[Loops] summaries on nanoflare debates in "coronalloopworkshops"

Fri Mar 6 17:44:47 MST 2009

"What is there before the flare?" - I attach a lightweight paper on  
this seldom-asked question.

Hugh

On Mar 6, 2009, at 2:41 PM, Bradshaw, Stephen J wrote:

>
> Dear all,
>
> It seems to me that the heating is responsible for establishing the  
> temperature profile of a coronal loop. Therefore, there is not much  
> point in asking a-priori whether it occurs in the chromosphere, TR  
> or corona. The crucial issue, I believe, is what are the conditions  
> (magnetic AND plasma) BEFORE the onset of heating? i.e. field  
> strengths, densities, etc. Once these have been established (with  
> great difficulty, I suspect) then one may ask what is it about  
> these conditions that leads to a particular height and / or spatial- 
> scale preference for the heating mechanism. This may help to avoid  
> the apparently messy necessity of specifying the location of the  
> heating with reference to a particular temperature regime...
>
> Regards,
>
> Steve
>
>
> Dr Stephen J. Bradshaw
>
> NASA Goddard Space Flight Center
> Solar Physics Laboratory, Code 671
> Greenbelt, MD 20771
> USA
>
> Tel:  1-301-286-9682
>
>
> ________________________________________
> From: loops-bounces at solar.physics.montana.edu [loops- 
> bounces at solar.physics.montana.edu] On Behalf Of Markus J.  
> Aschwanden [aschwanden at lmsal.com]
> Sent: Friday, March 06, 2009 7:25 PM
> To: A mailing list for scientists involved in the observation and  
> modeling of solar 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) ?
>
> 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 at solar.physics.montana.edu<mailto:loops- 
> bounces at solar.physics.montana.edu> [mailto:loops- 
> bounces at 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 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<mailto:aschwanden at lmsal.com>
> _______________________________________
> ____________________________________
>
>
>
>
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> >
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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 at lmsal.com<mailto:aschwanden at lmsal.com>
> _______________________________________
> ____________________________________
>
>
>
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+++++++++++++++++++++

In medias res
hhudson at ssl.berkeley.edu
+1 (510) 643-0333

AST:7731^29u18e3

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