110 research outputs found
The Force Balance of Electrons During Kinetic Anti-parallel Magnetic Reconnection
Fully kinetic simulations are applied to the study of 2D anti-parallel
reconnection, elucidating the dynamics by which the electron fluid maintains
force balance within both the electron diffusion region (EDR) and the ion
diffusion region (IDR). Inside the IDR, magnetic field-aligned electron
pressure anisotropy ( develops upstream of the
EDR. Compared to previous investigations, the use of modern computer facilities
allows for simulations at the natural proton to electron mass ratio
. In this high--limit the electron dynamics changes
qualitatively, as the electron inflow to the EDR is enhanced and mainly driven
by the anisotropic pressure. Using a coordinate system with the -direction
aligned with the reconnecting magnetic field and the -direction aligned with
the central current layer, it is well-known that for the much studied 2D
laminar anti-parallel and symmetric scenario the reconnection electric field at
the -line must be balanced by the and
off-diagonal electron pressure stress
components. We find that the electron anisotropy upstream of the EDR imposes
large values of within the EDR, and along the
direction of the reconnection -line this stress cancels with the stress of a
previously determined theoretical form for . The
electron frozen-in law is instead broken by pressure tensor gradients related
to the direct heating of the electrons by the reconnection electric field. The
reconnection rate is free to adjust to the value imposed externally by the
plasma dynamics at larger scales.Comment: Submitted to Physics of Plasmas, 11 October 202
ALPS: The Arbitrary Linear Plasma Solver
The Arbitrary Linear Plasma Solver (ALPS) is a parallelised numerical code
that solves the dispersion relation in a hot (even relativistic) magnetised
plasma with an arbitrary number of particle species with arbitrary gyrotropic
equilibrium distribution functions for any direction of wave propagation with
respect to the background field. ALPS reads the background momentum
distributions as tables of values on a grid, where
and are the momentum coordinates in the directions
perpendicular and parallel to the background magnetic field, respectively. We
present the mathematical and numerical approach used by ALPS and introduce our
algorithms for the handling of poles and the analytic continuation for the
Landau contour integral. We then show test calculations of dispersion relations
for a selection of stable and unstable configurations in Maxwellian,
bi-Maxwellian, -distributed, and J\"uttner-distributed plasmas. These
tests demonstrate that ALPS derives reliable plasma dispersion relations. ALPS
will make it possible to determine the properties of waves and instabilities in
the non-equilibrium plasmas that are frequently found in space, laboratory
experiments, and numerical simulations.Comment: 26 pages, 13 figures, submitte
Laboratory Study of Collisionless Magnetic Reconnection
A concise review is given on the past two decades' results from laboratory
experiments on collisionless magnetic reconnection in direct relation with
space measurements, especially by Magnetospheric Multiscale (MMS) mission.
Highlights include spatial structures of electromagnetic fields in ion and
electron diffusion regions as a function of upstream symmetry and guide field
strength; energy conversion and partition from magnetic field to ions and
electrons including particle acceleration; electrostatic and electromagnetic
kinetic plasma waves with various wavelengths; and plasmoid-mediated multiscale
reconnection. Combined with the progress in theoretical, numerical, and
observational studies, the physics foundation of fast reconnection in
colisionless plasmas has been largely established, at least within the
parameter ranges and spatial scales that were studied. Immediate and long-term
future opportunities based on multiscale experiments and space missions
supported by exascale computation are discussed, including dissipation by
kinetic plasma waves, particle heating and acceleration, and multiscale physics
across fluid and kinetic scales.Comment: 40 pages, 15 figure
Exploiting Laboratory And Heliophysics Plasma Synergies
Recent advances in space-based heliospheric observations, laboratory experimentation, and plasma simulation codes are creating an exciting new cross-disciplinary opportunity for understanding fast energy release and transport mechanisms in heliophysics and laboratory plasma dynamics, which had not been previously accessible. This article provides an overview of some new observational, experimental, and computational assets, and discusses current and near-term activities towards exploitation of synergies involving those assets. This overview does not claim to be comprehensive, but instead covers mainly activities closely associated with the authors\u27 interests and reearch. Heliospheric observations reviewed include the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) on the National Aeronautics and Space Administration (NASA) Solar Terrestrial Relations Observatory (STEREO) mission, the first instrument to provide remote sensing imagery observations with spatial continuity extending from the Sun to the Earth, and the Extreme-ultraviolet Imaging Spectrometer (EIS) on the Japanese Hinode spacecraft that is measuring spectroscopically physical parameters of the solar atmosphere towards obtaining plasma temperatures, densities, and mass motions. The Solar Dynamics Observatory (SDO) and the upcoming Solar Orbiter with the Heliospheric Imager (SoloHI) on-board will also be discussed. Laboratory plasma experiments surveyed include the line-tied magnetic reconnection experiments at University of Wisconsin (relevant to coronal heating magnetic flux tube observations and simulations), and a dynamo facility under construction there; the Space Plasma Simulation Chamber at the Naval Research Laboratory that currently produces plasmas scalable to ionospheric and magnetospheric conditions and in the future also will be suited to study the physics of the solar corona; the Versatile Toroidal Facility at the Massachusetts Institute of Technology that provides direct experimental observation of reconnection dynamics; and the Swarthmore Spheromak Experiment, which provides well-diagnosed data on three-dimensional (3D) null-point magnetic reconnection that is also applicable to solar active regions embedded in pre-existing coronal fields. New computer capabilities highlighted include: HYPERION, a fully compressible 3D magnetohydrodynamics (MHD) code with radiation transport and thermal conduction; ORBIT-RF, a 4D Monte-Carlo code for the study of wave interactions with fast ions embedded in background MHD plasmas; the 3D implicit multi-fluid MHD spectral element code, HiFi; and, the 3D Hall MHD code VooDoo. Research synergies for these new tools are primarily in the areas of magnetic reconnection, plasma charged particle acceleration, plasma wave propagation and turbulence in a diverging magnetic field, plasma atomic processes, and magnetic dynamo behavior
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