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1.
  • Stenflo, Lennart, et al. (författare)
  • Nonlinear beam generated plasma waves as a source for enhanced plasma and ion acoustic lines
  • 2011
  • Ingår i: Physics of Plasmas. - : American Institute of Physics (AIP). - 1070-664X .- 1089-7674. ; 18:15, s. 052107-1-052107-14
  • Tidskriftsartikel (refereegranskat)abstract
    • Observations by, for instance, the EISCAT Svalbard Radar (ESR) demonstrate that the symmetry of the naturally occurring ion line in the polar ionosphere can be broken by an enhanced, nonthermal, level of fluctuations (naturally enhanced ion-acoustic lines, NEIALs). It was in many cases found that the entire ion spectrum can be distorted, also with the appearance of a third line, corresponding to a propagation velocity significantly slower than the ion acoustic sound speed. It has been argued that selective decay of beam excited primary Langmuir waves can explain some phenomena similar to those observed. We consider a related model, suggesting that a primary nonlinear process can be an oscillating two-stream instability, generating a forced low frequency mode that does not obey any ion sound dispersion relation. At later times, the decay of Langmuir waves can give rise also to enhanced asymmetric ion lines. The analysis is based on numerical results, where the initial Langmuir waves are excited by a cold dilute electron beam. By this numerical approach, we can detect fine details of the physical processes, in particular, demonstrate a strong space-time intermittency of the electron waves in agreement with observations. Our code solves the full Vlasov equation for electrons and ions, with the dynamics coupled through the electrostatic field derived from Poisson's equation. The analysis distinguishes the dynamics of the background and beam electrons. This distinction simplifies the analysis for the formulation of the weakly nonlinear analytical model for the oscillating two-stream instability. The results have general applications beyond their relevance for the ionospheric observations.
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2.
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3.
  • Bingham, Robert, et al. (författare)
  • Ion acceleration by Alfven waves on auroral field lines
  • 2013
  • Ingår i: Physica Scripta. - : Institute of Physics. - 0031-8949 .- 1402-4896. ; 87:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Observations of ion acceleration along auroral field lines at the boundary of the plasma sheet and tail lobe of the Earth show that the energy of the ions increases with decreasing density. The observations can be explained by ion acceleration through Landau resonance with kinetic Alfven waves (KAWs) such that k(A) . v(i) = omega(A), where k(A) is the wave vector, v(i) is the ion resonance velocity and omega(A) is the Alfven wave frequency. The ion resonance velocities are proportional to the Alfven velocity which increases with decreasing density. This is in agreement with the data if the process is occurring at the plasma sheet tail lobe boundary. A quasi-linear theory of ion acceleration by KAWs is presented. These ions propagate both down towards and away from the Earth. The paths of the Freja and Polar satellites indicate that the acceleration takes place between the two satellites, between 1Re and 5Re. The downward propagating ions develop a horseshoe-type of distribution which has a positive slope in the perpendicular direction. This type of distribution can produce intense lower hybrid wave activity, which is also observed. Finally, the filamentation of shear Alfven waves is considered. It may be responsible for large-scale density striations.
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4.
  • Bingham, Robert, et al. (författare)
  • Solar coronal heating by plasma waves
  • 2010
  • Ingår i: Journal of Plasma Physics. - : Cambridge university. - 0022-3778 .- 1469-7807. ; 76:2, s. 135-158
  • Tidskriftsartikel (refereegranskat)abstract
    • The solar coronal plasma is maintained at temperatures of millions of degrees, much hotter than the photosphere, which is at a temperature of just 6000 K. In this paper, the plasma particle heating based on the kinetic theory of wave–particle interactions involving kinetic Alfvén waves and lower-hybrid drift modes is presented. The solar coronal plasma is collisionless and therefore the heating must rely on turbulent wave heating models, such as lower-hybrid drift models at reconnection sites or the kinetic Alfvén waves. These turbulent wave modes are created by a variety of instabilities driven from below. The transition region at altitudes of about 2000 km is an important boundary chromosphere, since it separates the collision-dominated photosphere/chromosphere and the collisionless corona. The collisionless plasma of the corona is ideal for supporting kinetic wave–plasma interactions. Wave–particle interactions lead to anisotropic non-Maxwellian plasma distribution functions, which may be investigated by using spectral analysis procedures being developed at the present time.
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5.
  • Brodin, Gert, et al. (författare)
  • A new decay channel for upper-hybrid waves
  • 2016
  • Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 91:10
  • Tidskriftsartikel (refereegranskat)abstract
    • We look here at a three-wave interaction process involving only electrostatic waves in an electron plasma with stationary ions. Special attention is given to the case with an upper-hybrid wave as a pump wave, where a new decay channel is pointed out. The corresponding growth rate is calculated.
