48 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
Toward Five-dimensional Core-collapse Supernova Simulations
The computational difficulty of six-dimensional neutrino radiation
hydrodynamics has spawned a variety of approximations, provoking a long history
of uncertainty in the core-collapse supernova explosion mechanism. Under the
auspices of the Terascale Supernova Initiative, we are honoring the physical
complexity of supernovae by meeting the computational challenge head-on,
undertaking the development of a new adaptive mesh refinement code for
self-gravitating, six-dimensional neutrino radiation magnetohydrodynamics. This
code--called {\em GenASiS,} for {\em Gen}eral {\em A}strophysical {\em
Si}mulation {\em S}ystem--is designed for modularity and extensibility of the
physics. Presently in use or under development are capabilities for Newtonian
self-gravity, Newtonian and special relativistic magnetohydrodynamics (with
`realistic' equation of state), and special relativistic energy- and
angle-dependent neutrino transport--including full treatment of the energy and
angle dependence of scattering and pair interactions.Comment: 5 pages. Proceedings of SciDAC 2005, Scientific Discovery through
Advanced Computing, San Francisco, CA, 26-30 June 200
Quasi-Periodic Releases of Streamer Blobs and Velocity Variability of the Slow Solar Wind near the Sun
We search for persistent and quasi-periodic release events of streamer blobs
during 2007 with the Large Angle Spectrometric Coronagraph on the \textit{Solar
and Heliospheric Observatory} and assess the velocity of the slow solar wind
along the plasma sheet above the corresponding streamer by measuring the
dynamic parameters of blobs. We find 10 quasi-periodic release events of
streamer blobs lasting for three to four days. In each day of these events, we
observe three-five blobs. The results are in line with previous studies using
data observed near the last solar minimum. Using the measured blob velocity as
a proxy for that of the mean flow, we suggest that the velocity of the
background slow solar wind near the Sun can vary significantly within a few
hours. This provides an observational manifestation of the large velocity
variability of the slow solar wind near the Sun.Comment: 14 pages, 5 figures, accepted by Soalr Physic