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/
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