Low-frequency Drift Waves Research Articles

Instability of Ion Cyclotron Waves (ICWS) at the Expense of Lower Hybrid Drift Waves (LHDWS) Turbulence Energy

Instability of ion cyclotron waves(ICWs) is investigated in presence of lower hybrid drift waves(LHDWs) turbulence. Plasma inhomogeneity in the Earth’s magnetopause region supports a range of low frequency drift wave turbulent fields due to gradients in density in different regions of the media. One of these drift phenomena is identified as lower hybrid drift waves (LHDWs) which satisfies resonant conditions ω − k · v = 0. We have considered a nonlinear wave-particle interaction model where the resonant wave that accelerates the particle in magnetopause may transfer its energy to ion cyclotron waves through a modulated field. In spite of the frequency gaps between the two waves, energy can be transferred nonlinearly to generate unstable ion cyclotron waves which always do not satisfy the resonant condition Ω−K · v ≠ 0 and the nonlinear scattering condition Ω − ω − (K − k) · v ̸= 0. Here, ω and Ω are frequencies of the resonant and the nonresonant waves respectively and k and K are the corresponding wave numbers. We have obtained a nonlinear dispersion relation for ion cyclotron waves(ICWs) in presence of lower hybrid drift waves(LHDWs)turbulence. The growth rate of the ion cyclotron waves using space observational data in the magnetopause region has been estimated.

Dual upper drift waves in RF produced magnetized helium plasma

Self-excited dual upper drift modes have been observed in a magnetized helium plasma, having frequencies less than the ion cyclotron frequency (fci) but higher than that of the conventional low frequency drift waves (f≪fci). The modes propagate mainly in the azimuthal direction with mode numbers m = 1 and m = 2 with frequencies 30 kHz and 50 kHz, respectively, and also have weak axial propagation. They coexist over a wide range of radial and axial locations and the direction of azimuthal propagation coincides with the electron diamagnetic drift. A local dispersion relation obtained from the fluid description of the plasma predicts an instability simultaneously for both m = 1 and m = 2 modes (with different frequencies) over a range of radial locations.

Formation of the Blue Core in Argon Helicon Plasma

Helicon plasmas are typically associated with a core, a radially localized central area of strong ion light emission. Here, we investigate the role of electrostatic instabilities that lead to the formation of the classic blue core. We show that helicon plasma can also occur without the distinct core. In these conditions, the plasma is dominated by low-frequency resistive drift wave (RDW) instabilities propagating in the electron diamagnetic drift direction. When the intense sharp core is present, a new global equilibrium state is achieved where three radially separated plasma instabilities exist simultaneously. The density gradient driven RDWs separate the plasma radially into an edge region and a core region. The edge is dominated by strong, turbulent, shear-driven instabilities, while the core shows very coherent high azimuthal mode number fluctuations propagating in the ion diamagnetic drift direction and associated with enhanced ion emission. The particle flux is directed outward for small radii and inward for large radii, thus forming a radial particle transport barrier. The radial extent of the inner mode and radial location of the particle transport barrier is the same as the radius of the blue core. This new equilibrium, with the three coexisting radially separated plasma instabilities, leads to the formation of a very strong enhanced blue core. For a range of operating parameters, just prior to the blue core formation, the system undergoes incomplete intermittent transitions between the two equilibrium states, leading to the visual perception of a broad less intense helicon core. This is the first time that the development of the helicon core is shown to be associated with changes in radial transport driven by inherent low-frequency plasma instabilities.

Rescaling effects on a low-frequency drift wave in dusty plasmas

The effect of dust on the low-frequency drift wave in inhomogeneous magnetized dusty plasmas is investigated. It is shown that a low-frequency drift wave can be modeled by the Hasegawa–Mima equation (HME) both in mobile and immobile dusty plasmas, which are dust-modified HME and HME in dusty background, respectively. The former is rescaled significantly by the presence of the dust and the space-time scale greatly increases with the increasing density and mass of dust, while the latter is not rescaled, but an additional driving force appears to drive the drift waves.

