ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

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
    On the dynamics of a plasma vortex street and its topological signatures (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 2125-2134 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A plasma vortex street configuration can evolve when two velocity and one magnetic shear layer interact strongly. A study of the interaction between two- and three-dimensional plasma modes and a mean sheared magnetic field is undertaken using a three-dimensional magnetohydrodynamic spectral Galerkin computation. The initial state is a simple magnetic shear in a plane perpendicular to the plasma velocity shear plane. In a very weak magnetic field, secondary instabilities (three-dimensional modes), expressed by the kinking of vortex tubes, lead to plasma flow along and around the axes of the vortex cores, creating characteristic patterns of kinetic helicity and linkages between vortex filaments. Three-dimensionality leads to the vortex breakdown process. A strong sheared magnetic field inhibits the kinking of vortex tubes, maintaining two-dimensionality. This inhibits vortex breakdown over long dynamical times. There is an anticorrelation in time between linkage indices of the vortex filament (related to kinetic helicity), suggesting that the ellipticity axes of the vortex cores along the street undergo a global inphase evolution. This anticorrelation has a dynamical interpretation. It extends to a relaxing plasma in the Navier–Stokes flow notion that helical regions of opposite helicities interact and screen each other off so that the global helicity remains bounded.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870610
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Coarse-graining and nonlocal processes in proton cyclotron resonant interactions (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 333-344 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Coarse-grained information from a hybrid simulation show that previously developed quasifluid equations of state capture some aspects of proton cyclotron resonant interactions for parallel propagation in a low β plasma. Direct kinetic information is used as a closure for the information exchanged with the higher-order moment quantities. The coarse-graining procedure involves averaging over many proton-inertial lengths and looking at long time scales associated with the wave envelopes. By use of the coarse-graining prior to statistical analysis, the anticorrelations predicted by the equations of state are very high for both the single resonant wave case and for a broadband spectrum centered on a resonant wave. These anticorrelations are also consistent with what one expects from a single particle orbit analysis. A similar analysis, but done without the prior averaging procedures, shows no relevant correlations, and no simple dynamics emerges from the kinetic data in this case. A comparison is made with a model based on quasilinear theory. These results suggest that, in addition to simply taking velocity moments of particle distributions, the proper averaging of kinetic information over space and time scales lying below the range accessible to a fluid model can be essential to its success. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872715
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Nonlinear entropy production operators for magnetohydrodynamic plasmas (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 1480-1493 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A method for constructing closure relations based on the invariants of the tensors representing nonequilibrium thermodynamic forcing within the plasma is presented. This approach leads to closure relations that describe all higher-order forcing effects contained within the continuum description. Nonlinear convective-momentum transport and nonlinear momentum-exchange operators are constructed as applications of the method. Closure is achieved by relating the pressure tensor to invariants of the rate of strain tensor, and the momentum-exchange operator to invariants of the gradient of magnetic field tensor. These operators lead to positive definite viscous and Joule entropy production and enhance high wave number dissipative couplings over all other dissipative couplings. The nonlinear dissipative action is localized in physical space, where velocity and magnetic gradients are large, while allowing nearly ideal behavior elsewhere. The operators are computationally tested against the standard magnetohydrodynamic (MHD) operators using three-dimensional configurations that lead to vortex street formation and magnetic reconnection. The nonlinear operators allow greater spatial structure and have flatter modal energy spectra than the standard MHD dissipation operators. Closures that describe the plasma response to nonequilibrium thermodynamic forcing of all orders can be constructed using this approach. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871363
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Magnetohydrodynamic Turbulence in the Solar Wind (1995)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Astronomy and Astrophysics 33 (1995), S. 283-325 
    Details
    ISSN: 0066-4146
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.aa.33.090195.001435
