Cosmic Magnetic Fields: Helicity Injection bySupermassive 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
Perseus Cluster radio galaxy Optical X-ray “sound ripples” Perseus A Fabian et al.
Energy and Flux Hydra A 70 kpc (Taylor & Perley’93; Colgate & Li’00)
Our own backyardGalactic Center Black hole mass 3.6 million solar Masses (Genzel et al.)
Cosmic Energy Flow Gravity IGM collapse “Feedback” Mechanical Chemical Thermal Non-Thermal Magnetic Stars, galaxies, galaxy clusters, large scale shocks, etc.
Cosmic Energy Flow Gravity IGM collapse “Feedback” Mechanical Chemical Thermal Non-Thermal Magnetic Radiation Kinetic Winds Magnetic fields Stars, galaxies, galaxy clusters, large scale shocks, etc. Black Holes 108 Msun 1062 ergs
Magnetic Energy of Radio Lobes Giants Cluster sources High z sources (Kronberg, Dufton, Li, Colgate’02)
Modeling Jets/Lobes Host galaxy Disk around black hole Mix with IGM? Black hole Radio lobes SCALES 1019 (10pc) 1022-23 (10 kpc) 1024 (300 kpc) • 1025 cm • (~3 Mpc) 1014 (solar system)
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: v2 >> B2
Problem Set-up W R-3/2 radius
Static Limit(vinj << vexpan) • Steps: a. Arcade on disk, Y(r,z); b. Specify twist profile, F(y); c. Bounded by pressure, p(y); d. Find sequences of equilibrium, with increasing toroidal flux, energy, and helicity; Accretion Disk Black Hole (Li et al. 2001)
Helix Expansion (Li et al. 2001) • Force-free fields expand 600 away from the axis; • Radial expansion of outer fields are prevented by the plasma pressure.
Twist Re-distribution --- Collimation Added twists are concentrated around the axis resulting in collimation.
“RFP in the sky?” Br Bz Bf q = rBz/Bf Radius
Viewing it as a magnetic system….. Key Model Ingredients • Poloidal flux: (r,z) • Electric field and voltage: (-vBz) dl = V(r,z) • Injection duration: tinj • Poloidal current: unspecifiedIz(r,z) • Mag. energy injection rate: dEmag/dt = Iz V - Ploss • Losses: radiation, pdV, heating, kinetic flows, CRs, etc. • Expansion: Iz(r,t), (r,t), and Ploss(r,t). BH disk Li et al. (2006)
Ipol r Caltech’s Experiment: Supermassive Black Hole: • Gcm2) • I ~ 1019-20 Amperes • r0 ~ 1015 cm (disk) ~ 0.1-10 • Gcm2) • I ~ 105 Amperes • r0 ~ 10 cm (gun) ~ 0.1-1 “Gun” Parameter
Consequences: • compresses the inner fluxes along the equatorial plane. • “squeezes” the flux vertically out. • expands the outer fluxes outwards. • no azimuthal rotation. Li et al. (2006)
“Ideal” MHD Simulations S. Li & H. Li (2003, 2006)
“Ideal” 3D MHD Simulations • Spherical isothermal background in density and pressure • T=8 keV, c = 3x10-3 cm-3, rc=150 kpc; Injection: 3x107 yrs, 3x1059 ergs • 320x320x320 simulation (700 kpc)3 • Mass injection: ~ 5 Msun/yr within central 35 kpc
log(density) Poloidal Jz Nakamura, Li & Li (2006)
Hydro-shock Tangential discontinuity Slow-wave
Jz @ t = 10 toroidal Bfrom Iz (“lobes”) “flux core: & Iz” (“helix/jet”) confinement (B2/8 ~ pgas)
Poloidal Current Iz Evolution Toroidal Flux Poloidal Flux z=0 Poloidal Flux z=6 Time
Stability: with initial perturbations log(density) Poloidal Jz Nakamura, Li & Li (2006)
Kink Unstable (m=1 mode) Nakamura & Li (2006)
Jz = 1.5 Jz = -0.5 Combined
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.
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. Why Plasma Astrophysics?
Laboratory Plasma Experiments for Understanding the Formation and Collimation of Jets You et al. 2005 Hsu & Bellan’03 Lebedev et al. 2005
Galaxy Clusters Individual Galaxy Super-Galactic Filaments The Magnetized Universe (?)
Farady Rotation Measure Kronberg et al’03