Ferromagnetic behavior in magnetized plasmas

Nonlinear excitations of magnetosonic solitary waves and their chaotic behavior in spin-polarized degenerate quantum magnetoplasma

The quantum hydrodynamic model is used to study the nonlinear propagation of small amplitude magnetosonic solitons and their chaotic motions in quantum plasma with degenerate inertialess spin-up electrons, spin-down electrons, and classical inertial ions. Spin effects are considered via spin pressure and macroscopic spin magnetization current, whereas the exchange effects are considered via adiabatic local density approximation. By applying the reductive perturbation method, the Korteweg-de Vries type equation is derived for small amplitude magnetosonic solitary waves. We present the numerical predictions about the conservative system's total energy in spin-polarized and usual electron-ion plasma and observed low energy in spin-polarized plasma. We also observe numerically that the soliton characteristics are significantly affected by different plasma parameters such as soliton phase velocity increases by increasing quantum statistics, magnetization energy, exchange effects, and spin polarization density ratio. Moreover, it is independent of the quantum diffraction effects. We have analyzed the dynamic system numerically and found that the magnetosonic solitary wave amplitude and width are getting larger as the quantum statistics and spin magnetization energy increase, whereas their amplitude and width decrease with increasing spin concentration. The wave width increases for high values of quantum statistic and exchange effects, while their amplitude remains constant. Most importantly, in the presence of external periodic perturbations, the periodic solitonic behavior is transformed to quasiperiodic and chaotic oscillations. It is found that a weakly chaotic system is transformed to heavy chaos by a small variation in plasma parameters of the perturbed spin magnetosonic solitary waves. The work presented is related to studying collective phenomena related to magnetosonic solitary waves, vital in dense astrophysical environments such as pulsar magnetosphere and neutron stars.

Magnetosonic shock waves in magnetized quantum plasma with the evolution of spin-up and spin-down electrons

The quantum hydrodynamic model is used to study the linear and nonlinear properties of small amplitude magnetosonic shock waves in dissipative plasma with degenerate inertialess spin-up and spin-down electrons and inertial classical ions. Spin effects are considered via spin pressure and macroscopic spin magnetization current. A linear dispersion relation is derived analytically and plotted numerically for different plasma parameters such as spin density, polarization ratio, plasma beta, quantum diffraction, spin magnetization energy, and magnetic diffusivity. Employing the standard reductive perturbation technique, a Korteweg-de Vries-Burgers-type equation is derived for small amplitude waves and studied numerically. We have observed that an oscillatory and monotonic shock waves are generated depending upon the plasma configurations. The phase portraits of both oscillatory and monotonic shock waves are also presented. Interestingly, different plasma parameters are found to play a significant role in the transition of oscillatory to monotonic shock waves or vice versa. Most importantly it is found that, the magnetosonic excitations obtained with spin-up and spin-down electrons are significantly different from the usual electron ion quantum plasma. The work presented is related to magnetosonic waves in dense astrophysical environments such as a pulsar magnetosphere and neutron stars.

Hydrodynamic theory for ion structure and stopping power in quantum plasmas

We present a theory for the dynamical ion structure factor (DISF) and ion stopping power in an unmagnetized collisional quantum plasma with degenerate electron fluids and nondegenerate strongly correlated ion fluids. Our theory is based on the fluctuation dissipation theorem and the quantum plasma dielectric constant that is deduced from a linearized viscoelastic quantum hydrodynamical (LVQHD) model. The latter incorporates the essential physics of quantum forces, which are associated with the quantum statistical pressure, electron-exchange, and electron-correlation effects, the quantum electron recoil effect caused by the dispersion of overlapping electron wave functions that control the dynamics of degenerate electron fluids, and the viscoelastic properties of strongly correlated ion fluids. Both degenerate electrons and nondegenerate strongly correlated ions are coupled with each other via the space charge electric force. Thus, our LVQHD theory is valid for a collisional quantum plasma at atomic scales with a wide range of the ion coupling parameter, the plasma composition, and plasma number densities that are relevant for compressed plasmas in laboratories (inertial confinement fusion schemes) and in astrophysical environments (e.g., warm dense matter and the cores of white dwarf stars). It is found that quantum electron effects and viscoelastic properties of strongly correlated ions significantly affect the features of the DISF and the ion stopping power (ISP). Unlike previous theories, which have studied ion correlations in terms of the ion coupling parameter, by neglecting the essential physics of collective effects that are competing among each other, we have here developed a method to evaluate the dependence of the plasma static and dynamical features in terms of individual parameters, like the Wigner-Seitz radius, the ion atomic number, and the ion temperature. It is found that due to the complex nature of charge screening in quantum plasmas, the ion coupling parameter alone cannot be a good measure for determining ion correlation effects in a collisional quantum plasma, and such a characteristic of a dense quantum plasma should be evaluated against each of the plasma parameters involved. The present investigation thus provides testable predictions for the DISF and ISP and is henceforth applicable to a wide range of compressed plasma categories ranging from laboratory to astrophysical warm dense matter.

