| 1. |
|
|
| 2. |
|
|
| 3. |
- Brodin, Gert, 1963-, et al.
(author)
-
Quantum-electrodynamical photon splitting in magnetized Nonlinear pair plasmas
- 2007
-
In: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 98:12
-
Journal article (peer-reviewed)abstract
- We present for the first time the nonlinear dynamics of quantum electrodynamic (QED) photon splitting in a strongly magnetized electron-positron (pair) plasma. By using a QED corrected Maxwell equation, we derive a set of equations that exhibit nonlinear couplings between electromagnetic (EM) waves due to nonlinear plasma currents and QED polarization and magnetization effects. Numerical analyses of our coupled nonlinear EM wave equations reveal the possibility of a more efficient decay channel, as well as new features of energy exchange among the three EM modes that are nonlinearly interacting in magnetized pair plasmas. Possible applications of our investigation to astrophysical settings, such as magnetars, are pointed out.
|
|
| 4. |
|
|
| 5. |
- Daldorff, L. K. S., et al.
(author)
-
Parallelization of a Vlasov-Maxwell solver in four-dimensional phase space
- 2009
-
In: Parallel Computing. - : Elsevier BV. - 0167-8191 .- 1872-7336. ; 35:2, s. 109-115
-
Journal article (peer-reviewed)abstract
- We present a parallelized algorithm for solving the time-dependent Vlasov–Maxwell system of equations in the four-dimensional phase space (two spatial and velocity dimensions). One Vlasov equation is solved for each particle species, from which charge and current densities are calculated for the Maxwell equations. The parallelization is divided into two different layers. For the first layer, each plasma species is given its own processor group. On the second layer, the distribution function is domain decomposed on its dedicated resources. By separating the communication and calculation steps, we have met the design criteria of good speedup and simplicity in the implementation.
|
|
| 6. |
- Dieckmann, Mark E, 1969-, et al.
(author)
-
Electron acceleration by a relativistic two stream instability with oblique B
- 2006
-
In: 33rd European Physical Society Conference on Plasma Physics,2006. - Rome : European Physical Society. ; , s. P4.071-
-
Conference paper (peer-reviewed)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.
|
|
| 7. |
- Dieckmann, Mark E, 1969-, et al.
(author)
-
Electron surfing acceleration in oblique magnetic fields
- 2006
-
In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 367:3, s. 865-872
-
Journal article (peer-reviewed)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.
|
|
| 8. |
- Dieckmann, Mark E, 1969-, et al.
(author)
-
Formation of electrostatic structures by wakefield acceleration in ultrarelativistic plasma flows : Electron acceleration to cosmic ray energies
- 2006
-
In: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 13:6, s. 062905-1-062905-8
-
Journal article (peer-reviewed)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.
|
|
| 9. |
|
|
| 10. |
- Dieckmann, Mark E, 1969-, et al.
(author)
-
Particle-in-cell simulations of plasma slabs colliding at a mildly relativistic speed
- 2006
-
In: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 8:October, s. 225-1-225-21
-
Journal article (peer-reviewed)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.
|
|
