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 UniverseCosmic 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)

3Bamba+ 2003Warren+ 2005

Tycho’s SNR SN1006

100Mkm/s 1000V ,cm 1.005.0

medium)lar (interstelG 3

A

3-

n

B

Shock

downstreamupstream

Electron Energy Spectrum at SNR Shocks

SN1006, Chandra X-ray, Bamba et al. 2003; Long et al. 2003

upstream downstream

V1

V2= V1/4

Fermi Acceleration Model

shock front

Shock Numerical Experiment

ｘ

ｙｚ B ｚE ｙ

p+,e-

injectionreflection

vdtdx

BcvEq

dtdp

)(

04

41

1

BE

Jc

BtE

c

EtB

c

c

　

Particle-in-Cell (PIC) SimulationModeling on Collisionless Shock

108-9 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/B1 >15& Va/Wci scale

X/(V1/Wci)

Ma=137, wpe/wce=140, mi/me=100

Shimada, MH & Amano,PoP 2010

Magnetic Bubbles in High Mach Number Shock

Kato and Takabe, 2010

Ma=100, wpe/wce=71, mi/me=30

Ion-ion Weibelwith Va/Wci scale

Reconnection in 3D

Magnetic ReconnectionSolar & 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

cVc

2nd order Acceleration

Fermi, Phys. Rev. (1949)

cVA

1st 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 = 1-10dynamo process

MHD simulationB-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 10-5M*/yr

net accretion rate 10-8M*/yr – thermal and nonthermal electrons (X-ray flare by observed

Chandra & XMM-Newton), power law index p~1.3 < 2

“Collisionless” MRIMHD + CGL + Landau Fluid Approx.

(Hammett+, PoP, 1992; Quataert+, ApJ, 2002; Sharma+, ApJ, 2006)

,12

)/(2

,)/(8

//

//

////

//

////

//

////////

kBik

pp

Bpc

kpikcq

kpikcq

Heat Flux q in Fourier space

1.0

1.1

1.2

0

45

90

0

0.8

Im(w

)/W

qtan -1(kr /kz)

/// pp

MRI Mirror Mode

z

r

WB

Kepler Disk

MRI in anisotropic pressure

1.0

1.1

1.2

0

45

90

0

0.8Im

(w)/W

qtan -1(kr /kz)

/// pp

Im(w

)/W

0

1

2

0

45

90 1

4

7/// pp

MRI

Mirror Modewithout Heat Flux

with Heat Flux

qtan -1(kr /kz)

β=100, Kepler rotation Ω256x256x256 grids 40 particles/cell,periodic shearing box, electron-positron plasma

MRI and Reconnection in PIC simulation

B

green: magnetic field linescolor contour: angular velocity

.

,4 ,41

,0 ,1

00*

0*0

BBcvE

cvBB

BcvEJ

cBB

cvE

tc

BEBtc

c

rrv W )( 000Local rotating system with

. ,23

lnln

,ˆ22

0

200

0

rrxr

q

xxqvmBcvEevm

dtd

r

W

WW

color contour: angular velocitygreen: B-lines

E-2/3

2D-PIC simulation

Kepler rotation Ω, Ω/ Ωc =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/ Ωc =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/ Ωc =0.1,gyro-radius Vi/ Ωc =1.7x102 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//

Dens

ityT ⊥

/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

SummaryShocks 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-pCANShttp://www.astro.phys.s.chiba-u.ac.jp/pcans/