I. Y. Dodin, N. J. Fisch
Charged particles can be accelerated via surfatron mechanism along dc magnetic field by obliquely propagating electrostatic waves. In plasma, this mechanism can, in principle, produce an average parallel current, even when the wave frequency is much larger than the gyrofrequency and the wave phase velocity is much larger than particle initial velocities.
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A theoretical investigation is carried out to understand the basic features of nonlinear propagation of heavy ion-acoustic (HIA) waves subjected to an external magnetic field in an electron-positron-ion (EPI) plasma which consists of cold magnetized positively charged heavy ion fluids, and superthermal distributed electrons and positrons. In the nonlinear regime, the Korteweg-de Vries (K-dV) and modified K-dV(MK-dV) equations describing the propagation of HIA waves are derived. The latter admits a solitary wave solution with both positive and negative potentials (for K-dV equation) and only po…
Using bifurcation theory on a dynamical system simulating the interaction of a particle with an obliquely propagating wave in relativistic regimes, we demonstrate that uniform acceleration arises as a consequence of Hopf bifurcations of Landau resonant particles. The acceleration process arises as a form of surfatron established through the locking in pitch angle, gyrophase, and physical trapping along the wave-vector direction. Integrating the dynamical system for large amplitudes ($δB/B_0\sim0.1$) obliquely propagating waves, we find that electrons with initial energies in the keV range can …
Kinetic simulations and theory demonstrate that whistler waves can excite oblique, short-wavelength fluctuations through secondary drift instabilities if a population of sufficiently cold plasma is present. The excited modes lead to heating of the cold populations and damping of the primary whistler waves. The instability threshold depends on the density and temperature of the cold population and can be relatively small if the temperature of the cold population is sufficiently low. This mechanism may thus play a significant role in controlling amplitude of whistlers in the regions of the Earth…
Relativistic unmagnetized cloud-plasma interaction is analyzed by performing linear analysis and particle-in-cell simulation. This course consists of an electron-ion cloud injected into a stationary ambient plasma and has long been a favorite topic in laboratory and space plasmas. An oblique electromagnetic instability dominates the unstable spectrum. In the interaction with the generated electromagnetic fields, the cloud electrons are entirely mixed with the ambient ones and form a hot electron population. The velocity of the cloud ions, however, has not changed significantly from the initial…
Based on the magnetohydrodynamics (MHD) model, an exact arbitrary-amplitude general solution is presented for oblique propagation of solitary excitations in two- and three-component quasineutral magnetoplasmas, adopting the standard pseudopotential approach. It is revealed that the necessary matching criterion of existence of such oblique nonlinear propagations in two and three-fluid magnetoplasmas share global features. These features are examined for the cases of electron-ion and electron-positron-ion magnetoplasmas with diverse equations of state. This study also reveals that for electron-i…
The linear and nonlinear properties of large amplitude electron-acoustic waves are investigated in a magnetized plasma comprising two distinct electron populations (hot and cold) and immobile ions. The hot electrons are assumed to be in a non-Maxwellian state, characterized by an excess of superthermal particles, here modelled by a kappa-type long-tailed distribution function. Waves are assumed to propagate obliquely to the ambient magnetic field. Two types of electrostatic modes are shown to exist in the linear regime, and their properties are briefly analyzed. A nonlinear pseudopotential typ…
A two-dimensional electromagnetic particle-in-cell simulation with the realistic ion-to-electron mass ratio of 1836 is carried out to investigate the electrostatic collisionless shocks in relatively high-speed (~3000 km s^-1) plasma flows and also the influence of both electrostatic and electromagnetic instabilities, which can develop around the shocks, on the shock dynamics. It is shown that the electrostatic ion-ion instability can develop in front of the shocks, where the plasma is under counter-streaming condition, with highly oblique wave vectors as was shown previously. The electrostatic…
The destabilizing role of neutrino beams on the Trivelpiece-Gould modes is considered, assuming electrostatic perturbations in a magnetized plasma composed by electrons in a neutralizing ionic background, coupled to a neutrino species by means of an effective neutrino force arising from the electro-weak interaction. The magnetic field is found to significantly improve the linear instability growth rate, as calculated for Supernova type II environments. On the formal level, for wave vector parallel or perpendicular to the magnetic field the instability growth rate is found from the unmagnetized…
