Collisionless Simon–Hoh instability in a strongly double-sheared electric field

It has been shown in an earlier paper [Phys. Fluids B 5, 344 (1993)] that the ion flow speed of a plasma can be much smaller than the E×B speed in a strongly double-sheared electric field. In this paper, the stability of the plasma is investigated. It is found that a new instability, driven by the difference between the ion and electron flow speed, occurs and may dominate the Kelvin–Helmholtz (KH) instability in a nonuniform plasma. This new instability has a driving mechanism similar to that of the Simon–Hoh instability and is thus called the collisionless Simon–Hoh (CSH) instability. When the CSH instability dominates, the plasma does not become more unstable as the electric field is increased, in contrast to scenarios where the KH instability is dominant.