Low-frequency Plasma Oscillations Research Articles

Longitudinally propagating arc wave in the pre‐onset optical aurora

We present the first systematic observational evidence for a traveling periodic structure in the pre‐onset optical aurora – the longitudinally propagating arc wave (LPAW) – associated with flapping oscillations in the magnetotail. The LPAW is characterized by azimuthally moving intensity enhancements inside auroral arcs as seen by THEMIS ground‐based all‐sky imagers. It travels westward in the pre‐midnight auroral sector during the 10–20 minutes preceding auroral breakup with a velocity of 2–10 km/s, time period 40–110 s, and wavelength 250–420 km. Magnetically conjugate measurements by THEMIS satellites show low frequency plasma oscillations consistent with the parameters of the arc wave in the course of current sheet thinning. When mapped into tail, wavelength (4800–9400 km) and velocity (70–190 km/s) of the LPAW are compatible with observations and theoretical predictions for current sheet flapping motions. Our results strongly suggest that LPAW is an auroral footprint of the drift wave mode (kink, sausage, ballooning, etc.) in a stretched magnetotail.

Aharonov-Bohm effect and plasma oscillations in superconducting tubes and rings

Low-frequency plasma oscillations in superconducting tubes are considered. The emergence of two different dimensionality regimes of plasma oscillations in tubes exhibiting a crossover from one-dimensional to two-dimensional behavior, depending on whether $kR⪡1$ or $kR⪢1$, where $k$ is the plasmon wave vector and $R$ is the radius of the tube, is discussed. The Aharonov-Bohm effect pertaining to plasma oscillations in superconducting tubes and rings, resulting in an oscillatory behavior of the plasmon frequency as a function of the magnetic flux, with a flux quantum period $hc/2e$ (analog of the Little-Parks effect) is studied. The amplitude of the oscillations is proportional to ${(\ensuremath{\xi}/R)}^{2}$, where $\ensuremath{\xi}$ is the superconducting coherence length.

Low‐frequency plasma oscillations at Mars during the October 2003 solar storm

The powerful x‐class flare which occurred on the Sun on 28 October 2003 had important effects on plasma environments throughout the solar system. We present here observations of the effects at Mars from the Mars Global Surveyor (MGS) Magnetometer/Electron Reflectometer experiment. In particular we focus on the changes in the nature of the magnetic oscillations observed at an altitude of 400 km (MGS's current orbital altitude) during the passage of the solar storm. We find that strong, regular oscillations are observed in both the B∥ and B⊥ components of the magnetic field at all solar zenith angles. We emphasize in particular the powerful, coherent oscillations observed in the normally quiet nightside region. These oscillations carry power at the proton gyrofrequency and at and below the oxygen gyrofrequency. This implies that ions of planetary origin are interacting with the solar wind plasma and raises the possibility that significant atmospheric loss may occur during the passage of large solar storms at Mars.

HF Conductivity of Parametrically Unstable Magnetized Plasma

In this paper the absorption processes of LH and UH pump waves in magnetized homogeneous and inhomogeneous plasmas are investigated. We determine the RF power absorbed in the plasma when the external pump parametrically excites low-frequency plasma oscillations (purely growing convective cells, modified convective cell modes and electron drift waves). Expressions for the effective absorption length of the external RF wave as a function of various plasma parameters are derived. For typical parameters of a hot ionospheric plasma, absorption length values are calculated.

Investigation of low-frequency waves in plasma-filled microwave oscillators

The excitation of microwave oscillations by an electron beam in a hybrid plasma waveguide—a slow-wave structure (a sequence of inductively coupled resonators) with a plasma-filled transport channel—is studied both experimentally and theoretically. It is shown that the governing role in the generation of microwaves and their transmission to a feeder line is played by the spatial and temporal plasma-density variations associated with low-frequency ion plasma oscillations. The microwave pressure gives rise to low-frequency plasma oscillations with a rise time shorter than their period. This nonlinear mechanism for the excitation of low-frequency oscillations has a threshold in terms of the microwave power. The unsteady character of the spatial distribution of the plasma density results in intermittent microwave generation and shortens the duration of microwave pulses.

Theoretical studies on the observation of the low-frequency plasma oscillation and its coupling with the Carlson-Goldman mode in dirty quasi-two-dimensional superconductors

Theoretical studies on the observation of the low-frequency plasma oscillation and its coupling with the Carlson-Goldman mode in dirty quasi-two-dimensional superconductors

Low frequency resonance properties of Phase-Slip Centers

The features of the signal amplitude-oscillation frequency dependence in the presence of the non-Josephson oscillation (NJO) effect are studied. They are found to be related to the resonance inside the sample. The analysis of the experimental results supports the idea that the resonance is due to low frequency plasma oscillations.

Energy conservation law for low-frequency plasma oscillations

A basic description of low-frequency plasma oscillations within the context of renormalized plasma electrodynamics is applied to derive a reduced energy conservation law with regard to finite Larmor radius (FLR) and nonlinear effects. The energy density for low-frequency flute oscillations in inhomogeneous plasmas is calculated as a quadratic functional of the electric field strength for arbitrary regimes of nonlinear interaction (either weak or strong). The nonlinear equilibrium spectrum of low-frequency FLR oscillations is derived.

