372 research outputs found
Stochastic electron heating in the laser and quasi-static electric and magnetic fields
The dynamics of relativistic electrons in the intense laser radiation and
quasi-static electromagnetic fields both along and across to the laser
propagating direction are studied in the 3/2 dimensional Hamiltonian framework.
It is shown that the unperturbed oscillations of the relativistic electron in
these electric fields could exhibit a long tail of harmonics which makes an
onset of stochastic electron motion be a primary candidate for electron
heating. The Poincar\'e mappings describing the electron motions in the laser
and electric fields only are derived from which the criterions for instability
are obtained. It follows that for both transverse and longitudinal electric
fields, there exist upper limits of the stochastic electron energy depending on
the laser intensity and electric field strength. Specifically, these maximum
stochastic energies are enhanced by a strong laser intensity but weak electric
field. Such stochastic heating would be reduced by the superluminal phase
velocity in both cases. The impacts of the magnetic fields on the electron
dynamics are different for these two cases and discussed qualitatively. These
analytic results are confirmed by the numerical simulations of solving the 3/2D
Hamiltonian equations directly
Role of crystallizational differention in the origin of island-arc andesitic melts: evidence from data on melt inclusions and oxygen isotopes
Axisymmetric equilibria of a gravitating plasma with incompressible flows
It is found that the ideal magnetohydrodynamic equilibrium of an axisymmetric
gravitating magnetically confined plasma with incompressible flows is governed
by a second-order elliptic differential equation for the poloidal magnetic flux
function containing five flux functions coupled with a Poisson equation for the
gravitation potential, and an algebraic relation for the pressure. This set of
equations is amenable to analytic solutions. As an application, the
magnetic-dipole static axisymmetric equilibria with vanishing poloidal plasma
currents derived recently by Krasheninnikov, Catto, and Hazeltine [Phys. Rev.
Lett. {\bf 82}, 2689 (1999)] are extended to plasmas with finite poloidal
currents, subject to gravitating forces from a massive body (a star or black
hole) and inertial forces due to incompressible sheared flows. Explicit
solutions are obtained in two regimes: (a) in the low-energy regime
, where
, , , and are related to the thermal,
poloidal-current, flow and gravitating energies normalized to the
poloidal-magnetic-field energy, respectively, and (b) in the high-energy regime
. It turns out
that in the high-energy regime all four forces, pressure-gradient,
toroidal-magnetic-field, inertial, and gravitating contribute equally to the
formation of magnetic surfaces very extended and localized about the symmetry
plane such that the resulting equilibria resemble the accretion disks in
astrophysics.Comment: 12 pages, latex, to be published in Geophys. Astrophys. Fluid
Dynamic
Two-dimensional effects in plasma radiation fronts and radiation front jumps in tokamak divertor plasmas
Axisymmetric plasma equilibrium in gravitational and magnetic fields
Plasma equilibria in gravitational and open-ended magnetic fields are considered for the case of topologically disconnected regions of the magnetic flux surfaces where plasma occupies just one of these regions. Special dependences of the plasma temperature and density on the magnetic flux are used which allow the solution of the Grad–Shafranov equation in a separable form permitting analytic treatment. It is found that plasma pressure tends to play the dominant role in the setting the shape of magnetic field equilibrium, while a strong gravitational force localizes the plasma density to a thin disc centered at the equatorial plane
Aspherical PIC code (APIC) for modeling non-spherical dust in plasmas using shape-conforming coordinates
The 2D3V Aspherical Particle-in-Cell (APIC) code is developed for modeling of
interactions of non-spherical dust grains with plasmas. It simulates the motion
of plasma electrons and ions in a self-consistent electric field of
plasma-screened charged dust particle. Due to absorption/recombination of
plasma particles impinging on the grain surface, they transfer charge,
momentum, angular momentum, as well as kinetic and binding energy, creating
currents, forces, torques, and heat fluxes to the grain. The values of such
physical parameters determine dust behavior in plasma, including its dynamics
and ablation, and can be used in various plasma studies and applications, such
as dusty plasmas, fusion devices, laboratory experiments, and astrophysical
research. Obtaining these physical values for select non-spherical shapes of
conducting dust grains is the main goal of the APIC code simulations
- …