HELIUM 10830 ANGSTROM MEASUREMENTS OF THE SUN

Measurements of the Sun in the near-infrared He I 10830 Angstrom absor ption line were performed using the echelle spectrograph with a disper sion of 6.71 m Angstrom per pixel at the Vacuum Tower Telescope (Germa n Solar Telescopes, Teide Observatory, Izana, Tenerife, Spain) on May 26, 1993. These measurements were compared with full-disc soft X-ray i mages of the Sun (Japanese solar satellite Yohkoh), full-disc solar im ages in H alpha (Big Bear Solar Observatory), full-disc solar images i n the He I 10830 Angstrom line (National Solar Observatory, Kitt Peak) and with full-disc microwave solar maps at 37 GHz (Metsahovi Radio Re search Station). In the He 10830 Angstrom line the Sun displays a limb darkening similar to that in the visible part of the spectrum. Active regions and Ha filaments show a strong absorption in the He 10830 Ang strom line, whereas the absorption is weak in coronal holes.