Finding the Flow Field

1
Finding the Flow Field

• Need flow information!
• ideal evolution of coronal B(x,y,z,t) determined
  entirely by B(x,y,z,0) and v(x,y,0) get v
  wrong and get topology wrong!
• energy flux into corona via Poynting flux
• S (v x B) x B
• Contending methods are
• Local Correlation Tracking (LCT)
• Minimum Energy Functional (MEF)

2
Minimum Energy Functional

• We want v to solve induction eqns z-comp

• Solution is underdetermined by data!

• Longcope try minimizing kinetic energy!

3
Local Correlation Tracking

• Essentially, relate signal in before and
  after images to find the best shift.
• DISAD no info about z-comp. of v!
• DISAD v not necess. consistent w/physics!

4
Testing MEF LCT

• Use MHD simulations from Abbett et al. and Magara
  w/known v B
• Compare inverted velocities with truth.

5
MEF
6
MEF zoom
7
Fishers LCT
8
Novembers LCT
9
Preliminary results

• MEF outperforms our LCT codes
• marginally!
• All routines make notable mistakes!
• LCT fails in regions of strong
• MEF finds asymmetric solutions from symmetric data

10
Take-home points

• Problems exist with LCT!
• - our community needs to know its limits
• MEF is just beginning to be understood
• smoothings/thresholds alter results
• still, might be our best bet for finding v
• This work is still in progress!