Geotail observation ofthe dissipation region in collisionlessmagnetic reconnection
Seiji Zenitani
National Astronomical Observatory of JapanIku Shinohara (JAXA/ISAS), Tsugunobu Nagai (Tokyo Tech)

Outline•1. Introduction– Structure of kinetic reconnection– Identification of the dissipation region: New measure De•2. Geotail observation– The 2003-05-15 event– Dissipation region (De)– EFD measurement in depth– Brief comparison with theory– Lorentz work (W)•3. Summary

Structure of kinetic reconnection
ZpYXe-Magnetic field lines from
2D kinetic (PIC) simulation+By (Quadrupole field)

Structure of kinetic reconnection
Dissipation Region

ZY

By (Quadrupole field)

e-XJJp+X
e-Outflow velocity -- electron overshoot50-5vixvex

vixvexe-How to identify the dissipation region? (1/2)
Magnetotail reconnection

Z

Nonideal layer stretches
in the outflow directions+Bz

Magnetopause reconnection

-Bz

ByZ

X

Pritchett & Mozer 2009 PoPX

Karimabadi+ 2007 GRL

In a kinetic plasma,nonidealness ≠magnetic dissipation

How to identify the dissipation region? (2/2)
Total energy
transfer
Generalizeddissipation
measure[Zenitani et al. 2011 PRL]Work by Lorentz force (Ideal MHD)

Nonideal energy transfer

GEOTAIL

20YEARS• 12s datasets• LEP 3D moment data (ni, vi, ve)• EFD data (Ex, Ey)• MGF data (B)Electron jet events+vix-vix

+vex

-vex
ve⊥x

2007-05-05
3000
2000
1000vi x

0-1000
-2000
-3000
-4000
658

660

662

664

666

668

• Only three events with electron overshoot in 2000s• 2003-05-15, 2007-05-05, 2010-08-28

The 2003-05-15 event [Nagai et al. 2011 JGR]
Bz reversal• The best reconnection event ever• 15 May 2003, 1050 - 1100 UT• (X, Y, Z) = (-27.8, +3.3, +3.5 RE)
Bz

Plasma velocity [km/s]

2003-05-15

3000
2000

V⊥x (ion)V⊥x (electron)

1000
0-1000
-2000

1053

1054

1055
1056
1057
Time [UT] - 15 May 2003

Bz reversal

1058

-3000

Nonideal dissipation
Approximate measure
Dissipation [pWm-3]

Plasma velocity [km/s]
3000

60
De* (raw 105745)
V⊥x (ion)V⊥x (electron)

1000• LEP moment data
J = eni (vi-ve)

0• EFD data (Ex, Ey)-20-1000• MGF data (B)-40-2000
Another-3000
dissipation1058
region?

4020

2000

0-60
1053

1054

1055
1056
1057
Time [UT] - 15 May 2003

Simulation
0.1
0.05

Devixvex

0-0.05-525-vix+vex-vex

50-0.120+vix303540455055

EFD instrument

e-e-e-100m• 1 spin = 3 sec

Tsuruda+ 1994

Photoelectrons

EFD data during 1057:45UT-1057:58UT
EFD raw dataExtreme
subspin burst
ΔE ~ 50mV/m• We examine EFD raw data throughout the 2003-05-15 event• We correct E by dropping two invalid 3s-dataNonideal dissipation
Approximate measure
Dissipation [pWm-3]

Plasma velocity [km/s]

60

3000
De* (raw 105745)
V⊥x (ion)V⊥x (electron)

40
20

2000
1000

00-20

-1000-40

-2000

-60
1053

1054

1055
1056
1057
Time [UT] - 15 May 2003

Simulation
0.1
0.05

Devix
vex

0-0.05

-525

1058

+vix

-vix

+vex

-vex

50-0.1
20

Corrected
Strange-3000

30

35

40

455055Observation vs Theory• Observation• Retreat speed: ~100 [km/s] (Nagai et al.) → Length: 2400-3600 [km]• Dissipation rate: 45 [pWm-3]• Theory

Dissipation [pWm-3]• Length (20deloc): 1000-2000 [km]60

• Dissipation rate: <160 [pWm-3]

20• In reasonable agreement

40-vix+vex-vex

3000
De*V⊥x (ion)V⊥x (electron)

2000
1000

00-20-1000

-40

-2000

-60
1053+vix

Plasma velocity [km/s]

1054

1055
1056
1057
Time [UT] - 15 May 2003

1058-3000

Lorentz work
Total energy transfer

Work by Lorentz force (Ideal MHD)

Nonideal energy transfer

Lorentz work: W= ( j x B ). vi
Geotail
Dissipation [pWm-3]

PIC simulation: 1D cut
65 [pWm ]-3

Plasma velocity [km/s]

60

3000

40

2000

20

1000

00-20-1000-40-2000-60
1053

-3000

1054

1055
1056
1057
Time [UT] - 15 May 2003

1058

0.04

864
20-2-4-6-8
100.020-0.02

20

30

4050

PIC simulation: 2D snapshot• Positive over reconnection region• Strong at a dipolarization front(tangential discontinuity)

60

-0.04

Summary• Geotail observation of M’tail reconnection on 2003-05-15– Plasma moment data
– EFD raw data

• Reconnection signatures– Plasma flow
• → Electron overshoot+vix-vix– Dissipation measure De• → Dissipation region+vex-vex– Lorentz work W• → Dipolarization front• Observation vs Theory: Reasonable• First detection of the dissipation region in a planetary M’tailMMS mission (2014~)• Higher time resolution (100x better: 30 msec. ⇔ 12 s [3 s])• Better moment data, full 3 components of E
• ⇒ We will be able to see clearer pictures of the critical regions

Thank you for your attention!!

Zenitani, Shinohara, & Nagai, Geophys. Res. Lett., 39, L11102 (2012)