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Brodin, Gert
Publications (10 of 128) Show all publications
Jenab, S. M. & Brodin, G. (2019). Head-on collision of nonlinear solitary solutions to Vlasov-Poisson equations. Physics of Plasmas, 26(2), Article ID 022303.
Open this publication in new window or tab >>Head-on collision of nonlinear solitary solutions to Vlasov-Poisson equations
2019 (English)In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 26, no 2, article id 022303Article in journal (Refereed) Published
Abstract [en]

Nonlinear solitary solutions to the Vlasov-Poisson set of equations are studied in order to investigate their stability by employing a fully kinetic simulation approach. This study is carried out in the ion-acoustic regime for a collisionless, electrostatic, and Maxwellian electron-ion plasma. The trapped population of electrons is modeled based on the well-known Schamel distribution function. Head-on mutual collisions of nonlinear solutions are performed in order to examine their collisional stability. The findings include three major aspects: (I) These nonlinear solutions are found to be divided into three categories based on their Mach numbers, i.e., stable, semi-stable, and unstable. Semi-stable solutions indicate a smooth transition from stable to unstable solutions for the increasing Mach number. (II) The stability of solutions is traced back to a condition imposed on averaged velocities, i.e., net neutrality. It is shown that a bipolar structure is produced in the flux of electrons, early in the temporal evolution. This bipolar structure acts as the seed of the net-neutrality instability, which tips off the energy balance of nonlinear solution during collisions. As the Mach number increases, the amplitude of the bipolar structure grows and results in a stronger instability. (III) It is established that during mutual collisions, a merging process of electron holes can occur to a variety of degrees, based on their velocity characteristics. Specifically, the number of rotations of electron holes around each other (in the merging phase) varies. Furthermore, it is observed that in the case of a non-integer number of rotations, two electron holes exchange their phase space cores.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2019
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-157593 (URN)10.1063/1.5078865 (DOI)000460094400021 ()
Available from: 2019-03-29 Created: 2019-03-29 Last updated: 2019-03-29Bibliographically approved
Ekman, R., Al-Naseri, H., Zamanian, J. & Brodin, G. (2019). Relativistic kinetic theory for spin-1/2 particles: Conservation laws, thermodynamics, and linear waves. Physical Review E. Statistical, Nonlinear, and Soft Matter Physics: Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, 100(2), Article ID 023201.
Open this publication in new window or tab >>Relativistic kinetic theory for spin-1/2 particles: Conservation laws, thermodynamics, and linear waves
2019 (English)In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics: Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, ISSN 1063-651X, E-ISSN 1095-3787, Vol. 100, no 2, article id 023201Article in journal (Refereed) Published
Abstract [en]

We study a recently derived fully relativistic kinetic model for spin-1/2 particles. First, the full set of conservation laws for energy, momentum, and angular momentum are given together with an expression for the (nonsymmetric) stress-energy tensor. Next, the thermodynamic equilibrium distribution is given in different limiting cases. Furthermore, we address the analytical complexity that arises when the spin and momentum eigenfunctions are coupled in linear theory by calculating the linear dispersion relation for such a case. Finally, we discuss the model and give some context by comparing with potentially relevant phenomena that are not included, such as radiation reaction and vacuum polarization.

National Category
Fusion, Plasma and Space Physics
Research subject
Theoretical Physics
Identifiers
urn:nbn:se:umu:diva-162463 (URN)10.1103/PhysRevE.100.023201 (DOI)000479192700004 ()
Available from: 2019-08-20 Created: 2019-08-20 Last updated: 2019-08-21Bibliographically approved
Jenab, S. M., Spanier, F. & Brodin, G. (2019). Scattering of electron holes in the context of ion-acoustic regime. Physics of Plasmas, 26(3), Article ID 034502.
Open this publication in new window or tab >>Scattering of electron holes in the context of ion-acoustic regime
2019 (English)In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 26, no 3, article id 034502Article in journal (Refereed) Published
Abstract [en]

Mutual collisions between ion-acoustic solitary waves are studied based on a fully kinetic simulation approach. Two cases, small and large relative velocities, are studied, and the effect of trapped electron population on the collision process is focused upon. It is shown that, for the case of small relative velocity, the repelling force between the trapped populations of electrons results in scattering of electron holes. However, this phenomenon cannot be witnessed if the relative velocity is considerably high since the impact of trapped population remains very weak.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2019
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-158755 (URN)10.1063/1.5055945 (DOI)000462916300078 ()
Available from: 2019-05-15 Created: 2019-05-15 Last updated: 2019-05-15Bibliographically approved
Jenab, S. M., Spanier, F. & Brodin, G. (2018). A study of the stability properties of Sagdeev solutions in the ion-acoustic regime using kinetic simulations. Physics of Plasmas, 25(7), Article ID 072304.
Open this publication in new window or tab >>A study of the stability properties of Sagdeev solutions in the ion-acoustic regime using kinetic simulations
2018 (English)In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 25, no 7, article id 072304Article in journal (Refereed) Published
Abstract [en]

