[Loops] loops and thermal nonequilibrium

Tue Dec 8 07:18:10 MST 2009

Hi Markus,

    Maybe the paper wasn't clear, but all the simulations we present have asymmetric heating.  That's what the asymmetry factor in the third column of the table refers to.  The condensations are definitely not stationary, as we discuss in several places and can be clearly seen in Figure 1, for example.  All of the condensations are eventually pushed to the chromosphere by a pressure imbalance.  Also, there is evaporation happening during most of the evolution, as discussed on page 10, for instance.
     Please let me know if you need more details.

Thanks,
Jim

From: loops-bounces at solar.physics.montana.edu [mailto:loops-bounces at solar.physics.montana.edu] On Behalf Of Markus J. Aschwanden
Sent: Monday, December 07, 2009 4:47 PM
To: A mailing list for scientists involved in the observation and modeling of solar loop structures
Subject: Re: [Loops] loops and thermal nonequilibrium

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<mailto:James.A.Klimchuk at nasa.gov>
Home page:  http://hsd.gsfc.nasa.gov/staff/bios/cs/James_Klimchuk.html

********************************************************************************

<klimchuk_submitted.pdf>_______________________________________________
Loops mailing list
Loops at solar.physics.montana.edu<mailto:Loops at solar.physics.montana.edu>
https://mithra.physics.montana.edu/mailman/listinfo/loops

____________________________________________
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<mailto:aschwanden at lmsal.com>
_______________________________________
____________________________________

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mithra.physics.montana.edu/pipermail/loops/attachments/20091208/9159f57a/attachment-0003.html>