Science.gov

Sample records for 3d magnetohydrodynamic mhd

  1. Tokamak Magnetohydrodynamic Equilibrium States with Axisymmetric Boundary and a 3D Helical Core

    SciTech Connect

    Cooper, W. A.; Graves, J. P.; Pochelon, A.; Sauter, O.; Villard, L.

    2010-07-16

    Magnetohydrodynamic (MHD) equilibrium states with imposed axisymmetric boundary are computed in which a spontaneous bifurcation develops to produce an internal three-dimensional (3D) configuration with a helical structure in addition to the standard axisymmetric system. Equilibrium states with similar MHD energy levels are shown to develop very different geometric structures. The helical equilibrium states resemble saturated internal kink mode structures.

  2. Tokamak magnetohydrodynamic equilibrium states with axisymmetric boundary and a 3D helical core.

    PubMed

    Cooper, W A; Graves, J P; Pochelon, A; Sauter, O; Villard, L

    2010-07-16

    Magnetohydrodynamic (MHD) equilibrium states with imposed axisymmetric boundary are computed in which a spontaneous bifurcation develops to produce an internal three-dimensional (3D) configuration with a helical structure in addition to the standard axisymmetric system. Equilibrium states with similar MHD energy levels are shown to develop very different geometric structures. The helical equilibrium states resemble saturated internal kink mode structures.

  3. 3D MHD disruptions simulations of tokamaks plasmas

    NASA Astrophysics Data System (ADS)

    Paccagnella, Roberto; Strauss, Hank; Breslau, Joshua

    2008-11-01

    Tokamaks Vertical Displacement Events (VDEs) and disruptions simulations in toroidal geometry by means of a single fluid visco-resistive magneto-hydro-dynamic (MHD) model are presented in this paper. The plasma model, implemented in the M3D code [1], is completed with the presence of a 2D homogeneous wall with finite resistivity. This allows the study of the relatively slowly growing magneto-hydro-dynamical perturbation, the resistive wall mode (RWM), which is, in this work, the main drive of the disruptions. Amplitudes and asymmetries of the halo currents pattern at the wall are also calculated and comparisons with tokamak experimental databases and predictions for ITER are given. [1] W. Park, E.V. Belova, G.Y. Fu, X.Z. Tang, H.R. Strauss, L.E. Sugiyama, Phys. Plasmas 6 (1999) 1796.

  4. 3D MHD Simulations of Tokamak Disruptions

    NASA Astrophysics Data System (ADS)

    Woodruff, Simon; Stuber, James

    2014-10-01

    Two disruption scenarios are modeled numerically by use of the CORSICA 2D equilibrium and NIMROD 3D MHD codes. The work follows the simulations of pressure-driven modes in DIII-D and VDEs in ITER. The aim of the work is to provide starting points for simulation of tokamak disruption mitigation techniques currently in the CDR phase for ITER. Pressure-driven instability growth rates previously observed in simulations of DIIID are verified; Halo and Hiro currents produced during vertical displacements are observed in simulations of ITER with implementation of resistive walls in NIMROD. We discuss plans to exercise new code capabilities and validation.

  5. Magnetohydrodynamic (MHD) channel corner seal

    DOEpatents

    Spurrier, Francis R.

    1980-01-01

    A corner seal for an MHD duct includes a compressible portion which contacts the duct walls and an insulating portion which contacts the electrodes, sidewall bars and insulators. The compressible portion may be a pneumatic or hydraulic gasket or an open-cell foam rubber. The insulating portion is segmented into a plurality of pieces of the same thickness as the electrodes, insulators and sidewall bars and aligned therewith, the pieces aligned with the insulator being of a different size from the pieces aligned with the electrodes and sidewall bars to create a stepped configuration along the corners of the MHD channel.

  6. Magnetohydrodynamic (MHD) driven droplet mixer

    DOEpatents

    Lee, Abraham P.; Lemoff, Asuncion V.; Miles, Robin R.

    2004-05-11

    A magnetohydrodynamic fluidic system mixes a first substance and a second substance. A first substrate section includes a first flow channel and a first plurality of pairs of spaced electrodes operatively connected to the first flow channel. A second substrate section includes a second flow channel and a second plurality of pairs of spaced electrodes operatively connected to the second flow channel. A third substrate section includes a third flow channel and a third plurality of pairs of spaced electrodes operatively connected to the third flow channel. A magnetic section and a control section are operatively connected to the spaced electrodes. The first substrate section, the second substrate section, the third substrate section, the first plurality of pairs of spaced electrodes, the second plurality of pairs of spaced electrodes, the third plurality of pairs of spaced electrodes, the magnetic section, and the control section are operated to move the first substance through the first flow channel, the second substance through the second flow channel, and both the first substance and the second substance into the third flow channel where they are mixed.

  7. Application of Magnetohydrodynamics (MHD) and Recent Research Trend

    NASA Astrophysics Data System (ADS)

    Harada, Nobuhiro

    As the applications of Magnetohydrodynamic (MHD) energy conversion, research and development for high-efficiency and low emission electric power generation system, MHD accelerations and/or MHD thrusters, and flow control around hypersonic and re-entry vehicles are introduced. For closed cycle MHD power generation, high-efficiency MHD single system is the most hopeful system and space power system using mixed inert gas (MIG) working medium is proposed. For open cycle MHD, high-efficiency coal fired MHD system with CO2 recovery has been proposed. As inverse process of MHD power generation, MHD accelerators/thrusters are expected as the next generation propulsion system. Heat flux reduction to protect re-entry vehicles is expected by an MHD process for safety return from space missions.

  8. Athena3D: Flux-conservative Godunov-type algorithm for compressible magnetohydrodynamics

    NASA Astrophysics Data System (ADS)

    Hawley, John; Simon, Jake; Stone, James; Gardiner, Thomas; Teuben, Peter

    2015-05-01

    Written in FORTRAN, Athena3D, based on Athena (ascl:1010.014), is an implementation of a flux-conservative Godunov-type algorithm for compressible magnetohydrodynamics. Features of the Athena3D code include compressible hydrodynamics and ideal MHD in one, two or three spatial dimensions in Cartesian coordinates; adiabatic and isothermal equations of state; 1st, 2nd or 3rd order reconstruction using the characteristic variables; and numerical fluxes computed using the Roe scheme. In addition, it offers the ability to add source terms to the equations and is parallelized based on MPI.

  9. 3D MHD Models of Active Region Loops

    NASA Technical Reports Server (NTRS)

    Ofman, Leon

    2004-01-01

    Present imaging and spectroscopic observations of active region loops allow to determine many physical parameters of the coronal loops, such as the density, temperature, velocity of flows in loops, and the magnetic field. However, due to projection effects many of these parameters remain ambiguous. Three dimensional imaging in EUV by the STEREO spacecraft will help to resolve the projection ambiguities, and the observations could be used to setup 3D MHD models of active region loops to study the dynamics and stability of active regions. Here the results of 3D MHD models of active region loops are presented, and the progress towards more realistic 3D MHD models of active regions. In particular the effects of impulsive events on the excitation of active region loop oscillations, and the generation, propagations and reflection of EIT waves are shown. It is shown how 3D MHD models together with 3D EUV observations can be used as a diagnostic tool for active region loop physical parameters, and to advance the science of the sources of solar coronal activity.

  10. OpenMHD: Godunov-type code for ideal/resistive magnetohydrodynamics (MHD)

    NASA Astrophysics Data System (ADS)

    Zenitani, Seiji

    2016-04-01

    OpenMHD is a Godunov-type finite-volume code for ideal/resistive magnetohydrodynamics (MHD). It is written in Fortran 90 and is parallelized by using MPI-2 and OpenMP. The code was originally developed for studying magnetic reconnection problems and has been made publicly available in the hope that others may find it useful.

  11. [Nonlinear magnetohydrodynamics]. [Threshold unstable MHD activity

    SciTech Connect

    Not Available

    1992-01-01

    Theoretical predictions were compared with available data from JET on the threshold unstable MHD activity in toroidal confinement devices. In particular, questions arising as to Hartmans number and the selection of a kinematic viscosity are discussed.

  12. Diagnostic development and support of MHD (magnetohydrodynamics) test facilities

    SciTech Connect

    Not Available

    1989-07-01

    Mississippi State University (MSU) is developing diagnostic instruments for Magnetohydrodynamics (MHD) power train data acquisition and for support of MHD component development test facilities. Microprocessor-controlled optical instruments, initially developed for HRSR support, are being refined, and new systems to measure temperatures and gas-seed-slag stream characteristics are being developed. To further data acquisition and analysis capabilities, the diagnostic systems are being interfaced with MHD Energy Center computers. Technical support for the diagnostic needs of the national MHD research effort is being provided. MSU personnel will also cooperate with government agencies and private industries to improve the transformation of research and development results into processes, products and services applicable to their needs.

  13. FARGO3D: A New GPU-oriented MHD Code

    NASA Astrophysics Data System (ADS)

    Benítez-Llambay, Pablo; Masset, Frédéric S.

    2016-03-01

    We present the FARGO3D code, recently publicly released. It is a magnetohydrodynamics code developed with special emphasis on the physics of protoplanetary disks and planet-disk interactions, and parallelized with MPI. The hydrodynamics algorithms are based on finite-difference upwind, dimensionally split methods. The magnetohydrodynamics algorithms consist of the constrained transport method to preserve the divergence-free property of the magnetic field to machine accuracy, coupled to a method of characteristics for the evaluation of electromotive forces and Lorentz forces. Orbital advection is implemented, and an N-body solver is included to simulate planets or stars interacting with the gas. We present our implementation in detail and present a number of widely known tests for comparison purposes. One strength of FARGO3D is that it can run on either graphical processing units (GPUs) or central processing units (CPUs), achieving large speed-up with respect to CPU cores. We describe our implementation choices, which allow a user with no prior knowledge of GPU programming to develop new routines for CPUs, and have them translated automatically for GPUs.

  14. FLIP MHD - A particle-in-cell method for magnetohydrodynamics

    NASA Technical Reports Server (NTRS)

    Brackbill, J. U.

    1991-01-01

    The fluid-implicit-particle, or 'FLIP' method presently extended to 2D and 3D MHD flow incorporates a Lagrangian field representation and yields a grid magnetic Reynolds number of up to 16 while preserving contact continuities that retain the Galilean invariance of the MHD flow equations. Analytical arguments and numerical examples demonstrate the conservation of mass, momentum, magnetic flux, and energy; 2D calculation results for the illustrative cases of contact discontinuity convection, Rayleigh-Taylor unstable flow.

  15. MHD-EMP analysis and protection. Technical report. [MHD-EMP (magnetohydrodynamic-electromagnetic pulse)

    SciTech Connect

    Barnes, P.R.; Tesche, F.M.; McConnell, B.W.; Vance, E.F.

    1993-09-01

    A large nuclear detonation at altitudes of several hundred kilometers above the earth distorts the earth's magnetic field and produces a strong magnetohydrodynamic-electromagnetic pulse (MHD-EMP). MHD-EMP is similar to solar geomagnetic storms in its global and low frequency (less than 1 Hz) nature except that it can be more intense with a shorter duration. It will induce quasi-dc currents in long lines. The MHD-EMP induced currents may cause large voltage fluctuations and severe harmonic distortion in commercial electric power systems. Several MHD-EMP coupling models for predicting the induced current on a wide variety of conducting structures are described, various simulation concepts are summarized, and the results from several MHD-EMP tests are presented. To mitigate the effects of MHD-EMP on a facility, long conductors must be isolated from the building, and the commercial power harmonics and voltage swings must be addressed. It is found that facilities can be protected against MHD-EMP by using methods which are consistent with standard engineering practices. MHD-EMP Interaction Analysis, Power Line Model, MHD-EMP Protection Guidelines, Transformer Test.

  16. Capabilities of a Global 3D MHD Model for Monitoring Extremely Fast CMEs

    NASA Astrophysics Data System (ADS)

    Wu, C. C.; Plunkett, S. P.; Liou, K.; Socker, D. G.; Wu, S. T.; Wang, Y. M.

    2015-12-01

    Since the start of the space era, spacecraft have recorded many extremely fast coronal mass ejections (CMEs) which have resulted in severe geomagnetic storms. Accurate and timely forecasting of the space weather effects of these events is important for protecting expensive space assets and astronauts and avoiding communications interruptions. Here, we will introduce a newly developed global, three-dimensional (3D) magnetohydrodynamic (MHD) model (G3DMHD). The model takes the solar magnetic field maps at 2.5 solar radii (Rs) and intepolates the solar wind plasma and field out to 18 Rs using the algorithm of Wang and Sheeley (1990, JGR). The output is used as the inner boundary condition for a 3D MHD model. The G3DMHD model is capable of simulating (i) extremely fast CME events with propagation speeds faster than 2500 km/s; and (ii) multiple CME events in sequence or simultaneously. We will demonstrate the simulation results (and comparison with in-situ observation) for the fastest CME in record on 23 July 2012, the shortest transit time in March 1976, and the well-known historic Carrington 1859 event.

  17. Jupiter Magnetotail Interaction with a Variable Solar Wind: A 3D MHD Simulation

    NASA Astrophysics Data System (ADS)

    Ranquist, D. A.; Bagenal, F.; Delamere, P. A.; Ma, X.

    2015-12-01

    Jupiter's magnetosphere is the largest object within the heliosphere. Voyager 2 detected its influence at Saturn's orbit, 4.3 AU away. It takes considerable time, therefore, for the solar wind to propagate such lengths down the tail. This propagation time is much greater than typical periods between changes in direction of the interplanetary magnetic field (IMF). We expect these variable magnetic fields to create a jumbled structure in Jupiter's magnetotail, resulting in magnetic reconnection and other magnetic processes. We simulate the global interaction of the solar wind with Jupiter's magnetosphere using a 3D magnetohydrodynamics (MHD) code. Delamere & Bagenal (2010) argue that the interaction is largely viscous, so we simulate the jovian magnetosphere as a region where the momentum equation has an added loss term. We also use in situ data gathered by the Ulysses spacecraft near Jupiter's orbit for solar wind input. Here, we report on the simulated dynamics in Jupiter's tail region.

  18. Particle Acceleration in the Low Corona Over Broad Longitudes: Coupling MHD and 3D Particle Simulations

    NASA Astrophysics Data System (ADS)

    Gorby, M.; Schwadron, N.; Torok, T.; Downs, C.; Lionello, R.; Linker, J.; Titov, V. S.; Mikic, Z.; Riley, P.; Desai, M. I.; Dayeh, M. A.

    2014-12-01

    Recent work on the coupling between the Energetic Particle Radiation Environment Module (EPREM, a 3D energetic particle model) and Magnetohydrodynamics Around a Sphere (MAS, an MHD code developed at Predictive Science, Inc.) has demonstrated the efficacy of compression regions around fast coronal mass ejections (CMEs) for particle acceleration low in the corona (˜ 3 - 6 solar radii). These couplings show rapid particle acceleration over a broad longitudinal extent (˜ 80 degrees) resulting from the pile-up of magnetic flux in the compression regions and their subsequent expansion. The challenge for forming large SEP events in such compression-acceleration scenarios is to have enhanced scattering within the acceleration region while also allowing for efficient escape of accelerated particles downstream (away from the Sun) from the compression region. We present here the most recent simulation results including energetic particle and CME plasma profiles, the subsequent flux and dosages at 1AU, and an analysis of the compressional regions as efficient accelerators.

  19. Impact of helical boundary conditions on nonlinear 3D magnetohydrodynamic simulations of reversed-field pinch

    NASA Astrophysics Data System (ADS)

    Veranda, M.; Bonfiglio, D.; Cappello, S.; Chacón, L.; Escande, D. F.

    2013-07-01

    Helical self-organized reversed-field pinch (RFP) regimes emerge both numerically—in 3D visco-resistive magnetohydrodynamic (MHD) simulations—and experimentally, as in the RFX-mod device at high current (IP above 1 MA). These states, called quasi-single helicity (QSH) states, are characterized by the action of a MHD mode that impresses a quasi-helical symmetry to the system, thus allowing a high degree of magnetic chaos healing. This is in contrast with the multiple helicity (MH) states, where magnetic fluctuations create a chaotic magnetic field degrading the confinement properties of the RFP. This paper reports an extensive numerical study performed in the frame of 3D visco-resistive MHD which considers the effect of helical magnetic boundary conditions, i.e. of a finite value of the radial magnetic field at the edge (magnetic perturbation, MP). We show that the system can be driven to a selected QSH state starting from both spontaneous QSH and MH regimes. In particular, a high enough MP can force a QSH helical self-organization with a helicity different from the spontaneous one. Moreover, MH states can be turned into QSH states with a selected helicity. A threshold in the amplitude of MP is observed above which is able to influence the system. Analysis of the magnetic topology of these simulations indicates that the dominant helical mode is able to temporarily sustain conserved magnetic structures in the core of the plasma. The region occupied by conserved magnetic surfaces increases reducing secondary modes' amplitude to experimental-like values.

  20. Observationally driven 3D magnetohydrodynamics model of the solar corona above an active region

    NASA Astrophysics Data System (ADS)

    Bourdin, Ph.-A.; Bingert, S.; Peter, H.

    2013-07-01

    Context. Aims: The goal is to employ a 3D magnetohydrodynamics (MHD) model including spectral synthesis to model the corona in an observed solar active region. This will allow us to judge the merits of the coronal heating mechanism built into the 3D model. Methods: Photospheric observations of the magnetic field and horizontal velocities in an active region are used to drive our coronal simulation from the bottom. The currents induced by this heat the corona through Ohmic dissipation. Heat conduction redistributes the energy that is lost in the end through optically thin radiation. Based on the MHD model, we synthesized profiles of coronal emission lines which can be directly compared to actual coronal observations of the very same active region. Results: In the synthesized model data we find hot coronal loops which host siphon flows or which expand and lose mass through draining. These synthesized loops are at the same location as and show similar dynamics in terms of Doppler shifts to the observed structures. This match is shown through a comparison with Hinode data as well as with 3D stereoscopic reconstructions of data from STEREO. Conclusions: The considerable match to the actual observations shows that the field-line braiding mechanism leading to the energy input in our corona provides the proper distribution of heat input in space and time. From this we conclude that in an active region the field-line braiding is the dominant heating process, at least at the spatial scales available to current observations. Parameters and simulation log-files are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/555/A123

  1. Scaling laws of coronal loops compared to a 3D MHD model of an active region

    NASA Astrophysics Data System (ADS)

    Bourdin, Ph.-A.; Bingert, S.; Peter, H.

    2016-05-01

    Context. The structure and heating of coronal loops have been investigated for decades. Established scaling laws relate fundamental quantities like the loop apex temperature, pressure, length, and coronal heating. Aims: We test these scaling laws against a large-scale 3D magneto-hydrodynamics (MHD) model of the solar corona, which became feasible with current high-performance computing. Methods: We drove an active region simulation with photospheric observations and find strong similarities to the observed coronal loops in X-rays and extreme-ultraviolet (EUV) wavelength. A 3D reconstruction of stereoscopic observations shows that our model loops have a realistic spatial structure. We compared scaling laws to our model data extracted along an ensemble of field lines. Finally, we fit a new scaling law that represents hot loops and also cooler structures, which was not possible before based only on observations. Results: Our model data gives some support for scaling laws that were established for hot and EUV-emissive coronal loops. For the Rosner-Tucker-Vaiana (RTV) scaling law we find an offset to our model data, which can be explained by 1D considerations of a static loop with a constant heat input and conduction. With a fit to our model data we set up a new scaling law for the coronal heat input along magnetic field lines. Conclusions: RTV-like scaling laws were fitted to hot loops and therefore do not predict well the coronal heat input for cooler structures that are barely observable. The basic differences between 1D and self-consistent 3D modeling account for deviations between earlier scaling laws and ours. We also conclude that a heating mechanism by MHD-turbulent dissipation within a braided flux tube would heat the corona stronger than is consistent with our model corona.

  2. 3D MHD modelling of low current-high voltage dc plasma torch under restrike mode

    NASA Astrophysics Data System (ADS)

    Lebouvier, A.; Delalondre, C.; Fresnet, F.; Cauneau, F.; Fulcheri, L.

    2012-01-01

    We present in this paper a magnetohydrodynamic (MHD) modelling of the gliding arc behaviour of a dc plasma torch operating with air under low current and high voltage conditions. The low current leads to instabilities and difficulties with simulating the process because the magnetic field is not sufficient to constrict the arc. The model is 3D, time dependent and the MHD equations are solved using CFD software Code_Saturne®. Although the arc is definitively non-local thermodynamic equilibrium (LTE), the LTE assumption is considered as a first approach. The injection of air is tangential. A hot gas channel reattachment model has been used to simulate the restriking process of the arc root. After the description of the model, the most appropriate electrical voltage breakdown parameter has been selected in comparing with experimental results. A typical operating point is then studied in detail and shows the helical shape of the arc discharge in the nozzle. Finally, the mass flow rate and the current have been varied in the range 0.16-0.5 g s-1 and 100-300 mA, respectively, corresponding to typical glidarc operating points of our experimental plasma torch. The model shows good consistency with experimental data in terms of global behaviour, arc length, mean voltage and glidarc frequency.

  3. 3D MHD simulations of radial wire arrays

    NASA Astrophysics Data System (ADS)

    Jennings, C.; Ampleford, D.; Ciardi, A.; Chittenden, J.; Bland, S.; Niasse, N.

    2008-04-01

    We present 3D resistive MHD simulations evaluating multi-MA radial wire arrays as a potential compact, high intensity source for inertial confinement fusion and laboratory astrophysics. A radial wire array consists of wires running radially outwards from a central electrode, and was first investigated at the 1 MA level on the MAGPIE generator at Imperial College. Originally used as a method of producing magnetic tower laboratory jets relevant to astrophysics[1], they have also shown potential as a high power x-ray source. Able to produce x-ray pulses with a rise time and peak power comparable to cylindrical wire arrays, radial arrays occupy a smaller volume and may consequently be able to access higher power densities. We discuss simulation results reproducing radial array experiments performed on the MAGPIE facility as a means of benchmarking our model. This model is then used to evaluate radial wire arrays in the multi-MA regime for planned experiments on the Saturn generator of Sandia National Laboratories. [1] A. Ciardi et al, Phys. Plasmas 14, 056501 (2007)

  4. Computational MHD on 3D Unstructured Lagrangian Meshes

    NASA Astrophysics Data System (ADS)

    Rousculp, C. L.; Barnes, D. C.

    1999-11-01

    Lagrangian computational meshes are typically employed to model multi-material problems because they do not require costly interface tracking methods. Our algorithms, for ideal and non-ideal 3D MHD, are designed for use on such meshes composed of polyhedral cells with an arbitrary number of faces. This allows for mesh refinement during a calculation to prevent the well known problem of mesh tangling. The action of the magnetic vector potential, A \\cdot δ l, is centered on edges. For ideal and non-ideal flow, this maintains nabla \\cdot B = 0 to round-off error. Vertex forces are derived by the variation of magnetic energy with respect to vertex positions, F = - partial WB / partial r. This assures symmetry as well as magnetic flux, momentum, and energy conservation. The method is local so that parallelization by domain decomposition is natural for large meshes. The resistive diffusion part is calculated using the support operator method, to obtain energy conservation, symmetry. Implicit time difference equations are solved by preconditioned, conjugate gradient methods. Results of convergence tests are presented. Boundary conditions at plasma vaccuum interfaces have been incorporated. Initial results of an annular Z-pinch implosion problem are shown.

  5. Simulations Of 3D MHD Jets: The Effects Of ICM Weather And AGN History On X-ray Cavities

    NASA Astrophysics Data System (ADS)

    Mendygral, Peter; Jones, T. W.; Dolag, K.

    2011-01-01

    The powerful jets from AGN produce low density bubbles in the ICM of the host galaxy cluster that are observed as X-ray cavities. The morphology of X-ray cavities is influenced by factors such as AGN history and ICM weather. We present 3D magnetohydrodynamical (MHD) simulations of hypersonic AGN jets in realistic cluster environments that explore the relationship between these factors and cavity properties. We will also discuss the consequences on observations of X-ray cavities with synthetic observations of these simulations. This work is supported by the NSF and by the University of Minnesota Supercomputing Institute.

  6. 3D Neutronic Analysis in MHD Calculations at ARIES-ST Fusion Reactors Systems

    NASA Astrophysics Data System (ADS)

    Hançerliogulları, Aybaba; Cini, Mesut

    2013-10-01

    In this study, we developed new models for liquid wall (FW) state at ARIES-ST fusion reactor systems. ARIES-ST is a 1,000 MWe fusion reactor system based on a low aspect ratio ST plasma. In this article, we analyzed the characteristic properties of magnetohydrodynamics (MHD) and heat transfer conditions by using Monte-Carlo simulation methods (ARIES Team et al. in Fusion Eng Des 49-50:689-695, 2000; Tillack et al. in Fusion Eng Des 65:215-261, 2003) . In fusion applications, liquid metals are traditionally considered to be the best working fluids. The working liquid must be a lithium-containing medium in order to provide adequate tritium that the plasma is self-sustained and that the fusion is a renewable energy source. As for Flibe free surface flows, the MHD effects caused by interaction with the mean flow is negligible, while a fairly uniform flow of thick can be maintained throughout the reactor based on 3-D MHD calculations. In this study, neutronic parameters, that is to say, energy multiplication factor radiation, heat flux and fissile fuel breeding were researched for fusion reactor with various thorium and uranium molten salts. Sufficient tritium amount is needed for the reactor to work itself. In the tritium breeding ratio (TBR) >1.05 ARIES-ST fusion model TBR is >1.1 so that tritium self-sufficiency is maintained for DT fusion systems (Starke et al. in Fusion Energ Des 84:1794-1798, 2009; Najmabadi et al. in Fusion Energ Des 80:3-23, 2006).

  7. WhiskyMHD: Numerical Code for General Relativistic Magnetohydrodynamics

    NASA Astrophysics Data System (ADS)

    Baiotti, Luca; Giacomazzo, Bruno; Hawke, Ian; et al.

    2010-10-01

    Whisky is a code to evolve the equations of general relativistic hydrodynamics (GRHD) and magnetohydrodynamics (GRMHD) in 3D Cartesian coordinates on a curved dynamical background. It was originally developed by and for members of the EU Network on Sources of Gravitational Radiation and is based on the Cactus Computational Toolkit. Whisky can also implement adaptive mesh refinement (AMR) if compiled together with Carpet. Whisky has grown from earlier codes such as GR3D and GRAstro_Hydro, but has been rewritten to take advantage of some of the latest research performed here in the EU. The motivation behind Whisky is to compute gravitational radiation waveforms for systems that involve matter. Examples would include the merger of a binary system containing a neutron star, which are expected to be reasonably common in the universe and expected to produce substantial amounts of radiation. Other possible sources are given in the projects list.

  8. Magnetohydrodynamics (MHD) Engineering Test Facility (ETF) 200 MWe power plant Conceptual Design Engineering Report (CDER)

    NASA Technical Reports Server (NTRS)

    1981-01-01

    The reference conceptual design of the magnetohydrodynamic (MHD) Engineering Test Facility (ETF), a prototype 200 MWe coal-fired electric generating plant designed to demonstrate the commercial feasibility of open cycle MHD, is summarized. Main elements of the design, systems, and plant facilities are illustrated. System design descriptions are included for closed cycle cooling water, industrial gas systems, fuel oil, boiler flue gas, coal management, seed management, slag management, plant industrial waste, fire service water, oxidant supply, MHD power ventilating

  9. DISCO: A 3D Moving-mesh Magnetohydrodynamics Code Designed for the Study of Astrophysical Disks

    NASA Astrophysics Data System (ADS)

    Duffell, Paul C.

    2016-09-01

    This work presents the publicly available moving-mesh magnetohydrodynamics (MHD) code DISCO. DISCO is efficient and accurate at evolving orbital fluid motion in two and three dimensions, especially at high Mach numbers. DISCO employs a moving-mesh approach utilizing a dynamic cylindrical mesh that can shear azimuthally to follow the orbital motion of the gas. The moving mesh removes diffusive advection errors and allows for longer time-steps than a static grid. MHD is implemented in DISCO using an HLLD Riemann solver and a novel constrained transport (CT) scheme that is compatible with the mesh motion. DISCO is tested against a wide variety of problems, which are designed to test its stability, accuracy, and scalability. In addition, several MHD tests are performed which demonstrate the accuracy and stability of the new CT approach, including two tests of the magneto-rotational instability, one testing the linear growth rate and the other following the instability into the fully turbulent regime.

  10. 3-D MHD disk wind simulations of protostellar jets

    NASA Astrophysics Data System (ADS)

    Staff, Jan E.; Koning, Nico; Ouyed, Rachid; Tanaka, Kei; Tan, Jonathan C.

    2016-01-01

    We present the results of large scale, three-dimensional magnetohydrodynamics simulations of disk winds for different initial magnetic field configurations. The jets are followed from the source to distances, which are resolvable by HST and ALMA observations. Our simulations show that jets are heated along their length by many shocks. The mass of the protostar is a free parameter that can be inserted in the post processing of the data, and we apply the simulations to both low mass and high mass protostars. For the latter we also compute the expected diagnostics when the outflow is photoionized by the protostar. We compute the emission lines that are produced, and find excellent agreement with observations. For a one solar mass protostar, we find the jet width to be between 20 and 30 au while the maximum velocities perpendicular to the jet are found to be 100 km s-1. The initially less open magnetic field configuration simulations result in a wider, two-component jet; a cylindrically shaped outer jet surrounding a narrow and much faster, inner jet. For the initially most open magnetic field configuration the kink mode creates a narrow corkscrew-like jet without a clear Keplerian rotation profile and even regions where we observe rotation opposite to the disk (counter-rotating). This is not seen in the less open field configurations.

  11. Trapping solids at the inner edge of the dead zone: 3-D global MHD simulations

    NASA Astrophysics Data System (ADS)

    Dzyurkevich, N.; Flock, M.; Turner, N. J.; Klahr, H.; Henning, Th.

    2010-06-01

    Context. The poorly-ionized interior of the protoplanetary disk or “dead zone” is the location where dust coagulation processes may be most efficient. However even here, planetesimal formation may be limited by the loss of solid material through radial drift, and by collisional fragmentation of the particles. Both depend on the turbulent properties of the gas. Aims: Our aim here is to investigate the possibility that solid particles are trapped at local pressure maxima in the dynamically evolving disk. We perform the first 3-D global non-ideal magnetohydrodynamical (MHD) calculations of a section of the disk treating the turbulence driven by the magneto-rotational instability (MRI). Methods: We use the ZeusMP code with a fixed Ohmic resistivity distribution. The domain contains an inner MRI-active region near the young star and an outer midplane dead zone, with the transition between the two modeled by a sharp increase in the magnetic diffusivity. Results: The azimuthal magnetic fields generated in the active zone oscillate over time, changing sign about every 150 years. We thus observe the radial structure of the “butterfly pattern” seen previously in local shearing-box simulations. The mean magnetic field diffuses from the active zone into the dead zone, where the Reynolds stress nevertheless dominates, giving a residual α between 10-4 and 10-3. The greater total accretion stress in the active zone leads to a net reduction in the surface density, so that after 800 years an approximate steady state is reached in which a local radial maximum in the midplane pressure lies near the transition radius. We also observe the formation of density ridges within the active zone. Conclusions: The dead zone in our models possesses a mean magnetic field, significant Reynolds stresses and a steady local pressure maximum at the inner edge, where the outward migration of planetary embryos and the efficient trapping of solid material are possible.

  12. Relativistic MHD simulations of core-collapse GRB jets: 3D instabilities and magnetic dissipation

    NASA Astrophysics Data System (ADS)

    Bromberg, Omer; Tchekhovskoy, Alexander

    2016-02-01

    Relativistic jets are associated with extreme astrophysical phenomena, like the core collapse of massive stars in gamma-ray bursts (GRBs) and the accretion on to supermassive black holes in active galactic nuclei. It is generally accepted that these jets are powered electromagnetically, by the magnetized rotation of a central compact object (black hole or neutron star). However, how the jets produce the observed emission and survive the propagation for many orders of magnitude in distance without being disrupted by current-driven instabilities is the subject of active debate. We carry out time-dependent 3D relativistic magnetohydrodynamic (MHD) simulations of relativistic, Poynting-flux-dominated jets. The jets are launched self-consistently by the rotation of a strongly magnetized central object. This determines the natural degree of azimuthal magnetic field winding, a crucial factor that controls jet stability. We find that the jets are susceptible to two types of instability: (i) a global, external kink mode that grows on long time-scales. It bodily twists the jet, reducing its propagation velocity. We show analytically that in flat density profiles, like the ones associated with galactic cores, the external mode grows and may stall the jet. In the steep profiles of stellar envelopes the external kink weakens as the jet propagates outward. (ii) a local, internal kink mode that grows over short time-scales and causes small-angle magnetic reconnection and conversion of about half of the jet electromagnetic energy flux into heat. We suggest that internal kink instability is the main dissipation mechanism responsible for powering GRB prompt emission.

  13. Numerical experimentation on spherically symmetric one-dimensional magnetohydrodynamic /MHD/ wave propagation

    NASA Technical Reports Server (NTRS)

    Han, S. M.; Wu, S. T.; Nakagawa, Y.

    1982-01-01

    Radial propagation of one-dimensional magnetohydrodynamic (MHD) waves are analyzed numerically on the basis of the Implicit-Continuous-Fluid-Eulerian (ICE) scheme. Accuracy of the numerical method and other properties are tested through the study of MHD wave propagation. The three different modes of MHD waves (i.e., fast-, slow- and Alfven (transverse) mode) are generated by applying physically consistent boundary perturbations derived from MHD compatibility relations. It is shown that the resulting flow following these waves depend upon the relative configurations of the initial magnetic field and boundary perturbations.

  14. 3D MHD modeling of twisted coronal loops

    NASA Astrophysics Data System (ADS)

    Reale, F.; Orlando, S.; Guarrasi, M.; Mignone, A.; Peres, G.; Hood, A. W.; Priest, E. R.

    2016-10-01

    We perform MHD modeling of a single bright coronal loop to include the interaction with a non-uniform magnetic field. The field is stressed by random footpoint rotation in the central region and its energy is dissipated into heating by growing currents through anomalous magnetic diffusivity that switches on in the corona above a current density threshold. We model an entire single magnetic flux tube in the solar atmosphere extending from the high-β chromosphere to the low-β corona through the steep transition region. The magnetic field expands from the chromosphere to the corona. The maximum resolution is ∼30 km. We obtain an overall evolution typical of loop models and realistic loop emission in the EUV and X-ray bands. The plasma confined in the flux tube is heated to active region temperatures (∼3 MK) after ∼2/3 hr. Upflows from the chromosphere up to ∼100 km s‑1 fill the core of the flux tube to densities above 109 cm‑3. More heating is released in the low corona than the high corona and is finely structured both in space and time.

  15. Plasma response measurements of external magnetic perturbations using electron cyclotron emission and comparisons to 3D ideal MHD equilibrium

    NASA Astrophysics Data System (ADS)

    Willensdorfer, M.; Denk, S. S.; Strumberger, E.; Suttrop, W.; Vanovac, B.; Brida, D.; Cavedon, M.; Classen, I.; Dunne, M.; Fietz, S.; Fischer, R.; Kirk, A.; Laggner, F. M.; Liu, Y. Q.; Odstrčil, T.; Ryan, D. A.; Viezzer, E.; Zohm, H.; Luhmann, I. C.; The ASDEX Upgrade Team; The EUROfusion MST1 Team

    2016-11-01

    The plasma response from an external n  =  2 magnetic perturbation field in ASDEX Upgrade has been measured using mainly electron cyclotron emission (ECE) diagnostics and a rigid rotating field. To interpret ECE and ECE-imaging (ECE-I) measurements accurately, forward modeling of the radiation transport has been combined with ray tracing. The measured data is compared to synthetic ECE data generated from a 3D ideal magnetohydrodynamics (MHD) equilibrium calculated by VMEC. The measured amplitudes of the helical displacement around the outboard midplane are in reasonable agreement with the one from the synthetic VMEC diagnostics. Both exceed the predictions from the vacuum field calculations and indicate the presence of a kink response at the edge, which amplifies the perturbation. VMEC and MARS-F have been used to calculate the properties of this kink mode. The poloidal mode structure of the magnetic perturbation of this kink mode at the edge peaks at poloidal mode numbers larger than the resonant components |m|>|nq| , whereas the poloidal mode structure of its displacement is almost resonant |m|≈ |nq| . This is expected from ideal MHD in the proximity of rational surfaces. The displacement measured by ECE-I confirms this resonant response.

  16. Magnetohydrodynamic (MHD) nuclear weapons effects on submarine cable systems. Volume 1. Experiments and analysis. Final report

    SciTech Connect

    Not Available

    1987-06-01

    This report presents a study of the nuclear weapons magnetohydrodynamic (MHD) effects on submarine communications cables. The study consisted of the analysis and interpretation of currently available data on submarine cable systems TAT-4, TAT-6, and TAT-7. The primary result of the study is that decrease of the effective resistivity with frequency over the available experimental range, coupled with the model results, leads to quite small effective resistivities at the MHD characteristic frequencies, and hence small earth potential differences. Thus, it appears that submarine cable systems are less susceptible to an MHD threat than their land-based counter-parts.

  17. Mitigation of magnetohydrodynamic electromagnetic pulse (MHD-EMP) effects from commerical electric power systems

    SciTech Connect

    Barnes, P.R. ); Tesche, F.M. , Dallas, TX ); Vance, E.F. , Fort Worth, TX )

    1992-03-01

    A large nuclear detonation at altitudes of several hundred kilometers above the earth distorts the earth's magnetic field and produces a strong magnetohydrodynamic electromagnetic pulse (MHD-EMP). This can adversely affect electrical power systems. In this report, the effects of this nuclear environment on critical facilities connected to the commercial power system are considered. Methods of mitigating the MHD-EMP impacts are investigated, and recommended protection schemes are presented. Guidelines for testing facilities to determine the effects of MHD-EMP and to validate the mitigation methods also are discussed.

  18. Magnetic fields near spacecraft-explored comets: 3D MHD numerical simulation

    NASA Astrophysics Data System (ADS)

    Baranov, V. B.; Alexashov, D. B.; Lebedev, M. G.

    2015-05-01

    The magnetohydrodynamic (MHD) model of the interaction between the solar wind and a cometary ionosphere is presented. The model accounts for photoionization of the neutral component of the cometary outflow and the resonance charge exchange between charged and neutral particles, together with the interplanetary magnetic field. The numerical implementation of the model is performed on the basis of the second-order shock-fitting Godunov method generalized to cover MHD flows. The results of the calculations are analysed with emphasis on the behaviour of the interplanetary magnetic field disturbed by the cometary outflow. The comparison of the numerical results with the spaceboard measured data obtained during the spacecraft flybys near comets Halley and Grigg-Skjellerup shows their good agreement, thus giving promise that the model will be capable to adequately describe the plasma and magnetic surrounding of comet Churyumov-Gerasimenko during the Rosetta spacecraft encounter.

  19. 3D MHD VDE and disruptions simulations of tokamaks plasmas including some ITER scenarios

    NASA Astrophysics Data System (ADS)

    Paccagnella, R.; Strauss, H. R.; Breslau, J.

    2009-03-01

    Tokamaks vertical displacement events (VDEs) and disruptions simulations in toroidal geometry by means of a single fluid visco-resistive magneto-hydro-dynamic (MHD) model are presented in this paper. The plasma model is completed with the presence of a 2D wall with finite resistivity which allows the study of the relatively slowly growing magnetic perturbation, the resistive wall mode (RWM), which is, in this paper, the main drive of the disruption evolution. Amplitudes and asymmetries of the halo currents pattern at the wall are also calculated and comparisons with tokamak experimental databases and predictions for ITER are given.

  20. M3D Simulations of Energetic Particle-driven MHD Mode with Unstructured Mesh

    NASA Astrophysics Data System (ADS)

    Fu, G. Y.; Park, W.; Strauss, H. R.

    2001-10-01

    The energetic particle-driven MHD modes are studied using a multi-level extended MHD code M3D(W. Park et al., Phys. Plasmas 6, 1796 (1999)). In a Extended-MHD model, the plasma is divided into the bulk part and the energetic particle component. The bulk plasma is treated as either a single fluid or two fluids. The energetic particles are described by gyrokinetic particles following the self-consistent electromagnetic field. The model is self-consistent, including nonlinear effects of hot particles on the MHD dynamics and the nonlinear MHD mode coupling. Previously we had shown the results of nonlinear saturation of TAEfootnote G.Y. Fu and W. Park, Phys. Rev. Lett. 74, 1594 (1995), energetic particle stabilization of an internal kink and excitation of fishbone^2, and nonlinear saturation of fishbone in circular tokamaks (G.Y. Fu et al, 2000 Sherwood Meeting, Paper 2C2.). In this work, we extend the simulations to general geometry using unstructured mesh(H.R. Strauss and W. Park, Phys. Plasmas 5, 2676 (1998). We also use a gyrofluid model for fishbone in order to study the role of MHD nonlinearity in saturation near the marginal stability. Results of applications to tokamaks and spherical tokamaks will be presented.

  1. Numerical Simulation of 3-D Supersonic Viscous Flow in an Experimental MHD Channel

    NASA Technical Reports Server (NTRS)

    Kato, Hiromasa; Tannehill, John C.; Gupta, Sumeet; Mehta, Unmeel B.

    2004-01-01

    The 3-D supersonic viscous flow in an experimental MHD channel has been numerically simulated. The experimental MHD channel is currently in operation at NASA Ames Research Center. The channel contains a nozzle section, a center section, and an accelerator section where magnetic and electric fields can be imposed on the flow. In recent tests, velocity increases of up to 40% have been achieved in the accelerator section. The flow in the channel is numerically computed using a new 3-D parabolized Navier-Stokes (PNS) algorithm that has been developed to efficiently compute MHD flows in the low magnetic Reynolds number regime. The MHD effects are modeled by introducing source terms into the PNS equations which can then be solved in a very e5uent manner. To account for upstream (elliptic) effects, the flowfield can be computed using multiple streamwise sweeps with an iterated PNS algorithm. The new algorithm has been used to compute two test cases that match the experimental conditions. In both cases, magnetic and electric fields are applied to the flow. The computed results are in good agreement with the available experimental data.

  2. Kinematic MHD Models of Collapsing Magnetic Traps: Extension to 3D

    SciTech Connect

    Grady, Keith J.; Neukirch, Thomas

    2009-02-16

    We show how fully 3D kinematic MHD models of collapsing magnetic traps (CMTs) can be constructed, thus extending previous work on 2D trap models. CMTs are thought to form in the relaxing magnetic field lines in solar flares and it has been proposed that they play an important role in the acceleration of high-energy particles. This work is a first step to understanding the physics of CMTs better.

  3. EDITORIAL: 15th Workshop on MHD Stability Control: 3D Magnetic Field Effects in MHD Control 15th Workshop on MHD Stability Control: 3D Magnetic Field Effects in MHD Control

    NASA Astrophysics Data System (ADS)

    Buttery, Richard

    2011-08-01

    This annual workshop on MHD Stability Control has been held since 1996 with a focus on understanding and developing control of MHD instabilities for future fusion reactors. The workshop generally covers a wide range of stability topics: from disruptions, to tearing modes, error fields, ELMs, resistive wall modes (RWMs) and ideal MHD. It spans many device types, particularly tokamaks, stellarators and reversed field pinches, to pull out commonalities in the physics and improve understanding. In 2010 the workshop was held on 15-17 November at the University of Wisconsin in Madison and was combined with the annual US-Japan MHD Workshop. The theme was `3D Magnetic Field Effects in MHD Control', with a focus on multidisciplinary sessions exploring issues of plasma response to 3D fields, the manifestation of such fields in the plasma, and how they influence stability. This has been a topic of renewed interest, with utilisation of 3D fields for ELM control now planned in ITER, and a focus on the application of such fields for error field correction, disruption avoidance, and RWM control. Key issues included the physics of the interaction, types of coils and harmonic spectra needed to control instabilities, and subsidiary effects such as braking (or rotating) the plasma. More generally, a wider range of issues were discussed including RWM physics, tearing mode physics, disruption mitigation, ballooning stability, the snowflake divertor concept, and the line tied pinch! A novel innovation to the meeting was a panel discussion session, this year on Neoclassical Toroidal Viscosity, which ran well; more will be tried next year. In this special section of Plasma Physics and Controlled Fusion we present several of the invited and contributed papers from the 2010 workshop, which have been subject to the normal refereeing procedures of the journal. These papers give a sense of the exceptional quality of the presentations at this workshop, all of which may be found at http://fusion.gat.com/conferences/mhd

  4. Magnetohydrodynamic (MHD) modelling of solar active phenomena via numerical methods

    NASA Technical Reports Server (NTRS)

    Wu, S. T.

    1988-01-01

    Numerical ideal MHD models for the study of solar active phenomena are summarized. Particular attention is given to the following physical phenomena: (1) local heating of a coronal loop in an isothermal and stratified atmosphere, and (2) the coronal dynamic responses due to magnetic field movement. The results suggest that local heating of a magnetic loop will lead to the enhancement of the density of the neighboring loops through MHD wave compression. It is noted that field lines can be pinched off and may form a self-contained magnetized plasma blob that may move outward into interplanetary space.

  5. Effects of a weakly 3-D equilibrium on ideal magnetohydrodynamic instabilities

    SciTech Connect

    Hegna, C. C.

    2014-07-15

    The effect of a small three-dimensional equilibrium distortion on an otherwise axisymmetric configuration is shown to be destabilizing to ideal magnetohydrodynamic modes. The calculations assume that the 3-D fields are weak and that shielding physics is present so that no islands appear in the resulting equilibrium. An eigenfunction that has coupled harmonics of different toroidal mode number is constructed using a perturbation approach. The theory is applied to the case of tokamak H-modes with shielded resonant magnetic perturbations (RMPs) present indicating RMPs can be destabilizing to intermediate-n peeling-ballooning modes.

  6. 3D Sun-to-Earth Solar Wind Modeling by SIP-CESE-MHD Model

    NASA Astrophysics Data System (ADS)

    Feng, Xueshang

    2012-07-01

    3D Sun-to-Earth Solar Wind Modeling by SIP-CESE-MHD Model Xueshang Feng, Xiang Changqing, Jiang Chaowei State Key Lab of Space Weather/CSSAR, CAS Beijing 100190 The objective is to present our solar-interplanetary space-time conservation element and solution element (CESE) model (SIP-CESE MHD model) (Feng, Zhou and Wu, Astrophys. J. 655, 1110, 2007; Feng et al., Astrophys. J. 723, 300, 2010; Feng et al., ApJ, 734, 50, 2011) with adaptive mesh refinement (AMR) implementation under six-component/Yin-Yang grid system. In this talk, we present the results of applying the SIP-AMR-CESE MHD model for modeling the coronal mass ejection and the solar wind background of different solar activity phases by comparison with SOHO observations and other spacecraft data from OMNI. Our numerical results show overall good agreements in the solar corona and in interplanetary space with these multiple spacecraft observations. From the modeler's experience, some limitations are addressed for this kind of initial-value boundary problems in Sun-to-Earth MHD modeling, and future out-of-ecliptic and in situ observations of the Sun and solar wind will be a solution to these limitations.

  7. Simulation of 3-D Nonequilibrium Seeded Air Flow in the NASA-Ames MHD Channel

    NASA Technical Reports Server (NTRS)

    Gupta, Sumeet; Tannehill, John C.; Mehta, Unmeel B.

    2004-01-01

    The 3-D nonequilibrium seeded air flow in the NASA-Ames experimental MHD channel has been numerically simulated. The channel contains a nozzle section, a center section, and an accelerator section where magnetic and electric fields can be imposed on the flow. In recent tests, velocity increases of up to 40% have been achieved in the accelerator section. The flow in the channel is numerically computed us ing a 3-D parabolized Navier-Stokes (PNS) algorithm that has been developed to efficiently compute MHD flows in the low magnetic Reynolds number regime: The MHD effects are modeled by introducing source terms into the PNS equations which can then be solved in a very efficient manner. The algorithm has been extended in the present study to account for nonequilibrium seeded air flows. The electrical conductivity of the flow is determined using the program of Park. The new algorithm has been used to compute two test cases that match the experimental conditions. In both cases, magnetic and electric fields are applied to the seeded flow. The computed results are in good agreement with the experimental data.

  8. A novel high-order, entropy stable, 3D AMR MHD solver with guaranteed positive pressure

    NASA Astrophysics Data System (ADS)

    Derigs, Dominik; Winters, Andrew R.; Gassner, Gregor J.; Walch, Stefanie

    2016-07-01

    We describe a high-order numerical magnetohydrodynamics (MHD) solver built upon a novel non-linear entropy stable numerical flux function that supports eight travelling wave solutions. By construction the solver conserves mass, momentum, and energy and is entropy stable. The method is designed to treat the divergence-free constraint on the magnetic field in a similar fashion to a hyperbolic divergence cleaning technique. The solver described herein is especially well-suited for flows involving strong discontinuities. Furthermore, we present a new formulation to guarantee positivity of the pressure. We present the underlying theory and implementation of the new solver into the multi-physics, multi-scale adaptive mesh refinement (AMR) simulation code FLASH (http://flash.uchicago.edu)

  9. Development of the PARVMEC Code for Rapid Analysis of 3D MHD Equilibrium

    NASA Astrophysics Data System (ADS)

    Seal, Sudip; Hirshman, Steven; Cianciosa, Mark; Wingen, Andreas; Unterberg, Ezekiel; Wilcox, Robert; ORNL Collaboration

    2015-11-01

    The VMEC three-dimensional (3D) MHD equilibrium has been used extensively for designing stellarator experiments and analyzing experimental data in such strongly 3D systems. Recent applications of VMEC include 2D systems such as tokamaks (in particular, the D3D experiment), where application of very small (delB/B ~ 10-3) 3D resonant magnetic field perturbations render the underlying assumption of axisymmetry invalid. In order to facilitate the rapid analysis of such equilibria (for example, for reconstruction purposes), we have undertaken the task of parallelizing the VMEC code (PARVMEC) to produce a scalable and temporally rapidly convergent equilibrium code for use on parallel distributed memory platforms. The parallelization task naturally splits into three distinct parts 1) radial surfaces in the fixed-boundary part of the calculation; 2) two 2D angular meshes needed to compute the Green's function integrals over the plasma boundary for the free-boundary part of the code; and 3) block tridiagonal matrix needed to compute the full (3D) pre-conditioner near the final equilibrium state. Preliminary results show that scalability is achieved for tasks 1 and 3, with task 2 still nearing completion. The impact of this work on the rapid reconstruction of D3D plasmas using PARVMEC in the V3FIT code will be discussed. Work supported by U.S. DOE under Contract DE-AC05-00OR22725 with UT-Battelle, LLC.

  10. Parametric analysis of closed cycle magnetohydrodynamic (MHD) power plants

    NASA Technical Reports Server (NTRS)

    Owens, W.; Berg, R.; Murthy, R.; Patten, J.

    1981-01-01

    A parametric analysis of closed cycle MHD power plants was performed which studied the technical feasibility, associated capital cost, and cost of electricity for the direct combustion of coal or coal derived fuel. Three reference plants, differing primarily in the method of coal conversion utilized, were defined. Reference Plant 1 used direct coal fired combustion while Reference Plants 2 and 3 employed on site integrated gasifiers. Reference Plant 2 used a pressurized gasifier while Reference Plant 3 used a ""state of the art' atmospheric gasifier. Thirty plant configurations were considered by using parametric variations from the Reference Plants. Parametric variations include the type of coal (Montana Rosebud or Illinois No. 6), clean up systems (hot or cold gas clean up), on or two stage atmospheric or pressurized direct fired coal combustors, and six different gasifier systems. Plant sizes ranged from 100 to 1000 MWe. Overall plant performance was calculated using two methodologies. In one task, the channel performance was assumed and the MHD topping cycle efficiencies were based on the assumed values. A second task involved rigorous calculations of channel performance (enthalpy extraction, isentropic efficiency and generator output) that verified the original (task one) assumptions. Closed cycle MHD capital costs were estimated for the task one plants; task two cost estimates were made for the channel and magnet only.

  11. A 3-D MHD equilibrium description of nonlinearly saturated ideal external kink/peeling structures in tokamaks

    NASA Astrophysics Data System (ADS)

    Cooper, W. A.; Graves, J. P.; Duval, B. P.; Porte, L.; Reimerdes, H.; Sauter, O.; Tran, T.-M.

    2015-12-01

    > Novel free boundary magnetohydrodynamic equilibrium states with spontaneous three-dimensional (3-D) deformations of the plasma-vacuum interface are computed. The structures obtained look like saturated ideal external kink/peeling modes. Large edge pressure gradients yield toroidal mode number distortions when the edge bootstrap current is large and higher corrugations when this current is small. Linear ideal MHD stability analyses confirm the nonlinear saturated ideal kink equilibrium states produced and we can identify the Pfirsch-Schlüter current as the main linear instability driving mechanism when the edge pressure gradient is large. The dominant non-axisymmetric component of this Pfirsch-Schlüter current drives a near resonant helical parallel current density ribbon that aligns with the near vanishing magnetic shear region caused by the edge bootstrap current. This current ribbon is a manifestation of the outer mode previously found on JET (Solano 2010). We claim that the equilibrium corrugations describe structures that are commonly observed in quiescent H-mode tokamak discharges.

  12. MHD (magnetohydrodynamic) simulation of a comet magnetosphere. Memorandum report

    SciTech Connect

    Fedder, J.A.; Brecht, S.H.; Lyon, J.G.

    1984-04-12

    This paper presents results of a numerical magnetohydrodynamic simulation of the interaction of the solar wind with a comet. It states that for a steady solar wind and interplanetary magnetic field (IMF) the cometary plasma has a distinctive structure; a spheroidal head and a long ribbon-like tail. Rotational discontinuities in the IMF lead to changes in the tail structure. It is shown how these effects occur and describe ray-like structures as well as a tail disconnection event. The simulation results provide a simple explanation for a number of observable features in cometary plasma tails.

  13. 3D passive stabilization of n = 0 MHD modes in EAST tokamak.

    PubMed

    Chen, S L; Villone, F; Xiao, B J; Barbato, L; Luo, Z P; Liu, L; Mastrostefano, S; Xing, Z

    2016-01-01

    Evidence is shown of the capability of non-axisymmetrical conducting structures in the Experimental Advanced Superconducting Tokamak (EAST) to guarantee the passive stabilization of the n = 0 MHD unstable mode. Suitable numerical modeling of the experiments allows a clear interpretation of the phenomenon. This demonstration and the availability of computational tools able to describe the effect of 3D conductors will have a huge impact on the design of future fusion devices, in which the conducting structures closest to plasma will be highly segmented. PMID:27597182

  14. 3D passive stabilization of n = 0 MHD modes in EAST tokamak

    PubMed Central

    Chen, S. L.; Villone, F.; Xiao, B. J.; Barbato, L.; Luo, Z. P.; Liu, L.; Mastrostefano, S.; Xing, Z.

    2016-01-01

    Evidence is shown of the capability of non-axisymmetrical conducting structures in the Experimental Advanced Superconducting Tokamak (EAST) to guarantee the passive stabilization of the n = 0 MHD unstable mode. Suitable numerical modeling of the experiments allows a clear interpretation of the phenomenon. This demonstration and the availability of computational tools able to describe the effect of 3D conductors will have a huge impact on the design of future fusion devices, in which the conducting structures closest to plasma will be highly segmented. PMID:27597182

  15. 3D passive stabilization of n = 0 MHD modes in EAST tokamak.

    PubMed

    Chen, S L; Villone, F; Xiao, B J; Barbato, L; Luo, Z P; Liu, L; Mastrostefano, S; Xing, Z

    2016-09-06

    Evidence is shown of the capability of non-axisymmetrical conducting structures in the Experimental Advanced Superconducting Tokamak (EAST) to guarantee the passive stabilization of the n = 0 MHD unstable mode. Suitable numerical modeling of the experiments allows a clear interpretation of the phenomenon. This demonstration and the availability of computational tools able to describe the effect of 3D conductors will have a huge impact on the design of future fusion devices, in which the conducting structures closest to plasma will be highly segmented.

  16. An Arbitrary Lagrangian-Eulerian Discretization of MHD on 3D Unstructured Grids

    SciTech Connect

    Rieben, R N; White, D A; Wallin, B K; Solberg, J M

    2006-06-12

    We present an arbitrary Lagrangian-Eulerian (ALE) discretization of the equations of resistive magnetohydrodynamics (MHD) on unstructured hexahedral grids. The method is formulated using an operator-split approach with three distinct phases: electromagnetic diffusion, Lagrangian motion, and Eulerian advection. The resistive magnetic dynamo equation is discretized using a compatible mixed finite element method with a 2nd order accurate implicit time differencing scheme which preserves the divergence-free nature of the magnetic field. At each discrete time step, electromagnetic force and heat terms are calculated and coupled to the hydrodynamic equations to compute the Lagrangian motion of the conducting materials. By virtue of the compatible discretization method used, the invariants of Lagrangian MHD motion are preserved in a discrete sense. When the Lagrangian motion of the mesh causes significant distortion, that distortion is corrected with a relaxation of the mesh, followed by a 2nd order monotonic remap of the electromagnetic state variables. The remap is equivalent to Eulerian advection of the magnetic flux density with a fictitious mesh relaxation velocity. The magnetic advection is performed using a novel variant of constrained transport (CT) that is valid for unstructured hexahedral grids with arbitrary mesh velocities. The advection method maintains the divergence free nature of the magnetic field and is second order accurate in regions where the solution is sufficiently smooth. For regions in which the magnetic field is discontinuous (e.g. MHD shocks) the method is limited using a novel variant of algebraic flux correction (AFC) which is local extremum diminishing (LED) and divergence preserving. Finally, we verify each stage of the discretization via a set of numerical experiments.

  17. The Effect of Magnetohydrodynamic (MHD) Energy Bypass on Specific Thrust for a Supersonic Turbojet Engine

    NASA Technical Reports Server (NTRS)

    Benyo, Theresa L.

    2010-01-01

    This paper describes the preliminary results of a thermodynamic cycle analysis of a supersonic turbojet engine with a magnetohydrodynamic (MHD) energy bypass system that explores a wide range of MHD enthalpy extraction parameters. Through the analysis described here, it is shown that applying a magnetic field to a flow path in the Mach 2.0 to 3.5 range can increase the specific thrust of the turbojet engine up to as much as 420 N/(kg/s) provided that the magnitude of the magnetic field is in the range of 1 to 5 Tesla. The MHD energy bypass can also increase the operating Mach number range for a supersonic turbojet engine into the hypersonic flight regime. In this case, the Mach number range is shown to be extended to Mach 7.0.

  18. MHD (magnetohydrodynamic) undersea propulsion: A novel concept with renewed interest

    SciTech Connect

    Doss, E.D.; Geyer, H.K. ); Roy, G.D. )

    1990-01-01

    This paper discusses the reasons for the national and international renewed interest in the concept of MHD seawater propulsion. The main advantages of this concept are presented, together with some of the technical challenges that need to be overcome to achieve reliability, performance, and stealth. The paper discusses in more detail some of the technical issues and loss mechanisms influencing the thruster performance in terms of its electrical efficiency. Among the issues discussed are the jet losses and nozzle efficiency. Ohmic losses and frictional losses inside the thruster. Also discussed are the electrical end losses caused by the fringing magnetic field near the end of the electrodes. It has been shown that the frictional and end losses can have strong adverse effects on the thruster performance. Furthermore, a parametric study has been performed to investigate the effects of several parameters on the performance of the MHD thrusters. Those parameters include the magnetic field, thruster diameter, all roughness, flow velocity, and electrical load factor. The results of the parametric study indicate that the thruster efficiency increases with the strength of the magnetic field and thruster diameter, and decreases with the wall roughness and the flow velocity. 8 refs., 8 figs.

  19. Existence of two MHD reconnection modes in a solar 3D magnetic null point topology

    NASA Astrophysics Data System (ADS)

    Pariat, Etienne; Antiochos, Spiro; DeVore, C. Richard; Dalmasse, Kévin

    2012-07-01

    Magnetic topologies with a 3D magnetic null point are common in the solar atmosphere and occur at different spatial scales: such structures can be associated with some solar eruptions, with the so-called pseudo-streamers, and with numerous coronal jets. We have recently developed a series of numerical experiments that model magnetic reconnection in such configurations in order to study and explain the properties of jet-like features. Our model uses our state-of-the-art adaptive-mesh MHD solver ARMS. Energy is injected in the system by line-tied motion of the magnetic field lines in a corona-like configuration. We observe that, in the MHD framework, two reconnection modes eventually appear in the course of the evolution of the system. A very impulsive one, associated with a highly dynamic and fully 3D current sheet, is associated with the energetic generation of a jet. Before and after the generation of the jet, a quasi-steady reconnection mode, more similar to the standard 2D Sweet-Parker model, presents a lower global reconnection rate. We show that the geometry of the magnetic configuration influences the trigger of one or the other mode. We argue that this result carries important implications for the observed link between observational features such as solar jets, solar plumes, and the emission of coronal bright points.

  20. 3D Reconstruction of Interplanetary Scintillation (IPS) Remote-Sensing Data: Global Solar Wind Boundaries for Driving 3D-MHD Models

    NASA Astrophysics Data System (ADS)

    Yu, H.-S.; Jackson, B. V.; Hick, P. P.; Buffington, A.; Odstrcil, D.; Wu, C.-C.; Davies, J. A.; Bisi, M. M.; Tokumaru, M.

    2015-09-01

    The University of California, San Diego, time-dependent analyses of the heliosphere provide three-dimensional (3D) reconstructions of solar wind velocities and densities from observations of interplanetary scintillation (IPS). Using data from the Solar-Terrestrial Environment Laboratory, Japan, these reconstructions provide a real-time prediction of the global solar-wind density and velocity throughout the whole heliosphere with a temporal cadence of about one day (ips.ucsd.edu). Updates to this modeling effort continue: in the present article, near-Sun results extracted from the time-dependent 3D reconstruction are used as inner boundary conditions to drive 3D-MHD models ( e.g. ENLIL and H3D-MHD). This allows us to explore the differences between the IPS kinematic-model data-fitting procedure and current 3D-MHD modeling techniques. The differences in these techniques provide interesting insights into the physical principles governing the expulsion of coronal mass ejections (CMEs). Here we detail for the first time several specific CMEs and an induced shock that occurred in September 2011 that demonstrate some of the issues resulting from these analyses.

  1. Two-dimensional magnetohydrodynamic simulations of poloidal flows in tokamaks and MHD pedestal

    SciTech Connect

    Guazzotto, L.; Betti, R.

    2011-09-15

    Poloidal rotation is routinely observed in present-day tokamak experiments, in particular near the plasma edge and in the high-confinement mode of operation. According to the magnetohydrodynamic (MHD) equilibrium theory [R. Betti and J. P. Freidberg, Phys. Plasmas 7, 2439 (2000)], radial discontinuities form when the poloidal velocity exceeds the poloidal sound speed (or rather, more correctly, the poloidal magneto-slow speed). Two-dimensional compressible magnetohydrodynamic simulations show that the transonic discontinuities develop on a time scale of a plasma poloidal revolution to form an edge density pedestal and a localized velocity shear layer at the pedestal location. While such an MHD pedestal surrounds the entire core, the outboard side of the pedestal is driven by the transonic discontinuity while the inboard side is caused by a poloidal redistribution of the mass. The MHD simulations use a smooth momentum source to drive the poloidal flow. Soon after the flow exceeds the poloidal sound speed, the density pedestal and the velocity shear layer form and persist into a quasi steady state. These results may be relevant to the L-H transition, the early stages of the pedestal and edge transport barrier formation.

  2. 3D MHD Simulations of Radial Wire Array Z-pinches

    NASA Astrophysics Data System (ADS)

    Niasse, N.; Chittenden, J. P.; Bland, S. N.; Suzuki-Vidal, F. A.; Hall, G. N.; Lebedev, S. V.; Calamy, H.; Zucchini, F.; Lassalle, F.; Bedoch, J. P.

    2009-01-01

    Recent experiments carried out on the MAGPIE (1 MA, 250 ns), OEDIPE (730 kA, 1.5 μs) and SPHINX (4 MA, 700 ns)[1] facilities have shown the relatively high level of scalability of the Radial Wire Array Z-pinches. These configurations where the wires stretch radially outwards from a central cathode offer numerous advantages over standard cylindrical arrays. In particular, imploding in a very stable and compact way, they seem suitable for coupling to small scale hohlraums. Making use of the 3D resistive magneto-hydrodynamic code GORGON[2] developed at Imperial College, the dynamic of the radial wire arrays is investigated. Influence of the cathode hotspots and wires angle on the x-ray emissions is also discussed. Comparison with experiments is offered to validate the numerical studies.

  3. 3D MHD Simulations of accreting neutron stars: evidence of QPO emission from the surface

    SciTech Connect

    Bachetti, Matteo; Burderi, Luciano; Romanova, Marina M.; Kulkarni, Akshay; Salvo, Tiziana di

    2010-07-15

    3D Magnetohydrodynamic simulations show that when matter accretes onto neutron stars, in particular if the misalignment angle is small, it does not constantly fall at a fixed spot. Instead, the location at which matter reaches the star moves. These moving hot spots can be produced both during stable accretion, where matter falls near the magnetic poles of the star, and unstable accretion, characterized by the presence of several tongues of matter which fall on the star near the equator, due to Rayleigh-Taylor instabilities. Precise modeling with Monte Carlo simulations shows that those movements could be observed as high frequency Quasi Periodic Oscillations. We performed a number of new simulation runs with a much wider set of parameters, focusing on neutron stars with a small misalignment angle. In most cases we observe oscillations whose frequency is correlated with the mass accretion rate M. Moreover, in some cases double QPOs appear, each of them showing the same correlation with M.

  4. 3D MHD Simulations of Radial Wire Array Z-pinches

    SciTech Connect

    Niasse, N.; Chittenden, J. P.; Bland, S. N.; Suzuki-Vidal, F. A.; Hall, G. N.; Lebedev, S. V.; Calamy, H.; Zucchini, F.; Lassalle, F.; Bedoch, J. P.

    2009-01-21

    Recent experiments carried out on the MAGPIE (1 MA, 250 ns), OEDIPE (730 kA, 1.5 {mu}s) and SPHINX (4 MA, 700 ns)[1] facilities have shown the relatively high level of scalability of the Radial Wire Array Z-pinches. These configurations where the wires stretch radially outwards from a central cathode offer numerous advantages over standard cylindrical arrays. In particular, imploding in a very stable and compact way, they seem suitable for coupling to small scale hohlraums. Making use of the 3D resistive magneto-hydrodynamic code GORGON[2] developed at Imperial College, the dynamic of the radial wire arrays is investigated. Influence of the cathode hotspots and wires angle on the x-ray emissions is also discussed. Comparison with experiments is offered to validate the numerical studies.

  5. Substorm features in MHD (magnetohydrodynamics) simulations of magnetotail dynamics

    SciTech Connect

    Birn, J.; Hesse, M.

    1990-01-01

    We present a review and extended analysis of characteristic results from our nonideal three-dimensional MHD simulations of unstable magnetotail evolution, which develops without the necessity of external driving or prescribed localization on nonideal effects. These modes involve magnetic reconnection at a near-Earth site in the tail, consistent with the near-Earth neutral line model of substorms. The evolution tailward of the reconnection site is characterized by plasmoid formation and ejection into the far tail, plasma sheet thinning between the near-Earth neutral line (X line) and the departing plasmoid, and fast tailward flow, which occupies large sections of the plasma sheet at larger distance from the X line, while it occurs only in very limited space and time sections close to the X line. The region earthward of the X line is characterized by dipolarization, propagating from midnight toward the flank regions and, perhaps, tailward. It is associated with the signatures of the substorm current wedge: reduction and diversion of cross-tail current from a region surrounding the reconnection site and increase of Region 1 type field-aligned currents. A mapping of these currents to the Earth on the basis of an empirical magnetic field model shows good agreement of the mapped current system with the observed Region 1 field-aligned current system and its substorm associated changes, including also a nightward and equatorward shift of the peaks of the field-aligned current density. The evolution of the mappings of the boundaries of the closed field line region bears strong resemblance to the formation and expansion of he auroral bulge. The consistency of all of these details with observed substorm features strongly supports the idea that substorm evolution in the tail is that of a large scale nonideal instability.

