High-energy–density systems and astrophysical systems both involve hydrodynamic effects, including sources of pressure, shock waves, rarefactions and plasma flows. In the evolution of such systems, hydrodynamic instabilities naturally evolve. As a result, a fundamental understanding of hydrodynamic instabilities is necessary to understand their behaviour. This paper discusses the validity of a hydrodynamic description in both cases, and, from the common perspective of the basic mechanisms at work, discusses the instabilities that appear in astrophysics and at high energy density. The high-energy–density research facilities of today, built to pursue inertial fusion, can accelerate small but macroscopic amounts of material to velocities above 100 km s−1, can heat such material to temperatures above 100 eV and can produce pressures far above a million atmospheres (1012 dyn cm−2 or 0.1 TPa). In addition to enabling inertial fusion research, this enables these facilities to do experiments under the conditions that address basic physics issues including issues from astrophysics. One can devise experiments aimed directly at important processes such as the Rayleigh Taylor instability at an ablating surface or at an embedded interface that is accelerating, the Richtmeyer Meshkov evolution of shocked interfaces and the Kelvin–Helmholtz instability of shear flows. The paper includes examples of such phenomena from the laboratory and from astrophysics.
High energy density laboratory astrophysics