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Flows in NOAA AR 8210: An overview of MURI progress to thru Feb.’04

Flows in NOAA AR 8210: An overview of MURI progress to thru Feb.’04. Modelers prescribe fields and flows ( B, v ) to drive eruptions in MHD simulations MURI goal: use data to do this! Must find ( B, v ). IVM & MDI tell us B . How do we get v ? LCT: commonly used method, but not acceptable!

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Flows in NOAA AR 8210: An overview of MURI progress to thru Feb.’04

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  1. Flows in NOAA AR 8210:An overview of MURI progress to thru Feb.’04 • Modelers prescribe fields and flows (B, v) to drive eruptions in MHD simulations • MURI goal: use data to do this! Must find (B, v). • IVM & MDI tell us B. How do we get v? • LCT: commonly used method, but not acceptable! • MEF: developed by UCB-MURI. • ILCT: modified LCT, developed by UCB-MURI. • NOAA AR 8210 Results

  2. Q: Can we simulate relevant CME process(es)? Traditionally, modellers: • start with magnetic field configuration B(x,y,z), 2. then drive boundary with velocities v(x,y,t) to store energy and, perhaps, 3. trigger an eruption!

  3. MURI: drive simulations directly from data • Start with photospheric mag’gram (IVM data just presented)…(*) • and best guess at initial field topology (also just presented)…(*) • then evolve with MHD simulations, consistent w/photospheric evolution, conserving topology along the way

  4. Q: How do we get velocities from magnetograms? 24 hour MDI movie on 1 May 1998

  5. Three Velocity Reconstruction Methods • Local Correlation Tracking (LCT) • Minimum Energy Fitting (MEF) • Induction + LCT (ILCT) • LCT: • i) cross-correlate subregions between two images; • ii) find shift that maximizes cross-correlation; • iii) interpret shift as velocity? tricky!

  6. LCT applied to MDI data • Note shear across neutral line near (10,40) --- track (+/-) indep. • Note flux emergence near (50,70) --- fools LCT!

  7. Minimum Energy Fitting (MEF): • LCT can’t drive codes: no vz, not consistent with • We developed method consistent w/z-comp. of ideal induction equation: • Represent unkown vector fields w/potentials:

  8. MEF, cont’d: • Induction eqn. determines : • Constrain by minimizing integrated velocity field, • this quadratic form resembles ‘energy,’ hence “MEF.” • assumes • Solution v(x,y) is “as small as possible, consistent with the data.”

  9. ILCT: Reinterpret LCT, a la Demoulin & Berger (2003) • Apparent horizontal motion can be either true horizontal motion, or vertical motion of a tilted field geometry.

  10. ILCT, cont’d: Find • Similar to MEF, use scalar potentials: • As w/MEF: indn eqn. fixes ; ass’d. • Instead of minimizing ‘energy’ to find , ILCT uses LCT to constrain :

  11. These data used in our AR 8210 simulations. (*)

  12. Conclusions Re: I-LCT, MEF • Some method of deriving from data is required to drive MHD codes. • Method must be consistent with magnetic field evolution, . (Will use .) • UCB-MURI team has developed two novel methods, where none existed before. • Our methods are only consistent with --- still more work to be done!

  13. Amari et al. Initial Velocity

  14. Cancellation flow in Amari et al. (BACK)

  15. Vector Field in AR 8210, c. 1 May Eruption

  16. NLFFF of AR 8210, from S.Regnier (BACK)

  17. Data-driven ZEUS Run (BACK)

  18. ‘STORAGE & RELEASE’ PARADIGM Q:What is the proximate cause of CMEs? • Energization: Field emerges (twisted?); flows in high-b photosphere stress ‘line-tied’ coronal field. • Impulsive Release: Corona undergoes massive, violent restructuring: a CME • Released Energy: is stored in currents, both those present at emergence and those induced by flows

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