Intensity measurements of chromospheric fine structures in Lyman-α

The intensity of the sun was measured in the Lyman- emission line with 2.5 arc-seconds of resolution. The experiment was flown in an Aerobee-150 rocket on April 28, 1966. It contained a Cassegrain telescope with a pinhole aperture placed at the focus followed by a gas-gain ionization chamber whose spectral response was 1050 Å to 1350 Å.An isophote map 1.5 by 3 arc-minutes in size made from a composite of 90 linear scans shows an enhanced region and adjacent to it a prominent dark lane 20 arc-seconds wide. The measured intensity ratio of these two regions is nine. Bright features between 6 and 20 arc-seconds in size showed typical peak intensities of 20% greater than the surrounding chromosphere. The smallest features observed were 2.5 arc-seconds in size. A direct measurement of the absolute intensity at 1216 Å gave a value of 5.9 × 10⁴ erg cm^–2 s^–1 sterad^–1 in the quiet chromosphere.Based on observations made by the author at the E. O. Hulburt Center for Space Research (supported jointly by the Office of Naval Research and the National Science Foundation) at the Naval Research Laboratory.