  6. Dynamics of tokamak plasma surface current in 3D ideal MHD model

    NASA Astrophysics Data System (ADS)

    Galkin, Sergei A.; Svidzinski, V. A.; Zakharov, L. E.

    2013-10-01

    Interest in the surface current which can arise on perturbed sharp plasma vacuum interface in tokamaks was recently generated by a few papers (see and references therein). In dangerous disruption events with plasma-touching-wall scenarios, the surface current can be shared with the wall leading to the strong, damaging forces acting on the wall A relatively simple analytic definition of δ-function surface current proportional to a jump of tangential component of magnetic field nevertheless leads to a complex computational problem on the moving plasma-vacuum interface, requiring the incorporation of non-linear 3D plasma dynamics even in one-fluid ideal MHD. The Disruption Simulation Code (DSC), which had recently been developed in a fully 3D toroidal geometry with adaptation to the moving plasma boundary, is an appropriate tool for accurate self-consistent δfunction surface current calculation. Progress on the DSC-3D development will be presented. Self-consistent surface current calculation under non-linear dynamics of low m kink mode and VDE will be discussed. Work is supported by the US DOE SBIR grant #DE-SC0004487.

  7. 3D MHD SIMULATION OF FLARE SUPRA-ARCADE DOWNFLOWS IN A TURBULENT CURRENT SHEET MEDIUM

    SciTech Connect

    Cécere, M.; Zurbriggen, E.; Costa, A.; Schneiter, M.

    2015-07-01

    Supra-arcade downflows (SADs) are sunward, generally dark, plasma density depletions originated above posteruption flare arcades. In this paper, using 3D MHD simulations we investigate whether the SAD cavities can be produced by a direct combination of the tearing mode and Kelvin–Helmholtz instabilities leading to a turbulent current sheet (CS) medium or if the current sheet is merely the background where SADs are produced, triggered by an impulsive deposition of energy. We find that to give an account of the observational dark lane structures an addition of local energy, provided by a reconnection event, is required. We suggest that there may be a closed relation between characteristic SAD sizes and CS widths that must be satisfied to obtain an observable SAD.

  8. Quasi 3D ECE imaging system for study of MHD instabilities in KSTAR

    SciTech Connect

    Yun, G. S. Choi, M. J.; Lee, J.; Kim, M.; Leem, J.; Nam, Y.; Choe, G. H.; Lee, W.; Park, H. K.; Park, H.; Woo, D. S.; Kim, K. W.; Domier, C. W.; Luhmann, N. C.; Ito, N.; Mase, A.; Lee, S. G.

    2014-11-15

    A second electron cyclotron emission imaging (ECEI) system has been installed on the KSTAR tokamak, toroidally separated by 1/16th of the torus from the first ECEI system. For the first time, the dynamical evolutions of MHD instabilities from the plasma core to the edge have been visualized in quasi-3D for a wide range of the KSTAR operation (B{sub 0} = 1.7∼3.5 T). This flexible diagnostic capability has been realized by substantial improvements in large-aperture quasi-optical microwave components including the development of broad-band polarization rotators for imaging of the fundamental ordinary ECE as well as the usual 2nd harmonic extraordinary ECE.

  9. Global regularity to the 3D MHD equations with large initial data in bounded domains

    NASA Astrophysics Data System (ADS)

    Yu, Haibo

    2016-08-01

    This paper considers the global regularity to the 3D incompressible MHD equations with large initial data in bounded domains. Let μ, ν, u, and b denote the viscosity coefficient, magnetic diffusivity, velocity field, and magnetic field, respectively. We construct new systems for (u - b) and (u + b) to overcome the difficulties caused by the large initial data. It is shown that ↑" separators=" ( u , b ) ↑ H 1 is globally bounded as long as ↑" separators=" ( u0 - b 0 ) ↑ H 1 + |" separators=" μ - ν | ( μ + ν ) - 1 or ↑" separators=" ( u0 + b 0 ) ↑ H 1 + |" separators=" μ - ν | ( μ + ν ) - 1 is sufficiently small, which indicates that the Navier-Stokes equations can be regularized by the magnetic field.

  10. A 3D MHD Model of the Solar Wind Driven by Turbulence Dissipation

    NASA Astrophysics Data System (ADS)

    Lionello, R.; Downs, C.; Linker, J.; Mikic, Z.; Velli, M. M.; Verdini, A.

    2013-12-01

    The mechanisms responsible for heating the Sun's corona and accelerating the solar wind are still actively investigated. However, it is largely accepted that photospheric motions provide the energy source and that the magnetic field must play a key role in the process. Verdini et al. (2010) presented a model for heating and accelerating the solar wind based on the turbulent dissipation of Alfven waves. We first use our time-dependent model of the solar wind to reproduce Verdini et al's solution; then we extend its application to the case when the energy equation includes thermal conduction and radiation losses, and the upper chromosphere is part of the computational domain. Finally, we show application of this formulation to our 3D MHD model of the solar corona and the solar wind.

  11. Interpreting Irradiance Distributions Using High-Resolution 3D MHD Simulations

    NASA Astrophysics Data System (ADS)

    Peck, Courtney; Rast, Mark; Criscuoli, Serena; Uitenbroek, Han; Rempel, Matthias D.

    2016-05-01

    We present initial results of studies aimed at understanding the impact of the unresolved magnetic field distribution on solar spectral irradiance. Using high-resolution 3D MHD simulations (from MURaM code) and spectral synthesis (with the RH code), we examine the emergent spectra of two atmospheres with similar mean field strengths but differing imposed-field conditions at wavelengths spanning from visible to infrared. Comparing the contrast against the magnetic field strength for the two magnetic simulations, we find differences in the distributions of contrasts versus field strength. We repeat the analysis after convolving the images with the PSF of a typical solar telescope (1-meter) and discuss the potential implications for irradiance modeling and future steps.

  12. A global 3-D MHD model of the solar wind with Alfven waves

    NASA Technical Reports Server (NTRS)

    Usmanov, A. V.

    1995-01-01

    A fully three-dimensional solar wind model that incorporates momentum and heat addition from Alfven waves is developed. The proposed model upgrades the previous one by considering self-consistently the total system consisting of Alfven waves propagating outward from the Sun and the mean polytropic solar wind flow. The simulation region extends from the coronal base (1 R(sub s) out to beyond 1 AU. The fully 3-D MHD equations written in spherical coordinates are solved in the frame of reference corotating with the Sun. At the inner boundary, the photospheric magnetic field observations are taken as boundary condition and wave energy influx is prescribed to be proportional to the magnetic field strength. The results of the model application for several time intervals are presented.

  13. The 3D MHD code GOEMHD3 for astrophysical plasmas with large Reynolds numbers. Code description, verification, and computational performance

    NASA Astrophysics Data System (ADS)

    Skála, J.; Baruffa, F.; Büchner, J.; Rampp, M.

    2015-08-01

    Context. The numerical simulation of turbulence and flows in almost ideal astrophysical plasmas with large Reynolds numbers motivates the implementation of magnetohydrodynamical (MHD) computer codes with low resistivity. They need to be computationally efficient and scale well with large numbers of CPU cores, allow obtaining a high grid resolution over large simulation domains, and be easily and modularly extensible, for instance, to new initial and boundary conditions. Aims: Our aims are the implementation, optimization, and verification of a computationally efficient, highly scalable, and easily extensible low-dissipative MHD simulation code for the numerical investigation of the dynamics of astrophysical plasmas with large Reynolds numbers in three dimensions (3D). Methods: The new GOEMHD3 code discretizes the ideal part of the MHD equations using a fast and efficient leap-frog scheme that is second-order accurate in space and time and whose initial and boundary conditions can easily be modified. For the investigation of diffusive and dissipative processes the corresponding terms are discretized by a DuFort-Frankel scheme. To always fulfill the Courant-Friedrichs-Lewy stability criterion, the time step of the code is adapted dynamically. Numerically induced local oscillations are suppressed by explicit, externally controlled diffusion terms. Non-equidistant grids are implemented, which enhance the spatial resolution, where needed. GOEMHD3 is parallelized based on the hybrid MPI-OpenMP programing paradigm, adopting a standard two-dimensional domain-decomposition approach. Results: The ideal part of the equation solver is verified by performing numerical tests of the evolution of the well-understood Kelvin-Helmholtz instability and of Orszag-Tang vortices. The accuracy of solving the (resistive) induction equation is tested by simulating the decay of a cylindrical current column. Furthermore, we show that the computational performance of the code scales very

  14. Initial Comparison Between a 3D MHD Model and the HAFv2 Kinematic 3D Model: The October/November 2003 Events from the Sun to 6 AU

    SciTech Connect

    Intriligator, Devrie S.; Detman, Thomas; Fry, Craig D.; Sun Wei; Deehr, Charles; Intriligator, James

    2005-08-01

    A first-generation 3D kinematic, space weather forecasting solar wind model (HAFv2) has been used to show the importance of solar generated disturbances in Voyager 1 and Voyager 2 observations in the outer heliosphere. We extend this work by using a 3D MHD model (HHMS) that, like HAFv2, incorporates a global, pre-event, inhomogeneous, background solar wind plasma and interplanetary magnetic field. Initial comparisons are made between the two models of the solar wind out to 6 AU and with in-situ observations at the ACE spacecraft before and after the October/November 2003 solar events.

  15. Coronal heating above active regions - 3D MHD model versus multi-spacecraft observations

    NASA Astrophysics Data System (ADS)

    Bourdin, Philippe-A.; Bingert, Sven; Peter, Hardi

    2014-05-01

    The plasma heating mechanism in the Solar corona is a puzzle since decades. Today high-performance computing together with multi-spacecraft observations offer new insights. We conducted a high-resolution simulation of the corona above an active region and compare synthetic emission deduced from the model with co-temporal observations. Photospheric observations act as a boundary condition for our model that drives magnetic-field braiding by advection and generates a net upwards Poynting flux. In particular, we do not only get a sufficient energy input to the base of the corona, but we also reproduce the observed coronal loops: the 3D structure of the hot AR loops system in the model compares well to joint STEREO-A/-B and Hinode observations. The plasma flows along these loops are similar to observed Doppler maps. Draining and siphon flows along magnetic structures at different temperatures offer a new alternative explanation for the average Doppler red-shifts in the transition region and coronal blue-shifts. This match between model and observations indicates a realistic distribution of the coronal heating in time and space and shows that our 3D MHD model of the corona captures the relevant processes involved.

  16. Fast Wave Trains Associated with Solar Eruptions: Insights from 3D Thermodynamic MHD Simulations

    NASA Astrophysics Data System (ADS)

    Downs, C.; Liu, W.; Torok, T.; Linker, J.; Mikic, Z.; Ofman, L.

    2015-12-01

    EUV imaging observations during the SDO/AIA era have provided new insights into a variety of wave phenomena occurring in the low solar corona. One example is the observation of quasi-periodic, fast-propagating wave trains that are associated with solar eruptions, including flares and CMEs. While there has been considerable progress in understanding such waves from both an observational and theoretical perspective, it remains a challenge to pin down their physical origin. In this work, we detail our results from a case-study 3D thermodynamic MHD simulation of a coronal mass ejection where quasi-periodic wave trains are generated during the simulated eruption. We find a direct correlation between the onset of non-steady reconnection in the flare current sheet and the generation of quasi-periodic wave train signatures when patchy, collimated downflows interact with the flare arcade. Via forward modeling of SDO/AIA observables, we explore how the appearance of the wave trains is affected by line-of-sight integration and the multi-thermal nature of the coronal medium. We also examine how the wave trains themselves are channeled by natural waveguides formed in 3D by the non-uniform background magnetic field. While the physical association of the reconnection dynamics to the generation of quasi-periodic wave trains appears to be a compelling result, unanswered questions posed from recent observations as well as future prospects will be discussed.

  17. Magnetohydrodynamic electromagnetic pulse (MHD-EMP) interaction with power transmission and distribution systems

    SciTech Connect

    Tesche, F.M. , Dallas, TX ); Barnes, P.R. ); Meliopoulos, A.P.S. . Dept. of Electrical Engineering)

    1992-02-01

    This report discusses the effects of the late-time high-altitude electromagnetic pulse (HEMP) on electrical transmission and distribution (T D) systems. This environment, known as the magnetohydrodynamic electromagnetic pulse (MHD-EMP), is a very slowly varying electric field induced in the earth's surface, similar to the field induced by a geomagnetic storm. It can result in the flow of a quasi-dc current in grounded power lines and in the subsequent magnetic saturation of transformers. This saturation, in turn, causes 6-Hz harmonic distortion and an increase in the reactive power required by generation facilities. This report analyzes and discusses these phenomena. The MHD-EMP environment is briefly discussed, and a simplified form of the earth-induced electric field is developed for use in a parametric study of transmission line responses. Various field coupling models are described, and calculated results for the responses of both transmission- and distribution-class power lines are presented. These calculated responses are compared with measurements of transformer operation under dc excitation to infer the MHD-EMP response of these power system components. It is found that the MHD-EMP environment would have a marked effect on a power system by inducing up to several hundreds of amperes of quasi-dc current on power lines. These currents will cause transformers to saturate which could result in excessive harmonic generation, voltage swings, and voltage suppression. The design of critical facilities which are required to operate during and after MHD-EMP events will have to be modified in order to mitigate the effects of these abnormal power system conditions.

  18. Magnetohydrodynamic electromagnetic pulse (MHD-EMP) interaction with power transmission and distribution systems

    SciTech Connect

    Tesche, F.M.; Barnes, P.R.; Meliopoulos, A.P.S.

    1992-02-01

    This report discusses the effects of the late-time high-altitude electromagnetic pulse (HEMP) on electrical transmission and distribution (T&D) systems. This environment, known as the magnetohydrodynamic electromagnetic pulse (MHD-EMP), is a very slowly varying electric field induced in the earth`s surface, similar to the field induced by a geomagnetic storm. It can result in the flow of a quasi-dc current in grounded power lines and in the subsequent magnetic saturation of transformers. This saturation, in turn, causes 6-Hz harmonic distortion and an increase in the reactive power required by generation facilities. This report analyzes and discusses these phenomena. The MHD-EMP environment is briefly discussed, and a simplified form of the earth-induced electric field is developed for use in a parametric study of transmission line responses. Various field coupling models are described, and calculated results for the responses of both transmission- and distribution-class power lines are presented. These calculated responses are compared with measurements of transformer operation under dc excitation to infer the MHD-EMP response of these power system components. It is found that the MHD-EMP environment would have a marked effect on a power system by inducing up to several hundreds of amperes of quasi-dc current on power lines. These currents will cause transformers to saturate which could result in excessive harmonic generation, voltage swings, and voltage suppression. The design of critical facilities which are required to operate during and after MHD-EMP events will have to be modified in order to mitigate the effects of these abnormal power system conditions.

  19. 3D Dynamics of Magnetopause Reconnection Using Hall-MHD Global Simulations

    NASA Astrophysics Data System (ADS)

    Maynard, K.; Germaschewski, K.; Raeder, J.; Bhattacharjee, A.

    2011-12-01

    Magnetic reconnection at Earth's magnetopause and in the magnetotail is of crucial importance for the dynamics of the global magnetosphere and space weather. Even though the plasma conditions in the magnetosphere are largely in the collisionless regime, most of the existing research using global computational models employ single-fluid magnetohydrodynamics (MHD) with artificial resistivity. Studies of reconnection in simplified, two-dimensional geometries have established that two-fluid and kinetic effects can dramatically alter dynamics and reconnection rates when compared with single-fluid models. These enhanced models also introduce particular signatures, for example a quadrupolar out-of-plane magnetic field component that has already been observed in space by satellite measurements. However, results from simplified geometries cannot be translated directly to the dynamics of three-dimensional magnetospheric reconnection. For instance, magnetic flux originating from the solar wind and arriving at the magnetopause can either reconnect or be advected around the magnetosphere. In this study, we use a new version of the OpenGGCM code that incorporates the Hall term in a Generalized Ohm's Law to study magnetopause reconnection under synthetic solar wind conditions and investigate how reconnection rates and dynamics of flux transfer events depend on the strength of the Hall term. The OpenGGCM, a global model of Earth's magnetosphere, has recently been ported to exploit modern computing architectures like the Cell processor and SIMD capabilities of conventional processors using an automatic code generator. These enhancements provide us with the performance needed to include the computationally expensive Hall physics.

  20. Mitigation of magnetohydrodynamic electromagnetic pulse (MHD-EMP) effects from commerical electric power systems. Power Systems Technology Program

    SciTech Connect

    Barnes, P.R.; Tesche, F.M.; Vance, E.F.

    1992-03-01

    A large nuclear detonation at altitudes of several hundred kilometers above the earth distorts the earth`s magnetic field and produces a strong magnetohydrodynamic electromagnetic pulse (MHD-EMP). This can adversely affect electrical power systems. In this report, the effects of this nuclear environment on critical facilities connected to the commercial power system are considered. Methods of mitigating the MHD-EMP impacts are investigated, and recommended protection schemes are presented. Guidelines for testing facilities to determine the effects of MHD-EMP and to validate the mitigation methods also are discussed.

  1. Nonlinear tearing mode study using the almost ideal magnetohydrodynamics (MHD) constraint

    SciTech Connect

    Ren, C.; Callen, J.D.; Jensen, T.H.

    1998-12-31

    The tearing mode is an important resistive magnetohydrodynamics (MHD) mode. It perturbs the initial equilibrium magnetic flux surfaces through magnetic field line reconnection to form new flux surfaces with magnetic islands. In the study of the tearing mode, usually the initial equilibria are one dimensional with two ignorable coordinates and the perturbed equilibria are two dimensional with one ignorable coordinate. The tearing mode can be linearly unstable and its growth saturates at a fine amplitude. The neoclassical tearing mode theory shows that the mode can be nonlinearly driven by the bootstrap current even when it is linearly stable to the classical tearing mode. It is important to study the nonlinear behavior of the tearing mode. As an intrinsically nonlinear approach, the use of the almost ideal MHD constraint is suited to study the nonlinear properties of the tearing mode. In this paper, as a validation of the method, the authors study two characteristics of the tearing mode using the almost ideal MHD constraint: (1) the linear stability condition for the initial one dimensional equilibrium; and (2) the final saturation level for the unstable case. In this work, they only consider the simplest case where no gradient of pressure or current density exists at the mode resonant surface.

  2. Quiescent H-Mode 3D MHD Free-Boundary Equilibrium

    NASA Astrophysics Data System (ADS)

    Cooper, W. Anthony; Graves, Jonathan P.; Duval, Basil P.; Porte, Laurie; Sauter, Olivier; Tran, Trach-Minh; Brunetti, Daniele; Pfefferle, David; Raghunathan, Madhusudan; Faustin, Jonathan M.; Patten, Hamish; Kleiner, Andreas; Reimerdes, Holger

    2015-11-01

    Free boundary magnetohydrodynamic equilibrium states with spontaneous three dimensional deformations of the plasma-vacuum interface are computed with the 3D VMEC solver [Hirshman et al., Comput. Phys. Commun. 43 (1986) 143]. The structures we have obtained have the appearance of saturated ideal external kink/peeling modes. Large edge pressure gradients yield toroidal mode number n = 1 corrugations when the edge bootstrap current is large and n = 4 distortions when this current is small. The deformations of the plasma boundary region induces a nonaxisymmetric Pfirsch-Schlüter current that drives a field-aligned current ribbon which is consistent with experimental observations reported. We claim that the equilibrium states we compute model the Edge Harmonic Oscillation [K.H. Burrell et al., Phys. Plasmas 22 (2005) 021805. W.M. Solomon et al., Phys. Rev. Lett. 113 (2014) 135001] observed on DIII-D and the Outer Mode [E.R. Solano et al., Phys. Rev. Lett. 104 (2014) 135001] found in JET during Quiescent H-mode operation. This work was supported in part by the Swiss National Science Foundation.

  3. The UCSD kinematic IPS solar wind boundary and its use in the ENLIL 3-D MHD prediction model

    NASA Astrophysics Data System (ADS)

    Jackson, B. V.; Odstrcil, D.; Yu, H.-S.; Hick, P. P.; Buffington, A.; Mejia-Ambriz, J. C.; Kim, J.; Hong, S.; Kim, Y.; Han, J.; Tokumaru, M.

    2015-02-01

    The University of California, San Diego interplanetary scintillation (IPS) time-dependent kinematic 3-D reconstruction technique has been used and expanded upon for over a decade to provide predictions of heliospheric solar wind parameters. These parameters include global reconstructions of velocity, density, and (through potential field modeling and extrapolation upward from the solar surface) radial and tangential interplanetary magnetic fields. Time-dependent results can be extracted at any solar distance within the reconstructed volume and are now being exploited as inner boundary values to drive the ENLIL 3-D MHD model in near real time. The advantage of this coupled system is that it uses the more complete physics of 3-D MHD modeling to provide an automatic prediction of coronal mass ejections and solar wind stream structures several days prior to their arrival at Earth without employing coronagraph observations. Here we explore, with several examples, the current differences between the IPS real-time kinematic analyses and those from the ENLIL 3-D MHD modeling using IPS-derived real-time boundaries. Future possibilities for this system include incorporating many different worldwide IPS stations as input to the remote sensing analysis using ENLIL as a kernel in the iterative 3-D reconstructions.

  4. 3D Radiative MHD Modeling of Quiet-Sun Magnetic Activity

    NASA Astrophysics Data System (ADS)

    Kitiashvili, Irina

    2016-05-01

    Quiet-Sun regions that cover most of the solar surface represent a background state that plays an extremely important role in the dynamics and energetics of the solar atmosphere. A clear understanding of these regions is required for accurate interpretation of solar activity events such as emergence of magnetic flux, sunspot formation, and eruptive dynamics. Modern high-resolution observations from ground and space telescopes have revealed a complicated dynamics of turbulent magnetoconvection and its effects in the solar atmosphere and corona, showing intense interactions across different temporal and spatial scales. Interpretation of the observed complex phenomena and understanding of their origins is impossible without advanced numerical models. I will present new results of realistic-type 3D radiative MHD simulations of the upper turbulent convective layer and atmosphere of the Sun. The results reveal the mechanism of formation and properties of the Sun’s “magnetic carpet” controlled by subsurface small-scale dynamo processes, and demonstrate interaction between the subsurface layers and the atmosphere via spontaneous small-scale eruptions and wave phenomena. To link the simulations to solar data the spectro-polarimetric radiative transfer code SPINOR is used to convert the simulated data into the Stokes profiles of various spectral lines, including the SDO and Hinode observables. The results provide a detailed physical understanding of the quiet-Sun dynamics, and show potential for future observations with the DKIST and other large solar telescopes.

  5. 3D MHD Simulations of Laser Plasma Guiding in Curved Magnetic Field

    NASA Astrophysics Data System (ADS)

    Roupassov, S.; Rankin, R.; Tsui, Y.; Capjack, C.; Fedosejevs, R.

    1999-11-01

    The guiding and confinement of laser produced plasma in a curved magnetic field has been investigated numerically. These studies were motivated by experiments on pulsed laser deposition of diamond-like films [1] in which a 1kG magnetic field in a curved solenoid geometry was utilized to steer a carbon plasma around a curved trajectory and thus to separate it from unwanted macroparticles produced by the laser ablation. The purpose of the modeling was to characterize the plasma dynamics during the propagation through the magnetic guide field and to investigate the effect of different magnetic field configurations. A 3D curvilinear ADI code developed on the basis of an existing Cartesian code [2] was employed to simulate the underlying resistive one-fluid MHD model. Issues such as large regions of low background density and nonreflective boundary conditions were addressed. Results of the simulations in a curved guide field will be presented and compared to experimental results. [1] Y.Y. Tsui, D. Vick and R. Fedosejevs, Appl. Phys. Lett. 70 (15), pp. 1953-57, 1997. [2] R. Rankin, and I. Voronkov, in "High Performance Computing Systems and Applications", pp. 59-69, Kluwer AP, 1998.

  6. Flux Emergence In The Solar Photosphere - Diagnostics Based On 3-D Rradiation-MHD Simulations

    NASA Astrophysics Data System (ADS)

    Yelles Chaouche, L.; Cheung, M.; Lagg, A.; Solanki, S.

    2006-08-01

    We investigate flux tube emergence in the solar photosphere using a diagnostic procedure based on analyzing Stokes signals from different spectral lines calculated in 3-D radiation-MHD simulations. The simulations include the effects of radiative transport and partial ionization and cover layers both above and below the solar surface. The simulations consider the emergence of a twisted magnetic flux tube through the solar surface. We consider different stages in the emergence process, starting from the early appearance of the flux tube at the solar surface, and following the emergence process until the emerged flux looks similar to a normal bipolar region. At every stage we compute line profiles by numerically solving the Unno-Rachkovsky equations at every horizontal grid point. Then, following observational practice, we apply Milne-Eddington-type inversions to the synthetic spectra in order to retrieve different atmospheric parameters. We include the influence of spatial smearing on the deduced atmospheric parameters to identify signatures of different stages of flux emergence in the solar photosphere.

  7. Warps, bending and density waves excited by rotating magnetized stars: results of global 3D MHD simulations

    NASA Astrophysics Data System (ADS)

    Romanova, M. M.; Ustyugova, G. V.; Koldoba, A. V.; Lovelace, R. V. E.

    2013-03-01

    We report results of the first global three-dimensional (3D) magnetohydrodynamic (MHD) simulations of the waves excited in an accretion disc by a rotating star with a dipole magnetic field misaligned from the star's rotation axis (which is aligned with the disc axis). The main results are the following. (1) If the magnetosphere of the star corotates approximately with the inner disc, then we observe a strong one-armed bending wave (a warp). This warp corotates with the star and has a maximum amplitude between corotation radius and the radius of the vertical resonance. The disc's centre of mass can deviate from the equatorial plane up to the distance of zw ≈ 0.1r. However, the effective height of the warp can be larger, hw ≈ 0.3r, due to the finite thickness of the disc. Stars with a range of misalignment angles excite warps. However, the amplitude of the warps is larger for misalignment angles between 15° and 60°. The location and amplitude of the warp do not depend on viscosity, at least for relatively small values of the standard alpha-parameter, up to 0.08. (2) If the magnetosphere rotates slower than the inner disc, then a bending wave is excited at the disc-magnetosphere boundary, but does not form a large-scale warp. Instead, persistent, high-frequency oscillations become strong at the inner region of the disc. These are (a) trapped density waves which form inside the radius where the disc angular velocity has a maximum, and (b) inner bending waves which appear in the case of accretion through magnetic Rayleigh-Taylor instability. These two types of waves are connected with the inner disc and their frequencies will vary with accretion rate. Bending oscillations at lower frequencies are also excited including global oscillations of the disc. In cases where the simulation region is small, slowly precessing warp forms with the maximum amplitude at the vertical resonance. The present simulations are applicable to young stars, cataclysmic variables and

  8. Lattice Boltzmann simulation of thermofluidic transport phenomena in a DC magnetohydrodynamic (MHD) micropump.

    PubMed

    Chatterjee, Dipankar; Amiroudine, Sakir

    2011-02-01

    A comprehensive non-isothermal Lattice Boltzmann (LB) algorithm is proposed in this article to simulate the thermofluidic transport phenomena encountered in a direct-current (DC) magnetohydrodynamic (MHD) micropump. Inside the pump, an electrically conducting fluid is transported through the microchannel by the action of an electromagnetic Lorentz force evolved out as a consequence of the interaction between applied electric and magnetic fields. The fluid flow and thermal characteristics of the MHD micropump depend on several factors such as the channel geometry, electromagnetic field strength and electrical property of the conducting fluid. An involved analysis is carried out following the LB technique to understand the significant influences of the aforementioned controlling parameters on the overall transport phenomena. In the LB framework, the hydrodynamics is simulated by a distribution function, which obeys a single scalar kinetic equation associated with an externally imposed electromagnetic force field. The thermal history is monitored by a separate temperature distribution function through another scalar kinetic equation incorporating the Joule heating effect. Agreement with analytical, experimental and other available numerical results is found to be quantitative.

  9. Development of materials for open-cycle magnetohydrodynamics (MHD): ceramic electrode. Final report

    SciTech Connect

    Bates, J.L.; Marchant, D.D.

    1986-09-01

    Pacific Northwest Laboratory, supported by the US Department of Energy, developed advanced materials for use in open-cycle, closed cycle magnetohydrodynamics (MHD) power generation, an advanced energy conversion system in which the flow of electrically conducting fluid interacts with an electric field to convert the energy directly into electricity. The purpose of the PNL work was to develop electrodes for the MHD channel. Such electrodes must have: (1) electrical conductivity above 0.01 (ohm-cm)/sup -1/ from near room temperature to 1900/sup 0/K, (2) resistance to both electrochemical and chemical corrosion by both slag and potassium seed, (3) resistance to erosion by high-velocity gases and particles, (4) resistance to thermal shock, (5) adequate thermal conductivity, (6) compatibility with other channel components, particularly the electrical insulators, (7) oxidation-reduction stability, and (8) adequate thermionic emission. This report describes the concept and development of high-temperature, graded ceramic composite electrode materials and their electrical and structural properties. 47 refs., 16 figs., 13 tabs.

  10. Electric fields and field-aligned currents in polar regions of the solar corona: 3-D MHD consideration

    NASA Technical Reports Server (NTRS)

    Pisanko, Yu. V.

    1995-01-01

    The calculation of the solar rotation electro-dynamical effects in the near-the-Sun solar wind seems more convenient from the non-inertial corotating reference frame. This implies some modification of the 3-D MHD equations generally on the base of the General Theory of Relativity. The paper deals with the search of stationary (in corotating non-inertial reference frame) solutions of the modified 3-D MHD equations for the in near-the-Sun high latitude sub-alfvenic solar wind. The solution is obtained requiring electric fields and field-aligned electric currents in the high latitude near-the-Sun solar wind. Various scenario are explored self-consistently via a number of numerical experiments. The analogy with the high latitude Earth's magnetosphere is used for the interpretation of the results. Possible observational manifestations are discussed.

  11. Expected IPS variations due to a disturbance described by a 3-D MHD model

    NASA Technical Reports Server (NTRS)

    Tappin, S. J.; Dryer, M.; Han, S. M.; Wu, S. T.

    1988-01-01

    The variations of interplanetary scintillation due to a disturbance described by a three-dimensional, time-dependent, MHD model of the interplanetary medium are calculated. The resulting simulated IPS maps are compared with observations of real disturbances and it is found that there is some qualitative agreement. It is concluded that the MHD model with a more realistic choice of input conditions would probably provide a useful description of many interplanetary disturbances.

  12. MODELING STATISTICAL PROPERTIES OF SOLAR ACTIVE REGIONS THROUGH DIRECT NUMERICAL SIMULATIONS OF 3D-MHD TURBULENCE

    SciTech Connect

    Malapaka, Shiva Kumar; Mueller, Wolf-Christian

    2013-09-01

    Statistical properties of the Sun's photospheric turbulent magnetic field, especially those of the active regions (ARs), have been studied using the line-of-sight data from magnetograms taken by the Solar and Heliospheric Observatory and several other instruments. This includes structure functions and their exponents, flatness curves, and correlation functions. In these works, the dependence of structure function exponents ({zeta}{sub p}) of the order of the structure functions (p) was modeled using a non-intermittent K41 model. It is now well known that the ARs are highly turbulent and are associated with strong intermittent events. In this paper, we compare some of the observations from Abramenko et al. with the log-Poisson model used for modeling intermittent MHD turbulent flows. Next, we analyze the structure function data obtained from the direct numerical simulations (DNS) of homogeneous, incompressible 3D-MHD turbulence in three cases: sustained by forcing, freely decaying, and a flow initially driven and later allowed to decay (case 3). The respective DNS replicate the properties seen in the plots of {zeta}{sub p} against p of ARs. We also reproduce the trends and changes observed in intermittency in flatness and correlation functions of ARs. It is suggested from this analysis that an AR in the onset phase of a flare can be treated as a forced 3D-MHD turbulent system in its simplest form and that the flaring stage is representative of decaying 3D-MHD turbulence. It is also inferred that significant changes in intermittency from the initial onset phase of a flare to its final peak flaring phase are related to the time taken by the system to reach the initial onset phase.

  13. Magnetohydrodynamic power generation

    NASA Technical Reports Server (NTRS)

    Smith, J. L.

    1984-01-01

    Magnetohydrodynamic (MHD) Power Generation is a concise summary of MHD theory, history, and future trends. Results of the major international MHD research projects are discussed. Data from MHD research is included. Economics of initial and operating costs are considered.

  14. Study of energy transfer from the solar wind to Earth's magnetosphere using the 3D- MHD BATS-R-US global model

    NASA Astrophysics Data System (ADS)

    Jauer, P. R.; Gonzalez, W. D.; de Souza Costa, C. L.; Souza, V. M.

    2013-12-01

    The interaction, transport and conversion of energy between the solar wind and Earth's magnetosphere have been studied for decades through in situ measurements and Magnetohydrodynamics simulation, (MHD). Nevertheless, due to the vast regions of space and nonlinearities of the physical processes there are many questions that still remain without conclusive answers. Currently, the MHD simulation is a powerful tool that helps other means of already existing research, even within its theoretical limitation; it provides information of the space regions where in situ measurements are rare or nonexistent. The aim of this work is the study of energy transfer from the solar wind through the calculation of the divergence of the Poynting vector for the inner regions of the Earth's magnetosphere, especially the magneto tail using 3D global MHD numerical code Space Weather Modelling Framework (SWMF) / (Block Adaptive Tree Solar wind Roe Upwind Scheme) (BATS-R-US), developed by the University of Michigan. We conducted a simulation study for the event that occurred on September 21-27, 1999, for which the peak value of the interplanetary magnetic field was -22 nT, and gave rise to an intense magnetic storm with peak Dst of -160 nT. Furthermore, we compare the results of the power estimated by the model - through the integration of the Poynting vector in rectangular region of the tail, with a domain -130 MHD simulation is a

  15. 3D Relativistic Magnetohydrodynamic Simulations of Magnetized Spine-Sheath Relativistic Jets

    NASA Technical Reports Server (NTRS)

    Mizuno, Yosuke; Hardee, Philip; Nishikawa, Ken-Ichi

    2006-01-01

    Numerical simulations of weakly magnetized and strongly magnetized relativistic jets embedded in a weakly magnetized and strongly magnetized stationary or weakly relativistic (v = c/2) sheath have been performed. A magnetic field parallel to the flow is used in these simulations performed by the new GRMHD numerical code RAISHIN used in its RMHD configuration. In the numerical simulations the Lorentz factor gamma = 2.5 jet is precessed to break the initial equilibrium configuration. In the simulations sound speeds are less than or equal to c/the square root of 3 in the weakly magnetized simulations and less than or equal to 0.56 c in the strongly magnetized simulations. The Alfven wave speed is less than or equal to 0.07 c in the weakly magnetized simulations and less than or equal to 0.56 c in the strongly magnetized simulations. The results of the numerical simulations are compared to theoretical predictions from a normal mode analysis of the linearized relativistic magnetohydrodynamic (RMHD) equations capable of describing a uniform axially magnetized cylindrical relativistic jet embedded in a uniform axially magnetized relativistically moving sheath. The theoretical dispersion relation allows investigation of effects associated with maximum possible sound speeds, Alfven wave speeds near light speed and relativistic sheath speeds. The prediction of increased stability of the weakly magnetized system resulting from c/2 sheath speeds and the stabilization of the strongly magnetized system resulting from c/2 sheath speeds is verified by the numerical simulation results.

  16. A Global 3D Radiation MHD Simulation of Super-Eddington Accretion Disks

    NASA Astrophysics Data System (ADS)

    Jiang, Yanfei

    2014-10-01

    We study how black holes can accrete above the Eddington limit using a global three dimensional radiation magneto-hydrodynamic simulation without ad-hoc assumptions. The simulation reaches an accretion rate ~ 220L_Edd/c^2 and forms a radiation driven outflow along the rotation axis. The radiative luminosity of this flow is ~ 10L_Edd. This yields a radiative efficiency ~ 4.5%, which is comparable to the value in a standard thin disk model. In our simulation, vertical advection of radiation caused by magnetic buoyancy transports energy faster than photon diffusion, allowing a significant fraction of the photons to escape from the surface of the disk before being advected into the black hole. We contrast our results with the lower radiative efficiencies inferred in slim disk model, which neglect vertical advection. The results have important implications for the growth of supermassive black holes in the early universe, tidal disruption events and ultra-luminous X-ray sources.

  17. Morphology and Dynamics of Solar Prominences from 3D MHD Simulations

    NASA Astrophysics Data System (ADS)

    Terradas, J.; Soler, R.; Luna, M.; Oliver, R.; Ballester, J. L.

    2015-01-01

    In this paper we present a numerical study of the time evolution of solar prominences embedded in sheared magnetic arcades. The prominence is represented by a density enhancement in a background-stratified atmosphere and is connected to the photosphere through the magnetic field. By solving the ideal magnetohydrodynamic equations in three dimensions, we study the dynamics for a range of parameters representative of real prominences. Depending on the parameters considered, we find prominences that are suspended above the photosphere, i.e., detached prominences, but also configurations resembling curtain or hedgerow prominences whose material continuously connects to the photosphere. The plasma-β is an important parameter that determines the shape of the structure. In many cases magnetic Rayleigh-Taylor instabilities and oscillatory phenomena develop. Fingers and plumes are generated, affecting the whole prominence body and producing vertical structures in an essentially horizontal magnetic field. However, magnetic shear is able to reduce or even to suppress this instability.

  18. Magnetohydrodynamics (MHD) Engineering Test Facility (ETF) 200 MWe power plant. Conceptual Design Engineering Report (CDER). Volume 4: Supplementary engineering data

    NASA Technical Reports Server (NTRS)

    1981-01-01

    The reference conceptual design of the Magnetohydrodynamic Engineering Test Facility (ETF), a prototype 200 MWe coal-fired electric generating plant designed to demonstrate the commercial feasibility of open cycle MHD is summarized. Main elements of the design are identified and explained, and the rationale behind them is reviewed. Major systems and plant facilities are listed and discussed. Construction cost and schedule estimates, and identification of engineering issues that should be reexamined are also given. The latest (1980-1981) information from the MHD technology program are integrated with the elements of a conventional steam power electric generating plant. Supplementary Engineering Data (Issues, Background, Performance Assurance Plan, Design Details, System Design Descriptions and Related Drawings) is presented.

  19. Viscous dissipation and thermal radiation effects on the magnetohydrodynamic (MHD) flow and heat transfer over a stretching slender cylinder

    NASA Astrophysics Data System (ADS)

    Kalteh, M.; Ghorbani, S.; Khademinejad, T.

    2016-05-01

    An axisymmetric magnetohydrodynamic (MHD) boundary layer flow and heat transfer of a fluid over a slender cylinder are investigated numerically. The effects of viscous dissipation, thermal radiation, and surface transverse curvature are taken into account in the simulations. For this purpose, the governing partial differential equations are transformed to ordinary differential equations by using appropriate similarity transformations. The resultant ordinary differential equations along with appropriate boundary conditions are solved by the fourth-order Runge-Kutta method combined with the shooting technique. The effects of various parameters on the velocity and temperature profiles, local skin friction coefficient, and Nusselt number are analyzed.

  20. MHD Simulations of Spherical Tori and Compact Stellarators Using M3D

    NASA Astrophysics Data System (ADS)

    Strauss, H. R.; Park, W.; Tang, X.; Fu, G. Y.; Sugiyama, L.

    1999-11-01

    The M3D++ unstructured mesh version of the M3D code is being applied to low aspect ratio spherical torus disruption simulations. In addition to spherical tokamaks (ST), similar to NSTX, we also study spherical pinches (SP). It is possible to produce SP equilibria with 1 > q > 1/2, and toroidal current decreasing to zero at the wall. These SP equilibria have reverse magnetic shear except in a narrow layer near the wall. The equilibria are free of the global m=1 modes that plague low q pinches such as RFPs. However there can be unstable (m,n) = (2,3) modes. The M3D++ code has been extended to have the capability of using a 3D mesh in configuration space, suitable for stellarator equilibrium, stability, and nonlinear studies, including resistive effects. Equilibria can be initialized with VMEC output or generated from initial data. Applications to compact stellarator configurations such as the PPPL quasi axisymmetric design will be presented.

  1. Non-twist map bifurcation of drift-lines and drift-island formation in saturated 3D MHD equilibria

    NASA Astrophysics Data System (ADS)

    Pfefferle, David; Cooper, Wilfred A.; Graves, Jonathan P.

    2015-11-01

    Based on non-canonical perturbation theory, guiding-centre drift equations are identified as perturbed magnetic field-line equations. The topology of passing-particle orbits, called drift-lines, is completely determined by the magnetic configuration. In axisymmetric tokamak fields, drift-lines lie on shifted flux-surfaces, called drift-surfaces. Field-lines and drift-lines are subject to island structures at rational surfaces only when a non-axisymmetric component is added. The picture is different in the case of 3D saturated MHD equilibrium like the helical core associated with a non-resonant internal kink mode. In assuming nested flux-surfaces, these bifurcated states, expected for a reversed q-profile with qmin close yet above unity and conveniently obtained in VMEC, feature integrable field-lines. The helical drift-lines however become resonant with the axisymmetric component in the region of qmin and spontaneously generate drift-islands. Due to the locally reversed sheared q-profile, the drift-island structure follows the bifurcation/reconnection mechanism of non-twist maps. This result provides a theoretical interpretation of NBI fast ion helical hot-spots in Long-Lived Modes as well as snake-like impurity density accumulation in internal MHD activity.

  2. Interpretation of solar irradiance monitor measurements through analysis of 3D MHD simulations

    SciTech Connect

    Criscuoli, S.; Uitenbroek, H.

    2014-06-20

    Measurements from the Spectral Irradiance Monitor (SIM) on board the Solar Radiation and Climate Experiment mission indicate that solar spectral irradiance at visible and IR wavelengths varies in counter phase with the solar activity cycle. The sign of these variations is not reproduced by most of the irradiance reconstruction techniques based on variations of surface magnetism employed so far, and it is not yet clear whether SIM calibration procedures need to be improved or if instead new physical mechanisms must be invoked to explain such variations. We employ three-dimensional magnetohydrodynamic simulations of the solar photosphere to investigate the dependence of solar radiance in SIM visible and IR spectral ranges on variations of the filling factor of surface magnetic fields. We find that the contribution of magnetic features to solar radiance is strongly dependent on the location on the disk of the features, which are negative close to disk center and positive toward the limb. If features are homogeneously distributed over a region around the equator (activity belt), then their contribution to irradiance is positive with respect to the contribution of HD snapshots, but decreases with the increase of their magnetic flux for average magnetic flux larger than 50 G in at least two of the visible and IR spectral bands monitored by SIM. Under the assumption that the 50 G snapshots are representative of quiet-Sun regions, we thus find that the Spectral Irradiance can be in counter-phase with the solar magnetic activity cycle.

  3. 3D relaxation MHD modeling with FOI-PERFECT code for electromagnetically driven HED systems

    NASA Astrophysics Data System (ADS)

    Wang, Ganghua; Duan, Shuchao; Xie, Weiping; Kan, Mingxian; Institute of Fluid Physics Collaboration

    2015-11-01

    One of the challenges in numerical simulations of electromagnetically driven high energy density (HED) systems is the existence of vacuum region. The electromagnetic part of the conventional model adopts the magnetic diffusion approximation (magnetic induction model). The vacuum region is approximated by artificially increasing the resistivity. On one hand the phase/group velocity is superluminal and hence non-physical in the vacuum region, on the other hand a diffusion equation with large diffusion coefficient can only be solved by implicit scheme. Implicit method is usually difficult to parallelize and converge. A better alternative is to solve the full electromagnetic equations for the electromagnetic part. Maxwell's equations coupled with the constitutive equation, generalized Ohm's law, constitute a relaxation model. The dispersion relation is given to show its transition from electromagnetic propagation in vacuum to resistive MHD in plasma in a natural way. The phase and group velocities are finite for this system. A better time stepping is adopted to give a 3rd full order convergence in time domain without the stiff relaxation term restriction. Therefore it is convenient for explicit & parallel computations. Some numerical results of FOI-PERFECT code are also given. Project supported by the National Natural Science Foundation of China (Grant No. 11172277,11205145).

  4. 3D Multifluid MHD simulation for Uranus and Neptune: the seasonal variations of their magnetosphere

    NASA Astrophysics Data System (ADS)

    Cao, X.; Paty, C. S.

    2015-12-01

    The interaction between Uranus' intrinsic magnetic field and the solar wind is quite different from the magnetospheric interactions of other planets. Uranus' large obliquity, coupled with the fact that its dipole moment is off-centered and highly tilted relative to the rotation axis, leads to unique and seasonally dependent interaction geometries with the solar wind. We present results from adapting a multifluid MHD simulation to examine these seasonally dependent geometries in terms of the global magnetospheric structure, magnetopause and bow shock location, and magnetotail configuration. The Voyager 2 spacecraft encountered Uranus near solstice, and was able to observe the magnetic field structure and plasma characteristics of a twisted magnetotail [Behannon et al., 1987]. We use such magnetometer and plasma observations as a basis for benchmarking our simulations for the solstice scenario. Auroral observations made by the Hubble Space Telescope during equinox [Lamy et al.,2012] give some indication of the magnetospheric interaction with the solar wind. We also demonstrate the structural difference of the magnetosphere between solstice and equinox seasons. The magnetosphere at equinox is quite distinct due to the orientation and rotation of the magnetic axis relative to the solar wind direction.

  5. A simulation of the IPS variations from a magnetohydrodynamical simulation

    NASA Technical Reports Server (NTRS)

    Tappin, S. J.; Dryer, M.; Han, S. M.; Wu, S. T.

    1987-01-01

    Calculations of the variations of interplanetary scintillation (IPS) from a disturbance simulated by a 3-D magnetohydrodynamical (MHD) model of the solar wind are presented. The simulated maps are compared with observations and it is found that the MHD model reproduces the qualitative features of observed disturbances. The disturbance produced by the MHD simulation is found to correspond in strength with the weakest disturbance which can be reliably detected by existing single station IPS observations.

  6. Analyses of Magnetic Structures of Active Region 11117 Evolution using a 3D Data-Driven Magnetohydrodynamic Model

    NASA Astrophysics Data System (ADS)

    Wu, Shi; Jiang, Chaowei; Feng, Xueshang

    We use the photospheric vector magnetograms obtained by Helioseismic and Magnetic Image (HMI) on-board the Solar Dynamic Observatory (SDO) as the boundary conditions for a Data-Driven CESE-MHD model (Jiang et al. 2012) to investigate the physical characteristics and evolution of magnetic field configurations in the corona before and after a solar eruptive event. Specifically, the evolution of AR11117 characteristics such as length of magnetic shear along the neutral line, current helicity, magnetic free energy and the energy flux across the photosphere due to flux emergence and surface flow are presented. The computed 3D magnetic field configuration are compared with AIA (Atmosphere Image Assembly) which shows remarkable resemblance. A topological analyses reveals that the small flare is correlated with a bald patch (BP, where the magnetic field is tangent to the photosphere), suggesting that the energy release of the flare is caused by magnetic reconnection associated with the BP separatrices. The total magnetic flux and energy keep increasing slightly in spite of flare, while the computed magnetic free energy drops during the flare by 10 (30) ergs which is adequate in providing the energy budget of a minor C-class confined flare as observed. Jiang, Chaowei, Xueshang, Feng, S. T Wu and Qiang Hu, Ap. J., 759:85, 2012 Nov 10

  7. Predicting multiprocessing efficiency on the Cray multiprocessors in a (CTSS) time-sharing environment/application to a 3-D magnetohydrodynamics code

    SciTech Connect

    Mirin, A.A.

    1988-07-01

    A formula is derived for predicting multiprocessing efficiency on Cray supercomputers equipped with the Cray Time-Sharing System (CTSS). The model is applicable to an intensive time-sharing environment. The actual efficiency estimate depends on three factors: the code size, task length, and job mix. The implementation of multitasking in a three-dimensional plasma magnetohydrodynamics (MHD) code, TEMCO, is discussed. TEMCO solves the primitive one-fluid compressible MHD equations and includes resistive and Hall effects in Ohm's law. Virtually all segments of the main time-integration loop are multitasked. The multiprocessing efficiency model is applied to TEMCO. Excellent agreement is obtained between the actual multiprocessing efficiency and the theoretical prediction.

  8. Magnetohydrodynamics (MHD) Engineering Test Facility (ETF) 200 MWe power plant. Design Requirements Document (DRD)

    NASA Technical Reports Server (NTRS)

    Rigo, H. S.; Bercaw, R. W.; Burkhart, J. A.; Mroz, T. S.; Bents, D. J.; Hatch, A. M.

    1981-01-01

    A description and the design requirements for the 200 MWe (nominal) net output MHD Engineering Test Facility (ETF) Conceptual Design, are presented. Performance requirements for the plant are identified and process conditions are indicated at interface stations between the major systems comprising the plant. Also included are the description, functions, interfaces and requirements for each of these major systems. The lastest information (1980-1981) from the MHD technology program are integrated with elements of a conventional steam electric power generating plant.

  9. Magnetohydrodynamics MHD Engineering Test Facility ETF 200 MWe power plant. Conceptual Design Engineering Report CDER. Volume 3: Costs and schedules

    NASA Technical Reports Server (NTRS)

    1981-01-01

    The estimated plant capital cost for a coal fired 200 MWE electric generating plant with open cycle magnetohydrodynamics is divided into principal accounts based on Federal Energy Regulatory Commision account structure. Each principal account is defined and its estimated cost subdivided into identifiable and major equipment systems. The cost data sources for compiling the estimates, cost parameters, allotments, assumptions, and contingencies, are discussed. Uncertainties associated with developing the costs are quantified to show the confidence level acquired. Guidelines established in preparing the estimated costs are included. Based on an overall milestone schedule related to conventional power plant scheduling experience and starting procurement of MHD components during the preliminary design phase there is a 6 1/2-year construction period. The duration of the project from start to commercial operation is 79 months. The engineering phase of the project is 4 1/2 years; the construction duration following the start of the man power block is 37 months.

  10. 2D/3D electron temperature fluctuations near explosive MHD instabilities accompanied by minor and major disruptions

    NASA Astrophysics Data System (ADS)

    Choi, M. J.; Park, H. K.; Yun, G. S.; Lee, W.; Luhmann, N. C., Jr.; Lee, K. D.; Ko, W.-H.; Park, Y.-S.; Park, B. H.; In, Y.

    2016-06-01

    Minor and major disruptions by explosive MHD instabilities were observed with the novel quasi 3D electron cyclotron emission imaging (ECEI) system in the KSTAR plasma. The fine electron temperature (T e) fluctuation images revealed two types of minor disruptions: a small minor disruption is a q∼ 2 localized fast transport event due to a single m/n  =  2/1 magnetic island growth, while a large minor disruption is partial collapse of the q≤slant 2 region with two successive fast heat transport events by the correlated m/n  =  2/1 and m/n  =  1/1 instabilities. The m/n  =  2/1 magnetic island growth during the minor disruption is normally limited below the saturation width. However, as the additional interchange-like perturbation grows near the inner separatrix of the 2/1 island, the 2/1 island can expand beyond the limit through coupling with the cold bubble formed by the interchange-like perturbation.

  11. Magnetohydrodynamic (MHD) analyses of various forms of activity and their propagation through helio spheric space

    NASA Technical Reports Server (NTRS)

    Wu, S. T.

    1987-01-01

    Theoretical and numerical modeling of solar activity and its effects on the solar atmosphere within the context of magnetohydrodynamics were examined. Specifically, the scientific objectives were concerned with the physical mechanisms for the flare energy build-up and subsequent release. In addition, transport of this energy to the corona and solar wind was also investigated. Well-posed, physically self-consistent, numerical simulation models that are based upon magnetohydrodynamics were sought. A systematic investigation of the basic processes that determine the macroscopic dynamic behavior of solar and heliospheric phenomena was conducted. A total of twenty-three articles were accepted and published in major journals. The major achievements are summarized.

  12. Fundamental Studies On Development Of MHD (Magnetohydrodynamic) Generator Implement On Wave Energy Harvesting

    NASA Astrophysics Data System (ADS)

    Majid, M. F. M. A.; Apandi, Muhamad Al-Hakim Md; Sabri, M.; Shahril, K.

    2016-02-01

    As increasing of agricultural and industrial activities each year has led to an increasing in demand for energy. Possibility in the future, the country was not able to offer a lot of energy and power demand. This means that we need to focus on renewable energy to supply the demand for energy. Energy harvesting is among a method that can contribute on the renewable energy. MHD power generator is a new way to harvest the energy especially Ocean wave energy. An experimental investigation was conducted to explore performance of MHD generator. The effect of intensity of NaCl Solution (Sea Water), flow rate of NaCl solution, magnetic strength and magnet position to the current produce was analyzed. The result shows that each factor is give a significant effect to the current produce, because of that each factor need to consider on develop of MHD generator to harvest the wave energy as an alternative way to support the demand for energy.

  13. Shear-induced instability and arch filament eruption - A magnetohydrodynamic (MHD) numerical simulation

    NASA Technical Reports Server (NTRS)

    Wu, S. T.; Song, M. T.; Martens, P. C. H.; Dryer, M.

    1991-01-01

    A situation wherein a bipolar magnetic field embedded in a stratified solar atmosphere undergoes symmetrical shear motion at the footpoints is investigated via a 2D (nonplanar) MHD simulation. It was found that the vertical plasma flow velocities grow exponentially, leading to a new type of global MHD instability. The growth rate increases almost linearly until it reaches the same order of magnitude as the Alfven speed. Then a nonlinear MHD instability occurs beyond this point. It was found that the central loops are pinched by opposing Lorentz forces, and the outer closed loops stretch upward with the vertically-rising mass flow. The nonlinear dynamical shearing instability is illustrated by a numerical example that is given for three different values of the plasma beta that span several orders of magnitude.

  14. ON THE RELIABILITY OF ZEUS-3D

    SciTech Connect

    Clarke, David A.

    2010-03-01

    Recent and not-so-recent critiques of the widely used magnetohydrodynamics (MHD) code, ZEUS-3D, challenge its reliability and efficiency suggesting that its MHD algorithm is capable of 'significant errors' in some simple one-dimensional shock-tube problems. I show that these concerns are either inapplicable in multi-dimensional astrophysical applications, or result from a misuse of the code rather than 'flaws' in its design. I also describe a few multi-dimensional test problems including one for super-Alfvenic turbulence, and highlight some recent innovations and improvements to the code now available online.

  15. Statistical comparison of inter-substorm timings in global magnetohydrodynamics (MHD) and observations

    NASA Astrophysics Data System (ADS)

    Haiducek, J. D.; Welling, D. T.; Morley, S.; Ozturk, D. S.

    2015-12-01

    Magnetospheric substorms are events in which energy stored in the magnetotail is released into the auroral zone and into the downstream solar wind. Because of the complex, nonlinear, and possibly chaotic nature of the substorm energy release mechanism, it may be extremely difficult to forecast individual substorms in the near term. However, the inter-substorm timing (the amount of time elapsed between substorms) can be reproduced in a statistical sense, as was demonstrated by Freeman and Morley (2004) using their Minimal Substorm Model (MSM), a simple solar-wind driven model with the only free parameter being a recurrence time. The goal of the present work is to reproduce the observed distribution of inter-substorm timings with a global MHD model. The period of 1-31 January 2005 was simulated using the Space Weather Modeling Framework (SWMF), driven by solar wind observations. Substorms were identified in the model output by synthesizing surface magnetometer data and by looking for tailward-moving plasmoids. Substorms identified in the MHD model are then compared with observational data from the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft, Los Alamos National Laboratory (LANL) geostationary satellite energetic particle data, and surface magnetometer data. For each dataset (MHD model and observations), we calculate the substorm occurrence rate, and for the MHD model we additionally calculate the timing error of the substorm onsets relative to the observed substorms. Finally, we calculate distribution functions for the inter-substorm timings in both the observations and the model. The results of this analysis will guide improvements to the MHD-based substorm model, including the use of Hall MHD and embedded particle in cell (EPIC), leading to a better reproduction of the observed inter-substorm timings and an improved understanding of the underlying physical processes. ReferencesM. P. Freeman and S. K. Morley. A minimal substorm model that

  16. A nonvariational code for calculating three-dimensional MHD (magnetohydrodynamic) equilibria

    SciTech Connect

    Greenside, H.S.; Reiman, A.H.; Salas, A.

    1987-09-01

    Details are presented of the PIES code, which uses a nonvariational algorithm for calculating fully three-dimensional MHD equilibria. The MHD equilibrium equations are directly iterated in special coordinates to find self-consistent currents and magnetic fields for given pressure and current profiles and for a given outermost magnetic surface. Three important advantages of this approach over previous methods are the ease with which net current profiles can be imposed, the explicit treatment of resonances, and the ability to handle magnetic islands and stochastic field lines. The convergence properties of the code are studied for several axisymmetric and nonaxisymmetric finite-..beta.. equilibria that have magnetic surfaces. 36 refs., 14 figs., 3 tabs.

  17. Design study of superconducting magnets for a combustion magnetohydrodynamic (MHD) generator

    NASA Technical Reports Server (NTRS)

    Thome, R. J.; Ayers, J. W.

    1977-01-01

    Design trade off studies for 13 different superconducting magnet systems were carried out. Based on these results, preliminary design characteristics were prepared for several superconducting magnet systems suitable for use with a combustion driven MHD generator. Each magnet generates a field level of 8 T in a volume 1.524 m (60 in.) long with a cross section 0.254 m x 0.254 m (10 in. x 10 in.) at the inlet and 0.406 m x .406 m (16 in. x 16 in.) at the outlet. The first design involves a racetrack coil geometry intended for operation at 4.2 K; the second design uses a racetrack geometry at 2.0 K; and the third design utilizes a rectangular saddle geometry at 4.2 K. Each case was oriented differently in terms of MHD channel axis and main field direction relative to gravity in order to evaluate fabrication ease. All cases were designed such that the system could be disassembled to allow for alteration of field gradient in the MHD channel by changing the angle between coils. Preliminary design characteristics and assembly drawings were generated for each case.

  18. Experiments in Magnetohydrodynamics

    ERIC Educational Resources Information Center

    Rayner, J. P.

    1970-01-01

    Describes three student experiments in magnetohydrodynamics (MHD). In these experiments, it was found that the electrical conductivity of the local water supply was sufficient to demonstrate effectively some of the features of MHD flowmeters, generators, and pumps. (LC)

  19. FORCED FIELD EXTRAPOLATION: TESTING A MAGNETOHYDRODYNAMIC (MHD) RELAXATION METHOD WITH A FLUX-ROPE EMERGENCE MODEL

    SciTech Connect

    Zhu, X. S.; Wang, H. N.; Du, Z. L.; Fan, Y. L.

    2013-05-10

    We undertake an attempt to reconstruct the Sun's non-force-free magnetic field. The solar corona is often considered to be magnetohydrostatic. We solve the full MHD equations with a semi-realistic atmosphere model to attain this stationary state. Our method is tested with a Sun-like model which simulates the emergence of a magnetic flux rope passing from below the photosphere into the corona. Detailed diagnostics shows that our method can model the forced field more successfully than the optimization and potential method, but it still needs to be applied to real data.

  20. Micro optical fiber display switch based on the magnetohydrodynamic (MHD) principle

    NASA Astrophysics Data System (ADS)

    Lian, Kun; Heng, Khee-Hang

    2001-09-01

    This paper reports on a research effort to design, microfabricate and test an optical fiber display switch based on magneto hydrodynamic (MHD) principal. The switch is driven by the Lorentz force and can be used to turn on/off the light. The SU-8 photoresist and UV light source were used for prototype fabrication in order to lower the cost. With a magnetic field supplied by an external permanent magnet, and a plus electrical current supplied across the two inert sidewall electrodes, the distributed body force generated will produce a pressure difference on the fluid mercury in the switch chamber. By change the direction of current flow, the mercury can turn on or cut off the light pass in less than 10 ms. The major advantages of a MHD-based micro-switch are that it does not contain any solid moving parts and power consumption is much smaller comparing to the relay type switches. This switch can be manufactured by molding gin batch production and may have potential applications in extremely bright traffic control,, high intensity advertising display, and communication.

  1. MAGNETOHYDRODYNAMIC WAVES AND CORONAL HEATING: UNIFYING EMPIRICAL AND MHD TURBULENCE MODELS

    SciTech Connect

    Sokolov, Igor V.; Van der Holst, Bart; Oran, Rona; Jin, Meng; Manchester, Ward B. IV; Gombosi, Tamas I.; Downs, Cooper; Roussev, Ilia I.; Evans, Rebekah M.

    2013-02-10

    We present a new global model of the solar corona, including the low corona, the transition region, and the top of the chromosphere. The realistic three-dimensional magnetic field is simulated using the data from the photospheric magnetic field measurements. The distinctive feature of the new model is incorporating MHD Alfven wave turbulence. We assume this turbulence and its nonlinear dissipation to be the only momentum and energy source for heating the coronal plasma and driving the solar wind. The difference between the turbulence dissipation efficiency in coronal holes and that in closed field regions is because the nonlinear cascade rate degrades in strongly anisotropic (imbalanced) turbulence in coronal holes (no inward propagating wave), thus resulting in colder coronal holes, from which the fast solar wind originates. The detailed presentation of the theoretical model is illustrated with the synthetic images for multi-wavelength EUV emission compared with the observations from SDO AIA and STEREO EUVI instruments for the Carrington rotation 2107.

  2. Magnetohydrodynamic (MHD) flow of Cu-water nanofluid due to a rotating disk with partial slip

    NASA Astrophysics Data System (ADS)

    Hayat, Tasawar; Rashid, Madiha; Imtiaz, Maria; Alsaedi, Ahmed

    2015-06-01

    This paper investigates MHD steady flow of viscous nanofluid due to a rotating disk. Water is treated as a base fluid and copper as nanoparticle. Nanofluid fills the porous medium. Effects of partial slip, viscous dissipation and thermal radiation are also considered. Similarity transformations reduce the nonlinear partial differential equations to ordinary differential equations. Flow and heat transfer characteristics are computed by HAM solutions. Also computations for skin friction coefficient and Nusselt number are presented and examined for pertinent parameters. It is noted that higher velocity slip parameter decreases the radial and azimuthal velocities while temperature decreases for larger values of the thermal slip parameter. Also the rate of heat transfer enhances when the nanoparticle volume fraction increases.

  3. (The MHD (magnetohydrodynamics) coal fired flow facility): Quarterly technical progress report, April-June 1987

    SciTech Connect

    Not Available

    1987-09-01

    In this Quarterly Technical Progress Report, UTSI reports on progress in a multitask program to develop MHD technology, currently oriented toward the steam bottoming plant and environmental considerations. Plans and preparation for resumption of testing in the DOE Coal Fired Flow Facility are summarized. The status of the new aerodynamic duct, nozzle and diffuser is reported. Plans for continued testing of tubes made of candidate materials in the superheater test module are discussed. Progress in preparing the facility for the upcoming tests are included. Plans formulated jointly with Mississippi State University for application of advanced instrumentation in future tests are detailed. Additional analyses of data from previous tests is included in particulate loading and size distribution, seed recovery and trace elements. Progress in the environmental program is reported for the water quality program, the trace element study and process gas analysis.

  4. Recovering Photospheric Velocities from Vector Magnetograms by using a Three-Dimensional, Fully Magnetohydrodynamic (MHD) Model

    NASA Technical Reports Server (NTRS)

    Wang, A. H.; Wu, S. T.; Liu, Yang; Hathaway, D.

    2008-01-01

    We introduce a numerical simulation method for recovering the photospheric velocity field from the vector magnetograms. The traditional method is local correlation tracking (LCT) which is based on measuring the relative displacements of features in blocks of pixels between successive white-light images or magnetograms. Within this method, there are a variety of implementations. One of recently developed implementations is induction local correlation tracking (ILCT) as described by Welsch et al. (2004). They employ the normal component of magnetic induction equation as a constraint to assure consistent solutions. Our numerical method uses the fully three-dimensional MHD equations to recover the photospheric velocity field with individual vector magnetograms. We compare our method to the ILCT method using NOAA AR8210 as an example. The differences and similarities are discussed in detail.

  5. Magnetohydrodynamic (MHD) flow of Cu-water nanofluid due to a rotating disk with partial slip

    SciTech Connect

    Hayat, Tasawar; Rashid, Madiha; Imtiaz, Maria; Alsaedi, Ahmed

    2015-06-15

    This paper investigates MHD steady flow of viscous nanofluid due to a rotating disk. Water is treated as a base fluid and copper as nanoparticle. Nanofluid fills the porous medium. Effects of partial slip, viscous dissipation and thermal radiation are also considered. Similarity transformations reduce the nonlinear partial differential equations to ordinary differential equations. Flow and heat transfer characteristics are computed by HAM solutions. Also computations for skin friction coefficient and Nusselt number are presented and examined for pertinent parameters. It is noted that higher velocity slip parameter decreases the radial and azimuthal velocities while temperature decreases for larger values of the thermal slip parameter. Also the rate of heat transfer enhances when the nanoparticle volume fraction increases.

  6. An innovative demonstration of high power density in a compact MHD (magnetohydrodynamic) generator

    SciTech Connect

    Schmidt, H.J.; Lineberry, J.T.; Chapman, J.N.

    1990-06-01

    The present program was conducted by the University of Tennessee Space Institute (UTSI). It was by its nature a high risk experimental program to demonstrate the feasibility of high power density operation in a laboratory scale combustion driven MHD generator. Maximization of specific energy was not a consideration for the present program, but the results have implications in this regard by virtue of high energy fuel used. The power density is the ratio of the electrical energy output to the internal volume of the generator channel. The MHD process is a volumetric process and the power density is therefore a direct measure of the compactness of the system. Specific energy, is the ratio of the electrical energy output to consumable energy used for its production. The two parameters are conceptually interrelated. To achieve high power density and implied commensurate low system volume and weight, it was necessary to use an energetic fuel. The high energy fuel of choice was a mixture of powdered aluminum and carbon seeded with potassium carbonate and burned with gaseous oxygen. The solid fuel was burned in a hybrid combustion scheme wherein the fuel was cast within a cylindrical combustor in analogy with a solid propellant rocket motor. Experimental data is limited to gross channel output current and voltage, magnetic field strength, fuel and oxidizer flow rates, flow train external temperatures and combustor pressure. Similarly, while instantaneous oxidizer flow rates were measured, only average fuel consumption based on pre and post test component weights and dimensions was possible. 4 refs., 60 figs., 9 tabs.

  7. MHD Power Generation

    ERIC Educational Resources Information Center

    Kantrowitz, Arthur; Rosa, Richard J.

    1975-01-01

    Explains the operation of the Magnetohydrodynamic (MHD) generator and advantages of the system over coal, oil or nuclear powered generators. Details the development of MHD generators in the United States and Soviet Union. (CP)

  8. Study of the 3D Coronal Magnetic Field of Active Region 11117 Around the Time of a Confined Flare Using a Data-Driven CESE-MHD Model

    NASA Astrophysics Data System (ADS)

    Jiang, C.; Feng, X.; Wu, S.; Hu, Q.

    2012-12-01

    Non-potentiality of the solar coronal magnetic field accounts for the solar explosion like flares and CMEs. We apply a data-driven CESE-MHD model to investigate the three-dimensional (3D) coronal magnetic field of NOAA active region (AR) 11117 around the time of a C-class confined flare occurred on 2010 October 25. The CESE-MHD model, based on the spacetime conservation-element and solution-element scheme, is designed to focus on the magnetic-field evolution and to consider a simplified solar atomsphere with finite plasma β. Magnetic vector-field data derived from the observations at the photoshpere is inputted directly to constrain the model. Assuming that the dynamic evolution of the coronal magnetic field can be approximated by successive equilibria, we solve a time sequence of MHD equilibria basing on a set of vector magnetograms for AR 11117 taken by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamic Observatory (SDO) around the time of flare. The model qualitatively reproduces the basic structures of the 3D magnetic field, as supported by the visual similarity between the field lines and the coronal loops observed by the Atmospheric Imaging Assembly (AIA), which shows that the coronal field can indeed be well characterized by the MHD equilibrium in most time. The magnetic configuration changes very limited during the studied time interval of two hours. A topological analysis reveals that the small flare is correlated with a bald patch (BP, where the magnetic field is tangent to the photoshpere), suggesting that the energy release of the flare can be understood by magnetic reconnection associated with the BP separatrices. The total magnetic flux and energy keep increasing slightly in spite of the flare, while the magnetic free energy drops during the flare with an amount of 1.7 × 1030 erg, which can be interpreted as the energy budget released by the minor C-class flare.

