Nonlinear interaction between three inertial Alfvén waves

Measurement of the electric fluctuation spectrum of magnetohydrodynamic turbulence

Magnetohydrodynamic (MHD) turbulence in the solar wind is observed to show the spectral behavior of classical Kolmogorov fluid turbulence over an inertial subrange and departures from this at short wavelengths, where energy should be dissipated. Here we present the first measurements of the electric field fluctuation spectrum over the inertial and dissipative wavenumber ranges in a $β\gtrsim 1$ plasma. The $k^{-5/3}$ inertial subrange is observed and agrees strikingly with the magnetic fluctuation spectrum; the wave phase speed in this regime is shown to be consistent with the Alfvén speed. At…

Three dimensional particle-in-cell simulation of particle acceleration by circularly polarised inertial Alfven waves in a transversely inhomogeneous plasma

The process of particle acceleration by left-hand, circularly polarised inertial Alfven waves (IAW) in a transversely inhomogeneous plasma is studied using 3D particle-in-cell simulation. A cylindrical tube with, transverse to the background magnetic field, inhomogeneity scale of the order of ion inertial length is considered on which IAWs with frequency $0.3 ω_{ci}$ are launched that are allowed to develop three wavelength. As a result time-varying parallel electric fields are generated in the density gradient regions which accelerate electrons in the parallel to magnetic field direction. Dri…

Particle acceleration by circularly and elliptically polarised dispersive Alfven waves in a transversely inhomogeneous plasma in the inertial and kinetic regimes

Dispersive Alfven waves (DAWs) offer, an alternative to magnetic reconnection, opportunity to accelerate solar flare particles. We study the effect of DAW polarisation, L-, R-, circular and elliptical, in different regimes inertial and kinetic on the efficiency of particle acceleration. We use 2.5D PIC simulations to study how particles are accelerated when DAW, triggered by a solar flare, propagates in transversely inhomogeneous plasma that mimics solar coronal loop. (i) In inertial regime, fraction of accelerated electrons (along the magnetic field), in density gradient regions is ~20% by th…

惯性范围抑制与 ponderomotive 密度空洞在等离子体尾部边界层条件下宽带次阿仑fein 涡流中

Inertial-Range Suppression and Ponderomotive Density Cavitation in Broadband Sub-Alfvénic Turbulence under Plasma Sheet Boundary Layer Conditions

研究通过数值模拟揭示了宽带次阿仑fein 涡流在等离子体尾部边界层条件下的自组织特性，发现惯性范围抑制和 ponderomotive 密度空洞现象。

Linear and nonlinear properties of Rao-dust-Alfvén waves in magnetized plasmas

The linear and nonlinear properties of the Rao-dust-magnetohydrodynamic (R-D-MHD) waves in a dusty magnetoplasma are studied. By employing the inertialess electron equation of motion, inertial ion equation of motion, Ampère's law, Faraday's law, and the continuity equation in a plasma with immobile charged dust grains, the linear and nonlinear propagation of two-dimensional R-D-MHD waves are investigated. In the linear regime, the existence of immobile dust grains produces the Rao cutoff frequency, which is proportional to the dust charge density and the ion gyrofrequency. On the other hand, t…

Remarks on nonlinear relation among phases and frequencies in modulational instabilities of parallel propagating Alfven waves

Nonlinear relations among frequencies and phases in modulational instability of circularly polarized Alfven waves are discussed, within the context of one dimensional, dissipation-less, unforced fluid system. We show that generation of phase coherence is a natural consequence of the modulational instability of Alfven waves. Furthermore, we quantitatively evaluate intensity of wave-wave interaction by using bi-coherence, and also by computing energy flow among wave modes, and demonstrate that the energy flow is directly related to the phase coherence generation.

Nonlinear interactions between kinetic Alfvén and ion-sound waves

The resonant interaction between kinetic Alfvén and ion-acoustic waves is considered using the Hall-MHD theory. The results of previous authors are generalized to cover both finite Larmor radius as well as the ideal MHD results. It is found that the three wave coupling is strongest when the wavelength is comparable to the ion-sound gyroradius. Applications of our work to weak turbulence theories as well as to the heating of the solar corona are pointed out.

