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  • 1.
    Anderson, D.
    et al.
    Department of Electromagnetics, Chalmers University of Technology, S-412 96 Göteborg, Sweden.
    Kim, A.
    Institute for Applied Physics, Nizhny Novgorod, 603600, Russian Federation.
    Lisak, M.
    Department of Electromagnetics, Chalmers University of Technology, S-412 96 Göteborg, Sweden.
    Madsen, K.
    Self-induced erosion and spectral breaking of high-power microwave pulses2000In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 63, no 4, p. 329-341Article in journal (Refereed)
    Abstract [en]

    An analysis is made of the phenomenon of self-induced erosion and spectral breaking of ionizing high-power microwave pulses propagating in a gas. The analysis describes in an analytically explicit and physically clear way the consistent interaction between the microwave pulse and the self-induced breakdown plasma. In particular, it clarifies, both qualitatively and quantitatively, the mechanisms behind the pulse erosion and the spectral breaking phenomenon, i.e. the splitting of the pulse spectrum into a redshifted and a blueshifted peak as observed in numerical simulation results as well as in experiments.

  • 2.
    Andres, N.
    et al.
    Univ Paris Sud, Sorbonne Univ, Lab Phys Plasmas, CNRS,Ecole Polytech,Observ Paris, F-91128 Palaiseau, France.
    Sahraoui, F.
    Univ Paris Sud, Sorbonne Univ, Lab Phys Plasmas, CNRS,Ecole Polytech,Observ Paris, F-91128 Palaiseau, France.
    Galtier, S.
    Univ Paris Sud, Sorbonne Univ, Lab Phys Plasmas, CNRS,Ecole Polytech,Observ Paris, F-91128 Palaiseau, France;Univ Paris Saclay, Univ Paris Sud, Paris, France.
    Hadid, Lina Z
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Dmitruk, P.
    UBA, CONICET, Inst Fis Buenos Aires, Ciudad Univ, RA-1428 Buenos Aires, DF, Argentina.
    Mininni, P. D.
    Univ Buenos Aires, Fac Ciencias Exactas & Nat, Dept Fis, Ciudad Univ, RA-1428 Buenos Aires, DF, Argentina.
    Energy cascade rate in isothermal compressible magnetohydrodynamic turbulence2018In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 84, no 4, article id 905840404Article in journal (Refereed)
    Abstract [en]

    Three-dimensional direct numerical simulations are used to study the energy cascade rate in isothermal compressible magnetohydrodynamic turbulence. Our analysis is guided by a two-point exact law derived recently for this problem in which flux, source, hybrid and mixed terms are present. The relative importance of each term is studied for different initial subsonic Mach numbers M-S and different magnetic guide fields B-0. The dominant contribution to the energy cascade rate comes from the compressible flux, which depends weakly on the magnetic guide field B-0, unlike the other terms whose moduli increase significantly with M s and B-0. In particular, for strong B-0 the source and hybrid terms are dominant at small scales with almost the same amplitude but with a different sign. A statistical analysis undertaken with an isotropic decomposition based on the SO(3) rotation group is shown to generate spurious results in the presence of B-0, when compared with an axisymmetric decomposition better suited to the geometry of the problem. Our numerical results are compared with previous analyses made with in situ measurements in the solar wind and the terrestrial magnetosheath.

  • 3. Andrushchenko, Zhanna N.
    et al.
    Jucker, Martin
    Pavlenko, Vladimir P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Self-consistent model of electron drift mode turbulence2008In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 74, no 1, p. 21-33Article in journal (Refereed)
    Abstract [en]

    The nonlinear dynamics of magnetic electron drift mode turbulence are outlined and the generation of large-scale magnetic Structures in a non-uniform magnetized plasma by turbulent Reynolds stress is demonstrated. The loop-back of large-scale flows on the microturbulence is elucidated and the modulation of the electron drift mode turbulence spectrum in a, medium with slowly varying parameters is presented. The wave kinetic equation in the presence of large-scale flows is derived and it can be seen that the small-scale turbulence and the large-scale structures form a, self-regulating system. Finally. it is shown by the use of quasilinear theory that the shearing of microturbulence by the flows can be described by a diffusion equation in k-space and the corresponding diffusion coefficients are calculated.

