Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Poloidal rotation effects on a simulated resistive kink mode (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 174-179 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Through the principal use of the reduced magnetohydrodynamic version of the finite aspect ratio code [L. A. Charlton et al., J. Comput. Phys. 86, 270 (1990)], an m/n=1/1 resistive kink mode was poloidally rotated with the accompanying rotational shear. It was observed that the growth rate of this unstable mode can either decrease or increase as the applied equilibrium rotation is increased to near poloidal sonic speeds. Shear in the poloidal rotation profile is stabilizing, but only if the destabilizing effects of bulk rotation can be overcome. Therefore, the mode's stability was sensitive to the location of the rotation's peak relative to the eigenmode's spatial extent. The destabilizing effects of bulk rotation are apparently a rotationally enhanced beta, and the stabilizing effects appear to be caused by exceeding a critical rotational shear spatially averaged over the eigenmode structure. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1326062
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Theory of beat wave excitation in an inhomogeneous plasma (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 36-47 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The theory of beat wave excitation in a slightly inhomogeneous plasma is presented. While the theory is general it applies directly to the experiments performed in Alaska by the ionospheric heating facilities HIPAS [High Power Auroral Simulation, Radio Sci. 25, 1269 (1990)] and HAARP [High Frequency Active Auroral Research Project, Geophys. Res. Lett. 25, 257 (1998)]. A ray tracing (WKB) formalism appropriate for computations is developed. The computational implementation of this formalism and extensive results will be presented in a follow up to this paper. Also the beat wave excitation of upper-hybrid waves is investigated analytically. The complicated trajectories of these waves in the plasma are described. When this beat wave reaches the plasma wave resonance it can, in the HIPAS–HAARP experiments, attain nonlinear amplitude. The electrostatic upper-hybrid waves are trapped around the density maximum of the ionosphere. This trapping is investigated in detail. Beat wave pumping of the trapped modes is possible using HAARP and HIPAS or with split beams from HAARP. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1329149
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Field-aligned coordinates for nonlinear simulations of tokamak turbulence (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 2687-2700 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Turbulence in tokamaks is characterized by long parallel wavelengths and short perpendicular wavelengths. A coordinate system for nonlinear fluid, gyrokinetic "Vlasov,'' or particle simulations is presented that exploits the elongated nature of the turbulence by resolving the minimum necessary simulation volume: a long thin twisting flux tube. It is very similar to the ballooning representation, although periodicity constraints can be incorporated in a manner that allows E×B nonlinearities to be evaluated efficiently with fast Fourier transforms (FFT's). If the parallel correlation length is very long, however, enforcing periodicity can introduce artificial correlations, so periodicity should not necessarily be enforced in the poloidal angle at θ=±π. This method is applied to high resolution three-dimensional simulations of toroidal ion temperature gradient (ITG) driven turbulence, which predict fluctuation spectra and ion heat transport similar to experimental measurements. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871232
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Nonlinear magnetohydrodynamic detonation: Part I (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 3565-3580 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The sudden release of magnetic free energy, as occurs in spectacular solar flare events, tokamak disruptions, and enigmatic magnetospheric substorms, has long defied any acceptable theoretical explanation. Usual attempts at explaining these explosive events invoke magnetic reconnection and/or ideal magnetohydrodynamic (MHD) instability. However, neither of these two mechanisms can explain the fast time scales without nonlinear destabilization. Recently, Cowley et al. [Phys. Plasmas 3, 1848 (1996)] have demonstrated a new mechanism for nonlinear explosive MHD destabilization of a line tied Rayleigh–Taylor model. In this paper, this picture is generalized to arbitrary magnetic field geometries. As an intermediate step, the ballooning equation in a general equilibrium is derived including the effects of magnetic field curvature, shear, and gravity. This equation determines the linear stability of the plasma configuration and the behavior of the plasma displacement along the magnetic field line. The nonlinear equation which determines the time and spatial dependence, transverse to the equilibrium magnetic field, of the plasma displacement is obtained in fifth order of the expansion. The equations show that explosive behavior is a natural and generic property of ballooning instabilities close to the linear stability boundary. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872252
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Calculation and interpretation of analytic high-beta poloidal equilibria in finite aspect ratio tokamaks (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 266-274 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The validity of the analytic large aspect ratio, high-β equilibria developed by Cowley et al. [Phys. Fluids B 3, 2066 (1991)] is extended to include finite aspect ratio equilibria with q2(very-much-greater-than)1, where q is the safety factor. These high-β equilibria have two regions. Most of the volume lies in the "core region,'' where ψ=ψ(R). The flux surfaces close in the "boundary layer region,'' which has thickness δ. The solutions are valid when δ/a∼O ((square root of)ε/βq2) is small, where a is the minor radius. Thus, finite ε is allowed when q2 is large. The equilibria are completely specified by the midplane profiles of pressure p(R) and poloidal magnetic field BP(R) and the shape of the plasma boundary, all of which can be measured experimentally. Note the departure from customary specification of p(ψ), q(ψ), or F(ψ). A fast numerical code, requiring a few seconds to execute, has been written to compute and illustrate the analytic high-β equilibria. The qualitative features of high-βP tokamaks are discussed in detail. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871852
