scholarly journals Toroidal magnetized plasma device with sheared magnetic field lines using an internal ring conductor

2013 ◽  
Vol 84 (1) ◽  
pp. 013504 ◽  
Author(s):  
Th. Pierre
Keyword(s):  
Magnetic Field ◽  
Magnetized Plasma ◽  
Internal Ring ◽  
Plasma Device ◽  
Field Lines

scholarly journals Effect of permanent magnets on plasma confinement and ion beam properties in a double layer helicon plasma source

2019 ◽  
Vol 85 (3) ◽  
Author(s):  
Erik Varberg ◽  
Åshild Fredriksen
Keyword(s):  
Magnetic Field ◽  
Permanent Magnets ◽  
Ion Beam ◽  
Plasma Source ◽  
Diffusion Chamber ◽  
Plasma Potential ◽  
Field Energy ◽  
Plasma Confinement ◽  
Plasma Device ◽  
Field Lines

The work described in this article was carried out to investigate how permanent magnets (PM) affect the plasma confinement and ion beam properties in an inductively coupled plasma which expands from a helicon source. The cylindrical plasma device Njord has a 13 cm long and 20 cm wide stainless steel port connecting the source chamber and the diffusion chamber. The source chamber has an axial magnetic field produced by two coils, with magnetic field lines expanding into the diffusion chamber. Simulations have shown that the field lines leaving the edge of the source hit the port wall, causing a loss of electrons in this section. In the experiments performed in this work, PMs were added around the port walls near the exit of a plasma source and the effect was investigated experimentally by means of a retarding field energy analyser probe. The plasma potential, ion density and ion beam parameters were estimated, and the results with and without the PMs were compared. The results showed that the plasma density in the centre can in some cases be doubled, and the density at the edges of the plasma increased significantly with PMs in place. Although the plasma potential was slightly affected, and the beam velocity dropped by ${\sim}$ 10 %, the ion beam flux increased by a factor of 1.5.

scholarly journals Excitation Magnetohydrodynamic Wave by Gravitational Wave Produced by Binary of Neutron Stars

2017 ◽  
Vol 45 ◽  
pp. 1760006
Author(s):  
Adam S. Gontijo ◽  
Oswaldo D. Miranda
Keyword(s):  
Magnetic Field ◽  
Neutron Stars ◽  
Gravitational Wave ◽  
Acoustic Mode ◽  
Magnetized Plasma ◽  
Uniform Field ◽  
Pressure Gradients ◽  
Magnetohydrodynamic Wave ◽  
Field Lines ◽  
The Magnetic Field

The gravitational wave, through the strongly magnetized plasma surrounding the neutron stars, in the [Formula: see text]-direction, deforms plasma particle rings in ellipses, alternating axes periodically along the direction of the magnetic field ([Formula: see text]-axis) and of the [Formula: see text]-axis. The uniform field leads to a modulation of the magnetic field, which results in magnetic pressure gradients (magneto-acoustic mode) or in the shear of the magnetic field lines (Alfvén mode). The gravitational wave drives MHD modes and transfers energy to the plasma, can become an important alternative process for the acceleration of baryons to high Lorentz factors observed in short GRBs. The total amount of energy that is transferred from the gravitational wave to the plasma is estimated ([Formula: see text]J - [Formula: see text] J), with [Formula: see text]. We compare our results with previously obtained results by other works.

Trade-off in perpendicular electric field control using negatively biased emissive end-electrodes

2022 ◽  
Author(s):  
Baptiste Trotabas ◽  
Renaud Gueroult
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Thermionic Emission ◽  
Potential Drop ◽  
Plasma Potential ◽  
Magnetized Plasma ◽  
Trade Off ◽  
Sheath Edge ◽  
Field Control ◽  
Field Lines

Abstract The benefits of thermionic emission from negatively biased electrodes for perpendicular electric field control in a magnetized plasma are examined through its combined effects on the sheath and on the plasma potential variation along magnetic field lines. By increasing the radial current flowing through the plasma thermionic emission is confirmed to improve control over the plasma potential at the sheath edge compared to the case of a cold electrode. Conversely, thermionic emission is shown to be responsible for an increase of the plasma potential drop along magnetic field lines in the quasi-neutral plasma. These results suggest that there exists a trade-off between electric field longitudinal uniformity and amplitude when using negatively biased emissive electrodes to control the perpendicular electric field in a magnetized plasma.

