1. Fluxon Modeling of Low-β Plasmas: Current Status & Results SHINE, Whistler August 1, 2007 SHINE, Whistler August 1, 2007 Fluxon modeling of active regions: status & future work C.E. DeForest, L. RACHMELER, C. C. KANKELBORG, & A.R. Davey Fluxon modeling of active regions: status & future work C.E. DeForest, L. RACHMELER, C. C. KANKELBORG, & A.R. Davey

2. DeForest 2007 A Quasi-Lagrangian Approach to MHD (vs. Eulerian grids) Concept: use the field line analogy backwards. Represent the field as a collection of “fluxons” - discrete field lines. Fluxons discretize topology, preventing unwanted reconnection (half of numeric resistivity) Field-aligned grids prevent fluid diffusion across field lines (the other half of numeric resistivity) Allow magnetic and gas forces to push the grid around (frozen-in flux condition).

3. DeForest 2005 Relaxation: a Low&Lou NLFFF (Over A photosphere)

4. 6x6 twisting flux tube: Fluxon simulation: - Time dependent sim - Emerging/twisting flux tube - Planar photosphere - No surrounding field - Low-β / force-free field Results: (not surprising): - No amount of twist is unstable - No dips form (more on that) - α (twist per unit length): * increases at first * decreases late in the sim

5. DeForest 2007 10-twist system Single NLFFF solution Topology: 10 twists Surrounding field: vacuum “Finite” size: 3e7 x sep. dist. Would tether-cut in reality (large, strong vertical current sheet)

6. DeForest 2007

8. flux rope before reconnection

9. DeForest 2007 flux rope after reconnection

10. DeForest 2007 Conclusions Fast CME ejection is in principle possible even without reconnection (but this scenario is unlikely for most CMEs due to the high required twist) MHD instability (“herniation”) may be important to other systems such as macrospicules or microjets where more twist is available. Tasks for Year 3: Code up a sim of the May 13 event and identify a current threshold that flares about the right time (using boundaries supplied by the TR&T group) Compare calculated magnetic energy in the May 13 event to the known flare & CME energies Release FLUX to the CCMC (write manual & test cases)