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Thank you very much, Markus<br>
we are aware of your very interesting work on the analysis of
STEREO data and your suggestion is very timely and appropriate. Sergio
is busy with the analysis of Hinode/XRT data at the moment, but we hope
to address STEREO data as next step.<br>
Thank you again<br>
Best regards<br>
Fabio<br>
<br>
<br>
On 02/16/2010 12:02 AM, Markus J. Aschwanden wrote:
<blockquote cite="mid:8E860308-B31A-498E-82A6-8301D2F456AF@lmsal.com"
type="cite">Sergio and Fabio,
<div><br>
</div>
<div>I like to encourage you to use STEREO EUVI data, which would
provide</div>
<div>you the ultimate test to subtract the correct background,
because you</div>
<div>see a loop from two different directions and have two independent</div>
<div>backgrounds. You can test the self-consistence of background
subtraction,</div>
<div>if you obtain the same EM of the loop from two spacecraft. </div>
<div>If you look into my recent STEREO paper, you see that one can</div>
<div>subtract the background with an accuracy of about 10%.</div>
<div>See Fig.8 therein.</div>
<div><br>
</div>
<div>Cheers,</div>
<div>Markus</div>
<div><br>
</div>
<div><span class="Apple-style-span" style="font-family: Times;"> Aschwanden,M.J.,
Nitta,N.V., Wuelser,J.P., and Lemen,J.R. 2008, The Astrophysical
Journal, 680, 1477-1495<br>
<a moz-do-not-send="true"
href="http://www.lmsal.com/%7Easchwand/eprints/2008_stereo2.pdf">URL1="http://www.lmsal.com/~aschwand/eprints/2008_stereo2.pdf"</a> <br>
<font size="4">First 3D reconstructions of coronal loops with the
STEREO A and B spacecraft: II. Electron Density and Temperature
Measurements</font></span></div>
<div><font class="Apple-style-span" face="Times"><span
class="Apple-style-span" style="font-size: large;"><br>
</span></font></div>
<div><font class="Apple-style-span" face="Times"><span
class="Apple-style-span" style="font-size: large;"></span></font></div>
<br>
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<br>
<div><font class="Apple-style-span" face="Times"><span
class="Apple-style-span" style="font-size: large;"></span></font></div>
<div><br>
<div>
<div>On Feb 11, 2010, at 3:02 AM, Fabio Reale wrote:</div>
<br class="Apple-interchange-newline">
<blockquote type="cite">
<div bgcolor="#ffffff" text="#000000">Dear friends<br>
let me inform you about the following preprint on Astro-PH, <br>
<br>
<a moz-do-not-send="true" class="moz-txt-link-freetext"
href="http://arxiv.org/abs/1002.2121">http://arxiv.org/abs/1002.2121</a><br>
<br>
regarding:<br>
<br>
<h1 class="title">the importance of background subtraction in the
analysis of coronal loops observed with TRACE</h1>
<br>
by Sergio Terzo and Fabio Reale, accepted for publication on A&A<br>
<br>
Abstract<br>
In the framework of TRACE coronal observations, we compare the analysis
and
diagnostics of a loop after subtracting the background with two
different and
independent methods. The dataset includes sequences of images in the
171 A, 195
A filter bands of TRACE. One background subtraction method consists in
taking
as background values those obtained from interpolation between
concentric
strips around the analyzed loop. The other method is a pixel-to-pixel
subtraction of the final image when the loop had completely faded out,
already
used by Reale & Ciaravella 2006. We compare the emission
distributions along
the loop obtained with the two methods and find that they are
considerably
different. We find differences as well in the related derive filter
ratio and
temperature profiles. In particular, the pixel-to-pixel subtraction
leads to
coherent diagnostics of a cooling loop. With the other subtraction the
diagnostics are much less clear. The background subtraction is a
delicate issue
in the analysis of a loop. The pixel-to-pixel subtraction appears to be
more
reliable, but its application is not always possible. Subtraction from
interpolation between surrounding regions can produce higher systematic
errors,
because of intersecting structures and of the large amount of
subtracted
emission in TRACE observations.<br>
<br>
<br>
<br>
</div>
<span><reale.vcf></span>_______________________________________________<br>
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</blockquote>
</div>
<br>
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class="Apple-style-span"
style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-indent: 0px; text-transform: none; orphans: 2; white-space: normal; widows: 2; word-spacing: 0px;"><span
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<div>____________________________________________</div>
<div>Dr. Markus J. Aschwanden</div>
<div>Solar & Astrophysics Laboratory</div>
<div>Lockheed Martin Advanced Techology Center</div>
<div>Org. ADBS, Bldg. 252</div>
<div>3251 Hanover St., Palo Alto, CA 94304, USA</div>
<div>Phone: 650-424-4001, FAX: 650-424-3994</div>
<div>URL: <a moz-do-not-send="true"
href="http://www.lmsal.com/%7Easchwand/">http://www.lmsal.com/~aschwand/</a></div>
<div>e-mail: <a moz-do-not-send="true"
href="mailto:aschwanden@lmsal.com">aschwanden@lmsal.com</a></div>
<div>_______________________________________</div>
<div>____________________________________</div>
<br class="Apple-interchange-newline">
</span></span></span><br class="Apple-interchange-newline">
</div>
<br>
</div>
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</blockquote>
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