Influence of thermal diffusion on plasma instabilities in the lower part of the ionosphere

The dispersion relation for low-frequency plasma oscillations in the lower part of the ionosphere has been deduced by taking the temperature dependence of the electron-neutral collision frequency into account. It is shown that the threshold values for short wavelength instabilities can be significantly reduced when the collision frequency increases with temperature.

Energy-loss rate and enhanced diffusion due to a low-frequency plasma oscillation

We have studied the relation of the energy-loss rate and the enhanced diffusion with the amplitude of spontaneously excited low-frequency plasma oscillation in a current-carrying argon plasma. The experimental results (radial distributions of the electron density, electric floating potential, and electric field) and the theoretical model that is developed showed the important role of the low-frequency plasma oscillations on the additional power losses of the plasma. Also, the energy-loss rate has been studied as a function of the plasma radius.

Observations of Nonlinear Behavior in a Low-Pressure Discharge Column

Sudden and abrupt jumps in the plasma density and discharge current of low-pressure magnetized argon and helium plasmas are observed. These jumps are found to depend on the discharge bias voltage, the neutral gas pressure, and the magnetic field strength and occur with a substantial hysteresis in those parameters. These jumps are accompanied by the onset of intense and coherent low-frequency plasma oscillations. In addition, under certain conditions, the radial density profile of the plasma is found to be significantly different following a jump. Some possibly related plasma instabilities are discussed.

Experimental observation of ionization waves

Ionization waves are a type of low-frequency plasma oscillation found in dc glow discharges. A conceptual discussion of this wave process is presented and an inexpensive and simple apparatus to observe standing ionization waves is described. Some simple measurements were made and found to agree well with empirical ideas that are discussed.

2181. Experimental investigation of parametric excitation of low-frequency plasma oscillations in magnetic field: L L Pasechnik and V F Semenyuk,Zh Tekh Fiz,45 (4), 1975, 779–782 ( in Russian)

2181. Experimental investigation of parametric excitation of low-frequency plasma oscillations in magnetic field: L L Pasechnik and V F Semenyuk,Zh Tekh Fiz,45 (4), 1975, 779–782 ( in Russian)

Low-frequency plasma oscillations in junction diodes

Low-frequency plasma oscillations in junction diodes

Oscillations of electrostatically trapped particles

A kinetic theory of longitudinal ionic oscillations is presented which pertains to an earlier hypothesis that low frequency plasma oscillations monitored in the wake of Ariel I Satellite are due to ions trapped in the potential trough behind a moving satellite. The treatment is one-dimensional. A self-consistent potential distribution in the trough is obtained from a linearized analysis, suitable for a potential trough of small depth. Dispersion relation of the plasma oscillations for the trapped particles are obtained. The conditions for instability of the oscillation are given. The present analysis further confirms the earlier hypothesis as stated above.

The method of geometrical optics for differential equations of the fourth order as applied to low-frequency plasma oscillations

The theory of osculations of a spatially inhomogeneous plasma [1] draws substantially on the theory of geometrical optics as applied to differential equations of the second order. The theory of asymptotic solutions for equations of the second order has now been thoroughly developed [2]. The quasi-classical quantization rules determining the spectrum of eigenvalues of such equations are written in the form of the well-known Bohr -Sommerfeld integrals [3]. However, in analyzing the spectrum of oscillations of an inhomogeneous plasma it is insufficient in many cases to confine oneself to equations of the second order. For example, in an inhomogeneous magnetoactive plasma, even when the thermal motion of the particles is neglected, the field equations, generally speaking, reduce to a differential equation of the fourth order. Equations of the fourth order also arise in investigating the stability of the hydrodynamical flow of a viscous fluid [4].

Effect of a cold-plasma component on the stability of an inhomogeneous hot plasma

By applying geometrical optics, the author investigates the effect of a volume component of cold plasma on the low-frequency oscillation spectrum and on the local stability conditions of an inhomogeneous hot plasma contained by a strong magnetic field. Allowance is made for the curvature of the lines of force of the containing magnetic field by introducing an effective gravitational field. The author points to the existence in such a system of a low-frequency oscillation branch, that is “electron” sound, with a frequency proportional to the square root of the ratio of hot to cold plasma densities. For very low cold-plasma densities a hydrodynamic growth of long-wave and short-wave oscillations of the inhomogeneous plasma results from the excitation of an “electron-acoustic” oscillation branch by the gravitational drift of the ions. For higher cold-plasma densities one observes a resonant growth of low-frequency plasma oscillations with frequencies approaching those of the diamagnetic particle drift. Further increases in the cold-plasma density such that the frequency of the electron sound exceeds all the drift frequencies of the plasma lead to an expansion of the stability region of the inhomogeneous plasma.

New Type of Two-Stream Plasma Instability

The stability of one of the low-frequency plasma oscillation modes is examined from the standpoint of two-fluid theory. It is found that when the scattering time is short enough, a density perturbation may actually grow at the frequency of one of the acoustic modes. In this short scattering time regime, the phase difference between the electron and hole perturbation velocities can lead to a net growth of the perturbation. If the damping effects of diffusion and recombination of excess carriers can be overcome by the growing mechanism, the net result would be a growing instability. The results presented are applicable to both gaseous and solid-state plasmas. Some discussion is given on which solid-state materials might exhibit this new instability. It is found that InSb is best, but that bismuth might also be suitable.