On the excitation of higher harmonic electrostatic dust cyclotron waves

2013 ◽  
Vol 79 (5) ◽  
pp. 721-726
Author(s):  
M. ROSENBERG
Keyword(s):  
Magnetic Field ◽  
Magnetized Plasma ◽  
Wave Number ◽  
Charged Dust ◽  
Plasma Parameters ◽  
Coulomb Collisions ◽  
Plasma Device ◽  
Higher Harmonic ◽  
Parameter Ranges ◽  
The Magnetic Field

AbstractIn a magnetized plasma containing charged dust whose motion is magnetized, one of the fundamental collective modes that could occur is the electrostatic dust cyclotron (EDC) wave with frequency near the dust cyclotron frequency. The EDC wave propagates nearly perpendicular to the magnetic field with a small parallel wave number, so that it can be driven unstable by ion flow along the magnetic field. Because unstable parallel wavelengths can be relatively large, this places constraints on the plasma device size. In this paper, we use linear kinetic theory to investigate the excitation of higher harmonic EDC waves that have wavelengths smaller than that of the fundamental mode. Collisions of charged particles with neutrals and Coulomb collisions including dust–dust collisions are taken into account. Constraints on possible parameter ranges arising from collisional effects or from requiring stability of other waves are discussed. Numerical results are presented for possible sets of laboratory dusty plasma parameters.

scholarly journals Gyrokinetic continuum simulation of turbulence in a straight open-field-line plasma

2017 ◽  
Vol 83 (3) ◽  
Author(s):  
E. L. Shi ◽  
G. W. Hammett ◽  
T. Stoltzfus-Dueck ◽  
A. Hakim
Keyword(s):  
Magnetic Field ◽  
Boundary Conditions ◽  
Field Line ◽  
Open Field ◽  
Turbulent Transport ◽  
Numerical Approach ◽  
Long Wavelength ◽  
Plasma Device ◽  
Open Field Line ◽  
Field Lines

Five-dimensional gyrokinetic continuum simulations of electrostatic plasma turbulence in a straight, open-field-line geometry have been performed using a full-$f$discontinuous-Galerkin approach implemented in the Gkeyll code. While various simplifications have been used for now, such as long-wavelength approximations in the gyrokinetic Poisson equation and the Hamiltonian, these simulations include the basic elements of a fusion-device scrape-off layer: localised sources to model plasma outflow from the core, cross-field turbulent transport, parallel flow along magnetic field lines, and parallel losses at the limiter or divertor with sheath-model boundary conditions. The set of sheath-model boundary conditions used in the model allows currents to flow through the walls. In addition to details of the numerical approach, results from numerical simulations of turbulence in the Large Plasma Device, a linear device featuring straight magnetic field lines, are presented.

scholarly journals 80 MHz Radioheliograph Evidence on Moving Type IV Bursts and Coronal Magnetic Fields

1971 ◽  
Vol 43 ◽  
pp. 616-641 ◽  
Author(s):  
S. F. Smerd ◽  
G. A. Dulk
Keyword(s):  
Magnetic Field ◽  
Synchrotron Radiation ◽  
Magnetic Fields ◽  
Magnetized Plasma ◽  
Relativistic Electrons ◽  
Radiation Mechanism ◽  
Type Iv ◽  
Coronal Magnetic Fields ◽  
Field Lines ◽  
Magnetic Arch

The characteristics of 12 moving type IV bursts observed with the 80 MHz radioheliograph at the Culgoora Observatory between February 1968 and April 1970 are summarized.Three classes of moving sources can be recognized; they are described as: (1) Expanding arch; (2) Advancing front; (3) Isolated source.The first class has been identified (Wild, 1969) with the expansion of a magnetic arch or loop; the second class is here identified with an advancing MHD disturbance which may accelerate the radiating electrons in situ when moving at greater than Alfvén speed; the third with solar ejecta in the form of magnetized plasma clouds, or plasmoids. In all cases the radiation mechanism is probably synchrotron radiation from mildly relativistic electrons; energies in the range ∼0.1 to ∼1 MeV could account for the observed strong circular polarizations.With an expanding magnetic arch, source and magnetic-field movement are inseparable; the field remains a closed loop throughout the event. The MHD front probably moves largely along and the plasmoids between the open magnetic-field lines of unipolar regions or helmet structures. In the latter case it is the internal magnetic field – possibly toroidal – of the moving plasmoid that determines the polarization of the synchrotron radiation. A preliminary comparison of moving type IV sources with Newkirk-Altschuler maps of coronal magnetic fields shows suitably located closed loops for 2 events identified as expanding magnetic arches and unipolar open field lines along the path of a moving source identified as a plasmoid.

