| 1. |
- Shukla, Nitin, et al.
(författare)
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Nonlinear electromagnetic wave equations for superdense magnetized plasmas
- 2009
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Ingår i: PHYSICS OF PLASMAS. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 16:7
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Tidskriftsartikel (refereegranskat)abstract
- By using the quantum hydrodynamic and Maxwell equations, we derive the generalized nonlinear electron magnetohydrodynamic, the generalized nonlinear Hall-MHD (HMHD), and the generalized nonlinear dust HMHD equations in a self-gravitating dense magnetoplasma. Our nonlinear equations include the self-gravitating, the electromagnetic, the quantum statistical electron pressure, as well as the quantum electron tunneling and electron spin forces. They are useful for investigating a number of wave phenomena including linear and nonlinear electromagnetic waves, as well as three-dimensional electromagnetic wave turbulence spectra and structures arising from mode coupling processes at nanoscales in dense quantum magnetoplasmas.
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| 2. |
- Shukla, Nitin, et al.
(författare)
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The dust acoustic wave in a bounded dusty plasma with strong electrostatic interactions between dust grains
- 2011
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Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 375:17, s. 1809-1811
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Tidskriftsartikel (refereegranskat)abstract
- The dispersion relation for the dust acoustic wave (DAW) in an unmagnetized dusty plasma cylindrical waveguide is derived, accounting for strong electrostatic interactions between charged dust grains. It is found that the boundary effect limits the radial extent of the DAW. The present result should be helpful for understanding the frequency spectrum of the DAW in a dusty plasma waveguide with strongly coupled charged dust grains.
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| 3. |
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| 4. |
- Ali, S, et al.
(författare)
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Dust acoustic solitary waves in a quantum plasma
- 2006
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Ingår i: Physics of Plasmas. - Melville : American Institute of Physics (AIP). - 1070-664X .- 1089-7674. ; 13:2
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Tidskriftsartikel (refereegranskat)abstract
- By employing one-dimensional quantum hydrodynamic (QHD) model for a three species quantum plasma, nonlinear properties of dust acoustic solitary waves are studied. For this purpose a Korteweg-de Vries (KdV) equation is derived, incorporating quantum corrections. The quantum mechanical effects are also examined numerically both on the profiles of the amplitude and the width of dust acoustic solitary waves. It is found that the amplitude remains constant but the width shrinks for different values of a dimensionless electron quantum parameter H-e=root(Z(d0)h(2)omega(2)(pd))/m(e)m(d)C(d)(4), where Z(d0) is the dust charge state, h is the Planck constant divided by 2 pi, omega(pd) is the dust plasma frequency, m(e) (m(d)) is the electron (dust) mass, and C-d is the dust acoustic speed.
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| 5. |
- Brodin, Gert, et al.
(författare)
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Dispersion relation for electromagnetic wave propagation in a strongly magnetized plasma
- 2006
-
Ingår i: New Journal of Physics. - Bristol, UK : Institute of Physics Pub.. - 1367-2630. ; 8:January, s. 16-
-
Tidskriftsartikel (refereegranskat)abstract
- A dispersion relation for electromagnetic wave propagation in a strongly magnetized cold plasma is deduced, taking photon–photon scattering into account. It is shown that the combined plasma and quantum electrodynamic effect is important for understanding the mode-structures in magnetar and pulsar atmospheres. The implications of our results are discussed.
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| 6. |
- Brodin, Gert, et al.
(författare)
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Generation of gravitational radiation in dusty plasmas and supernovae
- 2005
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Ingår i: JETP Letters. - : Pleiades Publishing Ltd. - 0021-3640 .- 1090-6487. ; 81:4, s. 135-139
-
Tidskriftsartikel (refereegranskat)abstract
- We present a novel nonlinear mechanism for exciting a gravitational radiation pulse (or a gravitational wave) by dust magnetohydrodynamic (DMHD) waves in dusty astrophysical plasmas. We derive the relevant equations governing the dynamics of nonlinearly coupled DMHD waves and a gravitational wave (GW). The system of equations is used to investigate the generation of a GW by compressional Alfvén waves in a type II supernova. The growth rate of our nonlinear process is estimated, and the results are discussed in the context of the gravitational radiation accompanying supernova explosions.
