scholarly journals Effect of dc-magnetic field on the growth rate of Raman backscattering of X-mode laser in magnetized collisional plasma

2015 ◽  
Vol 34 (1) ◽  
pp. 80-85 ◽  
Author(s):  
Alireza Paknezhad
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Ponderomotive Force ◽  
Fluid Model ◽  
Transverse Magnetic ◽  
Wave Number ◽  
Hybrid Wave ◽  
Incident Laser ◽  
Mode Laser ◽  
Relativistic Regime

AbstractStimulated Raman backward scattering of an X-mode laser beam propagating in a homogenous plasma is studied in the presence of a transverse magnetic field. As the laser propagates in its X-mode in plasma, it decays into an upper hybrid wave and a down-shifted sideband wave. Beating the incident laser with the sideband exerts a nonlinear ponderomotive force acting on plasma electrons driving the excited upper hybrid wave. The incident wave then parametrically couples with the upper hybrid wave to drive the sideband. Using the fluid model and nonlinear current density, the nonlinear ponderomotive force is obtained to find the dispersion relation of the scattered sideband wave and the growth rate of the instability in the weakly relativistic regime. It is shown that the growth rate decreases and the cut-off points in the normalized wave number of the upper-hybrid wave become smaller by increasing the static magnetic field.

scholarly journals Magnetic field generation in a jet-sheath plasma via the kinetic Kelvin-Helmholtz instability

2013 ◽  
Vol 31 (9) ◽  
pp. 1535-1541 ◽  
Author(s):  
K.-I. Nishikawa ◽  
P. Hardee ◽  
B. Zhang ◽  
I. Duţan ◽  
M. Medvedev ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Magnetic Fields ◽  
Electric Field ◽  
Flow Direction ◽  
Transverse Magnetic ◽  
Velocity Shear ◽  
Helmholtz Instability ◽  
Magnetic Field Generation ◽  
Relativistic Jet

Abstract. We have investigated the generation of magnetic fields associated with velocity shear between an unmagnetized relativistic jet and an unmagnetized sheath plasma. We have examined the strong magnetic fields generated by kinetic shear (Kelvin–Helmholtz) instabilities. Compared to the previous studies using counter-streaming performed by Alves et al. (2012), the structure of the kinetic Kelvin–Helmholtz instability (KKHI) of our jet-sheath configuration is slightly different, even for the global evolution of the strong transverse magnetic field. In our simulations the major components of growing modes are the electric field Ez, perpendicular to the flow boundary, and the magnetic field By, transverse to the flow direction. After the By component is excited, an induced electric field Ex, parallel to the flow direction, becomes significant. However, other field components remain small. We find that the structure and growth rate of KKHI with mass ratios mi/me = 1836 and mi/me = 20 are similar. In our simulations saturation in the nonlinear stage is not as clear as in counter-streaming cases. The growth rate for a mildly-relativistic jet case (γj = 1.5) is larger than for a relativistic jet case (γj = 15).

scholarly journals Effect of a magnetic field on the growth rate of the Rayleigh–Taylor instability of a laser-accelerated thin ablative surface

2004 ◽  
Vol 22 (1) ◽  
pp. 29-33 ◽  
Author(s):  
N. RUDRAIAH ◽  
B.S. KRISHNAMURTHY ◽  
A.S. JALAJA ◽  
TARA DESAI
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Transverse Magnetic Field ◽  
Plasma Layer ◽  
Fusion Energy ◽  
Transverse Magnetic ◽  
Taylor Instability ◽  
Electrically Conducting ◽  
Rayleigh Taylor Instability ◽  
Thin Plasma

The Rayleigh–Taylor instability (RTI) of a laser-accelerated ablative surface of a thin plasma layer in an inertial fusion energy (IFE) target with incompressible electrically conducting plasma in the presence of a transverse magnetic field is investigated using linear stability analysis. A simple theory based on Stokes-lubrication approximation is proposed. It is shown that the effect of a transverse magnetic field is to reduce the growth rate of RTI considerably over the value it would have in the absence of a magnetic field. This is useful in the extraction of IFE efficiently.

