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

RHESSI image reconstruction Energy band: 30 – 100 keV HXR images averaged over 5 RHESSI rotations (~ 20 sec) CLEAN algorithm Time range: 09:41:46 - 10:06:42 UT

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

RHESSI HXR flux measurements 1 2 Similar temporal behavior – indication of conjugate FPs

Reconnection rate – RHESSI FP motion 2 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

RHESSI FP motion

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

H ribbon expansion

Complexity of magnetic field MDI magnetogram H ribbon expansion (difference images) RHESSI FPs 30-100 keV

HXR FPs – avoiding of strong B Nearest-in-time MDI magnetogram – RHESSI FPs 30-100 keV Countours ~ [-900, -500, 0, 500, 900] G

HXR FPs – avoiding of umbrae

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

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...