We have studied long-term variations of galactic cosmic-ray (GCR) intensity in relation to the sunspot number (SSN) during the most recent solar cycles. This study analyses the time lag between the GCR intensity and SSN, and hysteresis plots of the GCR count rate against SSN for Solar Cycles 20 – 23, to validate a methodology against previous results in the literature, before applying the method to provide a timely update on the behaviour of Cycle 24. Plots of SSN versus GCR show a clear difference between the odd- and even-numbered cycles. Linear and elliptical models have been fit to the data, with the linear fit and elliptical model proving the more suitable model for even- and odd-numbered solar-activity cycles, respectively, in agreement with previous literature. Through the application of these methods for Solar Cycle 24, it has been shown that Cycle 24 experienced a lag of two to four months between the GCR intensity and SSN, and this follows the trend of the preceding activity cycles, albeit with a slightly longer lag than previous even-numbered cycles. It has been shown through the hysteresis analysis that the linear fit is a better representative model for Cycle 24, as the ellipse model does not show a significant improvement, which is also in agreement with previous even-numbered cycles.

We explore the sensitivity of the frequencies of low-degree solar p-modes to near-surface magnetic flux on different spatial scales and strengths, specifically to active regions with strong magnetic fields and ephemeral regions with weak magnetic fields. We also use model reconstructions from the literature to calculate average frequency offsets back to the end of the Maunder minimum. We find that the p-mode frequencies are at least three times less sensitive (at 95 % confidence) to the ephemeral-region field than they are to the active-region field. Frequency shifts between activity cycle minima and maxima are controlled predominantly by the change of active region flux. Frequency shifts at cycle minima (with respect to a magnetically quiet Sun) are determined largely by the ephemeral flux, and are estimated to have been 0.1 µHz or less over the last few minima. We conclude that at epochs of cycle minimum, frequency shifts due to near-surface magnetic activity are negligible compared to the offsets between observed and model frequencies that arise from inaccurate modelling of the near-surface layers (the so-called surface term). The implication is that this will be the case for other Sun-like stars with similar activity, which has implications for asteroseismic modelling of stars.

We have used very high-cadence (sub-minute) observations of the solar mean magnetic field (SMMF) from the Birmingham Solar Oscillations Network (BiSON) to investigate the morphology of the SMMF. The observations span a period from 1992–2012, and the high-cadence observations allowed the exploration of the power spectrum up to frequencies in the mHz range. The power spectrum contains several broad peaks from a rotationally-modulated (RM) component, whose linewidths allowed us to measure, for the first time, the lifetime of the RM source. There is an additional broadband, background component in the power spectrum which we have shown is an artefact of power aliasing due to the low fill of the data. The sidereal rotation period of the RM component was measured as 25.23 ± 0.11 days and suggests that the signal is sensitive to a time-averaged latitude of ∼12○. We have also shown the RM lifetime to be 139.6 ± 18.5 days. This provides evidence to suggest the RM component of the SMMF is connected to magnetic flux concentrations (MFCs) and active regions (ARs) of magnetic flux, based both on its lifetime and location on the solar disc.