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  • 1. Abdelsalam, UM
    et al.
    Moslem, WM
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics. Institut für Theoretische Physik IV, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, D-44780 Bochum, Germany; Nonlinear Physics Centre & Center for Plasma Science and Astrophysics, Ruhr-Universität Bochum, D-44780 Bochum, Germany; Max-Planck-Institut für extraterrestrische Physik, D-85741 Garching, Germany; GoLP/Instituto Superior Técnico, 1049-001 Lisbon, Portugal; CCLRC Centre for Fundamental Physics, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon 0X11 0QX, UK; SUPA Department of Physics, University of Strathclyde, Glasgow G 40NG, UK; School of Physics, Faculty of Science & Agriculture, University of Kwazulu-Natal, Durban 4000, South Africa; Department of Physics, CITT, Islamabad, Pakistan.
    Ion-acoustic solitary waves in a dense pair-ion plasma containing degenerate electrons and positrons2008In: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 372, no 22, p. 4057-4061Article in journal (Refereed)
    Abstract [en]

    Fully nonlinear propagation of ion-acoustic solitary waves in a collisionless dense/quantum electron-positron-ion plasma is investigated. The electrons and positrons are assumed to follow the Thomas-Fermi density distribution and the ions are described by the hydrodynamic equations. An energy balance-like equation involving a Sagdeev-type pseudo-potential is derived. Finite amplitude solutions are obtained numerically and their characteristics are discussed. The small-but finite-amplitude limit is also considered and an exact analytical solution is obtained. The present studies might be helpful to understand the excitation of nonlinear ion-acoustic solitary waves in a degenerate plasma such as in superdense white dwarfs.

  • 2. Abdelsalam, UM
    et al.
    Moslem, WM
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics. Institut für Theoretische Physik IV, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, D-44780 Bochum, Germany; Nonlinear Physics Centre & Center for Plasma Science and Astrophysics, Ruhr-Universität Bochum, D-44780 Bochum, Germany; Max-Planck-Institut für Extraterrestrische Physik, D-85741 Garching, Germany; GoLP/Instituto Superior Técnico, 1049-001 Lisbon, Portugal; CCLRC Centre for Fundamental Physics, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon 0X11 0QX, UK; SUPA Department of Physics, University of Strathclyde, Glasgow G 40NG, UK; School of Physics, Faculty of Science & Agriculture, University of Kwazulu-Natal, Durban 4000, South Africa; Department of Physics, CITT, Islamabad, Pakistan.
    Localized electrostatic excitations in a Thomas-Fermi plasma containing degenerate electrons2008In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 15, no 5, article id 052303Article in journal (Refereed)
    Abstract [en]

    By using the Thomas-Fermi electron density distribution for quantum degenerate electrons, the hydrodynamic equations for ions, and the Poisson equation, planar and nonplanar ion-acoustic solitary waves in an unmagnetized collisionless plasma are investigated. The reductive perturbation method is used to derive cylindrical and spherical Korteweg-de Vries equations. Numerical solutions of the latter are presented. The present results can be useful in understanding the features of small but finite amplitude localized ion-acoustic solitary pulses in a degenerate plasma.

  • 3. Ali, S
    et al.
    Moslem, WM
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics. Institut für Theoretische Physik IV, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, D-44780 Bochum, Germany; Max-Planck Institut für extraterrestrische Physik, D-85741 Garching, Germany; GoLP/Instituto Superior Técnico, 1049-001 Lisbon, Portugal; CCLRC Centre for Fundamental Physics, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon 0X11 0QX, UK; SUPA Department of Physics, University of Strathclyde, Glasgow G 40NG, UK.
    Wake potential with mobile positive/negative ions in multicomponent dusty plasmas2008In: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 372, no 44, p. 6650-6652Article in journal (Refereed)
    Abstract [en]

    We employ the test charge approach to calculate the electrostatic potential for a test charge in a multicomponent dusty plasma, whose constituents are the Boltzmann distributed electrons, mobile positive and negative ions, and immobile positive/negative charged dust particles. By using the modified dielectric constant of the dust-ion-acoustic (DIA) waves, the Debye screening and wake potentials are obtained. It is found that the presence of mobile negative ions significantly modify the DIA speed and the wake potential. The present results are relevant to polar mesosphere and microelectronic in the context of charged particle attraction and repulsion.

  • 4. Ali, S
    et al.
    Shukla, Padma K
    Umeå University, Faculty of Science and Technology, Department of Physics. Institut für Theoretische Physik IV, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, D-44780 Bochum, Germany; Max-Planck Institut für extraterrestrische Physik, D-85741 Garching, Germany, GoLP/Instituto Superior Técnico, 1049-001 Lisbon, Portugal, Centre for Fundamental Physics, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon 0X11 0QX, United Kingdom, and Department of Physics, University of Strathclyde, Glasgow, Scotland, United Kingdom .
    Dust acoustic solitary waves in a quantum plasma2006In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 13, no 2, article id 022313Article in journal (Refereed)
    Abstract [en]

    By employing one-dimensional quantum hydrodynamic (QHD) model for a three species quantum plasma, nonlinear properties of dust acoustic solitary waves are studied. For this purpose a Korteweg-de Vries (KdV) equation is derived, incorporating quantum corrections. The quantum mechanical effects are also examined numerically both on the profiles of the amplitude and the width of dust acoustic solitary waves. It is found that the amplitude remains constant but the width shrinks for different values of a dimensionless electron quantum parameter H-e=root(Z(d0)h(2)omega(2)(pd))/m(e)m(d)C(d)(4), where Z(d0) is the dust charge state, h is the Planck constant divided by 2 pi, omega(pd) is the dust plasma frequency, m(e) (m(d)) is the electron (dust) mass, and C-d is the dust acoustic speed.

  • 5. Ali, S
    et al.
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics. Institut für Theoretische Physik IV and Centre for Plasma Science and Astrophysics, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, D-44780 Bochum, Germany; Max-Planck Institut für extraterrestrische Physik, D-85741 Garching, Germany; GoLP/Instituto Superior Técnico, 1049-001 Lisbon, Portugal; Centre for Fundamental Physics, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon 0X11 0QX, United Kingdom; Department of Physics, University of Strathclyde, Glasgow, Scotland, United Kingdom.
    Dispersion properties of compressional electromagnetic waves in quantum dusty magnetoplasmas2006In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 13, no 5, article id 052113Article in journal (Refereed)
    Abstract [en]

    A new dispersion relation for low-frequency compressional electromagnetic waves is derived by employing quantum magnetohydrodynamic model and Maxwell equations in cold quantum dusty magnetoplasmas. The latter is composed of inertialess electrons, mobile ions, and immobile charged dust particulates. The dispersion relation for the low-frequency compressional electromagnetic modes is further analyzed for the waves propagating parallel, perpendicular, and oblique to the external magnetic field direction. It is found theoretically and numerically that the quantum parameter alpha(q)=(n(i0)/n(e0))h(2)/(4m(e)m(i)) affects the real angular frequencies and the phase speeds of the compressional electromagnetic modes. Here, n(i0) (n(e0)) is the equilibrium number density of the ions (electrons), m(e) (m(i)) is the electron (ion) mass, and h is the Plank constant divided by 2 pi.

