Observations of the center-to-limb variation of the solar brightness in the far infrared (10 to 25 microns)

Abstract

Existing models of the solar atmosphere predict a limb brightening in the far infrared wavelengths. At shorter wavelengths this effect is confined to the extreme limb but at 25 μ it extends inward from the limb to cosθ = 0.3. Observations of I(μ)/I(1.0) were made with the McMath Solar Telescope through atmospheric windows at 10.4, 17.9, 20.4, and 24.2 microns, respectively. The measurements, after having been smoothed, are compared with the theoretical predictions taking into account the diffraction pattern of the telescope. The expected brightening does not appear.