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Title: Three-dimensional particle-in-cell simulation of electron acceleration by Langmuir waves in an inhomogeneous plasma

A possible solution to the unexplained high intensity hard x-ray emission observable during solar flares was investigated via 3D fully relativistic, electromagnetic particle-in-cell simulations with realistic ion to electron mass ratio. A beam of accelerated electrons was injected into a magnetised, Maxwellian, homogeneous, and inhomogeneous background plasma. The electron distribution function was unstable to the beam-plasma instability and was shown to generate Langmuir waves, while relaxing to plateau formation. In order to estimate the role of the background density gradient on an unbound (infinite spatial extent) beam, three different scenarios were investigated: (a) a uniform density background; (b) a weak density gradient, n{sub e,R}/n{sub e,L} = 3; (c) a strong gradient case, n{sub e,R}/n{sub e,L} = 10, where n{sub e,R} and n{sub e,L} denote background electron densities on the left and right edges of the simulation box, respectively. The strong gradient case produced the largest fraction of electrons beyond 15v{sub th}. Furthermore, two cases (uniform and strong gradient background) with spatially localized beam injections were performed aiming to show drifts of the generated Langmuir wave wavenumbers, as suggested in previous studies. For the strong gradient case, the Langmuir wave power is shown to drift to smaller wavenumbers, as found in previous quasi-linear simulations.
Authors:
;  [1]
  1. School of Physics and Astronomy, Queen Mary University of London, London E1 4NS (United Kingdom)
Publication Date:
OSTI Identifier:
22252118
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 21; Journal Issue: 1; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ACCELERATION; BEAM INJECTION; BEAMS; DISTRIBUTION FUNCTIONS; ELECTRONS; HARD X RADIATION; INHOMOGENEOUS PLASMA; PLASMA INSTABILITY; RELATIVISTIC RANGE; SIMULATION; SOLAR FLARES; THREE-DIMENSIONAL CALCULATIONS; WAVE POWER