On plasma density blobs in drift turbulence
  By keeping nonlinear Boltzmann factor in electron density dependence on electrostatic potential it is demonstrated that large plasma density blobs, often seen in experiment inside separatrix, can exist within the framework of drift wave dynamics. The estimates show that plasma density in a blob can be ~3 times higher that average plasma density, but hardly exceeds this limit, which in a ball park is in agreement with experimental observations. 
S. I. Krasheninnikov
physics.plasm-ph