Spin Quantum Plasmas Research Articles

Instability analysis of spin-electron-acoustic waves and the appearance of separated spin electron cyclotron mode in spin-polarized magnetized quantum plasma

Linear and nonlinear characteristics of electrostatic waves are studied in a magnetized plasma consisting of spin-up (n_{↑}) and spin-down (n_{↓}) state populations with uniformly distributed static ions in the background. The linear analysis shows the existence of four modes. One of these modes, termed the separated spin electron cyclotron wave, is found to be due to the separated spin populations. The Zakharov-Kuznetsov equationis derived by the reductive perturbation technique. The instability growth rate γ is obtained from the same equation. It is observed that the magnetized spin quantum plasma admits rarefactive soliton with constant amplitude but increasing width with the increasing strength of the applied magnetic field. It has also been observed that the amplitude of soliton decreases and its width increases with the increasing values of polarization ratio κ. The unstable region expands with the increase in polarization ratio and contracts with the increased plasma number density and magnetic-field strength. The (growth rate) γ of instability reduces by increasing the κ and is increasing when the density of the plasma and the strength of the magnetic field increasing. The model developed in this work finds its scope in studying degenerate electron gas and astrophysical systems such as pulsar magnetosphere and neutron stars.

Drifts effect on the ordinary plasma wave and the existence of new spin dependent electron drift in the spin quantum plasma

Using a separated spin evolution quantum hydrodynamic model, we have derived generalized formula for drift effects of electrons in the inhomogeneous and nonuniform magnetized spin quantum plasma. We report, for the first time, the appearance of new spin dependent drift along with grad-B drift and diamagnetic drift. These results can be used to study the drift effects on various waves and instabilities. To check the applicability of our results, we have derived the dispersion relation of ordinary-mode (O-mode) incorporating electron spin, gradient in density, and magnetic field. We have studied various new features due to electron spin, perpendicular spin drifts, and grad B on the propagation of O-mode. Numerical analysis is presented for the choice of laboratory plasma parameters.

Magnetorotational Instability in Quantum Dusty Plasma

Abstract Magnetorotational instability (MRI) in complex quantum plasma, which comprises electron, ion, and dust grains, is investigated. Electrons are considered to be degenerate while ions and dust grains are taken as nondegenerate. The general dispersion relation for MRI with the effect of spin magnetization is derived using local approximations. The instability criteria for spin quantum plasma are derived using low-frequency approximations. Due to the complex nature of the dispersion relation, MHD assumptions are used to define the instability criteria. The dust mass plays a significant role in both the dispersion and growth rate of the magnetorotational mode. The complex mass of dust modifies the instability criteria. Spin magnetization force arises due to electron Pauli spin matrices and has an important role in low-temperature and highly dense plasmas that are found mainly in white dwarfs, neutron stars, and in core-collapse supernovae. It is found that spin magnetization influences the criteria for instability and hence the properties of MHD waves in the degenerate plasma.

Normal modes in magnetized two-fluid spin quantum plasmas

We extend the classical two-fluid magnetohydrodynamic (MHD) formalism to include quantum effects such as electron Fermi pressure, Bohm pressure and spin couplings. At scales smaller than the electron skin-depth, the Hall effect and electron inertia must be taken into account, and can overlap with the quantum effects. We write down the full set of two-fluid quantum MHD (QMHD) and analyze the relative importance ofthese effects in the high density environments of neutron star atmospheres and white dwarf interiors, finding that for a broad range of parameters all these effects are operative. Of all spin interactions we analyze only the spin-magnetic coupling, as it is linear in $\hbar$ and consequently it is the strongest spin effect. We re-obtain the classical two-fluid MHD dispersion relations corresponding to the magnetosonic and Alfv\'en modes, modified by quantum effects. In the zero-spin case, for propagation parallel to the magnetic field, we find that the frequency of the fast mode is due to quantum effects modified by electron inertia, while the frequency of the Alfv\'en-slow sector has no quantum corrections. For perpendicular propagation, the fast-mode frequency is the same as for the parallel propagation plus a correction due only to classical two-fluid effects. When spin is considered, a whistler mode appears, which is due to two-fluid spin-magnetic interaction. There are no modifications due to spin for parallel propagation of magnetosonic and Alfv\'en waves, while for perpendicular prop agation a dispersive term due to spin arises in the two-fluid expression for the fast magnetosonic mode.

