404 research outputs found
Spontaneous transition to a fast 3D turbulent reconnection regime
We show how the conversion of magnetic field energy via magnetic reconnection
can progress in a fully three-dimensional, fast, volume-filling regime. An
initial configuration representative of many laboratory, space and
astrophysical plasmas spontaneously evolves from the well-known regime of slow,
resistive reconnection to a new regime that allows to explain the rates of
energy transfer observed in jets emitted from accretion disks, in stellar/solar
flare processes as well as in laboratory plasmas. This process does not require
any pre-existing turbulence seed which often is not observed in the host
systems prior to the onset of the energy conversion. The dynamics critically
depends on the interplay of perturbations developing along the magnetic field
lines and across them, a process possible only in three-dimensions. The
simulations presented here are the first able to show this transition in a
fully three-dimensional configuration.Comment: 6 pages, 6 figure
Signatures of Secondary Collisionless Magnetic Reconnection Driven by Kink Instability of a Flux Rope
The kinetic features of secondary magnetic reconnection in a single flux rope
undergoing internal kink instability are studied by means of three-dimensional
Particle-in-Cell simulations. Several signatures of secondary magnetic
reconnection are identified in the plane perpendicular to the flux rope: a
quadrupolar electron and ion density structure and a bipolar Hall magnetic
field develop in proximity of the reconnection region. The most intense
electric fields form perpendicularly to the local magnetic field, and a
reconnection electric field is identified in the plane perpendicular to the
flux rope. An electron current develops along the reconnection line in the
opposite direction of the electron current supporting the flux rope magnetic
field structure. Along the reconnection line, several bipolar structures of the
electric field parallel to the magnetic field occur making the magnetic
reconnection region turbulent. The reported signatures of secondary magnetic
reconnection can help to localize magnetic reconnection events in space,
astrophysical and fusion plasmas
Physical origin of the power-law tailed statistical distributions
Starting from the BBGKY hierarchy, describing the kinetics of nonlinear
particle system, we obtain the relevant entropy and stationary distribution
function. Subsequently, by employing the Lorentz transformations we propose the
relativistic generalization of the exponential and logarithmic functions. The
related particle distribution and entropy represents the relativistic extension
of the classical Maxwell-Boltzmann distribution and of the Boltzmann entropy
respectively and define the statistical mechanics presented in [Phys. Rev. E
{\bf 66}, 056125 (2002)] and [Phys. Rev. E {\bf 72}, 036108 (2005). The
achievements of the present effort, support the idea that the experimentally
observed power law tailed statistical distributions in plasma physics, are
enforced by the relativistic microscopic particle dynamics.Comment: 6 pages. arXiv admin note: substantial text overlap with
arXiv:1110.3944, arXiv:1012.390
Interaction between dust grains near a conducting wall
The effect of the conducting electrode on the interaction of dust grains in a
an ion flow is discussed. It is shown that two grains levitating above the
electrode at the same height may attract one another. This results in the
instability of a dust layer in a plasma sheath.Comment: 9 pages. 3 figures. Submitted to Plasma Physics Report
A Multi Level Multi Domain Method for Particle In Cell Plasma Simulations
A novel adaptive technique for electromagnetic Particle In Cell (PIC) plasma
simulations is presented here. Two main issues are identified in designing
adaptive techniques for PIC simulation: first, the choice of the size of the
particle shape function in progressively refined grids, with the need to avoid
the exertion of self-forces on particles, and, second, the necessity to comply
with the strict stability constraints of the explicit PIC algorithm. The
adaptive implementation presented responds to these demands with the
introduction of a Multi Level Multi Domain (MLMD) system (where a cloud of
self-similar domains is fully simulated with both fields and particles) and the
use of an Implicit Moment PIC method as baseline algorithm for the adaptive
evolution. Information is exchanged between the levels with the projection of
the field information from the refined to the coarser levels and the
interpolation of the boundary conditions for the refined levels from the
coarser level fields. Particles are bound to their level of origin and are
prevented from transitioning to coarser levels, but are repopulated at the
refined grid boundaries with a splitting technique. The presented algorithm is
tested against a series of simulation challenges
Relativistic kinetics and power-law tailed distributions
The present paper is devoted to the relativistic statistical theory,
introduced in Phys. Rev. E {\bf 66} (2002) 056125 and Phys. Rev. E {\bf 72}
(2005) 036108, predicting the particle distribution function with , and . This, experimentally observed,
relativistic distribution, at low energies behaves as the exponential,
Maxwell-Boltzmann classical distribution, while at high energies presents power
law tails. Here, we obtain the evolution equation, conducting asymptotically to
the above distribution, by using a new deductive procedure, starting from the
relativistic BBGKY hierarchy and by employing the relativistic molecular chaos
hypothesis.Comment: 5 two-column page
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