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  • 1. 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.

  • 2.
    Brodin, Gert
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Forsberg, Mats
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Marklund, Mattias
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Eriksson, Daniel
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Interaction between gravitational waves and plasma waves in the Vlasov description2010In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, no 76, p. 345-353Article in journal (Refereed)
    Abstract [en]

    The nonlinear interaction between electromagnetic, electrostatic and gravitational waves in a Vlasov plasma is reconsidered. By using a orthonormal tetrad description the three-wave coupling coefficients are computed. Comparing with previous results, it is found that the present theory leads to algebraic expression that are much reduced, as compared to those computed using a coordinate frame formalism. Furthermore, here we calculate the back reaction on the gravitational waves, and a simple energy conservation law is deduced in the limit of a cold plasma.

  • 3.
    Brodin, Gert
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Holkundkar, Amol
    Umeå University, Faculty of Science and Technology, Department of Physics. Department of Physics, Birla Institute of Technology and Science, Rajasthan, India.
    Marklund, Mattias
    Umeå University, Faculty of Science and Technology, Department of Physics. Department of Applied Physics, Chalmers University of Technology, Göteborg, Sweden.
    Particle-in-cell simulations of electron spin effects in plasmas2013In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 79, no 4, p. 377-382Article in journal (Refereed)
    Abstract [en]

    We present a particle-in-cell code accounting for the magnetic dipole force and for the magnetization currents associated with the electron spin. The electrons are divided into spin-up and spin-down populations relative to the magnetic field, where the magnetic dipole force acts in opposite directions for the two species. To validate the code, we study wakefield generation by an electromagnetic pulse propagating parallel to an external magnetic field. The properties of the generated wakefield are shown to be in good agreement with previous theoretical results. Generalizations of the code to account for other quantum effects are discussed.

  • 4.
    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.

  • 5.
    Brodin, Gert
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stenflo, Lennart
    Alfven wave interactions within the Hall-MHD description2013In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 79, no 5, p. 909-911Article in journal (Refereed)
    Abstract [en]

    We show that comparatively simple expressions for the Alfven wave coupling coefficients can be deduced from the well-known Hall-magnetohydrodynamics (MHD) model equations.

  • 6.
    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.
    On the parametric decay of waves in magnetized plasmas2009In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 75, p. 9-13Article in journal (Refereed)
    Abstract [en]

    We reconsider the theory for three-wave interactions in cold plasmas. In particular, we demonstrate that previously overlooked formulations of the general theory are highly useful when deriving concrete expressions for specific cases. We also point out that many previous results deduced directly from the basic plasma equations contain inappropriate approximations leading to unphysical results. Finally, generalizations to more elaborate plasma models containing, for example, kinetic effects are given.

  • 7.
    Brodin, Gert
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stenflo, Lennart
    Department of Physics, Linköping University, SE-581 83 Linköping, Sweden .
    Stimulated Brillouin scattering in magnetized plasmas2013In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 79, no Special Issue 06, p. 983-986Article in journal (Refereed)
    Abstract [en]

    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.

  • 8.
    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.

  • 9.
    Eliasson, Bengt
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma Kant
    Dispersion properties of electrostatic oscillations in quantum plasmas2010In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 76, p. 7-17Article in journal (Refereed)
    Abstract [en]

    We present a derivation of the dispersion relation for electrostatic oscillations in a zero-temperature quantum plasma, in which degenerate electrons are governed by the Wigner equation, while non-degenerate ions follow the classical fluid equations. The Poisson equation determines the electrostatic wave potential. We consider parameters ranging from semiconductor plasmas to metallic plasmas and electron densities of compressed matter such as in laser compression schemes and dense astrophysical objects. Owing to the wave diffraction caused by overlapping electron wave function because of the Heisenberg uncertainty principle in dense plasmas, we have the possibility of Landau damping of the high-frequency electron plasma oscillations at large enough wavenumbers. The exact dispersion relations for the electron plasma oscillations are solved numerically and compared with the ones obtained by using approximate formulas for the electron susceptibility in the high- and low-frequency cases.