实验室等离子体中强非线性阿尔芬波相互作用

Strong Nonlinear Alfvén Wave Interactions in a Laboratory Plasma

本研究通过实验室等离子体实验和三维混合模拟，揭示了强阿尔芬波非线性相互作用的机制，验证了平衡与不平衡湍流中的能量级联过程。

由惯性阿尔芬波的 ponderomotive 力诱导的旋转测度子结构

Rotation Measure Substructures Induced by the Ponderomotive Force of Inertial \alfven Waves

研究通过惯性阿尔芬波的 ponderomotive 力解释快速射电暴中短时标旋转测度变化，揭示了非线性密度扰动与局部等离子体动态的关系。

Nonlinear dynamics of small-scale Alfvén waves

We study the nonlinear evolution of very oblique small-scale Alfvén waves with $k_\perp d_i\gtrsim 1$. At these scales, the waves become significantly compressive, unlike in MHD, due to the Hall term in the equations. We demonstrate that when frequencies are small compared to the ion gyrofrequency and amplitudes small compared to unity, no new nonlinear interaction appears due to the Hall term alone at the lowest non-trivial order, even when $k_\perp d_i \sim 1$. However, at the second non-trivial order, we discover that the Hall physics leads to a slow but resonant nonlinear interaction betwe…

Nonlinear Landau resonant interaction between kinetic Alfvén waves and thermal electrons: Excitation of time domain structures

Phase space holes, double layers and other solitary electric field structures, referred to as time domain structures (TDSs), often occur around dipolarization fronts in the Earth's inner magnetosphere. They are considered to be important because of their role in the dissipation of the injection energy and their potential for significant particle scattering and acceleration. Kinetic Alfvén waves are observed to be excited during energetic particle injections, and are typically present in conjunction with TDS observations. Despite the availability of a large number of spacecraft observations, th…

Nonlinear coupling of reversed shear Alfven eigenmode and toroidal Alfven eigenmode during current ramp

Two novel nonlinear mode coupling processes for reversed shear Alfven eigenmode (RSAE) nonlinear saturation are proposed and investigated. In the first process, RSAE nonlinearly couples to a co-propagating toroidal Alfven eigenmode (TAE) with the same toroidal and poloidal mode numbers, and generates a geodesic acoustic mode (GAM). In the second process, RSAE couples to a counter-propagating TAE and generates an ion acoustic wave quasi-mode (IAW). The condition for the two processes to occur is favored during current ramp. Both processes contribute to effectively saturate the Alfvenic instabil…

Collisionless Dissipative Nonlinear Alfven Waves: Nonlinear Steepening, Compressible Turbulence, and Particle Trapping

The magnetic energy of nonlinear Alfven waves in compressible plasmas may be ponderomotively coupled only to ion-acoustic quasi-modes which modulate the wave phase velocity and cause wave-front steepening. In the collisionless plasma with $β\not=0$, the dynamics of nonlinear Alfven wave is also affected by the resonant particle-wave interactions. Upon relatively rapid evolution (compared to the particle bounce time), the quasi-stationary wave structures, identical to the so called (Alfvenic) Rotational Discontinuities, form, the emergence and dynamics of which has not been previously understoo…

Laboratory observation of a nonlinear interaction between shear Alfvén waves

An experimental investigation of nonlinear interactions between shear Alfvén waves in a laboratory plasma is presented. Two Alfvén waves, generated by a resonant cavity, are observed to beat together, driving a low frequency nonlinear psuedo-mode at the beat frequency. The psuedo-mode then scatters the Alfvén waves, generating a series of sidebands. The observed interaction is very strong, with the normalized amplitude of the driven psuedo-mode comparable to the normalized magnetic field amplitude ($δB/B$) of the interacting Alfvén waves.

Nonlinear saturation of toroidal Alfven eigenmodes via nonlinear mode couplings

Gyrokinetic theory of nonlinear mode coupling as a mechanism for toroidal Alfven eigenmode (TAE) saturation in the fusion plasma related parameter regime is presented, including 1) para- metric decay of TAE into lower kinetic TAE (LKTAE) and geodesic acoustic mode (GAM), and 2) enhanced TAE coupling to shear Alfven wave (SAW) continuum via ion induced scattering. Our theory shows that, for TAE saturation in the parameter range of practical interest, several processes with comparable scattering cross sections can be equally important.

