<html><head><meta http-equiv="Content-Type" content="text/html charset=windows-1252"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;">Dear Serge and Hugh,<div><br></div><div>Thanks for your feedback. You are correct that it appears that there is</div><div>more free energy available during the flare duration than before or after.</div><div>However, a similar behavior appears in all flares, as you can see in the</div><div>analysis of the free energy in some 200 flares analyzed from HMI and AIA</div><div>(see Aschwanden, Xu, and Jing 2014, ApJ 797:50). This apparently</div><div>counter-intuitive behavior has been interpreted as a “coronal illumination</div><div>effect” (see Fig.3 in the quoted paper above). In short, most of the highly</div><div>twisted helical flare loops that carry non-potential magnetic energy are</div><div>invisible or undetectable before the start of the flare, but become visible</div><div>once they become filled up with heated plasma by the chromospheric</div><div>evaporation process that usually occurs in flares. So, it is not a contra-</div><div>diction, but just an observational problem. It is similar to the missing</div><div>mass problem in the universe: We detect only 4% luminous mass, but</div><div>when you add up all the dark matter and neutrinos you get to a much</div><div>more massive universe that may even be closed/ And nobody calls </div><div>the missing mass problem as contradictory, it’s just an observational </div><div>problem.</div><div><br></div><div>Regarding Hugh’s comment, the NLFFF model that has been used</div><div>to calculate the free energy is based on an analytical solution of the</div><div>force-free field in terms of vertical currents that introduce a helical</div><div>twist (Aschwanden 2013, Solar Phys. 287, 323). It is only an</div><div>approximation, but it should give the first-order non-potential field</div><div>pretty accurately. There is some consistency with standard NLFFF </div><div>models, or at least some correlation (e.g., Wiegelmann code).</div><div>The boundary conditions have been discussed in great detail in a</div><div>NLFFF comparison paper (DeRosa et al. 2009). The biggest problem</div><div>with standard NLFFF codes is that they extrapolate from a not</div><div>force-free boundary. In contrast, the analytical NLFFF model that</div><div>fits the geometry of coronal loops circumvents this problem and</div><div>thus yields complementary information. If you wish I can give your</div><div>more references on this “high-order theoretical matter”.</div><div><br></div><div>Thanks for the comments,</div><div>Best regards,</div><div><br></div><div>Markus</div><div><br></div><div><div apple-content-edited="true">
<div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">____________________________________</div><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Dr. Markus J. Aschwanden<br>Solar & Astrophysics Laboratory<br>Lockheed Martin Advanced Techology Center<br>A021S, Bldg. 252<br>3251 Hanover St., Palo Alto, CA 94304, USA<br>Phone: 650-424-4001, FAX: 650-424-3994<br>URL: <a href="http://www.lmsal.com/~aschwand/">http://www.lmsal.com/~aschwand/</a><br>e-mail: <a href="mailto:aschwanden@lmsal.com">aschwanden@lmsal.com</a><br>____________________________________</div>
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<br><div><div>On Apr 14, 2015, at 5:53 AM, Hugh Hudson <<a href="mailto:hhudson@ssl.berkeley.edu">hhudson@ssl.berkeley.edu</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><meta http-equiv="Content-Type" content="text/html charset=windows-1252"><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;">That’s how it appears to me too. I’d add that the localization of the free energy is a difficult subject, and it may be misleading just to identify it with the B^2/8pi excess. This is because the realization of the free energy, i.e. its actual definition, depends on the nature of the instability that releases it. Understanding this requires understanding the boundary conditions, so it must be a higher-order theoretical matter.<div><br></div><div>Hugh</div><div><br><div><div>On Apr 14, 2015, at 8:42 AM, Serge Koutchmy <<a href="mailto:koutchmy@iap.fr">koutchmy@iap.fr</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite">
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<div class="moz-cite-prefix">Thank you Markus for the preprint. <br>
Looking at your most important Fig. 3, you give the impression
that MORE free energy is available in the corona AFTER the peak of
the flare (GOES HXR, SXR emissions, etc) than before. <br>
Is not exactly the opposite of what we would wait following your
Introductory presentation of the topic and even the title of the
paper? <br>
Or did I miss something fundamental? <br>
Best, <br>
S. <br>
<br>
Le 13/04/2015 21:06, Markus J. Aschwanden a écrit :<br>
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<blockquote cite="mid:3484221D-FB2D-444A-AA62-48D3FD0DA4CF@lmsal.com" type="cite">
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<span style="font-family: Times; font-size: inherit;"> Aschwanden,M.J.
. 2015, ApJL ... (revised, 2015 Apr 2)</span><br style="font-family: Times;">
<a moz-do-not-send="true" href="http://www.lmsal.com/%7Easchwand/eprints/2015_iris.pdf" style="font-family: Times;">URL1="http://www.lmsal.com/~aschwand/eprints/2015_iris.pdf"</a><span style="font-family: Times; font-size: inherit;"> </span><br style="font-family: Times;">
<span style="font-family: Times; font-size: inherit;"></span><font style="font-family: Times;" size="4">Magnetic energy dissipation
during the 2014 Mar 29 flare: </font>
<div><font style="font-family: Times;" size="4">Consistent
measurements in the transition region and corona with IRIS and
AIA/SDO</font>
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<div style="word-wrap: break-word; -webkit-nbsp-mode: space;
-webkit-line-break: after-white-space; ">Dr. Markus J.
Aschwanden<br>
Solar & Astrophysics Laboratory<br>
Lockheed Martin Advanced Techology Center<br>
A021S, Bldg. 252<br>
3251 Hanover St., Palo Alto, CA 94304, USA<br>
Phone: 650-424-4001, FAX: 650-424-3994<br>
URL: <a moz-do-not-send="true" href="http://www.lmsal.com/%7Easchwand/">http://www.lmsal.com/~aschwand/</a><br>
e-mail: <a moz-do-not-send="true" href="mailto:aschwanden@lmsal.com">aschwanden@lmsal.com</a><br>
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