p-mode frequency variation in relation to global solar activity

Abstract

We show that p-mode frequency variations correlate remarkably well with the variations of six solar activity indices over a 6 yr period from 1984 October to 1990 November, including both the large variation from solar minimum to solar maximum and smaller variations observed over approximately 1 month intervals during solar maximum. The quality of correlation as seen visually and as measured by two statistical tests differs significantly among the six activity indices, and we briefly speculate on possible reasons for this. Observations used in this study come from the HAO/NSO Fourier tachometer (FTACH) and include the spherical harmonic degree range l greater than 20 and equal to 60 or less and frequency range between 2600 and 3200 micro-Hz. The data are divided into 18 separate epochs with time string duration ranging from a minimum of 18 days to a maximum of 45 days. We have particularly good coverage during the early part of solar maximum of cycle 22.