Filamentation instability in a collisional magnetoplasma with thermal conduction

2009 ◽  
Vol 75 (4) ◽  
pp. 563-573 ◽  
Author(s):  
MAHENDRA SINGH SODHA ◽  
MOHAMMAD FAISAL
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Static Magnetic Field ◽  
Power Loss ◽  
Thermal Conduction ◽  
Ohmic Heating ◽  
Wave Number ◽  
Main Beam ◽  
Rate Of Growth ◽  
Filamentation Instability

AbstractThis paper presents an analysis of the spatial growth of a transverse instability, corresponding to the propagation of an electromagnetic beam, with uniform irradiance along the wavefront in a collisional plasma, along the direction of a static magnetic field; expressions have been derived for the rate of growth, the maximum value of the rate of growth and the corresponding value of the wave number of the instability. The instability arises on account of the ejection of electrons from regions where the irradiance of the perturbation is large. The energy balance of the electrons taking into account ohmic heating and the power loss of electrons on account of (i) collisions with ions and neutral species and (ii) thermal conduction has been taken into account for the evaluation of the perturbation in electron temperature, which determines the subsequent growth of the instability. Further, the relationship between the electron density and temperature, as obtained from the kinetic theory, has been used. The filamentation instability becomes enhanced with the increase of the static magnetic field for the extraordinary mode while the reverse is true for the ordinary mode. Dependence of growth rate on irradiance of the main beam, magnetic field and a parameter proportional to the ratio of power loss of electrons by conduction to that by collisions has been numerically studied and illustrated by figures. The dependence of the maximum growth rate and the corresponding optimum value of the wave number of the instability on the irradiance of the main beam has also been studied. The paper concludes with a discussion of the numerical results, so obtained.

Magnetic stabilization of transverse plasma instabilitiest

1971 ◽  
Vol 5 (3) ◽  
pp. 467-474 ◽  
Author(s):  
B. Buti ◽  
G. S. Lakhina
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Cyclotron Frequency ◽  
Plasma Frequency ◽  
Electron Plasma ◽  
Wave Number ◽  
Uniform External Magnetic Field ◽  
Magnetic Stabilization ◽  
Streaming Velocity ◽  
The Magnetic Field

Waves, propagating transverse to the direction of the streaming of a plasma in the presence of a uniform external magnetic field, are unstable if the streaming exceeds a certain minimum value. The magnetic field reduces the growth rate of this instability, and also increases the value of the minimum streaming velocity, above which the system is unstable. The thermal motions in the plasma, however, tend to stabilize the system if the magnetic field is weak (i.e. , Ω being the electron cyclotron frequency, k the characteristic wave-number, and Vt the thermal velocity); but, in case of strong magnetic field (i.e. ), they increase the growth rate, provided (ωp being the electron plasma frequency).

Alfven Wave Excitation in a Cavity with a Transverse Magnetic Field

1983 ◽  
Vol 38 (6) ◽  
pp. 616-624
Author(s):  
M. Bureš
Keyword(s):  
Magnetic Field ◽  
Transverse Magnetic ◽  
Alfven Wave ◽  
Wave Number ◽  
Mass Motion ◽  
Wave Excitation ◽  
Frequency Range ◽  
Poloidal Magnetic Field ◽  
Cavity Modes ◽  
Shear Alfven Waves

A transversely magnetized cylindrical plasma model with an internal rod conductor is used to approximate the FIVA internal ring device of Spherator type with a purely poloidal magnetic field. It is shown that an excitation asymmetry along the plasma column, i.e. with a wave number k2 ≠ 0, introduces a coupling between the magnetoacoustic and shear Alfven waves in the frequency range ω ≪ ωci. The introduction of an equilibrium mass motion along the plasma cylinder introduces a flow continuum. Simultaneously the Alfven resonance frequency becomes Doppler shifted. The experimental observations indicate that cavity modes do not build up in the FIVA device in the case of nonsymmetric excitation. If on the other hand the exciting structure becomes symmetric, i.e. with k2 = 0, the magnetoacoustic resonances become excited. The resulting Q values are rather low which indicates that the coupling to the shear wave through the Hall electric field cannot be neglected

Cylindrical plasma equilibria maintained by means of a rotating magnetic field

1982 ◽  
Vol 28 (2) ◽  
pp. 369-378 ◽  
Author(s):  
W. N. Hugrass
Keyword(s):  
Magnetic Field ◽  
Axial Magnetic Field ◽  
Fluid Model ◽  
Radial Electric Field ◽  
Azimuthal Velocity ◽  
Transverse Magnetic ◽  
Rotating Magnetic Field ◽  
Two Fluid Model ◽  
Image Position ◽  
Rotating Field

The equilibrium of a plasma cylinder confined by means of a steady axial magnetic field, Bα, and a transverse magnetic field, Bω, which rotates about the axis of the cylinder is analysed using a two-fluid model. It is shown that the electron fluid is tied to the rotating field provided that The rotating field does not impart a steady azimuthal motion to the ions provided that However, the ion fluid acquires a steady azimuthal velocity due to electron-ion collisions. A self-consistent radial electric field is produced; this field plays an important role in establishing the steady ion flow.