Head-on collision of laser-induced plasma wakefields with differing profiles of electrostatic potential has been recently found to be an efficient mechanism for generating high-power electromagnetic emission at the second harmonic of the plasma frequency [I.V.Timofeev et al. Phys. Plasmas 24, 103106 (2017)]. This mechanism is attractive for creating a source of tunable narrow-band coherent radiation in the terahertz frequency range. In this paper, we generalize the theory of electromagnetic emission produced by nonlinear interaction of two plasma wakes to the case of an arbitrary collision ang…
The nonlinear amplitude modulation of known electrostatic plasma modes is examined in a generic manner, by applying a collisionless fluid model. Both cold (zero-temperature) and warm fluid descriptions are discussed and the results are compared. The moderately nonlinear oscillation regime is investigated by applying a multiple scale technique. The calculation leads to a Nonlinear Schrodinger-type Equation (NLSE), which describes the evolution of the slowly varying wave amplitude in time and space. The NLSE admits localized envelope (solitary wave) solutions of bright- (pulses) or dark- (holes,…
Cyclic reformation of subcritical perpendicular fast magnetosonic shocks due to oblique Whistler waves
研究亚临界垂直快磁声激波稳定性，通过二维PIC模拟发现斜向Whistler波驱动不稳定的环状重构，而非外部扰动。
Oblique propagation of the spin-electron acoustic waves in degenerate magnetized plasmas is considered in terms of quantum kinetics with the separate spin evolution, where the spin-up electrons and the spin-down electrons are considered as two different species with different equilibrium distributions. It is considered in the electrostatic limit. Corresponding dispersion equation is derived. Analytical analysis of the dispersion equation is performed in the long-wavelength limit to find an approximate dispersion equation describing the spin-electron acoustic wave. The approximate dispersion eq…
Temporal evolution of Langmuir waves is presented with two-dimensional electrostatic Vlasov simulations. In a mutiwavelength system, trapped electrons can generate sidebands including longitudinal, transverse and oblique sidebands. We demonstrated that oblique sidebands are important decay channels of Langmuir waves, and the growth rate of oblique sideband is smaller than the longitudinal sideband but higher than the transverse sideband. Bump-on-tailtype distribution function is formed because of the growth of sidebands, leading to a nonlinear growth of sidebands. When the amplitudes of sideba…
A rigorous theoretical investigation has been made on the nonlinear propagation of dust-ion-acoustic shock waves in a multi-component magnetized pair-ion plasma having inertial warm positive and negative ions, inertialess non-thermal electrons and positrons, and static negatively charged massive dust grains. The Burgers' equation is derived by employing reductive perturbation method. The plasma model supports both positive and negative shock structures in the presence of static negatively charged massive dust grains. It is found that the steepness of both positive and negative shock profiles d…
In the Universe matter outside of stars and compact objects is mostly composed of collisionless plasma. The interaction of a supersonic plasma flow with an obstacle results in collisionless shocks that are often associated with intense nonthermal radiation and the production of cosmic ray particles. Motivated by simulations of non-relativistic high-Mach-number shocks in supernova remnants, we investigate the instabilities excited by relativistic electron beams in the extended foreshock of oblique shocks. The phase-space distributions in the inner and outer foreshock regions are derived with a …
In this report, we present a dynamical systems' approach to study the exact nonlinear wave-particle interaction in relativistic regime. We give a particular attention to the effect of wave obliquity on the dynamics of the orbits by studying the specific cases of parallel ($θ=0$) and perpendicular ($θ=-π/2$) propagations in comparison to the general case of oblique propagation $θ=]-π/2, 0[$. We found that the fixed points of the system correspond to Landau resonance, and that the dynamics can evolve from trapping to surfatron acceleration for propagation angles obeying a Hopf bifurcations condi…
We investigate the propagation characteristics of electrostatic waves in a magnetized pair-ion plasma with immobile charged dusts. It is shown that obliquely propagating (OP) low-frequency (in comparison with the negative-ion cyclotron frequency) long-wavelength "slow" and "fast" modes can propagate, respectively, as dust ion-acoustic (DIA) and dust ion-cyclotron (DIC)-like waves. The properties of these modes are studied with the effects of obliqueness of propagation $(θ)$, the static magnetic field, the ratios of the negative to positive ion masses $(m)$ and temperatures $(T)$ as well as the…
Motivated by the recent Magnetospheric Multiscale (MMS) observations of oblique electron acoustic waves, we addressed the generation mechanism of the observed waves by utilizing the reductive perturbation technique. The nonlinear Zakharov-Kuznetsov (ZK) equation is derived for collisionless, magnetised plasma composed of cool inertial background electrons, the cool inertial electron beam, hot inertialess suprathermal electrons represented by a $κ$-distribution, and stationary ions. Moreover, the instability growth rate is derived by using the small-k perturbation expansion method. Our findings…
