Flares that are far more energetic than typical solar flares have been observed on solar like stars (e.g. Maehara et al., 2012), leading to predictions that the average occurrence rate of these so-called “superflares” on “stars with similar rotation periods to the Sun is about once in 500 to 600 years” (Maehara et al., 2015). However, given that these flares are far more energetic than typical solar flares, and that the data upon which these predictions are made consist of unresolved white light observations of the star in question’s brightness, it is reasonable to ask whether these predictions are justified.
The largest Earth-directed solar flare on record was the 1859 “Carrington flare”, which brought halt to the telegraph network across much of Europe and North America. Even this flare was orders of magnitude less energetic than stellar superflares. Our current reliance on technology makes us ever more susceptible to the impact of extreme space weather, associated with energetic events such as flares. Studying stellar flares is vital for understanding the mechanisms responsible for magnetic fields in stars, and the physical processes responsible for flares and space weather on our own Sun. However, to truly understand the link between stellar superflares and solar flares one must first create a solid link between the physical processes occurring in each case.
One feature of solar flares that appears to exist in stellar flares is quasi-periodic pulsations (QPPs), which have periods between fractions of a second to tens of minutes. In the Sun, QPPs can provide information concerning properties of the associated active region (e.g. Nakariakov & Melnikov, 2009). QPPs are thought to be a common feature of solar flares (Kupriyanova et al., 2010; Simões et al., 2015). Although, even this is not universally accepted, with Inglis et al. (2015) claiming that explicit oscillations are not required to explain observations. QPPs in stellar flares tend to be chance discoveries and studied in isolation (e.g. Anfinogentov et al., 2013). A dedicated survey of flaring light curves is required to enable statistical studies of these pulsating flares to be carried out, while exploiting the solar-stellar connection could prove insightful in establishing the presence (or absence) of QPPs in solar flares. This team will study both stellar and solar flare light curves,observed by, for example, Kepler, XMM-Newton and GALEX, particularly focusing on those with QPPs, with the aim of establishing a theoretical link between the two and designing a common methodology for detecting QPPs. We will use Hare-and-Hound exercises to isolate weaknesses in current methodologies, allowing us to refine procedures and establish robust detection techniques. We will consider light curves for stars with different spectral types, rotation rates, and ages, and observed in different wavelengths.
The potential of QPPs to link solar and stellar flares has already been recognised: Pugh, Nakariakov & Broomhall (2015) detected multiple periodicities in a Kepler flare light curve, the most plausible explanation for which is magnetohydrodynamic oscillations, analogous to those observed in solar flares. This not only implies a link between stellar flares and stellar magnetic activity but that the same physical processes are involved in solar and stellar flares. A dedicated survey and a combined consideration of solar and stellar flares may allow for scaling laws to be established, akin to those proposed for flares by Aschwanden et al. (2008) and those utilized by asteroseismology.