U. Schuhle et al., Signatures of coronal hole spectra between 660 Angstroms and 1460 Angstroms measured with SUMER on SOHO, SPACE SCI R, 87(1-2), 1999, pp. 299-302
Spectra of the northern polar coronal hole measured with the SUMER spectrom
eter on SOHO on 25 October 1996 are analyzed. We present spectra taken at l
ocations on the solar disk where part of the spectrometer slit intersects a
polar coronal hole region and an area of brighter emission from outside of
the coronal hole area. By comparing the line intensities between the parts
of the spectrum taken inside the "dark" area of the coronal holes and the
brighter regions, we work out the signatures of the specific coronal hole i
n the chromosphere, transition region and lower corona. We find that emissi
ons of neutral atom lines, of which there are many in the spectrum of SUMER
, show no difference between the coronal hole and the bright boundary areas
, whereas all ionized species show strong intensity enhancements, including
the continuum emissions of carbon and hydrogen. These enhancements are lar
ger than in normal quiet Sun areas.