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THEORY DEPARTMENT Theory seminars,
2004-2005 Standard Location: Theory Conference Room Standard Time: Thursday Refreshments are at 10:30am Seminar is at 10:45am Please contact mailto:Gwangson Choeif you would like to present a seminar, suggest a speaker or would like to be notified of seminars by email. Please note: All
visitor arrangements, including Site Access Notification , are the responsibility of the PPPL
host. Future seminars are subject to changes due to speakers’ availability. Local, flexible speakers maybe asked to reschedule their seminars to give opportunity for guests to deliver talks. Page last updated March 28, 2005. |
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Date |
Speaker |
Affiliation |
Title
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Comments |
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September 23 |
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September 30 |
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October 7 |
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October 14 |
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October 21 |
Roscoe White |
PPPL |
Zonal Flow Dynamics and anomalous Transport |
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October 28 |
Ben
Chandran |
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Thermal conduction in turbulent
magnetized plasmas, and its effects in clusters of galaxies. |
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November 4 |
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November 11 |
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November 18 |
no speaker |
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APS
Week |
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November23 |
Bedros Afeyan |
Polymath Research, Inc. |
KEEN Waves: Long Lived Non-stationary
Nonlinear Coherent Structures in the Spectral Gap of the
Vlasov-Poisson System |
Note-Tuesday |
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December 3 |
Roberto
Torasso |
NYU |
"Stability of
ballooning modes in the Hall-MHD Model" |
Note-friday |
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December 9 |
T.S. Hahm |
PPPL |
Review of IAEA
Theory papers |
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December 16 |
Theory meeting |
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December 28 |
No
speaker |
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Lab
holiday |
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December 30 |
no speaker |
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Lab
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January 4 |
Prof. Baofeng Feng |
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Stable solitary waves
in two-dimensional stabilized Kuramoto-Sivashinsky systems |
Note tuesday |
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January 13 |
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PPPL |
Study of unsolved
issues of
m=1 oscillation (ìSawtoothî) via 2-D ECE Imaging System on TEXTOR* |
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January 20 |
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January 27 |
Theory
Meeting |
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February 3 |
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February 10 |
David
J Strozzi |
MIT |
Electron Trapping in
Raman Scattering from Inhomogenous Plasmas |
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February 17 |
Theory meeting Guoyong Fu and Nikolai Gorelenkov |
PPPL |
Theory/energetic particle SFG micro-seminar |
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February 24 |
Mikhail Sitnov |
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Structure and dynamics
of thin non-Harris current sheets" |
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February 28 |
Greg Hammett |
PPPL |
Calculation of Particle
Noise-induced Diffusion and Its Effect on ETG Simulations |
Special
Monday Theory seminar located in the Display Wall Room at 1:30 |
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March 3 |
Jay Johnson |
PPPL |
The magnetospheric
response to the solar wind |
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March 10 |
Vladimir Yankov |
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Improvement of
confinement in tokamaks by weakening of poloidal magnetic field near boundary. |
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March 17 |
Theory meeting |
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March 24 |
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March 31 |
John Krommes |
PPPL |
The Fluctuation--Dissipation Theorem (and beyond) |
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April 7 |
Igor Kaganovich |
PPPL |
Dynamics of Ion Beam Interaction with Background
Plasma |
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April 15 |
D. VanEster |
Laboratory
for Plasma Physics, Association “EURATOM – |
A simple method
to account for drift orbit effects when modeling radio frequency heating in tokamaks |
Please note, this is a special Friday Seminar, to
be held in the Theory Seminar room at 11:00 am. |
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April 18 |
Michael Hesse |
Goddard Space Flight
Center/NASA |
Mechanisms of electron demagnetization in collisionless magnetic reconnection |
Please note, this is a special Monday Seminar, to be held in the
Display Wall room at 10:45 am. |
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April 21 |
Theory meeting |
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April 28 |
Harry Mynick |
PPPL |
Tutorial on Stellarator
Transport I |
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May 5 |
Masaaki Yamada and
Russell Kulsrud |
PPPL |
Study of Two-Fluid MHD Physics of Magnetic Reconnection in
Laboratory and Space Plasmas |
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May 10 |
Scott Parker |
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Gyrokinetic
simulation of the collisionless and semi-collisional tearing mode instability |
This is a special Tuesday seminar, to
be held at 2:00 pm in the Theory Seminar Room. |
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May 12 |
Harry Mynick |
PPPL |
Tutorial on Stellarator Transport
III |
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May 19 |
Theory meeting |
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May 26 |
Hong Qin |
PPPL |
A footnote on the adiabatic invariants |
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June 2 |
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June 9 |
Shuanghui Hu |
UC Irvine |
Discrete Alfven Eigenmodes Excited by Energetic Particles in High-Beta Tokamaks |
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June
16 |
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June 23 |
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June 30 |
Bruce Scott |
IPP |
Theory and Computation in Full-F Gyrokinetics |
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July 28 |
Matthew Hole |
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Stepped Pressure Profile Equilibria
in Cylindrical Plasmas via Partial |
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August
10 |
Xianzhu Tang |
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Magnetic Relaxation in Laboratory and Astrophysical
Plasmas |
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August 18 |
Hiroshi Naitou |
Gyro-Reduced MHD Simulation of Kinetic Internal Kink Modes |
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Thursday, October 21
10:45 am Roscoe White PPPL Zonal Flow Dynamisc and Anomalous TransportNonlinear equations for the
slow space-time evolution of the radial drift wave-ion temperature
gradient (DW-ITG) envelope and zonal flow (ZF)
amplitude have been derived within a coherent 4-wave drift wave-zonal
flow model. In the local limit this model demonstrates
spontaneous generation of zonal flow and
nonlinear drift wave-zonal flow dynamics in toroidal plasmas.
