Commentary on a putative magnetic field variation in the solar convection zone

The implications of a component δoscν, oscillatory with respect to frequency ν, of seismic frequency changes observed by Libbrecht and Woodard during the rising phase of solar cycle 22, first mooted by Goldreich, Murray, Willette and Kumar, and its relation to a putative magnetic field, is discussed in relation to more detailed analysis of data in a more limited frequency range obtained over the subsequent cycle. The oscillatory component is associated with helium ionization, and its temporal variation might be explained by a dilution of the effect of the ionization-induced influence on an effective adiabatic exponent of the stellar material by a relatively smooth magnetic field whose intensity increases with surface activity. To account for the magnitude of the variation in cycle 23 would require the field strength to change by some 30 T. Moreover, the change in δoscν in the high-frequency range that was analysed in cycle 23 implies changes at lower frequency that are significantly much greater than those observed by Libbrecht and Woodard in the previous cycle.