independent variable, u *, was used to compute z 0 in the first place; the plots thus suffer from fictitious correlation that causes z 0 to unavoidably increase with u * without any intervening physics. For these two datasets, when I plot z 0 against u * derived from a bulk flux algorithm—and thus minimize the fictitious correlation— z 0 is independent of u * in the drifting snow region, u * ≥ 0.30 ms-1. I conclude that the relation {z_0 = α u_ast^2/g} when snow is drifting is a fallacy fostered by analyses that suffer from fictitious correlation.
Wen, Xiao-Yong; Yan, Zhenya; Malomed, Boris A
2016-12-01
An integrable system of two-component nonlinear Ablowitz-Ladik equations is used to construct complex rogue-wave (RW) solutions in an explicit form. First, the modulational instability of continuous waves is studied in the system. Then, new higher-order discrete two-component RW solutions of the system are found by means of a newly derived discrete version of a generalized Darboux transformation. Finally, the perturbed evolution of these RW states is explored in terms of systematic simulations, which demonstrates that tightly and loosely bound RWs are, respectively, nearly stable and strongly unstable solutions.
NASA Astrophysics Data System (ADS)
Ding, Min; Li, Yachun
2017-04-01
We study the 1-D piston problem for the relativistic Euler equations under the assumption that the total variations of both the initial data and the velocity of the piston are sufficiently small. By a modified wave front tracking method, we establish the global existence of entropy solutions including a strong rarefaction wave without restriction on the strength. Meanwhile, we consider the convergence of the entropy solutions to the corresponding entropy solutions of the classical non-relativistic Euler equations as the light speed c→ +∞.
NASA Astrophysics Data System (ADS)
Wen, Xiao-Yong; Yan, Zhenya; Malomed, Boris A.
2016-12-01
An integrable system of two-component nonlinear Ablowitz-Ladik equations is used to construct complex rogue-wave (RW) solutions in an explicit form. First, the modulational instability of continuous waves is studied in the system. Then, new higher-order discrete two-component RW solutions of the system are found by means of a newly derived discrete version of a generalized Darboux transformation. Finally, the perturbed evolution of these RW states is explored in terms of systematic simulations, which demonstrates that tightly and loosely bound RWs are, respectively, nearly stable and strongly unstable solutions.
WORLD SURFACE CURRENTS FROM SHIP'S DRIFT OBSERVATIONS
Duncan, C.P.; Schladow, S.G.
1980-11-01
Over 4 million observations of ship's drift are on file at the U.S. National Oceanographic Data Centre, in Washington, D. C., representing a vast amount of information on ocean surface currents. The observed drift speeds are dependent on the frequency of occurence of the particular current speeds and the frequency of observation. By comparing frequency of observation with the drift speeds observed it is possible to confirm known current patterns and detect singularities in surface currents.
Electron injection in semiconductor drift detectors
Rehak, P. ); Gatti, E.; Longoni, A.; Sampietro, M.; Castoldi, A. ); Vacchi, A. )
1990-01-01
The paper reports the first successful results of a simple MOS structure to inject electrons at a given position in Silicon Drift Detectors. The structure allows on-line calibration of the drift velocity of electrons within the detector. The calibration is a practical method to trace the temperature dependence of the electron mobility. Several of these injection structures can be implemented in silicon drift detectors without additional steps in the fabrication process. 5 refs., 11 figs.
Drift chamber tracking with neural networks
Lindsey, C.S.; Denby, B.; Haggerty, H.
1992-10-01
We discuss drift chamber tracking with a commercial log VLSI neural network chip. Voltages proportional to the drift times in a 4-layer drift chamber were presented to the Intel ETANN chip. The network was trained to provide the intercept and slope of straight tracks traversing the chamber. The outputs were recorded and later compared off line to conventional track fits. Two types of network architectures were studied. Applications of neural network tracking to high energy physics detector triggers is discussed.
The collisional drift mode in a partially ionized plasma. [in the F region
NASA Technical Reports Server (NTRS)
Hudson, M. K.; Kennel, C. F.
1974-01-01
The structure of the drift instability was examined in several density regimes. Let sub e be the total electron mean free path, k sub z the wave-vector component along the magnetic field, and the ratio of perpendicular ion diffusion to parallel electron streaming rates. At low densities (k sub z lambda 1) the drift mode is isothermal and should be treated kineticly. In the finite heat conduction regime square root of m/M k sub z Lambda sub 1) the drift instability threshold is reduced at low densities and increased at high densities as compared to the isothermal threshold. Finally, in the energy transfer limit (k sub z kambda sub e square root of m/M) the drift instability behaves adiabatically in a fully ionized plasma and isothermally in a partially ionized plasma for an ion-neutral to Coulomb collision frequency ratio.
Drift-Alfven instabilities of a finite beta plasma shear flow along a magnetic field
NASA Astrophysics Data System (ADS)
Mikhailenko, V. V.; Mikhailenko, V. S.; Lee, Hae June
2016-02-01
It was derived that the drift-Alfven instabilities with the shear flow parallel to the magnetic field have significant difference from the drift-Alfven instabilities of a shearless plasma when the ion temperature is comparable with electron temperature for a finite plasma beta. The velocity shear not only modifies the frequency and the growth rate of the known drift-Alfven instability, which develops due to the inverse electron Landau damping, but also triggers a combined effect of the velocity shear and the inverse ion Landau damping, which manifests the development of the ion kinetic shear-flow-driven drift-Alfven instability. The excited unstable waves have the phase velocities along the magnetic field comparable with the ion thermal velocity, and the growth rate is comparable with the frequency. The development of this instability may be the efficient mechanism of the ion energization in shear flows.
Decameter type III bursts with positive and negative frequency drift rates
NASA Astrophysics Data System (ADS)
Melnik, V. N.; Brazhenko, A. I.; Konovalenko, A. A.; Briand, C.; Dorovskyy, V. V.; Zarka, P.; Frantzusenko, A. V.; Rucker, H. O.; Rutkevych, B. P.; Panchenko, M.; Zaqarashvili, T.; Shergelashvili, B.
2013-09-01
We report about observations of decameter type III bursts whose frequency drift rates vary their signs from negative to positive. Moreover drift rates of some bursts vary the sign some times. Positive drift rates for some bursts are changed from 0.44 MHz/s to 12 MHz/s. At the same time the negative drift rates of these bursts are standard values for decameter type III bursts. A possible interpretation of such phenomenon on the base of plasma mechanism of type III burst generation is discussed. The sense of this interpretation is that group velocity of type III electromagnetic waves generated by fast electrons at some conditions can be smaller than velocity of these electrons.
NASA Astrophysics Data System (ADS)
Gogoi, R.; Kalita, L.; Devi, N.
2010-02-01
Much interest was shown towards the studies on nonlinear stability in the late sixties. Plasma instabilities play an important role in plasma dynamics. More attention has been given towards stability analysis after recognizing that they are one of the principal obstacles in the way of a successful resolution of the problem of controlled thermonuclear fusion. Nonlinearity and dispersion are the two important characteristics of plasma instabilities. Instabilities and nonlinearity are the two important and interrelated terms. In our present work, the continuity and momentum equations for both ions and electrons together with the Poisson equation are considered as cold plasma model. Then we have adopted the modified reductive perturbation technique (MRPT) from Demiray [1] to derive the higher order equation of the Nonlinear Schrödinger equation (NLSE). In this work, detailed mathematical expressions and calculations are done to investigate the changing character of the modulation of ion acoustic plasma wave through our derived equation. Thus we have extended the application of MRPT to derive the higher order equation. Both progressive wave solutions as well as steady state solutions are derived and they are plotted for different plasma parameters to observe dark/bright solitons. Interesting structures are found to exist for different plasma parameters.
Gravitational radiation from neutron stars deformed by crustal Hall drift
NASA Astrophysics Data System (ADS)
Suvorov, A. G.; Mastrano, A.; Geppert, U.
2016-07-01
A precondition for the radio emission of pulsars is the existence of strong, small-scale magnetic field structures (`magnetic spots') in the polar cap region. Their creation can proceed via crustal Hall drift out of two qualitatively and quantitatively different initial magnetic field configurations: a field confined completely to the crust and another which penetrates the whole star. The aim of this study is to explore whether these magnetic structures in the crust can deform the star sufficiently to make it an observable source of gravitational waves. We model the evolution of these field configurations, which can develop, within ˜104-105 yr, magnetic spots with local surface field strengths ˜1014 G maintained over ≳106 yr. Deformations caused by the magnetic forces are calculated. We show that, under favourable initial conditions, a star undergoing crustal Hall drift can have ellipticity ɛ ˜ 10-6, even with sub-magnetar polar field strengths, after ˜105 yr. A pulsar rotating at ˜102 Hz with such ɛ is a promising gravitational wave source candidate. Since such large deformations can be caused only by a particular magnetic field configuration that penetrates the whole star and whose maximum magnetic energy is concentrated in the outer core region, gravitational wave emission observed from radio pulsars can thus inform us about the internal field structures of young neutron stars.
THERMAL EVALUATION OF DIFFERENT DRIFT DIAMETER SIZES
H.M. Wade
1999-01-04
The purpose of this calculation is to estimate the thermal response of a repository-emplaced waste package and its corresponding drift wall surface temperature with different drift diameters. The case examined is that of a 21 pressurized water reactor (PWR) uncanistered fuel (UCF) waste package loaded with design basis spent nuclear fuel assemblies. This calculation evaluates a 3.5 meter to 6.5 meter drift diameter range in increments of 1.0 meters. The time-dependent temperatures of interest, as determined by this calculation, are the spent nuclear fuel cladding temperature, the waste package surface temperature, and the drift wall surface temperature.
Biology Undergraduates’ Misconceptions about Genetic Drift
Andrews, T. M.; Price, R. M.; Mead, L. S.; McElhinny, T. L.; Thanukos, A.; Perez, K. E.; Herreid, C. F.; Terry, D. R.; Lemons, P. P.
