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Separators : Fault Lines in the Magnetic Field

Separators : Fault Lines in the Magnetic Field. Dana Longcope Montana State University. Acknowledgments. Graham Barnes Colin Beveridge Steve Cowley Charles Kankelborg Isaac Klapper KD Leka. Tetsuya Magara Eric Priest Aad van Ballegooijen Brian Welsch NASA NSF/ATM AFOSR.

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Separators : Fault Lines in the Magnetic Field

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  1. SPD June 16, 2003 Separators: Fault Lines in the Magnetic Field Dana Longcope Montana State University

  2. SPD June 16, 2003 Acknowledgments Graham Barnes Colin Beveridge Steve Cowley Charles Kankelborg Isaac Klapper KD Leka Tetsuya Magara Eric Priest Aad van Ballegooijen Brian Welsch NASA NSF/ATM AFOSR

  3. SPD June 16, 2003 The Changing Magnetic Field PHOTOSPHERE THE CORONA SoHO MDI TRACE 171A 8/10/01 12:51 UT 8/11/01 9:25 UT (movie) 8/11/01 17:39 UT

  4. SPD June 16, 2003 Is this Reconnection? PHOTOSPHERE THE CORONA SoHO MDI TRACE 171A 8/10/01 12:51 UT 8/11/01 9:25 UT (movie) 8/11/01 17:39 UT

  5. SPD June 16, 2003 Outline • The XBP: A simple example of 3d reconnection • Quantifying Reconnection • Numerical simulation • A more complex example

  6. SPD June 16, 2003 Example: X-ray bright points EIT 195A image of “quiet” solar corona

  7. SPD June 16, 2003 Example: X-ray bright points Small specks occur above pair of magnetic poles (Golub et al. 1977 Harvey 1985)

  8. SPD June 16, 2003 Example: X-ray bright points

  9. SPD June 16, 2003 When 2 Poles Collide Photospheric flux concentrations sources of coronal field

  10. SPD June 16, 2003 When 2 Poles Collide All field lines from positive source P1 All field lines to negative source N1

  11. SPD June 16, 2003 When 2 Poles Collide Poles approach: domains intersect

  12. SPD June 16, 2003 When 2 Poles Collide Reconnection = new field lines

  13. SPD June 16, 2003 Post-reconnection Flux Tube TRACE observations 6/17/98 (Kankelborg & Longcope 1999)

  14. SPD June 16, 2003 Quantifying Reconnection • Why does it release energy? • How much energy can it release? • What about reconnection in • complex magnetic fields?

  15. SPD June 16, 2003 Quasi-static Evolution W(x) Equilibrium: W’(x)=0

  16. SPD June 16, 2003 Quasi-static Evolution W(x) W(x) Equilibrium: W’(x)=0 W(x) evolves … SLOWLY

  17. SPD June 16, 2003 Equilibrium: Minimum Energy W(x) dW=W’ dx W’(x)=0 potential

  18. SPD June 16, 2003 Mimimum w/ Constraints Constrained min. –195’ Absolute min. –249’ Constraint curve US 190

  19. SPD June 16, 2003 A new type of constraint… (Longcope 2001, Longcope & Klapper 2002) Photospheric sources move Number of field lines linking each pair remains constant No reconnection

  20. SPD June 16, 2003 A new type of constraint… (Longcope 2001, Longcope & Klapper 2002) Minimize: Subject to flux constraints

  21. SPD June 16, 2003 Separators: where domains meet Distinct flux domains P1 N2 N1 P2

  22. SPD June 16, 2003 Separators: where domains meet Distinct flux domains Separator at interface

  23. SPD June 16, 2003 Separators: where domains meet Distinct flux domains Separator at interface Closed loop encloses all flux linking P2-N1

  24. SPD June 16, 2003 The Separator Constraint Constraint only at separator Closed loop encloses all flux linking P2-N1 P1 N2 Fluxes in remaining domains: set by BC N1 P2

  25. SPD June 16, 2003 Minimum W subj. to constraint Current-free within each domain Constraint on P2-N1 flux current sheet at separator

  26. SPD June 16, 2003 Minimum W subj. to constraint Constraint on P3-N2 flux 2d version: X-point @ boundary of 4 domains becomes current sheet

  27. SPD June 16, 2003 Constrained Miniumum Min. subject to constraint Wmcc Wpot Potential field: absolute min. 0

  28. SPD June 16, 2003 Constrained Miniumum Min. subject to constraint Wmcc Current Wpot Potential field: absolute min. 0

  29. SPD June 16, 2003 Constrained Miniumum Min. subject to constraint Wmcc Free energy Wpot Potential field: absolute min. 0

  30. SPD June 16, 2003 Reconnection Wmcc Min. Energy Drops Eliminate constraint Wpot Potential field: absolute min. 0

  31. SPD June 16, 2003 Numerical Test (Longcope & Magara 2003) Model: Current sheet in flux-constrained equilibrium Simulation: J/B @ midplane

  32. SPD June 16, 2003 A complex Example Approximate p-spheric field using discrete sources

  33. SPD June 16, 2003 The domain of new flux Emerging bipole P01-N03 New flux connects P01-N07

  34. SPD June 16, 2003 Summary • 3d reconnection occurs at separators • Currents accumulate at separators  store magnetic energy • Reconnection there releases energy

  35. SPD June 16, 2003 A Case Study (movie) (movie) TRACE & SOI/MDI observations 6/17/98 (Kankelborg & Longcope 1999)

  36. SPD June 16, 2003 Post-reconnection Flux Tube Flux Accumulated over Projected to bipole location

  37. SPD June 16, 2003 Post-reconnection Flux Tube Flux Accumulated over

  38. SPD June 16, 2003 Numerical Test (Longcope & Magara 2003) • Initially: potential field • Move 2 inner sources • slowly • Solve 3d MHD eqns. • (inside box)

  39. SPD June 16, 2003 Numerical Test (Longcope & Magara 2003)

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