
THEORY DEPARTMENT Theory seminars,
20042005 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. 
Date 
Speaker 
Affiliation 
Title

Comments 
September 23 




September 30 




October 7 




October 14 




October 21 
Roscoe White 
PPPL 
Zonal Flow Dynamics and anomalous Transport 

October 28 
Ben
Chandran 

Thermal conduction in turbulent
magnetized plasmas, and its effects in clusters of galaxies. 

November 4 




November 11 




November 18 
no speaker 


APS
Week 
November23 
Bedros Afeyan 
Polymath Research, Inc. 
KEEN Waves: Long Lived Nonstationary
Nonlinear Coherent Structures in the Spectral Gap of the
VlasovPoisson System 
NoteTuesday 
December 3 
Roberto
Torasso 
NYU 
"Stability of
ballooning modes in the HallMHD Model" 
Notefriday 
December 9 
T.S. Hahm 
PPPL 
Review of IAEA
Theory papers 

December 16 
Theory meeting 



December 28 
No
speaker 


Lab
holiday 
December 30 
no speaker 


Lab

January 4 
Prof. Baofeng Feng 

Stable solitary waves
in twodimensional stabilized KuramotoSivashinsky systems 
Note tuesday 
January 13 

PPPL 
Study of unsolved
issues of
m=1 oscillation (ěSawtoothî) via 2D ECE Imaging System on TEXTOR* 

January 20 




January 27 
Theory
Meeting 



February 3 




February 10 
David
J Strozzi 
MIT 
Electron Trapping in
Raman Scattering from Inhomogenous Plasmas 

February 17 
Theory meeting Guoyong Fu and Nikolai Gorelenkov 
PPPL 
Theory/energetic particle SFG microseminar 

February 24 
Mikhail Sitnov 

Structure and dynamics
of thin nonHarris current sheets" 

February 28 
Greg Hammett 
PPPL 
Calculation of Particle
Noiseinduced Diffusion and Its Effect on ETG Simulations 
Special
Monday Theory seminar located in the Display Wall Room at 1:30 
March 3 
Jay Johnson 
PPPL 
The magnetospheric
response to the solar wind 

March 10 
Vladimir Yankov 

Improvement of
confinement in tokamaks by weakening of poloidal magnetic field near boundary. 

March 17 
Theory meeting 



March 24 




March 31 
John Krommes 
PPPL 
The FluctuationDissipation Theorem (and beyond) 

April 7 
Igor Kaganovich 
PPPL 
Dynamics of Ion Beam Interaction with Background
Plasma 

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. 
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. 
April 21 
Theory meeting 



April 28 
Harry Mynick 
PPPL 
Tutorial on Stellarator
Transport I 

May 5 
Masaaki Yamada and
Russell Kulsrud 
PPPL 
Study of TwoFluid MHD Physics of Magnetic Reconnection in
Laboratory and Space Plasmas 

May 10 
Scott Parker 

Gyrokinetic
simulation of the collisionless and semicollisional tearing mode instability 
This is a special Tuesday seminar, to
be held at 2:00 pm in the Theory Seminar Room. 
May 12 
Harry Mynick 
PPPL 
Tutorial on Stellarator Transport
III 

May 19 
Theory meeting 



May 26 
Hong Qin 
PPPL 
A footnote on the adiabatic invariants 

June 2 




June 9 
Shuanghui Hu 
UC Irvine 
Discrete Alfven Eigenmodes Excited by Energetic Particles in HighBeta Tokamaks 

