Supernova, nuclear synthesis, fluid instabilities, and interfacial mixing

Abstract

Supernovae and their remnants are a central problem in astrophysics due to their role in the stellar evolution and nuclear synthesis. A supernova’s explosion is driven by a blast wave causing the development of Rayleigh–Taylor and Richtmyer–Meshkov instabilities and leading to intensive interfacial mixing of materials of a progenitor star. Rayleigh–Taylor and Richtmyer–Meshkov mixing breaks spherical symmetry of a star and provides conditions for synthesis of heavy mass elements in addition to light mass elements synthesized in the star before its explosion. By focusing on hydrodynamic aspects of the problem, we apply group theory analysis to identify the properties of Rayleigh–Taylor and Richtmyer–Meshkov dynamics with variable acceleration, discover subdiffusive character of the blast wave-induced interfacial mixing, and reveal the mechanism of energy accumulation and transport at small scales in supernovae.

On the Rayleigh-Taylor unstable dynamics of three-dimensional interfacial coherent structures with time-dependent acceleration

“…The Atwood bubble has a quasi-invariance property suggesting that nonlinear coherent RM dynamics is set by the interplay of two macroscopic length-scales -the wavelength and the amplitude. Our theory agrees with existing observations, and elaborates new benchmarks for observations 6,[8][9][10][11][12][13][14][20][21][22][23] .…”

“…The periodic nature of the large-scale coherent structure can be accommodated by appealing to the theory of space groups 5,14,15,25 . As a specific example, we focus on threedimensional flow with square symmetry.…”

“…RTI/RMI and RT/RM mixing play an important role in a broad range of processes in nature and technology, including stellar evolution and plasma fusion, and in the fossil fuel industry [7][8][9][10][11][12][13] . In this work we study the long-standing problem of RMI with variable acceleration 14 . We employ group theory to solve the boundary value problem for the early-time and late-time RMI 15 , directly link RM dynamics to the interfacial shear, identify its invariance properties, and reveal the interfacial and multi-scale character of RM dynamics.…”

“…RMI with variable acceleration commonly occur in fluids, plasmas, and materials [7][8][9][10][11][12][13][14] : RMI leads to the appearance of light-years-long structures in clouds of molecular hydrogen, influences the formation of hot spots in inertial confinement fusion, controls combustion processes in scramjets, and drives material transformation under impact in nano-fabrication. In these vastly different physical conditions, RM flows have similar qualitative features of their evolution.…”

“…In realistic environments, RT and RM flows are usually driven by variable acceleration [8][9][10][11][12][13][14] and only limited information is currently available on RM and RT dynamics under these conditions 14 . An important special case is that of acceleration with power-law time-dependence, because power-law functions may lead to new scaling properties of the dynamics and can be used to adjust the acceleration's time-dependence in applications [8][9][10][11][12][13][14]35,36 . For such accelerations, the early-time and late-time scale-dependent dynamics can be of RM or RT type, depending on the exponent in the acceleration powerlaw 14,37 .…”