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  • 1.
    Bergman, Jan
    et al.
    Swedish Institute of Space Physics, Box 537, SE-751 21 Uppsala, Sweden.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Erratum:: "Linear wave dispersion laws in unmagnetized relativistic plasma: Analytical and numerical results" [Phys. Plasmas 8, 1482 (2001)]2009In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 16, no 12, p. 129902-Article in journal (Refereed)
  • 2. 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.

  • 3.
    Brodin, Gert
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Marklund, Mattias
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Quantum-electrodynamical photon splitting in magnetized Nonlinear pair plasmas2007In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 98, no 12, p. 5001-4 sidorArticle in journal (Refereed)
    Abstract [en]

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

  • 4.
    Daldorff, Lars K. S.
    et al.
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden.
    Bengt, Eliasson
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Parallelization of a Vlasov–Maxwell solver in four-dimensional phase space2009In: Parallel Computing, ISSN 0167-8191, E-ISSN 1872-7336, Vol. 35, no 2, p. 109-115Article in journal (Refereed)
    Abstract [en]

    We present a parallelized algorithm for solving the time-dependent Vlasov–Maxwell system of equations in the four-dimensional phase space (two spatial and velocity dimensions). One Vlasov equation is solved for each particle species, from which charge and current densities are calculated for the Maxwell equations. The parallelization is divided into two different layers. For the first layer, each plasma species is given its own processor group. On the second layer, the distribution function is domain decomposed on its dedicated resources. By separating the communication and calculation steps, we have met the design criteria of good speedup and simplicity in the implementation.

  • 5.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Department of Physics. Theoretische Physik IV, Ruhr-Universität Bochum, Bochum, Germany.
    A nonuniform nested grid method for simulations of RF induced ionospheric turbulence2007In: Computer Physics Communications, ISSN 0010-4655, E-ISSN 1879-2944, Vol. 178, p. 8-14Article in journal (Refereed)
    Abstract [en]

    We present a numerical scheme to simulate radio-frequency (RF) induced ionospheric turbulence, in which an electromagnetic wave is injected into the overhead ionospheric plasma. At the turning point of the ordinary mode, the electromagnetic wave undergoes linear mode-conversion to electrostatic Langmuir and upper hybrid waves that can have a much shorter wavelength than the electromagnetic wave. In order to resolve both the electromagnetic and electrostatic waves, avoiding severe restrictions on the time step due to the Courant–Friedrich–Lewy (CFL) condition, the equation of motion for the plasma particles is solved on a denser grid than that for the Maxwell equations near the mode-conversion region. An interpolation scheme is employed to calculate the electromagnetic field in the equation of motion of the plasma particles, and an averaging scheme is used to calculate the current density acting as a source in the Maxwell equation. Special care has to be taken to reduce numerical recurrence effects when the wavelength of the electrostatic wave is of the same order or shorter than the coarse grid spacing of the electromagnetic wave.

  • 6.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Physics.
    Outflow boundary conditions for the Fourier transformed three-dimensional Vlasov-Maxwell system2007In: Journal of Computational Physics, ISSN 0021-9991, E-ISSN 1090-2716, Vol. 225, no 2, p. 1508-1532Article in journal (Refereed)
  • 7.
    Eliasson, Bengt
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Liu, Chuan S.
    Department of Physics, University of Maryland.
    Shao, Xi
    Department of Physics, University of Maryland.
    Sagdeev, Roald Z.
    Department of Physics, University of Maryland.
    Shukla, Padma Kant
    Institut für Theoretische Physik IV, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
    Laser acceleration of monoenergetic protons via a double layer emerging from an ultra-thin foil2009In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 11, p. 073006-073025Article in journal (Refereed)
    Abstract [en]

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

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

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

  • 9.
    Eliasson, Bengt
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Liu, Chuan Sheng
    Shao, Xi
    Sagdeev, Roald Z.
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Laser radiation pressure acceleration of monoenergetic protons in an ultra-thin foil2009In: New Developments in Nonlinear Plasma Physics: Proceedings of the 2009 ICTP Summer College on Plasma Physics and International Symposium on Cutting Edge Plasma Physics / [ed] Bengt Eliasson, Padma Kant Shukla, American Institute of Physics , 2009, p. 35-49Conference paper (Refereed)
    Abstract [en]

