results from magnetic reconnection experiment and possible application to solar b program
DESCRIPTION
Results from Magnetic Reconnection Experiment And Possible Application to Solar B program. Masaaki Yamada Princeton University, PPPL. In collaboration with Y. Ren, H. Ji, S. Gerhardt, R. Kuslrud, and A. Kuritsyn. For Solar B Science meeting, Kyoto, Japan November 8-11, 2005. - PowerPoint PPT PresentationTRANSCRIPT
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Results from Magnetic Reconnection ExperimentAnd Possible Application to Solar B program
For Solar B Science meeting,Kyoto, Japan
November 8-11, 2005
Masaaki YamadaPrinceton University, PPPL
In collaboration with Y. Ren, H. Ji, S. Gerhardt, R. Kuslrud, and A. Kuritsyn
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Solar flare
MagnetosphericAurora-substorm
Laboratoryreconnection
Tokamak disruption
Protostellarflare
time(hour)
time(hour)
MagneticField
strength
time(μsec)
time(sec)
time 105 sec
X-rayintensity
X-rayintensity
MagneticField
strength
Electrontemperature
Various “Flares” (Reconnection Phenomena)
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Physics Frontier Center for Magnetic Self-organization in Laboratory and Astrophysical plasmas [9/15/03-]
U. Wisconsin[PI], U. Chicago, Princeton U., SAIC, and Swarthmore
Global Plasma in Equilibrium State
Unstable PlasmaState
Self-organization Processes Dynamo Magnetic reconnection Magnetic chaos & waves Angular momentum transport Ion Heating Magnetic helicity conservation
External Energy Source
• New bridges, collaborations between lab and astrophysical scientists
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Outline• Introduction: Magnetic Reconnection in Lab Plasmas
– Examples
• MHD (magneto-hydrodynamic) analysis– Sweet-Parker model and its generalization– Fast reconnection <=> Resistivity enhancement
• Two-fluid MHD physics regimes– High frequency turbulence– Generalized ohm’s law
• Experimental study of Hall effects;– Verification of an out-of-plane quadrupole field
• A new scaling identified from MHD to 2-fluid regime• Summary [Interim report]• Opportunities for collaborative study
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QuickTime™ and aSorenson Video 3 decompressorare needed to see this picture.
reconn << SP
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Local view of reconnection in a tokamak
QuickTime™ and aVideo decompressor
are needed to see this picture.
From H. Park
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MRX upgraded in FY2004• Relocated the PF and TF power supplies, increased stored energy (500 kJ)• Extended vacuum vessel to allow greater flux-core separation
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Several dedicated experiments address the physics of magnetic reconnection
TS-3/SSX
process steady state transient
boundarylocal global
collisionalitycollisionless collisional
3-D
2-D
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Objectives of MRX [Magnetic Reconnection Experiment]MRX was built to provide fundamental data on magnetic reconnection, by creating a proto-typical reconnection layer,
in a controlled laboratory setting. The primary issues;
• How much the theoretical 2-D reconnection picture is valid in actual experiments,
• How does guide field affect reconnection rate• What kinds of non-MHD effects would dominate in the
reconnection layer,
• How the magnetic energy is converted to plasma flows and thermal energy,
• What is a guiding principles for global reconnectionGlobal 2-D and 3-D MHD effects on reconnection,
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Experimental Setup and Formation of Current Sheet
Experimentally measured flux plots
ne= 1-10 x1013 cm-3, Te~5-15 eV, B~100-500 G,
Flux core distance can be changed
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QuickTime™ and aSorenson Video 3 decompressorare needed to see this picture.
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The measured current sheet profiles agree well
with Harris theory
(Yamada et al.,→ . , Phys Plasmas7, 1781, 2000)
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Resistivity Enhancement Depends on Collisionality
η* ≡EθjθEθ +VR ×BZ =ηjθ
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Agreement with a Generalized Sweet-Parker Model
• The model modified to take into account of– Measured enhanced
resistivity
– Compressibility
– Higher pressure in downstream than upstream
(Ji et al. PoP ‘99)
GSP
model
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Fast Reconnection <=> Enhanced Resistivity
• Main question
– What is the cause of the observed enhanced
resistivity?
• Hall MHD Effects create a large E field
• Electrostatic Turbulence
• Electromagnetic Fluctuations» All Observed in MRX
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Two Models for Fast Reconnection
Generalized Sweet-Parker model with anomalous resistivity.
Two-fluid MHD model in which electrons and ions decouple in the diffusion region (~ c/pi).
