2.1 Some preliminary conclusions
- the 1 MK loops seen in TRACE 173 Å must be almost isothermal along the line of sight, otherwise
they would be visible in CDS lines emitted over a broad range of
temperatures.
-
Excellent consistency between the TRACE 173 Å image and
CDS images in lines emitted at 0.8-1.0 MK.
-
These 1 MK loops are much cooler than the surrounding diffuse
emission, since they are visible in CDS lines emitted at lower
temperatures.
-
1 MK loops are almost not visible in TRACE 195 Å band
(NO FILTER RATIOS!).
-
TRACE 195 Å emission is not always
due to Fe XII emission, otherwise all the loops would be
clearly visible by CDS in Fe XII lines.
- At higher temperatures, between 1.5 and 2 MK, the active region
produces only diffuse background emission.
-
The diffuse background along the line of sight represents a significant
fraction of the loop emission
(BACKGROUND SUBTRACTION!).
-
At even higher temperatures
low-lying hot loops are present, as seen in e.g. Fe XVI.
These loops do not have any direct spatial
relationship with the 1 MK loops, but are
the loops that are normally observed with e.g. Yohkoh/SXT.
-
Even with the TRACE resolution, most loop structures appear to be composed
of multiple threads.
-
For both TRACE and CDS:
almost no regions free of AR loop emission,
to be used for background subtraction.
