Large scale instabilities in the electromagnetic drift wave turbulence and transport

Large scale structures play an important role in self-organization of drift wave turbulence. Large scale perturbations of plasma flow and magnetic field are spontaneously generated in generic electromagnetic drift wave turbulence via the action of Reynolds stress and electromotive force. Initial large scale perturbations are amplifed by positive feedback due to the modulations of wave packets by the shearing effect of the large scale flow and/or by the perturbed large scale magnetic field. As a result, the propagation of small scale wave packets is accompanied by the instability of a low frequency, long wavelength components. Anomalous transport due to drift wave turbulence may also be unstable with respect to the large scale perturbations of plasma profile. In this case the instability occurs as a result of a positive feedback response of the anomalous flux to the large scale variations of plasma temperature

Dispersion of the surface magnetoplasmons

We study the dispersion properties and transmission of a p-polarized electro-magnetic wave in a two-layer plasma structure in presence of an external magnetic field. The conditions for resonance transmission are found. The anomalous transparency is attributed to excitation of surface waves at plasma-plasma interface. The dispersion relation for the surface mode at plasma-plasma interface in magnetic field is studied and compared with that for a plasma-vacuum system.Изучаются дисперсионные свойства и прохождение р-поляризованной электромагнитной волны в двухслойной плазменной структуре в присутствии внешнего магнитного поля. Получены условия резонансного прохождения. Аномальная прозрачность объясняется возбуждением поверхностной волны на границе плазма-плазма. Изучается дисперсионное соотношение для поверхностной волны на границе плазма-плазма в магнитном поле, проводится сравнение с дисперсией поверхностных волн в системе плазма-вакуум.Вивчаються дисперсійні властивості та проходження р-поляризованої електромагнітної хвилі в двошаровій плазмовій структурі за наявності зовнішнього магнітного поля. Отримано умови резонансного проходження. Аномальна прозорість пояснюється збудженням поверхневої хвилі на межі плазма-плазма. Вивчається дисперсійне співвідношення для поверхневої хвилі на межі плазма-плазма в магнітному полі, проводиться порівняння з дисперсією поверхневих хвиль в системі плазма-вакуум

Geodesic acoustic modes and zonal flows in rotating large-aspect-ratio tokamak plasmas

The effect of equilibrium plasma rotation (toroidal and poloidal) on low-frequency, electrostatic modes - the geodesic acoustic modes (GAMs) and the zonal flows (ZFs) - in large aspect ratio tokamaks is studied within the framework of ideal MHD. It is shown that the plasma rotation results in a frequency up-shift of the ordinary GAM. The new branch of continuum modes induced by the poloidal rotation is found. This mode originates from the opposite sign Doppler shift of frequency due to poloidal rotation for m = 1 poloidal side-band harmonics of the perturbed mass density, pressure and parallel velocity. In the case of slow poloidal rotation (ΩP ≪ cs/qR0) its frequency is close to the sound frequency cs/qR0 (ΩP is the poloidal angular velocity, cs is the speed of sound, q is the safety factor and R 0 is the major radius of tokamak). The mode can be called the rotation-induced acoustic mode. This mode disappears in the case of purely toroidal plasma rotation. The frequency of the new mode in the case of relatively slow poloidal rotation (ΩP ≤ c s/qR0) is lower than the frequency of the ordinary GAM modified by plasma rotation. In the case of larger poloidal angular velocities ΩP (ΩP ≥ 2cs/qR0) the mode becomes unstable and is identified as the unstable ZF. With a further increase in the poloidal angular velocity at constant toroidal angular velocity the instability is suppressed, and the mode turns again into a marginally stable, oscillating mode. © 2011 IOP Publishing Ltd

Nonlinear excitation of long-wavelength modes in Hall plasmas

Hall plasmas with magnetized electrons and unmagnetized ions exhibit a wide range of small scale fluctuations in the lower-hybrid frequency range as well as low-frequency large scale modes. Modulational instability of lower-hybrid frequency modes is investigated in this work for typical conditions in Hall plasma devices such as magnetrons and Hall thrusters. In these conditions, the dispersion of the waves in the lower-hybrid frequency range propagating perpendicular to the external magnetic field is due to the gradients of the magnetic field and the plasma density. It is shown that such lower-hybrid modes are unstable with respect to the secondary instability of the large scale quasimode perturbations. It is suggested that the large scale slow coherent modes observed in a number of Hall plasma devices may be explained as a result of such secondary instabilities. © 2016 Author(s)

Nonlinear excitation of long-wavelength modes in Hall plasmas

Hall plasmas with magnetized electrons and unmagnetized ions exhibit a wide range of small scale fluctuations in the lower-hybrid frequency range as well as low-frequency large scale modes. Modulational instability of lower-hybrid frequency modes is investigated in this work for typical conditions in Hall plasma devices such as magnetrons and Hall thrusters. In these conditions, the dispersion of the waves in the lower-hybrid frequency range propagating perpendicular to the external magnetic field is due to the gradients of the magnetic field and the plasma density. It is shown that such lower-hybrid modes are unstable with respect to the secondary instability of the large scale quasimode perturbations. It is suggested that the large scale slow coherent modes observed in a number of Hall plasma devices may be explained as a result of such secondary instabilities. © 2016 Author(s)

Geodesic acoustic modes and zonal flows in rotating large-aspect-ratio tokamak plasmas

The effect of equilibrium plasma rotation (toroidal and poloidal) on low-frequency, electrostatic modes - the geodesic acoustic modes (GAMs) and the zonal flows (ZFs) - in large aspect ratio tokamaks is studied within the framework of ideal MHD. It is shown that the plasma rotation results in a frequency up-shift of the ordinary GAM. The new branch of continuum modes induced by the poloidal rotation is found. This mode originates from the opposite sign Doppler shift of frequency due to poloidal rotation for m = 1 poloidal side-band harmonics of the perturbed mass density, pressure and parallel velocity. In the case of slow poloidal rotation (ΩP ≪ cs/qR0) its frequency is close to the sound frequency cs/qR0 (ΩP is the poloidal angular velocity, cs is the speed of sound, q is the safety factor and R 0 is the major radius of tokamak). The mode can be called the rotation-induced acoustic mode. This mode disappears in the case of purely toroidal plasma rotation. The frequency of the new mode in the case of relatively slow poloidal rotation (ΩP ≤ c s/qR0) is lower than the frequency of the ordinary GAM modified by plasma rotation. In the case of larger poloidal angular velocities ΩP (ΩP ≥ 2cs/qR0) the mode becomes unstable and is identified as the unstable ZF. With a further increase in the poloidal angular velocity at constant toroidal angular velocity the instability is suppressed, and the mode turns again into a marginally stable, oscillating mode. © 2011 IOP Publishing Ltd

Global structure of stationary zonal flow in rotating tokamak plasmas

[No abstract available