Theory for large-amplitude electrostatic ion shocks in quantum plasmas

We present a generalized nonlinear theory for large-amplitude electrostatic (ES) ion shocks in collisional quantum plasmas composed of mildly coupled degenerate electron fluid of arbitrary degeneracy and nondegenerate strongly correlated ion fluid with arbitrary atomic number. For our purposes, we use the inertialess electron momentum equation including the electrostatic force, pressure gradient, and relevant quantum forces, as well as a generalized viscoelastic ion momentum (GVIM) equation for strongly correlated nondegenerate ions. The ion continuity equation, in the quasineutral approximation, then closes our nonlinear system of equations. When the electric field force is eliminated from the GVIM equation by using the inertialess electron momentum equation, we then obtain a GVIM and ion continuity equations, which exhibit nonlinear couplings between the ion number density and the ion fluid velocity. The pair of nonlinear equations is numerically solved to study the dynamics of arbitrarily-large-amplitude planar and nonplanar ES shocks arising from a balance between harmonic generation nonlinearities and the ion fluid viscosity for a wide range of plasma mass densities and ion atomic numbers that are relevant for the cores of giant planets (viz., Jupiter) and compact stars (viz., white dwarfs). Our numerical results reveal that the ES shock density profiles strongly depend on the plasma number density and composition (the atomic-number) parameters. Furthermore, ion density perturbations propagate with Mach numbers which significantly depend on the studied plasma fractional parameters. It is concluded that the dynamics of the ES shocks in the superdense degenerate plasma is quite different in the core of a white dwarf star from that in the lower density crust region.

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.

Relativistic Klein-Gordon-Maxwell multistream model for quantum plasmas

A multistream model for spinless electrons in a relativistic quantum plasma is introduced by means of a suitable fluidlike version of the Klein-Gordon-Maxwell system. The one- and two-stream cases are treated in detail. A new linear instability condition for two-stream quantum plasmas is obtained, generalizing the previously known nonrelativistic results. In both the one- and two-stream cases, steady-state solutions reduce the model to a set of coupled nonlinear ordinary differential equations, which can be numerically solved, yielding a manifold of nonlinear periodic and soliton structures. The validity conditions for the applicability of the model are addressed.

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.

Pattern dynamics and spatiotemporal chaos in the quantum Zakharov equations

The dynamical behavior of the nonlinear interaction of quantum Langmuir waves (QLWs) and quantum ion-acoustic waves (QIAWs) is studied in the one-dimensional quantum Zakharov equations. Numerical simulations of coupled QLWs and QIAWs reveal that many coherent solitary patterns can be excited and saturated via the modulational instability of unstable harmonic modes excited by a modulation wave number of monoenergetic QLWs. The evolution of such solitary patterns may undergo the states of spatially partial coherence (SPC), coexistence of temporal chaos and spatiotemporal chaos (STC), as well as STC. The SPC state is essentially due to ion-acoustic wave emission and due to quantum diffraction, while the STC is caused by the combined effects of SPC and quantum diffraction, as well as by collisions and fusions among patterns in stochastic motion. The energy in the system is strongly redistributed, which may switch on the onset of weak turbulence in dense quantum plasmas.

Quantum plasma effects in the classical regime

For quantum effects to be significant in plasmas it is often assumed that the temperature over density ratio must be small. In this paper we challenge this assumption by considering the contribution to the dynamics from the electron spin properties. As a starting point we consider a multicomponent plasma model, where electrons with spin-up and spin-down are regarded as different fluids. By studying the propagation of Alfvén wave solitons we demonstrate that quantum effects can survive in a relatively high-temperature plasma. The consequences of our results are discussed.