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Acoustic solitons in dusty plasmas revisited ; Cattaert, Tom ; in AIP Conference Proceedings (2005), (799), 502-5 The usual description of dust-modified ion-acoustic and dust-acoustic solitons in plasmas containing negative dust is in terms of Boltzmann distributions for the hotter species. In the dust-modified ion ... [more ▼] The usual description of dust-modified ion-acoustic and dust-acoustic solitons in plasmas containing negative dust is in terms of Boltzmann distributions for the hotter species. In the dust-modified ion-acoustic regime, besides positive potential solitons, negative ones can also be generated, for non-Boltzmann as well as for Boltzmann electrons, subject to very mild conditions that were previously ignored or given for weakly nonlinear solutions only. In the dust-acoustic domain in plasmas with negatively charged dust, however, only negative potential solitons can occur, even when the lighter species have non-Boltzmann distributions [less ▲] Detailed reference viewed: 17 (2 ULg)Oblique propagation of large amplitude electromagnetic solitons in pair plasmas ; Cattaert, Tom in Physics of Plasmas (2005), 12(3), 8 Waves in pair plasmas have a fundamentally different dispersion due to the equal charge-to-mass ratios between negative and positive charges, which mix different time scales. In view of possible ... [more ▼] Waves in pair plasmas have a fundamentally different dispersion due to the equal charge-to-mass ratios between negative and positive charges, which mix different time scales. In view of possible applications, e. g., to electron-positron and fullerene pair plasmas, stationary nonlinear structures are investigated for oblique or perpendicular propagation with respect to the static magnetic field. A generalized large amplitude extraordinary mode is found, having a linearly polarized electric field that is orthogonal to both the directions of wave propagation and of the static magnetic field. When the Alfvenic Mach number is in a suitably defined range, the pseudoenergy integral admits solutions with a negative wave electric field, in a cone around parallel propagation, and solutions with a positive wave electric field, at all angles of propagation. The exact analytical solution describing these solitary waves has also been obtained. At weakly nonlinear amplitudes, the solutions reduce to familiar solutions of the Korteweg-de Vries or modified Korteweg- de Vries equations. (C) 2005 American Institute of Physics. [less ▲] Detailed reference viewed: 24 (2 ULg)Potential hill electron-acoustic solitons and double layers in plasmas with two electron species Cattaert, Tom ; ; in Physics of Plasmas (2005), 12(4), 10 In the description of (high-frequency) electron-acoustic solitons in a plasma consisting of positive ions, cool electrons, and hot electrons, the dynamics of the ions plays no essential role and can be ... [more ▼] In the description of (high-frequency) electron-acoustic solitons in a plasma consisting of positive ions, cool electrons, and hot electrons, the dynamics of the ions plays no essential role and can be eliminated from the treatment, the ions merely providing a constant positive background. It is widely believed that in such a plasma only potential dip solitary waves can be generated. In a potential dip the cooler electrons are compressed and the hotter electrons rarefied, both being driven towards their sonic points, the cooler ones from above, the hotter ones from below. This transonic feature gives rise to the solitary wave. However, it is shown that the restriction to potential dip solitons is due to the neglect of the inertia of the hot electrons, implicitly or explicitly assumed by most-authors. If hot electron inertia is retained, there exists a parameter range where-potential hill solitary waves are formed, with both electron species being driven away from their sonic points This has important consequences for the reinterpretation of several astrophysical phenomena involving two-electron plasmas. (c) 2005 American Institute of Physics. [less ▲] Detailed reference viewed: 32 (1 ULg)Large amplitude parallel propagating electromagnetic oscillitons Cattaert, Tom ; in Physics of Plasmas (2005), 12(1), 7 Earlier systematic nonlinear treatments of parallel propagating electromagnetic waves have been given within a fluid dynamic approach, in a frame where the nonlinear structures are stationary and various ... [more ▼] Earlier systematic nonlinear treatments of parallel propagating electromagnetic waves have been given within a fluid dynamic approach, in a frame where the nonlinear structures are stationary and various constraining first integrals can be obtained. This has lead to the concept of oscillitons that has found application in various space plasmas. The present paper differs in three main aspects from the previous studies: first, the invariants are derived in the plasma frame, as customary in the Sagdeev method, thus retaining in Maxwell's equations all possible effects. Second, a single differential equation is obtained for the parallel fluid