  • 6. Bingham, R
    et al.
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics. Institut für Theoretische Physik IV, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
    Spicer, DS
    Coronal heating by dissipating current sheets2004In: Physica scripta. T, ISSN 0281-1847, Vol. T107, p. 247-249Article in journal (Refereed)
    Abstract [en]

    It is shown that the lower-hybrid turbulence produced by the lower-hybrid-drift wave instability at current sheets can heat electrons and ions in the solar corona. The waves heat the plasma particles by collisionless Landau damping. The waves resonate with electrons moving in the direction of the magnetic field, while they resonate with ions moving in the perpendicular direction.

  • 7. Bingham, Robert
    et al.
    Shukla, Padma Kant
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Solar coronal heating by plasma waves2010In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 76, no 2, p. 135-158Article in journal (Refereed)
    Abstract [en]

    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.

  • 8.
    Brodin, Gert
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Marklund, Mattias
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Quantum-electrodynamical photon splitting in magnetized Nonlinear pair plasmas2007In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 98, no 12, p. 5001-4 sidorArticle in journal (Refereed)
    Abstract [en]

    We present for the first time the nonlinear dynamics of quantum electrodynamic (QED) photon splitting in a strongly magnetized electron-positron (pair) plasma. By using a QED corrected Maxwell equation, we derive a set of equations that exhibit nonlinear couplings between electromagnetic (EM) waves due to nonlinear plasma currents and QED polarization and magnetization effects. Numerical analyses of our coupled nonlinear EM wave equations reveal the possibility of a more efficient decay channel, as well as new features of energy exchange among the three EM modes that are nonlinearly interacting in magnetized pair plasmas. Possible applications of our investigation to astrophysical settings, such as magnetars, are pointed out.

  • 9.
    Brodin, Gert
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Marklund, Mattias
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma K.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Generation of gravitational radiation in dusty plasmas and supernovae2005In: JETP Letters: Journal of Experimental And Theoretical Physics Letters, ISSN 0021-3640, E-ISSN 1090-6487, Vol. 81, no 4, p. 135-139Article in journal (Refereed)
    Abstract [en]

    We present a novel nonlinear mechanism for exciting a gravitational radiation pulse (or a gravitational wave) by dust magnetohydrodynamic (DMHD) waves in dusty astrophysical plasmas. We derive the relevant equations governing the dynamics of nonlinearly coupled DMHD waves and a gravitational wave (GW). The system of equations is used to investigate the generation of a GW by compressional Alfvén waves in a type II supernova. The growth rate of our nonlinear process is estimated, and the results are discussed in the context of the gravitational radiation accompanying supernova explosions.

  • 10.
    Brodin, Gert
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Marklund, Mattias
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Anomalous reflection and excitation of surface waves in metamaterials2007In: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 367, no 3, p. 233-236Article in journal (Refereed)
    Abstract [en]

    We consider reflection of electromagnetic waves from layered structures with various dielectric and magnetic properties, including metamaterials. Assuming periodic variations in the permittivity, we find that the reflection is in general anomalous. In particular, we note that the specular reflection vanishes and that the incident energy is totally reflected in the backward direction, when the conditions for resonant excitation of leaking surface waves are fulfilled.

  • 11.
    Brodin, Gert
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics.
    A new decay channel for compressional Alfven waves in plasmas2008In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 74, no 1, p. 99-105Article in journal (Refereed)
    Abstract [en]

    We present a new efficient wave decay channel involving nonlinear interactions between a compressional Alfv´en wave, a kinetic Alfv´en wave, and a modified ion sound wave in a magnetized plasma. It is found that the wave coupling strength of the ideal magnetohydrodynamic (MHD) theory is much increased when the effects due to the Hall current are included in a Hall–MHD description of wave–wave interactions. In particular, with a compressional Alfv´en pump wave well described by the ideal MHD theory, we find that the growth rate is very high when the decay products have wavelengths of the order of the ion thermal gyroradius or shorter, in which case they must be described by the Hall–MHD equations. The significance of our results to the heating of space and laboratory plasmas as well as for the Solar corona and interstellar media are highlighted.

  • 12.
    Brodin, Gert
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma K.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Nonlinear interactions between three inertial Alfvén waves2007In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 73, no 1, p. 9-13Article in journal (Refereed)
    Abstract [en]

    The resonant coupling between Alfvén waves is reconsidered. New results are found for cold agnetoplasmas where temperature effects are negligible.

  • 13. Dieckmann, ME
    et al.
    Drury, LO
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics. Institute of Theoretical Physics IV, Ruhr-University Bochum, D-44780 Bochum, Germany.
    On the ultrarelativistic two-stream instability, electrostatic turbulence and Brownian motion2006In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 8, article id 40Article in journal (Refereed)
    Abstract [en]

    Experimental evidence indicates that bulk plasma flow at ultrarelativistic speeds is common in astrophysical settings, e. g. the collimated jets of active galactic nuclei and gamma ray bursts. The low-plasma density of such flows implies their collisionless relaxation by means of wave-particle interactions. Such processes are not well understood in the ultrarelativistic regime. The thermalization of two interpenetrating equally dense electron-proton (e(-)p) beams in the absence of a magnetic field is examined here by means of 1.5D particle-in-cell simulations. The relative beam speeds correspond to Lorentz factors in the range 200-1000. The constraint to one spatial simulation dimension, which is aligned with the beam velocity vectors, implies that only the two-stream (TS) instability and the Weibel-type instability can grow, while filamentation instabilities are excluded. With this constraint and for our plasma parameters, the TS instability dominates. The electrostatic waves grow, saturate by the trapping of electrons, and collapse. The interaction of the electrons with the electric fields after the wave collapse represents a relativistic Wiener process. In response, the electrons are rapidly thermalized. The final electron distribution can be interpreted as a relativistic Maxwellian distribution with a high-energy tail arising from ultrarelativistic phase space holes.

  • 14. Dieckmann, ME
    et al.
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics. Institute of Theoretical Physics IV, Ruhr-University Bochum, D-44780 Bochum, Germany; SUPA Department of Physics, University of Strathclyde, Glasgow, Scotland.
    Stenflo, L
    Simulation study of the filamentation of counter-streaming beams of the electrons and positrons in plasmas2009In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 51, no 6, article id 065015Article in journal (Refereed)
    Abstract [en]

    The filamentation instability (FI) driven by two spatially uniform and counter-streaming beams of charged particles in plasmas is modelled by a particle-in-cell simulation. Each beam consists of electrons and positrons. The four species are equally dense and have the same temperature. The one-dimensional simulation direction is orthogonal to the beam velocity vector. The magnetic field grows spontaneously and rearranges the particles in space, such that the distributions of the electrons of one beam and the positrons of the second beam match. The simulation demonstrates that as a result no electrostatic field is generated by the magnetic field through its magnetic pressure gradient prior to its saturation. This electrostatic field would be repulsive at the centres of the filaments and limit the maximum charge and current density. The filaments of electrons and positrons in this simulation reach higher charge and current densities than in one with no positrons. The oscillations of the magnetic field strength induced by the magnetically trapped particles result in an oscillatory magnetic pressure gradient force. The latter interplays with the statistical fluctuations in the particle density and it probably enforces a charge separation, by which electrostatic waves grow after the FI has saturated.

