3D magnetic reconnection: geometry and In situ measurements

肖池阶 1 , 王晓钢 2, 濮祖荫 3,马志为 4, 汪景琇 1, 赵辉 1, 周桂萍 1 , 傅绥燕 3, M.G. Kivelson5, 刘振兴 6, 宗秋刚 7, K.H. Glassmeier8,

A.Balogh9, A. Korth10, H. Reme11, C. P. Escoubet12

1 中国科学院国家天文台 ; 2 北京大学物理学院 ; 3 北京大学地球与空间科学学院 ; 4 浙江大学物理系 ; 5 IGPP, UCLA, USA; 6中国科学院空间科学与应用研究中心 ; 7 Center for Atmospheric Research, U. of Massachusetts Lowell, USA 8 IGM, TU Branuschweig, German; 9 SAPG, Imperial College, UK; 10 Max Planck Institute for Solar System Research, Lindau, German;11CESR/CNRC, France; 12 ESA/ESTEC, The Netherlands

OutlineOutline

Introduction: 2D v.s. 3D Reconnection

3D nulls and null-null lines detection

Conclusions

Reconnection is essential Reconnection is essential in Sun, Magnetosphere, Fusionin Sun, Magnetosphere, Fusion

太阳风

尾瓣 磁尾

磁鞘

磁层顶

等离子体片

d

From Kivelson et al., 1995

GSM coordinates system:North

Z

YSun Earthx

magnetotail

From Kivelson et al., 1995

GSM coordinates system:North

Z

YSun Earthx

Reconnection Regions

magnetotail

In-Situ Observations of MRIn-Situ Observations of MR High-speed plasma flows, energization of particles and other MR signatures were observed long ago by in-situ measurements (Phan et al., 2000; Hultqvist, 2000).

Evidences of collisionless MR have been detected by Geotail and Wind spacecraft (Deng et al., 2001; Øieroset

et al., 2001 ). 4-spacecraft of Cluster mission provides unique opportunity to study MR, with the MR events in/near the diffusion region being of great interest.

2D Collisionless Reconnection2D Collisionless Reconnection

Outside the diffusion Region

Traditional MHD theory holds

Diffusion Region: Ion inertial region (width Ion inertial region (width ddii))

– Hall current and quadrupole By

Electron inertial region Electron inertial region

(width (width ddee))

Magnetic nullMagnetic null

the magnetic vector field:

0 B

0 B B B x

1 2 3 0

( )( )( )

( )( )( )

Lau Y. T., & Finn, J. M. 1990, ApJ, 350,6721 2 3, ,u u u

fan

spine

z

B

y

B

x

Bz

B

y

B

x

Bz

B

y

B

x

B

zzz

yyy

xxx

B

Magnetic field lines near the nullMagnetic field lines near the null

Lau Y. T., & Finn, J. M. ApJ, 350, 672, 1990,

Pontin, D. I., Hornig G. and Priest, E. R., ESA SP-575: SOHO 15 Coronal Heating, 507, 2004

spine

fan

spine

fan

3D Reconnection at the null:3D Reconnection at the null:

Spine reconnection

Reconnection atReconnection at the A-B null line:A-B null line:

Separator reconnection

Fan reconnection

Lau Y. T., & Finn, J. M., ApJ, 350, 672, 1990

Lau Y. T., & Finn, J. M., ApJ, 350, 672, 1990

Buchner J., Astrophys. and Space Sci., 264, 25-42, 1999

3D PIC simulation

Cai D.S., et al., Earth Planets Space, 53, 1011–1019, 2001

Nulls detection in the solar atmosphereNulls detection in the solar atmosphere

Aulanier G., et al., ApJ, 540, 1126, 2000 Zhao h., et al., ChJAA, 5, 443-447, 2005

S. K. Antiochos, ApJ, 502:L181–L184, 1998Filippov, B, Sol. Phys., 185, 297, 1999

How to detect the “Null” ?How to detect the “Null” ? A mathematical isolated singular point Hard to determine the null based on

magnetic field data in a local point. 1) right at the null, the relative

measurement error is infinite with any small error-bar of data.

2) a single point measurement can’t distinguish the isolated null from a magnetic neutral line or a neutral sheet.

The null is associated with the topological property of its neighborhood.

