scholarly journals Nonlinear saturation of the Weibel instability in a dense Fermi plasma

2009 ◽  
Vol 75 (2) ◽  
pp. 251-258 ◽  
Author(s):  
F. HAAS ◽  
P. K. SHUKLA ◽  
B. ELIASSON
Keyword(s):  
Growth Rate ◽  
Dispersion Relation ◽  
Magnetic Fields ◽  
Intense Laser ◽  
Linear Growth Rate ◽  
Quantum Plasma ◽  
Temperature Anisotropy ◽  
Nonlinear Saturation ◽  
Linear Dispersion ◽  
Transverse Waves

AbstractWe present an investigation for the generation of intense magnetic fields in dense plasmas with an anisotropic electron Fermi–Dirac distribution. For this purpose, we use a new linear dispersion relation for transverse waves in the Wigner–Maxwell dense quantum plasma system. Numerical analysis of the dispersion relation reveals the scaling of the growth rate as a function of the Fermi energy and the temperature anisotropy. The nonlinear saturation level of the magnetic fields is found through fully kinetic simulations, which indicates that the final amplitudes of the magnetic fields are proportional to the linear growth rate of the instability. The present results are important for understanding the origin of intense magnetic fields in dense Fermionic plasmas, such as those in the next-generation intense laser–solid density plasma experiments.

scholarly journals Weibel instability in a plasma with nonzero external magnetic field

2012 ◽  
Vol 30 (7) ◽  
pp. 1051-1054 ◽  
Author(s):  
O. A. Pokhotelov ◽  
M. A. Balikhin
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Dispersion Relation ◽  
External Magnetic Field ◽  
Linear Growth ◽  
Cyclotron Frequency ◽  
Linear Growth Rate ◽  
Temperature Anisotropy ◽  
Formal Similarity ◽  
Weibel Instability

Abstract. The theory of the Weibel instability is generalized for the case of a plasma immersed in a nonzero external magnetic field. It is shown that the presence of this external field modifies the dispersion relation for this mode which now possesses a nonzero frequency. The explicit expression for the real and imaginary parts of the frequency is then calculated. It turns out that the linear growth rate remains unchanged, whereas the frequency becomes nonzero due to the finite value of the electron cyclotron frequency. The frequency of the Weibel mode is found to be proportional to the electron temperature anisotropy. The formal similarity of the Weibel and drift-mirror instabilities is outlined.

scholarly journals Amplification of magnetic fields by polaritonic flows in quantum pair plasmas

2007 ◽  
Vol 73 (3) ◽  
pp. 289-293 ◽  
Author(s):  
N. SHUKLA ◽  
P. K. SHUKLA ◽  
G. E. MORFILL
Keyword(s):  
Dispersion Relation ◽  
Magnetic Fields ◽  
Intense Laser ◽  
Linear Dispersion ◽  
Laser Plasma Interaction ◽  
Faraday’S Law ◽  
Electron Positron ◽  
Quantum Electron ◽  
Astrophysical Objects ◽  
Micromechanical Systems

AbstractIt is shown that equilibrium polaritonic flows can amplify magnetic fields in an ultra-cold quantum electron–positron/hole (polaritons) plasma. For this purpose, a linear dispersion relation has been derived by using the quantum generalized hydrodynamic equations for the polaritons, the Maxwell equation, and Faraday's law. The dispersion relation admits purely growing instabilities, the growth rates of which are proportional to the equilibrium streaming speeds of the polaritons. Possible applications of our work to the spontaneous excitation of magnetic fields and the associated cross-field transport of the polaritons in micromechanical systems, compact dense astrophysical objects (e.g. neutron stars), and intense laser–plasma interaction experiments are mentioned.

Kinetic Alfvén waves in an inhomogeneous anisotropic magnetoplasma in the presence of an inhomogeneous electric field: particle aspect analysis

2000 ◽  
Vol 63 (4) ◽  
pp. 311-328 ◽  
Author(s):  
A. BARONIA ◽  
M. S. TIWARI
Keyword(s):  
Growth Rate ◽  
Dispersion Relation ◽  
Electric Field ◽  
Alfven Waves ◽  
Alfven Wave ◽  
Larmor Radius ◽  
Alfvén Waves ◽  
Temperature Anisotropy ◽  
Inhomogeneous Electric Field ◽  
Kinetic Alfvén Waves

