Mixed diffusive-convective relaxation of a broad beam of energetic particles in cold plasma

Nakia Carlevaro; Alexander V. Milovanov; Matteo V. Falessi; Giovanni Montani; Davide Terzani; Fulvio Zonca

doi:10.3390/e18040143

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arXiv · 1512.07045

Mixed diffusive-convective relaxation of a broad beam of energetic particles in cold plasma

Nakia Carlevaro·Alexander V. Milovanov·Matteo V. Falessi·Giovanni Montani·Davide Terzani·Fulvio Zonca

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Abstract

We revisit the applications of quasi-linear theory as a paradigmatic model for weak plasma turbulence and the associated bump-on-tail problem. The work, presented here, is built around the idea that large-amplitude or strongly shaped beams do not relax through diffusion only and that there exists an intermediate time scale where the relaxations are convective (ballistic-like). We cast this novel idea in the rigorous form of a self-consistent nonlinear dynamical model, which generalizes the classic equations of the quasi-linear theory to "broad" beams with internal structure. We also present numerical simulation results of the relaxation of a broad beam of energetic particles in cold plasma. These generally demonstrate the mixed diffusive-convective features of supra-thermal particle transport; and essentially depend on nonlinear wave-particle interactions and phase-space structures. Taking into account modes of the stable linear spectrum is crucial for the self-consistent evolution of the distribution function and the fluctuation intensity spectrum.

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Nakia Carlevaro, Alexander V. Milovanov, Matteo V. Falessi, Giovanni Montani, Davide Terzani, Fulvio Zonca. 2015-12-22. Mixed diffusive-convective relaxation of a broad beam of energetic particles in cold plasma. https://doi.org/10.3390/e18040143

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