52 research outputs found
Energy-Conserving Truncations for Convection with Shear Flow
A method is presented for making finite Fourier mode truncations of the
Rayleigh--Benard convection system that preserve invariants of the full partial
differential equations in the dissipationless limit. These truncations are
shown to have no unbounded solutions and provide a description of the thermal
flux that has the correct limiting behavior in a steady-state. A particular
low-order truncation (containing 7 modes) is selected and compared with the 6
mode truncation of Howard and Krishnamurti (1986), which does not conserve the
total energy in the dissipationless limit. A numerical example is presented to
compare the two truncations and study the effect of shear flow on thermal
transport.Comment: 18 pages, 5 Postscript figures, uses RevTeX and epsf. Accepted for
publication in Physics of Fluid
Shear flow-interchange instability in nightside magnetotail causes auroral beads as a signature of substorm onset
A geometric wedge model of the near-earth nightside plasma sheet is used to
derive a wave equation for low frequency shear flow-interchange waves which
transmit sheared zonal flows along magnetic flux tubes
towards the ionosphere. Discrepancies with the wave equation result used in
Kalmoni et al. (2015) for shear flow-ballooning instability are discussed. The
shear flow-interchange instability appears to be responsible for substorm
onset. The wedge wave equation is used to compute rough expressions for
dispersion relations and local growth rates in the midnight region of the
nightside magnetotail where the instability develops, forming the auroral beads
characteristic of geomagnetic substorm onset. Stability analysis for the shear
flow-interchange modes demonstrates that nonlinear analysis is necessary for
quantitatively accurate results and determines the spatial scale on which the
instability varies
Ion temperature gradient driven turbulence in the weak density gradient limit
The anomalous heat transport arising from the ion temperature gradient driven mode or ηi-mode turbulence is extended to the range of the weak density gradient limit (ηi = Ln/ L Tâ â ), which is appropriate for H-mode dishcarges. It is shown that the anomalous ion heat conductivity Ïi with L nâ â scales as Ïi = g(Ïs/ LT) (cTi/eB) exp( - ÎČÏ) with Ï = (T e/Ti) (LT/Ls), ÎČâ4, and gâ1. This Ïi scaling is the natural extension for high ηi of the scaling of Ïi for K = (T i/Te) (1 + ηi) âČ 4 obtained [Phys. Fluids B 2, 1833 (1990)] from analytical and numerical studies. © 1990 American Institute of Physics.Satoshi Hamaguchi and Wendell Horton, Physics of Fluids B: Plasma Physics 2, 3040 (1990) https://doi.org/10.1063/1.85937
Dynamical range of WINDMI model: an exploration of possible magnetospheric plasma states
Abstract. This paper explores the dynamical range of the WINDMI model
Drift wave test particle transport in reversed shear profile
Drift wave maps, area preserving maps that describe the motion of charged particles in drift waves, are derived. The maps allow the integration of particle orbits on the long time scale needed to describe transport. Calculations using the drift wave maps show that dramatic improvement in the particle confinement, in the presence of a given level and spectrum E x B turbulence, can occur for q(r)-profiles with reversed shear. A similar reduction in the transport, i.e., one that is independent of the turbulence, is observed in the presence of an equilibrium radial electric field with shear. The transport reduction, caused by the combined effects of radial electric field shear and both monotonic and reversed shear magnetic q-profiles, is also investigated
Quasi-Two-Dimensional Dynamics of Plasmas and Fluids
In the lowest order of approximation quasi-twa-dimensional dynamics of planetary atmospheres and of plasmas in a magnetic field can be described by a common convective vortex equation, the Charney and Hasegawa-Mirna (CHM) equation. In contrast to the two-dimensional Navier-Stokes equation, the CHM equation admits "shielded vortex solutions" in a homogeneous limit and linear waves ("Rossby waves" in the planetary atmosphere and "drift waves" in plasmas) in the presence of inhomogeneity. Because of these properties, the nonlinear dynamics described by the CHM equation provide rich solutions which involve turbulent, coherent and wave behaviors. Bringing in non ideal effects such as resistivity makes the plasma equation significantly different from the atmospheric equation with such new effects as instability of the drift wave driven by the resistivity and density gradient. The model equation deviates from the CHM equation and becomes coupled with Maxwell equations. This article reviews the linear and nonlinear dynamics of the quasi-two-dimensional aspect of plasmas and planetary atmosphere starting from the introduction of the ideal model equation (CHM equation) and extending into the most recent progress in plasma turbulence.U. S. Department of Energy DE-FG05-80ET-53088Ministry of Education, Science and Culture of JapanFusion Research Cente
Search for the Invisible Decay of Neutrons with KamLAND
The Kamioka Liquid scintillator Anti-Neutrino Detector (KamLAND) is used in a
search for single neutron or two neutron intra-nuclear disappearance that would
produce holes in the -shell energy level of C nuclei. Such holes
could be created as a result of nucleon decay into invisible modes (),
e.g. or . The de-excitation of the corresponding
daughter nucleus results in a sequence of space and time correlated events
observable in the liquid scintillator detector. We report on new limits for
one- and two-neutron disappearance: years
and years at 90% CL. These results
represent an improvement of factors of 3 and over previous
experiments.Comment: 5 pages, 3 figure
Measurement of Neutrino Oscillation with KamLAND: Evidence of Spectral Distortion
We present results of a study of neutrino oscillation based on a 766 ton-year
exposure of KamLAND to reactor anti-neutrinos. We observe 258 \nuebar\
candidate events with energies above 3.4 MeV compared to 365.2 events expected
in the absence of neutrino oscillation. Accounting for 17.8 expected background
events, the statistical significance for reactor \nuebar disappearance is
99.998%. The observed energy spectrum disagrees with the expected spectral
shape in the absence of neutrino oscillation at 99.6% significance and prefers
the distortion expected from \nuebar oscillation effects. A two-neutrino
oscillation analysis of the KamLAND data gives \DeltaMSq =
7.9 eV. A global analysis of data from KamLAND
and solar neutrino experiments yields \DeltaMSq =
7.9 eV and \ThetaParam =
0.40, the most precise determination to date.Comment: 5 pages, 4 figures; submitted to Phys.Rev.Letter
The Linkage Between Neighborhood and Voluntary Association Patterns: a Comparison of Black and White Urban Populations
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68314/2/10.1177_089976407400300201.pd
The 2010 Interim Report of the Long-Baseline Neutrino Experiment Collaboration Physics Working Groups
Corresponding author R.J.Wilson ([email protected]); 113 pages, 90 figuresCorresponding author R.J.Wilson ([email protected]); 113 pages, 90 figuresIn early 2010, the Long-Baseline Neutrino Experiment (LBNE) science collaboration initiated a study to investigate the physics potential of the experiment with a broad set of different beam, near- and far-detector configurations. Nine initial topics were identified as scientific areas that motivate construction of a long-baseline neutrino experiment with a very large far detector. We summarize the scientific justification for each topic and the estimated performance for a set of far detector reference configurations. We report also on a study of optimized beam parameters and the physics capability of proposed Near Detector configurations. This document was presented to the collaboration in fall 2010 and updated with minor modifications in early 2011
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