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6.
  • Brodin, Gert, et al. (författare)
  • A simple electron plasma wave
  • 2017
  • Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 381:11, s. 1033-1035
  • Tidskriftsartikel (refereegranskat)abstract
    • Considering a class of solutions where the density perturbations are functions of time, but not of space, we derive a new exact large amplitude wave solution for a cold uniform electron plasma. This result illustrates that most simple analytical solutions can appear even if the density perturbations are large.
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7.
  • Brodin, Gert, et al. (författare)
  • Alfven wave interactions within the Hall-MHD description
  • 2013
  • Ingår i: Journal of Plasma Physics. - : Cambridge University Press (CUP). - 0022-3778 .- 1469-7807. ; 79, s. 909-911
  • Tidskriftsartikel (refereegranskat)abstract
    • We show that comparatively simple expressions for the Alfven wave coupling coefficients can be deduced from the well-known Hall-magnetohydrodynamics (MHD) model equations.
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8.
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9.
  • Brodin, Gert, et al. (författare)
  • Large amplitude electron plasma oscillations
  • 2014
  • Ingår i: Physics Letters A. - : Elsevier. - 0375-9601 .- 1873-2429. ; 378:22-23, s. 1632-1635
  • Tidskriftsartikel (refereegranskat)abstract
    • We consider a cold plasma in order to find new large-amplitude wave solutions in the long-wavelength limit. Accordingly we derive two generic coupled equations which describe the energy exchange between the electrostatic and electromagnetic waves. A new kind of quasi-periodic behavior is found. Our derivations may be considered as a prerequisite to extended studies of stimulated Raman scattering for cases where the wave amplitudes are so large that standard perturbation techniques are not applicable.
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10.
  • Brodin, Gert, et al. (författare)
  • Nonlinear dynamics of a cold collisional electron plasma
  • 2017
  • Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 24:12
  • Tidskriftsartikel (refereegranskat)abstract
    • We study the influence of collisions on the dynamics of a cold non-relativistic plasma. It is shown that even a comparatively small collision frequency can significantly change the large amplitude wave solution.
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11.
  • Brodin, Gert, et al. (författare)
  • Nonlinear dynamics of large amplitude modes in a magnetized plasma
  • 2014
  • Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 21:12
  • Tidskriftsartikel (refereegranskat)abstract
    • We derive two equations describing the coupling between electromagnetic and electrostatic oscillations in one-dimensional geometry in a magnetized cold and non-relativistic plasma. The nonlinear interaction between the wave modes is studied numerically. The effects of the external magnetic field strength and the initial electromagnetic polarization are of particular interest here. New results can, thus, be identified. 
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12.
  • Brodin, Gert, et al. (författare)
  • Nonlinear wave interactions of kinetic sound waves
  • 2015
  • Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 33:8, s. 1007-1010
  • Tidskriftsartikel (refereegranskat)abstract
    • We reconsider the nonlinear resonant interaction between three electrostatic waves in a magnetized plasma. The general coupling coefficients derived from kinetic theory are reduced here to the low-frequency limit. The main contribution to the coupling coefficient we find in this way agrees with the coefficient recently presented in Annales Geophysicae. But we also deduce another contribution which sometimes can be important, and which qualitatively agrees with that of an even more recent paper. We have thus demonstrated how results derived from fluid theory can be improved and generalized by means of kinetic theory. Possible extensions of our results are outlined.
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13.
  • Brodin, Gert, 1963-, et al. (författare)
  • Stimulated Brillouin scattering in magnetized plasmas
  • 2013
  • Ingår i: Journal of Plasma Physics. - : Cambridge University Press. - 0022-3778 .- 1469-7807. ; 79:Special Issue 06, s. 983-986
  • Tidskriftsartikel (refereegranskat)abstract
    • Previous theory for stimulated Brillouin scattering is reconsidered and generalized. We introduce an effective ion sound velocity that turns out to be useful in describing scattering instabilities.
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14.
  • Brodin, Gert, et al. (författare)
  • Three-wave coupling coefficients for a magnetized plasma
  • 2012
  • Ingår i: Physica Scripta. - Bristol : Institute of Physics. - 0031-8949 .- 1402-4896. ; 85:3, s. 035504-
  • Tidskriftsartikel (refereegranskat)abstract
    • The resonant interaction between three waves in a uniform magnetized plasma is reconsidered. Starting from previous kinetic expressions, which contain a general but too little used result, we are able to improve the formulae. This leads to an explicit expression for the three-wave coupling coefficient which applies for arbitrary wave propagation in a magnetized Vlasov plasma.
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15.
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16.