Kinetic Alfvén waves in the presence of an inhomogeneous electric field applied perpendicular to the ambient magnetic field in an anisotropic, inhomogeneous magnetoplasma are investigated. The particle aspect approach is adopted to investigate the trajectories of charged particles in the electromagnetic field of a kinetic Alfvén wave. Expressions are found for the field-aligned current, the perpendicular current, the dispersion relation and the particle energies. The growth rate of the wave is obtained by an energy- conservation method. It is predicted that plasma density inhomogeneity is the main source of instability, and an enhancement of the growth rate by electric field inhomogeneity and temperature anisotropy is found. The dispersion relation and growth rate involve the finite-Larmor-radius effect, electron inertia and the temperature anisotropy of the magnetoplasma. The applicability of the investigation to the auroral acceleration region is discussed.

scholarly journals Are Numerical Simulations Reliable? Proposed Improvements and Tests

1987 ◽  
Vol 117 ◽  
pp. 279-279
Author(s):  
F. R. Bouchet
Keyword(s):  
Growth Rate ◽  
Dispersion Relation ◽  
Numerical Experiments ◽  
Linear Growth ◽  
Numerical Dispersion ◽  
Linear Growth Rate ◽  
Linear Regime ◽  
Grid Spacing ◽  
Gravitational Clustering ◽  
Theoretical Predictions

When one builds a code to simulate numerically a process, the first concern is the range of validity of the results. This can be accessed empirically, though the results can be misleading if the tests are too naive. For particle-mesh codes simulating the gravitational clustering, an analytical theory has been proposed in Bouchet et al. 1985. It yields the numerical dispersion relation of the system in the linear regime, and thus describes how the linear growth rate is affected by the discretisation. The theoretical predictions are in agreement with the results of actual numerical experiments: both show that the results of standart particle-mesh codes should not be trusted at distances smaller than 6 to 8 grid-spacing Δx (depending on the detail of the algorithm).

Stability analysis of the polytropic solar wind

2014 ◽  
Vol 92 (11) ◽  
pp. 1419-1424 ◽  
Author(s):  
P.K. Karmakar ◽  
M. Gohain ◽  
U. Deka
Keyword(s):  
Growth Rate ◽  
Solar Wind ◽  
Stability Analysis ◽  
Dispersion Relation ◽  
Dynamic Equilibrium ◽  
Nonlinear Function ◽  
Linear Growth Rate ◽  
Polytropic Index ◽  
Solar Plasma ◽  
Polytropic Model

A linear stability analysis of a simple polytropic model for the solar wind dynamics within the framework of a magnetohydrodynamic equilibrium configuration is theoretically proposed. The simplistic analysis is based on the model developed based on the data available from the Advanced Composition Explorer (ACE) spacecraft mission. A unique form of dispersion relation is derived by coupling the adiabatic and polytropic processes in the limit of ideal gas approximation for the solar wind gas in accordance with the standard Fourier technique. Applying usual variable-separation methodology on the dispersion relation, we obtain the linear growth rate of the fluctuations. It is seen that the growth rate is an explicitly nonlinear function of the variable polytropic index (α) and radial position (r) with respect to the considered center of the Sun. Numerical analyses are carried out to understand the physical insight of the growth profiles of the fluctuations. It is shown that the growth is maximized near the solar corona, where α ∼ 1, relative to that observed elsewhere in the entire solar plasma system. The source for this growth may be attributed to the free flow of energy coming from the dynamic equilibrium of the solar plasma itself. As compared with existing model predictions, our results are qualitatively capable of reproducing the average behavior of the solar wind fluctuation and stability behaviors on the astrophysical scales of space and time.

New, almost electrostatic, temperature anisotropy instability

1975 ◽  
Vol 13 (2) ◽  
pp. 377-384 ◽  
Author(s):  
Ronald W. Landau
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Dispersion Relation ◽  
Uniform Magnetic Field ◽  
Plasma Frequency ◽  
Temperature Anisotropy ◽  
Maxwellian Plasma

A new, purely growing instability has been found for a bi-Maxwellian plasma in a uniform magnetic field. Instability exists for β;11 = 4βnkT11/B2 > O.591 when Tboxhu;= 0, and ions are neglected. The growth rate is near the electron gyro frequency (or v/c the plasma frequency), and the polarization is almost electrostatic for almost perpendicular propagation. The instability is obtainable only from the complete dispersion relation.

