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SLIDE SHOW 4 - Coronal Loops

CONTENTS Large-Scale Corona (eclipse) - images - models Local Regions of Corona (active regions) - images - models 3. Topology of Corona. SLIDE SHOW 4 - Coronal Loops. ("crown") -- See at ECLIPSE of Sun. 1. LARGE-SCALE CORONA. Another ECLIPSE.

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SLIDE SHOW 4 - Coronal Loops

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  1. CONTENTS • Large-Scale Corona (eclipse) - images - models • Local Regions of Corona (active regions) - images - models 3. Topology of Corona SLIDE SHOW 4 - Coronal Loops

  2. ("crown") -- See at ECLIPSE of Sun 1. LARGE-SCALE CORONA

  3. Another ECLIPSE

  4. X-ray telescope on Skylab (1974)

  5. Yohkoh

  6. How Model Global Corona ? Use observed Br at surface (on grid or treat as series of sources) and construct solutions to j x B = 0 Simplest - assume j = 0, so that

  7. Example Observed Calculated [Colour is velocity]

  8. 2. LOCAL REGIONS OF CORONA TRACE (Active region)

  9. Coronal Loops at Limb

  10. Ex 1. Potential Model of B above Supergranule

  11. New Model (2005)

  12. Ex 2. Observations of Location of Loops in an Emerging Flux Region

  13. Compare with Potential, Linear fff, Nonlinear fff (2005) Best fit -- nonlinear fff

  14. Ex 3. Magnetic Fragments in Superganule Magnetogram movie (white +ve , black -ve)- 20 hrs • Flux emerges ... cancels • Reprocessed very quickly (14 hrs !!!)

  15. “Magnetic Carpet” Magnetic sources in surface are concentrated Use observed Bn at photosphere to calculate coronal B from Laplace’s equation

  16. From observed magnetograms - construct coronal field lines - statistical properties: most close low down Time for all field lines to change connections only 1.5 hours

  17. 3. TOPOLOGY of CORONAL B In 2D -- Separatrix curves In 3D -- Separatrix surfaces -- intersect inSeparator

  18. Structure of Null Point Simplest B = (x, y, -2z) 2 families of field lines through null point: Spine Field Line FanSurface

  19. ? Reveal structure of complex field ? plot a few arbitrary B lines E.g. 2 unbalanced sources SKELETON -- set of nulls, separatrices -- from fans

  20. 2 Unbalanced Sources Skeleton: null + spine + fan (separatrix dome)

  21. Three-Source Topologies

  22. Simplest configuration w. separator: Sources, nulls, fans -> separator

  23. Looking Down on Structure Bifurcations from one state to another

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