Low-frequency solar p modes have long lifetimes and, therefore, narrow peaks in frequencypower spectra. This allows their frequencies to be obtained very precisely, making them useful inputs for inversions of the solar interior. However, these low-frequency p modes have limited sensitivity to the solar core, which is still relatively poorly constrained. Mixed and gravity modes, on the other hand, are far more sensitive to core regions. Low-frequency p modes, mixed modes, and gravity modes are all difficult to detect because they have relatively small amplitudes and because they are swamped by solar noise from, for example, convection. We have developed statistical techniques to try and uncover these low signal-to-noise modes. We have then used these techniques to search for previously undetected low-frequency oscillations in BiSON and GONG data, considering the data sets both individually and contemporaneously. To uncover the modes we have developed both frequentist and Bayesian approaches. The developed techniques are very flexible and could be useful for asteroseismic studies as well as helioseismology.

Anne-Marie Broomhall

The Sun’s magnetic activity cycle varies primarily on a time scale of 11yrs from minimum to maximum and back again. It is well-known that the properties of the Sun’s acoustic oscillations are affected by the near-surface internal magnetic field: Frequencies, damping rates, and powers are all known to vary systematically with solar cycle. Careful observation of these variations, therefore, allows aspects of the Sun’s internal magnetic field to be inferred. However, the Sun is just one star and with the advent of CoROT and Kepler, oscillations can now be observed for thousands of other stars. However, despite many stars showing signs of magnetic activity in their lightcurves, to date, activity cycle-like variations in the properties of asteroseimic oscillations are sparse. I will discuss recent observations of solar cycle associated variations in helioseismic oscillation parameters, demonstrating connections with other stars and implications for our understanding of solar and stellar magnetic fields. I will finish with a discussion on how seismology can provide insights into a star’s magnetic field, without necessarily observing activity cycle-like behaviour.

Helioseismology uses the Sun’s natural oscillations to probe beneath the surface of the Sun. Over the past several decades helioseismology has proven extremely successful at providing insights into the interior of the Sun: We have learnt about the structure of the solar interior, including the depth of the convection zone, we have learnt about the composition of the Sun, and we have learnt about rotation and other internal flows. I will review our current understanding of the solar interior based upon helioseismic results, and describe how the Sun’s interior varies over timescales commensurate with the solar cycle. For example, although it is difficult to detect solar-cycle related structural changes in the deep interior, variations in rotation have been observed in the form of the torsional oscillation. I will also discuss some of the remaining challenges for helioseismologists to address, including the search for internal gravity modes, whose detection would substantially advance our ability to infer properties of the structure and dynamics of the deep solar core.