  • Brodin, Gert, et al. (författare)
  • Three-wave coupling coefficients for perpendicular wave propagation in a magnetized plasma
  • 2015
  • Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 22:10
  • Tidskriftsartikel (refereegranskat)abstract
    • The resonant interaction between three waves in a uniform magnetized plasma is reconsidered. Starting from previous kinetic expressions, we limit our investigation to waves propagating perpendicularly to the external magnetic field. It is shown that reliable results can only be obtained in the two-dimensional case, i.e., when the wave vectors have both x and y components. 
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17.
  • Brodin, Gert, et al. (författare)
  • Wave Generation in a Warm Magnetized Multi-Component Plasma
  • 2014
  • Ingår i: Contributions to Plasma Physics. - : Wiley. - 0863-1042 .- 1521-3986. ; 54:7, s. 623-625
  • Tidskriftsartikel (refereegranskat)abstract
    • The resonant interaction between three waves propagating perpendicularly to an external magnetic field in a plasma is considered. We present the explicit expressions for the three wave coupling coefficients of a warm multi-component plasma. The results of previous work on the generation of THz radiation by laser plasma interaction are significantly improved. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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18.
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19.
  • Eliasson, Bengt, et al. (författare)
  • Full-scale simulation study of stimulated electromagnetic emissions: The first ten milliseconds
  • 2010
  • Ingår i: JOURNAL OF PLASMA PHYSICS. - : Cambridge University Press. - 0022-3778 .- 1469-7807. ; 76, s. 369-375
  • Tidskriftsartikel (refereegranskat)abstract
    • A full-scale numerical study is performed of the nonlinear interaction between a large-amplitude electromagnetic wave and the Earths ionosphere; and of the stimulated electromagnetic emission emerging from the turbulent layer, during the first 10 milliseconds after switch-on of the radio transmitter. The frequency spectra are downshifted in frequency and appear to emerge from a region somewhat below the cutoff of the O mode, which is characterized by Langmuir wave turbulence and localized Langmuir envelopes trapped in ion density cavities. The spectral features of escaping O-mode waves are very similar to those observed in experiments. The frequency components of Z-mode waves, trapped in the region between the O- and Z-mode cutoffs show strongly asymmetric and downshifted spectra.
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20.
  • Eliasson, B, et al. (författare)
  • Preface to special issue
  • 2013
  • Ingår i: Journal of Plasma Physics. - : Cambridge University Press. - 0022-3778 .- 1469-7807. ; 79:6, s. 981-981
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • This special issue is devoted to the memory of Professor Padma Kant Shukla, who passed away 26 January 2013 on his travel to New Delhi, India to receive the prestigious Hind Rattan (Jewel of India) award. Padma was born in Tulapur, Uttar Pradesh, India, 7 July 1950, where he grew up and got his education. He received a PhD degree in Physics at the Banaras Hindu University, Varanasi, Uttar Pradesh, India, in 1972, under the supervision of late Prof. R. N. Singh, and a second PhD degree in Theoretical Plasma Physics from Umeå University in Sweden in 1975, under the supervision of Prof. Lennart Stenflo. He worked at the Faculty of Physics & Astronomy, Ruhr-University Bochum, Germany since January 1973, where he was a permanent faculty member and Professor of International Affairs, a position that was created for him to honour his international accomplishments and reputation.
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21.
  • Gradov, O. M., et al. (författare)
  • Basic properties of nonlinear surface charge waves at a plasma boundary
  • 2018
  • Ingår i: Physics Letters A. - : ELSEVIER SCIENCE BV. - 0375-9601 .- 1873-2429. ; 42-43, s. 3083-3085
  • Tidskriftsartikel (refereegranskat)abstract
    • The nonlinear properties of surface charges are here analyzed under ideal conditions. We thus deduce a new single equation from the wellknown equations which govern the cold electron plasma motion. Simple formulas that describe the propagation of surface charge perturbations along the plasma boundary are also found. (C) 2018 Elsevier B.V. All rights reserved.
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22.
  • Journal of Plasma Physics vol 76 issue 3-4 : special issue in honor of professor Padma Kant Shukla on the occasion of his 60th birthday
  • 2010. - 76
  • Proceedings (redaktörskap) (övrigt vetenskapligt/konstnärligt)abstract
    • It is our great pleasure to dedicate this special issue of Journal of Plasma Physics to our dear friend and colleague Professor Padma Kant Shukla on the occasion of his 60th birthday on 7th July 2010. Padma is one of the most prominent and productive scientists in plasma physics and in neighboring fields, and has published more than 1300 papers in scientific journals. It has for some time been the aim of his friends to honor him on this occasion, and earlier this year we sent out invitations to distinguished scientists who have collaborated with Padma over the years. The response has been overwhelming, and we collected 43 manuscripts, covering a diverse range of topics in plasma physics, which are now published in this issue. We believe that these papers reflect some of the impact of Padma's research in plasma physics.