  • 10.
    Eliasson, Bengt
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Full-scale simulation study of stimulated electromagnetic emissions: The first ten milliseconds2010In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 78, no 3-4, p. 369-375Article in journal (Refereed)
    Abstract [en]

    A full-scale numerical study is performed of the nonlinear interaction between a large-amplitude electromagnetic wave and the Earth's 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.

  • 11.
    Haas, Fernando
    Umeå University, Faculty of Science and Technology, Department of Physics.
    On quantum plasma kinetic equations with a Bohmian force2010In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 76, no 3-4, p. 389-393Article in journal (Refereed)
    Abstract [en]

    The dispersion relation arising from a Vlasov-Poisson system with a Bohmian force term is examined and compared to the more fundamental Bohm and Pines dispersion relation for quantum plasmas. Discrepancies are found already when considering the leading order thermal effects. The time-averaged energy densities for longitudinal modes are also shown to be noticeably different.

  • 12.
    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.

  • 13.
    Iqbal, Mubashar
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Linear wave theory in magnetized quantum plasmas2013In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 79, no 1, p. 19-23Article in journal (Refereed)
    Abstract [en]

    We study the spin and ion effects in quantum plasma, where the two-fluid model of electrons is being used which treats the spin-up and -down populations relative to the magnetic field as different species. We find the susceptibility of electrons and ions where the ions are classical, but strongly coupled. The general dispersion relation is derived for wave propagation in homogeneous magnetized plasmas for arbitrary direction of propagation. We discuss the applicability of our results.

  • 14. Lu, G. M.
    et al.
    Liu, Y.
    Wang, Y. M.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Popel, S. I.
    Yu, M. Y.
    Fully nonlinear electrostatic waves in electron-positron plasmas2010In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 76, p. 267-275Article in journal (Refereed)
    Abstract [en]

    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.

  • 15.
    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.

  • 16. 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.

  • 17. Mendonca, J T
    et al.
    Shukla, Nitin
    Umeå University, Faculty of Science and Technology, Department of Physics. Also at GoLP/Instituto de Plasmas Fusão Nuclear, Instituto Superior Técnico, Universidade Técnica do Lisboa, Portugal.
    Shukla, P K
    Umeå University, Faculty of Science and Technology, Department of Physics. Institut für Theoretische Physik IV, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, Germany; Scottish Universities Physics Alliance (SUPA), Department of Physics, University of Strathclyde, Glasgow, UK; GoLP/Instituto de Plasmas Fusão Nuclear, Instituto Superior Técnico, Universidade Técnica do Lisboa, Portugal; School of Physics, University of KwaZulu-Natal, Durban, South Africa; Max-Planck Institut für Extraterrestrische Physik und Plasmaphysik, Garching, Germany.
    Magnetization of Rydberg plasmas by electromagnetic waves2010In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 76, p. 19-23Article in journal (Refereed)
    Abstract [en]

    It is shown that the ponderomotive force of a large-amplitude electro-magnetic wave in Rydberg plasmas can generate quasi-stationary magnetic fields. The present result can account for the origin of seed magnetic fields in the ultracold Rydberg plasmas when they irradiated by the high-frequency electromagnetic wave.

  • 18.
    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.

  • 19.
    Moslem, WM
    et al.
    Department of Physics, Faculty of Science, Port Said University, Port Said, Egypt .
    Sabry, R
    Theoretical Physics Group, Department of Physics, Faculty of Science, Mansoura University, Damietta Branch, New Damietta 34517, Egypt.
    Shukla, Padma K
    Umeå University, Faculty of Science and Technology, Department of Physics. UB International Chair, International Center for Advanced Studies in Physical Sciences, Faculty of Physics & Astronomy, Ruhr University Bochum, D-44780 Bochum, Germany.
    The optimum shielding around a test charge in plasmas containing two negative ions2011In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 77, no 5, p. 663-673Article in journal (Refereed)
    Abstract [en]