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| 7. |
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| 8. |
- Brodin, Gert, et al.
(författare)
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Nonlinear interactions between three inertial Alfvén waves
- 2007
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Ingår i: Journal of Plasma Physics. - 0022-3778 .- 1469-7807. ; 73:1, s. 9-13
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Tidskriftsartikel (refereegranskat)abstract
- The resonant coupling between Alfvén waves is reconsidered. New results are found for cold agnetoplasmas where temperature effects are negligible.
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| 9. |
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| 10. |
- Dieckmann, Mark E, 1969-, et al.
(författare)
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Aspects of self-similar current distributions resulting from the plasma filamentation instability
- 2007
-
Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 9, s. 10-1-10-22
-
Tidskriftsartikel (refereegranskat)abstract
- Colliding plasmas can form current filaments that are magnetically confined and interact through electromagnetic fields during the nonlinear evolution of this filamentation instability. A nonrelativistic and a relativistic electron flow are examined. Two-dimensional (2D) particle-in-cell (PIC) simulations evolve the instability in a plane orthogonal to the flow vector and confirm that the current filaments move, merge through magnetic reconnection and evolve into current sheets and large flux tubes. The current filaments overlap over limited spatial intervals. Electrons accelerate in the overlap region and their final energy distribution decreases faster than exponential. The spatial power spectrum of the filaments in the flow-aligned current component can be approximated by a power-law during the linear growth phase. This may reflect a phase transition. The power spectrum of the current component perpendicular to the flow direction shows a power-law also during the nonlinear phase, possibly due to preferential attachment. The power-law distributed power spectra evidence self-similarity over a limited scale size and the wavenumber of the maximum of the spatial power spectrum of the filament distribution decreases linearly in time. Power-law correlations of velocity fields, which could be connected to the current filaments, may imply super-diffusion.
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| 11. |
- Dieckmann, Mark E, 1969-, et al.
(författare)
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Aspects of self-similarity of the filamentation instability
- 2007
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Ingår i: 34th European Physical Society Conference on Plasma Physics,2007. - Warsaw : European Physical Society. ; , s. P2.080-
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Konferensbidrag (refereegranskat)abstract
- The filamentation instability (FI) is an aperiodically growing instability driven by counterpropagating electron beams. Its ability to generate magnetic fields is important for the energetic plasmas in gamma ray burst jets and inertial confinement fusion plasmas. The FI has been examined both analytically and with particle-in-cell (PIC) simulations. We perform PIC simulations and follow the FI through its nonlinear saturation. The power spectrum of the flow-aligned current component is self-similar during the linear phase. We show that the perpendicular current distribution is self-similar during the nonlinear evolution and that the filament size increases linearly with time. We demonstrate that, at least for warm plasmas, the current filaments can't be described by simple flux tubes. Instead, the filaments merge by magnetic reconnection to form larger, partially overlapping current sheets. In the filament overlap region the electrons are accelerated.
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| 12. |
- Dieckmann, Mark E, 1969-, et al.
(författare)
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Electron acceleration by a relativistic two stream instability with oblique B
- 2006
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Ingår i: 33rd European Physical Society Conference on Plasma Physics,2006. - Rome : European Physical Society. ; , s. P4.071-
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Konferensbidrag (refereegranskat)abstract
- Electrons that are trapped by a quasi-electrostatic wave move, on average, with the phase speed of the wave. In the presence of a magnetic field B, the trapped electrons could, in principle, be accelerated to cosmic ray energies through cross-field transport. We model this cross-field transport with a particle-in-cell (PIC) simulation for an oblique B. The electron energies at the simulation's end exceed 5 MeV for all pitch angles and they can reach GeV energies along the wavevector. We discuss environments, in which such conditions may exist and for which such an acceleration would be relevant.
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| 13. |
- Dieckmann, Mark E, 1969-, et al.
