NLFFF Extrapolation for AR 10486

J.McTiernan

• *Chromospheric* Vector Magnetogram of AR 10486 (from Tom Metcalf) 18:46 UT

• Image is of Line of sight B (Bz)

• Contours are RHESSI images, 6-12 keV, 25-50 keV from 20:42:20 UT to 20:44:00 UT

Optimization method: Wheatland, Sturrock, Roumeliotis, 2000 Apj, 540, 1150

Optimization method (cont):

• Iterative process, start with Potential or linear FF field, extrapolated from magnetogram. (We prefer the potential field, since we expect the field to be potential far from the active region.)

• Be sure that B does not change on the boundary

• Calculate F, set new B = B + F*dt

• “Objective function”, L, is guaranteed to decrease, but the change in L (dL) becomes smaller as you go.

• Keep going until dL approaches 0.

http://sprg.ssl.berkeley.edu/~krucker/oct29.html

Conclusions:

Left hand FP moves along feature seen in Magnetogram, not sure about Right FP

Hard to see connectivity Currently processing photospheric

magnetograms.

29-Oct-2003 (cont.)

Early phase: only low-energy emission

29-Oct-2003 (cont.)

Low energy source (thermal? looptop?)

in between HXR footpoints.

29-Oct-2003 (cont.)

Note that the footpoints have moved. The loop arcade is visible in 195A which has some high T response.