March 4, 2005
Bldg 21, Rm 183, 12:00 noon

The Coronal Loop Controversy
Dr. Joan Schmelz
University of Memphis

The temperature distribution along coronal loops provides a basic
observable to be predicted by any coronal heating model, so measuring
this distribution using data from the current fleet of solar imagers and
spectrometers has become a priority. Unfortunately, the results from
different instruments have not led to a consistent picture. Analysis of
coronal data obtained with SOHO-EIT and TRACE seems to imply that loops
have a uniform temperature (e.g., Neupert et al. 1998; Lenz et al.
1999), while Yohkoh-SXT and SOHO-CDS analyses show that loop
temperatures increase from the footpoints to the apex (e.g., Kano &
Tsuneta 1996; Schmelz et al. 2001). Have these observations revealed two
classes of loops - hot X-ray loops and cooler EUV loops - with
fundamentally different physical characteristics? How valid is the
isothermal approximation in each case? How does background subtraction
affect the loop temperature profiles? How does the limited temperature
coverage affect the results from imagers like TRACE which have the best
spatial resolution; and conversely, how does the coarse spatial
resolution affect the results from spectrometers like CDS which have the
best temperature coverage? These questions will be addressed in this
talk.