  9. MHD (magnetohydrodynamic) thermal hydraulic analysis of three-dimensional liquid metal flows in fusion blanket ducts

    SciTech Connect

    Hua, T.A.; Picologlou, B.F.; Reed, C.B.; Walker, J.S.

    1988-02-01

    Magnetohydrodynamic flows of liquid metals in thin conducting ducts of various geometries in the presence of strong nonuniform transverse magnetic fields are examined. The interaction parameter and Hartmann number are assumed to be large, whereas the magnetic Reynolds number is assumed to be small. Under these assumptions, viscous and inertial effects are confined in very thin boundary layers adjacent to the walls. At walls parallel to the magnetic field lines, as at the side walls of a rectangular duct, the boundary layers (side layers) carry a significant fraction of the volumetric flow rate in the form of high velocity jets. The presence of these jets strongly enhances heat transfer performance. In addition, heat transfer can be further improved by guiding the flow toward a heated wall by proper variation of wall thicknesses, duct cross sectional dimensions and/or shape. Flows in nonconducting circular ducts are also examined. Experimental results obtained from the ALEX experiments at the Argonne National Laboratory are used to validate the numerical predictions. 6 refs., 7 figs.

  10. Design study of superconducting magnets for a combustion magnetohydrodynamic /MHD/ generator

    NASA Technical Reports Server (NTRS)

    Thome, R. J.; Ayers, J. W.; Hrycaj, T. M.; Burkhart, J. A.

    1978-01-01

    Results are presented for a trade-off and preliminary design study on concepts of a superconducting magnet system for a combustion MHD generator test facility. The main objective is to gain insight into the magnitude of the project in terms of physical characteristics and cost. The net result of a first-phase evaluation of attractive design alternatives is to concentrate subsequent efforts on (1) a racetrack coil geometry with an operating temperature of 4.2 K, (2) a racetrack coil geometry with an operating temperature of 2.0 K, and (3) a rectangular saddle coil geometry with an operating temperature of 4.2 K. All three systems are to produce 8 T, and use NbTi superconductor and iron for field enhancement. Design characteristics of the three systems are described. It is shown that the racetrack and rectangular saddle coil geometries seem most suitable for this application, the former because of its simplicity and the latter because of its efficient use of material. Advantages of the rectangular saddle over the two other systems are stressed.

  11. Application of rank-ordered multifractal analysis (ROMA) to intermittent fluctuations in 3D turbulent flows, 2D MHD simulation and solar wind data

    NASA Astrophysics Data System (ADS)

    Wu, C.; Chang, T.

    2010-12-01

    A new method in describing the multifractal characteristics of intermittent events was introduced by Cheng and Wu [Chang T. and Wu C.C., Physical Rev, E77, 045401(R), 2008]. The procedure provides a natural connection between the rank-ordered spectrum and the idea of one-parameter scaling for monofractals. This technique has been demonstrated using results obtained from a 2D MHD simulation. It has also been successfully applied to in-situ solar wind observations [Chang T., Wu, C.C. and Podesta, J., AIP Conf Proc. 1039, 75, 2008], and the broadband electric field oscillations from the auroral zone [Tam, S.W.Y. et al., Physical Rev, E81, 036414, 2010]. We take the next step in this procedure. By using the ROMA spectra and the scaled probability distribution functions (PDFs), raw PDFs can be calculated, which can be compared directly with PDFs from observations or simulation results. In addition to 2D MHD simulation results and in-situ solar wind observation, we show clearly using the ROMA analysis the multifractal character of the 3D fluid simulation data obtained from the JHU turbulence database cluster at http://turbulence.pha.jhu.edu. In particular, we show the scaling of the non-symmetrical PDF for the parallel-velocity fluctuations of this 3D fluid data.

  12. Measurements of priority pollutants in combustion products derived from the Dept. of Energy's (DOE) coal-fired flow facility magnetohydrodynamic (MHD)

    SciTech Connect

    Parks, K.D.; Sheth, A.C. )

    1988-01-01

    Magnetohydrodynamics is a branch of the physical sciences dealing with the electromagnetic fields and electrically conduction gases and liquids. Examples of MHD are everywhere, from stars and nuclear fusion to applications like MHD electrical power generation, i.e. when electrical conductors cut magnetic field lines, an electromotive force (EMF) is induced. If electrodes and external circuits are connected, current will flow. In conventional electric generators, the copper wire conductors are rotated through a magnetic field, and are usually driven by a steam turbine. On the other hand, the conductor in an MHD system is a fluid (gas or liquid) which flows through a magnetic field. There are two basic types of MHD energy conversion systems - open cycle and closed cycle. In closed cycle, the working fluid or conducting medium is recycled, while in the open cycle it is appropriately utilized and discarded. In this paper, the authors discuss the priority pollutants study carried out for an open cycle concept in which the conductor is a high temperature combustion gas, which flows through a magnetic field from a high pressure source and is not recycled.

  13. Solwnd: A 3D Compressible MHD Code for Solar Wind Studies. Version 1.0: Cartesian Coordinates

    NASA Technical Reports Server (NTRS)

    Deane, Anil E.

    1996-01-01

    Solwnd 1.0 is a three-dimensional compressible MHD code written in Fortran for studying the solar wind. Time-dependent boundary conditions are available. The computational algorithm is based on Flux Corrected Transport and the code is based on the existing code of Zalesak and Spicer. The flow considered is that of shear flow with incoming flow that perturbs this base flow. Several test cases corresponding to pressure balanced magnetic structures with velocity shear flow and various inflows including Alfven waves are presented. Version 1.0 of solwnd considers a rectangular Cartesian geometry. Future versions of solwnd will consider a spherical geometry. Some discussions of this issue is presented.

  14. Characterisation of small-scale heating events in the solar atmosphere from 3D MHD simulations and their potential role in coronal heating

    NASA Astrophysics Data System (ADS)

    Haberreiter, M.; Guerreiro, N.; Hansteen, V. H.; Schmutz, W. K.

    2015-12-01

    The physical mechanism that heats the solar corona is one of the still open science questions in solar physics. One of the proposed mechanism for coronal heating are nanoflares. To investigate their role in coronal heating we study the properties of the small-scale heating events in the solar atmosphere using 3D MHD simulations. We present a method to identify and track these heating events in time which allows us to study their life time, energy, and spectral signatures. These spectal signatures will be compared with available spectrosopic observations obtained with IRIS and SUMER. Ultimately, these results will be important for the coordinated scientific exploitation of SPICE and EUI along with other instruments onboard Solar Orbiter to address the coronal heating problem.

  15. Characterization of small-scale heating events in the solar atmosphere from 3D-MHD simulations and their potential role in coronal heating

    NASA Astrophysics Data System (ADS)

    Guerreiro, Nuno; Haberreiter, Margit; Hansteen, Viggo; Schmutz, Werner

    2016-04-01

    Aiming at better understanding the mechanism(s) responsible for the coronal heating and the ubiquitous redshifts observed in the lower transition region we focus on analyzing the properties of small-scale heating events (SSHEs) in the solar atmosphere. We present a comprehensive method to follow SSHEs over time in 3D-MHD simulations of the solar atmosphere. Applying the method we are able to better understand the properties of the SSHEs and how the plasma in their vicinity respond to them. We present results for the lifetime, energy and spectral signatures of the SSHEs. Ultimately, these results will be important for the coordinated scientific exploration of SPICE and EUI along with other interments on board solar orbiter. ​

  16. Detection and characterization of small-scale heating events in the solar atmosphere from 3D-MHD simulations and their potential role in coronal heating

    NASA Astrophysics Data System (ADS)

    Guerreiro, Nuno; Haberreiter, Margit; Schmutz, Werner; Hansteen, Viggo

    2016-07-01

    Aiming at better understanding the mechanism(s) responsible for the coronal heating we focus on analyzing the properties of the magnetically generated small-scale heating events (SSHEs) in the solar atmosphere. We present a comprehensive method to detect and follow SSHEs over time in 3D-MHD simulations of the solar atmosphere. Applying the method we are able to better understand the properties of the SSHEs and how the plasma in their vicinity respond to them. We study the lifetime, energy and spectral signatures and show that the energy flux dissipated by them is enough to heat the corona. Ultimately, these results will be important for the coordinated scientific exploration of SPICE and EUI along with other instruments on board solar orbiter.

  17. From Coronal Observations to MHD Simulations, the Building Blocks for 3D Models of Solar Flares (Invited Review)

    NASA Astrophysics Data System (ADS)

    Janvier, M.; Aulanier, G.; Démoulin, P.

    2015-12-01

    Solar flares are energetic events taking place in the Sun's atmosphere, and their effects can greatly impact the environment of the surrounding planets. In particular, eruptive flares, as opposed to confined flares, launch coronal mass ejections into the interplanetary medium, and as such, are one of the main drivers of space weather. After briefly reviewing the main characteristics of solar flares, we summarise the processes that can account for the build-up and release of energy during their evolution. In particular, we focus on the development of recent 3D numerical simulations that explain many of the observed flare features. These simulations can also provide predictions of the dynamical evolution of coronal and photospheric magnetic field. Here we present a few observational examples that, together with numerical modelling, point to the underlying physical mechanisms of the eruptions.

  18. Analysis of the Magneto-Hydrodynamic (MHD) Energy Bypass Engine for High-Speed Air-Breathing Propulsion

    NASA Technical Reports Server (NTRS)

    Riggins, David W.

    2002-01-01

    The performance of the MHD energy bypass air-breathing engine for high-speed propulsion is analyzed in this investigation. This engine is a specific type of the general class of inverse cycle engines. In this paper, the general relationship between engine performance (specific impulse and specific thrust) and the overall total pressure ratio through an engine (from inlet plane to exit plane) is first developed and illustrated. Engines with large total pressure decreases, regardless of cause or source, are seen to have exponentially decreasing performance. The ideal inverse cycle engine (of which the MHD engine is a sub-set) is then demonstrated to have a significant total pressure decrease across the engine; this total pressure decrease is cycle-driven, degrades rapidly with energy bypass ratio, and is independent of any irreversibility. The ideal MHD engine (inverse cycle engine with no irreversibility other than that inherent in the MHD work interaction processes) is next examined and is seen to have an additional large total pressure decrease due to MHD-generated irreversibility in the decelerator and the accelerator. This irreversibility mainly occurs in the deceleration process. Both inherent total pressure losses (inverse cycle and MHD irreversibility) result in a significant narrowing of the performance capability of the MHD bypass engine. The fundamental characteristics of MHD flow acceleration and flow deceleration from the standpoint of irreversibility and second-law constraints are next examined in order to clarify issues regarding flow losses and parameter selection in the MM modules. Severe constraints are seen to exist in the decelerator in terms of allowable deceleration Mach numbers and volumetric (length) required for meaningful energy bypass (work interaction). Considerable difficulties are also encountered and discussed due to thermal/work choking phenomena associated with the deceleration process. Lastly, full engine simulations utilizing inlet

  19. Pressure driven currents near magnetic islands in 3D MHD equilibria: Effects of pressure variation within flux surfaces and of symmetry

    NASA Astrophysics Data System (ADS)

    Reiman, Allan H.

    2016-07-01

    In toroidal, magnetically confined plasmas, the heat and particle transport is strongly anisotropic, with transport along the field lines sufficiently strong relative to cross-field transport that the equilibrium pressure can generally be regarded as constant on the flux surfaces in much of the plasma. The regions near small magnetic islands, and those near the X-lines of larger islands, are exceptions, having a significant variation of the pressure within the flux surfaces. It is shown here that the variation of the equilibrium pressure within the flux surfaces in those regions has significant consequences for the pressure driven currents. It is further shown that the consequences are strongly affected by the symmetry of the magnetic field if the field is invariant under combined reflection in the poloidal and toroidal angles. (This symmetry property is called "stellarator symmetry.") In non-stellarator-symmetric equilibria, the pressure-driven currents have logarithmic singularities at the X-lines. In stellarator-symmetric MHD equilibria, the singular components of the pressure-driven currents vanish. These equilibria are to be contrasted with equilibria having B ṡ∇p =0 , where the singular components of the pressure-driven currents vanish regardless of the symmetry. They are also to be contrasted with 3D MHD equilibrium solutions that are constrained to have simply nested flux surfaces, where the pressure-driven current goes like 1 /x near rational surfaces, where x is the distance from the rational surface, except in the case of quasi-symmetric flux surfaces. For the purpose of calculating the pressure-driven currents near magnetic islands, we work with a closed subset of the MHD equilibrium equations that involves only perpendicular force balance, and is decoupled from parallel force balance. It is not correct to use the parallel component of the conventional MHD force balance equation, B ṡ∇p =0 , near magnetic islands. Small but nonzero values of B

  20. Analytical and computational investigations of a magnetohydrodynamics (MHD) energy-bypass system for supersonic gas turbine engines to enable hypersonic flight

    NASA Astrophysics Data System (ADS)

    Benyo, Theresa Louise

    Historically, the National Aeronautics and Space Administration (NASA) has used rocket-powered vehicles as launch vehicles for access to space. A familiar example is the Space Shuttle launch system. These vehicles carry both fuel and oxidizer onboard. If an external oxidizer (such as the Earth's atmosphere) is utilized, the need to carry an onboard oxidizer is eliminated, and future launch vehicles could carry a larger payload into orbit at a fraction of the total fuel expenditure. For this reason, NASA is currently researching the use of air-breathing engines to power the first stage of two-stage-to-orbit hypersonic launch systems. Removing the need to carry an onboard oxidizer leads also to reductions in total vehicle weight at liftoff. This in turn reduces the total mass of propellant required, and thus decreases the cost of carrying a specific payload into orbit or beyond. However, achieving hypersonic flight with air-breathing jet engines has several technical challenges. These challenges, such as the mode transition from supersonic to hypersonic engine operation, are under study in NASA's Fundamental Aeronautics Program. One propulsion concept that is being explored is a magnetohydrodynamic (MHD) energy- bypass generator coupled with an off-the-shelf turbojet/turbofan. It is anticipated that this engine will be capable of operation from takeoff to Mach 7 in a single flowpath without mode transition. The MHD energy bypass consists of an MHD generator placed directly upstream of the engine, and converts a portion of the enthalpy of the inlet flow through the engine into electrical current. This reduction in flow enthalpy corresponds to a reduced Mach number at the turbojet inlet so that the engine stays within its design constraints. Furthermore, the generated electrical current may then be used to power aircraft systems or an MHD accelerator positioned downstream of the turbojet. The MHD accelerator operates in reverse of the MHD generator, re-accelerating the

  1. Analytical and computational investigations of a magnetohydrodynamics (MHD) energy-bypass system for supersonic gas turbine engines to enable hypersonic flight

    NASA Astrophysics Data System (ADS)

    Benyo, Theresa Louise

    Historically, the National Aeronautics and Space Administration (NASA) has used rocket-powered vehicles as launch vehicles for access to space. A familiar example is the Space Shuttle launch system. These vehicles carry both fuel and oxidizer onboard. If an external oxidizer (such as the Earth's atmosphere) is utilized, the need to carry an onboard oxidizer is eliminated, and future launch vehicles could carry a larger payload into orbit at a fraction of the total fuel expenditure. For this reason, NASA is currently researching the use of air-breathing engines to power the first stage of two-stage-to-orbit hypersonic launch systems. Removing the need to carry an onboard oxidizer leads also to reductions in total vehicle weight at liftoff. This in turn reduces the total mass of propellant required, and thus decreases the cost of carrying a specific payload into orbit or beyond. However, achieving hypersonic flight with air-breathing jet engines has several technical challenges. These challenges, such as the mode transition from supersonic to hypersonic engine operation, are under study in NASA's Fundamental Aeronautics Program. One propulsion concept that is being explored is a magnetohydrodynamic (MHD) energy- bypass generator coupled with an off-the-shelf turbojet/turbofan. It is anticipated that this engine will be capable of operation from takeoff to Mach 7 in a single flowpath without mode transition. The MHD energy bypass consists of an MHD generator placed directly upstream of the engine, and converts a portion of the enthalpy of the inlet flow through the engine into electrical current. This reduction in flow enthalpy corresponds to a reduced Mach number at the turbojet inlet so that the engine stays within its design constraints. Furthermore, the generated electrical current may then be used to power aircraft systems or an MHD accelerator positioned downstream of the turbojet. The MHD accelerator operates in reverse of the MHD generator, re-accelerating the

  2. Identification of standing MHD modes in MHD simulations of planetary magnetospheres. Application to Mercury.

    NASA Astrophysics Data System (ADS)

    Griton, Léa; Pantellini, Filippo; Moncuquet, Michel

    2016-04-01

    We present 3D simulations of the interaction of the solar wind with Mercury's magnetosphere using the magnetohydrodynamic code AMRVAC. A procedure for the identification of standing MHD modes has been applied to these simulations showing that large scale standing slow mode structures may exist in Mercury's magnetosheath. The identification is mostly based on relatively simple approximate analytical solutions to the old problem of determining the family of all standing linear plane MHD waves in a flowing plasma. The question of the identification of standing slow mode structures using in situ measurements such as the future BepiColombo MMO mission to Mercury will be discussed as well.

  3. Gyroscopic analog for magnetohydrodynamics

    SciTech Connect

    Holm, D.D.

    1981-01-01

    The gross features of plasma equilibrium and dynamics in the ideal magnetohydrodynamics (MHD) model can be understood in terms of a dynamical system which closely resembles the equations for a deformable gyroscope.

  4. Gyroscopic analog for magnetohydrodynamics

    SciTech Connect

    Holm, D.D.

    1982-07-20

    The gross features of plasma equilibrium and dynamics in the ideal magnetohydrodynamics (MHD) model can be understood in terms of a dynamical system which closely resembles the equations for a deformable gyroscope.

  5. Magnetohydrodynamic electrode

    DOEpatents

    Boquist, Carl W.; Marchant, David D.

    1978-01-01

    A ceramic-metal composite suitable for use in a high-temperature environment consists of a refractory ceramic matrix containing 10 to 50 volume percent of a continuous high-temperature metal reinforcement. In a specific application of the composite, as an electrode in a magnetohydrodynamic generator, the one surface of the electrode which contacts the MHD fluid may have a layer of varying thickness of nonreinforced refractory ceramic for electrode temperature control. The side walls of the electrode may be coated with a refractory ceramic insulator. Also described is an electrode-insulator system for a MHD channel.

  6. Modeling of SDO/HMI spectro-polarimetric data and center-to-limb variation effects with 3D MHD simulations

    NASA Astrophysics Data System (ADS)

    Kitiashvili, Irina; Couvidat, Sebastien

    2014-06-01

    Observations with the Solar Dynamics Observatory (SDO), and, in particular, Helioseismic and Magnetic Imager (HMI) provide a unique opportunity to investigate various phenomena simultaneously over the whole solar disk. Current state-of-the-art numerical simulations allow us to model the observational data with a high degree of realism, and use the artificial data for interpretation of observed properties ("observables") in terms of the physical conditions, for the testing of new data analysis techniques and the improvement of data calibration. In the current study we use realistic-type 3D radiative MHD simulations of the upper turbulent convective layer and atmosphere of the Sun, obtained with the SolarBox code, and employ the spectro-polarimetric radiative transfer code SPINOR to convert the simulated data into Stokes profiles of the HMI Fe I 6173 A line for different conditions in the solar atmosphere. For testing the HMI calibration the synthetic Stokes profiles are processed through the SDO/JSOC simplified data analysis pipeline. We investigate properties of the HMI observables for various solar features, variations of the line formation height for different angular distances from the disk center, effects of the spatial resolution and iron abundance, and pay particular attention to the center-to-limb variations effects playing important role in local helioseismology measurements.

  7. Magnetohydrodynamics (MHD) Engineering Test Facility (ETF) 200 MWe power plant. Conceptual Design Engineering Report (CDER). Volume 1: Executive summary

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Main elements of the design are identified and explained, and the rationale behind them was reviewed. Major systems and plant facilities are listed and discussed. Construction cost and schedule estimates are presented, and the engineering issues that should be reexamined are identified. The latest (1980-1981) information from the MHD technology program is integrated with the elements of a conventional steam power electric generating plant.

  8. Three Dimensional Simulations of Compressible Hall MHD Plasmas

    SciTech Connect

    Shaikh, Dastgeer; Shukla, P. K.

    2008-10-15

    We have developed three dimensional, time dependent, compressible, non-adiabatic, driven and massively parallelized Hall magnetohydrodynamic (MHD) simulations to investigate turbulent spectral cascades in a regime where characteristic lengthscales associated with plasma fluctuations are smaller than ion gyro radii. Such regime is ubiquitously present in solar wind and many other collisionless space plasmas. Particularly in the solar wind, the high time resolution databases identify a spectral break at the end of MHD inertial range spectrum that corresponds to a high frequency regime. In the regime, turbulent cascades cannot be explained by the usual MHD models. With the help of our 3D Hall MHD code, we find that characteristic turbulent interactions in the high frequency regime evolve typically on kinetic Alfven time scales. The turbulent fluctuation associated with kinetic Alfven interactions are compressive and anisotropic and possess equipartition of kinetic and magnetic energies.

  9. A Self-Consistent Numerical Magnetohydrodynamic (MHD) Model of Helmet Streamer and Flux-Rope Interactions: Initiation and Propagation of Coronal Mass Ejections (CMEs)

    NASA Technical Reports Server (NTRS)

    Wu, S. T.; Guo, W. P.

    1997-01-01

    We present results for an investigation of the interaction of a helmet streamer arcade and a helical flux-rope emerging from the sub-photosphere. These results are obtained by using a three-dimensional axisymmetric, time-dependent ideal magnetohydrodynamic (MHD) model. Because of the physical nature of the flux-rope, we investigate two types of flux-ropes; (1) high density flux-rope (i.e. flux-rope without cavity), and (2) low density flux rope (i.e. flux-rope with cavity). When the streamer is disrupted by the flux-rope, it will evolve into a configuration resembling the typical observed loop-like Coronal Mass Ejection (CMES) for both cases. The streamer-flux rope system with cavity is easier to be disrupted and the propagation speed of the CME is faster than the streamer-flux rope system without cavity. Our results demonstrate that magnetic buoyancy force plays an important role in disrupting the streamer.

  10. Featured Image: Tests of an MHD Code

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-09-01

    Creating the codes that are used to numerically model astrophysical systems takes a lot of work and a lot of testing! A new, publicly available moving-mesh magnetohydrodynamics (MHD) code, DISCO, is designed to model 2D and 3D orbital fluid motion, such as that of astrophysical disks. In a recent article, DISCO creator Paul Duffell (University of California, Berkeley) presents the code and the outcomes from a series of standard tests of DISCOs stability, accuracy, and scalability.From left to right and top to bottom, the test outputs shown above are: a cylindrical Kelvin-Helmholtz flow (showing off DISCOs numerical grid in 2D), a passive scalar in a smooth vortex (can DISCO maintain contact discontinuities?), a global look at the cylindrical Kelvin-Helmholtz flow, a Jupiter-mass planet opening a gap in a viscous disk, an MHD flywheel (a test of DISCOs stability), an MHD explosion revealing shock structures, an MHD rotor (a more challenging version of the explosion), a Flock 3D MRI test (can DISCO study linear growth of the magnetorotational instability in disks?), and a nonlinear 3D MRI test.Check out the gif below for a closer look at each of these images, or follow the link to the original article to see even more!CitationPaul C. Duffell 2016 ApJS 226 2. doi:10.3847/0067-0049/226/1/2

  11. Extended magnetohydrodynamics with embedded particle-in-cell simulation of Ganymede's magnetosphere

    NASA Astrophysics Data System (ADS)

    Tóth, Gábor; Jia, Xianzhe; Markidis, Stefano; Peng, Ivy Bo; Chen, Yuxi; Daldorff, Lars K. S.; Tenishev, Valeriy M.; Borovikov, Dmitry; Haiducek, John D.; Gombosi, Tamas I.; Glocer, Alex; Dorelli, John C.

    2016-02-01

    We have recently developed a new modeling capability to embed the implicit particle-in-cell (PIC) model iPIC3D into the Block-Adaptive-Tree-Solarwind-Roe-Upwind-Scheme magnetohydrodynamic (MHD) model. The MHD with embedded PIC domains (MHD-EPIC) algorithm is a two-way coupled kinetic-fluid model. As one of the very first applications of the MHD-EPIC algorithm, we simulate the interaction between Jupiter's magnetospheric plasma and Ganymede's magnetosphere. We compare the MHD-EPIC simulations with pure Hall MHD simulations and compare both model results with Galileo observations to assess the importance of kinetic effects in controlling the configuration and dynamics of Ganymede's magnetosphere. We find that the Hall MHD and MHD-EPIC solutions are qualitatively similar, but there are significant quantitative differences. In particular, the density and pressure inside the magnetosphere show different distributions. For our baseline grid resolution the PIC solution is more dynamic than the Hall MHD simulation and it compares significantly better with the Galileo magnetic measurements than the Hall MHD solution. The power spectra of the observed and simulated magnetic field fluctuations agree extremely well for the MHD-EPIC model. The MHD-EPIC simulation also produced a few flux transfer events (FTEs) that have magnetic signatures very similar to an observed event. The simulation shows that the FTEs often exhibit complex 3-D structures with their orientations changing substantially between the equatorial plane and the Galileo trajectory, which explains the magnetic signatures observed during the magnetopause crossings. The computational cost of the MHD-EPIC simulation was only about 4 times more than that of the Hall MHD simulation.

  12. Lectures on magnetohydrodynamical drives

    NASA Astrophysics Data System (ADS)

    Loigom, Villem

    The paper deals with nonconventional types of electrical machines and drives - magnetohydrodynamical (MHD) machines and drives. In cardinal it is based on the research conducted with participation of the author in Tallinn Technical University at the Institute of Electrical Drives and Power Electronics, where the use of magnetohydrodynamical motors and drives in the metallurgical and casting industries have been studied for a long time. Major research interests include the qualities and applications of the induction MHD-drives for set in the motion (pumping, turning, dosing, mixing, etc.) non-ferrous molten metals like Al, Mg, Sn, Pb, Na, K, and their alloys. The first part of the paper describes induction MHD motors and their electrohydraulical qualities. In the second part energy conversion problems are described. Also, on the basis of the analogy between electromechanical and electrohydraulical phenomenas, static and dynamic qualities of MHD drives with induction MHD machines are discussed.

  13. Broken Ergodicity in Two-Dimensional Homogeneous Magnetohydrodynamic Turbulence

    NASA Technical Reports Server (NTRS)

    Shebalin, John V.

    2010-01-01

    Two-dimensional (2-D) homogeneous magnetohydrodynamic (MHD) turbulence has many of the same qualitative features as three-dimensional (3-D) homogeneous MHD turbulence.The se features include several ideal invariants, along with the phenomenon of broken ergodicity. Broken ergodicity appears when certain modes act like random variables with mean values that are large compared to their standard deviations, indicating a coherent structure or dynamo.Recently, the origin of broken ergodicity in 3-D MHD turbulence that is manifest in the lowest wavenumbers was explained. Here, a detailed description of the origins of broken ergodicity in 2-D MHD turbulence is presented. It will be seen that broken ergodicity in ideal 2-D MHD turbulence can be manifest in the lowest wavenumbers of a finite numerical model for certain initial conditions or in the highest wavenumbers for another set of initial conditions.T he origins of broken ergodicity in ideal 2-D homogeneous MHD turbulence are found through an eigen analysis of the covariance matrices of the modal probability density functions.It will also be shown that when the lowest wavenumber magnetic field becomes quasi-stationary, the higher wavenumber modes can propagate as Alfven waves on these almost static large-scale magnetic structures

  14. Battery-Powered RF Pre-Ionization System for the Caltech Magnetohydrodynamically-Driven Jet Experiment: RF Discharge Properties and MHD-Driven Jet Dynamics

    NASA Astrophysics Data System (ADS)

    Chaplin, Vernon H.

    This thesis describes investigations of two classes of laboratory plasmas with rather different properties: partially ionized low pressure radiofrequency (RF) discharges, and fully ionized high density magnetohydrodynamically (MHD)-driven jets. An RF pre-ionization system was developed to enable neutral gas breakdown at lower pressures and create hotter, faster jets in the Caltech MHD-Driven Jet Experiment. The RF plasma source used a custom pulsed 3 kW 13.56 MHz RF power amplifier that was powered by AA batteries, allowing it to safely float at 4-6 kV with the cathode of the jet experiment. The argon RF discharge equilibrium and transport properties were analyzed, and novel jet dynamics were observed. Although the RF plasma source was conceived as a wave-heated helicon source, scaling measurements and numerical modeling showed that inductive coupling was the dominant energy input mechanism. A one-dimensional time-dependent fluid model was developed to quantitatively explain the expansion of the pre-ionized plasma into the jet experiment chamber. The plasma transitioned from an ionizing phase with depressed neutral emission to a recombining phase with enhanced emission during the course of the experiment, causing fast camera images to be a poor indicator of the density distribution. Under certain conditions, the total visible and infrared brightness and the downstream ion density both increased after the RF power was turned off. The time-dependent emission patterns were used for an indirect measurement of the neutral gas pressure. The low-mass jets formed with the aid of the pre-ionization system were extremely narrow and collimated near the electrodes, with peak density exceeding that of jets created without pre-ionization. The initial neutral gas distribution prior to plasma breakdown was found to be critical in determining the ultimate jet structure. The visible radius of the dense central jet column was several times narrower than the axial current channel

  15. Magnetohydrodynamic fluidic system

    DOEpatents

    Lee, Abraham P.; Bachman, Mark G.

    2004-08-24

    A magnetohydrodynamic fluidic system includes a reagent source containing a reagent fluid and a sample source containing a sample fluid that includes a constituent. A reactor is operatively connected to the supply reagent source and the sample source. MHD pumps utilize a magnetohydrodynamic drive to move the reagent fluid and the sample fluid in a flow such that the reagent fluid and the sample fluid form an interface causing the constituent to be separated from the sample fluid.

  16. AC magnetohydrodynamic microfluidic switch

    SciTech Connect

    Lemoff, A V; Lee, A P

    2000-03-02

    A microfluidic switch has been demonstrated using an AC Magnetohydrodynamic (MHD) pumping mechanism in which the Lorentz force is used to pump an electrolytic solution. By integrating two AC MHD pumps into different arms of a Y-shaped fluidic circuit, flow can be switched between the two arms. This type of switch can be used to produce complex fluidic routing, which may have multiple applications in {micro}TAS.

  17. Ladyzhenskaya-Prodi-Serrin type regularity criteria for the 3D incompressible MHD equations in terms of 3 × 3 mixture matrices

    NASA Astrophysics Data System (ADS)

    Jia, Xuanji; Zhou, Yong

    2015-09-01

    We prove that a weak solution (u, b) to the MHD equations is smooth on (0, T ] if \\text{M}\\in {{L}α}≤ft(0,T;{{L}γ}≤ft({{{R}}3}\\right)\\right) with 2/α +3/γ =2 , 1≤slant α <∞ and 3/2<γ ≤slant ∞ , where \\text{M} is a 3× 3 mixture matrix (see its definition below). As we will explain later, this kind of regularity criteria is more likely to capture the nature of the coupling effects between the fluid velocity and the magnetic field in the evolution of the MHD flows. Moreover, the condition on \\text{M} is scaling invariant, i.e. it is of Ladyzhenskaya-Prodi-Serrin type.

  18. Numerical MHD codes for modeling astrophysical flows

    NASA Astrophysics Data System (ADS)

    Koldoba, A. V.; Ustyugova, G. V.; Lii, P. S.; Comins, M. L.; Dyda, S.; Romanova, M. M.; Lovelace, R. V. E.

    2016-05-01

    We describe a Godunov-type magnetohydrodynamic (MHD) code based on the Miyoshi and Kusano (2005) solver which can be used to solve various astrophysical hydrodynamic and MHD problems. The energy equation is in the form of entropy conservation. The code has been implemented on several different coordinate systems: 2.5D axisymmetric cylindrical coordinates, 2D Cartesian coordinates, 2D plane polar coordinates, and fully 3D cylindrical coordinates. Viscosity and diffusivity are implemented in the code to control the accretion rate in the disk and the rate of penetration of the disk matter through the magnetic field lines. The code has been utilized for the numerical investigations of a number of different astrophysical problems, several examples of which are shown.

  19. A Fast MHD Code for Gravitationally Stratified Media using Graphical Processing Units: SMAUG

    NASA Astrophysics Data System (ADS)

    Griffiths, M. K.; Fedun, V.; Erdélyi, R.

    2015-03-01

    Parallelization techniques have been exploited most successfully by the gaming/graphics industry with the adoption of graphical processing units (GPUs), possessing hundreds of processor cores. The opportunity has been recognized by the computational sciences and engineering communities, who have recently harnessed successfully the numerical performance of GPUs. For example, parallel magnetohydrodynamic (MHD) algorithms are important for numerical modelling of highly inhomogeneous solar, astrophysical and geophysical plasmas. Here, we describe the implementation of SMAUG, the Sheffield Magnetohydrodynamics Algorithm Using GPUs. SMAUG is a 1-3D MHD code capable of modelling magnetized and gravitationally stratified plasma. The objective of this paper is to present the numerical methods and techniques used for porting the code to this novel and highly parallel compute architecture. The methods employed are justified by the performance benchmarks and validation results demonstrating that the code successfully simulates the physics for a range of test scenarios including a full 3D realistic model of wave propagation in the solar atmosphere.

  20. VisAn MHD: a toolbox in Matlab for MHD computer model data visualisation and analysis

    NASA Astrophysics Data System (ADS)

    Daum, P.

    2007-03-01

    Among the many challenges facing modern space physics today is the need for a visualisation and analysis package which can examine the results from the diversity of numerical and empirical computer models as well as observational data. Magnetohydrodynamic (MHD) models represent the latest numerical models of the complex Earth's space environment and have the unique ability to span the enormous distances present in the magnetosphere from several hundred kilometres to several thousand kilometres above the Earth surface. This feature enables scientist to study complex structures of processes where otherwise only point measurements from satellites or ground-based instruments are available. Only by combining these observational data and the MHD simulations it is possible to enlarge the scope of the point-to-point observations and to fill the gaps left by measurements in order to get a full 3-D representation of the processes in our geospace environment. In this paper we introduce the VisAn MHD toolbox for Matlab as a tool for the visualisation and analysis of observational data and MHD simulations. We have created an easy to use tool which is capable of highly sophisticated visualisations and data analysis of the results from a diverse set of MHD models in combination with in situ measurements from satellites and ground-based instruments. The toolbox is being released under an open-source licensing agreement to facilitate and encourage community use and contribution.

  1. Extended Magnetohydrodynamics with Embedded Particle-in-Cell (XMHD-EPIC) Simulations of Magnetospheric Reconnection

    NASA Astrophysics Data System (ADS)

    Toth, Gabor; Gombosi, Tamas; Jia, Xianzhe; Welling, Daniel; Chen, Yuxi; Haiducek, John; Jordanova, Vania; Peng, Ivy Bo; Markidis, Stefano; Lapenta, Giovanni

    2016-04-01

    We have recently developed a new modeling capability to embed the implicit Particle-in-Cell (PIC) model iPIC3D into the BATS-R-US extended magnetohydrodynamic model. The PIC domain can cover the regions where kinetic effects are most important, such as reconnection sites. The BATS-R-US code with its block-adaptive grid can efficiently handle the rest of the computational domain where the MHD or Hall MHD description is sufficient. The current implementation of the MHD-EPIC model allows two-way coupled simulations in two and three dimensions with multiple embedded PIC regions. The MHD and PIC grids can have different grid resolutions and grid structures. The MHD variables and the moments of the PIC distribution functions are interpolated and message passed in an efficient manner through the Space Weather Modeling Framework (SWMF). Both BATS-R-US and iPIC3D are massively parallel codes fully integrated into, run by and coupled through the SWMF. We have successfully applied the MHD-EPIC code to model Ganymede's and Mercury's magnetospheres. We compared our results with Galileo and MESSENGER magnetic observations, respectively, and found good overall agreement. We will report our progress on modeling the Earth magnetosphere with MHD-EPIC with the goal of providing direct comparison with and global context for the MMS observations.

  2. Development of three-dimensional hydrodynamical and MHD codes using Adaptive Mesh Refinement scheme with TVD

    NASA Astrophysics Data System (ADS)

    den, M.; Yamashita, K.; Ogawa, T.

    A three-dimensional (3D) hydrodynamical (HD) and magneto-hydrodynamical (MHD) simulation codes using an adaptive mesh refinement (AMR) scheme are developed. This method places fine grids over areas of interest such as shock waves in order to obtain high resolution and places uniform grids with lower resolution in other area. Thus AMR scheme can provide a combination of high solution accuracy and computational robustness. We demonstrate numerical results for a simplified model of a shock propagation, which strongly indicate that the AMR techniques have the ability to resolve disturbances in an interplanetary space. We also present simulation results for MHD code.

  3. Small-scale behavior of Hall magnetohydrodynamic turbulence.

    PubMed

    Stawarz, Julia E; Pouquet, Annick

    2015-12-01

    Decaying Hall magnetohydrodynamic (HMHD) turbulence is studied using three-dimensional (3D) direct numerical simulations with grids up to 768(3) points and two different types of initial conditions. Results are compared to analogous magnetohydrodynamic (MHD) runs and both Laplacian and Laplacian-squared dissipative operators are examined. At scales below the ion inertial length, the ratio of magnetic to kinetic energy as a function of wave number transitions to a magnetically dominated state. The transition in behavior is associated with the advection term in the momentum equation becoming subdominant to dissipation. Examination of autocorrelation functions reveals that, while current and vorticity structures are similarly sized in MHD, HMHD current structures are narrower and vorticity structures are wider. The electric field autocorrelation function is significantly narrower in HMHD than in MHD and is similar to the HMHD current autocorrelation function at small separations. HMHD current structures are found to be significantly more intense than in MHD and appear to have an enhanced association with strong alignment between the current and magnetic field, which may be important in collisionless plasmas where field-aligned currents can be unstable. When hyperdiffusivity is used, a longer region consistent with a k(-7/3) scaling is present for right-polarized fluctuations when compared to Laplacian dissipation runs.

  4. Small-scale behavior of Hall magnetohydrodynamic turbulence.

    PubMed

    Stawarz, Julia E; Pouquet, Annick

    2015-12-01

    Decaying Hall magnetohydrodynamic (HMHD) turbulence is studied using three-dimensional (3D) direct numerical simulations with grids up to 768(3) points and two different types of initial conditions. Results are compared to analogous magnetohydrodynamic (MHD) runs and both Laplacian and Laplacian-squared dissipative operators are examined. At scales below the ion inertial length, the ratio of magnetic to kinetic energy as a function of wave number transitions to a magnetically dominated state. The transition in behavior is associated with the advection term in the momentum equation becoming subdominant to dissipation. Examination of autocorrelation functions reveals that, while current and vorticity structures are similarly sized in MHD, HMHD current structures are narrower and vorticity structures are wider. The electric field autocorrelation function is significantly narrower in HMHD than in MHD and is similar to the HMHD current autocorrelation function at small separations. HMHD current structures are found to be significantly more intense than in MHD and appear to have an enhanced association with strong alignment between the current and magnetic field, which may be important in collisionless plasmas where field-aligned currents can be unstable. When hyperdiffusivity is used, a longer region consistent with a k(-7/3) scaling is present for right-polarized fluctuations when compared to Laplacian dissipation runs. PMID:26764833

  5. Landau resonant modification of multiple kink mode contributions to 3D tokamak equilibria

    DOE PAGES

    King, J. D.; Strait, E. J.; Ferraro, N. M.; Hanson, J. M.; Haskey, S. R.; Lanctot, M. J.; Liu, Y. Q.; Logan, N.; Paz-Soldan, C.; Shiraki, D.; et al

    2015-12-17

    Detailed measurements of the plasma's response to applied magnetic perturbations provide experimental evidence that the form of three-dimensional (3D) tokamak equilibria, with toroidal mode number n = 1, is determined by multiple stable kink modes at high-pressure. For pressures greater than the ideal magnetohydrodynamic (MHD) stability limit, as calculated without a stabilizing wall, the 3D structure transitions in a way that is qualitatively predicted by an extended MHD model that includes kinetic wave-particle interactions. These changes in poloidal mode structure are correlated with the proximity of rotation profiles to thermal ion bounce and the precession drift frequencies suggesting that thesemore » kinetic resonances are modifying the relative amplitudes of the stable modes. These results imply that each kink may eventually be independently controlled.« less

  6. Landau resonant modification of multiple kink mode contributions to 3D tokamak equilibria

    SciTech Connect

    King, J. D.; Strait, E. J.; Ferraro, N. M.; Hanson, J. M.; Haskey, S. R.; Lanctot, M. J.; Liu, Y. Q.; Logan, N.; Paz-Soldan, C.; Shiraki, D.; Turnbull, A. D.

    2015-12-17

    Detailed measurements of the plasma's response to applied magnetic perturbations provide experimental evidence that the form of three-dimensional (3D) tokamak equilibria, with toroidal mode number n = 1, is determined by multiple stable kink modes at high-pressure. For pressures greater than the ideal magnetohydrodynamic (MHD) stability limit, as calculated without a stabilizing wall, the 3D structure transitions in a way that is qualitatively predicted by an extended MHD model that includes kinetic wave-particle interactions. These changes in poloidal mode structure are correlated with the proximity of rotation profiles to thermal ion bounce and the precession drift frequencies suggesting that these kinetic resonances are modifying the relative amplitudes of the stable modes. These results imply that each kink may eventually be independently controlled.

  7. Free-boundary ideal MHD stability of W7-X divertor equilibria

    NASA Astrophysics Data System (ADS)

    Nührenberg, C.

    2016-07-01

    Plasma configurations describing the stellarator experiment Wendelstein 7-X (W7-X) are computationally established taking into account the geometry of the test-divertor unit and the high-heat-flux divertor which will be installed in the vacuum chamber of the device (Gasparotto et al 2014 Fusion Eng. Des. 89 2121). These plasma equilibria are computationally studied for their global ideal magnetohydrodynamic (MHD) stability properties. Results from the ideal MHD stability code cas3d (Nührenberg 1996 Phys. Plasmas 3 2401), stability limits, spatial structures and growth rates are presented for free-boundary perturbations. The work focusses on the exploration of MHD unstable regions of the W7-X configuration space, thereby providing information for future experiments in W7-X aiming at an assessment of the role of ideal MHD in stellarator confinement.

  8. Magnetohydrodynamic electrode

    DOEpatents

    Marchant, David D.; Killpatrick, Don H.

    1978-01-01

    An electrode capable of withstanding high temperatures and suitable for use as a current collector in the channel of a magnetohydrodynamic (MHD) generator consists of a sintered powdered metal base portion, the upper surface of the base being coated with a first layer of nickel aluminide, an intermediate layer of a mixture of nickel aluminide - refractory ceramic on the first layer and a third or outer layer of a refractory ceramic material on the intermediate layer. The sintered powdered metal base resists spalling by the ceramic coatings and permits greater electrode compliance to thermal shock. The density of the powdered metal base can be varied to allow optimization of the thermal conductivity of the electrode and prevent excess heat loss from the channel.

  9. Ideal and non-ideal MHD regimes of wire array implosion obtained in 3D hybrid simulations and observed during experiments at NTF.

    SciTech Connect

    Sotnikov, Vladimir Isaakovich; Fiala, V.; Oliver, Bryan Velten; Ivanov, Vladimir V.; LePell, Paul David; Fedin, Dmitry; Mehlhorn, Thomas Alan; Kantsyrev, Victor Leonidovich; Coverdale, Christine Anne; Travnicek, P.; Hellinger, P.; Deeney, Christopher; Jones, Brent Manley; Safronova, Alla S.; Leboeuf, J. N.; Cowan, Thomas E.

    2004-11-01

    Recent 3D hybrid simulation of a plasma current-carrying column revealed two regimes of sausage and kink instability development. In the first regime, with small Hall parameter, development of instabilities leads to appearance of large-scale axial perturbations and eventually to the bending of the plasma column. In the second regime, with five times larger Hall parameter, small-scale perturbations dominated and no bending of the plasma column was observed. Simulation results are compared to recent experimental data, including laser probing, x-ray spectroscopy and time-gated x-ray imaging during wire array implosions at NTF.

  10. A computational magnetohydrodynamic model of a gasdynamic fusion space propulsion system

    NASA Astrophysics Data System (ADS)

    Ohlandt, Chad J. R.

    This work advances the gasdynamic mirror (GDM) fusion space propulsion system concept by testing the potential of an advanced aneutronic fusion fuel combination of proton-11boron and evaluating GDMs operating at less than breakeven being driven with nuclear electric reactors. Finding neither option to be a panacea, the author moves forward in developing an ideal 3-D magnetohydrodynamic (MHD) computational model for simulating concept GDMs. The challenges identified and remediated include Alfven wave-speeds a few percent the speed of light with characteristic lengths on the order of a centimeter, the extreme aspect ratio of GDM systems, massive background magnetic fields, and traveling waves along the length of the GDM. Due to the remaining physical challenges of modeling the GDM system, including a slow systemic relaxation time and localized radiation losses, the computational requirements of the full 3-D MHD model remains too computationally demanding, which suggests a future approach involving a hybrid of 1-D and 3-D models.

  11. Magnetohydrodynamic projects at the CDIF

    SciTech Connect

    Not Available

    1992-01-01

    The Component Development and Integration Facility (CDIF) is a major U.S. Department of Energy magnetohydrodynamics (MHD) test facility in Butte, Montana. The CDIF is operated by MSE, Inc. Within the national MHD program, MSE personnel are responsible for performing integration testing of vendor-supplied MHD power train components at the CDIF to support the goal of commercialization. During the second quarter of FY92, a second external water leak on the iron-core magnet was repaired, and MHD testing was completed on February 11; this was the final testing of the workhorse hardware. Workhorse hardware was removed, and installation of the proof-of-concept (POC) combustor began.

  12. Magnetohydrodynamic projects at the CDIF

    SciTech Connect

    Not Available

    1991-01-01

    The Component Development and Integration Facility (CDIF) is a major US Department of Energy magnetohydrodynamic (MHD) test facility in Butte, Montana. The CDIF is operated by MSE, Inc. Within the national MHD program, MSE personnel are responsible for performing integration testing of vendor-supplied MHD power train components at the CDIF to support the goal of commercialization. During the first quarter of FY92, MHD testing was initiated. Off-line and on-line calibration tests were completed for the Endress+Hauser flowmeter, and thermal, conductivity, and electrical testing was initiated.

  13. Magnetospheric Simulations With the Three-Dimensional Magnetohydrodynamics With Embedded Particle-in-Cell Model

    NASA Astrophysics Data System (ADS)

    Toth, G.; Jia, X.; Chen, Y.; Markidis, S.; Peng, B.; Daldorff, L. K. S.; Tenishev, V.; Borovikov, D.; Haiducek, J. D.; Gombosi, T. I.; Glocer, A.; Dorelli, J.; Lapenta, G.

    2015-12-01

    We have recently developed a new modeling capability to embed the implicit Particle-in-Cell (PIC) model iPIC3D into the BATS-R-US magnetohydrodynamic model. The PIC domain can cover the regions where kinetic effects are most important, such as reconnection sites. The BATS-R-US code, on the other hand, can efficiently handle the rest of the computational domain where the MHD or Hall MHD description is sufficient with its block-adaptive grid. The current implementation of the MHD-EPIC model allows two-way coupled simulations in two and three dimensions with multiple embedded PIC regions. The MHD and PIC grids can have different grid resolutions. The MHD variables and the moments of the PIC distribution functions are interpolated and message passed in an efficient manner through the Space Weather Modeling Framework (SWMF). Both BATS-R-US and iPIC3D are massively parallel codes fully integrated into, run by and coupled through the SWMF. We have successfully applied the MHD-EPIC code to model Ganymede's magnetosphere. Using four PIC regions we have in effect performed a fully kinetic simulation of the moon's mini-magnetosphere with a grid resolution that is about 5 times finer than the ion inertial length. The Hall MHD model provides proper boundary conditions for the four PIC regions and connects them with each other and with the inner and outer outer boundary conditions of the much larger MHD domain. We compare our results with Galileo magnetic observations and find good overall agreement with both Hall MHD and MHD-EPIC simulations. The power spectrum for the small scale fluctuations, however, agrees with the data much better for the MHD-EPIC simulation than for Hall MHD. In the MHD-EPIC simulation, unlike in the pure Hall MHD results, we also find signatures of flux transfer events (FTEs) that agree very well with the observed FTE signatures both in terms of shape and amplitudes. We will also highlight our ongoing efforts to model the magnetospheres of Mercury and

  14. Toward understanding the Sun-to-Earth evolution of the 2012 July 12-16 Coronal Mass Ejection Using Three-dimensional MHD Simulation

    NASA Astrophysics Data System (ADS)

    Shen, F.; Feng, X.; Shen, C.

    2013-12-01

    Dynamic process of coronal mass ejections (CMEs) in the heliosphere is the key information for us to evaluate the CMEs' geo-effectiveness and to improve the accurate prediction of CME induced Shock Arrival Time (SAT) at Earth's environment. We present a three-dimensional (3D) magnetohydrodynamic (MHD) simulation of the evolution of the CME in a realistic ambient solar wind for the July 12-16, 2012 event by using the 3D COIN-TVD MHD code. The influence of the background solar wind speed to the SAT is analyzed. The influence of the initial position and polarity of the plasma blob to IMF Bz is also studied. In the validation study of this CME event (July 12-16, 2012), we find that this 3D COIN-TVD MHD model, with the magnetized plasma blob as CME model, provide a relatively satisfactory comparison with the ACE spacecraft observations at the L1 point.

  15. Magnetohydrodynamics (MHD) Engineering Test Facility (ETF) 200 MWe power plant. Conceptual Design Engineering Report (CDER). Volume 2: Engineering. Volume 3: Costs and schedules

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Engineering design details for the principal systems, system operating modes, site facilities, and structures of an engineering test facility (ETF) of a 200 MWE power plant are presented. The ETF resembles a coal-fired steam power plant in many ways. It is analogous to a conventional plant which has had the coal combustor replaced with the MHD power train. Most of the ETF components are conventional. They can, however, be sized or configured differently or perform additional functions from those in a conventional coal power plant. The boiler not only generates steam, but also performs the functions of heating the MHD oxidant, recovering seed, and controlling emissions.

  16. Dynamo action in dissipative, forced, rotating MHD turbulence

    NASA Astrophysics Data System (ADS)

    Shebalin, John V.

    2016-06-01

    Magnetohydrodynamic (MHD) turbulence is an inherent feature of large-scale, energetic astrophysical and geophysical magnetofluids. In general, these are rotating and are energized through buoyancy and shear, while viscosity and resistivity provide a means of dissipation of kinetic and magnetic energy. Studies of unforced, rotating, ideal (i.e., non-dissipative) MHD turbulence have produced interesting results, but it is important to determine how these results are affected by dissipation and forcing. Here, we extend our previous work and examine dissipative, forced, and rotating MHD turbulence. Incompressibility is assumed, and finite Fourier series represent turbulent velocity and magnetic field on a 643 grid. Forcing occurs at an intermediate wave number by a method that keeps total energy relatively constant and allows for injection of kinetic and magnetic helicity. We find that 3-D energy spectra are asymmetric when forcing is present. We also find that dynamo action occurs when forcing has either kinetic or magnetic helicity, with magnetic helicity injection being more important. In forced, dissipative MHD turbulence, the dynamo manifests itself as a large-scale coherent structure that is similar to that seen in the ideal case. These results imply that MHD turbulence, per se, may play a fundamental role in the creation and maintenance of large-scale (i.e., dipolar) stellar and planetary magnetic fields.

  17. Solar wind interaction with Mars' upper atmosphere: Results from 3-D studies using one-way coupling between the Multi-fluid MHD, the M-GITM and the AMPS models

    NASA Astrophysics Data System (ADS)

    Dong, C.; Bougher, S. W.; Ma, Y.; Toth, G.; Lee, Y.; Nagy, A. F.; Tenishev, V.; Pawlowski, D. J.; Meng, X.; Combi, M. R.

    2013-12-01

    The study of the solar wind interaction with Mars upper atmosphere/ionosphere has triggered a great of interest in recent years. Among the large number of topics in this research area, the investigation of ion escape fluxes has become increasingly important due to its potential impact on the long-term evolution of Mars atmosphere (e.g., loss of water) over its history. In the present work, we adopt the 3-D Mars cold neutral atmosphere profiles (0~300 km) from the newly developed and validated Mars Global Ionosphere Thermosphere Model (M-GITM) and the 3-D hot oxygen profiles (100km~5RM) from the exosphere Monte Carlo model Adaptive Mesh Particle Simulator (AMPS). We apply these 3-D model outputs fields into the 3-D BATS-R-US Mars multi-fluid MHD model (100km~20RM) that can better simulate the interplay between Mars upper atmosphere and solar wind by considering the dynamics of individual ion species. The multi-fluid model solves separate continuity, momentum and energy equations for each ion species (H+, O+, O2+, CO2+). The M-GITM model together with the AMPS exosphere model take into account the effects of solar cycle and seasonal variations on both cold and hot neutral atmospheres, allowing us to investigate the corresponding effects on the Mars upper atmosphere ion escape by using a one-way coupling approach, i.e., both the M-GITM and AMPS model outputs are used as the inputs for the multi-fluid model and M-GITM is used as input into the AMPS exosphere model. The calculations are carried out for selected cases with different nominal solar wind, solar cycle and crustal field orientation conditions. This work has the potential to provide predictions of ion escape rates for comparison to future data to be returned by the MAVEN primary mission (2014-2016) and thereby improve our understanding of present day escape processes. Acknowledgments: The work presented here was supported by NASA grants NNH10CC04C, NNX09AL26G, NSF grant ATM-0535811.

  18. Two-dimensional behavior of three-dimensional magnetohydrodynamic flow with a strong guiding field.

    PubMed

    Alexakis, Alexandros

    2011-11-01

    The magnetohydrodynamic (MHD) equations in the presence of a guiding magnetic field are investigated by means of direct numerical simulations. The basis of the investigation consists of nine runs forced at the small scales. The results demonstrate that for a large enough uniform magnetic field the large scale flow behaves as a two-dimensional (2D) (non-MHD) fluid exhibiting an inverse cascade of energy in the direction perpendicular to the magnetic field, while the small scales behave like a three-dimensional (3D) MHD fluid cascading the energy forwards. The amplitude of the inverse cascade is sensitive to the magnetic field amplitude, the domain size, the forcing mechanism, and the forcing scale. All these dependences are demonstrated by the varying parameters of the simulations. Furthermore, in the case that the system is forced anisotropically in the small parallel scales an inverse cascade in the parallel direction is observed that is feeding the 2D modes k(//)=0.

  19. Particle Acceleration at Reconnecting 3D Null Points

    NASA Astrophysics Data System (ADS)

    Stanier, A.; Browning, P.; Gordovskyy, M.; Dalla, S.

    2012-12-01

    Hard X-ray observations from the RHESSI spacecraft indicate that a significant fraction of solar flare energy release is in non-thermal energetic particles. A plausible acceleration mechanism for these are the strong electric fields associated with reconnection, a process that can be particularly efficient when particles become unmagnetised near to null points. This mechanism has been well studied in 2D, at X-points within reconnecting current sheets; however, 3D reconnection models show significant qualitative differences and it is not known whether these new models are efficient for particle acceleration. We place test particles in analytic model fields (eg. Craig and Fabling 1996) and numerical solutions to the the resistive magnetohydrodynamic (MHD) equations near reconnecting 3D nulls. We compare the behaviour of these test particles with previous results for test particle acceleration in ideal MHD models (Dalla and Browning 2005). We find that the fan model is very efficient due to an increasing "guide field" that stabilises particles against ejection from the current sheet. However, the spine model, which was the most promising in the ideal case, gives weak acceleration as the reconnection electric field is localised to a narrow cylinder about the spine axis.

  20. Simulation of bootstrap current in 2D and 3D ideal magnetic fields in tokamaks

    NASA Astrophysics Data System (ADS)

    Raghunathan, M.; Graves, J. P.; Cooper, W. A.; Pedro, M.; Sauter, O.

    2016-09-01

    We aim to simulate the bootstrap current for a MAST-like spherical tokamak using two approaches for magnetic equilibria including externally caused 3D effects such as resonant magnetic perturbations (RMPs), the effect of toroidal ripple, and intrinsic 3D effects such as non-resonant internal kink modes. The first approach relies on known neoclassical coefficients in ideal MHD equilibria, using the Sauter (Sauter et al 1999 Phys. Plasmas 6 2834) expression valid for all collisionalities in axisymmetry, and the second approach being the quasi-analytic Shaing–Callen (Shaing and Callen 1983 Phys. Fluids 26 3315) model in the collisionless regime for 3D. Using the ideal free-boundary magnetohydrodynamic code VMEC, we compute the flux-surface averaged bootstrap current density, with the Sauter and Shaing–Callen expressions for 2D and 3D ideal MHD equilibria including an edge pressure barrier with the application of resonant magnetic perturbations, and equilibria possessing a saturated non-resonant 1/1 internal kink mode with a weak internal pressure barrier. We compare the applicability of the self-consistent iterative model on the 3D applications and discuss the limitations and advantages of each bootstrap current model for each type of equilibrium.

  1. Simulation of bootstrap current in 2D and 3D ideal magnetic fields in tokamaks

    NASA Astrophysics Data System (ADS)

    Raghunathan, M.; Graves, J. P.; Cooper, W. A.; Pedro, M.; Sauter, O.

    2016-09-01

    We aim to simulate the bootstrap current for a MAST-like spherical tokamak using two approaches for magnetic equilibria including externally caused 3D effects such as resonant magnetic perturbations (RMPs), the effect of toroidal ripple, and intrinsic 3D effects such as non-resonant internal kink modes. The first approach relies on known neoclassical coefficients in ideal MHD equilibria, using the Sauter (Sauter et al 1999 Phys. Plasmas 6 2834) expression valid for all collisionalities in axisymmetry, and the second approach being the quasi-analytic Shaing-Callen (Shaing and Callen 1983 Phys. Fluids 26 3315) model in the collisionless regime for 3D. Using the ideal free-boundary magnetohydrodynamic code VMEC, we compute the flux-surface averaged bootstrap current density, with the Sauter and Shaing-Callen expressions for 2D and 3D ideal MHD equilibria including an edge pressure barrier with the application of resonant magnetic perturbations, and equilibria possessing a saturated non-resonant 1/1 internal kink mode with a weak internal pressure barrier. We compare the applicability of the self-consistent iterative model on the 3D applications and discuss the limitations and advantages of each bootstrap current model for each type of equilibrium.

  2. Magnetic helicity conservation and inverse energy cascade in electron magnetohydrodynamic wave packets.

    PubMed

    Cho, Jungyeon

    2011-05-13

    Electron magnetohydrodynamics (EMHD) provides a fluidlike description of small-scale magnetized plasmas. An EMHD wave propagates along magnetic field lines. The direction of propagation can be either parallel or antiparallel to the magnetic field lines. We numerically study propagation of three-dimensional (3D) EMHD wave packets moving in one direction. We obtain two major results. (1) Unlike its magnetohydrodynamic (MHD) counterpart, an EMHD wave packet is dispersive. Because of this, EMHD wave packets traveling in one direction create opposite-traveling wave packets via self-interaction and cascade energy to smaller scales. (2) EMHD wave packets traveling in one direction clearly exhibit inverse energy cascade. We find that the latter is due to conservation of magnetic helicity. We compare inverse energy cascade in 3D EMHD turbulence and two-dimensional (2D) hydrodynamic turbulence.

  3. The Influence of Pickup Protons, from Interstellar Neutral Hydrogen, on the Propagation of Interplanetary Shocks from the Halloween 2003 Solar Events to ACE and Ulysses: A 3-D MHD Modeling Study

    NASA Technical Reports Server (NTRS)

    Detman, T. R.; Intriligator, D. S.; Dryer, M.; Sun, W.; Deehr, C. S.; Intriligator, J.

    2012-01-01

    We describe our 3-D, time ]dependent, MHD solar wind model that we recently modified to include the physics of pickup protons from interstellar neutral hydrogen. The model has a time-dependent lower boundary condition, at 0.1 AU, that is driven by source surface map files through an empirical interface module. We describe the empirical interface and its parameter tuning to maximize model agreement with background (quiet) solar wind observations at ACE. We then give results of a simulation study of the famous Halloween 2003 series of solar events. We began with shock inputs from the Fearless Forecast real ]time shock arrival prediction study, and then we iteratively adjusted input shock speeds to obtain agreement between observed and simulated shock arrival times at ACE. We then extended the model grid to 5.5 AU and compared those simulation results with Ulysses observations at 5.2 AU. Next we undertook the more difficult tuning of shock speeds and locations to get matching shock arrival times at both ACE and Ulysses. Then we ran this last case again with neutral hydrogen density set to zero, to identify the effect of pickup ions. We show that the speed of interplanetary shocks propagating from the Sun to Ulysses is reduced by the effects of pickup protons. We plan to make further improvements to the model as we continue our benchmarking process to 10 AU, comparing our results with Cassini observations, and eventually on to 100 AU, comparing our results with Voyager 1 and 2 observations.

  4. M3D-K simulations of sawteeth and energetic particle transport in tokamak plasmas

    SciTech Connect

    Shen, Wei; Sheng, Zheng-Mao; Fu, G. Y.; Breslau, J. A.; Wang, Feng

    2014-09-15

    Nonlinear simulations of sawteeth and related energetic particle transport are carried out using the kinetic/magnetohydrodynamic (MHD) hybrid code M3D-K. MHD simulations show repeated sawtooth cycles for a model tokamak equilibrium. Furthermore, test particle simulations are carried out to study the energetic particle transport due to a sawtooth crash. The results show that energetic particles are redistributed radially in the plasma core, depending on pitch angle and energy. For trapped particles, the redistribution occurs for particle energy below a critical value in agreement with existing theories. For co-passing particles, the redistribution is strong with little dependence on particle energy. In contrast, the redistribution level of counter-passing particles decreases with increasing particle energy.

  5. Energy Cascades in MHD

    NASA Astrophysics Data System (ADS)

    Alexakis, A.

    2009-04-01

    Most astrophysical and planetary systems e.g., solar convection and stellar winds, are in a turbulent state and coupled to magnetic fields. Understanding and quantifying the statistical properties of magneto-hydro-dynamic (MHD) turbulence is crucial to explain the involved physical processes. Although the phenomenological theory of hydro-dynamic (HD) turbulence has been verified up to small corrections, a similar statement cannot be made for MHD turbulence. Since the phenomenological description of Hydrodynamic turbulence by Kolmogorov in 1941 there have been many attempts to derive a similar description for turbulence in conducting fluids (i.e Magneto-Hydrodynamic turbulence). However such a description is going to be based inevitably on strong assumptions (typically borrowed from hydrodynamics) that do not however necessarily apply to the MHD case. In this talk I will discuss some of the properties and differences of the energy and helicity cascades in turbulent MHD and HD flows. The investigation is going to be based on the analysis of direct numerical simulations. The cascades in MHD turbulence appear to be a more non-local process (in scale space) than in Hydrodynamics. Some implications of these results to turbulent modeling will be discussed

  6. Newtonian CAFE: a new ideal MHD code to study the solar atmosphere

    NASA Astrophysics Data System (ADS)

    González, J. J.; Guzmán, F.

    2015-12-01

    In this work we present a new independent code designed to solve the equations of classical ideal magnetohydrodynamics (MHD) in three dimensions, submitted to a constant gravitational field. The purpose of the code centers on the analysis of solar phenomena within the photosphere-corona region. In special the code is capable to simulate the propagation of impulsively generated linear and non-linear MHD waves in the non-isothermal solar atmosphere. We present 1D and 2D standard tests to demonstrate the quality of the numerical results obtained with our code. As 3D tests we present the propagation of MHD-gravity waves and vortices in the solar atmosphere. The code is based on high-resolution shock-capturing methods, uses the HLLE flux formula combined with Minmod, MC and WENO5 reconstructors. The divergence free magnetic field constraint is controlled using the Flux Constrained Transport method.

  7. A solution accurate, efficient and stable unsplit staggered mesh scheme for three dimensional magnetohydrodynamics

    NASA Astrophysics Data System (ADS)

    Lee, Dongwook

    2013-06-01

    In this paper, we extend the unsplit staggered mesh scheme (USM) for 2D magnetohydrodynamics (MHD) [D. Lee, A.E. Deane, An unsplit staggered mesh scheme for multidimensional magnetohydrodynamics, J. Comput. Phys. 228 (2009) 952-975] to a full 3D MHD scheme. The scheme is a finite-volume Godunov method consisting of a constrained transport (CT) method and an efficient and accurate single-step, directionally unsplit multidimensional data reconstruction-evolution algorithm, which extends Colella's original 2D corner transport upwind (CTU) method [P. Colella, Multidimensional upwind methods for hyperbolic conservation laws, J. Comput. Phys. 87 (1990) 446-466]. We present two types of data reconstruction-evolution algorithms for 3D: (1) a reduced CTU scheme and (2) a full CTU scheme. The reduced 3D CTU scheme is a variant of a simple 3D extension of Collela's 2D CTU method and is considered as a direct extension from the 2D USM scheme. The full 3D CTU scheme is our primary 3D solver which includes all multidimensional cross-derivative terms for stability. The latter method is logically analogous to the 3D unsplit CTU method by Saltzman [J. Saltzman, An unsplit 3D upwind method for hyperbolic conservation laws, J. Comput. Phys. 115 (1994) 153-168]. The major novelties in our algorithms are twofold. First, we extend the reduced CTU scheme to the full CTU scheme which is able to run with CFL numbers close to unity. Both methods utilize the transverse update technique developed in the 2D USM algorithm to account for transverse fluxes without solving intermediate Riemann problems, which in turn gives cost-effective 3D methods by reducing the total number of Riemann solves. The proposed algorithms are simple and efficient especially when including multidimensional MHD terms that maintain in-plane magnetic field dynamics. Second, we introduce a new CT scheme that makes use of proper upwind information in taking averages of electric fields. Our 3D USM schemes can be easily

  8. Energy Conversion Alternatives Study (ECAS), Westinghouse phase 1. Volume 9: Closed-cycle MHD. [energy conversion efficiency of electric power plants using magnetohydrodynamics

    NASA Technical Reports Server (NTRS)

    Tsu, T. C.

    1976-01-01

    A closed-cycle MHD system for an electric power plant was studied. It consists of 3 interlocking loops, an external heating loop, a closed-cycle cesium seeded argon nonequilibrium ionization MHD loop, and a steam bottomer. A MHD duct maximum temperature of 2366 K (3800 F), a pressure of 0.939 MPa (9.27 atm) and a Mach number of 0.9 are found to give a topping cycle efficiency of 59.3%; however when combined with an integrated gasifier and optimistic steam bottomer the coal to bus bar efficiency drops to 45.5%. A 1978 K (3100 F) cycle has an efficiency of 55.1% and a power plant efficiency of 42.2%. The high cost of the external heating loop components results in a cost of electricity of 21.41 mills/MJ (77.07 mills/kWh) for the high temperature system and 19.0 mills/MJ (68.5 mills/kWh) for the lower temperature system. It is, therefore, thought that this cycle may be more applicable to internally heated systems such as some futuristic high temperature gas cooled reactor.

  9. Magneto-Hydrodynamics Based Microfluidics

    PubMed Central

    Qian, Shizhi; Bau, Haim H.

    2009-01-01

    In microfluidic devices, it is necessary to propel samples and reagents from one part of the device to another, stir fluids, and detect the presence of chemical and biological targets. Given the small size of these devices, the above tasks are far from trivial. Magnetohydrodynamics (MHD) offers an elegant means to control fluid flow in microdevices without a need for mechanical components. In this paper, we review the theory of MHD for low conductivity fluids and describe various applications of MHD such as fluid pumping, flow control in fluidic networks, fluid stirring and mixing, circular liquid chromatography, thermal reactors, and microcoolers. PMID:20046890

  10. Field topologies in ideal and near-ideal magnetohydrodynamics and vortex dynamics

    NASA Astrophysics Data System (ADS)

    Low, B. C.

