Laboratory Observation of a Very Low Frequency Instability in an Argon Plasma

Very low frequency (50 to 500 Hz) self-excited electrostatic waves are detected in a cylindrical argon plasma column with a weak axial magnetic field (10 to 100 G). The waves propagate azimuthally with a phase velocity in the electron diamagnetic drift direction, but with a speed at least an order of magnitude less than the ion acoustic speed. A number of known plasma instabilities are considered as possible explanations, though most of them do not seem to account for the observed characteristics of the waves.     

Behaviors of electrostatic ion cyclotron waves excited in ion beam-plasma systems

Experimental results are presented for a behavior of the electrostatic ion cyclotron waves excited in an ion beam-plasma system. This wave appears as forward and backward waves with respect to the propagating component along the magnetic field.     

Nonlinear amplitude osçillations of absolutely unstable electrostatic ion cyclotron waves in an ion beam-plasma system

We have observed experimentally the amplitude oscillations of absolutely unstable electrostatic ion cyclotron waves in an ion beam-plasma system due to nonlinear interaction between the beam ions and electrostatic ion cyclotron waves.     

Quantum interference electronic switch

A novel planar electron waveguide coupler is proposed as an electronic switch. The structure consists of two quantum wires interconnected by a dual branch coupling scheme which is assumed to be controlled by an electrostatic potential. Switching is provided by tuning the phase relations between the different scattered waves by the two coupling branch lines. Assuming ballistic transport, the analysis is conducted by solving the time independent two-dimensional Schrödinger equation in order to derive the conductance characteristics. At a resonant energy of 25 meV and for a waveguide width of 27.4 nm, over 90% of the electron wave has been transferred with a half picosecond time response.     

Electrostatic ion-cyclotron waves in a two-ion component plasma

The excitation of electrostatic ion cyclotron (EIC) waves is studied in a single-ended Q machine in a two-ion component plasma (Ca⁺ and K⁺). Over a large range of relative concentrations of Ca⁺ and K⁺ ions, two modes are excited with frequencies greater than the respective cyclotron frequencies of the ions. The results are discussed in terms of a fluid theory of electrostatic ion cyclotron waves in a two-ion component plasma     

Electrostatic global vortices in a nonuniform cylindrical magneto-plasma

We present nonlinear properties of the low-frequency nonlinear electrostatic waves in a nonuniform bounded magneto-plasma with the equilibrium density and parallel ion velocity gradients along the radial direction. The existence of electrostatic global vortices in a cylindrical magnetoplasma is established. The present results should help to understand the properties of coherent vortical structures in the presence of a magnetic field-aligned ion flow with a radial ion velocity gradient in laboratory magnetoplasmas that are bounded and nonuniform.     

Electrostatic Surface Waves on Semi-Bounded Quantum Electron-Hole Semiconductor Plasmas

The electrostatic surface waves on semi-bounded quantum electron-hole semiconductor plasmas are studied within the framework of the quantum hydrodynamic model, including the electrons and holes quantum recoil effects,quantum statistical pressures of the plasma species, as well as exchange and correlation effects. The dispersion characteristics of surface electrostatic oscillations are investigated by using the typical values of Ga As, Ga Sb and Ga N semiconductors. Numerical results show the existence of one low-frequency branch due to the mass difference between the electrons and holes in addition to one high-frequency branch due to charge-separation effects.     

Model experiment and analysis of pressure waves emitted from portals of a tunnel with a branch

A model experiment was performed to investigate pressure waves generated by a train passing by a branch and pulse waves radiated from portals of a main tunnel and the branch. For the experiment, the train speed was set as 400–500 km/h. The cross-sectional area ratio of the branch to the main tunnel was 0–0.5. The cross-sectional area ratio of the branch to the main tunnel was identified as a dominant factor in determining the magnitude of the pressure waves in the tunnel and the pulse waves radiated from the portals. Closed form expressions for the magnitude of the pressure changes generated by a train passing by a branch were derived using low Mach number approximation. Correlation between the pressure waves in the tunnel and the pulse waves radiated from the portals was clarified using simple acoustic theory. The overall tendency of the experimental results is explainable based on analytical results.     

Absolute and convective instabilities of electrostatic ion cyclotron waves excited in an ion beam-plasma system

Experimental results are presented for the observation of the absolute and convective instabilities of the electrostatic ion cyclotron waves excited in an ion beam-plasma system.     

