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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>Dear friends,<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal> You might be interested in my recent paper on “The Role of Type II Spicules in the Upper Solar Atmosphere,” which can be downloaded at <a href="http://arxiv.org/abs/1207.7048">http://arxiv.org/abs/1207.7048</a><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>ABSTRACT:<o:p></o:p></p><p class=MsoNormal>We examine the suggestion that most of the hot plasma in the Sun's <o:p></o:p></p><p class=MsoNormal>corona comes from type II spicule material that is heated as it is<o:p></o:p></p><p class=MsoNormal>ejected from the chromosphere. This contrasts with the traditional<o:p></o:p></p><p class=MsoNormal>view that the corona is filled via chromospheric evaporation that<o:p></o:p></p><p class=MsoNormal>results from coronal heating. We explore the observational<o:p></o:p></p><p class=MsoNormal>consequences of a hypothetical spicule dominated corona and conclude<o:p></o:p></p><p class=MsoNormal>from the large discrepancy between predicted and actual observations<o:p></o:p></p><p class=MsoNormal>that only a small fraction of the hot plasma can be supplied by<o:p></o:p></p><p class=MsoNormal>spicules (<2% in active regions and <5% in the quiet Sun). The<o:p></o:p></p><p class=MsoNormal>red-blue asymmetries of EUV spectral lines and the ratio of lower<o:p></o:p></p><p class=MsoNormal>transition region (LTR; T<0.1 MK) to coronal emission measures<o:p></o:p></p><p class=MsoNormal>are both predicted to be 2 orders of magnitude larger than observed. <o:p></o:p></p><p class=MsoNormal>Furthermore, hot spicule material would cool dramatically by<o:p></o:p></p><p class=MsoNormal>adiabatic expansion as it rises into the corona, so coronal heating<o:p></o:p></p><p class=MsoNormal>would be required to maintain the high temperatures that are seen at<o:p></o:p></p><p class=MsoNormal>all altitudes. The necessity of coronal heating is inescapable. <o:p></o:p></p><p class=MsoNormal>Traditional coronal heating models predict far too little emission<o:p></o:p></p><p class=MsoNormal>from the LTR, and we suggest that this emission comes primarily from<o:p></o:p></p><p class=MsoNormal>the bulk of the spicule material that is heated to <0.1 MK and<o:p></o:p></p><p class=MsoNormal>is visible in He II (304 A) as it falls back to the surface.<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>https://sedupdate.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 role as an officer of professional organizations (American Geophysical Union, International Astronomical Union, American Astronomical Society).<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>