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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>I was asked to define the cooling time, t_cool, in my last e-mail. Sorry, I should have done this. It is the thermal energy density divided by the energy loss rate: <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal> t_cool = (3/2) P / R_loss ,<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>where P is the pressure. When thermal conduction dominates the cooling, as is the case early in a nanoflare event, the loss rate is approximately<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal> R_loss = (2/7) kappa_0 T^(7/2) / L^2 ,<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>where T is the peak temperature in the strand, and L is the distance between the location of the peak and the chromosphere (typically the loop half length). Generally speaking, temperature decreases according to<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal> T(t) = T_0 exp(-t / t_cool) .<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I assumed this in getting the percentage temperature variations in the original e-mail.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Cheers,<o:p></o:p></p><p class=MsoNormal>Jim<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>********************************************************************************</span><o:p></o:p></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>James A. Klimchuk</span><o:p></o:p></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>NASA Goddard Space Flight Center</span><o:p></o:p></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Solar Physics Lab, Code 671</span><o:p></o:p></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Bldg. 21, Rm. 158</span><o:p></o:p></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Greenbelt, MD 20771</span><o:p></o:p></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>USA</span><o:p></o:p></p><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Phone: 1-301-286-9060</span><o:p></o:p></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Fax: 1-301-286-7194</span><o:p></o:p></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>E-mail: <a href="mailto:James.A.Klimchuk@nasa.gov"><span style='color:blue'>James.A.Klimchuk@nasa.gov</span></a> </span><o:p></o:p></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Homepage: </span>http://science.gsfc.nasa.gov/sed/index.cfm?fuseAction=people.jumpBio&&iPhonebookId=15844<o:p></o:p></p><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>No endorsement by NASA is implied for any correspondence related to my official role in professional organizations.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'> <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>********************************************************************************<o:p></o:p></span></p><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>