arXiv subjects

Matteo V. Falessi

Publications and source records attributed to Matteo V. Falessi.

3 recordsLinked to original sources

arXiv2026

Analysis of non-diffusive avalanche transport of energetic particles

The dynamics of energetic particles (EPs) interacting with Alfvén eigenmodes (AEs) for the ITER 15MA baseline scenario was described using a reduced 1D model in [Carlevaro et al. PPCF 64, 035010 (2022)], and successfully tested against nonlinear wave-particle simulations. In this paper, we introduce a detailed phase-space and statistical analysis of this case to characterize the emerging EP transport regimes. Deviations from pure diffusive dynamics are quantitatively addressed, indicating the limitations of standard quasi-linear descriptions. The phase space diagnostics introduced allows to describe the emergence of a very complex dynamics of overlapping resonances and substructure formation, reinforcing the evidence of non-diffusive domino-like AEs.

physics.plasm-ph↗

arXiv2016

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

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.

physics.plasm-ph↗

arXiv2015

Nonlinear physics and energetic particle transport features of the beam-plasma instability

In this paper, we study transport features of a one-dimensional beam-plasma system in the presence of multiple resonances. As a model description of the general problem of a warm energetic particle beam, we assume $n$ cold supra-thermal beams and investigate the self-consistent evolution in the presence of the complete spectrum of nearly degenerate Langmuir modes. A qualitative transport estimation is obtained by computing the Lagrangian Coherent Structures of the system on given temporal scales. This leads to the splitting of the phase space into regions where the local transport processes are relatively faster. The general theoretical framework is applied to the case of the nonlinear dynamics of two cold beams, for which numerical simulation results are illustrated and analyzed.

physics.plasm-ph↗