Propagation of a cloud of hot electrons in the regime of fast relaxation

Foroutan, G.; Li, B.; Robinson, P. A.; Cairns, Iver H.; Moslehi-Fard, M.

doi:10.1063/1.1884616

Cited by 13 publications

(11 citation statements)

References 21 publications

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“…Such a model could draw upon the dynamic quasilinear theories worked out to explain type III solar radio bursts. 244,245 In the GRB context, the aforementioned theoretical results are frequently applied to model the unstable processes arising within colliding plasma shells prior to the shock formation. But the concept of plasma shell collision necessarily implies that these shells have borders.…”

Section: Discussionmentioning

confidence: 99%

Multidimensional electron beam-plasma instabilities in the relativistic regime

2010

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The interest in relativistic beam-plasma instabilities has been greatly rejuvenated over the past two decades by novel concepts in laboratory and space plasmas. Recent advances in this long-standing field are here reviewed from both theoretical and numerical points of view. The primary focus is on the two-dimensional spectrum of unstable electromagnetic waves growing within relativistic, unmagnetized, and uniform electron beam-plasma systems. Although the goal is to provide a unified picture of all instability classes at play, emphasis is put on the potentially dominant waves propagating obliquely to the beam direction, which have received little attention over the years. First, the basic derivation of the general dielectric function of a kinetic relativistic plasma is recalled. Next, an overview of two-dimensional unstable spectra associated with various beam-plasma distribution functions is given. Both cold-fluid and kinetic linear theory results are reported, the latter being based on waterbag and Maxwell-Jüttner model distributions. The main properties of the competing modes ͑developing parallel, transverse, and oblique to the beam͒ are given, and their respective region of dominance in the system parameter space is explained. Later sections address particle-in-cell numerical simulations and the nonlinear evolution of multidimensional beam-plasma systems. The elementary structures generated by the various instability classes are first discussed in the case of reduced-geometry systems. Validation of linear theory is then illustrated in detail for large-scale systems, as is the multistaged character of the nonlinear phase. Finally, a collection of closely related beam-plasma problems involving additional physical effects is presented, and worthwhile directions of future research are outlined.

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Section: Discussionmentioning

confidence: 99%

Multidimensional electron beam-plasma instabilities in the relativistic regime

2010

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“…The quasilinear dynamics of a spatially limited electron beam (an electron cloud) streaming through a cold plasma with Maxwellian velocity distribution function has also been simulated (Foroutan et al 2005(Foroutan et al , 2008. In this work for a first time we are concerned with the investigation of the generation of Langmuir waves, its spectra and total energy density, and also the gas-dynamical parameters of the beam such as the height of the plateau in the beam distribution function, its upper velocity boundary, the beam width in velocity space, and its local and average velocity of propagation in the solar wind plasma by considering a Lorentzian background distribution function.…”

Section: Introductionmentioning

confidence: 99%

Beam propagation and Langmuir wave generation in a plasma with κ distribution function

Khalilpour

Foroutan

2011

Astrophys Space Sci

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Using a kappa velocity distribution function for the electrons of the background plasma, the dynamics of a beam of hot electrons streaming through the plasma and the generation of Langmuir waves are investigated in the frame work of quasilinear theory. It is shown that the Langmuir waves are strongly damped by high energy tail of the Kappa distribution function. The spatial expansion of the beam is reduced and the spectral density of Langmuir waves becomes narrower. The height of the plateau in the beam distribution function increases at small velocities and the average velocity of beam is larger than that of a Maxwellian distribution. The influence of Kappa velocity distribution function on the gasdynamical parameters is investigated. It is found that, the height of plateau in the beam distribution function, and its lower velocity boundary are enhanced while, the local beam width in velocity space decreases.

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“…[1][2][3][4][5][6][7][8] Locally heated in the solar flares, the ejected energetic electrons can excite Langmuir waves via a streaming instability as they propagate through the solar corona plasma. [1][2][3][4][5][6][7][8] Locally heated in the solar flares, the ejected energetic electrons can excite Langmuir waves via a streaming instability as they propagate through the solar corona plasma.…”

Section: Introductionmentioning

confidence: 99%

“…[1][2][3][4][5][6][7][8] Locally heated in the solar flares, the ejected energetic electrons can excite Langmuir waves via a streaming instability as they propagate through the solar corona plasma. [1][2][3]7,8 Thanks to these numerical works, Sturrock's dilemma on the stability of electron beams on large distances has been resolved with explanation that the reabsorption of the Langmuir waves by later arriving, slightly slower, electrons conserves the energy of the system. Back reaction of the excited plasma oscillations results in diffusion of particles in velocity space and formation of a plateaued beam distribution function.…”

Section: Introductionmentioning

confidence: 99%

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Quasilinear dynamics of a cloud of hot electrons propagating through a plasma in the presence of an externally applied uniform electric field

et al. 2007

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The propagation of a cloud of hot electrons through a plasma and the generation of Langmuir waves are investigated in the presence of an externally applied uniform electric field. Using numerical simulations of the quasilinear equations the evolution of the electron distribution function and the spectral density of Langmuir waves are monitored in coordinate and velocity space. It is found that the Langmuir waves are enhanced in the presence of the electric field and the distribution functions of the beam and Langmuir waves diffuse toward large velocities. The overall self-similar characteristic of the system is preserved in the presence of the electric field. The average beam velocity is no longer constant and increases with time along its trajectory, but the acceleration is much less than that of free streaming particles. The beam number density plateaus in coordinate space and large scale, small amplitude fluctuations develop on the top of this plateau. The level of the fluctuations depends on the strength of the electric field. We also investigated the influence of the external electric field on the evolution of gas-dynamical parameters such as the height of the plateau in the beam distribution function in velocity space, its upper velocity boundary, and the local velocity spread of the beam. Due to the finite quasilinear relaxation time and spatial inhomogeneity of the electron beam, different parts of the beam are in different states of relaxation. In the region of partial relaxation the plateau is specified by both upper and lower velocity boundaries. The upper boundary of plateau increases linearly with the strength of the electric field but the lower boundary is independent of it. Contrary to the free streaming of a beam in an electric field or quasilinear relaxation in the absence of the electric field, the local velocity spread of the beam increases during its propagation. Some of the electrons at the back of the beam are also transferred by the electric field to its front, so that the height of plateau increases at large distances.

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Propagation of a cloud of hot electrons in the regime of fast relaxation

Cited by 13 publications

References 21 publications

Multidimensional electron beam-plasma instabilities in the relativistic regime

Multidimensional electron beam-plasma instabilities in the relativistic regime

Beam propagation and Langmuir wave generation in a plasma with κ distribution function

Quasilinear dynamics of a cloud of hot electrons propagating through a plasma in the presence of an externally applied uniform electric field

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