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

[Marco Velli]

Dear all,
this is an interesting conversation. My tuppence: parker nanoflares  
work precisely in unipolar reasons, as it is the tangential stresses  
which are relaxed
in the original parker scenario. The presence of multiple polarities  
changes this in a way which has never been quantitatively estimated.
I would like to point you to the 2008/07 papers by Rappazzo and myself  
which I believe contain the only scalings for the Parker flt scenario
which have numerical simulation confirmation.

@ARTICLE{2008ApJ...677.1348R, author = {{Rappazzo}, A.~F. and {Velli},  
M. and {Einaudi}, G. and {Dahlburg}, R.~B. }, title = "{Nonlinear  
Dynamics of the Parker Scenario for Coronal Heating}", journal =  
{\apj}, archivePrefix = "arXiv", eprint = {0709.3687}, keywords =  
{Magnetohydrodynamics: MHD, Sun: Corona, Sun: Magnetic Fields,  
Turbulence}, year = 2008, month = apr, volume = 677, pages =  
{1348-1366}, doi = {10.1086/528786}, adsurl = {http://adsabs.harvard.edu/abs/2008ApJ...677.1348R 
}, adsnote = {Provided by the SAO/NASA Astrophysics Data System} }

On Mar 5, 2009, at 7:31 AM, Harry Warren wrote:

> Markus et al.,
>
> It is unambiguous that there is a lot of dynamic activity going on  
> in the
> transition region. However:
>
> . . . a significant fraction of the Sun's magnetic flux closes at low
> heights (several Mm), so it is unclear how much of this activity is  
> related
> to what we see in the corona.
>
> . . . my impression of SOT magnetic field measurements is that  
> active region
> plage (where many active region loops are rooted) is unipolar. It is  
> hard to
> see how small-scale reconnection in the transition region could be  
> important
> here. I could be wrong about this! I'm sure that an SOT person could  
> provide
> a more definitive answer.
>
> Best wishes,
>
> Harry
>
> //  
> ---------------------------------------------------------------------
> // Harry P. Warren             phone : 202-404-1453
> // Naval Research Laboratory   fax   : 202-404-7997
> // Code 7673HW                 email : hwarren at nrl.navy.mil
> // Washington, DC 20375        www   : http://tcrb.nrl.navy.mil/~hwarren
> //  
> ---------------------------------------------------------------------
>
>
> From: loops-bounces at mithra.physics.montana.edu
> [mailto:loops-bounces at mithra.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 modeling of 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
> _______________________________________
> ____________________________________
>
>
>
>
>
>
> _______________________________________________
> Loops mailing list
> Loops at solar.physics.montana.edu
> https://mithra.physics.montana.edu/mailman/listinfo/loops
>