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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.
    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 K.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Dispersion relation for electromagnetic wave propagation in a strongly magnetized plasma2006In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 8, no January, p. 16-Article in journal (Refereed)
    Abstract [en]

    A dispersion relation for electromagnetic wave propagation in a strongly magnetized cold plasma is deduced, taking photon–photon scattering into account. It is shown that the combined plasma and quantum electrodynamic effect is important for understanding the mode-structures in magnetar and pulsar atmospheres. The implications of our results are discussed.

  • 3.
    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.

  • 4.
    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.

  • 5.
    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.

  • 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.
    Wave Generation in a Warm Magnetized Multi-Component Plasma2014In: Contributions to Plasma Physics, ISSN 0863-1042, E-ISSN 1521-3986, Vol. 54, no 7, p. 623-625Article in journal (Refereed)
    Abstract [en]

    The resonant interaction between three waves propagating perpendicularly to an external magnetic field in a plasma is considered. We present the explicit expressions for the three wave coupling coefficients of a warm multi-component plasma. The results of previous work on the generation of THz radiation by laser plasma interaction are significantly improved. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • 7.
    Brodin, Gert
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stenflo, Lennart
    Linköping University, Sweden.
    Juul Rasmussen, Jens
    Focus issue to honour Hans L Pecseli on his 70th birthday2017In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 92, no 1, article id 010301Article in journal (Other academic)
  • 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. Daldorff, LKS
    et al.
    Pecseli, HL
    Trulsen, JK
    Ulriksen, MI
    Eliasson, Bengt
    Stenflo, Lennart
    Department of Physics, Linköping University, SE-58183 Linköping, Sweden .
    Nonlinear beam generated plasma waves as a source for enhanced plasma and ion acoustic lines2011In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 18, no 15, p. 052107-052114Article in journal (Refereed)
    Abstract [en]

    Observations by, for instance, the EISCAT Svalbard Radar (ESR) demonstrate that the symmetry of the naturally occurring ion line in the polar ionosphere can be broken by an enhanced, nonthermal, level of fluctuations (naturally enhanced ion-acoustic lines, NEIALs). It was in many cases found that the entire ion spectrum can be distorted, also with the appearance of a third line, corresponding to a propagation velocity significantly slower than the ion acoustic sound speed. It has been argued that selective decay of beam excited primary Langmuir waves can explain some phenomena similar to those observed. We consider a related model, suggesting that a primary nonlinear process can be an oscillating two-stream instability, generating a forced low frequency mode that does not obey any ion sound dispersion relation. At later times, the decay of Langmuir waves can give rise also to enhanced asymmetric ion lines. The analysis is based on numerical results, where the initial Langmuir waves are excited by a cold dilute electron beam. By this numerical approach, we can detect fine details of the physical processes, in particular, demonstrate a strong space-time intermittency of the electron waves in agreement with observations. Our code solves the full Vlasov equation for electrons and ions, with the dynamics coupled through the electrostatic field derived from Poisson's equation. The analysis distinguishes the dynamics of the background and beam electrons. This distinction simplifies the analysis for the formulation of the weakly nonlinear analytical model for the oscillating two-stream instability. The results have general applications beyond their relevance for the ionospheric observations.

  • 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.
    Eliasson, Bengt
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. Theoretische Physik IV, Ruhr – Universität Bochum, Bochum, Germany.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics. Department of Physics, Linköping University, Linköping, Sweden.
    Full-scale simulation study of the initial stage of ionospheric turbulence2008In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 113, no A2, article id A02305Article in journal (Refereed)
    Abstract [en]

    We present a full-scale simulation of the nonlinear interaction between an intense electromagnetic wave and the Earth's ionosphere, by means of a generalized Zakharov model. The radio wave propagates from the neutral atmosphere into the ionospheric plasma layer and reaches the turning points of the ordinary and extraordinary wave modes. At the turning point of the ordinary mode, a parametric instability takes place in which the electromagnetic wave decays into an electron plasma wave and an ion acoustic wave with a typical wavelength of one meter. This is followed by collapse and caviton formation and trapping of the intense electron plasma wave. The cavitons lead to an efficient excitation of slow X (or Z) waves that propagate further into the denser ionospheric layer at higher altitudes. We use a realistic ion (oxygen) mass, length scales, and other plasma parameters. This numerical study should be useful for understanding the nonlinear interaction between intense radio waves and the ionosphere.