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Time evolution from linear to nonlinear stages in magnetohydrodynamic parametric instabilities (1989)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 1 (1989), S. 1405-1415 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nonlinear evolution of the magnetohydrodynamic (MHD) parametric instability of wave fluctuations propagating along an unperturbed magnetic field is investigated. Both a magnetohydrodynamic perturbation-theoretical approach and a nonlinear MHD simulation are used. It is shown that high harmonic waves are rapidly excited by wave–wave coupling, and that the wave spectrum evolves from a state containing a small number of degrees of freedom in k space to one which contains a large number of degrees of freedom. It is found that the spectral evolution prior to nonlinear saturation is well described by the perturbation theory. During this stage, the ratio of the growth rate of the nth harmonic wave to the linear growth rate of the fundamental wave is n. The nonlinear saturation stage is characterized by a frequency shift of the fundamental wave that destroys the wave–wave resonance condition which, in turn, causes the wave amplitude to cease its growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858971
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    The alpha dynamo parameter and measurability of helicities in magnetohydrodynamic turbulence (1986)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 1504-1508 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Alpha, an important parameter in dynamo theory, is shown to be proportional to either the kinetic, current, magnetic, or velocity helicities of the fluctuating magnetic field and fluctuating velocity field. The particular helicity to which alpha is proportional depends on the assumptions used in deriving the first-order smoothed equations that describe the alpha effect. In two cases, viz., when alpha is proportional to either the magnetic helicity or velocity helicity, alpha can be determined experimentally from two-point measurements of the fluctuating fields in incompressible, homogeneous turbulence with arbitrary rotational symmetry. For the other two possibilities, alpha can be determined if the turbulence is isotropic.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865668
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Arcs in Saturn's radio spectra (1981)
    [s.l.] : Nature Publishing Group
    Nature 292 (1981), S. 728-731 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] ARC-LIKE structures appear sporadically in the dynamic spectra of Saturn radio emission measured by the Voyager 1 planetary radio astronomy (PRA) experiment. Arcs were pervasive in the dynamic spectra of Jupiter emission1"3 but they are not nearly as prevalent in Saturn data. There are some ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/292728a0
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    The nature of the solar wind (1996)
    [s.l.] : Nature Publishing Group
    Nature 381 (1996), S. 31-32 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR-Thomson et al.1 suggest that the wind flowing from the Sun contains many discrete, identifiable modes corresponding to solar internal pressure (/?) and gravity (g) modes, in sharp contrast to the standard paradigm of the solar wind as a turbulently evolving magnetofluid with a continuous ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/381031a0
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Problems with fitting to the power-law distribution (2004)
    Springer
    The European physical journal 41 (2004), S. 255-258 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. This short communication uses a simple experiment to show that fitting to a power law distribution by using graphical methods based on linear fit on the log-log scale is biased and inaccurate. It shows that using maximum likelihood estimation (MLE) is far more robust. Finally, it presents a new table for performing the Kolmogorov-Smirnov test for goodness-of-fit tailored to power-law distributions in which the power-law exponent is estimated using MLE. The techniques presented here will advance the application of complex network theory by allowing reliable estimation of power-law models from data and further allowing quantitative assessment of goodness-of-fit of proposed power-law models to empirical data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2004-00316-5
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Detection of langmuir solitons: implications for type III burst emission mechanisms at 2ω PE (1996)
    Springer
    Astrophysics and space science 243 (1996), S. 195-198 
    Details
    ISSN: 1572-946X
    Keywords: Langmuir Solitons ; Type III Bursts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present the experimental verification of existing theoretical models of emission mechanisms of solar type III bursts at the second harmonic of the plasma frequency, ω pe . This study is based on the detection of Langmuir and envelope solitons by the Ulysses spacecraft inside three type III burst source regions. We show that the oscillating-two-stream instability, coherent radiation by Langmuir solitons and stochastic phase mixing of the Langmuir waves in the strong turbulence regime are the appropriate emission mechanisms at 2ω pe .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00644054
    Location Call Number Expected 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...