[Loops] summaries on nanoflare debates in "coronal loopworkshops"

Thu Mar 5 15:36:36 MST 2009

To clarify, I was referring to the transition region layer in a (likely
sub-resolution) flux tube.  This will be ultra thin, but the layers will
occur at different heights in different flux tubes, so the transition
region plasma will span a wide range of heights in a typical
observation.

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 5:20 PM
To: A mailing list for scientists involved in the observation and
modeling ofsolar loop structures
Subject: Re: [Loops] summaries on nanoflare debates in "coronal
loopworkshops"

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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