Dmitrii Kolotkov, Valery Nakariakov

It is well-known that the Sun’s magnetic activity varies primarily on a time scale of 11yrs. It is also well known that the frequencies of the Sun’s natural acoustic oscillations vary in-phase with surface and atmospheric measures the Sun’s activity. Additionally, both atmospheric activity proxies and helioseimic frequencies exhibit variations on timescales much shorter than 11yrs, including the ‘quasi-biennial’ periodicity. Solar periodicities, including the 11yr cycle, are hard to characterise, as they vary in both length and amplitude. We have used empirical mode decomposition techniques to separate time variations in acoustic mode frequencies, the 10.7cm flux and sunspot areas into a set of intrinsic modes. We then use the Huang-Hilbert transform to characterise the periodicities of these intrinsic modes. The periodicities obtained are consistent between the different activity proxies, including the quasi-biennial periodicity. This indicates that the quasi-biennial behaviour observed at the solar surface and in the solar atmosphere is also symptomatic of the solar interior.

Chloe Pugh, Valery Nakariakov

Quasi-periodic pulsations (QPPs) are a common feature of solar flares that are observed in many different wavelengths. Although QPPs appear not to be as abundant in white light Kepler flare light curves as they are in solar flares, albeit in different wavelengths the structure of the pulsations are strikingly similar, hinting that the same underlying processes govern both solar and stellar flares. Here we consider a special case, observed on KIC9655129, which shows evidence of multiple periodicities. We speculate that the presence of multiple periodicities is a good indication that the QPPs were caused by magnetohydrodynamic oscillations, further strengthening the case that the physical processes in operation during stellar flares are at least analogous to those in solar flares.