velocity, in a form reminiscent of the Sagdeev integrals, hence allowing a fully nonlinear discussion of the oscilliton properties, at such amplitudes as the underlying Mach number restrictions allow. Third, the transition to weakly nonlinear whistler oscillitons is done in an analytical rather than a numerical fashion. (C) 2005 American Institute of Physics. [less ▲] Detailed reference viewed: 13 (2 ULg)Compressive and rarefactive electron-acoustic solitons and double layers in space plasmas ; Cattaert, Tom ; in Space Science Reviews (2005), 121(1-4), 299-311 Space observations in several near-Earth environments have revealed the presence of positive-potential, large-amplitude electrostatic structures, associated with high-frequency disturbances, and ... [more ▼] Space observations in several near-Earth environments have revealed the presence of positive-potential, large-amplitude electrostatic structures, associated with high-frequency disturbances, and indicative of electron dynamics. Earlier models proposed in terms of electron-acoustic solitary waves in a two-electron-temperature plasma were inadequate, because only negative potential structures could thus be obtained, whereas the observations point to positive potential structures. In this paper, it is shown that the theoretical restriction to negative potential solitons is due to the neglect of the inertia of the hot electrons, implicitly or explicitly assumed in previous papers. If hot electron inertia is retained, however, there exists a parameter range where positive potential solitary waves are formed, which can have important consequences for the re-interpretation of several astrophysical phenomena involving two-electron-temperature plasmas. [less ▲] Detailed reference viewed: 25 (2 ULg)Envelope solitons associated with electromagnetic waves in a magnetized pair plasma Cattaert, Tom ; ; in Physics of Plasmas (2005), 12(1), 6 The amplitude modulation of magnetic field-aligned circularly polarized electromagnetic (CPEM) waves in a magnetized pair plasma is reexamined. The nonlinear frequency shifts include the effects of the ... [more ▼] The amplitude modulation of magnetic field-aligned circularly polarized electromagnetic (CPEM) waves in a magnetized pair plasma is reexamined. The nonlinear frequency shifts include the effects of the radiation pressure driven density and compressional magnetic field perturbations as well as relativistic particle mass variations. The dynamics of the modulated CPEM wave packets is governed by a nonlinear Schrodinger equation, which has attractive and repulsive interaction potentials for fast and slow CPEM waves. The modulational stability of a constant amplitude CPEM wave is studied by deriving a nonlinear dispersion from the cubic Schrodinger equation. The fast (slow) CPEM mode is modulationally unstable (stable). Possible stationary amplitude solutions of the modulated fast (slow) CPEM mode can be represented in the form of bright and dark/gray envelope electromagnetic soliton structures. Localized envelope excitations can be associated with the microstructures in pulsar magnetospheres and in laboratory pair magnetoplasmas. (C) 2005 American Institute of Physics. [less ▲] Detailed reference viewed: 16 (1 ULg)Erratum: "Envelope solitons associated with electromagnetic waves in a magnetized pair plasma" [vol 12, pg 012319, 2005] Cattaert, Tom ; ; in Physics of Plasmas (2005), 12(5), 1 Detailed reference viewed: 7 (4 ULg)Gas-dynamic description of electrostatic solitons ; Cattaert, Tom ; et al in Journal of Plasma Physics (2004), 70 The nonlinear propagation of electrostatic solitary structures in unmagnetized multispecies plasmas is studied in the wave frame, where they are stationary, via the recently developed McKenzie approach as ... [more ▼] The nonlinear propagation of electrostatic solitary structures in unmagnetized multispecies plasmas is studied in the wave frame, where they are stationary, via the recently developed McKenzie approach as an alternative to the more usual Sagdeev pseudo-potential method. This way of looking at the problem brings out the gas-dynamic aspects, which then allow a straightforward characterization of the solitary wave possibilities in terms of the species' own sonic points and of the global charge neutral points. A qualitative discussion of ion-, dust- and electron-acoustic solitary waves is given in terms of these concepts and the results are contrasted with those obtained by other methods. Ion-acoustic solitons can be shown to always be compressive, without invoking simplifying assumptions such as cold ions or Boltzmann electrons. Beam-plasmas can also be studied, as in the elect non-acoustic solitary wave model for the spiky structures of the broadband electrostatic noise observed in the auroral regions of the Earth's magnetosphere. Such solitons always show a potential dip. [less ▲] Detailed reference viewed: 14 (2 ULg)Nonlinear electromagnetic modes in astrophysical plasmas with dust distributions ; Cattaert, Tom in Astronomy and Astrophysics (2004), 421(1), 17-21 A derivative nonlinear Schrodinger equation is obtained for