    This paper focuses on the progress in understanding the shielding around a test charge in the presence of ion-acoustic waves in multispecies plasmas, whose constituents are positive ions, two negative ions, and Boltzmann distributed electrons. By solving the linearized Vlasov equation with Poisson equation, the Debye-Huckel screening potential and wakefield (oscillatory) potential distribution around a test charge particle are derived. It is analytically found that both the Debye-Huckel potential and the wakefield potential are significantly modified due to the presence of two negative ions. The present results might be helpful to understand and to form new materials from plasmas containing two negative ions such as Xe(+) - F(-) - SF(6)(-) and Ar(+) - F(-) - SF(6)(-) plasmas, as well as to tackle extension of the test charge problem in multinegative ions' coagulation/agglomeration.

  • 20.
    Nairn, C.M.C.
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Bingham, R.
    Allen, J.E.
    Large amplitude solitary magnetized plasma waves2005In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 71, no 5, p. 631-643Article in journal (Refereed)
    Abstract [en]

    Waves launched into a magnetized plasma when it is rapidly compressed were studied in the late 1950s by Adlam and Allen. In this paper we show that the equations describing large amplitude magnetized plasma waves, or Adlam–Allen waves, can be reduced to a single nonlinear equation, namely the Korteweg–de Vries equation and that the solutions of this equation are in agreement with the results obtained previously by Adlam and Allen. The solutions of both the Adlam–Allen equations and the Korteweg–de Vries equation take the form of solitary waves and periodic wave trains.

  • 21. Shukla , N.
    et al.
    Shukla , P. K.
    Liu, C. S.
    Umeå University, Faculty of Science and Technology, Physics.
    Morfill, G.E.
    Generation of magnetic fields in a positive-negative dusty plasma2007In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 73, p. 141-Article in journal (Refereed)
  • 22.
    Shukla, N
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. Also at the Grupo de Lasers e Plasmas, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade Técnica de Lisboa, Lisbon, Portugal.
    Shukla, P K
    Polarization-force-induced dust grain acceleration and intrinsic magnetization of dusty plasmas2010In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 76, p. 677-680Article in journal (Refereed)
    Abstract [en]

    It is shown that the polarization force, arising from interactions between thermal ions and highly charged dust grains, can accelerate charged dust grains and can also create spontaneous magnetic fields in a quasi-neutral dusty plasma. The present results are relevant for understanding the origin of dust grain acceleration and the generation of spontaneous magnetic fields in cosmic dusty plasmas.

  • 23.
    Shukla, Nitin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, P. K.
    Generation of sheared flows by drift waves in a strongly magnetized electron-positron-ion plasma2011In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 77, p. 339-344Article in journal (Refereed)
    Abstract [en]

    It is shown that sheared/zonal flows (ZFs) can be nonlinearly excited by incoherent drift waves (DWs) in a strongly magnetized non-uniform plasma composed of electrons, positrons and ions. The dynamics of incoherent DWs in the presence of ZFs is governed by a wave-kinetic equation. The governing equation for ZFs in the presence of nonlinear forces (associated with nonlinear ion polarization and nonlinear ion-diamagnetic drifts) of the DWs is deduced by combining the Poisson equation, as well as the e-p-i continuity equations, together with appropriate plasma particle velocities in the DW and the ZF fields. Standard techniques are used to derive a nonlinear dispersion relation, which depicts two classes of the modulational instability of the DWs against the ZFs. Non-thermal ZFs can reduce the turbulent cross-field particle transport in non-uniform, strongly magnetized e-p-i plasmas.