2012-01-01
This study explores biology undergraduates’ misconceptions about genetic drift. We use qualitative and quantitative methods to describe students’ definitions, identify common misconceptions, and examine differences before and after instruction on genetic drift. We identify and describe five overarching categories that include 16 distinct misconceptions about genetic drift. The accuracy of students’ conceptions ranges considerably, from responses indicating only superficial, if any, knowledge of any aspect of evolution to responses indicating knowledge of genetic drift but confusion about the nuances of genetic drift. After instruction, a significantly greater number of responses indicate some knowledge of genetic drift (p = 0.005), but 74.6% of responses still contain at least one misconception. We conclude by presenting a framework that organizes how students’ conceptions of genetic drift change with instruction. We also articulate three hypotheses regarding undergraduates’ conceptions of evolution in general and genetic drift in particular. We propose that: 1) students begin with undeveloped conceptions of evolution that do not recognize different mechanisms of change; 2) students develop more complex, but still inaccurate, conceptual frameworks that reflect experience with vocabulary but still lack deep understanding; and 3) some new misconceptions about genetic drift emerge as students comprehend more about evolution. PMID:22949422
A maximally informative version of inelastic scattering of electromagnetic waves by Langmuir waves
NASA Astrophysics Data System (ADS)
Erofeev, V. I.
2015-09-01
The concept of informativeness of nonlinear plasma physics scenarios is explained. Natural ideas of developing highly informative models of plasma kinetics are spelled out. A maximally informative version of inelastic scattering of electromagnetic waves by Langmuir waves in a weakly turbulent inhomogeneous plasma is developed with consideration of possible changes in wave polarization. In addition, a new formula for wave drift in spatial positions and wave vectors is derived. New scenarios of the respective wave drift and inelastic scattering are compared with the previous visions. The results indicate the need for further revision of the traditional understanding of nonlinear plasma phenomena.
A maximally informative version of inelastic scattering of electromagnetic waves by Langmuir waves
Erofeev, V. I.
2015-09-15
The concept of informativeness of nonlinear plasma physics scenarios is explained. Natural ideas of developing highly informative models of plasma kinetics are spelled out. A maximally informative version of inelastic scattering of electromagnetic waves by Langmuir waves in a weakly turbulent inhomogeneous plasma is developed with consideration of possible changes in wave polarization. In addition, a new formula for wave drift in spatial positions and wave vectors is derived. New scenarios of the respective wave drift and inelastic scattering are compared with the previous visions. The results indicate the need for further revision of the traditional understanding of nonlinear plasma phenomena.
ERIC Educational Resources Information Center
Price, Rebecca M.; Andrews, Tessa C.; McElhinny, Teresa L.; Mead, Louise S.; Abraham, Joel K.; Thanukos, Anna; Perez, Kathryn E.
2014-01-01
Understanding genetic drift is crucial for a comprehensive understanding of biology, yet it is difficult to learn because it combines the conceptual challenges of both evolution and randomness. To help assess strategies for teaching genetic drift, we have developed and evaluated the Genetic Drift Inventory (GeDI), a concept inventory that measures…
The spaced antenna drift method
NASA Technical Reports Server (NTRS)
Hocking, W. K.
1983-01-01
The spaced antenna drift method is a simple and relatively inexpensive method for determination of atmospheric wind velocities using radars. The technique has been extensively tested in the mesosphere at high and medium frequencies, and found to give reliable results. Recently, the method has also been applied to VHF observations of the troposphere and stratosphere, and results appear to be reliable. This paper discusses briefly the principle of the method, and investigates both its strengths and weaknesses. Some discussions concerning criticisms of the technique are also given, and it is concluded that while these criticisms may be of some concern at times, appropriate care can ensure that the method is at least as viable as any other method of remote wind measurement. At times, the technique has definite advantages.
The ARGUS microvertex drift chamber
NASA Astrophysics Data System (ADS)
Michel, E.; Schmidt-Parzefall, W.; Appuhn, R. D.; Buchmüller, J.; Kolanoski, H.; Kreimeier, B.; Lange, A.; Siegmund, T.; Walther, A.; Edwards, K. W.; Fernholz, R. C.; Kapitza, H.; MacFarlane, D. B.; O'Neill, M.; Parsons, J. A.; Prentice, J. D.; Seidel, S. C.; Tsipolitis, G.; Ball, S.; Babaev, A.; Danilov, M.; Tichomirov, I.
1989-11-01
The ARGUS collaboration is currently building a new microvertex drift chamber (μVDC) as an upgrade of their detector. The μVDC is optimized for B-meson physics at DORIS energies. Important design features are minimal multiple scattering for low-momentum particles and three-dimensional reconstruction of decay vertices with equal resolutions in r- φ and r- z. Vertex resolutions of 15-25 μm are expected. Prototypes of the μVDC have been tested with different gas mixtures at various pressures. Spatial resolutions as small as 20 μm were obtained using CO 2/propane at 4 bar and DME at 1 bar. New readout electronics have been developed for the μVDC aiming at low thresholds for the TDC measurements. Employing a novel idea for noise and cross-talk suppression, which is based on a discrimination against short pulses, very low threshold settings are possible.
Single wire drift chamber design
Krider, J.
1987-03-30
This report summarizes the design and prototype tests of single wire drift chambers to be used in Fermilab test beam lines. The goal is to build simple, reliable detectors which require a minimum of electronics. Spatial resolution should match the 300 ..mu..m rms resolution of the 1 mm proportional chambers that they will replace. The detectors will be used in beams with particle rates up to 20 KHz. Single track efficiency should be at least 99%. The first application will be in the MT beamline, which has been designed for calibration of CDF detectors. A set of four x-y modules will be used to track and measure the momentum of beam particles.
NASA Technical Reports Server (NTRS)
Culick, F. E. C.
1976-01-01
The general problem of the nonlinear growth and limiting amplitude of acoustic waves in a combustion chamber is treated in three parts: (1) the general conservation equations are expanded in two small parameters, and then combined to yield a nonlinear inhomogeneous wave equation, (2) the unsteady pressure and velocity fields are expressed as a synthesis of the normal modes of the chamber, but with unknown time-varying amplitudes, and (3) the system of nonlinear equations is treated by the method of averaging to produce a set of coupled nonlinear first order differential equations for the amplitudes and phases of the modes. This approximate analysis is applied to the investigation of the unstable motions in a solid propellant rocket engine and in a T burner.
Chen, Hongjian; Sun, Dewei; Deng, Boxin; Li, Jinwei; Liu, Yuanfa; Wang, Fei
2016-01-01
Wheat germ (WG) is quite susceptible to deterioration due to the presence of lipase (LA) and lipoxygenase (LOX). Therefore it is indispensable to adopt a stabilization step to decrease the activity of LA and LOX while retaining a maximum level of nutrients. But over-drying can make foodstuffs more susceptible to autoxidation. So a stabilization protocol for inactivating LA and LOX of WG with a temperature- controlled short wave infrared (SIR) radiation system was adopted to retard its rancidity and retain a maximum level of fat-soluble nutrients. Meanwhile, the critical storage water activity (Aw) of WG for inhibiting both hydrolytic and oxidative rancidity was appraised. Results indicate that WG irradiated at 90°C for 20 min acquired the optimal stabilization effect, and its residual LA and LOX activity were 18.02% and 19.21%, respectively. At this condition, the free fatty acids (FFA) content and peroxide value (PV) increment of WG oil at 40°C remained below 5% and 2.24 meq O2/kg for 60 days, respectively. The residual Aw of this WG sample was 0.13, and it is near the Aw corresponding to its monolayer. No significant decrease of fatty acids was observed during SIR processing, while about 96.42% of its original tocopherols still retained in WG treated at 90°C for 20 min. PMID:27936025
Wave-Coupled Millimeter-Wave Electro-Optic Techniques
2001-03-01
This report details results on two antenna-coupled millimeter-wave electro - optic modulators, the slot-vee antenna-coupled modulator and a 94 GHz...study of the effects of velocity mismatch on linearized electro - optic modulators was made and the results published. A key result was that directional...drift in electro - optic modulators was made and protons were determined to be the cause. Several inventions were made to reduce or eliminate proton-caused bias drift.
Improving Drift Correction by Double Projection Preprocessing in Gas Sensor Arrays
NASA Astrophysics Data System (ADS)
Padilla, M.; Perera, A.; Montoliu, I.; Chaudry, A.; Persaud, K.; Marco, S.
2009-05-01
It is well known that gas chemical sensors are strongly affected by drift. Drift consist on changes in sensors responses along the time, which make that initial statistical models for gas or odor recognition become useless after a period of time of about weeks. Gas sensor arrays based instruments periodically need calibrations that are expensive and laborious. Many different statistical methods have been proposed to extend time between recalibrations. In this work, a simple preprocessing technique based on a double projection is proposed as a prior step to a posterior drift correction algorithm (in this particular case, Direct Orthogonal Signal Correction). This method highly improves the time stability of data in relation with the one obtained by using only such drift correction method. The performance of this technique will be evaluated on a dataset composed by measurements of three analytes by a polymer sensor array along ten months.
AN IMPLICIT"DRIFT-LORENTZ" PARTICLE MOVER FOR PLASMA AND BEAM SIMULATIONS
Friedman, A.; Grote, D.P.; Vay, J.-L; Cohen, R.H.
2008-07-15
In order to efficiently perform particle simulations in systems with widely varying magnetization, we developed a drift-Lorentz mover, which interpolates between full particle dynamics and drift kinetics in such a way as to preserve a physically correct gyroradius and particle drifts for both large and small ratios of the timestep to the cyclotron period. In order to extend applicability of the mover to systems with plasma frequency exceeding the cyclotron frequency such as one may have with fully neutralized drift compression of a heavy-ion beam we have developed an implicit version of the mover. A first step in this direction, in which the polarization charge was added to the field solver, was described previously. Here we describe a fully implicit algorithm (which is analogous to the direct-implicit method for conventionalparticle-in-cell simulation), summarize a stability analysis of it, and describe several tests of the resultant code.
