Resonance scattering from interstellar and interplanetary helium.

Abstract

The intensity and spatial distribution of the diffuse 584 A glow due to resonance scattering of solar He I, 584 A line radiation by neutral interstellar and interplanetary helium is derived. Two sources of neutral helium are considered: the local interstellar medium interacting with the solar system and dust deionization of the He(++) component of the solar wind. Which of these two sources will dominate the radiation field at 1 AU is dependent upon a number of parameters which have not yet been determined. Results are presented as a function of the width of the solar line, and the temperature and speed of approach of the interstellar medium. The calculated intensities for the most extreme cases vary from approximately .000001 Rayleighs to almost 100 Rayleighs. The relevance of these results to the study of the interplanetary and interstellar medium is discussed.