Axions from the Sun? H. S. Hudson SSL, UC Berkeley hhudson/presentations/berkeley.090220
Solar evidence for magnetic reconnection H. S. Hudson Space Sciences Lab, UC Berkeley.
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Transcript of Solar evidence for magnetic reconnection H. S. Hudson Space Sciences Lab, UC Berkeley.
Solar evidence for magnetic reconnection
H. S. Hudson
Space Sciences Lab, UC Berkeley
The Sun is remote
• Virtually all knowledge of solar conditions comes from remote sensing in the form of images and spectra
• There is no observational access to the fundamental scales of the plasma
• There are only limited signatures of non-thermal effects detectable by telescopes
• There is some indirect information available from the solar wind and from particles
Harry Petschek Symposium, March 22, 2006
G. A. Gary, Solar Phys. 203, 71 (2001)
(vA ~ 200 -1/2 km/s)
CH
Distribution of coronal plasma
Harry Petschek Symposium, March 22, 2006
The Semantics Problem
• Apparently, “reconnection” means changes of magnetic flux connectivity between distinct domains
• To a laboratory or space-plasma physicist, “reconnection” implies the microphysics
• To an astronomer, “reconnection” tends to be synonymous with “energy release”
• Are we talking about geometry, physics, or energy flow?
The answer is probably “YES”
Harry Petschek Symposium, March 22, 2006
Coronal reconnection sites
• “Emerging flux”
• Flares
• Coronal mass ejections
• Other coronal phenomena• Nanoflares?
Harry Petschek Symposium, March 22, 2006
QuickTime™ and aTIFF (Uncompressed) decompressor
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QuickTime™ and aTIFF (Uncompressed) decompressor
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Yohkoh soft X-rays Magnetic field
Harry Petschek Symposium, March 22, 2006
TRACE movie showing flux emergence
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Harry Petschek Symposium, March 22, 2006
Possible signatures in flares/CMEs
Phenomenon Reference Comment“Disconnection” Illing-Hundhausen Flux ropes instead?
SADs McKenzie-Hudson Flows too slow?
Helix formation One TRACE movie Fits cartoon well
Flare cusp shape SXT images In gradual phase
X-ray jets Shibata Promising
Ribbon edges H observers Fits cartoon well
Termination shock Masuda et al. 1994 No radio observation
Current sheets UVCS and RHESSI Promising?
Footpoint motions HUV, HXR Promising
Anzer-Pneuman 1982
Harry Petschek Symposium, March 22, 2006
Reconnection in flares/CMEs?
CuspQuickTime™ and a
TIFF (Uncompressed) decompressorare needed to see this picture.
QuickTime™ and aTIFF (Uncompressed) decompressor
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Jet
SAD QuickTime™ and aYUV420 codec decompressor
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QuickTime™ and aPhoto decompressor
are needed to see this picture.Helix Current sheet (?)
Harry Petschek Symposium, March 22, 2006
Giovanelli (1948)
Gold & Hoyle (1961)
Longcope & Noonan (2000)Anzer & Pneuman (1982)
Cartoons stand in for theory
http://solarmuri.ssl.berkeley.edu/~hhudson/cartoons/
Harry Petschek Symposium, March 22, 2006
Problem of time scales
• Present theory (numerical models) cannot deal with the range of scales involved in a flare
• Can we then trust the microphysics to dictate the behavior of the largest scales? How do we know when reconnection will happen?
Harry Petschek Symposium, March 22, 2006
A breakthrough: separator reconnection between active regions (Longcope et al. 2005 case study) - an end-to-end study
Harry Petschek Symposium, March 22, 2006
Tsuneta, ApJ 456, L63, 1996: Petschek reconnection at an X point?
Harry Petschek Symposium, March 22, 2006
Longcope et al., ApJ 630, 569 (2005): Not a Petschek X-point, but 3D separator
reconnection instead
Harry Petschek Symposium, March 22, 2006
A breakthrough: reliable observations of before/after fields (Sudol & Harvey 2005 case study) show permanent changes
Harry Petschek Symposium, March 22, 2006
GONG
SOHO/MDI
B dB
Flare of 2003 Oct. 29
Harry Petschek Symposium, March 22, 2006
Flare of 2001 Aug. 25GONG + TRACE 1600A
Other examples withGOES times
Harry Petschek Symposium, March 22, 2006
Interpretation of field changes
• The line-of-sight photospheric B field changes impulsively and irreversibly during every flare
• The patterns of change can guide us to a more complete understanding of the coronal restructuring: Will we at last have the means to observe flux transfer in flares directly?
• This can done much better with vector magnetograms at rapid temporal cadence (<< 1 min) - Solar-B? SDO? ATST? FASR?
Harry Petschek Symposium, March 22, 2006
Conclusions
• Magnetic reconnection certainly occurs on the quiet Sun (by the geometrical definition)
• It is not clear yet whether reconnection plays a causal role in flares or CMEs, but the circumstantial evidence is strong in the gradual phase
• Separator reconnection describes the energetics in the end-to-end study of Longcope et al.
Harry Petschek Symposium, March 22, 2006
Open questions
• Why does reconnection not happen more freely?
• What sets the time scale for flare occurrence?
• How do we understand the dominant non-thermal effects?