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

  • 10.
    Eliasson, Bengt
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Papadopoulos, K.
    Departments of Physics and Astronomy, University of Maryland, College Park, Maryland, USA.
    Penetration of ELF currents and electromagnetic fields into the Earth's equatorial ionosphere2009In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 114, p. A10301-A10314Article in journal (Refereed)
    Abstract [en]

    The penetration of extremely low frequency (ELF) transient electromagnetic fields and associated currents in the Earth's equatorial E-region plasma is studied theoretically and numerically. In the low-frequency regime, the plasma dynamics of the E-region is characterized by helicon waves since the ions are viscously coupled to neutrals while the electrons remain mobile. For typical equatorial E-region parameters, the plasma is magnetically insulated from penetration of very long timescale magnetic fields by a thin diffusive sheath. Wave penetration driven by a vertically incident pulse localized in space and time leads to both vertical penetration and the triggering of ELF helicon/whistler waves that carry currents obliquely to the magnetic field lines. The study presented here may have relevance for ELF wave generation by lightning discharges and seismic activity and can lead to new concepts in ELF/ULF injection in the earth-ionosphere waveguide.

  • 11.
    Eliasson, Bengt
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Shukla, Padma K.
    Umeå University, Faculty of Science and Technology, Physics.
    Theoretical and numerical studies of relativistic ion and electron holes in plasmas2007In: Physics of Plasmas, Vol. 14, p. 056703/1-7Article in journal (Refereed)
  • 12.
    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.

  • 13.
    Eliasson, Bengt
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics.
    New developments in nonlinear plasma physics:  2009In: Proceedings of the 2009 ICTP Summer College on Plasma Physics and International Symposium on Cutting Edge Plasma Physics, Trieste (Italy), 10–28 August 2009, American Institute of Physics , 2009, , p. 300Conference paper (Other academic)
  • 14.
    Eliasson, Bengt
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma KantUmeå University, Faculty of Science and Technology, Department of Physics.
    New frontiers in advanced plasma physics: Proceedings of the 2010 ICTP International Advanced Workshop on the Frontiers of Plasma Physics2010Conference proceedings (editor) (Other academic)
    Abstract [en]

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

  • 15.
    Eliasson, Bengt
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma Kant
    Theoretische Physik IV, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
    Nonlinear aspects of quantum plasma physics: Nanoplasmonics and nanostructures in dense plasmas2009In: Plasma and Fusion Research, ISSN 1880-6821, E-ISSN 1880-6821, Vol. 4, p. 032-Article in journal (Refereed)
    Abstract [en]

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

  • 16.
    Eliasson, Bengt
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Physics.
    Simulation study of magnetic holes at the Earth's collisionless bow shock2007In: New Journal of Physics, Vol. 9, p. 168-Article in journal (Other (popular science, discussion, etc.))
  • 17.
    Eliasson, Bengt
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Pavlenko, V.P.
    Department of Physics and Astronomy, Uppsala University, SE-751 20 Uppsala, Sweden.
    Dynamics of nonlinearly interacting magnetic electron drift vortex modes in a nonuniform plasma2009In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 16, p. 042306-Article in journal (Refereed)
    Abstract [en]

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

  • 18.
    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.

  • 19.
    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.

  • 20.
    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.

  • 21.
    Eliasson, Bengt
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Thidé, Bo
    Reply to comment by N. A. Gondarenko et al. on "Simulation study of the interaction between large-amplitude HF radio waves and the ionosphere"2007In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 34, p. L23105-Article in journal (Refereed)
  • 22.
    Eliasson, Bengt
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. Theoretische Physik IV, Ruhr – Universita¨t Bochum, Bochum, Germany.
    Thidé, Bo
    Zakharov simulation study of spectral features of on-demand Langmuir turbulence in an inhomogeneous plasma2008In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 113, no A2, article id A02313Article in journal (Refereed)
    Abstract [en]

    We have performed a simulation study of Langmuir turbulence in the Earth's ionosphere by means of a Zakharov model with parameters relevant for the F layer. The model includes dissipative terms to model collisions and Landau damping of the electrons and ions, and a linear density profile, which models the ionospheric plasma inhomogeneity whose length scale is of the order 10–100 km. The injection of energy into the system is modeled by a constant source term in the Zakharov equation. Langmuir turbulence is excited “on-demand” in controlled ionospheric modification experiments where the energy is provided by an HF radio beam injected into the overhead ionospheric plasma. The ensuing turbulence can be studied with radars and in the form of secondary radiation recorded by ground-based receivers. We have analyzed spectral signatures of the turbulence for different sets of parameters and different altitudes relative to the turning point of the linear Langmuir mode where the Langmuir frequency equals the local plasma frequency. By a parametric analysis, we have derived a simple scaling law, which links the spectral width of the turbulent frequency spectrum to the physical parameters in the ionosphere. The scaling law provides a quantitative relation between the physical parameters (temperatures, electron number density, ionospheric length scale, etc.) and the observed frequency spectrum. This law may be useful for interpreting experimental results.

