Chip ManchesterChip Manchester11, Fang Fang, Fang Fang11, Bart van , Bart van der Holstder Holst11, Bill Abbett, Bill Abbett22

(1)University of Michigan (2)University of California (1)University of Michigan (2)University of California BerkeleyBerkeley

Study of Flux Study of Flux Emergence: Emergence:

Photospheric Shear Photospheric Shear Flows That Produce Flows That Produce Coronal EruptionsCoronal Eruptions

OutlineOutline Flux emergence in a simple polytropic Flux emergence in a simple polytropic

mode of the convection zonemode of the convection zone Flux emergence with active convective Flux emergence with active convective

motionsmotions Common feature of active regions Common feature of active regions

found in both simuations, shear flowsfound in both simuations, shear flows Source of magnetic shear: a subtle Source of magnetic shear: a subtle

combination of the Lorentz force and combination of the Lorentz force and gravitational stratificationgravitational stratification

Development of a first-principles CME Development of a first-principles CME initiation model based on flux initiation model based on flux emergenceemergence

Velocity and Magnetic Velocity and Magnetic Shear in AR 10486 Shear in AR 10486

Source of the Halloween Source of the Halloween EventsEvents Velocity Shear Yang et al. 2004, ApJ 617 L151, Velocity Shear Yang et al. 2004, ApJ 617 L151,

Magnetic Shear Liu et al. 2005, ApJ 622, 722 Magnetic Shear Liu et al. 2005, ApJ 622, 722

Emergence of a 3D flux ropeEmergence of a 3D flux rope

Examples: Fan 2001, Magara Examples: Fan 2001, Magara and Longcope 2003, Archontis et and Longcope 2003, Archontis et al. 2004, Manchester et al. 2004al. 2004, Manchester et al. 2004

Numerical GridNumerical Grid R = 750 km Zc=-4500 km q=-1.2 R = 750 km Zc=-4500 km q=-1.2

Bo=10,000GBo=10,000G

QuickTime™ and aBMP decompressor

are needed to see this picture.

Subsurface Shear FlowsSubsurface Shear Flows

QuickTime™ and aBMP decompressor

are needed to see this picture.

QuickTime™ and aBMP decompressor

are needed to see this picture.

QuickTime™ and aBMP decompressor

are needed to see this picture.

Shear Flows in the Shear Flows in the AtmosphereAtmosphere

Shear Flows Driven by the Lorentz Shear Flows Driven by the Lorentz Force!!Force!! Manchester & Low 2000, Manchester 2001 Manchester & Low 2000, Manchester 2001

Shearing motions transport Bx flux into the expanding Shearing motions transport Bx flux into the expanding portion of the flux rope and tends to return Bx to constant portion of the flux rope and tends to return Bx to constant values along field lines to restore force balance values along field lines to restore force balance

Comparison of Shear VelocityComparison of Shear Velocity

The image on the left, the shear velocity at the mid-plane of the The image on the left, the shear velocity at the mid-plane of the simulation is shown.simulation is shown.

On the right, Doppler velocity maps of active regions at the limb made On the right, Doppler velocity maps of active regions at the limb made with SUMER with SUMER

Chae et al. 2000, ApJ 533, 535, Chae et al. 2000, ApJ 533, 535,

Eruption Process is Eruption Process is RobustRobust

Photospheric Magnetic Photospheric Magnetic FieldField

QuickTime™ and aBMP decompressor

are needed to see this picture.

Photospheric Flow FieldPhotospheric Flow Field

QuickTime™ and aBMP decompressor

are needed to see this picture.

Photospheric Shear Photospheric Shear Flows (Ux)Flows (Ux)

QuickTime™ and aBMP decompressor

are needed to see this picture.

Sun Spot RotationSun Spot Rotation Center of rotation on the edge of the flux concentrationCenter of rotation on the edge of the flux concentration Rotation rate 10s of degrees/hourRotation rate 10s of degrees/hour

Convection Zone Convection Zone Modeling (Fang Fang)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 = -1.5Ra= 225 km, Zo = -3500 km

Flux Emergence With Flux Emergence With Convection (Fang Fang)Convection (Fang Fang)

Abbett et al. 2007)

Red Uz = +2 km/s

Blue Uz = - 2 km/s

Shear Flows During Flux Shear Flows During Flux EmergenceEmergence

Shear flows Shear flows persist, but are persist, but are now a bit slower now a bit slower than in the than in the nonconvecting nonconvecting atmosphereatmosphere

QuickTime™ and aBMP decompressor

are needed to see this picture.

