Ward Manchester University of Michigan Coupling of the Coronal and Subphotospheric Magnetic Field in Active Regions by Shear Flows Driven by The Lorentz Force Coupling of the Coronal and Subphotospheric Magnetic Field in Active Regions by Shear Flows Driven by The Lorentz Force

Outline Universal feature of active regions that produce CMEs: magnetic shear Universal feature of active regions that produce CMEs: magnetic shear Source of magnetic shear: a subtle combination of the Lorentz force and gravitational pressure stratification of the solar atmosphere Source of magnetic shear: a subtle combination of the Lorentz force and gravitational pressure stratification of the solar atmosphere Examples of shearing motions in flux ropes, and magnetic layers Examples of shearing motions in flux ropes, and magnetic layers Picture of magnetic activity that couples the subphotospheric magnetic field to the corona Picture of magnetic activity that couples the subphotospheric magnetic field to the corona

Velocity and Magnetic Shear in AR 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

Recent CME Models That Impose Shear Magnetic Arcade Models Imposed shearing of foot points with magnetic reconnect at the base of the arcade (Amari et al ApJ 595, 1231 ) Imposed shearing of foot points with magnetic reconnect at the base of the arcade (Amari et al ApJ 595, 1231 ) Break-out model: Imposed shearing motions and reconnection above the arcade in a quadruple system (Antiochos 1999 ApJ 510, 485) Break-out model: Imposed shearing motions and reconnection above the arcade in a quadruple system (Antiochos 1999 ApJ 510, 485)

Emergence of a 3D flux rope Manchester, Gombosi, De Zeeuw and Fan. 2004, ApJ 610, 588

Flux Rope Emerging From the Convection Zone into the Corona Buoyant section of the flux rope reduced by a factor of two Buoyant section of the flux rope reduced by a factor of two

Spontaneous Shearing Motions Opposite sides of the flux rope move in opposite directions as the flux rope expands. Opposite sides of the flux rope move in opposite directions as the flux rope expands. Motions are driven by the Lorentz force! Motions are driven by the Lorentz force!

Development and Eruption of Magnetic Shear Core

The Lorentz Force Drives the Shearing!! 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

Dynamic Coupling By Shear Flows

Shearing During Flux Emergence From a Magnetic Layer

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,

Conclusions Shearing motions are a consequence of the Lorentz force that arises as the magnetic field expands in a highly stratified atmosphere which naturally explains: Shearing motions are a consequence of the Lorentz force that arises as the magnetic field expands in a highly stratified atmosphere which naturally explains: Magnitude of the shear velocity in the photosphere, chromosphere and corona that occur at a characteristic fraction of the local Alfven speed. Magnitude of the shear velocity in the photosphere, chromosphere and corona that occur at a characteristic fraction of the local Alfven speed. Shearing motions transport axial flux into expanding portion of flux rope or arcade and acts to return the axial component to constant values along field lines Shearing motions transport axial flux into expanding portion of flux rope or arcade and acts to return the axial component to constant values along field lines These shear flows strongly couple the low  corona to the high  photosphere and convection zone These shear flows strongly couple the low  corona to the high  photosphere and convection zone

Fundamental Assumptions The Sun possesses a gravitational field that results in large pressure stratification of the atmosphere The Sun possesses a gravitational field that results in large pressure stratification of the atmosphere Non-force-free magnetic structures pass that through the photosphere into the corona to form active regions are MUCH larger than pressure scale height at the photosphere (140 km) Non-force-free magnetic structures pass that through the photosphere into the corona to form active regions are MUCH larger than pressure scale height at the photosphere (140 km) Magnetic fields possess a horizontal axial component in addition to an azimuthal component Magnetic fields possess a horizontal axial component in addition to an azimuthal component The Lorentz force represented as (curl B) X B reverses direction across the expanding structure The Lorentz force represented as (curl B) X B reverses direction across the expanding structure Very general as it applies to flux ropes, arcades and magnetic layers Very general as it applies to flux ropes, arcades and magnetic layers

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