Particle pinch in collisionless drift-wave turbulence

Nonlinear numerical simulations show that the particle flux from collisionless drift-wave turbulence is directed up-gradient for sufficiently high values of ηe=Ln/LTe. This “particle pinch” results from the completely different perpendicular dynamics of slow (resonant) and fast (nonresonant) electrons, making it a genuinely kinetic effect which cannot easily be described by fluid models. Moreover, the linearly stable system self-sustains its turbulent state through a finite-amplitude (nonlinear) instability. Therefore, quasilinear estimates of turbulent transport caused by collisionless drift waves are practically useless and have to be replaced by nonlinear kinetic simulations like the present one.