1. The Poincare index method2. The linear interpolation method

After J.M. Greene ( 1988, 1992 , 993), Garth, C. et al. (2004) , Zhao et al. (2005), etc.

Calculating the index of a singularity by enclosing it with a surface small enough not to contain any other singularities.

Poincare Index— 3DPoincare Index— 3D

Greene, 1992, C. Garth, X. 2004, zhao, 2005Poincare index = ∑ solid angles / 4

2001-09-15 event2001-09-15 event

(1) Bs null detection

(2) Bipolar structure

(3) scale of structure

Cluster Location at Cluster Location at 05:00 UT on 01-09-1505:00 UT on 01-09-15

Z14=322km

C3C3 X = -18.7RX = -18.7REE

Y = 3.5RY = 3.5REE

Z = -2.9RZ = -2.9REE

Overview of B-V: 2D Hall reconnectionOverview of B-V: 2D Hall reconnection

05:03:36 UT—— Cluster around the X-point

Xiao C.J., et al., GRL, 2007

Null point detected by Cluster : Null point detected by Cluster : possible framepossible frame

05:03:36 UT—— Cluster around the X-point

05:03:30 05:03:32 05:03:34 05:03:36 05:03:38 05:03:40

0

1

Poi

ncar

e In

dex

UT

Poincare indexPoincare index calculation calculation

05:03:00 05:03:20 05:03:40 05:04:00

0

1

Po

inca

re in

de

x

time

B D

4s FGM data

0.04s FGM data

Find null position Find null position based on based on

“ “Linear Interpolation”

1000 500 0 -500 -1000

0

500

1000

1500

2000

1000 500 0 -500 -1000-1000

-500

0

500

1000

1500

Null

Z (

km

)

X (km)

C1

C2 C4

C3

Null

Y (

km

)

X (km)

C2

C1

C4

C3

Time: 05:03:35.990

X

-1000

-500

0

500

1000

Y

-1000

-500

0

500

1000

Z

0

500

1000

1500

2000

X

Y

ZFrame 001 07 Dec 2006 Example: Simple XY Plot

Bs Null – theoretical structureBs Null – theoretical structure

0 B

-0.0086

0.0105i - 0.0043

0.0105i + 0.0043

3

2

1

at 05:03:36(UT):

-0.0012550, -0.0110685, 0.0232983

0.0090147, 0.0015492, 0.0009428

0.0019898, -0.0047371, -0.0002319

δB

Bipolar structure Near Bipolar structure Near the reversal point the reversal point 05:03:36(UT)05:03:36(UT)

Scale of the bipolar structure ~di

2001-10-1 event2001-10-1 event

(1) A, As and B nulls detection

(2) A-B, As-B null lines detection

(3) Lower Hybrid wave detection

Cluster Location at Cluster Location at 09:50 UT on 2001-10-0109:50 UT on 2001-10-01

C3C3 X = -16.2RX = -16.2REE

Y = 7.9RY = 7.9REE

Z = -0.5RZ = -0.5REE

YY

YY

X

-2500-2000

-1500-1000

-5000

500

Y

-2000-1000

01000

2000

Z

0

500

1000

1500

2000

2500

XY

Z

C3

C1

C2

C4

Frame 001 16 Nov 2006 Cluster Positions (2001-10-1)

2001-10-1 event2001-10-1 eventOverviewOverview

09:48:20 09:48:25 09:48:30 09:48:35 09:48:40 09:48:45 09:48:50

-1

0

1

UT (2001-10-1, gsm data from UCLA)

Po

inca

re

-10

-5

0

5

10

Bz (

nT

)

-10

-5

0

5

10

By (

nT

)

-30-20-10

010203040

B

x (n

T)

B1 B

2 B

3 B

4

B null09:48:28.447 UT

A null09:48:25.593UT

As null09:48:32.104 UT

Characteristics of the null pair observed on 2001-Characteristics of the null pair observed on 2001-10-0110-01

