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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Hi Hugh,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> Thanks also to you for your
comments. Harry (thanks again!) is completely correct that my use of the
term “nanoflare” simply means an impulsive energy release on a
magnetic strand. There are many possible mechanisms that have this
property, including waves. In fact, I do not know of a single mechanism that
does not have this property under realistic conditions! Having said that,
if the impulsive bursts repeat sufficiently rapidly on a given strand, the
plasma conditions will not be greatly different from quasi-static.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> I’m confused by your suggestion that
“flow” is the same as “thermal nonequilibrium.”
Flows can happen for many reasons, with varying effects on the loop properties.
As I indicated in my response to Leon, steady flows cannot reproduce most
observed warm loops, and neither can the flows associated with thermal
nonequilibrium.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> Regarding nanoflares being a purely theoretical
construct with no observational support, all I can say is that impulsive
sub-resolution energy bursts are the only known way to explain the observed
properties of warm loops (fan loops at the perimeters of active regions, of the
type Leon has mentioned, may have an alternate explanation?). If you can
point to a rigorous paper that offers another explanation, please let me know.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> As Harry stated, quasi-steady heating seems
to be a valid explanation of hot loops. Impulsive heating (with long
intervals between repeats in a given strand) may also be a valid explanation for
these loops, although a lack of cospatial warm emission in the predicted
quantities might rule this out. We still need to work out the numbers. <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> I was interested to hear about Helen’s
EIS results and look forward to learning more. As you know, RHESSI observations
are consistent with there being a weak super-hot component at the levels found
by XRT and predicted by the nanoflare models. Kuen Ko and her colleagues
at NRL found that the sensitivity of EIS to Ca XVII (one of the strongest hot
lines in the EIS spectrum) is inadequate to prove or disprove nanoflares.
The intensities predicted by the models are too weak.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> I’m not sure what to make of your
comment about the low-temperature boundary in the models apparently negating the
results in your view. We never claim to model the chromosphere in enough detail
to compare with chromospheric observations. Our goal is to study the
corona, and our model accurately treats the energetic and dynamic interaction
between the corona and chromosphere (i.e., evaporation and condensation).
Do you have some reason to believe that our treatment of the chromosphere adversely
affects the coronal solution? If so, please explain in detail.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Thanks again for your interest,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Jim<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
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<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>
<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>
loops-bounces@solar.physics.montana.edu
[mailto:loops-bounces@solar.physics.montana.edu] <b>On Behalf Of </b>Hugh
Hudson<br>
<b>Sent:</b> Saturday, December 05, 2009 6:20 PM<br>
<b>To:</b> A mailing list for scientists involved in the observation and
modeling of solar loop structures<br>
<b>Subject:</b> Re: [Loops] loops and thermal nonequilibrium<o:p></o:p></span></p>
</div>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Dear Jim<o:p></o:p></p>
<div>
<p class=MsoNormal><o:p> </o:p></p>
</div>
<div>
<p class=MsoNormal>I have some comments. It looks like a nice piece of work,
but as usual the conclusion that only nanoflares can help is hopelessly
quixotic. You set up a strawman competing mechanism (why call it "thermal
nonequilibrium" when the one-syllable alternative "flow" works
as well?) and reject it on the basis of time scales. Who knows about the time
scales of the driver of the flows?<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><o:p> </o:p></p>
</div>
<div>
<p class=MsoNormal>The model itself seems highly questionable. I had cited its
predecessor in trying to explain the "chewy nougat" observation of
X-rays from prominences (<a
href="http://adsabs.harvard.edu/abs/1999ApJ...513L..83H">http://adsabs.harvard.edu/abs/1999ApJ...513L..83H</a>)
but realized later on that the model has a very artificial low-temperature
boundary and is thus not compelling. It is surprising to me that a decade later
this has not changed, especially since it is just this boundary region in which
the heating may be taking place.<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><o:p> </o:p></p>
</div>
<div>
<p class=MsoNormal>To be perfectly clear about nanoflares: I do not think that
there is any convincing observational evidence that they exist. It is a purely
theoretical construct.<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><o:p> </o:p></p>
</div>
<div>
<p class=MsoNormal>Cheers<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><o:p> </o:p></p>
</div>
<div>
<p class=MsoNormal>Hugh<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><o:p> </o:p></p>
</div>
<div>
<p class=MsoNormal>p.s. at the Hinode meeting just concluded, a nice poster by
Helen Mason made it very clear that EIS spectra emphatically do not agree with
the various XRT suggestions of a high-temperature component in the loop DEM.
The discrepancy is an order of magnitude.<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><o:p> </o:p></p>
<div>
<div>
<p class=MsoNormal>On 4 Dec 2009, at 14:04, Klimchuk, James A. (GSFC-6710)
wrote:<o:p></o:p></p>
</div>
<p class=MsoNormal><br>
<br>
<o:p></o:p></p>
<div>
<div>
<div>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:black'>Dear Loops Friends,<o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:black'> <o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:black'> If you are interested, the attached paper shows
that coronal loops cannot be explained by thermal nonequilibrium. The
results appear to rule out the widespread existence of coronal heating that is
both highly concentrated low in the corona and steady or quasi-steady (slowly
varying or impulsive with a rapid cadence). Comments are welcomed.<o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:black'> <o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:black'>Best wishes,<o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:black'>Jim<o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:black'> <o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:black'>********************************************************************************</span><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:black'><o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:black'>James A. Klimchuk</span><span style='font-size:11.0pt;font-family:
"Calibri","sans-serif";color:black'><o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:black'>NASA Goddard Space Flight Center</span><span style='font-size:
11.0pt;font-family:"Calibri","sans-serif";color:black'><o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:black'>Solar Physics Lab, Code 671</span><span style='font-size:11.0pt;
font-family:"Calibri","sans-serif";color:black'><o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:black'>Bldg. 21, Rm. 158</span><span style='font-size:11.0pt;font-family:
"Calibri","sans-serif";color:black'><o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:black'>Greenbelt, MD 20771</span><span style='font-size:11.0pt;
font-family:"Calibri","sans-serif";color:black'><o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:black'>USA</span><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:black'><o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='color:black'> </span><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:black'><o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:black'>Phone: 1-301-286-9060</span><span style='font-size:11.0pt;
font-family:"Calibri","sans-serif";color:black'><o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:black'>Fax: 1-301-286-7194</span><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:black'><o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:black'>E-mail: <a href="mailto:James.A.Klimchuk@nasa.gov">James.A.Klimchuk@nasa.gov</a></span><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:black'><o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:black'>Home page: <a
href="http://hsd.gsfc.nasa.gov/staff/bios/cs/James_Klimchuk.html">http://hsd.gsfc.nasa.gov/staff/bios/cs/James_Klimchuk.html</a></span><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:black'><o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:black'> </span><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:black'><o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:black'>********************************************************************************</span><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:black'><o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='color:black'> </span><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:black'><o:p></o:p></span></p>
</div>
<p class=MsoNormal><span style='font-size:13.5pt;font-family:"Helvetica","sans-serif";
color:black'><klimchuk_submitted.pdf><o:p></o:p></span></p>
</div>
<p class=MsoNormal><span style='font-size:13.5pt;font-family:"Helvetica","sans-serif";
color:black'>_______________________________________________<br>
Loops mailing list<br>
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<a href="https://mithra.physics.montana.edu/mailman/listinfo/loops">https://mithra.physics.montana.edu/mailman/listinfo/loops</a><o:p></o:p></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
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