  • 15. Eliasson, B
    et al.
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics. Institut für Theoretische Physik IV and Centre for Plasma Science and Astrophysics.
    Instability and dynamics of two nonlinearly coupled laser beams in a two-temperature electron plasma2006In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, E-ISSN 1550-2376, Vol. 74, no 4, article id 046401Article in journal (Refereed)
    Abstract [en]

    We consider nonlinear interactions between two colliding laser beams in an electron plasma, accounting for the relativistic electron mass increase in the laser fields and radiation pressure driven electron-acoustic (EA) perturbations that are supported by hot and cold electrons. By using the hydrodynamic and Maxwell equations, we obtain the relevant equations for nonlinearly coupled laser beams and EA perturbations. The coupled equations are then Fourier analyzed to obtain a nonlinear dispersion relation. The latter is numerically solved to show the existence of new classes of the parametric instabilities in the presence of two colliding laser beams in a two-electron plasma. The dynamics of nonlinearly coupled laser beams in our electron plasma is also investigated. The results should be useful in understanding the nonlinear propagation characteristics of multiple electromagnetic beams in laser-produced plasmas as well as in space plasmas.

  • 16.
    Eliasson, Bengt
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Liu, Chuan S.
    Department of Physics, University of Maryland.
    Shao, Xi
    Department of Physics, University of Maryland.
    Sagdeev, Roald Z.
    Department of Physics, University of Maryland.
    Shukla, Padma Kant
    Institut für Theoretische Physik IV, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
    Laser acceleration of monoenergetic protons via a double layer emerging from an ultra-thin foil2009In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 11, p. 073006-073025Article in journal (Refereed)
    Abstract [en]

    We present theoretical and numerical studies of the acceleration of monoenergetic protons in a double layer formed by the laser irradiation of an ultra-thin film. The ponderomotive force of the laser light pushes the electrons forward, and the induced space charge electric field pulls the ions and makes the thin foil accelerate as a whole. The ions trapped by the combined electric field and inertial force in the accelerated frame, together with the electrons trapped in the well of the ponderomotive and ion electric field, form a stable double layer. The trapped ions are accelerated to monoenergetic energies up to 100 MeV and beyond, making them suitable for cancer treatment. We present an analytic theory for the laser-accelerated ion energy and for the amount of trapped ions as functions of the laser intensity, foil thickness and the plasma number density. We also discuss the underlying physics of the trapped and untrapped ions in a double layer. The analytical results are compared with those obtained from direct Vlasov simulations of the fully nonlinear electron and ion dynamics that is controlled by the laser light.

  • 17. Eliasson, Bengt
    et al.
    Liu, Chuan S
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics. Institut für Theoretische Physik IV, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, D-44780 Bochum, Germany; Department of Physics, University of Strathclyde, Glasgow G4 0NG, UK.
    Kumar, Naveen
    Dynamics of relativistic laser pulses in plasmas2006In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 73, no 6, p. 632-638Article in journal (Refereed)
    Abstract [en]

    The dynamics of intense laser pulses in plasmas are investigated both theoretically and numerically. The linear growth and nonlinear saturation of relativistic stimulated Raman scattering of plasmons are investigated by means of a nonlinear dispersion relation and via direct Vlasov simulations. We observe acceleration of electrons up to ultra-relativistic energies by a positive electrostatic potential that is created by intense short laser pulses.

  • 18.
    Eliasson, Bengt
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Liu, Chuan Sheng
    Shao, Xi
    Sagdeev, Roald Z.
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Laser radiation pressure acceleration of monoenergetic protons in an ultra-thin foil2009In: New Developments in Nonlinear Plasma Physics: Proceedings of the 2009 ICTP Summer College on Plasma Physics and International Symposium on Cutting Edge Plasma Physics / [ed] Bengt Eliasson, Padma Kant Shukla, American Institute of Physics , 2009, p. 35-49Conference paper (Refereed)
    Abstract [en]

    Wepresent theoretical and numerical studies of the acceleration of monoenergeticprotons in a double layer formed by the laser irradiationof an ultra-thin film. The stability of the foil isinvestigated by direct Vlasov-Maxwell simulations for different sets of laser-plasmaparameters. It is found that the foil is stable, dueto the trapping of both electrons and ions in thethin laser-plasma interaction region, where the electrons are trapped ina potential well composed of the ponderomo-tive potential of thelaser light and the electrostatic potential due to the ions,and the ions are trapped in a potential well composedof the inertial potential in an accelerated frame and theelectrostatic potential due to the electrons. The result is astable double layer, where the trapped ions are accelerated tomonoenergetic energies up to 100 MeV and beyond, which makesthem suitable for medical applications cancer treatment. The underlying physicsof trapped and untapped ions in a double layer isalso investigated theoretically and numerically.

  • 19.
    Eliasson, Bengt
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics.
    New developments in nonlinear plasma physics:  2009In: Proceedings of the 2009 ICTP Summer College on Plasma Physics and International Symposium on Cutting Edge Plasma Physics, Trieste (Italy), 10–28 August 2009, American Institute of Physics , 2009, , p. 300Conference paper (Other academic)
  • 20.
    Eliasson, Bengt
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma KantUmeå University, Faculty of Science and Technology, Department of Physics.
    New frontiers in advanced plasma physics: Proceedings of the 2010 ICTP International Advanced Workshop on the Frontiers of Plasma Physics2010Conference proceedings (editor) (Other academic)
    Abstract [en]

    The main focus of the workshop was on tokamak physics and magnetic confinement fusion, plasma turbulence, dusty plasmas, intense laser-plasma interactions, plasma based particle acceleration, and quantum plasmas including quantum electrodynamic effects. The aim of the workshop was also to provide training for young scientists from all over the world, mainly from third world countries, and to give them the opportunity to interact with the senior scientists in an informal manner. A selected number of papers by the invited speakers appears in this book.

