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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
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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]
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Supernova Remnant Shock SN1006 (Chandra) shock width = electron gyro-radius of 10 TeV Bamba et al. (2002) 3 Bamba+ 2003Warren+ 2005 Tycho’s SNRSN1006 Shock downstreamupstream
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Electron Energy Spectrum at SNR Shocks SN1006, Chandra X-ray, Long et al. 2003 Bamba et al. 2003; Long et al. 2003 upstreamdownstream V1V1 V 2 = V 1 /4 Fermi Acceleration Model shock front
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Shock Numerical Experiment x y z BzBz EyEy p +,e - injection reflection Particle-in-Cell (PIC) Simulation Modeling on Collisionless Shock 10 8-9 particles wall 5 particles fields
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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
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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
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Magnetic Reconnection Solar & Stellar Flare, Magnetosphere, Accretion Disks, Pulsar Wind-Nebula, Astrophysical Jets,…. Plasma Heating & Nonthermal Particle Acceleration
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Reconnection around Heliopause Boundary Heliospheric Current Sheet Anomalous Cosmic Ray by Reconnection (Drake+ 2010) Termination shock in Heliosphere
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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
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2D PIC Simulation Particle Trajectories, Magnetic Field Lines Particle Energies
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Stochastic particle acceleration in multiple magnetic islands during reconnection MH, PRL (2012)
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2 nd order Acceleration Fermi, Phys. Rev. (1949) 1 st order Acceleration MH, PRL (2012) Fermi acceleration in magnetic islands
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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,….
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Magneto-Rotational Instability (MRI) Balbus and Hawley, 1998weak magnetic field (β>>1) β = 1-10 dynamo process MHD simulation B-lines
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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 10 - 5 M * /yr net accretion rate 10 -8 M * /yr – thermal and nonthermal electrons (X-ray flare by observed Chandra & XMM-Newton), power law index p ~ 1.3 < 2
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“Collisionless” MRI MHD + CGL + Landau Fluid Approx. (Hammett+, PoP, 1992; Quataert+, ApJ, 2002; Sharma+, ApJ, 2006) Heat Flux q in Fourier space
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1.0 1.1 1.2 0 45 90 0 0.8 Im( )/ tan -1 (k r /k z ) MRI Mirror Mode z r B Kepler Disk MRI in anisotropic pressure
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1.0 1.1 1.2 0 45 90 0 0.8 Im( )/ tan -1 (k r /k z ) Im( )/ 0 1 2 0 45 90 1 4 7 MRI Mirror Mode without Heat Flux with Heat Flux tan -1 (k r /k z )
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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
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Local rotating system with
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color contour: angular velocity green: B-lines
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E -2/3
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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
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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
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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
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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 //
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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
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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 http://www.astro.phys.s.chiba-u.ac.jp/pcans/
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