Post on 20-Dec-2015
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