June
16 




June 23 




June 30 
Bruce Scott 
IPP 
Theory and Computation in FullF Gyrokinetics 

July 28 
Matthew Hole 

Stepped Pressure Profile Equilibria
in Cylindrical Plasmas via Partial 

August
10 
Xianzhu Tang 

Magnetic Relaxation in Laboratory and Astrophysical
Plasmas 

August 18 
Hiroshi Naitou 
GyroReduced MHD Simulation of Kinetic Internal Kink Modes 
Thursday, October 21
10:45 am Roscoe White PPPL Zonal Flow Dynamisc and Anomalous TransportNonlinear equations for the
slow spacetime evolution of the radial drift waveion temperature
gradient (DWITG) envelope and zonal flow (ZF)
amplitude have been derived within a coherent 4wave drift wavezonal
flow model. In the local limit this model demonstrates
spontaneous generation of zonal flow and
nonlinear drift wavezonal flow dynamics in toroidal plasmas.
The model allows slow temporal and spatial variations of the DWITG radial envelope,
incorporating the effects of equilibrium variations, $ie$ turbulence spreading and sizedependence 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. 
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
galaxycluster plasmas. One of the most important heating mechanisms is
thermal conduction, which is modified by turbulent intracluster
magnetic fields. I will describe how the RechesterRosenbluth
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 fieldline
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. 
Tuesday,
November 28 10:45 am KEEN Waves: Long Lived Nonstationary Nonlinear Coherent
Structures in the Spectral Gap of the VlasovPoisson
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 VlasovPoisson 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 laserplasma 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 VlasovMaxwell
simulations and general nonlinear paradigms of instability saturation which have to be revisited in light of the existence of
KEEN waves. 
Friday Dec 3, 10:45
am "Stability of ballooning modes in the HallMHD
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
closedline systems such as the fieldreversed 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 Zpinch it is shown that the sufficient condition
derived here is also necessary for stability. 

Wednesday Jan 5 10:45
am Title: Stable solitary waves in twodimensional
stabilized KuramotoSivashinsky systems Prof. Baofeng Feng By linearly coupling generalized twodimensional Benney equations to an extra linear dissipative equation,
twodimensional (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. 

Thursday Feb 3 10:45 am Study of unsolved issues of m=1 oscillation (ěSawtoothî) via 2D ECE Imaging System on TEXTOR* A novel 2D Electron Cyclotron Emission Imaging
(ECEI) system for measuring electron temperature fluctuations applied to
study sawtooth crash physics on TEXTOR. A 128channel 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
16channel vertical array of antennas and wideband transmission line, has provided behaviours of the electron temperature fluctuations similar to the ěmagnetic reconnectionî process during crash time of m=1 (sawtooth) oscillations, revealing details not accessible
through conventional methods (1D 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 2D ECEI may provide a clue of
these issues. 

Thursday Feb 10 10:45
am David strozzi Electron Trapping in Raman Scattering from Inhomogenous Plasmas 
Thursday Feb 24 10:45
am Title: Structure and dynamics of thin nonHarris current
sheets Mikhail I. Sitnov Institute for Research in Electronics and Applied Physics,
University of Recent multiprobe observations of the current sheets in
