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Patterns of Large-Scale Flux Emegence

Patterns of Large-Scale Flux Emegence. Chip Manchester, Fang Fang, Bill Abbett , Bart van der Holst. Outline. Much more advanced simulations of flux emergence in a realistic convection zone and corona (Abbett 2007)

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Patterns of Large-Scale Flux Emegence

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  1. Patterns of Large-Scale Flux Emegence Chip Manchester, Fang Fang, Bill Abbett, Bart van der Holst

  2. Outline • Much more advanced simulations of flux emergence in a realistic convection zone and corona (Abbett 2007) • Confirm earlier simulations and show that shear flows driven by the Lorentz force are extremely robust. • Shear flows dominate the transport of magnetic energy from the convection zone into the corona • Lorentz-force driven shear flow are a mechanism by which energy builds up for CMEs, flares, filament eruptions

  3. Emergence of a 3D Flux Rope in a Simple Polytropic Atmosphere • Fan 2001, Manchester et al. 2004

  4. 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

  5. Current Sheet Formation • Shear Afven waves cause axial flux to accumulate where the rope expands • The sheared core lifts off and erupts forming a current sheet • In Parker’s picture, localized expansion along the length of the rope, causes torsional Alfven waves that transport azimuthal flux Cosmical Magnetic Fields 1979

  6. Flux Rope Eruption • Rope eruption occurs with the passage of a shear Alfven wave Fang et al. ApJ 2010 714, 1649

  7. Separation of Flux Rope at Sigmoid Current Sheet To the left, an iso-surface of current density and field lines are shown over the photosphere colored to show Bz. Right: Eruption of flux rope into the corona.

  8. Larger Scale Simulations • Large simulation recovers similar results

  9. Realistic Simulation of Flux Emergence • Model from upper convection zone to corona Abbett 2007 • Parameterized radiative losses • OPAL EOS • Magnetic Flux proportional coronal heating Fang et al. ApJ 2010 714, 1649

  10. Realistic Convection Zone Model vertical velocity shown in gray scale

  11. Emphemeral Region Scale 1018-19 Mx

  12. Magnetic Field Evolution at the Photosphere • Development of sheared field at the photosphere

  13. Comparison of EIS Shear Velocity The image on the left is an EIS Doppergram of AR10930 observed December 2006 over the western limb of the Sun. The image on the right shows shear flows ½ driven by the Lorentz ½ siphon flow parallel to B

  14. Magnetic Pore Scale 6x1020 Mx 30Mm scale

  15. Flow Patterns are Much More Complicated • White line = PIL • Color = Ux

  16. Photospheric Energy Flux • Total energy from horizontal flows is 1x1030 ergs 1% necessary for CMEs and X-class flares Manchester et al. 2004 Fang et al. 2010

  17. Magnetic Shear in AR6982 • Falconer 2001 JGR 106, 25185

  18. MHD Code: BATSRUS(SC/EE/IH/GM) • Block Adaptive Tree Solar-wind Roe-type Upwind Scheme • Conservative finite-volume method • Shock-capturing Total Variation Diminishing schemes • Explicit, implicit & explicit/implicit time stepping • Semi-relativistic MHD equations • Splitting the magnetic field into B0 + B1 • Various methods to control the divergence of B • AMR & data structure • Adaptive self-similar blocks • Octree data structure • Parallel implementation • Fortran-90 with MPI • Near-perfect scaling to >1500 PEs (explicit time-stepping) • Good scaling to ~256 PEs with implicit time-stepping • Highly portable (SGI Origin, Altix, Compaq, PC clusters, X-serve clusters, etc)

  19. SWMF Performance • Key algorithms to achieve this speed: • Concurrent/mixed execution of components. • Adaptive grid in BATSRUS (SC, IH and GM). • Implicit time stepping in SC/Heat Conduction.

  20. Eruptive Event Generator Inner Heliosphere Photosphere to Corona Solar Corona Solar Energetic Particles Coming Soon Global Magnetosphere Radiation belts SWMF Coming Soon Coming Soon Plasmasphere Inner Magnetosphere Polar Wind Ionosphere Electrodynamics Upper Atmosphere The SWMF is freely available at http://csem.engin.umich.edu

  21. Conclusions • Flux emergence from a realistic convection zone into the corona. • Shearing mechanism is extremely robust and persists even in a granular convection zone • Shear flows are slower and more structured than in the idealized polytropic model. • Shear velocities are in better agreement with observations of the photosphere and low corona. • The large scale pattern of magnetic shear in active regions is found, which increases with proximity to the neutral line • Transport of magnetic energy from the convection zone to the corona is dominated by horizontal flows • No Eruptions yet. Scaled to the size of an AR, shear flows would easily provide 1032 ergs. • Beginning simulations of 60x90 Mm & 1022Mx

  22. Thank You

  23. 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. 2003 ApJ 595, 1231 ) • Break-out model: Imposed shearing motions and reconnection above the arcade in a quadruple system (Antiochos 1999 ApJ 510, 485)

  24. 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

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