(författare)
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Electron surfing acceleration by mildly relativistic beams : wave magnetic field effects
- 2008
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 10:Januar, s. 013029-1-13029-2
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Tidskriftsartikel (refereegranskat)abstract
- Electron surfing acceleration (ESA) is based on the trapping of electrons by a wave and the transport of the trapped electrons across a perpendicular magnetic field. ESA can accelerate electrons to relativistic speeds and it may thus produce hot electrons in plasmas supporting fast ion beams, like close to astrophysical shocks. One-dimensional (1D) particle-in-cell (PIC) simulations have demonstrated that trapped electron structures (phase space holes) are stabilized by relativistic phase speeds of the waves, by which ESA can accelerate electrons to ultrarelativistic speeds. The 2(1/2)D electromagnetic and relativistic PIC simulations performed in the present paper model proton beam driven instabilities in the presence of a magnetic field perpendicular to the simulation plane. This configuration represents the partially electromagnetic mixed modes and the filamentation modes, in addition to the Buneman waves. The waves are found to become predominantly electromagnetic and nonplanar for beam speeds that would result in stable trapped electron structures. The relativistic boost of ESA reported previously is cancelled by this effect. For proton beam speeds of 0.6 and 0.8c, the electrons reach only million electron volt energies. The system with the slower beam is followed sufficiently long in time to reveal the development of a secondary filamentation instability. The instability forms a channel in the simulation domain that is void of any magnetic field. Proton beams may thereby cross perpendicular magnetic fields for distances beyond their gyroradius.
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| 14. |
- Dieckmann, Mark E, 1969-, et al.
(författare)
-
Electron surfing acceleration by the electron two-stream instability in a weak magnetic field
- 2006
-
Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 0741-3335 .- 1361-6587. ; 48:October, s. 1515-1530
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Tidskriftsartikel (refereegranskat)abstract
- The thermalization of relativistically flowing colliding plasmas is not well understood. The transition layer, in which both plasmas interact and thermalize, is wide and highly structured and the instabilities in this layer may yield non-thermal particle distributions and shock-less energy dissipation. The objective in this work is to explore the ability of an electron two-stream instability for thermalizing a plasma beam that moves at the mildly relativistic speed 0.3c through weakly magnetized plasma and to identify the resulting particle distributions. It is demonstrated here with particle-in-cell simulations that the electron two-stream instability leads to waves that propagate within a wide angular range relative to the flow velocity. The waves are thus not planar, as required for efficient electron surfing acceleration (ESA). The short lifetime of the waves implies, however, only weak modifications of the ESA by the oblique modes, since the waves are sufficiently homogeneous. The ion (proton) beams are not modulated, which would be required to extract some of their energy. The instability can thus heat the electrons significantly, but it fails to accelerate them to relativistic energies and it cannot form a shock layer by thermalizing the protons, at least not for the system and the resolved timescales considered here.
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| 15. |
- Dieckmann, Mark E, 1969-, et al.
(författare)
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Electron surfing acceleration in oblique magnetic fields
- 2006
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 367:3, s. 865-872
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Tidskriftsartikel (refereegranskat)abstract
- Initially, inhomogeneous plasma jets, ejected by active galactic nuclei and associated with gamma-ray bursts, are thermalized by the formation of internal shocks. Jet subpopulations can hereby collide at Lorentz factors of a few. As the resulting relativistic shock expands into the upstream plasma, a significant fraction of the upstream ions is reflected. These ions, together with downstream ions that leak through the shock, form relativistic beams of ions that outrun the shock. The thermalization of these beams via the two-stream instability is thought to contribute significantly to plasma heating and particle acceleration by the shock. Here, the capability of a two-stream instability to generate relativistic field-aligned and cross-field electron flow, is examined for a magnetized plasma by means of a particle-in-cell (PIC) simulation. The electrons interact with the developing quasi-electrostatic waves and oblique magnetic fields. The simulation results bring forward evidence that such waves, by their non-linear interactions with the plasma, produce a highly relativistic field-aligned electron flow and electron energies, which could contribute to the radio synchrotron emissions from astrophysical jets, to ultrarelativistic leptonic subpopulations propagating with the jet and to the halo particles surrounding the accretion disc of the black hole.
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| 16. |
- Dieckmann, Mark E, 1969-, et al.
