The seismic diversity of four successive solar cycle minima as observed by the Birmingham Solar-Oscillations Network (BiSON)

The He ii signature was larger, and the sound speed in the range to was slightly higher, during the cycle 23/24 minimum, than during the other minima. The cycle 23/24 minimum was the deepest, as measured by proxies of global solar activity. These findings are consistent with magnetic flux levels having been lower in this minimum than the others, resulting in a higher gas pressure, higher temperatures, and higher sound speed.

Our results demonstrate the potential of using asteroseismic data to perform similar analyses on other solar-type stars. The files contain frequency sets for each cycle minimum period, after weeding. Columns are: (1) angular degree, l (2) overtone number n (3) frequency (uHz) (4) error (uHz).