Nonlinear saturation of Rayleigh-Taylor instability and generation of shear flow in equatorial spread-F plasma

Abstract

Abstract. An analysis of low order mode coupling equations is used to describe the nonlinear behavior of the RayleighTaylor (RT) instability in the equatorial ionosphere. The nonlinear evolution of RT instability leads to the development of shear flow. It is found that there is an interplay between the nonlinearity and the shear flow which compete with each other and saturate the RT mode, both in the collisionless and collisional regime. However, the nonlinearly saturated state, normally known as vortices or bubbles, may not be stable. Under certain condition these bubbles are shown to be unstable to short scale secondary instabilities that are driven by the large gradients which develop within these structures. Some understanding of the role of collisional nonlinearity in the shear flow generations is also discussed.

Possible ionospheric preconditioning by shear flow leading to equatorial spread <i>F</i>

“…The issue of shear flow stabilization remains contentious, and a number of recent theoretical and computational studies continue to support the idea (Hassam, 1992;Sekar and Kelley, 1998;Chakrabarti and Lakhina, 2003). Chakrabarti and Lakhina (2001) further showed that the nonlinear evolution of the Rayleigh-Taylor instability itself induces shear flow which contributes to the saturation of the instability.…”

Collisional Rayleigh-Taylor instability and shear-flow in equatorial Spread-F plasma

“…where the various symbols have their usual meaning (Huba et al, 1985;Chakrabarti and Lakhina, 2001). Solving electron momentum Eq.…”

“…equatorial Spread-F and ionospheric plasma clouds). It is also known that the RT mode may self-consistently generate a velocity shear which can then stabilize the mode (Finn et al, 1992;Chakrabarti and Lakhina, 2001).…”