Dust gravitational drift wave in complex plasma under gravity

The dispersion relation of electrostatic waves in a complex plasma under gravity is presented. It is assumed that the waves propagate parallel to the external fields. The effects of weak electric field, neutral drag force, and ion drag force are also taken into account. The dispersion relation is numerically examined in an appropriate parameter space in which the gravity plays the dominant role in the dynamics of microparticles. The numerical results show that, in the low pressure complex plasma under gravity, a low frequency drift wave can be developed in the long wavelength limit. The stability state of this wave is switched at a certain critical wavenumber in such a way that the damped mode is transformed into a growing one. Furthermore, the influence of the external fields on the dispersion properties is analyzed. It is shown that the wave instability is essentially due to the electrostatic streaming of plasma particles. It is also found that by increasing the electric field strength, the stability switching occurs at smaller wavenumbers.

The MaPLE device: A linear machine for laboratory studies of the magnetized plasma physics phenomena

The Magnetized Plasma Linear Experimental (MaPLE) device is developed in the plasma physics laboratory of the Saha Institute of Nuclear Physics for studying basic plasma physics phenomena like waves, instabilities and their nonlinear behavior in magnetized plasma. Details description of the device and its plasma characteristics are presented. The machine provides flexibilities in terms of magnetic configuration and plasma sources. Recently, low frequency drift waves are excited in the weak density gradient region of electron cyclotron resonance (ECR) produced low density plasmas and their nonlinear coupling is studied. Results of this experiment and some more experiments done in the device are summarized. Reasoning behind a possible upgrade plan of the device for studying shear Alfven waves (SAW) and magnetic drift waves in future is also discussed.

Dust magneto-gravitational drift wave in g×B configuration

The dispersion relation of electrostatic waves in a magnetized complex plasma under gravity is presented. It is assumed that the waves propagate perpendicular to the external fields. The effects of weak electric field, neutral drag force, and ion drag force are also taken into account. The dispersion relation is numerically examined in an appropriate parameter space in which the gravity plays the dominant role in the dynamics of magnetized microparticles. The numerical results show that an unstable low frequency drift wave can be developed in the long wavelength limit. This unstable mode is transformed into an aperiodic stationary structure at a cut-off wavenumber. Furthermore, the influence of the external fields on the dispersion properties is analyzed. It is shown that the instability is essentially due to the E×B drift motion of plasma particles. However, in the absence of weak electric field, the g×B drift motion of microparticles can cause the instability in a wide range of wavenumbers. It is also found that by increasing the magnetic field strength, the wave frequency is first increased and then decreased. This behaviour is explained by the existence of an extremum point in the dust magneto-gravitational drift velocity.

Electrostatic instability in magnetically confined inhomogeneous plasma driven by nonlinear force

Abstract A theoretical investigation on amplification of electrostatic ion acoustic wave in magnetically confined plasma has been presented in this paper. This investigation considers nonlinear wave–particle interaction process, called plasma maser effect, in presence of drift wave turbulence supported by magnetically confined inhomogeneous plasma. The role of associated nonlinear dissipative force in this effect in a confined plasma has been analyzed. The nonlinear force, which arises as a result of resonant interaction between electrons and modulated fields, is shown to drive the instability. Using the ion fluid equation and the ion equation of continuity, the nonlinear dispersion relation of a test ion acoustic wave has been derived, and the growth rate of ion acoustic wave in presence of low frequency drift wave turbulence has been estimated using Helimak data.

Selective Excitation of Low Frequency Drift Waves by Density Modulation and Parametric Excitation of Higher Frequency Mode

Excitation of low frequency drift waves in a radial region of a weak density gradient is demonstrated experimentally by strong temporal modulation of the plasma density. Though a parallel electron current can destabilize drift waves throughout the region, we observe mode selection at the resonant location matching the frequency of modulation. Parametric mode-mode interaction among two excited drift modes to destabilize a higher frequency one is reported under the specific condition of the growth rate. Theoretically estimated growth rates fit well with the experiment.