  • 12.
    Eliasson, Bengt
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stenflo, LennartUmeå University, Faculty of Science and Technology, Department of Physics.Bingham, RobertMendonca, Jose TitoMamun, A. A.Shaikh, Dastgeer
    Journal of Plasma Physics vol 76 issue 3-4: special issue in honor of professor Padma Kant Shukla on the occasion of his 60th birthday 2010Conference proceedings (editor) (Other academic)
    Abstract [en]

    It is our great pleasure to dedicate this special issue of Journal of Plasma Physics to our dear friend and colleague Professor Padma Kant Shukla on the occasion of his 60th birthday on 7th July 2010. Padma is one of the most prominent and productive scientists in plasma physics and in neighboring fields, and has published more than 1300 papers in scientific journals. It has for some time been the aim of his friends to honor him on this occasion, and earlier this year we sent out invitations to distinguished scientists who have collaborated with Padma over the years. The response has been overwhelming, and we collected 43 manuscripts, covering a diverse range of topics in plasma physics, which are now published in this issue. We believe that these papers reflect some of the impact of Padma's research in plasma physics.

  • 13.
    Eriksson, Daniel
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Brodin, Gert
    Umeå University, Faculty of Science and Technology, Physics.
    Marklund, Mattias
    Umeå University, Faculty of Science and Technology, Physics.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Physics.
    Possibility to measure elastic photon-photon scattering in vacuum2004In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 70, no 1, p. 013808-Article in journal (Refereed)
    Abstract [en]

    Photon-photon scattering in vacuum due to the interaction with virtual electron-positron pairs is a consequence of quantum electrodynamics. A way for detecting this phenomenon has been devised based on interacting modes generated in microwave wave guides or cavities [G. Brodin, M. Marklund, and L. Stenflo, Phys. Rev. Lett. 87, 171801 (2001)]. Here we materialize these ideas, suggest a concrete cavity geometry, make quantitative estimates and propose experimental details. It is found that detection of photon-photon scattering can be within the reach of present day technology.

  • 14. Karimov, A. R.
    et al.
    Shatokhin, V. L.
    Yu, M. Y.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics. Linköping University, Linköping ,SE-58183, Sweden.
    The processes of nonequilibrium exchange in rotating plasma flows2016In: II CONFERENCE ON PLASMA & LASER RESEARCH AND TECHNOLOGIES, 2016, Vol. 747, article id 012077Conference paper (Refereed)
    Abstract [en]

    The mechanisms of energy/momentum exchange in rotating and compressing plasma flows have been discussed. It has been shown that such flows are capable of transforming the energy of different degrees of freedom into the energy of one degree owing to the interaction of the coupled nonlinear radial, axial and azimuthal electron-ion oscillations. These processes may lead to the additional acceleration of the flow in azimuthal or axial direction so they might be instrumental for the creation of space thrusters employing pulse transformations for propulsion.

  • 15.
    Karimov, A. R.
    et al.
    Institute for High Temperatures, Russian Academy of Sciences, Izhorskaya 13/19, Moscow 127412, Russia.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Yu, M. Y.
    Department of Physics, Institute for Fusion Theory and Simulation, Zhejiang University, 310027 Hangzhou, China.
    Coupled azimuthal and radial flows and oscillations in a rotating plasma2009In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 16, p. 062313-062319Article in journal (Refereed)
    Abstract [en]

    Nonlinear coupling between the radial, axial, and azimuthal flows in a cold rotating plasma is considered nonperturbatively by first constructing a basis solution for a rotating flow. Simple but exact solutions that describe an expanding plasma with oscillatory flow fields are then obtained. These solutions show that the energy in the radial and axial flow components can be transferred to the azimuthal component but not the vice versa. Nonlinear electron velocity oscillations in the absence of electron density oscillations at the same frequency are shown to exist.

  • 16. Karimov, A. R.
    et al.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Yu, M. Y.
    Coupled flows and oscillations in asymmetric rotating plasmas2009In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 16, no 10, p. 102303-102307Article in journal (Refereed)
    Abstract [en]

    Nonlinear coupling among the radial, axial, and azimuthal flows in an asymmetric cold rotating plasma is considered nonperturbatively. Exact solutions describing an expanding or contracting plasma with oscillations are then obtained. It is shown that despite the flow asymmetry the energy in the radial and axial flow components can be transferred to the azimuthal component but not the vice versa, and that flow oscillations need not be accompanied by density oscillations.