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

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

  • 24. Fedele, Renato
    et al.
    Jovanovic, Dusan
    de Nicola, Sergio
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma Kant
    Mathematical and physical aspects of controlling the exact solutions of the 3D Gross-Pitaevskii equation2010In: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 374, no 5, p. 788-795Article in journal (Refereed)
    Abstract [en]

    The possibility of the decomposition of the three-dimensional (3D) Gross–Pitaevskii equation (GPE) into a pair of coupled Schrödinger-type equations, is investigated. It is shown that, under suitable mathematical conditions, it is possible to construct the exact controlled solutions of the 3D GPE from the solutions of a linear 2D Schrödinger equation coupled with a 1D nonlinear Schrödinger equation (the transverse and longitudinal components of the GPE, respectively). The coupling between these two equations is the functional of the transverse and the longitudinal profiles. The applied method of nonlinear decomposition, called the controlling potential method (CPM), yields the full 3D solution in the form of the product of the solutions of the transverse and longitudinal components of the GPE. It is shown that the CPM constitutes a variational principle and sets up a condition on the controlling potential well. Its physical interpretation is given in terms of the minimization of the (energy) effects introduced by the control. The method is applied to the case of a parabolic external potential to construct analytically an exact BEC state in the form of a bright soliton, for which the quantitative comparison between the external and controlling potentials is presented.

  • 25.
    Grönlund, Andreas
    et al.
    Umeå Plant Science Center, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences - SE-901 83 Umeå, Sweden.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Marklund, Mattias
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Evolution of rogue waves in interacting wave systems2009In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 86, no 2, p. 24001-Article in journal (Refereed)
    Abstract [en]

    Large-amplitude water waves on deep water have long been known in the seafaring community, and are the cause of great concern for, e.g., oil platform constructions. The concept of such freak waves is nowadays, thanks to satellite and radar measurements, well established within the scientific community. There are a number of important models and approaches for the theoretical description of such waves. By analyzing the scaling behavior of freak wave formation in a model of two interacting waves, described by two coupled non-linear Schrödinger equations, we show that there are two different dynamical scaling behaviors above and below a critical angle θc of the direction of the interacting waves, below which all wave systems evolve and display statistics similar to a wave system of non-interacting waves. The results equally apply to other systems described by the non-linear Schrödinger equations, and should be of interest when designing optical wave guides.

  • 26. Gustavsson, Björn
    et al.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Physics.
    HF radio wave acceleration of ionospheric electrons: Analysis of HF-induced optical enhancements2008In: JOURNAL OF GEOPHYSICAL RESEARCH - SPACE PHYSICS, ISSN 0148-0227, Vol. 113, no 8, p. A08319-Article in journal (Refereed)
    Abstract [en]

    The shape of the HF-pump modified electron energy distribution has long been a central question in the field of ionospheric high-frequency radio wave modification experiments. Here we present estimates of the enhanced differential electron flux, from 1.9 to 100 eV based on optical multiwavelength (6300, 5577, 8446, and 4278 Å) data and 930 MHz incoherent scatter radar measurements of ion temperature, electron temperature and concentration. According to our estimate, the electron energy distribution is depleted in the energy range of 2 to approximately 4 eV, probably caused by electron excitation of vibrational states in N2. At the higher energies the electron energy distribution has a nonthermal tail. Further we show that the altitude variations of the four optical emissions should differ both in altitude coverage and center altitude.

  • 27.
    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.

  • 28. Mamun, A. A.
    et al.
    Shukla, P. K.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Solitary waves and double layers in a dusty electronegative plasma2009In: 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, no 4, p. 046406-Article in journal (Refereed)
    Abstract [en]

    A dusty electronegative plasma containing Boltzmann electrons, Boltzmann negative ions, cold mobile positive ions, and negatively charged stationary dust has been considered. The basic features of arbitrary amplitude solitary waves (SWs) and double layers (DLs), which have been found to exist in such a dusty electronegative plasma, have been investigated by the pseudopotential method. The small amplitude limit has also been considered in order to study the small amplitude SWs and DLs analytically. It has been shown that under certain conditions, DLs do not exist, which is in good agreement with the experimental observations of Ghim and Hershkowitz [Y. Ghim (Kim) and N. Hershkowitz, Appl. Phys. Lett. 94, 151503 (2009)].