Electron exchange-correlation effects on dispersion properties of electrostatic waves in degenerate quantum plasmas

Based on the quantum Magnetohydrodynamic (QMHD) model, the obliquely propagation of electrostatic waves in degenerate magnetized quantum plasmas with electron exchange-correlation effects are theoretically investigated. The modified linear dispersion relations of electrostatic waves are obtained and discussed in some specific cases. The analytical results clearly show that the dispersion properties of the high frequency electron waves (including the Langmuir wave and upper-hybrid wave) and the low frequency ion acoustic wave are modified by the quantum effects together with the electron exchange-correlation effects. The numerical results depict that the Langmuir wave and upper-hybrid wave can be unstable in the presence of the electron exchange-correlation effects, and it is also evidently indicated that the electron exchange-correlation effects can reduce the phase velocity of the waves, especially in the high wave number region. The corresponding results should be of relevance for identifying electrostatic fluctuations which transport in an inhomogeneous and magnetized quantum plasmas.     

Behaviors of absolute instabilities of electrostatic ion cyclotron waves in an ion beam-plasma system

Experimental results are presented for behaviors of the temporal growth and the threshold beam density of the absolute instability of the electrostatic ion cyclotron waves excited in an ion beam-plasma system, and compared with the linear theory.     

利用超快电子探针诊断受激拉曼散射静电波的数值模拟

利用二维粒子模拟程序EPOCH验证了超快电子束探针诊断受激拉曼散射产生的静电波的可行性。结果表明,电子束探针穿过静电波电场后会在电子束探针的横向上产生密度调制,密度调制呈周期性分布且沿静电波的传播方向移动,密度调制的波数对应静电波的波数且移动速度对应静电波的相速度,因此特定条件下可用于反推电子的温度、密度等信息。在诊断静电波的过程中,电子束探针的束长必须小于静电波的波长或者诊断设备的曝光时间必须小于静电波的周期。本研究提供了一种新型的直接诊断静电波和电子温度、密度的方法,对于推动受激拉曼散射等激光等离子体不稳定性的实验研究具有重要意义。     

Observation of inverse ion-cyclotron damping induced by parallel-velocity shear

The generation of broadband multiharmonic spectra of electrostatic ion-cyclotron waves is demonstrated in a magnetized laboratory plasma in which shear in the magnetic-field-aligned (parallel) ion flow and a relative parallel electron drift are present. Shear correlates with an increased number of harmonics and a decreased electron drift speed. Wave and particle measurements indicate that cyclotron damping is reduced and even becomes negative. The fluctuations in the time domain are spiky, similar to electric-field fluctuations observed both in Earth's auroral zone and in numerical simulations.     

Production of nonisothermal electrons and Langmuir waves because of colliding ion holes and trapping of plasmons in an ion hole

We present new simulation studies exhibiting production of nonisothermal electron distributions and Langmuir waves by colliding ion holes and trapping of plasmons in an ion hole. We find that, during head-on ion hole collisions, streams of accelerated electrons are produced by the electrostatic potentials supporting the ion holes. Subsequently, Langmuir waves are excited by a two-stream instability involving energetic electron beams. The resulting Langmuir waves can be trapped in an ion hole. The present ion-hole-Langmuir wave interactions are unique kinetic phenomena which can be dealt with a Vlasov code, which we developed recently. The results can have relevance to the understanding of particle and field data that are forthcoming from different spacecraft missions in Earth's auroral ionosphere and the magnetosphere.     

Collisionless Trapped Ion Temperature Gradient Instabilities

Under the fluid limit, the collisionless electrostatic trapped ion temperature gradient instabilities are investigated by retaining the trapped ion parallel compressibility in the long wavelength limit. The two-scale analysis should be employed in view of the fact that the eigenfunctions vary over the connection width scale with an envelope varying over a secular scale. The results show that the slab branch of trapped ion modes, corresponding to the aperiodic trapped ion instability discovered by Kadomtzev, propagates along ion diamagnetic direction. The toroidd branch is also obtained in low-frequency and long wavelength limit. In this case, besides the unstable one propagating in ion diamagnetic direction, there exists a marginally stable toroidal odd mode propagating in electron diamagnetic direction. The eigenfrequencies and perturbative structures of these unstable modes are given analytically and numerically. The numerical results are in good agreement with the analytical ones.     