The model allows slow temporal and spatial variations of the DW-ITG radial envelope,
incorporating the effects of equilibrium variations, $ie$ turbulence spreading and size-dependence of the saturated wave
intensities and transport coefficients. The competition between linear
drive/damping and drift wave spreading due to linear and
nonlinear group velocity and nonlinear energy transfer between DW
and ZF determines the saturation levels of the
fluctuating fields. The turbulence intensity level exhibits a
transition from Bohm scaling at small system size ($L/\rho$) to gyro Bohm for large system size. This system exhibits chaotic behavior and
intermittency, depending on system size and proximity to marginal
stability. The model is explored using Symbolic Dynamics, which
is shown to provide a useful means of analyzing turbulence levels using a single time
sequence data stream. |
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Thursday, October 28 10:45 am Ben Chandran Department of Physics & Astronomy Universtiy of Thermal conduction in turbulent magnetized plasmas, and its effects in clusters of galaxies. Clusters of galaxies are the largest gravitationally
bound objects in the universe. They host a wealth of interesting phenomena,
from star formation on a massive scale to powerful extragalactic jets powered
by supermassive black holes. In this talk I
will describe an outstanding theoretical puzzle in the study of galaxy
clusters, namely the need to explain the observationally inferred heating of
galaxy-cluster plasmas. One of the most important heating mechanisms is
thermal conduction, which is modified by turbulent intracluster
magnetic fields. I will describe how the Rechester-Rosenbluth
theory of heat conduction in stochastic fields can be applied to this case,
in which the mean field is negligible. I will also present recent
analytic and numerical results on electron diffusion and field-line
trajectories in strong magnetohydrodynamic
turbulence, as well as results on two other important heating mechanisms:
turbulent intracluster motions and active galactic
nuclei at the centers of clusters. |
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Tuesday,
November 28 10:45 am KEEN Waves: Long Lived Non-stationary Nonlinear Coherent
Structures in the Spectral Gap of the Vlasov-Poisson
System Bedros Afeyan,
Polymath Research Inc., We will discuss theoretical, computational and
experimental results concerning ponderomotively
driven (and released) Kinetic Electrostatic Electron Nonlinear (KEEN) waves.
Direct high resolution Vlasov-Poisson simulations,
nonlinear coupled mode theory in phase space, and optical mixing experiments on the Trident laser facility at LANL
will be described whereby KEEN waves' existence was discovered, further
explained and experimentally verified, respectively. Implications to laser-plasma interaction physics and the
large set of unresolved anomalies in SRS spectra, for instance, will be
touched upon. Mutual interaction of KEEN waves as well as their interactions with EPWs will also be
described which open up new vistas of plasma physics in the spectral gap that
was thought to exist in plasma physics based on linear theory, quasilinear reasoning and small amplitude nonlinear
theories. KEEN waves exist deep in the nonlinear regime with remarkable
stability properties. We will show links to Vlasov-Maxwell
simulations and general nonlinear paradigms of instability saturation which have to be revisited in light of the existence of
KEEN waves. |
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Friday Dec 3, 10:45
am "Stability of ballooning modes in the Hall-MHD
Model" Roberto Torasso NYU The equations of the ballooning modes are derived within the Hall~magnetohydrodynamics
(HMHD) model and given a standard Hamiltonian form. The Hamiltonian structure of the equations is used to derive sufficient conditions for
stability. In most cases, ideal magnetohydrodynamics
(MHD) stability of ballooning modes implies HMHD stability, as is the case for tokamak configurations as well as plasmas with constant entropy or incompressible plasmas. However, in the case of
closed-line systems such as the field-reversed configuration (FRC), or in a typical magnetospheric
magnetic field, MHD ballooning stability does not automatically guarantee HMHD stability. For the explicitly solvable configuration of the Z-pinch it is shown that the sufficient condition
derived here is also necessary for stability. |
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Wednesday Jan 5 10:45
am Title: Stable solitary waves in two-dimensional
stabilized Kuramoto-Sivashinsky systems Prof. Baofeng Feng By linearly coupling generalized two-dimensional Benney equations to an extra linear dissipative equation,
two-dimensional (2D) extensions of a stabilized Kuramoto
- Sivashinsky system are developed. The models apply to the description of surface waves on 2D
liquid layers in various physical settings. A perturbation
theory is developed by treating dissipation and gain in the models as small
perturbations. Stable solitary wave solutions are predicted and
numerically confirmed. |
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Thursday Feb 3 10:45 am Study of unsolved issues of m=1 oscillation (ìSawtoothî) via 2-D ECE Imaging System on TEXTOR* A novel 2-D Electron Cyclotron Emission Imaging
(ECEI) system for measuring electron temperature fluctuations applied to
study sawtooth crash physics on TEXTOR. A 128-channel prototype imaging system, covering 8 cm (radial)
by 16 cm (vertical),
with high spatial (1 cm x 1
cm) and temporal (up to ~5 msec) resolution employs large aperture optics
to form a spatially resolved image
of several cyclotron layers
simultaneously.
The ECEI system, which includes a
16-channel vertical array of antennas and wide-band transmission line, has provided behaviours of the electron temperature fluctuations similar to the ìmagnetic reconnectionî process during crash time of m=1 (sawtooth) oscillations, revealing details not accessible
through conventional methods (1-D ECE and/or tomography). Long history of
theoretical and experimental study of m=1 oscillation left remnants of
mysteries and unresolved issues of
physics such as current sheet and reconnection time scale. Details of poloidal and toroidal asymmetries of the measured electron fluctuation by 2-D ECEI may provide a clue of
these issues. |
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Thursday Feb 10 10:45
am |