F. Spineanu, M. Vlad
The space-uniform amplitude envelope of the Ion Temperature Gradient driven turbulence is unstable to small perturbations and evolves to nonuniform, soliton-like modulated profiles. The induced poloidal asymmetry of the transport fluxes can generate spontaneous poloidal spin-up of the tokamak plasma.
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The self-consistent spatiotemporal evolution of drift wave (DW) radial envelope and zonal flow (ZF) amplitude is investigated in a slab model [1]. Stationary solution of the coupled partial differential equations in a simple limit yields formation of DW-ZF soliton structures, which propagate at group velocity depending on the envelope peak amplitude. Additional interesting physics, e.g. generation, destruction, collision and reflection of solitons, as well as turbulence bursting can also be observed due to effects of linear growth/damping, dissipation, equilibrium nonuniformities and soliton d…
The basic features of nucleus-acoustic (NA) envelope bright and dark solitons, which exist in degenerate quantum plasmas, have been theoretically investigated by deriving the nonlinear Schrödinger (NLS) equation. The reductive perturbation method, which is valid for a small but finite amplitude limit, is employed. It is found that the bright envelope solitons are modulationally unstable, whereas the dark ones are stable. It is also observed that the fundamental properties (viz. Modulational instability (MI) growth rate, width and energy concentration of NA waves, etc.) of NA unstable bright en…
The generation of large-scale zonal flows by small-scale electrostatic drift waves in electron temperature gradient(ETG) driven turbulence model is considered. The generation mechanism is based on the modulational instability of a finite amplitude monochromatic drift wave. The threshold and growth rate of the instability as well as the optimal spatial scale of zonal flow are obtained.
Fast-moving electrostatic solitons in a plasma with turbulence heating
本文研究原行星盘“死区”中受湍流加热电子的等离子体，基于 Davydov 分布证明静电孤子可远超离子声速，并通过衰变与辐射促进能量平衡。
Modulational instability (MI) of ion-acoustic waves (IAWs) has been theoretically investigated in a plasma system which is composed of inertial warm adiabatic ions, isothermal positrons, and two temperature superthermal electrons. A nonlinear Schrödinger (NLS) equation is derived by using reductive perturbation method that governs the MI of the IAWs. The numerical analysis of the solution of NLS equation shows the existence of both stable (dark envelope solitons exist) and unstable (bright envelope solitons exist) regimes of IAWs. It is observed that the basic features (viz. stability of the w…
Theoretical and numerical studies are presented of the amplitude modulation of electron-acoustic waves (EAWs) propagating in space plasmas whose constituents are inertial cold electrons, Boltzmann distributed hot electrons and stationary ions. Perturbations oblique to the carrier EAW propagation direction have been considered. The stability analysis, based on a nonlinear Schroedinger equation (NLSE), reveals that the EAW may become unstable; the stability criteria depend on the angle $θ$ between the modulation and propagation directions. Different types of localized EA excitations are shown to…
A generalized plasma model having warm ions, iso-thermal electrons, super-thermal electrons and positrons is considered to theoretically investigate the modulational instability (MI) of ion-acoustic waves (IAWs). A standard nonlinear Schrödinger equation is derived by applying reductive perturbation method to study the MI of IAWs. It is observed that the MI criteria of the IAWs are significantly modified by various plasma parameters. The present results should be useful in understanding the conditions for MI of IAWs which are relevant to both space and laboratory plasma system.
Dust-acoustic (DA) waves (DAWs) and their modulational instability (MI) have been investigated theoretically in a plasma system consisting of inertial opposite polarity (positively and negatively) warm adiabatic charged dust particles as well as inertialess non-extensive $q$-distributed electrons and non-thermal ions. A nonlinear Schrödinger (NLS) equation is derived by using the reductive perturbation method. It has been observed from the analysis of NLS equaion that the modulationally stable solitary DAWs give rise to the existence of dark envelope solitons, and that the modulationally unsta…
Following the idea of three wave resonant interactions of lower hybrid waves it is shown that quantum -modified lower hybrid (QLH) wave in electron positron ion plasma with spatial dispersion can decay into another QLH wave ( where electron and positrons are activated whereas ions remain in the background) and another ultra low frequency QULH (where ions are mobile). Quantum effects like Bohm potential, exchange correlation and Fermi pressure on the lower hybrid wave significantly reshaped the dispersion properties of lower hybrid waves. Later a set of nonlinear Zakharov equations have been de…
External charge perturbation in a flowing plasma and electrostatic turbulence
本文利用一维静电 hybrid-PIC-MCC 模拟运动带电碎片在等离子体中诱发的 IICSI，揭示钉扎孤子的形成条件、速度依赖关系及 Kolmogorov 型能量级联。
The basic features of linear and nonlinear quantum electron-acoustic (QEA) waves in a degenerate quantum plasma (containing non-relativistically degenerate electrons, superthermal or $κ$-distributed electrons, and stationary ions) are theoretically investigated. The nonlinear Schödinger (NLS) equation is derived by employing thereductive perturbation method. The stationary solitonic solution of the NLS equation are obtained, and examined analytically as well as numerically to identify the basic features of the QEA envelope solitons. It has been found that the effects of the degeneracy and exch…
A four component space plasma system (consisting of immobile positive ions, inertial cold positrons as well as hot electrons and positrons following Cairns' nonthermal distribution function is considered. The nonlinear propagation of the positron-acoustic (PA) waves, in which the inertia (restoring force) is provided by the cold positron species (nonthermal pressure of both hot electron and positron species) has been theoretically investigated by deriving the nonlinear Schrödinger (NLS) equation. It is found from the numerical analysis of this NLS equation that the space plasma system under co…
We give a qualitative explanation of the analog of the Fermi-Pasta-Ulam (FPU) recurrence in a one-dimensional focusing nonlinear Schrodinger equation (NLSE). That recurrence can be considered as a result of the nonlinear development of modulation instability. All known exact localized solitons-type solutions describing propagation on the background of the modulationally unstable condensate show the recurrence to the condensate state after its interaction with solitons. The condensate state locally recovers its original form with the same amplitude but a different phase after soliton leave its …
Soliton generation and drift wave turbulence spreading via geodesic acoustic mode excitation
本研究推导环几何中漂移波与测地声模的非线性动力学两场方程，揭示线性增长与完全非线性两阶段特征，发现孤子结构增强湍流扩展并可引发芯部-边缘相互作用和非局域输运。
Kinetic effects with regard to a one dimensional Langmuir soliton-like pulse are investigated. Though thus far mainly transit-time accelerations have been investigated regarding strong Langmuir turbulence, it is found that ponderomotive reflections (generalized nonlinear Landau damping) may play important roles also. The former may diffuse fast electrons up to relativistic energies, while the latter reflects slow electrons as well as ions that have speeds comparable with the group velocity of the pulse, and tend to form flat-top electron distributions at and around the quasi-soliton.
Mean-field dynamo as a quantumlike modulational instability
本文提出平均场波动力学（MFWK）方法，将平均场发电机视为MHD湍流的调制不稳定性，无需尺度分离，并预测由湍流速度与电流相关性驱动的新发电机效应。
Velocity modulations in view of the elliptical approach at Wendelstein 7-X
本文应用椭圆方法分析W7-X和TEXTOR的密度涨落，证明其必要性，并研究速度调制与湍流衰减振荡，揭示与抗磁能量小振荡的关联。
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