Modeling the dominance of the gradient drift or Kelvin–Helmholtz instability in sheared ionospheric E × B flows

Studies have shown that in sheared E×B flows an inhomogeneous ionospheric plasma, the gradient drift (GDI) or Kelvin–Helmholtz (KHI) instability may grow. This work examines conditions cause one of these instabilities to dominate over other using a novel model study localized instabilities. The effect collisions with neutral particles plays important role development. It is found KHI dominant low collisionality regimes, GDI high and there exists intermediate region which both exist tandem. For cases velocity shear sufficiently far from density gradient, grow as secondary extending vortices. inclusion wind-driven electric field direction does not impact dominance either instability. Using data empirical models, two altitude limits are found. altitudes above higher limit, dominant. below lower In region, together. Increasing causes be altitude. implies for phenomena whose gradients span large ranges, such subauroral polarization streams, observed by space-based ground-based observation instruments could significantly different.