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23.
  • Karimov, AR, et al. (författare)
  • Flow oscillations in radial expansion of an inhomogeneous plasma layer
  • 2011
  • Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 375:27, s. 2629-2636
  • Tidskriftsartikel (refereegranskat)abstract
    • The cylindrically symmetric radial evolution of an inhomogeneous plasma layer expanding into vacuum is investigated nonperturbatively by first determining the spatial structure of the plasma flow structure. The evolution is then governed by a set of ordinary differential equations. The effect of the plasma inhomogeneity on the nonlinear coupling among the electron and ion flow components and oscillations is investigated
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24.
  • Karimov, A. R., et al. (författare)
  • A new class of exact solutions for Vlasov-Poisson plasmas
  • 2016
  • Ingår i: Physica Scripta. - : IOP PUBLISHING LTD. - 0031-8949 .- 1402-4896. ; 91:11, s. 114002-
  • Tidskriftsartikel (refereegranskat)abstract
    • A new class of exact solutions of the Vlasov-Poisson equations based on the Jeans theorem is considered. The self-consistent solutions for the evolution of the system from given initial particle distributions make use of particular invariants of particle motion with predetermined spatial structure. The relation between the time-dependent coefficients of the latter and the macroscopic plasma quantities, or moments of the distribution function, are obtained. As an illustration, the evolution of an expanding plasma with oscillations of the electron and ion expansion fronts is presented.
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25.
  • Karimov, A R, et al. (författare)
  • Asymmetric oscillatory expansion of a cylindrical plasma
  • 2013
  • Ingår i: Journal of Plasma Physics. - : Cambridge University Press. - 0022-3778 .- 1469-7807. ; 79:6, s. 1007-1009
  • Tidskriftsartikel (refereegranskat)abstract
    • Asymmetric oscillatory expansion of a cylindrical plasma layer into vacuum is investigated analytically by solving the fluid equations of the electrons and ions together with the Maxwell's equations. For the problem considered, it is found that the asymmetrical flow components are strongly affected by the symmetrical components, but not the vice versa.
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26.
  • Karimov, A. R., et al. (författare)
  • Expansion of a cold non-neutral plasma slab
  • 2014
  • Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 21, s. 122304-
  • Tidskriftsartikel (refereegranskat)abstract
    • Expansion of the ion and electron fronts of a cold non-neutral plasma slab with a quasi-neutral core bounded by layers containing only ions is investigated analytically and exact solutions are obtained. It is found that on average, the plasma expansion time scales linearly with the initial inverse ion plasma frequency as well as the degree of charge imbalance, and no expansion occurs if the cold plasma slab is stationary and overall neutral. However, in both cases, there can exist prominent oscillations on the electron front.
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27.
  • Karimov, A R, et al. (författare)
  • Large quasineutral electron velocity oscillations in radial expansion of an ionizing plasma
  • 2012
  • Ingår i: Physics of Plasmas. - : American Institute of Physics (AIP). - 1070-664X .- 1089-7674. ; 19:9, s. 092118-
  • Tidskriftsartikel (refereegranskat)abstract
    • Radial expansion of an ionizing gas or plasma cylinder into vacuum is investigated. An exact model for the evolution of the density and velocity fields of the electrons, ions, and neutrals, including the effect of photo and electron-impact ionization on the flow characteristics is developed and solutions obtained. A quasineutral nonlinear electrostatic mode involving rapid oscillations in the electron velocity but not in the density can occur in the expanding plasma. The mode turns out to be almost unaffected by weak ionization.
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28.
  • Karimov, A. R., et al. (författare)
  • Properties and evolution of anisotropic structures in collisionless plasmas
  • 2016
  • Ingår i: Journal of Plasma Physics. - : CAMBRIDGE UNIV PRESS. - 0022-3778 .- 1469-7807. ; 82
  • Tidskriftsartikel (refereegranskat)abstract
    • A new class of exact electrostatic solutions of the Vlasov-Maxwell equations based on the Jeanss theorem is proposed for studying the evolution and properties of two-dimensional anisotropic plasmas that are far from thermodynamic equilibrium. In particular, the free expansion of a slab of electron-ion plasma into vacuum is investigated.
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29.
  • Karimov, A. R., et al. (författare)
  • The processes of nonequilibrium exchange in rotating plasma flows
  • 2016
  • Ingår i: II CONFERENCE ON PLASMA & LASER RESEARCH AND TECHNOLOGIES. - : IOP Publishing.
  • Konferensbidrag (refereegranskat)abstract
    • The mechanisms of energy/momentum exchange in rotating and compressing plasma flows have been discussed. It has been shown that such flows are capable of transforming the energy of different degrees of freedom into the energy of one degree owing to the interaction of the coupled nonlinear radial, axial and azimuthal electron-ion oscillations. These processes may lead to the additional acceleration of the flow in azimuthal or axial direction so they might be instrumental for the creation of space thrusters employing pulse transformations for propulsion.
