Inhomogeneous plasma flows: A review of in situ observations and laboratory experiments

Sheared flows in near-Earth space plasmas, both magnetic-field-aligned and cross-field, contribute to a rich array of phenomena which can be simulated in the laboratory. This has led to improved knowledge of the basic processes involving velocity shear operative in space, where it is not possible to conduct detailed and repeatable experiments with control over background parameters. Depending upon the flow characteristics, shear can contribute to either growth or damping of various plasma modes or, if sufficiently strong, can itself drive instabilities. These instabilities can have significant consequences in redefining the plasma equilibrium and can lead to energization and transport. A number of laboratory experiments have been performed to investigate the detailed physics associated with inhomogeneous space plasma flows. In this work, a review of in situ observations of processes associated with sheared flows and details of complementary laboratory experimental investigations is presented.