the tail of Earth's magnetosphere and laboratory experiments, such
as MRX, revealed that the sheet properties become quite unusual when its thickness decreases to a few thermal ion gyroradii.
Such a thin current sheet may be embedded into a thicker plasma sheet or split into two
sheets, in contrast to the classical equilibrium theory and in the absence
of any conventional reconnection signatures. Thin current sheets in the tail
are often very dynamic, flapping in the northsouth direction. However,
their flapping waves are also unusual, as they propagate too slowly or
even in the direction opposite to the main current flow, at variance
with presently dominating theories and simulation results. To address
these issues, we present a steadystate Vlasov
theory of thin current sheets, which generalizes the wellknown isotropic Harris [1962]
equilibrium (a Cartesian geometry analog of the Bennett pinch) by
assuming anisotropic and nongyrotropic plasmas and
takes into account an additional invariant of particle motion, an analog of the magnetic moment,
applicable for regions with strong gradients. We consider the dynamics
of this new class of nonHarris equilibria using
a fullparticle code. The new equilibrium theory explains the effects of the current sheet
embedding and bifurcation, while simulations confirm the structural
stability of these new equilibria. The theory
reveals an important role of nongyrotropic effects arising from the figureofeight ion orbits in
thin sheets. We also discuss the distinctive features of very thin
sheets, with the thickness less than the thermal ion gyroradius,
which is of relevance to the MRX experiment. 
Thursday March 3 10:45
am Title: The magnetospheric response to the solar
wind Jay Johnson, PPPL Abstract. Understanding the dynamical evolution of the Earth’s magnetosphere is of practical interest because the magnetosphere occasionally evolves into a disturbed state that can affect the quality of life through large scale damage to power grids, loss of communications, and disruption of satellitebased defense strategy. The magnetospheric dynamics are ultimately driven by the solar wind while various dissipative processes cause the magnetosphere to evolve toward a quiescent state in the absence of strong driving. The magnetospheric dynamics are commonly characterized with various informationdynamical measures to understand dimensionality as well as the most important dependencies among observed plasma and electromagnetic field variables in the coupled solar wind/magnetosphere system. We identify nonlinear dependencies using mutual information and cumulantbased cost as discriminating statistics and discuss implications for modeling the magnetosphere and predicting its evolution. Application of the techniques to understand the dynamics of solar flares and neurosystems is also discussed. 
Thursday March 10
10:45 am Title: Improvement of confinement in tokamaks
by weakening of poloidal magnetic field near boundary. V. Yankov. Abstract. Theory of turbulent equipartition
and experiment both indicate that density, pressure, and temperature profiles follow to poloidal
magnetic field profile. An example is TFTR current rampdown experiments. Therefore it is suggested to change magnetic geometry between core and boundary by toroidal conductors and/or plasma
current. As a result density and temperature gradients will become steeper, and stored energy will be higher with low boundary plasma parameters. Suggested new mode of confinement may essentially simplify achieving of ignition. Stellarator applications will be discussed. 
Thursday, March 31, 10:45 am
John A. Krommes, PPPL,

