Topic/Type: 2.2 Kinetic methods, Particle-In-Cell and Vlasov, Invited

Nonlinear Nonstationary Self-Organized Asymptotic States in Vlasov Plasmas

B. Afeyan

Polymath Research Inc.

Nonlinear Nonstationary Self-Organized Asymptotic (NNSA) States in Vlasov plasmas arise due to the feedback between complicated particle orbits and the self consistent fields they create, which in turn accelerate the particles. To capture this highly complex dynamics, Eulerian Vlasov-Poisson and Vlasov-Maxwell solvers are used with a Ponderomotive, finite temporal duration drive, which is due to the optical mixing of two counter-propagating laser beams. But the trapping-untrapping and retrapping oscillations of particles participating in maintaing such waves are best captured using Lagrangian methods, once the self-consistent EM fields are found via Eulerian simulations, via backwards or forwards, Adams-Bashford or Runge-Kutta orbit calculations and detailed statistics accumulation. This is the way to catalog the sequence of transitions in behavior all representative particles make in a given partition of phase space. Furthermore, the self-organization of phase space into a few significant partitions (5 or 6) around the phase velocity of the driver field, in the case of Kinetic Electrostatic Electron Nonlinear (KEEN) waves (a particular realization of an NNSA state) will be demonstrated and various techniques by which to find those partitions in particular cases (ie ones driven at a particular frequency, wavenumber and amplitude) will be given. Finally, the influence of KEEN waves on electron plasma waves (EPW) will also be shown. In particular, when the 2:1 resonance is excited between these two waves, the first two (phase-locked) harmonics making up a KEEN wave and the EPW will interact in such a way as to disallow the trapping of particles in the EPW and the EPW will phase mix away. Off this resonance, a strong EPW can swallow up the KEEN wave or else persist with little trouble due to the pre-existence of a KEEN wave (all this at constant drive amplitudes for both waves and at the same wavenumber, just by changing the KEEN wave drive frequency). Such nonlocal in phase space techniques of highly nonlinear wave-wave interference are a novel property of these studies which lead to new ways of suppressing of Stimulated Raman Scattering or Two-Plasmon Decay in High Energy Density Plasmas (HEDP) and Inertial COnfinement Fusion (ICF) settings. Vlasov codes are ideal for the study of the intricate phase space structures created by these means in the spectral gap of conventional plasma physics lore, including their fascinating nonlocal interactions.