  • 4.
    Asp, Elina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics.
    Pavlenko, Vladimir P.
    Revenchuk, Sergey M.
    Stability of the Landau Resonance for Drift Modes in Rotating Tokamak Plasma2003In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 60, no 5, p. 371-Article in journal (Refereed)
    Abstract [en]

    The linear stability of drift waves in a poloidally rotating tokamak plasma is considered. The derived dispersion relation features a peaking of the diamagnetic frequency which gives the drift modes an irreducible two-dimensional character. We then show that inverse Landau damping can be suppressed and even stabilized, if the flow's shear is strong. Even though the instability, excited by the Landau resonance, is stronger at a high velocity shear for positive rotation velocities, effects due to the rotation of the plasma can reverse the sign and induce damping of the two-dimensional drift modes. This stabilizing mechanism works only for positive rotation velocities. For negative rotation velocities, we show that only modes with high poloidal mode numbers are unstable.

  • 5. 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.

  • 6.
    Brandenburg, Axel
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Nordic Institute for Theoretical Physics (Nordita). University of Colorado, USA.
    Advances in mean-field dynamo theory and applications to astrophysical turbulence2018In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 84, no 4, article id 735840404Article in journal (Refereed)
    Abstract [en]

    Recent advances in mean-field theory are reviewed and applications to the Sun, late-type stars, accretion disks, galaxies and the early Universe are discussed. We focus particularly on aspects of spatio-temporal non-locality, which provided some of the main new qualitative and quantitative insights that emerged from applying the test-field method to magnetic fields of different length and time scales. We also review the status of nonlinear quenching and the relation to magnetic helicity, which is an important observational diagnostic of modern solar dynamo theory. Both solar and some stellar dynamos seem to operate in an intermediate regime that has not yet been possible to model successfully. This regime is bracketed by antisolar-like differential rotation on one end and stellar activity cycles belonging to the superactive stars on the other. The difficulty in modelling this regime may be related to shortcomings in simulating solar/stellar convection. On galactic and extragalactic length scales, the observational constraints on dynamo theory are still less stringent and more uncertain, but recent advances both in theory and observations suggest that more conclusive comparisons may soon be possible also here. The possibility of inversely cascading magnetic helicity in the early Universe is particularly exciting in explaining the recently observed lower limits of magnetic fields on cosmological length scales. Such magnetic fields may be helical with the same sign of magnetic helicity throughout the entire Universe. This would be a manifestation of parity breaking.

  • 7.
    Brodin, G
    et al.
    Umeå University, Sweden .
    Stenflo, Lennart
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Alfven wave interactions within the Hall-MHD description2013In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 79, p. 909-911Article in journal (Refereed)
    Abstract [en]

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

  • 8.
    Brodin, G
    et al.
    Department of Physics, Umeå University, Umeå, Sweden.
    Stenflo, Lennart
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology. Department of Physics, Umeå University, Umeå, Sweden.
    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 (Other academic)
    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 pointout 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.

  • 9.
    Brodin, Gert
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Forsberg, Mats
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Marklund, Mattias
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Eriksson, Daniel
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Interaction between gravitational waves and plasma waves in the Vlasov description2010In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, no 76, p. 345-353Article in journal (Refereed)
    Abstract [en]

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

  • 10.
    Brodin, Gert
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Holkundkar, Amol
    Umeå University, Faculty of Science and Technology, Department of Physics. Department of Physics, Birla Institute of Technology and Science, Rajasthan, India.
    Marklund, Mattias
    Umeå University, Faculty of Science and Technology, Department of Physics. Department of Applied Physics, Chalmers University of Technology, Göteborg, Sweden.
    Particle-in-cell simulations of electron spin effects in plasmas2013In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 79, no 4, p. 377-382Article in journal (Refereed)
    Abstract [en]

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

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

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

  • 12.
    Brodin, Gert
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stenflo, Lennart
    Alfven wave interactions within the Hall-MHD description2013In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 79, no 5, p. 909-911Article in journal (Refereed)
    Abstract [en]

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

  • 13.
    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.