  • 21.
    Eliasson, Bengt
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma Kant
    Theoretische Physik IV, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
    Nonlinear aspects of quantum plasma physics: Nanoplasmonics and nanostructures in dense plasmas2009In: Plasma and Fusion Research, ISSN 1880-6821, E-ISSN 1880-6821, Vol. 4, p. 032-Article in journal (Refereed)
    Abstract [en]

    We present a short review of recent developments in nonlinear quantum plasma physics, including quantum hydrodynamic and effective nonlinear shrödinger equation formalisms, for describing collective phenomena in quantum plasmas. As examples we discuss simulation studies of the formation and dynamics of dark solitons and vortices, and of nonlinear interactions between intense circularly polarized electromagnetic (CPEM) waves and electron plasma oscillations (EPOs) in dense in quantum electron plasmas. The electron dynamics of dark solitons and vortices is governed by a pair of equations comprising the nonlinear Schrödinger and Poisson equations. Both dark solitons and singly charged electron vortices are robust, and the latter tend to form pairs of oppositely charged vortices. The two-dimensional quantum electron vortex pairs survive during collisions under the change of partners. The dynamics of the CPEM waves is governed by a nonlinear Schrödinger equation, which is nonlinearly coupled with the Schrödinger equation of the EPOs via the relativistic ponderomotive force, the relativistic electron mass increase in the CPEM field, and the electron density fluctuations. The present governing equations in one spatial dimension admit stationary solutions in the form dark envelope solitons. The nonlinear equations admit the modulational instability of an intense CPEM pump wave against EPOs, leading to the formation and trapping of localized CPEM wave envelopes in the electron density holes that are associated with positive potential profiles.

  • 22.
    Eliasson, Bengt
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Numerical investigation of the instability and nonlinear evolution of narrow-band directional ocean waves2010In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 105, no 1, p. 014501-Article in journal (Refereed)
    Abstract [en]

    The instability and nonlinear evolution of directional ocean waves is investigated numerically by means of simulations of the governing kinetic equation for narrow-band surface waves. Our simulation results reveal the onset of the modulational instability for long-crested wave trains, which agrees well with recent large-scale experiments in wave basins, where it was found that narrower directional spectra lead to self-focusing of ocean waves and an enhanced probability of extreme events. We find that the modulational instability is nonlinearly saturated by a broadening of the wave spectrum, which leads to the stabilization of the water-wave system. Applications of our results to other fields of physics, such as nonlinear optics and plasma physics, are discussed.

  • 23.
    Eliasson, Bengt
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Pavlenko, V.P.
    Department of Physics and Astronomy, Uppsala University, SE-751 20 Uppsala, Sweden.
    Dynamics of nonlinearly interacting magnetic electron drift vortex modes in a nonuniform plasma2009In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 16, p. 042306-Article in journal (Refereed)
    Abstract [en]

    Asimulation study of dynamical evolution of nonlinearly interacting two-dimensional magneticelectron drift vortex (MEDV) modes in a nonuniform plasma ispresented. Depending on the equilibrium density and temperature gradients, thesystem can either be stable or unstable. The unstable systemreveals spontaneous generation of magnetic fields from noise level, andlarge-scale magnetic field structures are formed. When the system islinearly stable, one encounters MEDV mode turbulence in which thereis a competition between zonons (zonal flows) and streamers. Forlarge MEDV mode amplitudes, one encounters the formation of localizedand small-scale magnetic vortices and vortex pairs with scale sizesof the order of the electron skin depth. The MEDVturbulence exhibits nonuniversal (non-Kolmogorov-type) spectra for different sets of plasmaparameters. The relevance of this work to laboratory and cosmicplasmas is briefly mentioned.

  • 24. El-Taibany, WF
    et al.
    Moslem, WM
    Wadati, Miki
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics. Institut für Theoretische Physik IV, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, D-44780 Bochum, Germany; School of Physics, University of KwaZulu-Natal, Durban 4000, South Africa.
    On the instability of electrostatic waves in a nonuniform electron-positron magnetoplasma2008In: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 372, no 22, p. 4067-4075Article in journal (Refereed)
    Abstract [en]

    The dispersion properties of three-dimensional electrostatic waves in a nonuniform electron-positron (EP) magnetoplasma are analyzed. A new dispersion relation is derived by use of the electron and positron density responses arising from the electron and positron continuity and Poisson equations. In the local approximation, the dispersion relation admits two wave modes with different velocities. The growth rates of various modes are illustrated both analytically and numerically. Considering the temperature gradients produces a linearly stable transverse mode. The growth rate of the slow mode instability due to the density inhomogeneity only is the highest one, though it appears at higher thermal energy. The angle of the wave propagation affects drastically on the instability features in each case. The applications of the present analysis are briefly discussed.

  • 25. Fedele, Renato
    et al.
    Eliasson, Bengt
    Institut für Theoretische Physik IV, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, Germany .
    Haas, Fernando
    Shukla, Padma Kant
    Institut für Theoretische Physik IV, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, Germany .
    Jovanovic, Dusan
    De Nicola, Sergio
    Soliton solutions of the 3D Gross-Pitaevskii equation by a potential control method2010In: New Frontiers in Advanced Plasma Physics: proceedings of the 2010 ICTP international advanced workshop on the frontiers of plasma physics / [ed] Bengt Eliasson, Padma Kant Shukla, 2010, p. 61-74Conference paper (Other academic)
    Abstract [en]

    We present a class of three-dimensional solitary waves solutions of the Gross-Pitaevskii (GP) equation, which governs the dynamics of Bose-Einstein condensates (BECs). By imposing an external controlling potential, a desired time-dependent shape of the localized BEC excitation is obtained. The stability of some obtained localized solutions is checked by solving the time-dependent GP equation numerically with analytic solutions as initial conditions. The analytic solutions can be used to design external potentials to control the localized BECs in experiment.

  • 26.
    Forsberg, Mats
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Brodin, Gert
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Marklund, Mattias
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma K.
    Institut für Theoretische Physik IV and Centre for Plasma Science and Astrophysics, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
    Moortgat, J.
    Department of Physics and Astronomy, University of Rochester, Bausch & Lomb Hall, P.O. Box 270171, 600 Wilson Boulevard, Rochester, New York 14627-0171, USA .
    Nonlinear interactions between gravitational radiation and modified Alfvén modes in astrophysical dusty plasmas2006In: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 74, p. 064014-064014-5Article in journal (Refereed)
    Abstract [en]

    We present an investigation of nonlinear interactions between gravitational radiation and modified Alfvén modes in astrophysical dusty plasmas. Assuming that stationary charged dust grains form neutralizing background in an electron-ion-dust plasma, we obtain the three-wave coupling coefficients and calculate the growth rates for parametrically coupled gravitational radiation and modified Alfvén-Rao modes. The threshold value of the gravitational wave amplitude associated with convective stabilization is particularly small if the gravitational frequency is close to twice the modified Alfvén wave frequency. The implication of our results to astrophysical dusty plasmas is discussed.

  • 27. Haas, F
    et al.
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics. Institut für Theoretische Physik IV, Ruhr-Universität Bochum, D-44780 Bochum, Germany; GOLP/Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade Técnica de Lisboa, 1049-001 Lisboa, Portugal; SUPA, Department of Physics, University of Strathclyde, Glasgow, G40NG, UK; School of Physics, University of Kwazulu-Natal, Durban 4000, South Africa.
    Nonlinear stationary solutions of the Wigner and Wigner-Poisson equations2008In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 15, no 11, article id 112302Article in journal (Refereed)
    Abstract [en]

    Exact nonlinear stationary solutions of the one-dimensional Wigner and Wigner-Poisson equations in the terms of the Wigner functions that depend not only on the energy but also on position are presented. In this way, the Bernstein-Greene-Kruskal modes of the classical plasma are adapted for the quantum formalism in the phase space. The solutions are constructed for the case of a quartic oscillator potential, as well as for the self-consistent Wigner-Poisson case. Conditions for well-behaved physically meaningful equilibrium Wigner functions are discussed.

