Hi Markus,
Just a quick response here....
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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
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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
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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@lmsal.com
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_______________________________________________ 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 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@lmsal.com
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