(författare)
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Evolution of the fastest-growing relativistic mixed mode instability driven by a tenuous plasma beam in one and two dimensions
- 2006
-
Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 13:11, s. 112110-1-112110-8
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Tidskriftsartikel (refereegranskat)abstract
- Particle-in-cell simulations confirm here that a mixed plasma mode is the fastest growing when a highly relativistic tenuous electron-proton beam interacts with an unmagnetized plasma. The mixed modes grow faster than the filamentation and two-stream modes in simulations with beam Lorentz factors Gamma of 4, 16, and 256, and are responsible for thermalizing the electrons. The mixed modes are followed to their saturation for the case of Gamma=4 and electron phase space holes are shown to form in the bulk plasma, while the electron beam becomes filamentary. The initial saturation is electrostatic in nature in the considered one- and two-dimensional geometries. Simulations performed with two different particle-in-cell simulation codes evidence that a finite grid instability couples energy into high-frequency electromagnetic waves, imposing simulation constraints.
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| 17. |
- Dieckmann, Mark E, 1969-, et al.
(författare)
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Formation of electrostatic structures by wakefield acceleration in ultrarelativistic plasma flows : Electron acceleration to cosmic ray energies
- 2006
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 13:6, s. 062905-1-062905-8
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Tidskriftsartikel (refereegranskat)abstract
- The ever increasing performance of supercomputers is now enabling kinetic simulations of extreme astrophysical and laser produced plasmas. Three-dimensional particle-in-cell (PIC) simulations of relativistic shocks have revealed highly filamented spatial structures and their ability to accelerate particles to ultrarelativistic speeds. However, these PIC simulations have not yet revealed mechanisms that could produce particles with tera-electron volt energies and beyond. In this work, PIC simulations in one dimension (1D) of the foreshock region of an internal shock in a gamma ray burst are performed to address this issue. The large spatiotemporal range accessible to a 1D simulation enables the self-consistent evolution of proton phase space structures that can accelerate particles to giga-electron volt energies in the jet frame of reference, and to tens of tera-electron volt in the Earth's frame of reference. One potential source of ultrahigh energy cosmic rays may thus be the thermalization of relativistically moving plasma.
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| 18. |
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| 19. |
- Dieckmann, Mark E, 1969-, et al.
(författare)
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Particle-in-cell simulation studies of the non-linear evolution of ultrarelativistic two-stream instabilities
- 2006
-
Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 367:3, s. 1072-1082
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Tidskriftsartikel (refereegranskat)abstract
- Gamma-ray bursts are associated with relativistic plasma flow and intense X-ray and soft gamma-ray emissions. We perform particle-in-cell simulations to explore the growth and saturation of waves driven by the electrostatic two-stream instability that may contribute to the thermalization of the relativistic plasma flows and to the electromagnetic emissions. We evolve self-consistently the instability driven by two charge-neutral and cool interpenetrating beams of electrons and protons that move at a relative Lorentz factor of 100. We perform three simulations with the beam density ratios of 1, 2 and 10. The simulations show that the electrostatic waves saturate by trapping the electrons of only one beam and that the saturated electrostatic wave fields spatially modulate the mean momentum of the second beam, while retaining its temperature. Cavities form in the charge density of the latter beam which, in turn, compress the electrostatic waves to higher intensities. A runaway process develops that terminates with the collapse of the waves and the development of an exponential electron high-energy tail. We bring forward evidence that this energetic tail interacts stochastically with the charge density fluctuations of the relativistic proton beam. In response, an electron momentum distribution develops that follows an inverse power law up to a spectral break at four times the beam Lorentz factor.
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| 20. |
- Dieckmann, Mark E, 1969-, et al.
(författare)
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Particle-in-cell simulations of plasma slabs colliding at a mildly relativistic speed
- 2006
-
Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 8:October, s. 225-1-225-21
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Tidskriftsartikel (refereegranskat)abstract
- Plasmas collide at relativistic speeds in many astrophysical and high-energy density laboratory environments. The boundaries that develop between such plasmas and expand at much larger speeds than the ion sound speed cs are not well understood. Here, we address two identical electron-proton plasma slabs that collide with a relativistic speed and a Mach number v/cs of over 400. The collision speed, the plasma temperature and magnetic field are such that the growth rate of the two-stream instability exceeds that of all other instabilities. We model a planar turbulent boundary (TB) with one-dimensional (1D) and 2D particle-in-cell (PIC) simulations. We show that the boundary dissipates its energy via electron phase space holes (EPSHs) that accelerate electrons at the boundary to relativistic speeds and increase significantly the speed of some protons. Our results are put into the context of a dynamic accretion disc and the jet of a microquasar. It is shown that the accelerated electrons could contribute to the disc wind and to relativistic leptonic jets, and possibly to the hard radiation component of the accretion disc.