An Implicit "Drift-Lorentz" Mover for Plasma and Beam Simulations
Cohen, R H; Friedman, A; Grote, D P; Vay, J
2009-02-12
In order to efficiently perform particle simulations in systems with widely varying magnetization, we developed a drift-Lorentz mover, which interpolates between full particle dynamics and drift kinetics in such a way as to preserve a physically correct gyroradius and particle drifts for both large and small ratios of the timestep to the cyclotron period. In order to extend applicability of the mover to systems with plasma frequency exceeding the cyclotron frequency such as one may have with fully neutralized drift compression of a heavy-ion beam we have developed an implicit version of the mover. A first step in this direction, in which the polarization charge was added to the field solver, was described previously. Here we describe a fully implicit algorithm (which is analogous to the direct-implicit method for conventional particle-in-cell simulation), summarize a stability analysis of it, and describe several tests of the resultant code.
Quantum-corrected drift-diffusion models for transport in semiconductor devices
De Falco, Carlo; Gatti, Emilio; Lacaita, Andrea L.; Sacco, Riccardo . E-mail: riccardo.sacco@mate.polimi.it
2005-04-10
In this paper, we propose a unified framework for Quantum-corrected drift-diffusion (QCDD) models in nanoscale semiconductor device simulation. QCDD models are presented as a suitable generalization of the classical drift-diffusion (DD) system, each particular model being identified by the constitutive relation for the quantum-correction to the electric potential. We examine two special, and relevant, examples of QCDD models; the first one is the modified DD model named Schroedinger-Poisson-drift-diffusion, and the second one is the quantum-drift-diffusion (QDD) model. For the decoupled solution of the two models, we introduce a functional iteration technique that extends the classical Gummel algorithm widely used in the iterative solution of the DD system. We discuss the finite element discretization of the various differential subsystems, with special emphasis on their stability properties, and illustrate the performance of the proposed algorithms and models on the numerical simulation of nanoscale devices in two spatial dimensions.
DRIFT: a directionally sensitive dark matter detector
NASA Astrophysics Data System (ADS)
Morgan, Ben; Drift; Uk Dark Matter Collaborations
2003-11-01
Directional Recoil Identification From Tracks-I (DRIFT) is the world's first WIMP dark matter detector with sensitivity to the directions of nuclear recoils. The distribution of WIMP induced nuclear recoil directions offers the most powerful way of positively identifying a WIMP signal. This paper discusses the DRIFT-I detector and considers future high spatial resolution readout schemes.
Spray drift reduction test method correlation
Technology Transfer Automated Retrieval System (TEKTRAN)
ASTM Standard E609 Terminology Relating to Pesticides defines drift as “The physical movement of an agrochemical through the air at the time of application or soon thereafter to any non or off target site.” Since there are many commercial tank mix adjuvants designed to reduce spray drift, ASTM esta...
The high momentum spectrometer drift chambers
NASA Astrophysics Data System (ADS)
Abbott, D.; Baker, O. K.; Beaufait, J.; Bennett, C.; Bryant, E.; Carlini, R.; Kross, B.; McCauley, A.; Naing, W.; Shin, T.; Vulcan, W.
1992-12-01
The High Momentum Spectrometer in Hall C will use planar drift chambers for charged particle track reconstruction. The chambers are constructed using well understood technology and a conventional gas mixture. Two (plus one spare) drift chambers will be constructed for this spectrometers. Each chamber will contain 6 planes of readout channels. This paper describes the chamber design and gas handling system used.
Spray Drift Issues and Technologies for Mitigation
Technology Transfer Automated Retrieval System (TEKTRAN)
Herbicide-induced plant damage due to off-target spray drift has become a major problem in some regions prompting States to take regulatory action regarding drift mitigation. For example, the Arkansas Plant Board has proposed new regulations regarding spray of Glyphosate and 2, 4-D. These regulation...
Biology Undergraduates' Misconceptions about Genetic Drift
ERIC Educational Resources Information Center
Andrews, T. M.; Price, R. M.; Mead, L. S.; McElhinny, T. L.; Thanukos, A.; Perez, K. E.; Herreid, C. F.; Terry, D. R.; Lemons, P. P.
2012-01-01
This study explores biology undergraduates' misconceptions about genetic drift. We use qualitative and quantitative methods to describe students' definitions, identify common misconceptions, and examine differences before and after instruction on genetic drift. We identify and describe five overarching categories that include 16 distinct…
NASA Astrophysics Data System (ADS)
Amaro de Faria Júnior, A. C.
2015-09-01
We have developed a analitical method based on the general theory of modulation of Whitham7 where the variational method is a particular case to generate nonlinear optical pulses and Optical Solitons. We show the equivalence of the solutions of the Nonlinear Schrödinger Equation (NLS) and the solutions derived from the method proposed here, demonstrating that these solutions lead to the Optical Solitons. We developed a new method to check the stability of the NLS equations. We show that the Optical Solitons obtained from a Lagrangian density can propagate through a waveguide such as an optical fiber, and are equivalent to Optical Solitons guided by an optical fiber. To analyze the stability of system solutions we have expanded the Lagrangian density and from the expanded Lagrangian we obtain the system equations of motion and restrict the solutions that have oscillating behavior when disturbed. The stability analysis can also be performed by expansion of the optical field as it is presented in section 4. Thus obtain a self-value equation whose spectrum is positive indicating that the solutions with the characteristics of reproducing the NLS solutions are stable. This method can be used and implemented computationally for linear stability analysis of any optical system or any NLS solution. Another important aspect of our research has been the discovery of a relationship between the Lagrangian of optical system and the optical pulse propagating through a waveguide. The paper is organized as follows. Section 1 is devoted to a quick presentation of NLS systems. The section 2 provides a description of modeling of an optical network. Section 3 and 4 are devoted to the presentation of the proposed method for obtaining this class of solutions and their stability analysis. Section 5 presents conclusions and comments and section 6 provides references.
``Drifting tadpoles'' in wavelet spectra of decimetric radio emission of fiber bursts
NASA Astrophysics Data System (ADS)
Mészárosová, H.; Karlický, M.; Rybák, J.; Jiřička, K.
2009-08-01
Aims: The solar decimetric radio emission of fiber bursts was investigated searching for the “drifting tadpole” structures proposed by theoretical studies. Methods: Characteristic periods with the tadpole pattern were searched for in the radio flux time series by wavelet analysis methods. Results: For the first time, we have found drifting tadpoles in the wavelet spectra of the decimetric radio emission associated with the fiber bursts observed in July 11, 2005. These tadpoles were detected at all radio frequencies in the 1602-1780 MHz frequency range. The characteristic period of the wavelet tadpole patterns was found to be 81.4 s and the frequency drift of the tadpole heads is -6.8 MHz s-1. These tadpoles are interpreted as a signature of the magnetoacoustic wave train moving along a dense flare waveguide and their frequency drift as a motion of the wave train modulating the radio emission produced by the plasma emission mechanism. Using the Aschwanden density model of the solar atmosphere, only low values of the Alfvén speed and the magnetic field strength in the loop guiding this wave train were derived which indicates a neutral current sheet as the guiding structure. The present analysis supports the model of fiber bursts based on whistler waves.
Low latitude electrodynamic plasma drifts - A review
NASA Technical Reports Server (NTRS)
Fejer, B. G.
1991-01-01
The characteristics and driving mechanisms of low latitude ExB plasma drifts and electric fields particularly at F-region heights are reviewed. It is concluded that the general characteristics of the quiet-time plasma can be explained as resulting from E- and F-region dynamo and interhemispheric coupling processes. The disturbance dynamo effects are found to be responsible for the drift perturbations following the periods of enhanced magnetic activity. The prompt penetration of high-latitude electric fields to lower latitudes produces large perturbations on the upward/poleward drifts, but has no significant effect on the low-latitude and the equatorial zonal drifts. Detailed low-latitude and global numerical models for studying the characteristics of plasma drifts are capable of reproducing the latitudinal variation of the perturbation electric fields and their diurnal variations.
Drift and pseudomomentum in bounded turbulent shear flows
NASA Astrophysics Data System (ADS)
Phillips, W. R. C.
2015-10-01
This paper is concerned with the evaluation of two Lagrangian measures which arise in oscillatory or fluctuating shear flows when the fluctuating field is rotational and the spectrum of wave numbers which comprise it is continuous. The measures are the drift and pseudomomentum. Phillips [J. Fluid Mech. 430, 209 (2001), 10.1017/S0022112000002858] has shown that the measures are, in such instances, succinctly expressed in terms of Lagrangian integrals of Eulerian space-time correlations. But they are difficult to interpret, and the present work begins by expressing them in a more insightful form. This is achieved by assuming the space-time correlations are separable as magnitude, determined by one-point velocity correlations, and spatial diminution. The measures then parse into terms comprised of the mean Eulerian velocity, one-point velocity correlations, and a family of integrals of spatial diminution, which in turn define a series of Lagrangian time and velocity scales. The pseudomomentum is seen to be strictly negative and related to the turbulence kinetic energy, while the drift is mixed and strongly influenced by the Reynolds stress. Both are calculated for turbulent channel flow for a range of Reynolds numbers and appear, as the Reynolds number increases, to approach a terminal form. At all Reynolds numbers studied, the pseudomomentum has a sole peak located in wall units in the low teens, while at the highest Reynolds number studied, Reτ=5200 , the drift is negative in the vicinity of that peak, positive elsewhere, and largest near the rigid boundary. In contrast, the time and velocity scales grow almost logarithmically over much of the layer. Finally, the drift and pseudomomentum are discussed in the context of coherent wall layer structures with which they are intricately linked.
Field investigation of the drift shadow
Su, Grace W.; Kneafsey, Timothy J.; Ghezzehei, Teamrat A.; Marshall, Brian D.; Cook, Paul J.