Magnetic Energy Transfer and Distribution between Protons and Electrons for Alfvénic Waves at Kinetic Scales in Wavenumber Space

Turbulent dissipation is considered a main source of heating and acceleration in cosmological plasmas. The alternating current Joule-like term, $\langleδj \cdot δE\rangle$, is used to measure the energy transfer between electromagnetic (EM) fields and particles. Because the electric field depends on the reference frame, in which frame to calculate $\langleδj\cdot δE\rangle$ is an important issue. We compute the scale-dependent energy transfer rate spectrum in wavevector space, and investigate the electric-field fluctuations in two reference frames: $δE$ in the mean bulk flow frame and $δE'$ in…

Nonlinear Interactions in Spherically Polarized Alfvénic Turbulence

Turbulent magnetic field fluctuations observed in the solar wind often maintain a constant magnitude condition accompanied by spherically polarized velocity fluctuations; these signatures are characteristic of large-amplitude Alfvén waves. Nonlinear energy transfer in Alfvénic turbulence is typically considered in the small-amplitude limit where the constant magnitude condition may be neglected; in contrast, nonlinear energy transfer in the large-amplitude limit remains relatively unstudied. We develop a method to analyze finite-amplitude turbulence through studying fluctuations as constant ma…

大振幅小尺度阿尔文波的非线性动力学

Nonlinear dynamics of large-amplitude, small-scale Alfvén waves

该研究推导了低β下小尺度大振幅倾斜阿尔文波的一维弱非线性演化方程，分类了不同孤子形态，其结果或可解释帕克太阳探测器观测到的近日太阳风磁场转向结构。

地球磁鞘中衰减的动能阿伏伽德罗波：数值模拟与MMS观测

Damped Kinetic Alfvén Waves in Earth's Magnetosheath: Numerical Simulations and MMS Observations

本研究通过数值模拟和MMS观测，揭示了兰道阻尼在地球磁鞘中调控动能阿伏伽德罗波湍流能量耗散的作用机制。

通过高频准模产生实现的反剪切阿尔芬本征模的非线性饱和

Nonlinear saturation of reversed shear Alfven eigenmode via high-frequency quasi-mode generation

本文提出反剪切阿尔芬本征模通过非线性耦合产生高频准模并受连续谱阻尼而实现饱和的机制，并给出非线性阻尼率估计，证明其适用于反应堆参数区域。

Nonlinear excitation of acoustic modes by large amplitude Alfvén waves in a laboratory plasma

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-…

Quantum Treatment of Kinetic Alfvén Waves instability in a dusty plasma: Magnetized ions

The dispersion relation of kinetic Alfvén wave in inertial regime is studied in a three component non-degenerate streaming plasma. A lin- ear dispersion relation using fluid- Vlasov equation for quantum plasma is also derived. The quantum correction CQ raised due to the insertion of Bohm potential in Vlasov model causes the suppression in the Alfven wave frequency and the growth rates of instability. A number of analytical expressions are derived for various modes of propagation. It is also found that many system parameters, i.e, streaming velocity, dust charge, num- ber density and quantum co…

Multiscale nature of the dissipation range in gyrokinetic simulations of Alfvénic turbulence

Nonlinear energy transfer and dissipation in Alfvén wave turbulence are analyzed in the first gyrokinetic simulation spanning all scales from the tail of the MHD range to the electron gyroradius scale. For typical solar wind parameters at 1 AU, about 30% of the nonlinear energy transfer close to the electron gyroradius scale is mediated by modes in the tail of the MHD cascade. Collisional dissipation occurs across the entire kinetic range $k_\perpρ_i\gtrsim 1$. Both mechanisms thus act on multiple coupled scales, which have to be retained for a comprehensive picture of the dissipation range in…

Global linear and nonlinear gyrokinetic modelling of Alfvén eigenmodes in ITER

Linear and nonlinear modelling of Alfvénic instabilities, most notably toroidal Alfvén eigenmodes (TAEs), obtained by using the global nonlinear electromagnetic gyrokinetic model of the code ORB5 are presented for the 15 MA scenario of the ITER tokamak. Linear simulations show that elliptic Alfvén eigenmodes and odd-parity TAEs are only weakly damped but not excited by alpha particles, whose drive favours even-parity TAEs. Low mode number TAEs are found to be global, requiring global treatment. Nonlinearly, even with double the nominal EP density, single mode simulations lead to saturation wit…