Electrostatic Instabilities at High Frequency in a Plasma Shock Front

New electrostatic instabilities in the plasma shock front are reported. These instabilities are driven by the electro- static field which is caused by charge separation and the parameter gradients in a plasma shock front. The linear analysis to the high frequency branch of electrostatic instabilities has been carried out and the dispersion relations are obtained numerically. There are unstable disturbing waves in both the parallel and perpendicular directions of shock propagation. The real frequencies of both unstable waves are similar to the electron electrostatic wave, and the unstable growth rate in the parallel direction is much greater than the one in the perpendicular direction. The dependence of growth rates on the electric field and parameter gradients is also presented.     

Ion-beam-excited electrostatic ion cyclotron waves

Self-excited electrostatic ion cyclotron waves were observed in an ion-beam-plasma system produced in a DP-operated Q-machine. The frequency of the waves showed the theoretically predicted variation with the magnetic field.     

Shock Structures in Charge Variable Dusty Plasmas with Effect of Strongly Coupled Dust Particles

A theoretical investigation has been carried out to study the effect of strong electrostatic interaction on the dust acoustic shock structures in strongly coupled dusty plasma with dust charge fluctuations.The fluid approach is employed,in which the strong electrostatic interaction is modeled by effective electrostatic temperature.A Burger-like equation,the coefficients of which are significantly modified by effects of strong coupling and dust charge Ructuation,is derived.It is shown that the combined effects of dust charge Ructuation,the ion/electron temperature,the ion/electron population,and strong coupling effect modify the basic properties of the dust acoustic waves in such a strongly coupled dusty plasma.The results of this work are compared with those observed by some laboratory experiments.     

The morphology of electrostatic tripolar regions

Electrostatic tripolar regions in plasmas develop a skewness of their own electric potential waveform as a peculiar morphological property, which distinguishes them from symmetric electrostatic solitary waves. Within the collision-less, kinetic treatment developed here, this property holds if the velocity distributions of electrons and ions are singular in value, irrespective of their smoothness at the region’s boundary and of the smoothness of the potential waveform and of the electron and ion density distributions. These singularities are integrable, and are of the logarithmic and jump type: the former occur at isolated points in phase space; the latter occur on the left branch of the electron separatrix and on the left branch of the ion sub-separatrix. The distributions are non-negative if, at its local extrema, the potential waveform is skewed to the left, in agreement with observations, and if the skewness is smaller than a given bound: a sufficient condition for such skewness to be small about the minimum of the potential waveform is that a sufficiently fast electron beam exists on the high-potential boundary of the tripolar region. In those special cases in which the particle distributions are continuous in value, the above mentioned singularities affect their space and velocity derivatives. These results could be extracted from very general considerations on the degree of smoothness of the spatial distribution of the electric potential and on the non-negativity of the electron and ion distributions, without the assistance of any specific models.     

Electrostatic cnoidal waves and soliton structures in multi‐ions plasmas

Using a reductive perturbation technique (RPT), the Korteweg‐de Vries (KdV) equation for nonlinear electrostatic waves in multi‐ion plasmas is derived with appropriate boundary conditions. Furthermore, compressive and rarefactive cnoidal wave and soliton solutions are discussed. In our model, the multi‐ion plasma consists of light dynamic warm ions, heavy cold ions, and inertialess electrons, which follows the Maxwell‐Boltzmann distribution. It is observed that in such an unmagnetized multi‐ion plasma, two characteristic electrostatic waves i.e., slow ion‐acoustic (SIA) waves and fast ion‐acoustic (FIA) waves, can propagate. The results are discussed by considering two types of multi‐ion plasmas i.e., H⁺–O⁺–e plasma and H^?–O⁺–e plasma that exist in space plasmas. It is found that for H⁺–O⁺–e plasma, the SIA cnoidal wave and soliton form both positive (compressive) and negative (rarefactive) potential pulses, which depend on the temperature and density of the light and warm ions. However, only electrostatic positive potential structures are obtained for FIA cnoidal wave and soliton in H⁺–O⁺–e plasma. In the case of H^?–O⁺–e plasma, the SIA cnoidal wave and soliton form only compressive structures, while the FIA cnoidal wave and soliton compose rarefactive structures. The effects of light ions' density and temperature on nonlinear potential structures are investigated in detail. The parametric results are also demonstrated, which are applicable to space and laboratory multi‐ion plasma situations.