Early time structuring at very high altitudes: Instability mechanism, properties and consequences

This report considers structuring that results from plasma streaming at sub Alfvenic speeds across at external magnetic field, as might occur in a very high altitude nuclear explosion (VHANE). In previous reports we have proposed the lower hybrid drift instability enhanced by the deceleration of the plasma by the field produces the flute modes observed on the surface of expanding laser produced plasmas. We have derived an appropriate dispersion equation to describe the properties of the unstable waves and carried out particle simulations to show the growth and evolution of the instability. We review the salient features of this earlier work and then describe recent additions and refinements to the theory and simulations. We discuss improvements to the dynamics of a 3-D expansion, some initial work on a nonlocal linear theory, the addition of finite electron beta effects to the linear theory, the scaling of the wave properties with the ratio of the ion gyroradius to the magnetic confinement radius, and a better understanding of the nonlinear evolution of the instability. Furthermore, we have considered nonsymmetric expansions, simulations of the instability in 3-D, the very weak limit of the instability, and the effect of collisions. Next, the consequences of these results both for NRL laser experiment as well as other experiments and for VHANEs are considered.