2005-09-08
A drift shadow is an area immediately beneath an undergroundvoidthat, in theory, will be relatively drier than the surrounding rockmass. Numerical and analytical models of water flow through unsaturatedrock predict the existence of a drift shadow, but field tests confirmingits existence have yet to be performed. Proving the existence of driftshadows and understanding their hydrologic and transport characteristicscould provide a better understanding of how contaminants move in thesubsurface if released from waste emplacement drifts such as the proposednuclear waste repository at Yucca Mountain, Nevada. We describe the fieldprogram that will be used to investigate the existence of a drift shadowand the corresponding hydrological process at the Hazel-Atlas silica-sandmine located at the Black Diamond Mines Regional Preserve in Antioch,California. The location and configuration of this mine makes it anexcellent site to observe and measure drift shadow characteristics. Themine is located in a porous sandstone unit of the Domengine Formation, anapproximately 230 meter thick series of interbedded Eocene-age shales,coals, and massive-bedded sandstones. The mining method used at the minerequired the development of two parallel drifts, one above the other,driven along the strike of the mined sandstone stratum. Thisconfiguration provides the opportunity to introduce water into the rockmass in the upper drift and to observe and measure its flow around theunderlying drift. The passive and active hydrologic tests to be performedare described. In the passive method, cores will be obtained in a radialpattern around a drift and will be sectioned and analyzed for in-situwater content and chemical constituents. With the active hydrologic test,water will be introduced into the upper drift of the two parallel driftsand the flow of the water will be tracked as it passes near the bottomdrift. Tensiometers, electrical resistance probes, neutron probes, andground penetrating radar may be
Continental drift and climate change drive instability in insect assemblages
NASA Astrophysics Data System (ADS)
Li, Fengqing; Tierno de Figueroa, José Manuel; Lek, Sovan; Park, Young-Seuk
2015-06-01
Global change has already had observable effects on ecosystems worldwide, and the accelerated rate of global change is predicted in the future. However, the impacts of global change on the stability of biodiversity have not been systematically studied in terms of both large spatial (continental drift) and temporal (from the last inter-glacial period to the next century) scales. Therefore, we analyzed the current geographical distribution pattern of Plecoptera, a thermally sensitive insect group, and evaluated its stability when coping with global change across both space and time throughout the Mediterranean region—one of the first 25 global biodiversity hotspots. Regional biodiversity of Plecoptera reflected the geography in both the historical movements of continents and the current environmental conditions in the western Mediterranean region. The similarity of Plecoptera assemblages between areas in this region indicated that the uplift of new land and continental drift were the primary determinants of the stability of regional biodiversity. Our results revealed that climate change caused the biodiversity of Plecoptera to slowly diminish in the past and will cause remarkably accelerated biodiversity loss in the future. These findings support the theory that climate change has had its greatest impact on biodiversity over a long temporal scale.
Continental drift and climate change drive instability in insect assemblages
Li, Fengqing; Tierno de Figueroa, José Manuel; Lek, Sovan; Park, Young-Seuk
2015-01-01
Global change has already had observable effects on ecosystems worldwide, and the accelerated rate of global change is predicted in the future. However, the impacts of global change on the stability of biodiversity have not been systematically studied in terms of both large spatial (continental drift) and temporal (from the last inter-glacial period to the next century) scales. Therefore, we analyzed the current geographical distribution pattern of Plecoptera, a thermally sensitive insect group, and evaluated its stability when coping with global change across both space and time throughout the Mediterranean region—one of the first 25 global biodiversity hotspots. Regional biodiversity of Plecoptera reflected the geography in both the historical movements of continents and the current environmental conditions in the western Mediterranean region. The similarity of Plecoptera assemblages between areas in this region indicated that the uplift of new land and continental drift were the primary determinants of the stability of regional biodiversity. Our results revealed that climate change caused the biodiversity of Plecoptera to slowly diminish in the past and will cause remarkably accelerated biodiversity loss in the future. These findings support the theory that climate change has had its greatest impact on biodiversity over a long temporal scale. PMID:26081036
Continental drift and climate change drive instability in insect assemblages.
Li, Fengqing; Tierno de Figueroa, José Manuel; Lek, Sovan; Park, Young-Seuk
2015-06-17
Global change has already had observable effects on ecosystems worldwide, and the accelerated rate of global change is predicted in the future. However, the impacts of global change on the stability of biodiversity have not been systematically studied in terms of both large spatial (continental drift) and temporal (from the last inter-glacial period to the next century) scales. Therefore, we analyzed the current geographical distribution pattern of Plecoptera, a thermally sensitive insect group, and evaluated its stability when coping with global change across both space and time throughout the Mediterranean region--one of the first 25 global biodiversity hotspots. Regional biodiversity of Plecoptera reflected the geography in both the historical movements of continents and the current environmental conditions in the western Mediterranean region. The similarity of Plecoptera assemblages between areas in this region indicated that the uplift of new land and continental drift were the primary determinants of the stability of regional biodiversity. Our results revealed that climate change caused the biodiversity of Plecoptera to slowly diminish in the past and will cause remarkably accelerated biodiversity loss in the future. These findings support the theory that climate change has had its greatest impact on biodiversity over a long temporal scale.
The electron drift velocity, ion acoustic speed and irregularity drifts in high-latitude E-region
NASA Astrophysics Data System (ADS)
Uspensky, M. V.; Pellinen, R. J.; Janhunen, P.
2008-10-01
The purpose of this study is to examine the STARE irregularity drift velocity dependence on the EISCAT line-of-sight (los or l-o-s) electron drift velocity magnitude, VE×Blos, and the flow angle ΘN,F (superscript N and/or F refer to the STARE Norway and Finland radar). In the noon-evening sector the flow angle dependence of Doppler velocities, VirrN,F, inside and outside the Farley-Buneman (FB) instability cone (|VE×Blos|>Cs and |VE×Blos|
Matzdorf; Fang; Ismail; Zhang; Kimura; Tokura; Terakura; Plummer
2000-08-04
Ferromagnetic (FM) spin fluctuations are believed to mediate the spin-triplet pairing for the p-wave superconductivity in Sr(2)RuO(4). Our experiments show that, at the surface, a bulk soft-phonon mode freezes into a static lattice distortion associated with an in-plane rotation of the RuO(6) octahedron. First-principle calculations confirm this structure and predict a FM ground state at the surface. This coupling between structure and magnetism in the environment of broken symmetry at the surface allows a reconsideration of the coupling mechanism in the bulk.
Performance of Thin-Window Silicon Drift Detectors
Carini, , G.A.; Chen, W.; De Geronimo, G.; Fried, J.; Gaskin, J.A.; Keister; J.W.; Li, Z.; Ramsey, B.D.; Rehak, P.; Siddons, D.P.
2008-10-20
Several sets of hexagonal Silicon Drift Detector (SDD) arrays were produced at BNL and by a commercial vendor, KETEK. Each array consists of 14 independent detectors (pixels) and two additional test pixels at two of the corners. The side of the detector upon which the X-ray radiation is incident (window side) has a thin junction covering the entire active area. The opposite side (device side) contains a drift-field electrode structure in the form of a hexagonal spiral and an electron collecting anode. There are 4 guard rings surrounding the 14-pixel array area on both sides of the detector. Within each array, 7 of the pixels have an aluminum field plate - interrupted spirals that stabilize the electric potential under the Si-SiO2 interface, while the other 7 do not. The drift field in the silicon volume is controlled by three biases: one is applied to a rectifying contact, one to the detector entrance window, and the third to a contact on the outer portion of the spiral common to all pixels in the array. Some arrays have been newly measured in NSLS beam line U3C at BNL. The complete assemblies were installed in the vacuum and cooled to ?27 C. During this run, spectra for energies ranging between 400 and 900 eV were collected in several pixels, some with field plates and others without. The detailed testing results of several arrays are reported here.
Macroscopic drift current in the inverse Faraday effect
NASA Astrophysics Data System (ADS)
Hertel, Riccardo; Fähnle, Manfred
2015-01-01
The inverse Faraday effect (IFE) describes the spontaneous magnetization of a conducting or dielectric medium due to irradiation with a circularly polarized electromagnetic wave. The effect has recently been discussed in the context of laser-induced magnetic switching of solids. We analyze analytically the electron dynamics induced by a circularly polarized laser beam within the framework of plasma theory. A macroscopic drift current is obtained, which circulates around the perimeter of the laser beam. The magnetic moment due to this macroscopic current has an opposite sign and half of the magnitude of the magnetic moment that is generated directly by the IFE. This constitutes an important contribution of angular momentum transferred from the wave to the medium and a classical mechanism for the light-induced generation of magnetic fields.
NASA Astrophysics Data System (ADS)
Cheung, David L.
2011-08-01
While the interaction of colloidal particles (sizes in excess of 100 nm) with liquid interfaces may be understood in terms of continuum models, which are grounded in macroscopic properties such as surface and line tensions, the behaviour of nanoparticles at liquid interfaces may be more complex. Recent simulations [D. L. Cheung and S. A. F. Bon, Phys. Rev. Lett. 102, 066103 (2009)], 10.1103/PhysRevLett.102.066103 of nanoparticles at an idealised liquid-liquid interface showed that the nanoparticle-interface interaction range was larger than expected due, in part, to the action of thermal capillary waves. In this paper, molecular dynamics simulations of a Lennard-Jones nanoparticle in a binary Lennard-Jones mixture are used to confirm that these previous results hold for more realistic models. Furthermore by including attractive interactions between the nanoparticle and the solvent, it is found that the detachment energy decreases as the nanoparticle-solvent attraction increases. Comparison between the simulation results and recent theoretical predictions [H. Lehle and M. Oettel, J. Phys. Condens. Matter 20, 404224 (2008)], 10.1088/0953-8984/20/40/404224 shows that for small particles the incorporation of capillary waves into the predicted effective nanoparticle-interface interaction improves agreement between simulation and theory.
NASA Astrophysics Data System (ADS)
Blázquez-Salcedo, Jose Luis; Macedo, Caio F. B.; Cardoso, Vitor; Ferrari, Valeria; Gualtieri, Leonardo; Khoo, Fech Scen; Kunz, Jutta; Pani, Paolo
2016-11-01
Gravitational waves emitted by distorted black holes—such as those arising from the coalescence of two neutron stars or black holes—carry not only information about the corresponding spacetime but also about the underlying theory of gravity. Although general relativity remains the simplest, most elegant, and viable theory of gravitation, there are generic and robust arguments indicating that it is not the ultimate description of the gravitational universe. Here, we focus on a particularly appealing extension of general relativity, which corrects Einstein's theory through the addition of terms which are second order in curvature: the topological Gauss-Bonnet invariant coupled to a dilaton. We study gravitational-wave emission from black holes in this theory and (i) find strong evidence that black holes are linearly (mode) stable against both axial and polar perturbations, (ii) discuss how the quasinormal modes of black holes can be excited during collisions involving black holes, and finally (iii) show that future ringdown detections with a large signal-to-noise ratio would improve current constraints on the coupling parameter of the theory.