Alfvén solitary waves with effect of arbitrary temperature degeneracy in spin quantum plasma

Nonlinear Alfvén waves are studied in a fluid model for nonrelativistic, magnetized spin-1/2 quantum plasmas with an arbitrary degeneracy effect. Following a local Fermi-Dirac distribution function, a modified equation of state is utilized which is applicable to both classical and degenerate limits. Using the fluid equations for Hall magnetohydrodynamics with quantum corrections due to statistical effects, Bohm potential, spin magnetization energy, and temperature degeneracy, a set of modified Zakharov equations are derived for circularly polarized nonlinear Alfvén waves. Ions are assumed to be cold, and the spin effects of electrons are incorporated through spin force along with spin magnetization current. A linear dispersion relation for finite amplitude Alfvén waves duly modified by spin magnetization and arbitrary temperature degeneracy effects is also obtained. Employing the Sagdeev potential approach, the properties of Alfvén solitary profiles in quantum plasmas with arbitrary degeneracy effects of electrons are analyzed. The amplitude of Sagdeev potential and of the associated soliton structure for both right and left-hand circularly polarized Alfvén waves is observed to decrease with the decrease in the value of the arbitrary temperature degeneracy factor G for the case of the nearly degenerate limit. Similarly, it is found that the amplitude of Sagdeev potential and of the related solitary profile increases for both kinds of circular polarized Alfvén waves with the increasing value of G in the case of the nearly non-degenerate limit.

Non-linear Alfvén waves in spin-1/2 quantum plasma

Nonlinear circularly polarized Alfvén waves are studied in Fermionic spin-1/2 quantum plasmas. Using the basic equations for Hall magnetohydrodynamics including quantum corrections, the set of Zakharov-like equations are obtained for circularly polarized nonlinear Alfvén waves. In order to investigate the properties of the Alfvén solitary structure in the presence of spin magnetization and quantum plasma beta, the Sagdeev potential approach is employed. For the case of right-handed circularly polarized Alfvén waves, the amplitude of the Sagdeev potential and the associated solitary profile is observed to enhance with the increase of quantum plasma beta and magnetization energy due to electron spin-1/2 effects. However, it is found that the amplitude of the Sagdeev potential and the related solitary profile decrease with the increasing values of quantum plasma beta and magnetization energy for the case of left-handed circularly polarized Alfvén waves. An increase in the width of the solitary structure is also observed with the increase in the value of magnetization energy for the case of the left-handed circularly polarized wave. An investigation of the modulational instability is also inspected with the effects of spin magnetization and quantum plasma beta.

Elliptically polarized modes in relativistic magnetized spin quantum plasma

The influence of relativistic correction on the propagation properties of a high-frequency range of the elliptically polarized extraordinary electromagnetic (EP-X-EM) waves in the magnetized spin quantum plasma (MSQP) is investigated by a quantum magneto hydrodynamics model. In such a situation, the relativistic effect becomes particularly noticeable in the presence of a very strong external magnetic field B0≥BQ≡4.4138×109 T and a highly dense plasma n0≫nQ≃1032 m−3 where BQ and nQ are the quantum critical magnetic field strength and electron density, respectively. For comparing with a non-relativistic regime, a new dispersion relation that extends the classical EP-X-EM waves to the quantum relativistic context is derived. Furthermore, the cut-off and resonance frequencies of this type of waves are also obtained, allowing us to define the pass and stop bands where waves can propagate in the plasma. As a new result of our work, it is found that the relativistic effect can lead to reduction in the group velocities of these waves through a MSQP. The paper discusses a number of consequential results that are useful in understanding the propagation properties of such waves in dense astrophysical bodies as well as intense laser-solid density plasma interaction experiments.

