Excitation of ion-acoustic waves by non-linear finite-amplitude standing Alfvén waves (original) (raw)
Related papers
Nonlinear Excitation of Acoustic Modes by Large-Amplitude Alfvén Waves in a Laboratory Plasma
Physical Review Letters, 2013
The nonlinear three-wave interaction process at the heart of the parametric decay process is studied by launching counter-propagating Alfvén waves from antennas placed at either end of the Large Plasma Device (LAPD). A resonance in the beat wave response produced by the two launched Alfvén waves is observed and is identified as a damped ion acoustic mode based on the measured dispersion relation. Other properties of the interaction including the spatial profile of the beat mode and response amplitude are also consistent with theoretical predictions for a three-wave interaction driven by a non-linear pondermotive force.
Nonlinear Alfvén, magnetosonic, sound, and electron inertial waves in fluid formalism
Journal of Geophysical Research, 2005
A fluid model of nonlinear electron and ion inertial waves in anisotropic plasmas is presented. The model has been verified for plasma beta (ratio of kinetic/magnetic pressures) in a range between 0.1 and 15. It is shown that warm plasmas support four types of nonlinear waves, which correspond to four linear modes, Alfvénic, magnetosonic, sound, and electron inertial waves. Each of these nonlinear modes has slow and fast versions. Modes slower than the sound speed have left-handed polarization for the transverse magnetic field, while the faster modes have right-handed polarization. It is shown by direct integration that the exponential growth rate of nonlinear modes is balanced by the ion and electron dispersion leading to solutions in the form of trains of solitons or cnoidal waves. By using a novel technique of phase portraits, it is shown how the dispersive properties of electron and ion inertial waves change at the transition between warm and hot plasmas (b % 1) and how trains of solitons (''mirror modes'') are produced in a hot, anisotropic plasma. The applicability of the model is illustrated by showing that the electric currents carried by nonlinear waves measured on Cluster spacecraft in the magnetosheath at b % 15 are well reproduced by currents derived from the theoretical model.
Excitation and steepening of ion-acoustic waves in the ionospheric Alfvén resonator
Journal of Geophysical Research, 2010
A nonlinear two-dimensional fluid model describing excitation of the ionospheric Alfvén resonator by a shear Alfvén wave coming from the magnetosphere is developed. Initially, the plasma is in an equilibrium defined by a balance between the gravity, electric field, and pressure gradient forces. This equilibrium is perturbed when a standing Alfvén wave is excited in the resonator. The nonlinear Lorentz force of the wave creates converging and diverging plasma flows along the geomagnetic field, thus producing compressions and rarefactions in the plasma density. Simulation reveals that density perturbations evolve into ion-acoustic shock waves in a process similar to the nonlinear steepening of sound waves in neutral gases. A shock associated with compression of hydrogen ions propagates faster than a shock associated with compression of oxygen ions. One-dimensional shock-capturing Poisson simulation reveals that the shocks appear as double layers at first, but then they decay into ion-acoustic wave packets. The drop of potential across each shock is negligible at any stage of shock's development, making these shocks unfavorable for auroral electron acceleration.
Alternative ion acoustic solitary waves behaviour in presences of Landau damping
Bandyopadhyay and Das [Phys. Plasmas, 9, 465-473, 2002] have derived a nonlinear macroscopic evolution equation for ion acoustic wave in a magnetized plasma consisting of warm adiabatic ions and non-thermal electrons including the effect of Landau damping. In that paper they have also derived the corresponding nonlinear evolution equation when coefficient of the nonlinear term of the above mentioned macroscopic evolution equation vanishes, the nonlinear behaviour of the ion acoustic wave is described by a modified macroscopic evolution equation. But they have not considered the case when the coefficient is very near to zero. This is the case we consider in this paper and we derive the corresponding evolution equation including the effect of Landau damping. Finally, a solitary wave solution of this macroscopic evolution is obtained, whose amplitude is found to decay slowly with time. The corresponding nonlinear evolution equation and its solitary wave solution without including the effect of Landau damping has been subject matter of study of the paper made by Das et al. [Phys. Plasmas, 14, 092304-1-10, 2007]
Excitation of ion-acoustic perturbations by incoherent kinetic Alfvén waves in plasmas
Physics of Plasmas, 2007
The dispersion relation for ion-acoustic perturbations ͑IAPs͒ in the presence of incoherent kinetic Alfvén waves ͑KAWs͒ in plasmas is derived. The wave-kinetic-approach is used to study the nonlinear interactions between an ensemble of random phase KAWs and IAPs. It is found that incoherent KAW spectrum is unstable against IAPs. The instability growth rates for particular cases are obtained. The present instability offers the possibility of heating ions in a turbulent magnetoplasma composed of incoherent KAWs.
