Observation of additional low-degree 5-min modes of solar oscillation

Abstract

By measuring the difference between the shifts in the Fe 5,124 spectrum line from light integrated from a central circular portion of the solar disk and from an annular portion exterior to it, we have detected high-order solar oscillations with degrees l = 3, 4 and 5. The frequencies of the octupole modes agree well with the values obtained from whole-disk measurements at the South Pole1. A least-squares fit of the observed frequencies to values interpolated between and extrapolated from the predictions of a sequence of solar models with different chemical compositions selects two models. One of these is almost identical to that obtained by a previous fit15 of modes with l≤2, and has a helium abundance somewhat greater than 25% by mass. © 1982 Nature Publishing Group.