  • 29.
    Mamun, A. A.
    et al.
    Institut für Theoretische Physik IV, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, Bochum D-44780, Germany.
    Shukla, Padma Kant
    Institut für Theoretische Physik IV, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, Bochum D-44780, Germany.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Arbitrary amplitude dust ion-acoustic shock waves in a dusty plasma with positive and negative ions2009In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 16, p. 114503-Article in journal (Refereed)
    Abstract [en]

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

  • 30.
    Marklund, Mattias
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Physics.
    Shukla, Padma K.
    Umeå University, Faculty of Science and Technology, Physics.
    Nonlinear propagation of broadband intense electromagnetic waves in an electron-positron plasma2006In: Physics of Plasmas, Vol. 13, no 8, p. 083102-Article in journal (Refereed)
  • 31.
    Marklund, Mattias
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Physics.
    Shukla, Padma K.
    Umeå University, Faculty of Science and Technology, Physics.
    Self-compression and catastrophic collapse of photon bullets in vacuum,2004In: JETP Letters, Vol. 79, p. 208-12Article in journal (Refereed)
  • 32.
    Marklund, Mattias
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Physics.
    Shukla, Padma K.
    Umeå University, Faculty of Science and Technology, Physics.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Physics.
    Dieckmann, M.E.
    Umeå University, Faculty of Science and Technology, Physics.
    Parviainen, M.
    Electrostatic pair creation and recombination in quantum plasmas2006In: JETP Letters, Vol. 83, p. 313-17Article in journal (Refereed)
  • 33.
    Marklund, Mattias
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Magnetosonic solitons in a fermionic quantum plasma2007In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics: Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, ISSN 1063-651X, E-ISSN 1095-3787, Vol. 76, no 6:2, article id 067401Article in journal (Refereed)
    Abstract [en]

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

  • 34.
    Marklund, Mattias
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Shukla, Padma K.
    Umeå University, Faculty of Science and Technology, Physics.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Physics.
    The intense radiation gas2005In: Europhysics Letters, Vol. 70, p. 327-333Article in journal (Refereed)
  • 35.
    Marklund, Mattias
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Shukla, Padma K.
    Umeå University, Faculty of Science and Technology, Physics.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Physics.
    Kourakis, I.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Physics.
    Fysiken bakom monstervågor2006In: Fysikaktuellt, ISSN 0283-9148, no 4, p. 6-7Article in journal (Other (popular science, discussion, etc.))
  • 36. Masood, W.
    et al.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Electrostatic solitary waves in a quantum plasma with relativistically degenerate electrons2011In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 18, no 3, article id 034503Article in journal (Refereed)
    Abstract [en]

    A model for nonlinear ion waves in an unmagnetized plasma with relativistically degenerate electrons and cold fluid ions is presented here. The inertia is given here by the ion mass while the restoring force is provided by the relativistic electron degeneracy pressure, and the dispersion is due to the deviation from charge neutrality. A nonlinear Korteweg-de Vries equation is derived for small but finite amplitude waves and is used to study the properties of localized ion acoustic solitons for parameters relevant for dense astrophysical objects such as white dwarf stars. Different degrees of relativistic electron degeneracy are discussed and compared.

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

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

  • 38. Sayed, Fatema
    et al.
    Haider, M. M.
    Mamun, A. A.
    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.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Adhikary, N.
    Dust ion-acoustic solitary waves in a dusty plasma with positive and negative ions2008In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 15, no 6, article id 063701Article in journal (Other (popular science, discussion, etc.))
    Abstract [en]

    Properties of small but finite amplitude dust ion-acoustic (DIA) solitary waves in a dusty plasma composed of inertialess electrons, positive and negative inertial ions, and immobile negative/positive charged dust grains are investigated. By using the multifluid dusty plasma model, the Kortweg–de Vries equation and energy integral for small and large amplitude solitary pulses, are derived. It is found that the presence of the negative ions modifies the properties of the solitary DIA waves, and provides the possibility of positive and negative solitary potential structures to coexist. The present results may be useful for understanding the salient features of localized DIA excitations that may appear in data from forthcoming laboratory experiments and space observations.