  • 28. Haas, F
    et al.
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics. Institut für Theoretische Physik IV, Ruhr-Universität Bochum, D-44780 Bochum, Germany; GOLP/Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade Técnica de Lisboa, 1049-001 Lisboa, Portugal; SUPA, Department of Physics, University of Strathclyde, Glasgow, G40NG, United Kingdom; School of Physics, University of Kwazulu-Natal, Durban 4000, South Africa.
    Nonlinear structure in a current-carrying collisional dusty plasma2008In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 15, no 9, article id 093702Article in journal (Refereed)
    Abstract [en]

    A perpendicular ion drift is proposed as a possible mechanism for the generation of magnetic field structures in a highly collisional dusty plasma. The basic dissipation mechanism is assumed to be the dust-neutral momentum exchange, so that plasmas with a small ionization fraction are natural candidates for experiments. The model reduces to a nonlinear partial differential equation for the vector potential. The conditions for linear instability are presented. Possible stationary states are periodic arrangements for the magnetic field, described by a Lienard equation. The fully depleted (ion-dust) case is also considered in detail. Applications of the present work to magnetic field structures in planetary rings, comets, and low-temperature dusty plasma experiments are discussed. A necessary condition for the validity of the model is a sufficiently slow time scale of the generated magnetic fields in dusty plasmas.

  • 29. Haas, F
    et al.
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics. Institut für Theoretische Physik IV, Ruhr-Universität Bochum, D-44780 Bochum, Germany; GOLP/Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade Técnica de Lisboa, 1049-001 Lisboa, Portugal; SUPA, Department of Physics, University of Strathclyde, Glasgow, G40NG, UK; School of Physics, University of Kwazulu-Natal, Durban 4000, South Africa.
    Quantum and classical dynamics of Langmuir wave packets2009In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, E-ISSN 1550-2376, Vol. 79, no 6, article id 066402Article in journal (Refereed)
    Abstract [en]

    The quantum Zakharov system in three spatial dimensions and an associated Lagrangian description, as well as its basic conservation laws, are derived. In the adiabatic and semiclassical cases, the quantum Zakharov system reduces to a quantum modified vector nonlinear Schroumldinger (NLS) equation for the envelope electric field. The Lagrangian structure for the resulting vector NLS equation is used to investigate the time dependence of the Gaussian-shaped localized solutions, via the Rayleigh-Ritz variational method. The formal classical limit is considered in detail. The quantum corrections are shown to prevent the collapse of localized Langmuir envelope fields, in both two and three spatial dimensions. Moreover, the quantum terms can produce an oscillatory behavior of the width of the approximate Gaussian solutions. The variational method is shown to preserve the essential conservation laws of the quantum modified vector NLS equation. The possibility of laboratory tests in the next generation intense laser-solid plasma compression experiment is discussed.

  • 30.
    Haas, Fernando
    et al.
    Institut für Theoretische Physik IV, Ruhr–Universität Bochum, D-44780 Bochum, Germany.
    Shukla, Padma Kant
    Institut für Theoretische Physik IV, Ruhr–Universität Bochum, D-44780 Bochum, Germany.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Nonlinear saturation of the Weibel instability in a dense Fermi plasma2009In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 75, no 2, p. 251-258Article in journal (Refereed)
    Abstract [en]

    We present an investigation for the generation of intense magnetic fields in dense plasmas with an anisotropic electron Fermi–Dirac distribution. For this purpose, we use a new linear dispersion relation for transverse waves in the Wigner–Maxwell dense quantum plasma system. Numerical analysis of the dispersion relation reveals the scaling of the growth rate as a function of the Fermi energy and the temperature anisotropy. The nonlinear saturation level of the magnetic fields is found through fully kinetic simulations, which indicates that the final amplitudes of the magnetic fields are proportional to the linear growth rate of the instability. The present results are important for understanding the origin of intense magnetic fields in dense Fermionic plasmas, such as those in the next-generation intense laser–solid density plasma experiments.

  • 31. Hasegawa, Akira
    et al.
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics. Institut für Theoretische Physik IV, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, Bochum, D-44780, Germany.
    A note on the ion surface waves in a pair-ion plasma2005In: Physica scripta, Stockholm: Royal Swedish academy of sciences , 2005, Vol. T116, p. 105-106Conference paper (Refereed)
    Abstract [en]

    The propagation of ion surface waves in a pair-ion plasma is considered. The dispersion relation for the ion surface waves is derived. The ion surface wave frequency is found to be in good agreement with observations from a recent laboratory experiment.

  • 32. Krasheninnikov, SI
    et al.
    Shevchenko, VI
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics. Institut für Theoretische Physik IV and Centre for Plasma Science and Astrophysics, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, D-44780 Bochum, Germany; SUPA Department of Physics, University of Strathclyde, Glasgow G4 0NG, United Kingdom; Centre for Fundamental Physics (CfFP), Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, United Kingdom; Centro de Fisica, Instituto Superior Técnico, Universidade Técnica de Lisboa, 1049-001 Lisboa, Portugal.
    Spinning of a charged dust particle in a magnetized plasma2007In: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 361, no 1-2, p. 133-135Article in journal (Refereed)
    Abstract [en]

    We present a novel mechanism for spinning of a charged dust particle in a magnetized plasma. Specifically, we show that the dust particle spinning is caused by a torque that is produced due to interactions between the electric field E and an asymmetric dust particle electric dipole that is induced by the cross-field (viz. the E x B, where B is the external magnetic field) plasma flow. The torque acting on the dust particle is proportional to vertical bar E vertical bar(2), so that both laminar and turbulent electric fields can cause dust particle spinning. For plasma parameters typical of tokamak edges. the characteristic dust spinning frequency is of the order of several hundred kHz.

  • 33.
    Lundin, Joakim
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Brodin, Gert
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Marklund, Mattias
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma K
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Circularly polarized waves in a plasma with vacuum polarization effects2007In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 14, no 6, p. 064503-3 sidorArticle in journal (Refereed)
    Abstract [en]

    The theory for large amplitude circularly polarized waves propagating along an external magnetic field is extended in order to also include vacuum polarization effects. A general dispersion relation, which unites previous results, is derived.

  • 34.
    Mamun, A. A.
    et al.
    Institut für Theoretische Physik IV, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, Bochum D-44780, Germany.
    Shukla, Padma Kant
    Institut für Theoretische Physik IV, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, Bochum D-44780, Germany.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Arbitrary amplitude dust ion-acoustic shock waves in a dusty plasma with positive and negative ions2009In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 16, p. 114503-Article in journal (Refereed)
    Abstract [en]

    Arbitraryamplitude dust ion-acoustic shock waves in a multi-ion dusty plasma(composed of electrons, light positive ions, heavy negative ions, andstationary massive dust grains) has been studied. For this purpose,the coupled Poisson and dust-charging equations, which accounts for thefluctuation of charges on static dust, have been numerically solved.The large amplitude shocks are associated with a sudden decreasein the electrostatic potential and of the dust grain charge.It is found that in the lower speed limit smallamplitude shocks are formed, while in the larger speed limitlarge amplitude shocks are formed. It is anticipated that theprofiles and amplitudes of the DIA shocks predicted here willbe observed in forthcoming laboratory and space experiments.