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| 21. |
- Dieckmann, Mark E, 1969-, et al.
(författare)
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Phase speed of electrostatic waves : the critical parameter for efficient electron surfing acceleration
- 2006
-
Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 0741-3335 .- 1361-6587. ; 48:4, s. 489-508
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Tidskriftsartikel (refereegranskat)abstract
- Particle acceleration by means of nonlinear plasma wave interactions is of great topical interest. Accordingly, in this paper we focus on the electron surfing process. Self-consistent kinetic simulations, using both relativistic Vlasov and particle-in-cell (PIC) approaches, show here that electrons can be accelerated to highly relativistic energies (up to 100mec2) if the phase speed of the electrostatic wave is mildly relativistic (0.6c to 0.9c for the magnetic field strengths considered). The acceleration is strong because of relativistic stabilization of the nonlinearly saturated electrostatic wave, seen in both relativistic Vlasov and PIC simulations. An inverse power law momentum distribution can arise for the most strongly accelerated electrons. These results are of relevance to observed rapid changes in the radio synchrotron emission intensities from microquasars, gamma ray bursts and other astrophysical objects that require rapid acceleration mechanisms for electrons.
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| 22. |
- Dieckmann, Mark E, 1969-, et al.
(författare)
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PIC simulations of relativistic electron flows : The fastest-growing mixed mode and the electromagnetic finite grid instability
- 2007
-
Ingår i: 34th European Physical Society Conference on Plasma Physics,2007. - Warsaw : European Physical Society. ; , s. P2.078-
-
Konferensbidrag (refereegranskat)abstract
- Instabilities driven by two electron beams that stream at the relativistic relative velocity vb are important as a plasma thermalization and magnetic field generation mechanism in astrophysics and in inertial confinement fusion. The time-evolution of such instabilities, which are subdivided into the two-stream, mixed mode and filamentation (beam-Weibel) instability, is multi-dimensional and nonlinear and the instabilities are usually modelled with particle-in-cell (PIC) simulations. We examine the wave spectrum we obtain, if both beams have a density ratio 9 and (1-vb^2/c^2)^(-1/2)=4. The mixed mode dominates and grows fastest for highly relativistic vb. An electromagnetic finite grid instability is shown to generate artificial magnetic fields, imposing a simulation constraint.
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| 23. |
- Dieckmann, Mark E, 1969-, et al.
(författare)
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Plasma collisions at mildly relativistic speeds : Formation of an electrostatic turbulent boundary layer
- 2007
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Ingår i: 34th European Physical Society Conference on Plasma Physics,2007. - Warsaw : European Physical Society. ; , s. P2.081-
-
Konferensbidrag (refereegranskat)abstract
- Plasmas collide at relativistic speeds in many astrophysical and high energy density laboratory environments. The collision boundaries are not well understood. In the absence of a magnetic field B0 that is parallel to the flow velocity vector vb the boundaries are filamentary, since waves grow with wavevectors k that are not parallel to vb. Modelling such boundaries requires large 3D particle-in-cell (PIC) simulations. A flow-aligned B0 can suppress wave modes other than k parallel to vb, as multi-dimensional PIC simulations show. We select a vb, a plasma temperature T and B0, for which the growth rate of the two-stream instability exceeds that of all other instabilities. We exploit this planarity to resort to a 1D simulation, that lets two identical electron-proton plasma slabs collide with a relativistic speed and a Mach number of over 400. The developing electrostatic turbulent boundary dissipates its energy via electron phase space holes that accelerate electrons to relativistic speeds and increase significantly the speed of some protons. The results are important in the context of a dynamic accretion disc and microquasar jets. The accelerated electrons may feed the disc wind and the relativistic leptonic jets, and possibly contribute to the hard radiation component of the accretion disc.