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30.
  • Lu, Gaimin, et al. (författare)
  • Fully nonlinear electrostatic waves in electron-positron plasmas
  • 2010
  • Ingår i: JOURNAL OF PLASMA PHYSICS. - : Cambridge University Press. - 0022-3778 .- 1469-7807. ; 76, s. 267-275
  • Tidskriftsartikel (refereegranskat)abstract
    • Fully nonlinear electrostatic waves in a plasma containing electrons, positrons, and ions are investigated by solving the governing equations exactly. It is found that both smooth and spiky quasistationary waves exist, and large-amplitude waves necessarily have large-phase velocities, but small-amplitude waves can be both fast and slow.
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31.
  • Mendonca, J. T., et al. (författare)
  • Acoustic-gravity waves in the atmosphere: from Zakharov equations to wave-kinetics
  • 2015
  • Ingår i: Physica Scripta. - : IOP Publishing: Hybrid Open Access. - 0031-8949 .- 1402-4896. ; 90:5, s. 055001-
  • Tidskriftsartikel (refereegranskat)abstract
    • We develop a wave-kinetic description of acoustic-gravity (AG) waves in the atmosphere. In our paper the high frequency spectrum of waves is described as a gas of quasi-particles. Starting from the Zakharov-type of equations, where coupling between fast and slow density perturbations is considered, we derive the corresponding wave-kinetic equations, written in terms of an appropriate Wigner function. This provides an alternative description for the nonlinear interaction between the two dispersion branches of the AG waves.
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32.
  • Mendonca, J. T., et al. (författare)
  • Wave-kinetic description of atmospheric turbulence
  • 2014
  • Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 89, s. 125004-
  • Tidskriftsartikel (refereegranskat)abstract
    • We propose a wave-kinetic description of atmospheric turbulence, where the turbulence spectrum is described as a gas of quasi-particles. We apply this description to the case of zonal structures in the atmosphere, which can be excited by internal gravity wave turbulence. A general expression for the instability growth rates is derived, and the particular example of a nearly mono-kinetic turbulent spectrum is discussed.
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33.
  • Onishchenko, O. G., et al. (författare)
  • Dust devil generation
  • 2014
  • Ingår i: Physica Scripta. - : IOP Publishing: Hybrid Open Access. - 0031-8949 .- 1402-4896. ; 89:7, s. 075606-
  • Tidskriftsartikel (refereegranskat)abstract
    • The equations describing axi-symmetric nonlinear internal gravity waves in an unstable atmosphere are derived. A hydrodynamic model of a dust devil generation mechanism in such an atmosphere is investigated. It is shown that in an unstably stratified atmosphere the convective plumes with poloidal motion can grow exponentially. Furthermore, it is demonstrated that these convective plumes in an atmosphere with weak large scale toroidal motion are unstable with respect to three-dimensional dust devil generation.
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34.
  • Onishchenko, O. G., et al. (författare)
  • Finite ion Larmor radius effects in magnetic curvature-driven Rayleigh-Taylor instability
  • 2011
  • Ingår i: AIP Conference Proceeding Joint ITER-IAEA-ICTP Advanced Workshop on Fusion and Plasma Physics. - : American Institute of Physics (AIP). - 9780735410411 ; , s. 68-73
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Incomplete finite ion Larmor radius stabilization of the magnetic Rayleigh-Taylor (RT)instability is investigated. In contrast to the previous studies the effects of both the gravity and magnetic field curvature are taken into account. New model hydrodynamic equations describing nonlinear flute waves with arbitrary spatial scales have been derived. Particular attention is paid to the waves with spatial scales of the order of the ion Larmor radius. In the linear approximation a Fourier transform of these equations yields a generalized dispersion relation for flute waves. The condition for gravity and magnetic curvature at which the instability cannot be stabilized by the finite ion Larmor radius effects is found. It is shown that in the absence of the magnetic curvature the complete stabilization arises due to the cancellation of gravitational and diamagnetic drifts. However, when the magnetic curvature drift is taken into account this synchronization is violated and the RT instability is stabilized at more complex conditions. Furthermore, the dependence of the instability growth rate on the equilibrium plasma parameters is investigated.
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35.