Fast wave stabilization/destabilization of drift waves in a plasma

Four wave-nonlinear coupling of a large amplitude whistler with low frequency drift wave and whistler wave sidebands is examined. The pump and whistler sidebands exert a low frequency ponderomotive force on electrons introducing a frequency shift in the drift wave. For whistler pump propagating along the ambient magnetic field Bsẑ with wave number k→0, drift waves of wave number k→=k→⊥+k||ẑ see an upward frequency shift when k⊥2/k02>4k||/k0 and are stabilized once the whistler power exceeds a threshold value. The drift waves of low transverse wavelength tend to be destabilized by the nonlinear coupling. Oblique propagating whistler pump with transverse wave vector parallel to k→⊥ is also effective but with reduced effectiveness.

Drift wave in pair-ion plasma

The conditions for the existence of low-frequency electrostatic drift wave in pair-ion plasma are discussed. It is shown that the temperature and/or mass difference of both species could produce drift wave in a pair-ion plasma. The results are discussed in the context of the fullerene pair-ion plasma experiment.

Dissipative drift wave instability in a radially bounded nonuniform dusty magnetoplasma

Properties of the dissipative drift wave instability in a radially bounded nonuniform dusty magnetoplasma are investigated. By using the two-fluid model for the electrons and ions, we derive a nonlocal wave equation for the low-frequency collisional drift wave in the bounded system. The charged dust is assumed to be immobile on the time scale of the instability. The wave equation admits a dispersion relation, which exhibits the modification of the drift wave frequency and the dissipative drift wave instability growth rate due to radial boundaries. Possible application of our investigation to forthcoming nonuniform dusty magnetoplasma experiments is discussed.

Dissipative drift instability in dusty plasma

An investigation has been done on the very low-frequency electrostatic drift waves in a collisional dusty plasma. The dust density gradient is taken perpendicular to the magnetic field \documentclass[12pt]{minimal}\begin{document}$\overrightarrow{B_{0}}$\end{document}B0⃗, which causes the drift wave. In this case, low-frequency drift instabilities can be driven by \documentclass[12pt]{minimal}\begin{document}$\overrightarrow{E_{1}}\times \overrightarrow{B_{0}}$\end{document}E1⃗×B0⃗ and diamagnetic drifts, where \documentclass[12pt]{minimal}\begin{document}$\overrightarrow{E_{1}}$\end{document}E1⃗ is the perturbed electric field. Dust charge fluctuation is also taken into consideration for our study. The dust- neutral and ion-neutral collision terms have been included in equations of motion. It is seen that the low-frequency drift instability gets damped in such a system. Both dust charging and collision of plasma particles with the neutrals may be responsible for the damping of the wave. Both analytical and numerical techniques have been used while developing the theory.

Nonlinear excitation of zonal flows and streamers in plasmas

Nonlinear excitation of zonal flows and streamers in plasmas is considered. The emphasis is given to the nonlinear interaction of low- and high-frequency drift waves which can result in the excitation of zonal flows and streamers in a plasma of fusion devices. For this purpose, an inhomogeneous nonisothermal plasma in a strong external magnetic field whose characteristic frequencies are lower than the ion Langmuir frequency but higher than the collision frequency is studied. The excitation of a long-wavelength low-frequency drift wave during the development of the nonlinear modulational interaction of a high-frequency drift pump wave is investigated. The growth rates of the modulational instability are obtained, and the conditions for its development are determined. Self-organized structures described by solutions of evolutionary equations for the modulational interaction are associated with zonal flows and streamers. A possible relation of the modulational interaction in Earth’s ionospheric plasma to the formation of dust flows and transport of dust particles in the ionosphere is also discussed. It is shown that one of the ways of transport of dust particles in the ionosphere is vertical flows (streamers), which are generated by dust vortices as a result of development of the modulational instability.