    2015-01-01

    Magnetic field topology frozen in ideal magnetohydrodynamics (MHD) and its breakage in near-ideal MHD are reviewed in two parts, clarifying and expanding basic concepts. The first part gives a physically complete description of the frozen field topology derived from magnetic flux conservation as the fundamental property, treating four conceptually related topics: Eulerian and Lagrangian descriptions of three dimensional (3D) MHD, Chandrasekhar-Kendall and Euler-potential field representations, magnetic helicity, and inviscid vortex dynamics as a fluid system in physical contrast to ideal MHD. A corollary of these developments clarifies the challenge of achieving a high degree of the frozen-in condition in numerical MHD. The second part treats field-topology breakage centered around the Parker Magnetostatic Theorem on a general incompatibility of a continuous magnetic field with the dual demand of force-free equilibrium and an arbitrarily prescribed, 3D field topology. Preserving field topology as a global constraint readily results in formation of tangential magnetic discontinuities, or, equivalently, electric current-sheets of zero thickness. A similar incompatibility is present in the steady force-thermal balance of a heated radiating fluid subject to an anisotropic thermal flux conducted strictly along its frozen-in magnetic field in the low- β limit. In a weakly resistive fluid the thinning of current sheets by these general incompatibilities inevitably results in sheet dissipation, resistive heating and topological changes in the field notwithstanding the small resistivity. Strong Faraday induction drives but also macroscopically limits this mode of energy dissipation, trapping or storing free energy in self-organized ideal-MHD structures. This property of MHD turbulence captured by the Taylor hypothesis is reviewed in relation to the Sun's corona, calling for a basic quantitative description of the breakdown of flux conservation in the low-resistivity limit

  11. Finite Volume TVD Schemes for Magnetohydrodynamics on Unstructered Grids

    NASA Astrophysics Data System (ADS)

    Tanaka, T.

    A three-dimensional (3-D) high-resolution magnetohydrodynamic (MHD) simulation scheme is developed on unstructured grid systems to solve the complex-system problems in space science and space weather in which numerical difficulties arise from inhomogeneity due to strong background potential fields, inclusion of multi-species ions, and formations of shocks and discontinuities. The ideal MHD equations are extended to the 9-component MHD equations for multi-component ions and modified soas to avoid a direct inclusion of background potential field in dependent variables through the use of new variables. The numerical scheme adopts the finite volume method (FVM) with an upwinding numerical flux based on the linearized Riemann solver. Upwindings on unstructured grid systems are realized from the fact that the MHD equations are symmetric with respect to the rotation of the space. Despite the modifications of the equation system, the eigenvectors in the mode-synthesis matrix necessary for the ev aluation of the upwinding numerical flux can still be written analytically. To get a higher order of accuracy, the upwinding flux is extended to the third-order total variation diminishing (TVD) numerical flux in the calculation of FVM, through the monotonic upstream scheme for conservation laws (MUSCL) approach and Van Leer's differentiable limiter. Three numerical examples are given in order to show the efficiency of the above scheme.

  12. 3D MHD Simulations of Spheromak Compression

    NASA Astrophysics Data System (ADS)

    Stuber, James E.; Woodruff, Simon; O'Bryan, John; Romero-Talamas, Carlos A.; Darpa Spheromak Team

    2015-11-01

    The adiabatic compression of compact tori could lead to a compact and hence low cost fusion energy system. The critical scientific issues in spheromak compression relate both to confinement properties and to the stability of the configuration undergoing compression. We present results from the NIMROD code modified with the addition of magnetic field coils that allow us to examine the role of rotation on the stability and confinement of the spheromak (extending prior work for the FRC). We present results from a scan in initial rotation, from 0 to 100km/s. We show that strong rotational shear (10km/s over 1cm) occurs. We compare the simulation results with analytic scaling relations for adiabatic compression. Work performed under DARPA grant N66001-14-1-4044.

  13. Magnetohydrodynamic Turbulence and the Geodynamo

    NASA Technical Reports Server (NTRS)

    Shebalin, John V.

    2016-01-01

    Recent research results concerning forced, dissipative, rotating magnetohydrodynamic (MHD) turbulence will be discussed. In particular, we present new results from long-time Fourier method (periodic box) simulations in which forcing contains varying amounts of magnetic and kinetic helicity. Numerical results indicate that if MHD turbulence is forced so as to produce a state of relatively constant energy, then the largest-scale components are dominant and quasistationary, and in fact, have an effective dipole moment vector that aligns closely with the rotation axis. The relationship of this work to established results in ideal MHD turbulence, as well as to models of MHD turbulence in a spherical shell will also be presented. These results appear to be very pertinent to understanding the Geodynamo and the origin of its dominant dipole component. Our conclusion is that MHD turbulence, per se, may well contain the origin of the Earth's dipole magnetic field.

  14. Parabolized Navier-Stokes Code for Computing Magneto-Hydrodynamic Flowfields

    NASA Technical Reports Server (NTRS)

    Mehta, Unmeel B. (Technical Monitor); Tannehill, J. C.

    2003-01-01

    This report consists of two published papers, 'Computation of Magnetohydrodynamic Flows Using an Iterative PNS Algorithm' and 'Numerical Simulation of Turbulent MHD Flows Using an Iterative PNS Algorithm'.

  15. Energy Conversion Alternatives Study (ECAS), Westinghouse phase 1. Volume 8: Open-cycle MHD. [energy conversion efficiency and design analysis of electric power plants employing magnetohydrodynamics

    NASA Technical Reports Server (NTRS)

    Hoover, D. Q.

    1976-01-01

    Electric power plant costs and efficiencies are presented for three basic open-cycle MHD systems: (1) direct coal fired system, (2) a system with a separately fired air heater, and (3) a system burning low-Btu gas from an integrated gasifier. Power plant designs were developed corresponding to the basic cases with variation of major parameters for which major system components were sized and costed. Flow diagrams describing each design are presented. A discussion of the limitations of each design is made within the framework of the assumptions made.

  16. Improvement of Scramjet Performance-Experimental Demonstration of MHD Acceleration

    NASA Technical Reports Server (NTRS)

    Bogdanoff, David W.; Park, Chul; Mehta, Unmeel B.; Arnold, James (Technical Monitor)

    2001-01-01

    One of the critical technologies of MHD (Magnetohydrodynamics) bypass scramjet propulsion for space launch and cruise vehicles is MHD acceleration. An experiment in a shock tunnel is described in which MHD acceleration is investigated experimentally. The objectives, the methods used and the preliminary results are described in this paper.

  17. Local conservative regularizations of compressible magnetohydrodynamic and neutral flows

    NASA Astrophysics Data System (ADS)

    Krishnaswami, Govind S.; Sachdev, Sonakshi; Thyagaraja, A.

    2016-02-01

    Ideal systems like magnetohydrodynamics (MHD) and Euler flow may develop singularities in vorticity ( w =∇×v ). Viscosity and resistivity provide dissipative regularizations of the singularities. In this paper, we propose a minimal, local, conservative, nonlinear, dispersive regularization of compressible flow and ideal MHD, in analogy with the KdV regularization of the 1D kinematic wave equation. This work extends and significantly generalizes earlier work on incompressible Euler and ideal MHD. It involves a micro-scale cutoff length λ which is a function of density, unlike in the incompressible case. In MHD, it can be taken to be of order the electron collisionless skin depth c/ωpe. Our regularization preserves the symmetries of the original systems and, with appropriate boundary conditions, leads to associated conservation laws. Energy and enstrophy are subject to a priori bounds determined by initial data in contrast to the unregularized systems. A Hamiltonian and Poisson bracket formulation is developed and applied to generalize the constitutive relation to bound higher moments of vorticity. A "swirl" velocity field is identified, and shown to transport w/ρ and B/ρ, generalizing the Kelvin-Helmholtz and Alfvén theorems. The steady regularized equations are used to model a rotating vortex, MHD pinch, and a plane vortex sheet. The proposed regularization could facilitate numerical simulations of fluid/MHD equations and provide a consistent statistical mechanics of vortices/current filaments in 3D, without blowup of enstrophy. Implications for detailed analyses of fluid and plasma dynamic systems arising from our work are briefly discussed.

  18. A hybrid numerical fluid dynamics code for resistive magnetohydrodynamics

    SciTech Connect

    Johnson, Jeffrey

    2006-04-01

    Spasmos is a computational fluid dynamics code that uses two numerical methods to solve the equations of resistive magnetohydrodynamic (MHD) flows in compressible, inviscid, conducting media[1]. The code is implemented as a set of libraries for the Python programming language[2]. It represents conducting and non-conducting gases and materials with uncomplicated (analytic) equations of state. It supports calculations in 1D, 2D, and 3D geometry, though only the 1D configuation has received significant testing to date. Because it uses the Python interpreter as a front end, users can easily write test programs to model systems with a variety of different numerical and physical parameters. Currently, the code includes 1D test programs for hydrodynamics (linear acoustic waves, the Sod weak shock[3], the Noh strong shock[4], the Sedov explosion[5], magnetic diffusion (decay of a magnetic pulse[6], a driven oscillatory "wine-cellar" problem[7], magnetic equilibrium), and magnetohydrodynamics (an advected magnetic pulse[8], linear MHD waves, a magnetized shock tube[9]). Spasmos current runs only in a serial configuration. In the future, it will use MPI for parallel computation.

  19. A hybrid numerical fluid dynamics code for resistive magnetohydrodynamics

    2006-04-01

    Spasmos is a computational fluid dynamics code that uses two numerical methods to solve the equations of resistive magnetohydrodynamic (MHD) flows in compressible, inviscid, conducting media[1]. The code is implemented as a set of libraries for the Python programming language[2]. It represents conducting and non-conducting gases and materials with uncomplicated (analytic) equations of state. It supports calculations in 1D, 2D, and 3D geometry, though only the 1D configuation has received significant testing to date. Becausemore » it uses the Python interpreter as a front end, users can easily write test programs to model systems with a variety of different numerical and physical parameters. Currently, the code includes 1D test programs for hydrodynamics (linear acoustic waves, the Sod weak shock[3], the Noh strong shock[4], the Sedov explosion[5], magnetic diffusion (decay of a magnetic pulse[6], a driven oscillatory "wine-cellar" problem[7], magnetic equilibrium), and magnetohydrodynamics (an advected magnetic pulse[8], linear MHD waves, a magnetized shock tube[9]). Spasmos current runs only in a serial configuration. In the future, it will use MPI for parallel computation.« less

  20. Plasma relaxation and topological aspects in Hall magnetohydrodynamics

    SciTech Connect

    Shivamoggi, B. K.

    2012-07-15

    Parker's formulation of isotopological plasma relaxation process in magnetohydrodynamics (MHD) is extended to Hall MHD. The torsion coefficient {alpha} in the Hall MHD Beltrami condition turns out now to be proportional to the potential vorticity. The Hall MHD Beltrami condition becomes equivalent to the potential vorticity conservation equation in two-dimensional (2D) hydrodynamics if the Hall MHD Lagrange multiplier {beta} is taken to be proportional to the potential vorticity as well. The winding pattern of the magnetic field lines in Hall MHD then appears to evolve in the same way as potential vorticity lines in 2D hydrodynamics.

  1. Extended Magnetohydrodynamic Simulations of the Helicity Injected Torus (HIT-SI) Spheromak Experiment with the NIMROD Code

    NASA Astrophysics Data System (ADS)

    Akcay, Cihan

    A comparative study of 3-D pressureless resistive (single-fluid) magnetohydrodynamic (rMHD) and 3-D pressureless two-fluid magnetohydrodynamic (2fl-MHD) models of the Helicity Injected Torus experiment (HIT-SI) is presented. HIT-SI is a spheromak current-drive experiment that uses two geometrically asymmetric helicity injectors to generate and sustain toroidal plasmas. The goal of the experiment is to demonstrate that steady inductive helicity injection (SIHI) is a viable method for driving and sustaining a magnetized plasma for the eventual purpose of electricity production with magnetic fusion power. The experiment has achieved sustainment of nearly 100 kA of plasma current for ˜1~ms. Fusion power plants are expected to sustain a burning plasma for many minutes to hours with more than 10~MA of plasma current. The purpose of project is to determine the validity of the single-fluid and two-fluid MHD models of HIT-SI. The comparable size of the collisionless ion skin depth to the diameter of the injectors and resistive skin depth predicates the importance of two-fluid effects. The simulations are run with NIMROD (non-ideal magnetohydrodynamics code with rotation-open discussion), an initial-value, 3-D extended MHD code. A constant and uniform plasma density and temperature are assumed. The helicity injectors are modeled as oscillating normal magnetic and parallel electric field boundary conditions. The simulations use parameters that closely match those of the experiment. The simulation output is compared to the formation time, plasma current, and internal and surface magnetic fields. Results of the study indicate 2fl-MHD shows quantitative agreement with the experiment while rMHD only captures the qualitative features. The validity of each model is assessed based on how accurately it reproduces the global quantities as well as the temporal and spatial dependence of the measured magnetic fields. 2fl-MHD produces the current amplification and formation time

  2. MHD simulation studies of z-pinch shear flow stabilization

    NASA Astrophysics Data System (ADS)

    Paraschiv, I.; Bauer, B. S.; Sotnikov, V. I.; Makhin, V.; Siemon, R. E.

    2003-10-01

    The development of the m=0 instability in a z-pinch in the presence of sheared plasma flows is investigated with the aid of a two-dimensional magnetohydrodynamic (MHD) simulation code (MHRDR). The linear growth rates are compared to the results obtained by solving the ideal MHD linearized equations [1] and to the results obtained using a 3D hybrid simulation code [2]. The instability development is followed into the nonlinear regime where its growth and saturation are examined. [1] V.I. Sotnikov, I. Paraschiv, V. Makhin, B.S. Bauer, J.-N. Leboeuf, and J.M. Dawson, "Linear analysis of sheared flow stabilization of global magnetohydrodynamic instabilities based on the Hall fluid mode", Phys. Plasmas 9, 913 (2002). [2] V.I. Sotnikov, V. Makhin, B.S. Bauer, P. Hellinger, P. Travnicek, V. Fiala, J.-N. Leboeuf, "Hybrid Simulations of Current-Carrying Instabilities in Z-pinch Plasmas with Sheared Axial Flow", AIP Conference Proceedings, Volume 651, Dense Z-Pinches: 5th International Conference on Dense Z-Pinches, edited by J. Davis et al., page 396, June 2002.

  3. Multiscaling in Hall-magnetohydrodynamic turbulence: insights from a shell model.

    PubMed

    Banerjee, Debarghya; Ray, Samriddhi Sankar; Sahoo, Ganapati; Pandit, Rahul

    2013-10-25

    We show that a shell-model version of the three-dimensional Hall-magnetohydrodynamic (3D Hall-MHD) equations provides a natural theoretical model for investigating the multiscaling behaviors of velocity and magnetic structure functions. We carry out extensive numerical studies of this shell model, obtain the scaling exponents for its structure functions, in both the low-k and high-k power-law ranges of three-dimensional Hall-magnetohydrodynamic, and find that the extended-self-similarity procedure is helpful in extracting the multiscaling nature of structure functions in the high-k regime, which otherwise appears to display simple scaling. Our results shed light on intriguing solar-wind measurements.

  4. Theory and Simulation of Real and Ideal Magnetohydrodynamic Turbulence

    NASA Technical Reports Server (NTRS)

    Shebalin, John V.

    2004-01-01

    Incompressible, homogeneous magnetohydrodynamic (MHD) turbulence consists of fluctuating vorticity and magnetic fields, which are represented in terms of their Fourier coefficients. Here, a set of five Fourier spectral transform method numerical simulations of two-dimensional (2-D) MHD turbulence on a 512(sup 2) grid is described. Each simulation is a numerically realized dynamical system consisting of Fourier modes associated with wave vectors k, with integer components, such that k = |k| less than or equal to k(sub max). The simulation set consists of one ideal (non-dissipative) case and four real (dissipative) cases. All five runs had equivalent initial conditions. The dimensions of the dynamical systems associated with these cases are the numbers of independent real and imaginary parts of the Fourier modes. The ideal simulation has a dimension of 366104, while each real simulation has a dimension of 411712. The real runs vary in magnetic Prandtl number P(sub M), with P(sub M) is a member of {0.1, 0.25, 1, 4}. In the results presented here, all runs have been taken to a simulation time of t = 25. Although ideal and real Fourier spectra are quite different at high k, they are similar at low values of k. Their low k behavior indicates the existence of broken symmetry and coherent structure in real MHD turbulence, similar to what exists in ideal MHD turbulence. The value of PM strongly affects the ratio of kinetic to magnetic energy and energy dissipation (which is mostly ohmic). The relevance of these results to 3-D Navier-Stokes and MHD turbulence is discussed.

  5. Viscosity and Vorticity in Reduced Magneto-Hydrodynamics

    SciTech Connect

    Joseph, Ilon

    2015-08-12

    Magneto-hydrodynamics (MHD) critically relies on viscous forces in order for an accurate determination of the electric eld. For each charged particle species, the Braginskii viscous tensor for a magnetized plasma has the decomposition into matrices with special symmetries.

  6. Channel-wall limitations in the magnetohydrodynamic induction generator

    NASA Technical Reports Server (NTRS)

    Jackson, W. D.; Pierson, E. S.

    1969-01-01

    Discussion of magnetohydrodynamic induction generator examines the machine in detail and materials problems influencing its design. The higher upper-temperature limit of the MHD system promises to be more efficient than present turbine systems for generating electricity.

  7. Generalized reduced magnetohydrodynamic equations

    SciTech Connect

    Kruger, S.E.

    1999-02-01

    A new derivation of reduced magnetohydrodynamic (MHD) equations is presented. A multiple-time-scale expansion is employed. It has the advantage of clearly separating the three time scales of the problem associated with (1) MHD equilibrium, (2) fluctuations whose wave vector is aligned perpendicular to the magnetic field, and (3) those aligned parallel to the magnetic field. The derivation is carried out without relying on a large aspect ratio assumption; therefore this model can be applied to any general configuration. By accounting for the MHD equilibrium and constraints to eliminate the fast perpendicular waves, equations are derived to evolve scalar potential quantities on a time scale associated with the parallel wave vector (shear-Alfven wave time scale), which is the time scale of interest for MHD instability studies. Careful attention is given in the derivation to satisfy energy conservation and to have manifestly divergence-free magnetic fields to all orders in the expansion parameter. Additionally, neoclassical closures and equilibrium shear flow effects are easily accounted for in this model. Equations for the inner resistive layer are derived which reproduce the linear ideal and resistive stability criterion of Glasser, Greene, and Johnson. The equations have been programmed into a spectral initial value code and run with shear flow that is consistent with the equilibrium input into the code. Linear results of tearing modes with shear flow are presented which differentiate the effects of shear flow gradients in the layer with the effects of the shear flow decoupling multiple harmonics.

  8. Method for manufacturing magnetohydrodynamic electrodes

    DOEpatents

    Killpatrick, D.H.; Thresh, H.R.

    1980-06-24

    A method of manufacturing electrodes for use in a magnetohydrodynamic (MHD) generator is described comprising the steps of preparing a billet having a core of a first metal, a tubular sleeve of a second metal, and an outer sheath of an extrusile metal; evacuating the space between the parts of the assembled billet; extruding the billet; and removing the outer jacket. The extruded bar may be made into electrodes by cutting and bending to the shape required for an MHD channel frame. The method forms a bond between the first metal of the core and the second metal of the sleeve strong enough to withstand a hot and corrosive environment.

  9. Smoothed MHD equations for numerical simulations of ideal quasi-neutral gas dynamic flows

    NASA Astrophysics Data System (ADS)

    Popov, Mikhail V.; Elizarova, Tatiana G.

    2015-11-01

    We introduce a mathematical model and related numerical method for numerical modeling of ideal magnetohydrodynamic (MHD) gas flows as an extension of previously known quasi-gasdynamic (QGD) equations. This approach is based on smoothing, or averaging of the original MHD equation system over a small time interval that leads to a new equation system, named quasi-MHD, or QMHD system. The QMHD equations are closely related to the original MHD system except for additional strongly non-linear dissipative τ-terms with a small parameter τ as a factor. The τ-terms depend on the solution itself and decrease in regions with the small space gradients of the solution. In this sense the QMHD system could be regarded as an approach with adaptive artificial dissipation. The QMHD is a generalization of regularized (or quasi-) gas dynamic equation system suggested in last three decades. In the QMHD numerical method the evolution of all physical variables is presented in a non-split divergence form. Divergence-free evolution of the magnetic field provides by using a constrained transport method based on Faraday's law of induction. Accuracy and convergence of the QMHD method is verified on a wide set of standard MHD tests including the 3D Orszag-Tang vortex flow.

  10. Remarkable connections between extended magnetohydrodynamics models

    SciTech Connect

    Lingam, M. Morrison, P. J. Miloshevich, G.

    2015-07-15

    Through the use of suitable variable transformations, the commonality of all extended magnetohydrodynamics (MHD) models is established. Remarkable correspondences between the Poisson brackets of inertialess Hall MHD and inertial MHD (which has electron inertia, but not the Hall drift) and extended MHD (which has both effects) are established. The helicities (two in all) for each of these models are obtained through these correspondences. The commonality of all the extended MHD models is traced to the existence of two Lie-dragged 2-forms, which are closely associated with the canonical momenta of the two underlying species. The Lie-dragging of these 2-forms by suitable velocities also leads to the correct equations of motion. The Hall MHD Poisson bracket is analyzed in detail, the Jacobi identity is verified through a detailed proof, and this proof ensures the Jacobi identity for the Poisson brackets of all the models.

  11. Magnetohydrodynamically generated velocities in confined plasma

    SciTech Connect

    Morales, Jorge A. Bos, Wouter J. T.; Schneider, Kai; Montgomery, David C.

    2015-04-15

    We investigate by numerical simulation the rotational flows in a toroid confining a conducting magnetofluid in which a current is driven by the application of externally supported electric and magnetic fields. The computation involves no microscopic instabilities and is purely magnetohydrodynamic (MHD). We show how the properties and intensity of the rotations are regulated by dimensionless numbers (Lundquist and viscous Lundquist) that contain the resistivity and viscosity of the magnetofluid. At the magnetohydrodynamic level (uniform mass density and incompressible magnetofluids), rotational flows appear in toroidal, driven MHD. The evolution of these flows with the transport coefficients, geometry, and safety factor are described.

  12. Magnetohydrodynamically generated velocities in confined plasma

    NASA Astrophysics Data System (ADS)

    Morales, Jorge A.; Bos, Wouter J. T.; Schneider, Kai; Montgomery, David C.

    2015-04-01

    We investigate by numerical simulation the rotational flows in a toroid confining a conducting magnetofluid in which a current is driven by the application of externally supported electric and magnetic fields. The computation involves no microscopic instabilities and is purely magnetohydrodynamic (MHD). We show how the properties and intensity of the rotations are regulated by dimensionless numbers (Lundquist and viscous Lundquist) that contain the resistivity and viscosity of the magnetofluid. At the magnetohydrodynamic level (uniform mass density and incompressible magnetofluids), rotational flows appear in toroidal, driven MHD. The evolution of these flows with the transport coefficients, geometry, and safety factor are described.

  13. Newtonian CAFE: a new ideal MHD code to study the solar atmosphere

    NASA Astrophysics Data System (ADS)

    González-Avilés, J. J.; Cruz-Osorio, A.; Lora-Clavijo, F. D.; Guzmán, F. S.

    2015-12-01

    We present a new code designed to solve the equations of classical ideal magnetohydrodynamics (MHD) in three dimensions, submitted to a constant gravitational field. The purpose of the code centres on the analysis of solar phenomena within the photosphere-corona region. We present 1D and 2D standard tests to demonstrate the quality of the numerical results obtained with our code. As solar tests we present the transverse oscillations of Alfvénic pulses in coronal loops using a 2.5D model, and as 3D tests we present the propagation of impulsively generated MHD-gravity waves and vortices in the solar atmosphere. The code is based on high-resolution shock-capturing methods, uses the Harten-Lax-van Leer-Einfeldt (HLLE) flux formula combined with Minmod, MC, and WENO5 reconstructors. The divergence free magnetic field constraint is controlled using the Flux Constrained Transport method.

  14. An MHD study of the interaction between the solar wind and the interstellar medium

    NASA Technical Reports Server (NTRS)

    Steinolfson, R. S.

    1993-01-01

    The overall objective of this research program is to obtain a better understanding of the interaction between the solar wind and the interstellar medium through the use of numerical solutions of the time-dependent magnetohydrodynamic (MHD) equations. The simulated results will be compared with observations where possible and with the results from previous analytic and numerical studies. The primary progress during the first two years has been to develop codes for 2-D models in both spherical and cylindrical coordinates and to apply them to the solar wind-interstellar medium interaction. Computations have been carried out for both a relatively simple gas-dynamic interaction and a flow-aligned interstellar magnetic field. The results have been shown to compare favorably with models that use more approximations and to modify and extend the previous results as would be expected. Work has also been initiated on the development of a 3-D MHD code in spherical coordinates.

  15. Lattice Boltzmann model for simulation of magnetohydrodynamics

    NASA Technical Reports Server (NTRS)

    Chen, Shiyi; Chen, Hudong; Martinez, Daniel; Matthaeus, William

    1991-01-01

    A numerical method, based on a discrete Boltzmann equation, is presented for solving the equations of magnetohydrodynamics (MHD). The algorithm provides advantages similar to the cellular automaton method in that it is local and easily adapted to parallel computing environments. Because of much lower noise levels and less stringent requirements on lattice size, the method appears to be more competitive with traditional solution methods. Examples show that the model accurately reproduces both linear and nonlinear MHD phenomena.

  16. MHD simulations on an unstructured mesh

    SciTech Connect

    Strauss, H.R.; Park, W.; Belova, E.; Fu, G.Y.; Longcope, D.W.; Sugiyama, L.E.

    1998-12-31

    Two reasons for using an unstructured computational mesh are adaptivity, and alignment with arbitrarily shaped boundaries. Two codes which use finite element discretization on an unstructured mesh are described. FEM3D solves 2D and 3D RMHD using an adaptive grid. MH3D++, which incorporates methods of FEM3D into the MH3D generalized MHD code, can be used with shaped boundaries, which might be 3D.

  17. Generalized reduced MHD equations

    SciTech Connect

    Kruger, S.E.; Hegna, C.C.; Callen, J.D.

    1998-07-01

    A new derivation of reduced magnetohydrodynamic (MHD) equations is presented. A multiple-time-scale expansion is employed. It has the advantage of clearly separating the three time scales of the problem associated with (1) MHD equilibrium, (2) fluctuations whose wave vector is aligned perpendicular to the magnetic field, and (3) those aligned parallel to the magnetic field. The derivation is carried out without relying on a large aspect ratio assumption; therefore this model can be applied to any general toroidal configuration. By accounting for the MHD equilibrium and constraints to eliminate the fast perpendicular waves, equations are derived to evolve scalar potential quantities on a time scale associated with the parallel wave vector (shear-alfven wave time scale), which is the time scale of interest for MHD instability studies. Careful attention is given in the derivation to satisfy energy conservation and to have manifestly divergence-free magnetic fields to all orders in the expansion parameter. Additionally, neoclassical closures and equilibrium shear flow effects are easily accounted for in this model. Equations for the inner resistive layer are derived which reproduce the linear ideal and resistive stability criterion of Glasser, Greene, and Johnson.

  18. MHD Energy Bypass Scramjet Engine

    NASA Technical Reports Server (NTRS)

    Mehta, Unmeel B.; Bogdanoff, David W.; Park, Chul; Arnold, Jim (Technical Monitor)

    2001-01-01

    Revolutionary rather than evolutionary changes in propulsion systems are most likely to decrease cost of space transportation and to provide a global range capability. Hypersonic air-breathing propulsion is a revolutionary propulsion system. The performance of scramjet engines can be improved by the AJAX energy management concept. A magneto-hydro-dynamics (MHD) generator controls the flow and extracts flow energy in the engine inlet and a MHD accelerator downstream of the combustor accelerates the nozzle flow. A progress report toward developing the MHD technology is presented herein. Recent theoretical efforts are reviewed and ongoing experimental efforts are discussed. The latter efforts also include an ongoing collaboration between NASA, the US Air Force Research Laboratory, US industry, and Russian scientific organizations. Two of the critical technologies, the ionization of the air and the MHD accelerator, are briefly discussed. Examples of limiting the combustor entrance Mach number to a low supersonic value with a MHD energy bypass scheme are presented, demonstrating an improvement in scramjet performance. The results for a simplified design of an aerospace plane show that the specific impulse of the MHD-bypass system is better than the non-MHD system and typical rocket over a narrow region of flight speeds and design parameters. Equilibrium ionization and non-equilibrium ionization are discussed. The thermodynamic condition of air at the entrance of the engine inlet determines the method of ionization. The required external power for non-equilibrium ionization is computed. There have been many experiments in which electrical power generation has successfully been achieved by magneto-hydrodynamic (MHD) means. However, relatively few experiments have been made to date for the reverse case of achieving gas acceleration by the MHD means. An experiment in a shock tunnel is described in which MHD acceleration is investigated experimentally. MHD has several

  19. Magnetohydrodynamic generators using two-phase liquid-metal flows

    NASA Technical Reports Server (NTRS)

    Petrick, M.

    1969-01-01

    Two-phase flow generator cycle of a magnetohydrodynamic /MHD/ generator uses a working fluid which is compressible and treated as an expanding gas. The two-phase mixture passes from the heat source through the MHD generator, where the expansion process takes place and the electrical energy is extracted.

  20. MHD simple waves and the divergence wave

    SciTech Connect

    Webb, G. M.; Pogorelov, N. V.; Zank, G. P.

    2010-03-25

    In this paper we investigate magnetohydrodynamic (MHD) simple divergence waves in MHD, for models in which nablacentre dotBnot =0. These models are related to the eight wave Riemann solvers in numerical MHD, in which the eighth wave is the divergence wave associated with nablacentre dotBnot =0. For simple wave solutions, all physical variables (the gas density, pressure, fluid velocity, entropy, and magnetic field induction in the MHD case) depend on a single phase function phi. We consider the form of the MHD equations used by both Powell et al. and Janhunen. It is shown that the Janhunen version of the equations possesses fully nonlinear, exact simple wave solutions for the divergence wave, but no physically meaningful simple divergence wave solution exists for the Powell et al. system. We suggest that the 1D simple, divergence wave solution for the Janhunen system, may be useful for the testing and validation of numerical MHD codes.

  1. Experimental onset threshold and magnetic pressure pileup for 3D Sweet-Parker reconnection

    SciTech Connect

    Intrator, Thomas P; Sun, Xuan; Lapenta, Giovanni; Furno, Ivo

    2008-01-01

    In space, astrophysical and laboratory plasmas, magnetic reconnect ion converts magnetic into particle energy during unsteady, explosive events. The abrupt onset and cessation has been a long standing puzzle. We show the first three-dimensional (3D) laboratory example of onset and stagnation of Sweet-Parker type magnetic reconnection between magnetized and parallel current (flux) ropes driven by magnetohydrodynamic (MHD) attraction and 3D instability. Mutually attracting flux ropes advect and merge oppositely directed magnetic fields. Magnetic flux is annihilated, but reaches soon a threshold where magnetic flux and pressure pile up, and reconnection magnetic topology appears. This occurs when inflow speeds exceed the SweetParker speed v{sub SP} = v{sub A} / S{sup 1/2}, where v{sub A} is the Alfven speed and S is the Lundquist number for the reconnection layer, as magnetic flux arrives faster than flux annihilation can process it. Finally piled up fields generate MHD reaction forces that stall the inflow and the reconnection process.

  2. Magnetohydrodynamic turbulence: Observation and experiment

    SciTech Connect

    Brown, M. R.; Schaffner, D. A.; Weck, P. J.

    2015-05-15

    We provide a tutorial on the paradigms and tools of magnetohydrodynamic (MHD) turbulence. The principal paradigm is that of a turbulent cascade from large scales to small, resulting in power law behavior for the frequency power spectrum for magnetic fluctuations E{sub B}(f). We will describe five useful statistical tools for MHD turbulence in the time domain: the temporal autocorrelation function, the frequency power spectrum, the probability distribution function of temporal increments, the temporal structure function, and the permutation entropy. Each of these tools will be illustrated with an example taken from MHD fluctuations in the solar wind. A single dataset from the Wind satellite will be used to illustrate all five temporal statistical tools.

  3. Magnetohydrodynamic Turbulence and the Geodynamo

    NASA Technical Reports Server (NTRS)

    Shebalin, John V.

    2014-01-01

    The ARES Directorate at JSC has researched the physical processes that create planetary magnetic fields through dynamo action since 2007. The "dynamo problem" has existed since 1600, when William Gilbert, physician to Queen Elizabeth I, recognized that the Earth was a giant magnet. In 1919, Joseph Larmor proposed that solar (and by implication, planetary) magnetism was due to magnetohydrodynamics (MHD), but full acceptance did not occur until Glatzmaier and Roberts solved the MHD equations numerically and simulated a geomagnetic reversal in 1995. JSC research produced a unique theoretical model in 2012 that provided a novel explanation of these physical observations and computational results as an essential manifestation of broken ergodicity in MHD turbulence. Research is ongoing, and future work is aimed at understanding quantitative details of magnetic dipole alignment in the Earth as well as in Mercury, Jupiter and its moon Ganymede, Saturn, Uranus, Neptune, and the Sun and other stars.

  4. A moving mesh unstaggered constrained transport scheme for magnetohydrodynamics

    NASA Astrophysics Data System (ADS)

    Mocz, Philip; Pakmor, Rüdiger; Springel, Volker; Vogelsberger, Mark; Marinacci, Federico; Hernquist, Lars

    2016-11-01

    We present a constrained transport (CT) algorithm for solving the 3D ideal magnetohydrodynamic (MHD) equations on a moving mesh, which maintains the divergence-free condition on the magnetic field to machine-precision. Our CT scheme uses an unstructured representation of the magnetic vector potential, making the numerical method simple and computationally efficient. The scheme is implemented in the moving mesh code AREPO. We demonstrate the performance of the approach with simulations of driven MHD turbulence, a magnetized disc galaxy, and a cosmological volume with primordial magnetic field. We compare the outcomes of these experiments to those obtained with a previously implemented Powell divergence-cleaning scheme. While CT and the Powell technique yield similar results in idealized test problems, some differences are seen in situations more representative of astrophysical flows. In the turbulence simulations, the Powell cleaning scheme artificially grows the mean magnetic field, while CT maintains this conserved quantity of ideal MHD. In the disc simulation, CT gives slower magnetic field growth rate and saturates to equipartition between the turbulent kinetic energy and magnetic energy, whereas Powell cleaning produces a dynamically dominant magnetic field. Such difference has been observed in adaptive-mesh refinement codes with CT and smoothed-particle hydrodynamics codes with divergence-cleaning. In the cosmological simulation, both approaches give similar magnetic amplification, but Powell exhibits more cell-level noise. CT methods in general are more accurate than divergence-cleaning techniques, and, when coupled to a moving mesh can exploit the advantages of automatic spatial/temporal adaptivity and reduced advection errors, allowing for improved astrophysical MHD simulations.

  5. Coupled neoclassical-magnetohydrodynamic simulations of axisymmetric plasmas

    NASA Astrophysics Data System (ADS)

    Lyons, Brendan C.

    2014-10-01

    Neoclassical effects (e.g., the bootstrap current and neoclassical toroidal viscosity [NTV]) have a profound impact on many magnetohydrodynamic (MHD) instabilities, including tearing modes, edge-localized modes (ELMs), and resistive wall modes. High-fidelity simulations of such phenomena require a multiphysics code that self-consistently couples the kinetic and fluid models. We present the first results of the DK4D code, a dynamic drift-kinetic equation (DKE) solver being developed for this application. In this study, DK4D solves a set of time-dependent, axisymmetric DKEs for the non-Maxwellian part of the electron and ion distribution functions (fNM) with linearized Fokker-Planck-Landau collision operators. The plasma is formally assumed to be in the low- to finite-collisionality regimes. The form of the DKEs used were derived in a Chapman-Enskog-like fashion, ensuring that fNM carries no density, momentum, or temperature. Rather, these quantities are contained within the background Maxwellian and are evolved by an appropriate set of extended MHD equations. We will discuss computational methods used and benchmarks to other neoclassical models and codes. Furthermore, DK4D has been coupled to a reduced, transport-timescale MHD code, allowing for self-consistent simulations of the dynamic formation of the ohmic and bootstrap currents. Several applications of this hybrid code will be presented, including an ELM-like pressure collapse. We will also discuss plans for coupling to the spatially three-dimensional, extended MHD code M3D-C1 and generalizing to nonaxisymmetric geometries, with the goal of performing self-consistent hybrid simulations of tokamak instabilities and calculations of NTV torque. This work supported by the U.S. Department of Energy (DOE) under Grant Numbers DE-FC02-08ER54969 and DE-AC02-09CH11466.

  6. A moving mesh unstaggered constrained transport scheme for magnetohydrodynamics

    NASA Astrophysics Data System (ADS)

    Mocz, Philip; Pakmor, Rüdiger; Springel, Volker; Vogelsberger, Mark; Marinacci, Federico; Hernquist, Lars

    2016-08-01

    We present a constrained transport (CT) algorithm for solving the 3D ideal magnetohydrodynamic (MHD) equations on a moving mesh, which maintains the divergence-free condition on the magnetic field to machine-precision. Our CT scheme uses an unstructured representation of the magnetic vector potential, making the numerical method simple and computationally efficient. The scheme is implemented in the moving mesh code AREPO. We demonstrate the performance of the approach with simulations of driven MHD turbulence, a magnetized disc galaxy, and a cosmological volume with primordial magnetic field. We compare the outcomes of these experiments to those obtained with a previously implemented Powell divergence-cleaning scheme. While CT and the Powell technique yield similar results in idealized test problems, some differences are seen in situations more representative of astrophysical flows. In the turbulence simulations, the Powell cleaning scheme artificially grows the mean magnetic field, while CT maintains this conserved quantity of ideal MHD. In the disc simulation, CT gives slower magnetic field growth rate and saturates to equipartition between the turbulent kinetic energy and magnetic energy, whereas Powell cleaning produces a dynamically dominant magnetic field. Such difference has been observed in adaptive-mesh refinement codes with CT and smoothed-particle hydrodynamics codes with divergence-cleaning. In the cosmological simulation, both approaches give similar magnetic amplification, but Powell exhibits more cell-level noise. CT methods in general are more accurate than divergence-cleaning techniques, and, when coupled to a moving mesh can exploit the advantages of automatic spatial/temporal adaptivity and reduced advection errors, allowing for improved astrophysical MHD simulations.

  7. Remarks on the regularity criteria of three-dimensional magnetohydrodynamics system in terms of two velocity field components

    SciTech Connect

    Yamazaki, Kazuo

    2014-03-15

    We study the three-dimensional magnetohydrodynamics system and obtain its regularity criteria in terms of only two velocity vector field components eliminating the condition on the third component completely. The proof consists of a new decomposition of the four nonlinear terms of the system and estimating a component of the magnetic vector field in terms of the same component of the velocity vector field. This result may be seen as a component reduction result of many previous works [C. He and Z. Xin, “On the regularity of weak solutions to the magnetohydrodynamic equations,” J. Differ. Equ. 213(2), 234–254 (2005); Y. Zhou, “Remarks on regularities for the 3D MHD equations,” Discrete Contin. Dyn. Syst. 12(5), 881–886 (2005)].

  8. Global Magnetohydrodynamic Modeling of the Solar Corona

    NASA Technical Reports Server (NTRS)

    Linker, Jon A.

    2001-01-01

    This report describes the progress made in the investigation of the solar corona using magnetohydrodynamic (MHD) simulations. Coronal mass ejections (CME) are believed to be the primary cause of nonrecurrent geomagnetic storms and these have been investigated through the use of three-dimensional computer simulation.

  9. Symmetry transforms for ideal magnetohydrodynamics equilibria.

    PubMed

    Bogoyavlenskij, Oleg I

    2002-11-01

    A method for constructing ideal magnetohydrodynamics (MHD) equilibria is introduced. The method consists of the application of symmetry transforms to any known MHD equilibrium [ O. I. Bogoyavlenskij, Phys. Rev. E. 62, 8616, (2000)]. The transforms break the geometrical symmetries of the field-aligned solutions and produce continuous families of the nonsymmetric MHD equilibria. The method of symmetry transforms also allows to obtain MHD equilibria with current sheets and exact solutions with noncollinear vector fields B and V. A model of the nonsymmetric astrophysical jets outside of their accretion disks is developed. The total magnetic and kinetic energy of the jet is finite in any layer c(1)MHD equilibria that model ball lightning with dynamics of plasma inside the fireball.

  10. Symmetry transforms for ideal magnetohydrodynamics equilibria.

    PubMed

    Bogoyavlenskij, Oleg I

    2002-11-01

    A method for constructing ideal magnetohydrodynamics (MHD) equilibria is introduced. The method consists of the application of symmetry transforms to any known MHD equilibrium [ O. I. Bogoyavlenskij, Phys. Rev. E. 62, 8616, (2000)]. The transforms break the geometrical symmetries of the field-aligned solutions and produce continuous families of the nonsymmetric MHD equilibria. The method of symmetry transforms also allows to obtain MHD equilibria with current sheets and exact solutions with noncollinear vector fields B and V. A model of the nonsymmetric astrophysical jets outside of their accretion disks is developed. The total magnetic and kinetic energy of the jet is finite in any layer c(1)MHD equilibria that model ball lightning with dynamics of plasma inside the fireball. PMID:12513610

  11. Is the 3-D magnetic null point with a convective electric field an efficient particle accelerator?

    NASA Astrophysics Data System (ADS)

    Guo, J.-N.; Büchner, J.; Otto, A.; Santos, J.; Marsch, E.; Gan, W.-Q.

    2010-04-01

    Aims: We study the particle acceleration at a magnetic null point in the solar corona, considering self-consistent magnetic fields, plasma flows and the corresponding convective electric fields. Methods: We calculate the electromagnetic fields by 3-D magnetohydrodynamic (MHD) simulations and expose charged particles to these fields within a full-orbit relativistic test-particle approach. In the 3-D MHD simulation part, the initial magnetic field configuration is set to be a potential field obtained by extrapolation from an analytic quadrupolar photospheric magnetic field with a typically observed magnitude. The configuration is chosen so that the resulting coronal magnetic field contains a null. Driven by photospheric plasma motion, the MHD simulation reveals the coronal plasma motion and the self-consistent electric and magnetic fields. In a subsequent test particle experiment the particle energies and orbits (determined by the forces exerted by the convective electric field and the magnetic field around the null) are calculated in time. Results: Test particle calculations show that protons can be accelerated up to 30 keV near the null if the local plasma flow velocity is of the order of 1000 km s-1 (in solar active regions). The final parallel velocity is much higher than the perpendicular velocity so that accelerated particles escape from the null along the magnetic field lines. Stronger convection electric field during big flare explosions can accelerate protons up to 2 MeV and electrons to 3 keV. Higher initial velocities can help most protons to be strongly accelerated, but a few protons also run the risk to be decelerated. Conclusions: Through its convective electric field and due to magnetic nonuniform drifts and de-magnetization process, the 3-D null can act as an effective accelerator for protons but not for electrons. Protons are more easily de-magnetized and accelerated than electrons because of their larger Larmor radii. Notice that macroscopic MHD

  12. Comparison between 2.5D and 3D simulations of coronal mass ejections

    NASA Astrophysics Data System (ADS)

    Jacobs, C.; van der Holst, B.; Poedts, S.

    2007-07-01

    Context: The shocks and magnetic clouds related to Coronal Mass Ejections (CMEs) in the solar corona and interplanetary space (IP) play an important role in the study of space weather. In order to study the evolution of these IP shocks, numerical simulations of a simplified CME model were performed. Aims: In an earlier study, the effect of the background wind on the evolution of interplanetary shock waves was investigated, where the computations were carried out under the assumption of axial symmetry. The assumption of axial symmetry might be a good approach for the solar corona under conditions of solar minimum, but for the study of CMEs this assumption is definitely no longer valid as CMEs possess clearly a fully three dimensional (3D) structure. From this perspective, the previous simulations were repeated, but now in a three dimensional set-up in order to point out the differences between the 2.5D and 3D simulations and to check the quality and reliability of the 2.5D simulations. Methods: The computations were performed in the framework of ideal magnetohydrodynamics (MHD) and to advance the ideal MHD equations in time a parallel finite volume code with explicit upwind solver was used. The shock waves are generated in a similar way in both the 3D and 2.5D simulations, namely by a simple density-blob model. The 3D and 2.5D simulations are all performed with the same numerical methods and on comparable grids, such that the differences between the simulations are purely due to the dimensionality of the problem, and/or the initial parameters for the CME generation. Results: Three different axisymmetric simulations of CME propagation are compared with the fully three dimensional computation. The 2.5D simulations differ from each other in the parameters used for CME initiation. In a first simulation, the same initial parameters as for the 3D case were taken, in a second simulation the initial amount of mass in the 2.5D and 3D CME was the same, and in a third

  13. Assessment of MHD power plants with coal gasification

    NASA Astrophysics Data System (ADS)

    Delallo, M. R., Jr.; Weinstein, R. E.; Cutting, J. C.; Owens, W. R.

    1981-12-01

    An assessment of the operational characteristics and cost of magnetohydrodynamic (MHD) power plants integrated with coal gasification was performed. The coal gasifier produces a slag and sulfur free fuel for the MHD combustor. This clean fuel eliminates slag and sulfur interactions with the MHD topping cycle and simplifies the design of the combustor, the MHD channel, and the heat and seed recovery (HRSR) subsystem components. This may increase MHD and HRSR system reliability and provide the potential for earlier commercial demonstration of MHD. Integration techniques with three advanced medium BTU gasifiers were evaluated and an optimum system defined. A detailed comparison was then performed with a direct coal fired MHD power plant using oxygen enrichment. Results indicate that incorporating a coal gasification process with MHD simplifies system design at the expense of lower overall net plant efficiency and higher levelized cost of electricity

  14. [Nonlinear magnetohydrodynamics

    SciTech Connect

    Not Available

    1992-11-01

    Theoretical predictions were compared with available data from JET on the threshold unstable MHD activity in toroidal confinement devices. In particular, questions arising as to Hartmans number and the selection of a kinematic viscosity are discussed.

  15. Efficient magnetohydrodynamic simulations on distributed multi-GPU systems using a novel GPU Direct-MPI hybrid approach

    NASA Astrophysics Data System (ADS)

    Wong, Un-Hong; Aoki, Takayuki; Wong, Hon-Cheng

    2014-07-01

    Modern graphics processing units (GPUs) have been widely utilized in magnetohydrodynamic (MHD) simulations in recent years. Due to the limited memory of a single GPU, distributed multi-GPU systems are needed to be explored for large-scale MHD simulations. However, the data transfer between GPUs bottlenecks the efficiency of the simulations on such systems. In this paper we propose a novel GPU Direct-MPI hybrid approach to address this problem for overall performance enhancement. Our approach consists of two strategies: (1) We exploit GPU Direct 2.0 to speedup the data transfers between multiple GPUs in a single node and reduce the total number of message passing interface (MPI) communications; (2) We design Compute Unified Device Architecture (CUDA) kernels instead of using memory copy to speedup the fragmented data exchange in the three-dimensional (3D) decomposition. 3D decomposition is usually not preferable for distributed multi-GPU systems due to its low efficiency of the fragmented data exchange. Our approach has made a breakthrough to make 3D decomposition available on distributed multi-GPU systems. As a result, it can reduce the memory usage and computation time of each partition of the computational domain. Experiment results show twice the FLOPS comparing to common 2D decomposition MPI-only implementation method. The proposed approach has been developed in an efficient implementation for MHD simulations on distributed multi-GPU systems, called MGPU-MHD code. The code realizes the GPU parallelization of a total variation diminishing (TVD) algorithm for solving the multidimensional ideal MHD equations, extending our work from single GPU computation (Wong et al., 2011) to multiple GPUs. Numerical tests and performance measurements are conducted on the TSUBAME 2.0 supercomputer at the Tokyo Institute of Technology. Our code achieves 2 TFLOPS in double precision for the problem with 12003 grid points using 216 GPUs.

  16. Modeling extreme "Carrington-type" space weather events using three-dimensional global MHD simulations

    NASA Astrophysics Data System (ADS)

    Ngwira, Chigomezyo M.; Pulkkinen, Antti; Kuznetsova, Maria M.; Glocer, Alex

    2014-06-01

    There is a growing concern over possible severe societal consequences related to adverse space weather impacts on man-made technological infrastructure. In the last two decades, significant progress has been made toward the first-principles modeling of space weather events, and three-dimensional (3-D) global magnetohydrodynamics (MHD) models have been at the forefront of this transition, thereby playing a critical role in advancing our understanding of space weather. However, the modeling of extreme space weather events is still a major challenge even for the modern global MHD models. In this study, we introduce a specially adapted University of Michigan 3-D global MHD model for simulating extreme space weather events with a Dst footprint comparable to the Carrington superstorm of September 1859 based on the estimate by Tsurutani et. al. (2003). Results are presented for a simulation run with "very extreme" constructed/idealized solar wind boundary conditions driving the magnetosphere. In particular, we describe the reaction of the magnetosphere-ionosphere system and the associated induced geoelectric field on the ground to such extreme driving conditions. The model setup is further tested using input data for an observed space weather event of Halloween storm October 2003 to verify the MHD model consistence and to draw additional guidance for future work. This extreme space weather MHD model setup is designed specifically for practical application to the modeling of extreme geomagnetically induced electric fields, which can drive large currents in ground-based conductor systems such as power transmission grids. Therefore, our ultimate goal is to explore the level of geoelectric fields that can be induced from an assumed storm of the reported magnitude, i.e., Dst˜=-1600 nT.

  17. One year in the Earth's magnetosphere: A global MHD simulation and spacecraft measurements

    NASA Astrophysics Data System (ADS)

    Facskó, G.; Honkonen, I.; Živković, T.; Palin, L.; Kallio, E.; Ã gren, K.; Opgenoorth, H.; Tanskanen, E. I.; Milan, S.

    2016-05-01

    The response of the Earth's magnetosphere to changing solar wind conditions is studied with a 3-D Magnetohydrodynamic (MHD) model. One full year (155 Cluster orbits) of the Earth's magnetosphere is simulated using Grand Unified Magnetosphere Ionosphere Coupling simulation (GUMICS-4) magnetohydrodynamic code. Real solar wind measurements are given to the code as input to create the longest lasting global magnetohydrodynamics simulation to date. The applicability of the results of the simulation depends critically on the input parameters used in the model. Therefore, the validity and the variance of the OMNIWeb data are first investigated thoroughly using Cluster measurement close to the bow shock. The OMNIWeb and the Cluster data were found to correlate very well before the bow shock. The solar wind magnetic field and plasma parameters are not changed significantly from the L1 Lagrange point to the foreshock; therefore, the OMNIWeb data are appropriate input to the GUMICS-4. The Cluster SC3 footprints are determined by magnetic field mapping from the simulation results and the Tsyganenko (T96) model in order to compare two methods. The determined footprints are in rather good agreement with the T96. However, it was found that the footprints agree better in the Northern Hemisphere than the Southern one during quiet conditions. If the By is not zero, the agreement of the GUMICS-4 and T96 footprint is worse in longitude in the Southern Hemisphere. Overall, the study implies that a 3-D MHD model can increase our insight of the response of the magnetosphere to solar wind conditions.

  18. BOOK REVIEW: Nonlinear Magnetohydrodynamics

    NASA Astrophysics Data System (ADS)

    Shafranov, V.

    1998-08-01

    equations of a plasma in a magnetic field (which will be used further in models of dynamic processes), approaches to the description of three dimensional (3-D) equilibrium are briefly discussed, and the basis of the theory of linear instabilities and the basic types of MHD instabilities, with account taken of ideal resistive modes, are considered. The value of the material of these chapters is that here in a brief form the results of numerous researches in this area are presented, and frequently with a fresh point of view of old results. Chapters 5 to 10 are devoted to the subject of the book, non-linear magnetohydrodynamics. In the introduction to Chapter 5 the author pays attention to the fact that long standing doubts about the feasibility of magnetic thermonuclear reactors because of inevitable instabilities of non-uniform plasmas have been overcome in the last two decades: the plasma in tokamaks is rather well confined, despite the presence of some instabilities. The latter, as a rule, result only in the redistribution of current and plasma pressure profiles and some increase of transport, but can also lead to extremely undesirable effects. In this connection in Chapter 5 the attention of the reader is directed to the physics of the most important plasma instabilities in tokamaks. Models of the development of external and internal kink modes in tokamaks are considered, including the `vacuum bubble' model in shearless plasmas, the evolution of the resistive tearing mode together with saturation of the magnetic islands arising at a tearing instability. The rather long Chapter 6 is devoted to the fundamentals of the magnetic hydrodynamic dissipative process in the magnetic field line reconnection. This process of rapid dissipation of the energy of a magnetic field, having in the simplest case different directions in two adjacent volumes of plasma, underlies the theory of the phenomenon of powerful flares in the solar chromosphere, resulting in the well-known `magnetic

  19. MHD program plan, FY 1991

    SciTech Connect

    Not Available

    1990-10-01

    The current magnetohydrodynamic MHD program being implemented is a result of a consensus established in public meetings held by the Department of Energy in 1984. The public meetings were followed by the formulation of a June 1984 Coal-Fired MHD Preliminary Transition and Program Plan. This plan focused on demonstrating the proof-of-concept (POC) of coal-fired MHD electric power plants by the early 1990s. MHD test data indicate that while there are no fundamental technical barriers impeding the development of MHD power plants, technical risk remains. To reduce the technical risk three key subsystems (topping cycle, bottoming cycle, and seed regeneration) are being assembled and tested separately. The program does not require fabrication of a complete superconducting magnet, but rather the development and testing of superconductor cables. The topping cycle system test objectives can be achieved using a conventional iron core magnet system already in place at a DOE facility. Systems engineering-derived requirements and analytical modeling to support scale-up and component design guide the program. In response to environmental, economic, engineering, and utility acceptance requirements, design choices and operating modes are tested and refined to provide technical specifications for meeting commercial criteria. These engineering activities are supported by comprehensive and continuing systems analyses to establish realistic technical requirements and cost data. Essential elements of the current program are to: Develop technical and environmental data for the integrated MHD topping cycle system through POC testing (1000 hours); and bottoming cycle (4000 hours); design, construct, and operate a POC seed regeneration system capable of processing spent seed materials from the MHD bottoming cycle, prepare conceptual designs for a site specific MHD retrofit plant, and continue supporting research necessary for system testing. 7 figs.

  20. Multirail electromagnetic launcher powered from a pulsed magnetohydrodynamic generator

    NASA Astrophysics Data System (ADS)

    Afonin, A. G.; Butov, V. G.; Panchenko, V. P.; Sinyaev, S. V.; Solonenko, V. A.; Shvetsov, G. A.; Yakushev, A. A.

    2015-09-01

    The operation of an electromagnetic multirail launcher of solids powered from a pulsed magnetohydrodynamic (MHD) generator is studied. The plasma flow in the channel of the pulsed MHD generator and the possibility of launching solids in a rapid-fire mode of launcher operation are considered. It is shown that this mode of launcher operation can be implemented by matching the plasma flow dynamics in the channel of the pulsed MHD generator and the launching conditions. It is also shown that powerful pulsed MHD generators can be used as a source of electrical energy for rapid-fire electromagnetic rail launchers operating in a burst mode.

  1. M3D-C1 simulations of plasma response in ELM-mitigated ASDEX Upgrade and DIII-D discharges

    NASA Astrophysics Data System (ADS)

    Lyons, B. C.; Ferraro, N. M.; Haskey, S. R.; Logan, N. C.

    2015-11-01

    The extended magnetohydrodynamics (MHD) code M3D-C1 is used to study the time-independent, linear response of tokamak equilibria to applied, 3D magnetic perturbations. In doing so, we seek to develop a more complete understanding of what MHD phenomena are responsible for the mitigation and suppression of edge-localized modes (ELMs) and to explain why the success of ELM suppression experiments differs both within a single tokamak and across different tokamaks. We consider such experiments on ASDEX Upgrade and DIII-D. We examine how resonant and non-resonant plasma responses are affected by varying the relative magnitude and phase of sets of magnetic coils. The importance of two-fluid effects, rotation profiles, plasma β, collisionality, bootstrap current profiles, and various numerical parameters are explored. The results are verified against other MHD codes (e.g., IPEC, MARS), correlated to observations of ELM mitigation or suppression, and validated against observed magnetic responses. Work supported in part by US DOE under DE-FC02-04ER54698, DE-AC02-09CH11466, and the FES Postdoctoral Research Program.

  2. MHD Integrated Topping Cycle Project

    SciTech Connect

    Not Available

    1992-03-01

    The Magnetohydrodynamics (MHD) Integrated Topping Cycle (ITC) Project represents the culmination of the proof-of-concept (POC) development stage in the US Department of Energy (DOE) program to advance MHD technology to early commercial development stage utility power applications. The project is a joint effort, combining the skills of three topping cycle component developers: TRW, Avco/TDS, and Westinghouse. TRW, the prime contractor and system integrator, is responsible for the 50 thermal megawatt (50 MW{sub t}) slagging coal combustion subsystem. Avco/TDS is responsible for the MHD channel subsystem (nozzle, channel, diffuser, and power conditioning circuits), and Westinghouse is responsible for the current consolidation subsystem. The ITC Project will advance the state-of-the-art in MHD power systems with the design, construction, and integrated testing of 50 MW{sub t} power train components which are prototypical of the equipment that will be used in an early commercial scale MHD utility retrofit. Long duration testing of the integrated power train at the Component Development and Integration Facility (CDIF) in Butte, Montana will be performed, so that by the early 1990's, an engineering data base on the reliability, availability, maintainability and performance of the system will be available to allow scaleup of the prototypical designs to the next development level. This Sixteenth Quarterly Technical Progress Report covers the period May 1, 1991 to July 31, 1991.

  3. A photolithographic fabrication technique for magnetohydrodynamic micropumps

    NASA Astrophysics Data System (ADS)

    Kuenstner, Stephen; Baylor, Martha-Elizabeth

    2014-03-01

    Magnetohydrodynamic (MHD) devices use perpendicular electric and magnetic fields to exert a Lorentz body force on a conducting fluid. Miniaturized MHD devices have been used to create pumps, stirrers, heat exchangers, and microfluidic networks. Compared to mechanical micropumps, MHD micropumps are appealing because they require no moving parts, which simplifies fabrication, and because they are amenable to electronic control. This abstract reports the fabrication and testing of a centimeter-scale MHD pump using a thiol-ene/methacrylate-based photopolymer and mask-based photolithographic technique. Pumps like this one could simplify the fabrication of sophisticated optofluidic devices, including liquid-core, liquid cladding (L2) waveguides, which are usually created with PDMS using stamps, or etched into silicon wafers. The photolithographic technique demonstrated here requires only one masking step to create fluid channels with complex geometries.

  4. Magnetohydrodynamic Augmented Propulsion Experiment

    NASA Technical Reports Server (NTRS)

    Litchford, Ron J.; Cole, John; Lineberry, John; Chapman, Jim; Schmidt, Harold; Cook, Stephen (Technical Monitor)

    2002-01-01

    A fundamental obstacle to routine space access is the specific energy limitations associated with chemical fuels. In the case of vertical take-off, the high thrust needed for vertical liftoff and acceleration to orbit translates into power levels in the 10 GW range. Furthermore, useful payload mass fractions are possible only if the exhaust particle energy (i.e., exhaust velocity) is much greater than that available with traditional chemical propulsion. The electronic binding energy released by the best chemical reactions (e.g., LOX/LH2 for example, is less than 2 eV per product molecule (approx. 1.8 eV per H2O molecule), which translates into particle velocities less than 5 km/s. Useful payload fractions, however, will require exhaust velocities exceeding 15 km/s (i.e., particle energies greater than 20 eV). As an added challenge, the envisioned hypothetical RLV (reusable launch vehicle) should accomplish these amazing performance feats while providing relatively low acceleration levels to orbit (2-3g maximum). From such fundamental considerations, it is painfully obvious that planned and current RLV solutions based on chemical fuels alone represent only a temporary solution and can only result in minor gains, at best. What is truly needed is a revolutionary approach that will dramatically reduce the amount of fuel and size of the launch vehicle. This implies the need for new compact high-power energy sources as well as advanced accelerator technologies for increasing engine exhaust velocity. Electromagnetic acceleration techniques are of immense interest since they can be used to circumvent the thermal limits associated with conventional propulsion systems. This paper describes the Magnetohydrodynamic Augmented Propulsion Experiment (MAPX) being undertaken at NASA Marshall Space Flight Center (MSFC). In this experiment, a 1-MW arc heater is being used as a feeder for a 1-MW magnetohydrodynamic (MHD) accelerator. The purpose of the experiment is to demonstrate

  5. Micromachined magnetohydrodynamic actuators and sensors

    DOEpatents

    Lee, Abraham P.; Lemoff, Asuncion V.

    2000-01-01

    A magnetohydrodynamic (MHD) micropump and microsensor which utilizes micromachining to integrate the electrodes with microchannels and includes a magnet for producing magnetic fields perpendicular to both the electrical current direction and the fluid flow direction. The magnet can also be micromachined and integrated with the micropump using existing technology. The MHD micropump, for example, can generate continuous, reversible flow, with readily controllable flow rates. The flow can be reversed by either reversing the electrical current flow or reversing the magnetic field. By mismatching the electrodes, a swirling vortex flow can be generated for potential mixing applications. No moving parts are necessary and the dead volume is minimal. The micropumps can be placed at any position in a fluidic circuit and a combination of micropumps can generate fluidic plugs and valves.

  6. Scale locality of magnetohydrodynamic turbulence.

    PubMed

    Aluie, Hussein; Eyink, Gregory L

    2010-02-26

    We investigate the scale locality of cascades of conserved invariants at high kinetic and magnetic Reynold's numbers in the "inertial-inductive range" of magnetohydrodynamic (MHD) turbulence, where velocity and magnetic field increments exhibit suitable power-law scaling. We prove that fluxes of total energy and cross helicity-or, equivalently, fluxes of Elsässer energies-are dominated by the contributions of local triads. Flux of magnetic helicity may be dominated by nonlocal triads. The magnetic stretching term may also be dominated by nonlocal triads, but we prove that it can convert energy only between velocity and magnetic modes at comparable scales. We explain the disagreement with numerical studies that have claimed conversion nonlocally between disparate scales. We present supporting data from a 1024{3} simulation of forced MHD turbulence.

  7. Production of MHD fluid

    DOEpatents

    Lacey, James J.; Kurtzrock, Roy C.; Bienstock, Daniel

    1976-08-24

    A hot gaseous fluid of low ash content, suitable for use in open-cycle MHD (magnetohydrodynamic) power generation, is produced by means of a three-stage process comprising (1) partial combustion of a fossil fuel to produce a hot gaseous product comprising CO.sub.2 CO, and H.sub.2 O, (2) reformation of the gaseous product from stage (1) by means of a fluidized char bed, whereby CO.sub.2 and H.sub.2 O are converted to CO and H.sub.2, and (3) combustion of CO and H.sub.2 from stage (2) to produce a low ash-content fluid (flue gas) comprising CO.sub.2 and H.sub.2 O and having a temperature of about 4000.degree. to 5000.degree.F.

  8. Reduced Extended MHD

    NASA Astrophysics Data System (ADS)

    Morrison, P. J.; Abdelhamid, H. M.; Grasso, D.; Hazeltine, R. D.; Lingam, M.; Tassi, E.

    2015-11-01

    Over the years various reduced fluid models have been obtained for modeling plasmas, with the goal of capturing important physics while maintaining computability. Such models have included the physics contained in various generalizations of Ohm's law, including Hall drift and electron inertia. In a recent publication it was shown that full 3D extended MHD is a Hamiltonian system by finding its noncanonical Poisson bracket. Subsequently, this bracket was shown to be derivable from that for Hall MHD by a series of remarkable transformations, which greatly simplifies the proof of the Jacobi identity and allows one to immediately obtain generalizations of the helicity and cross helicity. In this poster we use this structure to obtain exact reduced fluid models with the effects of full two-fluid theory. Results of numerical computations of collisionless reconnection using an exact reduced 4-field model will be presented and analytical comparisons of mode structure of previous reduced models will be made.

  9. Development of three-dimensional magnetohydrodynamic model for solar corona and solar wind simulation

    NASA Astrophysics Data System (ADS)

    Yuan, Xingqiu; Trichtchenko, Larisa; Boteler, David

    Propagation of coronal mass ejections from solar surface to the Earth magnetosphere is strongly influenced by the conditions in solar corona and ambient solar wind. Thus, reliable simulation of the background solar wind is the primary task toward the development of numerical model for the transient events. In this paper we introduce a new numerical model which has been specifically designed for numerical study of the solar corona and ambient solar wind. This model is based on our recently developed three-dimensional Spherical Coordinate Adaptive Magneto-Hydro-Dynamic (MHD) code (SCA-MHD-3D) [Yuan et al., 2009]. Modifications has been done to include the observed magnetic field at the photosphere as inner boundary conditions. The energy source term together with reduced plasma gamma are used in the nonlinear MHD equations in order to simulate the solar wind acceleration from subsonic speed at solar surface to supersonic speed at the inter-heliosphere region, and the absorbing boundary conditions are used at the solar surface. This model has been applied to simulate the background solar wind condition for several different solar rotations, and comparison between the observation and model output have shown that it reproduces many features of solar wind, including open and closed magnetic fields, fast and slow solar wind speed, sector boundaries, etc.

  10. Magnetohydrodynamics with Embedded Particle-in-Cell Simulation of Mercury's Magnetosphere

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Toth, G.; Jia, X.; Gombosi, T. I.; Markidis, S.

    2015-12-01

    Mercury's magnetosphere is much more dynamic than other planetary magnetospheres because of Mercury's weak intrinsic magnetic field and its proximity to the Sun. Magnetic reconnection and Kelvin-Helmholtz phenomena occur in Mercury's magnetopause and magnetotail at higher frequencies than in other planetary magnetosphere. For instance, chains of flux transfer events (FTEs) on the magnetopause, have been frequentlyobserved by the the MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) spacecraft (Slavin et al., 2012). Because ion Larmor radius is comparable to typical spatial scales in Mercury's magnetosphere, finite Larmor radius effects need to be accounted for. In addition, it is important to take in account non-ideal dissipation mechanisms to accurately describe magnetic reconnection. A kinetic approach allows us to model these phenomena accurately. However, kinetic global simulations, even for small-size magnetospheres like Mercury's, are currently unfeasible because of the high computational cost. In this work, we carry out global simulations of Mercury's magnetosphere with the recently developed MHD-EPIC model, which is a two-way coupling of the extended magnetohydrodynamic (XMHD) code BATS-R-US with the implicit Particle-in-Cell (PIC) model iPIC3D. The PIC model can cover the regions where kinetic effects are most important, such as reconnection sites. The BATS-R-US code, on the other hand, can efficiently handle the rest of the computational domain where the MHD or Hall MHD description is sufficient. We will present our preliminary results and comparison with MESSENGER observations.

  11. M3D project for simulation studies of plasmas

    SciTech Connect

    Park, W.; Belova, E.V.; Fu, G.Y.; Strauss, H.R.; Sugiyama, L.E.

    1998-12-31

    The M3D (Multi-level 3D) project carries out simulation studies of plasmas of various regimes using multi-levels of physics, geometry, and mesh schemes in one code package. This paper and papers by Strauss, Sugiyama, and Belova in this workshop describe the project, and present examples of current applications. The currently available physics models of the M3D project are MHD, two-fluids, gyrokinetic hot particle/MHD hybrid, and gyrokinetic particle ion/two-fluid hybrid models. The code can be run with both structured and unstructured meshes.

