ST15-08-D2-PM2-P-017

Kinetic aspects of
the ion current layer in areconnection outflow exhaust

Seiji ZENITANI
National Astronomical Observatory of Japan
I. Shinohara (JAXA/ISAS), T. Nagai (Titech), T. Wada (NAOJ)

S. Zenitani, I. Shinohara, T. Nagai, and T. Wada, Physics of Plasmas 20, 092120 (2013).

Electron-scale
Ion-scalestructure ofstructurereconnection
Inflow Alfvén
HybridNakamura et al. 1998 JGRLottermoser et al. 1998 JGRArzner & Scholer 2001 JGRHigashimori & Hoshino 2012 JGR

speed, cA,in(A) Quadrupolemagnetic field(B)-Byl cuHalrrent(F) Pedestal

Kinetic
Drake et al. 2009 JGR
Liu et al. 2011--2012 PoP+By(D) Dissipation regionzy(C) Electron current layerx(E) Super-Alfvénic electron jet

30-40% of inflow Alfvén speed
Karimabadi et al. 2007 GRL
Wu et al. 2011 PoP

Zenitani et al. 2011 PoP•Q1. Why is the ion ideal condition violated?
•Q2. Why is the ion flow sub-Alfvénic?

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

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

Vz

Vy

Vy

Bz

Vx
Vx

Two Speiser orbits• Global-type (classical one)(A) Quadrupole
magnetic field

(B)

Hall

entcurr(F) Pedestal(G) Electron shock& magnetic cavityzy(D) Dissipation regionx(C) Electron current layer(E) Electron diamagnetic jet• Local-type (local reflection)(A) Quadrupole
magnetic field

(B)

Hall

entcurr(F) Pedestal(G) Electron shock& magnetic cavityzy(D) Dissipation regionx(C) Electron current layer(E) Electron diamagnetic jet(Local-type) Speiser orbit

ZBz

Vz

Bz
Lyons & Speiser 1985 JGRSpeiser 1965 JGR

VyVxLottermoser et al. 1998 JGRNakamura et al. 1998 JGR

Orbit theory in a parabolic field
Nonlinear system

Curvature radius of B

~ Larmor radius
Büchner & Zelenyi 1986, 1989

BB

B??
Bounce motion(I-adiabatic)

Chaotic motion

Gyro motion(μ-adiabatic)

Orbit theory in a parabolic field

Chen & Palmadesso 1986

BB

B??
Bounce motion(I-adiabatic)

Chaotic motion

Gyro motion(μ-adiabatic)

Ion distribution function
By
Vy

ZXVx

By
ZVy
XVx

Ion distribution function
By
Vy

ZX

Vx

By
Z

Vy
X
• Two of 5 variables (x, y, Vx, Vy, Vz) at z=0•

with a factor of 1/vz

Vx

Distribution function ⇔ Poincaré map.
. .
• (x, x) ⇔ (-y, x)

Regular orbits

Speiser orbits(Transient orbits)

Chen & Palmadesso 1986 JGRRegular orbits(a) Distribution function(b) Phase-space diagram

viyzvix[vi - U]y'(c) Overplot - Fig. 5a(d) Overplot - Fig. 6b

viyzvix• Stationary orbit• + Weak perturbation[vi - U]y'See also http://th.nao.ac.jp/MEMBER/zenitani/files/regular_orbits.mp4

Nongyrotropic regime!!
ViVyxx• Since particles no longer gyrate,
we do not expect the idealness
in theregime.
VExB

Vx

B

Bounce motion(I-adiabatic)

B

B

Gyro motion(μ-adiabatic)

Dissipation region

Sub-Alfvénic
ion flow
ep+= Ensemble of theswing-by motion oflocal Speiser ions
Local Speiser
ionsZYX

Outﬂow speed (Vx) Inflow Alfvén speed (cA,in)

ViVyxx
VExB

VExB
VExB

Bz
ViX|Vi -VExB| sinαVxslow

Dissipation region

Super-Alfvénic
electron jet
e-= Ensemble of theswing-by motion oflocal Speiser electrons

p+JZ
Y

Local Speiser
electrons

X

e-Vy

VExB
VeVx
Chen et al. 2011 PoPGeotail 2007-05-05 event• Plasma velocity
vs E x B speed

Unmagnetized electron jets may be unresolved
Only 2000 km/s: magnetized electrons?
Sub-Alfvénic ion flow?

Nagai, SZ et al. 2013b JGRSummary• We have examined an ion velocity distribution function inthe reconnection outflow:– (1) Global Speiser ions
– (2) Local Speiser ions
– (3) Trapped ions
• Regular orbits in the chaos theory• First demonstration in PIC simulation• Plasma ideal condition– Easily violated in the κ<1 regime– Particles no longer gyrate• Local-Speiser motion explains– Sub-Alfvénic ion flow
– Super-Alfvénic electron jet• Better understanding of the outflow region
from the viewpoint of particle motion

Chaos in reconnection

Reconnection in chaos
Magnetic reconnection isa fascinating multi-scale process!