parallel electromagnetic modes in plasmas containing polydisperse charged dust. The coefficient of the dispersive term in that equation is ... [more ▼] A derivative nonlinear Schrodinger equation is obtained for parallel electromagnetic modes in plasmas containing polydisperse charged dust. The coefficient of the dispersive term in that equation is dominated by the dust rather than the (plasma) ions, and polydisperse dust yields a larger coefficient in absolute value than an equivalent monodisperse description. This leads to a significant broadening of the nonlinear structure due to the presence of polydisperse rather than monodisperse dust, the latter contributing in itself already to a substantial increase in the width of envelope solitons compared to dust-free plasmas. When modelling the charged dust by a power-law distribution occurring in planetary ring and other astrophysical systems, it depends very much on the power-law index whether the smaller or the larger grains are more important. For certain indices the more numerous smaller grains determine the charge and mass densities, but the larger dust dominates the linear and nonlinear dispersive effects. [less ▲] Detailed reference viewed: 11 (1 ULg)Magnetosonic modes with a beam of dust or secondary ions ; ; Cattaert, Tom et al in Physics of Plasmas (2004), 11(10), 4589-4595 Charged dust particles on near-Keplerian orbits in planetary rings drift relative to the corotating background plasma, and this relative streaming may drive dust-modified magnetosonic waves unstable ... [more ▼] Charged dust particles on near-Keplerian orbits in planetary rings drift relative to the corotating background plasma, and this relative streaming may drive dust-modified magnetosonic waves unstable. Using a magnetofluid model, this situation is revisited, and it is shown that a correct description can be obtained at frequencies and Doppler shifts that are small compared to the electron gyrofrequency. An excellent agreement is reached between the analytical approximation and the numerical solution of the full or reduced dispersion law. A very low-frequency, small wave number beam instability may occur at supermagnetosonic beam velocities of the dust component, but, based on the existing data, is unlikely to play a role in planetary rings. Instability is also found for submagnetosonic speeds, which might be relevant to Saturn's E ring. (C) 2004 American Institute of Physics. [less ▲] Detailed reference viewed: 25 (3 ULg)Kinetic theory of dust-acoustic waves in plasmas with dust distributions and charge fluctuations Cattaert, Tom ; in IEEE Transactions on Plasma Science (2004), 32(2), 537-541 Dust-acoustic waves in dusty plasmas are studied in a kinetic context incorporating dust distributions and charge fluctuations, two of the main features that distinguish dusty or complex from ordinary ... [more ▼] Dust-acoustic waves in dusty plasmas are studied in a kinetic context incorporating dust distributions and charge fluctuations, two of the main features that distinguish dusty or complex from ordinary plasmas. This is done by deriving a generalized Vlasov equation in an extended phase space. No specific charging model is used so that the results are generic. [less ▲] Detailed reference viewed: 22 (2 ULg)Large amplitude solitary electromagnetic waves in electron-positron plasmas ; Cattaert, Tom in Physics of Plasmas (2004), 11(6), 3078-3082 Waves in electron-positron plasmas have fundamentally different dispersion characteristics due to the equal charge-to-mass ratios between negative and positive charges, which mix different timescales, and ... [more ▼] Waves in electron-positron plasmas have fundamentally different dispersion characteristics due to the equal charge-to-mass ratios between negative and positive charges, which mix different timescales, and are of interest in understanding aspects of pulsars and active galactic nuclei, where astrophysical electron-positron plasmas occur. Earlier systematic nonlinear treatments of parallel propagating electromagnetic waves via a reductive perturbation analysis had indicated unusual results, namely a vector equivalent of the modified Korteweg-de Vries equation. The latter is nonintegrable except in the case of linear polarization when it becomes equivalent to the scalar (integrable) modified Korteweg-de Vries equation. Here large amplitude purely stationary nonlinear solitary waves are studied in their own reference frame via the McKenzie approach. The behavior of the wave magnetic field can be expressed through an energy integral that involves the Mach number of the structure. Possible solitons are super-Alfvenic and occur symmetrically for positive or negative fields, owing to the obvious symmetry between positive and negative charges with the same mass. The limits on the allowable Mach numbers and soliton amplitudes have also been computed. (C) 2004 American Institute of Physics. [less ▲] Detailed reference viewed: 15 (1 ULg)Waves in complex plasmas with dust distributions (charge/size/mass) revisited ; Cattaert, Tom in IEEE Transactions on Plasma Science (2004), 32(2), 653-658 