  • 17. Karimov, A. R.
    et al.
    Yu, M. Y.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics. Department of Physics, Linköping University, SE-58183 Linköping, Sweden.
    Expansion of a cold non-neutral plasma slab2014In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 21, no 12, article id 122304Article in journal (Refereed)
    Abstract [en]

    Expansion of the ion and electron fronts of a cold non-neutral plasma slab with a quasi-neutral core bounded by layers containing only ions is investigated analytically and exact solutions are obtained. It is found that on average, the plasma expansion time scales linearly with the initial inverse ion plasma frequency as well as the degree of charge imbalance, and no expansion occurs if the cold plasma slab is stationary and overall neutral. However, in both cases, there can exist prominent oscillations on the electron front. 

  • 18. Karimov, AR
    et al.
    Yu, MY
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Flow oscillations in radial expansion of an inhomogeneous plasma layer2011In: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 375, no 27, p. 2629-2636Article in journal (Refereed)
    Abstract [en]

    The cylindrically symmetric radial evolution of an inhomogeneous plasma layer expanding into vacuum is investigated nonperturbatively by first determining the spatial structure of the plasma flow structure. The evolution is then governed by a set of ordinary differential equations. The effect of the plasma inhomogeneity on the nonlinear coupling among the electron and ion flow components and oscillations is investigated

  • 19. 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.

  • 20.
    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.

  • 21.
    Marklund, Mattias
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Brodin, Gert
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics. Linkoping Univ, Dept Phys, SE-58183 Linkoping, Sweden.
    Liu, Chuan S
    New quantum limits in plasmonic devices2008In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 84, no 1, article id 17006Article in journal (Refereed)
    Abstract [en]

    Surface plasmon polaritons (SPPs) have recently been recognized as an important future technique for microelectronics. Such SPPs have been studied using classical theory. However, current state-of-the-art experiments are rapidly approaching nanoscales, and quantum effects can then become important. Here we study the properties of quantum SPPs at the interface between an electron quantum plasma and a dielectric material. It is shown that the effect of quantum broadening of the transition layer is most important. In particular, the damping of SPPs does not vanish even in the absence of collisional dissipation, thus posing a fundamental size limit for plasmonic devices. Consequences and applications of our results are pointed out.

  • 22.
    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.

  • 23.
    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.

  • 24.
    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.

  • 25.
    Shukla, Nitin
    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.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Nonlinear electromagnetic wave equations for superdense magnetized plasmas2009In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 16, no 7, p. 072114-4 sidorArticle in journal (Refereed)
    Abstract [en]

    By using the quantum hydrodynamic and Maxwell equations, we derive the generalized nonlinear electron magnetohydrodynamic, the generalized nonlinear Hall-MHD HMHD, and the generalized nonlinear dust HMHD equations in a self-gravitating dense magnetoplasma. Our nonlinear equations include the self-gravitating, the electromagnetic, the quantum statistical electron pressure, as well as the quantum electron tunneling and electron spin forces. They are useful for investigating a number of wave phenomena including linear and nonlinear electromagnetic waves, as well as three-dimensional electromagnetic wave turbulence spectra and structures arising from mode coupling processes at nanoscales in dense quantum magnetoplasmas.

  • 26.
    Shukla, Nitin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Brodin, Gert
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Ion streaming instability in a quantum dusty magnetoplasma2008In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 15, p. 044503-Article in journal (Refereed)
    Abstract [en]

    It is shown that a relative drift between the ions and the charged dust particles in a magnetized quantum dusty plasma can produce an oscillatory instability in a quantum dust acousticlike wave. The threshold and growth rate of the instability are presented. The result may explain the origin of low-frequency electrostatic fluctuations in semiconductors quantum wells.

  • 27.
    Shukla, Nitin
    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.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Magnetization of a quantum plasma by photons2010In: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 374, no 15-16, p. 1749-1750Article in journal (Refereed)
    Abstract [en]

    It is shown that the ponderomotive force of large-amplitude electromagnetic waves (photons), which includes the electron spin current and exchange potential contributions in a quantum plasma, can generate magnetic fields. The present result can account for the magnetic fields in dense compact astrophysical objects and in the next generation laser–solid density plasma interaction experiments.