Thursday, April 7, 10:45am Speaker: Igor Kaganovich, PPPL Title: Dynamics of Ion Beam Interaction with Background Plasma Abstract: The present concept for heavy ion fusion is based on the compression of intense ion beam pulses by means of ballistic focusing. To overcome the ion beam spacecharge force, the ion beams are transported and focused in a background plasma. This should enable more than 10,000 times compression of ion beam pulse (100 times transversely, and 100 longitudinally.) Currently, 2,000 times compression has been already achieved (100 times transversely, and 20 longitudinally.) Theory and simulations of the plasma response to the propagation of an intense ion beam pulse will be reviewed. Visualization of the electron dynamics reveals the complex nature of the physical processes. Particular attention will be paid to an analysis of common misconceptions and difficulties encountered in studies of collective phenomena in ion beamplasma interactions. 
A simple method to account for drift orbit
effects when modeling radio frequency heating in tokamaks D.
Van Eester ^{ } Laboratory for Plasma Physics, Association
“EURATOM – A semianalytical
method is proposed to evaluate the dielectric response of a plasma to
electromagnetic waves in the ion cyclotron domain of frequencies accounting
for drift orbit effects. The method relies on subdividing the orbit into
elementary segments in which the integrations can be performed analytically
or by tabulation, and it hinges on the local bookkeeping of the relation
between the variables defining an orbit and those describing the magnetic
geometry. 
Monday,
April 18, 10:45 am, Display Wall Room Speaker: Michael Hesse, Goddard Space Flight Center/NASA Title: Mechanisms of electron demagnetization in collisionless magnetic reconnection Abstract: Magnetic reconnection relies on the violation of the frozen flux constraint in a localized region of space. In this region, fluid elements of all individual plasma species relinquish their ties to the magnetic field, and they exchange magnetic connections. This phenomenon occurs on characteristic scales that depend on the nature of each plasma species. In a collisionless system, these scales are determined by certain kinetic processes that permit the scattering of individual particles off magnetic flux tubes. Since electrons are the lightest of species in classical plasmas, we will focus in this presentation on the electron dynamics in the inner reconnection region. Specifically, we will investigate the mechanisms that foster electron demagnetization in antiparallel and guidefield reconnection cases. For both cases, we will present results from 2.5D and 3D kinetic simulations, as well as from analytic theory that is applied to the determination of demagnetization scale sizes. Finally, we will discuss the implications the electron results have on the dynamics of heavier species. 
Thursday,
April 28, 10:45 am, Theory Seminar Room Speaker: Harry Mynick,
PPPL Title: Tutorial on Stellerator Transport I. Abstract: An introductory presentation on stellarator neoclassical transport will be given with a discussion on the various transport mechanisms, ambipolarity constraint, ion & electron roots, etc. The talk will be light on formalism, emphasizing the basic physics. 
Thursday,
May 5, 10:45 am, Theory Seminar Room Speakers: Masaaki Yamada and Russell Kulsrud, PPPL Title: Study of TwoFluid MHD Physics of Magnetic Reconnection in Laboratory and Space Plasmas Abstract: In the past few
years, the MRX experiment has generated key data to understand the physics of
collisionless reconnection. We will highlight the
most recent findings of the MRX (Magnetic Reconnection Experiment) laboratory
experiments which address the twofluids MHD physics
of magnetic reconnection [1] and the results are compared with the recent
space observations [2]. With the recent upgrade of MRX, our experimental
operation regime has moved from the collisional to
the collisionfree regime, and twofluid effects
have become more evident. The recent development from the onefluid MHD to
the twofluid MHD formulations is presented to illuminated
the physics of the Hall MHD in a collisionfree
reconnection layer. In particular, a clear experimental verification of an
outofplane Hall quadrupole field has been made in
a Harrislike neutral sheet, with the width comparable to the ion skin depth,
during magnetic reconnection [3]. High frequency fluctuations observed in the
reconnection layer [4] also exhibit two fluid effects demonstrating different
kinematics for electrons and ions. The recently developed theory investigate
the causal relationship between the observed fast reconnection rate, magnetic
turbulence and the Hall quadrupole fields are
discussed in this talk. In collaboration
with H. Ji, S. Gerhardt, A. Kuritsyn,
Y. Ren, Y. Wang. 
Tuesday,
May 10, 2:00 pm, Theory Seminar Room Speaker: Scott Parker, Title: Gyrokinetic simulation of the collisionless and semicollisional tearing mode instability Abstract: The nonlinear
evolution of the collisionless and semicollisional tearing mode instability is studied using an
electromagnetic gyrokinetic particleincell simulation.
Driftkinetic electrons are used. Simulation results show excellent agreement
with linear eigenmode analysis. Collisionless
nonlinear saturation compares well with existing theory in terms of
saturation level and electron bounce oscillations. Electronion collisions
are included to study the semicollisional regime.
The algebraic growth stage is observed and compares favorably with theory.
Nonlinear island saturation is found to depend on collisionality.

