Theory, simulation, and observation of discrete eigenmodes associated with lower hybrid solitary structures

Schuck, P. W.; Seyler, C. E.; Pinçon, Jean-Louis; Bonnell, J. W.; Kintner, P. M.

doi:10.1029/97ja02922

Cited by 56 publications

(90 citation statements)

References 38 publications

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“…This treatment showed a continuous spectrum of right-hand rotating modes above the ambient lower hybrid frequency f LH and a discrete spectrum of trapped left-hand rotating waves below f LH , that cannot propagate outside the depletion. The results very well describe the properties of LHCs observed on sounding rockets (Pinçon et al, 1997;Bonnell et al, 1998;Schuck et al, 1998) and also of a Cluster satellite observation (Tjulin et al, 2003) for the single event for which data rates allowed such detailed analysis.…”

Section: Introductionsupporting

confidence: 55%

“…(24) becomes Bessel's equation, for which the solutions are well known (Watson, 1944). This special case has been investigated by Schuck et al (1998), where the density profile was given by…”

Section: The Density Cavity and Rotating Wave Modesmentioning

confidence: 99%

“…This condition means that the ions can be considered unmagnetized and the electrons fully magnetized. Following the derivation of Schuck et al (1998) for a cold plasma with electrostatic linear perturbations we arrive at the following set of equations…”

Section: The Basic Equationsmentioning

confidence: 99%

“…It is clear that extensions of present cold electrostatic theory for LHC cavity modes to also include thermal and electromagnetic effects without sacrificing the Hall term are needed. The considerations above, however, show that it should still be worthwhile to further explore the cold electrostatic theory introduced by Schuck et al (1998). An attractive feature of this model is that it leads to a single Bessellike linear ordinary differential equation, which is very suitable for model studies.…”

Section: Introductionmentioning

confidence: 99%

“…Seyler (1994) introduced a model of LHCs as twodimensional cavity modes in a finite cavity of parabolic shape, with the boundary condition of vanishing electric field at infinity. Schuck et al (1998) described the wave field in LHCs in terms of electrostatic cavity modes in a finite parabolic density depletion, but included a parallel wave number and considered the scattering problem with propagating waves at infinity. This treatment showed a continuous spectrum of right-hand rotating modes above the ambient lower hybrid frequency f LH and a discrete spectrum of trapped left-hand rotating waves below f LH , that cannot propagate outside the depletion.…”

Section: Introductionmentioning

confidence: 99%

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Localization of wave fields in lower hybrid cavities

2004

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Abstract. We investigate lower hybrid wave trapping in cylindrically symmetric density depletions in the electrostatic approximation. Our investigation is inspired by previous observations of such trapping by spacecraft in the auroral region at altitudes up to about 2000 km, and the recent discovery of this phenomenon at altitudes above 20 000 km in the inner magnetosphere. No particular shape is assumed for the density depletion, which need not be strictly zero outside some value of the radial coordinate r. Important previously known properties concerning parabolic density depletions extending to finite r are shown to hold also for arbitrary shapes and infinite extent: for a given parallel wave number k z , modes below the ambient lower hybrid frequency f LH are trapped in the density depletion (in the sense that they are evanescent outside the cavity), have a discrete spectrum and rotate in a left-handed sense, while there is a continuous spectrum of freely propagating right-handed rotating modes above f LH . New results are such that even though the density depletion may go to zero slowly with increasing r, and thus be essentially infinite in extent, there is a maximum distance within which a trapped mode with given k z and azimuthal mode number m may propagate. Furthermore, we find that for any monotonic density cavity and given k z , there is a local relation between plasma density gradient and the lowest possible frequency that can be trapped. We combine our theoretical results with spacecraft observations to find an upper bound on k z . Our examples indicate that the length of the cavities is larger than the width by a factor of at least 100.

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Section: Introductionsupporting

confidence: 55%

Section: The Density Cavity and Rotating Wave Modesmentioning

confidence: 99%

Section: The Basic Equationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Localization of wave fields in lower hybrid cavities

2004

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Parametric coupling of whistler waves with gyrating ion beam in a complex plasma

Pahuja,

Kumar,

Sharma

et al. 2024

Contrib. Plasma Phys

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This manuscript examines the non‐linear interaction between the negative energy beam cyclotron mode and the high‐frequency whistler waves. The negative energy beam mode is supported in the vicinity of the beam gyro‐frequency harmonics by a gyrating ion beam with ring‐shaped velocity distribution. Using a gyrating ion beam, we have examined how dust charge variations affect the parametric up‐conversion of high‐frequency whistler waves (WWs) into a side band wave and a low‐frequency mode. For the linked modes, a non‐linear dispersion relation is obtained. It is demonstrated that the WWs divided by beam gyro‐frequency harmonics are up‐converted by a gyrating ion‐beam frequency. An expression for the ion cyclotron mode wave growth rate has been obtained. The estimation of the turbulence growth rate takes into account for the typical parameters of existing dusty plasma. It has been observed that an increased growth rate is reported with a rise in the pump wave amplitude, beam gyro‐frequency, number density of dust grains, and the relative density of dust grains. However, a decline in the growth rate has been observed with increasing gyrating ion beam density and dust grain's size.

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