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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 Various “Flares” (Reconnection Phenomena) X-ray intensity Solar flare time(hour) Magnetospheric Aurora-substorm Magnetic Field strength time(hour) Laboratory reconnection Magnetic Field strength time(μsec) Tokamak disruption Electron temperature time(sec) Protostellar flare X-ray intensity time 105 sec 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 Self-organization Processes External Energy Source Dynamo Magnetic reconnection Magnetic chaos & waves Angular momentum transport Ion Heating Magnetic helicity conservation Unstable Plasma State • 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 QuickTime™ and a Sorenson Video 3 decompressor are needed to see this picture. reconn << SP Local view of reconnection in a tokamak From H. Park QuickTime™ and a Video decompressor are needed to see this picture. 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 2-D 3-D TS-3/SSX local boundary steady state process collisionless collisionality global transient collisional 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 ne= 1-10 x1013 cm-3, Te~5-15 eV, B~100-500 G, Flux core distance can be changed QuickTime™ and a Sorenson Video 3 decompressor are needed to see this picture. The measured current sheet profiles agree well with Harris theory (Yamada et al.,Phys. Plasmas, 7, 1781, 2000) Resistivity Enhancement Depends on Collisionality E VR BZ j * E j Agreement with a Generalized Sweet-Parker Model (Ji et al. PoP ‘99) • The model modified to take into account of – Measured enhanced resistivity – Compressibility – Higher pressure in downstream than upstream 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 Vin Vout» Va Generalized Sweet-Parker model with anomalous resistivity. Two-fluid MHD model in which electrons and ions decouple in the diffusion region (~ c/pi). J B p me dVe E V B J 2 en e dt The Hall Effect During Reconnection Shown in 2D Simulation • The blue lines show the ion flow streamlines. • The red arrows show the electron flow. • The black lines show the magnetic flux. Different motions of ions and electrons In-plane current A out-of-plane quadrupole magnetic field The colors show the out-of-plane quadrupole magnetic field. 2-fluid MHD simulation performed by J. Breslau with the 2-D Magnetic Reconnection Code (MRC). 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 1.25 mm ≈ .5-2.5 mm. Fine Structure Probe [∆ =1mm] MRX Data Experimentally measured 3-D field line features in MRX e flow • Manifestation of Hall effects in MRX • Electrons would pull magnetic field lines with their flow Evolution of magnetic flux contours during MRX reconnection A reconnection layer has been documented in the magnetopause d ~ c/pi Mozer et al., PRL 2002 POLAR satellite The Electron Flow Velocity is Deduced Separatrix • Measurement • Simulation Good agreement between the measurement and the yellow region in the simulation. 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 < d Collisionlessl regime mfp > d Self-made quadrupole field size versus fill pressure Collisions reduce the Hall effects Bz is the shoulder value of reconnecting field. The Hall Term is Dominant in Generating the Reconnection Electric Field The Hall term is important when |d/mfp|<1. Collisionless Collisional • The ratio between the jrx Bz/ene and the reconnection electric field is evaluated. • The d/mfp denotes the collisionality of plasmas. 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 (Bale et al. ‘04) (Phan et al. ‘03) EM ES low high low b b b low b high b A linkage between space and lab on reconnection Breslau MRX scaling shows transition from collisional (MHD) regime to 2 fluid MHD regime w.r.t. normalized ion skin depth di/ dsp ~ 5( mfp/L)1/2 System L (cm) B (G) MRX/SSX 10 100-500 MST 30/100 1-3x103 Magnetosphere 109 10-3 Solar flare 109 ISM 1018 100 10-6 Protostar d / d >> 1 d i= c/pi(cm) 1-5 dsp (cm) di/ dsp 0.1-5 .2-100 10 0.1 100 107 104 >103 104 102 100 107 1010 0.001 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 basis using di/dSP in the transition from collisional to collisionless regimes • Effects 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 coronae Global Physics for Helicity Counter-helicity merging generates FRC and strong ion heating TS-3 Data