<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Dear Allen,<div><br></div><div>Great idea ! Essentially you want a space AND time-dependent background.</div><div>Since a second-order approximation is probably good enough for slowly-varying</div><div>density changes, it would be sufficient to use just 3 subsequent images in time</div><div>and model the background from </div><div><span class="Apple-tab-span" style="white-space:pre"> </span>f(x,t-dt), f(x,t), f(x,t+dt)</div><div>with second-order interpolation. Should be straightforward.</div><div>I hope some under-occupied PhD student will pick up on it!</div><div><br></div><div>Cheers,</div><div>Markus</div><div><br><div><div>On Feb 15, 2010, at 6:48 PM, Gary, Gilmer A. (MSFC-VP62) wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div>Markus,<br><br>A question --- has anyone tried to model "all" the loops in some manner so that the "background" variation for a loop could be removed using time dependencies of all the individual loops (or a major set of loops)?<br><br>This would be a temporal stereographic reconstruction and would be as arduous, but some STEREO sets might lead to interesting results. The matrix inversions might however by ill-posed and some special math might be neeeded. Anyway a thought that was generaqted from your commmet.<br><br>Someone might use some analytic test cases or examples might lead to some specific ideas for real observations.<br><br>Best regards,<br>Allen<br><br>________________________________________<br>From: <a href="mailto:loops-bounces@solar.physics.montana.edu">loops-bounces@solar.physics.montana.edu</a> [loops-bounces@solar.physics.montana.edu] On Behalf Of Markus J. Aschwanden [aschwanden@lmsal.com]<br>Sent: Monday, February 15, 2010 5:02 PM<br>To: A mailing list for scientists involved in the observation and modeling of solar loop structures<br>Subject: Re: [Loops] On the importance of background subtraction in the analysis of coronal loops observed with TRACE<br><br>Sergio and Fabio,<br><br>I like to encourage you to use STEREO EUVI data, which would provide<br>you the ultimate test to subtract the correct background, because you<br>see a loop from two different directions and have two independent<br>backgrounds. You can test the self-consistence of background subtraction,<br>if you obtain the same EM of the loop from two spacecraft.<br>If you look into my recent STEREO paper, you see that one can<br>subtract the background with an accuracy of about 10%.<br>See Fig.8 therein.<br><br>Cheers,<br>Markus<br><br> Aschwanden,M.J., Nitta,N.V., Wuelser,J.P., and Lemen,J.R. 2008, The Astrophysical Journal, 680, 1477-1495<br>URL1="<a href="http://www.lmsal.com/~aschwand/eprints/2008_stereo2.pdf">http://www.lmsal.com/~aschwand/eprints/2008_stereo2.pdf</a>"<<a href="http://www.lmsal.com/~aschwand/eprints/2008_stereo2.pdf">http://www.lmsal.com/~aschwand/eprints/2008_stereo2.pdf</a>><br>First 3D reconstructions of coronal loops with the STEREO A and B spacecraft: II. Electron Density and Temperature Measurements<br><br>_______________________________________________<br>Loops mailing list<br><a href="mailto:Loops@solar.physics.montana.edu">Loops@solar.physics.montana.edu</a><br>https://mithra.physics.montana.edu/mailman/listinfo/loops<br></div></blockquote></div><br><div>
<span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0; "><span class="Apple-style-span" style="border-collapse: separate; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; 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; -webkit-text-decorations-in-effect: none; text-indent: 0px; -webkit-text-size-adjust: auto; text-transform: none; orphans: 2; white-space: normal; widows: 2; word-spacing: 0px; "><span class="Apple-style-span" style="border-collapse: separate; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; 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; -webkit-text-decorations-in-effect: none; text-indent: 0px; -webkit-text-size-adjust: auto; text-transform: none; orphans: 2; white-space: normal; widows: 2; word-spacing: 0px; "><span class="Apple-style-span" style="border-collapse: separate; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; 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; -webkit-text-decorations-in-effect: none; text-indent: 0px; -webkit-text-size-adjust: auto; text-transform: none; orphans: 2; white-space: normal; widows: 2; word-spacing: 0px; "><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 href="http://www.lmsal.com/~aschwand/">http://www.lmsal.com/~aschwand/</a></div><div>e-mail: <a href="mailto:aschwanden@lmsal.com">aschwanden@lmsal.com</a></div><div>_______________________________________</div><div>____________________________________</div><br class="Apple-interchange-newline"></span></span></span></span><br class="Apple-interchange-newline">
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