  12. MHD power generation: not now, but ever

    SciTech Connect

    Not Available

    1981-10-01

    The basic concept of magnetohydrodynamics (MHD) has been known for over 100 years, but commercial viability is still a decade or more away despite US-Soviet collaborations to solve engineering problems. The simplicity of the concept offers advantages in terms of stress and efficiency, but implementation requires high-conductivity fluids and specially-designed subsystems. Other problems include the Hall field effect, the size and flux density requirements of superconducting magnets, ash, seed recovery, power inversion, and channel design. Researchers are developing both open-cycle and closed-cycle systems as well as technologies based on MHD and steam bottoming and MHD cogeneration. First-generation MHD plants will probably stress reliability above efficiency. Military applications could include space power generation. 4 figures. (DCK)

  13. MHD coal-fired flow facility. Annual technical progress report, October 1979-September 1980

    SciTech Connect

    Alstatt, M.C.; Attig, R.C.; Brosnan, D.A.

    1981-03-01

    The University of Tennessee Space Institute (UTSI) reports on significant activity, task status, planned research, testing, development, and conclusions for the Magnetohydrodynamics (MHD) Coal-Fired Flow Faclity (CFFF) and the Energy Conversion Facility (ECF).

  14. Magnetohydrodynamic Turbulence in Accretion Discs: A Test Case for Petascale Computing in Astrophysics

    NASA Astrophysics Data System (ADS)

    Joos, M.; Fromang, S.; Méheut, H.

    2015-10-01

    Angular momentum transport in accretion discs is one of the major issues of modern astrophysics and is crucial to understand as various astrophysical problematics as black hole dynamics or planet formation. Angular momentum transport relies on magnetohydrodynamic (MHD) turbulence, responsible for the non-linear evolution of the magneto-rotational instability (MRI). 3D simulations are essential to determine the physical properties of the flow resulting from that instability. In particular, the angular momentum transport rate induced by the MRI is difficult to estimate, depending on dissipation rates which are linked to viscous and resistive scales. These dissipation scales can be much smaller than the typical scale of the system and to simulate flows with such properties is very challenging. We recently realized a simulation on a BlueGene/Q with the smallest viscous dissipation coefficient ever reached. We discuss the challenges encountered in this context and the developments realized regarding efficient parallel Input/Output, hybridation and porting on GPGPU.

  15. Europeana and 3D

    NASA Astrophysics Data System (ADS)

    Pletinckx, D.

    2011-09-01

    The current 3D hype creates a lot of interest in 3D. People go to 3D movies, but are we ready to use 3D in our homes, in our offices, in our communication? Are we ready to deliver real 3D to a general public and use interactive 3D in a meaningful way to enjoy, learn, communicate? The CARARE project is realising this for the moment in the domain of monuments and archaeology, so that real 3D of archaeological sites and European monuments will be available to the general public by 2012. There are several aspects to this endeavour. First of all is the technical aspect of flawlessly delivering 3D content over all platforms and operating systems, without installing software. We have currently a working solution in PDF, but HTML5 will probably be the future. Secondly, there is still little knowledge on how to create 3D learning objects, 3D tourist information or 3D scholarly communication. We are still in a prototype phase when it comes to integrate 3D objects in physical or virtual museums. Nevertheless, Europeana has a tremendous potential as a multi-facetted virtual museum. Finally, 3D has a large potential to act as a hub of information, linking to related 2D imagery, texts, video, sound. We describe how to create such rich, explorable 3D objects that can be used intuitively by the generic Europeana user and what metadata is needed to support the semantic linking.

  16. Magnetohydrodynamic energy conversion by using convexly divergent channel

    SciTech Connect

    Murakami, Tomoyuki; Okuno, Yoshihiro

    2009-12-21

    We describe a magnetohydrodynamic (MHD) electrical power generator equipped with a convexly divergent channel, as determined through shock-tunnel-based experiments. The quality of MHD power-generating plasma and the energy conversion efficiency in the convexly divergent channel are compared with those from previous linearly divergent channel. The divergence enhancement in the channel upstream is effective for suppressing an excessive increase in static pressure, whereby notably high isentropic efficiency is achieved.

  17. Investigation of a liquid-metal magnetohydrodynamic power system.

    NASA Technical Reports Server (NTRS)

    Elliott, D. G.; Hays, L. G.; Cerini, D. J.; Bogdanoff, D. W.

    1972-01-01

    Liquid-metal magnetohydrodynamic power conversion is being investigated for nuclear-electric propulsion. A liquid-metal MHD converter has no moving mechanical parts and requires a heat source temperature of only 1300 K. Cycle efficiencies of 5% to 8% for single-stage converters and 10% for multistage converters appear attainable. The specific weight of a 240 kWe MHD power plant has been estimated as 30 kg/kWe with shielding for unmanned science missions.

  18. 3d-3d correspondence revisited

    NASA Astrophysics Data System (ADS)

    Chung, Hee-Joong; Dimofte, Tudor; Gukov, Sergei; Sułkowski, Piotr

    2016-04-01

    In fivebrane compactifications on 3-manifolds, we point out the importance of all flat connections in the proper definition of the effective 3d {N}=2 theory. The Lagrangians of some theories with the desired properties can be constructed with the help of homological knot invariants that categorify colored Jones polynomials. Higgsing the full 3d theories constructed this way recovers theories found previously by Dimofte-Gaiotto-Gukov. We also consider the cutting and gluing of 3-manifolds along smooth boundaries and the role played by all flat connections in this operation.

  19. 3d-3d correspondence revisited

    DOE PAGES

    Chung, Hee -Joong; Dimofte, Tudor; Gukov, Sergei; Sułkowski, Piotr

    2016-04-21

    In fivebrane compactifications on 3-manifolds, we point out the importance of all flat connections in the proper definition of the effective 3d N = 2 theory. The Lagrangians of some theories with the desired properties can be constructed with the help of homological knot invariants that categorify colored Jones polynomials. Higgsing the full 3d theories constructed this way recovers theories found previously by Dimofte-Gaiotto-Gukov. As a result, we also consider the cutting and gluing of 3-manifolds along smooth boundaries and the role played by all flat connections in this operation.

  20. Modeling RedOx-based magnetohydrodynamics in three-dimensional microfluidic channels

    NASA Astrophysics Data System (ADS)

    Kabbani, Hussameddine; Wang, Aihua; Luo, Xiaobing; Qian, Shizhi

    2007-08-01

    RedOx-based magnetohydrodynamic (MHD) flows in three-dimensional microfluidic channels are investigated theoretically with a coupled mathematical model consisting of the Nernst-Planck equations for the concentrations of ionic species, the local electroneutrality condition for the electric potential, and the Navier-Stokes equations for the flow field. A potential difference is externally applied across two planar electrodes positioned along the opposing walls of a microchannel that is filled with a dilute RedOx electrolyte solution, and a Faradaic current transmitted through the solution results. The entire device is positioned under a magnetic field which can be provided by either a permanent magnet or an electromagnet. The interaction between the current density and the magnetic field induces Lorentz forces, which can be used to pump and/or stir fluids for microfluidic applications. The induced currents and flow rates in three-dimensional (3D) planar channels obtained from the full 3D model are compared with the experimental data obtained from the literature and those obtained from our previous two-dimensional mathematical model. A closed form approximation for the average velocity (flow rate) in 3D planar microchannels is derived and validated by comparing its predictions with the results obtained from the full 3D model and the experimental data obtained from the literature. The closed form approximation can be used to optimize the dimensions of the channel and to determine the magnitudes and polarities of the prescribed currents in MHD networks so as to achieve the desired flow patterns and flow rates.

  1. MHD processes in the outer heliosphere

    NASA Technical Reports Server (NTRS)

    Burlaga, L. F.

    1984-01-01

    The magnetic field measurements from Voyager and the magnetohydrodynamic (MHD) processes in the outer heliosphere are reviewed. A bibliography of the experimental and theoretical work concerning magnetic fields and plasmas observed in the outer heliosphere is given. Emphasis in this review is on basic concepts and dynamical processes involving the magnetic field. The theory that serves to explain and unify the interplanetary magnetic field and plasma observations is magnetohydrodynamics. Basic physical processes and observations that relate directly to solutions of the MHD equations are emphasized, but obtaining solutions of this complex system of equations involves various assumptions and approximations. The spatial and temporal complexity of the outer heliosphere and some approaches for dealing with this complexity are discussed.

  2. Global Magnetohydrodynamic Modeling of the Solar Corona

    NASA Technical Reports Server (NTRS)

    Linker, Jon A.

    1997-01-01

    Under this contract, we have continued our investigations of the large scale structure of the solar corona and inner heliosphere using global magnetohydrodynamic (MHD) simulations. These computations have also formed the basis for studies of coronal mass ejections (CMES) using realistic coronal configurations. We have developed a technique for computing realistic magnetohydrodynamic (MHD) computations of the solar corona and inner heliosphere. To perform computations that can be compared with specific observations, it is necessary to incorporate solar observations into the boundary conditions. We have used the Wilcox Solar Observatory synoptic maps (collected during a solar rotation by daily measurements of the line-of-sight magnetic field at central meridian) to specify the radial magnetic field (B,) at the photosphere. For the initial condition, we use a potential magnetic field consistent with the specified distribution of B, at the lower boundary, and a wind solution consistent with the specified plasma density and temperature at the solar surface. Together this initial condition forms a (non-equilibrium) approximation of the state of the solar corona for the time-dependent MHD computation. The MHD equations are then integrated in time to steady state. Here we describe solutions relevant to a recent solar eclipse, as well as Ulysses observations. We have also developed a model configuration of solar minimum, useful for studying CME initiation and propagation.

  3. Global magnetohydrodynamic simulations on multiple GPUs

    NASA Astrophysics Data System (ADS)

    Wong, Un-Hong; Wong, Hon-Cheng; Ma, Yonghui

    2014-01-01

    Global magnetohydrodynamic (MHD) models play the major role in investigating the solar wind-magnetosphere interaction. However, the huge computation requirement in global MHD simulations is also the main problem that needs to be solved. With the recent development of modern graphics processing units (GPUs) and the Compute Unified Device Architecture (CUDA), it is possible to perform global MHD simulations in a more efficient manner. In this paper, we present a global magnetohydrodynamic (MHD) simulator on multiple GPUs using CUDA 4.0 with GPUDirect 2.0. Our implementation is based on the modified leapfrog scheme, which is a combination of the leapfrog scheme and the two-step Lax-Wendroff scheme. GPUDirect 2.0 is used in our implementation to drive multiple GPUs. All data transferring and kernel processing are managed with CUDA 4.0 API instead of using MPI or OpenMP. Performance measurements are made on a multi-GPU system with eight NVIDIA Tesla M2050 (Fermi architecture) graphics cards. These measurements show that our multi-GPU implementation achieves a peak performance of 97.36 GFLOPS in double precision.

  4. [Nonlinear magnetohydrodynamics

    SciTech Connect

    Not Available

    1994-01-01

    Resistive MHD equilibrium, even for small resistivity, differs greatly from ideal equilibrium, as do the dynamical consequences of its instabilities. The requirement, imposed by Faraday`s law, that time independent magnetic fields imply curl-free electric fields, greatly restricts the electric fields allowed inside a finite-resistivity plasma. If there is no flow and the implications of the Ohm`s law are taken into account (and they need not be, for ideal equilibria), the electric field must equal the resistivity times the current density. The vanishing of the divergence of the current density then provides a partial differential equation which, together with boundary conditions, uniquely determines the scalar potential, the electric field, and the current density, for any given resistivity profile. The situation parallels closely that of driven shear flows in hydrodynamics, in that while dissipative steady states are somewhat more complex than ideal ones, there are vastly fewer of them to consider. Seen in this light, the vast majority of ideal MHD equilibria are just irrelevant, incapable of being set up in the first place. The steady state whose stability thresholds and nonlinear behavior needs to be investigated ceases to be an arbitrary ad hoc exercise dependent upon the whim of the investigator, but is determined by boundary conditions and choice of resistivity profile.

  5. Computation of Multi-region Relaxed Magnetohydrodynamic Equilibria

    SciTech Connect

    Hudson, S. R.; Dewar, R. L.; Dennis, G.; Hole, M. J.; McGann, M.; von Nessi, G.; Lazerson, S.

    2013-03-29

    We describe the construction of stepped-pressure equilibria as extrema of a multi-region, relaxed magnetohydrodynamic (MHD) energy functional that combines elements of ideal MHD and Taylor relaxation, and which we call MRXMHD. The model is compatible with Hamiltonian chaos theory and allows the three-dimensional MHD equilibrium problem to be formulated in a well-posed manner suitable for computation. The energy-functional is discretized using a mixed finite-element, Fourier representation for the magnetic vector potential and the equilibrium geometry; and numerical solutions are constructed using the stepped-pressure equilibrium code, SPEC. Convergence studies with respect to radial and Fourier resolution are presented.

  6. Magnetohydrodynamic turbulence: Generalized formulation and extension to compressible cases

    SciTech Connect

    Shivamoggi, Bhimsen K.

    2008-06-15

    A general framework that incorporates the Iroshnikov-Kraichnan (IK) and Goldreich-Sridhar (GS) phenomenalogies of magnetohydrodynamic (MHD) turbulence is developed. This affords a clarification of the regimes of validity of the IK and GS models and hence help resolve some controversies on this aspect. This general formulation appears to have a certain robustness as revealed here by its form invariance with respect to inclusion of compressible effects. Generalizations of the IK and GS spectra to compressible MHD turbulence are given. These two branches are shown to merge with the MHD shockwave spectrum, as to be expected, in the infinite compressibility limit.

  7. Entropy generation analysis of magnetohydrodynamic induction devices

    NASA Astrophysics Data System (ADS)

    Salas, Hugo; Cuevas, Sergio; López de Haro, Mariano

    1999-10-01

    Magnetohydrodynamic (MHD) induction devices such as electromagnetic pumps or electric generators are analysed within the approach of entropy generation. The flow of an electrically-conducting incompressible fluid in an MHD induction machine is described through the well known Hartmann model. Irreversibilities in the system due to ohmic dissipation, flow friction and heat flow are included in the entropy-generation rate. This quantity is used to define an overall efficiency for the induction machine that considers the total loss caused by process irreversibility. For an MHD generator working at maximum power output with walls at constant temperature, an optimum magnetic field strength (i.e. Hartmann number) is found based on the maximum overall efficiency.

  8. Action principles for extended magnetohydrodynamic models

    SciTech Connect

    Keramidas Charidakos, I.; Lingam, M.; Morrison, P. J.; White, R. L.; Wurm, A.

    2014-09-15

    The general, non-dissipative, two-fluid model in plasma physics is Hamiltonian, but this property is sometimes lost or obscured in the process of deriving simplified (or reduced) two-fluid or one-fluid models from the two-fluid equations of motion. To ensure that the reduced models are Hamiltonian, we start with the general two-fluid action functional, and make all the approximations, changes of variables, and expansions directly within the action context. The resulting equations are then mapped to the Eulerian fluid variables using a novel nonlocal Lagrange-Euler map. Using this method, we recover Lüst's general two-fluid model, extended magnetohydrodynamic (MHD), Hall MHD, and electron MHD from a unified framework. The variational formulation allows us to use Noether's theorem to derive conserved quantities for each symmetry of the action.

  9. Nuclear magnetohydrodynamic EMP, solar storms, and substorms

    SciTech Connect

    Rabinowitz, M. ); Meliopoulous, A.P.S.; Glytsis, E.N. . School of Electrical Engineering); Cokkinides, G.J. )

    1992-10-20

    In addition to a fast electromagnetic pulse (EMP), a high altitude nuclear burst produces a relatively slow magnetohydrodynamic EMP (MHD EMP), whose effects are like those from solar storm geomagnetically induced currents (SS-GIC). The MHD EMP electric field E [approx lt] 10[sup [minus] 1] V/m and lasts [approx lt] 10[sup 2] sec, whereas for solar storms E [approx gt] 10[sup [minus] 2] V/m and lasts [approx gt] 10[sup 3] sec. Although the solar storm electric field is lower than MHD EMP, the solar storm effects are generally greater due to their much longer duration. Substorms produce much smaller effects than SS-GIC, but occur much more frequently. This paper describes the physics of such geomagnetic disturbances and analyzes their effects.

  10. MHD memes

    NASA Astrophysics Data System (ADS)

    Dewar, R. L.; Mills, R.; Hole, M. J.

    2009-05-01

    The celebration of Allan Kaufman's 80th birthday was an occasion to reflect on a career that has stimulated the mutual exchange of ideas (or memes in the terminology of Richard Dawkins) between many researchers. This paper will revisit a meme Allan encountered in his early career in magnetohydrodynamics, the continuation of a magnetohydrodynamic mode through a singularity, and will also mention other problems where Allan's work has had a powerful cross-fertilizing effect in plasma physics and other areas of physics and mathematics. To resolve the continuation problem we regularize the Newcomb equation, solve it in terms of Legendre functions of imaginary argument, and define the small weak solutions of the Newcomb equation as generalized functions in the manner of Lighthill, i.e. via a limiting sequence of analytic functions that connect smoothly across the singularity.

  11. The optimization air separation plants for combined cycle MHD-power plant applications

    NASA Technical Reports Server (NTRS)

    Juhasz, A. J.; Springmann, H.; Greenberg, R.

    1980-01-01

    Some of the design approaches being employed during a current supported study directed at developing an improved air separation process for the production of oxygen enriched air for magnetohydrodynamics (MHD) combustion are outlined. The ultimate objective is to arrive at conceptual designs of air separation plants, optimized for minimum specific power consumption and capital investment costs, for integration with MHD combined cycle power plants.

  12. 3D and Education

    NASA Astrophysics Data System (ADS)

    Meulien Ohlmann, Odile

    2013-02-01

    Today the industry offers a chain of 3D products. Learning to "read" and to "create in 3D" becomes an issue of education of primary importance. 25 years professional experience in France, the United States and Germany, Odile Meulien set up a personal method of initiation to 3D creation that entails the spatial/temporal experience of the holographic visual. She will present some different tools and techniques used for this learning, their advantages and disadvantages, programs and issues of educational policies, constraints and expectations related to the development of new techniques for 3D imaging. Although the creation of display holograms is very much reduced compared to the creation of the 90ies, the holographic concept is spreading in all scientific, social, and artistic activities of our present time. She will also raise many questions: What means 3D? Is it communication? Is it perception? How the seeing and none seeing is interferes? What else has to be taken in consideration to communicate in 3D? How to handle the non visible relations of moving objects with subjects? Does this transform our model of exchange with others? What kind of interaction this has with our everyday life? Then come more practical questions: How to learn creating 3D visualization, to learn 3D grammar, 3D language, 3D thinking? What for? At what level? In which matter? for whom?

  13. Regularity criterion for the 3D Hall-magneto-hydrodynamics

    NASA Astrophysics Data System (ADS)

    Dai, Mimi

    2016-07-01

    This paper studies the regularity problem for the 3D incompressible resistive viscous Hall-magneto-hydrodynamic (Hall-MHD) system. The Kolmogorov 41 phenomenological theory of turbulence [14] predicts that there exists a critical wavenumber above which the high frequency part is dominated by the dissipation term in the fluid equation. Inspired by this idea, we apply an approach of splitting the wavenumber combined with an estimate of the energy flux to obtain a new regularity criterion. The regularity condition presented here is weaker than conditions in the existing criteria (Prodi-Serrin type criteria) for the 3D Hall-MHD system.

  14. Flow development and analysis of MHD generators and seawater thrusters

    SciTech Connect

    Doss, E.D. ); Roy, G.D. )

    1992-03-01

    In this paper, the flow characteristics inside magnetohydrodynamic (MHD) plasma generators and seawater thrusters are analyzed and are compared using a three-dimensional computer model that solves the governing partial differential equations for fluid flow and electrical fields. Calculations have been performed for a Faraday plasma generator and for a continuous electrode seawater thruster. The results of the calculations show that the effects caused by the interaction of the MHD forces with the fluid flow are strongly manifested in the case of the MHD generator as compared to the flow development in the MHD thruster. The existence of velocity overshoots over the sidewalls confirm previously published results for MHD generators with strong MHD interaction. For MHD thrusters, the velocity profile is found to be slightly flatter over the sidewall as compared to that over the electrode wall. As a result, distinct enhancement of the skin friction exists over the sidewalls of MHD generators in comparison to that of MHD thrusters. Plots of velocity profiles and skin friction distributions are presented to illustrate and compare the flow development in MHD generators and thrusters.

  15. 3D Equilibrium Reconstructions in DIII-D

    NASA Astrophysics Data System (ADS)

    Lao, L. L.; Ferraro, N. W.; Strait, E. J.; Turnbull, A. D.; King, J. D.; Hirshman, H. P.; Lazarus, E. A.; Sontag, A. C.; Hanson, J.; Trevisan, G.

    2013-10-01

    Accurate and efficient 3D equilibrium reconstruction is needed in tokamaks for study of 3D magnetic field effects on experimentally reconstructed equilibrium and for analysis of MHD stability experiments with externally imposed magnetic perturbations. A large number of new magnetic probes have been recently installed in DIII-D to improve 3D equilibrium measurements and to facilitate 3D reconstructions. The V3FIT code has been in use in DIII-D to support 3D reconstruction and the new magnetic diagnostic design. V3FIT is based on the 3D equilibrium code VMEC that assumes nested magnetic surfaces. V3FIT uses a pseudo-Newton least-square algorithm to search for the solution vector. In parallel, the EFIT equilibrium reconstruction code is being extended to allow for 3D effects using a perturbation approach based on an expansion of the MHD equations. EFIT uses the cylindrical coordinate system and can include the magnetic island and stochastic effects. Algorithms are being developed to allow EFIT to reconstruct 3D perturbed equilibria directly making use of plasma response to 3D perturbations from the GATO, MARS-F, or M3D-C1 MHD codes. DIII-D 3D reconstruction examples using EFIT and V3FIT and the new 3D magnetic data will be presented. Work supported in part by US DOE under DE-FC02-04ER54698, DE-FG02-95ER54309 and DE-AC05-06OR23100.

  16. Accurate, meshless methods for magnetohydrodynamics

    NASA Astrophysics Data System (ADS)

    Hopkins, Philip F.; Raives, Matthias J.

    2016-01-01

    Recently, we explored new meshless finite-volume Lagrangian methods for hydrodynamics: the `meshless finite mass' (MFM) and `meshless finite volume' (MFV) methods; these capture advantages of both smoothed particle hydrodynamics (SPH) and adaptive mesh refinement (AMR) schemes. We extend these to include ideal magnetohydrodynamics (MHD). The MHD equations are second-order consistent and conservative. We augment these with a divergence-cleaning scheme, which maintains nabla \\cdot B≈ 0. We implement these in the code GIZMO, together with state-of-the-art SPH MHD. We consider a large test suite, and show that on all problems the new methods are competitive with AMR using constrained transport (CT) to ensure nabla \\cdot B=0. They correctly capture the growth/structure of the magnetorotational instability, MHD turbulence, and launching of magnetic jets, in some cases converging more rapidly than state-of-the-art AMR. Compared to SPH, the MFM/MFV methods exhibit convergence at fixed neighbour number, sharp shock-capturing, and dramatically reduced noise, divergence errors, and diffusion. Still, `modern' SPH can handle most test problems, at the cost of larger kernels and `by hand' adjustment of artificial diffusion. Compared to non-moving meshes, the new methods exhibit enhanced `grid noise' but reduced advection errors and diffusion, easily include self-gravity, and feature velocity-independent errors and superior angular momentum conservation. They converge more slowly on some problems (smooth, slow-moving flows), but more rapidly on others (involving advection/rotation). In all cases, we show divergence control beyond the Powell 8-wave approach is necessary, or all methods can converge to unphysical answers even at high resolution.

  17. Broken Symmetry and Coherent Structure in MHD Turbulence

    NASA Technical Reports Server (NTRS)

    Shebalin, John V.

    2007-01-01

    Absolute equilibrium ensemble theory for ideal homogeneous magnetohydrodynamic (MHD) turbulence is fairly well developed. Theory and Simulation indicate that ideal MHD turbulence non-ergodic and contains coherent structure. The question of applicability real (i.e., dissipative) MHD turbulence is examined. Results from several very long time numerical simulations on a 64(exp 3) grid are presented. It is seen that coherent structure begins to form before decay dominates over nonlinearity. The connection with inverse spectral cascades and selective decay will also be discussed.

  18. MHD augmented chemical rocket propulsion for space applications

    SciTech Connect

    Schulz, R.J.; Chapman, J.N.; Rhodes, R.P. )

    1992-07-01

    A performance analysis is carried out of a magnetohydrodynamic (MHD) augmented chemical thruster (based on a gaseous hydrogen-oxygen system) for space applications such as orbit transfer. The mathematical model used in the analysis is a one-dimensional flow model using equilibrium chemistry for the combustor, choked nozzle, and MHD channel portions of the system, and chemical nonequilibrium kinetics for the high area-ratio gas dynamic nozzle portion of the system. The performance of the chemical-MHD-augmented thruster is compared with that of a pure electric thruster of the same specific impulse level. 13 refs.

  19. MHD stability of incompressible coronal loops with radiative energy loss

    NASA Technical Reports Server (NTRS)

    An, C.-H.

    1983-01-01

    Previous studies of the magnetohydrodynamic (MHD) stability of solar coronal loops have not taken into account the effects of radiative energy loss in the energy equation. However, since coronal loops continuously lose energy by radiation and heat conduction, it is important to understand how these energy loss mechanisms affect MHD stability. We investigate the problem assuming that a magnetic loop has cylindrical geometry. As a first step, stability is studied for a localized mode, and the result is applied to a specific equilibrium. We find that the radiative energy loss effect not only changes the growth rate of ideally unstable modes, but also alters the stability boundary predicted by ideal MHD theory.

  20. MHD technology transfer, integration, and review committee

    NASA Astrophysics Data System (ADS)

    1990-05-01

    As part of Task 8 of the magnetohydrodynamic (MHD) Integrated Topping Cycle (ITC) project, TRW was given the responsibility to organize, charter and co-chair, with the Department of Energy (DOE), an MHD Technology Transfer, Integration and Review Committee (TTIRC). The TTIRC consists of an Executive Committee (EC) which acts as the governing body, and a General Committee (GC), also referred to as the main or full committee, consisting of representatives from the various POC contractors, participating universities and national laboratories, utilities, equipment suppliers, and other potential MHD users or investors. The purpose of the TTIRC is to: (1) review all Proof-of-Concept (POC) projects and schedules in the national MHD program; to assess their compatibility with each other and the first commercial MHD retrofit plant; (2) establish and implement technology transfer formats for users of this technology; (3) identify interfaces, issues, and funding structures directly impacting the success of the commercial retrofit; (4) investigate and identify the manner in which, and by whom, the above should be resolved; and (5) investigate and assess other participation (foreign and domestic) in the U.S. MHD Program. There are seven sections: introduction; Executive Committee and General Committee activity; Committee activities related to technology transfer; ongoing POC integration activities being performed under the auspices of the Executive Committee; recommendations passed on to the DOE by the Executive Committee; Planned activities for the next six months.

  1. Efficient magnetohydrodynamic simulations on graphics processing units with CUDA

    NASA Astrophysics Data System (ADS)

    Wong, Hon-Cheng; Wong, Un-Hong; Feng, Xueshang; Tang, Zesheng

    2011-10-01

    Magnetohydrodynamic (MHD) simulations based on the ideal MHD equations have become a powerful tool for modeling phenomena in a wide range of applications including laboratory, astrophysical, and space plasmas. In general, high-resolution methods for solving the ideal MHD equations are computationally expensive and Beowulf clusters or even supercomputers are often used to run the codes that implemented these methods. With the advent of the Compute Unified Device Architecture (CUDA), modern graphics processing units (GPUs) provide an alternative approach to parallel computing for scientific simulations. In this paper we present, to the best of the author's knowledge, the first implementation of MHD simulations entirely on GPUs with CUDA, named GPU-MHD, to accelerate the simulation process. GPU-MHD supports both single and double precision computations. A series of numerical tests have been performed to validate the correctness of our code. Accuracy evaluation by comparing single and double precision computation results is also given. Performance measurements of both single and double precision are conducted on both the NVIDIA GeForce GTX 295 (GT200 architecture) and GTX 480 (Fermi architecture) graphics cards. These measurements show that our GPU-based implementation achieves between one and two orders of magnitude of improvement depending on the graphics card used, the problem size, and the precision when comparing to the original serial CPU MHD implementation. In addition, we extend GPU-MHD to support the visualization of the simulation results and thus the whole MHD simulation and visualization process can be performed entirely on GPUs.

  2. 3D Imaging.

    ERIC Educational Resources Information Center

    Hastings, S. K.

    2002-01-01

    Discusses 3 D imaging as it relates to digital representations in virtual library collections. Highlights include X-ray computed tomography (X-ray CT); the National Science Foundation (NSF) Digital Library Initiatives; output peripherals; image retrieval systems, including metadata; and applications of 3 D imaging for libraries and museums. (LRW)

  3. Scalable implicit incompressible resistive MHD with stabilized FE and fully-coupled Newton–Krylov-AMG

    DOE PAGES

    Shadid, J. N.; Pawlowski, R. P.; Cyr, E. C.; Tuminaro, R. S.; Chacon, L.; Weber, P. D.

    2016-02-10

    Here, we discuss that the computational solution of the governing balance equations for mass, momentum, heat transfer and magnetic induction for resistive magnetohydrodynamics (MHD) systems can be extremely challenging. These difficulties arise from both the strong nonlinear, nonsymmetric coupling of fluid and electromagnetic phenomena, as well as the significant range of time- and length-scales that the interactions of these physical mechanisms produce. This paper explores the development of a scalable, fully-implicit stabilized unstructured finite element (FE) capability for 3D incompressible resistive MHD. The discussion considers the development of a stabilized FE formulation in context of the variational multiscale (VMS) method,more » and describes the scalable implicit time integration and direct-to-steady-state solution capability. The nonlinear solver strategy employs Newton–Krylov methods, which are preconditioned using fully-coupled algebraic multilevel preconditioners. These preconditioners are shown to enable a robust, scalable and efficient solution approach for the large-scale sparse linear systems generated by the Newton linearization. Verification results demonstrate the expected order-of-accuracy for the stabilized FE discretization. The approach is tested on a variety of prototype problems, that include MHD duct flows, an unstable hydromagnetic Kelvin–Helmholtz shear layer, and a 3D island coalescence problem used to model magnetic reconnection. Initial results that explore the scaling of the solution methods are also presented on up to 128K processors for problems with up to 1.8B unknowns on a CrayXK7.« less

  4. Magnetohydrodynamics Accelerator Research into Advanced Hypersonics (MARIAH). Part 2

    NASA Technical Reports Server (NTRS)

    Baughman, Jack A.; Micheletti, David A.; Nelson, Gordon L.; Simmons, Gloyd A.

    1997-01-01

    This report documents the activities, results, conclusions and recommendations of the Magnetohydrodynamics Accelerator Research Into Advanced Hypersonics (MARIAH) Project in which the use of magnetohydrodynamics (MHD) technology is investigated for its applicability to augment hypersonic wind tunnels. The long range objective of this investigation is to advance the development of ground test facilities to support the development of hypervelocity flight vehicles. The MHD accelerator adds kinetic energy directly to the wind tunnel working fluid, thereby increasing its Mach number to hypervelocity levels. Several techniques for MHD augmentation, as well as other physical characteristics of the process are studied to enhance the overall performance of hypersonic wind tunnel design. Specific recommendations are presented to improve the effectiveness of ground test facilities. The work contained herein builds on nearly four decades of research and experimentation by the aeronautics ground test and evaluation community, both foreign and domestic.

  5. Magnetohydrodynamics Accelerator Research Into Advanced Hypersonics (MARIAH). Part 1

    NASA Technical Reports Server (NTRS)

    Micheletti, David A.; Baughman, Jack A.; Nelson, Gordon L.; Simmons, Gloyd A.

    1997-01-01

    This report documents the activities, results, conclusions and recommendations of the Magnetohydrodynamics Accelerator Research Into Advanced Hypersonics (MARIAH) Project in which the use of magnetohydrodynamics (MHD) technology is investigated for its applicability to augment hypersonic wind tunnels. The long range objective of this investigation is to advance the development of ground test facilities to support the development of hypervelocity flight vehicles. The MHD accelerator adds kinetic energy directly to the wind tunnel working fluid, thereby increasing its Mach number to hypervelocity levels. Several techniques for MHD augmentation, as well as other physical characteristics of the process are studied to enhance the overall performance of hypersonic wind tunnel design. Specific recommendations are presented to improve the effectiveness of ground test facilities. The work contained herein builds on nearly four decades of research and experimentation by the aeronautics ground test and evaluation community, both foreign and domestic.

  6. 17th Workshop on MHD Stability Control: addressing the disruption challenge for ITER

    NASA Astrophysics Data System (ADS)

    Buttery, Richard

    2013-08-01

    This annual workshop on magnetohydrodynamic stability control was held on 5-7 November 2012 at Columbia University in the city of New York, in the aftermath of a violent hydrodynamic instability event termed 'Hurricane Sandy'. Despite these challenging circumstances, Columbia University managed an excellent meeting, enabling the full participation of the community. This Workshop has been held since 1996 to help in the development of understanding and control of magnetohydrodynamic (MHD) instabilities for future fusion reactors. It covers a wide range of stability topics—from disruptions, to tearing modes, error fields, edge-localized modes (ELMs), resistive wall modes (RWMs) and ideal MHD—spanning many device types (tokamaks, stellarators and reversed field pinches) to identify commonalities in the physics and a means of control. The theme for 2012 was 'addressing the disruption challenge for ITER', and thus the first day had a heavy focus on both the avoidance and mitigation of disruptions in ITER. Key elements included understanding how to apply 3D fields to maintain stability, as well as managing the disruption process itself through mitigating loads in the thermal quench and handling so called 'runaway electrons'. This culminated in a panel discussion on the disruption mitigation strategy for ITER, which noted that heat load asymmetries during the thermal quench appear to be an artifact of MHD processes, and that runaway electron generation may be inevitable, suggesting research should focus on control and dissipation of the runaway beam. The workshop was combined this year with the annual US-Japan MHD Workshop, with a special section looking more deeply at 'Fundamentals of 3D Perturbed Equilibrium Control', with interesting sessions on 3D equilibrium reconstruction, RWM physics, novel control concepts such as non-magnetic sensing, adaptive control, q < 2 tokamak operation, and the effects of flow. The final day turned to tearing mode interactions

  7. Slow shock and rotational discontinuity in MHD and Hall MHD models with anisotropic pressure

    NASA Astrophysics Data System (ADS)

    Hau, L.-N.; Wang, B.-J.

    2016-07-01

    Pressure anisotropy may modify the characteristics of magnetohydrodynamic (MHD) waves, in particular, the slow mode wave and the corresponding shocks and discontinuities. In this study the formation of slow shocks (SSs) in anisotropic plasmas is examined by solving the gyrotropic MHD and Hall MHD equations numerically for one-dimensional Riemann problem. The MHD shocks and discontinuities are generated by imposing a finite normal magnetic field on the Harris type current sheet with a guide magnetic By component. It is shown that anomalous SSs moving faster than the intermediate wave or with positive density-magnetic field correlation may be generated in gyrotropic MHD and Hall MHD models. Moreover, for some parameter values SSs may exhibit upstream wave trains with right-handed polarization in contrast with the earlier prediction that SSs shall possess downstream left-hand polarized wave trains based on the isotropic Hall MHD theory. For the cases of By ≠ 0, SSs with increased density and decreased magnetic field followed by noncoplanar intermediate mode or rotational discontinuity (RD)-like structures similar to the compound SS-RD structures observed in space plasma environments may possibly form in symmetric and asymmetric current layers. The Walén relation of these anomalous RDs without the correction of pressure anisotropy may significantly be violated.

  8. Global MHD modeling of an ICME focused on the physics involved in an ICME interacting with a solar wind

    NASA Astrophysics Data System (ADS)

    An, Jun-Mo; Magara, Tetsuya; Inoue, Satoshi; Hayashi, Keiji; Tanaka, Takashi

    2015-04-01

    We developed a three-dimensional (3D) magnetohydrodynamic (MHD) code to investigate the structure of a solar wind, the properties of a coronal mass ejection (CME) and the interaction between them. This MHD code is based on the finite volume method incorporating total variation diminishing (TVD) scheme with an unstructured grid system. In particular, this grid system can avoid the singularity at the north and south poles and relax tight CFL conditions around the poles, both of which would arise in a spherical coordinate system (Tanaka 1994). In this model, we first apply an MHD tomographic method (Hayashi et al. 2003) to interplanetary scintillation (IPS) observational data and derive a solar wind from the physical values obtained at 50 solar radii away from the Sun. By comparing the properties of this solar wind to observational data obtained near the Earth orbit, we confirmed that our model captures the velocity, temperature and density profiles of a solar wind near the Earth orbit. We then insert a spheromak-type CME (Kataoka et al. 2009) into the solar wind to reproduce an actual CME event occurred on 29 September 2013. This has been done by introducing a time-dependent boundary condition to the inner boundary of our simulation domain (50rs < r < 300rs). On the basis of a comparison between the properties of a simulated CME and observations near the Earth, we discuss the physics involved in an ICME interacting with a solar wind.

  9. MHD--Developing New Technology to Meet the Energy Crisis

    ERIC Educational Resources Information Center

    Fitch, Sandra S.

    1978-01-01

    Magnetohydrodynamics is a technology that could utilize the nation's most abundant fossil fuel and produce electrical energy more efficiently and cleanly than present-day turbines. A national research and development program is ongoing in Butte, Montana at the Montana Energy and MHD Research and Development Institute (MERDI). (Author/RK)

  10. Tokamak magneto-hydrodynamics and reference magnetic coordinates for simulations of plasma disruptions

    SciTech Connect

    Zakharov, Leonid E.; Li, Xujing

    2015-06-15

    This paper formulates the Tokamak Magneto-Hydrodynamics (TMHD), initially outlined by X. Li and L. E. Zakharov [Plasma Science and Technology 17(2), 97–104 (2015)] for proper simulations of macroscopic plasma dynamics. The simplest set of magneto-hydrodynamics equations, sufficient for disruption modeling and extendable to more refined physics, is explained in detail. First, the TMHD introduces to 3-D simulations the Reference Magnetic Coordinates (RMC), which are aligned with the magnetic field in the best possible way. The numerical implementation of RMC is adaptive grids. Being consistent with the high anisotropy of the tokamak plasma, RMC allow simulations at realistic, very high plasma electric conductivity. Second, the TMHD splits the equation of motion into an equilibrium equation and the plasma advancing equation. This resolves the 4 decade old problem of Courant limitations of the time step in existing, plasma inertia driven numerical codes. The splitting allows disruption simulations on a relatively slow time scale in comparison with the fast time of ideal MHD instabilities. A new, efficient numerical scheme is proposed for TMHD.

  11. Priority pollutant analysis of MHD-derived combustion products

    NASA Astrophysics Data System (ADS)

    Parks, Katherine D.

    An important factor in developing Magnetohydrodynamics (MHD) for commercial applications is environmental impact. Consequently, an effort was initiated to identify and quantify any possible undesirable minute chemical constituents in MHD waste streams, with special emphasis on the priority pollutant species. This paper discusses how priority pollutant analyses were used to accomplish the following goals at the University of Tennessee Space Institute (UTSI): comparison of the composition of solid combustion products collected from various locations along a prototypical MHD flow train during the firing of Illinois No. 6 and Montana Rosebud coals; comparison of solid waste products generated from MHD and conventional power plant technologies; and identification of a suitable disposal option for various MHD derived combustion products. Results from our ongoing research plans for gas phase sampling and analysis of priority pollutant volatiles, semi-volatiles, and metals are discussed.

  12. Method for manufacturing magnetohydrodynamic electrodes

    DOEpatents

    Killpatrick, Don H.; Thresh, Henry R.

    1982-01-01

    A method of manufacturing electrodes for use in a magnetohydrodynamic (MHD) generator comprising the steps of preparing a billet having a core 10 of a first metal, a tubular sleeve 12 of a second metal, and an outer sheath 14, 16, 18 of an extrusile metal; evacuating the space between the parts of the assembled billet; extruding the billet; and removing the outer jacket 14. The extruded bar may be made into electrodes by cutting and bending to the shape required for an MDH channel frame. The method forms a bond between the first metal of the core 10 and the second metal of the sleeve 12 strong enough to withstand a hot and corrosive environment.

  13. Relaxation model for extended magnetohydrodynamics: Comparison to magnetohydrodynamics for dense Z-pinches

    SciTech Connect

    Seyler, C. E.; Martin, M. R.

    2011-01-15

    It is shown that the two-fluid model under a generalized Ohm's law formulation and the resistive magnetohydrodynamics (MHD) can both be described as relaxation systems. In the relaxation model, the under-resolved stiff source terms constrain the dynamics of a set of hyperbolic equations to give the correct asymptotic solution. When applied to the collisional two-fluid model, the relaxation of fast time scales associated with displacement current and finite electron mass allows for a natural transition from a system where Ohm's law determines the current density to a system where Ohm's law determines the electric field. This result is used to derive novel algorithms, which allow for multiscale simulation of low and high frequency extended-MHD physics. This relaxation formulation offers an efficient way to implicitly advance the Hall term and naturally simulate a plasma-vacuum interface without invoking phenomenological models. The relaxation model is implemented as an extended-MHD code, which is used to analyze pulsed power loads such as wire arrays and ablating foils. Two-dimensional simulations of pulsed power loads are compared for extended-MHD and MHD. For these simulations, it is also shown that the relaxation model properly recovers the resistive-MHD limit.

  14. Two Types of Magnetohydrodynamic Sheath Jets

    NASA Astrophysics Data System (ADS)

    Kaburaki, Osamu

    2009-06-01

    Recent observations of astrophysical jets emanating from various galactic nuclei strongly suggest that a double-layered structure, or a spine-sheath structure, is likely to be their common feature. We propose that such a sheath jet structure can be formed magnetohydrodynamically within a valley of the magnetic pressures, which is formed between the peaks due to the poloidal and toroidal components, with the centrifugal force acting on the rotating sheath plasma being balanced by the hoop stress of the toroidal field. The poloidal field concentrated near the polar axis is maintained by a converging plasma flow toward the jet region, and the toroidal field is developed outside the jet cone owing to the poloidal current circulating through the jet. Under such situations, the set of magnetohydrodynamic (MHD) equations allows two main types of solutions, at least, in the region far from the footpoint. The first type solution describes the jets of marginally bound nature. This type is realized when the jet temperature decreases like a virial one, and neither the pressure-gradient nor the MHD forces, which are both determined consistently, cannot completely overcome the gravity, even at infinity. The second type is realized under an isothermal situation, and the gravity is cancelled exactly by the pressure-gradient force. Hence, the jets of this type are accelerated purely by the MHD force. It is also suggested that these two types correspond, respectively, to the jets from type I and II radio galaxies in the Fanaroff-Riley classification.

  15. Double-duct liquid metal magnetohydrodynamic engine

    DOEpatents

    Haaland, Carsten M.

    1995-01-01

    An internal combustion, liquid metal (LM) magnetohydrodynamic (MHD) engine and an alternating current (AC) magnetohydrodynamic generator, are used in combination to provide useful AC electric energy output. The engine design has-four pistons and a double duct configuration, with each duct containing sodium potassium liquid metal confined between free pistons located at either end of the duct. The liquid metal is forced to flow back and forth in the duct by the movement of the pistons, which are alternatively driven by an internal combustion process. In the MHD generator, the two LM-MHD ducts pass in close proximity through a Hartmann duct with output transformer. AC power is produced by operating the engine with the liquid metal in the two generator ducts always flowing in counter directions. The amount of liquid metal maintained in the ducts may be varied. This provides a variable stroke length for the pistons. The engine/generator provides variable AC power at variable frequencies that correspond to the power demands of the vehicular propulsion. Also the engine should maintain nearly constant efficiency throughout the range of power usage. Automobiles and trucks could be powered by the invention, with no transmission or power converter devices being required.

  16. Double-duct liquid metal magnetohydrodynamic engine

    DOEpatents

    Haaland, Carsten M.

    1997-01-01

    An internal combustion, liquid metal (LM) magnetohydrodynamic (MHD) engine and an alternating current (AC) magnetohydrodynamic generator, are used in combination to provide useful AC electric energy output. The engine design has four pistons and a double duct configuration, with each duct containing sodium potassium liquid metal confined between free pistons located at either end of the duct. The liquid metal is forced to flow back and forth in the duct by the movement of the pistons, which are alternatively driven by an internal combustion process. In the MHD generator, the two LM-MHD ducts pass in close proximity through a Hartmann duct with output transformer. AC power is produced by operating the engine with the liquid metal in the two generator ducts always flowing in counter directions. The amount of liquid metal maintained in the ducts may be varied. This provides a variable stroke length for the pistons. The engine/generator provides variable AC power at variable frequencies that correspond to the power demands of the vehicular propulsion. Also the engine should maintain nearly constant efficiency throughout the range of power usage. Automobiles and trucks could be powered by the invention, with no transmission or power converter devices being required.

  17. MHD turbulent processes

    NASA Technical Reports Server (NTRS)

    Montgomery, David

    1988-01-01

    Three areas of study in MHD turbulence are considered. These are the turbulent relaxation of the toroidal Z pinch, density fluctuations in MHD fluids, and MHD cellular automata. A Boolean computer game that updates a cellular representation in parallel and that has macroscopic averages converging to solutions of the two-dimensional MHD equations is discussed.

  18. ANALYTIC APPROXIMATE SEISMOLOGY OF PROPAGATING MAGNETOHYDRODYNAMIC WAVES IN THE SOLAR CORONA

    SciTech Connect

    Goossens, M.; Soler, R.; Arregui, I.

    2012-12-01

    Observations show that propagating magnetohydrodynamic (MHD) waves are ubiquitous in the solar atmosphere. The technique of MHD seismology uses the wave observations combined with MHD wave theory to indirectly infer physical parameters of the solar atmospheric plasma and magnetic field. Here, we present an analytical seismological inversion scheme for propagating MHD waves. This scheme uses the observational information on wavelengths and damping lengths in a consistent manner, along with observed values of periods or phase velocities, and is based on approximate asymptotic expressions for the theoretical values of wavelengths and damping lengths. The applicability of the inversion scheme is discussed and an example is given.

  19. Properties of mass-loading shocks. II - Magnetohydrodynamics. [of Giacobini-Zinner and Halley comets

    NASA Technical Reports Server (NTRS)

    Zank, G. P.; Oughton, S.; Neubauer, F. M.; Webb, G. M.

    1992-01-01

    The one-dimensional magnetohydrodynamics of mass-loading shocks is examined. These shocks, which are distinct from MHD shocks of classical nonreacting fluid dynamics and of combustion theory and which are characterized by the addition of mass within the shock transition, are to be found at comets and, depending upon circumstances, at nonmagnetized and weakly magnetized planets such as Venus and Mars. A completely general mass-loading form of the Hugoniot equation is derived, and some of the most important differences between mass-loading and nonreacting classical MHD shocks are identified. Two new types of MHD shocks are described which have no classical MHD analogues.

  20. Magnetohydrodynamic projects at the CDIF. Quarterly technical progress report, October 1, 1991--December 31, 1991

    SciTech Connect

    Not Available

    1991-12-31

    The Component Development and Integration Facility (CDIF) is a major US Department of Energy magnetohydrodynamic (MHD) test facility in Butte, Montana. The CDIF is operated by MSE, Inc. Within the national MHD program, MSE personnel are responsible for performing integration testing of vendor-supplied MHD power train components at the CDIF to support the goal of commercialization. During the first quarter of FY92, MHD testing was initiated. Off-line and on-line calibration tests were completed for the Endress+Hauser flowmeter, and thermal, conductivity, and electrical testing was initiated.

  1. Magnetohydrodynamic projects at the CDIF. Quarterly technical progress report, January 1--March 31, 1992

    SciTech Connect

    Not Available

    1992-08-01

    The Component Development and Integration Facility (CDIF) is a major U.S. Department of Energy magnetohydrodynamics (MHD) test facility in Butte, Montana. The CDIF is operated by MSE, Inc. Within the national MHD program, MSE personnel are responsible for performing integration testing of vendor-supplied MHD power train components at the CDIF to support the goal of commercialization. During the second quarter of FY92, a second external water leak on the iron-core magnet was repaired, and MHD testing was completed on February 11; this was the final testing of the workhorse hardware. Workhorse hardware was removed, and installation of the proof-of-concept (POC) combustor began.

  2. Solar Flares: Magnetohydrodynamic Processes

    NASA Astrophysics Data System (ADS)

    Shibata, Kazunari; Magara, Tetsuya

    2011-12-01

    This paper outlines the current understanding of solar flares, mainly focused on magnetohydrodynamic (MHD) processes responsible for producing a flare. Observations show that flares are one of the most explosive phenomena in the atmosphere of the Sun, releasing a huge amount of energy up to about 10^32 erg on the timescale of hours. Flares involve the heating of plasma, mass ejection, and particle acceleration that generates high-energy particles. The key physical processes for producing a flare are: the emergence of magnetic field from the solar interior to the solar atmosphere (flux emergence), local enhancement of electric current in the corona (formation of a current sheet), and rapid dissipation of electric current (magnetic reconnection) that causes shock heating, mass ejection, and particle acceleration. The evolution toward the onset of a flare is rather quasi-static when free energy is accumulated in the form of coronal electric current (field-aligned current, more precisely), while the dissipation of coronal current proceeds rapidly, producing various dynamic events that affect lower atmospheres such as the chromosphere and photosphere. Flares manifest such rapid dissipation of coronal current, and their theoretical modeling has been developed in accordance with observations, in which numerical simulations proved to be a strong tool reproducing the time-dependent, nonlinear evolution of a flare. We review the models proposed to explain the physical mechanism of flares, giving an comprehensive explanation of the key processes mentioned above. We start with basic properties of flares, then go into the details of energy build-up, release and transport in flares where magnetic reconnection works as the central engine to produce a flare.

  3. FLASH MHD simulations of experiments that study shock-generated magnetic fields

    NASA Astrophysics Data System (ADS)

    Tzeferacos, P.; Fatenejad, M.; Flocke, N.; Graziani, C.; Gregori, G.; Lamb, D. Q.; Lee, D.; Meinecke, J.; Scopatz, A.; Weide, K.

    2015-12-01

    We summarize recent additions and improvements to the high energy density physics capabilities in FLASH, highlighting new non-ideal magneto-hydrodynamic (MHD) capabilities. We then describe 3D Cartesian and 2D cylindrical FLASH MHD simulations that have helped to design and analyze experiments conducted at the Vulcan laser facility. In these experiments, a laser illuminates a carbon rod target placed in a gas-filled chamber. A magnetic field diagnostic (called a Bdot) employing three very small induction coils is used to measure all three components of the magnetic field at a chosen point in space. The simulations have revealed that many fascinating physical processes occur in the experiments. These include megagauss magnetic fields generated by the interaction of the laser with the target via the Biermann battery mechanism, which are advected outward by the vaporized target material but decrease in strength due to expansion and resistivity; magnetic fields generated by an outward expanding shock via the Biermann battery mechanism; and a breakout shock that overtakes the first wave, the contact discontinuity between the target material and the gas, and then the initial expanding shock. Finally, we discuss the validation and predictive science we have done for this experiment with FLASH.

  4. Analysis and design of an ultrahigh temperature hydrogen-fueled MHD generator

    NASA Technical Reports Server (NTRS)

    Moder, Jeffrey P.; Myrabo, Leik N.; Kaminski, Deborah A.

    1993-01-01

    A coupled gas dynamics/radiative heat transfer analysis of partially ionized hydrogen, in local thermodynamic equilibrium, flowing through an ultrahigh temperature (10,000-20,000 K) magnetohydrodynamic (MHD) generator is performed. Gas dynamics are modeled by a set of quasi-one-dimensional, nonlinear differential equations which account for friction, convective and radiative heat transfer, and the interaction between the ionized gas and applied magnetic field. Radiative heat transfer is modeled using nongray, absorbing-emitting 2D and 3D P-1 approximations which permit an arbitrary variation of the spectral absorption coefficient with frequency. Gas dynamics and radiative heat transfer are coupled through the energy equation and through the temperature- and density-dependent absorption coefficient. The resulting nonlinear elliptic problem is solved by iterative methods. Design of such MHD generators as onboard, open-cycle, electric power supplies for a particular advanced airbreathing propulsion concept produced an efficient and compact 128-MWe generator characterized by an extraction ratio of 35.5 percent, a power density of 10,500 MWe/cu m, and a specific (extracted) energy of 324 MJe/kg of hydrogen. The maximum wall heat flux and total wall heat load were 453 MW/sq m and 62 MW, respectively.

  5. Magnetohydrodynamic Propulsion for the Classroom

    NASA Astrophysics Data System (ADS)

    Font, Gabriel I.; Dudley, Scott C.

    2004-10-01

    The cinema industry can sometimes prove to be an ally when searching for material with which to motivate students to learn physics. Consider, for example, the electromagnetic force on a current in the presence of a magnetic field. This phenomenon is at the heart of magnetohydrodynamic (MHD) propulsion systems. A submarine employing this type of propulsion was immortalized in the movie Hunt for Red October. While mentioning this to students certainly gets their attention, it often elicits comments that it is only fiction and not physically possible. Imagine their surprise when a working system is demonstrated! It is neither difficult nor expensive to construct a working system that can be demonstrated in the front of a classroom.2 In addition, all aspects of the engineering hurdles that must be surmounted and myths concerning this "silent propulsion" system are borne out in a simple apparatus. This paper details how to construct an inexpensive MHD propulsion boat that can be demonstrated for students in the classroom.

  6. Magnetic levitation and MHD propulsion

    NASA Astrophysics Data System (ADS)

    Tixador, P.

    1994-04-01

    Magnetic levitation and MHD propulsion are now attracting attention in several countries. Different superconducting MagLev and MHD systems will be described concentrating on, above all, the electromagnetic aspect. Some programmes occurring throughout the world will be described. Magnetic levitated trains could be the new high speed transportation system for the 21st century. Intensive studies involving MagLev trains using superconductivity have been carried out in Japan since 1970. The construction of a 43 km long track is to be the next step. In 1991 a six year programme was launched in the United States to evaluate the performances of MagLev systems for transportation. The MHD (MagnetoHydroDynamic) offers some interesting advantages (efficiency, stealth characteristics, ...) for naval propulsion and increasing attention is being paid towards it nowadays. Japan is also up at the top with the tests of Yamato I, a 260 ton MHD propulsed ship. Depuis quelques années nous assistons à un redémarrage de programmes concernant la lévitation et la propulsion supraconductrices. Différents systèmes supraconducteurs de lévitation et de propulsion seront décrits en examinant plus particulièrement l'aspect électromagnétique. Quelques programmes à travers le monde seront abordés. Les trains à sustentation magnétique pourraient constituer un nouveau mode de transport terrestre à vitesse élevée (500 km/h) pour le 21^e siècle. Les japonais n'ont cessé de s'intéresser à ce système avec bobine supraconductrice. Ils envisagent un stade préindustriel avec la construction d'une ligne de 43 km. En 1991 un programme américain pour une durée de six ans a été lancé pour évaluer les performances des systèmes à lévitation pour le transport aux Etats Unis. La MHD (Magnéto- Hydro-Dynamique) présente des avantages intéressants pour la propulsion navale et un regain d'intérêt apparaît à l'heure actuelle. Le japon se situe là encore à la pointe des d

  7. Dipole Alignment in Rotating MHD Turbulence

    NASA Technical Reports Server (NTRS)

    Shebalin, John V.; Fu, Terry; Morin, Lee

    2012-01-01

    We present numerical results from long-term CPU and GPU simulations of rotating, homogeneous, magnetohydrodynamic (MHD) turbulence, and discuss their connection to the spherically bounded case. We compare our numerical results with a statistical theory of geodynamo action that has evolved from the absolute equilibrium ensemble theory of ideal MHD turbulence, which is based on the ideal MHD invariants are energy, cross helicity and magnetic helicity. However, for rotating MHD turbulence, the cross helicity is no longer an exact invariant, although rms cross helicity becomes quasistationary during an ideal MHD simulation. This and the anisotropy imposed by rotation suggests an ansatz in which an effective, nonzero value of cross helicity is assigned to axisymmetric modes and zero cross helicity to non-axisymmetric modes. This hybrid statistics predicts a large-scale quasistationary magnetic field due to broken ergodicity , as well as dipole vector alignment with the rotation axis, both of which are observed numerically. We find that only a relatively small value of effective cross helicity leads to the prediction of a dipole moment vector that is closely aligned (less than 10 degrees) with the rotation axis. We also discuss the effect of initial conditions, dissipation and grid size on the numerical simulations and statistical theory.

  8. Radiochromic 3D Detectors

    NASA Astrophysics Data System (ADS)

    Oldham, Mark

    2015-01-01

    Radiochromic materials exhibit a colour change when exposed to ionising radiation. Radiochromic film has been used for clinical dosimetry for many years and increasingly so recently, as films of higher sensitivities have become available. The two principle advantages of radiochromic dosimetry include greater tissue equivalence (radiologically) and the lack of requirement for development of the colour change. In a radiochromic material, the colour change arises direct from ionising interactions affecting dye molecules, without requiring any latent chemical, optical or thermal development, with important implications for increased accuracy and convenience. It is only relatively recently however, that 3D radiochromic dosimetry has become possible. In this article we review recent developments and the current state-of-the-art of 3D radiochromic dosimetry, and the potential for a more comprehensive solution for the verification of complex radiation therapy treatments, and 3D dose measurement in general.

  9. 3-D Seismic Interpretation

    NASA Astrophysics Data System (ADS)

    Moore, Gregory F.

    2009-05-01

    This volume is a brief introduction aimed at those who wish to gain a basic and relatively quick understanding of the interpretation of three-dimensional (3-D) seismic reflection data. The book is well written, clearly illustrated, and easy to follow. Enough elementary mathematics are presented for a basic understanding of seismic methods, but more complex mathematical derivations are avoided. References are listed for readers interested in more advanced explanations. After a brief introduction, the book logically begins with a succinct chapter on modern 3-D seismic data acquisition and processing. Standard 3-D acquisition methods are presented, and an appendix expands on more recent acquisition techniques, such as multiple-azimuth and wide-azimuth acquisition. Although this chapter covers the basics of standard time processing quite well, there is only a single sentence about prestack depth imaging, and anisotropic processing is not mentioned at all, even though both techniques are now becoming standard.

  10. Time-resolved observation of discrete and continuous magnetohydrodynamic dynamo in the reversed-field pinch edge

    SciTech Connect

    Ji, H.; Almagri, A.F.; Prager, S.C.; Sarff, J.S. )

    1994-08-01

    We report the first experimental verification of the magnetohydrodynamic (MHD) dynamo in the reversed-field pinch (RFP). A burst of MHD dynamo electric field is observed during the sawtooth crash, followed by an increase in the local parallel current in the Madison Symmetric Totus RFP edge. By measuring each term, the parallel MHD mean-field Ohm's law is observed to hold within experimental error bars both between and during sawtooth crashes.

  11. MHD Wave Modes Resolved in Fine-Scale Chromospheric Magnetic Structures

    NASA Astrophysics Data System (ADS)

    Verth, G.; Jess, D. B.

    2016-02-01

    Due to its complex and dynamic fine-scale structure, the chromosphere is a particularly challenging region of the Sun's atmosphere to understand. It is now widely accepted that to model chromospheric dynamics, even on a magnetohydrodynamic (MHD) scale, while also calculating spectral line emission, one must realistically include the effects of partial ionization and radiative transfer in a multi-fluid plasma under non-LTE conditions. Accurate quantification of MHD wave energetics must be founded on a precise identification of the actual wave mode being observed. This chapter focuses on MHD kink-mode identification, MHD sausage mode identification, and MHD torsional Alfvén wave identification. It then reviews progress in determining more accurate energy flux estimations of specific MHD wave modes observed in the chromosphere. The chapter finally examines how the discovery of these MHD wave modes has helped us advance the field of chromospheric magnetoseismology.

  12. Bootstrapping 3D fermions

    DOE PAGES

    Iliesiu, Luca; Kos, Filip; Poland, David; Pufu, Silviu S.; Simmons-Duffin, David; Yacoby, Ran

    2016-03-17

    We study the conformal bootstrap for a 4-point function of fermions <ψψψψ> in 3D. We first introduce an embedding formalism for 3D spinors and compute the conformal blocks appearing in fermion 4-point functions. Using these results, we find general bounds on the dimensions of operators appearing in the ψ × ψ OPE, and also on the central charge CT. We observe features in our bounds that coincide with scaling dimensions in the GrossNeveu models at large N. Finally, we also speculate that other features could coincide with a fermionic CFT containing no relevant scalar operators.

  13. Multi-region relaxed Hall magnetohydrodynamics with flow

    NASA Astrophysics Data System (ADS)

    Lingam, Manasvi; Abdelhamid, Hamdi M.; Hudson, Stuart R.

    2016-08-01

    The recent formulations of multi-region relaxed magnetohydrodynamics (MRxMHD) have generalized the famous Woltjer-Taylor states by incorporating a collection of "ideal barriers" that prevent global relaxation and flow. In this paper, we generalize MRxMHD with flow to include Hall effects, and thereby obtain the partially relaxed counterparts of the famous double Beltrami states as a special subset. The physical and mathematical consequences arising from the introduction of the Hall term are also presented. We demonstrate that our results (in the ideal MHD limit) constitute an important subset of ideal MHD equilibria, and we compare our approach against other variational principles proposed for deriving the partially relaxed states.

  14. Spontaneous chiral symmetry breaking of Hall magnetohydrodynamic turbulence.

    PubMed

    Meyrand, Romain; Galtier, Sébastien

    2012-11-01

    Hall magnetohydrodynamics (MHD) is investigated through three-dimensional direct numerical simulations. We show that the Hall effect induces a spontaneous chiral symmetry breaking of the turbulent dynamics. The normalized magnetic polarization is introduced to separate the right- (R) and left-handed (L) fluctuations. A classical k(-7/3) spectrum is found at small scales for R magnetic fluctuations which corresponds to the electron MHD prediction. A spectrum compatible with k(-11/3) is obtained at large-scales for the L magnetic fluctuations; we call this regime the ion MHD. These results are explained heuristically by rewriting the Hall MHD equations in a succinct vortex dynamical form. Applications to solar wind turbulence are discussed.

  15. The complete set of Casimirs in Hall-magnetohydrodynamics

    NASA Astrophysics Data System (ADS)

    Kawazura, Yohei; Hameiri, Eliezer

    2012-08-01

    A procedure for determining all the Casimir constants of motion in magnetohydrodynamics (MHD) [E. Hameiri, Phys. Plasmas 11, 3423 (2004)] is extended to Hall-MHD. We obtain and solve differential equations for the variational derivatives of all the Casimirs, which must be satisfied for any dynamically accessible motion in Hall-MHD. In an extension of the more commonly considered Hall-MHD model, we also include the electron fluid entropy. The most interesting case for plasma confinement, which is usually true for axisymmetric configurations but desirable in general, is when both the magnetic field and the ion velocity field form the two separate families of nested toroidal surfaces. The Casimirs are then three functionals for each surface, involving the fluxes of certain vector fields and the number of particles contained in each. We also determine a family of independent Casimirs in a general configuration.

  16. Toward textbook multigrid efficiency for fully implicit resistive magnetohydrodynamics

    DOE PAGES

    Adams, Mark F.; Samtaney, Ravi; Brandt, Achi

    2010-09-01

    Multigrid methods can solve some classes of elliptic and parabolic equations to accuracy below the truncation error with a work-cost equivalent to a few residual calculations – so-called ‘‘textbook” multigrid efficiency. We investigate methods to solve the system of equations that arise in time dependent magnetohydrodynamics (MHD) simulations with textbook multigrid efficiency. We apply multigrid techniques such as geometric interpolation, full approximate storage, Gauss–Seidel smoothers, and defect correction for fully implicit, nonlinear, second-order finite volume discretizations of MHD. We apply these methods to a standard resistive MHD benchmark problem, the GEM reconnection problem, and add a strong magnetic guide field,more » which is a critical characteristic of magnetically confined fusion plasmas. We show that our multigrid methods can achieve near textbook efficiency on fully implicit resistive MHD simulations.« less

  17. Toward textbook multigrid efficiency for fully implicit resistive magnetohydrodynamics

    SciTech Connect

    Adams, Mark F.; Samtaney, Ravi; Brandt, Achi

    2010-09-01

    Multigrid methods can solve some classes of elliptic and parabolic equations to accuracy below the truncation error with a work-cost equivalent to a few residual calculations – so-called ‘‘textbook” multigrid efficiency. We investigate methods to solve the system of equations that arise in time dependent magnetohydrodynamics (MHD) simulations with textbook multigrid efficiency. We apply multigrid techniques such as geometric interpolation, full approximate storage, Gauss–Seidel smoothers, and defect correction for fully implicit, nonlinear, second-order finite volume discretizations of MHD. We apply these methods to a standard resistive MHD benchmark problem, the GEM reconnection problem, and add a strong magnetic guide field, which is a critical characteristic of magnetically confined fusion plasmas. We show that our multigrid methods can achieve near textbook efficiency on fully implicit resistive MHD simulations.

  18. Toward textbook multigrid efficiency for fully implicit resistive magnetohydrodynamics

    SciTech Connect

    Adams, Mark F.; Samtaney, Ravi; Brandt, Achi

    2013-12-14

    Multigrid methods can solve some classes of elliptic and parabolic equations to accuracy below the truncation error with a work-cost equivalent to a few residual calculations – so-called “textbook” multigrid efficiency. We investigate methods to solve the system of equations that arise in time dependent magnetohydrodynamics (MHD) simulations with textbook multigrid efficiency. We apply multigrid techniques such as geometric interpolation, full approximate storage, Gauss-Seidel smoothers, and defect correction for fully implicit, nonlinear, second-order finite volume discretizations of MHD. We apply these methods to a standard resistive MHD benchmark problem, the GEM reconnection problem, and add a strong magnetic guide field, which is a critical characteristic of magnetically confined fusion plasmas. We show that our multigrid methods can achieve near textbook efficiency on fully implicit resistive MHD simulations.

  19. Alfvén-dynamo balance and magnetic excess in magnetohydrodynamic turbulence

    NASA Astrophysics Data System (ADS)

    Grappin, Roland; Müller, Wolf-Christian; Verdini, Andrea

    2016-05-01

    Context. Three-dimensional magnetohydrodynamic (3D MHD) turbulent flows with initially magnetic and kinetic energies at equipartition spontaneously develop a magnetic excess (or residual energy) in both numerical simulations and the solar wind. Closure equations obtained in 1983 describe the residual spectrum as resulting from a balance between a dynamo source proportional to the total energy spectrum and a linear Alfvén damping term. A good agreement was found in 2005 with incompressible simulations; however, recent solar wind measurements disagree with these results. Aims: The previous dynamo-Alfvén theory is generalized to a family of models, leading to simple relations between residual and total energy spectra. We want to assess these models in detail against MHD simulations and solar wind data. Methods: We tested the family of models against compressible decaying MHD simulations with a low Mach number, low cross-helicity, and zero-mean magnetic field with or without expansion terms (EBM; expanding box model). Results: A single dynamo-Alfvén model is found to describe correctly both solar wind scalings and compressible simulations without or with expansion. This model is equivalent to the 1983-2005 closure equation, but it incorporates the critical balance of nonlinear turnover and linear Alfvén times, while the dynamo source term remains unchanged. We elucidate the discrepancy with previous incompressible simulations. The model predicts a linear relation between the spectral slopes of total and residual energies mR = -1/2 + 3/2mT. By examining previous solar wind data, our relation is found to be valid for any cross-helicity, and is even better at high cross-helicity with the total energy slope varying from 1.7 to 1.55.

  20. Venus in 3D

    NASA Astrophysics Data System (ADS)

    Plaut, J. J.

    1993-08-01

    Stereographic images of the surface of Venus which enable geologists to reconstruct the details of the planet's evolution are discussed. The 120-meter resolution of these 3D images make it possible to construct digital topographic maps from which precise measurements can be made of the heights, depths, slopes, and volumes of geologic structures.

  1. 3D reservoir visualization

    SciTech Connect

    Van, B.T.; Pajon, J.L.; Joseph, P. )

    1991-11-01

    This paper shows how some simple 3D computer graphics tools can be combined to provide efficient software for visualizing and analyzing data obtained from reservoir simulators and geological simulations. The animation and interactive capabilities of the software quickly provide a deep understanding of the fluid-flow behavior and an accurate idea of the internal architecture of a reservoir.