R- and L-waves in electron–positron spin quantum plasmas

Using nonrelativistic spin quantum fluid theory, parallel propagating electromagnetic waves in electron–positron plasma immersed in a uniform external magnetic field have been investigated. With the inclusion of the spin effect of the plasma species, Faraday rotation appears, which is absent in usual electron–positron plasmas without spin effects. New resonance frequencies and extra cutoffs are observed for both right-hand and left-hand circularly polarized waves.

On the damping of right hand circularly polarized waves in spin quantum plasmas

General dispersion relation for the right hand circularly polarized waves has been derived using non-relativistic spin quantum kinetic theory. Employing the derived dispersion relation, temporal and spatial damping of the right hand circularly polarized waves are studied for both the degenerate and non-degenerate plasma regimes for two different frequency domains: (i) k∥v≫(ω+ωce),(ω+ωcg) and (ii) k∥v≪(ω+ωce),(ω+ωcg). Comparison of the cold and hot plasma regimes shows that the right hand circularly polarized wave with spin-effects exists for larger k-values as compared to the spinless case, before it damps completely. It is also found that the spin-effects can significantly influence the phase and group velocities of the whistler waves in both the degenerate and non-degenerate regimes. The results obtained are also analyzed graphically for some laboratory parameters to demonstrate the physical significance of the present work.

Quantum hydrodynamics approach to the research of quantum effects and vorticity evolution in spin quantum plasmas

In this paper we explicate a method of magneto quantum hydrodynamics (MQHD) for the study of the quantum evolution of a system of spinning fermions in an external electromagnetic field. The fundamental equations of microscopic quantum hydrodynamics (the momentum balance equation and the magnetic moment density equation) were derived from the many-particle microscopic Schroodinger equation with $Spin-Spin and Coulomb modified Hamiltonian. Using the developed approach the extended vorticity evolution equation for the quantum spinning plasma were derived. The effects of new spin forces and spin-spin interaction contributions on the motion of fermions, evolution of the magnetic moment density and vorticity generation were predicted. The influence of the intrinsic spin of electrons in the nonlinear whistler mode turbulence was investigated. This results can be used for the theoretical studies of spinning many-particle systems, especially dense quantum plasmas in compact astrophysical objects, plasmas in semiconductors and micro-mechanical systems, in quantum x-ray free-electron lasers.

Arbitrary amplitude magnetosonic solitary and shock structures in spin quantum plasma

A nonlinear analysis is carried out for the arbitrary amplitude magnetosonic solitary and shock structures in spin quantum plasmas. A quantum magnetohydrodynamic model is used to describe the magnetosonic quantum plasma with the Bohm potential and the pressure like spin force for electrons. Analytical calculations are used to simplify the basic equations, which are then studied numerically. It is shown that the magnetic diffusivity is responsible for dissipation, which causes the shock-like structures rather than the soliton structures. Additionally, wave speed, Zeeman energy, and Bohm potential are found to have significant impact on the shock wave structures.

On the kinetic Alfvén waves in nonrelativistic spin quantum plasmas

We have studied the effect of electron spin on the kinetic Alfvén waves in the presence of uniform static magnetic field in an electron–ion plasma. We deduce that the usual kinetic Alfvén waves are modified via spin quantum effects of electrons. The dimensionless parameters that determine the relative importance of the electron spin become prominent at higher densities. It is found that the kinetic Alfvén wave frequency decreases due to the electron spin contribution in the kinetic limit while in the inertial limit they are almost unaffected in a hot magnetized plasma. • Spin-modified Vlasov–Maxwell equations have been used to derive the generalized dispersion relation of kinetic Alfvén waves for spin quantum plasmas. • It is found that the spin quantum effects suppress the Alfvén wave frequency in a hot magnetized plasma. • The applicability of the present results to Inertial Confinement Fusion (ICF) as well as to astrophysical environments has been point out.

Neutron spin quantum plasmas – Ferromagnetism as a relaxed state

Abstract It is shown that a ferromagnetic “minimum energy relaxed state” is accessible to a neutron fluid. We model the neutron fluid as a spin quantum plasma where the electromagnetic interaction is trough the magnetic moment of the neutron. The neutron ferromagnetism results from the macroscopic spin alignment that occurs due to a profound interplay between the classical and spin quantum vorticities carried by the charge-less neutron fluid. The simplest manifestation of a neutron superfluidity comes about by an exact cancellation of the quantum and classical vorticities to create a helicity free system.

