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

[Klimchuk, James A. (GSFC-6710)]

Some quick comments....

 

1.  I agree with Markus and Marco that there is, in principle, no
problem having impulsive heating (nanoflares) in the low atmosphere
(chromosphere and transition region) of unipolar regions, as long as the
field is "tangled."  The resolvable events that Harry mentions are
interesting and important, but different from ordinary coronal heating.

 

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.

 

3.  The ten arguments that Markus gives in his paper are consistent with
heating in the transition region, but they are also consistent with
heating in the corona!  Thus, they do not disprove coronal nanoflares.
Perhaps we can discuss this in Florence.  (Markus:  I remember we went
over some of this during a wonderful lunch with retsina on a patio in
Santorini!  How about if we cover the rest with chianti?).

 

Cheers,

Jim

 

 

________________________________

From: loops-bounces at solar.physics.montana.edu
[mailto:loops-bounces at solar.physics.montana.edu] On Behalf Of Markus J.
Aschwanden
Sent: Thursday, March 05, 2009 10:16 AM
To: Hugh Hudson; A mailing list for scientists involved in the
observation and modelingof solar loop structures
Subject: [Loops] summaries on nanoflare debates in "coronal loop
workshops"

 

Dear Hugh,

 

Jim Klimchuk sent a great summary of the current status of a nanoflare
model around,

so it deals with all the PROs. An outside reader who wants to hear both
sides might be

interested to hear also the CONs, which you could find in the ApJ Letter
entitled

"An observational test that disproves coronal nanoflare heating models"
(Aschwanden

2008, ApJ 672, L135). The arguments made therein do not dismiss
nanoflares

altogether, but come to the conclusion that they occur in the transition
region,

rather than in the corona (as Parker originally suggested).

 

Cheers,

Markus

 

 

On Mar 3, 2009, at 7:32 AM, Klimchuk, James A. (GSFC-6710) wrote:





Dear loops friends,

 

     Here is a paper I wrote for the Hinode II conference proceedings.
In it, I try to do three things:  (1) review the arguments leading to
the conclusion that warm EUV loops must by bundles of strands heated by
storms of nanoflares (the flow chart some of you have asked about); (2)
reconcile the isothermal/multi-thermal debate in terms of the duration
of the nanoflare storm; and (3) address the possibility that loops can
be explained by thermal nonequilibrium.  Comments are welcomed.

 

Thanks,

James A. Klimchuk

 

____________________________________________

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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