1 / 18

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!

darcie
Download Presentation

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

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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

More Related