  • 35.
    Marklund, Mattias
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Magnetosonic solitons in a fermionic quantum plasma2007In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics: Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, ISSN 1063-651X, E-ISSN 1095-3787, Vol. 76, no 6:2, article id 067401Article in journal (Refereed)
    Abstract [en]

    Starting from the governing equations for a quantum magnetoplasma including the quantum Bohm potential and electron spin-1/2 effects, we show that the system of quantum magnetohydrodynamic (QMHD) equations admits rarefactive solitons due to the balance between nonlinearities and quantum diffraction and tunneling effects. It is found that the electron spin-1/2 effect introduces a pressurelike term with negative sign in the QMHD equations, which modifies the shape of the solitary magnetosonic waves and makes them wider and shallower. Numerical simulations of the time-dependent system shows the development of rarefactive QMHD solitary waves that are modified by the spin effects.

  • 36.
    Marklund, Mattias
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma K.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Lundin, Joakim
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Nonlinear propagation of partially coherent dispersive Alfvén waves.2006In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Physica Scripta, Vol. 74, no 3, p. 373-376Article in journal (Refereed)
    Abstract [en]

    The effects of partial coherence on the propagation of dispersive Alfvén waves in a magnetoplasma are investigated. In particular, nonlinear interactions between dispersive Alfvén waves and ion-acoustic perturbations are considered by means of a Wigner formalism. A set of governing equations consisting of a kinetic equation for dispersive Alfvén waves coupled nonlinearly to a ponderomotive force driven ion-acoustic wave equation is obtained. The governing nonlinear equations are used to derive a nonlinear dispersion relation that is appropriate for investigating the modulational instability of broadband Alfvén wavepackets. The spectral broadening of the Alfvén waves gives rise to new regimes for the growth rate of the modulational instability.

  • 37.
    Marklund, Mattias
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stenflo, Lennart
    Shukla, Padma K.
    Magnetosonic solitons in a dusty plasma slab2008In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 74, no 5, p. 601-605Article in journal (Refereed)
    Abstract [en]

    The existence of magnetosonic solitons in dusty plasmas is investigated. The nonlinear magnetohydrodynamic equations for a warm dusty magnetoplasma are thus derived. A solution of the nonlinear equations is presented. It is shown that, owing to the presence of dust, static structures are allowed. This is in sharp contrast to the formation of the so-called shocklets in usual magnetoplasmas. A comparatively small number of dust particles can thus drastically alter the behavior of the nonlinear structures in magnetized plasmas.

  • 38.
    Marklund, Mattias
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. Centre for Fundamental Physics, Rutherford Appleton Laboratory, Chilton Didcot, Oxfordshire OX11 0QX, United Kingdom .
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics. Centre for Fundamental Physics, Rutherford Appleton Laboratory, Chilton Didcot, Oxfordshire OX11 0QX, United Kingdom .
    Brodin, Gert
    Umeå University, Faculty of Science and Technology, Department of Physics. Centre for Fundamental Physics, Rutherford Appleton Laboratory, Chilton Didcot, Oxfordshire OX11 0QX, United Kingdom .
    Quantum electrodynamical effects in dusty plasmas2005In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 12, no 7, article id 072111Article in journal (Refereed)
    Abstract [en]

    A new nonlinear electromagnetic wave mode in a magnetized dusty plasma is predicted. Its existence depends on the interaction of an intense circularly polarized electromagnetic wave with a dusty plasma, where quantum electrodynamical photon-photon scattering is taken into account. Specifically, we consider a dusty electron-positron-ion plasma and show that the propagation of the new mode is admitted. It could be of significance for the physics of supernova remnants and in neutron star formation.

  • 39. Masoud, Waqas
    et al.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma K
    Institut für Theoretische Physik IV, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, Germany .
    Electromagnetic wave equations for relativistically degenerate quantum magnetoplasmas2010In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics: Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, ISSN 1063-651X, E-ISSN 1095-3787, Vol. 81, no 6, p. 066401-5 pagesArticle in journal (Refereed)
    Abstract [en]

    A generalized set of nonlinear electromagnetic quantum hydrodynamic (QHD) equations is derived for a magnetized quantum plasma, including collisional, electron spin-1/2, and relativistically degenerate electron pressure effects that are relevant for dense astrophysical systems, such as white dwarfs. For illustrative purposes, linear dispersion relations are derived for one-dimensional magnetoacoustic waves for a collisionless nonrelativistic degenerate gas in the presence of the electron spin-1/2 contribution and for magnetoacoustic waves in a plasma containing relativistically degenerate electrons. It is found that both the spin and relativistic degeneracy at high densities tend to slow down the magnetoacoustic wave due to the Pauli paramagnetic effect and relativistic electron mass increase. The present study outlines the theoretical framework for the investigation of linear and nonlinear behaviors of electromagnetic waves in dense astrophysical systems. The results are applied to calculate the magnetoacoustic speeds for both the nonrelativistic and relativistic electron degeneracy cases typical for white dwarf stars.

  • 40. Mendoca, JT
    et al.
    Ribeiro, JE
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics. Institut für Theoretische Physik IV, Ruhr-Universität Bochum, D-44780 Bochum, Germany; SUPA Department of Physics, University of Strathclyde, Glasgow G4 0NG, UK.
    Wave kinetic description of quantum pair plasmas2008In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 74, no 1, p. 91-97Article in journal (Refereed)
    Abstract [en]

    The dispersion relation for a quantum pair plasma is derived, by using a wave kinetic description. A general form of the kinetic dispersion relation for eleetrostatic waves in a two-component quantum plasma is established. The particular case of an electron positron pair plasma is considered in detail. Exact expressions for Landau damping are derived, and the quasi-classical limit is discussed.

  • 41. Mendonca, J T
    et al.
    Bingham, R
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics. Institut für Theoretische Physik IV, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, D-44780, Bochum, Germany.
    A kinetic approach to Bose-Einstein condensates: self-phase modulation and Bogoliubov oscillations2005In: Journal of Experimental and Theoretical Physics, ISSN 1063-7761, E-ISSN 1090-6509, Vol. 101, no 5, p. 942-948Article in journal (Refereed)
    Abstract [en]

    A kinetic approach to Bose-Einstein condensates (BECs) is proposed based on the Wigner-Moyal equation (WME). In the semiclassical limit, the WME reduces to the particle-number conservation equation. Two examples of applications are (i) a self-phase modulation of a BE condensate beam, where we show that part of the beam is decelerated and eventually stops as a result of the gradient of the effective self-potential, and (ii) the derivation of a kinetic dispersion relation for sound waves in BECs, including collisionless Landau damping.