Waves and instabilities in plasmas
Chen, L.
1987-01-01
The contents of this book are: Plasma as a Dielectric Medium; Nyquist Technique; Absolute and Convective Instabilities; Landau Damping and Phase Mixing; Particle Trapping and Breakdown of Linear Theory; Solution of Viasov Equation via Guilding-Center Transformation; Kinetic Theory of Magnetohydrodynamic Waves; Geometric Optics; Wave-Kinetic Equation; Cutoff and Resonance; Resonant Absorption; Mode Conversion; Gyrokinetic Equation; Drift Waves; Quasi-Linear Theory; Ponderomotive Force; Parametric Instabilities; Problem Sets for Homework, Midterm and Final Examinations.
VLBI measurement of the secular aberration drift
NASA Astrophysics Data System (ADS)
Titov, O.; Lambert, S. B.; Gontier, A.-M.
2011-05-01
Aims: While analyzing decades of very long baseline interferometry (VLBI) data, we detected the secular aberration drift of the extragalatic radio source proper motions caused by the rotation of the Solar System barycenter around the Galactic center. Our results agree with the predicted estimate to be 4-6 micro arcseconds per year (μas/yr) towards α = 266° and δ = -29°. In addition, we tried to detect the quadrupole systematics of the velocity field. Methods: The analysis method consisted of three steps. First, we analyzed geodetic and astrometric VLBI data to produce radio source coordinate time series. Second, we fitted proper motions of 555 sources with long observational histories over the period 1990-2010 to their respective coordinate time series. Finally, we fitted vector spherical harmonic components of degrees 1 and 2 to the proper motion field. Results: Within the error bars, the magnitude and the direction of the dipole component agree with predictions. The dipole vector has an amplitude of 6.4 ± 1.5 μas/yr and is directed towards equatorial coordinates α = 263° and δ = -20°. The quadrupole component has not been detected. The primordial gravitational wave density, integrated over a range of frequencies less than 10-9 Hz, has a limit of 0.0042h-2 where h is the normalized Hubble constant is H0/(100 km s-1). We dedicate this work to the memory of Anne-Marie Gontier, our colleague and personal friend, and a widely recognized specialist of VLBI. She passed away shortly after this paper was submitted.Proper motion data is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/529/A91
Drift mechanism of laser-induced electron acceleration in vacuum
NASA Astrophysics Data System (ADS)
Morgovsky, L.
2015-12-01
Laser-induced electron acceleration in vacuum is possible due to the ejection of electrons from the beam as a consequence of the transverse drift orthogonal to the propagation direction. The transverse drift is derived from the general solution of the equations of motion of the electrons in the field of a plane electromagnetic wave with arbitrary polarization. It is shown that the energy gain is proportional to the square of the field strength additionally modulated by the function of the injection and ejection phases. In particular, for a linearly polarized beam this function is reduced to the squared difference between the cosines of these phases. The finite laser pulse duration restricts the range of the field strength suitable for direct electron acceleration in vacuum within certain limits. It is demonstrated that the high efficiency of energy transfer from the laser wave into the kinetic energy of the accelerated electrons demands phase matching between the electron quiver phase at the exit point and the phase of the energy transfer.
Genetic Drift of HIV Populations in Culture
Voronin, Yegor; Holte, Sarah; Overbaugh, Julie; Emerman, Michael
2009-01-01
Populations of Human Immunodeficiency Virus type 1 (HIV-1) undergo a surprisingly large amount of genetic drift in infected patients despite very large population sizes, which are predicted to be mostly deterministic. Several models have been proposed to explain this phenomenon, but all of them implicitly assume that the process of virus replication itself does not contribute to genetic drift. We developed an assay to measure the amount of genetic drift for HIV populations replicating in cell culture. The assay relies on creation of HIV populations of known size and measurements of variation in frequency of a neutral allele. Using this assay, we show that HIV undergoes approximately ten times more genetic drift than would be expected from its population size, which we defined as the number of infected cells in the culture. We showed that a large portion of the increase in genetic drift is due to non-synchronous infection of target cells. When infections are synchronized, genetic drift for the virus is only 3-fold higher than expected from its population size. Thus, the stochastic nature of biological processes involved in viral replication contributes to increased genetic drift in HIV populations. We propose that appreciation of these effects will allow better understanding of the evolutionary forces acting on HIV in infected patients. PMID:19300501
The Electron Drift Instrument for Cluster
NASA Technical Reports Server (NTRS)
Paschmann, G.; Melzner, F.; Frenzel, R.; Vaith, H.; Parigger, P.; Pagel, U.; Bauer, O. H.; Haerendel, G.; Baumjohann, W.; Scopke, N.
1997-01-01
The Electron Drift Instrument (EDI) measures the drift of a weak beam of test electrons that, when emitted in certain directions, return to the spacecraft after one or more gyrations. This drift is related to the electric field and the gradient in the magnetic field, and these quantities can, by use of different electron energies, be determined separately. As a by-product, the magnetic field strength is also measured. The present paper describes the scientific objectives, the experimental method, and the technical realization of the various elements of the instrument.
FIELD INVESTIGATIONS OF THE DRIFT SHADOW
G. W. Su, T. J. Kneafsey, T. A. Ghezzehei, B. D. Marshall, and P. J. Cook
2006-01-15
The ''Drift Shadow'' is defined as the relatively drier region that forms below subsurface cavities or drifts in unsaturated rock. Its existence has been predicted through analytical and numerical models of unsaturated flow. However, these theoretical predictions have not been demonstrated empirically to date. In this project they plan to test the drift shadow concept through field investigations and compare our observations to simulations. Based on modeling studies they have an identified suitable site to perform the study at an inactive mine in a sandstone formation. Pretest modeling studies and preliminary characterization of the site are being used to develop the field scale tests.
Ion Drift Meter for Dynamics Explorer
NASA Technical Reports Server (NTRS)
Heelis, R. A.; Hanson, W. B.; Lippincott, C. R.; Zuccaro, D. R.
1982-01-01
The ion drift meter for Dynamics Explorer B is discussed. It measures two mutually perpendicular angles of arrival of thermal ions with respect to the sensor look directions. These angles lie in the vertical and horizontal planes and may be thought of as pitch and yaw in the conventional aerodynamic sense. The components of the ion drift velocity along vertical and horizontal axes through the spacecraft body are derived to first order from knowledge of the spacecraft velocity vector and more accurately with additional knowledge of the component of ion drift along the sensor look direction.
NASA Astrophysics Data System (ADS)
Bender, Stefan; Mokwa, W.
1998-12-01
In the current paper a dual-delay-line- and a resonator- device based on CMOS-silicon-technology is presented. As a piezoelectric layer ZnO is used. The layer was deposited at room temperature in a RF magnetron sputter process. Using x- ray diffraction it could be shown that the crystals are mostly oriented with the c-axis (hexagonal structure) perpendicular to the surface which is necessary to conduct surface acoustic waves. Pt electrodes were designed for frequencies between 140 and 600 MHz and were deposited on top using a lift-off-process. A poly-silicon heating resistor was integrated as a sublayer for controlling and changing of the temperature of the SAW-device for studying the influence of temperature on the mass sensitive layer. A Pt thin film resistance served for temperature measurement. The performance of the devices were compared to standard quartz based SAWs.
Sources of low-latitude ionospheric E × B drifts and their variability
NASA Astrophysics Data System (ADS)
Maute, A.; Richmond, A. D.; Roble, R. G.
2012-06-01
The complete mechanism of how upward propagating tropospheric tides connect to the upper atmosphere is not yet fully understood. One proposed mechanism is via ionospheric wind dynamo. However, other sources can potentially alter the vertical E × B drift: gravity and plasma pressure gradient driven current, the geomagnetic main field, and longitudinal variation in the conductivities. In this study we examine the contribution to the vertical drift from these sources, and compare them. We use March equinox results from the Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model. We found that the gravity and plasma pressure gradient driven current and the longitudinal variation of the conductivities excluding the variation due to the geomagnetic main field do not change the longitudinal variation of the vertical drift significantly. Modifying the geomagnetic main field will change the vertical drift at 5-6 LT, 18-19 LT and 23-24 LT at almost all longitudes. In general the influence of the geomagnetic main field on the vertical drift is larger, with respect to the maximum difference, at 18-19 LT and 23-24 LT, equal at 5-6 LT, and smaller at 14-15 LT than the influence due to nonmigrating tidal components in the neutral winds. Examination of the contribution from E- and F-region neutral winds to the vertical drift shows that their importance depends on the local time and the solar activity. This implies that the vertical drift has to be analyzed at specific local times to examine the relation between the wave number in the vertical drift and in the neutral winds.
Theory and calculation of finite beta drift wave turbulence
Beasley, C.O. Jr.; Molvig, K.; Freidberg, J.P.; van Rij, W.I.
1984-11-01
Using numerical techniques, we calculate eigenmodes of the nonlinear universal mode with finite beta in order to determine the scaling of the saturation level of the instability with beta. We use two different renormalizations in the calculations and find that using the appropriate renormalization, we are able to recover Alcator density scaling, as originally found in analytic work by Molvig and Hirshman. We also find that the universal mode should be stable in ohmically heated tokamaks above a critical beta on the order of 0.02.
Effects of magnetic islands on drift wave instability
Jiang, P.; Lin, Z. Holod, I.; Xiao, C.
2014-12-15
Magnetic islands have been implemented in the gyrokinetic toroidal code to study the effects of the islands on microturbulence. The pressure profile flattening is verified in the simulation with the islands. Simulations of ion temperature gradient instability find that different toroidal modes are linearly coupled together and that toroidal spectra become broader when the island width increases. The real frequencies and growth rates of different toroidal modes approach each other with the averaged value independent of the island width. The linear mode structures are enhanced at the island separatrices and weakened at the island centers, consistent with the flattening of the pressure profile inside the islands.