B0.0020188 -0.0006625 0.0190302

-0.0026838 -0.0004505 -0.0031328

0.0026553 -0.0006486 -0.0015461

0.0010699 0.0015164 0.0181359

-0.0023046 0.0014864 -0.0016364

0.0034104 -0.0000067 -0.0016901

0.0032706 0.0053054 0.0185452

-0.0037311 -0.0017031 -0.0023048

0.0009760 -0.0024340 -0.0017568

B 52.2 1048.6 10 41.9 10

| |

| |

B

B

Time 09:48:25.593 UT 09:48:28.447 UT 09:48:32.104 UT

Poincare Index

1 -1 1

Null Type A-null (Negative) B-null (Positive) As-null (Negative)

0.13% 1.1% 0.19%

Eigen- values

1 = +0.0081

2 = - 0.0070

3 = - 0.0011

1 = - 0.0082

2 = +0.0072

3 = +0.0018

1=0.0059

2=-0.0031+0.0038i

3=-0.0031-0.0038i

Eigen-vectors

b1 = (-0.89, 0.38, -0.27)

b2 = ( 0.89, 0.17, -0.42)

b3 = (-0.24, 0.97, -0.01)

a1 = ( 0.88, 0.13, -0.46)

a2 = ( 0.84, -0.43, 0.32)

a3 = (-0.09, 0.99, -0.09)

c1 = (-0.83, 0.49, -0.26)

c2 = (0.78, 0.17+0.51i, -0.32+0.02i)

c3 = (0.78, 0.17-0.51i, -0.32-0.02i)

Angles between

A (a1) and B (b2, b3) 2.4o; A (a1) and A (a2, a3) 41.7o

B (b1) and A (a2, a3) 3.5o; B (b1) and B (b2, b3) 45.9o

null-null line a3 and B (b2, b3) 0o

null-null line b3 and A (a2, a3) 1.8o

B (c1) and A (a2, a3) 3.4o;

B0.0020188 -0.0006625 0.0190302

-0.0026838 -0.0004505 -0.0031328

0.0026553 -0.0006486 -0.0015461

0.0010699 0.0015164 0.0181359

-0.0023046 0.0014864 -0.0016364

0.0034104 -0.0000067 -0.0016901

0.0032706 0.0053054 0.0185452

-0.0037311 -0.0017031 -0.0023048

0.0009760 -0.0024340 -0.0017568

B 52.2 10 48.6 1041.9 10

| |

| |

B

B

A-B null line09:48:25.593 UT-09:48:28.447 UT

B-As null line09:48:28.447 UT- 09:48:32.104 UT

Null positions in the Cluster frameNull positions in the Cluster frame

—— via the linear interpolation—— via the linear interpolation

09:48:24.30 09:48:24.60 09:48:24.90 09:48:25.20-1000

-500

0

500

1000

Vn

ull (

km/s

)

UT

VL

VM

VN

0 10 20 30 40 50 60

0

50

100

150

200

250

300

Am

plitu

de

(Hz)

FFT(VL)

FFT(VM)

FFT(VN)

-500 0 500 1000-1000

-500

0

500

(a)

(c)

(b)

Linear Fit: VM

=286.2-1.0VL

VM (

km/s

)

VL (km/s)

10 15 20

0

1

2

(d)

K

(Hz)

KL

KM

KN

The lower-hybrid oscillation: The lower-hybrid oscillation: LHLH ~ 13 Hz (with magnetic field 20 nT); ~ 13 Hz (with magnetic field 20 nT);

a maximum power at 10-15Hza maximum power at 10-15Hz

12Hz

13Hz

ConclusionsConclusions All four types of nulls, A, B, As and Bs, have been detected

by Cluster in situ measurements; Typical 3D geometry feature of Bs-type null (flux tube) has

been captured; The scale of structure is about the order of local di

An A-B null pair and a Bs-A null pair with their neighbouring geometry are identified in a typical reconnection event.

The separation between the nulls is measured as ~ 0.7±0.3 di,

A lower hybrid oscillation is also identified in the immediate vicinity of the line with a wavelength of ~ de,

It is the first in situ evidence for complete 3D reconnection geometry and associated electron dynamics

Thanks for your attention!

Ref. :Ref. :

Xiao C. J., et al., Nature Physics, 3(9), 609-613, doi:10.1038/nphys650, 2007

Xiao C. J., et al., Geophys. Rev. Lett., 34 , L01101, doi:10.1029/ 2006GL028006, 2007.

Xiao C. J., et al., Nature Physics, 2, 478-483, doi:10.1038/nphys342, 2006.