Large-scale momentum exchange by microinstabilities: a process happening in laboratory and space plasmas

Based on a recent theory (Coppi 2002 Nucl. Fusion 42 1) of spontaneous toroidal rotation in tokamaks (Lee et al 2003 Phys. Rev. Lett. 91 205003) and in astrophysical accretion disks, we propose that an analogous process could be at play also in the Earth space environment. We use fully kinetic particle-in-cell simulations to study the evolution of drift instabilities. We show that indeed a macroscopic velocity shear is generated spontaneously in the plasma. As in tokamaks, the microscopic fluctuations remain limited to the edge of the plasma channel but the momentum spreads over the whole macroscopic system.