1. HXR emission and flare ribbon expansion – X3.8 flare of 17-Jan-2005
1Temmer M., 1Veronig A., 1Miklenic C., 2Vršnak B.
1IGAM/Institute of Physics, University of Graz, Austria
2Hvar Observatory, Faculty of Geodesy,
University of Zagreb, Croatia

2. RHESSI image reconstruction
Energy band: 30 – 100 keV
HXR images averaged over 5
RHESSI rotations (~ 20 sec)
CLEAN algorithm
Time range:
09:41: :06:42 UT

3. RHESSI HXR flux measurements
HXR flux measured over entire time series
separately for the strongest FPs moving within region 1 (positive polarity) and region 2 (negative polarity) 2 1

4. RHESSI HXR flux measurements1 2
Similar temporal behavior – indication of conjugate FPs

5. Reconnection rate – RHESSI FP motion2
points of intersection 1
points of intersection
B determined by:
MDI - mean of 36 arcsec2 box
around center of gravity from RHESSI (30-100keV) FPs
v determined by:
distance between point of
intersection and RHESSI FP ( to H
ribbon movement,  to neutral line)
time range: ~ 09:42 – 10:05 UT

6. RHESSI FP motion

7. Reconnection rate – H ribbon expansion
B determined by:
MDI - mean of 36 arcsec2 box around ribbon front measured along direction of motion ( to the neutral line)
v determined by:
distance measurements -
front of ribbon along direction of motion
time range: ~ 09:40 – 10:00 UT
Movie: H-alpha ribbon
and RHESSI FP motion

8. H ribbon expansion

9. Complexity of magnetic field
MDI magnetogram
H ribbon expansion (difference images)
RHESSI FPs keV

10. HXR FPs – avoiding of strong B
Nearest-in-time MDI magnetogram – RHESSI FPs keV
Countours ~ [-900, -500, 0, 500, 900] G

11. HXR FPs – avoiding of umbrae

12. Inclination of magnetic field lines??
strong magnetic field (mirror effect)
vertical field lines

13. Summary reconnection rate – H ribbons vs. HXR FPs
region 1: peaks are different and not contemporal
region 2: first peak coincides
correlation of B(t) and v(t)
no FPs within sunspot umbrae – inclination of magnetic field lines (?)
work in progress...