Wave collapse at the lower-hybrid resonance

Theoretical description of experiments on excitation of magnetic field perturbations correlated with large amplitude lower-hybrid (LH) wave bursts in a high-voltage linear plasma discharge is presented. It is shown that the magnetic field perturbations, which are excited in the experiments mostly in the paramagnetic sense, are associated with the development of the magneto-modulational processes. The theoretical results are compared with the experimental data using the following parameters: the values of the magnitude of the magnetic field perturbations; the direction of the vector of the magnetic field perturbation; the correlation between the magnetic field perturbations and the electron density perturbations. It is shown that for LH waves propagating in one plane theoretical predictions are in a good agreement with the experimental results. Keywords:high-current linear plasma discharge, lower-hybrid wave, modulational interaction, magnetic field perturbation, magneto-modulational processThe experiments in a high-current linear plasma discharge carried out at the Nihon University [1] have shown the possibility of the excitation of magnetic field perturbations related to intense lower-hybrid turbulence. The value of the magnitude of the perturbations is |δB| ≈ 10 G and |δB|/|B 0 | ≈ 0.01, where B 0 is the unperturbed magnetic field. The characteristic features of the observations are: 1) the magnetic field perturbations are excited in the experiments mostly in the paramagnetic sense; 2) there is a correlation between the magnetic field perturbations and the electron density perturbations; 3) the power spectrum of the associated electric field fluctuations shows widely broadened profile and has multiple peaks around the lower-hybrid (LH) frequency.All the results show that the excitation of the magnetic field perturbations can be associated with the development of the magneto-modulational processes [2]. We check this assumption. Equation for magneto-modulational perturbationsThe theoretical investigation of the magneto-modulational processes with the participation of LH waves has been performed for tokamak plasmas [3,4]. The conditions of the

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“…In this case the result for δn~ (E × E * ) z coincides with that found in Ref. [7]. The sign of δn is not determined.…”

Section: Electron Density Perturbationssupporting

confidence: 76%

Magnetic field perturbations correlated with large amplitude lower-hybrid waves in a high-voltage linear plasma discharge

et al. 2003

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“…We calculated estimates of threshold wave amplitudes for the modulational instability [e.g., Shapiro et al, 1993] and then converted the electric field amplitudes to magnetic field amplitudes [e.g., Huba et al, 1978]. We find that 10/11 of the MIXED modes satisfy the threshold criteria for the modulational instability.…”

Section: Interpretation Of Wave Modesmentioning

confidence: 99%

Electromagnetic waves and electron anisotropies downstream of supercritical interplanetary shocks

et al. 2013

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[1] We present waveform observations of electromagnetic lower hybrid and whistler waves with f ci ≪ f < f ce downstream of four supercritical interplanetary shocks using the Wind search coil magnetometer. The whistler waves were observed to have a weak positive correlation between dB and normalized heat flux magnitude and an inverse correlation with T eh /T ec . All were observed simultaneous with electron distributions satisfying the whistler heat flux instability threshold and most with T ⊥ h /T k h > 1.01. Thus, the whistler mode waves appear to be driven by a heat flux instability and cause perpendicular heating of the halo electrons. The lower hybrid waves show a much weaker correlation between dB and normalized heat flux magnitude and are often observed near magnetic field gradients. A third type of event shows fluctuations consistent with a mixture of both lower hybrid and whistler mode waves. These results suggest that whistler waves may indeed be regulating the electron heat flux and the halo temperature anisotropy, which is important for theories and simulations of electron distribution evolution from the Sun to the Earth.

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“…In the case of large-amplitude LFWs, strong lower hybrid (LH) turbulence could be produced Khazanov et al, 1996]. Strong LH turbulence results in plasma heating and acceleration [Shapiro et al, 1993], the formation of ion conics [Chang and Coppi, 1981;Retterer et al, 1986], and possibly the saturation of Alfv6n oscillations in the ring current region . Weak LH turbulence can also lead to important changes in the plasma state; for example, Ornelchenko et al [1994] found that the LH "fan" instability may accelerate ions.…”

Section: Description Of the Problemmentioning

confidence: 99%

Lower hybrid oscillations in multicomponent space plasmas subjected to ion cyclotron waves

Khazanov¹,

Krivorutsky²,

Moore³

et al. 1997

J. Geophys. Res.

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Abstract. It is found that in multicomponent plasmas subjected to Alfv6n or fast magnetosonic waves, such as are observed in regions of the outer plasmasphere and ring currentplasmapause overlap, lower hybrid oscillations are generated. The addition of a minor heavy ion component to a proton-electron plasma significantly lowers the low-frequen9y electric wave amplitude needed for lower hybrid wave excitation. It is found that the lower hybrid wave energy density level is determined by the nonlinear process of induced scattering by ions and electrons; hydrogen ions in the region of resonant velocities are accelerated; and nonresonant particles are weakly heated due to the induced scattering. For a given example, the ligh.t resonant ions have an energy gain factor of 20, leading to the development of a high-energy tail in the H + distribution function due to low-frequency waves. By interacting with charged particles, the waves influence the behavior of the plasma as a whole, and therefore wave effects must be included in corresponding models. Ganguli and Palmadesso [1987, 1988], Singh [1988], Singh and Torr [1990], Brown et al. [1991, 1995], and Lin et al. [1992, 1994] took into account effects from the low-frequency (LF) electrostatic turbulence, and they demonstrated that wave-particle interactions lead to significant effects on the evolution of the core plasma distribution functions.In developing a mathematical model to describe plasma transport in the magnetosphere-ionosphere system that accounts for the active wave processes which occur there, we must develop a general scheme to include an analysis of the dispersion characteristics of the medium in order to choose suitable wave modes, a wave-particle interaction mechanism, and a system of hydrodynamical equations governing ma6ro-scopic plasma parameters which properly accounts for the presence of wave-particle interactions. One basis for this scheme's development has been described elsewhere Khazanov et al. [1996] assumed that the plasma consists of only electrons and protons and that the LFW electric field is strong enough not only to make the relative proton velocity greater than its thermal velocity, but also to create strong LHW turbulence. From (1), however, it can be seen that the LFW energy density needed for LHW excitation may be lower in the presence of a heavy ion component. Since the magnetosphere and ionosphere have multicomponent plasmas, it can be supposed that LHWs can be excited in such plasmas by LFWs with amplitudes less than that needed for a proton-electron plasma.This leads us to the problem of LFW interaction with a multicomponent plasma due to LHW excitation. In accordance with this problem, we will study the following questions:1 LHW excitation are analyzed, and an estimation of particle

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Wave collapse at the lower-hybrid resonance

Cited by 120 publications

References 10 publications

Magnetic field perturbations correlated with large amplitude lower-hybrid waves in a high-voltage linear plasma discharge

Magnetic field perturbations correlated with large amplitude lower-hybrid waves in a high-voltage linear plasma discharge

Electromagnetic waves and electron anisotropies downstream of supercritical interplanetary shocks

Lower hybrid oscillations in multicomponent space plasmas subjected to ion cyclotron waves

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