Longitudinal waves in a perpendicular collisionless plasma shock: I. Cold ions

1970 ◽  
Vol 4 (4) ◽  
pp. 739-751 ◽  
Author(s):  
S. Peter Gary ◽  
J. J. Sanderson
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Collisionless Plasma ◽  
Maximum Growth ◽  
Maximum Growth Rate ◽  
Wave Number ◽  
Zero Magnetic Field ◽  
Linear Dispersion ◽  
Electrostatic Waves ◽  
Cold Ions

This paper considers electrostatic waves in a Vlasov plasma of unmagnetized ions and magnetized, Maxwellian electrons. The linear dispersion relation is derived for waves in a perpendicular shock such that the most important sources of instability are the E × B and ∇B electron drifts. For the case of cold ions, propagation perpendicular to the applied magnetic field, and the E × B drift alone, a numerical analysis of frequency vs. wave-number is presented. The effects of the ∇B drift are also considered, and it is shown that the maximum growth rate can be larger than the maximum growth rate for the zero magnetic field ion acoustic instabifity under comparable conditions.

Nonlinear interaction of a Gaussian electromagnetic beam with an electrostatic lower-hybrid wave: Brillouin scattering

1981 ◽  
Vol 25 (3) ◽  
pp. 403-412
Author(s):  
M. S. Sodha ◽  
Tarsem Singh ◽  
R. P. Sharma
Keyword(s):  
Magnetic Field ◽  
Intensity Distribution ◽  
Nonlinear Interaction ◽  
Ponderomotive Force ◽  
Brillouin Scattering ◽  
Lower Hybrid ◽  
Hybrid Wave ◽  
Lower Hybrid Wave ◽  
Ion Density ◽  
Plane Transverse

In the present paper we have studied the nonlinear interaction of an electrostatic lower-hybrid wave with a high-power Gaussian EM beam, propagating perpendicular to the static magnetic field in the ordinary mode in a collisionless hot magnetoplasma. On account of the Gaussian intensity distribution of the EM beam in a plane transverse to the direction of propagation, a d.c. component of the ponderomotive force becomes finite and leads to the modification of the background electron/ion density. Thus the electrostatic lower-hybrid wave gets coupled with the pump EM wave. This coupling can lead to the focusing of the lower-hybrid wave and if appropriate conditions are satisfied leads to Brillouin scattering.

Article

1998 ◽  
Vol 76 (12) ◽  
pp. 937-947
Author(s):  
M Takashima
Keyword(s):  
Magnetic Field ◽  
Couette Flow ◽  
Transverse Magnetic Field ◽  
Wave Speed ◽  
Critical Reynolds Number ◽  
Maximum Velocity ◽  
Transverse Magnetic ◽  
Wave Number ◽  
Magnetic Prandtl Number ◽  
The Stability

The stability of combined plane Poiseuille and Couette flow of an electricallyconducting fluid under a transverse magnetic field is investigated using linear stability theory.In deriving the equations governing the stability, the so-called magnetic Stokes approximationis made using the fact that the magnetic Prandtl number Prm for most electrically conductingfluids is extremely small. The Chebyshev collocation method is adopted to obtain theeigenvalue equation, which is then solved numerically. The critical Reynolds number Rec,the critical wave number αc, and the critical wave speed cc are obtained for wide ranges ofthe Hartmann number Ha and the parameter k = U0 / (U0 + nu0), where U0 is the maximumvelocity of pure Couette flow and nu0 is the maximum velocity of pure Poiseuille flow. It isfound that a transverse magnetic field has both stabilizing and destabilizing effects on theflow depending on the value of k.PACS Nos. 47.20

scholarly journals Effect of an axial magnetic field and ion space charge on laser beat wave acceleration and surfatron acceleration of electrons

2009 ◽  
Vol 27 (3) ◽  
pp. 459-464 ◽  
Author(s):  
R. Prasad ◽  
R. Singh ◽  
V.K. Tripathi
Keyword(s):  
Magnetic Field ◽  
Space Charge ◽  
Plasma Wave ◽  
Cyclotron Resonance ◽  
Ponderomotive Force ◽  
Axial Magnetic Field ◽  
Resonance Effect ◽  
Transverse Magnetic ◽  
Interaction Length ◽  
Oscillatory Velocity

AbstractThe presence of an axial magnetic field in a laser beat wave accelerator enhances the oscillatory velocity of electrons due to cyclotron resonance effect leading to higher amplitude of the ponderomotive force driven plasma wave, and higher energy of accelerating electrons. The axial magnetic field inhibits the transverse escape of electrons and thus causes a growth of the interaction length. The surfatron acceleration of electrons also shows a similar enhancement. A surfatron transverse magnetic field deflects the electrons parallel to the phase fronts of the accelerating wave keeping them in phase with it. However, the electron continues to move away radially.

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