Results from Magnetic Reconnection Experiment And Possible Application to Solar B program

1. 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

2. Various “Flares” (Reconnection Phenomena) X-ray intensity Solar flare time(hour) Magnetic Field strength Magnetospheric Aurora-substorm time(hour) Magnetic Field strength Laboratory reconnection time(μsec) Tokamak disruption Electron temperature time(sec) X-ray intensity Protostellar flare time 105 sec

3. 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 Dynamo Magnetic reconnection Magnetic chaos & waves Angular momentum transport Ion Heating Magnetic helicity conservation External Energy Source Unstable Plasma State • New bridges, collaborations between lab and astrophysical scientists

4. 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

5. reconn << SP

6. Local view of reconnection in a tokamak From H. Park

7. 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

8. global boundary local steady state process transient collisionality collisionless collisional Several dedicated experiments address the physics of magnetic reconnection 2-D 3-D TS-3/SSX

9. 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,

10. 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

13. The measured current sheet profiles agree well with Harris theory

14. Resistivity Enhancement Depends on Collisionality

15. 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

16. 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

17. Two Models for Fast Reconnection Vin Vout» Va Two-fluid MHD model in which electrons and ions decouple in the diffusion region (~ c/pi). Generalized Sweet-Parker model with anomalous resistivity.

18. 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).

19. The Out-of-plane Magnetic Field is Generated by Differential Electron Flow

20. 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

21. Fine Structure Probe [∆ =1mm] MRX Data

22. 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

23. Evolution of magnetic flux contours during MRX reconnection

24. A reconnection layer has been documented in the magnetopause d ~ c/wpi Mozer et al., PRL 2002 POLAR satellite

25. The Electron Flow Velocity is Deduced Separatrix • A new MRX high resolution probe array (R =0.25mm) shows electron flow patterns to create a quadrupole field (preliminary data) Measurement Simulation • Good agreement between the measurement and the yellow region in the simulation.

26. Comparison of high and low density cases: • No Q-P field seen in collisional plasmas Collisional regime mfp <  Collisionlessl regime mfp > 

27. Self-made quadrupole field size versus fill pressure Collisions reduce the Hall effects Bz is the shoulder value of reconnecting field.

28. 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. The Hall term is important when |/mfp|<1. Collisionless Collisional

29. 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]

30. Similar Observation by Spacecraft at Earth’s Magnetopause (Phan et al. ‘03) (Bale et al. ‘04) EM ES low b high b low b low b high b

31. A linkage between space and lab on reconnection MRX scaling shows transition from collisional (MHD) regime to 2 fluid MHD regime w.r.t. normalized ion skin depth Breslau di/ dsp ~ 5( mfp/L)1/2

32. 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

33. Opportunities for Collaborative Research • Transition scaling can be checked in a broader basis using di/SP 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

34. Global Physics for Helicity Counter-helicity merging generates FRC and strong ion heating TS-3 Data