Power spectrum analysis of LMSU (Lomonosov Moscow State University) nuclear decay-rate data: Further indication of r-mode oscillations in an inner solar tachocline

This article presents a power-spectrum analysis of 2350 measurements of the 90 Sr - 90 Y decay process acquired over the interval August 4 2002 to February 6 2009 at the Lomonosov Moscow State University. As we have found for other long sequences of decay measurements, the power spectrum is dominated by a very strong annual oscillation. However, we also find a set of low-frequency peaks, ranging from 0.26 to 3.98 year−1, which are very similar to an array of peaks in a power spectrum formed from Mt Wilson diameter measurements. The Mt Wilson measurements have been interpreted in terms of r-mode oscillations in a region where the sidereal rotation frequency is 12.08 year−1. We find that the LMSU measurements may also be attributed to the same type of r-mode oscillations in a solar region with the same sidereal rotation frequency. We propose that these oscillations occur in an inner tachocline that separates the radiative zone from a more slowly rotating solar core.