Thursday,
May 12, 10:45 am, Theory Seminar Room Speaker: Harry Mynick,
PPPL Title: Tutorial on Stellarator Transport III Abstract: Stefan Gerhardt's talk last week on flows in stellarators introduced some of the approaches to transport optimization which are now being implemented in the present generation of stellarator experiments in the US and abroad. This 3rd and final tutorial talk on stellarator transport will address in more depth the physics underlying these and other transport optimization approaches, discussing as part of this energetic particle confinement and mitigating turbulent transport in stellarators. 
Thursday,
May 26^{, }10:45 am, Theory Seminar Room Speaker: Hong Qin,PPPL Title: A footnote on the adiabatic invariants Abstract: It turns out that the
adiabatic invariant for the timedependent oscillator equation is just an
asymptotic approximation to an exact invariant, the CourantSnyder invariant.
A thorough study of the symmetry and invariance of the related dynamics
reveals many deeper, interesting structures that have important implications.
For example, we can show that the adiabatic invariant is actually a stronger
invariant than that proved by 
Thursday,
June 9, 10:45 am, Theory Seminar Room Speaker: Shuanghui Hu, UC Irvine Title: Discrete Alfven Eigenmodes Excited by Energetic Particles in HighBeta Tokamaks Abstract: A new type of highn
discrete Alfven eigenmodes
(termed alphaTAE) is found in the highbeta second ballooningmode stable toroidal plasmas. Here, n is the toroidal
wavenumber, alpha denotes the ballooning drive due
to pressure gradient and curvature, and beta is the ratio of plasma to
magnetic pressures. Multiple branches of the alphaTAEs
are observed due to the existence of multiple alphainduced potential wells
and, correspondingly, the eigenmodes can either be
marginally stable or experience small but finite Alfvencontinuum
damping. Due to their trapped features, the alphaTAEs
exist independently of the toroidal Alfven frequency gap, in contrast to the usual TAE (toroidicityinduced Alfven eigenmode). Both the quasimarginally stable and the
finitely damped alphaTAEs can be readily
destabilized by energetic particles via waveparticle resonances. For
negative magnetic shear, the alphaTAE can extend into the smallalpha regime
and evolve into the lowbeta TAE. A twodimensional eigenmode
analysis, employing WKB approximation in the radial direction, demonstrates
that the global alphaTAE can be formed around the radial location with the
maximal alpha value. 
Thursday, June 30, 10:45
am, Theory Seminar Room Speaker: Bruce Scott, IPP,
Garching, Germany Title: Theory and
Computation in FullF Gyrokinetics The theory behind the FEFI
code is presented. The gyrokinetic model is
reviewed and then the particular version used is motivated by 
Thursday, July 28, 10:45
am, Theory Seminar Room Speaker: Matthew Hole, Title: Stepped Pressure Profile Equilibria in Cylindrical Plasmas via Partial Magnetohydrodynamic (MHD) equilibrium states in threedimensions (3D) with smooth pressure profiles have long bedeviled containment theory. Magnetic islands are formed at rational surfaces, resulting in pressure flattening. In this work, a new model is presented: the steppedpressure profile equilibrium. The system comprises multiple Taylor relaxed plasma regions, which are separated by ideal MHD barriers. Such a model is well posed mathematically, and follows rigorous existence proofs of MHD equilibria with stepped pressure in weakly toroidally asymmetric plasmas. In addition to a description of 3D equilibria, the model is also motivated by observations of internal transport barrier formation at irrational flux surfaces in magnetic confinement experiments. This formulation may provide a minimum energy explanation for the existence of ITB's. In
cylindrical geometry, where analytic progress is possible, we have
constructed equilibrium solutions, and analyzed stability by a variational formulation. We show the existence of tokamaklike equilibria, with
increasing smooth safety factor and steppedpressure profiles. Unlike reverse
field pinch q profiles, only the plasma core necessarily has reverse magnetic
shear. Recent observations of ITB formation at minima in the safety factor provide
some preliminary guidance for these calculations. 
Wednesday, August 10,
10:45 am, Theory Seminar Room Speaker: Xianzhu Tang, Title: Magnetic Relaxation in Laboratory and
Astrophysical Plasmas Magnetic
relaxation is an extreme form of selforganization by which magnetic energy
and helicity injected on small scale are
transported to and accumulated on system scale magnetic fields by small scale
plasma fluctuations. A large class of fusion concepts such as RFP, Spheromak, STPCC, and STCHI, relies on magnetic
relaxation to achieve high efficiency in comparison with the usual Tokamak and stellarator
devices. Naturally occurring plasma such as that in the giant radio lobes is
also subject to magnetic relaxation. The physical implications of Taylor's helicityconserving minimum energy state in laboratory
and radio lobe plasmas are understood in terms of two classes of resonance
phenomena, which are demonstrated using ChandrasekharKendall forcefree eigenmodes. The linear resonances are regularized by any
of plasma inertia, finite pressure, and nonuniform normalized parallel
current density. The emergence of bifurcated regularized solutions is shown,
along with their physics interpretation and significance. Finally, the
nonlinear dynamics that lead to magnetic relaxation is investigated by
initial value 3D MHD simulations. The relaxation of the driven plasma is
shown to follow a helical instability cascade. 
Friday, August 18, 10:45 am, Theory Seminar Room Speaker: Hiroshi Naitou, Yamaguchi University Title: GyroReduced MHD Simulation of Kinetic Internal Kink Modes The simulation of kinetic internal kink modes using gyroreducedMHD 