scholarly journals Generation of magnetic fields in a positive–negative dusty plasma

2007 ◽  
Vol 73 (2) ◽  
pp. 141-144 ◽  
Author(s):  
NITIN SHUKLA ◽  
P.K. SHUKLA ◽  
C.S. LIU ◽  
G.E. MORFILL
Keyword(s):  
Dispersion Relation ◽  
Magnetic Fields ◽  
Dusty Plasma ◽  
Charged Dust ◽  
Hydrodynamic Equations ◽  
Dust Grains ◽  
Physical Explanation ◽  
Linear Dispersion ◽  
Linear Dispersion Relation ◽  
Faraday Law

Abstract.It is shown that purely growing magnetic fields in a two-component dusty plasma can e generated due to the equilibrium drift of positive and negative dust grains. For this purpose, a linear dispersion relation has been derived by using the hydrodynamic equations for the charged dust fluids, the Maxwell equation and Faraday' law. The dispersion relation admits a purely growing instability, the growth rate of which is proportional to the equilibrium streaming speeds of positive and negative dust grains. A possible physical explanation for the instability is offered. Applications of our investigation to magnetic fields in the thin Martian environments, interplanetary spaces and dense molecular clouds are mentioned.

Particle aspect analysis of drift wave in the presence of inhomogeneous magnetic field

1985 ◽  
Vol 34 (1) ◽  
pp. 163-175 ◽  
Author(s):  
M. S. Tiwari ◽  
R. P. Pandey ◽  
K. D. Misra
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Dispersion Relation ◽  
Magnetic Field Gradient ◽  
Inhomogeneous Magnetic Field ◽  
Temperature Anisotropy ◽  
Plasma Parameters ◽  
Drift Wave ◽  
Effects Of Temperature ◽  
Particle Aspect Analysis

The theory of particle aspect analysis is extended to the drift wave in the presence of an inhomogeneous magnetic field. The dispersion relation and growth rate of the wave are evaluated and discussed when the magnetic field gradient is directed opposite to the density gradient. The plasma under consideration is assumed to be anisotropic and the effects of temperature anisotropy on the dispersion characteristics and growth rate of the wave are also studied. The dispersion relation and the growth rate are evaluated for the space plasma parameters.

scholarly journals Generation of magnetic fields by the ponderomotive force of electromagnetic waves in dense plasmas

2009 ◽  
Vol 76 (1) ◽  
pp. 25-28 ◽  
Author(s):  
P. K. SHUKLA ◽  
NITIN SHUKLA ◽  
L. STENFLO
Keyword(s):  
Electromagnetic Wave ◽  
Magnetic Fields ◽  
Electromagnetic Waves ◽  
Ponderomotive Force ◽  
Intense Laser ◽  
Quantum Plasma ◽  
Dense Plasmas ◽  
Solid Density ◽  
Astrophysical Objects ◽  
Density Plasma

AbstractWe show that the non-stationary ponderomotive force of a large-amplitude electromagnetic wave in a very dense quantum plasma with streaming degenerate electrons can spontaneously create d.c. magnetic fields. The present result can account for the seed magnetic fields in compact astrophysical objects and in the next-generation intense laser–solid density plasma interaction experiments.

scholarly journals Proton-temperature-anisotropy-driven magnetic fields in plasmas with cold and relativistically hot electrons

2009 ◽  
Vol 76 (1) ◽  
pp. 1-5 ◽  
Author(s):  
NITIN SHUKLA ◽  
P. K. SHUKLA
Keyword(s):  
Free Energy ◽  
Electromagnetic Wave ◽  
Dispersion Relation ◽  
Magnetic Fields ◽  
Hot Electrons ◽  
Temperature Anisotropy ◽  
Astrophysical Plasmas ◽  
Proton Temperature ◽  
Component Plasma ◽  
Cold Electrons

AbstractWe present a dispersion relation for a plane-polarized electromagnetic wave in plasmas composed of cold electrons, relativistically hot electrons and bi-Maxwellian protons. It is shown that the free energy in proton-temperature anisotropy drives purely growing electromagnetic modes in our three-component plasma. Expressions for the growth rates and thresholds of instabilities are presented. The present results are relevant for explaining the origin of spontaneously generated magnetic fields in laboratory and astrophysical plasmas.

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