Evolution of nonlinear waves in compressing plasma

Abstract

Through particle-in-cell simulations, the evolution of nonlinear plasma waves is examined in one-dimensional collisionless plasma undergoing mechanical compression. Unlike linear waves, whose wavelength decreases proportionally to the system length L(t), nonlinear waves, such as solitary electron holes, conserve their characteristic size D during slow compression. This leads to a substantially stronger adiabatic amplification as well as rapid collisionless damping when L approaches D. On the other hand, cessation of compression halts the wave evolution, yielding a stable mode.

On Variational Methods In the Physics of Plasma Waves

“…(For WTP parallel compression, see Ref. [96].) Then k remains fixed, so the ACT yields I/n = const, or…”

Current drive in recombining plasma

“…Recently, however, a number of studies [11][12][13][14][15] of waveparticle interactions in nonstationary plasmas has revealed previously unexplored phenomenology and potentially useful mechanisms. Such phenomena are intrinsically non-steady-state, and hence require a modification of the methods typically used to analyze and describe the physics in stationary systems.…”

“…[11][12][13][14] from the work done on current drive schemes in other time-varying conditions, e.g., during plasma current ramp-up in tokamaks, where the current and magnetic field are time-varying [16][17][18][19][20][21], is the direct influence of the time-variation on wave-particle processes in the plasma. Time variation in neither the application of rf power nor changes in the current or poloidal magnetic field alters the underlying wave dynamics or the particle collisionality.…”

“…Such phenomena are intrinsically non-steady-state, and hence require a modification of the methods typically used to analyze and describe the physics in stationary systems. In particular, References [11][12][13][14][15] focus primarily on non-steady-state effects associated with expanding or compressing plasma. When a wave is embedded in such a nonstationary plasma and is undamped initially, modification of the bulk plasma parameters through the nonstationary processes changes the wave dynamics and can lead to an induced waveparticle resonance with the fast-particles on the tail of the bulk plasma distribution [12].…”

Nonlinear Amplification and Decay of Phase-Mixed Waves in Compressing Plasma

“…In particular, the averaged-Lagrangian theory of Refs. [11][12][13] renders analytical transparency, while, numerically, one-dimensional (1D) particle-in-cell (PIC) simulations are distinctly enlightening [7,[16][17][18]. Below we combine these tools to explore the dynamics of BGK-like waves in time-evolving plasma, which exhibit a host of interesting paradigmatic phenomena.…”