Modification of solar lines propagating through the interplanetary medium

The optical depths of the solar H Lyman-alpha and the He 584-A lines in interplanetary space are calculated. From these the solar line profiles at Saturn and Uranus are determined. It is found that the solar H Lyman-alpha line can be diminished strongly within a spectral region of less than 0.2 A from the line center. On the other hand, there is no significant absorption of the He 584-A line except in the downwind region, where absorption occurs within a spectral region of about 0.04 A. The effects of solar line modification on planetary and interplanetary glow observations are discussed.