  • 24.
    Shukla, Nitin
    et al.
    Institut für Theoretische Physik IV, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, Bochum, Germany.
    Shukla, P. K.
    Proton-temperature-anisotropy-driven magnetic fields in plasmas with cold and relativistically hot electrons2010In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 76, p. 1-5Article in journal (Refereed)
    Abstract [en]

    We present a dispersion relation for a plane-polarized electromagnetic wave in plasmas composed of cold electrons, relativistically hot electrons and bi- Maxwellian protons. It is shown that the free energy in proton-temperature aniso- tropy drives purely growing electromagnetic modes in our three-component plasma. Expressions for the growth rates and thresholds of instabilities are presented. The present results are relevant for explaining the origin of spontaneously generated magnetic fields in laboratory and astrophysical plasmas. 

  • 25.
    Shukla, Nitin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, P. K.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Morfill, G.E.
    Amplification of magnetic fields by polaritonic flows in quantum pair plasmas2007In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 73, p. 289-293Article in journal (Refereed)
    Abstract [en]

    It is shown that equilibrium polaritonic flows can amplify magnetic fields in an ultra-cold quantum electron–positron/hole (polaritons) plasma. For this purpose, a linear dispersion relation has been derived by using the quantum generalized hydrodynamic equations for the polaritons, the Maxwell equation, and Faraday's law. The dispersion relation admits purely growing instabilities, the growth rates of which are proportional to the equilibrium streaming speeds of the polaritons. Possible applications of our work to the spontaneous excitation of magnetic fields and the associated cross-field transport of the polaritons in micromechanical systems, compact dense astrophysical objects (e.g. neutron stars), and intense laser–plasma interaction experiments are mentioned.

  • 26.
    Shukla, Nitin
    et al.
    GoLP/Instituto de Plasmas e Fusão Nuclear – Laboratório Associado, Instituto Superior Técnico, Lisboa, Portugal.
    Stockem, A.
    GoLP/Instituto de Plasmas e Fusão Nuclear – Laboratório Associado, Instituto Superior Técnico, Lisboa, Portugal.
    Fiúza, F.
    GoLP/Instituto de Plasmas e Fusão Nuclear – Laboratório Associado, Instituto Superior Técnico, Lisboa, Portugal.
    Silva, L. O.
    GoLP/Instituto de Plasmas e Fusão Nuclear – Laboratório Associado, Instituto Superior Técnico, Lisboa, Portugal.
    Enhancement in the electromagnetic beam-plasma instability due to ion streaming2012In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 78, p. 181-187Article in journal (Refereed)
    Abstract [en]

    We investigate the Weibel instability in counterpropagating electron-ion plasmas with the focus on the ion contribution, considering a realistic mass ratio. A generalized dis- persion relation is derived from relativistic theory by assuming an initially anisotropic temperature, which is represented by a waterbag distribution in momentum space which shows an enhanced growth rate due to the ion response. Two-dimensional particle-in- cell simulations support the theoretical analysis, showing a further amplification of the magnetic field on the ion time scale. The effect of an initially anisotropic temperature is investigated showing that the growth rate is monotonously decreased if the transverse spread is increased. Nevertheless, the presence of ions generates that the instability can develop for significantly higher electron temperatures. Suppression of the oblique mode is also explored by introducing a parallel velocity spread. 

  • 27.
    Shukla, P K
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. Institut für Theoretische Physik IV, Ruhr-Universität Bochum, Bochum, Germany; the Scottish Universities of Physics Alliance (SUPA), Department of Physics, University of Strathclyde, Glasgow, Scotland, UK; Grupo de Lasers e Plasmas, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade Técnica de Lisboa, Lisbon, Portugal.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics. Department of Physics, Linköping University, Linköping, Sweden.
    Potential distribution around a charged dust grain in an electronegative plasma2010In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 76, p. 673-676Article in journal (Refereed)
    Abstract [en]

    The potential distribution around a charged dust grain in an electronegative plasma is obtained by using the appropriate dielectric susceptibilities for the Boltzmann distributed electrons and negative ions, and for the inertial positive ions that are streaming from the bulk plasma into the electronegative plasma sheath. The existence of oscillatory ion wakefields is shown. Positive ions are trapped/focused in the ion wakefields, and subsequently the negative dust particles are attracted to each other, forming ordered dust structures.