  • 14.
    Brodin, Gert
    et al.
    Umeå University, Umeå, Sweden.
    Stenflo, Lennart
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Stimulated Brillouin scattering in magnetized plasmas2013In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 79, no 6, 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.

  • 15.
    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.

  • 16.
    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.

  • 17.
    Brunetti, Daniele
    et al.
    CNR, IFP, Milan, Italy.
    Graves, J. P.
    SPC, Lausanne, Switzerland.
    Lazzaro, E.
    CNR, IFP, Milan, Italy.
    Mariani, A.
    CNR, IFP, Milan, Italy.
    Nowak, S.
    CNR, IFP, Milan, Italy.
    Cooper, W. A.
    SPC, Lausanne, Switzerland.
    Wahlberg, Christer
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Analytic study on low-n external ideal infernal modes in tokamaks with large edge pressure gradients2018In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 84, no 2, article id 745840201Article in journal (Refereed)
    Abstract [en]

    The problem of pressure driven infernal type perturbations near the plasma edge is addressed analytically for a circular limited tokamak configuration which presents an edge flattened safety factor. The plasma is separated from a metallic wall, either ideally conducting or resistive, by a vacuum region. The dispersion relation for such types of instabilities is derived and discussed for two classes of equilibrium profiles for pressure and mass density.

  • 18. Chapman, I. T.
    et al.
    Graves, J. P.
    Lennholm, M.
    Faustin, J.
    Lerche, E.
    Johnson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. EUROfusion Consortium, England.
    Tholerus, Simon
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. EUROfusion Consortium, England.
    The merits of ion cyclotron resonance heating schemes for sawtooth control in tokamak plasmas2015In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 81, no 06, article id 365810601Article in journal (Refereed)
    Abstract [en]

    JET experiments have compared the efficacy of low-and high field side ion cyclotron resonance heating (ICRH) as an actuator to deliberately minimise the sawtooth period. It is found that low-field side ICRH with low minority concentration is optimal for saw tooth control for two main reasons. Firstly, low-field side heating means that any toroidal phasing of the ICRH (-90 degrees, +90 degrees or dipole) has a destabilising effect on the sawteeth, meaning that dipole phasing can be employed, since tins is preferable due to less plasma wall interaction from Resonant Frequency (RI) sheaths. Secondly, the resonance position of the low field side ICRH does not have to be very accurately placed to achieve saw tooth control, relaxing the requirement for real-time control of the RF frequency. These empirical observations have been confirmed by hybrid kinetic-magnetohydrodynamic modelling, and suggest that the ICRH antenna design for ITER is well positioned to provide a control actuator capable of having a significant effect on the sawtooth behaviour.

  • 19.
    Dieckmann, Mark Eric
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Bret, Antoine
    University of Castilla La Mancha, ETSI Ind, Ciudad Real, Spain.
    Simulation study of the formation of a non-relativistic pair shock2017In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 83, p. 1-19, article id 905830104Article in journal (Refereed)
    Abstract [en]

    We examine with a particle-in-cell (PIC) simulation the collision of two equally dense clouds of cold pair plasma. The clouds interpenetrate until instabilities set in, which heat up the plasma and trigger the formation of a pair of shocks. The fastest-growing waves at the collision speed $c/5$, where $c$ is the speed of light in vacuum, and low temperature are the electrostatic two-stream mode and the quasi-electrostatic oblique mode. Both waves grow and saturate via the formation of phase space vortices. The strong electric fields of these nonlinear plasma structures provide an efficient means of heating up and compressing the inflowing upstream leptons. The interaction of the hot leptons, which leak back into the upstream region, with the inflowing cool upstream leptons continuously drives electrostatic waves that mediate the shock. These waves heat up the inflowing upstream leptons primarily along the shock normal, which results in an anisotropic velocity distribution in the post-shock region. This distribution gives rise to the Weibel instability. Our simulation shows that even if the shock is mediated by quasi-electrostatic waves, strong magnetowaves will still develop in its downstream region.

