RHESSI OBSERVATIONS OFFLARE FOOTPOINTS

AND RIBBONS

H. Hudson and M. Fivian (SSL/UCB)

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.

Energy Inflow and Footpoint Motion

Poynting flux into reconnection region:

Conservation of magnetic flux:

Correlation of energy deposition rate and footpoint velocity:

vin

vfp

Total Deposited Energy and Footpoint Separation

Integrating

Correlation of Deposited Energywith footpoint separation

assuming Bcorona, Bfp, Ar are constant

Data overview, 18-Mar-2003 event

TRACE ribbons and RHESSI footpoints

Imaging and Spectroscopy• Image footpoint• Determine centroids• Timeseries color-coded

over Magnetogram

• Fit timeseries of spectra• Determine energy of non-thermal

component

X-ray Flux and Footpoint Separation

Deposited Energy vs Footpoint Separation

Mar 18, 2003

From Magnetogram:

Bfp 500 G

Assume:

Bcorona Bfp/5

Ar = Lh·Lv 360 arcsec2

Perpendicular motion

From HXR image:

Lh 5-10 arcsec

Lv 36-72 arcsec (lower limit !!)

Mar 18, 2003 Jul 23, 2002

Comparison with analysis of July 23 flare

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

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