  • Onishchenko, O G, et al. (författare)
  • Stabilization of magnetic curvature-driven Rayleigh-Taylor instabilities
  • 2012
  • Ingår i: Journal of Plasma Physics. - : Cambridge University Press (CUP). - 0022-3778 .- 1469-7807. ; 78, s. 93-97
  • Tidskriftsartikel (refereegranskat)abstract
    • The finite ion Larmor radius (FLR) stabilization of the magnetic curvature-driven Rayleigh Taylor (MCD RT) instability in a low beta plasma with nonzero ion temperature gradient is investigated. Finite electron temperature effects and ion temperature perturbations are incorporated. A new set of nonlinear equations for flute waves with arbitrary wavelengths as compared with the ion Larmor radius in a plasma with curved magnetic field lines is derived. Particular attention is paid to the waves with spatial scales of the order of the ion Larmor radius. In the linear limit, a Fourier transform of these equations yields an improved dispersion relation for flute waves. The dependence of the M CD RT instability growth rate on the equilibrium plasma parameters and the wavelengths is studied. The condition for which the instability cannot be stabilized by the FLR effects is found.
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36.
  • Onishchenko, O G, et al. (författare)
  • The magnetic Rayleigh-Taylor instability and flute waves at the ion Larmor radius scales
  • 2011
  • Ingår i: PHYSICS OF PLASMAS. - : American Institute of Physics. - 1070-664X .- 1089-7674. ; 18:2, s. 022106-
  • Tidskriftsartikel (refereegranskat)abstract
    • The theory of flute waves (with arbitrary spatial scales compared to the ion Larmor radius) driven by the Rayleigh-Taylor instability (RTI) is developed. Both the kinetic and hydrodynamic models are considered. In this way we have extended the previous analysis of RTI carried out in the long wavelength limit. It is found that complete finite ion Larmor radius stabilization is absent when the ion diamagnetic velocity attains the ion gravitation drift velocity. The hydrodynamic approach allowed us to deduce a new set of nonlinear equations for flute waves with arbitrary spatial scales. It is shown that the previously deduced equations are inadequate when the wavelength becomes of the order of the ion Larmor radius. In the linear limit a Fourier transform of these equations yields the dispersion relation which in the so-called Pade approximation corresponds to the results of the fully kinetic treatment. The development of such a theory gives us enough grounds for an adequate description of the RTI stabilization by the finite ion Larmor radius effect.
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37.
  • Pokhotelov, O.A., et al. (författare)
  • Physical mechanisms for electron mirror and field swelling modes
  • 2013
  • Ingår i: Physica Scripta. - : Institute of Physics. - 0031-8949 .- 1402-4896. ; 87:6, s. 065303-
  • Tidskriftsartikel (refereegranskat)abstract
    • Ion mirror instability is dominant in planetary and cometary magnetosheaths and other high-beta plasmas where the ions are hotter than the electrons. It is associated with a zero-frequency non-propagating mode with the wave vector nearly perpendicular to the ambient magnetic field. The counterparts of this instability in hot electron plasmas are the field swelling and electron mirror instabilities. A theory for these instabilities was developed more than two decades ago (Basu B and Coppi B 1982 Phys. Rev. Lett. 48 799, 1984 Phys. Fluids 27 1187) within the framework of a fluid model. The connection between the two types of instabilities has been analyzed in (Migliuolo S 1986 J. Geophys. Res. 91 7981). In contrast to these papers, we shall here adopt the standard quasi-hydrodynamic approach that is usually used for the study of mirror instabilities. To analyze the electron mirror and field swelling instabilities, we will only use the perpendicular balance condition and the Liouville theorem. We have found that such a description is easier to understand and gives us increased physical insight into the basic physical features of both these instabilities.
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38.
  • Shukla, Nitin, et al. (författare)
  • Magnetization of a quantum plasma by photons
  • 2010
  • Ingår i: PHYSICS LETTERS A. - : Elsevier Science B.V., Amsterdam.. - 0375-9601 .- 1873-2429. ; 374:15-16, s. 1749-1750
  • Tidskriftsartikel (refereegranskat)abstract
    • It is shown that the ponderomotive force of large-amplitude electromagnetic waves (photons), which includes the electron spin current and exchange potential contributions in a quantum plasma, can generate magnetic fields. The present result can account for the magnetic fields in dense compact astrophysical objects and in the next generation laser-solid density plasma interaction experiments.
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39.
  • Shukla, P K, et al. (författare)
  • Acoustic gravity tornadoes in the atmosphere
  • 2012
  • Ingår i: Physica Scripta. - : Institute of Physics. - 0031-8949 .- 1402-4896. ; 86:6
  • Tidskriftsartikel (refereegranskat)abstract
    • It is shown that three-dimensional (3D) acoustic gravity waves (AGWs) in the atmosphere can appear in the form of acoustic gravity tornadoes (AGTs) characterized by twisted density structures or density ropes carrying orbital angular momentum. For our purposes, we use a previously obtained 3D wave equation for AGWs, and show that this equation in the paraxial approximation admits solutions in the form of Laguerre-Gauss acoustic gravity vortex beams or AGTs/AG whirls with twisted density structures supporting the dynamics of the AGTs.