scholarly journals Magnetic field structure of large-scale plasmoid generated by the fast reconnection mechanism in a sheared current sheet

2010 ◽  
Vol 28 (8) ◽  
pp. 1511-1521 ◽  
Author(s):  
M. Ugai
Keyword(s):  
Magnetic Field ◽  
Current Sheet ◽  
Large Scale ◽  
Field Component ◽  
Three Dimensional ◽  
Magnetized Plasma ◽  
The North ◽  
Magnetic Field Region ◽  
Field Lines ◽  
Fast Reconnection

Abstract. On the basis of the spontaneous fast reconnection model, three-dimensional magnetic field profiles associated with a large-scale plasmoid propagating along the antiparallel magnetic fields are studied in the general sheared current sheet system. The plasmoid is generated ahead of the fast reconnection jet as a result of distinct compression of the magnetized plasma. Inside the plasmoid, the sheared (east-west) field component has the peak value at the plasmoid center located at x=XC, where the north-south field component changes its sign. The plasmoid center corresponds to the so-called contact discontinuity that bounds the reconnected field lines in x<XC and the field lines without reconnection in x>XC. Hence, contray to the conventional prediction, the reconnected sheared field lines in x<XC are not spiral or helical, since they cannot be topologically connected to the field lines in x>XC. It is demonstrated that the resulting profiles of magnetic field components inside the plasmoid are, in principle, consistent with satellite observations. In the ambient magnetic field region outside the plasmoid too, the magnetic field profiles are in good agreement with the well-known observations of traveling compression regions (TCRs).

Self-organization, anomalous resistance and anomalous heating in magnetized plasmas

1998 ◽  
Vol 59 (1) ◽  
pp. 103-123 ◽  
Author(s):  
Z. YOSHIDA ◽  
N. INOUE ◽  
T. FUJITA ◽  
K. HATTORI ◽  
S. ISHIDA ◽  
...  
Keyword(s):  
Magnetic Field ◽  
The Self ◽  
Self Organization ◽  
Plasma Current ◽  
Toroidal Plasma ◽  
Plasma Device ◽  
Field Lines ◽  
Kink Instability ◽  
Fluctuation Energy ◽  
Mhd Relaxation

The nonlinear dynamics and structure of plasmas with tightly twisted magnetic field lines have been studied using a toroidal plasma device. Stepwise magnetohydrodynamic (MHD) relaxation occurs, resulting in a discontinuous change in the pitch of magnetic field lines. This discrete nature of the pitch stems from the instability of kink (torsional) modes. The MHD relaxation stabilizes kink modes by selecting (self-organizing) appropriate pitches. The self-organized state displays the characteristic of a ‘dissipative structure’ in that it is accompanied by enhanced energy dissipation; the global resistance of the plasma current is substantially enhanced. The magnetic energy, which is generated by the internal plasma current, first changes into fluctuation energy through the kink instability, and then it goes mainly to ion thermal energy through viscous dissipation of the fluctuating flow. The viscosity dissipates the fluctuation energy with conservation of helicity. The self-organization of the stabilized magnetic field is characterized by the preferential conservation of the helicity.

Stochastic magnetic field lines diffusion in a toroidal configuration (Tokamak)

2000 ◽  
Vol 12 (2) ◽  
pp. 145-153 ◽  
Author(s):  
R. Tabet ◽  
H. Imrane ◽  
D. Saifaoui ◽  
A. Dezairi ◽  
F. Miskane
Keyword(s):  
Magnetic Field ◽  
Field Lines ◽  
Stochastic Magnetic Field

Exact nonlinear wave solutions of the incompressible magnetohydrodynamic equations in a sheared magnetic field

1990 ◽  
Vol 44 (1) ◽  
pp. 25-32 ◽  
Author(s):  
Hiromitsu Hamabata
Keyword(s):  
Magnetic Field ◽  
Incompressible Fluid ◽  
Large Amplitude ◽  
Uniform Magnetic Field ◽  
Magnetohydrodynamic Equations ◽  
Wave Solutions ◽  
Field Lines ◽  
Incompressible Magnetohydrodynamic Equations ◽  
Physical Quantities ◽  
Nonlinear Wave Solutions

Exact wave solutions of the nonlinear jnagnetohydrodynamic equations for a highly conducting incompressible fluid are obtained for the cases where the physical quantities are independent of one Cartesian co-ordina.te and for where they vary three-dimensionally but both the streamlines and magnetic field lines lie in parallel planes. It is shown that there is a class of exact wave solutions with large amplitude propagating in a straight but non-uniform magnetic field with constant or non-uniform velocity.

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