Plasma Theory Group Hiroshima University Magnetic Helicity Injection

Plasma Theory Group, Hiroshima University Magnetic Helicity Injection and Flares K. Kusano (Hiroshima University) Collaboration with T. Maeshiro (Hiroshima University) T. Yokoyama, T. Sakurai (NAOJ) 6/11/2021 Solar B Science Meeting 1

Contents n Introduction n n Measurement of helicity? n n A new method Demonstration (AR 8100) n n n What is helicity? Why helicity? Helicity in the active region Relation between Helicity and Flares A New Model n 6/11/2021 Numerical Simulation Solar B Science Meeting 2

Magnetic Helicity Magnetic Linkage n n Conserved in ideal-MHD Associated with Magnetic Free Energy n n Source of the MHD energy relaxation Stability Criterion f y H=2 fy 6/11/2021 magnetic energy n free energy potential field energy magnetic helicity Solar B Science Meeting 3

Measurement of Helicity n new n Morphology (sigmoid) Extrapolation Magnetic Shear (current helicity) Helicity Flux (Kusano et al. 2002) corona S 6/11/2021 photosphere Solar B Science Meeting 4

Helicity Flux n n Relative Helicity (Berger, Field 1984) n: normal flux Helicity flux photosphere t：tangential S Emergence of Sheared Flux 6/11/2021 Shear & Twist Motion Solar B Science Meeting 5

Reconstruction of Inductive Velocity n t SOHO/MDI Correlation tracking solution Vector magnetograph (NAOJ, Tokyo) Kusano et al. 2002, Ap. J 577: 501 -512. 6/11/2021 Solar B Science Meeting 6

Helicity & Energy Flux (AR 8100) energy flux helicity flux magnetic energy magnetic helicity total free energy potential shear 1 2 3 4 5 date (1997/11) 6/11/2021 6 1 2 3 4 5 date (1997/11) Solar B Science Meeting 6 7

Helicity Flux Density emergence shear 11/3/0 UT 11/3/23 UT 6/11/2021 Solar B Science Meeting 8

Helicity Flux in Flare Site 6/11/2021 Solar B Science Meeting 9

Flares and Helicity Reversal n n Sheared Field Helicity sign is sharply reversed in any flare sites. 6/11/2021 Solar B Science Meeting 10

Helicity and Reconnection n Ejection n Annihilation 6/11/2021 Solar B Science Meeting 11

3 D MHD Simulation 6/11/2021 Solar B Science Meeting 12

Helicity Annahilation Model n n n n Injection of Magnetic Helicity A condition for flare Injection of Counter Helicity Formation of Helicity Inversion Competitive process (pre-flare phase) Tearing mode instability trigger Nonlinear instability Reconnection (annihilation) Plasma circulation Reconnection (ejection) d 6/11/2021 Solar B Science Meeting 13

Ha ribbons on Helicity Reversal 6/11/2021 Solar B Science Meeting 14

Summary n n 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. 6/11/2021 Solar B Science Meeting 15

What we can do with Solar-B? n Continuous observation of vector field. → Merging of Observation and Numerical Simulation. induction equation for Bn 3 D MHD Equations self-consistent solution induction equation for Bt observation 6/11/2021 Solar B Science Meeting 16

Numerical Corona Project (NCP) observations Numerical Corona Virtual reality Boundary Condition Bn, Bt, Vn, Vt on solar surface 6/11/2021 3 D MHD solver B & V in corona Solar B Science Meeting 17