Sung-Hong Park Space Weather Research Laboratory New Jersey Institute of Technology

1. Study of Magnetic Helicity and Its Relationship with Solar Activities: Flares, CMEs, and Solar Cycle 23 Sung-Hong Park Space Weather Research Laboratory New Jersey Institute of Technology

2. < Flare Index > 1.1. Correlation Study between Helicity and Flare Index - Simple Motivation:1. Helicity ↑ => Non-potentiality ↑ (True) 2. Non-potentiality ↑ => Flare Productivity↑ (??) (Magnitude & Occurrence Probability) - Data Analysis • 378 Active Regions • Full-disk 96 minute SOHO/MDI magnetograms • 24-hour profiles of helicity injection rate, dH/dt, and unsigned magnetic flux, Φ, right after an active region appears or rotates to a position within 0.6 RSun from the disk center. • Two parameters, |<dH/dt>| and <Φ>, averaged during the entire 24-hour period. • We compare these two parameters with the flare index derived from GOES soft X-rayobservation and calculate flare-productive probabilityfor the next 24-hour time window after the measurement of the parameters. < Flare-Productive Probability > i = GOES class

3. Fidx > 10 1 < Fidx < 10 Fidx < 1 dH/dt[1040Mx2 hr-1] ~46 ~25 ~10 Φ[1020Mx] ~540 ~470 ~250 Time[ hours ] 1.2. Time Profile of dH/dt and Φ

4. Twice !! 1.3. Correlation between Two Parameters and Flare Index Flaring # 153 Non-flaring # 225

5. 1.4. |< dH/dt >| vs. < Φ> <Φ>[1020Mx] | < dH/dt > |[1040Mx2 hr-1]

6. 1.5. Two Parameters vs. Solar Flare Productivity

7. 1.6. Time Profile of ΔH, Φ, and GOES soft X-ray Fast Increasing Phase Slow Increasing or Constant Phase Inverse Sing Helicity Injection Phase

8. 1.7. Daily Flare Index Forecast in NJIT/SWRL website

9. 1.8. Summary • Helicity physically considers bothstructure and evolution of magnetic fields while other previous forecasting studies are based on snap-shot morphology only. • For 91 AR samples having similarly large magnetic flux, the flaring AR group has the average helicity injection rate about twice greater than that of the non-flaring AR group. • The flare-productive probability of the helicity parameter for C-class flares shows a welldefined cut-off between flare-productive and flare- quiet ARs. • Helicity accumulates significantly and consistently over 1-1.5 days in major flare producing ARs so that a warning sign of flares can be given by the presence of a phase of monotonically increasing helicity. Some of major flares occurred when the helicity injection became slow (sometimes almost zero) or the opposite sign of helicity started to be injected after the significant helicity accumulation phase.

10. 2.1. Relative Magnetic Helicity in an Open Volume (Berger & Field 1984) ( 1 ) ( 2 ) where P is the potential field having the same normal flux distribution as B on the z = 0 boundary, and Ap is the vector potential for P. The expression of Equation (2) reduced to that of Equation (1) with the specific A* and Ap* derived by DeVore (2000): ( 3 ) ( 4 ) ( 5 )

11. 2.2. 3D NLFF magnetic field data( produced by Jing Ju ) • December 8, 21:20 UT ~ December 14, 5:00 UT • It is computed with the optimization method (Wheatland et al. 2000) as implemented by Wiegelmann (2004). • As the boundary conditions for the extrapolation, we use the preprocessed Hinode/SP vector magnetograms in which the net Lorentz force and toque in the photosphere are minimized (Wiegelmann et al. 2006). • The dimensions of the 3D NLFF field data are 240×132×180 pixel3, which correspond to 288×158×216 Mm3.

12. 2.3. Overview of NOAA AR 10930 G-band Images Hinode/FG/Stokes-V Hinode/FG/G-band Hinode/FG/Ca II H Hinode/XRT Figures from Min & Chae (2009)

13. 2.4. Time Profile of Magnetic Helicity, Flux, and GOES X-ray NLFF MDI • A negative (left-handed) helicity of -5×1043 Mx2 in the AR corona right before the X3.4 flare. • The major flare is preceded by a significantly and consistently large amount of negative helicity injection (-2×1043 Mx2) into the corona over ~2 days. (3) The temporal variation of helicity is comparable to that of the rotational speed in the southern sunspot with positive polarity. (4) In general, the time profile of the coronal helicity is well-matched with that of the helicity accumulation by the time integration of the simplified helicity injection rate (Chae 2001) determined by using SOHO MDI magnetograms (5) At the time period of the channel structure development (December 11, 4:00-8:00 UT) with newly emerging flux and just right before the C5.7 class flare, the time variation of the coronal helicity shows a rapid and huge increase of negative helicity, but that of the helicity accumulation by MDI magnetograms indicates a monotonous increase of negative helicity.

14. Cycle 23 Hemispheric Helicity Distribution 1999-2002 1998, 2003-2006 3. AR Helicity Survey during Solar Cycle 23

15. 4. Long-Term Evolution of Helicity and Flux in ARs Producing Halo CMEs • Motivation:Hood & Priest (1981) studied the stability of line line-tied, uniformly twisted, force-free cylindrical flux tubes and found that the tubes become kink-unstable when the number of rotations that each field line winds about the axis between the line-tied ends exceeds 1.25. - Fan & Gibson (2004) Fan & Gibson (2004) performed isothermal MHD simulations of the three-dimensional evolution of the coronal magnetic field as an arched, twisted magnetic flux tube emerges gradually into a pre-existing coronal arcade, under the condition of low β-plasma and high electric conductivity.

16. 4. Long-Term Evolution of Helicity and Flux in ARs Producing Halo CMEs • Φ is almost constant. • ΔH ~ 8×1043 Mx2 • ΔH/ Φ2 ~ 0.007 • Δt ~ 4.5 days • CME linear speed ~ 1333km/s • CME accel. ~ 7m/s2 : positive accel. • Φ is increasing • ΔH ~ 2×1043 Mx2 • ΔH/ Φ2 = 0.009 • Δt ~ 1 day • 1st & 2nd CME speeds ~ 818 km/s & 1759km/s • 1st & 2nd CME accel. ~ -81.5 m/s2 & -19.7m/s • negative accel.