Measurements of the Sun in the near-infrared He I 10830 A absorption line
were performed using the echelle spectrograph with adispersion of 6.71 mA
per pixel at the Vacuum Tower Telescope (German Solar Telescopes, Teide
Observatory, Izana, Tenerife, Spain) on May 26, 1993. These measurements
were compared with full-disc soft X-ray images of the SUN (Japanese solar
satellite Yohkoh), full-disc solar images in H alpha (Big Bear Solar
Observatory), full-disc solar images in the He I 10830 A line (National
Solar Observatory, Kitt Peak) and with full-disc microwave solar maps at
37 GHz (Metsähovi Radio Research Station). In the He 10830 A line
the Sun displays a limb darkening similar to that in the visible part of
the spectrum. Active regions and H alpha filaments show a strong
absorption in the He I 10830 A line, whereas the absorption is weak in
coronal holes.
Last update: December 27, 1996, Hubertus Wöhl,
<hw@kis.uni-freiburg.de>