1. RHESSI OBSERVATIONS OF FLARE FOOTPOINTS AND RIBBONS H. Hudson and M. Fivian (SSL/UCB)

2. Summary Flare models involving large-scale magnetic reconnection may require effective electric fields as large as a few V/m (Kopp & Pneuman, 1986), a magnitude also represented as a magnetic reconnection rate. The hard X-ray footpoint sources in a flare present a particularly interesting view of this situation (Fletcher & Hudson, 2001). The hard X-rays show the bulk of the energy release (Lin & Hudson, 1976), while the coronal magnetic structure connected to the hard X-ray footpoints (within model errors) includes the site of particle acceleration. This poster presents an analysis of another event, that of March 18, 2003, making use of the integrated non-thermal energy input (Fivian, 2005). We find evidence for the expected correlations, but also discrepancies.

3. Energy Inflow and Footpoint Motion Poynting flux into reconnection region: Conservation of magnetic flux: Correlation of energy deposition rate and footpoint velocity: v in v fp

4. Total Deposited Energy and Footpoint Separation Integrating Correlation of Deposited Energy with footpoint separation assuming B corona, B fp, A r are constant

5. Data overview, 18-Mar-2003 event

6. TRACE ribbons and RHESSI footpoints

7. Imaging and Spectroscopy Image footpoint Determine centroids Timeseries color-coded over Magnetogram Fit timeseries of spectra Determine energy of non-thermal component

8. X-ray Flux and Footpoint Separation

9. Deposited Energy vs Footpoint Separation Mar 18, 2003 From Magnetogram: B fp  500 G Assume: B corona  B fp /5 A r = L h ·L v  360 arcsec 2 Perpendicular motion From HXR image: L h  5-10 arcsec  L v  36-72 arcsec (lower limit !!)

10. Mar 18, 2003Jul 23, 2002 Comparison with analysis of July 23 flare

11. Conclusions Can add flare of March 13, 2003 to list of events showing correlated footpoint motion and energy release RHESSI data can precisely locate the energy sources The epoch 00:31-00:35 UT in the July 23, 2002 event clearly does not match the assumed model

12. Remarks We (and others) use a crude simplification of the standard reconnection cartoon But restructuring (plasma motions), rather than reconnection, is the essential phenomenon The apparent motions imply complicated restructuring patterns