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40.
  • Shukla, P.K., et al. (författare)
  • Alfvenic shock waves in a collisional magnetoplasma
  • 2011
  • Ingår i: Physics Letters A. - : Elsevier Science B.V., Amsterdam.. - 0375-9601 .- 1873-2429. ; 375:24, s. 2371-2373
  • Tidskriftsartikel (refereegranskat)abstract
    • Compressional Alfvenic shock waves in a cold collisional magnetoplasma are investigated. For this purpose, we use the hydrodynamic equations and Faradays law to derive the governing nonlinear equations for the compressional Alfven waves. It is shown that the latter can appear in the form of Alfvenic shock waves.
  •  
41.
  • Shukla, Padma Kant, et al. (författare)
  • Alfvénic Solitary and Shock Waves in Plasmas
  • 2012
  • Ingår i: Multi-scale Dynamical Processes in Space and Astrophysical Plasmas. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783642304415 - 9783642304422 ; , s. 129-141
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
    • We present a review of nonlinear Alfvénic solitary and shock waves in a magnetized electron-ion plasma. The dynamics of these nonlinear dispersive Alfvén waves is governed by the two-fluid equations, coupled with Faraday’s and Ampère’s laws. First, we demonstrate the existence of large amplitude compressional Alfvénic solitary and shock waves propagating across the external magnetic field in a warm electron-ion magnetoplasma. It is found that these nonlinear structures can exist in well defined speed ranges above the Alfvén speed, and their widths are several times larger than the electron skin depths. Second, we study the formation of nonlinear slow magnetosonic solitary (SMS) waves propagating almost perpendicular to the external magnetic field direction. The propagation speed of the SMS waves is below the Alfvén speed and their width is a few ion skin depth in a collisionless magnetoplasma. The nonlinear dispersive Alfvén waves, as discussed here, can be associated with localized electromagnetic field excitations in magnetized laboratory and space plasmas that are composed of magnetized electrons and ions.
  •  
42.
  • Shukla, Padma Kant, et al. (författare)
  • Compressional Alfvénic shocks and solitary waves in plasmas
  • 2011
  • Ingår i: Joint ITER-IAEA-ICTP Advanced Workshop on Fusion and Plasma Physics. - : American Institute of Physics (AIP). - 9780735410411 ; , s. 2-14
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • We present a review of recent results for compressional Alfvénic shocks and solitary waves in electron-ion and electron-positron plasmas, which are governed by the two-fluid equations, coupled with Faraday's and Ampère's laws. We consider large amplitude compressional Alfvénic shock waves and solitary pulses in a warm collisional electron-ion (e-i) magnetoplasma, and large amplitude compressional Alfvénic solitary pulses in magnetized e-i and electron-positron (e-p) plasmas. These nonlinear structures can exist in well defined speed ranges above the Alfvén speed. They can be associated with localized electromagnetic field excitations in magnetized laboratory and space plasmas that are composed of electrons, ions, and/or positrons.
  •  
43.
  • Shukla, P.K., et al. (författare)
  • Dark and grey compressional dispersive Alfven solitons in plasmas
  • 2011
  • Ingår i: Physics of Plasmas. - : American Institute of Physics. - 1070-664X .- 1089-7674. ; 18:6, s. 064511-
  • Tidskriftsartikel (refereegranskat)abstract
    • The amplitude modulation of compressional dispersive Alfven (CDA) waves in a low-beta plasma is considered. It is shown that the dynamics of modulated CDA waves is governed by a cubic nonlinear Schrodinger equation, which depicts the formation of a dark/grey envelope CDA soliton.
  •  
44.
  • Shukla, P K, et al. (författare)
  • Electromagnetic solitary pulses in a magnetized electron-positron plasma
  • 2011
  • Ingår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. - : American Physical Society. - 1539-3755 .- 1550-2376. ; 84:3, s. 037401-
  • Tidskriftsartikel (refereegranskat)abstract
    • A theory for large amplitude compressional electromagnetic solitary pulses in a magnetized electron-positron (e-p) plasma is presented. The pulses, which propagate perpendicular to the external magnetic field, are associated with the compression of the plasma density and the wave magnetic field. Here the solitary wave magnetic field pressure provides the restoring force, while the inertia comes from the equal mass electrons and positrons. The solitary pulses are formed due to a balance between the compressional wave dispersion arising from the curl of the inertial forces in Faradays law and the nonlinearities associated with the divergence of the electron and positron fluxes, the nonlinear Lorentz forces, the advection of the e-p fluids, and the nonlinear plasma current densities. The compressional solitary pulses can exist in a well-defined speed range above the Alfven speed. They can be associated with localized electromagnetic field excitations in magnetized laboratory and space plasmas composed of electrons and positrons.