  • 20.
    Eliasson, B
    et al.
    University of Strathclyde, Glasgow, UK.
    Stenflo, Lennart
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Bingham, R
    Rutherford Appleton Laboratory, Didcot, UK.
    Mendonca, J T
    Institute Superior Tecnico, Lisboa, Portugal.
    Preface to special issue2013In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 79, no 6, p. 981-981Article in journal (Other academic)
    Abstract [en]

    This special issue is devoted to the memory of Professor Padma Kant Shukla, who passed away 26 January 2013 on his travel to New Delhi, India to receive the prestigious Hind Rattan (Jewel of India) award. Padma was born in Tulapur, Uttar Pradesh, India, 7 July 1950, where he grew up and got his education. He received a PhD degree in Physics at the Banaras Hindu University, Varanasi, Uttar Pradesh, India, in 1972, under the supervision of late Prof. R. N. Singh, and a second PhD degree in Theoretical Plasma Physics from Umeå University in Sweden in 1975, under the supervision of Prof. Lennart Stenflo. He worked at the Faculty of Physics & Astronomy, Ruhr-University Bochum, Germany since January 1973, where he was a permanent faculty member and Professor of International Affairs, a position that was created for him to honour his international accomplishments and reputation.

  • 21.
    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.

  • 22.
    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.

  • 23. Faghihi, M.
    et al.
    Scheffel, Jan
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Stability of Small Axial Wavelength Internal Kink Modes of an Anisotropic Plasma1987In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 38, p. 495-Article in journal (Refereed)
    Abstract [en]

    The double adiabatic equations are used to study the stability of a cylindrical Z-pinch with respect to small axial wavelength, internal kink (m ≥ 1) modes. It is found that marginally (ideally) unstable, isotropic equilibria are stabilized. Also, constant-current-density equilibria can be stabilized for P⊥ > P∥ and large β⊥

  • 24. Faghihi, M.
    et al.
    Scheffel, Jan
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Stability of Small Axial Wavelength Internal Kink Modes of an Anisotropic Plasma: Corrigendum1988In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 40, p. 603-Article in journal (Refereed)
    Abstract [en]

    A minor correction, having no major influence on our results, is reported here.

  • 25. Gedalin, M.
    et al.
    Spitkovsky, A.
    Medvedev, M.
    Balikhin, M.
    Krasnoselskikh, V.
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Perri, S.
    Relativistic filamentary equilibria2011In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 77, p. 193-205Article in journal (Refereed)
    Abstract [en]

    Plasma filamentation is often encountered in collisionless shocks and inertial confinement fusion. We develop a general analytical description of the two-dimensional relativistic filamentary equilibrium and derive the conditions for existence of potential-free equilibria. A pseudopotential equation for the vector-potential is constructed for cold and relativistic Maxwellian distributions. The role of counter-streaming is explained. We present single current sheet and periodic current sheet solutions, and analyze the equilibria with electric potential. These solutions can be used to study linear and nonlinear evolution of the relativistic filamentation instability.

  • 26. Gedalin, M.
    et al.
    Spitkovsky, A.
    Medvedev, M.
    Balikhin, M.
    Krasnoselskikh, V.
    Vaivads, Andris
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Perri, S.
    Relativistic filamentary equilibria2011In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 77, p. 193-205Article in journal (Refereed)
    Abstract [en]

    Plasma filamentation is often encountered in collisionless shocks and inertial confinement fusion. We develop a general analytical description of the two-dimensional relativistic filamentary equilibrium and derive the conditions for existence of potential-free equilibria. A pseudopotential equation for the vector-potential is constructed for cold and relativistic Maxwellian distributions. The role of counter-streaming is explained. We present single current sheet and periodic current sheet solutions, and analyze the equilibria with electric potential. These solutions can be used to study linear and nonlinear evolution of the relativistic filamentation instability.

