Unstable entropy mode in a current-carrying turbulent plasma and double layer formation

In this manuscript, we developed an analytical model for double layer and unstable entropy formation in current-carrying turbulent plasma. In the presence of a strong axial current, ion acoustic turbulence can give rise to enhanced anomalous resistivity and inhibited thermal conductivity. This state of uniform turbulence is, however, shown to be unstable to a purely growing axial perturbation when v02υ/ve2>k2χ, where v0,ve,υ,and χ are the electron drift velocity, thermal velocity, collision frequency, and thermal conductivity, respectively. The temperature perturbation enhances the local resistivity of electrons and raises their heating rate, further enhancing the temperature perturbation. When this tendency overpowers the opposing effect of thermal conduction, the instability grows. The nonlinear state of this instability has been analyzed and its possible relevance to the experimental results with double layer formation in a long plasma column has been discussed.