Magnetohydrodynamic Turbulence Powered by Magnetorotational Instability in Nascent Proto-Neutron Stars

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Magnetorotational instability (MRI) in a convectively-stable layer around the neutrinosphere is simulated by a three-dimensional model of supernova core. To resolve MRI-unstable modes, a thin layer approximation considering only the radial global stratification is adopted. Our intriguing finding is that the convectively-stable layer around the neutrinosphere becomes fully-turbulent due to the MRI and its nonlinear penetration into the strongly-stratified MRI-stable region. The intensity of the MRI-driven turbulence increases with magnetic flux threading the core, but is limited by a free energy stored in the differential rotation. The turbulent neutrinosphere is a natural consequence of rotating core-collapse and could exert a positive impact on the supernova mechanism.