  • 42. Mendonca, JT
    et al.
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics. Centre for Fundamental Physics (CfFP), STFC Rutherford Appleton Laboratory, Chilton, Didcot, UK; Institut für Theoretische Physik IV, Ruhr-Universität Bochum, D-44780 Bochum, Germany; SUPA Department of Physics, University of Strathclyde, Glasgow G4 0NG, UK .
    Bingham, R
    Nonlinear excitation of zonal flows by Rossby wave turbulence2009In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 11, article id 073038Article in journal (Refereed)
    Abstract [en]

    We apply the wave-kinetic approach to study nonlinearly coupled Rossby wave-zonal flow fluid turbulence in a two-dimensional rotating fluid. Specifically, we consider for the first time nonlinear excitations of zonal flows by a broad spectrum of Rossby wave turbulence. Short-wavelength Rossby waves are described here as a fluid of quasi-particles, and are referred to as the 'Rossbyons'. It is shown that Reynolds stresses of Rossbyons can generate large-scale zonal flows. The result should be useful in understanding the origin of large-scale planetary and near-Earth atmospheric circulations. It also provides an example of a turbulent wave background driving a coherent structure.

  • 43.
    Misra, Amar P
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Brodin, Gert
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Marklund, Mattias
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma K
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Circularly polarized modes in magnetized spin plasmas2010In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, ISSN 0022-3778, Vol. 76, no 3/4, p. 857-864Article in journal (Refereed)
    Abstract [en]

    The influence of the intrinsic spin of electrons on the propagation of circularly polarized waves in a magnetized plasma is considered. New eigenmodes are identified, one of which propagates below the electron cyclotron frequency, one above the spin-precession frequency, and another close to the spin-precession frequency. The latter corresponds to the spin modes in ferromagnets under certain conditions. In the non-relativistic motion of electrons, the spin effects become noticeable even when the external magnetic field B0 is below the quantum critical magnetic field strength, i.e. B0 < BQ = 4.4138 × 109T and the electron density satisfies n0nc ≃ 1032m−3. The importance of electron spin (paramagnetic) resonance (ESR) for plasma diagnostics is discussed.

  • 44.
    Misra, Amar P
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Brodin, Gert
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Marklund, Mattias
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma K
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Generation of wakefields by whistlers in spin quantum magnetoplasmas2010In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 17, no 12, article id 122306Article in journal (Refereed)
    Abstract [en]

    The excitation of electrostatic wakefields in a magnetized spin quantum plasma by the classical and the spin-induced ponderomotive force (CPF and SPF, respectively) due to whistler waves is reported. The nonlinear dynamics of the whistlers and the wakefields is shown to be governed by a coupled set of nonlinear Schrodinger and driven Boussinesq-like equations. It is found that the quantum force associated with the Bohm potential introduces two characteristic length scales, which lead to the excitation of multiple wakefields in a strongly magnetized dense plasma (with a typical magnetic field strength B(0)greater than or similar to 10(9) T and particle density n(0)greater than or similar to 10(36) m(-3)), where the SPF strongly dominates over the CPF. In other regimes, namely, B(0)less than or similar to 10(8) T and n(0)less than or similar to 10(35) m(-3), where the SPF is comparable to the CPF, a plasma wakefield can also be excited self-consistently with one characteristic length scale. Numerical results reveal that the wakefield amplitude is enhanced by the quantum tunneling effect; however, it is lowered by the external magnetic field. Under appropriate conditions, the wakefields can maintain high coherence over multiple plasma wavelengths and thereby accelerate electrons to extremely high energies. The results could be useful for particle acceleration at short scales, i.e., at nanometer and micrometer scales, in magnetized dense plasmas where the driver is the whistler wave instead of a laser or a particle beam.

  • 45.
    Misra, Amar P
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Brodin, Gert
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Marklund, Mattias
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma K
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Localized whistlers in magnetized spin quantum plasmas2010In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics: Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, ISSN 1063-651X, E-ISSN 1095-3787, Vol. 82, p. 056406-Article in journal (Refereed)
    Abstract [en]

    The nonlinear propagation of electromagnetic (EM) electron-cyclotron waves (whistlers) along an external magnetic field, and their modulation by electrostatic small but finite amplitude ion-acoustic density perturbations are investigated in a uniform quantum plasma with intrinsic spin of electrons. The effects of the quantum force associated with the Bohm potential and the combined effects of the classical as well as the spin-induced ponderomotive forces (CPF and SPF, respectively) are taken into consideration. The latter modify the local plasma density in a self-consistent manner. The coupled modes of wave propagation is shown to be governed by a modified set of nonlinear Schrödinger-Boussinesq-like equations which admit exact solutions in form of stationary localized envelopes. Numerical simulation reveals the existence of large-scale density fluctuations that are self-consistently created by the localized whistlers in a strongly magnetized high density plasma. The conditions for the modulational instability (MI) and the value of its growth rate are obtained. Possible applications of our results, e.g., in strongly magnetized dense plasmas and in the next generation laser-solid density plasma interaction experiments are discussed.

  • 46.
    Misra, Amar P
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Marklund, Mattias
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Brodin, Gert
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma K
    RUB International Chair, International Centre for Advanced Studies in Physical Sciences, Faculty of Physics and Astronomy, Ruhr University Bochum, Bochum, Germany.
    Stability of two-dimensional ion-acoustic wave packets in quantum plasmas2011In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 18, no 4, p. 042102-042109Article in journal (Refereed)
    Abstract [en]

    The nonlinear propagation of two-dimensional (2D) quantum ion-acoustic waves (QIAWs) is studied in a quantum electron–ion plasma. By using a 2D quantum hydrodynamic model and the method of multiple scales, a new set of coupled nonlinear partial differential equations is derived which governs the slow modulation of the 2D QIAW packets. The oblique modulational instability (MI) is then studied by means of a corresponding nonlinear Schrödinger equation derived from the coupled nonlinear partial differential equations. It is shown that the quantum parameter H (ratio of the plasmon energy density to Fermi energy) shifts the MI domains around the kθ -plane, where k is the carrier wave number and θ is the angle of modulation. In particular, the ion-acoustic wave (IAW), previously known to be stable under parallel modulation in classical plasmas, is shown to be unstable in quantum plasmas. The growth rate of the MI is found to be quenched by the obliqueness of modulation. The modulation of 2D QIAW packets along the wave vector k is shown to be described by a set of Davey–Stewartson-like equations. The latter can be studied for the 2D wave collapse in dense plasmas. The predicted results, which could be important to look for stable wave propagation in laboratory experiments as well as in dense astrophysical plasmas, thus generalize the theory of MI of IAW propagations both in classical and quantum electron–ion plasmas.

