Presentation on theme: "Results from Magnetic Reconnection Experiment And Possible Application to Solar B program For Solar B Science meeting, Kyoto, Japan November 8-11, 2005."— Presentation transcript:
Results from Magnetic Reconnection Experiment And Possible Application to Solar B program For Solar B Science meeting, Kyoto, Japan November 8-11, 2005 Masaaki Yamada Princeton University, PPPL In collaboration with Y. Ren, H. Ji, S. Gerhardt, R. Kuslrud, and A. Kuritsyn
Solar flare Magnetospheric Aurora-substorm Laboratory reconnection Tokamak disruption Protostellar flare time(hour) Magnetic Field strength time(μsec) time(sec) time 10 5 sec X-ray intensity X-ray intensity Magnetic Field strength Electron temperature Various “Flares” (Reconnection Phenomena)
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 Plasma State 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
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
Local view of reconnection in a tokamak From H. Park
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
Several dedicated experiments address the physics of magnetic reconnection TS-3/SSX processsteady statetransient boundary local global collisionality collisionlesscollisional 3-D 2-D
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 reconnection Global 2-D and 3-D MHD effects on reconnection,
Experimental Setup and Formation of Current Sheet Experimentally measured flux plots n e = 1-10 x10 13 cm -3, T e ~5-15 eV, B~100-500 G, Flux core distance can be changed
The measured current sheet profiles agree well with Harris theory
Resistivity Enhancement Depends on Collisionality
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
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
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 ). V in V out » V a
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.
The Out-of-plane Magnetic Field is Generated by Differential Electron Flow
The Fine Structure Probe allows measurements within the current sheet with 1.25 mm resolution 5 cm c pi ≈ 2-10 cm. c pe ≈.5-2.5 mm. 1.25 mm
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
Evolution of magnetic flux contours during MRX reconnection
Mozer et al., PRL 2002 POLAR satellite A reconnection layer has been documented in the magnetopause ~ c/ pi
The Electron Flow Velocity is Deduced Good agreement between the measurement and the yellow region in the simulation. Separatrix MeasurementSimulation A new MRX high resolution probe array ( R =0.25mm) shows electron flow patterns to create a quadrupole field (preliminary data)
Comparison of high and low density cases: No Q-P field seen in collisional plasmas Collisional regime mfp < Collisionlessl regime mfp >
Self-made quadrupole field size versus fill pressure Collisions reduce the Hall effects B z is the shoulder value of reconnecting field.
The Hall Term is Dominant in Generating the Reconnection Electric Field The ratio between the j r x B z /en e and the reconnection electric field is evaluated. The / mfp denotes the collisionality of plasmas. CollisionalCollisionless The Hall term is important when | / mfp |<1.
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]
Similar Observation by Spacecraft at Earth’s Magnetopause (Phan et al. ‘03) ES EM (Bale et al. ‘04) high low high low
System L (cm)B (G) d i = c/ pi (cm) sp (cm)d i / sp MRX/SSX10100-5001-50.1-5.2-100 MST 30/100 1-3x10 3 10 0.1100 Magnetosphere 10 9 10 -3 10 7 10 4 >10 3 Solar flare 10 9 100 10 4 10 2 100 ISM10 18 10 -6 10 710 0.001 Protostar d i / s >> 1 MRX scaling shows transition from collisional (MHD) regime to 2 fluid MHD regime w.r.t. normalized ion skin depth A linkage between space and lab on reconnection Breslau d i / sp ~ 5( mfp /L) 1/2
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
Opportunities for Collaborative Research Transition scaling can be checked in a broader basisTransition scaling can be checked in a broader basis using d i / SP in the transition from collisional to collisionless regimes using d i / SP in the transition from collisional to collisionless regimes 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
Global Physics for Helicity Counter-helicity merging generates FRC and strong ion heating TS-3 Data
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