Hi Markus,
Just a quick response
here….
From:
loops-bounces@solar.physics.montana.edu
[mailto:loops-bounces@solar.physics.montana.edu] On Behalf Of Markus J. Aschwanden
Sent: Friday, March 06, 2009 2:25
PM
To: A mailing list for scientists
involved in the observation and modeling ofsolar loop structures
Subject: Re: [Loops] summaries on
nanoflare debates in "coronalloopworkshops"
Dear Jim,
Ok, we agree we need heating of chromospheric material to fill coronal
loops (i.e. the well-established
chromospheric evaporation scenario for flares), which is a kind of a
secondary step. What we are not
sure is where is the primary energy release that leads up to the
chromospheric heating:
(1) Is it in coronal reconnection sites that produces precipitating
particles/donward conduction like in flares?
(2) Is it coronal nanoflares that could also produce precipitating
particles and/or downward conduction?
(3) Is it reconnection events in the chromosphere/transition region
Since I see a continous transition from high-lying reconnection regions
in large flares to low-lying
reconnection regions in microflares or EUV nanoflares, it appears
natural to me that there is a
continuouity from (1) to (3). But do we need case (2), which was
postulated by Parker ?
As long we do not have any observational measurements for case (2), it
remains a
theoretical construct. So, what observational diagnostics can people
come up to test case (2) ?
First, what is the difference between (1)
and (2) other than the magnitude of the energy release? Having asked
that, I would make the point that I see a fundamental difference between large
erupting flares and smaller compact flares. The evolution of the magnetic
field is completely different in the two cases.
I would argue that the observational evidence
for (2) is stronger than the observational evidence for (3). However, in
both cases the evidence might be thought of as circumstantial. It is
quite easy to reproduce loop observations (at least EUV loops) in terms of
bundles of strands heated by storms of nanoflares that occur in the corona. To
my knowledge, no one has demonstrated that the observations can be reproduced
by (3).
Have a nice weekend!
Jim
Markus
On Mar 6, 2009, at 11:11 AM, Klimchuk, James A. (GSFC-6710) wrote:
Markus, you are definitely right that all
coronal material originates in the chromosphere. If the energy release
(heating) occurs in the corona, a downward thermal conduction flux (and
possibly also a downward flux of nonthermal particles) causes material to
evaporate into the corona. That is the traditional view. What
other people (including you?) are proposing is that the energy release occurs
directly in the chromosphere or transition region, and this process both heats
the cool plasma and injects it upward.
Jim
From: loops-bounces@solar.physics.montana.edu [mailto:loops-bounces@solar.physics.montana.edu] On
Behalf Of Markus J.
Aschwanden
Sent: Friday, March 06, 2009 11:52 AM
To: A mailing list for scientists involved
in the observation and modeling ofsolar loop structures
Subject: Re: [Loops] summaries on nanoflare
debates in "coronalloopworkshops"
On Mar 6, 2009, at 8:44 AM, Klimchuk,
James A. (GSFC-6710) wrote:
By the way, I do NOT believe that observations necessarily point to low
altitude heating. My view is that observations are consistent with both
low altitude and high altitude heating. Perhaps this should be a topic
for Loops IV.
Jim
There is no way around to heat up first
chromospheric material to fill coronal
loops to produce the enhanced soft X-ray
and EUV emission we see from
coronal loops (like in flares). Any
heating mechanism that heats directly
in the corona, does not increase the local
density, so we would not see
any loops.
Markus
____________________________________________
Dr. Markus J.
Aschwanden
Solar &
Astrophysics Laboratory
Lockheed Martin
Advanced
Org. ADBS, Bldg. 252
Phone: 650-424-4001,
FAX: 650-424-3994
e-mail: aschwanden@lmsal.com
_______________________________________
____________________________________
_______________________________________________
Loops mailing list
Loops@solar.physics.montana.edu
https://mithra.physics.montana.edu/mailman/listinfo/loops
____________________________________________
Dr. Markus J.
Aschwanden
Solar &
Astrophysics Laboratory
Lockheed Martin
Advanced
Org. ADBS, Bldg. 252
Phone: 650-424-4001,
FAX: 650-424-3994
e-mail: aschwanden@lmsal.com
_______________________________________
____________________________________