1. Chip Manchester 1, Fang Fang 1, Bart van der Holst 1, Bill Abbett 2 (1)University of Michigan (2)University of California Berkeley Study of Flux Emergence: Photospheric Shear Flows That Produce Coronal Eruptions Study of Flux Emergence: Photospheric Shear Flows That Produce Coronal Eruptions

2. Outline Flux emergence in a simple polytropic mode of the convection zone Flux emergence in a simple polytropic mode of the convection zone Flux emergence with active convective motions Flux emergence with active convective motions Common feature of active regions found in both simuations, shear flows Common feature of active regions found in both simuations, shear flows Source of magnetic shear: a subtle combination of the Lorentz force and gravitational stratification Source of magnetic shear: a subtle combination of the Lorentz force and gravitational stratification Development of a first-principles CME initiation model based on flux emergence Development of a first-principles CME initiation model based on flux emergence

3. Velocity and Magnetic Shear in AR 10486 Source of the Halloween Events Velocity Shear Yang et al. 2004, ApJ 617 L151, Magnetic Shear Liu et al. 2005, ApJ 622, 722 Velocity Shear Yang et al. 2004, ApJ 617 L151, Magnetic Shear Liu et al. 2005, ApJ 622, 722

4. Emergence of a 3D flux rope Examples: Fan 2001, Magara and Longcope 2003, Archontis et al. 2004, Manchester et al. 2004

5. Numerical Grid R = 750 km Zc=-4500 km q=-1.2 Bo=10,000G R = 750 km Zc=-4500 km q=-1.2 Bo=10,000G

6. Subsurface Shear Flows

8. Shear Flows in the Atmosphere

9. Shear Flows Driven by the Lorentz Force!! Manchester & Low 2000, Manchester 2001 Shearing motions transport Bx flux into the expanding portion of the flux rope and tends to return Bx to constant values along field lines to restore force balance

10. Comparison of Shear Velocity The image on the left, the shear velocity at the mid-plane of the simulation is shown. On the right, Doppler velocity maps of active regions at the limb made with SUMER Chae et al. 2000, ApJ 533, 535,

11. Eruption Process is Robust

12. Photospheric Magnetic Field

13. Photospheric Flow Field

14. Photospheric Shear Flows (Ux)

15. Sun Spot Rotation Center of rotation on the edge of the flux concentration Center of rotation on the edge of the flux concentration Rotation rate 10s of degrees/hour Rotation rate 10s of degrees/hour

16. Convection Zone Modeling (Fang Fang) Abbett et al. 2007) Atmosphere with coronal heating and radiative losses (Abbett 2007) Photosphere z = - 2100 km Flux Rope Parameters: Bo= 3920 G, twist factor q = -1.5 Ra= 225 km, Zo = -3500 km

17. Flux Emergence With Convection (Fang Fang) Abbett et al. 2007) Red Uz = +2 km/s Blue Uz = - 2 km/s

18. Shear Flows During Flux Emergence Shear flows persist, but are now a bit slower than in the nonconvecting atmosphere Shear flows persist, but are now a bit slower than in the nonconvecting atmosphere

19. Photospheric Flow Velocity Magnetic field alters the convection pattern Magnetic field alters the convection pattern

20. Magnetic Field Evolution at the Photosphere

21. Simulation Without Convection Manchester et al. 2004 Manchester et al. 2004 Bo=7000 G, q=-1 Ro=300 km Bo=7000 G, q=-1 Ro=300 km

22. Emerging Field Evolve to Highly Sheared Configuration

23. Field Emerged In the Corona

24. Convection Zone Module (EE) Coupled to Global Heliosphere Radiation MHD code (CRASH) is being adapted to treat the convection zone and corona (Bart & Fang). Will then be coupled to the global solar corona.

25. This shearing mechanism explains the following: Coincidence of the magnetic neutral line and the velocity neutral line Coincidence of the magnetic neutral line and the velocity neutral line Impulsive nature of shearing in newly emerged flux Impulsive nature of shearing in newly emerged flux Magnitude of the shear velocity in the photosphere, chromosphere and corona Magnitude of the shear velocity in the photosphere, chromosphere and corona The large scale pattern of magnetic shear in active regions which increases with proximity to the neutral line The large scale pattern of magnetic shear in active regions which increases with proximity to the neutral line transport of axial flux that strongly couples the low  corona to the high  photosphere and convection zone transport of axial flux that strongly couples the low  corona to the high  photosphere and convection zone The eruptions of the flux rope and arcade are driven by shearing motions and reconnection, which explains CMEs The eruptions of the flux rope and arcade are driven by shearing motions and reconnection, which explains CMEs

26. This shearing mechanism is very robust: Polytropic model predicts complex shear flows below the photosphere, can they be observed? Polytropic model predicts complex shear flows below the photosphere, can they be observed? Vortex flows near the sunspots Vortex flows near the sunspots With convection: magnetic field concentrations are weaker and fragmented with serpentine flux making multiple photospheric crossings. With convection: magnetic field concentrations are weaker and fragmented with serpentine flux making multiple photospheric crossings. Shear flows persist within the convection zone with a reduced amplitude (1 km/s vs 3 km/s) that is washed out convective motions. Shear flows persist within the convection zone with a reduced amplitude (1 km/s vs 3 km/s) that is washed out convective motions. In the low Corona, shear flows reach magnitudes of 5-10 km/s. In the low Corona, shear flows reach magnitudes of 5-10 km/s.

27. Questions: How does emerging flux coalesce to form sunspots? How does emerging flux coalesce to form sunspots? Magnetic flux expands so much in a simple polytropic atmosphere that it is difficult to get photospheric field strengths above 1 kilogauss. Magnetic flux expands so much in a simple polytropic atmosphere that it is difficult to get photospheric field strengths above 1 kilogauss. How does the flux in active regions remain confined to form strong gradients across the polarity inversion line? How does the flux in active regions remain confined to form strong gradients across the polarity inversion line? In simulations of flux emergence, the foot photospheric footpoints of the flux rope continually separate. In simulations of flux emergence, the foot photospheric footpoints of the flux rope continually separate.