
February 3, Friday 2PM
ERF 1207, Large Conference Room

Prof. Troy Carter, UCLA
Electromagnetic turbulence and transport in increasedbeta LAPD plasmas

February 8, Wednesday 4PM
ERF 1207, Large Conference Room

Open

February 15, Wednesday 4PM
ERF 1207, Large Conference Room

Open

February 22, Wednesday 4PM
ERF 1207, Large Conference Room

Dr. Alfred Mallet, University of New Hampshire Intermittency and Anisotropy in
Alfvenic Turbulence
On length scales larger than the ion gyroradius, the turbulence
in a plasma with a strong mean magnetic field may be modelled
using the equations of reduced magnetohydrodynamics, which
describe the evolution of Alfvenic fluctuations propagating up
and down the magnetic field. This (strongly nonlinear) turbulence is
(i) anisotropic with respect to the direction of the local mean magnetic field  a steeper spectral index (for example) in the parallel direction
compared to the perpendicular.
(ii) "aligned"  vector fluctuations in the fields in the perpendicular plane point in the same direction to within a small angle.
(iii) highly intermittent  the shape of the probability distributions of many (but not all!) turbulent quantities depends on scale in a nontrivial
way.
I will discuss the work we have performed connecting these phenomena, and the resulting statistical model for the Alfvenic turbulence we have
developed.

March 1, Wednesday 4PM
ERF 1207, Large Conference Room

Open

March 8, Wednesday 4PM
ERF 1207, Large Conference Room

External Review

March 15, Wednesday 4PM
ERF 1207, Large Conference Room

Prof. Ben Maruca, University of Delaware Thermalization of SolarWind Ions via Coulomb
Collisions
The solar wind consists of hot, magnetized plasma that supersonically streams from the solar corona into deep space. The ions therein are rarely in
thermal equilibrium because Coulomb collisions, through which particles exchange energy, act in the solar wind on timescales comparable to those of
its expansion. Even the two most abundant ionspecies, protons (ionized hydrogen) and alphaparticles (fully ionized helium), rarely have equal
temperatures. Insitu observations from the Wind spacecraft's Faraday cups reveal that, at 1 AU from the Sun, values of the alphaproton
temperatureratio have a complex, bimodal distribution. To better understand this, a theoretical model was developed to account for collisional and
expansion effects and was then applied to the observations to backtrack them from 1 AU to the corona. Remarkably, the extrapolated alphaproton
temperatureratios show a simple, monomodal distribution. Thus, the bimodality observed in the 1AU distribution may simply result from the
incomplete thermalization of protons and alphaparticles. This result suggests that the relative heating of different ion species in the corona may
be more uniform than previously believed.

March 22, Wednesday 4PM
ERF 1207, Large Conference Room

Spring Break  No Seminar

March 29, Wednesday 4PM
ERF 1207, Large Conference Room

Eric Shi, Princeton University Gyrokinetic continuum simulations of turbulence in
openfieldline plasmas
The scrape off layer (SOL) of a tokamak is an edge region in which plasma flows freely along open magnetic field lines towards a material surface,
where plasma losses are mediated by a Debye sheath. It is important to develop numerical codes to study the SOL because an accurate prediction for the
SOL heatfluxchannel width in ITER is necessary to address major concerns regarding damage to plasmafacing components by the exhaust power. While
the use of sophisticated gyrokinetic particleincell and continuum codes for studies in the tokamak core region has become widespread, major code
extensions or new codes are required to handle the additional challenges of the edge region. In this talk, I will present results from my thesis work
on developing a gyrokinetic continuum code for the simulation of plasma turbulence in a model SOL. I will discuss details about our numerical
approach, which is based on discontinuous Galerkin methods, and gyrokinetic sheath model boundary conditions. I will show results from our simulations
of turbulence in the Large Plasma Device at UCLA, including the suppression of turbulence by applied flow shear, and results from our recent work in
modeling a NSTXlike SOL to investigate turbulent heatflux spreading.

April 5, Wednesday 4PM
ERF 1207, Large Conference Room

Dr. Colin Komar, NASA/Catholic University

April 12, Wednesday 4PM
ERF 1207, Large Conference Room

Dr. Fatima Ebrahimi, Princeton Plasma Physics Lab

April 19, Wednesday 4PM
ERF 1207, Large Conference Room

Dr. Luca Comisso, Princeton Plasma Physics Lab Plasmoid Instability in General Current
Sheets
We present the recent formulation of a general theory of the onset and development of the plasmoid instability [1]. We consider the general
problem of a reconnecting current sheet that can evolve in time, rather than assuming a fixed SweetParker current sheet. The new theoretical
framework has lead to completely new results, which have shown that previously obtained power laws are insufficient to capture the correct properties
of the plasmoid instability. The new scaling laws are shown to depend on the initial perturbation amplitude, the characteristic rate of current sheet
evolution, and the Lundquist number. The detailed dynamics of the instability is also elucidated, and shown to comprise of a long period of quiescence
followed by sudden growth over a short time scale.
[1] L. Comisso, M. Lingam, Y.M. Huang, A. Bhattacharjee, Phys. Plasmas 23, 100702 (2016)

April 26, Wednesday 4PM
ERF 1207, Large Conference Room

Dr. Leila Mays, NASA/Goddard

May 4, Thursday 4PM
ERF 1207, Large Conference Room

Prof. Tünde Fülöp, Chalmers University of Technology, Sweden

May 10, Wednesday 4PM
ERF 1207, Large Conference Room

Dr. Chris Crabtree, Naval Research Lab


