| 1. |
- Akner, Gunnar, et al.
(författare)
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Styrningen har blivit ett hot
- 2016
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Ingår i: Svenska Dagbladet. - 1101-2412. ; 25 jul
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 2. |
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| 3. |
- Ahrné, Karin, et al.
(författare)
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Rödlista över fjärilar Lepidoptera
- 2015
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Ingår i: Rödlistade arter i Sverige 2015. - Uppsala : ArtDatabanken SLU. - 9789187853104 ; , s. 98-112
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 4. |
- Andersson, Joel, 1981-, et al.
(författare)
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HIP-Densification of Alloy 718 and ATI 718Plus
- 2014
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Ingår i: 8th International Symposium on Superalloy 718 and Derivatives. - Hoboken, NJ, USA : John Wiley & Sons. - 9781119016809 - 9781119016854 ; , s. 425-436
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Konferensbidrag (refereegranskat)
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| 5. |
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| 6. |
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| 7. |
- Axberg, Stefan, et al.
(författare)
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Lärobok i Militärteknik, vol. 9 : Teori och metod
- 2013. - 1
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- Ämnet militärteknik utgår från att tekniska system är officerens arbetsredskap och att en förståelse för och kunskap om dessa verktyg är central för att kunna utöva professionen framgångsrikt. Denna nionde volym av Lärobok i Militärteknik, benämnd Teori och Metod, behandlar centrala begrepp, teorier och postulat samt metoder för värdering av teknik och består av ett antal texter författade av 16 forskare och lärare vid den militärtekniska avdelningen. Volymen riktar sig främst till de som inlett sin officersutbildning och utgörs till stora delar av ett kompilat av publicerade och opublicerade militärtekniska texter och kan sägas utgöra militärteknikens ”state of the art”.
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| 8. |
- Bengtsson, Bengt Å., et al.
(författare)
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Fjärilar
- 2010. - 1
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Ingår i: Rödlistade arter i Sverige 2010. - Uppsala : Artdatabanken i samarbete med Naturvårdsverket. - 9789188506351 ; , s. 361-392
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 9. |
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| 10. |
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| 11. |
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| 12. |
- Bingham, Robert, et al.
(författare)
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Ion acceleration by Alfven waves on auroral field lines
- 2013
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Ingår i: Physica Scripta. - : Institute of Physics. - 0031-8949 .- 1402-4896. ; 87:5
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Tidskriftsartikel (refereegranskat)abstract
- Observations of ion acceleration along auroral field lines at the boundary of the plasma sheet and tail lobe of the Earth show that the energy of the ions increases with decreasing density. The observations can be explained by ion acceleration through Landau resonance with kinetic Alfven waves (KAWs) such that k(A) . v(i) = omega(A), where k(A) is the wave vector, v(i) is the ion resonance velocity and omega(A) is the Alfven wave frequency. The ion resonance velocities are proportional to the Alfven velocity which increases with decreasing density. This is in agreement with the data if the process is occurring at the plasma sheet tail lobe boundary. A quasi-linear theory of ion acceleration by KAWs is presented. These ions propagate both down towards and away from the Earth. The paths of the Freja and Polar satellites indicate that the acceleration takes place between the two satellites, between 1Re and 5Re. The downward propagating ions develop a horseshoe-type of distribution which has a positive slope in the perpendicular direction. This type of distribution can produce intense lower hybrid wave activity, which is also observed. Finally, the filamentation of shear Alfven waves is considered. It may be responsible for large-scale density striations.
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| 13. |
- Bingham, Robert, et al.
(författare)
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Solar coronal heating by plasma waves
- 2010
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Ingår i: Journal of Plasma Physics. - : Cambridge university. - 0022-3778 .- 1469-7807. ; 76:2, s. 135-158
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 14. |
- Brodin, Gert, 1963-, et al.
(författare)
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Plasma dynamics at the Schwinger limit and beyond
- 2023
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Ingår i: Physical review. E. - : American Physical Society. - 2470-0045 .- 2470-0053. ; 107:3
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Tidskriftsartikel (refereegranskat)abstract
- Strong field physics close to or above the Schwinger limit are typically studied with vacuum as initial condition or by considering test particle dynamics. However, with a plasma present initially, quantum relativistic mechanisms such as Schwinger pair creation are complemented by classical plasma nonlinearities. In this work we use the Dirac-Heisenberg-Wigner formalism to study the interplay between classical and quantum mechanical mechanisms in the regime of ultrastrong electric fields. In particular, the effects of initial density and temperature on the plasma oscillation dynamics are determined. Finally, comparisons with competing mechanisms such as radiation reaction and Breit-Wheeler pair production are made.
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| 15. |
- Brodin, Gert, 1963-, et al.
(författare)
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Quantum-electrodynamical photon splitting in magnetized Nonlinear pair plasmas
- 2007
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 98:12
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Tidskriftsartikel (refereegranskat)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.
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| 16. |
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| 17. |
- Daldorff, L. K. S., et al.
(författare)
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Parallelization of a Vlasov-Maxwell solver in four-dimensional phase space
- 2009
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Ingår i: Parallel Computing. - : Elsevier BV. - 0167-8191 .- 1872-7336. ; 35:2, s. 109-115
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Tidskriftsartikel (refereegranskat)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.
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| 18. |
- 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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| 19. |
- 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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| 20. |
- 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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| 21. |
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| 22. |
- 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
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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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| 23. |
- Dieckmann, Mark Eric, et al.
(författare)
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PIC simulations of stable surface waves on a subcritical fast magnetosonic shock front
- 2023
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Ingår i: Physica Scripta. - : IOP Publishing Ltd. - 0031-8949 .- 1402-4896. ; 98:9
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Tidskriftsartikel (refereegranskat)abstract
- We study with particle-in-cell (PIC) simulations the stability of fast magnetosonic shocks. They expand across a collisionless plasma and an orthogonal magnetic field that is aligned with one of the directions resolved by the 2D simulations. The shock speed is 1.6 times the fast magnetosonic speed when it enters a layer with a reduced density of mobile ions, which decreases the shock speed by up to 15% in 1D simulations. In the 2D simulations, the density of mobile ions in the layer varies sinusoidally perpendicularly to the shock normal. We resolve one sine period. This variation only leads to small changes in the shock speed evidencing a restoring force that opposes a shock deformation. As the shock propagates through the layer, the ion density becomes increasingly spatially modulated along the shock front and the magnetic field bulges out where the mobile ion density is lowest. The perturbed shock eventually reaches a steady state. Once it leaves the layer, the perturbations of the ion density and magnetic field oscillate along its front at a frequency close to the lower-hybrid frequency; the shock is mediated by a standing wave composed of obliquely propagating lower-hybrid waves. We perform three 2D simulations with different box lengths along the shock front. The shock front oscillations are aperiodically damped in the smallest box with the fastest variation of the ion density, strongly damped in the intermediate one, and weakly damped in the largest box. The shock front oscillations perturb the magnetic field in a spatial interval that extends by several electron skin depths upstream and downstream of the shock front and could give rise to Whistler waves that propagate along the shock's magnetic field overshoot. Similar waves were observed in hybrid and PIC simulations and by the MMS satellite mission.
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| 24. |
- 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-
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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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| 25. |
- 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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