  • 47.
    Misra, Amar P
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, PK
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Nonlinear wave-wave interactions in quantum plasmas2010In: New frontiers in advanced plasma physics, American Institute of Physics (AIP), 2010, p. 103-110Conference paper (Refereed)
    Abstract [en]

    Wave-wave interaction in plasmas is a topic of important research since the 16th century. The formation of Langmuir solitons through the coupling of high-frequency (hf) Langmuir and low-frequency (If) ion-acoustic waves, is one of the most interesting features in the context of turbulence in modern plasma physics. Moreover, quantum plasmas, which are ubiquitous in ultrasmall electronic devices, micromechanical systems as well as in dense astrophysical environments are a topic of current research. In the light of notable interests in such quantum plasmas, we present here a theoretical investigation on the nonlinear interaction of quantum Langmuir waves (QLWs) and quantum ion-acoustic waves (QIAWs), which are governed by the one-dimensional quantum Zakharov equations (QZEs). It is shown that a transition to spatiotemporal chaos (STC) occurs when the length scale of excitation of linear modes is larger than that of the most unstable ones. Such length scale is, however, to be larger (compared to the classical one) in presence of the quantum tunneling effect. The latter induces strong QIAW emission leading to the occurrence of collision and fusion among the patterns at an earlier time than the classical case. Moreover, numerical simulation of the QZEs reveals that many solitary patterns can be excited and saturated through the modulational instability (MI) of unstable harmonic modes. In a longer time, these solitons are seen to appear in the state of STC due to strong QIAW emission as well as by the collision and fusion in stochastic motion. The energy in the system is thus strongly redistributed, which may switch on the onset of Langmuir turbulence in quantum plasmas.

  • 48.
    Misra, Amar Prasad
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Modulational instability and nonlinear evolution of two-dimensional electrostatic wave packets in ultra-relativistic degenerate dense plasmas2011In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 18, no 4, article id 042308Article in journal (Refereed)
    Abstract [en]

    We consider the nonlinear propagation of electrostatic wave packets in an ultra-relativistic (UR) degenerate dense electron-ion plasma, whose dynamics is governed by the nonlocal two-dimensional nonlinear Schrodinger-like equations. The coupled set of equations is then used to study the modulational instability (MI) of a uniform wave train to an infinitesimal perturbation of multidimensional form. The condition for the MI is obtained, and it is shown that the nondimensional parameter, beta proportional to lambda(C)n(0)(1/3) (where lambda(C) is the reduced Compton wavelength and n(0) is the particle number density) associated with the UR pressure of degenerate electrons, shifts the stable (unstable) regions at n(0) similar to 10(30)cm(-3) to unstable (stable) ones at higher densities, i.e., n(0) greater than or similar to 7 x 10(33). It is also found that the higher the values of n(0), the lower is the growth rate of MI with cut-offs at lower wave numbers of modulation. Furthermore, the dynamical evolution of the wave packets is studied numerically. We show that either they disperse away or they blowup in a finite time, when the wave action is below or above the threshold. The results could be useful for understanding the properties of modulated wave packets and their multidimensional evolution in UR degenerate dense plasmas, such as those in the interior of white dwarfs and/or pre-Supernova stars.

  • 49. Misra, AP
    et al.
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics. Institut für Theoretische Physik IV and Centre for Plasma Science and Astrophysics, Fakultät für Physik and Astronomie, Ruhr-Universität Bochum, D-44780 Bochum, Germany; School of Physics, University of KwaZulu-Natal, 4000 Durban, South Africa; Nonlinear Physics Centre, Ruhr-Universität Bochum, D-44780 Bochum, Germany; Max-Planck Institut für Extraterrestrische Physik, D-85741 Garching, Germany; GoLP/Instituto de Plasmas e Fusao Nuclear, Instituto Superior T’ecnico, 1049-001 Lisboa, Portugal; CCLRC Centre for Fundamental Physics, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon 0X11 0QX, United Kingdom; SUPA Department of Physics, University of Strathclyde, Glasgow G40NG, United Kingdom; Department of Physics, COMSATS Institute of Information Technology, Islamabad, Pakistan.
    Modulational instability of magnetosonic waves in a spin 1/2 quantum plasma2008In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 15, no 5, article id 052105Article in journal (Refereed)
    Abstract [en]

    The modulational instability (MI) of magnetosonic waves (MSWs) is analyzed, by using a two-fluid quantum magnetohydrodynamic model that includes the effects of the electron-1/2 spin and the plasma resistivity. The envelope modulation is then studied by deriving the corresponding nonlinear Schrodinger equation from the governing equations. The plasma resistivity is shown to play a dissipative role for the onset of MI. In the absence of resistivity, the microscopic spin properties of electrons can also lead to MI. In such a situation, the dominant spin contribution corresponds to a dense quantum plasma with the particle number density, n(0)greater than or similar to 10(28) m(-3). Also, in such a dissipative (absorbing) medium, where the group velocity vector is usually complex for real values of the wave vector, the role of the real group velocity in the propagation of one-dimensional MSW packets in a homogeneous absorbing medium is reported. The effects of quantum spin on the stability/instability conditions of the magnetosonic envelope are obtained and examined numerically. From the nonlinear dispersion relation of the modulated wave packet it is found that the effect of the spin (plasma resistivity) is to decrease (increase) the instability growth rate provided the normalized Zeeman energy does not exceed a critical value. The theoretical results may have relevance to astrophysical (e.g., magnetars) as well as to ultracold laboratory plasmas (e.g., Rydberg plasmas).

  • 50. Misra, AP
    et al.
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics. Institut für Theoretische Physik IV and Centre for Plasma Science and Astrophysics, Fakultät für Physik and Astronomie, Ruhr-Universität Bochum, D-44780 Bochum, Germany; School of Physics, University of KwaZulu-Natal, 4000 Durban, South Africa; Nonlinear Physics Centre, Ruhr-Universität Bochum, D-44780 Bochum, Germany; Max-Planck Institut für extraterrestrische Physik, D-85741 Garching, Germany; GoLP/Instituto de Plasmas e Fusao Nuclear, Instituto Superior T’ecnico, 1049-001 Lisboa, Portugal; CCLRC Centre for Fundamental Physics, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon 0X11 0QX, UK; SUPA Department of Physics, University of Strathclyde, Glasgow G40NG, UK; Department of Physics, COMSATS Institute of Information Technology, Islamabad, Pakistan.
    Relativistic modulational instability of electron-acoustic waves in an electron-pair ion plasma2008In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 15, no 12, article id 122107Article in journal (Refereed)
    Abstract [en]

    The modulational instability of finite amplitude electron-acoustic waves (EAWs) along the external magnetic field is studied in an electron-pair ion plasma. Accounting for the relativistic electron mass variation nonlinearity and the Boltzmann distribution of both positive and negative ions, new regimes for the relativistic modulational instability (MI) for the low frequency (below the electron gyrofrequency) short-wavelength (in comparison with the ion gyroradius) modes are obtained numerically. It is found that the presence of a significant fraction of negative ions suppresses the MI growth/decay rate for the modulated EAW packets. The results could be of important for understanding the origin of amplitude modulated EAW packets in space (e.g., Earth's magnetotail) as well as in laboratory plasmas.

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