Measurement of the profile and intensity of the solar He I λ584‐Å resonance line

Abstract

The intensity and profile of the helium resonance line at 584 Å from the entire disc of the sun was investigated by using a rocket‐borne helium‐filled spectrometer and a curve of growth technique. The line profile was found to be accurately represented by a gaussian profile with full width at half maximum of 122 10 mÅ, while the integrated intensity was measured to be (2.6 ± 1.3) × 109 photons s−1 cm−2 at solar activity levels of F10.7 = 90.8 × 10−22 m−2 Hz−1 and Rz = 27. The measured line width is in good agreement with previous spectrographic measurements, but the integrated intensity is larger than most previous photoelectric measurements. However, the derived line center flux of (2.0 ± 1.0) × 1010 photons s−1 cm−2 Å−1 is in good agreement with values inferred from airglow measurements.