Magnetic field spectral evolution in the inner heliosphere

Parker Solar Probe and Solar Orbiter data are used to investigate the radial evolution of magnetic turbulence between $0.06 ~ \lesssim R ~\lesssim 1$ au. The spectrum is studied as a function of scale, normalized to the ion inertial scale $d_{i}$. In the vicinity of the Sun, the inertial range is limited to a narrow range of scales and exhibits a power-law exponent of, $α_{B} = -3/2$, independent of plasma parameters. The inertial range grows with distance, progressively extending to larger spatial scales, while steepening towards a $α_{B} =-5/3$ scaling. It is observed that spectra for interv…

Nonlinear interaction between three kinetic Alfvén waves

Using Hall-MHD theory, we focus on the resonant interaction between three kinetic Alfvén waves. We thus derive three coupled equations which govern this process. It turns out that these equations contain the same coupling coefficient, directly showing that they satisfy the Manley-Rowe relations. The coupling coefficient can be written in a comparatively very simple form, that has not been deduced before. The decay rate, when a pump kinetic Alfvén wave decays into two similar Alfvén waves, is therefore easily estimated for plasmas of astrophysical interest.

Asymptotic Theory of Particle Trapping in Coherent Nonlinear Alfven Waves

A fully nonlinear, time-asymptotic theory of resonant particle trapping in large-amplitude quasi-parallel Alfven waves is presented. The effect of trapped particles on the nonlinear dynamics of quasi-stationary Alfvenic discontinuities and coherent Alfven waves is highly non-trivial and forces to a significant departure of the theory from the conventional DNLS and KNLS equation models. The virial theorem is used to determine the time-asymptotic distribution function.

Some unexplored features of the nonlinear compressive magnetoacoustic Alfvenic waves

The theory of nonlinear magnetoacoustic wave in the past has strictly been focused on purely compressive features of the mode. We show that a complete set of nonlinear equations necessarily includes both compressional and shear components of the magnetic field. These two turn out to be described by exactly the same nonlinear equations, which make the use of such a complete full set of equations far less complicated than expected. Present results should considerably enrich the theory of these waves by opening up new frontiers of investigation and providing some completely new types of nonlinear…

日冕加热：动理学与惯性阿尔芬波在加热及带电粒子加速中的作用

Solar Coronal Heating: Role of Kinetic and Inertial Alfvén Waves in Heating and Charged Particle Acceleration

本文利用广义Vlasov-Maxwell动理学框架研究动理学与惯性阿尔芬波对日冕加热和粒子加速的贡献，揭示坡印廷通量、电势及共振速度随温度比和电子惯性长度的变化规律，并量化了两种波通过磁通环管输运的功率。

Nonlinear energy transfer and current sheet development in localized Alfven wavepacket collisions in the strong turbulence limit

In space and astrophysical plasmas, turbulence is responsible for transferring energy from large scales driven by violent events or instabilities, to smaller scales where turbulent energy is ultimately converted into plasma heat by dissipative mechanisms. The nonlinear interaction between counterpropagating Alfven waves, denoted Alfven wave collisions, drives this turbulent energy cascade, as recognized by early work with incompressible magnetohydrodynamic (MHD) equations. Recent work employing analytical calculations and nonlinear gyrokinetic simulations of Alfven wave collisions in an ideali…

Nonlinear evolution of short-wavelength torsional Alfven waves

We analyse nonlinear evolution of torsional Alfvén waves in a straight magnetic flux tube filled in with a low-$β$ plasma, and surrounded with a plasma of lower density. Such magnetic tubes model, in particular, a segment of a coronal loop or a polar plume. The wavelength is taken comparable to the tube radius. We perform numerical simulation of the wave propagation using ideal magnetohydrodynamics. We find that a torsional wave nonlinearly induces three kinds of compressive flows: the parallel flow at the Alfvén speed, that constitutes a bulk plasma motion along the magnetic field, the tube w…