  • 27.
    Haas, Fernando
    Umeå University, Faculty of Science and Technology, Department of Physics.
    On quantum plasma kinetic equations with a Bohmian force2010In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 76, no 3-4, p. 389-393Article in journal (Refereed)
    Abstract [en]

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

  • 28.
    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.

  • 29.
    Iqbal, Mubashar
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Linear wave theory in magnetized quantum plasmas2013In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 79, no 1, p. 19-23Article in journal (Refereed)
    Abstract [en]

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

  • 30.
    Karimov, A R
    et al.
    Russian Academy of Sciences, Moscow, Russia.
    Yu, M Y
    Zhejiang University, Hangzhou, China .
    Stenflo, Lennart
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Asymmetric oscillatory expansion of a cylindrical plasma2013In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 79, no 6, p. 1007-1009Article in journal (Refereed)
    Abstract [en]

    Asymmetric oscillatory expansion of a cylindrical plasma layer into vacuum is investigated analytically by solving the fluid equations of the electrons and ions together with the Maxwell's equations. For the problem considered, it is found that the asymmetrical flow components are strongly affected by the symmetrical components, but not the vice versa.

  • 31.
    Karimov, A. R.
    et al.
    Russian Academic Science, Russia; National Research Nucl University of MEPhI, Russia.
    Yu, M. Y.
    Zhejiang University, Peoples R China; Ruhr University of Bochum, Germany.
    Stenflo, Lennart
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Properties and evolution of anisotropic structures in collisionless plasmas2016In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 82, article id 905820502Article in journal (Refereed)
    Abstract [en]

    A new class of exact electrostatic solutions of the Vlasov-Maxwell equations based on the Jeanss theorem is proposed for studying the evolution and properties of two-dimensional anisotropic plasmas that are far from thermodynamic equilibrium. In particular, the free expansion of a slab of electron-ion plasma into vacuum is investigated.

  • 32.
    Kleeorin, Nathan
    et al.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Ben-Gurion University of the Negev, Israel.
    Rogachevskii, Igor
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Ben-Gurion University of the Negev, Israel.
    Generation of large-scale vorticity in rotating stratified turbulence with inhomogeneous helicity: mean-field theory2018In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 84, no 3, article id 735840303Article in journal (Refereed)
    Abstract [en]

    We discuss a mean-field theory of the generation of large-scale vorticity in a rotating density stratified developed turbulence with inhomogeneous kinetic helicity. We show that the large-scale non-uniform flow is produced due to either a combined action of a density stratified rotating turbulence and uniform kinetic helicity or a combined effect of a rotating incompressible turbulence and inhomogeneous kinetic helicity. These effects result in the formation of a large-scale shear, and in turn its interaction with the small-scale turbulence causes an excitation of the large-scale instability (known as a vorticity dynamo) due to a combined effect of the large-scale shear and Reynolds stress-induced generation of the mean vorticity. The latter is due to the effect of large-scale shear on the Reynolds stress. A fast rotation suppresses this large-scale instability.

  • 33.
    Kleeorin, Nathan
    et al.
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.
    Rogachevskii, l.
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.
    Generation of large-scale vorticity in rotating stratified turbulence with inhomogeneous helicity: mean-field theory2018In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 84, no 3, article id 735840303Article in journal (Refereed)
    Abstract [en]

    We discuss a mean-field theory of the generation of large-scale vorticity in a rotating density stratified developed turbulence with inhomogeneous kinetic helicity. We show that the large-scale non-uniform flow is produced due to either a combined action of a density stratified rotating turbulence and uniform kinetic helicity or a combined effect of a rotating incompressible turbulence and inhomogeneous kinetic helicity. These effects result in the formation of a large-scale shear, and in turn its interaction with the small-scale turbulence causes an excitation of the large-scale instability (known as a vorticity dynamo) due to a combined effect of the large-scale shear and Reynolds stress-induced generation of the mean vorticity. The latter is due to the effect of large-scale shear on the Reynolds stress. A fast rotation suppresses this large-scale instability.

