experimental study of magnetic reconnection on …experimental study of magnetic reconnection on mrx...
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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