  • 28.
    Shukla, Padma
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Bingham, Robert
    Scottish Universities Physics Alliance (SUPA), Department of Physics, University of Strathclyde, Glasgow G4 0NG, UK.
    Phelps, A.D.R
    Scottish Universities Physics Alliance (SUPA), Department of Physics, University of Strathclyde, Glasgow G4 0NG, UK.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Dark and grey electromagnetic electron-cyclotron envelope solitons in an electron-positron magnetoplasma2009In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 75, no 5, p. 575-580Article in journal (Refereed)
    Abstract [en]

    We present an investigation of the amplitude modulation of an external magnetic field-aligned right-hand circularly polarized electromagnetic electron-cyclotron (EMEC) wave in a strongly magnetized electron-positron plasma. It is shown that the dynamics of the modulated EMEC wave packet is governed by a cubic nonlinear Schrödinger equation. The latter reveals that a modulated wave packet can propagate in the form of either a dark or a grey envelope soliton. This result could have relevance to the transport of electromagnetic wave energy over long distances via envelope solitons in the magnetospheres of pulsars and magnetars.

  • 29.
    Shukla, Padma K
    et al.
    Institut für Theoretische Physik IV, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
    Shukla, Nitin
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Generation of magnetic fields by the ponderomotive force of electromagnetic waves in dense plasmas2010In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 76, no 1, p. 25-28Article in journal (Refereed)
    Abstract [en]

    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.

  • 30.
    Shukla, Padma K.
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Physics.
    Zonal flow excitation in plasmas by electron-temperature-gradient modes2004In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 70, no 1, p. 41-46Article in journal (Refereed)
  • 31.
    Shukla, Padma K.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Amplitude modulation of whistlers by modified ion-cyclotron perturbations in plasmas2006In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 72, no 2, p. 149-152Article in journal (Refereed)
    Abstract [en]

    The nonlinear interaction between a large-amplitude whistler pump and the modified ion-cyclotron perturbations is studied. A nonlinear dispersion relation for the modulation/filamentation interaction is derived and solved numerically to investigate the instability properties. We discuss the relevance of the present study with regard to recent laboratory experiments where the modulation/filamentation of a whistler pump by the modified ion-cyclotron waves has been observed.

  • 32.
    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, and Centre for Fundamental Physics, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon 0X11 0QX, United Kingdom.
    Acceleration of ions by the radiation pressure in a magnetized electron-positron-ion plasma2006In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 72, no 2, p. 159-162Article in journal (Refereed)
    Abstract [en]

    It is shown that the ponderomotive force of magnetic-field aligned circularly polarized electromagnetic waves can create space charge electric fields in a magnetized electron-positron-ion plasma. The space charge electric fields can; in turn, accelerate ions. Possible applications to the origin of energetic ions in laboratory plasmas and astrophysical settings axe discussed.

  • 33.
    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-Durban, Durban 4000, South Africa; The Nonlinear Physics Centre & Centre for Plasma Science and Astrophysics, Ruhr-Universität Bochum, D-44780 Bochum, Germany; Max-Planck-Institut für extraterrestrische Physik, D-85741 Garching, Germany; Grupo de Lasers e Plasmas, Departamento de Física do Instituto Superior Técnico, Universidade Técnica de Lisboa, 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 G4 0NG, UK.
    Compressional magnetoacoustic waves in a quantum dusty magnetoplasma2008In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 74, no 1, p. 107-110Article in journal (Refereed)
    Abstract [en]

    The linear dispersion relation for compressional magnetoacoustic waves in a quantum magnetoplasma, is derived, taking into account the quantum Bohm potential and the rnagnetization of electrons due to the electron-1/2 spin effect. It is found that the quantum forces produce the wave dispersion at quantum scales, which depend on the external magnetic field strength.

