Аннотация
We carried out 2D-axisymmetric MHD simulations of core-collapse supernovae
for rapidly-rotating magnetized progenitors. By changing both the strength of
the magnetic field and the spatial resolution, the evolution of the
magnetorotational instability (MRI) and its impacts upon the dynamics are
investigated. We found that the MRI greatly amplifies the seed magnetic fields
in the regime where not the Alfvén mode but the buoyant mode plays a primary
role in the exponential growth phase. The MRI indeed has a powerful impact on
the supernova dynamics. It makes the shock expansion faster and the explosion
more energetic, with some models being accompanied by the collimated-jet
formations. These effects, however, are not made by the magnetic pressure
except for the collimated-jet formations. The angular momentum transfer induced
by the MRI causes the expansion of the heating region, by which the accreting
matter gain an additional time to be heated by neutrinos. The MRI also drifts
low-\$Y\_p\$ matter from the deep inside of the core to the heating region, which
makes the net neutrino heating rate larger by the reduction of the cooling due
to the electron capture. These two effects enhance the efficiency of the
neutrino heating, which is found to be the key to boost the explosion. Indeed
we found that our models explode far more weakly when the net neutrino heating
is switched off. The contribution of the neutrino heating to the explosion
energy is estimated to be more than 90\%.
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