Nonlinear interaction of a low density electron beam with a uniform plasma is studied using two-dimensional particle-in-cell (PIC) simulations. We focus on formation of coherent phase space structures in the case, when a wide two-dimensional wave spectrum is driven unstable, and we also study how nonlinear evolution of these structures is affected by the external magnetic field. In the case of isotropic plasma, nonlinear buildup of filamentation modes due to the combined effects of two-stream and oblique instabilities is found to exist and growth mechanisms of secondary instabilities destroyin…
Oblique Instability of Quasi-Parallel Whistler Waves in the Presence of Cold and Warm Electron Populations
本文将准平行哨声波斜向不稳定性分析推广到冷、暖电子群共存情形，揭示增长率双峰结构及不稳定性在冷电子群缺失时仍存在，并通过粒子模拟证明该不稳定性可产生观测到的电子分布平台/束流特征，反转了以往关于斜向合声波激发机制的因果解释。
Injection process of pickup ion acceleration at an oblique heliospheric termination shock
本研究利用二维全动能粒子模拟，探讨了倾斜日球层终端激波处拾起离子加速的注入过程，发现反射离子驱动的大振幅波会重构激波表面，且离子通过激波冲浪与漂移加速机制被加速至数十倍上游流能量。
Dynamics of a charged relativistic particle in a uniform magnetic field and an obliquely propagating electrostatic shock wave is considered. The system is reduced to a two degrees of freedom Hamiltonian system with slow and fast variables. In this system, the phenomenon of capture into resonance can take place. Under certain condition, a captured phase point stays captured forever. This corresponds to unlimited surfing acceleration of the particle. The preprint is a more detailed version of a comment on the paper by D.Ucer and V.D.Shapiro (Phys.Rev.Lett., vol. 87, 075001, 2001), intended for t…
We present a statistical analysis of more than two thousand bipolar electrostatic solitary waves (ESW) collected from ten quasi-perpendicular Earth's bow shock crossings by Magnetospheric Multiscale spacecraft. We developed and implemented a correction procedure for reconstruction of actual electric fields, velocities, and other properties of ESW from measurements, whose spatial scales are typically comparable with or smaller than spatial distance between voltage-sensitive probes. We determined the optimal ratio between frequency response factors of axial and spin plane antennas to be around 1…
For more than 12 hours beginning on January 18, 2021, continuous narrowband electrostatic emissions were observed on Parker Solar Probe near 20 solar radii. The observed <1000 Hz frequencies were well below the local ion plasma frequency. Surprisingly, the emissions consisted of electrostatic wave packets with shock-like envelopes, appearing repetitively at a ~1.5 Hz rate. This repetitiveness correlated and was in phase with low frequency electromagnetic fluctuations. The emissions were associated with simultaneously observed ion beams and conditions favorable for ion-acoustic wave excitation,…
We examine with a particle-in-cell (PIC) simulation the collision of two equally dense clouds of cold pair plasma. The clouds interpenetrate until instabilities set in, which heat up the plasma and trigger the formation of a pair of shocks. The fastest-growing waves at the collision speed c/5 and low temperature are the electrostatic two-stream mode and the quasi-electrostatic oblique mode. Both waves grow and saturate via the formation of phase space vortices. The strong electric fields of these nonlinear plasma structures provide an efficient means of heating up and compressing the inflowing…
AIM: Large amplitude narrowband obliquely propagating whistler-mode waves at frequencies of ~0.2 fce (electron cyclotron frequency) are commonly observed at 1 AU, and are most consistent with the whistler heat flux fan instability. We want to determine whether similar whistler-mode waves occur inside 0.2 AU, and how their properties compare to those at 1 AU. METHODS: We utilize the waveform capture data from the Parker Solar Probe Fields instrument to develop a data base of narrowband whistler waves. The SWEAP instrument, in conjunction with the quasi-thermal noise measurement form Fields, pro…
Relativistic collisionless shocks are believed to be efficient particle accelerators. Nonlinear outcome of the interaction of accelerated particles that run ahead of the shock, the so-called "precursor", with the unperturbed plasma of the shock upstream, is thought to facilitate additional acceleration of these particles and to possibly modify the hydrodynamic structure of the shock. We explore here the linear growth of kinetic modes appearing in the precursor-upstream interaction in relativistic shocks propagating in non and weakly magnetized plasmas: electrostatic two-stream parallel mode an…
To undergo diffusive shock acceleration, electrons need to be pre-accelerated to increase their energies by several orders of magnitude, else their gyro-radii are smaller than the finite width of the shock. In oblique shocks, where the upstream magnetic field orientation is neither parallel or perpendicular to the shock normal, electrons can escape to the shock upstream, modifying the shock foot to a region called the electron foreshock. To determine the pre-acceleration in this region, we undertake PIC simulations of oblique shocks while varying the obliquity and in-plane angles. We show that…
