A Method for Determining the Photospheric ~4He Abundance

摘要

The photospheric ~4He/H ratio is not measured directly but is inferred from stellar evolution models, helioseismology, and coronal observations. We suggest a procedure for determining the photospheric ratio on the basis of solar wind isotopic He abundances and γ-ray line measurements. Recent Ulysses measurements of the ~4He/~3He isotopic ratio in the solar wind indicate that it is constant over a large range of velocities; long-term averages in the ratio from different experiments are also consistent with one another, with values ranging from 2050 to 2350 and uncertainties ranging from 120 to 200.