Experimental Study of MagneticReconnection on MRX

IPELS 2009, Sweden

Masaaki Yamada

In collaboration with S. Dorfman, H. Ji, R. Kulsrud, E. Oz, J. YooPrinceton Plasma Physics Laboratory

2

Outline• Introduction

– dedicated reconnection experiments• Recent results from Magnetic Reconnection Experiment

(MRX)– Collisionless reconnection => Two fluids physics– Two-scale diffusion region– MRX scaling regarding collisionality

• Outstanding issues on reconnection• New experiment for solar flare dynamics

Goals of Lab Experiments

• Learn the physics of fundamentalprocesses from plasmas

(Not to simulate space phenomena)

• Check/verify theoretical concepts

• Compare data with observations/simulations

• Discover new physics

Dedicated Reconnection Experiments

Device Site Built PI’s Geometry Res. Thrust

3D-CS Russia 1970 Syrovatskii, Frank Linear Guide fieldLPD, LAPD UCLA 1980 Stenzel, Gekelman Linear Heating,

wavesTS-3/4 Tokyo 1990 Katsurai, Ono Toroidal

MergingHeating

MRX Princeton 1995 Yamada, Ji Driven,merging

2-fluid effects,waves, scaling

SSX Swarthmore 1996 Brown Merging Heating

VTF MIT 1998 Egedal Toroidalwith guide B

Trigger,waves

RSX Los Alamos 2002 Intrator Linear Boundary

RWX Wisconsin 2002 Forest Linear Line-tying

Magnetic Reconnection: Recent Progress

• Two-fluid effects in the local reconnection layer analyzed thru strong collaboration between space and lab research - Ion diffusion region and electron diffusion regions identified:

in 2-scales- Electromagnetic and electrostatic fluctuations analyzed

• Transition from collisional MHD to collisionless regimeestablished

• Role of reconnection in magnetic self-organizationinvestigated

• Multiple reconnection layers <=> Global reconnection

Magnetic Reconnection in Space and Laboratory

Magnetic Reconnection Experiment (MRX).

Goals: Create a prototypical reconnectionlayer to study the elementary processes

Magnetic reconnection happens atboth magnetopause and magnetotail.

Two fluid effects are dominant when δns~ c/ωpi

Experimental Setup and Formation ofCurrent Sheet on MRX

Experimentally measured flux evolution

ne= 1-10 x1013 cm-3,Te~5-15 eV,B~100-500 G,

Neutral sheet Shape in MRXchanges from “Rectangular S-P” type to “Double edge X” shape as collisionality is reduced

Rectangular shapeCollisional regime: λmfp < δSlow reconnection

No Q-P field

Collisionless regime: λmfp > δFast reconnection

Q-P field presentHall effects

X-type shape

Evolution of magnetic field lines during reconnection in MRX

Measured region

Two-scale Diffusion Region measured in MRX

d ~ 5-7 (c/ωpe) >> dTheory

The electron diffusion regionidentified inside of the iondiffusion region<=> The first observation of two-scale diffusion region[Ren et al, PRL 08]

EM (LHW)fluctuations observed

=> Close collaboration with space physics community

Electrostatic waves observed at CS Edge:Electromagnetic waves at the center appear to be more important

EM

ES

Bale et al. GRL (’02) Vaivads et al. GRL (’04)

MRX Polar Cluster

Identified as LHDWCarter et al. PRL (’02)

EM waves=>S. Dorfman

MRX scaling shows a transition from the MHD to 2 fluidregime based on (c/ωpi)/ δsp

MRX Scaling: η* vs (c/ωi)/ δsp

Breslau(c/ωpi)/ δsp

~ 5( λmfp/L)1/2

A linkage between space and lab on reconnection

!* "E#j#

Nom

alize

d by

ηSp

itz

Yamada et al, PoP 2006

System L (cm) B (G) di= c/ωpi(cm) δsp (cm) di/ δsp

MRX/SSX 10 100-500 1-5 0.1-5 .2-100

MST/Tokamak 30/100 103/ 104 10 0.1 100

Magnetosphere 109 10-3 107 104 1000

Solar flare 109 100 104 102 100

ISM 1018 10-6 107 1010 0.001

Proto-star di/ δs >> 1

Linkages between space and lab on reconnection

di/ δsp ~ 5( λmfp/L)1/2

Future main issuesfor magnetic reconnection research

• Identify main mechanisms for energy dissipation in the 2-fluiddiffusion regionParticle acceleration and heating

• Effects of guide field (2D &3D)• Effects of EM/ES fluctuations•• Effects of boundary conditionsEffects of boundary conditions

• Find guiding principles for 3-D global reconnection phenomena– Global energy flows– Multiple current sheets– Magnetic self-organization– Impulsive reconnection

⇒ Yamada, Kulsrud, Ji; Rev. Mod. Phys. (2009) Zweibel &Yamada; Ann Rep AA. (2009)

Guide Field (Bt) Coilsz

r

φ

Plasma arcMagnetic Probes

Electrodes

•Bt:Toroidal field 0 -1200 Gauss•Bz:Strapping field 0-100 Gauss

New Setup for MRX-Solar Flare Experiment

• Electrodes ~ 15 cmdiameter• R = 15-30 cmAngle 90o-180o

•The flux cores were not utilized in the experiments

Safety factor q determines the stabilityof simulated flux loop in MRX

STA

BLE

Bpvectors & j counters (color): Framing camera photos

UN

STA

BLE

qa valueRp

t(µs)t(µs)

Plasmaposition

Arc center position

Btoroidal = 360 G

Btoroidal = 1055 G