Speaker
Leping Li
(National Astronomical Observatories, Chinese Academy of Sciences)
Description
Context. From the profiles of emission lines, thermal and dynamic information of the
plasma parcel can be achieved. The enhanced emissions in the line wings and the
red-blue asymmetry (RBA) have been widely observed, but not yet fully understood.
Aims. We try to understand the enhancements in the line wings and the RBA of the
emission lines in the solar transition region. Methods. Using far ultraviolet (UV)
spectra and slit-jaw images from IRIS, we studied an emerging active region loop,
connecting two plage-type faculae with opposite polarities, scanned by the IRIS
raster. Single Gaussian (SG) fit is employed to the line core of the Si IV (1394 Å)
line, and the residual of the observed line profiles to the SG is obtained. Several
parameters about the line profiles are measured to indicate the evolution and
distribution of the emission line along the loop. Results. A proper motion just
before the IRIS raster scanning is observed along the loop, indicating that the slit
scanned the moving plasma parcel. The Doppler shift map shows blueshift in the east,
and redshift in the west, consistent with a siphon flow along the loop. Spectral
tilts are detected along the loop, meaning the inside twisting motions. The
enhancements in the blue and red wings, and their distribution and evolution along
the loop, are observed. These, also, lead to the evolution of the RBA of the
transition region line along the loop. Conclusions. The enhanced emission in the blue
wing near the eastern footpoint indicates an injection at this footpoint. The proper
motion along the loop and the Doppler shift support that the loop is a flat one. The
twisting motions of the plasma parcel may cause the evolution and distribution of the
enhancements of the line wings and the RBA.
Primary author
Leping Li
(National Astronomical Observatories, Chinese Academy of Sciences)