  •  
45.
  • Shukla, P K, et al. (författare)
  • Generation of magnetic fields by the ponderomotive force of electromagnetic waves in dense plasmas
  • 2010
  • Ingår i: JOURNAL OF PLASMA PHYSICS. - : Cambridge University Press. - 0022-3778 .- 1469-7807. ; 76, s. 25-28
  • Tidskriftsartikel (refereegranskat)abstract
    • We show that the non-stationary ponderomotive force of a, large-amplitude electromagnetic move in a very dense quantum plasma wall streaming degenerate electrons can spontaneously create d.c. magnetic fields. The present result can account for the seed magnetic fields in compact astrophysical objects and in the next-generation intense laser-solid density, plasma interaction experiments.
  •  
46.
  •  
47.
  • Shukla, P K, et al. (författare)
  • Instability of plasma waves caused by incoherent photons in dense plasmas
  • 2010
  • Ingår i: JOURNAL OF PLASMA PHYSICS. - : Cambridge University Press. - 0022-3778. ; 76:Part 6 Sp. Iss. SI, s. 845-851
  • Tidskriftsartikel (refereegranskat)abstract
    • We consider the nonlinear instability of modified Langmuir and ion-sound waves caused by partially coherent photons in dense quantum plasmas. In our model, the dynamics of the photons is governed by a wave kinetic equation. The evolution equations for the Langmuir and ion-sound waves are deduced from the quantum hydrodynamic equations accounting for the incoherent photon pressure, the quantum statistical electron pressure, and the quantum Bohm force acting on the degenerate electrons. The governing equations are Fourier analyzed to obtain nonlinear dispersion relations. The latter are analyzed to predict instability of the modified Langmuir and ion-sound waves in the presence of partially coherent photons. Possible applications of our investigation to the next generation of intense laser-solid dense plasma experiments and compact dense astrophysical bodies are mentioned.
  •  
48.
  • Shukla, P K, et al. (författare)
  • Large-amplitude Alfvenic shocks in a collisional magnetoplasma
  • 2011
  • Ingår i: Europhysics letters. - : Institute of Physics / EDP Sciences. - 0295-5075 .- 1286-4854. ; 95:4, s. 45001-
  • Tidskriftsartikel (refereegranskat)abstract
    • A theory for large-amplitude Alfvenic shocks across the external magnetic field in a collisional magnetoplasma is presented. For this purpose, we use the continuity and momentum equations for the electrons and ions, together with Amperes and Faradays laws, to derive the governing nonlinear equations for large-amplitude compressional Alfvenic waves. It is found that the latter can appear in the form of large-amplitude Alfvenic shocks that propagate with the super-Alfvenic speed.
  •  
49.
  • Shukla, Padma Kant, et al. (författare)
  • Magnetization of plasmas
  • 2010
  • Ingår i: New Frontiers in Advanced Plasma Physics. - : AIP. ; , s. 1-6
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Wecritically examine and evaluate several physical mechanisms that are responsiblefor the seed magnetic fields in plasmas. The plasma magnetizationis attributed to sources that foster motion of the backgroundplasma electrons against the ions. The resulting space charge electricfield and currents, in turn, are detrimental for the plasmamagnetization.
  •  
50.
  • Shukla, P K, et al. (författare)
  • Nonlinear propagation of coherent electromagnetic waves in a dense magnetized plasma
  • 2012
  • Ingår i: Physics of Plasmas. - : American Institute of Physics (AIP). - 1070-664X .- 1089-7674. ; 19:7, s. 072302-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present an investigation of the nonlinear propagation of high-frequency coherent electromagnetic waves in a uniform quantum magnetoplasma. Specifically, we consider nonlinear couplings of right-hand circularly polarized electromagnetic-electron-cyclotron (CPEM-EC) waves with dispersive shear Alfven (DSA) and dispersive compressional Alfven (DCA) perturbations in plasmas composed of degenerate electron fluids and non-degenerate ion fluids. Such interactions lead to amplitude modulation of the CPEM-EC wave packets, the dynamics of which is governed by a three-dimensional nonlinear Schrodinger equation (NLSE) with the frequency shift arising from the relativistic electron mass increase in the CPEM-EC fields and density perturbations associated with the DSA and DCA perturbations. Accounting for the electromagnetic and quantum forces, we derive the evolution equation for the DSA and DCA waves in the presence of the magnetic field-aligned ponderomotive force of the CPEM-EC waves. The NLSE and the driven DSA and DCA equations are then used to investigate the modulational instability. The relevance of our investigation to laser-plasma interaction experiments and the cores of white dwarf stars is pointed out.
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