Whistler wave stabilization/destabilization of drift waves in a plasma cylinder

The nonlinear coupling of a large amplitude whistler wave with low frequency drift waves in an inhomogeneous magnetized plasma cylinder is investigated. The coupling produces whistler wave sidebands. The pump and sidebands exert a ponderomotive force on electrons causing a frequency shift in the drift wave, leading to its stabilization/destabilization, depending on the relative wave numbers of the interacting waves as well as with whistler pump power. The whistler wave stabilizes the drift wave for K0z < 2.9 × 102 and destabilizes for K0z > 2.9 × 102, with K0z = k0zc/ωci, where k0z is the wave number of the whistler pump, c is the velocity of light and ωci is the ion cyclotron frequency. The whistler pump power above 5 MW also stabilizes the drift wave.

On the recently discovered pulsations from RX J1856.5-3754

An explanation of the recently discovered 7 s pulsations from the isolated neutron star RX J1856.5-3754 is presented. It is assumed that the real spin period of this source is ≈1 s, whereas the observed spin-modulation is caused by the presence of a nearly transverse, very low frequency drift waves in the pulsar magnetosphere. It is supposed that the period of the drift wave is equal to a recently observed one. The simulated lightcurve is plotted, the angular parameters are defined and the value of the pulsed fraction of only ∼1.2% is explained.

Self-gravitation effect on the nonlinear dynamics of an electron–positron–ion magnetoplasma

A new set of nonlinear equations governing the dynamics of low-frequency electrostatic drift waves in a self-gravitating electron–positron–ion (e–p–i) magnetoplasma with equilibrium density, temperature, magnetic field and velocity gradients has been derived. It is shown that possible stationary solutions of the nonlinear equations can be represented in the form of dipolar and tripolar vortices of gravitational potential. The results of the present investigation are useful to understand the nonlinear dynamics of low-frequency gravitational-drift waves in laboratory and astrophysical e–p–i magnetoplasmas.

Low-frequency waves in bounded streaming plasma

An analysis of low-frequency (drift and sound) waves in a spatially bounded plasma is presented. The plasma has a radial density gradient and flows along the magnetic field lines with a radially bell-shaped flow profile. An equation for the radially dependent wave amplitude is derived and solved analytically for a class of density and flow profiles. The solutions represent global modes that are twisted around magnetic lines and vanish at the plasma axis and at the boundary.

Dust-lower-hybrid drift instabilities with dust charge fluctuations in an inhomogeneous dusty magnetoplasma.

Effects of a uniform magnetic field, the plasma inhomogeneity, and dust charge fluctuations on low-frequency dust-lower-hybrid drift waves have been investigated. Charging currents of electrons and ions to a spherical dust grain in a nonuniform magnetized dusty plasma have been calculated to study the charge fluctuation induced damping or growth of low-frequency drift waves. It is found that for strongly magnetized electrons and ions, the charge fluctuation damping is reduced significantly from that of an unmagnetized plasma. For sufficiently hot electrons, the drift wave exhibits instability in the absence of dust charge fluctuation damping.

원유 생산.저장.하역선의 갑판침수에 관한 연구

As the number of offshore structure is glowing in deep waters, there have been increased damages of it. These floating structures in offshore locations exposed to harsh environmental conditions. In recent years, there has been a slowing attention around damages on bow and deck on FPSO caused by waves in steep storm condition. This paper describes a study of the water on deck due to the dynamic behavior of a FPSO with turret mooring system. The nonlinear motions of the FPSO are simulated under external forces due to wave, current, wind, and mooring forces in the time domain. The direct integration method is employed to estimate low frequency drift wave forces. The current forces are calculated by using slow motion maneuvering equations in the horizontal plane. The coefficients of a model for wind forces are calculated from Isherwood's experimental data and the variation of wind speed is estimated by wind spectrum according to the guidelines of API-RP2A.