  2. Magnetohydrodynamic Modeling of the Jovian Magnetosphere

    NASA Technical Reports Server (NTRS)

    Walker, Raymond

    2005-01-01

    Under this grant we have undertaken a series of magnetohydrodynamic (MHD) simulation and data analysis studies to help better understand the configuration and dynamics of Jupiter's magnetosphere. We approached our studies of Jupiter's magnetosphere in two ways. First we carried out a number of studies using our existing MHD code. We carried out simulation studies of Jupiter s magnetospheric boundaries and their dependence on solar wind parameters, we studied the current systems which give the Jovian magnetosphere its unique configuration and we modeled the dynamics of Jupiter s magnetosphere following a northward turning of the interplanetary magnetic field (IMF). Second we worked to develop a new simulation code for studies of outer planet magnetospheres.

  3. Numerical Methods for Radiation Magnetohydrodynamics in Astrophysics

    SciTech Connect

    Klein, R I; Stone, J M

    2007-11-20

    We describe numerical methods for solving the equations of radiation magnetohydrodynamics (MHD) for astrophysical fluid flow. Such methods are essential for the investigation of the time-dependent and multidimensional dynamics of a variety of astrophysical systems, although our particular interest is motivated by problems in star formation. Over the past few years, the authors have been members of two parallel code development efforts, and this review reflects that organization. In particular, we discuss numerical methods for MHD as implemented in the Athena code, and numerical methods for radiation hydrodynamics as implemented in the Orion code. We discuss the challenges introduced by the use of adaptive mesh refinement in both codes, as well as the most promising directions for future developments.

  4. Nonlinear magnetohydrodynamics of electron-positron plasmas

    NASA Astrophysics Data System (ADS)

    Shukla, P. K.; Dasgupta, B.; Sakanaka, P. H.

    2000-05-01

    A set of nonlinear magnetohydrodynamic (MHD) equations for magnetized, nonrelativistic electron-positron plasmas is derived by employing a two fluid model that is supplemented by Ampère's and Faraday's laws. The nonlinear equations show how the baroclinic driver (the Biermann battery) generates the electron positron flows and how these flows give rise to plasma currents which act as a source for the magnetic fields. The newly derived nonlinear equations form a basis for investigating waves, instabilities, as well as coherent nonlinear structures, in addition to studying exact equilibria of electron-positron jets in a magnetoplasma.

  5. MHD Turbulence and Magnetic Dynamos

    NASA Technical Reports Server (NTRS)

    Shebalin, John V

    2014-01-01

    Incompressible magnetohydrodynamic (MHD) turbulence and magnetic dynamos, which occur in magnetofluids with large fluid and magnetic Reynolds numbers, will be discussed. When Reynolds numbers are large and energy decays slowly, the distribution of energy with respect to length scale becomes quasi-stationary and MHD turbulence can be described statistically. In the limit of infinite Reynolds numbers, viscosity and resistivity become zero and if these values are used in the MHD equations ab initio, a model system called ideal MHD turbulence results. This model system is typically confined in simple geometries with some form of homogeneous boundary conditions, allowing for velocity and magnetic field to be represented by orthogonal function expansions. One advantage to this is that the coefficients of the expansions form a set of nonlinearly interacting variables whose behavior can be described by equilibrium statistical mechanics, i.e., by a canonical ensemble theory based on the global invariants (energy, cross helicity and magnetic helicity) of ideal MHD turbulence. Another advantage is that truncated expansions provide a finite dynamical system whose time evolution can be numerically simulated to test the predictions of the associated statistical mechanics. If ensemble predictions are the same as time averages, then the system is said to be ergodic; if not, the system is nonergodic. Although it had been implicitly assumed in the early days of ideal MHD statistical theory development that these finite dynamical systems were ergodic, numerical simulations provided sufficient evidence that they were, in fact, nonergodic. Specifically, while canonical ensemble theory predicted that expansion coefficients would be (i) zero-mean random variables with (ii) energy that decreased with length scale, it was found that although (ii) was correct, (i) was not and the expected ergodicity was broken. The exact cause of this broken ergodicity was explained, after much

  6. Lattice Boltzmann model for resistive relativistic magnetohydrodynamics.

    PubMed

    Mohseni, F; Mendoza, M; Succi, S; Herrmann, H J

    2015-08-01

    In this paper, we develop a lattice Boltzmann model for relativistic magnetohydrodynamics (MHD). Even though the model is derived for resistive MHD, it is shown that it is numerically robust even in the high conductivity (ideal MHD) limit. In order to validate the numerical method, test simulations are carried out for both ideal and resistive limits, namely the propagation of Alfvén waves in the ideal MHD and the evolution of current sheets in the resistive regime, where very good agreement is observed comparing to the analytical results. Additionally, two-dimensional magnetic reconnection driven by Kelvin-Helmholtz instability is studied and the effects of different parameters on the reconnection rate are investigated. It is shown that the density ratio has a negligible effect on the magnetic reconnection rate, while an increase in shear velocity decreases the reconnection rate. Additionally, it is found that the reconnection rate is proportional to σ-1/2, σ being the conductivity, which is in agreement with the scaling law of the Sweet-Parker model. Finally, the numerical model is used to study the magnetic reconnection in a stellar flare. Three-dimensional simulation suggests that the reconnection between the background and flux rope magnetic lines in a stellar flare can take place as a result of a shear velocity in the photosphere.

  7. Lattice Boltzmann model for resistive relativistic magnetohydrodynamics.

    PubMed

    Mohseni, F; Mendoza, M; Succi, S; Herrmann, H J

    2015-08-01

    In this paper, we develop a lattice Boltzmann model for relativistic magnetohydrodynamics (MHD). Even though the model is derived for resistive MHD, it is shown that it is numerically robust even in the high conductivity (ideal MHD) limit. In order to validate the numerical method, test simulations are carried out for both ideal and resistive limits, namely the propagation of Alfvén waves in the ideal MHD and the evolution of current sheets in the resistive regime, where very good agreement is observed comparing to the analytical results. Additionally, two-dimensional magnetic reconnection driven by Kelvin-Helmholtz instability is studied and the effects of different parameters on the reconnection rate are investigated. It is shown that the density ratio has a negligible effect on the magnetic reconnection rate, while an increase in shear velocity decreases the reconnection rate. Additionally, it is found that the reconnection rate is proportional to σ-1/2, σ being the conductivity, which is in agreement with the scaling law of the Sweet-Parker model. Finally, the numerical model is used to study the magnetic reconnection in a stellar flare. Three-dimensional simulation suggests that the reconnection between the background and flux rope magnetic lines in a stellar flare can take place as a result of a shear velocity in the photosphere. PMID:26382548

  8. Magnetohydrodynamic Augmentation of Pulse Detonation Engines

    NASA Astrophysics Data System (ADS)

    Zeineh, Christopher; Cole, Lord; Karagozian, Ann

    2010-11-01

    Pulse detonation engines (PDEs) are the focus of increasing attention due to their potentially superior performance over constant pressure engines. Yet due to its unsteady chamber pressure, the PDE system will either be over- or under-expanded for the majority of the cycle, with energy being used without maximum gain. Magnetohydrodynamic (MHD) augmentation offers the opportunity to extract energy and apply it to a separate stream where the net thrust will be increased. With MHD augmentation, such as in the Pulse Detonation Rocket-Induced MHD Ejector (PDRIME) concept, energy could be extracted from the high speed portion of the system, e.g., through a generator in the nozzle, and then applied directly to another flow or portion of the flow as a body force. The present high resolution numerical simulations explore the flow evolution and potential performance of such propulsion systems. An additional magnetic piston applying energy in the PDE chamber can also act in concert with the PDRIME for separate thrust augmentation. Results show that MHD can indeed influence the flow and pressure fields in a beneficial way in these configurations, with potential performance gains under a variety of flight and operating conditions. There are some challenges associated with achieving these gains, however, suggesting further optimization is required.

  9. Examination of the four-fifths law for longitudinal third-order moments in incompressible magnetohydrodynamic turbulence in a periodic box.

    PubMed

    Yoshimatsu, Katsunori

    2012-06-01

    The four-fifths law for third-order longitudinal moments is examined, using direct numerical simulation (DNS) data on three-dimensional (3D) forced incompressible magnetohydrodynamic (MHD) turbulence without a uniformly imposed magnetic field in a periodic box. The magnetic Prandtl number is set to one, and the number of grid points is 512(3). A generalized Kármán-Howarth-Kolmogorov equation for second-order velocity moments in isotropic MHD turbulence is extended to anisotropic MHD turbulence by means of a spherical average over the direction of r. Here, r is a separation vector. The viscous, forcing, anisotropic and nonstationary terms in the generalized equation are quantified. It is found that the influence of the anisotropic terms on the four-fifths law is negligible at small scales, compared to that of the viscous term. However, the influence of the directional anisotropy, which is measured by the departure of the third-order moments in a particular direction of r from the spherically averaged ones, on the four-fifths law is suggested to be substantial, at least in the case studied here.

  10. Nuclear-electric magnetohydrodynamic propulsion for submarine. Master's thesis

    SciTech Connect

    Bednarczyk, A.A.

    1989-05-01

    The thesis analyzes the superconducting technology for a shipboard magnetohydrodynamic propulsion system. Based on the the principles of magnetohydrodynamics (MHD), the concept of open-water efficiency was used to optimize the preliminary design of the MHD thruster. After the baseline submarine hull modeled after the Los Angeles class submarine was selected, propulsive efficiency and the top speed for four variant MHD submarines were evaluated. The design criteria were set at a 100-MWt nuclear reactor power upper limit and a requirement of 30 knots for the top speed. This required advanced reactor plants and advanced energy conversion systems. The selection of High Temperature Gas Reactor (HTGR) and Liquid-Metal Fast Breeder Reactor (LMFBR) was based on the combined merits of safety, environmental impact, high source temperature and maximum-volume power density (KW/L). With the reactor outlet temperatures of 2000 K, direct-cycle energy conversion-systems gave the best results in terms of thermal efficiency and propulsion plant power density. Two energy conversion systems selected were closed-cycle gas turbine geared to a superconducting generator, and closed-cycle liquid-metal MHD generator. Based on submarine reliability and safety, the option of using an intermediate heat exchanger was also considered. Finally, non-nuclear support systems affected by the advanced power plant and MHD propulsion, stressing submarine safety, are proposed.

  11. Understanding Accretion Disks through Three Dimensional Radiation MHD Simulations

    NASA Astrophysics Data System (ADS)

    Jiang, Yan-Fei

    I study the structures and thermal properties of black hole accretion disks in the radiation pressure dominated regime. Angular momentum transfer in the disk is provided by the turbulence generated by the magneto-rotational instability (MRI), which is calculated self-consistently with a recently developed 3D radiation magneto-hydrodynamics (MHD) code based on Athena. This code, developed by my collaborators and myself, couples both the radiation momentum and energy source terms with the ideal MHD equations by modifying the standard Godunov method to handle the stiff radiation source terms. We solve the two momentum equations of the radiation transfer equations with a variable Eddington tensor (VET), which is calculated with a time independent short characteristic module. This code is well tested and accurate in both optically thin and optically thick regimes. It is also accurate for both radiation pressure and gas pressure dominated flows. With this code, I find that when photon viscosity becomes significant, the ratio between Maxwell stress and Reynolds stress from the MRI turbulence can increase significantly with radiation pressure. The thermal instability of the radiation pressure dominated disk is then studied with vertically stratified shearing box simulations. Unlike the previous results claiming that the radiation pressure dominated disk with MRI turbulence can reach a steady state without showing any unstable behavior, I find that the radiation pressure dominated disks always either collapse or expand until we have to stop the simulations. During the thermal runaway, the heating and cooling rates from the simulations are consistent with the general criterion of thermal instability. However, details of the thermal runaway are different from the predictions of the standard alpha disk model, as many assumptions in that model are not satisfied in the simulations. We also identify the key reasons why previous simulations do not find the instability. The thermal

  12. Finite difference weighted essentially non-oscillatory schemes with constrained transport for ideal magnetohydrodynamics

    NASA Astrophysics Data System (ADS)

    Christlieb, Andrew J.; Rossmanith, James A.; Tang, Qi

    2014-07-01

    In this work we develop a class of high-order finite difference weighted essentially non-oscillatory (FD-WENO) schemes for solving the ideal magnetohydrodynamic (MHD) equations in 2D and 3D. The philosophy of this work is to use efficient high-order WENO spatial discretizations with high-order strong stability-preserving Runge-Kutta (SSP-RK) time-stepping schemes. Numerical results have shown that with such methods we are able to resolve solution structures that are only visible at much higher grid resolutions with lower-order schemes. The key challenge in applying such methods to ideal MHD is to control divergence errors in the magnetic field. We achieve this by augmenting the base scheme with a novel high-order constrained transport approach that updates the magnetic vector potential. The predicted magnetic field from the base scheme is replaced by a divergence-free magnetic field that is obtained from the curl of this magnetic potential. The non-conservative weakly hyperbolic system that the magnetic vector potential satisfies is solved using a version of FD-WENO developed for Hamilton-Jacobi equations. The resulting numerical method is endowed with several important properties: (1) all quantities, including all components of the magnetic field and magnetic potential, are treated as point values on the same mesh (i.e., there is no mesh staggering); (2) both the spatial and temporal orders of accuracy are fourth-order; (3) no spatial integration or multidimensional reconstructions are needed in any step; and (4) special limiters in the magnetic vector potential update are used to control unphysical oscillations in the magnetic field. Several 2D and 3D numerical examples are presented to verify the order of accuracy on smooth test problems and to show high-resolution on test problems that involve shocks.

  13. Magnetohydrodynamic waves and coronal seismology: an overview of recent results.

    PubMed

    De Moortel, Ineke; Nakariakov, Valery M

    2012-07-13

    Recent observations have revealed that magnetohydrodynamic (MHD) waves and oscillations are ubiquitous in the solar atmosphere, with a wide range of periods. We give a brief review of some aspects of MHD waves and coronal seismology that have recently been the focus of intense debate or are newly emerging. In particular, we focus on four topics: (i) the current controversy surrounding propagating intensity perturbations along coronal loops, (ii) the interpretation of propagating transverse loop oscillations, (iii) the ongoing search for coronal (torsional) Alfvén waves, and (iv) the rapidly developing topic of quasi-periodic pulsations in solar flares. PMID:22665899

  14. Magnetohydrodynamic waves and coronal seismology: an overview of recent results.

    PubMed

    De Moortel, Ineke; Nakariakov, Valery M

    2012-07-13

    Recent observations have revealed that magnetohydrodynamic (MHD) waves and oscillations are ubiquitous in the solar atmosphere, with a wide range of periods. We give a brief review of some aspects of MHD waves and coronal seismology that have recently been the focus of intense debate or are newly emerging. In particular, we focus on four topics: (i) the current controversy surrounding propagating intensity perturbations along coronal loops, (ii) the interpretation of propagating transverse loop oscillations, (iii) the ongoing search for coronal (torsional) Alfvén waves, and (iv) the rapidly developing topic of quasi-periodic pulsations in solar flares.

  15. Microwave imaging of magnetohydrodynamic instabilities in fusion plasma

    NASA Astrophysics Data System (ADS)

    Sabot, Roland; Elbèze, Didier; Lee, Woochang; Nam, Yoonbum; Park, Hyeon; Shen, Junsong; Yun, Gunsu; Choi, Minjun; Giacalone, Jean-Claude; Nicolas, Timothée; Bottereau, Christine; Clairet, Frédéric; Lotte, Philippe; Molina, Diego

    2016-11-01

    Microwave imaging diagnostics are extremely useful for observing magnetohydrodynamic (MHD) instabilities in magnetic fusion plasmas. Two imaging diagnostics will be available on the WEST tokamak. A method was developed to reconstruct electron density maps from electron density profiles measured by ultrafast reflectometry, a technique based on FM-CW radar principle. It relies on plasma rotation to perform 2D reconstruction. An Electron Cyclotron Emission Imaging (ECEI) diagnostic will image directly the temperature fluctuations. It will be equivalent to 24 stacked vertically radiometers, each probing a spot of few centimetres. These two complementary techniques will contribute to the validation of MHD models. xml:lang="fr"

  16. Laser-powered MHD generators for space application

    NASA Technical Reports Server (NTRS)

    Jalufka, N. W.

    1986-01-01

    Magnetohydrodynamic (MHD) energy conversion systems of the pulsed laser-supported detonation (LSD) wave, plasma MHD, and liquid-metal MHD (LMMHD) types are assessed for their potential as space-based laser-to-electrical power converters. These systems offer several advantages as energy converters relative to the present chemical, nuclear, and solar devices, including high conversion efficiency, simple design, high-temperature operation, high power density, and high reliability. Of these systems, the Brayton cycle liquid-metal MHD system appears to be the most attractive. The LMMHD technology base is well established for terrestrial applications, particularly with regard to the generator, mixer, and other system components. However, further research is required to extend this technology base to space applications and to establish the technology required to couple the laser energy into the system most efficiently. Continued research on each of the three system types is recommended.

  17. 3D rapid mapping

    NASA Astrophysics Data System (ADS)

    Isaksson, Folke; Borg, Johan; Haglund, Leif

    2008-04-01

    In this paper the performance of passive range measurement imaging using stereo technique in real time applications is described. Stereo vision uses multiple images to get depth resolution in a similar way as Synthetic Aperture Radar (SAR) uses multiple measurements to obtain better spatial resolution. This technique has been used in photogrammetry for a long time but it will be shown that it is now possible to do the calculations, with carefully designed image processing algorithms, in e.g. a PC in real time. In order to get high resolution and quantitative data in the stereo estimation a mathematical camera model is used. The parameters to the camera model are settled in a calibration rig or in the case of a moving camera the scene itself can be used for calibration of most of the parameters. After calibration an ordinary TV camera has an angular resolution like a theodolite, but to a much lower price. The paper will present results from high resolution 3D imagery from air to ground. The 3D-results from stereo calculation of image pairs are stitched together into a large database to form a 3D-model of the area covered.

  18. Thermodynamic Cycle Analysis of Magnetohydrodynamic-Bypass Hypersonic Airbreathing Engines

    NASA Technical Reports Server (NTRS)

    Litchford, R. J.; Cole, J. W.; Bityurin, V. A.; Lineberry, J. T.

    2000-01-01

    The prospects for realizing a magnetohydrodynamic (MHD) bypass hypersonic airbreathing engine are examined from the standpoint of fundamental thermodynamic feasibility. The MHD-bypass engine, first proposed as part of the Russian AJAX vehicle concept, is based on the idea of redistributing energy between various stages of the propulsion system flow train. The system uses an MHD generator to extract a portion of the aerodynamic heating energy from the inlet and an MHD accelerator to reintroduce this power as kinetic energy in the exhaust stream. In this way, the combustor entrance Mach number can be limited to a specified value even as the flight Mach number increases. Thus, the fuel and air can be efficiently mixed and burned within a practical combustor length, and the flight Mach number operating envelope can be extended. In this paper, we quantitatively assess the performance potential and scientific feasibility of MHD-bypass engines using a simplified thermodynamic analysis. This cycle analysis, based on a thermally and calorically perfect gas, incorporates a coupled MHD generator-accelerator system and accounts for aerodynamic losses and thermodynamic process efficiencies in the various engin components. It is found that the flight Mach number range can be significantly extended; however, overall performance is hampered by non-isentropic losses in the MHD devices.

  19. Alfvén-dynamo balance and magnetic excess in MHD turbulence

    NASA Astrophysics Data System (ADS)

    Grappin, Roland; Müller, Wolf Christian; Verdini, Andrea

    2016-04-01

    - - - 3D Magnetohydrodynamic (MHD) turbulent flows with initially magnetic and kinetic energies at equipartition spontaneously develop a magnetic excess (or residual energy), as well in numerical simulations and in the solar wind. Closure equations obtained in 1983 describe the residual spectrum as being produced by a dynamo source proportional to the total energy spectrum, balanced by a linear Alfvén damping term. A good agreement was found in 2005 with incompressible simulations; however, recent solar wind measurements disagree with these results. The previous dynamo-Alfvén theory is generalized to a family of models, leading to simple relations between residual and total energy spectra. We want to assess these models in detail against MHD simulations and solar wind data. The family of models is tested against compressible decaying MHD simulations with low Mach number, zero cross-helicity, zero mean magnetic field, without or with expansion terms (EBM or expanding box model). A single dynamo-Alfvén model is found to describe correctly both solar wind scalings and compressible simulations without or with expansion. It is equivalent to the 1983-2005 closure equation but with critical balance of nonlinear turnover and linear Alfvén times, while the dynamo source term remains unchanged. The discrepancy with previous incompressible simulations is elucidated. The model predicts a linear relation between the spectral slopes of total and residual energies mR = ‑1/2 + 3/2mT. Examining the solar wind data as in [?], our relation is found to be valid whatever the cross-helicity, even better so at high cross-helicity, with the total energy slope varying from 1.7 to 1.55. - - -

  20. Feasibility of MHD submarine propulsion

    SciTech Connect

    Doss, E.D. ); Sikes, W.C. )

    1992-09-01

    This report describes the work performed during Phase 1 and Phase 2 of the collaborative research program established between Argonne National Laboratory (ANL) and Newport News Shipbuilding and Dry Dock Company (NNS). Phase I of the program focused on the development of computer models for Magnetohydrodynamic (MHD) propulsion. Phase 2 focused on the experimental validation of the thruster performance models and the identification, through testing, of any phenomena which may impact the attractiveness of this propulsion system for shipboard applications. The report discusses in detail the work performed in Phase 2 of the program. In Phase 2, a two Tesla test facility was designed, built, and operated. The facility test loop, its components, and their design are presented. The test matrix and its rationale are discussed. Representative experimental results of the test program are presented, and are compared to computer model predictions. In general, the results of the tests and their comparison with the predictions indicate that thephenomena affecting the performance of MHD seawater thrusters are well understood and can be accurately predicted with the developed thruster computer models.

  1. Multimegawatt NEP with vapor core reactor MHD

    NASA Astrophysics Data System (ADS)

    Smith, Blair; Knight, Travis; Anghaie, Samim

    2002-01-01

    Efforts at the Innovative Nuclear Space Power and Propulsion Institute have assessed the feasibility of combining gaseous or vapor core reactors with magnetohydrodynamic power generators to provide extremely high quality, high density, and low specific mass electrical power for space applications. Innovative shielding strategies are employed to maintain an effective but relatively low mass shield, which is the most dominating part of multi-megawatt space power systems. The fission driven magnetohydrodynamic generator produces tens of kilowatt DC power at specific mass of less than 0.5 kg/kW for the total power system. The MHD output with minor conditioning is coupled to magnetoplasmadynamic thruster to achieve an overall NEP system specific mass of less than 1.0 kg/kW for power levels above 20 MWe. Few other concepts would allow comparable ensuing payload savings and flexible mission abort options for manned flights to Mars for example. .

  2. From MHD regime to quiescent non-inductive discharges in Tore Supra: experimental observations and MHD modelling

    NASA Astrophysics Data System (ADS)

    Maget, P.; Huysmans, G. T. A.; Lütjens, H.; Ottaviani, M.; Moreau, Ph; Ségui, J.-L.

    2009-06-01

    Attempts to run non-inductive plasma discharges on Tore Supra sometimes fail due to the triggering of magneto-hydro-dynamic (MHD) instabilities that saturate at a large amplitude, producing degraded confinement and loss of wave driven fast electrons (the so-called MHD regime (Maget et al 2005 Nucl. Fusion 45 69-80)). In this paper we investigate the transition to this soft (in the sense of non-disruptive) MHD limit from experimental observations, and compare it with non-linear code predictions. Such a comparison suggests that different non-linear regimes, with periodic relaxations or saturation, are correctly understood. However, successful non-inductive discharges without detectable magnetic island at q = 2 cannot be reproduced if realistic transport coefficients are used in the computation. Additional physics seems mandatory for explaining these discharges, such as diamagnetic effects, that could also justify cases of abrupt transition to the MHD regime.

  3. Classical MHD shocks: theory and numerical simulation

    SciTech Connect

    Pogorelov, Nikolai V.

    2005-08-01

    Recent results are surveyed in the investigation of the behavior of shocks in ideal magnetohydrodynamics (MHD) and corresponding structures in dissipative/resistive plasma flows. In contrast to evolutionary shocks, a solution of the problem of the nonevolutionary shock interaction with small perturbations is either nonunique or does not exist. The peculiarity of non-ideal MHD is in that some nonevolutionary shocks have dissipative structures. Since this structure is always non-plane, it can reveal itself in problems where transverse perturbations do not exist due to symmetries restrictions. We discuss the numerical behavior of nonevolutionary shocks and argue that they necessarily disappear once the problem is solved in a genuinely three-dimensional statement.

  4. MHD Waves in the Solar Wind

    NASA Astrophysics Data System (ADS)

    Ofman, L.

    2016-02-01

    This chapter focuses on reviewing several observational aspects of magnetohydrodynamic (MHD) waves in the solar wind, in particular on Alfvén waves, Alfvénic turbulent spectrum, and their role in heating and accelerating the solar wind. It also reviews computational models that incorporate Alfvén waves as the driving source of the wind in the lower corona (coronal holes) and in the inner heliosphere, with emphasis on multi-dimensional models. Evidence for MHD waves in the solar wind is obtained from interplanetary scintillation (IPS) observations using Earth-based radio telescope observations of distant (galactic) radio sources. The solar wind electron density variability in the line of sight affects the received radio signal. The propagating fluctuations and their correlations are used to estimate the solar wind velocity and the wave amplitude in the parallel and the perpendicular directions in line of sight.

  5. MHD shocks in coronal mass ejections

    NASA Technical Reports Server (NTRS)

    Steinolfson, R. S.

    1991-01-01

    The primary objective of this research program is the study of the magnetohydrodynamic (MHD) shocks and nonlinear simple waves produced as a result of the interaction of ejected lower coronal plasma with the ambient corona. The types of shocks and nonlinear simple waves produced for representative coronal conditions and disturbance velocities were determined. The wave system and the interactions between the ejecta and ambient corona were studied using both analytic theory and numerical solutions of the time-dependent, nonlinear MHD equations. Observations from the SMM coronagraph/polarimeter provided both guidance and motivation and are used extensively in evaluating the results. As a natural consequence of the comparisons with the data, the simulations assisted in better understanding the physical interactions in coronal mass ejections (CME's).

  6. Taming supersymmetric defects in 3d-3d correspondence

    NASA Astrophysics Data System (ADS)

    Gang, Dongmin; Kim, Nakwoo; Romo, Mauricio; Yamazaki, Masahito

    2016-07-01

    We study knots in 3d Chern-Simons theory with complex gauge group {SL}(N,{{C}}), in the context of its relation with 3d { N }=2 theory (the so-called 3d-3d correspondence). The defect has either co-dimension 2 or co-dimension 4 inside the 6d (2,0) theory, which is compactified on a 3-manifold \\hat{M}. We identify such defects in various corners of the 3d-3d correspondence, namely in 3d {SL}(N,{{C}}) CS theory, in 3d { N }=2 theory, in 5d { N }=2 super Yang-Mills theory, and in the M-theory holographic dual. We can make quantitative checks of the 3d-3d correspondence by computing partition functions at each of these theories. This Letter is a companion to a longer paper [1], which contains more details and more results.

  7. Experimental investigation of the magnetohydrodynamic parachute effect in a hypersonic air flow

    NASA Astrophysics Data System (ADS)

    Fomichev, V. P.; Yadrenkin, M. A.

    2013-01-01

    New data on experimental implementation of the magnetohydrodynamic (MHD) parachute configuration in an air flow with Mach number M = 6 about a flat plate are considered. It is shown that MHD interaction near a flat plate may transform an attached oblique shock wave into a normal detached one, which considerably extends the area of body-incoming flow interaction. This effect can be employed in optimizing return space vehicle deceleration conditions in the upper atmosphere.

  8. 3D Audio System

    NASA Technical Reports Server (NTRS)

    1992-01-01

    Ames Research Center research into virtual reality led to the development of the Convolvotron, a high speed digital audio processing system that delivers three-dimensional sound over headphones. It consists of a two-card set designed for use with a personal computer. The Convolvotron's primary application is presentation of 3D audio signals over headphones. Four independent sound sources are filtered with large time-varying filters that compensate for motion. The perceived location of the sound remains constant. Possible applications are in air traffic control towers or airplane cockpits, hearing and perception research and virtual reality development.

  9. New Era in 3-D Modeling of Convection and Magnetic Dynamos in Stellar Envelopes and Cores

    NASA Astrophysics Data System (ADS)

    Toomre, J.; Augustson, K. C.; Brown, B. P.; Browning, M. K.; Brun, A. S.; Featherstone, N. A.; Miesch, M. S.

    2012-09-01

    The recent advances in asteroseismology and spectropolarimetry are beginning to provide estimates of differential rotation and magnetic structures for a range of F and G-type stars possessing convective envelopes, and in A-type stars with convective cores. It is essential to complement such observational work with theoretical studies based on 3-D simulations of highly turbulent convection coupled to rotation, shear and magnetic fields in full spherical geometries. We have so employed the anelastic spherical harmonic (ASH) code, which deals with compressible magnetohydrodynamics (MHD) in spherical shells, to examine the manner in which the global-scale convection can establish differential rotation and meridional circulations under current solar rotation rates, and these make good contact with helioseismic findings. For younger G stars rotating 3 to 5 times faster than the current Sun, the convection establishes ever stronger angular velocity contrasts between their fast equators and slow poles, and these are accompanied by prominent latitudinal temperature contrasts as well. Turning to MHD simulation of magnetic dynamo action within these younger G stars, the resulting magnetism involves wreaths of strong toroidal magnetic fields (up to 50 to 100 kG strengths) in the bulk of the convection zone, typically of opposite polarity in the northern and southern hemispheres. These fields can persist for long intervals despite being pummeled by the fast convective downflows, but they can also exhibit field reversals and cycles. Turning to shallower convective envelopes in the more luminous F-type stars that range in mass from 1.2 to 1.4 solar masses and for various rotation rates, we find that the convection can again establish solar-like differential rotation profiles with a fast equator and slow poles, but the opposite is achieved at the slower rotation rates. The F stars are also capable of building strong magnetic fields, often as wreaths, through dynamo action. We also

  10. Evidence of the Correspondence of EIT Waves and Coronal Mass Ejections Induced Waves Using a Three-Dimensional Magnetohydrodynamic Simulation

    NASA Astrophysics Data System (ADS)

    Wu, S. T.; Wu, C.-C.; Liou, K.

    2013-04-01

    Before the discovery of EIT waves and coronal mass ejections (CMEs) it was already known that Moreton waves were observed to propagate across the solar disk during some solar flares. This magnetohydrodynamic wave was explained as the intersecting line between the edge of an expanding global coronal wavefront and the chromosphere (Uchida, 1968) where Uchida concluded that the Moreton wave was a fast mode MHD wave. In this presentation, we will show that the EIT wave could be a part of a CME induced wave propagating across the solar disk. To illustrate this scenario, we have employed a global 3D MHD model (Wu et al. 2001) to simulate this phenomenon for the May 12, 1997 event which was an Earth-directed CME observed by SOHO/EIT (Thompson et al. 1998). To carry out this simulation, the measured global magnetic fields obtained from the Stanford University Wilcox Solar Observatory (WSO) were used as the inputs to the simulation model. We were able to show that the scenario suggested by Uchida (1968), namely, the observed EIT wave propagating across the solar disk could be caused by the intersection line between the edge of an expanding CME induced wave front and the chromosphere. In addition to the flare source scenario, we concluded that an EIT (or EUV) wave can also be a part of a flare induced coronal wave with its foot print on the Sun's surface.

  11. Massive-Star Magnetospheres: Now in 3-D!

    NASA Astrophysics Data System (ADS)

    Townsend, Richard

    Magnetic fields are unexpected in massive stars, due to the absence of a dynamo convection zone beneath their surface layers. Nevertheless, kilogauss-strength, ordered fields were detected in a small subset of these stars over three decades ago, and the intervening years have witnessed the steady expansion of this subset. A distinctive feature of magnetic massive stars is that they harbor magnetospheres --- circumstellar environments where the magnetic field interacts strongly with the star's radiation-driven wind, confining it and channelling it into energetic shocks. A wide range of observational signatures are associated with these magnetospheres, in diagnostics ranging from X-rays all the way through to radio emission. Moreover, these magnetospheres can play an important role in massive-star evolution, by amplifying angular momentum loss in the wind. Recent progress in understanding massive-star magnetospheres has largely been driven by magnetohydrodynamical (MHD) simulations. However, these have been restricted to two- dimensional axisymmetric configurations, with three-dimensional configurations possible only in certain special cases. These restrictions are limiting further progress; we therefore propose to develop completely general three-dimensional models for the magnetospheres of massive stars, on the one hand to understand their observational properties and exploit them as plasma-physics laboratories, and on the other to gain a comprehensive understanding of how they influence the evolution of their host star. For weak- and intermediate-field stars, the models will be based on 3-D MHD simulations using a modified version of the ZEUS-MP code. For strong-field stars, we will extend our existing Rigid Field Hydrodynamics (RFHD) code to handle completely arbitrary field topologies. To explore a putative 'photoionization-moderated mass loss' mechanism for massive-star magnetospheres, we will also further develop a photoionization code we have recently

  12. Computational Methods for Ideal Magnetohydrodynamics

    NASA Astrophysics Data System (ADS)

    Kercher, Andrew D.

    Numerical schemes for the ideal magnetohydrodynamics (MHD) are widely used for modeling space weather and astrophysical flows. They are designed to resolve the different waves that propagate through a magnetohydro fluid, namely, the fast, Alfven, slow, and entropy waves. Numerical schemes for ideal magnetohydrodynamics that are based on the standard finite volume (FV) discretization exhibit pseudo-convergence in which non-regular waves no longer exist only after heavy grid refinement. A method is described for obtaining solutions for coplanar and near coplanar cases that consist of only regular waves, independent of grid refinement. The method, referred to as Compound Wave Modification (CWM), involves removing the flux associated with non-regular structures and can be used for simulations in two- and three-dimensions because it does not require explicitly tracking an Alfven wave. For a near coplanar case, and for grids with 213 points or less, we find root-mean-square-errors (RMSEs) that are as much as 6 times smaller. For the coplanar case, in which non-regular structures will exist at all levels of grid refinement for standard FV schemes, the RMSE is as much as 25 times smaller. A multidimensional ideal MHD code has been implemented for simulations on graphics processing units (GPUs). Performance measurements were conducted for both the NVIDIA GeForce GTX Titan and Intel Xeon E5645 processor. The GPU is shown to perform one to two orders of magnitude greater than the CPU when using a single core, and two to three times greater than when run in parallel with OpenMP. Performance comparisons are made for two methods of storing data on the GPU. The first approach stores data as an Array of Structures (AoS), e.g., a point coordinate array of size 3 x n is iterated over. The second approach stores data as a Structure of Arrays (SoA), e.g. three separate arrays of size n are iterated over simultaneously. For an AoS, coalescing does not occur, reducing memory efficiency

  13. Supersonic MHD generator system

    SciTech Connect

    Rahman, M.A.

    1983-11-29

    An improved MHD electrical power generating system of the type having a MHD topping cycle and a steam generating bottoming cycle is disclosed. The system typically includes a combustion system, a conventional MHD generator and a first diffuser radiant boiler. The improvement comprises a first supersonic MHD generator and ramjet engine configuration operatively connected in series with each other and with the conventional MHD generator. The first supersonic MHD generator and ramjet engine configuration increase the power output and improve the operating efficiency of the electrical generating system. A diffuser system is also disclosed which is in fluid communication with the supersonic MHD generator and the ramjet engine for collecting bypass plasma gas to be used for heating a second radiant boiler adapted for powering a steam turbine generator.

  14. H2OTSTUF: Appropriate Operating Regimes for Magnetohydrodynamic Augmentation

    NASA Technical Reports Server (NTRS)

    Jones, Jonathan E.; Hawk, Clark W.

    1998-01-01

    A trade study of magnetohydrodynamic (MHD) augmented propulsion reveals a unique operating regime at lower thrust levels. Substantial mass savings are realized over conventional chemical, solar, and electrical propulsion concepts when MHD augmentation is used to obtain optimal I(sub sp). However, trip times for the most conservative estimates of power plant specific impulse and accelerator efficiency may be prohibitively long. Quasi-one-dimensional calculations show that a solar or nuclear thermal system augmented by MHD can provide competitive performance while utilizing a diverse range of propellants including water, which is available from the Space Shuttle, the Moon, asteroids, and various moons and planets within our solar system. The use of in-situ propellants will reduce costs of space operations as well as enable human exploration of our Solar System. The following conclusions can be drawn from the results of the mission trade study: (1) There exists a maximum thrust or mass flow rate above which MHD augmentation increases the initial mass in low earth orbit (LEO); (2) Mass saving of over 50% can be realized for unique combination of solar/MHD systems; (3) Trip times for systems utilizing current power supply technology may be prohibitively long. Theoretical predictions of MHD performance for in space propulsion systems show that improved efficiencies can reduce trip times to acceptable levels; (4) Long trip times indicative of low thrust systems can be shortened by an increase in the MHD accelerator efficiency or a decrease in the specific mass of the power supply and power processing unit; and (5) As for all propulsion concepts, missions with larger (Delta)v's benefit more from the increased specific impulse resulting from MHD augmentation. Using a quasi-one-dimensional analysis, the required operating conditions for a MHD accelerator to reach acceptable efficiencies are outlined. This analysis shows that substantial non-equilibrium ionization is

  15. Measurements of Prompt and MHD-Induced Fast Ion Loss from National Spherical Torus Experiment Plasmas

    SciTech Connect

    D.S. Darrow; S.S. Medley; A.L. Roquemore; W.W. Heidbrink; A. Alekseyev; F.E. Cecil; J. Egedal; V.Ya. Goloborod'ko; N.N. Gorelenkov; M. Isobe; S. Kaye; M. Miah; F. Paoletti; M.H. Redi; S.N. Reznik; A. Rosenberg; R. White; D. Wyatt; V.A. Yavorskij

    2002-10-15

    A range of effects may make fast ion confinement in spherical tokamaks worse than in conventional aspect ratio tokamaks. Data from neutron detectors, a neutral particle analyzer, and a fast ion loss diagnostic on the National Spherical Torus Experiment (NSTX) indicate that neutral beam ion confinement is consistent with classical expectations in quiescent plasmas, within the {approx}25% errors of measurement. However, fast ion confinement in NSTX is frequently affected by magnetohydrodynamic (MHD) activity, and the effect of MHD can be quite strong.

  16. COLLAPSE AND FRAGMENTATION OF MAGNETIC MOLECULAR CLOUD CORES WITH THE ENZO AMR MHD CODE. I. UNIFORM DENSITY SPHERES

    SciTech Connect

    Boss, Alan P.; Keiser, Sandra A.

    2013-02-20

    Magnetic fields are important contributors to the dynamics of collapsing molecular cloud cores, and can have a major effect on whether collapse results in a single protostar or fragmentation into a binary or multiple protostar system. New models are presented of the collapse of magnetic cloud cores using the adaptive mesh refinement code Enzo2.0. The code was used to calculate the ideal magnetohydrodynamics (MHD) of initially spherical, uniform density, and rotation clouds with density perturbations, i.e., the Boss and Bodenheimer standard isothermal test case for three-dimensional (3D) hydrodynamics codes. After first verifying that Enzo reproduces the binary fragmentation expected for the non-magnetic test case, a large set of models was computed with varied initial magnetic field strengths and directions with respect to the cloud core axis of rotation (parallel or perpendicular), density perturbation amplitudes, and equations of state. Three significantly different outcomes resulted: (1) contraction without sustained collapse, forming a denser cloud core; (2) collapse to form a single protostar with significant spiral arms; and (3) collapse and fragmentation into binary or multiple protostar systems, with multiple spiral arms. Comparisons are also made with previous MHD calculations of similar clouds with a barotropic equations of state. These results for the collapse of initially uniform density spheres illustrate the central importance of both magnetic field direction and field strength for determining the outcome of dynamic protostellar collapse.

  17. THREE-DIMENSIONAL KINETIC-MHD MODEL OF THE GLOBAL HELIOSPHERE WITH THE HELIOPAUSE-SURFACE FITTING

    SciTech Connect

    Izmodenov, V. V.; Alexashov, D. B.

    2015-10-15

    This paper provides a detailed description of the latest version of our model of the solar wind (SW) interaction with the local interstellar medium (LISM). This model has already been applied to the analysis of Lyα absorption spectra toward nearby stars and for analyses of Solar and Heliospheric Observatory/SWAN data. Katushkina et al. (this issue) used the model results to analyze IBEX-Lo data. At the same time, the details of this model have not yet been published. This is a three-dimensional (3D) kinetic-magnetohydrodynamical (MHD) model that takes into account SW and interstellar plasmas (including α particles in SW and helium ions in LISM), the solar and interstellar magnetic fields, and interstellar hydrogen atoms. The latitudinal dependence of SW and the actual flow direction of the interstellar gas with respect to the Sun are also taken into account in the model. It was very essential that our numerical code was developed in such a way that any numerical diffusion or reconnection across the heliopause were not allowed in the model. The heliospheric current sheet is a rotational discontinuity in the ideal MHD and can be treated kinematically. In the paper, we focus in particular on the effects of the heliospheric magnetic field and on the heliolatitudinal dependence of SW.

  18. Three-dimensional Kinetic-MHD Model of the Global Heliosphere with the Heliopause-surface Fitting

    NASA Astrophysics Data System (ADS)

    Izmodenov, V. V.; Alexashov, D. B.

    2015-10-01

    This paper provides a detailed description of the latest version of our model of the solar wind (SW) interaction with the local interstellar medium (LISM). This model has already been applied to the analysis of Lyα absorption spectra toward nearby stars and for analyses of Solar and Heliospheric Observatory/SWAN data. Katushkina et al. (this issue) used the model results to analyze IBEX-Lo data. At the same time, the details of this model have not yet been published. This is a three-dimensional (3D) kinetic-magnetohydrodynamical (MHD) model that takes into account SW and interstellar plasmas (including α particles in SW and helium ions in LISM), the solar and interstellar magnetic fields, and interstellar hydrogen atoms. The latitudinal dependence of SW and the actual flow direction of the interstellar gas with respect to the Sun are also taken into account in the model. It was very essential that our numerical code was developed in such a way that any numerical diffusion or reconnection across the heliopause were not allowed in the model. The heliospheric current sheet is a rotational discontinuity in the ideal MHD and can be treated kinematically. In the paper, we focus in particular on the effects of the heliospheric magnetic field and on the heliolatitudinal dependence of SW.

  19. Magnetohydrodynamic sea water propulsion

    SciTech Connect

    Petrick, M.; Thomas, A.; Genens, L.; Libera, J.; Nietert, R.; Bouillard, J.; Pierson, E.; Hill, D.; Picologlou, B.; Ohlsson, O.; Kasprzyk, T.; Berry, G.

    1991-01-01

    An experimental and theoretical investigation of a large scale MHD propulsor has been undertaken whose objectives are to (1) investigate the transient and steady state performance of the thruster over operating parameter ranges that are compatible with achievement of high efficiency, (2) to quantify the principal loss mechanisms within the thruster and (3) to obtain preliminary hydroacoustic data. The performance of the thruster was first investigated theoretically with a 3-D code to quantify the loss mechanisms and identify experimental parameter ranges of interest. The loss mechanisms of interest are ohmic losses within the channel and those resulting from electrical currents at the entrance and exit of the thruster, and enhanced frictional losses. The analysis indicated that the relative importance of the loss mechanisms was a function of the thruster design and operating parameters. The experimental investigation of the large scale propulsor is being conducted on a sea water test facility that was designed to match the capabilities of a large 6-T superconducting magnet. The facility design was such that {approximately}90{degrees} of all losses occurred within the propulsion test train (inlet nozzle, propulsor and diffuser) thus facilitating isolation of the loss mechanisms. The test thruster itself is heavily instrumented to provide local measurements of velocity, pressure, and electric fields. The predicted overall thruster performance and value of the loss mechanisms will be compared with measured values. Comparisons will also be presented of the voltage gradients between electrodes, overall thruster efficiency, axial pressure gradients across the propulsor, change in velocity profiles, axial and vertical current distributions and exit distribution of the electrolytic gases.

  20. Magnetohydrodynamic sea water propulsion

    SciTech Connect

    Petrick, M.; Thomas, A.; Genens, L.; Libera, J.; Nietert, R.; Bouillard, J.; Pierson, E.; Hill, D.; Picologlou, B.; Ohlsson, O.; Kasprzyk, T.; Berry, G.

    1991-12-31

    An experimental and theoretical investigation of a large scale MHD propulsor has been undertaken whose objectives are to (1) investigate the transient and steady state performance of the thruster over operating parameter ranges that are compatible with achievement of high efficiency, (2) to quantify the principal loss mechanisms within the thruster and (3) to obtain preliminary hydroacoustic data. The performance of the thruster was first investigated theoretically with a 3-D code to quantify the loss mechanisms and identify experimental parameter ranges of interest. The loss mechanisms of interest are ohmic losses within the channel and those resulting from electrical currents at the entrance and exit of the thruster, and enhanced frictional losses. The analysis indicated that the relative importance of the loss mechanisms was a function of the thruster design and operating parameters. The experimental investigation of the large scale propulsor is being conducted on a sea water test facility that was designed to match the capabilities of a large 6-T superconducting magnet. The facility design was such that {approximately}90{degrees} of all losses occurred within the propulsion test train (inlet nozzle, propulsor and diffuser) thus facilitating isolation of the loss mechanisms. The test thruster itself is heavily instrumented to provide local measurements of velocity, pressure, and electric fields. The predicted overall thruster performance and value of the loss mechanisms will be compared with measured values. Comparisons will also be presented of the voltage gradients between electrodes, overall thruster efficiency, axial pressure gradients across the propulsor, change in velocity profiles, axial and vertical current distributions and exit distribution of the electrolytic gases.

  1. Relativistic magnetohydrodynamics in dynamical spacetimes: Numerical methods and tests

    SciTech Connect

    Duez, Matthew D.; Liu, Yuk Tung; Shapiro, Stuart L.; Stephens, Branson C.

    2005-07-15

    Many problems at the forefront of theoretical astrophysics require the treatment of magnetized fluids in dynamical, strongly curved spacetimes. Such problems include the origin of gamma-ray bursts, magnetic braking of differential rotation in nascent neutron stars arising from stellar core collapse or binary neutron star merger, the formation of jets and magnetized disks around newborn black holes, etc. To model these phenomena, all of which involve both general relativity (GR) and magnetohydrodynamics (MHD), we have developed a GRMHD code capable of evolving MHD fluids in dynamical spacetimes. Our code solves the Einstein-Maxwell-MHD system of coupled equations in axisymmetry and in full 3+1 dimensions. We evolve the metric by integrating the Baumgarte-Shapiro-Shibata-Nakamura equations, and use a conservative, shock-capturing scheme to evolve the MHD equations. Our code gives accurate results in standard MHD code-test problems, including magnetized shocks and magnetized Bondi flow. To test our code's ability to evolve the MHD equations in a dynamical spacetime, we study the perturbations of a homogeneous, magnetized fluid excited by a gravitational plane wave, and we find good agreement between the analytic and numerical solutions.

  2. Magnetohydrodynamic Power Generation in the Laboratory Simulated Martian Entry Plasma

    NASA Technical Reports Server (NTRS)

    Vuskovic, L.; Popovic, S.; Drake, J.; Moses, R. W.

    2005-01-01

    This paper addresses the magnetohydrodynamic (MHD) conversion of the energy released during the planetary entry phase of an interplanetary vehicle trajectory. The effect of MHD conversion is multi-fold. It reduces and redirects heat transferred to the vehicle, and regenerates the dissipated energy in reusable and transportable form. A vehicle on an interplanetary mission carries about 10,000 kWh of kinetic energy per ton of its mass. This energy is dissipated into heat during the planetary atmospheric entry phase. For instance, the kinetic energy of Mars Pathfinder was about 4220 kWh. Based on the loss in velocity, Mars Pathfinder lost about 92.5% of that energy during the plasma-sustaining entry phase that is approximately 3900 kWh. An ideal MHD generator, distributed over the probe surface of Mars Pathfinder could convert more than 2000 kWh of this energy loss into electrical energy, which correspond to more than 50% of the kinetic energy loss. That means that the heat transferred to the probe surface can be reduced by at least 50% if the converted energy is adequately stored, or re-radiated, or directly used. Therefore, MHD conversion could act not only as the power generating, but also as the cooling process. In this paper we describe results of preliminary experiments with light and microwave emitters powered by model magnetohydrodynamic generators and discuss method for direct use of converted energy.

  3. The effects of 3-D shaping on ITG stability

    NASA Astrophysics Data System (ADS)

    Rorvig, Mordechai; Hegna, Chris

    2012-03-01

    In this work we seek to understand how 3-D shaping can be used to improve ion temperature gradient stability. Part of the difficulty in deducing the role of 3-D shaping is the generation of 3-D MHD equilibria necessary for the calculations. In this work, MHD equilibrium surfaces are generated using local 3-D magnetostatic equilibrium theory [1]. We distinguish three different types of toroidal magnetic surface shaping: axisymmetric shaping, toroidal rotation of the cross section, and toroidal translation of the magnetic axis. We study these types of shaping independently and in combination to look for improvements. Linear growth rates for ITG modes are calculated using the gyrokinetics code GENE [2]. The geometric interface package GIST [3] accepts the equilibrium input data from the local equilibrium calculation. Growth rates for both axisymmetric and 3-D equilibrium calculations are presented. [4pt] [1] C. C. Hegna, Physics of Plasmas 7, 3921 (2000).[0pt] [2] F. Jenko, W. Dorland, M. Kotschenreuther, and B. N. Rogers, Physical Review Letters 7, 1904 (2000).[0pt] [3] P. Xanthopoulos, W. A. Cooper, F. Jenko, Yu. Turkin, A. Runov, and J. Geiger, Physics of Plasmas 16, 082303 (2009).

  4. Time-dependent magnetohydrodynamic simulations of the inner heliosphere

    NASA Astrophysics Data System (ADS)

    Merkin, V. G.; Lyon, J. G.; Lario, D.; Arge, C. N.; Henney, C. J.

    2016-04-01

    This paper presents results from a simulation study exploring heliospheric consequences of time-dependent changes at the Sun. We selected a 2 month period in the beginning of year 2008 that was characterized by very low solar activity. The heliosphere in the equatorial region was dominated by two coronal holes whose changing structure created temporal variations distorting the classical steady state picture of the heliosphere. We used the Air Force Data Assimilate Photospheric Flux Transport (ADAPT) model to obtain daily updated photospheric magnetograms and drive the Wang-Sheeley-Arge (WSA) model of the corona. This leads to a formulation of a time-dependent boundary condition for our three-dimensional (3-D) magnetohydrodynamic (MHD) model, LFM-helio, which is the heliospheric adaptation of the Lyon-Fedder-Mobarry MHD simulation code. The time-dependent coronal conditions were propagated throughout the inner heliosphere, and the simulation results were compared with the spacecraft located near 1 astronomical unit (AU) heliocentric distance: Advanced Composition Explorer (ACE), Solar Terrestrial Relations Observatory (STEREO-A and STEREO-B), and the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft that was in cruise phase measuring the heliospheric magnetic field between 0.35 and 0.6 AU. In addition, during the selected interval MESSENGER and ACE aligned radially allowing minimization of the effects of temporal variation at the Sun versus radial evolution of structures. Our simulations show that time-dependent simulationsreproduce the gross-scale structure of the heliosphere with higher fidelity, while on smaller spatial and faster time scales (e.g., 1 day) they provide important insights for interpretation of the data. The simulations suggest that moving boundaries of slow-fast wind transitions at 0.1 AU may result in the formation of inverted magnetic fields near pseudostreamers which is an intrinsically time-dependent process

  5. Magnetohydrodynamic Numerical Simulations of Magnetic Reconnection in Interstellar Medium

    NASA Astrophysics Data System (ADS)

    Tanuma, Syuniti

    2000-03-01

    In this thesis, we perform two-dimensional (2D) resistive magnetohydrodynamic (MHD) numerical simulations of the magnetic reconnection in interstellar medium. Part I is introduction. The motivation of the study is to investigate the origin of hot gas in interstellar medium. A scenario for generating X-ray gas in Galaxy is proposed, and examined by performing 2D MHD simulations with simple assumptions (Part II). The magnetic reconnection triggered by a supernova (Part III) and Parker instability (Part IV) are studied in detail, by performing 2D MHD simulations. Furthermore, the magnetic reconnection is also studied by performing three-dimensional (3D) MHD numerical simulation in (Part V). % Finally, we discuss and summarize the thesis (Parts VI and VII). Part I First, we review observation of Galactic Ridge X-ray Emission (GRXE) and its problems. Second, we describe observation of interstellar magnetic field briefly. Third, we review magnetic reconnection, theoretical models, numerical simulations, observations and experiments, and tearing instability. Forth, Parker instability (undular mode of magnetobuoyancy instability) is mentioned. Finally, we show the purpose of this thesis. Part II We present a scenario for the origin of the hot plasma in Galaxy as a model of strong X-ray emission [sim 3-10 keV; LX(2-10 keV) sim 1038 erg s-1], called GRXE, which has been observed near to the galactic plane. GRXE is thermal emission from a hot component (sim 7 keV) and a cool component (sim 0.8 keV). Observations suggest that the hot component is diffuse, and that it is not escaping away freely. Both what heats the hot component and what confines it in Galactic ridge still remain puzzling, while the cool component is believed to be created by supernovae. We propose a new scenario: the hot component is heated by magnetic reconnection, and confined by a helical magnetic field produced by magnetic reconnection. We solved 2D MHD equations numerically to study how magnetic

  6. ON THE ROLE OF INVOLUTIONS IN THE DISCONTINUOUS GALERKIN DISCRETIZATION OF MAXWELL AND MAGNETOHYDRODYNAMIC SYSTEMS

    NASA Technical Reports Server (NTRS)

    Barth, Timothy

    2005-01-01

    The role of involutions in energy stability of the discontinuous Galerkin (DG) discretization of Maxwell and magnetohydrodynamic (MHD) systems is examined. Important differences are identified in the symmetrization of the Maxwell and MHD systems that impact the construction of energy stable discretizations using the DG method. Specifically, general sufficient conditions to be imposed on the DG numerical flux and approximation space are given so that energy stability is retained These sufficient conditions reveal the favorable energy consequence of imposing continuity in the normal component of the magnetic induction field at interelement boundaries for MHD discretizations. Counterintuitively, this condition is not required for stability of Maxwell discretizations using the discontinuous Galerkin method.

  7. Zonal flow driven by energetic particle during magneto-hydro-dynamic burst in a toroidal plasma

    NASA Astrophysics Data System (ADS)

    Ohshima, S.; Fujisawa, A.; Shimizu, A.; Nakano, H.; Iguchi, H.; Yoshimura, Y.; Nagaoka, K.; Minami, T.; Isobe, M.; Nishimura, S.; Suzuki, C.; Akiyama, T.; Takahashi, C.; Takeuchi, M.; Ito, T.; Watari, T.; Kumazawa, R.; Itoh, S.-I.; Itoh, K.; Matsuoka, K.; Okamura, S.

    2007-11-01

    The internal structural measurements of electric field and density using twin heavy ion beam probes have been performed to elucidate the nonlinear evolution of the magneto-hydro-dynamic (MHD) bursty phenomenon driven by the interaction with high-energy particles in a toroidal plasma. The results have given the finest observation of the internal structure of plasma quantities, such as electric field, density and magnetic field distortion, which nonlinearly develop during the MHD phenomenon. In particular, the finding of a new kind of oscillating zonal flow driven by interaction between energetic particles and MHD modes should be emphasized for burning state plasmas.

  8. Directional multi-scale statistics of quasi-static magnetohydrodynamic turbulence

    NASA Astrophysics Data System (ADS)

    Okamoto, Naoya; Yoshimatsu, Katsunori; Schneider, Kai; Farge, Marie; Multiscale methodsturbulence Collaboration

    2013-10-01

    Anisotropy and intermittency of quasi-static magnetohydrodynamic (MHD) turbulence in an imposed magnetic field are examined, using three-dimensional orthonormal wavelet analysis. This analysis is applied to two turbulent MHD flows computed by direct numerical simulation with 5123 grid points and with different intensities of the imposed magnetic field. It is found that the imposed magnetic field leads to a substantial amplification of intermittency in the velocity field, especially in the direction of the imposed magnetic field. The Eulerian and Lagrangian accelerations are also examined by applying directional multi-scale analyses. This work was supported by the contract SiCoMHD (ANR-Blanc 2011-045).

  9. FLASH magnetohydrodynamic simulations of shock-generated magnetic field experiments

    NASA Astrophysics Data System (ADS)

    Tzeferacos, P.; Fatenejad, M.; Flocke, N.; Gregori, G.; Lamb, D. Q.; Lee, D.; Meinecke, J.; Scopatz, A.; Weide, K.

    2012-12-01

    We report the results of benchmark FLASH magnetohydrodynamic (MHD) simulations of experiments conducted by the University of Oxford High Energy Density Laboratory Astrophysics group and its collaborators at the Laboratoire pour l'Utilisation des Lasers Intenses (LULI). In these experiments, a long-pulse laser illuminates a target in a chamber filled with Argon gas, producing shock waves that generate magnetic fields via the Biermann battery mechanism. We first outline the implementation of 2D cylindrical geometry in the unsplit MHD solver in FLASH and present results of verification tests. We then describe the results of benchmark 2D cylindrical MHD simulations of the LULI experiments using FLASH that explore the impact of external fields along with the possibility of magnetic field amplification by turbulence that is associated with the shock waves and that is induced by a grid placed in the gas-filled chamber.

  10. Chiral exact relations for helicities in Hall magnetohydrodynamic turbulence.

    PubMed

    Banerjee, Supratik; Galtier, Sébastien

    2016-03-01

    Besides total energy, three-dimensional incompressible Hall magnetohydrodynamics (MHD) possesses two inviscid invariants, which are the magnetic helicity and the generalized helicity. Exact relations are derived for homogeneous (nonisotropic) stationary Hall MHD turbulence (and also for its inertialess electron MHD limit) with nonzero helicities and in the asymptotic limit of large Reynolds numbers. The universal laws are written only in terms of mixed second-order structure functions, i.e., the scalar product of two different increments. It provides, therefore, a direct measurement of the dissipation rates for the corresponding invariant flux. This study shows that the generalized helicity cascade is strongly linked to the left polarized fluctuations, while the magnetic helicity cascade is linked to the right polarized fluctuations. PMID:27078460

  11. Chiral exact relations for helicities in Hall magnetohydrodynamic turbulence.

    PubMed

    Banerjee, Supratik; Galtier, Sébastien

    2016-03-01

    Besides total energy, three-dimensional incompressible Hall magnetohydrodynamics (MHD) possesses two inviscid invariants, which are the magnetic helicity and the generalized helicity. Exact relations are derived for homogeneous (nonisotropic) stationary Hall MHD turbulence (and also for its inertialess electron MHD limit) with nonzero helicities and in the asymptotic limit of large Reynolds numbers. The universal laws are written only in terms of mixed second-order structure functions, i.e., the scalar product of two different increments. It provides, therefore, a direct measurement of the dissipation rates for the corresponding invariant flux. This study shows that the generalized helicity cascade is strongly linked to the left polarized fluctuations, while the magnetic helicity cascade is linked to the right polarized fluctuations.

  12. Concomitant Hamiltonian and topological structures of extended magnetohydrodynamics

    NASA Astrophysics Data System (ADS)

    Lingam, Manasvi; Miloshevich, George; Morrison, Philip J.

    2016-07-01

    The paper describes the unique geometric properties of ideal magnetohydrodynamics (MHD), and demonstrates how such features are inherited by extended MHD, viz. models that incorporate two-fluid effects (the Hall term and electron inertia). The generalized helicities, and other geometric expressions for these models are presented in a topological context, emphasizing their universal facets. Some of the results presented include: the generalized Kelvin circulation theorems; the existence of two Lie-dragged 2-forms; and two concomitant helicities that can be studied via the Jones polynomial, which is widely utilized in Chern-Simons theory. The ensuing commonality is traced to the existence of an underlying Hamiltonian structure for all the extended MHD models, exemplified by the presence of a unique noncanonical Poisson bracket, and its associated energy.

  13. Three-Dimensional Numerical Modeling of Magnetohydrodynamic Augmented Propulsion Experiment

    NASA Technical Reports Server (NTRS)

    Turner, M. W.; Hawk, C. W.; Litchford, R. J.

    2009-01-01

    Over the past several years, NASA Marshall Space Flight Center has engaged in the design and development of an experimental research facility to investigate the use of diagonalized crossed-field magnetohydrodynamic (MHD) accelerators as a possible thrust augmentation device for thermal propulsion systems. In support of this effort, a three-dimensional numerical MHD model has been developed for the purpose of analyzing and optimizing accelerator performance and to aid in understanding critical underlying physical processes and nonideal effects. This Technical Memorandum fully summarizes model development efforts and presents the results of pretest performance optimization analyses. These results indicate that the MHD accelerator should utilize a 45deg diagonalization angle with the applied current evenly distributed over the first five inlet electrode pairs. When powered at 100 A, this configuration is expected to yield a 50% global efficiency with an 80% increase in axial velocity and a 50% increase in centerline total pressure.

  14. Imbalanced relativistic force-free magnetohydrodynamic turbulence

    SciTech Connect

    Cho, Jungyeon; Lazarian, A.

    2014-01-01

    When magnetic energy density is much larger than that of matter, as in pulsar/black hole magnetospheres, the medium becomes force-free and we need relativity to describe it. As in non-relativistic magnetohydrodynamics (MHD), Alfvénic MHD turbulence in the relativistic limit can be described by interactions of counter-traveling wave packets. In this paper, we numerically study strong imbalanced MHD turbulence in such environments. Here, imbalanced turbulence means the waves traveling in one direction (dominant waves) have higher amplitudes than the opposite-traveling waves (sub-dominant waves). We find that (1) spectrum of the dominant waves is steeper than that of sub-dominant waves, (2) the anisotropy of the dominant waves is weaker than that of sub-dominant waves, and (3) the dependence of the ratio of magnetic energy densities of dominant and sub-dominant waves on the ratio of energy injection rates is steeper than quadratic (i.e., b{sub +}{sup 2}/b{sub −}{sup 2}∝(ϵ{sub +}/ϵ{sub −}){sup n} with n > 2). These results are consistent with those obtained for imbalanced non-relativistic Alfvénic turbulence. This corresponds well to the earlier reported similarity of the relativistic and non-relativistic balanced magnetic turbulence.

  15. Solar-Driven Liquid-Metal MHD Generator

    NASA Technical Reports Server (NTRS)

    Hohl, F.; Lee, J. H.

    1982-01-01

    Liquid-metal magnetohydrodynamic (MHD) power generator with solar oven as its heat source has potential to produce electric power in space and on Earth at high efficiency. Generator focuses radiation from Sun to heat driving gas that pushes liquid metal past magnetic coil. Power is extracted directly from electric currents set up in conducting liquid. Using solar energy as fuel can save considerable costs and payload weight, compared to previous systems.

  16. Prominent rocks - 3D

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Many prominent rocks near the Sagan Memorial Station are featured in this image, taken in stereo by the Imager for Mars Pathfinder (IMP) on Sol 3. 3D glasses are necessary to identify surface detail. Wedge is at lower left; Shark, Half-Dome, and Pumpkin are at center. Flat Top, about four inches high, is at lower right. The horizon in the distance is one to two kilometers away.

    Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is an operating division of the California Institute of Technology (Caltech). The Imager for Mars Pathfinder (IMP) was developed by the University of Arizona Lunar and Planetary Laboratory under contract to JPL. Peter Smith is the Principal Investigator.

    Click below to see the left and right views individually. [figure removed for brevity, see original site] Left [figure removed for brevity, see original site] Right

  17. 'Diamond' in 3-D

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This 3-D, microscopic imager mosaic of a target area on a rock called 'Diamond Jenness' was taken after NASA's Mars Exploration Rover Opportunity ground into the surface with its rock abrasion tool for a second time.

    Opportunity has bored nearly a dozen holes into the inner walls of 'Endurance Crater.' On sols 177 and 178 (July 23 and July 24, 2004), the rover worked double-duty on Diamond Jenness. Surface debris and the bumpy shape of the rock resulted in a shallow and irregular hole, only about 2 millimeters (0.08 inch) deep. The final depth was not enough to remove all the bumps and leave a neat hole with a smooth floor. This extremely shallow depression was then examined by the rover's alpha particle X-ray spectrometer.

    On Sol 178, Opportunity's 'robotic rodent' dined on Diamond Jenness once again, grinding almost an additional 5 millimeters (about 0.2 inch). The rover then applied its Moessbauer spectrometer to the deepened hole. This double dose of Diamond Jenness enabled the science team to examine the rock at varying layers. Results from those grindings are currently being analyzed.

    The image mosaic is about 6 centimeters (2.4 inches) across.

  18. Martian terrain - 3D

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This area of terrain near the Sagan Memorial Station was taken on Sol 3 by the Imager for Mars Pathfinder (IMP). 3D glasses are necessary to identify surface detail.

    The IMP is a stereo imaging system with color capability provided by 24 selectable filters -- twelve filters per 'eye.' It stands 1.8 meters above the Martian surface, and has a resolution of two millimeters at a range of two meters.

    Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is an operating division of the California Institute of Technology (Caltech). The Imager for Mars Pathfinder (IMP) was developed by the University of Arizona Lunar and Planetary Laboratory under contract to JPL. Peter Smith is the Principal Investigator.

    Click below to see the left and right views individually. [figure removed for brevity, see original site] Left [figure removed for brevity, see original site] Right

  19. Conceptual design analysis of an MHD power conversion system for droplet-vapor core reactors. Final report

    SciTech Connect

    Anghaie, S.; Saraph, G.

    1995-12-31

    A nuclear driven magnetohydrodynamic (MHD) generator system is proposed for the space nuclear applications of few hundreds of megawatts. The MHD generator is coupled to a vapor-droplet core reactor that delivers partially ionized fissioning plasma at temperatures in range of 3,000 to 4,000 K. A detailed MHD model is developed to analyze the basic electrodynamics phenomena and to perform the design analysis of the nuclear driven MHD generator. An incompressible quasi one dimensional model is also developed to perform parametric analyses.

  20. Collisionless magnetic reconnection under anisotropic MHD approximation

    NASA Astrophysics Data System (ADS)

    Hirabayashi, Kota; Hoshino, Masahiro

    We study the formation of slow-mode shocks in collisionless magnetic reconnection by using one- and two-dimensional collisionless magneto-hydro-dynamic (MHD) simulations based on the double adiabatic approximation, which is an important step to bridge the gap between the Petschek-type MHD reconnection model accompanied by a pair of slow shocks and the observational evidence of the rare occasion of in-situ slow shock observation. According to our results, a pair of slow shocks does form in the reconnection layer. The resultant shock waves, however, are quite weak compared with those in an isotropic MHD from the point of view of the plasma compression and the amount of the magnetic energy released across the shock. Once the slow shock forms, the downstream plasma are heated in highly anisotropic manner and a firehose-sense (P_{||}>P_{⊥}) pressure anisotropy arises. The maximum anisotropy is limited by the marginal firehose criterion, 1-(P_{||}-P_{⊥})/B(2) =0. In spite of the weakness of the shocks, the resultant reconnection rate is kept at the same level compared with that in the corresponding ordinary MHD simulations. It is also revealed that the sequential order of propagation of the slow shock and the rotational discontinuity, which appears when the guide field component exists, changes depending on the magnitude of the guide field. Especially, when no guide field exists, the rotational discontinuity degenerates with the contact discontinuity remaining at the position of the initial current sheet, while with the slow shock in the isotropic MHD. Our result implies that the slow shock does not necessarily play an important role in the energy conversion in the reconnection system and is consistent with the satellite observation in the Earth's magnetosphere.