Spin-Gradient-Driven Light Amplification in a Quantum Plasma

It is shown that the gradient "free-energy" contained in equilibrium spin vorticity can cause electromagnetic modes, in particular the light wave, to go unstable in a spin quantum plasma of mobile electrons embedded in a neutralizing ion background. For densities characteristic of both the solid state and very high density astrophysical systems, the growth rates are sufficiently high to overcome the expected collisional damping. Preliminary results suggest a powerful spin-inhomogeneity driven mechanism for stimulating light amplification.

Generation of wakefields by whistlers in spin quantum magnetoplasmas

The excitation of electrostatic wakefields in a magnetized spin quantum plasma by the classical and the spin-induced ponderomotive force (CPF and SPF, respectively) due to whistler waves is reported. The nonlinear dynamics of the whistlers and the wakefields is shown to be governed by a coupled set of nonlinear Schrödinger and driven Boussinesq-like equations. It is found that the quantum force associated with the Bohm potential introduces two characteristic length scales, which lead to the excitation of multiple wakefields in a strongly magnetized dense plasma (with a typical magnetic field strength B0≳109 T and particle density n0≳1036 m−3), where the SPF strongly dominates over the CPF. In other regimes, namely, B0≲108 T and n0≲1035 m−3, where the SPF is comparable to the CPF, a plasma wakefield can also be excited self-consistently with one characteristic length scale. Numerical results reveal that the wakefield amplitude is enhanced by the quantum tunneling effect; however, it is lowered by the external magnetic field. Under appropriate conditions, the wakefields can maintain high coherence over multiple plasma wavelengths and thereby accelerate electrons to extremely high energies. The results could be useful for particle acceleration at short scales, i.e., at nanometer and micrometer scales, in magnetized dense plasmas where the driver is the whistler wave instead of a laser or a particle beam.

Localized whistlers in magnetized spin quantum plasmas

The nonlinear propagation of electromagnetic (EM) electron-cyclotron waves (whistlers) along an external magnetic field, and their modulation by electrostatic small but finite amplitude ion-acoustic density perturbations are investigated in a uniform quantum plasma with intrinsic spin of electrons. The effects of the quantum force associated with the Bohm potential and the combined effects of the classical as well as the spin-induced ponderomotive forces (CPF and SPF, respectively) are taken into consideration. The latter modify the local plasma density in a self-consistent manner. The coupled modes of wave propagation is shown to be governed by a modified set of nonlinear Schrödinger-Boussinesq-like equations which admit exact solutions in form of stationary localized envelopes. Numerical simulation reveals the existence of large-scale density fluctuations that are self-consistently created by the localized whistlers in a strongly magnetized high density plasma. The conditions for the modulational instability (MI) and the value of its growth rate are obtained. Possible applications of our results, e.g., in strongly magnetized dense plasmas and in the next generation laser-solid density plasma interaction experiments are discussed.

Fast and slow magnetosonic waves in two-dimensional spin-1/2 quantum plasma

Using the spin-1/2 resistive quantum magnetohydrodynamics model, linear and nonlinear relations for slow and fast magnetosonic modes are derived. Spin effects are incorporated via spin force and macroscopic spin magnetization current. The plasma resistivity is shown to play a role of dissipation in the system. With the aid of tanh method the traveling wave solution of Kadomstev–Petviashvili–Burgers is obtained. The solution shows a general shock wave profile superposed by a perturbative solitary-wave contribution. The dynamics of fast and slow magnetosonic shock and soliton, respectively, in the presence and absence of dissipation is investigated with respect to electron spin magnetization, quantum diffraction, and plasma statistic. It is found that results obtained from the spin quantum plasmas differ significantly from the nonspin quantum plasmas. The relevance of the present work to dense astrophysical plasmas such as pulsar magnetosphere is pointed out.