  • 28.
    Shukla, Nitin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma
    Institut für Theoretische Physik IV, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
    Stenflo, Lennart
    Department of Physics, Linköping University,SE-58183 Linköping, Sweden.
    Magnetization of a warm plasma by the nonstationary ponderomotive force of an electromagnetic wave2009In: 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. 80, p. 027401-Article in journal (Refereed)
    Abstract [en]

    It is shown that magnetic fields can be generated in a warm plasma by the nonstationary ponderomotive force of a large-amplitude electromagnetic wave. In the present Brief Report, we derive simple and explicit results that can be useful for understanding the origin of the magnetic fields that are produced in intense laser-plasma interaction experiments.

  • 29.
    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.

  • 30.
    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.

  • 31.
    Shukla, Padma
    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.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wake field generation and nonlinear evolution in a magnetized electron-positron-ion plasma2008In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 15, no 8, p. 082305-Article in journal (Refereed)
    Abstract [en]

    The nonlinear propagation of a circularly polarized electromagnetic (CPEM) wave in a strongly magnetized electron-positron-ion plasma is investigated. Two coupled equations describing the interaction between a high-frequency CPEM wave and the low-frequency electrostatic wake field are derived. It is found that the generation of the wake fields partly depends on the presence of the ion species and the external magnetic field. The wake field generation in turn leads to deceleration and frequency down conversion of the electromagnetic pulse.

  • 32.
    Shukla, Padma K
    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.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Excitation of multiple wakefields by short laser pulses in quantum plasmas2009In: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 373, no 35, p. 3165-3168Article in journal (Refereed)
    Abstract [en]

    We present a theoretical investigation of the excitation of multiple electrostatic wakefields by the ponderomotive force of a short electromagnetic pulse propagating through a dense plasma. It is found that the inclusion of the quantum statistical pressure and quantum electron tunneling effects can qualitatively change the classical behavior of the wakefield. In addition to the well-known plasma oscillation wakefield, with a wavelength of the order of the electron skin depth (λe=c/ωpe, which in a dense plasma is of the order of several nanometers, where c is the speed of light in vacuum and ωpe is the electron plasma frequency), wakefields in dense plasmas with a shorter wavelength (in comparison with λe) are also excited. The wakefields can trap electrons and accelerate them to extremely high energies over nanoscales.

  • 33.
    Shukla, Padma K
    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.
    Modulational instability of nonlinearly interacting incoherent sea states2007In: JETP Letters: Journal of Experimental And Theoretical Physics Letters, ISSN 0021-3640, E-ISSN 1090-6487, Vol. 84, no 12, p. 645-649Article in journal (Refereed)
    Abstract [en]

    The modulational instability of nonlinearly interacting spatially incoherent Stokes waves is analyzed. Starting from a pair of nonlinear Schrödinger equations, we derive a coupled set of wave-kinetic equations by using the Wigner transform technique. It is shown that the partial coherence of the interacting waves induces novel effects on the dynamics of crossing sea states.

  • 34.
    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.

  • 35.
    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.

  • 36.
    Shukla, Padma Kant
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Eliasson, BengtUmeå University, Faculty of Science and Technology, Department of Physics.Stenflo, LennartUmeå University, Faculty of Science and Technology, Department of Physics.
    Frontiers in Modern Plasma Physics: 2008 ICTP International Workshop on the Frontiers of Modern Plasma Physics2008Conference proceedings (editor) (Other academic)
  • 37.
    Shukla, Padma Kant
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Magnetization of plasmas2010In: 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. 1-6Conference paper (Other academic)
    Abstract [en]

    Wecritically examine and evaluate several physical mechanisms that are responsiblefor the seed magnetic fields in plasmas. The plasma magnetizationis attributed to sources that foster motion of the backgroundplasma electrons against the ions. The resulting space charge electricfield and currents, in turn, are detrimental for the plasmamagnetization.

