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. 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
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
q can we simulate relevant cme process es
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!

muri drive simulations directly from data
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
q how do we get velocities from magnetograms
Q: How do we get velocities from magnetograms?

24 hour MDI movie on 1 May 1998

three velocity reconstruction methods
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
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
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
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
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
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
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!
q what is the proximate cause of cmes
‘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
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