  • 34. Lapenta, Giovanni
    et al.
    Markidis, Stefano
    Divin, Andrey
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Newman, David
    Goldman, Martin
    Separatrices: The crux of reconnection2015In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 81, article id 325810109Article in journal (Refereed)
    Abstract [en]

    Magnetic reconnection is one of the key processes in astrophysical and laboratory plasmas: it is the opposite of a dynamo. Looking at energy, a dynamo transforms kinetic energy in magnetic energy while reconnection takes magnetic energy and returns it to its kinetic form. Most plasma processes at their core involve first storing magnetic energy accumulated over time and then releasing it suddenly. We focus here on this release. A key concept in analysing reconnection is that of the separatrix, a surface (line in 2D) that separates the fresh unperturbed plasma embedded in magnetic field lines not yet reconnected with the hotter exhaust embedded in reconnected field lines. In kinetic physics, the separatrices become a layer where many key processes develop. We present here new results relative to the processes at the separatrices that regulate the plasma flow, the energization of the species, the electromagnetic fields and the instabilities developing at the separatrices.

  • 35. Lapenta, Giovanni
    et al.
    Markidis, Stefano
    KTH, School of Computer Science and Communication (CSC), High Performance Computing and Visualization (HPCViz).
    Divin, Andrey
    Newman, David
    Goldman, Martin
    Separatrices: The crux of reconnection2015In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 81, no 1, article id 325810109Article in journal (Refereed)
    Abstract [en]

    Magnetic reconnection is one of the key processes in astrophysical and laboratory plasmas: it is the opposite of a dynamo. Looking at energy, a dynamo transforms kinetic energy in magnetic energy while reconnection takes magnetic energy and returns it to its kinetic form. Most plasma processes at their core involve first storing magnetic energy accumulated over time and then releasing it suddenly. We focus here on this release. A key concept in analysing reconnection is that of the separatrix, a surface (line in 2D) that separates the fresh unperturbed plasma embedded in magnetic field lines not yet reconnected with the hotter exhaust embedded in reconnected field lines. In kinetic physics, the separatrices become a layer where many key processes develop. We present here new results relative to the processes at the separatrices that regulate the plasma flow, the energization of the species, the electromagnetic fields and the instabilities developing at the separatrices.

  • 36.
    Lazar, Marian
    et al.
    Leuven University, Belgium.
    Dieckmann, Mark Eric
    Linköping University, Department of Science and Technology, Visual Information Technology and Applications (VITA). Linköping University, The Institute of Technology.
    Resonant Weibel instability in counterstreaming plasmas with temperature anisotropies2010In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 76, no 1, p. 49-56Article in journal (Refereed)
    Abstract [en]

    The Weibel instability, driven by a plasma temperature anisotropy, is non-resonant with plasma particles: it is purely growing in time, and does not oscillate. The effect of a counterstreaming plasma is examined. In a counterstreaming plasma with an excess of transverse temperature, the Weibel instability arises along the streaming direction. Here it is proved that for large wave-numbers the instability becomes resonant with a finite real (oscillation) frequency, ωr ≠ 0. When the plasma flows faster, with a bulk velocity larger than the parallel thermal velocity, the instability becomes dominantly resonant. This new feature of the Weibel instability can be relevant for astrophysical sources of non-thermal emissions and the stability of counterflowing plasma experiments.

  • 37.
    Lehnert, Bo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Dark energy and dark matter as due to zero point energy2013In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 79, no 3, p. 327-334Article in journal (Refereed)
    Abstract [en]

    An attempt is made to explain dark energy and dark matter of the expanding universe in terms of the zero point vacuum energy. This analysis is mainly limited to later stages of an observable nearly flat universe. It is based on a revised formulation of the spectral distribution of the zero point energy, for an ensemble in a defined statistical equilibrium having finite total energy density. The steady and dynamic states are studied for a spherical cloud of zero point energy photons. The 'antigravitational' force due to its pressure gradient then represents dark energy, and its gravitational force due to the energy density represents dark matter. Four fundamental results come out of the theory. First, the lack of emitted radiation becomes reconcilable with the concepts of dark energy and dark matter. Second, the crucial coincidence problem of equal orders of magnitude of mass density and vacuum energy density cannot be explained by the cosmological constant, but is resolved by the present variable concepts, which originate from the same photon gas balance. Third, the present approach becomes reconcilable with cosmical dimensions and with the radius of the observable universe. Fourth, the deduced acceleration of the expansion agrees with the observed one. In addition, mass polarity of a generalized gravitation law for matter and antimatter is proposed as a source of dark flow.