  • 39.
    Shaikh, Dastgeer
    et al.
    Department of Physics and Center for Space Plasma and Aeronomic Research (CSPAR), The University of Alabama in Huntsville, Huntsville, Alabama 35899, USA.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma Kant
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Numerical study of the magnetic electron drift vortex mode turbulence in a nonuniform magnetoplasma2009In: 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. 79, no 6, p. 066404-066410Article in journal (Refereed)
    Abstract [en]

    Asimulation study of the magnetic electron drift vortex (MEDV) modeturbulence in a magnetoplasma in the presence of inhomogeneities inthe plasma temperature and density, as well as in theexternal magnetic field, is presented. The study shows that theinfluence of the magnetic field inhomogeneity is to suppress streamerlikestructures observed in previous simulation studies without background magnetic fields.The MEDV mode turbulence exhibits nonuniversal (non-Kolmogorov-type) spectra for differentsets of the plasma parameters. In the presence of aninhomogeneous magnetic field, the spectrum changes to a 7/3 powerlaw, which is flatter than without magnetic field gradients. Therelevance of this work to laser-produced plasmas in the laboratoryis briefly mentioned.

  • 40.
    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.

  • 41.
    Shukla, Padma
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Physics.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Physics.
    Bingham, Robert
    Nonlinear dispersive Alfven waves in magnetoplasmas2008In: New Aspects of Plasma Physics: Proceedings of the 2007 ICTP College on Plasma Physics, 2008, p. 232-255Conference paper (Refereed)
  • 42.
    Shukla, Padma
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Physics.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Physics.
    Bingham, Robert
    Nonlinear effects introduced by Alfven waves in plasmas2007In: Recent Research Developments in Plasma Physics, Transworld Research Network, Kerala, India , 2007, p. 51-74Chapter in book (Refereed)
  • 43.
    Shukla, Padma K.
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Bingham, R.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Physics.
    Dieckmann, M.E.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Physics.
    Nonlinear aspects of the solar coronal heating2006In: Plasma Physics and Controlled Fusion B, Vol. 48, p. 249-Article in journal (Refereed)
  • 44.
    Shukla, Padma K.
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Physics.
    Kourakis, I.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Physics.
    Parametric instabilities and localization of nonlinearly coupled electromagnetic modes in astrophysical dusty plasmas2006In: Journal of Plasma Physics, Vol. 72, p. 397-Article in journal (Refereed)
  • 45.
    Shukla, Padma K.
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Physics.
    Marklund, Mattias
    Umeå University, Faculty of Science and Technology, Physics.
    Relativistic self-compression approaching the Schwinger limit2005In: Journal of Plasma Physics, Vol. 71, p. 213-215Article in journal (Refereed)
  • 46.
    Shukla, Padma K.
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Physics.
    Marklund, Mattias
    Umeå University, Faculty of Science and Technology, Physics.
    Vacuum compression of trapped electromagnetic waves2004In: Optics Communications, Vol. 235, p. 373-6Article in journal (Refereed)
  • 47.
    Shukla, Padma K.
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Physics.
    Marklund, Mattias
    Umeå University, Faculty of Science and Technology, Physics.
    Bingham, R.
    Nonlinear model for magnetosonic shocklets in plasmas2004In: Physics of Plasmas, Vol. 11, p. 2311-3Article in journal (Refereed)
  • 48.
    Shukla, Padma K.
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Eliasson, Bengt
    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.
    Kourakis, I.
    Parvianen, M.
    Dieckmann, M.E.
    Instability and dynamics of two nonlinearly coupled laser beams in a plasma2006In: Physics of Plasmas, Vol. 13, p. 053104-Article in journal (Refereed)
  • 49.
    Shukla, Padma K.
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Eliasson, Bengt
    Umeå University, Faculty of Science and Technology, Physics.
    Stenflo, Lennart
    Umeå University, Faculty of Science and Technology, Physics.
    Correction to stimulated scattering of intense radio waves in partially ionized space dusty plasmas2004In: Journal of Geophysical Research A, Vol. 109, p. A08303-Article in journal (Refereed)
  • 50.
    Shukla, Padma K.
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Kourakis, I.
    Eliasson, Bengt
    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.
    Instability and evolution of nonlinearly interacting water waves.2006In: Physical Review Letters, Vol. 97, p. 094501-Article in journal (Refereed)
12 1 - 50 of 62
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