[Loops] summaries on nanoflare debates in "coronal loop workshops"

[Markus J. Aschwanden]

Jim Klimchuk wrote:
> 2.  However, the transition region is an extremely thin layer that  
> moves up and down flux tubes in response to changes in the coronal  
> pressure resulting from heating and cooling.  It is very difficult  
> for me to see why the magnetic energy dissipation that gives rise to  
> heating should always follow this layer.  Dissipation in the thicker  
> chromosphere is much easier to swallow.
>


Dear Jim,

Well, the transition region was only an extremely thin layer in old  
hydrostatic models, which nobody
believes anymore. The current observations from TRACE, SoHO, and  
Hinode clearly show a highly
dynamic transition region, which shows all kind of variabilities  
(including the ominous spicules and
macrospicules) in a height range of h=2000-8000 km. Since the granular  
magneto-convection
stirs up the magnetic field on horizontal scales of w~1000-2000 km,  
this is exactly the height range where
you have most of the braiding, stressing, and reconnection, which is  
another plausibility argument
for the most likely place of plasma heating that fills up the  
overlying corona. Of course, dissipation
in the upper chromosphere is included, which provides all the mass for  
coronal filling with heated
plasma.

Cheers,
Markus

P.S. What Marco Velli alluded to, is most relevant for open-field  
regions such as coronal holes
	I gather. So we are talking about two different heating mechanisms  
for AR and solar wind.

____________________________________________
Dr. Markus J. Aschwanden
Solar & Astrophysics Laboratory
Lockheed Martin Advanced Techology Center
Org. ADBS, Bldg. 252
3251 Hanover St., Palo Alto, CA 94304, USA
Phone: 650-424-4001, FAX: 650-424-3994
URL: http://www.lmsal.com/~aschwand/
e-mail: aschwanden at lmsal.com
_______________________________________



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