
January 24th, Wed. 3:30PM
ERF 1207, Large Conference Room

Open

January 31st, Wed. 3:30PM
ERF 1207, Large Conference Room

Open

February 7th, Wed. 3:30PM
ERF 1207, Large Conference Room

Open

February 14th, Wed. 3:30PM
ERF 1207, Large Conference Room

Dave Gates, Thea Energy
Thea Energy: Reinventing the stellarator
Thea Energy (formerly Princeton Stellarators,
Inc.) is a new stellarator fusion company that is focused on the use
of an entirely new way of building the stellarator coil system using
only non interlocking planar coils  which we refer to as the
allplanar coil stellarator. The coil set includes hundreds of small,
individually controllable coils, allowing for an unprecedented degree
of configurability and controllability. Initial work has focused on
demonstrating viable techniques to optimize this new configuration,
both the plasma and the coil set. As an initial use case, we propose a
beamtarget deuteriumdeuterium stellarator neutron source at ~1/2 the
linear dimensions of a fusion pilot plant based on the same
concept. We present the concepts behind the allplanar coil
stellarator as well as the methods we have developed to perform the
field coil optimization. We also discuss the compatibility of the
concept with reliability, accessibility, maintenance, and
inspectability as well as the ability to incorporate a
blanket. Additionally we will present initial studies of blanket
design for the stellarator neutron source.

February 21st, Wed. 3:30PM
ERF 1207, Large Conference Room

Open

February 28th, Wed. 3:30PM
ERF 1207, Large Conference Room

Henry Freund, University of
Maryland
The State of the Art in FreeElectron Laser
Simulations
Freeelectron Lasers have come a long
way since the concept was first proposed by Hans Motz in
1950. Early FELs relied on the available accelerator/gun
technology and were largely confined to operation in the IR
and longer wavelength regimes. However, the development of
laserdriven photocathodes permitted the production of
extremely low emittance electron beams in RF linacs and has
enabled the development of xray FELs, which are now under
construction around the world. The fundamental theory
explaining the operation of FELs was quickly developed and
simulations, starting with onedimensional formulations,
were extended to include complete threedimensional
models. Two distinct simulation paths have been
followed. One integrates the full 3D Lorentz force equations
for the particles and uses a modal superposition for the
fields. Another uses a wiggleraveraged orbit analysis in
which only two equations are integrated; specifically, for
the particle phase and energy. One or twodimensional field
solvers are typically used with the wiggleraveraged
formulations. In this seminar, I will discuss the basic
physics of FELs and then go on to discuss the nonlinear
simulation codes that are in use. Examples showing the
level of agreement between the nonwiggleraveraged
formulation and experiments will be presented.

March 6th, Wed. 3:30PM
ERF 1207, Large Conference Room

Open

March 13th, Wed. 3:30PM
ERF 1207, Large Conference Room

Andy Inglis, GSFC
Quasiperiodic pulsations in solar flares
Quasiperiodic pulsations (QPPs) are a
regularly observed phenomenon during both the impulsive
and decay phases of solar flare emission. They have been
observed and studied over a wide range of wavelengths for
more than 50 years. QPPs are crucial to understand because
they are signatures of fundamental physical processes that
occur during solar flare energy release, including
magnetic reconnection, particle acceleration, and
magnetohydrodynamic (MHD) wave generation. However,
disambiguation of different explanations of QPPs remains
elusive. In this talk, we explore the history of
observations of QPPs, the different possible physical
mechanisms and how to disambiguate them, the statistical
picture of QPPs, as well as recent developments and future
needs in determining the nature of this phenomenon.

March 20th, Wed. 3:30PM
ERF 1207, Large Conference Room

UMD Spring Break

March 27th, Wed. 3:30PM
ERF 1207, Large Conference Room

Sijie Yu, NJIT
LongLasting Auroralike Radio Emission Above a
Sunspot and Implications for SolarStellar Connection
Planetary radio aurorae are typically
characterized by highly polarized, intense radio
bursts. These emissions are generally attributed to
electron cyclotron maser (ECM) emission from energetic
electrons in regions with converging magnetic fields, such
as planetary polar areas. Similar radio emissions have
been observed in magnetically active lowmass stars and
brown dwarfs, often prompting analogous
interpretations. In this talk, we detail our observations
of longlasting solar radio bursts with high brightness
temperature, wide bandwidth, and high circular
polarization fraction akin to these auroral and
exoauroral radio emissions, albeit two to three orders of
magnitude weaker than those on certain lowmass stars.
Notably, longlasting radio emissions originate above a
sunspot with a strong, converging magnetic field. Our
spatial, spectral, and temporal analysis suggest that the
morphology and frequency dispersion of the source align
with ECM emissions, likely driven by energetic electrons
from recurring nearby solar flares. These observations
provide new insights into the nature of intense solar
radio bursts and suggest a potential model for
understanding auroralike radio emissions in other flare
stars with significant starspots.