2013
The nonlinear three-wave interaction process at the heart of the parametric decay process is studied by launching counter-propagating Alfvén waves from antennas placed at either end of the Large Plasma Device (LAPD). A resonance in the beat wave response produced by the two launched Alfvén waves is observed and is identified as a damped ion acoustic mode based on the measured dispersion relation. Other properties of the interaction including the spatial profile of the beat mode and response amplitude are also consistent with theoretical predictions for a three-wave interaction driven by a non-linear pondermotive force.
Alfvén Waves in a Partially Ionized Two-Fluid Plasma
The Astrophysical Journal, 2013
Alfvén waves are a particular class of magnetohydrodynamic waves relevant in many astrophysical and laboratory plasmas. In partially ionized plasmas the dynamics of Alfvén waves is affected by the interaction between ionized and neutral species. Here we study Alfvén waves in a partially ionized plasma from the theoretical point of view using the two-fluid description. We consider that the plasma is composed of an ion-electron fluid and a neutral fluid, which interact by means of particle collisions. To keep our investigation as general as possible we take the neutral-ion collision frequency and the ionization degree as free parameters. First, we perform a normal mode analysis. We find the modification due to neutral-ion collisions of the wave frequencies and study the temporal and spatial attenuation of the waves. In addition, we discuss the presence of cutoff values of the wavelength that constrain the existence of oscillatory standing waves in weakly ionized plasmas. Later, we go beyond the normal mode approach and solve the initial-value problem in order to study the time-dependent evolution of the wave perturbations in the two fluids. An application to Alfvén waves in the low solar atmospheric plasma is performed and the implication of partial ionization for the energy flux is discussed.
Solitary kinetic Alfvén waves in the two-fluid model
Physics of …, 1996
Employing the two-fluid model, a generalized Sagdeev equation governing solitary kinetic Alfvén waves ͑SKAWs͒ and the criterion for the existence of SKAWs, which are valid for different ranges of plasma pressure parameter , are presented. In the limit cases of ӷm e /m i and Ӷm e /m i , the present results correspond, respectively, with conclusions obtained by Hasegawa et al. ͓Phys. Rev. Lett. 37, 690 ͑1976͔͒ and by Shukla et al. ͓J. Plasma Phys. 28, 125 ͑1982͔͒, that is, SKAWs accompanied by, respectively, hump and dip density solitons for ӷm e /m i and Ӷm e /m i . However, for the case of ϳm e /m i , the present results show that SKAWs accompanied by both hump and dip density solitons are possible, and lead to KdV solitons in the small amplitude limit. In addition, the possibility for applying these results to electromagnetic spikes observed by the Freja scientific satellite is discussed ͓detailed information about the Freja satellite experiments can be found in serial papers presented in Space Sci. Rev. 70, Nos. 3/4 ͑1994͔͒.
Physics of Plasmas, 2006
Parametric instabilities of parallel propagating, circularly polarized finite amplitude Alfvén waves in a uniform background plasma is studied, within a framework of one-dimensional Vlasov description for ions and massless electron fluid, so that kinetic perturbations in the longitudinal direction (ion Landau damping) are included. The present formulation also includes the Hall effect. The obtained results agree well with relevant analysis in the past, suggesting that kinetic effects in the longitudinal direction play essential roles in the parametric instabilities of Alfvén waves when the kinetic effects react "passively". Furthermore, existence of the kinetic parametric instabilities is confirmed for the regime with small wave number daughter waves. Growth rates of these instabilities are sensitive to ion temperature. The formulation and results demonstrated here can be applied to Alfvén waves observed in the solar wind and in the earth's foreshock region.
Nonlinear ion acoustic wave in a pair-ion plasma in a uniform weak magnetic field
Physica Scripta, 2015
The dynamics of the nonlinear ion acoustic waves are investigated in the presence of an external weak magnetic field in pair-ion plasma in which the mass (temperature) of the positive ions are smaller (larger) than that of the negative ions. The linear dispersion relation of the ion acoustic wave is found to be modified by the externally applied magnetic field. The standard perturbative approach leads to a modified form of Korteweg-de Vries equation. The analytical as well as numerical solutions reveal that the localized (solitary wave) solutions decay slowly algebraically due to the Lorentz force by radiating energy to the tails of the dispersive ion acoustic waves. The results are discussed in the context of the lower region of D-layer ionospheric plasma.