Blobs in the framework of drift wave dynamics
NASA Astrophysics Data System (ADS)
Zhang, Yanzeng; Krasheninnikov, S. I.
2016-12-01
Analytic solutions for blob-like structures obtained in S. I. Krasheninnikov [Phys. Lett. A 380, 3905 (2016)], are examined in detail. Numerical solutions for the cases where analytic consideration is not possible are provided.
Generation of electrostatic drift zonal flows under the action of mean sheared flows
NASA Astrophysics Data System (ADS)
Kaladze, T. D.; Kharshiladze, O.
2016-12-01
Generation of large-scale zonal flows by the small-scale electrostatic drift wave turbulence in the magnetized plasma under the action of mean poloidal sheared flow is considered. Attention to large-scale (compared to the ion Larmor radius) drift structures is paid. To this end, the generalized Hasegawa-Mima equation containing both vector and scalar nonlinearities is derived, and the appropriate eigenvalue problem is solved numerically. Destabilizing role of the small amplitude mean shear flow and spatial inhomogeneity of electron temperature is shown.
NASA Astrophysics Data System (ADS)
Kirby, Jason R.; Kirby, Robert
2008-11-01
This paper presents the results of an 11-year study into mudflat elevation changes within the intertidal zone at Stert Flats in Bridgwater Bay, Somerset. This site is located in the outer Severn Estuary/inner Bristol Channel which is a macro-hypertidal regime dominated by physical processes, characterized by strong tidal currents, high turbidity and a significant degree of exposure to wind generated waves. Two transects of stakes were installed perpendicular to the coast, extending seawards 300 m from the edge of the saltmarsh onto the mudflats, against which variations in accretion or erosion could be measured. The mudflats themselves consisted of an underlying consolidated clay of Holocene age and a surface veneer of fluid mud and/or mobile sand patches which varied both spatially and temporally. Mudflat development was recorded over both short-term (monthly/seasonal) and medium-term (inter-annual) timescales. The results display a significant degree of scatter over all timescales. Such variability in response may be expected in such a dynamic system where noise can be attributed to a combination of factors such as the mobility of surface fluid mud and sand patches and the migration of the underlying ridge-runnel drainage network. Despite this, the expected short-term variations related to neap-spring tidal conditions and seasonal influences were observed at a number of locations on the transects although these were weakly expressed. The over-riding feature of the profiles is a consistent long-term trend of erosion which appears to be masking shorter term trends within the dataset. Viewed over the 11-year period, the changes in mudflat elevation closely match the pattern of the index of the North Atlantic Oscillation (NAO) during the 1990s, suggesting a strong climatic control over mudflat development on a medium-term/decadal scale. Most profiles display a strong erosional trend during the early 1990s when the NAO index was positive. The erosional trend peaked in
A Scale Drift Study. Research Report. ETS RR-09-43
ERIC Educational Resources Information Center
Liu, Jinghua; Curley, Edward; Low, Albert
2009-01-01
This study examines the stability of the SAT® scale from 1994 to 2001. A 1994 form and a 2001 form were readministered in a 2005 SAT administration, and the 1994 form was equated to the 2001 form. The new conversion was compared to the old conversion. Both the verbal and math sections exhibit a similar degree of scale drift, but in opposite…
Drift of continental rafts with asymmetric heating.
Knopoff, L; Poehls, K A; Smith, R C
1972-06-02
A laboratory model of a lithospheric raft is propelled through a viscous asthenospheric layer with constant velocity of scaled magnitude appropriate to continental drift. The propulsion is due to differential heat concentration in the model oceanic and continental crusts.
Drift-resistive-inertial ballooning modes in quasihelical stellarators
Rafiq, T.; Kritz, A. H.; Hegna, C. C.; Callen, J. D.
2010-02-15
A linear stability theory of nonideal magnetohydrodynamic (MHD) ballooning modes is investigated using a two fluid model for electron-ion plasmas. Drift-resistive-inertial ballooning mode eigenvalues and eigenfunctions are calculated for a variety of equilibria including axisymmetric shifted circular geometry (s-alpha model) as well as for three dimensional configurations relevant for the Helically Symmetric Stellarator (HSX) [F. S. B. Anderson, A. F. Almagri, D. T. Anderson, et al., Fusion Technology 27, 273 (1995)]. For typical HSX parameters, characteristic ballooning mode growth rates exceed the electron collision frequency. In this regime, electron inertial effects dominate plasma resistivity and produce an instability whose growth rate scales with the electromagnetic skin depth. However, as plasma beta is increased, the resistive and inertial effects become unimportant. Under these conditions, the mode is completely stabilized by drift frequency effects, which dominate resistivity and inertia. Numerical results indicate that in the absence of drift effects, the resistive-inertial MHD modes are purely growing and persist in regimes where ideal MHD ballooning modes are stable. It is found that the magnitudes of the linear growth rates are not sensitive to the addition of a mirror term to the magnetic spectrum that spoils the quasihelical symmetry of the configuration. The eigenvalues and eigenvectors in the strong ballooning approximation are used together with a quasilinear mixing length estimate to determine particle flux and particle diffusivity. The particle diffusivity increases with rising density gradient and collisionality in a plasma with a low electron temperature. This increase in transport is consistent with the increase observed in the edge region of HSX plasmas. The magnitude of the particle diffusivity is computed to be in the range from 5 to 10 m{sup 2}/s, which is consistent with the experimental measured particle diffusivity at the edge of HSX
Baumgaertel, J. A.; Redi, M. H.; Budny, R. V.; Rewoldt, G.; Dorland, W.
2005-10-19
Insight into plasma microturbulence and transport is being sought using linear simulations of drift waves on the National Spherical Torus Experiment (NSTX), following a study of drift wave modes on the Alcator C-Mod Tokamak. Microturbulence is likely generated by instabilities of drift waves, which cause transport of heat and particles. Understanding this transport is important because the containment of heat and particles is required for the achievement of practical nuclear fusion. Microtearing modes may cause high heat transport through high electron thermal conductivity. It is hoped that microtearing will be stable along with good electron transport in the proposed low collisionality International Thermonuclear Experimental Reactor (ITER). Stability of the microtearing mode is investigated for conditions at mid-radius in a high density NSTX high performance (H-mode) plasma, which is compared to the proposed ITER plasmas. The microtearing mode is driven by the electron temperature gradient, and believed to be mediated by ion collisions and magnetic shear. Calculations are based on input files produced by TRXPL following TRANSP (a time-dependent transport analysis code) analysis. The variability of unstable mode growth rates is examined as a function of ion and electron collisionalities using the parallel gyrokinetic computational code GS2. Results show the microtearing mode stability dependence for a range of plasma collisionalities. Computation verifies analytic predictions that higher collisionalities than in the NSTX experiment increase microtearing instability growth rates, but that the modes are stabilized at the highest values. There is a transition of the dominant mode in the collisionality scan to ion temperature gradient character at both high and low collisionalities. The calculations suggest that plasma electron thermal confinement may be greatly improved in the low-collisionality ITER.
Self-shielding flex-circuit drift tube, drift tube assembly and method of making
Jones, David Alexander
2016-04-26
The present disclosure is directed to an ion mobility drift tube fabricated using flex-circuit technology in which every other drift electrode is on a different layer of the flex-circuit and each drift electrode partially overlaps the adjacent electrodes on the other layer. This results in a self-shielding effect where the drift electrodes themselves shield the interior of the drift tube from unwanted electro-magnetic noise. In addition, this drift tube can be manufactured with an integral flex-heater for temperature control. This design will significantly improve the noise immunity, size, weight, and power requirements of hand-held ion mobility systems such as those used for explosive detection.
Assessment of HF Drift Data Reliability
2005-06-13
the array, making the beamforming computations very efficient. The station can operate in four different modes: 1) Scanning ionogram , 2) Drift ionogram ...3) Fixed Frequency ionogram 4) Oblique ionogram . Real-time ionograms with the results of their automatic scaling and the history of past soundings...are currently available on the official web site of Athens Digisonde (http://www.iono.noa.gr). For the post-processing of the drift ionogram , the
Canuel, B; Genin, E; Mantovani, M; Marque, J; Ruggi, P; Tacca, M
2014-05-01
In this paper, a simple and effective control system to monitor and suppress the beam jitter noise at the input of an optical system, called a beam pointing control (BPC) system, will be described, showing the theoretical principle and an experimental demonstration for the application of large-scale gravitational wave (GW) interferometers (ITFs), in particular for the Advanced Virgo detector. For this purpose, the requirements for the control accuracy and the sensing noise will be computed by taking into account the Advanced Virgo optical configuration, and the outcomes will be compared with the experimental measurement obtained in the laboratory. The system has shown unprecedented performance in terms of control accuracy and sensing noise. The BPC system has achieved a control accuracy of ~10⁻⁸ rad for the tilt and ~10⁻⁷ m for the shift and a sensing noise of less than 1 n rad/√Hz, which is compliant with the Advanced Virgo GW ITF requirements.
Hollweg, Joseph V.; Verscharen, Daniel; Chandran, Benjamin D. G. E-mail: daniel.verscharen@unh.edu
2014-06-10
The MHD slow mode wave has application to coronal seismology, MHD turbulence, and the solar wind where it can be produced by parametric instabilities. We consider analytically how a drifting ion species (e.g. He{sup ++}) affects the linear slow mode wave in a mainly electron-proton plasma, with potential consequences for the aforementioned applications. Our main conclusions are as follows. 1. For wavevectors highly oblique to the magnetic field, we find solutions that are characterized by very small perturbations of total pressure. Thus, our results may help to distinguish the MHD slow mode from kinetic Alfvén waves and non-propagating pressure-balanced structures, which can also have very small total pressure perturbations. 2. For small ion concentrations, there are solutions that are similar to the usual slow mode in an electron-proton plasma, and solutions that are dominated by the drifting ions, but for small drifts the wave modes cannot be simply characterized. 3. Even with zero ion drift, the standard dispersion relation for the highly oblique slow mode cannot be used with the Alfvén speed computed using the summed proton and ion densities, and with the sound speed computed from the summed pressures and densities of all species. 4. The ions can drive a non-resonant instability under certain circumstances. For low plasma beta, the threshold drift can be less than that required to destabilize electromagnetic modes, but damping from the Landau resonance can eliminate this instability altogether, unless T{sub e} /T{sub p} >> 1.