Polydisperse dust, as in astrophysical observations, occurs in a range of sizes, compositions, charges, and masses, with corresponding changes to linear dispersion laws. At the fluid level the charged ... [more ▼] Polydisperse dust, as in astrophysical observations, occurs in a range of sizes, compositions, charges, and masses, with corresponding changes to linear dispersion laws. At the fluid level the charged dust can be treated as a discrete collection of different fluids or as the continuous limit over a charge range. On the other hand, one global dust fluid needs appropriate model equations, derivable from a Klimontovich or extended Vlasov approach, in which charge, mass, and/or size enter as extra phase space variables. Due to differing charge-to-mass weightings, this is sometimes quite involved. An extended kinetic theory allows for a more correct picture, including possible microscopic damping mechanisms, but quickly becomes very unwieldy. An intermediate procedure is to use results for monodisperse dust and integrate afterwards over dust distributions. This cannot be applied blindly, so that it is necessary to check results on their applicability and consistency. Selected applications have,been treated for parallel electromagnetic, oblique electrostatic (and possibly self-gravitational), and fluid dust-Bernstein modes, to illustrate the methodological aspects of this part of dusty plasma physics. [less ▲] Detailed reference viewed: 11 (2 ULg)Whistler oscillitons revisited: the role of charge neutrality? ; Cattaert, Tom ; et al in Nonlinear Processes in Geophysics (2004), 11(4), 447-452 When studying transverse modes propagating parallel to a static magnetic field, an apparent contradiction arises between the weakly nonlinear results obtained from the derivative nonlinear Schrodinger ... [more ▼] When studying transverse modes propagating parallel to a static magnetic field, an apparent contradiction arises between the weakly nonlinear results obtained from the derivative nonlinear Schrodinger equation, predicting envelope solitons (where the amplitude is stationary in the wave frame, but the phase is not), and recent results for whistler oscillitons, indicating that really stationary structures of large amplitude are possible. Revisiting this problem in the fluid dynamic approach, care has been taken not to introduce charge neutrality from the outset, because this not only neglects electric stresses compared to magnetic stresses, which is reasonable, but could also imply from Poisson's equation a vanishing of the wave electric field. Nevertheless, the fixed points of the remaining equations are the same, whether charge neutrality is assumed from the outset or not, so that the solitary wave solutions at not too large amplitudes will be very similar. This is home out by numerical simulations of the solutions under the two hypotheses, showing that the lack of correspondence with the DNLS envelope solitons indicates the limitations of the reductive perturbation approach, and is not a consequence of assuming charge neutrality. [less ▲] Detailed reference viewed: 30 (1 ULg)Dust-acoustic modes in plasmas with dust distributions and charge fluctuations ; ; Cattaert, Tom in New Journal of Physics (2003), 5 Charge fluctuations in dusty plasmas are discussed starting from charge, mass, momentum and current equations for the combined dusty plasma. This allows a generic description of low-frequency waves in ... [more ▼] Charge fluctuations in dusty plasmas are discussed starting from charge, mass, momentum and current equations for the combined dusty plasma. This allows a generic description of low-frequency waves in plasmas with dust distributions, and leads to the damping and other modifications of the dust-acoustic and related modes, like generalized dust-Coulomb modes. [less ▲] Detailed reference viewed: 20 (2 ULg)Electromagnetic modes in dusty plasmas with charge and mass distributions ; Cattaert, Tom in Physics of Plasmas (2003), 10(4), 956-962 Electromagnetic modes in dusty plasmas are studied for polydisperse dust grains with a distribution in charge and mass. Owing to the different charge and mass weightings of the velocities, there occurs an ... [more ▼] Electromagnetic modes in dusty plasmas are studied for polydisperse dust grains with a distribution in charge and mass. Owing to the different charge and mass weightings of the velocities, there occurs an infinite chain of equations of motion, coupled through the magnetic part of the Lorentz force. Depending on the frequency and associated convergence regimes, one has to close the chain in ascending or in descending order. Both series together lead to the polydisperse dispersion law that is a generalization of monodisperse or size distributed dust. Power-law distributions typical for heliospheric plasmas are discussed as an application. (C) 2003 American Institute of Physics. [less ▲] Detailed reference viewed: 8 (1 ULg)Kwantumveldentheorie met onbepaalde massa Cattaert, Tom Master's dissertation (2002) Detailed reference viewed: 32 (6 ULg) |
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