Effect of the electron redistribution on the nonlinear saturation of Alfvén eigenmodes and the excitation of zonal flows

Numerical simulations of Alfvén modes (AM) driven by energetic particles are performed with the GK global PIC code ORB5. A reversed shear equilibrium magnetic field is adopted. A simplified configuration with circular flux surfaces and large aspect ratio is considered. The nonlinear saturation of beta-induced Alfvén eigenmodes (BAE) is investigated. The roles of the wave-particle nonlinearity of the different species, i.e. thermal ions, electrons, and energetic ions are described, in particular for their role in the saturation of the BAE and the generation of zonal flows. The nonlinear redistr…

Nonlinear dynamics of beta induced Alfvén eigenmode driven by energetic particles

Nonlinear saturation of beta induced Alfvén eigenmode, driven by slowing down energetic particles via transit resonance, is investigated by the nonlinear hybrid magnetohyrodynamic gyro-kinetic code (XHMGC). Saturation is characterized by frequency chirping and symmetry breaking between co- and counter-passing particles, which can be understood as the the evidence of resonance-detuning. The scaling of the saturation amplitude with the growth rate is also demonstrated to be consistent with radial resonance detuning due to the radial non-uniformity and mode structure.

Nonlinear excitation of geodesic acoustic mode by toroidal Alfvén eigenmodes and impact on plasma performance

Spontaneous nonlinear excitation of geodesic acoustic mode (GAM) by toroidal Alfvén eigenmode (TAE) is investigated using nonlinear gyrokinetic theory. It is found that, the nonlinear decay process depends on thermal ion βvalue. Here, βis the plasma thermal to magnetic pressure ratio. In the low-βlimit, TAE decays into a GAM and a lower TAE sideband in the toroidicity induced shear Alfvén wave continuous spectrum gap; while in the high-βlimit, TAE decays into a GAM and a propagating kinetic TAE in the continuum. Both cases are investigated for the spontaneous decay conditions. The nonlinear sa…

Nonlinear Alfvén waves in extended magnetohydrodynamics

Large-amplitude Alfvén waves are observed in various systems in space and laboratories, demonstrating an interesting property that the wave shapes are stable even in the nonlinear regime. The ideal magnetohydrodynamics (MHD) model predicts that an Alfvén wave keeps an arbitrary shape constant when it propagates on a homogeneous ambient magnetic field. However, such arbitrariness is an artifact of the idealized model that omits the dispersive effects. Only special wave forms, consisting of two component sinusoidal functions, can maintain the shape; we derive fully nonlinear Alfvén waves by an e…

Nonlinear Damping and Field-aligned Flows of Propagating Shear Alfvén Waves with Braginskii Viscosity

Braginskii MHD provides a more accurate description of many plasma environments than classical MHD since it actively treats the stress tensor using a closure derived from physical principles. Stress tensor effects nonetheless remain relatively unexplored for solar MHD phenomena, especially in nonlinear regimes. This paper analytically examines nonlinear damping and longitudinal flows of propagating shear Alfvén waves. Most previous studies of MHD waves in Braginskii MHD considered the strict linear limit of vanishing wave perturbations. We show that those former linear results only apply to Al…

Nonlinear excitation of fine-radial-scale zonal structures by toroidal Alfven eigenmode

The set of equations describing nonlinear evolution of a single toroidal Alfven eigenmode are derived, including both zero frequency zonal structure (ZFZS) generation and wave-particle phase space nonlinearities. The simplified case of neglecting wave-particle phase space nonlinearity is then investigated to focus on different roles of energetic particles and bulk plasmas on ZFZS generation. It is shown that energetic particles and bulk plasma play dominant roles in ZFZS generation in different nonlinear stages, and the corresponding processes are qualitatively different. Several properties of…

等离子体非均匀性对环向阿尔芬本征模非线性衰变的影响

Effects of plasma nonuniformity on toroidal Alfvén eigenmode nonlinear decay

该研究采用非线性回旋动理学方程分析非均匀等离子体中TAE参量衰变，揭示非均匀性增强耦合并改变自发衰变判据，同时探讨其对模式饱和与高能粒子输运的意义。

On nonlinear Alfvén-cyclotron waves in multi-species plasma

Large-amplitude Alfvén waves are ubiquitous in space plasmas and a main component of magnetohydrodynamic (MHD) turbulence in the heliosphere. As pump waves they are prone to parametric instability by which they can generate cyclotron and acoustic daughter waves. Here we revisit a related process within the framework of the multi-fluid equations for a plasma consisting of many species. The nonlinear coupling of the Alfvén wave to acoustic waves is studied, and a set of compressive and coupled wave equations for the transverse magnetic field and longitudinal electric field is derived for waves p…