The Sagdeev pseudo-potential approach has been employed extensively in theoretical studies to determine large-amplitude (fully) nonlinear solutions in a variety of multi-species plasmas. Although these solutions are repeatedly considered as solitary waves (and even solitons), their temporal stability has never been proven. In this paper, a numerical study of the Vlasov-Poisson system is made to follow their temporal evolution in the presence of numerical noise and thereby test their long-time propagation stability. Considering the ion-acoustic regime, both constituents of the plasma, i.e., electrons and ions are treated following their distribution functions in these sets of fully-kinetic simulations. The findings reveal that the stability of the Sagdeev solution depends on a combination of two parameters, i.e., velocity and trapping parameter. It is shown that there exists a critical value of trapping parameter for both fast and slow solutions which separates stable from unstable solutions. In the case of stable solutions, it is shown that these nonlinear structures can propagate for long periods, which confirms their status as solitary waves. Stable solutions are reported for both Maxwellian and Kappa distribution functions. For unstable solutions, it is demonstrated that the instability causes the Sagdeev solution to decay by emitting ion-acoustic wave-packets on its propagation trail. The instability is shown to take place in a large range of velocities and even for Sagdeev solutions with a velocity much higher than the ion-sound speed. Besides, in order to validate our simulation code, two precautionary measures are taken. First, the well-known effect of the ion dynamics on a stationary electron hole solution is presented as a benchmarking test of the approach. Second, In order to verify the numerical accuracy of the simulations, the conservation of energy and entropy is presented.

National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-150841 (URN)10.1063/1.5036764 (DOI)000440589100031 ()
Funder
Swedish Research Council, 2016-03806
Available from: 2018-09-04 Created: 2018-09-04 Last updated: 2018-09-04Bibliographically approved
Brodin, G., Ekman, R. & Zamanian, J. (2018). Nonlinear wave damping due to multi-plasmon resonances. Plasma Physics and Controlled Fusion, 60(2), Article ID 025009.
Open this publication in new window or tab >>Nonlinear wave damping due to multi-plasmon resonances
2018 (English)In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 60, no 2, article id 025009Article in journal (Refereed) Published
Abstract [en]

For short wavelengths, it is well known that the linearized Wigner-Moyal equation predicts wave damping due to wave-particle interaction, where the resonant velocity shifted from the phase velocity by a velocity v(q) = hk/2m. Here h is the reduced Planck constant, k is the wavenumber and m is the electron mass. Going beyond linear theory, we find additional resonances with velocity shifts nv(q), n= 2,3, ..., giving rise to a new wave-damping mechanism that we term multi-plasmon damping, as it can be seen as the simultaneous absorption (or emission) of multiple plasmon quanta. Naturally this wave damping is not present in classical plasmas. For a temperature well below the Fermi temperature, if the linear (n = 1) resonant velocity is outside the Fermi sphere, the number of linearly resonant particles is exponentially small, while the multi-plasmon resonances can be located in the bulk of the distribution. We derive sets of evolution equations for the case of two-plasmon and three-plasmon resonances for Langmuir waves in the simplest case of a fully degenerate plasma. By solving these equations numerically for a range of wave-numbers we find the corresponding damping rates, and we compare them to results from linear theory to estimate the applicability. Finally, we discuss the effects due to a finite temperature.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2018
Keywords
wave-particle interaction, Wigner equation, Langmuir waves, nonlinear wave damping
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-143622 (URN)10.1088/1361-6587/aa979d (DOI)000418145500002 ()
Funder
Swedish Research Council, 2012-3320
Available from: 2018-01-30 Created: 2018-01-30 Last updated: 2019-08-21Bibliographically approved
Holkundkar, A. R. & Brodin, G. (2018). Transition from wakefield generation to soliton formation. Physical review. E, 97(4), Article ID 043204.
Open this publication in new window or tab >>Transition from wakefield generation to soliton formation
2018 (English)In: Physical review. E, ISSN 2470-0045, E-ISSN 2470-0053, Vol. 97, no 4, article id 043204Article in journal (Refereed) Published
Abstract [en]

It is well known that when a short laser pulse propagates in an underdense plasma, it induces longitudinal plasma oscillations at the plasma frequency after the pulse, typically referred to as the wakefield. However, for plasma densities approaching the critical density, wakefield generation is suppressed, and instead the EM-pulse (electromagnetic pulse) undergoes nonlinear self-modulation. In this article we have studied the transition from the wakefield generation to formation of quasi-solitons as the plasma density is increased. For this purpose we have applied a one-dimensional relativistic cold fluid model, which has also been compared with particle-in-cell simulations. A key result is that the energy loss of the EM-pulse due to wakefield generation has its maximum for a plasma density of the order 10% of the critical density, but that wakefield generation is sharply suppressed when the density is increased further.

