pctr physics and “chewy nougats*” ssl, uc berkeley * this nomenclature due either to greg slater...
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PCTR Physics and“Chewy Nougats*”
SSL, UC Berkeley
* This nomenclature due either to Greg Slater or Sam Freeland, SXT data pioneers (most likely Greg)
ISSI Jan. 14, 2009
What is the prominence-corona transition region (PCTR)?
• Analogous (?) with the horizontally stratified ordinary TR, it separates the cold prominence from the hot corona
• It must be closely aligned with the separatrix between filament fields and cavity fields
• There are several approaches to understanding it: DEM, radio, filaments, hydrodynamic, MHD, each seemingly with its own literature
ISSI Jan. 14, 2009
Vernazza, Avrett & Loeser 1981
Behind the DEM approach
ISSI Jan. 14, 2009
Different views of the prominence-corona transition region
Kucera & Landi, 2008
Cirigliano et al. 2004
Antiochos & Klimchuk 1991 Heinzel et al. 2008
ISSI Jan. 14, 2009
“Chewy Nougat” There is a hot (soft X-ray) brightening around the cold prominence
Hudson et al. 1999
ISSI Jan. 14, 2009
The original nougat as seen on the disk
Some polar nougats found by Okumura
ISSI Jan. 14, 2009
EIT 284 EIT 304EIT 195
(Aulanier)
cavity
prominence
cavity
Filament material in dips of magnetic
field lines
Multiwavelength Nougat (thanks, Brigitte!)
ISSI Jan. 14, 2009
Nougats and flares?
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
ISSI Jan. 14, 2009
The Nougat’s basic messages
• If the PCTR is hotter than the corona surrounding it, the PCTR is unlikely to depend on static conduction as in normal TR models.
- We don’t really know if the nougats observed by SXT were hotter than the cavity, since the cavity temperature is hard to determine
• A filamentary (Chiuderi-type) PCTR would need to extend to heights well above the cold prominence material
• The PCTR is likely not to be a TR at all, just loops
ISSI Jan. 14, 2009
Is a “PCTR” as suchobservable or even relevant?
• Transport perpendicular to the field may be negligible;
“conductive heating is completely insignificant”*• If so the TR-temperature regions may be physically
separated from the prominence• Large perpendicular gradients of gas pressure would
be expected even at low plasma beta
*Anzer & Heinzel 2008
ISSI Jan. 14, 2009
Is “magnetic reconnection” observable or even relevant?
• The boundary between corona and prominence should correspond to a current system, which can support instabilities
• The standard reconnection model of a flare/CME involves shocks and jets, whose heating is not local
ISSI Jan. 14, 2009
Conclusions
• The “Nougat” signature may just be space-filling hot branches of the actual prominence fields
• Need a proper electrodynamic theory to understand the true (perpendicular) boundary structure in the corona
• Need high resolution and sensitivity to understand how hot loops relate to prominence-bearing fields
• The term “PCTR” is probably misleading, except to a spectroscopist*
*n.b. PCTR ≈ PETR
ISSI Jan. 14, 2009
Challenge
• Is it possible to show that the cavity itself does not consist of just the hot branches of the prominence field?