Spatially Localized Particle Energization by Landau Damping in Current Sheets Produced by Strong Alfven Wave Collisions

Understanding the removal of energy from turbulent fluctuations in a magnetized plasma and the consequent energization of the constituent plasma particles is a major goal of heliophysics and astrophysics. Previous work has shown that nonlinear interactions among counterpropagating Alfven waves---or Alfven wave collisions---are the fundamental building block of astrophysical plasma turbulence and naturally generate current sheets in the strongly nonlinear limit. A nonlinear gyrokinetic simulation of a strong Alfven wave collision is used to examine the damping of the electromagnetic fluctuation…

Alfven Wave Collisions, The Fundamental Building Block of Plasma Turbulence III: Theory for Experimental Design

Turbulence in space and astrophysical plasmas is governed by the nonlinear interactions between counterpropagating Alfven waves. Here we present the theoretical considerations behind the design of the first laboratory measurement of an Alfven wave collision, the fundamental interaction underlying Alfvenic turbulence. By interacting a relatively large-amplitude, low-frequency Alfven wave with a counterpropagating, smaller-amplitude, higher-frequency Alfven wave, the experiment accomplishes the secular nonlinear transfer of energy to a propagating daughter Alfven wave. The predicted properties o…

Fluid Models for Kinetic Effects on Coherent Nonlinear Alfven Waves. I. Fundamental Theory

Collisionless regime kinetic models for coherent nonlinear Alfven wave dynamics are studied using fluid moment equations with an approximate closure anzatz. Resonant particle effects are modelled by incorporating an additional term representing dissipation akin to parallel heat conduction. Unlike collisional dissipation, parallel heat conduction is presented by an integral operator. The modified derivative nonlinear Schrodinger equation thus has a spatially nonlocal nonlinear term describing the long-time evolution of the envelope of parallel-propagating Alfven waves, as well. Coefficients in …

孤立阿尔文波

Solitary Alfvén Waves

提出孤立阿尔文波作为孤立远场极限下的理想非线性阿尔文解，并构建三维数值模型Alfvénon，通过MHD模拟验证其相干有限时间传播行为。

环形 Alfvén 本征模与离子温度梯度模之间由带状结构介导的间接非线性相互作用

Indirect nonlinear interaction between toroidal Alfvén eigenmode and ion temperature gradient mode mediated by zonal structures

本文基于非线性回旋动理学理论研究TAE与ITG间的间接非线性相互作用，推导并求解非线性ITG模方程，发现TAE拍驱动的带状结构对ITG仅有微弱失稳效应，纠正了以往推测。

Effects of energetic particles on zonal flow generation by toroidal Alfven eigenmode

Generation of zonal ow (ZF) by energetic particle (EP) driven toroidal Alfven eigenmode (TAE) is investigated using nonlinear gyrokinetic theory. It is found that, nonlinear resonant EP contri- bution dominates over the usual Reynolds and Maxwell stresses due to thermal plasma nonlinear response. ZF can be forced driven in the linear growth stage of TAE, with the growth rate being twice the TAE growth rate. The ZF generation mechanism is shown to be related to polarization induced by resonant EP nonlinearity. The generated ZF has both the usual meso-scale and micro- scale radial structures. Po…

Exact nonlinear solutions for three-dimensional Alfvén-wave packets in relativistic magnetohydrodynamics

We show that large-amplitude, non-planar, Alfvén wave (AW) packets are exact nonlinear solutions of the relativistic MHD equations when the total magnetic-field strength in the local fluid rest frame ($b$) is a constant. We derive analytic expressions relating the components of the fluctuating velocity and magnetic field. We also show that these constant-$b$ AWs propagate without distortion at the relativistic Alfvén velocity and never steepen into shocks. These findings and the observed abundance of large-amplitude, constant-$b$ AWs in the solar wind suggest that such waves may be present in …

