[Loops] loops and thermal nonequilibrium

[Markus J. Aschwanden]

Dear Jim,

I read your paper with interest. You made a faithful attempt to explain five observed 
loop properties, which I really appreciate. The hydrodynamic simulations indeed show 
some puzzling condensation blobs that remain at stationary locations that seem not
to correspond to observations. However, I have the impression that this puzzling
effect, which you use as main argument that cooling loops are not consistent
with observations, is an artifact of the perfect pressure balance in your model.
When you watch TRACE movies, you will see that real coronal loops always evolve:
sway, expand, twist, or shrink on time scales of an hour, which slowly changes the 
pressure balance along the loop and would move condensation blobs to one side.
Loops are also always asymmetric, have diverging and converging cross-sections,
which causes siphon flows and drains condensation blobs to one side. So, I think
that the simulations are too idealized to tell us the long-term evolution. 
It is like balancing a ball on the Eiffeltower - an equilibrium solution is mathematically
possible - but is impossible in reality, there are always vibrations or wind ...
Perhaps you can repeat a simulation by superimposing some slowly-varying
pressure disturbances, use a varying cross-section, and fill it by upflows from
gentle chromospheric evaporation (more like in flares).

Cheers,
Markus



On Dec 4, 2009, at 2:04 PM, Klimchuk, James A. (GSFC-6710) wrote:

> Dear Loops Friends,
>  
>     If you are interested, the attached paper shows that coronal loops cannot be explained by thermal nonequilibrium.  The results appear to rule out the widespread existence of coronal heating that is both highly concentrated low in the corona and steady or quasi-steady (slowly varying or impulsive with a rapid cadence).  Comments are welcomed.
>  
> Best wishes,
> Jim
>  
> ********************************************************************************
> James A. Klimchuk
> NASA Goddard Space Flight Center
> Solar Physics Lab, Code 671
> Bldg. 21, Rm. 158
> Greenbelt, MD  20771
> USA
>  
> Phone:  1-301-286-9060
> Fax:      1-301-286-7194
> E-mail:  James.A.Klimchuk at nasa.gov
> Home page:  http://hsd.gsfc.nasa.gov/staff/bios/cs/James_Klimchuk.html
>  
> ********************************************************************************
>  
> <klimchuk_submitted.pdf>_______________________________________________
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____________________________________________
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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