Ward Manchester Ward Manchester

University of MichiganUniversity of Michigan

Coupling of the Coupling of the Coronal and Coronal and

Subphotospheric Subphotospheric Magnetic Field in Magnetic Field in Active Regions by Active Regions by

Shear Flows Driven by Shear Flows Driven by The Lorentz ForceThe Lorentz Force

OutlineOutline Universal feature of active regions Universal feature of active regions

that produce CMEs: magnetic shearthat produce CMEs: magnetic shear 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 pressure stratification gravitational pressure stratification of the solar atmosphereof the solar atmosphere

Examples of shearing motions in flux Examples of shearing motions in flux ropes, and magnetic layersropes, and magnetic layers

Picture of magnetic activity that Picture of magnetic activity that couples the subphotospheric couples the subphotospheric magnetic field to the coronamagnetic field to the corona

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

Recent CME Models That Impose Recent CME Models That Impose Shear Shear

Magnetic Arcade ModelsMagnetic Arcade Models Imposed Imposed shearing of foot points with magnetic shearing of foot points with magnetic

reconnect at the base of the arcade (Amari et al. 2003 reconnect at the base of the arcade (Amari et al. 2003 ApJ 595, 1231 )ApJ 595, 1231 )

Break-out model: Break-out model: Imposed Imposed shearing motions and shearing motions and reconnection above the arcade in a quadruple system reconnection above the arcade in a quadruple system (Antiochos 1999 ApJ 510, 485)(Antiochos 1999 ApJ 510, 485)

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

Manchester, Manchester, Gombosi, De Zeeuw Gombosi, De Zeeuw and Fan. 2004, ApJ and Fan. 2004, ApJ 610, 588610, 588

Flux Rope Emerging From the Flux Rope Emerging From the Convection Zone into the CoronaConvection Zone into the Corona

Buoyant Buoyant section of section of the flux the flux rope rope reduced by reduced by a factor of a factor of twotwo

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Spontaneous Shearing MotionsSpontaneous Shearing Motions

Opposite sides Opposite sides of the flux rope of the flux rope move in move in opposite opposite directions as directions as the flux rope the flux rope expands. expands.

Motions are Motions are driven by the driven by the Lorentz force!Lorentz force!

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Development and Development and Eruption of Magnetic Eruption of Magnetic

Shear CoreShear Core

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The Lorentz Force Drives The Lorentz Force Drives the Shearing!!the Shearing!!

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

Dynamic Coupling By Dynamic Coupling By Shear FlowsShear Flows

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Shearing During Flux Emergence Shearing During Flux Emergence From a Magnetic LayerFrom a Magnetic Layer

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,

Conclusions Conclusions Shearing motions are a consequence of the Lorentz Shearing motions are a consequence of the Lorentz

force that arises as the magnetic field expands in a force that arises as the magnetic field expands in a highly stratified atmosphere which naturally explains:highly stratified atmosphere which naturally explains:

Magnitude of the shear velocity in the photosphere, Magnitude of the shear velocity in the photosphere, chromosphere and corona that occur at a chromosphere and corona that occur at a characteristic fraction of the local Alfven speed. characteristic fraction of the local Alfven speed.

Shearing motions transport axial flux into Shearing motions transport axial flux into expanding portion of flux rope or arcade and acts expanding portion of flux rope or arcade and acts to return the axial component to constant values to return the axial component to constant values along field linesalong field lines

These shear flows strongly couple the low These shear flows strongly couple the low corona to the high corona to the high photosphere and photosphere and convection zoneconvection zone

Fundamental AssumptionsFundamental Assumptions

The Sun possesses a gravitational field that results The Sun possesses a gravitational field that results in large pressure stratification of the atmospherein large pressure stratification of the atmosphere

Non-force-free magnetic structures pass that Non-force-free magnetic structures pass that through the photosphere into the corona to form through the photosphere into the corona to form active regions are MUCH larger than pressure active regions are MUCH larger than pressure scale height at the photosphere (140 km)scale height at the photosphere (140 km)

Magnetic fields possess a horizontal axial Magnetic fields possess a horizontal axial component in addition to an azimuthal componentcomponent in addition to an azimuthal component

The Lorentz force represented as (curl B) X B The Lorentz force represented as (curl B) X B reverses direction across the expanding structurereverses direction across the expanding structure

Very general as it applies to flux ropes, arcades Very general as it applies to flux ropes, arcades and magnetic layersand magnetic layers

Thank YouThank You