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Radial electric field required to suppress ion temperature gradient modes in the Electric Tokamak (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 4722-4727 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Electric Tokamak (ET), currently under construction at the University of California–Los Angeles, is designed to rotate poloidally via a radial current induced by fast wave rf heating fast enough to bifurcate the plasma into a global "H mode" ("high confinement mode"). A global gyrokinetic code is used to explore and illustrate some of the effects on ion temperature gradient turbulence. The realistic radial electric field required to completely suppress these modes for ET parameters is demonstrated to be 〈−30 V/cm at its maximum near the half radius. The effects of both a poloidally supersonic bulk rotation threshold and the shear in this rotation near that supersonic threshold were shown to be important in reducing these modes. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873759
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    The continuum of unstable magnetohydrodynamic modes in a simple magnetized atmosphere (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 1259-1264 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The spectrum of unstable perturbations of a simple magnetized atmosphere is studied. Magnetic field lines are straight, horizontal, and line tied to conducting walls at both ends. The temperature has horizontal variation across the field lines as well as vertical variation. The unstable spectrum close to marginal stability is found to be continuous from zero to a maximum growth rate. The structure of the unstable continuum modes is calculated in the dissipationless limit. The presence of singularities in the eigenfunction does not affect the growth rate significantly, nor does it lead to plasma heating. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872783
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Current sheet formation along three-dimensional magnetic separators (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 2885-2897 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It was shown by Syrovatskii [Sov. Phys. JETP 33, 933 (1971)] that a perfectly conducting two-dimensional magnetic field stressed externally develops a current sheet at an X point. A generalization of this analysis shows that a generic three-dimensional magnetic field develops a closed ribbon of current along separators already existing in the field. A separator is a field line that begins and ends at different magnetic null points. A current ribbon will occur if there are two distinct separators beginning and ending at the same two nulls, thus forming a loop. The magnetic field containing the current ribbon is in force-free equilibrium. An expression is found for the net current induced in the ribbon, and the magnetic energy stored by it, in terms of the amount of external stress. An electric field parallel to the current will facilitate reconnection and will dissipate the current and release the stored energy. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871627
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Tearing modes in toroidal geometry (1988)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 31 (1988), S. 577-590 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The separation of the cylindrical tearing mode stability problem into a resistive resonant layer calculation and an external marginal ideal magnetohydrodynamic (MHD) calculation (Δ' calculation) is generalized to axisymmetric toroidal geometry. The general structure of this separation is analyzed and the marginal ideal MHD information (the toroidal generalization of Δ') required to discuss stability is isolated. This can then, in principle, be combined with relevant resonant layer calculations to determine tearing mode growth rates in realistic situations. Two examples are given: the first is an analytic treatment of toroidally coupled (m=1, n=1) and (m=2, n=1) tearing modes in a large aspect ratio torus; the second, a numerical treatment of the toroidal coupling of three tearing modes through finite pressure effects in a large aspect ratio torus. In addition, the use of a coupling integral approach for determining the stability of coupled tearing modes is discussed. Finally, the possibility of using initial value resistive MHD codes in realistic toroidal geometry to determine the necessary information from the ideal MHD marginal solution is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866840
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Modeling transport in toroidal plasmas: Status and issues (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 2913-2925 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The scope and detail of physics contained in computational models for fluid (density, momentum, energy) transport in toroidal plasmas have steadily increased during the past two decades. There has been considerable success in the development and verification of models for sources and sinks of particles, energy, momentum, and magnetic flux. Transport codes have collectively become very useful tools in interpreting experimental data and in providing guidance for new experiments. However, a more thorough understanding of the fundamental transport processes of magnetically confined plasmas and development of improved computational models are needed to enhance the predictive capabilities of transport codes. It is argued that fluid transport modeling by itself cannot lead to a complete understanding of transport—there must be a very strong collaboration among theory, experiment, and modeling on both the fluid and kinetic levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.859360
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...