  • 34.
    Shukla, Padma Kant
    Institut für Theoretische Physik IV, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
    Excitation of electrostatic ion-cyclotron-like modes by the electron density ripple in dusty magnetoplasmas2009In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 75, p. 433-436Article in journal (Other academic)
    Abstract [en]

    It is shown that electrostatic ion-eyelotron (EIC)-like modes can be excited by the pre-existing electron density ripple across the external magnetic field in a dusty magnetoplasma. For this purpose, we use the ion continuity and momentum equations, together with the Boltzmann-distributed electrons, and derive the standard Mathieu equation. The latter admits unstable solutions, demonstrating that the EIC-like modes in dusty magnetoplasms can be driven due to the free energy in the electron density ripple. the electron density ripple.

  • 35.
    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; Scottish Universities Physics Alliance Department of Physics, University of Strathclyde, Glasgow, Scotland; Centre for Fundamental Physics, Rutherford Appleton Laboratory, Chilton, Didcot, UK; GoLP/Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, 1049-001 Lisboa, Portugal; School of Physics, University of KwaZulu-Natal, 4000 Durban, South Africa.
    Excitation of ion wakefields by electromagnetic pulses in dense plasmas2009In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 75, no 1, p. 15-18Article in journal (Other academic)
    Abstract [en]

    The excitation of electrostatic ion wakefields by electromagnetic pulses in a very dense plasma is considered. For this purpose a wave equation for the ion wakefield in the presence of the ponderomotive force of the electromagnetic waves is obtained. Choosing a typical profile for the electromagnetic pulse, the form of the ion wakefields is deduced. The electromagnetic wave-generated ion wakefields can trap protons and accelerate them to high energies in dense plasmas.

  • 36.
    Shukla, Padma Kant
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. Institut für Theoretische Physik IV, Ruhr-Universität Bochum, D-44780 Bochum, Germany; Scottish Universities Physics Alliance (SUPA), Department of Physics, University of Strathclyde, Glasgow G4 0NG, Scotland, United Kingdom; Science and Technology Facilities Council (STFC) Centre for Fundamental Physics, Rutherford Appleton Laboratory, Harwell Science and Innovation Centre, Chilton, Didcot, Oxon, OX11 0QX, United Kingdom; GoLP/Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, 1049-001 Lisboa, Portugal; School of Physics, University of KwaZulu-Natal, 4000 Durban, South Africa.
    Morfill, GE
    Low-frequency electrostatic wave in a metallic electron-hole-ion plasma with nanoparticles2009In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 75, p. 581-585Article in journal (Other academic)
    Abstract [en]

    We investigate die dispersion property of a, low-frequency, electrostatic wave in a dense metallic electron-hole-ion plasma with nanoparticles. The latter are charged due to the Held emission, and hence the metallic can be regarded as charged dust rods surrounded by degenerate electrons and holes and non-degenerate ions. By using a quantum hydrodynamic model for the electrons and holes, we obtain the electron and hole number density perturbations, Mile be In awl dust rod number density perturbations follow the classical expressions. A dispersion relation for the low-frequency electrostatic wave in our multi-species dense metallic plasma 4 derived and analyzed. The possibility of exciting non-thermal electrostatic waves is also discussed.

  • 37. Shukla, Padma
    et al.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Physics.
    Quantum Hall-MHD equations for a non-uniform dense magnetoplasma with electron temperature anisotropy2008In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 74, no 5, p. 575-579Article in journal (Refereed)
  • 38.
    Stefan, Martin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Brodin, Gert
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Haas, Fernando
    Marklund, Mattias
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Effects of the electron spin on the nonlinear generation of quasi-static magnetic fields in a plasma2010In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 76, no 6, p. 865-873Article in journal (Refereed)
    Abstract [en]

    Through an extended kinetic model, we study the nonlinear generation of quasi-static magnetic fields by high-frequency fields in a plasma, taking into account the effects of the electron spin. It is found that although the largest part of the nonlinear current in a moderate density, moderate temperature plasma is due to the classical terms, the spin may still give a significant contribution to the magnetic field generation mechanism. Applications of our results are discussed.

