Formation of streamers in plasma with an ion temperature gradient

The nonlinear growth and saturation of the negative compressibility ηi instability in an inhomogeneous plasma confined by a straight magnetic field is investigated. A set of nonlinear equations that describe the two-dimensional fluid motion along and across (in the direction of ∇⊥Ti ) the local magnetic field is derived. These equations are basically the same as those describing a one-dimensional nonlinear sound wave, but the compressibility is negative for ηi=̇d log(Ti)/log(ni) exceeding a threshold. The nonlinearity in the equations arises from the parallel convective motion of the fluid. The solution of these equations evolves to a final state in which plasma flows are driven into a low temperature region along the local magnetic field and then jet across the magnetic field along ∇⊥Ti in narrow streams. The structure of these streams is consistent with previous two-dimensional simulations. Results for the scaling of the transport due to these streams are presented.