Magnetic Twist of EUV Coronal Loops Observed by TRACE
RyunYoung Kwon, Jongchul Chae
EUV images taken by TRACE clearly display a number of thin coronal loops
that represent one million degree plasma tracing magnetic field line in the
corona. We estimate the magnetic twist of coronal loops that can explain
the constriction of plasma into a loop without dispersion. We assume that
the segment of a coronal loop taken by TRACE 171 image is a part of a
straight, non-force-free twisted flux tube and that the variation of the
axial field strength along the tube is determined by the large scale three-
dimensional configuration of the coronal magnetic field calculated by
linear force-free extrapolation of photospheric magnetic field observed by
SOHO/MDI.
We selected a number of conspicuous loops which are bright enough and well
separated from other adjacent loops on TRACE EUV images so that we can fit
a magnetic field line to each loop from one footpoint to the other
footpoint. We have applied our method to several coronal loops and found
that these loops have twist values from 1.5 to 2.5, which suggest that
the winding number of EUV coronal loop may be around one.
Correspondence
Ryun-Young Kwon (luxmundi@astro.snu.ac.kr), Astronomy Program, School of Earth and Environmental
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