A Turbulent Dynamo in Rotating Magnetized Core-Collapse Supernovae

Transcription

1 A Turbulent Dynamo in Rotating Magnetized Core-Collapse Supernovae David Radice R. Haas, P. Mösta, L. Roberts, C.D. Ott, E. Schnetter

2 Core-Collapse Supernovae Core-Collapse Supernovae in Numbers ~ (50 yr) -1 per galaxy ~ tens every second in the observable universe Peak luminosity ~10 10 solar erg radiation erg kinetic energy Cassiopeia-A erg neutrinos

3 Core-Collapse Supernovae From Janka et al. 2012

4 Extreme Supernovae SN 1998bw Hypernovae BATSE Gamma-Ray Bursts Absolute magnitude [mag] SLSN threshold From Gal-Yam Days from peak [day] SLSN I SLSN II SLSN R SN IIn SN Ia SN Ib/c SN IIb SN II P Super-Luminous Supernovae Large explosion energies, collimated outflows, extreme luminosities Cannot be produced by the neutrino mechanism alone! What powers them? Need another energy source!

5 Rotational Powered Explosions Rotational energy up to ~ few x erg (Woosley & Heger 2006) = Large-scale magnetar-level magnetic fields can extract this energy over timescales of several 10 s ms Asymmetric explosions Proto-magnetar -> SLSN Collapsar -> LGRB From Burrows From Mösta Does it really work?

6 Magnetic Field Amplification G fields and 1 ms rotation periods needed Period is compatible with stellar evolution predictions for stripped progenitors Pre-collapse supernova fields: 10 9 G Flux freezing during collapse: ~10 3 amplification An extra ~10 4 factor is needed!!!

7 Magnetorotational Instability (I) Balbus & Hawley 1991 Fast growing Weak field Small spatial scales

8 Magnetorotational Instability (II) The MRI Must Be Operating!

9 Magnetorotational Instability (III) 3796 T. Rembiasz et al. Figu the l angl solid expe Figure 6. Distribution of the radial component of the magnetic field br across the surface of the computational 11. Evolution of the average magnetic energy density associated times. The times of the snapshot are marked by green vertical Figure lines in Fig. 5. with the MRI channels (emri, α ) and the parasitic instabilities (ep, α ) for From Rembiasz+different 2015components bα of the magnetic field for model #7. by computing the energy-weighted barycenter in the relevant part of Fourier space,!! W tion befo for m

10 Open Questions Does the MRI work in not-idealized core-collapse supernovae? Can it produce net flux? Dynamo action? Need global simulations!

11 Global GRMHD Simulations Relativistic magneto-hydrodynamics Neutrino radiation Need extremely high-resolution (~50/100 m) ~7x higher than previous highestresolution simulations 3000x more expensive!

12 Computational Setup Start from lower-res. run Small domain Uniform grid Freeze the spacetime evolution Minimize MPI communications Evolve only for ~10 ms

13 The Einstein Toolkit Ideal MHD High-order reconstruction Nuclear EOS Dynamical space-time Neutrino transport (Leakage/M1) Massively parallel (100k+ cores) Open-Source, publicly available, 3D GRMHD with microphysics at petascale!

14 Need for sustained petascale performances: Blue Waters 10 billion grid points cores, 7M node hours, 500 Tb of output Simulation data to be public soon: stay tuned!

15 Magnetic Field Structure dx = 500m dx = 200m dx = 100m dx = 50m P. Mösta, C.D. Ott, DR+, Nature 2015

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17 Dynamo Action E(k) [erg] E mag (k) t = 0ms t = 1ms t = 6ms t = 2ms t = 8ms t = 4ms t = 10 ms erg k 5/3 E kin (k) t = 7ms k E k,mag (t)[10 33 erg] 7 ( ms 1 (t t map )) e (t t map)/t, t = 3.5 ms k = 4 5 k = 6 k = 8 4 k = 10 k = 20 3 k = 50 k = t t map [ms] Fast growth at small scale and inverse cascade P. Mösta, C.D. Ott, DR+, Nature 2015

18 Conclusions Explosive growth of magnetic field Strong evidences for dynamo action Required petascale computational resources