7 research outputs found
Turbulent magnetic field amplification from spiral SASI modes in core-collapse supernovae
We describe the initial implementation of magnetohydrodynamics (MHD) in our
astrophysical simulation code \genasis. Then, we present MHD simulations
exploring the capacity of the stationary accretion shock instability (SASI) to
generate magnetic fields by adding a weak magnetic field to an initially
spherically symmetric fluid configuration that models a stalled shock in the
post-bounce supernova environment. Upon perturbation and nonlinear SASI
development, shear flows associated with the spiral SASI mode contributes to a
widespread and turbulent field amplification mechanism. While the SASI may
contribute to neutron star magnetization, these simulations do not show
qualitatively new features in the global evolution of the shock as a result of
SASI-induced magnetic field amplification.Comment: 15 pages, 7 figures, To appear in the Journal of Physics: Conference
Series. Proceedings of the IUPAP Conference on Computational Physics
(CCP2011
Magnetic field generation by the stationary accretion shock instability
By adding a weak magnetic field to a spherically symmetric fluid
configuration that caricatures a stalled shock in the post-bounce supernova
environment, we explore the capacity of the stationary accretion shock
instability (SASI) to generate magnetic fields. The SASI develops upon
perturbation of the initial condition, and the ensuing flow generates--{\em in
the absence of rotation}--dynamically significant magnetic fields ( G) on a time scale that is relevant for the explosion mechanism of
core-collapse supernovae. We describe our model, present some recent results,
and discuss their potential relevance for supernova models.Comment: 5 pages, 3 figures, submitted to Journal of Physics: Conference
Series, SciDAC 200
Parallel implementation and performance optimization of the configuration-interaction method
The configuration-interaction (CI) method, long a popular approach to describe quantum many-body systems, is cast as a very large sparse matrix eigenpair problem with matrices whose dimension can exceed one billion. Such formulations place high demands on memory capacity and memory bandwidth - - two quantities at a premium today. In this paper, we describe an efficient, scalable implementation, BIGSTICK, which, by factorizing both the basis and the interaction into two levels, can reconstruct the nonzero matrix elements on the fly, reduce the memory requirements by one or two orders of magnitude, and enable researchers to trade reduced resources for increased computational time. We optimize BIGSTICK on two leading HPC platforms - - the Cray XC30 and the IBM Blue Gene/Q. Specifically, we not only develop an empirically-driven load balancing strategy that can evenly distribute the matrix-vector multiplication across 256K threads, we also developed techniques that improve the performance of the Lanczos reorthogonalization. Combined, these optimizations improved performance by 1.3-8× depending on platform and configuration
2018 SI2-SSE Lightning Talk: Neutrino Radiation Hydrodynamics in GenASiS
Lightning Talk Slide for 2018 SI2 PI Meeting<br
Neutrino Radiation Hydrodynamics in GenASiS
Radiation transport and kinetic theory of particles are relevant to many areas of astrophysics, a prime example of which is the physics of core-collapse supernovae. The goal of this project is to develop and deploy a software element to solve radiation hydrodynamics problems on modern supercomputers. This functionality will be developed within<br>GenASiS, a new framework to facilitate simulation of astrophysical phenomena on leading capability supercomputers.<br><br