April 3rd, Wed. 3:30PM
ERF 1207, Large Conference Room

Jimmy Juno, PPPL
Novel parallelkinetic perpendicularmoment model for
magnetized plasmas
Many astrophysical plasma systems, from
pulsar magnetospheres to the solar wind, are highly
magnetized. However, the derivation of large magnetization
asymptotic models applicable to this wide variety of
plasmas is challenging. Relativistic energies, strong
flows, and temperature anisotropies complicate the
asymptotics and even if the derivation can be made
sufficiently rigorous, the subsequent equations may resist
easy discretization via standard numerical methods. I will
discuss a recent innovation which addresses these
challenges by separating the parallel and perpendicular
dynamics starting from the kinetic equation while staying
agnostic to the inclusion of effects such as relativity or
strong flows. The key component of the derivation lies in
a spectral expansion of only the perpendicular degrees of
freedom, analogous to spectral methods which have grown in
popularity in recent years for gyrokinetics, while
retaining the complete dynamics parallel to the magnetic
field. We thus leverage our intuition that a magnetized
plasma's motion is different parallel and perpendicular to
the magnetic field, while allowing for the treatment of
complex phase space dynamics parallel to the magnetic
field. This approach also naturally couples to Maxwell's
equations, allowing easy transitions across energy scales
and potentially novel hybrid approaches. A number of
benchmarks and tests will be presented to demonstrate the
power of this approach.

April 10th, Wed. 3:30PM
ERF 1207, Large Conference Room

Ian DesJardin, UMD
The critical velocity bounds of ion acoustic soliton
generation by a charged supersonic grain
Ion
acoustic solitons are solitary nonlinear waves observed in
space plasmas. They can be generated by a millimeter to
centimeter sized conducting grains moving supersonically
relative to the ion acoustic velocity through the
ionosphere. In this system, soliton generation is an
unsteady flow phenomenon, qualitatively like Von Karman
vortex shedding. However, instead of propagating in the
wake, solitons can propagate upstream. This behavior is
predicted to exist in a narrow range of Mach
numbers. However, there is tension between experiments and
theory, modeled by the forced Korteweg  de Vries equation,
as to where the critical transition Mach numbers are. In
this talk, we show the results of multifluid simulations to
understand the physics of this velocity bound. New theory is
created to explain our simulation results. We will also
demonstrate some of the higherorder nonlinearities in this
system that have until now gone unnoticed. This work has
applications to detecting space debris in low Earth orbit
via plasma soliton emission.

April 17th, Wed. 3:30PM
ERF 1207, Large Conference Room

Open

April 24th, Wed. 3:30PM
ERF 1207, Large Conference Room

Dylan Kee, GSFC
Developing Generally Applicable DataDriven and Open
Boundary Conditions for Magnetohydrodynamics Simulations
In constructing and analyzing
threedimensional, timedependent magnetohydrodynamics
simulations, it is common for the majority of the effort
to be dedicated to the physics of the simulation
interior. However, there are a variety of applications
where a careful description of the boundary conditions is
equally important. This is notably true when a substantial
fraction of the plasma, energy, and magnetic field being
modeled enter the simulation through one boundary and exit
through a different one, as is for instance the case with
simulations of the solar atmosphere. In such cases,
representing the plasma state directly depends on the way
these semipermeable simulation boundaries are
treated. Particularly, it is essential but nontrivial
that these boundary conditions be specified in a way that
is consistent with the underlying equations of
magnetohydrodynamics (MHD), which govern the simulation as
a whole.
In this seminar, I discuss socalled characteristicsbased boundary
conditions which naturally separate information entering the
simulation from information leaving the simulation, thereby rendering
the problem of appropriately specifying the numerical boundary
condition more straightforward by ensuring that the boundary is
neither under nor overspecified at all locations and
times. Specifically, I discuss a novel application of such boundary
conditions to the problem of datadriving, where the simulation
ingests a timeseries of observationally inferred plasma properties on
a 2D surface, e.g. the solar photosphere, as a direct boundary
condition to the simulation. I also discuss the application of
characteristicsbased methods to general open boundaries where there
are few if any a priori constraints.

May 1st, Wed. 3:30PM
ERF 1207, Large Conference Room

M. Hasan Barbhuiya, West
Virginia University
Higherorder nonequilibrium term (HORNET): An
effective power density quantifying evolution towards or away from
local thermodynamic equilibrium
When studying energy conversion in plasma
systems, such as space plasma, it is common to compare the power
densities of different energy conversion mechanisms. A prominent
research area focuses on quantifying energy conversion for such weakly
collisional plasmas that are routinely not in local thermodynamic
equilibrium (LTE), meaning their local phase space densities can be
arbitrarily far from a Maxwellian. We introduce the "higherorder
nonequilibrium term" (HORNET) effective power density, which
measures the time rate of change of the departure of local phase space
densities from LTE. With dimensions of power density, HORNET enables
quantitative comparisons with standard power densities, such as the
pressurestrain interaction. We compute HORNET using highresolution
particleincell simulations of two plasma phenomena that inherently
exhibit nonLTE effects, namely magnetic reconnection and decaying
kinetic turbulence in collisionless magnetized plasmas. Comparing
HORNET with pressure dilatation, PiD, and the divergence of the
vector heat flux density (that describe changes to internal energy)
reveals that HORNET can be a significant fraction of these other power
densities in reconnection and in turbulence, underscoring the
importance of capturing the nonLTE evolution in collisionless plasma
systems.

May 8th, Wed. 3:30PM
ERF 1207, Large Conference Room

Suying Jin, Princeton University