  • 39.
    Stenflo, Lennart
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Brodin, Gert
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Large amplitude circularly polarized waves in quantum plasmas2010In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 76, no 3-4, p. 261-265Article in journal (Refereed)
    Abstract [en]

    Some previous dispersion relations for large amplitude waves in plasmas are generalized so that also quantum effects are included.

  • 40.
    Stenflo, Lennart
    et al.
    Department of Physics, Linkoping University, SE-581 83 Linkoping, Sweden.
    Brodin, Gert
    Umeå University, Faculty of Science and Technology, Department of Physics.
    On the parametric decay of a circularly polarized wave2011In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 77, no 4, p. 431-435Article in journal (Refereed)
    Abstract [en]

    The nonlinear decay of a circularly polarized wave is reconsidered. We deduce an explicit expression for the growth rate, and present it in a form which is significantly simpler than those of previous papers.

  • 41.
    Stenflo, Lennart
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Marklund, Mattias
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Three-dimensional instability of two nonlinearly coupled electromagnetic waves in a plasma2008In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 74, no 3, p. 371-379Article in journal (Refereed)
    Abstract [en]

    The three-dimensional instability of two coupled electromagnetic waves in an unmagnetized plasma is investigated theoretically and numerically. In the regime of two-plasmon decay, where one pump wave frequency is approximately twice the electron plasma frequency, we find that the coupled pump waves give rise to enhanced instability with wavevectors between those of the two beams. In the case of ion parametric decay instability, where the pump wave decays into one Langmuir wave and one ion acoustic wave, the instability regions are added with no distinct amplification. Our investigation can be useful in interpreting laser-plasma as well as ionospheric heating experiments.

  • 42. Stenflo, Lennart
    et al.
    Marklund, Mattias
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Rogue waves in the atmosphere2010In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 76, no Part 3-4, p. 293-295Article in journal (Refereed)
    Abstract [en]

    The appearance of rogue waves is well known in oceanographics, optics, and cold matter systems. Here we show a possibility for the existence of atmospheric rogue waves.

  • 43.
    Stenflo, Lennart
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Nonlinear acoustic-gravity waves2009In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 75, no 6, p. 841-847Article in journal (Refereed)
    Abstract [en]

    Previous results on nonlinear acoustic–gravity waves are reconsidered. It turns out that the mathematical techniques used are somewhat similar to those already adopted by the plasma physics community. Consequently, a future interaction between physicists in different fields, e.g. in meteorology and plasma physics, can be very fruitful.

  • 44.
    Vedin, Jörgen
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Rönnmark, Kjell
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Parallel electric fields: variations in space and time on auroral field lines2008In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 74, no 1, p. 53-64Article in journal (Refereed)
    Abstract [en]

    We present results from a particle–fluid simulation of auroral electrons and discuss the distribution of parallel electric fields along auroral field lines and the processes occurring during the build up of these electric fields. Neglecting field-aligned ion dynamics, the main potential drop has a width of about 5000, km and is centered at an altitude of roughly 5000, km. We find that the gradient in the potential becomes steeper and the build up of the potential drop becomes faster if the temperature of the magnetospheric electrons is lower.

  • 45.
    Wallin, Erik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Zamanian, Jens
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Brodin, Gert
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Three-wave interaction and Manley-Rowe relations in quantum hydrodynamics2014In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 80, p. 643-652Article in journal (Refereed)
    Abstract [en]

    The theory for nonlinear three-wave interaction in magnetized plasmas is reconsidered using quantum hydrodynamics. The general coupling coefficients are calculated for the generalized Bohm de Broglie term. It is found that the Manley-Rowe relations are fulfilled only if the form of the particle dispersive term coincides with the standard expression. The implications of our results are discussed.

1 - 45 of 45
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