Richtmyer-Meshkov instability in an ion-electron multi-fluid plasma: the planar shock case in 3D and cylindrical converging shock case in 2D*

The Richtmyer-Meshkov instability (RMI) results from the impulsive acceleration of a perturbed or planar (with perturbed flow field) density interface.

The RMI is ubiquitous in shock environments, inlcuding inertial confinement fusion (ICF), and may arise due to an interface of fluid species, isotopes, and temperature.

The plasma RMI is significantly affected by electromagnetic effects and can be modelled more accurately by a multifluid plasma (MFP) model rather than conventional magnetohydrodynamics.

We present MFP simulation results of a 3D ideal single-mode double-sine perturbation with a planar shock-wave, and 2D single-mode sine perturbation with a cylindrically converging shock-wave and elastic collisions.

The addition of elastic collisions and more complicated geometry/dimensionality is vital for understanding the plasma RMI and ICF fuel capsule dynamics.

The elastic collisions are modelled by Braginskii transport coefficients, representing the physical processes of thermal equilibration, inter-species drag, viscous momentum- and energy-transfers, and thermal conductivity.

The 3D results show strong symmetry and introduce large and small scale secondary perturbations along the primary density interface not previously seen in the 2D analogue.

The 2D simulations show the key effects of elastic collisions are: reduction of relative motion between the ion and electron fluids (consequently affecting the self-generated electromagnetic fields), introduction of momentum and energy anisotropy, and damping of high frequency plasma waves.

The net result is a general suppression of: the secondary electromagnetically driven Rayleigh-Taylor instability, Kelvin-Helmholtz instability, and small scale interface perturbations.