粒子シミュレーションで観る粒子加速 : 衝撃波、リコネクション、降着円盤 星野 真弘

Nonthermal Universe Cosmic Rays ACRs [Stone et al., 2008] Where and How are non-thermal particles produced? [Lin et al., 2003] Solar Flares [Nagano & Watson, 2000]

Supernova Remnant Shock SN1006 (Chandra) shock width ＝ electron gyro-radius of 10 TeV Bamba et al. (2002) 3 Bamba+ 2003Warren Tycho’s SNRSN1006 Shock downstreamupstream

Electron Energy Spectrum at SNR Shocks SN1006, Chandra X-ray, Long et al Bamba et al. 2003; Long et al upstreamdownstream V1V1 V 2 = V 1 /4 Fermi Acceleration Model shock front

Shock Numerical Experiment ｘ ｙ ｚ BｚBｚ EｙEｙ p +,e - injection reflection Particle-in-Cell (PIC) Simulation Modeling on Collisionless Shock particles wall 5 particles fields

Magnetic Bubbles in High Mach Number Shock Ion-Ion streaming Instability in Hot Electrons (Wu et al. 1984) large B field with B/B 1 >15 & V a /  ci scale X/(V 1 /  ci ) Ma=137,  pe /  ce =140, mi/me=100 Shimada, MH & Amano,PoP 2010

Magnetic Bubbles in High Mach Number Shock Kato and Takabe, 2010 Ma=100,  pe /  ce =71, mi/me=30 Ion-ion Weibel with V a /  ci scale Reconnection in 3D

Magnetic Reconnection Solar & Stellar Flare, Magnetosphere, Accretion Disks, Pulsar Wind-Nebula, Astrophysical Jets,…. Plasma Heating & Nonthermal Particle Acceleration

Reconnection around Heliopause Boundary Heliospheric Current Sheet Anomalous Cosmic Ray by Reconnection (Drake+ 2010) Termination shock in Heliosphere

Gamma Ray Flares from Crab Nebula Pulsar Magnetosphere & Wind Reconnection Model: Coroniti ApJ 1990, Kirk+ PRL 2003, Zenitani & MH PRL 2005, Jaroschek & MH PRL 2009,... Crab Nebula Tavani+, Science, 2011, Abdo+, Science, 2011

2D PIC Simulation Particle Trajectories, Magnetic Field Lines Particle Energies

Stochastic particle acceleration in multiple magnetic islands during reconnection MH, PRL (2012)

2 nd order Acceleration Fermi, Phys. Rev. (1949) 1 st order Acceleration MH, PRL (2012) Fermi acceleration in magnetic islands

Plasma processes in Accretion Disk Courtesy of Kato Magneto-Rotational Instability (MRI) Velikov 1958, Chandrasekhar 1961, Balbus & Hawly 1991,…. Matsumoto & Tajima 1995,…Sano and Inutsuka 2001,….

Magneto-Rotational Instability (MRI) Balbus and Hawley, 1998weak magnetic field (β>>1)  β = 1-10 dynamo process MHD simulation B-lines

Collisionless Accretion Disk? Kinetic Magneto-Rotational Instability (MRI) and particle acceleration is important – Massive black hole (Sgr A*) – Radiatively Inefficient Accretion Flow (RIAF) – Accretion rate much smaller than the Bondi rate of M * /yr  net accretion rate M * /yr – thermal and nonthermal electrons (X-ray flare by observed Chandra & XMM-Newton), power law index p ~ 1.3 < 2

“Collisionless” MRI MHD + CGL + Landau Fluid Approx. (Hammett+, PoP, 1992; Quataert+, ApJ, 2002; Sharma+, ApJ, 2006) Heat Flux q in Fourier space

Im(  )/   tan -1 (k r /k z ) MRI Mirror Mode z r  B Kepler Disk MRI in anisotropic pressure

Im(  )/   tan -1 (k r /k z ) Im(  )/  MRI Mirror Mode without Heat Flux with Heat Flux  tan -1 (k r /k z )

β=100, Kepler rotation Ω 256x256x256 grids 40 particles/cell, periodic shearing box, electron-positron plasma MRI and Reconnection in PIC simulation B green: magnetic field lines color contour: angular velocity

Local rotating system with

color contour: angular velocity green: B-lines

E -2/3

2D-PIC simulation Kepler rotation Ω, Ω/ Ω c =0.1, β=1400, 300x300 grids 100 particles/cell, periodic box in meridian plane, electron-positron plasma B R Z

2D-PIC simulation Kepler rotation Ω, Ω/ Ω c =0.1, β=1400, 300x300 grids 100 particles/cell, periodic box in meridian plane, electron-positron plasma B R Y

2D-PIC simulation Kepler rotation Ω, Ω/ Ω c =0.1, gyro-radius V i / Ω c =1.7x10 2 at t=0 β=20000, 200x200 grids 8000 particles/cell, periodic box in meridian plane, electron-positron plasma B R Z

Onset of Reconnection Laval and Pellat (1968), Chen and Palmadesso (1984) Before Reconnection After onset of Reconnection Growth rate of tearing mode is enhanced for T ⊥ > T // Density T ⊥ /T // T ⊥ > T // T ⊥ ～ T //

high energetic particles (γ>20) are located outside magnetic islands middle energetic particles (γ>5) are located at outer edge of islands thermal plasma is confined inside magnetic islands E -4/3 void

Summary Shocks Injection/Turbulent Reconnection/Kinetic MRI – High Mach number shocks with magnetic bubbles – Particle acceleration by multiple magnetic island reconnection in a large scale system – Onset of reconnection by T ⊥ > T // during MRI evolution – Hard energy spectrum with N(E) ∝ E -1 (in 2d & 3d PIC simulations) 公開粒子コード： Astro-pCANS