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

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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?