National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-147458 (URN)10.1103/PhysRevE.97.043204 (DOI)000430062100007 ()
Funder
Swedish Research Council, 2016-03806
Available from: 2018-05-29 Created: 2018-05-29 Last updated: 2018-06-09Bibliographically approved
Brodin, G. & Stenflo, L. (2017). A simple electron plasma wave. Physics Letters A, 381(11), 1033-1035
Open this publication in new window or tab >>A simple electron plasma wave
2017 (English)In: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 381, no 11, p. 1033-1035Article in journal (Refereed) Published
Abstract [en]

Considering a class of solutions where the density perturbations are functions of time, but not of space, we derive a new exact large amplitude wave solution for a cold uniform electron plasma. This result illustrates that most simple analytical solutions can appear even if the density perturbations are large.

Keywords
Large amplitude waves, Plasma oscillations, Parametric processes
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-133754 (URN)10.1016/j.physleta.2016.11.034 (DOI)000395230300015 ()
Available from: 2017-05-05 Created: 2017-05-05 Last updated: 2018-06-09Bibliographically approved
Misra, A. P., Chatterjee, D. & Brodin, G. (2017). Effects of group velocity and multiplasmon resonances on the modulation of Langmuir waves in a degenerate plasma. Physical review. E, 96(5), Article ID 053209.
Open this publication in new window or tab >>Effects of group velocity and multiplasmon resonances on the modulation of Langmuir waves in a degenerate plasma
2017 (English)In: Physical review. E, ISSN 2470-0045, E-ISSN 2470-0053, Vol. 96, no 5, article id 053209Article in journal (Refereed) Published
Abstract [en]

We study the nonlinear wave modulation of Langmuir waves (LWs) in a fully degenerate plasma. Using the Wigner-Moyal equation coupled to the Poisson equation and the multiple scale expansion technique, a modified nonlocal nonlinear Schrodinger (NLS) equation is derived which governs the evolution of LW envelopes in degenerate plasmas. The nonlocal nonlinearity in the NLS equation appears due to the group velocity and multiplasmon resonances, i.e., resonances induced by the simultaneous particle absorption of multiple wave quanta. We focus on the regime where the resonant velocity of electrons is larger than the Fermi velocity and thereby the linear Landau damping is forbidden. As a result, the nonlinear wave-particle resonances due to the group velocity and multiplasmon processes are the dominant mechanisms for wave-particle interaction. It is found that in contrast to classical or semiclassical plasmas, the group velocity resonance does not necessarily give rise the wave damping in the strong quantum regime where hk similar to mv(F) with _ h denoting the reduced Planck's constant, m the electron mass, and v(F) the Fermi velocity; however, the three-plasmon process plays a dominant role in the nonlinear Landau damping of wave envelopes. In this regime, the decay rate of the wave amplitude is also found to be higher compared to that in the modest quantum regime where the multiplasmon effects are forbidden.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2017
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-143012 (URN)10.1103/PhysRevE.96.053209 (DOI)000416316100012 ()
Available from: 2017-12-14 Created: 2017-12-14 Last updated: 2018-06-09Bibliographically approved
Brodin, G., Stenflo, L. & Juul Rasmussen, J. (2017). Focus issue to honour Hans L Pecseli on his 70th birthday. Physica Scripta, 92(1), Article ID 010301.
Open this publication in new window or tab >>Focus issue to honour Hans L Pecseli on his 70th birthday
2017 (English)In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 92, no 1, article id 010301Article in journal, Editorial material (Other academic) Published
Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2017
National Category
Physical Sciences
Identifiers
urn:nbn:se:umu:diva-130076 (URN)10.1088/0031-8949/92/1/010301 (DOI)000389326000001 ()
Available from: 2017-01-13 Created: 2017-01-11 Last updated: 2018-06-09Bibliographically approved
Brodin, G. & Stenflo, L. (2017). Nonlinear dynamics of a cold collisional electron plasma. Physics of Plasmas, 24(12), Article ID 124505.
Open this publication in new window or tab >>Nonlinear dynamics of a cold collisional electron plasma
2017 (English)In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 24, no 12, article id 124505Article in journal (Refereed) Published
Abstract [en]

We study the influence of collisions on the dynamics of a cold non-relativistic plasma. It is shown that even a comparatively small collision frequency can significantly change the large amplitude wave solution.

National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-144118 (URN)10.1063/1.5011299 (DOI)000418957200104 ()
Available from: 2018-01-26 Created: 2018-01-26 Last updated: 2018-06-09Bibliographically approved
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