  1. WOMBAT: sWift Objects for Mhd BAsed on Tvd

    NASA Astrophysics Data System (ADS)

    Mendygral, Peter; Porter, David; Edmon, Paul; Delgado, Jennifer

    2012-04-01

    WOMBAT (sWift Objects for Mhd BAsed on Tvd) is an astrophysical fluid code that is an implementation of a non-relativistic MHD TVD scheme; an extension for relativistic MHD has been added. The code operates on 1, 2, and 3D Eulerian meshes (cartesian and cylindrical coordinates) with magnetic field divergence restriction controlled by a constrained transport (CT) scheme. The user can tune code performance to a given processor based on chip cache sizes. Proper settings yield significant speed-ups due to efficient cache reuse.

  2. Plasma flow structures as analytical solution of a magneto-hydro-dynamic model with pressure

    NASA Astrophysics Data System (ADS)

    Paccagnella, R.

    2012-03-01

    In this work starting from a set of magnetohydrodynamic (MHD) equations that describe the dynamical evolution for the pressure driven resistive/interchange modes in a magnetic confinement system, global solutions for the plasma flow relevant for toroidal pinches like tokamaks and reversed field pinches (RFPs) are derived. Analytical solutions for the flow stream function associated with the dominant modes are presented.

  3. An extended HLLC Riemann solver for the magneto-hydrodynamics including strong internal magnetic field

    NASA Astrophysics Data System (ADS)

    Guo, Xiaocheng

    2015-06-01

    By revisiting the derivation of the previously developed HLLC Riemann solver for magneto-hydrodynamics (MHD), the paper presents an extended HLLC Riemann solver specifically designed for the MHD system in which the magnetic field can be decomposed into a strong internal magnetic field and an external component. The derived HLLC Riemann solver satisfies the conservation laws. The numerical tests show that the extended solver deals with the global MHD simulation of the Earth's magnetosphere well, and maintains high numerical resolution. It recovers the previously developed HLLC Riemann solver for the MHD as long as the internal field is set to zero. Thus, it is backward compatible with the previous HLLC solver, and suitable for the MHD simulations no matter whether a strong internal magnetic field is included or not.

  4. Gas-Kinetic Theory Based Flux Splitting Method for Ideal Magnetohydrodynamics

    NASA Technical Reports Server (NTRS)

    Xu, Kun

    1998-01-01

    A gas-kinetic solver is developed for the ideal magnetohydrodynamics (MHD) equations. The new scheme is based on the direct splitting of the flux function of the MHD equations with the inclusion of "particle" collisions in the transport process. Consequently, the artificial dissipation in the new scheme is much reduced in comparison with the MHD Flux Vector Splitting Scheme. At the same time, the new scheme is compared with the well-developed Roe-type MHD solver. It is concluded that the kinetic MHD scheme is more robust and efficient than the Roe- type method, and the accuracy is competitive. In this paper the general principle of splitting the macroscopic flux function based on the gas-kinetic theory is presented. The flux construction strategy may shed some light on the possible modification of AUSM- and CUSP-type schemes for the compressible Euler equations, as well as to the development of new schemes for a non-strictly hyperbolic system.

  5. Plasmoid Instabilities Mediated Three-Dimensional Magnetohydrodynamic Turbulent Reconnection

    SciTech Connect

    Huang, Yi-min; Guo, Fan

    2015-07-21

    After some introductory remarks on fast reconnection in resistive MHD due to plasmoid instability, oblique tearing modes in 3D, and previous studies on 3D turbulent reconnection, the subject is presented under the following topics: 3D simulation setup, time evolution of the 3D simulation, comparison with Sweet-Parker and 2D plasmoid reconnection, and diagnostics of the turbulent state (decomposition of mean fields and fluctuations, power spectra of energy fluctuations, structure function and eddy anisotropy with respect to local magnetic field). Three primary conclusions were reached: (1) The results suggest that 3D plasmoid instabilities can lead to self-generated turbulent reconnection (evidence of energy cascade and development of inertial range, energy fluctuations preferentially align with the local magnetic field, which is one of the characteristics of MHD turbulence); (2) The turbulence is highly inhomogeneous, due to the presence of magnetic shear and outflow jets (conventional MHD turbulence theories or phenomenologies may not be applicable – e.g. scale-dependent anisotropy as predicted by Goldreich & Sridhar is not found); (3) 3D turbulent reconnection is different from 2D plasmoid-dominated reconnection in many aspects. However, in fully developed state, reconnection rates in 2D and 3D are comparable — this result needs to be further checked in higher S.

  6. Study of the Three-dimensional Coronal Magnetic Field of Active Region 11117 around the Time of a Confined Flare Using a Data-Driven CESE-MHD Model

    NASA Astrophysics Data System (ADS)

    Jiang, Chaowei; Feng, Xueshang; Wu, S. T.; Hu, Qiang

    2012-11-01

    We apply a data-driven magnetohydrodynamics (MHD) model to investigate the three-dimensional (3D) magnetic field of NOAA active region (AR) 11117 around the time of a C-class confined flare that occurred on 2010 October 25. The MHD model, based on the spacetime conservation-element and solution-element scheme, is designed to focus on the magnetic field evolution and to consider a simplified solar atomsphere with finite plasma β. Magnetic vector-field data derived from the observations at the photosphere is inputted directly to constrain the model. Assuming that the dynamic evolution of the coronal magnetic field can be approximated by successive equilibria, we solve a time sequence of MHD equilibria based on a set of vector magnetograms for AR 11117 taken by the Helioseismic and Magnetic Imager on board the Solar Dynamic Observatory around the time of the flare. The model qualitatively reproduces the basic structures of the 3D magnetic field, as supported by the visual similarity between the field lines and the coronal loops observed by the Atmospheric Imaging Assembly, which shows that the coronal field can indeed be well characterized by the MHD equilibrium in most cases. The magnetic configuration changes very little during the studied time interval of 2 hr. A topological analysis reveals that the small flare is correlated with a bald patch (BP, where the magnetic field is tangent to the photosphere), suggesting that the energy release of the flare can be understood by magnetic reconnection associated with the BP separatrices. The total magnetic flux and energy keep increasing slightly in spite of the flare, while the computed magnetic free energy drops during the flare by ~1030 erg, which seems to be adequate in providing the energy budget of a minor C-class confined flare.

  7. STUDY OF THE THREE-DIMENSIONAL CORONAL MAGNETIC FIELD OF ACTIVE REGION 11117 AROUND THE TIME OF A CONFINED FLARE USING A DATA-DRIVEN CESE-MHD MODEL

    SciTech Connect

    Jiang Chaowei; Feng Xueshang; Wu, S. T.; Hu Qiang E-mail: fengx@spaceweather.ac.cn E-mail: qh0001@uah.edu

    2012-11-10

    We apply a data-driven magnetohydrodynamics (MHD) model to investigate the three-dimensional (3D) magnetic field of NOAA active region (AR) 11117 around the time of a C-class confined flare that occurred on 2010 October 25. The MHD model, based on the spacetime conservation-element and solution-element scheme, is designed to focus on the magnetic field evolution and to consider a simplified solar atomsphere with finite plasma {beta}. Magnetic vector-field data derived from the observations at the photosphere is inputted directly to constrain the model. Assuming that the dynamic evolution of the coronal magnetic field can be approximated by successive equilibria, we solve a time sequence of MHD equilibria based on a set of vector magnetograms for AR 11117 taken by the Helioseismic and Magnetic Imager on board the Solar Dynamic Observatory around the time of the flare. The model qualitatively reproduces the basic structures of the 3D magnetic field, as supported by the visual similarity between the field lines and the coronal loops observed by the Atmospheric Imaging Assembly, which shows that the coronal field can indeed be well characterized by the MHD equilibrium in most cases. The magnetic configuration changes very little during the studied time interval of 2 hr. A topological analysis reveals that the small flare is correlated with a bald patch (BP, where the magnetic field is tangent to the photosphere), suggesting that the energy release of the flare can be understood by magnetic reconnection associated with the BP separatrices. The total magnetic flux and energy keep increasing slightly in spite of the flare, while the computed magnetic free energy drops during the flare by {approx}10{sup 30} erg, which seems to be adequate in providing the energy budget of a minor C-class confined flare.

  8. MHD Simulations of Disruptions in NSTX

    NASA Astrophysics Data System (ADS)

    Breslau, J. A.; Strauss, H. R.; Paccagnella, R.; Jardin, S. C.

    2011-10-01

    Research tokamaks such as ITER must be designed to tolerate a limited number of disruptions without sustaining significant damage. It is therefore vital to have numerical tools that can accurately predict the effects of these events. The 3D nonlinear extended MHD code M3D has been augmented with models of the vacuum/halo region and a thin axisymmetric resistive shell that allow it to simulate disruptions and calculate the associated wall currents and forces. Its reliability, however, must be assessed with careful validation studies against disruption databases from existing experiments. Here we compare M3D VDE/kink disruption calculations with data from NSTX. The results of high-resolution numerical simulations at realistic Lundquist numbers show reasonable agreement with experimental data and provide confidence that M3D will be a useful tool for future ITER calculations. The effects of different choices of plasma outflow boundary conditions will also be reported.

  9. Magnetohydrodynamic modes analysis and control of Fusion Advanced Studies Torus high-current scenarios

    SciTech Connect

    Villone, F.; Mastrostefano, S.; Calabrò, G.; Vlad, G.; Crisanti, F.; Fusco, V.; Marchiori, G.; Bolzonella, T.; Marrelli, L.; Martin, P.; Liu, Y. Q.

    2014-08-15

    One of the main FAST (Fusion Advanced Studies Torus) goals is to have a flexible experiment capable to test tools and scenarios for safe and reliable tokamak operation, in order to support ITER and help the final DEMO design. In particular, in this paper, we focus on operation close to a possible border of stability related to low-q operation. To this purpose, a new FAST scenario has then been designed at I{sub p} = 10 MA, B{sub T} = 8.5 T, q{sub 95} ≈ 2.3. Transport simulations, carried out by using the code JETTO and the first principle transport model GLF23, indicate that, under these conditions, FAST could achieve an equivalent Q ≈ 3.5. FAST will be equipped with a set of internal active coils for feedback control, which will produce magnetic perturbation with toroidal number n = 1 or n = 2. Magnetohydrodynamic (MHD) mode analysis and feedback control simulations performed with the codes MARS, MARS-F, CarMa (both assuming the presence of a perfect conductive wall and using the exact 3D resistive wall structure) show the possibility of the FAST conductive structures to stabilize n = 1 ideal modes. This leaves therefore room for active mitigation of the resistive mode (down to a characteristic time of 1 ms) for safety purposes, i.e., to avoid dangerous MHD-driven plasma disruption, when working close to the machine limits and magnetic and kinetic energy density not far from reactor values.

  10. Cosmic ray transport in heliospheric magnetic structures. I. Modeling background solar wind using the CRONOS magnetohydrodynamic code

    SciTech Connect

    Wiengarten, T.; Kleimann, J.; Fichtner, H.; Kühl, P.; Kopp, A.; Heber, B.; Kissmann, R.

    2014-06-10

    The transport of energetic particles such as cosmic rays is governed by the properties of the plasma being traversed. While these properties are rather poorly known for galactic and interstellar plasmas due to the lack of in situ measurements, the heliospheric plasma environment has been probed by spacecraft for decades and provides a unique opportunity for testing transport theories. Of particular interest for the three-dimensional (3D) heliospheric transport of energetic particles are structures such as corotating interaction regions, which, due to strongly enhanced magnetic field strengths, turbulence, and associated shocks, can act as diffusion barriers on the one hand, but also as accelerators of low energy CRs on the other hand as well. In a two-fold series of papers, we investigate these effects by modeling inner-heliospheric solar wind conditions with a numerical magnetohydrodynamic (MHD) setup (this paper), which will serve as an input to a transport code employing a stochastic differential equation approach (second paper). In this first paper, we present results from 3D MHD simulations with our code CRONOS: for validation purposes we use analytic boundary conditions and compare with similar work by Pizzo. For a more realistic modeling of solar wind conditions, boundary conditions derived from synoptic magnetograms via the Wang-Sheeley-Arge (WSA) model are utilized, where the potential field modeling is performed with a finite-difference approach in contrast to the traditional spherical harmonics expansion often utilized in the WSA model. Our results are validated by comparing with multi-spacecraft data for ecliptical (STEREO-A/B) and out-of-ecliptic (Ulysses) regions.

  11. Pulse Detonation Rocket Magnetohydrodynamic Power Experiment

    NASA Technical Reports Server (NTRS)

    Litchford, R. J.; Jones, J. E.; Dobson, C. C.; Cole, J. W.; Thompson, B. R.; Plemmons, D. H.; Turner, M. W.

    2003-01-01

    The production of onboard electrical power by pulse detonation engines is problematic in that they generate no shaft power; however, pulse detonation driven magnetohydrodynamic (MHD) power generation represents one intriguing possibility for attaining self-sustained engine operation and generating large quantities of burst power for onboard electrical systems. To examine this possibility further, a simple heat-sink apparatus was developed for experimentally investigating pulse detonation driven MHD generator concepts. The hydrogen oxygen fired driver was a 90 cm long stainless steel tube having a 4.5 cm square internal cross section and a short Schelkin spiral near the head end to promote rapid formation of a detonation wave. The tube was intermittently filled to atmospheric pressure and seeded with a CsOH/methanol prior to ignition by electrical spark. The driver exhausted through an aluminum nozzle having an area contraction ratio of A*/A(sub zeta) = 1/10 and an area expansion ratio of A(sub zeta)/A* = 3.2 (as limited by available magnet bore size). The nozzle exhausted through a 24-electrode segmented Faraday channel (30.5 cm active length), which was inserted into a 0.6 T permanent magnet assembly. Initial experiments verified proper drive operation with and without the nozzle attachment, and head end pressure and time resolved thrust measurements were acquired. The exhaust jet from the nozzle was interrogated using a polychromatic microwave interferometer yielding an electron number density on the order of 10(exp 12)/cm at the generator entrance. In this case, MHD power generation experiments suffered from severe near-electrode voltage drops and low MHD interaction; i.e., low flow velocity, due to an inherent physical constraint on expansion with the available magnet. Increased scaling, improved seeding techniques, higher magnetic fields, and higher expansion ratios are expected to greatly improve performance.

  12. Evaluation of materials for the MHD steam bottoming plant

    SciTech Connect

    Natesan, K.; Swift, W.M.

    1989-05-01

    Test data have been obtained on the corrosion of several commercial ASME-coded alloys and their weldments by exposing internally cooled ring specimens to simulated magnetohydrodynamics (MHD) environments. The specimens, coated with a K/sub 2/SO/sub 4/-rich deposit, were exposed for times up to 2000 h at metal temperatures of 762, 593, and 567/degree/C to simulated MHD conditions for the intermediate-temperature air heater (ITAH), ITAH transition region (transition from a low- to medium-chromium alloy to a high-chromium steel), and secondary superheater (SSH), respectively. This paper discusses, in detail, the observed corrosion scale morphologies of various exposed specimens. Data on scale thickness, depth of intergranular penetration, and metal recession are presented, and the results are used to assess the corrosion behavior of various materials for application in the MHD steam bottoming plant. 6 refs., 7 figs., 3 tabs.

  13. Diagnostic development and support of MHD test facilities

    SciTech Connect

    Not Available

    1990-01-01

    The Diagnostic Instrumentation and Analysis Laboratory (DIAL) at Mississippi State University (MSU) is developing diagnostic instruments for Magnetohydrodynamics (MHD) power train data acquisition and for support of MHD component development test facilities. Microprocessor-controlled optical instruments, initially developed for Heat Recovery/Seed Recovery support, are being refined, and new systems to measure temperatures and gas-seed-slag stream characteristics are being developed. To further data acquisition and analysis capabilities, the diagnostic systems are being interfaced with DIAL's computers. Technical support for the diagnostic needs of the national MHD research effort is being provided. DIAL personnel will also cooperate with government agencies and private industries to improve the transformation of research and development results into processes, products and services applicable to their needs. 9 figs., 1 tab.

  14. Outline of fast analyzer for MHD equilibrium FAME

    NASA Astrophysics Data System (ADS)

    Sakata, Shinya; Haginoya, Hirofumi; Tsuruoka, Takuya; Aoyagi, Tetsuo; Saito, Naoyuki; Harada, Hiroo; Tani, Keiji; Watanabe, Hideto

    1994-02-01

    The FAME (Fast Analyzer for Magnetohydrodynamic (MHD) Equilibrium) system has been developed in order to provide more than 100 MHD equilibria in time series which are enough for the non-stationary analysis of the experimental data of JT-60 within about 20 minutes shot interval. The FAME is an MIMD type small scale parallel computer with 20 microprocessors which are connected by a multi-stage switching system. The maximum theoretical speed is 250 MFLOPS. For the software system of FAME, MHD equilibrium analysis code SELENE and its input data production code FBI are tuned up taking the parallel processing into consideration. Consequently, the computational performance of the FAME system becomes more than 7 times faster than the existing general purpose computer FACOM M780-10s. This report summarizes the outline of the FAME system including hardware, soft-ware and peripheral equipments.

  15. RADIATION MAGNETOHYDRODYNAMIC SIMULATIONS OF PROTOSTELLAR COLLAPSE: NONIDEAL MAGNETOHYDRODYNAMIC EFFECTS AND EARLY FORMATION OF CIRCUMSTELLAR DISKS

    SciTech Connect

    Tomida, Kengo; Okuzumi, Satoshi; Machida, Masahiro N. E-mail: okuzumi@geo.titech.ac.jp

    2015-03-10

    The transport of angular momentum by magnetic fields is a crucial physical process in the formation and evolution of stars and disks. Because the ionization degree in star-forming clouds is extremely low, nonideal magnetohydrodynamic (MHD) effects such as ambipolar diffusion and ohmic dissipation work strongly during protostellar collapse. These effects have significant impacts in the early phase of star formation as they redistribute magnetic flux and suppress angular momentum transport by magnetic fields. We perform three-dimensional nested-grid radiation magnetohydrodynamic simulations including ohmic dissipation and ambipolar diffusion. Without these effects, magnetic fields transport angular momentum so efficiently that no rotationally supported disk is formed even after the second collapse. Ohmic dissipation works only in a relatively high density region within the first core and suppresses angular momentum transport, enabling formation of a very small rotationally supported disk after the second collapse. With both ohmic dissipation and ambipolar diffusion, these effects work effectively in almost the entire region within the first core and significant magnetic flux loss occurs. As a result, a rotationally supported disk is formed even before a protostellar core forms. The size of the disk is still small, about 5 AU at the end of the first core phase, but this disk will grow later as gas accretion continues. Thus, the nonideal MHD effects can resolve the so-called magnetic braking catastrophe while keeping the disk size small in the early phase, which is implied from recent interferometric observations.

  16. Impact-generated magnetic fields on the Moon : a magnetohydrodynamic numerical investigation

    NASA Astrophysics Data System (ADS)

    Oran, Rona; Shprits, Yuri; Weiss, Benjamin; Gombosi, Tamas

    2015-04-01

    derive a simplified picture of what the effects would be on an ambient magnetized plasma using general magnetohydrodynamic (MHD) arguments. The solar wind drag acting on the cloud, as well as MHD effects such as field lines stretching and magnetic reconnection were not taken into ac-count. With the advances made in computational MHD models in recent years, we can now revisit these ear-lier important models. Our goal is to perform the first MHD simulations of an impact-generated vapor cloud expanding in the solar wind around the Moon, using BATSRUS, a 3D highly-parallelized versatile MHD code developed at the University of Michigan, in order to self-consistently test the previous estima-tions of the strength and duration of the magnetic field enhancement at the antipodal points. We will con-sider different MHD processes, such as: 1) the finite resistivity of the lunar mantle 2) magnetic diffusion between the solar wind and the initially non-magnetized cloud, 3) magnetic reconnection at the antipode, and 4) viscous drag and the transport of magnetic flux due to solar wind motion, and 4) MHD instabili-ties. This will allow us to systematically examine whether impact-generated fields can indeed be respon-sible for the formation of crustal field enhancements on the Moon.

  17. New Exact Relations for Helicities in Hall Magnetohydrodynamic Turbulence

    NASA Astrophysics Data System (ADS)

    Banerjee, Supratik; Galtier, Sebastien

    2016-04-01

    Hall magnetohydrodynamics is a mono-fluid plasma model appropriate for probing Final{some of the} physical processes (other than pure kinetic effects) at length scales smaller than the scales of standard MHD. In sub-ionic space plasma turbulence (e.g. the solar wind) this fluid model has been proved to be useful. Three-dimensional incompressible Hall magnetohydrodynamics (MHD) possesses three inviscid invariants which are the total energy, the magnetic helicity and the generalized helicity. In this presentation, we would like to discuss new exact relations for helicities (magnetic helicities and generalized helicities) which are derived for homogeneous stationary (not necessarily isotropic) Hall MHD turbulence (and also for its inertialess electron MHD limit) in the asymptotic limit of large Reynolds numbers. The universal laws are written only in terms of mixed second-order structure functions, i.e. the scalar product of two different increments and are written simply as ηM = di < δ ( {b} × {j}) \\cdot δ {b} >, with ηM the average magnetic helicity flux rate, {b} the magnetic field, {j} the current and ± ηG = < δ ( {v} × {Ω} ) \\cdot δ {Ω} > , with ηM the average generalized helicity flux rate, {v} the fluid velocity and {Ω} = {b} + dI {ω} being the generalized helicity where ω is simply the fluid vorticity ( = nabla × {v}). It provides, therefore, a direct measurement of the dissipation rates for the corresponding helicities even in case of an anisotropic plasma turbulence. This study shows that the generalized helicity cascade is strongly linked to the left polarized fluctuations while the magnetic helicity cascade is linked to the right polarized fluctuations. The newly derived relations also show that like energy, a non-zero helicity flux can only be associated to a departure of Beltrami flow state. {Reference} S. Banerjee & S. Galtier, {Chiral Exact Relations for Helicities in Hall Magnetohydrodynamic Turbulence} (submitted).

  18. Robust preconditioners for incompressible MHD models

    NASA Astrophysics Data System (ADS)

    Ma, Yicong; Hu, Kaibo; Hu, Xiaozhe; Xu, Jinchao

    2016-07-01

    In this paper, we develop two classes of robust preconditioners for the structure-preserving discretization of the incompressible magnetohydrodynamics (MHD) system. By studying the well-posedness of the discrete system, we design block preconditioners for them and carry out rigorous analysis on their performance. We prove that such preconditioners are robust with respect to most physical and discretization parameters. In our proof, we improve the existing estimates of the block triangular preconditioners for saddle point problems by removing the scaling parameters, which are usually difficult to choose in practice. This new technique is applicable not only to the MHD system, but also to other problems. Moreover, we prove that Krylov iterative methods with our preconditioners preserve the divergence-free condition exactly, which complements the structure-preserving discretization. Another feature is that we can directly generalize this technique to other discretizations of the MHD system. We also present preliminary numerical results to support the theoretical results and demonstrate the robustness of the proposed preconditioners.

  19. FEMHD: An adaptive finite element method for MHD and edge modelling

    SciTech Connect

    Strauss, H.R.

    1995-07-01

    This paper describes the code FEMHD, an adaptive finite element MHD code, which is applied in a number of different manners to model MHD behavior and edge plasma phenomena on a diverted tokamak. The code uses an unstructured triangular mesh in 2D and wedge shaped mesh elements in 3D. The code has been adapted to look at neutral and charged particle dynamics in the plasma scrape off region, and into a full MHD-particle code.

  20. A solution of two-dimensional magnetohydrodynamic flow using the finite element method

    SciTech Connect

    Verardi, S.L.L.; Cardoso, J.R.; Motta, C.C.

    1998-09-01

    The problem of magnetohydrodynamic flow through channels has become important because of several engineering applications such as design of nuclear reactor cooling systems, electromagnetic pumps, MHD flowmeters, MHD generators, blood flow measurements, etc. A numerical code based on the Finite Element Method (FEM) was developed to solve the two-dimensional, steady-state magnetohydrodynamic (MHD) flow in a rectangular channel. In order to apply the FEM, the Galerkin Weak Formulation was used. In this analysis, in contrast with the previous works, the thickness of the duct wall is taken into account and the results are compared to those obtained in the limit case when the thickness is much smaller than a characteristic dimension of the duct. In this case, convergence behavior of several iterative methods, for high Hartmann numbers, was also investigated.

  1. Edge localized linear ideal magnetohydrodynamic instability studies in an extended-magnetohydrodynamic code

    NASA Astrophysics Data System (ADS)

    Burke, B. J.; Kruger, S. E.; Hegna, C. C.; Zhu, P.; Snyder, P. B.; Sovinec, C. R.; Howell, E. C.

    2010-03-01

    A linear benchmark between the linear ideal MHD stability codes ELITE [H. R. Wilson et al., Phys. Plasmas 9, 1277 (2002)], GATO [L. Bernard et al., Comput. Phys. Commun. 24, 377 (1981)], and the extended nonlinear magnetohydrodynamic (MHD) code, NIMROD [C. R. Sovinec et al.., J. Comput. Phys. 195, 355 (2004)] is undertaken for edge-localized (MHD) instabilities. Two ballooning-unstable, shifted-circle tokamak equilibria are compared where the stability characteristics are varied by changing the equilibrium plasma profiles. The equilibria model an H-mode plasma with a pedestal pressure profile and parallel edge currents. For both equilibria, NIMROD accurately reproduces the transition to instability (the marginally unstable mode), as well as the ideal growth spectrum for a large range of toroidal modes (n =1-20). The results use the compressible MHD model and depend on a precise representation of "ideal-like" and "vacuumlike" or "halo" regions within the code. The halo region is modeled by the introduction of a Lundquist-value profile that transitions from a large to a small value at a flux surface location outside of the pedestal region. To model an ideal-like MHD response in the core and a vacuumlike response outside the transition, separate criteria on the plasma and halo Lundquist values are required. For the benchmarked equilibria the critical Lundquist values are 108 and 103 for the ideal-like and halo regions, respectively. Notably, this gives a ratio on the order of 105, which is much larger than experimentally measured values using Te values associated with the top of the pedestal and separatrix. Excellent agreement with ELITE and GATO calculations are made when sharp boundary transitions in the resistivity are used and a small amount of physical dissipation is added for conditions very near and below marginal ideal stability.

  2. 3D toroidal physics: Testing the boundaries of symmetry breaking

    SciTech Connect

    Spong, Donald A.

    2015-05-15

    Toroidal symmetry is an important concept for plasma confinement; it allows the existence of nested flux surface MHD equilibria and conserved invariants for particle motion. However, perfect symmetry is unachievable in realistic toroidal plasma devices. For example, tokamaks have toroidal ripple due to discrete field coils, optimized stellarators do not achieve exact quasi-symmetry, the plasma itself continually seeks lower energy states through helical 3D deformations, and reactors will likely have non-uniform distributions of ferritic steel near the plasma. Also, some level of designed-in 3D magnetic field structure is now anticipated for most concepts in order to provide the plasma control needed for a stable, steady-state fusion reactor. Such planned 3D field structures can take many forms, ranging from tokamaks with weak 3D edge localized mode suppression fields to stellarators with more dominant 3D field structures. This motivates the development of physics models that are applicable across the full range of 3D devices. Ultimately, the questions of how much symmetry breaking can be tolerated and how to optimize its design must be addressed for all fusion concepts. A closely coupled program of simulation, experimental validation, and design optimization is required to determine what forms and amplitudes of 3D shaping and symmetry breaking will be compatible with the requirements of future fusion reactors.

  3. 3D toroidal physics: Testing the boundaries of symmetry breakinga)

    NASA Astrophysics Data System (ADS)

    Spong, Donald A.

    2015-05-01

    Toroidal symmetry is an important concept for plasma confinement; it allows the existence of nested flux surface MHD equilibria and conserved invariants for particle motion. However, perfect symmetry is unachievable in realistic toroidal plasma devices. For example, tokamaks have toroidal ripple due to discrete field coils, optimized stellarators do not achieve exact quasi-symmetry, the plasma itself continually seeks lower energy states through helical 3D deformations, and reactors will likely have non-uniform distributions of ferritic steel near the plasma. Also, some level of designed-in 3D magnetic field structure is now anticipated for most concepts in order to provide the plasma control needed for a stable, steady-state fusion reactor. Such planned 3D field structures can take many forms, ranging from tokamaks with weak 3D edge localized mode suppression fields to stellarators with more dominant 3D field structures. This motivates the development of physics models that are applicable across the full range of 3D devices. Ultimately, the questions of how much symmetry breaking can be tolerated and how to optimize its design must be addressed for all fusion concepts. A closely coupled program of simulation, experimental validation, and design optimization is required to determine what forms and amplitudes of 3D shaping and symmetry breaking will be compatible with the requirements of future fusion reactors.

  4. Numerical Simulation of Turbulent MHD Flows Using an Iterative PNS Algorithm

    NASA Technical Reports Server (NTRS)

    Kato, Hiromasa; Tannehill, John C.; Mehta, Unmeel B.

    2003-01-01

    A new parabolized Navier-Stokes (PNS) algorithm has been developed to efficiently compute magnetohydrodynamic (MHD) flows in the low magnetic Reynolds number regime. In this regime, the electrical conductivity is low and the induced magnetic field is negligible compared to the applied magnetic field. The MHD effects are modeled by introducing source terms into the PNS equation which can then be solved in a very efficient manner. To account for upstream (elliptic) effects, the flowfields are computed using multiple streamwise sweeps with an iterated PNS algorithm. Turbulence has been included by modifying the Baldwin-Lomax turbulence model to account for MHD effects. The new algorithm has been used to compute both laminar and turbulent, supersonic, MHD flows over flat plates and supersonic viscous flows in a rectangular MHD accelerator. The present results are in excellent agreement with previous complete Navier-Stokes calculations.

  5. Coal-gasification/MHD/steam-turbine combined-cycle (GMS) power generation

    SciTech Connect

    Lytle, J.M.; Marchant, D.D.

    1980-11-01

    The coal-gasification/MHD/steam-turbine combined cycle (GMS) refers to magnetohydrodynamic (MHD) systems in which coal gasification is used to supply a clean fuel (free of mineral matter and sulfur) for combustion in an MHD electrical power plant. Advantages of a clean-fuel system include the elimination of mineral matter or slag from all components other than the coal gasifier and gas cleanup system; reduced wear and corrosion on components; and increased seed recovery resulting from reduced exposure of seed to mineral matter or slag. Efficiencies in some specific GMS power plants are shown to be higher than for a comparably sized coal-burning MHD power plant. The use of energy from the MHD exhaust gas to gasify coal (rather than the typical approach of burning part of the coal) results in these higher efficiencies.

  6. Magneto-hydrodynamics Simulation in Astrophysics

    NASA Astrophysics Data System (ADS)

    Pang, Bijia

    2011-08-01

    Magnetohydrodynamics (MHD) studies the dynamics of an electrically conducting fluid under the influence of a magnetic field. Many astrophysical phenomena are related to MHD, and computer simulations are used to model these dynamics. In this thesis, we conduct MHD simulations of non-radiative black hole accretion as well as fast magnetic reconnection. By performing large scale three dimensional parallel MHD simulations on supercomputers and using a deformed-mesh algorithm, we were able to conduct very high dynamical range simulations of black hole accretion of Sgr A* at the Galactic Center. We find a generic set of solutions, and make specific predictions for currently feasible observations of rotation measure (RM). The magnetized accretion flow is subsonic and lacks outward convection flux, making the accretion rate very small and having a density slope of around -1. There is no tendency for the flows to become rotationally supported, and the slow time variability of th! e RM is a key quantitative signature of this accretion flow. We also provide a constructive numerical example of fast magnetic reconnection in a three-dimensional periodic box. Reconnection is initiated by a strong, localized perturbation to the field lines and the solution is intrinsically three-dimensional. Approximately 30% of the magnetic energy is released in an event which lasts about one Alfvén time, but only after a delay during which the field lines evolve into a critical configuration. In the co-moving frame of the reconnection regions, reconnection occurs through an X-like point, analogous to the Petschek reconnection. The dynamics appear to be driven by global flows rather than local processes. In addition to issues pertaining to physics, we present results on the acceleration of MHD simulations using heterogeneous computing systems te{shan2006heterogeneous}. We have implemented the MHD code on a variety of heterogeneous and multi-core architectures (multi-core x86, Cell, Nvidia and

  7. 3D toroidal physics: testing the boundaries of symmetry breaking

    NASA Astrophysics Data System (ADS)

    Spong, Don

    2014-10-01

    Toroidal symmetry is an important concept for plasma confinement; it allows the existence of nested flux surface MHD equilibria and conserved invariants for particle motion. However, perfect symmetry is unachievable in realistic toroidal plasma devices. For example, tokamaks have toroidal ripple due to discrete field coils, optimized stellarators do not achieve exact quasi-symmetry, the plasma itself continually seeks lower energy states through helical 3D deformations, and reactors will likely have non-uniform distributions of ferritic steel near the plasma. Also, some level of designed-in 3D magnetic field structure is now anticipated for most concepts in order to lead to a stable, steady-state fusion reactor. Such planned 3D field structures can take many forms, ranging from tokamaks with weak 3D ELM-suppression fields to stellarators with more dominant 3D field structures. There is considerable interest in the development of unified physics models for the full range of 3D effects. Ultimately, the questions of how much symmetry breaking can be tolerated and how to optimize its design must be addressed for all fusion concepts. Fortunately, significant progress is underway in theory, computation and plasma diagnostics on many issues such as magnetic surface quality, plasma screening vs. amplification of 3D perturbations, 3D transport, influence on edge pedestal structures, MHD stability effects, modification of fast ion-driven instabilities, prediction of energetic particle heat loads on plasma-facing materials, effects of 3D fields on turbulence, and magnetic coil design. A closely coupled program of simulation, experimental validation, and design optimization is required to determine what forms and amplitudes of 3D shaping and symmetry breaking will be compatible with future fusion reactors. The development of models to address 3D physics and progress in these areas will be described. This work is supported both by the US Department of Energy under Contract DE

  8. Spatial and temporal analysis of DIII-D 3D magnetic diagnostic data

    NASA Astrophysics Data System (ADS)

    Strait, E. J.; King, J. D.; Hanson, J. M.; Logan, N. C.

    2016-11-01

    An extensive set of magnetic diagnostics in DIII-D is aimed at measuring non-axisymmetric "3D" features of tokamak plasmas, with typical amplitudes ˜10-3 to 10-5 of the total magnetic field. We describe hardware and software techniques used at DIII-D to condition the individual signals and analysis to estimate the spatial structure from an ensemble of discrete measurements. Applications of the analysis include detection of non-rotating MHD instabilities, plasma control, and validation of MHD stability and 3D equilibrium models.

  9. MHD simulations: Corotating Interaction Regions

    NASA Astrophysics Data System (ADS)

    Wiengarten, T.; Kleimann, J.; Fichtner, H.; Kühl, P.; Heber, B.; Kissmann, R.

    2013-12-01

    Corotating Interaction Regions (CIRs) form in the solar wind when parcels of fast-speed wind interact with slow-speed wind due to the rotation of the Sun. The resulting buildup of pressure generates disturbances that, with increasing time (or distance from the Sun), may develop into a so-called forward-reverse shock-pair. During solar-quiet times CIRs can be the dominant force shaping large-scale structures in the heliosphere. Studying CIRs is therefore important because the associated shocks are capable of e.g. accelerating energetic particles or deflecting cosmic rays. The global structure of CIRs can be modeled with an MHD approach that gives the plasma quantities needed to model the transport of particles in the heliosphere (with e.g. stochastic differential equations (SDEs)). Our MHD code CRONOS employs a semi-discrete finite volume scheme with adaptive time-stepping Runge-Kutta integration. The solenoidality of the magnetic field is ensured via constrained transport and the code supports Cartesian, Cylindrical and Spherical coordinates (including coordinate singularities) with the option for non-equidistant grids. The code runs in parallel (MPI) and supports the HDF5 output data format. Here, we show results from 3D-MHD simulations with our code CRONOS for a) analytic boundary conditions where results can be compared to those obtained with a different code and b) boundary conditions derived with the Wang-Sheeley-Arge model from observational data (WSO), which are compared to spacecraft observations. Comparison with Pizzo (1982) for analytic boundary conditions Comparison with STEREO A for Carrington Rotation 2060

  10. SCALING PROPERTIES OF SMALL-SCALE FLUCTUATIONS IN MAGNETOHYDRODYNAMIC TURBULENCE

    SciTech Connect

    Perez, Jean Carlos; Mason, Joanne; Boldyrev, Stanislav; Cattaneo, Fausto E-mail: j.mason@exeter.ac.uk E-mail: cattaneo@flash.uchicago.edu

    2014-09-20

    Magnetohydrodynamic (MHD) turbulence in the majority of natural systems, including the interstellar medium, the solar corona, and the solar wind, has Reynolds numbers far exceeding the Reynolds numbers achievable in numerical experiments. Much attention is therefore drawn to the universal scaling properties of small-scale fluctuations, which can be reliably measured in the simulations and then extrapolated to astrophysical scales. However, in contrast with hydrodynamic turbulence, where the universal structure of the inertial and dissipation intervals is described by the Kolmogorov self-similarity, the scaling for MHD turbulence cannot be established based solely on dimensional arguments due to the presence of an intrinsic velocity scale—the Alfvén velocity. In this Letter, we demonstrate that the Kolmogorov first self-similarity hypothesis cannot be formulated for MHD turbulence in the same way it is formulated for the hydrodynamic case. Besides profound consequences for the analytical consideration, this also imposes stringent conditions on numerical studies of MHD turbulence. In contrast with the hydrodynamic case, the discretization scale in numerical simulations of MHD turbulence should decrease faster than the dissipation scale, in order for the simulations to remain resolved as the Reynolds number increases.

  11. General polytropic magnetohydrodynamic cylinder under self-gravity

    NASA Astrophysics Data System (ADS)

    Lou, Yu-Qing; Xing, Heng-Rui

    2016-02-01

    Based on general polytropic (GP) magnetohydrodynamics (MHD), we offer a self-similar dynamic formalism for a magnetized, infinitely long, axially uniform cylinder of axisymmetry under self-gravity with radial and axial flows and with helical magnetic field. We identify two major classes of solution domains and obtain a few valuable MHD integrals in general. We focus on one class that has the freedom of prescribing a GP dynamic equation of state including the isothermal limit and derive analytic asymptotic solutions for illustration. In particular, we re-visit the isothermal MHD problem of Tilley & Pudritz (TP) and find that TP's main conclusion regarding the MHD solution behaviour for a strong ring magnetic field of constant toroidal flux-to-mass ratio Γϕ to be incorrect. As this is important for conceptual scenarios, MHD cylinder models, testing numerical codes and potential observational diagnostics of magnetized filaments in various astrophysical contexts, we show comprehensive theoretical analysis and reasons as well as extensive numerical results to clarify pertinent points in this Letter. In short, for any given Γϕ value be it small or large, the asymptotic radial scaling of the reduced mass density α(x) at sufficiently large x should always be ˜x-4 instead of ˜x-2 contrary to the major claim of TP.

  12. Temporal evolution of a Current Sheet with Initial Finite Perturbations by Three-dimensional MHD Simulations

    NASA Astrophysics Data System (ADS)

    Yokoyama, Takaaki

    Temporal evolution of a current sheet with initial perturbations is studied by using the threedimensional resistive magnetohydrodynamic (MHD) simulations. The magnetic reconnection is considered to be the main engine of the energy rele ase in solar flares. The structure of the diffusion region is, however, not stil l understood under the circumstances with enormously large magnetic Reynolds num ber as the solar corona. In particular, the relationship between the flare's macroscopic physics and the microscopic ones are unclear. It is generally believed that the MHD turbulence s hould play a role in the intermediate scale. The initial current sheet is in an approximately hydromagnetic equilibrium with anti-parallel magnetic field in the y-direction. We imposed a finite-amplitude perturbations (=50ee what happens. Special attention is paid upon the evolution of a three-dimens ional structure in the direction along the initial electric current (z-direction ). Our preliminary results are as follows: (1) In the early phase of the evolut ion, high wavenumber modes in the z-direction are excited and grow. (2) Many "X "-type neutral points (lines) are generated along the magnetic neutral line (pla ne) in the current sheet. When they evolve into the non-linear phase, three-dime nsional structures in the z-direction also evolve. The spatial scale in the z-di rection seems to be almost comparable with that in the xy-plane. (3) The energy release rate is reduced in case of 3D simulations compared with 2D ones probably because of the reduction of the inflow cross sections by the formation of pattc hy structures in the current sheet.

  13. 3D Elevation Program—Virtual USA in 3D

    USGS Publications Warehouse

    Lukas, Vicki; Stoker, J.M.

    2016-01-01

    The U.S. Geological Survey (USGS) 3D Elevation Program (3DEP) uses a laser system called ‘lidar’ (light detection and ranging) to create a virtual reality map of the Nation that is very accurate. 3D maps have many uses with new uses being discovered all the time.  

  14. 3D Elevation Program—Virtual USA in 3D

    USGS Publications Warehouse

    Lukas, Vicki; Stoker, J.M.

    2016-04-14

    The U.S. Geological Survey (USGS) 3D Elevation Program (3DEP) uses a laser system called ‘lidar’ (light detection and ranging) to create a virtual reality map of the Nation that is very accurate. 3D maps have many uses with new uses being discovered all the time.  

  15. The Rossiter-McLaughlin effect reloaded: Probing the 3D spin-orbit geometry, differential stellar rotation, and the spatially-resolved stellar spectrum of star-planet systems

    NASA Astrophysics Data System (ADS)

    Cegla, H. M.; Lovis, C.; Bourrier, V.; Beeck, B.; Watson, C. A.; Pepe, F.

    2016-04-01

    When a planet transits its host star, it blocks regions of the stellar surface from view; this causes a distortion of the spectral lines and a change in the line-of-sight (LOS) velocities, known as the Rossiter-McLaughlin (RM) effect. Since the LOS velocities depend, in part, on the stellar rotation, the RM waveform is sensitive to the star-planet alignment (which provides information on the system's dynamical history). We present a new RM modelling technique that directly measures the spatially-resolved stellar spectrum behind the planet. This is done by scaling the continuum flux of the (HARPS) spectra by the transit light curve, and then subtracting the in- from the out-of-transit spectra to isolate the starlight behind the planet. This technique does not assume any shape for the intrinsic local profiles. In it, we also allow for differential stellar rotation and centre-to-limb variations in the convective blueshift. We apply this technique to HD 189733 and compare to 3D magnetohydrodynamic (MHD) simulations. We reject rigid body rotation with high confidence (>99% probability), which allows us to determine the occulted stellar latitudes and measure the stellar inclination. In turn, we determine both the sky-projected (λ ≈ -0.4 ± 0.2°) and true 3D obliquity (ψ ≈ 7+12-4°). We also find good agreement with the MHD simulations, with no significant centre-to-limb variations detectable in the local profiles. Hence, this technique provides a new powerful tool that can probe stellar photospheres, differential rotation, determine 3D obliquities, and remove sky-projection biases in planet migration theories. This technique can be implemented with existing instrumentation, but will become even more powerful with the next generation of high-precision radial velocity spectrographs.

  16. COSMOLOGICAL ADAPTIVE MESH REFINEMENT MAGNETOHYDRODYNAMICS WITH ENZO

    SciTech Connect

    Collins, David C.; Xu Hao; Norman, Michael L.; Li Hui; Li Shengtai

    2010-02-01

    In this work, we present EnzoMHD, the extension of the cosmological code Enzo to include the effects of magnetic fields through the ideal magnetohydrodynamics approximation. We use a higher order Godunov method for the computation of interface fluxes. We use two constrained transport methods to compute the electric field from those interface fluxes, which simultaneously advances the induction equation and maintains the divergence of the magnetic field. A second-order divergence-free reconstruction technique is used to interpolate the magnetic fields in the block-structured adaptive mesh refinement framework already extant in Enzo. This reconstruction also preserves the divergence of the magnetic field to machine precision. We use operator splitting to include gravity and cosmological expansion. We then present a series of cosmological and non-cosmological test problems to demonstrate the quality of solution resulting from this combination of solvers.

  17. General Relativistic Magnetohydrodynamic Simulations of Collapsars

    NASA Technical Reports Server (NTRS)

    Mizuno, Yosuke; Yamada, S.; Koider, S.; Shipata, K.

    2005-01-01

    We have performed 2.5-dimensional general relativistic magnetohydrodynamic (MHD) simulations of collapsars including a rotating black hole. Initially, we assume that the core collapse has failed in this star. A rotating black hole of a few solar masses is inserted by hand into the calculation. The simulation results show the formation of a disklike structure and the generation of a jetlike outflow near the central black hole. The jetlike outflow propagates and accelerated mainly by the magnetic field. The total jet velocity is approximately 0.3c. When the rotation of the black hole is faster, the magnetic field is twisted strongly owing to the frame-dragging effect. The magnetic energy stored by the twisting magnetic field is directly converted to kinetic energy of the jet rather than propagating as an Alfven wave. Thus, as the rotation of the black hole becomes faster, the poloidal velocity of the jet becomes faster.

  18. A pressure-based high resolution numerical method for resistive MHD

    NASA Astrophysics Data System (ADS)

    Xisto, Carlos M.; Páscoa, José C.; Oliveira, Paulo J.

    2014-10-01

    In the paper we describe in detail a numerical method for the resistive magnetohydrodynamic (MHD) equations involving viscous flow and report the results of application to a number of typical MHD test cases. The method is of the finite volume type but mixes aspects of pressure-correction and density based solvers; the algorithm arrangement is patterned on the well-known PISO algorithm, which is a pressure method, while the flux computation makes use of the AUSM-MHD scheme, which originates from density based methods. Five groups of test cases are addressed to verify and validate the method. We start with two resistive MHD cases, namely the Shercliff and Hunt flow problems, which are intended to validate the method for low-speed resistive MHD flows. The remaining three test cases, namely the cloud-shock interaction, the MHD rotor and the MHD blast wave, are standard 2D ideal MHD problems that serve to validate the method under high-speed flow and complex interaction of MHD shocks. Finally, we demonstrate the method with a more complex application problem, and discuss results of simulation for a quasi-bi-dimensional self-field magnetoplasmadynamic (MPD) thruster, for which we study the effect of cathode length upon the electromagnetic nozzle performance.

  19. Shock-capturing approach and nonevolutionary solutions in magnetohydrodynamics

    SciTech Connect

    Barmin, A.A.; Kulikovskiy, A.G.; Pogorelov, N.V.

    1996-06-01

    Shock-capturing methods have become an effective tool for the solution of hyperbolic partial differential equations. Both upwind and symmetric TVD schemes in the framework of the shock-capturing approach are thoroughly investigated and applied with great success to a number of complicated multidimensional gasdynamic problems. The extension of these schemes to magnetohydrodynamic (MHD) equations is not a simple task. First, the exact solution of the MHD Riemann problem is too multivariant to be used in regular calculations. On the other hand, the extensions of Roe`s approximate Riemann problem solvers for MHD equations in general case are nonunique and need further investigation. That is why, some simplified approaches should be constructed. In this work, the second order of accuracy in time and space high-resolution Lax-Friedrichs type scheme is suggested that gives a drastic simplification of the numerical algorithm comparing to the precise characteristic splitting of Jacobian matrices. The necessity is shown to solve the full set of MHD equations for modeling of multishocked flows, even when the problem is axisymmetric, to obtain evolutionary solutions. for the numerical example, the MHD Riemann problem is used with the initial data consisting of two constant states lying to the right and to the left from the centerline of the computational domain. If the problem is solved as purely coplanar, a slow compound wave appears in the self-similar solution obtained by any shock-capturing scheme. If the full set of MHD equations is used and a small uniform tangential disturbance is added to the magnetic field vector, a rotational jump splits from the compound wave, and it degrades into a slow shock. The reconstruction process of the nonevolutionary compound wave into evolutionary shocks is investigated. Presented results should be taken into account in the development of shock-capturing methods for MHD flows. 18 refs., 17 figs.

  20. Dissipation of Molecular Cloud Turbulence by Magnetohydrodynamic Shockwaves

    NASA Astrophysics Data System (ADS)

    Lehmann, Andrew; Wardle, Mark

    2015-08-01

    The character of star formation is intimately related to the supersonic magnetohydrodynamic (MHD) turbulent dynamics of the giant molecular clouds in which stars form. A significant amount of the turbulent energy dissipates in low velocity shock waves. These shocks cause molecular line cooling of the compressed and heated gas, and so their radiative signatures probe the nature of the turbulence. In MHD fluids the three distinct families of shocks—fast, intermediate and slow—differ in how they compress and heat the molecular gas, and so observational differences between them may also distinguish driving modes of turbulent regions.Here we use a two-fluid model to compare the characteristics of one-dimensional fast and slow MHD shocks. Fast MHD shocks are magnetically driven, forcing ion species to stream through the neutral gas ahead of the shock front. This magnetic precursor heats the gas sufficiently to create a large, warm transition zone where all the fluid variables only weakly change in the shock front. In contrast, slow MHD shocks are driven by gas pressure where neutral species collide with ion species in a thin hot slab that closely resembles an ordinary gas dynamic shock.We computed observational diagnostics for fast and slow shocks at velocities vs = 2-4 km/s and preshock Hydrogen nuclei densities n(H) = 102-4 cm-3. We followed the abundances of molecules relevant for a simple oxygen chemistry and include cooling by CO, H2 and H2O. Estimates of intensities of CO rotational lines show that high-J lines, above J = 6→5, are more strongly excited in slow MHD shocks. We discuss how these shocks could help interpret recently observed anomalously strong mid- and high-J CO lines emitted by warm gas in the Milky Way and external galaxies, and implications for simulations of MHD turbulence.

  1. Statistical Theory of the Ideal MHD Geodynamo

    NASA Technical Reports Server (NTRS)

    Shebalin, J. V.

    2012-01-01

    A statistical theory of geodynamo action is developed, using a mathematical model of the geodynamo as a rotating outer core containing an ideal (i.e., no dissipation), incompressible, turbulent, convecting magnetofluid. On the concentric inner and outer spherical bounding surfaces the normal components of the velocity, magnetic field, vorticity and electric current are zero, as is the temperature fluctuation. This allows the use of a set of Galerkin expansion functions that are common to both velocity and magnetic field, as well as vorticity, current and the temperature fluctuation. The resulting dynamical system, based on the Boussinesq form of the magnetohydrodynamic (MHD) equations, represents MHD turbulence in a spherical domain. These basic equations (minus the temperature equation) and boundary conditions have been used previously in numerical simulations of forced, decaying MHD turbulence inside a sphere [1,2]. Here, the ideal case is studied through statistical analysis and leads to a prediction that an ideal coherent structure will be found in the form of a large-scale quasistationary magnetic field that results from broken ergodicity, an effect that has been previously studied both analytically and numerically for homogeneous MHD turbulence [3,4]. The axial dipole component becomes prominent when there is a relatively large magnetic helicity (proportional to the global correlation of magnetic vector potential and magnetic field) and a stationary, nonzero cross helicity (proportional to the global correlation of velocity and magnetic field). The expected angle of the dipole moment vector with respect to the rotation axis is found to decrease to a minimum as the average cross helicity increases for a fixed value of magnetic helicity and then to increase again when average cross helicity approaches its maximum possible value. Only a relatively small value of cross helicity is needed to produce a dipole moment vector that is aligned at approx.10deg with the

  2. An Experimental MHD Dynamo

    SciTech Connect

    Forest, C. B.

    2002-11-15

    The project is designed to understand current and magnetic field generation in plasmas and other magnetohydrodynamic systems. The experiments will investigate the generation of a dynamo using liquid Na.

  3. Market study: 3-D eyetracker

    NASA Technical Reports Server (NTRS)

    1977-01-01

    A market study of a proposed version of a 3-D eyetracker for initial use at NASA's Ames Research Center was made. The commercialization potential of a simplified, less expensive 3-D eyetracker was ascertained. Primary focus on present and potential users of eyetrackers, as well as present and potential manufacturers has provided an effective means of analyzing the prospects for commercialization.

  4. 3D World Building System

    ScienceCinema

    None

    2016-07-12

    This video provides an overview of the Sandia National Laboratories developed 3-D World Model Building capability that provides users with an immersive, texture rich 3-D model of their environment in minutes using a laptop and color and depth camera.

  5. 3D World Building System

    SciTech Connect

    2013-10-30

    This video provides an overview of the Sandia National Laboratories developed 3-D World Model Building capability that provides users with an immersive, texture rich 3-D model of their environment in minutes using a laptop and color and depth camera.

  6. LLNL-Earth3D

    SciTech Connect

    2013-10-01

    Earth3D is a computer code designed to allow fast calculation of seismic rays and travel times through a 3D model of the Earth. LLNL is using this for earthquake location and global tomography efforts and such codes are of great interest to the Earth Science community.

  7. [3-D ultrasound in gastroenterology].

    PubMed

    Zoller, W G; Liess, H

    1994-06-01

    Three-dimensional (3D) sonography represents a development of noninvasive diagnostic imaging by real-time two-dimensional (2D) sonography. The use of transparent rotating scans, comparable to a block of glass, generates a 3D effect. The objective of the present study was to optimate 3D presentation of abdominal findings. Additional investigations were made with a new volumetric program to determine the volume of selected findings of the liver. The results were compared with the estimated volumes of 2D sonography and 2D computer tomography (CT). For the processing of 3D images, typical parameter constellations were found for the different findings, which facilitated processing of 3D images. In more than 75% of the cases examined we found an optimal 3D presentation of sonographic findings with respect to the evaluation criteria developed by us for the 3D imaging of processed data. Great differences were found for the estimated volumes of the findings of the liver concerning the three different techniques applied. 3D ultrasound represents a valuable method to judge morphological appearance in abdominal findings. The possibility of volumetric measurements enlarges its potential diagnostic significance. Further clinical investigations are necessary to find out if definite differentiation between benign and malign findings is possible.

  8. Euro3D Science Conference

    NASA Astrophysics Data System (ADS)

    Walsh, J. R.

    2004-02-01

    The Euro3D RTN is an EU funded Research Training Network to foster the exploitation of 3D spectroscopy in Europe. 3D spectroscopy is a general term for spectroscopy of an area of the sky and derives its name from its two spatial + one spectral dimensions. There are an increasing number of instruments which use integral field devices to achieve spectroscopy of an area of the sky, either using lens arrays, optical fibres or image slicers, to pack spectra of multiple pixels on the sky (``spaxels'') onto a 2D detector. On account of the large volume of data and the special methods required to reduce and analyse 3D data, there are only a few centres of expertise and these are mostly involved with instrument developments. There is a perceived lack of expertise in 3D spectroscopy spread though the astronomical community and its use in the armoury of the observational astronomer is viewed as being highly specialised. For precisely this reason the Euro3D RTN was proposed to train young researchers in this area and develop user tools to widen the experience with this particular type of data in Europe. The Euro3D RTN is coordinated by Martin M. Roth (Astrophysikalisches Institut Potsdam) and has been running since July 2002. The first Euro3D science conference was held in Cambridge, UK from 22 to 23 May 2003. The main emphasis of the conference was, in keeping with the RTN, to expose the work of the young post-docs who are funded by the RTN. In addition the team members from the eleven European institutes involved in Euro3D also presented instrumental and observational developments. The conference was organized by Andy Bunker and held at the Institute of Astronomy. There were over thirty participants and 26 talks covered the whole range of application of 3D techniques. The science ranged from Galactic planetary nebulae and globular clusters to kinematics of nearby galaxies out to objects at high redshift. Several talks were devoted to reporting recent observations with newly

  9. 3D printing in dentistry.

    PubMed

    Dawood, A; Marti Marti, B; Sauret-Jackson, V; Darwood, A

    2015-12-01

    3D printing has been hailed as a disruptive technology which will change manufacturing. Used in aerospace, defence, art and design, 3D printing is becoming a subject of great interest in surgery. The technology has a particular resonance with dentistry, and with advances in 3D imaging and modelling technologies such as cone beam computed tomography and intraoral scanning, and with the relatively long history of the use of CAD CAM technologies in dentistry, it will become of increasing importance. Uses of 3D printing include the production of drill guides for dental implants, the production of physical models for prosthodontics, orthodontics and surgery, the manufacture of dental, craniomaxillofacial and orthopaedic implants, and the fabrication of copings and frameworks for implant and dental restorations. This paper reviews the types of 3D printing technologies available and their various applications in dentistry and in maxillofacial surgery. PMID:26657435

  10. PLOT3D user's manual

    NASA Technical Reports Server (NTRS)

    Walatka, Pamela P.; Buning, Pieter G.; Pierce, Larry; Elson, Patricia A.

    1990-01-01

    PLOT3D is a computer graphics program designed to visualize the grids and solutions of computational fluid dynamics. Seventy-four functions are available. Versions are available for many systems. PLOT3D can handle multiple grids with a million or more grid points, and can produce varieties of model renderings, such as wireframe or flat shaded. Output from PLOT3D can be used in animation programs. The first part of this manual is a tutorial that takes the reader, keystroke by keystroke, through a PLOT3D session. The second part of the manual contains reference chapters, including the helpfile, data file formats, advice on changing PLOT3D, and sample command files.

  11. 3D printing in dentistry.

    PubMed

    Dawood, A; Marti Marti, B; Sauret-Jackson, V; Darwood, A

    2015-12-01

    3D printing has been hailed as a disruptive technology which will change manufacturing. Used in aerospace, defence, art and design, 3D printing is becoming a subject of great interest in surgery. The technology has a particular resonance with dentistry, and with advances in 3D imaging and modelling technologies such as cone beam computed tomography and intraoral scanning, and with the relatively long history of the use of CAD CAM technologies in dentistry, it will become of increasing importance. Uses of 3D printing include the production of drill guides for dental implants, the production of physical models for prosthodontics, orthodontics and surgery, the manufacture of dental, craniomaxillofacial and orthopaedic implants, and the fabrication of copings and frameworks for implant and dental restorations. This paper reviews the types of 3D printing technologies available and their various applications in dentistry and in maxillofacial surgery.

  12. Hall effect in a strong magnetic field: Direct comparisons of compressible magnetohydrodynamics and the reduced Hall magnetohydrodynamic equations

    SciTech Connect

    Martin, L. N.; Dmitruk, P.; Gomez, D. O.

    2010-11-15

    In this work we numerically test a model of Hall magnetohydrodynamics in the presence of a strong mean magnetic field: the reduced Hall magnetohydrodynamic model (RHMHD) derived by [Gomez et al., Phys. Plasmas 15, 102303 (2008)] with the addition of weak compressible effects. The main advantage of this model lies in the reduction of computational cost. Nevertheless, up until now the degree of agreement with the original Hall MHD system and the range of validity in a regime of turbulence were not established. In this work direct numerical simulations of three-dimensional Hall MHD turbulence in the presence of a strong mean magnetic field are compared with simulations of the weak compressible RHMHD model. The results show that the degree of agreement is very high (when the different assumptions of RHMHD, such as spectral anisotropy, are satisfied). Nevertheless, when the initial conditions are isotropic but the mean magnetic field is maintained strong, the results differ at the beginning but asymptotically reach a good agreement at relatively short times. We also found evidence that the compressibility still plays a role in the dynamics of these systems, and the weak compressible RHMHD model is able to capture these effects. In conclusion the weak compressible RHMHD model is a valid approximation of the Hall MHD turbulence in the relevant physical context.

  13. PLOT3D/AMES, APOLLO UNIX VERSION USING GMR3D (WITHOUT TURB3D)

    NASA Technical Reports Server (NTRS)

    Buning, P.

    1994-01-01

    PLOT3D is an interactive graphics program designed to help scientists visualize computational fluid dynamics (CFD) grids and solutions. Today, supercomputers and CFD algorithms can provide scientists with simulations of such highly complex phenomena that obtaining an understanding of the simulations has become a major problem. Tools which help the scientist visualize the simulations can be of tremendous aid. PLOT3D/AMES offers more functions and features, and has been adapted for more types of computers than any other CFD graphics program. Version 3.6b+ is supported for five computers and graphic libraries. Using PLOT3D, CFD physicists can view their computational models from any angle, observing the physics of problems and the quality of solutions. As an aid in designing aircraft, for example, PLOT3D's interactive computer graphics can show vortices, temperature, reverse flow, pressure, and dozens of other characteristics of air flow during flight. As critical areas become obvious, they can easily be studied more closely using a finer grid. PLOT3D is part of a computational fluid dynamics software cycle. First, a program such as 3DGRAPE (ARC-12620) helps the scientist generate computational grids to model an object and its surrounding space. Once the grids have been designed and parameters such as the angle of attack, Mach number, and Reynolds number have been specified, a "flow-solver" program such as INS3D (ARC-11794 or COS-10019) solves the system of equations governing fluid flow, usually on a supercomputer. Grids sometimes have as many as two million points, and the "flow-solver" produces a solution file which contains density, x- y- and z-momentum, and stagnation energy for each grid point. With such a solution file and a grid file containing up to 50 grids as input, PLOT3D can calculate and graphically display any one of 74 functions, including shock waves, surface pressure, velocity vectors, and particle traces. PLOT3D's 74 functions are organized into

  14. PLOT3D/AMES, APOLLO UNIX VERSION USING GMR3D (WITH TURB3D)

    NASA Technical Reports Server (NTRS)

    Buning, P.

    1994-01-01

    PLOT3D is an interactive graphics program designed to help scientists visualize computational fluid dynamics (CFD) grids and solutions. Today, supercomputers and CFD algorithms can provide scientists with simulations of such highly complex phenomena that obtaining an understanding of the simulations has become a major problem. Tools which help the scientist visualize the simulations can be of tremendous aid. PLOT3D/AMES offers more functions and features, and has been adapted for more types of computers than any other CFD graphics program. Version 3.6b+ is supported for five computers and graphic libraries. Using PLOT3D, CFD physicists can view their computational models from any angle, observing the physics of problems and the quality of solutions. As an aid in designing aircraft, for example, PLOT3D's interactive computer graphics can show vortices, temperature, reverse flow, pressure, and dozens of other characteristics of air flow during flight. As critical areas become obvious, they can easily be studied more closely using a finer grid. PLOT3D is part of a computational fluid dynamics software cycle. First, a program such as 3DGRAPE (ARC-12620) helps the scientist generate computational grids to model an object and its surrounding space. Once the grids have been designed and parameters such as the angle of attack, Mach number, and Reynolds number have been specified, a "flow-solver" program such as INS3D (ARC-11794 or COS-10019) solves the system of equations governing fluid flow, usually on a supercomputer. Grids sometimes have as many as two million points, and the "flow-solver" produces a solution file which contains density, x- y- and z-momentum, and stagnation energy for each grid point. With such a solution file and a grid file containing up to 50 grids as input, PLOT3D can calculate and graphically display any one of 74 functions, including shock waves, surface pressure, velocity vectors, and particle traces. PLOT3D's 74 functions are organized into

  15. MHD Ballooning Instability in the Plasma Sheet

    SciTech Connect

    C.Z. Cheng; S. Zaharia

    2003-10-20

    Based on the ideal-MHD model the stability of ballooning modes is investigated by employing realistic 3D magnetospheric equilibria, in particular for the substorm growth phase. Previous MHD ballooning stability calculations making use of approximations on the plasma compressibility can give rise to erroneous conclusions. Our results show that without making approximations on the plasma compressibility the MHD ballooning modes are unstable for the entire plasma sheet where beta (sub)eq is greater than or equal to 1, and the most unstable modes are located in the strong cross-tail current sheet region in the near-Earth plasma sheet, which maps to the initial brightening location of the breakup arc in the ionosphere. However, the MHD beq threshold is too low in comparison with observations by AMPTE/CCE at X = -(8 - 9)R(sub)E, which show that a low-frequency instability is excited only when beq increases over 50. The difficulty is mitigated by considering the kinetic effects of ion gyrorad ii and trapped electron dynamics, which can greatly increase the stabilizing effects of field line tension and thus enhance the beta(sub)eq threshold [Cheng and Lui, 1998]. The consequence is to reduce the equatorial region of the unstable ballooning modes to the strong cross-tail current sheet region where the free energy associated with the plasma pressure gradient and magnetic field curvature is maximum.

  16. MHD aspects of fire-hose type instabilities

    NASA Astrophysics Data System (ADS)

    Wang, B.; Hau, L.

    2003-12-01

    In a homogeneous anisotropic plasma the magnetohydrodynamic (MHD) Alfvén wave may become unstable for p∥ > pperpendicular to + B2/μ 0. Recently a new type of fire-hose instability is found by Hellinger and Matsumoto [2000] that has maximum growth rate occurring for oblique propagation and may grow faster than the Alfvén mode. This new mode is compressional and may be more efficient at destroying pressure anisotropy than the standard fire hose. In this study we examines the fire-hose type (p∥ > pperpendicular to ) instabilities based on the linear and nonlinear double-polytropic MHD theory. It is shown that there exist two types of MHD fire-hose instabilities associated with the intermediate and slow modes, respectively, and with suitable choice of polytropic exponents the linear instability criteria become the same as those based on the Vlasov theory in the hydromagnetic limit. Moreover, the properties of the nonlinear MHD fire-hose instabilities are found to have great similarities with those obtained from the kinetic theory and hybrid simulation. In particular, the classical fire-hose instability evolves toward the linear fire-hose stability threshold while the nonlinear marginal stability associated with the new fire hose is well below the condition of β ∥ - β perpendicular to = 2 but complies with less stringent linear stability threshold for MHD slow-mode wave.

  17. On the generation of magnetohydrodynamic waves in a stratified and magnetized fluid. II - Magnetohydrodynamic energy fluxes for late-type stars

    NASA Technical Reports Server (NTRS)

    Musielak, Z. E.; Rosner, R.

    1988-01-01

    Magnetohydrodynamic (MHD) wave energy fluxes for late-type stars are calculated, using previously obtained formulae for the source functions for the generation of MHD waves in a stratified, but otherwise uniform, turbulent atmosphere; the magnetic fields in the wave generation region are assumed to be homogeneous. In contradiction to previous results, it is shown that in this uniform magnetic field case there is no significant increase in the efficiency of MHD wave generation, at least within the theory's limits of applicability. The major results are that the MHD energy fluxes calculated for late-type stars are less than those obtained for compressible modes in the magnetic field-free case, and that these MHD energy fluxes do not vary enough for a given spectral type to explain the observed range of UV and X-ray fluxes from such stars. It is therefore concluded that MHD waves in stellar atmospheres with homogeneous magnetic fields in the wave generation region cannot explain the observed stellar coronal emissions; if such MHD waves are responsible for a significant component of stellar coronal heating, then nonuniform fields within the generation region must be appealed to.

  18. Magnetohydrodynamic Augmented Propulsion Experiment

    NASA Technical Reports Server (NTRS)

    Litchford, Ron J.

    2008-01-01

    Over the past several years, efforts have been under way to design and develop an operationally flexible research facility for investigating the use of cross-field MHD accelerators as a potential thrust augmentation device for thermal propulsion systems. The baseline configuration for this high-power experimental facility utilizes a 1.5-MWe multi-gas arc-heater as a thermal driver for a 2-MWe MHD accelerator, which resides in a large-bore 2-tesla electromagnet. A preliminary design study using NaK seeded nitrogen as the working fluid led to an externally diagonalized segmented MHD channel configuration based on an expendable heat-sink design concept. The current status report includes a review of engineering/design work and performance optimization analyses and summarizes component hardware fabrication and development efforts, preliminary testing results, and recent progress toward full-up assembly and testing

  19. Large-scale quasi-geostrophic magnetohydrodynamics

    SciTech Connect

    Balk, Alexander M.

    2014-12-01

    We consider the ideal magnetohydrodynamics (MHD) of a shallow fluid layer on a rapidly rotating planet or star. The presence of a background toroidal magnetic field is assumed, and the 'shallow water' beta-plane approximation is used. We derive a single equation for the slow large length scale dynamics. The range of validity of this equation fits the MHD of the lighter fluid at the top of Earth's outer core. The form of this equation is similar to the quasi-geostrophic (Q-G) equation (for usual ocean or atmosphere), but the parameters are essentially different. Our equation also implies the inverse cascade; but contrary to the usual Q-G situation, the energy cascades to smaller length scales, while the enstrophy cascades to the larger scales. We find the Kolmogorov-type spectrum for the inverse cascade. The spectrum indicates the energy accumulation in larger scales. In addition to the energy and enstrophy, the obtained equation possesses an extra (adiabatic-type) invariant. Its presence implies energy accumulation in the 30° sector around zonal direction. With some special energy input, the extra invariant can lead to the accumulation of energy in zonal magnetic field; this happens if the input of the extra invariant is small, while the energy input is considerable.

