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Cosmic Magnetic Fields: Helicity Injection by Supermassive Black Holes, Galaxies and Laboratory Experiments Hui Li 李暉 Los Alamos National Laboratory and a member of Center for Magnetic Self-Organization Collaborators: M. Nakamura, S. Li, S. Colgate, J. Finn, K. Fowler Overview of astrophysical observations of cosmic magnetic fields Global Electro-Magnetic model for astrophysical jets Synergy between astrophysics and laboratory plasma physics
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OpticalX-ray“sound ripples” radio galaxy Fabian et al. Perseus Cluster Perseus A
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Black Hole Accretion Disk
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Hydra A (Taylor & Perley’93; Colgate & Li’00) 70 kpc Energy and Flux
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Black hole mass 3.6 million solar Masses (Genzel et al.) Our own backyard Galactic Center
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Ubiquity of Supermassive Black Holes (Kormendy et al. 2001)
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Cosmic Energy Flow Gravity Stars, galaxies, galaxy clusters, large scale shocks, etc. IGM “Feedback” Mechanical Chemical Thermal Non-Thermal Magnetic collapse
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Cosmic Energy Flow Gravity Stars, galaxies, galaxy clusters, large scale shocks, etc. IGM “Feedback” Mechanical Chemical Thermal Non-Thermal Magnetic collapse Black Holes Radiation Kinetic Winds Magnetic fields 10 8 M sun 10 62 ergs
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High z sources Giants Cluster sources (Kronberg, Dufton, Li, Colgate’02) Magnetic Energy of Radio Lobes
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Modeling Jets/Lobes 10 14 (solar system) SCALES 10 19 (10pc) 10 22-23 (10 kpc) 10 24 (300 kpc) 10 25 cm (~3 Mpc) Black hole Disk around black hole Host galaxy Radio lobes Mix with IGM?
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Kinetically Dominated vs. Magnetically Dominated e.g., Norman et al., Clark et al. in 80’s Jones & Ryu et al., Ferrari et al. in 90’s Many, many, others Kinetic Energy Dominated Regime: v 2 >> B 2
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Problem Set-up radius R -3/2
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Static Limit (v inj << v expan ) Steps: a. Arcade on disk, (r,z); b. Specify twist profile, ( ); c. Bounded by pressure, p( ); d. Find sequences of equilibrium, with increasing toroidal flux, energy, and helicity; Black Hole Accretion Disk (Li et al. 2001)
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Helix Expansion (Li et al. 2001) Force-free fields expand 60 0 away from the axis; Radial expansion of outer fields are prevented by the plasma pressure.
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Squeezing Flux Tubes (Parker)
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Twist Re-distribution --- Collimation Added twists are concentrated around the axis resulting in collimation.
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Radius q = rB z /B BB BzBz BrBr “RFP in the sky?”
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disk Viewing it as a magnetic system….. Key Model Ingredients Poloidal flux: (r,z) Electric field and voltage: (-v B z ) dl = V(r,z) Injection duration: t inj Poloidal current: unspecified I z (r,z) Mag. energy injection rate: dE mag /dt = I z V - P loss Losses: radiation, pdV, heating, kinetic flows, CRs, etc. Expansion: I z (r,t), (r,t), and P loss (r,t). BH Li et al. (2006)
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Laboratory Plasma Experiments (Bellan et al.)
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“Gun” Parameter Gcm 2 ) I ~ 10 19-20 Amperes r 0 ~ 10 15 cm (disk) ~ 0.1-10 Gcm 2 ) I ~ 10 5 Amperes r 0 ~ 10 cm (gun) ~ 0.1-1 Supermassive Black Hole: Caltech’s Experiment: I pol r
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Li et al. (2006) compresses the inner fluxes along the equatorial plane. “squeezes” the flux vertically out. expands the outer fluxes outwards. no azimuthal rotation. Consequences:
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“Ideal” MHD Simulations S. Li & H. Li (2003, 2006)
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“Ideal” 3D MHD Simulations Spherical isothermal background in density and pressure T=8 keV, c = 3x10 -3 cm -3, r c =150 kpc; Injection: 3x10 7 yrs, 3x10 59 ergs 320x320x320 simulation (700 kpc) 3 Mass injection: ~ 5 M sun /yr within central 35 kpc
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log(density) Nakamura, Li & Li (2006) Poloidal J z
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Hydro-shock Tangential discontinuity Slow-wave
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“flux core: & I z ” (“helix/jet”) toroidal B from I z (“lobes”) confinement (B 2 /8 ~ p gas) J z @ t = 10
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Lobes: Pressure Confinement and Nearly Force-Free
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Evolution Time Toroidal Flux Poloidal Flux z=0 Poloidal Flux z=6 Poloidal Current I z
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log(density) Nakamura, Li & Li (2006) Poloidal J z Stability: with initial perturbations
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Nakamura, Li & Li (2006)
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Kink Unstable (m=1 mode) Nakamura & Li (2006)
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J z = 1.5 J z = -0.5Combined
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KH Stable
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Perseus A426
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M87
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Summary on Jet/Lobe Modeling Lobes are magnetically dominated and are confined by the surrounding pressure. Lobes form via background density/pressure changes, accompanied by flux conversion. Helix is kink-unstable, though the overall structure is not completely destroyed. Lobes are far from relaxation.
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Why Plasma Astrophysics? Common physical processes: dynamo (magnetic field generation) and flux-conversion dynamo ideal and resistive MHD stabilities magnetic reconnection flow generation angular momentum transport particle acceleration Common numerical tools: ideal and resistive MHD codes PIC gyrokinetic, hybrid, etc.
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Laboratory Magnetized Plasma Astrophysics
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You et al. 2005 Hsu & Bellan’03 Laboratory Plasma Experiments for Understanding the Formation and Collimation of Jets Lebedev et al. 2005
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Individual Galaxy Clusters Super-Galactic Filaments The Magnetized Universe (?)
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Kronberg et al’03 Farady Rotation Measure
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Thank you!
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