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A Topological Analysis of the Magnetic Breakout Model

A Topological Analysis of the Magnetic Breakout Model. by Rhona Maclean University of St Andrews 10 th August 2004 Collaborators: Colin Beveridge, Dana Longcope, Dan Brown and Eric Priest. Magnetic Charge Topology (MCT). Simple yet powerful Based on three assumptions:

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A Topological Analysis of the Magnetic Breakout Model

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  1. A Topological Analysis of the Magnetic Breakout Model by Rhona Maclean University of St Andrews 10th August 2004 Collaborators: Colin Beveridge, Dana Longcope, Dan Brown and Eric Priest

  2. Magnetic Charge Topology (MCT) • Simple yet powerful • Based on three assumptions: 1) point magnetic sources 2) sources lie in z=0 plane, the photosphere 3) potential field • Leads to explicit expression for magnetic field:

  3. The Skeletonof the Field Important structural features: • null points • spines • separatrices • separators

  4. Topological Bifurcations • Changes from one topological state to another • Two types: • local: change in number of nulls • global: change in structure of field; number of nulls unaffected

  5. What is Magnetic Breakout? • Explanation for onset of solar flare • central flux system initially enclosed by overlying arcade • shear applied near neutral line in photosphere • magnetic reconnection in vicinity of coronal null • overlying field weakens and allows originally enclosed flux to ‘break out’ explosively • Simplest configuration is delta sunspot • new flux emerging inside pre-existing sunspot region

  6. Delta Sunspot Model • Six unbalanced sources • Positive central source corresponds to emerging flux • Two separatrix domes prevent flux from connecting to infinity

  7. Experiment 1: Source Strength Before global spine-fan bifurcation: After bifurcation:

  8. Experiment 2: Source Position

  9. Experiment 3: Changing α • linear force-free field • central source fixed • series of 3 global spine-fan bifurcations (α=-0.01, -0.028 and -0.197) • 3rd bifurcation causes breakout

  10. Conclusions • New flux domain created in process of breakout • This can only be caused by global bifurcations • Examples here are global spine-fan and global separator • Breakout behaviour can occur due to change of: • source strength • source position • force-free parameter α

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