  20. Magneto-hydrodynamically stable axisymmetric mirrors

    SciTech Connect

    Ryutov, D. D.; Cohen, B. I.; Molvik, A. W.; Berk, H. L.; Simonen, T. C.

    2011-09-15

    Making axisymmetric mirrors magnetohydrodynamically (MHD) stable opens up exciting opportunities for using mirror devices as neutron sources, fusion-fission hybrids, and pure-fusion reactors. This is also of interest from a general physics standpoint (as it seemingly contradicts well-established criteria of curvature-driven instabilities). The axial symmetry allows for much simpler and more reliable designs of mirror-based fusion facilities than the well-known quadrupole mirror configurations. In this tutorial, after a summary of classical results, several techniques for achieving MHD stabilization of the axisymmetric mirrors are considered, in particular: (1) employing the favorable field-line curvature in the end tanks; (2) using the line-tying effect; (3) controlling the radial potential distribution; (4) imposing a divertor configuration on the solenoidal magnetic field; and (5) affecting the plasma dynamics by the ponderomotive force. Some illuminative theoretical approaches for understanding axisymmetric mirror stability are described. The applicability of the various stabilization techniques to axisymmetric mirrors as neutron sources, hybrids, and pure-fusion reactors are discussed; and the constraints on the plasma parameters are formulated.

  1. Lack of universality in decaying magnetohydrodynamic turbulence.

    PubMed

    Lee, E; Brachet, M E; Pouquet, A; Mininni, P D; Rosenberg, D

    2010-01-01

    Using computations of three-dimensional magnetohydrodynamic (MHD) turbulence with a Taylor-Green flow, whose inherent time-independent symmetries are implemented numerically, and in the absence of either a forcing function or an imposed uniform magnetic field, we show that three different inertial ranges for the energy spectrum may emerge for three different initial magnetic fields, the selecting parameter being the ratio of nonlinear eddy to Alfvén time. Equivalent computational grids range from 128(3) to 2048(3) points with a unit magnetic Prandtl number and a Taylor Reynolds number of up to 1500 at the peak of dissipation. We also show a convergence of our results with Reynolds number. Our study is consistent with previous findings of a variety of energy spectra in MHD turbulence by studies performed in the presence of both a forcing term with a given correlation time and a strong, uniform magnetic field. However, in contrast to the previous studies, here the ratio of characteristic time scales can only be ascribed to the intrinsic nonlinear dynamics of the paradigmatic flows under study.

  2. Multiple time scale methods in tokamak magnetohydrodynamics

    SciTech Connect

    Jardin, S.C.

    1984-01-01

    Several methods are discussed for integrating the magnetohydrodynamic (MHD) equations in tokamak systems on other than the fastest time scale. The dynamical grid method for simulating ideal MHD instabilities utilizes a natural nonorthogonal time-dependent coordinate transformation based on the magnetic field lines. The coordinate transformation is chosen to be free of the fast time scale motion itself, and to yield a relatively simple scalar equation for the total pressure, P = p + B/sup 2//2..mu../sub 0/, which can be integrated implicitly to average over the fast time scale oscillations. Two methods are described for the resistive time scale. The zero-mass method uses a reduced set of two-fluid transport equations obtained by expanding in the inverse magnetic Reynolds number, and in the small ratio of perpendicular to parallel mobilities and thermal conductivities. The momentum equation becomes a constraint equation that forces the pressure and magnetic fields and currents to remain in force balance equilibrium as they evolve. The large mass method artificially scales up the ion mass and viscosity, thereby reducing the severe time scale disparity between wavelike and diffusionlike phenomena, but not changing the resistive time scale behavior. Other methods addressing the intermediate time scales are discussed.

  3. Multicomponent diffusion in two-temperature magnetohydrodynamics

    NASA Astrophysics Data System (ADS)

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

    1996-06-01

    A recent hydrodynamic theory of multicomponent diffusion in multitemperature gas mixtures [J. D. Ramshaw, J. Non-Equilib. Thermodyn. 18, 121 (1993)] is generalized to include the velocity-dependent Lorentz force on charged species in a magnetic field B. This generalization is used to extend a previous treatment of ambipolar diffusion in two-temperature multicomponent plasmas [J. D. Ramshaw and C. H. Chang, Plasma Chem. Plasma Process. 13, 489 (1993)] to situations in which B and the electrical current density are nonzero. General expressions are thereby derived for the species diffusion fluxes, including thermal diffusion, in both single- and two-temperature multicomponent magnetohydrodynamics (MHD). It is shown that the usual zero-field form of the Stefan-Maxwell equations can be preserved in the presence of B by introducing generalized binary diffusion tensors dependent on B. A self-consistent effective binary diffusion approximation is presented that provides explicit approximate expressions for the diffusion fluxes. Simplifications due to the small electron mass are exploited to obtain an ideal MHD description in which the electron diffusion coefficients drop out, resistive effects vanish, and the electric field reduces to a particularly simple form. This description should be well suited for numerical calculations.

  4. Unassisted 3D camera calibration

    NASA Astrophysics Data System (ADS)

    Atanassov, Kalin; Ramachandra, Vikas; Nash, James; Goma, Sergio R.

    2012-03-01

    With the rapid growth of 3D technology, 3D image capture has become a critical part of the 3D feature set on mobile phones. 3D image quality is affected by the scene geometry as well as on-the-device processing. An automatic 3D system usually assumes known camera poses accomplished by factory calibration using a special chart. In real life settings, pose parameters estimated by factory calibration can be negatively impacted by movements of the lens barrel due to shaking, focusing, or camera drop. If any of these factors displaces the optical axes of either or both cameras, vertical disparity might exceed the maximum tolerable margin and the 3D user may experience eye strain or headaches. To make 3D capture more practical, one needs to consider unassisted (on arbitrary scenes) calibration. In this paper, we propose an algorithm that relies on detection and matching of keypoints between left and right images. Frames containing erroneous matches, along with frames with insufficiently rich keypoint constellations, are detected and discarded. Roll, pitch yaw , and scale differences between left and right frames are then estimated. The algorithm performance is evaluated in terms of the remaining vertical disparity as compared to the maximum tolerable vertical disparity.

  5. Criteria for selecting a magnet for a MHD device

    SciTech Connect

    Geri, A.; Veca, G.M. ); Pasotti, G. )

    1992-01-01

    In this paper the authors analyze the influence of the type of superconducting (s.c.) magnet (in air or in iron) on the behavior of one same MHD device for different shapes of duct. The features of the device are evaluated by means of a code which analyses a 3D lumped-parameter electrical network, equivalent to the fluid flow.

  6. Local and nonlocal advected invariants and helicities in magnetohydrodynamics and gas dynamics: II. Noether's theorems and Casimirs

    NASA Astrophysics Data System (ADS)

    Webb, G. M.; Dasgupta, B.; McKenzie, J. F.; Hu, Q.; Zank, G. P.

    2014-03-01

    Conservation laws in ideal gas dynamics and magnetohydrodynamics (MHD) associated with fluid relabeling symmetries are derived using Noether's first and second theorems. Lie dragged invariants are discussed in terms of the MHD Casimirs. A nonlocal conservation law for fluid helicity applicable for a non-barotropic fluid involving Clebsch variables is derived using Noether's theorem, in conjunction with a fluid relabeling symmetry and a gauge transformation. A nonlocal cross helicity conservation law involving Clebsch potentials, and the MHD energy conservation law are derived by the same method. An Euler-Poincaré variational approach is also used to derive conservation laws associated with fluid relabeling symmetries using Noether's second theorem.

  7. Magneto-hydrodynamically stable axisymmetric mirrors

    NASA Astrophysics Data System (ADS)

    Ryutov, Dmitri

    2010-11-01

    The achievement of high beta (60%) plasma with near classical confinement in a linear axisymmetric magnetic configuration has sparked interest in the Gas Dynamic Trap concept. The significance of these results is that they can be projected directly to a neutron source for materials testing. The possibility of axisymmetric mirrors (AM) being magneto-hydrodynamically (MHD) stable is also of interest from a general physics standpoint (as it seemingly contradicts to well-established criteria of curvature-driven instabilities). The axial symmetry allows for much simpler and more reliable designs of mirror-based fusion facilities than the well-known quadrupole mirror configurations. In this tutorial, after a brief summary of classical results (in particular of the Rosenbluth-Longmire theory and of the energy principle as applied to AM) several approaches towards achieving MHD stabilization of the AM will be considered: 1) Employing the favorable field-line curvature in the end tanks; 2) Using the line-tying effect; 3) Setting the plasma in a slow or fast differential rotation; 4) Imposing a divertor configuration on the solenoidal magnetic field; 5) Controlling the plasma dynamics by the ponderomotive force; 6) Other techniques. Several of these approaches go beyond pure MHD and require accounting for finite Larmor radius effects and trapped particle modes. Some illuminative theoretical approaches for understanding axisymmetric mirror stability will be described. Wherever possible comparison of theoretical and experimental results on AM will be provided. The applicability of the various stabilization techniques to axisymmetric mirrors as neutron sources, hybrids, and pure-fusion reactors will be discussed and the constraints on the plasma parameters will be formulated. Prepared by LLNL under Contract DE-AC52-07NA27344.

  8. Validation of Magnetospheric Magnetohydrodynamic Models

    NASA Astrophysics Data System (ADS)

    Curtis, Brian

    Magnetospheric magnetohydrodynamic (MHD) models are commonly used for both prediction and modeling of Earth's magnetosphere. To date, very little validation has been performed to determine their limits, uncertainties, and differences. In this work, we performed a comprehensive analysis using several commonly used validation techniques in the atmospheric sciences to MHD-based models of Earth's magnetosphere for the first time. The validation techniques of parameter variability/sensitivity analysis and comparison to other models were used on the OpenGGCM, BATS-R-US, and SWMF magnetospheric MHD models to answer several questions about how these models compare. The questions include: (1) the difference between the model's predictions prior to and following to a reversal of Bz in the upstream interplanetary field (IMF) from positive to negative, (2) the influence of the preconditioning duration, and (3) the differences between models under extreme solar wind conditions. A differencing visualization tool was developed and used to address these three questions. We find: (1) For a reversal in IMF Bz from positive to negative, the OpenGGCM magnetopause is closest to Earth as it has the weakest magnetic pressure near-Earth. The differences in magnetopause positions between BATS-R-US and SWMF are explained by the influence of the ring current, which is included in SWMF. Densities are highest for SWMF and lowest for OpenGGCM. The OpenGGCM tail currents differ significantly from BATS-R-US and SWMF; (2) A longer preconditioning time allowed the magnetosphere to relax more, giving different positions for the magnetopause with all three models before the IMF Bz reversal. There were differences greater than 100% for all three models before the IMF Bz reversal. The differences in the current sheet region for the OpenGGCM were small after the IMF Bz reversal. The BATS-R-US and SWMF differences decreased after the IMF Bz reversal to near zero; (3) For extreme conditions in the solar

  9. Drag reduction in turbulent MHD pipe flows

    NASA Technical Reports Server (NTRS)

    Orlandi, P.

    1996-01-01

    This is a preliminary study devoted to verifying whether or not direct simulations of turbulent Magneto-Hydro-Dynamic (MHD) flows in liquid metals reproduce experimental observations of drag reduction. Two different cases have been simulated by a finite difference scheme which is second order accurate in space and time. In the first case, an external azimuthal magnetic field is imposed. In this case, the magnetic field acts on the mean axial velocity and complete laminarization of the flow at N(sub a) = 30 has been achieved. In the second case, an axial magnetic field is imposed which affects only fluctuating velocities, and thus the action is less efficient. This second case is more practical, but comparison between numerical and experimental results is only qualitative.

  10. Observational Tests of Recent MHD Turbulence Perspectives

    NASA Technical Reports Server (NTRS)

    Ghosh, Sanjoy; Guhathakurta, M. (Technical Monitor)

    2001-01-01

    This grant seeks to analyze the Heliospheric Missions data to test current theories on the angular dependence (with respect to mean magnetic field direction) of magnetohydrodynamic (MHD) turbulence in the solar wind. Solar wind turbulence may be composed of two or more dynamically independent components. Such components include magnetic pressure-balanced structures, velocity shears, quasi-2D turbulence, and slab (Alfven) waves. We use a method, developed during the first two years of this grant, for extracting the individual reduced spectra of up to three separate turbulence components from a single spacecraft time series. The method has been used on ISEE-3 data, Pioneer Venus Orbiter, Ulysses, and Voyager data samples. The correlation of fluctuations as a function of angle between flow direction and magnetic-field direction is the focus of study during the third year.

  11. Observational Tests of Recent MHD Turbulence Perspectives

    NASA Astrophysics Data System (ADS)

    Ghosh, Sanjoy

    2001-06-01

    This grant seeks to analyze the Heliospheric Missions data to test current theories on the angular dependence (with respect to mean magnetic field direction) of magnetohydrodynamic (MHD) turbulence in the solar wind. Solar wind turbulence may be composed of two or more dynamically independent components. Such components include magnetic pressure-balanced structures, velocity shears, quasi-2D turbulence, and slab (Alfven) waves. We use a method, developed during the first two years of this grant, for extracting the individual reduced spectra of up to three separate turbulence components from a single spacecraft time series. The method has been used on ISEE-3 data, Pioneer Venus Orbiter, Ulysses, and Voyager data samples. The correlation of fluctuations as a function of angle between flow direction and magnetic-field direction is the focus of study during the third year.

  12. Statistical Analysis of Current Sheets in Three-dimensional Magnetohydrodynamic Turbulence

    NASA Astrophysics Data System (ADS)

    Zhdankin, Vladimir; Uzdensky, Dmitri A.; Perez, Jean C.; Boldyrev, Stanislav

    2013-07-01

    We develop a framework for studying the statistical properties of current sheets in numerical simulations of magnetohydrodynamic (MHD) turbulence with a strong guide field, as modeled by reduced MHD. We describe an algorithm that identifies current sheets in a simulation snapshot and then determines their geometrical properties (including length, width, and thickness) and intensities (peak current density and total energy dissipation rate). We then apply this procedure to simulations of reduced MHD and perform a statistical analysis on the obtained population of current sheets. We evaluate the role of reconnection by separately studying the populations of current sheets which contain magnetic X-points and those which do not. We find that the statistical properties of the two populations are different in general. We compare the scaling of these properties to phenomenological predictions obtained for the inertial range of MHD turbulence. Finally, we test whether the reconnecting current sheets are consistent with the Sweet-Parker model.

  13. An approximate Riemann solver for magnetohydrodynamics (that works in more than one dimension)

    NASA Technical Reports Server (NTRS)

    Powell, Kenneth G.

    1994-01-01

    An approximate Riemann solver is developed for the governing equations of ideal magnetohydrodynamics (MHD). The Riemann solver has an eight-wave structure, where seven of the waves are those used in previous work on upwind schemes for MHD, and the eighth wave is related to the divergence of the magnetic field. The structure of the eighth wave is not immediately obvious from the governing equations as they are usually written, but arises from a modification of the equations that is presented in this paper. The addition of the eighth wave allows multidimensional MHD problems to be solved without the use of staggered grids or a projection scheme, one or the other of which was necessary in previous work on upwind schemes for MHD. A test problem made up of a shock tube with rotated initial conditions is solved to show that the two-dimensional code yields answers consistent with the one-dimensional methods developed previously.

  14. A blowup criterion for viscous, compressible, and heat-conductive magnetohydrodynamic flows

    NASA Astrophysics Data System (ADS)

    Du, Lili; Wang, Yongfu

    2015-09-01

    In this paper, we proved a blowup criterion for the two-dimensional (2D) viscous, compressible, and heat-conducting magnetohydrodynamic (MHD) flows for Cauchy problem, which depends only on the divergence of the velocity vector field, as well as for the case of bounded domain with Dirichlet boundary conditions. This result indicates that the nature of the blowup for compressible models of viscous media in 2D space is similar to the barotropic compressible Navier-Stokes equations and does not depend on further sophistication of the MHD model. More precisely, taking into account the magnetic effects and heat conductivity does not introduce any new features in the blowup mechanism of full MHD flows, especially, which is independent of the temperature and the magnetic field. The results also imply the global regularity of the strong solution to compressible MHD flows, provided that velocity divergence remains bounded.

  15. A Global Magnetohydrodynamic Model of Jovian Magnetosphere

    NASA Technical Reports Server (NTRS)

    Walker, Raymond J.; Sharber, James (Technical Monitor)

    2001-01-01

    The goal of this project was to develop a new global magnetohydrodynamic model of the interaction of the Jovian magnetosphere with the solar wind. Observations from 28 orbits of Jupiter by Galileo along with those from previous spacecraft at Jupiter, Pioneer 10 and 11, Voyager I and 2 and Ulysses, have revealed that the Jovian magnetosphere is a vast, complicated system. The Jovian aurora also has been monitored for several years. Like auroral observations at Earth, these measurements provide us with a global picture of magnetospheric dynamics. Despite this wide range of observations, we have limited quantitative understanding of the Jovian magnetosphere and how it interacts with the solar wind. For the past several years we have been working toward a quantitative understanding of the Jovian magnetosphere and its interaction with the solar wind by employing global magnetohydrodynamic simulations to model the magnetosphere. Our model has been an explicit MHD code (previously used to model the Earth's magnetosphere) to study Jupiter's magnetosphere. We continue to obtain important insights with this code, but it suffers from some severe limitations. In particular with this code we are limited to considering the region outside of 15RJ, with cell sizes of about 1.5R(sub J). The problem arises because of the presence of widely separated time scales throughout the magnetosphere. The numerical stability criterion for explicit MHD codes is the CFL limit and is given by C(sub max)(Delta)t/(Delta)x less than 1 where C(sub max) is the maximum group velocity in a given cell, (Delta)x is the grid spacing and (Delta)t is the time step. If the maximum wave velocity is C(sub w) and the flow speed is C(sub f), C(sub max) = C(sub w) + C(sub f). Near Jupiter the Alfven wave speed becomes very large (it approaches the speed of light at one Jovian radius). Operating with this time step makes the calculation essentially intractable. Therefore under this funding we have been designing a

  16. Spatially resolved 3D noise

    NASA Astrophysics Data System (ADS)

    Haefner, David P.; Preece, Bradley L.; Doe, Joshua M.; Burks, Stephen D.

    2016-05-01

    When evaluated with a spatially uniform irradiance, an imaging sensor exhibits both spatial and temporal variations, which can be described as a three-dimensional (3D) random process considered as noise. In the 1990s, NVESD engineers developed an approximation to the 3D power spectral density (PSD) for noise in imaging systems known as 3D noise. In this correspondence, we describe how the confidence intervals for the 3D noise measurement allows for determination of the sampling necessary to reach a desired precision. We then apply that knowledge to create a smaller cube that can be evaluated spatially across the 2D image giving the noise as a function of position. The method presented here allows for both defective pixel identification and implements the finite sampling correction matrix. In support of the reproducible research effort, the Matlab functions associated with this work can be found on the Mathworks file exchange [1].

  17. Autofocus for 3D imaging

    NASA Astrophysics Data System (ADS)

    Lee-Elkin, Forest

    2008-04-01

    Three dimensional (3D) autofocus remains a significant challenge for the development of practical 3D multipass radar imaging. The current 2D radar autofocus methods are not readily extendable across sensor passes. We propose a general framework that allows a class of data adaptive solutions for 3D auto-focus across passes with minimal constraints on the scene contents. The key enabling assumption is that portions of the scene are sparse in elevation which reduces the number of free variables and results in a system that is simultaneously solved for scatterer heights and autofocus parameters. The proposed method extends 2-pass interferometric synthetic aperture radar (IFSAR) methods to an arbitrary number of passes allowing the consideration of scattering from multiple height locations. A specific case from the proposed autofocus framework is solved and demonstrates autofocus and coherent multipass 3D estimation across the 8 passes of the "Gotcha Volumetric SAR Data Set" X-Band radar data.

  18. Accepting the T3D

    SciTech Connect

    Rich, D.O.; Pope, S.C.; DeLapp, J.G.

    1994-10-01

    In April, a 128 PE Cray T3D was installed at Los Alamos National Laboratory`s Advanced Computing Laboratory as part of the DOE`s High-Performance Parallel Processor Program (H4P). In conjunction with CRI, the authors implemented a 30 day acceptance test. The test was constructed in part to help them understand the strengths and weaknesses of the T3D. In this paper, they briefly describe the H4P and its goals. They discuss the design and implementation of the T3D acceptance test and detail issues that arose during the test. They conclude with a set of system requirements that must be addressed as the T3D system evolves.

  19. Combinatorial 3D Mechanical Metamaterials

    NASA Astrophysics Data System (ADS)

    Coulais, Corentin; Teomy, Eial; de Reus, Koen; Shokef, Yair; van Hecke, Martin

    2015-03-01

    We present a class of elastic structures which exhibit 3D-folding motion. Our structures consist of cubic lattices of anisotropic unit cells that can be tiled in a complex combinatorial fashion. We design and 3d-print this complex ordered mechanism, in which we combine elastic hinges and defects to tailor the mechanics of the material. Finally, we use this large design space to encode smart functionalities such as surface patterning and multistability.

  20. Three dimensional magnetohydrodynamic simulation of linearly polarised Alfven wave dynamics in Arnold-Beltrami-Childress magnetic field

    NASA Astrophysics Data System (ADS)

    Tsiklauri, David

    2015-04-01

    Previous studies (e.g., Malara et al., Astrophys. J. 533, 523 (2000)) considered small-amplitude Alfven wave (AW) packets in Arnold-Beltrami-Childress (ABC) magnetic field using WKB approximation. They draw a distinction between 2D AW dissipation via phase mixing and 3D AW dissipation via exponentially divergent magnetic field lines. In the former case, AW dissipation time scales as S 1/3 and in the latter as log(S) , where S is the Lundquist number. In this work [1], linearly polarised Alfven wave dynamics in ABC magnetic field via direct 3D magnetohydrodynamic (MHD) numerical simulation is studied for the first time. A Gaussian AW pulse with length-scale much shorter than ABC domain length and a harmonic AW with wavelength equal to ABC domain length are studied for four different resistivities. While it is found that AWs dissipate quickly in the ABC field, contrary to an expectation, it is found the AW perturbation energy increases in time. In the case of the harmonic AW, the perturbation energy growth is transient in time, attaining peaks in both velocity and magnetic perturbation energies within timescales much smaller than the resistive time. In the case of the Gaussian AW pulse, the velocity perturbation energy growth is still transient in time, attaining a peak within few resistive times, while magnetic perturbation energy continues to grow. It is also shown that the total magnetic energy decreases in time and this is governed by the resistive evolution of the background ABC magnetic field rather than AW damping. On contrary, when the background magnetic field is uniform, the total magnetic energy decrease is prescribed by AW damping, because there is no resistive evolution of the background. By considering runs with different amplitudes and by analysing the perturbation spectra, possible dynamo action by AW perturbation-induced peristaltic flow and inverse cascade of magnetic energy have been excluded. Therefore, the perturbation energy growth is attributed

  1. Three dimensional magnetohydrodynamic simulation of linearly polarised Alfven wave dynamics in Arnold-Beltrami-Childress magnetic field

    SciTech Connect

    Tsiklauri, D.

    2014-05-15

    Previous studies (e.g., Malara et al., Astrophys. J. 533, 523 (2000)) considered small-amplitude Alfven wave (AW) packets in Arnold-Beltrami-Childress (ABC) magnetic field using WKB approximation. They draw a distinction between 2D AW dissipation via phase mixing and 3D AW dissipation via exponentially divergent magnetic field lines. In the former case, AW dissipation time scales as S{sup 1∕3} and in the latter as log(S), where S is the Lundquist number. In this work, linearly polarised Alfven wave dynamics in ABC magnetic field via direct 3D magnetohydrodynamic (MHD) numerical simulation is studied for the first time. A Gaussian AW pulse with length-scale much shorter than ABC domain length and a harmonic AW with wavelength equal to ABC domain length are studied for four different resistivities. While it is found that AWs dissipate quickly in the ABC field, contrary to an expectation, it is found the AW perturbation energy increases in time. In the case of the harmonic AW, the perturbation energy growth is transient in time, attaining peaks in both velocity and magnetic perturbation energies within timescales much smaller than the resistive time. In the case of the Gaussian AW pulse, the velocity perturbation energy growth is still transient in time, attaining a peak within few resistive times, while magnetic perturbation energy continues to grow. It is also shown that the total magnetic energy decreases in time and this is governed by the resistive evolution of the background ABC magnetic field rather than AW damping. On contrary, when the background magnetic field is uniform, the total magnetic energy decrease is prescribed by AW damping, because there is no resistive evolution of the background. By considering runs with different amplitudes and by analysing the perturbation spectra, possible dynamo action by AW perturbation-induced peristaltic flow and inverse cascade of magnetic energy have been excluded. Therefore, the perturbation energy growth is

  2. Turbulent two-dimensional magnetohydrodynamics and conformal field theory

    SciTech Connect

    Rahimi Tabar, M.R.; Rouhani, S. |

    1996-03-01

    We show that an infinite number of non-unitary minimal models may describe two dimensional turbulent magnetohydrodynamics (MHD), both in the presence and absence of the Alf{close_quote}ven effect. We argue that the existence of a critical dynamical index results in the Alf{close_quote}ven effect or equivalently the equipartition of energy. We show that there are an infinite number of conserved quantities in 2{ital D}{endash}{ital MHD} turbulent systems both in the limit of vanishing the viscocities and in force free case. In the force free case, using the non-unitary minimal model {ital M}{sub 2,7} we derive the correlation functions for the velocity stream function and magnetic flux function. Generalizing this simple model we find the exponents of the energy spectrum in the inertial range for a class of conformal field theories. Copyright {copyright} 1996 Academic Press, Inc.

  3. Global magnetohydrodynamic instabilities in the L-2M stellarator

    SciTech Connect

    Mikhailov, M. I.; Shchepetov, S. V.; Nührenberg, C.; Nührenberg, J.

    2015-12-15

    Analysis of global magnetohydrodynamic (MHD) instabilities in the L-2M stellarator (Prokhorov General Physics Institute, Russian Academy of Sciences) is presented. The properties of free-boundary equilibria states are outlined, the stability conditions for small-scale modes are briefly discussed, and the number of trapped particles is estimated. All the magnetic configurations under study are stable against ballooning modes. It is shown that global ideal internal MHD modes can be found reliably only in Mercier unstable plasmas. In plasma that is stable with respect to the Mercier criterion, global unstable modes that are localized in the vicinity of the free plasma boundary and are not associated with any rational magnetic surface inside the plasma (the so-called peeling modes) can be found. The radial structure of all perturbations under study is almost entirely determined by the poloidal coupling of harmonics. The results of calculations are compared with the available experimental data.

  4. Magnetohydrodynamic turbulent cascade of coronal loop magnetic fields.

    PubMed

    Rappazzo, A F; Velli, M

    2011-06-01

    The Parker model for coronal heating is investigated through a high resolution simulation. An inertial range is resolved where fluctuating magnetic energy EMk[Please see symbol]) [Please see symbol] k[Please see symbol](-2.7) exceeds kinetic energy EK(k[Please see symbol])[Please see symbol]k[Please see symbol](-0.6). Increments scale as δbℓ ~/= ℓ(-0.85) and δuℓ ~/= ℓ(+0.2) with velocity increasing at small scales, indicating that magnetic reconnection plays a prime role in this turbulent system. We show that spectral energy transport is akin to standard magnetohydrodynamic (MHD) turbulence even for a system of reconnecting current sheets sustained by the boundary. In this new MHD turbulent cascade, kinetic energy flows are negligible while cross-field flows are enhanced, and through a series of "reflections" between the two fields, cascade more than half of the total spectral energy flow.

  5. MAGNETOHYDRODYNAMIC SIMULATION OF A SIGMOID ERUPTION OF ACTIVE REGION 11283

    SciTech Connect

    Jiang Chaowei; Feng Xueshang; Wu, S. T.; Hu Qiang E-mail: fengx@spaceweather.ac.cn E-mail: qh0001@uah.edu

    2013-07-10

    Current magnetohydrodynamic (MHD) simulations of the initiation of solar eruptions are still commonly carried out with idealized magnetic field models, whereas the realistic coronal field prior to eruptions can possibly be reconstructed from the observable photospheric field. Using a nonlinear force-free field extrapolation prior to a sigmoid eruption in AR 11283 as the initial condition in an MHD model, we successfully simulate the realistic initiation process of the eruption event, as is confirmed by a remarkable resemblance to the SDO/AIA observations. Analysis of the pre-eruption field reveals that the envelope flux of the sigmoidal core contains a coronal null and furthermore the flux rope is prone to a torus instability. Observations suggest that reconnection at the null cuts overlying tethers and likely triggers the torus instability of the flux rope, which results in the eruption. This kind of simulation demonstrates the capability of modeling the realistic solar eruptions to provide the initiation process.

  6. Temporal intermittency of energy dissipation in magnetohydrodynamic turbulence.

    PubMed

    Zhdankin, Vladimir; Uzdensky, Dmitri A; Boldyrev, Stanislav

    2015-02-13

    Energy dissipation in magnetohydrodynamic (MHD) turbulence is known to be highly intermittent in space, being concentrated in sheetlike coherent structures. Much less is known about intermittency in time, another fundamental aspect of turbulence which has great importance for observations of solar flares and other space or astrophysical phenomena. In this Letter, we investigate the temporal intermittency of energy dissipation in numerical simulations of MHD turbulence. We consider four-dimensional spatiotemporal structures, "flare events," responsible for a large fraction of the energy dissipation. We find that although the flare events are often highly complex, they exhibit robust power-law distributions and scaling relations. We find that the probability distribution of dissipated energy has a power-law index close to α≈1.75, similar to observations of solar flares, indicating that intense dissipative events dominate the heating of the system. We also discuss the temporal asymmetry of flare events as a signature of the turbulent cascade.

  7. Disk Emission from Magnetohydrodynamic Simulations of Spinning Black Holes

    NASA Astrophysics Data System (ADS)

    Schnittman, Jeremy D.; Krolik, Julian H.; Noble, Scott C.

    2016-03-01

    We present the results of a new series of global, three-dimensional, relativistic magnetohydrodynamic (MHD) simulations of thin accretion disks around spinning black holes. The disks have aspect ratios of H/R˜ 0.05 and spin parameters of a/M=0,0.5,0.9, and 0.99. Using the ray-tracing code Pandurata, we generate broadband thermal spectra and polarization signatures from the MHD simulations. We find that the simulated spectra can be well fit with a simple, universal emissivity profile that better reproduces the behavior of the emission from the inner disk, compared to traditional analyses carried out using a Novikov-Thorne thin disk model. Finally, we show how spectropolarization observations can be used to convincingly break the spin-inclination degeneracy well known to the continuum-fitting method of measuring black hole spin.

  8. Plasma relaxation and topological aspects in electron magnetohydrodynamics

    NASA Astrophysics Data System (ADS)

    Shivamoggi, B. K.

    2016-07-01

    Parker's formulation of isotopological plasma relaxation process toward minimum magnetics energy states in magnetohydrodynamics (MHD) is extended to electron MHD (EMHD). The lower bound on magnetic energy in EMHD is determined by both the magnetic field and the electron vorticity field topologies, and is shown to be reduced further in EMHD by an amount proportional to the sum of total electron-flow kinetic energy and total electron-flow enstrophy. The EMHD Beltrami condition becomes equivalent to the potential vorticity conservation equation in two-dimensional (2D) hydrodynamics, and the torsion coefficient α turns out to be proportional to potential vorticity. The winding pattern of the magnetic field lines appears to evolve, therefore, in the same way as potential vorticity lines in 2D hydrodynamics.

  9. Numerical Simulations and Diagnostics in Astrophysics:. a Few Magnetohydrodynamics Examples

    NASA Astrophysics Data System (ADS)

    Peres, Giovanni; Bonito, Rosaria; Orlando, Salvatore; Reale, Fabio

    2007-12-01

    We discuss some issues related to numerical simulations in Astrophysics and, in particular, to their use both as a theoretical tool and as a diagnostic tool, to gain insight into the physical phenomena at work. We make our point presenting some examples of Magneto-hydro-dynamic (MHD) simulations of astrophysical plasmas and illustrating their use. In particular we show the need for appropriate tools to interpret, visualize and present results in an adequate form, and the importance of spectral synthesis for a direct comparison with observations.

  10. Magnetohydrodynamic Characteristic Boundary Conditions

    NASA Astrophysics Data System (ADS)

    Schaffenberger, Werner; Stein, R.

    2009-05-01

    We implemented MHD characteristic boundary conditions for a non-ideal plasma in the "stagger-code" (Gudiksen and Nordlund, 2005, ApJ 618, 1020). The aim of these boundary conditions is to reduce reflection at the boundaries which is important for the simulation of wave propagation. We present some test simulations of propagating waves demonstrating the capability of these boundary conditions.

  11. LASTRAC.3d: Transition Prediction in 3D Boundary Layers

    NASA Technical Reports Server (NTRS)

    Chang, Chau-Lyan

    2004-01-01

    Langley Stability and Transition Analysis Code (LASTRAC) is a general-purpose, physics-based transition prediction code released by NASA for laminar flow control studies and transition research. This paper describes the LASTRAC extension to general three-dimensional (3D) boundary layers such as finite swept wings, cones, or bodies at an angle of attack. The stability problem is formulated by using a body-fitted nonorthogonal curvilinear coordinate system constructed on the body surface. The nonorthogonal coordinate system offers a variety of marching paths and spanwise waveforms. In the extreme case of an infinite swept wing boundary layer, marching with a nonorthogonal coordinate produces identical solutions to those obtained with an orthogonal coordinate system using the earlier release of LASTRAC. Several methods to formulate the 3D parabolized stability equations (PSE) are discussed. A surface-marching procedure akin to that for 3D boundary layer equations may be used to solve the 3D parabolized disturbance equations. On the other hand, the local line-marching PSE method, formulated as an easy extension from its 2D counterpart and capable of handling the spanwise mean flow and disturbance variation, offers an alternative. A linear stability theory or parabolized stability equations based N-factor analysis carried out along the streamline direction with a fixed wavelength and downstream-varying spanwise direction constitutes an efficient engineering approach to study instability wave evolution in a 3D boundary layer. The surface-marching PSE method enables a consistent treatment of the disturbance evolution along both streamwise and spanwise directions but requires more stringent initial conditions. Both PSE methods and the traditional LST approach are implemented in the LASTRAC.3d code. Several test cases for tapered or finite swept wings and cones at an angle of attack are discussed.

  12. SPECTRA OF STRONG MAGNETOHYDRODYNAMIC TURBULENCE FROM HIGH-RESOLUTION SIMULATIONS

    SciTech Connect

    Beresnyak, Andrey

    2014-04-01

    Magnetohydrodynamic (MHD) turbulence is present in a variety of solar and astrophysical environments. Solar wind fluctuations with frequencies lower than 0.1 Hz are believed to be mostly governed by Alfvénic turbulence with particle transport depending on the power spectrum and the anisotropy of such turbulence. Recently, conflicting spectral slopes for the inertial range of MHD turbulence have been reported by different groups. Spectral shapes from earlier simulations showed that MHD turbulence is less scale-local compared with hydrodynamic turbulence. This is why higher-resolution simulations, and careful and rigorous numerical analysis is especially needed for the MHD case. In this Letter, we present two groups of simulations with resolution up to 4096{sup 3}, which are numerically well-resolved and have been analyzed with an exact and well-tested method of scaling study. Our results from both simulation groups indicate that the asymptotic power spectral slope for all energy-related quantities, such as total energy and residual energy, is around –1.7, close to Kolmogorov's –5/3. This suggests that residual energy is a constant fraction of the total energy and that in the asymptotic regime of Alfvénic turbulence magnetic and kinetic spectra have the same scaling. The –1.5 slope for energy and the –2 slope for residual energy, which have been suggested earlier, are incompatible with our numerics.

  13. Thermodynamic Cycle Analysis of Magnetohydrodynamic-Bypass Airbreathing Hypersonic Engines

    NASA Technical Reports Server (NTRS)

    Litchford, Ron J.; Bityurin, Valentine A.; Lineberry, John T.

    1999-01-01

    Established analyses of conventional ramjet/scramjet performance characteristics indicate that a considerable decrease in efficiency can be expected at off-design flight conditions. This can be explained, in large part, by the deterioration of intake mass flow and limited inlet compression at low flight speeds and by the onset of thrust degradation effects associated with increased burner entry temperature at high flight speeds. In combination, these effects tend to impose lower and upper Mach number limits for practical flight. It has been noted, however, that Magnetohydrodynamic (MHD) energy management techniques represent a possible means for extending the flight Mach number envelope of conventional engines. By transferring enthalpy between different stages of the engine cycle, it appears that the onset of thrust degradation may be delayed to higher flight speeds. Obviously, the introduction of additional process inefficiencies is inevitable with this approach, but it is believed that these losses are more than compensated through optimization of the combustion process. The fundamental idea is to use MHD energy conversion processes to extract and bypass a portion of the intake kinetic energy around the burner. We refer to this general class of propulsion system as an MHD-bypass engine. In this paper, we quantitatively assess the performance potential and scientific feasibility of MHD-bypass airbreathing hypersonic engines using ideal gasdynamics and fundamental thermodynamic principles.

  14. Neoclassical viscosity effects on resistive magnetohydrodynamic modes in toroidal geometry

    SciTech Connect

    Yang, J.G.; Oh, Y.H.; Choi, D.I. ); Kim, J.Y.; Horton, W. )

    1992-03-01

    The flux-surface-averaged linearized resistive magnetohydrodynamic (MHD) boundary-layer equations including the compressibility, diamagnetic drift, and neoclassical viscosity terms are derived in toroidal geometry. These equations describe the resistive layer dynamics of resistive MHD modes over the collisionality regime between the banana plateau and the Pfirsch--Schlueter. From the resulting equations, the effects of neoclassical viscosity on the stability of the tearing and resistive ballooning modes are investigated numerically. Also, a study is given for the problem of how the neoclassical resistive MHD mode is generated as the collisionality is reduced. It is shown that the neoclassical viscosity terms give a significant destabilizing effect for the tearing and resistive ballooning modes. This destabilization comes mainly from the reduction of the stabilizing effect of the parallel ion sound compression by the ion neoclassical viscosity. In the banana-plateau collisionality limit, where the compressibility is negligible, the dispersion relations of the tearing and resistive ballooning modes reduce to the same form, with the threshold value of the driving force given by {Delta}{sub {ital c}}=0. On the other hand, with the finite neoclassical effect it is found that the neoclassical resistive MHD instability is generated in agreement with previous results. Furthermore, it is shown that this later instability can be generated in a wide range of the collisionality including near the Pfirsch--Schlueter regime as well as the banana-plateau regime, suggesting that this mode is a probable cause of anomalous transport.

  15. Magnetic discontinuities in magnetohydrodynamic turbulence and in the solar wind.

    PubMed

    Zhdankin, Vladimir; Boldyrev, Stanislav; Mason, Joanne; Perez, Jean Carlos

    2012-04-27

    Recent measurements of solar wind turbulence report the presence of intermittent, exponentially distributed angular discontinuities in the magnetic field. In this Letter, we study whether such discontinuities can be produced by magnetohydrodynamic (MHD) turbulence. We detect the discontinuities by measuring the fluctuations of the magnetic field direction, Δθ, across fixed spatial increments Δx in direct numerical simulations of MHD turbulence with an imposed uniform guide field B(0). A large region of the probability density function (pdf) for Δθ is found to follow an exponential decay, proportional to exp(-Δθ/θ(*)), with characteristic angle θ(*)≈(14°)(b(rms)/B(0))(0.65) for a broad range of guide-field strengths. We find that discontinuities observed in the solar wind can be reproduced by MHD turbulence with reasonable ratios of b(rms)/B(0). We also observe an excess of small angular discontinuities when Δx becomes small, possibly indicating an increasing statistical significance of dissipation-scale structures. The structure of the pdf in this case closely resembles the two-population pdf seen in the solar wind. We thus propose that strong discontinuities are associated with inertial-range MHD turbulence, while weak discontinuities emerge from dissipation-range turbulence. In addition, we find that the structure functions of the magnetic field direction exhibit anomalous scaling exponents, which indicates the existence of intermittent structures.

  16. Approximate Riemann Solvers for the Cosmic Ray Magnetohydrodynamical Equations

    NASA Astrophysics Data System (ADS)

    Kudoh, Yuki; Hanawa, Tomoyuki

    2016-08-01

    We analyze the cosmic-ray magnetohydrodynamic (CR MHD) equations to improve the numerical simulations. We propose to solve them in the fully conservation form, which is equivalent to the conventional CR MHD equations. In the fully conservation form, the CR energy equation is replaced with the CR "number" conservation, where the CR number density is defined as the three fourths power of the CR energy density. The former contains an extra source term, while latter does not. An approximate Riemann solver is derived from the CR MHD equations in the fully conservation form. Based on the analysis, we propose a numerical scheme of which solutions satisfy the Rankine-Hugoniot relation at any shock. We demonstrate that it reproduces the Riemann solution derived by Pfrommer et al. (2006) for a 1D CR hydrodynamic shock tube problem. We compare the solution with those obtained by solving the CR energy equation. The latter solutions deviate from the Riemann solution seriously, when the CR pressure dominates over the gas pressure in the post-shocked gas. The former solutions converge to the Riemann solution and are of the second order accuracy in space and time. Our numerical examples include an expansion of high pressure sphere in an magnetized medium. Fast and slow shocks are sharply resolved in the example. We also discuss possible extension of the CR MHD equations to evaluate the average CR energy.

  17. Approximate Riemann solvers for the cosmic ray magnetohydrodynamical equations

    NASA Astrophysics Data System (ADS)

    Kudoh, Yuki; Hanawa, Tomoyuki

    2016-11-01

    We analyse the cosmic ray magnetohydrodynamic (CR MHD) equations to improve the numerical simulations. We propose to solve them in the fully conservation form, which is equivalent to the conventional CR MHD equations. In the fully conservation form, the CR energy equation is replaced with the CR `number' conservation, where the CR number density is defined as the three-fourths power of the CR energy density. The former contains an extra source term, while latter does not. An approximate Riemann solver is derived from the CR MHD equations in the fully conservation form. Based on the analysis, we propose a numerical scheme of which solutions satisfy the Rankine-Hugoniot relation at any shock. We demonstrate that it reproduces the Riemann solution derived by Pfrommer et al. for a 1D CR hydrodynamic shock tube problem. We compare the solution with those obtained by solving the CR energy equation. The latter solutions deviate from the Riemann solution seriously, when the CR pressure dominates over the gas pressure in the post-shocked gas. The former solutions converge to the Riemann solution and are of the second-order accuracy in space and time. Our numerical examples include an expansion of high-pressure sphere in a magnetized medium. Fast and slow shocks are sharply resolved in the example. We also discuss possible extension of the CR MHD equations to evaluate the average CR energy.

  18. From 3D view to 3D print

    NASA Astrophysics Data System (ADS)

    Dima, M.; Farisato, G.; Bergomi, M.; Viotto, V.; Magrin, D.; Greggio, D.; Farinato, J.; Marafatto, L.; Ragazzoni, R.; Piazza, D.

    2014-08-01

    In the last few years 3D printing is getting more and more popular and used in many fields going from manufacturing to industrial design, architecture, medical support and aerospace. 3D printing is an evolution of bi-dimensional printing, which allows to obtain a solid object from a 3D model, realized with a 3D modelling software. The final product is obtained using an additive process, in which successive layers of material are laid down one over the other. A 3D printer allows to realize, in a simple way, very complex shapes, which would be quite difficult to be produced with dedicated conventional facilities. Thanks to the fact that the 3D printing is obtained superposing one layer to the others, it doesn't need any particular work flow and it is sufficient to simply draw the model and send it to print. Many different kinds of 3D printers exist based on the technology and material used for layer deposition. A common material used by the toner is ABS plastics, which is a light and rigid thermoplastic polymer, whose peculiar mechanical properties make it diffusely used in several fields, like pipes production and cars interiors manufacturing. I used this technology to create a 1:1 scale model of the telescope which is the hardware core of the space small mission CHEOPS (CHaracterising ExOPlanets Satellite) by ESA, which aims to characterize EXOplanets via transits observations. The telescope has a Ritchey-Chrétien configuration with a 30cm aperture and the launch is foreseen in 2017. In this paper, I present the different phases for the realization of such a model, focusing onto pros and cons of this kind of technology. For example, because of the finite printable volume (10×10×12 inches in the x, y and z directions respectively), it has been necessary to split the largest parts of the instrument in smaller components to be then reassembled and post-processed. A further issue is the resolution of the printed material, which is expressed in terms of layers

  19. YouDash3D: exploring stereoscopic 3D gaming for 3D movie theaters

    NASA Astrophysics Data System (ADS)

    Schild, Jonas; Seele, Sven; Masuch, Maic

    2012-03-01

    Along with the success of the digitally revived stereoscopic cinema, events beyond 3D movies become attractive for movie theater operators, i.e. interactive 3D games. In this paper, we present a case that explores possible challenges and solutions for interactive 3D games to be played by a movie theater audience. We analyze the setting and showcase current issues related to lighting and interaction. Our second focus is to provide gameplay mechanics that make special use of stereoscopy, especially depth-based game design. Based on these results, we present YouDash3D, a game prototype that explores public stereoscopic gameplay in a reduced kiosk setup. It features live 3D HD video stream of a professional stereo camera rig rendered in a real-time game scene. We use the effect to place the stereoscopic effigies of players into the digital game. The game showcases how stereoscopic vision can provide for a novel depth-based game mechanic. Projected trigger zones and distributed clusters of the audience video allow for easy adaptation to larger audiences and 3D movie theater gaming.

  20. Relativistic magnetohydrodynamics in dynamical spacetimes: A new adaptive mesh refinement implementation

    SciTech Connect

    Etienne, Zachariah B.; Liu, Yuk Tung; Shapiro, Stuart L.

    2010-10-15

    We have written and tested a new general relativistic magnetohydrodynamics code, capable of evolving magnetohydrodynamics (MHD) fluids in dynamical spacetimes with adaptive-mesh refinement (AMR). Our code solves the Einstein-Maxwell-MHD system of coupled equations in full 3+1 dimensions, evolving the metric via the Baumgarte-Shapiro Shibata-Nakamura formalism and the MHD and magnetic induction equations via a conservative, high-resolution shock-capturing scheme. The induction equations are recast as an evolution equation for the magnetic vector potential, which exists on a grid that is staggered with respect to the hydrodynamic and metric variables. The divergenceless constraint {nabla}{center_dot}B=0 is enforced by the curl of the vector potential. Our MHD scheme is fully compatible with AMR, so that fluids at AMR refinement boundaries maintain {nabla}{center_dot}B=0. In simulations with uniform grid spacing, our MHD scheme is numerically equivalent to a commonly used, staggered-mesh constrained-transport scheme. We present code validation test results, both in Minkowski and curved spacetimes. They include magnetized shocks, nonlinear Alfven waves, cylindrical explosions, cylindrical rotating disks, magnetized Bondi tests, and the collapse of a magnetized rotating star. Some of the more stringent tests involve black holes. We find good agreement between analytic and numerical solutions in these tests, and achieve convergence at the expected order.

  1. Higher Order Lagrange Finite Elements In M3D

    SciTech Connect

    J. Chen; H.R. Strauss; S.C. Jardin; W. Park; L.E. Sugiyama; G. Fu; J. Breslau

    2004-12-17

    The M3D code has been using linear finite elements to represent multilevel MHD on 2-D poloidal planes. Triangular higher order elements, up to third order, are constructed here in order to provide M3D the capability to solve highly anisotropic transport problems. It is found that higher order elements are essential to resolve the thin transition layer characteristic of the anisotropic transport equation, particularly when the strong anisotropic direction is not aligned with one of the Cartesian coordinates. The transition layer is measured by the profile width, which is zero for infinite anisotropy. It is shown that only higher order schemes have the ability to make this layer converge towards zero when the anisotropy gets stronger and stronger. Two cases are considered. One has the strong transport direction partially aligned with one of the element edges, the other doesn't have any alignment. Both cases have the strong transport direction misaligned with the grid line by some angles.

  2. Remote 3D Medical Consultation

    NASA Astrophysics Data System (ADS)

    Welch, Greg; Sonnenwald, Diane H.; Fuchs, Henry; Cairns, Bruce; Mayer-Patel, Ketan; Yang, Ruigang; State, Andrei; Towles, Herman; Ilie, Adrian; Krishnan, Srinivas; Söderholm, Hanna M.

    Two-dimensional (2D) video-based telemedical consultation has been explored widely in the past 15-20 years. Two issues that seem to arise in most relevant case studies are the difficulty associated with obtaining the desired 2D camera views, and poor depth perception. To address these problems we are exploring the use of a small array of cameras to synthesize a spatially continuous range of dynamic three-dimensional (3D) views of a remote environment and events. The 3D views can be sent across wired or wireless networks to remote viewers with fixed displays or mobile devices such as a personal digital assistant (PDA). The viewpoints could be specified manually or automatically via user head or PDA tracking, giving the remote viewer virtual head- or hand-slaved (PDA-based) remote cameras for mono or stereo viewing. We call this idea remote 3D medical consultation (3DMC). In this article we motivate and explain the vision for 3D medical consultation; we describe the relevant computer vision/graphics, display, and networking research; we present a proof-of-concept prototype system; and we present some early experimental results supporting the general hypothesis that 3D remote medical consultation could offer benefits over conventional 2D televideo.

  3. Speaking Volumes About 3-D

    NASA Technical Reports Server (NTRS)

    2002-01-01

    In 1999, Genex submitted a proposal to Stennis Space Center for a volumetric 3-D display technique that would provide multiple users with a 360-degree perspective to simultaneously view and analyze 3-D data. The futuristic capabilities of the VolumeViewer(R) have offered tremendous benefits to commercial users in the fields of medicine and surgery, air traffic control, pilot training and education, computer-aided design/computer-aided manufacturing, and military/battlefield management. The technology has also helped NASA to better analyze and assess the various data collected by its satellite and spacecraft sensors. Genex capitalized on its success with Stennis by introducing two separate products to the commercial market that incorporate key elements of the 3-D display technology designed under an SBIR contract. The company Rainbow 3D(R) imaging camera is a novel, three-dimensional surface profile measurement system that can obtain a full-frame 3-D image in less than 1 second. The third product is the 360-degree OmniEye(R) video system. Ideal for intrusion detection, surveillance, and situation management, this unique camera system offers a continuous, panoramic view of a scene in real time.

  4. Tungsten and tungsten-copper for coal-fired MHD power generation

    SciTech Connect

    Farrar, L.C. ); Shields, J.A. Jr. )

    1992-08-01

    This paper reports that magnetohydrodynamics (MHD) can improve the thermal efficiency and reduce levels of SO{sub x} and NO emissions of existing coal-fired power generation plants. Although the thermal and electrochemical environments for a coal-fired MHD channel challenge the materials used, platinum, tungsten, and tungsten-copper have been found to be suitable choices. Evaluations indicate these materials perform adequately as electrodes and other gas-side surfaces in the coal-fired MHD channel. Analysis of test elements has resulted in the identification of wear mechanisms. Testing of a prototypical coal-fired MHD channel incorporating these materials is under way and will be completed in 1993.

  5. Finite volume TVD scheme on an unstructured grid system for three-dimensional MHD simulation of inhomogeneous systems including strong background potential fields

    NASA Astrophysics Data System (ADS)

    Tanaka, T.

    1994-04-01

    A three-dimensional (3D) high-resolution magnetohydrodynamic (MHD) simulation scheme on an unstructured grid system is developed for inhomogeneous systems, including strong background potential fields. The scheme is based on the finite volume method (FVM) with an upwinding numerical flux by the linearized Riemann solver. Upwindings on an unstructured grid system are realized from the fact that the MHD equations are symmetric with the rotation of the space. The equation system is modified to avoid direct inclusions of the background potential field as a dependent variable, through the use of changed dependent variables. Despite such a change of the equation system, the eigenvectors in the mode-synthesis matrix that are necessary for the evaluation of the upwinding numerical flux vectors can still be written analytically. The eigenvalues of the MHD flux Jacobian matrix that are also necessary for the upwinding calculations are derived from the well-known Alfven, fast and slow, velocities. The calculations of the eigenvectors is done with special care when the wave propagations become parallel or perpendicular to the ambient magnetic field, because degeneration of the eigenvalues occurs in these cases. To obtain a higher order of accuracy, the upwinding flux is extended to the second-order TVD numerical flux in the calculation of FVM, through the MUSCL approach and Van Leer's differentiable limiter. In order to show the efficiency of the above scheme, a numerical example is given for the interaction process of high-beta supersonic plasma flow with the region of a strong dipole field, including magnetized low-beta plasma.

  6. Non-linear Simulations of MHD Instabilities in Tokamaks Including Eddy Current Effects and Perspectives for the Extension to Halo Currents

    NASA Astrophysics Data System (ADS)

    Hoelzl, M.; Huijsmans, G. T. A.; Merkel, P.; Atanasiu, C.; Lackner, K.; Nardon, E.; Aleynikova, K.; Liu, F.; Strumberger, E.; McAdams, R.; Chapman, I.; Fil, A.

    2014-11-01

    The dynamics of large scale plasma instabilities can be strongly influenced by the mutual interaction with currents flowing in conducting vessel structures. Especially eddy currents caused by time-varying magnetic perturbations and halo currents flowing directly from the plasma into the walls are important. The relevance of a resistive wall model is directly evident for Resistive Wall Modes (RWMs) or Vertical Displacement Events (VDEs). However, also the linear and non-linear properties of most other large-scale instabilities may be influenced significantly by the interaction with currents in conducting structures near the plasma. The understanding of halo currents arising during disruptions and VDEs, which are a serious concern for ITER as they may lead to strong asymmetric forces on vessel structures, could also benefit strongly from these non-linear modeling capabilities. Modeling the plasma dynamics and its interaction with wall currents requires solving the magneto-hydrodynamic (MHD) equations in realistic toroidal X-point geometry consistently coupled with a model for the vacuum region and the resistive conducting structures. With this in mind, the non-linear finite element MHD code JOREK [1, 2] has been coupled [3] with the resistive wall code STARWALL [4], which allows us to include the effects of eddy currents in 3D conducting structures in non-linear MHD simulations. This article summarizes the capabilities of the coupled JOREK-STARWALL system and presents benchmark results as well as first applications to non-linear simulations of RWMs, VDEs, disruptions triggered by massive gas injection, and Quiescent H-Mode. As an outlook, the perspectives for extending the model to halo currents are described.

  7. MHD can clean up the environment

    SciTech Connect

    Sheth, A.C.; Crawford, L.W.; Holt, J.K.

    1993-01-01

    Magnetohydrodynamics (MHD) involves interactions among electromagnetic fields and electrically conducting gases and liquids. The most developed application for MM in the United States is for central station electric power generation using a coal-fired combined cycle system. Proof-of-Concept (POC) scale demonstration of the downstream components used in this technology is currently being carried out at the US Department of Energy's (DOE) Coal-Fired Flow Facility (CFFF), located at the University of Tennessee Space Institute (UTSI). Some of the attractive features of MHD include: A potential for increasing overall plant efficiency to 60% as compared to <40% for conventional power plants. Provision of built-in controls to eliminate/reduce the emissions of acid rain precursors, such as SO[sub 2] and NO[sub x] well below the existing New Source Performance Standards (NSPS) and Clean Air Act requirements. Provision of adequate particulate resistivity for easy and efficient capture of submicron sized panicles in dry and wet electrostatic precipitators. Provision of built-in control to eliminate/reduce the Cl[sub 2]/HCl emission problems common to waste incinerators. Producing nearly zero emissions of priority pollutants (inorganics as well as organics on a pound per pound of coal basis) in comparison to conventional coal-fired facilities. Environmentally acceptable solid and liquid waste streams, and release of less CO[sub 2] (a suspected greenhouse gas) per unit of electricity generated than the conventional power plant due to the increased efficiency.

  8. Investigations for biogas operated MHD power generators

    SciTech Connect

    Dahiya, R.P.; Chand, A.; Sharma, S.C.

    1983-12-01

    Biogas is produced from the anaerobic fermentation of the organic matter containing cellulose, such as agricultural wastes, human wastes, animal wastes, etc. It contains methane (50-70%), carbon dioxide (30-50%), and very small amounts of hydrogen and hydrogen sulphide. Adequate quantities of raw material to generate biogas are normally available in rural areas, and therefore, there is a possibility that almost all the energy requirements of the rural sector may be fulfilled by biogas. Presently in the rural sector, biogas is used mainly to provide thermal energy (for cooking, etc.), and up to a limited extent, to meet the electrical energy requirements by running electrical generators with engines powered by a mixture of oil and biogas. In this paper, the authors propose a scheme in which biogas can be used to generate electricity more efficiently by using magnetohydrodynamic (MHD) power generators. Investigations have been carried out to make feasibility studies for biogas-operated open cycle MHD power generators. Composition, temperature and electrical conductivity of the seeded (with potassium) combustion products of biogas-air/oxygen systems have been analytically investigated for different percentages of CO/sub 2/ in biogas and at various combustor pressures for a seeding ratio of 1 percent by weight. The effect of preheating and enrichment of air on temperature and electrical conductivity of the seeded combustion plasmas has also been studied.

  9. DIII-D Equilibrium Reconstructions with New 3D Magnetic Probes

    NASA Astrophysics Data System (ADS)

    Lao, Lang; Strait, E. J.; Ferraro, N. M.; Ferron, J. R.; King, J. D.; Lee, X.; Meneghini, O.; Turnbull, A. D.; Huang, Y.; Qian, J. G.; Wingen, A.

    2015-11-01

    DIII-D equilibrium reconstructions with the recently installed new 3D magnetic diagnostic are presented. In addition to providing information to allow more accurate 2D reconstructions, the new 3D probes also provide useful information to guide computation of 3D perturbed equilibria. A new more comprehensive magnetic compensation has been implemented. Algorithms are being developed to allow EFIT to reconstruct 3D perturbed equilibria making use of the new 3D probes and plasma responses from 3D MHD codes such as GATO and M3D-C1. To improve the computation efficiency, all inactive probes in one of the toroidal planes in EFIT have been replaced with new probes from other planes. Other 3D efforts include testing of 3D reconstructions using V3FIT and a new 3D variational moment equilibrium code VMOM3D. Other EFIT developments include a GPU EFIT version and new safety factor and MSE-LS constraints. The accuracy and limitation of the new probes for 3D reconstructions will be discussed. Supported by US DOE under DE-FC02-04ER54698 and DE-FG02-95ER54309.

  10. Thermoacoustic magnetohydrodynamic electrical generator

    DOEpatents

    Wheatley, J.C.; Swift, G.W.; Migliori, A.

    1984-11-16

    A thermoacoustic magnetohydrodynamic electrical generator includes an intrinsically irreversible thermoacoustic heat engine coupled to a magnetohydrodynamic electrical generator. The heat engine includes an electrically conductive liquid metal as the working fluid and includes two heat exchange and thermoacoustic structure assemblies which drive the liquid in a push-pull arrangement to cause the liquid metal to oscillate at a resonant acoustic frequency on the order of 1000 Hz. The engine is positioned in the field of a magnet and is oriented such that the liquid metal oscillates in a direction orthogonal to the field of the magnet, whereby an alternating electrical potential is generated in the liquid metal. Low-loss, low-inductance electrical conductors electrically connected to opposite sides of the liquid metal conduct an output signal to a transformer adapted to convert the low-voltage, high-current output signal to a more usable higher voltage, lower current signal.

  11. Thermoacoustic magnetohydrodynamic electrical generator

    DOEpatents

    Wheatley, John C.; Swift, Gregory W.; Migliori, Albert

    1986-01-01

    A thermoacoustic magnetohydrodynamic electrical generator includes an intrinsically irreversible thermoacoustic heat engine coupled to a magnetohydrodynamic electrical generator. The heat engine includes an electrically conductive liquid metal as the working fluid and includes two heat exchange and thermoacoustic structure assemblies which drive the liquid in a push-pull arrangement to cause the liquid metal to oscillate at a resonant acoustic frequency on the order of 1,000 Hz. The engine is positioned in the field of a magnet and is oriented such that the liquid metal oscillates in a direction orthogonal to the field of the magnet, whereby an alternating electrical potential is generated in the liquid metal. Low-loss, low-inductance electrical conductors electrically connected to opposite sides of the liquid metal conduct an output signal to a transformer adapted to convert the low-voltage, high-current output signal to a more usable higher voltage, lower current signal.

  12. Magnetohydrodynamic instability excited by interplay between a resistive wall mode and stable ideal magnetohydrodynamic modes in rotating tokamak plasmas

    SciTech Connect

    Aiba, N.; Hirota, M.

    2015-08-15

    In a rotating toroidal plasma surrounded by a resistive wall, it is shown that linear magnetohydrodynamic (MHD) instabilities can be excited by interplay between the resistive wall mode (RWM) and stable ideal MHD modes, where the RWM can couple with not only a stable external kink mode but also various stable Alfvén eigenmodes that abound in a toroidal plasma. The RWM growth rate is shown to peak repeatedly as the rotation frequency reaches specific values for which the frequencies of the ideal MHD modes are Doppler-shifted to the small RWM frequency. Such destabilization can be observed even when the RWM in a static plasma is stable. A dispersion relation clarifies that the unstable mode changes from the RWM to the ideal MHD mode destabilized by wall resistivity when the rotation frequency passes through these specific values. The unstable mode is excited at these rotation frequencies even though plasma rotation also tends to stabilize the RWM from the combination of the continuum damping and the ion Landau damping.

  13. Cascades and dissipation ratio in rotating magnetohydrodynamic turbulence at low magnetic Prandtl number.

    PubMed

    Plunian, Franck; Stepanov, Rodion

    2010-10-01

    A phenomenology of isotropic magnetohydrodynamic (MHD) turbulence subject to both rotation and applied magnetic field is presented. It is assumed that the triple correlation decay time is the shortest between the eddy turn-over time and the ones associated to the rotating frequency and the Alfvén wave period. For Pm=1 it leads to four kinds of piecewise spectra, depending on four parameters: injection rate of energy, magnetic diffusivity, rotation rate, and applied field. With a shell model of MHD turbulence (including rotation and applied magnetic field), spectra for Pm ≤ 1 are presented, together with the ratio between magnetic and viscous dissipations.

  14. Trigonometric and hyperbolic functions method for constructing analytic solutions to nonlinear plane magnetohydrodynamics equilibrium equations

    SciTech Connect

    Moawad, S. M.

    2015-02-15

    In this paper, we present a solution method for constructing exact analytic solutions to magnetohydrodynamics (MHD) equations. The method is constructed via all the trigonometric and hyperbolic functions. The method is applied to MHD equilibria with mass flow. Applications to a solar system concerned with the properties of coronal mass ejections that affect the heliosphere are presented. Some examples of the constructed solutions which describe magnetic structures of solar eruptions are investigated. Moreover, the constructed method can be applied to a variety classes of elliptic partial differential equations which arise in plasma physics.

  15. Theory of energetic/alpha particle effects on magnetohydrodynamic modes in tokamaks

    SciTech Connect

    Chen, L.; White, R.B.; Rewoldt, G.; Colestock, P.; Rutherford, P.H.; Chen, Y.P.; Ke, F.J.; Tsai, S.T.; Bussac, M.N.

    1989-01-01

    The presence of energetic particles is shown to qualitatively modify the stability properties of ideal as well as resistive magnetohydrodynamic (MHD) modes in tokamaks. Specifically, we demonstrate that, consistent with highpower ICRF heating experiments in JET, high energy trapped particles can effectively stabilize the sawtooth mode, providing a possible route to stable high current tokamak operation. An alternative stabilization scheme employing barely circulating energetic particles is also proposed. Finally, we present analytical and numerical studies on the excitations of high-n MHD modes via transit resonances with circulating alpha particles. 14 refs., 3 figs.

  16. Two-dimensional magnetohydrodynamic equilibria with flow and studies of equilibrium fluctuations

    SciTech Connect

    Agim, Y.Z.

    1989-01-01

    A set of reduced ideal MHD (magnetohydrodynamic) equations is derived to investigate equilibria of plasmas with mass flow in general two-dimensional geometry. These equations provide a means of investigating the effects of flow on self-consistent equilibria in a number of new two-dimensional configurations such as helically symmetric configurations with helical axis, which are relevant to stellarators, as well as axisymmetric configurations. In the second part, magnetic fluctuations due to the thermally excited MHD waves are investigated using fluid and kinetic models to describe a stable, uniform, compressible plasma in the range above the drift wave frequency and below the ion cyclotron frequency.

  17. Simulated annealing applied to two-dimensional low-beta reduced magnetohydrodynamics

    SciTech Connect

    Chikasue, Y.; Furukawa, M.

    2015-02-15

    The simulated annealing (SA) method is applied to two-dimensional (2D) low-beta reduced magnetohydrodynamics (R-MHD). We have successfully obtained stationary states of the system numerically by the SA method with Casimir invariants preserved. Since the 2D low-beta R-MHD has two fields, the relaxation process becomes complex compared to a single field system such as 2D Euler flow. The obtained stationary state can have fine structure. We have found that the fine structure appears because the relaxation processes are different between kinetic energy and magnetic energy.

  18. 3D-Printed Microfluidics.

    PubMed

    Au, Anthony K; Huynh, Wilson; Horowitz, Lisa F; Folch, Albert

    2016-03-14

    The advent of soft lithography allowed for an unprecedented expansion in the field of microfluidics. However, the vast majority of PDMS microfluidic devices are still made with extensive manual labor, are tethered to bulky control systems, and have cumbersome user interfaces, which all render commercialization difficult. On the other hand, 3D printing has begun to embrace the range of sizes and materials that appeal to the developers of microfluidic devices. Prior to fabrication, a design is digitally built as a detailed 3D CAD file. The design can be assembled in modules by remotely collaborating teams, and its mechanical and fluidic behavior can be simulated using finite-element modeling. As structures are created by adding materials without the need for etching or dissolution, processing is environmentally friendly and economically efficient. We predict that in the next few years, 3D printing will replace most PDMS and plastic molding techniques in academia.

  19. Phenomenology treatment of magnetohydrodynamic turbulence with non-equipartition and anisotropy

    SciTech Connect

    Zhou, Y; Matthaeus, W H

    2005-02-07

    Magnetohydrodynamics (MHD) turbulence theory, often employed satisfactorily in astrophysical applications, has often focused on parameter ranges that imply nearly equal values of kinetic and magnetic energies and length scales. However, MHD flow may have disparity magnetic Prandtl number, dissimilar kinetic and magnetic Reynolds number, different kinetic and magnetic outer length scales, and strong anisotropy. Here a phenomenology for such ''non-equipartitioned'' MHD flow is discussed. Two conditions are proposed for a MHD flow to transition to strong turbulent flow, extensions of (1) Taylor's constant flux in an inertial range, and (2) Kolmogorov's scale separation between the large and small scale boundaries of an inertial range. For this analysis, the detailed information on turbulence structure is not needed. These two conditions for MHD transition are expected to provide consistent predictions and should be applicable to anisotropic MHD flows, after the length scales are replaced by their corresponding perpendicular components. Second, it is stressed that the dynamics and anisotropy of MHD fluctuations is controlled by the relative strength between the straining effects between eddies of similar size and the sweeping action by the large-eddies, or propagation effect of the large-scale magnetic fields, on the small scales, and analysis of this balance in principle also requires consideration of non-equipartition effects.

  20. 3D Computations and Experiments

    SciTech Connect

    Couch, R; Faux, D; Goto, D; Nikkel, D

    2004-04-05

    This project consists of two activities. Task A, Simulations and Measurements, combines all the material model development and associated numerical work with the materials-oriented experimental activities. The goal of this effort is to provide an improved understanding of dynamic material properties and to provide accurate numerical representations of those properties for use in analysis codes. Task B, ALE3D Development, involves general development activities in the ALE3D code with the focus of improving simulation capabilities for problems of mutual interest to DoD and DOE. Emphasis is on problems involving multi-phase flow, blast loading of structures and system safety/vulnerability studies.