Pilot-Wave Theory and Financial Option Pricing
NASA Astrophysics Data System (ADS)
Haven, Emmanuel
2005-11-01
This paper tries to argue why pilot-wave theory could be of use in financial economics. We introduce the notion of information wave. We consider a stochastic guidance equation and part of the drift term of that equation makes reference to the phase of the wave. In order to embed information in financial option pricing we could use such a drift. We also briefly argue how we could embed information in the pricing kernel of the option price.
Thermodynamics Insights for the Redshift Drift
NASA Astrophysics Data System (ADS)
Zhang, Ming-Jian; Liu, Wen-Biao
2015-01-01
The secular redshift drift is a potential measurement to directly probe the cosmic expansion. Previous study on the redshift drift mainly focused on the model-dependent simulation. Apparently, the physical insights on the redshift drift are very necessary. So in this paper, it is investigated using thermodynamics on the apparent, Hubble and event horizons. Thermodynamics could analytically present the model-independent upper bounds of redshift drift. For specific assumption on the cosmological parameters, we find that the thermodynamics bounds are nearly one order of magnitude larger than the expectation in standard ΛCDM model. We then examine ten observed redshift drift from Green Bank Telescope at redshift 0.09 < z < 0.69, and find that these observational results are inconsistent with the thermodynamics. The size of the errorbars on these measurements is about three orders of magnitude larger than the effect of thermodynamical bounds for the redshift drift. Obviously, we have not yet hit any instrumental systematics at the shift level of 1m s-1 yr-1.
High-beta equilibria of drift-optimized compact stellarators.
Ware, A S; Hirshman, S P; Spong, D A; Berry, L A; Deisher, A J; Fu, G Y; Lyon, J F; Sanchez, R
2002-09-16
Compact stellarator configurations have been obtained with good neoclassical confinement that are stable to both pressure- and current-driven modes for high values of beta. These configurations are drift-optimized tokamak-stellarator hybrids with a high-shear tokamak-like rotational transform profile and /B/ that is approximately poloidally symmetric. The bootstrap current is consistent with the required equilibrium current and, while larger than that in existing stellarators, is typically only a small fraction (1/3-1/5) of that in an equivalent tokamak. These configurations have strong magnetic wells and consequently high interchange stability beta limits up to beta=23%. Because of the reduced bootstrap current, these configurations are stable to low-n ideal MHD kink modes with no wall stabilization for values of beta ( approximately 7%-11%) significantly larger than in an equivalent advanced tokamak.
Role of mechanical stress in the resistance drift of Ge2Sb2Te5 films and phase change memories
NASA Astrophysics Data System (ADS)
Rizzi, M.; Spessot, A.; Fantini, P.; Ielmini, D.
2011-11-01
In a phase change memory (PCM), the device resistance increases slowly with time after the formation of the amorphous phase, thus affecting the stability of stored data. This work investigates the resistance drift in thin films of amorphous Ge2Sb2Te5 and in PCMs, demonstrating a common kinetic of drift in stressed/unstressed films and in the nanometer-size active volume of a PCM with different stress levels developed via stressor layers. It is concluded that stress is not the root cause of PCM drift, which is instead attributed to intrinsic structural relaxation due to the disordered, metastable nature of the amorphous chalcogenide phase.
NASA Astrophysics Data System (ADS)
Maute, A.; Hagan, M. E.; Richmond, A. D.; Roble, R. G.
2014-02-01
This modeling study quantifies the daytime low-latitude vertical E×B drift changes in the longitudinal wave number 1 (wn1) to wn4 during the major extended January 2006 stratospheric sudden warming (SSW) period as simulated by the National Center for Atmospheric Research thermosphere-ionosphere-mesosphere electrodynamics general circulation model (TIME-GCM), and attributes the drift changes to specific tides and planetary waves (PWs). The largest drift amplitude change (approximately 5 m/s) is seen in wn1 with a strong temporal correlation to the SSW. The wn1 drift is primarily caused by the semidiurnal westward propagating tide with zonal wave number 1 (SW1), and secondarily by a stationary planetary wave with zonal wave number 1 (PW1). SW1 is generated by the nonlinear interaction of PW1 and the migrating semidiurnal tide (SW2) at high latitude around 90-100 km. The simulations suggest that the E region PW1 around 100-130 km at the different latitudes has different origins: at high latitudes, the PW1 is related to the original stratospheric PW1; at midlatitudes, the model indicates PW1 is due to the nonlinear interaction of SW1 and SW2 around 95-105 km; and at low latitudes, the PW1 might be caused by the nonlinear interaction between DE2 and DE3. The time evolution of the simulated wn4 in the vertical E×B drift amplitude shows no temporal correlation with the SSW. The wn4 in the low-latitude vertical drift is attributed to the diurnal eastward propagating tide with zonal wave number 3 (DE3), and the contributions from SE2, TE1, and PW4 are negligible.
NASA Astrophysics Data System (ADS)
Danylov, Andriy A.; Waldman, Jerry; Light, Alexander R.; Goyette, Thomas M.; Giles, Robert H.; Qian, Xifeng; Chandrayan, Neelima; Goodhue, William D.; Nixon, William E.
2012-02-01
Operational temperature increase of CW THz QCLs to 77 K has enabled us to employ solid nitrogen (SN2) as the cryogen. A roughing pump was used to solidify liquid nitrogen and when the residual vapor pressure in the nitrogen reservoir reached the pumping system's minimum pressure the temperature equilibrated and remained constant until all the nitrogen sublimated. The hold time compared to liquid helium has thereby increased approximately 70-fold, and at a greatly reduced cost. The milliwatt CW QCL was at a temperature of approximately 60 K, dissipating 5 W of electrical power. To measure the long-term frequency, current, and temperature stability, we heterodyned the free-running 2.31 THz QCL with a CO2 pumped far-infrared gas laser line in methanol (2.314 THz) in a corner-cube Schottky diode and recorded the IF frequency, current and temperature. Under these conditions the performance characteristics of the QCL, which will be reported, exceeded that of a device mounted in a mechanical cryocooler.
Wang, Zhenyu; Lin, Yu; Wang, Xueyi; ...
2016-07-07
The eigenmode stability properties of three-dimensional lower-hybrid-drift-instabilities (LHDI) in a Harris current sheet with a small but finite guide magnetic field have been systematically studied by employing the gyrokinetic electron and fully kinetic ion (GeFi) particle-in-cell (PIC) simulation model with a realistic ion-to-electron mass ratio mi/me. In contrast to the fully kinetic PIC simulation scheme, the fast electron cyclotron motion and plasma oscillations are systematically removed in the GeFi model, and hence one can employ the realistic mi/me. The GeFi simulations are benchmarked against and show excellent agreement with both the fully kinetic PIC simulation and the analytical eigenmode theory. Our studies indicate that, for small wavenumbers, ky, along the current direction, the most unstable eigenmodes are peaked at the location wheremore » $$\\vec{k}$$• $$\\vec{B}$$ =0, consistent with previous analytical and simulation studies. Here, $$\\vec{B}$$ is the equilibrium magnetic field and $$\\vec{k}$$ is the wavevector perpendicular to the nonuniformity direction. As ky increases, however, the most unstable eigenmodes are found to be peaked at $$\\vec{k}$$ •$$\\vec{B}$$ ≠0. Additionally, the simulation results indicate that varying mi/me, the current sheet width, and the guide magnetic field can affect the stability of LHDI. Simulations with the varying mass ratio confirm the lower hybrid frequency and wave number scalings.« less
NASA Astrophysics Data System (ADS)
Wang, Zhenyu; Lin, Yu; Wang, Xueyi; Tummel, Kurt; Chen, Liu
2016-07-01
The eigenmode stability properties of three-dimensional lower-hybrid-drift-instabilities (LHDI) in a Harris current sheet with a small but finite guide magnetic field have been systematically studied by employing the gyrokinetic electron and fully kinetic ion (GeFi) particle-in-cell (PIC) simulation model with a realistic ion-to-electron mass ratio mi/me . In contrast to the fully kinetic PIC simulation scheme, the fast electron cyclotron motion and plasma oscillations are systematically removed in the GeFi model, and hence one can employ the realistic mi/me . The GeFi simulations are benchmarked against and show excellent agreement with both the fully kinetic PIC simulation and the analytical eigenmode theory. Our studies indicate that, for small wavenumbers, ky, along the current direction, the most unstable eigenmodes are peaked at the location where k →.B → =0 , consistent with previous analytical and simulation studies. Here, B → is the equilibrium magnetic field and k → is the wavevector perpendicular to the nonuniformity direction. As ky increases, however, the most unstable eigenmodes are found to be peaked at k →.B → ≠0 . In addition, the simulation results indicate that varying mi/me , the current sheet width, and the guide magnetic field can affect the stability of LHDI. Simulations with the varying mass ratio confirm the lower hybrid frequency and wave number scalings.
NASA Astrophysics Data System (ADS)
Zheng, L. J.; Kotschenreuther, M. T.; Valanju, P.
2014-06-01
The diamagnetic drift effects on the low-n magnetohydrodynamic instabilities at the high-mode (H-mode) pedestal are investigated in this paper with the inclusion of bootstrap current for equilibrium and rotation effects for stability, where n is the toroidal mode number. The AEGIS (Adaptive EiGenfunction Independent Solutions) code [L. J. Zheng and M. T. Kotschenreuther, J. Comp. Phys. 211 (2006)] is extended to include the diamagnetic drift effects. This can be viewed as the lowest order approximation of the finite Larmor radius effects in consideration of the pressure gradient steepness at the pedestal. The H-mode discharges at Jointed European Torus is reconstructed numerically using the VMEC code [P. Hirshman and J. C. Whitson, Phys. Fluids 26, 3553 (1983)], with bootstrap current taken into account. Generally speaking, the diamagnetic drift effects are stabilizing. Our results show that the effectiveness of diamagnetic stabilization depends sensitively on the safe factor value (qs) at the safety-factor reversal or plateau region. The diamagnetic stabilization are weaker, when qs is larger than an integer; while stronger, when qs is smaller or less larger than an integer. We also find that the diamagnetic drift effects also depend sensitively on the rotation direction. The diamagnetic stabilization in the co-rotation case is stronger than in the counter rotation case with respect to the ion diamagnetic drift direction.