  • 38.
    Shukla, Padma Kant
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Eliasson, BengtUmeå University, Faculty of Science and Technology, Department of Physics.Stenflo, LennartUmeå University, Faculty of Science and Technology, Department of Physics.
    New Aspects of Plasma Physics: Proceedings of the 2007 ICTP Summer College on Plasma Physics2008Conference proceedings (editor) (Other academic)
    Abstract [en]

    The “2007 ICTP Summer College on Plasma Physics'' was held at the Abdus Salam International Centre for Theoretical Physics (ICTP), Trieste, Italy, during the period 30 July to 24 August 2007. The purpose of the summer college was 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 senior scientists in an informal manner. A large number of talks were given by invited speakers and experts, with information about the most recent advances in magnetic confinement fusion and tokamak physics, intense laser–plasma interactions and plasma-based particle acceleration, turbulence, dusty plasmas, and the emerging field of quantum plasmas. A selected number of papers from the invited speakers appear in this book.

  • 39. Shukla, Padma Kant
    et al.
    Eliasson, Bengt
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stimulated scattering of intense radio waves in partially ionized space dusty plasmas2004In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 109, no A3, article id A03301Article in journal (Refereed)
    Abstract [en]

    The nonlinear interaction between intense ordinary mode (O-mode) radio waves and modified magnetoacoustic waves in partially ionized space dusty plasmas is considered, including the combined action of the radio wave pressure and the electron Joule heating caused by the O-mode electric field. A set of equations containing the wave equation for the radio waves and the electron density and temperature fluctuations associated with the modified magnetoacoustic waves is derived. The set is then used to investigate decay and modulational instabilities of a constant amplitude O-mode radio wave in the Earth's ionosphere and mesosphere.

  • 40.
    Shukla, Padma
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wiklund, Krister
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Excitation of zonal flows by electron convective cells in a nonuniform dusty magnetoplasma2001In: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 283, no 5-6, p. 371-375Article in journal (Refereed)
    Abstract [en]

    It is shown that the ponderomotive force of electron convective cells can generate zonal flows (or dust convective cells) in a nonuniform magnetoplasma. For this purpose, two fluid equations are used to derive a pair of coupled equations which govern the nonlinear coupling between electron and dust convective cells. A dispersion relation for the parametric interactions is deduced from the mode coupling equations. Explicit expressions for the growth rates of electron convective cell driven zonal flows are then obtained. The relevance of our investigation to laboratory and space plasmas is pointed out.

  • 41.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Minnen från min tid som gästforskare i Sovjetunionen2011In: Thule: norrländsk kulturtidskrift, ISSN 0280-8692Article in journal (Other (popular science, discussion, etc.))
  • 42.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Minnen från Sovjetunionen2012Book (Other (popular science, discussion, etc.))
  • 43.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Rysslands Vetenskapsakademi2009In: Thule: Kungliga Skytteanska Samfundets årsbok 2009, Umeå: Kungl. Skytteanska samfundet , 2009, p. 11-17Chapter in book (Refereed)
  • 44.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Öppna Säpo-arkiven2011In: Axess, ISSN 1651-0941Article in journal (Other (popular science, discussion, etc.))
  • 45.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Övervakad av KGB2012In: Kungl. Skytteanska samfundets årsbok. 2012, umeå: Kungl. Skytteanska Samfundet , 2012, Vol. 25, p. 45-51Chapter in book (Other (popular science, discussion, etc.))
  • 46.
    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.
    Comment on "Terahertz wave generation by the upper hybrid wave"2011In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 18, p. 074701-Article in journal (Refereed)
  • 47.
    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.
    Decay interactions involving two electrostatic waves and one arbitrary polarized wave in a magnetized plasma2010In: AIP Conference Proceedings, ISSN 0094-243X, E-ISSN 1551-7616, Vol. 1306, p. 14-17Article in journal (Refereed)
    Abstract [en]

    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 some previous results deduced directly from the basic plasma equations contain inappropriate approximations leading to unphysical results. Finally, the generalization to more elaborate plasma models, containing e.g. kinetic effects, is presented.

  • 48.
    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.

  • 49.
    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.

  • 50.
    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.
    Parametric decay of whistler waves in electron magnetohydrodynamics2011In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 83, no 3, p. 035503-035503Article in journal (Refereed)
    Abstract [en]

    The nonlinear interaction between three whistler waves is reconsidered. We argue that the squared growth rate of parametric decay instability has to be expressed in a form that is always positive.

12 1 - 50 of 56
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