Magnetorotational Instability: Plans at MPA, IPP and TU Berlin

Transcription

1 Magnetorotational Instability: Plans at MPA, IPP and TU Berlin Wolf-Christian Müller 1, Ewald Müller 2, Thomas Janka 2, Frank Jenko 3 1 Max-Planck-Institut für Plasmaphysik, Garching 2 Max-Planck-Institut für Astrophysik, Garching 3 Technical University of Berlin

2 Black Hole Accretion (T. Janka, O. Just) MHD-driven outflows Gamma-Ray-Bursts (GRBs)! MHD-driven outflows

3 Black Hole Accretion (T. Janka, O. Just) BH-Torus Outflows Methodical Approach: New Newtonian MHD-code with 2D/3D energy-dependent neutrino transport based on two-moment closure scheme. (Obergaulinger, PhD Thesis 2008; Just, PhD Thesis 2012; Just, Obergaulinger, THJ, in prep.) BH treated by Artemova- Novikov potential. Hydrodynamical 2D and 3D models of BH-torus evolution. (Just, PhD Thesis 2012; Just, Obergaulinger, THJ, in prep.) Displayed model based on Shakura-Sunyaev α-viscosity

4 Black Hole Accretion (T. Janka, O. Just) Goal: Outflows from Magnetized BH-Torus MHD yields turbulent tori Simulate magnetohydrodynamically and neutrino-driven outflows from magnetized tori with energy-dependent neutrino transport. Compute nucleosynthesis in these ejecta Explore radiation signatures of associated optical transients and GRBs. Include general relativistic effects in the BH-torus model.

5 The role of magnetic fields Core-collapse Supernovae (E. Müller) efficient angular momentum transport possible ( structure and rotation of PNS) conversion of rotational into thermal energy ( additional pressure contribution) weak (realistic) seed fields < G collapse dynamics unaffected strong seed fields G dynamics changed qualitatively, core slowed down, bipolar mildly relativistic outflows Still awaiting exploration MHD models with realistic microphysics, neutrino-driven convection secular evolution importance for SN explosion mechanism

6 Core-collapse Supernovae (E. Müller) Semi-global MRI-simulations yielding B sat shearing-box periodicity (global gradients) 2D & 3D configurations taken from idealized model of post-collapse core no neutrino transport new high-resolution, finite-volume, flux-conservative MHD code Simulations hampered by resolution requirements and numerical dissipation

7 Core-collapse Supernovae (E. Müller) HLL Riemann solver, tearing-mode growth rate R α m, α = const. MP5 MP7 reconstruction doubling resolution

8 MRI-Experiment Simulations (F. Jenko, A. Limone) SFEMaNS SFEMaNS developed by J.- L. Guermond, J. Léorat, F. Luddens, C. Nore, A. Ribeiro (Journal of Computa.onal Physics (2011)) - Spectral Finite Element code for Maxwell and Navier- Stokes equahons - Cylindrical geometry r, θ, z - Two levels of parallelizahon: the spectral domain and the meridional plane - Incompressible - Heterogeneous domains (e.g., disconhnuous magnehc permeability ) - Already used to model the MRI instability in thin Keplerian disks by A. Ribeiro (unpublished, see his PhD thesis)

9 MRI-Experiment Simulations (F. Jenko, A. Limone) HERACLES HERACLES: 3D parallel code for hydrodynamics, MHD, radiahve transfer and gravity - Cartesian, cylindrical and spherical coordinates (but only cylindrical coordinates if viscosity and resishvity are included) - Parallelized with the MPI library (domain decomposihon, no Fourier decomposihon) - Compressible - Already used to model the MRI instability and the Princeton experiment (see Gissinger et al., The role of boundaries in the MagnetoRota.onal Instability, arxiv preprint arxiv: (2012)) The code has been developed by: Code architecture: Edouard Audit ParallelizaHon: Edouard Audit Hydrodynamics: Edouard Audit RadiaHve transfer: MaWhias González, Edouard Audit & Neil Vaytet MHD: SebasHen Fromang, Patrick Hennebelle & Romain Teyssier Viscosity and resishvity: Christophe Gissinger Gravity: Pascal Tremblin HDF5 output: Bruno Thooris Website (hwp://irfu.cea.fr/projets/site_heracles/): Neil Vaytet

10 MRI-Experiment Simulations (F. Jenko, A. Limone) Experimental results and open queshons Erik Spence, AusHn Roach, Christoff Gissinger, Peter Sloboda, Hantao Ji 1) Are HERACLES and SFEMaNS able to reproduce this data- collapse? 2) Does the MRI change this behavior? If yes, this could provide an experimentally measurable signature of the MRI 3) If not, what is a good observable in order to detect the MRI in the experiment? 4) Finally, can we suggest some achon to take in order to increase the MRI amplitude?

11 MRI-Turbulence (W.-C. Müller, P. Singh Verma) Fundamental aspects of MRI-driven MHD turbulence flow driven over band of wave numbers interaction with cascade process characterization of induced anisotropy driving efficiency with growing turbulence intensity (weak) compressibility effects dynamo process structure formation (magnetic helicity)

12 MRI-Turbulence (W.-C. Müller, P. Singh Verma) Direct numerical MHD simulations shearing-box periodic configuration (local co-moving volume) simple isothermal equation of state efficient shock-capturing numerics based on Kurganov-Tadmor central scheme integrated Fourier diagnostics Code benchmark with ATHENA (Princeton)

13 MRI-Turbulence (W.-C. Müller, P. Singh Verma) Interesting things to find out link between incompressible MHD turbulence and MRI turbulence Vishniac-Cho dynamo mechanism interaction of magnetic helicity and MRI (magnetic structure formation) saturation of MRI turbulence