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| 24. |
- Dieckmann, Mark E, 1969-, et al.
(författare)
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Simulation study of a two stream instability with a beam gamma = 100
- 2004
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Ingår i: 33rd European Physical Society Conference of Plasma Physics,2006. - Rome : European Physical Society. ; , s. P2.049-
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Konferensbidrag (refereegranskat)abstract
- A better understanding of the relaxation of relativistic plasma flow is required to identify particle acceleration and radiation generation mechanisms at gamma ray bursts (GRBs). We perform particle-in-cell (PIC) simulations of the electrostatic two-stream instability for a beam speed VB with Gamma (v_b) = 100. The two p+e- beams are charge neutral and have comparable densities. The instability saturates by trapping the electrons of one beam and it modulates the electron density of the second beam. The electrostatic fields are compressed in the forming cavities to high intensities. The waves collapse, after which the electrons show an exponential tail that is eventually transformed into a power law tail.
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| 25. |
- Dieckmann, Mark E, 1969-, et al.
(författare)
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The formation of a relativistic partially electromagnetic planar plasma shock
- 2008
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 675:1, s. 586-595
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Tidskriftsartikel (refereegranskat)abstract
- Relativistically colliding plasma is modeled by particle-in-cell simulations in one and two spatial dimensions, with an ion-to-electron mass ratio of 400 and a temperature of 100 keV. The energy of an initial quasi-parallel magnetic field is 1% of the plasma kinetic energy. Energy dissipation by a growing wave pulse of mixed polarity, probably an oblique whistler wave, and different densities of the colliding plasma slabs result in the formation of an energetic electromagnetic structure within milliseconds. The structure, which develops for an initial collision speed of 0.9c, accelerates electrons to Lorentz factors of several hundred. A downstream region forms, separating the forward and reverse shocks. In this region, the plasma approaches an energy equipartition between electrons, ions, and the magnetic field. The electron energy spectrum resembles a power law at high energies, with an exponent close to −2.7, or . The magnetic field reflects upstream ions, which form a beam and drag the electrons along to preserve the plasma quasineutrality. The forward and reverse shocks are asymmetric due to the unequal slab densities. The forward shock may be representative for the internal shocks of gamma-ray bursts.
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| 26. |
- Dieckmann, Mark E, 1969-, et al.
(författare)
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Two-stream instability in collisionless shocks and foreshock
- 2006
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Ingår i: Plasma Physics and Controlled Fusion. - 0741-3335 .- 1361-6587. ; 48:12 B, s. B303-B311
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Shocks play a key role in plasma thermalization and particle acceleration in the near Earth space plasma, in astrophysical plasma and in laser plasma interactions. An accurate understanding of the physics of plasma shocks is thus of immense importance. We give an overview over some recent developments in particle-in-cell simulations of plasma shocks and foreshock dynamics. We focus on ion reflection by shocks and on the two-stream instabilities these beams can drive, and these are placed in the context of experimental observations, e.g. by the Cluster mission. We discuss how we may expand the insight gained from the observation of proton beam driven instabilities at near Earth plasma shocks to better understand their astrophysical counterparts, such as ion beam instabilities triggered by internal and external shocks in the relativistic jets of gamma ray bursts, shocks in the accretion discs of micro-quasars and supernova remnant shocks. It is discussed how and why the peak energy that can be reached by particles that are accelerated by two-stream instabilities increases from keV energies to GeV energies and beyond, as we increase the streaming speed to relativistic values, and why the particle energy spectrum sometimes resembles power law distributions.
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| 27. |
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| 28. |
- Eliasson, Bengt, et al.
(författare)
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Theoretical and simulation studies of relativistic ion holes in astrophysical plasmas
- 2006
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 8:April, s. 55-1-55-12
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Tidskriftsartikel (refereegranskat)abstract
- Theoretical and numerical studies of relativistic ion holes in a relativistically hot electron-ion plasma are presented. Previous particle-in-cell (PIC) simulations have shown that the ion holes are formed as a result of relativistic beam-plasma instabilities in the foreshock region of internal shocks of gamma-ray bursts and the relativistic jets of active galactic nuclei. In this process, the electrons are heated to ultra-relativistic temperatures so that their relativistic mass becomes comparable to the proton mass, and relativistic ion holes are formed by a secondary ion beam instability. The electrostatic potentials associated with the ion holes are large enough to accelerate particles to GeV energies. We use a semi-analytical model to construct relativistic ion holes and investigate their stability by means of fully relativistic Vlasov simulations. This investigation is relevant for astrophysical settings where the ion holes may work as efficient particle accelerators.
