PCTR Physics and

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PCTR Physics andChewy Nougats

• SSL, UC Berkeley

This nomenclature due either to Greg Slater or
Sam Freeland, SXT data pioneers (most likely Greg)
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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

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Vernazza, Avrett Loeser 1981
Behind the DEM approach
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Different views of the prominence- corona
transition region
Kucera Landi, 2008
Cirigliano et al. 2004
Heinzel et al. 2008
Antiochos Klimchuk 1991
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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
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Multiwavelength Nougat (thanks, Brigitte!)
EIT 284
EIT 304
EIT 195
cavity
cavity
Filament material in dips of magnetic field lines
prominence
(Aulanier)
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Nougats and flares?
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The Nougats 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 dont 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

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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
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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

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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
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Challenge

• Is it possible to show that the cavity itself
  does not consist of just the hot branches of the
  prominence field?