Collapse of Langmuir solitons in inhomogeneous plasmas
  Propagation of Langmuir solitons in inhomogeneous plasmas is investigated numerically. Through numerical simulation solving Zakharov equations, the solitons are accelerated toward the low density side. As a consequence, isolated cavities moving at ion sound velocities are emitted. When the acceleration is further increased, solitons collapse and the cavities separate into two lumps released at ion sound velocities. The threshold is estimated by an analogy between the soliton and a particle overcoming the self-generated potential well. 
Y. A. Chen, Y. Nishimura, Y. Nishida and C.Z.Cheng
physics.plasm-ph