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| 29. |
- Eliasson, Bengt, et al.
(författare)
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Theory and simulations of nonlinear kinetic structures in plasmas
- 2006
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Ingår i: Plasma Physics and Controlled Fusion. - 0741-3335 .- 1361-6587. ; 48:12 B, s. B257-B265
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We present analytical and numerical studies of the dynamics of relativistic electron and ion holes in a collisionless plasma. Electromagnetic radiation can be trapped in relativistic electron phase-space holes mainly due to the relativistic mass increase of the electrons that are accelerated by the potential of the phase-space hole and by the quivering component of the electromagnetic field. Relativistic ion holes may exist in plasmas where the electrons are thermalized to extremely ultra-relativistic energies. They may be responsible for the acceleration of particles to GeV energies in active galactic nuclei and supernova remnant shocks. The analytic solutions are employed as initial conditions for numerical simulations in which the dynamics and stability of the phase-space holes are investigated. The results have relevance for intense laser-plasma experiments and for astrophysical plasmas.
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| 30. |
- Forsberg, Mats, 1978-, et al.
(författare)
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Nonlinear interactions between gravitational radiation and modified Alfvén modes in astrophysical dusty plasmas
- 2006
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Ingår i: Physical Review D. Particles and fields. - : American Physical Society. - 0556-2821 .- 1089-4918. ; 74, s. 064014-064014-5
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Tidskriftsartikel (refereegranskat)abstract
- We present an investigation of nonlinear interactions between gravitational radiation and modified Alfvén modes in astrophysical dusty plasmas. Assuming that stationary charged dust grains form neutralizing background in an electron-ion-dust plasma, we obtain the three-wave coupling coefficients and calculate the growth rates for parametrically coupled gravitational radiation and modified Alfvén-Rao modes. The threshold value of the gravitational wave amplitude associated with convective stabilization is particularly small if the gravitational frequency is close to twice the modified Alfvén wave frequency. The implication of our results to astrophysical dusty plasmas is discussed.
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| 31. |
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| 32. |
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| 33. |
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| 34. |
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| 35. |
- Lundin, Joakim, 1978-, et al.
(författare)
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Circularly polarized waves in a plasma with vacuum polarization effects
- 2007
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Ingår i: Physics of Plasmas. - : American Institute of Physics. - 1070-664X .- 1089-7674. ; 14:6, s. 064503-3 sidor
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Tidskriftsartikel (refereegranskat)abstract
- The theory for large amplitude circularly polarized waves propagating along an external magnetic field is extended in order to also include vacuum polarization effects. A general dispersion relation, which unites previous results, is derived.
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| 36. |
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| 37. |
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| 38. |
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| 39. |
- Marklund, Mattias, et al.
(författare)
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Electrostatic pair creation and recombination in quantum plasmas
- 2006
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Ingår i: JETP Letters. - 0021-3640 .- 1090-6487. ; 83:8, s. 313-317
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Tidskriftsartikel (refereegranskat)abstract
- The production of electron-positron pairs by electrostatic waves in quantum plasmas is investigated. In particular, a semiclassical governing set of equations for a self-consistent treatment of pair creation by the Schwinger mechanism in a quantum plasma is derived.
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| 40. |
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| 41. |
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| 42. |
- Marklund, Mattias, et al.
(författare)
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Fysiken bakom monstervågor
- 2006
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Ingår i: Fysikaktuellt. - 0283-9148. ; :4, s. 6-7
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Tidskriftsartikel (populärvet., debatt m.m.)
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- Marklund, Mattias, et al.
(författare)
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Magnetosonic solitons in a dusty plasma slab
- 2008
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Ingår i: Journal of Plasma Physics. - Cambridge : Cambridge University Press. - 0022-3778 .- 1469-7807. ; 74:5, s. 601-605
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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