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

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# Flows in NOAA AR 8210: An overview of MURI progress to thru Feb.’04 - PowerPoint PPT Presentation

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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Presentation Transcript
• 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
Q: Can we simulate relevant CME process(es)?

2. then drive boundary with velocities v(x,y,t) to store energy and, perhaps,

3. trigger an eruption!

MURI: drive simulations directly from data
• and best guess at initial field topology (also just presented)…(*)
• then evolve with MHD simulations, consistent w/photospheric evolution, conserving topology along the way
Q: How do we get velocities from magnetograms?

24 hour MDI movie on 1 May 1998

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!
LCT applied to MDI data
• Note shear across neutral line near (10,40) --- track (+/-) indep.
• Note flux emergence near (50,70) --- fools LCT!
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:
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.”
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.
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 :
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!
‘STORAGE & RELEASE’ PARADIGMQ: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