SM12A-04

Magnetic diffusion andion nonlinear dynamics inmagnetic reconnection

Seiji ZENITANI
National Astronomical
Observatory of Japan

Collaborators: I. Shinohara (JAXA/ISAS), T. Nagai (Titech),T. Wada (NAOJ), T. Umeda (Nagoya U)Electron-scale structure(A) Quadrupole
magnetic field

(B)

-By

H

rreucallnt(F) Pedestal+By(D) Dissipation regionzy(C) Electron current layerx

Zenitani et al. 2011 PoP(E) Super-Alfvénic electron jetElectron-scalestructure
Ion-scalestructure(E+vi xB)yZ(A) Quadrupolemagnetic field(B)-ByHalnturrelc(F) Pedestal+By(D) Dissipation regionzy(C) Electron current layer

xZenitani et al. 2011 PoPX(E) Super-Alfvénic electron jetHybridNakamura et al. 1998 JGRLottermoser et al. 1998 JGRArzner & Scholer 2001 JGRHigashimori & Hoshino 2012 JGRKinetic
Drake et al. 2009 JGR
Liu et al. 2011--2012 PoPElectron-scale
structure
Ion-scalestructure(E+vi xB)yInflow AlfvénZspeed, cA,in(A) Quadrupole
magnetic field(B)-ByHalnturrelc(F) Pedestal+By(D) Dissipation regionzy(C) Electron current layer

xZenitani et al. 2011 PoPX(E) Super-Alfvénic electron jetHybridNakamura et al. 1998 JGRLottermoser et al. 1998 JGRArzner & Scholer 2001 JGRHigashimori & Hoshino 2012 JGR
30-40% of inflow Alfvén
speed
Kinetic
Karimabadi et al. 2007
GRL
Drake et al. 2009 JGR
Bessho & Bhattacharjee
PoP
Liu et 2010
al. 2011--2012
PoPElectron-scale
structure
Ion-scalestructure(E+vi xB)yInflow Alfvén

Z

speed, cA,in(A) Quadrupole
magnetic field(B)-ByHal

nturrelc(F) Pedestal+By(D) Dissipation regionzy(C) Electron current layer

xZenitani et al. 2011 PoPX(E) Super-Alfvénic electron jet

HybridNakamura et al. 1998 JGRLottermoser et al. 1998 JGRArzner & Scholer 2001 JGRHigashimori & Hoshino 2012 JGR
30-40% of inflow Alfvén
speed
Kinetic
Karimabadi et al. 2007
GRL
Drake et al. 2009 JGR
Bessho & Bhattacharjee
PoP
Liu et 2010
al. 2011--2012
PoP•Q1. Is this a “[ion] diffusion region”?
•Q2. Why is the ion ideal condition violated?
•Q3. Why is the ion flow sub-Alfvénic?

Diffusion• Something spreads out• Relaxation to a flat stateMagnetic diffusion• Arbitrary Ohm’s law

Frozen-in condition

Magnetic diffusion(Flux preservation)

Bv• Relaxation to the frozen-in state

Newcomb 1958

Stern 1966, Vasyliunus 1972,
Scudder 1997, Hornig 2001

Magnetic diffusion• Arbitrary Ohm’s law

Frozen-in condition

Magnetic diffusion(Flux preservation)

Bv• Relaxation to the frozen-in state

Newcomb 1958

Stern 1966, Vasyliunus 1972,
Scudder 1997, Hornig 2001

Relative concepts that depend
on a reference velocity field v

Effective magnetic diffusivity
Nonideal(E+vi xB)yZXElectron diffusion region
based on its literal meaning

Ion diffusion region
based on its literal meaning

Frozen-in
2D PIC simulations

Ion velocity distribution function(E+vi xB)yZX• Non-ideal, but outside
the ion diffusion region

Vy• Non-Maxwellian

Bz
VxIon velocity distribution function• (1) global Speiser ions
• (2) local Speiser ions
• (3) trapped ions

Vz

VyVy

BzVxVx(Local-type) Speiser orbit

ZBz

Vz

Bz
Lyons & Speiser 1985 JGRSpeiser 1965 JGR

Vy

VxLottermoser et al. 1998 JGRNakamura et al. 1998 JGRIon velocity distribution function• (1) global Speiser ions
• (2) local Speiser ions
• (3) trapped ions

Vz

Vy

Vy

Bz

VxVx

Nonlinear dynamics in 1980’s• The night before
kinetic PIC simulations• Poincaré
map:.
(x, x) at z=0

Empty islands

Sea of chaos
Great onion

One can visuallyclassify particle orbits.
Chen & Palmadesso 1986 JGRDistribution function ⇔ Poincaré map.
. .
• (x, x) ⇔ (-y, x)

Regular orbits

Speiser orbits(Transient orbits)

Chen & Palmadesso 1986 JGRConfined on a
hyper-surface

by T. Wada @ NAOJ

http://th.nao.ac.jp/MEMBER/zenitani/research-e.html
http://th.nao.ac.jp/MEMBER/zenitani/files/regular_orbits.mp4

Particle orbits

Phase diagram @x=51

3 orbitRegularZ 2
Main
population

10

Vy’
3.5

33

2.5

Z 22

Orbit theory

1.5

8-shaped regular orbit

110.500-2-10Vy’

12Macroscopic properties
Vx along the outﬂow line
Inflow Alfvén speed (cA,in)

ViVy

VExB

Vi

• Slow outflow: An apparent effect• Nonidealness: Nongyrotropic motion• Speiser ions do not fully gyrate about Bz !!

x
VExB

VExBXxBz
Vx

Macroscopic properties
Vx along the outﬂow line
Inflow Alfvén speed (cA,in)

Vi

Vy

VExB

x
VExB

VExB

ViX

x

Bz
|Vi -VExB| sinα

Vx
slow

• Slow outflow: An apparent effect• Nonidealness: Nongyrotropic motion• Speiser ions do not fully gyrate about Bz !!

Electron-scalestructure
Ion-scalestructure(E+vi xB)yZ(A) Quadrupole
magnetic field-ByH(B)allencurrXt(F) Pedestal

HERE+By(D) Dissipation regionzy(C) Electron current layerx(E) Super-Alfvénic electron jet•Q1. Is this a “diffusion region”? No.
•Q2. Why is the ion ideal condition violated?
•Q3. Why is the ion flow sub-Alfvénic?
Nongyrotropic ion motion is responsible.

Zenitani et al. 2011 PoP

Summary• Magnetic diffusion– Relaxation to the frozen-in state– Relative concept that depends on one’s choice of v

• Poincaré map ⇔ Ion velocity distribution function– Nongyrotropic particle motion– (1) Global Speiser ions
– (2) Local Speiser ions
• Violation of the ideal condition• Sub-Alfvénic ion flow

– (3) Trapped ions: (NEW)• Regular orbits in the chaos theory• Better understanding of the reconnection outflow region,
both from the macroscopic and microscopic viewpoints

Thank you for your attention!

Zenitani, Shinohara, Nagai, & Wada, Phys. Plasmas, 20, 092120 (2013)
Zenitani & Umeda, Phys. Plasmas, to be submitted