Zheng, L. J.; Kotschenreuther, M. T.; Valanju, P.
2014-06-15
The diamagnetic drift effects on the low-n magnetohydrodynamic instabilities at the high-mode (H-mode) pedestal are investigated in this paper with the inclusion of bootstrap current for equilibrium and rotation effects for stability, where n is the toroidal mode number. The AEGIS (Adaptive EiGenfunction Independent Solutions) code [L. J. Zheng and M. T. Kotschenreuther, J. Comp. Phys. 211 (2006)] is extended to include the diamagnetic drift effects. This can be viewed as the lowest order approximation of the finite Larmor radius effects in consideration of the pressure gradient steepness at the pedestal. The H-mode discharges at Jointed European Torus is reconstructed numerically using the VMEC code [P. Hirshman and J. C. Whitson, Phys. Fluids 26, 3553 (1983)], with bootstrap current taken into account. Generally speaking, the diamagnetic drift effects are stabilizing. Our results show that the effectiveness of diamagnetic stabilization depends sensitively on the safe factor value (q{sub s}) at the safety-factor reversal or plateau region. The diamagnetic stabilization are weaker, when q{sub s} is larger than an integer; while stronger, when q{sub s} is smaller or less larger than an integer. We also find that the diamagnetic drift effects also depend sensitively on the rotation direction. The diamagnetic stabilization in the co-rotation case is stronger than in the counter rotation case with respect to the ion diamagnetic drift direction.
SYNCHROTRON EMISSION DRIVEN BY THE CHERENKOV-DRIFT INSTABILITY IN ACTIVE GALACTIC NUCLEI
Osmanov, Z.; Chkheidze, N.
2013-02-10
In the present paper, we study the generation of synchrotron emission by means of the feedback of Cherenkov-drift waves on the particle distribution through the diffusion process. Despite the efficient synchrotron losses, it is demonstrated that the excited Cherenkov-drift instability leads to the quasi-linear diffusion (QLD), the effect of which is balanced by dissipation factors and, as a result, the pitch angles are prevented from damping, thus maintaining the corresponding synchrotron emission. We analyze the model for a wide range of physical parameters and determine that the mechanism of QLD guarantees the generation of electromagnetic radiation from soft X-rays up to soft {gamma}-rays, which is strongly correlated with Cherenkov-drift emission ranging from IR up to UV energy domains.
Base metal thermocouples drift rate dependence from thermoelement diameter
NASA Astrophysics Data System (ADS)
Pavlasek, P.; Duris, S.; Palencar, R.
2015-02-01
Temperature measurements are one of the key factors in many industrial applications that directly affect the quality, effectiveness and safety of manufacturing processes. In many industrial applications these temperature measurements are realized by thermocouples. Accuracy of thermocouples directly affects the quality of the final product of manufacturing and their durability determines the safety margins required. One of the significant effects that affect the precision of the thermocouples is short and long term stability of their voltage output. This stability issue occurs in every type of thermocouples and is caused by multiple factors. In general these factors affect the Seebeck coefficient which is a material constant, which determines the level of generated voltage when exposed to a temperature gradient. Changes of this constant result in the change of the thermocouples voltage output thus indicated temperature which can result in production quality issues, safety and health hazards. These alternations can be caused by physical and chemical changes within the thermocouple lead material. Modification of this material constant can be of temporary nature or permanent. This paper concentrates on the permanent, or irreversible changes of the Seebeck coefficient that occur in commonly used swaged MIMS Type N thermocouples. These permanent changes can be seen as systematic change of the EMF of the thermocouple when it is exposed to a high temperature over a period of time. This change of EMF by time is commonly known as the drift of the thermocouple. This work deals with the time instability of thermocouples EMF at temperatures above 1200 °C. Instability of the output voltage was taken into relation with the lead diameter of the tested thermocouples. This paper concentrates in detail on the change of voltage output of thermocouples of different diameters which were tested at high temperatures for the overall period of more than 210 hours. The gather data from this
Traveling waves and breathers in an excitatory-inhibitory neural field
NASA Astrophysics Data System (ADS)
Folias, Stefanos E.
2017-03-01
We study existence and stability of traveling activity bump solutions in an excitatory-inhibitory (E-I) neural field with Heaviside firing rate functions by deriving existence conditions for traveling bumps and an Evans function to analyze their spectral stability. Subsequently, we show that these existence and stability results reduce, in the limit of wave speed c →0 , to the equivalent conditions developed for the stationary bump case. Using the results for the stationary bump case, we show that drift bifurcations of stationary bumps serve as a mechanism for generating traveling bump solutions in the E-I neural field as parameters are varied. Furthermore, we explore the interrelations between stationary and traveling types of bumps and breathers (time-periodic oscillatory bumps) by bridging together analytical and simulation results for stationary and traveling bumps and their bifurcations in a region of parameter space. Interestingly, we find evidence for a codimension-2 drift-Hopf bifurcation occurring as two parameters, inhibitory time constant τ and I-to-I synaptic connection strength w¯i i, are varied and show that the codimension-2 point serves as an organizing center for the dynamics of these four types of spatially localized solutions. Additionally, we describe a case involving subcritical bifurcations that lead to traveling waves and breathers as τ is varied.
Drift emplaced waste package thermal response
Ruffner, D.J.; Johnson, G.L.; Platt, E.A.; Blink, J.A.; Doering, T.W.
1993-01-01
Thermal calculations of the effects of radioactive waste decay heat on the I repository at Yucca Mountain, Nevada have been conducted by the Yucca Mountain Site Characterization Project (YMP) at Lawrence Livermore National Laboratory (LLNL) in conjunction with the B&W Fuel Company. For a number of waste package spacings, these 3D transient calculations use the TOPAZ3D code to predict drift wall temperatures to 10,000 years following emplacement. Systematic tcniperature variation occurs as a function of fuel age at emplacement and Areal Mass Loading (AML) during the first few centuries after emplacement. After about 1000 years, emplacement age is not a strong driver on rock temperature; AML has a larger impact. High AMLs occur when large waste packages are emplaced end-tocnd in drifts. Drift emplacement of equivalent packages results in lower rock teniperatures than borehole emplacement. For an emplacement scheme with 50% of the drift length occupied by packages, an AML of 138 MTU/acre is about three times higher than the Site Characterization Plan-Conceptual Design (SCP-CD) value. With this higher AML (requiring only 1/3 of the SCP-CD repository footprint), peak drift wall temperatures do not exceed 160*C, but rock temperatures excetd the boiling point of water for about 3000 years. These TOPAZ3D results Iiive been compared with reasonable agreement with two other computer codes.
Drift emplaced waste package thermal response
Ruffner, D.J.; Johnson, G.L.; Platt, E.A.; Blink, J.A.; Doering, T.W.
1993-12-31
Thermal calculations of the effects of radioactive waste decay heat on the potential repository at Yucca Mountain, Nevada, have been conducted by the Yucca Mountain Site Characterization Project (YMP) at Lawrence Livermore National Lab. (LLNL) in conjunction with the B&W Fuel Co. For a number of waste package spacings, these 3D transient calculations use the TOPAZ3D code to predict drift wall temperatures to 10,000 years following emplacement. Systematic temperature variation occurs as a function of fuel age at emplacement and Areal Mass Loading (AML) during the first few centuries after emplacement. After about 1000 years, emplacement age is not a strong driver on rock temperature; AML has a larger impact. High AMLs occur when large waste packages are emplaced end-to-end in drifts. Drift emplacement of equivalent packages results in lower rock temperatures than borehole emplacement. For an emplacement scheme with 50% of the drift length occupied by packages, an AML of 138 MTU/acre is about three times higher than the Site Characterization Plan-Conceptual Design (SCP-CD) value. With this higher AML (requiring only 1/3 of the SCP-CD repository footprint), peak drift wall temperatures do not exceed 160{degrees}C, but rock temperatures exceed the boiling point of water for about 3000 years. These TOPAZ3D results have been compared with reasonable agreement with two other computer codes.
NASA Technical Reports Server (NTRS)
2007-01-01
With its Multispectral Visible Imaging Camera (MVIC), half of the Ralph instrument, New Horizons captured several pictures of mesoscale gravity waves in Jupiter's equatorial atmosphere. Buoyancy waves of this type are seen frequently on Earth - for example, they can be caused when air flows over a mountain and a regular cloud pattern forms downstream. In Jupiter's case there are no mountains, but if conditions in the atmosphere are just right, it is possible to form long trains of these small waves. The source of the wave excitation seems to lie deep in Jupiter's atmosphere, below the visible cloud layers at depths corresponding to pressures 10 times that at Earth's surface. The New Horizons measurements showed that the waves move about 100 meters per second faster than surrounding clouds; this is about 25% of the speed of sound on Earth and is much greater than current models of these waves predict. Scientists can 'read' the speed and patterns these waves to learn more about activity and stability in the atmospheric layers below.
Hydroacoustic monitoring of drifting icebergs in the South Pacific Ocean
NASA Astrophysics Data System (ADS)
Chazette, J.; Hyvernaud, O.; Reymond, D.
2009-12-01
The french Commissariat à l'Energie Atomique has settled in French Polynesia a 'T-Wave' seismic network since 1960. These 10 high sensitivity broad band stations transmitted in real time enable to monitor natural submarine processes such as volcanic eruptions, colliding icebergs and seismic activity in the Pacific. During the 2008-2009 summer season in Antarctic, we have tracked the giant drifting iceberg B15a in the roaring fifties. During 4 months, we have recorded and located the hydroacoustic cracks which accompany the progressive breaking-up of B15a into small bergs and growlers. The use of arrival times and azimuth of IMS hydrophones triplet and enhanced hydroacoustic velocity model reduced significantly the error ellipse of locations. The locations have been compared with well-dated visible and infrared satellite images of iceberg B15a, providing some insights into the fracturation process.