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<title>RE: [Loops] summaries on nanoflare debates in
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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Sounds good!<o:p></o:p></span></font></p>
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10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Jim<o:p></o:p></span></font></p>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
loops-bounces@solar.physics.montana.edu
[mailto:loops-bounces@solar.physics.montana.edu] <b><span style='font-weight:
bold'>On Behalf Of </span></b>Nakariakov, Valery<br>
<b><span style='font-weight:bold'>Sent:</span></b> Monday, March 09, 2009 1:29
PM<br>
<b><span style='font-weight:bold'>To:</span></b> A mailing list for scientists
involved in the observation and modeling ofsolar loop structures; A mailing
list for scientists involved in the observation andmodelingofsolar loop
structures; A mailing list for scientists involved in the observation
andmodelingofsolar loop structures<br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [Loops] summaries on
nanoflare debates in "coronalloopworkshops"</span></font><o:p></o:p></p>
</div>
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12.0pt'><o:p> </o:p></span></font></p>
<p style='margin-bottom:12.0pt'><font size=2 face="Times New Roman"><span
style='font-size:10.0pt'>Hi Jim,<br>
<br>
I was talking about the waves with observed (relatively low, > 2 min)
periods and low amplitudes, which are not likely to<br>
energetically contribute to heating,<br>
but are excellent diagnostics tools. They have already been used for this
purpose and gave results which indicate the presence of fine (sub-resolution)
structuring.<br>
<br>
Concerning triggering of reconnection events by waves: it can be achieved by
waves of relatively low amplitude and this option, I think,<br>
needs detailed attention.<br>
<br>
Cheers,<br>
<br>
Valery<br>
<br>
<br>
-----Original Message-----<br>
From: loops-bounces@mithra.physics.montana.edu on behalf of Klimchuk, James A.
(GSFC-6710)<br>
Sent: Mon 09/03/2009 17:02<br>
To: A mailing list for scientists involved in the observation andmodeling
ofsolar loop structures; A mailing list for scientists involved in the
observation and modelingofsolar loop structures<br>
Subject: Re: [Loops] summaries on nanoflare debates in
"coronalloopworkshops"<br>
<br>
Valery and Robert,<br>
<br>
<br>
<br>
Thanks for bringing up waves. I have two quick points.<br>
<br>
<br>
<br>
1. The internal plasma structure of a loop (multi-stranded or not) is<br>
determined by the heating and cannot be decoupled from the wave<br>
dissipation (unless the wave is energetically insignificant). See<br>
Section 4.3 of the attached.<br>
<br>
<br>
<br>
2. There may be different opinions of what is meant by
"nanoflare."<br>
Some people define it to be an identifiable point-like brightening that<br>
probably occurs in a tiny bipole. Most loops modelers define it to be<br>
an impulsive energy release in a long and unresolved magnetic strand.<br>
It cannot be directly observed. With this definition, even resonant<br>
wave absorption produces nanoflare heating (also explained in Sections<br>
4.3 and 4.2). I'm very curious about David Berghmans' talk and have my<br>
doubts about the conclusions!<br>
<br>
<br>
<br>
Cheers,<br>
<br>
Jim<br>
<br>
<br>
<br>
________________________________<br>
<br>
From: loops-bounces@solar.physics.montana.edu<br>
[<a href="mailto:loops-bounces@solar.physics.montana.edu">mailto:loops-bounces@solar.physics.montana.edu</a>]
On Behalf Of<br>
Nakariakov, Valery<br>
Sent: Saturday, March 07, 2009 9:02 AM<br>
To: A mailing list for scientists involved in the observation and<br>
modeling ofsolar loop structures; A mailing list for scientists involved<br>
in the observation and modelingofsolar loop structures<br>
Subject: Re: [Loops] summaries on nanoflare debates in<br>
"coronalloopworkshops"<br>
<br>
<br>
<br>
Hi Robertus, hi all,<br>
<br>
>however, both hinode and very recent <st1:place w:st="on">rosa</st1:place>
observations have shown the<br>
omnipotent presence of mhd waves ... that have the necessary poyting<br>
flux to heat the lower<br>
atmosphere or corona. so, it is not just reconnection!<br>
<br>
There are two important aspects, in my opinion:<br>
(a) even if the Poynting flux is sufficient, there also should be<br>
sufficiently effective mechanisms for the wave energy dissipation at a<br>
reasonable height. The efficiency of both phase mixing and RA is<br>
determined by the steepness of the transverse structuring of the<br>
waveguiding plasma structures.<br>
<br>
Structuring is definitely an unknown parameter, as you've pointed out:<br>
>if (IF) we want to get closer to loop fine structure<br>
(multi-thread vs whatever) or uncover the operating heating function, a<br>
very promising and currently already available way is of the one by<br>
magneto-seismology.<br>
<br>
I agree. As I have mentioned in this forum before, there are several<br>
coronal seismological indications of the subresolution structuring of<br>
the corona. But, what is important is not only the spatial scale of<br>
structuring, but also the gradients of the plasma parameters.<br>
<br>
(b) The amplitudes of the observed transverse waves are sufficiently<br>
high to produce a significant change of the magnetic field in the<br>
vicinity of the potential reconnection<br>
sites. Hence, the waves can effectively contribute to reconnection, and<br>
then the separation of "wave-based" and
"reconnection-based" mechanisms<br>
for heating seems to be a bit too artificial.<br>
<br>
All the best,<br>
<br>
Valery<br>
<br>
<br>
<br>
</span></font><o:p></o:p></p>
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