Electrostatic Waves and Electron Holes in Simulations of Low-Mach Quasi-Perpendicular Shocks
本文利用二维PIC模拟研究低马赫数准垂直激波，揭示电子束驱动EAWs并演化为ESWs的机制，且其尺度和振幅依赖激波速度。
1.5D PIC, relativistic, fully electromagnetic (EM) simulations are used to model EM wave emission generation in the context of solar type III radio bursts. The model studies generation of EM waves by a super-thermal, hot beam of electrons injected into a plasma thread that contains uniform longitudinal magnetic field and a parabolic density gradient. In effect, a single magnetic line connecting Sun to earth is considered, for which several cases are studied. (i) We find that the physical system without a beam is stable and only low amplitude level EM drift waves (noise) are excited. (ii) The b…
The ionization efficiency of helicon plasma discharge is explored by changing the low axial magnetic field gradients near the helicon antenna. The highest plasma density is found for a most possible diverging field near the antenna by keeping the other operating condition constant. Measurement of axial wave number together with estimated radial wavenumber suggests the oblique mode propagation of helicon wave along the resonance cone boundary. Propagation of helicon wave near the resonance cone angle boundary can excite electrostatic fluctuations which subsequently can deposit energy in the pla…
The existence of low frequency waveguide modes of ion acoustic waves is demonstrated in magnetized plasmas for electron temperature striated along the magnetic field lines. At higher frequencies, in a band between the ion cyclotron and the ion plasma frequency, radiative modes develop and propagate obliquely to the field away from the striation. Arguments for the subsequent formation and propagation of electrostatic shock are presented and demonstrated numerically. For such plasma conditions, the dissipation mechanism is the "leakage" of the harmonics generated by the wave steepening.
Understanding cold electron impact on parallel-propagating whistler chorus waves via moment-based quasilinear theory
本文通过动量基准准线性理论研究冷电子对平行传播哨鸣波的影响，揭示二次不稳定性在能量传输中的作用及对磁层内波振幅的限制。
(Abridged) This paper addresses the issue of magnetic field generation in a relativistic shock precursor through micro-instabilities. The level of magnetization of the upstream plasma turns out to be a crucial parameter, notably because the length scale of the shock precursor is limited by the Larmor rotation of the accelerated particles in the background magnetic field and by the speed of the shock wave. We discuss in detail and calculate the growth rates of the following beam plasma instabilities seeded by the accelerated and reflected particle populations: for an unmagnetized shock, the Wei…
Depending on the physical conditions involved the beam plasma systems may reveal new unstable regimes triggered by the wave instabilities of different nature. We show through linear theory and numerical simulations the existence of an aperiodic electromagnetic instability which solely develops and control the stability of two symmetric plasma populations counter-moving along the regular magnetic field with a relative drift, $v_d$, small enough to not exceed the particle thermal speed, $α_e$. Emerging at highly oblique angles this mode resembles properties of the aperiodic firehose instability …
Nonlinear effects of the trapping of resonant particles by the combined action of the electric field and the magnetic mirror force is studied using a gyrokinetic description that includes the finite Larmor radius effects. A general nonlinear solution is found that is supported by the nonlinearity arising from the resonant particles, trapped by the combined action of the parallel electric field and the magnetic mirror force. Applying these results to the space plasma conditions, we demonstrate that in the magnetosheath plasma, coherent nonlinear magnetic depression may be created associated wit…
A full particle simulation study is carried out for studying microinstabilities generated at the shock front of perpendicular collisionless shocks. The structure and dynamics of shock waves are determined by Alfven Mach number and plasma beta, while microinstabilities are controlled by the ratio of the upstream bulk velocity to the electron thermal velocity and the plasma-to-cyclotron frequency. Thus, growth rates of microinstabilities are changed by the ion-to-electron mass ratio, even with the same Mach number and plasma beta. The present two-dimensional simulations show that the electron cy…
In this work we used Particle-In-Cell simulations to study the interaction of circularly polarised Alfvén waves with one dimensional plasma density inhomogeneities transverse to the uniform magnetic field (phase mixing) in collisionless plasmas. In our preliminary work we reported discovery of a new electron acceleration mechanism, in which progressive distortion of the Alfvén wave front, due to the differences in local Alfvén speed, generates an oblique (nearly parallel to the magnetic field) electrostatic field. The latter accelerates electrons through the Landau resonance. Here we report a …
Sheath constraints on turbulent magnetised plasmas
研究小倾角磁化等离子体鞘层对湍流边界的约束，通过尺度分离与沿场结构假设推导广义动力学 Bohm-Chodura 判据，揭示切向电场和 ExB 漂移的作用。
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