地球高β磁鞘中离子惯性尺度处动力学阿尔芬波湍流的电磁特征

Electromagnetic Signatures of Kinetic Alfvén Wave Turbulence at Ion Inertial Scales in Earth's High-$β$ Magnetosheath

利用MMS卫星爆发模式数据，通过电场磁场比、平行电场、谱断裂和磁压缩率四个判据，在β_i≈14的磁鞘中识别出动力学阿尔芬波，并明确谱断裂尺度为离子惯性长度d_i而非离子回旋半径ρ_i。

托卡马克等离子体中环向阿尔芬本征模对漂移波的非线性散射

On Nonlinear Scattering of Drift Wave by Toroidal Alfven Eigenmode in Tokamak Plasmas

本文以电子漂移波为范例，解析研究了托卡马克等离子体中其与环向阿尔芬本征模的直接波-波相互作用，发现TAE非线性散射对eDW稳定性的净效应可忽略，与反向过程存在显著差异。

低β等离子体中阿尔文波参量衰变的粒子模拟

Particle-in-cell simulations of Alfvén wave parametric decay in a low-beta plasma

本文用一维全动理学模拟研究低β等离子体中阿尔文波参量衰变，揭示质子俘获与快型可压缩前沿两种加热机制，发现质子获得约50%、电子获得约10%的泵波能量。

Dissipative Dynamics of Collisionless Nonlinear Alfven Wave Trains

The nonlinear dynamics of collisionless Alfven trains, including resonant particle effects is studied using the kinetic nonlinear Schroedinger (KNLS) equation model. Numerical solutions of the KNLS reveal the dynamics of Alfven waves to be sensitive to the sense of polarization as well as the angle of propagation with respect to the ambient magnetic field. The combined effects of both wave nonlinearity and Landau damping result in the evolutionary formation of stationaryOA S- and arc-polarized directional and rotational discontinuities. These waveforms are freqently observed in the interplanet…

Dissipation of parallel and oblique Alfvén-cyclotron waves: implications for minor ion heating in the solar wind

We perform 2.5D hybrid simulations with massless fluid electrons and kinetic particle-in-cell ions to study the temporal evolution of ion temperatures, temperature anisotropies and velocity distribution functions in relation to the dissipation and turbulent evolution of a broad-band spectrum of parallel and obliquely propagating Alfvén-cyclotron waves. The purpose of this paper is to study the relative role of parallel versus oblique Alfvén-cyclotron waves in the observed heating and acceleration of minor ions in the fast solar wind. We consider collisionless homogeneous multi-species plasma, …

Alfven Wave Collisions, The Fundamental Building Block of Plasma Turbulence I: Asymptotic Solution

The nonlinear interaction between counterpropagating Alfven waves is the physical mechanism underlying the cascade of energy to small scales in astrophysical plasma turbulence. Beginning with the equations for incompressible MHD, an asymptotic analytical solution for the nonlinear evolution of these Alfven wave collisions is derived in the weakly nonlinear limit. The resulting qualitative picture of nonlinear energy transfer due to this mechanism involves two steps: first, the primary counterpropagating Alfven waves interact to generate an inherently nonlinear, purely magnetic secondary fluctu…

论非线性扭转阿尔文波的集体性质

On collective nature of nonlinear torsional Alfvén waves

本文结合 Athena++ 数值模拟与二阶微扰理论，发现非线性扭转阿尔文波会产生径向均匀的集体密度扰动，为太阳大气观测识别提供新特征。

Nonlinear Alfvén wave dynamics at a 2D magnetic null point: ponderomotive force

Context : In the linear, β=0 MHD regime, the transient properties of MHD waves in the vicinity of 2D null points are well known. The waves are decoupled and accumulate at predictable parts of the magnetic topology: fast waves accumulate at the null point; whereas Alfvén waves cannot cross the separatricies. However, in nonlinear MHD mode conversion can occur at regions of inhomogeneous Alfvén speed, suggesting that the decoupled nature of waves may not extend to the nonlinear regime. Aims: We investigate the behaviour of low-amplitude Alfvén waves about a 2D magnetic null point in nonlinear, β…