  • 38.
    Lehnert, Bo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    On angular momentum and rest mass of the photon2013In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 79, no 6, p. 1133-1135Article in journal (Refereed)
    Abstract [en]

    A reconsideration is made on the basic concepts of the individual photon, including its angular momentum (spin) and a possibly existing very small rest mass. In terms of conventional classical theory, as well as of its quantum mechanical counterpart, the results from a so far established Standard Model of an empty vacuum state are not found to be reconcilable with an experimentally relevant photon model. The main properties of such a model would on the other hand become compatible with the results of a recently established revised quantum electrodynamic theory based on a non-zero electric field divergence in the vacuum and a corresponding symmetry breaking of the electromagnetic field.

  • 39.
    Lehnert, Bo
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Höök, L. Josef
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    An electron model with elementary charge2010In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 76, no 3-4, p. 419-428Article in journal (Refereed)
    Abstract [en]

    An earlier elaborated model of the electron, being based on a revised quantum electrodynamic theory, is further investigated in terms of an improved numerical iteration scheme. This point-charge-like model is based on the "infinity" of a divergent generating function being balanced by the "zero" of a shrinking characteristic radius. This eliminates the self-energy problem. According to the computations, the quantum conditions on spin, magnetic moment, and magnetic flux, plus the requirement of an elementary charge having the experimental value, can all be satisfied within rather narrow limits by a single scalar parameter. The revised model prevents the electron from "exploding" due to its eigencharge.

  • 40. 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.

  • 41.
    Lundberg, Jonas
    et al.
    Luleå tekniska universitet.
    Flå, Tor
    Tromsø University.
    Perturbation method for the Vlasov-Poisson system1998In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 60, p. 181-192Article in journal (Refereed)
    Abstract [en]

    A perturbation method for the Vlasov-Poisson system is presented. It is self-consistent and entirely based on Lie transformations, which are considered as active transformations, generating the dynamics of the particle distribution function in the space of distribution functions. The main result is a set of three equations that forms a good starting point for a wide variety of problems concerning nonlinear wave propagation. Besides being efficient, the new perturbation method is systematic and therefore also suited for the use of computer algebra.

  • 42.
    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.

  • 43.
    McClements, K. G.
    et al.
    UKAEA Culham Division Culham Science Centre.
    Dendy, R. O.
    UKAEA Culham Division Culham Science Centre.
    Dieckmann, Mark E
    Linköping University, Department of Science and Technology, Visual Information Technology and Applications (VITA). Linköping University, The Institute of Technology.
    Ynnerman, Anders
    Linköping University, Department of Science and Technology, Visual Information Technology and Applications (VITA). Linköping University, The Institute of Technology.
    Chapman, S. C.
    Department of Physics University of Warwick.
    Surfatron and stochastic acceleration of electrons in astrophysical plasmas2005In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 71, no 2, p. 127-141Article in journal (Refereed)
    Abstract [en]