Vin
Vout» Va
€
E + V × B = ηJ +J × B −∇p
en+
me
e2
dVe
dt
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The Hall Effect During Reconnection Shown in 2D Simulation
A out-of-plane quadrupole magnetic field
2-fluid MHD simulation performed by J. Breslau with the 2-D Magnetic Reconnection Code (MRC).
Different motions of ions and electrons
In-plane current
• The blue lines show the ion flow streamlines.
• The red arrows show the electron flow.
• The black lines show the magnetic flux.
The colors show the out-of-plane
quadrupole magnetic field.
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The Out-of-plane Magnetic Field is Generated by Differential Electron Flow
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The Fine Structure Probe allows measurements within the current sheet with 1.25 mm resolution
5 cm cpi
≈ 2-10 cm.
cpe
≈ .5-2.5 mm.
1.25 mm
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Fine Structure Probe [∆ =1mm]
MRX Data
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Experimentally measured 3-D field line features in MRX
• Manifestation of Hall effects in MRX• Electrons would pull magnetic field lines with their flow
e flow
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Evolution of magnetic flux contours during MRX reconnection
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Measurements of Diffusion Regionwith a Hall effect signature
Mozer et al., PRL 2002
POLAR satellite
A reconnection layer has been documented in the magnetopause
~ c/pi
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The Electron Flow Velocity is Deduced
• Good agreement between the measurement and the yellow region in the simulation.
Separatrix
Measurement Simulation• A new MRX high resolution
probe array (R =0.25mm) shows electron flow patterns to create a quadrupole field
(preliminary data)
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• Comparison of high and low density cases:
• No Q-P field seen in collisional plasmas
Collisional regimemfp <
Collisionlessl regimemfp >
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Self-made quadrupole field size versus fill pressure Collisions reduce the Hall effects
Bz is the shoulder value of reconnecting field.
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The Hall Term is Dominant in Generating the Reconnection Electric Field
• The ratio between the jrx Bz/ene and the reconnection electric field is evaluated.
• The /mfp denotes the
collisionality of plasmas.
CollisionalCollisionless
The Hall term is important when |/mfp|<1.
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EM LHDW Amplitudes Correlate with Resistivity Enhancement
The lower hybrid drift waves [LHDW] are excited by electron drift again ions [Ji et al., PRL-04]
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Similar Observation by Spacecraft at Earth’s Magnetopause
(Phan et al. ‘03)
ES
EM
(Bale et al. ‘04)
high
low
high
low
low
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System L (cm) B (G)di= c/pi(cm)
sp (cm) di/ sp
MRX/SSX 10 100-500 1-5 0.1-5 .2-100
MST 30/100 1-3x103 10 0.1 100
Magnetosphere 109 10-3 107 104 >103
Solar flare 109 100 104 102 100
ISM 1018 10-6 107 1010 0.001
Protostar di/ s >> 1
MRX scaling shows transition from collisional (MHD) regime to 2 fluid MHD regimew.r.t. normalized ion skin depth
A linkage between space and lab on reconnection
Breslau
di/ sp ~ 5( mfp/L)1/2
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Summary
• Important progress has been made both in laboratory experiments and solar and space observations making it possible to collaborate in study of magnetic reconnection/self-orhanization
– Transition from collisional to collisionless regime documented– Generalized Sweet Parker model was tested in an axisymmetric (2-D) plasma
• Progress maid for identifying causes of fast reconnection– Electrostatic and magnetic LHDW fluctuations have been observed; Magnetic
not electrostatic turbulence in the sheet correlates well with resistivity enhancement
– Two fluid MHD physics plays dominant role in the collisionless regime. Hall effects have been verified through a quadrupole field
– Causal relationship between these processes with fast reconnection is yet to be determined
• Guiding principles yet to be found for 3-D global reconnection phenomena in the collisionless regime
– Magnetic self-organization– Global energy flows
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Opportunities for Collaborative Research
• Transition scaling can be checkedTransition scaling can be checked in a broader basis in a broader basis
using dusing dii//SPSP in the transition from collisional to collisionless in the transition from collisional to collisionless regimesregimes
• Effects of guide field on magnetic reconnectionEffects of guide field on magnetic reconnection
• Guiding principles can be sought together for 3-D global reconnection phenomena– Magnetic self-organization-Minimum energy state– Multiple reconnection models for global self-organization– Conservation of magnetic helicities– Plasmoid formation
• Mechanisms of effective ion heating both in Lab and coronaeMechanisms of effective ion heating both in Lab and coronae
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Global Physics for Helicity
Counter-helicity merging generates
FRC and strong ion heating
TS-3 Data