Magnetohydrodynamic implosion symmetry and suppression of Richtmyer-Meshkov instability in an octahedrally symmetric field

Abstract

Magnetohydrodynamic implosion symmetry and suppression ofRichtmyer-Meshkov instability in an octahedrally symmetric field We present numerical simulations of ideal magnetohydrodynamics showing suppression of the Richtmyer-Meshkov instability in spherical implosions in the presence of an octahedrally symmetric magnetic field. This field configuration is of interest owing to its high degree of spherical symmetry in comparison with previously considered dihedrally symmetric fields. The simulations indicate that the octahedral field suppresses the instability comparably to the other previously considered candidate fields for light-heavy interface accelerations while retaining a highly symmetric underlying flow even at high field strengths. With this field, there is a reduction in the root-mean-square perturbation amplitude of up to approximately 50% at representative time under the strongest field tested while maintaining a homogeneous suppression pattern compared to the other candidate fields. KAUST Repository

The magnetised Richtmyer–Meshkov instability in two-fluid plasmas

“…This explains the previously discussed ω z oscillation in time and indeed the regular sign inversion of the various components of vorticity when viewed in the x-y plane, as depicted in the left-hand panels of figure 12. This mechanism, which leads to suppression of the RMI, is not supported by the ideal MHD equations and thus was not observed in previous ideal MHD studies (Samtaney 2003;Wheatley et al 2005;Cao et al 2008;Sano et al 2013;Wheatley et al 2014;Mostert et al 2015Mostert et al , 2017. In figure 12(b) τ B can be seen to lead ω with a relative phase angle of approximately 90 • .…”

“…The magnetic suppression of the MHD RMI has then been investigated in the converging geometries relevant to the ICF for a variety of realisable imposed magnetic-field configurations (Mostert et al. 2015, 2017; Li, Samtaney & Wheatley 2018) with the goal of supressing the instabilities while minimising implosion distortion or weakening. Experimental work has also been carried out by Hohenberger et al.…”

“…In these physical phenomena, the materials involved are in the plasma state. The RMI is most frequently modelled with the equations of hydrodynamics (Lombardini, Pullin & Meiron 2014) or, for the plasma RMI, magnetohydrodynamics (Wheatley, Samtaney & Pullin 2005;Sano, Inoue & Nishihara 2013;Mostert et al 2015Mostert et al , 2017, which are single-fluid models. These do not account for the effects of finite plasma length scales, electron inertia and a finite speed of light, which include phenomena such as charge separation and self-consistently generated electromagnetic fields.…”

“…The influence of a magnetic field on the evolution of the RMI has been investigated previously in the context of ideal magnetohydrodynamics (MHD) (Samtaney 2003;Wheatley et al 2005;Sano et al 2013;Wheatley et al 2014;Mostert et al 2015Mostert et al , 2017 where it was found that the RMI is suppressed due to the transport of vorticity on discontinuous waves. In Hall-MHD, incompressible linear theory shows that vorticity transport is instead via a dispersive wave system, but the growth of the RMI is still mitigated (Shen et al 2019).…”

“…In Hall-MHD, incompressible linear theory shows that vorticity transport is instead via a dispersive wave system, but the growth of the RMI is still mitigated (Shen et al 2019). The magnetic suppression of the MHD RMI has then been investigated in the converging geometries relevant to the ICF for a variety of realisable imposed magnetic-field configurations (Mostert et al 2015(Mostert et al , 2017 with the goal of supressing the instabilities while minimising implosion distortion or weakening. Experimental work has also been carried out by Hohenberger et al (2012) resulting in increased ion temperature and neutron yield and thus demonstrating the potential benefits of applied magnetic fields in ICF experiments.…”