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Magnetic Relaxation in the Solar Corona

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Magnetic Relaxation in the Solar Corona

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    1. 1 Magnetic Relaxation in the Solar Corona Kanya Kusano Earth Simulator Center, JAMSTEC /Hiroshima University Collaboration with T.Maeshiro (Hiroshima Univ.), T.Yokoyama (Univ. of Tokyo), T.Sakurai (NOAJ)

    2. 2 Solar Flares as MHD Relaxation

    3. 3 Questions Q1: Is the magnetic helicity relevant to the coronal dynamics? Q2: What is the sigmoidal formation mechanism? Q3: What is the sudden onset mechanism of flares & CME? Q4: Can the Taylors theory help us to understand the solar coronal phenomena? Q5: What is the key nonlinearity in the relaxation of the solar corona?

    4. 4 contents magnetic helicity in the solar corona Kusano et al. (2002, ApJ) Maeshiro, Kusano et al. (2005, ApJ) the onset mechanism of solar flares Kusano et al. (2004, ApJ) sigmoid formation as Taylors relaxation Kusano (2005, submitted to ApJ) comments on the nonlinearity in the relaxation physics.

    5. 5 Magnetic helicity in the solar corona

    6. 6 Magnetic Helicity Measurement

    7. 7 AR8100 evolution of X-ray & helicity

    8. 8 Correlation with Soft X-ray Soft X-ray flux statistically well correlates with magnetic helicity flux and the structural complexity.

    9. 9 The onset mechanism of solar flares

    10. 10 Helicity Injection & Solar Flare Injected magnetic helicity is insufficient to make one turn twist of the whole magnetic flux. Amplitude of helicity flux does NOT directly correlate with flare onset.

    11. 11 Flaring from shear reversal

    12. 12 Simulation Model (3D MHD) Finite difference: 512 X 256 X 1024 (D~10-3) Initial state: linear force-free (2D arcade) Boundary Condition: shear motion reversing magnetic shear (0.05VA) Anomalous resistivity

    13. 13 Simulation of the Shear Reversal

    14. 14 Reversed-Shear Model

    15. 15 mutual excitation of reconnections

    16. 16 Current Sheet Evolution Spontaneous to Driven

    17. 17 Dependency on Shear Reversal tearing growth saturation eruption

    18. 18

    19. 19 The formation mechanism of sigmoids

    20. 20 Sigmoids as precursor of eruption

    21. 21 Fan & Gibson 2004 flux emerging, kink instability, current sheet, sigmoid

    22. 22 Leamon et al. 2003 (ApJL) No eruptions occur for the total twist approaching the critical value Tc~2pi.

    23. 23 sigmoid formation due to shear reversal

    24. 24

    25. 25

    26. 26 Sigmoids in the 4 cases

    27. 27 Comparison with Taylors state

    28. 28 Structure of a a is almost uniform inside the sigmoid. a is limited by 2p/h.

    29. 29 Nandy et al. 2003 (ApJL) a=[curl B]z/bz Spatial variation in a tends to be reduced with big flares.

    30. 30 Filament eruption by kink mode

    31. 31 filament eruption by kink mode

    32. 32 comments The relaxation dynamics in high magnetic Reynolds number regime (S>10^4) is much different from the lower S regime.

    33. 33 Nonlinearity

    34. 34 Summary Solar coronal dynamics must be a sort of MHD relaxation, which is associated with the magnetic helicity injection that is now measurable. The mutual excitation between multiple reconnections is a promising model to explain the sudden onset mechanism of flares. similar to the DTM disruption in tokamak. (Ref. Ishii et al 2003 Nucl. Fusion 43 539-546 )

    35. 35 Summary Nonlinear coupling of the tearing instability can drive the self-organization of sigmoidal structure. consistent with the Taylors relaxation Nonlinear coupling of the kink instability may cause the local eruption of flux rope. similar to the phase-locking event in RFP

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