Speaker
Dr
Hidetomo Sawai
Description
Magnetically driven supernovae have been studied well for
several years. Although core-collapse simulations without
magnetic fields to date cannot reproduce a successful
explosion, every numerical simulation with initially strong
magnetic field and rotation shows a jet-like explosion along
the rotation axis. There a key agent of explosion is
toroidal-magnetic pressure amplified by differential
rotation around a proto-neutron star surface. Meanwhile,
Thompson et al. (2005) showed by their 1-D hydrodynamic
simulations that a turbulent resistivity originating from
magnetorotational instability (MRI) dissipates magnetic
fields, and generated thermal pressure helps the explosion.
However, in their study, dynamical roles of magnetic
pressure are not treated, since their computation is
hydrodynamic and in 1-D. Here, we have done 2-D
magnetohydrodynamic simulations of a collapse of massive
star with inclusion of a magnetic dissipation. We found that
a magnetic dissipation is negative reinforcer for an
energetic explosion. Due to magnetic dissipation, the
amplification rate of toroidal magnetic fields decreases,
which in turn lower the power of the engine. The low-power
engine in principle could produce finally same explosion
energy as a high-power one, provided sizes of energy
reservoirs are same. However, the deeper the collapse
proceeds, the harder the matter to be ejected, and thus the
low-power engine results in a weak explosion