Cold plasma wavebreaking: Production of energetic electrons

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Abstract
Nonlinear electron plasma oscillations are investigated in the wavebreaking regime where collective energy is converted into random energy. The Lagrangian description of the electrons is extended beyond fluid element orbit crossing, thereby exposing the essential physics of wavebreaking and permitting simple analytical interpretation of it. In driven cold inhomogeneous plasma a region of large resonant oscillations decays by producing energetic electrons which escape into the less dense plasma. The maximum energy of the fast electrons produced during the driver period in which the first wave breaks is much larger than the energy of an electron oscillating freely in the driver field. The total energy of the fast electrons exceeds that supplied the system by the driver in a period and can be a significant fraction of the total energy in the oscillations at the onset of wavebreaking.