    Electron acceleration by large amplitude electrostatic waves in astro-physical plasmas is studied using particle-in-cell (PIC) simulations. The waves are excited initially at the electron plasma frequency ωpe by a Buneman instability driven by ion beams: the parameters of the ion beams are appropriate for high Mach number astrophysical shocks, such as those associated with supernova remnants (SNRs). If ωpe is much higher than the electron cyclotron frequency Ωe, the linear phase of the instability does not depend on the magnitude of the magnetic field. However, the subsequent time evolution of particles and waves depends on both ωpe/Ωeand the size of the simulation box L. If L is equal to one wavelength, λ0, of the Buneman-unstable mode, electrons trapped by the waves undergo acceleration via the surfatron mechanism across the wave front. This occurs most efficiently when ωpe/Ω ≃ 100: in this case electrons are accelerated to speeds of up c/2 where c is the speed of light. In a simulation with L = 4λ0 and ωpe/ Ωe = 100, it is found that sideband instabilities give rise to a broad spectrum of wavenumbers, with a power law tail. Some stochastic electron acceleration is observed in this case, but not the surfatron process. Direct integration of the electron equations of motion, using parameters approximating to those of the wave modes observed in the simulations, suggests that the surfatron is compatible with the presence of a broad wave spectrum if Ωpe/Ωe > 100. It is concluded that a combination of stochastic and surfatron acceleration could provide an efficient generator of mildly relativistic electrons at SNR shocks.

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

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

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

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

  • 46.
    Misra, Amar P
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Brodin, Gert
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Marklund, Mattias
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shukla, Padma K
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Circularly polarized modes in magnetized spin plasmas2010In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, ISSN 0022-3778, Vol. 76, no 3/4, p. 857-864Article in journal (Refereed)
    Abstract [en]

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

  • 47.
    Moiseenko, Vladimir E.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Ågren, Olov
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    A numerical model for radiofrequency heating of sloshing ions in a mirror trap2006In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 72, no 6, p. 1133-1137Article in journal (Refereed)
    Abstract [en]

    A newly developed numerical model calculating the distribution and damping of radiofrequency fields by sloshing ions is presented. The model solves time-harmonic Maxwell's equations written in terms of the electric field. It uses a two-dimensional grid and a Fourier series in the third coordinate and is based on a non-staggered mesh not aligned along the steady magnetic field. The numerical stability of the scheme is discussed, and the convergence analysis is presented.

  • 48.
    Moslem, WM
    et al.
    Department of Physics, Faculty of Science, Port Said University, Port Said, Egypt .
    Sabry, R
    Theoretical Physics Group, Department of Physics, Faculty of Science, Mansoura University, Damietta Branch, New Damietta 34517, Egypt.
    Shukla, Padma K
    Umeå University, Faculty of Science and Technology, Department of Physics. UB International Chair, International Center for Advanced Studies in Physical Sciences, Faculty of Physics & Astronomy, Ruhr University Bochum, D-44780 Bochum, Germany.
    The optimum shielding around a test charge in plasmas containing two negative ions2011In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 77, no 5, p. 663-673Article in journal (Refereed)
    Abstract [en]

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

  • 49.
    Nairn, C.M.C.
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Bingham, R.
    Allen, J.E.
    Large amplitude solitary magnetized plasma waves2005In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 71, no 5, p. 631-643Article in journal (Refereed)
    Abstract [en]

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

  • 50. Olshevsky, Vyacheslav
    et al.
    Lapenta, Giovanni
    Markidis, Stefano
    KTH, School of Computer Science and Communication (CSC), High Performance Computing and Visualization (HPCViz).
    Divin, Andrey
    Role of Z-pinches in magnetic reconnection in space plasmas2015In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 81, no 1, article id 325810105Article in journal (Refereed)
    Abstract [en]

    A widely accepted scenario of magnetic reconnection in collisionless space plasmas is the breakage of magnetic field lines in X-points. In laboratory, reconnection is commonly studied in pinches, current channels embedded into twisted magnetic fields. No model of magnetic reconnection in space plasmas considers both nullpoints and pinches as peers. We have performed a particle-in-cell simulation of magnetic reconnection in a three-dimensional configuration where null-points are present initially, and Z-pinches are formed during the simulation along the lines of spiral null-points. The non-spiral null-points are more stable than spiral ones, and no substantial energy dissipation is associated with them. On the contrary, turbulent magnetic reconnection in the pinches causes the magnetic energy to decay at a rate of similar to 1.5% per ion gyro period. Dissipation in similar structures is a likely scenario in space plasmas with large fraction of spiral null-points.

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