Magnetic Helicity Injection and Flares

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Magnetic Helicity Injection and Flares
Plasma Theory Group, Hiroshima University

• K.Kusano (Hiroshima University)
• Collaboration with
• T.Maeshiro (Hiroshima University)
• T.Yokoyama, T.Sakurai (NAOJ)

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Contents

• Introduction
• What is helicity? Why helicity?
• Measurement of helicity?
• A new method
• Demonstration (AR8100)
• Helicity in the active region
• Relation between Helicity and Flares
• A New Model
• Numerical Simulation

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Magnetic Helicity

• Magnetic Linkage
• Conserved in ideal-MHD
• Associated with Magnetic Free Energy
• Source of the MHD energy relaxation
• Stability Criterion

free energy
magnetic energy
potential field energy
magnetic helicity
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Measurement of Helicity

• Morphology (sigmoid)
• Extrapolation
• Magnetic Shear
• (current helicity)
• Helicity Flux (Kusano et al. 2002)

new
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Helicity Flux

• Relative Helicity (Berger, Field 1984)
• Helicity flux

flux
photosphere
S
Shear Twist Motion
Emergence of Sheared Flux
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Reconstruction of Inductive Velocity
solution
Correlation tracking
Kusano et al. 2002, ApJ 577501-512.
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Helicity Energy Flux (AR8100)
energy flux
helicity flux
magnetic energy
magnetic helicity
total
free energy
total
potential
shear
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Helicity Flux Density
emergence
shear
11/3/0 UT
11/3/23 UT
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Helicity Flux in Flare Site
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Flares and Helicity Reversal

• Sheared Field
• Helicity sign is sharply reversed in any flare
  sites.

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Helicity and Reconnection

• Ejection

• Annihilation

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3D MHD Simulation
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Helicity Annahilation Model

• Injection of Magnetic Helicity
• Injection of Counter Helicity
• Formation of Helicity Inversion
• Tearing mode instability
• Nonlinear instability
• Reconnection (annihilation)
• Plasma circulation
• Reconnection (ejection)

A condition for flare
Competitive process (pre-flare phase)
trigger
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Ha ribbons on Helicity Reversal
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Summary

• New methodology to measure the helicity flux was
  developed.
• Helicity structure in the active region is more
  complicated than previous thought.
• Flares tend to occur at the helicity inversion
  line.
• We propose that helicity annihilation triggers
  flares.

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What we can do with Solar-B?

• Continuous observation of vector field.
• ? Merging of Observation and Numerical
  Simulation.

induction equation for Bn
self-consistent solution
3D MHD Equations
induction equation for Bt
observation
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Numerical Corona Project (NCP)
observations
Numerical Corona
Virtual reality
3D MHD solver B V in corona
Boundary Condition Bn,Bt,Vn,Vt on solar surface