Beam-plasma instability and density holes: Langmuir wave-packet formation and particle acceleration

A. Sgattoni; F. Amiranoff; C. Briand; Pierre Henri; M. Grech; C. Riconda

doi:10.1063/1.4989724

Beam-plasma instability and density holes: Langmuir wave-packet formation and particle acceleration

A. Sgattoni ^{1, 2} F. Amiranoff ² C. Briand ¹ Pierre Henri ³ M. Grech ² C. Riconda ²

1 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique

2 LULI - Laboratoire pour l'utilisation des lasers intenses

3 LPC2E - Laboratoire de Physique et Chimie de l'Environnement et de l'Espace

Abstract : The role of density perturbations of the background plasma in the development of Langmuir waves generated by beam-plasma instabilities is a very debated issue in space physics. The presence of clumpy electrostatic wave-packets (in particular Langmuir waves), from in situ observations, is indeed puzzling. Several processes have been proposed to explain the formation of waveforms, such as Stochastic Growth Theory and trapping in eigenmodes. Here we explore another mechanism considering the seeding of the beam-plasma instability by density holes. We have performed several 1D-1V Vlasov simulations in the electrostatic limit. We show that in the presence of a density hole, a large amplitude solitary wave-packet of Langmuir waves is formed and that it evolves towards clumpier waveforms. Moreover, the large-amplitude wave-packets generated near the hole can reach saturation and accelerate the electrons of the beam: their velocity distribution is strongly distorted, leading to a multi-peaked structure that generates new unstable modes having phase velocities both larger and smaller than the average speed of the beam. The relationship between the wave amplitude and the characteristics of the density hole is also described, showing how the electron beam may select specific holes to generate enhanced localised Langmuir wave-packets.

Keywords : Plasma oscillations Electric fields Electrostatic waves Accelerated electron beams Electrostatics

Document type :

Journal articles

Domain :

Sciences of the Universe [physics]

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https://hal-insu.archives-ouvertes.fr/insu-01685241
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Submitted on : Tuesday, January 16, 2018 - 11:24:37 AM
Last modification on : Friday, April 5, 2019 - 8:19:29 PM

Beam-plasma instability and density holes: Langmuir wave-packet formation and particle acceleration

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Beam-plasma instability and density holes: Langmuir wave-packet formation and particle acceleration

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