Photospheric Flow Photospheric Flow VelocityVelocity

Magnetic field Magnetic field alters the alters the convection patternconvection pattern

QuickTime™ and aBMP decompressor

are needed to see this picture.

Magnetic Field Evolution at Magnetic Field Evolution at the Photospherethe Photosphere

QuickTime™ and aBMP decompressor

are needed to see this picture.

Simulation Without Simulation Without ConvectionConvection

Manchester et Manchester et al. 2004al. 2004

Bo=7000 G, Bo=7000 G, q=-1 Ro=300 q=-1 Ro=300 kmkm

QuickTime™ and aBMP decompressor

are needed to see this picture.

Emerging Field Evolve to Emerging Field Evolve to Highly Sheared Highly Sheared ConfigurationConfiguration

Field Emerged In the Field Emerged In the CoronaCorona

Convection Zone Module Convection Zone Module (EE) Coupled to Global (EE) Coupled to Global

HeliosphereHeliosphere Radiation MHD code (CRASH) is being adapted to Radiation MHD code (CRASH) is being adapted to treat the convection zone and corona (Bart & Fang). treat the convection zone and corona (Bart & Fang). Will then be coupled to the global solar corona. Will then be coupled to the global solar corona.

QuickTime™ and aBMP decompressor

are needed to see this picture.

This shearing This shearing mechanism explains the mechanism explains the

following: following: Coincidence of the magnetic neutral line and the Coincidence of the magnetic neutral line and the

velocity neutral linevelocity neutral line Impulsive nature of shearing in newly emerged fluxImpulsive nature of shearing in newly emerged flux Magnitude of the shear velocity in the photosphere, Magnitude of the shear velocity in the photosphere,

chromosphere and coronachromosphere and corona The large scale pattern of magnetic shear in active The large scale pattern of magnetic shear in active

regions which increases with proximity to the neutral regions which increases with proximity to the neutral line line

transport of axial flux that strongly couples the low transport of axial flux that strongly couples the low corona to the high corona to the high photosphere and convection zone photosphere and convection zone

The eruptions of the flux rope and arcade are driven by The eruptions of the flux rope and arcade are driven by shearing motions and reconnection, which explains shearing motions and reconnection, which explains CMEsCMEs

This shearing This shearing mechanism is very mechanism is very

robust: robust: Polytropic model predicts complex shear flows Polytropic model predicts complex shear flows

below the photosphere, can they be observed?below the photosphere, can they be observed? Vortex flows near the sunspotsVortex flows near the sunspots With convection: magnetic field concentrations With convection: magnetic field concentrations

are weaker and fragmented with serpentine flux are weaker and fragmented with serpentine flux making multiple photospheric crossings.making multiple photospheric crossings.

Shear flows persist within the convection zone Shear flows persist within the convection zone with a reduced amplitude (1 km/s vs 3 km/s) that with a reduced amplitude (1 km/s vs 3 km/s) that is washed out convective motions.is washed out convective motions.

In the low Corona, shear flows reach magnitudes In the low Corona, shear flows reach magnitudes of 5-10 km/s.of 5-10 km/s.

Questions: Questions: How does emerging flux coalesce to form How does emerging flux coalesce to form

sunspots? sunspots? Magnetic flux expands so much in a simple Magnetic flux expands so much in a simple

polytropic atmosphere that it is difficult to get polytropic atmosphere that it is difficult to get photospheric field strengths above 1 kilogauss.photospheric field strengths above 1 kilogauss.

How does the flux in active regions remain How does the flux in active regions remain confined to form strong gradients across the confined to form strong gradients across the polarity inversion line? polarity inversion line?

In simulations of flux emergence, the foot In simulations of flux emergence, the foot photospheric footpoints of the flux rope photospheric footpoints of the flux rope continually separate.continually separate.