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Into the Engine: GRMHD Simulations

Into the Engine: GRMHD Simulations. Jonathan McKinney Stanford/KIPAC. Black Hole Accretion Systems. 10 38 erg/s M~10M ¯. 10 52 erg/s M~3M ¯. 10 44 erg/s M~10 7 M ¯. Mirabel & Rodriguez (Sky & Telescope, 2002). GRB Jets. Issues: Launch:  -  vs. MHD Jets Jet: Fireball vs. EM

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Into the Engine: GRMHD Simulations

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  1. Into the Engine:GRMHD Simulations Jonathan McKinney Stanford/KIPAC

  2. Black Hole Accretion Systems 1038erg/s M~10M¯ 1052erg/s M~3M¯ 1044erg/s M~107M¯ Mirabel & Rodriguez (Sky & Telescope, 2002)

  3. GRB Jets • Issues: • Launch: - vs. MHD Jets • Jet: Fireball vs. EM • Prompt: Shocks vs. EM dissipation Taylor et al. 2004 Fireball Model (Sari, Piran, Meszaros, Rees >1993) EM Model (Lyutikov & Blandford 2003)

  4. AGN Jets M87 Junor/Biretta/Walker • Jet Issues: • Some Dark (non-dissipative?) • Origin of FRI vs. FRII Classes? • Radio Loud-Quiet Dichotomy? • Blazars (-ray and TeV Emission?) • Implication for GRBs? Pictor A Mrk501 Cygnus-A 3C31

  5. Example Solutions to AGN Dichotomy • Changes in Field Geometry • Non-Dipolar Fields (Beckwith/McKinney ‘09) • Changes in Jet Confinement • Triggers Magnetic Switch (Meier et al. ’97, Komissarov 2009) • Variation in amount of BH/Disk Magnetic Flux • Flux trapping (Reynolds 06, Garafalo ‘09) • Magnetically-dominated disk (Igumenshchev ‘09) • Difference in Disk Thickness (Meier ’01) • Application to GRBs? (flux trapping: Proga ‘06)

  6. BH X-Ray Binaries Belloni et al. Orosz Mirabel & Rodriguez • Questions: • What determines the Spectral (and Temporal) States? • How are X-ray binary states related to AGN and GRBs?

  7. Disk-Jet Coupling Effects • Role of Large-Scale vs. Small-Scale Magnetic Fields? • Disk dominates BH in powering jet?(Ghosh & Abramowicz 1997;Livio, Ogilvie, Pringle 1999) • Weak Magnetic Field Threads BH?(Ghosh & Abramowicz 1997;Livio, Ogilvie, Pringle 1999) • Jet Power / a2 (weak dependence)? (Blandford & Znajek 1977 vs. McKinney 2005) MacDonald & Thorne ‘82 BZ77 Blandford & Payne ‘82

  8. 3D GRMHD Simulations • Issues: • Jet from Disk or BH? • Unstable to Turbulence in Disk? • Unstable to Accreting Disordered Field? Quadrupolar Dipolar

  9. Quadrupolar Field Jet Fails • Magnetic field geometry crucially determines existence of jet Fully 3D GRMHD Jet Simulations McKinney & Blandford (2009)

  10. Dipolar Field Jet Succeeds • Suggests jets require accretion of organized field Fully 3D GRMHD Jet Simulations McKinney & Blandford (2009)

  11. Quadrupolar Dipolar X-Ray Binaries: Origin of States? No Ordered Field Igumenshchev (2009) McKinney & Blandford (2009)

  12. Poynting Jet “Matter” Jet BH Engine Flow Structure CORONA: MA~EM FUNNEL: EM dominated JETS: Unbound, outbound flow McKinney & Gammie (2004) DeVilliers, Hawley, Krolik (2003-2004)

  13. Field becomes super-equipartition for high spin Komissarov & McKinney (2007) McKinney (2005) Tchekhovskoy, Narayan, McKinney (2010)

  14. z B RL j R L Jet Propagation Stability: Kink • |m|=1 most dangerous: Center-of-mass shifted • Kruskal-Shafranov non-rel. criterion • Tomimatsu (2001) ~rel. criterion • Narayan et al. (2009) rel. criterion • Expansion & Finite Mass-loading: Jet goes out of causal contact McKinney (2006) Narayan et al. (2009)

  15. Dipolar Field • Dipolar Field Jet Succeeds: • Relativistic Rotation, Expansion, Non-linear Saturation

  16. Applications to GRBs 1 • Setup: • Collapsar Model • 2D GRMHD • Start with BH and collapsing star • Realistic EOS • Neutrino Cooling (no heating) • Strong and Ordered Magnetic Field • Result: • BZ-effect drives MHD jet • Still no high Lorentz factors • 3D and resolution needed to study boundary instabilities Komissarov & Barkov (2008-2009)

  17. Applications to GRBs 2 Problem: • Ultrarelativistic motion:  ~ 400 (Lithwick & Sari 2001, Piran 2005) • Afterglow Breaks: » 2-20 • Standard MHD Jet Models give » 1 Any Resolution? • Stellar Break-Out Rarefaction ”Achromatic break” in the light curve when(µ)t≃1 Light curve modeling givesµ=2{10 100 days 1 day 10 days Tchekhovskoy, Narayan, McKinney (2010)

  18. Jet Break-Out 0 2 3 1 log() =100 µ =0.02 µ=2 =500 µ =0.04 µ=20 star BH BH Tchekhovskoy, Narayan, McKinney (2010) Komissarov et al. (2010)

  19. Effects of Time-Variability • Idea: • Time-variable Jet leads to magnetized jet bubble separated by a near-vacuum if envelope cannot relax fast enough to fill-in hole left by the jet • Problem: • Compact object + disk generate wind and fills-in hole when jet is turned off • No forward rarefaction would occur • Solution: Transient suppression of jet+wind by ram pressure of fresh in-falling material Granot et al. (2010) & Lyutikov (2010)

  20. z R GRMHD Simulations of Thin Disks Results: 1) Thin Disk theory (Novikov & Thorne 1973) holds fairly well as long as H/R. 0.07 2)  and shear stress not good indicators of dissipation or transport near ISCO or horizon 3) Assumed initial Magnetic Field controls level of deviations from Thin Disk Theory PA Shafee, McKinney, et al. (2008) Penna, McKinney, et al. (2010)

  21. Review: • BH Driven Jet becomes Relativistic if Ordered Field • GRB Jets: Stellar Break-out Leads to À 1 » 20 • Disk Driven Wind-Jet is Weakly Relativistic • Mass-Loaded by Disk Turbulence • Jet Stability Maintained by (e.g.) • Relativistic Rotation of Field Lines & Expansion of Jet • Non-linear Saturation • Standard (Novikov-Thorne) Thin Disk theory holds • Much prior work on GRB accretion solutions are ~ valid

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